A mouse model of sporadic Alzheimer’s disease with elements of major depression

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Bobkova, L.N. Chuvakova, V.I. Kovalev, D.Y. Zdanova, A.V. Chaplygina, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3781115/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 7 You are reading this latest preprint version Abstract Animals after bulbectomy are often used as a model of major depression or sporadicAlzheimer’s disease and, hence, the status of this model is still disputable. To elucidate the nature of alterations in the expression of the genome after the operation we analyzed transcriptomes (RNA-seq data) of the cortex, hippocampus, and cerebellum of olfactory bulbectomized (OBX) mice. Analysis of the functional significance of genes in the brain of OBX mice indicates that the balance of the GABA/glutamatergic systems is disturbed with hyperactivation of the latter in the hippocampus leading to the development of excitotoxicity and induction of apoptosis on the background of severe mitochondrial dysfunction and astrogliosis. On top of this, the synthesis of neurotrophic factors decreases leading to the disruption of the cytoskeleton of neurons, an increase in the level of intracellular calcium, and activation of tau protein hyperphosphorylation and beta-amyloid depositions. Moreover, the acetylcholinergic system is deficient in the background of hyperactivation of acetylcholinesterase. Importantly, the activity of the dopaminergic, endorphin, and opiate systems in OBX mice decreases leading to hormonal dysfunction. Genes responsible for the regulation of circadian rhythms, cell migration, and impaired innate immunity are activated in OBX animals. All this takes place on the background of drastic down-regulation of ribosomal protein genes in the brain. The obtained results indicate that OBX mice represent a model of Alzheimer's disease with elements of major depression. This model can be tentatively attributed to AD subtype B2 in humans. bulbectomized mice Alzheimer's disease depression transcriptomic analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction Alzheimer's disease (AD) is the most common form of dementia among older patients and one of the leading causes of their death. Currently, there is an active search for new treatment of AD, since effective methods to cure this disease have not yet been found due to the complex etiology and multifactorial nature of AD, the genesis of which involves both genetic disorders and the influence of adverse environmental factors [ 1 ]. Recently, analysis of transcriptomic data from AD patients, as well as several transgenic animal models of AD, has made it possible to identify at least three major subtypes of AD with different pathophysiological mechanisms. These mechanisms include combinations of dysregulation associated with sensitivity to tau-mediated neurodegeneration, amyloid formation and neuroinflammation, synaptic signaling, immune status, mitochondrial organization and myelination [ 2 ]. Subtypes of AD vary in sensitivity to different drugs, which makes it important to determine them for targeted therapeutic intervention. Although there are currently more than a hundred transgenic models of AD of the first, second, and third generations [ 3 ], experience has shown a very limited possibility of translating the data obtained from their studies to the clinic. Therefore, modeling different subtypes of the most common sporadic AD is necessary both to study the mechanisms of pathology and to develop effective treatment. In contrast to numerous transgenic models of AD [ 4 – 6 ], there is a very limited number of rodent models of sporadic AD. One such model is represented by various rodents with removed olfactory bulbs [ 7 ]. The idea of a relationship between AD and a decrease in olfactory sensitivity was first proposed by Ferreyra-Moyano and Barragan [ 8 ], who demonstrated that deterioration of the sense of smell is often observed at the early stages of the AD. Changes in olfactory sensitivity occur in 90% of patients with this pathology and can be used to diagnose this disease [ 9 , 10 ]. It is also known that patients with AD exhibit morphological changes in the cortical and subcortical olfactory structures connected with the olfactory bulbs, where generation of numerous senile plaques containing beta-amyloid protein, neurofibrillary tangles and death of mitral cells are noted [ 11 ]. However, the question remains unresolved: either olfactory disorders in AD represent a consequence of pathology developing in the brain, or they can act as an initiating factor of the pathology [ 12 ]. A model for studying the consequences of olfactory impairment is represented by animals with removed olfactory bulbs, the so-called “olfactory bulbectomized” (OBX) mice and rats. OBX animals were characterized by a pronounced impairment of spatial memory, correlated with a progressive neurodegenerative process in brain structures such as cortex and hippocampus also observed in patients with AD. Characteristically, in OBX rodents, the volume of the hippocampus decreases [ 13 ], the functioning of synapses and mitochondrial metabolism is disrupted [ 14 ], and increased cell death is observed [ 15 , 16 ]. All this happens on the background of severe dysfunction of the acetylcholinergic [ 17 ], and serotonergic brain systems [ 18 ]. In extracts of the neocortex and hippocampus of OBX animals, an increased level of the soluble β-amyloid peptide is detected [ 19 ]. Interestingly, in OBX guinea pigs, which have a primary Aβ structure similar to the structure of human Aβ, typical Aβ plaques are formed in the cortex and hippocampus [ 20 ]. Moreover, ablation of the olfactory bulbs in B6C3Tg (APPswe, PSEN1dE9) 85Dbo/J transgenic mice significantly accelerated the deposition of amyloid plaques in the brain [ 7 ]. Mice knockout for the cyclic nucleotide-gated channel alpha 2 ( Cnga2 ) gene, which is important for the transduction of olfactory signals, also exhibited signs of AD, including impaired learning and memory, loss of dendrite spines, as well as decrement of synaptic proteins [ 21 ]. Experiments on live brain slices from OBX rats revealed a significant decrease in long-term potentiation on synapses of Schaffer collaterals in neurons in the CA1 field of the hippocampus [ 22 , 23 ] and a decrease in the level of synaptophysin in the temporal cortex and hippocampus, indicating disorders of synaptic plasticity. This animal model also showed a decrease in mushroom-type spines and tau hyperphosphorylation [ 24 ]. It should be noted that drugs approved for the treatment of AD, in particular cholinesterase inhibitors and the NMDA receptor antagonist memantine, is able to alleviate cognitive impairment in OBX mice [ 25 ]. We have also previously showed that OBX mice respond similarly to therapeutic intranasal administration of recombinant human HSP70 as the classical transgenic model of AD, the 5XFAD mice [ 26 ]. All of the above facts indicate the validity of using OBX animals as a model of the sporadic AD. An important advantage of the OBX model is its speed (symptoms are evident one month after bulbectomy) and high reproducibility, which distinguishes it from most other models of sporadic and familial AD. It should be noted, however, that OBX animals is currently more often used as a model of endogenous depression (major depression - MD) [ 27 ], which is believed to develop as a result of deprivation of basic for rodents odor information about the environment. OBX mice exhibit a few behavioral and morphological changes that are also characteristic of this pathology, which has become a source of controversy and dispute as to which disease OBX animals are a model of [ 11 , 28 ]. Indeed, in OBX rodents, increased locomotor activity, aggressiveness, and increased sensitivity to stress are observed, along with deficits in passive avoidance and hyperactivity in the open field test, that are normalized by antidepressants [ 29 ]. OBX surgery leads to a decrease in the concentrations of norepinephrine, serotonin, and 5-hydroxy-indoleacetic acid in the amygdala, frontal cortex, and midbrain [ 30 ]. Furthermore, compensatory mechanisms ensure an increase in the level of β-adrenergic receptors on blood lymphocytes and in the amygdala cortex, as well as 5HT2 receptors in the neocortex [ 18 ], that are characteristic symptoms of patients suffering from endogenous depression. Interestingly, caffeine has a therapeutic effect in OBX animals [ 31 ]. Based on the above, we may conclude that OBX mice are a unique and very convenient model for studying the mechanisms underlying AD-MD comorbidity. Herein, we report the results of transcriptomic analysis of tissues of three brain structures (the cortex, hippocampus, and cerebellum) of OBX mice in comparison with sham-operated (SO) mice. We evaluated the enrichment in gene sets and compared them with the data obtained from various public resources containing functional and disease information for MD and different subtypes of AD. This analysis revealed significant changes in gene expression in the studied brain regions of OBX mice characteristic for AD and major depression which enable to conclude that this model belongs to a new subtype of AD, characterized by a few manifestations of MD. Materials and Methods 2.1. Animals Male NMRI (22–24 g) mice were purchased from Beijing HFK Bioscience Co., LTD (Beijing, China). Animals were maintained under conditions of standard lighting (light on at 08:00–20:00), temperature (23- 25 0 C), and humidity (55%) with free access to food and water. All animal experiments were conducted in agreement with the Provision and General Recommendation of Chinese Experimental Animals Administration Legislation and were approved by the Animal Ethics Committee in Institute (SLXD-20180912006, 12 September 2018). 2.2. OBX Surgery After a seven-day adaptation, mice were subjected to bilateral OBX according to the previously described methods [ 26 ]. Mice were anesthetized with 2% pentobarbital sodium (40 mg/kg, intraperitoneal injection (i.p.), and fixed in stereotaxic apparatus. After the skull was exposed, one hole was drilled on the midline (2 mm in diameter, 3 mm anterior to bregma). The removal of the olfactory bulbs was performed by aspiration with a blunt syringe needle attached to a vacuum pump. The hole was filled with an absorbable collagen sponge immediately to control the bleeding. Sham-operated mice (SO) experienced the same procedures, but their bulbs were left intact. After surgery, the mice were housed in an individual cage and given penicillin sodium (10,000 U in normal saline, i.m.) once a day to prevent probable infection. All procedures were conducted by national and EU (Directive 2010-63EU) guidelines regulating animal research and were approved by the local ethics committee (CEEA-PRBB). 2.3. RNA Isolation, Library Preparation, and Transcriptome Sequencing For the transcriptomic analysis, three brain tissues (the hippocampus, cortex, and cerebellum) from two groups (OBX and sham-operated) were used. Brains were dissected and stored at 80 0 C until the RNA isolation. The extraction RNA was made using RNAzol RT (Molecular Research Center, Cincinnati, OH, USA) according to the company’s protocol. The concentration and quality of RNA were determined via a Qubit Fluorometer (Invitrogen) and an Agilent BioAnalyzer 2100, respectively, using an RNA 6000 nano kit (Agilent Technologies, Santa-Clara, CA, USA). For libraries RNA with Integrity Number (RIN), no less than 8 were taken. Illumina NEB Next Ultra II Directional RNA Library Prep Kit (NEB, Ipswich, MA, USA) was used for mRNA library preparation. The sequencing was performed on the Illumina NextSeq 2000 platform. RNA sequencing and further differential expression estimation were performed using the equipment of the Engelhardt Institute of Molecular Biology RAS “Genome” center ( http://www.eimb.ru/rus/ckp/ccu_genome_c.php , accessed on 22 February 2022). The sequencing data obtained in the present work are available at the NCBI Sequence Read Archive (project ID GSE249297 GEO base). 2.4. RNA data processing As a result of deep RNA sequencing, we obtained 10–20 mln 75-bp single-end reads per one biological sample. Raw RNA-seq reads processing was performed using the PPLine package [ 32 ]. We used Adaptor sequences that were trimmed off, and low-quality reads were removed using Cutadapt [ 33 ]. Reads were aligned to the reference genome (GRCm39 v.104) using STAR aligner [ 34 ] with total alignment rate > 95%. SAM file post-processing was performed using the Samtools software package [ 35 ]. Reads, assigned to exons of protein-coding genes were counted using feature Counts utility from the subread package [ 36 ]. Subsequent analysis of differential expression was performed in R language version 4.2.2, using RTrans pipeline. Raw gene expression counts were normalized using the TMM method implemented in the edgeR package [ 37 ], and, subsequently, each gene was tested on differential expression using the quasi-likelihood negative binomial generalized log-linear model. Genes with p-value < 0.05 were considered as differentially expressed. Gene set enrichment analysis (GSEA) was performed using the clusterProfiler package [ 38 ] with GeneOntology [ 39 ] and KEGG [ 40 ] databases. Heatmaps and Venn diagrams were plotted using ComplexHeatmap and VennDiagram R packages. Genes, representing key markers of Alzheimer’s disease [ 2 , 41 , 42 ], major depression disorder [ 43 ], apoptosis (KEGG pathway mmu04210 ), ferroptosis [ 44 ] and metabolism of mitochondria [ 45 ] were downloaded from open-access published data. To estimate a resemblance of gene expression patterns between OBX mice and human subtypes of Alzheimer’s disease, we used LogFC values published in open-access data [ 46 ]. Pairs of orthologous genes among mouse and human genomes were matched using OrthoDB database v.11 [ 47 ]. Arrays of LogFC values were compared using Spearman’s coefficient of correlation. Protein-protein interaction networks of products of differentially-expressed genes were created in StringDB v.11 [ 48 ] with parameters “physical interaction network” and “confidence level = 0.7”. Non-interacting nodes were removed. The network was clustered using k-means (mcl method) with several clusters k = 5, each cluster was tested separately on representative sets of enriched biological processes with the clusterProfiler package [ 38 ]. Visualization of the interaction network was performed using Cytoscape software. Results 1. RNA sequencing and analysis of differentially expressed mRNAs in three brain structures of OBX mice. We performed the comparative analysis of the transcriptome signatures of three brain structures of OBX and control SO 4-month-old mice, one month after bulbectomy when major impairments of spatial memory are already developed [49]. We determined the significant differentially expressed (DE) genes with adjusted p-value < 0.05, deregulated in the three brain areas indicated above. The removal of the olfactory bulbs had a strong effect on gene expression in all brain areas studied. Among the total genes expressed in the hippocampus of the OBX mice, there were 944 up-regulated and 1036 down-regulated genes as compared with control SO animals. In the сortex and cerebellum, 879 and 557 genes are expressed correspondently, of which 487 up-regulated and 392 down-regulated genes in the cortex while 277 up-regulated and 280 down-regulated genes were revealed in the cerebellum (Fig.1 A, B, C). The comparative analysis did not reveal significant differences between the number of up and down-regulated genes in each of the studied brain areas in OBX mice (Figure 1C). However, the hippocampus was significantly superior to other brain areas in terms of the total number of genes with changed expression in OBX mice in comparison to SO animals (Figure 1). The results of transcriptome analysis were corroborated by the RT-PCR technique in all three brain areas. Four genes differentially expressed in OBX mice i.e., Apba1 , Atn1 , Kmt2d , and Ttbk1 were used for PCR analysis. (Suppl. Figure S1). 2. Functional annotation of genome expression changes in OBX mice The olfactory bulbectomy led to drastic changes in gene expression, resulting in the activation of several signaling pathways. Fig 2 depicts the top GO enrichment domains of the target genes with the significantly dysregulated mRNAs. The major affected biological processes according to GO enrichment are involved in neurotransmitter secretion, cognition, learning and memory, neuropeptide signaling pathway, metabolic processes, ribosome processing and biogenesis, cell-matrix adhesion, etc. The hippocampus represents a structure where the most drastic changes in the expression of pertinent genetic pathways took place in the OBX mice. GSEA analysis using the GO database revealed pronounced up-regulation in many important pathways and signal systems taking place in the studied brain areas with the hippocampus being the structure where most drastic changes took place. Thus, up-regulation of genes responsible for neuronal plasticity, neuropeptide signaling pathway, neurotransmitter transport, and secretion, as well genes responsible for regulation of glucose metabolism and WNT as well as Notch signaling were significantly up-regulated in the hippocampus of OBX mice. Similarly, the KEGG pathway analysis also revealed pronounced up-regulation in the expression of genes involved in axon guidance, GABAergic synapse, and other synapses as well as synaptic vesicle cycle, circadian entrainment, different signaling pathways, including WNT and Notch signaling in OBX-mice (Fig. S2). In all these gene categories most pronounced up-regulation also took place in the hippocampus of OBX mice and to a significantly lesser degree in the cortex and cerebellum. Characteristically, pronounced down-regulation of genes involved in the protein synthesis such as rRNA processing and ribosome biogenesis represent prominent exceptions demonstrated by using both GSEA and KEGG databases. At the next step, we monitored the expression of genes involved in the metabolism of β-amyloid and Tau protein in the brain of OBX mice. 3. Study of gene expression in the brain regions of OBX mice related to the metabolism of beta-amyloid and tau protein It is well known that neurodegenerative changes in the brain of AD patients are associated with the presence of oligomeric forms of amyloid beta protein and tau protein fibrils, as well as with the processes of their formation and utilization. Therefore, we analyzed the expression of known genes related to these proteins, as well as the pathways of their production and utilization in OBX mice (Figure 3). Analysis of gene expression in three brain regions of OBX mice indicates that the most dramatic changes took place in the hippocampus. The detected genes with altered expression are related to both the formation of beta-amyloid and possible compensatory mechanisms aimed to ameliorate this process. It is noteworthy that in the hippocampus, 28 genes out of 45 showed upregulation and only 8 exhibited downregulation. Several genes that increased their expression in the hippocampus and partially in the cortex of OBX mice are of particular interest. They are represented by the Ywhag gene encoding 14-3-3γ protein, which increased GSK-3β activation and promoted tau phosphorylation in Alzheimer's disease [50], Fn1 – fibronectin1, which declined at the onset of remyelination of the lesion area of the CNS and is implicated in BBB breakdown [51]. All studied brain structures of OBX mice were characterized by a pronounced increase in the level of expression of the Sox9 gene, which responds to Aβ deposition [52]. Increased expression in the cortex and hippocampal formation was also demonstrated by the Tau tubulin kinase-1 ( Ttbk1 ) genes, the activity of which leads to the deposition of hyperphosphorylated tau. Among the genes that showed decreased expression in the brain of OBX mice, the prefoldin genes Pfdn5 in the hippocampus, as well as Pfdn2 in all analyzed structures, should be mentioned. These genes normally function as chaperones. Furthermore, in the hippocampus of OBX mice, the reduced expression of the gene Prepl encoding protein PREPL and down-regulation of the neuron-specific gene, Rasgefl1c (RasGEF Domain Family Member 1C), were observed which may be involved in cytoskeletal degeneration [53], and late-onset neurocognitive disorders [54]. On the other hand, most of the genes involved in β-amyloid synthesis exhibited significant up-regulation in OBX mice. We also detected probably compensatory up-regulation of genes responsible for APP stabilization ( Apba1 , Apba2 ) and receptor-mediated activation of Syk , which should reduce Aβ load by up-regulation of microglial phagocytosis [55]. Finally, the observed up-regulation of Piezo1 and Sorla/Sorl1 genes in the brain of OBX mice is also apparently of a compensatory nature because it ameliorates brain Aβ burden [56] and can decrease the number of amyloidogenic products in the affected individuals [57]. To this end, it was shown that microglia lacking Piezo1 led to the exacerbation of Aβ pathology and cognitive decline, whereas pharmacological activation of microglial Piezo1 ameliorated brain Aβ burden and cognitive impairment in 5xFAD mice [56]. Thus, in the brain of OBX mice, the expression was significantly changed for genes that promote beta-amyloid deposition and hyperphosphorylation of tau protein characteristic of AD and for genes that may compensatory prevent the development of this neuropathology. At the next stage we analyzed genes involved in the functioning of neurotransmitter systems that changed their expression after bulbectomy in the studied brain regions. 4. Expression of genes involved in various neurotransmitter systems in the brain of OBX mice Since the main goal of this study was to determine what pathology MD or AD represent OBX animals, we first analyzed the expression of genes, judging by the literature data, related to the functioning of neurotransmitter and several other receptor systems characteristic for AD and MD in the studied brain structures of OBX mice. Table 1 lists the genes of neurotransmitter systems that underwent the greatest changes in expression in the brain of OBX mice. Table 1. Genes involved in the activity of the main neurotransmitter systems, with the largest changes in expression in OBX mice compared to SO animals. Blue–down reg. genes, red–up reg. genes System Gene Hippocampus Cortex Cerebellum Glutamatergic Grm1 Grm4 Slc1a1 Slc1a2 Slc1a2 GABAergic Gabarapl2 Gabarapl2 Cholinergic Ache Ache Chrm1 Chrm4 Chrna4 Dopaminergic Arpp21 Drd2 Neurotransmitter transport Slc6a20b Slc6a20b Long-term depression Irs2 Irs2 Irs2 Neuroactive ligand-receptor interaction Adcyap1r1 Adcyap1r1 Adora2a Cckbr Hrh3 Mas1 Oprl1 Sstr1 Sstr4 Table 1 demonstrates that OBX mice are characterized by a deficiency of the GABAergic system since the expression of the gene gamma-aminobutyric acid (GABA) A receptor-associated protein-like 2 which mediates the fast inhibitory synaptic transmission in the central nervous system is drastically reduced. At the same time, activation of the glutamatergic system is noted in the hippocampus, which is manifested in increased expression of metabotropic glutamate receptors. Activation of the glutamatergic system may also be indicated by a compensatory increase in the expression of Slc1a1 genes encoding members of the high-affinity glutamate transporters. OBX mice were also characterized by impaired expression of the Chrm1 and Chrm4 genes, associated with the activity of the acetylcholinergic system and responsible for the synthesis of muscarinic acetylcholine receptors M1 and M4, that have long been considered to be involved in the pathophysiology of AD [58-60]. In the cortex and hippocampus of OBX mice, there is an increase in the expression of the gene encoding the alpha-4 subunit of the neuronal nicotinic acetylcholine receptor ( Chrna4 ) [61, 62], as well as a strong increase in the expression of the acetylcholinesterase gene ( Ache ). Hyperactivation of this gene is associated with synaptic acetylcholine deficiency and the development of cognitive impairment in AD [63-66]. On the other hand, in the hippocampus of OBX animals, a pronounced decrease in the expression of dopamine D2 receptor genes ( Drd2 ) is observed, as well as a decrease in the expression of the gene that regulates the effects of dopamine itself ( Arpp21 ). In addition, down-regulation of the expression of the Slc6a20b gene, responsible for the transport of neurotransmitters, is observed in the hippocampus and cerebellum of OBX mice. Similar disturbances in the dopaminergic system, along with loss of dopaminergic neurons, as well as decreased expression of dopamine D2 receptors in the hippocampus, have been revealed in a classical mouse model of AD, and these disturbances have been associated with early manifestations of AD [67, 68]. Interestingly, OBX mice also showed changes in the expression of genes responsible for the synthesis of peptide receptor ligands, which was manifested in a decrease in the expression of somatostatin receptor genes 1 and 4 ( Sstr1 and Sstr4 ). These results are consistent with other data enabling to suggest that the downregulation of these genes (SSTs) represents an early pathological signature of AD ([69, 70]. In the cortex of OBX mice, an increase in the expression of the histamine receptor 3 ( Hrh3 ) gene was demonstrated. This gene is one of the targets of therapeutic agents being developed for the treatment of numerous disorders, including cognitive diseases such as attention deficit hyperactivity disorder and AD [71]. It is noteworthy that in the cortex of OBX mice, there is a decrease in the expression level of the MAS1 receptor gene ( Mas1 ), the activation of which leads to a decrease in blood pressure. Besides, in the hippocampus and cortex an increased level of expression of the substrate of insulin receptor gene ( Irs2 ) was noted. Deficiency of MAS receptors ( Masr ) and angiotensin (1-7) on the background of excess amounts of angiotensin II was often observed in sporadic AD, and its restoration has a positive effect in AD patients [72, 73]. It should be underlined that the expression of genes that determine the development of pathology does not always coincide in OBX and AD. For example, OBX animals exhibited a significant decrease in the expression of the adenosine receptor A2a ( Adora2a ) gene, while patients with AD, on the contrary, are characterized by increased expression of this receptor [74, 75]. Interestingly, bulbectomy also caused an increase in the expression of the nociceptin opioid peptide receptor gene ( Oprl1 ) in the hippocampus, which is characteristic of both depression and AD [76]. From the data presented in Table 1, it is clear that the bulbectomy causes serious changes in the expression of genes of receptor systems. These changes manifest in an imbalance of the inhibitory and excitatory systems in the brain of OBX mice, and also lead to a deficiency of the dopaminergic and acetylcholinergic systems. The observed changes in the activity of neurotransmitter systems are probably responsible for the characteristic behavioral changes observed in OBX animals. 3. Mitochondrial genes differentially expressed in OBX mice . At the next stage, we analyzed differentially expressed genes associated with the functional state of mitochondria in OBX mice using the MitoCarta 3.0 database. From the top 50 genes related to the state of mitochondria, 36 genes decreased their expression in the brain of OBX mice compared to SO animals. It is necessary to emphasize the drastic decrease in the expression of genes belonging to Mrp and Nduf families. The activity of these genes is associated with the synthesis of mitochondrial ribosomal proteins and subunits of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) which plays a vital role in cellular ATP production, the primary source of energy for many crucial processes in living cell. It is known that mitochondrial Complex I deficiency causes adult-onset of several neurodegenerative disorders [78]. In OBX mice the expression of the Fmc1 gene, encoding assembly factor 1, responsible for the formation of mitochondrial Complex V, is significantly reduced in all three studied brain areas. Pronounced down-regulation was also noted for the Pet117 gene. Depletion of Pet117 reduced mitochondrial oxygen consumption rate and impaired mitochondrial function. This gene plays a role in the biogenesis of mitochondrial complex IV or cytochrome c oxidase, which is part of the respiratory electron transport chain of mitochondria [79]. Furthermore, the decrease in Mgst gene expression observed in the brain of OBX mice should reduce the protection of the outer mitochondrial membrane from oxidative stress [80]. Only 14 genes out of 50 depicted in Figure 4 exhibited moderate, apparently compensatory activation of expression, including the Mief1 and Slc25a51 genes. These genes help to maintain energy metabolism in the cell [81] and improve mitochondrial respiration [82]. There is also activation of genes encoding the GPT2 proteins in the hippocampus and cortex, as well as Mcu in the cortex, that are responsible for the regulation of cell growth, amino acid metabolism, and level mitochondrial calcium. An increase in their expression also apparently indicates the compensatory nature of these changes. Increased expression of the Kmt2d gene [83] observed in all three brain areas, and up-regulation of three other genes in hippocampus ( Mlxip , [84], Wdfy4 [85], and Lamb2 [86], whose activity is associated with the suppression of apoptosis and stabilization of synapses (Figure 4) are probably also represent compensatory reaction. However, given the deficiency of mitochondrial ribosomal proteins found in OBX, even increased expression of genes aimed at compensating for severe mitochondrial dysfunction is unlikely to have a significant effect. Next, we analyzed the state of gene expression in OBX mice associated with apoptosis-programmed cell death, as well as ferroptosis, that are characteristic features of various forms of AD. 4. Apoptosis and ferroptosis. The main manifestation of any neurodegenerative process is massive cell death. It has been established that AD is characterized by neuronal death, predominantly due to apoptosis pathway activation. Therefore, we analyzed the expression of apoptosis-related genes in the brains of OBX mice. The obtained data are presented in Fig. 5. The list of genes associated with apoptosis and ferroptosis processes was taken from the database http://deathbase.org/ and [44], respectively. The results indicate that the number of apoptosis-related genes that increased their expression was two times larger in comparison with genes with decreased expression. Obviously, in the brain of OBX mice, the hippocampus represents the structure where the largest number of genes with altered expression associated with apoptosis was noted. The activation of the Dab2ip gene in all studied areas of the brain is noteworthy. This gene encodes a protein which acts as a scaffold protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. In particular, this protein modulates the balance between phosphatidylinositol 3-kinase (PI3K)-AKT-mediated cell survival and apoptosis-stimulated kinase (MAP3K5)-JNK signaling pathways [87]. Direct activation of apoptosis in OBX mice is associated with activation of the Casp9 gene in the hippocampus and the Apaf-1 gene in the cortex. Both genes are involved in the activation cascade of caspases responsible for apoptosis. It is also necessary to note the activation of the Hrk gene (DP5) in the cortex of OBX mice. This gene plays an important role in neuronal cell death [88]. On the other hand, the activation of the Bcl2l1 gene observed in the hippocampus of OBX mice may indicate a protective, compensatory effect against apoptosis, since this gene is a potent inhibitor of cell death [89]. Ferroptosis is a nonapoptotic form of cell death dependent upon intracellular iron [90]. Iron homeostasis disturbance has also been implicated in Alzheimer’s disease (AD), and excess iron exacerbates oxidative damage and cognitive defects [91]. In the hippocampus of OBX mice, only four genes related to this type of cell death changed their expression. Thus, Trf gene exhibited upregulation while Pcbp1 , Ftl1 , and Gpx4 genes were down-regulated (Figure 5). All these genes are associated with the maintenance of iron homeostasis, and their insufficient expression may lead to cell death by the ferroptosis pathway. It is of note that drastic down-regulation of the Pik3r3 gene is observed in the brain of OBX mice (Figure 5). This gene under normal conditions, promoted hepatic fatty acid oxidation via PIK3R3-induced expression of Pparα [92]. Drastic inhibition of this gene in two brain areas of OBX mice should disrupt lipid metabolism which may lead to the induction of the ferroptosis process. 5. Changes in the transcription of genes characteristic for different cell types in the brain of OBX mice Next, we analyzed the expression of genes in the cortex, hippocampus, and cerebellum related to the state and activity of different major types of cells in these brain regions and presented this in the form of histograms, where we plotted the number of genes that increased or decreased expression in OBX mice compared to SO animals in each of 6 major cell types: neurons, astrocytes, oligodendrocytes, microglia, endothelial cells and oligodendrocyte progenitor cells (OPC) (Figure 6). A complete list of genes expressed in different cell types in the compared brain structures is provided in Table S1. The hippocampus again turned out to be the brain structure of OBX mice with the largest number of genes with altered expression related to the functioning of different types of cells of the nervous tissue. In the hippocampus and cortex, the largest proportion of genes, predominantly with increased expression, has been revealed for astrocytes, neurons, and progenitor cells, and in the cerebellum for microglia. An analysis of the synchronicity of changes of the same genes for different types of cells presented in Figure 6B demonstrated an interesting pattern: the same types of brain cells in the OBX mice were characterized predominantly by altered expression of different genes depending on the brain area studied. When analyzing neuronal genes, we demonstrated that Map2 , Camk4 , and Lamp5 genes drastically reduced their expression in OBX mice, which according to the literature, is characteristic for AD [94-97]. The Arpp21 gene, which greatly decreases its expression in hippocampal neurons, is directly associated with a reduced dopamine receptor activation [98]. On the other hand, several genes with increased expression in OBX animals may also be associated with the development of AD-like pathology. Thus, up-regulation of both the Scn2b and Efr3a genes is associated with the impairing of learning and memory [99] and reduced survival of newly born neurons in the hippocampus by inhibiting the maturation [100]. The protein encoded by the Ap2a2 gene often co-localizes with neurofibrillary tangles and promotes their deposition [101]. Analysis of microglial genes in hippocampus of OBX mice with changed expression logFC < -0.8 enabled to conclude that these genes are involved in protein synthesis regulation ( Eif5 - ribosomal initiation complex and chain elongations), metabolic coordination between cytoplasm and mitochondria ( Ptp4a1 ), as well as in regulation of ionic homeostasis ( Slc39a12 ). When studying astrocytes, we observed down-regulation of expression of gene Naaa [102] and the Grm3 - gene of glutamate receptor metabotropic 3, associated with the accumulation of glutamate in the synaptic cleft leading to the development of neurotoxicity [103]. On the other hand, in the astrocytes of OBX mice, we revealed a significant increase in the expression of the Slc6a11 - gene encoding GABA transporter in the brain [104]. The activity of this gene which may ameliorate the hyperactivation of the glutamatergic system probably represents a compensatory reaction. The observed increased expression of the GFAP gene (Glial fibrillary acidic protein) in OBX mice represents the manifestation of astrogliosis, a characteristic feature of AD [105, 106] as well as up-regulation of the Sox9 gene playing an important role in Aβ deposition being an important feature of the hippocampus in AD patients [52]. In microglia of OBX mice preferential up-regulation of large majority of genes was revealed. Characteristically, an increase in the expression of several highly specific genes for non-activated mouse microglia, such as Sall1 (transcription factor) was noted. The observed increased Trim8 expression in OBX mice, probably also represents the mechanism to protect microglial cells from cytotoxicity and inflammation [107]. Overexpression of the Ski gene demonstrated in all analyzed brain regions of the OBX mice, leading to the loss of neurons bearing NMDA receptors represents a manifestation of excitotoxicity apparently associated with excessive release of glutamate [108]. On the other hand, in microglia we revealed up-regulation of several genes activated by bulbectomy such as Nrp1 which activates the Syk gene to inhibit Aβ deposition and regulate microglial phagocytosis and disease-associated microglia (DAM) acquisition [55, 109]. All the above data enable to conclude that it is unlikely that an active process of neuroinflammation takes place in OBX animals. It is of note, that microglia cells are characterized by a drastic drop in the expression of genes involved in ribosome function (e.g. Rps27 , Rpl22 , Rps27a ), transcription activation ( Junb ), protein transport ( Rab11a ) and neurogenesis ( Hbp1 , [110]). The observed significant activation of genes in endothelial cells in OBX mice is also of interest because it may reflect changes in the permeability of the BBB. Besides, these cells as well as microglia cells exhibited reduced expression of ribosomal proteins ( Rps27 , Rps27a), splicing (Cwc15), protein transport and cell differentiation and degradation (Gabarapl2) , [111]. It is of note, that in the cortex and cerebellum of OBX mice, the expression of only 6 genes associated with oligodendrocytes changed their expression, while in the hippocampus, there were 16 of such genes. Dysregulation of the activity of these genes can lead to a decrease in the intensity of axonal myelination. Indeed, impaired axonal myelination in the brain at the early stages of AD development has been demonstrated [112, 113]. Therefore, we have shown that OBX mice are characterized by pronounced changes in the expression of genes associated with different types of nerve cells, and the direction of these changes often coincides with the patterns observed in the brains of AD patients. 6. Expression of genes involved in major depression in the brain of OBX mice It should be noted that OBX mice and rats are often considered in the literature as a valid model of depression [27, 114, 115]. Figure 7 depicts differentially-expressed genes in the three brain structures of OBX mice that are associated with MD phenotype in humans (gene sets from [43]). When analyzing differentially expressed genes in OBX mice, it is obvious that several of them coincided with genes responsible for the development of depression (including the genes Drd2 , Map2 , and the so-called canonical clock genes: Per2 , Arntl , Nr1d1 ). These genes play an important role in the regulation of circadian rhythm. It is known that changes in their expression are accompanied by sleep disturbance, a characteristic symptom of both MD and AD [116, 117]. It is known that depression is the result of dysregulation in neurotransmitter functioning in different brain regions [118]. In OBX animals, as mentioned above, we observed pronounced changes in the expression of genes associated with the activity of dopaminergic ( Th , Drd1 , Drd2 ), serotonergic ( Htr1a , Htr2c , Htr6 ), adrenergic ( Adra2a ) and cholinergic ( Chrm1 , Chrm4 ) brain systems. Probably the observed increase in the expression of the Sox9 gene encoding a transcription factor [119] represents a direct consequence of such disturbances. It is of note that the revealed changes in gene expression in OBX mice associated with the state of the peptidergic system, endorphin, and opiate systems are similar to those observed in MD, as well as observed hormonal dysfunction. At the same time, while in OBX mice the synthesis of neurotrophic factors decreases, the level of intracellular calcium increases. Furthermore, in OBX animals the phosphorylation of tau protein is activated while apoptosis is induced on the background of astrogliosis. All these changes observed in OBX mice are also characteristic of animals with MD. Importantly, several genes depicted in Figure 7 are known to be involved both in MD and AD pathologies. 7. Determination of the subtype of AD-like pathology exhibited by OBX mice Attempts are being made all the time to organize data into certain types or categories, both for pathologies like AD in humans and for the numerous animal models used to study this disease based on RNA-seq data [2]. We also analyzed DEG expression in OBX mice and found 20 genes (Table S2) belonging to the 101 “key regulators” identified in the article describing AD subtypes, that were obtained as a result of transcriptomic analysis of the hippocampus of AD patients from two large populations [2]. The performed comparison enables to conclude that the pattern of expression of OBX mice genome may be placed with caution into B2 subtype of AD (Table S2). Thus, protein degradation–related genes, involved in ubiquitination and polyubiquitination ( Fbxo41 , Fbx16 ), protein catabolism, the proteasome biogenesis, and proteins targeting for destruction, as well as genes responsible for the formation of vesicles and endosomes ( Csrnp3 , Cltc ), were predominantly up-regulated in the hippocampus of OBX mice. The enhanced transcription in OBX animals was also shown for the genes responsible for intracellular and transmembrane traffic ( Rab9b ), influencing cell differentiation and phagocytosis ( Syk ). Thus, in an attempt to assign hallmarks of AD pathology in OBX mice to subtypes of human AD [2], we found a modest, but statistically significant correlation between RNA expression patterns in the hippocampus of OBX mice and B2 subtype of AD (R= 0.209, p=1.897906e-85) (Figure S3). Next, we analyzed how the protein products of differentially expressed genes in different regions of the brain of OBX mice interact with several proteins of key AD-associated genes. The latter genes involved in the formation and processing of beta-amyloid, the processes of synaptic transmission and protein folding. The results of this analysis are depicted in Figure 8. It can be seen in Figure 8 that the products of genes differentially expressed in different parts of the brain of OBX mice interact at the protein level with certain categories of genes involved in AD. This suggests that changes in the expression of certain genes in the brain of OBX animals lead to disruption of several key protein-protein interactions, which in turn triggers a cascade of changes leading to disruption of major regulatory systems in various parts of the brain. Interestingly, these systems include synaptic transmission, protein folding, beta-amyloid formation, etc. The largest number of DEGs that changed their expression after OBX was observed in the hippocampus, which is consistent with the results of other studies that found a high correlation between the number of DEGs in the hippocampus and the progression of AD and including the intensity of amyloid plaque deposition [120]. From the results obtained, it follows that OBX mice are a model of a fairly common type of sporadic AD with manifestations of agitated depression observed in more than 30% of AD patients. DISCUSSION Intensive studies of AD in clinics and experiments exploring numerous models of this disease have made it possible to put forward several hypotheses for the genesis of this pathology. The generally accepted hypotheses are the amyloid cascade, the neurotransmitter hypothesis, the mitochondrial dysfunction hypothesis, neuroinflammation, and excitotoxicity hypothesis. Each of them is confirmed by abundant behavioral and biochemical data, as well as a description of a specific set of genes involved in the development of the pathological process in AD. Since the main goal of this study was to determine whether OBX animals represent a model of AD or MD, we analyzed gene expression in three brain regions of OBX mice and compared them with known sets of genes implicated in AD or MD. The removal of the olfactory bulbs has a strong effect on gene transcription in the brain. The hippocampus was the leader in this respect. These data agree with the abundant data accumulated in the process of AD investigation that demonstrated a high correlation between the number of DEGs in the hippocampus with the progression of AD and the intensity of amyloid plaque deposition [ 120 ]. The olfactory bulbectomy resulted in the activation of several signaling pathways leading to an AD-like neurological phenotype. Thus, the major affected biological processes according to GO enrichment are responsible for neurotransmitter secretion, cognition, learning, memory, neuropeptide signaling pathway, metabolic processes, ribosome processing and biogenesis, cell-matrix adhesion, etc. Characteristically, genes responsible for neuronal plasticity, neuropeptide signaling pathway, neurotransmitter transport, and secretion, as well as genes responsible for the regulation of glucose metabolism and WNT and Notch signaling were significantly up-regulated in the hippocampus of OBX mice. On the other hand, down-regulated genes were involved in protein synthesis and ribosome biogenesis. The transcriptomic analysis of genes in the brain of OBX mice demonstrated that 36 out of 45 Alzheimer’s disease-associated genes changed their expression, while increased expression was demonstrated by genes directly associated with the development of a neurodegenerative process similar to AD (Fig. 3 ). In our analysis we have demonstrated unidirectional changes change in the expression of genes involved in deposition of beta-amyloid (e.g. up-regulation of the Sox9 gene) [ 52 ] or hyperphosphorylation and deposition of tau protein [ 121 , 122 ], i.e. most of them exhibited increased expression. Interestingly, in the OBX brain, even several genes with reduced activity apparently contributed to the development of the pathology. Thus, a decrease in the expression of the prefoldin genes ( Pfdn5 and Pfdn2 ), that perform the function of chaperones, was observed, probably contributing to the formation of beta-amyloid oligomers. It is interesting to note, that the enhanced expression of several genes in the brain of OBX mice was probably compensatory in nature leading to APP stabilization (e.g. Apba1 , Apba2 ) or reducing Aβ load ( Syk ) by up-regulation of microglial phagocytosis ( Piezo1 ) [ 55 ]. The presence of compensatory mechanisms that slow down the development of pathology is also characteristic for AD [ 123 ] and the very fact of activation of specific compensatory mechanisms can serve as an early diagnostic sign of the development of hidden pathology. It is known that beta amyloid and tau protein deposits exhibit neurotoxic effects leading to neuron loss. It is also known that in AD the death of neurons occurs mainly through apoptosis [ 124 ]. In our case, the removal of the olfactory bulbs induces predominantly in hippocampus the synthesis of proapoptotic factors e.g. the expression of the Apaf-1 and Casp9 genes, that play a central role in the initiation of apoptosis [ 125 , 126 ]. It is known that oligomeric Apaf-1 mediates the cytochrome c-dependent autocatalytic activation of pro-caspase-9 (Apaf-3), leading to the activation of caspase-3 and apoptosis. The increased level of the protein product of the Hrk gene, activated in OBX mice (DP5 [ 88 ]), also leads to activation of caspase-3 and, consequently, to neuronal cell death. In recent years, in addition to apoptosis, significant attention has been paid to other types of cell death, in particular, ferroptosis [ 44 ], which has been also implicated in Alzheimer's disease. Although only 4 genes associated with maintaining iron homeostasis changed their expression in OBX mice, downregulation of three of them is sufficient to induce ferroptosis ( Pcbp1 , Ftl1 и GPx4 ) [ 127 , 128 ]. It is important to note that the inhibition of ferroptosis ameliorates brain damage in Alzheimer, Parkinson, and Huntington's diseases [ 129 ]. It is known that neurons loss observed in AD patients may be due to glutamate neurotoxicity. Therefore, we analyzed genes involved in the functioning of neurotransmitter systems that changed their expression after bulbectomy in the studied brain regions. The observed imbalance of glutamate/GABA systems with a deficiency of the inhibitory GABA system (i.e. reduced expression of the GABA A receptor-associated protein-like 2 genes) represents a characteristic feature of OBX mice transcriptome. Activation of the glutamatergic system in OBX mice was also evident based on the increased expression of metabotropic glutamate receptors and, apparently, a compensatory increase in the expression of the slc1a1 gene of the high-affinity glutamate transporters. Activation of this gene accompanies the accumulation of glutamate in the synaptic cleft and further development of glutamatergic neurotoxicity, leading to neuronal death [ 130 ]. Furthermore, a decrease in the expression of the mGlu3s receptor revealed in transcriptome of astrocytes in OBX mice may be associated with the accumulation of glutamate in the synaptic cleft and development of astrocyte-mediated excitotoxicity and neuronal death in OBX mice [ 103 ]. The overexpression of the Ski gene demonstrated in all brain areas in OBX mice is probably also associated with excessive release of glutamate, excitotoxicity and the death of neurons carrying NMDA receptors, which is typical for AD [ 108 ]. On the other hand, the increased expression of the Slc6a11 gene, encoding the GABA transporter, observed in astrocytes of OBX mice [ 104 ] may indirectly counteract the hyperactivation of the glutamatergic system. It is believed that an imbalance of these two systems may be a prerequisite for the development of AD [ 131 ]. Moreover, GABAergic dysfunction may contribute to the disruption of functional connections in the brain and thereby contribute to the development of AD [ 132 ]. The hypothesis of the genesis of AD associated with excitotoxicity caused by excess glutamate has become popular [ 133 ]. A decrease in the expression of genes, responsible for the synthesis of acetylcholine receptors M1 and M4, and the increased expression of the acetylcholinesterase enzyme gene represent another characteristic feature of OBX mice. It is necessary to emphasize, that a deficiency of the cholinergic system with hyperactivity of the acetylcholinesterase enzyme is a major symptom of AD and reflects the death of acetylcholine-synthesizing neurons in the nucleus basalis of the Meynert [ 134 , 135 ]. A drop in the content of these receptors in human peripheral blood is used as a marker of AD [ 136 ]. Moreover, the development of pharmacological agents that enhance the expression of the Chrm1 and Chrm4 genes is one of the promising directions in AD treatment since the proteins they encode have neuroprotective activity and increase the survival of neurons in AD models [ 59 , 60 ]. The observed increased expression of the acetylcholinesterase enzyme gene in the brain of OBX mice represents significant evidence of the validity of these animals as a model of AD. At the present time the use of acetylcholinesterase enzyme blockers remains practically the only FDA approved method for improving memory in AD patients while the development of new agents with similar activity is a promising direction in pharmacology [ 63 – 66 , 137 ]. It is believed that the deficiency of acetylcholinenergic system is associated with impaired cognitive functions in AD patients [ 61 , 62 ]. Importantly, our transcriptomic data corroborate the results of our previous histoimmunochemical studies, that showed a decrease in the density of acetylcholine-synthesizing neurons in the forebrain basal ganglia of OBX mice [ 138 ]. The performed transcriptomic analysis also demonstrated the changes in the activity of the dopaminergic system in OBX mice. Thus, we revealed a decrease in the expression of dopamine type D2 receptors in the hippocampus, which is a characteristic symptom of both depression and AD [ 67 , 139 ]. Previously, using a classical transgenic model of AD in 5XFAD mice, we also showed disturbances in the dopaminergic system, including the death of dopaminergic neurons, which is considered to be an early manifestation of AD [ 68 ]. The downregulation of genes encoding somatostatin ( SSTs ) in the brain of OBX mice can be also considered as the pathological signature of AD since low levels of both mRNA and correspondent protein are characteristic features of AD brain [ 69 , 70 ]. Recently, the mitochondrial hypothesis of the pathogenesis of AD has taken the leading place in popularity [ 140 , 141 ]. According to this hypothesis, energy deficiency caused by mitochondrial dysfunction is one of the major causes of AD development [ 142 ]. To this end, in the brain of OBX mice the vast majority of genes related to the functioning of mitochondria exhibited decreased expression, which indicates a disruption in the functioning of complexes 1 (the multisubunit NADH: ubiquinone oxidoreductase) and IV (cytochrome C oxidase) of the mitochondrial respiratory chain (down-regulation genes of the Nduf and Pet100 families), respectively), as well as complex V (ATP synthetase) (decreased expression of the Fmc1 gene). Deficiency of these mitochondrial complexes is a feature of several neurodegenerative disorders, including AD [ 143 – 145 ]. Data from transcriptomic analysis of the mitochondria state in OBX mice are consistent with our previously obtained results on impaired mitochondrial functions in these animals, similar to those occurring in transgenic familial mouse AD models and patients with sporadic AD [ 14 ]. Summarizing the discussion of the results of transcriptomic analysis of genes associated with the functioning of mitochondria and the rate of cell death in the brain of OBX mice it should be noted that although the number of genes associated with these processes and changing their activity in OBX mice was relatively small, the altered expression was observed in several major genes which directly indicates a deficiency of mitochondrial functions and the induction of apoptosis in the brain of OBX animals representing key symptoms of the development of Alzheimer's-like neurodegeneration. It is necessary to mention that recently we have demonstrated that intranasal administration of mitochondria isolated from control mice improves spatial memory in OBX mice [ 146 ]. Furthermore, we demonstrated that OBX animals are characterized by pronounced changes in the expression of genes associated with different types of nerve cells, and the direction of these changes often coincides with those observed in AD patients. Characteristically, the greatest changes for all six cell types were observed in the hippocampus. Thus, a decrease in the expression of neuronal genes (e.g. Map2 , Camk4 , Lamp5 ) directly indicated the development of Alzheimer’s-type neurodegeneration [ 97 , 147 ]. Dysregulation of the Ap2a2 and Efr3a genes observed in OBX mice and characteristic of animal models of AD is often associated with neurofibrillary tangles [ 101 ] and inhibition of hippocampal neurogenesis characteristic for AD [ 100 ]. The performed analysis of gene expression in astrocytes and microglia, is of special interest because the transition of these cells into disease-associated state may induce neuroinflammation which plays the leading role in the genesis of AD [ 148 ]. However, our analysis of transcriptome of OBX mice brain regions failed to reveal clear-cut transcriptomic signatures of neuroinflammation with the only exception of activation of the pro-inflammatory cell surface marker galectin 3 gene ( Lgals3 in cortex). An increased level of expression of the Trim8 gene in microglia [ 107 ], as well as activation of Syk signaling, which can interfere with the development of disease-associated microglia (DAM) suggest certain protection of microglial cells of OBX mice from cytotoxicity and inflammation. On the other hand, the observed activation of Gfap gene in astrocytes of OBX mice is evidence of astrogliosis, characteristic for several neurodegenerative diseases, including AD [ 148 ]. It is of note, that increased expression of the Axl gene (tyrosine kinase receptor), in astrocytes in OBX mice is associated with inhibition of proinflammatory responses [ 149 , 150 ]. The increased expression of the gene that controls the synthesis of glial fibrillary acidic protein ( Gfap ) in the brain of OBX mice indicates the validity of the model because this astrocytic cytoskeletal protein is a potential biomarker for AD [ 105 , 106 ]. The demonstrated activation of genes associated with microglia may result in the release of glutamate, causing excitotoxicity and death of neurons bearing NMDA receptors, directly related to learning and memory [ 151 ]. The activation of the immune system of OBX mice takes place in the cerebral cortex judging by the high level of expression of genes involved in the interferon response ( Ifitm3 ). It is well known that the induction of type 1 interferons, may be associated with neuron death and DNA damage [ 152 ]. Based on the accumulated data we conclude that neuroinflammation probably does not play an important role in the development of neurodegeneration in the brain of OBX mice. Characteristic feature of OBX mice is a dramatic decrease in the expression genes of ribosomal proteins in astrocyte, microglial cells and in particular genes for ribosomal mitochondrial proteins, which may lead to astrocytes and microglia dysfunction. It is well known that a drastic reduction of total protein synthesis is a characteristic feature of neurodegenerative process [ 153 ]. Analyzing the processes linked with OPC genes (oligodendrocyte progenitor cells), we discovered multidirectional changes associated both with the development of a neurodegenerative process and with a compensatory reaction in the brain of OBX mice. It is known, that genes of endothelial cells are able to maintain homeostasis and preserve the function of these cells even under conditions of bulbectomy and the development of neurodegeneration. We observed dysregulation the expression of genes in oligodendrocytes in the cortex and cerebellum of OBX mice, that may lead to a decrease in the intensity of axonal myelination, characteristic for the early stages of AD development [ 112 , 113 ]. In this regard, it is interesting to note that the B2 subtype of AD in humans, which based on our data most closely corresponds to OBX mice, is also characterized by a marked down-regulation of genes in oligodendrocytes with up-regulation in other cell types, suggesting that a demyelinating process may take place in OBX mice. Recently, special attention has been paid to comorbid diseases associated with AD, such as hypertension and diabetes, associated with disruption of the renin-angiotensin system (RAS) and insulin resistance. To this end, in OBX mice, we found a decrease in the expression level of the MAS1 receptor gene ( Mas1 ). A shift in the balance of the two branches of the RAS, caused by a lack of MAS receptor ( Masr ) and angiotensin (1–7) against the background of an excess amount of angiotensin II, was often noted in sporadic AD, and its restoration has a positive effect in this pathology [ 154 , 155 ]. Until now it was not clear whether major depression is a risk factor for AD, a symptom, a stress reaction in AD, or a comorbid disease. However, the very fact of comorbidity of AD, depression is a phenomenon long known. Serious studies have been devoted to the overlap between symptoms of depression and neurodegeneration processes in patients with mild AD [ 156 ]. The prevalence of symptoms of MD in Alzheimer's disease ranged widely from 22.5–54.4% [ 157 ]. However, due to the lack of convenient animal models, the question remained unclear. It was not clear whether depression arises as a psychological reaction to the disease and due to difficulties in the adaptation to AD, or depression and AD have common neurobiological basic mechanisms [ 158 , 159 ]. It is of note, that transcriptional analysis of brain tissue in OBX mice revealed that some of the changes in receptor systems are more typical for MD, than for AD. Thus, the observed decrease in the expression of the adenosine receptor A2a gene ( Adora2a ) that we observed is a characteristic sign of depression [ 160 , 161 ], while in AD patients, on the contrary, there is an increased expression of this receptor [ 74 , 75 , 162 ]. On the other hand, a decrease in the expression of dopamine type D2 receptors also demonstrated in the hippocampus in OBX mice is a characteristic feature of both depression and AD [ 67 , 139 ]. Recently, using classical transgenic model of AD (APP/PSEN1-Tg mice) it was shown that depressive manifestations, such as a decrease in olfactory sensitivity represent an early stage of the pathology [ 163 ] Importantly, in the brain of OBX mice we observed the downregulation of the genes encoding somatostatin (SSTs) the dopaminergic) receptors, endorphin, and opiate systems, as well as genes associated with hormonal dysfunction. The analysis of transcription in the brains of OBX mice revealed up-regulation of genes associated with the regulation of circadian rhythms, cell migration, and impaired innate immunity, characteristic for the MD. Therefore, the transcriptomic analysis showed that in OBX mice, changes in the expression of genes responsible for the functioning of receptor systems are similar to those observed in AD, while changes characteristic of depression are less frequent and less pronounced. It is clear that OBX mice represent a model of complex neuropathology with elements of AD and MD. It is necessary in this context to underline that according to various studies [ 164 ], chronic use of antidepressants which has a protective effect in depression development in OBX mice is not able to reverse the development of neurodegenerative process in these animals including ventricular enlargement, hippocampal volume reduction, and neuronal loss, induced by bulbectomy. CONCLUSIONS In general, analysis of the functional significance of genes in the brain of OBX mice indicates that the balance of the GABA/glutamatergic systems is disturbed with hyperactivation of the latter, which leads to the development of excitotoxicity and induction of apoptosis on the background of severe mitochondrial dysfunction and astrogliosis. The synthesis of neurotrophic factors the OBX mice decreases, which leads to disruption of the cytoskeleton of neurons, an increase in the level of intracellular calcium, and activation of tau protein phosphorylation. The acetylcholinergic system is deficient on the background of hyperactivation of acetylcholinesterase. Importantly, the activity of the dopaminergic, endorphin, and opiate systems decreases, and hormonal dysfunction develops. Genes associated with the regulation of circadian rhythms, cell migration, and impaired innate immunity are activated in the model animals. All this occurs on the background of pronounced down-regulation of genes of ribosomal proteins. It is clear that OBX mice represent a model of complex neuropathology with elements of Alzheimer's disease and major depression. Apparently, OBX mice have neurobiological basic mechanisms responsible for complex symptomatology. Therefore, we demonstrated that OBX mice have a common transcriptomic signature associated with both AD and MD. The similarity of the genetic basis of these pathologies also determines the simultaneous manifestation of symptoms of AD and MD in OBX mice. Interestingly, dynamic changes in the gene regulation characteristic for depression were evident in mouse AD model before the onset of AD. From the presented data it follows that in OBX animals AD-like neurodegenerative process develops, including several elements of MD. Based on accumulated data this model can be tentatively attributed to subtype B2 of AD in humans. Declarations Acknowledgements: The study was supported by the grant of the Russian Federation Government no 22-74-10050 Author Declarations : Author Contribution: NVB, MBE designed the experiments; NVB, MBE, LNC, APR supervised the design and course of the experiments; NVB, VIK, DYZ, APR, CLN, AVC performed the experiments; NVB, MBE, LNC, APR performed the analyses and interpretation of the experiments; NVB, MBE, LNC, APR wrote the manuscript, NVB, MBE, LNC reviewed and edited the manuscript. All of the authors read and approved the final manuscript. Funding The study was supported by the grant of the Russian Federation Government no. 22-74-10050. Competing Interest The authors declare no competing interests. Data availability statement Data will be made available under the reasonable request Ethics approval All animal experiments were conducted in agreement with the Provision and General Recommendation of Chinese Experimental Animals Administration Legislation and were approved by the Animal Ethics Committee in Institute (SLXD-20180912006, 12 September 2018) in compliance with Russian Federation legislation. Consent to participate Informed consent was obtained from all individual participants and authors involved in the study Consent to publish We confirming that consent to publish has been received from all participants involved in this stud References Khan S, Barve KH, Kumar MS (2020) Recent Advancements in Pathogenesis, Diagnostics and Treatment of Alzheimer's Disease. Curr Neuropharmacol 18(11):1106-1125. doi:10.2174/1570159X18666200528142429 Neff RA, Wang M, Vatansever S, et al (2021) Molecular subtyping of Alzheimer's disease using RNA sequencing data reveals novel mechanisms and targets. Sci Adv 7(2) doi:10.1126/sciadv.abb5398 Sasaguri H, Hashimoto S, Watamura N, et al (2022) Recent Advances in the Modeling of Alzheimer's Disease. Front Neurosci 16:807473. doi:10.3389/fnins.2022.807473 McGowan E, Eriksen J, Hutton M (2006) A decade of modeling Alzheimer's disease in transgenic mice. Trends Genet 22(5):281-9. doi:10.1016/j.tig.2006.03.007 Chin J (2011) Selecting a mouse model of Alzheimer's disease. Methods Mol Biol 670:169-89. doi:10.1007/978-1-60761-744-0_13 Bilkei-Gorzo A (2014) Genetic mouse models of brain ageing and Alzheimer's disease. Pharmacol Ther 142(2):244-57. doi:10.1016/j.pharmthera.2013.12.009 Gulyaeva NV, Bobkova NV, Kolosova NG, Samokhin AN, Stepanichev MY, Stefanova NA (2017) Molecular and Cellular Mechanisms of Sporadic Alzheimer's Disease: Studies on Rodent Models in vivo. Biochemistry (Mosc) 82(10):1088-1102. doi:10.1134/S0006297917100029 Ferreyra-Moyano H, Barragan E (1989) The olfactory system and Alzheimer's disease. Int J Neurosci 49(3-4):157-97. doi:10.3109/00207458909084824 Djordjevic J, Jones-Gotman M, De Sousa K, Chertkow H (2008) Olfaction in patients with mild cognitive impairment and Alzheimer's disease. Neurobiol Aging 29(5):693-706. doi:10.1016/j.neurobiolaging.2006.11.014 Attems J, Walker L, Jellinger KA (2014) Olfactory bulb involvement in neurodegenerative diseases. Acta Neuropathol 127(4):459-75. doi:10.1007/s00401-014-1261-7 Marine N, Boriana A (2014) Olfactory markers of depression and Alzheimer's disease. Neurosci Biobehav Rev 45:262-70. doi:10.1016/j.neubiorev.2014.06.016 Kovács T, Cairns NJ, Lantos PL (1999) beta-amyloid deposition and neurofibrillary tangle formation in the olfactory bulb in ageing and Alzheimer's disease. Neuropathol Appl Neurobiol 25(6):481-91. doi:10.1046/j.1365-2990.1999.00208.x Almeida RF, Ganzella M, Machado DG, et al (2017) Olfactory bulbectomy in mice triggers transient and long-lasting behavioral impairments and biochemical hippocampal disturbances. Prog Neuropsychopharmacol Biol Psychiatry 76:1-11. doi:10.1016/j.pnpbp.2017.02.013 Avetisyan AV, Samokhin AN, Alexandrova IY, Zinovkin RA, Simonyan RA, Bobkova NV (2016) Mitochondrial Dysfunction in Neocortex and Hippocampus of Olfactory Bulbectomized Mice, a Model of Alzheimer's Disease. Biochemistry (Mosc) 81(6):615-23. doi:10.1134/S0006297916060080 Bobkova NV, Nesteroval IV, Dana R, et al (2004) Morphofunctional changes in neurons in the temporal cortex of the brain in relation to spatial memory in bulbectomized mice after treatment with mineral ascorbates. Neurosci Behav Physiol 34(7):671-6. doi:10.1023/b:neab.0000036005.70153.3b Han F, Shioda N, Moriguchi S, Qin ZH, Fukunaga K (2008) The vanadium (IV) compound rescues septo-hippocampal cholinergic neurons from neurodegeneration in olfactory bulbectomized mice. Neuroscience 06;151(3):671-9. doi:10.1016/j.neuroscience.2007.11.011 Hozumi S, Nakagawasai O, Tan-No K, et al (2003) Characteristics of changes in cholinergic function and impairment of learning and memory-related behavior induced by olfactory bulbectomy. Behav Brain Res 138(1):9-15. doi:10.1016/s0166-4328(02)00183-3 Gurevich EV, Aleksandrova IA, Otmakhova NA, Katkov YA, Nesterova IV, Bobkova NV (1993) Effects of bulbectomy and subsequent antidepressant treatment on brain 5-HT2 and 5-HT1A receptors in mice. Pharmacol Biochem Behav 45(1):65-70. doi:10.1016/0091-3057(93)90087-a Aleksandrova IY, Kuvichkin VV, Kashparov IA, et al (2004) Increased level of beta-amyloid in the brain of bulbectomized mice. Biochemistry (Mosc) 200469(2):176-80. doi:10.1023/b:biry.0000018948.04559.ab Beck M, Bigl V, Rossner S (2003) Guinea pigs as a nontransgenic model for APP processing in vitro and in vivo. Neurochem Res 28(3-4):637-44. doi:10.1023/a:1022850113083 Xie AJ, Liu EJ, Huang HZ, et al (2016) Cnga2 Knockout Mice Display Alzheimer's-Like Behavior Abnormities and Pathological Changes. Mol Neurobiol 53(7):4992-9. doi:10.1007/s12035-015-9421-x Battaglia F, Wang HY, Ghilardi MF, et al (2007) Cortical plasticity in Alzheimer's disease in humans and rodents. Biol Psychiatry 15;62(12):1405-12. doi:10.1016/j.biopsych.2007.02.027 Miller AH, Raison CL (2016) The role of inflammation in depression: from evolutionary imperative to modern treatment target. Nat Rev Immunol 16(1):22-34. doi:10.1038/nri.2015.5 Hu J, Huang HZ, Wang X, et al (2015) Activation of Glycogen Synthase Kinase-3 Mediates the Olfactory Deficit-Induced Hippocampal Impairments. Mol Neurobiol 52(3):1601-1617. doi:10.1007/s12035-014-8953-9 Takahashi K, Nakagawasai O, Nemoto W, et al (2018) Memantine ameliorates depressive-like behaviors by regulating hippocampal cell proliferation and neuroprotection in olfactory bulbectomized mice. Neuropharmacology 15;137:141-155. doi:10.1016/j.neuropharm.2018.04.013 Bobkova NV, Garbuz DG, Nesterova I, et al (2014) Therapeutic effect of exogenous hsp70 in mouse models of Alzheimer's disease. J Alzheimers Dis 38(2):425-35. doi:10.3233/JAD-130779 Song C, Leonard BE (2005) The olfactory bulbectomised rat as a model of depression. Neurosci Biobehav Rev 29(4-5):627-47. doi:10.1016/j.neubiorev.2005.03.010 Attems J, Lintner F, Jellinger KA (2005) Olfactory involvement in aging and Alzheimer's disease: an autopsy study. J Alzheimers Dis 7(2):149-57; discussion 173-80. doi:10.3233/jad-2005-7208 Harkin A, Kelly JP, Leonard BE (2003) A review of the relevance and validity of olfactory bulbectomy as a model of depression. Clinical Neuroscience Research 3(4-5):253-262. Otmakhova NA, Gurevich EV, Katkov YA, Nesterova IV, Bobkova NV (1992) Dissociation of multiple behavioral effects between olfactory bulbectomized C57Bl/6J and DBA/2J mice. Physiol Behav 52(3):441-8. doi:10.1016/0031-9384(92)90329-z Machado DG, Lara MVS, Dobler PB, Almeida RF, Porciúncula LO (2020) Caffeine prevents neurodegeneration and behavioral alterations in a mice model of agitated depression. Prog Neuropsychopharmacol Biol Psychiatry 98:109776. doi:10.1016/j.pnpbp.2019.109776 Krasnov GS, Dmitriev AA, Kudryavtseva AV, et al (2015) PPLine: An Automated Pipeline for SNP, SAP, and Splice Variant Detection in the Context of Proteogenomics. J Proteome Res 14(9):3729-37. doi:10.1021/acs.jproteome.5b00490 Kechin A, Boyarskikh U, Kel A, Filipenko M (2017) cutPrimers: A New Tool for Accurate Cutting of Primers from Reads of Targeted Next Generation Sequencing. J Comput Biol 24(11):1138-1143. doi:10.1089/cmb.2017.0096 Dobin A, Davis CA, Schlesinger F, et al (2013) STAR: ultrafast universal RNA-seq aligner. Bioinformatics 29(1):15-21. doi:10.1093/bioinformatics/bts635 Li H, Handsaker B, Wysoker A, et al (2009) The Sequence Alignment/Map format and SAMtools. Bioinformatics 15;25(16):2078-9. doi:10.1093/bioinformatics/btp352 Liao Y, Smyth GK, Shi W (2014) featureCounts: an efficient general purpose program for assigning sequence reads to genomic features. Bioinformatics 01;30(7):923-30. doi:10.1093/bioinformatics/btt656 Robinson MD, McCarthy DJ, Smyth GK (2010) edgeR: a Bioconductor package for differential expression analysis of digital gene expression data. Bioinformatic 26(1):139-40. doi:10.1093/bioinformatics/btp616 Yu G, Wang LG, Han Y, He QY (2012) clusterProfiler: an R package for comparing biological themes among gene clusters. OMICS 16(5):284-7. doi:10.1089/omi.2011.0118 Consortium GO (2015) Gene Ontology Consortium: going forward. Nucleic Acids Res 43(Database issue):D1049-56. doi:10.1093/nar/gku1179 Kanehisa M, Goto S (2000) KEGG: kyoto encyclopedia of genes and genomes. Nucleic Acids Res 01;28(1):27-30. doi:10.1093/nar/28.1.27 Bellenguez C, Küçükali F, Jansen IE, et al (2022) New insights into the genetic etiology of Alzheimer's disease and related dementias. Nat Genet 54(4):412-436. doi:10.1038/s41588-022-01024-z Prokopenko D, Morgan SL, Mullin K, et al (2021) Whole-genome sequencing reveals new Alzheimer's disease-associated rare variants in loci related to synaptic function and neuronal development. Alzheimers Dement 17(9):1509-1527. doi:10.1002/alz.12319 Gutiérrez-Sacristán A, Grosdidier S, Valverde O, et al (2015) PsyGeNET: a knowledge platform on psychiatric disorders and their genes. Bioinformatics 15;31(18):3075-7. doi:10.1093/bioinformatics/btv301 Wang Y, Chen G, Shao W (2022) Identification of Ferroptosis-Related Genes in Alzheimer's Disease Based on Bioinformatic Analysis. Front Neurosci 16:823741. doi:10.3389/fnins.2022.823741 Calvo SE, Clauser KR, Mootha VK (2016) MitoCarta2.0: an updated inventory of mammalian mitochondrial proteins. Nucleic Acids Res 04;44(D1):D1251-7. doi:10.1093/nar/gkv1003 Herholz K (2022) Imaging Clinical Subtypes and Associated Brain Networks in Alzheimer's Disease. Brain Sci 23;12(2)doi:10.3390/brainsci12020146 Kuznetsov D, Tegenfeldt F, Manni M, et al (2023) OrthoDB v11: annotation of orthologs in the widest sampling of organismal diversity. Nucleic Acids Res 06;51(D1):D445-D451. doi:10.1093/nar/gkac998 Szklarczyk D, Gable AL, Nastou KC, et al (2021) The STRING database in 2021: customizable protein-protein networks, and functional characterization of user-uploaded gene/measurement sets. Nucleic Acids Res 08;49(D1):D605-D612. doi:10.1093/nar/gkaa1074 Bobkova N, Guzhova I, Margulis B, et al (2013) Dynamics of endogenous Hsp70 synthesis in the brain of olfactory bulbectomized mice. Cell Stress Chaperones 18(1):109-18. doi:10.1007/s12192-012-0359-x Park H, Lee YB, Chang KA (2022) miR-200c suppression increases tau hyperphosphorylation by targeting 14-3-3γ in early stage of 5xFAD mouse model of Alzheimer's disease. Int J Biol Sci 18(5):2220-2234. doi:10.7150/ijbs.66604 van Schaik PEM, Zuhorn IS, Baron W (2022) Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery. Int J Mol Sci 29;23(15)doi:10.3390/ijms23158418 Alamoudi AA (2023) SOX9 Expression Is Increased in Alzheimer's Disease (AD) and Is Associated With Disease Progression and APOE4 Genotype: A Computational Approach. Cureus 15(3):e36129. doi:10.7759/cureus.36129 Morawski M, Nuytens K, Juhasz T, et al (2013) Cellular and ultra structural evidence for cytoskeletal localization of prolyl endopeptidase-like protein in neurons. Neuroscience 09;242:128-39. doi:10.1016/j.neuroscience.2013.02.038 Jafarian Z, Khamse S, Afshar H, Khorshid HRK, Delbari A, Ohadi M (2021) Natural selection at the RASGEF1C (GGC) repeat in human and divergent genotypes in late-onset neurocognitive disorder. Sci Rep 28;11(1):19235. doi:10.1038/s41598-021-98725-y Ennerfelt H, Frost EL, Shapiro DA, et al (2022) SYK coordinates neuroprotective microglial responses in neurodegenerative disease. Cell 27;185(22):4135-4152.e22. doi:10.1016/j.cell.2022.09.030 Hu J, Chen Q, Zhu H, et al (2023) Microglial Piezo1 senses Aβ fibril stiffness to restrict Alzheimer's disease. Neuron 04;111(1):15-29.e8. doi:10.1016/j.neuron.2022.10.021 Spoelgen R, von Arnim CA, Thomas AV, et al (2006) Interaction of the cytosolic domains of sorLA/LR11 with the amyloid precursor protein (APP) and beta-secretase beta-site APP-cleaving enzyme. J Neurosci 11;26(2):418-28. doi:10.1523/JNEUROSCI.3882-05.2006 Weiner DM, Goodman MW, Colpitts TM, et al (2004) Functional screening of drug target genes: m1 muscarinic acetylcholine receptor phenotypes in degenerative dementias. Am J Pharmacogenomics 4(2):119-28. doi:10.2165/00129785-200404020-00006 Lin M, Li P, Liu W, Niu T, Huang L (2022) Germacrone alleviates okadaic acid-induced neurotoxicity in PC12 cells via M1 muscarinic receptor-mediated Galphaq (Gq)/phospholipase C beta (PLCβ)/ protein kinase C (PKC) signaling. Bioengineered 13(3):4898-4910. doi:10.1080/21655979.2022.2036918 Zhu G, Fang Y, Cui X, Jia R, Kang X, Zhao R (2022) Magnolol upregulates CHRM1 to attenuate Amyloid-β-triggered neuronal injury through regulating the cAMP/PKA/CREB pathway. J Nat Med 76(1):188-199. doi:10.1007/s11418-021-01574-2 Gogliotti RG, Fisher NM, Stansley BJ, et al (2018) Total RNA Sequencing of Rett Syndrome Autopsy Samples Identifies the M. J Pharmacol Exp Ther 365(2):291-300. doi:10.1124/jpet.117.246991 Popiolek M, Mandelblat-Cerf Y, Young D, et al (2019) In Vivo Modulation of Hippocampal Excitability by M4 Muscarinic Acetylcholine Receptor Activator: Implications for Treatment of Alzheimer's Disease and Schizophrenic Patients. ACS Chem Neurosci 20;10(3):1091-1098. doi:10.1021/acschemneuro.8b00496 Choi J, Yoon J, Kim M (2022) Optimization of Fermentation Conditions of Artemisia capillaris for Enhanced Acetylcholinesterase and Butyrylcholinesterase. Foods . 29;11(15) doi:10.3390/foods11152268 Miao S, He Q, Li C, et al (2022) Aaptamine - a dual acetyl - and butyrylcholinesterase inhibitor as potential anti-Alzheimer's disease agent. Pharm Biol 60(1):1502-1510. doi:10.1080/13880209.2022.2102657 Nascimento LA, Nascimento É, Martins JBL (2022) In silico study of tacrine and acetylcholine binding profile with human acetylcholinesterase: docking and electronic structure. J Mol Model 10;28(9):252. doi:10.1007/s00894-022-05252-2 Fide E, Yerlikaya D, Öz D, Öztura İ, Yener G (2023) Normalized Theta but Increased Gamma Activity after Acetylcholinesterase Inhibitor Treatment in Alzheimer's Disease: Preliminary qEEG Study. Clin EEG Neurosci 54(3):305-315. doi:10.1177/15500594221120723 Martorana A, Koch G (2014) "Is dopamine involved in Alzheimer's disease?". Front Aging Neurosci 6:252. doi:10.3389/fnagi.2014.00252 Nobili A, Latagliata EC, Viscomi MT, et al (2017) Dopamine neuronal loss contributes to memory and reward dysfunction in a model of Alzheimer's disease. Nat Commun 03;8:14727. doi:10.1038/ncomms14727 Davies P, Katzman R, Terry RD (1980) Reduced somatostatin-like immunoreactivity in cerebral cortex from cases of Alzheimer disease and Alzheimer senile dementa. Nature 20;288(5788):279-80. doi:10.1038/288279a0 Guennewig B, Lim J, Marshall L, et al (2021) Defining early changes in Alzheimer's disease from RNA sequencing of brain regions differentially affected by pathology. Sci Rep . Mar 01;11(1):4865. doi:10.1038/s41598-021-83872-z Sadek B, Saad A, Sadeq A, Jalal F, Stark H (2016) Histamine H3 receptor as a potential target for cognitive symptoms in neuropsychiatric diseases. Behav Brain Res 01;312:415-30. doi:10.1016/j.bbr.2016.06.051 Chen JL, Zhang DL, Sun Y, et al (2017) Angiotensin-(1-7) administration attenuates Alzheimer's disease-like neuropathology in rats with streptozotocin-induced diabetes via Mas receptor activation. Neuroscience 27;346:267-277. doi:10.1016/j.neuroscience.2017.01.027 Duan R, Xue X, Zhang QQ, et al (2020) ACE2 activator diminazene aceturate ameliorates Alzheimer's disease-like neuropathology and rescues cognitive impairment in SAMP8 mice. Aging (Albany NY) 23;12(14):14819-14829. doi:10.18632/aging.103544 Meng SX, Wang B, Li WT (2020) Serum expression of EAAT2 and ADORA2A in patients with different degrees of Alzheimer's disease. Eur Rev Med Pharmacol Sci 24(22):11783-11792. doi:10.26355/eurrev_202011_23833 Merighi S, Battistello E, Casetta I, et al (2021) Upregulation of Cortical A2A Adenosine Receptors Is Reflected in Platelets of Patients with Alzheimer's Disease. J Alzheimers Dis 80(3):1105-1117. doi:10.3233/JAD-201437 Xu C, Liu G, Ji H, et al (2018) Elevated methylation of OPRM1 and OPRL1 genes in Alzheimer's disease. Mol Med Rep 18(5):4297-4302. doi:10.3892/mmr.2018.9424 Rath S, Sharma R, Gupta R, et al (2021) MitoCarta3.0: an updated mitochondrial proteome now with sub-organelle localization and pathway annotations. Nucleic Acids Res 08;49(D1):D1541-D1547. doi:10.1093/nar/gkaa1011 Chithra Y, Dey G, Ghose V, et al (2023) Mitochondrial Complex I Inhibition in Dopaminergic Neurons Causes Altered Protein Profile and Protein Oxidation: Implications for Parkinson's disease. Neurochem Res 48(8):2360-2389. doi:10.1007/s11064-023-03907-x Sun Q, Shi L, Li S, et al (2023) PET117 assembly factor stabilizes translation activator TACO1 thereby upregulates mitochondria-encoded cytochrome C oxidase 1 synthesis. Free Radic Biol Med 20;205:13-24. doi:10.1016/j.freeradbiomed.2023.05.023 Mendsaikhan A, Takeuchi S, Walker DG, Tooyama I (2018) Differences in Gene Expression Profiles and Phenotypes of Differentiated SH-SY5Y Neurons Stably Overexpressing Mitochondrial Ferritin. Front Mol Neurosci 11:470. doi:10.3389/fnmol.2018.00470 Losón OC, Song Z, Chen H, Chan DC (2013) Fis1, Mff, MiD49, and MiD51 mediate Drp1 recruitment in mitochondrial fission. Mol Biol Cell 24(5):659-67. doi:10.1091/mbc.E12-10-0721 Jeong SM, Xiao C, Finley LW, et al (2013) SIRT4 has tumor-suppressive activity and regulates the cellular metabolic response to DNA damage by inhibiting mitochondrial glutamine metabolism. Cancer Cell 15;23(4):450-63. doi:10.1016/j.ccr.2013.02.024 Pacelli C, Adipietro I, Malerba N, et al (2020) Loss of Function of the Gene Encoding the Histone Methyltransferase KMT2D Leads to Deregulation of Mitochondrial Respiration. Cells 13;9(7)doi:10.3390/cells9071685 Yamamoto-Imoto H, Minami S, Shioda T, et al (2022) Age-associated decline of MondoA drives cellular senescence through impaired autophagy and mitochondrial homeostasis. Cell Rep 01;38(9):110444. doi:10.1016/j.celrep.2022.110444 Li Y, Li J, Yuan Q, et al (2021) Deficiency in WDFY4 reduces the number of CD8. Mol Immunol 139:131-138. doi:10.1016/j.molimm.2021.08.022 Egles C, Claudepierre T, Manglapus MK, Champliaud MF, Brunken WJ, Hunter DD (2007) Laminins containing the beta2 chain modulate the precise organization of CNS synapses. Mol Cell Neurosci 34(3):288-98. doi:10.1016/j.mcn.2006.11.004 Xie D, Gore C, Zhou J, et al (2009) DAB2IP coordinates both PI3K-Akt and ASK1 pathways for cell survival and apoptosis. Proc Natl Acad Sci U S A 24;106(47):19878-83. doi:10.1073/pnas.0908458106 Imaizumi K, Benito A, Kiryu-Seo S, et al (2004) Critical role for DP5/Harakiri, a Bcl-2 homology domain 3-only Bcl-2 family member, in axotomy-induced neuronal cell death. J Neurosci 14;24(15):3721-5. doi:10.1523/JNEUROSCI.5101-03.2004 Luo K, Zhao X, Shan Y, et al (2023) GABA regulates the proliferation and apoptosis of head and neck squamous cell carcinoma cells by promoting the expression of CCND2 and BCL2L1. Life Sci 20;334:122191. doi:10.1016/j.lfs.2023.122191 Dixon SJ, Lemberg KM, Lamprecht MR, et al (2012) Ferroptosis: an iron-dependent form of nonapoptotic cell death. Cell 25;149(5):1060-72. doi:10.1016/j.cell.2012.03.042 Bao WD, Pang P, Zhou XT, et al (2021) Loss of ferroportin induces memory impairment by promoting ferroptosis in Alzheimer's disease. Cell Death Differ 28(5):1548-1562. doi:10.1038/s41418-020-00685-9 Yang X, Fu Y, Hu F, Luo X, Hu J, Wang G (2018) PIK3R3 regulates PPARα expression to stimulate fatty acid β-oxidation and decrease hepatosteatosis. Exp Mol Med 19;50(1):e431. doi:10.1038/emm.2017.243 McKenzie AT, Wang M, Hauberg ME, et al (2018) Brain Cell Type Specific Gene Expression and Co-expression Network Architectures. Sci Rep 11;8(1):8868. doi:10.1038/s41598-018-27293-5 Dehmelt L, Halpain S (2005) The MAP2/Tau family of microtubule-associated proteins. Genome Biol 6(1):204. doi:10.1186/gb-2004-6-1-204 Fukushima H, Maeda R, Suzuki R, et al (2008) Upregulation of calcium/calmodulin-dependent protein kinase IV improves memory formation and rescues memory loss with aging. J Neurosci 01;28(40):9910-9. doi:10.1523/JNEUROSCI.2625-08.2008 Deng Y, Bi M, Delerue F, et al (2022) Loss of LAMP5 interneurons drives neuronal network dysfunction in Alzheimer's disease. Acta Neuropathol 144(4):637-650. doi:10.1007/s00401-022-02457-w Holden MR, Krzesinski BJ, Weismiller HA, Shady JR, Margittai M (2023) MAP2 caps tau fibrils and inhibits aggregation. J Biol Chem 299(7):104891. doi:10.1016/j.jbc.2023.104891 Caporaso GL, Bibb JA, Snyder GL, et al (2000) Drugs of abuse modulate the phosphorylation of ARPP-21, a cyclic AMP-regulated phosphoprotein enriched in the basal ganglia. Neuropharmacology 10;39(9):1637-44. doi:10.1016/s0028-3908(99)00230-0 Tan YX, Hong Y, Jiang S, et al (2020) MicroRNA‑449a regulates the progression of brain aging by targeting SCN2B in SAMP8 mice. Int J Mol Med 45(4):1091-1102. doi:10.3892/ijmm.2020.4502 Qian Q, Liu Q, Zhou D, et al (2017) Brain-specific ablation of Efr3a promotes adult hippocampal neurogenesis. FASEB J 31(5):2104-2113. doi:10.1096/fj.201601207R Katsumata Y, Fardo DW, Bachstetter AD, et al (2020) Alzheimer Disease Pathology-Associated Polymorphism in a Complex Variable Number of Tandem Repeat Region Within the MUC6 Gene, Near the AP2A2 Gene. J Neuropathol Exp Neurol 01;79(1):3-21. doi:10.1093/jnen/nlz116 Bottemanne P, Guillemot-Legris O, Paquot A, et al (2021) N-Acylethanolamine-Hydrolyzing Acid Amidase Inhibition, but Not Fatty Acid Amide Hydrolase Inhibition, Prevents the Development of Experimental Autoimmune Encephalomyelitis in Mice. Neurotherapeutics 18(3):1815-1833. doi:10.1007/s13311-021-01074-x Aronica E, Gorter JA, Ijlst-Keizers H, et al (2003) Expression and functional role of mGluR3 and mGluR5 in human astrocytes and glioma cells: opposite regulation of glutamate transporter proteins. Eur J Neurosci 17(10):2106-18. doi:10.1046/j.1460-9568.2003.02657.x Zhou Y, Danbolt NC (2013) GABA and Glutamate Transporters in Brain. Front Endocrinol (Lausanne) 4:165. doi:10.3389/fendo.2013.00165 Pereira JB, Janelidze S, Smith R, et al (2021) Plasma GFAP is an early marker of amyloid-β but not tau pathology in Alzheimer's disease. Brain 16;144(11):3505-3516. doi:10.1093/brain/awab223 Kim KY, Shin KY, Chang KA (2023) GFAP as a Potential Biomarker for Alzheimer's Disease: A Systematic Review and Meta-Analysis. Cells 04;12(9)doi:10.3390/cells12091309 Zhang X, Feng Y, Li J, et al (2020) MicroRNA-665-3p attenuates oxygen-glucose deprivation-evoked microglial cell apoptosis and inflammatory response by inhibiting NF-κB signaling via targeting TRIM8. Int Immunopharmacol 85:106650. doi:10.1016/j.intimp.2020.106650 Biber K, Möller T, Boddeke E, Prinz M (2016) Central nervous system myeloid cells as drug targets: current status and translational challenges. Nat Rev Drug Discov 15(2):110-24. doi:10.1038/nrd.2015.14 Hansen DV, Hanson JE, Sheng M (2018) Microglia in Alzheimer's disease. J Cell Biol 05;217(2):459-472. doi:10.1083/jcb.201709069 Watanabe N, Kageyama R, Ohtsuka T (2015) Hbp1 regulates the timing of neuronal differentiation during cortical development by controlling cell cycle progression. Development 01;142(13):2278-90. doi:10.1242/dev.120477 Chan JCY, Gorski SM (2022) Unlocking the gate to GABARAPL2. Biol Futur 73(2):157-169. doi:10.1007/s42977-022-00119-2 Cai Z, Xiao M (2016) Oligodendrocytes and Alzheimer's disease. Int J Neurosci 126(2):97-104. doi:10.3109/00207454.2015.1025778 Chen JF, Liu K, Hu B, et al (2021) Enhancing myelin renewal reverses cognitive dysfunction in a murine model of Alzheimer's disease. Neuron 21;109(14):2292-2307.e5. doi:10.1016/j.neuron.2021.05.012 Hendriksen H, Korte SM, Olivier B, Oosting RS (2015) The olfactory bulbectomy model in mice and rat: one story or two tails? Eur J Pharmacol 15;753:105-13. doi:10.1016/j.ejphar.2014.10.033 Morales-Medina JC, Iannitti T, Freeman A, Caldwell HK (2017) The olfactory bulbectomized rat as a model of depression: The hippocampal pathway. Behav Brain Res 15;317:562-575. doi:10.1016/j.bbr.2016.09.029 Pandi-Perumal SR, Monti JM, Burman D, et al (2020) Clarifying the role of sleep in depression: A narrative review. Psychiatry Res 291:113239. doi:10.1016/j.psychres.2020.113239 Uddin MS, Tewari D, Mamun AA, et al (2020) Circadian and sleep dysfunction in Alzheimer's disease. Ageing Res Rev 60:101046. doi:10.1016/j.arr.2020.101046 Kishi T, Yoshimura R, Fukuo Y, et al (2013) The serotonin 1A receptor gene confer susceptibility to mood disorders: results from an extended meta-analysis of patients with major depression and bipolar disorder. Eur Arch Psychiatry Clin Neurosci 263(2):105-18. doi:10.1007/s00406-012-0337-4 Sekiya I, Tsuji K, Koopman P, et al (2000) SOX9 enhances aggrecan gene promoter/enhancer activity and is up-regulated by retinoic acid in a cartilage-derived cell line, TC6. J Biol Chem 14;275(15):10738-44. doi:10.1074/jbc.275.15.10738 Wang M, Li A, Sekiya M, et al (2019) Molecular networks and key regulators of the dysregulated neuronal system in Alzheimer’s disease. bioRxiv 788323. Hook V, Schechter I, Demuth HU, Hook G (2008) Alternative pathways for production of beta-amyloid peptides of Alzheimer's disease. Biol Chem 389(8):993-1006. doi:10.1515/BC.2008.124 Reiss AB, Arain HA, Stecker MM, Siegart NM, Kasselman LJ (2018) Amyloid toxicity in Alzheimer's disease. Rev Neurosci 28;29(6):613-627. doi:10.1515/revneuro-2017-0063 Bobkova N, Vorobyov V (2015) The brain compensatory mechanisms and Alzheimer's disease progression: a new protective strategy. Neural Regen Res 10(5):696-7. doi:10.4103/1673-5374.156954 Sharma VK, Singh TG, Singh S, Garg N, Dhiman S (2021) Apoptotic Pathways and Alzheimer's Disease: Probing Therapeutic Potential. Neurochem Res 46(12):3103-3122. doi:10.1007/s11064-021-03418-7 Marks N, Berg MJ, Guidotti A, Saito M (1998) Activation of caspase-3 and apoptosis in cerebellar granule cells. J Neurosci Res 01;52(3):334-41. doi:10.1002/(SICI)1097-4547(19980501)52:33.0.CO;2-E Zou H, Li Y, Liu X, Wang X (1999) An APAF-1.cytochrome c multimeric complex is a functional apoptosome that activates procaspase-9. J Biol Chem 23;274(17):11549-56. doi:10.1074/jbc.274.17.11549 Yant LJ, Ran Q, Rao L, et al (2003) The selenoprotein GPX4 is essential for mouse development and protects from radiation and oxidative damage insults. Free Radic Biol Med 15;34(4):496-502. doi:10.1016/s0891-5849(02)01360-6 Yang WS, SriRamaratnam R, Welsch ME, et al (2014) Regulation of ferroptotic cancer cell death by GPX4. Cell 16;156(1-2):317-331. doi:10.1016/j.cell.2013.12.010 Wang Y, Lv MN, Zhao WJ (2023) Research on ferroptosis as a therapeutic target for the treatment of neurodegenerative diseases. Ageing Res Rev 91:102035. doi:10.1016/j.arr.2023.102035 Mira RG, Cerpa W (2021) Building a Bridge Between NMDAR-Mediated Excitotoxicity and Mitochondrial Dysfunction in Chronic and Acute Diseases. Cell Mol Neurobiol 41(7):1413-1430. doi:10.1007/s10571-020-00924-0 Cox MF, Hascup ER, Bartke A, Hascup KN (2022) Friend or Foe? Defining the Role of Glutamate in Aging and Alzheimer's Disease. Front Aging 3:929474. doi:10.3389/fragi.2022.929474 Bi D, Wen L, Wu Z, Shen Y (2020) GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer's disease. Alzheimers Dement 16(9):1312-1329. doi:10.1002/alz.12088 Wang R, Reddy PH (2017) Role of Glutamate and NMDA Receptors in Alzheimer's Disease. J Alzheimers Dis 57(4):1041-1048. doi:10.3233/JAD-160763 Bartus RT, Dean RL, Beer B, Lippa AS (1982) The cholinergic hypothesis of geriatric memory dysfunction. Science 30;217(4558):408-14. doi:10.1126/science.7046051 Chen XQ, Mobley WC (2019) Exploring the Pathogenesis of Alzheimer Disease in Basal Forebrain Cholinergic Neurons: Converging Insights From Alternative Hypotheses. Front Neurosci 13:446. doi:10.3389/fnins.2019.00446 Reale M, Carrarini C, Russo M, et al (2022) Muscarinic Receptors Expression in the Peripheral Blood Cells Differentiate Dementia with Lewy Bodies from Alzheimer's Disease. J Alzheimers Dis 85(1):323-330. doi:10.3233/JAD-215285 Ahmad S, Gul N, Ahmad M, et al (2022) Isolation, crystal structure, DFT calculation and molecular docking of uncinatine-A isolated from Delphinium uncinatum. Fitoterapia 162:105268. doi:10.1016/j.fitote.2022.105268 Bobkova NV, Nesterova IV, Nesterov VV (2001) The state of cholinergic structures in forebrain of bulbectomized mice. Bull Exp Biol Med 131(5):427-31. doi:10.1023/a:1017907511482 Gloria Y, Ceyzériat K, Tsartsalis S, Millet P, Tournier BB (2021) Dopaminergic dysfunction in the 3xTg-AD mice model of Alzheimer's disease. Sci Rep 30;11(1):19412. doi:10.1038/s41598-021-99025-1 Swerdlow RH, Burns JM, Khan SM (2014) The Alzheimer's disease mitochondrial cascade hypothesis: progress and perspectives. Biochim Biophys Acta 1842(8):1219-31. doi:10.1016/j.bbadis.2013.09.010 Sukhorukov VS, Mudzhiri NM, Voronkova AS, Baranich TI, Glinkina VV, Illarioshkin SN (2021) Mitochondrial Disorders in Alzheimer's Disease. Biochemistry (Mosc) 86(6):667-679. doi:10.1134/S0006297921060055 Cabezas-Opazo FA, Vergara-Pulgar K, Pérez MJ, Jara C, Osorio-Fuentealba C, Quintanilla RA (2015) Mitochondrial Dysfunction Contributes to the Pathogenesis of Alzheimer's Disease. Oxid Med Cell Longev 2015:509654. doi:10.1155/2015/509654 Aksenov MY, Tucker HM, Nair P, et al (1999) The expression of several mitochondrial and nuclear genes encoding the subunits of electron transport chain enzyme complexes, cytochrome c oxidase, and NADH dehydrogenase, in different brain regions in Alzheimer's disease. Neurochem Res 24(6):767-74. doi:10.1023/a:1020783614031 Maurer I, Zierz S, Möller HJ (2000) A selective defect of cytochrome c oxidase is present in brain of Alzheimer disease patients. Neurobiol Aging 21(3):455-62. doi:10.1016/s0197-4580(00)00112-3 Ohta S, Ohsawa I (2006) Dysfunction of mitochondria and oxidative stress in the pathogenesis of Alzheimer's disease: on defects in the cytochrome c oxidase complex and aldehyde detoxification. J Alzheimers Dis 9(2):155-66. doi:10.3233/jad-2006-9208 Bobkova NV, Zhdanova DY, Belosludtseva NV, Penkov NV, Mironova GD (2022) Intranasal administration of mitochondria improves spatial memory in olfactory bulbectomized mice. Exp Biol Med (Maywood) 247(5):416-425. doi:10.1177/15353702211056866 Fisher DW, Dunn JT, Keszycki R, et al (2023) Unique Transcriptional Signatures Correlate with Behavioral and Psychological Symptom Domains in Alzheimer's Disease. Res Sq 11;doi:10.21203/rs.3.rs-2444391/v1 Brandebura AN, Paumier A, Onur TS, Allen NJ (2023) Astrocyte contribution to dysfunction, risk and progression in neurodegenerative disorders. Nat Rev Neurosci 24(1):23-39. doi:10.1038/s41583-022-00641-1 Rothlin CV, Ghosh S, Zuniga EI, Oldstone MB, Lemke G (2007) TAM receptors are pleiotropic inhibitors of the innate immune response. Cell 14;131(6):1124-36. doi:10.1016/j.cell.2007.10.034 Herrera-Rivero M, Santarelli F, Brosseron F, Kummer MP, Heneka MT (2019) Dysregulation of TLR5 and TAM Ligands in the Alzheimer's Brain as Contributors to Disease Progression. Mol Neurobiol 56(9):6539-6550. doi:10.1007/s12035-019-1540-3 Hickman S, Izzy S, Sen P, Morsett L, El Khoury J (2018) Microglia in neurodegeneration. Nat Neurosci 21(10):1359-1369. doi:10.1038/s41593-018-0242-x Härtlova A, Erttmann SF, Raffi FA, et al (2015) DNA damage primes the type I interferon system via the cytosolic DNA sensor STING to promote anti-microbial innate immunity. Immunity 17;42(2):332-343. doi:10.1016/j.immuni.2015.01.012 Baytas O, Kauer JA, Morrow EM (2022) Loss of mitochondrial enzyme GPT2 causes early neurodegeneration in locus coeruleus. Neurobiol Dis 15;173:105831. doi:10.1016/j.nbd.2022.105831 Gebre AK, Altaye BM, Atey TM, Tuem KB, Berhe DF (2018) Targeting Renin-Angiotensin System Against Alzheimer's Disease. Front Pharmacol 9:440. doi:10.3389/fphar.2018.00440 Gouveia F, Camins A, Ettcheto M, et al (2022) Targeting brain Renin-Angiotensin System for the prevention and treatment of Alzheimer's disease: Past, present and future. Ageing Res Rev 77:101612. doi:10.1016/j.arr.2022.101612 Hynninen MJ, Breitve MH, Rongve A, Aarsland D, Nordhus IH (2012) The frequency and correlates of anxiety in patients with first-time diagnosed mild dementia. Int Psychogeriatr 24(11):1771-8. doi:10.1017/S1041610212001020 Zubenko GS, Zubenko WN, McPherson S, et al (2003) A collaborative study of the emergence and clinical features of the major depressive syndrome of Alzheimer's disease. Am J Psychiatry 160(5):857-66. doi:10.1176/appi.ajp.160.5.857 Brommelhoff JA, Gatz M, Johansson B, McArdle JJ, Fratiglioni L, Pedersen NL (2009) Depression as a risk factor or prodromal feature for dementia? Findings in a population-based sample of Swedish twins. Psychol Aging 24(2):373-84. doi:10.1037/a0015713 Botto R, Callai N, Cermelli A, Causarano L, Rainero I (2022) Anxiety and depression in Alzheimer's disease: a systematic review of pathogenetic mechanisms and relation to cognitive decline. Neurol Sci 43(7):4107-4124. doi:10.1007/s10072-022-06068-x Gass N, Ollila HM, Utge S, et al (2010) Contribution of adenosine related genes to the risk of depression with disturbed sleep. J Affect Disord 126(1-2):134-9. doi:10.1016/j.jad.2010.03.009 Oliveira S, Ardais AP, Bastos CR, et al (2019) Impact of genetic variations in ADORA2A gene on depression and symptoms: a cross-sectional population-based study. Purinergic Signal 15(1):37-44. doi:10.1007/s11302-018-9635-2 Madeira D, Domingues J, Lopes CR, Canas PM, Cunha RA, Agostinho P (2023) Modification of astrocytic Cx43 hemichannel activity in animal models of AD: modulation by adenosine A. Cell Mol Life Sci 29;80(11):340. doi:10.1007/s00018-023-04983-6 Martín-Sánchez A, Piñero J, Nonell L, et al (2021) Comorbidity between Alzheimer's disease and major depression: a behavioural and transcriptomic characterization study in mice. Alzheimers Res Ther 02;13(1):73. doi:10.1186/s13195-021-00810-x Yurttas C, Schmitz C, Turgut M, Strekalova T, Steinbusch HWM (2017) The olfactory bulbectomized rat model is not an appropriate model for studying depression based on morphological/stereological studies of the hippocampus. Brain Res Bull 134:128-135. doi:10.1016/j.brainresbull.2017.07.010 Additional Declarations No competing interests reported. Supplementary Files Supplefiles.zip Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 12 Feb, 2024 Reviews received at journal 19 Jan, 2024 Reviewers agreed at journal 06 Jan, 2024 Reviewers invited by journal 06 Jan, 2024 Editor assigned by journal 03 Jan, 2024 Submission checks completed at journal 03 Jan, 2024 First submitted to journal 20 Dec, 2023 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3781115","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":265011446,"identity":"2a630fb8-09dc-4f54-ad45-dd9201f9e66b","order_by":0,"name":"N.V. Bobkova","email":"","orcid":"","institution":"Institute of Cell Biophysics of the Russian Academy of Sciences-Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"N.V.","middleName":"","lastName":"Bobkova","suffix":""},{"id":265011447,"identity":"284e99e3-4538-4e38-b6e3-90b73bfa4206","order_by":1,"name":"L.N. Chuvakova","email":"","orcid":"","institution":"Engelhardt Institute of Molecular Biology","correspondingAuthor":false,"prefix":"","firstName":"L.N.","middleName":"","lastName":"Chuvakova","suffix":""},{"id":265011448,"identity":"f9592cd5-f473-4592-9b8c-27f8c59a9043","order_by":2,"name":"V.I. Kovalev","email":"","orcid":"","institution":"Institute of Cell Biophysics of the Russian Academy of Sciences-Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"V.I.","middleName":"","lastName":"Kovalev","suffix":""},{"id":265011449,"identity":"321a6cb8-9949-4304-946e-3df670da9c22","order_by":3,"name":"D.Y. Zdanova","email":"","orcid":"","institution":"Institute of Cell Biophysics of the Russian Academy of Sciences-Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"D.Y.","middleName":"","lastName":"Zdanova","suffix":""},{"id":265011450,"identity":"474fee0d-55d7-4c6a-b2fa-02b8ec5a48b6","order_by":4,"name":"A.V. Chaplygina","email":"","orcid":"","institution":"Institute of Cell Biophysics of the Russian Academy of Sciences-Federal Research Center, Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences","correspondingAuthor":false,"prefix":"","firstName":"A.V.","middleName":"","lastName":"Chaplygina","suffix":""},{"id":265011451,"identity":"eef2818f-f21d-4201-8e65-b1c907cad98b","order_by":5,"name":"A.P. Rezvykh","email":"","orcid":"","institution":"Engelhardt Institute of Molecular Biology","correspondingAuthor":false,"prefix":"","firstName":"A.P.","middleName":"","lastName":"Rezvykh","suffix":""},{"id":265011452,"identity":"e2b686b5-ed20-487f-9f0b-18e8b7076655","order_by":6,"name":"M.B. Evgen'ev","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIiWNgGAWjYDACZgY2BoaK/3JszIyNDxgYDhCr5QyzMT87c7MBcVoYgFoYW5gTZ/azt0kQpUW3nf3Zg58NbIwbDjO2VfPU3JHjZ2B++OgGHi1mh3nMDXt38DAbALXc5jn2zFiygc3YOAe/FjYJ3jMSbBAtbIcTNxzgYZPGr4X9meTfNgMekJZinn9EaWEwk+ZtS5CQbGZsY+ZtI0oLj5m0zJkDBvzMjM2Sc/sOG0s2E/LL+ePPJN9UHKhv4z/+8MObb4fl+NmbHz7GpwUFMPGASGZilYMA4w9SVI+CUTAKRsGIAQAUJUxiBYCD3gAAAABJRU5ErkJggg==","orcid":"","institution":"Engelhardt Institute of Molecular Biology","correspondingAuthor":true,"prefix":"","firstName":"M.B.","middleName":"","lastName":"Evgen'ev","suffix":""}],"badges":[],"createdAt":"2023-12-20 09:44:16","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3781115/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3781115/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":49169293,"identity":"696d4b04-f174-4acb-9623-252ca3fa37b6","added_by":"auto","created_at":"2024-01-04 09:38:51","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1121223,"visible":true,"origin":"","legend":"\u003cp\u003eVenn diagram depicting the quantity of up-regulated (\u003cstrong\u003eА\u003c/strong\u003e) and down-regulated genes (\u003cstrong\u003eB\u003c/strong\u003e) in the three brain regions compared. (C) The total number of differentially expressed genes (p\u0026lt;0.05, QLF test) in the brain regions studied of OBX mice. Up- and down-regulated genes are highlighted by different colors.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/8b883d31587c11d4dbcaf885.png"},{"id":49169290,"identity":"2ccc6f31-2e16-4fd8-8a41-c51d5b8609bd","added_by":"auto","created_at":"2024-01-04 09:38:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":137251,"visible":true,"origin":"","legend":"\u003cp\u003eGene Set Enrichment Analysis (GSEA) with the GeneOntology database was applied to explore differentially expressed genes of the hippocampus, cortex, and cerebellum. (OBX vs SO).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/9984cbc8d2b21982a94cd0c4.png"},{"id":49168893,"identity":"ff76f29b-730a-42fd-9645-d23571687f34","added_by":"auto","created_at":"2024-01-04 09:30:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":132508,"visible":true,"origin":"","legend":"\u003cp\u003eDifferentially expressed Alzheimer’s disease-associated genes (Y axis) in OBX mice in the hippocampus, cortex, and cerebellum (X-axis). Gene sets were taken from GWAS studies [41, 42], as well as RNA-seq studies [2]. Color represents Log2FC value. Genes with significant (p\u0026lt;0.05) changes are filled with colors on a “blue-red” scale, otherwise filled with white.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/7edf7cdbafdf458f4e852a84.png"},{"id":49169456,"identity":"c743a969-66ee-4281-af01-ca3f1a5607e9","added_by":"auto","created_at":"2024-01-04 09:46:51","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":50551,"visible":true,"origin":"","legend":"\u003cp\u003eDifferentially expressed genes (Y axis) associated with mitochondria metabolism (gene sets were taken from [77].\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/4933043921ecd2a4fee1bebf.png"},{"id":49169291,"identity":"a7b60661-1bda-4fbe-adda-dbbedd043e5c","added_by":"auto","created_at":"2024-01-04 09:38:51","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":25565,"visible":true,"origin":"","legend":"\u003cp\u003eDifferentially-expressed genes (Y axis) associated with processes of apoptosis (Gene set taken from KEGG database [40], pathway number mmu04210) and ferroptosis [44], ferroptosis genes are marked with *.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/fb9a03ce0dda447dfee36ed3.png"},{"id":49168891,"identity":"791aa924-4a9b-4782-9266-951a0ab9f556","added_by":"auto","created_at":"2024-01-04 09:30:51","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":133970,"visible":true,"origin":"","legend":"\u003cp\u003eAnalysis of genes that changed their expression in different regions of the brain of OBX mice. \u003cstrong\u003eA.\u003c/strong\u003e Cell-specific profiling of differentially expressed genes in OBX mice: Each gene was assigned to one of 6 major cell types abundant in the CNS [93]: Astrocyte, Endoteliocyte, Microglia, Neuron, oligodendrocyte, and OPC (X-axis). The y-axis represents the quantity of differentially expressed up- and downregulated genes highlighted in different colors (red and blue). \u003cstrong\u003eB.\u003c/strong\u003eAnalysis of the synchronicity of changes in the same genes in the studied structures for the different cell types.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/0977e7465a685c63cae1ae0a.png"},{"id":49168894,"identity":"1a709b6d-6d8b-4891-a590-e9f4caa18b67","added_by":"auto","created_at":"2024-01-04 09:30:51","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":240543,"visible":true,"origin":"","legend":"\u003cp\u003eDifferentially-expressed genes (Y axis) in different brain areas of OBX mice associated with major depression (gene sets from [43].\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/300b902c6450828aea7646fe.png"},{"id":49168898,"identity":"e73e3fe5-8302-4151-a2e6-0b0f74bdf64d","added_by":"auto","created_at":"2024-01-04 09:30:51","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":599047,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProtein-protein interaction network of differentially expressed genes in OBX mice with genes associated with AD. \u003c/strong\u003eEach node represents the product of gene, edge - edge-protein-protein interaction between specific proteins (StringDB v.11 [48], performed with parameters “physical interaction network” and “confidence level = 0.7”.). Non-interacting nodes were removed. Differentially expressed genes in any tissue are labeled in red color, and other interactors - in blue. The interaction network was clustered with k-means (mcl method) with k=5, and each cluster was analyzed on representative sets of enriched biological processes with cluster Profiler package [38]. As a result, each cluster of nodes was labeled with the top term. Genes with shared functions were placed in the center of the network.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/6f333206262942054e7e1eda.png"},{"id":49169757,"identity":"159820be-bc06-49d9-9253-e5f4675bbbf2","added_by":"auto","created_at":"2024-01-04 09:54:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1870522,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/33b8fa18-73b8-44c1-9b43-c1da573dcf08.pdf"},{"id":49168899,"identity":"403dc37b-150b-4ea6-9d25-070e8f55ff36","added_by":"auto","created_at":"2024-01-04 09:30:51","extension":"zip","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":844017,"visible":true,"origin":"","legend":"","description":"","filename":"Supplefiles.zip","url":"https://assets-eu.researchsquare.com/files/rs-3781115/v1/d73ac95e82c41bd3b44d442b.zip"}],"financialInterests":"No competing interests reported.","formattedTitle":"A mouse model of sporadic Alzheimer’s disease with elements of major depression","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAlzheimer's disease (AD) is the most common form of dementia among older patients and one of the leading causes of their death. Currently, there is an active search for new treatment of AD, since effective methods to cure this disease have not yet been found due to the complex etiology and multifactorial nature of AD, the genesis of which involves both genetic disorders and the influence of adverse environmental factors [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecently, analysis of transcriptomic data from AD patients, as well as several transgenic animal models of AD, has made it possible to identify at least three major subtypes of AD with different pathophysiological mechanisms. These mechanisms include combinations of dysregulation associated with sensitivity to tau-mediated neurodegeneration, amyloid formation and neuroinflammation, synaptic signaling, immune status, mitochondrial organization and myelination [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Subtypes of AD vary in sensitivity to different drugs, which makes it important to determine them for targeted therapeutic intervention. Although there are currently more than a hundred transgenic models of AD of the first, second, and third generations [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], experience has shown a very limited possibility of translating the data obtained from their studies to the clinic. Therefore, modeling different subtypes of the most common sporadic AD is necessary both to study the mechanisms of pathology and to develop effective treatment.\u003c/p\u003e \u003cp\u003eIn contrast to numerous transgenic models of AD [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], there is a very limited number of rodent models of sporadic AD. One such model is represented by various rodents with removed olfactory bulbs [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe idea of a relationship between AD and a decrease in olfactory sensitivity was first proposed by Ferreyra-Moyano and Barragan [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], who demonstrated that deterioration of the sense of smell is often observed at the early stages of the AD. Changes in olfactory sensitivity occur in 90% of patients with this pathology and can be used to diagnose this disease [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is also known that patients with AD exhibit morphological changes in the cortical and subcortical olfactory structures connected with the olfactory bulbs, where generation of numerous senile plaques containing beta-amyloid protein, neurofibrillary tangles and death of mitral cells are noted [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. However, the question remains unresolved: either olfactory disorders in AD represent a consequence of pathology developing in the brain, or they can act as an initiating factor of the pathology [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA model for studying the consequences of olfactory impairment is represented by animals with removed olfactory bulbs, the so-called \u0026ldquo;olfactory bulbectomized\u0026rdquo; (OBX) mice and rats. OBX animals were characterized by a pronounced impairment of spatial memory, correlated with a progressive neurodegenerative process in brain structures such as cortex and hippocampus also observed in patients with AD. Characteristically, in OBX rodents, the volume of the hippocampus decreases [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], the functioning of synapses and mitochondrial metabolism is disrupted [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], and increased cell death is observed [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. All this happens on the background of severe dysfunction of the acetylcholinergic [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], and serotonergic brain systems [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn extracts of the neocortex and hippocampus of OBX animals, an increased level of the soluble β-amyloid peptide is detected [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Interestingly, in OBX guinea pigs, which have a primary Aβ structure similar to the structure of human Aβ, typical Aβ plaques are formed in the cortex and hippocampus [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Moreover, ablation of the olfactory bulbs in B6C3Tg (APPswe, PSEN1dE9) 85Dbo/J transgenic mice significantly accelerated the deposition of amyloid plaques in the brain [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eMice knockout for the cyclic nucleotide-gated channel alpha 2 (\u003cem\u003eCnga2\u003c/em\u003e) gene, which is important for the transduction of olfactory signals, also exhibited signs of AD, including impaired learning and memory, loss of dendrite spines, as well as decrement of synaptic proteins [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Experiments on live brain slices from OBX rats revealed a significant decrease in long-term potentiation on synapses of Schaffer collaterals in neurons in the CA1 field of the hippocampus [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and a decrease in the level of synaptophysin in the temporal cortex and hippocampus, indicating disorders of synaptic plasticity. This animal model also showed a decrease in mushroom-type spines and tau hyperphosphorylation [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt should be noted that drugs approved for the treatment of AD, in particular cholinesterase inhibitors and the NMDA receptor antagonist memantine, is able to alleviate cognitive impairment in OBX mice [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. We have also previously showed that OBX mice respond similarly to therapeutic intranasal administration of recombinant human HSP70 as the classical transgenic model of AD, the 5XFAD mice [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. All of the above facts indicate the validity of using OBX animals as a model of the sporadic AD.\u003c/p\u003e \u003cp\u003eAn important advantage of the OBX model is its speed (symptoms are evident one month after bulbectomy) and high reproducibility, which distinguishes it from most other models of sporadic and familial AD. It should be noted, however, that OBX animals is currently more often used as a model of endogenous depression (major depression - MD) [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], which is believed to develop as a result of deprivation of basic for rodents odor information about the environment. OBX mice exhibit a few behavioral and morphological changes that are also characteristic of this pathology, which has become a source of controversy and dispute as to which disease OBX animals are a model of [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIndeed, in OBX rodents, increased locomotor activity, aggressiveness, and increased sensitivity to stress are observed, along with deficits in passive avoidance and hyperactivity in the open field test, that are normalized by antidepressants [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOBX surgery leads to a decrease in the concentrations of norepinephrine, serotonin, and 5-hydroxy-indoleacetic acid in the amygdala, frontal cortex, and midbrain [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, compensatory mechanisms ensure an increase in the level of β-adrenergic receptors on blood lymphocytes and in the amygdala cortex, as well as 5HT2 receptors in the neocortex [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], that are characteristic symptoms of patients suffering from endogenous depression. Interestingly, caffeine has a therapeutic effect in OBX animals [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Based on the above, we may conclude that OBX mice are a unique and very convenient model for studying the mechanisms underlying AD-MD comorbidity.\u003c/p\u003e \u003cp\u003eHerein, we report the results of transcriptomic analysis of tissues of three brain structures (the cortex, hippocampus, and cerebellum) of OBX mice in comparison with sham-operated (SO) mice. We evaluated the enrichment in gene sets and compared them with the data obtained from various public resources containing functional and disease information for MD and different subtypes of AD. This analysis revealed significant changes in gene expression in the studied brain regions of OBX mice characteristic for AD and major depression which enable to conclude that this model belongs to a new subtype of AD, characterized by a few manifestations of MD.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e\u003cb\u003e2.1. Animals\u003c/b\u003e\u003c/h2\u003e \u003cp\u003eMale NMRI (22\u0026ndash;24 g) mice were purchased from Beijing HFK Bioscience Co., LTD (Beijing, China). Animals were maintained under conditions of standard lighting (light on at 08:00\u0026ndash;20:00), temperature (23- 25\u003csup\u003e0\u003c/sup\u003eC), and humidity (55%) with free access to food and water. All animal experiments were conducted in agreement with the Provision and General Recommendation of Chinese Experimental Animals Administration Legislation and were approved by the Animal Ethics Committee in Institute (SLXD-20180912006, 12 September 2018).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. OBX Surgery\u003c/h2\u003e \u003cp\u003eAfter a seven-day adaptation, mice were subjected to bilateral OBX according to the previously described methods [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Mice were anesthetized with 2% pentobarbital sodium (40 mg/kg, intraperitoneal injection (i.p.), and fixed in stereotaxic apparatus. After the skull was exposed, one hole was drilled on the midline (2 mm in diameter, 3 mm anterior to bregma). The removal of the olfactory bulbs was performed by aspiration with a blunt syringe needle attached to a vacuum pump. The hole was filled with an absorbable collagen sponge immediately to control the bleeding. Sham-operated mice (SO) experienced the same procedures, but their bulbs were left intact. After surgery, the mice were housed in an individual cage and given penicillin sodium (10,000 U in normal saline, i.m.) once a day to prevent probable infection.\u003c/p\u003e \u003cp\u003e All procedures were conducted by national and EU (Directive 2010-63EU) guidelines regulating animal research and were approved by the local ethics committee (CEEA-PRBB).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. RNA Isolation, Library Preparation, and Transcriptome Sequencing\u003c/h2\u003e \u003cp\u003eFor the transcriptomic analysis, three brain tissues (the hippocampus, cortex, and cerebellum) from two groups (OBX and sham-operated) were used. Brains were dissected and stored at 80\u003csup\u003e0\u003c/sup\u003eC until the RNA isolation.\u003c/p\u003e \u003cp\u003eThe extraction RNA was made using RNAzol RT (Molecular Research Center, Cincinnati, OH, USA) according to the company\u0026rsquo;s protocol. The concentration and quality of RNA were determined via a Qubit Fluorometer (Invitrogen) and an Agilent BioAnalyzer 2100, respectively, using an RNA 6000 nano kit (Agilent Technologies, Santa-Clara, CA, USA). For libraries RNA with Integrity Number (RIN), no less than 8 were taken. Illumina NEB Next Ultra II Directional RNA Library Prep Kit (NEB, Ipswich, MA, USA) was used for mRNA library preparation. The sequencing was performed on the Illumina NextSeq 2000 platform. RNA sequencing and further differential expression estimation were performed using the equipment of the Engelhardt Institute of Molecular Biology RAS \u0026ldquo;Genome\u0026rdquo; center (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.eimb.ru/rus/ckp/ccu_genome_c.php\u003c/span\u003e\u003cspan address=\"http://www.eimb.ru/rus/ckp/ccu_genome_c.php\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e, accessed on 22 February 2022). The sequencing data obtained in the present work are available at the NCBI Sequence Read Archive (project ID GSE249297 GEO base).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. RNA data processing\u003c/h2\u003e \u003cp\u003eAs a result of deep RNA sequencing, we obtained 10\u0026ndash;20 mln 75-bp single-end reads per one biological sample. Raw RNA-seq reads processing was performed using the PPLine package [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. We used Adaptor sequences that were trimmed off, and low-quality reads were removed using Cutadapt [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Reads were aligned to the reference genome (GRCm39 v.104) using STAR aligner [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] with total alignment rate\u0026thinsp;\u0026gt;\u0026thinsp;95%. SAM file post-processing was performed using the Samtools software package [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Reads, assigned to exons of protein-coding genes were counted using feature Counts utility from the subread package [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Subsequent analysis of differential expression was performed in R language version 4.2.2, using RTrans pipeline. Raw gene expression counts were normalized using the TMM method implemented in the edgeR package [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], and, subsequently, each gene was tested on differential expression using the quasi-likelihood negative binomial generalized log-linear model. Genes with p-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 were considered as differentially expressed.\u003c/p\u003e \u003cp\u003eGene set enrichment analysis (GSEA) was performed using the clusterProfiler package [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e] with GeneOntology [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e] and KEGG [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] databases. Heatmaps and Venn diagrams were plotted using ComplexHeatmap and VennDiagram R packages.\u003c/p\u003e \u003cp\u003eGenes, representing key markers of Alzheimer\u0026rsquo;s disease [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e], major depression disorder [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e], apoptosis (KEGG pathway \u003cem\u003emmu04210\u003c/em\u003e), ferroptosis [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e] and metabolism of mitochondria [\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e] were downloaded from open-access published data.\u003c/p\u003e \u003cp\u003eTo estimate a resemblance of gene expression patterns between OBX mice and human subtypes of Alzheimer\u0026rsquo;s disease, we used LogFC values published in open-access data [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Pairs of orthologous genes among mouse and human genomes were matched using OrthoDB database v.11 [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. Arrays of LogFC values were compared using Spearman\u0026rsquo;s coefficient of correlation.\u003c/p\u003e \u003cp\u003eProtein-protein interaction networks of products of differentially-expressed genes were created in StringDB v.11 [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e] with parameters \u0026ldquo;physical interaction network\u0026rdquo; and \u0026ldquo;confidence level\u0026thinsp;=\u0026thinsp;0.7\u0026rdquo;. Non-interacting nodes were removed. The network was clustered using k-means (mcl method) with several clusters k\u0026thinsp;=\u0026thinsp;5, each cluster was tested separately on representative sets of enriched biological processes with the clusterProfiler package [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Visualization of the interaction network was performed using Cytoscape software.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003e1. RNA sequencing and analysis of differentially expressed mRNAs in three brain structures of OBX mice.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe performed the comparative analysis of the transcriptome signatures of three brain structures of OBX and control SO 4-month-old mice, one month after bulbectomy when major impairments of spatial memory are already developed [49]. We determined the significant differentially expressed (DE) genes with adjusted p-value \u0026lt; 0.05, deregulated in the three brain areas indicated above. The removal of the olfactory bulbs had a strong effect on gene expression in all brain areas studied. Among the total genes expressed in the hippocampus of the OBX mice, there were 944 up-regulated and 1036 down-regulated genes as compared with control SO animals. In the сortex and cerebellum, 879 and 557 genes are expressed correspondently, of which 487 up-regulated and 392 down-regulated genes in the cortex while 277 up-regulated and 280 down-regulated genes were revealed in the cerebellum (Fig.1 A, B, C).\u003c/p\u003e\n\u003cp\u003eThe comparative analysis did not reveal significant differences between the number of up and down-regulated genes in each of the studied brain areas in OBX mice (Figure 1C). However, the hippocampus was significantly superior to other brain areas in terms of the total number of genes with changed expression in OBX mice in comparison to SO animals (Figure 1).\u003c/p\u003e\n\u003cp\u003eThe results of transcriptome analysis were corroborated by the RT-PCR technique in all three brain areas. Four genes differentially expressed in OBX mice i.e., \u003cem\u003eApba1\u003c/em\u003e, \u003cem\u003eAtn1\u003c/em\u003e, \u003cem\u003eKmt2d\u003c/em\u003e, and \u003cem\u003eTtbk1\u003c/em\u003e were used for PCR analysis. (Suppl. Figure S1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2. \u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eFunctional annotation of genome expression changes in OBX mice\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe olfactory bulbectomy led to drastic changes in gene expression, resulting in the activation of several signaling pathways. Fig 2 depicts the top GO enrichment domains of the target genes with the significantly dysregulated mRNAs. The major affected biological processes according to GO enrichment are involved in neurotransmitter secretion, cognition, learning and memory, neuropeptide signaling pathway, metabolic processes, ribosome processing and biogenesis, cell-matrix adhesion, etc. The hippocampus represents a structure where the most drastic changes in the expression of pertinent genetic pathways took place in the OBX mice.\u003c/p\u003e\n\u003cp\u003eGSEA analysis using the GO database revealed pronounced up-regulation in many important pathways and signal systems taking place in the studied brain areas with the hippocampus being the structure where most drastic changes took place. Thus, up-regulation of genes responsible for neuronal plasticity, neuropeptide signaling pathway, neurotransmitter transport, and secretion, as well genes responsible for regulation of glucose metabolism and WNT as well as Notch signaling were significantly up-regulated in the hippocampus of OBX mice.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSimilarly, the KEGG pathway analysis also revealed pronounced up-regulation in the expression of genes involved in axon guidance, GABAergic synapse, and other synapses as well as synaptic vesicle cycle, circadian entrainment, different signaling pathways, including WNT and Notch signaling in OBX-mice (Fig. S2). In all these gene categories most pronounced up-regulation also took place in the hippocampus of OBX mice and to a significantly lesser degree in the cortex and cerebellum. Characteristically, pronounced down-regulation of genes involved in the protein synthesis such as rRNA processing and ribosome biogenesis represent prominent exceptions demonstrated by using both GSEA and KEGG databases.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAt the next step, we monitored the expression of genes involved in the metabolism of \u0026beta;-amyloid and Tau protein in the brain of OBX mice.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. \u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eStudy of gene expression in the brain regions of OBX mice related to the metabolism of beta-amyloid and tau protein\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIt is well known that neurodegenerative changes in the brain of AD patients are associated with the presence of oligomeric forms of amyloid beta protein and tau protein fibrils, as well as with the processes of their formation and utilization. Therefore, we analyzed the expression of known genes related to these proteins, as well as the pathways of their production and utilization in OBX mice (Figure 3).\u003c/p\u003e\n\u003cp\u003eAnalysis of gene expression in three brain regions of OBX mice indicates that the most dramatic changes took place in the hippocampus. The detected genes with altered expression are related to both the formation of beta-amyloid and possible compensatory mechanisms aimed to ameliorate this process. It is noteworthy that in the hippocampus, 28 genes out of 45 showed upregulation and only 8 exhibited downregulation.\u003c/p\u003e\n\u003cp\u003eSeveral genes that increased their expression in the hippocampus and partially in the cortex of OBX mice are of particular interest. They are represented by the \u003cem\u003eYwhag\u003c/em\u003e gene encoding 14-3-3\u0026gamma; protein, which increased GSK-3\u0026beta; activation and promoted tau phosphorylation in Alzheimer\u0026apos;s disease\u0026nbsp;[50], \u003cem\u003eFn1\u003c/em\u003e \u0026ndash; fibronectin1, which declined at the onset of remyelination of the lesion area of the CNS and is implicated in BBB breakdown\u0026nbsp;[51]. All studied brain structures of OBX mice were characterized by a pronounced increase in the level of expression of the \u003cem\u003eSox9\u003c/em\u003e gene, which responds to A\u0026beta; deposition\u0026nbsp;[52]. Increased expression in the cortex and hippocampal formation was also demonstrated by the Tau tubulin kinase-1 (\u003cem\u003eTtbk1\u003c/em\u003e) genes, the activity of which leads to the deposition of hyperphosphorylated tau.\u003c/p\u003e\n\u003cp\u003eAmong the genes that showed decreased expression in the brain of OBX mice, the prefoldin genes \u003cem\u003ePfdn5\u003c/em\u003e in the hippocampus, as well as \u003cem\u003ePfdn2\u003c/em\u003e in all analyzed structures, should be mentioned. These genes normally function as chaperones. Furthermore, in the hippocampus of OBX mice, the reduced expression of the gene \u003cem\u003ePrepl\u003c/em\u003e encoding protein PREPL and down-regulation of the neuron-specific gene, \u003cem\u003eRasgefl1c\u003c/em\u003e (RasGEF Domain Family Member 1C), were observed which may be involved in cytoskeletal degeneration\u0026nbsp;[53], and late-onset neurocognitive disorders\u0026nbsp;[54].\u003c/p\u003e\n\u003cp\u003eOn the other hand, most of the genes involved in \u0026beta;-amyloid synthesis exhibited significant up-regulation in OBX mice. We also detected probably compensatory up-regulation of genes responsible for APP stabilization (\u003cem\u003eApba1\u003c/em\u003e, \u003cem\u003eApba2\u003c/em\u003e) and receptor-mediated activation of \u003cem\u003eSyk\u003c/em\u003e, which should reduce A\u0026beta; load by up-regulation of microglial phagocytosis [55]. Finally, the observed up-regulation of \u003cem\u003ePiezo1\u003c/em\u003e and \u003cem\u003eSorla/Sorl1\u003c/em\u003e genes in the brain of OBX mice is also apparently of a compensatory nature because it ameliorates brain A\u0026beta; burden [56] and can decrease the number of amyloidogenic products in the affected individuals [57]. To this end, it was shown that microglia lacking \u003cem\u003ePiezo1\u003c/em\u003e led to the exacerbation of A\u0026beta; pathology and cognitive decline, whereas pharmacological activation of microglial \u003cem\u003ePiezo1\u003c/em\u003e ameliorated brain A\u0026beta; burden and cognitive impairment in 5xFAD mice [56].\u003c/p\u003e\n\u003cp\u003eThus, in the brain of OBX mice, the expression was significantly changed for genes that promote beta-amyloid deposition and hyperphosphorylation of tau protein characteristic of AD and for genes that may compensatory prevent the development of this neuropathology. At the next stage we analyzed genes involved in the functioning of neurotransmitter systems that changed their expression after bulbectomy in the studied brain regions.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4. Expression of genes involved in various neurotransmitter systems in the brain of OBX mice\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSince the main goal of this study was to determine what pathology MD or AD represent OBX animals, we first analyzed the expression of genes, judging by the literature data, related to the functioning of neurotransmitter and several other receptor systems characteristic for AD and MD in the studied brain structures of OBX mice. Table 1 lists the genes of neurotransmitter systems that underwent the greatest changes in expression in the brain of OBX mice.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1.\u003c/strong\u003e Genes involved in the activity of the main neurotransmitter systems,\u0026nbsp;\u003c/p\u003e\n\u003cp\u003ewith the largest changes in expression in OBX mice compared to SO animals.\u0026nbsp;Blue\u0026ndash;down reg. genes, red\u0026ndash;up reg. genes\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" rowspan=\"2\" valign=\"bottom\"\u003e\n \u003cp\u003eSystem\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"60.46511627906977%\" colspan=\"3\" valign=\"bottom\"\u003e\n \u003cp\u003eGene\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\" valign=\"bottom\"\u003e\n \u003cp\u003eHippocampus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003eCortex\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003eCerebellum\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" rowspan=\"4\"\u003e\n \u003cp\u003eGlutamatergic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\"\u003e\n \u003cp\u003e\u003cem\u003eGrm1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eGrm4\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eSlc1a1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eSlc1a2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003eSlc1a2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\"\u003e\n \u003cp\u003eGABAergic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\"\u003e\n \u003cp\u003e\u003cem\u003eGabarapl2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eGabarapl2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" rowspan=\"4\"\u003e\n \u003cp\u003eCholinergic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\"\u003e\n \u003cp\u003e\u003cem\u003eAche\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eAche\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eChrm1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eChrm4\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eChrna4\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" rowspan=\"2\"\u003e\n \u003cp\u003eDopaminergic\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\"\u003e\n \u003cp\u003e\u003cem\u003eArpp21\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eDrd2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" valign=\"bottom\"\u003e\n \u003cp\u003eNeurotransmitter transport\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eSlc6a20b\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eSlc6a20b\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" valign=\"bottom\"\u003e\n \u003cp\u003eLong-term depression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eIrs2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eIrs2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003eIrs2\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"39.53488372093023%\" rowspan=\"8\"\u003e\n \u003cp\u003eNeuroactive ligand-receptor interaction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.507399577167018%\"\u003e\n \u003cp\u003e\u003cem\u003eAdcyap1r1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"19.873150105708245%\"\u003e\n \u003cp\u003e\u003cem\u003eAdcyap1r1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"20.084566596194502%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eAdora2a\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eCckbr\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003eHrh3\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003eMas1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eOprl1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eSstr1\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd width=\"33.91608391608391%\"\u003e\n \u003cp\u003e\u003cem\u003eSstr4\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"32.86713286713287%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd width=\"33.21678321678322%\" valign=\"bottom\"\u003e\n \u003cp\u003e\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 1 demonstrates that OBX mice are characterized by a deficiency of the GABAergic system since the expression of the gene gamma-aminobutyric acid (GABA) A receptor-associated protein-like 2 which mediates the fast inhibitory synaptic transmission in the central nervous system is drastically reduced. At the same time, activation of the glutamatergic system is noted in the hippocampus, which is manifested in increased expression of metabotropic glutamate receptors. Activation of the glutamatergic system may also be indicated by a compensatory increase in the expression of \u003cem\u003eSlc1a1\u003c/em\u003e genes encoding members of the high-affinity glutamate transporters. OBX mice were also characterized by impaired expression of the \u003cem\u003eChrm1\u003c/em\u003e and \u003cem\u003eChrm4\u003c/em\u003e genes, associated with the activity of the acetylcholinergic system and responsible for the synthesis of muscarinic acetylcholine receptors M1 and M4, that have long been considered to be involved in the pathophysiology of AD [58-60].\u003c/p\u003e\n\u003cp\u003eIn the cortex and hippocampus of OBX mice, there is an increase in the expression of the gene encoding the alpha-4 subunit of the neuronal nicotinic acetylcholine receptor (\u003cem\u003eChrna4\u003c/em\u003e)\u0026nbsp;[61, 62], as well as a strong increase in the expression of the acetylcholinesterase gene (\u003cem\u003eAche\u003c/em\u003e). Hyperactivation of this gene is associated with synaptic acetylcholine deficiency and the development of cognitive impairment in AD\u0026nbsp;[63-66].\u003c/p\u003e\n\u003cp\u003eOn the other hand, in the hippocampus of OBX animals, a pronounced decrease in the expression of dopamine D2 receptor genes (\u003cem\u003eDrd2\u003c/em\u003e) is observed, as well as a decrease in the expression of the gene that regulates the effects of dopamine itself (\u003cem\u003eArpp21\u003c/em\u003e). In addition, down-regulation of the expression of the \u003cem\u003eSlc6a20b\u003c/em\u003e gene, responsible for the transport of neurotransmitters, is observed in the hippocampus and cerebellum of OBX mice. Similar disturbances in the dopaminergic system, along with loss of dopaminergic neurons, as well as decreased expression of dopamine D2 receptors in the hippocampus, have been revealed in a classical mouse model of AD, and these disturbances have been associated with early manifestations of AD\u0026nbsp;[67, 68].\u003c/p\u003e\n\u003cp\u003eInterestingly, OBX mice also showed changes in the expression of genes responsible for the synthesis of peptide receptor ligands, which was manifested in a decrease in the expression of somatostatin receptor genes 1 and 4 (\u003cem\u003eSstr1\u003c/em\u003e and \u003cem\u003eSstr4\u003c/em\u003e). These results are consistent with other data enabling to suggest that the downregulation of these genes (SSTs) represents an early pathological signature of AD ([69, 70].\u003c/p\u003e\n\u003cp\u003eIn the cortex of OBX mice, an increase in the expression of the histamine receptor 3 (\u003cem\u003eHrh3\u003c/em\u003e) gene was demonstrated. This gene is one of the targets of therapeutic agents being developed for the treatment of numerous disorders, including cognitive diseases such as attention deficit hyperactivity disorder and AD\u0026nbsp;[71].\u003c/p\u003e\n\u003cp\u003eIt is noteworthy that in the cortex of OBX mice, there is a decrease in the expression level of the MAS1 receptor gene (\u003cem\u003eMas1\u003c/em\u003e), the activation of which leads to a decrease in blood pressure. Besides, in the hippocampus and cortex an increased level of expression of the substrate of insulin receptor gene (\u003cem\u003eIrs2\u003c/em\u003e) was noted. Deficiency of MAS receptors (\u003cem\u003eMasr\u003c/em\u003e) and angiotensin (1-7) on the background of excess amounts of angiotensin II was often observed in sporadic AD, and its restoration has a positive effect in AD patients\u0026nbsp;[72, 73].\u003c/p\u003e\n\u003cp\u003eIt should be underlined that the expression of genes that determine the development of pathology does not always coincide in OBX and AD. For example, OBX animals exhibited a significant decrease in the expression of the adenosine receptor A2a (\u003cem\u003eAdora2a\u003c/em\u003e) gene, while patients with AD, on the contrary, are characterized by increased expression of this receptor\u0026nbsp;[74, 75].\u003c/p\u003e\n\u003cp\u003eInterestingly, bulbectomy also caused an increase in the expression of the nociceptin opioid peptide receptor gene (\u003cem\u003eOprl1\u003c/em\u003e) in the hippocampus, which is characteristic of both depression and AD\u0026nbsp;[76].\u003c/p\u003e\n\u003cp\u003eFrom the data presented in Table 1, it is clear that the bulbectomy causes serious changes in the expression of genes of receptor systems. These changes manifest in an imbalance of the inhibitory and excitatory systems in the brain of OBX mice, and also lead to a deficiency of the dopaminergic and acetylcholinergic systems. The observed changes in the activity of neurotransmitter systems are probably responsible for the characteristic behavioral changes observed in OBX animals.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3. Mitochondrial genes differentially expressed in OBX mice\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003eAt the next stage, we analyzed differentially expressed genes associated with the functional state of mitochondria in OBX mice using the MitoCarta 3.0 database.\u003c/p\u003e\n\u003cp\u003eFrom the top 50 genes related to the state of mitochondria, 36 genes decreased their expression in the brain of OBX mice compared to SO animals. It is necessary to emphasize the drastic decrease in the expression of genes belonging to Mrp and Nduf families. The activity of these genes is associated with the synthesis of mitochondrial ribosomal proteins and subunits of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) which plays a vital role in cellular ATP production, the primary source of energy for many crucial processes in living cell. It is known that mitochondrial Complex I deficiency causes adult-onset of several neurodegenerative disorders\u0026nbsp;[78].\u003c/p\u003e\n\u003cp\u003eIn OBX mice the expression of the \u003cem\u003eFmc1\u003c/em\u003e gene, encoding assembly factor 1, responsible for the formation of mitochondrial Complex V, is significantly reduced in all three studied brain areas. Pronounced down-regulation was also noted for the \u003cem\u003ePet117\u003c/em\u003e gene.\u0026nbsp;Depletion of \u003cem\u003ePet117\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003ereduced mitochondrial oxygen consumption rate and impaired mitochondrial function. This gene\u0026nbsp;plays a role in the biogenesis of mitochondrial complex IV or cytochrome c oxidase, which is part of the respiratory electron transport chain of mitochondria\u0026nbsp;[79]. Furthermore, the decrease in \u003cem\u003eMgst\u003c/em\u003e gene expression observed in the brain of OBX mice should reduce the protection of the outer mitochondrial membrane from oxidative stress\u0026nbsp;[80].\u003c/p\u003e\n\u003cp\u003eOnly 14 genes out of 50 depicted in Figure 4 exhibited moderate, apparently compensatory activation of expression, including the \u003cem\u003eMief1\u003c/em\u003e and \u003cem\u003eSlc25a51\u003c/em\u003e genes. These genes help to maintain energy metabolism in the cell\u0026nbsp;[81]\u0026nbsp;and improve mitochondrial respiration\u0026nbsp;[82]. There is also activation of genes encoding the GPT2 proteins in the hippocampus and cortex, as well as \u003cem\u003eMcu\u003c/em\u003e in the cortex, that are responsible for the regulation of cell growth, amino acid metabolism, and level mitochondrial calcium. An increase in their expression also apparently indicates the compensatory nature of these changes.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIncreased expression of the \u003cem\u003eKmt2d\u003c/em\u003e gene [83] observed in all three brain areas, and up-regulation of three other genes in hippocampus (\u003cem\u003eMlxip\u003c/em\u003e, [84], \u003cem\u003eWdfy4\u003c/em\u003e [85], and \u003cem\u003eLamb2\u003c/em\u003e [86], whose activity is associated with the suppression of apoptosis and stabilization of synapses (Figure 4) are probably also represent compensatory reaction. However, given the deficiency of mitochondrial ribosomal proteins found in OBX, even increased expression of genes aimed at compensating for severe mitochondrial dysfunction is unlikely to have a significant effect.\u003c/p\u003e\n\u003cp\u003eNext, we analyzed the state of gene expression in OBX mice associated with apoptosis-programmed cell death, as well as ferroptosis, that are characteristic features of various forms of AD.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4. Apoptosis and ferroptosis.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe main manifestation of any neurodegenerative process is massive cell death. It has been established that AD is characterized by neuronal death, predominantly due to apoptosis pathway activation. Therefore, we analyzed the expression of apoptosis-related genes in the brains of OBX mice. The obtained data are presented in Fig. 5. The list of genes associated with apoptosis and ferroptosis processes was taken from the database http://deathbase.org/ and [44], respectively. The results indicate that the number of apoptosis-related genes that increased their expression was two times larger in comparison with genes with decreased expression. Obviously, in the brain of OBX mice, the hippocampus represents the structure where the largest number of genes with altered expression associated with apoptosis was noted.\u003c/p\u003e\n\u003cp\u003eThe activation of the \u003cem\u003eDab2ip\u003c/em\u003e gene in all studied areas of the brain is noteworthy. This gene encodes a protein which acts as a scaffold protein implicated in the regulation of a large spectrum of both general and specialized signaling pathways. In particular, this protein modulates the balance between phosphatidylinositol 3-kinase (PI3K)-AKT-mediated cell survival and apoptosis-stimulated kinase (MAP3K5)-JNK signaling pathways\u0026nbsp;[87].\u003c/p\u003e\n\u003cp\u003eDirect activation of apoptosis in OBX mice is associated with activation of the \u003cem\u003eCasp9\u003c/em\u003e gene in the hippocampus and the \u003cem\u003eApaf-1\u003c/em\u003e gene in the cortex. Both genes are involved in the activation cascade of caspases responsible for apoptosis. It is also necessary to note the activation of the \u003cem\u003eHrk\u003c/em\u003e gene (DP5) in the cortex of OBX mice. This gene plays an important role in neuronal cell death\u0026nbsp;[88]. On the other hand, the activation of the \u003cem\u003eBcl2l1\u003c/em\u003e gene observed in the hippocampus of OBX mice may indicate a protective, compensatory effect against apoptosis, since this gene is a potent inhibitor of cell death\u0026nbsp;[89].\u003c/p\u003e\n\u003cp\u003eFerroptosis is a nonapoptotic form of cell death dependent upon intracellular iron\u0026nbsp;[90]. Iron homeostasis disturbance has also been implicated in Alzheimer\u0026rsquo;s disease (AD), and excess iron exacerbates oxidative damage and cognitive defects\u0026nbsp;[91].\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;In the hippocampus of OBX mice, only four genes related to this type of cell death changed their expression. Thus, \u003cem\u003eTrf\u003c/em\u003e gene exhibited upregulation while \u003cem\u003ePcbp1\u003c/em\u003e, \u003cem\u003eFtl1\u003c/em\u003e, and \u003cem\u003eGpx4\u003c/em\u003e genes were down-regulated (Figure 5). All these genes are associated with the maintenance of iron homeostasis, and their insufficient expression may lead to cell death by the ferroptosis pathway. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;It is of note that drastic down-regulation of the \u003cem\u003ePik3r3\u003c/em\u003e gene is observed in the brain of OBX mice (Figure 5). This gene under normal conditions, promoted hepatic fatty acid oxidation via PIK3R3-induced expression of \u003cem\u003ePpar\u0026alpha;\u003c/em\u003e [92]. Drastic inhibition of this gene in two brain areas of OBX mice should disrupt lipid metabolism which may lead to the induction of the ferroptosis process.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5. Changes in the transcription of genes characteristic for different cell types in the brain of OBX mice\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNext, we analyzed the expression of genes in the cortex, hippocampus, and cerebellum related to the state and activity of different major types of cells in these brain regions and presented this in the form of histograms, where we plotted the number of genes that increased or decreased expression in OBX mice compared to SO animals in each of 6 major cell types: neurons, astrocytes, oligodendrocytes, microglia, endothelial cells and oligodendrocyte progenitor cells (OPC) (Figure 6). A complete list of genes expressed in different cell types in the compared brain structures is provided in Table S1.\u003c/p\u003e\n\u003cp\u003eThe hippocampus again turned out to be the brain structure of OBX mice with the largest number of genes with altered expression related to the functioning of different types of cells of the nervous tissue. In the hippocampus and cortex, the largest proportion of genes, predominantly with increased expression, has been revealed for astrocytes, neurons, and progenitor cells, and in the cerebellum for microglia. An analysis of the synchronicity of changes of the same genes for different types of cells presented in Figure 6B demonstrated an interesting pattern: the same types of brain cells in the OBX mice were characterized predominantly by altered expression of different genes depending on the brain area studied.\u003c/p\u003e\n\u003cp\u003eWhen analyzing neuronal genes, we demonstrated that \u003cem\u003eMap2\u003c/em\u003e, \u003cem\u003eCamk4\u003c/em\u003e, and \u003cem\u003eLamp5\u003c/em\u003e genes drastically reduced their expression in OBX mice, which according to the literature, is characteristic for AD\u0026nbsp;[94-97]. The \u003cem\u003eArpp21\u003c/em\u003e gene, which greatly decreases its expression in hippocampal neurons, is directly associated with a reduced dopamine receptor activation\u0026nbsp;[98]. On the other hand, several genes with increased expression in OBX animals may also be associated with the development of AD-like pathology. Thus, up-regulation of both the \u003cem\u003eScn2b\u003c/em\u003e and \u003cem\u003eEfr3a\u003c/em\u003e genes is associated with the impairing of learning and memory\u0026nbsp;[99]\u0026nbsp;and reduced survival of newly born neurons in the hippocampus by inhibiting the maturation\u0026nbsp;[100]. The protein encoded by the \u003cem\u003eAp2a2\u003c/em\u003e gene often co-localizes with neurofibrillary tangles and promotes their deposition\u0026nbsp;[101].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAnalysis\u0026nbsp;of microglial genes in hippocampus of OBX mice with changed expression logFC \u0026lt; -0.8 enabled to conclude that these genes are involved in protein synthesis regulation (\u003cem\u003eEif5\u003c/em\u003e - ribosomal initiation complex and chain elongations), metabolic coordination between cytoplasm and mitochondria\u0026nbsp;(\u003cem\u003ePtp4a1\u003c/em\u003e), as well as in regulation of ionic homeostasis\u0026nbsp;(\u003cem\u003eSlc39a12\u003c/em\u003e).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen studying astrocytes, we observed down-regulation of expression of gene \u003cem\u003eNaaa\u003c/em\u003e [102]\u0026nbsp;and the \u003cem\u003eGrm3\u003c/em\u003e - gene of glutamate receptor metabotropic 3, associated with the accumulation of glutamate in the synaptic cleft leading to the development of neurotoxicity\u0026nbsp;[103]. On the other hand, in the astrocytes of OBX mice, we revealed a significant increase in the expression of the \u003cem\u003eSlc6a11\u003c/em\u003e - gene encoding GABA transporter in the brain\u0026nbsp;[104]. The activity of this gene which may ameliorate the hyperactivation of the glutamatergic system probably represents a compensatory reaction. \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe observed increased expression of the \u003cem\u003eGFAP\u003c/em\u003e gene (Glial fibrillary acidic protein) in OBX mice represents the manifestation of astrogliosis, a characteristic feature of AD\u0026nbsp;[105, 106]\u0026nbsp;as well as up-regulation of the \u003cem\u003eSox9\u003c/em\u003e gene playing an important role in A\u0026beta; deposition being an important feature of the hippocampus in AD patients\u0026nbsp;[52].\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eIn microglia of OBX mice preferential up-regulation of large majority of genes was revealed. Characteristically, an increase in the expression of several highly specific genes for non-activated mouse microglia, such as \u003cem\u003eSall1\u003c/em\u003e (transcription factor) was noted. The observed increased \u003cem\u003eTrim8\u003c/em\u003e expression in OBX mice, probably also represents the mechanism to protect microglial cells from cytotoxicity and inflammation\u0026nbsp;[107]. \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOverexpression of the \u003cem\u003eSki\u003c/em\u003e gene demonstrated in all analyzed brain regions of the OBX mice, leading to the loss of neurons bearing NMDA receptors represents a manifestation of excitotoxicity apparently associated with excessive release of glutamate\u0026nbsp;[108]. On the other hand, in microglia we revealed up-regulation of several genes activated by bulbectomy such as \u003cem\u003eNrp1\u003c/em\u003e which activates the \u003cem\u003eSyk\u003c/em\u003e gene to inhibit A\u0026beta; deposition and regulate microglial phagocytosis and disease-associated microglia (DAM) acquisition\u0026nbsp;[55, 109].\u003c/p\u003e\n\u003cp\u003eAll the above data enable to conclude that it is unlikely that an active process of neuroinflammation takes place in OBX animals. It is of note, that microglia cells are characterized by a drastic drop in the expression of genes involved in ribosome function\u0026nbsp;(e.g.\u0026nbsp;\u003cem\u003eRps27\u003c/em\u003e, \u003cem\u003eRpl22\u003c/em\u003e, \u003cem\u003eRps27a\u003c/em\u003e), transcription activation (\u003cem\u003eJunb\u003c/em\u003e), protein transport (\u003cem\u003eRab11a\u003c/em\u003e) and neurogenesis\u0026nbsp;(\u003cem\u003eHbp1\u003c/em\u003e,\u0026nbsp;[110]).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe observed significant activation of genes in endothelial cells in OBX mice is also of interest because it may reflect changes in the permeability of the BBB. Besides, these cells as well as microglia cells exhibited reduced expression of ribosomal proteins\u0026nbsp;(\u003cem\u003eRps27\u003c/em\u003e, Rps27a), splicing (Cwc15), protein transport and cell differentiation and degradation (Gabarapl2) ,\u0026nbsp;[111].\u0026nbsp;It is of note, that in the cortex and cerebellum of OBX mice, the expression of only 6 genes associated with oligodendrocytes changed their expression, while in the hippocampus, there were 16 of such genes. Dysregulation of the activity of these genes can lead to a decrease in the intensity of axonal myelination. Indeed, impaired axonal myelination in the brain at the early stages of AD development has been demonstrated\u0026nbsp;[112, 113].\u003c/p\u003e\n\u003cp\u003eTherefore, we have shown that OBX mice are characterized by pronounced changes in the expression of genes associated with different types of nerve cells, and the direction of these changes often coincides with the patterns observed in the brains of AD patients.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e6. Expression of genes involved in major depression in the brain of OBX mice\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIt should be noted that OBX mice and rats are often considered in the literature as a valid model of depression [27, 114, 115]. Figure 7 depicts differentially-expressed genes in the three brain structures of OBX mice that are associated with MD phenotype in humans (gene sets from [43]).\u003c/p\u003e\n\u003cp\u003eWhen analyzing differentially expressed genes in OBX mice, it is obvious that several of them coincided with genes responsible for the development of depression (including the genes \u003cem\u003eDrd2\u003c/em\u003e, \u003cem\u003eMap2\u003c/em\u003e, and the so-called canonical clock genes: \u003cem\u003ePer2\u003c/em\u003e, \u003cem\u003eArntl\u003c/em\u003e, \u003cem\u003eNr1d1\u003c/em\u003e). These genes play an important role in the regulation of circadian rhythm. It is known that changes in their expression are accompanied by sleep disturbance, a characteristic symptom of both MD and AD\u0026nbsp;[116, 117].\u003c/p\u003e\n\u003cp\u003eIt is known that depression is the result of dysregulation in neurotransmitter functioning in different brain regions\u0026nbsp;[118]. In OBX animals, as mentioned above, we observed pronounced changes in the expression of genes associated with the activity of dopaminergic (\u003cem\u003eTh\u003c/em\u003e, \u003cem\u003eDrd1\u003c/em\u003e, \u003cem\u003eDrd2\u003c/em\u003e), serotonergic (\u003cem\u003eHtr1a\u003c/em\u003e, \u003cem\u003eHtr2c\u003c/em\u003e, \u003cem\u003eHtr6\u003c/em\u003e), adrenergic (\u003cem\u003eAdra2a\u003c/em\u003e) and cholinergic (\u003cem\u003eChrm1\u003c/em\u003e, \u003cem\u003eChrm4\u003c/em\u003e) brain systems. Probably the observed increase in the expression of the \u003cem\u003eSox9\u003c/em\u003e gene encoding a transcription factor [119] represents a direct consequence of such disturbances. It is of note that the revealed changes in gene expression in OBX mice associated with the state of the peptidergic system, endorphin, and opiate systems are similar to those observed in MD, as well as observed hormonal dysfunction. \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAt the same time, while in OBX mice the synthesis of neurotrophic factors decreases, the level of intracellular calcium increases. Furthermore, in OBX animals the phosphorylation of tau protein is activated while apoptosis is induced on the background of astrogliosis. All these changes observed in OBX mice are also characteristic of animals with MD. Importantly, several genes depicted in Figure 7 are known to be involved both in MD and AD pathologies.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e7. Determination of the subtype of AD-like pathology exhibited by OBX mice\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAttempts are being made all the time to organize data into certain types or categories, both for pathologies like AD in humans and for the numerous animal models used to study this disease based on RNA-seq data\u0026nbsp;[2]. We also analyzed DEG expression in OBX mice and found 20 genes (Table S2) belonging to the 101 \u0026ldquo;key regulators\u0026rdquo; identified in the article describing AD subtypes, that were obtained as a result of transcriptomic analysis of the hippocampus of AD patients from two large populations\u0026nbsp;[2].\u003c/p\u003e\n\u003cp\u003eThe performed comparison enables to conclude that the pattern of expression of OBX mice genome may be placed with caution into B2 subtype of AD (Table S2). Thus, protein degradation\u0026ndash;related genes, involved in ubiquitination and polyubiquitination (\u003cem\u003eFbxo41\u003c/em\u003e, \u003cem\u003eFbx16\u003c/em\u003e), protein catabolism, the proteasome biogenesis, and proteins targeting for destruction, as well as genes responsible for the formation of vesicles and endosomes (\u003cem\u003eCsrnp3\u003c/em\u003e, \u003cem\u003eCltc\u003c/em\u003e), were predominantly up-regulated in the hippocampus of OBX mice. The enhanced transcription in OBX animals was also shown for the genes responsible for intracellular and transmembrane traffic (\u003cem\u003eRab9b\u003c/em\u003e), influencing cell differentiation and phagocytosis (\u003cem\u003eSyk\u003c/em\u003e). Thus, in an attempt to assign hallmarks of AD pathology in OBX mice to subtypes of human AD\u0026nbsp;[2], we found a modest, but statistically significant correlation between RNA expression patterns in the hippocampus of OBX mice and B2 subtype of AD (R= 0.209, p=1.897906e-85) (Figure S3).\u003c/p\u003e\n\u003cp\u003eNext, we analyzed how the protein products of differentially expressed genes in different regions of the brain of OBX mice interact with several proteins of key AD-associated genes. The latter genes involved in the formation and processing of beta-amyloid, the processes of synaptic transmission and protein folding. The results of this analysis are depicted in Figure 8.\u003c/p\u003e\n\u003cp\u003eIt can be seen in Figure 8 that the products of genes differentially expressed in different parts of the brain of OBX mice interact at the protein level with certain categories of genes involved in AD. This suggests that changes in the expression of certain genes in the brain of OBX animals lead to disruption of several key protein-protein interactions, which in turn triggers a cascade of changes leading to disruption of major regulatory systems in various parts of the brain. Interestingly, these systems include synaptic transmission, protein folding, beta-amyloid formation, etc.\u003c/p\u003e\n\u003cp\u003eThe largest number of DEGs that changed their expression after OBX was observed in the hippocampus, which is consistent with the results of other studies that found a high correlation between the number of DEGs in the hippocampus and the progression of AD and including the intensity of amyloid plaque deposition\u0026nbsp;[120].\u003c/p\u003e\n\u003cp\u003eFrom the results obtained, it follows that OBX mice are a model of a fairly common type of sporadic AD with manifestations of agitated depression observed in more than 30% of AD patients.\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eIntensive studies of AD in clinics and experiments exploring numerous models of this disease have made it possible to put forward several hypotheses for the genesis of this pathology. The generally accepted hypotheses are the amyloid cascade, the neurotransmitter hypothesis, the mitochondrial dysfunction hypothesis, neuroinflammation, and excitotoxicity hypothesis. Each of them is confirmed by abundant behavioral and biochemical data, as well as a description of a specific set of genes involved in the development of the pathological process in AD. Since the main goal of this study was to determine whether OBX animals represent a model of AD or MD, we analyzed gene expression in three brain regions of OBX mice and compared them with known sets of genes implicated in AD or MD. The removal of the olfactory bulbs has a strong effect on gene transcription in the brain. The hippocampus was the leader in this respect. These data agree with the abundant data accumulated in the process of AD investigation that demonstrated a high correlation between the number of DEGs in the hippocampus with the progression of AD and the intensity of amyloid plaque deposition [\u003cspan citationid=\"CR120\" class=\"CitationRef\"\u003e120\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe olfactory bulbectomy resulted in the activation of several signaling pathways leading to an AD-like neurological phenotype. Thus, the major affected biological processes according to GO enrichment are responsible for neurotransmitter secretion, cognition, learning, memory, neuropeptide signaling pathway, metabolic processes, ribosome processing and biogenesis, cell-matrix adhesion, etc. Characteristically, genes responsible for neuronal plasticity, neuropeptide signaling pathway, neurotransmitter transport, and secretion, as well as genes responsible for the regulation of glucose metabolism and WNT and Notch signaling were significantly up-regulated in the hippocampus of OBX mice. On the other hand, down-regulated genes were involved in protein synthesis and ribosome biogenesis.\u003c/p\u003e \u003cp\u003eThe transcriptomic analysis of genes in the brain of OBX mice demonstrated that 36 out of 45 Alzheimer\u0026rsquo;s disease-associated genes changed their expression, while increased expression was demonstrated by genes directly associated with the development of a neurodegenerative process similar to AD (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In our analysis we have demonstrated unidirectional changes change in the expression of genes involved in deposition of beta-amyloid (e.g. up-regulation of the \u003cem\u003eSox9\u003c/em\u003e gene) [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e] or hyperphosphorylation and deposition of tau protein [\u003cspan citationid=\"CR121\" class=\"CitationRef\"\u003e121\u003c/span\u003e, \u003cspan citationid=\"CR122\" class=\"CitationRef\"\u003e122\u003c/span\u003e], i.e. most of them exhibited increased expression. Interestingly, in the OBX brain, even several genes with reduced activity apparently contributed to the development of the pathology. Thus, a decrease in the expression of the prefoldin genes (\u003cem\u003ePfdn5\u003c/em\u003e and \u003cem\u003ePfdn2\u003c/em\u003e), that perform the function of chaperones, was observed, probably contributing to the formation of beta-amyloid oligomers. It is interesting to note, that the enhanced expression of several genes in the brain of OBX mice was probably compensatory in nature leading to APP stabilization (e.g. \u003cem\u003eApba1\u003c/em\u003e, \u003cem\u003eApba2\u003c/em\u003e) or reducing Aβ load (\u003cem\u003eSyk\u003c/em\u003e) by up-regulation of microglial phagocytosis (\u003cem\u003ePiezo1\u003c/em\u003e) [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. The presence of compensatory mechanisms that slow down the development of pathology is also characteristic for AD [\u003cspan citationid=\"CR123\" class=\"CitationRef\"\u003e123\u003c/span\u003e] and the very fact of activation of specific compensatory mechanisms can serve as an early diagnostic sign of the development of hidden pathology.\u003c/p\u003e \u003cp\u003eIt is known that beta amyloid and tau protein deposits exhibit neurotoxic effects leading to neuron loss. It is also known that in AD the death of neurons occurs mainly through apoptosis [\u003cspan citationid=\"CR124\" class=\"CitationRef\"\u003e124\u003c/span\u003e]. In our case, the removal of the olfactory bulbs induces predominantly in hippocampus the synthesis of proapoptotic factors e.g. the expression of the \u003cem\u003eApaf-1\u003c/em\u003e and \u003cem\u003eCasp9\u003c/em\u003e genes, that play a central role in the initiation of apoptosis [\u003cspan citationid=\"CR125\" class=\"CitationRef\"\u003e125\u003c/span\u003e, \u003cspan citationid=\"CR126\" class=\"CitationRef\"\u003e126\u003c/span\u003e]. It is known that oligomeric Apaf-1 mediates the cytochrome c-dependent autocatalytic activation of pro-caspase-9 (Apaf-3), leading to the activation of caspase-3 and apoptosis. The increased level of the protein product of the \u003cem\u003eHrk\u003c/em\u003e gene, activated in OBX mice (DP5 [\u003cspan citationid=\"CR88\" class=\"CitationRef\"\u003e88\u003c/span\u003e]), also leads to activation of caspase-3 and, consequently, to neuronal cell death. In recent years, in addition to apoptosis, significant attention has been paid to other types of cell death, in particular, ferroptosis [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e], which has been also implicated in Alzheimer's disease. Although only 4 genes associated with maintaining iron homeostasis changed their expression in OBX mice, downregulation of three of them is sufficient to induce ferroptosis (\u003cem\u003ePcbp1\u003c/em\u003e, \u003cem\u003eFtl1\u003c/em\u003e и \u003cem\u003eGPx4\u003c/em\u003e) [\u003cspan citationid=\"CR127\" class=\"CitationRef\"\u003e127\u003c/span\u003e, \u003cspan citationid=\"CR128\" class=\"CitationRef\"\u003e128\u003c/span\u003e]. It is important to note that the inhibition of ferroptosis ameliorates brain damage in Alzheimer, Parkinson, and Huntington's diseases [\u003cspan citationid=\"CR129\" class=\"CitationRef\"\u003e129\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is known that neurons loss observed in AD patients may be due to glutamate neurotoxicity. Therefore, we analyzed genes involved in the functioning of neurotransmitter systems that changed their expression after bulbectomy in the studied brain regions. The observed imbalance of glutamate/GABA systems with a deficiency of the inhibitory GABA system (i.e. reduced expression of the GABA A receptor-associated protein-like 2 genes) represents a characteristic feature of OBX mice transcriptome. Activation of the glutamatergic system in OBX mice was also evident based on the increased expression of metabotropic glutamate receptors and, apparently, a compensatory increase in the expression of the slc1a1 gene of the high-affinity glutamate transporters. Activation of this gene accompanies the accumulation of glutamate in the synaptic cleft and further development of glutamatergic neurotoxicity, leading to neuronal death [\u003cspan citationid=\"CR130\" class=\"CitationRef\"\u003e130\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, a decrease in the expression of the mGlu3s receptor revealed in transcriptome of astrocytes in OBX mice may be associated with the accumulation of glutamate in the synaptic cleft and development of astrocyte-mediated excitotoxicity and neuronal death in OBX mice [\u003cspan citationid=\"CR103\" class=\"CitationRef\"\u003e103\u003c/span\u003e]. The overexpression of the \u003cem\u003eSki\u003c/em\u003e gene demonstrated in all brain areas in OBX mice is probably also associated with excessive release of glutamate, excitotoxicity and the death of neurons carrying NMDA receptors, which is typical for AD [\u003cspan citationid=\"CR108\" class=\"CitationRef\"\u003e108\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, the increased expression of the \u003cem\u003eSlc6a11\u003c/em\u003e gene, encoding the GABA transporter, observed in astrocytes of OBX mice [\u003cspan citationid=\"CR104\" class=\"CitationRef\"\u003e104\u003c/span\u003e] may indirectly counteract the hyperactivation of the glutamatergic system. It is believed that an imbalance of these two systems may be a prerequisite for the development of AD [\u003cspan citationid=\"CR131\" class=\"CitationRef\"\u003e131\u003c/span\u003e]. Moreover, GABAergic dysfunction may contribute to the disruption of functional connections in the brain and thereby contribute to the development of AD [\u003cspan citationid=\"CR132\" class=\"CitationRef\"\u003e132\u003c/span\u003e]. The hypothesis of the genesis of AD associated with excitotoxicity caused by excess glutamate has become popular [\u003cspan citationid=\"CR133\" class=\"CitationRef\"\u003e133\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA decrease in the expression of genes, responsible for the synthesis of acetylcholine receptors M1 and M4, and the increased expression of the acetylcholinesterase enzyme gene represent another characteristic feature of OBX mice. It is necessary to emphasize, that a deficiency of the cholinergic system with hyperactivity of the acetylcholinesterase enzyme is a major symptom of AD and reflects the death of acetylcholine-synthesizing neurons in the nucleus basalis of the Meynert [\u003cspan citationid=\"CR134\" class=\"CitationRef\"\u003e134\u003c/span\u003e, \u003cspan citationid=\"CR135\" class=\"CitationRef\"\u003e135\u003c/span\u003e]. A drop in the content of these receptors in human peripheral blood is used as a marker of AD [\u003cspan citationid=\"CR136\" class=\"CitationRef\"\u003e136\u003c/span\u003e]. Moreover, the development of pharmacological agents that enhance the expression of the \u003cem\u003eChrm1\u003c/em\u003e and \u003cem\u003eChrm4\u003c/em\u003e genes is one of the promising directions in AD treatment since the proteins they encode have neuroprotective activity and increase the survival of neurons in AD models [\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e, \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e]. The observed increased expression of the acetylcholinesterase enzyme gene in the brain of OBX mice represents significant evidence of the validity of these animals as a model of AD.\u003c/p\u003e \u003cp\u003eAt the present time the use of acetylcholinesterase enzyme blockers remains practically the only FDA approved method for improving memory in AD patients while the development of new agents with similar activity is a promising direction in pharmacology [\u003cspan additionalcitationids=\"CR64 CR65\" citationid=\"CR63\" class=\"CitationRef\"\u003e63\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e, \u003cspan citationid=\"CR137\" class=\"CitationRef\"\u003e137\u003c/span\u003e]. It is believed that the deficiency of acetylcholinenergic system is associated with impaired cognitive functions in AD patients [\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e, \u003cspan citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eImportantly, our transcriptomic data corroborate the results of our previous histoimmunochemical studies, that showed a decrease in the density of acetylcholine-synthesizing neurons in the forebrain basal ganglia of OBX mice [\u003cspan citationid=\"CR138\" class=\"CitationRef\"\u003e138\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe performed transcriptomic analysis also demonstrated the changes in the activity of the dopaminergic system in OBX mice. Thus, we revealed a decrease in the expression of dopamine type D2 receptors in the hippocampus, which is a characteristic symptom of both depression and AD [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e, \u003cspan citationid=\"CR139\" class=\"CitationRef\"\u003e139\u003c/span\u003e]. Previously, using a classical transgenic model of AD in 5XFAD mice, we also showed disturbances in the dopaminergic system, including the death of dopaminergic neurons, which is considered to be an early manifestation of AD [\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e]. The downregulation of genes encoding somatostatin (\u003cem\u003eSSTs\u003c/em\u003e) in the brain of OBX mice can be also considered as the pathological signature of AD since low levels of both mRNA and correspondent protein are characteristic features of AD brain [\u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e69\u003c/span\u003e, \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e70\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecently, the mitochondrial hypothesis of the pathogenesis of AD has taken the leading place in popularity [\u003cspan citationid=\"CR140\" class=\"CitationRef\"\u003e140\u003c/span\u003e, \u003cspan citationid=\"CR141\" class=\"CitationRef\"\u003e141\u003c/span\u003e]. According to this hypothesis, energy deficiency caused by mitochondrial dysfunction is one of the major causes of AD development [\u003cspan citationid=\"CR142\" class=\"CitationRef\"\u003e142\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTo this end, in the brain of OBX mice the vast majority of genes related to the functioning of mitochondria exhibited decreased expression, which indicates a disruption in the functioning of complexes 1 (the multisubunit NADH: ubiquinone oxidoreductase) and IV (cytochrome C oxidase) of the mitochondrial respiratory chain (down-regulation genes of the Nduf and Pet100 families), respectively), as well as complex V (ATP synthetase) (decreased expression of the \u003cem\u003eFmc1\u003c/em\u003e gene). Deficiency of these mitochondrial complexes is a feature of several neurodegenerative disorders, including AD [\u003cspan additionalcitationids=\"CR144\" citationid=\"CR143\" class=\"CitationRef\"\u003e143\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR145\" class=\"CitationRef\"\u003e145\u003c/span\u003e]. Data from transcriptomic analysis of the mitochondria state in OBX mice are consistent with our previously obtained results on impaired mitochondrial functions in these animals, similar to those occurring in transgenic familial mouse AD models and patients with sporadic AD [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Summarizing the discussion of the results of transcriptomic analysis of genes associated with the functioning of mitochondria and the rate of cell death in the brain of OBX mice it should be noted that although the number of genes associated with these processes and changing their activity in OBX mice was relatively small, the altered expression was observed in several major genes which directly indicates a deficiency of mitochondrial functions and the induction of apoptosis in the brain of OBX animals representing key symptoms of the development of Alzheimer's-like neurodegeneration. It is necessary to mention that recently we have demonstrated that intranasal administration of mitochondria isolated from control mice improves spatial memory in OBX mice [\u003cspan citationid=\"CR146\" class=\"CitationRef\"\u003e146\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eFurthermore, we demonstrated that OBX animals are characterized by pronounced changes in the expression of genes associated with different types of nerve cells, and the direction of these changes often coincides with those observed in AD patients. Characteristically, the greatest changes for all six cell types were observed in the hippocampus. Thus, a decrease in the expression of neuronal genes (e.g. \u003cem\u003eMap2\u003c/em\u003e, \u003cem\u003eCamk4\u003c/em\u003e, \u003cem\u003eLamp5\u003c/em\u003e) directly indicated the development of Alzheimer\u0026rsquo;s-type neurodegeneration [\u003cspan citationid=\"CR97\" class=\"CitationRef\"\u003e97\u003c/span\u003e, \u003cspan citationid=\"CR147\" class=\"CitationRef\"\u003e147\u003c/span\u003e]. Dysregulation of the \u003cem\u003eAp2a2\u003c/em\u003e and \u003cem\u003eEfr3a\u003c/em\u003e genes observed in OBX mice and characteristic of animal models of AD is often associated with neurofibrillary tangles [\u003cspan citationid=\"CR101\" class=\"CitationRef\"\u003e101\u003c/span\u003e] and inhibition of hippocampal neurogenesis characteristic for AD [\u003cspan citationid=\"CR100\" class=\"CitationRef\"\u003e100\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe performed analysis of gene expression in astrocytes and microglia, is of special interest because the transition of these cells into disease-associated state may induce neuroinflammation which plays the leading role in the genesis of AD [\u003cspan citationid=\"CR148\" class=\"CitationRef\"\u003e148\u003c/span\u003e]. However, our analysis of transcriptome of OBX mice brain regions failed to reveal clear-cut transcriptomic signatures of neuroinflammation with the only exception of activation of the pro-inflammatory cell surface marker galectin 3 gene (\u003cem\u003eLgals3\u003c/em\u003e in cortex). An increased level of expression of the \u003cem\u003eTrim8\u003c/em\u003e gene in microglia [\u003cspan citationid=\"CR107\" class=\"CitationRef\"\u003e107\u003c/span\u003e], as well as activation of \u003cem\u003eSyk\u003c/em\u003e signaling, which can interfere with the development of disease-associated microglia (DAM) suggest certain protection of microglial cells of OBX mice from cytotoxicity and inflammation.\u003c/p\u003e \u003cp\u003eOn the other hand, the observed activation of \u003cem\u003eGfap\u003c/em\u003e gene in astrocytes of OBX mice is evidence of astrogliosis, characteristic for several neurodegenerative diseases, including AD [\u003cspan citationid=\"CR148\" class=\"CitationRef\"\u003e148\u003c/span\u003e]. It is of note, that increased expression of the \u003cem\u003eAxl\u003c/em\u003e gene (tyrosine kinase receptor), in astrocytes in OBX mice is associated with inhibition of proinflammatory responses [\u003cspan citationid=\"CR149\" class=\"CitationRef\"\u003e149\u003c/span\u003e, \u003cspan citationid=\"CR150\" class=\"CitationRef\"\u003e150\u003c/span\u003e]. The increased expression of the gene that controls the synthesis of glial fibrillary acidic protein (\u003cem\u003eGfap\u003c/em\u003e) in the brain of OBX mice indicates the validity of the model because this astrocytic cytoskeletal protein is a potential biomarker for AD [\u003cspan citationid=\"CR105\" class=\"CitationRef\"\u003e105\u003c/span\u003e, \u003cspan citationid=\"CR106\" class=\"CitationRef\"\u003e106\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe demonstrated activation of genes associated with microglia may result in the release of glutamate, causing excitotoxicity and death of neurons bearing NMDA receptors, directly related to learning and memory [\u003cspan citationid=\"CR151\" class=\"CitationRef\"\u003e151\u003c/span\u003e]. The activation of the immune system of OBX mice takes place in the cerebral cortex judging by the high level of expression of genes involved in the interferon response (\u003cem\u003eIfitm3\u003c/em\u003e). It is well known that the induction of type 1 interferons, may be associated with neuron death and DNA damage [\u003cspan citationid=\"CR152\" class=\"CitationRef\"\u003e152\u003c/span\u003e]. Based on the accumulated data we conclude that neuroinflammation probably does not play an important role in the development of neurodegeneration in the brain of OBX mice. Characteristic feature of OBX mice is a dramatic decrease in the expression genes of ribosomal proteins in astrocyte, microglial cells and in particular genes for ribosomal mitochondrial proteins, which may lead to astrocytes and microglia dysfunction. It is well known that a drastic reduction of total protein synthesis is a characteristic feature of neurodegenerative process [\u003cspan citationid=\"CR153\" class=\"CitationRef\"\u003e153\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAnalyzing the processes linked with OPC genes (oligodendrocyte progenitor cells), we discovered multidirectional changes associated both with the development of a neurodegenerative process and with a compensatory reaction in the brain of OBX mice. It is known, that genes of endothelial cells are able to maintain homeostasis and preserve the function of these cells even under conditions of bulbectomy and the development of neurodegeneration. We observed dysregulation the expression of genes in oligodendrocytes in the cortex and cerebellum of OBX mice, that may lead to a decrease in the intensity of axonal myelination, characteristic for the early stages of AD development [\u003cspan citationid=\"CR112\" class=\"CitationRef\"\u003e112\u003c/span\u003e, \u003cspan citationid=\"CR113\" class=\"CitationRef\"\u003e113\u003c/span\u003e]. In this regard, it is interesting to note that the B2 subtype of AD in humans, which based on our data most closely corresponds to OBX mice, is also characterized by a marked down-regulation of genes in oligodendrocytes with up-regulation in other cell types, suggesting that a demyelinating process may take place in OBX mice.\u003c/p\u003e \u003cp\u003eRecently, special attention has been paid to comorbid diseases associated with AD, such as hypertension and diabetes, associated with disruption of the renin-angiotensin system (RAS) and insulin resistance. To this end, in OBX mice, we found a decrease in the expression level of the MAS1 receptor gene (\u003cem\u003eMas1\u003c/em\u003e). A shift in the balance of the two branches of the RAS, caused by a lack of MAS receptor (\u003cem\u003eMasr\u003c/em\u003e) and angiotensin (1\u0026ndash;7) against the background of an excess amount of angiotensin II, was often noted in sporadic AD, and its restoration has a positive effect in this pathology [\u003cspan citationid=\"CR154\" class=\"CitationRef\"\u003e154\u003c/span\u003e, \u003cspan citationid=\"CR155\" class=\"CitationRef\"\u003e155\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eUntil now it was not clear whether major depression is a risk factor for AD, a symptom, a stress reaction in AD, or a comorbid disease. However, the very fact of comorbidity of AD, depression is a phenomenon long known. Serious studies have been devoted to the overlap between symptoms of depression and neurodegeneration processes in patients with mild AD [\u003cspan citationid=\"CR156\" class=\"CitationRef\"\u003e156\u003c/span\u003e]. The prevalence of symptoms of MD in Alzheimer's disease ranged widely from 22.5\u0026ndash;54.4% [\u003cspan citationid=\"CR157\" class=\"CitationRef\"\u003e157\u003c/span\u003e]. However, due to the lack of convenient animal models, the question remained unclear. It was not clear whether depression arises as a psychological reaction to the disease and due to difficulties in the adaptation to AD, or depression and AD have common neurobiological basic mechanisms [\u003cspan citationid=\"CR158\" class=\"CitationRef\"\u003e158\u003c/span\u003e, \u003cspan citationid=\"CR159\" class=\"CitationRef\"\u003e159\u003c/span\u003e]. It is of note, that transcriptional analysis of brain tissue in OBX mice revealed that some of the changes in receptor systems are more typical for MD, than for AD. Thus, the observed decrease in the expression of the adenosine receptor A2a gene (\u003cem\u003eAdora2a\u003c/em\u003e) that we observed is a characteristic sign of depression [\u003cspan citationid=\"CR160\" class=\"CitationRef\"\u003e160\u003c/span\u003e, \u003cspan citationid=\"CR161\" class=\"CitationRef\"\u003e161\u003c/span\u003e], while in AD patients, on the contrary, there is an increased expression of this receptor [\u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e74\u003c/span\u003e, \u003cspan citationid=\"CR75\" class=\"CitationRef\"\u003e75\u003c/span\u003e, \u003cspan citationid=\"CR162\" class=\"CitationRef\"\u003e162\u003c/span\u003e]. On the other hand, a decrease in the expression of dopamine type D2 receptors also demonstrated in the hippocampus in OBX mice is a characteristic feature of both depression and AD [\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e, \u003cspan citationid=\"CR139\" class=\"CitationRef\"\u003e139\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eRecently, using classical transgenic model of AD (APP/PSEN1-Tg mice) it was shown that depressive manifestations, such as a decrease in olfactory sensitivity represent an early stage of the pathology [\u003cspan citationid=\"CR163\" class=\"CitationRef\"\u003e163\u003c/span\u003e] Importantly, in the brain of OBX mice we observed the downregulation of the genes encoding somatostatin (SSTs) the dopaminergic) receptors, endorphin, and opiate systems, as well as genes associated with hormonal dysfunction. The analysis of transcription in the brains of OBX mice revealed up-regulation of genes associated with the regulation of circadian rhythms, cell migration, and impaired innate immunity, characteristic for the MD. Therefore, the transcriptomic analysis showed that in OBX mice, changes in the expression of genes responsible for the functioning of receptor systems are similar to those observed in AD, while changes characteristic of depression are less frequent and less pronounced. It is clear that OBX mice represent a model of complex neuropathology with elements of AD and MD. It is necessary in this context to underline that according to various studies [\u003cspan citationid=\"CR164\" class=\"CitationRef\"\u003e164\u003c/span\u003e], chronic use of antidepressants which has a protective effect in depression development in OBX mice is not able to reverse the development of neurodegenerative process in these animals including ventricular enlargement, hippocampal volume reduction, and neuronal loss, induced by bulbectomy.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eIn general, analysis of the functional significance of genes in the brain of OBX mice indicates that the balance of the GABA/glutamatergic systems is disturbed with hyperactivation of the latter, which leads to the development of excitotoxicity and induction of apoptosis on the background of severe mitochondrial dysfunction and astrogliosis. The synthesis of neurotrophic factors the OBX mice decreases, which leads to disruption of the cytoskeleton of neurons, an increase in the level of intracellular calcium, and activation of tau protein phosphorylation. The acetylcholinergic system is deficient on the background of hyperactivation of acetylcholinesterase. Importantly, the activity of the dopaminergic, endorphin, and opiate systems decreases, and hormonal dysfunction develops. Genes associated with the regulation of circadian rhythms, cell migration, and impaired innate immunity are activated in the model animals. All this occurs on the background of pronounced down-regulation of genes of ribosomal proteins. It is clear that OBX mice represent a model of complex neuropathology with elements of Alzheimer's disease and major depression. Apparently, OBX mice have neurobiological basic mechanisms responsible for complex symptomatology. Therefore, we demonstrated that OBX mice have a common transcriptomic signature associated with both AD and MD. The similarity of the genetic basis of these pathologies also determines the simultaneous manifestation of symptoms of AD and MD in OBX mice. Interestingly, dynamic changes in the gene regulation characteristic for depression were evident in mouse AD model before the onset of AD. From the presented data it follows that in OBX animals AD-like neurodegenerative process develops, including several elements of MD. Based on accumulated data this model can be tentatively attributed to subtype B2 of AD in humans.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements:\u003c/strong\u003e The study was supported by the grant of the Russian Federation Government no 22-74-10050\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Declarations\u003c/strong\u003e:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor Contribution:\u003c/strong\u003e NVB, MBE designed the experiments; NVB, MBE, LNC, APR supervised the design and course of the experiments; NVB, VIK, DYZ, APR, CLN, AVC performed the experiments; NVB, MBE, LNC, APR performed the analyses and interpretation of the experiments; NVB, MBE, LNC, APR wrote the manuscript, NVB, MBE, LNC reviewed and edited the manuscript.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAll of the authors read and approved the final manuscript.\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e The study was supported by the grant of the Russian Federation Government no. 22-74-10050.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting Interest\u003c/strong\u003e The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e Data will be made available under the reasonable request\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eapproval\u003c/strong\u003e All animal experiments were conducted in agreement with the Provision and General Recommendation of Chinese Experimental Animals Administration Legislation and were approved by the Animal Ethics Committee in Institute (SLXD-20180912006, 12 September 2018)\u0026nbsp;in compliance with Russian Federation legislation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e Informed consent was obtained from all individual participants and authors involved in the study\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e We confirming that consent to publish has been received from all participants involved in this stud\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKhan S, Barve KH, Kumar MS (2020) Recent Advancements in Pathogenesis, Diagnostics and Treatment of Alzheimer\u0026apos;s Disease. \u003cem\u003eCurr Neuropharmacol\u003c/em\u003e 18(11):1106-1125. doi:10.2174/1570159X18666200528142429\u003c/li\u003e\n\u003cli\u003eNeff RA, Wang M, Vatansever S, et al (2021) Molecular subtyping of Alzheimer\u0026apos;s disease using RNA sequencing data reveals novel mechanisms and targets. \u003cem\u003eSci Adv\u003c/em\u003e 7(2) doi:10.1126/sciadv.abb5398\u003c/li\u003e\n\u003cli\u003eSasaguri H, Hashimoto S, Watamura N, et al (2022) Recent Advances in the Modeling of Alzheimer\u0026apos;s Disease. \u003cem\u003eFront Neurosci\u003c/em\u003e 16:807473. doi:10.3389/fnins.2022.807473\u003c/li\u003e\n\u003cli\u003eMcGowan E, Eriksen J, Hutton M (2006) A decade of modeling Alzheimer\u0026apos;s disease in transgenic mice. \u003cem\u003eTrends Genet\u003c/em\u003e 22(5):281-9. doi:10.1016/j.tig.2006.03.007\u003c/li\u003e\n\u003cli\u003eChin J (2011) Selecting a mouse model of Alzheimer\u0026apos;s disease. \u003cem\u003eMethods Mol Biol\u003c/em\u003e 670:169-89. doi:10.1007/978-1-60761-744-0_13\u003c/li\u003e\n\u003cli\u003eBilkei-Gorzo A (2014) Genetic mouse models of brain ageing and Alzheimer\u0026apos;s disease. \u003cem\u003ePharmacol Ther\u003c/em\u003e 142(2):244-57. doi:10.1016/j.pharmthera.2013.12.009\u003c/li\u003e\n\u003cli\u003eGulyaeva NV, Bobkova NV, Kolosova NG, Samokhin AN, Stepanichev MY, Stefanova NA (2017) Molecular and Cellular Mechanisms of Sporadic Alzheimer\u0026apos;s Disease: Studies on Rodent Models in vivo. \u003cem\u003eBiochemistry (Mosc)\u003c/em\u003e 82(10):1088-1102. doi:10.1134/S0006297917100029\u003c/li\u003e\n\u003cli\u003eFerreyra-Moyano H, Barragan E (1989) The olfactory system and Alzheimer\u0026apos;s disease. \u003cem\u003eInt J Neurosci\u003c/em\u003e 49(3-4):157-97. doi:10.3109/00207458909084824\u003c/li\u003e\n\u003cli\u003eDjordjevic J, Jones-Gotman M, De Sousa K, Chertkow H (2008) Olfaction in patients with mild cognitive impairment and Alzheimer\u0026apos;s disease. \u003cem\u003eNeurobiol Aging\u003c/em\u003e 29(5):693-706. doi:10.1016/j.neurobiolaging.2006.11.014\u003c/li\u003e\n\u003cli\u003eAttems J, Walker L, Jellinger KA (2014) Olfactory bulb involvement in neurodegenerative diseases. \u003cem\u003eActa Neuropathol\u003c/em\u003e 127(4):459-75. doi:10.1007/s00401-014-1261-7\u003c/li\u003e\n\u003cli\u003eMarine N, Boriana A (2014) Olfactory markers of depression and Alzheimer\u0026apos;s disease. \u003cem\u003eNeurosci Biobehav Rev\u003c/em\u003e 45:262-70. doi:10.1016/j.neubiorev.2014.06.016\u003c/li\u003e\n\u003cli\u003eKov\u0026aacute;cs T, Cairns NJ, Lantos PL (1999) beta-amyloid deposition and neurofibrillary tangle formation in the olfactory bulb in ageing and Alzheimer\u0026apos;s disease. \u003cem\u003eNeuropathol Appl Neurobiol\u003c/em\u003e 25(6):481-91. doi:10.1046/j.1365-2990.1999.00208.x\u003c/li\u003e\n\u003cli\u003eAlmeida RF, Ganzella M, Machado DG, et al (2017) Olfactory bulbectomy in mice triggers transient and long-lasting behavioral impairments and biochemical hippocampal disturbances. \u003cem\u003eProg Neuropsychopharmacol Biol Psychiatry\u003c/em\u003e 76:1-11. doi:10.1016/j.pnpbp.2017.02.013\u003c/li\u003e\n\u003cli\u003eAvetisyan AV, Samokhin AN, Alexandrova IY, Zinovkin RA, Simonyan RA, Bobkova NV (2016) Mitochondrial Dysfunction in Neocortex and Hippocampus of Olfactory Bulbectomized Mice, a Model of Alzheimer\u0026apos;s Disease. \u003cem\u003eBiochemistry (Mosc)\u003c/em\u003e 81(6):615-23. doi:10.1134/S0006297916060080\u003c/li\u003e\n\u003cli\u003eBobkova NV, Nesteroval IV, Dana R, et al (2004) Morphofunctional changes in neurons in the temporal cortex of the brain in relation to spatial memory in bulbectomized mice after treatment with mineral ascorbates. \u003cem\u003eNeurosci Behav Physiol\u003c/em\u003e 34(7):671-6. doi:10.1023/b:neab.0000036005.70153.3b\u003c/li\u003e\n\u003cli\u003eHan F, Shioda N, Moriguchi S, Qin ZH, Fukunaga K (2008) The vanadium (IV) compound rescues septo-hippocampal cholinergic neurons from neurodegeneration in olfactory bulbectomized mice. \u003cem\u003eNeuroscience\u003c/em\u003e 06;151(3):671-9. doi:10.1016/j.neuroscience.2007.11.011\u003c/li\u003e\n\u003cli\u003eHozumi S, Nakagawasai O, Tan-No K, et al (2003) Characteristics of changes in cholinergic function and impairment of learning and memory-related behavior induced by olfactory bulbectomy. \u003cem\u003eBehav Brain Res\u003c/em\u003e 138(1):9-15. doi:10.1016/s0166-4328(02)00183-3\u003c/li\u003e\n\u003cli\u003eGurevich EV, Aleksandrova IA, Otmakhova NA, Katkov YA, Nesterova IV, Bobkova NV (1993) Effects of bulbectomy and subsequent antidepressant treatment on brain 5-HT2 and 5-HT1A receptors in mice. \u003cem\u003ePharmacol Biochem Behav\u003c/em\u003e 45(1):65-70. doi:10.1016/0091-3057(93)90087-a\u003c/li\u003e\n\u003cli\u003eAleksandrova IY, Kuvichkin VV, Kashparov IA, et al (2004) Increased level of beta-amyloid in the brain of bulbectomized mice. \u003cem\u003eBiochemistry (Mosc)\u003c/em\u003e 200469(2):176-80. doi:10.1023/b:biry.0000018948.04559.ab\u003c/li\u003e\n\u003cli\u003eBeck M, Bigl V, Rossner S (2003) Guinea pigs as a nontransgenic model for APP processing in vitro and in vivo. \u003cem\u003eNeurochem Res \u003c/em\u003e28(3-4):637-44. doi:10.1023/a:1022850113083\u003c/li\u003e\n\u003cli\u003eXie AJ, Liu EJ, Huang HZ, et al (2016) Cnga2 Knockout Mice Display Alzheimer\u0026apos;s-Like Behavior Abnormities and Pathological Changes. \u003cem\u003eMol Neurobiol\u003c/em\u003e 53(7):4992-9. doi:10.1007/s12035-015-9421-x\u003c/li\u003e\n\u003cli\u003eBattaglia F, Wang HY, Ghilardi MF, et al (2007) Cortical plasticity in Alzheimer\u0026apos;s disease in humans and rodents. \u003cem\u003eBiol Psychiatry\u003c/em\u003e 15;62(12):1405-12. doi:10.1016/j.biopsych.2007.02.027\u003c/li\u003e\n\u003cli\u003eMiller AH, Raison CL (2016) The role of inflammation in depression: from evolutionary imperative to modern treatment target. \u003cem\u003eNat Rev Immunol\u003c/em\u003e 16(1):22-34. doi:10.1038/nri.2015.5\u003c/li\u003e\n\u003cli\u003eHu J, Huang HZ, Wang X, et al (2015) Activation of Glycogen Synthase Kinase-3 Mediates the Olfactory Deficit-Induced Hippocampal Impairments. \u003cem\u003eMol Neurobiol\u003c/em\u003e 52(3):1601-1617. doi:10.1007/s12035-014-8953-9\u003c/li\u003e\n\u003cli\u003eTakahashi K, Nakagawasai O, Nemoto W, et al (2018) Memantine ameliorates depressive-like behaviors by regulating hippocampal cell proliferation and neuroprotection in olfactory bulbectomized mice. \u003cem\u003eNeuropharmacology\u003c/em\u003e 15;137:141-155. doi:10.1016/j.neuropharm.2018.04.013\u003c/li\u003e\n\u003cli\u003eBobkova NV, Garbuz DG, Nesterova I, et al (2014) Therapeutic effect of exogenous hsp70 in mouse models of Alzheimer\u0026apos;s disease. \u003cem\u003eJ Alzheimers Dis \u003c/em\u003e38(2):425-35. doi:10.3233/JAD-130779\u003c/li\u003e\n\u003cli\u003eSong C, Leonard BE (2005) The olfactory bulbectomised rat as a model of depression. \u003cem\u003eNeurosci Biobehav Rev \u003c/em\u003e29(4-5):627-47. doi:10.1016/j.neubiorev.2005.03.010\u003c/li\u003e\n\u003cli\u003eAttems J, Lintner F, Jellinger KA (2005) Olfactory involvement in aging and Alzheimer\u0026apos;s disease: an autopsy study. \u003cem\u003eJ Alzheimers Dis\u003c/em\u003e 7(2):149-57; discussion 173-80. doi:10.3233/jad-2005-7208\u003c/li\u003e\n\u003cli\u003eHarkin A, Kelly JP, Leonard BE (2003) A review of the relevance and validity of olfactory bulbectomy as a model of depression. \u003cem\u003eClinical Neuroscience Research\u003c/em\u003e 3(4-5):253-262. \u003c/li\u003e\n\u003cli\u003eOtmakhova NA, Gurevich EV, Katkov YA, Nesterova IV, Bobkova NV (1992) Dissociation of multiple behavioral effects between olfactory bulbectomized C57Bl/6J and DBA/2J mice. \u003cem\u003ePhysiol Behav\u003c/em\u003e 52(3):441-8. doi:10.1016/0031-9384(92)90329-z\u003c/li\u003e\n\u003cli\u003eMachado DG, Lara MVS, Dobler PB, Almeida RF, Porci\u0026uacute;ncula LO (2020) Caffeine prevents neurodegeneration and behavioral alterations in a mice model of agitated depression. \u003cem\u003eProg Neuropsychopharmacol Biol Psychiatry\u003c/em\u003e 98:109776. doi:10.1016/j.pnpbp.2019.109776\u003c/li\u003e\n\u003cli\u003eKrasnov GS, Dmitriev AA, Kudryavtseva AV, et al (2015) PPLine: An Automated Pipeline for SNP, SAP, and Splice Variant Detection in the Context of Proteogenomics. \u003cem\u003eJ Proteome Res\u003c/em\u003e 14(9):3729-37. doi:10.1021/acs.jproteome.5b00490\u003c/li\u003e\n\u003cli\u003eKechin A, Boyarskikh U, Kel A, Filipenko M (2017) cutPrimers: A New Tool for Accurate Cutting of Primers from Reads of Targeted Next Generation Sequencing. \u003cem\u003eJ Comput Biol\u003c/em\u003e 24(11):1138-1143. doi:10.1089/cmb.2017.0096\u003c/li\u003e\n\u003cli\u003eDobin A, Davis CA, Schlesinger F, et al (2013) STAR: ultrafast universal RNA-seq aligner. \u003cem\u003eBioinformatics \u003c/em\u003e29(1):15-21. doi:10.1093/bioinformatics/bts635\u003c/li\u003e\n\u003cli\u003eLi H, Handsaker B, Wysoker A, et al (2009) The Sequence Alignment/Map format and SAMtools. \u003cem\u003eBioinformatics\u003c/em\u003e 15;25(16):2078-9. doi:10.1093/bioinformatics/btp352\u003c/li\u003e\n\u003cli\u003eLiao Y, Smyth GK, Shi W (2014) featureCounts: an efficient general purpose program for assigning sequence reads to genomic features. \u003cem\u003eBioinformatics\u003c/em\u003e 01;30(7):923-30. doi:10.1093/bioinformatics/btt656\u003c/li\u003e\n\u003cli\u003eRobinson MD, McCarthy DJ, Smyth GK (2010) edgeR: a Bioconductor package for differential expression analysis of digital gene expression data. \u003cem\u003eBioinformatic \u003c/em\u003e26(1):139-40. doi:10.1093/bioinformatics/btp616\u003c/li\u003e\n\u003cli\u003eYu G, Wang LG, Han Y, He QY (2012) clusterProfiler: an R package for comparing biological themes among gene clusters. \u003cem\u003eOMICS\u003c/em\u003e 16(5):284-7. doi:10.1089/omi.2011.0118\u003c/li\u003e\n\u003cli\u003eConsortium GO (2015) Gene Ontology Consortium: going forward. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 43(Database issue):D1049-56. doi:10.1093/nar/gku1179\u003c/li\u003e\n\u003cli\u003eKanehisa M, Goto S (2000) KEGG: kyoto encyclopedia of genes and genomes. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 01;28(1):27-30. doi:10.1093/nar/28.1.27\u003c/li\u003e\n\u003cli\u003eBellenguez C, K\u0026uuml;\u0026ccedil;\u0026uuml;kali F, Jansen IE, et al (2022) New insights into the genetic etiology of Alzheimer\u0026apos;s disease and related dementias. \u003cem\u003eNat Genet\u003c/em\u003e 54(4):412-436. doi:10.1038/s41588-022-01024-z\u003c/li\u003e\n\u003cli\u003eProkopenko D, Morgan SL, Mullin K, et al (2021) Whole-genome sequencing reveals new Alzheimer\u0026apos;s disease-associated rare variants in loci related to synaptic function and neuronal development. \u003cem\u003eAlzheimers Dement\u003c/em\u003e 17(9):1509-1527. doi:10.1002/alz.12319\u003c/li\u003e\n\u003cli\u003eGuti\u0026eacute;rrez-Sacrist\u0026aacute;n A, Grosdidier S, Valverde O, et al (2015) PsyGeNET: a knowledge platform on psychiatric disorders and their genes. \u003cem\u003eBioinformatics\u003c/em\u003e 15;31(18):3075-7. doi:10.1093/bioinformatics/btv301\u003c/li\u003e\n\u003cli\u003eWang Y, Chen G, Shao W (2022) Identification of Ferroptosis-Related Genes in Alzheimer\u0026apos;s Disease Based on Bioinformatic Analysis. \u003cem\u003eFront Neurosci\u003c/em\u003e 16:823741. doi:10.3389/fnins.2022.823741\u003c/li\u003e\n\u003cli\u003eCalvo SE, Clauser KR, Mootha VK (2016) MitoCarta2.0: an updated inventory of mammalian mitochondrial proteins. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 04;44(D1):D1251-7. doi:10.1093/nar/gkv1003\u003c/li\u003e\n\u003cli\u003eHerholz K (2022) Imaging Clinical Subtypes and Associated Brain Networks in Alzheimer\u0026apos;s Disease. \u003cem\u003eBrain Sci\u003c/em\u003e 23;12(2)doi:10.3390/brainsci12020146\u003c/li\u003e\n\u003cli\u003eKuznetsov D, Tegenfeldt F, Manni M, et al (2023) OrthoDB v11: annotation of orthologs in the widest sampling of organismal diversity. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 06;51(D1):D445-D451. doi:10.1093/nar/gkac998\u003c/li\u003e\n\u003cli\u003eSzklarczyk D, Gable AL, Nastou KC, et al (2021) The STRING database in 2021: customizable protein-protein networks, and functional characterization of user-uploaded gene/measurement sets. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 08;49(D1):D605-D612. doi:10.1093/nar/gkaa1074\u003c/li\u003e\n\u003cli\u003eBobkova N, Guzhova I, Margulis B, et al (2013) Dynamics of endogenous Hsp70 synthesis in the brain of olfactory bulbectomized mice. \u003cem\u003eCell Stress Chaperones\u003c/em\u003e 18(1):109-18. doi:10.1007/s12192-012-0359-x\u003c/li\u003e\n\u003cli\u003ePark H, Lee YB, Chang KA (2022) miR-200c suppression increases tau hyperphosphorylation by targeting 14-3-3\u0026gamma; in early stage of 5xFAD mouse model of Alzheimer\u0026apos;s disease. \u003cem\u003eInt J Biol Sci\u003c/em\u003e 18(5):2220-2234. doi:10.7150/ijbs.66604\u003c/li\u003e\n\u003cli\u003evan Schaik PEM, Zuhorn IS, Baron W (2022) Targeting Fibronectin to Overcome Remyelination Failure in Multiple Sclerosis: The Need for Brain- and Lesion-Targeted Drug Delivery. \u003cem\u003eInt J Mol Sci\u003c/em\u003e 29;23(15)doi:10.3390/ijms23158418\u003c/li\u003e\n\u003cli\u003eAlamoudi AA (2023) SOX9 Expression Is Increased in Alzheimer\u0026apos;s Disease (AD) and Is Associated With Disease Progression and APOE4 Genotype: A Computational Approach. \u003cem\u003eCureus\u003c/em\u003e 15(3):e36129. doi:10.7759/cureus.36129\u003c/li\u003e\n\u003cli\u003eMorawski M, Nuytens K, Juhasz T, et al (2013) Cellular and ultra structural evidence for cytoskeletal localization of prolyl endopeptidase-like protein in neurons. \u003cem\u003eNeuroscience\u003c/em\u003e 09;242:128-39. doi:10.1016/j.neuroscience.2013.02.038\u003c/li\u003e\n\u003cli\u003eJafarian Z, Khamse S, Afshar H, Khorshid HRK, Delbari A, Ohadi M (2021) Natural selection at the RASGEF1C (GGC) repeat in human and divergent genotypes in late-onset neurocognitive disorder. \u003cem\u003eSci Rep\u003c/em\u003e 28;11(1):19235. doi:10.1038/s41598-021-98725-y\u003c/li\u003e\n\u003cli\u003eEnnerfelt H, Frost EL, Shapiro DA, et al (2022) SYK coordinates neuroprotective microglial responses in neurodegenerative disease. \u003cem\u003eCell\u003c/em\u003e 27;185(22):4135-4152.e22. doi:10.1016/j.cell.2022.09.030\u003c/li\u003e\n\u003cli\u003eHu J, Chen Q, Zhu H, et al (2023) Microglial Piezo1 senses A\u0026beta; fibril stiffness to restrict Alzheimer\u0026apos;s disease. \u003cem\u003eNeuron\u003c/em\u003e 04;111(1):15-29.e8. doi:10.1016/j.neuron.2022.10.021\u003c/li\u003e\n\u003cli\u003eSpoelgen R, von Arnim CA, Thomas AV, et al (2006) Interaction of the cytosolic domains of sorLA/LR11 with the amyloid precursor protein (APP) and beta-secretase beta-site APP-cleaving enzyme. \u003cem\u003eJ Neurosci\u003c/em\u003e 11;26(2):418-28. doi:10.1523/JNEUROSCI.3882-05.2006\u003c/li\u003e\n\u003cli\u003eWeiner DM, Goodman MW, Colpitts TM, et al (2004) Functional screening of drug target genes: m1 muscarinic acetylcholine receptor phenotypes in degenerative dementias. \u003cem\u003eAm J Pharmacogenomics \u003c/em\u003e4(2):119-28. doi:10.2165/00129785-200404020-00006\u003c/li\u003e\n\u003cli\u003eLin M, Li P, Liu W, Niu T, Huang L (2022) Germacrone alleviates okadaic acid-induced neurotoxicity in PC12 cells via M1 muscarinic receptor-mediated Galphaq (Gq)/phospholipase C beta (PLC\u0026beta;)/ protein kinase C (PKC) signaling. \u003cem\u003eBioengineered\u003c/em\u003e 13(3):4898-4910. doi:10.1080/21655979.2022.2036918\u003c/li\u003e\n\u003cli\u003eZhu G, Fang Y, Cui X, Jia R, Kang X, Zhao R (2022) Magnolol upregulates CHRM1 to attenuate Amyloid-\u0026beta;-triggered neuronal injury through regulating the cAMP/PKA/CREB pathway. \u003cem\u003eJ Nat Med\u003c/em\u003e 76(1):188-199. doi:10.1007/s11418-021-01574-2\u003c/li\u003e\n\u003cli\u003eGogliotti RG, Fisher NM, Stansley BJ, et al (2018) Total RNA Sequencing of Rett Syndrome Autopsy Samples Identifies the M. \u003cem\u003eJ Pharmacol Exp Ther \u003c/em\u003e365(2):291-300. doi:10.1124/jpet.117.246991\u003c/li\u003e\n\u003cli\u003ePopiolek M, Mandelblat-Cerf Y, Young D, et al (2019) In Vivo Modulation of Hippocampal Excitability by M4 Muscarinic Acetylcholine Receptor Activator: Implications for Treatment of Alzheimer\u0026apos;s Disease and Schizophrenic Patients. \u003cem\u003eACS Chem Neurosci \u003c/em\u003e 20;10(3):1091-1098. doi:10.1021/acschemneuro.8b00496\u003c/li\u003e\n\u003cli\u003eChoi J, Yoon J, Kim M (2022) Optimization of Fermentation Conditions of Artemisia capillaris for Enhanced Acetylcholinesterase and Butyrylcholinesterase. \u003cem\u003eFoods\u003c/em\u003e. 29;11(15) doi:10.3390/foods11152268\u003c/li\u003e\n\u003cli\u003eMiao S, He Q, Li C, et al (2022) Aaptamine - a dual acetyl - and butyrylcholinesterase inhibitor as potential anti-Alzheimer\u0026apos;s disease agent. \u003cem\u003ePharm Biol\u003c/em\u003e 60(1):1502-1510. doi:10.1080/13880209.2022.2102657\u003c/li\u003e\n\u003cli\u003eNascimento LA, Nascimento \u0026Eacute;, Martins JBL (2022) In silico study of tacrine and acetylcholine binding profile with human acetylcholinesterase: docking and electronic structure. \u003cem\u003eJ Mol Model\u003c/em\u003e 10;28(9):252. doi:10.1007/s00894-022-05252-2\u003c/li\u003e\n\u003cli\u003eFide E, Yerlikaya D, \u0026Ouml;z D, \u0026Ouml;ztura İ, Yener G (2023) Normalized Theta but Increased Gamma Activity after Acetylcholinesterase Inhibitor Treatment in Alzheimer\u0026apos;s Disease: Preliminary qEEG Study. \u003cem\u003eClin EEG Neurosci\u003c/em\u003e 54(3):305-315. doi:10.1177/15500594221120723\u003c/li\u003e\n\u003cli\u003eMartorana A, Koch G (2014) \u0026quot;Is dopamine involved in Alzheimer\u0026apos;s disease?\u0026quot;. \u003cem\u003eFront Aging Neurosci\u003c/em\u003e 6:252. doi:10.3389/fnagi.2014.00252\u003c/li\u003e\n\u003cli\u003eNobili A, Latagliata EC, Viscomi MT, et al (2017) Dopamine neuronal loss contributes to memory and reward dysfunction in a model of Alzheimer\u0026apos;s disease. \u003cem\u003eNat Commun\u003c/em\u003e 03;8:14727. doi:10.1038/ncomms14727\u003c/li\u003e\n\u003cli\u003eDavies P, Katzman R, Terry RD (1980) Reduced somatostatin-like immunoreactivity in cerebral cortex from cases of Alzheimer disease and Alzheimer senile dementa. \u003cem\u003eNature\u003c/em\u003e 20;288(5788):279-80. doi:10.1038/288279a0\u003c/li\u003e\n\u003cli\u003eGuennewig B, Lim J, Marshall L, et al (2021) Defining early changes in Alzheimer\u0026apos;s disease from RNA sequencing of brain regions differentially affected by pathology. \u003cem\u003eSci Rep\u003c/em\u003e. Mar 01;11(1):4865. doi:10.1038/s41598-021-83872-z\u003c/li\u003e\n\u003cli\u003eSadek B, Saad A, Sadeq A, Jalal F, Stark H (2016) Histamine H3 receptor as a potential target for cognitive symptoms in neuropsychiatric diseases. \u003cem\u003eBehav Brain Res\u003c/em\u003e 01;312:415-30. doi:10.1016/j.bbr.2016.06.051\u003c/li\u003e\n\u003cli\u003eChen JL, Zhang DL, Sun Y, et al (2017) Angiotensin-(1-7) administration attenuates Alzheimer\u0026apos;s disease-like neuropathology in rats with streptozotocin-induced diabetes via Mas receptor activation. \u003cem\u003eNeuroscience\u003c/em\u003e 27;346:267-277. doi:10.1016/j.neuroscience.2017.01.027\u003c/li\u003e\n\u003cli\u003eDuan R, Xue X, Zhang QQ, et al (2020) ACE2 activator diminazene aceturate ameliorates Alzheimer\u0026apos;s disease-like neuropathology and rescues cognitive impairment in SAMP8 mice. \u003cem\u003eAging (Albany NY)\u003c/em\u003e 23;12(14):14819-14829. doi:10.18632/aging.103544\u003c/li\u003e\n\u003cli\u003eMeng SX, Wang B, Li WT (2020) Serum expression of EAAT2 and ADORA2A in patients with different degrees of Alzheimer\u0026apos;s disease. \u003cem\u003eEur Rev Med Pharmacol Sci\u003c/em\u003e 24(22):11783-11792. doi:10.26355/eurrev_202011_23833\u003c/li\u003e\n\u003cli\u003eMerighi S, Battistello E, Casetta I, et al (2021) Upregulation of Cortical A2A Adenosine Receptors Is Reflected in Platelets of Patients with Alzheimer\u0026apos;s Disease. \u003cem\u003eJ Alzheimers Dis\u003c/em\u003e 80(3):1105-1117. doi:10.3233/JAD-201437\u003c/li\u003e\n\u003cli\u003eXu C, Liu G, Ji H, et al (2018) Elevated methylation of OPRM1 and OPRL1 genes in Alzheimer\u0026apos;s disease. \u003cem\u003eMol Med Rep\u003c/em\u003e 18(5):4297-4302. doi:10.3892/mmr.2018.9424\u003c/li\u003e\n\u003cli\u003eRath S, Sharma R, Gupta R, et al (2021) MitoCarta3.0: an updated mitochondrial proteome now with sub-organelle localization and pathway annotations. \u003cem\u003eNucleic Acids Res\u003c/em\u003e 08;49(D1):D1541-D1547. doi:10.1093/nar/gkaa1011\u003c/li\u003e\n\u003cli\u003eChithra Y, Dey G, Ghose V, et al (2023) Mitochondrial Complex I Inhibition in Dopaminergic Neurons Causes Altered Protein Profile and Protein Oxidation: Implications for Parkinson\u0026apos;s disease. \u003cem\u003eNeurochem Res\u003c/em\u003e 48(8):2360-2389. doi:10.1007/s11064-023-03907-x\u003c/li\u003e\n\u003cli\u003eSun Q, Shi L, Li S, et al (2023) PET117 assembly factor stabilizes translation activator TACO1 thereby upregulates mitochondria-encoded cytochrome C oxidase 1 synthesis. \u003cem\u003eFree Radic Biol Med\u003c/em\u003e 20;205:13-24. doi:10.1016/j.freeradbiomed.2023.05.023\u003c/li\u003e\n\u003cli\u003eMendsaikhan A, Takeuchi S, Walker DG, Tooyama I (2018) Differences in Gene Expression Profiles and Phenotypes of Differentiated SH-SY5Y Neurons Stably Overexpressing Mitochondrial Ferritin. \u003cem\u003eFront Mol Neurosci \u003c/em\u003e11:470. doi:10.3389/fnmol.2018.00470\u003c/li\u003e\n\u003cli\u003eLos\u0026oacute;n OC, Song Z, Chen H, Chan DC (2013) Fis1, Mff, MiD49, and MiD51 mediate Drp1 recruitment in mitochondrial fission. \u003cem\u003eMol Biol Cell\u003c/em\u003e 24(5):659-67. doi:10.1091/mbc.E12-10-0721\u003c/li\u003e\n\u003cli\u003eJeong SM, Xiao C, Finley LW, et al (2013) SIRT4 has tumor-suppressive activity and regulates the cellular metabolic response to DNA damage by inhibiting mitochondrial glutamine metabolism. \u003cem\u003eCancer Cell\u003c/em\u003e 15;23(4):450-63. doi:10.1016/j.ccr.2013.02.024\u003c/li\u003e\n\u003cli\u003ePacelli C, Adipietro I, Malerba N, et al (2020) Loss of Function of the Gene Encoding the Histone Methyltransferase KMT2D Leads to Deregulation of Mitochondrial Respiration. \u003cem\u003eCells\u003c/em\u003e 13;9(7)doi:10.3390/cells9071685\u003c/li\u003e\n\u003cli\u003eYamamoto-Imoto H, Minami S, Shioda T, et al (2022) Age-associated decline of MondoA drives cellular senescence through impaired autophagy and mitochondrial homeostasis. \u003cem\u003eCell Rep\u003c/em\u003e 01;38(9):110444. doi:10.1016/j.celrep.2022.110444\u003c/li\u003e\n\u003cli\u003eLi Y, Li J, Yuan Q, et al (2021) Deficiency in WDFY4 reduces the number of CD8. \u003cem\u003eMol Immunol\u003c/em\u003e 139:131-138. doi:10.1016/j.molimm.2021.08.022\u003c/li\u003e\n\u003cli\u003eEgles C, Claudepierre T, Manglapus MK, Champliaud MF, Brunken WJ, Hunter DD (2007) Laminins containing the beta2 chain modulate the precise organization of CNS synapses. \u003cem\u003eMol Cell Neurosci\u003c/em\u003e 34(3):288-98. doi:10.1016/j.mcn.2006.11.004\u003c/li\u003e\n\u003cli\u003eXie D, Gore C, Zhou J, et al (2009) DAB2IP coordinates both PI3K-Akt and ASK1 pathways for cell survival and apoptosis. \u003cem\u003eProc Natl Acad Sci U S A\u003c/em\u003e 24;106(47):19878-83. doi:10.1073/pnas.0908458106\u003c/li\u003e\n\u003cli\u003eImaizumi K, Benito A, Kiryu-Seo S, et al (2004) Critical role for DP5/Harakiri, a Bcl-2 homology domain 3-only Bcl-2 family member, in axotomy-induced neuronal cell death. \u003cem\u003eJ Neurosci\u003c/em\u003e 14;24(15):3721-5. doi:10.1523/JNEUROSCI.5101-03.2004\u003c/li\u003e\n\u003cli\u003eLuo K, Zhao X, Shan Y, et al (2023) GABA regulates the proliferation and apoptosis of head and neck squamous cell carcinoma cells by promoting the expression of CCND2 and BCL2L1. \u003cem\u003eLife Sci\u003c/em\u003e 20;334:122191. doi:10.1016/j.lfs.2023.122191\u003c/li\u003e\n\u003cli\u003eDixon SJ, Lemberg KM, Lamprecht MR, et al (2012) Ferroptosis: an iron-dependent form of nonapoptotic cell death. \u003cem\u003eCell\u003c/em\u003e 25;149(5):1060-72. doi:10.1016/j.cell.2012.03.042\u003c/li\u003e\n\u003cli\u003eBao WD, Pang P, Zhou XT, et al (2021) Loss of ferroportin induces memory impairment by promoting ferroptosis in Alzheimer\u0026apos;s disease. \u003cem\u003eCell Death Differ\u003c/em\u003e 28(5):1548-1562. doi:10.1038/s41418-020-00685-9\u003c/li\u003e\n\u003cli\u003eYang X, Fu Y, Hu F, Luo X, Hu J, Wang G (2018) PIK3R3 regulates PPAR\u0026alpha; expression to stimulate fatty acid \u0026beta;-oxidation and decrease hepatosteatosis. \u003cem\u003eExp Mol Med\u003c/em\u003e 19;50(1):e431. doi:10.1038/emm.2017.243\u003c/li\u003e\n\u003cli\u003eMcKenzie AT, Wang M, Hauberg ME, et al (2018) Brain Cell Type Specific Gene Expression and Co-expression Network Architectures. \u003cem\u003eSci Rep\u003c/em\u003e 11;8(1):8868. doi:10.1038/s41598-018-27293-5\u003c/li\u003e\n\u003cli\u003eDehmelt L, Halpain S (2005) The MAP2/Tau family of microtubule-associated proteins. \u003cem\u003eGenome Biol\u003c/em\u003e 6(1):204. doi:10.1186/gb-2004-6-1-204\u003c/li\u003e\n\u003cli\u003eFukushima H, Maeda R, Suzuki R, et al (2008) Upregulation of calcium/calmodulin-dependent protein kinase IV improves memory formation and rescues memory loss with aging. \u003cem\u003eJ Neurosci\u003c/em\u003e 01;28(40):9910-9. doi:10.1523/JNEUROSCI.2625-08.2008\u003c/li\u003e\n\u003cli\u003eDeng Y, Bi M, Delerue F, et al (2022) Loss of LAMP5 interneurons drives neuronal network dysfunction in Alzheimer\u0026apos;s disease. \u003cem\u003eActa Neuropathol\u003c/em\u003e 144(4):637-650. doi:10.1007/s00401-022-02457-w\u003c/li\u003e\n\u003cli\u003eHolden MR, Krzesinski BJ, Weismiller HA, Shady JR, Margittai M (2023) MAP2 caps tau fibrils and inhibits aggregation. \u003cem\u003eJ Biol Chem\u003c/em\u003e 299(7):104891. doi:10.1016/j.jbc.2023.104891\u003c/li\u003e\n\u003cli\u003eCaporaso GL, Bibb JA, Snyder GL, et al (2000) Drugs of abuse modulate the phosphorylation of ARPP-21, a cyclic AMP-regulated phosphoprotein enriched in the basal ganglia. \u003cem\u003eNeuropharmacology\u003c/em\u003e 10;39(9):1637-44. doi:10.1016/s0028-3908(99)00230-0\u003c/li\u003e\n\u003cli\u003eTan YX, Hong Y, Jiang S, et al (2020) MicroRNA‑449a regulates the progression of brain aging by targeting SCN2B in SAMP8 mice. \u003cem\u003eInt J Mol Med\u003c/em\u003e 45(4):1091-1102. doi:10.3892/ijmm.2020.4502\u003c/li\u003e\n\u003cli\u003eQian Q, Liu Q, Zhou D, et al (2017) Brain-specific ablation of Efr3a promotes adult hippocampal neurogenesis. \u003cem\u003eFASEB J\u003c/em\u003e 31(5):2104-2113. doi:10.1096/fj.201601207R\u003c/li\u003e\n\u003cli\u003eKatsumata Y, Fardo DW, Bachstetter AD, et al (2020) Alzheimer Disease Pathology-Associated Polymorphism in a Complex Variable Number of Tandem Repeat Region Within the MUC6 Gene, Near the AP2A2 Gene. \u003cem\u003eJ Neuropathol Exp Neurol\u003c/em\u003e 01;79(1):3-21. doi:10.1093/jnen/nlz116\u003c/li\u003e\n\u003cli\u003eBottemanne P, Guillemot-Legris O, Paquot A, et al (2021) N-Acylethanolamine-Hydrolyzing Acid Amidase Inhibition, but Not Fatty Acid Amide Hydrolase Inhibition, Prevents the Development of Experimental Autoimmune Encephalomyelitis in Mice. \u003cem\u003eNeurotherapeutics\u003c/em\u003e 18(3):1815-1833. doi:10.1007/s13311-021-01074-x\u003c/li\u003e\n\u003cli\u003eAronica E, Gorter JA, Ijlst-Keizers H, et al (2003) Expression and functional role of mGluR3 and mGluR5 in human astrocytes and glioma cells: opposite regulation of glutamate transporter proteins. \u003cem\u003eEur J Neurosci\u003c/em\u003e 17(10):2106-18. doi:10.1046/j.1460-9568.2003.02657.x\u003c/li\u003e\n\u003cli\u003eZhou Y, Danbolt NC (2013) GABA and Glutamate Transporters in Brain. \u003cem\u003eFront Endocrinol (Lausanne)\u003c/em\u003e 4:165. doi:10.3389/fendo.2013.00165\u003c/li\u003e\n\u003cli\u003ePereira JB, Janelidze S, Smith R, et al (2021) Plasma GFAP is an early marker of amyloid-\u0026beta; but not tau pathology in Alzheimer\u0026apos;s disease. \u003cem\u003eBrain\u003c/em\u003e 16;144(11):3505-3516. doi:10.1093/brain/awab223\u003c/li\u003e\n\u003cli\u003eKim KY, Shin KY, Chang KA (2023) GFAP as a Potential Biomarker for Alzheimer\u0026apos;s Disease: A Systematic Review and Meta-Analysis. \u003cem\u003eCells\u003c/em\u003e 04;12(9)doi:10.3390/cells12091309\u003c/li\u003e\n\u003cli\u003eZhang X, Feng Y, Li J, et al (2020) MicroRNA-665-3p attenuates oxygen-glucose deprivation-evoked microglial cell apoptosis and inflammatory response by inhibiting NF-\u0026kappa;B signaling via targeting TRIM8. \u003cem\u003eInt Immunopharmacol\u003c/em\u003e 85:106650. doi:10.1016/j.intimp.2020.106650\u003c/li\u003e\n\u003cli\u003eBiber K, M\u0026ouml;ller T, Boddeke E, Prinz M (2016) Central nervous system myeloid cells as drug targets: current status and translational challenges. \u003cem\u003eNat Rev Drug Discov\u003c/em\u003e 15(2):110-24. doi:10.1038/nrd.2015.14\u003c/li\u003e\n\u003cli\u003eHansen DV, Hanson JE, Sheng M (2018) Microglia in Alzheimer\u0026apos;s disease. \u003cem\u003eJ Cell Biol\u003c/em\u003e 05;217(2):459-472. doi:10.1083/jcb.201709069\u003c/li\u003e\n\u003cli\u003eWatanabe N, Kageyama R, Ohtsuka T (2015) Hbp1 regulates the timing of neuronal differentiation during cortical development by controlling cell cycle progression. \u003cem\u003eDevelopment\u003c/em\u003e 01;142(13):2278-90. doi:10.1242/dev.120477\u003c/li\u003e\n\u003cli\u003eChan JCY, Gorski SM (2022) Unlocking the gate to GABARAPL2. \u003cem\u003eBiol Futur\u003c/em\u003e 73(2):157-169. doi:10.1007/s42977-022-00119-2\u003c/li\u003e\n\u003cli\u003eCai Z, Xiao M (2016) Oligodendrocytes and Alzheimer\u0026apos;s disease. \u003cem\u003eInt J Neurosci\u003c/em\u003e 126(2):97-104. doi:10.3109/00207454.2015.1025778\u003c/li\u003e\n\u003cli\u003eChen JF, Liu K, Hu B, et al (2021) Enhancing myelin renewal reverses cognitive dysfunction in a murine model of Alzheimer\u0026apos;s disease. \u003cem\u003eNeuron\u003c/em\u003e 21;109(14):2292-2307.e5. doi:10.1016/j.neuron.2021.05.012\u003c/li\u003e\n\u003cli\u003eHendriksen H, Korte SM, Olivier B, Oosting RS (2015) The olfactory bulbectomy model in mice and rat: one story or two tails? \u003cem\u003eEur J Pharmacol\u003c/em\u003e 15;753:105-13. doi:10.1016/j.ejphar.2014.10.033\u003c/li\u003e\n\u003cli\u003eMorales-Medina JC, Iannitti T, Freeman A, Caldwell HK (2017) The olfactory bulbectomized rat as a model of depression: The hippocampal pathway. \u003cem\u003eBehav Brain Res\u003c/em\u003e 15;317:562-575. doi:10.1016/j.bbr.2016.09.029\u003c/li\u003e\n\u003cli\u003ePandi-Perumal SR, Monti JM, Burman D, et al (2020) Clarifying the role of sleep in depression: A narrative review. \u003cem\u003ePsychiatry Res\u003c/em\u003e 291:113239. doi:10.1016/j.psychres.2020.113239\u003c/li\u003e\n\u003cli\u003eUddin MS, Tewari D, Mamun AA, et al (2020) Circadian and sleep dysfunction in Alzheimer\u0026apos;s disease. \u003cem\u003eAgeing Res Rev\u003c/em\u003e 60:101046. doi:10.1016/j.arr.2020.101046\u003c/li\u003e\n\u003cli\u003eKishi T, Yoshimura R, Fukuo Y, et al (2013) The serotonin 1A receptor gene confer susceptibility to mood disorders: results from an extended meta-analysis of patients with major depression and bipolar disorder. \u003cem\u003eEur Arch Psychiatry Clin Neurosci\u003c/em\u003e 263(2):105-18. doi:10.1007/s00406-012-0337-4\u003c/li\u003e\n\u003cli\u003eSekiya I, Tsuji K, Koopman P, et al (2000) SOX9 enhances aggrecan gene promoter/enhancer activity and is up-regulated by retinoic acid in a cartilage-derived cell line, TC6. \u003cem\u003eJ Biol Chem\u003c/em\u003e 14;275(15):10738-44. doi:10.1074/jbc.275.15.10738\u003c/li\u003e\n\u003cli\u003eWang M, Li A, Sekiya M, et al (2019) Molecular networks and key regulators of the dysregulated neuronal system in Alzheimer\u0026rsquo;s disease. \u003cem\u003ebioRxiv\u003c/em\u003e 788323. \u003c/li\u003e\n\u003cli\u003eHook V, Schechter I, Demuth HU, Hook G (2008) Alternative pathways for production of beta-amyloid peptides of Alzheimer\u0026apos;s disease. \u003cem\u003eBiol Chem\u003c/em\u003e 389(8):993-1006. doi:10.1515/BC.2008.124\u003c/li\u003e\n\u003cli\u003eReiss AB, Arain HA, Stecker MM, Siegart NM, Kasselman LJ (2018) Amyloid toxicity in Alzheimer\u0026apos;s disease. \u003cem\u003eRev Neurosci\u003c/em\u003e 28;29(6):613-627. doi:10.1515/revneuro-2017-0063\u003c/li\u003e\n\u003cli\u003eBobkova N, Vorobyov V (2015) The brain compensatory mechanisms and Alzheimer\u0026apos;s disease progression: a new protective strategy. \u003cem\u003eNeural Regen Res\u003c/em\u003e 10(5):696-7. doi:10.4103/1673-5374.156954\u003c/li\u003e\n\u003cli\u003eSharma VK, Singh TG, Singh S, Garg N, Dhiman S (2021) Apoptotic Pathways and Alzheimer\u0026apos;s Disease: Probing Therapeutic Potential. \u003cem\u003eNeurochem Res\u003c/em\u003e 46(12):3103-3122. doi:10.1007/s11064-021-03418-7\u003c/li\u003e\n\u003cli\u003eMarks N, Berg MJ, Guidotti A, Saito M (1998) Activation of caspase-3 and apoptosis in cerebellar granule cells. \u003cem\u003eJ Neurosci Res\u003c/em\u003e 01;52(3):334-41. doi:10.1002/(SICI)1097-4547(19980501)52:3\u0026lt;334::AID-JNR9\u0026gt;3.0.CO;2-E\u003c/li\u003e\n\u003cli\u003eZou H, Li Y, Liu X, Wang X (1999) An APAF-1.cytochrome c multimeric complex is a functional apoptosome that activates procaspase-9. \u003cem\u003eJ Biol Chem\u003c/em\u003e 23;274(17):11549-56. doi:10.1074/jbc.274.17.11549\u003c/li\u003e\n\u003cli\u003eYant LJ, Ran Q, Rao L, et al (2003) The selenoprotein GPX4 is essential for mouse development and protects from radiation and oxidative damage insults. \u003cem\u003eFree Radic Biol Med\u003c/em\u003e 15;34(4):496-502. doi:10.1016/s0891-5849(02)01360-6\u003c/li\u003e\n\u003cli\u003eYang WS, SriRamaratnam R, Welsch ME, et al (2014) Regulation of ferroptotic cancer cell death by GPX4. \u003cem\u003eCell\u003c/em\u003e 16;156(1-2):317-331. doi:10.1016/j.cell.2013.12.010\u003c/li\u003e\n\u003cli\u003eWang Y, Lv MN, Zhao WJ (2023) Research on ferroptosis as a therapeutic target for the treatment of neurodegenerative diseases. \u003cem\u003eAgeing Res Rev\u003c/em\u003e 91:102035. doi:10.1016/j.arr.2023.102035\u003c/li\u003e\n\u003cli\u003eMira RG, Cerpa W (2021) Building a Bridge Between NMDAR-Mediated Excitotoxicity and Mitochondrial Dysfunction in Chronic and Acute Diseases. \u003cem\u003eCell Mol Neurobiol\u003c/em\u003e 41(7):1413-1430. doi:10.1007/s10571-020-00924-0\u003c/li\u003e\n\u003cli\u003eCox MF, Hascup ER, Bartke A, Hascup KN (2022) Friend or Foe? Defining the Role of Glutamate in Aging and Alzheimer\u0026apos;s Disease. \u003cem\u003eFront Aging\u003c/em\u003e 3:929474. doi:10.3389/fragi.2022.929474\u003c/li\u003e\n\u003cli\u003eBi D, Wen L, Wu Z, Shen Y (2020) GABAergic dysfunction in excitatory and inhibitory (E/I) imbalance drives the pathogenesis of Alzheimer\u0026apos;s disease. \u003cem\u003eAlzheimers Dement\u003c/em\u003e 16(9):1312-1329. doi:10.1002/alz.12088\u003c/li\u003e\n\u003cli\u003eWang R, Reddy PH (2017) Role of Glutamate and NMDA Receptors in Alzheimer\u0026apos;s Disease. \u003cem\u003eJ Alzheimers Dis\u003c/em\u003e 57(4):1041-1048. doi:10.3233/JAD-160763\u003c/li\u003e\n\u003cli\u003eBartus RT, Dean RL, Beer B, Lippa AS (1982) The cholinergic hypothesis of geriatric memory dysfunction. \u003cem\u003eScience\u003c/em\u003e 30;217(4558):408-14. doi:10.1126/science.7046051\u003c/li\u003e\n\u003cli\u003eChen XQ, Mobley WC (2019) Exploring the Pathogenesis of Alzheimer Disease in Basal Forebrain Cholinergic Neurons: Converging Insights From Alternative Hypotheses. \u003cem\u003eFront Neurosci\u003c/em\u003e13:446. doi:10.3389/fnins.2019.00446\u003c/li\u003e\n\u003cli\u003eReale M, Carrarini C, Russo M, et al (2022) Muscarinic Receptors Expression in the Peripheral Blood Cells Differentiate Dementia with Lewy Bodies from Alzheimer\u0026apos;s Disease. \u003cem\u003eJ Alzheimers Dis\u003c/em\u003e 85(1):323-330. doi:10.3233/JAD-215285\u003c/li\u003e\n\u003cli\u003eAhmad S, Gul N, Ahmad M, et al (2022) Isolation, crystal structure, DFT calculation and molecular docking of uncinatine-A isolated from Delphinium uncinatum. \u003cem\u003eFitoterapia\u003c/em\u003e 162:105268. doi:10.1016/j.fitote.2022.105268\u003c/li\u003e\n\u003cli\u003eBobkova NV, Nesterova IV, Nesterov VV (2001) The state of cholinergic structures in forebrain of bulbectomized mice. \u003cem\u003eBull Exp Biol Med\u003c/em\u003e 131(5):427-31. doi:10.1023/a:1017907511482\u003c/li\u003e\n\u003cli\u003eGloria Y, Ceyz\u0026eacute;riat K, Tsartsalis S, Millet P, Tournier BB (2021) Dopaminergic dysfunction in the 3xTg-AD mice model of Alzheimer\u0026apos;s disease. \u003cem\u003eSci Rep\u003c/em\u003e 30;11(1):19412. doi:10.1038/s41598-021-99025-1\u003c/li\u003e\n\u003cli\u003eSwerdlow RH, Burns JM, Khan SM (2014) The Alzheimer\u0026apos;s disease mitochondrial cascade hypothesis: progress and perspectives. \u003cem\u003eBiochim Biophys Acta\u003c/em\u003e 1842(8):1219-31. doi:10.1016/j.bbadis.2013.09.010\u003c/li\u003e\n\u003cli\u003eSukhorukov VS, Mudzhiri NM, Voronkova AS, Baranich TI, Glinkina VV, Illarioshkin SN (2021) Mitochondrial Disorders in Alzheimer\u0026apos;s Disease. \u003cem\u003eBiochemistry (Mosc)\u003c/em\u003e 86(6):667-679. doi:10.1134/S0006297921060055\u003c/li\u003e\n\u003cli\u003eCabezas-Opazo FA, Vergara-Pulgar K, P\u0026eacute;rez MJ, Jara C, Osorio-Fuentealba C, Quintanilla RA (2015) Mitochondrial Dysfunction Contributes to the Pathogenesis of Alzheimer\u0026apos;s Disease. \u003cem\u003eOxid Med Cell Longev\u003c/em\u003e 2015:509654. doi:10.1155/2015/509654\u003c/li\u003e\n\u003cli\u003eAksenov MY, Tucker HM, Nair P, et al (1999) The expression of several mitochondrial and nuclear genes encoding the subunits of electron transport chain enzyme complexes, cytochrome c oxidase, and NADH dehydrogenase, in different brain regions in Alzheimer\u0026apos;s disease. \u003cem\u003eNeurochem Res\u003c/em\u003e 24(6):767-74. doi:10.1023/a:1020783614031\u003c/li\u003e\n\u003cli\u003eMaurer I, Zierz S, M\u0026ouml;ller HJ (2000) A selective defect of cytochrome c oxidase is present in brain of Alzheimer disease patients. \u003cem\u003eNeurobiol Aging\u003c/em\u003e 21(3):455-62. doi:10.1016/s0197-4580(00)00112-3\u003c/li\u003e\n\u003cli\u003eOhta S, Ohsawa I (2006) Dysfunction of mitochondria and oxidative stress in the pathogenesis of Alzheimer\u0026apos;s disease: on defects in the cytochrome c oxidase complex and aldehyde detoxification. \u003cem\u003eJ Alzheimers Dis\u003c/em\u003e 9(2):155-66. doi:10.3233/jad-2006-9208\u003c/li\u003e\n\u003cli\u003eBobkova NV, Zhdanova DY, Belosludtseva NV, Penkov NV, Mironova GD (2022) Intranasal administration of mitochondria improves spatial memory in olfactory bulbectomized mice. \u003cem\u003eExp Biol Med (Maywood)\u003c/em\u003e 247(5):416-425. doi:10.1177/15353702211056866\u003c/li\u003e\n\u003cli\u003eFisher DW, Dunn JT, Keszycki R, et al (2023) Unique Transcriptional Signatures Correlate with Behavioral and Psychological Symptom Domains in Alzheimer\u0026apos;s Disease. \u003cem\u003eRes Sq\u003c/em\u003e 11;doi:10.21203/rs.3.rs-2444391/v1\u003c/li\u003e\n\u003cli\u003eBrandebura AN, Paumier A, Onur TS, Allen NJ (2023) Astrocyte contribution to dysfunction, risk and progression in neurodegenerative disorders. \u003cem\u003eNat Rev Neurosci\u003c/em\u003e 24(1):23-39. doi:10.1038/s41583-022-00641-1\u003c/li\u003e\n\u003cli\u003eRothlin CV, Ghosh S, Zuniga EI, Oldstone MB, Lemke G (2007) TAM receptors are pleiotropic inhibitors of the innate immune response. \u003cem\u003eCell\u003c/em\u003e 14;131(6):1124-36. doi:10.1016/j.cell.2007.10.034\u003c/li\u003e\n\u003cli\u003eHerrera-Rivero M, Santarelli F, Brosseron F, Kummer MP, Heneka MT (2019) Dysregulation of TLR5 and TAM Ligands in the Alzheimer\u0026apos;s Brain as Contributors to Disease Progression. \u003cem\u003eMol Neurobiol\u003c/em\u003e 56(9):6539-6550. doi:10.1007/s12035-019-1540-3\u003c/li\u003e\n\u003cli\u003eHickman S, Izzy S, Sen P, Morsett L, El Khoury J (2018) Microglia in neurodegeneration. \u003cem\u003eNat Neurosci\u003c/em\u003e 21(10):1359-1369. doi:10.1038/s41593-018-0242-x\u003c/li\u003e\n\u003cli\u003eH\u0026auml;rtlova A, Erttmann SF, Raffi FA, et al (2015) DNA damage primes the type I interferon system via the cytosolic DNA sensor STING to promote anti-microbial innate immunity. \u003cem\u003eImmunity\u003c/em\u003e 17;42(2):332-343. doi:10.1016/j.immuni.2015.01.012\u003c/li\u003e\n\u003cli\u003eBaytas O, Kauer JA, Morrow EM (2022) Loss of mitochondrial enzyme GPT2 causes early neurodegeneration in locus coeruleus. \u003cem\u003eNeurobiol Dis\u003c/em\u003e 15;173:105831. doi:10.1016/j.nbd.2022.105831\u003c/li\u003e\n\u003cli\u003eGebre AK, Altaye BM, Atey TM, Tuem KB, Berhe DF (2018) Targeting Renin-Angiotensin System Against Alzheimer\u0026apos;s Disease. \u003cem\u003eFront Pharmacol\u003c/em\u003e 9:440. doi:10.3389/fphar.2018.00440\u003c/li\u003e\n\u003cli\u003eGouveia F, Camins A, Ettcheto M, et al (2022) Targeting brain Renin-Angiotensin System for the prevention and treatment of Alzheimer\u0026apos;s disease: Past, present and future. \u003cem\u003eAgeing Res Rev\u003c/em\u003e 77:101612. doi:10.1016/j.arr.2022.101612\u003c/li\u003e\n\u003cli\u003eHynninen MJ, Breitve MH, Rongve A, Aarsland D, Nordhus IH (2012) The frequency and correlates of anxiety in patients with first-time diagnosed mild dementia. \u003cem\u003eInt Psychogeriatr\u003c/em\u003e 24(11):1771-8. doi:10.1017/S1041610212001020\u003c/li\u003e\n\u003cli\u003eZubenko GS, Zubenko WN, McPherson S, et al (2003) A collaborative study of the emergence and clinical features of the major depressive syndrome of Alzheimer\u0026apos;s disease. \u003cem\u003eAm J Psychiatry\u003c/em\u003e 160(5):857-66. doi:10.1176/appi.ajp.160.5.857\u003c/li\u003e\n\u003cli\u003eBrommelhoff JA, Gatz M, Johansson B, McArdle JJ, Fratiglioni L, Pedersen NL (2009) Depression as a risk factor or prodromal feature for dementia? Findings in a population-based sample of Swedish twins. \u003cem\u003ePsychol Aging\u003c/em\u003e 24(2):373-84. doi:10.1037/a0015713\u003c/li\u003e\n\u003cli\u003eBotto R, Callai N, Cermelli A, Causarano L, Rainero I (2022) Anxiety and depression in Alzheimer\u0026apos;s disease: a systematic review of pathogenetic mechanisms and relation to cognitive decline. \u003cem\u003eNeurol Sci\u003c/em\u003e 43(7):4107-4124. doi:10.1007/s10072-022-06068-x\u003c/li\u003e\n\u003cli\u003eGass N, Ollila HM, Utge S, et al (2010) Contribution of adenosine related genes to the risk of depression with disturbed sleep. \u003cem\u003eJ Affect Disord\u003c/em\u003e 126(1-2):134-9. doi:10.1016/j.jad.2010.03.009\u003c/li\u003e\n\u003cli\u003eOliveira S, Ardais AP, Bastos CR, et al (2019) Impact of genetic variations in ADORA2A gene on depression and symptoms: a cross-sectional population-based study. \u003cem\u003ePurinergic Signal\u003c/em\u003e 15(1):37-44. doi:10.1007/s11302-018-9635-2\u003c/li\u003e\n\u003cli\u003eMadeira D, Domingues J, Lopes CR, Canas PM, Cunha RA, Agostinho P (2023) Modification of astrocytic Cx43 hemichannel activity in animal models of AD: modulation by adenosine A. \u003cem\u003eCell Mol Life Sci\u003c/em\u003e 29;80(11):340. doi:10.1007/s00018-023-04983-6\u003c/li\u003e\n\u003cli\u003eMart\u0026iacute;n-S\u0026aacute;nchez A, Pi\u0026ntilde;ero J, Nonell L, et al (2021) Comorbidity between Alzheimer\u0026apos;s disease and major depression: a behavioural and transcriptomic characterization study in mice. \u003cem\u003eAlzheimers Res Ther\u003c/em\u003e 02;13(1):73. doi:10.1186/s13195-021-00810-x\u003c/li\u003e\n\u003cli\u003eYurttas C, Schmitz C, Turgut M, Strekalova T, Steinbusch HWM (2017) The olfactory bulbectomized rat model is not an appropriate model for studying depression based on morphological/stereological studies of the hippocampus. \u003cem\u003eBrain Res Bull\u003c/em\u003e 134:128-135. doi:10.1016/j.brainresbull.2017.07.010\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"molecular-neurobiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"moln","sideBox":"Learn more about [Molecular Neurobiology](https://www.springer.com/journal/12035)","snPcode":"12035","submissionUrl":"https://submission.nature.com/new-submission/12035/3","title":"Molecular Neurobiology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"bulbectomized mice, Alzheimer's disease, depression, transcriptomic analysis","lastPublishedDoi":"10.21203/rs.3.rs-3781115/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3781115/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAnimals after bulbectomy are often used as a model of major depression or sporadicAlzheimer’s disease and, hence, the status of this model is still disputable.\u003cstrong\u003e \u003c/strong\u003eTo elucidate the nature of alterations in the expression of the genome after the operation we analyzed transcriptomes (RNA-seq data) of the cortex, hippocampus, and cerebellum of olfactory bulbectomized (OBX) mice. Analysis of the functional significance of genes in the brain of OBX mice indicates that the balance of the GABA/glutamatergic systems is disturbed with hyperactivation of the latter in the hippocampus leading to the development of excitotoxicity and induction of apoptosis on the background of severe mitochondrial dysfunction and astrogliosis. On top of this, the synthesis of neurotrophic factors decreases leading to the disruption of the cytoskeleton of neurons, an increase in the level of intracellular calcium, and activation of tau protein hyperphosphorylation and beta-amyloid depositions. Moreover, the acetylcholinergic system is deficient in the background of hyperactivation of acetylcholinesterase. Importantly, the activity of the dopaminergic, endorphin, and opiate systems in OBX mice decreases leading to hormonal dysfunction. Genes responsible for the regulation of circadian rhythms, cell migration, and impaired innate immunity are activated in OBX animals. All this takes place on the background of drastic down-regulation of ribosomal protein genes in the brain. The obtained results indicate that OBX mice represent a model of Alzheimer's disease with elements of major depression. This model can be tentatively attributed to AD subtype B2 in humans.\u003c/p\u003e","manuscriptTitle":"A mouse model of sporadic Alzheimer’s disease with elements of major depression","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-01-04 09:30:46","doi":"10.21203/rs.3.rs-3781115/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2024-02-13T04:05:38+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2024-01-19T08:47:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"52759683-4d29-4ddc-a309-9c3643d36f2b","date":"2024-01-06T19:27:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-01-06T17:06:37+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-01-03T08:17:20+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2024-01-03T08:17:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Molecular Neurobiology","date":"2023-12-20T09:40:10+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"molecular-neurobiology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"moln","sideBox":"Learn more about [Molecular Neurobiology](https://www.springer.com/journal/12035)","snPcode":"12035","submissionUrl":"https://submission.nature.com/new-submission/12035/3","title":"Molecular Neurobiology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"8ced0050-461b-436d-b465-625a53f28306","owner":[],"postedDate":"January 4th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2024-07-02T19:22:35+00:00","versionOfRecord":[],"versionCreatedAt":"2024-01-04 09:30:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3781115","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3781115","identity":"rs-3781115","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}