A Compound Enhancing Lysosomal Function Reduces Tau Pathology, Microglial Reactivity and Rescues Working Memory in 3xTg AD Mice

Background Recent advancements in Alzheimer’s disease (AD) therapeutics have validated the use of amyloid beta (Aβ)-clearing antibodies, which reduce Aβ pathology but leave other disease hallmarks largely unaddressed. Since AD involves multiple pathological processes, additional strategies are needed to target complementary mechanisms. One such target is autophagy, a lysosomal mediated degradation pathway essential for cellular homeostasis that removes toxic protein aggregates and damaged organelles. This process is implicated in AD, as impaired lysosomal function promotes Aβ and tau accumulation. Our laboratory recently identified a novel natural mitophagy-inducing compound (MIC) that may serve as a therapeutic intervention for AD.

We evaluated the effects of MIC in aged 3xTgAD mice, a transgenic model displaying both Aβ and tau pathology. Mice received either standard diet or diet containing MIC beginning at age 4 months until 20 months on alternating weeks. Age-matched non-transgenic (NonTg) controls were included under standard and MIC-supplemented diets to assess compound effects during normal aging. Neuropathological changes were assessed using immunohistochemistry (IHC) for Aβ, phosphorylated tau (pTau), and microglial reactivity. Cognitive performance was evaluated using the Morris Water Maze (MWM) to assess spatial learning and memory and the Y-maze to measure working memory.

At 20 months of age, our neuropathological assessment showed that 3xTgAD mice fed an MIC-supplemented diet had a significant reduction in pTau accumulation and microglial reactivity, although Aβ burden remained unchanged. At 15 months, MIC diet also improved spatial learning and memory in aged NonTg controls but not in 3xTgAD mice. However, in younger 8-month-old 3xTgAD mice, MIC restored working memory performance to NonTg levels, indicating an age-dependent therapeutic response.

MIC emerges as a potential modulator of tau pathology and neuroinflammation. As a naturally derived compound, MIC offers potential for combination therapy with FDA-approved Aβ-clearing antibodies, enabling a multimodal approach to AD treatment that addresses amyloid, tau, and microglia-related pathology. Competing Interest Statement The authors have declared no competing interest. Footnotes Four citations were not working correctly, because they were not registered by the ctitation tool, and were not listed in the references as a result. I have corrected this. They now appear in the references as intended. We also adjusted the title from the last version to "A Compound Enhancing Lysosomal Function Reduces Tau Pathology, Microglial Reactivity, and Restores Working Memory in 3xTg AD Mice" Data Availability The datasets used and/or analyzed during this study are available from the corresponding author upon reasonable request. Abbreviations - 3xTg AD - Triple-transgenic Alzheimer’s disease mouse model - AD - Alzheimer’s disease - ADRDs - Alzheimer’s disease and related dementias - Aβ - Amyloid-beta - pTau - Phosphorylated tau - NFTs - Neurofibrillary tangles - APP - Amyloid precursor protein - PSEN1/2 - Presenilin 1/2 genes - TFEB - Transcription Factor EB - ALP - Autophagy-lysosomal pathway - NonTg - Non-transgenic (control) mice - IHC - Immunohistochemistry - MIC - Mitophagy-Inducing Compound - MWM - Morris Water Maze - Y-maze - Behavioral test for working memory - CTRL - Control diet - Iba1 - Ionized calcium-binding adaptor molecule 1 (microglial marker) - DAPI - 4’,6-diamidino-2-phenylindole (nuclear stain) - PBS - Phosphate-buffered saline - TBS - Tris-buffered saline - NDS - Normal donkey serum - ROI - Region of interest - PHFs - Paired helical filaments - ASO - Antisense oligonucleotide - UA - Urolithin A - IACUC - Institutional Animal Care and Use Committee - OCT - Optimal Cutting Temperature compound - RRID - Research Resource Identifier - SEM - Standard error of the mean - ANOVA - Analysis of variance