The Role of Ferroptosis in Women's Health and Diseases.

Qiang Xu, Chongying Zhu, and Lin Li wrote the original manuscript. Qiang Xu, Jiayong Li, and Zihao An prepared the figures and tables. Chao Tang designed and edited the manuscript. All authors have read and approved the final manuscript.

Not applicable.

Ferroptosis is usually accompanied by iron overload and accumulation of phospholipid hydroperoxides (PLOOHs) [ 15 , 16 ], and plays a key role in ferroptosis‐induced programmed death as the initiator of downstream cascades [ 17 ]. Polyunsaturated fatty acids (PUFAs), especially arachidonic acid and adrenal acid, are lipoylated by acyl‐CoA synthetase long‐chain family member 4 (ACSL4) and lipoxygenase through the lipoxygenase pathway [ 18 , 19 , 20 ], and are subsequently fixed on the membrane phospholipids to form polyunsaturated fatty acids (PUFA‐PLs) [ 21 ]. Free Fe 2+ can catalyze membrane high expression of PUFA‐PLs with molecular oxygen in the Fenton reaction, electron transfer to hydrogen peroxide and oxygen free radicals, leading to reactive oxygen species and decomposition products of lipid peroxides such as 4‐hydroxynonenal (4‐HNE) and malondialdehyde (MDA) accumulation [ 22 , 23 ]. Ferroptosis is the result of the imbalance of the cellular redox system and lipid oxide metabolism disorders, which leads to the impairment of the intracellular antioxidant clearance mechanism through a variety of ways, and the accumulation of specific lipid ROS, resulting in irreparable damage to the cell membrane and further cell death [ 24 , 25 ]. Ferroptosis is divided into classical signaling pathways and nonclassical signaling pathways, and there are many key regulatory molecules in these processes, including GPX4, System Xc‐, ACSL4, etc. [ 18 , 19 , 20 ]. We herein elaborate on the role and significance of each regulatory molecule by describing the mechanism. The typical regulatory pathways are the exogenous pathway with the transporter as the core and the endogenous pathway mediated by GPX4 [ 26 ]. Ferroptosis is characterized by impairment of intracellular antioxidant defenses, accompanied by decreased glutathione cycling and decreased activity of the core antioxidant enzyme GPX4. The cystine/glutamate antiporter system (System Xc) is distributed in the cell membrane. As the main subunit of System Xc, Solute carrier protein 7 family member 11(SLC7A11) mediates the exchange of glutamate and cystine and provides an active substrate for the synthesis of reduced glutathione (GSH) [ 27 ]. GPX4 reduces phospholipid peroxide PLOOHs by consuming GSH, inhibits the activation of arachidonic acid metabolic enzymes in microsomal lipid peroxidation and phospholipid peroxidation pathway, and is the only antioxidant enzyme that directly clears phospholipid peroxides in cells [ 28 ]. When GSH is in short supply, it directly affects the function of GPX4 [29]. Cysteine, glutamine metabolism, and some small molecule compounds, such as Erastin and Sorafenib, lead to the depletion of intracellular GSH cycle, the accumulation of oxidative GSH, and the inactivation of GPX4 by inhibiting the activity of the cell membrane transport carrier System Xc, and then increase the toxicity of lipid hydroperoxides and trigger ferroptosis [ 29 , 30 , 31 ]. Recently, the tetrahydrobiopterin (BH4) pathway has been reported as a compensatory mechanism for the GPX4 ‐deficient enzyme catalytic system [ 32 ]. Kraft et al. reported that BH4 can inhibit ferroptosis by producing CoQ10 or blocking the production of specific lipid hydroperoxide, and guanosine triphosphate cyclohydrolase 1 (GCH1) acts as the rate‐limiting step of BH4 production to dynamically regulate ferroptosis [ 33 ]. In particular, an antioxidant defense mechanism parallel to the mitochondrial GPX4 pathway is proposed [ 34 ]: dihydroorotate dehydrogenase (DHODH) is located on the inner mitochondrial membrane surface and catalyzes the generation and metabolism of pyrimidine nucleotides. DHODH acts enzymatically to oxidize dihydroorotate while transferring electrons to CoQ10 and reducing them to free radicals to capture the antioxidant CoQH2, regulating the sensitivity of cells to GPX4 inhibitors and further attenuating the mitochondrial lipid peroxidation and ferroptosis cascade mediated by GPX4 inactivation. The above outcome illustrates that DHODH plays a regulatory role as a background‐dependent antioxidant defense mechanism within the cell. In addition, studies have reported that ferroptosis suppressor protein 1 (FSP1) has an antiferroptosis effect after being modified by myristate [ 35 , 36 ]. FSP1 is mainly localized in the cell membrane and lipid droplets, where it uses nicotinamide adenine dinucleotide phosphate (NADPH) to catalyze the production of mitochondrial electron transport chain coenzyme ubiquinone (CoQ10), In its reduced form, ubiquinol (CoQH2) traps lipid peroxy radicals and terminates the lipid peroxidation process [ 37 , 38 ]. However, this ferroptosis inhibitor effect is independent of GSH level, GPX4 activity, or oxidizable fatty acid content, suggesting that the FSP1‐CoQ10‐NADPH pathway, as an independent and parallel pathway, plays an essential role in maintaining phospholipid redox homeostasis [ 36 ]. With the development of research, the mechanism of iron‐dependent lipid peroxidation in cells, including mitochondria, has been gradually revealed. Intracellular ferroptosis‐related non‐GPX4 pathways, including FSP1‐CoQ10, GCH1‐BH4, and DHODH‐CoQ10 pathways, and the typical enzymatic System with System Xc‐GSH‐GPX4 as the core, together regulate the balance between oxidative damage and antioxidant defense during ferroptosis. Ferroptosis is the intersection of multiple metabolic pathways in cells. Amino acid metabolism, lipid metabolism, iron metabolism, and other metabolic pathways regulate the sensitivity of cells to ferroptosis (Figure 1 ). A brief overview of ferroptosis and two pathways to inhibit ferroptosis. The schematic shows that ferroptosis is performed by phospholipid peroxidation, a process that depends on ROS, PUFAs, PUFA‐PLs, and Fe 2+ , among others. GPX4‐mediated ferroptosis pathway is mainly mediated by GPX4‐mediated GSH/GSSG interaction and PL‐OOH reduction to produce the corresponding P‐LOH. The GPX4‐independent ferroptosis pathway is mainly involved in the FSP1/CoQ10/NADPH axis and the GCH1/BH4 axis, in addition to mitochondrial DHODH/CoQ10. Finally, it is also described that Fe 2+ can be transported throungh FPN transporters, as well as the TfR1/STEAP3/DMT1 pathways. In the process of ferroptosis, several organelles absorb and release iron ions and lipids. Therefore, there could be extensive crosstalk with autophagy. Among them, the excessive activation of selective autophagy, including ferritinophagy, clockophagy, lipophagy, and chaperone‐mediated autophagy, facilitates ferroptosis by degrading ferritin, circadian protein, lipid droplets, and GPX4, respectively [ 39 ]. Ferritinophagy is a process involving the promotion of selective autophagy of ferritin by nuclear receptor co‐activator 4 (NCOA4), which requires the recognition of ferritin by NCOA4 and then its delivery to autophagosomes [40]. Clockophagy is the selective autophagic degradation of the circadian clock regulator ARNTL/BMAL1. Clockophagy promotes lipid peroxidation and subsequent ferroptosis by blocking HIF1A‐dependent fatty acid absorption and lipid storage [ 40 ]. Lipophagy, which is defined as the autophagic degradation of intracellular lipid droplets, is another type of autophagy that crosstalks with ferroptosis. RAB7, as a key molecule, mediates lipid droplet digestion and releases free fatty acids. Then it promotes mitochondrial oxidation and ferritin proliferation [ 41 ]. Chaperon‐mediated autophagy (CMA) is a cellular lysosomal degradation mechanism regulated by HSP90. CMA effectively promotes the occurrence of ferroptosis by facilitating the degradation of GPX4 [ 42 ]. In addition to autophagy, apoptosis is also interfered with by ferroptosis. Studies have shown that lipid peroxidation can also induce the occurrence of apoptosis [ 43 ]. Through the NF‐κB pathway and the antiapoptotic protein BCL‐2, lipid peroxides effectively interfere with the apoptotic behavior of cells. Furthermore, lipid peroxidation products form complexes with P38, JNK, and ERK to activate mitogen‐activated protein kinase (MAPK) and Caspase signaling to initiate cell apoptosis [ 44 ]. Through the characteristics of ferroptosis, the occurrence of ferroptosis under physiological and pathological conditions can be determined. Furthermore, the role of ferroptosis in female health and disease was further explored. At present, there are four markers considered for detecting ferroptosis behavior, including lipid peroxidation, mitochondrial morphological changes, gene expression changes, and TFR1 relocalization [ 45 ]. First, the lipid peroxidation behavior in ferroptosis can be detected by five methods, including MDA, 4‐HNE staining, thiobarbituric acid reactive substances (TBARS), BODIPY 581/591 C11 fluorescent probes, and lipidomics methods. Second, during the process of ferroptosis, multiple organelles are involved. Among them, the morphological changes of mitochondria, characterized by contraction, increased density, and reduced crystals, are regarded as the characteristic morphology of ferroptosis and can be observed using a transelectric microscope [ 45 , 46 ]. Third, specific gene expression changes can be detected in ferroptotic cells, such as increased CHAC1, PTGS2, SLC7A11 , and ACSL4 [ 29 , 45 ]. Finally, the repositioning of TFR1, which introduces extracellular iron into cells through endothelial cell proliferation, helps to reduce the burden required for iron cleavage. The negative iron pool has been proven to be a marker of iron cleavage. The transfer of TFR1 from the region surrounding Golgi to the plasma membrane can be observed by staining with a 373‐FMA antibody [ 47 ]. To exactly determine the occurrence of ferroptosis, several markers are required, and these markers must be detected before cell death. Choosing an appropriate time point is very important for detecting the markers of ferroptosis. Among these markers, lipid peroxidation is indispensable, while other indicators may not be fully detectable.

With the continuous in‐depth study of ferroptosis, it is closely related to the life and health of women. The research on common pregnancy diseases, gynecological diseases, and malignant tumors is the focus of our attention. In this regard, from the perspective of disease development, the molecular mechanism of ferroptosis regulating disease development in women is expounded. According to the content of the summary, there are several research directions worthy of further exploration. First, ferroptosis is regulated by a complex network composed of genetic, immune, metabolic, and other mechanisms. However, the regulatory mechanisms between ferroptosis and different female diseases have not yet been thoroughly studied. It is still difficult to clarify the relationship between ferroptosis‐related targets and specific signaling pathways and female diseases, and it is difficult to conduct accurate treatment. Therefore, continuous in‐depth exploration is needed. Second, some drugs currently on the market may have mechanisms to induce or inhibit ferroptosis in female diseases but lack theoretical support, which deserves further investigation. Launching more sustained basic and clinical drug trials and translating these drugs into clinical treatments earlier could provide new ways to address clinical treatment issues. Finally, most of the current research on ferroptosis between the above diseases and other disciplines mainly focuses on the analysis of biogenesis and the study of drug resistance mechanisms. Its detection methods are relatively limited, such as immunohistochemistry of pathological tissue sections. However, it is not possible to perform continuous invasive procedures to obtain specimens during clinical treatment to verify the therapeutic effect of ferroptosis. Therefore, it is still necessary to find a simpler and more standardized detection means to better detect the occurrence of ferroptosis and thereby intervene early. Ferroptosis plays an important role in the occurrence and development of female diseases. There is a strong relationship between ferroptosis and common pregnancy diseases. It is believed that simple and convenient detection methods will be found in the future so that their related genes can be used as early screening indicators for common obstetric diseases. In addition, ferroptosis‐related genes are used as prognostic indicators in gynecological malignant tumors and are even closely related to tumor immune cell infiltration disorder and tumor drug resistance. Therefore, in the future, targeted ferroptosis therapy for common pregnancy diseases, combined with conventional chemoradiotherapy and immunotherapy for gynecological malignant tumors, may become an emerging treatment strategy to reduce the mortality of certain diseases.

In addition to the diseases described above, there are a number of female diseases that are also strongly associated with ferroptosis (Table  2 ). Recent evidence suggests that the emerging role of iron overload and ferroptosis in female infertility is to induce hypogonadism, resulting in ovarian dysfunction, damage to preimplantation embryos, diminished endometrial receptivity, and crosstalk between subfertility‐related disorders such as polycystic ovary syndrome and endometriosis [ 213 ]. In the report of Fan et al., it was pointed out that tubal factor infertility is characterized by ectopic pregnancy caused by tubal obstruction, which is manifested in the accelerated accumulation of lipids and ROS [ 197 ], consistent with the trend of ferroptosis [ 4 ]. In addition, the gut microbiota and its metabolites are involved in iron metabolism, ferroptosis, and female infertility. Furthermore, it shows that the relationship between ferroptosis and female infertility is close. In another study [ 214 ], investigators demonstrated an increased ferroptosis burden in the endometrium of Intrauterine adhesions (IUA). Moreover, Erastin‐induced ferroptosis promoted EMT and fibrosis of endometrial epithelial cells in vitro. In parallel, Fer‐1 significantly ameliorated endometrial fibrosis in a double‐injury IUA mouse model. It is demonstrated that increased ferroptosis leads to fibrosis of the endometrial adhesions in utero. Sun et al. found that exposure to bisphenol A (BPA) during pregnancy causes fetal growth restriction [ 215 ]. It was subsequently confirmed in their study that YAP or TAZ siRNA enhanced BPA‐induced ferroptosis, suggesting that trophoblast siderosis depends on YAP/TAZ downregulation after BPA stimulation. It has also been shown that caffeic acid inhibits inflammation and siderosis by regulating the AMPKα/mTOR/HIF‐1α signaling pathway to alleviate Staphylococcus aureus ‐induced endometritis [ 216 ]. In addition, SmgGDS (small GDP‐binding protein dissociative stimulators) have been shown to modulate estradiol‐dependent cardioprotective effects via the AMPK/mTOR signaling pathway, inducing the occurrence of takotsubo syndrome [ 217 ]. These diseases fully demonstrate the close relationship between ferroptosis and a variety of women's health and diseases (Table  3 ). Ferroptosis, as one of the nonprogrammed cell death behaviors, may play an important role as a method of disease diagnosis and treatment. Ferroptosis in other female‐related diseases. Iron overload and ferroptosis can induce hypogonadism, lead to ovarian dysfunction, damage preimplantation embryos, and attenuate endometrial receptivity. Tubal factor infertility accelerates accumulation of lipids and ROS; The gut microbiota and its metabolites are involved in iron metabolism, ferroptosis, and female infertility. An increased ferroptosis burden in the endometrium of Intrauterine adhesions; Erastin‐induced ferroptosis promoted EMT and fibrosis of endometrial epithelial cells in vitro; Fer‐1 significantly ameliorated endometrial fibrosis in a double‐injury IUA mouse model. Exposure to bisphenol A (BPA) during pregnancy causes fetal growth restriction; YAP or TAZ siRNA enhanced BPA‐induced ferroptosis Caffeic acid inhibits inflammation and siderosis by regulating the AMPKα/mTOR/HIF‐1α signaling pathway. SmgGDS modulates estradiol‐dependent cardioprotective effects via the AMPK/mTOR signaling pathway

For the convenience of reference, we have summarized some current drugs for the targeted treatment of ferroptosis. From the three pathways of coordinated control of ferroptosis by iron metabolism, redox, and lipid metabolism, respectively, the small molecule inducers or inhibitors and natural compounds that affect the mechanism of ferroptosis are listed [ 218 ]. The main small‐molecule compounds mediating the iron metabolism pathway in ferroptosis include various inhibitors (Compound 9a, ciclopirox, deferoxamine, deferiprone, deferasirox, and dexrazoxane) and inducer JQ1 [ 219 , 220 , 221 , 222 ]. There are currently no inducers or inhibitors for female disease models in the iron metabolism pathway. The main compounds in the redox pathway of ferroptosis include multiple inhibitors (aminooxyacetic acid, curculigoside, dihydroartemisinin, Edaravone, Fer‐1, Liproxsatin‐1, NAC, and UAMC‐3203) and multiple inducers (acetaminophen, auranofin, Brequinar, buthionine sulphoximine, CH004, Erastin, Erastin‐acetaminophen, imidazole ketone erastin, piperazine erastin, RSL3, sulfasalazine, TRG, TRG+erastin+Sorafenib, and WA) [ 8 , 34 , 222 , 223 , 224 , 225 , 226 , 227 , 228 ]. Among them, Sulfasalazine and Olaparib were applied in the ovarian cancer disease model [ 229 , 230 ]. Sorafenib and NAC were, respectively, utilized in disease models of cervical cancer and endometriosis. Ferrostatin‐1 and Erastin have been involved in multiple studies on female diseases. The main compounds in the lipid metabolism pathway of ferroptosis include various inhibitors (Baicalein, IMA‐1, ML355, NDGA, PRGL493, Zileuton) and various inducers (Pioglitazone, Rosiglitazone, and Troglitazone) [ 229 , 231 , 232 , 233 ]. Among them, Pioglitazone has been applied for treating BC. Therefore, there are still a large number of compounds that have not been applied to cure female diseases, and the possibilities need to be continuously explored in the future. In addition to small molecule inhibitors, some natural compounds can effectively regulate ferroptosis. Among them, some iron chelators, Glutathione, Selenium, and RTAs can effectively inhibit ferroptosis, whereas compounds such as Trigonelline effectively stimulate ferroptosis [ 223 ]. Among the natural compounds described above, there are those with relatively clear pharmacological mechanisms studied. However, in this article, we have also summarized that some natural compounds play a certain role in female health and diseases, such as melatonin and adiponectin, that can protect patients with GDM by inhibiting ferroptosis. MAP30 and artesunate can induce the occurrence of ferroptosis and thereby inhibit the occurrence and progression of ovarian cancer. Oleanolic acid, triptolide, Cassia poria, and Cardanone can induce the occurrence of ferroptosis and protect patients with cervical cancer from invasion. Nuciferine inhibits ferroptosis to protect PCOS patients, while caffeic acid can inhibit ferroptosis and thus prevent damage from endometritis. At present, the mechanism of action of these natural compounds remains unclear, and further in‐depth research on the mechanism is needed. At present, ferroptosis, as a nonapoptotic programmed cell death, is mainly used as an emerging therapeutic target for cancer treatment. However, with the continuous development of biotechnology in the field of biology, there are currently ferroptosis‐driven nanotherapeutics for combined treatment. During this process, ferroptosis is combined with other different therapeutic strategies such as tumor imaging, immune regulation, chemotherapy, and phototherapy [ 234 ], which is highly expected in future treatments and is one of the possible directions for the treatment of female tumors. At present, most of the studies on the mechanism of ferroptosis are still at the level of animal models and/or cell models, and there are a large number of challenges that prevent the possibility of further clinical practice. Although many molecules have been proven to regulate ferroptosis, the drug‐available molecules for humans are very limited. Moreover, poor pharmacokinetic problems also limit the further development of drugs targeting ferroptosis. We have discussed herein some issues regarding the drug resistance mechanism of gynecological tumors. Ferroptosis, as a means of synergistic treatment, has great research space and development value. Therefore, some researchers are exploring the possibility of some traditional herbs targeting and regulating ferroptosis, hoping to develop more effective drugs for targeted ferroptosis treatment

In 2012, the concept of ferroptosis was first introduced in the study by Dixon et al. [ 1 ]. Different from other programmed cell death methods such as apoptosis and necrosis, the morphological characteristics of ferroptosis are mitochondrial atrophy, increased bilayer membrane density, and decreased mitochondrial cristae, but there is no rupture of the cell membrane and no chromatin condensation [ 2 , 3 ]. Recent studies have indicated that ferroptosis may be involved in regulating the pathophysiological processes of various female reproductive disorders, including trophoblast invasion, oocyte development, embryonic development, endometrial shedding, and oxidative stress and metabolism of granulation cells [ 4 ]. In addition, ferroptosis also plays a significant role in the development of common gynecologic tumors (such as ovarian cancer, endometrial cancer, cervical cancer, etc.) [ 5 , 6 , 7 , 8 ]. It is not difficult to conclude that ferroptosis is closely related to the field of female health and disease and is an emerging focus for future research in women. At present, there have been reports summarizing the correlations between other systems and ferroptosis [ 9 , 10 , 11 , 12 ]. Although there are many reports on the relationship between ferroptosis and women's health and disease, systematic descriptions are lacking [ 13 , 14 ]. This review briefly describes the pathogenesis of common female diseases, generalizes the signaling mechanisms of ferroptosis in female health and disease, and finally summarizes the function and significance of ferroptosis in various female diseases, indicating ferroptosis may be a possible approach for treating various female diseases.

The authors declare no conflicts of interest.