As an essential nutrient for living organisms, iron homeostasis in cells refers to the balance among iron absorption, output, utilization, and storage. The presence of excess iron may lead to tissue damages and increased cancer risk. Fenton reaction, a mechanism that leads to ROS accumulation in cells and hydroxyl radical production in cells, is one of the most important mechanisms of iron biotoxicity, which could result in the damages of cellular proteins, lipids as well as DNA. It has become an effective therapy for cancer and other diseases by affecting iron metabolism and absorption. By regulating iron metabolism pathways, cancer cells can increase intracellular iron content, increasing the sensitivity of cancer tissues to ferroptosis. Application of iron-based nanoparticles inhibits tumor growth by inducing ferroptosis in tumor cells [13]. It has been shown that knockout of the transferrin receptor (TFRC) at the cell surface could reduce intracellular iron overload, while iron storage in the inert pool could be increased through cytoplasmic ferritin up-regulation to inhibit ferroptosis [14]. In the same way, ferroptosis may also be suppressed by inhibiting iron responsive element binding protein 2 (IREB2) by regulating iron metabolism [2]. A knockout of the solute carrier family 40 member A1 (SLC40A1) in neuroblastoma cells has been demonstrated to accelerate Erastin-induced ferroptosis in neuroblastoma cells [15]. Therefore, iron metabolic pathways as well as ferritin phagocytosis are critical for the regulation of ferroptosis.

Lipid ROS accumulation is a distinguishing characteristic of ferroptosis. When ROS level is too high and the redox homeostasis is completely disrupted, lipid peroxidation may be induced through both enzymatic and non-enzymatic pathways. Free polyunsaturated fatty acids (PUFAs) contain easily extractable bisallyl hydrogen atoms and are vulnerable to lipid peroxidation [16]. In the presence of large amounts of iron ions, cytoplasmic lipoxygenase participates in the generation of iron-dependent ROS through catalyzing the oxidation of free PUFAs into lipid hydroperoxides and generating toxic free radicals, which ultimately results in the destruction of membrane stability and ferroptosis [17]. Furthermore, 1,2-dioxolane (FINO2) is an organic substance containing internal peroxides, which promotes extensive lipid peroxidation and preferentially triggers ferroptosis by directly inducing iron oxidation and indirectly inhibiting GPX4 [18]. Both the cytoplasmic ROS eliminator N-acetylcysteine and the mitochondria-targeted antioxidants can alleviate ferroptosis induced by erastin and its analogs by blocking ROS production [19].

Ferroptosis caused by abnormal amino acid metabolism is related to glutathione (GSH), GPX4 and glutamate/cystine transporter (System Xc-) [20]. A series of genes and regulatory factors related to GSH biosynthesis and degradation can participate in the regulation of ferroptosis. GPX4 sits at the intersection of GSH metabolism and lipid peroxidation, both of which are implicated in ferroptosis. As a key enzyme in removing lipid oxygen free radicals, once GPX4 was activated, GSH catalyzes the reduction of lipid hydrogen peroxide to non-toxic lipid alcohol and water, removes lipid oxides caused by iron aggregation, thus resisting the peroxidation of phospholipid bilayer membrane and inhibiting ferroptosis [21]. GSH is an essential substrate for GPX4 and exhibits anti-ferroptosis activity. The GSH/GPX4 antioxidant system is considered to be one of the most critical endogenous factors against ferroptosis in cells. Studies have shown that many diseases are related to GPX4 knockdown, such as mouse models with conditioned GPX4 deletion in forebrain neurons are prone to ferroptosis and may promote cognitive impairment and neurodegeneration [22].

In addition, GPX4 inactivation can lead to acute renal failure. System Xc-, composed of solute carrier family 7 member 1 (SLC7A11) and solute carrier family 3 member 2 (SLC3A2) heterodimer, is a membrane Na⁺-dependent amino acid reverse transporter widely distributed in the phospholipid bilayer of cells [23]. The System Xc- system is responsible for transporting cysteine, the raw material of GSH synthesis, into the cell, exchanging glutamic acid and cystine in a ratio of 1:1 and converting cystine into cysteine to participate in the synthesis of GSH [24].

Tumor suppressor genes P53, BRCA1-associated protein 1 (BAP1) and Beclin 1 (BECN1) can restrain the activity of System Xc- through down-regulating the expression of SLC7A11, thus reducing GSH synthesis and therefore inducing lipid peroxidation and cell ferroptosis [25]. Therefore, cancer cells with mutated P53 or BRCA1/2 could use SLC7A11 antioxidant activity against chemotherapeutics treatments favoring chemoresistance, especially the platinum-derived dugs.

Endometriosis (EMs), a common gynecological disease, is generally chronic, inflammatory and hormone-dependent. Although there have been many related studies and discussions, the pathogenesis of the disease has not been fully clarified. The most widely accepted theory is menstrual reflux, which is thought to occur when tissue from the endometrium falls off in reverse through the fallopian tube and flows into the pelvic cavity. Studies dating back to the 1990s [35] have shown that patients with EMs have iron overload in peritoneal fluid, ectopic endometrial tissue, peritoneum near the lesion, and macrophages. High levels of iron can induce inflammation, oxidative stress and lipid peroxidation in cell membranes and may ultimately lead to widespread programmed cell death [36].

Recently, studies have confirmed that ferroptosis resistance is associated with the proliferation and migration abilities of endometrial stromal cells (ESC) [37], and the underlying mechanism may be related to the up-regulation of the extracellular glucose protein fibulin 1 [38]. According to the related reports, the expression of transferrin was up-regulated, while the expression of nuclear receptor coactivator 4 (NCOA4) and ferritin was down-regulated, which enhanced the tolerance of ectopic endometrial cells to ferroptosis by reducing the concentration of intracellular free Fe²⁺. Voltage dependent anion channel 2 (VDAC2)-mediated pathway is of great significance for transporting metabolites in mitochondrial outer membrane [26]. As an important gene involved in intracellular reduction, it regulates ROS metabolism and promotes ferroptosis. Its expression was significantly down-regulated in ectopic endometrium tissue. SLC3A2, a chaperone subunit of cystine transport channel Xc-system, is up-regulated in ectopic intima tissue and increases the level of cystine, which is the raw material for the synthesis of reduced glutathione in cells. Erastin-induced ferroptosis promoted the proliferation, endothelial angiogenesis and cytokine secretion of ESCs through activation of MAPK/signal transducer and activator of transcription (STAT6) signaling pathway and up-regulation of endothelial growth factor A (VEGFA) and IL-8 expressions, and ferroptosis inhibitor N-acetylcysteine could lead to the regression of EMs lesions [39]. The apparent regulation of ferroptosis by long noncoding RNA (lncRNA) is related to EMs, and lncRNA ADAMTS9-AS1, which is mediated by miRNA-6516-5 (miR-6516-5)/GPX4 pathway, is significantly up-regulated in the ectopic intima, thereby inhibiting ferroptosis and accelerating ESC proliferation and migration [11]. The expression of lncRNA metastasis-associated lung adenocarcinoma Transcript 1 (MALAT1) has also been reported to upregulate in ectopic endometrium cells. MALAT1 knockdown can promote erastin to induce ferroptosis in ESC through miR-145-5p/MUC1 signaling pathway [40]. Li B’s research [41] also found that the enhancement of ferroptosis resistance of endometrial tissue can prevent the apoptosis process of endometrial cells countercurrent with menstrual blood in abdominal cavity to a certain extent, so as to realize the implantation and proliferation of endometrial cells in abdominal cavity. These characteristics of EMs suggest that ferroptosis may be a mechanism of ectopic endometrium removal in normal human body, and the imbalance could lead to the occurrence and spread of EMs.

In vitro treatment of human ovarian granular cell line (KGN) with follicular fluid (EMFF) from EMs patients proved that the proliferation and migration activity of KGN were inhibited and the expressions of ferroptosis-related genes were abnormal, such as autophagy related 5 (ATG5), nuclear receptor coactivator 4 (NCOA4), ferritin heavy chain 1 (FTH1), GPX4 and tumor suppressor protein p53 (TP53). These differentially expressed genes could effectively distinguish patients with EMs from normal patients, thus providing potential molecular biomarkers and promising targets for the diagnosis and treatment of EMs [42].

Ferroptosis has also been studied in preeclampsia (PE) [43]. Ng SW et al. [43] believe that some studies directly measuring iron status have shown that high iron status is associated with preterm birth (PTB) and low birth weight (LBW). High level of iron and/or iron intake can be harmful to pregnancy and may lead to developmental reproductive disorders such as PE. This is due to the excess of iron in the cell leading to ferroptosis. This programmed cell death process can trigger PE through the membrane by iron-dependent lipid peroxidation. Studies have shown that ferroptosis plays an important role in aseptic inflammatory diseases such as hypoxia/reperfusion injury. At 8 to 10 weeks of gestation, some pregnant women may experience an acute reaction with elevated oxygen and iron due to physiologic hypoxia/reperfusion. This increase in oxygen and iron leads to membrane lipid peroxidation and ferroptosis, mainly in trophoblasts, resulting in shallow endovascular invasion of extra villous cytotrophoblast (EVCT) and suboptimal remodeling of maternal spiral arteries, thereby leading to the pathological features of PE [44].

Peng et al. [27] analyzed GPX4 alleles in 1008 cases of preeclampsia and 1386 cases of normal pregnant women, and found that pregnant women with GPX4 rs713041 genotype had higher risk in developing early onset and severe preeclampsia, indicating that GPX4 activity and gene polymorphism were closely related to the onset of preeclampsia. Sakai O et al. [45] found that knockout GPX4 gene in vascular endothelial cells can increase membrane lipid oxidation level, increase cytotoxicity and delay cell proliferation, indicating that GPX4 is involved in the regulation of ferroptosis in vascular endothelial cells. It is speculated that the loss of its activity can promote ferroptosis of vascular endothelial cells, inhibit cell migration and invasion, and lead to poor remodeling of spiral arteries, and mediate pathological placental tissue to participate in the pathogenesis of PE. Zhang et al. [28] found that the contents of GSH and GPX4 decreased, while the contents of ferric ion and malondialdehyde increased in the placental trophoblast cells of preeclampsia when comparing with normal maternal placental, indicating that ferroptosis was critical for the occurrence and development of preeclampsia. Han D et al. [29] found that after the treatment of the human trophoblast cell line HTR8/SVneo and the porcine trophoblast cell line pTr2 with ferroptosis inducing compounds expression of Sirtuin 3 (SIRT3, also known as silent mating type information regulator 3), was significantly increased. They found that autophagy inhibition weakened SIRT3-enhanced ferroptosis, and SIRT3 deficiency inhibited both autophagy and ferroptosis. They concluded that SIRT3 activated the AMPK-mTOR pathway to enhance autophagy and decreased GPX4 levels to synergistically induce ferroptosis, and that enhanced autophagy and decreased GPX4 acted synergistically to induce ferroptosis. Decreased GPX4 levels result in increased lipid ROS, and excessive accumulation of lipid ROS in trophoblast cell membranes can inhibit their proliferation, invasion, and other biological functions. This could participate in the pathogenesis of PE by inducing poor trophoblast invasion and spiral artery remodeling disorders [46].

By inducing human chorionic trophoblast cell line HTR-8/SVneo cells to establish a cell model of preeclampsia in vitro, the content of GSH and the activities of System Xc- and GPX4 were found decreased, while the concentrations of divalent iron and malondialdehyde increased, with ferroptosis significantly activated in trophoblast cells. Therefore, the activity and invasion ability of trophoblast cells were significantly decreased. Ferroptosis inhibitor (desferoxamine mesylate) could reverse the decrease of trophoblast activity under hypoxia condition. Yang et al. [47] convinced that quercetin exhibited positive effects on the L-NAME-induced pre-eclampsia rats. Furthermore, iron chelators, such as deferoxamine and ferrostatin-1, have been proved to block trophoblast ferroptosis through decreasing the concentration of placenta in PE rat models [48]. Animal experiments also confirmed that ferroptosis inhibitor can attenuate the symptoms of preeclampsia in hypertensive rat models and reduce the levels of malondialdehyde, ROS and other ferroptosis markers in serum and placental trophoblast cells. Together, the studies provide a better understanding of the critical role of ferroptosis in pregnancy-related diseases, thus proposing new opportunities for the diagnosis and therapeutic interventions for diseases such as PE.

Spontaneous abortion (SA), a clinically proven loss of pregnancy within 24 weeks of gestation, is the most common pregnancy-related disorder. Embryogenesis is a complex process of synergistic interaction between embryo and mother. The successful implantation of human embryos, the formation of placenta, and the growth and development of embryos are closely related to the functions of proliferation, differentiation and invasion of trophoblasts [49]. Some scholars have observed excessive ferroptosis in aborted rats under oxidative stress, which is manifested by the decreased levels of GPX4, superoxide dismutase, malondialdehyde and glutathione, as well as the increased levels of acyl-CoA synthetase long-chain family member 4 (ACSL4) and activation of Nod-like receptor protein 1 (NLRP1) inflammatory bodies [30]. In the chronic inflammatory state, NLRP1 is over-activated for a long time and continuously converted into caspase-1. As a factor related to NLRP1, caspase-1 can promote the production of apoptotic proteins and factors, and also increase the damage caused by oxidative stress. In the over-activated state of ferroptosis, NLRP1 is also overexpressed, thus exacerbating the inflammatory state [30]. And the administration of ferroptosis inhibitors could decrease NLRP1 expression inflammatory vesicles, as well as the downstream inflammatory factors, thus inducing the dysfunction of placenta [30]. To date, these studies have provided valuable references for the connection between ferroptosis and spontaneous abortion and proposed NLRP1 as a promising target for the treatment of spontaneous abortion.

Intrahepatic cholestasis of pregnancy (ICP), generally occurring in the third trimester, is a complication in 0.3%–15% of pregnancies in various populations [50]. Characterized by pruritus with higher liver transaminases and serum bile acid levels, ICP could lead to meconium-stained amniotic fluid, fetal distress, preterm birth and stillbirth [50]. Increasingly evidence showed that oxidative stress generated by bile acids could induce the occurrence of ICP [51]. Patients with ICP had lower levels of Se and GPX4 with higher level of malondialdehyde (MDA) when compared with normal pregnancies [31, 52].

It was reported that Se, through up-regulating GPX4 expression, could protect placental trophoblasts against oxidative stress, especially ICP. Furthermore, CoQ10 supplementation could significantly improve estradiol-induced cholestasis in rats [53, 54]. Analysis of differentially expressed genes related to ferroptosis between ICP patients and healthy pregnancies showed that EGFR, associated with destroyed autophagy and ferroptosis, was markedly upregulated in human placenta, indicating EGFR as a potential target for ICP therapy [55]. Meanwhile, regulation of oxidative stress induced by ferroptosis might be a therapeutic strategy for ICP. Further researches, especially more in vitro and in experiments, are demanded to verify the relationship between ferroptosis and ICP.

Placental trophoblast cells regulate maternal-blood glucose stability through secreting various steroid hormones and cytokines. Placental endocrine dysfunction caused by trophoblast cell injury is a significant pathogenesis of gestational diabetes [56]. Meanwhile, gestational diabetes mellitus (GDM) is associated with various metabolic disorder phenotypes, including low-grade inflammation which could modulate ferroptosis to certain extend [57]. Hyperglycemia will stimulate oxidative stress of trophoblast cells, thereby producing excessive ROS, aggravating the damage of trophoblast cells, inhibiting their proliferation and invasion abilities, and increasing the risk of placental dysfunction diseases, such as preeclampsia, FGR and fetal distress [58]. A study from the National Institute of Child Health and Human Development looked at 107 patients with gestational diabetes and 214 healthy pregnant women, and found that women with high ferritin levels in early pregnancy had a 21% increased risk of developing gestational diabetes. The concentration of iron in gestational diabetes mellitus was 16% higher than that in healthy pregnant women (mean values of 6.4 ng/mL versus 5.5 ng/mL, p = 0.02), and was positively correlated with the risk of gestational diabetes mellitus (adjusted odds ratios (aOR) = 2.61, 95% Confidence interval (CI): 1.07–6.36). Ferritin levels were also reported to be positively associated with the risk of gestational diabetes (aOR = 2.43, 95% CI: 1.12–5.28; aOR = 3.95, 95% CI: 1.38–11.30) at 15–26 weeks of gestation [32]. In vitro cell experiments have demonstrated that high glucose environment can induce ferroptosis of trophoblast cells through down-regulating GPX4 expression in trophoblast cells and activating lipid peroxidation, thereby resulting in increased concentrations of ROS and malondialdehyde; while ferroptosis inhibitors can alleviate the degree of ferroptosis induced by high glucose of trophoblast cells [29]. Recently, Sun et al. [59] established a GDM rat model and found that melatonin, an ferroptosis inhibitor, may inhibit oxidative stress and ferroptosis signaling pathways, including up-regulating GPX4 and ferritin heavy chain (FTH1) gene expressions and down-regulating ACSL4 gene expression. It significantly increased the activity of antioxidant enzymes and the level of antioxidant GSH in pancreatic tissue, decreased the content of hydrogen peroxide, MDA and iron, therefore alleviating the pathological damage of GDM [59]. In conclusion, ferroptosis caused by redox imbalance and metabolites disorder in trophoblast cells is particularly involved in the occurrence and development of gestational diabetes mellitus. Targeting ferroptosis through regulation of ROS and metabolites, such as iron, ferritin and malondialdehyde, is expected to be a therapeutic strategy for gestational diabetes mellitus.

Preterm birth is an important cause of neonatal death, with the global occurrence rate ranging from 5% to 18% [60]. Preterm birth is a syndrome with many origins. Among them, infection or inflammation are the major risk factors [61]. Existing studies have found that ferroptosis may also be involved in the occurrence and development of preterm birth. Bai and Tang [33] found that compared with women in full-term delivery, plasma malondialdehyde (MDA) concentration in patients with spontaneous preterm delivery increased, while GSH concentration decreased significantly. The accumulation of PUFAs in the placental trophoblast cells suggests that ferroptosis may play a critical role in preterm birth. Beharier et al. [48] also observed changes in markers related to ferroptosis in placental trophoblast cells of patients with spontaneous preterm delivery, and applied PLA2G6 to intervene in placental trophoblast cells, which inhibited ferroptosis in trophoblast cells and partially restored activity of trophoblast cells, confirming the existence of ferroptosis in placental trophoblast cells of patients with preterm delivery. Meanwhile, Qiu et al. [62] demonstrated that PSMA3-AS1 overexpression may be a promising strategy to prevent preterm delivery through attenuating inflammatory responses thus suppressing ferroptosis. Together, ferroptosis has been proved to be an important part in preterm delivery and may be targeted as a promising therapeutic intervention into clinical application [30].

As the study progressed, ferroptosis were also found to be strongly linked to other obstetrical and gynecological diseases. Bielfeld et al. [63] compared the endometrial tissues of patients with repeated implantation failure and those with normal fertility and the proteins of isolated primary cells, and found that molecules related to ferroptosis pathway were changed in patients with repeated implantation failure. Lai et al. [34] also observed increased MDA content, decreased GSH and GPX levels, and up-regulated protein expression promoting. Ferroptosis in villi tissues of tubal pregnancy patients, indicating the occurrence of ferroptosis during tubal pregnancy.