Induction of apoptotic cell death via accumulation of autophagosomes in rat granulosa cells

HIF-1α Protects Granulosa Cells From Hypoxia-Induced Apoptosis During Follicular Development by Inducing Autophagy

Owing to the avascular structure of the ovarian follicle, proliferation of granulosa cells (GCs) and development of follicles occur under hypoxia, which is obviously different from the cell survival requirements of most mammalian cells. We hypothesized that autophagy may exert an inhibitory effect on GC apoptosis. To decipher the underlying mechanism, we constructed a rat follicular development model using pregnant mare serum gonadotropin and a cell culture experiment in hypoxic conditions (3% O₂). The present results showed that the autophagy level was obviously increased and was accompanied by the concomitant elevation of hypoxia inducible factor (HIF)-1α and BNIP3 (Bcl-2/adenovirus E1B 19kDa-interacting protein 3) in GCs during follicular development. The levels of Bax (Bcl2-associated X) and Bcl-2 (B-cell lymphoma-2) were increased, while the activation of caspase-3 exhibited no obvious changes during follicular development. However, inhibition of HIF-1α attenuated the increase in Bcl-2 and promoted the increase in Bax and cleaved caspase-3. Furthermore, we observed the downregulation of BNIP3 and the decrease in autophagy after treatment with a specific HIF-1α activity inhibitor (echinomycin), indicating that HIF-1α/BNIP3 was involved in autophagy regulation in GCs in vivo. In an in vitro study, we also found that hypoxia did not obviously promote GC apoptosis, while it significantly enhanced the activation of HIF-1α/BNIP3 and the induction of autophagy. Expectedly, this effect could be reversed by 3-methyladenine (3-MA) treatment. Taken together, these findings demonstrated that hypoxia drives the activation of HIF-1α/BNIP3 signaling, which induces an increase in autophagy, protecting GC from apoptosis during follicular development.

Expression Regulation and Physiological Role of Transcription Factor FOXO3a During Ovarian Follicular Development

In mammals, developing ovarian follicles transform from primordial follicles to primary follicles, secondary follicles, and mature follicles, accompanied by changes in follicular secretory functions. FoxO3a is a member of the forkhead transcription factor family (FoxO), which plays an important role in the cell cycle, DNA damage repair, apoptosis, oxidative stress, and energy metabolism. Recent studies have shown that FOXO3a is involved in the physiological regulation of follicular development and pathological progression of related ovarian diseases, which will provide useful concepts and strategies for retarding ovarian aging, prolonging the ovarian life span, and treating ovarian diseases. Therefore, the regulation of FOXO3a expression, as well as the physiological contribution during ovarian follicular development are detailed in this paper, presenting an important reference for the further study of ovarian biology.

Association of an APBA3 Missense Variant with Risk of Premature Ovarian Failure in the Korean Female Population

Premature ovarian failure (POF) is a complex disease of which the etiology is influenced by numerous genetic variations. Several POF candidate genes have been reported. However, no causal genes with high odds ratio (OR) have yet been discovered. This study included 564 females of Korean ethnicity, comprising 60 patients with POF and 182 controls in the discovery set and 105 patients with POF and 217 controls in the replication set. We conducted genome-wide association analysis to search for novel candidate genes predicted to influence POF development using Axiom Precision Medicine Research Arrays and additive model logistic regression analysis. One statistically significant single nucleotide polymorphism (SNP), rs55941146, which encodes a missense alteration (Val > Gly) in the APBA3 gene, was identified with OR values for association with POF of 13.33 and 4.628 in the discovery and replication sets, respectively. No rs55941146 minor allele homozygotes were present in either cases or controls. The APBA3 protein binds FIH-1 that inhibits hypoxia inducible factor-1α (HIF-1α). HIF-1α contributes to granulosa cell proliferation, which is crucial for ovarian follicle growth, by regulating cell proliferation factors and follicle stimulating hormone-mediated autophagy. Our data demonstrate that APBA3 is a candidate novel causal gene for POF.

Autophagy Contributes to Oxidative Stress-Induced Apoptosis in Porcine Granulosa Cells

Oxidative stress-induced granulosa cell (GC) death is a major cause of follicular atresia. As the major types of programmed cell death, autophagy and apoptosis have been observed in response to H₂O₂-mediated oxidative stress and have been demonstrated to be responsible for porcine GC death. To date, however, the cellular reactions linking autophagy to the apoptosis of porcine GC under oxidative stress are still poorly understood. Porcine GC were treated with H₂O₂, and autophagic flux was examined by western blotting. Cell viability and cell death assays were performed after cotreatment of porcine GC with autophagy activator (rapamycin) or inhibitor (3-methyladenine, 3-MA) together with H₂O₂. We revealed that short exposure (1-3 h) of porcine GC to H₂O₂ dramatically increased autophagic flux (1.8- to 2.5-fold over that in the control), whereas 6-12 h prolonged treatment decreased autophagy but elevated the caspase-3 activity and GC apoptotic rate. Furthermore, we showed that pretreatment with rapamycin exacerbated H₂O₂-mediated cytotoxicity and caspase-3 activation but that 3-MA or siRNAs specific for Beclin 1 and Atg7 genes ameliorated H₂O₂-mediated GC apoptosis. Together, our results indicate that autophagy plays a pivotal role in H₂O₂-mediated porcine GC apoptosis. Importantly, we show that the early induction of autophagic flux contributes to oxidative stress-induced apoptosis in porcine GC. The results also suggest that regulating the autophagy response in porcine GC under oxidative stress might be a new strategy for abnormal follicular atresia.

miRNA-21-3p targeting of FGF2 suppresses autophagy of bovine ovarian granulosa cells through AKT/mTOR pathway

It is widely thought that the main reason for ovarian follicular atresia is apoptosis of granulosa cells, however, accumulating evidence suggests that autophagy plays a role in the fate of granulosa cells. Although epigenetic regulation including miR-21-3p associated with autophagy process has been reported in many cancer types, nevertheless, the mechanism of miR-21-3p in bovine ovary is poorly understood. In the present study, bovine ovarian granulosa cells (BGCs) were used as a model to elucidate the autophagy and role of miR-21-3p in a cattle ovary. The results from gene expression and tagged autophagosomes showed the autophagy in BGCs and miR-21-3p was identified as an important miRNA regulating autophagy of BGCs. The current results indicated that FGF2 was a validated target of miR-21-3p in autophagy regulation of BGCs according to the results from FGF2 luciferase reporter assays and FGF2 overexpression (oe-FGF2) or small interference (si-FGF2). Transfection of miR-21-3p mimic and si-FGF2 plasmids resulted in decreasing phosphorylated AKT and mTOR, while transfection of miR-21-3p inhibitor and oe-FGF2 increased the phosphorylated level of AKT and mTOR in BGCs. These data indicate that regulation of miR-21-3p on BGCs autophagy through AKT/mTOR pathway. In summary, this study suggests that miR-21-3p targets FGF2 to inhibit BGCs autophagy by repressing AKT/mTOR signaling.

Acrylamide impairs ovarian function by promoting apoptosis and affecting reproductive hormone release, steroidogenesis and autophagy-related genes: An in vivo study

Acrylamide (ACR) toxicity is quite common due to its widespread use in industry and due to the Maillard browning reaction that occurs in foods containing high concentrations of hydrocarbons subjected to high temperatures. This study aimed to elucidate the female reproductive toxicity of ACR in vivo. Fifty-day-old Wistar-Albino female rats were treated with different dosages of ACR (2.5, 10, and 50 mg/kg/day). After treatment, the animals were sacrificed, and serum and ovary samples were collected for histological examination, hormone analysis, TUNEL analysis, and RT-PCR studies. We found that ACR acts by significantly reducing ovarian weight and serum progesterone and estradiol concentrations. In addition, ACR treatment led to pyknotic, heterochromatic characteristics and nuclear fragmentation, as evidenced by hematoxylin staining. The TUNEL assay revealed that granulosa cells were affected after the oral administration of ACR, leading to the apoptosis of follicles at different stages of growth. Compared with the control condition, high doses of ACR (50 mg/kg/day) significantly induced the overexpression of INSL3, CYP17a, IGF1, ESR1, ESR2, ATG5, ATG12 and LC3 in the ovary. Moreover, LC3 mRNA levels significantly increased with increasing doses of ACR (2.5, 10 and 50 mg/kg/day), suggesting that ACR treatment induced autophagy. In conclusion, ACR induced ovarian dysfunction by affecting steroid hormone release, increasing apoptosis and mRNA levels of autophagy-related genes. The eventual correlation between apoptotic granulosa cell death and autophagy needs to be further explored.

MicroRNA-204-5p regulates apoptosis by targeting Bcl2 in rat ovarian granulosa cells exposed to cadmium†

This study aimed to investigate whether cadmium (Cd) cytotoxicity in rat ovarian granulosa cells (OGCs) is mediated through apoptosis or autophagy and to determine the role of microRNAs (miRNAs) in Cd cytotoxicity. To test this hypothesis, rat OGCs were exposed to 0, 10, and 20 μM CdCl2 in vitro. As the Cd concentration increased, OGC apoptosis increased. In addition, Cd promoted apoptosis by decreasing the mRNA and protein expression levels of inhibition of B-cell lymphoma 2 (Bcl2). However, under our experimental conditions, no autophagic changes in rat OGCs were observed, and the mRNA and protein expression levels of the autophagic markers microtubule-associated protein 1 light chain 3 alpha (Map1lc3b) and Beclin1 (Becn1) were not changed. Microarray chip analysis, miRNA screening, and bioinformatics approaches were used to further explore the roles of apoptosis regulation-related miRNAs. In total, 19 miRNAs putatively related to Cd-induced apoptosis in rat OGCs were identified. Notably, miR-204-5p, which may target Bcl2, was identified. Then, rat OGCs were cultured in vitro and used to construct the miR-204-5p-knockdown cell line LV2-short hairpin RNA (shRNA). LV2-shRNA cells were exposed to 20 μM Cd for 12 h, and the mRNA and protein expression levels of Bcl2 were increased. Our findings suggest that Cd is cytotoxic to rat OGCs, and mitochondrial apoptosis rather than autophagy mediates Cd-induced damage to OGCs. Cd also affects apoptosis-related miRNAs, and the underlying apoptotic mechanism may involve the Bcl2 gene.

Thyroid hormones T3 and T4 regulate human luteinized granulosa cells, counteracting apoptosis and promoting cell survival

PURPOSE

Fine and balanced regulation of cell proliferation and apoptosis are key to achieve ovarian follicle development from the primordial to the preovulatory stage and therefore assure female reproductive function. While gonadotropins are the major and most recognized regulators of follicle cell growth and function, other factors, both systemic and local, play equally important roles. This work is aimed at evaluating the effects of thyroid hormones (THs) on human granulosa luteinized (hGL) viability.

METHODS

Human GL cells derived from assisted reproduction treatments were exposed to T3 or T4. Cell viability was evaluated by MTT assay. Apoptosis was evaluated by the TUNEL assay and active caspase-3 staining. StAR, CYP19A1,Caspase-3, P53 and BAX mRNA were evaluated by real-time PCR. LC3-I/-II, AKT and pAKT were evaluated by western blot.

RESULTS

T3 and T4 promoted cell viability in a dose-dependent modality and modulate StAR and CYP19A1 expression. T3 and to a lesser extent T4 mitigated cell death induced by serum starvation by inhibition of caspase-3 activity and expression of P53 and BAX; and attenuate cell death experimentally induced by C2-ceramide. Cell death derived from starvation appeared to be involved in autophagic processes, as the levels of autophagic markers (LC3-II/LC3-I ratio) decreased when starved cells were exposed to T3 and T4. This effect was associated with an increase in pAkt levels.

CONCLUSION

From the present study, THs emerge as potent anti-apoptotic agents in hGL cells. This effect is achieved by inhibiting the apoptosis signalling pathway of BAX and caspase-3, while maintaining active the PI3K/AKT pathway.

HMGB1-induced aberrant autophagy contributes to insulin resistance in granulosa cells in PCOS

Insulin resistance (IR) disrupts ovarian functions in polycystic ovary syndrome (PCOS). The contributing factors remains elusive. High mobility group box 1 (HMGB1), a damage-associated molecular pattern molecule, has been shown to be related to IR and autophagy, respectively, in peripheral tissues. Here, we investigated whether increased HMGB1 contributes to IR in granulosa cells of PCOS patients via induction of aberrant autophagy. Results showed that HMGB1 abundance in the follicular fluid was significantly increased with enhanced autophagy in granulosa cells in PCOS patients with IR. HMGB1 exacerbated autophagy in granulosa cells as evinced by increased LC3B II/I ratio and ATG7 as well as decreased p62, the markers for autophagy. Concurrently, HMGB1 impaired insulin sensitivities by attenuating the abundance of insulin receptor substrate-1, Akt phosphorylation, GLUT4 translocation, and glucose uptake in granulosa cells, which were reversed by blocking autophagy pathways with siRNA-mediated knockdown of ATG7 or with chloroquine and bafilomycin A1, the lysosome inhibitors. In conclusion, our results indicate that increased HMGB1 contributes to IR development in granulosa cells of PCOS patients, which is associated with exacerbation of autophagy by HMGB1. Control of HMGB1 production may be benefical for the improvement of insulin sensitivity in granulosa cells in PCOS.

A dual death/survival role of autophagy in the adult ovary of Lagostomus maximus (Mammalia- Rodentia)

Follicular atresia is a cell death event that occurs in the great majority of follicles before ovulation in the mature mammalian ovary. Germ cell loss has been mainly associated to apoptosis although autophagy also seems to be at play. Aimed to increase our understanding on the possible cooperating role of autophagy and apoptosis in follicular atresia and/or follicular survival, we analyzed both programmed cell death mechanisms in a rodent model, the South American plains vizcacha, Lagostomus maximus. Female vizcacha shows highly suppressed apoptosis-dependent follicular atresia in the adult ovary, with continuous folliculogenesis and massive polyovulation. This strategy of massive ovulation requires a permanent remodeling of the ovarian architecture to maintain the availability of quiescent primordial follicles throughout the individual's reproductive lifespan. We report here our analysis of autophagy (BECN1, LAMP1 and LC3B-I/II) and apoptosis (BCL2 and ACTIVE CASPASE-3) markers which revealed interactive behaviors between both processes, with autophagy promoting survival or cell death depending on the ovarian structure. Strong BECN1, LC3B-II and LAMP1 staining was observed in atretic follicles and degenerating corpora lutea that also expressed nuclear ACTIVE CASPASE-3. Healthy follicles showed a slight expression of autophagy proteins but a strong expression of BCL2 and no detectable ACTIVE CASPASE-3. Transmission electron microscopy revealed a high formation of autophagosomes, autolysosomes and lysosomes in atretic follicles and degenerating corpora lutea and a low number of autophagic vesicles in normal follicles. The co-expression of LC3B-BECN1, LC3B-LAMP1 and LC3B-ACTIVE CASPASE-3 was only detected in atretic follicles and degenerating corpora lutea, while co-expression of BCL2-BECN1 was only observed in normal follicles. We propose that autophagy could act as a mechanism to eliminate altered follicles and remnant corpora lutea providing the necessary space for maturation of primordial follicles that continuously enter the growing follicular pool to sustain massive ovulation.

The protective effects of pretreatment with resveratrol in cyclophosphamide-induced rat ovarian granulosa cell injury: In vitro study

Cyclophosphamide (Cy), a chemotherapeutic agent, is widely used to treat tumoursand is also associated with premature ovarian insufficiency. 4-Hydroperoxycyclophosphamide (4-HC), an active metabolite of Cy, was used for in vitro experiments. Granulosa cells (GCs) are crucial for maintaining follicle development and are also used in reproductive toxicity research in vitro. Resveratrol (Res), a polyphenolic compound, exhibits multiple effects in cells and animal models. To date, whether Res pretreatment has a protective effect on GCs induced by Cy remains unclear. This was an in vitro study, and primary cultures of rat GCs were used. Rat GCs were treated with 4-HC alone, Res + 4-HC or Res + 4-HC + EX527, and GCs survival rates, oxidative stress levels, apoptosis rates and related Sirt1 pathway proteins were evaluated. We demonstrated that 4-HC caused GC damage by increasing oxidative stress, autophagy and apoptosis. Res pretreatment improved 4-HC-induced GC damage by increasing Sirt1 expression, reducing oxidative stress levels and decreasing Beclin1, LC3B, Bax and Caspase-3 levels. Importantly, the addition of EX527, which is a selective inhibitor of Sirt1, reversed the protective effect of Res pretreatment, indicating that Sirt1 may be an important mediator of the protective effect of Res. Taken together, we demonstrated that Res may be a potential drug to improve fertility preservation for patients undergoing chemotherapy.

Exposure of adult mice to perfluorobutanesulfonate impacts ovarian functions through hypothyroxinemia leading to down-regulation of Akt-mTOR signaling

Perfluorobutanesulfonate (PFBS), a short-chain perfluoroalkyl substance, is used in many industrial products. Preliminary evidence suggests that exposure to PFBS may increase the risk of infertility. The aim of this study was to investigate the influence of PFBS on ovarian function. Herein, we show that exposure of adult female mice to PFBS (200 mg/kg/day) (PFBS-mice) caused a decrease in the levels of serum total triiodothyronine and thyroxine, which depended on the activation of peroxisome proliferator-activated receptor α (PPARα). The numbers of secondary, early antral and antral follicles were reduced in PFBS-mice with an increase in the atretic follicles, and these changes were recovered by the replacement of L-thyroxinein or the treatment with PPARα antagonist GW6471. PFBS-induced hypothyroxinemia led to a decrease in the levels of Akt, mTOR and p70S6K phosphorylation in ovarian granular cells and cumulus cells, which suppressed the proliferation of these cells and enhanced autophagic death of granular cells and cumulus cells. The levels of serum estradiol and progesterone were reduced in PFBS-mice with a low expression of the steroidogenic genes Star and P450scc in ovarian tissues, which were sensitive to the replacement of L-thyroxinein or the blockade of PPARα. The results indicate that exposure to PFBS (≥200 mg/kg/day) through reducing thyroid hormones causes down-regulation of Akt-mTOR signaling in granular cells and cumulus cells, leading to the deficits in the development of follicles and the biosynthesis of ovarian hormones.

Cell organelles as targets of mammalian cadmium toxicity

Ever increasing environmental presence of cadmium as a consequence of industrial activities is considered a health hazard and is closely linked to deteriorating global health status. General animal and human cadmium exposure ranges from ingestion of foodstuffs sourced from heavily polluted hotspots and cigarette smoke to widespread contamination of air and water, including cadmium-containing microplastics found in household water. Cadmium is promiscuous in its effects and exerts numerous cellular perturbations based on direct interactions with macromolecules and its capacity to mimic or displace essential physiological ions, such as iron and zinc. Cell organelles use lipid membranes to form complex tightly-regulated, compartmentalized networks with specialized functions, which are fundamental to life. Interorganellar communication is crucial for orchestrating correct cell behavior, such as adaptive stress responses, and can be mediated by the release of signaling molecules, exchange of organelle contents, mechanical force generated through organelle shape changes or direct membrane contact sites. In this review, cadmium effects on organellar structure and function will be critically discussed with particular consideration to disruption of organelle physiology in vertebrates.

Autophagy in Female Fertility: A Role in Oxidative Stress and Aging

Significance: The precipitous age-related decline in female fertility is intimately associated with a reduction in both the quantity and quality of the germline (oocytes). Although complex etiologies undoubtedly contribute to the deterioration of oocyte quality, increasing attention has focused on the pervasive impact of oxidative stress. Indeed, the prolonged lifespan of the meiotically arrested oocyte places this cell at heightened risk of oxidative lesions, which commonly manifest in dysregulation of protein homeostasis (proteostasis). Although oocytes are able to mitigate this threat via the mobilization of a sophisticated network of surveillance, repair, and proteolytic pathways, these defenses are themselves prone to age-related defects, reducing their capacity to eliminate oxidatively damaged proteins. Recent Advances: Here, we give consideration to the quality control mechanisms identified within the ovary that afford protection to the female germline. Our primary focus is to review recent advances in our understanding of the autophagy pathway and its contribution to promoting oocyte longevity and modulating pathophysiological responses to oxidative stress. In addition, we explore the therapeutic potential of emerging strategies to fortify autophagic activity. Critical Issues: The complex interplay of oxidative stress and autophagy has yet to be fully elucidated within the context of the aging oocyte and surrounding ovarian environment. Future Directions: Emerging evidence provides a strong impetus to resolve the causal link between autophagy and oxidative stress-driven pathologies in the aging oocyte. Such research may ultimately inform novel therapeutic strategies to combat the age-related loss of female fertility via fortification of intrinsic autophagic activity.

Autophagy and Apoptosis of Porcine Ovarian Granulosa Cells During Follicular Development

Simple Summary

Granulosa cells (GCs) provide nutrients and information for oocytes in porcine follicles. Follicular atresia is closely related to both apoptosis and autophagy of granulosa cells in ovarian follicles; however, the follicular stages of granulosa cell apoptosis or autophagy during follicular development or atresia are poorly understood. We found that autophagy and apoptosis of GCs occurred in GCs from different size follicles during follicular development, and autophagy was mainly found in GCs of medium follicles, while apoptosis was mainly found in GCs of large follicles. These data provided some useful information to understand follicular atresia which is related to the fertility of sows.

Abstract

Follicular atresia is closely related to both apoptosis and autophagy of granulosa cells (GCs) in ovarian follicles. In the present study, GCs were isolated from pig ovaries in small, medium and large antral follicles, and the current results showed that the proliferation of GCs was higher in medium follicles, and lower in large follicles compared to small follicles. The Bax and Caspase 3 mRNA levels were significantly higher, but the ratio of Bcl-2/Bax was lower in GCs of large follicles. The marker genes of autophagy, Atg3, Atg7 and LC3 mRNA levels were higher in GCs from medium follicles. Apoptosis- and autophagy-related proteins had a similar expression pattern to the mRNA level. Our results showed that phosphorylated ERK (p-ERK) was activated in GCs of large follicles, while phosphorylated AKT (p-AKT) and phosphorylated mTOR (p-mTOR) were inhibited in GCs of medium follicles. Labeling of autophagic vesicles with 4’,6-diamidino-2-phenylindole (DAPI) and monodansylcadaverine (MDC) confirmed the results of gene transcription and protein expression in GCs of different size follicles. We conclude that autophagy and apoptosis of GCs occurred in different size follicles during follicular development, and autophagy was mainly found in GCs of medium follicles, while apoptosis was mainly found in GCs of large follicles.

Autophagy in hypoxic ovary

Oxygen deprivation affects human health by modulating system as well as cellular physiology. Hypoxia generates reactive oxygen species (ROS), causes oxidative stress and affects female reproductive health by altering ovarian as well as oocyte physiology in mammals. Hypoxic conditions lead to several degenerative changes by inducing various cell death pathways like autophagy, apoptosis and necrosis in the follicle of mammalian ovary. The encircling somatic cell death interrupts supply of nutrients to the oocyte and nutrient deprivation may result in the generation of ROS. Increased level of ROS could induce granulosa cells as well as oocyte autophagy. Although autophagy removes damaged proteins and subcellular organelles to maintain the cell survival, irreparable damages could induce cell death within intra-follicular microenvironment. Hypoxia-induced autophagy is operated through 5' AMP activated protein kinase-mammalian target of rapamycin, endoplasmic reticulum stress/unfolded protein response and protein kinase C delta-c-junN terminal kinase 1 pathways in a wide variety of somatic cell types. Similar to somatic cells, we propose that hypoxia may induce granulosa cell as well as oocyte autophagy and it could be responsible at least in part for germ cell elimination from mammalian ovary. Hypoxia-mediated germ cell depletion may cause several reproductive impairments including early menopause in mammals.

The role of androgen in autophagy of granulosa cells from PCOS

Hyperandrogenism is one of the most common causes for anovulation in women and increases the risk for metabolic disorder in PCOS patients. Autophagy plays an important role in dysfunction of endocrine and anovulation. However, the relationship between hyperandrogenism and autophagy in human granulosa cells of PCOS patients remains unclear. By collecting granulosa cells from PCOS patients and non-PCOS patients, we found that the abundance of autophagy-related genes ATG5, ATG7, BECN1 mRNA and the ratio of autophagy marker protein light chain 3B II/I (LC3 II/I) were significantly increased whereas the abundance of the autophagy substrate SQSTM1/p62 was decreased in ovarian granulosa cells from PCOS patients. Furthermore, we demonstrated that BECN1 mRNA abundance in human granulosa cells positively correlated with the basal level of serum total testosterone and androgen up-regulated the abundance of BECN1 mRNA and the ratio of LC3II/LC3I in a dose-dependent manner in cultured granulosa cells. These observations indicated that androgen-induced activation of autophagy may play an important role in the development of PCOS and to explore the autophagy mechanisms involved in PCOS yield new insight into the pathophysiology and therapy of the disorder.

FOXO3 Is Expressed in Ovarian Tissues and Acts as an Apoptosis Initiator in Granulosa Cells of Chickens

FOXO3, which encodes the transcription factor forkhead box O-3 (FoxO3), is a member of the FOXO subfamily of the forkhead box (FOX) family. FOXO3 can be negatively regulated by its phosphorylation by the PI3K/Akt signaling pathway and ultimately drives apoptosis when activated. In mammalian ovaries, the FOXO3 protein regulates atresia and follicle growth by promoting apoptosis of ovarian granulosa cells. Nonetheless, the specific effects of the FOXO3 protein on granulosa apoptosis of avian ovaries have not been elucidated. Therefore, we studied FOXO3 expression in follicles with different organization and at all hierarchical levels of chicken follicles. Via an immunofluorescence assay, the chicken follicular theca at all hierarchical levels were found to be strongly stained with an anti-FOXO3 antibody. In chicken primary ovarian granulosa cells, mRNA levels of proapoptotic factors BNIP3 and BCL2L11 decreased in the absence of FOXO3, and so did PARP-1 and cleaved caspase 3 protein levels. After treatment with a recombinant FOXO3 protein, PARP-1 and caspase 3 protein levels increased, along with mRNA levels of Bnip3 and BCL2L11 (significantly, p<0.05). In addition, FOXO3 was downregulated in chicken granulosa cells when different estradiol or FSH concentrations were applied. In conclusion, FOXO3 is expressed in chicken reproductive tissues, including follicles and ovarian granulosa cells, and promotes apoptosis of chicken ovarian granulosa cells.

Essential role of autophagy in resource allocation during sexual reproduction

Sexual reproduction is the most common form of reproduction among eukaryotes, which is characterized by a series of massive cellular or tissue renovations. Recent studies have revealed novel functions of autophagy during sexual reproductive processes, ranging from yeast to mammals. In mammals, autophagy is indispensable for spermatogenesis and oogenesis, and it participates in early embryonic development and maternal-fetus crosstalk to ensure the development of embryos or fetuses. Thus, autophagy provides the molecular basis for resource allocation among parents and their offspring, providing an important way to benefit the next generation.Abbreviations: ATG: autophagy-related; Becn1: beclin 1, autophagy related; CMA: chaperone-mediated autophagy; epg: ectopic PGL granules; ES: ectoplasmic specialization; EVTs: extravillous trophoblasts; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PCD: programmed cell death; PTB: preterm birth; STB: syncytiotrophoblast.

Puerarin prevents cadmium-induced hepatic cell damage by suppressing apoptosis and restoring autophagic flux

Cadmium (Cd) is a common heavy metal contamination that is highly toxic to liver. Puerarin (PU), a potent free radical scavenger, has been shown to exert cytoprotective effect in numerous pathological processes. However, whether PU affords protection against Cd-induced hepatotoxicity remains unclear to be known. Here, we aimed to investigate the protective effect of PU on Cd-induced hepatotoxicity in an immortalized mouse hepatocyte line, AML-12. First, Cd-induced cytotoxicity in AML-12 cells was obviously ameliorated by PU treatment. Also, Cd-induced apoptotic cell death was markedly alleviated by PU treatment, evidenced by two methods. Simultaneously, Cd-elevated malondialdehyde and reactive oxygen species levels were significantly reduced by PU administration, demonstrating the antioxidant effect of PU against Cd exposure. Moreover, Cd-induced blockage of autophagic flux in AML-12 cells was obviously restored by PU treatment, evidenced by immunoblot analysis of autophagy marker proteins and tandem fluorescent-tagged LC3 method. Resultantly, Cd-induced autophagosome accumulation was significantly alleviated by PU treatment. In conclusion, these observations demonstrate that PU treatment alleviates Cd-induced hepatic cell damage by inhibiting apoptosis and restoring autophagy activity, which is intimately related with its antioxidant activity.

Autophagy in Ovarian Follicular Development and Atresia

Autophagy is a mechanism that exists in all eukaryotes under a variety of physiological and pathological conditions. In the mammalian ovaries, less than 1% of follicles ovulate, whereas the remaining 99% undergo follicular atresia. Autophagy and apoptosis have been previously found to be involved in the regulation of both primordial follicular development as well as atresia. The relationship between autophagy, follicular development, and atresia have been summarized in this review with the aim to obtain a more comprehensive understanding of the role played by autophagy in follicular development and atresia.

NFAT5 is Regulated by p53/miR-27a Signal Axis and Promotes Mouse Ovarian Granulosa Cells Proliferation

MicroRNAs (miRNAs) play key roles in mammalian folliculogenesis (a complex process in which primordial follicles develop into mature oocytes) by inhibiting mRNA translation or by inducing its degradation, while the role of miRNA in folliculogenesis and regulation mechanism remain unclear. In this study, we explored the role of the p53/miR-27a/nuclear factor of activated T-cells 5 (NFAT5) signaling axis in mouse ovarian granulosa cell proliferation. Luciferase reporter assay, overexpression, site-directed mutagenesis, and chromatin immunoprecipitation (ChIP) assay results showed that the transcription factor p53 significantly decreased the expression level of miR-27a by binding to sites 4 (-646 to -637 bp) and 10 (-50 to -41 bp) of the miR-27a promoter. Moreover, miR-27a directly targeted the 3′-untranslated region of the target gene, NFAT5, to regulate its expression levels. p53 also upregulated the expression of NFAT5. Meanwhile, overexpression of NFAT5 strongly upregulated the mRNA and protein levels of the Wnt signaling genes, β-catenin and B-Cell CLL/Lymphoma 2 (Bcl-2). In addition, NFAT5 promoted mouse granulosa cell proliferation; this was confirmed by EdU/Hoechst immunostaining. Taken together, our findings define a novel pathway p53/miR-27a/NFAT5, and NFAT5 regulates mouse granulosa cell functions via activating Wnt signaling pathway.

Mitochondrial division inhibitor-1 potentiates cisplatin-induced apoptosis via the mitochondrial death pathway in cholangiocarcinoma cells

AIMS

Mdivi-1, a selective Drp-1 inhibitor, impedes mitochondrial dynamics and suppresses cancer proliferation and progression. Cholangiocarcinoma (CCA) is a very aggressive malignancy which is refractory to chemotherapy. The study investigated the mechanism of the chemosensitizing effect of mdivi-1 in cholangiocarcinoma.

MAIN METHODS

CCA cells and HEK293 T cells were employed in the study. Cell viability and induction of apoptotic cell death were determined by the MTT and acridine orange-ethidium bromide methods. Cellular glutathione content and reactive oxygen species (ROS) formation were assessed using thiol green and 2',7'-dichlorofluorescin diacetate fluorescent probes, respectively. Mitochondrial transmembrane potential and autophagy were detected by JC-1 dye and autophagy assay. Cell cycle progression was analyzed by flow cytometry. Cell migration was measured using the wound healing assay. Proteins involved in cell proliferation and cell cycle were analyzed by western immunoblotting.

KEY FINDINGS

Mdivi-1 enhanced cisplatin-induced cytotoxicity in CCA cells but not in HEK293 T cells. Mdivi-1 enhanced cisplatin induced glutathione redox stress, ROS formation, and loss of mitochondrial transmembrane potential. Moreover, mdivi-1 also inhibited autophagic flux and suppressed CCA cell migration.

SIGNIFICANCE

Mdivi-1 sensitized CCA cells to cytotoxicity of cisplatin in association with increases of oxidative stress and autophagosomes, and induced cell death via the mitochondrial pathway. Disruption of mitochondrial dynamics may be a novel strategy to improve the efficacy of chemotherapy to treat CCA.

The physiological roles of autophagy in the mammalian life cycle

Autophagy is primarily an efficient intracellular catabolic pathway used for degradation of abnormal cellular protein aggregates and damaged organelles. Although autophagy was initially proposed to be a cellular stress responder, increasing evidence suggests that it carries out normal physiological roles in multiple biological processes. To date, autophagy has been identified in most organs and at many different developmental stages, indicating that it is not only essential for cellular homeostasis and renovation, but is also important for organ development. Herein, we summarize our current understanding of the functions of autophagy (which here refers to macroautophagy) in the mammalian life cycle.

The Mechanism of Melatonin and Its Receptor MT2 Involved in the Development of Bovine Granulosa Cells

Ovarian granulosa cells (GCs) are a critical approach to investigate the mechanism of gene regulation during folliculogenesis. The objective of this study was to investigate the role of MT2 in bovine GCs, and assess whether MT2 silencing affected GCs response to melatonin. We found that MT2 silencing significantly decreased the secretion of progesterone and estradiol, and increased the concentration of inhibin B and activin B. To further reveal the regulatory mechanism of MT2 silencing on steroids synthesis, it was found that the expression of CYP19A1 and CYP11A1 enzymes (steroid hormone synthesis) were down-regulated, while genes related to hormonal synthesis (StAR, RUNX2, INHA and INHBB) were up-regulated without affecting the expression of INHBA, suggesting that MT2 silencing may regulate hormone abundance. Furthermore, MT2 silencing significantly increased the expression of TGFBR3 and BMP6, and decreased the expression of LHR and DNMT1A without significant difference in the expression of FSHR and EGFR. In addition, MT2 silencing didn’t affect the effect of melatonin on increasing the expression of DNMT1A, EGFR, INHBA and LHR, and progesterone level, or decreasing INHA, TGFBR3 and StAR expression, and production of inhibin B. Moreover, MT2 silencing could disrupt the role of melatonin in decreasing the FSHR, INHBB and BMP6 expression, and activin B secretion. In conclusion, these results reveal that melatonin and MT2 are essential regulator of bovine GCs function by modulating reproduction-related genes expression, hormones secretion and other regulators of folliculogenesis.

Melatonin protects mouse granulosa cells against oxidative damage by inhibiting FOXO1-mediated autophagy: Implication of an antioxidation-independent mechanism

Oxidative stress has been described as a prime driver of granulosa cell (GCs) death during follicular atresia. Increasing evidence suggests potential roles of melatonin in protecting GCs from oxidative injury, though the underlying mechanisms remain largely undetermined. Here we first proposed that the inhibition of autophagy through some novel regulators contributes to melatonin-mediated GCs survival under conditions of oxidative stress. Oxidant-induced loss of GCs viability was significantly reduced after melatonin administration, which was correlated with attenuated autophagic signals upon oxidative stimulation both in vivo and in vitro. Compared with melatonin treatment, suppression of autophagy displayed similar preventive effect on GCs death during oxidative stress, but melatonin provided no additional protection in GCs pretreated with autophagy inhibitors. Notably, we found that melatonin-directed regulation of autophagic death was independent of its antioxidation/radical scavenging ability. Further investigations identified FOXO1 as a critical downstream effector of melatonin in promoting GCs survival from oxidative stress-induced autophagy. Specifically, suppression of FOXO1 via the melatonin-phosphatidylinositol 3-kinase (PI3K)-AKT axis not only improved GCs resistance to oxidative stress, but also abolished the autophagic response, from genes expression to the formation of autophagic vacuoles. Moreover, the activation of SIRT1 signaling was required for melatonin-mediated deacetylation of FOXO1 and its interaction with ATG proteins, as well as the inhibition of autophagic death in GCs suffering oxidative stress. These findings reveal a brand new mechanism of melatonin in defense against oxidative damage to GCs by repressing FOXO1, which may be a potential therapeutic target for anovulatory disorders.

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Melatonin inhibits oxidative damage in GC without scavenging oxidative stress itself.

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Melatonin protects GC from oxidative damage via inhibiting autophagic cell death.

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Inhibition of FOXO1-dependent autophagy by melatonin reduces oxidative damage in GC.

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Suppression of autophagy through melatonin-PI3K-AKT-FOXO1 axis improves GC survival.

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Melatonin reduces oxidative injury by inhibiting SIRT1-FOXO1-ATG7-dependent autophagy.

Combining chloroquine with RAD001 inhibits tumor growth in a NEN mouse model

Patients with neuroendocrine neoplasms (NENs) often require systemic treatment, which is frequently limited by the emergence of drug resistance. mTOR inhibitors (mTORi), such as RAD001 (everolimus), have been shown to inhibit neoplasm progression. mTORi stimulates autophagy, a degradation pathway that might promote the survival of neoplasm cells that are exposed to anti-cancer therapy. Chloroquine (CQ), a well-known anti-malarial and anti-rheumatic drug, suppresses autophagy. Based on our previous results, we hypothesized that CQ may enhance the anti-tumorigenic effects of mTORi by inhibiting autophagy and we aimed to examine the anti-tumorigenic effect of CQ, alone or in combination with RAD001. We established a NEN subcutaneous xenograft mouse model and evaluated the effect of the drugs on tumor growth, mTOR pathway, autophagy and apoptosis. CQ alone and in combination with RAD001 significantly decreased neoplasm volume. Histopathological analysis revealed that the combination of CQ and RAD001 markedly inhibited mTOR activity and neoplasm cell growth, along with accumulation of autophagosomes and increased apoptosis. In conclusion, CQ enhances the anti-tumorigenic effect of RAD001 in vivo by inhibiting autophagy. Clinical trials addressing the effects of CQ therapy on neoplasm progression in patients with NENs, mainly in those treated with mTORi, are warranted.

Autophagy, Cell Viability, and Chemoresistance Are Regulated By miR-489 in Breast Cancer

It is postulated that the complexity and heterogeneity in cancer may hinder most efforts that target a single pathway. Thus, discovery of novel therapeutic agents targeting multiple pathways, such as miRNAs, holds promise for future cancer therapy. One such miRNA, miR-489, is downregulated in a majority of breast cancer cells and several drug-resistant breast cancer cell lines, but its role and underlying mechanism for tumor suppression and drug resistance needs further investigation. The current study identifies autophagy as a novel pathway targeted by miR-489 and reports Unc-51 like autophagy activating kinase 1 (ULK1) and lysosomal protein transmembrane 4 beta (LAPTM4B) to be direct targets of miR-489. Furthermore, the data demonstrate autophagy inhibition and LAPTM4B downregulation as a major mechanism responsible for miR-489-mediated doxorubicin sensitization. Finally, miR-489 and LAPTM4B levels were inversely correlated in human tumor clinical specimens, and more importantly, miR-489 expression levels predict overall survival in patients with 8q22 amplification (the region in which LAPTM4B resides).Implications: These findings expand the understanding of miR-489-mediated tumor suppression and chemosensitization in and suggest a strategy for using miR-489 as a therapeutic sensitizer in a defined subgroup of resistant breast cancer patients. Mol Cancer Res; 16(9); 1348-60. ©2018 AACR.

RNAi-mediated knockdown of MTNR1B without disrupting the effects of melatonin on apoptosis and cell cycle in bovine granulose cells

Melatonin is well known as a powerful free radical scavenger and exhibits the ability to prevent cell apoptosis. In the present study, we investigated the role of melatonin and its receptor MTNR1B in regulating the function of bovine granulosa cells (GCs) and hypothesized the involvement of MTNR1B in mediating the effect of melatonin on GCs. Our results showed that MTNR1B knockdown significantly promoted GCs apoptosis but did not affect the cell cycle. These results were further verified by increasing the expression of pro-apoptosis genes (BAX and CASP3), decreasing expression of the anti-apoptosis genes (BCL2 and BCL-XL) and anti-oxidant genes (SOD1 and GPX4) without affecting cell cycle factors (CCND1, CCNE1 and CDKN1A) and TP53. In addition, MTNR1B knockdown did not disrupt the effects of melatonin in suppressing the GCs apoptosis or blocking the cell cycle. Moreover, MTNR1B knockdown did not affect the role of melatonin in increasing BCL2, BCL-XL, and CDKN1A expression, or decreasing BAX, CASP3, TP53, CCND1 and CCNE1 expression. The expression of MTNR1A was upregulated after MTNR1B knockdown, and melatonin promoted MTNR1A expression with or without MTNR1B knockdown. However, despite melatonin supplementation, the expression of SOD1 and GPX4 was still suppressed after MTNR1B knockdown. In conclusion, these findings indicate that melatonin and MTNR1B are involved in BCL2 family and CASP3-dependent apoptotic pathways in bovine GCs. MTNR1A and MTNR1B may coordinate the work of medicating the appropriate melatonin responses to GCs.

Germ cell depletion from mammalian ovary: possible involvement of apoptosis and autophagy

Mammalian ovary contains millions of germ cells during embryonic life but only few of them are culminated into oocytes that achieve meiotic competency just prior to ovulation. The majority of germ cells are depleted from ovary through several pathways. Follicular atresia is one of the major events that eliminate germ cells from ovary by engaging apoptotic as well as non-apoptotic pathways of programmed cell death. Apoptosis is characterized by several morphological changes that include cell shrinkage, nuclear condensation, membrane blebbing and cytoplasmic fragmentation by both mitochondria- as well as death receptor-mediated pathways in encircling granulosa cells and oocyte. Although necroapoptosis have been implicated in germ cell depletion, autophagy seems to play an active role in the life and death decisions of ovarian follicles. Autophagy is morphologically characterized by intracellular reorganization of membranes and increased number of autophagic vesicles that engulf bulk cytoplasm as well as organelles. Autophagy begins with the encapsulation of cytoplasmic constituents in a membrane sac known as autophagosomes. The autophagic vesicles are then destroyed by the lysosomal enzymes such as hydrolases that results in follicular atresia. It seems that apoptosis as well as autophagy could play active roles in germ cells depletion from ovary. Hence, it is important to prevent these two pathways in order to retain the germ cells in ovary of several mammalian species that are either threatened or at the verge of extinction. The involvement of apoptosis and autophagy in germ cell depletion from mammalian ovary is reviewed and possible pathways have been proposed.

Trehalose protects against cadmium-induced cytotoxicity in primary rat proximal tubular cells via inhibiting apoptosis and restoring autophagic flux

Autophagy has an important renoprotective function and we recently found that autophagy inhibition is involved in cadmium (Cd)-induced nephrotoxicity. Here, we aimed to investigate the protective effect of trehalose (Tre), a novel autophagy activator, against Cd-induced cytotoxicity in primary rat proximal tubular (rPT) cells. First, data showed that Tre treatment significantly decreased Cd-induced apoptotic cell death of rPT cells via inhibiting caspase-dependent apoptotic pathway, evidenced by morphological analysis, flow cytometric and immunoblot assays. Also, administration with Tre protected rPT cells against Cd-induced lipid peroxidation. Inhibition of autophagic flux in Cd-exposed rPT cells was markedly restored by Tre administration, demonstrated by immunoblot analysis of autophagy marker proteins and GFP and RFP tandemly tagged LC3 method. Resultantly, Cd-induced autophagosome accumulation was obviously alleviated by Tre treatment. Meanwhile, blockage of autophagosome-lysosome fusion by Cd exposure was noticeably restored by Tre, which promoted the autophagic degradation in Cd-exposed rPT cells. Moreover, Tre treatment markedly recovered Cd-induced lysosomal alkalinization and impairment of lysosomal degradation capacity in rPT cells, demonstrating that Tre has the ability to restore Cd-impaired lysosomal function. Collectively, these findings demonstrate that Tre treatment alleviates Cd-induced cytotoxicity in rPT cells by inhibiting apoptosis and restoring autophagic flux.

Administration of follicle-stimulating hormone induces autophagy via upregulation of HIF-1α in mouse granulosa cells

Recent studies reported the important role of autophagy in follicular development. However, the underlying molecular mechanisms remain elusive. In this study, we investigated the effect of follicle-stimulating hormone (FSH) on mouse granulosa cells (MGCs). Results indicated that autophagy was induced by FSH, which is known to be the dominant hormone regulating follicular development and granulosa cell (GC) proliferation. The activation of mammalian target of rapamycin (mTOR), a master regulator of autophagy, was inhibited during the process of MGC autophagy. Moreover, MHY1485 (an agonist of mTOR) significantly suppressed autophagy signaling by activating mTOR. The expression of hypoxia-inducible factor 1-alpha (HIF-1α) was increased after FSH treatment. Blocking hypoxia-inducible factor 1-alpha attenuated autophagy signaling. In vitro, CoCl₂-induced hypoxia enhanced cell autophagy and affected the expression of beclin1 and BCL2/adenovirus E1B interacting protein 3 (Bnip3) in the presence of FSH. Knockdown of beclin1 and Bnip3 suppressed autophagy signaling in MGCs. Furthermore, our in vivo study demonstrated that the FSH-induced increase in weight was significantly reduced after effectively inhibiting autophagy with chloroquine, which was correlated with incomplete mitophagy process through the PINK1-Parkin pathway, delayed cell cycle, and reduced cell proliferation rate. In addition, chloroquine treatment decreased inhibin alpha subunit, but enhanced the expression of 3 beta-hydroxysteroid dehydrogenase. Blocking autophagy resulted in a significantly lower percentage of antral and preovulatory follicles after FSH stimulation. In conclusion, our results indicate that FSH induces autophagy signaling in MGCs via HIF-1α. In addition, our results provide evidence that autophagy induced by FSH is related to follicle development and atresia.

Hatching enzymes disrupt aberrant gonadal degeneration by the autophagy/apoptosis cell fate decision

Environmental stressors, gonadal degenerative diseases and tumour development can significantly alter the oocyte physiology, and species fertility and fitness. To expand the molecular understanding about oocyte degradation, we isolated several spliced variants of Japanese anchovy hatching enzymes (AcHEs; ovastacin homologue) 1 and 2, and analysed their potential in oocyte sustenance. Particularly, AcHE1b, an ovary-specific, steroid-regulated, methylation-dependent, stress-responsive isoform, was neofunctionalized to regulate autophagic oocyte degeneration. AcHE1a and 2 triggered apoptotic degeneration in vitellogenic and mature oocytes, respectively. Progesterone, starvation, and high temperature elevated the total degenerating oocyte population and AcHE1b transcription by hyper-demethylation. Overexpression, knockdown and intracellular zinc ion chelation study confirmed the functional significance of AcHE1b in autophagy induction, possibly to mitigate the stress effects in fish, via ion-homeostasis. Our finding chronicles the importance of AcHEs in stress-influenced apoptosis/autophagy cell fate decision and may prove significant in reproductive failure assessments, gonadal health maintenance and ovarian degenerative disease therapy.

Protective mechanism of FSH against oxidative damage in mouse ovarian granulosa cells by repressing autophagy

Oxidative stress-induced granulosa cell (GCs) death represents a common reason for follicular atresia. Follicle-stimulating hormone (FSH) has been shown to prevent GCs from oxidative injury, although the underlying mechanism remains to be elucidated. Here we first report that the suppression of autophagic cell death via some novel signaling effectors is engaged in FSH-mediated GCs protection against oxidative damage. The decline in GCs viability caused by oxidant injury was remarkably reduced following FSH treatment, along with impaired macroautophagic/autophagic flux under conditions of oxidative stress both in vivo and in vitro. Blocking of autophagy displayed similar levels of suppression in oxidant-induced cell death compared with FSH treatment, but FSH did not further improve survival of GCs pretreated with autophagy inhibitors. Further investigations revealed that activation of the phosphoinositide 3-kinase (PI3K)-AKT-MTOR (mechanistic target of rapamycin [serine/threonine kinase]) signaling pathway was required for FSH-mediated GCs survival from oxidative stress-induced autophagy. Additionally, the FSH-PI3K-AKT axis also downregulated the autophagic response by targeting FOXO1, whereas constitutive activation of FOXO1 in GCs not only abolished the protection from FSH, but also emancipated the autophagic process, from the protein level of MAP1LC3B-II to autophagic gene expression. Furthermore, FSH inhibited the production of acetylated FOXO1 and its interaction with Atg proteins, followed by a decreased level of autophagic cell death upon oxidative stress. Taken together, our findings suggest a new mechanism involving FSH-FOXO1 signaling in defense against oxidative damage to GCs by restraining autophagy, which may be a potential avenue for the clinical treatment of anovulatory disorders.

Autophagy regulation of physiological and pathological processes in the female reproductive tract

Autophagy is a ubiquitous cell recycling pathway that delivers cytoplasmic constituents to the lysosome and is essential for normal cellular function. Autophagic activity is up-regulated under physiological conditions as well as stressful conditions such as nutrient deprivation, oxidative stress, hypoxia, inflammation, and infection. Thus, it is essential to regard the functional importance of the pathway and its components in a given tissue context. Here we review what is known about the involvement of autophagy process during physiological processes in the female reproductive tract and in pregnancy from preimplantation to oocyte function to placental development, parturition, and postpartum remodeling of the uterus; as well as in pathological and adverse events during these processes.

Aberrant PTEN expression in response to progesterone reduces endometriotic stromal cell apoptosis

In some human cancer cells, PTEN (phosphatase and tensin homolog deleted on chromosome 10) is known to regulate autophagy induction positively through the inhibition of PI3K/AKT pathway, leading to the activation of mTOR, a major negative regulator of autophagy. Recent studies reported that PTEN expression is abnormally decreased in endometriotic lesions. In endometriosis, abnormal PTEN expression may contribute to the alteration of endometrial cell autophagy, which may affect apoptosis because endometrial cell autophagy is directly involved in the regulation of apoptosis. To test this hypothesis, we evaluated the involvement of PTEN in the regulation of autophagy induction in human normal endometrial stromal cells (NESCs). In addition, we sought to determine whether aberrant PTEN expression in endometriotic cyst stromal cells (ECSCs) is associated with autophagy dysregulation, and a subsequent decrease in apoptosis. Our results show that PTEN expression was enhanced by progesterone treatment in NESCs. Subsequently, autophagy and apoptosis induction increased through the inhibition of AKT and mTOR activity. This progesterone-induced increase in apoptosis was reversed by the inhibition of autophagy induction using either mifepristone (progesterone receptor modulator) or PTEN inhibitor. In contrast, progesterone had no significant effects on PTEN expression, AKT, mTOR activity, autophagy or apoptosis in ECSCs. Furthermore, in contrast to normal eutopic endometrium, endometriotic tissues have constant PTEN expression, autophagy and apoptosis throughout the menstrual cycle. In conclusion, our results suggest abnormal PTEN expression in response to progesterone was observed in ECSCs, which led to the dysregulation of autophagy induction via AKT/mTOR signalling and a subsequent decrease in apoptosis.

FSH protects mouse granulosa cells from oxidative damage by repressing mitophagy

Oxidative stress has been implicated in triggering granulosa cell (GC) death during follicular atresia. Recent studies suggested that follicle-stimulating hormone (FSH) has a pivotal role in protecting GCs from oxidative injury, although the exact mechanism remains largely unknown. Here, we report that FSH promotes GC survival by inhibiting oxidative stress-induced mitophagy. The loss of GC viability caused by oxidative stress was significantly reduced after FSH treatment, which was correlated with impaired activation of mitophagy upon oxidative stress. Compared with FSH treatment, blocking mitophagy displayed approximate preventive effect on oxidative stress-induced GC death, but FSH did not further restore viability of cells pretreated with mitophagy inhibitor. Importantly, FSH suppressed the induction of serine/threonine kinase PINK1 during oxidative stress. This inhibited the mitochondrial translocation of the E3 ligase Parkin, which is required for the subsequent clearance of mitochondria, and ultimately cell death via mitophagy. In addition, knocking down PINK1 using RNAi confirmed the role of the FSH-PINK1-Parkin-mitophagy pathway in regulating GC survival under oxidative conditions. These findings introduce a novel physiological function of FSH in protecting GCs against oxidative damage by targeting PINK1-Parkin-mediated mitophagy.

Autophagic regulation in steroid hormone-responsive systems

Two female sex steroid hormones, estrogen and progesterone, are crucial regulators of many physiological functions of reproductive organs. These two hormones are versatile factors linking growth, differentiation, metabolism, and death of cells in the uterus. In recent years, it has become evident that autophagy is involved in the effects of estrogen and progesterone on various cellular events in reproductive organs. Autophagy is the self-eating catabolic process which is linked to cell survival and death in many contexts. In this review, we focus on the new findings concerning the regulation of autophagic response by sex steroid hormones in responsive target organs. We also attempt to further expand our insight into intracellular signaling mediators governing this regulation.

MicroRNA let-7g regulates mouse granulosa cell autophagy by targeting insulin-like growth factor 1 receptor

As an important type of somatic cell, granulosa cells play a major role in deciding the fate of follicles. Therefore, analyses of granulosa cell apoptosis and follicular atresia have become hotspots of animal research. Autophagy is a cellular catabolic mechanism that protects cells from stress conditions, including starvation, hypoxia, and accumulation of misfolded proteins. However, the relationship between autophagy and apoptosis in granulosa cells is not well known. Here, we demonstrate that let-7g regulates the mouse granulosa cell autophagy signaling pathway by inhibiting insulin-like growth factor 1 receptor expression and affecting the phosphorylation of protein kinase B/mammalian target of rapamycin. Small interference-mediated knockdown of insulin-like growth factor 1 receptor significantly promoted autophagy signaling of mouse granulosa cells. In contrast, overexpression of insulin-like growth factor 1 receptor in mouse granulosa cells attenuated autophagy activity in the presence of let-7g. In addition, overexpression of let-7g increased the apoptosis rate, as indicated by an increased number of terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling-positive cells. Finally, 3-methyladenine as well as the lysosomal enzyme inhibitor chloroquine partially blocked apoptosis. In summary, this study demonstrates that let-7g regulates autophagy in mouse granulosa cells by targeting insulin-like growth factor 1 receptor and downregulating protein kinase B/mammalian target of rapamycin signaling, and that mouse granulosa cell autophagy induced by let-7g participates in apoptosis.

Critical Role of FoxO1 in Granulosa Cell Apoptosis Caused by Oxidative Stress and Protective Effects of Grape Seed Procyanidin B2

Reactive oxygen species (ROS) are closely related to the follicular granulosa cell apoptosis. Grape seed procyanidin B2 (GSPB2) has been reported to possess potent antioxidant activity. However, the GSPB2-mediated protective effects and the underlying molecular mechanisms in granulosa cell apoptosis process remain unknown. In this study, we showed for the first time that GSPB2 treatment decreased FoxO1 protein level, improved granulosa cell viability, upregulated LC3-II protein level, and reduced granulosa cell apoptosis rate. Under a condition of oxidative stress, GSPB2 reversed FoxO1 nuclear localization and increased its level in cytoplasm. In addition, FoxO1 knockdown inhibited the protective effects of GSPB2 induced. Our findings suggest that FoxO1 plays a pivotal role in regulating autophagy in granulosa cells, GSPB2 exerts a potent and beneficial role in reducing granulosa cell apoptosis and inducing autophagy process, and targeting FoxO1 could be significant in fighting against oxidative stress-reduced female reproductive system diseases.

PI3K/PTEN/Akt and TSC/mTOR signaling pathways, ovarian dysfunction, and infertility: an update

Abnormalities in ovarian function, including defective oogenesis and folliculogenesis, represent a key female reproductive deficiency. Accumulating evidence in the literature has shown that the PI3K/PTEN/Akt and TSC/mTOR signaling pathways are critical regulators of ovarian function including quiescence, activation, and survival of primordial follicles, granulosa cell proliferation and differentiation, and meiotic maturation of oocytes. Dysregulation of these signaling pathways may contribute to infertility caused by impaired follicular development, intrafollicular oocyte development, and ovulation. This article reviews the current state of knowledge of the functional role of the PI3K/PTEN/Akt and TSC/mTOR pathways during mammalian oogenesis and folliculogenesis and their association with female infertility.

Beclin-1 deficiency in the murine ovary results in the reduction of progesterone production to promote preterm labor

Autophagy is an important cellular process that serves as a companion pathway to the ubiquitin-proteasome system to degrade long-lived proteins and organelles to maintain cell homeostasis. Although initially characterized in yeast, autophagy is being realized as an important regulator of development and disease in mammals. Beclin1 (Becn1) is a putative tumor suppressor gene that has been shown to undergo a loss of heterozygosity in 40-75% of human breast, ovarian, and prostate cancers. Because Becn1 is a key regulator of autophagy, we sought to investigate its role in female reproduction by using a conditional knockout approach in mice. We find that pregnant females lacking Becn1 in the ovarian granulosa cell population have a defect in progesterone production and a subsequent preterm labor phenotype. Luteal cells in this model exhibit defective autophagy and a failure to accumulate lipid droplets needed for steroidogenesis. Collectively, we show that Becn1 provides essential functions in the ovary that are essential for mammalian reproduction.

Interplay between autophagy and apoptosis in the development of Danio rerio follicles and the effects of a probiotic

The present study investigated autophagic processes in Danio rerio preovulatory follicles (Stage III and IV). There were more autophagosomes, as revealed by electron microscopy, in follicles from females fed the probiotic Lactobacillus rhamnosus IMC 501. This was confirmed by increased expression of genes involved in the autophagic process, namely ambra1, becn1, lc3 and uvrag. In addition, preovulatory follicles from females fed the probiotic contained more microtubule-associated protein 1 light chain 3 isoform II (LC3-II) and less p62 protein. The increased autophagy in preovulatory follicles from females fed the probiotic was concomitant with a decrease in the apoptotic process in the ovary, as evidenced by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling analysis and confirmed by lower expression of genes involved in apoptosis (i.e., p53, bax, apaf and cas3) and higher expression as igfII and igf1r. The results of the present study provide preliminary evidence of the involvement of autophagy during follicle development in the zebrafish ovary. In addition, we have demonstrated for the first time that a functional food, such as L. rhamnosus IMC 501, can modulate the balance between apoptosis and autophagy that regulates ovary physiology in zebrafish by inhibiting follicular apoptosis and improving follicular survival.

AKT is involved in granulosa cell autophagy regulation via mTOR signaling during rat follicular development and atresia

In this study, we examined whether granulosa cell autophagy during follicular development and atresia was regulated by the class I phosphoinositide-3 kinase/protein kinase B (AKT) pathway, which is known to control the activity of mammalian target of rapamycin (mTOR), a major negative regulator of autophagy. Ovaries and granulosa cells were obtained using an established gonadotropin-primed immature rat model that induces follicular development and atresia. Autophagy was evaluated by measuring the expression level of microtubule-associated protein light chain 3-II (LC3-II) using western blots and immunohistochemistry. The activity of AKT and mTOR was also examined by observing the phosphorylation of AKT and ribosomal protein S6 kinase (S6K) respectively. After gonadotropin injection, LC3-II expression was suppressed and phosphorylation of AKT and S6K increased in rat granulosa cells. By contrast, gonadotropin withdrawal by metabolic clearance promoted LC3-II expression and decreased phosphorylation of AKT and S6K. In addition,in-vitroFSH treatment of rat granulosa cells also indicated inhibition of LC3-II expression accompanied by a marked increase in phosphorylation of AKT and S6K. Inhibition of AKT phosphorylation using AKT inhibitor VIII suppressed FSH-mediated phosphorylation of S6K, followed by an increase in LC3-II expression. Furthermore, co-treatment with FSH and AKT inhibitor increased the levels of apoptosis and cell death of granulosa cells compared with the single treatment with FSH. Taken together, our findings indicated that AKT-mediated activation of mTOR suppresses granulosa cell autophagy during follicular development and is involved in the regulation of apoptotic cell death.

Microcystin-LR induces autophagy and apoptosis in rat Sertoli cells in vitro

Although microcystin-LR (MC-LR) produced by cyanobacteria has been demonstrated with strong reproductive toxicity, the mechanisms remain unclear. This study aimed to probe the effects of MC-LR on induction of autophagy in Sertoli cells, as well as the relationship between autophagy and apoptosis. After exposure to various concentrations of MC-LR for 24 or 48 h, cell viability and membrane integrity were significantly decreased under high MC-LR conditions (50-500 nM). The autophagosome marker protein LC3 was increased at mild MC-LR concentrations (0.5-5 nM). However, autophagosomes accumulated to their peak level under high MC-LR conditions in parallel with significantly up-regulated apoptosis. Treatment with an autophagy inhibitor (3-MA) abrogated autophagosome accumulation and apoptosis. This study demonstrated that MC-LR had toxic effects on Sertoli cells by inducing autophagy and apoptosis. The autophagosome accumulation may be involved in the apoptosis induced by MC-LR.