Bisphenol S Impairs Oestradiol Secretion during In Vitro Basal Folliculogenesis in a Mono-Ovulatory Species Model

Perinatal bisphenol S exposure exacerbates the oxidative burden and apoptosis in neonatal ovaries by suppressing the mTOR/autophagy axis

Bisphenol S (BPS) is an emerging environmental endocrine disruptor capable of crossing the placental barrier, resulting in widespread exposure to pregnant women due to its extensive usage. However, the impact of perinatal maternal exposure to BPS on reproductive health in offspring and the underlying molecular mechanism remain underexplored. In this study, gestational ICR mice were provided with drinking water containing 3.33 mg/L BPS to mimic possible human exposure in some countries. Results demonstrated that BPS accelerated the breakdown of germ-cell cysts and the assembly of primordial follicles in neonates, leading to oocyte over-loss. Furthermore, the expression levels of folliculogenesis-related genes (Kit, Nobox, Gdf9, Sohlh2, Kitl, Bmp15, Lhx8, Figla, and Tgfb1) decreased, thus compromising oocyte quality and disrupting early folliculogenesis dynamics. BPS also disrupted other aspects of offspring reproduction, including advancing puberty onset, disrupting the estrus cycle, and impairing fertility. Further investigation found that BPS exposure inhibited the activities and expression levels of antioxidant-related enzymes in neonatal ovaries, leading to the substantial accumulation of MDA and ROS. The increased oxidative burden exacerbated the intracellular apoptotic signaling, manifested by increased expression levels of pro-apoptotic markers (Bax, Caspase 3, and Caspase 9) and decreased expression levels of anti-apoptotic marker (Bcl2). Concurrently, BPS inhibited autophagy by increasing p-mTOR/mTOR and decreasing p-ULK1/ULK1, subsequently down-regulating autophagy flux-related biomarkers (LC3b/LC3a and Beclin-1) and impeding the degradation of autophagy substrate p62. However, the imbalanced crosstalk between autophagy, apoptosis and oxidative stress homeostasis was restored after rapamycin treatment. Collectively, the findings demonstrated that BPS exposure induced reproductive disorders in offspring by perturbing the mTOR/autophagy axis, and such autophagic dysfunction exacerbated redox imbalance and promoted excessive apoptosis. These results provide novel mechanistic insights into the role of autophagy in mitigating BPS-induced intergenerational reproductive dysfunction.

Invisible Hand behind Female Reproductive Disorders: Bisphenols, Recent Evidence and Future Perspectives

Reproductive disorders are considered a global health problem influenced by physiological, genetic, environmental, and lifestyle factors. The increased exposure to bisphenols, a chemical used in large quantities for the production of polycarbonate plastics, has raised concerns regarding health risks in humans, particularly their endocrine-disrupting effects on female reproductive health. To provide a basis for future research on environmental interference and reproductive health, we reviewed relevant studies on the exposure patterns and levels of bisphenols in environmental matrices and humans (including susceptible populations such as pregnant women and children). In addition, we focused on in vivo, in vitro, and epidemiological studies evaluating the effects of bisphenols on the female reproductive system (the uterus, ovaries, fallopian tubes, and vagina). The results indicate that bisphenols cause structural and functional damage to the female reproductive system by interfering with hormones; activating receptors; inducing oxidative stress, DNA damage, and carcinogenesis; and triggering epigenetic changes, with the damaging effects being intergenerational. Epidemiological studies support the association between bisphenols and diseases such as cancer of the female reproductive system, reproductive dysfunction, and miscarriage, which may negatively affect the establishment and maintenance of pregnancy. Altogether, this review provides a reference for assessing the adverse effects of bisphenols on female reproductive health.

Different types of bisphenols alter ovarian steroidogenesis: Special attention to BPA

Endocrine disruptors such as bisphenol A (BPA) and some of its analogues, including BPS, BPAF, and BPE, are used extensively in the manufacture of plastics. These synthetic chemicals could seriously alter the functionality of the female reproductive system. Although the number of studies conducted on other types of bisphenols is smaller than the number of studies on BPA, the purpose of this review study was to evaluate the effects of bisphenol compounds, particularly BPA, on hormone production and on genes involved in ovarian steroidogenesis in both in vitro (human and animal cell lines) and in vivo (animal models) studies. The current data show that exposure to bisphenol compounds has adverse effects on ovarian steroidogenesis. For example, BPA, BPS, and BPAF can alter the normal function of the hypothalamic-pituitary-gonadal (HPG) axis by targeting kisspeptin neurons involved in steroid feedback signals to gonadotropin-releasing hormone (GnRH) cells, resulting in abnormal production of LH and FSH. Exposure to BPA, BPS, BPF, and BPB had adverse effects on the release of some hormones, namely 17-β-estradiol (E2), progesterone (P4), and testosterone (T). BPA, BPE, BPS, BPF, and BPAF are also capable of negatively altering the transcription of a number of genes involved in ovarian steroidogenesis, such as the steroidogenic acute regulatory protein (StAR, involved in the transfer of cholesterol from the outer to the inner mitochondrial membrane, where the steroidogenesis process begins), cytochrome P450 family 17 subfamily A member 1 (Cyp17a1, which is involved in the biosynthesis of androgens such as testosterone), 3 beta-hydroxysteroid dehydrogenase enzyme (3β-HSD, involved in the biosynthesis of P4), and cytochrome P450 family 19 subfamily A member 1 (Cyp19a1, involved in the biosynthesis of E2). Exposure to BPA, BPB, BPF, and BPS at prenatal or prepubertal stages could decrease the number of antral follicles by activating apoptosis and autophagy pathways, resulting in decreased production of E2 and P4 by granulosa cells (GCs) and theca cells (TCs), respectively. BPA and BPS impair ovarian steroidogenesis by reducing the function of some important cell receptors such as estrogens (ERs, including ERα and ERβ), progesterone (PgR), the orphan estrogen receptor gamma (ERRγ), the androgen receptor (AR), the G protein-coupled estrogen receptor (GPER), the FSHR (follicle-stimulating hormone receptor), and the LHCGR (luteinizing hormone/choriogonadotropin receptor). In animal models, the effects of bisphenol compounds depend on the type of animals, their age, and the duration and dose of bisphenols, while in cell line studies the duration and doses of bisphenols are the matter.

Cumulative and potential synergistic effects of seven different bisphenols on human granulosa cells in vitro?

Bisphenol (BP) structural analogues of BPA are widely used. Previous studies showed similar effects of BPA and BPS on reproduction in several species including human. We hypothesised that the similar effects of several bisphenols (BPs) could accumulate in granulosa cells (GCs) and affects steroidogenesis. This study investigated the effects of seven BP analogues and their equimolar cocktail on human granulosa cells (hGC) and assessed BPA, BPS, BPF and BPAF level exposures in the follicular fluid of 277 women undergoing Assisted Reproductive Technology. The hGCs were recovered after women oocyte punctures and treated with the seven BP analogues (BPS, BPA, BPAF, BPF, BPAP, BPE and BPB) or their equimolar cocktail of 7 × 1.43 or 7 × 7.14 μM for each of the seven BPs, the sum of BPs reaching 10 ("∑BPs 10 μM"), or 50 μM ("∑BPs 50 μM"), respectively. Oestradiol and progesterone secretion, cell proliferation, viability and expression of steroidogenic enzymes were investigated. Progesterone secretion was decreased by 6 BPs 10 μM and the cocktail "∑BPs 10 μM", (-17.8 to -41.3%) and by all seven BPs 50 μM and "∑BPs 50 μM" (-21.8 to -84.2%). Oestradiol secretion was decreased only by 50 μM BPAF and BPAP (-37.8% and -44%, respectively), with corresponding decreases in CYP17A1 and CYP19A1 gene expression. Cellular proliferation was decreased after treatment with 50 μM BPAF (-32.2%), BPAP (-29%), BPB (-24%) and the equimolar cocktail "∑BPs 50 μM" (-33.1%). BPB (50 μM) and the cocktail "∑BPs 50 μM" increased HSD3B2 mRNA expression. At least one BP was detected in 64 of 277 (23.1%) women follicular fluids. Similar effects of the seven BPs or their cocktail were observed on progesterone secretion and/or on cell proliferation, suggesting cumulative effects of BPs. Our results highlight the urge to consider all BPs simultaneously and to further investigate the potential additive or synergistic effects of several BPs.