Reproductive and transgenerational toxicity of bisphenol S exposure in pregnant rats: Insights into hormonal imbalance and steroid biosynthesis pathway disruption

Bisphenol S (BPS) is an alternative chemical to bisphenol A commonly used in food packaging materials. It raises concerns due to potential adverse effects on human health. However, limited evidence exists regarding reproductive toxicity from BPS exposure, and the mechanism of associated transgenerational toxicity remains unclear. In this study, pregnant SD rats were exposed to two different doses of BPS (0.05 or 20 mg/kg) from GD6 to PND21. The objective was to investigate reproductive and transmissible toxicity induced by BPS, explore endocrine effects, and uncover potential underlying mechanisms in rats. Perinatal exposure to BPS in the F0 generation significantly decreased the rate of body weight, ovarian organ coefficient, and growth and development of the F1 generation. Notably, these changes included abnormal increases in body weight and length, estrous cycle disruption, and embryonic dysplasia in F1. 4D-DIA proteomic and PRM analyses revealed that exposure to 20 mg/kg group significantly altered the expression of proteins, such as Lhcgr and Akr1c3, within the steroid biosynthetic pathway. This led to elevated levels of FSH and LH in the blood. The hypothalamic-pituitary-ovarian (HPO) axis, responsible for promoting fertility through the cyclic secretion of gonadotropins and steroid hormones, was affected. RT-qPCR and Western blot results demonstrated that the expression of GnRH in the hypothalamus was decreased, the GnRHR in the pituitary gland was decreased, and the expression of FSHβ and LHβ in the pituitary gland was increased. Overall, BPS exposure disrupts the HPO axis, hormone levels, and steroid biosynthesis in the ovaries, affecting offspring development and fertility. This study provides new insights into the potential effects of BPS exposure on the reproductive function of the body and its relevant mechanisms of action.

The prolactin receptor gene (PRLR) is linked and associated with the risk of polycystic ovarian syndrome

The prolactin receptor gene (PRLR) may contribute to polycystic ovarian syndrome (PCOS) since it plays important roles in physiological ovarian functions. PRLR-knockout mice have irregular cycles and subfertility and variants in or around the PRLR gene were associated in humans with female testosterone levels and recurrent miscarriage. We tested 40 variants in the PRLR gene in 212 Italian families phenotyped by type 2 diabetes (T2D) and PCOS and found two intronic PRLR-variants (rs13436213 and rs1604428) significantly linked to and/or associated with the risk of PCOS. This is the first study to report PRLR as a novel risk gene in PCOS. Functional studies are needed to confirm these results.

Advances in clinical applications of kisspeptin-GnRH pathway in female reproduction

BACKGROUND

Kisspeptin is the leading upstream regulator of pulsatile and surge Gonadotrophin-Releasing Hormone secretion (GnRH) in the hypothalamus, which acts as the key governor of the hypothalamic-pituitary-ovary axis.

MAIN TEXT

Exogenous kisspeptin or its receptor agonist can stimulate GnRH release and subsequent physiological gonadotropin secretion in humans. Based on the role of kisspeptin in the hypothalamus, a broad application of kisspeptin and its receptor agonist has been recently uncovered in humans, including central control of ovulation, oocyte maturation (particularly in women at a high risk of ovarian hyperstimulation syndrome), test for GnRH neuronal function, and gatekeepers of puberty onset. In addition, the kisspeptin analogs, such as TAK-448, showed promising agonistic activity in healthy women as well as in women with hypothalamic amenorrhoea or polycystic ovary syndrome.

CONCLUSION

More clinical trials should focus on the therapeutic effect of kisspeptin, its receptor agonist and antagonist in women with reproductive disorders, such as hypothalamic amenorrhoea, polycystic ovary syndrome, and endometriosis.

Zihuai recipe alleviates cyclophosphamide-induced diminished ovarian reserve via suppressing PI3K/AKT-mediated apoptosis

ETHNOPHARMACOLOGICAL RELEVANCE

Zihuai recipe (ZHR), a Chinese herbal prescription, is widely used for the clinical treatment of Diminished ovarian reserve (DOR) infertility. However, little is known regarding its underlying mechanisms of DOR treatment.

AIM OF THE STUDY

This study aimed to investigate the beneficial effects of ZHR on the treatment of DOR and to reveal the underlying mechanisms.

MATERIALS AND METHODS

Sixty female 8-week-old Sprague-Dawley rats were randomly divided into the following six groups (n=10 per group): control, DOR, low-dose(2.7 g/kg/day) ZHR (L-ZHR), medium-dose(5.4 g/kg/day), ZHR (M-ZHR), high-dose(10.8 g/kg/day) ZHR (H-ZHR), and hormone replacement therapy (HRT) treatment groups. The DOR model was established in all the groups, except the control group, by a single intraperitoneal injection of 90 mg/kg cyclophosphamide. After the induction of the DOR model, rats were weighed and administered either the relevant dose of ZHR or an equal volume of saline solution (in the control and DOR groups). Rats in the HRT group received estradiol valerate tablets (0.16 mg/kg/day), and with medroxyprogesterone acetate tablets (0.86 mg/kg/day) added on day 4. After 32 days of treatment, the rats were euthanized and the ovaries were collected for sampling. Ovarian morphology was observed by hematoxylin and eosin staining and the number of follicles was counted under a microscope. The serum levels of anti-Müllerian hormone (AMH), gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were quantified by ELISA. A TUNEL assay was used to analyze the level of apoptosis of the ovarian cells. The protein expressions of p-PI3K, p-AKT, PI3K, AKT, cleaved caspase-3, BAX, and Bcl-2 were measured by western blotting and immunohistochemistry. Data analysis was performed with SPSS 20.0 software.

RESULTS

ZHR administration increased the ovarian index and the serum levels of AMH, GnRH, and E2, while lowering those of FSH and LH. ZHR treatment also increased the number of primordial, primary, secondary, and antral follicles, as well as the number of corpora lutea, but decreased the number of atretic follicles. Furthermore, ZHR administration decreased the percentage of TUNEL-positive ovarian cells. After treatment with ZHR, the protein expression levels of p-PI3K/PI3K, p-AKT/AKT, cleaved caspase-3 and BAX were decreased, whereas the level of Bcl-2 was increased.

CONCLUSIONS

ZHR improved the ovarian reserve in CTX-induced DOR rats. The mechanisms of ZHR on DOR may be mediated through the regulation of gonadal hormones of the hypothalamic-pituitary-ovarian axis (HPOA), and the inhibition of PI3K/AKT-mediated apoptosis in granulosa cells.

Effects of glyphosate-based herbicide-contaminated diets on reproductive organ toxicity and hypothalamic-pituitary-ovarian axis hormones in weaned piglets

At present, glyphosate (GLP) is the most produced and used herbicide in the world. With the large-scale use of glyphosate-based herbicides (GBHs), their toxic effects on animals and plants have increasingly become a concern. Based on the Codex Alimentarius Commission (CODEX) dose (20 mg kg-1) and the dose set by the government (40 mg kg-1), four experimental groups in which Roundup® (R) herbicide was added to the feed of weaned piglets at GLP concentrations of 0, 10, 20, and 40 mg kg-1 were designed. The results showed that R had no significant effect on the vulvar size or index of reproductive organs but that it could affect the tissue morphology and ultrastructure of the uterus and ovary. With the increase in GLP concentration, the activities of antioxidant enzymes [SOD (P < 0.05) and GPx (P = 0.002)] in the uterus showed significant increases. Compared with the control group, the content of hydrogen peroxide (H2O2) in the treatment groups increased significantly (P < 0.05), the malondialdehyde (MDA) content in the 10 mg kg-1 treatment group was significantly higher than that in the control group. We measured hypothalamic-pituitary-ovarian axis (HPOA) hormones and also found that GLP significantly increased luteinizing hormone-releasing hormone (LHRH), gonadotropin-releasing hormone (GnRH) and testosterone (T) content (P < 0.05) and decreased follicle-stimulating hormone (FSH) content (P < 0.05). In summary, although R does not affect the vulvar size or reproductive organ index of weaned piglets, it changes the morphology and ultrastructure of the uterus and ovaries, interferes with the synthesis and secretion of HPOA hormones, and causes changes in the balance of the antioxidant system of uterus. This study provided a theoretical basis for preventing reproductive system harm caused by GBHs.

[Effect of electroacupuncture on expression of Kisspeptin protein in hypothalamus of rats with polycystic ovary syndrome]

OBJECTIVE

To investigate the effect of electroacupuncture (EA) on the expression of Kisspeptin protein and activities of the hypothalamic-pituitary-ovarian axis(HPOA) in rats with Letrozole-induced polycystic ovary syndrome (PCOS).

METHODS

Female SD rats were randomly divided into normal control, PCOS model and EA groups (n=6 rats in each group). The PCOS model was established by continuous gavage of letrozole for 21 d. EA(2 Hz/100 Hz, 0.6-1.4 mA) was applied to bilateral "Daimai" (GB26) for 20 min, once every day for 15 d. Body mass was measured every 4 days. Serum follicular stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and testosterone (T) were detected by radioimmunoassay. Histopathological changes of the ovarian were observed after H.E. staining, and the expression level of Kisspeptin protein in the hypothalamus was detected by Western blot.

RESULTS

Following modeling, the body mass, serum T and LH contents, hypothalamic Kisspeptin protein expression and the number of ovarian follicles were significantly increased (P<0.05, P<0.01), while the number of ovarian corpus luteum was apparently decreased in comparison with the normal group (P<0.01). After EA intervention, the serum T, LH and E2 contents, the expression of Kisspeptin protein and the number of ovarian follicles were notably down-regulated (P<0.05, P<0.01), and the number of corpus luteum was significantly increased (P<0.01) in comparison with the model group.

CONCLUSION

EA can regulate the levels of sex hormones and HPOA of PCOS rats, which may be related to its effect in down-regulating the expression of Kisspeptin protein in the hypothalamus.

Crosstalk between the muscular estrogen receptor α and BDNF/TrkB signaling alleviates metabolic syndrome via 7,8-dihydroxyflavone in female mice

Objective

7,8-Dihydroxyflavone (7,8-DHF), a small molecular mimetic of brain-derived neurotrophic factor (BDNF), alleviates high-fat diet-induced obesity in female mice in a sex-specific manner by activating muscular tropomyosin-related kinase B (TrkB). However, the underlying molecular mechanism for this sex difference is unknown. Moreover, muscular estrogen receptor α (ERα) plays a critical role in metabolic diseases. Impaired ERα action is often accompanied by metabolic syndrome (MetS) in postmenopausal women. This study investigated whether muscular ERα is involved in the metabolic effects of 7,8-DHF.

Methods

For the in vivo studies, 72 female C57BL/6J mice were given a low-fat diet or high-fat diet, and both received daily intragastric administration of vehicle or 7,8-DHF for 24 weeks. The hypothalamic-pituitary-ovarian (HPO) axis function was assessed by investigating typical sex-related serum hormones and the ovarian reserve. Indicators of menopausal MetS, including lipid metabolism, insulin sensitivity, bone density, and serum inflammatory cytokines, were also evaluated. The expression levels of ERα and other relevant signaling molecules were also examined. In vitro, the molecular mechanism involved in the interplay of ERα and TrkB receptors was verified in differentiated C2C12 myotubes using several inhibitors and a lentivirus short hairpin RNA-knockdown strategy.

Results

Long-term oral administration of 7,8-DHF acted as a protective factor for the female HPO axis function, protecting against ovarian failure, earlier menopause, and sex hormone disorders, which was paralleled by the alleviation of MetS coupled with the production of ERα-rich, TrkB-activated, and uncoupling protein 1 (UCP1) high thermogenic skeletal muscle tissues. 7,8-DHF-stimulated transactivation of ERα at serine 118 (S118) and tyrosine 537 (Y537), which was crucial to activate the BDNF/TrkB signaling cascades. In turn, activation of BDNF/TrkB signaling was also required for the ligand-independent activation of ERα, especially at the Y537 phosphorylation site. In addition, Src family kinases played a core role in the interplay of ERα and TrkB, synergistically activating the signaling pathways related to energy metabolism.

Conclusions

These findings revealed a novel role of 7,8-DHF in protecting the function of the female HPO axis and activating tissue-specific ERα, which improves our understanding of this sex difference in 7,8-DHF-mediated maintenance of metabolic homeostasis and provides new therapeutic strategies for managing MetS in women.

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7,8-DHF improves hypothalamic-pituitary-ovarian axis function in mature adult female mice.

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7,8-DHF protects against ovarian failure and onset of earlier menopause.

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7,8-DHF-induced transactivation of ERα is crucial to activate BDNF/TrkB signaling cascades.

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7,8-DHF-induced activations of ERα and BDNF/TrkB signaling are interdependent.

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Src family kinases play a core role in the crosstalk of ERα and BDNF/TrkB signaling pathways.