BPS-induced ovarian dysfunction: Protective actions of melatonin via modulation of SIRT-1/Nrf2/NFĸB and IR/PI3K/pAkt/GLUT-4 expressions in adult golden hamster.

Ever-increasing occurrence of plastic-manufacturing industries leads to environmental pollution that has been associated with declined human health and increased incidence of compromised reproductive health. Female subfertility/infertility is a complex phenomenon and environmental toxicants as well as lifestyle factors have a crucial role to play. Bisphenol S (BPS) was believed to be a "safer" replacement of bisphenol A (BPA) but recent data documented its neurotoxic, hepatotoxic, nephrotoxic, and reprotoxic attributes. Hence based on the scarcity of reports, we investigated molecular insights into BPS-induced ovarian dysfunction and protective actions of melatonin against it in adult golden hamsters, Mesocricetus auratus. Hamsters were administered with melatonin (3 mg/kg BW i.p. alternate days) and BPS (150 mg/kg BW orally every day) for 28 days. BPS treatment disrupted hypothalamo-pituitary-ovarian (HPO) axis as evident by reduced gonadotropins such as luteinizing hormone (LH) and follicle-stimulating hormone (FSH), ovarian steroids such as estradiol (E2) and progesterone (P4), thyroid hormones namely triiodothyronine (T3) and thyroxine (T4) and melatonin levels along with their respective receptors (ERα, TRα, and MT-1) thereby reducing ovarian folliculogenesis. BPS exposure also led to ovarian oxidative stress/inflammation by increasing reactive oxygen species and metabolic disturbances. However, melatonin supplementation to BPS restored ovarian folliculogenesis/steroidogenesis as indicated by increased number of growing follicles/corpora lutea and E2/P4 levels. Further, melatonin also stimulated key redox/survival markers such as silent information regulator of transcript-1 (SIRT-1), forkhead box O-1 (FOXO-1), nuclear factor E2-related factor-2 (Nrf2), and phosphoinositide 3-kinase/protein kinase B (PI3K/pAkt) expressions along with enhanced ovarian antioxidant capacity. Moreover, melatonin treatment reduced inflammatory load including ovarian nuclear factor kappa-B (NFĸB), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) expressions, serum tumor necrosis factor α (TNFα), C-reactive protein (CRP) and nitrite-nitrate levels as well as upregulated ovarian insulin receptor (IR), glucose uptake transporter-4 (GLUT-4), connexin-43, and proliferating cell nuclear antigen (PCNA) expressions in ovary thereby ameliorating inflammatory and metabolic alterations due to BPS. In conclusion, we found severe deleterious impact of BPS on ovary while melatonin treatment protected ovarian physiology from these detrimental changes suggesting it to be a potential preemptive candidate against environmental toxicant-compromised female reproductive health.