Arsenic exposure diminishes ovarian follicular reserve and induces abnormal steroidogenesis by DNA methylation

Arsenic contamination is a worldwide public health problem, and the effect of arsenic on male reproduction has been extensively studied; however, data on the biotoxicity of arsenic in terms of female reproduction are more scarce. In this study, a human-cell-animal translational strategy was applied to explore the effect of arsenic exposure on ovarian steroidogenesis and its potential mechanism. We conducted a 1:1 propensity score matched case-control study involving 127 diminished ovarian reserve (DOR) cases and 127 healthy controls. The ovarian follicular fluid levels of 21 metal elements, including arsenic, were measured. The results showed that there were significant differences in follicular fluid metal profiles between DOR patients and controls and that arsenic, molybdenum, and strontium played important roles in DOR progression [OR (95 % CI): 2.203 (1.385, 3.503), 2.308 (1.490, 3.575) and 2.922 (1.864, 4.580), respectively]. In the primary ovarian granulosa cell culture model, we found that treatment with 8 μM arsenic for 24 and 48 h induced a decrease in human granulosa cell viability. The estradiol (E2) level was significantly decreased after arsenic exposure (P < 0.05), which was dependent on significant alterations (P < 0.05) in key enzymes in steroidogenesis. In addition, a model for sodium arsenite exposure through water in rats from weaning to sexual maturity was established. We evaluated ovarian development by monitoring the estrous cycle, observing ovarian pathology, and calculating the follicular proportion. RT-qPCR, Western blotting, and bisulfite-sequencing PCR were used to investigate the effect of arsenic exposure on ovarian steroidogenesis and its possible mechanism. The results indicated that steroidogenic factor-1 (SF-1) was an important target of the steroidogenesis disorder induced by arsenic exposure. Arsenic significantly increased the DNA methylation level (P < 0.05) in the promoter region of SF-1 to reduce its expression, subsequently decreasing the levels of steroidogenic acute regulatory protein (StAR), P450 cholesterol side-chain cleavage enzyme (CYP11A1), and aromatase (CYP19A1) (P < 0.05), leading to premature depletion of ovarian follicles.