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.

As the most commonly used plasticizer, Di-(2-ethylhexyl)-phthalate (DEHP) exists everywhere in the environment due to the widespread use of polyvinyl chloride (PVC) in human life, and it is also a recognized environmental pollutant. Studies have proved the hepatotoxicity of DEHP, however the mechanism has not been adequately explored, especially the role of the reactive oxygen species (ROS) in it. In the present study, 21 day-old ICR mice were administered DEHP with dose of 0, 125, 250, and 375 mg/kg/day for 28 days by intragastrical gavage. After contamination, histopathology displayed that liver tissue were damaged mildly with the effect of DEHP; a significant increase of the serum liver function index (including aspartate transaminase (AST) and alanine transaminase (ALT)) were observed. Additionally, the level of lipid peroxidation markedly rise, especially ROS and malondialdehyde (MDA), but the activation of superoxide dismutase (SOD) was obviously decreased in mice liver. In addition, DEHP promoted the phosphorylation of JNK and p38MAPK proteins in mice liver, as well as increased the expression of p53 protein and decreased the level of DNA methylation in the p53 gene promoter region. These results indicated that the hepatotoxicity of mice caused by DEHP may be through activating the JNK/p38MAPK/p53 signaling pathway and further promoting the generation of ROS to induce lipid peroxidation in liver, and the role of DNA methylation may be inevitable.

This study aimed to investigate whether cadmium induces ovarian granulosa cell damage by activating PERK-eIF2α-ATF4 through endoplasmic reticulum (ER) stress and to elucidate the underlying regulation mechanism. Two models of cadmium exposure were established. In one model, ovarian granulosa cells isolated from 21-day-old female Sprague Dawley (SD) rats were cultured in vitro for 36 h and exposed to CdCl₂ (0, 5, 10, and 20 μM), and in another model, a human ovarian granulosa tumor cell line (COV434) was used to construct the BIP- knockdown cell line sh-BIP and exposed to 0 and 20 μM CdCl₂. after exposure to cadmium for 12 h, the expression mRNA and protein levels of BIP, p-PERK and p-eIF2α were determined in the two models. miRNAs related to BIP were also detected in granulosa cells after cadmium exposure. We found that mRNA and protein levels of all factors were up-regulated in each cadmium-dose group, except for BIP mRNA expression in the 5 μM Cd group. The BIP gene was knocked down in COV434 cells before exposure to cadmium. All factors were up-regulated in COV434 cells exposed to Cd, and the expression of the p-eIF2α protein was down-regulated in sh-BIP cells exposed to Cd. In addition, no differences in BIP related miRNAs were detected in cadmium-exposed rat ovarian granulosa cells versus the control group. Cadmium induces ovarian granulosa cell damage by inducing ER stress.

Increasing evidence has shown that gut microbes play an important role in the reproductive endocrine system and the development of polycystic ovary syndrome (PCOS). However, whether environmental factors are involved in these gut microbiota alterations has seldom been studied. In this study, we aimed to explore the crucial role of an imbalanced gut microbiota on abnormal ovarian follicle development induced by Cu. A 1:1 matched case-control study with 181 PCOS patients and 181 controls was conducted using a propensity score matching protocol. Information regarding dietary Cu intake was obtained from a face-to-face dietary intake interview. Alterations in the gut microbiota were detected by high-throughput 16 S rDNA sequencing. The results showed that dietary Cu intake was positively correlated with the risk of PCOS, and the risk threshold was approximately 1.992 mg/d. Compared with those with dietary Cu intakes lower than 1.992 mg/d, those who had a higher dietary Cu intake had a 1.813-fold increased risk of PCOS (OR=1.813, 95% CI: 1.150-2.857). PCOS patients had a lower relative abundance of Bacteroides than controls (P = 0.003), and Bacteroides played a partial mediating role between dietary Cu exposure and PCOS (P_{indirect effect}=0.026, 95% CI: 0.002-0.072). In addition, an animal model of Cu exposure through the diet showed that Cu can induce gut microbiota disorder; increase serum levels of LPS, MDA, and IL-6; and alter host ovarian steroidogenesis to affect ovarian follicle development. Staphylococcus played a partial mediating role between Cu exposure and CYP17A1 (P_{g_Staphylococcus}=0.083, 95% CI: 0.001-0.228). Overall, this study shows that long-term exposure to high dietary Cu levels can affect the composition of the gut microbiota, cause inflammation and oxidative stress, and then interfere with hormone signaling, ultimately affecting ovarian follicle development.