Effect and mechanism of Bisphenol A on apolipoprotein E gene in rare minnow (Gobiocypris rarus)

Bisphenol A (BPA), a plasticizer with estrogenic effects, has significant effects on male reproduction, and apolipoprotein E (ApoE) has an important role in the transport process of lipids such as triglycerides and cholesterol in the spermatozoa. In this study, we investigated the effects of BPA on the ApoE gene in testis and its regulatory mechanism, in order to find the potential relationship between male reproductive problems caused by BPA and lipid metabolism. Rare minnow were exposed to BPA (15 μg/L) for 1, 3 and 5 weeks, and the effects of BPA on ApoE gene expression and distribution were detected by real-time fluorescence quantification (qPCR), immunoblotting (WB) and immunofluorescence (IF), and the regulatory mechanisms of BPA on ApoE were investigated by chromatin immunoprecipitation (ChIP) and DNA methylation assay. The results of qPCR, WB and IF showed that BPA could significantly affect the expression and distribution of ApoE gene in spermatozoa; ChIP results showed that there was an estrogen-associated receptor γ (Esrrg) positive effect site in the promoter region of ApoE, and the changes of ApoE mRNA expression were consistent with the changes of Esrrg recruitment; DNA methylation assay results showed that the promoter region of ApoE was in a unmethylated state, and BPA treatment had no significant effect on it. The results of this experiment indicated that BPA directly interferes with ApoE gene expression by regulating Esrrg recruitment in ApoE gene promoter region, and BPA may affect reproductive function of rare minnow by affecting testicular lipid transport transport. The results of this study will provide reference for the subsequent research on the effects of environmental endocrine disruptors on male reproduction from the perspective of lipid metabolism.