Synthetic Phenolic Antioxidants Cause Perturbation in Steroidogenesis in Vitro and in Vivo

Synthetic phenolic antioxidants (SPAs) are closely correlated with human life due to their extensive usages, and increasing concerns have been raised on their biosafety. The previous controversial findings caused continuous debates on their potential endocrine disrupting effects. In the present study, four commonly used SPAs, including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tert-butyl hydroquinone (TBHQ) and 2,2'-methylenebis(6-tert-butyl-4-methylphenol) (AO2246), were investigated for their estrogenic effects, and the results from in vitro screening assays showed SPAs themselves had negligible estrogen receptor binding affinities. Nevertheless, significant increase in E₂ secretion was observed in H295R cells treated with SPAs, especially for BHA. The transcriptional levels of steroidogenic enzymes, including StAR, 3βHSD, CYP11B1, and CYP11B2 were up-regulated via the mediation of protein kinase A (PKA) signaling pathway. In vivo experiment confirmed that waterborne exposure to BHA disturbed E₂ and testosterone (T) levels in zebrafish gonad, thus causing potential estrogenic effects through the regulation of hypothalamic-pituitary-gonadal-liver axis (HPGL-axis). Accordingly, this study has provided new insights for SPA-induced endocrine disrupting effects. Considering the allowable maximum level of individual BHA or in combination with TBHQ and BHT in foodstuffs (200 mg kg^-1), the perturbation in steroidogenesis observed for relatively low concentrations of SPAs would need more public attention.