Background
Endocrine-disrupting chemicals (EDCs) are widely found in the environment. Estrogen-like activity is attributed to EDCs, such as bisphenol A (BPA), bisphenol AF (BPAF), and zearalenone (Zea), but mechanisms of action and diversity of effects are poorly understood. Objectives: We used in vitro models to evaluate the mechanistic actions of BPA, BPAF, and Zea on estrogen receptor (ER) α and ERβ.
Conclusion
BPA and BPAF can function as EDCs by acting as cell type-specific agonists (≥ 10 nM) or antagonists (≤ 10 nM) for ERα and ERβ. Zea had strong estrogenic activity and activated both the AF-1 and AF-2 functions of ERα. In addition, all three compounds induced the rapid action-mediated response for ERα.
Methods
We used three human cell lines (Ishikawa, HeLa, and HepG2) representing three cell types to evaluate the estrogen promoter activity of BPA, BPAF, and Zea on ERα and ERβ. Ishikawa/ERα stable cells were used to determine changes in estrogen response element (ERE)-mediated target gene expression or rapid action-mediated effects.
Results
The three EDCs showed strong estrogenic activity as agonists for ERα in a dose-dependent manner. At lower concentrations, BPA acted as an antagonist for ERα in Ishikawa cells and BPAF acted as an antagonist for ERβ in HeLa cells, whereas Zea was only a partial antagonist for ERα. ERE-mediated activation by BPA and BPAF was via the AF-2 function of ERα, but Zea activated via both the AF-1 and AF-2 functions. Endogenous ERα target genes and rapid signaling via the p44/42 MAPK pathway were activated by BPA, BPAF, and Zea.