Comprehensive analysis of cellular estrogen signaling in representative estrogen receptor ligands

The estrogen receptor (ER)-mediated signaling pathway in physiological and biochemical aspects is very important in the environment, including food. The physiological action of estrogen is mediated by ER alpha (ER alpha) and beta (ER8), whose physiological action on estrogenic substances is complex because of the relatively low ligand-binding domain (LBD) similarity of the two ERs. In this study, the comprehensive activity of repre-sentative ER ligands was evaluated by using BRET-based ER alpha and ER8 dimerization and ER transactivation assays to differentiate the specific binding and function of ER alpha and ER8 from 12 representative natural and synthetic estrogenic substances. Results revealed that 11 chemicals mediated receptor ER alpha and ER8 dimerization, 7 out of 12 chemicals were confirmed to be estrogen agonists, and 5 chemicals were antagonistic. Overall, this study demonstrated consistency between BRET dimerization and transactivation responses, supporting potential sup-plementary application of mechanism-based BRET assays as high-throughput screening methods for evaluation of potential endocrine-disrupting activity of environmental agents. This study also provided information about receptor specificity of ligand-mediated estrogenic activity via dimerization assays and elucidated cellular es-trogen signaling pathways.