An In vitro dimerization assay for the adverse outcome pathway approach in risk assessment of human estrogen receptor α-mediated endocrine-disrupting chemicals

Abstract

The adverse outcome pathway (AOP) has been recently proposed as an effective framework for chemical risk assessment. The AOP framework offers the advantage of effectively integrating individual in vitro studies and in silico prediction models. Thus, the development of an effective testing method to measure key events caused by chemicals is essential for chemical risk assessment through a fully developed AOP framework. We developed a human cell-based estrogen receptor alpha (ER alpha) dimerization assay using the bioluminescence resonance energy transfer (BRET) technique and evaluated the ER alpha dimerization activities of 72 chemicals. Fifty-one chemicals were identified to mediate dimerization of ER alpha, and the BRET-based ER alpha dimerization assay could effectively measure the events that mediated dimerization of ER alpha by the estrogenic chemicals. These results were compared with the results of pre-existing assay to determine whether the BRET-based ER alpha dimerization assay could be employed as an in vitro test method to provide scientific information for explaining key events as a part of the AOP framework. Consequently, we propose that the BRET-based ER alpha dimerization assay is suitable for measuring the chemical-mediated dimerization of ER alpha, a key event in the AOP framework for cellular-level risk assessment of estrogenic chemicals.