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

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.

Automated summary

The adverse outcome pathway (AOP) has been proposed as an effective framework for chemical risk assessment, integrating in vitro studies and prediction models. In this study, a human cell-based dimerization assay using bioluminescence resonance energy transfer (BRET) technique was developed to evaluate the dimerization activities of chemicals on estrogen receptor alpha (ER alpha). Results showed that 51 out of 72 chemicals mediated the dimerization of ER alpha, and the BRET-based assay effectively measured these events. The findings suggest that the BRET-based assay could be used as an in vitro test method for assessing the risks of estrogenic chemicals within the AOP framework.