Science Inventory

Characterization of Organophosphorous Pesticides on Acetylcholinesterase Inhibition Using In Vitro Assays with Xenobiotic Metabolic Capability

Citation:

Li, S., J. Zhao, R. Huang, M. Santillo, K. Houck, AND M. Xia. Characterization of Organophosphorous Pesticides on Acetylcholinesterase Inhibition Using In Vitro Assays with Xenobiotic Metabolic Capability. Presented at Society of Toxicology 58th Annual Meeting & ToxExpo, Baltimore, MD, March 10 - 14, 2019. https://doi.org/10.1016/j.tiv.2019.01.002

Impact/Purpose:

Abstract for presentation at Society of Toxicology Annual Meeting in March 2019

Description:

Acetylcholinesterase (AChE) inhibition can have significant impacts on human health. A large number of environmental chemicals such as synthesized drug candidates, food additives, and industrial chemicals have not been tested for AChE inhibition activity. Moreover, some chemicals may need to be metabolically activated to show inhibitory effects. In our study, we have developed and characterized a high-throughput screening method with metabolic capability for identifying AChE inhibitors. An enzyme-based high-throughput assay was developed in the current study by using recombinant human AChE combined with human or rat liver microsomes. AChE activity was measured by two methods, one with colormetric and the other with fluorescent readouts. The enzymatic assay with human microsomes (n = 72) showed good performance with coefficient of variation (CV), signal to background ratio (S/B) and z’ factor of 2.03 ± 0.05, 3.29 ± 0.01 and 0.85 ± 0.02, respectively. The assays with microsomes were characterized by testing a group of well-known AChE inhibitors including parent compounds and their metabolites. Many organophosphorous pesticides (OPs), such as chlorpyrifos, tebupirimfos and chlorethoxyfos, only showed inhibitory effects on AChE in the presence of microsomes, showing that these OPs need to be metabolically activated to inhibit AChE. The sensitivities of the assays +/- microsomes ranged from 58% to 85% depending on the assay format and species of microsomes. These results demonstrate that the enzyme-based assays with or without liver microsomes provide a promising tool for the profiling of AChE inhibitors and to study the metabolism of OPs. (This abstract does not reflect EPA policy).