Cytochrome 2C19 Substrate Characterization of Organophosphate Pesticides
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Date
2024-05
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The Ohio State University
Abstract
Organophosphorus compounds (OPs) are a class of compounds used as pesticides and chemical warfare nerve agents that act by irreversibly inhibiting acetylcholinesterase. Potent OPs such as sarin, an agent used in the Syrian civil war, have been developed as chemical warfare nerve agents. Other compounds have been used in notable terror attempts such as the assassination of Russian dissenter Alexei Navalny. Additionally, OP pesticides are responsible for an estimated 385 million acute poisonings per year (Boedeker et al., 2020). Despite the occurrences of poisonings, little is known about the human metabolism of OPs. To address this, a high throughput fluorogenic assay was developed to evaluate human liver metabolism of OPs by cytochrome P450 enzymes (CYP450). Distinct substrates that are metabolized by different isoforms of CYP450 enzymes to yield fluorescent products were used to assay enzyme activity. A total of 45 OPs were screened for their inhibition characteristics of CYP2C19. It was found that while some agents inhibited the enzyme, others activated the enzyme. This led to further investigation into the metabolism of the OPs by CYP2C19 by evaluating the time-dependency of inhibition or activation. The most potent OP inhibitors were further investigated by determining their IC50. Several compounds were found to have IC50 values in the nanomolar range, indicating potent inhibition. Additionally, several compounds were found to demonstrate time-dependent inhibition characteristics, indicating likely metabolism by CYP2C19. This demonstrates that OP compounds exhibit inhibition of human CYP2C19, and likewise may be metabolized by the enzyme. Our results may guide future development of a therapy to treat organophosphate intoxication.
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Keywords
Metabolism, Assay, CYP450, High Throughput, Toxicology