The Effects of Benoxacor on the Liver and Gut Microbiome of C57BL/6 Mice

Abstract

The toxicity of many “inert” ingredients of pesticide formulations, such as safeners, is poorly characterized, despite evidence that humans may be exposed to these chemicals. Analysis of ToxCast data for dichloroacetamide safeners with the ToxPi tool identified benoxacor as the safener with the highest potential for toxicity, especially liver toxicity. Benoxacor was subsequently administered to mice via oral gavage for three days at concentrations of 0, 0.5, 5, and 50 mg/kg bodyweight (b.w.). Bodyweight-adjusted liver and testes weights were significantly increased in the 50 mg/kg b.w. group. There were no overt pathologies in either the liver or the intestine. 16S rRNA analysis of the cecal microbiome revealed no effects of benoxacor on α- or β-diversity; however, changes were observed in the abundance of certain bacteria. RNAseq analysis identified 163 hepatic genes affected by benoxacor exposure. Benoxacor exposure expressed a gene regulation profile similar to dichloroacetic acid and the fungicide sedaxane. Metabolomic analysis identified nine serum and fifteen liver metabolites that were affected by benoxacor exposure, changes that were not significant after correcting for multiple comparisons. The activity of antioxidant enzymes was not altered by benoxacor exposure. In vitro metabolism studies with liver microsomes and cytosol from male mice demonstrated that benoxacor is enantioselectively metabolized by cytochrome P450 enzymes (CYPs), carboxylesterases (CESs), and glutathione S-transferases (GSTs). These findings suggest that the minor toxic effects of benoxacor may be due to its rapid metabolism to toxic metabolites, such as dichloroacetic acid. This result challenges the assumption that inert ingredients of pesticide formulations are safe.

Disposition and Metabolomic Effects of 2,2’,5,5’-Tetrachlorobiphenyl in Female Rats Following Intraperitoneal Exposure

“…Targeted metabolomic data were collected with a target list containing 94 metabolites. The data were processed following a previously published procedure (Simonsen et al, 2022). Briefly, metabolites with > 50 % missing values were removed from further analysis.…”