Assessing the Impact of Benzalkonium Chlorides on Gut Microbiome and Liver Metabolism

Abstract ID 29280 Poster Board 420 Benzalkonium chlorides (BACs) are widely used disinfectants in a variety of consumer and food-processing settings, and the ongoing COVID-19 pandemic has increased the use of BACs. The prevalence of BACs in our daily environment raises the concern that regularly recurring BAC exposure could disrupt the gastrointestinal microbiota, thus interfering with the beneficial functions microbes provide to host health. Gut microbiota is known to be important for the expression of hepatic CYPs. We recently reported that BACs are metabolized by cytochrome P450s (CYPs) in the liver. Our preliminary data supports biliary excretion from the liver to the intestine being the major route of elimination for BACs and their metabolites. Thus, we hypothesize that exposure to BACs can alter the gut microbiome diversity and composition, which will lead to alterations in bile acid homeostasis, sterol biosynthesis, and xenobiotic metabolism in the liver. In this study, we exposed male and female mice to C12- and C16-BACs at 120 mg /g/day for one week via oral dosing. Intestinal content from cecum was collected and 16S rRNA sequencing was carried out on the isolated bacterial DNA. We found that treatment with either C12- or C16-BACs led to decreased alpha diversity and differential composition of gut bacteria, notably, the complete elimination of the actinobacteria phylum. Additionally, through a targeted bile acid quantitation analysis, we have found decreases in secondary bile acids in BAC treated mice. This finding is supported by decreases in bacteria known to metabolize primary bile acids into secondary bile acids, such as the families of Ruminococcaceae and Lachnospiraceae. Furthermore, targeted sterolomics analysis of liver extracts revealed that BACs caused decreased sterol abundance, including decreased cholesterol and lanosterol. Additionally, RNA sequencing analysis on RNA isolated from the livers of all groups found differential gene expression changes in relevant genes. Specifically, C16-BAC treatment in the female cohort led to upregulation of Hmgcr, a gene that encodes the rate-limiting enzyme in cholesterol synthesis. C16-BAC treatment in the male cohort led to upregulation of Cyp4a10, Cyp4f13, Cyp2j6 and Cyp2c38 genes, all encoding for hepatic lipid and xenobiotic metabolism. Lastly, UPLC-MS/MS analysis of intestinal sections and livers of BAC treated mice demonstrated the absorption and metabolism of BACs. Both parent compounds were detected in the liver along with their major Phase-I metabolites: the ω-OH, (ω-1)- OH, (ω-1)-ketone, and ω-COOH metabolites. Together, these data signify the potential impact BAC exposure may have on human health through disturbance of the gut microbiome and gut-liver interactions.