Short-Term Exposure to Environmentally Relevant doses of Chlorpyrifos Impact both the Gut Microbiome and Metabolome in Mice

Chlorpyrifos is one of the most used organophosphate insecticides globally. Although the neurotoxic effects of chlorpyrifos are well-documented, its potential impact on the gut microbiome at environmentally relevant exposure levels remains unclear. In the current study we investigate how chronic exposure to chlorpyrifos at and near the EPA reference dose of 0.3 ug/kg/day affects the gut microbiome in C57BL/6J mice. We employed a multi-omic strategy including 16S rRNA gene sequencing, metatranscriptomics and metabolomics (NMR and LCMS) to investigate the effects of chlorpyrifos on the gut microbiome and mouse host. The mice were split into four groups; control (N=5), low dose (N=5, 0.049ug of chlorpyrifos per day), medium dose (N=5, 0.49ug of chlorpyrifos per day), and high dose (N=5, 4.9ug of chlorpyrifos per day), and were treated with a vehicle or chlorpyrifos via dough pills for 5 days. After the 5-day exposure, mice were sacrificed and cecal contents, intestinal tissue, liver, and blood were collected. We saw significant shifts in the community structure of the gut microbiome at both low and high doses of chlorpyrifos. Additionally, we saw the emergence of opportunistic pathogens like Salmonella, Clostridium XI and Escherichia Shigella after high dose chlorpyrifos exposure. Chlorpyrifos also caused a significant decrease of the enzymes involved in glucose metabolism and caused a dysregulation of the enzymes involved in the citric acid cycle, shifting products to short chain fatty acid production, rather than normal energy production. Additionally, chlorpyrifos caused increases in harmful metabolites like urate and trimethylamine. Taken together, environmentally relevant doses of chlorpyrifos drastically affect the gut microbiome and potentially could lead to metabolic disorders like obesity and diabetes, or an inflamed gut.