Risk of chronic low-dose pesticide cocktail exposure: Increased inflammatory bowel disease susceptibility through microbiota-mediated immune dysregulation

Human exposure to concurrent multiple pesticide residues is inevitable given the application of pesticides in modern agricultural, yet the associated health risks remain insufficiently characterized. A mixture of ten frequently detected pesticides was incorporated into the diet of male ICR mice at three dose levels (ADI, 100 ×ADI, and 10 ×NOAEL) for 17 weeks to evaluate intestinal risks. ADI exposure caused no significant colonic inflammation or injury, whereas 100 ×ADI and 10 ×NOAEL caused IBD, characterized by shortened colon length, epithelial injury, upregulated pro-inflammatory cytokines ( IL-1β , IL-6 , IL-22 ), and downregulated tight junIction proteins ( ZO-1 , occludin ). In DSS-induced model, even ADI group developed evident IBD, and those at 100 ×ADI and 10 ×NOAEL group exhibited more exacerbated intestinal inflammatory responses and tissue injury, indicating that chronic ADI dose pesticide cocktail exposure markedly increased susceptibility to IBD. At 10 ×NOAEL dose, the relative abundances of Lactobacillus , Streptococcus , and Candidatus_Saccharimonas were significantly reduced, whereas Faecalibaculum and Akkermansia were significantly enriched, which was closely associated with increased pro-inflammatory cytokines ( IL-6 , IL-22 ) and upregulation of RORγt and IL-17a alongside reduced Foxp3 and IL-10 , indicating a disrupted Th17/Treg balance linked to colonic inflammation and barrier dysfunction. FMT confirmed the critical role of the gut microbiota in mediating both pesticide-induced colonic inflammation and aggravation of DSS-induced colitis. Collectively, these findings demonstrate that chronic low-dose pesticide cocktail exposure disrupts gut microbial homeostasis, alters the Th17/Treg balance, upregulates pro-inflammatory cytokines, and compromises intestinal barrier integrity, thereby triggering colonic inflammation and exacerbating DSS-induced IBD. This work highlights the necessity of the evaluation of mixed pesticide residue.