Microbial metabolite Urolithin A protects against inorganic arsenic-induced gut barrier dysfunction in humanized AS3MT mice.

Chronic exposure to inorganic arsenic (iAs) remains a major environmental health concern and is associated with significant gastrointestinal (GI) disorders, including gastroenteritis, diarrhea, and inflammatory bowel disease-like symptoms. Gut microbiota plays a critical role in mitigating arsenic toxicity, as germ-free or antibiotic-treated mice exhibit reduced fecal arsenic excretion and greater tissue accumulation. We previously showed that the microbial metabolite Urolithin A (UroA) protects against iAs-induced cytotoxicity, apoptosis, oxidative stress, and ROS production in vitro. In this study, using humanized AS3MT mice (mouse arsenic methyltransferase gene (As3mt)replaced with human AS3MT, hAS3MT), we evaluated the in vivo effects of iAs and UroA on gut barrier function. Long-term iAs exposure (100 ppb for 28 weeks) significantly reduced expression of tight junction proteins, indicating compromised intestinal barrier integrity. UroA treatment protected hAS3MT mice from iAs-induced gut permeability, inflammation, colon shortening, and elevated colon weight/length ratio. UroA also reduced iAs-induced inflammatory cytokines, myeloperoxidase (MPO) activity and preserved intestinal epithelial cell tight junction protein expression. Further, microbiome and metabolomic analysis suggested that UroA treatment protected from iAs-induced gut microbial dysbiosis, especially restored several beneficial bacterial strains and short chain fatty acids (e.g., acetate and butyrate) and led to gut homeostasis. Together, these findings demonstrate that UroA mitigates iAs-induced gut toxicity and restores microbiota homeostasis.