Abstract

The escalating global prevalence of inflammatory bowel disease (IBD) parallels widespread dietary exposure to microplastics (MPs), yet causal mechanisms linking polydisperse MPs to colitis remain elusive. Here, we show that polydisperse polystyrene microspheres (PS-MS) exacerbate dextran sulfate sodium (DSS)-induced colitis in mice by disrupting a microbiota-butyrate-PPARγ signaling axis. Mechanistically, PS-MS treatment alone does not directly induce colon inflammation in healthy mice; however, it suppresses intestinal Muc2 protein expression and impairs the mucus barrier by reducing the abundance of Lachnospiraceae_NK4A136_group and butyrate levels, thereby inhibiting PPARγ signaling and aggravating colitis. An antibiotic cocktail (ABX)-mediated microbiota ablation abolishes PS-MS-induced colitis aggravation, whereas fecal microbiota transplantation (FMT) from PS-MS-exposed donors transmits susceptibility to antibiotic-treated mice, confirming microbiota-dependent pathogenesis. Exogenous sodium butyrate supplementation restores mucosal homeostasis via PPARγ activation, as evidenced by the abolition of protection following administration of the PPARγ antagonist GW9662, and by the comparable efficacy of the PPARγ agonist 5-ASA. Our findings establish the microbiota-butyrate-PPARγ axis as a critical target for counteracting the adverse effects of environmental MPs and propose butyrate-boosting therapies as a translatable strategy against IBD.