Weathered microplastics reshape gastrointestinal responses to per- and polyfluoroalkyl substances during co-exposure

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants, yet the biological consequences of their co-exposure remain poorly understood. Here, we investigated the individual and combined effects of weathered polyethylene MPs and three representative PFAS (PFOA, PFOS, and PFBA) using Caco-2 cells and a mouse oral-exposure model, complemented by tissue distribution analysis and multi-omics profiling. PFAS induced concentration-dependent cytotoxicity, oxidative stress, mitochondrial dysfunction, and cell-cycle disruption, with PFOA showing the greatest cytotoxic potency. Co-exposure with MPs attenuated PFAS-induced acute cytotoxicity, ROS accumulation, and membrane damage in vitro, while aggravating mitochondrial dysfunction and cell-cycle arrest, indicating an endpoint-dependent modulatory effect. In mice, MPs and PFAS were concurrently detected in multiple tissues, and co-exposure altered PFAS tissue burdens and produced organ-specific toxicological responses, including enhanced intestinal oxidative and inflammatory disturbances despite partial attenuation of PFAS-associated metabolic abnormalities. PFOA concentrations showed the strongest associations with hepatic and intestinal injury biomarkers. Multi-omics analyses further revealed pronounced restructuring of the gut microbiota, metabolic reprogramming, and extensive intestinal transcriptional responses under co-exposure, involving Rap1, MAPK, PI3K-Akt, chemokine, Th17-related, and intestinal immune pathways. Collectively, these findings demonstrate that weathered MPs do not simply enhance or reduce PFAS toxicity but reshape PFAS-associated biological responses across cellular, organ, metabolic, microbial, and molecular levels, highlighting the need to consider dynamic interactions among co-occurring emerging contaminants in gastrointestinal health-risk assessment.