Polystyrene micro- and nanoplastics aggravates colitis in a mouse model - effects on biodistribution, macrophage polarization, and gut microbiome

Background: The increasing prevalence of inflammatory bowel disease (IBD) and rising pollution from micro- and nanoplastic (MNP) particles has prompted investigations on their potential interconnection. To elucidate the complex relationship between IBD and exposure to MNPs, we induced colitis in mice using dextran sodium sulfate (DSS) and orally administered a solution of differently sized polystyrene (PS) MNPs (diameter 10, 1, and 0.29 µm). These particles facilitated a detailed examination of MNP biodistribution, macrophage response, and gut microbiome alterations under inflammatory conditions. Results: Specifically nanosized PS particles accumulated in the bloodstream and excretory organs, with enhanced accumulation in the colitis model. Macrophages shifted towards a pro-inflammatory phenotype, with decreased anti-inflammatory markers highlighting the intricate effects of MNPs on inflammation and immune cell behavior. Moreover, MNPs significantly disrupted the gut microbiome, reducing microbial diversity and shifting bacterial populations towards pro-inflammatory and potentially pathogenic species. Conclusions: These changes suggest that MNP exposure could exacerbate colitis through complex interactions involving MNPs, immune responses, and microbial dynamics. The fast growing exposure to MNPs underscores the urgent need for comprehensive public health strategies to address MNP pollution, its implications for disease and potential impacts on public health.