Microplastic Toxicity on Gut Microbiota and Intestinal Cells: Evidence from the Simulator of the Human Intestinal Microbial Ecosystem (SHIME).

Microplastics (MPs) have become widespread environmental contaminants, with increasing evidence of their harmful impacts on human health. MPs generally enter the human body via ingestion, inhalation, or dermal exposure, with the gastrointestinal tract acting as a crucial entrance route. This work utilized the SHIME system to evaluate the effects of polystyrene (PS) MPs on gut microbiota and short-chain fatty acid (SCFA) metabolism in distinct colonic areas. The results demonstrated regional and individual-specific variations in microbial diversity, significant shifts in Firmicutes/Bacteroidetes (F/B) ratio, and declines in beneficial bacteria, such as Bifidobacteriaceae. Moreover, SHIME supernatants were then tested with a co-cultured cell model (Caco-2/HT29-MTX-E12). Results indicated a deteriorative effect on the intestinal model, characterized by enhanced oxidative stress and mitochondrial malfunction. No significant effect on intestinal barrier integrity or mucus secretion was detected. These findings highlight the potential systemic toxicity of PS-MPs on human gut microbiota-mediated mechanisms, emphasizing the necessity for immediate mitigation efforts.