Polystyrene microplastics exposure: Disruption of intestinal barrier integrity and hepatic function in infant mice

The pervasive presence of microplastics (MPs) in infant formula and care products has emerged as a significant and underappreciated risk to public health. Notably, infants are at an elevated risk due to their underdeveloped intestinal defenses and liver detoxification capabilities, factors that could heighten their vulnerability to MPs. This study presents a comprehensive evaluation of the health implications linked to polystyrene microplastics (PSMPs) exposure during early life, examining both environmentally plausible and elevated levels. Based on histological analysis, in vivo imaging analysis, biochemical analysis and 16S rRNA sequencing results, our study found that oral PSMPs exposure in infant mice led to profound toxicological consequences, such as intestinal barrier impairment and hepatic injury, in a dose-dependent manner. Strikingly, even low ambient concentration of PSMPs (20 ppb) was sufficient to inflict considerable harm, disrupting the intestinal barrier, manifested that lessened mucus secretion, elevated iFABP level (276.50±10.73 pg/mL), decreased sIgA levels (0.60±0.03 mg/g), and pathological damage of intestinal tissues, allowing PSMPs accumulation and leakage into blood, inducing hepatotoxicity, such as increased TG levels (0.99±0.05 mmol/gprot) and lipid droplet accumulation. Furthermore, PSMPs exposure gives rise to aberrant bacterial colonization, dropping the abundance of probiotics as well as altering the abundance of pathogenic bacteria, which may contribute to the toxicity outcomes. The study underscores the critical need for vigilance regarding the insidious effects of PSMPs at environmental-relevant concentrations, especially in the context of infant exposure.