Early-life exposure to polystyrene micro- and nanoplastics disrupts metabolic homeostasis and gut microbiota in juvenile mice with a size-dependent manner

Early-life exposure to different sizes of micro- and nanoplastics (MNPs) affects biotoxicity, which is related not only to the dose but also directly to particle size. In this study, pregnant ICR mice received drinking water containing 5 μm polystyrene microplastics (5 μm PS-MPs) or 0.05 μm polystyrene nanoplastics (0.05 μm PS-NPs) from pregnancy to the end of lactation. Histopathological and molecular biological detection, 16s rRNA sequencing for intestinal flora analysis, and targeted metabolomics analysis were used to look into how early-life exposure to MNPs of various sizes affects young mice's growth and development, gut flora, and metabolism. The outcomes showed that 0.05 μm and 5 μm PS-MNPs can pass through the placental and mammary barriers, and MNPs accumulating in various organs were size-dependent: the greater the accumulation in organs, the smaller the particle size. Further studies found that the larger 5 μm PS-MPs caused only small accumulation in organs, with the main health hazard being the disruption of intestinal barrier and liver function, indirectly causing gut dysbiosis and metabolic disorders. In contrast, the smaller 0.05 μm PS-NPs caused excessive accumulation in organs, not only impaired the function of the intestine and liver, but also caused direct mechanical damage to physical tissues, and ultimately resulted in more severe intestinal and metabolic disorders. Our findings underline the size-dependent risks associated with micro- and nanoplastics exposure early in life and highlight the necessity for tailored approaches to address health damages from early MNPs exposure.