Effects of polystyrene nanoplastics on apoptosis, digestive enzymes, and intestinal histological structure and flora of swamp eel (Monopterus albus)

Abstract

Nanoplastics (NPs) in the environment have attracted attention worldwide as a new class of pollutants. However, their impacts on aquatic organisms are only beginning to be unraveled. The current study investigated the toxic effects and mechanisms of action of polystyrene NPs (PS-NPs, 100 nm) on liver apoptosis and the intestinal histological structure and flora of the economically important eel Monopterus albus after exposure to 0, 0.5, 1, 5, or 10 mg L⁻¹ PS-NPs for 28 days. The results showed that intestinal trypsin and amylase of M. albus treated with 10 mg L⁻¹ PS-NPs were significantly different from the control group (p < 0.05), and that the intestinal structure was slightly damaged. 16S rRNA sequencing showed that Lactococcus garvieae and Bifidobacterium longum were the dominant flora in the intestinal tract of M. albus treated with 10 mg L⁻¹ PS-NPs. For gene expression, TGF-β, Hsp70, Caspase-9, and Bax were significantly elevated in the liver of M. albus in the groups treated with PS-NPs compared with the control group, suggesting that PS-NPs triggered an immune response and apoptosis in liver tissue. In conclusion, the exposure to high concentrations of PS-NPs can produce apoptosis in the liver of M. albus and affect the immune response and intestinal bacterial community structure, leading to intestinal flora dysbiosis. The results of this study provide a scientific basis for understanding the toxic effects of PS-NPs on M. albus and potential ecological risk assessment strategies.