Long-term exposure to microplastics induces intestinal function dysbiosis in rare minnow (Gobiocypris rarus)

Microplastics are ubiquitous in the natural environment, especially in waters, and their potential impact is also a key issue of concern. In this study, we used 1 µm, 1000 μg/L, polystyrene (PS-MPs) particles to analyze the effects after exposure for 14 and 28 days in rare minnow (Gobiocypris rarus). Results indicated that PS-MPs induce structural alterations in the intestinal tissue, including epithelial damage, villi damage and the inflammatory cell infiltration, while the changes were severer after exposure for 28 days. Polystyrene microplastics also significantly increased the activities of catalase (CAT, increased 142 % and 385 % in 14d and 28d), superoxide dismutase (SOD, increased 17.76 % and 23.43 % in the 14d and 28d) and the content of malondialdehyde (MDA, increased 14.5 % and 442 % in the 14d and 28d), glutathione (GSH, increased 146 % and 298 % in the 14d and 28d). The results not only showed the characterization of gut microbial communities in rare minnow, but also indicated that microbial diversity and composition were altered in gut of fish exposed to PS-MPs. In the control groups, Proteobacteria (31.36-54.54 %), Actinobacteriota (39.99-52.54 %), Fusobacteriota (1.43-1.78 %), Bacteriadota (0.31-0.57 %) were the four dominant bacterial phyla in the intestinal of rare minnow. After exposure to microplastics, In the gut microbiota, the proportion of Proteobacteria increased 9.27 % and 30 % with exposure time, while Actinobacteria decreased 37.89 % and significantly different after 28 days. In addition, metabolomic analysis suggested that exposure to PS-MPs induced alterations of metabolic profiles in rare minnow and differential metabolites were involved in energy metabolism, inflammatory responsible secretion, oxidative stress, nucleotide and its metabolomics. In conclusion, our findings suggest that long-term exposure to microplastics could induce intestinal inflammation, oxidative stress, microbiota dysbiosis and metabolic disorder in rare minnow, and the alterations and severity were exacerbated by prolonged exposure. This study has extended our cognition of the toxicity of polystyrene, and enriched theoretical data for exploring the toxicological mechanism of microplastics.