Combined toxicity of polyethylene micro/nanoplastics and PFOA in zebrafish (Danio rerio): Impacts on antioxidant, neurotransmission, and gut microbiota.

Polyethylene micro/nano plastics (PE-MPs, PE-NPs), being the predominant plastic pollutants in aquaculture environments, frequently coexist with emerging contaminants such as perfluorinated compounds (PFOA) within closed aquaculture systems. Nevertheless, the combined biotoxicological impacts and underlying mechanisms of PE-MPs, PE-NPs, and PFOA co-pollutants remain poorly understood in zebrafish. This study revealed induced oxidative stress in zebrafish, as evidenced by aberrant levels of antioxidant enzymes (CAT, SOD, GST) and lipid peroxidation markers (LPO, GSH) as well as neurotoxicity (AChE) in the targeted organs (gills, intestine, and liver). Specifically, the Integrated Biomarker Responses (IBRv2) revealed that the combined toxic effects exhibited synergism in the gills and liver but antagonism in the gut of zebrafish, showing distinct tissue and organ specificity. The exposure of PFOA to environmental concentrations reduced the richness and diversity of intestinal microbiota, whereas the presence of MPs and NPs increased them. Compared to single exposure to PFOA, the combined-exposure of MPs and PFOA decreased the metabolism of xenobiotics by cytochrome P450 and naphthalene degradation of metabolic pathway. The combined-exposure of NPs and PFOA decreased the abundance of African trypanosomiasis, NOD-like receptor signaling pathway, pathways in cancer, and naphthalene degradation pathway, while increasing the abundance of Wnt signaling pathway. In the combined-exposure group of MPs + NPs and PFOA, the abundance of African trypanosomiasis and naphthalene degradation metabolic pathways decreased, while the ethylbenzene degradation metabolic pathway increased. The present study offers a scientific foundation for conducting comprehensive ecological risk assessments and joint toxicological evaluations of PE-MPs, PE-NPs and PFOA.