Integration of physiology, microbiota and metabolomics reveals toxic response of zebrafish gut to co-exposure to polystyrene nanoplastics and arsenic.

Both nanoplastic (NP) particles and arsenic (As) are widespread in aquatic environments and pose a combined risk of exposure to aquatic organisms. How the gut of aquatic organisms responds to combined risk of exposure is still unclear. In this study, zebrafish (Danio rerio) were subjected to three distinct As stress environments: only As group (10 μg/L), and As combined with different concentrations of polystyrene (PS) NPs (1 mg/L and 10 mg/L) groups for 21 days via semi-static waterborne exposure. The physiological responses to combined stress, the diversity of gut microorganisms, and the metabolomic response of the gut were investigated. The findings indicated that PSNPs were prevalent in the intestines of zebrafish in the co-exposed group. Furthermore, the administration of 1 mg/L and 10 mg/L of PSNPs in the co-exposed group was observed to elevate As levels in the intestines by 24.88% and 76.95%, respectively, in comparison to As treatment alone. Simultaneous exposure of the gut to PSNPs and As resulted in increased contents/activities of MDA, SOD, CAT, and GST, and a decrease in contents/activities of GSH and GPx, when compared to As exposure alone. Additionally, the combined exposure led to an elevated expression of the Cu/Zn-sod, Mn-sod, gpx, and cat genes. The combined treatment with NPs and As resulted in an increase in the abundance of Proteobacteria and Fusobacteriota at the phylum level, as well as a significant increase in the abundance of Cetobacterium, Rhodococcus, and Bacteroides at the genus level. Non-targeted metabolomics analyses suggest that metabolic pathways affected by co-exposure include glycerophospholipid metabolism, glycerolipid metabolism, ABC transporters and autophagy. The findings of this study are of considerable significance for the evaluation of the toxicological impact of co-existing pollutants.