Polystyrene microplastics decrease F-53B bioaccumulation but induce inflammatory stress in larval zebrafish

There is growing concern that microplastics (MPs), which act as carriers of other organic contaminants, are mistakenly ingested by aquatic organisms, consequently causing unpredictable adverse effects. In this study, zebrafish larvae (6 d post fertilization) were exposed to either 6:2 chlorinated polyfluorinated ether sulfonate (F-53B), polystyrene microplastics (PS-MPs) or their combination for 7 d to evaluate the effects of the presence of PS-MPs on the bioaccumulation and immunomodulation of F-53B. PS-MPs greatly promoted the sorption of F-53B, which reduced the bioavailability and bioaccumulation of F-53B in zebrafish larvae. F-53B, PS-MPs, or their mixture significantly reduced the body weight of zebrafish larvae. Combined exposure of PS-MPs and F-53B resulted in a significant reduction in superoxide dismutase (SOD) and lysozyme activity, indicating the occurrence of oxidative stress and inflammatory response in zebrafish larvae. The content of malondialdehyde (MDA) and immunoglobulin M (IgM) was not affected by F-53B or PS-MPs, but significantly increased in their combined exposure. Furthermore, co-exposure of F-53B and PS-MPs significantly upregulated the transcripts of pro-inflammatory cxcl-clc and il-1β genes and increased the levels of iNOS protein in zebrafish larvae. In addition, enhanced protein expression of NF-κB paralleled the upregulation in the expression of most immune-related genes, suggesting NF-κB pathway was mechanistically involved in these responses. Collectively, the presence of MPs decreased F-53B bioaccumulation, but induced inflammatory stress in larval zebrafish. These findings highlight the health risks of co-contamination of MPs and F-53B in aquatic environments.