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Co-exposure to microplastics and tire particles exacerbates oxidative stress and gut microbiome dysbiosis in zebrafish (Danio rerio)
Summary
Researchers exposed zebrafish for 21 days to environmentally relevant mixtures of microplastics and tire particles and found that combined exposure caused more severe oxidative stress and gut microbiome disruption than either pollutant alone. Particle accumulation occurred mainly in the gut with secondary deposition in the liver, and the most pronounced tissue damage was observed under the highest combined exposure. Gut microbiota analysis revealed significant shifts in community structure, including reduced beneficial bacteria and increased pollutant-tolerant species.
Microplastics (MPs) and tire particles (TPs) are widespread aquatic pollutants, yet their combined toxic effects, particularly under realistic mixture scenarios, is poorly investigated. In this study, adult zebrafish were chronically exposed for 21 days to environmentally relevant concentrations (1 and 5 mg/L) of mixture of MPs comprising polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) fragments of different sizes (6.5, 13, and 75 μm for each polymer type), as well as PET and PP fibers (300-450 × 18 μm and 300-500 × 20 μm, respectively), TPs alone, and combined MPs and TPs (MPs-TPs). Particle accumulation occurred predominantly in the gut, with secondary deposition in the liver. All exposure groups exhibited oxidative stress responses in gill, gut, and liver tissues, with the most pronounced malondialdehyde (MDA) elevation and antioxidant enzyme disruption observed in the liver under 5 mg/L MPs-TPs exposure, reflecting its central role in detoxification. Gut microbiota analysis revealed significant shifts in community structure and diversity, including reduced Proteobacteria abundance and increased pollutant-tolerant taxa, indicating dysbiosis. Principal Coordinates Analysis (PCoA) confirmed distinct microbial clustering by treatment, indicating that MPs, TPs, and especially MPs-TPs co-exposure caused significant structural reorganization of the gut microbiome. These alterations reflected dysbiosis characterized by disrupted microbial balance, followed by partial recovery indicating microbial resilience. Taken together, these results demonstrate that combined exposure to MPs and TPs results in more severe toxicological effects than exposure to either MPs or TPs alone, highlighting the ecological risks associated with complex contaminant mixtures in aquatic environments.