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Synergistic toxicity of abamectin with nanoplastics in rainbow trout mediated by gut-liver axis disruption: Insights into oxidative stress, metabolic dysregulation, and microbiota change
Summary
Scientists found that when a common pesticide (used in fish farming) combines with tiny plastic particles called nanoplastics, the mix causes far more damage to fish than either one alone—harming gut health, triggering liver inflammation, and disrupting the balance of good and bad gut bacteria. This matters because it shows how pollutants can team up to create bigger health problems than expected, raising concerns about how the growing mix of plastics and chemicals in our water might similarly affect other animals—and potentially humans—who are exposed to combinations of contaminants rather than just one at a time.
Abamectin (ABM), a widely used pesticide in aquaculture, may interact with pervasive environmental contaminants like nanoplastics (NPs), potentially altering its toxicity to non-target organisms. This study investigated the synergistic effects and underlying mechanisms of polystyrene NPs and ABM at environmentally relevant concentrations in juvenile rainbow trout (Oncorhynchus mykiss) during a 28-day exposure. Compared to ABM alone, co-exposure with NPs induced significantly greater synergistic toxicity. This was evidenced by exacerbated intestinal barrier dysfunction, including downregulation of tight junction proteins (Occludin, Claudin-23, ZO-1) and a shift in the gut microbiota characterized by the enrichment of potential pathogens, such as Neochlamydia. In the liver, the combined exposure markedly enhanced oxidative stress and inflammatory responses. Untargeted metabolomics further revealed that the co-exposure disturbed fundamental metabolic pathways more profoundly than either contaminant alone, particularly affecting amino acid, carbohydrate, and nucleotide metabolism. Critically, correlation analyses integrated gut microbiota dysbiosis with hepatic metabolic disorders, supporting a pivotal role for gut-liver axis disruption in the synergistic toxicity. Our findings demonstrate that NPs can act as an aggravating factor, significantly potentiating the physiological and toxicological impacts of ABM on fish via interconnected intestinal and hepatic pathways. This study provides crucial mechanistic insights for the risk assessment of pesticide interactions with emerging contaminants in aquatic environments.