Microplastic-induced changes in the rainbow trout gut: Insights from transcriptomic, proteomic, and microbial approaches

This study examined the intestinal effects ofpolyethylene (PE; size 46.6±11.3µm) and polystyrene (PS;size 52.5±11.5µm) microparticles atthree different concentrations (0.5%, 2%, and 5%) onjuvenile rainbow trout (Oncorhynchus mykiss) using anintegrative approach combining transcriptomics, proteomics, and microbiome analysis. After asix-week experiment, molecular analyses identified concentration-dependent transcriptional responses, including downregulation ofgenes involved inion exchange (slc9a1b) and appetite regulation (ghrl), alongside upregulation ofimmune- and stress-related genes (il10, tfa), particularly athigher concentrations. Proteomic profiling showed amore pronounced effect ofPScompared toPE, including suppression ofdigestive enzymes, disruption oflipid and energy metabolism, and activation ofproteins associated with oxidative stress and immune responses. Microbiome analysis confirmed plastic-induced dysbiosis, characterised byreduced microbial diversity, depletion ofbeneficial taxa (e.g., Bacteroidota, Actinobacteriota), and shifts in short-chain fatty acid–producing bacteria. By integrating multiple levels of biological organisation, this study provides new insights into how microplastics interfere with intestinal physiology, beyond acute toxicity. The findings emphasise the relevance of polymer type and exposure concentration in shaping biological responses and highlight the vulnerability of freshwater species to environmental microplastics.