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Toxic effects of microplastics on freshwater fish (Channa argus): mechanisms of inflammation, apoptosis, and autophagy
Summary
Freshwater snakehead fish exposed to polystyrene microplastics for four weeks developed inflammation, cell death, and tissue damage in their liver, intestines, kidneys, and gills. The damage worsened with higher microplastic concentrations and involved disruption of the fish's antioxidant defenses and immune system. Since snakehead is a commonly consumed fish in Asia, these findings raise questions about whether microplastics in aquaculture environments could affect the safety of fish as human food.
This study examined the impact of Polystyrene microplastics (PS-MPs) on inflammation, apoptosis and autophagy within the liver, intestine, kidney, and gill of northern snakehead (Channa argus). In this study, 600 snakeheads (mean body weight: 10.5 ± 0.5 g) were randomly divided into four groups, each with three replicates. These groups were administered diets with incremental concentrations of PS (0 (CON), 500 (PS500), 1000 (PS1000), and 2000 ng/L (PS2000)) over a duration of four weeks. Histopathological analysis of the liver, intestine, kidney, and gill showed different degrees of pathological changes in the PS-added groups. Exposure to PS significantly increased ROS levels and elevated MDA content, while simultaneously reducing the activity of antioxidant enzymes (CAT, GSH, SOD, and GSH-PX) in these organs. The immune parameters (C3, C4, LYS, and IgM) in the liver, kidney, intestine, and gills of C. argus exposed to varying PS also changes. Additionally, increases in PS levels were accompanied by decreased expression of genes associated with antioxidant functions (cat, sod, gsh-px, nqo-1, ho-1, and gst). Analysis via quantitative real-time PCR (qRT-PCR) revealed changes in the mRNA levels of genes related to inflammation (tnf-α, il-8, nf-κb, jnk, il-1β, il-12, myd88, il-10 and iκbα), apoptosis (p53, bad, csa-9, cyt-c, bax, fas-2, and apaf-1), and autophagy (p62, atg5, lc-3, and beclin-1) in the liver, intestine, kidney, and gill. In summary, current research indicates that microplastics in water damage the antioxidant defense system, induce cell apoptosis, enhance inflammation, and lead to tissue damage. The adverse effects of microplastics on tissues may be due to TNF-α/ NF-κB/ Beclin-1 signaling pathways.