Copper mediates oxidative stress and immune response in snakehead (Channa argus) through Nrf2 and NF-κB pathway

Acute copper exposure can exert toxicological effects on fish. This study aims to evaluate the antioxidant and immune responses of snakehead under acute copper exposure. Based on 96-h LC₅₀ (0.226 mg/L), snakehead (Channa argus) [(13.32 ± 0.68) g] were divided into CK group, 10 %LC50 group, 30 %LC50 group and 50 %LC50 group for a 96-h copper exposure trial. Results indicated that acute copper exposure significantly caused damage to liver, intestine, kidney, spleen and gill of snakehead. Parameters related to liver function (TBIL, TBA, AST and ALT), kidney function (CRE and BUN) and immune function (LZM, IgM, C4 and C3) in serum were markedly inhibited. Meanwhile, immune-related enzymes contents (TNF-α, IL-6 and IL-1β) and gene expression levels (tnf-α, tgf-β, nf-κb, il-6, il-1β and ikb-α) in liver, intestine, kidney, spleen and gill tissues were significantly altered. Similarly, antioxidant-related enzymes contents (SOD, MDA, GSH, GPx and CAT) and gene expression levels (sod, nrf2, mad, keap1, gsh, gr, gpx and cat) were also dramatically affected. Interestingly, genes related to Nrf2 and NF-κB signaling pathways showed significant correlation. They exhibited a synergistic effect in response to acute copper exposure. This study provided a theoretical basis for understanding the mechanisms of copper toxicity in aquatic animals and for preventing related diseases.