Impact of nitrite exposure on plasma biochemical parameters and immune-related responses in Takifugu rubripes.

Nitrite is a major environmental pollutant in aquatic environments that negatively affects aquatic species. In this study, we investigated the impact of nitrite exposure on plasma biochemical parameters and immune responses in Takifugu rubripes. Fish were exposed to various concentrations of nitrite (0, 0.5, 1, 3, and 6 mM) for 96 h. After 0, 12, 24, 48, and 96 h of exposure, fish blood samples were collected to assay the levels of total protein (TP), albumin (Alb), glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (ALT), complement C3 (C3), complement C4 (C4), immunoglobulin (IgM), and lysozyme activity (LZM). The gills were sampled to analyze the mRNA levels of heat shock protein 70 (hsp70), heat shock protein 90 (hsp90), tumor necrosis factor α (tnf-α), B-cell activating factor (baff), interleukin-6 (il-6), and interleukin-12 (il-12). Levels of GOT, ALT, C3, and C4 were significantly enhanced in the high nitrite concentration group (3 and 6 mM), whereas those of TP, Alb, LZM, and IgM decreased significantly with the same treatments. Nitrite significantly upregulated hsp70, hsp90, tnf-α, il-6, il-12, and baff mRNA levels after 96 h of exposure. These results indicated that nitrite exposure altered the blood physiological status and immune system response, resulting in dysfunction and immunotoxicity in T. rubripes. Furthermore, our results reveal the possible mechanism of aquatic-nitrite-induced toxicity in fish.

Effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus).

Nitrite (NO2(-)) is commonly present as contaminant in aquatic environment and toxic to aquatic organisms. In the present study, we investigated the effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus). Fish were exposed to various concentrations of nitrite (0, 0.02, 0.08, 0.4 and 0.8mM) for 96 h. Fish blood and gills were collected to assay haematological parameters, oxidative stress and expression of genes after 0, 24, 48 and 96 h of exposure. In blood, the data showed that the levels of methemoglobin (MetHb), triglyceride (TG), potassium (K(+)), cortisol, heat shock protein 70 (HSP70) and glucose significantly increased in treatments with higher concentrations of nitrite (0.4 and/or 0.8mM) after 48 and 96 h, while the levels of haemoglobin (Hb) and sodium (Na(+)) significantly decreased in these treatments. In gills, nitrite (0.4 and/or 0.8mM) apparently reduced the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH), increased the formation of malondialdehyde (MDA), up-regulated the mRNA levels of c-jun amino-terminal kinase (JUK1), p53, caspase-3, caspase-7 and caspase-9 after 48 and 96 h of exposure. The results suggested caspase-dependent and JUK signaling pathways played important roles in nitrite-induced apoptosis in fish. Further, this study provides new insights into how nitrite affects the physiological responses and apoptosis in a marine fish.