Nano­zinc enhances gene regulation of non­specific immunity and antioxidative status to mitigate multiple stresses in fish.

The toxicity of ammonia surged with arsenic pollution and high temperature (34 °C). As climate change enhances the pollution in water bodies, however, the aquatic animals are drastically affected and extinct from nature. The present investigation aims to mitigate arsenic and ammonia toxicity and high-temperature stress (As + NH3 + T) using zinc nanoparticles (Zn-NPs) in Pangasianodon hypophthalmus. Zn-NPs were synthesized using fisheries waste to developing Zn-NPs diets. The four isonitrogenous and isocaloric diets were formulated and prepared. The diets containing Zn-NPs at 0 (control), 2, 4 and 6 mg kg-1 diets were included. Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-s-transferase (GST) were noticeably improved using Zn-NPs diets in fish reared under with or without stressors. Interestingly, lipid peroxidation was significantly reduced, whereas vitamin C and acetylcholine esterase were enhanced with supplementation of Zn-NPs diets. Immune-related attributes such as total protein, globulin, albumin, myeloperoxidase (MPO), A:G ratio, and NBT were also improved with Zn-NPs at 4 mg kg-1 diet. The immune-related genes such as immunoglobulin (Ig), tumor necrosis factor (TNFα), and interleukin (IL1b) were strengthening in the fish using Zn-NPs diets. Indeed, the gene regulations of growth hormone (GH), growth hormone regulator (GHR1), myostatin (MYST) and somatostatin (SMT) were significantly improved with Zn-NPs diets. Blood glucose, cortisol and HSP 70 gene expressions were significantly upregulated by stressors, whereas the dietary Zn-NPs downregulated the gene expression. Blood profiling (RBC, WBC and Hb) was reduced considerably with stressors (As + NH3 + T), whereas Zn-NPs enhanced the RBC, WBC, and Hb count in fish reread in control or stress conditions. DNA damage-inducible protein gene and DNA damage were significantly reduced using Zn-NPs at 4 mg kg-1 diet. Moreover, the Zn-NPs also enhanced the arsenic detoxification in different fish tissues. The present investigation revealed that Zn-NPs diets mitigate ammonia and arsenic toxicity, and high-temperature stress in P. hypophthalmus.