Eco-friendly Nano-copper Synthesis: Gene and Enzyme Modulation for Combating Cadmium and Ammonia Toxicity in Fish

The major threats to aquaculture systems include water pollution, which significantly impacts the production and yield of fisheries. These pollutants adversely affect aquatic organisms, including fish, as well as plants, animals, and humans. To address this issue, we conducted an experiment to investigate the role of copper nanoparticles (Cu-NPs) in mitigating cadmium and ammonia toxicity in fish. Cu-NPs were synthesized from fish waste and incorporated into fish feed at 0.8 and 1.2 mg kg^-1 of diet. The study included four treatments: control, Cu-NPs diet at 0.8 and 1.2 mg kg^-1 with Cd+NH₃ exposure, and concurrent exposure to cadmium and ammonia, fed with control diet. Stressors (Cd+NH₃) considerably increased the catalase (CAT) and superoxide dismutase (SOD), while diets containing Cu-NPs significantly decreased these levels. Tumor necrosis factor (TNFα), total immunoglobulin (Ig), and growth hormone (GH) were markedly downregulated by Cd+NH₃ toxicity, while the gene expressions of Heat Shock protein (HSP 70), inducible nitric oxide synthase (iNOS), caspase (Cas 3a), cytochrome P 450 (CYP 450), and myostatin (MYST) were considerably increased. Furthermore, both under normal and stressful circumstances, the Cu-NPs diet regulated the expression of all these genes. Cu-NPs protected the tissues from DNA damage;, however, the group subjected to Cd+NH₃ toxicity had the highest level of DNA damage. Cd+NH₃ toxicity was found to significantly increase the levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) malate dehydrogenase (MDH), and lactate dehydrogenase (LDH), in the liver and gill tissues. In contrast, the Cu-NPs diet controlled and protected the tissues from the metabolism of proteins and carbohydrates. It is interesting to note that the Cu-NPs diet significantly increased the neurotransmitter enzyme acetylcholinesterase in brain tissue. The outcomes also showed that Cu-NPs improve the cadmium detoxification process in fish tissues. The research findings indicate that dietary Cu-NPs, by their action on gene regulation and enzymatic systems, mitigate the effects of cadmium and ammonia toxicity in Oreochromis niloticus (GIFT strain).