Effect of copper nanoparticles and copper sulphate on oxidation stress, cell apoptosis and immune responses in the intestines of juvenile Epinephelus coioides

Abstract

Copper nanoparticles (Cu-NPs) are widely used in various industrial and commercial applications, but little is known about their potential hazard in the intestines of marine teleosts. In this study we investigated the effects of Cu-NPs and soluble Cu in the intestines of juvenile Epinephelus coioides. The fish were exposed in triplicate to control, 20 or 100 μg Cu L−1 as either copper sulphate (CuSO4) or Cu-NPs for 25 days. With an increase in Cu-NPs or CuSO4 dose, the concentration of malonaldehyde in the intestines significantly increased, whereas the activities of total superoxide dismutase and catalase as well as glutathione concentration decreased compared to the control. Statistical analysis of an apoptosis index of intestinal cells showed that general dose-dependent apoptosis was induced by Cu-NPs or CuSO4, with Cu-NPs inducing the significantly higher apoptosis index than CuSO4. Caspase-3 and caspase-9 activities were increased with an increase in Cu-NPs or CuSO4 dose, more so in the Cu-NPs than CuSO4 treatment. With an increase in Cu-NPs or CuSO4 dose, succinate dehydrogenase and Na+-K+-ATPase activity and cytochrome c concentration in mitochondria decreased, accompanied by increased cytochrome c concentration in the cytosol. Concentration of heat shock proteins 70 and 90 in the intestines and expression of corresponding genes were enhanced with an increase in the Cu-NPs or CuSO4 dose, but the concentrations and expressions of immunoglobulin M and lysozyme decreased (more in the Cu-NPs than CuSO4 treatment) compared to the control. Expression of interleukin-1beta and tumor necrosis factor-alpha showed a dose-dependent increase with the increased Cu-NPs or CuSO4 dose, with the highest expression found in the Cu-NPs treatment. In conclusion, Cu-NPs had similar toxic effects as CuSO4 in the intestines of juvenile E. coioides, but toxicity of Cu-NPs was more severe than that of CuSO4.