Effects of glutamine on hydrogen peroxide-induced oxidative damage in intestinal epithelial cells of Jian carp (Cyprinus carpio var. Jian)

The present study explored the effects of glutamine on hydrogen peroxide (H2O2)-induced oxidative stress in isolated carp enterocytes. In order to select an optimal H2O2 concentration to induce oxidative stress in enterocytes, cultures were treated with different concentrations of H2O2 (0-100 μM) for 16 h. The results showed that exposure to H2O2 increased lactate dehydrogenase activity and malondialdehyde levels in a dose-dependent manner in the culture medium, suggesting increase toxicity of H2O2. Thus, 100 μM was an appropriate concentration for inducing oxidative stress. We then examined the cytoprotective effects of glutamine under conditions of oxidative stress. Cells were treated with glutamine (0-20 mM) in the presence of H2O2 (100 μM) for 16 h. The control cells were kept in the glutamine-free MEM only. Results showed that glutamine completely blocked H2O2-stimulated release of lactate dehydrogenase. Furthermore, glutamine reduced H2O2-induced increase in malondialdehyde level and protein carbonyls content to the level seen in the control culture. In addition, glutamine treatment completely prevented the decrease in Na+-K+-ATPase, superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione S-transferase activities as well as reduced glutathione concentration and the ratio between reduced and oxidized glutathione induced by H2O2. No significant difference was observed between cells incubated with glutamine in the presence of H2O2 and control cells in values for most of the markers mentioned above. Complete protection was obtained at a concentration of glutamine as small as 4 mM. The present results indicate that glutamine is effective in protecting against H2O2-induced oxidative stress in carp intestinal epithelial cells.