The antioxidant system mediated by Nrf2 in C2C12 cells responding to H2O2 stimulus under different oxygen concentration

Abstract

To apply hypoxia of different oxygen concentration on C2C12 cells to study the changes of Nrf2 antioxidant system under H2O2. The perfect simulative effect time and concentration of H2O2 were chosen. Cell vitality was tested after C2C12 cells cultured in 0.1 mmol/L, 0.25 mmol/L, 0.5 mmol/L, 0.75 mmol/L, 1 mmol/L and 2 mmol/L H2O2 for 1 or 2 h respectively. The C2C12 cells were divided into different oxygen concentration group: 21%O2, 12%O2, 8%O2, 5%O2 respectively. And then cells were treated with H2O2 for 1 h, and collected for determination. Immunofluorescence of Nrf2 and the protein expression of Nrf2 were detected. The expressions of antioxidant enzymes superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), catalase(CAT), NADPH quinine oxidoreductase-1 (NQO-1), glutathione peroxidase-1 (GPX-1), Heme oxygenase-1 (HO-1) mRNA and cellular ROS levels were tested by high quality fluorescence assay. 0.5 mmol/L H2O2 for 1 h was selected as the conditions of H2O2stimulation. Compared with 21% O2 group, the expressions of Nrf2 mRNA and protein, antioxidant enzymes SOD1, SOD2, CAT, HO-1, NQO-1, GPX-1 mRNA were increased significantly (P＜0.05 or P＜0.01), and ROS level was lower (P＜0.01) in 12%O2 group cells; only the expression of GPX-1 mRNA was increased (P＜0.05) in 8%O2 group; the expressions of Nrf2 mRNA and protein expression, antioxidant enzymes SOD1, SOD2, NQO-1, GPX-1 mRNA were decreased significantly(P＜0.05 or P＜0.01), and ROS level was higher (P＜0.01) in 5%O2 group. Hypoxia can affect the Nrf2 antioxidant system, and the different oxygen concentrations have different impact. In addition, 12% O2 for 12 h could promote the Nrf2 antioxidant system, and 5% extremely low oxygen may inhibit it.