H₂O₂ down-regulated the expression level of SOD2 protein in a dose-dependent manner.

<p>(A) Along with the increase of H₂O₂ concentrations, the SOD2 protein was decreased gradually. Interestingly, the SOD2 protein showed an evident higher level with 12.5 µM and 25 µM H₂O₂ stimulation. With the higher concentration 200 µM H₂O₂ stimulation, it decreased significantly with a lower level than control group. (B) The relative amounts of SOD2, which were represented by the intensity ratio between SOD2 and β-actin in each lane. Data are shown mean ± SD from 3 independent experiments, each with 6 replicates. (C) H₂O₂ had no obvious effect on <i>sod2</i> mRNA expression in PC12 cells. After 6 h treatment with different concentrations of H₂O₂, the RT-PCR assay demonstrated there were no statistical differences of PC12 <i>sod2</i> mRNA expression levels between the groups. Data are shown the mean ± SD (n = 6). ANOVA (Dunnett) *<i>P</i><0.05, as compared with control.