[Effect of oxidative damage on expression of myocardin and NF-E2-related factor 2 in myocardial cells]

With the oxidative damage model established in rat myocardial cells by hydrogen peroxide (H ₂O ₂), the expression of myocardin and nuclear factor erythroid 2-related factor 2 (Nrf2) during oxidative damage and effect of myocardin on Nrf2 were preliminarily explored. The expression of the target gene was increased or decreased by transfection of plasmid DNA or shRNA, respectively. Cell proliferation was detected by sulforhodamine B (SRB) assay. The expression of myocardin mRNA and Nrf2 mRNA was detected by Real-time PCR, and their protein levels were detected by Western blot. The results showed that oxidative damage was induced by H ₂O ₂ with an optimized incubation condition of 200 μmol/L H ₂O ₂ for 24 hours. H ₂O ₂ inhibited expression of myocardin in mRNA and protein levels, and increased expression of Nrf2 in mRNA and protein levels. The overexpression of myocardin or the knockdown of Nrf2 significantly decreased cell viability compared with the control group, while the knockdown of myocardin or the overexpression of Nrf2 significantly increased cell viability. The overexpression of myocardin significantly down-regulated the expression of Nrf2 in mRNA and protein levels, while the knockdown of myocardin dramatically up-regulated the expression of Nrf2. Thus, it is deduced that myocardin may inhibit cell proliferation and Nrf2 may promote cell proliferation. Oxidative damage induced by H ₂O ₂ in rat myocardial cell might activate Nrf2-related signaling pathway through down-regulation of myocardin.