Mipu1 Protects H9c2 Myogenic Cells from Hydrogen Peroxide-Induced Apoptosis through Inhibition of the Expression of the Death Receptor Fas

Mipu1 (myocardial ischemic preconditioning upregulated protein 1), a novel rat gene recently identified in our lab, was expressed abundantly and predominantly in the brain and heart and upregulated in myocardium during myocardial ischemia/reperfusion in rats. In our previous study we found that Mipu1 was an evolutionarily conserved zinc finger-containing transcription factor. However, whether Mipu1 confers myocardial protection remains unknown. In this study, H9c2 myogenic cells were treated with hydrogen peroxide (H2O2) to simulate oxidative stress during myocardial ischemia-reperfusion injury. The expression of Mipu1 at mRNA and protein levels was detected by RT-PCR and Western blotting analysis. To study the effect of Mipu1 on apoptosis and expression of Fas induced by H2O2, full-length Mipu1 cDNA and Mipu1-RNAi plasmids were transiently transfected into H9c2 myogenic cells, and flow cytometry was used to quantitate the percentage of apoptotic cells. The expression of Fas was analyzed by Western blotting assay. The DNA binding and transcription activities of Mipu1 to the Fas promoter were detected by chromatin immunoprecipitation and luciferase reporter assays. The results showed that exposure of H9c2 myogenic cells to H2O2 resulted in a dose- and time-dependent increase in Mipu1 mRNA and protein levels; Mipu1 over-expression inhibited H2O2-induced apoptosis and upregulation of Fas induced by H2O2 in H9c2 myogenic cells; and knockdown of Mipu1 by RNAi promoted apoptosis and upregulation of Fas induced by H2O2. The chromatin immunoprecipition and reporter assays showed the DNA binding and transcription suppressor activities of Mipu1 to Fas promoter region. These results indicate that Mipu1 protected H9c2 myogenic cells from H2O2-induced apoptosis through inhibiting the expression of Fas.