Abstract: Objective To investigate the effect of helix B surfacepeptide（HBSP） on transposition of Omi/HtrA2 and apoptosis of myocardial cells Induced by Hypoxia- reoxygenation. Methods neonatal rat myocardial cells (H9C2 cells) was used to be research object, the cells were divideded into 4 groups：control group, H/R group, HBSP group and EPO group. The cell viability was measured by MTS assay, the concentration of LDH of cell supernatant was assessed by ELISA, the intracellular expression changes of cleaved Caspase3 was detected by Western blot. apoptosis of cardiomyocytes was detected by TUNEL.Using Mitochondria/cytosol Isolation Kit to isolate Mitochondria from cytosol, Western blot was used to detect the expression of Omi/HtrA2 protein changes in the mitochondrial and cytosolic.Results Compared with the control group, H/R group cell survival rate decreased significantly, cell supernatant LDH concentration increased significantly,the expression of cleaved caspase-3 was increased, the cardiomyocyte apoptosis and the expression of Omi/HtrA2 protein in the cytoplasm is increased，the differences were statistically significant (P<0.05); compared with H/R group, EPO and HBSP group cell survival rate increased, cell supernatant concentrations of LDH、cleaved caspase-3、cardiomyocyte apoptosis and the Omi/HtrA2 protein in the cytoplasm expression decreased, the difference was statistically significance (P<0.05).conclusion H / R can induce apoptosis of myocardial cell,which can be reduced by EPO or HBSP,its mechanism may be related to the inhibition of Omi/HtrA2 protein in mitochondrial translocation, thus inhibiting the Caspases pathway activation.

Key words: hypoxia-reoxygenation , HBSP , EPO , apoptosis , Omi/HtrA2