Objective To investigate the role of endoplasmic reticulum stress in Bim-induced cardiomyocytes injured by hypoxia.
Methods Bim-siRNA were transfected transiently into H9C2 cells by lipofectamine 2000. Establish a model of hypoxia (The cells after 48 h transfection, were given a deal with hypoxia for 12 h). The experiments were divided into five groups: Blank Control Group, Hypoxia Group, Hypoxia + Negative Control siRNA Group, Hypoxia + Mock control Group, Hypoxia + Bim-siRNA Group. The cell survival rate was determined by MTT method; the cell apoptosis rate and the change of the calcium concentration in cells were detdemined by flow cytometry; the expression of Bim and the markers of endoplasmic reticulum stress Caspase-12 and In SP3 were assessed by Western Blotting.
Results Green fluorescence was observed in the cells transfected of negative control siRNA group though the fluorescence microscope. Compared with the blank control group, The MTT assay determined that the survival rate of H9C2 was decreased (p < 0.05) after the injured by hypoxia. And the results of flow cytometry showed that hypoxia increased cell apoptosis rate (P < 0.01) and the concentration of calcium (p < 0.01), while the transfection of Bim-siRNA reduced the effects caused by hypoxia (P < 0.05 or P < 0.01). Compared with the hypoxia group, the transfection of Bim-siRNA increased the cell survival rate, decreased cell apoptosis rate and the concentration of calcium (p < 0.01 or p < 0.05). While there was no significant difference among Hypoxia Group, Hypoxia + Negative Control siRNA Group and Hypoxia + Mock control Group (p > 0.05). The results of Western blotting showed that the transfection of Bim-siRNA reduced the expression of Bim obviously (p < 0.01); meanwhile, reduced the expression of endoplasmic reticulum stress markers Caspase-12 and InSP3 (p < 0.05 or p < 0.01), and reduced the effects that hypoxia increased the expression of Caspase-12 and InSP3 (p < 0.05 or p < 0.01).
Conclusions The down-regulation of the expression of Bim can suppress the apoptosis of H9C2 induced by hypoxia. Its mechanism is associated with the endoplasmic reticulum stress. It is likely to be a new direction for treatment of coronary atherosclerotic heart disease.