Objectives Bim is a BH3-only member of the Bcl-2 family, previous research showed Bim could induce the apoptosis of cardiomyocytes in rat model of myocardial infarction, the area of infarction and the expression of Bim were increased sharply when its subjected to cold stress, but the mechanism is unclear. To investigate the relationship between Pim-2 and Bim in cardiomyocytes when subjected to deeper temperature (25°), and discuss the biological functions of Pim-2.
Methods Cultured rat cardiomyocytes H9c2 cells, cells were exposed to 25° for 4h, 12h, 24h to build the different degree model of cold stress. Transfected the overexpression and interference plasmid of Pim-2 to control and cold stress group. The ratio of apoptosis was determined by AnnexinV-FITC/PI, the activity of LDH were observed by automatic biochemistry analyser and the expression of Pim-2, Bim, caspase-3 were tested by Western blotting. Immunoprecipitation assay were used to identify the interaction of Pim-2 and Bim.
Results Compared to the control group, apoptosis ratio, the LDH activity and the expression of Pim-2, Bim, caspase-3 were all increased in cold stress group (P < 0.005), and there had a time dependence in these biological indicators. What interesting was the injury of cardiomyocytes and the expression of Bim were decreased when the cells were transfected to Pim-2 overexpression plasmid, and the opposite results were appeared when transfected to Pim-2 interference plasmid. Endogenous and exogenous immunoprecipitation indicated that there was an interaction between Pim-2 and Bim.
Conclusions Pim-2 can resist the cardiomyocytes injury which caused by cold stress, the maight mechanism is to regulated the expression of Bim.