Inhibitory effect of hypoxia preconditioning on hypoxia/ reoxygenation-induced apoptosis in cardiomyocytes

AIM: To study the role of hypoxia precondit io ning (HP) in hypoxia-reoxygenation (HR)-induced apoptosis in neonatal rat cardio myocytes and the possible mechanisms. METHODS: Cultured neonatal rat cardiomyocytes were divided into three groups: normal group, HP+H/R group and H/R group. Acridine orange (AO) sta ining was performed to detect morphological changes of apoptotic cells. Apoptosi s rates of cardiomyocytes were detected by flow cytometry. Colorimetric assay wa s used to detect caspase-3 activity. Expression of Bcl-2 protein was detected by immunohistochemistry combined with computer image analysis. RESULTS: Apoptotic cells were detected by AO staining after hypo xia of 6 h followed by 3 h-reoxygenation. The hypodiploid apoptotic peak was det ected by flow cytometry with the apoptotic rates of (29.7±5.4)%. A significan tly reduced apoptotic rates of (7.8±1.3)% was detected in HP group(P0 .01). The caspase-3 relative activity of cardiomyocytes induced by H/R was 5. 9±0.8, significantly higher than that of control group. HP markedly reduced ca spase-3 relative activity to 2.6±0.5 in contrast with H/R group (P 0.0 1). Bcl-2 protein was positive in normal cardiomyocytes with an A value of 119.4±7.1. The A value of H/R group was 99.6±5.0, significantly lower than that in normal group (P0.01). The A value of HP+H/R group was 126.5±6.2, significantly higher than that in H/R group(P0.01). CONCLUSION: HP inhibits H/R-induced apoptosis of cardiomyocytes by improving the expression of Bcl-2 and reducing caspase-3 activity.