Effects of diazoxide pretreatment on the expression of hypoxia- inducible factor-1α mRNA and p53 mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation

Objective To investigate the effects of diazoxide pretreatment on the expression of hypoxia-inducible factor-1α (HIF-1α) mRNA and p53 mRNA in rat myocardial microvascular endothelial cells exposed to hypoxia-reoxygenation (H/R).Methods The SD rat myocardial microvascular endothelial cells were cultured. The cells were seeded in 96-well plates ( 100 μl/hole) or in 6 cm diameter dishes (2 ml/dish) with the density of 1 ×106/ml and randomly divided into 4 groups ( n = 24 each): normal control group (group C), H/R group, H/R +diazoxide pretreatment group (group DZ) and H/R + diazoxide pretreatment + mitochondrial ATP-sensitive potassium channel blocker 5-hydroxydecanoate (5-HD) group (group DZ + 5-HD). The cells were exposed to 2 h hypoxia followed by 2 h reoxygenation. Diazoxide 100 μmol/L and diazoxide 100 μmol/L + 5-HD 100 μmol/L were added to the culture medium 2 h before hypoxia in DZ and DZ + 5-HD groups respectively. The cell vitality, apoptotic rate and expression of HIF-1α mRNA and p53 mRNA were detected at the end of reoxygenation. Results Compared with group C, the cell vitality was significantly decreased, apoptotic rate increased and the expression of HIF- 1α mRNA and p53 mRNA up-regulated in H/R group ( P ＜ 0.01). Compared with group H/R, the cell vitality was significantly increased, apoptotic rate decreased, the expression of HIF-1α mRNA up-regulated and the expression of p53 mRNA down-regulated in group DZ ( P ＜ 0.05 or 0.01 ). 5-HD could inhibit diazoxide pretreatment-induced changes mentioned above (P ＜ 0.05 ). Conclusion Diazoxide pretreatment can reduce H/R injury in rat myocardial microvascular endothelial cells through up-regulating the expression of HIF-1α and down-regulating the expression of p53, and the mechanism is related to activation of mitochondrial ATP-sensitive potassium channels. Key words: Dazoxide;  Heart;  Endothelium, vascular;  Oxygen;  Cell hpoxia;  Hypoxia-inducible factor 1, alpha subunit;  Tumor suppressor protein p53