Research On The Role Of Heme Oxygenase-1 In The Myocardial Ischemic Preconditioning

AIM: The oxygen demand of myocardium increases acutely during excessive exercise and labor. Consequently blood flow in coronary arteries is relatively deficient, which results in relative ischemia reperfusion injury. It is pathophysiologically analogous with ischemia reperfusion injury. Mechanism of ischemic preconditioning protective effects involves in one or more endogenous active molecules. We aimed to explore the role of heme oxygenase-l in ischemic preconditioning and mechanism of ischemic preconditioning, and to provide some theoretic foundation on protection against ischemia reperfusion injury, especially relative ischemia reperfusion injury due to excessive exercise and labor.METHODS: Model of Langendorff was used in rat isolated heart perfusion. Relative ischemia protocol: weak current stimulus on isolated rat hearts. 48 male Wistar rats were randomly divided into 6 groups(n=8): (1)CN (perfusion 120min);(2)IR (perfusion 30 min, relative ischemia 30 min and reperfusion 60 min); (3)PC (perfusion 10 min, 2 cycles of relative ischemia 5 min, reperfusion 5 min before relative ischemia 30 min and reperfusion 60 min); (4)HM (hemin 10 μmol/kg ip, then IR protocol); (5)ZP (ZnPP-9 10 umol/kg ip, then PC protocol); (6)HP (hemin 10 μwol/kg ip, then PC protocol). The cardiac function was recorded at baseline (10 min perfusion) and at 1, 3, 5, 15, 30, 60 min reperfusion by Pclab biomedical signals collection system. The content of malondialdehyde (MDA) in coronary effluent at baseline and the 30th min after relative ischemic was determined by thiobarbituric acid test. HO-1 activity in myocardium was assayed by spectrophotometry method. Myocardial HO-lmRNA expression was measured by RT-PCR. RESULTS: (1)Ischemic preconditioning which up-regulated HO-1 mRNA expressionand induced HO-1 activity could protect ischemia reperfusion myocardium, including improving recovery of cardiac function and alleviating peroxidative injury. PRP recovery rate at 60 min reperfusion in PC group was significantly higher (P<0.01) and MDA level in coronary effluent lower than IR group(P<0.05). (2) HO-1 inducer hemin which also up-regualted HO-1 mRNA expression and increased HO-1 activity could exert protective effects similar to ischemic preconditioning on ischemia reperfusion myocardium. PRP recovery rate in HM group was significantly higher (P<0.01) and MDA level in coronary effluent lower than IR group (P<0.05) .(3) HO-1 inhibitor ZnPP-9 which down-regulated HO-1 mRNA expression and inhibited HO-1 activity partly abolished the protective effects of ischemic preconditioning . PRP recovery rate in ZP group was significantly lower( P<0.01 )and MDA level in coronary effluent higher than PC group (P<0.01) . (4) There was significant correlation between HO-1 mRNA and HO-1 activity (P<0.01) . Cardiac function recovery and MDA levels in coronary effluent both had significant correlation with HO-1 activity (P<0.05, P<0.01) .(5) Ischemic preconditioning could cooperate with HO-1 inducer hemin to prevent myocardial ischemia reperfusion injury.CONCLUSION: HO-1 should be one of the endogenous active molecules which participate in preconditioning procedure. HO-1 inducer and ischemic preconditioning could cooperate with each other to strengthen the protective effects on relative ischemia reperfusion myocardium.