脂质胞壁酸诱导的预适应对自发性高血压大鼠心肌缺血再灌注损伤的保护作用

Effects of lipoteichoic acid induced delayed preconditioning on myocardial ischemia/reperfusion injury in spontaneous hypertensive rat

目的:探讨脂质胞壁酸(LTA)诱导的延迟预适应对自发性高血压大鼠(SHR)心脏缺血/再灌注(I/R)损伤的保护作用及诱导型一氧化氮合酶(iNOS)是否参与其作用。方法:采用结扎左冠状动脉前降支30min,再灌注复制大鼠心肌I/R模型,结扎前24h注射LTA,检测心肌再灌注60min后血清心肌型肌酸激酶同工酶(CK-MB)、乳酸脱氢酶(LDH),并用dUTP缺口末端标记法检测心肌细胞凋亡,用Western Blot方法检测凋亡蛋白Bcl-2和Bax的蛋白表达。同时采用实时RT-PCR技术和Western Blot方法分别检测心肌再灌注末iNOS mRNA和蛋白的表达。结果:与I/R组比较,LTA预适应组能显著减少室性心律失常(VA)评分值(P<0.01);LTA预适应还能明显减少I/R后血清CK-MB和LDH的漏出(P<0.01,P<0.05),减少心肌细胞凋亡(P<0.01),凋亡相关蛋白Bcl-2表达明显上调(P<0.01),而Bax蛋白表达则下调(P<0.01)。再灌注末,预适应组iNOS mRNA的平均相对表达量较I/R组增加了0.71倍(P<0.01),LTA预适应组iNOS蛋白的表达量较I/R组增加了0.96倍(P<0.05)。不论在LTA预适应前或缺血前期给予iNOS抑制剂氨基胍或是单独给予氨基胍,上述观测指标均与I/R组比较差异无统计学意义。结论:LTA预适应能显著减轻SHRI/R导致肥厚心肌的坏死和细胞凋亡,iNOS/NO作为触发和效应环节在介导LTA预适应中发挥关键作用。

Objective：To explore the potential effects of lipoteichoic acid （LTA） induced delayed preconditioning （PC） on myocardial ischemia/reperfusion injury （I/R） in spontaneous hypertensive rat and whether inducible nitric oxide synthase （iNOS） was participated the mechanisms. Method： I/R model was induced by left anterior descending coronary artery （LAD） ligation for 30 min, followed by 60 min reperfusion. Preconditiong was produced by pretreated with LTA （1 mg/kg） 24 h before the experiment. The amounts of MB isoenzyme of creatine kinase （CK-MB） and lactate dehydrogenase （LDH） of serum at the end of reperfusion were measured by colorimetric method. Myocardial apoptosis on tissue samples of left ventricle were detected by TUNEL staining in situ at the end of reperfusion, and the changes of apoptosis correlated protein, Bcl-2 and Bax, were detected by western blot. Meanwhile, the expression of iNOS mRNA and protein of left ventricle were detected by real time RT-PCR and western blot respectively. Result： LTA preconditioning could obviously decrease ventricular arrhythmia （VA） score （P〈0.01） during ischemia and reperfusion. Pretreated with LTA, the level of Ck-MB and LDH in serum were significantly reduced, and the apoptosis index in left lentricle was markedly decreased at the end of reperfusion （P 〈0.01）. The expression of Bax protein was obviously decreased but the expression of Bcl-2 protein was obviously increased in LTA preconditioning group compared with those of I/R group （P〈0.01, P〈0.01）. The mean relativity expression of iNOS mRNA in LTA preconditioning group was increased 0.71 times （P〈0.01） and the expression of iNOS protein was increased 0.96 times （P〈0.05） compared with I/R group. There were no disparations no matter pretreatment of the rats with the inhibitor of iNOS, aminoguanidine （AG） before LTA preconditioning, or 30 min before ischemia or pretreatment with AG alone. Conelusion：LTA induced delayed preconditioning could obviously decreases myocardial necrosis and apoptosis induced by I/R in SHR. iNOS/NO acted as a trigger and an effetor playing a key role in the mechanisms of LTA protection.