JNK信号通路和p38MAPK信号通路在吗啡预处理减轻心力衰竭大鼠心肌缺血再灌注损伤中的作用

Role of JNK and p38MAPK signaling pathways in reduction of ischemia-reperfusion injury by morphine preconditioning in rats with heart failure

目的评价c-Jun氨基末端激酶（JNK）信号通路和p38丝裂原活化蛋白激酶（p38MAPK）信号通路在吗啡预处理减轻心力衰竭大鼠心肌缺血再灌注损伤中的作用。方法健康成年雄性SD大鼠，200～230g，尾静脉注射盐酸多柔比星2mg／kg，1次／周，连续6周，建立大鼠慢性心力衰竭模型。于第8周末，取成功制备慢性心力衰竭模型的45只大鼠，采用随机数字表法分为5组（n=9）：假手术组（S组）、缺血再灌注组（I／R组）、吗啡预处理组（MPC组）、JNK抑制剂SP600125＋吗啡预处理组（MSP组）和p38MAPK抑制剂SB203580＋吗啡预处理组（MSB组）。采用结扎冠状动脉左前降支30min，再灌注120min的方法建立心肌缺血再灌注损伤模型；MPC组于缺血前股静脉输注吗啡0．1mg／kg，输注5min后停止输注5min，重复3次进行预处理；MSP组和MSB组于吗啡预处理前10min时股静脉注射SP6001250．5mg／kg或SB2035800．2mg／kg。于再灌注120min时处死大鼠，取心肌组织，计算左心室与右心室总体积（LV＋RV），测定缺血危险区体积（AAR）和梗死区体积（IS），计算IS／AAR比值；采用免疫组化法测定心肌组织蛋白激酶δ（PKCδ）的表达水平。结果5组间LV＋RV和AAR比较差异无统计学意义（P〉0．05）；与S组比较，I／R组和MSB组IS和IS／AAR比值升高，心肌组织PKCδ表达上调（P〈0．05）；与I／R组比较，MPC组和MSP组IS和IS／AAR比值降低，心肌组织PKCδ表达下调（P〈0．05），与MPC组比较，MSB组IS和IS／AAR比值升高，心肌组织PKCδ表达上调（P〈0．05），MSP组上述各指标差异无统计学意义（P〉0．05）。结论p38MAPK信号通路的激活参与了吗啡预处理减轻心力衰竭大鼠心肌缺血再灌注损伤，其机制与下调PKCδ的表达有关；JNK信号通路无此作用。

Objective To evaluate the role of c-Jun N-terminal kinase （JNK） and p38 mitogen-activated protein kinase （p38MAPK） signaling pathways in reduction of ischemia-reperfusion （I/R） injury by morphine preconditioning in the rats with heart failure. Methods Adult male Sprague-Dawley rats, weighing 200-230 g, in which doxorubicin 2 mg/kg was injected via the tail vein once a week for 6 consecutive weeks to induce chronic heart failure, were studied. At the end of 8th week, 45 rats with chronic heart failure were randomly divided into 5 groups （n = 9 each） using a random number table： sham operation group （group S）, group I/R, morphine preconditioning group （group MPC ）, SP600125 （JNK inhibitor） ＋ morphine preconditioning group （group MSP） and SB203580 （p38MAPK inhibitor） ＋ morphine preconditioning group （group MSB）. Myocardial I/R was induced by 30 min occlusion of the anterior descending branch of the coronary artery followed by 120 min reperfusion in each group except group S. In group MPC, the rats were subjected to 3 cycles of 5-rain infusion of O. I mg/kg morphine via the femoral vein at 5 min interval before ischemia. In MSP and MSB groups, SP600125 0.5 mg/kg and SB203580 0.2 mg/kg were injected via the femoral vein, respectively, at 10 rain before morphine preconditioning. The animals were sacrificed at 120 rain of reperfusion, and the myocardial specimens were obtained for determination of the total areas of right and /eft ventricles （LV＋RV） , area at risk （AAR）, infarct size （IS）, and expression of PKC δ in myocardial tissues （by immunohistochemistry） , and IS/AAR ratio was calculated. Results There was no significant difference in LV＋RV and AAR between the five groups （P〉0.05）. Compared with group S, IS and IS/AAR were significantly increased, and the expression of PKCδ was upregulated in I/R and MSB groups （P〈O. 05）. Compared with group I/R, IS and IS/AAR were significantly decreased, and the expression of PKC δ was down-regulated in MPC and MSP groups （P〈0. 05）. Compared with group MPC, IS and IS/AAR were significantly increased, and the expression of PKC δwas up regulated in group MSB （P〈0.05） , and no significant change was found in the parameters mentioned above in group MSP （P〉0.05）. Conclusion Activation of p38MAPK signaling pathway is involved in reduction of myocardial I/R injury by morphine preconditioning, and the mechanism is related to down-regulation of PKC δ expression in rats with heart failure; JNK signaling pathway is not involved in this process.