PI3K/Akt通路在内吗啡肽-1后处理减轻大鼠心肌缺血再灌注损伤中的作用

目的 探讨内吗啡肽-1对心肌缺血再灌注损伤中PI3K/Akt信号通路的作用以及对细胞凋亡的影响。方法 将50只SD雄性大鼠随机分为5组：假手术组（S组）、缺血再灌注组（IR组）、内吗啡肽-1后处理组（EM50组）、内吗啡肽-1+渥曼青霉素后处理组（EM50+Wort组）和PI3K/Akt信号通路抑制剂渥曼青霉素后处理组（Wort组）。采用结扎大鼠心脏左冠状动脉前降支30 min，再灌注120 min复制心肌缺血再灌注模型，实验期间动态监测大鼠心率、平均动脉压；再灌注结束后检测大鼠血浆乳酸脱氢酶、肌酸激酶、肌钙蛋白I、白介素-6、肿瘤坏死因子-α、氧化应激指标超氧化物歧化酶和丙二醛等生化指标，RT-PCR检测Bax和Bcl-2基因的表达情况，Western blot检测心肌组织中凋亡相关蛋白cleaved caspase-3、磷酸化Akt蛋白和总Akt蛋白的表达。结果 与S组比较，IR组心率和血压降低（P<0.05）；与IR组比较，EM50组心率和血压有所增高（339.94±26.65 vs 284.01±34.99；75.02±14.45 vs 55.83±20.98，P<0.05）；血浆中乳酸脱氢酶、肌酸激酶、肌钙蛋白I、白介素-6、肿瘤坏死因子-α和丙二醛含量或活性下降（P<0.05），氧化应激指标超氧化物歧化酶活性增加（132.77±8.25 vs 84.10±12.42，P<0.05）；p-Akt蛋白表达水平较高（0.61± 0.06 vs 0.38±0.04，P<0.05），Bax基因和cleaved caspase-3蛋白表达量降低（1.70±0.39 vs 3.78±0.71；0.30±0.08 vs 0.53±0.07，P< 0.05），Bcl-2基因的表达量升高（1.20±0.44 vs 0.55±0.25，P<0.05）；与EM50组比较，EM50+Wort组心率和血压降低（P<0.05）；血浆中乳酸脱氢酶、肌酸激酶、肌钙蛋白I、白介素-6、肿瘤坏死因子-α和丙二醛含量或活性增加（P<0.05），氧化应激指标超氧化物歧化酶活性降低（P<0.05）；p-Akt蛋白表达水平较低（P<0.05），Bax基因和cleaved caspase-3蛋白表达量升高（P<0.05），Bcl-2基因表达量降低（P<0.05）。结论 EM-1后处理可调节细胞凋亡，减轻心肌缺血再灌注损伤。PI3K/Akt信号通路可能对EM-1后处理产生的心肌保护效应发挥一定的介导作用。

PI3K/Akt signaling pathway mediates the protective effect of endomorphin-1 post-conditioning against myocardial ischemia-reperfusion injury in rats

Objective To investigate the role of PI3K/Akt signaling pathway in mediating the protective effect of endomorphin-1 against myocardial ischemia-reperfusion (IR) injury. Methods Fifty SD male rats were randomly divided into sham operation group, myocardial IR group, endomorphin-1 post- treatment group (EM50 group), endomorphin-1 +wortmannin (a PI3K/Akt signaling pathway inhibitor) treatment group (EM50+Wort group), and wortmannin treatment group (Wort group). Rat models of myocardial IR injury were established by ligation of the left anterior descending coronary artery for 30 min followed by reperfusion for 120 min. The heart rate and mean arterial pressure were monitored during the experiment. Plasma levels of LDH, CK-MB, cTnI, IL-6, TNF-α, SOD and MDA were measured after reperfusion. The mRNA expression of Bax and Bcl-2 was detected using RT-PCR, and the expression of apoptosis- related protein cleaved caspase-3, phosphorylated Akt protein and total Akt protein in myocardial tissue was detected using Western blotting. Results Myocardial IR injury significantly decreased heart rate and blood pressure of the rats in comparison with the sham operation (P<0.05). Compared with those in the IR group, the rats in EM50 group showed significantly increased heart rate and blood pressure (P<0.05) with decreased plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels (P<0.05), increased SOD activity (P<0.05), increased expression of p-Akt protein and Bcl-2 mRNA (P<0.05), and decreased expression of Bax mRNA and cleaved caspase-3 protein (P<0.05). In EM50+Wort group, the heart rate and blood pressure were significantly lowered (P<0.05), plasma LDH, CK-MB, cTnI, IL-6, TNF-α and MDA levels increased (P<0.05), SOD activity decreased (P<0.05), the expression of p-Akt protein and Bcl-2 mRNA was reduced (P<0.05), and the expression of Bax mRNA and cleaved caspase-3 protein increased (P<0.05) as compared with those in EM50 group. Conclusion EM-1 postconditioning can regulate cardiac myocyte apoptosis and reduce myocardial IR injury in rats. The PI3K/Akt signaling pathway may play a role in mediating the myocardial protective effects of EM-1 postconditioning.