运动锻炼上调M_3R对MI大鼠心脏产生保护效应及其机制探讨

Cardioprotective Effect and Its Mechanism of Exercise Training Up-Regulating the Expression of M_3 Receptor on Myocardial Infarction in Rats

目的:探讨运动上调M3受体(M3R)对心肌梗死(MI)大鼠心脏产生保护效应及其机制。方法:雄性SD大鼠48只,随机分为正常对照组(C),心梗组(MI),心梗+中强度持续有氧运动组(ME1),心梗+高强度间歇运动组(ME2),每组12只。C组常规饲养,MI组采用左冠脉前降支结扎法(LAD)建立MI模型。ME1和ME2组心梗手术1周后进行跑台运动,60min/次,1次/d,5d/1周×8周。ME1组以10m/min×5min,再以3m/min速度递增至16m/min。ME2组以10m/min×10 min后,逐渐递增至25 m/min×7 min;之后以15 m/min×3min间歇运动,依次交替进行。训练结束后次日,腹腔麻醉进行颈动脉插管测定LVSP、LVEDP、±dp/dtmax等指标,评定心功能变化。之后迅速开胸摘取心脏,分别进行组织学制片、Masson染色观察心肌胶原纤维变化,免疫荧光法观察分析心肌M3R表达,Western Blot法检测心肌M3R、MEK1/2、p-ERK1/2、ERK1/2、Bcl-2和Bax蛋白表达。结果:MI组胶原容积百分比(CVF%)和LVEDP较C组显著升高(P<0.01),LVSP和±dp/dtmax较C组均显著降低(P<0.01)。MI后可见心肌M3R阳性染色,且M3R、MEK1/2、p-ERK1/2/ERK1/2表达较C组均显著升高(P<0.01),Bcl-2/Bax比值较C组显著降低(P<0.01)。ME1和ME2组CVF%和LVEDP较MI组均显著降低(P<0.01),ME1组-dP/dt max较MI组显著升高(P<0.01),ME2组LVSP较MI组显著升高(P<0.01)。ME1和ME2组均可见心肌M3R阳性染色,M3R、MEK1/2、p-ERK1/2/ERK1/2表达较MI组显著增加(P<0.01),Bcl-2/Bax比值较MI组显著升高(P<0.01,P<0.05),ME1组和ME2组间无显著差异。结论:持续有氧运动和高强度间歇运动均可上调心梗心肌M3R-MEK1/2-ERK1/2通路,抑制心肌细胞凋亡,改善心肌纤维化程度,保护心梗大鼠心功能。心梗心肌M3R-MEK1/2-ERK1/2-细胞凋亡途径与持续和间歇运动方式及运动强度关系不密切。

objective： Cardioprotective effect and mechanism of exercise training up-regulating the expression of M3 receptor on myocardial infarction. Methods. 48 male Sprague-Dawley rats were randomly assigned to four groups （n= 12, per group） .-control group （C）, myocardial in- farction group （MI）, moderate-intensity aerobic exercise with myocardial infarction group （ME1） and high-intensity aerobic interval exercise with myocardial infarction group （ME2）, Rats in C group are breed normally. MI was induced by ligation of the left anterior descending （LAD） coronary artery in MI group~ Rats in ME1 and ME2 group take treadmill exercise for 8wk after lwk post-operation. ME1 group running began at the speed of 10m/min for 5min, then accelerate from 3m/min to 16m/rain. ME2 group running began at the speed of 10m/ rain for 10min,then the speed increases to 25 m/min, after 7min, slow down at the speed of 15m/min for 3min. Take the process alternatively. The total exercise time of ME1 and ME2 are both 60 min, 5 d/lwk X 8 wk. LVSP, LVEDP, ± dp/dtmax and the cardiac function changes are measured after training. Myocardial collagen fibers were observed by histological section and Masson staining. The expression of myocardial Ma R was observed and analyzed by immun- oflourecence. The myocardial protein content of M3 R, MEK1/2, P-ERK1/2, ERK1/2 and apoptosis related Bcl-2 and Bax were assayed by Western Blot. Results ： MI increased CVF and LV- EDP （P〈0. 01）, but decreased LVSP and -dp/dtmax （P%0. 01）. After MI myocardial M3 positive staining, after MI Ma protein expression significantly higher （ P 〈 0.01 ）, MEK1/2 , P- ERK1/2/ERKI/2 protein expression were significantly increased （P 〈 0. 01, P 〈 0. 01 ）, after the MI the Bcl-2/Bax expression significantly reduced （P 〈 0. 01）. ME1 and ME2 group CVF, LVEDP significantly reduced （P%0.01）, ME1 -dp/dtm^x significantly increased （P 〈 0.01）, ME2 LVSP increased significantly （P 〈0.01）. ME1 and ME2 groups were identified myocardial Ma, ME1 and ME2 Ma protein expression significantly increased （ P 〈 0.01, P 〈. 0.01）. ME1 and ME2 group Bcl-2/Bax expression significantly reduced in the MI group （P d0.01,P%0.01）. ME1 and ME2 index had no significant difference. Conclusions.. Moder- ate-intensity aerobic exercise and high-intensity aerobic interval exercise can upregulate the M3 R-MEK1/2-ERK1/2 signaling pathway, thus inhibit the apoptosis of myocardial cells, reduce myocardial interstitial fibrosis and promote cardiac function after MI.