衣霉素诱导内质网应激预处理对大鼠心肌缺血再灌注损伤的影响

Endoplasmic reticnium stress preconditioning induced by tunicamycin attenuates myocardial ische- mla - reperfusion injury in rats

目的观察衣霉素诱导内质网应激预处理对大鼠心肌缺血再灌注损伤（I／R）的影响。方法将40只SD大鼠随机分为4组：假手术组（Sham组）、I／R组、单纯衣霉素处理组（TM组）和衣霉素处理＋I／R组（TM＋I／R组），I／R组和TM＋I／R组通过结扎左冠状动脉前降支并再灌注的方法建立I／R模型，TM组和TM＋I／R组造模前30min腹腔注射衣霉素0．6mg／kg，记录正常时及再灌注30min、1h和2h时的左心室内收缩压（LVSP）、左心室内舒张末压（LVEDP）、左心室内压上升和下降最大速率（±ap／dtmax），分别于开胸后、再灌注2h取颈动脉血，酶联免疫吸附试验（ELISA）法测定肌酸激酶同工酶（CK—MB）及心肌肌钙蛋白（cTnI）水平。再灌注2h后处死大鼠，检测心肌葡萄糖调节蛋白78（GRF78）蛋白和mRNA表达。结果Sham组、TM组造模后血流动力学与正常时比较差异无统计学意义（P〉0．05）；其他两组LVSP、4-dp／dtmax减小，LVEDP增加，I／R组变化较TM＋I／R组明显（P〈0．05）。再灌注2h时CK-MB和cTnI：Sham组分别为（13．62±2．33）U／L和（2．37±0．31）μg／，L、TM组为（13．52±2．94）U／L和（2．32±0．83）μg／L，两组与开胸后比较差异无统计学意义（P〉0．05），I／R组为（39．22±2．59）U／L和（46．89±5．07）μg／L，TM＋I／R组为（27．17±2．95）U／L和（26．49±3．16）μg／L[与Sham组、TM组、I／R组比较，差异有统计学意义（P〈0．05）]，两组与开胸后比较升高（P〈0．05）。GRP78蛋白和mRNA表达：Sham组分别为0．073±0．008和0．058±0．007，L／R组为0．279±0．033和0．247±0．029，TM组为0．168±0．024和0．128±0．021，TM＋L／R组为0．469±0．041和0．353±0．046，Sham组、TM组和I／R组均低于TM＋I／R组（P〈0．05）。结论衣霉素诱导轻度的内质网应激预处理可通过上调GRP78的表达减轻大鼠心肌缺血再灌注损伤。

Objective To investigate the effects of endoplasmic reticulum stress （ERS） precondi- tioning induced by tunicamycin （TM） on myocardial ischemia -reperfusion （I/R） injury in rats. Methods Forty Sprague - Dawley rats were randomly divided into four groups ： Sham, I/R, TM, and TM ＋ I/R. The I/R models were established by occlusion of the left anterior descending coronary artery for 0. 5 h followed by 2 h of reperfusion in I/R group and TM ＋ I/R group. TM group and TM ＋ I/R group were treatmentd by TM O. 6 mg/kg at 30 min before modeling. Left ventricular contraction was recorded after thoracotomy and 30 min, 1 h and 2 h after reperfusion in all rats. Blood samples were withdrawn from carotid artery after thoracotomy and 2 h after reperfusion for detection of cardiac troponin I （cTnl） and creatine kinase isozyme （CK- MB） by enzyme linked immunosorbent assay （ELISA）. The protein and mRNA expression of glu- cose regulated protein 78 （ GRP78 ） in heart at the end of the I/R was examined by Western blotting and real- time quantitative polymerase chain reaction （Real -time PCR） respectively in all group. Results Compared with the baseline, changes of ventricular contraction were not significant in Sham group and TM group, while LVSP and dp/dtmax decreased, LVEDP increased in the other two groups, especially in I/R group. The levels of CK - MB and cTnI, and the expression levels of GRP78 protein and mRNA in I/R group [ （39.22±2. 59） U/L, （46. 89±5.07） μg/L, 0. 279 ±0. 033, and 0. 247 ± 0. 029 respectively] and TM ＋ I/R group [ （27.17± 2. 95） U/L, （26. 49±3.16）μg/L, 0. 469 ± 0. 041 and 0. 353 ± 0. 046 respectively] were higher than Sham group [ （ 13.62 ± 2. 33 ） U/L, （2. 37 ±0. 31 ） μg/L, 0. 073 ± 0. 008 and 0. 058 ±0. 007 respectively] and TM group [ （13.52 ±2. 94） U/L, （2. 38 ±0. 83） μg/L, 0. 168± 0. 024 and 0. 128±0. 021 respectively] at 2 h after reperfusion （P 〈 0.05 ）. The levels of CK - MB and cTnI were higher, while those of GRP78 protein and mRNA in I/R group were lower than TM ＋ I/R group （ P 〈 0. 05 ）. Conclusion ERS preconditioning induced by low dose TM attenuates myocardial I/R injury in rats, which may be associated with the regluation of GRP78.