D-D Gong1, J Yu, J-C Yu, X-D Jiang. 1. Department of Cardiology, Dalian Municipal Central Hospital, Dalian, China. jxddoc@163.com.
Abstract
OBJECTIVE: The aim of this study was to evaluate the effect of micro ribonucleic acid (miR)-26a on myocardial ischemia-reperfusion (I/R) injury in rats and to explore its potential mechanism. Our findings might help to provide references for clinical prevention and treatment of myocardial I/R. MATERIALS AND METHODS: A total of 60 male Sprague-Dawley (SD) rats were randomly divided into three groups using a random number table, including: Control group (n=20), I/R group (n=20) and I/R + miR-26a siRNA group (n=20). I/R model was established via recanalization after ligation of left anterior descending coronary artery (LAD). The model of miR-26a knockdown was established in rats of I/R + miR-26a siRNA group via tail intravenous injection of miR-26a siRNA. Ejection fraction (EF%) and fractional shortening (FS%) of rats in each group were detected via echocardiography. The infarction area of each group was detected via 2,3,5-triphenyltetrazolium chloride (TTC) assay. Subsequently, morphological changes in myocardial cells of each group were detected via hematoxylin-eosin (H&E) staining. Myocardial apoptosis level was measured via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. At the same time, the expression levels of pro-apoptotic proteins Bcl-2 associated X protein (Bax) and cleaved (C)-caspase3 in myocardial tissues of the three groups were determined using Western blotting. Finally, the effects of miR-26a knockdown on the expressions of glycogen synthase kinase (GSK)-3β/β-catenin signaling pathway-related proteins were detected via Western blotting and immunohistochemistry. RESULTS: The expression of miR-26a in myocardial tissues of I/R group increased significantly when compared with that in Control group (p<0.05). Knockdown of miR-26a significantly improved cardiac insufficiency caused by I/R, which also obviously increased both EF% and FS% in rats (p<0.05). In addition, knockdown of miR-26a significantly inhibited myocardial infarction caused by I/R injury, and reduced infarction area from (43.08±2.43) to (21.54±1.82) (p<0.05). The results of H&E staining revealed that in I/R + miR-26a siRNA group, myofilaments were arranged more orderly, the degree of degradation and necrosis was significantly lower, and cellular edema was significantly alleviated when compared with I/R group. Subsequent TUNEL staining demonstrated that rats in I/R + miR-26a siRNA group showed a remarkably lower level of myocardial apoptosis than I/R group (p<0.05). Meanwhile, the protein expression levels of Bax and C-caspase3 were remarkably declined in I/R + miR-26a siRNA group (p<0.05). Furthermore, the results of Western blotting showed that miR-26a siRNA could significantly reverse the inhibition of GSK-3β/β-catenin signaling pathway induced by I/R injury (p<0.05). CONCLUSIONS: Knockdown of miR-26a could significantly improve I/R-induced myocardial injury and promote cardiac function in rats. The possible underlying mechanism might be related to targeted regulation of miR-26a on GSK-3β/β-catenin signaling pathway. Therefore, miR-26a was expected to be a new therapeutic target for myocardial I/R injury.
OBJECTIVE: The aim of this study was to evaluate the effect of micro ribonucleic acid (miR)-26a on myocardial ischemia-reperfusion (I/R) injury in rats and to explore its potential mechanism. Our findings might help to provide references for clinical prevention and treatment of myocardial I/R. MATERIALS AND METHODS: A total of 60 male Sprague-Dawley (SD) rats were randomly divided into three groups using a random number table, including: Control group (n=20), I/R group (n=20) and I/R + miR-26a siRNA group (n=20). I/R model was established via recanalization after ligation of left anterior descending coronary artery (LAD). The model of miR-26a knockdown was established in rats of I/R + miR-26a siRNA group via tail intravenous injection of miR-26a siRNA. Ejection fraction (EF%) and fractional shortening (FS%) of rats in each group were detected via echocardiography. The infarction area of each group was detected via 2,3,5-triphenyltetrazolium chloride (TTC) assay. Subsequently, morphological changes in myocardial cells of each group were detected via hematoxylin-eosin (H&E) staining. Myocardial apoptosis level was measured via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. At the same time, the expression levels of pro-apoptotic proteins Bcl-2 associated X protein (Bax) and cleaved (C)-caspase3 in myocardial tissues of the three groups were determined using Western blotting. Finally, the effects of miR-26a knockdown on the expressions of glycogen synthase kinase (GSK)-3β/β-catenin signaling pathway-related proteins were detected via Western blotting and immunohistochemistry. RESULTS: The expression of miR-26a in myocardial tissues of I/R group increased significantly when compared with that in Control group (p<0.05). Knockdown of miR-26a significantly improved cardiac insufficiency caused by I/R, which also obviously increased both EF% and FS% in rats (p<0.05). In addition, knockdown of miR-26a significantly inhibited myocardial infarction caused by I/R injury, and reduced infarction area from (43.08±2.43) to (21.54±1.82) (p<0.05). The results of H&E staining revealed that in I/R + miR-26a siRNA group, myofilaments were arranged more orderly, the degree of degradation and necrosis was significantly lower, and cellular edema was significantly alleviated when compared with I/R group. Subsequent TUNEL staining demonstrated that rats in I/R + miR-26a siRNA group showed a remarkably lower level of myocardial apoptosis than I/R group (p<0.05). Meanwhile, the protein expression levels of Bax and C-caspase3 were remarkably declined in I/R + miR-26a siRNA group (p<0.05). Furthermore, the results of Western blotting showed that miR-26a siRNA could significantly reverse the inhibition of GSK-3β/β-catenin signaling pathway induced by I/R injury (p<0.05). CONCLUSIONS: Knockdown of miR-26a could significantly improve I/R-induced myocardial injury and promote cardiac function in rats. The possible underlying mechanism might be related to targeted regulation of miR-26a on GSK-3β/β-catenin signaling pathway. Therefore, miR-26a was expected to be a new therapeutic target for myocardial I/R injury.