尿激酶原对急性心肌梗死模型大鼠心功能的保护作用及机制探究

Protective effects and mechanism of prourokinase on cardiac function in a rat model of acute myocardial infarction

目的探究尿激酶原对急性心肌梗死(AMI)模型大鼠心功能的保护作用及可能机制。方法36只SD大鼠,采用随机数字法分为Sham组(n=12)、AMI组(n=12)和尿激酶原组(n=12)。采用结扎左冠状动脉前降支的方法建立大鼠AMI模型。建模后,尿激酶原组大鼠每天经尾静脉注射2.5 mg/kg尿激酶原,Sham组和AMI组予以等量生理盐水,持续4周,最终各纳入10只大鼠。采用超声心动图评价大鼠心功能,TTC染色观察心肌梗死面积,天狼星红染色观察心肌纤维化情况,Western blot法检测肌红蛋白(Mb)、肌酸激酶同工酶(CK-MB)、肌钙蛋白I(cTnI)、α平滑肌肌动蛋白(α-SMA)、Ⅰ型胶原(collagenⅠ)、转化生长因子β1(TGF-β1)、Smad3和Smad7蛋白表达水平。结果与Sham组比较,AMI组左心室射血分数(LVEF)降低(P<0.05),左心室收缩末期直径(LVESD)、左心室舒张末期直径(LVEDD)、左心室收缩末期容积(LVESV)和左心室舒张末期容积(LVEDV)升高(均为P<0.05);与AMI组比较,尿激酶原组LVEF升高(P<0.05),LVESD、LVEDD、LVESV和LVEDV明显降低(均为P<0.05)。Western blot检测显示,与Sham组比较,AMI组Mb、CK-MB、cTnI、α-SMA、collagenⅠ及TGF-β1、Smad3蛋白水平升高(均为P<0.05),Smad7蛋白水平降低(P<0.05);与AMI组比较,尿激酶原组Mb、CK-MB、cTnI、α-SMA、collagenⅠ及TGF-β1、Smad3蛋白水平降低(均为P<0.05),Smad7蛋白水平升高(P<0.05)。结论尿激酶原可能通过TGF-β1/Smad3信号通路对AMI大鼠心脏重构起到保护作用,从而减轻心肌纤维化,保护心功能。

Objective To investigate the protective effects and possible mechanism of prourokinase on cardiac function in a rat model of acute myocardial infarction(AMI).Methods Thirty six SD rats were randomly divided into sham group(n=12),AMI group(n=12)and prourokinase group(n=12).The AMI rat model was established by ligation of the left anterior descending coronary artery.After modeling,rats in prourokinase group were injected 2.5 mg/kg of prourokinase daily via the tail vein,while the rats in sham group and AMI group were given equal amount of normal saline and lasted for 4 weeks.The 10 rats were enrolled in each group finally.Echocardiography was used to evaluate the cardiac function of rats,and TTC staining was used to observe the myocardial infarction area and Sirius red staining was used for myocardial fibrosis.Western blot was used to detect the protein expressions of myoglobin(Mb),creatine kinase isoenzyme(CK-MB),cardiac troponin I(cTnI),α-smooth muscle actin(α-SMA),collagenⅠ,transforming growth factor-β1(TGF-β1),Smad3 and Smad7.Results Compared with the sham group,the left ventricular ejection fraction(LVEF)decreased while the left ventricular end systolic diameter(LVESD),left ventricular end diastolic diameter(LVEDD),left ventricular end systolic volume(LVESV)and left ventricular end diastolic volume(LVEDV)increased in the AMI group(all P<0.05).Compared with the AMI group,LVEF was higher while the LVESD,LVEDD,LVESV and LVEDV were lower in the prourokinase group(all P<0.05).Western blot showed that compared with the sham group,the protein levels of Mb,CK-MB,cTnI,α-SMA,collagen Ⅰ,TGF-β1 and Smad3 were higher while the Smad7 protein level was lower in the AMI group(all P<0.05).Compared with the AMI group,the protein levels of Mb,CK-MB,cTnI,α-SMA,collagen Ⅰ,TGF-β1 and Smad3 were lower while the Smad7 protein level was higher in the prourokinase group(all P<0.05).Conclusions Prourokinase may protect cardiac function by inhibiting the cardiac remodeling in AMI rats through the TGF-β1/Smad3 signaling pathway,leading to myocardial fibrosis suppression.