沙库巴曲缬沙坦通过下调转化生长因子β_(1)/Smads信号通路改善急性心肌梗死大鼠心肌纤维化和心功能

Sacubitril/valsartan improves cardiac fibrosis and function via inhibiting transforming growth factor beta 1/Smads pathway in rats with acute myocardial infarction

目的探讨沙库巴曲缬沙坦对急性心肌梗死大鼠心肌纤维化和心功能的影响及可能作用机制。方法32只无特定病原体(SPF)级雄性SD大鼠结扎左冠状动脉前降支建立心肌梗死模型,另取8只作为假手术组(Sham)只开胸不结扎。1周后存活的24只心肌梗死大鼠随机接受沙库巴曲缬沙坦68 mg/(kg·d)[心肌梗死-沙库巴曲缬沙坦组(MI-SV组),n=8]或缬沙坦32 mg/(kg·d)[心肌梗死-缬沙坦组(MI-V组),n=8]或等容量生理盐水[心肌梗死模型组(MI组),n=8],灌胃治疗4周。4周后超声心动图评价心脏结构及功能,天狼猩红苦味酸染色计算梗死区胶原容积分数(CVF),酶联免疫吸附试验(ELISA)法检测心肌Ⅰ、Ⅲ型胶原含量,Western blot技术测量心肌组织转化生长因子β_(1)(TGF-β_(1))、Smad3和p-Smad3的蛋白表达水平。结果与Sham组比较,MI组左心室舒张末期内径(LVEDd)、左心室收缩末期内径(LVEDs)和左心室后壁厚度(LVPWT)增加,左心室射血分数(LVEF)降低,梗死区CVF和Ⅰ、Ⅲ型胶原含量升高,TGF-β_(1)和p-Smad3蛋白表达增加(均P<0.05);与MI组比较,MI-SV组和MI-V组LVEDd、LVEDs和LVPWT降低,LVEF升高,CVF和Ⅰ、Ⅲ型胶原含量降低,TGF-β_(1)和p-Smad3蛋白表达降低(均P<0.05),且以MI-SV组改善更显著[MI-SV组比MI-V组,LVEDd:(8.00±0.33)比(8.25±0.45)mm;LVEF:(55.23±3.96)%比(48.41±5.34)%;Ⅰ型胶原:(464.40±41.96)比(621.71±23.42)μg/g,均P<0.05]。结论沙库巴曲缬沙坦能够降低心肌梗死大鼠心肌纤维化程度,改善心脏功能,其作用机制可能与下调TGF-β_(1)/Smad3信号通路激活有关,且这一效应优于缬沙坦。

Objective To investigate the effects of sacubitril/valsartan(SV) on cardiac fibrosis and function in rats with acute myocardial infarction(MI) and its possible mechanisms. Methods MI model was established by ligating the left anterior descending coronary artery in 32 special pathogen free(SPF) male SD rats. Eight rats performed thoracotomy without ligation were used as sham operation group. After one week, 24 surviving rats with MI were randomly divided into three groups of 8 animals in each. They were treated with sacubitril/valsartan [68 mg/(kg·d), MI-S/V group], valsartan [32 mg/(kg·d), MI-V group], or placebo(equal volume normal saline, MI group), by gavage for 4 weeks. Then, cardiac structure and function were evaluated by echocardiography, myocardial collagen volume fraction(CVF) in the infarcted zone was calculated by sirius red picric acid staining, typeⅠand Ⅲ collagen contents were determined by enzyme-linked immunosorbent assay(ELISA), transforming growth factor-β_(1)(TGF-β_(1)), Smad3 and phosphorylated Smad3(p-Smad3) protein expression in myocardium were analyzed by immunoblotting. Results Compared with the sham group, left ventricular end-diastolic dimension(LVEDd), left ventricular end-systolic dimension(LVEDs) and left ventricular posterior wall thickness(LVPWT) in the MI group were significantly increased, left ventricular ejection fraction(LVEF) was significantly decreased, CVF as well as typeⅠand type Ⅲ collagen content were significantly elevated(P<0.05), protein expression of TGF-β_(1) and p-Smad3 were also significantly enhanced(all P<0.05). And these indexes were improved in the MI-SV group and MI-V group, which were more obvious in MI-SV group than in MI-V group [MI-SV vs MI-V group, LVEDd:(8.00±0.33) vs(8.25±0.45) mm;LVEF:(55.23±3.96)% vs(48.41±5.34)%;typeⅠcollagen:(464.40±41.96) vs(621.71±23.42) μg/g, all P<0.05]. Conclusions Sacubitril/valsartan can alleviate myocardial fibrosis and improve cardiac function in rats with myocardial infarction, and its mechanism may be related to the down-regulation of TGF-β_(1)/Smad3 signaling pathway. Those effects of sacubitril/valsartan are superior to valsartan.