五味子乙素对心房颤动大鼠心肌重构和心电图改变的影响及其机制

Effect and mechanism of schisandrin B on myocardial remodeling and electrocardiogram changes of rats with atrial fibrillation

目的探讨五味子乙素(Sch B)对心房颤动(简称房颤)大鼠心肌重构和心电图改变的影响及其可能的机制。方法60只SD大鼠随机分为正常组、模型组、阳性对照组、Sch B低剂量组和Sch B高剂量组(n=12)。除正常组外,其余组大鼠尾静脉注射乙酰胆碱-氯化钙(Ach-CaCl_(2))混合液建立房颤模型,从建模第4天开始,尾静脉注射Ach-CaCl_(2)混合液前1 h,阳性对照组、Sch B低和高剂量组大鼠分别以胺碘酮50 mg/kg、Sch 40 mg/kg、Sch 80 mg/kg灌胃,1次/d,连续7 d。末次尾静脉注射Ach-CaCl_(2)混合液时记录各组大鼠心电图,超声心动图检测左心室射血分数(LVEF)、左心室缩短分数(LVFS)、左心室舒张末期内径(LVEDD)、左心室收缩末期内径(LVESD)。qRT-PCR检测Ⅰ型胶原(ColⅠ)和Ⅲ型胶原(ColⅢ)mRNA相对表达水平,HE染色观察心房组织病理学变化,Masson染色检测心肌纤维化情况,Western blotting检测磷酸化蛋白激酶B(p-Akt)、磷酸化哺乳动物雷帕霉素靶蛋白(p-mTOR)和磷酸化核糖体蛋白S6激酶(p-S6K)的相对表达水平。结果心电图检测结果显示,与模型组比较,阳性对照组、Sch B低和高剂量组大鼠房颤诱发时间延长,持续时间缩短(P<0.05);与Sch B低剂量组比较,Sch B高剂量组大鼠房颤诱发时间延长,持续时间缩短(P<0.05)。超声心动图检测结果显示,与模型组比较,阳性对照组、Sch B低和高剂量组大鼠LVEF和LVFS明显升高,LVEDD和LVESD明显缩短;与Sch B低剂量组比较,Sch B高剂量组大鼠LVEF和LVFS明显升高,LVEDD和LVESD明显缩短(P<0.05)。qRT-PCR检测结果显示,与模型组比较,阳性对照组、Sch B低和高剂量组ColⅠ和ColⅢmRNA相对表达水平降低;与Sch B低剂量组比较,Sch B高剂量组ColⅠ和ColⅢmRNA相对表达水平降低(P<0.05)。HE染色结果显示,正常组大鼠心肌细胞排列整齐、致密,细胞形态正常,间质无水肿;模型组大鼠心肌细胞排列紊乱,细胞间隙增宽,细胞间质水肿;阳性对照组及Sch B低、高剂量组大鼠心肌细胞损伤情况明显改善。Masson染色结果显示,与模型组比较,阳性对照组、Sch B低和高剂量组大鼠心房组织胶原面积百分比降低;与Sch B低剂量组比较,Sch B高剂量组大鼠心房组织胶原面积百分比降低(P<0.05)。Western blotting检测结果显示,与模型组比较,阳性对照组、Sch B低和高剂量组p-Akt、p-mTOR和p-S6K蛋白相对表达量降低;与Sch B低剂量组比较,Sch B高剂量组p-Akt、p-mTOR和p-S6K蛋白相对表达量降低(P<0.05)。结论Sch B可减轻房颤大鼠心房纤维化,缓解心房肌细胞损伤和心功能障碍,其可能的机制为通过抑制Akt/mTOR/S6K信号通路发挥作用。

Objective To explore the effects of schisandrin B(Sch B)on myocardial remodeling and electrocardiogram changes of atrial fibrillation rats.Methods A total of 60 SD rats were randomly divided into normal group,model group,positive control group,low-dose group and high-dose group(12 rats each).Except normal group,rats in other groups were injected with Ach-CaCl_(2) mixed solution through tail vein to establish atrial fibrillation model.From the 4th day of modeling,1 h before Ach-CaCl_(2) mixture injection through tail vein injection,rats in positive control group,low-dose and high-dose Sch B group were given intragastric administration of amiodarone 50 mg/kg,Sch 40 mg/kg and Sch 80 mg/kg,respectively,once a day for consecutive 7 days.ECG of each group was recorded during the last caudal vein injection of Ach-CaCl_(2) mixture.Echocardiography was used to measure left ventricular ejection fraction(LVEF),left ventricular shortening fraction(LVFS),left ventricular end-diastolic diameter(LVEDD)and left ventricular end-systolic diameter(LVESD).The relative expression levels of collagenⅠ(ColⅠ)and collagenⅢ(ColⅢ)mRNA were detected by qRT-PCR,the pathological changes of atrial tissue were observed by HE staining,the myocardial fibrosis was detected by Masson staining,and the relative expression levels of p-Akt,p-mTOR and p-S6K were detected by Western blotting.Results The results of echocardiography showed that LVEF and LVFS were higher,while LVEDD and LVESD were shorter in positive control group,low-dose and high-dose Sch B groups than in model group;Compared with the low-dose Sch B group,the LVEF and LVFS increased significantly,and the LVEDD and LVESD shortened significantly in high-dose Sch B group(P<0.05).The results of qRT-PCR showed that the relative expression levels of ColⅠand ColⅢmRNA were lower in positive control group,lowdose and high-dose Sch B group than in model group;Compared with the low-dose Sch B group,the relative expression levels of ColⅠand ColⅢmRNA were decreased in high-dose Sch B group(P<0.05).The results of HE staining showed that the cardiomyocytes in normal group were in order and dense,and the morphology of the cells was normal with no edema in the interstitium.While those in model group were out of order,intercellular space widened and intercellular interstitium was with edema.The injury of myocardial cells in positive control group,low-dose and high-dose Sch B group was significantly improved.Masson staining showed that the percentage of collagen area in atrial tissue of rats decreased in positive control group,low-dose and high-dose Sch B groups than that in model group;Compared with the low-dose Sch B group,the percentage of collagen area in atrial tissue of rats decreased in high-dose Sch B group(P<0.05).Western blotting results showed that the relative protein expression levels of p-Akt,p-mTOR and p-S6K were lower in positive control group,low-dose and high-dose Sch B groups than those in model group;Compared with the low-dose Sch B group,the relative expression levels of p-Akt,p-mTOR and p-S6K proteins were decreased in high-dose Sch B group(P<0.05).Conclusion Sch B can mitigate rats'atrial fibrillation,improve myocardial injury and cardiac dysfunction,possibly by inhibiting the Akt/mTOR/S6K signaling pathway.