美托洛尔对心力衰竭大鼠心肌细胞磷酸化缝隙连接蛋白43表达及心肌细胞凋亡的影响

 目的：观察美托洛尔对心力衰竭（HF）大鼠在体心肌组织磷酸化缝隙连接蛋白43（p-Cx43）表达水平和心肌细胞凋亡的影响，并探讨其可能机制。方法：SD大鼠100只随机分为5组（n=20）：假手术（sham）组、HF组、小剂量（1.25 mg·kg-1·d-1）美托洛尔治疗（MetoA）组、中剂量（5 mg·kg-1·d-1）美托洛尔治疗（MetoB）组和大剂量（20 mg·kg-1·d-1）美托洛尔治疗（MetoC）组。缩窄腹主动脉建立HF动物模型，术后第4周开始给药至第8周。术后第4周和第8周超声心动图测定血流动力学指标；术后第8周取出心脏，HE和Masson染色观察心脏结构改变和胶原纤维增生情况，Western blotting检测p-Cx43表达水平，TUNEL法检测心肌细胞凋亡，p-Cx43表达水平与心肌细胞凋亡指数进行Pearson相关分析。结果：(1) 美托洛尔治疗改善HF大鼠血流动力学，在治疗剂量范围内美托洛尔剂量增加可有效逆转HF时的心肌重塑，呈剂量依赖效应。(2) HF组中p-Cx43表达量显著高于sham组（P<001），而随美托洛尔治疗剂量的增加，p-Cx43表达量较HF组逐渐降低，各治疗组间两两比较亦有显著差异（P<001）。(3) HF组心肌细胞凋亡指数［(51.17±6.94)%］较sham组［(4.62±1.60)%］明显增加（P<001）；MetoA组凋亡指数为(40.60±4.15)%， MetoB组凋亡指数为(30.66±4.00)%，MetoC组凋亡指数为(22.24±5.69)%，均显著低于HF组（P<001），各治疗组间两两比较亦有显著差异（P<001）。(4) 大鼠心肌组织p-Cx43表达水平与心肌细胞凋亡指数呈显著正相关（r=0.905, P<001）。结论: 美托洛尔对抗HF诱导的心肌细胞凋亡的机制可能与其抑制p-Cx43表达有关。

Effects of metoprolol on phosphorylated connexin 43 expression in myocardial tissues and apoptosis of myocardial cells in heart failure rats

AIM：To explore the in vivo effects of metoprolol on the expression of phosphorylated connexin 43 (p-Cx43) in myocardial tissues and the apoptosis of myocardial cells in rats with heart failure (HF).METHODS：One hundred Sprague-Dawley rats were randomly divided into 5 groups (each n=20): sham group, HF group, low-dose (1.25 mg·kg-1·d-1) metoprolol treatment (MetoA) group, middle-dose (5 mg·kg-1·d-1) metoprolol treatment (MetoB) group and high-dose (20 mg·kg-1·d-1) metoprolol treatment (MetoC) group.The rats in HF group and metoprolol treatment groups were subject to abdominal aortic ligation, and different doses of metoprolol were given 4 weeks later till 8 weeks after operation.Echocardiography was conducted to monitor the hemodynamic parameters at the 4th and 8th weeks, and the rat hearts were taken at the 8th week after operation.The morphological changes and the proliferation of collagen fibers in myocardial tissues were observed by HE and Masson staining, respectively.The expression level of p-Cx43 was detected by Western blotting and the apoptosis of myocardial cells was assessed by TUNEL method.The relationship between p-Cx43 expression level and apoptotic index was analyzed by Pearson’s correlation.RESULTS：(1) Echocardiography showed that metoprolol could effectively improved cardiac hemodynamics in HF rats, and pathological findings suggested that metoprolol could effectively reverse HF-induced cardiac remodeling in a dose-dependent manner within the therapeutic dose range.(2) Western blotting showed that p-Cx43 expression in HF group was significantly higher than that in sham group (P<001), and that in all metoprolol treatment groups was significantly decreased compared with HF group (P<005 or P<001), among which pairwise comparisons also showed significant differences (P<001).(3) The myocardial apoptotic index in HF group ［(51.17±6.94)%］ was significantly increased compared with sham group ［(4.62±160)%, P<001］.Compared with HF group, myocardial apoptotic indexes in MetoA group ［(40.60±4.15)%］, MetoB group ［(30.66±4.00)%］ and MetoC group ［(22.24±5.69)%］ were significantly decreased (P<001), among which pairwise comparisons also showed significant differences (P<001).(4) The expression level of p-Cx43 was positively correlated with the apoptotic index (r=0.905, P<001).CONCLUSION: The mechanism of metoprolol against HF-induced myocardial apoptosis may be related to inhibition of p-Cx43 expression.