β1-AR持久兴奋通过CaMKIIδ-内质网应激凋亡通路导致心力衰竭的机制

目的研究β1-AR持久兴奋通过CaMKIIδ内质网应激（ERS）凋亡通路导致心力衰竭的机制。方法30只SD大鼠随机分成三组，正常对照组（Control）、异丙肾上腺组（Iso）和、异丙肾上腺＋美托洛尔组（Iso＋Meto），每组10只，所有动物均自由进食进水。（1）Iso组大鼠背部皮下注射Iso5mg／（kg·d），连续10d；Control组背部皮下注射相同体积的生理盐水；Iso＋Meto组大鼠背部皮下注射Iso5mg／（kg·d），连续10d，在背部皮下注射Iso前一天开始Meto 10mg／（kg·d）灌胃，连续4周；（2）所有大鼠饲养4周后，采用美国Millar公司P—V Loop导管经颈动脉插管至左心室，使用Pow—erlab生理记录系统测量血流动力学相关指标；统计各组大鼠心脏重量和心脏重量／体重比值；（3）TUNEL法和Caspase-3活性检测心肌细胞凋亡；（4）Western blot分析CaMKIIδERS相关基因（GRP78、CHOP和caspase-12）和凋亡相关基因Bcl-2／Bax的表达水平。结果30只SD大鼠实验过程精神状态好，进食进水正常。（1）与Control组比较，Iso组SD大鼠心脏重塑和血流动力学指标有显著性差异（P〈0．05）；而Iso＋Meto组心脏重塑和血流动力学指标与Iso组相比明显改善（P〈0．05）；（2）TUNEL法原位检测各组大鼠心肌细胞凋亡示与Control组比较，Iso组TUNEL阳性细胞数明显增高（P〈0．05）；而Iso＋Met组明显低于Iso组（P〈0．05）。心肌细胞Caspase-3活性和TUNEL凋亡阳性细胞核指数各组变化一致。Western blot检测心肌细胞凋亡相关基因bcl-2／Bax蛋白表达。与Control组相比，Iso组bcl-2蛋白表达明显降低和Bax蛋白表达明显增加（P〈0．05）；而Iso＋Met组与Iso组相比,bcl-2明显增高和Bax明显降低（P〈0．05）；（3）Western blot分析CaMKIIδp-CaMKIIδ白表达显示，与Control组比较，Iso组CAMKII活性和p-CaMKIIδ蛋白表达明显增加；而Iso＋Meto组与Iso组相比，CAMKII活性和p-

The cardiac apoptotic effects ot sustained β1-adrenergic stimulation are associated with CaMKIIδ-ERS apoptosis pathway

Objectives To investigate The cardiac apoptotic effects of sustained β1-adrenergic stimulation are associated with CaMKIIδ-ERS apoptosis pathway. Methods 30 male SD rats were randomly divided into 3 groups： 1 ） Control group, 2） Iso group, Iso 5mg/（ kg · d）, for 10d; 3） Isol plus Meto group,Iso 5mg/（kg · d）, for 10d; Meto 10mg/（kg · d）, for 4weeks. Heart function was measured bycatheterization. TUNEL and caspase-3 activity were employed to assess myocyte apoptosis. ER stress signals （GRP78, CHOP, caspase-12） expression,CaMKIIδ activation and Bcl-2/Bax were detected by Western blot. Results Isoproterenol produced progressive LV dilation, systolic dysfunction, increased in heart weight and myocyte apoptosis. These changes were associated with upregulation of GRP78 and CHOP, increased cleavage of caspase 12, increased phosphorylation of CaMKIIδ. Metoprolol administration to cardiomyopathy produced by isoproterenol exhibited attenuation the phosphorylation of CaMKIIδ. Metoprolol administration also reduced activation of GRP78, CHOP and cleaved caspase-12. In addition, it also increased Bcl-2/Bax, and decreased cell death. Conclusions The cardiac apoptotic effects of sustained β1-adrenergic stimulation are associated with the increased phosphorylation of CaMKIIδ, and activation of GRP78, CHOP and cleaved caspase-12 in the ER. Metoprolol .exert cardioprotective effects to cardiomyopathy produced by isoproterenol via attenuation the phosphorylation of CaMKIIδ, reduced the ER stress, caspase activation and cell death.