Ferreira Anderson J, Castro Carlos H, Guatimosim Silvia, Almeida Pedro W M, Gomes Enéas R M, Dias-Peixoto Marco Fabrício, Alves Márcia N M, Fagundes-Moura Cristiane R, Rentzsch Brit, Gava Elisandra, Almeida Alvair P, Guimarães Alexandre M, Kitten Gregory T, Reudelhuber Timothy, Bader Michael, Santos Robson A S
Department of Morphology, Federal University of Minas Gerais, Belo Horizonte, Brazil.
Ther Adv Cardiovasc Dis. 2010 Apr;4(2):83-96. doi: 10.1177/1753944709353426. Epub 2010 Jan 5.
It has been shown that Ang-(1-7) has cardioprotective actions. To directly investigate the effects of Ang-(1-7) specifically in the heart, we generated and characterized transgenic (TG) rats which express an Ang-(1-7)-producing fusion protein driven by the alpha-MHC promoter.
After microinjection of the transgene into fertilized rat zygotes, we obtained four different transgenic lines. Homozygous animals were analyzed with regard to the expression profile of the transgene by ribonuclease protection assay. Transgene expression was detected mainly in the heart with weak or no expression in other organs. Heterozygous TG(hA-1-7)L7301 rats presented a significant increase in cardiac Ang-(1-7) concentration compared with control rats (17.1+/-2.1 versus 3.9+/-1.4 pg/mg protein in SD rats). Radiotelemetry analysis revealed that TG rats presented no significant changes in blood pressure and heart rate compared with normal rats. Overexpression of Ang-(1-7) in the heart produced slight improvement in resting cardiac function (+ dT/dt: 81530+/-1305.0 versus 77470+/-345.5 g/s bpm in SD rats, p < 0.05), which was in keeping with the enhanced [Ca(2+)] handling observed in cardiomyocytes of TG rats. TG(hA-1-7)L7301 rats also showed a greater capacity to withstand stress since TG rats showed a less pronounced deposition of collagen type III and fibronectin induced by isoproterenol treatment in the subendocardial area than in corresponding controls. In addition, hearts from TG rats showed reduced incidence and duration of reperfusion arrhythmias in comparison with SD rats.
These results indicate that Ang-(1-7) has blood pressure-independent, antifibrotic effects, acting directly in the heart.
已有研究表明血管紧张素-(1-7)（Ang-(1-7)）具有心脏保护作用。为直接研究Ang-(1-7)在心脏中的特异性作用，我们构建并鉴定了由α-肌球蛋白重链（α-MHC）启动子驱动表达产生Ang-(1-7)融合蛋白的转基因（TG）大鼠。
将转基因显微注射到受精大鼠受精卵后，我们获得了四个不同的转基因品系。通过核糖核酸酶保护试验分析纯合动物转基因的表达谱。转基因表达主要在心脏中检测到，在其他器官中表达较弱或无表达。与对照大鼠相比，杂合TG(hA-1-7)L7301大鼠心脏Ang-(1-7)浓度显著增加（SD大鼠中分别为17.1±2.1与3.9±1.4 pg/mg蛋白）。无线电遥测分析显示，与正常大鼠相比，TG大鼠血压和心率无显著变化。心脏中Ang-(1-7)的过表达使静息心脏功能略有改善（+dT/dt：SD大鼠中为81530±1305.0与77470±345.5 g/s bpm，p<0.05），这与在TG大鼠心肌细胞中观察到的钙处理增强一致。TG(hA-1-7)L7301大鼠也表现出更强的应激承受能力，因为与相应对照相比，TG大鼠经异丙肾上腺素处理后心内膜下区域III型胶原蛋白和纤连蛋白的沉积不那么明显。此外，与SD大鼠相比，TG大鼠心脏再灌注心律失常的发生率和持续时间降低。
这些结果表明，Ang-(1-7)具有不依赖血压的抗纤维化作用，直接作用于心脏。
