Giani Jorge F, Gironacci Mariela M, Muñoz Marina C, Turyn Daniel, Dominici Fernando P
Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Argentina.
Exp Physiol. 2008 May;93(5):570-8. doi: 10.1113/expphysiol.2007.014269.
Angiotensin (ANG) II contributes to cardiac remodelling by inducing the activation of several signalling molecules, including ERK1/2, Rho kinase and members of the STAT family of proteins. Angiotensin-(1-7) is produced in the heart and inhibits the proliferative actions of ANG II, although the mechanisms of this inhibition are poorly understood. Accordingly, in the present study we examined whether ANG-(1-7) affects the ANG II-mediated activation of ERK1/2 and Rho kinase, STAT3 and STAT5a/b in rat heart in vivo. We hypothesized that ANG-(1-7) inhibits these growth-promoting pathways, counterbalancing the trophic action of ANG II. Solutions of normal saline (0.9% NaCl) containing ANG II (8 pmol kg(-1)) plus ANG-(1-7) in increasing doses (from 0.08 to 800 pmol kg(-1)) were administered via the inferior vena cava to anaesthetized male Sprague-Dawley rats. After 5 min, hearts were removed and ERK1/2, Rho kinase, STAT3 and STAT5a/b phosphorylation was determined by Western blotting using phosphospecific antibodies. Angiotensin II stimulated ERK1/2 and Rho kinase phosphorylation (2.3 +/- 0.2- and 2.1 +/- 0.2-fold increase over basal values, respectively), while ANG-(1-7) was without effect. The ANG II-mediated phosphorylation of ERK1/2 and Rho kinase was prevented in a dose-dependent manner by ANG-(1-7) and disappeared in the presence of the Mas receptor antagonist d-Ala7-ANG-(1-7). Both ANG II and ANG-(1-7) increased STAT3 and STAT5a/b phosphorylation to a similar extent (130-140% increase). The ANG-(1-7)-stimulated STAT phosphorylation was blocked by the AT(1) receptor antagonist losartan and not by d-Ala7-ANG-(1-7). Our results show a dual action of ANG-(1-7), that is, a stimulatory effect on STAT3 and 5a/b phosphorylation through AT(1) receptors and a blocking action on ANG II-stimulated ERK1/2 and Rho kinase phosphorylation through Mas receptor activation. The latter effect could be representative of a mechanism for a protective role of ANG-(1-7) in the heart by counteracting the effects of locally generated ANG II.
血管紧张素（ANG）II通过诱导包括ERK1/2、Rho激酶和信号转导及转录激活蛋白（STAT）家族成员在内的多种信号分子激活，促进心脏重塑。血管紧张素-（1-7）在心脏中产生，并抑制ANG II的增殖作用，尽管这种抑制机制尚不清楚。因此，在本研究中，我们检测了血管紧张素-（1-7）是否在体内影响大鼠心脏中ANG II介导的ERK1/2、Rho激酶、STAT3和STAT5a/b的激活。我们假设血管紧张素-（1-7）抑制这些促进生长的途径，从而平衡ANG II的营养作用。将含有ANG II（8 pmol kg⁻¹）加不同剂量（从0.08至800 pmol kg⁻¹）血管紧张素-（1-7）的生理盐水（0.9% NaCl）溶液经下腔静脉注射给麻醉的雄性Sprague-Dawley大鼠。5分钟后，取出心脏，使用磷酸特异性抗体通过蛋白质印迹法测定ERK1/2、Rho激酶、STAT3和STAT5a/b的磷酸化水平。ANG II刺激ERK1/2和Rho激酶磷酸化（分别比基础值增加2.3±0.2倍和2.1±0.2倍），而血管紧张素-（1-7）无此作用。血管紧张素-（1-7）以剂量依赖方式阻止ANG II介导的ERK1/2和Rho激酶磷酸化，且在Mas受体拮抗剂d-Ala7-血管紧张素-（1-7）存在时消失。ANG II和血管紧张素-（1-7）均使STAT3和STAT5a/b磷酸化程度增加相似（增加130 - 140%）。血管紧张素-（1-7）刺激引起的STAT磷酸化被AT₁受体拮抗剂氯沙坦阻断，而不被d-Ala7-血管紧张素-（1-7）阻断。我们的结果显示了血管紧张素-（1-7）的双重作用，即通过AT₁受体对STAT3和5a/b磷酸化产生刺激作用，以及通过激活Mas受体对ANG II刺激的ERK1/2和Rho激酶磷酸化产生阻断作用。后一种作用可能代表了血管紧张素-（1-7）通过抵消局部产生的ANG II的作用，在心脏中发挥保护作用的一种机制。
