Institute of Experimental and Clinical Pharmacology and Toxicology, Medical Faculty Mannheim, University of Heidelberg, Maybachstrasse 14, D-68169 Mannheim, Germany.
Cell Signal. 2012 Jun;24(6):1261-9. doi: 10.1016/j.cellsig.2012.02.005. Epub 2012 Feb 20.
Vascular endothelial growth factor (VEGF) is a main stimulator of pathological vessel formation. Nevertheless, increasing evidence suggests that Angiotensin II (Ang II) can play an augmentory role in this process. We thus analyzed the contribution of the two Ang II receptor types, AT(1)R and AT(2)R, in a mouse model of VEGF-driven angiogenesis, i.e. oxygen-induced proliferative retinopathy. Application of the AT(1)R antagonist telmisartan but not the AT(2)R antagonist PD123,319 largely attenuated the pathological response. A direct effect of Ang II on endothelial cells (EC) was analyzed by assessing angiogenic responses in primary bovine retinal and immortalized rat microvascular EC. Selective stimulation of the AT(1)R by Ang II in the presence of PD123,319 revealed a pro-angiogenic activity which further increased VEGF-driven EC sprouting and migration. In contrast, selective stimulation of the AT(2)R by either CGP42112A or Ang II in the presence of telmisartan inhibited the VEGF-driven angiogenic response. Using specific inhibitors (pertussis toxin, RGS proteins, kinase inhibitors) we identified G(12/13) and G(i) dependent signaling pathways as the mediators of the AT(1)R-induced angiogenesis and the AT(2)R-induced inhibition, respectively. As AT(1)R and AT(2)R stimulation displays opposing effects on the activity of the monomeric GTPase RhoA and pro-angiogenic responses to Ang II and VEGF requires activation of Rho-dependent kinase (ROCK), we conclude that the opposing effects of the Ang II receptors on VEGF-driven angiogenesis converge on the regulation of activity of RhoA-ROCK-dependent EC migration.
血管内皮生长因子 (VEGF) 是病理性血管形成的主要刺激物。然而，越来越多的证据表明，血管紧张素 II (Ang II) 在这个过程中可以发挥增强作用。因此，我们在 VEGF 驱动的血管生成的小鼠模型（即氧诱导的增殖性视网膜病变）中分析了两种 Ang II 受体类型，即 AT(1)R 和 AT(2)R 的作用。AT(1)R 拮抗剂替米沙坦的应用，但不是 AT(2)R 拮抗剂 PD123,319，在很大程度上减弱了病理性反应。通过评估原代牛视网膜和永生化大鼠微血管内皮细胞 (EC) 的血管生成反应来分析 Ang II 对 EC 的直接作用。在 PD123,319 存在的情况下，选择性刺激 Ang II 对 AT(1)R 的作用揭示了一种促血管生成活性，进一步增加了 VEGF 驱动的 EC 出芽和迁移。相比之下，在替米沙坦存在的情况下，无论是用 CGP42112A 还是 Ang II 选择性刺激 AT(2)R 均抑制了 VEGF 驱动的血管生成反应。使用特异性抑制剂（百日咳毒素、RGS 蛋白、激酶抑制剂），我们确定 G(12/13) 和 G(i) 依赖性信号通路分别作为 AT(1)R 诱导的血管生成和 AT(2)R 诱导的抑制的介导物。由于 AT(1)R 和 AT(2)R 刺激对单体 GTPase RhoA 的活性显示出相反的作用，并且 Ang II 和 VEGF 的促血管生成反应需要 Rho 依赖性激酶 (ROCK) 的激活，因此我们得出结论，Ang II 受体对 VEGF 驱动的血管生成的相反作用集中在 RhoA-ROCK 依赖性 EC 迁移的活性调节上。
