Ushio-Fukai M, Alexander R W, Akers M, Yin Q, Fujio Y, Walsh K, Griendling K K
Department of Medicine, Division of Cardiology, Emory University, Atlanta, Georgia 30322, USA.
J Biol Chem. 1999 Aug 6;274(32):22699-704. doi: 10.1074/jbc.274.32.22699.
Angiotensin II, a hypertrophic/anti-apoptotic hormone, utilizes reactive oxygen species (ROS) as growth-related signaling molecules in vascular smooth muscle cells (VSMCs). Recently, the cell survival protein kinase Akt/protein kinase B (PKB) was proposed to be involved in protein synthesis. Here we show that angiotensin II causes rapid phosphorylation of Akt/PKB (6- +/- 0.4-fold increase). Exogenous H(2)O(2) (50-200 microM) also stimulates Akt/PKB phosphorylation (maximal 8- +/- 0.2-fold increase), suggesting that Akt/PKB activation is redox-sensitive. Both angiotensin II and H(2)O(2) stimulation of Akt/PKB are abrogated by the phosphatidylinositol 3-kinase (PI3-K) inhibitors wortmannin and LY294002 (2(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one), suggesting that PI3-K is an upstream mediator of Akt/PKB activation in VSMCs. Furthermore, diphenylene iodonium, an inhibitor of flavin-containing oxidases, or overexpression of catalase to block angiotensin II-induced intracellular H(2)O(2) production significantly inhibits angiotensin II-induced Akt/PKB phosphorylation, indicating a role for ROS in agonist-induced Akt/PKB activation. In VSMCs infected with dominant-negative Akt/PKB, angiotensin II-stimulated [(3)H]leucine incorporation is attenuated. Thus, our studies indicate that Akt/PKB is part of the remarkable spectrum of angiotensin II signaling pathways and provide insight into the highly organized signaling mechanisms coordinated by ROS, which mediate the hypertrophic response to angiotensin II in VSMCs.
血管紧张素II是一种促肥大/抗凋亡激素，它利用活性氧（ROS）作为血管平滑肌细胞（VSMCs）中与生长相关的信号分子。最近，细胞存活蛋白激酶Akt/蛋白激酶B（PKB）被认为参与蛋白质合成。在此我们表明，血管紧张素II可导致Akt/PKB快速磷酸化（增加6 - ±0.4倍）。外源性H₂O₂（50 - 200 μM）也能刺激Akt/PKB磷酸化（最大增加8 - ±0.2倍），这表明Akt/PKB的激活对氧化还原敏感。磷脂酰肌醇3激酶（PI3 - K）抑制剂渥曼青霉素和LY294002（2-(4 - 吗啉基)-8 - 苯基 - 4H - 1 - 苯并吡喃 - 4 - 酮）可消除血管紧张素II和H₂O₂对Akt/PKB的刺激，这表明PI3 - K是VSMCs中Akt/PKB激活的上游介质。此外，含黄素氧化酶抑制剂二亚苯基碘鎓，或过氧化氢酶的过表达以阻断血管紧张素II诱导的细胞内H₂O₂产生，可显著抑制血管紧张素II诱导的Akt/PKB磷酸化，这表明ROS在激动剂诱导的Akt/PKB激活中起作用。在用显性负性Akt/PKB感染的VSMCs中，血管紧张素II刺激的[³H]亮氨酸掺入减弱。因此，我们的研究表明Akt/PKB是血管紧张素II信号通路显著谱的一部分，并为ROS协调的高度有序信号机制提供了见解，ROS介导了VSMCs对血管紧张素II的肥大反应。
