Haider Ursula G B, Roos Thomas U, Kontaridis Maria I, Neel Benjamin G, Sorescu Dan, Griendling Kathy K, Vollmar Angelika M, Dirsch Verena M
Department of Pharmacy, Center of Drug Research, Butenandtstrasse 5-13, D-81377 Munich, Germany.
Mol Pharmacol. 2005 Jul;68(1):41-8. doi: 10.1124/mol.104.005421. Epub 2005 Apr 22.
trans-Resveratrol (RV), a polyphenolic stilbene derivative found in grape skin and other food products, has been proposed to exert beneficial effects in cardiovascular disease. Our group has shown previously that RV inhibits angiotensin II (Ang II)-induced Akt activation and, consequently, vascular smooth muscle cell (VSMC) hypertrophy. In this work, to identify the molecular target of RV, we investigated the impact of RV on early signaling cascades in rat aortic VSMCs triggered by Ang II and epidermal growth factor (EGF). We show that RV does not influence Ang II-mediated transactivation of EGF-receptor but potently inhibits EGF-induced phosphorylation of Akt kinase, suggesting that RV acts downstream of EGF-receptor transactivation in VSMCs. Recent evidence indicates that the adapter molecule Gab1, together with the protein tyrosine phosphatase Shp2, is critically involved in regulating the strength and duration of phosphatidylinositol-3-kinase (PI3K) and Akt activation upon EGF stimulation in fibroblasts. Our results show that stimulation of VSMCs with EGF as well as Ang II leads to a rapid tyrosine phosphorylation of Gab1 and its association with the p85 subunit of PI3K. RV attenuates these processes. Experiments performed in Shp2-deficient fibroblasts revealed that RV does not inhibit EGF-stimulated Akt activation in these cells, suggesting that Shp2 is necessary for the inhibitory effect of RV on the PI3K/Akt pathway. Furthermore, RV treatment activates Shp2. We therefore propose that RV blocks Akt activation in Ang II- and EGF-stimulated VSMCs by activating Shp2, thus preventing interaction between Gab1 and PI3K that is necessary for further signal transduction.
反式白藜芦醇（RV）是一种存在于葡萄皮和其他食品中的多酚芪衍生物，有人提出它对心血管疾病具有有益作用。我们小组之前已经表明，RV可抑制血管紧张素II（Ang II）诱导的Akt激活，从而抑制血管平滑肌细胞（VSMC）肥大。在这项研究中，为了确定RV的分子靶点，我们研究了RV对由Ang II和表皮生长因子（EGF）触发的大鼠主动脉VSMC早期信号级联反应的影响。我们发现，RV不影响Ang II介导的EGF受体反式激活，但能有效抑制EGF诱导的Akt激酶磷酸化，这表明RV在VSMC中作用于EGF受体反式激活的下游。最近的证据表明，衔接分子Gab1与蛋白酪氨酸磷酸酶Shp2一起，在成纤维细胞中EGF刺激后磷脂酰肌醇-3-激酶（PI3K）和Akt激活的强度和持续时间调节中起关键作用。我们的结果表明，用EGF以及Ang II刺激VSMC会导致Gab1迅速发生酪氨酸磷酸化，并使其与PI3K的p85亚基结合。RV可减弱这些过程。在Shp2缺陷型成纤维细胞中进行的实验表明，RV在这些细胞中不抑制EGF刺激的Akt激活，这表明Shp2是RV对PI3K/Akt途径抑制作用所必需的。此外，RV处理可激活Shp2。因此，我们提出RV通过激活Shp2来阻断Ang II和EGF刺激的VSMC中的Akt激活，从而阻止Gab1与PI3K之间的相互作用，而这种相互作用是进一步信号转导所必需的。
