Epidermal growth factor receptor transactivation by angiotensin II requires reactive oxygen species in vascular smooth muscle cells

Angiotensin II (Ang II) is a vasoactive hormone with critical roles in vasc ular smooth muscle cell growth, an important feature of hypertension and at herosclerosis. Many of these effects are dependent on the production of rea ctive oxygen species (ROS), Ang II induces phosphorylation of the epidermal growth factor (EGF) receptor (EGF-R), which serves as a scaffold for vario us signaling molecules. Here, we provide novel evidence that ROS are critic al mediators of EGF-R transactivation by Ang II. Pretreatment. of vascular smooth muscle cells with the antioxidants diphenylene iodonium, Tiron, N-ac etylcysteine, and ebselen significantly inhibited (approximate to 80% to 90 %) tyrosine phosphorylation of the EGF-R by Ang II but not by EGF. Of the 5 autophosphorylation sites on the EGF-R, Ang II mainly phosphorylated Tyr10 68 and Tyr1173 in a redox-sensitive manner. The Src family kinase inhibitor PPI, overexpression of kinase-inactive c-Src, or chelation of intracellula r Ca2+ attenuated EGF-R transactivation, Although antioxidants had no effec ts on the Ca2+ mobilization or phosphorylation of Ca2+-dependernt tyrosine kinase Pyk2, they inhibited c-Src activation by Ang II, suggesting that c-S rc is signaling molecule that links ROS and EGF-R phosphorylation. Furtherm ore, Ang II-induced tyrosine phosphorylation of the autophosphorylation sit e and the SH2 domain of c-Src was redox sensitive. These findings emphasize the importance of ROS in specific Ang II-stimulated growth-related signali ng pathways and suggest that redox-sensitive EGF-R transactivation may be a potential target for antioxidant therapy in vascular disease.