Redox-dependent MAP kinase signaling by Ang II in vascular smooth muscle cells: role of receptor tyrosine kinase transactivation

• Published in: Canadian journal of physiology and pharmacology 2003-02, Vol.81 (2), p.159-167
• Main Authors: Touyz, Rhian M, Cruzado, Montserrat, Tabet, Fatiha, Yao, Guoying, Salomon, Steven, Schiffrin, Ernesto L
• Format: Article
• Language: English
• Subjects: Angiotensin II - physiology; Biological and medical sciences; Blood vessels and receptors; Cells; Enzyme Activation - physiology; Enzymes; Epidermal Growth Factor - metabolism; Fundamental and applied biological sciences. Psychology; Heart disease; In Vitro Techniques; Insulin-Like Growth Factor I - metabolism; MAP Kinase Signaling System - physiology; Mitogen-Activated Protein Kinase 12; Mitogen-Activated Protein Kinase 7; Mitogen-Activated Protein Kinases - metabolism; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - physiology; NADPH Oxidases - physiology; Oxidation-Reduction; Reactive Oxygen Species - metabolism; Receptor Protein-Tyrosine Kinases - physiology; Receptor, Epidermal Growth Factor - metabolism; Vertebrates: cardiovascular system
• ISSN: 0008-4212; 1205-7541
• DOI: 10.1139/y02-164

We investigated the role of receptor tyrosine kinases in Ang II-stimulated generation of reactive oxygen species (ROS) and assessed whether MAP kinase signaling by Ang II is mediated via redox-sensitive pathways. Production of ROS and activation of NADPH oxidase were determined by DCFDA (dichlorodihydrofluorescein diacetate; 2 μmol/L) fluorescence and lucigenin (5 μmol/L) chemiluminescence, respectively, in rat vascular smooth muscle cells (VSMC). Phosphorylation of ERK1/2, p38MAP kinase and ERK5 was determined by immunoblotting. The role of insulin-like growth factor-1 receptor (IGF-1R) and epidermal growth factor receptor (EGFR) was assessed with the antagonists AG1024 and AG1478, respectively. ROS bioavailability was manipulated with Tiron (10 –5 mol/L), an intra cellular scavanger, and diphenylene iodinium (DPI; 10 –6 mol/L), an NADPH oxidase inhibitor. Ang II stimulated NADPH oxidase activity and dose-dependently increased ROS production (p < 0.05). These actions were reduced by AG1024 and AG1478. Ang II-induced ERK1/2 phosphorylation (276% of control) was decreased by AG1478 and AG1024. Neither DPI nor tiron influenced Ang II-stimulated ERK1/2 activity. Ang II increased phosphorylation of p38 MAP kinase (204% of control) and ERK5 (278% of control). These effects were reduced by AG1024 and AG1478 and almost abolished by DPI and tiron. Thus Ang II stimulates production of NADPH-inducible ROS partially through transactivation of IGF-1R and EGFR. Inhibition of receptor tyrosine kinases and reduced ROS bioavaliability attenuated Ang II-induced phosphorylation of p38 MAP kinase and ERK5, but not of ERK1/2. These findings suggest that Ang II activates p38MAP kinase and ERK5 via redox-dependent cascades that are regulated by IGF-1R and EGFR transactivation. ERK1/2 regulation by Ang II is via redox-insensitive pathways.Key words: ERK1/2, p38MAP kinase, EGFR, IGF-1R, signal transduction.