title: Redox-dependent MAP kinase signaling by Ang II in vascular smooth muscle cells: role of receptor tyrosine kinase transactivation.
abstract: 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 micromol/L) fluorescence and lucigenin (5 micromol/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 intracellular scavenger, 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.
authors.affiliation: Multidisciplinary Research Group on Hypertension, Clinical Research Institute of Montreal, University of Montréal, QC H2W 1R7, Canada. touyzr@ircm.qc.ca
authors.forename: Rhian M
authors.initials: RM
authors.lastname: Touyz
authors.forename: Montserrat
authors.initials: M
authors.lastname: Cruzado
authors.forename: Fatiha
authors.initials: F
authors.lastname: Tabet
authors.forename: Guoying
authors.initials: G
authors.lastname: Yao
authors.forename: Steven
authors.initials: S
authors.lastname: Salomon
authors.forename: Ernesto L
authors.initials: EL
authors.lastname: Schiffrin
mesh_terms: D000804:Angiotensin II / Q000502:physiology*; D004789:Enzyme Activation / Q000502:physiology; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D066298:In Vitro Techniques; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D048291:Mitogen-Activated Protein Kinase 12; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000502:physiology; D019255:NADPH Oxidases / Q000502:physiology; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology*
chemical_list: D017382:Reactive Oxygen Species; D000804:Angiotensin II; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D019255:NADPH Oxidases; D048291:Mitogen-Activated Protein Kinase 12; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases; D048054:Mitogen-Activated Protein Kinase 7; D020928:Mitogen-Activated Protein Kinases