Published online before print June 19, 2008, doi: 10.1161/CIRCRESAHA.108.178608
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Submitted on October 26, 2006
Revised on May 21, 2008
Accepted on June 11, 2008
Redox-Sensitive Signaling by Angiotensin II Involves Oxidative Inactivation and Blunted Phosphorylation of Protein Tyrosine Phosphatase SHP-2 in Vascular Smooth Muscle Cells From SHR
Fatiha Tabet ;
From the Kidney Research Centre (F.T., G.C., Y.H., R.M.T.), Ottawa Health Research Institute, University of Ottawa, Ontario, Canada; Sir Mortimer B Davis-Jewish General Hospital (E.L.S., G.Y.), McGill University, Montreal, Canada; the Cancer Center Karolinska, Department of Pathology and Oncology (A.O., K.K.), Karolinska Institute, Sweden; and Cold Spring Harbor Laboratory (N.K.T.), Cold Spring Harbor, New York.
* To whom correspondence should be addressed. E-mail: rtouyz{at}uottawa.ca.
Angiotensin II (Ang II) signaling in vascular smooth muscle cells (VSMCs) involves reactive oxygen species (ROS) through unknown mechanisms. We propose that Ang II induces phosphorylation of growth signaling kinases by redox-sensitive regulation of protein tyrosine phosphatases (PTP) in VSMCs and that augmented Ang II signaling in spontaneously hypertensive rats (SHRs) involves oxidation/inactivation and blunted phosphorylation of the PTP, SHP-2. PTP oxidation was assessed by the in-gel PTP method. SHP-2 expression and activity were evaluated by immunoblotting and by a PTP activity assay, respectively. SHP-2 and Nox1 were downregulated by siRNA. Ang II induced oxidation of multiple PTPs, including SHP-2. Basal SHP-2 content was lower in SHRs versus WKY. Ang II increased SHP-2 phosphorylation and activity with blunted responses in SHRs. Ang II—induced SHP-2 effects were inhibited by valsartan (AT1R blocker), apocynin (NAD(P)H oxidase inhibitor), and Nox1 siRNA. Ang II stimulation increased activation of ERK1/2, p38MAPK, and AKT, with enhanced effects in SHR. SHP-2 knockdown resulted in increased AKT phosphorylation, without effect on ERK1/2 or p38MAPK. Nox1 downregulation attenuated Ang II–mediated AKT activation in SHRs. Hence, Ang II regulates PTP/SHP-2 in VSMCs through AT1R and Nox1-based NAD(P)H oxidase via two mechanisms, oxidation and phosphorylation. In SHR Ang II–stimulated PTP oxidation/inactivation is enhanced, basal SHP-2 expression is reduced, and Ang II–induced PTP/SHP-2 phosphorylation is blunted. These SHP-2 actions are associated with augmented AKT signaling. We identify a novel redox-sensitive SHP-2–dependent pathway for Ang II in VSMCs. SHP-2 dysregulation by increased Nox1-derived ROS in SHR is associated with altered Ang II–AKT signaling.
Key words: redox signaling • protein tyrosine phosphatases • SHP-2 • MAP kinases • AKT • vascular smooth muscle cells