Negative regulation of RhoA/Rho kinase by angiotensin II type 2 receptor in vascular smooth muscle cells: role in angiotensin II-induced vasodilation in stroke-prone spontaneously hypertensive rats

Savoia, C., Tabet, F., Yao, G., Schiffrin, E.L. and Touyz, R.M. (2005) Negative regulation of RhoA/Rho kinase by angiotensin II type 2 receptor in vascular smooth muscle cells: role in angiotensin II-induced vasodilation in stroke-prone spontaneously hypertensive rats. Journal of Hypertension, 23(5), pp. 1037-1045.

Abstract

Objective: To test whether angiotensin II (Ang II) through the Ang II type 2 receptor (AT2R), downregulates RhoA/Rho kinase, which plays a role in AT1 receptor (AT1R)-mediated function.<p></p> Methods: In vitro studies were performed in A10 vascular smooth muscle cells (VSMC) and in vivo studies in mesenteric arteries from Wistar-Kyoto (WKY) and stroke-prone spontaneously hypertensive (SHRSP) rats. VSMC were stimulated with Ang II (10-7 mol/l), CGP42112A (10-7 mol/l, a selective AT2R agonist) ± valsartan (10-5 mol/l, an AT1R antagonist), or the Rho kinase inhibitor fasudil (10-5 mol/l). AT1R and AT2R expression and myosin light chain (MLC) phosphorylation were determined by immunoblotting. RhoA activity was assessed by measuring membrane translocation. Functional significance between AT2R, RhoA/Rho kinase and vasodilation was assessed in arteries from valsartan-treated (30 mg/kg per day, 14 days) WKY and SHRSP rats. Vasodilatory responses to Ang II (10-9-10-6 mol/l) were performed in norepinephrine pre-contracted vessels ± valsartan(10-6 mol/l), PD123319 (10-6 mol/l, an AT2R antagonist) or fasudil (10-6 mol/l).<p></p> Results: A10 VSMC expressed AT1R and AT2R. In valsartan-treated cells, Ang II-induced RhoA translocation was reduced versus controls (42 ± 6%, P < 0.05). Similar responses were obtained with CGP42112A (45 ± 6%, P < 0.05). This was associated with decreased MLC activation. Fasudil abrogated Ang II- and CGP42112A-mediated effects. Ang II evoked a significant vasodilatory response only in valsartan-treated SHRSP (max dilation 40 ± 7%). PD123319 blocked these effects. Fasudil increased AngII-induced relaxation in SHRSP vessels. AT2R expression was increased by valsartan (two- to three-fold) in SHRSP arteries. RhoA translocation was increased two-fold in untreated SHRSP (P < 0.05) and was reduced by valsartan (P < 0.05). These changes were associated with decreased MLC phosphorylation.<p></p> Conclusions: Ang II/AT2R negatively regulates vascular RhoA/Rho kinase/MLC phosphorylation. These processes may play a role in Ang II-mediated vasodilation in conditions associated with vascular AT2R upregulation, such as in SHRSP chronically treated with AT1R blockers, which may contribute to blood pressure lowering by these antihypertensive agents.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Touyz, Professor Rhian
• Authors: Savoia, C., Tabet, F., Yao, G., Schiffrin, E.L., and Touyz, R.M.
• College/School: College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
• Journal Name: Journal of Hypertension
• ISSN: 0263-6352
• ISSN (Online): 1473-5598