Mitogen-activated protein/extracellular signal regulated kinase inhibition attenuates angiotensin II mediated signaling and contraction in spontaneously hypertensive rat vascular smooth muscle cells

Touyz, R.M. , El Mabrouk, M., He, G., Wu, X.-H. and Schiffrin, E.L. (1999) Mitogen-activated protein/extracellular signal regulated kinase inhibition attenuates angiotensin II mediated signaling and contraction in spontaneously hypertensive rat vascular smooth muscle cells. Circulation Research, 84(5), pp. 505-515. (doi: 10.1161/01.RES.84.5.505)

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Abstract

This study investigates the role of extracellular signal–regulated kinases (ERKs) in angiotensin II (Ang II)–generated intracellular second messengers (cytosolic free Ca2+ concentration, ie, [Ca2+]i, and pHi) and in contraction in isolated vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) and control Wistar Kyoto rats (WKY) using the selective mitogen-activated protein (MAP)/ERK inhibitor, PD98059. VSMCs from mesenteric arteries were cultured on Matrigel basement membrane matrix. These cells, which exhibit a contractile phenotype, were used to measure [Ca2+]i, pHi, and contractile responses to Ang II (10–12 to 10–6 mol/L) in the absence and presence of PD98059 (10–5 mol/L). [Ca2+]i and pHi were measured by fura-2 and BCECF methodology, respectively, and contraction was determined by photomicroscopy. Ang II–stimulated ERK activity was measured by Western blot analysis using a phospho-specific ERK-1/ERK-2 antibody and by an MAPK enzyme assay. Ang II increased [Ca2+]i and pHi and contracted cells in a dose-dependent manner. Maximum Ang II–elicited contraction was greater (P<0.05) in SHR (41.9±5.1% reduction in cell length relative to basal length) than in WKY (28.1±3.0% reduction in cell length relative to basal length). Basal [Ca2+]i, but not basal pHi, was higher in SHR compared with WKY. [Ca2+]i and pHi effects of Ang II were enhanced (P<0.05) in SHR compared with WKY (maximum Ang II–induced response [Emax] of [Ca2+]i, 576±24 versus 413±43 nmol/L; Emax of pHi, 7.33±0.01 versus 7.27±0.03, SHR versus WKY). PD98059 decreased the magnitude of contraction and attenuated the augmented Ang II–elicited contractile responses in SHR (Emax,19.3±3% reduction in cell length relative to basal length). Ang II–stimulated [Ca2+]i (Emax, 294±55 nmol/L) and pHi (Emax, 7.27±0.04) effects were significantly reduced by PD98059 in SHR. Ang II–induced ERK activity was significantly greater (P<0.05) in SHR than in WKY. In conclusion, Ang II–stimulated signal transduction and associated VSMC contraction are enhanced in SHR. MAP/ERK inhibition abrogated sustained contraction and normalized Ang II effects in SHR. These data suggest that ERK-dependent signaling pathways influence contraction and that they play a role in vascular hyperresponsiveness in SHR.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Touyz, Professor Rhian
Authors: Touyz, R.M., El Mabrouk, M., He, G., Wu, X.-H., and Schiffrin, E.L.
College/School:College of Medical Veterinary and Life Sciences > Institute of Cardiovascular and Medical Sciences
Journal Name:Circulation Research
ISSN:0009-7330

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