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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2008;28:1511.)
© 2008 American Heart Association, Inc.

Cell Biology/Signaling

Aldosterone and Angiotensin II Synergistically Stimulate Migration in Vascular Smooth Muscle Cells Through c-Src-Regulated Redox-Sensitive RhoA Pathways

A.C. Montezano; G.E. Callera; A. Yogi; Y. He; R.C. Tostes; G. He; E.L. Schiffrin; R.M. Touyz

From the Ottawa Health Research Institute (A.C.M., G.E.C., A.Y., Y.H., G.H., R.M.T.), Kidney Research Centre, University of Ottawa, Ontario, Canada; the Institute of Biomedical Sciences (A.Y., R.C.T.), University of Sao Paulo, Brazil; and Lady Davis Institute (E.L.S.), McGill University, Montreal, Quebec, Canada.

Correspondence to Rhian M Touyz, MD, PhD, Kidney Research Centre, OHRI/University of Ottawa, 451 Smyth Road, Ottawa, K1H 8M5, Ontario, Canada. E-mail rtouyz{at}uottawa.ca

Abstract

Objective— Synergistic interactions between aldosterone (Aldo) and angiotensin II (Ang II) have been implicated in vascular inflammation, fibrosis, and remodeling. Molecular mechanisms underlying this are unclear. We tested the hypothesis that c-Src activation, through receptor tyrosine kinase transactivation, is critically involved in synergistic interactions between Aldo and Ang II and that it is upstream of promigratory signaling pathways in vascular smooth muscle cells (VSMCs).

Methods and Results— VSMCs from WKY rats were studied. At low concentrations (10^–10 mol/L) Aldo and Ang II alone did not influence c-Src activation, whereas in combination they rapidly increased phosphorylation (P<0.01), an effect blocked by eplerenone (Aldo receptor antagonist) and irbesartan (AT1R blocker). This synergism was attenuated by AG1478 and AG1296 (inhibitors of EGFR and PDGFR, respectively), but not by AG1024 (IGFR inhibitor). Aldo and Ang II costimulation induced c-Src-dependent activation of NAD(P)H oxidase and c-Src-independent activation of ERK1/2 (P<0.05), without effect on ERK5, p38MAPK, or JNK. Aldo/Ang II synergistically activated RhoA/Rho kinase and VSMC migration, effects blocked by PP2, apocynin, and fasudil, inhibitors of c-Src, NADPH oxidase, and Rho kinase, respectively.

Conclusions— Aldo/Ang II synergistically activate c-Src, an immediate signaling response, through EGFR and PDGFR, but not IGFR transactivation. This is associated with activation of redox-regulated RhoA/Rho kinase, which controls VSMC migration. Although Aldo and Ang II interact to stimulate ERK1/2, such effects are c-Src-independent. These findings indicate differential signaling in Aldo-Ang II crosstalk and highlight the importance of c-Src in redox-sensitive RhoA, but not ERK1/2 signaling. Blockade of Aldo/Ang II may be therapeutically useful in vascular remodeling associated with abnormal VSMC migration.

We questioned whether synergism between aldosterone and Ang II involves c-Src in vascular smooth muscle cells (VSMCs). Findings show that Aldo/Ang II synergistically phosphorylate c-Src through EGFR and PDGF transactivation, an effect associated with activation of redox-regulated RhoA/Rho kinase-mediated VSMC migration. Our findings highlight the importance of c-Src in redox-sensitive RhoA, but not ERK1/2 signaling. Aldo/Ang II blockade may be useful in treating vascular remodeling associated with abnormal VSMC migration.

Key Words: aldosterone • angiotensin II • c-Src • Rho A • synergism