Aldosterone Activates Vascular p38MAP Kinase and NADPH Oxidase Via c-Src

Increasing evidence indicates that aldosterone elicits vascular effects through nongenomic signaling pathways. We tested the hypothesis that aldosterone induces activation of vascular mitogen-activated protein (MAP) kinases and NADPH oxidase via c-Src–dependent mechanisms in vascular smooth muscle cells (VSMCs). Aldosterone effects on activation of c-Src, p38MAP kinase, and NADPH oxidase, and incorporation of [ 3 H]proline, an index of collagen synthesis, were assessed in cultured rat VSMCs. Studies were performed in the absence and presence of eplerenone, a selective mineralocorticoid receptor blocker, PP2, a selective Src inhibitor, and SB212190, a selective p38MAPK inhibitor. Phosphorylation of c-Src was dose-dependently increased by aldosterone, with maximal responses obtained at 10 −7 mol/L. Aldosterone increased p38MAP kinase phosphorylation, NAD(P)H oxidase activation, and [ 3 H]proline incorporation. These responses were abrogated by eplerenone and almost abolished by PP2. Aldosterone-stimulated incorporation of [ 3 H]proline was significantly reduced by SB212190, indicating that p38MAP kinase plays a role in profibrotic actions of aldosterone. To unambiguously demonstrate the importance of aldosterone in c-Src signaling, VSMCs from c-Src +/+ and c-Src +/− mice were also studied. Aldosterone increased phosphorylation of c-Src, p38MAP kinase, and cortactin, a Src-specific substrate, in c-Src +/+ VSMCs, but not in c-Src-deficient cells. Taken together, our findings demonstrate that nongenomic signaling by aldosterone occurs through c-Src–dependent pathways. These processes may play an important role in profibrotic actions of aldosterone.