Abstract
AimsWe questioned whether aldosterone and oxidative stress play a role in vascular damage in severe hypertension and investigated the role of Nox1 in this process. Materials and methodsWe studied mesenteric arteries, aortas and vascular smooth muscle cells (VSMC) from WKY and SHRSP rats. Vascular effects of eplerenone or canrenoic acid (CA) (mineralocorticoid receptor (MR) blockers), ML171 (Nox1 inhibitor) and EHT1864 (Rac1/2 inhibitor) were assessed. Nox1-knockout mice were also studied. Vessels and VSMCs were probed for Noxs, reactive oxygen species (ROS) and pro-fibrotic/inflammatory signaling. Key findingsBlood pressure and plasma levels of aldosterone and galectin-3 were increased in SHRSP versus WKY. Acetylcholine-induced vasorelaxation was decreased (61% vs 115%) and phenylephrine-induced contraction increased in SHRSP versus WKY (Emax 132.8% vs 96.9%, p<0.05). Eplerenone, ML171 and EHT1864 attenuated hypercontractility in SHRSP. Vascular expression of collagen, fibronectin, TGFβ, MCP-1, RANTES, MMP2, MMP9 and p66Shc was increased in SHRSP versus WKY. These changes were associated with increased ROS generation, 3-nitrotyrosine expression and Nox1 upregulation. Activation of vascular p66Shc and increased expression of Nox1 and collagen I were prevented by CA in SHRSP. Nox1 expression was increased in aldosterone-stimulated WKY VSMCs, an effect that was amplified in SHRSP VSMCs (5.2vs9.9 fold-increase). ML171 prevented aldosterone-induced VSMC Nox1-ROS production. Aldosterone increased vascular expression of fibronectin and PAI-1 in wild-type mice but not in Nox1-knockout mice. SignificanceOur findings suggest that aldosterone, which is increased in SHRSP, induces vascular damage through MR-Nox1-p66Shc-mediated processes that modulate pro-fibrotic and pro-inflammatory signaling pathways.
Highlights
Hypertension-associated vascular damage is characterised by functional, structural and mechanical alterations comprising hypercontractility, endothelial dysfunction, inflammation, calcification and fibrosis [1,2]
Elevated blood pressure is associated with increased plasma aldosterone and galectin-3 levels in SHRSP rats
Findings from our study demonstrate that in SHRSP 1) elevated blood pressure is associated with increased levels of plasma aldosterone and galectin-3, vascular stiffness, arterial fibrosis and inflammation, 2) vascular hypercontractility and pro-inflammatory and pro-fibrotic signaling is ameliorated by mineralocorticoid receptor (MR) blockade and Nox1 inhibition, and 3) aldosterone-mediated signaling and vascular fibrosis is partially Nox1dependent
Summary
Hypertension-associated vascular damage is characterised by functional, structural and mechanical alterations comprising hypercontractility, endothelial dysfunction, inflammation, calcification and fibrosis [1,2]. Molecular mechanisms underlying vascular changes in hypertension are incompletely understood, but a role for the mineralocorticoid hormone aldosterone, has been suggested. ⁎ Corresponding author at: Institute of Cardiovascular and Medical Sciences, University of Glasgow, 126 University Place, Glasgow G12 8TA, United Kingdom that aldosterone has direct vascular effects and that it is a potent pro-fibrotic agent in cardiovascular remodeling in hypertension [3]. Evidence from animal models and clinical trials in patients with heart failure demonstrate that blockade of the mineralocorticoid receptor (MR) through which aldosterone signals, is cardio- and vaso-protective [4, 5]. A role for reactive oxygen species (ROS) has been suggested to mediate the detrimental effects of aldosterone in the vasculature [3]
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