Reduced NAD(P)H Oxidase in Low Renin Hypertension

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Abstract
Endothelial dysfunction (ED) complicates hypertension and is a precursor of atherosclerosis. Reduced NO bioactivity, because of increased reduced NAD(P)H oxidase-derived reactive oxygen species (ROS), plays a critical role in ED. gp91phox, predominantly expressed in the endothelium and adventitia, is a subunit of NAD(P)H oxidase important for its activation in response to angiotensin (Ang) II. Human atherosclerotic plaques are heavy laden with gp91phox. We have shown that in Dahl salt-sensitive (DS) rats, a paradigm of low renin salt-sensitive (SS) hypertension in humans, Ang II receptor blockade normalizes ROS production and endothelium-dependent relaxation (EDR) without significantly affecting systolic blood pressure (SBP). To additionally elucidate the mechanisms involved in the functional association of Ang II in SS hypertension, we administered a cell-permeable inhibitor of the assembly of p47phox with gp91phox in NAD(P)H oxidase, gp91ds-tat (10 mg/kg body weight, 3 weeks by minipump), to DS rats fed a 4% salt diet. Control rats received either vehicle or an inactive scramb-tat peptide. Vehicle-treated DS developed hypertension (SBP 168+/-5 mm Hg), left ventricular hypertrophy (LVH), proteinuria, impaired EDR, and increased aortic ROS production (superoxide 115% and peroxynitrite 157%) and expression of the proatherogenic molecules LOX-1 (130%) and MCP-1 (166%). gp91ds-tat, but not scramb-tat, normalized ROS and EDR, as well as LOX-1 and MCP-1, despite nonsignificant effects on SBP (159+/-5 mm Hg; P>0.05), left ventricular hypertrophy, and proteinuria. Our findings support the notion that in SS hypertension, activation of NAD(P)H oxidase promotes ED and atherogenesis via decreased nitric oxide bioactivity and increased LOX-1 and MCP-1, independent of blood pressure.