Role of p47 ^phox in Vascular Oxidative Stress and Hypertension Caused by Angiotensin II

Abstract

Hypertension caused by angiotensin II is dependent on vascular superoxide (O ₂ ·−) production. The nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase is a major source of vascular O ₂ ·− and is activated by angiotensin II in vitro. However, its role in angiotensin II-induced hypertension in vivo is less clear. In the present studies, we used mice deficient in p47 ^phox , a cytosolic subunit of the NADPH oxidase, to study the role of this enzyme system in vivo. In vivo, angiotensin II infusion (0.7 mg/kg per day for 7 days) increased systolic blood pressure from 105±2 to 151±6 mm Hg and increased vascular O ₂ ·− formation 2- to 3-fold in wild-type (WT) mice. In contrast, in p47 ^phox-/- mice the hypertensive response to angiotensin II infusion (122±4 mm Hg; P <0.05) was markedly blunted, and there was no increase of vascular O ₂ ·− production. In situ staining for O ₂ ·− using dihydroethidium revealed a marked increase of O ₂ ·−production in both endothelial and vascular smooth muscle cells of angiotensin II-treated WT mice, but not in those of p47 ^phox-/- mice. To directly examine the role of the NAD(P)H oxidase in endothelial production of O ₂ ·−, endothelial cells from WT and p47 ^phox-/- mice were cultured. Western blotting confirmed the absence of p47 ^phox in p47 ^phox-/- mice. Angiotensin II increased O ₂ ·− production in endothelial cells from WT mice, but not in those from p47 ^phox-/- mice, as determined by electron spin resonance spectroscopy. These results suggest a pivotal role of the NAD(P)H oxidase and its subunit p47 ^phox in the vascular oxidant stress and the blood pressure response to angiotensin II in vivo.