Role of p47phox in vascular oxidative stress and hypertension caused by angiotensin II

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 min 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.