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 (O2*-) production. The nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase is a major source of vascular O2*- 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 O2*- 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 O2*- production. In situ staining for O2*- using dihydroethidium revealed a marked increase of O2*-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 O2*-, 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 O2*- 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.

NAD(P)H Oxidase-derived Hydrogen Peroxide Mediates Endothelial Nitric Oxide Production in Response to Angiotensin II

“…The endothelial production of NO ⅐ evoked by 30 min of treatment with either the calcium ionosphere A23187 (1 mol/liter) or bradykinin (1 mol/liter) was not affected by PEG-catalase (Fig. 6, A and B (24). Angiotensin II had no effect on NO ⅐ production in MAECs from p47 phoxϪ/Ϫ mice (Fig.…”

Angiotensin II-induced NADPH Oxidase Activation Impairs Insulin Signaling in Skeletal Muscle Cells

“…Evidence that p47 phox plays a central role in NADPH oxidase activation comes in part from p47 phox(Ϫ/Ϫ) knock-out mice, which exhibit significantly lower Ang II-induced superoxide production in endothelial cells (56). It appears that p47 phox is required for stable complex of cytosolic subunits with membrane-bound cytochrome b 558 (22) and the recruitment of p67 phox (21,23,24).…”

Mechanism of Angiotensin II-induced Superoxide Production in Cells Reconstituted with Angiotensin Type 1 Receptor and the Components of NADPH Oxidase

“…There are some hints for the functional coupling between Nox1 and AT 1 R; Nox1 is up-regulated upon Ang II stimulation of vascular smooth muscle cells (VSMCs) (31,32), Ang II fails to induce ROS production in Nox1-deficient VSMCs (31), and Ang II-mediated hypertension and blood pressure are decreased in Nox1-deficient mice (33,34). Nox2 as an Ang II-responsive enzyme has also been speculated based on the observations that Nox2 components (Nox2, p22 phox , p47 phox , p67 phox , and p40 phox ) are induced by Ang II in endothelial cells (35)(36)(37)(38)(39)(40)(41), that Ang II-dependent cardiac hypertrophy and blood pressure are moderately decreased in Nox 2-deficient mice (42)(43)(44), and that Ang II-dependent ROS production is severely compromised in endothelial cells (45) and VSMCs (46) derived from mice deficient in p47 phox , the Nox subunit that is most effective for the activation of Nox2.…”