Background — NAD(P)H oxidases are important sources of superoxide in the vasculature, the activity of which is associated with risk factors for human atherosclerosis. This study was designed to investigate the localization of superoxide production and the expression of the Nox family of NAD(P)H oxidase proteins (gp91phox, Nox1, and Nox4) in nonatherosclerotic and atherosclerotic human coronary arteries. Methods and Results — In coronary artery segments from explanted human hearts, we examined intracellular superoxide production with dihydroethidium. In nonatherosclerotic coronary arteries, superoxide was present homogenously throughout the intima, media, and adventitia. In atherosclerotic arteries, there was an additional intense area of superoxide in the plaque shoulder, which is rich in macrophages and α-actin–positive cells. p22phox colocalized with gp91phox mainly in macrophages, whereas Nox4 was found only in nonphagocytic vascular cells. Expression of gp91phox and p22phox mRNA was associated with the severity of atherosclerosis. gp91phox correlated with the plaque macrophage content, whereas Nox4 correlated with the content of α-actin–positive cells. Nox1 expression was low both in human coronary arteries and isolated vascular cells. Conclusions — Several Nox proteins, including gp91phox and Nox4, may contribute to increased intracellular oxidative stress in human coronary atherosclerosis in a cell-specific manner and thus may be involved in the genesis and progression of human coronary atherosclerotic disease.

Objective— Reactive oxygen species (ROS) that act as signaling molecules in vascular smooth muscle cells (VSMC) and contribute to growth, hypertrophy, and migration in atherogenesis are produced by multi-subunit NAD(P)H oxidases. Nox1 and Nox4, two homologues to the phagocytic NAD(P)H subunit gp91 ^phox , both generate ROS in VSMC but differ in their response to growth factors. We hypothesize that the opposing functions of Nox1 and Nox4 are reflected in their differential subcellular locations. Methods and Results— We used immunofluorescence to visualize the NAD(P)H subunits Nox1, Nox4, and p22 ^phox in cultured rat and human VSMC. Optical sectioning using confocal microscopy showed that Nox1 is co-localized with caveolin in punctate patches on the surface and along the cellular margins, whereas Nox4 is co-localized with vinculin in focal adhesions. These immunocytochemical distributions are supported by membrane fractionation experiments. Interestingly, p22 ^phox , a membrane subunit that interacts with the Nox proteins, is found in surface labeling and in focal adhesions in patterns similar to Nox1 and Nox4, respectively. Conclusions— The differential roles of Nox1 and Nox4 in VSMC may be correlated with their differential compartmentalization in specific signaling domains in the membrane and focal adhesions.

A major source of vascular smooth muscle cell (VSMC) superoxide is NAD(P)H oxidase. However, the molecular characteristics and regulation of this enzyme are unclear. We investigated whether VSMCs from human resistance arteries (HVSMCs) possess a functionally active, angiotensin II (Ang II)–regulated NAD(P)H oxidase that contains neutrophil oxidase subunits, including p22phox, gp91phox, p40phox, p47phox, and p67phox. mRNA expression of gp91phox homologues, nox1 and nox4, was also assessed in HVSMCs, human aortic smooth muscle cells, and rat VSMCs. HVSMCs were obtained from resistance arteries from gluteal biopsies of healthy subjects. gp91phox and nox4, but not nox1, were detected in HVSMCs. Nox1 and nox4, but not gp91phox, were expressed in human aortic smooth muscle cells and rat VSMCs. All NAD(P)H oxidase subunits were present in HVSMCs as detected by reverse transcriptase–polymerase chain reaction and immunoblotting. Ang II increased NAD(P)H oxidase subunit abundance. These effects were inhibited by cycloheximide. Acute Ang II stimulation (10 to 15 minutes) increased p47phox serine phosphorylation and induced p47phox and p67phox translocation. This was associated with NAD(P)H oxidase activation. In cells transfected with gp91phox antisense oligonucleotides, Ang II–mediated actions were abrogated. NADPH-induced superoxide generation was reduced by gp91ds-tat and apocynin, inhibitors of p47phox-gp91phox interactions. Our results suggest that HVSMCs possess a functionally active gp91phox-containing neutrophil-like NAD(P)H oxidase. Ang II regulates the enzyme by inducing phosphorylation of p47phox, translocation of cytosolic subunits, and de novo protein synthesis. These novel findings provide insight into the molecular regulation of NAD(P)H oxidase by Ang II in HVSMCs. Furthermore, we identify differences in gp91phox homologue expression in VSMCs from rats and human small and large arteries.

We previously reported enhanced expression of the p67^phoxand gp91^phoxcomponents of NAD(P)H oxidase in angiotensin (Ang) II–induced hypertension, suggesting de novo assembly in response to Ang II. To examine the direct involvement of NAD(P)H oxidases in Ang II–induced O₂⁻production, we designed a chimeric peptide that inhibits p47^phoxassociation with gp91^phoxin NAD(P)H oxidase (gp91ds-tat). This was achieved by linking a 9-amino acid peptide (aa) derived from HIV-coat protein (tat) to a 9-aa sequence of gp91^phox(known to interact with p47^phox). As a control, we constructed a chimera containingtatand a scrambled gp91 sequence (scramb-tat). We found that gp91ds-tatdecreased O₂⁻levels in aortic rings treated with Ang II (10 pmol/L) but had no effect on either the O₂⁻-generating enzyme xanthine oxidase or potassium superoxide–generated O₂⁻. We infused vehicle, Ang II (0.75 mg · kg⁻¹· d⁻¹), Ang II+gp91ds-tat(10 mg · kg⁻¹· d⁻¹), or Ang II+scramb-tatintraperitoneally in C57Bl/6 mice and measured systolic blood pressure (SBP) on days 0, 3, 5, and 7 of infusion. SBP increased by day 3 in mice given Ang II and Ang II+scramb-tatbut was significantly lower with Ang II+gp91-tat. On day 7, SBP was still significantly inhibited in mice given Ang II+gp91ds-tat, whereas Ang II–induced O₂⁻production was inhibited throughout the aorta as detected by dihydroethidium staining, consistent with the ability of this inhibitor to block the various vascular NAD(P)H oxidase isoforms. These data support the hypothesis that inhibition of the interaction of p47^phoxand gp91^phox(or its homologues) can block O₂⁻production and attenuate blood pressure elevation in mice.