Opposing roles of p47phox in basal versus angiotensin II-stimulated alterations in vascular O2- production, vascular tone, and mitogen-activated protein kinase activation.
BACKGROUND
NADPH oxidase is a major source of vascular superoxide (O2-) production and is implicated in angiotensin II (Ang II)-induced oxidant stress. The p47phox subunit plays an important role in Ang II-induced oxidase activation, but its role in basal oxidase activity and vascular function is unclear.


RESULTS
Aortae from p47phox-/- and matched wild-type (WT) mice (n=9/group) were incubated ex vivo with or without Ang II (200 nmol/L, 30 minutes) and then examined for (1) NADPH-dependent O2- production, (2) endothelium-dependent and -independent vascular relaxation, and (3) activation of mitogen-activated protein kinases (MAPKs). In the absence of Ang II, p47phox-/- vessels had slightly but significantly higher (1.3+/-0.1-fold; P<0.05) NADPH-dependent O2- production than WT; impaired relaxation to acetylcholine (maximum 54+/-4% versus 80+/-3%; P<0.05), which was normalized to WT levels by the O2- scavenger tiron or by Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin pentachloride, and increased basal phosphorylation of ERK1/2, p38MAPK, and JNK compared with WT. In WT aortae, Ang II increased NADPH-dependent O2- production (2.5+/-0.5-fold; P<0.05), impaired relaxation to acetylcholine (maximum 60+/-6% versus 80+/-3%; P<0.05), and increased ERK1/2, p38MAPK, and JNK phosphorylation (P<0.05). In contrast, Ang II failed to increase O2- production, impair acetylcholine responses, or increase MAPK activation in p47phox-/- aortae.


CONCLUSIONS
p47phox plays a complex dual role in the vasculature. It inhibits basal NADPH oxidase activity but is critical for Ang II-induced vascular dysfunction via activation of NADPH oxidase.
Li
Jian-Mei
JM
Department of Cardiology, Guy's, King's, and St Thomas' School of Medicine, King's College London, London, UK.
Wheatcroft
Stephen
S
Fan
Lampson M
LM
Kearney
Mark T
MT
Shah
Ajay M
AM
D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000109:Acetylcholine / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic; D004730:Endothelium, Vascular / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D016166:Free Radical Scavengers / Q000494:pharmacology; D066298:In Vitro Techniques; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008665:Metalloporphyrins / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D010750:Phosphoproteins / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases
D016166:Free Radical Scavengers; D008665:Metalloporphyrins; D020030:Nitric Oxide Donors; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; D000804:Angiotensin II; D009599:Nitroprusside; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; C050950:tetrakis(N-methyl-4-pyridiniumyl)porphine manganese(III) complex; D019255:NADPH Oxidases; C060505:neutrophil cytosolic factor 1; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; D000109:Acetylcholine; D010100:Oxygen