Increased NADH-oxidase-mediated superoxide production in the early stages of atherosclerosis: evidence for involvement of the renin-angiotensin system.
BACKGROUND
Angiotensin II activates NAD(P)H-dependent oxidases via AT1-receptor stimulation, the most important vascular source of superoxide (O2*-). The AT1 receptor is upregulated in vitro by low-density lipoprotein. The present study was designed to test whether hypercholesterolemia is associated with increased NAD(P)H-dependent vascular O2*- production and whether AT1-receptor blockade may inhibit this oxidase and in parallel improve endothelial dysfunction.


RESULTS
Vascular responses were determined by isometric tension studies, and relative rates of vascular O2*- production were determined by use of chemiluminescence with lucigenin, a cypridina luciferin analogue, and electron spin resonance studies. AT1-receptor mRNA was quantified by Northern analysis, and AT1-receptor density was measured by radioligand binding assays. Hypercholesterolemia was associated with impaired endothelium-dependent vasodilation and increased O2*- production in intact vessels. In vessel homogenates, we found a significant activation of NADH-driven O2*- production in both models of hyperlipidemia. Treatment of cholesterol-fed animals with the AT1-receptor antagonist Bay 10-6734 improved endothelial dysfunction, normalized vascular O2*- and NADH-oxidase activity, decreased macrophage infiltration, and reduced early plaque formation. In the setting of hypercholesterolemia, the aortic AT1 receptor mRNA was upregulated to 166+/-11%, accompanied by a comparable increase in AT1-receptor density.


CONCLUSIONS
Hypercholesterolemia is associated with AT1-receptor upregulation, endothelial dysfunction, and increased NADH-dependent vascular O2*- production. The improvement of endothelial dysfunction, inhibition of the oxidase, and reduction of early plaque formation by an AT1-receptor antagonist suggests a crucial role of angiotensin II-mediated O2*- production in the early stage of atherosclerosis.
Warnholtz
A
A
Abteilung für Kardiologie, Universitäts-Krankenhaus Eppendorf, University of Hamburg, Germany.
Nickenig
G
G
Schulz
E
E
Macharzina
R
R
Bräsen
J H
JH
Skatchkov
M
M
Heitzer
T
T
Stasch
J P
JP
Griendling
K K
KK
Harrison
D G
DG
Böhm
M
M
Meinertz
T
T
Münzel
T
T
D000109:Acetylcholine / Q000494:pharmacology; D000166:Acridines / Q000032:analysis; D017311:Amlodipine / Q000494:pharmacology / Q000627:therapeutic use; D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology / Q000627:therapeutic use; D001161:Arteriosclerosis / Q000201:enzymology* / Q000209:etiology / Q000503:physiopathology; D004036:Diet, Atherogenic; D004095:Dihydropyridines / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D006937:Hypercholesterolemia / Q000150:complications / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D008055:Lipids / Q000097:blood; D008163:Luminescent Measurements; D008264:Macrophages / Q000473:pathology; D008297:Male; D009097:Multienzyme Complexes / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000096:biosynthesis / Q000502:physiology; D011973:Receptors, LDL / Q000172:deficiency / Q000235:genetics; D012084:Renin-Angiotensin System / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism*; D013777:Tetrazoles / Q000494:pharmacology; D015854:Up-Regulation; D014661:Vasoconstriction / Q000187:drug effects; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology / Q000627:therapeutic use
D000166:Acridines; D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D000959:Antihypertensive Agents; D004095:Dihydropyridines; D008055:Lipids; D009097:Multienzyme Complexes; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D011973:Receptors, LDL; D013777:Tetrazoles; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D013481:Superoxides; D017311:Amlodipine; D010656:Phenylephrine; C033472:10,10'-dimethyl-9,9'-biacridinium; C109119:embusartan; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D000109:Acetylcholine