Endothelial regulation of vasomotion in apoE-deficient mice: implications for interactions between peroxynitrite and tetrahydrobiopterin.
BACKGROUND
Altered endothelial cell nitric oxide (NO(*)) production in atherosclerosis may be due to a reduction of intracellular tetrahydrobiopterin, which is a critical cofactor for NO synthase (NOS). In addition, previous literature suggests that inactivation of NO(*) by increased vascular production superoxide (O(2)(*-)) also reduces NO(*) bioactivity in several disease states. We sought to determine whether these 2 seemingly disparate mechanisms were related.


RESULTS
Endothelium-dependent vasodilation was abnormal in aortas of apoE-deficient (apoE(-/-)) mice, whereas vascular superoxide production (assessed by 5 micromol/L lucigenin) was markedly increased. Treatment with either liposome-entrapped superoxide dismutase or sepiapterin, a precursor to tetrahydrobiopterin, improved endothelium-dependent vasodilation in aortas from apoE(-/-) mice. Hydrogen peroxide had no effect on the decay of tetrahydrobiopterin, as monitored spectrophotometrically. In contrast, superoxide modestly and peroxynitrite strikingly increased the decay of tetrahydrobiopterin over 500 seconds. Luminol chemiluminescence, inhibitable by the peroxynitrite scavengers ebselen and uric acid, was markedly increased in apoE(-/-) aortic rings. In vessels from apoE(-/-) mice, uric acid improved endothelium-dependent relaxation while having no effect in vessels from control mice. Treatment of normal aortas with exogenous peroxynitrite dramatically increased vascular O(2)(*-) production, seemingly from eNOS, because this effect was absent in vessels lacking endothelium, was blocked by NOS inhibition, and did not occur in vessels from mice lacking eNOS.


CONCLUSIONS
Reactive oxygen species may alter endothelium-dependent vascular relaxation not only by the interaction of O(2)(*-) with NO(*) but also through interactions between peroxynitrite and tetrahydrobiopterin. Peroxynitrite oxidation of tetrahydrobiopterin may represent a pathogenic cause of "uncoupling" of NO synthase.
Department of Medicine, Emory University School of Medicine, and Veterans Administration Hospital, Atlanta, GA 30322, USA.
J B
JB
Laursen
M
M
Somers
S
S
Kurz
L
L
McCann
A
A
Warnholtz
B A
BA
Freeman
M
M
Tarpey
T
T
Fukai
D G
DG
Harrison
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D001057:Apolipoproteins E / Q000172:deficiency* / Q000235:genetics; D001708:Biopterins / Q000031:analogs & derivatives* / Q000378:metabolism; D000001:Calcimycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009566:Nitrates / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000172:deficiency / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D005996:Nitroglycerin / Q000494:pharmacology; D011621:Pteridines / Q000494:pharmacology; D011622:Pterins; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
D001057:Apolipoproteins E; D007476:Ionophores; D009566:Nitrates; D011621:Pteridines; D011622:Pterins; D014665:Vasodilator Agents; D013481:Superoxides; D001708:Biopterins; C039642:peroxynitric acid; D000001:Calcimycin; C016727:sepiapterin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; C003402:sapropterin; D005996:Nitroglycerin; D000109:Acetylcholine