Overexpression of dimethylarginine dimethylaminohydrolase inhibits asymmetric dimethylarginine-induced endothelial dysfunction in the cerebral circulation.
OBJECTIVE
Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase (NOS). An elevation of plasma ADMA levels is associated with cardiovascular disease. ADMA is hydrolyzed by dimethylarginine dimethylaminohydrolases (DDAHs). The goal of this study was to determine whether overexpression of human DDAH-1 in transgenic (DDAH-1-Tg) mice inhibits the vascular effects of ADMA.


METHODS
Using nontransgenic (non-Tg) and DDAH-1-Tg mice, we compared responses of the carotid artery and aorta (in vitro) and of the cerebral arterioles (in vivo) in the absence or presence of ADMA. DDAH-1 expression and plasma levels of ADMA were also measured.


RESULTS
Western blotting indicated that vascular expression of DDAH-1 was increased markedly in DDAH-1-Tg mice. Plasma levels of ADMA were reduced by approximately 50% in DDAH-1-Tg mice compared with non-Tg mice (0.19+/-0.02 vs 0.37+/-0.04 micromol/L, P<0.05). Contraction of the aorta to nitro-l-arginine methyl ester (an inhibitor of NOS), an index of basal production of NO, was increased in DDAH-1-Tg mice compared with controls (50+/-4% vs 34+/-4%, P<0.05). Relaxation of the carotid artery to acetylcholine (an endothelium-dependent agonist) was enhanced in DDAH-1-Tg animals compared with control mice (relaxation of 74+/-6% vs 59+/-5%, respectively, in response to 10 micromol/L acetylcholine, P<0.05). ADMA (100 micromol/L) impaired the vascular response to acetylcholine in both non-Tg and DDAH-1-Tg mice, but the relative difference between the 2 strains remained. Responses to the endothelium-independent NO donor nitroprusside were similar in all groups. In vivo, ADMA (10 micromol/L) reduced responses of the cerebral arterioles to acetylcholine by approximately 70% in non-Tg mice (P<0.05), and this inhibitory effect was largely absent in DDAH-1-Tg mice.


CONCLUSIONS
These findings provide the first evidence that overexpression of DDAH-1 increases basal levels of vascular NO and protects against ADMA-induced endothelial dysfunction in the cerebral circulation.
Department of Internal Medicine, E318-2-GH, University of Iowa, Carver College of Medicine, Iowa City, IA 52242-1081, USA.
Hayan
H
Dayoub
Roman N
RN
Rodionov
Cynthia
C
Lynch
John P
JP
Cooke
Erland
E
Arning
Teodoro
T
Bottiglieri
Steven R
SR
Lentz
Frank M
FM
Faraci
D000109:Acetylcholine / Q000494:pharmacology; D000581:Amidohydrolases / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D001120:Arginine / Q000031:analogs & derivatives* / Q000378:metabolism; D001160:Arterioles / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002318:Cardiovascular Diseases / Q000378:metabolism / Q000517:prevention & control; D002339:Carotid Arteries / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009599:Nitroprusside / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D009599:Nitroprusside; D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D019001:Nitric Oxide Synthase; D000581:Amidohydrolases; C059999:dimethylargininase; D000109:Acetylcholine