Asymmetric dimethyl L-arginine (ADMA) is a critical regulator of myocardial reperfusion injury.
OBJECTIVE
Endothelial dysfunction by the loss of nitric oxide (NO) is a critical event during reperfusion of ischemic myocardium. Reduced NO availability signals important pathophysiological changes leading to myocardial reperfusion injury. We have recently shown that NO biosynthesis can be disturbed by the endogenous NO synthase (NOS) inhibitor ADMA and that these changes are mediated by an impairment of its metabolism by dimethylarginine dimethylaminohydrolase (DDAH). We therefore analyzed the role of ADMA and its metabolism in the setting of myocardial ischemia and reperfusion.


METHODS
C57-bl6 mice underwent myocardial ischemia for exactly 30 min followed by 2, 4, 8, 12, 24, and 72 h of reperfusion achieved by occlusion and re-opening of the left coronary artery. The reperfused left ventricle was subsequently homogenized for measurements of determinants of the NO synthase pathway. Furthermore, the effects and its mechanisms of ADMA on reperfusion injury were analyzed in a genetic mouse model.


RESULTS
A significant accumulation of ADMA was found in myocardial tissue when mice were subjected to 30 min of ischemia followed by reperfusion in our in vivo model. The maximum increase of tissue ADMA at 4 h of reperfusion coincided with reductions of NO tissue concentrations and DDAH activity; protein expression of NOS isoforms, however, was not changed. Furthermore, DDAH overexpression in a genetic mouse model as well as treatment with oral L-arginine markedly reduced reperfusion injury by 40-50% at 4 h of reperfusion. The effects of ADMA on reperfusion injury were shown to be mediated by reduced eNOS activity and phosphorylation, expression of adhesion molecules, and leukocyte activity.


CONCLUSIONS
Accumulation of tissue ADMA by impairment of DDAH was found to be a significant determinant of reperfusion injury. Our results indicate that ADMA could be a potential new target for the treatment of myocardial ischemia/reperfusion injury.
Stühlinger
Markus C
MC
Department of Cardiology, Medical University of Innsbruck, 6020 Innsbruck, Austria. markus.stuehlinger@uki.at
Conci
Elisabetta
E
Haubner
Bernhard J
BJ
Stocker
Eva-Maria
EM
Schwaighofer
Julia
J
Cooke
John P
JP
Tsao
Philip S
PS
Pachinger
Otmar
O
Metzler
Bernhard
B
D000581:Amidohydrolases / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D015153:Blotting, Western / Q000379:methods; D004730:Endothelium, Vascular / Q000737:chemistry / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D017202:Myocardial Ischemia / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D009195:Peroxidase / Q000032:analysis / Q000378:metabolism
D009569:Nitric Oxide; C018524:N,N-dimethylarginine; D001120:Arginine; D009195:Peroxidase; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D000581:Amidohydrolases; C059999:dimethylargininase