title: Adenosine produces nitric oxide and prevents mitochondrial oxidant damage in rat cardiomyocytes.
abstract: OBJECTIVE
  To examine if adenosine prevents oxidant-induced mitochondrial dysfunction by producing nitric oxide (NO) in cardiomyocytes.
  
  
  RESULTS
  Adenosine significantly enhanced the fluorescence of DAF-FM, a dye specific for NO, implying that adenosine induces synthesis of NO. Adenosine-induced NO production was blocked by both the nonspecific NOS inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) and N(5)-(1-Iminoethyl)-l-ornithine dihydrochloride (l-NIO), an inhibitor of endothelial NOS (eNOS), but not by N(6)-(1-Iminoethyl)-l-lysine hydrochloride (l-NIL), an inhibitor of inducible NOS (iNOS), indicating that adenosine activates eNOS. Adenosine also enhances eNOS phosphorylation and its activity. The adenosine A(2) receptor antagonist 8-(3-chlorostyryl)caffeine but not the A(1) antagonist 8-cyclopentyl-1,3-dipropylxanthine prevented the increase in NO production. CGS21680, an adenosine A(2) receptor agonist, markedly increased NO, further supporting the involvement of A(2) receptors. Adenosine-induced NO production was blocked by 4-Amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo(3,4-d)pyrimidine (PP2), a selective Src tyrosine kinase inhibitor, suggesting that Src tyrosine kinase is crucial for adenosine-induced NO production. Adenosine-induced NO production was partially reversed by both wortmannin and Akt inhibitor indicating an involvement of PI3-kinase/Akt. Pretreatment of cells with adenosine prevented H(2)O(2)-induced depolarization of mitochondrial membrane potential (DeltaPsi(m)). The protective effect was blocked by l-NAME and l-NIO but not by l-NIL, indicating that eNOS plays a role in the action of adenosine. The protective effect of adenosine was further suppressed by KT5823, a specific inhibitor of protein kinase G (PKG), indicating the PKG may serve as a downstream target of adenosine.
  
  
  CONCLUSIONS
  Adenosine protects mitochondria from oxidant damage through a pathway involving A(2) receptors, eNOS, NO, PI3-kinase/Akt, and Src tyrosine kinase.
authors.affiliation: Department of Anesthesiology, CB#7010 University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7010, USA. zxu@aims.unc.edu
authors.forename: Zhelong
authors.initials: Z
authors.lastname: Xu
authors.forename: Sung-Sik
authors.initials: SS
authors.lastname: Park
authors.forename: Robert A
authors.initials: RA
authors.lastname: Mueller
authors.forename: Robert C
authors.initials: RC
authors.lastname: Bagnell
authors.forename: Cam
authors.initials: C
authors.lastname: Patterson
authors.forename: Philip G
authors.initials: PG
authors.lastname: Boysen
mesh_terms: D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D008297:Male; D018613:Microscopy, Confocal; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000502:physiology; D052250:Nitric Oxide Synthase Type III; D018384:Oxidative Stress / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D043683:Receptors, Adenosine A2 / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D043683:Receptors, Adenosine A2; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D000241:Adenosine