title: N6-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide confers cardioprotection at reperfusion by inhibiting mitochondrial permeability transition pore opening via glycogen synthase kinase 3 beta.
abstract: Although the adenosine A(3) receptor agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methylcarboxamide (IB-MECA) has been reported to be cardioprotective at reperfusion, little is known about the mechanisms underlying the protection. We hypothesized that IB-MECA may protect the heart at reperfusion by preventing the opening of mitochondrial permeability transition pore (mPTP) through inactivation of glycogen synthase kinase (GSK) 3beta. IB-MECA (1 microM) applied during reperfusion reduced infarct size in isolated rat hearts, an effect that was abrogated by the selective A3 receptor antagonist 1,4-dihydro-2-methyl-6-phenyl-4-(phenylethynyl)-3,5-pyridinedicarboxylic acid 3-ethyl-5-[(3-nitrophenyl)-methyl]ester (MRS1334) (100 nM). The effect of IB-MECA was abrogated by the mPTP opener atractyloside (20 microM), implying that the action of IB-MECA may be mediated by inhibition of the mPTP opening. In cardiomyocytes, IB-MECA attenuated oxidant-induced loss of mitochondrial membrane potential (DeltaPsim), which was reversed by MRS1334. IB-MECA also reduced Ca2+-induced mitochondrial swelling. IB-MECA enhanced phosphorylation of GSK-3beta (Ser9) upon reperfusion, and the GSK-3 inhibitor 3-(2,4-dichlorophenyl)-4-(1-methyl-1H-indol-3-yl)-1H-pyrrole-2,5-dione (SB216763) (3 microM) mimicked the protective effect of IB-MECA by attenuating both infarction and the loss of DeltaPsim. In addition, the effect of IB-MECA on GSK-3beta was reversed by wortmannin (100 nM), and IB-MECA was shown to enhance Akt phosphorylation upon reperfusion. In contrast, rapamycin (2 nM) failed to affect GSK-3beta phosphorylation by IB-MECA, and IB-MECA did not alter phosphorylation of either mTOR (Ser2448) or 70s6K (Thr389). Taken together, these data suggest that IB-MECA prevents myocardial reperfusion injury by inhibiting the mPTP opening through the inactivation of GSK-3beta at reperfusion. IB-MECA-induced GSK-3beta inhibition is mediated by the PI3-kinase/Akt signal pathway but not by the mTOR/p70s6K pathway.
authors.affiliation: Department of Anesthesiology, CB 7010, University of North Carolina, Chapel Hill, NC 27599, USA.
authors.forename: Sung-Sik
authors.initials: SS
authors.lastname: Park
authors.forename: Hong
authors.initials: H
authors.lastname: Zhao
authors.forename: Yeongho
authors.initials: Y
authors.lastname: Jang
authors.forename: Robert A
authors.initials: RA
authors.lastname: Mueller
authors.forename: Zhelong
authors.initials: Z
authors.lastname: Xu
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology / Q000627:therapeutic use*; D038362:Glycogen Synthase Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D008297:Male; D033681:Mitochondrial Membrane Transport Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000201:enzymology / Q000517:prevention & control*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002316:Cardiotonic Agents; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3; D000241:Adenosine