title: Sustained cardioprotection afforded by A2A adenosine receptor stimulation after 72 hours of myocardial reperfusion.
abstract: This study was designed to determine whether cardioprotection afforded by A2A adenosine receptor stimulation can be sustained and to determine the effect of an A2A adenosine receptor agonist on Akt and cAMP response element binding protein (CREB) activation, as well as Hsp27 and Hsp70 protein expression in such events. The left anterior descending coronary artery was occluded for 40 minutes in anesthetized rats followed by 72 hours of reperfusion. A2A agonist (CGS21680 at 0.2 microg/kg/min) was administered for 120 minutes, starting either 5 minutes before (early) or after (late) the beginning of reperfusion. Infarct size was reduced significantly in the early compared with the control group (35.2 +/- 1.9% and 52.5 +/- 3.4%, respectively; P < 0.05), whereas no difference was observed with the late group (44.5 +/- 7.1%). After 72 hours of reperfusion, drug administration was accompanied by Akt activation (early, 121.8 +/- 17.6%; late, 118.1 +/- 16.4%; P < 0.05), as well as elevated Hsp27 expression (early, 197.2 +/- 27.7%; late, 203.8 +/- 36.8%; P < 0.05); CREB activation and Hsp70 expression were not altered. In another set of experiments in which reperfusion was limited to 15 minutes, Akt was activated only in the early group (121.8 +/- 17.6%; P < 0.05). Moreover, CREB was activated in both the early and late groups (98.4 +/- 8.3% and 107.0 +/- 6.5%, respectively; P < 0.05), whereas Hsp27 and Hsp70 expression were not altered. These results demonstrate that A2A adenosine receptor activation induces a sustained cardioprotection only if the therapy is instituted before reperfusion. This myocardial protection is associated by an early prosurvival Akt activation. CREB activation and Hsp27 content do not seem to be associated with cardioprotection because they are enhanced in both treated groups, suggesting indirect A2A agonist and pathology-related effects.
authors.affiliation: Centre de Biomédecine, Hôpital du Sacré-Coeur de Montréal, Montréal, Québec, Canada.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Boucher
authors.forename: Boubacar Pasto
authors.initials: BP
authors.lastname: Wann
authors.forename: Sevan
authors.initials: S
authors.lastname: Kaloustian
authors.forename: Rachel
authors.initials: R
authors.lastname: Massé
authors.forename: Erick
authors.initials: E
authors.lastname: Schampaert
authors.forename: René
authors.initials: R
authors.lastname: Cardinal
authors.forename: Guy
authors.initials: G
authors.lastname: Rousseau
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D058908:Adenosine A2 Receptor Agonists; D000818:Animals; D015153:Blotting, Western; D002316:Cardiotonic Agents / Q000494:pharmacology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D009203:Myocardial Infarction / Q000503:physiopathology; D017202:Myocardial Ischemia / Q000503:physiopathology; D015425:Myocardial Reperfusion; D010627:Phenethylamines / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
chemical_list: D058908:Adenosine A2 Receptor Agonists; D002316:Cardiotonic Agents; D017362:Cyclic AMP Response Element-Binding Protein; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010627:Phenethylamines; D011518:Proto-Oncogene Proteins; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D000241:Adenosine