title: Adenosine-mediated inhibition of platelet aggregation by acadesine. A novel antithrombotic mechanism in vitro and in vivo.
abstract: Inhibition of platelet aggregation by acadesine was evaluated both in vitro and ex vivo in human whole blood using impedance aggregometry, as well as in vivo in a canine model of platelet-dependent cyclic coronary flow reductions. In vitro, incubation of acadesine in whole blood inhibited ADP-induced platelet aggregation by 50% at 240 +/- 60 microM. Inhibition of platelet aggregation was time dependent and was prevented by the adenosine kinase inhibitor, 5'-deoxy 5-iodotubercidin, which blocked conversion of acadesine to its 5'-monophosphate, ZMP, and by adenosine deaminase. Acadesine elevated platelet cAMP in whole blood, which was also prevented by adenosine deaminase. In contrast, acadesine had no effect on ADP-induced platelet aggregation or platelet cAMP levels in platelet-rich plasma, but inhibition of aggregation was restored when isolated erythrocytes were incubated with acadesine before reconstitution with platelet-rich plasma. Acadesine (100 mg/kg i.v.) administered to human subjects also inhibited platelet aggregation ex vivo in whole blood. In the canine Folts model of platelet thrombosis, acadesine (0.5 mg/kg per min, i.v.) abolished coronary flow reductions, and this activity was prevented by pretreatment with the adenosine receptor antagonist, 8-sulphophenyltheophylline. These results demonstrate that acadesine exhibits antiplatelet activity in vitro, ex vivo, and in vivo through an adenosine-dependent mechanism. Moreover, the in vitro studies indicate that inhibition of platelet aggregation requires the presence of erythrocytes and metabolism of acadesine to acadesine monophosphate (ZMP).
authors.affiliation: Department of Cardiovascular Pharmacology, Gensia Inc., San Diego, California 92121.
authors.forename: D A
authors.initials: DA
authors.lastname: Bullough
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Montag
authors.forename: K M
authors.initials: KM
authors.lastname: Mullane
authors.forename: M A
authors.initials: MA
authors.lastname: Young
mesh_terms: D000241:Adenosine / Q000502:physiology*; D000243:Adenosine Deaminase / Q000494:pharmacology; D000248:Adenosine Kinase / Q000037:antagonists & inhibitors; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D000818:Animals; D001241:Aspirin / Q000494:pharmacology; D001790:Blood Physiological Phenomena; D003328:Coronary Thrombosis / Q000097:blood; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D004176:Dipyridamole / Q000494:pharmacology; D004195:Disease Models, Animal; D004285:Dogs; D004912:Erythrocytes / Q000187:drug effects; D006801:Humans; D008297:Male; D010949:Plasma / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects*; D058915:Purinergic P1 Receptor Antagonists; D012039:Regional Blood Flow / Q000187:drug effects; D012263:Ribonucleosides / Q000378:metabolism / Q000494:pharmacology*; D013806:Theophylline / Q000031:analogs & derivatives / Q000494:pharmacology; D014372:Tubercidin / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: C040541:5'-deoxy-5-iodotubercidin; D058915:Purinergic P1 Receptor Antagonists; D012263:Ribonucleosides; D000620:Aminoimidazole Carboxamide; C011651:acadesine; D004176:Dipyridamole; C031433:8-(4-sulfophenyl)theophylline; D013806:Theophylline; D000248:Adenosine Kinase; D000243:Adenosine Deaminase; D000241:Adenosine; D014372:Tubercidin; D001241:Aspirin