title: A novel pharmacological approach to treating cardiac ischemia. Binary conjugates of A1 and A3 adenosine receptor agonists.
abstract: Adenosine released during cardiac ischemia exerts a potent, protective effect in the heart via activation of A(1) or A(3) receptors. However, the interaction between the two cardioprotective adenosine receptors and the question of which receptor is the more important anti-ischemic receptor remain largely unexplored. The objective of this study was to test the hypothesis that activation of both receptors exerted a cardioprotective effect that was significantly greater than activation of either receptor individually. This was accomplished by using a novel design in which new binary conjugates of adenosine A(1) and A(3) receptor agonists were synthesized and tested in a novel cardiac myocyte model of adenosine-elicited cardioprotection. Binary drugs having mixed selectivity for both A(1) and A(3) receptors were created through the covalent linking of functionalized congeners of adenosine agonists, each being selective for either the A(1) or A(3) receptor subtype. MRS 1740 and MRS 1741, thiourea-linked, regioisomers of a binary conjugate, were highly potent and selective in radioligand binding assays for A(1) and A(3) receptors (K(i) values of 0.7-3.5 nm) versus A(2A) receptors. The myocyte models utilized cultured chick embryo cells, either ventricular cells expressing native adenosine A(1) and A(3) receptors, or engineered atrial cells, in which either human A(3) receptors alone or both human A(1) and A(3) receptors were expressed. The binary agonist MRS 1741 coactivated A(1) and A(3) receptors simultaneously, with full cardioprotection (EC(50) approximately 0.1 nm) dependent on expression of both receptors. Thus, co-activation of both adenosine A(1) and A(3) receptors by the binary A(1)/A(3) agonists represents a novel general cardioprotective approach for the treatment of myocardial ischemia.
authors.affiliation: Molecular Recognition Section, Laboratory of Bioorganic Chemistry, NIDDK, National Institutes of Health, Bethesda, Maryland 20892, USA. kajacobs@helix.nih.gov
authors.forename: K A
authors.initials: KA
authors.lastname: Jacobson
authors.forename: R
authors.initials: R
authors.lastname: Xie
authors.forename: L
authors.initials: L
authors.lastname: Young
authors.forename: L
authors.initials: L
authors.lastname: Chang
authors.forename: B T
authors.initials: BT
authors.lastname: Liang
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002317:Cardiovascular Agents / Q000494:pharmacology*; D015687:Cell Hypoxia; D002478:Cells, Cultured; D002642:Chick Embryo; D015195:Drug Design; D006325:Heart Atria / Q000166:cytology; D006352:Heart Ventricles / Q000166:cytology; D006801:Humans; D017202:Myocardial Ischemia / Q000378:metabolism*; D058906:Purinergic P1 Receptor Agonists; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1 / Q000235:genetics; D011994:Recombinant Proteins / Q000819:agonists; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D002317:Cardiovascular Agents; C414621:MRS 1740; C414622:MRS 1741; D058906:Purinergic P1 Receptor Agonists; D043684:Receptor, Adenosine A3; D018047:Receptors, Purinergic P1; D011994:Recombinant Proteins; D013890:Thiourea; D000241:Adenosine