title: The infarct-sparing effect of IB-MECA against myocardial ischemia/reperfusion injury in mice is mediated by sequential activation of adenosine A3 and A 2A receptors.
abstract: Conflicting results exist regarding the role of A3 adenosine receptors (A3ARs) in mediating cardioprotection during reperfusion following myocardial infarction. We hypothesized that the effects of the A3AR agonist IB-MECA to produce cardioprotection might involve activation of other adenosine receptor subtypes. C57Bl/6 (B6), A3AR KO, A2AAR KO, and A2AAR KO/WT bone marrow chimeric mice were assigned to 12 groups undergoing either hemodynamic studies or 45 min of LAD occlusion and 60 min of reperfusion. IB-MECA (100 μg/kg) or vehicle was administered by iv bolus 5 min before reperfusion. Radioligand binding assays showed that IB-MECA has high affinity for the mouse A3AR (K i = 0.17 ± 0.05 nM), but also can bind with lower affinity to the A1AR (9.0 ± 2.4 nM) or the A2AAR (56.5 ± 10.2 nM). IB-MECA caused bi-phasic hemodynamic changes, which were completely absent in A3AR KO mice and were modified by A2AAR blockade or deletion. IB-MECA stimulated histamine release, increased heart rate, and significantly reduced IF size in B6 mice from 61.5 ± 1.4 to 48.6 ± 2.4% of risk region (RR; 21% reduction, p < 0.05) but not in A3AR KO mice. Compared to B6, A3AR KO mice had significantly reduced IF size (p < 0.05). In B6/B6 bone marrow chimeras, IB-MECA caused a 47% reduction of IF size (from 47.3 ± 3.9 to 24.7 ± 4.5, p < 0.05). However, no significant cardioprotective effect of IB-MECA was observed in A2AARKO/B6 mice, which lacked A2AARs only on their bone marrow-derived cells. Activation of A3ARs induces a bi-phasic hemodynamic response, which is partially mediated by activation of A2AARs. The cardioprotective effect of IB-MECA is due to the initial activation of A3AR followed by activation of A2AARs in bone marrow-derived cells.
authors.affiliation: Departments of Surgery, University of Virginia Health System, Box 800709, Charlottesville, VA, 22908, USA.
authors.forename: Yikui
authors.initials: Y
authors.lastname: Tian
authors.forename: Melissa
authors.initials: M
authors.lastname: Marshall
authors.forename: Brent A
authors.initials: BA
authors.lastname: French
authors.forename: Joel
authors.initials: J
authors.lastname: Linden
authors.forename: Zequan
authors.initials: Z
authors.lastname: Yang
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D006439:Hemodynamics / Q000187:drug effects; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000378:metabolism*; D015428:Myocardial Reperfusion Injury / Q000378:metabolism*; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D043684:Receptor, Adenosine A3 / Q000378:metabolism*
chemical_list: D043705:Receptor, Adenosine A2A; D043684:Receptor, Adenosine A3; C084956:N(6)-(3-iodobenzyl)-5'-N-methylcarboxamidoadenosine; D000241:Adenosine