bay-60-6583 and Myocardial-Infarction

Adenosine A2B receptor (A. C57BL6 (wild type [WT]) mice underwent 40 min of left coronary artery occlusion followed by 60 min of reperfusion. A. BAY 60-6583 reduced the myocardial IS in intact mice but failed to reduce the same in splenectomized mice, which had a smaller IS than intact mice. BAY 60-6583 reduced the IS in splenectomized mice with the acute transfer of WT splenic leukocytes; however, it did not protect the heart of splenectomized mice with the acute transfer of A

Topics: Adenosine A2 Receptor Agonists; Aminopyridines; Animals; Interleukin-10; Leukocytes; Mice; Mice, Inbred C57BL; Myocardial Infarction; Myocardial Reperfusion Injury; Phosphatidylinositol 3-Kinases; Proto-Oncogene Proteins c-akt; Signal Transduction; Spleen

Activation of the adenosine A2B receptor (A2BR) can reduce myocardial ischemia/reperfusion (IR) injury. However, the mechanism underlying the A2BR-mediated cardioprotection is less clear. The present study was designed to investigate the potential mechanisms of cardioprotection mediated by A2BR.. C57BL/6 mice underwent 40-minute ischemia and 60-minute reperfusion. ATL-801, a potent selective A2BR antagonist, could not block ischemic preconditioning induced protection. BAY 60-6583, a highly selective A2BR agonist, significantly reduced myocardial infarct size, and its protective effect could be blocked by either ATL-801 or wortmannin. BAY 60-6583 increased phosphorylated Akt (p-Akt) levels in the heart at 10 min of reperfusion, and this phosphorylation could also be blocked by ATL-801 or wortmannin. Furthermore, BAY 60-6583 significantly increased M2 macrophages and decreased M1 macrophage and neutrophils infiltration in reperfused hearts, which also could be blocked by wortmannin. Meanwhile, confocal imaging studies showed that the majority of Akt phosphorylation in the heart was colocalized to CD206+ cells in both control and BAY 60-6583 pretreated hearts.. Our results indicated that pretreatment with BAY 60-6583 protects the heart against myocardial IR injury by its anti-inflammatory effects, probably by modulating macrophages phenotype switching via a PI3K/Akt pathway.

Topics: Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Aminopyridines; Androstadienes; Animals; Cell Differentiation; Heart Rate; Ischemic Preconditioning, Myocardial; Macrophages; Male; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Myocardial Infarction; Myocardial Reperfusion Injury; Neutrophil Infiltration; Phosphatidylinositol 3-Kinases; Phosphorylation; Proto-Oncogene Proteins c-akt; Receptor, Adenosine A2B; Signal Transduction; Wortmannin

Pre- and postconditioning depend on the activation of adenosine receptors (ARs) at the end of the index ischemia. The aim of this study was to determine which receptor subtypes must be activated. In situ mouse hearts underwent 30 min of regional ischemia, followed by 2 h of reperfusion. As expected, either ischemic postconditioning (6 cycles of 10 s of reperfusion and 10 s of coronary occlusion) or infusion of the selective A(2b) adenosine receptor (A(2b)AR) agonist BAY60-6583 (BAY60) for 60 min, starting 5 min before reperfusion reduced infarct size in wild-type C57Bl/6N mice. Protection from either was abolished by the selective A(2b)AR antagonist MRS-1754, confirming a role for A(2b)AR. Additionally, the coadministration of ischemic postconditioning and a selective A(2a)AR antagonist led to the loss of protection as well. 5'-Ectonucleotidase (CD73) is thought to be necessary for the production of adenosine during ischemia. As predicted, ischemic postconditioning did not protect CD73 knockout mice. Selective agonists of either A(2b)AR (BAY60) or A(2a)AR (CGS-21680), as well as the coadministration of ischemic postconditioning and BAY60, also failed to protect hearts of the CD73 knockout mice. But the nonselective A(1)/A(2)AR agonist 5'-(N-ethylcarboxamido)adenosine (NECA) was protective, suggesting that the activation of multiple AR subtypes might be required. The coadministration of CGS-21680 and BAY60 also elicited profound protection, indicating that two AR subtypes, A(2a) and A(2b), must be simultaneously activated for protection to occur.

Topics: 5'-Nucleotidase; Acetamides; Adenosine; Adenosine A2 Receptor Agonists; Adenosine A2 Receptor Antagonists; Adenosine-5'-(N-ethylcarboxamide); Aminopyridines; Animals; Mice; Mice, Inbred C57BL; Mice, Knockout; Models, Animal; Myocardial Infarction; Myocardial Reperfusion Injury; Phenethylamines; Purines; Receptor, Adenosine A2A; Receptor, Adenosine A2B

Ischemic preconditioning (IPC) is a protective phenomenon in which brief ischemia renders the myocardium resistant to subsequent ischemic insults. Here, we used A(2B)AR gene knock-out (A(2B)KO)/β-galactosidase reporter gene knock-in mice and the A(2B)AR antagonist ATL-801 to investigate the potential involvement of the A(2B)AR in IPC, focusing on the acute phase of protection. Cardioprotection provided by acute IPC elicited by two 3-min occlusion/3-min reperfusion cycles was readily apparent in an isolated, Langendorff-perfused mouse heart model in studies using hearts from A(2B)KO mice. IPC equivalently improved the recovery of contractile function following 20 min of global ischemia and 45 min of reperfusion in both WT and A(2B)KO hearts by ~30-40%, and equivalently decreased the release of cardiac troponin I during the reperfusion period (from 5969 ± 925 to 1595 ± 674 ng/g and 4376 ± 739 to 2278 ± 462 ng/g using WT and A(2B)KO hearts, respectively). Similarly, the infarct size-reducing capacity of acute IPC in an in vivo model of infarction was fully manifested in experiments using A(2B)KO mice, as well as in experiments using rats pretreated with ATL-801. We did observe, however, a marked reduction in infarct size in rats following administration of the selective A(2B)AR agonist BAY 60-6583 (~25% reduction at a dose of 1.0mg/kg). While supportive of its concept as a cardioprotective receptor, these experiments indicate that the mechanism of the early phase of IPC is not dependent on signaling by the A(2B)AR. We present the idea that the A(2B)AR may contribute to the later stages of IPC dependent on the induction of stress-responsive genes.

Topics: Aminopyridines; Animals; Blood Pressure; Heart Function Tests; Heart Rate; In Vitro Techniques; Ischemic Preconditioning, Myocardial; Mice; Mice, Inbred C57BL; Myocardial Infarction; Myocardial Reperfusion Injury; Rats; Rats, Sprague-Dawley; Receptor, Adenosine A2B; Signal Transduction

Ecto-5'-nucleotidase (CD73)-dependent adenosine generation has been implicated in tissue protection during acute injury. Once generated, adenosine can activate cell-surface adenosine receptors (A1 AR, A2A AR, A2B AR, A3 AR). In the present study, we define the contribution of adenosine to cardioprotection by ischemic preconditioning.. On the basis of observations of CD73 induction by ischemic preconditioning, we found that inhibition or targeted gene deletion of cd73 abolished infarct size-limiting effects. Moreover, 5'-nucleotidase treatment reconstituted cd73-/- mice and attenuated infarct sizes in wild-type mice. Transcriptional profiling of adenosine receptors suggested a contribution of A2B AR because it was selectively induced by ischemic preconditioning. Specifically, in situ ischemic preconditioning conferred cardioprotection in A1 AR-/-, A2A AR-/-, or A3 AR-/- mice but not in A2B AR-/- mice or in wild-type mice after inhibition of the A2B AR. Moreover, A2B AR agonist treatment significantly reduced infarct sizes after ischemia.. Taken together, pharmacological and genetic evidence demonstrate the importance of CD73-dependent adenosine generation and signaling through A2B AR for cardioprotection by ischemic preconditioning and suggests 5'-nucleotidase or A2B AR agonists as therapy for myocardial ischemia.

Topics: 5'-Nucleotidase; Adenosine; Aminopyridines; Animals; Cardiotonic Agents; Cell Hypoxia; Drug Evaluation, Preclinical; Extracellular Fluid; Female; Ischemic Preconditioning, Myocardial; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Myocardial Infarction; Myocardial Ischemia; Neutrophils; Receptor, Adenosine A2B; Up-Regulation; Xanthines

Although protein kinase C (PKC) plays a key role in ischemic preconditioning (IPC), the actual mechanism of that protection is unknown. We recently found that protection from IPC requires activation of adenosine receptors during early reperfusion. We, therefore, hypothesized that PKC might act to increase the heart's sensitivity to adenosine. IPC limited infarct size in isolated rabbit hearts subjected to 30-min regional ischemia/2-h reperfusion and IPC's protection was blocked by the PKC inhibitor chelerythrine given during early reperfusion revealing involvement of PKC at reperfusion. Similarly chelerythrine infused in the early reperfusion period blocked the increased phosphorylation of the protective kinases Akt and ERK1/2 observed after IPC. Infusing phorbol 12-myristate 13-acetate (PMA), a PKC activator, during early reperfusion mimicked IPC's protection. As expected, the protection triggered by PMA at reperfusion was blocked by chelerythrine, but surprisingly it was also blocked by MRS1754, an adenosine A(2b) receptor-selective antagonist, suggesting that PKC was somehow facilitating signaling from the A(2b) receptors. NECA [5'-(N-ethylcarboxamido) adenosine], a potent but not selective A(2b) receptor agonist, increased phosphorylation of Akt and ERK1/2 in a dose-dependent manner. Pretreating hearts with PMA or brief preconditioning ischemia had no effect on phosphorylation of Akt or ERK1/2 per se but markedly lowered the threshold for NECA to induce their phosphorylation. BAY 60-6583, a highly selective A(2b) agonist, also caused phosphorylation of ERK1/2 and Akt. MRS1754 prevented phosphorylation induced by BAY 60-6583. BAY 60-6583 limited infarct size when given to ischemic hearts at reperfusion. These results suggest that activation of cardiac A(2b) receptors at reperfusion is protective, but because of the very low affinity of the receptors endogenous cardiac adenosine is unable to trigger their signaling. We propose that the key protective event in IPC occurs when PKC increases the heart's sensitivity to adenosine so that endogenous adenosine can activate A(2b)-dependent signaling.

Topics: Acetamides; Adenosine A2 Receptor Agonists; Adenosine-5'-(N-ethylcarboxamide); Alkaloids; Aminopyridines; Animals; Benzophenanthridines; Ischemic Preconditioning, Myocardial; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Myocardial Infarction; Myocardial Reperfusion Injury; Perfusion; Phosphorylation; Protein Kinase C; Purines; Rabbits; Receptor, Adenosine A2B; Signal Transduction; Tetradecanoylphorbol Acetate