Adenosine receptor-mediated coronary vascular protection in post-ischemic mouse heart

摘要

This study evaluated the ability of A(1) and A(3) adenosme receptor (AR) agonism, and A(1), A(2A), A(2B) and A(3)AR antagonism (revealing "intrinsic" responses), to modify post-ischemic coronary dysfunction in mouse heart. Vascular function was assessed before and after 20 min global ischemia and 30-45 min reperfusion in Langendorff perfused C57/B16 mouse hearts. Ischemic insult impaired coronary sensitivity to the endothelial-dependent dilators ADP (pEC(50)=6.8 +/- 0.1 vs. 7.6 +/- 0.1, non-ischemic) and acetylcholine (pEC(50)=6.1 +/- 0.1 vs 7.3 +/- 0.1 in nonischemic), and for the mixed endothelial-dependent/independent dilator 2-chloroadenosine (pEC(50)=7.5 +/- 0.1 vs. 8.4 +/- 0.1, non-ischemic). Endothelium-independent dilation in response to nitroprusside was unaltered (pEC(50)=7.0 +/- 0.1 vs. 7.1 +/- 0.1 in non-ischemic). Pre-treatment with a selective AIAR agonist (50 nM CHA) failed to modify coronary dysfunction, whereas AIAR antagonism (200 nM DPCPX) worsened the effects of I/R (2-chloroadenosine pEC(50)=6.9 +/- 0.1). Conversely, A(3)AR agonism (100 nM CI-IB-MECA) did reduce effects of I/R (pEC(50)s=8.0 +/- 0.1 and 7.3 +/- 0.1 for 2-chloroadenosine and ADP, respectively), whereas antagonism (100 nM MRS1220) was without effect. While A(2A)AR agonism could not be assessed (due to pronounced vasodilatation), A(2A)AR antagonism (100 nM SCH58261) was found to exert no effect, and antagonism of A(2B)ARs (50 nM MRS 1754) was also ineffective. The protective actions of A(3)AR agonism were also manifest as improved reactive hyperemic responses. Interestingly, post-ischemic coronary dysfunction was also limited by: Na+-H+ exchange (NHE) inhibition with 10 or 50 mu M BIIB-513 (2-chloroadenosine pEC(50)s=7.8 +/- 0.1, either dose), an effect not additive with A(3)AR agonism; Ca2+ antagonism with 0.3 mu M verapamil (2-chloroadenosine pEC(50)=7.9 +/- 0.1); and Ca2+ desensitization with 5 mM BDM (2-chloroadenosine pEC(50)=7.8 +/- 0.1). In contrast, endothelin antagonism (200 nM PD142893) and anti-oxidant therapy (300 mu M MPG+150 U/ml SOD+600 U/ml catalase) were ineffective. Our data collectively confirm that ischemia selectively impairs endothelial function and reactive hyperemia independently of blood cells. Vascular injury is intrinsically limited by endogenous (but not exogenous) activation of A(1)ARs, whereas exogenous A3AR activation further limits dysfunction (improving post-ischemic vasoregulation). Finally, findings suggest this form of postischemic coronary injury is unrelated to endothelin or oxidant stress, but may involve modulation of Ca2+ overload and/or related ionic perturbations. (c) 2005 Elsevier Inc. All rights reserved.