The A3 adenosine receptor agonist CP-532,903 [N6-(2,5-dichlorobenzyl)-3'-aminoadenosine-5'-N-methylcarboxamide] protects against myocardial ischemia/reperfusion injury via the sarcolemmal ATP-sensitive potassium channel.
We examined the cardioprotective profile of the new A(3) adenosine receptor (AR) agonist CP-532,903 [N(6)-(2,5-dichlorobenzyl)-3'-aminoadenosine-5'-N-methylcarboxamide] in an in vivo mouse model of infarction and an isolated heart model of global ischemia/reperfusion injury. In radioligand binding and cAMP accumulation assays using human embryonic kidney 293 cells expressing recombinant mouse ARs, CP-532,903 was found to bind with high affinity to mouse A(3)ARs (K(i) = 9.0 +/- 2.5 nM) and with high selectivity versus mouse A(1)AR (100-fold) and A(2A)ARs (1000-fold). In in vivo ischemia/reperfusion experiments, pretreating mice with 30 or 100 microg/kg CP-532,903 reduced infarct size from 59.2 +/- 2.1% of the risk region in vehicle-treated mice to 42.5 +/- 2.3 and 39.0 +/- 2.9%, respectively. Likewise, treating isolated mouse hearts with CP-532,903 (10, 30, or 100 nM) concentration dependently improved recovery of contractile function after 20 min of global ischemia and 45 min of reperfusion, including developed pressure and maximal rate of contraction/relaxation. In both models of ischemia/reperfusion injury, CP-532,903 provided no benefit in studies using mice with genetic disruption of the A(3)AR gene, A(3) knockout (KO) mice. In isolated heart studies, protection provided by CP-532,903 and ischemic preconditioning induced by three brief ischemia/reperfusion cycles were lost in Kir6.2 KO mice lacking expression of the pore-forming subunit of the sarcolemmal ATP-sensitive potassium (K(ATP)) channel. Whole-cell patch-clamp recordings provided evidence that the A(3)AR is functionally coupled to the sarcolemmal K(ATP) channel in murine cardiomyocytes. We conclude that CP-532,903 is a highly selective agonist of the mouse A(3)AR that protects against ischemia/reperfusion injury by activating sarcolemmal K(ATP) channels.
Wan
Tina C
TC
Department of Pharmacology and Toxicology, Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI 53226, USA.
Ge
Zhi-Dong
ZD
Tampo
Akihito
A
Mio
Yasushi
Y
Bienengraeber
Martin W
MW
Tracey
W Ross
WR
Gross
Garrett J
GJ
Kwok
Wai-Meng
WM
Auchampach
John A
JA
D058909:Adenosine A3 Receptor Agonists; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D005663:Furans / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006632:Histamine / Q000097:blood; D006801:Humans; D066298:In Vitro Techniques; D054086:KATP Channels / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008929:Mitochondria, Heart / Q000502:physiology; D009203:Myocardial Infarction / Q000188:drug therapy* / Q000503:physiopathology; D015428:Myocardial Reperfusion Injury / Q000503:physiopathology / Q000517:prevention & control*; D011687:Purines / Q000494:pharmacology*; D011869:Radioligand Assay; D043682:Receptor, Adenosine A1 / Q000378:metabolism; D043684:Receptor, Adenosine A3 / Q000172:deficiency / Q000502:physiology*; D012508:Sarcolemma / Q000502:physiology
D058909:Adenosine A3 Receptor Agonists; C479779:CP-532,903; D002316:Cardiotonic Agents; D005663:Furans; D054086:KATP Channels; D011687:Purines; D043682:Receptor, Adenosine A1; D043684:Receptor, Adenosine A3; D006632:Histamine; D000242:Cyclic AMP