Pharmacologic characterization of novel adenosine A2A receptor agonists in equine neutrophils.
OBJECTIVE
To evaluate anti-inflammatory effects of several novel adenosine receptor agonists and to determine their specificity for various adenosine receptor subtypes on neutrophils, cells heterologously expressing equine adenosine receptors, or equine brain membranes.


METHODS
Neutrophils isolated from 8 healthy horses.


METHODS
Radioligand binding experiments were performed to compare binding affinities of adenosine receptor agonists to equine adenosine A(1), A(2A), and A(3) receptor subtypes. Effects of these agonists on endotoxin-induced production of reactive oxygen species (ROS) by equine neutrophils and roles of specific adenosine receptor subtypes and cAMP production in mediating these effects were determined.


RESULTS
Radioligand binding experiments yielded a ranked order of affinity for the brain equine A(2A) receptor on the basis of 50% inhibitory concentrations (IC(50)) of the agonists as follows: ATL307 (IC(50) = 1.9nM) and ATL313 > ATL309 and ATL310 > ATL202 > 2-([p-2- carboxyethyl] phenylethylamino)-5'-N-ethylcarboxyamidoadenosine > 5'-N-ethylcarboxamidoadenosine. Furthermore, ATL313 had approximately 100-fold greater selectivity for A(2A) over A(1) and A(3) receptors. In functional assays with equine neutrophils, the compounds inhibited endotoxin-induced ROS production and stimulated production of cAMP with the same ranked order of potency. Results of experiments performed with selective adenosine receptor antagonists indicated that functional effects of ATL313 were via stimulation of A(2A) receptors.


CONCLUSIONS
Results indicated that activation of A(2A) receptors exerted anti-inflammatory effects on equine neutrophils and that stable, highly selective adenosine A(2A) receptor agonists may be developed for use in management of horses and other domestic animals with septic and nonseptic inflammatory diseases.
Sun
Wan-chun
WC
Department of Large Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA.
Moore
James N
JN
Hurley
David J
DJ
Vandenplas
Michel L
ML
Linden
Joel M
JM
Murray
Thomas F
TF
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D058908:Adenosine A2 Receptor Agonists; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D001667:Binding, Competitive; D000242:Cyclic AMP / Q000276:immunology; D006736:Horses / Q000276:immunology*; D020128:Inhibitory Concentration 50; D007700:Kinetics; D008070:Lipopolysaccharides / Q000276:immunology; D009504:Neutrophils / Q000187:drug effects* / Q000276:immunology; D010627:Phenethylamines / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011869:Radioligand Assay / Q000662:veterinary; D017382:Reactive Oxygen Species / Q000276:immunology; D043705:Receptor, Adenosine A2A / Q000276:immunology / Q000378:metabolism; D014970:Xanthines / Q000494:pharmacology
C510376:ATL 313; D058908:Adenosine A2 Receptor Agonists; D008070:Lipopolysaccharides; D010627:Phenethylamines; D010880:Piperidines; D017382:Reactive Oxygen Species; D043705:Receptor, Adenosine A2A; D014970:Xanthines; C061282:2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine; D019830:Adenosine-5'-(N-ethylcarboxamide); C051360:1,3-dipropyl-8-cyclopentylxanthine; C089722:N(6)-(4-amino-3-iodobenzyl)adenosine-5'-N-methyluronamide; D000242:Cyclic AMP; D000241:Adenosine