Cyclic AMP‐dependent inhibition of human neutrophil oxidative activity by substituted 2‐propynylcyclohexyl adenosine A2A receptor agonists

Novel 2‐propynylcyclohexyl‐5′‐N‐ehtylcarboxamidoadenosines, trans‐substituted in the 4‐position of the cyclohexyl ring, were evaluated in binding assays to the four subtypes of adenosine receptors (ARs). Two esters, 4‐{3‐[6‐amino‐9‐(5‐ethylcarbamoyl‐3,4‐dihydroxy‐tetrahydro‐furan‐2‐yl)‐9H‐purin‐2‐yl]‐prop‐2‐ynyl}‐cyclohexanecarboxylic acid methyl ester (ATL146e) and acetic acid 4‐{3‐[6‐amino‐9‐(5‐ethylcarbamoyl‐3, 4‐dihydroxy‐tetrahydro‐furan ‐2‐yl)‐9H‐purin‐2‐yl] ‐prop‐2‐ynyl}‐cyclohexylmethyl ester (ATL193) were >50×more potent than 2‐[4‐(2‐carboxyethyl)phenethylamino]‐5′‐N‐ethylcarboxamidoadenosine (CGS21680) for human A2A AR binding. Human A2A AR affinity for substituted cyclohexyl‐propynyladenosine analogues was inversely correlated with the polarity of the cyclohexyl side chain. There was a comparable order of potency for A2A AR agonist stimulation of human neutrophil [cyclic AMP]i, and inhibition of the neutrophil oxidative burst. ATL146e and CGS21680 were ∼equipotent agonists of human A3 ARs. We measured the effects of selective AR antagonists on agonist stimulated neutrophil [cyclic AMP]i and the effect of PKA inhibition on A2A AR agonist activity. ATL193‐stimulated neutrophil [cyclic AMP]i was blocked by antagonists with the potency order: ZM241385 (A2A‐selective)>MRS1220 (A3‐selective)>>N‐(4‐Cyano‐phenyl)‐2‐[4‐(2,6‐dioxo‐1,3‐dipropyl‐2,3,4,5,6,7‐hexahydro‐1H‐purin‐8‐yl)‐phenoxy]‐acetamide (MRS1754; A2B‐selective) ∼amp; 8‐(N‐methylisopropyl)amino‐N6‐(5′‐endohydroxy‐endonorbornyl)‐9‐methyladenine (WRC0571; A1‐selective). The type IV phosphodiesterase inhibitor, rolipram (100 nM) potentiated ATL193 inhibition of the oxidative burst, and inhibition by ATL193 was counteracted by the PKA inhibitor H‐89. The data indicate that activation of A2AARs inhibits neutrophil oxidative activity by activating [cyclic AMP]i/PKA. British Journal of Pharmacology (2001) 132, 1017–1026; doi:10.1038/sj.bjp.0703893