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

1 Novel 2-prupynylcyclohexyl-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 x more potent than 2-[4-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS21680) for human AZA AR binding. Human A A 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 A:A AR agonist stimulation of human neutrophil [cyclic AMP](i), and inhibition of the neutrophil oxidative burst. ATL146e and CGS21680 were similar to equipotent agonists of human A(3) ARs. 2 We measured the effects of selective AR antagonists on agonist stimulated neutrophil [cyclic AMP](i) and the effect of PKA inhibition on A(2A) AR agonist activity. ATL193-stimulated neutrophil [cyclic AMP](i) was blocked by antagonists with the potency order: ZM241385 (A(2A)- selective)> MRS1220 (A(3)-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; A(2B)-selective) approximate to 8-(N-methylisopropyl)amino-N-6-(5'-endohydroxy-endonorbornyl)-9-mthyladenine (WRC0571; A(1)-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. 3 The data indicate that activation of A(2A)ARs inhibits neutrophil oxidative activity by activating [cyclic AMP](i)/PKA.