A2A Adenosine Receptor Induction Inhibits IFN-γ Production in Murine CD4+ T Cells

Incubation of purified C57BL/6 murine CD4(+) T lymphocytes with anti-CD3 mAb serves as a model of TCR-mediated activation and results in increased IFN-gamma production and cell surface expression of CD25 and CD69. We demonstrate here that signaling through the TCR causes a rapid (4-h) 5-fold increase in A(2A) adenosine receptor (AR) mRNA, which is correlated with a significant increase in the efficacy of A(2A)AR-mediated cAMP accumulation in these cells. A(2A)AR activation reduces TCR-mediated production of IFN-gamma by 98% with a potency order of 4-{3-[6-amino-9-(5-ethylcarbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl]prop-2-ynyl}cyclohexanecarboxylic acid methyl ester (ATL146e; EC(50) = 0.19 +/- 0.03 nM) > 4-{3-[6-amino-9-(5-cyclopropyl-carbamoyl-3,4-dihydroxytetrahydrofuran-2-yl)-9H-purin-2-yl]prop-2-ynyl}piperidine-1-carboxylic acid methyl ester (ATL313; 0.43 +/- 0.06 nM) > 5'-N-ethylcarboxamidoadenosine (3.5 +/- 0.77 nM) > 2-[4-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS21680; 7.2 +/- 1.4 nM) >> N(6)-cyclohexyladenosine (110 +/- 33 nM) > 2-chloro-N(6)-(3-iodobenzyl)-5'-N-methylcarboxamide (390 +/- 160 nM), similar to the potency order to compete for radioligand binding to the recombinant murine A(2A)AR but not the A(3)AR. The selective A(2A)AR antagonist, 4-(2-[7-amino-2-[2-furyl][1,2,4]triazolo[2,3-a][1,3,5]triazin-5-yl-amino]ethyl)phenol (ZM241385), inhibits the effect of ATL146e with a pA(2) of 0.34 nM and also inhibits the effects of N(6)-cyclohexyl-adenosine and 2-chloro-N(6)-(3-iodobenzyl)-5'-N-methylcarboxamide. In CD4(+) T cells derived from A(2A)AR(-/-) and A(2A)AR(+/-) mice, the IFN-gamma release response to ATL146e is reduced by 100 and 50%, respectively, indicative of a gene dose effect. The response of T cells to the phosphodiesterase inhibitor, 4-(3'-cyclopentyloxy-4'-methoxyphenyl)-2-pyrrolidone (rolipram), is not affected by A(2A)AR deletion. We conclude that the rapid induction of the A(2A)AR mRNA in T cells provides a mechanism for limiting T cell activation and secondary macrophage activation in inflamed tissues.