Presentation: The Anti-Inflammatory Adenosine A2a Receptor (a2aR) Modulates Production of Il-10 and Il-12 Via cAMP/PKA-Dependent and Independent Pathways (2007)

156 The Anti-Inflammatory Adenosine A2a Receptor (a2aR) Modulates Production of Il-10 and Il-12 Via cAMP/PKA-Dependent and Independent Pathways

Background: We and other have demonstrated that adenosine, acting at its receptors, especially A2AR, on inflammatory and immune cells, suppresses production of various proinflammatory cytokines including IL-12, and enhances production of the anti-inflammatory cytokine IL-10. Moreover, the inflammatory cytokines IL-1 and TNF-α enhance the effects of A2AR on cytokine production. Most cellular functions of Gαs-coupled receptors, including A2AR, are mediated by the second messenger cAMP, which has been recently shown to activate both protein kinase A (PKA) and EPAC, the exchange proteins activated directly by cAMP and exchange factors for Rap proteins. This study was to elucidate which of these pathways mediates A2AR regulation of IL-10 and IL-12 production. Methods: Human monocytoid THP-1 cells were treated with TNF-α or medium alone (Control) for 4 hrs then stimulated with either CGS-21680 (selective A2AR agonist, 1 µM) or one of the two cAMP analogues, O-Me-cAMP (EPAC-selective, 100 µM), or 6-Bnz-cAMP (PKA-selective, 100 µM), and the cultures continued overnight in the presence of LPS with or without PKA inhibitor KT5720 or MEK1/2 inhibitor PD098059. The levels of IL-10 and IL-12 in the culture supernates were quantitated by standard ELISA. Results: In control THP-1 cells, both CGS-21680 and 6-Bnz-cAMP significantly increased IL-10 production (to 131±7% and 121±8% of control, respectively, p<0.05 for both) and decreased IL-12 production (to 71±8% and 69±10% of control, respectively, p<0.05 for both), whereas O-Me-cAMP decreased IL-12 production (to 81±7% of control, p<0.05) but did not affect IL-10 production. Following TNF-α treatment, the effects of CGS-21680 and the cAMP analogues were similar to their effects in control cells, except that the magnitude of the CGS-21680 effect was greater in TNF-α-treated cells (146±9% increase in IL-10 and 59±12% decrease in IL-12 by CGS-21680, p<0.01 for both). As expected, inhibition of PKA by KT5720 completely reversed the effects of 6-Bnz-cAMP but did not alter the effects of O-Me-cAMP. PKA inhibition also largely reversed the effects of CGS-21680 on IL-10 and IL-12 in TNF-α-treated cells and partly reversed these effects in control cells. Inhibition of MAPK by PD098059 slightly decreased IL-12 production in both control and TNF-α-treated cells and IL-10 production in control cells, but did not affect the capacity of either CGS-21680 or the cAMP analogues to regulate cytokine secretion. Surprisingly, in TNF-α-treated cells, MAPK inhibition markedly enhanced the effects of CGS-21680 and 6-Bnz-cAMP on IL-10 production (p<0.05 for both). Conclusions: These results suggest that A2AR regulation of IL-10 and IL-12 production is differentially mediated by both cAMP/PKA dependent and independent pathways and the TNF-α-enhanced effects of A2AR on IL-10 and IL-12 production are mostly mediated via the cAMP/PKA signaling pathway, which is further amplified by the blockage of TNF-α-mediated MAPK cascades.

 K.D. Nguyen, None; G.G. Holz, None; B.N. Cronstein, Canfite Biopharma, 1; King Pharmaceuticals, NIH, 2; CanFite Biopharma, King Pharmaceuticals, Amgen, Biogen, Endocyte, Protalex, Prometheus, Bristol-Myers Squibb, Tap Pharmaceuticals, Prometheus, Regeneron, Sepracor, Amgen, Protalex, 5; Vilcek Foundation, 6; Intellectual Property, 9.

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