Functional expression of adenosine A2A and A3 receptors in the mouse dendritic cell line XS-106

There is increasing evidence to suggest that adenosine receptors can modulate the function of cells involved in the immune system. For example, human dendritic cells derived from blood monocytes have recently been described to express functional adenosine A 1 , A 2A and A 3 receptors. Therefore, in the present study, we have investigated whether the recently established murine dendritic cell line XS-106 expresses functional adenosine receptors. The selective adenosine A 3 receptor agonist 1-[2-chloro-6[[(3-iodophenyl)methyl]amino]-9 H -purin-9-yl]-1-deoxy- N -methyl-β- d -ribofuranuronamide (2-Cl-IB-MECA) inhibited forskolin-mediated [ 3 H]cyclic AMP accumulation and stimulated concentration-dependent increases in p42/p44 mitogen-activated protein kinase (MAPK) phosphorylation. The selective adenosine A 2A receptor agonist 4-[2-[[-6-amino-9-( N -ethyl-β- d -ribofuranuronamidosyl)-9 H -purin-2-yl]amino]ethyl]benzene-propanoic acid (CGS 21680) stimulated a robust increase in [ 3 H]cyclic AMP accumulation and p42/p44 MAPK phosphorylation. In contrast, the selective adenosine A 1 receptor agonist CPA ( N 6 -cyclopentyladenosine) did not inhibit forskolin-mediated [ 3 H]cyclic AMP accumulation or stimulate increases in p42/p44 MAPK phosphorylation. These observations suggest that XS-106 cells express functional adenosine A 2A and A 3 receptors. The non-selective adenosine receptor agonist 5′- N -ethylcarboxamidoadenosine (NECA) inhibited lipopolysaccharide-induced tumour necrosis factor-α (TNF-α) release from XS-106 cells in a concentration-dependent fashion. Furthermore, treatment with Cl-IB-MECA (1 μM) or CGS 21680 (1 μM) alone produced a partial inhibition of lipopolysaccharide-induced TNF-α release (when compared to NECA), whereas a combination of both agonists resulted in the inhibition of TNF-α release comparable to that observed with NECA alone. Treatment of cells with the adenosine A 2A receptor selective antagonists 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3- a ][1,3,5]triazin-5ylamino]ethyl)phenol (ZM 241385; 100 nM) and 5-amino-2-(2-furyl)-7-phenylethyl-pyrazolo[4,3- e ]-1,2,4-triazolo[1,5 c ]pyrimidine (SCH 58261; 100 nM) and the adenosine A 3 receptor selective antagonist N -[9-chloro-2-(2-furanyl)[1,2,4]-triazolo[1,5- c ]quinazolin-5-benzeneacetamide (MRS 1220; 100 nM) partially blocked the inhibitory effects of NECA on lipopolysaccharide-induced TNF-α release. Combined addition of MRS 1220 and SCH 58261 completely blocked the inhibitory effects of NECA on lipopolysaccharide-induced TNF-α release. In conclusion, we have shown that the mouse dendritic cell line XS-106 expresses functional adenosine A 2A and A 3 receptors, which are capable of modulating TNF-α release.