The acute antiinflammatory effects of methotrexate are mediated, at least in part, by increased extracellular adenosine concentrations at inflamed sites. This observation suggests that other agents that increase extracellular adenosine concentrations might also reduce inflammation. Since adenosine can be rapidly taken up by cells, phosphorylated by adenosine kinase, and maintained intracellularly as adenine nucleotides, we investigated whether a potent inhibitor of adenosine kinase, GP-1-515, could increase exudate adenosine concentration and thereby diminish inflammation in the murine air pouch model of inflammation.
Methods. We studied the effect of various oral doses of GP-1-515 on carrageenan-induced inflammation in air pouches induced on BALB/c mice. Adenosine concentration in pouch exudates was determined by high performance liquid chromatography, and intensity of inflammation was determined by leukocyte counts in the exudate fluid.
Results. There was a greater concentration of adenosine in the pouch exudates of animals treated with GP-1-515 than of those treated with saline (P < 0.002). GP-1-515 inhibited, in a dose-dependent manner (P < 0.01), leukocyte accumulation in the murine air pouch in response to carrageenan. Inhibition of inflammation by GP-1-515 in this model depended upon increased adenosine concentration in the inflamed pouch since injection of adenosine deaminase into the air pouch with the carrageenan completely reversed the antiinflammatory effects of GP-1-515 at all doses of GP-1-515 tested.