Polyglutamation of antifolates is not required for induction of extracellular release of adenosine or expression of their anti-inflammatory effects

Methotrexate (MTX) exerts an anti-inflammatory effect, reportedly by enhanc ing the release of adenosine, through an accumulation of 5-amino-3-imidazol ecarboxamide ribonucleotide (AICAR). To examine the role of polyglutamation in promoting anti-inflammatory effects by antifolates, we tested whether a new antifolate designed to be resistant to intracellular polyglutamation ( MX-68) exhibited anti-inflammatory effects and stimulated adenosine release . Both MX-68 and MTX (at concentrations greater than 0.1 mu M) increased th e release of adenosine from Daudi cells in vitro. Inhibition of AICAR synth esis suppressed adenosine release by MX-68 and MTX. The anti-inflammatory e ffects of antifolates were estimated using the murine air pouch model, in w hich a BALB/c mouse was intraperitoneally injected with MX-68 or MTX once a week fur 3 weeks, MX-68 (0.5 me, kg(-1) week-1), as well as MTX, inhibited infiltration of leukocytes into the air pouch. This inhibitory effect was suppressed in the presence of an adenosine A, receptor antagonist, 3,7-dime thyl-1-propargylxanthine (DMPX), These results suggest that MX-68, like MTX , exerts anti-inflammatory effects through the accumulation of AICAR and re lease of adenosine, These results suggest that polyglutamation of antifolat e is not required for expression of anti-inflammatory effects. (C) 2000 Els evier Science B.V. All rights reserved.