PROSTAGLANDIN E-2 PRODUCTION DEPENDENT UPON CYCLOOXYGENASE-1 AND CYCLOOXYGENASE-2 AND ITS CONTRADICTORY MODULATION BY AURANOFIN IN RAT PERITONEAL-MACROPHAGES

Rat peritoneal macrophages were incubated in the presence of cyclohexi mide or dexamethasone to inhibit the induction of cyclooxygenase (COX) -2 protein synthesis. Thereafter, when the macrophages were incubated in the presence of arachidonic acid, PGE(2) production was increased. Western blot analysis demonstrated that COX-2 protein levels were low and were not affected by arachidonic acid treatment. COX-1 protein lev els were not affected by arachidonic acid treatment either. The COX-2 inhibitors NS-398 and nimesulide only slightly inhibited PGE(2) produc tion, whereas the COX-1/COX-2 inhibitors indomethacin, piroxicam and t enoxicam strongly inhibited PGE(2) production. This suggests that unde r these conditions, PGE(2) production is dependent on COX-1. After the macrophages were treated with aspirin to inactivate existing COX-1 an d COX-2, however, treatment with 12-O-tetradecanoylphorbol13-acetate i ncreased PGE(2) production. Furthermore, COX-2 protein levels were mar kedly increased by 12-0-tetradecanoylphorbol 13-acetate treatment, whe reas COX-1 protein levels did not change. In this case, both the COX-2 and the COX-1/COX-2 inhibitors inhibited PGE(2) production. This sugg ests that under these conditions, PGE(2) production is dependent on CO X-2. Effects of auranofin on COX-1-dependent and COX-2-dependent PGE(2 ) production were examined. We found that auranofin stimulated COX-1-d ependent PGE(2) production but inhibited COX-2-dependent PGE(2) produc tion in a concentration-dependent manner. The latter effect was found to be due to the inhibition of COX-2 protein induction. These findings might explain the mechanism of the antirheumatic and antiinflammatory activities of auranofin.