Superoxide production by polymorphonuclear leucocytes in rheumatoid arthritis and osteoarthritis: in vivo inhibition by the antirheumatic drug piroxicam due to interference with the activation of the NADPH-oxidase.

The superoxide (O2-) production of stimulated polymorphonuclear leucocytes is increased in patients with rheumatoid arthritis and osteoarthritis compared with controls. Treatment of these different groups with pharmacological amounts of the non-steroidal anti-inflammatory drug piroxicam in vivo resulted in a decrease of about 25% in O2- secretion by isolated granulocytes. In vitro experiments showed that piroxicam inhibits O2- production of granulocytes by interference with the stimulation of the NADPH-oxidase. Piroxicam caused diminished O2- production of membrane fragments if it was present during the stimulation of the NADPH-oxidase of the intact cells. During the actual O2- production of the stimulated membrane fragments piroxicam had no effect. It is concluded that piroxicam is able to inhibit granulocyte O2- production by blocking the activation of NADPH-oxidase, which results in diminished tissue destruction by oxygen free radicals in inflammatory diseases.