Superoxide Scavenging Activity of Leukocytes in Rheumatoid Arthritis and Behcet's Diseases

Superoxide radical anion (O_2^-) has been suggested to mediate tissue damage associated with chronic inflammatory disorders such as rheumatoid arthritis (RA) and Behcet's disease (BD). Despite that protection from O_2^- is provided by superoxide dismutase (SOD), there are controversial results about SOD-like activity of polymorhonuclear cells (PMN) in RA and there are no reports about it in BD. In addition, colchicine, a potent inhibitor of phagocytosis, has been used for the treatment of BD, no report about its effect on SOD-like activity of PMN is available. The present study investigates the superoxide scavenging activity (SSA) of PMN and mononuclear cells (MNC) in both RA and BD, and it examines the effect─of colchicine on SSA of PMN in BD using the electron paramagnetic resonance/ spin trapping method. The SSA of PMN, but not MNC, was significantly lower in patients with either RA or BD, as compared with that in healthy controls. The SSA of PMN in both RA and BD showed a strong negative correlation with erythrocyte sedimentation rates and C-reactive protein levels. Colchicine treatment increased the SSA of PMN toward normal level in BD patients, and prevented the decrease of SSA in PMN obtained from healthy adults after the stimulation with opsonized zymosan in vitro. Our results suggest that the decrease of SSA in PMN is not disease specific and it is probably the results of the increased amount of O_2^- generated by these cells. Colchicine may prevent the decrease of SSA in PMN by blocking the phagocytosis and indirectly the O_2^- generation by these cells.