Rheumatoid arthritis synovial fluid phospholipase A2 activating protein (PLAP) stimulates human neutrophil degranulation and superoxide ion production.

Rheumatoid arthritis is characterized by excessive eicosanoid production, and phospholipase enzymes are the rate limiting step in eicosanoid synthesis. We have shown previously that cells from patients with rheumatoid arthritis express enhanced phospholipase A2 enzyme activities. Recently, we have isolated a phospholipase A2 activating protein termed PLAP from rheumatoid synovial fluid. This novel human protein shares biochemical and antigenic similarities with melittin, a bee venom phospholipase activating protein. Because melittin has been shown to induce neutrophil degranulation and superoxide formation, and because exuberent release of lysosomal enzymes and superoxide have been implicated in the pathogenesis of rheumatoid arthritis, we examined the role of PLAP on inducing these neutrophil functions.