Interleukin‐1 activates phospholipase a2 IN HUMAN SYNOVIAL CELLS

Abstract

Interleukin‐1 (IL‐1) treatment of synovial cells from rheumatoid arthritis and osteoarthritis patients resulted in a dose‐dependent secretion of phospholipase A₂ (PLA₂). IL‐1 also stimulated prostaglandin E₂ and plasminogen activator synthesis, in parallel with PLA₂ activation; all 3 were detectable within 6 hours of IL‐1 treatment and peaked by 24 hours. Synovial cell PLA₂ required calcium (5 mM) and a neutral pH (7.5) for maximal activity and appears similar to the PLA₂ in synovial fluid, which has been described previously. We conclude that PLA₂ can be induced by IL‐1, and its secretion may contribute significantly to the inflammatory actions of IL‐1.