Interleukin‐1β and interleukin‐1α stimulate the plasminogen activator activity and prostaglandin E 2 levels of human synovial cells

Monocyte—macrophage polypeptides (monokines) cause synovial cells to increase the levels of putative mediators of destruction and inflammation. This interaction may account for some of the properties of rheumatoid pannus. We report here that samples of purified human interleukin‐1β(IL‐1β) and recombinant IL‐1β stimulate both the plasminogen activator activity and prostaglandin E 2 levels of human synovial fibroblast‐like cells. The same holds true for purified pig IL‐1 (catabolin) and recombinant murine IL‐1. The elevation in plasminogen activator activity was inhibited by indomethacin, and this suggests that endogenous prostanoids are important in the IL‐1‐mediated stimulation of proteinase activity.