INTERLEUKIN-1-BETA INDUCES CYTOSOLIC PHOSPHOLIPASE A(2) AND PROSTAGLANDIN-H SYNTHASE IN RHEUMATOID SYNOVIAL FIBROBLASTS - EVIDENCE FOR THEIR ROLES IN THE PRODUCTION OF PROSTAGLANDIN E(2)

Objective. In order to investigate potential regulatory mechanisms for the increased production of prostaglandin E(2) (PGE(2)) in interleuki n-1 beta (IL-1 beta)-stimulated rheumatoid synovial fibroblasts (RSF), this study examined the induction of phospholipase A(2) (PLA(2)) and prostaglandin H synthase (PGHS) enzymes and the correlation of these e vents with PGE(2) production in IL-1 beta-stimulated RSF. Methods. Pro tein and messenger RNA (mRNA) levels of cytosolic PLA(2) (cPLA(2)) and PGHS-2 enzymes in IL-1 beta-stimulated RSF were measured by Western a nd Northern blotting, respectively, using specific antisera and comple mentary DNA probes. Enzymatic activity of cPLA(2) was determined in ce ll-free reaction mixtures utilizing mixed micelles of C-14-phosphatidy lcholine and Triton X-100 as the substrate. PGE(2) levels were quantit ated using a commercial enzyme immunoassay kit. Results. Incubation of RSF with IL-1 beta increased the mRNA and protein levels for the high molecular weight cPLA(2) as well as for the mitogen/growth factor-res ponsive PGHS (PGHS-2). The IL-1 receptor antagonist completely abolish ed the induction of these two enzymes and the stimulation of PGE, prod uction by IL-1 beta in RSF. In contrast, levels of the other known for ms of these enzymes, i.e., the 14-kd secretory group II PLA(2) (sPLA(2 )) and the constitutive form of PGHS (PGHS-1), were unaffected by IL-1 beta treatment. Conclusion. These are the first data to demonstrate t he coordinate induction by IL-1 of cPLA(2) and PGHS-2 in RSF. The time -course for the induction of these enzymes suggests that their increas e contributes to the increased production of PGE, in IL-1-treated RSF, and may help explain the capacity of RSF to produce large amounts of PGE(2).