PROSTAGLANDIN E(2) REQUIREMENT FOR TRANSFORMING GROWTH-FACTOR BETA(1)INHIBITION OF ELICITED MACROPHAGE 14 KDA PHOSPHOLIPASE A(2) RELEASE

1 Cultured elicited-peritoneal macrophages release a soluble type II 1 4 kDa phospholipase A(2) (PLA(2)) over time, reaching a plateau by 20- 24 h of incubation and maintaining these levels over 72 h. Prostagland in E(2) (PGE(2)) is also produced but does not plateau until 48-72 h. 2 Transforming growth factor beta(1) (TGF beta(1)) reduces cellular 14 kDa PLA(2) and its subsequent release by approximately half, but does not alter PGE(2) production. Go-incubation of TGF beta(1) with indome thacin interfered, in a concentration-dependent manner, with the abili ty of TGF beta, to reduce cellular 14 kDa PLA(2) and its subsequent re lease over 24 h. The regulation of TGF beta(1) was not specific to ind omethacin since other non-steroidal anti-inflammatory drugs had the sa me effect. This suggested that cyclooxygenase activity was essential f or TGF beta(1) to exert its effect and indeed, the addition of exogeno us PGE(2) restored the TGF beta(1) action. 3 PGE(2) alone exerted a co ncentration-dependent negative feedback action on elicited-macrophage 14 kDa PLA(2) release. The inhibitory concentration (IC50 = similar to 180 ng PGE(2) ml(-1)) approximated the PGE(2) levels measured in the 24 h macrophage conditioned media (85-140 ng PGE(2) ml(-1)) where PLA( 2) release began to plateau. Further, incubation of cells with indomet hacin over 48 h resulted in the enhancement of 14 kDa PLA(2) activity compared to that released from untreated cells. Forskolin failed to in hibit 14 kDa PLA(2) release, suggesting PGE(2) was not acting through an increase in adenylate cyclase. 4 Taken together, the data are consi stent with the immunosuppressive aspects reported for both mediators d uring inflammation and demonstrates the requirement of PGE(2) for TGF beta(1) action on the elicited macrophage.