Interleukin-1-induced prostaglandin E2 biosynthesis in human synovial cells involves the activation of cytosolic phospholipase A2 and cyclooxygenase-2.
Treatment of human synovial cells with interleukin-1 (IL-1) results in a large increase in the production of prostaglandin E2 (PGE2), a function in which the activation of phospholipase A2 (PLA2) is a key step. In order to identify the enzymes that are linked to IL-1-mediated arachidonate availability and subsequent PGE2 production, we have investigated the changes in gene expression of the 85-kDa cytosolic PLA2 (cPLA2), the 14-kDa secretory PLA2 (sPLA2) and the two forms of cyclooxygenase in human synoviocytes after stimulation with recombinant IL-1 beta. Northern-blot analysis revealed that both cPLA2 and cyclooxygenase-2 mRNA were progressively upregulated upon exposure to IL-1 for 5 hours and the glucocorticoid, dexamethasone, blocked the increased expression of these two genes. In contrast, IL-1-induced sPLA2 gene expression determined in the same cell samples was weak and most often rapid, and dexamethasone further stimulated it. In addition, IL-1 did not modify the levels of the constitutive cyclooxygenase-1. The cPLA2 and cyclooxygenase-2 enzymic activities are dependent upon de novo synthesis of mRNA and protein, since they were inhibited by actinomycin D and cycloheximide. Our data suggest that the IL-1-induced production of PGE2 in human synoviocytes can be attributed to the stimulation of both cPLA2 and cyclooxygenase-2. These enzymes may represent appropriate targets for selective blockade of prostanoid production in the inflammed joints.
INSERM U 283, Université René Descartes, Paris, France.
J
J
Angel
F
F
Berenbaum
C
C
Le Denmat
T
T
Nevalainen
J
J
Masliah
C
C
Fournier
D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis*; D004789:Enzyme Activation; D004790:Enzyme Induction; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D010741:Phospholipases A / Q000235:genetics / Q000378:metabolism*; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D013583:Synovial Membrane / Q000166:cytology / Q000378:metabolism*
D007375:Interleukin-1; D012333:RNA, Messenger; D003907:Dexamethasone; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone