title: An accessory role for ceramide in interleukin-1beta induced prostaglandin synthesis.
abstract: Interleukin-1beta (IL-1) is a potent inducer of prostaglandin E2 (PGE2) synthesis. We previously showed that ceramide accumulates in fibroblasts treated with IL-1 and that it enhances IL-1-induced PGE2 production. The present study was undertaken to determine the mechanism(s) by which ceramide and IL-1 interact to enhance PGE2 production by examining their respective effects on the rate-limiting enzymes in PGE2 synthesis, cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and cytosolic phospholipase A2 (cPLA2). IL-1-induced PGE2 synthesis required approximately 8 h even though COX-1 was constitutively expressed (both mRNA and protein) and enzymatically active in untreated cells. Conversely, COX-2 mRNA was barely detectable in untreated cells but within 2 h, ceramide or IL-1 alone induced a 5 and 20 fold increase in COX-2 mRNA, respectively. However, IL-1 induced COX-2 protein synthesis was only detectable 6-7 h after maximal COX-2 mRNA induction; COX-2 protein accumulation was not induced by ceramide alone. Ceramide however, reduced the length of time required for IL-1 to induce COX-2 protein accumulation and increased COX-2 protein accumulation. IL-1 induced a 15 fold increase in COX-1 mRNA including an alternatively spliced form of COX-1. IL-1, but not ceramide induced cPLA2 mRNA and protein expression which corresponded with the initiation of PGE2 synthesis. These observations indicate that, (1) while either ceramide or IL-1 rapidly induced COX-2 mRNA, COX-2 protein only accumulated in IL-1 treated cells after a delay of 6-7 h, (2) IL-1-induced PGE2 synthesis required both COX-2 and cPLA2 protein synthesis and, (3) ceramide enhanced (temporally and quantitatively) IL-1-induced COX-2 protein
authors.affiliation: Department of Medicine, College of Medicine, The University of Tennessee, Memphis, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kirtikara
authors.forename: S J
authors.initials: SJ
authors.lastname: Laulederkind
authors.forename: R
authors.initials: R
authors.lastname: Raghow
authors.forename: T
authors.initials: T
authors.lastname: Kanekura
authors.forename: L R
authors.initials: LR
authors.lastname: Ballou
mesh_terms: D017398:Alternative Splicing; D016718:Arachidonic Acid / Q000494:pharmacology; D002478:Cells, Cultured; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D015232:Dinoprostone / Q000096:biosynthesis*; D005347:Fibroblasts; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D007527:Isoenzymes / Q000096:biosynthesis / Q000235:genetics; D008565:Membrane Proteins; D010741:Phospholipases A / Q000096:biosynthesis / Q000235:genetics; D054467:Phospholipases A2; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis / Q000235:genetics; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D007375:Interleukin-1; D007527:Isoenzymes; D008565:Membrane Proteins; C064769:N-acetylsphingosine; D016718:Arachidonic Acid; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; C496511:PTGS1 protein, human; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D015232:Dinoprostone; D013110:Sphingosine