The induction of cyclooxygenase-2 mRNA in macrophages is biphasic and requires both CCAAT enhancer-binding protein beta (C/EBP beta ) and C/EBP delta transcription factors.
Prostaglandins are important mediators of activated macrophage functions, and their inducible synthesis is mediated by cyclooxygenase-2 (COX-2). Here, we make use of the murine macrophage cells RAW264 as well as of immortalized macrophages derived from mice deficient for the transcription factor CCAAT enhancer-binding protein beta (C/EBP beta) to explore the molecular mechanisms regulating COX-2 induction in activated macrophages. We demonstrate that lipopolysaccharide-mediated COX-2 mRNA induction is biphasic. The initial phase is independent of de novo protein synthesis, correlates with cAMP-response element-binding protein (CREB) activation, is inhibited by treatments that abolish CREB phosphorylation and reduce NF-kappa B-mediated gene activation, and requires the presence of the transcription factor C/EBP beta. On the other hand, C/EBP delta appears to be essential in addition to C/EBP beta to effect the second phase of COX-2 gene transcription, which is important for maintaining the induced state and requires de novo protein synthesis. Indeed, both phases of COX-2 induction were defective in C/EBP beta-/- macrophages. Moreover, the synthesis of C/EBP delta was increased dramatically by treatment with lipopolysaccharide and, like COX-2 induction, repressed by combined inhibition of the MAPK and of the SAPK2/p38 cascades. Taken together, these data identify CREB, NF-kappa B, and both C/EBP beta and -delta as key factors in coordinately orchestrating transcription from the COX-2 promoter in activated macrophages.
Caivano
M
M
Medical Research Council Protein Phosphorylation Unit, University of Dundee, Dundee DD1 5EH, Scotland.
Gorgoni
B
B
Cohen
P
P
Poli
V
V
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002458:Cell Fractionation; D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D051546:Cyclooxygenase 2; D004247:DNA / Q000378:metabolism; D004790:Enzyme Induction; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008262:Macrophage Activation; D008264:Macrophages / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D051379:Mice; D008954:Models, Biological; D016328:NF-kappa B / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011451:Prostaglandin-Endoperoxide Synthases / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*
D002070:Butadienes; D022762:CCAAT-Enhancer-Binding Proteins; D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007527:Isoenzymes; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009570:Nitriles; D011725:Pyridines; D012333:RNA, Messenger; D014157:Transcription Factors; C113580:U 0126; D005576:Colforsin; D004247:DNA; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C093642:SB 203580; D015056:1-Methyl-3-isobutylxanthine