TY - JOUR
T1 - The Induction of Cyclooxygenase-2 mRNA in Macrophages Is Biphasic and Requires both CCAAT Enhancer-binding protein β (C/EBPβ) and C/EBPδ Transcription Factors
AU - Caivano, Matilde
AU - Gorgoni, Barbara
AU - Cohen, Philip
AU - Poli, Valeria
PY - 2001/12/28
Y1 - 2001/12/28
N2 - 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 β (C/EBPβ) 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-κB-mediated gene activation, and requires the presence of the transcription factor C/EBPβ. On the other hand, C/EBPδ appears to be essential in addition to C/EBPβ 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/EBPβ-/- macrophages. Moreover, the synthesis of C/EBPδ 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-κB, and both C/EBPβ and -δ as key factors in coordinately orchestrating transcription from the COX-2 promoter in activated macrophages.
AB - 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 β (C/EBPβ) 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-κB-mediated gene activation, and requires the presence of the transcription factor C/EBPβ. On the other hand, C/EBPδ appears to be essential in addition to C/EBPβ 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/EBPβ-/- macrophages. Moreover, the synthesis of C/EBPδ 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-κB, and both C/EBPβ and -δ as key factors in coordinately orchestrating transcription from the COX-2 promoter in activated macrophages.
UR - http://www.scopus.com/inward/record.url?scp=0035966082&partnerID=8YFLogxK
U2 - 10.1074/jbc.M108282200
DO - 10.1074/jbc.M108282200
M3 - Article
C2 - 11668179
AN - SCOPUS:0035966082
SN - 0021-9258
VL - 276
SP - 48693
EP - 48701
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 52
ER -