C/EBP beta blocks p65 phosphorylation and thereby NF-kappa B-mediated transcription in TNF-tolerant cells.
TNF is a major mediator of inflammation, immunity, and apoptosis. Pre-exposure to TNF reduces sensitivity to restimulation, a phenomenon known as tolerance, considered as protective in sepsis, but also as a paradigm for immunoparalysis. Earlier experiments in TNF-tolerant cells display inhibition of NF-kappaB-dependent IL-8 gene expression at the transcriptional level with potential involvement of C/EBPbeta. In this study, we have shown that a kappaB motive was sufficient to mediate transcriptional inhibition under TNF tolerance conditions in monocytic cells. Furthermore, in tolerant cells, TNF-induced NF-kappaB p65 phosphorylation was markedly decreased, which was accompanied by the formation of C/EBPbeta-p65 complexes. Remarkably, in C/EBPbeta(-/-) cells incubated under the conditions of TNF tolerance, neither impairment of transcription nor inhibition of p65 phosphorylation was observed. Finally, we showed that C/EBPbeta overexpression reduced p65-mediated transactivation and that association of C/EBPbeta with p65 specifically prevented p65 phosphorylation. Our data demonstrate that C/EBPbeta is an essential signaling component for inhibition of NF-kappaB-mediated transcription in TNF-tolerant cells and suggest that this is caused by blockade of p65 phosphorylation. These results define a new molecular mechanism responsible for TNF tolerance in monocytic cells that may contribute to the unresponsiveness seen in patients with sepsis.
Zwergal
Andreas
A
Institute of Clinical Chemistry and Pathobiochemistry, Klinikum Rechts der Isar, Technische Universität München, Ismaninger Strasse 22, D-81675 Munich, Germany.
Quirling
Martina
M
Saugel
Bernd
B
Huth
Karin C
KC
Sydlik
Carmen
C
Poli
Valeria
V
Neumeier
Dieter
D
Ziegler-Heitbrock
H W Löms
HW
Brand
Korbinian
K
D022782:CCAAT-Enhancer-Binding Protein-beta / Q000172:deficiency / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D045744:Cell Line, Tumor; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D007108:Immune Tolerance / Q000235:genetics; D016209:Interleukin-8 / Q000037:antagonists & inhibitors / Q000235:genetics; D046912:Multiprotein Complexes / Q000378:metabolism; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology; D015534:Trans-Activators / Q000037:antagonists & inhibitors / Q000378:metabolism; D051996:Transcription Factor RelA / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014158:Transcription, Genetic / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors / Q000502:physiology*
D022782:CCAAT-Enhancer-Binding Protein-beta; D016209:Interleukin-8; D046912:Multiprotein Complexes; D016328:NF-kappa B; D021122:Protein Subunits; D015534:Trans-Activators; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha