title: Transcriptional inhibition of interleukin-8 expression in tumor necrosis factor-tolerant cells: evidence for involvement of C/EBP beta.
abstract: There is some evidence that the potent cytokine tumor necrosis factor (TNF) is able to induce tolerance after repeated stimulation of cells. To investigate the molecular mechanisms mediating this phenomenon, the expression of interleukin-8 (IL-8), which is regulated by transcription factors NF-kappaB and C/EBPbeta, was monitored under TNF tolerance conditions. Pretreatment of monocytic cells for 72 h with low TNF doses inhibited TNF-induced (restimulation with a high dose) IL-8 promoter-dependent transcription as well as IL-8 production. Under these conditions neither activation of NF-kappaB nor IkappaB proteolysis was affected after TNF re-stimulation, albeit a slightly reduced IkappaB-alpha level was found in the TNF pretreated but not re-stimulated sample. Remarkably, in tolerant cells an increased binding of C/EBPbeta to its IL-8 promoter-specific DNA motif as well as an elevated association of C/EBPbeta protein with p65-containing NF-kappaB complexes was observed. Finally, overexpression of C/EBPbeta, but not p65 or Oct-1, markedly prevented TNF-induced IL-8 promoter-dependent transcription. Taken together, these data indicate that the expression of IL-8 is inhibited at the transcriptional level in TNF-tolerant cells and C/EBPbeta is involved under these conditions in mediating the negative-regulatory effects, a mechanism that may play a role in inflammatory processes such as sepsis.
authors.affiliation: Institute of Clinical Chemistry and Pathobiochemistry, Klinikum rechts der Isar, Technische Universität, 81675 München, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Weber
authors.forename: Carmen
authors.initials: C
authors.lastname: Sydlik
authors.forename: Martina
authors.initials: M
authors.lastname: Quirling
authors.forename: Caroline
authors.initials: C
authors.lastname: Nothdurfter
authors.forename: Andreas
authors.initials: A
authors.lastname: Zwergal
authors.forename: Peter
authors.initials: P
authors.lastname: Heiss
authors.forename: Susanne
authors.initials: S
authors.lastname: Bell
authors.forename: Dieter
authors.initials: D
authors.lastname: Neumeier
authors.forename: H W Loms
authors.initials: HW
authors.lastname: Ziegler-Heitbrock
authors.forename: Korbinian
authors.initials: K
authors.lastname: Brand
mesh_terms: D022762:CCAAT-Enhancer-Binding Proteins / Q000502:physiology; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000502:physiology; D004361:Drug Tolerance / Q000235:genetics; D051863:Host Cell Factor C1; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000235:genetics; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D016328:NF-kappa B / Q000502:physiology; D050811:Octamer Transcription Factor-1; D011401:Promoter Regions, Genetic / Q000187:drug effects; D014157:Transcription Factors / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; D004268:DNA-Binding Proteins; C497692:HCFC1 protein, human; D051863:Host Cell Factor C1; D016209:Interleukin-8; D016328:NF-kappa B; D050811:Octamer Transcription Factor-1; C494165:POU2F1 protein, human; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha