Inflammatory cytokine production by human neutrophils involves C/EBP transcription factors.
A growing number of neutrophil-derived cytokines have proven to be crucial to various inflammatory and immune processes in vivo. Whereas C/EBP (CCAAT/enhancer-binding protein) transcription factors are important for neutrophil differentiation from myeloid precursors, we report herein that they also regulate cytokine production in mature neutrophils. All known C/EBP proteins but C/EBPgamma are expressed in neutrophils; most isoforms localize to the nucleus, except for C/EBPalpha, which is cytoplasmic. Neutrophil stimulation does not alter the overall levels, cellular distribution, or turnover of C/EBP proteins; it also does not further induce the constitutive DNA-binding activity detected in nuclear extracts, consisting of C/EBPbeta and C/EBPepsilon. However, nuclear C/EBPbeta is rapidly phosphorylated upon cell stimulation, suggesting that it can activate cytokine promoters. Indeed, the transactivation of an IL-8 promoter-luciferase construct in a human neutrophil-like cell line was impaired when its C/EBP or NF-kappaB sites were mutated. Overexpression of a C/EBP repressor also impeded IL-8 promoter transactivation, as well as the generation of IL-8, Mip-1alpha, and Mip-1beta in this cellular model, whereas TNF-alpha generation was mostly unaffected. Finally, overexpression of a C/EBPbeta mutant (T235A) as well as chromatin immunoprecipitation assays unveiled an important role for this residue in cytokine induction. This is the first demonstration that C/EBP factors are important regulators of cytokine expression in human neutrophils.
Cloutier
Alexandre
A
Pulmonary Division, Faculty of Medicine, Université de Sherbrooke, and Centre de recherche du CHUS, Sherbrooke, Québec, Canada.
Guindi
Chantal
C
Larivée
Pierre
P
Dubois
Claire M
CM
Amrani
Abdelaziz
A
McDonald
Patrick P
PP
D000818:Animals; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D016466:CHO Cells; D002454:Cell Differentiation / Q000276:immunology; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D016207:Cytokines / Q000096:biosynthesis*; D005786:Gene Expression Regulation / Q000276:immunology; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism; D009504:Neutrophils / Q000276:immunology* / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000276:immunology; D011485:Protein Binding / Q000276:immunology; D015533:Transcriptional Activation / Q000276:immunology
D022782:CCAAT-Enhancer-Binding Protein-beta; D022762:CCAAT-Enhancer-Binding Proteins; D002843:Chromatin; D016207:Cytokines; D018836:Inflammation Mediators; D016209:Interleukin-8; C070790:CEBPE protein, human