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* Pulmonary Division and
Immunology Division, Faculty of Medicine, Université de Sherbrooke, and Centre de recherche du CHUS, Sherbrooke, Québec, Canada
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/EBP
are expressed in neutrophils; most isoforms localize to the nucleus, except for C/EBP
, 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/EBPβ and C/EBP
. However, nuclear C/EBPβ 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-
B sites were mutated. Overexpression of a C/EBP repressor also impeded IL-8 promoter transactivation, as well as the generation of IL-8, Mip-1, and Mip-1β in this cellular model, whereas TNF- generation was mostly unaffected. Finally, overexpression of a C/EBPβ 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.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
A.C. designed a portion of the research, performed experiments, analyzed the data, and wrote the first draft; C.G. performed some experiments; A.A. mentored the second author; P.L. mentored the first author; C.M.D. provided conceptual input; and P.P.McD. designed the research, mentored the first author, and wrote the final version of the paper.
1 This work was supported by grants to P.P.McD. from the Canadian Arthritis Society and from the Canadian Foundation for Innovation. A.C. is the recipient of a Ph.D. Studentship from the Canadian Institutes of Health Research.
2 Address correspondence and reprint requests to Dr. Patrick P. McDonald, Pulmonary Division, Faculty of Medicine, Université de Sherbrooke, 3001, 12e avenue Nord, pièce 4849, Sherbrooke, Québec J1H 5N4, Canada. E-mail address: patrick.mcdonald{at}USherbrooke.ca
3 Abbreviations used in this paper: C/EBP, CCAAT/enhancer-binding protein; ChIP, chromatin immunoprecipitation; DFP, diisopropylfluorophosphate; dn, dominant negative.
4 The online version of this article contains supplemental material.
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  A. E. John, Y. M. Zhu, C. E. Brightling, L. Pang, and A. J. Knox Human Airway Smooth Muscle Cells from Asthmatic Individuals Have CXCL8 Hypersecretion Due to Increased NF-{kappa}B p65, C/EBP{beta}, and RNA Polymerase II Binding to the CXCL8 Promoter J. Immunol., October 1, 2009; 183(7): 4682 - 4692. [Abstract] [Full Text] [PDF]
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