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Requirement of tumor necrosis factor α and nuclear factor‐κB in the induction by IFN‐γ of inducible nitric oxide synthase in macrophages
Author(s) -
Viladel Sol Virginia,
DíazMuñoz Manuel D.,
Fresno Manuel
Publication year - 2007
Publication title -
journal of leukocyte biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.819
H-Index - 191
eISSN - 1938-3673
pISSN - 0741-5400
DOI - 10.1189/jlb.0905529
Subject(s) - biology , nitric oxide synthase , microbiology and biotechnology , tumor necrosis factor alpha , autocrine signalling , transcription factor , chromatin immunoprecipitation , cytokine , nfkb1 , nf κb , interferon , promoter , nitric oxide , gene expression , signal transduction , immunology , biochemistry , receptor , endocrinology , gene
IFN‐γ induces NO production, inducible NO synthase (iNOS) protein, and promoter expression in mouse macrophage cells. Mutation of IFN regulatory factor 1 responsive element, γ‐activated site, as well as NF‐κB elements in the murine iNOS promoter strongly reduced IFN‐γ‐induced iNOS transcriptional activity. The role of NF‐κB activation in iNOS induction by IFN‐γ was corroborated by overexpression of the NF‐κB inhibitory protein IκBα, which inhibited iNOS promoter activity induced by IFN‐γ. In addition, IFN‐γ treatment induced p65 binding to the iNOS promoter by chromatin immunoprecipitation asay and NF‐κB binding to DNA by EMSA, although with a delayed kinetics, suggesting an indirect autocrine role for another cytokine produced in response to IFN‐γ. It is interesting that we found that IFN‐γ induced TNF‐α secretion, and the induction of iNOS expression by IFN‐γ was abolished in primary peritoneal macrophages from TNF‐α‐deficient (TNF‐α −/− ) mice or in RAW 264.7 cells treated with anti‐TNF‐α neutralizing antibodies. Moreover, exogenous addition of recombinant mouse TNF‐α restored iNOS expression induced by IFN‐γ in TNF‐α −/− mice. It is intriguing that NF‐κB binding to DNA in response to IFN‐γ treatment was absent in TNF‐α −/− mice. Taken together, our data suggest that the TNF‐α produced in response to IFN‐γ is required for iNOS induction by activating NF‐κB transcription factor.