Triggering of peritoneal macrophages with IFN-alpha/beta attenuates the expression of inducible nitric oxide synthase through a decrease in NF-kappaB activation.
Triggering peritoneal macrophages with IFN-gamma and a low concentration of LPS induced the expression of the inducible form of nitric oxide synthase (iNOS). This process was significantly inhibited when IFN-alpha/beta was added during the initial 2 h after the start of IFN-gamma/LPS activation. Evaluation of the transcriptional activity using run-on assays indicated that IFN-alpha/beta inhibited the transcription of iNOS. Transfection experiments using a 1.7-kb promoter sequence corresponding to the 5' flanking region of the murine iNOS gene showed decreased promoter activity in the presence of type I IFNs. Analysis of the transcription factors that participate in iNOS expression revealed a marked decrease of NF-kappaB activation, a nuclear factor required for the transcription of this gene. The degradation of IkappaB alpha and IkappaB beta, which is required for the translocation of NF-kappaB to the nucleus, was inhibited in the presence of IFN-alpha/beta. However, the activity of other transcription factors such as IFN regulatory factor 1, which is involved in the expression of iNOS in response to IFN-gamma, was not affected by IFN-alpha/beta stimulation. These results suggest that in the presence of IFN-alpha/beta, the activity of the iNOS promoter is impaired, and this attenuated nitric oxide synthase expression could be important in pathophysiologic situations in which secretion of type I IFNs occurs.
López-Collazo
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E
Instituto de Bioquímica (Centro Mixto Consejo Superior de Investigaciones Cientificas-Universidad Compluteuse de Madrid), Facultad de Farmacia, Spain.
Hortelano
S
S
Rojas
A
A
Boscá
L
L
D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D016898:Interferon-alpha / Q000494:pharmacology*; D016899:Interferon-beta / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D017737:Macrophages, Peritoneal / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis* / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D011401:Promoter Regions, Genetic
D016898:Interferon-alpha; D008070:Lipopolysaccharides; D016328:NF-kappa B; D016899:Interferon-beta; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse