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J Leukoc Biol. 2008 Dec;84(6):1585-93. doi: 10.1189/jlb.0508304. Epub 2008 Sep 17.

Induction of iNOS by Chlamydophila pneumoniae requires MyD88-dependent activation of JNK.

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Institut für Medizinische Mikrobiologie, Immunologie und Hygiene, Technische Universität München, München, Germany.


Innate immune cells produce NO via inducible NO synthase (iNOS) in response to certain infections or upon stimulation with cytokines such as IFN-gamma and TNF. NO plays an important role in host defense against intracellular bacteria including Chlamydophila pneumoniae as a result of its microbicidal activity. In MyD88-deficient mice, which succumb to C. pneumoniae infection, iNOS induction is impaired 6 days postinfection, although pulmonary levels of IFN-gamma and TNF are elevated as in wild-type mice at this time-point. Here, we demonstrate that induction of iNOS in macrophages upon C. pneumoniae infection is controlled by MyD88 via two pathways: NF-kappaB activation and phosphorylation of the MAPK JNK, which leads to the nuclear translocation of c-Jun, one of the two components of the AP-1 complex. In addition, phosphorylation of STAT1 and expression of IFN regulatory factor 1 (IRF-1) were delayed in the absence of MyD88 after C. pneumoniae infection but not after IFN-gamma stimulation. Taken together, our data show that for optimal induction of iNOS during C. pneumoniae infection, the concerted action of the MyD88-dependent transcription factors NF-kappaB and AP-1 and of the MyD88-independent transcription factors phosphorylated STAT1 and IRF-1 is required.

[Indexed for MEDLINE]

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