title: Intracellular bacteria recognition contributes to maximal interleukin (IL)-12 production by IL-10-deficient macrophages.
abstract: Interleukin (IL)-12 is a key factor that induces T helper cell type 1-mediated immunity and inflammatory diseases. In some colitis models, such as IL-10 knock-out (KO) mice, IL-12 triggers intestinal inflammation. An abundant amount of IL-12 is produced by intestinal macrophages in response to stimulation by commensal bacteria in IL-10 KO mice. Intact bacteria are more potent inducers of macrophage IL-12 production than cell surface components in this model. This suggested that cell surface receptor signalling and intracellular pathogen recognition mechanisms are important for the induction of IL-12. We addressed the importance of intracellular recognition mechanisms and demonstrated that signal transducers and activator of transcription 1 (STAT1) signalling activated bacterial phagocytosis and was involved in the induction of abnormal IL-12 production. In IL-10 KO mouse bone marrow-derived (BM) macrophages, Escherichia coli stimulation induced increased IL-12p70 production compared to lipopolysaccharide combined with interferon (IFN)-γ treatment. Significant repression of IL-12 production was achieved by inhibition of phagocytosis with cytochalasin D, and inhibition of de novo protein synthesis with cycloheximide. Induction of IFN regulatory factors-1 and -8, downstream molecules of STAT1 and the key transcription factors for IK-12 transcription, following E. coli stimulation, were mediated by phagocytosis. Interestingly, STAT1 was activated after stimulation with E. coli in IL-10 KO BM macrophages, although IFN-γ could not be detected. These data suggest that molecules other than IFN-γ are involved in hyper-production mechanisms of IL-12 induced by E. coli stimulation. In conclusion, enteric bacteria stimulate excessive IL-12p70 production in IL-10 KO BM macrophages via phagocytosis-dependent signalling.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Naruse
authors.forename: T
authors.initials: T
authors.lastname: Hisamatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Yamauchi
authors.forename: J E
authors.initials: JE
authors.lastname: Chang
authors.forename: K
authors.initials: K
authors.lastname: Matsuoka
authors.forename: M T
authors.initials: MT
authors.lastname: Kitazume
authors.forename: K
authors.initials: K
authors.lastname: Arai
authors.forename: S
authors.initials: S
authors.lastname: Ando
authors.forename: T
authors.initials: T
authors.lastname: Kanai
authors.forename: N
authors.initials: N
authors.lastname: Kamada
authors.forename: T
authors.initials: T
authors.lastname: Hibi
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001854:Bone Marrow Cells / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D002478:Cells, Cultured; D004926:Escherichia coli / Q000276:immunology* / Q000502:physiology; D054884:Host-Pathogen Interactions / Q000276:immunology; D007371:Interferon-gamma / Q000494:pharmacology; D016753:Interleukin-10 / Q000172:deficiency* / Q000235:genetics; D018664:Interleukin-12 / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010587:Phagocytosis / Q000276:immunology; D010766:Phosphorylation / Q000187:drug effects; D014176:Protein Biosynthesis / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050794:STAT1 Transcription Factor / Q000276:immunology / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology
chemical_list: D008070:Lipopolysaccharides; D050794:STAT1 Transcription Factor; D016753:Interleukin-10; D018664:Interleukin-12; D007371:Interferon-gamma