title: Toll-like receptor 9 signaling has anti-inflammatory effects on the early phase of Helicobacter pylori-induced gastritis.
abstract: Helicobacter pylori (H. pylori)-induced immune responses in the gastric mucosa are skewed toward T helper (Th) 1 phenotype, which is characterized by predominant production of tumor necrosis factor (TNF)-α and interferon (IFN)-γ by helper T cells. Toll-like receptors (TLRs) play an essential role in mucosal defense against microbes through the recognition of bacterial molecules. Among the members of the TLR family, TLR9 recognizes bacterial unmethylated CpG DNA sites, and signal transduction of TLR9 induces production of a variety of cytokines, including type-I IFN (IFN-α/β). We investigated the expression and role of TLR9 in H. pylori-induced gastritis in mice. Expression of TLR9 mRNA in the gastric tissue increased after infection with H. pylori. TLR9 was mainly expressed in the macrophages, dendritic cells, and CD3(+) cells in the gastric mucosa. Neutrophil infiltration and the expression levels of TNF-α and IFN-γ mRNA were higher in TLR9 knockout (KO) mice than in wild-type mice at 2 and 4 months after H. pylori inoculation. These differences in inflammatory parameters between H. pylori-infected wild-type and TLR9 KO mice disappeared 6 months after H. pylori inoculation. Expression of interleukin-4 mRNA, typical Th2 cytokine, in the gastric tissue did not differ between H. pylori-infected wild-type and TLR9 KO mice. Expression level of IFN-α/β mRNA in the TLR9 KO mice was lower than that in wild-type mice by 4 months after inoculation. Administration of IFN-α reduced H. pylori infection-induced increase in neutrophil infiltration and the expression levels of TNF-α and IFN-γ mRNA in TLR9 KO mice. Our findings suggest that TLR9 signaling plays important roles in the suppression of H. pylori-induced gastritis in the early phase via downregulation of Th1-type cytokines modulated by IFN-α.
authors.affiliation: Department of Gastroenterology, Osaka City University Graduate School of Medicine, 1-4-3 Asahimachi, Osaka 545-8585, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Otani
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Tanigawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Watanabe
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nadatani
authors.forename: Mitsue
authors.initials: M
authors.lastname: Sogawa
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Yamagami
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Shiba
authors.forename: Kenji
authors.initials: K
authors.lastname: Watanabe
authors.forename: Kazunari
authors.initials: K
authors.lastname: Tominaga
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Fujiwara
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Arakawa
mesh_terms: D000818:Animals; D005756:Gastritis / Q000188:drug therapy / Q000276:immunology* / Q000382:microbiology*; D016481:Helicobacter Infections / Q000188:drug therapy / Q000276:immunology*; D016480:Helicobacter pylori; D007370:Interferon Type I / Q000096:biosynthesis; D016898:Interferon-alpha / Q000008:administration & dosage; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015398:Signal Transduction; D018417:Th1 Cells / Q000187:drug effects / Q000276:immunology; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*
chemical_list: D007370:Interferon Type I; D016898:Interferon-alpha; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9