title: The innate immune molecule, NOD1, regulates direct killing of Helicobacter pylori by antimicrobial peptides.
abstract: The cytosolic innate immune molecule, NOD1, recognizes peptidoglycan (PG) delivered to epithelial cells via the Helicobacter pylori cag pathogenicity island (cagPAI), and has been implicated in host defence against cagPAI(+)H. pylori bacteria. To further clarify the role of NOD1 in host defence, we investigated NOD1-dependent regulation of human beta-defensins (DEFBs) in two epithelial cell lines. Our findings identify that NOD1 activation, via either cagPAI(+) bacteria or internalized PG, was required for DEFB4 and DEFB103 expression in HEK293 cells. To investigate cell type-specific induction of DEFB4 and DEFB103, we generated stable NOD1'knockdown' (KD) and control AGS cells. Reporter gene assay and RT-PCR analyses revealed that only DEFB4 was induced in an NOD1-/cagPAI-dependent fashion in AGS cells. Moreover, culture supernatants from AGS control, but not AGS NOD1 KD cells, stimulated with cagPAI(+)H. pylori, significantly reduced H. pylori bacterial numbers. siRNA studies confirmed that human beta-defensin 2 (hBD-2), but not hBD-3, contributes to the antimicrobial activity of AGS cell supernatants against H. pylori. This study demonstrates, for the first time, the involvement of NOD1 and hBD-2 in direct killing of H. pylori bacteria by epithelial cells and confirms the importance of NOD1 in host defence mechanisms against cagPAI(+)H. pylori infection.
authors.affiliation: Department of Microbiology, Monash University, Clayton, Victoria, Australia.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Grubman
authors.forename: Maria
authors.initials: M
authors.lastname: Kaparakis
authors.forename: Jérôme
authors.initials: J
authors.lastname: Viala
authors.forename: Cody
authors.initials: C
authors.lastname: Allison
authors.forename: Luminita
authors.initials: L
authors.lastname: Badea
authors.forename: Abdulgader
authors.initials: A
authors.lastname: Karrar
authors.forename: Ivo G
authors.initials: IG
authors.lastname: Boneca
authors.forename: Lionel
authors.initials: L
authors.lastname: Le Bourhis
authors.forename: Shane
authors.initials: S
authors.lastname: Reeve
authors.forename: Ian A
authors.initials: IA
authors.lastname: Smith
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Hartland
authors.forename: Dana J
authors.initials: DJ
authors.lastname: Philpott
authors.forename: Richard L
authors.initials: RL
authors.lastname: Ferrero
mesh_terms: D002460:Cell Line; D004847:Epithelial Cells / Q000276:immunology*; D055785:Gene Knockdown Techniques; D016480:Helicobacter pylori / Q000276:immunology*; D006801:Humans; D050296:Microbial Viability; D053474:Nod1 Signaling Adaptor Protein / Q000235:genetics / Q000276:immunology*; D010457:Peptidoglycan / Q000276:immunology; D023083:beta-Defensins / Q000096:biosynthesis / Q000276:immunology*
chemical_list: C106641:DEFB4A protein, human; C119067:NOD1 protein, human; D053474:Nod1 Signaling Adaptor Protein; D010457:Peptidoglycan; D023083:beta-Defensins