The innate immune molecule, NOD1, regulates direct killing of Helicobacter pylori by antimicrobial peptides.
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.
Grubman
Alexandra
A
Department of Microbiology, Monash University, Clayton, Victoria, Australia.
Kaparakis
Maria
M
Viala
Jérôme
J
Allison
Cody
C
Badea
Luminita
L
Karrar
Abdulgader
A
Boneca
Ivo G
IG
Le Bourhis
Lionel
L
Reeve
Shane
S
Smith
Ian A
IA
Hartland
Elizabeth L
EL
Philpott
Dana J
DJ
Ferrero
Richard L
RL
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*
C106641:DEFB4A protein, human; C119067:NOD1 protein, human; D053474:Nod1 Signaling Adaptor Protein; D010457:Peptidoglycan; D023083:beta-Defensins