P0877 HELICOBACTER PEPTIDOGLYCAN INDUCES NOD1-DEPENDENT PRO-INFLAMMATORY ACTIVATION

Abstract

Introduction:Helicobacter pylori that harbor the cag pathogenicity island (cag PAI) induce NFkappaB activation and IL-8 synthesis in gastric epithelial cells and are responsible for the most severe inflammatory gastric lesions in humans. Since the intracellular receptor NOD1/CARD4 detects Gram-negative bacterial peptidoglycan, we studied the role of NOD1 in mediating the inflammatory response during H. pylori infection. Methods: Epithelial HEK293 cells were transfected with an NFkappaB-dependent luciferase reporter gene plus a NOD1 dominant negative construct or vector control. NFkappaB activation was determined after co-culture with different H. pylori strains or after intracellular delivery of bacterial compounds. IL-8 was measured by ELISA in infected gastric epithelial cells (AGS). The cellular distribution of H. pylori peptidoglycan was analyzed in AGS cells that were co-cultured with functional or non-functional cag PAI H. pylori in which the peptidoglycan had been tritium labeled. NOD1-/- and +/+ mice were infected by different Helicobacter strains and the bacterial loads were determined after 7 and 30 days post-infection. Results: Our results demonstrate that a functional cag PAI was necessary for H. pylori to activate NFkappaB and IL-8 synthesis in epithelial cells. A functionnal cag PAI was required for the translocation of peptidoglycan to the host cells. The transfec-tion of dominant negative NOD1 in HEK293 cells reduced NFkap-paB activation during H. pylori infection. Finally, NOD1 −/− mice were more sensitive to cag PAI-positive-H. pylori infection compared to wild-type controls. Conclusion: In conclusion, our findings suggest that H. pylori uses its cag PAI encoded secretion system to translocate peptidoglycan inside gastric epithelial cells where it can interact with NOD1 and thereby induce inflammatory signaling through NFkappaB activation. NOD1 is an intracellular receptor involved in the inflammatory response induced during the H. pylori infection and could hence participate in the ability of epithelial cells to differentiate between commensal flora and pathogens.