Nod1 imprints inflammatory and carcinogenic responses toward the gastric pathogen Helicobacter pylori

Helicobacter pylori is the strongest known risk for gastric cancer. The H. pylori cag type IV secretion system is an oncogenic locus which translocates peptidoglycan into host cells where it is recognized by NOD1, an innate immune receptor. Beyond this, the role of NOD1 in H. pylori-induced cancer remains undefined. To address this knowledge gap, we infected two genetic models of Nod1 deficiency with the H. pylori cag+ strain PMSS1: C57BL/6 mice which rarely develop cancer, and INS-GAS FVB/N mice which commonly develop cancer. Infected C57BL/6Nod1-/- and INS-GASNod1-/- mice acutely developed more severe gastritis, and INS-GASNod1-/- mice developed gastric dysplasia more frequently compared to Nod1+/+ mice. Because Nod1 genotype status did not alter microbial phenotypes of in vivo-adapted H. pylori, we investigated host immunological responses. H. pylori infection of Nod1-/- mice led to significantly increased gastric mucosal levels of Th1, Th17, and Th2 cytokines compared to Nod1 wild-type mice. To define the role of specific innate immune cells, we quantified cytokine secretion from H. pylori-infected primary gastric organoids generated from WT or Nod1-/- mice, that were co-cultured with or without WT or Nod1-/- macrophages. Infection increased cytokine production from gastric epithelial cells and macrophages and elevations were significantly increased with Nod1 deficiency. Further, H. pylori infection altered the polarization status of Nod1-/- macrophages compared to Nod1+/+ macrophages. Collectively, these studies demonstrate that loss of Nod1 augments inflammatory and injury responses to H. pylori. Nod1 may exert its restrictive role by altering macrophage polarization, leading to immune evasion and microbial persistence.

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