Helicobacter pylori
infection is associated with chronic
gastritis,
peptic ulcer, gastric
carcinoma, and gastric mucosa-associated lymphoid tissue
lymphomas. Apoptosis induced by microbial
infections is implicated in the pathogenesis of H. pylori
infection. Enhanced gastric epithelial cell apoptosis during H. pylori
infection was suggested to play an important role in the pathogenesis of chronic
gastritis and gastric pathology. In addition to directly triggering apoptosis, H. pylori induces sensitivity to
tumor necrosis factor-related apoptosis-inducing
ligand (TRAIL)-mediated apoptosis in gastric epithelial cells. Human gastric epithelial cells sensitized to H. pylori confer susceptibility to TRAIL-mediated apoptosis via modulation of
death-receptor signaling. The induction of TRAIL sensitivity by H. pylori is dependent upon the activation of
caspase-8 and its downstream pathway. H. pylori induces
caspase-8 activation via enhanced assembly of the TRAIL death-inducing signaling complex through downregulation of cellular
FLICE-inhibitory protein. Moreover, H. pylori
infection induces infiltration of T lymphocytes and triggers
inflammation to augment apoptosis. In H. pylori
infection, significant increases in CCR6+ CD3+ T cell infiltration in the gastric mucosa was observed, and the CCR6
ligand,
CCL20 chemokine, was selectively expressed in inflamed gastric tissues. These mechanisms initiate
chemokine-mediated T lymphocyte trafficking into inflamed epithelium and induce mucosal injury during
Helicobacter infection. This article will review recent findings on the interactions of H. pylori with host-epithelial signaling pathways and events involved in the initiation of gastric pathology, including gastric
inflammation and mucosal damage.