Role of protease-activated receptor-2 on cell death and DNA fragmentation in Helicobacter pylori-infected gastric epithelial cells

ABSTRACT Helicobacter pylori infection is associated with altered gastric epithelial cell turnover. To evaluate the role of oxidative stress in cell death, gastric epithelial cells were exposed to various strains of H. pylori, inflammatory cytokines, and hydrogen peroxide in the absence or presence of antioxidant agents. Increased intracellular reactive oxygen species (ROS) were detected using a redox-sensitive fluorescent dye, a cytochrome c reduction assay, and measurements of glutathione. Apoptosis was evaluated by detecting DNA fragmentation and caspase activation. Infection with H. pylori or exposure of epithelial cells to hydrogen peroxide resulted in apoptosis and a dose-dependent increase in ROS generation that was enhanced by pretreatment with inflammatory cytokines. Basal levels of ROS were greater in epithelial cells isolated from gastric mucosal biopsy specimens from H. pylori-infected subjects than in cells from uninfected individuals. H. pylori strains bearing the cag pathogenicity island (PAI) induced higher levels of intracellular oxygen metabolites than isogenic cag PAI-deficient mutants. H. pylori infection and hydrogen peroxide exposure resulted in similar patterns of caspase 3 and 8 activation. Antioxidants inhibited both ROS generation and DNA fragmentation by H. pylori. These results indicate that bacterial factors and the host inflammatory response confer oxidative stress to the gastric epithelium during H. pylori infection that may lead to apoptosis.

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Helicobacter pylori Induces Gastric Epithelial Cell Apoptosis in Association with Increased Fas Receptor Expression

Infection and Immunity ◽

10.1128/iai.67.8.4237-4242.1999 ◽

1999 ◽

Vol 67 (8) ◽

pp. 4237-4242 ◽

Cited By ~ 106

Author(s):

Nicola L. Jones ◽

Andrew S. Day ◽

Hilary A. Jennings ◽

Philip M. Sherman

Keyword(s):

Cell Death ◽

Helicobacter Pylori ◽

Epithelial Cells ◽

Receptor Expression ◽

Gastric Epithelial Cells ◽

Ags Cells ◽

Fas Receptor ◽

Epithelial Cell Apoptosis ◽

H Pylori

ABSTRACT The mechanisms involved in mediating the enhanced gastric epithelial cell apoptosis observed during infection withHelicobacter pylori in vivo are unknown. To determine whether H. pylori directly induces apoptosis of gastric epithelial cells in vitro and to define the role of the Fas-Fas ligand signal transduction cascade, human gastric epithelial cells were infected with H. pylori for up to 72 h under microaerophilic conditions. As assessed by both transmission electron microscopy and fluorescence microscopy, incubation with acagA-positive, cagE-positive, VacA-positive clinical H. pylori isolate stimulated an increase in apoptosis compared to the apoptosis of untreated AGS cells (16.0% ± 2.8% versus 5.9% ± 1.4%, P < 0.05) after 72 h. In contrast, apoptosis was not detected following infection withcagA-negative, cagE-negative, VacA-negative clinical isolates or a Campylobacter jejuni strain. In addition to stimulating apoptosis, infection with H. pylorienhanced Fas receptor expression in AGS cells to a degree comparable to that of treatment with a positive control, gamma interferon (12.5 ng/ml) (148% ± 24% and 167% ± 24% of control, respectively). The enhanced Fas receptor expression was associated with increased sensitivity to Fas-mediated cell death. Ligation of the Fas receptor with an agonistic monoclonal antibody resulted in an increase in apoptosis compared to the apoptosis of cells infected with the bacterium alone (38.5% ± 7.1% versus 16.0% ± 2.8%,P < 0.05). Incubation with neutralizing anti-Fas antibody did not prevent apoptosis of H. pylori-infected cells. Taken together, these findings demonstrate that the gastric pathogen H. pylori stimulates apoptosis of gastric epithelial cells in vitro in association with the enhanced expression of the Fas receptor. These data indicate a role for Fas-mediated signaling in the programmed cell death that occurs in response toH. pylori infection.

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Up-Regulation of Inducible Nitric Oxide Synthase and Nitric Oxide in Helicobacter pylori-Infected Human Gastric Epithelial Cells: Possible Role of Interferon-gamma in Polarized Nitric Oxide Secretion

Helicobacter ◽

10.1046/j.1083-4389.2002.00068.x ◽

2002 ◽

Vol 7 (2) ◽

pp. 116-128 ◽

Cited By ~ 29

Author(s):

Jung Mogg Kim ◽

Joo Sung Kim ◽

Hyun Chae Jung ◽

In Sung Song ◽

Chung Yong Kim

Keyword(s):

Nitric Oxide ◽

Helicobacter Pylori ◽

Nitric Oxide Synthase ◽

Epithelial Cells ◽

Interferon Gamma ◽

Inducible Nitric Oxide Synthase ◽

Gastric Epithelial Cells ◽

Oxide Synthase ◽

Inducible Nitric Oxide

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Role of glutamine and arginase in protection against ammonia-induced cell death in gastric epithelial cells

AJP Gastrointestinal and Liver Physiology ◽

10.1152/ajpgi.00235.2002 ◽

2002 ◽

Vol 283 (6) ◽

pp. G1264-G1275 ◽

Cited By ~ 26

Author(s):

Eiji Nakamura ◽

Susan J. Hagen

Keyword(s):

Cell Death ◽

Epithelial Cells ◽

Ammonium Chloride ◽

Gastric Epithelial Cells ◽

Cytotoxic Factor ◽

Ammonia Detoxification ◽

Dose Dependent Increase ◽

Dose Dependent ◽

Detoxification Pathways

Ammonia is a cytotoxic factor produced during Helicobacter pylori infection that may reduce the survival of surface epithelial cells. Here we examine whether ammonia kills cells and whether l-glutamine (l-Gln) protects against cell death by stimulating ammonia detoxification pathways. Cell viability and vacuolation were quantified in rat gastric epithelial (RGM1) cells incubated with ammonium chloride at pH 7.4 in the presence or absence of l-Gln. Incubation of RGM1 cells with ammonium chloride caused a dose-dependent increase in cell death and vacuolation, which were both inhibited byl-Gln. We show that RGM1 cells metabolize ammonia to urea via arginase, a process that is stimulated by l-Gln and results in reduced ammonia cytotoxicity. l-Gln also inhibits the uptake and facilitates the extrusion of ammonia from cells. Blockade of glutamine synthetase did not reduce the survival of RGM1 cells, demonstrating that the conversion ofl-glutamate and ammonia to l-Gln is not involved in ammonia detoxification. Thus our data support a role forl-Gln and arginase in protection against ammonia-induced cell death in gastric epithelial cells.

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