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Glutamate‐gated N‐methyl‐D‐aspartate (NMDA) channels are the mechanistic link between ammonia and epithelial cell cytotoxicity in Helicobacter pylori infection
Author(s) -
Seo Ji Hye,
Fox James G,
Hagen Susan J
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1122.3
Subject(s) - viability assay , microbiology and biotechnology , intracellular , helicobacter pylori , apoptosis , membrane potential , chemistry , programmed cell death , biology , biochemistry , genetics
Background Ammonia (A), a cytotoxin liberated by Helicobacter pylori , is thought to play an important role in cancer development by affecting cell death mechanisms. Our aim was to determine how A is cytotoxic to gastric epithelial cells. Methods Live gastric epithelial cells were used to examine, by microscopy, changes in intracellular Ca 2+ , mitochondrial membrane potential, and the simultaneous localization of numerous organelle markers in the presence of A with or without specific cellular pathway inhibitors. Biochemical assays were used to quantify cell viability, ATP, protease activation, and the expression of pro‐apoptotic proteins. Results A dose‐dependently induced Ca 2+ influx that was dependent on cAMP. A‐induced Ca 2+ influx reduced mitochondrial membrane potential and ATP, increased cell death effectors, and activated proteases that overall reduced the viability of gastric epithelial cells. The effects of A could be blocked completely by chelating Ca 2+ or by blocking NMDA channels, which are Ca 2+ influx channels, with highly specific antagonists. Conclusions Our results are the first to identify NMDA channel activity in epithelial cells, particularly in GI epithelial cells. Our data strongly support that NMDA channels regulate gastric cell viability in the presence of A, rather than other proposed mechanisms including A‐induced changes in intracellular pH. Supported by NIH DK‐015681.