Ammonia-induced apoptosis is accelerated at higher pH in gastric surface mucous cells.
Gastric luminal ammonia produced by Helicobacter pylori has been shown to cause gastric mucosal injury. This study was conducted to examine the mechanisms by which gastric luminal ammonia causes apoptosis of gastric epithelial cells. Monolayers of GSM06 cells, developed from murine gastric surface mucous cells, were cultured in the absence or presence of 10-30 mM NH(4)Cl at ambient pH of 5.0, 6.0, and 7.0. In the presence of luminal NH(4)Cl, GSM06 cells showed 1) cell shrinkage and nuclear chromatin condensation, 2) DNA fragmentation into oligonucleosomes, 3) leakage of cytochrome c into cytosolic fraction without affecting bax expression, and 4) increases in activity of caspases-3 and -9. These changes were accentuated when the cells were cultured at pH 7.0. In the absence of NH(4)Cl, none of these changes was detected at any pH examined. These results suggest that gastric luminal ammonia, at concentrations detected in H. pylori-infected subjects, induces apoptosis of gastric epithelial cells by release of cytochrome c from mitochondria, followed by activation of caspases-9 and -3, especially at higher ambient pH.
Suzuki
Hideo
H
Department of Gastroenterology, Institute of Clinical Medicine, University of Tsukuba, Ibaraki 305-8575, Japan.
Yanaka
Akinori
A
Shibahara
Takeshi
T
Matsui
Hirofumi
H
Nakahara
Akira
A
Tanaka
Naomi
N
Muto
Hiroshi
H
Momoi
Takashi
T
Uchiyama
Yasuo
Y
D000641:Ammonia / Q000494:pharmacology*; D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D048429:Cell Size; D002470:Cell Survival / Q000187:drug effects; D002843:Chromatin / Q000648:ultrastructure; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D017097:Electric Impedance; D005753:Gastric Mucosa / Q000502:physiology* / Q000648:ultrastructure*; D016480:Helicobacter pylori / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D020287:In Situ Nick-End Labeling; D051379:Mice; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D008928:Mitochondria / Q000378:metabolism
D002843:Chromatin; D003574:Cytochrome c Group; D000643:Ammonium Chloride; D000641:Ammonia; C505409:Casp3 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases