title: Contribution of glutamine synthetase to ammonia-induced apoptosis in gastric mucosal cells.
abstract: OBJECTIVE
  Glutamine synthetase is a key enzyme necessary for ammonia detoxification in the brain, but excessive activation of this enzyme can be cytotoxic to neural cells as a consequence of excessive consumption of ATP and glutamate. The stomach also expresses high levels of glutamine synthetase and this study aimed to investigate a possible pathophysiological role of glutamine synthetase in ammonia-induced gastric mucosal injury.
  
  
  METHODS
  Normal rat gastric mucosal epithelial (RGM-1) cells were treated with ammonia, and a specific glutamine synthetase inhibitor (methionine sulfoximine) was used to assess the action of glutamine synthetase.
  
  
  RESULTS
  Treatment with ammonia induced apoptotic cell death. Increased expression of p21 and Bax, decreased expression of Bcl-2, cytochrome C release from the mitochondria into the cytosol and subsequent activation of caspase-9 and -3 were identified in the cells treated with ammonia, although there was no apparent change in p53 expression. On the other hand, pretreatment with various concentrations of methionine sulfoximine reduced the glutamine synthetase activity in ammonia-treated RGM-1 cells, and prevented the induction of apoptosis and the reduction in intracellular ATP levels in a dose-dependent manner.
  
  
  CONCLUSIONS
  Our results suggested that the energy exhaustion which resulted from an overload of ammonia to glutamine synthetase may have initiated the apoptotic signaling in gastric mucosal cells.
authors.affiliation: Division of Gastroenterology, Tohoku University Graduate School of Medicine, Sendai, Miyagi, Japan.
authors.forename: Yuuji
authors.initials: Y
authors.lastname: Kubota
authors.forename: Katsuaki
authors.initials: K
authors.lastname: Kato
authors.forename: Naohiro
authors.initials: N
authors.lastname: Dairaku
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Koike
authors.forename: Katsunori
authors.initials: K
authors.lastname: Iijima
authors.forename: Akira
authors.initials: A
authors.lastname: Imatani
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sekine
authors.forename: Shuichi
authors.initials: S
authors.lastname: Ohara
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Matsui
authors.forename: Tooru
authors.initials: T
authors.lastname: Shimosegawa
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000641:Ammonia / Q000633:toxicity*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D018929:Cell Culture Techniques; D045304:Cytochromes c / Q000378:metabolism; D004734:Energy Metabolism; D020869:Gene Expression Profiling; D005974:Glutamate-Ammonia Ligase / Q000494:pharmacology*; D016481:Helicobacter Infections / Q000150:complications; D016480:Helicobacter pylori / Q000472:pathogenicity; D007413:Intestinal Mucosa / Q000473:pathology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D000641:Ammonia; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D005974:Glutamate-Ammonia Ligase