title: Endoplasmic reticulum stress contributes to Helicobacter pylori VacA-induced apoptosis.
abstract: Vacuolating cytotoxin A (VacA) is one of the important virulence factors produced by H. pylori. VacA induces apoptotic cell death, which is potentiated by ammonia. VacA also causes cell death by mitochondrial damage, via signaling pathways that are not fully defined. Our aim was to determine whether endoplasmic reticulum (ER) stress is associated with VacA-induced mitochondrial dysfunction and apoptosis. We found that C/EBP homologous protein (CHOP), a key signaling protein of ER stress-induced apoptosis, was transcriptionally up-regulated following incubation of gastric epithelial cells with VacA. The effect of VacA on CHOP induction was significantly enhanced by co-incubation with ammonium chloride. Phosphorylation of eukaryotic initiation factor 2 (eIF2)-alpha, which is known to occur downstream of the ER stress sensor PKR-like ER-localized eIF2-alpha kinase (PERK) and to regulate CHOP expression, was also observed following incubation with VacA in the presence of ammonium chloride. Knockdown of CHOP by siRNA resulted in inhibition of VacA-induced apoptosis. Further studies showed that silencing of the PERK gene with siRNA attenuated VacA-mediated phosphorylation of eIF2-alpha, CHOP induction, expression of BH3-only protein Bim and Bax activation, and cell death induced by VacA with ammonium chloride, indicating that ER stress may lead to mitochondrial dysfunction during VacA-induced toxicity. Activation of ER stress and up-regulation of BH3-only proteins were also observed in human H. pylori-infected gastric mucosa. Collectively, this study reveals a possible association between VacA-induced apoptosis in gastric epithelial cells, and activation of ER stress in H. pylori-positive gastric mucosa.
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Akazawa
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Isomoto
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Kayoko
authors.initials: K
authors.lastname: Matsushima
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kanda
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Hitomi
authors.initials: H
authors.lastname: Minami
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Yamaghchi
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Naota
authors.initials: N
authors.lastname: Taura
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Shiozawa
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Ohnita
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Fuminao
authors.initials: F
authors.lastname: Takeshima
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nakano
authors.affiliation: Cardiovascular and Pulmonary Branch, NHLBI, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Joel
authors.initials: J
authors.lastname: Moss
authors.affiliation: Department of Bacteriology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Toshiya
authors.initials: T
authors.lastname: Hirayama
authors.affiliation: Department of Gastroenterology and Hepatology, Nagasaki University Hospital, Nagasaki, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Nakao
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D015415:Biomarkers / Q000378:metabolism; D045744:Cell Line, Tumor; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D016480:Helicobacter pylori / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051742:Transcription Factor CHOP / Q000378:metabolism; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism; D019892:eIF-2 Kinase / Q000378:metabolism
chemical_list: D000643:Ammonium Chloride; D051017:Apoptosis Regulatory Proteins; D001426:Bacterial Proteins; D000072224:Bcl-2-Like Protein 11; D015415:Biomarkers; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D019892:eIF-2 Kinase; C000606775:BCL2L11 protein, human; C074689:VacA protein, Helicobacter pylori