title: Analysis of apoptotic and antiapoptotic signalling pathways induced by Helicobacter pylori.
abstract: OBJECTIVE
  Although it is reported that Helicobacter pylori induces apoptosis on gastric epithelial cells, the mechanism remains unknown. Antiapoptotic effects generated by H pylori have not yet been evaluated.
  
  
  METHODS
  (1) H pylori strains (type 1 wild, TN2-DeltacagE, TN2-DeltavacA) were cocultured with MKN45, TMK1, and HeLa cells, and cell viability and apoptosis were assessed by trypan blue exclusion and DNA laddering, respectively. (2) Activation of caspases-3, 7, and 8, cytochrome c release from the mitochondria, and Fas, Fas associated death domain protein (FADD), Bax, Bak, and Bcl-X expression were evaluated by immunoblot analysis. (3) To investigate whether nuclear factor kappa B (NFkappaB) activation induced by cag pathogenicity island (PAI) positive H pylori affects antiapoptosis, MKN45 cells stably expressing super-repressor Ikappabetaalpha were cocultured with H pylori, and cell viability and caspase activation were evaluated. NFkappaB regulated gene expression was also evaluated by ribonuclease protection assay.
  
  
  RESULTS
  (1) Wild-type and DeltavacA mutant H pylori induced apoptosis more potently than the DeltacagE mutant. Inhibition of cell contact between H pylori and cancer cells and heat killing H pylori diminished cell death. (2) Caspases-3, 7, and 8 were activated time dependently by H pylori as well as by the agonist anti-Fas. Cytochrome c release from mitochondria was observed and was not inhibited by caspase-8 inhibitor. Although protein expression of Fas, FADD, Bax, Bak, and Bcl-X in the whole cell lysates was not changed by H pylori, Bax was decreased from mitochondria free cytosol suggesting that Bax was translocated into mitochondria. (3) Cell death and the activities of caspases-3 and 8 were promoted in MKN45 cells stably expressing super-repressor Ikappabetaalpha that inhibits NFkappaB activation. Antiapoptotic proteins c-IAP1 and c-IAP2 were upregulated by the wild-type strains.
  
  
  CONCLUSIONS
  cag PAI positive H pylori is capable of inducing apoptotic effects mainly through the mitochondrial pathway. Antiapoptotic effects mediated by NFkappaB activation were also observed.
authors: Department of Gastroenterology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. MAEDA-2IM@h.u-tokyo.ac.jp
authors: S
authors: S
authors: Maeda
authors: H
authors: H
authors: Yoshida
authors: Y
authors: Y
authors: Mitsuno
authors: Y
authors: Y
authors: Hirata
authors: K
authors: K
authors: Ogura
authors: Y
authors: Y
authors: Shiratori
authors: M
authors: M
authors: Omata
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D017209:Apoptosis / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002450:Cell Communication / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D003574:Cytochrome c Group / Q000378:metabolism*; D053938:DNA Fragmentation / Q000502:physiology; D053200:Fas-Associated Death Domain Protein; D016481:Helicobacter Infections / Q000473:pathology*; D016480:Helicobacter pylori / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D013274:Stomach Neoplasms / Q000382:microbiology / Q000473:pathology; D014407:Tumor Cells, Cultured; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C494826:BAX protein, human; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D016328:NF-kappa B; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D019014:fas Receptor; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases