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 IkappaBalpha 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 IkappaBalpha 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.
mesh_terms: D017209:Apoptosis; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D004273:DNA, Neoplasm / Q000235:genetics; D006367:HeLa Cells; D016481:Helicobacter Infections / Q000378:metabolism / Q000473:pathology*; D016480:Helicobacter pylori / Q000472:pathogenicity*; D006801:Humans; D008928:Mitochondria / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D015398:Signal Transduction; D013274:Stomach Neoplasms / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D014407:Tumor Cells, Cultured; D014774:Virulence
chemical_list: D003574:Cytochrome c Group; D004273:DNA, Neoplasm; D016328:NF-kappa B; D009363:Neoplasm Proteins; D020169:Caspases