BACKGROUND AND AIMS: 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. CONCLUSION: 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.
BACKGROUND AND AIMS: 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. CONCLUSION: 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: R M Peek; S F Moss; K T Tham; G I Pérez-Pérez; S Wang; G G Miller; J C Atherton; P R Holt; M J Blaser Journal: J Natl Cancer Inst Date: 1997-06-18 Impact factor: 13.506
Authors: M Aihara; D Tsuchimoto; H Takizawa; A Azuma; H Wakebe; Y Ohmoto; K Imagawa; M Kikuchi; N Mukaida; K Matsushima Journal: Infect Immun Date: 1997-08 Impact factor: 3.441
Authors: J Rudi; D Kuck; S Strand; A von Herbay; S M Mariani; P H Krammer; P R Galle; W Stremmel Journal: J Clin Invest Date: 1998-10-15 Impact factor: 14.808
Authors: Andrew D Jones; Kathy D Bacon; Blair A Jobe; Brett C Sheppard; Clifford W Deveney; Michael J Rutten Journal: J Gastrointest Surg Date: 2003-01 Impact factor: 3.452