Analysis of apoptotic and antiapoptotic signalling pathways induced by Helicobacter pylori. Issue 6 (1st June 2002)

• Record Type: Journal Article
• Authors: Maeda, S; Yoshida, H; Mitsuno, Y; Hirata, Y; Ogura, K; Shiratori, Y; Omata, M
• Is Part Of: Gut. Volume 50:Issue 6(2002)
• Page Start: 771
• Page End: 778
• Publication Date: 2002-06-01
• Subjects: Helicobacter pylori -- apoptosis -- antiapoptosis -- signalling pathway; PAI, pathogenicity island -- NFκB, nuclear factor kappa B -- FADD, Fas associated death domain protein -- IFN, interferon -- PBS, phosphate buffered saline -- BSA, bovine serum albumin -- VacA, vacuolating cytotoxin -- FBS, fetal bovine serum -- MyD88, myeloid differentiation factor 88; Gastroenterology -- Periodicals; 616.33
• DOI: 10.1136/gut.50.6.771
• Languages: English
• ISSNs: 0017-5749

Abstract

Abstract : 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-Δ cagE, TN2-Δ vacA ) 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 (NFκB) activation induced by cag pathogenicity island (PAI) positive H pylori affects antiapoptosis, MKN45 cells stably expressing super-repressor Iκβα were cocultured with H pylori, and cell viability and caspase activation were evaluated. NFκB regulated gene expression was also evaluated by ribonuclease protection assay. Results: (1) Wild-type and Δ vacA mutant H pylori induced apoptosis more potently than the Δ cagE 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 Iκβα that inhibits NFκB 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 NFκB activation were also observed.