Helicobacter pylori vacuolating cytotoxin (VacA) alters cytoskeleton-associated proteins and interferes with re-epithelialization of wounded gastric epithelial monolayers.

In previous studies, we demonstrated that Helicobacter pylori vacuolating cytotoxin (VacA) inhibits gastric epithelial cell proliferation and inhibits epidermal growth factor (EGF)-activated signal transduction. Cell proliferation and migration, both essential for mucosal healing are dependent on the cell cytoskeleton. Other investigators demonstrated that VacA induces vacuolation of eukaryotic cells. Since in some cells, control of actin cytoskeleton involves GTP-binding proteins of Rho family, in this study we examined whether VacA affects wound re-epithelialization, cell cytoskeleton-associated proteins Rho, Rac1 in a gastric epithelial (RGM1) cell monolayer wound model, and whether these changes correlate with vacuolation. VacA treatment significantly inhibited wound re-epithelialization, cell proliferation vs control. VacA-induced cell vacuolation strongly correlated with inhibition of wound re-epithelialization. Furthermore, VacA reduced Rac-1 protein expression and distribution, and C3-mediated ADP-ribosylation of Rho. These findings suggest that VacA may interfere with repair of gastric mucosal injury and ulcer re-epithelialization by altering cytoskeleton-dependent cell functions and signaling.

Pai R ，Sasaki E ，Tarnawski AS 《CELL BIOLOGY INTERNATIONAL》

Helicobacter pylori vacuolating cytotoxin (VacA) disorganizes the cytoskeletal architecture of gastric epithelial cells.

Helicobacter pylori colonization of the gastric mucosa induces peptic ulcer disease and interferes with ulcer healing. Re-epithelialization is an essential component of ulcer healing. It requires cell migration and proliferation which are dependent on the cell cytoskeleton. Most H. pylori strains produce a toxin (VacA) that induces multiple structural and functional changes in epithelial cells. In this study, we investigated the effects of VacA on the gastric epithelial cell cytoskeletal architecture. Exposure of rat gastric epithelial cells to purified VacA from H. pylori 60190 significantly inhibited actin stress fiber formation (83 +/- 5% reduction; p < 0.0001) and disorganized microtubule pattern (90 +/- 8%; p < 0.001). Furthermore, VacA treatment significantly reduced tyrosine phosphorylation of focal adhesion kinase (FAK) (by 45 +/- 6%; p < 0.002) and its expression in focal adhesions (73 +/- 8%; p < 0.0001). These findings suggest that H. pylori VacA interferes with cytoskeleton-dependent cell functions and with the transmission of signals related to cell spreading and growth.

Pai R ，Cover TL ，Tarnawski AS 《BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS》

Induction of gastric epithelial cell apoptosis by Helicobacter pylori vacuolating cytotoxin.

Chronic gastritis induced by Helicobacter pylori is a strong risk factor for the development of distal gastric adenocarcinoma. A specific host response to H. pylori that may contribute to gastric carcinogenesis is epithelial cell apoptosis. The aim of this study was to investigate the capacity of H. pylori vacuolating toxin (VacA) to induce gastric epithelial cell apoptosis. When cocultured with AGS gastric epithelial cells, H. pylori strain 60190, which expresses a type s1/m1 VacA toxin, induced significantly higher levels of apoptosis than did an isogenic vacA null mutant strain. VacA purified from strain 60190 induced apoptosis in a dose-dependent manner, which required acid activation of the purified toxin and the presence of ammonium chloride. In contrast, apoptosis was not induced after incubation with a chimeric s2/m1 toxin (in which the s1 sequence at the NH(2) terminus of VacA from strain 60190 was replaced with the s2 sequence from the nontoxigenic strain Tx30a) or a VacA mutant protein (VacA Delta 6-27) that lacks a unique strongly hydrophobic region near the VacA NH(2) terminus. Moreover, when an equimolar mixture of purified VacA Delta 6-27 and purified wild-type VacA were added simultaneously to AGS cells, the mutant toxin exhibited a dominant negative effect, completely inhibiting the apoptosis-inducing activity of wild-type VacA. These results indicate that VacA induces gastric epithelial cell apoptosis and suggest that differences in levels of gastric mucosal epithelial apoptosis among H. pylori-infected persons may result from strain-dependent variations in VacA structure.

Cover TL ，Krishna US ，Israel DA ，Peek RM Jr ... -  《CANCER RESEARCH》

Use of a novel coinfection system reveals a role for Rac1, H-Ras, and CrkII phosphorylation in Helicobacter pylori-induced host cell actin cytoskeletal rearrangements.

Brandt S ，Shafikhani S ，Balachandran P ，Jin S ，Hartig R ，König W ，Engel J ，Backert S ... -  《fems immunology and medical microbiology》

Helicobacter pylori Hp(2-20) promotes migration and proliferation of gastric epithelial cells by interacting with formyl peptide receptors in vitro and accelerates gastric mucosal healing in vivo.

de Paulis A ，Prevete N ，Rossi FW ，Rivellese F ，Salerno F ，Delfino G ，Liccardo B ，Avilla E ，Montuori N ，Mascolo M ，Staibano S ，Melillo RM ，D'Argenio G ，Ricci V ，Romano M ，Marone G ... -  《-》