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》

Vacuolating cytotoxin of Helicobacter pylori induces apoptosis in the human gastric epithelial cell line AGS.

Kuck D ，Kolmerer B ，Iking-Konert C ，Krammer PH ，Stremmel W ，Rudi J ... -  《-》

Vacuolating cytotoxin purified from Helicobacter pylori causes mitochondrial damage in human gastric cells.

We investigated the effects of vacuolating cytotoxin (VacA) prepared from Helicobacter pylori on the metabolism of gastric epithelial cells, AZ-521. VacA caused the ATP levels to decrease in a time-dependent manner; by approximately 20% in 6 h, 35% in 12 h and 50% in 24 h, at a concentration of 120 nM. This decrease was also dependent on the concentration of VacA. To evaluate the impairment of mitochondria by VacA, mitochondrial membrane potential was estimated by flow cytometric analysis using 3, 3'-dihexyloxacarbocyanine iodide as a substrate. VacA decreased membrane potential with the relative fluorescence intensity of AZ-521 cells in 6 h from 52+/-3 to 24+/-1. Treatment of the cells with bafilomycin A1, a specific inhibitor of vacuolar ATPase proton pump, showed no apparent effect on these changes in the levels of ATP and the mitochondrial membrane potential. Secondly, we estimated the effect of VacA on oxygen consumption. VacA inhibited oxygen consumption in AZ-521 cells: the levels of PO 2 in the medium of control cells decreased by 73% in 3 h and 37% in 6 h, whereas those in VacA-treated cells were 84% in 3 h and 59% in 6 h. Flow cytometric analysis showed the number of cells in the G0/G1 phase was increased by VacA. Taken together, VacA induced an inactivation of energy metabolism followed by mitochondrial damage, leading to impairment of the cell cycle in gastric epithelial cells.

Kimura M ，Goto S ，Wada A ，Yahiro K ，Niidome T ，Hatakeyama T ，Aoyagi H ，Hirayama T ，Kondo T ... -  《MICROBIAL PATHOGENESIS》

A 12-amino-acid segment, present in type s2 but not type s1 Helicobacter pylori VacA proteins, abolishes cytotoxin activity and alters membrane channel formation.

McClain MS ，Cao P ，Iwamoto H ，Vinion-Dubiel AD ，Szabo G ，Shao Z ，Cover TL ... -  《-》

Immunohistochemical detection of Helicobacter pylori vacuolating cytotoxin in the hepatocytes of patients with isolated hypertransaminasaemia.

Francavilla A ，Ierardi E ，Francavilla R ，Principi M ，Gentile A ，Margiotta M ，Balzano T ，Passaro S ，Noviello F ，Panella C ，Pollice L ... -  《italian journal of gastroenterology and hepatology》