Outer membrane vesicles enhance the carcinogenic potential of Helicobacter pylori

Abstract

Chronic Helicobacter pylori infection is associated with an increased risk of gastric carcinogenesis. These non-invasive bacteria colonize the gastric mucosa and constitutively shed small outer membrane vesicles (OMV). In this study, we investigated the direct effect of H.pylori OMV on cellular events associated with carcinogenesis. We observed increased micronuclei formation in AGS human gastric epithelial cells treated with OMV isolated from a toxigenic H.pylori strain (60190). This effect was absent in OMV from strain 60190v:1 that has a mutant vacA, indicating VacA-dependent micronuclei formation. VacA induces intracellular vacuolation, and reduced acridine orange staining indicated disruption in the integrity of these vacuoles. This was accompanied by an alteration in iron metabolism and glutathione (GSH) loss, suggesting a role for oxidative stress in genomic damage. Increasing intracellular GSH levels with a GSH ester abrogated the VacA-mediated increase in micronuclei formation. In conclusion, OMV-mediated delivery of VacA to the gastric epithelium may constitute a new mechanism for H.pylori-induced gastric carcinogenesis.

Uptake ofHelicobacter pyloriOuter Membrane Vesicles by Gastric Epithelial Cells

“…We and others have previously shown that H. pylori OMV are internalized by gastric epithelial cells (8,15,44,45). In this study, we sought to examine the rate and mechanism of OMV internalization using the lipophilic fluorescent membrane dye DiO to monitor OMV localization.…”

“…However, despite the ability to adhere to the gastric epithelium, the majority of organisms remain unattached to surface cells (32), leading to speculation that lipopolysaccharide (LPS)-enriched outer membrane vesicles (OMV) shed by these bacteria (15,19,26) contribute to H. pylori pathogenesis via the persistent delivery of bacterial virulence factors (including the vacuolating cytotoxin VacA) and antigens to the gastric mucosa (26,27). Observations that H. pylori OMV modulate gastric epithelial cell proliferation (22), induce apoptosis (3), stimulate secretion of the proinflammatory cytokine interleukin-8 (22), increase micronucleus formation (8), and are at the luminal surface (15,26) and within cells of the gastric epithelium (15) support this hypothesis.…”

Prokaryotic membrane vesicles: new insights on biogenesis and biological roles

“…OMVs contribute in bacterial pathogenesis because adhesins, toxins and immunomodulatory compounds have been identified as OMV cargo (Figure 1) (Grenier and Mayrand, 1987;Kadurugamuwa and Beveridge, 1995;Horstman and Kuehn, 2002;Wai et al, 2003;Kesty et al, 2004;Chitcholtan et al, 2008). Heat labile enterotoxin (enterotoxigenic E. coli), VacA (Helicobacter pylori), Shiga toxin (Shigella dysenteriae and enterohemorrhagic E. coli) and ClyA (enterohemorrhagic E. coli) are some examples of the several toxins that have been reported to be associated with OMVs (Horstman and Kuehn, 2000;Horstman and Kuehn, 2002;Wai et al, 2003;Dutta et al, 2004;Kesty et al, 2004;Chitcholtan et al, 2008).…”

“…Heat labile enterotoxin (enterotoxigenic E. coli), VacA (Helicobacter pylori), Shiga toxin (Shigella dysenteriae and enterohemorrhagic E. coli) and ClyA (enterohemorrhagic E. coli) are some examples of the several toxins that have been reported to be associated with OMVs (Horstman and Kuehn, 2000;Horstman and Kuehn, 2002;Wai et al, 2003;Dutta et al, 2004;Kesty et al, 2004;Chitcholtan et al, 2008). Also, the enteric pathogen, Salmonella typhi was shown to induce hemolysin packing into OMVs in response to norepinephrine (Karavolos et al, 2011).…”

Significances of OMV and Extracellular Vesicle Proteomics

“…Cancer has traditionally been considered as a human disease resulting from gene mutations but new finding suggest that extracellular vesicles which are derived from tumour can carry polypeptides, polysaccharides, DNA and RNA causative of cancer progression [151]. Intake of the tumor derived extracellular vesicles (EVs) by non-tumor cells can be converted into cancerous cell [152]. EV released by cancer cells also acts against the stress response [93].…”