Published online Apr 14, 2006. doi: 10.3748/wjg.v12.i14.2174
Revised: October 1, 2005
Accepted: November 18, 2005
Published online: April 14, 2006
AIM: To determine whether Helicobacter pylori (H pylori) vacuolating cytotoxin (VacA) regulates release of pro-inflammatory cytokines (IL-1β, IL-8, TNF-α, and IL-6) or alters gastric epithelial cell viability and to determine whether NaCl affects these VacA-induced changes.
METHODS: Vacuolating activity was determined by measuring the uptake of neutral red into vacuoles of VacA-treated human gastric epithelial (AGS) cells. AGS cell viability was assessed by direct cell counting. Specific enzyme-linked immunosorbent assays (ELISA) and reverse transcriptase-polymerase chain reaction(RT-PCR) were performed to examine the effects of H pylori VacA and NaCl on cell pro-inflammatory cytokine production in AGS cells. Immunohistochemical staining of gastric tissue from Mongolian gerbils was used to confirm VacA-induced pro-inflammatory cytokine production and the effects of NaCl on this VacA-induced response.
RESULTS: Addition of VacA alone reduced AGS cell viability (P < 0.05), and this reduction was enhanced by high doses of NaCl (P < 0.05). VacA alone induced expression of TNF-α, IL-8 and IL-1β, while NaCl alone induced expression of TNF-α and IL-1β. Changes in mRNA levels in the presence of both VacA and NaCl were more complicated. For the case of TNF-α, expression was dose-dependent on NaCl. IL-6 mRNA was not detected. However, low levels of IL-6 were detected by ELISA. Positive immunohistochemical staining of IL-1, IL-6, and TNF-α was found in gastric tissue of H pylori-infected gerbils fed with either a normal diet or a high salt diet. However, the staining of these three cytokines was stronger in H pylori-infected animals fed with a 5g/kg NaCl diet.
CONCLUSION: VacA decreases the viability of AGS cells, and this effect can be enhanced by NaCl. NaCl also affects the production of pro-inflammatory cytokines induced by VacA, suggesting that NaCl plays an important role in H pylori-induced gastric epithelial cell cytotoxicity.