Helicobacter pylori VacA toxin up-regulates vascular endothelial growth factor expression in MKN 28 gastric cells through an epidermal growth factor receptor-, cyclooxygenase-2-dependent mechanism.

Abstract

Helicobacter pylori causes gastric damage and is involved in gastric carcinogenesis. Vascular endothelial growth factor (VEGF) plays a major role in gastric mucosa repair and is overexpressed in gastric cancer. We investigated: (a) whether H. pylori, and in particular H. pylori VacA toxin, affected VEGF expression in gastric epithelial cells in culture; and (b) the signal transduction pathway involved in any effect exerted by H. pylori. MKN-28 cells were incubated with uninoculated BCF (control) or with BCF obtained from VacA-producing wild-type H. pylori 60190 strain or from its isogenic mutant 60190:v1, specifically lacking vacA gene in the presence or absence of ZD 1839, a selective inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase, PD098059, a selective inhibitor of mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK) kinase, the kinase responsible for ERK phosphorylation, or SC-236, a selective inhibitor of cyclooxygenase (COX)-2 for 24-48 h. (a) Toxigenic H. pylori up-regulated VEGF mRNA and protein expression and caused a 2.5-fold increase in VEGF release compared with control, whereas nontoxigenic H. pylori did not; (b) H. pylori VacA toxin-induced up-regulation of VEGF was counteracted by selective inhibition of EGFR tyrosine kinase; (c) toxigenic H. pylori activated the ERK/MAP kinase cascade, and inhibition of MAP kinase activation counteracted H. pylori-induced VEGF up-regulation; (d) toxigenic H. pylori up-regulated COX-2 expression, and this effect was counteracted by blockade of EGFR tyrosine kinase; and (e) COX-2 selective inhibition counteracted H. pylori-induced up-regulation of VEGF. (a) H. pylori up-regulates VEGF expression in gastric epithelial cells; and (b) this effect is specifically related to VacA toxin and seems to depend on the activation of an EGFR-, MAP kinase-, and COX-2-mediated pathway.