Helicobacter pylori water extract induces interleukin-8 production by gastric epithelial cells

In Helicobacter pylori-associated gastric mucosal injury, interleukin (IL)- 8, a potent leukocyte chemoattractant, is produced by epithelial cells infe cted by H. pylori and directs neutrophils to the gastric mucosa. According to previous studies, the IL-8 production requires direct contact between th e bacteria and epithelial cells. The aims of the present study were to dete rmine whether an H. pylori water extract (HPE) induces IL-8 production by g astric epithelial cells and to characterize IL-8-inducing substances in HPE . Extracts were prepared from a standard strain and from strains obtained f rom patients with gastric ulcers. After addition of HPE to MKN 45 cells, a gastric cancer cell line, IL-8 in supernatants and IL-8 mRNA were measured by immunoassay and reverse transcription-polymerase chain reaction, respect ively. For characterization, active fractions obtained by gel filtration of standard-strain HPE were treated by heating or trypsinization. To study th e signal pathway leading to IL-8 production, inhibitors for protein kinase A (PKA), protein kinase C (PKC), or protein tyrosine kinase (PTK) were incu bated with MKN45 cells before HPE stimulation. HPE from the standard strain and one of these clinical strains induced IL-S production. Lipopolysacchar ide or cagA in the strains showed no correlation with IL-8 concentration. S tandard-strain HPE induced IL-8 mRNA expression in MKN 45 cells. Gel filtra tion localized activity to a low-molecular-weight fraction of about 7 kDa, which was resistant to heat and trypsin digestion. PKC inhibitors significa ntly blocked HPE-induced IL-S production by MKN 45 cells; however, the PKA inhibitor or PTK inhibitors showed a partial inhibitory effect. HPE contain s a nonprotein substance of low molecular weight that is responsible for IL -8 induction in gastric epithelial cells. This induction is mainly dependen t on the activation of PKC but partially also dependent on PKA or PTK.