Role of adherence in interleukin-8 induction in Helicobacter pylori-associated gastritis

Abstract

Active Helicobacter pylori-associated gastritis is characterized by a dense mucosal infiltration with granulocytes. Since H. pylori is noninvasive, secondary signals must induce the accumulation of granulocytes. Interleukin-8 (IL-8) has been shown to play a key role in this event. Using competitive reverse transcriptase-PCR on mRNA from gastric biopsies, we could show a clear correlation between the amount of IL-8 transcripts and the activity of H. pylori gastritis. Due to the inability of the bacterium to invade host cells, the epithelial layer is a potential candidate as an IL-8 source. To study the mechanism of IL-8 induction, established gastric carcinoma epithelial cell lines (AGS and Kato III) and well-defined H. pylori strains were used in a modified in vitro system. The experimental design enabled us to prevent direct contact of bacteria with epithelial cells by use of a filter membrane which did not block secreted bacterial products crossing the membrane. The data clearly showed that the direct contact of the bacterial cell with the epithelial cell is necessary for optimal IL-8 production because not only live bacteria, but also metabolically inactive bacteria, increased IL-8 secretion. Neither purified lipopolysaccharide nor water-soluble protein fractions of H. pylori NCTC 11637 and Tx30a nor the cytotoxin of H. pylori was able to increase IL-8 production significantly by the epithelial cells used. Furthermore, preparations of total membrane and outer membrane proteins of H. pylori were not able to stimulate IL-8 release in vitro. Accumulatively, these results imply that active metabolism is not necessary for stimulation as long as there is an intact membrane aiding the presentation of a stimulating membrane complex or aggregate on the surface of the bacteria. From these results, we conclude that whole bacteria and their direct contact with epithelial cells may be critical for IL-8 induction in vivo.

IFN-γsynergizes with TNF-αbut not with viableH. pyloriin up-regulating CXC chemokine secretion in gastric epithelial cells

“…Chemokine secretion was measured in supernatants by ELISA measurement. In agreement with previous studies [23] we found a strong IL-8 production by gastric epithelial cells in response to TNF-a . Fractions of H. pylori neither alone nor in combination with TNF-a and IFN-g stimulated IL-8 secretion.…”

Suppression of Helicobacter pylori‐induced interleukin‐8 production in vitro and within the gastric mucosa by a live Lactobacillus strain

“…Such adherence of live H. pylori to gastric epithelial cells is indispensable for the stimulation of IL-8 secretion. 17 Therefore, firm contact between H. pylori and the host cell by such adhesion is thought to be a prerequisite for the H. pylori to transport effecter molecules into the host cell using the cagPAI-encoded type IV secretion system, which is regarded as the pathway leading to the generation of IL-8 in the coculture system together with MKN45 and H. pylori. Lactobacilli have been reported to inhibit the adhesion of many kinds of pathogenic bacteria to epithelial cells.…”

Suppression of Helicobacter pylori‐induced interleukin‐8 production in gastric cancer cell lines by an anti‐ulcer drug, geranylgeranylacetone

“…Several studies have reported that IL-8 production requires direct contact between H. pylori and epithelial cells. [34][35][36] Accordingly, gastric epithelial cells in culture produce IL-8 in the presence of viable H. pylori, but not when the bacterium is killed or is viable but separated from cells by a membrane or by H. pylori culture supernatant. 18,34 In addition, H. pylori induces protein tyrosine phosphorylation, which is involved in IL-8 production, in gastric epithelial cells.…”