Highly-purifiedHelicobacter pyloriLPS preparations induce weak inflammatory reactions and utilize Toll-like receptor 2 complex but not Toll-like receptor 4 complex

Abstract

Helicobacter pylori is recognized as an etiologic agent of gastroduodenal diseases. Among toxic substances produced by H. pylori, LPS exhibits extremely low endotoxic activity as compared to the typical LPSs, such as that produced by Escherichia coli. We found that the LPS-low-responder stomach cancer cell line MKN28, which expresses Toll-like receptor 4 (TLR4) at extremely low levels, showed similar levels of interleukin-8 (IL-8) induction by H. pylori or E. coli LPS preparations. Weak IL-8 induction by H. pylori LPS preparations was suppressed by expression of a dominant negative mutant of TLR2 but not of TLR4. Data from luciferase reporter analysis indicated that cotransfection of TLR2-TLR1 or TLR2-TLR6 was required for the activation induced by H. pylori LPS preparations. In conclusion, the H. pylori LPS preparations significantly induce an inflammatory reaction via the receptor complex containing TLR2-TLR1 or TLR2-TLR6 but not that containing TLR4. The TLR2-TLR1 complex was preferentially recognized by the H. pylori LPS preparations over the TLR2-TLR6 complex. Whereas the magnitude of response to H. pylori LPS preparation was markedly less than that to E. coli LPS preparation in LPS-high-responder cells strongly expressing TLR4, it was comparable to that of E. coli LPS in low-responder cells expressing negligible amount of TLR4.

Flagellin promotes the proliferation of gastric cancer cells via the Toll-like receptor 5

“…Only TLR2 and TLR5, but not TLR4, were required for H. pylori-induced NF-κB activation in MKN45 cells (25). In addition, it was clarified that E. coli LPS produced very low levels of IL-8 in intact gastric epithelial cells (MKN28 and MKN45 cells), which was due to a low level expression of TLR4 (30,31). However, H. pylori LPS up-regulated TLR4 expression in those cells via TLR2 signaling, which enhanced the E. coli LPS-induced IL-8 production (30).…”

Ceramide and Toll-Like Receptor 4 Are Mobilized into Membrane Rafts in Response to Helicobacter pylori Infection in Gastric Epithelial Cells

“…Several studies have reported that immune responses to intact H. pylori may not involve TLR4 (5,15). In addition, LPS derived from H. pylori reportedly induces TLR2 rather than TLR4 signaling (52,60). The reasons for these discrepancies may potentially be explained by variations in the bacterial strains or experimental systems employed in the studies.…”

“…Moreover, TLR4 recognizes LPS of Gram-negative bacteria and activates NF-B and activator protein-1 (AP-1) (13,50,62). Several reports have suggested that TLR2 contributes to H. pylori LPS-induced signaling (33,57,60). Other studies support the notion that H. pylori-induced signal transduction is mediated through TLR4 (25,47,53,61).…”

Implication of Antigenic Conversion of Helicobacter pylori Lipopolysaccharides That Involve Interaction with Surfactant Protein D

“…LPS was prepared by hot phenol-water extraction and ultracentrifugation, as described previously (38). Highly purified LPS preparation used for biological assays was prepared previously (41). Briefly, the LPS preparation was treated with DNase I, RNase, and two lipoprotein lipases derived from bovine milk and Pseudomonas sp., followed by treatment with proteinase K. The resulting material was applied to an octyl-Sepharose column, and LPS was eluted with a linear gradient of 1-propanol.…”

“…The low level of endotoxic activity is due to the variability in the chemical structures, i.e., the molecular species and the number of fatty acid residues of the lipid A portion (24). Some groups, including ours, have suggested that H. pylori LPS acts as a Toll-like receptor 2 (TLR2) agonist but not as a TLR4 agonist (16,32,41). In addition, there is a report that LPS derived from some strains can act as an antagonist of TLR4 (16).…”