Phenol/water extract of Treponema socranskii subsp. socranskii as an antagonist of Toll-like receptor 4 signalling

Abstract

Treponema socranskii is one of the most frequently found oral spirochaetes in periodontitis and endodontic infections. LPS or glycolipids from bacteria are potent stimulators of innate immune and inflammatory systems. In this study the bioactivity of a phenol/water extract from T. socranskii subsp. socranskii (TSS-P) was analysed. TSS-P showed minimal endotoxicity and no inducing potential for proinflammatory cytokines (TNF-α and IL-8) or for intercellular adhesion molecule-1 (ICAM-1) in human monocyte cell line THP-1 cells and primary cultured human gingival fibroblasts. Rather, it inhibited ICAM-1 expression and IL-8 secretion from cells stimulated by the LPS of Escherichia coli and Actinobacillus actinomycetemcomitans, which are known to be Toll-like receptor 4 (TLR4) agonists. However, this antagonistic activity was not shown in cells stimulated by peptidoglycan or IL-1β. As its antagonistic mechanism, TSS-P blocked the binding of E. coli LPS to LPS-binding protein (LBP) and CD14, which are molecules involved in the recruitment of LPS to the cell membrane receptor complex TLR4–MD-2 for the intracellular signalling of LPS. TSS-P itself did not bind to MD-2 or THP-1 cells, but inhibited the binding of E. coli LPS to MD-2 or to the cells in the presence of serum (which could be replaced by recombinant human LBP and recombinant human CD14). The results suggest that TSS-P acts as an antagonist of TLR4 signalling by interfering with the functioning of LBP/CD14.

The Major Outer Membrane Protein of a Periodontopathogen Induces IFN-β and IFN-Stimulated Genes in Monocytes via Lipid Raft and TANK-Binding Kinase 1/IFN Regulatory Factor-3

“…However, phenol waterextracted LPS-like molecules from some oral treponemes act as antagonists to E. coli LPS (20,28). In our previous experiments, phenol water extracts from T. lecithinolyticum were biologically inert (20). Therefore, in the present study, we selected MspTL as a representative molecule for investigations of the molecular basis of host immune response to the bacterium.…”

“…Since the cell wall of oral treponemes, including T. lecithinolyticum, is similar to that of Gram-negative bacteria, LPS or LPS-like molecules are expected to be important surface molecules for stimulating immune responses. However, phenol waterextracted LPS-like molecules from some oral treponemes act as antagonists to E. coli LPS (20,28). In our previous experiments, phenol water extracts from T. lecithinolyticum were biologically inert (20).…”

“…LPS has been one of the most intensively studied OM molecules, and it belongs to well-known PAMPs. However, in our preliminary study, phenol-water extracts of T. lecithinolyticum, which contained LPSlike molecules, did not show any cell-stimulating activity (20). Since multiple bacterial species are known to be associated with periodontitis, functional elucidation of representative major OM proteins from various periodontopathogens is required to understand the unique and common elements of molecular pathogenesis.…”

Involvement of Toll-Like Receptors 2 and 4 in the Innate Immune Response toTreponema denticolaand Its Outer Sheath Components

“…There is an ongoing literature that these outer membrane glycolipids may be important activators of the innate immune system and contributors to the pathogenesis of spirochetal diseases. However, the glycolipids from different microorganisms differ in the capacity to induce cytokines via TLRs and the structural basis of their interaction with the host receptors is still unknown (26). Glycolipids from T. denticola, T. maltophilum, and T. brennaborense were found to induce the release of proinflammatory cytokines from macrophages.…”

Inhibitory Effect of Enterohepatic Helicobacter hepaticus on Innate Immune Responses of Mouse Intestinal Epithelial Cells

“…Porphyromonas gingivalis LPS inhibits the TLR4 signaling complex primarily by competitive binding of the cofactor MD2 (16). Treponema socranskii and Treponema medium use molecules similar to LPS or glycolipids for inhibition of TLR4 activation mainly through LBP/CD14-dependent mechanisms (5,35,50). A known structural feature of LPS of both H. pylori and dental pathogens that very likely contributes to low activity is a hypoacylated lipid A (penta-or tetraacylated).…”