Oral Treponemes and Their Outer Membrane Extracts Activate Human Gingival Epithelial Cells through Toll-Like Receptor 2

Abstract

Oral treponemes are considered to be important in the development and progression of periodontal diseases. We investigated the mechanisms of recognition and activation of human gingival epithelial cells (HGEC) with the oral treponemes Treponema denticola, Treponema vincentii, and Treponema medium and their outer membrane extracts (OMEs). T. vincentii and T. medium but not T. denticola produced interleukin 8 (IL-8) in an HGEC culture. Further, all three treponemes induced IL-8 mRNA expression and NF-B activation in HGEC. Among them, T. denticola especially exhibited trypsin-and chymotrypsin-like protease activities, and the addition of chymostatin, a chymotrypsin protease inhibitor, resulted in detectable IL-8 production by HGEC cultured with T. denticola. Additionally, IL-8 mRNA expression in HGEC cultured with the three treponemes and their OMEs was definitely inhibited by the mouse anti-human Toll-like receptor 2 (TLR2) monoclonal antibody TL2.1. These findings suggest that oral treponemes and their OMEs activate HGEC through TLR2.Periodontal diseases are clinically defined as inflammation of gingival tissues followed by destruction of periodontal ligaments and alveolar bone, processes which are the result of augmentation of numerous bacterial species in subgingival plaque. Among these bacteria, oral treponemes and gramnegative, anaerobic, motile, and helical rods are generally isolated from patients with periodontal diseases (15); in contrast, no or only a few treponemes are found in healthy people (31). These oral treponemes have been revealed to be closely associated with various types of periodontal diseases (10, 13, 42). Further, human immunodeficiency virus-positive people with gingivitis or adult periodontitis have been shown to have increased numbers of oral treponemes in subgingival plaque (41,45). Among them, Treponema denticola and Treponema vincentii have been observed to adhere to and invade connective tissues as well as gingival epithelial cells (9,27,39,54), and T. denticola has also been shown to induce cytokine production from human gingival fibroblasts (34). Further, Asai et al. recently examined the frequency of occurrence of oral treponemes in subgingival plaque samples using real-time PCR assays and found that the numbers of T. denticola and T. medium organisms were increased in plaque samples from deep periodontal pockets, whereas T. vincentii was mainly found in shallow pockets (3).Various cytokines have been shown to play important roles in the pathogenesis of periodontal diseases (43, 58). Among them, interleukin 8 (IL-8), a CXC chemokine produced by gingival epithelial cells, is considered to be an important factor that initiates inflammatory reactions in gingival tissues (24). IL-8 has been detected in the gingival tissues of patients with periodontal diseases, and the level of IL-8 mRNA has also been demonstrated to correspond to the severity of periodontal diseases (53).Human gingival epithelial cells (HGEC) play an important role as the first barrier against periodontopathic bacte...

Upregulation of Intercellular Adhesion Molecule 1 and Proinflammatory Cytokines by the Major Surface Proteins of Treponema maltophilum and Treponema lecithinolyticum , the Phylogenetic Group IV Oral Spirochetes Associated with Periodontitis and Endodontic Infections

“…In this context, future studies should focus on determining the involvement of the TLRs in MspA or MspTL recognition and mapping the common regions of the Msps that recognize and transduce the signal to stimulate the host cells to secrete ICAM-1 and the proinflammatory cytokines. Interestingly, outer membrane extracts of T. denticola, T. vincentii, and Treponema medium stimulated IL-8 production in the human gingival epithelial cells, which appeared to be mediated through Toll-like receptor 2 (2).…”

“…The surface molecules that showed enhanced IL-8 secretion were P. gingivalis gingipain-R (40), a glycoprotein fraction in the cell surface from P. intermedia (48), and a capsular polysaccharide from Actinobacillus actinomycetemcomitans (39). Several oral treponemes have been reported to stimulate proinflammatory cytokines in various cell types, such as gingival fibroblasts and gingival epithelial cells (2,25,37,43). However, with the exception of their LPS or LPS-like materials, none of them has been analyzed at the molecular level.…”

Mutagenesis of a Novel Gene in the prcA-prtP Protease Locus Affects Expression of Treponema denticola Membrane Complexes

“…Recent reports implicate Msp in the disruption of fibroblast calcium responses and cytoskeletal assembly (1,3). PrtP activity contributes to T. denticola tissue penetration (4,12) and modulation of inflammatory cytokine responses (2,5). PrtP is reported to either contribute to (15) or interfere with (21) T. denticola binding to Porphyromonas gingivalis.…”

Treponema denticola Activates Mitogen-Activated Protein Kinase Signal Pathways through Toll-Like Receptor 2

“…The ability of the host to recognize and initially respond to microbes as well as microbial components has been largely attributed to a family of type I transmembrane Toll-like receptors (TLRs) (20,34,38). Previous studies analyzing how T. denticola stimulates innate immune responses have demonstrated that T. denticola can stimulate human gingival epithelial cells (HGECs) through TLR2 (3). However, the functional significance of other TLRs involved in mediating cellular responses to T. denticola and how this recognition mediates qualitative and quantitative aspects of the host inflammatory response are currently not well understood (29).…”