Oral treponemes and their outer membrane extracts activate human gingival epithelial cells through toll-like receptor 2

Stimulation of Human Periodontal Ligament Fibroblasts Using Purified Dentilisin Extracted from Treponema denticola

Periodontal disease is a chronic multifactorial disease triggered by a complex of bacterial species. These interact with host tissues to cause the release of a broad array of pro-inflammatory cytokines, chemokines, and tissue remodelers, such as matrix metalloproteinases (MMPs), which lead to the destruction of periodontal tissues. Patients with severe forms of periodontitis are left with a persistent pro-inflammatory transcriptional profile throughout the periodontium, even after clinical intervention, leading to the destruction of teeth-supporting tissues. The oral spirochete, Treponema denticola , is consistently found at significantly elevated levels at sites with advanced periodontal disease. Of all T. denticola virulence factors that have been described, its chymotrypsin-like protease complex, also called dentilisin, has demonstrated a multitude of cytopathic effects consistent with periodontal disease pathogenesis, including alterations in cellular adhesion activity, degradation of various endogenous extracellular matrix-substrates, degradation of host chemokines and cytokines, and ectopic activation of host MMPs. Thus, the following model of T. denticola -human periodontal ligament cell interactions may provide new knowledge about the mechanisms that drive the chronicity of periodontal disease at the protein, transcriptional, and epigenetic levels, which could afford new putative therapeutic targets. This protocol was validated in: PLOS Pathog (2021), DOI: 10.1371/journal.ppat.1009311.

Pathogenic Mechanisms of Fusobacterium nucleatum on Oral Epithelial Cells

Periodontitis is an oral chronic inflammatory disease and may cause tooth loss in adults. Oral epithelial cells provide a barrier for bacteria and participate in the immune response. Fusobacterium nucleatum (F. nucleatum) is one of the common inhabitants of the oral cavity and has been identified as a potential etiologic bacterial agent of oral diseases, such as periodontitis and oral carcinomas. F. nucleatum has been shown to be of importance in the development of diverse human cancers. In the dental biofilm, it exhibits a structural role as a bridging organism, connecting primary colonizers to the largely anaerobic secondary colonizers. It expresses adhesins and is able to induce host cell responses, including the upregulation of defensins and the release of chemokines and interleukins. Like other microorganisms, its detection is achieved through germline-encoded pattern-recognition receptors (PRRs) and pathogen-associated molecular patterns (PAMPs). By identification of the pathogenic mechanisms of F. nucleatum it will be possible to develop effective methods for the diagnosis, prevention, and treatment of diseases in which a F. nucleatum infection is involved. This review summarizes the recent progress in research targeting F. nucleatum and its impact on oral epithelial cells.

Bacterial-Specific Induction of Inflammatory Cytokines Significantly Decreases upon Dual Species Infections of Implant Materials with Periodontal Pathogens in a Mouse Model

Cytokine profiles are often perturbed after infections of medical implants. With a non-invasive in vivo imaging system, we report in a mouse model that interferon expression after infection of subcutaneous implants with Streptococcus oralis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, and Treponema denticola (alone or as a combination) was species-specific, persisted longer in the presence of implants, and notably decreased upon dual species infections. This type I interferon expression disappeared within two weeks; however, histology of implant–tissue interface indicated high recruitment of immune cells even after three weeks. This was suggestive that biomaterial-associated infections could have prolonged effects, including the systemic stimulation of inflammatory cytokines. The present study investigated the systemic impact of this chronic peri-implant inflammation on the systemic expression of inflammatory cytokines (23) using a multiplex assay. Initially, the cytokine measurement in murine fibroblasts exposed to periodontal pathogens remained limited to the expression of five cytokines, namely, IL-6, G-CSF, CXCL-1/KC, MCP-1 (MCAF), and IL-12 (p40). The systemic determination of cytokines in mice increased to 19 cytokines (IL-1α, IL-2, IL-3, IL-5, IL-6, IL-9, IL-12 (p40), IL-12 (p70), IL-13, IL-17A, CCL-11/Eotaxin, G-CSF, IFN-γ, CXCL1/KC, MCP-1 (MCAF), MIP-1α/CCL3, MIP-1β/CCL4, CCL5/RANTES, and TNF-α). Systemic induction of cytokines was species-specific in the mouse model. The cytokine induction from infected implants differed significantly from sole tissue infections and sterile implants. Notably, systemic cytokine induction decreased after infections with dual species compared to single species infections. These findings describe the systemic effect of chronic peri-implant inflammation on the systemic induction of inflammatory cytokines, and this effect was strongly correlated to the type and composition of initial infection. Systemic modulations in cytokine expression upon dual species infections exhibit an exciting pattern that might explain the complications associated with biomaterial-related infection in patients. Moreover, these findings validate the requirement of multispecies infections for pre-clinical studies involving animal models.

Paradigm shift in the pathogenesis and treatment of oral cancer and other cancers focused on the oralome and antimicrobial-based therapeutics

The oral microbiome is a community of microorganisms, comprised of bacteria, fungi, viruses, archaea, and protozoa, that form a complex ecosystem within the oral cavity. Although minor perturbations in the environment are frequent and compensable, major shifts in the oral microbiome can promote an unbalanced state, known as dysbiosis. Dysbiosis can promote oral diseases, including periodontitis. In addition, oral dysbiosis has been associated with other systemic diseases, including cancer. The objective of this review is to evaluate the epidemiologic evidence linking periodontitis to oral, gastrointestinal, lung, breast, prostate, and uterine cancers, as well as describe new evidence and insights into the role of oral dysbiosis in the etiology and pathogenesis of the cancer types discussed. Finally, we discuss how antimicrobials, antimicrobial peptides, and probiotics may be promising tools to prevent and treat these cancers, targeting both the microbes and associated carcinogenesis processes. These findings represent a novel paradigm in the pathogenesis and treatment of cancer focused on the oral microbiome and antimicrobial‐based therapies.

Treponema denticola dentilisin triggered TLR2/MyD88 activation upregulates a tissue destructive program involving MMPs via Sp1 in human oral cells

Periodontal disease is driven by dysbiosis in the oral microbiome, resulting in over-representation of species that induce the release of pro-inflammatory cytokines, chemokines, and tissue-remodeling matrix metalloproteinases (MMPs) in the periodontium. These chronic tissue-destructive inflammatory responses result in gradual loss of tooth-supporting alveolar bone. The oral spirochete Treponema denticola, is consistently found at significantly elevated levels in periodontal lesions. Host-expressed Toll-Like Receptor 2 (TLR2) senses a variety of bacterial ligands, including acylated lipopolysaccharides and lipoproteins. T. denticola dentilisin, a surface-expressed protease complex comprised of three lipoproteins has been implicated as a virulence factor in periodontal disease, primarily due to its proteolytic activity. While the role of acylated bacterial components in induction of inflammation is well-studied, little attention has been given to the potential role of the acylated nature of dentilisin. The purpose of this study was to test the hypothesis that T. denticola dentilisin activates a TLR2-dependent mechanism, leading to upregulation of tissue-destructive genes in periodontal tissue. RNA-sequencing of periodontal ligament cells challenged with T. denticola bacteria revealed significant upregulation of genes associated with extracellular matrix organization and degradation including potentially tissue-specific inducible MMPs that may play novel roles in modulating host immune responses that have yet to be characterized within the context of oral disease. The Gram-negative oral commensal, Veillonella parvula, failed to upregulate these same MMPs. Dentilisin-induced upregulation of MMPs was mediated via TLR2 and MyD88 activation, since knockdown of expression of either abrogated these effects. Challenge with purified dentilisin upregulated the same MMPs while a dentilisin-deficient T. denticola mutant had no effect. Finally, T. denticola-mediated activation of TLR2/MyD88 lead to the nuclear translocation of the transcription factor Sp1, which was shown to be a critical regulator of all T. denticola-dependent MMP expression. Taken together, these data suggest that T. denticola dentilisin stimulates tissue-destructive cellular processes in a TLR2/MyD88/Sp1-dependent fashion.

A Differential Innate Immune Response in Active and Chronic Stages of Bovine Infectious Digital Dermatitis

Digital dermatitis (DD) commonly associated with Treponema spp. infection is a prevalent infectious bovine foot disease characterized by ulcerative and necrotic lesions. Lesions associated with DD are often classified using the M-stage scoring system, with M0 indicating healthy heel skin and M4 indicating chronic lesions. Current treatments utilizing antimicrobials or chemical footbaths are often ineffective and rarely cure DD lesions. Understanding the function of the innate immune response in the pathogenesis of DD will help to identify novel therapeutic approaches. In this study, the expression of the local innate host defense peptides cathelicidins and β-defensins was investigated in cows with DD and associated with the presence of treponemes and inflammatory reactions. Samples from active ulcerative DD lesions (M2) had considerable epidermal neutrophilic infiltration and increased gene expression of β-defensin tracheal antimicrobial peptides compared to control skin. Samples from acute lesions also had elevated local Cxcl-8 and TLR4 gene expression and abundant treponemes as identified by direct visualization, immunohistochemistry, and culture. Conversely, the anti-inflammatory peptide IL-10 was elevated in skin from chronic (M4) lesions, whereas bovine cathelicidin myeloid antimicrobial peptide 28 (Bmap-28) was increased in skin from oxytetracycline-treated M2 lesions. Experiments using cultured human keratinocytes challenged with Treponema spp. isolated from clinical cases of bovine DD showed that structural products from treponemes are able to initiate the innate immune response, in part through TLR2 signaling. These findings indicate that neutrophil influx, Cxcl-8, and β-defensin are key markers of active DD. Cathelicidins and IL-10 seem important in response to treatment or during the chronic proliferative stages of the disease.

Activation of the Innate Immune System by Treponema denticola Periplasmic Flagella through Toll-Like Receptor 2

Treponema denticola is an indigenous oral spirochete that inhabits the gingival sulcus or periodontal pocket. Increased numbers of oral treponemes within this environment are associated with localized periodontal inflammation, and they are also part of an anaerobic polymicrobial consortium responsible for endodontic infections. Previous studies have indicated that T. denticola stimulates the innate immune system through Toll-like receptor 2 (TLR2); however, the pathogen-associated molecular patterns (PAMPs) responsible for T. denticola activation of the innate immune system are currently not well defined. In this study, we investigated the role played by T. denticola periplasmic flagella (PF), unique motility organelles of spirochetes, in stimulating an innate immune response. Wild-type T. denticola stimulated the production of the cytokines tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), IL-6, IL-10, and IL-12 by monocytes from human peripheral blood mononuclear cells, while its isogenic nonmotile mutant lacking PF resulted in significantly diminished cytokine stimulation. In addition, highly purified PF were able to dose dependently stimulate cytokine TNF-α, IL-1β, IL-6, IL-10, and IL-12 production in human monocytes. Wild-type T. denticola and the purified PF triggered activation of NF-κB through TLR2, as determined using a variety of TLR-transfected human embryonic 293 cell lines, while the PF-deficient mutants lacked the ability to stimulate, and the complemented PF-positive T. denticola strain restored the activation. These findings suggest that T. denticola stimulates the innate immune system in a TLR2-dependent fashion and that PF are a key bacterial component involved in this process.

Differential Responses of Pattern Recognition Receptors to Outer Membrane Vesicles of Three Periodontal Pathogens

Highly purified outer membrane vesicles (OMVs) of the periodontal pathogens, Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia were produced using tangential flow ultrafiltration, ultracentrifugation and Optiprep density gradient separation. Cryo-TEM and light scattering showed OMVs to be single lipid-bilayers with modal diameters of 75 to 158 nm. Enumeration of OMVs by nanoparticle flow-cytometry at the same stage of late exponential culture indicated that P. gingivalis was the most prolific OMV producer. P. gingivalis OMVs induced strong TLR2 and TLR4-specific responses and moderate responses in TLR7, TLR8, TLR9, NOD1 and NOD2 expressing-HEK-Blue cells. Responses to T. forsythia OMVs were less than those of P. gingivalis and T. denticola OMVs induced only weak responses. Compositional analyses of OMVs from the three pathogens demonstrated differences in protein, fatty acids, lipopolysaccharide, peptidoglycan fragments and nucleic acids. Periodontal pathogen OMVs induced differential pattern recognition receptor responses that have implications for their role in chronic periodontitis.

Inhibition of toll-like receptor 2 (TLR-2)-mediated response in human alveolar epithelial cells by mycolic acids and Mycobacterium tuberculosis mce1 operon mutant

In human lungs, the earliest encounter of Mycobacterium tuberculosis, the agent of tuberculosis, involves alveolar epithelial cells. Droplets expectorated by a patient with tuberculosis are likely to contain a mixed population of M. tuberculosis cells in different physiologic and metabolic states from the lung lesions of the patient. Here, we compared the chemokine expression patterns of human epithelial cell line A549 and RAW 264.7 macrophage cells infected with wild-type M. tuberculosis H37Rv against patterns induced by a mutant that accumulates free mycolic acids in its cell wall (Δmce1). We also examined the effect of free mycolic acids on toll-like receptor-2 (TLR-2). Wild-type M. tuberculosis induced significantly higher levels of IL-8, MCP-1, RANTES, and IP-10 in both cell types than did Δmce. Free mycolic acids reduced the ability of the mammalian cells to respond to a TLR-2 agonist in a dose-dependent manner. These observations suggest that differences in mycolic acid abundance in the M. tuberculosis cell wall can affect TLR-2-mediated pro-inflammatory response in both epithelial and macrophage cells. The final fate of a new infection may be ultimately determined by the proportion of M. tuberculosis cells expressing free mycolates in the infecting inoculum population.

Porphyromonas gingivalis, Treponema denticola and toll-like receptor 2 are associated with hypertensive disorders in placental tissue: a case-control study

AIM(S)

To explore the associations between the presence of periodontal pathogens and the expression of toll-like receptors (TLR-2 and TLR-4) in the placental tissue of patients with hypertensive disorders compared to the placentas of healthy normotensive patients.

MATERIAL AND METHODS

A case-control study was performed. From a cohort composed of 126 pregnant women, 33 normotensive healthy pregnant women were randomly selected, and 25 cases of patients with hypertensive disorders of pregnancy, including gestational hypertension and pre-eclampsia, were selected. Placental biopsy was obtained after aseptic placental collection at the time of delivery. All of the samples were processed and analysed for the detection of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Treponema denticola and Tannerella forsythia using the polymerase chain reaction (PCR) technique. Determination of the expressions of TLR-2 and TLR-4 was performed in samples of total purified protein isolated from placental tissues and analysed by ELISA. The data were assessed using descriptive statistics. The associations among variables were estimated through multiple logistic regression models and the Mann-Whitney test to evaluate the differences between the two groups.

RESULTS

A significant increase was observed in the expression of TLR-2 in the placentas of patients with hypertensive disorders (p = 0.04). Additionally, the multiple logistic regression models demonstrated an association between the presence of T. denticola and P. gingivalis in placental tissues and hypertensive disorders (OR: 9.39, p = 0.001, CI 95% 2.39-36.88 and OR: 7.59, p = 0.019, CI 95% 1.39-41.51, respectively).

CONCLUSIONS

In the present study, pregnant women with periodontal disease presented an association in the placental tissue between the presence of T. denticola and P. gingivalis and hypertensive disorders. Additionally, increased expression of TLR-2 was observed. However, further studies are required to determine the specific roles of periodontal pathogens and TLRs in the placental tissue of patients with pregnancy-related hypertensive disorders.

Treponema denticola interactions with host proteins

Oral Treponema species, most notably T. denticola, are implicated in the destructive effects of human periodontal disease. Progress in the molecular analysis of interactions between T. denticola and host proteins is reviewed here, with particular emphasis on the characterization of surface-expressed and secreted proteins of T. denticola involved in interactions with host cells, extracellular matrix components, and components of the innate immune system.

Composition and localization of Treponema denticola outer membrane complexes

The Treponema denticola outer membrane lipoprotein-protease complex (dentilisin) contributes to periodontal disease by degrading extracellular matrix components and disrupting intercellular host signaling pathways. We recently demonstrated that prcB, located upstream of and cotranscribed with prcA and prtP, encodes a 22-kDa lipoprotein that interacts with PrtP and is required for its activity. Here we further characterize products of the protease locus and their roles in expression, formation, and localization of outer membrane complexes. PrcB migrates in native gels as part of a >400-kDa complex that includes PrtP and PrcA, as well as the major outer sheath protein Msp. PrcB is detectable as a minor constituent of the purified active protease complex, which was previously reported to consist of only PrtP and auxiliary polypeptides PrcA1 and PrcA2. Though it lacks the canonical ribosome binding site present upstream of both prcA and prtP, PrcB is present at levels similar to those of PrtP in whole-cell extracts. Immunofluorescence microscopy demonstrated cell surface exposure of the mature forms of PrtP, PrcA1, PrcB, and Msp. The 16-kDa N-terminal acylated fragment of PrtP (predicted to be released during activation of PrtP) was present in cell extracts but was detected neither in the purified active protease complex nor on the cell surface. PrcA2, detectable on the surface of Msp-deficient cells but not that of wild-type cells, coimmunoprecipitated with Msp. Our results indicate that PrcB is a component of the outer membrane lipoprotein protease complex and that Msp and PrcA2 interaction may mediate formation of a very-high-molecular-weight outer membrane complex.

Treponema denticola PrcB is required for expression and activity of the PrcA-PrtP (dentilisin) complex

The Treponema denticola surface protease complex, consisting of PrtP protease (dentilisin) and two auxiliary polypeptides (PrcA1 and PrcA2), is believed to contribute to periodontal disease by degrading extracellular matrix components and disrupting host intercellular signaling. Previously, we showed that transcription of the protease operon initiates upstream of TDE0760 (herein designated prcB), the open reading frame immediately 5' of prcA-prtP. The prcB gene is conserved in T. denticola strains. PrcB localizes to the detergent phase of Triton X-114 cell surface extracts and migrates as a 22-kDa polypeptide, in contrast to the predicted 17-kDa cytoplasmic protein encoded in the annotated T. denticola genome. Consistent with this observation, the PrcB N terminus is unavailable for Edman sequencing, suggesting that it is acylated. Nonpolar deletion of prcB in T. denticola showed that PrcB is required for production of PrtP protease activity, including native PrtP cleavage of PrcA to PrcA1 and PrcA2. A 6xHis-tagged PrcB protein coimmunoprecipitates with native PrtP, using either anti-PrtP or anti-His-tag antibodies, and recombinant PrtP copurifies with PrcB-6xHis in nickel affinity chromatography. Taken together, these data are consistent with identification of PrcB as a PrtP-binding lipoprotein that likely stabilizes the PrtP polypeptide during localization to the outer membrane.

Mixture of periodontopathogenic bacteria influences interaction with KB cells

INTRODUCTION

The purpose of this study was to investigate the adhesion and invasion of periodontopathogenic bacteria in varied mixed infections and the release of interleukins from an epithelial cell line (KB cells).

METHODS

KB cells were co-cultured with Porphyromonas gingivalis ATCC 33277 and M5-1-2, Tannerella forsythia ATCC 43037, Treponema denticola ATCC 35405 and Fusobacterium nucleatum ATCC 25586 in single and mixed infections. The numbers of adherent and internalized bacteria were determined up to 18 h after bacterial exposure. Additionally, the mRNA expression and concentrations of released interleukin (IL)-6 and IL-8 were measured.

RESULTS

All periodontopathogenic bacteria adhered and internalized in different numbers to KB cells, but individually without any evidence of co-aggregation also to F. nucleatum. High levels of epithelial mRNA of IL-6 and IL-8 were detectable after all bacterial challenges. After the mixed infection of P. gingivalis ATCC 33277 and F. nucleatum ATCC 25586 the highest levels of released interleukins were found. No IL-6 and IL-8 were detectable after the mixed infection of P. gingivalis M5-1-2 and F. nucleatum ATCC 25586 and the fourfold infection of P. gingivalis ATCC 33277, T. denticola ATCC 35405, T. forsythia ATCC 43037 and F. nucleatum ATCC 25586.

CONCLUSION

Anaerobic periodontopathogenic bacteria promote the release of IL-6 and IL-8 by epithelial cells. Despite a continuous epithelial expression of IL-8 mRNA by all bacterial infections these effects are temporary because of the time-dependent degradation of cytokines by bacterial proteases. Mixed infections have a stronger virulence potential than single bacteria. Further research is necessary to evaluate the role of mixed infections and biofilms in the pathogenesis of periodontitis.

Involvement of Toll-like receptors 2 and 4 in the innate immune response to Treponema denticola and its outer sheath components

Treponema denticola is considered an important oral pathogen in the development and progression of periodontal diseases. In the present study, the mechanisms of recognition and activation of murine macrophages by T. denticola and its major outer sheath protein (MSP) and lipooligosaccharide (LOS or glycolipid) were investigated. T. denticola cells and the MSP induced innate immune responses through TLR2-MyD88, whereas LOS induced a macrophage response through TLR4-MyD88. The presence of gamma interferon (IFN-gamma), or of high numbers of T. denticola, circumvented the requirement for TLR2 for the macrophage response to T. denticola, although the response was still dependent on MyD88. In contrast, synergy with IFN-gamma did not alter the TLR dependence of the response to the T. denticola surface components LOS and MSP, despite enhanced sensitivity. These data suggest that although there is flexibility in the requirements for recognition of T. denticola cells (TLR2 dependent or independent), MyD88 is a requirement for the downstream signaling events that lead to inflammation. We also demonstrate that both outer sheath molecules LOS and MSP induce macrophage tolerance to further stimulation with enterobacterial lipopolysaccharide. Tolerance induced by T. denticola components during mixed infections may represent a general mechanism through which bacteria evade clearance.

Treponema denticola does not induce production of common innate immune mediators from primary gingival epithelial cells

It has been hypothesized that the neutrophil chemoattractant interleukin-8 (IL-8) forms a gradient in the oral cavity, with the highest concentration of IL-8 produced closest to the bacterial biofilm. In periodontitis, this gradient is disrupted, impairing neutrophil chemotaxis to diseased sites. Treponema denticola is prominently associated with periodontal disease, yet little is known about its ability to modulate the production of inflammatory mediators by epithelial cells. Others have shown that dentilisin, the major outer membrane protease of T. denticola, degrades IL-8 in vitro. We now provide evidence that T. denticola also fails to induce IL-8 production from primary gingival epithelial cells (PGEC). The lack of IL-8 production is not explained by IL-8 degradation, because a protease mutant that does not degrade IL-8 does not induce IL-8 production with these stimuli either. The lack of innate immune mediator production may be a more global phenomenon because T. denticola fails to induce IL-6 or intercellular adhesion molecule 1 production from PGEC. T. denticola also fails to induce transcription of IL-8 and human beta-defensin-2 messenger RNA. The lack of immune mediator production is not explained by the failure of T. denticola to interact with Toll-like receptor 2 (TLR-2), as T. denticola stimulates nuclear factor-kappaB nuclear translocation in TLR-2-transfected HEK293 cells. Not only can T. denticola degrade the IL-8 present in the periodontal lesion, but this organism also fails to induce IL-8 production by PGEC. The lack of an epithelial cell response to T. denticola may contribute to the pathogenesis of periodontitis by failing to trigger chemotaxis of neutrophils into the periodontal pocket.

Beyond good and evil in the oral cavity: insights into host-microbe relationships derived from transcriptional profiling of gingival cells

In many instances, the encounter between host and microbial cells, through a long-standing evolutionary association, can be a balanced interaction whereby both cell types co-exist and inflict a minimal degree of harm on each other. In the oral cavity, despite the presence of large numbers of diverse organisms, health is the most frequent status. Disease will ensue only when the host-microbe balance is disrupted on a cellular and molecular level. With the advent of microarrays, it is now possible to monitor the responses of host cells to bacterial challenge on a global scale. However, microarray data are known to be inherently noisy, which is caused in part by their great sensitivity. Hence, we will address several important general considerations required to maximize the significance of microarray analysis in depicting relevant host-microbe interactions faithfully. Several advantages and limitations of microarray analysis that may have a direct impact on the significance of array data are highlighted and discussed. Further, this review revisits and contextualizes recent transcriptional profiles that were originally generated for the specific study of intricate cellular interactions between gingival cells and 4 important plaque micro-organisms. To our knowledge, this is the first report that systematically investigates the cellular responses of a cell line to challenge by 4 different micro-organisms. Of particular relevance to the oral cavity, the model bacteria span the entire spectrum of documented pathogenic potential, from commensal to opportunistic to overtly pathogenic. These studies provide a molecular basis for the complex and dynamic interaction between the oral microflora and its host, which may lead, ultimately, to the development of novel, rational, and practical therapeutic, prophylactic, and diagnostic applications.

Innate immune responses of gingival epithelial cells to nonperiodontopathic and periodontopathic bacteria

BACKGROUND AND OBJECTIVE

We have previously reported different susceptibilities of periodontopathic and nonperiodontopathic bacteria to antimicrobial peptides and phagocytosis by neutrophils. Differences between the two groups of bacteria may exist also in their ability to induce immune responses from the host. Therefore, we evaluated the effects of various oral bacteria on innate immune responses by gingival epithelial cells.

MATERIAL AND METHODS

HOK-16B cells were cocultured with live or lysed nonperiodontopathic (n = 3) and periodontopathic (n = 5) bacterial species. The levels of human beta defensin-1, -2 and -3, and of the cathelicidin, LL-37, were examined by real-time reverse transcription-polymerase chain reaction, and the accumulated interleukin-8 and interleukin-1 alpha were measured by enzyme-linked immunosorbent assay.

RESULTS

Nonperiodontopathic bacteria up-regulated some antimicrobial peptides without affecting the levels of cytokines. In the periodontopathic group, the orange-complex bacteria induced antimicrobial peptides and interleukin-8 efficiently, but the red-complex bacteria often demonstrated suppressive effects. In contrast to live bacteria, bacterial lysates had no suppressive effects. In addition, some bacterial lysates demonstrated a reduced ability to induce antimicrobial peptides compared with live bacteria.

CONCLUSION

The nonperiodontopathic, the orange-complex, and the red-complex bacteria had different effects on the innate immune responses from gingival epithelial cells, which may affect the outcome of their host-microbial interaction in gingival sulcus.

Possible requirement of intercellular adhesion molecule-1 for invasion of gingival epithelial cells byTreponema medium

Oral treponemes are members of the spirochete family of bacteria associated with periodontal diseases. In the present study, we demonstrate that intercellular adhesion molecule-1 (ICAM-1) on human gingival epithelial cells (HGEC) contributed to the invasion of Treponema medium , a medium-sized oral Treponema, into those cells. The quantity of T. medium in HGEC was found to peak at 2 h after inoculation and then decreased gradually. Immunofluorescence microscopy findings showed that the bacteria were colocalized with ICAM-1 on HGEC. Furthermore, knockdown of ICAM-1 in HGEC resulted in inhibition of T. medium invasion by RNA interference, whereas that of Toll-like receptor 2 did not. These results suggest that ICAM-1 may be required for the invasion of T. medium into HGEC, and they indicate that the molecule plays a principal role in the primary stages of the development and progression of chronic periodontitis.

Treponema denticola activates mitogen-activated protein kinase signal pathways through Toll-like receptor 2

Treponema denticola, a spirochete indigenous to the oral cavity, is associated with host inflammatory responses to anaerobic polymicrobial infections of the root canal, periodontium, and alveolar bone. However, the cellular mechanisms responsible for the recognition of T. denticola by the innate immune system and the underlying cell signaling pathways that regulate the inflammatory response to T. denticola are currently unresolved. In this study, we demonstrate that T. denticola induces innate immune responses via the utilization of Toll-like receptor 2 (TLR2) but not TLR4. Assessment of TLR2/1 and TLR2/6 heterodimers revealed that T. denticola predominantly utilizes TLR2/6 for the induction of cellular responses. Analysis of the mitogen-activated protein kinase (MAPK) signaling pathway in T. denticola-stimulated monocytes identified a prolonged up-regulation of the MAPK extracellular signal-related kinase 1/2 (ERK1/2) and p38, while no discernible increase in phospho-c-Jun N-terminal kinase 1/2 (JNK1/2) levels was observed. With the aid of pharmacological inhibitors selectively targeting ERK1/2 via the mitogen-activated protein kinase/extracellular signal-related kinase 1/2 kinase and p38, we further demonstrate that ERK1/2 and p38 play a major role in T. denticola-mediated pro- and anti-inflammatory cytokine production.

Treponema denticola induces interleukin-8 and macrophage chemoattractant protein 1 production in human umbilical vein epithelial cells

Treponema denticola, a major pathogen of periodontitis, has also been detected in the lesions of atherosclerosis. The aim of this study was to investigate induction of chemokine production in human umbilical vein endothelial cells (HUVECs) by T. denticola and determine whether those chemokines were degraded by a protease, dentilisin. T. denticola ATCC35405 or dentilisin-deficient mutant K1 were added to HUVECs and levels of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) in the culture supernatants were determined by enzyme-linked immunosorbent assay. T. denticola ATCC35405 induced production of IL-8 in a time-dependent manner, with both production of IL-8 and expression of IL-8 mRNA showing higher levels than with exposure to dentilisin-deficient mutant K1. Although exposure to ATCC35405 induced expression of MCP-1 mRNA in the HUVECs, MCP-1 levels were remained similar to that in unstimulated cells. IL-8 and MCP-1 showed partial hydrolysis with exposure to T. denticola ATCC35405, but not with T. denticola K1. These results suggest that T. denticola can evade host defense mechanisms by modulating production of IL-8 and MCP-1, and that this play a role in the development of chronic infections such as periodontitis. The association of T. denticola infection to atherosclerosis was also discussed based on the present study.

Association of Eubacterium nodatum and Treponema denticola with human periodontitis lesions

BACKGROUND

The purpose of the present investigation was to compare the levels, proportions and percentage of sites colonized by 40 bacterial species in subgingival plaque samples from periodontally healthy subjects and patients with chronic periodontitis to seek possible pathogens other than the consensus pathogens Porphyromonas gingivalis and Tannerella forsythia.

METHOD

Subgingival plaque samples were taken from the mesial aspect of each tooth in 635 subjects with chronic periodontitis and 189 periodontally healthy subjects. The samples were individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization (total samples = 21,832). Mean counts, % DNA probe counts and percentage of sites colonized at >10(5) were determined for each species in each subject and then averaged in each clinical group. Significance of difference between groups was determined using the Mann-Whitney test. Association between combinations of species and periodontal status was examined by stepwise logistic regression analysis. Analyses were repeated using a subset of subjects from both clinical groups who had proportions of P. gingivalis plus T. forsythia less than the median (4.42%) found in periodontally healthy subjects. All analyses were adjusted for multiple comparisons.

RESULTS

For the 824 subjects the consensus pathogens P. gingivalis and T. forsythia as well as Eubacterium nodatum and Treponema denticola had significantly higher mean counts, proportions and percentage of sites colonized in samples from subjects with periodontitis than from periodontally healthy subjects. There were significantly more Capnocytophaga gingivalis, Streptococcus gordonii and Veillonella parvula in periodontally healthy subjects. E. nodatum, T. denticola, Streptococcus oralis, Streptococcus intermedius, Fusobacterium nucleatum ssp. vincentii all had higher counts and proportions in diseased than healthy subjects who had low proportions of P. gingivalis and T. forsythia. Logistic regression analysis indicated that the same species groups were associated with disease status after adjusting for the proportions of the other species.

CONCLUSIONS

This investigation confirmed the strong association of P. gingivalis and T. forsythia with chronic periodontitis and emphasized a strong association of E. nodatum and T. denticola with periodontitis whether in the presence or absence of high levels of the consensus pathogens. Other species, including S. oralis, Eikenella corrodens, S. intermedius and F. nucleatum ssp. vincentii, were associated with disease when P. gingivalis and T. forsythia were present in low proportions.

Porphyromonas gingivalis enhances FasL expression via up-regulation of NFkappaB-mediated gene transcription and induces apoptotic cell death in human gingival epithelial cells

The interaction between epithelial cells and micro-organisms is often a crucial initiating event in infectious diseases. Infection with Porphyromonas gingivalis, a Gram-negative anaerobe, is strongly associated with severe periodontal disease. This bacterium possesses an array of virulence factors, some of which can induce apoptosis. The tumour necrosis factor (TNF) receptor family is involved in the regulation of cellular homeostasis, cell surface molecules involved in phagocytosis, Fas ligand (L) expression and activation of the caspase cascade resulting in DNA fragmentation and cell blebbing. The current study examined the role of nuclear factor-kappaB (NFkappaB) in FasL-mediated apoptotic cell death in primary human gingival epithelial cells (HGEC) induced by heat-killed P. gingivalis, probably through TLR signalling pathways. A marked up-regulation of TLR2 and Fas-FasL was detected in HGEC stimulated with P. gingivalis. Activation of NFkappaB by P. gingivalis in HGEC was demonstrated by an NFkappaB promoter luciferase assay as well as by phosphorylation of p65 as detected by Western blotting. Activation of cleaved caspase-3 and caspase-8 resulted in apoptotic cell death of HGEC. The survival proteins c-IAP-1/c-IAP-2 were decreased in HGEC exposed to P. gingivalis. HGEC apoptosis induced by P. gingivalis was inhibited by an anti-human FasL monoclonal antibody. Blockade of NFkappaB by helenalin resulted in down-regulation of FasL whereas a caspase-8 inhibitor did not decrease FasL. Taken together, these studies show that P. gingivalis can induce epithelial cell apoptosis through Fas-FasL up-regulation and activation of caspase-3 and caspase-8.

The Treponema denticola surface protease dentilisin degrades interleukin-1 beta (IL-1 beta), IL-6, and tumor necrosis factor alpha

Dentilisin is a major surface protease and virulence factor of the bacterium Treponema denticola. In this study, we found that T. denticola reduced inflammatory cytokines, including interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor alpha, in peripheral blood mononuclear cells through degradation by dentilisin.

The metabolism of cholesterol and certain hormonal steroids by Treponema denticola

The aim was to investigate whether reference cultures and fresh isolates of Treponema denticola are able to 5alpha-reduce and further metabolise testosterone, 4-androstenedione, progesterone, corticosterone, cortisol or cholesterol. Two reference and five freshly isolated cultures of T. denticola were incubated with either radiolabeled or unlabeled steroid substrates; in the first case products were identified by thin layer chromatography and in the latter by gas chromatography-mass spectroscopy. All the substrates were 5alpha-reduced. Both reference cultures and fresh isolates of T. denticola presented 3beta- and 17beta-hydroxy steroid dehydrogenase activity. It was concluded that T. denticola was capable of steroid metabolism and hypotheses are discussed regarding the in vivo function of this metabolism including, T. denticola utilising host supplied steroids as growth factors and T. denticola steroid metabolism acting as a virulence factor.

Uroepithelial cells can directly respond to Mycobacterium bovis bacillus Calmette-Guérin through Toll-like receptor signalling

OBJECTIVE

To investigate, in a human urinary tract cell line, the interaction of Toll-like receptor (TLR) signals with cytoplasmic adapter proteins MyD88 and bacillus Calmette-Guérin (BCG), and evaluate the epithelial cytokine response to BCG infection. Intravesical BCG therapy is effective against carcinoma in situ and as prophylaxis for recurrence, but although immunological mechanisms have been assumed, the mechanisms of the antitumour effects of BCG have not been completely elucidated.

MATERIALS AND METHODS

The cell line was first screened for TLR expression by reverse transcription-polymerase chain reaction (RT-PCR). Total RNA was isolated from a human urinary cell line, Hu35E6E7, and cDNA synthesised. PCR was used to measure the gene expression of TLR-2, -3, -4, -5, -9, MyD88, MD-2, CD14 and interleukin-8 and -6. The Hu35E6E7 cell line was cultured in keratinocyte serum-free medium, and BCG was added to the cell culture. After Hu35E6E7 cells were stimulated by BCG for various periods, the total RNA of the cells was extracted. Quantitative real-time PCR was conducted for MyD88 using appropriate probes, and the expression of MyD88 analysed. The cell supernatant was collected, and the levels of interferon-gamma, tumour necrosis factor-alpha, interleukin-2, -12, -4, -6, -10, -8 and -1beta were assayed using an enzyme-linked immunosorbent assay.

RESULTS

Uroepithelial cells expressed TLR-2, -3, -4 and -9, and MyD88, MD2, CD14, interleukin-6 and -8 were also detected. At 3, 6, 9 and 12 h after adding BCG, quantitative PCR assay showed that the expression of MyD88 was maximal at 6 h. The presence of BCG stimulated the release only of interleukin-6 and -8 from Hu35E6E7 cells after 6 h. By contrast, interferon-gamma, tumour necrosis factor-alpha, interleukin-2, -12, -4, -10 and -1beta were not detected in the culture supernatant.

CONCLUSION

These results show that uroepithelial cells, but not immune cells, responded directly to BCG through TLR signalling. Further investigation is needed to determine the role of cytokines released from uroepithelial cells after BCG infection.

Cellular and humoral systemic and mucosal immune responses stimulated in volunteers by an oral polybacterial immunomodulator "Dentavax"

The oral polybacterial immunomodulator Dentavax (D), composed of killed cells from Klebsiella pneumoniae, Streptococcus pyogenes, Staphylococcus aureus, Candida albicans and Lactobacillus acidophilus and their lysates was created for immunoprophylaxis and therapy of oral mucosa and parodont inflammations. The stimulating effect of the preparation was evaluated in twelve volunteers immunized for 10 consecutive days. On days 7, 14, 21, 28 and 49 after the last immunization peripheral blood (PB) lymphocyte subsets, T lymphocyte activation and PB phagocytic activity, were studied by flow cytometry. PB lymphocyte proliferative responses to PHA, rIL-2, LPS and D were evaluated radiometrically. The production of TNF-alpha in supernatants of in vitro stimulated lymphocytes and specific IgA, IgM and IgG antibodies in serum and saliva was determined by ELISA. Ultrastructural morphologic changes in T and B lymphocyte populations were also investigated. Although no significant changes in the levels of basic lymphocyte subsets were detected, the early/late (CD57+/CD57-) CD8 T effectors ratio was increased at the end of the studied period, as were the percentage of PHA-responding (CD69+) T cells and PB phagocytizing cells. The most prominent lymphoprolipherative responses were measured upon costimulation with LPS+D and PHA+D on day 21. Electron-microscopic studies demonstrated a significant effect of D on both T and B cell activity. TNF-alpha concentration increased progressively from day 7 till the end of the investigation. Maximal concentrations were observed after stimulation with D and LPS. An increased level of specific salivary and serum antibodies against the components of D was found, with highest levels between days 7 and 21. Specific secretory IgA predominated in saliva as compared to IgM and IgG. Our results demonstrate the stimulating effect of Dentavax on PB lymphocyte functional activity and the specific humoral systemic and mucosal immunity.

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

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.

Inflammatory responses of a macrophage/epithelial cell co-culture model to mono and mixed infections with Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia

Accumulated evidence points to Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia as three major etiologic agents of chronic periodontitis. Epithelial cells and macrophages play a major role in the host response to periodontopathogens, and the secretion of inflammatory mediators and matrix metalloproteinases (MMPs) by these host cells is believed to contribute to periodontal tissue destruction. The aim of this study was to investigate the inflammatory response of a macrophage/epithelial cell co-culture model following mono or mixed infections with the above three periodontopathogens. An in vitro co-culture model composed of epithelial-like transformed cells (HeLa cell line) and macrophage-like cells (phorbol myristic acid-differentiated U937 monocytic cell line) was challenged with whole cells or lipopolysaccharides (LPS) of P. gingivalis, T. denticola, and T. forsythia, individually and in combination. Following stimulation, the production of interleukin-1 beta (IL-1beta), IL-6, IL-8, tumor necrosis factor alpha (TNF-alpha), regulated on activation normal T cell expressed and secreted (RANTES), prostaglandin E2 (PGE2), and MMP-9 were quantified by enzyme-linked immunoassays. We observed that mono or mixed infections of the co-culture model induced the secretion of IL-1beta, IL-6, IL-8, PGE2, and MMP-9. P. gingivalis and T. forsythia induced an increase in RANTES secretion, whereas T. denticola alone or in combination resulted in a significant decrease in RANTES levels. All LPS challenges induced an increase in chemokine, MMP-9, and PGE2 production. No synergistic effect on the production of cytokines, chemokines, PGE2, and MMP-9 was observed for any of the bacterial or LPS mixtures tested. This study supports the view that P. gingivalis, T. denticola, and T. forsythia may induce high levels of pro-inflammatory mediators and MMP-9 in periodontal lesions, thus contributing to the progression of periodontitis.

Probiotic Lactobacillus-induced improvement in murine chronic inflammatory bowel disease is associated with the down-regulation of pro-inflammatory cytokines in lamina propria mononuclear cells

IL-6/STAT-3 signals play key roles in inflammatory bowel disease (IBD). It is known that Lactobacillus casei strain Shirota (LcS) improves inflammatory disorders. This study aimed to elucidate the effect of LcS on murine chronic IBD and to clarify the mechanism. We focused the inhibitory effect of LcS on the production of IL-6 in lipopolysaccharide (LPS)-stimulated large intestinal lamina propria mononuclear cells (LI-LPMC) isolated from mice with chronic colitis and in RAW264.7 cells in vitro. We also determined in vivo the effect of LcS on murine chronic IBD models induced with dextran sodium sulphate and SAMP1/Yit mice. Finally, we examined the cellular determinants of LcS for the down-regulation of IL-6 secretion by LI-LPMC, RAW264.7 cells and peripheral blood mononuclear cells (PBMC) derived from patients with ulcerative colitis (UC). LcS, but not other strains of Lactobacillus, inhibited the production of IL-6 in LPS-stimulated LI-LPMC and RAW264.7 cells, down-regulating the nuclear translocation of NF-kappaB. The LcS-diet-improved murine chronic colitis is associated with the reduction of IL-6 synthesis by LI-LPMC. LcS also improved chronic ileitis in SAMP1/Yit mice. The release of IL-6 in vitro in LPS-stimulated LI-LPMC, RAW 264.7 cells and UC-PBMC was inhibited by a polysaccharide-peptidoglycan complex (PSPG) derived from LcS. This probiotic-induced improvement in murine chronic inflammatory bowel disease is associated with the down-regulation of pro-inflammatory cytokines such as IL-6 and IFN-gamma production in LPMC. Therefore, LcS may be a useful probiotic for the treatment of human inflammatory bowel disease.

The structure and biological characteristics of the Spirochaeta aurantia outer membrane glycolipid LGLB

In an attempt to isolate lipopolysaccharide from Spirochaeta aurantia, Darveau-Hancock extraction of the cell mass was performed. While no lipopolysaccharide was found, two carbohydrate-containing compounds were detected. They were resolved by size-exclusion chromatography into high molecular mass (LGLA) and low molecular mass (LGLB) fractions. Here we present the results of the analysis of the glycolipid LGLB. Deacylation of LGLB with hydrazine and separation of the products by using anion-exchange chromatography gave two major products. Their structure was determined by using chemical methods, NMR and mass spectrometry. All monosaccharides had the D-configuration, and aspartic acid had the L-configuration. Intact LGLB contained two fatty groups at O-2 and O-3 of the glycerol residue. Nonhydroxylated C14 to C18 fatty acids were identified, which were predominantly unsaturated or branched. LGLB was able to gel Limulus amebocyte lysate, albeit at a lower level than that observed for Escherichia coli O113 lipopolysaccharide. However, even large amounts of LGLB were unable to stimulate any Toll-like receptor (TLR) examined, including TLR4 and TLR2, previously shown to be sensitive to lipopolysaccharide and glycolipids from diverse bacterial origins, including other spirochetes.

Lipopolysaccharide preparation extracted from Porphyromonas gingivalis lipoprotein-deficient mutant shows a marked decrease in toll-like receptor 2-mediated signaling

We recently demonstrated that a new PG1828-encoded lipoprotein (PG1828LP) was able to be separated from a Porphyromonas gingivalis lipopolysaccharide (LPS) preparation, and we found that it exhibited strong cell activation, similar to that of Escherichia coli LPS, through a Toll-like receptor 2 (TLR2)-dependent pathway. In order to determine the virulence of PG1828LP toward cell activation, we generated a PG1828-deficient mutant of P. gingivalis strain 381 by allelic exchange mutagenesis using an ermF-ermAM antibiotic resistance cassette. A highly purified preparation of LPS from a PG1828-deficient mutant (DeltaPG1828-LPS) showed nearly the same ladder-like patterns in silver-stained gels as a preparation of LPS from a wild-type strain (WT-LPS), as well as Limulus amoebocyte lysate activities that were similar to those of the WT-LPS preparation. However, the ability of the DeltaPG1828-LPS preparation to activate NF-kappaB in TLR2-expressing cells was markedly attenuated. Cytokine production by human gingival fibroblasts was also decreased in response to the DeltaPG1828-LPS preparation in comparison with the WT-LPS preparation, and the activity was comparable to the stimulation of highly purified lipid A of P. gingivalis by TLR4. Further, lethal toxicity was rarely observed following intraperitoneal injection of the PG1828-deficient mutant into mice compared to that with the wild-type strain, while the DeltaPG1828-LPS preparation showed no lethal toxicity. Taken together, these results clearly indicate that PG1828LP plays an essential role in inflammatory responses and may be a major virulence factor of P. gingivalis.

Mutagenesis of a novel gene in the prcA-prtP protease locus affects expression of Treponema denticola membrane complexes

A novel gene was identified in the Treponema denticola prcA-prtP protease operon. Strains with mutations in either the prcA-prtP or the msp region showed altered expression of a product(s) of the other locus. Together, these results provide information on the assembly of outer membrane complexes involved in T. denticola interaction with host cells and tissue.

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

Treponema maltophilum and Treponema lecithinolyticum belong to the group IV oral spirochetes and are associated with endodontic infections, as well as periodontitis. Recently, the genes encoding the major surface proteins (Msps) of these bacteria (MspA and MspTL, respectively) were cloned and sequenced. The amino acid sequences of these proteins showed significant similarity. In this study we analyzed the functional role of these homologous proteins in human monocytic THP-1 cells and primary cultured periodontal ligament (PDL) cells using recombinant proteins. The complete genes encoding MspA and MspTL without the signal sequence were cloned into Escherichia coli by using the expression vector pQE-30. Fusion proteins tagged with N-terminal hexahistidine (recombinant MspA [rMspA] and rMspTL) were obtained, and any possible contamination of the recombinant proteins with E. coli endotoxin was removed by using polymyxin B-agarose. Flow cytometry showed that rMspA and rMspTL upregulated the expression of intercellular adhesion molecule 1 (ICAM-1) in both THP-1 and PDL cells. Expression of proinflammatory cytokines, such as interleukin-6 (IL-6) and IL-8, was also induced significantly in both cell types by the Msps, as determined by reverse transcription-PCR and an enzyme-linked immunosorbent assay, whereas IL-1beta synthesis could be detected only in the THP-1 cells. The upregulation of ICAM-1, IL-6, and IL-8 was completely inhibited by pretreating the cells with an NF-kappaB activation inhibitor, l-1-tosylamido-2-phenylethyl chloromethyl ketone. This suggests involvement of NF-kappaB activation. The increased ICAM-1 and IL-8 expression in the THP-1 cells obtained with rMsps was not inhibited in the presence of the IL-1 receptor antagonist (IL-1ra), a natural inhibitor of IL-1. Our results show that the Msps of the group IV oral spirochetes may play an important role in amplifying the local immune response by continuous inflammatory cell recruitment and retention at an infection site by stimulation of expression of ICAM-1 and proinflammatory cytokines.

Treponemal phospholipids inhibit innate immune responses induced by pathogen-associated molecular patterns

Host innate immune responses to microbial components, known as pathogen-associated molecular patterns (PAMPs), are regulated and modified by cellular receptors and serum proteins, including Toll-like receptors (TLRs), CD14, and LPS-binding protein (LBP). We demonstrated that a treponemal membrane lipid inhibited PAMPs-induced immune responses. The chemical structure of the lipid was elucidated as a phosphatidylglycerol (PG) derivative, which is scarce in most mammalian tissues, but relatively abundant in treponemal membrane lipids. Natural and synthetic PG counterparts as well as related natural anionic phospholipids, phosphatidylinositol, phosphatidylserine, and cardiolipin, also demonstrated an inhibitory effect. Further, we noted that PG inhibited PAMPs-induced immune responses by blocking the binding of PAMPs with LBP and CD14. In addition, PG decreased proinflammatory cytokine production in serum of LPS-injected mice and depressed abscess formation in mice infected with treponemes. These results suggest that treponemal phospholipid interfere the function of LBP/CD14 and act as a modulator of innate immune responses.

Structural elucidation of polysaccharide part of glycoconjugate from Treponema medium ATCC 700293

Glycoconjugates are distributed on the cell surfaces of some small-sized treponemes and have been reported to be completely different from lipopolysaccharides. We separated a glycoconjugate fraction from Treponema medium ATCC 700293, a medium-sized oral spirochete, to assess its immunobiological activities and elucidate the chemical structure of its polysaccharide part using phenol/water extraction, hydrophobic chromatography, and gel filtration. The glycoconjugate showed negligible or weak endotoxic and immunobiological properties. The chemical structure of the polysaccharide part was shown by two-dimensional NMR and MALDI-TOF-MS to be a tetrasaccharide backbone with two amino acids: [-->4)beta-d-GlcpNAc3NAcA(1-->4)beta-d-ManpNAc3NAOrn(1-->3)beta-d-GlcpNAc(1-->3)alpha-D-Fucp4NAsp(1-->] where GlcNAc3NAcA is 2,3-diacetamido-2,3-dideoxyglucuronic acid, ManNAc3NAOrn is Ndelta-(2-acetamido-3-amino-2,3-dideoxymannuronyl)ornithine, and Fuc4NAsp is 4-(alpha-aspartyl)amino-4,6-dideoxygalactose.