Mixture of periodontopathogenic bacteria influences interaction with KB cells

Oral Dysbiosis in Severe Forms of Periodontitis Is Associated With Gut Dysbiosis and Correlated With Salivary Inflammatory Mediators: A Preliminary Study

Inflammation is a driven force in modulating microbial communities, but little is known about the interplay between colonizing microorganisms and the immune response in periodontitis. Since local and systemic inflammation may play a whole role in disease, we aimed to evaluate the oral and fecal microbiome of patients with periodontitis and to correlate the oral microbiome data with levels of inflammatory mediator in saliva. Methods: Nine patients with periodontitis (P) in Stage 3/Grade B and nine age-matched non-affected controls (H) were evaluated. Microbial communities of oral biofilms (the supra and subgingival from affected and non-affected sites) and feces were determined by sequencing analysis of the 16SrRNA V3-V4 region. Salivary levels of 40 chemokines and cytokines were correlated with oral microbiome data. Results: Supragingival microbial communities of P differed from H (Pielou's evenness index, and Beta diversity, and weighted UniFrac), since relative abundance (RA) of Defluviitaleaceae, Desulfobulbaceae, Mycoplasmataceae, Peptostreococcales-Tissierellales, and Campylobacteraceae was higher in P, whereas Muribaculaceae and Streptococcaceae were more abundant in H. Subgingival non-affected sites of P did not differ from H, except for a lower abundance of Gemellaceae. The microbiome of affected periodontitis sites (PD ≥ 4 mm) clustered apart from the subgingival sites of H. Oral pathobionts was more abundant in sub and supragingival biofilms of P than H. Fecal samples of P were enriched with Acidaminococcus, Clostridium, Lactobacillus, Bifidobacterium, Megasphaera, and Romboutsia when compared to H. The salivary levels of interleukin 6 (IL-6) and inflammatory chemokines were positively correlated with the RA of several recognized and putative pathobionts, whereas the RA of beneficial species, such as Rothia aeria and Haemophilus parainfluenzae was negatively correlated with the levels of Chemokine C-C motif Ligand 2 (CCL2), which is considered protective. Dysbiosis in patients with periodontitis was not restricted to periodontal pockets but was also seen in the supragingival and subgingival non-affected sites and feces. Subgingival dysbiosis revealed microbial signatures characteristic of different immune profiles, suggesting a role for candidate pathogens and beneficial organisms in the inflammatory process of periodontitis.

A novel in vitro periodontal pocket model to evaluate the effect of root surface instrumentation on biofilm-epithelial cell interactions

Objective

To develop a novel in vitro periodontal pocket model for evaluating the effect of two different root surface instrumentation modalities on biofilm-epithelial cell interactions.

Materials and methods

An artificial periodontal pocket model was created using an impression material. Dentin discs were prepared and incubated for 3.5 days with a biofilm consisting of 12 bacterial strains. Then, the discs were inserted into the pocket model and instrumented for 10 s or 10 strokes either with ultrasonics (US) or hand instruments (HI). Subsequently, a glass slide coated with epithelial cells was placed in close vicinity to the discs. After incubation of the pocket model in a 5% CO2 atmosphere for 6 h, residual bacteria of the biofilm as well as bacteria adhering to or invaded into epithelial cells were determined using colony-forming unit (cfu) counts and real-time PCR. Further, as a parameter of the pro-inflammatory cell response, interleukin (IL)-8 expression was determined by ELISA.

Results

Compared to untreated control, HI reduced the cfu counts by 0.63 log10 (not significant) and US by 1.78 log10 (p = 0.005) with a significant difference between the treatment modalities favoring US (p = 0.048). By trend, lower detection levels of Tannerella forsythia were detected in the US group compared to HI. Concerning the interaction with epithelial cells, half of the control and the HI samples showed epithelial cells with attaching or invading bacteria, while US displayed bacteria only in two out of eight samples. In addition, US resulted in significantly lower IL-8 secretion by epithelial cells compared to the untreated control. Between HI and controls, no statistically significant difference in IL-8 secretion was found.

Conclusion

This newly developed in vitro model revealed in terms of biofilm-epithelial cell interaction after root surface instrumentation that compared to hand curettes, ultrasonic instrumentation appeared to be more effective in removing bacterial biofilm and in decreasing the inflammatory response of epithelium to biofilm.

Clinical relevance

Ultrasonic instrumentation might be more advantageous to reduce cellular inflammatory response than hand instruments.

IL-1 Receptor Antagonist Protects the Osteogenesis Capability of Gingival-Derived Stem/Progenitor Cells under Inflammatory Microenvironment Induced by Porphyromonas gingivalis Lipopolysaccharides

Mesenchymal stem cells (MSCs) have been considered to be a future treatment option for periodontitis due to their excellent regenerative capability. However, it is still a challenge to protect MSCs' biological properties from multiple bacterial toxins in local inflammatory environment. The present study is aimed at investigating the treatment effect of interleukin-1 receptor antagonist (IL-1ra) on cell proliferation, migration, and osteogenic differentiation of gingival-derived mesenchymal stem cells (GMSCs) under an inflammatory microenvironment induced by Porphyromonas gingivalis lipopolysaccharides (P. gingivalis-LPS). GMSCs derived from Sprague-Dawley (SD) rats' free gingival tissues were treated with P. gingivalis-LPS (10 μg/mL) to create in vitro inflammatory environment. Different concentrations of IL-1ra (0.01-1 μg/mL) were used to antagonize the negative effect of LPS. Cell behaviors including proliferation, cloning formation unit (CFU), cell migration, osteogenic differentiation, mineral deposition, and cytokine production were assessed to investigate the protection effect of IL-1ra on GMSCs under inflammation. The toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) pathway activated by LPS was evaluated by real-time quantitative polymerase chain reaction (RT-PCR) and western blot. In response to P. gingivalis-LPS treatment, cell numbers, cloning formation rate, cell migration rate, proinflammatory cytokine production, and osteogenic differentiation-associated protein/mRNA expressions as well as mineralized nodules were suppressed in a time-dependent manner. These negative effects were effectively attenuated by IL-1ra administration in a time- and dose-dependent manner. In addition, mRNA expressions of TLR4 and IkBα decreased dramatically when IL-1ra was added into LPS-induced medium. IL-1ra also reversed the LPS-induced TLR4/NF-κB activation as indicated by western blot. The present study revealed that IL-1ra decreased inflammatory cytokine production in a supernatant, so as to protect GMSCs' osteogenesis capacity and other biological properties under P. gingivalis-LPS-induced inflammatory environment. This might be explained by IL-1ra downregulating TLR4-mediated NF-κB signaling pathway activation.

Characterization of Porphyromonas gingivalis sialidase and disruption of its role in host-pathogen interactions

Key to onset and progression of periodontitis is a complex relationship between oral bacteria and the host. The organisms most associated with severe periodontitis are the periodontal pathogens of the red complex: Tannerella forsythia, Treponema denticola and Porphyromonas gingivalis. These organisms express sialidases, which cleave sialic acid from host glycoproteins, and contribute to disease through various mechanisms. Here, we expressed and purified recombinant P. gingivalis sialidase SiaPG (PG_0352) and characterized its activity on a number of substrates, including host sialoglycoproteins and highlighting the inability to cleave diacetylated sialic acids - a phenomenon overcome by the NanS sialate-esterase from T. forsythia. Indeed SiaPG required NanS to maximize sialic acid harvesting from heavily O-acetylated substrates such as bovine salivary mucin, hinting at the possibility of interspecies cooperation in sialic acid release from host sources by these members of the oral microbiota. Activity of SiaPG and P. gingivalis was inhibited using the commercially available chemotherapeutic zanamivir, indicating its potential as a virulence inhibitor, which also inhibited sialic acid release from mucin, and was capable of inhibiting biofilm formation of P. gingivalis on oral glycoprotein sources. Zanamivir also inhibited attachment and invasion of oral epithelial cells by P. gingivalis and other periodontal pathogens, both in monospecies but also in multispecies infection experiments, indicating potential to suppress host-pathogen interactions of a mixed microbial community. This study broadens our understanding of the multifarious roles of bacterial sialidases in virulence, and indicates that their inhibition with chemotherapeutics could be a promising strategy for periodontitis therapy.

Porphyromonas gingivalis degrades integrin β1 and induces AIF-mediated apoptosis of epithelial cells

Background: Porphyromonas gingivalis, a major pathogen of chronic periodontitis, adheres to and invades epithelial cells via an interaction between fimbriae and integrin. P. gingivalis proliferation and infection may affect the survival of cells. In this study, we further examined alternative signaling pathways mediating epithelial-cell death induced by P. gingivalis and the role of the cell-adhesion molecule integrin. Methods: Human epithelial KB cells interacted with P. gingivalis to evaluate cell death by Annexin V-propidium iodide (PI) staining. JC-1 staining was used to measure mitochondrial membrane potential (MMP). The mRNA and protein of integrin β1, apoptosis-inducing factor (AIF) and caspase-3 were detected by real-time PCR and western blot. Caspase-3 activity was analyzed by spectrophotometry. Results: P. gingivalis infection downregulated integrin β1 and led to cell detachment in a dose and time-dependent manner. Large amount of P. gingivalis induced MMP depolarization and apoptosis in KB cells. Moreover, P. gingivalis up-regulated AIF, but not activate caspase-3 during apoptosis. In addition, AIF inhibitor N-Phenylmaleimide almost inhibited the P. gingivalis-induced apoptosis. Conclusions: P. gingivalis disrupts epithelial-cell adhesion by degrading integrin β1 and induces caspase-independent, AIF-mediated mitochondrial apoptosis, which may promote the damage of oral tissue.

Response of epithelial cells infected by Treponema denticola

OBJECTIVE

In the gingival crevice, the interaction between epithelial cells and periodontopathic bacteria is important for the development of periodontitis. Treponema denticola is a major pathogen of chronic periodontitis and possesses several virulence factors, such as major surface protein (Msp) and prolyl-phenylalanine-specific protease (dentilisin). Here, we investigated the behaviours of epithelial cells infected with T. denticola by measuring the expression of interleukin (IL)-1β, IL-6, β defensin 2 (BD-2) and heat-shock protein 70 (HSP70).

METHODS

Epithelial cells were infected with T. denticola wild-type strain, Msp-deficient mutant or dentilisin-deficient mutant, and the expression levels of the above targets were analysed by polymerase chain reaction.

RESULTS

Infection with T. denticola wild-type strain and mutants induced the production of IL-6 and HSP70. The level of BD-2 induced by T. denticola wild-type strain at 24 hr was significantly higher than that of the dentilisin-deficient mutant. The level of IL-1β mRNA in the wild-type strain and dentilisin-deficient mutant was slightly lower than that in the uninfected control.

CONCLUSION

These results suggest that the levels of BD-2 were affected by Msp and dentilisin. This effect may contribute to the disruption of the response of epithelial cells to eradicate T. denticola.

An in vitro model of Fusobacterium nucleatum and Porphyromonas gingivalis in single- and dual-species biofilms

Purpose

The goal of this study was to develop and validate a standardized in vitro pathogenic biofilm attached onto saliva-coated surfaces.

Methods

Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis) strains were grown under anaerobic conditions as single species and in dual-species cultures. Initially, the bacterial biomass was evaluated at 24 and 48 hours to determine the optimal timing for the adhesion phase onto saliva-coated polystyrene surfaces. Thereafter, biofilm development was assessed over time by crystal violet staining and scanning electron microscopy.

Results

The data showed no significant difference in the overall biomass after 48 hours for P. gingivalis in single- and dual-species conditions. After adhesion, P. gingivalis in single- and dual-species biofilms accumulated a substantially higher biomass after 7 days of incubation than after 3 days, but no significant difference was found between 5 and 7 days. Although the biomass of the F. nucleatum biofilm was higher at 3 days, no difference was found at 3, 5, or 7 days of incubation.

Conclusions

Polystyrene substrates from well plates work as a standard surface and provide reproducible results for in vitro biofilm models. Our biofilm model could serve as a reference point for studies investigating biofilms on different surfaces.

The Effect of Scaling and Root Planning on Salivary TNF-α and IL-1α Concentrations in Patients with Chronic Periodontitis

OBJECTIVE

Periodontitis is one of the main diseases in the oral cavity that causes tooth loss. The host immune response and inflammatory factors have important role in periodontal tissue. The current study was done with the objective to determine the effect of scaling and root planning on the salivary concentrations of tumor necrosis factor-alpha (TNF-α) and interleukin-1-alpha (IL-1α).

METHODS

In this quasi-experimental clinical trial, 29 patients with chronic periodontitis and 29 healthy subjects without periodontitis were studied. Clinical examination findings and salivary TNF-α and IL-1α (using ELISA method) were compared before and after scaling, root planning.

RESULTS

Before starting treatment, salivary TNF-α and IL-1α concentrations were higher in healthy control group than in periodontitis group (P< 0.05). Non-surgical treatment increased the concentration of these two biomarkers in the saliva. However, increase in IL-1α concentration was not statistically significant (P= 0.056). There was a negative relationship between TNF-α and IL-1α levels with pocket depth and attachment loss (P< 0.05).

CONCLUSION

Scaling and root planning improved periodontal disease indices and salivary TNF-α and IL-1α levels.

Human dental stem cells suppress PMN activity after infection with the periodontopathogens Prevotella intermedia and Tannerella forsythia

Periodontitis is characterized by inflammation associated with the colonization of different oral pathogens. We here aimed to investigate how bacteria and host cells shape their environment in order to limit inflammation and tissue damage in the presence of the pathogen. Human dental follicle stem cells (hDFSCs) were co-cultured with gram-negative P. intermedia and T. forsythia and were quantified for adherence and internalization as well as migration and interleukin secretion. To delineate hDFSC-specific effects, gingival epithelial cells (Ca9-22) were used as controls. Direct effects of hDFSCs on neutrophils (PMN) after interaction with bacteria were analyzed via chemotactic attraction, phagocytic activity and NET formation. We show that P. intermedia and T. forsythia adhere to and internalize into hDFSCs. This infection decreased the migratory capacity of the hDFSCs by 50%, did not disturb hDFSC differentiation potential and provoked an increase in IL-6 and IL-8 secretion while leaving IL-10 levels unaltered. These environmental modulations correlated with reduced PMN chemotaxis, phagocytic activity and NET formation. Our results suggest that P. intermedia and T. forsythia infected hDFSCs maintain their stem cell functionality, reduce PMN-induced tissue and bone degradation via suppression of PMN-activity, and at the same time allow for the survival of the oral pathogens.

Periodontal bacterial invasion and infection: contribution to atherosclerotic pathology

OBJECTIVE

The objective of this review was to perform a systematic evaluation of the literature reporting current scientific evidence for periodontal bacteria as contributors to atherosclerosis.

METHODS

Literature from epidemiological, clinical and experimental studies concerning periodontal bacteria and atherosclerosis were reviewed. Gathered data were categorized into seven "proofs" of evidence that periodontal bacteria: 1) disseminate from the oral cavity and reach systemic vascular tissues; 2) can be found in the affected tissues; 3) live within the affected site; 4) invade affected cell types in vitro; 5) induce atherosclerosis in animal models of disease; 6) non-invasive mutants of periodontal bacteria cause significantly reduced pathology in vitro and in vivo; and 7) periodontal isolates from human atheromas can cause disease in animal models of infection.

RESULTS

Substantial evidence for proofs 1 to 6 was found. However, proof 7 has not yet been fulfilled.

CONCLUSIONS

Despite the lack of evidence that periodontal bacteria obtained from human atheromas can cause atherosclerosis in animal models of infection, attainment of proofs 1 to 6 provides support that periodontal pathogens can contribute to atherosclerosis.

Periodontal bacterial invasion and infection: contribution to atherosclerotic pathology

OBJECTIVE

The objective of this review was to perform a systematic evaluation of the literature reporting current scientific evidence for periodontal bacteria as contributors to atherosclerosis.

METHODS

Literature from epidemiological, clinical and experimental studies concerning periodontal bacteria and atherosclerosis were reviewed. Gathered data were categorized into seven "proofs" of evidence that periodontal bacteria: 1) disseminate from the oral cavity and reach systemic vascular tissues; 2) can be found in the affected tissues; 3) live within the affected site; 4) invade affected cell types in vitro; 5) induce atherosclerosis in animal models of disease; 6) non-invasive mutants of periodontal bacteria cause significantly reduced pathology in vitro and in vivo; and 7) periodontal isolates from human atheromas can cause disease in animal models of infection.

RESULTS

Substantial evidence for proofs 1 to 6 was found. However, proof 7 has not yet been fulfilled.

CONCLUSIONS

Despite the lack of evidence that periodontal bacteria obtained from human atheromas can cause atherosclerosis in animal models of infection, attainment proofs 1 to 6 provides support that periodontal pathogens can contribute to atherosclerosis.

Surface interactions between two of the main periodontal pathogens: Porphyromonas gingivalis and Tannerella forsythia

PURPOSE

Porphyromonas gingivalis and Tannerella forsythia have been implicated as the major etiologic agents of periodontal disease. These two bacteria are frequently isolated together from the periodontal lesion, and it has been suggested that their interaction may increase each one's virulence potential. The purpose of this study was to identify proteins on the surface of these organisms that are involved in interbacterial binding.

METHODS

Biotin labeling of surface proteins of P. gingivalis and T. forsythia and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was performed to identify surface proteins involved in the coaggregating activity between P. gingivalis and T. forsythia.

RESULTS

It was found that three major T. forsythia proteins sized 161, 100, and 62 kDa were involved in binding to P. gingivalis, and P. gingivalis proteins sized 35, 32, and 26 kDa were involved in binding to T. forsythia cells.

CONCLUSIONS

LC-MS/MS analysis identified one T. forsythia surface protein (TonB-linked outer membrane protein) involved in interbacterial binding to P. gingivalis. However, the nature of other T. forsythia and P. gingivalis surface proteins identified by biotin labeling could not be determined. Further analysis of these proteins will help elucidate the molecular mechanisms that mediate coaggregation between P. gingivalis and T. forsythia.

Enhancement of Rhodobacter sphaeroides growth and carotenoid production through biostimulation

Bacillus thuringiensis/cereus L2 was added as a biostimulant to enhance the biomass accumulation and carotenoid yield of Rhodobacter sphaeroides using wastewater as the culturing medium. Results showed that biostimulation could significantly enhance the R. sphaeroides biomass production and carotenoid yield. The optimal biostimulant proportion was 40 μL (about 6.4×10(5) CFU). Through the use of biostimulation, chemical oxygen demand removal, R. sphaeroides biomass production, carotenoid concentration, and carotenoid yield were improved by 178%, 67%, 214%, and 70%, respectively. Theoretical analysis revealed that there were two possible reasons for such increases. One was that biostimulation enhanced the R. sphaeroides wastewater treatment efficiency. The other was that biostimulation significantly decreased the peroxidase activity in R. sphaeroides. The results showed that the highest peroxidase activity dropped by 87% and the induction ratio of the RSP_3419 gene was 3.1 with the addition of biostimulant. The enhanced carotenoid yield in R. sphaeroides could thus be explained by a decrease in peroxidase activity.

[Clinical and microbiological rationale for laser removal of infected epithelia in patients with periodontitis]

The aim of the study was to identify clinical microbiological criteria for the necessity of removal of infected epithelium in the periodontal pocket in patients with periodontitis. A total of 90 patients diagnosed with periodontal disease of varying severity were assessed. Clinical examination of the patients was performed, including the definition of index numbers and microbiological diagnosis of the content of periodontal pocket and periodontal tissues by biopsy culture seeding. Epithelial integration of lactobacilli and bifidobacteria was established, indicating the need for a differentiated approach to the removal of gingival epithelium. Diagnostic criteria for deepitalization was identified: marked inflammatory response of periodontal tissues, characterized by performance indexes PMA > 50%, Mulleman > 1.5, Svrakov > 2.7, correlated with the degree of contamination biopsy 4IgKOE/ml and Candida spp. 2IgKOE/ml.

Treponema denticola upregulates MMP-2 activation in periodontal ligament cells: interplay between epigenetics and periodontal infection

OBJECTIVE

Periodontal pathogens initiate chronic dysregulation of inflammation and tissue homeostasis that characterize periodontal disease. To better understand oral microbe-host tissue interactions, we investigated expression and activation of MMP-2 in periodontal ligament cells following Treponema denticola challenge.

DESIGN

Cultured PDL cells were challenged with T. denticola, and bacterial adherence, internalization and survival were assayed by immunofluorescence microscopy and antibiotic protection assays, respectively. MMP-2 activation was detected by zymography. MMP-2, MT1/MMP and TIMP-2 expression following T. denticola challenge was determined by qRT-PCR. Promoter methylation of MMP-2 and MT1/MMP was screened by methylation-sensitive restriction analysis and by bisulfite DNA sequencing.

RESULTS

T. denticola adhered to and was internalized by PDL cells but did not survive intracellularly beyond 24h. Importantly, while dentilisin activity in PDL culture supernatants gradually decreased following T. denticola challenge, MMP-2 activation persisted for up to 5 days, suggesting involvement of other regulatory mechanisms. Transcription and expression of MT1/MMP and TIMP-2 increased in response to T. denticola challenge. However, consistent with previously reported constitutive pro-MMP-2 expression in PDL cells, the MMP-2 promoter was hypomethylated, independent of T. denticola challenge.

CONCLUSIONS

MMP-2 promoter hypomethylation is consistent with constitutive pro-MMP-2 expression in PDL cells. This, coupled with T. denticola-mediated upregulation of MMP-2-related genes and chronic activation of pro-MMP-2, mimics key in vivo mechanisms of periodontal disease chronicity, in particular MMP-2-dependent matrix degradation and bone resorption. Adherence and/or internalization of T. denticola may contribute to these processes by one or more regulatory mechanisms, including contact-dependent signal transduction or other epigenetic mechanisms.

Colonisation of gingival epithelia by subgingival biofilms in vitro: role of "red complex" bacteria

OBJECTIVES

Biofilm formation on tooth surface results in colonisation and invasion of the juxtaposed gingival tissue, eliciting strong inflammatory responses that lead to periodontal disease. This in vitro study investigated the colonisation of human gingival multi-layered epithelium by multi-species subgingival biofilms, and evaluated the relative effects of the "red complex" species (Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola).

METHODS

The grown biofilm consisted of Fusobacterium nucleatum, Campylobacter rectus, Veillonella dispar, P. gingivalis, Prevotella intermedia, T. forsythia, T. denticola, Actinomyces oris, Streptococcus anginosus and Streptococcus oralis, or its variant lacking the "red complex". After 48h in co-culture with the gingival epithelia, the bacterial species in the biofilm were quantified, whereas their localisation on the cell surface was investigated by combining confocal-laser scanning microscopy (CLSM) and fluorescence in situ hybridisation (FISH), as well as by scanning electron microscopy (SEM).

RESULTS

Exclusion of the "red complex" quantitatively affected S. oralis, but not other species. The "red-complex" species were all able to colonise the gingival epithelial cells. A co-localisation trend was observed between P. gingivalis and T. denticola, as determined by FISH. However, in the absence of all three "red complex" bacteria from the biofilm, an immense colonisation of streptococci (potentially S. oralis) was observed on the gingival epithelia, as confirmed by both CLSM and SEM.

CONCLUSIONS

While the "red complex" species synergise in colonizing gingival epithelia, their absence from the biofilm enhances streptococcal colonisation. This antagonism with streptococci reveals that the "red complex" may regulate biofilm virulence, with potential implications in periodontal pathogenesis.

Porphyromonas gingivalis stimulates IL-6 and IL-8 secretion in GMSM-K, HSC-3 and H413 oral epithelial cells

Infection of oral epithelial cells with periodontopathogenic bacteria results in the production of pro-inflammatory cytokines involved in the initiation and progression of periodontal disease. The purpose of this study was to examine the release of interleukin (IL)-6 and IL-8 by oral epithelial cells after exposure to Porphyromonas gingivalis. Non-tumor-derived, immortalized human GMSM-K cells, and human oral squamous cell carcinoma, HSC-3 and H413 cells, were co-cultured with live and heat-inactivated P. gingivalis 2561 (ATCC 33277) and W83 (ATCC BAA-308™). IL-6 and IL-8 were quantified in the culture supernatants after 6 and 24 h. The basal levels of both cytokines and the responses to P. gingivalis were strongly dependent on cell type. GMSM-K cells produced less IL-8 than HSC-3 and H413 cells. Live P. gingivalis induced significant IL-6 and IL-8 secretion in GMSM-K and HSC-3 cells, and heat-inactivation of bacteria enhanced greatly IL-6 and IL-8 stimulation in these cells. Uninfected H413 cells produced high levels of IL-6 and IL-8, but were not responsive to live P. gingivalis; heat-inactivated P. gingivalis up-regulated IL-6 and IL-8 secretion in these cells. Since base-line secretion of IL-6 and IL-8, and responses to P. gingivalis depend on the cell type, conclusions on the responses to P. gingivalis should not be based on studies with a single cell type.

Treponema denticola improves adhesive capacities of Porphyromonas gingivalis

Porphyromonas gingivalis, an important etiological agent of periodontal disease, is frequently found associated with Treponema denticola, an anaerobic spirochete, in pathogenic biofilms. However, interactions between these two bacteria are not well understood at the molecular level. In this study, we seek to link the influence of T. denticola on the expression of P. gingivalis proteases with its capacities to adhere and to form biofilms. The P. gingivalis genes encoding Arg-gingipain A (RgpA), Lys-gingipain (Kgp), and hemagglutinin A (HagA) were more strongly expressed after incubation with T. denticola compared with P. gingivalis alone. The amounts of the three resulting proteins, all of which contain hemagglutinin adhesion domains, were increased in culture supernatants. Moreover, incubation of P. gingivalis with T. denticola promoted static and dynamic biofilm formation, primarily via a time-dependent enhancement of P. gingivalis adhesion capacities on bacterial partners such as Streptococcus gordonii. Adhesion of P. gingivalis to human cells was also increased. These results showed that interactions of P. gingivalis with other bacterial species, such as T. denticola, induce increased adhesive capacities on various substrata by hemagglutinin adhesion domain-containing proteins.

Co-localized or randomly distributed? Pair cross correlation of in vivo grown subgingival biofilm bacteria quantified by digital image analysis

The polymicrobial nature of periodontal diseases is reflected by the diversity of phylotypes detected in subgingival plaque and the finding that consortia of suspected pathogens rather than single species are associated with disease development. A number of these microorganisms have been demonstrated in vitro to interact and enhance biofilm integration, survival or even pathogenic features. To examine the in vivo relevance of these proposed interactions, we extended the spatial arrangement analysis tool of the software daime (digital image analysis in microbial ecology). This modification enabled the quantitative analysis of microbial co-localization in images of subgingival biofilm species, where the biomass was confined to fractions of the whole-image area, a situation common for medical samples. Selected representatives of the disease-associated red and orange complexes that were previously suggested to interact with each other in vitro (Tannerella forsythia with Fusobacterium nucleatum and Porphyromonas gingivalis with Prevotella intermedia) were chosen for analysis and labeled with specific fluorescent probes via fluorescence in situ hybridization. Pair cross-correlation analysis of in vivo grown biofilms revealed tight clustering of F. nucleatum/periodonticum and T. forsythia at short distances (up to 6 µm) with a pronounced peak at 1.5 µm. While these results confirmed previous in vitro observations for F. nucleatum and T. forsythia, random spatial distribution was detected between P. gingivalis and P. intermedia in the in vivo samples. In conclusion, we successfully employed spatial arrangement analysis on the single cell level in clinically relevant medical samples and demonstrated the utility of this approach for the in vivo validation of in vitro observations by analyzing statistically relevant numbers of different patients. More importantly, the culture-independent nature of this approach enables similar quantitative analyses for “as-yet-uncultured” phylotypes which cannot be characterized in vitro.

Fusobacterium nucleatum and Tannerella forsythia induce synergistic alveolar bone loss in a mouse periodontitis model

Tannerella forsythia is strongly associated with chronic periodontitis, an inflammatory disease of the tooth-supporting tissues, leading to tooth loss. Fusobacterium nucleatum, an opportunistic pathogen, is thought to promote dental plaque formation by serving as a bridge bacterium between early- and late-colonizing species of the oral cavity. Previous studies have shown that F. nucleatum species synergize with T. forsythia during biofilm formation and pathogenesis. In the present study, we showed that coinfection of F. nucleatum and T. forsythia is more potent than infection with either species alone in inducing NF-κB activity and proinflammatory cytokine secretion in monocytic cells and primary murine macrophages. Moreover, in a murine model of periodontitis, mixed infection with the two species induces synergistic alveolar bone loss, characterized by bone loss which is greater than the additive alveolar bone losses induced by each species alone. Further, in comparison to the single-species infection, mixed infection caused significantly increased inflammatory cell infiltration in the gingivae and osteoclastic activity in the jaw bones. These data show that F. nucleatum subspecies and T. forsythia synergistically stimulate the host immune response and induce alveolar bone loss in a murine experimental periodontitis model.

Tannerella forsythia invasion in oral epithelial cells requires phosphoinositide 3-kinase activation and clathrin-mediated endocytosis

Tannerella forsythia, a Gram-negative anaerobe implicated in periodontitis, has been detected within human buccal epithelial cells and shown to invade oral epithelial cells in vitro. We have previously shown that this bacterium triggers host tyrosine kinase-dependent phosphorylation and actin-dependent cytoskeleton reorganization for invasion. On the bacterial side, the leucine-rich repeat cell-surface BspA protein is important for entry. The present study was undertaken to identify host signalling molecules during T. forsythia entry into human oral and cervical epithelial cells. Specifically, the roles of phosphatidylinositol 3-kinase (PI3K), Rho-family GTPases, cholesterol-rich membrane microdomains and the endocytic protein clathrin were investigated. For this purpose, cell lines were pretreated with chemical inhibitors or small interfering RNAs (siRNAs) that target PI3Ks, Rho GTPases, clathrin and cholesterol (a critical component of 'lipid rafts'), and the resulting effects on T. forsythia uptake were determined. Our studies revealed that T. forsythia entry is dependent on host PI3K signalling, and that purified BspA protein causes activation of this lipid kinase. Bacterial entry also requires the cooperation of host Rac1 GTPase. Finally, our findings indicate an important role for clathrin and cholesterol-rich lipid microdomains in the internalization process.