Effects of Porphyromonas gingivalis LipopolysaccharideTolerized Monocytes on Inflammatory Responses in Neutrophils

Periodontitis is a chronic inflammatory disease induced by bacteria. Exposure of the host to periodontal pathogens and their virulence factors induces a state of hyporesponsiveness to subsequent stimulations, which is termed endotoxin tolerance. The role and mechanism of lipopolysaccharide (LPS)–tolerized monocytes in inflammatory responses in neutrophils are currently unclear. Here, conditioned supernatants were collected from THP-1 cells treated with or without repeated 1 μg/ml Porphyromonas gingivalis (P.gingivalis) LPS. The chemotactic response of freshly isolated neutrophils recruited by supernatants was determined by a transwell migration assay, which demonstrated a reduced migration of neutrophils stimulated with supernatants from tolerized THP-1 cells in comparison to non-tolerized THP-1 cells. In addition, there was a marked increase in reactive oxygen species (ROS) generation and a significant decrease in Caspase 3 activities in neutrophils treated with supernatants from THP-1 cells that were treated repeatedly with P.gingivalis LPS in comparison to single treatment. A cytokine antibody array was then used to assess cytokine expression patterns in THP-1 cells. In tolerized THP-1 cells, 43 cytokine (43/170) expression levels were decreased, including chemokine ligand 23 (CCL23) and IFN-γ, while 11 cytokine (11/170) expression levels were increased, such as death receptor 6 (DR6). Furthermore, there was decreased production of IFN-γ and epithelial neutrophil activating peptide-78 (ENA-78) in THP-1 cells after stimulation with repeated P. gingivalis LPS in comparison to single challenge, which was confirmed by ELISA. Therefore, P.gingivalis LPS- tolerized THP-1 cells were able to depress neutrophil chemotaxis and apoptosis, and contribute to respiratory burst, which might be related to the changes in cytokine expression patterns in THP-1 cells.

Unprimed, M1 and M2 Macrophages Differentially Interact with Porphyromonas gingivalis

Porphyromonas gingivalis is a keystone pathogen in the development of chronic periodontitis. Tissue macrophages are amongst the first immune cells to respond to bacteria and depending on the cytokine profile at the infection site, macrophages are primed to react to infection in different ways. Priming of naive macrophages with IFN-γ produces a classical pro-inflammatory, antibacterial M1 macrophage after TLR ligation, whereas priming with IL-4 induces an anti-inflammatory tissue-repair M2 phenotype. Previous work has shown that M1 are preferentially generated in gingival tissue following infection with P. gingivalis. However, few studies have investigated the interactions of macrophage subsets with P. gingivalis cells. The aim of this study was to determine the ability of naive, M1 and M2 macrophages to phagocytose P. gingivalis and investigate how this interaction affects both the bacterial cell and the macrophage. M1 and M2 macrophages were both found to have enhanced phagocytic capacity compared with that of naive macrophages, however only the naive and M1 macrophages were able to produce a respiratory burst in order to clear the bacteria from the phagosome. P. gingivalis was found to persist in naive and M2, but not M1 macrophages for 24 hours. Phagocytosis of P. gingivalis also induced high levels of TNF-α, IL-12 and iNOS in M1 macrophages, but not in naive or M2 macrophages. Furthermore, infection of macrophages with P. gingivalis at high bacteria to macrophage ratios, while inducing an inflammatory response, was also found to be deleterious to macrophage longevity, with high levels of apoptotic cell death found in macrophages after infection. The activation of M1 macrophages observed in this study may contribute to the initiation and maintenance of a pro-inflammatory state during chronic periodontitis.

The effects of P. gingivalis and E. coli LPS on the expression of proinflammatory mediators in human mast cells and their relevance to periodontal disease

Mast cells (MCs) are tissue-resident immune cells that participate in a variety of allergic and inflammatory conditions, including periodontal disease, through the release of cytokines, chemokines and proteolytic enzymes. Porhyromonas gingivalis (P. g) is widely recognized as a major pathogen in the development and progression of periodontitis. Here we compared the differential effects of lipopolysaccharides (LPS) from P. g and E. coli on the expression and production of tumor necrosis factor (TNF), vascular endothelial growth factor (VEGF) and monocyte chemoattractant protein (MCP-1) by human MCs. Human LAD2 MCs were stimulated with LPS from either P. g or E. coli (1-1000 ng/ml). MCs were also stimulated with SP (2μM) serving as the positive control or media alone as the negative control. After 24 h, the cells and supernatant fluids were collected and analyzed for β-Hexosaminidase (β-hex) spectrophotometrically, TNF, VEGF and MCP-1 release by ELISA and real-time polymerase chain reaction (PCR) for mediator gene expression, respectively. To assess the functional role of tolllike receptors (TRL) in mediator release, MCs were pre-incubated with either anti-TLR2 or anti- TLR4 (2 μg/ml) polyclonal antibody for 1 h before stimulation with LPS. When MCs were stimulated with SP (2 μM), there was a statistically significant β-hex release as well as release of TNF, VEGF and MCP-1. Stimulation of MCs with either type of LPS did not induce degranulation based on the lack of β-hex release. However, both types of LPS stimulated expression and release of TNF, VEGF and MCP-1. Although, P. g LPS induced significant release of TNF, VEGF and MCP-1, the effect was not concentration-dependent. There was no statistically significant difference between the effects of P. g and E. coli LPS. P. g LPS stimulated TNF through TLR-2 while E. coli utilized TRL-4 instead. In contrast, VEGF release by P. g LPS required both TRL-2 and TRL-4 while E. coli LPS required TLR-4. Release of MCP-1 was independent of TLR-2 or TLR-4. P. g LPS activates human MCs to generate and release TNF, VEGF and MCP-1 through different TLRs than E. coli LPS. MCs may, therefore, be involved in the inflammatory processes responsible for periodontal disease.

High-throughput dental biofilm growth analysis for multiparametric microenvironmental biochemical conditions using microfluidics

Dental biofilm formation is not only a precursor to tooth decay, but also induces more serious systematic health problems such as cardiovascular disease and diabetes. Understanding the conditions promoting colonization and subsequent biofilm development involving complex bacteria coaggregation is particularly important. In this paper, we report a high-throughput microfluidic 'artificial teeth' device offering controls of multiple microenvironmental factors (e.g. nutrients, growth factors, dissolved gases, and seeded cell populations) for quantitative characteristics of long-term dental bacteria growth and biofilm development. This 'artificial teeth' device contains multiple (up to 128) incubation chambers to perform parallel cultivation and analyses (e.g. biofilm thickness, viable-dead cell ratio, and spatial distribution of multiple bacterial species) of bacteria samples under a matrix of different combinations of microenvironmental factors, further revealing possible developmental mechanisms of dental biofilms. Specifically, we applied the 'artificial teeth' to investigate the growth of two key dental bacteria, Streptococci species and Fusobacterium nucleatum, in the biofilm under different dissolved gas conditions and sucrose concentrations. Together, this high-throughput microfluidic platform can provide extended applications for general biofilm research, including screening of the biofilm properties developing under combinations of specified growth parameters such as seeding bacteria populations, growth medium compositions, medium flow rates and dissolved gas levels.

Porphyromonas gingivalis Gingipain-Dependently Enhances IL-33 Production in Human Gingival Epithelial Cells

The cytokine IL-33 is constitutively expressed in epithelial cells and it augments Th2 cytokine-mediated inflammatory responses by regulating innate immune cells. We aimed to determine the role of the periodontal pathogen, Porphyromonas gingivalis, in the enhanced expression of IL-33 in human gingival epithelial cells. We detected IL-33 in inflamed gingival epithelium from patients with chronic periodontitis, and found that P. gingivalis increased IL-33 expression in the cytoplasm of human gingival epithelial cells in vitro. In contrast, lipopolysaccharide, lipopeptide, and fimbriae derived from P. gingivalis did not increase IL-33 expression. Specific inhibitors of P. gingivalis proteases (gingipains) suppressed IL-33 mRNA induction by P. gingivalis and the P. gingivalis gingipain-null mutant KDP136 did not induce IL-33 expression. A small interfering RNA for protease-activated receptor-2 (PAR-2) as well as inhibitors of phospholipase C, p38 and NF-κB inhibited the expression of IL-33 induced by P. gingivalis. These results indicate that the PAR-2/IL-33 axis is promoted by P. gingivalis infection in human gingival epithelial cells through a gingipain-dependent mechanism.

Modulation of Candida albicans virulence by bacterial biofilms on titanium surfaces

Whilst Candida albicans occurs in peri-implant biofilms, its role in peri-implantitis remains unclear. This study therefore examined the virulence of C. albicans in mixed-species biofilms on titanium surfaces. Biofilms of C. albicans (Ca), C. albicans with streptococci (Streptococcus sanguinis, S. mutans) (Ca-Ss-Sm) and those incorporating Porphyromonas gingivalis (Ca-Pg and Ca-Ss-Sm-Pg) were developed. Expression of C. albicans genes associated with adhesion (ALS1, ALS3, HWP1) and hydrolytic enzymes (SAP2, SAP4, SAP6, PLD1) was measured and hyphal production by C. albicans quantified. Compared with Ca biofilms, significant (p<0.05) up-regulation of ALS3, HWP1, SAP2 and SAP6, and hyphal production occurred in biofilms containing streptococci (Ca-Ss-Sm). In Ca-Pg biofilms, down-regulation of HWP1 and SAP4 expression, with reduced hyphal production occurred. Ca-Ss-Sm-Pg biofilms had increased hyphal proportions and up-regulation of ALS3, SAP2 and SAP6. In conclusion, C. albicans expressed virulence factors in biofilms that could contribute to peri-implantitis, but this was dependent on associated bacterial species.

The Cytochrome bd Oxidase of Porphyromonas gingivalis Contributes to Oxidative Stress Resistance and Dioxygen Tolerance

Porphyromonas gingivalis is an etiologic agent of periodontal disease in humans. The disease is associated with the formation of a mixed oral biofilm which is exposed to oxygen and environmental stress, such as oxidative stress. To investigate possible roles for cytochrome bd oxidase in the growth and persistence of this anaerobic bacterium inside the oral biofilm, mutant strains deficient in cytochrome bd oxidase activity were characterized. This study demonstrated that the cytochrome bd oxidase of Porphyromonas gingivalis, encoded by cydAB, was able to catalyse O2 consumption and was involved in peroxide and superoxide resistance, and dioxygen tolerance.

[The impact of S.gordonii on P. gingivalis on the form of biofilm]

PURPOSE

To investigate the impact of S.gordonii on the ultrastructure of P. gingivalis biofilm and on the amount of P. gingivalis in biofilm.

METHODS

P. gingivalis and/or S.gordonii grew on the culture slides to form single P. gingivalis biofilm and heterotypic biofilm of P.gingivalis-S.gordonii. Then the ultrastructure of the 2 kinds of film were examined by scanning electron microscope, and the amount of P. gingivalis in the biofilm was detected by qPCR. Statistical analysis was performed using pair t test with SPSS 13.0 statistical package.

RESULTS

At 72 h, the amount of heterotypic biofilm was much more than that of the single P. gingivalis biofilm. Moreover, the structure of the heterotypic biofilm was more regular and with more pore space compared to the single P. gingivalis biofilm. Compared to single P. gingivalis biofilm, the amount of P. gingivalis in heterotypic biofilm was 5.4, 3.8 and 4.4 fold at 24, 48 and 72 h, respectively.

CONCLUSIONS

The growth of P. gingivalis was promoted by S. gordonii in the form of heterotypic biofilm compared to single P. gingivalis biofilm.

Mfa4, an Accessory Protein of Mfa1 Fimbriae, Modulates Fimbrial Biogenesis, Cell Auto-Aggregation, and Biofilm Formation in Porphyromonas gingivalis

Porphyromonas gingivalis, a gram-negative obligate anaerobic bacterium, is considered to be a key pathogen in periodontal disease. The bacterium expresses Mfa1 fimbriae, which are composed of polymers of Mfa1. The minor accessory components Mfa3, Mfa4, and Mfa5 are incorporated into these fimbriae. In this study, we characterized Mfa4 using genetically modified strains. Deficiency in the mfa4 gene decreased, but did not eliminate, expression of Mfa1 fimbriae. However, Mfa3 and Mfa5 were not incorporated because of defects in posttranslational processing and leakage into the culture supernatant, respectively. Furthermore, the mfa4-deficient mutant had an increased tendency to auto-aggregate and form biofilms, reminiscent of a mutant completely lacking Mfa1. Notably, complementation of mfa4 restored expression of structurally intact and functional Mfa1 fimbriae. Taken together, these results indicate that the accessory proteins Mfa3, Mfa4, and Mfa5 are necessary for assembly of Mfa1 fimbriae and regulation of auto-aggregation and biofilm formation of P. gingivalis. In addition, we found that Mfa3 and Mfa4 are processed to maturity by the same RgpA/B protease that processes Mfa1 subunits prior to polymerization.

Intraspecies Variability Affects Heterotypic Biofilms of Porphyromonas gingivalis and Prevotella intermedia: Evidences of Strain-Dependence Biofilm Modulation by Physical Contact and by Released Soluble Factors

It is well known that strain and virulence diversity exist within the population structure of Porphyromonas gingivalis. In the present study we investigate intra- and inter-species variability in biofilm formation of Porphyromonas gingivalis and partners Prevotella intermedia and Prevotella nigrescens. All strains tested showed similar hydrophobicity, except for P. gingivalis W83 which has roughly half of the hydrophobicity of P. gingivalis ATCC33277. An intraspecies variability in coaggregation of P. gingivalis with P. intermedia was also found. The association P. gingivalis W83/P. intermedia 17 produced the thickest biofilm and strain 17 was prevalent. In a two-compartment system P. gingivalis W83 stimulates an increase in biomass of strain 17 and the latter did not stimulate the growth of P. gingivalis W83. In addition, P. gingivalis W83 also stimulates the growth of P. intermedia ATCC25611 although strain W83 was prevalent in the association with P. intermedia ATCC25611. P. gingivalis ATCC33277 was prevalent in both associations with P. intermedia and both strains of P. intermedia stimulate the growth of P. gingivalis ATCC33277. FISH images also showed variability in biofilm structure. Thus, the outcome of the association P. gingivalis/P. intermedia seems to be strain-dependent, and both soluble factors and physical contact are relevant. The association P. gingivalis-P. nigrescens ATCC33563 produced larger biomass than each monotypic biofilm, and P. gingivalis was favored in consortia, while no differences were found in the two-compartment system. Therefore, in consortia P. gingivalis-P. nigrescens physical contact seems to favor P. gingivalis growth. The intraspecies variability found in our study suggests strain-dependence in ability of microorganisms to recognize molecules in other bacteria which may further elucidate the dysbiosis event during periodontitis development giving additional explanation for periodontal bacteria, such as P. gingivalis and P. intermedia, among others, to persist and establish chronic infections in the host.

Cigarette smoke condensate modulates migration of human gingival epithelial cells and their interactions with Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Epithelial cells are recognized as the first line of defense against bacterial infection and environmental harmful stimuli such as cigarette smoke (CS). Although previous studies explored the effects of nicotine on host cells, mechanisms by which CS affects cellular functions remain uncertain. The present study investigated the effects of CS condensate (CSC) on in vitro wound closure of gingival epithelial cells and their potential interactions with a major periodontal pathogen, Porphyromonas gingivalis.

MATERIAL AND METHODS

Human gingival epithelial cells (Ca9-22) were treated with CSC for 24 h. Cell proliferation was determined using a WST-1 assay. Cell migration was assessed using a wound closure model. The expression of integrins was analyzed by confocal scanning laser microscopy and real-time PCR. Intracellular invasion of P. gingivalis was evaluated by confocal scanning laser microscopy and an antibiotic protection assay.

RESULTS

Low concentrations (1-10 μg/mL) of CSC showed no significant effect on cell proliferation. CSC demonstrated dual effects on epithelial wound closure of Ca9-22 cells: high concentrations (i.e. 250 μg/mL) significantly inhibited the wound closure whereas low concentrations (i.e. 10 μg/mL) promoted it (p < 0.01). CSC induced distinct changes in cytoskeleton. When CSC-exposed cells were infected with P. gingivalis for 2 h, a significant inhibition of wound closure was observed concurrent with a decrease in integrin α3 expression near the wound area. A significantly increased P. gingivalis invasion into Ca9-22 was observed when exposed to low concentrations of CSC.

CONCLUSION

Low concentrations of CSC increased invasion of human gingival epithelial cells by P. gingivalis and induced changes in cytoskeleton and integrin expression, thereby modulating the cell migration.

Functional Advantages of Porphyromonas gingivalis Vesicles

Porphyromonas gingivalis is a keystone pathogen of periodontitis. Outer membrane vesicles (OMVs) have been considered as both offense and defense components of this bacterium. Previous studies indicated that like their originating cells, P. gingivalis vesicles, are able to invade oral epithelial cells and gingival fibroblasts, in order to promote aggregation of some specific oral bacteria and to induce host immune responses. In the present study, we investigated the invasive efficiency of P. gingivalis OMVs and compared results with that of the originating cells. Results revealed that 70-90% of human primary oral epithelial cells, gingival fibroblasts, and human umbilical vein endothelial cells carried vesicles from P. gingivalis 33277 after being exposed to the vesicles for 1 h, while 20-50% of the host cells had internalized P. gingivalis cells. We also detected vesicle-associated DNA and RNA and a vesicle-mediated horizontal gene transfer in P. gingivalis strains, which represents a novel mechanism for gene transfer between P. gingivalis strains. Moreover, purified vesicles of P. gingivalis appear to have a negative impact on biofilm formation and the maintenance of Streptococcus gordonii. Our results suggest that vesicles are likely the best offence weapon of P. gingivalis for bacterial survival in the oral cavity and for induction of periodontitis.

Periodontitis and Porphyromonas gingivalis in preclinical stage of arthritis patients

Purpose

To determine whether the presence of periodontitis (PD) and Porphyromonas gingivalis (Pg) in the subgingival biofilm associates with the development of rheumatoid arthritis (RA) in treatment naïve preclinical stage of arthritis patients.

Methods

We conducted a prospective cohort study of 72 consecutive patients with arthralgia who had never been treated with any anti-rheumatic drugs or glucocorticoids. Periodontal status at baseline was assessed by dentists. PD was defined stringently by the maximal probing depth≧4 mm, or by the classification by the 5th European Workshop in Periodontology (EWP) in 2005 using attachment loss. Up to eight plaque samples were obtained from each patient and the presence of Pg was determined by Taqman PCR. The patients were followed up for 2 years and introduction rate of methotrexate (MTX) treatment on the diagnosis of RA was compared in patients with or without PD or Pg.

Results

Patients with PD (probing depth≧4mm) had higher arthritis activity (p = 0.02) and higher risk for future introduction of MTX treatment on the diagnosis of RA during the follow up than patients without PD (Hazard ratio 2.68, p = 0.03). Arthritis activity and risk for MTX introduction increased with the severity of PD assessed by EWP, although not statistically significant. On the other hand, presence of Pg was not associated with arthritis activity (p = 0.72) or the risk for MTX introduction (p = 0.45).

Conclusion

In treatment naïve arthralgia patients, PD, but not the presence of Pg, associates with arthritis activity and future requirement of MTX treatment on the diagnosis of RA.

Efficacy of a solar-powered TiO2 semiconductor electric toothbrush on P. gingivalis biofilm

PURPOSE

To determine the efficacy of a solar-powered TiO2 semiconductor electric toothbrush on Porphyromonas gingivalis biofilm.

METHODS

P. gingivalis cells were cultivated on sterilized coverslips under anaerobic conditions and were used as a biofilm. To evaluate the efficacy of the solar-powered TiO2 electric toothbrush on the P. gingivalis biofilm, the bacterial cell biofilm coverslips were placed into sterilized phosphate buffered saline (PBS) and brushed for 1 minute. Following mechanical brushing, the coverslips were stained with 1% crystal violet (CV) for 10 seconds at room temperature. The efficacy of P. gingivalis biofilm removal by the solar-powered TiO2 electric toothbrush was measured through the absorbance of the CV-stained solution containing the removed biofilm at 595 nm. The antimicrobial effect of the solar-powered TiO2 semiconductor was evaluated by the P. gingivalis bacterial count in PBS by blacklight irradiation for 0 to 60 minutes at a distance of 7 cm. The electrical current though the solar-powered TiO2 semiconductor was measured by a digital multimeter. The biofilm removal by the solar-powered TiO2 semiconductor was also evaluated by scanning electron microscopy (SEM).

RESULTS

The biofilm removal rate of the solar-powered TiO2 electric toothbrush was 90.1 ± 1.4%, which was 1.3-fold greater than that of non-solar-powered electric toothbrushes. The solar-powered TiO2 semiconductor significantly decreased P. gingivalis cells and biofilm microbial activity in a time-dependent manner (P< 0.01). The electrical current passing through the solar-powered TiO2 semiconductor was 70.5 ± 0.1 µA, which was a 27-fold higher intensity than the non-solar-powered brush. SEM analysis revealed that the solar-powered TiO2 semiconductor caused a biofilm disruption and that cytoplasmic contents were released from the microbial cells.

Extract from Rumex acetosa L. for prophylaxis of periodontitis: inhibition of bacterial in vitro adhesion and of gingipains of Porphyromonas gingivalis by epicatechin-3-O-(4β→8)-epicatechin-3-O-gallate (procyanidin-B2-Di-gallate)

BACKGROUND

The aerial parts of Rumex acetosa L. have been used in traditional European medicine for inflammatory diseases of the mouth epithelial tissue. The following study aimed to investigate the influence of a proanthocyanidin-enriched extract from R. acetosa extract against the adhesion of Porphyromonas gingivalis (P. gingivalis), a pathogen strongly involved in chronic and aggressive periodontitis. A further goal was to define the bioactive lead structures responsible for a potential antiadhesive activity and to characterize the underlying molecular mechanisms of the antiadhesive effects.

METHODOLOGY

An extract of R. acetosa (RA1) with a defined mixture of flavan-3-ols, oligomeric proanthocyanidins and flavonoids, was used. Its impact on P. gingivalis adhesion to KB cells was studied by flow cytometry, confocal laser scanning microscopy and in situ adhesion assay using murine buccal tissue. RA1 and its compounds 1 to 15 were further investigated for additional effects on gingipain activity, hemagglutination and gene expression by RT-PCR.

PRINCIPAL FINDINGS

RA1 (5 to 15 μg/mL) reduced P. gingivalis adhesion in a dose-dependent manner to about 90%. Galloylated proanthocyanidins were confirmed to be responsible for this antiadhesive effect with epicatechin-3-O-gallate-(4β,8)-epicatechin-3'-O-gallate (syn. procyanidin B2-di-gallate) being the lead compound. Ungalloylated flavan-3-ols and oligomeric proanthocyanidins were inactive. RA1 and the galloylated proanthocyanidins strongly interact with the bacterial virulence factor Arg-gingipain, while the corresponding Lys-gingipain was hardly influenced. RA1 inhibited also hemagglutination. In silico docking studies indicated that epicatechin-3-O-gallate-(4β,8)-epicatechin-3'-O-gallate interacts with the active side of Arg-gingipain and hemaglutinin from P. gingivalis; the galloylation of the molecule seems to be responsible for fixation of the ligand to the protein. In conclusion, the proanthocyanidin-enriched extract RA1 and its main active constituent procyanidin B2-di-gallate protect cells from P. gingivalis infection by inhibiting bacterial adhesion to the host cell. RA1 and procyanidin B2-di-gallate appear to be promising candidates for future cytoprotective preparations for oral mouth care products.

Changes in lipopolysaccharide profile of Porphyromonas gingivalis clinical isolates correlate with changes in colony morphology and polymyxin B resistance

Virulence factors on the surface of Porphyromonas gingivalis constitute the first line of interaction with host cells and contribute to immune modulation and periodontitis progression. In order to characterize surface virulence factors present on P. gingivalis, we obtained clinical isolates from healthy and periodontitis subjects and compared them with reference strains. Colony morphology, aggregation in liquid medium, surface charge, membrane permeability to bactericidal compounds, novobiocin and polymyxin B resistance, capsule presence and lipopolysaccharide (LPS) profiles were evaluated. By comparing isolates from healthy and periodontitis subjects, differences in colony morphology and aggregation in liquid culture were found; the latter being similar to two reference strains. These differences were not a consequence of variations in bacterial surface charge. Furthermore, isolates also presented differences in polymyxin B and novobiocin resistance; isolates from healthy subjects were susceptible to polymyxin B and resistant to novobiocin and, in contrast, isolates from periodontitis subjects were resistant to polymyxin B and susceptible to novobiocin. These changes in antimicrobial resistance levels correlate with variations in LPS profiles, since -unlike periodontitis isolates-isolates from healthy samples synthesize LPS molecules lacking both O-antigen moieties and anionic polysaccharide. Additionally, this phenotype correlated with the absence of O-antigen ligase activity. Altogether, our results reveal novel variations on surface components of P. gingivalis isolates obtained from healthy and periodontitis subjects that could be associated with differences in bacterial virulence and periodontitis progression.

Interactions of anaerobic bacteria with dental stem cells: an in vitro study

BACKGROUND

In patients with periodontitis, it is highly likely that local (progenitor) cells encounter pathogenic bacteria. The purpose of this in vitro study was to elucidate how human dental follicle stem cells (hDFSC) react towards a direct challenge with anaerobic periodontal pathogens under their natural oxygen-free atmosphere. HDFSC were compared to human bone marrow mesenchymal stem cells (hBMSC) and differentiated primary human gingival fibroblasts (hGiF), as well as permanent gingival carcinoma cells (Ca9-22).

METHODOLOGY/PRINCIPAL FINDINGS

The different cell types were investigated in a co-culture system with Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum). The viability of the cells and pathogens under anaerobic conditions, as well as interactions in terms of adherence and internalization, were examined. Additionally, the release of pro-inflammatory interleukin-8 (IL-8) and anti-inflammatory interleukin-10 (IL-10) was quantified via enzyme-linked immunosorbent assay. The bacteria adhered less efficiently to hDFSC compared to Ca9-22 (P. gingivalis: 0.18% adherence to hDFSC; 3.1% adherence to Ca9-22). Similar results were observed for host cell internalization (F. nucleatum: 0.002% internalization into hDFSC; 0.09% internalization into Ca9-22). Statistically significantly less IL-8 was secreted from hDFSC after stimulation with F. nucleatum and P. gingivalis in comparison with hGiF (F. nucleatum: 2080.0 pg/ml--hGiF; 19.7 pg/ml--hDFSC). The IL-10 response of the differentiated cells was found to be low in relation to their pro-inflammatory IL-8 response.

CONCLUSIONS/SIGNIFICANCE

The results indicate that dental stem cells are less prone to interactions with pathogenic bacteria than differentiated cells in an anaerobic environment. Moreover, during bacterial challenge, the stem cell immune response seems to be more towards an anti-inflammatory reaction. For a potential future therapeutic use of hDFSC, these findings support the idea of a save application.

[Features of adhesion of anaerobic periodontopathogenic bacteria and Candida albicans fungi to experimental samples of basis dental plastic depending on surface roughness and polishing method]

AIM

Study the main surface parameters of milled polyacrylic materials using atomic force microscopy and primary microbial adhesion of periodontopathogenic group bacteria and Candida albicans fungi taking into consideration the method of sample polishing.

MATERIALS AND METHODS

Studied samples: mill-treated without polishing (control); ergobox polished; polished in dental laboratory conditions; polished by a rubber brush in dentists' office. Microbial strains belonging to periodontopathogenic species (clinical isolates) that had been isolated from periodontal pockets of periodontitis patients: Porphyromonas gingivalis, Fusobacterium nucleatum, Streptococcus sanguis, C. albicans fungi were used for modelling experiments of primary adhesion of microbes to the material samples.

RESULTS

S. sanguis had the highest degree of adhesion to polymer after milling, P. gingivalis, C. albicans--medium, F. nucleatum--low. A significant reduction of adhesion is observed during polishing in dental laboratory conditions or ergobox, less significant--during polishing in dental office.

CONCLUSION

The data obtained allow to make a conclusion that the samples from polymer materials for preparation of prosthesis basis have varying degree of intensity of microbial adhesion of members of periodontopathogenic microflora and C. albicans fungi that depends on the polishing method, that accordingly determined the differences in colonization resistance against formation of microbial biofilm during polymer use in clinical conditions. . ,

Porphyromonas gingivalis lipopolysaccharide upregulates insulin secretion from pancreatic β cell line MIN6

BACKGROUND

A close association between periodontitis and diabetes has been demonstrated in human cross-sectional studies, but an exact relationship between periodontitis and prediabetes has not been established. Previous studies using animal model systems consistently have shown that hyperinsulinemia occurs in animals with periodontitis compared to animals with healthy periodontium (while maintaining normoglycemia). Because bacterial lipopolysaccharide (LPS) plays an important role in the pathogenesis of periodontitis, we hypothesized that LPS may stimulate insulin secretion through a direct effect on β cell function. To test this hypothesis, pancreatic β cell line MIN6 cells were used to determine the effect of Porphyromonas gingivalis (Pg) LPS on insulin secretion. Furthermore, expression of genes altered by Pg LPS in innate immunity and insulin-signaling pathways was determined.

METHODS

MIN6 cells were grown in medium with glucose concentration of normoglycemia (5.5 mM). Pg LPS was added to each well at final concentrations of 50, 200, and 500 ng/mL. Insulin secretion was measured using enzyme-linked immunosorbent assay. Gene expression levels altered by Pg LPS were determined by polymerase chain reaction (PCR) array for mouse innate and adaptive immunity response and mouse insulin-signaling pathways, and results were confirmed for specific genes of interest by quantitative PCR.

RESULTS

Pg LPS stimulated insulin secretion in the normoglycemic condition by ≈1.5- to 3.0-fold depending on the concentration of LPS. Pg LPS treatment altered the expression of several genes involved in innate and adaptive immune response and insulin-signaling pathway. Pg LPS upregulated the expression of the immune response-related genes cluster of differentiation 8a (Cd8a), Cd14, and intercellular adhesion molecule-1 (Icam1) by about two-fold. LPS also increased the expression of two insulin signaling-related genes, glucose-6-phosphatase catalytic subunit (G6pc) and insulin-like 3 (Insl3), by three- to four-fold.

CONCLUSIONS

We have demonstrated for the first time that Pg LPS stimulates insulin secretion by pancreatic β cell line MIN cells. Pg LPS may have significant implications on the development of β cell compensation and insulin resistance in prediabetes in individuals with periodontitis.

The role of Porphyromonas gingivalis in the development of atherosclerosis and its relationship with fim A genotype

BACKGROUND

Porphyromonas gingivalis, a major periodontal pathogen, is gaining increasing attention for its possible association with atherosclerosis. Its fimbriae are classified into six genotypes (Types I-V, Ib) based on the diversity of the fim A genes encoding the fimbrial subunits. In this study, fim A genotype's distribution of P. gingivalis was analyzed in atherosclerotic plaque specimens.

METHODS

A total of 50 atherosclerotic plaque specimens and 50 non-atherosclerotic, post stenotic aneurysm specimens were collected from patients undergoing cardiovascular surgery. Bacterial DNA was also extracted from each specimen, as real-time PCR was carried out with P. gingivalis-specific primer sets. The positive specimens of P. gingivalis were further analyzed to discriminate the fim A genotype using real-time and nested PCR methods.

RESULTS

P. gingivalis was detected only in one atherosclerotic plaque; however, the genotype was nontypable in this specimen.

CONCLUSIONS

We state that it is not easy to show a significant relationship between P. gingivalis, its fim A genotype, and atherosclerosis. We suggest that new extended studies based especially upon the quantitave determination of P. gingivalis and its genotype distribution on atherosclerotic specimens are needed to show an evident relationship between atherosclerosis and P. gingivalis.

Nanoparticle-encapsulated chlorhexidine against oral bacterial biofilms

BACKGROUND

Chlorhexidine (CHX) is a widely used antimicrobial agent in dentistry. Herein, we report the synthesis of a novel mesoporous silica nanoparticle-encapsulated pure CHX (Nano-CHX), and its mechanical profile and antimicrobial properties against oral biofilms.

METHODOLOGY/PRINCIPAL FINDINGS

The release of CHX from the Nano-CHX was characterized by UV/visible absorption spectroscopy. The antimicrobial properties of Nano-CHX were evaluated in both planktonic and biofilm modes of representative oral pathogenic bacteria. The Nano-CHX demonstrated potent antibacterial effects on planktonic bacteria and mono-species biofilms at the concentrations of 50-200 µg/mL against Streptococcus mutans, Streptococcus sobrinus, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Enterococccus faecalis. Moreover, Nano-CHX effectively suppressed multi-species biofilms such as S. mutans, F. nucleatum, A. actinomycetemcomitans and Porphyromonas gingivalis up to 72 h.

CONCLUSIONS/SIGNIFICANCE

This pioneering study demonstrates the potent antibacterial effects of the Nano-CHX on oral biofilms, and it may be developed as a novel and promising anti-biofilm agent for clinical use.

Proteome analysis of coinfection of epithelial cells with Filifactor alocis and Porphyromonas gingivalis shows modulation of pathogen and host regulatory pathways

Changes in periodontal status are associated with shifts in the composition of the bacterial community in the periodontal pocket. The relative abundances of several newly recognized microbial species, including Filifactor alocis, as-yet-unculturable organisms, and other fastidious organisms have raised questions on their impact on disease development. We have previously reported that the virulence attributes of F. alocis are enhanced in coculture with Porphyromonas gingivalis. We have evaluated the proteome of host cells and F. alocis during a polymicrobial infection. Coinfection of epithelial cells with F. alocis and P. gingivalis strains showed approximately 20% to 30% more proteins than a monoinfection. Unlike F. alocis ATCC 35896, the D-62D strain expressed more proteins during coculture with P. gingivalis W83 than with P. gingivalis 33277. Proteins designated microbial surface component-recognizing adhesion matrix molecules (MSCRAMMs) and cell wall anchor proteins were highly upregulated during the polymicrobial infection. Ultrastructural analysis of the epithelial cells showed formation of membrane microdomains only during coinfection. The proteome profile of epithelial cells showed proteins related to cytoskeletal organization and gene expression and epigenetic modification to be in high abundance. Modulation of proteins involved in apoptotic and cell signaling pathways was noted during coinfection. The enhanced virulence potential of F. alocis may be related to the differential expression levels of several putative virulence factors and their effects on specific host cell pathways.

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 in periodontal pockets and heart valves

BACKGROUND

There is evidence that advanced infectious chronic periodontal inflammatory disease may have an impact on general health including cardiovascular diseases. The aim of this clinical study was to evaluate the ability of Porphyromonas gingivalis to colonize heart valves and, subsequently, to assess whether there is an association between the presence of the DNA of Porphyromonas gingivalis in periodontal pockets and in degenerated heart valves.

MATERIALS AND METHODS

Thirty patients were enrolled in the study and 31 valve specimens harvested during cardiac surgery operations were examined. All patients underwent a periodontal examination. To evaluate the periodontal status of the patients the following clinical parameters were recorded: the pocket depth, bleeding on probing (BOP) and aproximal plaque index (API). The presence of P. gingivalis in heart valve specimens and samples from periodontal pockets was analyzed using a single-step PCR method.

RESULTS

P. gingivalis DNA was detected in periodontal pockets of 15 patients (50%). However, the DNA of this periopathogen was found neither in the aortic nor in the mitral valve specimens.

CONCLUSIONS

This study suggests that P. gingivalis may not have an influence on the development of the degeneration of aortic and mitral valves.