Porphyromonas gingivalis-epithelial cell interactions in periodontitis

Should Antibiotics Be Prescribed to Treat Chronic Periodontitis?

Although scaling and root planing is a cost-effective approach for initial treatment of chronic periodontitis, it fails to eliminate subgingival pathogens and halt progressive attachment loss in some patients. Adjunctive use of systemic antibiotics immediately after completion of scaling and root planing can enhance the degree of clinical attachment gain and probing depth reduction provided by nonsurgical periodontal treatment. This article discusses the rationale for prescribing adjunctive antibiotics, reviews the evidence for their effectiveness, and outlines practical issues that should be considered before prescribing antibiotics to treat chronic periodontitis.

Coinfection with Fusobacterium nucleatum can enhance the attachment and invasion of Porphyromonas gingivalis or Aggregatibacter actinomycetemcomitans to human gingival epithelial cells

OBJECTIVE

This study was conducted to investigate effects of coinfection of Porphyromonas gingivalis (P. gingivalis) or Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) with Fusobacterium nucleatum (F. nucleatum) on their adhering and invasive capacity to human gingival epithelial cells as well as the expression of interleukin-8 (IL-8) and human beta-defensin-2 (hBD-2) in human gingival epithelial cells.

DESIGN

P. gingivalis and A. actinomycetemcomitans were tested for their ability to attach and invade a human gingival epithelial cell line (Ca9-22) alone or coinfecting with F. nucleatum. Also, expression levels of IL-8 and hBD-2 were detected respectively using enzyme linked immunosorbent assay (ELISA) and real-time reverse transcription PCR (RT-PCR) when Ca9-22 cells were infected with P. gingivalis and A. actinomycetemcomitans alone or coinfecting with F. nucleatum.

RESULTS

F. nucleatum, P. gingivalis and A. actinomycetemcomitans were allowed to adhere and invade Ca9-22 cells, either each strain alone or under coinfection. The adhering and invasive abilities of P. gingivalis and A. actinomycetemcomitans were significantly greater when they were coincubated with F. nucleatum (P<0.05) than either of them alone. These enhancements were inhibited by galactose. In addition, P. gingivalis and A. actinomycetemcomitans inhibited the activation of IL-8 and hBD-2 by F. nucleatum. Also, galactose disrupted this inhibition on the expression of IL-8 and hBD-2.

CONCLUSION

These results suggested coinfection with F. nucleatum can enhance adhesion and invasion of P. gingivalis and A. actinomycetemcomitans to Ca9-22 cells, as well as inhibition on host innate immune response.

Inhibition of initial bacterial adhesion on titanium surfaces by lactoferrin coating

Because dental implant abutments are located at transmucosal sites, their surface should inhibit bacterial accumulation to prevent peri-implantitis. The authors examined the effects of human lactoferrin (LF), an antibacterial protein present in saliva, as an antibacterial coating on the titanium surface and evaluated its effects before and after mucin-containing artificial saliva (AS) incubation. In the control group, titanium disks were soaked in distilled water, whereas in the LF group, titanium disks were soaked in LF solution to coat the disks. In the control-AS and LF-AS groups, half of the control and LF disks were incubated with AS. To confirm LF adsorption, the fluorescence intensity of fluorescein isothiocyanate-labeled LF was measured. The LF and LF-AS groups showed significantly higher intensity than the control and control-AS groups (P < 0.01). There was no significant difference between the LF and LF-AS groups (P > 0.05). The amount of adhered Streptococcus gordonii significantly increased by incubation with AS (P < 0.01) and significantly decreased by adsorption of LF (P < 0.01). There was no interaction between the two factors, LF adsorption and AS incubation (P = 0.561). These results suggest that the adsorbed LF inhibited bacterial adhesion following AS incubation. According to qualitative LIVE/DEAD analysis, viable bacteria appeared to be decreased in the presence of LF and SEM observation indicated that altered morphologies increased in LF and LF-AS groups. These results suggest that the adsorbed LF remained on the titanium surface after incubation with AS, and the remaining LF inhibited bacterial adhesion and exhibited bactericidal effects. Therefore, the adsorption of LF on the abutment material appears to be effective in preventing peri-implantitis.

CD24 activates the NLRP3 inflammasome through c-Src kinase activity in a model of the lining epithelium of inflamed periodontal tissues

Chronic periodontitis is characterized by perturbation of the epithelial attachment to the tooth with subsequent migration of the lining epithelium and formation of a cleft or pocket. This non-keratinized lining epithelium provides initial responses to bacterial products by signalling through receptors of innate immunity to activate inflammasome pathways. These comprise an intracellular network of regulatory and effector molecules leading to synthesis and activation of pro-inflammatory cytokines. Conversely, CD24 is characteristically strongly expressed by the pocket epithelium and is reported to function as an important negative regulator for danger signals, protecting tissues from excessive leukocyte activity. The objective of the study was to determine the impact of ligation of CD24 on expression of inflammasome components. An epithelial mimic of pocket epithelium was used to evaluate activation of the NLRP3 inflammasome pathway. Surprisingly, antibody ligation of CD24 enhanced expression of NLRP3 together with co-activators ASC and caspase-1 resulting in burst release of activated interleukin (IL)-18. Potent product inhibition was detected with IL-18 suppressing expression of NLRP3, ASC, and caspase-1. Scant distribution of these products within pocket epithelium compared with healthy gingival attachment provided indication of potential cycling of NLRP3 inflammasome expression. As subjects with mild chronic periodontitis have increased titres of serum antibodies auto-reactive with CD24 compared with those of subjects with severe periodontitis, a molecular mechanism for regulated expression of the NLRP3 inflammasome mediated by c-Src kinase activity, is proposed. This pathway could be regionally disrupted by products of pathogenic bacteria with profound downregulation in the dysbiosis associated with severe disease.

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.

Porphyromonas gingivalis gingipains selectively reduce CD14 expression, leading to macrophage hyporesponsiveness to bacterial infection

Cysteine proteases (gingipains) from Porphyromonas gingivalis are key virulence factors in chronic periodontitis. Innate immune receptors CD14, Toll-like receptor (TLR) 2 and TLR4 are important in P. gingivalis recognition. We examined the ability of gingipains to cleave CD14, TLR2 and TLR4, and the consequences for the cellular response to bacterial challenge. Macrophages were exposed to Arg (RgpA and RgpB)- and Lys (Kgp)-gingipains, and residual expression of TLR2, TLR4 and CD14 was determined by flow cytometry. The cellular response to live bacteria following exposure to purified gingipains was evaluated by TNFα production and bacterial phagocytosis. RgpA and Kgp decreased CD14 detection in a concentration (p = 0.0000002)- and time (p = 0.03)-dependent manner, whereas RgpB had no significant effect. TLR2 and TLR4 expression were unaffected. Reduction in CD14 expression was more efficient with Lys-gingipain than with Arg-gingipain. A reduced CD14 surface level correlated with decreased TNFα secretion and bacterial phagocytosis following challenge with live P. gingivalis, but the response to heat-killed bacteria was unaffected. Therefore, gingipains reduce CD14 expression without affecting expression of the bacterial-sensing TLRs. Reduced CD14 expression depends on the gingipain hemagglutinin/adhesion site and results in macrophage hyporesponsiveness to bacterial challenge. Further studies are needed to determine if reduced CD14 expression is linked to periodontitis induced by P. gingivalis.

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.

The Kampo medicine Rokumigan possesses antibiofilm, anti-inflammatory, and wound healing properties

Periodontal diseases, which are inflammatory diseases of bacterial origin affecting the tooth-supporting tissues, are characterized by inflammation and destruction of gingival connective tissue and alveolar bone, and may lead to tooth loss. The aim of the study was to investigate Rokumigan, a Kampo Japanese traditional medicine made of six different plants, for its capacity to prevent biofilm formation by Fusobacterium nucleatum, to inhibit interleukin-6 (IL-6) and interleukin-8 (IL-8) secretion by mucosal cells, and to promote wound healing in a fibroblast model. Using a microplate colorimetric assay, Rokumigan prevented biofilm formation by F. nucleatum, while it had no effect on bacterial growth. Rokumigan inhibited IL-6 secretion in both epithelial cells and fibroblasts stimulated with lipopolysaccharide. However, it caused no significant inhibition of IL-8 secretion by both cell types. Rokumigan significantly increased proliferation and migration of gingival fibroblasts in a wound healing assay. In conclusion, the Kampo formulation Rokumigan, through suppression of biofilm formation by F. nucleatum, inhibition of IL-6 secretion by gingival epithelial cells and fibroblasts, and promotion of wound healing in a fibroblast model, may have potential application for periodontal diseases.

Porphyromonas gingivalis: major periodontopathic pathogen overview

Porphyromonas gingivalis is a Gram-negative oral anaerobe that is involved in the pathogenesis of periodontitis and is a member of more than 500 bacterial species that live in the oral cavity. This anaerobic bacterium is a natural member of the oral microbiome, yet it can become highly destructive (termed pathobiont) and proliferate to high cell numbers in periodontal lesions: this is attributed to its arsenal of specialized virulence factors. The purpose of this review is to provide an overview of one of the main periodontal pathogens—Porphyromonas gingivalis. This bacterium, along with Treponema denticola and Tannerella forsythia, constitute the “red complex,” a prototype polybacterial pathogenic consortium in periodontitis. This review outlines Porphyromonas gingivalis structure, its metabolism, its ability to colonize the epithelial cells, and its influence upon the host immunity.

Transglutaminase 2 is essential for adherence of Porphyromonas gingivalis to host cells

Porphyromonas gingivalis is the major causative agent of periodontitis, and it may also be involved in the development of systemic diseases (atherosclerosis, rheumatoid arthritis). P. gingivalis is found on and within oral and gingival epithelial cells following binding to surface components of host cells, which serve as receptors for the bacterium. Evidence is presented in this study that shows that transglutaminase 2 (TG2) plays a critical role in the adherence of P. gingivalis to host cells. Studies of confocal microscopy indicate colocalization of P. gingivalis with TG2 on the surface of HEp-2 epithelial cells, with clusters of TG2 seen at bacterial attachment sites. By silencing the expression of TG2 with siRNA in HEp-2 cells, P. gingivalis association was greatly diminished. The bacterium does not bind well to a mouse fibroblast cell line that produces low amounts of surface TG2, but binding can be restored by introduction of TG2 expressed on a plasmid. TG2 can form very tight complexes with fibronectin (FN), and the complementary binding sites of the two proteins are known. A synthetic peptide that mimics the main FN-binding sequence of TG2 blocks the formation of TG2-FN complexes and is highly effective in inhibiting adherence of P. gingivalis to host cells. These findings provide evidence of a role for cell-surface TG2 in bacterial attachment and subsequent internalization.

Bio-inspired stable antimicrobial peptide coatings for dental applications

We developed a novel titanium coating that has applications for preventing infection-related implant failures in dentistry and orthopedics. The coating incorporates an antimicrobial peptide, GL13K, derived from parotid secretory protein, which has been previously shown to be bactericidal and bacteriostatic in solution. We characterized the resulting physicochemical properties, resistance to degradation, activity against Porphyromonas gingivalis and in vitro cytocompatibility. Porphyromonas gingivalis is a pathogen associated with dental peri-implantitis, an inflammatory response to bacteria resulting in bone loss and implant failure. Our surface modifications obtained a homogeneous, highly hydrophobic and strongly anchored GL13K coating that was resistant to mechanical, thermochemical and enzymatic degradation. The GL13K coatings had a bactericidal effect and thus significantly reduced the number of viable bacteria compared to control surfaces. Finally, adequate proliferation of osteoblasts and human gingival fibroblasts demonstrated the GL13K coating's cytocompatibility. The robustness, antimicrobial activity and cytocompatibility of GL13K-biofunctionalized titanium make it a promising candidate for sustained inhibition of bacterial biofilm growth. This surface chemistry provides a basis for development of multifunctional bioactive surfaces to reduce patient morbidities and improve long-term clinical efficacy of metallic dental and orthopedic implants.

Development of animal experimental periodontitis models

Purpose

An animal periodontitis model is essential for research on the pathogenesis and treatment of periodontal disease. In this study, we have introduced a lipopolysaccharide (LPS) of a periodontal pathogen to the alveolar bone defect of experimental animals and investigated its suitability as a periodontitis model.

Methods

Alveolar bone defects were made in both sides of the mandibular third premolar region of nine beagle dogs. Then, the animals were divided into the following groups: silk ligature tied on the cervical region of tooth group, Porphyromonas gingivalis LPS (P.g. LPS)-saturated collagen with silk ligature group, and no ligature or P.g. LPS application group as the control. The plaque index and gingival index were measured at 0 and 4 weeks postoperatively. The animals were then euthanized and prepared for histologic evaluation.

Results

The silk ligature group and P.g. LPS with silk ligature group showed a significantly higher plaque index at 4 weeks compared to the control (P<0.05). No significant difference was found in the plaque index between the silk ligature group and P.g. LPS with silk ligature group. The P.g. LPS with silk ligature group showed a significantly higher gingival index compared to the silk ligature group or the control at 4 weeks (P<0.05). Histologic examination presented increased inflammatory cell infiltration in the gingival tissue and alveolar bone of the P.g. LPS with silk ligature group.

Conclusions

An additional P.g. LPS-saturated collagen with silk ligature ensured periodontal inflammation at 4 weeks. Therefore, P.g. LPS with silk ligature application to surgically created alveolar bone defects may be a candidate model for experimental periodontitis.

A periodontal pathogen Treponema denticola hijacks the Fusobacterium nucleatum-driven host response

Periodontitis is a polymicrobial disease that arises from the dysbiosis of the plaque biofilm. To study polymicrobial interactions with gingival epithelial cells, the oral commensal Fusobacterium nucleatum and the periodontal pathogen Treponema denticola were chosen due to their opposing effects on the expression of human beta-defensins (HBDs) and interleukin (IL)-8 in gingival epithelial cells. Immortalized gingival epithelial HOK-16B cells were infected with either F. nucleatum or T. denticola alone or together, and the expression of HBDs and IL-8 was investigated. Coinfection with F. nucleatum and T. denticola neutralized the stimulatory and suppressive effects on the expression of HBD-2 and -3, but the suppressive effect of T. denticola on IL-8 expression remained. In CHO/CD14/TLR2 reporter cells, T. denticola attenuated F. nucleatum-induced activation of TLR2, a receptor that mediates HBD induction. Although F. nucleatum facilitated the invasion of T. denticola into host cells, T. denticola interfered with the fusion of internalized F. nucleatum with lysosomes, which may avert TLR9-dependent IL-8 induction. Furthermore, T. denticola suppressed the F. nucleatum-stimulated accumulation of intracellular reactive oxygen species (ROS), a group of essential signaling molecules for the TLR2 and TLR9 pathways. The elimination of ROS using N-acetyl cysteine completely blocked the inductions of HBD-3 and IL-8 and significantly reduced HBD-2 induction by F. nucleatum, confirming the importance of ROS in the host response. In sum, T. denticola incapacitates the F. nucleatum-induced expression of HBDs and IL-8 in gingival epithelial cells by interrupting endo-lysosomal maturation and ROS-dependent TLR activation. These results may provide new insights into polymicrobial interactions in the gingival sulcus.

Porphyromonas gingivalis downregulates the immune response of fibroblasts

Background

Porphyromonas gingivalis is a key pathogen in periodontitis, an inflammatory disease leading to destruction of bone and tooth-supporting tissue. P. gingivalis possesses a number of pathogenic properties to enhance growth and survival, including proteolytic gingipains. Accumulating data shows that gingipains are involved in the regulation of host inflammatory responses. The aim of this study was to determine if P. gingivalis infection modulates the inflammatory response of fibroblasts, including the release of chemokines and cytokines. Human gingival fibroblasts or primary dermal fibroblasts were pre-stimulated with tumor-necrosis factor-α (TNF- α) and cocultured with P. gingivalis. Gingipain inhibitors were used to explore the effect of gingipains. CXCL8 levels were determined with ELISA and the relative levels of various inflammatory mediators were determined by a cytokine assay.

Results

TNF-α-triggered CXCL8 levels were completely abolished by viable P. gingivalis, whereas heat-killed P. gingivalis did not suppress CXCL8. Accumulation of CXCL8 was partially restored by an arginine-gingipain inhibitor. Furthermore, fibroblasts produced several inflammatory mediators, notably chemokines, all of which were suppressed by viable P. gingivalis.

Conclusion

These findings provide evidence that fibroblast-derived inflammatory signals are modulated by heat-instable gingipains, whereby the bacteria can escape killing by the host immune system and promote its own growth and establishment. In addition, we show that fibroblasts are important mediators of inflammation in response to infection and thereby play a crucial role in determining the nature and magnitude of the invasion of immune cells.

Gingipain-dependent degradation of mammalian target of rapamycin pathway proteins by the periodontal pathogen Porphyromonas gingivalis during invasion

Porphyromonas gingivalis and Tannerella forsythia are gram-negative pathogens strongly associated with periodontitis. Their abilities to interact, invade and persist within host cells are considered crucial to their pathogenicity, but the mechanisms by which they subvert host defences are not well understood. In this study, we set out to investigate whether P. gingivalis and T. forsythia directly target key signalling molecules that may modulate the host cell phenotype to favour invasion and persistence. Our data identify, for the first time, that P. gingivalis, but not T. forsythia, reduces levels of intracellular mammalian target of rapamycin (mTOR) in oral epithelial cells following invasion over a 4-h time course, via the action of gingipains. The ability of cytochalasin D to abrogate P. gingivalis-mediated mTOR degradation suggests that this effect is dependent upon cellular invasion. We also show that levels of several other proteins in the mTOR signalling pathway are modulated by gingipains, either directly or as a consequence of mTOR degradation including p-4E-BP1. Taken together, our data suggest that P. gingivalis manipulates the mTOR pathway, providing evidence for a potentially novel mechanism by which P. gingivalis mediates its effects on host cell responses to infection.

Regulation of ICAM-1 expression in gingival fibroblasts infected with high-glucose-treated P. gingivalis

Porphyromonas gingivalis is a major pathogen in the initiation and progression of periodontal disease, which is recognized as a common complication of diabetes. ICAM-1 expression by human gingival fibroblasts (HGFs) is crucial for regulating local inflammatory responses in inflamed periodontal tissues. However, the effect of P. gingivalis in a high-glucose situation in regulating HGF function is not understood. The P. gingivalis strain CCUG25226 was used to study the mechanisms underlying the modulation of HGF ICAM-1 expression by invasion of high-glucose-treated P. gingivalis (HGPg). A high-glucose condition upregulated fimA mRNA expression in P. gingivalis and increased its invasion ability in HGFs. HGF invasion with HGPg induced increases in the expression of ICAM-1. By using specific inhibitors and short hairpin RNA (shRNA), we have demonstrated that the activation of p38 MAPK and Akt pathways is critical for HGPg-induced ICAM-1 expression. Luciferase reporters and chromatin immunoprecipitation assays suggest that HGPg invasion increases NF-κB- and Sp1-DNA-binding activities in HGFs. Inhibition of NF-κB and Sp1 activations blocked the HGPg-induced ICAM-1 promoter activity and expression. The effect of HGPg on HGF signalling and ICAM-1 expression is mediated by CXC chemokine receptor 4 (CXCR4). Our findings identify the molecular pathways underlying HGPg-dependent ICAM-1 expression in HGFs, providing insight into the effect of P. gingivalis invasion in HGFs.

The expression and regulation of matrix metalloproteinase-3 is critically modulated by Porphyromonas gingivalis lipopolysaccharide with heterogeneous lipid A structures in human gingival fibroblasts

Background

Porphyromonas gingivalis lipopolysaccharide (LPS) is a crucial virulence factor strongly associated with chronic periodontitis which is the primary cause of tooth loss in adults. It exhibits remarkable heterogeneity containing tetra-(LPS_1435/1449) and penta-(LPS₁₆₉₀) acylated lipid A structures. Human gingival fibroblasts (HGFs) as the main resident cells of human gingiva play a key role in regulating matrix metalloproteinases (MMPs) and contribute to periodontal homeostasis. This study investigated the expression and regulation of MMPs1-3 and tissue inhibitors of MMP-1 (TIMP-1) in HGFs in response to P. gingivalis LPS_1435/1449 and LPS₁₆₉₀ and hexa-acylated E. coli LPS as a reference. The expression of MMPs 1–3 and TIMP-1 was evaluated by real-time PCR and ELISA.

Results

The MMP-3 mRNA and protein were highly upregulated in P. gingivalis LPS₁₆₉₀- and E. coli LPS-treated cells, whereas no induction was observed in P. gingivalis LPS_1435/1449-treated cells. On the contrary, the expression of MMP-1 and −2 was not significantly affected by P. gingivalis LPS lipid A heterogeneity. The TIMP-1 mRNA was upregulated in P. gingivalis LPS_1435/1449- and E. coli LPS-treated cells. Next, signal transduction pathways involved in P. gingivalis LPS-induced expression of MMP-3 were examined by blocking assays. Blockage of p38 MAPK and ERK significantly inhibited P. gingivalis LPS₁₆₉₀-induced MMP-3 expression in HGFs.

Conclusion

The present findings suggest that the heterogeneous lipid A structures of P. gingivalis LPS differentially modulate the expression of MMP-3 in HGFs, which may play a role in periodontal pathogenesis.

25-hydroxyvitamin D3 ameliorates periodontitis by modulating the expression of inflammation-associated factors in diabetic mice

Periodontitis is a complication of diabetes mellitus, and the two diseases are highly associated with the dysfunction of inflammatory mediators. 25-hydroxyvitamin D(3) (25(OH)D(3)) plays a pivotal role in inflammatory modulation, but little is known about its effects on the progression of diabetic periodontitis and the underlying mechanism. In this paper, we showed that 25(OH)D(3) ameliorated experimental periodontitis in diabetic mice. The intraperitoneal administration of 25(OH)D(3) to streptozotocin-induced diabetic mice reduced fasting glucose and serum TNF-α levels, leading to decreased alveolar bone loss. Western blot analyses of gingival epithelia showed that vitamin D receptor (VDR) and protein tyrosine phosphatase N2 (PTPN2) were upregulated, while the expression of NF-κB and the phosphorylation of Janus family kinase 1 (JAK1) were attenuated upon 25(OH)D(3) treatment. These data may provide an explanation for the therapeutic benefits and anti-inflammatory effects of 25(OH)D(3). Our findings should have important implications for the clinical therapy of diabetic periodontitis.

Effect of Porphyromonas gingivalis and Lactobacillus acidophilus on secretion of IL1B, IL6, and IL8 by gingival epithelial cells

Porphyromonas gingivalis alters cytokine expression in gingival epithelial cells, stimulating inflammatory responses that may lead to periodontal disease. This study explored the effect of Lactobacillus acidophilus on the specific expressions of the interleukins (ILs) IL1B, IL6, and IL8 induced by the pathogen. Human gingival epithelial cells were co-cultured with P. gingivalis, L. acidophilus, or L. acidophilus + P. gingivalis; the control group consisted of the cells alone. Protein and gene expression levels of the ILs were detected using ELISA and qRT-PCR, respectively. The supernatant from the P. gingivalis group held significantly higher protein and mRNA levels of IL1B, IL6, and IL8, compared to the control group. In the mixed bacterial group (L. acidophilus + P. gingivalis), the levels of all three ILs decreased with increasing concentrations of L. acidophilus and were significantly different from the P. gingivalis group. This suggests that in gingival cells, L. acidophilus offsets the P. gingivalis-induced secretion of these ILs in a dose-dependent manner.

Integrin α5β1-fimbriae binding and actin rearrangement are essential for Porphyromonas gingivalis invasion of osteoblasts and subsequent activation of the JNK pathway

BACKGROUND

Chronic periodontitis is an infectious disease of the periodontium, which includes the gingival epithelium, periodontal ligament and alveolar bone. The signature clinical feature of periodontitis is resorption of alveolar bone and subsequent tooth loss. The Gram-negative oral anaerobe, Porphyromonas gingivalis, is strongly associated with periodontitis, and it has been shown previously that P. gingivalis is capable of invading osteoblasts in a dose- and time-dependent manner resulting in inhibition of osteoblast differentiation and mineralization in vitro. It is not yet clear which receptors and cytoskeletal components mediate the invasive process, nor how the signaling pathways and viability of osteoblasts are affected by bacterial internalization. This study aimed to investigate these issues using an in vitro model system involving the inoculation of P. gingivalis ATCC 33277 into primary osteoblast cultures.

RESULTS

It was found that binding between P. gingivalis fimbriae and integrin α5β1 on osteoblasts, and subsequent peripheral condensation of actin, are essential for entry of P. gingivalis into osteoblasts. The JNK pathway was activated in invaded osteoblasts, and apoptosis was induced by repeated infections.

CONCLUSIONS

These observations indicate that P. gingivalis manipulates osteoblast function to promote its initial intracellular persistence by prolonging the host cell life span prior to its intercellular dissemination via host cell lysis. The identification of molecules critical to the interaction between P. gingivalis and osteoblasts will facilitate the development of new therapeutic strategies for the prevention of periodontal bone loss.

In vitro invasion and survival of Porphyromonas gingivalis in gingival fibroblasts; role of the capsule

Porphyromonas gingivalis is a Gram-negative, anaerobic bacterium involved in periodontitis and peri-implantitis that can invade and survive inside host cells in vitro. P. gingivalis can invade human gingival fibroblasts (GF), but no data are available about the role of P. gingivalis' capsule in GF invasion. In the current study, we aimed to determine the ability of three strains of P. gingivalis (encapsulated wild type W83, non-encapsulated HG91 and the non-encapsulated insertional isogenic knockout mutant of W83, ΔEpsC) to invade GF and the ability of internalized P. gingivalis to survive in vitro antibiotic treatment. The ability of P. gingivalis strains to invade GF was tested using an antibiotic protection assay at multiplicity of infection (MOI) 100 and 1000. The survival of internalized P. gingivalis cells was further analyzed by subsequent in vitro treatment with either metronidazole or amoxicillin alone or a combination of metronidazole and amoxicillin and anaerobic culture viability counts. All strains of P. gingivalis used in this study were able to invade GFs. The non-encapsulated mutant of W83 (ΔEpsC mutant) was significantly more invasive than the wild type W83 at MOI 100 (p value 0.025) and MOI 1000 (p value 0.038). Furthermore, internalized P. gingivalis was able to resist in vitro antibiotic treatment. As demonstrated by the differences in invasion efficiencies of P. gingivalis strain W83 and its isogenic mutant ΔEpsC, the capsule of P. gingivalis makes it less efficient in invading gingival fibroblasts. Moreover, internalized P. gingivalis can survive antibiotic treatment in vitro.

Human intestinal lumen and mucosa-associated microbiota in patients with colorectal cancer

Recent reports have suggested the involvement of gut microbiota in the progression of colorectal cancer (CRC). We utilized pyrosequencing based analysis of 16S rRNA genes to determine the overall structure of microbiota in patients with colorectal cancer and healthy controls; we investigated microbiota of the intestinal lumen, the cancerous tissue and matched noncancerous normal tissue. Moreover, we investigated the mucosa-adherent microbial composition using rectal swab samples because the structure of the tissue-adherent bacterial community is potentially altered following bowel cleansing. Our findings indicated that the microbial structure of the intestinal lumen and cancerous tissue differed significantly. Phylotypes that enhance energy harvest from diets or perform metabolic exchange with the host were more abundant in the lumen. There were more abundant Firmicutes and less abundant Bacteroidetes and Proteobacteria in lumen. The overall microbial structures of cancerous tissue and noncancerous tissue were similar; howerer the tumor microbiota exhibited lower diversity. The structures of the intestinal lumen microbiota and mucosa-adherent microbiota were different in CRC patients compared to matched microbiota in healthy individuals. Lactobacillales was enriched in cancerous tissue, whereas Faecalibacterium was reduced. In the mucosa-adherent microbiota, Bifidobacterium, Faecalibacterium, and Blautia were reduced in CRC patients, whereas Fusobacterium, Porphyromonas, Peptostreptococcus, and Mogibacterium were enriched. In the lumen, predominant phylotypes related to metabolic disorders or metabolic exchange with the host, Erysipelotrichaceae, Prevotellaceae, and Coriobacteriaceae were increased in cancer patients. Coupled with previous reports, these results suggest that the intestinal microbiota is associated with CRC risk and that intestinal lumen microflora potentially influence CRC risk via cometabolism or metabolic exchange with the host. However, mucosa-associated microbiota potentially affects CRC risk primarily through direct interaction with the host.

The plant coumarins auraptene and lacinartin as potential multifunctional therapeutic agents for treating periodontal disease

BACKGROUND

Periodontal diseases are bacterial infections leading to chronic inflammation disorders that are frequently observed in adults. In the present study, we evaluated the effect of auraptene and lacinartin, two natural oxyprenylated coumarins, on the growth, adherence properties, and collagenase activity of Porphyromonas gingivalis. We also investigated the capacity of these compounds to reduce cytokine and matrix metalloproteinase (MMP) secretion by lipopolysaccharide (LPS)-stimulated macrophages and to inhibit MMP-9 activity.

METHODS

Microplate dilution assays were performed to determine the effect of auraptene and lacinartin on P. gingivalis growth as well as biofilm formation stained with crystal violet. Adhesion of FITC-labeled P. gingivalis to oral epithelial cells was monitored by fluorometry. The effects of auraptene and lacinartin on LPS-induced cytokine and MMP secretion by macrophages were determined by immunological assays. Fluorogenic assays were used to evaluate the capacity of the two coumarins to inhibit the activity of P. gingivalis collagenase and MMP-9.

RESULTS

Only lacinartin completely inhibited P. gingivalis growth in a complex culture medium. However, under iron-limiting conditions, auraptene and lacinartin both inhibited the growth of P. gingivalis. Lacinartin also inhibited biofilm formation by P. gingivalis and promoted biofilm desorption. Both compounds prevented the adherence of P. gingivalis to oral epithelial cells, dose-dependently reduced the secretion of cytokines (IL-8 and TNF-α) and MMP-8 and MMP-9 by LPS-stimulated macrophages, and inhibited MMP-9 activity. Lacinartin also inhibited P. gingivalis collagenase activity.

CONCLUSIONS

By acting on multiple targets, including pathogenic bacteria, tissue-destructive enzymes, and the host inflammatory response, auraptene and lacinartin may be promising natural compounds for preventing and treating periodontal diseases.

Periodontal disease and atherosclerotic vascular disease: does the evidence support an independent association?: a scientific statement from the American Heart Association

A link between oral health and cardiovascular disease has been proposed for more than a century. Recently, concern about possible links between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) has intensified and is driving an active field of investigation into possible association and causality. The 2 disorders share several common risk factors, including cigarette smoking, age, and diabetes mellitus. Patients and providers are increasingly presented with claims that PD treatment strategies offer ASVD protection; these claims are often endorsed by professional and industrial stakeholders. The focus of this review is to assess whether available data support an independent association between ASVD and PD and whether PD treatment might modify ASVD risks or outcomes. It also presents mechanistic details of both PD and ASVD relevant to this topic. The correlation of PD with ASVD outcomes and surrogate markers is discussed, as well as the correlation of response to PD therapy with ASVD event rates. Methodological issues that complicate studies of this association are outlined, with an emphasis on the terms and metrics that would be applicable in future studies. Observational studies to date support an association between PD and ASVD independent of known confounders. They do not, however, support a causative relationship. Although periodontal interventions result in a reduction in systemic inflammation and endothelial dysfunction in short-term studies, there is no evidence that they prevent ASVD or modify its outcomes.

E-selectin mediates Porphyromonas gingivalis adherence to human endothelial cells

Porphyromonas gingivalis, a major periodontal pathogen, may contribute to atherogenesis and other inflammatory cardiovascular diseases. However, little is known about interactions between P. gingivalis and endothelial cells. E-selectin is a membrane protein on endothelial cells that initiates recruitment of leukocytes to inflamed tissue, and it may also play a role in pathogen attachment. In the present study, we examined the role of E-selectin in P. gingivalis adherence to endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with tumor necrosis factor alpha (TNF-α) to induce E-selectin expression. Adherence of P. gingivalis to HUVECs was measured by fluorescence microscopy. TNF-α increased adherence of wild-type P. gingivalis to HUVECs. Antibodies to E-selectin and sialyl Lewis X suppressed P. gingivalis adherence to stimulated HUVECs. P. gingivalis mutants lacking OmpA-like proteins Pgm6 and -7 had reduced adherence to stimulated HUVECs, but fimbria-deficient mutants were not affected. E-selectin-mediated P. gingivalis adherence activated endothelial exocytosis. These results suggest that the interaction between host E-selectin and pathogen Pgm6/7 mediates P. gingivalis adherence to endothelial cells and may trigger vascular inflammation.

Comparative evaluation of the effects of different photoablative laser irradiation protocols on the gingiva of periodontopathic patients

OBJECTIVE

We aimed at quantifying the presence of periodontopathogens in gingival biopsies from periodontitis patients treated with different photoablative lasers (diode GaAs, Er:YAG, Nd:YAG, and CO(2) lasers) and histologically analyzing their effects on the gingiva.

BACKGROUND DATA

Substantial evidence indicates that intracellular location of periodontal bacteria in the gingival epithelium may contribute to chronic periodontitis.

METHODS

Sixteen adult subjects with chronic periodontitis were subjected to conventional scaling/root planing and topical chlorhexidine, and immediately laser-irradiated on the inner and outer free gingiva. Small gingival biopsies were subjected to real-time polymerase chain reaction and cytofluorescence to identify periodontopathogens; tissue damage and endothelial ICAM-1 expression were assessed by histological and immunofluorescence analyses.

RESULTS

High DNA levels of Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium nucleatum, Treponema denticola, Prevotella intermedia, and Ekenella corrodens, were detected in all samples. Nd:YAG and diode lasers were capable of eradicating periodontopathogenic bacteria endowed within gingival epithelial cells outside periodontal pockets, without causing connective tissue damage and microvessel rupture. They also reduced ICAM-1 immunolabelling by the vascular endothelium. Conversely, Er:YAG lasers induced marked microvessel rupture and bleeding and failed to completely and selectively ablate the infected gingival epithelium, whereas CO(2) laser caused heat-induced coagulation of the lamina propria.

CONCLUSIONS

This study indicates that periodontopathogens can persist within cells outside the pocket epithelium, despite conventional periodontal treatment. Nd:YAG and diode lasers are able to eradicate intra- and extracellular bacteria from these sites, suggesting that they can be considered suitable devices to improve the clinical outcome of periodontal disease.

Identification of the putative specific pathogenic genes of Porphyromonas gingivalis with type II fimbriae

Porphyromonas gingivalis, the key etiologic agent of periodontitis, can be classified into six types (I to V and Ib) based on the fimA genes that encode FimA (a subunit of fimbriae). Accumulated evidence indicates that P. gingivalis expressing Type II fimbriae (Pg-II) is the most frequent isolate from severe periodontitis cases and is more virulent than other types of P. gingivalis. However, during the Pg-II infection process, which specific virulence factors play the key role is still unclear. In this study, we examined the capabilities of three Pg-II strains to invade and modulate the inflammatory cytokine expression of human gingival epithelial cells (GECs) compared to two Pg-I strains. P. gingivalis oligo microarrays were used to compare gene expression profiles of Pg-II strains that invade GECs with Pg-I strains. The differential gene expression of Pg-II was confirmed by quantitative reverse transcription-polymerase chain reaction. Our results showed that all of the Pg-II strains could induce interleukin (IL)-1β and IL-6 secretion significantly when compared to Pg-I strains. Thirty-seven genes that were specifically expressed during the pathogenic process of Pg-II were identified by a microarray assay. These findings provide a new insight at the molecular level to explain the specific pathogenic mechanism of Pg-II strains.

Benzyl isothiocyanate, a major component from the roots of Salvadora persica is highly active against Gram-negative bacteria

Plants produce a number of antimicrobial substances and the roots of the shrub Salvadora persica have been demonstrated to possess antimicrobial activity. Sticks from the roots of S. persica, Miswak sticks, have been used for centuries as a traditional method of cleaning teeth. Diverging reports on the chemical nature and antimicrobial repertoire of the chewing sticks from S. persica led us to explore its antibacterial properties against a panel of pathogenic or commensal bacteria and to identify the antibacterial component/s by methodical chemical characterization. S. persica root essential oil was prepared by steam distillation and solid-phase microextraction was used to sample volatiles released from fresh root. The active compound was identified by gas chromatography-mass spectrometry and antibacterial assays. The antibacterial compound was isolated using medium-pressure liquid chromatography. Transmission electron microscopy was used to visualize the effect on bacterial cells. The main antibacterial component of both S. persica root extracts and volatiles was benzyl isothiocyanate. Root extracts as well as commercial synthetic benzyl isothiocyanate exhibited rapid and strong bactericidal effect against oral pathogens involved in periodontal disease as well as against other Gram-negative bacteria, while Gram-positive bacteria mainly displayed growth inhibition or remained unaffected. The short exposure needed to obtain bactericidal effect implies that the chewing sticks and the essential oil may have a specific role in treatment of periodontal disease in reducing Gram-negative periodontal pathogens. Our results indicate the need for further investigation into the mechanism of the specific killing of Gram-negative bacteria by S. persica root stick extracts and its active component benzyl isothiocyanate.

Effect of periodontopathogen lipopolysaccharides and proinflammatory cytokines on CD46, CD55, and CD59 gene/protein expression by oral epithelial cells

Membrane-anchored complement regulatory proteins (CRPs), including CD46, CD55, and CD59, protect host cells from complement attack. In the present study, we investigated whether periodontopathogen lipopolysaccharide and proinflammatory cytokines modulate CRP gene/protein expression in human oral epithelial cells. The lipopolysaccharide of Treponema denticola and Tannerella forsythia were the most potent for increasing the gene expression of CD55 and CD59, and to a lesser extent CD46, after a 48-h stimulation. An lipopolysaccharide-induced upregulation of epithelial cell-surface CRP was also demonstrated. The stimulation of epithelial cells with lipopolysaccharide was associated with interleukin-6 (IL-6) and IL-8 secretion. Although these two cytokines had no effect on CD46 and CD55 gene expression in epithelial cells, IL-1β and tumor necrosis factor-α induced a significant upregulation. The cell-surface expression of CRP was also increased by the stimulation of epithelial cells with cytokines. The CD46, CD55, and CD59 gene/protein expression was upregulated by periodontopathogen lipopolysaccharide and proinflammatory cytokines. It can be hypothesized that, when faced with bacterial challenges and inflammatory conditions associated with active periodontal sites, oral epithelial cells may respond by increasing CRP gene/protein expression to avoid cell lysis by the complement system, which is activated during periodontitis.

Exit of intracellular Porphyromonas gingivalis from gingival epithelial cells is mediated by endocytic recycling pathway

Gingival epithelial cells function as an innate host defence system to prevent intrusion by periodontal bacteria. Nevertheless, Porphyromonas gingivalis, the most well-known periodontal pathogen, can enter gingival epithelial cells and pass through the epithelial barrier into deeper tissues. However, it is poorly understood how this pathogen exits from infected cells for further transcellular spreading. The present study was performed to elucidate the cellular machinery exploited by P. gingivalis to exit from immortalized human gingival epithelial cells. P. gingivalis was shown to be internalized with early endosomes positive for the FYVE domain of EEA1 and transferrin receptor, and about half of the intracellular bacteria were then sorted to lytic compartments, including autolysosomes and late endosomes/lysosomes, while a considerable number of the remaining organisms were sorted to Rab11- and RalA-positive recycling endosomes. Inhibition experiments revealed that bacterial exit was dependent on actin polymerization, lipid rafts and microtubule assembly. Dominant negative forms and RNAi knockdown of Rab11, RalA and exocyst complex subunits (Sec5, Sec6 and Exo84) significantly disturbed the exit of P. gingivalis. These results strongly suggest that the recycling pathway is exploited by intracellular P. gingivalis to exit from infected cells to neighbouring cells as a mechanism of cell-to-cell spreading.

Adsorption of components of the plasma kinin-forming system on the surface of Porphyromonas gingivalis involves gingipains as the major docking platforms

Enhanced production of proinflammatory bradykinin-related peptides, the kinins, has been suggested to contribute to the pathogenesis of periodontitis, a common inflammatory disease of human gingival tissues. In this report, we describe a plausible mechanism of activation of the kinin-generating system, also known as the contact system or kininogen-kallikrein-kinin system, by the adsorption of its plasma-derived components such as high-molecular-mass kininogen (HK), prekallikrein (PK), and Hageman factor (FXII) to the cell surface of periodontal pathogen Porphyromonas gingivalis. The adsorption characteristics of mutant strains deficient in selected proteins of the cell envelope suggested that the surface-associated cysteine proteinases, gingipains, bearing hemagglutinin/adhesin domains (RgpA and Kgp) serve as the major platforms for HK and FXII adhesion. These interactions were confirmed by direct binding tests using microplate-immobilized gingipains and biotinylated contact factors. Other bacterial cell surface components such as fimbriae and lipopolysaccharide were also found to contribute to the binding of contact factors, particularly PK. Analysis of kinin release in plasma upon contact with P. gingivalis showed that the bacterial surface-dependent mechanism is complementary to the previously described kinin generation system dependent on HK and PK proteolytic activation by the gingipains. We also found that several P. gingivalis clinical isolates differed in the relative significance of these two mechanisms of kinin production. Taken together, these data show the importance of this specific type of bacterial surface-host homeostatic system interaction in periodontal infections.

Competition between yogurt probiotics and periodontal pathogens in vitro

OBJECTIVE

To investigate the competition between probiotics in bio-yogurt and periodontal pathogens in vitro.

MATERIAL AND METHODS

The antimicrobial activity of bio-yogurt was studied by agar diffusion assays, using eight species of putative periodontal pathogens and a 'protective bacteria' as indicator strains. Four probiotic bacterial species (Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus acidophilus, and Bifidobacterium) were isolated from yogurt and used to rate the competitive exclusion between probiotics and periodontal pathogens.

RESULTS

Fresh yogurt inhibited all the periodontal pathogens included in this work, showing inhibition zones ranging from 9.3 (standard deviation 0.6) mm to 17.3 (standard deviation 1.7) mm, whereas heat-treated yogurt showed lower antimicrobial activity. In addition, neither fresh yogurt nor heat-treated yogurt inhibited the 'protective bacteria', Streptococcus sanguinis. The competition between yogurt probiotics and periodontal pathogens depended on the sequence of inoculation. When probiotics were inoculated first, Bifidobacterium inhibited Porphyromonas gingivalis, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, Porphyromonas circumdentaria, and Prevotella nigrescens; L. acidophilus inhibited P. gingivalis, A. actinomycetemcomitans, P. circumdentaria, P. nigrescens, and Peptostreptococcus anaerobius; L. bulgaricus inhibited P. gingivalis, A. actinomycetemcomitans, and P. nigrescens; and S. thermophilus inhibited P. gingivalis, F. nucleatum, and P. nigrescens. However, their antimicrobial properties were reduced when both species (probiotics and periodontal pathogens) were inoculated simultaneously. When periodontal pathogens were inoculated first, Prevotella intermedia inhibited Bifidobacterium and S. thermophilus.

CONCLUSIONS

The results demonstrated that bio-yogurt and the probiotics that it contains are capable of inhibiting specific periodontal pathogens but have no effect on the periodontal protective bacteria.

Differential effects of periopathogens on host protease inhibitors SLPI, elafin, SCCA1, and SCCA2

Objective

Secretory leukocyte peptidase inhibitors (SLPI), elafin, squamous cell carcinoma antigen 1 and 2 (SCCA1 and SCCA2) are specific endogenous serine protease inhibitors expressed by epithelial cells that prevent tissue damage from excessive proteolytic enzyme activity due to inflammation. To determine the effects of various periopathogens on these protease inhibitors, we utilized human gingival epithelial cells (GECs) challenged with cell-free bacteria supernatants of various periopathogens Porphyromonas gingivalis, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, and Fusobacterium nucleatum.

Design

The gene expression and secretion of SLPI, elafin, SCCA1, and SCCA2 were determined using real-time PCR and ELISA, respectively. The direct effects of periopathogens and P. gingivalis gingipain mutants on these inhibitors were examined in vitro by Western Blot. The effect on the innate immune response of GECs was measured by expression of antimicrobial peptides: human beta-defenisin-2 (hBD2) and chemokine (C-C motif) ligand 20 (CCL20).

Results

We found that SLPI, SCCA2, elafin, hBD2, and CCL20 gene expression levels were significantly induced (p<0.001) in response to P. gingivalis, whose virulence factors include cysteine proteases, but not in response to stimulation by other bacteria. P. gingivalis reduced the secretion of SLPI and elafin significantly in GECs, and degraded recombinant SLPI, elafin, SCCA1, and SCCA2. Differential degradation patterns of SLPI, elafin, SCCA1, and SCCA2 were observed with different bacteria as well as P. gingivalis mutants associated with the loss of specific gingipains secreted by P. gingivalis. In addition, pretreatment of GECs with SLPI, SCCA1, or SCCA2 partially blocked hBD2 and CCL20 mRNA expression in response to P. gingivalis, suggesting a protective effect.

Conclusion

Our results suggest that different periopathogens affect the host protease inhibitors in a different manner, suggesting host susceptibility may differ in the presence of these pathogens. The balance between cellular protease inhibitors and their degradation may be an important factor in susceptibility to periodontal infection.

Effects of tobacco and P. gingivalis on gingival fibroblasts

Cigarette smoke condensate (CSC) is the particulate matter of cigarette smoke. Porphyromonas gingivalis (P. gingivalis) is an opportunistic pathogen involved in periodontitis. It was hypothesized that the combination of CSC and P. gingivalis would increase the collagen-degrading ability of human gingival fibroblasts (HGFs). In this study, HGFs were exposed to CSC, P. gingivalis supernatant, and CSC plus P. gingivalis supernatant. The collagen-degrading ability and protein/mRNA levels of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) of HGFs were examined. The combined treatment increased collagen degradation, protein levels of active forms of MMP-1, MMP-2, MMP-3, and MMP-14 in conditioned media, and the low-molecular-weight fragment of MMP-14 in membrane extracts, as well as mRNA levels of MMP-1, MMP-2, and MMP-14. In conclusion, the combined effects of CSC and P. gingivalis increased HGF-mediated collagen degradation by destroying the balance between MMPs and TIMPs at multiple levels.

Interleukin-1 receptor-associated kinase-M in gingival epithelial cells attenuates the inflammatory response elicited by Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Recent studies have revealed that negative regulatory molecules, including interleukin-1 receptor-associated kinase-M (IRAK-M), control the overactivation of Toll-like receptor (TLR) signaling. The role of IRAK-M in human gingival epithelial cells (HGECs), which express TLRs, remains unclear. The present study examined the role of IRAK-M on interleukin-8 and macrophage chemoattractant protein-1 (MCP-1) expression in HGECs stimulated with Porphyromonas gingivalis and TLR ligands.

MATERIAL AND METHODS

Primary HGECs and an SV40 T-antigen-immortalized HGEC line (epi 4) were stimulated with live or heat-killed P. gingivalis, P. gingivalis lipopolysaccharide or the synthetic lipopeptide PAM(3)CSK(4), and subsequent expression of IRAK-M, interleukin-8 and MCP-1 was evaluated at the mRNA and protein levels. The effects of IRAK-M on interleukin-8 and MCP-1 expressions were evaluated by IRAK-M-specific RNA interference (RNAi)-based loss-of-function assay.

RESULTS

All tested stimulants up-regulated the expression of IRAK-M in HGECs. The P. gingivalis lipopolysaccharide or PAM(3)CSK(4) increased MCP-1 expression, whereas live P. gingivalis down-regulated the MCP-1 expression in HGECs. However, IRAK-M RNAi increased the expression of MCP-1 irrespective of up- or down-regulation mediated by the respective stimulants. Interleukin-8 gene expression, up-regulated by all tested stimulants, was further enhanced by IRAK-M RNAi. In contrast, IRAK-M RNAi had no effect on the interleukin-8 protein levels, irrespective of the stimulant, indicating that post-translational modification, not IRAK-M, controls interleukin-8 protein expression.

CONCLUSION

Interleukin-1 receptor-associated kinase-M appeared to have distinct regulatory roles on the interleukin-8 and MCP-1 produced by HGECs, further suggesting an important role for interleukin-8 in the immune response to periodontopathic bacteria.

Anti-Porphyromonas gingivalis and anti-inflammatory activities of A-type cranberry proanthocyanidins

A-type cranberry proanthocyanidins (AC-PACs) have recently been reported to be beneficial for human health, especially urinary tract health. The effect of these proanthocyanidins on periodontitis, a destructive disease of tooth-supporting tissues, needs to be investigated. The purpose of this study was to investigate the effects of AC-PACs on various virulence determinants of Porphyromonas gingivalis as well as on the inflammatory response of oral epithelial cells stimulated by this periodontopathogen. We examined the effects of AC-PACs on P. gingivalis growth and biofilm formation, adherence to human oral epithelial cells and protein-coated surfaces, collagenase activity, and invasiveness. We also tested the ability of AC-PACs to modulate the P. gingivalis-induced inflammatory response by human oral epithelial cells. Our results showed that while AC-PACs neutralized all the virulence properties of P. gingivalis in a dose-dependent fashion, they did not interfere with growth. They also inhibited the secretion of interleukin-8 (IL-8) and chemokine (C-C motif) ligand 5 (CCL5) but did not affect the secretion of IL-6 by epithelial cells stimulated with P. gingivalis. This anti-inflammatory effect was associated with reduced activation of the nuclear factor-kappaB (NF-kappaB) p65 pathway. AC-PACs may be potentially valuable bioactive molecules for the development of new strategies to treat and prevent P. gingivalis-associated periodontal diseases.

Production of Monoclonal Antibodies Specific to FimA of Porphyromonas gingivalis and Their Inhibitory Activity on Bacterial Binding

Background

The FimA of Porphyromonas gingivalis is a crucial pathogenic component of the bacteria and has been implicated as a target for vaccine development against the periodontal diseases.

Methods

In this study, the purified fimbriae (FimA subunit polymers) protein was used for immunization in their native form and B hybridoma clones producing antibodies specific to FimA were established.

Results

The monoclonal antibodies prepared from selected two clones, designated #123 (IgG2b/ kappa) and #265 (IgG1/kappa), displayed different patterns of binding activity against the cognate antigen. Both antibodies reacted with conformational epitopes expressed by partially dissociated oligomers, but not with monomer as elucidated by Western blot analysis. Ascites fluid containing the monoclonal antibodies showed the inhibitory activity against P. gingivalis to saliva-coated hydroxyapatite beads, an in vitro model for the pellicle-coated tooth surface.

Conclusion

These results suggest that the monoclonal antibodies could be used as vaccine material against the periodontal diseases through passive immunization.

Anchoring and length regulation of Porphyromonas gingivalis Mfa1 fimbriae by the downstream gene product Mfa2

Porphyromonas gingivalis, a causative agent of periodontitis, has at least two types of thin, single-stranded fimbriae, termed FimA and Mfa1 (according to the names of major subunits), which can be discriminated by filament length and by the size of their major fimbrilin subunits. FimA fimbriae are long filaments that are easily detached from cells, whereas Mfa1 fimbriae are short filaments that are tightly bound to cells. However, a P. gingivalis ATCC 33277-derived mutant deficient in mfa2, a gene downstream of mfa1, produced long filaments (10 times longer than those of the parent), easily detached from the cell surface, similar to FimA fimbriae. Longer Mfa1 fimbriae contributed to stronger autoaggregation of bacterial cells. Complementation of the mutant with the wild-type mfa2 allele in trans restored the parental phenotype. Mfa2 is present in the outer membrane of P. gingivalis, but does not co-purify with the Mfa1 fimbriae. However, co-immunoprecipitation demonstrated that Mfa2 and Mfa1 are associated with each other in whole P. gingivalis cells. Furthermore, immunogold microscopy, including double labelling, confirmed that Mfa2 was located on the cell surface and likely associated with Mfa1 fimbriae. Mfa2 may therefore play a role as an anchor for the Mfa1 fimbriae and also as a regulator of Mfa1 filament length. Two additional downstream genes (pgn0289 and pgn0290) are co-transcribed with mfa1 (pgn0287) and mfa2 (pgn0288), and proteins derived from pgn0289, pgn0290 and pgn0291 appear to be accessory fimbrial components.

Distinct roles of long/short fimbriae and gingipains in homotypic biofilm development by Porphyromonas gingivalis

Background

Porphyromonas gingivalis, a periodontal pathogen, expresses a number of virulence factors, including long (FimA) and short (Mfa) fimbriae as well as gingipains comprised of arginine-specific (Rgp) and lysine-specific (Kgp) cysteine proteinases. The aim of this study was to examine the roles of these components in homotypic biofilm development by P. gingivalis, as well as in accumulation of exopolysaccharide in biofilms.

Results

Biofilms were formed on saliva-coated glass surfaces in PBS or diluted trypticase soy broth (dTSB). Microscopic observation showed that the wild type strain formed biofilms with a dense basal monolayer and dispersed microcolonies in both PBS and dTSB. A FimA deficient mutant formed patchy and small microcolonies in PBS, but the organisms proliferated and formed a cohesive biofilm with dense exopolysaccharides in dTSB. A Mfa mutant developed tall and large microcolonies in PBS as well as dTSB. A Kgp mutant formed markedly thick biofilms filled with large clumped colonies under both conditions. A RgpA/B double mutant developed channel-like biofilms with fibrillar and tall microcolonies in PBS. When this mutant was studied in dTSB, there was an increase in the number of peaks and the morphology changed to taller and loosely packed biofilms. In addition, deletion of FimA reduced the autoaggregation efficiency, whereas autoaggregation was significantly increased in the Kgp and Mfa mutants, with a clear association with alteration of biofilm structures under the non-proliferation condition. In contrast, this association was not observed in the Rgp-null mutants.

Conclusion

These results suggested that the FimA fimbriae promote initial biofilm formation but exert a restraining regulation on biofilm maturation, whereas Mfa and Kgp have suppressive and regulatory roles during biofilm development. Rgp controlled microcolony morphology and biovolume. Collectively, these molecules seem to act coordinately to regulate the development of mature P. gingivalis biofilms.

New methods for selective isolation of bacterial DNA from human clinical specimens

Separation of bacterial DNA from human DNA in clinical samples may have an important impact on downstream applications, involving microbial diagnostic systems. We evaluated two commercially available reagents (MolYsis), Molzym GmbH & Co. KG, Bremen and Pureprove, SIRS-Lab GmbH, Jena, both Germany) for their potential to isolate and purify bacterial DNA from human DNA. We chose oral samples, which usually contain very high amounts of both human and bacterial cells. Three different DNA preparations each were made from eight caries and eight periodontal specimens using the two reagents above and a conventional DNA extraction strategy as reference. Based on target-specific real-time-quantitative PCR assays we compared the reduction of human DNA versus loss of bacterial DNA. Human DNA was monitored by targeting the beta-2-microglobulin gene, while bacteria were monitored by targeting 16S rDNA (total bacteria and Porphyromonas gingivalis) or the glycosyltransferase gene (Streptococcus mutans). We found that in most cases at least 90% of human DNA could successfully be removed, with complete removal in eight of 16 cases using MolYsis, and two (of 16) cases using Pureprove. Conversely, detection of bacterial DNA was possible in all cases with a recovery rate generally ranging from 35% to 50%. In conclusion, both strategies have the potential to reduce background interference from the host DNA which may be of remarkable value for nucleic-acid based microbial diagnostic systems.

Neutrophils rescue gingival epithelial cells from bacterial-induced apoptosis

In the pathogenesis of chronic inflammatory periodontal disease, neutrophils are recognized as a major cellular component from the histopathology of the periodontal lesion around teeth and from clinical cases where absence or dysfunction of neutrophils results in major periodontal destruction. Neutrophils are recruited in vast numbers into the gingival crevice during periodontal inflammation, attracted by microbial plaque chemoattractants and chemokines released following microbial perturbation of gingival epithelial cells. Porphyromonas gingivalis, a major periodontopathogen, triggers a vast array of cellular responses in gingival epithelial cells but also induces apoptosis. We demonstrate here that neutrophils, when combined in a P. gingivalis challenge assay of epithelial cells, prevent epithelial cell apoptosis by phagocytosing P. gingivalis and later undergoing apoptosis themselves. By removing P. gingivalis by phagocytosis, neutrophils also protect the host from the harmful effects of its microbial proteases, which degrade inflammatory cytokines and other host molecules.

Porphyromonas gingivalis fimbriae-dependent interleukin-6 autocrine regulation by increase of gp130 in endothelial cells

BACKGROUND AND OBJECTIVE

Local persistent infection by Porphyromonas gingivalis leads to inflammatory systemic diseases, such as atherosclerosis. We have reported previously that avirulent P. gingivalis fimbriae-dependent invasion into endothelial cells might be involved in progression of atherosclerosis. Although interleukin-6 (IL-6) regulates progression of atherosclerosis, little is known about the relationship of P. gingivalis fimbriae-dependent invasion to IL-6 regulation in endothelial cells.

MATERIAL AND METHODS

We examined the secretion of IL-6 and the expression of the IL-6 signal transducer gp130 in human umbilical vein endothelial cells (HUVEC) infected with the wild-type FDC381 strain of P. gingivalisand a fimbriae-deficient mutant (fimA) by enzyme-linked immunosorbent assay, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry (fluorescence-activated cell sorting, FACS) analysis.

RESULTS

Coculture of HUVEC with P. gingivalis resulted in increase of IL-6 secretion at 24 h postinfection. Interestingly, the increase was inhibited significantly in HUVEC infected with the P. gingivalis fimA mutant. In addition, the increase of IL-6 secretion induced by P. gingivalis infection was significantly impaired by the meiosis specific kinase 1 inhibitor, PD98059, or the nuclear factor kappaB inhibitor, Bay11-7082. Furthermore, we demonstrated that gp130 expression increased with P. gingivalis infection. Importantly, gp130 expression was significantly impaired by P gingivalis fimA mutant infection compared with wild-type P. gingivalis infection, as assessed by both quantitative RT-PCR and FACS analysis.

CONCLUSION

Our findings indicate that P. gingivalis fimbriae are important factors in the autocrine regulation of IL-6, by increasing gp130 in endothelial cells.