Molecular mechanisms of Porphyromonas gingivalis-host cell interaction on periodontal diseases

Comprehensive comparative analysis of the periodontal pathogen Porphyromonas gingivalis: exploring the pan-genome, the reconstruction of the gene regulatory network and genome-scale metabolic network

Porphyromonas gingivalis is a nonmotile, obligate anaerobic, Gram-negative bacterium known for its association with periodontal disease and its involvement in systemic diseases such as atherosclerosis, cardiovascular disease, colon cancer, and Alzheimer's disease. This bacterium produces several virulence factors, including capsules, fimbriae, lipopolysaccharides, proteolytic enzymes, and hemagglutinins. A comparative genomic analysis revealed the open pangenome of P. gingivalis and identified complete type IV secretion systems in strain KCOM2805 and almost complete type VI secretion systems in strains KCOM2798 and ATCC49417, which is a new discovery as previous studies did not find the proteins involved in secretion systems IV and VI. Conservation of some virulence factors between different strains was observed, regardless of their genetic diversity and origin. In addition, we performed for the first time a reconstruction analysis of the gene regulatory network, identifying transcription factors and proteins involved in the regulatory mechanisms of bacterial pathogenesis. In particular, QseB regulates the expression of hemagglutinin and arginine deaminase, while Rex may suppress the release of gingipain through interactions with PorV and the formatum/nitrate transporter. Our study highlights the central role of conserved virulence factors and regulatory pathways, particularly QseB and Rex, in P. gingivalis and provides insights into potential therapeutic targets.

Leucine-rich alpha-2-glycoprotein 1 affects bone destruction via IL-6 in mouse periodontitis model

OBJECTIVE

To investigate the production of leucine-rich α-2-glycoprotein-1 (LRG1) in periodontitis patients and its effectiveness as a new diagnostic marker for periodontitis.

SUBJECTS AND METHODS

In vitro experiments were conducted to analyze LRG1 mRNA expression in human gingival epithelial cells and fibroblasts via quantitative real-time PCR. In vivo experiments were conducted to analyze LRG1 localization in periodontitis patients. The correlation between the serum LRG1 levels and alveolar bone resorption in the mouse periodontitis model was also investigated.

RESULTS

A positive correlation existed between the periodontal inflamed surface area and serum LRG1 levels (Spearman's rank correlation coefficient: 0.60). LRG1 mRNA expression in human gingival epithelial cells and fibroblasts was upregulated by Porphyromonas gingivalis stimulation or tumor necrosis factor-α stimulation. Interleukin-6 in human gingival epithelial cells and fibroblasts induced the production of LRG1 and transforming growth factor-β. LRG1 levels in the periodontal tissue and serum in the periodontitis model were higher than those in control mice. LRG1 local administration resulted in alveolar bone resorption, whereas the administration of interleukin-6R antibody inhibited bone resorption.

CONCLUSIONS

LRG1 levels in serum and periodontal tissue are upregulated in periodontitis and are implicated in periodontal tissue destruction through interleukin-6 production.

Porphyromonas gingivalis can degrade dental zirconia

OBJECTIVES

The aim of present study was to examine the effect of Porphyromonas gingivalis (P.g.) adhesion on dental zirconia by characterizing the physical and chemical properties.

METHODS

Eighty polished-sintered zirconia discs were prepared and randomly distributed to 5 groups (n = 16): Zirconia cultured with - Group 1: broth containing P.g. for - 3 days; Group 2: 7 days; Group 3: broth (alone) for - 3 days; Group 4: 7 days; and Group 5: dry discs (negative control). After experimental period, broths were analyzed for pH and Zr release with inductively coupled plasma-optical emission spectroscopy (ICP-OES). The zirconia surface was evaluated by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), water contact angle (WCA), and biaxial flexural strength (BFS).

RESULTS

The mean pH with zirconia adhesion to P.g. group was significantly higher than the broth control (p < 0.05). As per ICP-OES, Zr ion/particulate release with P.g. adhesion to zirconia were significantly higher than the controls (p < 0.05). Post-experimental incubation, no defects were found on zirconia surfaces; tetragonal phase remained constant with no transformation to monoclinic phase but lower peak intensities were identified in experimental groups. WCA of zirconia surfaces with P.g. bacteria for 3 days (12.04° ± 2.05°) and 7 days (15.09° ± 2.95°) were significantly higher than zirconia surfaces immersed with broth (only) for 3 days (7.17° ± 1.09°) and 7 days (7.55° ± 0.65°), respectively (p < 0.05). BFS values of zirconia with P.g. for 3 days (632.57 ± 119.96 MPa) and 7 days (656.17 ± 100.29 MPa) were significantly lower than zirconia incubated in broth alone (765.01 ± 20.12 MPa) conditions (p < 0.05).

SIGNIFICANCE

Under the conditions of present study, it can be concluded that P.g. adhesion on zirconia leads to structural alterations of dental zirconia further contributing to zirconia degradation.

Microstructured Polymer System Containing Proanthocyanidin-Enriched Extract from Limonium brasiliense as a Prophylaxis Strategy to Prevent Recurrence of Porphyromonas gingivalis

Periodontal diseases are a global oral health problem affecting almost 10% of the global population. Porphyromonas gingivalis is one of the main bacteria involved in the initiation and progression of inflammatory processes as a result of the action of the cysteine proteases lysin- and arginine-gingipain. Surelease/polycarbophil microparticles containing a lyophilized proanthocyanidin-enriched fraction from the rhizomes of Limonium brasiliense, traditionally named "baicuru" (ethyl acetate fraction), were manufactured. The ethyl acetate fraction was characterized by UHPLC by the presence of samarangenins A and B (12.10 ± 0.07 and 21.05 ± 0.44%, respectively) and epigallocatechin-3-O-gallate (13.44 ± 0.27%). Physiochemical aspects of Surelease/polycarbophil microparticles were characterized concerning particle size, zeta potential, entrapment efficiency, ethyl acetate fraction release, and mucoadhesion. Additionally, the presence of the ethyl acetate fraction-loaded microparticles was performed concerning potential influence on viability of human buccal KB cells, P. gingivalis adhesion to KB cells, gingipain activity, and P. gingivalis biofilm formation. In general, all Surelease/polycarbophil microparticles tested showed strong adhesion to porcine cheek mucosa (93.1 ± 4.2% in a 30-min test), associated with a prolonged release of the ethyl acetate fraction (up to 16.5 ± 0.8% in 24 h). Preincubation of KB cells with Surelease/polycarbophil microparticles (25 µg/mL) resulted in an up to 93 ± 2% reduced infection rate by P. gingivalis. Decreased activity of the P. gingivalis-specific virulence factors lysin- and arginine-gingipain proteases by Surelease/polycarbophil microparticles was confirmed. Surelease/polycarbophil microparticles decreased biofilm formation of P. gingivalis (97 ± 2% at 60 µg/mL). Results from this study prove the promising activity of Surelease/polycarbophil microparticles containing ethyl acetate fraction microparticles as a prophylaxis strategy to prevent the recurrence of P. gingivalis.

Phylogenomic analysis of the Porphyromonas gingivalis - Porphyromonas gulae duo: approaches to the origin of periodontitis

Porphyromonas gingivalis is an oral human pathogen associated with the onset and progression of periodontitis, a chronic immune-inflammatory disease characterized by the destruction of the teeth-supporting tissue. P. gingivalis belongs to the genus Porphyromonas, which is characterized by being composed of Gram-negative, asaccharolytic, non-spore-forming, non-motile, obligatory anaerobic species, inhabiting niches such as the oral cavity, urogenital tract, gastrointestinal tract and infected wound from different mammals including humans. Among the Porphyromonas genus, P. gingivalis stands out for its specificity in colonizing the human oral cavity and its keystone pathogen role in periodontitis pathogenesis. To understand the evolutionary process behind P. gingivalis in the context of the Pophyoromonas genus, in this study, we performed a comparative genomics study with publicly available Porphyromonas genomes, focused on four main objectives: (A) to confirm the phylogenetic position of P. gingivalis in the Porphyromonas genus by phylogenomic analysis; (B) the definition and comparison of the pangenomes of P. gingivalis and its relative P. gulae; and (C) the evaluation of the gene family gain/loss events during the divergence of P. gingivalis and P. gulae; (D) the evaluation of the evolutionary pressure (represented by the calculation of Tajima-D values and dN/dS ratios) comparing gene families of P. gingivalis and P. gulae. Our analysis found 84 high-quality assemblies representing P. gingivalis and 14 P. gulae strains (from a total of 233 Porphyromonas genomes). Phylogenomic analysis confirmed that P. gingivalis and P. gulae are highly related lineages, close to P. loveana. Both organisms harbored open pangenomes, with a strong core-to-accessory ratio for housekeeping genes and a negative ratio for unknown function genes. Our analyses also characterized the gene set differentiating P. gulae from P. gingivalis, mainly associated with unknown functions. Relevant virulence factors, such as the FimA, Mfa1, and the hemagglutinins, are conserved in P. gulae, P. gingivalis, and P. loveana, suggesting that the origin of those factors occurred previous to the P. gulae - P. gingivalis divergence. These results suggest an unexpected evolutionary relationship between the P. gulae - P. gingivalis duo and P. loveana, showing more clues about the origin of the role of those organisms in periodontitis.

Host insulin resistance caused by Porphyromonas gingivalis-review of recent progresses

Porphyromonas gingivalis (P. gingivalis) is a Gram-negative oral anaerobic bacterium that plays a key role in the pathogenesis of periodontitis. P. gingivalis expresses a variety of virulence factors that disrupt innate and adaptive immunity, allowing P. gingivalis to survive and multiply in the host and destroy periodontal tissue. In addition to periodontal disease, P.gingivalis is also associated with systemic diseases, of which insulin resistance is an important pathological basis. P. gingivalis causes a systemic inflammatory response, disrupts insulin signaling pathways, induces pancreatic β-cell hypofunction and reduced numbers, and causes decreased insulin sensitivity leading to insulin resistance (IR). In this paper, we systematically review the studies on the mechanism of insulin resistance induced by P. gingivalis, discuss the association between P. gingivalis and systemic diseases based on insulin resistance, and finally propose relevant therapeutic approaches. Overall, through a systematic review of the mechanisms related to systemic diseases caused by P. gingivalis through insulin resistance, we hope to provide new insights for future basic research and clinical interventions for related systemic diseases.

Porphyromonas gingivalis induces an inflammatory response via the cGAS-STING signaling pathway in a periodontitis mouse model

Periodontitis is an inflammatory disease initiated by periodontopathogenic bacteria in the dental plaque biofilms. Understanding the role of Porphyromonas gingivalis (P. gingivalis), a keystone pathogen associated with chronic periodontitis, in the inflammatory response is crucial. Herein, we investigated whether P. gingivalis infection triggers the expression of the type I IFN gene and various cytokines and leads to activation of the cGAMP synthase-stimulator of IFN genes (cGAS-STING) pathway both in vitro and in a mouse model. Additionally, in an experimental model of periodontitis using P. gingivalis, Sting^Gt mice showed lower levels of inflammatory cytokines and bone resorption than wild-type mice. Furthermore, we report that a STING inhibitor (SN-011) significantly decreased inflammatory cytokine production and osteoclast formation in a periodontitis mouse model with P. gingivalis. In addition, STING agonist (SR-717) -treated periodontitis mice displayed enhanced macrophage infiltration and M1 macrophage polarization in periodontal lesions compared with that in vehicle-treated periodontitis mice. In conclusion, our results demonstrate that the cGAS-STING signaling pathway may be one of the key mechanisms crucial for the P. gingivalis-induced inflammatory response that leads to chronic periodontitis.

Structure based High-Throughput Virtual Screening, Molecular Docking and Molecular Dynamics Study of anticancer natural compounds against fimbriae (FimA) protein of Porphyromonas gingivalis in oral squamous cell carcinoma

Oral cancer is among the most common cancer in the world. Tobacco, alcohol, and viruses have been regarded as a well- known risk factors of OCC however, 15% of OSCC cases occurred each year without these known risk factors. Recently a myriad of studies has shown that bacterial infections lead to cancer. Accumulated shreds of evidence have demonstrated the role of Porphyromonas gingivalis (P. gingivalis) in OSCC. The virulence factor FimA of P. gingivalis activates the oncogenic pathways in OSCC by upregulating various cytokines. It also led to the inactivation of a tumor suppressor protein p53. The present Insilico study uses High-Throughput Virtual Screening, molecular docking, and molecular dynamics techniques to find the potential compounds against the target protein FimA. The goal of this study is to identify the anti-cancer lead compounds retrieved from natural sources that can be used to develop potent drug molecules to treat P.gingivalis-related OSCC. The anticancer natural compounds library was screened to identify the potential lead compounds. Furthermore, these lead compounds were subjected to precise docking, and based on the docking score potential lead compounds were identified. The top docked receptor-ligand complex was subjected to molecular dynamics simulation. A study of this insilico finding provides potent lead molecules which help in the development of therapeutic drugs against the target protein FimA in OSCC. Workflow of Structure based High-Throughput Virtual Screening, Molecular Docking and Molecular Dynamics Study of anticancer natural compounds against Fimbriae (FimA) protein of P. gingivalis in oral squamous cell carcinoma.

Evaluation of heat-inactivated Limosilactobacillus fermentum CCFM1139 and its supernatant for the relief of experimental periodontitis in rats

Periodontitis is a chronic inflammatory disease induced by subgingival microbial dysbiosis, characterised by inflammation of the soft tissues of the periodontium and progressive loss of alveolar bone. Limosilactobacillus fermentum CCFM1139 is a probiotic with the potential to relieve periodontitis in vitro and in vivo. Due to the cost of active strain in production applications, we considered the effectiveness of bacterial components and metabolites in alleviating experimental periodontitis. Therefore, this study investigated the effect of heat-inactivated Limosilactobacillus fermentum CCFM1139 and its supernatant in the development of experimental periodontitis through animal experiments. The results showed that active, heat-inactivated Limosilactobacillus fermentum CCFM1139 and its supernatant all significantly reduced IL-1β levels in gingival tissue and serum (p < 0.05). Micro-computed tomography (micro CT) analysis showed that the active and heat-inactivated Limosilactobacillus fermentum CCFM1139 reduced alveolar bone loss in rats with periodontitis by 25.6% and 15.9% respectively (p < 0.05), with no change in percentage of bone volume (p > 0.05). In histomorphometric analysis, active Limosilactobacillus fermentum CCFM1139 showed better results in reducing alveolar bone loss and reducing inflammatory cell recruitment at the second molar. In addition, there was no significant difference in the number of tartrate-resistant acid phosphatase (TRAP) positive cells after in all experimental groups (p > 0.05). Therefore, heat-inactivated Limosilactobacillus fermentum CCFM1139 or its supernatant also have the ability to relieve periodontitis, and their alleviating effect may focus on the regulation of inflammatory response.

Dysbiosis of Oral Microbiota and Metabolite Profiles Associated with Type 2 Diabetes Mellitus

Several previous studies have shown that oral microbial disorders may be closely related to the occurrence and development of type 2 diabetes mellitus (T2DM). However, whether the function of oral microorganisms and their metabolites have changed in patients with T2DM who have not suffered from any oral diseases has not been reported. We performed metagenomic analyses and nontargeted metabolic analysis of saliva and supragingival plaque samples from patients with T2DM who have not suffered any oral diseases and normal controls. We found that periodontal pathogens such as Porphyromonas gingivalis and Prevotella melaninogenica were significantly enriched, while the abundances of dental caries pathogens such as Streptococcus mutans and Streptococcus sobrinus were not significantly different in patients with T2DM compared to those in normal controls. Metabolomic analyses showed that the salivary levels of cadaverine and L-(+)-leucine of patients with T2DM were significantly higher than those of normal controls, while the supragingival plaque levels of N-acetyldopamine and 3,4-dimethylbenzoic acid in patients with T2DM were significantly higher than those in the normal controls. Additionally, we identified the types of oral microorganisms related to the changes in the levels of circulating metabolites, and the oral microorganisms were involved in the dysregulation of harmful metabolites such as cadaverine and n, n-dimethylarginine. Overall, our study first described the changes in the composition of oral microorganisms and their metabolites in patients with T2DM who have not suffered any oral diseases, which will provide a direct basis for finding oral biomarkers for early warning of oral diseases in T2DM. IMPORTANCE The incidence of oral diseases in type 2 diabetic patients might increase, and the severity might also be more serious. At present, the relationship between oral microorganisms and type 2 diabetes mellitus (T2DM) has become a hot topic in systemic health research. However, whether the function of oral microorganisms and their metabolites have changed in patients with T2DM who have not suffered from any oral diseases has not been reported. We found that even if the oral condition of T2DM is healthy, their oral microbes and metabolites have changed, thus increasing the risk of periodontal disease. Our study first described the changes in the composition of oral microorganisms and their metabolites in T2DM who have not suffered any oral diseases and revealed the correlation between oral microorganisms and their metabolites, which will provide a direct basis for finding oral biomarkers for early warning of oral diseases in patients with T2DM.

Potential Impact of Prosthetic Biomaterials on the Periodontium: A Comprehensive Review

The success of a prosthetic treatment is closely related to the periodontal health of the individual. The aim of this article was to review and present the importance of prosthetic restorative materials on the condition of the periodontium, the changes that occur in the composition of the subgingival microbiota and the levels of inflammatory markers in gingival crevicular fluid. Articles on the influence of different prosthetic restorative materials on subgingival microbiota and proinflammatory cytokines were searched for using the keywords "prosthetic biomaterials", "fixed prosthesis", "periodontal health", "subgingival microbiota", "periodontal biomarkers" and "gingival crevicular fluid" in PubMed/Medline, Science Direct, Scopus and Google Scholar. The type of material used for prosthesis fabrication together with poor marginal and internal fit can result in changes in the composition of the subgingival microbiota, as well as increased accumulation and retention of dentobacterial plaque, thus favoring the development of periodontal disease and prosthetic treatment failure. Biological markers have helped to understand the inflammatory response of different prosthetic materials on periodontal tissues with the main purpose of improving their clinical application in patients who need them. Metal-free ceramic prostheses induce a lower inflammatory response regardless of the fabrication method; however, the use of CAD/CAM systems is recommended for their fabrication. In addition, it is presumed that metal-ceramic prostheses cause changes in the composition of the subgingival microbiota producing a more dysbiotic biofilm with a higher prevalence of periodontopathogenic bacteria, which may further favor periodontal deterioration.

Regulation of gingival keratinocyte monocyte chemoattractant protein-1-induced protein (MCPIP)-1 and mucosa-associated lymphoid tissue lymphoma translocation protein (MALT)-1 expressions by periodontal bacteria, lipopolysaccharide, and interleukin-1β

BACKGROUND

The aim of this study was to evaluate oral bacteria- and interleukin (IL)-1β-induced protein and mRNA expression profiles of monocyte chemoattractant protein-1-induced protein (MCPIP)-1 and mucosa-associated lymphoid tissue lymphoma translocation protein (MALT)-1 in human gingival keratinocyte monolayers and organotypic oral mucosal models.

METHODS

Human gingival keratinocyte (HMK) monolayers were incubated with Porphyromonas gingivalis, Fusobacterium nucleatum, P. gingivalis lipopolysaccharide (LPS) and IL-1β. The protein levels of MCPIP-1 and MALT-1 were examined by immunoblots and mRNA levels by qPCR. MCPIP-1 and MALT-1 protein expression levels were also analyzed immunohistochemically using an organotypic oral mucosal model. One-way analysis of variance followed by Tukey correction was used in statistical analyses.

RESULTS

In keratinocyte monolayers, MCPIP-1 protein expression was suppressed by F. nucleatum and MALT-1 protein expression was suppressed by F. nucleatum, P. gingivalis LPS and IL-1β. P. gingivalis seemed to degrade MCPIP-1 and MALT-1 at all tested time points and degradation was inhibited when P. gingivalis was heat-killed. MCPIP-1 mRNA levels were increased by P. gingivalis, F. nucleatum, and IL-1β, however, no changes were observed in MALT-1 mRNA levels.

CONCLUSION

Gingival keratinocyte MCPIP-1 and MALT-1 mRNA and protein expression responses are regulated by infection and inflammatory mediators. These findings suggest that periodontitis-associated bacteria-induced modifications in MCPIP-1 and MALT-1 responses can be a part of periodontal disease pathogenesis.

[Porphyromonas gingivalis HmuY and Its Possible Effect on the Pathogenesis of Periodontitis]

Periodontitis, one of the most common inflammatory oral diseases in human beings, threatens the health of teeth and mouth and is closely associated with the development of many systemic diseases. Existing research about the pathogenesis of periodontitis mainly focuses on the oral microbial homeostasis and its complex interaction with the immune system. Among all the oral microorganisms, Porphyromonas gingivalis ( P. gingivalis) is considered to be the main pathogen causing chronic periodontitis. Recent studies have shown that P. gingivalis poesseses HmuY, a special heme binding protein, which binds with heme to provide essential nutrition for P. gingivalis and activates the host immune system. Therefore, HmuY plays an important role in the growth, proliferation, invasion, and pathogenesis of P. gingivalis and is a potential virulence factor of the bacteria. Existing studies on HmuY are limited to the host immune response that HmuY triggers, and there are still no conclusive findings on whether HmuY participates in the pathogenesis of periodontitis through other ways, such as influencing periodontal bone metabolism. Herein, we reviewed the latest research findings on the biological characteristics and physiological functions of HmuY and its relationship with chronic periodontitis, so as to provide new ideas for in-depth research and further explorations into the pathogenesis of chronic periodontitis.

Continuous Oral Administration of Sonicated P. gingivalis Delays Rat Skeletal Muscle Healing Post-Treadmill Training

BACKGROUND

A delay in muscle repair interferes with the effect of training or exercise; therefore, it is important to identify the factors that delay muscle repair. P. gingivalis, one of the most common periodontal disease pathogens, has the potential to inhibit muscle repair after training, as inferred from a previous study. To assess the expression of satellite cells in this in vivo study, we evaluated the relationship between P. gingivalis and muscle regeneration after training.

METHODS

A total of 20 male Wistar rats (eight weeks in age) were randomly divided into two groups: one orally administered sonicated P. gingivalis four times per week for six weeks (PG group) and one given no treatment (NT group). After four weeks of training using a treadmill, the gastrocnemius was evaluated using histology of the cross-sectional area (CSA) of myotubes and immunohistochemistry of the expression of skeletal muscle satellite cells. In addition, an endurance test was performed a day before euthanization.

RESULTS

The CSA and expression of Pax7+/MyoD- and Pax7+/MyoD+ cells were not significantly different between the groups. However, the expression of Pax7-/MyoD+ cells and running time until exhaustion were significantly lower in the PG group.

CONCLUSIONS

Infection with P. gingivalis likely interferes with muscle repair after training.

Porphyromonas gingivalis and dental stem cells crosstalk amplify inflammation and bone loss in the periodontitis niche

Periodontitis is the sixth most prevalent disease, and almost 3.5 billion people are affected globally by dental caries and periodontal diseases. The microbial shift from a symbiotic microbiota to a dysbiotic microbiota in the oral cavity generally initiates periodontal disease. Pathogens in the periodontal microenvironment interact with stem cells to modulate their regenerative potential. Therefore, this review focuses on the interaction between microbes and stem cells in periodontitis conditions. Microbes direct dental stem cells to secrete a variety of pro-inflammatory cytokines and chemokines, which increase the inflammatory burden in the damaged periodontal tissue, which further aggravates periodontitis. Microbial interaction also decreases the osteogenic differentiation potential of dental stem cells by downregulating alkaline phosphatase, runt-related transcription factor 2, type 1 collagen, osteocalcin, osteopontin, and so on. Microbe and stem cell interaction amplifies pro-inflammatory cytokine signaling in the periodontitis niche, decreasing the osteogenic commitment of dental stem cells. A clear understanding of microbial stem cell interactions is crucial in designing regenerative therapies using stem cells in the management of periodontitis.

Lenabasum Reduces Porphyromonas gingivalis-Driven Inflammation

The aim of this study was to evaluate the potential anti-inflammatory and anti-resorptive effects of lenabasum in the context of Porphyromonas gingivalis (Pg)-induced inflammation. Lenabasum or ajulemic acid (1',1'-dimethylheptyl-THC-11-oic-acid), a synthetic analog of THC-11-oic acid, has already demonstrated anti-inflammatory properties for the treatment of several inflammatory diseases. In vitro, the cytocompatibility of lenabasum was evaluated in human oral epithelial cells (EC), oral fibroblasts and osteoblasts by metabolic activity assay. The effect of lenabasum (5 µM) treatment of Pg-LPS- and P. gingivalis-infected EC on the pro- and anti-inflammatory markers was studied through RTqPCR. In vivo, lenabasum was injected subcutaneously in a P. gingivalis-induced calvarial abscess mouse model to assess its pro-healing effect. Concentrations of lenabasum up to 5 µM were cytocompatible in all cell types. Treatment of Pg-LPS and Pg-infected EC with lenabasum (5 µM; 6 h) reduced the gene expression of TNF-α, COX-2, NF-κB, and RANKL, whereas it increased the expression of IL-10 and resolvin E1 receptor respectively (p < 0.05). In vivo, the Pg-elicited inflammatory lesions' clinical size was significantly reduced by lenabasum injection (30 µM) vs untreated controls (45%) (p < 0.05). Histomorphometric analysis exhibited improved quantity and quality of bone (with reduced lacunae) and significantly reduced calvarial soft tissue inflammatory score in mice treated with lenabasum (p < 0.05). Tartrate-resistant acid phosphatase activity assay (TRAP) also demonstrated decreased osteoclastic activity in the treatment group compared to that in the controls. Lenabasum showed promising anti-inflammatory and pro-resolutive properties in the management of Pg-elicited inflammation, and thus, its potential as adjuvant periodontal treatment should be further investigated.

Dental Materials for Oral Microbiota Dysbiosis: An Update

The balance or dysbiosis of the microbial community is a major factor in maintaining human health or causing disease. The unique microenvironment of the oral cavity provides optimal conditions for colonization and proliferation of microbiota, regulated through complex biological signaling systems and interactions with the host. Once the oral microbiota is out of balance, microorganisms produce virulence factors and metabolites, which will cause dental caries, periodontal disease, etc. Microbial metabolism and host immune response change the local microenvironment in turn and further promote the excessive proliferation of dominant microbes in dysbiosis. As the product of interdisciplinary development of materials science, stomatology, and biomedical engineering, oral biomaterials are playing an increasingly important role in regulating the balance of the oral microbiome and treating oral diseases. In this perspective, we discuss the mechanisms underlying the pathogenesis of oral microbiota dysbiosis and introduce emerging materials focusing on oral microbiota dysbiosis in recent years, including inorganic materials, organic materials, and some biomolecules. In addition, the limitations of the current study and possible research trends are also summarized. It is hoped that this review can provide reference and enlightenment for subsequent research on effective treatment strategies for diseases related to oral microbiota dysbiosis.

Metagenomic Analysis Reveals A Possible Association Between Respiratory Infection and Periodontitis

Periodontitis is an inflammatory disease that is characterized by progressive destruction of the periodontium and causes tooth loss in adults. Periodontitis is known to be associated with dysbiosis of the oral microflora, which is often linked to various diseases. However, the complexity of plaque microbial communities of periodontitis, antibiotic resistance, and enhanced virulence make this disease difficult to treat. In this study, using metagenomic shotgun sequencing, we investigated the etiology, antibiotic resistance genes (ARGs), and virulence genes (VirGs) of periodontitis. We revealed a significant shift in the composition of oral microbiota as well as several functional pathways that were represented significantly more abundantly in periodontitis patients than in controls. In addition, we observed several positively selected ARGs and VirGs with the Ka/Ks ratio > 1 by analyzing our data and a previous periodontitis dataset, indicating that ARGs and VirGs in oral microbiota may be subjected to positive selection. Moreover, 5 of 12 positively selected ARGs and VirGs in periodontitis patients were found in the genomes of respiratory tract pathogens. Of note, 91.8% of the background VirGs with at least one non-synonymous single-nucleotide polymorphism for natural selection were also from respiratory tract pathogens. These observations suggest a potential association between periodontitis and respiratory infection at the gene level. Our study enriches the knowledge of pathogens and functional pathways as well as the positive selection of antibiotic resistance and pathogen virulence in periodontitis patients, and provides evidence at the gene level for an association between periodontitis and respiratory infection.

Palmitate-Triggered COX2/PGE2-Related Hyperinflammation in Dual-Stressed PdL Fibroblasts Is Mediated by Repressive H3K27 Trimethylation

The interrelationships between periodontal disease, obesity-related hyperlipidemia and mechanical forces and their modulating effects on the epigenetic profile of periodontal ligament (PdL) cells are assumed to be remarkably complex. The PdL serves as a connective tissue between teeth and alveolar bone and is involved in pathogen defense and the inflammatory responses to mechanical stimuli occurring during tooth movement. Altered inflammatory signaling could promote root resorption and tooth loss. Hyperinflammatory COX2/PGE2 signaling was reported for human PdL fibroblasts (HPdLFs) concomitantly stressed with Porphyromonas gingivalis lipopolysaccharides and compressive force after exposure to palmitic acid (PA). The aim of this study was to investigate the extent to which this was modulated by global and gene-specific changes in histone modifications. The expression of key epigenetic players and global H3Kac and H3K27me3 levels were quantitatively evaluated in dual-stressed HPdLFs exposed to PA, revealing a minor force-related reduction in repressive H3K27me3. UNC1999-induced H3K27me3 inhibition reversed the hyperinflammatory responses of dual-stressed PA cultures characterized by increased COX2 expression, PGE2 secretion and THP1 adhesion. The reduced expression of the gene encoding the anti-inflammatory cytokine IL-10 and the increased presence of H3K27me3 at its promoter-associated sites were reversed by inhibitor treatment. Thus, the data highlight an important epigenetic interplay between the different stimuli to which the PdL is exposed.

Porphyromonas gingivalis Gingipains Induce Cyclooxygenase-2 Expression and Prostaglandin E2 Production via ERK1/2-Activated AP-1 (c-Jun/c-Fos) and IKK/NF-κB p65 Cascades

Porphyromonas gingivalis is commonly known as one of the major pathogens contributing to periodontitis, and its persistent infection may increase the risk for the disease. The proinflammatory mediators, including IL-6, TNF-α, and cyclooxygenase-2 (COX-2)/PGE₂, are closely associated with progression of periodontitis. In this study, we focused on the cysteine protease "gingipains," lysine-specific gingipain, arginine-specific gingipain (Rgp) A, and RgpB, produced by P. gingivalis, and used the wild-type strain and several gene-deletion mutants (rgpA, rgpB, kgp, and fimA) to elucidate the involvement of gingipains in COX-2 expression and PGE₂ production. We infected human monocytes, which are THP-1 cells and primary monocytes, with these bacterial strains and found that gingipains were involved in induction of COX-2 expression and PGE₂ production. We have shown that the protease activity of gingipains was crucial for these events by using gingipain inhibitors. Furthermore, activation of ERK1/2 and IκB kinase was required for gingipain-induced COX-2 expression/PGE₂ production, and these kinases activated two transcription factors, c-Jun/c-Fos (AP-1) and NF-κB p65, respectively. In particular, these data suggest that gingipain-induced c-Fos expression via ERK is essential for AP-1 formation with c-Jun, and activation of AP-1 and NF-κB p65 plays a central role in COX-2 expression/PGE₂ production. Thus, we show the (to our knowledge) novel finding that gingipains with the protease activity from P. gingivalis induce COX-2 expression and PGE₂ production via activation of MEK/ERK/AP-1 and IκB kinase/NF-κB p65 in human monocytes. Hence it is likely that gingipains closely contribute to the inflammation of periodontal tissues.

Oral and Gut Microbial Dysbiosis and Non-alcoholic Fatty Liver Disease: The Central Role of Porphyromonas gingivalis

Gut microbiota play many important roles, such as the regulation of immunity and barrier function in the intestine, and are crucial for maintaining homeostasis in living organisms. The disruption in microbiota is called dysbiosis, which has been associated with various chronic inflammatory conditions, food allergies, colorectal cancer, etc. The gut microbiota is also affected by several other factors such as diet, antibiotics and other medications, or bacterial and viral infections. Moreover, there are some reports on the oral-gut-liver axis indicating that the disruption of oral microbiota affects the intestinal biota. Non-alcoholic fatty liver disease (NAFLD) is one of the systemic diseases caused due to the dysregulation of the oral-gut-liver axis. NAFLD is the most common liver disease reported in the developed countries. It includes liver damage ranging from simple steatosis to nonalcoholic steatohepatitis (NASH), cirrhosis, and cancer. Recently, accumulating evidence supports an association between NAFLD and dysbiosis of oral and gut microbiota. Periodontopathic bacteria, especially Porphyromonas gingivalis, have been correlated with the pathogenesis and development of NAFLD based on the clinical and basic research, and immunology. P. gingivalis was detected in the liver, and lipopolysaccharide from this bacteria has been shown to be involved in the progression of NAFLD, thereby indicating a direct role of P. gingivalis in NAFLD. Moreover, P. gingivalis induces dysbiosis of gut microbiota, which promotes the progression of NAFLD, through disrupting both metabolic and immunologic pathways. Here, we review the roles of microbial dysbiosis in NAFLD. Focusing on P. gingivalis, we evaluate and summarize the most recent advances in our understanding of the relationship between oral-gut microbiome symbiosis and the pathogenesis and progression of non-alcoholic fatty liver disease, as well as discuss novel strategies targeting both P. gingivalis and microbial dysbiosis.

GDF15 Supports the Inflammatory Response of PdL Fibroblasts Stimulated by P. gingivalis LPS and Concurrent Compression

Periodontitis is characterized by bacterially induced inflammatory destruction of periodontal tissue. This also affects fibroblasts of the human periodontal ligaments (HPdLF), which play a coordinating role in force-induced tissue and alveolar bone remodeling. Excessive inflammation in the oral tissues has been observed with simultaneous stimulation by pathogens and mechanical forces. Recently, elevated levels of growth differentiation factor 15 (GDF15), an immuno-modulatory member of the transforming growth factor (TGFB) superfamily, were detected under periodontitis-like conditions and in force-stressed PdL cells. In view of the pleiotropic effects of GDF15 in various tissues, this study aims to investigate the role of GDF15 in P. gingivalis-related inflammation of HPdLF and its effect on the excessive inflammatory response to concurrent compressive stress. To this end, the expression and secretion of cytokines (IL6, IL8, COX2/PGE2, TNFα) and the activation of THP1 monocytic cells were analyzed in GDF15 siRNA-treated HPdLF stimulated with P. gingivalis lipopolysaccharides alone and in combination with compressive force. GDF15 knockdown significantly reduced cytokine levels and THP1 activation in LPS-stimulated HPdLF, which was less pronounced with additional compressive stress. Overall, our data suggest a pro-inflammatory role for GDF15 in periodontal disease and demonstrate that GDF15 partially modulates the force-induced excessive inflammatory response of PdLF under these conditions.

Anti-Inflammatory Effect of Charantadiol A, Isolated from Wild Bitter Melon Leaf, on Heat-Inactivated Porphyromonas gingivalis-Stimulated THP-1 Monocytes and a Periodontitis Mouse Model

Porphyromonas gingivalis has been identified as one of the major periodontal pathogens. Activity-directed fractionation and purification processes were employed to identify bioactive compounds from bitter melon leaf. Ethanolic extract of bitter melon leaf was separated into five subfractions by open column chromatography. Subfraction-5-3 significantly inhibited P. gingivalis-induced interleukin (IL)-8 and IL-6 productions in human monocytic THP-1 cells and then was subjected to separation and purification by using different chromatographic methods. Consequently, 5β,19-epoxycucurbita-6,23(E),25(26)-triene-3β,19(R)-diol (charantadiol A) was identified and isolated from the subfraction-5-3. Charantadiol A effectively reduced P. gingivalis-induced IL-6 and IL-8 productions and triggered receptors expressed on myeloid cells (TREM)-1 mRNA level of THP-1 cells. In a separate study, charantadiol A significantly suppressed P. gingivalis-stimulated IL-6 and tumor necrosis factor-α mRNA levels in gingival tissues of mice, confirming the inhibitory effect against P. gingivalis-induced periodontal inflammation. Thus, charantadiol A is a potential anti-inflammatory agent for modulating P. gingivalis-induced inflammation.

Porphyromonas gingivalis outside the oral cavity

Porphyromonas gingivalis, a Gram-negative anaerobic bacillus present in periodontal disease, is considered one of the major pathogens in periodontitis. A literature search for English original studies, case series and review articles published up to December 2019 was performed using the MEDLINE, PubMed and GoogleScholar databases, with the search terms "Porphyromonas gingivalis" AND the potentially associated condition or systemic disease Abstracts and full text articles were used to make a review of published research literature on P. gingivalis outside the oral cavity. The main points of interest of this narrative review were: (i) a potential direct action of the bacterium and not the systemic effects of the inflammatory acute-phase response induced by the periodontitis, (ii) the presence of the bacterium (viable or not) in the organ, or (iii) the presence of its virulence factors. Virulence factors (gingipains, capsule, fimbriae, hemagglutinins, lipopolysaccharide, hemolysin, iron uptake transporters, toxic outer membrane blebs/vesicles, and DNA) associated with P. gingivalis can deregulate certain functions in humans, particularly host immune systems, and cause various local and systemic pathologies. The most recent studies linking P. gingivalis to systemic diseases were discussed, remembering particularly the molecular mechanisms involved in different infections, including cerebral, cardiovascular, pulmonary, bone, digestive and peri-natal infections. Recent involvement of P. gingivalis in neurological diseases has been demonstrated. P. gingivalis modulates cellular homeostasis and increases markers of inflammation. It is also a factor in the oxidative stress involved in beta-amyloid production.

Genetic Susceptibility to Periodontal Disease in Down Syndrome: A Case-Control Study

Severe periodontitis is prevalent in Down syndrome (DS). This study aimed to identify genetic variations associated with periodontitis in individuals with DS. The study group was distributed into DS patients with periodontitis (n = 50) and DS patients with healthy periodontium (n = 36). All samples were genotyped with the “Axiom Spanish Biobank” array, which contains 757,836 markers. An association analysis at the individual marker level using logistic regression, as well as at the gene level applying the sequence kernel association test (SKAT) was performed. The most significant genes were included in a pathway analysis using the free DAVID software. C12orf74 (rs4315121, p = 9.85 × 10⁻⁵, OR = 8.84), LOC101930064 (rs4814890, p = 9.61 × 10⁻⁵, OR = 0.13), KBTBD12 (rs1549874, p = 8.27 × 10⁻⁵, OR = 0.08), PIWIL1 (rs11060842, p = 7.82 × 10⁻⁵, OR = 9.05) and C16orf82 (rs62030877, p = 8.92 × 10⁻⁵, OR = 0.14) showed a higher probability in the individual analysis. The analysis at the gene level highlighted PIWIL, MIR9-2, LHCGR, TPR and BCR. At the signaling pathway level, PI3K-Akt, long-term depression and FoxO achieved nominal significance (p = 1.3 × 10⁻², p = 5.1 × 10⁻³, p = 1.2 × 10⁻², respectively). In summary, various metabolic pathways are involved in the pathogenesis of periodontitis in DS, including PI3K-Akt, which regulates cell proliferation and inflammatory response.

Hyperlipidemic Conditions Impact Force-Induced Inflammatory Response of Human Periodontal Ligament Fibroblasts Concomitantly Challenged with P. gingivalis-LPS

In obese patients, enhanced serum levels of free fatty acids (FFA), such as palmitate (PA) or oleate (OA), are associated with an increase in systemic inflammatory markers. Bacterial infection during periodontal disease also promotes local and systemic low-grade inflammation. How both conditions concomitantly impact tooth movement is largely unknown. Thus, the aim of this study was to address the changes in cytokine expression and the secretion of human periodontal ligament fibroblasts (HPdLF) due to hyperlipidemic conditions, when additionally stressed by bacterial and mechanical stimuli. To investigate the impact of obesity-related hyperlipidemic FFA levels on HPdLF, cells were treated with 200 µM PA or OA prior to the application of 2 g/cm² compressive force. To further determine the additive impact of bacterial infection, HPdLF were stimulated with lipopolysaccharides (LPS) obtained from Porphyromonas gingivalis. In mechanically compressed HPdLF, PA enhanced COX2 expression and PGE2 secretion. When mechanically stressed HPdLF were additionally stimulated with LPS, the PGE2 and IL6 secretion, as well as monocyte adhesion, were further increased in PA-treated cultures. Our data emphasize that a hyperlipidemic condition enhances the susceptibility of HPdLF to an excessive inflammatory response to compressive forces, when cells are concomitantly exposed to bacterial components.

Porphyromonas gingivalis lipopolysaccharide induces interleukin-6 and c-c motif chemokine ligand 2 expression in cultured hCMEC/D3 human brain microvascular endothelial cells

OBJECTIVE

This paper describes the effect of Porphyromonas gingivalis (P gingivalis) lipopolysaccharide (LPS) on the expression of interleukin-6 (IL-6) and C-C motif chemokine ligand 2 (CCL2) in cultured hCMEC/D3 human brain microvascular endothelial cells.

BACKGROUND

P gingivalis is one of the important pathogens in periodontitis, and periodontitis is a risk factor for brain disorders including cerebrovascular diseases and Alzheimer's disease. However, the mechanisms underlying the pathogenesis of P gingivalis-mediated brain diseases are incompletely understood. Effects of P gingivalis LPS on brain endothelial cells are not known well.

METHODS

The hCMEC/D3 human brain microvascular endothelial cells were cultured and treated with P gingivalis LPS. The expression of IL-6 and CCL2 mRNA and protein was examined using quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay, respectively. Effect of inhibitors of Toll-like receptor (TLR) 2, TLR4, nuclear factor-κB (NF-κB), p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) was also investigated. Phosphorylation of NF-κB p65, p38 MAPK and JNK was examined using Western blotting.

RESULTS

P gingivalis LPS-induced mRNA and protein expression of IL-6 and CCL2 in hCMEC/D3 cells in a concentration-dependent manner at the concentration of 0.5-50 µg/mL. Maximal mRNA expression of IL-6 and CCL2 was found 2 and 4 hours after stimulation, respectively. Induction of IL-6 and CCL2 by P gingivalis LPS was almost completely inhibited by pretreatment of cells with TLR4 inhibitor but not by TLR2 inhibitor. Treatment of cells with P gingivalis LPS for up to 2 hours induced phosphorylation of NF-κB p65, p38 MAPK and JNK. IL-6 induction was decreased by pretreatment of cells with NF-κB inhibitor SN50 or p38 MAPK inhibitor SB203580, while CCL2 induction was reduced by SN50 or JNK inhibitor SP600125.

CONCLUSIONS

IL-6 and CCL2 produced upon P gingivalis LPS stimulation may contribute to the inflammatory reactions in brain endothelial cells and subsequent neurological disorders such as cerebrovascular and Alzheimer's diseases.

Exacerbation of AMD Phenotype in Lasered CNV Murine Model by Dysbiotic Oral Pathogens

Emerging evidence underscores an association between age-related macular degeneration (AMD) and periodontal disease (PD), yet the biological basis of this linkage and the specific role of oral dysbiosis caused by PD in AMD pathophysiology remains unclear. Furthermore, a simple reproducible model that emulates characteristics of both AMD and PD has been lacking. Hence, we established a novel AMD+PD murine model to decipher the potential role of oral infection (ligature-enhanced) with the keystone periodontal pathogen Porphyromonas gingivalis, in the progression of neovasculogenesis in a laser-induced choroidal-neovascularization (Li-CNV) mouse retina. By a combination of fundus photography, optical coherence tomography, and fluorescein angiography, we documented inflammatory drusen-like lesions, reduced retinal thickness, and increased vascular leakage in AMD+PD mice retinae. H&E further confirmed a significant reduction of retinal thickness and subretinal drusen-like deposits. Immunofluorescence microscopy revealed significant induction of choroidal/retinal vasculogenesis in AMD+PD mice. qPCR identified increased expression of oxidative-stress, angiogenesis, pro-inflammatory mediators, whereas antioxidants and anti-inflammatory genes in AMD+PD mice retinae were notably decreased. Through qPCR, we detected Pg and its fimbrial 16s-RrNA gene expression in the AMD+PD mice retinae. To sum-up, this is the first in vivo study signifying a role of periodontal infection in augmentation of AMD phenotype, with the aid of a pioneering AMD+PD murine model established in our laboratory.

Effects of a tart cherry (Prunus cerasus L.) phenolic extract on Porphyromonas gingivalis and its ability to impair the oral epithelial barrier

Periodontal diseases, including gingivitis and periodontitis, are a global oral health problem. Porphyromonas gingivalis, a key pathogen involved in the onset of periodontitis, is able to colonize the subgingival epithelium and invade the underlying connective tissue due to the contribution of cysteine proteases known as gingipains. In this study, we investigated the effects of a phenolic extract prepared from tart cherry (Prunus cerasus L.) juice on the growth, adherence, and protease activity of P. gingivalis. We also assessed the protective effect of the tart cherry extract on the disruption of the oral epithelial barrier induced by P. gingivalis. The tart cherry extract that contains procyanidins and quercetin and its derivatives (rutinoside, glucoside) as the most important phenolic compounds attenuated P. gingivalis growth, reduced adherence to an experimental basement membrane matrix model, and decreased the protease activities of P. gingivalis. The tart cherry extract also exerted a protective effect on the integrity of the oral epithelial barrier in an in vitro model infected with P. gingivalis. More specifically, the extract prevented a decrease in transepithelial electrical resistance as well as the destruction of tight junction proteins (zonula occludens-1 and occludin). These results suggest that the tart cherry phenolic extract may be a promising natural product for the treatment of periodontitis through its ability to attenuate the virulence properties of P. gingivalis and curtail the ability of this pathogen to impair the oral epithelial barrier.

Porphyromonas gingivalis infection alters Nrf2-phase II enzymes and nitric oxide in primary human aortic endothelial cells

BACKGROUND

Periodontal disease (PD) is known to be associated with endothelial dysfunction in patients with coronary artery and/or cardiovascular disease. In our study, we sought to explore the virulence of P. gingivalis (Pg) affecting glycogen synthase kinase 3 beta (GSK-3β)/nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/tetrahydrobiopterin (BH₄ )/ nitric oxide synthase (NOS) expression in primary human aortic endothelial cells (pHAECs).

METHODS

pHAECs were infected for 48 hours with Pg in vitro using the Human oxygen-Bacteria anaerobic coculture technique. Cell viability was determined, and target gene expression changes were evaluated by quantitative real-time polymerase chain reaction at the end of each incubation period.

RESULTS

Pg impaired pHAEC viability 24 hours post-infection. Pg infection reduced mRNA expression levels of endothelial NOS (eNOS), Nrf2, and Phase II enzymes (heme oxygenase-1, catalase, superoxide dismutase-1) in a time-dependent manner. Significant (P <0.05) increase in the inflammatory markers (interleukin [IL]-1β, IL-6, and tumor necrosis factor-α) were observed in the medium as well as in the infected cells. Interestingly, inducible NOS mRNA levels showed a significant (P <0.05) increase at 12 hours and 24 hours and were reduced at later time points. BH₄ (cofactor of eNOS) biosynthesis enzyme dihydrofolate reductase (DHFR, salvage pathway) mRNA levels showed a significant (P <0.05) decrease, while mRNA levels of GSK-3β were elevated.

CONCLUSIONS

These results suggest that periodontal bacterial infection may cause significant changes in the endothelial GSK-3β/BH₄ /eNOS/Nrf2 pathways, which may lead to impaired vascular relaxation. Greater understanding of the factors that adversely affect endothelial cell function could contribute to the development of new therapeutic compounds to treat PD-induced vascular diseases.

A novel gingipain regulatory gene in Porphyromonas gingivalis mediates host cell detachment and inhibition of wound closure

The black pigmentation-related genes in Porphyromonas gingivalis are primarily involved in regulating gingipain functions. In this study, we identified a pigmentation-related gene, designated as pgn_0361. To characterize the role of pgn_0361 in regulating P. gingivalis-mediated epithelial cell detachment and inhibition of wound closure, PgΔ0361, an isogenic pgn_0361-defective mutant strain, and PgΔ0361C, a complementation strain, were constructed using P. gingivalis ATCC 33277. The gingipain and hemagglutination activities, as well as biofilm formation, were examined in all three strains. The effect of P. gingivalis strains on epithelial cell detachment was investigated using the HO-1-N-1 and Ca9-22 epithelial cell lines. The inhibition of wound closure by heat-killed P. gingivalis cells and culture supernatant was analyzed using an in vitro wound closure assay. Compared to the wild-type strain, the PgΔ0361 strain did not exhibit gingipain or hemagglutination activity but exhibited enhanced biofilm formation. Additionally, the PgΔ0361 strain exhibited attenuated ability to detach the epithelial cells and to inhibit wound closure in vitro. Contrastingly, the culture supernatant of PgΔ0361 exhibited high gingipain activity and strong inhibition of wound closure. The characteristics of PgΔ0361C and wild-type strains were comparable. In conclusion, the pgn_0361 gene is involved in regulating gingipains. The PGN_0361-defective strain exhibited reduced virulence in terms of epithelial cell detachment and inhibition of wound closure. The culture supernatant of the mutant strain highly inhibited wound closure, which may be due to high gingipain activity.

Construction and characterization of the PGN_0296 mutant of Porphyromonas gingivalis

The periodontal pathogen Porphyromonas gingivalis produces gingipains (Kgp, RgpA, and RgpB), cysteine proteases involved in the organism's virulence, and pigmentation. We previously showed that deletion of the PGN_0297 and PGN_0300 genes reduced the proteolytic activity of gingipains. The role of the PGN_0296 gene, consisting of an operon with the PGN_0297 and PGN_0300 genes, is unclear. Herein, we examined the effect of PGN_0296 gene deletion on the proteolytic activity. Although the proteolytic activity of the gingipains did not decrease in the culture supernatant of a PGN_0296 gene deletion mutant (ΔPGN_0296), the growth was delayed.

Heritability of Oral Microbiota and Immune Responses to Oral Bacteria

Maintaining a symbiotic oral microbiota is essential for oral and dental health, and host genetic factors may affect the composition or function of the oral microbiota through a range of possible mechanisms, including immune pathways. The study included 836 Swedish twins divided into separate groups of adolescents (n = 418) and unrelated adults (n = 418). Oral microbiota composition and functions of non-enzymatically lysed oral bacteria samples were evaluated using 16S rRNA gene sequencing and functional bioinformatics tools in the adolescents. Adaptive immune responses were assessed by testing for serum IgG antibodies against a panel of common oral bacteria in adults. In the adolescents, host genetic factors were associated with both the detection and abundance of microbial species, but with considerable variation between species. Host genetic factors were associated with predicted microbiota functions, including several functions related to bacterial sucrose, fructose, and carbohydrate metabolism. In adults, genetic factors were associated with serum antibodies against oral bacteria. In conclusion, host genetic factors affect the composition of the oral microbiota at a species level, and host-governed adaptive immune responses, and also affect the concerted functions of the oral microbiota as a whole. This may help explain why some people are genetically predisposed to the major dental diseases of caries and periodontitis.

Osteocyte-derived exosomes induced by mechanical strain promote human periodontal ligament stem cell proliferation and osteogenic differentiation via the miR-181b-5p/PTEN/AKT signaling pathway

BACKGROUND

The oral cavity is a complex environment in which periodontal tissue is constantly stimulated by external microorganisms and mechanical forces. Proper mechanical force helps maintain periodontal tissue homeostasis, and improper inflammatory response can break the balance. Periodontal ligament (PDL) cells play crucial roles in responding to these challenges and maintaining the homeostasis of periodontal tissue. However, the mechanisms underlying PDL cell property changes induced by inflammatory and mechanical force microenvironments are still unclear. Recent studies have shown that exosomes function as a means of cell-cell and cell-matrix communication in biological processes.

METHODS

Human periodontal ligament stem cells (HPDLSCs) were tested by the CCK8 assay, EdU, alizarin red, and ALP staining to evaluate the functions of exosomes induced by a mechanical strain. MicroRNA sequencing was used to find the discrepancy miRNA in exosomes. In addition, real-time PCR, FISH, luciferase reporter assay, and western blotting assay were used to investigate the mechanism of miR-181b-5p regulating proliferation and osteogenic differentiation through the PTEN/AKT pathway.

RESULTS

In this study, the exosomes secreted by MLO-Y4 cells exposed to mechanical strain (Exosome-MS) contributed to HPDLSC proliferation and osteogenic differentiation. High-throughput miRNA sequencing showed that miR181b-5p was upregulated in Exosome-MS compared to the exosomes derived from MLO-Y4 cells lacking mechanical strain. The luciferase reporter assay demonstrated that miR-181b-5p may target phosphatase tension homolog deletion (PTEN). In addition, PTEN was negatively regulated by overexpressing miR-181b-5p. Real-time PCR and western blotting assay verified that miR-181b-5p enhanced the protein kinase B (PKB, also known as AKT) activity and improved downstream factor transcription. Furthermore, miR-181b-5p effectively ameliorated the inhibition of HPDLSC proliferation and promoted HPDLSC induced by inflammation.

CONCLUSIONS

This study concluded that exosomes induced by mechanical strain promote HPDLSC proliferation via the miR-181b-5p/PTEN/AKT signaling pathway and promote HPDLSC osteogenic differentiation by BMP2/Runx2, suggesting a potential mechanism for maintaining periodontal homeostasis.

Surfactin-Loaded ĸ-Carrageenan Oligosaccharides Entangled Cellulose Nanofibers as a Versatile Vehicle Against Periodontal Pathogens

PURPOSE

Periodontitis is a chronic inflammatory disease associated with microbial accumulation. The purpose of this study was to reuse the agricultural waste to produce cellulose nanofibers (CNF) and further modification of the CNF with κ-carrageenan oligosaccharides (CO) for drug delivery. In addition, this study is focused on the antimicrobial activity of surfactin-loaded CO-CNF towards periodontal pathogens.

MATERIALS AND METHODS

A chemo-mechanical method was used to extract the CNF and the modification was done by using CO. The studies were further proceeded by adding different quantities of surfactin [50 mg (50 SNPs), 100 mg (100 SNPs), 200 mg (200 SNPs)] into the carrier (CO-CNF). The obtained materials were characterized, and the antimicrobial activity of surfactin-loaded CO-CNF was evaluated.

RESULTS

The obtained average size of CNF and CO-CNF after ultrasonication was 263 nm and 330 nm, respectively. Microscopic studies suggested that the CNF has a short diameter with long length and CO became cross-linked to form as beads within the CNF network. The addition of CO improved the degradation temperature, crystallinity, and swelling property of CNF. The material has a controlled drug release, and the entrapment efficiency and loading capacity of the drug were 53.15 ± 2.36% and 36.72 ± 1.24%, respectively. It has antioxidant activity and inhibited the growth of periodontal pathogens such as Streptococcus mutans and Porphyromonas gingivalis by preventing the biofilm formation, reducing the metabolic activity, and promoting the oxidative stress.

CONCLUSION

The study showed the successful extraction of CNF and modification with CO improved the physical parameters of the CNF. In addition, surfactin-loaded CO-CNF has potential antimicrobial activity against periodontal pathogens. The obtained biomaterial is economically valuable and has great potential for biomedical applications.

Porphyromonas gingivalis and rheumatoid arthritis

PURPOSE OF REVIEW

To explore the pathogenic association between periodontal disease and rheumatoid arthritis focusing on the role of Porphyromonas gingivalis.

RECENT FINDINGS

In the last decades our knowledge about the pathogenesis of rheumatoid arthritis substantially changed. Several evidences demonstrated that the initial production of autoantibodies is not localized in the joint, rather in other immunological-active sites. A central role seems to be played by periodontal disease, in particular because of the ability of P. gingivalis to induce citrullination, the posttranslational modification leading to the production of anticitrullinated protein/peptide antibodies, the most sensitive and specific rheumatoid arthritis biomarker.

SUMMARY

The pathogenic role of P. gingivalis has been demonstrated in mouse models in which arthritis was either triggered or worsened in infected animals. P. gingivalis showed its detrimental role not only by inducing citrullination but also by means of other key mechanisms including induction of NETosis, osteoclastogenesis, and Th17 proinflammatory response leading to bone damage and systemic inflammation.

Metronidazole-Treated Porphyromonas gingivalis Persisters Invade Human Gingival Epithelial Cells and Perturb Innate Responses

Periodontitis as a biofilm-associated inflammatory disease is highly prevalent worldwide. It severely affects oral health and yet closely links to systemic diseases like diabetes and cardiovascular disease. Porphyromonas gingivalis as a "keystone" periodontopathogen drives the shift of microbe-host symbiosis to dysbiosis and critically contributes to the pathogenesis of periodontitis. Persisters represent a tiny subset of biofilm-associated microbes highly tolerant to lethal treatment of antimicrobials, and, notably, metronidazole-tolerant P. gingivalis persisters have recently been identified by our group. This study further explored the interactive profiles of metronidazole-treated P. gingivalis persisters (M-PgPs) with human gingival epithelial cells (HGECs). P. gingivalis cells (ATCC 33277) at stationary phase were treated with a lethal dosage of metronidazole (100 μg/ml, 6 h) for generating M-PgPs. The interaction of M-PgPs with HGECs was assessed by microscopy, flow cytometry, cytokine profiling, and quantitative PCR (qPCR). We demonstrated that the overall morphology and ultracellular structure of M-PgPs remained unchanged. Importantly, M-PgPs maintained the capabilities to adhere to and invade HGECs. Moreover, M-PgPs significantly suppressed proinflammatory cytokine expression in HGECs at a level comparable to that seen with the untreated P. gingivalis cells, through the thermosensitive components. The present report reveals that P. gingivalis persisters induced by lethal treatment of antibiotics were able to maintain their capabilities to adhere to and invade human gingival epithelial cells and to perturb the innate host responses. Novel strategies and approaches need to be developed for tackling P. gingivalis and favorably modulating the dysregulated immunoinflammatory responses for oral/periodontal health and general well-being.

Amixicile targets anaerobic bacteria within the oral microbiome

OBJECTIVES

Anaerobic bacteria are the major causative agents of periodontal disease. However, so far, targeted therapy aimed at reducing those pathogens has not been widely implemented. We have previously reported on a novel antimicrobial, amixicile, that targets anaerobic bacteria through inhibition of the function of the major anaerobic metabolic enzyme pyruvate ferredoxin oxidoreductase (PFOR), while not affecting aerotolerant organisms. It effectively inhibited the growth of oral anaerobes both in monocultures as well as in mixed in vitro mixed cultured however, amixicile's activity in in vivo-like conditions remained to be established.

METHODS

Here, we expand our study using an ex vivo oral microbiome combined with metagenomic sequencing to determine the effect of amixicile treatment on the composition of the microbiome and compare it to that of metronidazole.

RESULTS

Our results show that in the complex microbiomes, anaerobic bacteria are selectively inhibited, while the growth of aerotolerant ones, such as Streptococcus, Klebsiella, Neisseria, and Rothia is unaffected. Veillonella was the most abundant anaerobic genus in our ex vivo microbiome, and we observed complete inhibition of its growth. In addition, growth of other anaerobes, Fusobacterium and Prevotella, was significantly inhibited. It is noteworthy that a change in abundance of bacteriophages, such as Siphoviridae and Myoviridae, associated with the oral microbiome was observed.

CONCLUSIONS

Collectively, our data expand on the so far reported inhibitory spectrum of amixicile and demonstrates that it inhibits anaerobic bacteria, including both clinical isolates and laboratory strains.

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

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

Blockade of Immune-Checkpoint B7-H4 and Lysine Demethylase 5B in Esophageal Squamous Cell Carcinoma Confers Protective Immunity against P. gingivalis Infection

Pathogens are capable of hijacking immune defense mechanisms, thereby creating a tolerogenic environment for hypermutated malignant cells that arise within the site of infection. Immune checkpoint-oriented immunotherapies have shown considerable promise. Equally important, the epigenetic reprogramming of an immune-evasive phenotype that activates the immune system in a synergistic manner can improve immunotherapy outcomes. These advances have led to combinations of epigenetic- and immune-based therapeutics. We previously demonstrated that Porphyromonas gingivalis isolated from esophageal squamous cell carcinoma (ESCC) lesions represents a major pathogen associated with this deadly disease. In this study, we examined the mechanisms associated with host immunity during P. gingivalis infection and demonstrated that experimentally infected ESCC responds by increasing the expression of B7-H4 and lysine demethylase 5B, which allowed subsequent in vivo analysis of the immunotherapeutic effects of anti-B7-H4 and histone demethylase inhibitors in models of chronic infection and immunity against xenografted human tumors. Using three different preclinical mouse models receiving combined therapy, we showed that mice mounted strong resistance against P. gingivalis infection and tumor challenge. This may have occurred via generation of a T cell-mediated response in the microenvironment and formation of immune memory. In ESCC subjects, coexpression of B7-H4 and KDM5B correlated more significantly with bacterial load than with the expression of either molecule alone. These results highlight the unique ability of P. gingivalis to evade immunity and define potential targets that can be exploited therapeutically to improve the control of P. gingivalis infection and the development of associated neoplasia.

Pathogenesis of Important Virulence Factors of Porphyromonas gingivalis via Toll-Like Receptors

Periodontitis is a common intraoral infection and is inextricably linked to systemic diseases. Recently, the regulation between host immunologic response and periodontal pathogens has become a hotspot to explain the mechanism of periodontitis and related systemic diseases. Since Porphyromonas gingivalis (P. gingivalis) was proved as critical periodontal pathogen above all, researches focusing on the mechanism of its virulence factors have received extensive attention. Studies have shown that in the development of periodontitis, in addition to the direct release of virulent factors by periodontal pathogens to destroy periodontal tissues, over-low or over-high intrinsic immune and inflammatory response mediated by Toll-like receptors (TLRs) can lead to more lasting destruction of periodontal tissues. It is very necessary to sort out how various cytopathic factors of P. gingivalis mediate inflammation and immune responses between the host through TLRs so as to help precisely prevent, diagnose, and treat periodontitis in clinic. This review summarizes the role of three most widely studied pathogenic factors produced by P. gingivalis (lipopolysaccharide, gingipains, pili) and their interactions with TLRs at the cellular and molecular level in the progress of periodontitis.

Activation of calcium signaling in human gingival fibroblasts by recombinant Porphyromonas gingivalis RgpB protein

Arginine-specific cysteine proteinases, such as Arg-gingipain B (RgpB), mediate inflammation by activating protease-activated receptors (PARs). Arg-gingipain B is produced by Porphyromonas gingivalis, and is implicated in the causation of periodontal disease. The purpose of the present study was to observe the influence of recombinant RgpB protein (rRgpB) on PAR activation by monitoring intracellular Ca2+ ion concentration ([Ca2+]i) and inositol-1,4,5-triphosphate (IP3) levels in human gingival fibroblasts (HGFs). Our findings showed that rRgpB could cause a transient increase in [Ca2+]i. This increase in [Ca2+]i was completely suppressed by vorapaxar, a PAR-1 antagonist. Recombinant Arg-gingipain B increased the concentration of IP3, reaching a maximum at 60 s after treatment; this was completely inhibited by vorapaxar. We therefore conclude that rRgpB-induced calcium signaling in HGFs is mainly caused by PAR-1 activation. This suggests that PAR-1 activation plays a significant role in chronic inflammatory periodontal disease induced by P. gingivalis RgpB.

CXXC5 Mediates P. gingivalis-suppressed Cementoblast Functions Partially via MAPK Signaling Network

Porphyromonas (P.) gingivalis associates tightly with periodontal diseases and it is also a dominant pathogen of periapical periodontitis. However, the influence of P. gingivalis on cementoblasts, root surface cells pivotal in the apical areas, and the possible involvement of other molecules remain largely elusive. CXXC5 is a nuclear protein that regulates gene expression as well as cell growth, differentiation, and apoptosis. In this study, P. gingivalis repressed the mineralization capacity of cementoblasts by inducing inflammatory reactions and inhibiting cell differentiation. Intriguingly, the expression of CXXC5 decreased in P. gingivalis-treated OCCM-30 cells and apical periodontitis models but gradually increased during mineralization. Furthermore, RNA interference of CXXC5 significantly inhibited cementoblast differentiation, represented by decline of bone-associated markers Osterix, osteocalcin (OCN), and alkaline phosphatase (ALP). CXXC5 overexpression facilitated differentiation, and therefore attenuated the P. gingivalis-repressed effects on OCCM-30 cells. In addition, Erk1/2, p38, and PI3K-Akt were inactivated by silencing CXXC5 and activated upon its overexpression, whereas Wnt/β-catenin exhibited an opposite trend. The employment of specific inhibitors revealed that the CXXC5-dependent promotions of cementoblast differentiation were partially abrogated by p38 and PI3K-Akt inhibitors but were exacerbated by inhibiting Erk1/2. Overall, our experiment demonstrated a novel function of CXXC5 in the regeneration of impaired cementum caused by P. gingivalis invasion and suggested that MAPK signaling network balances the facilitation effects of CXXC5 in cementoblast differentiation.

Inhibitory effects of azithromycin on the adherence ability of Porphyromonas gingivalis

BACKGROUND

Porphyromonas gingivalis is a major pathogen and has a high detection rate in periodontal disease. Fimbriae and hemagglutinin are expressed by P. gingivalis, and these play an important role in the adherence of the bacteria to periodontal tissue and biofilm formation. The aim of this study was to investigate the effects of sub-minimal inhibitory concentrations (sub-MICs) of azithromycin on the adherence of P. gingivalis, focusing on the inhibition of fimbriae expression and hemagglutinin activity.

METHODS

P. gingivalis ATCC 33277 were incubated anaerobically with sub-MICs of azithromycin at 37°C by gentle shaking for 18 hours. The bacterial cells were harvested, washed twice with phosphate-buffered saline (PBS), and the proteins analyzed by 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and western blotting. Adherence assay and hemagglutinin activity tests were done with the same culture.

RESULTS

The results of SDS-PAGE indicated that the sub-MICs of azithromycin inhibited 41-kDa fimbrial protein expression and hemagglutinin activities. The disappearance of 41-kDa fimbrial protein expression and long fimbriae in 0.4 µg/mL, 0.2 µg/mL, and 0.1 µg/mL of azithromycin was confirmed by western blotting and transmission electron microscopy. The adherence of P. gingivalis to human gingival epithelial cells was reduced by sub-MICs of azithromycin compared with the adherence levels without antibiotic.

CONCLUSIONS

These results suggest that sub-MICs of azithromycin may reduce the adherence of P. gingivalis to host cells, by inhibiting production of fimbriae and hemagglutinin activities. Therefore, azithromycin can be used as a biofilm treatment of periodontal disease caused by P. gingivalis.

Protein-Based Salivary Profiles as Novel Biomarkers for Oral Diseases

The Global Burden of Oral Diseases affects 3.5 billion people worldwide, representing the number of people affected by the burden of untreated dental caries, severe periodontal disease, and edentulism. Thus, much more efforts in terms of diagnostics and treatments must be provided in the fight of these outcomes. In this sense, recently, the study of saliva as biological matrix has been identified as a new landmark initiative in the search of novel and useful biomarkers to prevent and diagnose these conditions. Specifically, saliva is a rich reservoir of different proteins and peptides and accessible due to recent advances in molecular biology and specially in targeted and unbiased proteomics technologies. Nonetheless, emerging barriers are an obstacle to the study of the salivary proteome in an effective way. This review aims at giving an overall perspective of salivary biomarkers identified in several oral diseases by means of molecular biology approaches.

An orally administered oral pathobiont and commensal have comparable and innocuous systemic effects in germ-free mice

BACKGROUND AND OBJECTIVES

We recently proposed a novel mechanism linking periodontitis and systemic diseases, in which orally administered Porphyromonas gingivalis affects gut microbiota composition and subsequently leads to systemic inflammation. However, the mechanism by which P. gingivalis generates systemic effects from the gut is unknown.

MATERIAL AND METHODS

Six-week-old germ-free mice were orally administered with either an oral pathobiont P. gingivalis or an oral commensal Lactobacillus salivarius twice a week for 5 weeks. Control mice were administered with vehicle only. Alveolar bone resorption was evaluated histologically. The expression profile of various genes was analyzed in gingival tissue, liver, small intestine and large intestine using real-time polymerase chain reaction. Sera were analyzed for antibody, endotoxin and interleukin (IL)-6 levels. Antibody levels were also analyzed for culture supernatant of cells from mesenteric lymph nodes and spleens. A proportion of T-helper 17 and Treg in the cells from mesenteric lymph nodes and spleens was analyzed by flow cytometry. The level of IL-6 and IL-17 in the cell culture supernatants was analyzed by enzyme-linked immunosorbent assay.

RESULTS

P. gingivalis administration did not induce alveolar bone resorption. Although P. gingivalis elicited systemic antibody response in germ-free mice, unlike in specific pathogen-free mice, P. gingivalis did not induce an inflammatory response in gingiva, liver and intestinal tissue, or alter the proportion of T-helper 17 and Treg. However, IL-6 and IL-17 productions were significantly elevated and tended to be elevated, respectively, in the cells from mesenteric lymph nodes of P. gingivalis-administered mice. Interestingly, the expression of IL-10 and tight junction protein in the gingiva and intestine, respectively, was significantly upregulated in P. gingivalis-treated mice. Administration of L. salivarius elicited almost similar effects as P. gingivalis.

CONCLUSION

The oral pathobiont P. gingivalis did not induce any detectable pathogenic changes or any major host responses when administered to germ-free mice. There may be indirect mechanisms for gut-mediated systemic effects by P. gingivalis.

Identification of Porphyromonas isolates from clinical origin using MALDI-TOF Mass Spectrometry

Despite the wide implementation of MALDI-TOF MS for the rapid and reliable identification of most microorganisms, some taxonomic groups such as the Porphyromonas genus remain largely untested. In this study we evaluated the performance of MALDI-TOF MS on this genus using a collection of 39 isolates sent for routine identification to our institution over a 16-year period. All of them were identified by DNA-sequencing analysis of the 16S rRNA gene plus the hsp60 gene when the previous one did not yield species-level assignment. MALDI-TOF MS provided correct identification at least at the genus level of 21/39 isolates (53.9%). Twelve isolates were correctly identified at the species level with a score value ≥ 2.0 and 9 more with score values < 2.0 and ≥ 1.7. The species most represented in the database (P. gingivalis and P. somerae) lay within this category. However, the species poorly represented in this database (P. asaccharolytica and P. uenonis) were mostly identified with lower scores (1.35-1.67) or remained unidentified by MALDI-TOF MS. The addition of two P. asaccharolytica reference spectra to our in-house library allowed 72.9% of genus-level identifications with 17/37 isolates (45.9%) identified with score values ≥ 2.0. Our results showed a high level of correlation between MALDI-TOF MS and DNA-based identification for Porphyromonas spp. strains at the species level, even with score values < 2.0. The reliability provided by MALDI-TOF MS increased when the database was fed with spectra from the species poorly represented in the commercial database.

Silver ions blocking crystallization of guanosine-based hydrogel for potential antimicrobial applications

In this work, the detailed crystallization process of 2′-deoxy-2′-fluoroguanosine (^FG_d) hydrogel has been studied using single crystal X-ray diffraction, variable-temperature nuclear magnetic resonance (VT-NMR), and scanning electron microscopy (SEM). Both solid and solution results indicated that the K⁺-mediated G-quartet structures were unstable and easily resulted in the breakdown of the hydrogel to form linear ribbon structures by forming mimic reverse Watson–Crick base pairs between the two faces with an intermolecular hydrogen-bond (N10H–O11). Accordingly, Ag⁺ was introduced to block the crystallization of ^FG_d to form long lifetime stable supramolecular hydrogel (>6 months) and possible silver-ions-mediated base pair motifs were suggested via NMR, UV, and mass spectroscopy (MS) in combination with powder X-ray diffraction (PXRD) and circular dichroism spectroscopy (CD). Furthermore, ^FG_dAg hydrogel exhibited low toxicity for normal oral keratinocyte cells (NOK-SI) and good antibacterial activities for Fusobacterium nucleatum in vitro.

Ag⁺ was introduced to block the crystallization of ^FG_d forming long lifetime stability supramolecular hydrogel (>6 months), which displayed low toxicity for NOK-SI cell and good antibacterial activities.