Gingipain-carrying outer membrane vesicles from Porphyromonas gingivalis cause barrier dysfunction of Caco-2 cells by releasing gingipain into the cytosol

Ingestion of Porphyromonas gingivalis, a periodontal pathogen, disrupts the intestinal barrier in mice. However, the involvement of outer membrane vesicles (OMVs) secreted from P. gingivalis in the destruction of the intestinal barrier remains unclear. In this study, we tested the hypothesis that OMVs carrying gingipains, the major cysteine proteases produced by P. gingivalis, affects the intestinal barrier function. OMVs increased the permeability of the Caco-2 cell monolayer, a human intestinal epithelial cell line, accompanied by degradation of the tight junction protein occludin. In contrast, OMVs prepared from mutant strains devoid of gingipains failed to induce intestinal barrier dysfunction or occludin degradation in Caco-2 cells. A close histological examination revealed the intracellular localization of gingipain-carrying OMVs. Gingipain activity was detected in the cytosolic fraction of Caco-2 cells after incubation with OMVs. These results suggest that gingipains were internalized into intestinal cells through OMVs and transported into the cytosol, where they then directly degraded occludin from the cytosolic side. Thus, P. gingivalis OMVs might destroy the intestinal barrier and induce systemic inflammation via OMV itself or intestinal substances leaked into blood vessels, causing various diseases.

Activatable prodrug for controlled release of an antimicrobial peptide via the proteases overexpressed in Candida albicans and Porphyromonas gingivalis

Candida albicans and Porphyromonas gingivalis are prevalent in the subgingival area where the frequency of fungal colonization increases with periodontal disease. Candida's transition to a pathogenic state and its interaction with P. gingivalis exacerbate periodontal disease severity. However, current treatments for these infections differ, and combined therapy remains unexplored. This work is based on an antimicrobial peptide that is therapeutic and induces a color change in a nanoparticle reporter. Methods: We built and characterized two enzyme-activatable prodrugs to treat and detect C. albicans and P. gingivalis via the controlled release of the antimicrobial peptide. The zwitterionic prodrug quenches the antimicrobial peptide's activity until activation by a protease inherent to the pathogens (SAP9 for C. albicans and RgpB for P. gingivalis). The toxicity of the intact prodrugs was evaluated against fungal, bacterial, and mammalian cells. Therapeutic efficacy was assessed through microscopy, disk diffusion, and viability assays, comparing the prodrug to the antimicrobial peptide alone. Finally, we developed a colorimetric detection system based on the aggregation of plasmonic nanoparticles. Results: The intact prodrugs showed negligible toxicity to cells absent a protease trigger. The therapeutic impact of the prodrugs was comparable to that of the antimicrobial peptide alone, with a minimum inhibitory concentration of 3.1 - 16 µg/mL. The enzymatic detection system returned a detection limit of 10 nM with gold nanoparticles and 3 nM with silver nanoparticles. Conclusion: This approach offers a convenient and selective protease sensing and protease-induced treatment mechanism based on bioinspired antimicrobial peptides.

Intestinal Translocation of Live Porphyromonas gingivalis Drives Insulin Resistance

Periodontitis has been emphasized as a risk factor of insulin resistance-related systemic diseases. Accumulating evidence has suggested a possible "oral-gut axis" linking oral infection and extraoral diseases, but it remains unclear whether periodontal pathogens can survive the barriers of the digestive tract and how they play their pathogenic roles. The present study established a periodontitis mouse model through oral ligature plus Porphyromonas gingivalis inoculation and demonstrated that periodontitis aggravated diet-induced obesity and insulin resistance, while also causing P. gingivalis enrichment in the intestine. Metabolic labeling strategy validated that P. gingivalis could translocate to the gastrointestinal tract in a viable state. Oral administration of living P. gingivalis elicited insulin resistance, while administration of pasteurized P. gingivalis had no such effect. Combination analysis of metagenome sequencing and nontargeted metabolomics suggested that the tryptophan metabolism pathway, specifically indole and its derivatives, was involved in the pathogenesis of insulin resistance caused by oral administration of living P. gingivalis. Moreover, liquid chromatography-high-resolution mass spectrometry analysis confirmed that the aryl hydrocarbon receptor (AhR) ligands, mainly indole acetic acid, tryptamine, and indole-3-aldehyde, were reduced in diet-induced obese mice with periodontitis, leading to inactivation of AhR signaling. Supplementation with Ficz (6-formylindolo (3,2-b) carbazole), an AhR agonist, alleviated periodontitis-associated insulin resistance, in which the restoration of gut barrier function might play an important role. Collectively, these findings reveal that the oral-gut translocation of viable P. gingivalis works as a fuel linking periodontitis and insulin resistance, in which reduction of AhR ligands and inactivation of AhR signaling are involved. This study provides novel insight into the role of the oral-gut axis in the pathogenesis of periodontitis-associated comorbidities.

A novel fluorescent traceable carbon quantum dots with selective antibacterial activity against Porphyromonas gingivalis

Antibiotics can kill bacteria, but their continued use can easily lead to drug resistance, particularly the main pathogenic bacteria of periodontitis, Porphyromonas gingivalis. However, to avoid drug resistance, carbon quantum dots (CDs) have great potential as a bioactive material in antimicrobial therapy. Herein, we use ornidazole as raw material to prepare CDs of different sizes by microwave irradiation and screen CDs with fluorescence and bacteriostatic properties. The inhibition experiments and live/dead assays of P. gingivalis exhibited outstanding antibacterial effects. This research aimed to develop nano-level antibacterial active materials that also have fluorescence traceability. This study offers a different method for the development of multifunctional CDs, provides valuable strategies for the treatment of diseases associated with P. gingivalis, and predicts great application prospects in the field of biomedicine.

Spatiotemporal monitoring of a periodontal multispecies biofilm model: demonstration of prebiotic treatment responses

Biofilms are complex polymicrobial communities which are often associated with human infections such as the oral disease periodontitis. Studying these complex communities under controlled conditions requires in vitro biofilm model systems that mimic the natural environment as close as possible. This study established a multispecies periodontal model in the drip flow biofilm reactor in order to mimic the continuous flow of nutrients at the air-liquid interface in the oral cavity. The design is engineered to enable real-time characterization. A community of five bacteria, Streptococcus gordonii-GFPmut3*, Streptococcus oralis-GFPmut3*, Streptococcus sanguinis-pVMCherry, Fusobacterium nucleatum, and Porphyromonas gingivalis-SNAP26 is visualized using two distinct fluorescent proteins and the SNAP-tag. The biofilm in the reactor develops into a heterogeneous, spatially uniform, dense, and metabolically active biofilm with relative cell abundances similar to those in a healthy individual. Metabolic activity, structural features, and bacterial composition of the biofilm remain stable from 3 to 6 days. As a proof of concept for our periodontal model, the 3 days developed biofilm is exposed to a prebiotic treatment with L-arginine. Multifaceted effects of L-arginine on the oral biofilm were validated by this model setup. L-arginine showed to inhibit growth and incorporation of the pathogenic species and to reduce biofilm thickness and volume. Additionally, L-arginine is metabolized by Streptococcus gordonii-GFPmut3* and Streptococcus sanguinis-pVMCherry, producing high levels of ornithine and ammonium in the biofilm. In conclusion, our drip flow reactor setup is promising in studying spatiotemporal behavior of a multispecies periodontal community.ImportancePeriodontitis is a multifactorial chronic inflammatory disease in the oral cavity associated with the accumulation of microorganisms in a biofilm. Not the presence of the biofilm as such, but changes in the microbiota (i.e., dysbiosis) drive the development of periodontitis, resulting in the destruction of tooth-supporting tissues. In this respect, novel treatment approaches focus on maintaining the health-associated homeostasis of the resident oral microbiota. To get insight in dynamic biofilm responses, our research presents the establishment of a periodontal biofilm model including Streptococcus gordonii, Streptococcus oralis, Streptococcus sanguinis, Fusobacterium nucleatum, and Porphyromonas gingivalis. The added value of the model setup is the combination of simulating continuously changing natural mouth conditions with spatiotemporal biofilm profiling using non-destructive characterization tools. These applications are limited for periodontal biofilm research and would contribute in understanding treatment mechanisms, short- or long-term exposure effects, the adaptation potential of the biofilm and thus treatment strategies.

Penetrating Macrophage-Based Nanoformulation for Periodontitis Treatment

Periodontitis is a chronic inflammatory disease caused by the interaction of oral microorganisms with the host immune response. Porphyromonas gingivalis (P.g.) acts as a key mediator in subverting the homeostasis of the local immune system. On the one hand, P.g. inhibits phagocytosis and the killing capacity of immune cells. On the other hand, P.g. increases selective cytokine release, which is beneficial to its further proliferation. Here, we prepared a penetrating macrophage-based nanoformulation (MZ@PNM)-encapsulating hydrogel (MZ@PNM@GCP) that responded to the periodontitis microenvironment. MZ@PNM targeted P.g. via the Toll-like receptor complex 2/1 (TLR2/1) on its macrophage-mimicking membrane, then directly killed P.g. through disruption of bacterial structural integrity by the cationic nanoparticles and intracellular release of an antibacterial drug, metronidazole (MZ). Meanwhile, MZ@PNM interrupted the specific binding of P.g. to immune cells and neutralized complement component 5a (C5a), preventing P.g. subversion of periodontal host immune response. Overall, MZ@PNM@GCP showed potent efficacy in periodontitis treatment, restoring local immune function and killing pathogenic bacteria, while exhibiting favorable biocompatibility, all of which have been demonstrated both in vivo and in vitro.

Coating and Corruption of Human Neutrophils by Bacterial Outer Membrane Vesicles

Porphyromonas gingivalis is a keystone oral pathogen that successfully manipulates the human innate immune defenses, resulting in a chronic proinflammatory state of periodontal tissues and beyond. Here, we demonstrate that secreted outer membrane vesicles (OMVs) are deployed by P. gingivalis to selectively coat and activate human neutrophils, thereby provoking degranulation without neutrophil killing. Secreted granule components with antibacterial activity, especially LL-37 and myeloperoxidase (MPO), are subsequently degraded by potent OMV-bound proteases known as gingipains, thereby ensuring bacterial survival. In contrast to neutrophils, the P. gingivalis OMVs are efficiently internalized by macrophages and epithelial cells. Importantly, we show that neutrophil coating is a conserved feature displayed by OMVs of at least one other oral pathogen, namely, Aggregatibacter actinomycetemcomitans. We conclude that P. gingivalis deploys its OMVs for a neutrophil-deceptive strategy to create a favorable inflammatory niche and escape killing. IMPORTANCE Severe periodontitis is a dysbiotic inflammatory disease that affects about 15% of the adult population, making it one of the most prevalent diseases worldwide. Importantly, periodontitis has been associated with the development of nonoral diseases, such as rheumatoid arthritis, pancreatic cancer, and Alzheimer's disease. Periodontal pathogens implicated in periodontitis can survive in the oral cavity only by avoiding the insults of neutrophils while at the same time promoting an inflamed environment where they successfully thrive. Our present findings show that outer membrane vesicles secreted by the keystone pathogen Porphyromonas gingivalis provide an effective delivery tool of virulence factors that protect the bacterium from being killed while simultaneously activating human neutrophils.

Plasma treatment effects on destruction and recovery of Porphyromonas gingivalis biofilms

The objective of this study was to investigate the treatment effects of non-thermal atmospheric gas plasmas (NTAP) on destruction and the recovery (or re-colonization) of Porphyromonas gingivalis (P. gingivalis) in biofilms. P. gingivalis is a well-known keystone periodontal pathogen strongly associated with periodontal diseases, especially periodontitis. P. gingivalis biofilms were formed on stainless steel coupons and treated for 1, 2, and 5 minutes by NTAP of pure argon gas and argon+oxygen gas mixture. MTT assay, colony forming unit (CFU) counting assay and confocal laser scanning microscopy (CLSM) were used to assess the destruction efficiency. In addition, the plasma treated biofilms were re-cultured in the medium supplemented with antibiotics and oxidative stress sources to determine the synergy of the NTAP with other antimicrobial agents. The results showed the plasma treatment could result in 2.7 log unit reduction in bacterial load. The recovered biofilm CFU with NTAP treatment combined with sub minimal inhibition concentration of amoxicillin was 0.33 log units less than the biofilm treated with amoxicillin alone. The recovered biofilm CFU in NTAP groups was about 2.0 log units less than that in the untreated controls under H₂O₂ treatment. There was approximately 1.0 log unit reduction of biofilm CFU in plasma treated biofilm compared with untreated control under paraquat treatment. The plasma treated biofilms exhibited less resistance to amoxicillin and greater susceptibility to hydrogen peroxide (H₂O₂) and paraquat, suggesting that NTAP may enhance biofilm susceptibility to host defense. These in vitro findings suggested that NTAP could be a novel and effective treatment method of oral biofilms that cause periodontal diseases.

Interaction Between Autophagy and Porphyromonas gingivalis-Induced Inflammation

Autophagy is an immune homeostasis process induced by multiple intracellular and extracellular signals. Inflammation is a protective response to harmful stimuli such as pathogen microbial infection and body tissue damage. Porphyromonas gingivalis infection elicits both autophagy and inflammation, and dysregulation of autophagy and inflammation promotes pathology. This review focuses on the interaction between autophagy and inflammation caused by Porphyromonas gingivalis infection, aiming to elaborate on the possible mechanism involved in the interaction.

Overexpression of DEL-1 Downregulates SH3BP2 Expression and Inhibits Porphyromonas gingivalis-induced Gingival Inflammation In Vivo and In Vitro

PURPOSE

The role of developmental endothelial locus-1 (DEL-1) in Porphyromonas gingivalis (P. gingivalis)-induced periodontitis and the related molecular mechanisms are unclear. This study aimed to investigate the effect of DEL-1 on SH3 Domain Binding Protein 2 (SH3BP2) expression, and to explore the regulatory role of DEL-1 in periodontal inflammation.

MATERIALS AND METHODS

We constructed a P. gingivalis-induced rat experimental periodontitis model, and cultured P. gingivalis-stimulated THP-1 cells in vitro. THP-1 cell viability and cell cycle were examined by CCK-8 and flow cytometry. Rat gingival tissues were collected for hematoxylin-eosin staining. The expression of SH3BP2 and nicotinamide phosphoribosyltransferase (NAMPT) was examined using Western blot.

RESULTS

We found that the proliferation of P. gingivalis-infected THP-1 cells was increased by DEL-1. DEL-1 inhibited the expression of NAMPT and SH3BP2 in gingiva tissues of rats with periodontitis as well as in P. gingivalis-infected THP-1 cells.

CONCLUSIONS

Overexpression of DEL-1 downregulated SH3BP2 expression and reduced gingival inflammation induced by P. gingivalis. DEL-1 presents some regulatory effects on gingival inflammation in a P. gingivalis-induced rat experimental periodontitis model, suggesting the therapeutic potential of DEL-1 in regulating periodontal inflammation.

Microbiome-mediated incapacitation of interferon lambda production in the oral mucosa

Here, we show that Porphyromonas gingivalis (Pg), an endogenous oral pathogen, dampens all aspects of interferon (IFN) signaling in a manner that is strikingly similar to IFN suppression employed by multiple viral pathogens. Pg suppressed IFN production by down-regulating several IFN regulatory factors (IRFs 1, 3, 7, and 9), proteolytically degrading STAT1 and suppressing the nuclear translocation of the ISGF3 complex, resulting in profound and systemic repression of multiple interferon-stimulated genes. Pg-induced IFN paralysis was not limited to murine models but was also observed in the oral tissues of human periodontal disease patients, where overabundance of Pg correlated with suppressed IFN generation. Mechanistically, multiple virulence factors and secreted proteases produced by Pg transcriptionally suppressed IFN promoters and also cleaved IFN receptors, making cells refractory to exogenous IFN and inducing a state of broad IFN paralysis. Thus, our data show a bacterial pathogen with equivalence to viruses in the down-regulation of host IFN signaling.

Er:YAG laser irradiation enhances bacterial and lipopolysaccharide clearance and human gingival fibroblast adhesion on titanium discs

To investigate the effect of Er:YAG laser treatment on lipopolysaccharide (LPS) clearance and fibroblast adhesion on titanium disks. Grade IV titanium discs (n = 216) were used and allocated to 6 groups. Group 1 was the negative control without Porphyromonas gingivalis inoculation. Discs in Groups 2-6 were incubated with P. gingivalis to form a biofilm. Group 3 received 0.12% chlorhexidine irrigation and Group 4 received titanium curettage to remove the biofilm. Group 5 was treated with Er:YAG laser irradiation and Group 6 was treated with titanium curettage plus Er:YAG laser irradiation. The contact angle and surface roughness were measured after the various treatments. The surface microstructure and residual bacteria were examined using scanning electron microscopy and confocal laser scanning microscopy, respectively. Residual LPS was examined using a limulus amoebocyte lysate assay and human gingival fibroblast adhesion was quantified using fluorescent microscopy. Curettage plus Er:YAG laser irradiation was the most effective method for removing bacteria and LPS. No significant difference in the amount of fibroblast adhesion was found between the control and Group 6. Combined use of Er:YAG laser irradiation and curettage optimizes LPS clearance and fibroblast adhesion on titanium discs.

Porphyromonas gingivalis Components/Secretions Synergistically Enhance Pneumonia Caused by Streptococcus pneumoniae in Mice

Streptococcus pneumoniae is an important causative organism of respiratory tract infections. Although periodontal bacteria have been shown to influence respiratory infections such as aspiration pneumonia, the synergistic effect of S. pneumoniae and Porphyromonas gingivalis, a periodontopathic bacterium, on pneumococcal infections is unclear. To investigate whether P. gingivalis accelerates pneumococcal infections, we tested the effects of inoculating P. gingivalis culture supernatant (PgSup) into S. pneumoniae-infected mice. Mice were intratracheally injected with S. pneumoniae and PgSup to induce pneumonia, and lung histopathological sections and the absolute number and frequency of neutrophils and macrophages in the lung were analyzed. Proinflammatory cytokine/chemokine expression was examined by qPCR and ELISA. Inflammatory cell infiltration was observed in S. pneumoniae-infected mice and S. pnemoniae and PgSup mixed-infected mice, and mixed-infected mice showed more pronounced inflammation in lung. The ratios of monocytes/macrophages and neutrophils were not significantly different between the lungs of S. pneumoniae-infected mice and those of mixed-infected mice. PgSup synergistically increased TNF-α expression/production and IL-17 production compared with S. pneumoniae infection alone. We demonstrated that PgSup enhanced inflammation in pneumonia caused by S. pneumoniae, suggesting that virulence factors produced by P. gingivalis are involved in the exacerbation of respiratory tract infections such as aspiration pneumonia.

Porphyromonas gingivalis Induces Proinflammatory Cytokine Expression Leading to Apoptotic Death through the Oxidative Stress/NF-κB Pathway in Brain Endothelial Cells

Porphyromonas gingivalis, a periodontal pathogen, has been proposed to cause blood vessel injury leading to cerebrovascular diseases such as stroke. Brain endothelial cells compose the blood-brain barrier that protects homeostasis of the central nervous system. However, whether P. gingivalis causes the death of endothelial cells and the underlying mechanisms remain unclear. This study aimed to investigate the impact and regulatory mechanisms of P. gingivalis infection in brain endothelial cells. We used bEnd.3 cells and primary mouse endothelial cells to assess the effects of P. gingivalis on endothelial cells. Our results showed that infection with live P. gingivalis, unlike heat-killed P. gingivalis, triggers brain endothelial cell death by inducing cell apoptosis. Moreover, P. gingivalis infection increased intracellular reactive oxygen species (ROS) production, activated NF-κB, and up-regulated the expression of IL-1β and TNF-α. Furthermore, N-acetyl-L-cysteine (NAC), a most frequently used antioxidant, treatment significantly reduced P. gingivalis-induced cell apoptosis and brain endothelial cell death. The enhancement of ROS production, NF-κB p65 activation, and proinflammatory cytokine expression was also attenuated by NAC treatment. The impact of P. gingivalis on brain endothelial cells was also confirmed using adult primary mouse brain endothelial cells (MBECs). In summary, our results showed that P. gingivalis up-regulates IL-1β and TNF-α protein expression, which consequently causes cell death of brain endothelial cells through the ROS/NF-κB pathway. Our results, together with the results of previous case-control studies and epidemiologic reports, strongly support the hypothesis that periodontal infection increases the risk of developing cerebrovascular disease.

Oral infection with a periodontal pathogen alters oral and gut microbiomes

Periodontal disease, an inflammatory bone disease of the oral cavity, affects more than 50% of the United States population over the age of 30. The Gram-negative, anaerobic bacterium Porphyromonas gingivalis, the etiological agent of periodontal disease, is known to induce dysbiosis of the oral microbiome while promoting inflammatory bone loss. We have recently reported that P. gingivalis can also alter the gut microbiota of mice prone to develop inflammatory atherosclerosis. However, it is still unknown whether P. gingivalis induces similar changes to the gut microbiome as it does to oral microbiome. In this study, we demonstrate that P. gingivalis infection increases the diversity of the oral microbiome, allowing for colonization of potentially opportunistic species in the oral microbiome and overgrowth of commensal species in both the oral and gut microbiomes. Since periodontal disease treatment in humans typically involves antibiotic treatment, we also examined the combined effect of P. gingivalis infection on mice pretreated with oral antibiotics. By correlating the oral and cecal microbiota of P. gingivalis-infected mice fed a normal chow diet, we identified blooms of the Gram-negative genera Barnesiella and Bacteroides and imbalances of mucin-degrading bacteria. These disrupted community structures were predicted to have increased detrimental functional capacities including increased flavonoid degradation and l-histidine fermentation. Though antibiotic pretreatment (without P. gingivlais) had a dominant impact on the cecal microbiome, P. gingivalis infection of mice with or without antibiotic pretreatment increased the abundance of the phylum Firmicutes and the Porphyromonadaceae family in the cecum. Collectively, our study demonstrates that P. gingivalis oral infection disrupted the oral and cecal microbiomes of otherwise unperturbed mice, altering their community membership and functional potential.

Metabolic plasticity enables lifestyle transitions of Porphyromonas gingivalis

Our understanding of how the oral anaerobe Porphyromonas gingivalis can persist below the gum line, induce ecological changes, and promote polymicrobial infections remains limited. P. gingivalis has long been described as a highly proteolytic and asaccharolytic pathogen that utilizes protein substrates as the main source for energy production and proliferation. Here, we report that P. gingivalis displays a metabolic plasticity that enables the exploitation of non-proteinaceous substrates, specifically the monocarboxylates pyruvate and lactate, as well as human serum components, for colonization and biofilm formation. We show that anabolism of carbohydrates from pyruvate is powered by catabolism of amino acids. Concomitantly, the expression of fimbrial adhesion is upregulated, leading to the enhancement of biofilm formation, stimulation of multispecies biofilm development, and increase of colonization and invasion of the primary gingival epithelial cells by P. gingivalis. These studies provide the first glimpse into the metabolic plasticity of P. gingivalis and its adaptation to the nutritional condition of the host niche. Our findings support the model that in response to specific nutritional parameters, P. gingivalis has the potential to promote host colonization and development of a pathogenic community.

Tooth extraction in mice administered zoledronate increases inflammatory cytokine levels and promotes osteonecrosis of the jaw

INTRODUCTION

Osteonecrosis of the jaw (ONJ) occurring after invasive dental treatment often adversely affects patients' activities of daily living. Long-term administration of strong anti-bone resorptive agents such as bisphosphonates prior to invasive dental treatment is considered an ONJ risk factor; however, pathological mechanisms underlying ONJ development remain unclear.

MATERIALS AND METHODS

We developed an ONJ mouse model in which a tooth is extracted during treatment with the bisphosphonate zoledronate.

RESULTS

We observed induction of apoptosis in osteocytes, resulting in formation of empty lacunae in jaw bones at sites of tooth extraction but not in other bones of the same mice. We also observed elevated levels of inflammatory cytokines such as TNFα, IL-6 and IL-1 in jaw bone at the extraction site relative to other sites in zoledronate-treated mice. We also report that treatment in vitro with either zoledronate or an extract from Porphyromonas gingivalis, an oral bacteria, promotes expression of inflammatory cytokines in osteoclast progenitor cells. We demonstrate that gene-targeting of either TNFα, IL-6 or IL-1 or treatment with etanercept, a TNFα inhibitor, or a neutralizing antibody against IL-6 can antagonize ONJ development caused by combined tooth extraction and zoledronate treatment.

CONCLUSIONS

Taken together, the cytokine storm induced by invasive dental treatment under bisphosphonate treatment promotes ONJ development due to elevated levels of inflammatory cytokine-producing cells. Our work identifies novel targets potentially useful to prevent ONJ.

The Role of Alcohol, LPS Toxicity, and ALDH2 in Dental Bony Defects

It is estimated that 560 million people carry an East Asian-specific ALDH2*2 dominant-negative mutation which leads to enzyme inactivation. This common ALDH2 polymorphism has a significant association with osteoporosis. We hypothesized that the ALDH2*2 mutation in conjunction with periodontal Porphyromonas gingivalis bacterial infection and alcohol drinking had an inhibitory effect on osteoblasts and bone regeneration. We examined the prospective association of ALDH2 activity with the proliferation and mineralization potential of human osteoblasts in vitro. The ALDH2 knockdown experiments showed that the ALDH2 knockdown osteoblasts lost their proliferation and mineralization capability. To mimic dental bacterial infection, we compared the dental bony defects in wild-type mice and ALDH2*2 knockin mice after injection with purified lipopolysaccharides (LPS), derived from P. gingivalis which is a bacterial species known to cause periodontitis. Micro-computed tomography (micro-CT) scan results indicated that bone regeneration was significantly affected in the ALDH2*2 knockin mice with about 20% more dental bony defects after LPS injection than the wild-type mice. Moreover, the ALDH2*2 knockin mutant mice had decreased osteoblast growth and more dental bone loss in the upper left jaw region after LPS injection. In conclusion, these results indicated that the ALDH2*2 mutation with alcohol drinking and chronic exposure to dental bacterial-derived toxin increased the risk of dental bone loss.

Porphyromonas gingivalis promotes tumor progression in esophageal squamous cell carcinoma

PURPOSE

Increasing evidence indicates that the microbiome may influence tumor growth and modulate the tumor microenvironment of gastrointestinal cancers. However, the role of oral bacteria in the development of esophageal squamous cell carcinoma (EsoSCC) has remained unclear. Herein, we investigated the relationship between the periodontal pathogen Porphyromonas gingivalis and EsoSCC.

METHODS

To identify bacterial biomarkers associated with EsoSCC, we analyzed microbiomes in oral biofilms. The presence of P. gingivalis in esophageal tissues and relationships of P. gingivalis infection with clinicopathologic characteristics in 156 patients with EsoSCC were assessed using immunohistochemistry. The role of P. gingivalis infection in in vitro and in vivo EsoSCC progression was also assessed.

RESULTS

Microbiota profiles in oral biofilms revealed that P. gingivalis abundance was associated with an increased risk of EsoSCC development. In total, 57% of patients with EsoSCC were found to be infected with P. gingivalis. The presence of P. gingivalis was found to be associated with advanced clinical stages and a poor prognosis. It was also found to be associated with an elevated esophageal cancer incidence in a 4-nitroquinoline 1-oxide-induced mouse model and with an increased xenograft tumor growth. P. gingivalis infection increased interleukin (IL)-6 production and it promoted epithelial-mesenchymal transition and the recruitment of myeloid-derived suppressor cells. Furthermore, inhibited IL-6 signaling attenuated the tumor-promoting effects of P. gingivalis in 4-nitroquinoline 1-oxide-treated mice and xenograft mouse models.

CONCLUSIONS

Our data indicate that P. gingivalis may promote esophageal cancer development and progression. Direct targeting of P. gingivalis or concomitant IL-6 signaling may be a promising strategy to prevent and/or treat EsoSCC associated with P. gingivalis infection.

Structure and mechanism of the proton-driven motor that powers type 9 secretion and gliding motility

Three classes of ion-driven protein motors have been identified to date: ATP synthase, the bacterial flagellar motor and a proton-driven motor that powers gliding motility and the type 9 protein secretion system in Bacteroidetes bacteria. Here, we present cryo-electron microscopy structures of the gliding motility/type 9 protein secretion system motors GldLM from Flavobacterium johnsoniae and PorLM from Porphyromonas gingivalis. The motor is an asymmetric inner membrane protein complex in which the single transmembrane helices of two periplasm-spanning GldM/PorM proteins are positioned inside a ring of five GldL/PorL proteins. Mutagenesis and single-molecule tracking identify protonatable amino acid residues in the transmembrane domain of the complex that are important for motor function. Our data provide evidence for a mechanism in which proton flow results in rotation of the periplasm-spanning GldM/PorM dimer inside the intra-membrane GldL/PorL ring to drive processes at the bacterial outer membrane.

Catechin as the Most Efficient Bioactive Compound from Azadirachta indica with Antibiofilm and Anti-quorum Sensing Activities Against Dental Biofilm: an In Vitro and In Silico Study

Neem (Azadirachta indica [AI]) is a unique and traditional source of antioxidant and antibacterial compounds. The GC-MS studies revealed that phytoextract of Azadirachta indica comprises a large number of phytocompounds that possess the efficacy of inhibiting the biofilm. It was observed that phytocompounds like catechin showed maximum eradication of biofilm along with the degradation of EPS structural components like carbohydrates and proteins compared to quercetin, nimbolide, nimbin, and azardirachtin, and hence, catechin was proved to be the best against dental plaque-forming bacteria. It was also observed that catechin was able to bring about a marked reduction in quorum sensing (QS) both in Alcaligenes faecalis and Pseudomonas gingivalis dental biofilm-forming strains. The extent of such reduction was maximum for catechin (94.56±2.56% in P. gingivalis & 96.56±2.5 in A. faecalis) in comparison to other bioactive compounds. It was further observed that the bioactive compounds possess the ability to quickly pass across the membrane and bring about inhibition in the DNA and RNA content of the sessile cells. This was further validated by microscopic and in silico studies. Thus, this study revealed that catechin obtained from the phytoextract of AI showed a marked ability to inhibit the dental biofilm and can be used as a natural drug-like compound in treating biofilm-associated chronic infections.

Existence of natural mouse IgG mAbs recognising epitopes shared by malondialdehyde acetaldehyde adducts and Porphyromonas gingivalis

Natural Abs are produced by B lymphocytes in the absence of external Ag stimulation. They recognise self, altered self and foreign Ags, comprising an important first-line defence against invading pathogens and serving as innate recognition receptors for tissue homeostasis. Natural IgG Abs have been found in newborns and uninfected individuals. Yet, their physiological role remains unclear. Previously, no natural IgG Abs to oxidation-specific epitopes have been reported. Here, we show the cloning and characterisation of mouse IgG mAbs against malondialdehyde acetaldehyde (MAA)-modified low-density lipoprotein. Sequence analysis reveals high homology with germline genes, suggesting that they are natural. Further investigation shows that the MAA-specific natural IgG Abs cross-react with the major periodontal pathogen Porphyromonas gingivalis and recognise its principle virulence factors gingipain Kgp and long fimbriae. The study provides evidence that natural IgGs may play an important role in innate immune defence and in regulation of tissue homeostasis by recognising and removing invading pathogens and/or modified self-Ags, thus being involved in the development of periodontitis and atherosclerosis.

Periodontal pathogens alter the synovial proteome. Periodontal pathogens do not exacerbate macroscopic arthritis but alter the synovial proteome in mice

Rheumatoid arthritis (RA) and periodontitis (PD) are chronic inflammatory diseases that appear to occur in tandem. However, the mutual impact PD exerts on RA and vice versa has not yet been defined. To address this issue, we set up an animal model and analyzed how two prime inducers of periodontitis—Porphyromonas gingivalis (Pg) and Aggregatibacter actinomycetemcomitans (Aa)–differ in their pathogenic potential. Our experimental setup included collagen induced arthritis (CIA) in the mouse, oral inoculation with Pg or Aa to induce alveolar bone loss and the combination of both diseases in inverted orders of events. Neither pathobiont impacted on macroscopic arthritis and arthritis did not exacerbate alveolar bone loss. However, there were subtle differences between Pg and Aa with the former inducing more alveolar bone loss if PD was induced before CIA. On a molecular level, Pg and Aa led to differential expression patterns in the synovial membranes that were reminiscent of cellular and humoral immune responses, respectively. The Pg and Aa specific signatures in the synovial proteomes suggest a role for oral pathogens in shaping disease subtypes and setting the stage for subsequent therapy response.

Porphyromonas gingivalis promotes progression of esophageal squamous cell cancer via TGFβ-dependent Smad/YAP/TAZ signaling

Microbial dysbiosis in the upper digestive tract is linked to an increased risk of esophageal squamous cell carcinoma (ESCC). Overabundance of Porphyromonas gingivalis is associated with shorter survival of ESCC patients. We investigated the molecular mechanisms driving aggressive progression of ESCC by P. gingivalis. Intracellular invasion of P. gingivalis potentiated proliferation, migration, invasion, and metastasis abilities of ESCC cells via transforming growth factor-β (TGFβ)-dependent Drosophila mothers against decapentaplegic homologs (Smads)/Yes-associated protein (YAP)/Transcriptional coactivator with PDZ-binding motif (TAZ) activation. Smads/YAP/TAZ/TEA domain transcription factor1 (TEAD1) complex formation was essential to initiate downstream target gene expression, inducing an epithelial-mesenchymal transition (EMT) and stemness features. Furthermore, P. gingivalis augmented secretion and bioactivity of TGFβ through glycoprotein A repetitions predominant (GARP) up-regulation. Accordingly, disruption of either the GARP/TGFβ axis or its activated Smads/YAP/TAZ complex abrogated the tumor-promoting role of P. gingivalis. P. gingivalis signature genes based on its activated effector molecules can efficiently distinguish ESCC patients into low- and high-risk groups. Targeting P. gingivalis or its activated effectors may provide novel insights into clinical management of ESCC.

Porphyromonas gingivalis induces penetration of lipopolysaccharide and peptidoglycan through the gingival epithelium via degradation of junctional adhesion molecule 1

Porphyromonas gingivalis is a major pathogen in severe and chronic manifestations of periodontal disease, which is one of the most common infections of humans. A central feature of P. gingivalis pathogenicity is dysregulation of innate immunity at the gingival epithelial interface; however, the molecular basis underlying P. gingivalis–dependent abrogation of epithelial barrier function remains unknown. Gingival epithelial cells express junctional adhesion molecule (JAM1), a tight junction–associated protein, and JAM1 homodimers regulate epithelial barrier function. Here we show that Arg-specific or Lys-specific cysteine proteases (gingipains) secreted by P. gingivalis can specifically degrade JAM1 at K134 and R234 in gingival epithelial cells, resulting in permeability of the gingival epithelium to 40 kDa dextran, lipopolysaccharide (LPS), and proteoglycan (PGN). A P. gingivalis strain lacking gingipains was impaired in degradation of JAM1. Knockdown of JAM1 in monolayer cells and a three-dimensional multilayered tissue model also increased permeability to LPS, PGN, and gingipains. Inversely, overexpression of JAM1 in epithelial cells prevented penetration by these agents following P. gingivalis infection. Our findings strongly suggest that P. gingivalis gingipains disrupt barrier function of stratified squamous epithelium via degradation of JAM1, allowing bacterial virulence factors to penetrate into subepithelial tissues.

Periodontal diseases, which are among the most common infections of humans, are characterized by gingival inflammation and destruction of the hard and soft tissues that support the tooth, eventually causing tooth loss. Porphyromonas gingivalis is a major pathogen in periodontal diseases. Infection of gingival epithelial cells by P. gingivalis increases epithelial permeability. However, the molecular mechanism and pathological significance of P. gingivalis–dependent barrier dysfunction in human gingival epithelium remain unknown. In this study, we developed a three-dimensional multilayered tissue model of gingival epithelium infected by P. gingivalis and used it to monitor penetration of bacterial products derived from P. gingivalis and other bacteria. We found that P. gingivalis proteases, called gingipains, have a potent and specific ability to degrade JAM1, which regulates epithelial barrier function. Mechanistically, gingipains degrade mature form of JAM1 on the plasma membrane, increasing penetration of 40 kDa dextran, lipopolysaccharide, peptidoglycan, and gingipains. Our study provides new insights into the etiological role of P. gingivalis, leading to periodontal destruction.

Porphyromonas gingivalis Tyrosine Phosphatase Php1 Promotes Community Development and Pathogenicity

Protein-tyrosine phosphorylation in bacteria plays a significant role in multiple cellular functions, including those related to community development and virulence. Metal-dependent protein tyrosine phosphatases that belong to the polymerase and histindinol phosphatase (PHP) family are widespread in Gram-positive bacteria. Here, we show that Porphyromonas gingivalis, a Gram-negative periodontal pathogen, expresses a PHP protein, Php1, with divalent metal ion-dependent tyrosine phosphatase activity. Php1 tyrosine phosphatase activity was attenuated by mutation of conserved histidine residues that are important for the coordination of metal ions and by mutation of a conserved arginine residue, a key residue for catalysis in other bacterial PHPs. The php1 gene is located immediately downstream of the gene encoding the bacterial tyrosine (BY) kinase Ptk1, which was a substrate for Php1 in vitro Php1 rapidly caused the conversion of Ptk1 to a state of low tyrosine phosphorylation in the absence of discernible intermediate phosphoforms. Active Php1 was required for P. gingivalis exopolysaccharide production and for community development with the antecedent oral biofilm constituent Streptococcus gordonii under nutrient-depleted conditions. In contrast, the absence of Php1 had no effect on the ability of P. gingivalis to form monospecies biofilms. In vitro, Php1 enzymatic activity was resistant to the effects of the streptococcal secreted metabolites pABA and H2O2, which inhibited Ltp1, an enzyme in the low-molecular-weight (LMW) phosphotyrosine phosphatase family. Ptk1 reciprocally phosphorylated Php1 on tyrosine residues 159 and 161, which independently impacted phosphatase activity. Loss of Php1 rendered P. gingivalis nonvirulent in an animal model of periodontal disease. Collectively, these results demonstrate that P. gingivalis possesses active PHP and LMW tyrosine phosphatases, a unique configuration in Gram-negatives which may allow P. gingivalis to maintain phosphorylation/dephosphorylation homeostasis in multispecies communities. Moreover, Php1 contributes to the pathogenic potential of the organism.IMPORTANCE Periodontal diseases are among the most common infections of humans and are also associated with systemic inflammatory conditions. Colonization and pathogenicity of P. gingivalis are regulated by signal transduction pathways based on protein tyrosine phosphorylation and dephosphorylation. Here, we identify and characterize a novel component of the tyrosine (de)phosphorylation axis: a polymerase and histindinol phosphatase (PHP) family enzyme. This tyrosine phosphatase, designated Php1, was required for P. gingivalis community development with other oral bacteria, and in the absence of Php1 activity P. gingivalis was unable to cause disease in a mouse model of periodontitis. This work provides significant insights into the protein tyrosine (de)phosphorylation network in P. gingivalis, its adaptation to heterotypic communities, and its contribution to colonization and virulence.

Composite-derived monomers affect cell viability and cytokine expression in human leukocytes stimulated with Porphyromonas gingivalis

OBJECTIVES

Dental composites release unreacted resin monomers into the oral environment, even after polymerization. Periodontal cells are, therefore, exposed to substances that potentially elicit the immune inflammatory response. The underlying molecular mechanisms associated with the interaction between resin monomers and human immune cells found in the gingival crevicular fluid are not fully understood yet. This study investigated the ability of bisphenol A-glycidyl methacrylate (BISGMA), urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) to induce apoptosis and cytokine release by human leukocytes stimulated with a periodontal pathogen.

METHODOLOGY

Peripheral blood mononuclear cells (PBMC) from 16 healthy individuals were included in this study. To determine the toxicity, the PBMC were incubated for 20 hours, with monomers, for the analysis of cell viability using MTT assay. To evaluate cell death in the populations of monocytes and lymphocytes, they were exposed to sub-lethal doses of each monomer and of heat-inactivated Porphyromonas gingivalis (P. gingivalis) for 5 hours. Secretions of IL-1β, IL-6, IL-10 and TNF-α were determined by ELISA after 20 hours.

RESULTS

UDMA and TEGDMA induced apoptosis after a short-time exposure. Bacterial challenge induced significant production of IL-1β and TNF-α (p<0.05). TEGDMA reduced the bacterial-induced release of IL-1β and TNF-α, whereas UDMA reduced IL-1β release (p<0.05). These monomers did not affect IL-10 and IL-6 secretion. BISGMA did not significantly interfere in cytokine release.

CONCLUSIONS

These results show that resin monomers are toxic to PBMC in a dose-dependent manner, and may influence the local immune inflammatory response and tissue damage mechanisms via regulation of bacterial-induced IL-1β and TNF-α secretion by PBMC.

Amino acids as wetting agents: surface translocation by Porphyromonas gingivalis

Our understanding of how oral microbiota adapt in response to changes in their surroundings remains limited. This is particularly true of the slow-growing anaerobes that persist below the gum line. Here, we report that the oral anaerobe Porphyromonas gingivalis strain 381 can surface translocate when sandwiched between two surfaces. We show that during movement, this bacterium alters its metabolism, specifically side products of arginine utilization including citrulline and ornithine accumulated in the translocating cells; while arginine, N-acetyl-arginine, and the polyamine putrescine, which is produced from arginine were consumed. In addition, our results indicate that movement requires modification of the surrounding environment via proteolysis, cell dispersion, cell-on-cell rolling, and sub-diffusive cell-driven motility. We also show that production of fimbriae and fimbriae-associated proteins; as well as the regulation of contact-dependent growth inhibition genes, which are known to be involved in self-nonself discrimination, and the type IX secretion system are central to surface translocation. These studies provide a first glimpse into P. gingivalis motility and its relationship to ecological variables.

Nitrosative stress sensing in Porphyromonas gingivalis: structure of and heme binding by the transcriptional regulator HcpR

Although the HcpR regulator plays a vital step in initiation of the nitrosative stress response in many Gram-negative anaerobic bacteria, the molecular mechanisms that it uses to mediate gas sensing are not well understood. Here, a 2.6 Å resolution crystal structure of the N-terminal sensing domain of the anaerobic periodontopathogen Porphyromonas gingivalis HcpR is presented. The protein has classical features of the regulators belonging to the FNR-CRP family and contains a hydrophobic pocket in its N-terminal sensing domain. It is shown that heme bound to HcpR exhibits heme iron as a hexacoordinate system in the absence of nitric oxide (NO) and that upon nitrosylation it transitions to a pentacoordinate system. Finally, small-angle X-ray scattering experiments on full-length HcpR reveal that the C-terminal DNA-binding domain of HcpR has a high degree of interdomain flexibility.

Citrullination mediated by PPAD constrains biofilm formation in P. gingivalis strain 381

Porphyromonas gingivalis is the only known human-associated prokaryote that produces a peptidylarginine deiminase (PPAD), a protein-modifying enzyme that is secreted along with a number of virulence factors via a type IX secretion system (T9SS). While the function of PPAD in P. gingivalis physiology is not clear, human peptidylarginine deiminases are known to convert positively charged arginine residues within proteins to neutral citrulline and, thereby, impact protein conformation and function. Here, we report that the lack of citrullination in a PPAD deletion mutant (Δ8820) enhances biofilm formation. More Δ8820 cells attached to the surface than the parent strain during the early stages of biofilm development and, ultimately, mature Δ8820 biofilms were comprised of significantly more cell-cell aggregates and extracellular matrix. Imaging by electron microscopy discovered that Δ8820 biofilm cells secrete copious amounts of protein aggregates. Furthermore, gingipain-derived adhesin proteins, which are also secreted by the T9SS were predicted by mass spectrometry to be citrullinated and citrullination of these targets by wild-type strain 381 in vitro was confirmed. Lastly, Δ8820 biofilms contained more gingipain-derived adhesin proteins and more gingipain activity than 381 biofilms. Overall, our findings support the model that citrullination of T9SS cargo proteins known to play a key role in colonization, such as gingipain-derived adhesin proteins, is an underlying mechanism that modulates P. gingivalis biofilm development.

Chronic oral application of a periodontal pathogen results in brain inflammation, neurodegeneration and amyloid beta production in wild type mice

Background

The results from cross sectional and longitudinal studies show that periodontitis is closely associated with cognitive impairment (CI) and Alzhemer’s Disease (AD). Further, studies using animal model of periodontitis and human post-mortem brain tissues from subjects with AD strongly suggest that a gram-negative periodontal pathogen, Porphyromonas gingivalis (Pg) and/or its product gingipain is/are translocated to the brain. However, neuropathology resulting from Pg oral application is not known. In this work, we tested the hypothesis that repeated exposure of wild type C57BL/6 mice to orally administered Pg results in neuroinflammation, neurodegeneration, microgliosis, astrogliosis and formation of intra- and extracellular amyloid plaque and neurofibrillary tangles (NFTs) which are pathognomonic signs of AD.

Methods

Experimental chronic periodontitis was induced in ten wild type 8-week old C57BL/6 WT mice by repeated oral application (MWF/week) of Pg/gingipain for 22 weeks (experimental group). Another 10 wild type 8-week old C57BL/6 mice received vehicle alone (control group) MWF per week for 22 weeks. Brain tissues were collected and the presence of Pg/gingipain was determined by immunofluorescence (IF) microscopy, confocal microscopy, and quantitative PCR (qPCR). The hippocampi were examined for the signs of neuropathology related to AD: TNFα, IL1β, and IL6 expression (neuroinflammation), NeuN and Fluoro Jade C staining (neurodegeneration) and amyloid beta_1-42 (Aβ₄₂) production and phosphorylation of tau protein at Ser396 were assessed by IF and confocal microscopy. Further, gene expression of amyloid precursor protein (APP), beta-site APP cleaving enzyme 1 (BACE1), a disintegrin and metalloproteinase domain-containing protein10 (ADAM10) for α-secretase and presenilin1 (PSEN1) for ɣ-secretase, and NeuN (rbFox3) were determined by RT-qPCR. Microgliosis and astrogliosis were also determined by IF microscopy.

Results

Pg/gingipain was detected in the hippocampi of mice in the experimental group by immunohistochemistry, confocal microscopy, and qPCR confirming the translocation of orally applied Pg to the brain. Pg/gingipain was localized intra-nuclearly and peri-nuclearly in microglia (Iba1+), astrocytes (GFAP+), neurons (NeuN+) and was evident extracellularly. Significantly greater levels of expression of IL6, TNFα and IL1β were evident in experimental as compared to control group (p<0.01, p<0.00001, p<0.00001 respectively). In addition, microgliosis and astrogliosis were evident in the experimental but not in control group (p <0.01, p<0.0001 respectively). Neurodegeneration was evident in the experimental group based on a fewer number of intact neuronal cells assessed by NeuN positivity and rbFOX3 gene expression, and there was a greater number of degenerating neurons in the hippocampi of experimental mice assessed by Fluoro Jade C positivity. APP and BACE1 gene expression were increased in experimental group compared with control group (p<0.05, p<0.001 respectively). PSEN1 gene expression was higher in experimental than control group but the difference was not statistically significant (p = 0.07). ADAM10 gene expression was significantly decreased in experimental group compared with control group (p<0.01). Extracellular Aβ₄₂ was detected in the parenchyma in the experimental but not in the control group (p< 0.00001). Finally, phospho-Tau (Ser396) protein was detected and NFTs were evident in experimental but not in the control group (p<0.00001).

Conclusions

This study is the first to show neurodegeneration and the formation of extracellular Aβ₄₂ in young adult WT mice after repeated oral application of Pg. The neuropathological features observed in this study strongly suggest that low grade chronic periodontal pathogen infection can result in the development of neuropathology that is consistent with that of AD.

Tolerance induced by Porphyromonas gingivalis may occur independently of TLR2 and TLR4

OBJECTIVE

Periodontitis is a microbe-induced chronic inflammatory disease. Previous exposure of the host to bacteria or their virulence factors leads to refractory responses to further stimuli, which is called tolerance. Porphyromonas gingivalis (P. gingivalis) is one of the most important pathogenic microorganisms associated with periodontitis, and is a potent inducer of pro- and anti-inflammatory cytokines. The aim of this study was to explore the roles and possible mechanisms of tolerance induced by P. gingivalis.

METHODS

THP-1-derived macrophages were pretreated with 1x108 colony-forming units/ml P. gingivalis ATCC 33277 or 21 clinical isolates from moderate to severe chronic periodontitis patients (24 h), washed (2 h) and treated with P. gingivalis ATCC 33277 or the same clinical isolates again (24 h). Levels of pro-inflammatory cytokines TNF-α and IL-1β and anti-inflammatory cytokine IL-10 in supernatants were detected by ELISA. Moreover, to identify the possible mechanisms for the changes in cytokine secretion, Toll-like receptor 2 (TLR2) and TLR4 protein expressions were explored in these cells by flow cytometry.

RESULTS

After repeated challenge with P. gingivalis ATCC 33277 or clinical isolates, production of TNF-α and IL-1β in macrophages was decreased significantly compared with that following a single stimulation (p<0.05), while only comparable levels of IL-10 were detected in P. gingivalis ATCC 33277 or clinical isolate-tolerized cells (p>0.05). In addition, there was interstrain variability in the ability to induce IL-1β and IL-10 production after repeated P. gingivalis stimulation. However, no significant changes in TLR2 or TLR4 were detected in macrophages that were repeatedly treated with P. gingivalis ATCC 33277 or clinical isolates compared with those stimulated with P. gingivalis only once (p>0.05).

CONCLUSIONS

Repeated P. gingivalis stimulation triggered tolerance, which might contribute to limiting periodontal inflammation. However, tolerance induced by P. gingivalis might develop independently of TLR2 and TLR4 and be related to molecules in signaling pathways downstream of TLR2 and TLR4.

Inhibition of Oral Pathogens Adhesion to Human Gingival Fibroblasts by Wine Polyphenols Alone and in Combination with an Oral Probiotic

Several benefits have been described for red wine polyphenols and probiotic strains in the promotion of colonic metabolism and health. On the contrary, knowledge about their role in the management of oral health is still scarce. In this work, the antiadhesive capacity of selected red wine polyphenols and oenological extracts against the oral pathogens Porphyromonas gingivalis, Fusobacterium nucleatum, and Streptococcus mutans in an in vitro model of human gingival fibroblasts has been explored as well as their complementary action with the candidate oral probiotic Streptococcus dentisani. Results highlighted the antiadhesive capacity of caffeic and p-coumaric acids as well as grape seed and red wine oenological extracts. Both, caffeic and p-coumaric acids increased their inhibition potential against S. mutans adhesion when combined with S. dentisani. Additionally, UHPLC-MS/MS analysis demonstrated the oral metabolism of wine phenolics due to both, cellular and bacterial activity.

Evaluation of Emdogain® antimicrobial effectiveness against biofilms containing the keystone pathogen Porphyromonas gingivalis

This study aimed to evaluate the antimicrobial activity of Emdogain® (EMD) against biofilms containing the periopathogen Porphyromonas gingivalis. A brain-Heart infusion broth inoculated with S. gordonii and P. gingivalis was perfused (7-d, anaerobiosis) through a closed circuit containing two Robbins devices as to form biofilms. The latter were then treated for 2 min with various antimicrobials (Chlorhexidine (CHX) 0.2%, Povidone iodine (PVI) 5%, PVI 10%, essential oils (EO), EO ZeroTM or EMD) (n=8) and cell densities were calculated and compared. In the present in vitro model, Emdogain® was not statistically effective (p>0.05) in killing biofilm bacteria unlike the other tested molecules.

Endogenous acid ceramidase protects epithelial cells from Porphyromonas gingivalis-induced inflammation in vitro

Ceramidases are a group of enzymes that degrade pro-inflammatory ceramide by cleaving a fatty acid to form anti-inflammatory sphingosine lipid. Thus far, acid, neutral and alkaline ceramidase isozymes have been described. However, the expression patterns of ceramidase isoforms as well as their role in periodontal disease pathogenesis remain unknown. In this study, expression patterns of ceramidase isoforms were quantified by real-time PCR and immunohistochemistry in gingival samples of patients with periodontitis and healthy subjects, as well as in EpiGingivalTM-3D culture and OBA-9 gingival epithelial cells both of which were stimulated with or without the presence of live Porphyromonas gingivalis (ATCC 33277 strain). A significantly lower level of acid ceramidase expression was detected in gingival tissues from periodontal patients compared to those from healthy subjects. In addition, acid-ceramidase expression in EpiGingival™ 3D culture and OBA-9 cells was suppressed by stimulation with P. gingivalis in vitro. No significant fluctuation was detected for neutral or alkaline ceramidases in either gingival samples or cell cultures. Next, to elucidate the role of acid ceramidase in P. gingivalis-induced inflammation in vitro, OBA-9 cells were transduced with adenoviral vector expressing the human acid ceramidase (Ad-ASAH1) gene or control adenoviral vector (Ad-control). In response to stimulation with P. gingivalis, ASAH1-over-expressing OBA-9 cells showed significantly lower mRNA expressions of caspase-3 as well as the percentage of Annexin V-positive cells, when compared with OBA-9 cells transduced with Ad-control vector. Furthermore, in response to stimulation with P. gingivalis, ASAH1-over-expressing OBA-9 cells produced less TNF-α, IL-6, and IL1β pro-inflammatory cytokines than observed in OBA-9 cells transduced with Ad-control vector. Collectively, our data show the novel discovery of anti-inflammatory and anti-apoptotic effects of acid ceramidase in host cells exposed to periodontal bacteria, and the attenuation of the expression of host-protective acid ceramidase in periodontal lesions.

Polymorphism IL-1RN rs419598 reduces the susceptibility to generalized periodontitis in a population of European descent

Interleukin (IL) 1-ra is a potent endogenous competitive inhibitor of IL-α and β and has an anti-inflammatory role. Study objectives were: 1) to assess the associations of IL-1RN genetic single nucleotide polymorphism (SNP) (rs419598) with generalized chronic periodontitis (GCP), generalized aggressive periodontitis (GAgP), and absence of periodontitis and 2) to assess its association with the load of five periodontopathogenic bacteria and periodontal clinical variables. A cross-sectional analytic study was conducted in 123 patients with GCP, 60 patients with GAgP, and 20 controls. Reverse hybridization PCR was used for genotyping analysis to detect SNPs in IL-1A (rs1800587), IL-1B (rs1143634), and IL-1RN (rs419598) genes and for determination of the load of five periodontopathogenic bacteria. The severity and extension of periodontitis were assessed. Multinomial logistic regression and mediated regression analyses were performed. Considering results for GCP and GAgP patients together, the presence of polymorphism in IL-1A and/or IL-1B gene was associated with a higher likelihood of periodontitis, (OR = 8.11; 95%CI [1.85–35.48]), but this likelihood was reduced when IL-1RN polymorphism was also present, (OR = 5.91; 95%CI [1.08–32.27]). IL-1RN polymorphism was significantly associated with lower counts of red complex bacteria, specifically Porphyromona gingivalis, Tannerella forsythia, and Prevotella intermedia, which were associated with improved clinical outcomes. The polymorphic expression of IL-1RN (rs419598) gene may be associated with a reduced susceptibility to GAgP and GCP in populations of European descent. This effect may be mediated by a decreased load of Porphyromona gingivalis, Tannerella forsythia, and Prevotella intermedia.

Differences in survival, virulence and biofilm formation between sialidase-deficient and W83 wild-type Porphyromonas gingivalis strains under stressful environmental conditions

BACKGROUND

Porphyromonas gingivalis is a major causative pathogen of chronic periodontitis. Within the inflammatory microenvironment, there exists extreme pH values, elevated temperatures and oxidative stress. Pathogens adapt to these stressful environmental conditions by regulating the transcription of virulence genes, modifying themselves with macromolecules and by aggregating and entering into a biofilm growth phase. Our previous study showed that the P. gingivalis sialidase can help cells obtain sialic acid from the environment, which is used to modify macromolecules on the surface of P. gingivalis cells. In this study, we compared the survival, virulence factors and biofilm formation of a sialidase-deficient strain (ΔPG0352) and the wild-type P. gingivalis W83 strain under various pH values, temperatures and oxidative stress conditions to identify the roles of sialidase in the adaptation of P. gingivalis to stressful conditions.

RESULTS

Compared to the growth of the P. gingivalis W83 strain, the growth of the △PG0352 was more inhibited by oxidative stress (0.25 and 0.5 mM H2O2) and exhibited greater cell structure damage when treated with H2O2 as assessed by transmission electron microscopy. Both Lys-gingipain (Kgp) and Arg-gingipain (Rgp) activities were lower in the ΔPG0352 than those in the P. gingivalis W83 strain under all the assayed culture conditions. The lipopolysaccharide (LPS) activity of the W83 strain was higher than that of the ΔPG0352 under acidic conditions (pH 5.0), but no differences between the strains were observed under other conditions. Compared to the biofilms formed by P. gingivalis W83, those formed by the ΔPG0352 were decreased and discontinuous under acidic, alkaline and oxidative stress conditions.

CONCLUSION

Compared to the P. gingivalis W83 strain, the survival, virulence and biofilm formation of the ΔPG0352 were decreased under stressful environmental conditions.

Periodontal microbioma and rheumatoid arthritis: The role of Porhyromonas gingivalis

Rheumatoid Arthritis is a disease, which can be described as an autoimmune response after molecular mimicry caused by infective agents. The current study aims at evaluating the correlation between Rhematoid Arthritis (RA) and Periodontal Disease (PD), with special attention to the microbioma detected in the gums. Thirty-four patients with RD were recruited into the current study. Among rheumatic parameters, Rheumatoid Factor (RF), anti-citrullinated protein antibody (CCP), HLA-BDR1 and DAS28 were collected. A dental clinician evaluated the periodontal screening record (PSR). Afterwards, 1 paper cone was inserted for 30 seconds into the gingival sulcus then sent to the laboratory for evaluation. Quantitative PCR of 16S rRNA genes was performed with the hydrolysis probes method to identify and evaluate the amount Porphyromonas gingivalis, Tannerella forsythensis, Treponema denticola, Fusobacterium nucleatum and Campylobacter rectus. There were no statistical differences in the composition of oral microbioma between PSR groups. There were no statistical significant differences between bacterial loads and serum values. On the contrary, a positive correlation was found between the presence of Porphyromonas gingivalis in periodontal pockets on one side and RF and CCP on the other. Therefore, the presence of Porhyromonas gingivalis in periodontal pockets is associated to RA inflammatory indices.

A new mathematical model of bacterial interactions in two-species oral biofilms

Periodontitis are bacterial inflammatory diseases, where the bacterial biofilms present on the tooth-supporting tissues switch from a healthy state towards a pathogenic state. Among bacterial species involved in the disease, Porphyromonas gingivalis has been shown to induce dysbiosis, and to induce virulence of otherwise healthy bacteria like Streptococcus gordonii. During biofilm development, primary colonizers such as S. gordonii first attach to the surface and allow the subsequent adhesion of periodontal pathogens such as P. gingivalis. Interactions between those two bacteria have been extensively studied during the adhesion step of the biofilm. The aim of the study was to understand interactions of both species during the growing phase of the biofilm, for which little knowledge is available, using a mathematical model. This two-species biofilm model was based on a substrate-dependent growth, implemented with damage parameters, and validated thanks to data obtained on experimental biofilms. Three different hypothesis of interactions were proposed and assayed using this model: independence, competition between both bacteria species, or induction of toxicity by one species for the other species. Adequacy between experimental and simulated biofilms were found with the last hypothetic mathematical model. This new mathematical model of two species bacteria biofilms, dependent on different substrates for growing, can be applied to any bacteria species, environmental conditions, or steps of biofilm development. It will be of great interest for exploring bacterial interactions in biofilm conditions.

[Effect of molar ligation and local Porphyromonas gingivalis inoculation on alveolar bone loss in the mouse]

OBJECTIVE

To compare the extent and time course of alveolar bone loss and osteoclast activation in two murine models of periodontal disease: molar ligation and Porphyromonas gingivalis (P. gingivalis) oral inoculation.

METHODS

A split-mouth design was applied to two groups of mice (C57BL6, 6-8 weeks old, n=24 in both groups), resulting in four treatment groups: (1) Control group: unligated upper right 2nd molars receiving CMC only, (2)Ligature group: ligation of a 9-0 suture around the upper left 2nd molar, (3) P. gingivalis group: unligated upper right 2nd molar receiving P. gingivalis challenge only, (4)Ligature+P.gingivalis group: ligation of the upper left 2nd molar in combination with oral inoculation with 109 colony-forming units(CFU) P. gingivalis. Alveolar bone loss was measured as the cementoenamel junction and alveolar bone crest (CEJ-ABC) distance. In the study, 48 C57BL6 mice were designed and treated as described above, and osteoclasts were counted on histological sections following tartrate-resistant acid phosphatase (TRAP) staining and counts were normalized to alveolar bone surface distance. Then 36 C57BL6 mice were investigated, of which 30 were ligated a 9-0 silk ligature around the 2nd molar in the left maxillary quadrant and 6 were not ligated. After ligation for 1 week, the ligatures in 12 mice were taken off for either 1 week or 2 weeks. The CEJ-ABC distance of the 6 mice without ligation was baseline. The CEJ-ABC distances were measured and analyzed. The data were analyzed with one-way ANOVA.

RESULTS

Molar ligation induced marked alveolar bone loss after 3, 6, 9 and 12 weeks [(0.16±0.04) mm, (0.16±0.02) mm, (0.18±0.03) mm, (0.17±0.02) mm], vs. corresponding controls [(0.09±0.03)mm,(0.10±0.01)mm,(0.12±0.04)mm,(0.12±0.01)mm] and P. gingivalis group [(0.09±0.03)mm, (0.12±0.01)mm,(0.12±0.02)mm,(0.10±0.01)mm], P<0.05. Combined treatment with molar ligation and P. gingivalis did not further increase the CEJ-ABC distance. Evidence for osteoclast activation was found one day after molar ligation, and TRAP-positive cell numbers peaked on day 3 (12±4 vs. control 2±2, P<0.01). After taking off ligature following ligation for 2 weeks, it showed significantly regrowth of alveolar bone compared with that before removal of the ligature on day 7 [(0.07±0.02)mm vs. (0.13±0.01)mm, P<0.01].

CONCLUSION

Molar ligation is a rapid and effective way to induce periodontal bone loss in mice. Osteoclast activation occurs within 24 hours of ligature placement, and the extent of bone loss well exceeds that of the P.gingivalis-induced bone loss. Removing ligature after periodontal disease might help bone regeneration by regrowth of the alveolar bone.

In Vitro Effect of Porphyromonas gingivalis Methionine Gamma Lyase on Biofilm Composition and Oral Inflammatory Response

Methanethiol (methyl mercaptan) is an important contributor to oral malodour and periodontal tissue destruction. Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum are key oral microbial species that produce methanethiol via methionine gamma lyase (mgl) activity. The aim of this study was to compare an mgl knockout strain of P. gingivalis with its wild type using a 10-species biofilm co-culture model with oral keratinocytes and its effect on biofilm composition and inflammatory cytokine production. A P. gingivalis mgl knockout strain was constructed using insertion mutagenesis from wild type W50 with gas chromatographic head space analysis confirming lack of methanethiol production. 10-species biofilms consisting of Streptococcus mitis, Streptococcus oralis, Streptococcus intermedius, Fusobacterium nucleatum ssp polymorphum, Fusobacterium nucleatum ssp vincentii, Veillonella dispar, Actinomyces naeslundii, Prevotella intermedia and Aggregatibacter actinomycetemcomitans with either the wild type or mutant P. gingivalis were grown on Thermanox cover slips and used to stimulate oral keratinocytes (OKF6-TERT2), under anaerobic conditions for 4 and 24 hours. Biofilms were analysed by quantitative PCR with SYBR Green for changes in microbial ecology. Keratinocyte culture supernatants were analysed using a multiplex bead immunoassay for cytokines. Significant population differences were observed between mutant and wild type biofilms; V. dispar proportions increased (p<0.001), whilst A. naeslundii (p<0.01) and Streptococcus spp. (p<0.05) decreased in mutant biofilms. Keratinocytes produced less IL-8, IL-6 and IL-1α when stimulated with the mutant biofilms compared to wild type. Lack of mgl in P. gingivalis has been shown to affect microbial ecology in vitro, giving rise to a markedly different biofilm composition, with a more pro-inflammatory cytokine response from the keratinocytes observed. A possible role for methanethiol in biofilm formation and cytokine response with subsequent effects on oral malodor and periodontitis is suggested.

Heterogeneity of Surfaces of Subgingival Bacteria as Detected by Zeta Potential Measurements

Porphyromonasgingivalis, Prevotella intermedia, and Actinobacillus actinomycetemcomitans (A.a.) are Gram-negative bacteria which are implicated in various forms of periodontal disease. The Gram-positive Peptostreptococcus micros may also play an important role. For investigation of the possible adhesion and colonization mechanisms of these organisms, the charge properties of the outermost layers of bacterial cell surfaces were studied through the measurement of zeta potentials at various pH values. Eleven fresh clinical isolates, representing the four species, and one laboratory strain, P. gingivalis W83, were examined. Eleven of the 12 strains displayed heterogeneity with respect to pH-dependent zeta potentials. Within single cultures of each of these strains, two distinct populations of cells were found, one which was more negatively charged than the other. For the Gram-negative strains, the more negatively charged subpopulation was in the majority, while the P. micros strains appeared to be composed mainly of a less-negatively-charged subpopulation. Vesicles prepared from two strains displayed the same pH dependence and heterogeneity of zeta potentials as the parent cells. An A.a. strain which was passaged several times in fluid medium had lost its fimbriae and became homogeneous with respect to charge.

Pro-inflammatory Cytokines Up-regulate MUC1 Gene Expression in Oral Epithelial Cells

The membrane-bound mucin MUC1 is expressed ubiquitously on epithelial surfaces and is thought to provide protection from bacterial and chemical injury. The present study was undertaken to determine whether MUC1 was expressed in cultured oral epithelial cells and whether expression is modulated by pro-inflammatory mediators released as part of the host response to infection by oral pathogens. Northern and Western blotting experiments showed that KB cells express MUC1 mRNA and protein. When cells were treated with interleukins (IL-1β, IL-6), tumor necrosis factor-alpha (TNF-α), or interferon-gamma (IFN-γ), or combinations of these, real-time PCR demonstrated that MUC1 mRNA increased 1.4- to 3.2-fold. Interestingly, a significant increase in levels of MUC1 protein was also observed. While no effect was observed when KB cells were incubated with LPS from Porphyromonas gingivalis, infection of KB monolayers with this oral pathogen caused a 2.85-fold increase in MUC1 transcript levels. These results suggest that increased MUC1 synthesis may be a key element in the host response to infection with oral pathogens.

Treponema medium Glycoconjugate Inhibits Activation of Human Gingival Fibroblasts Stimulated with Phenol-Water Extracts of Periodontopathic Bacteria

Oral treponemes are well-known as causative agents of periodontal diseases; however, the details have not been fully clarified. Here, we examined the effects of Treponema medium glycoconjugate on the activation of human gingival fibroblasts using phenol-water extracts from Porphyromonas gingivalis, Prevotella intermedia, Fusobacterium nucleatum subsp. nucleatum, and Actinobacillus actinomycetemcomitans. The phenol-water extracts activated human gingival fibroblasts to mediate IL-8 production, as well as IL-8 mRNA expression, phosphorylation of p38 mitogen-activated protein kinase, and expression of intercellular adhesion molecule-1. T. medium glycoconjugate exhibited no activation of human gingival fibroblasts, while phenol-water extract-induced activation of human gingival fibroblasts was clearly inhibited by T. medium glycoconjugate. Furthermore, binding of biotinylated phenol-water extracts to CD14 in the presence of LPS-binding protein was blocked with T. medium glycoconjugate. These results suggest that T. medium glycoconjugate has an inhibitory effect on host cell activation by periodontopathic bacteria caused by binding to CD14- and LPS-binding protein.

Melatonin Receptor Agonists as the "Perioceutics" Agents for Periodontal Disease through Modulation of Porphyromonas gingivalis Virulence and Inflammatory Response

Aim

“Perioceutics” including antimicrobial therapy and host modulatory therapy has emerged as a vital adjunctive treatment of periodontal disease. Melatonin level was significantly reduced in patients with periodontal diseases suggesting melatonin could be applied as a potential “perioceutics” treatment of periodontal diseases. This study aims to investigate the effects of melatonin receptor agonists (melatonin and ramelteon) on Porphyromonas gingivalis virulence and Porphyromonas gingivalis-derived lipopolysaccharide (Pg-LPS)-induced inflammation.

Methods

Effects of melatonin receptor agonists on Porphyromonas gingivalis planktonic cultures were determined by microplate dilution assays. Formation, reduction, and viability of Porphyromonas gingivalis biofilms were detected by crystal violet staining and MTT assays, respectively. Meanwhile, biofilms formation was also observed by confocal laser scanning microscopy (CLSM). The effects on gingipains and hemolytic activities of Porphyromonas gingivalis were evaluated using chromogenic peptides and sheep erythrocytes. The mRNA expression of virulence and iron/heme utilization was assessed using RT-PCR. In addition, cell viability of melatonin receptor agonists on human gingival fibroblasts (HGFs) was evaluated by MTT assays. After pretreatment of melatonin receptor agonists, HGFs were stimulated with Pg-LPS and then release of cytokines (IL-6 and lL-8) was measured by enzyme-linked immunosorbent assay (ELISA).

Results

Melatonin and ramelteon did exhibit antimicrobial effects against planktonic culture. Importantly, they inhibited biofilm formation, reduced the established biofilms, and decreased biofilm viability of Porphyromonas gingivalis. Furthermore, they at sub-minimum inhibitory concentration (sub-MIC) concentrations markedly inhibited the proteinase activities of gingipains and hemolysis in a dose-dependent manner. They at sub-MIC concentrations significantly inhibited the mRNA expression of virulence factors (kgp, rgpA, rgpB, hagA, and ragA), while increasing the mRNA expression of ferritin (ftn) or hemolysin (hem). They did not show obvious cytotoxicity toward HGFs. They inhibited Pg-LPS-induced IL-6 and IL-8 secretion, which was reversed by luzindole, the melatonin receptor antagonist.

Conclusion

Melatonin receptor agonists can inhibit planktonic and biofilm growth of Porphyromonas gingivalis by affecting the virulent properties, as well as Pg-LPS-induced inflammatory response. Our study provides new evidence that melatonin receptor agonists might be useful as novel “perioceutics” agents to prevent and treat Porphyromonas gingivalis-associated periodontal diseases.

Role of mitogen-activated protein kinase pathways in migration of gingival epithelial cells in response to stimulation by cigarette smoke condensate and infection by Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

Previous studies have shown that cigarette smoke (CS) and periodontal pathogens could alter wound healing responses of gingival epithelial cells. To elucidate molecular mechanisms leading to these epithelial changes, we studied the signaling pathway involved in the modulation of cell migration by CS condensate (CSC) and the infection by a prominent periodontal pathogen, Porphyromonas gingivalis.

MATERIAL AND METHODS

Human gingival epithelial cells (Ca9-22) were treated with CSC or vehicle control for 24 h. Activation of mitogen-activated protein kinases (MAPK) in cells with or without infection by P. gingivalis was assessed by polymerase chain reaction array and immunoblotting using phospho-specific antibodies. Cell migration was assessed using in vitro wound closure model, and specific pharmacologic inhibitors of MAPK pathways were used to characterize further the extent of involvement of the MAPK pathways.

RESULTS

Polymerase chain reaction array showed that gene expression of several members of the MAPK, particularly p38 and JNK, was upregulated more than twofold in Ca9-22 cells stimulated with 10 μg/mL CSC. Coincubation with P. gingivalis induced a different pattern of gene expression for MAPK pathways, but it did not suppress the MAPK-related genes upregulated by CSC. A significant phosphorylation of ERK1/2 and p38 was observed in cells stimulated with 10 μg/mL CSC (p < 0.05), whereas coincubation with a higher concentration of CSC (250 μg/mL) evoked no such activation. P. gingivalis infection resulted in a tendency to reduce the phosphorylation of ERK1/2 and p38, which had been enhanced by stimulation with 10 μg/mL CSC. Incubation with ERK1/2 and p38 inhibitors significantly reduced the wound closure of CSC-stimulated cells, by approximately 43% and 46%, respectively (p < 0.05).

CONCLUSION

CSC exerts effects on the migration of human gingival epithelial cells through the activation of the MAPK ERK1/2 and p38 signaling pathways. P. gingivalis infection attenuates the CSC-induced migration at least partly by suppressing the phosphorylation of ERK1/2 and p38, but other pathways are likely to be involved in this modulatory process.

Effects of Porphyromonas gingivalis LipopolysaccharideTolerized Monocytes on Inflammatory Responses in Neutrophils

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

Unprimed, M1 and M2 Macrophages Differentially Interact with Porphyromonas gingivalis

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

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

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