Porphyromonas gingivalis-host interactions: open war or intelligent guerilla tactics?

Frankincense (Boswellia serrata) Extract Effects on Growth and Biofilm Formation of Porphyromonas gingivalis, and Its Intracellular Infection in Human Gingival Epithelial Cells

Frankincense is produced by Boswellia trees, which can be found throughout the Middle East and parts of Africa and Asia. Boswellia serrata extract has been shown to have anti-cancer, anti-inflammatory, and antimicrobial effects. Periodontitis is an oral chronic inflammatory disease that affects nearly half of the US population. We investigated the antimicrobial effects of B. serrata extract on two oral pathogens associated with periodontitis. Using the minimum inhibitory concentration and crystal violet staining methods, we demonstrated that Porphyromonas gingivalis growth and biofilm formation were impaired by treatment with B. serrata extracts. However, the effects on Fusobacterium nucleatum growth and biofilm formation were not significant. Using quantification of colony-forming units and microscopy techniques, we also showed that concentrations of B. serrata that were not toxic for host cells decreased intracellular P. gingivalis infection in human gingival epithelial cells. Our results show antimicrobial activity of a natural product extracted from Boswellia trees (B. serrata) against periodontopathogens. Thus, B. serrata has the potential for preventing and/or treating periodontal diseases. Future studies will identify the molecular components of B. serrata extracts responsible for the beneficial effects.

Oral microbiota-host interaction: the chief culprit of alveolar bone resorption

There exists a bidirectional relationship between oral health and general well-being, with an imbalance in oral symbiotic flora posing a threat to overall human health. Disruptions in the commensal flora can lead to oral diseases, while systemic illnesses can also impact the oral cavity, resulting in the development of oral diseases and disorders. Porphyromonas gingivalis and Fusobacterium nucleatum, known as pathogenic bacteria associated with periodontitis, play a crucial role in linking periodontitis to accompanying systemic diseases. In periodontal tissues, these bacteria, along with their virulence factors, can excessively activate the host immune system through local diffusion, lymphatic circulation, and blood transmission. This immune response disruption contributes to an imbalance in osteoimmune mechanisms, alveolar bone resorption, and potential systemic inflammation. To restore local homeostasis, a deeper understanding of microbiota-host interactions and the immune network phenotype in local tissues is imperative. Defining the immune network phenotype in periodontal tissues offers a promising avenue for investigating the complex characteristics of oral plaque biofilms and exploring the potential relationship between periodontitis and associated systemic diseases. This review aims to provide an overview of the mechanisms underlying Porphyromonas gingivalis- and Fusobacterium nucleatum-induced alveolar bone resorption, as well as the immunophenotypes observed in host periodontal tissues during pathological conditions.

Association between Porphyromonas Gingivalis and systemic diseases: Focus on T cells-mediated adaptive immunity

The association between periodontal disease and systemic disease has become a research hotspot. Porphyromonas gingivalis (P. gingivalis), a crucial periodontal pathogen, affects the development of systemic diseases. The pathogenicity of P. gingivalis is largely linked to interference with the host's immunity. This review aims to discover the role of P. gingivalis in the modulation of the host's adaptive immune system through a large number of virulence factors and the manipulation of cellular immunological responses (mainly mediated by T cells). These factors may affect the cause of large numbers of systemic diseases, such as atherosclerosis, hypertension, adverse pregnancy outcomes, inflammatory bowel disease, diabetes mellitus, non-alcoholic fatty liver disease, rheumatoid arthritis, and Alzheimer's disease. The point of view of adaptive immunity may provide a new idea for treating periodontitis and related systemic diseases.

Entamoeba gingivalis is associated with periodontal conditions in Chinese young patients: A cross-sectional study

Background

This study investigated the prevalence and relative abundance of Entamoeba gingivalis (E. gingivalis) in Chinese young patients with different periodontal conditions, and its association with subgingival microbial composition, periodontal parameters, and cytokines in gingival crevicular fluid.

Methods

Participants (age: 18–45 years) diagnosed with stage II–IV periodontitis, gingivitis, or periodontal health underwent periodontal examination and sampling. Subgingival plaque was analyzed by 16S+18S sequencing for E. gingivalis detection and microbial analysis. The distribution of E. gingivalis in subgingival plaque was illustrated by fluorescence in situ hybridization. Interleukin-1β, interleukin-8, and tumor necrosis factor-α in gingival crevicular fluid were measured by multiplexed flow cytometric assay.

Results

This cross-sectional study included 120 sites from 60 participants. The prevalence and relative abundance of E. gingivalis were significantly increased in periodontitis (p<0.05). The sites were classified into three subgroups according to the relative abundance of E. gingivalis: negative group (Eg0, n=56); low-abundance group (Eg1, n=32); and high-abundance group (Eg2, n=32). The subgingival microflora in the subgroups showed stepwise changes at both the phylum and genus levels. The microflora compositions were significantly altered from Eg0 to Eg2 (p<0.001). Co-occurrence network analysis showed that Porphyromonas, Treponema, Tannerella, Filifactor, TG5, and Desulfobulbus were highly correlated with E. gingivalis (r>0.6, p<0.001). Correlation analysis showed that E. gingivalis was closely associated with important periodontal parameters and cytokines (p<0.01).

Conclusion

E. gingivalis was enriched in periodontitis and closely associated with subgingival microbial dysbiosis, periodontal parameters and cytokines in gingival crevicular fluid. Thus, it may be an important pathogen in periodontal disease.

Do Oral Pathogens Inhabit the Eye and Play a Role in Ocular Diseases?

Fascinatingly, the immune-privileged healthy eye has a small unique population of microbiota. The human microbiome project led to continuing interest in the ocular microbiome. Typically, ocular microflorae are commensals of low diversity that colonize the external and internal sites of the eye, without instigating any disorders. Ocular commensals modulate immunity and optimally regulate host defense against pathogenic invasion, both on the ocular surface and neuroretina. Yet, any alteration in this symbiotic relationship culminates in the perturbation of ocular homeostasis and shifts the equilibrium toward local or systemic inflammation and, in turn, impaired visual function. A compositional variation in the ocular microbiota is associated with surface disorders such as keratitis, blepharitis, and conjunctivitis. Nevertheless, innovative studies now implicate non-ocular microbial dysbiosis in glaucoma, age-related macular degeneration (AMD), uveitis, and diabetic retinopathy. Accordingly, prompt identification of the extra-ocular etiology and a methodical understanding of the mechanisms of invasion and host-microbial interaction is of paramount importance for preventative and therapeutic interventions for vision-threatening conditions. This review article aims to explore the current literature evidence to better comprehend the role of oral pathogens in the etiopathogenesis of ocular diseases, specifically AMD.

Dendritic cells a critical link to alveolar bone loss and systemic disease risk in periodontitis: Immunotherapeutic implications

Extensive research in humans and animal models has begun to unravel the complex mechanisms that drive the immunopathogenesis of periodontitis. Neutrophils mount an early and rapid response to the subgingival oral microbiome, producing destructive enzymes to kill microbes. Chemokines and cytokines are released that attract macrophages, dendritic cells, and T cells to the site. Dendritic cells, the focus of this review, are professional antigen-presenting cells on the front line of immune surveillance. Dendritic cells consist of multiple subsets that reside in the epithelium, connective tissues, and major organs. Our work in humans and mice established that myeloid dendritic cells are mobilized in periodontitis. This occurs in lymphoid and nonlymphoid oral tissues, in the bloodstream, and in response to Porphyromonas gingivalis. Moreover, the dendritic cells mature in situ in gingival lamina propria, forming immune conjugates with cluster of differentiation (CD) 4+ T cells, called oral lymphoid foci. At such foci, the decisions are made as to whether to promote bone destructive T helper 17 or bone-sparing regulatory T cell responses. Interestingly, dendritic cells lack potent enzymes and reactive oxygen species needed to kill and degrade endocytosed microbes. The keystone pathogen P. gingivalis exploits this vulnerability by invading dendritic cells in the tissues and peripheral blood using its distinct fimbrial adhesins. This promotes pathogen dissemination and inflammatory disease at distant sites, such as atherosclerotic plaques. Interestingly, our recent studies indicate that such P. gingivalis-infected dendritic cells release nanosized extracellular vesicles called exosomes, in higher numbers than uninfected dendritic cells do. Secreted exosomes and inflammasome-related cytokines are a key feature of the senescence-associated secretory phenotype. Exosomes communicate in paracrine with neighboring stromal cells and immune cells to promote and amplify cellular senescence. We have shown that dendritic cell-derived exosomes can be custom tailored to target and reprogram specific immune cells responsible for inflammatory bone loss in mice. The long-term goal of these immunotherapeutic approaches, ongoing in our laboratory and others, is to promote human health and longevity.

Regulation of olfactomedin 4 by Porphyromonas gingivalis in a community context

At mucosal barriers, the virulence of microbial communities reflects the outcome of both dysbiotic and eubiotic interactions with the host, with commensal species mitigating or potentiating the action of pathogens. We examined epithelial responses to the oral pathogen Porphyromonas gingivalis as a monoinfection and in association with a community partner, Streptococcus gordonii. RNA-Seq of oral epithelial cells showed that the Notch signaling pathway, including the downstream effector olfactomedin 4 (OLFM4), was differentially regulated by P. gingivalis alone; however, regulation was overridden by S. gordonii. OLFM4 was required for epithelial cell migratory, proliferative and inflammatory responses to P. gingivalis. Activation of Notch signaling was induced through increased expression of the Notch1 receptor and the Jagged1 (Jag1) agonist. In addition, Jag1 was released in response to P. gingivalis, leading to paracrine activation. Following Jag1-Notch1 engagement, the Notch1 extracellular domain was cleaved by P. gingivalis gingipain proteases. Antagonism by S. gordonii involved inhibition of gingipain activity by secreted hydrogen peroxide. The results establish a novel mechanism by which P. gingivalis modulates epithelial cell function which is dependent on community context. These interrelationships have relevance for innate inflammatory responses and epithelial cell fate decisions in oral health and disease.

Porphyromonas gingivalis lipopolysaccharide promotes T-hel per17 cell differentiation by upregulating Delta-like ligand 4 expression on CD14+ monocytes

Backgroud

To investigate the effect and mechanism of Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) on Th17 cell differentiation mediated by CD14⁺ monocytes.

Methods

P. gingivalis LPS-activated CD14⁺ monocytes were co-cultured with CD4⁺T cells in different cell ratios. An indirect co-culture system was also established using transwell chambers. Furthermore, anti- Delta-like ligand 4 (Dll-4) antibody was used to investigate the role of Dll-4 in Th17 cell response. The mRNA expression was analyzed using quantitative reverse transcription-polymerase chain reaction, and secreted cytokines in culture supernatant were detected using enzyme-linked immunosorbent assay. Flow cytometry was used to determine the frequencies of Th17 cells. IL-17 protein expression levels were determined using western blotting assay.

Results

P. gingivalis LPS increased the expressions of interleukin (IL)-1β, IL-6, IL-23 and transforming growth factor (TGF)-β in CD14⁺ monocytes. Th17 cell frequency upregulated, which is not solely cytokine-dependent but rather requires cell-cell contact with activated monocytes, particularly in the 1:10 cell ratio. Furthermore, P. gingivalis LPS increased t he expression of Dll-4 on CD14⁺ monocytes, whereas the anti- Dll-4 a ntibody decreased the response of Th17 cells. The results suggest that P. gingivalis LPS enhances Th17 cell response via Dll-4 upregulation on CD14⁺ monocytes.

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.

Eye on the Enigmatic Link: Dysbiotic Oral Pathogens in Ocular Diseases; The Flip Side

Mouth and associated structures were regarded as separate entities from the rest of the body. However, there is a paradigm shift in this conception and oral health is now considered as a fundamental part of overall well-being. In recent years, the subject of oral-foci of infection has attained a resurgence in terms of systemic morbidities while limited observations denote the implication of chronic oral inflammation in the pathogenesis of eye diseases. Hitherto, there is a paucity for mechanistic insights underlying the reported link between periodontal disease (PD) and ocular comorbidities. In light of prevailing scientific evidence, this review article will focus on the understudied theme, that is, the impact of oral dysbiosis in the induction and/or progression of inflammatory eye diseases like diabetic retinopathy, scleritis, uveitis, glaucoma, age-related macular degeneration (AMD). Furthermore, the plausible mechanisms by which periodontal microbiota may trigger immune dysfunction in the Oro-optic-network and promote the development of PD-associated AMD have been discussed.

Proteome Analysis of Molecular Events in Oral Pathogenesis and Virus: A Review with a Particular Focus on Periodontitis

Some systemic diseases are unquestionably related to periodontal health, as periodontal disease can be an extension or manifestation of the primary disease process. One example is spontaneous gingival bleeding, resulting from anticoagulant treatment for cardiac diseases. One important aspect of periodontal therapy is the care of patients with poorly controlled disease who require surgery, such as patients with uncontrolled diabetes. We reviewed research on biomarkers and molecular events for various diseases, as well as candidate markers of periodontal disease. Content of this review: (1) Introduction, (2) Periodontal disease, (3) Bacterial and viral pathogens associated with periodontal disease, (4) Stem cells in periodontal tissue, (5) Clinical applications of mass spectrometry using MALDI-TOF-MS and LC-MS/MS-based proteomic analyses, (6) Proteome analysis of molecular events in oral pathogenesis of virus in GCF, saliva, and other oral Components in periodontal disease, (7) Outlook for the future and (8) Conclusions. This review discusses proteome analysis of molecular events in the pathogenesis of oral diseases and viruses, and has a particular focus on periodontitis.

Herpesvirus-bacteria synergistic interaction in periodontitis

The etiopathogenesis of severe periodontitis includes herpesvirus-bacteria coinfection. This article evaluates the pathogenicity of herpesviruses (cytomegalovirus and Epstein-Barr virus) and periodontopathic bacteria (Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis) and coinfection of these infectious agents in the initiation and progression of periodontitis. Cytomegalovirus and A. actinomycetemcomitans/P. gingivalis exercise synergistic pathogenicity in the development of localized ("aggressive") juvenile periodontitis. Cytomegalovirus and Epstein-Barr virus are associated with P. gingivalis in adult types of periodontitis. Periodontal herpesviruses that enter the general circulation may also contribute to disease development in various organ systems. A 2-way interaction is likely to occur between periodontal herpesviruses and periodontopathic bacteria, with herpesviruses promoting bacterial upgrowth, and bacterial factors reactivating latent herpesviruses. Bacterial-induced gingivitis may facilitate herpesvirus colonization of the periodontium, and herpesvirus infections may impede the antibacterial host defense and alter periodontal cells to predispose for bacterial adherence and invasion. Herpesvirus-bacteria synergistic interactions, are likely to comprise an important pathogenic determinant of aggressive periodontitis. However, mechanistic investigations into the molecular and cellular interaction between periodontal herpesviruses and bacteria are still scarce. Herpesvirus-bacteria coinfection studies may yield significant new discoveries of pathogenic determinants, and drug and vaccine targets to minimize or prevent periodontitis and periodontitis-related systemic diseases.

Exploring the putative interactions between chronic kidney disease and chronic periodontitis

Chronic kidney disease (CKD) and chronic periodontitis (CP) are both common diseases, which are found disproportionately comorbid with each other and have been reported to have a detrimental effect on the progression of each respective disease. They have an overlap in risk factors and both are a source of systemic inflammation along with a wide selection of immunological and non-specific effects that can affect the body over the lifespan of the conditions. Previous studies have investigated the directionality of the relationship between these two diseases; however, there is a lack of literature that has examined how these diseases may be interacting at the localized and systemic level. This review discusses how oral microorganisms have the ability to translocate and have distal effects and provides evidence for microbial involvement in a systemic disease. Furthermore, it summarizes the reported local and systemic effects of CKD and CP and discusses how the interaction of these effects may be responsible for directionality associations reported.

Porphyromonas gingivalis: Immune subversion activities and role in periodontal dysbiosis

Purpose of review

This review summarizes mechanisms by which Porphyromonas gingivalis interacts with community members and the host so that it can persist in the periodontium under inflammatory conditions that drive periodontal disease.

Recent findings

Recent advances indicate that, in great part, the pathogenicity of P. gingivalis is dependent upon its ability to establish residence in the subgingival environment and to subvert innate immunity in a manner that uncouples the nutritionally favorable (for the bacteria) inflammatory response from antimicrobial pathways. While the initial establishment of P. gingivalis is dependent upon interactions with early colonizing bacteria, the immune subversion strategies of P. gingivalis in turn benefit co-habiting species.

Summary

Specific interspecies interactions and subversion of the host response contribute to the emergence and persistence of dysbiotic communities and are thus targets of therapeutic approaches for the treatment of periodontitis.

Roles of Porphyromonas gingivalis and its virulence factors in periodontitis

Periodontitis is an infection-driven inflammatory disease, which is characterized by gingival inflammation and bone loss. Periodontitis is associated with various systemic diseases, including cardiovascular, respiratory, musculoskeletal, and reproductive system related abnormalities. Recent theory attributes the pathogenesis of periodontitis to oral microbial dysbiosis, in which Porphyromonas gingivalis acts as a critical agent by disrupting host immune homeostasis. Lipopolysaccharide, proteases, fimbriae, and some other virulence factors are among the strategies exploited by P. gingivalis to promote the bacterial colonization and facilitate the outgrowth of the surrounding microbial community. Virulence factors promote the coaggregation of P. gingivalis with other bacteria and the formation of dental biofilm. These virulence factors also modulate a variety of host immune components and subvert the immune response to evade bacterial clearance or induce an inflammatory environment. In this chapter, our focus is to discuss the virulence factors of periodontal pathogens, especially P. gingivalis, and their roles in regulating immune responses during periodontitis progression.

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.

Dextran-Coated Zinc-Doped Hydroxyapatite for Biomedical Applications

Dextran-coated zinc-doped hydroxyapatite (ZnHApD) was synthesized by an adapted sol-gel method. The stability of ZnHApD nanoparticles in an aqueous solution was analyzed using ultrasonic measurements. The analysis of the evolution in time of the attenuation for each of the frequencies was performed. The X-ray diffraction (XRD) investigations exhibited that no impurity was found. The morphology, size and size distribution of the ZnHApD sample was investigated by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The TEM and SEM results showed that the ZnHApD particles have an ellipsoidal shape and a narrow distribution of sizes. The cell growth and toxicity of HEK-293 cells were investigated on the ZnHApD solution for four different concentrations and analyzed after 24 and 48 h. The ZnHApD solution presented a non-toxic activity against HEK-293 cells for all analyzed concentrations. The antibacterial assay revealed that all the tested microorganisms were inhibited by the ZnHApD dispersion after 24 and 48 h of incubation. It was observed that the effect of the ZnHApD solution on bacteria growth depended on the bacterial strain. The Porphyromonas gingivalis ATCC 33277 bacterial strain was the most sensitive, as a growth inhibition in the presence of 0.075 μg/mL ZnHApD in the culture medium was observed.

Porphyromonas gingivalis and digestive system cancers

Porphyromonas gingivalis (P. gingivalis) is an anaerobic gram-negative bacterium that colonizes in the epithelium and has been strongly associated with periodontal disease. Recently, various degrees of associations between P. gingivalis and digestive system cancers, including oral squamous cell carcinoma in the oral cavity, oesophageal squamous carcinoma in the digestive tract, and pancreatic cancer in pancreatic tissues, have been displayed in multiple clinical and experimental studies. Since P. gingivalis has a strong association with periodontal diseases, not only the relationships between P. gingivalis and digestive system tumours but also the effects induced by periodontal diseases on cancers are well-illustrated in this review. In addition, the prevention and possible treatments for these digestive system tumours induced by P. gingivalis infection are also included in this review. At the end, we also highlighted the possible mechanisms of cancers caused by P. gingivalis. One important carcinogenic effect of P. gingivalis is inhibiting the apoptosis of epithelial cells, which also plays an intrinsic role in protecting cancerous cells. Some signalling pathways activated by P. gingivalis are involved in cell apoptosis, tumourigenesis, immune evasion and cell invasion of tumour cells. In addition, metabolism of potentially carcinogenic substances caused by P. gingivalis is also one of the connections between this bacterium and cancers.

Polymicrobial synergy within oral biofilm promotes invasion of dendritic cells and survival of consortia members

Years of human microbiome research have confirmed that microbes rarely live or function alone, favoring diverse communities. Yet most experimental host-pathogen studies employ single species models of infection. Here, the influence of three-species oral microbial consortium on growth, virulence, invasion and persistence in dendritic cells (DCs) was examined experimentally in human monocyte-derived dendritic cells (DCs) and in patients with periodontitis (PD). Cooperative biofilm formation by Streptococcus gordonii, Fusobacterium nucleatum and Porphyromonas gingivalis was documented in vitro using growth models and scanning electron microscopy. Analysis of growth rates by species-specific 16s rRNA probes revealed distinct, early advantages to consortium growth for S. gordonii and F. nucleatum with P. gingivalis, while P. gingivalis upregulated its short mfa1 fimbriae, leading to increased invasion of DCs. F. nucleatum was only taken up by DCs when in consortium with P. gingivalis. Mature consortium regressed DC maturation upon uptake, as determined by flow cytometry. Analysis of dental plaques of PD and healthy subjects by 16s rRNA confirmed oral colonization with consortium members, but DC hematogenous spread was limited to P. gingivalis and F. nucleatum. Expression of P. gingivalis mfa1 fimbriae was increased in dental plaques and hematogenous DCs of PD patients. P. gingivalis in the consortium correlated with an adverse clinical response in the gingiva of PD subjects. In conclusion, we have identified polymicrobial synergy in a three-species oral consortium that may have negative consequences for the host, including microbial dissemination and adverse peripheral inflammatory responses.

Kampo Therapies and the Use of Herbal Medicines in the Dentistry in Japan

Dental caries and periodontal disease are two major diseases in the dentistry. As the society is aging, their pathological meaning has been changing. An increasing number of patients are displaying symptoms of systemic disease and so we need to pay more attention to immunologic aggression in our medical treatment. For this reason, we focused on natural products. Kampo consists of natural herbs-roots and barks-and has more than 3000 years of history. It was originated in China as traditional medicine and introduced to Japan. Over the years, Kampo medicine in Japan has been formulated in a way to suit Japan's natural features and ethnic characteristics. Based on this traditional Japanese Kampo medicine, we have manufactured a Kampo gargle and Mastic Gel dentifrice. In order to practically utilize the effectiveness of mastic, we have developed a dentifrice (product name: IMPLA CARE) and treated implant periodontitis and severe periodontitis.

Aberrant Periodontal and Systemic Immune Response of Overweight Rodents to Periodontal Infection

This study aimed to explore periodontal and systemic immune response of overweight hosts to periodontitis. Forty C57 BL/6J male mice were divided into high (HF) or low fat (LF) diet groups and fed with the two diets, respectively, for 8 weeks. Each diet group was then divided into periodontitis (P) or control (C) groups (n = 10 per group) for 10-day ligation or sham-ligation. Overweight-related parameters including body weight were measured. Alveolar bone loss (ABL) was morphometrically analyzed and periodontal osteoclasts were stained. Periodontal immune response including leukocyte and macrophage number and inflammatory cytokines were analyzed by histology and quantitative PCR. Serum cytokine and lipid levels were quantified using electrochemiluminescence immunoassays, enzyme-linked immunosorbent assays, and biochemistry. It was found that HF group had 14.4% body weight gain compared with LF group (P < 0.01). ABL and periodontal osteoclast, leukocyte, and macrophage number were higher in P group than C group regardless of diet (P < 0.05). ABL and periodontal osteoclast number were not affected by diet regardless of ligation or sham-ligation. Leukocyte and macrophage number and protein level of tumor necrosis factor α (TNF-α) in periodontium and serum interleukin-6 level were downregulated by HF diet in periodontitis mice (P < 0.05). Periodontal protein level of TNF-α was highly correlated with serum interleukin-6 and low-density lipoprotein cholesterol levels (P < 0.01). These findings indicated that impaired immune response occurs both periodontally and systemically in preobesity overweight individuals. Given a well-reported exacerbating effect of obesity on periodontitis, overweight, if let uncontrolled, might place the individuals at potential risk for future periodontal tissue damage.

Polyphenols in the prevention and treatment of periodontal disease: A systematic review of in vivo, ex vivo and in vitro studies

Plant-derived polyphenols with antimicrobial and immunomodulatory characteristics appear to provide a variety of oral health benefits. Thus, the aim of the present study was to review the scientific literature to identify these effects of polyphenols on periodontal pathogens and inflammation. A MEDLINE search from 1st January 2013 to 18th January 2018 was performed to identify studies reporting polyphenol-containing plant extracts. Reports regarding pure compounds and essential oils, as well as effects on bacteria that are not defined as periodontal pathogens, were excluded. Thirty-eight studies matched the selection criteria. Studies on immunomodulatory effects included in vitro, ex vivo, and in vivo studies (n = 23), whereas studies reporting antibacterial effects against periodontal pathogens included only in vitro studies (n = 18). Three studies were included in both groups. The antibacterial effects were characterised by inhibition of bacterial growth, adhesion to oral cells, and enzymatic activity. Decreased secretion of pro-inflammatory and increased secretion of anti-inflammatory cytokines were demonstrated. Higher attachment levels, lower inflammation, and bone loss were reported by in vivo studies. Due to the high heterogeneity, it is difficult to draw clear conclusions for applicability; nevertheless, polyphenols have great potential as antimicrobial and immunomodulatory substances in the treatment and prevention of periodontal disease.

Associations Between Poor Oral Health and Risk of Squamous Cell Carcinoma of the Head and Neck: A Meta-Analysis of Observational Studies

PURPOSE

Many epidemiologic studies have reported an association of poor oral health, especially periodontal disease (PD) and tooth loss, with the risk of squamous cell carcinoma of the head and neck (SCCHN). However, these studies have yielded inconsistent results. Therefore, the present study investigated whether poor oral health is an independent predictor of SCCHN through a meta-analysis of observational studies.

MATERIALS AND METHODS

The PubMed, EMBASE, and Cochrane Library databases were systematically searched for relevant observational studies of the association between oral health and risk of SCCHN conducted up to October 2017. The meta-analysis was conducted using STATA 12.0 (StataCorp, College Station, TX). A fixed- or random-effects model was applied to evaluate pooled risk estimates, and sensitivity and subgroup analyses were performed to identify sources of heterogeneity and pooled estimation. Publication bias was assessed using the Begg test, the Egger test, and funnel plots.

RESULTS

Twenty-seven relevant observational studies were identified, consisting of 24 case-and-control studies, 2 prospective studies, and 1 cross-sectional study, with 26,750 participants. Notably, oral health correlated meaningfully with SCCHN (odds ratio [OR] = 2.24; 95% confidence interval [CI], 1.77-2.82). In subgroup analyses, participants with PD (OR = 2.52; 95% CI, 1.43-4.44) had a higher risk of developing SCCHN than those with tooth loss (OR = 2.13; 95% CI, 1.63-2.78). The risk estimates exhibited substantial heterogeneity. Evidence of publication bias was limited.

CONCLUSIONS

The results of this meta-analysis suggest that patients with tooth loss or PD might face a substantial and independent risk of SCCHN, even after adjusting for smoking and alcohol consumption. However, the pooled estimates from observational studies could not establish a causative relation among PD, tooth loss, and SCCHN. Additional investigations of this correlation are warranted.

Clinical and microbiological effects of the supplementary use of an erythritol powder air-polishing device in non-surgical periodontal therapy: a randomized clinical trial

Purpose

This study was undertaken to evaluate the clinical and microbiological effects of an erythritol powder air-polishing device (EPAP) as a supplement to scaling and root planing (SRP) therapy in patients with moderate chronic periodontitis.

Methods

Clinical and microbiological evaluations were performed at 21 sites treated with SRP (control) and 21 sites treated with SRP+EPAP (test). All examinations were performed before treatment, 1 month after treatment, and 3 months after treatment.

Results

There were no significant clinical differences between the test group and the control group. Microbiological analysis revealed that the relative expression level of Porphyromonas gingivalis was significantly lower in the test group than in the control group at 1 month after treatment. Clinical and microbiological results showed improvements at 1 month compared to baseline; in contrast, the results at 3 months after treatment were worse than those at 1 month after treatment.

Conclusions

In this study, both SRP and SRP+EPAP were clinically and microbiologically effective as non-surgical periodontal treatments. In particular, the SRP+EPAP group showed an antimicrobial effect on P. gingivalis, a keystone bacterium associated with the onset of chronic periodontitis, in a short-term period. Periodic periodontal therapy, at intervals of at least every 3 months, is important for sustaining the microbiological effects of this treatment.

Linkage of Infection to Adverse Systemic Complications: Periodontal Disease, Toll-Like Receptors, and Other Pattern Recognition Systems

Toll-like receptors (TLRs) are a group of pattern recognition receptors (PRRs) that provide innate immune sensing of conserved pathogen-associated molecular patterns (PAMPs) to engage early immune recognition of bacteria, viruses, and protozoa. Furthermore, TLRs provide a conduit for initiation of non-infectious inflammation following the sensing of danger-associated molecular patterns (DAMPs) generated as a consequence of cellular injury. Due to their essential role as DAMP and PAMP sensors, TLR signaling also contributes importantly to several systemic diseases including cardiovascular disease, diabetes, and others. The overlapping participation of TLRs in the control of infection, and pathogenesis of systemic diseases, has served as a starting point for research delving into the poorly defined area of infection leading to increased risk of various systemic diseases. Although conflicting studies exist, cardiovascular disease, diabetes, cancer, rheumatoid arthritis, and obesity/metabolic dysfunction have been associated with differing degrees of strength to infectious diseases. Here we will discuss elements of these connections focusing on the contributions of TLR signaling as a consequence of bacterial exposure in the context of the oral infections leading to periodontal disease, and associations with metabolic diseases including atherosclerosis and type 2 diabetes.

Analysis of differential expression of tight junction proteins in cultured oral epithelial cells altered by Porphyromonas gingivalis, Porphyromonas gingivalis lipopolysaccharide, and extracellular adenosine triphosphate

Tight junctions (TJs) are the most apical intercellular junctions of epithelial cells formed by occludin, claudins, junctional adhesion molecules (JAMs), and zonula occludens (ZO). Tight junction proteins can sense the presence of bacteria and regulate the transcription of target genes that encode effectors and regulators of the immune response. The aim of this study was to determine the impact of TJ proteins in response to Porphyromonas gingivalis (P. gingivalis), P. gingivalis lipopolysaccharide (P. gingivalis LPS), and extracellular adenosine triphosphate (ATP) in the oral epithelial cell culture model. Quantified real time-polymerase chain reaction (RT-PCR), immunoblots, and immunostaining were performed to assess the gene and protein expression in TJs. It was found that P. gingivalis infection led to transient upregulation of the genes encoding occludin, claudin-1, and claudin-4 but not JAM-A, claudin-15, or ZO-1, while P. gingivalis LPS increased claudin-1, claudin-15, and ZO-1 and decreased occludin, JAM-A, and claudin-4. Tight junction proteins showed significant upregulation in the above two groups when cells were pretreated with ATP for 3 h. The findings indicated that P. gingivalis induced the host defence responses at an early stage. P. gingivalis LPS exerted a more powerful stimulatory effect on the disruption of the epithelial barrier than P. gingivalis. ATP stimulation enhanced the reaction of TJ proteins to P. gingivalis invasion and LPS destruction of the epithelium.

Kava-241 reduced periodontal destruction in a collagen antibody primed Porphyromonas gingivalis model of periodontitis

AIM

The aim of this study was to evaluate the effect of Kava-241, an optimized Piper methysticum Kava compound, on periodontal destruction in a collagen antibody primed oral gavage model of periodontitis.

METHODS

Experimental periodontitis was induced by oral gavage of Porphyromonas gingivalis (P. gingivalis) + type II collagen antibody (AB) in mice during 15 days. Mice were treated with Kava-241 concomitantly or prior to P. gingivalis gavage and compared to untreated mice. Comprehensive histomorphometric analyses were performed.

RESULTS

Oral gavage with P. gingivalis induced mild epithelial down-growth and alveolar bone loss, while oral gavage with additional AB priming had greater tissular destruction in comparison with gavage alone (p < .05). Kava-241 treatment significantly (p < .05) reduced epithelial down-growth (72%) and alveolar bone loss (36%) in P. gingivalis+AB group. This Kava-241 effect was associated to a reduction in inflammatory cell counts within soft tissues and an increase in fibroblasts (p < .05).

CONCLUSION

Priming with type II collagen antibody with oral gavage is a fast and reproducible model of periodontal destruction adequate for the evaluation of novel therapeutics. The effect of Kava-241 shows promise in the prevention and treatment of inflammation and alveolar bone loss associated with periodontitis. Further experiments are required to determine molecular pathways targeted by this therapeutic agent.

Differential Regulation of Mas-Related G Protein-Coupled Receptor X2-Mediated Mast Cell Degranulation by Antimicrobial Host Defense Peptides and Porphyromonas gingivalis Lipopolysaccharide

Porphyromonas gingivalis is a keystone pathogen that contributes to periodontal pathogenesis by disrupting host-microbe homeostasis and promoting dysbiosis. The virulence of P. gingivalis likely reflects an alteration in the lipid A composition of its lipopolysaccharide (LPS) from the penta-acylated (PgLPS₁₆₉₀) to the tetra-acylated (PgLPS_1435/1449) form. Mast cells play an important role in periodontitis, but the mechanisms of their activation and regulation remain unknown. The expression of epithelium- and neutrophil-derived host defense peptides (HDPs) (LL-37 and human β-defensin-3), which activate mast cells via Mas-related G protein-coupled receptor X2 (MRGPRX2), is increased in periodontitis. We found that MRGPRX2-expressing mast cells are present in normal gingiva and that their numbers are elevated in patients with chronic periodontitis. Furthermore, HDPs stimulated degranulation in a human mast cell line (LAD2) and in RBL-2H3 cells stably expressing MRGPRX2 (RBL-MRGPRX2). PgLPS₁₆₉₀ caused substantial inhibition of HDP-induced mast cell degranulation, but PgLPS_1435/1449 had no effect. A fluorescently labeled HDP (FAM-LL-37) bound to RBL-MRGPRX2 cells, and PgLPS₁₆₉₀ inhibited this binding, but PgLPS_1435/1449 had no effect. These findings suggest that low-level inflammation induced by HDP/MRGPRX2-mediated mast cell degranulation contributes to gingival homeostasis but that sustained inflammation due to elevated levels of both HDPs and MRGPRX2-expressing mast cells promotes periodontal disease. Furthermore, differential regulation of HDP-induced mast cell degranulation by PgLPS₁₆₉₀ and PgLPS_1435/1449 may contribute to the modulation of disease progression.

Crystal structure of Porphyromonas gingivalis dipeptidyl peptidase 4 and structure-activity relationships based on inhibitor profiling

The Gram-negative anaerobe Porphyromonas gingivalis is associated with chronic periodontitis. Clinical isolates of P. gingivalis strains with high dipeptidyl peptidase 4 (DPP4) expression also had a high capacity for biofilm formation and were more infective. The X-ray crystal structure of P. gingivalis DPP4 was solved at 2.2 Å resolution. Despite a sequence identity of 32%, the overall structure of the dimer was conserved between P. gingivalis DPP4 and mammalian orthologues. The structures of the substrate binding sites were also conserved, except for the region called S2-extensive, which is exploited by specific human DPP4 inhibitors currently used as antidiabetic drugs. Screening of a collection of 450 compounds as inhibitors revealed a structure-activity relationship that mimics in part that of mammalian DPP9. The functional similarity between human and bacterial DPP4 was confirmed using 124 potential peptide substrates.

Ubiquitination in Periodontal Disease: A Review

Periodontal disease (periodontitis) is a chronic inflammatory condition initiated by microbial infection that leads to gingival tissue destruction and alveolar bone resorption. The periodontal tissue's response to dental plaque is characterized by the accumulation of polymorphonuclear leukocytes, macrophages, and lymphocytes, all of which release inflammatory mediators and cytokines to orchestrate the immunopathogenesis of periodontal disease. Ubiquitination is achieved by a mechanism that involves a number of factors, including an ubiquitin-activating enzyme, ubiquitin-conjugating enzyme, and ubiquitin-protein ligase. Ubiquitination is a post-translational modification restricted to eukaryotes that are involved in essential host processes. The ubiquitin system has been implicated in the immune response, development, and programmed cell death. Increasing numbers of recent reports have provided evidence that many approaches are delivering promising reports for discovering the relationship between ubiquitination and periodontal disease. The scope of this review was to investigate recent progress in the discovery of ubiquitinated protein in diseased periodontium and to discuss the ubiquitination process in periodontal diseases.

Porphyromonas gingivalis disturbs host-commensal homeostasis by changing complement function

Porphyromonas gingivalis is a Gram-negative anaerobic rod that has been proposed as an orchestrator of complement-dependent dysbiotic inflammation. This notion was suggested from its capacities to manipulate the complement–Toll-like receptor crosstalk in ways that promote dysbiosis and periodontal disease in animal models. Specifically, while at low colonization levels, P. gingivalis interferes with innate immunity and leads to changes in the counts and composition of the oral commensal microbiota. The resulting dysbiotic microbial community causes disruption of host–microbial homeostasis, leading to inflammatory bone loss. These findings suggested that P. gingivalis can be considered as a keystone pathogen. The concept of keystone pathogens is one where their effects have community-wide significance and are disproportionate of their abundance. The present review summarizes the relevant literature and discusses whether the results from the animal models can be extrapolated to man.

Dendritic cells: microbial clearance via autophagy and potential immunobiological consequences for periodontal disease

Dendritic cells are potent antigen‐capture and antigen‐presenting cells that play a key role in the initiation and regulation of the adaptive immune response. This process of immune homeostasis, as maintained by dendritic cells, is susceptible to dysregulation by certain pathogens during chronic infections. Such dysregulation may lead to disease perpetuation with potentially severe systemic consequences. Here we discuss in detail how intracellular pathogens exploit dendritic cells and escape degradation by altering or evading autophagy. This novel mechanism explains, in part, the chronic, persistent nature observed in several immuno‐inflammatory diseases, including periodontal disease. We also propose a hypothetical model of the plausible role of autophagy in the context of periodontal disease. Promotion of autophagy may open new therapeutic strategies in the search of a ‘cure’ for periodontal disease in humans.

Zebrafish as a new model to study effects of periodontal pathogens on cardiovascular diseases

Porphyromonas gingivalis (Pg) is a keystone pathogen in the aetiology of chronic periodontitis. However, recent evidence suggests that the bacterium is also able to enter the bloodstream, interact with host cells and tissues, and ultimately contribute to the pathogenesis of cardiovascular disease (CVD). Here we established a novel zebrafish larvae systemic infection model showing that Pg rapidly adheres to and penetrates the zebrafish vascular endothelium causing a dose- and time-dependent mortality with associated development of pericardial oedemas and cardiac damage. The in vivo model was then used to probe the role of Pg expressed gingipain proteases using systemically delivered gingipain-deficient Pg mutants, which displayed significantly reduced zebrafish morbidity and mortality compared to wild-type bacteria. In addition, we used the zebrafish model to show efficacy of a gingipain inhibitor (KYT) on Pg-mediated systemic disease, suggesting its potential use therapeutically. Our data reveal the first real-time in vivo evidence of intracellular Pg within the endothelium of an infection model and establishes that gingipains are crucially linked to systemic disease and potentially contribute to CVD.

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.

Role of OmpA2 surface regions of Porphyromonas gingivalis in host-pathogen interactions with oral epithelial cells

Outer membrane protein A (OmpA) is a key outer membrane protein found in Gram‐negative bacteria that contributes to several crucial processes in bacterial virulence. In Porphyromonas gingivalis, OmpA is predicted as a heterotrimer of OmpA1 and OmpA2 subunits encoded by adjacent genes. Here we describe the role of OmpA and its individual subunits in the interaction of P. gingivalis with oral cells. Using knockout mutagenesis, we show that OmpA2 plays a significant role in biofilm formation and interaction with human epithelial cells. We used protein structure prediction software to identify extracellular loops of OmpA2, and determined these are involved in interactions with epithelial cells as evidenced by inhibition of adherence and invasion of P. gingivalis by synthetic extracellular loop peptides and the ability of the peptides to mediate interaction of latex beads with human cells. In particular, we observe that OmpA2‐loop 4 plays an important role in the interaction with host cells. These data demonstrate for the first time the important role of P. gingivalis OmpA2 extracellular loops in interaction with epithelial cells, which may help design novel peptide‐based antimicrobial therapies for periodontal disease.

Antimicrobial Efficacy of Various Essential Oils at Varying Concentrations against Periopathogen Porphyromonas gingivalis

INTRODUCTION

Porphyromonas gingivalis (P.gingivalis) is a notorious perio-pathogen with the ability to evade host defense mechanism and invade into the periodontal tissues. Many antimicrobial agents have been tested that curb its growth, although these agents tend to produce side effects such as antibiotic resistance and opportunistic infections. Therefore search for naturally occurring anti-microbials with lesser side effects is the need of the hour.

AIM

The aim of this study was to substantiate the antimicrobial activity of various essential oils; eucalyptus oil, chamomile oil, tea tree oil and turmeric oil against P. gingivalis.

MATERIALS AND METHODS

Pure cultures of P. gingivalis were grown on selective blood agar. Antimicrobial efficacy of various concentrations of essential oils (0%, 25%, 50% and 100%) was assessed via disc diffusion test. Zone of inhibition were measured around disc after 48 hours in millimeters.

RESULTS

Zones of inhibition were directly proportional to the concentration of essential oils tested. At 100% concentration all the tested oils possess antimicrobial activity against P.gingivalis with eucalyptus oil being most effective followed by tea tree oil, chamomile oil and turmeric oil.

CONCLUSION

All essential oils tested were effective against P.gingivalis. After testing for their clinical safety they could be developed into local agents to prevent and treat periodontitis.

Assessment of outer membrane vesicles of periodontopathic bacterium Porphyromonas gingivalis as possible mucosal immunogen

Periodontitis is the most prevalent infectious disease and related to oral and systemic health, therefore novel prophylaxis to prevent the disease is highly desirable. Here, we assessed the outer membrane vesicles (OMVs) of a keystone periodontal pathogen, Porphyromonas gingivalis, as a candidate mucosal immunogen and adjuvant for a periodontitis vaccine. The structural and functional stability of OMVs, demonstrated by proteinase K resistance and ability to withstand long-term storage, are considered advantageous for carrying the OMV components into the host immune system. Intranasal vaccination of OMVs in mice elicited production of P. gingivalis-specific antibodies in blood and saliva by OMVs in a dose-dependent manner, which was dramatically enhanced by addition of a TLR3 agonist, Poly(I:C). Serum samples from mice immunized with OMVs plus Poly(I:C) adjuvant [OMV+Poly(I:C)] showed significant inhibition of gingipain proteolytic activity of not only the vaccine strain, but also heterologous strains. The viability of P. gingivalis was also decreased by preincubation with OMV+Poly(I:C)-immunized sera, while the killing effect was partially blocked by heat-inactivation of the sera. Saliva samples from mice immunized with OMV+Poly(I:C) enhanced bacterial agglutination of both the vaccine and heterologous strains. In an oral infection mouse model, the numbers of P. gingivalis in the oral cavity were significantly decreased in mice intranasally immunized with OMV+Poly(I:C) as compared to mock (only Poly[I:C])-immunized mice. The high levels of serum IgG (including IgG1 and IgG2a) and salivary S-IgA were elicited in mice intranasally immunized with OMV+Poly(I:C), which were maintained for at least 28 and 18weeks, respectively, after immunization. An experiment examining the accumulation of OMVs after intranasal immunization in proximal organs and an intracerebral injection experiment confirmed the safety of OMVs. Based on our results, we propose that intranasal immunization with OMV+Poly(I:C) is a feasible vaccine strategy in the context of bacterial clearance and safety.

Macrophages Play a Key Role in the Obesity-Induced Periodontal Innate Immune Dysfunction via Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3 Pathway

BACKGROUND

Obesity is associated with infiltration of macrophages into adipose tissue. However, effects of obesity on macrophage infiltration and activation in periodontal tissues with periodontitis are still to be elucidated.

METHODS

A diet-induced obesity 16-week mouse model was constructed, and periodontitis was induced by periodontal ligation for 10 days. The model consisted of periodontitis (P) and control (C) groups, with high fat (HF) and normal (N) diet conditions. Bone loss (BL) was analyzed by microcomputed tomography. In periodontal tissues, immunohistochemical staining and quantitative polymerase chain reaction (qPCR) detected expressions of: 1) nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) pathway; 2) macrophage-specific marker (F4/80); and 3) macrophage chemotactic protein 1 (MCP1). Bone marrow-derived macrophages (BMDMs) from the mouse model were stimulated by Porphyromonas gingivalis lipopolysaccharide (LPS) in vitro (NC/NC + LPS: BMDMs from NC group without/with LPS stimulation; HFC/HFC + LPS: BMDMs from HFC group without/with LPS stimulation). Expressions of NLRP3 pathway in BMDMs were detected by immunocytochemical staining and qPCR.

RESULTS

BL increased significantly with periodontitis (NC versus NP; HFC versus HFP) and obesity (NP versus HFP). Expressions of NLRP3 pathway were significantly elevated in gingival tissues with periodontitis (NC versus NP; HFC versus HFP), but not with obesity (NC versus HFC; NP versus HFP). F4/80 and MCP1 expressions were significantly upregulated in gingival tissues with periodontitis (NC versus NP; HFC versus HFP) but significantly downregulated in the context of obesity (NP versus HFP). In vitro, NLRP3 pathway expressions were significantly upregulated in BMDMs after LPS stimulation (NC + LPS versus NC; HFC + LPS versus HFC), but significantly downregulated in HFC groups (HFC versus NC; HFC + LPS versus NC + LPS).

CONCLUSION

Obesity may paralyze innate immune response of periodontium via attenuating infiltration and activation of macrophages and further aggravate periodontal disease.

The GroEL protein of Porphyromonas gingivalis regulates atherogenic phenomena in endothelial cells mediated by upregulating toll-like receptor 4 expression

Porphyromonas gingivalis (P. gingivalis) is a bacterial species that causes periodontitis. GroEL from P. gingivalis may possess biological activity and may be involved in the destruction of periodontal tissues. However, it is unclear whether P. gingivalis GroEL enhances the appearance of atherogenic phenomena in endothelial cells and vessels. Here, we constructed recombinant GroEL from P. gingivalis to investigate its effects in human coronary artery endothelial cells (HCAECs) in vitro and on aortas of high-cholesterol (HC)-fed B57BL/6 and B57BL/6-Tlr4(lps-del) mice in vivo. The results showed that GroEL impaired tube-formation capacity under non-cytotoxic conditions in HCAECs. GroEL increased THP-1 cell/HCAEC adhesion by increasing the expression of intracellular adhesion molecule (ICAM)-1 and vascular adhesion molecule (VCAM)-1 in endothelial cells. Additionally, GroEL increased DiI-oxidized low density lipoprotein (oxLDL) uptake, which may be mediated by elevated lectin-like oxLDL receptor (LOX)-1 but not scavenger receptor expressed by endothelial cells (SREC) and scavenger receptor class B1 (SR-B1) expression. Furthermore, GroEL interacts with toll-like receptor 4 (TLR4) and plays a causal role in atherogenesis in HCAECs. Human antigen R (HuR), an RNA-binding protein with a high affinity for the 3' untranslated region (3'UTR) of TLR4 mRNA, contributes to the up-regulation of TLR4 induced by GroEL in HCAECs. In a GroEL animal administration study, GroEL elevated ICAM-1, VCAM-1, LOX-1 and TLR4 expression in the aortas of HC diet-fed wild C57BL/6 but not C57BL/6-Tlr4(lps-del) mice. Taken together, our findings suggest that P. gingivalis GroEL may contribute to cardiovascular disorders by affecting TLR4 expression.

[Research progress on the relationship between Porphyromonas gingivalis and oral squamous cell carcinoma]

Substantial evidence supports the relationship between chronic inflammation and cancer development. Numerous studies suggest that chronic inflammatory disease, such as periodontitis, contributes to head and neck squamous cell carcinoma development. Oral squamous cell carcinoma (OSCC) is the most common malignant tumor in the oral and maxillofacial regions. Porphyromonas gingivalis, one of the most important pathogens in association with periodontal disease, might have a potential correlation with OSCC. Along with the development of molecular biological techniques, the association between Porphyromonas gingivalis and OSCC has been greatly emphasized in recent years. This review summarizes the association between these variables and the potential mechanisms involved in such relationship.

Gingipains: Critical Factors in the Development of Aspiration Pneumonia Caused by Porphyromonas gingivalis

Aspiration pneumonia is a life-threatening infectious disease often caused by oral anaerobic and periodontal pathogens such as Porphyromonas gingivalis. This organism produces proteolytic enzymes, known as gingipains, which manipulate innate immune responses and promote chronic inflammation. Here, we challenged mice with P. gingivalis W83 and examined the role of gingipains in bronchopneumonia, lung abscess formation, and inflammatory responses. Although gingipains were not required for P. gingivalis colonization and survival in the lungs, they were essential for manifestation of clinical symptoms and infection-related mortality. Pathologies caused by wild-type (WT) P. gingivalis W83, including hemorrhage, necrosis, and neutrophil infiltration, were absent from lungs infected with gingipain-null isogenic strains or WT bacteria preincubated with gingipain-specific inhibitors. Damage to lung tissue correlated with systemic inflammatory responses, as manifested by elevated levels of TNF, IL-6, IL-17, and C-reactive protein. These effects were unequivocally dependent on gingipain activity. Gingipain activity was also implicated in the observed increase in IL-17 in lung tissues. Furthermore, gingipains increased platelet counts in the blood and activated platelets in the lungs. Arginine-specific gingipains made a greater contribution to P. gingivalis-related morbidity and mortality than lysine-specific gingipains. Thus, inhibition of gingipain may be a useful adjunct treatment for P. gingivalis-mediated aspiration pneumonia.

Variants of Porphyromonas gingivalis lipopolysaccharide alter lipidation of autophagic protein, microtubule-associated protein 1 light chain 3, LC3

Porphyromonas gingivalis often subverts host cell autophagic processes for its own survival. Our previous studies document the association of the cargo sorting protein, melanoregulin (MREG), with its binding partner, the autophagic protein, microtubule-associated protein 1 light chain 3 (LC3) in macrophages incubated with P. gingivalis (strain 33277). Differences in the lipid A moiety of lipopolysaccharide (LPS) affect the virulence of P. gingivalis; penta-acylated LPS₁₆₉₀ is a weak Toll-like receptor 4 agonist compared with Escherichia coli LPS, whereas tetra-acylated LPS_1435/1449 acts as an LPS₁₆₉₀ antagonist. To determine how P. gingivalis LPS₁₆₉₀ affects autophagy we assessed LC3-dependent and MREG-dependent processes in green fluorescent protein (GFP)-LC3-expressing Saos-2 cells. LPS₁₆₉₀ stimulated the formation of very large LC3-positive vacuoles and MREG puncta. This LPS₁₆₉₀ -mediated LC3 lipidation decreased in the presence of LPS_1435/1449 . When Saos-2 cells were incubated with P. gingivalis the bacteria internalized but did not traffic to GFP-LC3-positive structures. Nevertheless, increases in LC3 lipidation and MREG puncta were observed. Collectively, these results suggest that P. gingivalis internalization is not necessary for LC3 lipidation. Primary human gingival epithelial cells isolated from patients with periodontitis showed both LC3II and MREG puncta whereas cells from disease-free individuals exhibited little co-localization of these two proteins. These results suggest that the prevalence of a particular LPS moiety may modulate the degradative capacity of host cells, so influencing bacterial survival.

The prevalence rate of Porphyromonas gingivalis and its association with cancer: A systematic review and meta-analysis

It seems that Porphyromanas gingivalis is carcinogenic, because it activates a number of inflammatory immune responses in the host and causes disorders in bacterial clearance mechanisms. There is little information on the prevalence of this bacterium in cancer patients. The aim of this study was to evaluate and compare the prevalence of P. gingivalis in cancer patients by meta-analysis methods.Different databases including PubMed, EMBASE, the Cochrane Library, Scopus, and ISI web of Knowledge were investigated and eight relevant articles published in 2000-2013 were finally analyzed. Data were analyzed by meta-analysis method, fixed effect model. I² statistics were calculated to examine the heterogeneity of papers. The information was analyzed by R and STATA Ver 12.2.A total of 711 people infected with P. gingivalis were included in this study. In total, the prevalence of P. gingivalis was 40.7% (95% CI, 19.3-62.1). The prevalence of P. gingivalis was evaluated in four case-control studies. The results of this study showed that P. gingivalis increased the chance of cancer development and periodontal disease as much as 1.36 times (OR, 1.36; 95%CI, 0.47-3.97).Although there was no significant correlation between P. gingivalis and cancer, this bacterium increased the chance of cancer and periodontal disease and could be considered as a main potential risk factor.

The roles of RgpB and Kgp in late onset gingipain activity in the vimA-defective mutant of Porphyromonas gingivalis W83

Previous studies have shown that VimA, an acetyltransferase, can modulate gingipain biogenesis in Porphyromonas gingivalis. Inactivation of the vimA gene resulted in isogenic mutants that showed a late onset of gingipain activity that only occurred during the stationary growth phase. To further elucidate the role and contribution of the gingipains in this VimA-dependent process, isogenic mutants defective in the gingipain genes in the vimA-deficient genetic background were evaluated. In contrast with the wild-type strain, RgpB and Kgp gingipain activities were absent in exponential phase in the ∆rgpA::tetQ-vimA::ermF mutant. However, these activities increased to 31 and 53%, respectively, of that of the wild-type during stationary phase. In the ∆rgpA::cat-∆kgp::tetQ-vimA::ermF mutant, the RgpB protein was observed in the extracellular fraction but no activity was present even at the stationary growth phase. There was no gingipain activity observed in the ∆rgpB::cat-∆kgp::tetQ-vimA::ermF mutant whereas Kgp activity in ∆rgpA::cat-∆rgpB::tetQ-vimA::ermF mutant was 24% of the wild-type at late stationary phase. In contrast to RgpA, the glycosylation profile of the RgpB catalytic domain from both W83 and P. gingivalis FLL92 (vimA::ermF) showed similarity. Taken together, the results suggest multiple gingipain activation pathways in P. gingivalis. Whereas the maturation pathways for RgpA and RgpB are different, the late-onset gingipain activity in the vimA-defective mutant was due to activation/maturation of RgpB and Kgp. Moreover, unlike RgpA, which is VimA-dependent, the maturation/activation pathways for RgpB and Kgp are interdependent in the absence VimA.

Heritability of periodontal bone loss in mice

BACKGROUND

Periodontitis is an inflammatory disease of the periodontal tissues that compromises tooth support and can lead to tooth loss. Although bacterial biofilm is central in disease pathogenesis, the host response plays an important role in the progression and severity of periodontitis. Indeed, clinical genetic studies indicate that periodontitis is 50% heritable. In this study, we hypothesized that lipopolysaccharide (LPS) injections lead to a strain-dependent periodontal bone loss pattern.

MATERIAL AND METHODS

We utilized five inbred mouse strains that derive the recombinant strains of the hybrid mouse diversity panel. Mice received Porphyromonas gingivalis-LPS injections for 6 wk.

RESULTS AND CONCLUSION

Micro-computed tomography analysis demonstrated a statistically significant strain-dependent bone loss. The most susceptible strain, C57BL/6J, had a fivefold higher LPS-induced bone loss compared to the most resistant strain, A/J. More importantly, periodontal bone loss revealed 49% heritability, which closely mimics periodontitis heritability for patients. To evaluate further the functional differences that underlie periodontal bone loss, osteoclast numbers of C57BL/6J and A/J mice were measured in vivo and in vitro. In vitro analysis of osteoclastogenic potential showed a higher number of osteoclasts in C57BL/6J compared to A/J mice. In vivo LPS injections statistically significantly increased osteoclast numbers in both groups. Importantly, the number of osteoclasts was higher in C57BL/6J vs. A/J mice. These data support a significant role of the genetic framework in LPS-induced periodontal bone loss and the feasibility of utilizing the hybrid mouse diversity panel to determine the genetic factors that affect periodontal bone loss. Expanding these studies will contribute in predicting patients genetically predisposed to periodontitis and in identifying the biological basis of disease susceptibility.