Porphyromonas gingivalis fimbria-dependent activation of inflammatory genes in human aortic endothelial cells

An update on the role and mechanisms of periodontitis in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death worldwide. Despite extensive studies into the causes and therapies for CVDs, their incidence and prevalence continue to increase. Periodontitis is a multifactorial, chronic inflammatory disease related to systemic health. Current research suggests that periodontitis may be an unconventional risk factor for CVDs and it may increase the risk of CVDs such as atherosclerosis, coronary heart disease, myocardial infarction, hypertension, heart failure as well as cardiomyopathy. For all these reasons, it is quite plausible that prevention of periodontitis has an impact on the onset or progression of CVDs. Therefore, in this review, we investigated the association between periodontitis caused by oral microorganisms and different CVDs. In addition, we discuss the various mechanisms by which periodontitis contributes to the onset and progression of CVDs. Our review aims to raise global awareness of periodontitis, particularly its role in CVDs, provide a basis for the prevention and treatment of CVDs and offer potential therapeutic targets.

The role of salivary metabolomics in chronic periodontitis: bridging oral and systemic diseases

BACKGROUND

Chronic periodontitis is a condition impacting approximately 50% of the world's population. As chronic periodontitis progresses, the bacteria in the oral cavity change resulting in new microbial interactions which in turn influence metabolite production. Chronic periodontitis manifests with inflammation of the periodontal tissues, which is progressively developed due to bacterial infection and prolonged bacterial interaction with the host immune response. The bi-directional relationship between periodontitis and systemic diseases has been reported in many previous studies. Traditional diagnostic methods for chronic periodontitis and systemic diseases such as chronic kidney diseases (CKD) have limitations due to their invasiveness, requiring practised individuals for sample collection, frequent blood collection, and long waiting times for the results. More rapid methods are required to detect such systemic diseases, however, the metabolic profiles of the oral cavity first need to be determined.

AIM OF REVIEW

In this review, we explored metabolomics studies that have investigated salivary metabolic profiles associated with chronic periodontitis and systemic illnesses including CKD, oral cancer, Alzheimer's disease, Parkinsons's disease, and diabetes to highlight the most recent methodologies that have been applied in this field.

KEY SCIENTIFIC CONCEPTS OF THE REVIEW

Of the rapid, high throughput techniques for metabolite profiling, Nuclear magnetic resonance (NMR) spectroscopy was the most applied technique, followed by liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS). Furthermore, Raman spectroscopy was the most used vibrational spectroscopic technique for comparison of the saliva from periodontitis patients to healthy individuals, whilst Fourier Transform Infra-Red Spectroscopy (FT-IR) was not utilised as much in this field. A recommendation for cultivating periodontal bacteria in a synthetic medium designed to replicate the conditions and composition of saliva in the oral environment is suggested to facilitate the identification of their metabolites. This approach is instrumental in assessing the potential of these metabolites as biomarkers for systemic illnesses.

Ethanol extract from Astilbe chinensis inflorescence suppresses inflammation in macrophages and growth of oral pathogenic bacteria

Chronic oral inflammation and biofilm-mediated infections drive diseases such as dental caries and periodontitis. This study investigated the anti-inflammatory and antibacterial potential of an ethanol extract from Astilbe chinensis inflorescence (GA-13-6) as a prominent candidate for natural complex substances (NCS) with therapeutic potential. In LPS-stimulated RAW 264.7 macrophages, GA-13-6 significantly suppressed proinflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor (TNF), and nitric oxide (NO), surpassing purified astilbin, a known bioactive compound found in A. chinensis. Furthermore, GA-13-6 downregulated the expression of cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS), indicating an inhibitory effect on the inflammatory cascade. Remarkably, GA-13-6 exhibited selective antibacterial activity against Streptococcus mutans, Streptococcus sanguinis, and Porphyromonas gingivalis, key players in dental caries and periodontitis, respectively. These findings suggest that complex GA-13-6 holds the potential for the treatment or prevention of periodontal and dental diseases, as well as various other inflammation-related conditions, while averting the induction of antibiotic resistance.

Human Coronary Artery Endothelial Cell Response to Porphyromonas gingivalis W83 in a Collagen Three-Dimensional Culture Model

P. gingivalis has been reported to be an endothelial cell inflammatory response inducer that can lead to endothelial dysfunction processes related to atherosclerosis; however, these studies have been carried out in vitro in cell culture models on two-dimensional (2D) plastic surfaces that do not simulate the natural environment where pathology develops. This work aimed to evaluate the pro-inflammatory response of human coronary artery endothelial cells (HCAECs) to P. gingivalis in a 3D cell culture model compared with a 2D cell culture. HCAECs were cultured for 7 days on type I collagen matrices in both cultures and were stimulated at an MOI of 1 or 100 with live P. gingivalis W83 for 24 h. The expression of the genes COX-2, eNOS, and vWF and the levels of the pro-inflammatory cytokines thromboxane A2 (TXA-2) and prostaglandin I2 (PGI2) were evaluated. P. gingivalis W83 in the 2D cell culture increased IL-8 levels at MOI 100 and decreased MCP-1 levels at both MOI 100 and MOI 1. In contrast, the 3D cell culture induced an increased gene expression of COX-2 at both MOIs and reduced MCP-1 levels at MOI 100, whereas the gene expression of eNOS, vWF, and IL-8 and the levels of TXA2 and PGI2 showed no significant changes. These data suggest that in the collagen 3D culture model, P. gingivalis W83 induces a weak endothelial inflammatory response.

The Role of Inflammation in CKD

Chronic kidney disease (CKD) affects many adults worldwide. Persistent low-grade inflammation is a substantial factor in its development and progression and has correlated with increased mortality and cardiovascular problems. This low-grade inflammation is a product of dysregulation of the normal balance between pro- and anti-inflammatory markers. Various factors such as increased innate immune system activation, reactive oxygen species production, periodontal disease, dysregulation of anti-inflammatory systems and intestinal dysbiosis result in the dysregulation of this balance. Furthermore, this low-grade inflammation has down-effects such as hypertension, renal fibrosis and acceleration of renal function decline. Moreover, low-grade inflammation over time has been linked to malignancy in CKD. As CKD progresses, many patients require dialysis, which has a negative bidirectional relationship with persistent inflammation. Treatment options for inflammation in CKD are vast, including cytokine inhibitors, statins and diets. However, more research is needed to create a standardized management plan. In this review, we will examine the normal physiology of the kidney and its relationship with the immune system. We will then delve into the pathology behind persistent inflammation, the various causes of inflammation, the downstream effects of inflammation, dialysis and potential treatments for inflammation in CKD.

Potential Roles of Selectins in Periodontal Diseases and Associated Systemic Diseases: Could They Be Targets for Immunotherapy?

Periodontal diseases are predisposing factors to the development of many systemic disorders, which is often initiated via leukocyte infiltration and vascular inflammation. These diseases could significantly affect human health and quality of life. Hence, it is vital to explore effective therapies to prevent disease progression. Periodontitis, which is characterized by gingival bleeding, disruption of the gingival capillary's integrity, and irreversible destruction of the periodontal supporting bone, appears to be caused by overexpression of selectins in periodontal tissues. Selectins (P-, L-, and E-selectins) are vital members of adhesion molecules regulating inflammatory and immune responses. They are mainly located in platelets, leukocytes, and endothelial cells. Furthermore, selectins are involved in the immunopathogenesis of vascular inflammatory diseases, such as cardiovascular disease, diabetes, cancers, and so on, by mediating leukocyte recruitment, platelet activation, and alteration of endothelial barrier permeability. Therefore, selectins could be new immunotherapeutic targets for periodontal disorders and their associated systemic diseases since they play a crucial role in immune regulation and endothelium dysfunction. However, the research on selectins and their association with periodontal and systemic diseases remains limited. This review aims to discuss the critical roles of selectins in periodontitis and associated systemic disorders and highlights the potential of selectins as therapeutic targets.

Leaky Gum: The Revisited Origin of Systemic Diseases

The oral cavity is the gateway for microorganisms into your body where they disseminate not only to the directly connected respiratory and digestive tracts but also to the many remote organs. Oral microbiota, travelling to the end of the intestine and circulating in our bodies through blood vessels, not only affect a gut microbiome profile but also lead to many systemic diseases. By gathering information accumulated from the era of focal infection theory to the age of revolution in microbiome research, we propose a pivotal role of "leaky gum", as an analogy of "leaky gut", to underscore the importance of the oral cavity in systemic health. The oral cavity has unique structures, the gingival sulcus (GS) and the junctional epithelium (JE) below the GS, which are rarely found anywhere else in our body. The JE is attached to the tooth enamel and cementum by hemidesmosome (HD), which is structurally weaker than desmosome and is, thus, vulnerable to microbial infiltration. In the GS, microbial biofilms can build up for life, unlike the biofilms on the skin and intestinal mucosa that fall off by the natural process. Thus, we emphasize that the GS and the JE are the weakest leaky point for microbes to invade the human body, making the leaky gum just as important as, or even more important than, the leaky gut.

Periodontitis Exacerbates and Promotes the Progression of Chronic Kidney Disease Through Oral Flora, Cytokines, and Oxidative Stress

Periodontitis is a type of systemic immune inflammation that is caused by the complex infection of a variety of microorganisms in the subgingival plaque and the imbalance of the microbial ecological environment in the mouth. Periodontitis and chronic kidney disease (CKD) share many risk factors, such as obesity, smoking, and age. A growing body of data supports a strong correlation between periodontitis and kidney disease. Evidence supports the role of periodontal inflammation and elevated serum inflammatory mediators in renal atherosclerosis, renal deterioration, and end-stage renal disease (ESRD) development. Periodontitis is a risk factor for kidney disease. However, to our knowledge, there are few studies detailing the possible link between periodontitis and CKD. This review summarizes the possible mechanisms underlying periodontitis and CKD. More importantly, it highlights novel and potential pathogenic factors for CKD, including bacteria, pro-inflammatory mediators and oxidative stress. However, most research on the relationship between periodontitis and systemic disease has not determined causality, and these diseases are largely linked by bidirectional associations. Future research will focus on exploring these links to contribute to new treatments for CKD.

Quantitative Detection of Periodontopathogenic Bacteria in Atherosclerotic Plaques from Coronary Arteries by Real-Time PCR

Objectives:

Epidemiologic studies have suggested periodontitis as a risk factor for Coronary Artery Diseas (CAD). Detection of periopathogens in atheromatous plaque provides some evidence for the causal relationship between these two conditions. The aim of this study was to determine the presence and quantity of periopathogens in coronary atherosclerotic plaques in patients undergoing Coronary Artery Bypass Graft (CABG) surgery.

Methods:

20 patients who were candidates for endarterectomy were enrolled in this study for the periodontal examination. Subgingival and coronary atherosclerotic plaque samples were then collected. Thereafter, quantitative detection of Aggregatibacter actinomycetemcomitans (A.a), Porphyromonas gingivali (P.g), and all bacteria detected by Real-Time PCR (RT-PCR) were measured. The correlation analysis was also used to evaluate the relationship between quantities of periopathogens in atherosclerotic and subgingival plaque samples.

Results:

A.a was detected in 13 patients (65%) with subgingival plaques and 4 patients (20%) with atherosclerotic plaques. In addition, P.g was found in 15 patients (75%) with subgingival and 10 patients (50%) with atherosclerotic plaques. A.a represented means of 2.7% and 10.04% of detected bacteria in both atherosclerotic and subgingival plaque samples, respectively. The mean of quantity of P.g was 10.85% and 12.87% of the detected bacteria obtained from atherosclerotic and subginigival samples, respectively. Correlation analysis showed a significant correlation between the quantities of A.a in the atherosclerotic and subgingival plaques, but such a significant relationship was not found for P.g.

Conclusion:

This study confirmed the detection of A.a and P.g in atheromatous plaque. The quantitative data suggested that periopathogens comprise a significant proportion of atherosclerotic plaque microbiome, which may consequently contribute to the development of CAD.

Repeated Porphyromonas gingivalis W83 exposure leads to release pro-inflammatory cytokynes and angiotensin II in coronary artery endothelial cells

The role of Porphyromonas gingivalis (P. gingivalis) or its virulence factors, including lipopolysaccharide (LPS) not only has been related with periodontitis but also with endothelial dysfunction, a key mechanism involved in the genesis of atherosclerosis and hypertension that involving systemic inflammatory markers as angiotensin II (Ang II) and cytokines. This study compares the effect of repeated and unique exposures of P. gingivalis W83 LPS and live bacteria on the production and expression of inflammatory mediators and vasoconstrictor molecules with Ang II. Human coronary artery endothelial cells (HCAEC) were stimulated with purified LPS of P. gingivalis (1.0, 3.5 or 7.0 μg/mL) or serial dilutions of live bacteria (MOI 1: 100 - 1:0,1) at a single or repeated exposure for a time of 24 h. mRNA expression levels of AGTR1, AGTR2, IL-8, IL-1β and MCP-1 were determined by RT-qPCR, and IL-6, MCP-1, IL-8, IL-1β and GM-CSF levels were measured by flow cytometry, ELISA determined Ang II levels. Live bacteria in a single dose increased mRNA levels of AGTR1, and repeated doses increased mRNA levels of IL-8 and IL-1β (p < 0.05). Repeated exposure of live-P. gingivalis induced significant production IL-6, MCP-1 and GM-CSF (p < 0.05). Moreover, these MCP-1, IL-6 and GM-CSF levels were greater than in cells treated with single exposure (p < 0.05), The expression of AGTR1 and production of Ang II induced by live-P. gingivalis W83 showed a vasomotor effect of whole bacteria in HCAEC more than LPS. In conclusion, the findings of this study suggest that repeated exposure of P. gingivalis in HCAEC induces the activation of proinflammatory and vasoconstrictor molecules that lead to endothelial dysfunction being a key mechanism of the onset and progression of arterial hypertension and atherosclerosis.

The Distinct Immune-Stimulatory Capacities of Porphyromonas gingivalis Strains 381 and ATCC 33277 Are Determined by the fimB Allele and Gingipain Activity

The Porphyromonas gingivalis strain ATCC 33277 (33277) and 381 genomes are nearly identical. However, strain 33277 displays a significantly diminished capacity to stimulate host cell Toll-like receptor 2 (TLR2)-dependent signaling and interleukin-1β (IL-1β) production relative to 381, suggesting that there are strain-specific differences in one or more bacterial immune-modulatory factors. Genomic sequencing identified a single nucleotide polymorphism in the 33277 fimB allele (A→T), creating a premature stop codon in the 33277 fimB open reading frame relative to the 381 fimB allele. Gene exchange experiments established that the 33277 fimB allele reduces the immune-stimulatory capacity of this strain. Transcriptome comparisons revealed that multiple genes related to carboxy-terminal domain (CTD) family proteins, including the gingipains, were upregulated in 33277 relative to 381. A gingipain substrate degradation assay demonstrated that cell surface gingipain activity is higher in 33277, and an isogenic mutant strain deficient for the gingipains exhibited an increased ability to induce TLR2 signaling and IL-1β production. Furthermore, 33277 and 381 mutant strains lacking CTD cell surface proteins were more immune-stimulatory than the parental wild-type strains, consistent with an immune-suppressive role for the gingipains. Our data show that the combination of an intact fimB allele and limited cell surface gingipain activity in P. gingivalis 381 renders this strain more immune-stimulatory. Conversely, a defective fimB allele and high-level cell surface gingipain activity reduce the capacity of P. gingivalis 33277 to stimulate host cell innate immune responses. In summary, genomic and transcriptomic comparisons identified key virulence characteristics that confer divergent host cell innate immune responses to these highly related P. gingivalis strains.

Macrophage Migration Inhibitory Factor Levels in Gingival Crevicular Fluid, Saliva, and Serum of Chronic Periodontitis Patients

Chronic periodontitis (CP) is an infection that affects the teeth supporting structure. Macrophage migration inhibitory factor (MIF) is an important effector cytokine of the innate immune system. Due to its functional characteristics, MIF may be involved in the immunopathology of CP. The aim of the present study was to evaluate MIF levels in gingival crevicular fluid (GCF), saliva, and serum of CP patients. A cross-sectional study was conducted on 60 subjects divided into two groups: subjects with CP (n= 30) and periodontally healthy subjects without CP (n=30). MIF was quantified in GCF, saliva, and serum of all participants by enzyme-linked immunosorbent assay. MIF concentrations were higher in GCF, saliva, and serum in the group with CP compared with the group without CP and a higher MIF concentration was observed in GCF (p=0.001) and saliva (p=0.009) in the group with CP. MIF intragroup comparisons between fluids demonstrated significant high levels of MIF in saliva compared with GCF and serum in both study groups (p<0.05). A positive correlation was found between clinical signs and MIF concentration in GCF (p<0.05). There is an association between the MIF and the clinical signs of the disease. Therefore, MIF could have an important role in the pathology and progression of CP.

Pseudomonas aeruginosa Invades Human Aortic Endothelial Cells and Induces Cell Damage in vitro

BACKGROUND

Cardiovascular diseases such as endocarditis are the second most common cause of death worldwide. Infective Endocarditis (IE) is the most severe infection of the heart associated with significant mortality and morbidity. The binding and invasion of Human Aortic Endothelial Cells (HAECs) by pathogenic microbes can play an important role in the pathogenesis of IE.

OBJECTIVE

Pseudomonas aeruginosa is an emerging pathogen that has been associated with IE. However, it is not known whether P. aeruginosa can bind and interact with HAECs. The aim of this study was to determine whether P. aeruginosa can bind and colonize HAECs.

METHODS

The invasion of HAECs by P. aeruginosa was assessed by gentamicin protection assay. Cytokine levels were determined by enzyme-linked Immunosorbent Assay (ELISA) kits. Cell damage was determined by Lactate Dehydrogenase (LDH) assay.

RESULTS

P. aeruginosa can bind and invade HAECs. Infection of HAECs with P. aeruginosa induces TNF-α IL-1β, IL-6 and IL-8 cytokine production leading to the generation of inflammatory milieu that can cause tissue damage as observed in human clinical cases of IE. We also observed that P. aeruginosa induces cell damage in HAECs.

CONCLUSION

In this study, we demonstrate for first time that P. aeruginosa can invade and survive inside HAECs. This cell culture model can be of immense importance to determine the efficacy of drug targets against IE.

Porphyromonas gingivalis can invade periodontal ligament stem cells

Background

Porphyromonas gingivalis is strongly associated with the development, progression, severity and recurrence of periodontitis. Periodontal ligament stem cells (PDLSCs) play an important role in the maintenance of periodontal tissue self-renewal and repair. The purpose of this study was to investigate the ability of P. gingivalis to infect PDLSCs using an in vitro monolayer model.

Methods

We separated and cultured primary PDLSCs using the tissue block with limiting dilution method. The efficiency of P. gingivalis (ATCC 33277) infection of PDLSCs was measured using agar plate culture and quantitative polymerase chain reaction (q-PCR) methods. PDLSCs infected with P. gingivalis were also observed by transmission electron microscopy.

Results

We assessed stem cell properties including cell morphology, clone formation, growth activity, cell surface antigens and multiple differentiation capacity. The infection rates of P. gingivalis in PDLSC at MOIs of 50, 100, 200, and 500 were 5.83%, 8.12%, 7.77% and 7.53% according to the agar plate culture method. By q-PCR, the efficiencies of P. gingivalis infection of PDLSCs at MOIs of 50, 100, 200, and 500 were 6.74%, 10.56%, 10.36% and 9.78%, respectively. Overall, the infection efficiency based on q-PCR was higher than that according to agar plate culture. Using transmission electron microscopy, we verified that P. gingivalis (ATCC 33277) could infect and invade PDLSCs after 2 h of incubation, and endocytic vacuoles were not found surrounding the internalized bacteria.

Conclusions

In conclusion, our data demonstrate that P. gingivalis can invade PDLSCs.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-0950-5) contains supplementary material, which is available to authorized users.

Porphyromonas gingivalis oral infection promote T helper 17/Treg imbalance in the development of atherosclerosis

Background/purpose

Increasing studies have indicated the involvement of Porphyromonas gingivalis in atherosclerosis. T helper 17 (Th17)/Treg balance is critical during atherosclerosis. However, whether P. gingivalis oral infection is associated with Th17/Treg imbalance is unclear. The aim of the present study was to investigate the effect of P. gingivalis on Th17/Treg balance during atherosclerosis.

Materials and methods

ApoE^–/– and C57BL/6 mice were inoculated orally with P. gingivalis ATCC 33277 for 9 weeks. The alveolar bone loss was assessed by microcomputerized tomography. The area of atherosclerosis plaque was identified by oil red O staining. Plaque stability was analyzed by CD68 and αSMA immunohistochemistry staining and Masson staining. The frequency of Th17 and Treg in spleen was detected by flow cytometry. The mRNA expression of Th17- and Treg-related factors was determined by quantitative polymerase chain reaction. Interleukin (IL)-6, a critical factor in modulating T-cell differentiation, was determined from spleen cells and mouse dendritic cells by enzyme-linked immunosorbent assay.

Results

Long-term P. gingivalis oral infection induced alveolar bone resorption. In ApoE^–/– mice, P. gingivalis enhanced atherosclerotic lesion formation and plaque instability accompanied with a decreased Treg frequency and an increased Th17 cell frequency. In addition, mRNA expression of retinoic acid receptor-related orphan receptor γt and IL-17 was increased, and that of transforming growth factor (TGF) β and IL-10 was decreased in P. gingivalis-infected ApoE^–/– mice. Furthermore, secretion of IL-6 was elevated in the spleen of P. gingivalis-infected ApoE^–/– mice, as well as in mouse dendritic cells after P. gingivalis infection.

Conclusion

P. gingivalis oral infection may promote Th17/Treg imbalance by influencing T-cell differentiation during the process of atherosclerosis, with a larger lesion area and decreasing plaque instability.

Characterization of Innate Immune Responses of Human Endothelial Cells Induced by Porphyromonas gingivalis and Their Derived Outer Membrane Vesicles

Atherosclerosis, a chronic inflammatory disease of the blood vessels, is one of the most common causes of morbidity and mortality world-wide. Involvement of Porphyromonas gingivalis in atherosclerosis is supported by observations from epidemiological, clinical, immunological, and molecular studies. Previously we reported that P. gingivalis vesicles have a much higher invasive efficiency than their originating cells. Here, we further compare the role of P. gingivalis cells and their vesicles in expression of chemoattractant proteins including CXCL1, CXCL2, and CXCL8, and adhesive molecules such as E-selectin in human umbilical vein endothelial cells (HUVECs). Both P. gingivalis 33277 cells and vesicles were able to up-regulate expression of these molecules, while the vesicles acted as more potent inducers of the inflammatory response associated with the development of atherosclerosis, consequently resulting in significant monocyte adhesion to a monolayer of HUVECs. Interestingly, we found that elevated expression of CXCL8 and E-selectin in endothelial cells induced by P. gingivalis correlated with the invasive ability of P. gingivalis cells and vesicles. Non-invasive bacterial cells and vesicles had no effect on expression of these genes. This study highlights the potential risk of P. gingivalis cells and vesicles in initiation of atherosclerosis and provides a potential target for the development of novel therapeutics against bacteria-associated atherosclerosis.

Immune dysregulation mediated by the oral microbiome: potential link to chronic inflammation and atherosclerosis

Cardiovascular disease is an inflammatory disorder characterized by the progressive formation of plaque in coronary arteries, termed atherosclerosis. It is a multifactorial disease that is one of the leading causes of death worldwide. Although a number of risk factors have been associated with disease progression, the underlying inflammatory mechanisms contributing to atherosclerosis remain to be fully delineated. Within the last decade, the potential role for infection in inflammatory plaque progression has received considerable interest. Microbial pathogens associated with periodontal disease have been of particular interest due to the high levels of bacteremia that are observed after routine dental procedures and every day oral activities, such as tooth brushing. Here, we explore the potential mechanisms that may explain how periodontal pathogens either directly or indirectly elicit immune dysregulation and consequently progressive inflammation manifested as atherosclerosis. Periodontal pathogens have been shown to contribute directly to atherosclerosis by disrupting endothelial cell function, one of the earliest indicators of cardiovascular disease. Oral infection is thought to indirectly induce elevated production of inflammatory mediators in the systemic circulation. Recently, a number of studies have been conducted focusing on how disruption of the gut microbiome influences the systemic production of proinflammatory cytokines and consequently exacerbation of inflammatory diseases such as atherosclerosis. It is clear that the immune mechanisms leading to atherosclerotic plaque progression, by oral infection, are complex. Understanding the immune pathways leading to disease progression is essential for the future development of anti-inflammatory therapies for this chronic disease.

Periodontal bacterial invasion and infection: contribution to atherosclerotic pathology

OBJECTIVE

The objective of this review was to perform a systematic evaluation of the literature reporting current scientific evidence for periodontal bacteria as contributors to atherosclerosis.

METHODS

Literature from epidemiological, clinical and experimental studies concerning periodontal bacteria and atherosclerosis were reviewed. Gathered data were categorized into seven "proofs" of evidence that periodontal bacteria: 1) disseminate from the oral cavity and reach systemic vascular tissues; 2) can be found in the affected tissues; 3) live within the affected site; 4) invade affected cell types in vitro; 5) induce atherosclerosis in animal models of disease; 6) non-invasive mutants of periodontal bacteria cause significantly reduced pathology in vitro and in vivo; and 7) periodontal isolates from human atheromas can cause disease in animal models of infection.

RESULTS

Substantial evidence for proofs 1 to 6 was found. However, proof 7 has not yet been fulfilled.

CONCLUSIONS

Despite the lack of evidence that periodontal bacteria obtained from human atheromas can cause atherosclerosis in animal models of infection, attainment of proofs 1 to 6 provides support that periodontal pathogens can contribute to atherosclerosis.

Periodontal bacterial invasion and infection: contribution to atherosclerotic pathology

OBJECTIVE

The objective of this review was to perform a systematic evaluation of the literature reporting current scientific evidence for periodontal bacteria as contributors to atherosclerosis.

METHODS

Literature from epidemiological, clinical and experimental studies concerning periodontal bacteria and atherosclerosis were reviewed. Gathered data were categorized into seven "proofs" of evidence that periodontal bacteria: 1) disseminate from the oral cavity and reach systemic vascular tissues; 2) can be found in the affected tissues; 3) live within the affected site; 4) invade affected cell types in vitro; 5) induce atherosclerosis in animal models of disease; 6) non-invasive mutants of periodontal bacteria cause significantly reduced pathology in vitro and in vivo; and 7) periodontal isolates from human atheromas can cause disease in animal models of infection.

RESULTS

Substantial evidence for proofs 1 to 6 was found. However, proof 7 has not yet been fulfilled.

CONCLUSIONS

Despite the lack of evidence that periodontal bacteria obtained from human atheromas can cause atherosclerosis in animal models of infection, attainment proofs 1 to 6 provides support that periodontal pathogens can contribute to atherosclerosis.

Activation and resolution of periodontal inflammation and its systemic impact

Inflammation is a highly organized event impacting upon organs, tissues and biological systems. Periodontal diseases are characterized by dysregulation or dysfunction of resolution pathways of inflammation that results in failure to heal and in a dominant chronic, progressive, destructive and predominantly unresolved inflammation. The biological consequences of inflammatory processes may be independent of the etiological agents, such as trauma, microbial organisms and stress. The impact of the inflammatory pathological process depends upon the tissues or organ system affected. Whilst mediators are similar, there is tissue specificity for the inflammatory events. It is plausible that inflammatory processes in one organ could directly lead to pathologies in another organ or tissue. Communication between distant parts of the body and their inflammatory status is also mediated by common signaling mechanisms mediated via cells and soluble mediators. This review focuses on periodontal inflammation, its systemic associations and advances in therapeutic approaches based on mediators acting through orchestration of natural pathways to resolution of inflammation. We also discuss a new treatment concept in which natural pathways of resolution of periodontal inflammation can be used to limit systemic inflammation and promote healing and regeneration.

Invasion of Porphyromonas gingivalis strains into vascular cells and tissue

Porphyromonas gingivalis is considered a major pathogen in adult periodontitis and is also associated with multiple systemic diseases, for example, cardiovascular diseases. One of its most important virulence factors is invasion of host cells. The invasion process includes attachment, entry/internalization, trafficking, persistence, and exit. The present review discusses these processes related to P. gingivalis in cardiovascular cells and tissue. Although most P. gingivalis strains invade, the invasion capacity of strains and the mechanisms of invasion including intracellular trafficking among them differ. This is consistent with the fact that there are significant differences in the pathogenicity of P. gingivalis strains. P. gingivalis invasion mechanisms are also dependent on types of host cells. Although much is known about the invasion process of P. gingivalis, we still have little knowledge of its exit mechanisms. Nevertheless, it is intriguing that P. gingivalis can remain viable in human cardiovascular cells and atherosclerotic plaque and later exit and re-enter previously uninfected host cells.

Infections and cardiovascular disease: is Bartonella henselae contributing to this matter?

Cardiovascular disease is still the major cause of death worldwide despite the remarkable progress in its prevention and treatment. Endothelial progenitor cells (EPCs) have recently emerged as key players of vascular repair and regenerative medicine applied to cardiovascular disease. A large amount of effort has been put into discovering the factors that could aid or impair the number and function of EPCs, and also into characterizing these cells at the molecular level in order to facilitate their therapeutic applications in vascular disease. Interestingly, the major cardiovascular risk factors have been associated with reduced number and function of EPCs. The bacterial contribution to cardiovascular disease represents a long-standing controversy. The discovery that Bartonella henselae can infect and damage EPCs revitalizes the enduring debate about the microbiological contribution to atherosclerosis, thus allowing the hypothesis that this infection could impair the cardiovascular regenerative potential and increase the risk for cardiovascular disease. In this review, we summarize the rationale suggesting that Bartonella henselae could favour atherogenesis by infecting and damaging EPCs, thus reducing their vascular repair potential. These mechanisms suggest a novel link between communicable and non-communicable human diseases, and put forward the possibility that Bartonella henselae could enhance the susceptibility and worsen the prognosis in cardiovascular disease.

Distinct lipid a moieties contribute to pathogen-induced site-specific vascular inflammation

Several successful pathogens have evolved mechanisms to evade host defense, resulting in the establishment of persistent and chronic infections. One such pathogen, Porphyromonas gingivalis, induces chronic low-grade inflammation associated with local inflammatory bone loss and systemic inflammation manifested as atherosclerosis. P. gingivalis expresses an atypical lipopolysaccharide (LPS) structure containing heterogeneous lipid A species, that exhibit Toll-like receptor-4 (TLR4) agonist or antagonist activity, or are non-activating at TLR4. In this study, we utilized a series of P. gingivalis lipid A mutants to demonstrate that antagonistic lipid A structures enable the pathogen to evade TLR4-mediated bactericidal activity in macrophages resulting in systemic inflammation. Production of antagonistic lipid A was associated with the induction of low levels of TLR4-dependent proinflammatory mediators, failed activation of the inflammasome and increased bacterial survival in macrophages. Oral infection of ApoE^−/− mice with the P. gingivalis strain expressing antagonistic lipid A resulted in vascular inflammation, macrophage accumulation and atherosclerosis progression. In contrast, a P. gingivalis strain producing exclusively agonistic lipid A augmented levels of proinflammatory mediators and activated the inflammasome in a caspase-11-dependent manner, resulting in host cell lysis and decreased bacterial survival. ApoE^−/− mice infected with this strain exhibited diminished vascular inflammation, macrophage accumulation, and atherosclerosis progression. Notably, the ability of P. gingivalis to induce local inflammatory bone loss was independent of lipid A expression, indicative of distinct mechanisms for induction of local versus systemic inflammation by this pathogen. Collectively, our results point to a pivotal role for activation of the non-canonical inflammasome in P. gingivalis infection and demonstrate that P. gingivalis evades immune detection at TLR4 facilitating chronic inflammation in the vasculature. These studies support the emerging concept that pathogen-mediated chronic inflammatory disorders result from specific pathogen-mediated evasion strategies resulting in low-grade chronic inflammation.

Several human pathogens express structurally divergent forms of lipid A, the endotoxic portion of lipopolysaccharide (LPS), as a strategy to evade host innate immune detection and establish persistent infection. Expression of modified lipid A species promotes pathogen evasion of host recognition by Toll-like receptor-4 (TLR4) and the non-canonical inflammasome. The Gram-negative oral anaerobe, Porphyromonas gingivalis, expresses lipid A structures that function as TLR4 agonists or antagonists, or are immunologically inert. It is currently unclear how modulation of P. gingivalis lipid A expression contributes to innate immune recognition, survival, and the ability of the pathogen to induce local and systemic inflammation. In this study, we demonstrate that P. gingivalis expression of antagonist lipid A species results in attenuated production of proinflammatory mediators and evasion of non-canonical inflammasome activation, facilitating bacterial survival in the macrophage. Infection of atherosclerosis-prone ApoE^−/− mice with this strain resulted in progression of chronic inflammation in the vasculature. Notably, the ability of P. gingivalis to induce local inflammatory bone loss was independent of lipid A modifications, supporting distinct mechanisms for induction of local versus systemic inflammation. Our work demonstrates that evasion of immune detection at TLR4 contributes to pathogen persistence and facilitates low-grade chronic inflammation.

Periodontal pathogens and atherosclerosis: implications of inflammation and oxidative modification of LDL

Inflammation is well accepted to play a crucial role in the development of atherosclerotic lesions, and recent studies have demonstrated an association between periodontal disease and cardiovascular disease. Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, causative agents of destructive chronic inflammation in the periodontium, can accelerate atheroma deposition in animal models. Emerging evidence suggests that vaccination against virulence factors of these pathogens and anti-inflammatory therapy may confer disease resistance. In this review, we focus on the role of inflammatory mechanisms and oxidative modification in the formation and activation of atherosclerotic plaques accelerated by P. gingivalis or A. actinomycetemcomitans in an ApoE-deficient mouse model and high-fat-diet-fed mice. Furthermore, we examine whether mucosal vaccination with a periodontal pathogen or the anti-inflammatory activity of catechins can reduce periodontal pathogen-accelerated atherosclerosis.

Prevelance of periodontopathogenic bacteria in subgingival biofilm and atherosclerotic plaques of patients undergoing coronary revascularization surgery

Aim:

The objective of the present study was to detect the presence of specific periodontopathogenic bacteria in the coronary plaque of patients with coronary artery disease and to find out the significant association between the periodontal status and the presence of pathogenic bacteria in the coronary plaque.

Materials and Methods:

The study population consisted of 51 patients with chronic generalized periodontitis undergoing coronary artery bypass grafting. Periodontal parameters were recorded and deoxyribonucleic acid was extracted from the subgingival plaque and coronary atherosclerotic plaque samples of the same patients. Polymerase chain reaction was used to amplify the part of 16S ribosomal ribonucleic acid (rRNA) gene to detect the presence of Aggregatibacter actinomycetemcomitans (Aa), Tannerella forsythia (Tf), Porphyromonas gingivali (Pg), Porphyromonas gingivalis (fimA) gene and Treponema denticola (Td).

Results:

Aa, Tf, Pg, Pg (fimA) gene and Td were detected in 0%, 31.4%, 45.1% 39.2% and 51% of atherosclerotic plaque samples, respectively. Tf was detected in 19.6%, Pg in 39.2%, Pg (fimA) gene in 33.3% and Td in 35.3% of both, subgingival plaque and atherosclerotic plaque samples. Periodontal parameters correlated with the presence of bacteria in coronary plaque. Aa could not be detected in coronary plaque samples.

Conclusions:

The study confirmed the detection of Red complex bacteria in coronary plaque samples and these bacteria correlated with the severity of periodontal destruction.

Porphyromonas gingivalis infection reduces regulatory T cells in infected atherosclerosis patients

Increasing evidence has shown periodontal pathogen Porphyromonas gingivalis (P.gingivalis) infection contributes to atherosclerosis (AS) progression. P.gingivalis fimbriae act as an important virulence factor in AS. Regulatory T cells (Tregs) may play a crucial role in autoimmune response during this process. However, whether P.gingivalis infection is associated with Tregs dysregulation during AS is still unknown and the prevalence of different P.gingivalis FimA genotypes during this process is unclear. Here we analyzed the distribution of Tregs and in P.gingivalis-infected atherosclerotic patients to reveal the relationship between P.gingivalis infection and Tregs reduction/dysfunction and to elucidate their role in periodontitis-AS interaction. FimA genotype was also examined to determine the prevalence of fimbriae. Our results showed that P.gingivalis infection reduced Tregs in atherosclerotic patients compared with non-atherosclerotic patients and health controls. Concentration of TGF-β1, which plays an important role in the development of Tregs, also decreased in P.gingivalis infected patients. Furthermore, type II FimA seems to show higher prevalence than the other five detected types. The population of Tregs further decreased in patients with type II FimA compared with the other types. P.gingivlias FimA genotype II was the dominant type associated with decreased Treg population. These results indicate that P.gingivalis infection may be associated with Tregs dysregulation in AS; type II FimA may be a predominant genotype in this process.

Porphyromonas gingivalis fimbriae

Marginal periodontitis is not a homogeneous disease but is rather influenced by an intricate set of host susceptibility differences as well as diversities in virulence among the harbored organisms. It is likely that clonal heterogeneity of subpopulations with both high and low levels of pathogenicity exists among organisms harbored by individuals with negligible, slight, or even severe periodontal destruction. Therefore, specific virulent clones of periodontal pathogens may cause advanced and/or aggressive periodontitis. Porphyromonas gingivalis is a predominant periodontal pathogen that expresses a number of potential virulence factors involved in the pathogenesis of periodontitis, and accumulated evidence shows that its expression of heterogenic virulence properties is dependent on clonal diversity. Fimbriae are considered to be critical factors that mediate bacterial interactions with and invasion of host tissues, with P. gingivalis shown to express two distinct fimbria-molecules, long and short fimbriae, on the cell surface, both of which seem to be involved in development of periodontitis. Long fimbriae are classified into six types (I to V and Ib) based on the diversity of fimA genes encoding FimA (a subunit of long fimbriae). Studies of clones with type II fimA have revealed their significantly greater adhesive and invasive capabilities as compared to other fimA type clones. Long and short fimbriae induce various cytokine expressions such as IL-1α, IL-β, IL-6, and TNF-α, which result in alveolar bone resorption. Although the clonal diversity of short fimbriae is unclear, distinct short fimbria-molecules have been found in different strains. These fimbriae variations likely influence the development of periodontal disease.

Atherosclerosis and infection: is the jury still not in?

Atherosclerosis is a chronic inflammatory process accounting for increased cardiovascular and cerebrovascular morbidity and mortality. A wealth of recent data has implicated several infectious agents, mainly Chlamydophila pneumoniae, Helicobacter pylori, CMV and periodontal pathogens, in atherosclerosis. Thus, we sought to comprehensively review the available data on the topic, exploring in particular the pathogenetic mechanisms, and discuss anticipated future directions.

Porphyromonas gingivalis strain specific interactions with human coronary artery endothelial cells: a comparative study

Both epidemiologic and experimental findings suggest that infection with Porphyromonas gingivalis exacerbates progression of atherosclerosis. As P. gingivalis exhibits significant strain variation, it is reasonable that different strains possess different capabilities and/or mechanisms by which they promote atherosclerosis. Using P. gingivalis strains that have been previously evaluated in the ApoE null atherosclerosis model, we assessed the ability of W83, A7436, 381, and 33277 to adhere, invade, and persist in human coronary artery endothelial (HCAE) cells. W83 and 381 displayed an equivalent ability to adhere to HCAE cells, which was significantly greater than both A7436 and 33277 (P<0.01). W83, 381, and 33277 were more invasive than A7436 (P<0.0001). However, only W83 and A7436 were able to remain viable up to 48 hours in HCAE cell cultures, whereas 381 was cleared by 48 hours and 33277 was cleared by 24 hours. These differences in persistence were in part due to strain specific differences in intracellular trafficking. Both W83 and 381 trafficked through the autophagic pathway, but not A7436 or 33277. Internalized 381 was the only strain that was dependent upon the autophagic pathway for its survival. Finally, we assessed the efficacy of these strains to activate HCAE cells as defined by production of IL-6, IL-8, IL-12p40, MCP-1, RANTES, TNF-α, and soluble adhesion molecules (sICAM-1, sVCAM-1, and sE-selectin). Only moderate inflammation was observed in cells infected with either W83 or A7436, whereas cells infected with 381 exhibited the most profound inflammation, followed by cells infected with 33277. These results demonstrate that virulence mechanisms among different P. gingivalis strains are varied and that pathogenic mechanisms identified for one strain are not necessarily applicable to other strains.

Trypanosoma cruzi SSP4 Amastigote Protein Induces Expression of Immunoregulatory and Immunosuppressive Molecules in Peripheral Blood Mononuclear Cells

The acute phase of Chagas' disease in mice and human is marked by states of immunosuppression, in which Trypanosoma cruzi replicates extensively and releases immunomodulatory molecules that delay parasite-specific responses mediated by effector T cells. This mechanism of evasion allows the parasite to spread in the host. Parasite molecules that regulate the host immune response during Chagas' disease have not been fully identified, particularly proteins of the amastigote stage. In this work, we evaluated the role of the GPI anchored SSP4 protein of T. cruzi as an immunomodulatory molecule in peripheral blood mononuclear cells (PBMCs). rMBP::SSP4 protein was able to stimulate nitric oxide (NO) production. Likewise, rMBP::SSP4 induced the expression of genes and production of molecules involved in the inflammatory process, such as, cytokines, chemokines, and adhesion molecules (CAMs) as determined by RT-PCR and ELISA. These results suggest that the amastigote SSP4 molecule could play a key role in the immunoregulatory and/or immunosuppressive process observed in the acute phase of infection with T. cruzi.

Pathogen-mediated proteolysis of the cell death regulator RIPK1 and the host defense modulator RIPK2 in human aortic endothelial cells

Porphyromonas gingivalis is the primary etiologic agent of periodontal disease that is associated with other human chronic inflammatory diseases, including atherosclerosis. The ability of P. gingivalis to invade and persist within human aortic endothelial cells (HAEC) has been postulated to contribute to a low to moderate chronic state of inflammation, although how this is specifically achieved has not been well defined. In this study, we demonstrate that P. gingivalis infection of HAEC resulted in the rapid cleavage of receptor interacting protein 1 (RIPK1), a mediator of tumor necrosis factor (TNF) receptor-1 (TNF-R1)-induced cell activation or death, and RIPK2, a key mediator of both innate immune signaling and adaptive immunity. The cleavage of RIPK1 or RIPK2 was not observed in cells treated with apoptotic stimuli, or cells stimulated with agonists to TNF-R1, nucleotide oligomerization domain receptor 1(NOD1), NOD2, Toll-like receptor 2 (TLR2) or TLR4. P. gingivalis-induced cleavage of RIPK1 and RIPK2 was inhibited in the presence of a lysine-specific gingipain (Kgp) inhibitor. RIPK1 and RIPK2 cleavage was not observed in HAEC treated with an isogenic mutant deficient in the lysine-specific gingipain, confirming a role for Kgp in the cleavage of RIPK1 and RIPK2. Similar proteolysis of poly (ADP-ribose) polymerase (PARP) was observed. We also demonstrated direct proteolysis of RIPK2 by P. gingivalis in a cell-free system which was abrogated in the presence of a Kgp-specific protease inhibitor. Our studies thus reveal an important role for pathogen-mediated modification of cellular kinases as a potential strategy for bacterial persistence within target host cells, which is associated with low-grade chronic inflammation, a hallmark of pathogen-mediated chronic inflammatory disorders.

Bacterial invasion of vascular cell types: vascular infectology and atherogenesis

To portray the chronic inflammation in atherosclerosis, leukocytic cell types involved in the immune response to invading pathogens are often the focus. However, atherogenesis is a complex pathological deterioration of the arterial walls, where vascular cell types are participants with regards to deterioration and disease. Since other recent reviews have detailed the role of both the innate and adaptive immune response in atherosclerosis, herein we will summarize the latest developments regarding the association of bacteria with vascular cell types: infections as a risk factor for atherosclerosis; bacterial invasion of vascular cell types; the atherogenic sequelae of bacterial presence such as endothelial activation and blood clotting; and the identification of the species that are able to colonize this niche. The evidence of a polybacterial infectious component of the atheromatous lesions opens the doors for exploration of the new field of vascular infectology and for the study of atherosclerosis microbiome.

Mechanisms involved in the association between periodontal diseases and cardiovascular disease

It is now well accepted that besides the cholesterol associated mechanisms of atherogenesis, inflammation plays a crucial role in all stages of the development of the atherosclerotic lesion. This 'inflammation hypothesis' raises the possibility that through systemic elevations of pro-inflammatory cytokines, periodontal diseases might also contribute to systemic inflammation and, therefore, to atherogenesis. In fact, there is evidence that periodontal diseases are associated with higher systemic levels of high-sensitivity C-reactive protein and a low grade systemic inflammation. This phenomenon has been explained based on mechanisms associated with either the infectious or the inflammatory nature of periodontal diseases. The purposes of this article were to review (1) the evidence suggesting a role for oral bacterial species, particularly periodontal pathogens, in atherogenesis; (2) the potential mechanisms explaining an etiological role for oral bacteria in atherosclerosis; (3) the evidence suggesting that periodontal infections are accompanied by a heightened state of systemic inflammation; (4) the potential sources of systemic inflammatory biomarkers associated with periodontal diseases; and (5) the effects of periodontal therapy on systemic inflammatory biomarkers and cardiovascular risk.

Bacteroides fragilis enterotoxin upregulates intercellular adhesion molecule-1 in endothelial cells via an aldose reductase-, MAPK-, and NF-κB-dependent pathway, leading to monocyte adhesion to endothelial cells

Enterotoxigenic Bacteroides fragilis (ETBF) produces a ∼ 20-kDa heat-labile enterotoxin (BFT) that plays an essential role in mucosal inflammation. Although a variety of inflammatory cells is found at ETBF-infected sites, little is known about leukocyte adhesion in response to BFT stimulation. We investigated whether BFT affected the expression of ICAM-1 and monocytic adhesion to endothelial cells (ECs). Stimulation of HUVECs and rat aortic ECs with BFT resulted in the induction of ICAM-1 expression. Upregulation of ICAM-1 was dependent on the activation of IκB kinase (IKK) and NF-κB signaling. In contrast, suppression of AP-1 did not affect ICAM-1 expression in BFT-stimulated cells. Suppression of NF-κB activity in HUVECs significantly reduced monocytic adhesion, indicating that ICAM-1 expression is indispensable for BFT-induced adhesion of monocytes to the endothelium. Inhibition of JNK resulted in a significant attenuation of BFT-induced ICAM-1 expression in ECs. Moreover, inhibition of aldose reductase significantly reduced JNK-dependent IKK/NF-κB activation, ICAM-1 expression, and adhesion of monocytes to HUVECs. These results suggest that a signaling pathway involving aldose reductase, JNK, IKK, and NF-κB is required for ICAM-1 induction in ECs exposed to BFT, and may be involved in the leukocyte-adhesion cascade following infection with ETBF.

The effect of proatherogenic microbes on macrophage cholesterol homeostasis in apoE-deficient mice

BACKGROUND

Pathogens such as Aggregatibacter actinomycetemcomitans (Aa) and Chlamydia pneumoniae (Cpn) associate with an increased risk for cardiovascular diseases by inducing inflammation. We hypothesized that the pathogens affect the vascular wall by disturbing cholesterol homeostasis and endothelial function.

METHODS

Aa- and Cpn-infections were induced in apoE-deficient mice by intravenous and intranasal applications, respectively. Cholesterol efflux from mouse peritoneal macrophages to apo(lipoprotein)A-I was assessed. The efflux capacity of mouse sera as acceptors of cholesterol from RAW264.7-macrophages was determined. Additionally, endothelial function was studied by following the relaxation capacity of rat mesenteric arteries after incubation in the conditioned culture media of the peritoneal macrophages isolated from the mice.

RESULTS

Infection increased serum phospholipid transfer protein (PLTP) and lipopolysaccharide (LPS) activity, as well as serum amyloid A (SAA) and TNF-α concentrations. Peritoneal macrophages of mice with Aa-infection showed increased cholesterol uptake and reduced cholesterol efflux. Sera of Cpn and Cpn + Aa-infected mice had reduced cholesterol efflux capacity from RAW264.7-macrophages. Conditioned macrophage medium from mice with chronic C. pneumoniae infection induced endothelial dysfunction. Additionally, concentrations of serum adhesion molecules, intercellular adhesion molecule (ICAM) and vascular cell adhesion molecule (VCAM) in Cpn-groups and E-selectin in Cpn + Aa-group, were elevated. The serum markers of endothelial function correlated positively with SAA.

CONCLUSIONS

Aa- and Cpn-infections may generate proatherogenic changes in the vascular wall by affecting the macrophage cholesterol homeostasis and endothelial function.

Periodontal treatment effects on endothelial function and cardiovascular disease biomarkers in subjects with chronic periodontitis: protocol for a randomized clinical trial

Background

Periodontal disease (PD) is an infectious clinical entity characterized by the destruction of supporting tissues of the teeth as the result of a chronic inflammatory response in a susceptible host. It has been proposed that PD as subclinical infection may contribute to the etiology and to the pathogenesis of several systemic diseases including Atherosclerosis. A number of epidemiological studies link periodontal disease/edentulism as independent risk factor for acute myocardial infarction, peripheral vascular disease, and cerebrovascular disease. Moreover, new randomized controlled clinical trials have shown an improvement on cardiovascular surrogate markers (endothelial function, sICAM, hsPCR level, fibrinogen) after periodontal treatment. Nonetheless, such trials are still limited in terms of external validity, periodontal treatment strategies, CONSORT-based design and results consistency/extrapolation. The current study is designed to evaluate if periodontal treatment with scaling and root planning plus local delivered chlorhexidine improves endothelial function and other biomarkers of cardiovascular disease in subjects with moderate to severe periodontitis.

Methods/Design

This randomized, single-blind clinical trial will be performed at two health centers and will include two periodontal treatment strategies. After medical/periodontal screening, a baseline endothelium-dependent brachial artery flow-mediated dilatation (FMD) and other systemic surrogate markers will be obtained from all recruited subjects. Patients then will be randomized to receive either supragingival/subgingival plaque cleaning and calculus removal plus chlorhexidine (treatment group) or supragingival plaque removal only (control group). A second and third FMD will be obtained after 24 hours and 12 weeks in both treatment arms. Each group will consist of 49 patients (n = 98) and all patients will be followed-up for secondary outcomes and will be monitored through a coordinating center. The primary outcomes are FMD differences baseline, 24 hours and 3 months after treatment. The secondary outcomes are differences in C-reactive protein (hs-CRP), glucose serum levels, blood lipid profile, and HOMA index.

Discussion

This RCT is expected to provide more evidence on the effects of different periodontal treatment modalities on FMD values, as well as to correlate such findings with different surrogate markers of systemic inflammation with cardiovascular effects.

Trial registration number

ClinicalTrials.gov Identifier: NCT00681564.

Tannerella forsythia infection-induced calvarial bone and soft tissue transcriptional profiles

Tannerella forsythia is associated with subgingival biofilms in adult periodontitis, although the molecular mechanisms contributing to chronic inflammation and loss of periodontal bone remain unclear. We examined changes in the host transcriptional profiles during a T. forsythia infection using a murine calvarial model of inflammation and bone resorption. Tannerella forsythia was injected into the subcutaneous soft tissue over calvariae of BALB/c mice for 3 days, after which the soft tissues and calvarial bones were excised. RNA was isolated and Murine GeneChip (Affymetrix, Santa Clara, CA) array analysis of transcript profiles showed that 3226 genes were differentially expressed in the infected soft tissues (P < 0.05) and 2586 genes were differentially transcribed in calvarial bones after infection. Quantitative real-time reverse transcription-polymerase chain reaction analysis of transcription levels of selected genes corresponded well with the microarray results. Biological pathways significantly impacted by T. forsythia infection in calvarial bone and soft tissue included leukocyte transendothelial migration, cell adhesion molecules (immune system), extracellular matrix-receptor interaction, adherens junction, and antigen processing and presentation. Histologic examination revealed intense inflammation and increased osteoclasts in calvariae compared with controls. In conclusion, localized T. forsythia infection differentially induces transcription of a broad array of host genes, and the profiles differ between inflamed soft tissues and calvarial bone.

Review: Pathogen-induced inflammation at sites distant from oral infection: bacterial persistence and induction of cell-specific innate immune inflammatory pathways

A hallmark of infection with the gram-negative pathogen Porphyromonas gingivalis is the induction of a chronic inflammatory response. P. gingivalis induces a local chronic inflammatory response that results in oral inflammatory bone destruction, which manifests as periodontal disease. In addition to chronic inflammation at the initial site of infection, mounting evidence has accumulated supporting a role for P. gingivalis-mediated periodontal disease as a risk factor for several systemic diseases including, diabetes, preterm birth, stroke, and atherosclerotic cardiovascular disease. A growing number of in vitro studies have demonstrated that P. gingivalis infection stimulates cell activation commensurate with expected responses paralleling inflammatory atherosclerotic-type responses. Furthermore, various mouse models have been used to examine the ability of P. gingivalis to stimulate chronic inflammatory plaque accumulation and recent studies have pointed to a pivotal role for innate immune signaling via the Toll-like receptors in the chronic inflammation associated with P. gingivalis infection. In this review we discuss the pathogen and host cell specificity of these responses and discuss possible mechanisms by which this oral pathogen can induce and maintain a chronic state of inflammation at sites distant from oral infection.

Immune response of macrophages from young and aged mice to the oral pathogenic bacterium Porphyromonas gingivalis

Periodontal disease is a chronic inflammatory gum disease that in severe cases leads to tooth loss. Porphyromonas gingivalis (Pg) is a bacterium closely associated with generalized forms of periodontal disease. Clinical onset of generalized periodontal disease commonly presents in individuals over the age of 40. Little is known regarding the effect of aging on inflammation associated with periodontal disease. In the present study we examined the immune response of bone marrow derived macrophages (BMM) from young (2-months) and aged (1-year and 2-years) mice to Pg strain 381. Pg induced robust expression of cytokines; tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-10, chemokines; neutrophil chemoattractant protein (KC), macrophage colony stimulating factor (MCP)-1, macrophage inflammatory protein (MIP)-1α and regulated upon activation normal T cell expressed and secreted (RANTES), as well as nitric oxide (NO, measured as nitrite), and prostaglandin E2 (PGE2) from BMM of young mice. BMM from the 2-year age group produced significantly less TNF-α, IL-6 and NO in response to Pg as compared with BMM from 2-months and 1-year of age. We did not observe any difference in the levels of IL-1β, IL-10 and PGE2 produced by BMM in response to Pg. BMM from 2-months and 1-year of age produced similar levels of all chemokines measured with the exception of MCP-1, which was reduced in BMM from 1-year of age. BMM from the 2-year group produced significantly less MCP-1 and MIP-1α compared with 2-months and 1-year age groups. No difference in RANTES production was observed between age groups. Employing a Pg attenuated mutant, deficient in major fimbriae (Pg DPG3), we observed reduced ability of the mutant to stimulate inflammatory mediator expression from BMMs as compared to Pg 381, irrespective of age. Taken together these results support senescence as an important facet of the reduced immunological response observed by BMM of aged host to the periodontal pathogen Pg.

Molecular characterization of Treponema denticola infection-induced bone and soft tissue transcriptional profiles

Treponema denticola is associated with subgingival biofilms in adult periodontitis and with acute necrotizing ulcerative gingivitis. However, the molecular mechanisms by which T. denticola impacts periodontal inflammation and alveolar bone resorption remain unclear. Here, we examined changes in the host transcriptional profiles during a T. denticola infection using a murine calvarial model of inflammation and bone resorption. T. denticola was injected into the subcutaneous soft tissue over the calvaria of BALB/c mice for 3 days, after which the soft tissues and the calvarial bones were excised. RNA was isolated and analysed for transcript profiling using Murine GeneChip arrays. Following T. denticola infection, 2905 and 1234 genes in the infected calvarial bones and soft tissues, respectively, were differentially expressed (P <or= 0.05). Biological pathways significantly impacted by T. denticola infection in calvarial bone and calvarial tissue included leukocyte transendothelial migration, cell adhesion (immune system) molecules, cell cycle, extracellular matrix-receptor interaction, focal adhesion, B-cell receptor signaling and transforming growth factor-beta signaling pathways resulting in proinflammatory, chemotactic effects, and T-cell stimulation. In conclusion, localized T. denticola infection differentially induces transcription of a broad array of host genes, the profiles of which differed between inflamed calvarial bone and soft tissues.

"Gum bug, leave my heart alone!"--epidemiologic and mechanistic evidence linking periodontal infections and atherosclerosis

Evidence from epidemiologic studies suggests that periodontal infections are independently associated with subclinical and clinical atherosclerotic vascular disease. Although the strength of the reported associations is modest, the consistency of the data across diverse populations and a variety of exposure and outcome variables suggests that the findings are not spurious or attributable only to the effects of confounders. Analysis of limited data from interventional studies suggests that periodontal treatment generally results in favorable effects on subclinical markers of atherosclerosis, although such analysis also indicates considerable heterogeneity in responses. Experimental mechanistic in vitro and in vivo studies have established the plausibility of a link between periodontal infections and atherogenesis, and have identified biological pathways by which these effects may be mediated. However, the utilized models are mostly mono-infections of host cells by a limited number of 'model' periodontal pathogens, and therefore may not adequately portray human periodontitis as a polymicrobial, biofilm-mediated disease. Future research must identify in vivo pathways in humans that may (i) lead to periodontitis-induced atherogenesis, or (ii) result in treatment-induced reduction of atherosclerosis risk. Data from these studies will be essential for determining whether periodontal interventions have a role in the primary or secondary prevention of atherosclerosis.

Distribution of Porphyromonas gingivalis fimA genotypes in primary endodontic infections

OBJECTIVE

Long fimbriae (FimA) are important virulence factors of Porphyromonas gingivalis. Based on the diversity of the fimA gene, this species is classified into 6 genotypes. This study surveyed samples from primary endodontic infections for the presence of these P. gingivalis fimA variants.

STUDY DESIGN

Genomic DNA isolated from samples taken from 25 root canals of teeth with chronic apical periodontitis and 25 aspirates from acute apical abscess was used as template in polymerase chain reaction (PCR) assays directed toward the detection of the different P. gingivalis fimA genotypes.

RESULTS

Porphyromonas gingivalis was detected by a 16S rRNA gene-based PCR in 36% of the total number of cases sampled (44% of chronic apical periodontitis and 28% of abscess aspirates). In cases of chronic apical periodontitis, P. gingivalis variant type IV was the most prevalent (24%), followed by types I (20%), II (16%), and III (8%). In acute abscess samples, variant type II was the most prevalent (12%), followed by types III and IV (8% of each) and type I (4%). Combinations of up to 3 different genotypes were detected in a few cases. No single fimA genotype variant or combination thereof was significantly associated with symptoms. Overall, fimA types IV (16%), II (14%), and I (12%) were the most prevalent.

CONCLUSIONS

Findings demonstrated that different P. gingivalis fimA genotypes can be present in primary endodontic infections.

Porphyromonas gingivalis infection-induced tissue and bone transcriptional profiles

Porphyromonas gingivalis has been associated with subgingival biofilms in adult periodontitis. However, the molecular mechanisms of its contribution to chronic gingival inflammation and loss of periodontal structural integrity remain unclear. This investigation aimed to examine changes in the host transcriptional profiles during a P. gingivalis infection using a murine calvarial model of inflammation and bone resorption. P. gingivalis FDC 381 was injected into the subcutaneous soft tissue over the calvaria of BALB/c mice for 3 days, after which the soft tissues and calvarial bones were excised. RNA was isolated from infected soft tissues and calvarial bones and was analysed for transcript profiles using Murine GeneChip((R)) arrays to provide a molecular profile of the events that occur following infection of these tissues. After P. gingivalis infection, 6452 and 2341 probe sets in the infected soft tissues and calvarial bone, respectively, were differentially expressed (P </= 0.05). Biological pathways significantly impacted by P. gingivalis infection in tissues and calvarial bone included cell adhesion (immune system) molecules, Toll-like receptors, B-cell receptor signaling, transforming growth factor-beta cytokine family receptor signaling, and major histocompatibility complex class II antigen processing pathways resulting in proinflammatory, chemotactic effects, T-cell stimulation, and downregulation of antiviral and T-cell chemotactic effects. P. gingivalis-induced inflammation activated osteoclasts, leading to local bone resorption. This is the first in vivo evidence that localized P. gingivalis infection differentially induces transcription of a broad array of host genes, the profiles of which differed between inflamed soft tissues and calvarial bone.

Enhanced monocyte migration and pro-inflammatory cytokine production by Porphyromonas gingivalis infection

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis, a major periodontal pathogen, has been reported to be involved in atherogenesis. In order to further understand this pathogen's link with systemic inflammation and vascular disease, we investigated its influence on murine monocytes and macrophages from three different sources.

MATERIAL AND METHODS

Concanavalin A-elicited peritoneal macrophages, peripheral blood monocyte-derived macrophages and WEHI 274.1 monocytes were infected with either P. gingivalis 381 or its non-invasive fimbriae-deficient mutant, DPG3.

RESULTS

Infection with P. gingivalis 381 markedly induced monocyte migration and significantly enhanced production of the pro-inflammatory cytokines, tumor necrosis factor-alpha and interleukin-6. Consistent with a role for this pathogen's major fimbriae and/or its invasive capacity, infection with DPG3 had a minimal effect on both monocyte attraction and pro-inflammatory cytokine production.

CONCLUSION

Since monocyte recruitment and activation are important steps in the development of vascular inflammation and atherosclerosis, these results suggest that P. gingivalis infection may be involved in these processes.