Effects of Porphyromonas gingivalis antigens and proinflammatory cytokines on human coronary artery endothelial cells

Vitamin D decreases Porphyromonas gingivalis internalized into macrophages by promoting autophagy

OBJECTIVES

This paper aims to study the effect of the active form of vitamin D (calcitriol) on the internalized Porphyromonas gingivalis in macrophages and to assess the role of autophagy during this process.

MATERIALS AND METHODS

Quantitative RT-PCR and bacteria culture were used to quantify live P. gingivalis internalized into U937-derived macrophages. Western blot assays were performed to detect the effect of P. gingivalis and calcitriol on autophagy in macrophages. Transmission electron microscope was used to observe the effect of calcitriol on the status of internalized P. gingivalis. Colocalization of P. gingivalis with the autophagosome and lysosome markers was observed by confocal laser scanning microscopy.

RESULTS

Calcitriol caused a dose-dependent decrease in live P. gingivalis numbers and promoted both the endogenous and P. gingivalis-induced autophagy in macrophages. Calcitriol significantly promoted the destruction of P. gingivalis and the colocalization of P. gingivalis with autophagosome and lysosome markers. Conversely, with 3-MA, live P. gingivalis numbers in macrophages increased significantly and inhibition effect of calcitriol on the number of live P. gingivalis was attenuated.

CONCLUSION

In U937-derived macrophages, calcitriol may promote colocalization of P. gingivalis with autophagosomes and lysosomes, namely autophagy process, to degrade live P. gingivalis.

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.

Eikenella corrodens lipopolysaccharide stimulates the pro-atherosclerotic response in human coronary artery endothelial cells and monocyte adhesion

Eikenella corrodens is a gram-negative bacterium, and although primarily associated with periodontal infections or infective endocarditis, it has been identified in coronary atheromatous plaques. The effect of its lipopolysaccharide (LPS) on human coronary artery endothelial cells (HCAECs) is unknown. Our aim was to examine the mechanism underlying the inflammatory response in HCAECs stimulated with E. corrodens-LPS and to evaluate monocyte adhesion. Endothelial responses were determined by measuring the levels of chemokines and cytokines using flow cytometry. The surface expression of intercellular adhesion molecule 1 (ICAM-1) was determined using a cell-based ELISA, and the adhesion of THP-1 monocytes to HCAECs was also monitored. The involvement of toll-like receptors (TLRs) 2 and 4 was examined using TLR-neutralizing antibodies, and activation of extracellular signal-regulated kinase (ERK)1/2 and nuclear factor-kappa B (NF-κB) p65 were measured by western blotting and ELISA, respectively. Eikenella corrodens-LPS increased secretion of interleukin-8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and granulocyte-macrophage colony-stimulating factor (GM-CSF), and expression of ICAM-1 on the surface of HCAECs, consistent with the increased adhesion of THP-1 cells. Moreover, E. corrodens-LPS interacted with TLR4, a key receptor able to maintain the levels of IL-8, MCP-1, and GM-CSF in HCAECs. Phosphorylation of ERK1/2 and activation of NF-κB p65 were also increased. The results indicate that E. corrodens-LPS activates HCAECs through TLR4, ERK, and NF-κB p65, triggering a pro-atherosclerotic endothelial response and enhancing monocyte adhesion.

Relationship between the burden of major periodontal bacteria and serum lipid profile in a cross-sectional Japanese study

Background

The association of periodontal bacteria with lipid profile alteration remains largely unknown, although it has been suggested that chronic periodontitis increases the atherosclerotic risk. This cross-sectional study investigated the relationship between the prevalence and total burden of periodontal bacteria and serum lipid profile.

Methods

Saliva from enrolled participants was collected to detect 4 major periodontal bacteria (Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Prevotella intermedia) using Polymerase Chain Reaction method. High-density lipoprotein (HDL) cholesterol, triglycerides (TG), and low-density lipoprotein cholesterol were assessed using blood samples. We compared the averages of each lipid in association with the prevalence of each bacterial species, their burden (low, moderate, and high), and the combination of bacterial burden and periodontal status, defined as periodontitis, using the Community Periodontal Index, after adjustment for other potential confounding factors, by employing general linear models with least square means.

Results

A total of 385 Japanese individuals (176 men, 209 women; mean age 69.2 years) were enrolled. The number of bacterial species and their co-existence with periodontitis were significantly related to a decrease in HDL (p for trend < 0.01) and increase in TG (p for trend = 0.04). The adjusted mean HDL levels (mg/dL) in individuals with low, moderate, and high levels of bacterial species were 66.1, 63.0, and 58.9, respectively, and those in the 6 groups defined by combination of the two factors were 67.9, 64.6, 64.3, 65.4, 61.5, and 54.7, respectively.

Conclusion

Periodontal bacterial burden is suggested to be independently involved in lowering serum HDL level. Our findings suggest that bacterial tests in a clinical setting could be a useful approach for predicting the risk of HDL metabolism dysregulation.

The implication of periodontitis in vascular endothelial dysfunction

BACKGROUND

Periodontitis is the most common oral infection seen in humans worldwide. It is characterized by gradual destruction of tooth supporting tissues, eventually leading to loss of tooth. The periodontal biofilm associated with periodontitis comprises of gram-positive and gram-negative bacteria, instrumental for the initiation and progression of periodontitis. Evidence-based literature has identified the nature of periodontal infection as a possible causative condition in the inducement of 'low-grade systemic inflammation and infection'. The periodontal pathogens exert systemic effects via the haematogenous route.

AIM

The present review provides an insight into the pathophysiology of the endothelial dysfunction with reference to periodontal infection and highlights the association between periodontitis and endothelial dysfunction. Various studies addressing the implication of periodontitis on endothelial dysfunction will be described, with a focus of periodontal treatment on improvement of endothelial function.

MATERIALS AND METHODS

Studies examining the effects of periodontitis on vascular endothelial function were segregated. Studies conducted on both animal and human models were identified using MEDLINE database search with key search terms such as 'Periodontitis', 'vascular endothelium', 'endothelial dysfunction', 'periodontal bacteria' and 'periodontal therapy'. Systematic reviews and meta-analysis were also screened. Only studies published in English language were considered. The review has been prepared by screening MEDLINE database from 1989 to 2012.

RESULTS AND CONCLUSIONS

Chronic periodontitis results in altered vascular response, increased expression of pro-inflammatory cytokines and adhesion molecules inducing vascular endothelial dysfunction. Periodontal therapy may ameliorate the perturbed vascular endothelial function.

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.

Effect of nicotine and porphyromonas gingivalis lipopolysaccharide on endothelial cells in vitro

Smoking is considered a significant risk factor for both periodontal disease and cardiovascular disease (CVD). Endothelial cells play an important role in the progression of both diseases. In the present study, we investigated in vitro the impact of nicotine on functional properties of human umbilical vein endothelial cells (HUVECs) stimulated with lipopolysaccharide (LPS) of periodontal pathogen Porphyromonas gingivalis. HUVECs were stimulated with different concentrations of nicotine (10 µM-10 mM) and/or P. gingivalis LPS. Expression levels of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, E-selectin, monocyte chemoattractant protein 1, and interleukin-8 were measured on both gene and protein levels. Cell proliferation/viability, apoptosis, and migration were also investigated. Nicotine at a concentration of 10 mM significantly decreased P. gingivalis LPS-induced expression of all investigated proteins after 4 h stimulation, while lower nicotine concentrations had no significant effect on protein expression with or without P. gingivalis LPS. Proliferation/viability of HUVECs was also significantly inhibited by 10-mM nicotine but not by lower concentrations. Migration of HUVECs was significantly decreased by nicotine at concentrations of 1–10 mM. Nicotine at a concentration similar to that observed in the serum of smokers had no significant effect on the functional properties of HUVECs. However, high concentrations of nicotine, similar to that observed in the oral cavity of smokers, inhibited the inflammatory response of HUVECs. This effect of nicotine might be associated with decreased gingival bleeding indices in smoking periodontitis patients.

miR-584 expressed in human gingival epithelial cells is induced by Porphyromonas gingivalis stimulation and regulates interleukin-8 production via lactoferrin receptor

BACKGROUND

MicroRNAs (miRNAs) are short, non-coding RNAs that are involved in post-transcriptional regulation of gene expression. Differential miRNA expression in innate and acquired immunity has been shown to regulate immune cell development and function. miRNA expression has been demonstrated to affect pathophysiology of inflammatory diseases, such as rheumatoid arthritis and lupus. As such, this study explores the role of miRNA in the context of pathophysiology of destructive periodontitis. Specifically, this investigation profiles the differentially expressed miRNA of Porphyromonas gingivalis (Pg)-stimulated human gingival epithelial cells (HGECs).

METHODS

The specific miRNAs differentially expressed in Pg-stimulated OBA-9, immortalized HGECs, were analyzed using microarray. Real-time polymerase chain reaction (PCR) and Western blotting were performed to confirm the level of miRNA expression and determine target production of miRNA in OBA-9. The production of interleukin (IL)-8 was measured to determine the bioactivity of target protein regulated by miRNA.

RESULTS

miR-584, which targets lactoferrin receptor (LfR), was 3.39-fold upregulated by Pg stimulation. This upregulation of miR-584 was confirmed by real-time PCR. Pg stimulation resulted in the suppression of LfR at mRNA and protein levels. The transfection of the miR inhibitor for miR-584 in OBA-9 recovered Pg-induced suppression of LfR. The addition of human lactoferrin (hLf) had a suppressive effect on IL-8 production in Pg-stimulated OBA-9. However, hLf also decreased IL-8 production strongly in Pg-stimulated OBA-9 in the presence of the miR inhibitor for miR-584.

CONCLUSION

These findings suggest that the upregulation of miR-584 by Pg in OBA-9 inhibits the anti-inflammatory effects of hLf via the suppression of LfR.

Mobilization of endothelial progenitors by recurrent bacteremias with a periodontal pathogen

Background

Periodontal infections are independent risk factors for atherosclerosis. However, the exact mechanisms underlying this link are yet unclear. Here, we evaluate the in vivo effects of bacteremia with a periodontal pathogen on endothelial progenitors, bone marrow-derived cells capable of endothelial regeneration, and delineate the critical pathways for these effects.

Methods

12-week old C57bl6 wildtype or toll-like receptor (TLR)-2 deficient mice were repeatedly intravenously challenged with 10⁹ live P. gingivalis 381 or vehicle. Numbers of Sca1+/flk1+ progenitors, circulating angiogenic cells, CFU-Hill, and late-outgrowth EPC were measured by FACS/culture. Endothelial function was assessed using isolated organ baths, reendothelization was measured in a carotid injury model. RANKL/osteoprotegerin levels were assessed by ELISA/qPCR.

Results

In wildtype mice challenged with intravenous P.gingivalis, numbers of Sca1+/flk1+ progenitors, CAC, CFU-Hill, and late-outgrowth EPC were strongly increased in peripheral circulation and spleen, whereas Sca1+/flk1+ progenitor numbers in bone marrow decreased. Circulating EPCs were functional, as indicated by improved endothelial function and improved reendothelization in infected mice. The osteoprotegerin/RANKL ratio was increased after P. gingivalis challenge in the bone marrow niche of wildtype mice and late-outgrowth EPC in vitro. Conversely, in mice deficient in TLR2, no increase in progenitor mobilization or osteoprotegerin/RANKL ratio was detected.

Conclusion

Recurrent transient bacteremias, a feature of periodontitis, increase peripheral EPC counts and decrease EPC pools in the bone marrow, thereby possibly reducing overall endothelial regeneration capacity, conceivably explaining pro-atherogenic properties of periodontal infections. These effects are seemingly mediated by toll-like receptor (TLR)-2.

Cross-reacting antibacterial auto-antibodies are produced within coronary atherosclerotic plaques of acute coronary syndrome patients

Coronary atherosclerosis, the main condition predisposing to acute myocardial infarction, has an inflammatory component caused by stimuli that are yet unknown. We molecularly investigated the nature of the immune response within human coronary lesion in four coronary plaques obtained by endoluminal atherectomy from four patients. We constructed phage-display libraries containing the IgG1/kappa antibody fragments produced by B-lymphocytes present in each plaque. By immunoaffinity, we selected from these libraries a monoclonal antibody, arbitrarily named Fab7816, able to react both with coronary and carotid atherosclerotic tissue samples. We also demonstrated by confocal microscopy that this monoclonal antibody recognized human transgelin type 1, a cytoskeleton protein involved in atherogenesis, and that it co-localized with fibrocyte-like cells transgelin+, CD68+, CD45+ in human sections of coronary and carotid plaques. In vitro fibrocytes obtained by differentiating CD14+ cells isolated from peripheral blood mononuclear cells also interacted with Fab7816, thus supporting the hypothesis of a specific recognition of fibrocytes into the atherosclerotic lesions. Interestingly, the same antibody, cross-reacted with the outer membrane proteins of Proteus mirabilis and Klebsiella pneumoniae (and possibly with homologous proteins of other enterobacteriaceae present in the microbiota). From all the other three libraries, we were able to clone, by immunoaffinity selection, human monoclonal antibodies cross-reacting with bacterial outer membrane proteins and with transgelin. These findings demonstrated that in human atherosclerotic plaques a local cross-reactive immune response takes place.

Relationship between serum antibody titres to Porphyromonas gingivalis and hs-CRP levels as inflammatory markers of periodontitis

OBJECTIVE

The present study was designed to investigate whether titres of antibody to two strains of Porphyromonas gingivalis, FDC381 and SU63, are associated with serum high-sensitivity C-reactive protein (hs-CRP) levels in Japanese periodontitis patients.

DESIGN

Forty-nine patients with moderate to advanced periodontitis and 40 periodontally healthy control subjects were included in this study. hs-CRP levels and antibody titres to P. gingivalis were measured at baseline and reassessment 3-4 months after periodontal treatment in periodontitis patients as well as at the time of examination in the periodontally healthy subjects. Further, the effect of periodontal therapy, including surgical treatment and use of antibacterials on both markers, was analysed in patients.

RESULTS

hs-CRP levels and antibody titres to P. gingivalis were higher in periodontitis patients than in control subjects, and they significantly decreased following periodontal treatment (p < 0.005). Also, a significant decrease in hs-CRP levels as a result of periodontal treatment was found in patients with hs-CRP levels >1 mgl(-1) at baseline (p < 0.005). Probing depth, clinical attachment level, and alveolar bone loss in patients were significantly associated with a higher antibody titre to both strains of P. gingivalis (p < 0.05), but were not related to hs-CRP levels. No relationship was observed between hs-CRP levels and tertiles as defined by titres of antibody to P. gingivalis strains FDC381 and SU63.

CONCLUSIONS

Our data indicate that hs-CRP levels were independent of antibody titres to P. gingivalis in Japanese periodontitis patients.

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.

"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.

Periodontal disease and risk of atherosclerotic coronary heart disease

Atherosclerosis is an important component of coronary heart disease (CHD), which is the leading cause of death worldwide, including in Japan. Because atherosclerotic processes are typified by chronic inflammatory responses, which are similar to those elicited by chronic infection, the role of infection in promoting or accelerating atherosclerosis has received considerable focus. Increasing evidence supports the notion that periodontitis is associated with increased risk of atherosclerosis through dysfunction of endothelial cells induced by either periodontopathic bacteria or their products, or inflammatory mediators derived from infected periodontal tissue. Here we review whether periodontitis represents a risk factor for CHD or atherosclerosis, particularly in a Japanese population.

Cardiovascular disease and periodontitis: an update on the associations and risk

BACKGROUND

Associations between periodontitis and cardiovascular diseases have been recognized.

MATERIAL AND METHODS

New literature since the last European Workshop on Periodontology has been reviewed.

RESULTS

The lack of reliable epidemiological data on disease prevalence makes an assessment of the associations and risks between periodontitis and cardiovascular diseases difficult. Two recent meta-analysis reports have identified associations between periodontitis and cardiovascular diseases (odds ratios: 1.1-2.2). Different surrogate markers for both disease entities, including serum biomarkers, have been investigated. Brachial artery flow-mediated dilatation, and carotid intima media thickness have in some studies been linked to periodontitis. Studies are needed to confirm early results of improvements of such surrogate markers following periodontal therapy. While intensive periodontal therapy may enhance inflammatory responses and impair vascular functions, studies are needed to assess the outcome of periodontal therapies in subjects with confirmed cardiovascular conditions. Tooth eradication may also reduce the systemic inflammatory burden of individuals with severe periodontitis. The role of confounders remain unclear.

CONCLUSIONS

Periodontitis may contribute to cardiovascular disease and stroke in susceptible subjects. Properly powered longitudinal case-control and intervention trials are needed to identify how periodontitis and periodontal interventions may have an impact on cardiovascular diseases.

Periodontal infections and atherosclerotic vascular disease: an update

The role of periodontal infections as a putative risk factor for atherosclerotic vascular disease (ASVD) has been reported in the literature over the past decade. This review provides insights into biologically plausible pathways that can potentially mediate such an association, and discusses recent findings from epidemiological studies and intervention trials. Accumulating epidemiological evidence suggests that clinical, microbiological and serological markers of periodontal infection are associated with subclinical and manifest ASVD. Early evidence from intervention studies suggests that the control of periodontal infections may result in improved levels of markers of systemic inflammation and measures of endothelial dysfunction. The extent to which the control of periodontal infections results in lower incidence of ASVD events is logistically difficult to assess and has not been addressed in any study so far.

Infection with a periodontal pathogen increases mononuclear cell adhesion to human aortic endothelial cells

BACKGROUND

As a link between periodontal infections and an increased risk for vascular disease has been demonstrated, we assessed the ability of the Gram-negative periodontal pathogen Porphyromonas gingivalis to modulate properties of endothelial cells linked to inflammation and proatherogenic pathways.

METHODS AND RESULTS

Primary human aortic endothelial cells (HAEC) were infected with either P. gingivalis strain 381 or its non-invasive fimbriae-deficient mutant, DPG3, and incubated with U-937 monocytes, or Jurkat T cells. P. gingivalis-infected HAEC demonstrated significantly increased adhesion of immune cells compared to non-infected cells or those infected with DPG3. Heat-killed bacteria had no effect on mononuclear cell adhesion and P. gingivalis LPS had only a minimal effect. P. gingivalis infection significantly increased HAEC expression of VCAM-1, ICAM-1 and E-selectin, and enhanced production of IL-6, IL-8 and MCP-1.

CONCLUSION

These data demonstrate that live invasive P. gingivalis 381 elicits a pro-atherogenic response in HAEC.