Oral infection with a periodontal pathogen accelerates early atherosclerosis in apolipoprotein E-null mice

Active invasion of oral and aortic tissues by Porphyromonas gingivalis in mice causally links periodontitis and atherosclerosis

Atherosclerotic vascular disease is a leading cause of myocardial infarction and cerebrovascular accident, and independent associations with periodontal disease (PD) are reported. PD is caused by polymicrobial infections and aggressive immune responses. Genomic DNA of Porphyromonas gingivalis, the best-studied bacterial pathogen associated with severe PD, is detected within atherosclerotic plaque. We examined causal relationships between chronic P. gingivalis oral infection, PD, and atherosclerosis in hyperlipidemic ApoE^null mice. ApoE^null mice (n = 24) were orally infected with P. gingivalis for 12 and 24 weeks. PD was assessed by standard clinical measurements while the aorta was examined for atherosclerotic lesions and inflammatory markers by array. Systemic inflammatory markers serum amyloid A, nitric oxide, and oxidized low-density lipoprotein were analyzed. P. gingivalis infection elicited specific antibodies and alveolar bone loss. Fluorescent in situ hybridization detected viable P. gingivalis within oral epithelium and aorta, and genomic DNA was detected within systemic organs. Aortic plaque area was significantly increased in P. gingivalis-infected mice at 24 weeks (P<0.01). Aortic RNA and protein arrays indicated a strong Th2 response. Chronic oral infection with P. gingivalis results in a specific immune response, significant increases in oral bone resorption, aortic inflammation, viable bacteria in oral epithelium and aorta, and plaque development.

Porphyromonas gingivalis in periodontal pockets and heart valves

BACKGROUND

There is evidence that advanced infectious chronic periodontal inflammatory disease may have an impact on general health including cardiovascular diseases. The aim of this clinical study was to evaluate the ability of Porphyromonas gingivalis to colonize heart valves and, subsequently, to assess whether there is an association between the presence of the DNA of Porphyromonas gingivalis in periodontal pockets and in degenerated heart valves.

MATERIALS AND METHODS

Thirty patients were enrolled in the study and 31 valve specimens harvested during cardiac surgery operations were examined. All patients underwent a periodontal examination. To evaluate the periodontal status of the patients the following clinical parameters were recorded: the pocket depth, bleeding on probing (BOP) and aproximal plaque index (API). The presence of P. gingivalis in heart valve specimens and samples from periodontal pockets was analyzed using a single-step PCR method.

RESULTS

P. gingivalis DNA was detected in periodontal pockets of 15 patients (50%). However, the DNA of this periopathogen was found neither in the aortic nor in the mitral valve specimens.

CONCLUSIONS

This study suggests that P. gingivalis may not have an influence on the development of the degeneration of aortic and mitral valves.

Human cytomegalovirus-encoded miR-US25-1 aggravates the oxidised low density lipoprotein-induced apoptosis of endothelial cells

Human cytomegalovirus (HCMV) infection is linked to the development and severity of the cardiovascular disease atherosclerosis; however, there is little known about the promotion of atherosclerosis. miR-US25-1 is one of HCMV-encoded miRNAs and targets cellular genes that are essential for virus growth to control the life cycle of the virus and host cells. The prominent regulation on cell cycle genes of the miR-US25-1 attracts us to explore its role in the atherosclerosis promotion. It was indicated that miR-US25-1 level was upregulated in subjects or in endothelial cells with HCMV infection; and the miR-US25-1 downregulated the expression of BRCC 3 by targeting the 5′ UTR of BRCC 3. And a miR-US25-1 mimics transfection could reduce the EAhy926 cell viability but did not induce apoptosis in EAhy926 cells. And what is more, miR-US25-1 mimicis transfection deteriorated the ox-LDL-induced apoptosis and aggravated the upregulation of apoptosis-associated molecules by oxidised low density lipoprotein (ox-LDL) in EAhy926 cells. And we have also confirmed the deregulation of BRCC 3 expression by miR-US25-1 by targeting the 5′ UTR of it. Given the vital role of BRCC 3 in DNA damage repairing, we speculated that the targeting inhibition of BRCC 3 by miR-US25-1 may contribute to the aggravation of ox-LDL-promoted apoptosis of endothelial EAhy926 cells.

Periodontitis as a risk factor of atherosclerosis

Over the last two decades, the amount of evidence corroborating an association between dental plaque bacteria and coronary diseases that develop as a result of atherosclerosis has increased. These findings have brought a new aspect to the etiology of the disease. There are several mechanisms by which dental plaque bacteria may initiate or worsen atherosclerotic processes: activation of innate immunity, bacteremia related to dental treatment, and direct involvement of mediators activated by dental plaque and involvement of cytokines and heat shock proteins from dental plaque bacteria. There are common predisposing factors which influence both periodontitis and atherosclerosis. Both diseases can be initiated in early childhood, although the first symptoms may not appear until adulthood. The formation of lipid stripes has been reported in 10-year-old children and the increased prevalence of obesity in children and adolescents is a risk factor contributing to lipid stripes development. Endothelium damage caused by the formation of lipid stripes in early childhood may lead to bacteria penetrating into blood circulation after oral cavity procedures for children as well as for patients with aggressive and chronic periodontitis.

Invasion of oral and aortic tissues by oral spirochete Treponema denticola in ApoE(-/-) mice causally links periodontal disease and atherosclerosis

Treponema denticola is a predominantly subgingival oral spirochete closely associated with periodontal disease and has been detected in atherosclerosis. This study was designed to evaluate causative links between periodontal disease induced by chronic oral T. denticola infection and atherosclerosis in hyperlipidemic ApoE(-/-) mice. ApoE(-/-) mice (n = 24) were orally infected with T. denticola ATCC 35404 and were euthanized after 12 and 24 weeks. T. denticola genomic DNA was detected in oral plaque samples, indicating colonization of the oral cavity. Infection elicited significantly (P = 0.0172) higher IgG antibody levels and enhanced intrabony defects than sham infection. T. denticola-infected mice had higher levels of horizontal alveolar bone resorption than sham-infected mice and an associated significant increase in aortic plaque area (P ≤ 0.05). Increased atherosclerotic plaque correlated with reduced serum nitric oxide (NO) levels and increased serum-oxidized low-density lipoprotein (LDL) levels compared to those of sham-infected mice. T. denticola infection altered the expression of genes known to be involved in atherosclerotic development, including the leukocyte/endothelial cell adhesion gene (Thbs4), the connective tissue growth factor gene (Ctgf), and the selectin-E gene (Sele). Fluorescent in situ hybridization (FISH) revealed T. denticola clusters in both gingival and aortic tissue of infected mice. This is the first study examining the potential causative role of chronic T. denticola periodontal infection and vascular atherosclerosis in vivo in hyperlipidemic ApoE(-/-) mice. T. denticola is closely associated with periodontal disease and the rapid progression of atheroma in ApoE(-/-) mice. These studies confirm a causal link for active oral T. denticola infection with both atheroma and periodontal disease.

Recent progress in engineering human-associated microbiomes

Recent progress in molecular biology and genetics opens up the possibility of engineering a variety of biological systems, from single-cellular to multicellular organisms. The consortia of microbes that reside on the human body, the human-associated microbiota, are particularly interesting as targets for forward engineering and manipulation due to their relevance in health and disease. New technologies in analysis and perturbation of the human microbiota will lead to better diagnostic and therapeutic strategies against diseases of microbial origin or pathogenesis. Here, we discuss recent advances that are bringing us closer to realizing the true potential of an engineered human-associated microbial community.

Comparison of anti-endotoxin activity of apoE and apoA mimetic derivatives of a model amphipathic peptide 18A

Endotoxemia is a major cause of chronic inflammation, and is an important pathogenic factor in the development of metabolic syndrome and atherosclerosis. Human apolipoprotein E (apoE) and apoA-I are protein components of high-density lipoprotein, which have strong anti-endotoxin activity. Here, we compared anti-endotoxin activity of Ac-hE18A-NH2 and 4F peptides, modified from model amphipathic helical 18A peptide, to mimic, respectively, apoE and apoA-I properties. Ac-hE18A-NH2, stronger than 4F, inhibited endotoxin activity and disaggregated Escherichia coli 055:B5 (wild smooth serotype). Ac-hE18A-NH2 and 4F inhibited endotoxin activity of E. coli 026:B6 (rough-like serotype) to a similar degree. This suggests that Ac-hE18A-NH2 as a dual-domain molecule might interact with both the lipid A and headgroup of smooth LPS, whereas 4F binds lipid A. In C57BL/6 mice, Ac-hE18A-NH2 was superior to 4F in inhibiting the inflammatory responses mediated by E. coli 055:B5, but not E. coli 026:B6. However, in THP-1 cells, isolated human primary leukocytes, and whole human blood, Ac-hE18A-NH2 reduced responses more strongly than 4F to both E. coli serotypes either when peptides were pre-incubated or co-incubated with LPS, indicating that Ac-hE18A-NH2 also has strong anti-inflammatory effects independent of endotoxin-neutralizing properties. In conclusion, Ac-hE18A-NH2 is more effective than 4F in inhibiting LPS-mediated inflammation, which opens prospective clinical applications for Ac-hE18A-NH2.

Changes in clinical and microbiological periodontal profiles relate to progression of carotid intima-media thickness: the Oral Infections and Vascular Disease Epidemiology study

Background

No prospective studies exist on the relationship between change in periodontal clinical and microbiological status and progression of carotid atherosclerosis.

Methods and Results

The Oral Infections and Vascular Disease Epidemiology Study examined 420 participants at baseline (68±8 years old) and follow‐up. Over a 3‐year median follow‐up time, clinical probing depth (PD) measurements were made at 75 766 periodontal sites, and 5008 subgingival samples were collected from dentate participants (average of 7 samples/subject per visit over 2 visits) and quantitatively assessed for 11 known periodontal bacterial species by DNA‐DNA checkerboard hybridization. Common carotid artery intima‐medial thickness (CCA‐IMT) was measured using high‐resolution ultrasound. In 2 separate analyses, change in periodontal status (follow‐up to baseline), defined as (1) longitudinal change in the extent of sites with a ≥3‐mm probing depth (Δ%PD≥3) and (2) longitudinal change in the relative predominance of bacteria causative of periodontal disease over other bacteria in the subgingival plaque (Δetiologic dominance), was regressed on longitudinal CCA‐IMT progression adjusting for age, sex, race/ethnicity, diabetes, smoking status, education, body mass index, systolic blood pressure, and low‐density lipoprotein cholesterol and high‐density lipoprotein cholesterol. Mean (SE) CCA‐IMT increased during follow‐up by 0.139±0.008 mm. Longitudinal IMT progression attenuated with improvement in clinical or microbial periodontal status. Mean CCA‐IMT progression varied inversely across quartiles of longitudinal improvement in clinical periodontal status (Δ%PD≥3) by 0.18 (0.02), 0.16 (0.01), 0.14 (0.01), and 0.07 (0.01) mm (P for trend<0.0001). Likewise, mean CCA‐IMT increased by 0.20 (0.02), 0.18 (0.02), 0.15 (0.02), and 0.12 (0.02) mm (P<0.0001) across quartiles of longitudinal improvement in periodontal microbial status (Δetiologic dominance).

Conclusion

Longitudinal improvement in clinical and microbial periodontal status is related to a decreased rate of carotid artery IMT progression at 3‐year average follow‐up.

Prevalence and severity of oral disease in adults with chronic kidney disease: a systematic review of observational studies

BACKGROUND

Oral disease may be increased in people with chronic kidney disease (CKD) and, due to associations with inflammation and malnutrition, represents a potential modifiable risk factor for cardiovascular disease and mortality. We summarized the prevalence of oral disease in adults with CKD and explored any association between oral disease and mortality.

METHODS

We used systematic review of observational studies evaluating oral health in adults with CKD identified in MEDLINE (through September 2012) without language restriction. We summarized prevalence and associations with all-cause and cardiovascular mortality using random-effects meta-analysis. We explored for sources of heterogeneity between studies using meta-regression.

RESULTS

Eighty-eight studies in 125 populations comprising 11 340 adults were eligible. Edentulism affected one in five adults with CKD Stage 5D (dialysis) {20.6% [95% confidence interval (CI), 16.4-25.6]}. Periodontitis was more common in CKD Stage 5D [56.8% (CI, 39.3-72.8)] than less severe CKD [31.6% (CI, 19.0-47.6)], although data linking periodontitis with premature death were scant. One-quarter of patients with CKD Stage 5D reported never brushing their teeth [25.6% (CI, 10.2-51.1)] and a minority used dental floss [11.4% (CI, 6.2-19.8)]; oral pain was reported by one-sixth [18.7% (CI, 8.8-35.4)], while half of patients experienced a dry mouth [48.4% (CI, 37.5-59.5)]. Data for kidney transplant recipients and CKD Stages 1-5 were limited.

CONCLUSIONS

Oral disease is common in adults with CKD, potentially reflects low use of preventative dental services, and may be an important determinant of health in this clinical setting.

Is obesity a possible modifier of periodontal disease as a chronic inflammatory process? A case-control study

BACKGROUND AND OBJECTIVE

This cross-sectional case-control study was conducted to provide a comparative evaluation of clinical periodontal measurements, together with serum levels of certain bioactive peptides and inflammatory cytokines, in relation to obesity. For this purpose, clinical periodontal measurements and the levels of serum leptin, adiponectin, interleukin-6 (IL-6), C-reactive protein and soluble intercellular adhesion molecule-1 of obese female individuals and their nonobese counterparts were compared.

MATERIAL AND METHODS

Sixty obese (body mass index (BMI) > 30) and 31 nonobese (BMI < 30) female subjects were recruited for the present study. Before any periodontal intervention, serum samples were obtained and full-mouth clinical periodontal measurements were recorded at six sites per tooth. ELISA was used for the biochemical analysis. Data were tested statistically.

RESULTS

Clinical attachment level was significantly higher in the obese group compared with the nonobese control group (p < 0.05). Serum levels of leptin and IL-6 were significantly higher in the obese group (p < 0.05). BMI correlated with the serum levels of inflammatory molecules (p < 0.05), but not with clinical periodontal parameters, in the obese group.

CONCLUSION

In conclusion, obesity does not seem to have a prominent effect on clinical periodontal parameters but it does have many correlations with circulating inflammatory molecules. As suggested in the literature, increased levels of leptin and IL-6 in the obese group might be one explanation for a possible relationship between obesity and periodontal disease. A prospective study is warranted to clarify, in greater detail, the effects of obesity on periodontal health.

Particle-induced pulmonary acute phase response correlates with neutrophil influx linking inhaled particles and cardiovascular risk

BACKGROUND

Particulate air pollution is associated with cardiovascular disease. Acute phase response is causally linked to cardiovascular disease. Here, we propose that particle-induced pulmonary acute phase response provides an underlying mechanism for particle-induced cardiovascular risk.

METHODS

We analysed the mRNA expression of Serum Amyloid A (Saa3) in lung tissue from female C57BL/6J mice exposed to different particles including nanomaterials (carbon black and titanium dioxide nanoparticles, multi- and single walled carbon nanotubes), diesel exhaust particles and airborne dust collected at a biofuel plant. Mice were exposed to single or multiple doses of particles by inhalation or intratracheal instillation and pulmonary mRNA expression of Saa3 was determined at different time points of up to 4 weeks after exposure. Also hepatic mRNA expression of Saa3, SAA3 protein levels in broncheoalveolar lavage fluid and in plasma and high density lipoprotein levels in plasma were determined in mice exposed to multiwalled carbon nanotubes.

RESULTS

Pulmonary exposure to particles strongly increased Saa3 mRNA levels in lung tissue and elevated SAA3 protein levels in broncheoalveolar lavage fluid and plasma, whereas hepatic Saa3 levels were much less affected. Pulmonary Saa3 expression correlated with the number of neutrophils in BAL across different dosing regimens, doses and time points.

CONCLUSIONS

Pulmonary acute phase response may constitute a direct link between particle inhalation and risk of cardiovascular disease. We propose that the particle-induced pulmonary acute phase response may predict risk for cardiovascular disease.

Acute toxicity and the effect of andrographolide on Porphyromonas gingivalis-induced hyperlipidemia in rats

The aim of the current study is to evaluate the effect of andrographolide on hyperlipidemia induced by Porphyromonas gingivalis in rats. Thirty male Sprague Dawley (SD) rats were divided into five groups as follows: group 1 (vehicle) and four experimental groups (groups 2, 3, 4, and 5) were challenged orally with P. gingivalis ATCC 33277 (0.2 mL of 1.5 ×10(12) bacterial cells/mL in 2% carboxymethylcellulose (CMC) with phosphate-buffered saline (PBS)) five times a week for one month to induce hyperlipidemia. Then, group 3 received a standard oral treatment with simvastatin 100 mg/kg, and groups 4 and 5 received oral treatment with andrographolide 20 mg/kg and 10 mg/kg, respectively, for another month. The results showed that total cholesterol (TC), low-density lipoprotein (LDL-C), and triglycerides (TG) were reduced significantly in groups treated with andrographolide. The malondialdehyde (MDA) level was low in treated groups, while antioxidant enzymes, superoxide dismutase (SOD), and glutathione peroxidase (GPx) were significantly increased in these groups (P < 0.05). Liver tissues of the groups treated with andrographolide reduce the accumulation of lipid droplets in hepatic tissue cells. An acute toxicity test did not show any toxicological symptoms in rats.

Level of serum antibody against a periodontal pathogen is associated with atherosclerosis and hypertension

Inflammation has a role in the pathogenesis of atherosclerosis, which causes hypertension. Results from some studies have suggested links between periodontal disease and atherosclerosis, but links between periodontal disease and hypertension have been seldom studied. We investigated whether periodontal disease and serum antibody level were associated with hypertension. We studied 127 patients (93 men and 34 women, mean age 68±9 years) who were admitted with ischemic heart disease to our institution. A composite periodontal risk score was calculated from five periodontal vector scores. The levels of serum antibody against Porphyromonas gingivalis (Pg) were measured. Pulse pressure, mean blood pressure (BP) and pulse wave velocity were used as indices of atherosclerosis. We divided patients into two groups according to the levels of serum antibody against Pg: higher or equal to the median (high Pg antibody group) and lower than the median (low Pg antibody group).There was no difference in the use of antihypertensive agents between the two groups. The composite periodontal risk score (P=0.0003), systolic BP (P=0.030), diastolic BP (P=0.038), pulse pressure (P=0.050) and mean BP (P=0.055) were higher in the high Pg antibody group than in the low Pg antibody group. The composite periodontal risk score (r=0.320, P=0.0003), systolic BP (r=0.212, P=0.017), diastolic BP (r=0.188, P=0.035) and mean BP (r=0.225, P=0.011) correlated with the level of serum antibody against Pg, even after adjustment for age. An elevated antibody level against Pg indicates advanced periodontal disease and suggests advancement of atherosclerosis and hypertension.

Natural killer T cells mediate alveolar bone resorption and a systemic inflammatory response in response to oral infection of mice with Porphyromonas gingivalis

BACKGROUND AND OBJECTIVE

T and B cells are known to be involved in the disease process of periodontitis. However, the role of natural killer T cells in the pathogenesis of periodontitis has not been clarified.

MATERIALS AND METHODS

To examine the role of these cells, C57BL/6J (wild-type), CD1d(-/-) and α-galactosylceramide (αGC)-stimulated wild-type mice were orally infected with Porphyromonas gingivalis strain W83.

RESULTS

Apart from CD1d(-/-) mice, the level of alveolar bone resorption was elevated by the infection and was further accelerated in αGC-stimulated mice. The infection induced elevated levels of serum amyloid A and P. gingivalis-specific IgG in the sera, although the degree of elevation was much smaller in the CD1d(-/-) mice. Infection-induced RANKL elevation was only observed in αGC-stimulated mice. Although the cytokines produced by splenocytes were mainly T-helper 1 type in wild-type mice, those in αGC-stimulated mice were predominantly T-helper 2 type. In the liver, the infection demonstrated no effect on the gene expression for interferon-γ, interleukin-4 and RANKL except αGC-stimulated mice in which the infection upregulated the gene expressions.

CONCLUSION

This study is the first to show that natural killer T cells upregulated systemic and local inflammatory responses induced by oral infection with P. gingivalis, thereby contributing to the progression of alveolar bone resorption.

Discovering medical conditions associated with periodontitis using linked electronic health records

AIM

To use linked electronic medical and dental records to discover associations between periodontitis and medical conditions independent of a priori hypotheses.

MATERIALS AND METHODS

This case-control study included 2475 patients who underwent dental treatment at the College of Dental Medicine at Columbia University and medical treatment at NewYork-Presbyterian Hospital. Our cases are patients who received periodontal treatment and our controls are patients who received dental maintenance but no periodontal treatment. Chi-square analysis was performed for medical treatment codes and logistic regression was used to adjust for confounders.

RESULTS

Our method replicated several important periodontitis associations in a largely Hispanic population, including diabetes mellitus type I (OR = 1.6, 95% CI 1.30-1.99, p < 0.001) and type II (OR = 1.4, 95% CI 1.22-1.67, p < 0.001), hypertension (OR = 1.2, 95% CI 1.10-1.37, p < 0.001), hypercholesterolaemia (OR = 1.2, 95% CI 1.07-1.38, p = 0.004), hyperlipidaemia (OR = 1.2, 95% CI 1.06-1.43, p = 0.008) and conditions pertaining to pregnancy and childbirth (OR = 2.9, 95% CI: 1.32-7.21, p = 0.014). We also found a previously unreported association with benign prostatic hyperplasia (OR = 1.5, 95% CI 1.05-2.10, p = 0.026) after adjusting for age, gender, ethnicity, hypertension, diabetes, obesity, lipid and circulatory system conditions, alcohol and tobacco abuse.

CONCLUSIONS

This study contributes a high-throughput method for associating periodontitis with systemic diseases using linked electronic records.

Polymicrobial infection with major periodontal pathogens induced periodontal disease and aortic atherosclerosis in hyperlipidemic ApoE(null) mice

Periodontal disease (PD) and atherosclerosis are both polymicrobial and multifactorial and although observational studies supported the association, the causative relationship between these two diseases is not yet established. Polymicrobial infection-induced periodontal disease is postulated to accelerate atherosclerotic plaque growth by enhancing atherosclerotic risk factors of orally infected Apolipoprotein E deficient (ApoE^null) mice. At 16 weeks of infection, samples of blood, mandible, maxilla, aorta, heart, spleen, and liver were collected, analyzed for bacterial genomic DNA, immune response, inflammation, alveolar bone loss, serum inflammatory marker, atherosclerosis risk factors, and aortic atherosclerosis. PCR analysis of polymicrobial-infected (Porphyromonas gingivalis [P. gingivalis], Treponema denticola [T. denticola], and Tannerella forsythia [T. forsythia]) mice resulted in detection of bacterial genomic DNA in oral plaque samples indicating colonization of the oral cavity by all three species. Fluorescent in situ hybridization detected P. gingivalis and T. denticola within gingival tissues of infected mice and morphometric analysis showed an increase in palatal alveolar bone loss (p<0.0001) and intrabony defects suggesting development of periodontal disease in this model. Polymicrobial-infected mice also showed an increase in aortic plaque area (p<0.05) with macrophage accumulation, enhanced serum amyloid A, and increased serum cholesterol and triglycerides. A systemic infection was indicated by the detection of bacterial genomic DNA in the aorta and liver of infected mice and elevated levels of bacterial specific IgG antibodies (p<0.0001). This study was a unique effort to understand the effects of a polymicrobial infection with P. gingivalis, T. denticola and T. forsythia on periodontal disease and associated atherosclerosis in ApoE^null mice.

Toll-like receptor 2 and palmitic acid cooperatively contribute to the development of nonalcoholic steatohepatitis through inflammasome activation in mice

Innate immune signaling associated with Toll-like receptors (TLRs) is a key pathway involved in the progression of nonalcoholic steatohepatitis (NASH). Here we show that both TLR2 and palmitic acid are required for activation of the inflammasome, interleukin (IL)-1α, and IL-1β, resulting in the progression of NASH. Wild-type (WT) and TLR2(-/-) mice were fed a choline-deficient amino acid-defined (CDAA) diet for 22 weeks to induce NASH. Bone marrow-transplanted TLR2 chimeric mice were generated after the recipient mice were lethally irradiated. Kupffer cells and hepatic stellate cells (HSCs) were isolated from WT mice and stimulated with TLR2 ligand and/or palmitic acid. WT mice on the CDAA diet developed profound steatohepatitis and liver fibrosis. In contrast, TLR2(-/-) mice had suppressed progression of NASH. Although both Kupffer cells and HSCs respond to TLR2 ligand, TLR2 bone marrow chimeric mice demonstrated that Kupffer cells were relatively more important than HSCs in TLR2-mediated progression of NASH. In vitro, palmitic acid alone did not increase TLR2 signaling-target genes, including cytokines and inflammasome components in Kupffer cells and HSCs. The TLR2 ligand increased Nod-like receptor protein 3, an inflammasome component, in Kupffer cells but not in HSCs. In the presence of TLR2 ligand, palmitic acid did induce caspase-1 activation and release of IL-1α and IL-1β in Kupffer cells; however, these effects were not observed in HSCs. In vivo, WT mice on the CDAA diet showed increased caspase-1 activation in the liver and elevated serum levels of IL-1α and IL-1β levels, which were suppressed in TLR2(-/-) mice.

CONCLUSION

TLR2 and palmitic acid cooperatively activate the inflammasome in Kupffer cells and/or macrophages in the development of NASH.

Role of MyD88-dependent and MyD88-independent signaling in Porphyromonas gingivalis-elicited macrophage foam cell formation

Clinical studies and experimental modeling identify a potential link between periodontal disease and periodontal pathogens such as Porphyromonas gingivalis and atherosclerosis and formation of macrophage foam cells. Toll-like receptors and molecules governing their intracellular signaling pathways such as MyD88 play roles in atherosclerosis, as well as host response to P. gingivalis. The aim of this study was to define roles of MyD88 and TRIF during macrophage foam cell formation in response to P. gingivalis. In the presence of human low-density lipoprotein (LDL) mouse bone-marrow-derived macrophages (BMφ) cultured with P. gingivalis responded with significant reduction in tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The BMφ stained strongly with oil red O, regardless of whether bacterial challenge occurred concurrent with or before LDL treatment. Heat-killed P. gingivalis stimulated foam cell formation in a similar way to live bacteria. The BMφ from MyD88-knockout and Lps2 mice revealed a significant role for MyD88, and a minor role for TRIF in P. gingivalis-elicited foam cell formation. Porphyromonas gingivalis-elicited TNF-α and IL-6 were affected by MyD88 ablation and to a lesser extent by TRIF status. These data indicate that LDL affects the TNF-α and IL-6 response of macrophages to P. gingivalis challenge and that MyD88 and TRIF play important roles in P. gingivalis-elicited foam cell formation.

Oxidized LDLs inhibit TLR-induced IL-10 production by monocytes: a new aspect of pathogen-accelerated atherosclerosis

It is widely accepted that oxidized low-density lipoproteins and local infections or endotoxins in circulation contribute to chronic inflammatory process at all stages of atherosclerosis. The hallmark cells of atherosclerotic lesions-monocytes and macrophages-are able to detect and integrate complex signals derived from lipoproteins and pathogens, and respond with a spectrum of immunoregulatory cytokines. In this study, we show strong inhibitory effect of oxLDLs on anti-inflammatory interleukin-10 production by monocytes responding to TLR2 and TLR4 ligands. In contrast, pro-inflammatory tumor necrosis factor secretion was even slightly increased, when stimulated with lipopolysaccharide from Porphyromonas gingivalis-an oral pathogen associated with atherosclerosis. The oxLDLs modulatory activity may be explained by altered recognition of pathogen-associated molecular patterns, which involves serum proteins, particularly vitronectin. We also suggest an interaction between vitronectin receptor, CD11b, and TLR2. The presented data support a novel pathway for pathogen-accelerated atherosclerosis, which relies on oxidized low-density lipoprotein-mediated modulation of anti-inflammatory response to TLR ligands.

Oxidized LDLs inhibit TLR-induced IL-10 production by monocytes: a new aspect of pathogen-accelerated atherosclerosis

It is widely accepted that oxidized low-density lipoproteins and local infections or endotoxins in circulation contribute to chronic inflammatory process at all stages of atherosclerosis. The hallmark cells of atherosclerotic lesions-monocytes and macrophages-are able to detect and integrate complex signals derived from lipoproteins and pathogens, and respond with a spectrum of immunoregulatory cytokines. In this study, we show strong inhibitory effect of oxLDLs on anti-inflammatory interleukin-10 production by monocytes responding to TLR2 and TLR4 ligands. In contrast, pro-inflammatory tumor necrosis factor secretion was even slightly increased, when stimulated with lipopolysaccharide from Porphyromonas gingivalis-an oral pathogen associated with atherosclerosis. The oxLDLs modulatory activity may be explained by altered recognition of pathogen-associated molecular patterns, which involves serum proteins, particularly vitronectin. We also suggest an interaction between vitronectin receptor, CD11b, and TLR2. The presented data support a novel pathway for pathogen-accelerated atherosclerosis, which relies on oxidized low-density lipoprotein-mediated modulation of anti-inflammatory response to TLR ligands.

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.

Periodontal bacteria aggravate experimental autoimmune myocarditis in mice

Periodontitis is one of the most common infections in humans. Recently, published reports assert that periodontitis is associated with cardiovascular disease. Although it is said that viral, bacterial infections and autoimmune diseases may be the cause of myocarditis, the pathogenesis of it remains unclear. The aim of this study was to investigate the influence of a periodontal pathogen on experimental autoimmune myocarditis (EAM). Porphyromonas gingivalis (P.g.), PBS as a control, were injected into the mice. Histopathological and immunohistochemical analyses were performed. We examined heart mRNA levels using quantitative RT-PCR. The anti-P.g. IgG antibody level in plasma samples of the P.g.-injected group significantly increased compared with the PBS-injected group. Histopathological analysis detected that the myocarditis-affected areas and the fibrotic area in the P.g.-injected EAM group significantly increased compared with the PBS-injected EAM group (P < 0.05). Immunohistochemical analysis detected that more CD11b-positive cells were shown in the heart of the P.g.-injected EAM group compared with the PBS EAM-injected group (P < 0.05). Hearts from the P.g.-injected EAM group showed significantly increased expression of monocyte chemoattractant protein-1, IFN-γ, and matrix metalloproteinase-9 (MMP-9) mRNA compared with the hearts from the PBS-injected EAM group (P < 0.05). On day 7, serum levels of IL-6 were significantly enhanced in the P.g.-injected EAM group compared with the PBS-injected EAM group (P < 0.05). These results showed that P.g. injection could deteriorate EAM in mice through CD11b-positive cells, cytokines, and MMP-9 expression.

Effect of angiotensin II receptor blocker on experimental periodontitis in a mouse model of Marfan syndrome

Marfan syndrome is an autosomal dominant disease characterized by aneurysm and dilatation of the aortic root, tall stature, and ectopia lentis. These manifestations reflect excessive signaling of transforming growth factor beta (TGF-β). Moreover, cases are frequently associated with severe periodontitis, which is a chronic inflammation of the gingiva, periodontal ligament, and alveolar bone. Recently, angiotensin II receptor blockers (ARBs) were discovered to be an effective drug class that can prevent aortic aneurysm and dilation in Marfan syndrome by inhibiting TGF-β signaling. To investigate the effect of ARB on the progression of periodontitis, the application of a potent ARB, telmisartan, was examined in a mouse model of Marfan syndrome (MgΔ). Six-week-old male heterozygous MgΔ and wild-type mice were challenged with Porphyromonas gingivalis, which causes chronic periodontitis, with and without telmisartan application. After infection, alveolar bone resorption was measured by micro-computed tomography (μCT), and inflammatory cytokine levels were examined. Infection of Porphyromonas gingivalis induced alveolar bone resorption in both MgΔ and wild-type mice. The amount of resorption was significantly larger in the former than the latter. Immunoarray and enzyme-linked immunosorbent assay (ELISA) analyses demonstrated that interleukin-17 (IL-17) and tumor necrosis factor alpha (TNF-α) levels were significantly higher in infected MgΔ mice than infected wild-type mice. Telmisartan treatment significantly suppressed the alveolar bone resorption of infected MgΔ mice. Telmisartan also significantly decreased levels of TGF-β, IL-17, and TNF-α in infected MgΔ mice to levels seen in infected wild-type mice. This study suggests that ARB can prevent the severe periodontitis frequently seen in Marfan syndrome.

Protective role for TLR4 signaling in atherosclerosis progression as revealed by infection with a common oral pathogen

Clinical and epidemiological studies have implicated chronic infections in the development of atherosclerosis. It has been proposed that common mechanisms of signaling via TLRs link stimulation by multiple pathogens to atherosclerosis. However, how pathogen-specific stimulation of TLR4 contributes to atherosclerosis progression remains poorly understood. In this study, atherosclerosis-prone apolipoprotein-E null (ApoE(-/-)) and TLR4-deficient (ApoE(-/-)TLR4(-/-)) mice were orally infected with the periodontal pathogen Porphyromonas gingivalis. ApoE(-/-)TLR4(-/-) mice were markedly more susceptible to atherosclerosis after oral infection with P. gingivalis. Using live animal imaging, we demonstrate that enhanced lesion progression occurs progressively and was increasingly evident with advancing age. Immunohistochemical analysis of lesions from ApoE(-/-)TLR4(-/-) mice revealed an increased inflammatory cell infiltrate composed primarily of macrophages and IL-17 effector T cells (Th17), a subset linked with chronic inflammation. Furthermore, enhanced atherosclerosis in TLR4-deficient mice was associated with impaired development of Th1 immunity and regulatory T cell infiltration. In vitro studies suggest that the mechanism of TLR4-mediated protective immunity may be orchestrated by dendritic cell IL-12 and IL-10, which are prototypic Th1 and regulatory T cell polarizing cytokines. We demonstrate an atheroprotective role for TLR4 in response to infection with the oral pathogen P. gingivalis. Our results point to a role for pathogen-specific TLR signaling in chronic inflammation and atherosclerosis.

Effects of systemic ornidazole, systemic and local compound ornidazole and pefloxacin mesylate on experimental periodontitis in rats

Background

The purpose of the current study is to evaluate the effects of systemic ornidazole (SO) and systemic and local compound ornidazole and pefloxacin mesylate (SCOPM/LCOMP) on the inflammatory response associated with rat experimental chronic periodontitis (ECP) in sites with subgingival debridement.

Material/Methods

Periodontitis was induced in male Sprague-Dawley rats by placing a thin steel ligature around the upper first molars and inoculating them with Porphyromonas gingivalis 381. After the successful induction of the rat ECP, the periodontitis rats were randomly divided into 3 different combined treatment groups: (A) SO with scaling and root planing (SRP); (B) SCOMP with SRP; and (C) LCOMP with SRP. After 2 weeks the effects of the treatments were evaluated based on gingivitis, plaque index, probing pocket depth, aspartate aminotransferase, alveolar bone loss, and hematoxylin-eosin staining of the region around the first molars.

Results

After treatment, comparison with ECP was performed. The mean percentage reductions of SBI in SO, SCOPM, and LCOPM were 27.73%, 33.61%, and 58.82%, respectively. Those of PI were 33.20%, 42.80%, and 60.00%; those of PPD were 48.66%, 55.70%, and 72.48%; those of GCF-AST were 41.64%, 49.03%, and 66.42%; and those of ABL were 41.19%, 43.63%, and 54.47%, respectively. The inflammatory score of H&E showed median scores of 2.5, 1.75, 1.63, and 0.95 for ECP, SO, SCOMP, and LCOMP, respectively. All 3 treatment groups exhibited significantly reduced inflammation indicators (P<0.05). Of the 3, group C was the most effective (P<0.05).

Conclusions

Although all the combined treatment groups responded to therapy with significant resolution of the infection, adjunctive LCOMP therapy is more effective for periodontitis.

Periodontal and systemic responses in various mice models of experimental periodontitis: respective roles of inflammation duration and Porphyromonas gingivalis infection

BACKGROUND

The great variability of periodontal and systemic responses to experimental periodontitis reflects the inherent pathogenic complexity of mice models and could limit the resulting interpretations and their extension to human diseases. This study compared the effect of Porphyromonas gingivalis (Pg) infection and experimental periodontitis duration at local and systemic levels in various models.

METHODS

Periodontitis was induced in C57BL/6J mice by ligatures previously incubated with Pg (LIGPG group) or not (LIG group) or by oral gavage (GAV) with Pg ATCC 33277. Blood samples were taken, and mice were euthanized at different times. Periodontal tissue destruction, osteoclast number, and inflammation were assessed by histomorphometry, tartrate-resistant acid phosphatase histoenzymology, and cathepsin B (CATB) and matrix metalloproteinase 9 (MMP9) immunochemistry. Serum levels of interleukin-6 (IL-6) and IL-1β were measured using enzyme-linked immunosorbent assay bioplex methods.

RESULTS

Periodontal tissue destruction and osteoclast numbers were significantly elevated in LIGPG models compared to LIG and GAV models. They increased with time with the exception of osteoclast numbers in the LIG model. CATB and MMP9 expression was related to bone destruction processes and Pg infection. The highest serum levels of IL-6 and IL-1β were observed in the LIGPG group. A decrease of IL-6 and an increase of IL-1β serum level were observed with time in LIGPG group contrary to LIG group.

CONCLUSIONS

These data indicate that Pg infection worsened periodontal tissue destruction through specific pathogenic pathways and modified systemic response to periodontal inflammation. Furthermore, the blood cytokine response to ligature models showed their relevance for evaluating the systemic impact of periodontal disease.

Oral inflammatory diseases and systemic inflammation: role of the macrophage

Inflammation is a complex reaction to injurious agents and includes vascular responses, migration, and activation of leukocytes. Inflammation starts with an acute reaction, which evolves into a chronic phase if allowed to persist unresolved. Acute inflammation is a rapid process characterized by fluid exudation and emigration of leukocytes, primarily neutrophils, whereas chronic inflammation extends over a longer time and is associated with lymphocyte and macrophage infiltration, blood vessel proliferation, and fibrosis. Inflammation is terminated when the invader is eliminated, and the secreted mediators are removed; however, many factors modify the course and morphologic appearance as well as the termination pattern and duration of inflammation. Chronic inflammatory illnesses such as diabetes, arthritis, and heart disease are now seen as problems that might have an impact on the periodontium. Reciprocal effects of periodontal diseases are potential factors modifying severity in the progression of systemic inflammatory diseases. Macrophages are key cells for the inflammatory processes as regulators directing inflammation to chronic pathological changes or resolution with no damage or scar tissue formation. As such, macrophages are involved in a remarkably diverse array of homeostatic processes of vital importance to the host. In addition to their critical role in immunity, macrophages are also widely recognized as ubiquitous mediators of cellular turnover and maintenance of extracellular matrix homeostasis. In this review, our objective is to identify macrophage-mediated events central to the inflammatory basis of chronic diseases, with an emphasis on how control of macrophage function can be used to prevent or treat harmful outcomes linked to uncontrolled inflammation.

Periodontal disease and atherosclerotic vascular disease: does the evidence support an independent association?: a scientific statement from the American Heart Association

A link between oral health and cardiovascular disease has been proposed for more than a century. Recently, concern about possible links between periodontal disease (PD) and atherosclerotic vascular disease (ASVD) has intensified and is driving an active field of investigation into possible association and causality. The 2 disorders share several common risk factors, including cigarette smoking, age, and diabetes mellitus. Patients and providers are increasingly presented with claims that PD treatment strategies offer ASVD protection; these claims are often endorsed by professional and industrial stakeholders. The focus of this review is to assess whether available data support an independent association between ASVD and PD and whether PD treatment might modify ASVD risks or outcomes. It also presents mechanistic details of both PD and ASVD relevant to this topic. The correlation of PD with ASVD outcomes and surrogate markers is discussed, as well as the correlation of response to PD therapy with ASVD event rates. Methodological issues that complicate studies of this association are outlined, with an emphasis on the terms and metrics that would be applicable in future studies. Observational studies to date support an association between PD and ASVD independent of known confounders. They do not, however, support a causative relationship. Although periodontal interventions result in a reduction in systemic inflammation and endothelial dysfunction in short-term studies, there is no evidence that they prevent ASVD or modify its outcomes.

Recognition of Porphyromonas gingivalis gingipain epitopes by natural IgM binding to malondialdehyde modified low-density lipoprotein

Objective

Increased risk for atherosclerosis is associated with infectious diseases including periodontitis. Natural IgM antibodies recognize pathogen-associated molecular patterns on bacteria, and oxidized lipid and protein epitopes on low-density lipoprotein (LDL) and apoptotic cells. We aimed to identify epitopes on periodontal pathogen Porphyromonas gingivalis recognized by natural IgM binding to malondialdehyde (MDA) modified LDL.

Methods and Results

Mouse monoclonal IgM (MDmAb) specific for MDA-LDL recognized epitopes on P. gingivalis on flow cytometry and chemiluminescence immunoassays. Immunization of C57BL/6 mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and apoptotic cells. Immunization of LDLR^−/− mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and diminished aortic lipid deposition. On Western blot MDmAb bound to P. gingivalis fragments identified as arginine-specific gingipain (Rgp) by mass spectrometry. Recombinant domains of Rgp produced in E. coli were devoid of phosphocholine epitopes but contained epitopes recognized by MDmAb and human serum IgM. Serum IgM levels to P. gingivalis were associated with anti-MDA-LDL levels in humans.

Conclusion

Gingipain of P. gingivalis is recognized by natural IgM and shares molecular identity with epitopes on MDA-LDL. These findings suggest a role for natural antibodies in the pathogenesis of two related inflammatory diseases, atherosclerosis and periodontitis.

Oxidized low-density lipoprotein as a biomarker of in vivo oxidative stress: from atherosclerosis to periodontitis

Oxidized low-density lipoprotein is known as an important factor in the development of atherosclerosis. The introduction of a sensitive procedure for the determination of oxidized low-density lipoprotein in human circulating plasma using a monoclonal antibody recognizing oxidized phosphatidylcholines has opened new fields of research based on in vivo oxidized low-density lipoprotein. The plasma oxidized low-density lipoprotein levels are significantly elevated in patients with acute myocardial infarction, cerebral infarction or chronic renal failure accompanied by hemodialysis. It was found that the plasma oxidized low-density lipoprotein level increased prior to aortic atherosclerotic lesion enlargement in apolipoprotein E-knockout mice. Recent studies have pointed out that oxidized low-density lipoprotein is transferrable between vessel wall tissue and the circulation, so it is a reasonable hypothesis that plasma oxidized low-density lipoprotein levels reflect the oxidative status at local sites of atherogenesis. Oxidized low-density lipoprotein measurement has been applied to human gingival crevicular fluids, which can be collected easily and safely, and relatively high levels of oxidized low-density lipoprotein were shown to be present. These findings, together with recent clinical follow-up studies, suggest that oxidized low-density lipoprotein is a predictive biomarker of a variety of diseases related to oxidative stress. This review summarizes the current understanding of in vivo oxidized low-density lipoprotein and its potential significance as a biomarker of disease.

Description of comprehensive dental services supported by the Medicare Chronic Disease Dental Scheme in the first 23 months of operation

OBJECTIVE

Australia's Medicare universal insurance system has supported comprehensive dental service through the Chronic Disease Dental Scheme (CDDS) since November 2007. Public debate opposing CDDS includes claims of over-servicing, calls for expansion to universal eligibility, and government threat of closure. Here we examine CDDS services over the first 23 months of operation.

METHODS

CDDS statistics on patient age, gender and item numbers claimed from November 2007 to December 2009 from Medicare were subjected to analysis.

RESULTS

The distribution of 404,768 total CDDS patients varied across Australia from 3.6% of the population in NSW to 0.07% in NT, while uptake increased over time. The average patient had 7.58 dental treatments, and the most common were: direct restorations (2.27), preventive and periodontal services (1.46), diagnostic services (1.43), extractions (0.77), and new dentures (0.53). Crown and bridgework appeared over-represented (0.48).

CONCLUSION

Although data do suggest over-servicing in crown and bridgework, there also appears to be significant community need for the CDDS.

IMPLICATION

Clear guidelines for dental clinical diagnosis and treatment planning, as well as a pre-approval process for crown and bridgework is suggested to improve the CDDS, and this could form the basis for expansion to universal eligibility for dental Medicare.

Both the unique and repeat regions of the Porphyromonas gingivalis hemagglutin A are involved in adhesion and invasion of host cells

Porphyromonas gingivalis is one of the major etiologic agents of adult periodontitis and has been associated with cardiovascular diseases. It expresses multiple hemagglutinins that are significant virulence factors and play an important role in bacterial attachment and invasion of host cells. The objective of this study was to determine the impact of P. gingivalis hemagglutinin A (HagA) on the attachment to and invasion of human coronary artery endothelial cells (HCAEC) and gingival epithelial cells (GEC). Bacterial strains expressing the HagA protein (or subunits), including Escherichia coli carrying plasmid pEKS5, E. coli carrying plasmid ST2, and Salmonella enterica serovar Typhimurium with plasmid pNM1.1 were used in this study. The strains were tested for their ability to attach to and invade HCAEC and GEC using antibiotic protection assays. In addition, the unique 5' N-terminal non-repeated segment of HagA was purified in recombinant form and a monoclonal antibody was created against the polypeptide. The monoclonal antibody against the unique portion of HagA was tested for inhibitory activity in these assays. The attachment of both E. coli strains expressing HagA fragment to host cells was significantly increased compared to their respective controls. However, they did not invade GEC or HCAEC. Interestingly, HagA expression in the Salmonella strain increased both adherence to and invasion of HCAEC, which may be due to the presence of the entire hagA ORF. A monoclonal antibody against the unique 5' N-terminal portion of HagA reduced invasion. Further experiments are needed to determine the role of the unique and the repeat segments of P. gingivalis HagA.

A prospective cohort study of periodontal disease measures and cardiovascular disease markers in HIV-infected adults

The determinants of HIV-associated cardiovascular disease (CVD) are not well understood. Periodontal disease (PD) has been linked to CVD but this connection has not been examined in HIV infection. We followed a cohort of HIV-infected adults to ascertain whether PD was associated with carotid artery intima media thickness (IMT) and brachial artery flow-mediated dilation (FMD). We performed a longitudinal observational study of HIV-infected adults on HAART for <2 years with no known heart disease. PD was characterized clinically and microbiologically. Cardiovascular disease was assessed by IMT/FMD. Linear mixed models assessed cross-sectional and longitudinal associations between PD and FMD/IMT. Forty three HIV(+) adults completed a median of 24 (6-44) months on the study. Defining delta to be the change in a variable between baseline and a follow-up time, longitudinally, on average and after adjusting for change in time, CVD-specific and HIV-specific potential confounding covariates, a 1-log(10) increase in delta Porphyromonas gingivalis was associated with a 0.013 mm increase in delta IMT (95% CI: 0.0006-0.0262; p=0.04). After adjusting for the same potential confounding covariates, a 10% increase in delta gingival recession was associated with a 2.3% increase in delta FMD (95% CI: 0.4-4.2; p=0.03). In a cohort of HIV-infected adults, an increase in subgingival Porphyromonas gingivalis, a known periodontal pathogen, was significantly associated with longitudinal increases in IMT, while increased gingival recession, which herein may represent PD resolution, was significantly associated with longitudinal improvement in FMD. In the context of HIV infection, PD may contribute to CVD risk. Intervention studies treating PD may help clarify this association.

Pathogens and atherosclerosis: update on the potential contribution of multiple infectious organisms to the pathogenesis of atherosclerosis

It is currently unclear what causes the chronic inflammation within atherosclerotic plaques. One emerging paradigm suggests that infection with bacteria and/or viruses can contribute to the pathogenesis of atherosclerosis either via direct infection of vascular cells or via the indirect effects of cytokines or acute phase proteins induced by infection at non-vascular sites. This paradigm has been supported by multiple epidemiological studies that have established positive associations between the risk of cardiovascular disease morbidity and mortality and markers of infection. It has also been supported by experimental studies showing an acceleration of the development of atherosclerosis following infection of hyperlipidaemic animal models. There are now a large number of different infectious agents that have been linked with an increased risk of cardiovascular disease. These include: Chlamydia pneumoniae, Porphyromonas gingivalis, Helicobacter pylori , influenza A virus, hepatitis C virus, cytomegalovirus, and human immunodeficiency virus. However, there are significant differences in the strength of the data supporting their association with cardiovascular disease pathogenesis. In some cases, the infectious agents are found within the plaques and viable organisms can be isolated suggesting a direct effect. In other cases, the association is entirely based on biomarkers. In the following review, we evaluate the strength of the data for individual or groups of pathogens with regard to atherosclerosis pathogenesis and their potential contribution by direct or indirect mechanisms and discuss whether the established associations are supportive of the infectious disease paradigm. We also discuss the failure of antibiotic trials and the question of persistent infection.

Impact of monocytic cells on recovery of uncultivable bacteria from atherosclerotic lesions

OBJECTIVE

Epidemiological evidence suggests that infections may contribute to atherogenesis. However, with the exception of Chlamydophila pneumoniae, cultivable bacteria have not been recovered from atherosclerotic lesions. Therefore, we aimed at developing an approach to recover uncultivable bacteria from atherectomy tissues.

METHODS

We cultured homogenates from atherectomy specimens from seven nonseptic patients undergoing surgery for arterial obstruction either alone or together with THP-1 monocyte-like cells. We performed 16S rDNA analysis, biochemical tests, random amplification of polymorphic DNA PCR analysis, quantitative polymerase chain reaction (qPCR) and immunohistofluorescence to identify the cultivated bacteria. Wilcoxon signed-rank tests were used to determine whether THP-1 treatment yielded a higher number of isolates than did the untreated controls.

RESULTS

We recovered more bacteria from cocultures of atherectomy specimens with THP-1 cells than atherectomy specimens cultured alone. On average, tissue homogenates incubated with THP-1 cells versus control yielded 124 vs. 22 colony-forming units, a median of 140 vs. 7, respectively (P = 0.02). We recovered 872 isolates of limited number of species, including Propionibacterium acnes, Staphylococcus epidermidis and Streptococcus infantis and the fastidious anaerobe Porphyromonas gingivalis, and confirmed its presence in tissue using double immunofluorescence imaging. qPCR demonstrated the presence of ≥3.5 × 10(3) P. gingivalis genomes per gram of atheromatous tissue.

CONCLUSIONS

These results indicate that viable previously uncultivable bacterial species are present within atheromas. Our results suggest revisiting the hypothesis that infections may have a causative role in atherosclerotic inflammation and have implications for research regarding novel diagnostics and treatments for cardiovascular disease.

Chronic oral infection with Porphyromonas gingivalis accelerates atheroma formation by shifting the lipid profile

Background

Recent studies have suggested that periodontal disease increases the risk of atherothrombotic disease. Atherosclerosis has been characterized as a chronic inflammatory response to cholesterol deposition in the arteries. Although several studies have suggested that certain periodontopathic bacteria accelerate atherogenesis in apolipoprotein E-deficient mice, the mechanistic link between cholesterol accumulation and periodontal infection-induced inflammation is largely unknown.

Methodology/Principal Findings

We orally infected C57BL/6 and C57BL/6.KOR-Apoe^shl (B6.Apoeshl) mice with Porphyromonas gingivalis, which is a representative periodontopathic bacterium, and evaluated atherogenesis, gene expression in the aorta and liver and systemic inflammatory and lipid profiles in the blood. Furthermore, the effect of lipopolysaccharide (LPS) from P. gingivalis on cholesterol transport and the related gene expression was examined in peritoneal macrophages. Alveolar bone resorption and elevation of systemic inflammatory responses were induced in both strains. Despite early changes in the expression of key genes involved in cholesterol turnover, such as liver X receptor and ATP-binding cassette A1, serum lipid profiles did not change with short-term infection. Long-term infection was associated with a reduction in serum high-density lipoprotein (HDL) cholesterol but not with the development of atherosclerotic lesions in wild-type mice. In B6.Apoeshl mice, long-term infection resulted in the elevation of very low-density lipoprotein (VLDL), LDL and total cholesterols in addition to the reduction of HDL cholesterol. This shift in the lipid profile was concomitant with a significant increase in atherosclerotic lesions. Stimulation with P. gingivalis LPS induced the change of cholesterol transport via targeting the expression of LDL receptor-related genes and resulted in the disturbance of regulatory mechanisms of the cholesterol level in macrophages.

Conclusions/Significance

Periodontal infection itself does not cause atherosclerosis, but it accelerates it by inducing systemic inflammation and deteriorating lipid metabolism, particularly when underlying hyperlidemia or susceptibility to hyperlipidemia exists, and it may contribute to the development of coronary heart disease.

Oral P. gingivalis infection alters the vascular reactivity in healthy and spontaneously atherosclerotic mice

Background

Considering that recent studies have demonstrated endothelial dysfunction in subjects with periodontitis and that there is no information about vascular function in coexistence of periodontitis and atherosclerosis, we assessed the impact of oral inoculation with the periodontal pathogen Porphyromonas gingivalis on vascular reactivity in healthy and hypercholesterolemic apolipoprotein E-deficient (ApoE) mice. In vitro preparations of mesenteric arteriolar bed were used to determine the vascular responses to acetylcholine, sodium nitroprusside and phenylephrine (PE).

Results

Alveolar bone resorption, an evidence of periodontitis, was assessed and confirmed in all infected mice. Acetylcholine- and sodium nitroprusside-induced vasorelaxations were similar among all groups. Non-infected ApoE mice were hyperreactive to PE when compared to non-infected healthy mice. P gingivalis infection significantly enhanced the vasoconstriction to PE in both healthy and spontaneous atherosclerotic mice, when compared to their respective controls.

Conclusions

This study demonstrates that oral P gingivalis affects the alpha-adrenoceptor-mediated vascular responsiveness in both healthy and spontaneous atherosclerotic mice, reinforcing the association between periodontitis and cardiovascular diseases.