Role for Porphyromonas gingivalis in the progression of atherosclerosis

A systematic review of the impact of Porphyromonas gingivalis on foam cell formation: Implications for the role of periodontitis in atherosclerosis

BACKGROUND

The current literature suggests the significant role of foam cells in the initiation of atherosclerosis through the formation of a necrotic core in atherosclerotic plaques. Moreover, an important periodontal pathogen called Porphyromonas gingivalis (P. gingivalis) is indicated to play a significant role in this regard. Thus, the aim of this systematic review was to comprehensively study the pathways by which P. gingivalis as a prominent bacterial species in periodontal disease, can induce foam cells that would initiate the process of atherosclerosis formation.

METHODS

An electronic search was undertaken in three databases (Pubmed, Scopus, and Web of Science) to identify the studies published from January 2000 until March 2023. The risk of bias in each study was also assessed using the QUIN risk of bias assessment tool.

RESULTS

After the completion of the screening process, 11 in-vitro studies met the inclusion criteria and were included for further assessments. Nine of these studies represented a medium risk of bias, while the other two had a high risk of bias. All of the studies have reported that P. gingivalis can significantly induce foam cell formation by infecting the macrophages and induction of oxidized low-density lipoprotein (oxLDL) uptake. This process is activated through various mediators and pathways. The most important factors in this regard are the lipopolysaccharide of P. gingivalis and its outer membrane vesicles, as well as the changes in the expression rate of transmembrane lipid transportation channels, including transient receptor potential channel of the vanilloid subfamily 4 (TRPV4), lysosomal integral protein 2 (LIMP2), CD36, etc. The identified molecular pathways involved in this process include but are not limited to NF-κB, ERK1/2, p65.

CONCLUSION

Based on the results of this study, it can be concluded that P. gingivalis can effectively promote foam cell formation through various pathogenic elements and this bacterial species can affect the expression rate of various genes and the function of specific receptors in the cellular and lysosomal membranes. However, due to the moderate to high level of risk of bias among the studies, further studies are required in this regard.

Tanshinone IIA Attenuates Atherosclerosis in Apolipoprotein E Knockout Mice Infected with Porphyromonas gingivalis

Tanshinone IIA (TSA), a pharmacologically active component isolated from Danshen, may prevent cardiovascular diseases due to its anti-inflammatory, anti-oxidative, and anti-adipogenic effects. Porphyromonas gingivalis, a major periodontal pathogen, may contribute to the progression of atherosclerosis. Here, we studied the effects of TSA on atherosclerosis in ApoE^-/- mice with P. gingivalis infection. Eight-week-old ApoE^-/- mice were randomized to (a) phosphate-buffered saline (PBS), (b) P. gingivalis, and (c) P. gingivalis + TSA (60 mg kg^-1 day^-1). The mice were injected with (a) PBS, or (b) and (c) P. gingivalis 3 times per week for a total of 10 times. After 8 weeks, atherosclerotic risk factors in serum and in heart, aorta, and liver tissues were analyzed in all mice using Oil Red O, atherosclerosis cytokine antibody arrays, enzyme-linked immunosorbent assay (ELISA), real-time PCR, and microRNA array. CD40, G-CSF, IFN-γ, interleukin (IL)-1β, IL-6, MCP-1, MIP-3α, tumor necrosis factor-α (TNF-α), and VEGF were attenuated by TSA in atherosclerosis cytokine antibody arrays. TSA-treated mice showed a significant reduction of C-reactive protein (CRP), ox-LDL, IL-1β, IL-6, IL-12, and TNF-α in ELISA data. Real-time PCR analyses showed that TSA decreased the expression of CCL-2, CD40, IL-1β, IL-6, TNF-α, and MMP-2 in heart and aorta tissues. Moreover, hepatic CRP was downregulated by TSA, although FASN and HMG-CoA were not. The relative expressions of miR-146b and miR-155 were elevated by P. gingivalis infection and were downregulated by TSA treatment. These results suggest that TSA was a potential therapeutic agent that may have the ability to prevent P. gingivalis-induced atherosclerosis associated with anti-inflammatory and anti-oxidative effects.

Oral cancer cells sustainedly infected with Porphyromonas gingivalis exhibit resistance to Taxol and have higher metastatic potential

Major obstacles to improving the prognosis of patients with oral squamous cell carcinoma (OSCC) are the acquisition of resistance to chemotherapeutic agents and development of metastases. Recently, inflammatory signals are suggested to be one of the most important factors in modulating chemoresistance and establishing metastatic lesions. In addition, epidemiological studies have demonstrated that periodontitis, the most common chronic inflammatory condition of the oral cavity, is closely associated with oral cancer. However, a correlation between chronic periodontitis and chemoresistance/metastasis has not been well established. Herein, we will present our study on whether sustained infection with Porphyromonas gingivalis, a major pathogen of chronic periodontitis, could modify the response of OSCC cells to chemotherapeutic agents and their metastatic capability in vivo. Tumor xenografts composed of P. gingivalis–infected OSCC cells demonstrated a higher resistance to Taxol through Notch1 activation, as compared with uninfected cells. Furthermore, P. gingivalis–infected OSCC cells formed more metastatic foci in the lung than uninfected cells.

Silver-zeolite combined to polyphenol-rich extracts of Ascophyllum nodosum: potential active role in prevention of periodontal diseases

The purpose of this study was to evaluate various biological effects of silver-zeolite and a polyphenol-rich extract of A. nodosum (ASCOP) to prevent and/or treat biofilm-related oral diseases. Porphyromonas gingivalis and Streptococcus gordonii contribute to the biofilm formation associated with chronic periodontitis. In this study, we evaluated in vitro antibacterial and anti-biofilm effects of silver-zeolite (Ag-zeolite) combined to ASCOP on P. gingivalis and S. gordonii growth and biofilm formation capacity. We also studied the anti-inflammatory and antioxidant capacities of ASCOP in cell culture models. While Ag-zeolite combined with ASCOP was ineffective against the growth of S. gordonii, it showed a strong bactericidal effect on P. gingivalis growth. Ag-zeolite combined with ASCOP was able to completely inhibit S. gordonii monospecies biofilm formation as well as to reduce the formation of a bi-species S. gordonii/P. gingivalis biofilm. ASCOP alone was ineffective towards the growth and/or biofilm formation of S. gordonii and P. gingivalis while it significantly reduced the secretion of inflammatory cytokines (TNFα and IL-6) by LPS-stimulated human like-macrophages. It also exhibited antioxidant properties and decreased LPS induced lipid peroxidation in gingival epithelial cells. These findings support promising use of these products in future preventive or therapeutic strategies against periodontal diseases.

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.

Therapeutic approaches to drug targets in atherosclerosis

Non-communicable diseases such as cancer, atherosclerosis and diabetes are responsible for major social and health burden as millions of people are dying every year. Out of which, atherosclerosis is the leading cause of deaths worldwide. The lipid abnormality is one of the major modifiable risk factors for atherosclerosis. Both genetic and environmental components are associated with the development of atherosclerotic plaques. Immune and inflammatory mediators have a complex role in the initiation and progression of atherosclerosis. Understanding of all these processes will help to invent a range of new biomarkers and novel treatment modalities targeting various cellular events in acute and chronic inflammation that are accountable for atherosclerosis. Several biochemical pathways, receptors and enzymes are involved in the development of atherosclerosis that would be possible targets for improving strategies for disease diagnosis and management. Earlier anti-inflammatory or lipid-lowering treatments could be useful for alleviating morbidity and mortality of atherosclerotic cardiovascular diseases. However, novel drug targets like endoglin receptor, PPARα, squalene synthase, thyroid hormone analogues, scavenger receptor and thyroid hormone analogues are more powerful to control the process of atherosclerosis. Therefore, the review briefly focuses on different novel targets that act at the starting stage of the plaque form to the thrombus formation in the atherosclerosis.

Relationship between periodontal disease, Porphyromonas gingivalis, peripheral vascular resistance markers and coronary artery disease in Asian Indians

INTRODUCTION

A close association exists between oral health and cardiovascular disease. Periodontal disease induces early vascular changes while oral pathogens have been detected in sub gingival and atheromatous plaques. We examined the interrelationship between Periodontal disease, oral bacteria, surrogate sub-clinical markers and coronary artery disease (CAD) in a representative Asian Indian cohort.

MATERIALS AND METHODS

532 Gingivitis cases and 282 Periodontitis cases were assessed for early peripheral vascular changes, namely pulse wave velocity (PWV), arterial stiffness index (ASI) and ankle brachial index (ABI) using computerized oscillometry method. Relative quantitation (RQ) of Porphyromonas gingivalis (Pg) was estimated in saliva samples of 54 Periodontitis, 25 Gingivitis and 51 CAD cases (38 also had oral disease) by Taqman assay by amplifying pathogen-specific gene targets, 16srRNA and IktA, respectively, and 16s universal bacterial rRNA as endogenous control.

RESULTS

PWV and ASI were elevated in Periodontitis compared to Gingivitis cases (p<0.0001) and in those with diabetes and hypertension. Cases with Periodontitis showed higher mean expression of Pg than Gingivitis (0.37±0.05 versus 0.15±0.04, p<0.0001), while CAD patients with oral disease (N=38) showed lower mean Pg expression than those without oral disease (N=13) (0.712±0.119 versus 1.526±0.257, p=0.008). Higher Pg expression was recorded in subjects with diabetes and hypertension.

CONCLUSION

Oral disease induces early changes in the peripheral blood vessels. Further, common presence of Pg in subjects with oral disease, in those with established cardiovascular risk factors and in patients with symptomatic CAD reflects the importance of oral hygiene in the development of Coronary Artery Disease in Asian Indians.

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.

Species specificity, surface exposure, protein expression, immunogenicity, and participation in biofilm formation of Porphyromonas gingivalis HmuY

BACKGROUND

Porphyromonas gingivalis is a major etiological agent of chronic periodontitis. The aim of this study was to examine the species specificity, surface exposure, protein expression, immunogenicity, and participation in biofilm formation of the P. gingivalis heme-binding protein HmuY.

RESULTS

HmuY is a unique protein of P. gingivalis since only low amino-acid sequence homology has been found to proteins encoded in other species. It is exposed on the cell surface and highly abundant in the outer membrane of the cell, in outer-membrane vesicles, and is released into culture medium in a soluble form. The protein is produced constitutively at low levels in bacteria grown under high-iron/heme conditions and at higher levels in bacteria growing under the low-iron/heme conditions typical of dental plaque. HmuY is immunogenic and elicits high IgG antibody titers in rabbits. It is also engaged in homotypic biofilm formation by P. gingivalis. Anti-HmuY antibodies exhibit inhibitory activity against P. gingivalis growth and biofilm formation.

CONCLUSIONS

Here it is demonstrated that HmuY may play a significant role not only in heme acquisition, but also in biofilm accumulation on abiotic surfaces. The data also suggest that HmuY, as a surface-exposed protein, would be available for recognition by the immune response during chronic periodontitis and the production of anti-HmuY antibodies may inhibit biofilm formation.