Aggregation of human platelets by gingipain-R from Porphyromonas gingivalis cells and membrane vesicles

Extracellular vesicle production by oral bacteria related to dental caries and periodontal disease: role in microbe-host and interspecies interactions

Extracellular vesicles (EVs) are cell membrane-derived structures between 20-400 nm in size. In bacteria, EVs play a crucial role in molecule secretion, cell wall biogenesis, cell-cell communication, biofilm development, and host-pathogen interactions. Despite these increasing reports of bacterial-derived vesicles, there remains a limited number of studies that summarize oral bacterial EVs, their cargo, and their main biological functions. Therefore, the aim of this review is to present the latest research on oral bacteria-derived EVs and how they can modulate various physiological and pathological processes in the oral cavity, including the pathogenesis of highly relevant diseases such as dental caries and periodontitis and their systemic complications. Overall, caries-associated bacteria (such as Streptococcus mutans) as well as periodontal pathogens (including the red complex pathogens Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) have all been shown to produce EVs that carry an array of virulent factors and molecules involved in biofilm and immune modulation, bacterial adhesion, and extracellular matrix degradation. As bacterial EV production is strongly impacted by genotypic and environmental variations, the inhibition of EV genesis and secretion remains a key potential future approach against oral diseases.

Luteolin inhibits Porphyromonas gingivalis growth and alleviates alveolar bone destruction in experimental murine periodontitis

Periodontal disease is a major oral infectious disease that destroys alveolar bones and causes tooth loss. Porphyromonas gingivalis is a key pathogen that plays a crucial role in periodontitis. In our previous study on the anti-P. gingivalis activity of flavonoid, luteolin, a major flavonoid in edible plants, inhibited the proteolytic activity of gingipains, the major virulence factor in P. gingivalis. This study demonstrated luteolin in vitro and in vivo anti-bacterial activities. Thus, luteolin inhibits planktonic growth and biofilm formation in P. gingivalis. Furthermore, oral administration of luteolin alleviated maxillary alveolar bone resorption (ABR) in murine periodontitis induced by P. gingivalis infection. These results indicate that luteolin may be a potential therapeutic compound that targets P. gingivalis by hindering its growth, biofilm formation, and ABR in the oral cavity.

Oral microbiome mediated inflammation, a potential inductor of vascular diseases: a comprehensive review

The dysbiosis of the oral microbiome and vascular translocation of the periodontopathic microorganism to peripheral blood can cause local and systemic extra-oral inflammation. Microorganisms associated with the subgingival biofilm are readily translocated to the peripheral circulation, generating bacteremia and endotoxemia, increasing the inflammation in the vascular endothelium and resulting in endothelial dysfunction. This review aimed to demonstrate how the dysbiosis of the oral microbiome and the translocation of oral pathogen-induced inflammation to peripheral blood may be linked to cardiovascular diseases (CVDs). The dysbiosis of the oral microbiome can regulate blood pressure and activate endothelial dysfunction. Similarly, the passage of periodontal microorganisms into the peripheral circulation and their virulence factors have been associated with a vascular compartment with a great capacity to activate endothelial cells, monocytes, macrophages, and plaquettes and increase interleukin and chemokine secretion, as well as oxidative stress. This inflammatory process is related to atherosclerosis, hypertension, thrombosis, and stroke. Therefore, oral diseases could be involved in CVDs via inflammation. The preclinic and clinical evidence suggests that periodontal disease increases the proinflammatory markers associated with endothelial dysfunction. Likewise, the evidence from clinical studies of periodontal treatment in the long term evidenced the reduction of these markers and improved overall health in patients with CVDs.

Platelet Behavior Contributes to Neuropathologies: A Focus on Alzheimer's and Parkinson's Disease

The functions of platelets are broad. Platelets function in hemostasis and thrombosis, inflammation and immune responses, vascular regulation, and host defense against invading pathogens, among others. These actions are achieved through the release of a wide set of coagulative, vascular, inflammatory, and other factors as well as diverse cell surface receptors involved in the same activities. As active participants in these physiological processes, platelets become involved in signaling pathways and pathological reactions that contribute to diseases that are defined by inflammation (including by pathogen-derived stimuli), vascular dysfunction, and coagulation. These diseases include Alzheimer's and Parkinson's disease, the two most common neurodegenerative diseases. Despite their unique pathological and clinical features, significant shared pathological processes exist between these two conditions, particularly relating to a central inflammatory mechanism involving both neuroinflammation and inflammation in the systemic environment, but also neurovascular dysfunction and coagulopathy, processes which also share initiation factors and receptors. This triad of dysfunction-(neuro)inflammation, neurovascular dysfunction, and hypercoagulation-illustrates the important roles platelets play in neuropathology. Although some mechanisms are understudied in Alzheimer's and Parkinson's disease, a strong case can be made for the relevance of platelets in neurodegeneration-related processes.

Platelet plug formation in whole blood is enhanced in the presence of Porphyromonas gingivalis

Porphyromonas gingivalis is a gram-negative anaerobic bacterium and an etiologic agent of adult periodontitis. By inducing a dysbiotic state within the host microbiota it contributes to a chronic inflammatory environment in the oral cavity. Under some circumstances, the oral bacteria may gain access to systemic circulation. While the most widely recognized function of platelets is to reduce hemorrhage in case of vascular damage, it is known that platelets are also involved in the hematologic responses to bacterial infections. Some pathogenic bacteria can interact with platelets, triggering their activation and aggregation. The aim of this study was to assess platelet responses to the presence of P. gingivalis in whole blood. Human whole blood was pretreated with P. gingivalis and then platelet plug formation was measured under high shear conditions using the PFA-100. In the presence of P. gingivalis, time for a platelet plug to occlude the aperture in the collagen/ADP cartridge was shortened in a manner dependent on bacterial concentration and the duration of bacterial preincubation of blood. P. gingivalis enhances thrombus forming potential of platelets in whole blood.

A Champion of Host Defense: A Generic Large-Scale Cause for Platelet Dysfunction and Depletion in Infection

Thrombocytopenia is commonly associated with sepsis and infections, which in turn are characterized by a profound immune reaction to the invading pathogen. Platelets are one of the cellular entities that exert considerable immune, antibacterial, and antiviral actions, and are therefore active participants in the host response. Platelets are sensitive to surrounding inflammatory stimuli and contribute to the immune response by multiple mechanisms, including endowing the endothelium with a proinflammatory phenotype, enhancing and amplifying leukocyte recruitment and inflammation, promoting the effector functions of immune cells, and ensuring an optimal adaptive immune response. During infection, pathogens and their products influence the platelet response and can even be toxic. However, platelets are able to sense and engage bacteria and viruses to assist in their removal and destruction. Platelets greatly contribute to host defense by multiple mechanisms, including forming immune complexes and aggregates, shedding their granular content, and internalizing pathogens and subsequently being marked for removal. These processes, and the nature of platelet function in general, cause the platelet to be irreversibly consumed in the execution of its duty. An exaggerated systemic inflammatory response to infection can drive platelet dysfunction, where platelets are inappropriately activated and face immunological destruction. While thrombocytopenia may arise by condition-specific mechanisms that cause an imbalance between platelet production and removal, this review evaluates a generic large-scale mechanism for platelet depletion as a repercussion of its involvement at the nexus of responses to infection.

A natural anti-periodontitis agent, epimedokoreanin B, inhibits virulence activities of gingipains from Porphyromonas gingivalis

Gingipains are potent virulence cysteine proteases secreted by Porphyromonas gingivalis, a major pathogen of periodontitis. We previously reported that epimedokoreanin B inhibits the activities of gingipains. In this report, we show that epimedokoreanin B inhibits the virulence of gingipains-containing P. gingivalis culture supernatants, indicating the potential use of this prenylated flavonoid as a new agent to combat against periodontal pathogens.

Association Between Periodontitis and Cognitive Impairment in Adults: A Systematic Review

Periodontitis is an oral inflammatory disease and may contribute to low-grade systemic inflammation. Based on the contribution of periodontitis to systemic inflammation and the potential role of systemic inflammation in neuroinflammation, many epidemiological studies have investigated a possible association between periodontitis and mild cognitive impairment or dementia. The purpose of this study was to evaluate the clinical/epidemiological evidence regarding the association between periodontitis and cognitive decline in adult patients. A search conducted between September and October 2018 was performed in the electronic databases PubMed, Scopus, Web of Science, The Cochrane Library, LILACS, OpenGrey, and Google Scholar, with no publication date or language restrictions. Analytical observational studies in adults (P—Participants), with (E—Exposure) and without periodontitis (C—Comparison) were included in order to determine the association between periodontitis and cognitive decline (O—Outcome). The search identified 509 references, of which eight observational studies were accorded with the eligibility criteria and evaluated. The results should, however, be interpreted cautiously due to the limited number of studies. This systematic review points to the need for further well-designed studies, such as longitudinal observational studies with control of modifiable variables, as diagnostic criteria and time since diagnosis of periodontitis and cognitive impairment, to confirm the proposed association.

Platelet interaction with bacterial toxins and secreted products

Bacteria that enter the bloodstream will encounter components of the cellular and soluble immune response. Platelets contribute to this response and have emerged as an important target for bacterial pathogens. Bacteria produce diverse extracellular proteins and toxins that have been reported to modulate platelet function. These interactions can result in complete or incomplete platelet activation or inhibition of platelet activation, depending on the bacteria and bacterial product. The nature of the platelet response may be highly relevant to disease pathogenesis.

The nucleoid-associated protein HUβ affects global gene expression in Porphyromonas gingivalis

HU is a non-sequence-specific DNA-binding protein and one of the most abundant nucleoid-associated proteins in the bacterial cell. Like Escherichia coli, the genome of Porphyromonas gingivalis is predicted to encode both the HUα (PG1258) and the HUβ (PG0121) subunit. We have previously reported that PG0121 encodes a non-specific DNA-binding protein and that PG0121 is co-transcribed with the K-antigen capsule synthesis operon. We also reported that deletion of PG0121 resulted in downregulation of capsule operon expression and produced a P. gingivalis strain that is phenotypically deficient in surface polysaccharide production. Here, we show through complementation experiments in an E. coli MG1655 hupAB double mutant strain that PG0121 encodes a functional HU homologue. Microarray and quantitative RT-PCR analysis were used to further investigate global transcriptional regulation by HUβ using comparative expression profiling of the PG0121 (HUβ) mutant strain to the parent strain, W83. Our analysis determined that expression of genes encoding proteins involved in a variety of biological functions, including iron acquisition, cell division and translation, as well as a number of predicted nucleoid associated proteins were altered in the PG0121 mutant. Phenotypic and quantitative real-time-PCR (qRT-PCR) analyses determined that under iron-limiting growth conditions, cell division and viability were defective in the PG0121 mutant. Collectively, our studies show that PG0121 does indeed encode a functional HU homologue, and HUβ has global regulatory functions in P. gingivalis; it affects not only production of capsular polysaccharides but also expression of genes involved in basic functions, such as cell wall synthesis, cell division and iron uptake.

Microvesicles at the crossroads between infection and cardiovascular diseases

Observational and experimental studies continue to support the association of infection and infection-stimulated inflammation with development of cardiovascular disease (CVD) including atherosclerosis and thrombosis. Microvesicles (MV) are heterogeneous populations of sealed membrane-derived vesicles shed into circulation by activated mammalian cells and/or pathogenic microbes that may represent an interface between bacterial/microbial infection and increased risk of CVD. This review evaluates how MV act to modulate and intersect immunological and inflammatory responses to infection with particular attention to progression of CVD. Although infection-related stimuli provoke release of MV from blood and vascular cells, MV express phosphatidylserine and other procoagulant factors on their surface, which initiate and amplify blood coagulation. In addition, MV mediate cell-cell adhesion, which may stimulate production of pro-inflammatory cytokines in vascular cells, which in turn aggravate progression of CVD and propagate atherothrombosis. MV transfer membrane receptors, RNA and proteins among cells, and present auto-antigens from their cells of origin to proximal or remote target cells. Because MV harbor cell surface proteins and contain cytoplasmic components of the parent cell, they mediate biological messages and play a pivotal role in the crossroad between infection-stimulated inflammation and CVDs.

Simultaneous detection of periodontal pathogens in subgingival plaque and placenta of women with hypertension in pregnancy

BACKGROUND

There are many studies documenting increased prevalence of periodontal infection in women with preeclampsia. But, very few studies have attempted to establish causal relationship between the two.

OBJECTIVE

To find out causal circumstantial evidence by isolating specific periodontal pathogens in oral and placental samples.

MATERIALS AND METHODS

Antenatal periodontal screening and subgingival plaque collection was carried out in ten women with hypertension in pregnancy and ten normotensive controls on their hospital admission at term for cesarean delivery. Placental biopsy was obtained after aseptic placental collection at the time of elective cesarean delivery. Subgingival plaque and placental biopsy were studied for Porphyromonas gingivalis, Fusobacterium nucleatum, Treponema denticola, Prevotella intermedia and Aggregatibacter actinomycetemcomitans using quantitative polymerase chain reaction technique. Periodontist and laboratory personnel were unaware of case or control status. Periodontal status was not informed to the obstetrician recruiting the cases and laboratory. Microbiology report was not revealed till end of the study.

RESULTS

Periodontal pathogens were found to be high in the group with hypertension than the controls. P gingivalis was found in all the samples from subgingival plaque and placenta, irrespective of the periodontal disease status.

CONCLUSION

In cases with hypertension, periodontal pathogens are present in higher proportion in subgingival plaque and placenta.

The periodontal anaerobe Porphyromonas gingivalis induced platelet activation and increased aggregation in whole blood by rat model

INTRODUCTION

More and more evidence show that periodontal anaerobes contribute to pathogenesis of peripheral artery diseases. As a typical oral anaerobe that results in periodontitis, P.gingivalis aggregates platelets in PRP in vitro and participated in artery thrombosis. However, in vivo effect on platelet activation and aggregation remains unclear. This study aimed to clarify its role on platelets activation on more physiological environment, that is, on whole blood and systemic circulation.

MATERIALS AND METHODS

To fully estimate platelet activation, CD62P(P-selectin) expression on platelet surface and fibrinogen binding of platelet via conjugated glycoprotein GPIIb/IIIa in whole blood were assayed by flow cytometry, and platelet aggregation was measured on an impedance aggregometor. As primary study, platelet reactivity was assessed after in vitro rat whole blood incubation with P.gingivalis strain 381 in tubes, followed or not followed by ADP and arachidonic acid stimulation. In addition, PBS solution of P.gingivalis was infused into rat to produce transient bacteremia model for 5 minutes and blood samples were subjected to analysis for platelet activation in vivo.

RESULTS

P.gingivalis could not induce rat platelet aggregation in whole blood in vitro, but increased aggregation when irritated by collagen stimulation. Flow cytometric study showed that incubation with P.gingivalis increased CD62P expression and fibrinogen binding of platelet. Moreover, further stress by 10 μmol/L ADP and 260 mmlol/L arachidonic acid yielded additional expression. As in vivo study, after P.gingivalis solution challenged, rat platelet aggregability was enhanced, and CD62P positive percentage of platelets and further reactivity to ADP stimulation improved.

CONCLUSION

In whole blood and in systemic circulation, P.gingivalis could induce rat platelet activation and increase aggregability transiently. The results helped to understand the mechanism underlining which P.gingivalis promoted arteriosclerosis and thrombo-embolic disorders. Further study about chronic infection with P.gingivalis on platelet activity is expected.

Lipoxin A₄ inhibits porphyromonas gingivalis-induced aggregation and reactive oxygen species production by modulating neutrophil-platelet interaction and CD11b expression

Porphyromonas gingivalis is an etiological agent that is strongly associated with periodontal disease, and it correlates with numerous inflammatory disorders, such as cardiovascular disease. Circulating bacteria may contribute to atherogenesis by promoting CD11b/CD18-mediated interactions between neutrophils and platelets, causing reactive oxygen species (ROS) production and aggregation. Lipoxin A₄ (LXA₄) is an endogenous anti-inflammatory and proresolving mediator that is protective of inflammatory disorders. The aim of this study was to investigate the effect of LXA₄ on the P. gingivalis-induced activation of neutrophils and platelets and the possible involvement of Rho GTPases and CD11b/CD18 integrins. Platelet/leukocyte aggregation and ROS production was examined by lumiaggregometry and fluorescence microscopy. Integrin activity was studied by flow cytometry, detecting the surface expression of CD11b/CD18 as well as the exposure of the high-affinity integrin epitope, whereas the activation of Rac2/Cdc42 was examined using a glutathione S-transferase pulldown assay. The study shows that P. gingivalis activates Rac2 and Cdc42 and upregulates CD11b/CD18 and its high-affinity epitope on neutrophils, and that these effects are diminished by LXA₄. Furthermore, we found that LXA₄ significantly inhibits P. gingivalis-induced aggregation and ROS generation in whole blood. However, in platelet-depleted blood and in isolated neutrophils and platelets, LXA₄ was unable to inhibit either aggregation or ROS production, respectively. In conclusion, this study suggests that LXA₄ antagonizes P. gingivalis-induced cell activation in a manner that is dependent on leukocyte-platelet interaction, likely via the inhibition of Rho GTPase signaling and the downregulation of CD11b/CD18. These findings may contribute to new strategies in the prevention and treatment of periodontitis-induced inflammatory disorders, such as atherosclerosis.

Mechanisms of oral bacteria-induced platelet activation

The oral cavity is inhabited by over 500 different bacterial species that normally exist in ecological balance both with each other and with the host. When this equilibrium is disturbed, an overgrowth of individual organisms can occur, which, in turn, can lead to the onset of pathological processes, notably dental caries and periodontitis. Generally, bacteraemias occur more frequently in individuals with periodontal disease, and these bacteraemias have been implicated in the development of a range of systemic diseases, including atherothrombotic disorders. The mechanism underlying this relationship remains to be precisely defined, although studies have shown a link between bacteria of oral origin and platelet activation. Several orally derived species of bacteria interact with platelets, including those of the Streptococcus ( Streptococcus sanguinis , Streptococcus mutans , Streptococcus agalactiae , Streptococcus pyogenes , Streptococcus gordonii , Streptococcus pneumoniae , Streptococcus mitis ) and Staphylococcus ( Staphylococcus epidermidis , Staphylococcus capitis ) genera, as well as Pseudomonas aeruginosa and Porphyromonas gingivalis . In addition, some members of both the Streptococcus and the Staphylococcus genera, as well as Porphyromonas gingivalis , can activate platelets in vitro. The current review describes the heterogeneous mechanisms of platelet activation employed by individual bacterial species. The pathological and clinical implications of platelet activation by orally derived bacteria are discussed.

The role of inflammation in regulating platelet production and function: Toll-like receptors in platelets and megakaryocytes

Platelets have been extensively studied as hemostatic regulators, stopping uncontrolled flow of blood from an injured vessel and allowing for repair. However, multiple studies have shown that platelets can interact with bacterial proteins, particularly seen during sepsis and inflammation. Immune cells recognize pathogens through Toll-like Receptors (TLRs). These same receptors allow platelets to recognize bacterial proteins and regulate platelet immunity and function. This review examines the TLRs expressed on platelets and megakaryocytes and how these receptors affect the function of these cells. Through TLRs, platelets go beyond hemostatic regulation and play a pivotal role in inflammation and infection.

Entry of Porphyromonas gingivalis outer membrane vesicles into epithelial cells causes cellular functional impairment

Porphyromonas gingivalis, a periodontal pathogen, secretes outer membrane vesicles (MVs) that contain major virulence factors, including proteases termed gingipains (Arg-gingipain [Rgp] and Lys-gingipain [Kgp]). We recently showed that P. gingivalis MVs swiftly enter host epithelial cells via an endocytosis pathway and are finally sorted to lytic compartments. However, it remains unknown whether MV entry impairs cellular function. Herein, we analyzed cellular functional impairment following entry of P. gingivalis into epithelial cells, including HeLa and immortalized human gingival epithelial (IHGE) cells. After being taken up by endocytic vacuoles, MVs degraded the cellular transferrin receptor (TfR) and integrin-related signaling molecules, such as paxillin and focal adhesion kinase (FAK), which resulted in depletion of intracellular transferrin and inhibition of cellular migration. Few Rgp-null MVs entered the cells, and these negligibly degraded TfR, whereas paxillin and FAK degradation was significant. In contrast, Kgp-null MVs clearly entered the cells and degraded TfR, while they scarcely degraded paxillin and FAK. In addition, both wild-type and Kgp-null MVs significantly impaired cellular migration, whereas the effect of Rgp-null MVs was limited. Our findings suggest that, following entry of P. gingivalis MVs into host cells, MV-associated gingipains degrade cellular functional molecules such as TfR and paxillin/FAK, resulting in cellular impairment, indicating that P. gingivalis MVs are potent vehicles for transmission of virulence factors into host cells and are involved in the etiology of periodontitis.

The thrombotic potential of oral pathogens

In recent times the concept of infectious agents playing a role in cardiovascular disease has attracted much attention. Chronic oral disease such as periodontitis, provides a plausible route for entry of bacteria to the circulation. Upon entry to the circulation, the oral bacteria interact with platelets. It has been proposed that their ability to induce platelet aggregation and support platelet adhesion is a critical step in the pathogenesis of the infection process. Many published studies have demonstrated multiple mechanisms through which oral bacteria are able to bind to and activate platelets. This paper will review the various mechanisms oral bacteria use to interact with platelets.

Porphyromonas gingivalis outer membrane vesicles enter human epithelial cells via an endocytic pathway and are sorted to lysosomal compartments

Porphyromonas gingivalis, a periodontal pathogen, secretes outer membrane vesicles (MVs) that contain major virulence factors, including major fimbriae and proteases termed gingipains, although it is not confirmed whether MVs enter host cells. In this study, we analyzed the mechanisms involved in the interactions of P. gingivalis MVs with human epithelial cells. Our results showed that MVs swiftly adhered to HeLa and immortalized human gingival epithelial cells in a fimbria-dependent manner and then entered via a lipid raft-dependent endocytic pathway. The intracellular MVs were subsequently routed to early endosome antigen 1-associated compartments and then were sorted to lysosomal compartments within 90 min, suggesting that intracellular MVs were ultimately degraded by the cellular digestive machinery. However, P. gingivalis MVs remained there for over 24 h and significantly induced acidified compartment formation after being taken up by the cellular digestive machinery. In addition, MV entry was shown to be mediated by a novel pathway for transmission of bacterial products into host cells, a Rac1-regulated pinocytic pathway that is independent of caveolin, dynamin, and clathrin. Our findings indicate that P. gingivalis MVs efficiently enter host cells via an endocytic pathway and survive within the endocyte organelles for an extended period, which provides better understanding of the role of MVs in the etiology of periodontitis.

The periodontal pathogen Porphyromonas gingivalis sensitises human blood platelets to epinephrine

Recent studies indicate connections between periodontitis and atherothrombosis, and the periodontal pathogen Porphyromonas gingivalis has been found within atherosclerotic lesions. P. gingivalis-derived proteases, designated gingipains activate human platelets, probably through a "thrombin-like" activity on protease-activated receptors (PARs). However, the potential interplay between P. gingivalis and other physiological platelet activators has not been investigated. The aim of this study was to elucidate consequences and mechanisms in the interaction between P. gingivalis and the stress hormone epinephrine. By measuring changes in light transmission through platelet suspensions, we found that P. gingivalis provoked aggregation, whereas epinephrine alone never had any effect. Intriguingly, pre-treatment of platelets with a low, sub-threshold number of P. gingivalis (i.e. a density that did not directly provoke platelet aggregation) resulted in a marked aggregation response when epinephrine was added. This synergistic action was not inhibited by the cyclooxygenas inhibitor aspirin. Furthermore, fura-2-measurements revealed that epinephrine caused an intracellular Ca(2+) mobilization in P. gingivalis pre-treated platelets, whereas epinephrine alone had no effect. Inhibition of the arg-specific gingipains, but not the lys-specific gingipains, abolished the aggregation and the Ca(2+) response provoked by epinephrine. Similar results were achieved by separate blockage of platelet alpha(2)-adrenergic receptors and PARs. In conclusion, the present study shows that a sub-threshold number of P. gingivalis sensitizes platelets to epinephrine. We suggest that P. gingivalis-derived arg-specific gingipains activates a small number of PARs on the surface of the platelets. This leads to an unexpected Ca(2+) mobilization and a marked aggregation response when epinephrine subsequently binds to the alpha(2)-adrenergic receptor. The present results are consistent with a direct connection between periodontitis and stress, and describe a novel mechanism that may contribute to pathological platelet activation.

Inflammation as a potential mediator for the association between periodontal disease and Alzheimer's disease

Periodontal disease (PDD) is associated with increased risk of cardiovascular disease, cerebrovascular disease, and mortality in many studies, while other studies have begun to suggest an association of PDD with Alzheimer's disease (AD). This paper discusses how infectious pathogens and systemic infection may play a role in AD. The roles of infection and inflammation are addressed specifically with regard to known AD pathologic lesions including senile plaques, neuron death, neurofibrillary tangles, and cerebrovascular changes. A testable model of proposed pathways between periodontal infection and AD is presented including three possible mechanisms: a) direct effects of infectious pathogens, b) inflammatory response to pathogens, and c) the effects on vascular integrity. The role of gene polymorphisms is discussed, including apolipoprotein (APOE) varepsilon4 as a pro-inflammatory and pro-infection genotype.

The periodontal pathogen Porphyromonas gingivalis cleaves apoB-100 and increases the expression of apoM in LDL in whole blood leading to cell proliferation

OBJECTIVE

Several studies support an association between periodontal disease and atherosclerosis with a crucial role for the pathogen Porphyromonas gingivalis. This study aims at investigating the proteolytic and oxidative activity of P. gingivalis on LDL in a whole blood system using a proteomic approach and analysing the effects of P. gingivalis-modified LDL on cell proliferation.

METHODS

The cellular effects of P. gingivalis in human whole blood were assessed using lumi-aggregometry analysing reactive oxygen species production and aggregation. Blood was incubated for 30 min with P. gingivalis, whereafter LDL was isolated and a proteomic approach was applied to examine protein expression. LDL-oxidation was determined by analysing the formation of protein carbonyls. The effects of P. gingivalis-modified LDL on fibroblast proliferation were studied using the MTS assay.

RESULTS

Incubation of whole blood with P. gingivalis caused an extensive aggregation and ROS production, indicating platelet and leucocyte activation. LDL prepared from bacteria-exposed blood showed an increased protein oxidation, elevated levels of apoM and formation of two apoB-100 N-terminal fragments. Porphyromonas gingivalis-modified LDL markedly increased the growth of fibroblasts. Inhibition of gingipain R suppressed the modification of LDL by P. gingivalis.

CONCLUSIONS

The ability of P. gingivalis to change the protein expression and proliferative capacity of LDL may represent a crucial event in periodontitis-associated atherosclerosis.

Periodontitis is associated with preeclampsia in pregnant women

BACKGROUND

Recent investigations have demonstrated a positive association between periodontitis and pregnancy complications. The purpose of this study was to determine the effect of periodontitis and the subgingival microbial composition on preeclampsia.

METHODS

A case-control study was carried out in Cali, Colombia that included 130 preeclamptic and 243 non-preeclamptic women between 26 to 36 weeks of pregnancy. Sociodemographic data, obstetric risk factors, periodontal status, and subgingival microbial composition were determined in both groups. Preeclampsia was defined as blood pressure>or=140/90 mm Hg, and >or=2+ proteinuria, confirmed by 0.3 g proteinuria/24 hours of urine specimens. Controls were healthy pregnant women. Odds ratios (ORs) for periodontitis and subgingival microbiota compositions were calculated.

RESULTS

A total of 83 out of 130 preeclamptic women (63.8%) and 89 out of 243 controls (36.6%) had chronic periodontitis (OR: 3.0; 95% confidence interval (CI): 1.91 to 4.87; P<0.001). Clinical attachment loss increased in the case group (4.0+/-0.10 mm) compared to the control group (3.0+/-0.08 mm) (P<0.001). The average newborn birth weight from preeclamptic mothers was 2.453 g, whereas in controls was 2.981 g (P<0.001). Two red complex microorganisms, Porphyromonas gingivalis and Tannerella forsythensis, and the green complex microorganism Eikenella corrodens were more prevalent in the preeclamptic group than in controls (P<0.01).

CONCLUSIONS

Chronic periodontal disease and the presence of P. gingivalis, T. forsythensis, and E. corrodens were significantly associated with preeclampsia in pregnant women. Further research is needed to establish pathogenic mechanisms of active periodontal disease and subgingival periodontopathogens related to preeclampsia development.

Porphyromonas gingivalis bacteremia induces coronary and aortic atherosclerosis in normocholesterolemic and hypercholesterolemic pigs

OBJECTIVES

The aim of this study was to determine whether recurrent intravenous injections with Porphyromonas gingivalis (P gingivalis), mimicking periodontitis-associated bacteremia, promotes coronary artery and aortic atherosclerosis in pigs.

METHODS AND RESULTS

Pigs (n=36) fed low- or high-fat chow were divided into P gingivalis-sensitized and P gingivalis-challenged groups or P gingivalis-sensitized controls and saline-treated controls. Pigs were sensitized with 10(9) killed P gingivalis subcutaneously. Four weeks later all sensitized pigs in the group to be challenged started intravenous injections thrice weekly for 5 months with 10(6) to 10(7) colony forming units of P gingivalis while controls received saline. Anti-P gingivalis antibody, serum cholesterol, and complete blood counts were assayed monthly. Pigs were euthanized 2 weeks after the last injection, and coronary arteries and aortas were analyzed by histomorphometry and immunohistochemistry. Anti-P gingivalis antibody was increased by P gingivalis exposure. P gingivalis-challenged pigs developed a significantly greater amount of coronary and aortic atherosclerosis than controls in the normocholesterolemic group and nearly significant in the hypercholesterolemic group. P gingivalis was detected by polymerase chain reaction in arteries from most (94%, 16 of 17) P gingivalis-challenged pigs but not controls.

CONCLUSIONS

Recurrent P gingivalis bacteremia induces aortic and coronary lesions consistent with atherosclerosis in normocholesterolemic pigs and increases aortic and coronary atherosclerosis in hypercholesterolemic pigs.