Is Porphyromonas gingivalis involved in Parkinson's disease?

Porphyromonas gingivalis, a major subgingival plaque bacterium in periodontitis, has recently attracted much attention as a possible microbial driver in Alzheimer's disease. In the present paper, another common neuroinflammatory disease, Parkinson's disease (PD), is discussed. A recent study found major virulence factors of P. gingivalis such as gingipain R1 (RgpA) and lipopolysaccharide in the blood circulation of a PD population. The current review reveals how features such as systemic inflammation, hypercoagulation, presence of amyloid fibrin(ogen) in plasma, and marked ultrastructural changes in platelets, probably induced by P. gingivalis, may affect the development of PD. Several other clinical studies have also demonstrated an association between periodontitis and PD. Even if the risk of periodontal diseases causing neurological disorders needs to be better substantiated, that should not keep us from trying to prevent them by performing careful daily dental hygiene.

Oral health and cardiovascular disease risk factors and mortality of cerebral haemorrhage, cerebral infarction and unspecified stroke in elderly men: A prospective cohort study.

Background: Stroke mortality comprises different specific diagnoses as cerebral infarction, different haemorrhagic conditions and unspecified stroke. This study seeks to explore the prediction of oral health indicators versus known cardiovascular disease risk factors for stroke mortality. Methods: Altogether, 12,764 men aged 58 to 77 years were invited to the health screening Oslo II in the year 2000. It included general medical measurements and questionnaire information. Mortality data were supplied by Statistics Norway for the 6530 attending men. Cox proportional hazards regression analyses were used to establish prediction models for mortality. Results: Oral health by number of tooth extractions >10 was found to be an independent predictor for cerebral infarction hazard ratio = 2.92, 95% confidence interval (1.24-6.89). This was independent of HDL-Cholesterol (inversely) hazard ratio = 0.21, 95% confidence interval (0.06-0.76), frequent alcohol consumption (drinking 4-7 times per week) hazard ratio = 3.58, 95% confidence interval (1.40-9.13) and diabetes hazard ratio = 4.28, 95% confidence interval (1.68-10.89). Predictors for cerebral haemorrhage were age, hs-C-reactive protein and body mass index (inversely). Age and total cholesterol (inversely) were predictors for unspecified stroke. Conclusions: Oral health measured by number of tooth extractions >10 was an independent predictor for cerebral infarction in addition to age, HDL-C, hs-C-reactive protein and diabetes. The pattern of risk factors varied between the specific stroke diagnoses.

Are Sphingolipids and Serine Dipeptide Lipids Underestimated Virulence Factors of Porphyromonas gingivalis?

The keystone periodontal pathogen Porphyromonas gingivalis produces phosphorylated dihydroceramide lipids (sphingolipids) such as phosphoethanolamine dihydroceramide (PE DHC) and phosphoglycerol dihydroceramide (PG DHC) lipids. Phosphorylated DHCs (PDHCs) from P. gingivalis can affect a number of mammalian cellular functions, such as potentiation of prostaglandin secretion from gingival fibroblasts, promotion of RANKL-induced osteoclastogenesis, promotion of apoptosis, and enhancement of autoimmunity. In P. gingivalis, these lipids affect anchoring of surface polysaccharides, resistance to oxidative stress, and presentation of surface polysaccharides (anionic polysaccharides and K-antigen capsule). In addition to phosphorylated dihydroceramide lipids, serine dipeptide lipids of P. gingivalis are implicated in alveolar bone loss in chronic periodontitis through interference with osteoblast differentiation and function and promotion of osteoclast activity. As a prerequisite for designation as bacterial virulence factors, bacterial sphingolipids and serine dipeptide lipids are recovered in gingival/periodontal tissues, tooth calculus, human blood, vascular tissues, and brain. In addition to P. gingivalis, other bacteria of the genera Bacteroides, Parabacteroides, Porphyromonas, Tannerella, and Prevotella produce sphingolipids and serine dipeptide lipids. The contribution of PDHCs and serine dipeptide lipids to the pathogenesis of periodontal and extraoral diseases may be an underappreciated area in microbe-host interaction and should be more intensively investigated.

From the Acta Prize Lecture 2014: the periodontal-systemic connection seen from a microbiological standpoint.

OBJECTIVE: To give an overview of the periodontal-systemic connection seen from a microbiologist. METHODS: Original research papers, review articles and workshop proceedings were consulted. RESULTS: Periodontal bacteria can cross epithelial cells, enter the circulation, invade endothelial cells, induce endothelial cell dysfunction and activate inflammatory and immune responses. Several studies support the association between periodontitis (PD) and cardiovascular disease. Severe PD involves a risk for development of type 2 diabetes. Maternal PD is moderately associated with adverse pregnancy outcome and pre-eclampsia. Dental plaque can contain respiratory pathogens able to promote chronic obstructive pulmonary disease and pneumonia. Periodontal bacterial DNA has been detected in synovial fluid of patients with rheumatoid arthritis. Minor evidence exists for associations between PD and chronic kidney disease, obesity, cancer, metabolic syndrome and cognitive impairment. Concerns can be raised as to the interpretation of some study results due to heterogeneity in definitions used for PD, too much weight upon in vitro studies with a few selected organisms and failing recognition that the majority of the periodontal microbiota is not yet cultivated. CONCLUSION: Periodontal bacteria may participate in extra-oral infections such as CVD, diabetes, APO, pre-eclampsia, COPD, pneumonia, RA, CKD, obesity, cancer, MetS and cognitive impairment. Most knowledge is based on associations which do not necessarily imply causality. Future studies should reach consensus on the definition of PD and systemic disease outcomes, recognize the full spectrum of the microbiota in PD and bacteremia, including not-yet-cultivated organisms and delineate the clinical significance of genetic strain variations and the role of periodontopathogenic vs gut organisms within atheromatous lesions. For demonstration of causality, large, long-term clinical studies should use well-defined criteria for PD and robust disease outcomes to elucidate the importance of PD intervention and prevention.

Acute focal infections of dental origin.

This article describes the most important pus-producing acute oral infections (dental infections) that can spread extra-orally. Most of these infections are spread by bacteria entering the bloodstream. However, dental infections have a number of other pathways for dissemination. By forming abscesses or phlegmon they can reach facial spaces that communicate with each other and then spread downwards to the mediastinum or upwards to the brain. In such cases dental infections can become, if not properly treated, life-threatening. It seems that early diagnosis and treatment are imperative, and potentially infectious foci should be traced and eliminated. Dental hygiene and prophylaxis to prevent dental biofilm formation are important measures to reduce the risk of these calamities. The more compromised the host defense is, the more importance should be put on these measures. Although commensal bacteria are often involved in these infections, attention should also be paid to specific periodontal pathogens, and a proper microbial diagnosis, obtained using molecular methods plus bacterial sensitivity testing, can provide the patient with optimal care. Drainage of pus must be established where possible so that the optimal effect of antibiotics can be achieved. Penicillin is still the drug of first choice in settings where suspicion of methicillin-resistant Staphylococcus aureus is low.

Comparing clinical attachment level and pocket depth for predicting periodontal disease progression in healthy sites of patients with chronic periodontitis using multi-state Markov models.

AIM: To understand degeneration of healthy sites and identify factors associated with disease progression in patients with chronic periodontitis. MATERIAL AND METHODS: Data on healthy sites from 163 American and Swedish subjects were analysed using two-three-state (health, gingivitis, chronic periodontitis) Markov models based on bleeding on probing (BOP), and either clinical attachment level (CAL) + BOP or pocket depth (PD) + BOP. RESULTS: In 2 years, 10% (CAL + BOP) and 3% (PD + BOP) of healthy sites developed chronic periodontitis. On average, healthy sites remained healthy for 32 months before transiting in both models. Most transitions (87-97%) from health were to the gingivitis state. The expected duration of the gingivitis lesion was 4-5 months and sites recovered with a high probability (96-98%). Disease severity as measured by number of sites with CAL/PD > 4 mm at baseline and smoking, were associated with fast progression from health to chronic periodontitis within 6 months as were gingival redness in the PD + BOP model only. With age, the rate of disease progression to gingivitis decreased. CONCLUSION: Transition probabilities for gingivitis and chronic periodontitis were higher with CAL + BOP than with PD + BOP. Smoking and disease severity were significant predictors for fast progression.

Comparative analysis of antibodies to four major periodontal bacteria in respiratory diseases: a cohort study.

OBJECTIVES: To make a descriptive comparison of antibodies to four major periodontal bacteria and their relation to the respiratory diseases asthma and bronchitis/emphysema, and to cancer incidence. METHODS: The serum of a random sample of men with no history of cancer incidence (n=621) was analysed by the ELISA method for antibody levels of four periodontal bacteria; the anaerobes of the so-called red complex Tannerella forsythia (TF), Porphyromonas gingivalis (PG), and Treponema denticola (TD), and the facultative anaerobe Aggregatibacter actinomycetemcomitans (AA). The antibody readings were divided into quartiles and the distribution of cases of the relevant diseases as compared with the non-cases. Comparisons of the quartile distributions were by the Pearson χ2 test. Data and serum from the Oslo II study of Norwegian men from 2000 were used. The ELISA analyses were performed on thawed frozen serum. Cancer data from 17.5 years of follow-up were provided by the Norwegian Cancer Registry. RESULTS: In all, 52 men had reported asthma and 23 men had bronchitis/emphysema at the health screening. Results on cancer incidence are given for all respiratory cancers, n=23, and bronchi and lung cancers separately, n=18. Stratified analyses were performed for the four endpoints showing significant association with low levels of TD antibodies for bronchitis; p=0.035. Both TF and TD were significant for low levels of antibodies among daily smokers; p=0.030 for TF and p<0.001 for TD in the analysis of the full study sample. For PG and AA, no such associations were observed. An association with respiratory cancers was not observed. CONCLUSION: A low level of TD was associated with bronchitis/emphysema compared with the rest of the cohort. In the total study sample, low levels of antibodies to both TF and TD were associated with daily smoking.

Changes in the supragingival microbiota surrounding brackets of upper central incisors during orthodontic treatment.

OBJECTIVE: The aim of this study was to determine how fixed orthodontic appliances affect microbiota of supragingival plaque over 5 months. MATERIALS AND METHODS: Twenty individuals of Scandinavian origin, aged 10-16 years, were included. All subjects were fitted with fixed orthodontic appliances in both the maxillary and mandibular tooth arches. Pooled supragingival plaque samples from the labial surface of the two maxillary central incisors were collected before bonding (T1) and afterwards at 4 weeks (T2), 3 months (T3) and 5 months (T4). The plaque index (PI) was recorded for each sampling. The gingival status was documented at T1 and T4 by using clinical photographs. Plaque microbiota was identified using the Human Oral Microbe Identification Microarray (HOMIM). RESULTS: Increased plaque levels were recorded after bonding, however the increase was not significant. The prevalence of gingivitis at the maxillary central incisors increased from 25% at T1 to 74% at T4. No significant changes of the plaque microbiota from the sample area were detected during the 5-month period. Trends toward a microbiota containing more periodontitis- and caries-associated bacteria were detected. CONCLUSIONS: Although trends toward a microbiota containing more periodontitis- and caries-associated bacteria were detected, the changes were not severe enough to be significant. Treatment with fixed orthodontics does not necessarily shift the microbiota to a more pathogenic composition.

Comprehensive transcriptome analysis of the periodontopathogenic bacterium Porphyromonas gingivalis W83.

High-density tiling microarray and RNA sequencing technologies were used to analyze the transcriptome of the periodontopathogenic bacterium Porphyromonas gingivalis. The compiled P. gingivalis transcriptome profiles were based on total RNA samples isolated from three different laboratory culturing conditions, and the strand-specific transcription profiles generated covered the entire genome, including both protein coding and noncoding regions. The transcription profiles revealed various operon structures, 5'- and 3'-end untranslated regions (UTRs), differential expression patterns, and many novel, not-yet-annotated transcripts within intergenic and antisense regions. Further transcriptome analysis identified the majority of the genes as being expressed within operons and most 5' and 3' ends to be protruding UTRs, of which several 3' UTRs were extended to overlap genes carried on the opposite/antisense strand. Extensive antisense RNAs were detected opposite most insertion sequence (IS) elements. Pairwise comparative analyses were also performed among transcriptome profiles of the three culture conditions, and differentially expressed genes and metabolic pathways were identified. With the growing realization that noncoding RNAs play important biological functions, the discovery of novel RNAs and the comprehensive transcriptome profiles compiled in this study may provide a foundation to further understand the gene regulation and virulence mechanisms in P. gingivalis. The transcriptome profiles can be viewed at and downloaded from the Microbial Transcriptome Database website, http://bioinformatics.forsyth.org/mtd.

Clinical color intensity of white spot lesions might be a better predictor of enamel demineralization depth than traditional clinical grading.

INTRODUCTION: The aims of this study were to calculate the volume of white spot lesions by using microcomputed tomography and to determine which clinical attribute of the white spot lesion could better predict its volume: the clinically visible white spot lesion surface area or its color intensity. METHODS: White spot lesions were induced in 8 patients in vivo on 23 healthy premolars destined for extraction during orthodontic treatment by using specially designed plaque-retaining orthodontic bands. After 7 weeks, the premolars were extracted. After extraction, the resulting white spot lesions were photographed and clinically graded. The teeth were analyzed with microcomputed tomography. RESULTS: After 7 weeks, 70% of the teeth developed clinical white spot lesions. Clinically, the size of the lesions varied from minor to severe. Their volumes varied from 0 to 1.2931 mm(3). The traditional grades for white spot lesions correlated significantly with color intensity. A significant correlation was found between white spot lesion color intensity and lesion volume. This correlation was found to be better than that between the white spot lesion clinical score and lesion volume. CONCLUSIONS: Our results indicate that white spot lesion color intensity might predict the depth of enamel demineralization as well as or better than traditional white spot lesion scoring. Therefore, the dentist could use this information when planning treatment for white spot lesions.

Low level of antibodies to the oral bacterium Tannerella forsythia predicts bladder cancers and Treponema denticola predicts colon and bladder cancers: A prospective cohort study.

This study explores the risk for cancer by level of antibodies to the anaerobe oral bacteria of periodontitis Tannerella forsythia (TF), Porphyromonas gingivalis (PG), and Treponema denticola (TD) all three collectively termed the red complex, and the facultative anaerobe bacterium Aggregatibacter actinomycetemcomitans (AA). The prospective cohort, the Oslo II-study from 2000, the second screening of the Oslo study of 1972/73, has been followed for 17 ½ years with regard to cancer incidence and mortality. A random sample of 697 elderly men comprised the study cohort. The antibody results measured by enzyme linked immunosorbent assay (ELISA) were used in the Cox proportional hazards analyses, and quartile risk on cancer incidence in a 17 ½ years follow-up. Among the 621 participants with no prior cancer diagnoses, 221 men developed cancer. The incidence trend was inverse, and the results are shown as 1st quartile of highest value and 4th as lowest of antibody levels. The results of the Cox proportional regression analyses showed that TF inversely predicts bladder cancer (n = 22) by Hazard Ratio (HR) = 1.71 (95% CI: 1.12, 2.61). TD inversely predicts colon cancer (n = 26) by HR = 1.52 (95% CI: 1.06, 2.19) and bladder cancer (n = 22) by HR = 1.60 (95% CI: 1.05, 2.43). Antibodies to two oral bacteria, TF and TD, showed an inverse risk relationship with incidence of specific cancers: TF bladder cancer, TD bladder and colon cancer. Lowered immunological response to the oral infection, periodontitis, is shown to be a risk factor in terms of cancer aetiology.

Strand-specific transcriptome profiling with directly labeled RNA on genomic tiling microarrays.

BACKGROUND: With lower manufacturing cost, high spot density, and flexible probe design, genomic tiling microarrays are ideal for comprehensive transcriptome studies. Typically, transcriptome profiling using microarrays involves reverse transcription, which converts RNA to cDNA. The cDNA is then labeled and hybridized to the probes on the arrays, thus the RNA signals are detected indirectly. Reverse transcription is known to generate artifactual cDNA, in particular the synthesis of second-strand cDNA, leading to false discovery of antisense RNA. To address this issue, we have developed an effective method using RNA that is directly labeled, thus by-passing the cDNA generation. This paper describes this method and its application to the mapping of transcriptome profiles. RESULTS: RNA extracted from laboratory cultures of Porphyromonas gingivalis was fluorescently labeled with an alkylation reagent and hybridized directly to probes on genomic tiling microarrays specifically designed for this periodontal pathogen. The generated transcriptome profile was strand-specific and produced signals close to background level in most antisense regions of the genome. In contrast, high levels of signal were detected in the antisense regions when the hybridization was done with cDNA. Five antisense areas were tested with independent strand-specific RT-PCR and none to negligible amplification was detected, indicating that the strong antisense cDNA signals were experimental artifacts. CONCLUSIONS: An efficient method was developed for mapping transcriptome profiles specific to both coding strands of a bacterial genome. This method chemically labels and uses extracted RNA directly in microarray hybridization. The generated transcriptome profile was free of cDNA artifactual signals. In addition, this method requires fewer processing steps and is potentially more sensitive in detecting small amount of RNA compared to conventional end-labeling methods due to the incorporation of more fluorescent molecules per RNA fragment.

Porphyromonas gingivalis-Induced Neuroinflammation in Alzheimer's Disease.

"Chronic" periodontitis and its keystone pathogen Porphyromonas gingivalis have repeatedly been associated with Alzheimer's disease (AD). Pathological hallmarks in AD are brain accumulations of amyloid-beta and neurofibrillary tangles consisting of aggregated and hyperphosphorylated tau. In addition, neuroinflammation induced by P. gingivalis has increasingly been recognized as a factor in the pathogenesis of AD. The present mini-review discusses possible mechanisms for the induction of neuroinflammation by P. gingivalis in AD, involving factors such as pro-inflammatory mediators, amyloid-beta, tau, microglia, cathepsin B, and protein kinase R. Inflammagens of P. gingivalis such as lipopolysaccharide and gingipains are also discussed.

Can Porphyromonas gingivalis Contribute to Alzheimer's Disease Already at the Stage of Gingivitis?

Alzheimer's disease (AD) has been associated with periodontitis, which starts as gingivitis. Similar to periodontitis, gingivitis bacteria, bacterial products, and inflammatory mediators can travel to the brain via the blood stream and promote brain inflammation. Periodontal pathogens such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, both associated with AD, have been found in dental plaque of children already at the age of 3. It is suggested that these bacteria during long-term exposure may drive microglia (brain resident macrophage cells) into a pro-inflammatory M1 phase where they contribute to AD rather than protect against it. This notion comes from studies in mice showing that microglia actually can "remember" previous inflammatory challenge and become "trained" or "tolerant" to toxins like lipopolysaccharide. If gingivitis has an impact on AD, which should be verified, AD prophylaxis should start already at this pre-periodontitis stage with removal of supragingival plaque.

Porphyromonas Gingivalis May Seek the Alzheimer's Disease Brain to Acquire Iron from Its Surplus.

Iron accumulates in the brain of subjects with Alzheimer's disease (AD). Here it promotes the aggregation of amyloid-ß plaques in which it is abundant. Iron induces amyloid-ß neurotoxicity by damaging free radicals and causing oxidative stress in brain areas with neurodegeneration. It can also bind to tau in AD and enhance the toxicity of tau through co-localization with neurofibrillary tangles and induce accumulation of these tangles. Porphyromonas gingivalis is a key oral pathogen in the widespread biofilm-induced disease "chronic" periodontitis, and recently, has been suggested to have an important role in the pathogenesis of AD. P. gingivalis has an obligate requirement for iron. The current paper suggests that P. gingivalis seeks the AD brain, where it has been identified, to satisfy this need. If this is correct, iron chelators binding iron could have beneficial effects in the treatment of AD. Indeed, studies from both animal AD models and humans with AD have indicated that iron chelators, e.g., lactoferrin, can have such effects. Lactoferrin can also inhibit P. gingivalis growth and proteinases and its ability to form biofilm.

Low levels of salivary lactoferrin may affect oral dysbiosis and contribute to Alzheimer's disease: A hypothesis.

Recently it has been reported that reduced levels of salivary lactoferrin (LF) can be a plausible biomarker for amyloid beta (Aß) accumulation in Alzheimer's disease (AD) brains. This could mean that reduced levels of salivary LF act as a trigger for oral dysbiosis and that low LF levels could change the oral microbiota. A chemical change in the composition of saliva has not yet been considered as a cause for microbial dysbiosis but does present an opportunity to view oral dysbiosis as a plausible contributory factor in the development of AD pathophysiology. Oral dysbiosis has largely been reported as a result of inadequate oral hygiene and dry mouth in elderly subjects. Here we discuss if the deficiency of LF in saliva and gingival fluid of AD patients can facilitate proliferation of oral pathogens, and as a result their spread elsewhere in the body. Additionally, we ask if LF in the AD brain could be overexposed as a result of chronic infection. Together these outcomes will indicate if reduced levels of salivary LF can act as a trigger of oral dysbiosis.

Experiments on in vivo biofilm formation and in vitro adhesion of Candida species on polysiloxane liners.

OBJECTIVES: Microorganisms may colonise polysiloxane soft liners leading to bio-deterioration. The aim of this study was to investigate in vitro adhesion and in vivo biofilm formation of Candida species on polysiloxane surfaces. METHODS: The materials used in this study were Molloplast B, GC Reline soft, Mollosil Plus, Silagum Comfort and Palapress Vario. The in vitro retention of clinical isolates of Candida albicans to the relining and denture-base materials by microscopic (scanning electron microscopy, SEM), conventional culturing methods and antimicrobial properties of these materials were studied. Candida found on materials and mucosa following long-term use were identified and quantified, and biofilms covering the surfaces were investigated by SEM. RESULTS: There was a significant decrease in the number of cells attached in vitro to saliva-coated surfaces compared with non-treated surfaces. An oral Candida carriage of 78% was found. Candida albicans, C. glabrata, C. intermedia and C. tropicalis were identified. In vivo biofilm formation on the liners appeared as massive colonisation by microorganisms. CONCLUSIONS: The results of the in vitro experiments suggest that salivary film influences early colonisation of different C. albicans strains. The film layer also minimises the differences among different strains. The Candida carriage of these patients was similar to denture-wearing patients without soft liners.

[Mouth-rinsing with chlorhexidine for prevention of pneumonia]. / Munnskylling med klorheksidin for å forebygge pneumoni.

Oral decontamination with chlorhexidine prevents accumulation of pathogens in the oral cavity, and can thereby reduce the risk of translocation to and colonization of the lungs. The antiseptic agent chlorhexidine has been widely used in dentistry, it has an excellent record of safety and efficacy and a broad antimicrobial spectrum. Mouth-rinsing with chlorhexidine may result in 90 % reduction of oral microbes. Cooperation between physicians and dentists is important in this area on the borderline between the two professions.

Mucus is more than just a physical barrier for trapping oral microorganisms.

Mucus is thought to serve as a protective coating on wet epithelial surfaces. Recent research has shown that glycans, which are branched sugar molecules found in mucin, a part of mucus, can prevent bacteria from communicating with each other and forming biofilms. This could hinder microbes from causing infections. The present editorial, focusing on a paper by Wheeler et al. [1], published in October 2019 in Nature Microbiology, describes how mucus can attenuate the virulence of Pseudomonas aeruginosa. In addition, streptococci and Candida albicans can be 'tamed' by mucin.

Role of EphA2 in host defense against oro-pharyngeal candidiasis.

Oral defense should be able to sense the burden of, and distinguish between fungal commensals and pathogens, so that an adequate inflammatory response can be set up. Recently, Ephrin type-A receptor 2 (EphA2) was identified on oral epithelial cells and neutrophils that recognizes Candida albicans and induces adaptive protective host responses against this organism. The studies have increased our knowledge of how epithelial cells and neutrophils contribute to host defense against oral yeast infection.