Oral microbial dysbiosis linked to worsened periodontal condition in rheumatoid arthritis patients

BugSigDB captures patterns of differential abundance across a broad range of host-associated microbial signatures

The literature of human and other host-associated microbiome studies is expanding rapidly, but systematic comparisons among published results of host-associated microbiome signatures of differential abundance remain difficult. We present BugSigDB, a community-editable database of manually curated microbial signatures from published differential abundance studies accompanied by information on study geography, health outcomes, host body site and experimental, epidemiological and statistical methods using controlled vocabulary. The initial release of the database contains >2,500 manually curated signatures from >600 published studies on three host species, enabling high-throughput analysis of signature similarity, taxon enrichment, co-occurrence and coexclusion and consensus signatures. These data allow assessment of microbiome differential abundance within and across experimental conditions, environments or body sites. Database-wide analysis reveals experimental conditions with the highest level of consistency in signatures reported by independent studies and identifies commonalities among disease-associated signatures, including frequent introgression of oral pathobionts into the gut.

Unravelling the Link between the Gut Microbiome and Autoimmune Kidney Diseases: A Potential New Therapeutic Approach

The gut microbiota and short chain fatty acids (SCFA) have been associated with immune regulation and autoimmune diseases. Autoimmune kidney diseases arise from a loss of tolerance to antigens, often with unclear triggers. In this review, we explore the role of the gut microbiome and how disease, diet, and therapy can alter the gut microbiota consortium. Perturbations in the gut microbiota may systemically induce the translocation of microbiota-derived inflammatory molecules such as liposaccharide (LPS) and other toxins by penetrating the gut epithelial barrier. Once in the blood stream, these pro-inflammatory mediators activate immune cells, which release pro-inflammatory molecules, many of which are antigens in autoimmune diseases. The ratio of gut bacteria Bacteroidetes/Firmicutes is associated with worse outcomes in multiple autoimmune kidney diseases including lupus nephritis, MPO-ANCA vasculitis, and Goodpasture's syndrome. Therapies that enhance SCFA-producing bacteria in the gut have powerful therapeutic potential. Dietary fiber is fermented by gut bacteria which in turn release SCFAs that protect the gut barrier, as well as modulating immune responses towards a tolerogenic anti-inflammatory state. Herein, we describe where the current field of research is and the strategies to harness the gut microbiome as potential therapy.

Higher odds of periodontitis in systemic lupus erythematosus compared to controls and rheumatoid arthritis: a systematic review, meta-analysis and network meta-analysis

Introduction

Periodontitis as a comorbidity in systemic lupus erythematosus (SLE) is still not well recognized in the dental and rheumatology communities. A meta-analysis and network meta-analysis were thus performed to compare the (i) prevalence of periodontitis in SLE patients compared to those with rheumatoid arthritis (RA) and (ii) odds of developing periodontitis in controls, RA, and SLE.

Methods

Pooled prevalence of and odds ratio (OR) for periodontitis were compared using meta-analysis and network meta-analysis (NMA).

Results

Forty-three observational studies involving 7,800 SLE patients, 49,388 RA patients, and 766,323 controls were included in this meta-analysis. The pooled prevalence of periodontitis in SLE patients (67.0%, 95% confidence interval [CI] 57.0-77.0%) was comparable to that of RA (65%, 95% CI 55.0-75.0%) (p>0.05). Compared to controls, patients with SLE (OR=2.64, 95% CI 1.24-5.62, p<0.01) and RA (OR=1.81, 95% CI 1.25-2.64, p<0.01) were more likely to have periodontitis. Indirect comparisons through the NMA demonstrated that the odds of having periodontitis in SLE was 1.49 times higher compared to RA (OR=1.49, 95% CI 1.09-2.05, p<0.05).

Discussion

Given that RA is the autoimmune disease classically associated with periodontal disease, the higher odds of having periodontitis in SLE are striking. These results highlight the importance of addressing the dental health needs of patients with SLE.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/ identifier CRD42021272876.

Periodontitis and rheumatoid arthritis-Global efforts to untangle two complex diseases

Understanding the impact of oral health on rheumatoid arthritis (RA) will inform how best to manage patients with both periodontitis and RA. This review seeks to provide an update on interventional and mechanistic investigations, including a brief summary of European Research programs investigating the link between periodontitis and RA. Recent clinical studies are described that evaluate how the treatment of one disease impacts on the other, as are studies in both humans and animal models that have sought to identify the potential mechanisms linking the two diseases.

Methotrexate and Non-Surgical Periodontal Treatment Change the Oral-Gut Microbiota in Rheumatoid Arthritis: A Prospective Cohort Study

This study evaluated the changes in the composition of oral-gut microbiota in patients with rheumatoid arthritis (RA) caused by methotrexate (MTX) and non-surgical periodontal treatment (NSPT). Assessments were performed at baseline (T0), 6 months after MTX treatment (T1), and 45 days after NSPT (T2). The composition of the oral and gut microbiota was assessed by amplifying the V4 region of the 16S gene from subgingival plaques and stools. The results of the analysis of continuous variables were presented descriptively and non-parametric tests and Spearman's correlation were adopted. A total of 37 patients (27 with periodontitis) were evaluated at T0; 32 patients (24 with periodontitis) at T1; and 28 patients (17 with periodontitis) at T2. MTX tended to reduce the alpha diversity of the oral-gut microbiota, while NSPT appeared to increase the number of different species of oral microbiota. MTX and NSPT influenced beta diversity in the oral microbiota. The relative abundance of oral microbiota was directly influenced by periodontal status. MTX did not affect the periodontal condition but modified the correlations that varied from weak to moderate (p < 0.05) between clinical parameters and the microbiota. MTX and NSPT directly affected the composition and richness of the oral-gut microbiota. However, MTX did not influence periodontal parameters.

Periodontitis and periodontopathic bacteria as risk factors for rheumatoid arthritis: A review of the last 10 years

Rheumatoid arthritis (RA) is characterized by chronic inflammatory destruction of joint tissue and is caused by an abnormal autoimmune response triggered by interactions between genetics, environmental factors, and epigenetic and posttranslational modifications. RA has been suggested to be interrelated with periodontitis, a serious form or stage of chronic inflammatory periodontal disease associated with periodontopathic bacterial infections, genetic predisposition, environmental factors, and epigenetic influences. Over the last decade, a number of animal and clinical studies have been conducted to assess whether or not periodontitis and associated periodontopathic bacteria constitute risk factors for RA. The present review introduces recent accumulating evidence to support the associations of periodontitis and periodontopathic bacteria with the risk of RA or the outcome of RA pharmacological treatment with disease-modifying antirheumatic drugs. In addition, the results from intervention studies have suggested an improvement in RA clinical parameters after nonsurgical periodontal treatment. Furthermore, the potential causal mechanisms underlying the link between periodontitis and periodontopathic bacteria and RA are summarized.

Assessment of Epstein-Barr virus, Candida albicans, and some periodontal pathogens in rheumatoid arthritis patients with periodontitis

OBJECTIVE

To comparatively investigate the periodontal results and microbial load in subgingival biofilm samples (SBS) in rheumatoid arthritis subjects and healthy volunteers.

METHODS

One hundred twenty subjects were classified into different cohorts: healthy (H-C); periodontitis with good systemic health (H-P); rheumatoid arthritis (RA) and good periodontal health (RA-C); and periodontitis with RA (RA-P). The periodontal parameters were recorded, and SBS were collected to determine periodontal pathogens including Epstein-Barr Virus (EBV) and Candida albicans using reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

Subjects that had greater disease course, determined by moderate or high disease activity scores 28 (DAS28), suffered from worse oral health conditions (higher plaque index, gingival index, bleeding on probing, probing depth, and excessive clinical attachment loss) than those with low DAS28 scores. A higher prevalence of Treponema denticola (T. denticola) was observed in the RA-P group. Cyclic citrullinated peptide was associated with the occurrence of T. denticola and Campylobacter rectus. DAS28 using C-reactive protein (DAS28-CRP) had a significant association with Capnocytophaga gingivalis and EBV. The duration of the RA disease was associated with the presence of T. denticola.

CONCLUSION

Subgingival microbial difference could reliably discriminate RA from healthy individuals. Especially, T. denticola and EBV may play a key role in periodontitis associated with RA.

Nitrate and a nitrate-reducing Rothia aeria strain as potential prebiotic or synbiotic treatments for periodontitis

A few studies indicate that nitrate can reduce dysbiosis from a periodontitis point of view. However, these experiments were performed on samples from healthy individuals, and it is unknown if nitrate will be effective in periodontal patients, where the presence of nitrate-reducing bacteria is clearly reduced. The aim of this study was to test the effect of nitrate and a nitrate-reducing R. aeria (Ra9) on subgingival biofilms of patients with periodontitis. For this, subgingival plaque was incubated with 5 mM nitrate for 7 h (n = 20) or 50 mM nitrate for 12 h (n = 10), achieving a ~50% of nitrate reduction in each case. Additionally, Ra9 was combined with 5 mM nitrate (n = 11), increasing the nitrate reduced and nitrite produced (both p < 0.05). The addition of nitrate to periodontitis communities decreased biofilm mass (50 mM > 5 mM, both p < 0.05). Five millimolar nitrate, 50 mM nitrate and 5 mM nitrate + Ra9 led to 3, 28 and 20 significant changes in species abundance, respectively, which were mostly decreases in periodontitis-associated species. These changes led to a respective 15%, 63% (both p < 0.05) and 6% (not significant) decrease in the dysbiosis index. Using a 10-species biofilm model, decreases in periodontitis-associated species in the presence of nitrate were confirmed by qPCR (all p < 0.05). In conclusion, nitrate metabolism can reduce dysbiosis and biofilm growth of periodontitis communities. Five millimolar nitrate (which can be found in saliva after vegetable intake) was sufficient, while increasing this concentration to 50 mM (which could be achieved by topical applications such as a periodontal gel) increased the positive effects. Ra9 increased the nitrate metabolism of periodontitis communities and should be tested in vivo.

The role of bacterial infections in rheumatoid arthritis development and novel therapeutic interventions: Focus on oral infections

BACKGROUND

Rheumatoid arthritis (RA) represents a primary public health challenge, which is a major source of pain, disability, and socioeconomic effects worldwide. Several factors contribute to its pathogenesis. Infections are an important concern in RA patients, which play a key role in mortality risk. Despite major advances in the clinical treatment of RA, long-term use of disease-modifying anti-rheumatic drugs can cause serious adverse effects. Therefore, effective strategies for developing novel prevention and RA-modifying therapeutic interventions are sorely needed.

OBJECTIVE

This review investigates the available evidence on the interplay between various bacterial infections, particularly oral infections and RA, and focuses on some potential interventions such as probiotics, photodynamic therapy, nanotechnology, and siRNA that can have therapeutic effects.

Simultaneous Analysis of Bacterial and Fungal Communities in Oral Samples from Intubated Patients in Intensive Care Unit

Intubated patients in intensive care units (ICUs) too frequently contract ventilator-associated pneumonia or Candida infections. Oropharyngeal microbes are believed to play an important etiologic role. This study was undertaken to determine whether next-generation sequencing (NGS) can be used to simultaneously analyze bacterial and fungal communities. Buccal samples were collected from intubated ICU patients. Primers targeting the V1-V2 region of bacterial 16S rRNA and the internal transcribed spacer 2 (ITS2) region of fungal 18S rRNA were used. V1-V2, ITS2, or mixed V1-V2/ITS2 primers were used to prepare an NGS library. Bacterial and fungal relative abundances were comparable for V1-V2, ITS2, or mixed V1-V2/ITS2 primers, respectively. A standard microbial community was used to adjust the relative abundances to theoretical abundance, and NGS and RT-PCR-adjusted relative abundances showed a high correlation. Using mixed V1-V2/ITS2 primers, bacterial and fungal abundances were simultaneously determined. The constructed microbiome network revealed novel interkingdom and intrakingdom interactions, and the simultaneous detection of bacterial and fungal communities using mixed V1-V2/ITS2 primers enabled analysis across two kingdoms. This study provides a novel approach to simultaneously determining bacterial and fungal communities using mixed V1-V2/ITS2 primers.

Impacts of Porphyromonas gingivalis periodontitis on rheumatoid arthritis autoimmunity

In RA patients' synovial sites, citrullinated RA-related antigens such as type II collagens, fibrin (ogen), vimentin, and α-enolase could be targeted by ACCPAs. Since ACCPA production can be initiated a long time before RA sign appearance, primary auto-immunization against these citrullinated proteins can be originated from extra-articular sites. It has been shown that there is a significant association between P. gingivalis periodontitis, anti- P. gingivalis antibodies, and RA. P. gingivalis gingipains (Rgp, Kgp) can degrade proteins such as fibrin and α-enolase into some peptides in the form of Arg in the C-terminal which is converted to citrulline by PPAD. Also, PPAD can citrullinate type II collagen and vimentins (SA antigen). P. gingivalis induces inflammation and chemoattraction of immune cells such as neutrophils and macrophages through the increase of C5a (gingipain C5 convertase-like activity) and SCFA secretion. Besides, this microorganism stimulates anoikis, a special type of apoptosis, and NETosis, an antimicrobial form of neutrophil death, leading to the release of PAD1-4, α-enolase, and vimentin from apoptotic cells into the periodontal site. In addition, gingipains can degrade macrophages CD14 and decrease their ability in apoptotic cell removal. Gingipains also can cleave IgGs in the Fc region and transform them into rheumatoid factor (RF) antigens. In the present study, the effects of P. gingivalis on rheumatoid arthritis autoimmune response have been reviewed, which could attract practical insight both in bench and clinic.

Differential associations of rheumatoid arthritis and periodontitis or tooth loss: A cross-sectional study

AIM

To study the association between periodontitis, tooth loss, and rheumatoid arthritis (RA) by using a large national dataset.

MATERIALS AND METHODS

An observational cross-sectional study was performed using the National Health and Nutrition Examination Survey cycles (2009-2014). RA status was detected using a questionnaire. Periodontal status was assigned on the basis of the clinical attachment level and periodontal pocket depth. Dentition status was assessed by the number of permanent teeth observed. We examined the association between RA as exposure and moderate/severe periodontitis and non-functional dentition as outcomes. We progressively adjusted our models for different sets of potential confounders.

RESULTS

Moderate/severe periodontitis was more prevalent in participants reporting RA (53% vs. 41.5%, p = .0003). Non-functional dentition was more prevalent in participants with RA (41% vs. 15.5%, p = .0001). The fully adjusted model showed that participants with RA had higher odds of having non-functional dentition (odds ratio 1.8, 95% confidence interval [CI] 1.3-2.3, p = .0001) but no association with moderate/severe periodontitis (prevalence ratio 1.01, 95% CI 0.9-1.1, p = .9).

CONCLUSION

RA was associated with a higher likelihood of having non-functional dentition but did not show any association with periodontitis after adjusting for the risk factors to control their confounding effect.

Influence of periodontitis on levels of autoantibodies in rheumatoid arthritis patients: A systematic review

BACKGROUND AND OBJECTIVE

Periodontitis (PD) is a dysbiotic disease of tooth-supporting structures that has been associated with various systemic diseases including rheumatoid arthritis (RA). To date, evidence demonstrated increased prevalence of RA among PD patients and postulated PD to have a role in the development of autoantibodies in RA patients. Therefore, a systematic review was conducted to assess the available evidence to ascertain the effect of PD on levels of autoantibodies in the serum, saliva and gingival crevicular fluid (GCF) of RA patients.

MATERIAL AND METHODS

The systematic review was conducted in compliance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. Relevant literature was searched from PubMed, Web of Science, Scopus and Ebscohost databases from inception until 31 August 2020. The risk of bias in each study was determined based on the Newcastle-Ottawa Scale tool. Results from random-effect meta-analyses were presented as summary estimates of odds ratios (ORs) for seropositivity and standardised mean difference (SMD) of autoantibody levels with 95% confidence intervals. Sensitivity tests and meta-regression were performed to assess the robustness of the results and potential cause of heterogeneity.

RESULTS

The electronic and manual searches gathered 932 articles. Following screening and full-text assessment, a total of 29 studies were included in the analysis. Twenty-eight published observational studies were included in the quantitative analysis in the form of random-effect meta-analysis which revealed that PD was associated with anti-citrullinated proteins autoantibodies (ACPAs) and Rheumatoid Factor (RF) seropositive RA patients (OR for ACPA seropositivity: 1.82; 95% CI: 1.13-2.93) (OR for RF seropositivity: 1.53; 95% CI: 1.05-2.24). Also, RA patients with PD had increased serum levels of ACPA and RF. However, high heterogeneity among studies' results, partially ascribed to the unstandardised case definition of PD and laboratory testing of autoantibodies. Apart from ACPA and RF in serum, studies which reported on other RA-related autoantibodies, as well as autoantibody levels in saliva and GCF were scarce.

CONCLUSION

RA patients with PD tend to have greater ACPA and RF levels in their serum when compared with the RA patients without PD supporting the plausible role of PD in the development of systemic autoimmunity in RA patients.

Influence of Environmental Factors on Salivary Microbiota and Their Metabolic Pathway: Next-Generation Sequencing Approach

The current study aimed to investigate the effect of periodontitis and long-term heavy metal (HM) exposure on the salivary microbiome. The patients were divided into four groups as Wu Wei control (WWC) group involved healthy individuals, Wu Wei periodontitis (WWP) patients having periodontitis, Jing Chang with metal pollution periodontally healthy individuals (JCP), and Kuang periodontitis (KP). The most abundant bacteria identified at the phylum level in the WWC group were Bacteroides, Firmicutes, and Fusobacteria. Firmicutes were observed in a significantly higher proportion in the KP group than in the WWC, WWP, and JCP. At the genus level, the WWC has major dominating bacterial genera (such as Leptotrichia, Neisseria, and Fusobacterium) which were similar to WWP and KP group. The significant difference (p < 0.05) was found in alpha diversity while in beta diversity, the significant (p = 0.005) results were found among the four groups. The correlation of oral microbiota revealed that HMs present in the soil (Cr, Ni, and Cu) are associated with the growth of Capnocytophaga, Selenomonas, Aggregatibacter, and Campylobacter. The bacterial functions in the KP group were higher in translation and nucleotide metabolism than in the WWP group. This demonstrated that long-term exposure to HMs can influence the salivary microbiota which can alter the functioning, and diversity of bacteria.

Immune Responses at Host Barriers and Their Importance in Systemic Autoimmune Diseases

Host barriers such as the skin, the lung mucosa, the intestinal mucosa and the oral cavity are crucial at preventing contact with potential threats and are populated by a diverse population of innate and adaptive immune cells. Alterations in antigen recognition driven by genetic and environmental factors can lead to autoimmune systemic diseases such rheumatoid arthritis, systemic lupus erythematosus and food allergy. Here we review how different immune cells residing at epithelial barriers, host-derived signals and environmental signals are involved in the initiation and progression of autoimmune responses in these diseases. We discuss how regulation of innate responses at these barriers and the influence of environmental factors such as the microbiota can affect the susceptibility to develop local and systemic autoimmune responses particularly in the cases of food allergy, systemic lupus erythematosus and rheumatoid arthritis. Induction of pathogenic autoreactive immune responses at host barriers in these diseases can contribute to the initiation and progression of their pathogenesis.

Risk of Periodontitis in Patients with Gastroesophageal Reflux Disease: A Nationwide Retrospective Cohort Study

Background: Gastroesophageal reflux disease (GERD) is the most common digestive clinical problem worldwide that affects approximately 20% of the adult populations in Western countries. Poor oral hygiene has been reported to be associated with GERD as an atypical clinical complication. However, evidence showing the relationship between GERD and the risk of periodontitis is less clear. The present study aimed to use a retrospective cohort study design to further clarify the association between GERD and the subsequent risk of periodontitis. Methods: The risk of periodontitis in patients with GERD was investigated by analyzing epidemiological data from the Taiwan National Health Insurance Research Database from 2008 to 2018. We selected 20,125 participants with a minimum age of 40 years in the GERD group and 1:1 propensity-matched these with non-GERD individuals by sex, age, and comorbidities. The incidence of periodontitis was determined at the end of 2018. A Cox proportional hazards regression model was used to evaluate the risk of periodontitis in patients with GERD. Results: The overall incidence rate of the periodontitis risk was 1.38-fold higher (30.0 vs. 21.7/1000 person years, adjusted hazard ratio (aHR) = 1.36, 95% confidence interval (CI) = 1.28−1.45) in patients with GERD than in those without GERD. After stratified analyses for sex, age, and comorbidity, patients with GERD had a higher risk of periodontitis for age (aHR = 1.31, 95% CI = 1.20−1.42 for 40−54 years and aHR = 1.42, 95% CI =1.28−1.57 for 55−69 years), sex (aHR = 1.40, 95% CI = 1.28−1.54 for men and aHR = 1.33, 95% CI = 1.23−1.45 for women), and presence (aHR = 1.36, 95% CI = 1.27−1.45) and absence (aHR = 1.40, 95% CI = 1.21−1.62) of comorbidity than those without GERD. Among the GERD cohort, the risk for periodontitis was increased with an increasing number of emergency room visits (≥ 1 vs. <1, aHR = 5.19, 95% CI = 2.16−12.5). Conclusions: Our results revealed that patients with GERD have a higher risk of periodontitis development than those without GERD. Clinicians should pay more attention to identifying and managing periodontitis in patients with GERD.

Anti-Citrullinated Peptide Antibodies Control Oral Porphyromonas and Aggregatibacter species in Patients with Rheumatoid Arthritis

Oral microbiome changes take place at the initiation of rheumatoid arthritis (RA); however, questions remain regarding the oral microbiome at pre-RA stages in individuals with clinically suspect arthralgia (CSA). Two cross-sectional cohorts were selected including 84 Tatarstan women (15 early-RA as compared to individuals with CSA ranging from CSA = 0 [n = 22], CSA = 1 [n = 19], CSA = 2 [n = 11], and CSA ≥ 3 [n = 17]) and 42 women with established RA (median: 5 years from diagnosis [IQ: 2–11]). Amplicon sequence variants (ASVs) obtained from oral samples (16S rRNA) were analyzed for alpha and beta diversity along with the abundance at the genus level. A decrease in oral Porphyromonas sp. is observed in ACPA-positive individuals, and this predominates in early-RA patients as compared to non-RA individuals irrespective of their CSA score. In the RA-established cohort, Porphyromonas sp. and Aggregatibacter sp. reductions were associated with elevated ACPA levels. In contrast, no associations were reported when considering individual, genetic and clinical RA-associated factors. Oral microbiome changes related to the genera implicated in post-translational citrullination (Porphyromonas sp. and Aggregatibacter sp.) characterized RA patients with elevated ACPA levels, which supports that the role of ACPA in controlling the oral microbiome needs further evaluation.

Intestinal microbiome–rheumatoid arthritis crosstalk: The therapeutic role of probiotics

Rheumatoid arthritis (RA) is a common systemic autoimmune disease with a global health importance. It is characterized by long-term complications, progressive disability and high mortality tied to increased social-economic pressures. RA has an inflammatory microenvironment as one of the major underlying factors together with other complex processes. Although mechanisms underlying the triggering of RA remain partially elusive, microbiota interactions have been implicated. Again, significant alterations in the gut microbiome of RA patients compared to healthy individuals have intimated a chronic inflammatory response due to gut dysbiosis. Against this backdrop, myriads of studies have hinted at the prospective therapeutic role of probiotics as an adjuvant for the management of RA in the quest to correct this dysbiosis. In this article, the major gut microbiome alterations associated with RA are discussed. Subsequently, the role of the gut microbiome dysbiosis in the initiation and progression of RA is highlighted. Lastly, the effect and mechanism of action of probiotics in the amelioration of symptoms and severity of RA are also espoused. Although strain-specific, probiotic supplementation as adjuvant therapy for the management of RA is very promising and warrants more research.

Targeting the succinate receptor effectively inhibits periodontitis

Periodontal disease (PD) is one of the most common inflammatory diseases in humans and is initiated by an oral microbial dysbiosis that stimulates inflammation and bone loss. Here, we report an abnormal elevation of succinate in the subgingival plaque of subjects with severe PD. Succinate activates succinate receptor-1 (SUCNR1) and stimulates inflammation. We detected SUCNR1 expression in the human and mouse periodontium and hypothesize that succinate activates SUCNR1 to accelerate periodontitis through the inflammatory response. Administration of exogenous succinate enhanced periodontal disease, whereas SUCNR1 knockout mice were protected from inflammation, oral dysbiosis, and subsequent periodontal bone loss in two different models of periodontitis. Therapeutic studies demonstrated that a SUCNR1 antagonist inhibited inflammatory events and osteoclastogenesis in vitro and reduced periodontal bone loss in vivo. Our study reveals succinate’s effect on periodontitis pathogenesis and provides a topical treatment for this disease.

Periodontitis is the most prevalent adult oral disease. Guo et al. show elevation of succinate in periodontitis, which aggravates the disease through the succinate receptor (SUCNR1). They developed a gel formulation of a small compound specifically blocking SUCNR1 to prevent and treat periodontitis by inhibiting dysbiosis, inflammation, and bone loss.

Subgingival Microbiome in Rheumatoid Arthritis Patients with Periodontitis

Rheumatoid arthritis (RA) and periodontitis are suggested to be closely linked based on microbial dysbiosis, but limited subgingival bacteria have been proven in the pathogenesis of RA. We enrolled 30 RA patients and 25 controls and divided them into three groups with matched age, gender, and diabetes statuses: group AM (all of the matched participants), group PD (periodontally diseased), and group PH (periodontally healthy). Their subgingival microbial composition was determined by V3–V4 16S rRNA gene sequencing. Significant differences in subgingival microbial clustering between the RA patients and controls were observed in groups AM and PD. Among the taxa enriched in RA, Aminipila butyrica and Peptococcus simiae were the only two species displaying positive correlation to the level of anti-citrullinated protein antibodies (ACPAs) in both of the groups. Surprisingly, the median of relative abundances of A. butyrica and P. simiae were 0% in the controls of group PD. Furthermore, a gene encoding arginine deiminase with the capability to produce citrulline was addressed in the complete genome sequence of A. butyrica. This is the first study to elucidate the important roles of A. butyrica and P. simiae as periodontal bacteria leading to RA possibly through the induction of ACPA production.

The Oral Microbiome and Its Role in Systemic Autoimmune Diseases: A Systematic Review of Big Data Analysis

Introduction

Despite decades of research, systemic autoimmune diseases (SADs) continue to be a major global health concern and the etiology of these diseases is still not clear. To date, with the development of high-throughput techniques, increasing evidence indicated a key role of oral microbiome in the pathogenesis of SADs, and the alterations of oral microbiome may contribute to the disease emergence or evolution. This review is to present the latest knowledge on the relationship between the oral microbiome and SADs, focusing on the multiomics data generated from a large set of samples.

Methodology

By searching the PubMed and Embase databases, studies that investigated the oral microbiome of SADs, including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren's syndrome (SS), were systematically reviewed according to the PRISMA guidelines.

Results

One thousand and thirty-eight studies were found, and 25 studies were included: three referred to SLE, 12 referred to RA, nine referred to SS, and one to both SLE and SS. The 16S rRNA sequencing was the most frequent technique used. HOMD was the most common database aligned to and QIIME was the most popular pipeline for downstream analysis. Alterations in bacterial composition and population have been found in the oral samples of patients with SAD compared with the healthy controls. Results regarding candidate pathogens were not always in accordance, but Selenomonas and Veillonella were found significantly increased in three SADs, and Streptococcus was significantly decreased in the SADs compared with controls.

Conclusion

A large amount of sequencing data was collected from patients with SAD and controls in this systematic review. Oral microbial dysbiosis had been identified in these SADs, although the dysbiosis features were different among studies. There was a lack of standardized study methodology for each study from the inclusion criteria, sample type, sequencing platform, and referred database to downstream analysis pipeline and cutoff. Besides the genomics, transcriptomics, proteomics, and metabolomics technology should be used to investigate the oral microbiome of patients with SADs and also the at-risk individuals of disease development, which may provide us with a better understanding of the etiology of SADs and promote the development of the novel therapies.

Influence of Oral Microbiota on the Presence of IgA Anti-Citrullinated Protein Antibodies in Gingival Crevicular Fluid

Introduction

The relation between rheumatoid arthritis (RA) and periodontitis (PD) has been investigated ever since the discovery of the citrullinating enzyme peptidyl arginine deaminase presents in the oral bacterium Porphyromonas gingivalis. Recently, we demonstrated the presence of RA autoantibodies, especially of IgA anti-citrullinated protein antibody (ACPA), in gingival crevicular fluid (GCF) of Indonesian patients with and without RA or PD which might indicate the local formation of RA antibodies in the periodontium.

Aim

The purpose of this study was to assess whether the subgingival microbiome is related to the presence of IgA ACPA in the GCF of healthy individuals with or without PD.

Patients and Methods

Healthy individuals with a known periodontal status and high IgA ACPA (>0.1 U/ml) in GCF (n = 27) were selected and matched for age, gender, periodontal status, and smoking status with 27 healthy individuals without IgA ACPA in their GCF. Taxonomic profiling of the subgingival microbiome was based on bacterial 16S rRNA gene sequencing. Downstream analyses were performed to assess compositional differences between healthy subjects with or without IgA ACPA in GCF and with or without PD.

Results

Between groups with or without PD, or with or without IgA ACPA in GCF, no differences in alpha diversity were seen. Beta diversity was different between groups with or without PD (p < 0.0001), and a trend was seen in subjects with PD between subjects with or without IgA ACPA in GCF (p = 0.084). Linear discriminant analysis effect size (LEfSe) revealed no significant differences in the total population between subjects with IgA ACPA compared to subjects without IgA ACPA in GCF. Although Porphyromonas was not identified by LEfSe, its relative abundance was significantly higher in healthy individuals with high IgA ACPA in GCF compared to individuals without IgA ACPA in GCF (p = 0.0363). Zooming in on the subgroup with PD, LEfSe revealed that species Neisseriaceae, Tannerella, and Haemophilus were more abundant in the subjects with IgA ACPA in GCF compared to subjects without IgA ACPA in GCF.

Conclusion

Periodontitis and certain taxa, including Porphyromonas, seem to be associated with the local presence of ACPA in the periodontium.

Methotrexate promotes recovery of arthritis-induced alveolar bone loss and modifies the composition of the oral-gut microbiota

OBJECTIVES

The impact of rheumatoid arthritis (RA) on the shaping of the oral and gut microbiome raises the question of whether and how RA treatment modifies microbial communities. We examined changes in the oral and gut microbiota in a mouse model of antigen-induced arthritis (AIA) treated or not with methotrexate (MTX).

METHODS

Maxillae and stools were evaluated by the MiSeq platform of the V4 region of the 16S rRNA gene. Alveolar bone parameters were analysed by micro-computed tomography. Moreover, arthritis-induced changes in hyperalgesia and oedema were assessed, along with the impact on periodontal bone health.

RESULTS

Microbial communities in MTX-treated AIA mice revealed distinct clusters compared to the control and AIA groups. Overall, MTX impacted the richness and variability of microorganisms in the oral-gut axis microbiome at the phylum level. Regarding the oral microbiome, while in the control group the most dominant phylum was Firmicutes, in the AIA group there was a shift towards the predominance of Campilobacteriota and Bacteroidetes associated with the disease. MTX treatment led to greater dominance of the health-associated phylum Proteobacteria. In the gut microbiome, AIA induction resulted in increased abundance of the Verrucomicrobiota phylum, and MTX treatment restored its levels compared to control. Importantly, the MTX-treated AIA animals had significantly less periodontal bone loss, as well as decreased hyperalgesia and joint oedema compared to the AIA animals.

CONCLUSION

Data suggest the benefit of MTX treatment in protecting alveolar bone, in addition to providing new insights on the drug-microbiome interaction in the course of RA.

Oral Microbiome: Getting to Know and Befriend Neighbors, a Biological Approach

The oral microbiome, forming a biofilm that covers the oral structures, contains a high number of microorganisms. Biofilm formation starts from the salivary pellicle that allows bacterial adhesion–colonization–proliferation, co-aggregation and biofilm maturation in a complex microbial community. There is a constant bidirectional crosstalk between human host and its oral microbiome. The paper presents the fundamentals regarding the oral microbiome and its relationship to modulator factors, oral and systemic health. The modern studies of oral microorganisms and relationships with the host benefits are based on genomics, transcriptomics, proteomics and metabolomics. Pharmaceuticals such as antimicrobials, prebiotics, probiotics, surface active or abrasive agents and plant-derived ingredients may influence the oral microbiome. Many studies found associations between oral dysbiosis and systemic disorders, including autoimmune diseases, cardiovascular, diabetes, cancers and neurodegenerative disorders. We outline the general and individual factors influencing the host–microbial balance and the possibility to use the analysis of the oral microbiome in prevention, diagnosis and treatment in personalized medicine. Future therapies should take in account the restoration of the normal symbiotic relation with the oral microbiome.

Associations between inflammation-related LL-37 with subgingival microbial dysbiosis in rheumatoid arthritis patients

OBJECTIVE

This study investigated the subgingival microbial profile of rheumatoid arthritis (RA) patients and its associations with disease parameters and the inflammation-related antimicrobial peptide, LL-37.

METHODS

RA and non-RA (NRA) patients were assessed for periodontal status and divided into periodontitis (CP), gingivitis (G), and healthy (H) groups. Subgingival plaque 16s rRNA gene sequencing data was processed and analyzed using the CLC Genomic Workbench (Qiagen). Bacterial diversity and co-occurrence patterns were examined. Differential abundance between groups was also investigated. Associations between bacterial genera with disease parameters and LL-37 levels were explored qualitatively using canonical correlation analysis.

RESULTS

Subgingival microbial community clustered in CP status. Co-occurrence network in NRA-H was dominated by health-associated genera, while the rest of the networks' key genera were both health- and disease-associated. RA-CP displayed highly inter-generic networks with a statistically significant increase in periodontal disease-associated genera (p<0.05). In NRA-H, disease parameters and LL-37 were correlated positively with disease-associated genera while negatively with health-associated genera. However, in the remaining groups, mixed positive and negative correlations were noted with genera.

CONCLUSION

RA patients demonstrated subgingival microbial dysbiosis where the bacteria networks were dominated by health- and disease-associated genera. Mixed correlations with disease parameters and LL-37 levels were noted.

CLINICAL RELEVANCE

The subgingival microbial dysbiosis in RA may predispose these patients to developing periodontal inflammation with an associated detrimental effect on host immune responses. Routine periodontal assessment may allow initiation of treatment strategies to minimize the effects of gingival inflammation on the existing heightened immune response present in RA patients.

The Importance of Nitrate Reduction for Oral Health

Salivary glands concentrate plasma nitrate into saliva, leading to high nitrate concentrations that can reach the millimolar range after a nitrate-rich vegetable meal. Whereas human cells cannot reduce nitrate to nitrite effectively, certain oral bacteria can. This leads to an increase in systemic nitrite that can improve conditions such as hypertension and diabetes through nitric oxide availability. Apart from systemic benefits, it has been proposed that microbial nitrate reduction can also promote oral health. In this review, we discuss evidence associating dietary nitrate with oral health. Oral bacteria can reduce nitrite to nitric oxide, a free radical with antimicrobial properties capable of inhibiting sensitive species such as anaerobes involved in periodontal diseases. Nitrate has also been shown to increase resilience against salivary acidification in vivo and in vitro, thus preventing caries development. One potential mechanism is proton consumption during denitrification and/or bacterial reduction of nitrite to ammonium. Additionally, lactic acid (organic acid involved in oral acidification) and hydrogen sulfide (volatile compound involved in halitosis) can act as electron donors for these processes. The nitrate-reducing bacteria Rothia and Neisseria are consistently found at higher levels in individuals free of oral disease (vs. individuals with caries, periodontitis, and/or halitosis) and increase when nitrate is consumed in clinical studies. Preliminary in vitro and clinical evidence show that bacteria normally associated with disease, such as Veillonella (caries) and Prevotella (periodontal diseases and halitosis), decrease in the presence of nitrate. We propose nitrate as an ecologic factor stimulating eubiosis (i.e., an increase in health-associated species and functions). Finally, we discuss the preventive and therapeutic potential, as well as safety issues, related to the use of nitrate. In vivo evidence is limited; therefore, robust clinical studies are required to confirm the potential benefits of nitrate reduction on oral health.

Aggregatibacter actinomycetemcomitans as the Aetiological Cause of Rheumatoid Arthritis: What Are the Unsolved Puzzles?

Leukotoxin A (LtxA) is the major virulence factor of an oral bacterium known as Aggregatibacter actinomycetemcomitans (Aa). LtxA is associated with elevated levels of anti-citrullinated protein antibodies (ACPA) in rheumatoid arthritis (RA) patients. LtxA targets leukocytes and triggers an influx of extracellular calcium into cytosol. The current proposed model of LtxA-mediated hypercitrullination involves the dysregulated activation of peptidylarginine deiminase (PAD) enzymes to citrullinate proteins, the release of hypercitrullinated proteins through cell death, and the production of autoantigens recognized by ACPA. Although model-based evidence is yet to be established, its interaction with the host’s immune system sparked interest in the role of LtxA in RA. The first part of this review summarizes the current knowledge of Aa and LtxA. The next part highlights the findings of previous studies on the association of Aa or LtxA with RA aetiology. Finally, we discuss the unresolved aspects of the proposed link between LtxA of Aa and RA.

Higher Risk of Gastric Helicobacter pylori Infection in Patients with Periodontitis: A Nationwide Population-Based Retrospective Cohort Study in Taiwan

Periodontitis is the most prevalent chronic inflammatory oral disease that is characterized by tooth loss and is commonly associated with several systemic inflammatory diseases. Some epidemiological studies suggest that those suffering from periodontitis might be at a greater risk of developing gastric Helicobacter pylori (Hp) infection; however, evidence that showing the association between periodontitis and the risk of gastric Hp infection is less clear. We conducted a large-scale, population-based study in Taiwan with a 13-year follow-up period to evaluate the risk of gastric Hp in a periodontitis patient cohort. To conduct this study, we used epidemiological data from the Taiwanese Longitudinal National Health Insurance Research Database (NHIRD) from 2000 to 2013. We selected 134,474 participants (64,868 males and 69,606 females with a minimum age of 20 years), with and without periodontitis, and matched patient cohort groups for age, sex, index year, and co-morbidities. The Cox proportional hazards regression model was used to examine the risk of gastric Hp infection in patients with periodontitis. Patients with periodontitis exhibited a higher risk of developing gastric Hp infection compared to those individuals/groups without periodontitis (1.35 vs. 0.87 per 1000 person-years, adjusted the hazards ratio (aHR 1.52), and 95% confidence intervals (CIs) 1.38–1.67, p < 0.001). The risk of gastric Hp infection persisted even after stratifying by age (aHR = 1.96 (1.79–2.13) for 50–64 years and 1.70 (1.49–1.94) for ≥65 years), gender (aHR = 1.20 (1.11–1.29) for men), and presence of comorbidities of hypertension (aHR = 1.24 (1.11–1.38)), hyperlipidemia (aHR = 1.28 (1.14–1.42)), COPD (aHR = 1.45 (1.31–1.61)), CLD (aHR = 1.62 (1.47–1.77)) and CKD (aHR = 1.44 (1.04–1.99)). Overall, our findings showed that periodontitis patients have a greater risk for gastric Hp than individuals without periodontitis. Clinicians should perform regular good oral hygiene practices, along with newer treatments, for patients with periodontitis, especially those at higher risk of gastric Hp infection.

Sustained Drug Treatment Alters the Gut Microbiota in Rheumatoid Arthritis

Several studies have investigated the causative role of the microbiome in the development of rheumatoid arthritis (RA), but changes in the gut microbiome in RA patients during drug treatment have been less well studied. Here, we tracked the longitudinal changes in gut bacteria in 22 RA patients who were randomized into two groups and treated with Huayu-Qiangshen-Tongbi formula (HQT) plus methotrexate (MTX) or leflunomide (LEF) plus MTX. There were differences in the gut microbiome between untreated (at baseline) RA patients and healthy controls, with 37 species being more abundant in the RA patients and 21 species (including Clostridium celatum) being less abundant. Regarding the functional analysis, vitamin K2 biosynthesis was associated with RA-enriched bacteria. Additionally, in RA patients, alterations in gut microbial species appeared to be associated with RA-related clinical indicators through changing various gut microbiome functional pathways. The clinical efficacy of the two treatments was further observed to be similar, but the response trends of RA-related clinical indices in the two treatment groups differed. For example, HQT treatment affected the erythrocyte sedimentation rate (ESR), while LEF treatment affected the C-reactive protein (CRP) level. Further, 11 species and 9 metabolic pathways significantly changed over time in the HQT group (including C. celatum, which increased), while only 4 species and 2 metabolic pathways significantly changed over time in the LEF group. In summary, we studied the alterations in the gut microbiome of RA patients being treated with HQT or LEF. The results provide useful information on the role of the gut microbiota in the pathogenesis of RA, and they also provide potentially effective directions for developing new RA treatments.

The facultative human oral pathogen Prevotella histicola in equine cheek tooth apical/ periapical infection: a case report

BACKGROUND

Prevotella histicola is a facultative oral pathogen that under certain conditions causes pathologies such as caries and periodontitis in humans. Prevotella spp. also colonize the oral cavity of horses and can cause disease, but P. histicola has not yet been identified.

CASE PRESENTATION

A 12-year-old Tinker mare was referred to the clinic for persistent, malodorous purulent nasal discharge and quidding. Conservative antibiotic (penicillin), antiphlogistic (meloxicam), and mucolytic (dembrexine-hydrochloride) treatment prior to referral was unsuccessful and symptoms worsened. Oral examination, radiography, sino-/ rhinoscopy, and standing computed tomography revealed severe apical/ periapical infection of the upper cheek tooth 209 with accompanying unilateral sinonasal inflammation and conchal necrosis. The tooth exhibited extensive subocclusal mesial infundibular cemental hypoplasia and caries, and an occlusal fissure fracture. After mechanical debridement and thermoplastic resin filling of the spacious subocclusal carious infundibular lesion, the tooth was extracted intraorally. The sinusitis and conchal necrosis were treated transendoscopically. Selective bacteriological swab cultures of affected tooth roots and subsequent matrix-assisted laser desorption ionization-time of flight mass spectrometry showed an infection with the obligate anaerobic, Gram-negative bacterium P. histicola. Surgical intervention and adapted antibiotic therapy led to normal healing without complications.

CONCLUSIONS

This study provides the first documented case of dental infection in a horse caused by P. histicola at once indicating necessity of more sufficient microbiological diagnostics and targeted antibiotic treatment in equine dental practice. This finding is also conducive to understand species-specific Prevotella diversity and cross-species distribution.

Association of Bitter Taste Receptor T2R38 Polymorphisms, Oral Microbiota, and Rheumatoid Arthritis

The association of taste genetics and the oral microbiome in autoimmune diseases such as rheumatoid arthritis (RA) has not been reported. We explored a novel oral mucosal innate immune pathway involving the bitter taste G protein-coupled receptor T2R38. This case–control study aimed to evaluate whether T2R38 polymorphisms associate with the buccal microbial composition in RA. Genomic DNA was obtained from buccal swabs of 35 RA patients and 64 non-RA controls. TAS2R38 genotypes were determined by Sanger sequencing. The buccal microbiome was assessed by Illumina MiSeq sequencing of the V4-16S rRNA gene. Bacterial community differences were analyzed with alpha and beta diversity measures. Linear discriminant analysis effect size identified taxa discriminating between RA versus non-RA and across TAS2R38 genotypes. TAS2R38 genotype frequency was similar between RA and non-RA controls (PAV/PAV; PAV/AVI; AVI/AVI: RA 42.9%; 45.7%; 11.4% versus controls 32.8%; 48.4%; 18.8%, chi-square (2, N = 99) = 2.1, p = 0.35). The relative abundance of Porphyromonas, among others, differed between RA and non-RA controls. The relative abundance of several bacterial species also differed across TAS2R38 genotypes. These findings suggest an association between T2R38 polymorphisms and RA buccal microbial composition. However, further research is needed to understand the impact of T2R38 in oral health and RA development.

Periodontitis and rheumatoid arthritis: What have we learned about their connection and their treatment?

Rheumatoid arthritis and periodontitis are chronic inflammatory diseases defined respectively by the destruction of the articular cartilage and tooth-supporting periodontal tissues. Although the epidemiologic evidence for an association between these two diseases is still scarce, there is emerging scientific information linking specific bacterial periodontal pathogens, such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, in the citrullination process, leading to autoantibody formation and compromised immunotolerance of the susceptible patient to rheumatoid arthritis. In this review, we update the existing information on the evidence, not only regarding the epidemiologic association, but also the biologic mechanisms linking these two diseases. Finally, we review information emerging from intervention studies evaluating whether periodontal treatment could influence the initiation and progression of rheumatoid arthritis.

IL-23/IL-17 axis and soluble receptors isoforms sIL-23R and sIL-17RA in patients with rheumatoid arthritis-presenting periodontitis

BACKGROUND

Rheumatoid arthritis (RA) and periodontitis (P) are chronic inflammatory diseases characterized by joint and radiographic bone loss, respectively. IL-23 and IL-17 have an essential role in the immunopathogenesis of RA, and P. IL-23 stimulates Th17 cells through which produces IL-17, IL-21, and RANKL. IL-17 stimulates fibroblasts to produce RANKL, which initiates bone loss in the joints in RA and the periodontal tissue in periodontitis. The aim of this study was to determine the expression pattern of IL-23/IL-17 axis and soluble receptors isoforms sIL-23R and sIL-17RA of patients with RA presenting P (RAP).

MATERIAL AND METHODS

Healthy subjects (HS) (n = 42), patients with P (n = 40), RA (n = 20), and patients with RAP (n = 40) were included. Plasma samples were obtained to evaluate the IL-23, IL-17A, sIL-23R, and sIL-17RA by ELISA technique. A nonparametric Mann-Whitney U test was used to compare the differences between groups. A Chi-square was used to compare gender, grade and stage of periodontitis, and DAS28-ESR between the groups. Spearman's rank correlation coefficient was used to study the association between the molecules and clinical parameters.

RESULTS

IL-23 levels were increased in the RAP group, and lower sIL-23R levels were found in the RAP groups. However, IL-17A was lower in the P and RAP group but not in RA patients. RAP group showed a decrease IL-17A levels in advanced stages of the periodontal disease.

CONCLUSION

These results suggest that IL-23 and IL-17A tend to downregulate their expression patterns when patients present both rheumatoid arthritis and periodontitis.

Oral Microbiota Identifies Patients in Early Onset Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common autoimmune inflammatory disease, and single periodontitis-associated bacteria have been suggested in disease manifestation. Here, the oral microbiota was characterized in relation to the early onset of RA (eRA) taking periodontal status into consideration. 16S rRNA gene amplicon sequencing of saliva bacterial DNA from 61 eRA patients without disease-modifying anti-rheumatic drugs and 59 matched controls was performed. Taxonomic classification at 98.5% was conducted against the Human Oral Microbiome Database, microbiota functions were predicted using PICRUSt, and periodontal status linked from the Swedish quality register for clinically assessed caries and periodontitis. The participants were classified into three distinct microbiota-based cluster groups with cluster allocation differences by eRA status. Independently of periodontal status, eRA patients had enriched levels of Prevotella pleuritidis, Treponema denticola, Porphyromonas endodontalis and Filifactor alocis species and in the Porphyromonas and Fusobacterium genera and functions linked to ornithine metabolism, glucosylceramidase, beta-lactamase resistance, biphenyl degradation, fatty acid metabolism and 17-beta-estradiol-17-dehydrogenase metabolism. The results support a deviating oral microbiota composition already in eRA patients compared with healthy controls and highlight a panel of oral bacteria that may be useful in eRA risk assessment in both periodontally healthy and diseased persons.

Premature Senescence of T-cells Favors Bone Loss During Osteolytic Diseases. A New Concern in the Osteoimmunology Arena

Cellular senescence is a biological process triggered in response to time-accumulated DNA damage, which prioritizes cell survival over cell function. Particularly, senescent T lymphocytes can be generated prematurely during chronic inflammatory diseases regardless of chronological aging. These senescent T lymphocytes are characterized by the loss of CD28 expression, a co-stimulatory receptor that mediates antigen presentation and effective T-cell activation. An increased number of premature senescent CD4+CD28- T lymphocytes has been frequently observed in osteolytic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, ankylosing spondylitis, osteopenia, osteoporosis, and osteomyelitis. Indeed, CD4+CD28- T lymphocytes produce higher levels of osteoclastogenic molecular mediators directly related to pathologic bone loss, such as tumor necrosis factor (TNF)-α, interleukin (IL)-17A, and receptor-activator of nuclear factor κB ligand (RANKL), as compared with regular CD4+CD28+ T lymphocytes. In addition, premature senescent CD8+CD28- T lymphocytes have been negatively associated with bone healing and regeneration by inhibiting osteoblast differentiation and mesenchymal stromal cell survival. Therefore, accumulated evidence supports the role of senescent T lymphocytes in osteoimmunology. Moreover, premature senescence of T-cells seems to be associated with the functional imbalance between the osteolytic T-helper type-17 (Th17) and bone protective T regulatory (Treg) lymphocytes, as well as the phenotypic instability of Treg lymphocytes responsible for its trans-differentiation into RANKL-producing exFoxp3Th17 cells, a key cellular phenomenon directly related to bone loss. Herein, we present a framework for the understanding of the pathogenic characteristics of T lymphocytes with a premature senescent phenotype; and particularly, we revise and discuss their role in the osteoimmunology of osteolytic diseases.

Exploring the Oral Microbiome in Rheumatic Diseases, State of Art and Future Prospective in Personalized Medicine with an AI Approach

The oral microbiome is receiving growing interest from the scientific community, as the mouth is the gateway for numerous potential etiopathogenetic factors in different diseases. In addition, the progression of niches from the mouth to the gut, defined as "oral-gut microbiome axis", affects several pathologies, as rheumatic diseases. Notably, rheumatic disorders (RDs) are conditions causing chronic, often intermittent pain affecting the joints or connective tissue. In this review, we examine evidence which supports a role for the oral microbiome in the etiology and progression of various RDs, including rheumatoid arthritis (RA), Sjogren's syndrome (SS), and systemic lupus erythematosus (SLE). In addition, we address the most recent studies endorsing the oral microbiome as promising diagnostic biomarkers for RDs. Lastly, we introduce the concepts of artificial intelligence (AI), in particular, machine learning (ML) and their general application for understanding the link between oral microbiota and rheumatic diseases, speculating the application of a possible AI approach-based that can be applied to personalized medicine in the future.

The oral and gut microbiome in rheumatoid arthritis patients: a systematic review

BACKGROUND

Recently, researchers have proposed a possible relationship between RA and the microbiome of the oral cavity and gut. However, this relation has not been systematically established. Herein, we conducted a comprehensive review of the pertinent literature to describe this possible association.

METHODS

We systematically performed searches in databases, namely EMBASE, the Cochrane Library, and PubMed, from inception to 7 June 2020 to identify case-control studies that compared the oral and gut microbiome in adult RA patients with those of controls. The primary outcome was specific bacterial changes between RA and controls. The secondary outcome was microbial diversity changes between RA and controls.

RESULTS

In total, 26 articles were considered eligible for inclusion and reported some differences. Therein, ≥3 articles reported decreased Faecalibacterium in the gut of early-RA (ERA)/RA patients compared with healthy controls (HCs). Also, ≥3 articles reported decreased Streptococcus and Haemophilus and increased Prevotella in the oral cavity of ERA/RA patients compared with HCs. In addition, some Prevotella species, including P. histicola and P. oulorum, showed increased trends in RA patients' oral cavity, compared with HCs. The α-diversity of the microbiome was either increased or not changed in the oral cavity of RA patients, but it was more commonly either decreased or not changed in the gut of RA patients.

CONCLUSIONS

In this systematic review, we identified the microbiome associated with RA patients in comparison with controls. More research is needed in the future to find the deep relationship between RA and the microbiome.

Correlation of periodontal diseases with intracranial aneurysm formation: novel predictive indicators

Background

We investigated whether periodontal diseases, specifically, periodontitis and gingivitis, could be risk factors of the incidence of intracranial aneurysms (IAs).

Methods

We performed a case–control study to compare the differences in the periodontal disease parameters of 281 cases that were divided into the IAs group and non-IAs group. All cases underwent complete radiographic examination for IAs and examination for periodontal health.

Results

Comparing with those in the non-IAs group, the cases in the IAs group were older (53.95 ± 8.56 vs 47.79 ± 12.33, p < 0.001) and had a higher incidence of hypertension (76 vs 34, p = 0.006). Univariate logistic regression analysis revealed that age (> 50 years) and hypertension were predictive risk factors of aneurysm formation (odds ratio [OR] 1.047, 95% confidence interval [95% CI] 1.022–1.073, p < 0.001 and OR 2.047, 95% CI 1.232–3.401, p = 0.006). In addition, univariate and multivariate logistic regression analyses showed that the parameters of periodontal diseases, including gingival index, plaque index, clinical attachment loss, and alveolar bone loss, were significantly associated with the occurrence of IAs (all p < 0.05). For further statistical investigation, the parameters of periodontal diseases were divided into four layers based on the quartered data. Poorer periodontal health condition (especially gingival index > 1.1 and plaque index > 1.5) had the correlation with IAs formation (p = 0.007 and p < 0.001).

Conclusion

Severe gingivitis or periodontitis, combining with hypertension, is significantly associated with the incidence of IAs.

The oral microbiome in early rheumatoid arthritis patients and individuals at risk differs from healthy controls

OBJECTIVE

It has been suggested that rheumatoid arthritis (RA) may originate at the oral mucosa. Our aim was to assess the oral microbiome and the periodontal condition in patients with early rheumatoid arthritis (ERA) and individuals at risk of RA.

METHODS

Three groups were recruited (50 participants each): (1) ERA patients (2010 ACR/EULAR criteria), (2) at-risk individuals (arthralgia and autoantibodies), and (3) healthy controls. A periodontal examination resulted in scores for bleeding on probing (BOP), pocket probing depth (PPD), and periodontal inflamed surface area (PISA). The microbial composition of subgingival dental plaque, saliva, and tongue coating was assessed using 16S rDNA amplicon sequencing, and compared between groups with permutational multivariate analyses of variance (PERMANOVA).

RESULTS

There was no difference between the groups on the periodontal variables (BOP p=0.70; PPD p=0.30; PISA p=0.56). PERMANOVA showed a difference between the groups in the microbial composition of saliva (F=2.08, p<0.001) and tongue coating (F=2.04, p=0.008), but not plaque (p=0.51). Post-hoc tests showed no difference between the ERA group and at-risk group (saliva F=1.12, p=0.28; tongue coating F=0.834, p=0.59). Discriminative zero-radius operational taxonomic units (zOTUs) were identified: in ERA patients and at-risk individuals, Prevotella in saliva and Veillonella in saliva and tongue coating were at higher relative abundance compared to healthy controls.

CONCLUSION

The results show similarities in the oral microbiome between ERA patients and at-risk individuals, both presenting with increased relative abundance of potentially pro-inflammatory species compared to healthy controls, suggesting a possible association between the oral microbiome and RA onset.

Systemic Lupus Erythematosus and Periodontal Disease: A Complex Clinical and Biological Interplay

Reports on the association of periodontal disease (PD) with systemic lupus erythematosus (SLE) have regularly been published. PD is a set of chronic inflammatory conditions linked to a dysbiotic microbial biofilm, which affects the periodontal tissues, resulting eventually in their destruction and contributing to systemic inflammation. SLE is a multi-system chronic inflammatory autoimmune disease that has a wide range of clinical presentations, touching multiple organ systems. Many epidemiological studies have investigated the two-way relationship between PD and SLE, though their results are heterogeneous. SLE and PD are multifactorial conditions and many biological-based hypotheses suggest common physiopathological pathways between the two diseases, including genetics, microbiology, immunity, and environmental common risk factors. By focusing on recent clinical and translational research, this review aimed to discuss and give an overview of the relationship of SLE with PD, as well as looking at the similarities in the immune-pathological aspects and the possible mechanisms connecting the development and progression of both diseases.

Rheumatoid arthritis associated with the occurrence, severity and extension of periodontitis: A case-control study

Background

Emerging evidence pointed to a potential association between periodontitis (PE) and rheumatoid arthritis (RA), based on shared characteristics and similarities in risk factors, immunogenetics and pathways of tissue destruction. The aim of this study was to evaluate the potential association between RA and PE, as well as the influence of risk variables in this association.

Material and Methods

The present case-control study comprised 471 individuals (157 cases with RA and 314 controls) that underwent a full-mouth periodontal examination. The association between risk variables and the occurrence of AR and PE were evaluated through univariate and multivariate logistic analysis.

Results

Higher frequency (p<0.001), severity (p=0.006) and extension (p=0.018) of PE was observed among the cases when compared to controls. Variables retained in the final multivariate models for the occurrence of PE were: lower number of teeth, smoking, no use of dental floss, ≥4 daily toothbrushing and RA; for the occurrence of RA were: higher age, female gender, smoking, alcohol use and PE. It is important to stress that RA (OR=2.53; 95%CI 1.24-3.86; p<0.001) was retained in the model for PE, and PE (OR=3.12; 95%CI 1.47-4.26; p<0.001) was retained in the model for RA.

Conclusions

The present study demonstrated a high frequency of PE among individuals with RA and an important association among the occurrence, severity and extension of PE and RA and smoking. Key words:Case-control study, risk factors, periodontitis, rheumatoid arthritis.

Host Modulation and Treatment of Periodontal Disease

Periodontitis is the sixth-most prevalent disease in the world and the first cause for tooth loss in adults. With focus shifted to the inflammatory/immune response in the pathogenesis of periodontitis, there is a critical need to evaluate host modulatory agents. Synthetic and biological disease-modifying antirheumatic drugs are a cornerstone for the treatment of inflammatory diseases. Recent prospective cohort studies showed that synthetic disease-modifying antirheumatic drugs improved periodontal clinical parameters following nonsurgical periodontal treatment in patients with rheumatoid arthritis. Treatment with recombinant humanized monoclonal antibodies against CD20 (rituximab) and IL-6 receptor (tocilizumab), the latter also in clinical trials for the treatment of COVID-19 pneumonia, resulted in decreased periodontal inflammation and improved periodontal status. Studies on the effect of TNF-α inhibitors in patients with periodontitis yielded inconsistent results. Recent data suggest that probiotics provide anti-inflammatory clinical benefit, as do nutritional supplements, such as n-3 fatty acids, when combined with periodontal therapy. Probiotics reduce the production of proinflammatory cytokines/chemokines by suppressing NF-κB pathways and promote the accumulation of T regulatory cells. Statins, like aspirin, have been shown to exhibit anti-inflammatory and bone-preserving actions by upregulating production of Specialized Proresolving Mediators (SPMs). Currently, there is insufficient scientific support for the topical delivery of statins or bisphosphonates as adjuncts to periodontal therapy. Here, we present a critical review of the most recent host modulatory agents applied in humans and the key immune pathways that they target. Emerging evidence from novel drug candidates, including SPMs and complement inhibitors as previously studied in animal models and currently in human clinical trials, suggests future availability of adjunctive therapeutic strategies for the management of periodontitis.

The composition of microbial communities in inflammatory periodontal diseases in young adults Tatars

Host susceptibility and environmental factors are important for the development of gingivitis and periodontitis, but bacterial biofilms attached to the teeth and gingival tissues play a crucial role. We have analyzed and compared the subgingival microbial communities between subjects with dental plaque biofilm-induced generalized chronic gingivitis (CG), localized initial (Stage I) periodontitis (IP) and healthy controls (HC) of young people aged 18-19 years permanently residing in the city of Kazan (Tatarstan, Russia). The results showed that the α-diversity in groups with CG and IP was higher than in the healthy group. In a course of periodontal disease, a decrease in the relative abundance of dominates genera Rothia and Streptococcus was observed along with increase of class TM7-3 (Candidatus Saccharibacteria phylum) representatives. Also, the increase of red complex representatives Porphyromonadeceae, Treponema and Tannerella was detected together with statistically significant increase of Filifactor, Parvimonas, Peptostreptococcaceae, Veillonellaceae, Tissierelaceae and Mogibacteriaceae. Analysis of our data suggests that transition from HC to IP may be accompanied by a decrease in microbial diversity and a reduction in the abundance of family Rs-045 (Candidatus Saccharibacteria phylum), Desulfovibrionaceae Corynebacterium, Campylobacter and Selenomonas in young adults Kazan Tatars.

Modulation of inflammatory responses by gastrointestinal Prevotella spp. - From associations to functional studies

Numerous studies have associated alterations in the gut microbiota composition with almost every known inflammatory disease. However, proving the biological relevance of distinct microbial signatures and linking specific microorganisms to host phenotypes, remains a considerable challenge. Correspondingly, increased abundance of members of Prevotella genus within microbial communities colonizing distinct mucosal surfaces has been found in individuals diagnosed with rheumatoid arthritis, periodontitis, metabolic disorders, and intestinal and vaginal dysbiosis. Still, the role of Prevotella spp. in the incidence of these diseases continues to be debated. For many years, poor understanding of Prevotella biology could be in large part attributed to the lack of experimental tools. However, in the recent years significant advances have been made towards overcoming these limitations, including increased number of isolates and improved understanding of genetic diversity. Besides discussing the most relevant associations between Prevotella spp. and inflammatory disorders, in the present review we examine the recent efforts to expand the Prevotella experimental "toolbox" and we highlight remaining experimental challenges that should advance future research and our understanding of Prevotella-host interplay.

Comparison of Blood Bacterial Communities in Periodontal Health and Periodontal Disease

The use of Next Generation Sequencing (NGS) techniques has generated a wide variety of blood microbiome data. Due to the large variation in bacterial DNA profiles between studies and the likely high concentrations of cell-free bacterial DNA in the blood, it is still not clear how such microbiome data relates to viable microbiota. For these reasons much remains to be understood about the true nature of any possible healthy blood microbiota and of bacteraemic events associated with disease. The gut, reproductive tracts, skin, and oral cavity are all likely sources of blood-borne bacteria. Oral bacteria, especially those associated with periodontal diseases, are also commonly associated with cardiovascular diseases such as infective endocarditis, and also have been linked to rheumatoid arthritis and Alzheimer’s disease. Periodontal treatment, dental probing, and toothbrushing have been shown to cause transient bacteraemia and oral bacteria from the phyla Firmicutes (e.g. Streptococci) and Bacteroidetes (e.g. Porphyromonas) are found in cardiovascular lesions (CVD). Many studies of blood bacterial DNA content however, find Proteobacteria DNA to be the dominant microbiome component, suggesting a gut origin. Most studies of this type use total DNA extracted from either whole blood or blood fractions, such as buffy coat. Here, using a method that purifies DNA from intact bacterial cells only, we examined blood donated by those with active, severe periodontitis and periodontally healthy controls and show that 43–52% of bacterial species in blood are classified as oral. Firmicutes, consisting largely of members of the Streptococcus mitis group and Staphylococcus epidermidis, were predominant at 63.5% of all bacterial sequences detected in periodontal health and, little changed at 66.7% in periodontitis. Compared to studies using total DNA Proteobacteria were found here at relatively low levels in blood at 13.3% in periodontitis and 17.6% in health. This study reveals significant phylogenetic differences in blood bacterial population profiles when comparing periodontal health to periodontal disease cohorts.

Gut microbiota and the periodontal disease: role of hyperhomocysteinemia

Periodontal disease is one of the most common conditions resulting from poor oral hygiene and is characterized by a destructive process in the periodontium that essentially includes gingiva, alveolar mucosa, cementum, periodontal ligament, and alveolar bone. Notably, the destructive event in the alveolar bone has been linked to homocysteine (Hcy) metabolism; however, it has not been fully investigated. Therefore; the implication of Hcy towards initiation, progression, and maintenance of the periodontal disease remains incompletely understood. Higher levels of Hcy (also known as hyperhomocysteinemia (HHcy)) exerts deleterious effects on gum health and teeth in distinct ways. Firstly, increased production of proinflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-8 leads to an inflammatory cascade of events that affect methionine (Met) and Hcy metabolism (i.e., 1-carbon metabolism) leading to HHcy. Secondly, metabolic dysregulation during chronic medical conditions increases systemic inflammation leading to a decrease in vitamins, more specifically B6, B12, and folic acid, that play important roles as cofactors in Hcy metabolism. Also, given the folate level in the HHcy state that is important during dysbiosis, these two conditions appear to be intimately related, and in this context, HHcy-induced dysbiosis may be one of the potential causes of periodontal disease. This paper sums up the link between periodontitis and HHcy, with a special emphasis on the "oral-gut microbiome axis" and the potential probiotic intervention towards warding off some of the serious periodontal disease conditions.