Association between periodontitis and anti-citrullinated protein antibodies in rheumatoid arthritis patients: a cross-sectional study

The Role of Citrullination Modification in CD4+ T Cells in the Pathogenesis of Immune-Related Diseases

The post-translational modifications (PTMs) of proteins play a crucial role in increasing the functional diversity of proteins and are associated with the pathogenesis of various diseases. This review focuses on a less explored PTM called citrullination, which involves the conversion of arginine to citrulline. This process is catalyzed by peptidyl arginine deiminases (PADs). Different members of the PAD family have distinct tissue distribution patterns and functions. Citrullination is a post-translational modification of native proteins that can alter their structure and convert them into autoantigens; thus, it mediates the occurrence of autoimmune diseases. CD4+ T cells, including Th1, Th2, and Th17 cells, are important immune cells involved in mediating autoimmune diseases, allergic reactions, and tumor immunity. PADs can induce citrullination in CD4+ T cells, suggesting a role for citrullination in CD4+ T cell subset differentiation and function. Understanding the role of citrullination in CD4+ T cells may provide insights into immune-related diseases and inflammatory processes.

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.

Genetic causal association between rheumatoid arthritis and periodontitis: a bidirectional two-sample Mendelian randomization analysis

BACKGROUND

A link between rheumatoid arthritis (RA) and periodontitis (PD) has been established. However, their causal relationship remains unclear and the effect of different serotypes of RA on the PD development has not been investigated. This study aims to elucidate the causal association between PD and different serotypes of RA using Mendelian randomization (MR).

METHODS

A bidirectional two-sample MR analysis was performed using available large-scale genome-wide association studies statistics. The inverse-variance weighted (IVW) or multiplicative random-effects IVW was used to determine causality, depending on the heterogeneity of instrumental variables. Additional sensitivity analyses were also performed.

RESULTS

The forward MR analysis identified that seropositive RA (odds ratio (OR), 1.26; 95% confidence interval (CI), 1.07-1.44; p = 0.0018), but not seronegative RA (OR, 1.01; 95% CI, 0.95-1.06; p = 0.9098), was associated with an increased risk of PD. The reverse MR analysis did not show any significant causal effect of PD on RA, independent of the serotypes. The sensitivity tests (p > 0.05) confirmed the robustness and accuracy of these findings.

CONCLUSION

This study revealed that there was a genetic causal effect of seropositive RA on PD, suggesting that this subtype of RA patients may require specific clinical attention to prevent the development of PD.

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.

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.

Treatment resistance of rheumatoid arthritis relates to infection of periodontal pathogenic bacteria: a case-control cross-sectional study

Recent studies have shown that periodontitis is associated with rheumatoid arthritis (RA) and periodontal bacteria, such as Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) are involved in the pathogenesis of RA via citrullinated proteins. Smoking has also been shown to be involved in the pathogenesis of RA; however, the extent of this involvement is still poorly understood. In addition, RA and polymyalgia rheumatica (PMR) are sometimes difficult to differentiate; however, the relationship between PMR and the factors from smoking and periodontal bacteria is unclear. The aim of this study was to clarify the relationship between periodontal pathogenic bacterial infections and smoking in patients with RA or PMR. This case–control study included 142 patients with untreated RA or PMR. This study evaluated the serum antibody titers against periodontal pathogenic bacterial antigens and an anti-citrullinated peptide antibody (ACPA). In patients with RA, the relationship between antibody titers and disease activity of RA and response after 3 months of treatment was also investigated. Additionally, the effects of smoking were evaluated. Although there was no significant difference in serum antibody titer against periodontal pathogenic bacteria between the ACPA-positive RA group and the ACPA-negative PMR group, we found an association between the elevated antibody titer against Pg and the degree of ACPA value, especially between negative group and high-value positive group (≥ 100 U/mL). The antibody titers against Aa and Pg did not differ depending on disease activity score 28 (DAS28) at baseline; however, patients with high antibody titers had poor RA therapeutic response as judged by DAS28 after 3 months. We could not find any association between smoking and any of these parameters. Periodontal pathogenic bacteria, especially Pg, are associated with elevated ACPA levels. Our findings suggest that Pg and Aa infections interfere with the therapeutic response of RA.

Presence of Autoantibodies in Males and Females With Rheumatoid Arthritis: A Systematic Review and Metaanalysis

OBJECTIVE

Rheumatoid arthritis (RA) is more common in females, and although the cause of RA is unknown, it is characterized by the production of autoantibodies. The aims of this study were to determine whether RA-associated autoantibodies are more often found in females than males and to identify factors that influence the relationship between sex and seropositivity.

METHODS

Databases were searched and studies of RA (N ≥ 100) were included if they reported proportion of seropositive patients with RA by sex. Metaanalyses and metaregression were conducted using the random-effects model. Covariates regressed were smoking, age, BMI, Health Assessment Questionnaire-Disability Index (HAQ-DI), and the Disease Activity Score in 28 joints (DAS28).

RESULTS

Eighty-four studies with a total of 141,381 subjects with rheumatoid factor (RF) seropositivity and 95,749 subjects with anticitrullinated protein antibody (ACPA) seropositivity met inclusion criteria. The mean age of participants ranged from 37 to 68 years and the proportion of female subjects ranged from 9% to 92%. Results indicated that females were less likely than males to be seropositive: odds ratio (OR) 0.84 [95% CI 0.77-0.91] for RF and OR 0.88 [95% CI 0.81-0.95] for ACPA. BMI, smoking, mean age, DAS28, and HAQ-DI did not affect the relationship between sex and seropositivity.

CONCLUSION

Although studies report that females have higher RA disease activity than males and that seropositivity predicts worse outcomes, females were less likely to be seropositive than males.

Role of Interleukin-17A in the Pathomechanisms of Periodontitis and Related Systemic Chronic Inflammatory Diseases

Periodontitis is a chronic inflammatory and destructive disease caused by periodontal microbial infection and mediated by host immune response. As the main cause of loosening and loss of teeth in adults, it is considered to be one of the most common and serious oral diseases in the world. The co-existence of periodontitis and systemic chronic inflammatory diseases such as rheumatoid arthritis, psoriasis, inflammatory bowel disease, diabetes and so on is very common. It has been found that interleukin-17A (IL-17A) secreted by various innate and adaptive immune cells can activate a series of inflammatory cascade reactions, which mediates the occurrence and development of periodontitis and related systemic chronic inflammatory diseases. In this work, we review the role of IL-17A in the pathomechanisms of periodontitis and related systemic chronic inflammatory diseases, and briefly discuss the therapeutic potential of cytokine targeted agents that modulate the IL-17A signaling. A deep understanding of the possible molecular mechanisms in the relationship between periodontitis and systemic diseases will help dentists and physicians update their clinical diagnosis and treatment ideas.

Citrullination in the pathology of inflammatory and autoimmune disorders: recent advances and future perspectives

Numerous post-translational modifications (PTMs) govern the collective metabolism of a cell through altering the structure and functions of proteins. The action of the most prevalent PTMs, encompassing phosphorylation, methylation, acylations, ubiquitination and glycosylation is well documented. A less explored protein PTM, conversion of peptidylarginine to citrulline, is the subject of this review. The process of citrullination is catalysed by peptidylarginine deiminases (PADs), a family of conserved enzymes expressed in a variety of human tissues. Accumulating evidence suggest that citrullination plays a significant role in regulating cellular metabolism and gene expression by affecting a multitude of pathways and modulating the chromatin status. Here, we will discuss the biochemical nature of arginine citrullination, the enzymatic machinery behind it and also provide information on the pathological consequences of citrullination in the development of inflammatory diseases (rheumatoid arthritis, multiple sclerosis, psoriasis, systemic lupus erythematosus, periodontitis and COVID-19), cancer and thromboembolism. Finally, developments on inhibitors against protein citrullination and recent clinical trials providing a promising therapeutic approach to inflammatory disease by targeting citrullination are discussed.

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.

Association Between Rheumatoid Arthritis Disease Activity and Periodontitis Defined by Tooth Loss: Longitudinal and Cross-Sectional Data From Two Observational Studies

OBJECTIVE

To analyze the effect of tooth loss/periodontitis on disease activity in early and established rheumatoid arthritis (RA).

METHODS

Participants of the Course And Prognosis of Early Arthritis (CAPEA) early arthritis cohort reported their number of teeth at baseline. The number of teeth had been validated as a predictor of periodontitis. Clinical end points, including disease activity score (Disease Activity Score in 28 joints using the erythrocyte sedimentation rate [ESR]), swollen joint count (SJC), ESR, and C-reactive protein level were collected at baseline, 3, 6, 12, 18, and 24 months. We used linear mixed regression models to estimate the association between tooth loss and clinical end points over time in early arthritis. For established RA, we analyzed cross-sectional data from the German National Database (NDB). All models accounted for age, sex, smoking, seropositivity, education level, and disease duration (only NDB).

RESULTS

Among 1,124 CAPEA participants with early arthritis, those with higher tooth loss were older, more often male, smokers, and seropositive, and they had higher disease activity and inflammation markers at baseline. Tooth loss was associated with higher disease activity and ESR values over time. Inflammatory markers decreased comparably across tooth loss categories. Glucocorticoid use was higher among those with more tooth loss, whereas dose reduction was similar across tooth loss categories. Among 7,179 NDB participants with longstanding RA, disease activity and inflammation markers but not SJC were significantly higher in patients with more tooth loss.

CONCLUSION

Although we observed an association between tooth loss and disease activity scores and inflammation markers in early and established RA, longitudinal results suggest that tooth loss does not hamper treatment response.

Crosstalk between B cells and neutrophils in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic autoimmune disease without known cure that primarily affects synovial joints. RA has a prevalence of approximately 1% of the population worldwide. A vicious circle between two critical immune cell types, B cells and neutrophils, develops and promotes disease. Pathogenic anti‐citrullinated protein antibodies (ACPA) directed against a range of citrullinated epitopes are abundant in both plasma and synovial fluid of RA patients. In addition to stimulating numerous cell types, ACPA and other autoantibodies, notably rheumatoid factor, form immune complexes (ICs) that potently activate neutrophils. Attracted to the synovium by abundant chemokines, neutrophils are locally stimulated by ICs. They generate cytokines and release cytotoxic compounds including neutrophil extracellular traps (NETs), strands of decondensed chromatin decorated with citrullinated histones and granule‐derived neutrophil proteins, which are particularly abundant in the synovial fluid. In this way, neutrophils generate citrullinated epitopes and release peptidylarginine deiminase (PAD) enzymes capable of citrullinating extracellular proteins in the rheumatic joint, contributing to renewed ACPA generation. This review article focusses on the central function of citrullination, a post‐translational modification of arginine residues in RA. The discussion includes ACPA and related autoantibodies, somatic hypermutation‐mediated escape from negative selection by autoreactive B cells, promotion of the dominance of citrullinated antigens by genetic and lifestyle susceptibility factors and the vicious circle between ACPA‐producing pathogenic B cells and NET‐producing neutrophils in RA.

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.

Periodontal disease in seropositive rheumatoid arthritis: scoping review of the epidemiological evidence

The link between periodontal disease (PD) and rheumatoid arthritis (RA) has been hypothesized to lie in the anti-cyclic citrullinated protein antibody (ACPA) molecules present in seropositive RA. This review aimed to discuss how RA and specifically ACPA-positive RA link to PD, and appraise the epidemiological evidence on the relationship between ACPA-positive RA and PD. Articles were searched following the PRISMA guideline across the MEDLINE, Web of Science, Scopus and Cochrane Library databases. A total of 21 articles met the inclusion criteria of reporting the epidemiological data on the different ACPA status of the subjects with RA and PD (or periodontitis) parameters. A discrepancy is noted in the epidemiological evidence on the difference in the prevalence and severity of PD between ACPA-positive and ACPA-negative RA patients. Although the link between RA and PD is mostly discussed in terms of ACPA, reports on the different manifestations of PD between the two RA subsets remains inconclusive.

Rheumatoid arthritis serotype and synthetic disease-modifying anti-rheumatic drugs in patients with periodontitis: A case-control study

Patients with rheumatoid arthritis (RA) experience a higher prevalence of periodontitis. This study aimed to examine the variation of periodontitis experienced with different serotypes suffered by RA patients and to examine the relationship between the different medications taken for RA that may influence this relationship. Two hundred and sixty RA and control participants underwent standardized periodontal examinations. Medical, serological and radiological (Sharp/van der Heijde) records were assessed. Functional status was assessed using the administered Health Assessment Questionnaire. Moreover, disease parameters, including disease activity (DAS28-ESR) and anti-citrullinated protein antibodies (ACPA) and rheumatoid factor (RF) seropositivity were evaluated. Periodontitis was higher in RA (71.54%) compared with controls (54.62%). The stage of periodontitis experienced by ACPA-positive participants were higher than APCA-negative participants. The probing pocket depth and recession experienced by RF-positive participants were higher than those who were RF-negative. RA participants on methotrexate had lower clinical attachment loss and lower periodontal probing depth compared with participants on a combination methotrexate and other disease-modifying antirheumatic drugs. Participants taking corticosteroids had lower gingival index scores. The association between seropositivity and the type of medications taken with periodontal health parameters in this group of patients suggests that both seropositivity and medications taken are important modifiers in the relationship between periodontitis and RA.

Periodontitis in Italian patients with established rheumatoid arthritis: A cross-sectional study

OBJECTIVE

To assess the prevalence and severity of periodontitis (P) among Italian patients affected by rheumatoid arthritis (RA).

MATERIALS AND METHODS

A full-mouth periodontal examination and a rheumatologic examination were performed. RA disease activity was scored using the DAS28. Serum analyses investigated levels of rheumatoid factor, anti-citrullinated protein antibodies (ACPAs), C-reactive protein, erythrocyte sedimentation rate and fibrinogen. Information concerning smoking, body mass index and RA medical therapy was collected. Data were analysed by Student's t test, chi-square test, binary logistic regression and Spearman's rank.

RESULTS

This cross-sectional study included 120 subjects, 77 had both diseases while 43 only had RA. The number of teeth present was statistically lower in the RA-P compared to the RA group (p < .05). There were statistically more subjects seropositive for ACPAs in the RA-P group (62.3% vs. 32.6%, p < .05). RA-P patients had an adjusted OR = 2.9 of presenting a moderate-severe DAS28 score (DAS28 ≥ 3.2).

CONCLUSIONS

Higher prevalence of severe P was noted among RA subjects. The clinical severity of RA was strongly correlated with the clinical periodontal parameters, and RA subjects also affected by P had an OR of 2.9 for presenting with a moderate-severe RA (DAS28 score ≥ 3.2).

Does periodontitis affect the treatment response of biologics in the treatment of rheumatoid arthritis?

BACKGROUND

Rheumatoid arthritis (RA) and periodontitis (PD) have been suggested to share many clinical and pathological features. However, few reports have investigated the relationship between the degree of PD and the treatment response to RA. This study aimed to examine the relationship between the extent of PD and the treatment response to biologics in RA patients using FDG-PET/CT.

METHODS

Sixty RA patients (male, n = 14; female, n = 46; average age, 58.3 years) treated with biologic agents were included in this study. FDG-PET/CT was performed at baseline and 6 months after the initiation of biological therapy. The maximum standardized uptake value (SUVmax) was used as a representative value for the assessment of the FDG uptake in periodontal tissue and joints including the bilateral shoulders, elbows, wrists, hip, knees, and ankle joints. The Disease Activity Score (DAS) 28-CRP and the following clinical parameters were assessed: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), anti-cyclic citrullinated peptide antibody (ACPA), rheumatoid factor (RF), and matrix metalloproteinase 3 (MMP-3). The relationship between the treatment response of RA and the baseline SUVmax of the periodontal tissue was evaluated.

RESULTS

The baseline periodontal SUVmax was related to patient age (r = 0.302, p = 0.009) and the ACPA level (r = 0.265, p = 0.025). The DAS28-CRP, CRP, ESR, MMP-3, and joint SUVmax values were significantly decreased after 6 months of biological therapy. However, the mean periodontal SUVmax, ACPA, and RF showed no significant changes after treatment. There was a significantly negative correlation between the baseline periodontal SUVmax and the treatment response of DAS28-CRP (r = - 0.369, p = 0.004).

CONCLUSION

There was a negative correlation between the extent of PD at baseline and the treatment response of RA patients who received biological therapy. The evaluation of the periodontal condition is considered to be an essential part for the management of RA.