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

Glucose as a Potential Key to Fuel Inflammation in Rheumatoid Arthritis

Glucose is the most important source of energy and homeostasis. Recent investigations are clarifying that glucose metabolism might be altered in rheumatoid arthritis (RA), which would play a role in the inflammatory phenotype of rheumatoid synovial fibroblasts. It may also play a role in a variety of autoimmune diseases’ pathophysiology by modulating immune responses and modifying autoantigen expressions. The research into glucose and its metabolism could lead to a better understanding of how carbohydrates contribute to the occurrence and duration of RA and other autoimmune diseases.

B cell depletion in patients with rheumatoid arthritis is associated with reduced IL-1β in GCF

OBJECTIVES

We evaluated the effect of B cell depletion on the clinical periodontal findings and IL-1β and MMP-8 levels of the gingival crevicular (GCF) fluid in patients with rheumatoid arthritis (RA).

MATERIALS AND METHODS

Seventy patients were included in this case-control study. Twenty patients with RA were undergoing B-cell depletion treatment. The second group of RA patients (n = 20) were undergoing non-B-cell depletion treatment with Disease-Modifying Anti-Rheumatic Drugs (DMARD). Control group, with no RA, consisted of 30 individuals. Periodontal parameters including probing depth (PD), clinical attachment level (CAL), bleeding on probing (BOP), gingival index (GI), and plaque index (PI) were recorded. IL-1β and MMP-8 levels in GCF were determined using enzyme-linked immunosorbent assay. Rheumatological parameters including Disease Activity Score-28 (DAS-28), rheumatoid factor levels (RF), and anti-cyclic citrullinated peptide levels were included in the data analyses.

RESULTS

All groups were similar in PD, CAL, BOP, GI, and PI measures. GCF IL-1β levels were 1.85 ± 1.67 pg in the B-cell depletion group, 10.50 ± 13.16 pg in the DMARD group, and 34.12 ± 29.45 pg in the control group (p < 0.001). MMP-8 levels were 21.00 ± 4.23 pg in the B-cell depletion group, 8.16 ± 6.94 pg in the DMARD group, and 21.45 ± 8.67 pg in the control group (p < 0.001). DAS 28, RF, and anti-CCP were similar in RA groups.

CONCLUSIONS

GCF IL-1β levels were significantly lower in B cell depletion group, and MMP-8 levels were significantly lower in DMARD group, suggesting that rheumatoid arthritis treatments may modify biochemical parameters of GCF.

CLINICAL RELEVANCE

This study suggests that host modulation therapies in RA can reduce local production of IL-1β and MMP-8. Reduction of these inflammatory cytokines and enzymes may have a beneficial effect in controlling periodontal tissue destruction.

Identification of Cross-Talk and Pyroptosis-Related Genes Linking Periodontitis and Rheumatoid Arthritis Revealed by Transcriptomic Analysis

BACKGROUND

The current study is aimed at identifying the cross-talk genes between periodontitis (PD) and rheumatoid arthritis (RA), as well as the potential relationship between cross-talk genes and pyroptosis-related genes.

METHODS

Datasets for the PD (GSE106090, GSE10334, GSE16134) and RA (GSE55235, GSE55457, GSE77298, and GSE1919) were downloaded from the GEO database. After batch correction and normalization of datasets, differential expression analysis was performed to identify the differentially expressed genes (DEGs). The cross-talk genes linking PD and RA were obtained by overlapping the DEGs dysregulated in PD and DEGs dysregulated in RA. Genes involved in pyroptosis were summarized by reviewing literatures, and the correlation between pyroptosis genes and cross-talk genes was investigated by Pearson correlation coefficient. Furthermore, the weighted gene coexpression network analysis (WGCNA) was carried out to identify the significant modules which contained both cross-talk genes and pyroptosis genes in both PD data and RA data. Thus, the core cross-talk genes were identified from the significant modules. Receiver-operating characteristic (ROC) curve analysis was performed to identify the predictive accuracy of these core cross-talk genes in diagnosing PD and RA. Based on the core cross-talk genes, the experimentally validated protein-protein interaction (PPI) and gene-pathway network were constructed.

RESULTS

A total of 40 cross-talk genes were obtained. Most of the pyroptosis genes were not differentially expressed in disease and normal samples. By selecting the modules containing both cross-talk genes or pyroptosis genes, the blue module was identified to be significant module. Three genes, i.e., cross-talk genes (TIMP1, LGALS1) and pyroptosis gene-GPX4, existed in the blue module of PD network, while two genes (i.e., cross-talk gene-VOPP1 and pyroptosis gene-AIM2) existed in the blue module of RA network. ROC curve analysis showed that three genes (TIMP1, VOPP1, and AIM2) had better predictive accuracy in diagnosing disease compared with the other two genes (LGALS1 and GPX4).

CONCLUSIONS

This study revealed shared mechanisms between RA and PD based on cross-talk and pyroptosis genes, supporting the relationship between the two diseases. Thereby, five modular genes (TIMP1, LGALS1, GPX4, VOPP1, and AIM2) could be of relevance and might serve as potential biomarkers. These findings are a basis for future research in the field.

Another Look at the Contribution of Oral Microbiota to the Pathogenesis of Rheumatoid Arthritis: A Narrative Review

Although autoimmunity contributes to rheumatoid arthritis (RA), several lines of evidence challenge the dogma that it is mainly an autoimmune disorder. As RA-associated human leukocyte antigens shape microbiomes and increase the risk of dysbiosis in mucosae, RA might rather be induced by epigenetic changes in long-lived synovial presenting cells, stressed by excessive translocations into joints of bacteria from the poorly cultivable gut, lung, or oral microbiota (in the same way as more pathogenic bacteria can lead to "reactive arthritis"). This narrative review (i) lists evidence supporting this scenario, including the identification of DNA from oral and gut microbiota in the RA synovium (but in also healthy synovia), and the possibility of translocation through blood, from mucosae to joints, of microbiota, either directly from the oral cavity or from the gut, following an increase of gut permeability worsened by migration within the gut of oral bacteria such as Porphyromonas gingivalis; (ii) suggests other methodologies for future works other than cross-sectional studies of periodontal microbiota in cohorts of patients with RA versus controls, namely, longitudinal studies of oral, gut, blood, and synovial microbiota combined with transcriptomic analyses of immune cells in individual patients at risk of RA, and in overt RA, before, during, and following flares of RA.

Impact of photodynamic therapy as an adjunct to non-surgical periodontal treatment on clinical and biochemical parameters among patients having mild rheumatoid arthritis with periodontitis

PURPOSE

To evaluate the efficacy of photodynamic therapy (PDT) as an adjunct to non-surgical periodontal therapy on the clinical periodontal and biochemical parameters among patients with rheumatoid arthritis (RA) having periodontitis.

METHODS

A total of 50 RA patients with periodontitis were included. The subjects were equally divided into two groups: Group A - scaling and root planning (SRP) + PDT; Group B - SRP only, respectively. Plaque score (PS), bleeding on probing (BOP), and pocket depth (PD) were estimated. The biochemical parameters included the assessment of interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α) and rheumatoid factors (RFs).

RESULTS

Plaque scores and BOP significantly reduced in both the groups at both 6 and 12 weeks with significant difference between both the groups at 6 weeks follow up (p<0.05). On inter-group comparison, there was a statistically significant reduction seen for BOP in Group A at 12 weeks (p<0.001). PD significantly reduced in both the groups at both time points; however, significant reduction was noted for Group A compared to Group B (p<0.01). IL-6 and TNF-α significantly reduced in both the groups at 6 and 12 weeks follow up. However, the proinflammatory cytokine levels significantly reduced in group A as compared to group B at both 6 and 12 weeks (p<0.05). GCF levels of RF did not show any change in either of the groups at either time point or between the groups (p>0.05).

CONCLUSION

PDT significantly reduced the proinflammatory burden in terms of periodontal attachment level and bleeding on probing within the periodontal inflammatory pockets in patients having RA.

Periodontal Inflammation and Systemic Diseases: An Overview

Periodontitis is a common inflammatory disease of infectious origins that often evolves into a chronic condition. Aside from its importance as a stomatologic ailment, chronic periodontitis has gained relevance since it has been shown that it can develop into a systemic condition characterized by unresolved hyper-inflammation, disruption of the innate and adaptive immune system, dysbiosis of the oral, gut and other location's microbiota and other system-wide alterations that may cause, coexist or aggravate other health issues associated to elevated morbi-mortality. The relationships between the infectious, immune, inflammatory, and systemic features of periodontitis and its many related diseases are far from being fully understood and are indeed still debated. However, to date, a large body of evidence on the different biological, clinical, and policy-enabling sources of information, is available. The aim of the present work is to summarize many of these sources of information and contextualize them under a systemic inflammation framework that may set the basis to an integral vision, useful for basic, clinical, and therapeutic goals.

Oral health's inextricable connection to systemic health: Special populations bring to bear multimodal relationships and factors connecting periodontal disease to systemic diseases and conditions

The landscape in dentistry is changing as emerging studies continue to reveal that periodontal health impacts systemic health, and vice versa. Population studies, clinical studies, and in vitro animal studies underscore the critical importance of oral health to systemic health. These inextricable relationships come to the forefront as oral diseases, such as periodontal disease, take root. Special populations bring to bear the multimodal relationships between oral and systemic health. Specifically, periodontal disease has been associated with diabetes, metabolic syndrome, obesity, eating disorders, liver disease, cardiovascular disease, Alzheimer disease, rheumatoid arthritis, adverse pregnancy outcomes, and cancer. Although bidirectional relationships are recognized, the potential for multiple comorbidities, relationships, and connections (multimodal relationships) also exists. Proposed mechanisms that mediate this connection between oral and systemic health include predisposing and precipitating factors, such as genetic factors (gene polymorphisms), environmental factors (stress, habits-such as smoking and high-fat diets/consumption of highly processed foods), medications, microbial dysbiosis and bacteremias/viremias/microbemias, and an altered host immune response. Thus, in a susceptible host, these predisposing and precipitating factors trigger the onset of periodontal disease and systemic disease/conditions. Further, high-throughput sequencing technologies are shedding light on the dark matter that comprises the oral microbiome. This has resulted in better characterization of the oral microbial dysbiosis, including putative bacterial periodontopathogens and shifts in oral virome composition during disease. Multiple laboratory and clinical studies have illustrated that both eukaryotic and prokaryotic viruses within subgingival plaque and periodontal tissues affect periodontal inflammation, putative periodontopathogens, and the host immune response. Although the association between herpesviruses and periodontitis and the degree to which these viruses directly aggravate periodontal tissue damage remain unclear, the benefits to periodontal health found from prolonged administration of antivirals in immunocompromised or immunodeficient individuals demonstrates that specific populations are possibly more susceptible to viral periodontopathogens. Thus, it may be important to further examine the implications of viral pathogen involvement in periodontitis and perhaps it is time to embrace the viral dark matter within the periodontal environment to fully comprehend the pathogenesis and systemic implications of periodontitis. Emerging data from the coronavirus disease 2019 pandemic further underscores the inextricable connection between oral and systemic health, with high levels of the severe acute respiratory syndrome coronavirus 2 angiotensin-converting enzyme 2 receptor noted on oral tissues (tongue) and an allostatic load or overload paradigm of chronic stress likely contributing to rapid breakdown of oral/dental, periodontal, and peri-implant tissues. These associations exist within a framework of viremias/bacteremias/microbemias, systemic inflammation, and/or disturbances of the immune system in a susceptible host. A thorough review of systemic and oral diseases and conditions and their mechanistic, predisposing, and precipitating factors are paramount to better addressing the oral and systemic health and needs of our patients.