Rheumatoid arthritis is linked to oral bacteria: etiological association. Mod Rheumatol. 2009;19:453-456. [PMID: 19554393 DOI: 10.1007/s10165-009-0194-9]

The Role of Chlamydia pneumoniae in the Aetiology of Autoimmune Diseases

Introduction The most prevalent chronic human autoimmune disorder worldwide is rheumatoid arthritis. Synovial samples from acute-phase patients are polymerase chain reaction-positive for Chlamydia pneumoniae (C. pneumoniae) DNA and express chlamydial hsp60. Furthermore, anti-cyclic citrullinated peptide (anti-CCP) antibodies promote apoptosis of mature human Saos-2 osteoblasts via cell surface binding to citrullinated heat shock protein 60 (HSP60). Hence, we hypothesised that C. pneumoniae infection is associated with anti-CCP antibodies. Methods C. pneumoniae IgA and anti-CCP antibody levels were determined in 26 healthy subjects in this cross-sectional study. Serum C. pneumoniae IgA antibody levels were assessed using an enzyme-linked immunosorbent assay. Serum anti-CCP antibody levels were assessed using fluoroenzymeimmunoassay. Results There was a highly significant positive correlation between the two sets of antibodies (rs = 0.621; P = 0.0007). Linear regression analysis showed that this correlation was not the result of age or sex. Discussion A biologically plausible mechanism is put forward for these results, involving HSP60 acting as an endogenous ligand for toll-like receptor 4 (TLR4) and the interaction of TLR4 with lipopolysaccharides, which occur in the outer membrane of the C. pneumoniae elementary body. Pronounced pro-inflammatory mediator secretion then takes place. The release of Ca2+ ions may then activate local peptidylarginine deiminases, leading to the formation of CCPs and thus the reported finding. Confirmation of these results may have potential clinical implications in terms of diagnosis, including pre-symptomatic diagnosis, and treatment.

Unexpected lower level of oral periodontal pathogens in patients with high numbers of systemic diseases

Background

Periodontal disease is associated with systemic conditions such as diabetes, arthritis, and cardiovascular disease, all diseases with large inflammatory components. Some, but not all, reports show periopathogens Porphyromonas gingivialis and Tannerella forsythia at higher levels orally in people with one of these chronic diseases and in people with more severe cases. These oral pathogens are thought to be positively associated with systemic inflammatory diseases through induction of oral inflammation that works to distort systemic inflammation or by directly inducing inflammation at distal sites in the body. This study aimed to determine if, among patients with severe periodontal disease, those with multi-morbidity (or many chronic diseases) showed higher levels of periodontal pathogens.

Methods

A total of 201 adult subjects, including 84 with severe periodontal disease were recruited between 1/2017 and 6/2019 at a city dental clinic. Electronic charts supplied self-reported diseases and conditions which informed a morbidity index based on the number of chronic diseases and conditions present. Salivary composition was determined by 16S rRNA gene sequencing.

Results

As expected, patients with severe periodontal disease showed higher levels of periodontal pathogens in their saliva. Also, those with severe periodontal disease showed higher levels of multiple chronic diseases (multimorbidity). An examination of the 84 patients with severe periodontal disease revealed some subjects despite being of advanced age were free or nearly free of systemic disease. Surprisingly, the salivary microbiota of the least healthy of these 84 subjects, defined here as those with maximal multimorbidity, showed significantly lower relative numbers of periodontal pathogens, including Porphyromonas gingivalis and Tannerella Forsythia, after controlling for active caries, tobacco usage, age, and gender. Analysis of a control group with none to moderate periodontal disease revealed no association of multimorbidity or numbers of medications used and specific oral bacteria, indicating the importance of severe periodontal disease as a variable of interest.

Conclusion

The hypothesis that periodontal disease patients with higher levels of multimorbidity would have higher levels of oral periodontal pathogens is false. Multimorbidity is associated with a reduced relative number of periodontal pathogens Porphyromonas gingivalis and Tannerella forsythia.

Portable biosensor-based oral pathogenic bacteria detection for community and family applications

Detection of oral pathogens is essential in the management of oral diseases, as their occurrence and progression are closely linked to an imbalance in these microorganisms. Detection techniques such as microbial cultures, enzyme-linked immunosorbent assays and polymerase chain reactions are highly dependent on complex testing procedures and specialized laboratory equipment, making prevention and early diagnosis of oral diseases difficult. To comprehensively implement oral disease prevention and early diagnosis in social groups, there is an urgent need for portable testing methods for oral pathogenic bacteria that can be applied in community and home settings. In this review, several common portable biosensors for pathogenic bacteria are first described. Based on the goal of achieving primary prevention and diagnosis of oral diseases, we elaborate and summarize portable biosensors for common oral pathogenic bacteria in terms of how to achieve portability of the technique. This review aims to reflect the current status of portable biosensors for common oral pathogens and to lay the foundation for the further realization of portable detection of oral pathogens.

No Genetic Causal Association Between Periodontitis and Arthritis: A Bidirectional Two-Sample Mendelian Randomization Analysis

Objectives

Periodontitis (PD) has been linked to arthritis in previous epidemiological observational studies; however, the results are inconclusive. It remains unclear whether the association between PD and arthritis is causal. The purpose of this study was to investigate the causal association of PD with arthritis, including rheumatoid arthritis (RA) and osteoarthritis (OA).

Methods

We performed a two-sample bidirectional Mendelian randomization (MR) analysis using publicly released genome-wide association studies (GWAS) statistics. The inverse-variance weighted (IVW) method was used as the primary analysis. We applied four complementary methods, including weighted median, weighted mode, MR-Egger regression and MR pleiotropy residual sum and outlier (MR-PRESSO) to detect and correct for the effect of horizontal pleiotropy.

Results

Genetically determined PD did not have a causal effect on OA (OR = 1.06, 95% CI: 0.99-1.15, P = 0.09) and RA (OR = 0.99, 95% CI: 0.87-1.13, P = 0.89). Furthermore, we did not find a significant causal effect of arthritis on PD in the reverse MR analysis. The results of MR-Egger regression, Weighted Median, and Weighted Mode methods were consistent with those of the IVW method. Horizontal pleiotropy was unlikely to distort the causal estimates according to the sensitivity analysis.

Conclusions

Our MR analysis reveals non-causal association of PD with arthritis, despite observational studies reporting an association between PD and arthritis.

Relationships Between Oral Microecosystem and Respiratory Diseases

Oral microecosystem is a very complicated ecosystem that is located in the mouth and comprises oral microbiome, diverse anatomic structures of oral cavity, saliva and interactions between oral microbiota and between oral microbiota and the host. More and more evidence from studies of epidemiology, microbiology and molecular biology is establishing a significant link between oral microecosystem and respiratory diseases. Microbiota settling down in oral microecosystem is known as the main source of lung microbiome and has been associated with the occurrence and development of respiratory diseases like pneumonia, chronic obstructive pulmonary disease, lung cancer, cystic fibrosis lung disease and asthma. In fact, it is not only indigenous oral microbes promote or directly cause respiratory infection and inflammation when inhaled into the lower respiratory tract, but also internal environment of oral microecosystem serves as a reservoir for opportunistic respiratory pathogens. Moreover, poor oral health and oral diseases caused by oral microecological dysbiosis (especially periodontal disease) are related with risk of multiple respiratory diseases. Here, we review the research status on the respiratory diseases related with oral microecosystem. Potential mechanisms on how respiratory pathogens colonize oral microecosystem and the role of indigenous oral microbes in pathogenesis of respiratory diseases are also summarized and analyzed. Given the importance of oral plaque control and oral health interventions in controlling or preventing respiratory infection and diseases, we also summarize the oral health management measures and attentions, not only for populations susceptible to respiratory infection like the elderly and hospitalized patients, but also for dentist or oral hygienists who undertake oral health care. In conclusion, the relationship between respiratory diseases and oral microecosystem has been established and supported by growing body of literature. However, etiological evidence on the role of oral microecosystem in the development of respiratory diseases is still insufficient. Further detailed studies focusing on specific mechanisms on how oral microecosystem participate in the pathogenesis of respiratory diseases could be helpful to prevent and treat respiratory diseases.

Porphyromonas gingivalis outside the oral cavity

Porphyromonas gingivalis, a Gram-negative anaerobic bacillus present in periodontal disease, is considered one of the major pathogens in periodontitis. A literature search for English original studies, case series and review articles published up to December 2019 was performed using the MEDLINE, PubMed and GoogleScholar databases, with the search terms "Porphyromonas gingivalis" AND the potentially associated condition or systemic disease Abstracts and full text articles were used to make a review of published research literature on P. gingivalis outside the oral cavity. The main points of interest of this narrative review were: (i) a potential direct action of the bacterium and not the systemic effects of the inflammatory acute-phase response induced by the periodontitis, (ii) the presence of the bacterium (viable or not) in the organ, or (iii) the presence of its virulence factors. Virulence factors (gingipains, capsule, fimbriae, hemagglutinins, lipopolysaccharide, hemolysin, iron uptake transporters, toxic outer membrane blebs/vesicles, and DNA) associated with P. gingivalis can deregulate certain functions in humans, particularly host immune systems, and cause various local and systemic pathologies. The most recent studies linking P. gingivalis to systemic diseases were discussed, remembering particularly the molecular mechanisms involved in different infections, including cerebral, cardiovascular, pulmonary, bone, digestive and peri-natal infections. Recent involvement of P. gingivalis in neurological diseases has been demonstrated. P. gingivalis modulates cellular homeostasis and increases markers of inflammation. It is also a factor in the oxidative stress involved in beta-amyloid production.

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.

Is periodontal disease a risk factor for severe COVID-19 illness?

Periodontal disease (PD) comprises a group of diseases involving inflammatory aspects of the host and dysbiotic events that affect periodontal tissues and could have systemic implications. Diverse factors and comorbidities have been closely associated with PD such as diabetes, obesity, aging, hypertension, and so on; although, underlying mechanisms or causal associations have not been established completely. Interestingly, these same factors have been widely associated with progression or severe coronavirus disease 2019 (COVID-19), an illness caused by coronavirus SARS-CoV-2. Since inflammatory and dysbiotic factors as well as comorbidities affect systemic health, it is possible that periodontal status indicates the risk of complication of COVID-19. However, assessment of oral health history including periodontal status in COVID-19 patients has not been reported. Knowing PD is associated with severe COVID-19 could help identify risk groups and establish pertinent recommendations.

Molecular characterisation of the synovial fluid microbiome in rheumatoid arthritis patients and healthy control subjects

METHODS

The presence and identity of bacterial and fungal DNA in the synovial fluid of rheumatoid arthritis (RA) patients and healthy control subjects was investigated through amplification and sequencing of the bacterial 16S rRNA gene and fungal internal transcribed spacer region 2 respectively. Synovial fluid concentrations of the cytokines IL-6, IL-17A, IL22 and IL-23 were determined by ELISA.

RESULTS

Bacterial 16S rRNA genes were detected in 87.5% RA patients, and all healthy control subjects. At the phylum level, the microbiome was predominated by Proteobacteria (Control = 83.5%, RA = 79.3%) and Firmicutes (Control = 16.1%, RA = 20.3%), and to a much lesser extent, Actinobacteria (Control = 0.2%, RA = 0.3%) and Bacteroidetes (Control = 0.1%, RA = 0.1%). Fungal DNA was identified in 75% RA samples, and 88.8% healthy controls. At the phylum level, synovial fluid was predominated by members of the Basidiomycota (Control = 53.9%, RA = 46.9%) and Ascomycota (Control = 35.1%, RA = 50.8%) phyla. Statistical analysis revealed key taxa that were differentially present or abundant dependent on disease status.

CONCLUSIONS

This study reports the presence of a synovial fluid microbiome, and determines that this is modulated by disease status (RA) as are other classical microbiome niches.

Oral-Gut Microbiota and Arthritis: Is There an Evidence-Based Axis?

The gut microbiome appears to be a significant contributor to musculoskeletal health and disease. Recently, it has been found that oral microbiota are involved in arthritis pathogenesis. Microbiome composition and its functional implications have been associated with the prevention of bone loss and/or reducing fracture risk. The link between gut–oral microbiota and joint inflammation in animal models of arthritis has been established, and it is now receiving increasing attention in human studies. Recent papers have demonstrated substantial alterations in the gut and oral microbiota in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). These alterations resemble those established in systemic inflammatory conditions (inflammatory bowel disease, spondyloarthritides, and psoriasis), which include decreased microbial diversity and a disturbance of immunoregulatory properties. An association between abundance of oral Porphyromonas gingivalis and intestinal Prevotella copri in RA patients compared to healthy controls has been clearly demonstrated. These new findings open important future horizons both for understanding disease pathophysiology and for developing novel biomarkers and treatment strategies. The changes and decreased diversity of oral and gut microbiota seem to play an important role in the etiopathogenesis of RA and OA. However, specific microbial clusters and biomarkers belonging to oral and gut microbiota need to be further investigated to highlight the mechanisms related to alterations in bones and joints inflammatory pathway.

Distal Consequences of Oral Inflammation

Periodontitis is an incredibly prevalent chronic inflammatory disease, which results in the destruction of tooth supporting structures. However, in addition to causing tooth and alveolar bone loss, this oral inflammatory disease has been shown to contribute to disease states and inflammatory pathology at sites distant from the oral cavity. Epidemiological and experimental studies have linked periodontitis to the development and/or exacerbation of a plethora of other chronic diseases ranging from rheumatoid arthritis to Alzheimer's disease. Such studies highlight how the inflammatory status of the oral cavity can have a profound impact on systemic health. In this review we discuss the disease states impacted by periodontitis and explore potential mechanisms whereby oral inflammation could promote loss of homeostasis at distant sites.

The Influence of Porphyromonas Gingivalis Bacterium Causing Periodontal Disease on the Pathogenesis of Rheumatoid Arthritis: Systematic Review of Literature

Periodontal pathologies are highly widespread throughout the world. Epidemiological studies have shown that as much as 1% of the population is suffering from periodontal disease. In recent years, there has been a growing number of studies linking these diseases with autoimmune diseases, especially with rheumatoid arthritis. This literature review evaluates changes in the relationship between periodontal pathologies caused by the bacterium Porphyromonas gingivalis and rheumatoid arthritis. The systematic review of the literature was performed according to the PRISMA analysis protocol. The review was performed with articles from the PubMed database. Searched articles were not older than 5 years. Only full texts and research performed with people were selected. A total of 56 results were received. A review and analysis of their full texts have been carried out and 10 articles were selected according to the established criteria. They were analyzed and results were presented. The results obtained from the literature were based on the influence of Porphyromonas gingivalis on the pathogenesis of rheumatoid arthritis. In the literature, the activity of this bacterium is explained by the analysis of its enzyme peptidylarginine deiminase and its principle of action. Studies have also been found to prove the presence of Porphyromonas gingivalis not only in the oral cavity but its DNA is also found in synovial fluid and plasma. In the researched articles, direct links between Porphyromonas gingivalis and rheumatoid arthritis have led doctors to draw attention to patients' oral hygiene and the condition of parodentium, as this may be the cause of autoimmune lesions. Treatment of periodontal disease will not only help maintain a healthy oral cavity but prevent the spread of bacteria to the surrounding tissues.

The oral microbiota - a mechanistic role for systemic diseases

Human oral microbiota is the ecological community of commensal, symbiotic, and pathogenic microorganisms found in the oral cavity. Oral microbiota generally exists in the form of a biofilm and plays a crucial role in maintaining oral homeostasis, protecting the oral cavity and preventing disease development. Human oral microbiota has recently become a new focus research for promoting the progress of disease diagnosis, assisting disease treatment, and developing personalised medicines. In this review, the scientific evidence supporting the association that endogenous and exogenous factors (diet, smoking, drinking, socioeconomic status, antibiotics use and pregnancy) modulate oral microbiota. It provides insights into the mechanistic role in which oral microbiota may influence systemic diseases, and summarises the challenges of clinical diagnosis and treatment based on the microbial community information. It provides information for noninvasive diagnosis and helps develop a new paradigm of personalised medicine. All these benefit human health in the post-metagenomics era.

Variations in oral microbiome profiles in rheumatoid arthritis and osteoarthritis with potential biomarkers for arthritis screening

The key to arthritis management is early diagnosis and treatment to prevent further joint destruction and maximize functional ability. Osteoarthritis (OA) and rheumatoid arthritis (RA) are two common types of arthritis that the primary care provider must differentiate, in terms of diagnosis and treatment. Effective and non-invasive strategies for early detection and disease identification are sorely needed. Growing evidence suggests that RA has a correlation with oral microbiome and may be affected by its dynamic variations. There is already a study comparing oral microbiome in patients with RA and OA, however, it did not screen for potential biomarkers for arthritis. In this study, we assessed the oral microbiome in saliva samples from 110 RA patients, 67 OA patients and 155 healthy subjects, using 16S rRNA gene amplicon sequencing. The structure and differences in oral microbiome between RA, OA and healthy subjects were analyzed. Eight oral bacterial biomarkers were identified to differentiate RA from OA. This report provides proof of oral microbiota as an informative source for discovering non-invasive biomarkers for arthritis screening.

Detection and characterization of bacterial nucleic acids in culture-negative synovial tissue and fluid samples from rheumatoid arthritis or osteoarthritis patients

Human intestinal microbes can mediate development of arthritis – Studies indicate that certain bacterial nucleic acids may exist in synovial fluid (SF) and could be involved in arthritis, although the underlying mechanism remains unclear. To characterize potential SF bacterial nucleic acids, we used 16S rRNA gene amplicon sequencing to assess bacterial nucleic acid communities in 15 synovial tissue (ST) and 110 SF samples from 125 patients with rheumatoid arthritis (RA) and 16 ST and 42 SF samples from 58 patients with osteoarthritis (OA). Our results showed an abundant diversity of bacterial nucleic acids in these clinical samples, including presence of Porphyromonas and Bacteroides in all 183 samples. Agrobacterium, Comamonas, Kocuria, Meiothermus, and Rhodoplanes were more abundant in synovial tissues of rheumatoid arthritis (STRA). Atopobium, Phascolarctobacterium, Rhodotorula mucilaginosa, Bacteroides uniformis, Rothia, Megasphaera, Turicibacter, Leptotrichia, Haemophilus parainfluenzae, Bacteroides fragilis, Porphyromonas, and Streptococcus were more abundant in synovial tissues of osteoarthritis (STOA). Veillonella dispar, Haemophilus parainfluenzae, Prevotella copri and Treponema amylovorum were more abundant in synovial fluid of rheumatoid arthritis (SFRA), while Bacteroides caccae was more abundant in the synovial fluid of osteoarthritis (SFOA). Overall, this study confirms existence of bacterial nucleic acids in SF and ST samples of RA and OA lesions and reveals potential correlations with degree of disease.

The evidence for microbiome manipulation in inflammatory arthritis

The human body consists of millions of commensal bacteria (the microbiome), with the intestinal tract being the most prevalent site of colonization. This colonization process begins at birth, and despite numerous factors such as ageing, diet and drug use affecting the microbiome make-up, by adulthood the composition of the gut bacteria is relatively consistent across local populations. The recent advent of new scientific techniques has enabled us to explore how the microbiome affects health and, in particular, has shed light on the involvement of the microbiome in the pathogenesis of inflammatory disease. In this review we highlight the current evidence for microbiome manipulation in inflammatory arthritis in animal and human models and discuss potential therapeutics targeting the microbiome as treatment for these diseases.

The inflammasome and danger molecule signaling: at the crossroads of inflammation and pathogen persistence in the oral cavity

Inflammasomes are an oligomeric assembly of multiprotein complexes that activate the caspase-1-dependent maturation and the subsequent secretion of inflammatory interleukin-1beta and interleukin-18 cytokines in response to a 'danger signal' in vertebrates. The assessment of their significance continues to grow rapidly as the complex biology of various chronic inflammatory conditions is better dissected. Increasing evidence strongly links inflammasomes and host-derived small 'danger molecule ATP' signaling with the modulation of the host immune response by microbial colonizers as well as with potential altering of the microbiome structure and intermicrobial interactions in the host. All of these factors eventually lead to the destructive chronic inflammatory disease state. In the oral cavity, a highly dynamic and multifaceted interplay takes place between the signaling of endogenous danger molecules and colonizing microbes on the mucosal surfaces. This interaction may redirect the local microenvironment to favor the conversion of the resident microbiome toward pathogenicity. This review outlines the major components of the known inflammasome complexes/mechanisms and highlights their regulation, in particular, by oral microorganisms, in relation to periodontal disease pathology. Better characterization of the cellular and molecular biology of the inflammasome will probably identify important potential therapeutic targets for the treatment and prevention of periodontal disease, as well as for other debilitating chronic diseases.

How Rheumatoid Arthritis Can Result from Provocation of the Immune System by Microorganisms and Viruses

The pathogenesis of rheumatoid arthritis (RA), similar to development of a majority of inflammatory and autoimmune disorders, is largely due to an inappropriate or inadequate immune response to environmental challenges. Among these challenges, infectious agents are the undisputed leaders. Since the 1870s, an impressive list of microorganisms suspected of provoking RA has formed, and the list is still growing. Although a definite causative link between a specific infectious agent and the disease has not been established, several arguments support such a possibility. First, in the absence of a defined pathogen, the spectrum of triggering agents may include polymicrobial communities or the cumulative effect of several bacterial/viral factors. Second, the range of infectious episodes (i.e., clinical manifestations caused by pathogens) may vary in the process of RA development from preclinical to late-stage disease. Third, infectious agents might not trigger RA in all cases, but trigger it in a certain subset of the cases, or the disease onset may arise from an unfortunate combination of infections along with, for example, psychological stress and/or chronic joint tissue microtrauma. Fourth, genetic differences may have a role in the disease onset. In this review, two aspects of the problem of “microorganisms and RA” are debated. First, is there an acquired immune deficiency and, in turn, susceptibility to infections in RA patients due to the too frequent and too lengthy infections, which at last break the tolerance of self antigens? Or, second, is there a congenital deficiency in tolerance and inflammation control, which may occur even with ordinary infection frequency and duration?

The dormant blood microbiome in chronic, inflammatory diseases

Blood in healthy organisms is seen as a ‘sterile’ environment: it lacks proliferating microbes. Dormant or not-immediately-culturable forms are not absent, however, as intracellular dormancy is well established. We highlight here that a great many pathogens can survive in blood and inside erythrocytes. ‘Non-culturability’, reflected by discrepancies between plate counts and total counts, is commonplace in environmental microbiology. It is overcome by improved culturing methods, and we asked how common this would be in blood. A number of recent, sequence-based and ultramicroscopic studies have uncovered an authentic blood microbiome in a number of non-communicable diseases. The chief origin of these microbes is the gut microbiome (especially when it shifts composition to a pathogenic state, known as ‘dysbiosis’). Another source is microbes translocated from the oral cavity. ‘Dysbiosis’ is also used to describe translocation of cells into blood or other tissues. To avoid ambiguity, we here use the term ‘atopobiosis’ for microbes that appear in places other than their normal location. Atopobiosis may contribute to the dynamics of a variety of inflammatory diseases. Overall, it seems that many more chronic, non-communicable, inflammatory diseases may have a microbial component than are presently considered, and may be treatable using bactericidal antibiotics or vaccines.

Atopobiosis of microbes (the term describing microbes that appear in places other than where they should be), as well as the products of their metabolism, seems to correlate with, and may contribute to, the dynamics of a variety of inflammatory diseases.

Deficiency of cathepsin K prevents inflammation and bone erosion in rheumatoid arthritis and periodontitis and reveals its shared osteoimmune role

Using rheumatoid arthritis (RA) and periodontitis mouse models, we demonstrate that RA and periodontitis share many pathological features, such as deregulated cytokine production, increased immune-cell infiltration, increased expression of Toll-like receptors (TLRs), and enhanced osteoclast activity and bone erosion. We reveal that genetic deletion of cathepsin K (Ctsk) caused a radical reduction in inflammation and bone erosion within RA joint capsules and periodontal lesions, a drastic decrease in immune-cell infiltration, and a significant reduction in osteoclasts, macrophages, dendritic and T-cells. Deficiency of Ctsk greatly decreased the expression of TLR-4, 5, and 9 and their downstream cytokines in periodontal gingival epithelial lesions and synovial RA lesions. Hence, Ctsk may be targeted to treat RA and periodontitis simultaneously due to its shared osteoimmune role.

Autoimmune correlation of rheumatoid arthritis and periodontitis

Rheumatoid arthritis and periodontitis, both, chronic inflammatory diseases share certain common diagnostic, pathological, immunogenetic and therapeutic features. A recently discovered enzymatic mimicry between human and bacterial species is novel and it opens up a new terrain for therapeutic blockade in the management of rheumatoid arthritis.

Does a biological link exist between periodontitis and rheumatoid arthritis?

Periodontitis or Periodontal disease (PD) and Rheumatoid arthritis (RA) are two the most common chronic inflammatory diseases. Periodontitis is a biofilm associated destructive inflammatory disease of the periodontium caused by specific microorganisms. Rheumatoid arthritis is an autoimmune condition and is identified by elevated serum autoantibody titre directed against citrullinated peptides or rheumatoid factor. Periodontitis may involve some elements of autoimmunity. Recent studies have established that PD and RA show a common pathway and could be closely associated through a common dysregulation and dysfunction in inflammatory mechanism. The enzyme peptidyl arginine deiminase (PAD), expressed by Porphyromonas gingivalis (P. gingivalis) is responsible for the enzymatic deimination of arginine residuals to citrulline resulting in protein citrullination and its increased accumulation in RA. Citrullination by PAD may act as a putative biologic link between PD and RA. Association of Human leukocytic antigen-DR4 antigen has been established both with RA and PD. Several interleukins and inflammatory mediators (ILs) and Nuclear factor kappa beta ligand are linked to these common chronic inflammatory diseases. Antibodies directed against heat shock protein (hsp 70 ab) of P. gingivalis, P. melanogenicus and P. intermedia are raised in PD as well as RA. Both the conditions share many pathological and immunological similarities. Bacterial infection, genetic susceptibility, altered immune reaction and inflammatory mediators considered responsible for RA are also associated with PD. So it is plausible that a biological link may exist between PD and RA. Therapies aimed at modifying the expression and effect of inflammatory mediators and effector molecules such as matrix metalloproteinases, proinflammatory cytokines and autoantibodies of structural proteins may probably reduce the severity of both RA and PD.

Periodontitis and etanercept discontinuation risk in anti-tumor necrosis factor-naive rheumatoid arthritis patients: a nationwide population-based cohort study

OBJECTIVE

The objective of this study was to investigate the association between periodontitis (PD) and etanercept (ETN) discontinuation in anti-tumor necrosis factor (anti-TNF)-naive patients with rheumatoid arthritis (RA).

METHODS

This retrospective nationwide population-based cohort study identified 3359 anti-TNF-naive patients with RA (age at diagnosis ≥16 years) in whom ETN treatment was initiated using administrative data. We identified PD exposure within 5 years before ETN initiation and during ETN treatment. Cox proportional hazard models were used to assess ETN discontinuation risk associated with PD within 5 years before ETN initiation, shown as hazard ratios with 95% confidence intervals (CIs). Stratified analyses were performed on the basis of PD during ETN treatment to avoid violating the Cox regression assumptions.

RESULTS

Patients with PD history during the 5 years before ENT initiation had a higher risk of ETN discontinuation compared with those without such history; the hazard ratios of ETN discontinuation were 1.27 (95% CI, 1.01-1.60) and 1.17 (95% CI, 1.06-1.30) among patients with and without PD during ETN treatment, respectively. Other risk factors included age older than 65 years and daily prednisolone dose greater than 10 mg/d within 1 year before ETN initiation. Concomitant methotrexate, leflunomide, salazopyrin, or hydroxychloroquine administration had a protective effect on ETN discontinuation in patients without PD during ETN treatment, but the protective effect by leflunomide, salazopyrin, and hydroxychloroquine was attenuated in patients with PD during ETN treatment (P for interaction <0.05).

CONCLUSIONS

A PD history within 5 years before ETN administration was associated with increased ETN discontinuation risk in anti-TNF-naive patients with RA.

Porphyromonas gingivalis oral infection exacerbates the development and severity of collagen-induced arthritis

INTRODUCTION

Clinical studies suggest a direct influence of periodontal disease (PD) on serum inflammatory markers and disease assessment of patients with established rheumatoid arthritis (RA). However, the influence of PD on arthritis development remains unclear. This investigation was undertaken to determine the contribution of chronic PD to immune activation and development of joint inflammation using the collagen-induced arthritis (CIA) model.

METHODS

DBA1/J mice orally infected with Porphyromonas gingivalis were administered with collagen II (CII) emulsified in complete Freund's adjuvant (CFA) or incomplete Freund's adjuvant (IFA) to induce arthritis. Arthritis development was assessed by visual scoring of paw swelling, caliper measurement of the paws, mRNA expression, paw micro-computed tomography (micro-CT) analysis, histology, and tartrate resistant acid phosphatase for osteoclast detection (TRAP)-positive immunohistochemistry. Serum and reactivated splenocytes were evaluated for cytokine expression.

RESULTS

Mice induced for PD and/or arthritis developed periodontal disease, shown by decreased alveolar bone and alteration of mRNA expression in gingival tissues and submandibular lymph nodes compared to vehicle. P. gingivalis oral infection increased paw swelling and osteoclast numbers in mice immunized with CFA/CII. Arthritis incidence and severity were increased by P. gingivalis in mice that received IFA/CII immunizations. Increased synovitis, bone erosions, and osteoclast numbers in the paws were observed following IFA/CII immunizations in mice infected with P gingivalis. Furthermore, cytokine analysis showed a trend toward increased serum Th17/Th1 ratios when P. gingivalis infection was present in mice receiving either CFA/CII or IFA/CII immunizations. Significant cytokine increases induced by P. gingivalis oral infection were mostly associated to Th17-related cytokines of reactivated splenic cells, including IL-1β, IL-6, and IL-22 in the CFA/CII group and IL-1β, tumor necrosis factor-α, transforming growth factor-β, IL-6 and IL-23 in the IFA/CII group.

CONCLUSIONS

Chronic P. gingivalis oral infection prior to arthritis induction increases the immune system activation favoring Th17 cell responses, and ultimately accelerating arthritis development. These results suggest that chronic oral infection may influence RA development mainly through activation of Th17-related pathways.

Clinical implications of shared genetics and pathogenesis in autoimmune diseases

Many endocrine diseases, including type 1 diabetes mellitus, Graves disease, Addison disease and Hashimoto disease, originate as an autoimmune reaction that affects disease-specific target organs. These autoimmune diseases are characterized by the development of specific autoantibodies and by the presence of autoreactive T cells. They are caused by a complex genetic predisposition that is attributable to multiple genetic variants, each with a moderate-to-low effect size. Most of the genetic variants associated with a particular autoimmune endocrine disease are shared between other systemic and organ-specific autoimmune and inflammatory diseases, such as rheumatoid arthritis, coeliac disease, systemic lupus erythematosus and psoriasis. Here, we review the shared and specific genetic background of autoimmune diseases, summarize their treatment options and discuss how identifying the genetic and environmental factors that predispose patients to an autoimmune disease can help in the diagnosis and monitoring of patients, as well as the design of new treatments.

Clarithromycin in rheumatoid arthritis: the addition to methotrexate and low-dose methylprednisolone induces a significant additive value--a 24-month single-blind pilot study

To compare the efficacy of the addition of clarithromycin (CM) to methotrexate (MTX) and methylprednisolone (MP) in active rheumatoid arthritis (RA). 32 patients with RA consecutively randomized.

CONTROL GROUP

sixteen patients treated for 24 months with MTX 10-15 mg i.m. weekly and MP 4-6 mg daily. CM group: sixteen patients treated with MTX 10-15 mg i.m. weekly and MP 4-6 mg daily for 24 months; CM therapy added in the first month (500 mg twice a day for the first 15 days followed by 500 mg a day for the remaining 15 days). Evaluation of the improvement following ACR criteria was performed at months 1 (primary endpoint), 3 and 6. Patients were furthermore observed after 12, 18 and 24 months from the study beginning. At month 1, following ACR70 improvement criteria, we found a significant additive value in CM group (10/16 = 63% vs 4/16 = 25%, p = 0.033--chi-square test). After discontinuation of CM, the difference between groups was anymore evident (month 3: CM group 10/16 = 63% vs control group 9/16 = 56%). At month 24, 7/16 (44%) in control group and 12/16 (75%) in CM group completed the follow-up. The addition of CM to MTX and MP can induce the remission ACR 70 in the majority of RA patients within 4 weeks, while MTX and MP alone need about 3 months to achieve the same result.

Periodontal disease immunology: 'double indemnity' in protecting the host

During the last two to three decades our understanding of the immunobiology of periodontal disease has increased exponentially, both with respect to the microbial agents triggering the disease process and the molecular mechanisms of the host engagement maintaining homeostasis or leading to collateral tissue damage. These foundational scientific findings have laid the groundwork for translating cell phenotype, receptor engagement, intracellular signaling pathways and effector functions into a 'picture' of the periodontium as the host responds to the 'danger signals' of the microbial ecology to maintain homeostasis or succumb to a disease process. These findings implicate the chronicity of the local response in attempting to manage the microbial challenge, creating a 'Double Indemnity' in some patients that does not 'insure' health for the periodontium. As importantly, in reflecting the title of this volume of Periodontology 2000, this review attempts to inform the community of how the science of periodontal immunology gestated, how continual probing of the biology of the disease has led to an evolution in our knowledge base and how more recent studies in the postgenomic era are revolutionizing our understanding of disease initiation, progression and resolution. Thus, there has been substantial progress in our understanding of the molecular mechanisms of host-bacteria interactions that result in the clinical presentation and outcomes of destructive periodontitis. The science has embarked from observations of variations in responses related to disease expression with a focus for utilization of the responses in diagnosis and therapeutic outcomes, to current investigations using cutting-edge fundamental biological processes to attempt to model the initiation and progression of soft- and hard-tissue destruction of the periodontium. As importantly, the next era in the immunobiology of periodontal disease will need to engage more sophisticated experimental designs for clinical studies to enable robust translation of basic biologic processes that are in action early in the transition from health to disease, those which stimulate microenvironmental changes that select for a more pathogenic microbial ecology and those that represent a rebalancing of the complex host responses and a resolution of inflammatory tissue destruction.

Rheumatoid arthritis is an autoimmune disease caused by periodontal pathogens

A statistically significant association between periodontal disease (PD) and systemic diseases has been identified. Rheumatoid arthritis (RA), which is a chronic inflammatory joint disease, exhibits similar characteristics and pathogenesis to PD. The association between RA and PD has been investigated, and numerous publications on this subject exist. Approximately 20 bacterial species have been identified as periodontal pathogens, and these organisms are linked to various types of PD. The most analyzed species of periodontopathic bacteria are Porphyromonas gingivalis, Prevotella intermedia, Tannerella forsythia, and Aggregatibacter actinomycetemcomitans. Antibodies and DNA from these oral pathogens have been isolated from the sera and synovial fluids of RA patients. This rapid communication describes the role of periodontal pathogens in the etiopathogenesis of RA.

Heightened immune response to autocitrullinated Porphyromonas gingivalis peptidylarginine deiminase: a potential mechanism for breaching immunologic tolerance in rheumatoid arthritis

Background

Rheumatoid arthritis (RA) is characterised by autoimmunity to citrullinated proteins, and there is increasing epidemiologic evidence linking Porphyromonas gingivalis to RA. P gingivalis is apparently unique among periodontal pathogens in possessing a citrullinating enzyme, peptidylarginine deiminase (PPAD) with the potential to generate antigens driving the autoimmune response.

Objectives

To examine the immune response to PPAD in patients with RA, individuals with periodontitis (PD) and controls (without arthritis), confirm PPAD autocitrullination and identify the modified arginine residues.

Methods

PPAD and an inactivated mutant (C351A) were cloned and expressed and autocitrullination of both examined by immunoblotting and mass spectrometry. ELISAs using PPAD, C351A and another P gingivalis protein arginine gingipain (RgpB) were developed and antibody reactivities examined in patients with RA (n=80), individuals with PD (n=44) and controls (n=82).

Results

Recombinant PPAD was a potent citrullinating enzyme. Antibodies to PPAD, but not to Rgp, were elevated in the RA sera (median 122 U/ml) compared with controls (median 70 U/ml; p<0.05) and PD (median 60 U/ml; p<0.01). Specificity of the anti-peptidyl citrullinated PPAD response was confirmed by the reaction of RA sera with multiple epitopes tested with synthetic citrullinated peptides spanning the PPAD molecule. The elevated antibody response to PPAD was abolished in RA sera if the C351A mutant was used on ELISA.

Conclusions

The peptidyl citrulline-specific immune response to PPAD supports the hypothesis that, as a bacterial protein, it might break tolerance in RA, and could be a target for therapy.

Effects of periodontal therapy on disease activity and systemic inflammation in rheumatoid arthritis patients

OBJECTIVE

This observational prospective cohort study aimed to evaluate the effects of non-surgical periodontal treatment on clinical periodontal measurements and systemic inflammatory mediator levels in low or moderate to highly active rheumatoid arthritis (RA) patients with chronic periodontitis.

SUBJECTS AND METHODS

Rheumatoid arthritis activity was assessed with disease activity score test (DAS28). Thirty patients with RA with moderate to high disease activity (DAS28 ≥ 3.2) and chronic periodontitis (MHDA group) and thirty patients with RA with low disease activity (DAS28 < 3.2) and chronic periodontitis (LDA group) were enrolled in the study. The patients were monitored at the beginning and 3 months after undergoing periodontal therapy. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), tumour necrosis factor-alpha (TNF-α) levels in serum, DAS28 and periodontal parameters were evaluated.

RESULTS

Erythrocyte sedimentation rate, CRP, TNF-α levels in serum, DAS28 and periodontal parameters exhibited similar and significant reduction 3 months after the non-surgical periodontal treatment.

CONCLUSION

Non-surgical periodontal treatment may prove beneficial in reducing RA severity as measured by ESR, CRP, TNF-α levels in serum and DAS28 in low or moderate to highly active RA patients with chronic periodontitis.

Association between a history of periodontitis and the risk of rheumatoid arthritis: a nationwide, population-based, case-control study

OBJECTIVE

To investigate the association between the risk of rheumatoid arthritis (RA) and a history of periodontitis.

METHODS

This nationwide, population-based, case-control study used administrative data to identify 13 779 newly diagnosed patients with RA (age ≥16 years) as the study group and 137 790 non-patients with RA matched for age, sex, and initial diagnosis date (index date) as controls. Using conditional logistic regression analysis after adjustment for potential confounders, including geographical region and a history of diabetes and Sjögren's syndrome, ORs with 95% CI were calculated to quantify the association between RA and periodontitis. To evaluate the effects of periodontitis severity and the lag time since the last periodontitis visit on RA development, ORs were calculated for subgroups of patients with periodontitis according to the number of visits, cumulative cost, periodontal surgery and time interval between the last periodontitis-related visit and the index date.

RESULTS

An association was found between a history of periodontitis and newly diagnosed RA (OR=1.16; 95% CI 1.13 to 1.21). The strength of this association remained statistically significant after adjustment for potential confounders (OR=1.16; 95% CI 1.12 to 1.20), and after variation of periodontitis definitions. The association was dose- and time-dependent and was strongest when the interval between the last periodontitis-related visit and the index date was <3 months (OR=1.64; 95% CI 1.49 to 1.79).

CONCLUSIONS

This study demonstrates an association between periodontitis and incident RA. This association is weak and limited to lack of individual smoking status.

The role of human xanthine oxidoreductase (HXOR), anti-HXOR antibodies, and microorganisms in synovial fluid of patients with joint inflammation

This work is to investigate the levels of human xanthine oxidoreductase (HXOR), its antibodies, and microorganisms in synovial fluid of patients with untreated rheumatoid joint diseases. Synovial fluids were collected from sixty-four patients with rheumatoid joint diseases. Sixty-four age-matched individuals were included as control. Xanthine oxidoreductase (XOR) proteins level and anti-XOR antibodies were determined in the blood and synovial fluid, using human XOR as antigen, by enzyme-linked immunosorbent (ELISA) assay. Synovial fluids were cultured for bacteria and fungi. The titers of XOR protein in the synovial fluid of patients with rheumatoid arthritis were 90.43 ± 23.37 μg/ml (mean ± SD, n = 29) and up to 62.42 ± 8.74 μg/ml (mean ± SD, n = 35) in other joint inflammation. Anti-HXOR antibodies titers in patients were 167.72 ± 23.64 μg/ml, n = 64, which was significantly higher in rheumatoid arthritis patients. The results indicated that anti-HXOR antibodies in synovial fluids have a protective role as high concentrations against XOR were detected in inflammatory arthritis. These antibodies play a role in eliminating XOR from synovial fluids. However, immune complex formation could activate complement and participate in propagating the inflammatory cycle. Synovial aspirate ordinary microbial cultures were negative for any bacteria or fungi, but that does not exclude organisms of special culture requirements.

The association between rheumatoid arthritis and periodontal disease

Chronic, plaque-associated inflammation of the gingiva and the periodontium are among the most common oral diseases. Periodontitis (PD) is characterized by the inflammatory destruction of the periodontal attachment and alveolar bone, and its clinical appearance can be influenced by congenital as well as acquired factors. The existence of a rheumatic or other inflammatory systemic disease may promote PD in both its emergence and progress. However, there is evidence that PD maintains systemic diseases. Nevertheless, many mechanisms in the pathogenesis have not yet been examined sufficiently, so that a final explanatory model is still under discussion, and we hereby present arguments in favor of this. In this review, we also discuss in detail the fact that oral bacterial infections and inflammation seem to be linked directly to the etiopathogenesis of rheumatoid arthritis (RA). There are findings that support the hypothesis that oral infections play a role in RA pathogenesis. Of special importance are the impact of periodontal pathogens, such as Porphyromonas gingivalis on citrullination, and the association of PD in RA patients with seropositivity toward rheumatoid factor and the anti-cyclic citrullinated peptide antibody.

Periodontitis in RA-the citrullinated enolase connection

Autoimmunity in rheumatoid arthritis (RA) is characterized by an antibody response to citrullinated proteins. Two of the risk factors for RA-HLA-DRB1 shared epitope alleles and smoking-are also associated with periodontitis, which is largely, but not exclusively, caused by Porphyromonas gingivalis infection. Furthermore, RA and periodontitis have a similar pathophysiology, characterized by destructive inflammation. The citrullination of proteins by P. gingivalis and the subsequent generation of autoantigens that drive autoimmunity in RA represents a possible causative link between these two diseases. Antibodies directed towards the immunodominant epitope of human citrullinated α-enolase cross-react with a conserved sequence on citrullinated P. gingivalis enolase. On the basis of this cross-reactivity, in this Perspectives article we explore the hypothesis of molecular mimicry in the etiology of RA, with citrullinated enolase as the specific antigen involved.