Genetics of rheumatoid arthritis: an impressionist perspective

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

BACKGROUND

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

OBJECTIVE

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

Fc receptor-like 1, 3, and 6 variants are associated with rheumatoid arthritis risk in the Chinese Han population

BACKGROUND

Rheumatoid arthritis (RA) is the most common autoimmune system diseases in our world. More studies in recent years have shown that FCRL gene polymorphisms is closely related to autoimmune diseases. It is suggested that genetic factors play a crucial role in the pathogenesis of this disease. In this study, we aimed to investigate the relationship between FCRL1 rs2050568, FCRL3 rs2317230 and FCRL6 rs58240276 polymorphisms and RA risk in the Chinese Han population. 506 with RA patients and 509 healthy controls were recruited in this study, and the single nucleotide polymorphisms (SNPs) was successfully genotyped using the Agena MassARRAY platform. Odds ratios (ORs) and 95% confidence intervals (95% CIs) after adjusting for age and gender were conducted to assess these SNPs polymorphisms and RA risk. The multifactor dimensionality reduction (MDR) method was conducted to analyze SNP-SNP interaction.

RESULTS

Our results revealed that there no significant association was observed between the allele and genotype frequencies among these SNPs and RA risk (all p > 0.05). Straified analysis by age and gender, the results confirmed that FCRL1 rs2050568 T/T genotype enhanced the risk of RA in females (p = 0.014). The G/T - T/T genotype of FCRL3 rs2317230 was correlated with a decreased RA risk in males (p = 0.021). We also observed that the C/T-T/T genotype of FCRL6 rs58240276 was increased the risk of RA in the group at age >  54 years (p = 0.016). In addition, FCRL1 rs2050568-TT, FCRL6 rs58240276-TT and FCRL1 rs2050568-TT, FCRL3 rs2317230-TT, FCRL6 rs58240276-TT are the best models for multi-site MDR analysis (p < 0.05), and the two best models mentioned above and classes RA have the most significant correlation.

CONCLUSIONS

Our study demonstrated that FCRL1 rs2050568, FCRL3 rs2317230, and FCRL6 rs58240276 polymorphisms were correlated with RA susceptibility in the Chinese Han population.

Is There a Feasible Link between Vitamin D Receptor Genotypic and Allelic Frequencies with Analytical Biomarkers of Rheumatoid Arthritis Disease?

Rheumatoid arthritis (RA) is one of the most widespread autoimmune disorders and it has a genetic background with a variety of genes affecting the degradation of the immune system. Along these lines, we assessed the relationship between the BsmI, and FokI VDR polymorphisms and inflammable records identified with infections activity. Such as interleukins (IL-6, IL-8), hypoxia inducible factor-alpha (HIF-α), soluble receptor of advanced glycation end product (sRAGE), oxidized low-density lipoprotein cholesterol (oxLDL), neutrophil gelatinase-associated lipocalin (NGAL) and procollagen N-propeptide of type III collagen (P3NP) and the allelic frequencies of BsmI VDR rs1544410 and FokI VDR rs2228570 polymorphism on the RA. Total of 131 subjects [70 RA patients and 61 age and sex matched apparently healthy controls (HC)] were monitored for inflammatory biomarkers using ELISA. All patients were screened for the BsmI and FokI using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The all biomarkers were significantly higher in RA patients in comparison with HC. There were positive correlations between NGAL, oxLDL and s-RAGE, oxLDL. On BsmI, 'GG' and 'AG' genotypes were significantly associated with high RA activity as well as the frequency of genotypes 'AG & GG" were higher in high activity RA as compared to low RA activity. However on FokI, was observed that in high activity patients the frequency of 'CC' & 'CT' was more prevalent as compared to low activity ones. These outcomes support the immunoregulatory role of vitamin D which is associated with several inflammatory diseases, signifying a credible anti-inflammatory role in perturbation of the RA.

Periodontal treatment prevents arthritis in mice and methotrexate ameliorates periodontal bone loss

Recent studies indicate a causal relationship between the periodontal pathogen P. gingivalis and rheumatoid arthritis involving the production of autoantibodies against citrullinated peptides. We therefore postulated that therapeutic eradication P. gingivalis may ameliorate rheumatoid arthritis development and here turned to a mouse model in order to challenge our hypothesis. F1 (DBA/1 x B10.Q) mice were orally inoculated with P. gingivalis before collagen-induced arthritis was provoked. Chlorhexidine or metronidazole were orally administered either before or during the induction phase of arthritis and their effects on arthritis progression and alveolar bone loss were compared to intraperitoneally injected methotrexate. Arthritis incidence and severity were macroscopically scored and alveolar bone loss was evaluated via microcomputed tomography. Serum antibody titres against P. gingivalis were quantified by ELISA and microbial dysbiosis following oral inoculation was monitored in stool samples via microbiome analyses. Both, oral chlorhexidine and metronidazole reduced the incidence and ameliorated the severity of collagen-induced arthritis comparable to methotrexate. Likewise, all three therapies attenuated alveolar bone loss. Relative abundance of Porphyromonadaceae was increased after oral inoculation with P. gingivalis and decreased after treatment. This is the first study to describe beneficial effects of non-surgical periodontal treatment on collagen-induced arthritis in mice and suggests that mouthwash with chlorhexidine or metronidazole may also be beneficial for patients with rheumatoid arthritis and a coexisting periodontitis. Methotrexate ameliorated periodontitis in mice, further raising the possibility that methotrexate may also positively impact on the tooth supporting tissues of patients with rheumatoid arthritis.

Interplay between P. gingivalis, F. nucleatum and A. actinomycetemcomitans in murine alveolar bone loss, arthritis onset and progression

Increasing evidence supports the association of periodontitis with rheumatoid arthritis. Even though a prominent role has been postulated for Porphyromonas gingivalis, many bacterial species contribute to the pathogenesis of periodontal disease. We therefore investigated the impact of Porphyromonas gingivalis as well as other major pathobionts on the development of both, periodontitis and arthritis in the mouse. Pathobionts used - either alone or in combination - were Porphyromonas gingivalis, Fusobacterium nucleatum and Aggregatibacter actinomycetemcomintans. Periodontitis was induced via oral gavage in SKG, DBA/1 and F1 (DBA/1 × B10.Q) mice and collagen-induced arthritis was provoked via immunization and boost with bovine collagen type II. Alveolar bone loss was quantified via micro computed tomography, arthritis was evaluated macroscopically and histologically and serum antibodies were assessed. Among the strains tested, only F1 mice were susceptible to P. gingivalis induced periodontitis and showed significant alveolar bone loss. Bone loss was paralleled by antibody titers against P. gingivalis. Of note, mice inoculated with the mix of all three pathobionts showed less alveolar bone loss than mice inoculated with P. gingivalis alone. However, oral inoculation with either F. nucleatum or A. actinomycetemcomintans alone accelerated subsequent arthritis onset and progression. This is the first report of a triple oral inoculation of pathobionts combined with collagen-induced arthritis in the mouse. In this interplay and this particular genetic setting, F. nucleatum and A. actinomycetemcomitans exerted a protective impact on P. gingivalis induced alveolar bone loss. By themselves they did not induce periodontitis yet accelerated arthritis onset and progression.

Guidelines for management of rheumatic diseases in developing countries from basics to real-world situation: relevance, need, and processes for development

Guidelines or recommendations help to provide uniform standards in medical practice. The development of guidelines requires adherence to pre-defined norms prescribed by different international organizations such as the European League against Rheumatism (EULAR). We searched Pubmed and LILACS to identify published papers in five major rheumatic diseases (rheumatoid arthritis, systemic lupus erythematosus, spondyloarthropathies, osteoarthritis, and scleroderma) from different countries based on their economic prosperity and could find a lack of published literature from most economically weaker regions. Similarly, published guidelines in these rheumatic diseases were sparse from Asia and Africa, which are economically developed to a lesser extent than other regions of the world. Considering differing economic realities driving patient care in different regions of the world, unique challenges in certain geographic areas such as musculoskeletal manifestations of infectious diseases like leprosy and tuberculosis, as well as distinct risk of malignancies and other comorbid conditions, National Rheumatology societies should work towards developing more guidelines for rheumatic diseases from regions such as Asia and Africa, while following strictly the prescribed norms for the same. With a paucity of guidelines for such regions currently, an alternative (although less preferable) suggestion would be that major international societies, whose guidelines are widely read and followed the world over, should consider inputs from experts from diverse regions of the world while developing these guidelines.

Polymorphisms and expression of inflammasome genes are associated with the development and severity of rheumatoid arthritis in Brazilian patients

OBJECTIVE

In the present study, we analyzed the possible association of inflammasome gene variants and expression to rheumatoid arthritis (RA)'s development and severity in the Brazilian population.

MATERIALS AND METHODS

Thirteen single nucleotide polymorphisms within six inflammasome genes (NLRP1, NLRP3, NLRC4, AIM2, CARD8, CASP1) as well as IL1B and IL18 genes in two different Brazilian populations (from Northeast and Southeast Brazil) were analyzed. We also evaluated inflammasome gene expression profile in resting and LPS + ATP-treated monocytes from RA patients and healthy individuals. For genetic association study, 218 patients and 307 healthy controls were genotyped. For gene expression study, inflammasome genes mRNA levels of 12 patients and ten healthy individuals were assessed by qPCR.

RESULTS

Our results showed that rs10754558 NLRP3 and rs2043211 CARD8 polymorphisms are associated with RA development (p value = 0.044, OR = 1.77, statistical power = 0.999) and severity measured by Health Assessment Questionnaire (HAQ) (p value = 0.03), respectively. Gene expression analyses showed that RA patients display activation of CASP1, IL1B and IL1R genes independently of LPS + ATP activation. In LPS + ATP-treated monocytes, NLRP3 and NLRC4 expressions were also significantly higher in patients compared with controls.

CONCLUSIONS

The first reported results in Brazilian populations support the role of inflammasome in the development of RA.

Association of NKG2D gene variants with susceptibility and severity of rheumatoid arthritis

NKG2D (KLRK1) is a C-type lectin receptor present on natural killer (NK) cells, γδ, CD8⁺ and CD4⁺ T cells. Upon ligand binding, NKG2D mediates activatory and co-stimulatory signals to NK cells and activated CD4⁺ T cells, respectively. Polymorphisms in NKG2D predispose to infectious diseases, cancer, transplantation and autoimmune disorders. We studied the influence of this NK receptor polymorphism on predisposition to and modification of the disease phenotype in patients with rheumatoid arthritis (RA). Eight different single nucleotide polymorphisms (SNP) in the NKG2 gene were genotyped in 236 patients with RA and 187 controls using Taqman 5' nuclease assays. NKG2D genotype/allele frequency did not differ between patients and controls. Subgroup analysis showed that the frequency of A allele of NKG2D9 and T allele of NKG2D10 was significantly higher in patients with deformities (a marker of severe disease) [11 versus 5%, Pc = 0·03, odds ratio (OR) = 2·44, 95% confidence interval (CI) = 1·09-5·98 and 10 versus 4%, Pc = 0·04, OR = 2·45, 95% CI = 1·05-6·39, respectively], while the frequency of alleles G of NKG2D9 and A of NKG2D10 was greater in patients without deformities (Pc = 0·03, OR = 0·41, 95% CI = 0·17-0·91 and Pc = 0·04, OR = 0·41, 95% CI = 0·16-0·96). Similar trends of association were observed with deforming phenotype of RA in female patients and deforming young onset RA subgroups. Haplotype analysis revealed that the frequency of haplotype G-C-A-G-A-T-C-C was higher in patients than in controls (12 versus 8%, P = 0·04, OR = 1·61, 95% CI = 1·01-2·55), suggesting that it may predispose to RA. Our study suggests that the NKG2D gene polymorphisms may modify the risk of development and severity of RA.

Vitamin D receptor polymorphisms and expression profile in rheumatoid arthritis Brazilian patients

Rheumatoid arthritis (RA) is an autoimmune disease characterized by chronic inflammation and important joint commitment, being the most common systemic autoimmune disease worldwide. RA displays important genetic background with a variety of genes contributing to the immune balance breakdown. Recent studies have demonstrated that vitamin D, through its receptor (VDR), is able to regulate the immune balance and suppress the autoimmunity process, being a potential target in autoimmune diseases. In the present genetic association study, we assessed 5 Tag single nucleotide polymorphisms (SNPs) (rs11168268, rs2248098, rs1540339, rs4760648 and rs3890733), which cover most of the VDR gene, in three different Brazilian populations (from Northeast, Southeast and South Brazil). We also evaluated the VDR expression profile in whole blood and monocytes from RA patients. For genotyping study, 428 RA patients and 616 healthy controls were genotyped with fluorogenic allele specific probes on an ABI7500 platform. For gene expression study, VDR mRNA levels of 15 RA patients and 26 healthy individuals were assessed by RT-PCR. Our results showed that SNPs rs4760648 and rs3890733 are associated to RA susceptibility (p value = 0.0026, OR 1.31 and p value = 0.0091, OR 1.28 with statistical power = 0.999 and 0.993, respectively). Regarding RA clinical features, the studied SNPs did not show significant associations. The gene expression assays showed that VDR mRNA levels were down regulated in both whole blood (-3.3 fold) and monocytes (-3.2 fold) of RA patients when compared to healthy controls. Our results, the first reported for distinct Brazilian populations, support a role of the VDR gene in the susceptibility to RA.

Randomised controlled trial of tumour necrosis factor inhibitors against combination intensive therapy with conventional disease-modifying antirheumatic drugs in established rheumatoid arthritis: the TACIT trial and associated systematic reviews

BACKGROUND

Rheumatoid arthritis (RA) is initially treated with methotrexate and other disease-modifying antirheumatic drugs (DMARDs). Active RA patients who fail such treatments can receive tumour necrosis factor inhibitors (TNFis), which are effective but expensive.

OBJECTIVE

We assessed whether or not combination DMARDs (cDMARDs) give equivalent clinical benefits at lower costs in RA patients eligible for TNFis.

DESIGN

An open-label, 12-month, pragmatic, randomised, multicentre, two-arm trial [Tumour necrosis factor inhibitors Against Combination Intensive Therapy (TACIT)] compared these treatment strategies. We then systematically reviewed all comparable published trials.

SETTING

The TACIT trial involved 24 English rheumatology clinics.

PARTICIPANTS

Active RA patients eligible for TNFis.

INTERVENTIONS

The TACIT trial compared cDMARDs with TNFis plus methotrexate or another DMARD; 6-month non-responders received (a) TNFis if in the cDMARD group; and (b) a second TNFi if in the TNFi group.

MAIN OUTCOME MEASURES

The Heath Assessment Questionnaire (HAQ) was the primary outcome measure. The European Quality of Life-5 Dimensions (EQ-5D), joint damage, Disease Activity Score for 28 Joints (DAS28), withdrawals and adverse effects were secondary outcome measures. Economic evaluation linked costs, HAQ changes and quality-adjusted life-years (QALYs).

RESULTS

In total, 432 patients were screened; 104 started on cDMARDs and 101 started on TNFis. The initial demographic and disease assessments were similar between the groups. In total, 16 patients were lost to follow-up (nine in the cDMARD group, seven in the TNFi group) and 42 discontinued their intervention but were followed up (23 in the cDMARD group and 19 in the TNFi group). Intention-to-treat analysis with multiple imputation methods used for missing data showed greater 12-month HAQ score reductions with initial cDMARDs than with initial TNFis [adjusted linear regression coefficient 0.15, 95% confidence interval (CI) -0.003 to 0.31; p = 0.046]. Increases in 12-month EQ-5D scores were greater with initial cDMARDs (adjusted linear regression coefficient -0.11, 95% CI -0.18 to -0.03; p = 0.009) whereas 6-month changes in HAQ and EQ-5D scores and 6- and 12-month changes in joint damage were similar between the initial cDMARD group and the initial TNFi group. Longitudinal analyses (adjusted general estimating equations) showed that the DAS28 was lower in the initial TNFi group in the first 6 months (coefficient -0.63, 95% CI -0.93 to -0.34; p < 0.001) but there were no differences between the groups in months 6-12. In total, 36 patients in the initial cDMARD group and 44 in the initial TNFi group achieved DAS28 remission. The onset of remission did not differ between groups (p = 0.085 on log-rank test). In total, 10 patients in the initial cDMARD group and 18 in the initial TNFi group experienced serious adverse events; stopping therapy because of toxicity occurred in 10 and six patients respectively. Economic evaluation showed that the cDMARD group had similar or better QALY outcomes than TNFi with significantly lower costs at 6 and 12 months. In the systematic reviews we identified 32 trials (including 20-1049 patients) on early RA and 19 trials (including 40-982 patients) on established RA that compared (1) cDMARDs with DMARD monotherapy; (2) TNFis/methotrexate with methotrexate monotherapy; and (3) cDMARDs with TNFis/methotrexate. They showed that cDMARDs and TNFis had similar efficacies and toxicities.

CONCLUSIONS

Active RA patients who have failed methotrexate and another DMARD achieve equivalent clinical benefits at a lower cost from starting cDMARDs or from starting TNFis (reserving TNFis for non-responders). Only a minority of patients achieve sustained remission with cDMARDs or TNFis; new strategies are needed to maximise the frequency of remission.

TRIAL REGISTRATION

Current Control Trials ISRCTN37438295.

FUNDING

This project was funded by the National Institute for Health Research Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 18, No. 66. See the NIHR Journals Library website for further project information.

T-cell metabolism in autoimmune disease

Cancer cells have long been known to fuel their pathogenic growth habits by sustaining a high glycolytic flux, first described almost 90 years ago as the so-called Warburg effect. Immune cells utilize a similar strategy to generate the energy carriers and metabolic intermediates they need to produce biomass and inflammatory mediators. Resting lymphocytes generate energy through oxidative phosphorylation and breakdown of fatty acids, and upon activation rapidly switch to aerobic glycolysis and low tricarboxylic acid flux. T cells in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) have a disease-specific metabolic signature that may explain, at least in part, why they are dysfunctional. RA T cells are characterized by low adenosine triphosphate and lactate levels and increased availability of the cellular reductant NADPH. This anti-Warburg effect results from insufficient activity of the glycolytic enzyme phosphofructokinase and differentiates the metabolic status in RA T cells from those in cancer cells. Excess production of reactive oxygen species and a defect in lipid metabolism characterizes metabolic conditions in SLE T cells. Owing to increased production of the glycosphingolipids lactosylceramide, globotriaosylceramide and monosialotetrahexosylganglioside, SLE T cells change membrane raft formation and fail to phosphorylate pERK, yet hyperproliferate. Borrowing from cancer metabolomics, the metabolic modifications occurring in autoimmune disease are probably heterogeneous and context dependent. Variations of glucose, amino acid and lipid metabolism in different disease states may provide opportunities to develop biomarkers and exploit metabolic pathways as therapeutic targets.

Presence of the full-length KIR2DS4 gene reduces the chance of rheumatoid arthritis patients to respond to methotrexate treatment

Background

KIR genes coding for natural killer cell immunoglobulin-like receptors, KIR, influence the effector and regulatory function of NK cells as well as some subpopulations of T lymphocytes (e.g. CD4+CD28-KIR+) depending on presence of ligands (particularly HLA-C molecules). KIR-KIR ligand interaction may lead to the development of autoimmune disorders, including rheumatoid arthritis (RA). However, their role in the response of RA patients to methotrexate therapy is not known.

Methods

KIR genes and KIR-ligand (HLA-C C1/C2 allomorphs) genotyping was performed using the PCR-SSP method in 312 RA patients (179 classified as good responders and 133 as poor responders using DAS28 criteria). Thus, we evaluated the association of KIR genes and HLA-C allomorphs with the response to methotrexate (MTX) treatment.

Results

We observed that patients possessing the full-length KIR2DS4 (KIR2DS4f) gene had a lower chance of responding in comparison to KIR2DS4f-negative cases. This phenomenon was observed both in erosive disease (ED) and rheumatoid factor (RF) positive and in ED- and RF-negative patients. Interestingly, the observed effect of the KIR2DS4f gene was strongest in individuals possessing medium values (20-33 mm/h) of the erythrocyte sedimentation rate (ESR). Patients with high ESR values had low probability and, in contrast, patients with low ESR had a high probability of MTX response, and the presence of KIR2DS4f did not affect their outcome. Additionally, we show that the KIR2DS4f effect did not depend on the presence of either C1 or C2 allomorphs.

Conclusion

Our results suggest that the response of RA patients with medium ESR values to MTX treatment may be dependent on the full-length KIR2DS4 gene.

Epstein-Barr virus in systemic autoimmune diseases

Systemic autoimmune diseases (SADs) are a group of connective tissue diseases with diverse, yet overlapping, symptoms and autoantibody development. The etiology behind SADs is not fully elucidated, but a number of genetic and environmental factors are known to influence the incidence of SADs. Recent findings link dysregulation of Epstein-Barr virus (EBV) with SAD development. EBV causes a persistent infection with a tight latency programme in memory B-cells, which enables evasion of the immune defence. A number of immune escape mechanisms and immune-modulating proteins have been described for EBV. These immune modulating functions make EBV a good candidate for initiation of autoimmune diseases and exacerbation of disease progression. This review focuses on systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and Sjögren's syndrome (SS) and sum up the existing data linking EBV with these diseases including elevated titres of EBV antibodies, reduced T-cell defence against EBV, and elevated EBV viral load. Together, these data suggest that uncontrolled EBV infection can develop diverse autoreactivities in genetic susceptible individuals with different manifestations depending on the genetic background and the site of reactivation.

Killer cell immunoglobulin-like receptor gene associations with autoimmune and allergic diseases, recurrent spontaneous abortion, and neoplasms

Killer cell immunoglobulin-like receptors (KIRs) are a family of cell surface inhibitory or activating receptors expressed on natural killer cells and some subpopulations of T lymphocytes. KIR genes are clustered in the 19q13.4 region and are characterized by both allelic (high numbers of variants) and haplotypic (different numbers of genes for inhibitory and activating receptors on individual chromosomes) polymorphism. This contributes to diverse susceptibility to diseases and other clinical situations. Associations of KIR genes, as well as of genes for their ligands, with selected diseases such as psoriasis vulgaris and atopic dermatitis, rheumatoid arthritis, recurrent spontaneous abortion, and non-small cell lung cancer are discussed in the context of NK and T cell functions.