Genetic basis of rheumatoid arthritis

Anti-HLA Class II Antibodies Correlate with C-Reactive Protein Levels in Patients with Rheumatoid Arthritis Associated with Interstitial Lung Disease

The pathogenesis of Rheumatoid Arthritis (RA) is not fully understood, probably influenced by genetic and environmental factors. Interstitial Lung Disease (ILD) is an extra-articular manifestation of RA, which contributes significantly to morbidity and mortality. The identification of anti-HLA antibodies has been useful in the transplantation field; however, its contribution to autoimmune diseases as RA has not been fully studied. We aimed to determine the presence of anti-HLA antibodies in RA patients with and without ILD and its possible association with clinical and biochemical markers. One-hundred and forty-seven RA patients, of which 65 had ILD (RA-ILD group), were included. Sera samples for Anti-HLA Class II LABScreen panel-reactive antibodies (PRA) were analyzed. In both groups, women predominated, and lung function was worse in patients with ILD. The anti-CCP+ (UI/mL) was higher in the RA group in comparison to RA-ILD (p < 0.001). Expositional risk factors (tobacco smoking and biomass-burning smoke) were higher in RA-ILD patients. PRA+ was identified in ~25% RA-ILD patients, while ~29% in the RA group. The CRP levels have a positive correlation with the percentage of reactivity (%PRA, p = 0.02, r² = 0.60) in the RA-ILD group. In conclusion, anti-HLA antibodies correlate with C-reactive protein levels in RA patients with ILD.

Association of MICA-129Met/Val polymorphism with clinical outcome of anti-TNF therapy and MICA serum levels in patients with rheumatoid arthritis

MHC class I polypeptide-related sequence A (MICA) is a stress-induced protein involved in activation of NK and T cells through interaction with NKG2D receptor. These molecules are atypically expressed in synovium of patients diagnosed with rheumatoid arthritis (RA). A total of 279 patients with RA, qualified to TNF-blockade therapy, were genotyped for MICA rs1051792 SNP. The effectiveness of anti-TNF agents was assessed with European League Against Rheumatism criteria. Significant relationship between MICA rs1051792 and outcome of TNF-blockade therapy has been found. The MICA rs1051792 GG genotype was overrepresented in patients non-responsive to anti-TNF drugs in comparison with other genotypes (p = 0.010). On the other hand, beneficial therapeutic response was more frequently detected among RA subjects possessing heterozygous genotype than those with homozygous genotypes (p = 0.003). Furthermore, increased MICA concentrations in serum were observed in patients possessing MICA rs1051792 GG genotype as compared with those with GA or AA genotypes (p = 1.8 × 10^-5). The results from this study indicate the potential influence of MICA rs1051792 polymorphism on modulation of therapeutic response to TNF-blockade treatment in RA.

Rheumatoid arthritis and systemic lupus erythematosus: Pathophysiological mechanisms related to innate immune system

Rheumatoid arthritis and systemic lupus erythematosus are two highly prevalent autoimmune diseases that generate disability and low quality of life. The innate immune system, a long-forgotten issue in autoimmune diseases, is becoming increasingly important and represents a new focus for the treatment of these entities. This review highlights the role that innate immune system plays in the pathophysiology of rheumatoid arthritis and systemic lupus erythematosus. The role of the innate immune system in rheumatoid arthritis and systemic lupus erythematosus pathophysiology is not only important in early stages but is essential to maintain the immune response and to allow disease progression. In rheumatoid arthritis, genetic and environmental factors are involved in the initial stimulation of the innate immune response in which macrophages are the main participants, as well as fibroblast-like synoviocytes. In systemic lupus erythematosus, all the cells contribute to the inflammatory response, but the complement system is the major effector of the inflammatory process. Detecting alterations in the normal function of these cells, besides its contribution to the understanding of the pathophysiology of autoimmune diseases, could help to establish new treatment strategies for these diseases.

Association between CD226 polymorphism and soluble levels in rheumatoid arthritis: Relationship with clinical activity

OBJECTIVE

To study the relation between CD226 rs763361 gene polymorphism and CD226 serum level and to evaluate their role in susceptibility and disease activity of RA in a cohort of Egyptian individuals.

METHODS

The serum level of CD226 was measured using a suitable ELISA kit and the CD226 rs763361 gene polymorphism was typed by PCR-RFLP for 112 RA patients and 100 healthy controls.

RESULTS

Significant association with RA was found with CD226 T allele (OR (95%CI) = 1.6 (1.04-2.4), P = 0.032), and higher CD226 serum level (P = 0.001). Higher CD226 levels were associated with higher ESR values (P = 0.035), positive CRP (0.048), increased number of tender joints (P = 0.045), and higher DAS score (P = 0.035). Serum CD226 is an independent risk factor for the prediction of RA (P = 0.001). No correlations were found between the serum level of CD226 and different CD226 genotypes and also between them and RA activity grades.

CONCLUSION

The CD226 T allele may be susceptibility risk factors for the development of RA and the higher serum level of CD226 may be involved in the pathogenesis of RA in Egyptian patients. The serum level of CD226 and not CD226 genotypes could be considered as an independent risk factor for the prediction of RA within healthy individuals and also for RA disease activity.

TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 gene polymorphisms as possible risk factor for rheumatoid arthritis: relation to activity and severity

This study was aimed to evaluate the impact of both TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 polymorphisms on susceptibility to rheumatoid arthritis (RA) in a cohort of Egyptian population and to evaluate for the first time their relation to activity, severity, disease-related disability and erosion. TIM-1 rs41297579 G>A (-1454) and TIM-4 rs7700944 gene polymorphisms were typed by RFLP for 128 patients with RA and 125 healthy controls. The A allele, A-containing genotypes (GA and AA) of the TIM-4 and GA haplotype were present with significant higher frequency in patients with RA than healthy controls (Pc  < 0.001). These findings suggest that the A allele, A-containing genotypes (GA and AA) and GA haplotype may be a susceptibility risk factor for RA [OR = 5.83 (3.6-9.4), OR = 9.41 (5.0-17.6) and OR = 4.21 (1.07-19.2), respectively]. No associations were found between TIM genotypes and disease activity, severity or presence of erosion. However, the RA patients with GA genotype of TIM-4 have higher grade of rheumatoid factor (RF) positivity (P = 0.018), and have worse disease-related disability (P = 0.007) and worse pain (0.025). TIM-4 rs7700944 and not TIM-1 rs41297579 G>A (-1454) is associated with RA in the present cohort of Egyptian and may be a risk factor for development of RA in Egyptian. Both SNPs have no effect on disease activity, severity or erosion. However, TIM-4 GA genotype is associated with higher grade of RF positivity and worse disease-related disability and pain.

Association study of MICA gene polymorphisms with rheumatoid arthritis susceptibility in south Tunisian population

The aim of this study was to investigate the role of major histocompatibility complex (MHC) class I chain-related gene A (MICA) polymorphisms, important in natural killer (NK) cell function, in patients with rheumatoid arthritis (RA). A transmembrane (TM) alanine-encoding GCT repeats, termed A4, A5, A5.1, A6 and A9 in the MICA gene, and single-nucleotide polymorphisms (SNPs): the Met129Val polymorphism (rs1051792) and the nonsynonymously coding SNP (rs1051794) were genotyped in 142 patients with RA and 123 unrelated healthy individuals using, respectively, PCR fluorescent method, nested PCR-RFLP and allele specific PCR (ASP). Association was assessed based on the χ2 test, genotype relative risk (GRR) and odds ratio (OR) with 95% confidence intervals (CIs). Our results show a trend of association of the different MICA genotypes G/G, G/A and A/A (P = 0.029) which did not attain the significance after Bonferroni's correction (pc = 0.08). Although, we revealed a significant association of the genotype A/A of MICA-250 in patients with RA compared to healthy controls (pc = 0.033). In contrast, no significant differences between alleles and genotypes frequencies were found either with MICA-TM or MICA met129 val (P > 0.05) in our sample. Moreover, stratification of patients with RA according to clinical and immunological data for the different polymorphisms studied shows a significant association of both MICA-250 G allele (pc = 0.0075) and MICA-250 GG genotype (pc = 0.008) and both allelic (val) (pc = 0.021) and genotypic (val/val) distribution (pc = 0.0095) for MICA met129 val in the RF-positive subgroup compared to RF-negative patients with RA. In contrast, we found a strong association of the MICA-TM A9 allele in RF-negative patients with RA (pc = 0.0003). This study indicates the involvement of the MICA-250 polymorphism in the genetic susceptibility and severity to RA and suggests that variations in MICA-TM and MICA met129 val may have an effect on RA severity in our south Tunisian sample.

HLA shared epitope and ACPA: just a marker or an active player?

Autoantibody production is genetically controlled and anti-citrullinated protein/peptide antibodies (ACPA) are not an exception to the rule. ACPA are highly specific markers of rheumatoid arthritis (RA) and are also associated with a more severe disease course. The production of ACPA is almost invariably observed in HLA-shared epitope (SE) positive patients. The DRB1 alleles sharing SE are those conferring susceptibility to RA. SE alleles behave like immune response genes, controlling both the specificity and the amount of ACPA produced. These data suggest a role of SE in the presentation of citrullinated antigens. The ability of SE alleles to bind selectively to citrullinated sequences as compared to the native counterparts has been demonstrated in the case of peptides derived from several joint associated proteins (vimentin, fibrinogen and cartilage intermediate-layer protein). On the contrary, EBV-derived citrullinated peptides do not display a biologically relevant binding to SE alleles even if the immune response to VCPs is under the genetic control of these alleles (namely *0401 and *0404). Thus, the presentation of citrullinated epitopes does not represent the only molecular mechanisms underlying the HLA-DRB1 effect on ACPA production.

IL-4 and MTHFR gene polymorphism in rheumatoid arthritis and their effects

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease that mainly affects the joints. Polymorphic variations of the cytokine genes and MTHFR gene have received attention as potential markers of susceptibility, severity, and/or protection in RA. The aim of this study was to investigate the MTHFR C677T and IL-4 70bp VNTR variation in Turkish patients with RA and evaluate if there was an association with clinical features, especially ocular involvement, in RA patients. The study included 297 persons (147 patients with RA and 150 healthy controls). Genomic DNA was isolated and genotyped using PCR assay for the MTHFR gene C677T and IL-4 gene 70bp VNTR polymorphisms. Our results show that there was statistically significant difference between the groups with respect to IL-4 genotype (p=0.01) and allele frequencies (p<0.002). There was no statistical significant difference in the genotype frequencies MTHFR gene, but allele frequencies showed statistically significant association (p=0.01). When we examined MTHFR and IL-4 genotype frequencies according to the clinical characteristics, we found that there was a difference between MTHFR genotypes and ocular involvement but it is not to a statistical significant degree (p=0.09). In the combined genotype analysis, MTHFR/IL-4 CCP2P2 combine genotype was estimated to have protective effect against RA, CTP1P2 combine genotype was found to be risk for RA. Our findings suggest that there is an association of IL-4 gene 70bp VNTR polymorphism and MTHFR C677T polymorphism with susceptibility of a person for development of RA.

Association of angiotensin converting enzyme (ACE) gene I/D polymorphism and rheumatoid arthritis

We sought to determine the frequency of I/D polymorphism genotypes of angiotensin converting enzyme gene in Turkish patients with rheumatoid arthritis. Genomic DNA obtained from 256 individuals (110 patients with rheumatoid arthritis and 146 healthy controls) was used in the study. ACE gene I/D polymorphism genotypes were determined using polymerase chain reaction using I and D allele-specific primers. There was a statistically significant difference between the groups with respect to genotype distribution (p=0.001). A significant difference was found in frequencies of ACE I/D alleles between patients and controls, with RA patients having a higher representation of D and lower representation of I alleles compared to controls (p<0.001). As a result of our study, angiotensin converting enzyme gene I/D polymorphism DD genotype could be a genetic marker in rheumatoid arthritis in the Turkish study population.

PADI4 polymorphisms and susceptibility to rheumatoid arthritis: a meta-analysis

The objective of the study was to investigate the association between peptidylarginine deiminase 4 (PADI4) polymorphism and susceptibility to rheumatoid arthritis (RA). An electronic searching strategy was employed to collect relevant studies on the association between PADI4 polymorphism and susceptibility to RA. The odds ratio (OR) with the 95 % confidence interval (95 % CI) was used to evaluate the RA risk presented by PADI4 polymorphism. Fixed or random effects models were selected based on heterogeneity. Publication bias was assessed using funnel plots, Begg's test, and Egger's test. A total of 27 studies from 21 articles were included. Six gene loci (padi4_94, 104, 92, 90, 89, and 100) were chosen for the meta-analysis. The pooled ORs (95 % CI) for allele 2 versus 1 were 1.08 (1.05-1.12), 1.17 (1.12-1.23), 1.26 (1.18-1.36), 1.17 (1.10-1.24), 1.30 (1.17-1.44), and 1.25 (1.11-1.40), respectively. All six SNPs were significantly associated with RA in Asian populations. Three SNPs (PADI4_104, 90, 89) showed significant associations, while the other three SNPs (PADI4_94, 92, 100) exhibited no associations in the European population. A dose-response relationship between allele 2 of PADI4 and the risk of RA was also identified. In conclusion, this meta-analysis suggests that PADI4 polymorphisms represent a significant risk factor for RA, especially in Asians.

Association study of human leukocyte antigen-DRB1 alleles with rheumatoid arthritis in south Tunisian patients

The aim of this study is to explore relationship between HLA-DRB1 alleles and the susceptibility and clinical features of rheumatoid arthritis (RA) in the south Tunisian population. We studied 142 RA patients and 123 controls matched for age, sex, and ethnicity. HLA-DRB1 genotyping and HLA-DRB1*04 subtypes were performed using polymerase chain reaction/sequence-specific primers. Association was assessed based on the χ (2) test and odds ratio with 95% confidence interval. For multiple comparisons, p value was corrected (p (c)) with Bonferroni test. Two alleles, HLA-DRB1*04 (p=0.045, p(c)=NS) and HLA-DRB1*10 (p=0.021, p(c)=NS), were found to have increased frequencies in RA patients compared to controls. In contrast HLA-DRB1*08 allele was found to have a decreased frequency in patients compared to controls (p=0.044, p(c)=NS). Molecular subtyping of the most prevalent allele (DRB1*04) revealed increased frequencies of HLA-DRB1*04:05 in patients compared to controls (p=0.013, p(c)=NS) whereas HLA-DRB1*04:02 showed a protective effect (p=0.005, p(c)=0.04). Moreover, stratified analyses indicated statistically significant associations between HLA-DRB1*04 allele and anti-cyclic peptides antibodies positivity (ACPA(+)) and rheumatoid factor positivity (RF(+); p(c)=0.03, for both subgroups), HLA-DRBI*10 and ACPA(+) and the presence of another autoimmune disease (p(c)=0.05 and p(c)=0.007, respectively), and HLA-DRB1*04:05 and RF(+) and erosion (p(c)=0.005 and p(c)=0.049; respectively). A significant decrease in the frequency of the DRB1*04:02 allele was observed in patients with ACPA(+) and RF(+) subgroups (p(c)=0.04 and p(c)=0.02, respectively). Our results showed that there was a trend of positive association of HLA-DRB1*04 and HLA-DRB1*10 with RA as such and significant associations with the disease severity in the south Tunisian population.

Transforming growth factor β 869C/T and interleukin 6 -174G/C polymorphisms relate to the severity and progression of bone-erosive damage detected by ultrasound in rheumatoid arthritis

Introduction

Single nucleotide polymorphisms (SNPs) of transforming growth factor β (TGF-β) and IL-6 genes (respectively, 869C/T and -174G/C) have been associated with radiographic severity of bone-erosive damage in patients with rheumatoid arthritis (RA). Musculoskeletal ultrasound (US) is more sensitive than radiography in detecting bone erosion. We analyzed the association between TGF-β 869C/T and IL-6 -174G/C SNPs and bone-erosive damage, evaluated by US, in a cohort of patients with severely active RA.

Methods

Seventy-seven patients were enrolled before beginning anti-TNF treatment. Disease activity was measured using the disease activity score in 28 joints, and the clinical response was evaluated according to the European League Against Rheumatism response criteria. Rheumatoid factor (RF) and anticitrullinated protein/peptide antibodies (ACPAs) were detected. The 869C/T TGF-β and -174G/C IL-6 SNPs were analyzed by PCR amplification. US was performed to assess the bone surfaces of metacarpophalengeal (MCP), proximal interphalangeal (PIP) and metatarsophalangeal (MTP) joints by obtaining multiplanar scans. According to the number of erosions per joint, a semiquantitative score ranging from 0 to 3 was calculated in each anatomical site to obtain a MCP total erosion score (TES), a PIP TES and a MTP TES, all ranging from 0 to 30, and a global patient TES calculated as the sum of these scores (range, 0 to 90).

Results

Patients carrying the TGF-β 869TT genotype showed a statistically significant lower MTP TES than those with the CC or CT genotype (mean MTP TES ± standard deviation for 869TT 6.3 ± 5.7 vs. 869CC/CT 11.7 ± 7.8; P = 0.011). Interestingly, patients with the TT genotype showed dichotomous behavior that was dependent on autoantibody status. In the presence of ACPAs and/or RF, the TT genotype was associated with lower erosion scores at all anatomical sites compared with the CC and CT genotypes. Conversely, the same 869TT patients showed higher erosion scores in the absence of ACPAs or RF.

Conclusions

In RA patients, TGF-β 869C/T SNPs could influence the bone-erosive damage as evaluated by US. The serological autoantibody status (ACPAs and RF) can modulate this interaction.

An overview on the genetic of rheumatoid arthritis: a never-ending story

Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory, multi-factorial disease sustained by environmental and genetic factors. These seem to be necessary but not sufficient in the disease development, nonetheless they can be responsible of different clinical pictures and response to therapy, and they can represent potential therapeutic targets. Several genes have been indicated so far in the pathogenesis of RA. The most important region is the Human Leukocyte Antigen (HLA) that contributes to approximately half of the genetic susceptibility for RA. The association seems to be stronger or specific for anti-citrullinated protein antibodies positive disease. Several alleles in the epitope-recognition part of the HLA molecule that show the highest association with RA susceptibility, also share a common string of amminoacid residues (the so-called shared-epitope hypothesis). Other variants in potentially pathogenic genes located in non-MHC regions have been implicated by recently performed genome wide analysis studies. These genes include PTPN22, TRAF1-C5, PADI4, STAT4. Other polymorphisms seem to be responsible for more aggressive disease phenotype such as those located at TNF, IL-1, IL-6, IL-4, IL-5, OPN, PRF1. However, still nowadays, the genetic background of RA remains to be clearly depicted, and the efforts in the post-genomic era can bring to an estimation of the real likelihood of the genetic effect on RA. Finally, the discovery of new genes associated with the disease can be relevant in finding potential biomarkers, potentially useful in disease diagnosis and treatment.

Association of the PTPN22 gene (-1123G > C) polymorphism with rheumatoid arthritis in Chinese patients

This study aimed at examining the association of the single nucleotide polymorphism (SNP) in the protein tyrosine phosphatase gene (PTPN22) with the risk of rheumatoid arthritis (RA) in a Chinese population. A total of 200 RA patients and age and gender-matched healthy controls were recruited. Their genotypes and allelic frequency were determined by the TaqMan-MGB probe-based polymerase chain reaction (PCR). The frequencies of the CC genotype and C allele in RA patient group were significantly higher than that of controls (P < 0.01 or P < 0.05) with an odds ratio of 1.67, respectively. These data suggest, the CC genotype and C allele of the -1123G > C in the PTPN22 gene are associated with an increased risk for RA in Chinese population. Therefore, the CC genotype and C allele of the -1123G > C in the PTPN22 gene may be used as a genetic marker for the predisposition of RA in Chinese.

HLA-DRB1 allele distribution and its relation to rheumatoid arthritis in eastern Black Sea Turkish population

Rheumatoid arthritis (RA [MIM 180300]) is a complex, polygenic inflammatory autoimmune disease, resulting from interactions between genetic and environmental factors. Some of the RA-associated HLA-DRB1 alleles have shared epitope, but their distribution varies among different racial/ethnic groups. This study was aimed at investigating the distribution of HLA-DRB1 alleles in patients with RA in eastern Black Sea region of Turkey. DNA samples of 320 patients with RA and 360 healthy controls were studied for the determination of HLA-DRB1 allele distribution using PCR-SSP method. The allele frequencies of HLA-DRB1*01, *04, and *09 were higher in patients with RA compared with the controls (P < 0.005, P < 0.0001, and P < 0.01, respectively). On the other hand, in patients with RA, HLA-DRB1*13 allele was lower than the controls (P < 0.001). Of the HLA-DRB1*04 subgroups, *0401 (40.83% vs. 18.75%, P < 0.001) was the most frequent allele in patients with RA, while DRB1*0402 (30.00% vs. 12.50%, P < 0.005) allele in the controls. HLA-DRB1 allele frequencies in the patients with RA and the controls showed Hardy-Weinberg rule compliance. Results of this study indicate that HLA-DRB1*01, *04, and *09 alleles were associated with RA, and HLA-DRB1*13 was protective allele against RA. Among the subgroups of HLA-DRB1*04, *0401 was detected to be RA associated, while *0402 was being protective. These results have some differences compared with previous reports originating from other regions of Turkey.

Lithium protects cartilage from cytokine-mediated degradation by reducing collagen-degrading MMP production via inhibition of the P38 mitogen-activated protein kinase pathway

OBJECTIVES

To determine the effects and mechanism of action of lithium chloride (LiCl) on cartilage destruction induced by the pro-inflammatory cytokines IL-1, IL-1 + oncostatin M and TNF-α.

METHODS

The release of collagen was assessed in bovine cartilage explant cultures, whereas collagenolytic activities (active and total) in conditioned culture supernatants were determined by bioassay. The expression and production of MMP from chondrocytes were analysed by real-time RT-PCR and ELISA. Signalling pathway analysis was performed using a phospho-antibody array and standard immunoblotting.

RESULTS

LiCl, but not selective glycogen synthase kinase 3 (GSK-3) inhibitor compounds SB-415286 and TDZD-8, significantly decreased pro-inflammatory cytokine-induced collagen release from bovine cartilage via the down-regulation of collagenolytic activity. Furthermore, MMP-1 and MMP-13 expression was reduced in both bovine and human chondrocytes. Pathway analysis revealed that LiCl selectively inhibited activation of the p38 mitogen-activated protein kinase pathway; effects that were recapitulated by specific p38 pathway inhibition.

CONCLUSIONS

This study demonstrates for the first time that LiCl can protect against cartilage damage induced by pro-inflammatory cytokines, and indicates that LiCl-mediated cartilage protection is not via a GSK-3-dependent mechanism, but potentially via inhibition of the p38 pathway. These data indicate that lithium administration may represent a potential therapy for arthritis.

IL10 GGC Haplotype Is Positively and HLA-DQA1*05-DQB1*02 Is Negatively Associated with Radiographic Progression in Undifferentiated Arthritis

Objective.

In rheumatoid arthritis (RA), many genetic markers, such as the shared-epitope (SE) alleles, are described in association with radiographic progression, but limited data are available on undifferentiated arthritis (UA). We investigated whether single-nucleotide polymorphisms (SNP) and haplotypes in immune response genes and HLA class II alleles are associated with radiographic progression in patients with early UA.

Methods.

Progression of radiographic damage was determined in white Dutch patients with early UA after 2 years of followup. Severe progression was defined as an increase in Sharp/van der Heijde Score ≥ 5 points after 2 years of followup. The remainder was classified as mild. These SNP were genotyped by Taqman technology: tumor necrosis factor (TNF) −1031, −863, −857, −308, −238; lymphotoxin-α (LTA) +368, +252; interleukin 10 (IL10) −2849, −1082, −819; IL1A −889, IL1B −31, +3953; and IL1RN +2018. Carriage of SE alleles and HLA-DQA1*05-DQB1*02 haplotype was established. These markers were analyzed in relation to radiographic progression.

Results.

Forty-eight out of 151 patients with early UA had severe radiographic progression. Severe radiographic progression was associated with an increased carrier frequency of SE alleles (OR 5.12, 95% CI 2.0–13.1, p < 0.001) and IL10 GGC haplotype (OR 2.8, 95% CI 1.4–5.8, p = 0.003). Mild radiographic progression was associated with the HLA-DQA1*05-DQB1*02 haplotype (OR 0.3, 95% CI, 0.1–0.8, p = 0.013) and with allele TNF −308A (OR 0.4, 95% CI, 0.2–0.9, p = 0.02).

Conclusion.

The SE and the IL10 GGC haplotype are associated with severe progression of radiographic damage, in contrast to the DQA1*05-DQB1*02 haplotype and the TNF −308A allele, which are associated with mild radiographic progression in early UA.

Update on the genetic risk factors for rheumatoid arthritis

Rheumatoid arthritis (RA) is a complex disease, meaning that multiple genetic variants, environmental factors and random events interact to trigger pathological pathways. Although many of these etiological factors have not yet been identified, recent groundbreaking advances have expanded our knowledge about the genetic factors that contribute to RA. Here, we review the most recent findings on the genetic risk factors for RA. First, we give an overview of the genetics of RA and briefly describe the susceptibility loci discovered prior to the availability of genome-wide association studies (GWAS). Second, we focus on the newly discovered RA loci that have arisen from GWAS in populations of European ancestry. Through these studies, the number of established RA susceptibility loci has now grown to 13. Third, we discuss several important issues emerging from GWAS, such as ethnic heterogeneity and shared autoimmunity risk loci. Finally, we discuss what still needs to be accomplished before a more complete picture of the genetic risk to RA can be attained.

Allelic based gene-gene interactions in rheumatoid arthritis

The detection of gene-gene interaction is an important approach to understand the etiology of rheumatoid arthritis (RA). The goal of this study is to identify gene-gene interaction of SNPs at the allelic level contributing to RA using real data sets (Problem 1) of North American Rheumatoid Arthritis Consortium (NARAC) provided by Genetic Analysis Workshop 16 (GAW16). We applied our novel method that can detect the interaction by a definition of nonrandom association of alleles that occurs when the contribution to RA of a particular allele inherited in one gene depends on a particular allele inherited at other unlinked genes. Starting with 639 single-nucleotide polymorphisms (SNPs) from 26 candidate genes, we identified ten two-way interacting genes and one case of three-way interacting genes. SNP rs2476601 on PTPN22 interacts with rs2306772 on SLC22A4, which interacts with rs881372 on TRAF1 and rs2900180 on C5, respectively. SNP rs2900180 on C5 interacts with rs2242720 on RUNX1, which interacts with rs881375 on TRAF1. Furthermore, rs2476601 on PTPN22 also interacts with three SNPs (rs2905325, rs1476482, and rs2106549) in linkage disequilibrium (LD) on IL6. The other three SNPs (rs2961280, rs2961283, and rs2905308) in LD on IL6 interact with two SNPs (rs477515 and rs2516049) on HLA-DRB1. SNPs rs660895 and rs532098 on HLA-DRB1 interact with rs2834779 and four SNPs in LD on RUNX1. Three-way interacting genes of rs10229203 on IL6, rs4816502 on RUNX1, and rs10818500 on C5 were also detected.

DA rats from two colonies differ genetically and in their arthritis susceptibility

The arthritis-susceptible DA rat is one of the most commonly used rat strains for genetic linkage analysis and is instrumental for the identification of many genetic loci. Even though DA rats were kept as inbred lines at different institutes and suppliers, it became obvious that the various breeding stocks differed genetically. To be able to compare the results from different linkage studies it is very import to verify the genetic background of the substrains used in those studies. We performed a genetic and phenotypic analysis of two DA substrains, DA/ZtmRhd and DA/OlaHsd, and found several genetic differences. One of the allelic differences between the DA/ZtmRhd and the DA/OlaHsd strain was located at rat chromosome 3, a 17-Mb large fragment, including the peak marker of a previously identified quantitative trait locus (QTL) for collagen-induced arthritis, Cia11. In addition, the substrains exhibited a significant difference in the susceptibility to pristane-induced arthritis (PIA) and disease severity of collagen-induced arthritis and PIA. However, by generating and testing a congenic line, we could demonstrate that phenotypic differences were not due to the contaminating fragment on chromosome 3. Nevertheless, we conclude that DA substrains show distinct genetic differences and caution should be taken when comparing arthritis data from different DA substrains.

Modeling of PTPN22 and HLA-DRB1 susceptibility to rheumatoid arthritis

In the present paper, we used the North American Rheumatoid Arthritis Consortium data provided for Genetic Analysis Workshop 15 Problem 2 to: 1) estimate the penetrances of PTPN22 and HLA-DRB1 and, 2) test the selected model of PTPN22 conditional on the rheumatoid factor status. To achieve these aims, we used the marker association segregation chi-square method, fitting simultaneously both genotype frequency and identical by descent distributions in a sample of 3690 White individuals from 604 nuclear families. A co-dominant model fitted the rs2476601 (R620W) single-nucleotide polymorphism (SNP) of the PTPN22 gene well, whereas a lack of fit for all models was observed for the HLA-DRB1 locus. Testing genetic models of rheumatoid arthritis that include the PTPN22 SNP in addition to the HLA-DRB1 locus did not affect the results, nor did subgroup analysis of PTPN22 conditional on the rheumatoid factor status. In conclusion, PTPN22 R620W SNP is a risk factor for rheumatoid arthritis. The genetic architecture of the HLA-DRB1 locus is highly complex, and more elaborate modeling of this locus is required.

Necrotising anterior scleritis in a late-onset rheumatoid arthritis (LORA) patient

Late-onset rheumatoid arthritis (LORA) is a clinically distinct entity from rheumatoid arthritis of younger onset (YORA). We present a case of necrotising anterior scleritis in an elderly lady with new-onset LORA that was initially thought to be infective. Oestrogen receptors have been identified on B cells, T cells, and macrophages with oestrogens demonstrated to increase their activation and enhance RA synovial inflammation. The presence of long-term oestrogen supplementation may have contributed to the development and perpetuation of her RA, thereby necessitating awareness of the possible immunomodulatory role of the sex steroids in immune-mediated diseases which affect the eye.

B cells in rheumatoid arthritis

Though its etiology remains unknown thus far, the role that autoimmune processes play in rheumatoid arthritis (RA) pathogenesis has been widely proven. Given the easier accessibility of humoral components, the first feature of this contribution to be recognized has been the occurrence of the so-called rheumatoid factor in a large proportion of RA patients. This antibody recognizes the Fc portion of human IgG. By investigating RA pathologic processes and also through experimental models where immune complexes play a fundamental role, many other autoantibodies have then come to our knowledge to be associated with the disease. Their presence and persistence implies that clones of autoreactive B cells survive and proliferate in RA patients under a continuous stimulation. Whether this is a mechanism of disease initiation or just an epiphenomenon is still unclear but no doubt exists that autoantibodies represent a very useful tool in both diagnostic and prognostic terms. Being much more than simple autoantibody producers, B cells are able to secrete many important cytokines and to efficiently present antigens to T lymphocytes in the synovial environment. All of these functions are essential in the development of RA, and lately have claimed attention as B cell depletion has become a common and effective strategy of treatment in RA.

Genetic predictors of acute and chronic pain

Although broad agreement exists that genetic factors are important contributors to individual differences in pain sensitivity and risk for developing painful clinical conditions, the field of pain genetics is still in its infancy. This article reviews recent human studies of the genetics of acute and chronic pain, which implicate polymorphisms in genes coding for catechol-O-methyltransferase activity and micro-opioid receptors, among a number of others, as influential in explaining variability among the pain responses of individuals. Growing interest in pain genetics and accelerating methodologic advances in the field will almost certainly alter our understanding of which genes contribute to nociception and how dynamic interactions between multiple genes and environmental events shape the human experience of pain.

Association of the microsatellite in the 3' untranslated region of the CD154 gene with rheumatoid arthritis in females from a Spanish cohort: a case-control study

CD40-CD154 interaction is an important mediator of inflammation and has been implicated in T helper type 1-mediated autoimmune diseases including rheumatoid arthritis (RA). Linkage studies have shown association of markers in the proximity of the CD154 gene. In the present work we investigated whether specific allele variants of the microsatellite in the 3' UTR of the CD154 gene might modulate the risk of RA. The study, in a case-control setting, included 189 patients and 150 healthy controls from the Canary Islands, Spain. The 24CAs allele was less represented in female patients than in controls (0.444 in controls versus 0.307 in patients, P = 0.006, odds ratio (OR) 0.556, 95% confidence interval (CI) 0.372 to 0.831) but not in males (0.414 versus 0.408), and only when homozygous (P = 0.012; OR 0.35, 95% CI 0.16 to 0.77). We also verified that CD154 association with RA was independent of human leukocyte antigen (HLA) phenotype. A further functional study showed that after stimulation anti-CD3, CD154 mRNA was more stable in CD4+ T lymphocytes from patients with RA bearing the 24CAs allele (mRNA half-life 208 minutes) than in patients without the 24CAs allele (109 minutes, P = 0.009). However, a lower percentage of CD154+CD4+ T lymphocytes was seen in freshly isolated peripheral blood mononuclear cells from patients carrying 24CAs alleles (mean 4.28 versus 8.12; P = 0.033), and also in CD4+ T lymphocytes stimulated with anti-CD3 (median 29.40 versus 47.60; P = 0.025). These results were concordant with the smaller amounts of CD154 mRNA isolated from stimulated T lymphocytes with 24CAs alleles. The CD154 microsatellite therefore seems to affect the expression of the gene in a complex manner that implies not only mRNA stability. These data suggest that the CD154 microsatellite contributes to the regulation of mRNA and protein expression, although further studies will be necessary to elucidate its role in disease predisposition.

Association of a BTLA gene polymorphism with the risk of rheumatoid arthritis

B and T lymphocyte attenuator (BTLA) is an immuno-inhibitory receptor with the ability to deliver inhibitory signal for suppressing lymphocyte activation. To test the potential association of the human BTLA gene with the development of rheumatoid arthritis (RA), a genetic case-control association study was conducted, by using a single nucleotide polymorphism (SNP), C+800T SNP, in the exon 5 of the human BTLA gene for genotyping 93 RA patients and 294 normal control individuals. The results showed that there is statistically significant difference in the genotype distributions between RA and control groups (p = 0.022). When compared with the heterozygous genotype (C/T genotype), the homozygous genotype (C/C or T/T genotype) appears to confer the increased risk of the RA susceptibility with the odds ratio of 1.88 (p = 0.015). These data indicate the significant association between the C+800T SNP in the BTLA gene with the RA susceptibility.

Genetic markers of treatment response in rheumatoid arthritis

Rheumatoid arthritis patients exhibit a considerable interindividual variability in response to drug treatment. Although many disease-related and demographic factors have been studied to predict treatment outcome, the effective disease-modifying antirheumatic drug (DMARD) therapy is not yet allocated based on factors that predict efficacy. Individual genetic characteristics are thought to play an important role in treatment response; therefore, current research aims to identify these genetic predictors for clinical response. Pharmacogenetic studies are beginning to provide results, which suggests that personalized treatment maximization of DMARD efficacy and minimization of adverse drug reactions are feasible.