Association study of TRAF1-C5 polymorphisms with susceptibility to rheumatoid arthritis and systemic lupus erythematosus in Japanese.

OBJECTIVE: The primary aim of this study was to investigate the association of polymorphisms of TRAF1-C5, a newly identified rheumatoid arthritis (RA) risk locus in Caucasians, with susceptibility to RA and systemic lupus erythematosus (SLE) in Japanese populations. Gene expression levels of TRAF1 and C5 to assess the functional significance of genotypes were also analysed. METHODS: A multicentre association study consisting of 4 RA case-control series (4397 cases and 2857 controls) and 3 SLE case-control series (591 cases and 2199 shared controls) was conducted. Genotyping was performed using TaqMan genotyping assay for two single nucleotide polymorphisms (SNPs) that showed the best evidence of association in the previous Caucasian studies. Quantifications of TRAF1 and C5 expression were performed with TaqMan expression assay. RESULTS: Significant differences in allele frequency for both SNPs were observed between RA and control subjects (combined odds ratio = 1.09), while no significant difference was detected between patients with SLE and controls. Interestingly, alleles rs3761847 A and rs10818488 G had increased the risk for RA in the present study, while they decreased the risk in the original studies. A significant difference was found between risk allele carriers and non-carriers of rs10818488 for the expression level of TRAF1 in phorbol myristate acetate-stimulated lymphoblastoid cell lines (p = 0.04). CONCLUSION: Association of TRAF1-C5 locus with RA susceptibility was detected in the Japanese populations with modest magnitude, while no significant association was observed for SLE. Significant positive effect of genotype on the expression of TRAF1 might support the genetic association between TRAF1 and RA.

A single nucleotide polymorphism in the IRF5 promoter region is associated with susceptibility to rheumatoid arthritis in the Japanese population.

OBJECTIVES: Interferon regulatory factor 5 (IRF5) is a member of the IRF family of transcription factors, which regulate the production of proinflammatory cytokines. Polymorphisms in the IRF5 gene have been associated with susceptibility to systemic lupus erythaematosus (SLE) in Caucasian and Asian populations, but their involvement in other autoimmune diseases is still uncertain. Here, we assessed the genetic role of IRF5 in susceptibility to rheumatoid arthritis (RA) in Japanese subjects. METHODS: We selected 13 single nucleotide polymorphisms (SNPs) and a CGGGG insertion-deletion polymorphism in the IRF5 gene. We performed 2 sets of case-control comparisons using Japanese subjects (first set: 830 patients with RA and 658 controls; second set: 1112 patients with RA and 940 controls), and then performed a stratified analysis using human leukocyte antigen (HLA)-DRB1 shared epitope (SE) status. We genotyped the SNPs using TaqMan assays. RESULTS: A significant association of the rs729302 A allele with RA susceptibility was found in both sets (odds ratio (OR) 1.22, 95% CI 1.09 to 1.35, p<0.001 in the combined analysis). When the patients were stratified by the SE, the rs729302 A allele was found to confer increased risk to RA in patients that were SE negative (OR 1.50, 95% CI 1.17 to 1.92, p = 0.001) as compared with patients carrying the SE (OR 1.11, 95% CI 0.93 to 1.33, p = 0.24). In both sets, no genotyped polymorphisms were significantly associated with RA susceptibility, but rs729302 was significantly associated. CONCLUSIONS: These findings indicate that the promoter polymorphism of IRF5 is a genetic factor conferring predisposition to RA, and that it contributes considerably to disease pathogenesis in patients that were SE negative.

Citrullination of fibronectin in rheumatoid arthritis synovial tissue.

OBJECTIVES: Citrullination, catalysed by peptidylarginine deiminase (PAD), is the post-translational modification of peptidylarginine to citrulline, which is intimately involved in the pathogenesis of rheumatoid arthritis (RA). Fibronectin (Fn), a large glycoprotein, is expressed at high levels in arthritic joints and it mediates various physiological processes through interactions with cell-surface integrin receptors and growth factors. We investigated the citrullination of Fn and its potential contribution to the pathogenesis of RA. METHODS: We localized Fn expression and citrullination in RA synovial tissue by immunohistochemistry, immunoprecipitation and western blotting. We also determined levels of citrullinated Fn in plasma from RA patients using sandwich enzyme-linked immunosorbent assay (ELISA). After incubating Fn with rabbit skeletal muscle PAD, we examined the binding ability of citrullinated Fn to vascular endothelial growth factor (VEGF) and integrin beta1 using a solid-phase receptor binding assay as well as the effect of the citrullinated Fn on apoptosis using cultured HL-60 cells. RESULTS: Immunohistochemistry and western blotting analysis indicated that Fn formed extracellular aggregates that were specifically citrullinated in RA synovial tissue. No Fn deposits were observed in synovial tissues of osteoarthritis (OA). Sandwich ELISA detected higher levels of citrullinated Fn in plasma from patients with RA than from healthy controls or those with systemic lupus erythematosus. Following citrullination in vitro, the affinity of Fn for VEGF increased, but binding activity to integrin beta1 decreased and Fn no longer stimulated the apoptosis of monocytes induced from cultured HL-60 cells. CONCLUSIONS: Our results suggest that the citrullination of Fn is a specific event for RA synovium, although others have detected citrullinated total proteins in inflamed synovial tissue of RA and non-RA patients. Citrullination of Fn could alter interactions between Fn and its receptors and growth factors, consequently contributing to mechanisms of RA pathogenesis such as perturbed angiogenesis and apoptosis.

CUL1, a component of E3 ubiquitin ligase, alters lymphocyte signal transduction with possible effect on rheumatoid arthritis.

Ubiquitination affects various immune processes and E3 ubiquitin ligases (E3) play an important role in determining substrate specificity. We identified 11 human E3 ligase genes of potential importance in pathogenesis of autoimmune diseases by search of public databases and screened them for candidacy of biological investigation with case-control linkage disequilibrium tests on multiple SNPs in the genes using rheumatoid arthritis (RA) as a model of autoimmune diseases. Significant association with RA was observed in an SNP in intron 3 of Cullin 1 (CUL1) that affected transcriptional efficiency of the promoter activity in lymphocytic cell lines. Quantitative expression analysis revealed that CUL1 mRNA was highly detected in lymphoid tissues including spleen and tonsil, and was specifically expressed in T and B lymphocytes in fractionated peripheral leukocytes. Histological evaluation of tonsils indicated that CUL1 protein expression was relatively specific for maturing germinal centers. Suppression of CUL1 expression had influence on the phenotype of T-cell line, that is, it inhibited IL-8 induction, which is known to play an important role in the migration of inflammatory cells into the affected area seen in RA. Our data suggest that the regulation of CUL1 expression in immunological tissues may affect the susceptibility of RA via altering lymphocyte signal transduction.

The inhibition of antithrombin by peptidylarginine deiminase 4 may contribute to pathogenesis of rheumatoid arthritis.

OBJECTIVE: The gene for peptidylarginine deiminase 4 (PADI4) has been found to be closely associated with rheumatoid arthritis (RA). Peptidylarginine deiminase (PADI) catalyses the post-translational modification of peptidylarginine to citrulline, a reaction known as citrullination. PADI extracted from rabbit muscle has been reported to citrullinate antithrombin, a principal plasma inhibitor of thrombin. Thrombin is known to induce angiogenesis, fibrin formation and inflammation, the primary events of the RA joint. Here, we investigate whether human PADI4 can inhibit antithrombin by catalysing antithrombin citrullination and how the enzyme is involved in RA pathogenesis. METHODS: Antithrombin was incubated with recombinant PADI4 protein, and the inactivation of antithrombin was determined by reduction of its thrombin-inhibiting activity. Citrullination of antithrombin was detected by western blotting and enzyme-linked immunosorbent assay (ELISA). In addition, the citrullination level, activity and concentration of antithrombin in RA plasma were investigated by sandwich ELISA. RESULTS: Incubation of antithrombin with PADI4 resulted in loss of thrombin-inhibitory activity and in citrullination of antithrombin. RA plasma showed higher levels of citrullinated antithrombin than controls with non-arthritis disease and healthy individuals. CONCLUSION: The results indicate that PADI4 could inactivate antithrombin through citrullination. The abnormal expression or activation of PADI4 in RA synovium is suggested to be responsible for the high level of citrullinated antithrombin in RA plasma. Local inhibition of antithrombin activity in RA synovium might lead to the excessive angiogenesis, fibrin deposition and inflammation of the tissue.

Natural disasters and alcohol consumption in a cultural context: the Great Hanshin Earthquake in Japan.

AIMS: To assess changes in alcohol consumption attributable to the Great Hanshin Earthquake to test the assumption that alcohol consumption increases after natural disasters. METHODS: Quarterly alcohol sales figures were compared for three periods: before, immediately after and subsequent to the Great Hanshin Earthquake in three areas of the Hyogo prefecture: the severely affected area, the moderately affected area and the unaffected area. Possible confounding by population movement, damage to retail outlets and normal variation in sales, was assessed. FINDINGS: The quantity of alcoholic beverages consumed in the heavily damaged areas as well as throughout the prefecture decreased from the 1994 pre-disaster level, both immediately after the Great Hanshin Earthquake (January-March 1995) and 2 years after the disaster. This finding remained once possible confounding factors were taken into consideration. CONCLUSIONS: More attention should be placed on drinking in the cultural context where a disaster occurs. It may sometimes deter, rather than encourage, drinking among the affected population.