Arthritis Research & Therapy - Latest Articles

ERAP1 genetic variations associated with HLA-B27 interaction and disease severity of syndesmophytes formation in Taiwanese ankylosing spondylitis

Chin-Man Wang — 2012-05-25T00:00:00Z

IntroductionAnkylosing spondylitis (AS) is a familial, heritable disease specified by syndesmophytes formation leads to ankylosed spine. Endoplasmic reticulum aminopeptidase 1 (ERAP1) genetic variations have been widely proved to be associated with AS in several ethnic populations. The aim of this study was to investigate whether ERAP1 single nucleotide polymorphisms (SNPs) are associated with AS susceptibility and disease severity in Taiwanese. Methods: Four ERAP1 SNPs (rs27037, rs27980, rs27044 and rs30187) were genotyped in 797 Taiwanese AS patients and 1150 healthy controls. Distributions of Genotype and alleles were compared between AS patients and healthy controls and among AS patients stratified by clinical parameters. Results: The SNP rs27037T allele appeared to be a risk factor for AS susceptibility (P = 5.510-5, OR 1.30, 95% CI: 1.15-1.48; GT+TT vs. GG P = 9.310-5, OR 1.49, 95% CI: 1.22-1.82). In addition, the coding SNP (cSNP) rs27044G allele (P = 1.510-4, OR 1.28, 95% CI: 1.13-1.46; CG+GG vs. CC, P = 1.710-3, OR 1.44, 95% CI: 1.15-1.81) and the cSNP rs30187T allele (P = 1.710-3, OR 1.23, 95% CI: 1.08-1.40; CT+TT vs. CC P = 6.110-3, OR 1.38, 95% CI: 1.10-1.74) were predisposing factors for AS. Notably, the rs27044G allele carriers (CG+GG vs. CC, P = 0.015, OR 1.59, 95% CI: 1.33-2.30) and rs30187T allele carriers (CT+TT vs. CC, P = 0.011, OR 1.63, 95% CI: 1.12-2.38) were susceptible to syndesmophyte formation in AS patients. Furthermore, two cSNPs (rs27044 and rs30187) strongly associated with HLA-B27 positivity in AS patients. Finally, the ERAP1 SNP haplotype TCG (rs27037T/rs27980C/rs27044G) is a major risk factor for AS (P < 0.00001, OR 1.38, 95% CI: 1.12-1.58) in Taiwanese. Conclusions: This study provides the first evidence of ERAP1 SNPs involving syndesmophyte formation. The interactions between ERAP1 SNPs and HLA-B27 play critical roles in pMHC I pathway processing contribute to the pathogenesis of AS in multiple populations.

Can erosions on MRI of the sacroiliac joints be reliably detected in patients with ankylosing spondylitis? A cross-sectional study

Ulrich Weber — 2012-05-24T00:00:00Z

IntroductionErosions of the sacroiliac joints (SIJ) on pelvic radiographs of patients with ankylosing spondylitis (AS) are an important feature of the modified New York classification criteria. However, radiographic SIJ erosions are often difficult to identify. Recent studies have shown that erosions can be detected also on magnetic resonance imaging (MRI) of the SIJ early in the disease course before they can be seen on radiography. The goals of this study were to assess the reproducibility of erosion and related features, namely, extended erosion (EE) and backfill (BF) of excavated erosion, in the SIJ using a standardized MRI methodology. Methods: Four readers independently assessed T1-weighted and short tau inversion recovery sequence (STIR) images of the SIJ from 30 AS patients and 30 controls (15 patients with non-specific back pain and 15 healthy volunteers aged 45 years). Erosions, EE, and BF were recorded according to standardized definitions. Reproducibility was assessed by percentage concordance among 6 possible reader pairs, kappa statistics (erosion as binary variable) and intraclass correlation coefficient (ICC) (erosion as sum score) for all readers jointly. Results: SIJ erosions were detected in all AS patients and 6 controls by [greater than or equal to]2 readers. The median number of SIJ quadrants affected by erosion recorded by 4 readers in 30 AS patients was 8.6 in the iliac and 2.1 in the sacral joint portion (P <0.0001). For all 60 subjects and for all 4 readers, the kappa value for erosion was 0.72, 0.73 for EE, and 0.63 for BF. ICC for erosion was 0.79, 0.72 for EE, and 0.55 for BF, respectively. For comparison, the kappa and ICC values for bone marrow edema were 0.61 and 0.93, respectively. Conclusions: Erosions can be detected on MRI to a comparable degree of reliability as bone marrow edema despite the significant heterogeneity of their appearance on MRI.

Aberrant CD200/CD200R1 expression and function in systemic lupus erythematosus contributes to abnormal T cell responsiveness and dendritic cell activity

Yang Li — 2012-05-23T00:00:00Z

IntroductionCD200 is a type I transmembrane glycoprotein that can regulate the activation threshold of inflammatory immune responses, polarize cytokine production and maintain immune homeostasis. We therefore evaluated the functional status of CD200/CD200 receptor 1 (CD200R1) interactions in subjects with systemic lupus erythematosus (SLE). Methods: Serum CD200 level was detected by ELISA. The expression of CD200/CD200R1 by CD4+ T cells and dendritic cells (DCs) was examined by flow cytometry, then compared between SLE patients and healthy controls (HCs). Peripheral blood mononuclear cells were stained with Carboxyfluorescein Diacetate Succinimidyl Ester (CFSE) and Annexin V/propidium iodide for evaluation of the effect of CD200 on cell proliferation and apoptosis. In addition, the effect of CD200 on DC function was determined by transwell migration assay as well as by measurement of binding and phagocytosis of apoptotic cells. Results: In SLE patients, the number of CD200+ cells and the level of soluble CD200 were significantly higher than in HCs, whereas the expression of CD200R1 by CD4+T cells and DCs was decreased. Furthermore, the increased CD200 expression by early apoptotic cells contributed to their diminished binding and phagocytosis by DCs in SLE. Importantly, the engagement of CD200 receptor on CD4+ T cells with CD200-Fc fusion protein in vitro reduced the differentiation of T helper 17 (Th17) cells and reversed the defective induction of CD4+CD25highFoxP3+ T cells by transforming growth factor beta (TGFbeta) in SLE patients. Conversely, blockade of CD200-CD200R1 interaction with anti-CD200R1 antibody promoted CD4+ T cell proliferation. Conclusions: CD200 and CD200R1 expression and function are abnormal in SLE and may contribute to the immunologic abnormalities in SLE.

Disruption of rhythms of molecular clocks in primary synovial fibroblasts of patients with osteoarthritis and rheumatoid arthritis, role of interleukin1 beta and tumor necrosis factor

Stefanie Haas — 2012-05-23T00:00:00Z

IntroductionCircadian rhythms play an important role in the body and in single cells. Rhythms of molecular clocks have not been investigated in synovial fibroblasts (SF) of patients with osteoarthritis (OA) and rheumatoid arthritis (RA). The study was initiated to fill this gap and to study effects of IL 1beta/TNF on rhythmicity in synovial fibroblasts of RA and OA patients. Methods: Presence of BMAL-1, CLOCK, Period 1, and Period 2 proteins in synovial tissue was investigated by immunofluorescence. Presence of mRNA of molecular clocks was studied during 72hr by qPCR. Characteristics of rhythms were studied with time series analysis. Results: BMAL-1, CLOCK, Period 1, and Period 2 proteins were abundantly present in synovial tissue of OA, RA, and controls. Receiving synovial tissue at different operation time points during the day (8.00am-4.00pm) did not reveal a rhythm of BMAL-1 or Period 1 protein. In OASF and RASF, no typical rhythm curve of molecular clock mRNA was observed. Time series analysis identified a first peak between 2 and 18 hours after synchronization but a period was not detectable due to loss of rhythm. TNF inhibited mRNA of CLOCK, Period 1, and Period 2 in OASF, while IL-1beta and TNF increased these factors in RASF. This was supported by dose-dependently increased levels in MH7A RA fibroblasts. In RASF, IL 1beta and TNF shifted the first peak of BMAL-1 mRNA to later time points (8hr to 14hr). Conclusion: Rhythmicity is not present in primary OASF and RASF, which is unexpected because fibroblasts usually demonstrate perfect rhythms during several days. This might lead to uncoupling of important cellular pathways.

Limited effect of anti-rheumatic treatment on 15-prostaglandin dehydrogenase in rheumatoid arthritis synovial tissue

Karina Roxana Gheorghe — 2012-05-22T00:00:00Z

IntroductionRheumatoid arthritis (RA) is a chronic inflammatory disease in which prostaglandin E2 (PGE2) displays important pathogenic role. The enzymes involved in its synthesis are highly expressed in the inflamed synovium, while little is known about 15- prostaglandin dehydrogenase (15-PGDH) that metabolizes PGE2.Here we aimed to evaluate the localization of 15-PGDH in the synovial tissue of healthy individuals or patients with inflammatory arthritis and determine the influence of common RA therapy on its expression. Methods: Synovial tissue specimens from healthy individuals, psoriatic arthritis, ostheoarthritis and RA patients were immunohistochemically stained to describe the expression pattern of 15-PGDH. In addition, the degree of enzyme staining was evaluated by computer analysis on stained synovial biopsies from two groups of RA patients, before and after RA specific treatment with either intra-articular glucocorticoids or oral methotrexate therapy. Prostaglandins derived from the cyclooxygenase (COX) pathway were determined by liquid-chromatography mass spectrometry in supernatants from interleukin (IL) 1beta- activated fibroblast-like synoviocytes (FLS) treated with methotrexate. Results: 15-PGDH was present in healthy and inflamed synovial tissue, mainly in lining macrophages, fibroblasts and vessels. Intra-articular glucocorticoids showed a trend towards reduced 15-PGDH expression in RA synovium (p = 0.08) while methotrexate treatment left the PGE2 pathway unaltered both in biopsies ex vivo and in cultured FLS. Conclusion: Early methotrexate therapy has little influence on the expression of 15-PGDH and on any of the PGE2 synthesizing enzymes or COX-derived metabolites. Thus therapeutic strategies involving blocking induced PGE2 synthesis may find a rationale in additionally reducing local inflammatory mediators.

Enhanced susceptibility to lipopolysaccharide-induced arthritis and endotoxin shock in interleukin-32 alpha transgenic mice through induction of tumor necrosis factor alpha

Masanori Nakayama — 2012-05-21T00:00:00Z

IntroductionThe present study assessed the potential functions of interleukin (IL)-32alpha on inflammatory arthritis and endotoxin shock models using IL-32alpha transgenic (Tg) mice. The potential signaling pathway for the IL-32-tumor necrosis factor (TNF)alpha axis was analyzed in vitro. Methods: IL-32alpha Tg mice were generated under control of a ubiquitous promoter. Two disease models were used to examine in vivo effects of overexpressed IL-32alpha: Toll-like receptor (TLR) ligand-induced arthritis developed using a single injection of lipopolysaccharide (LPS) or zymosan into the knee joints; and endotoxin shock induced with intraperitoneal injection of LPS and D-galactosamine. TNFalpha antagonist etanercept was administered simultaneously with LPS in some mice. Using RAW264.7 cells, in vitro effects of exogenous IL-32alpha on TNFalpha, IL-6 or macrophage inflammatory protein 2 (MIP-2) production were assessed with or without inhibitors for nuclear factor kappa B (NFkappaB) or mitogen-activated protein kinase (MAPK). Results: Single injection of LPS, but not zymosan, resulted in development of severe synovitis with substantial articular cartilage degradation in knees of the Tg mice. The expression of TNFalpha mRNA in inflamed synovia was highly upregulated in the LPS-injected Tg mice. Moreover, the Tg mice were more susceptive to endotoxin-induced lethality than the wild-type control mice 48 hours after LPS challenge; but blockade of TNFalpha by etanercept protected from endotoxin lethality. In cultured bone marrow cells derived from the Tg mice, overexpressed IL-32alpha accelerated production of TNFalpha upon stimulation with LPS. Of note, exogenously added IL-32alpha alone stimulated RAW264.7 cells to express TNFalpha, IL-6, and MIP-2 mRNAs. Particularly, IL-32alpha -induced TNFalpha, but not IL-6 or MIP-2, was inhibited by dehydroxymethylepoxyquinomicin (DHMEQ) and U0126, which are specific inhibitors of nuclear factor kappa B (NFkappaB) and extracellular signal regulated kinase1/2 (ERK1/2), respectively. Conclusions: These results show that IL-32alpha contributed to the development of inflammatory arthritis and endotoxin lethality. Stimulation of TLR signaling with LPS appeared indispensable for activating the IL-32alpha-TNFalpha axis in vivo. However, IL-32alpha alone induced TNFalpha production in RAW264.7 cells through phosphorylation of inhibitor kappa B (IkappaB) and ERK1/2 MAPK. Further studies on the potential involvement of IL-32alpha-TNFalpha axis will be beneficial in better understanding the pathology of autoimmune-related arthritis and infectious immunity.

Serum amyloid A triggers the MSU-mediated mature interleukin-1beta production from human synovial fibroblasts

Kiyoshi Migita — 2012-05-18T00:00:00Z

Background: Monosodium urate (MSU) has been shown to promote inflammasome activation and interleukin-1beta (IL-1beta) secretion in monocyte/macrophages, but the cellular pathway and nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in synovial tissues, remain elusive. In this study, we investigated the effects of MSU on synovial fibroblasts to elucidate the process of MSU-mediated synovial inflammation. Methods: Human synovial fibroblasts were stimulated with MSU in the presence or absence of serum amyloid A (SAA). The cellular supernatants were analyzed by immunoblotting using anti-IL-1 or anti-caspase-1 antibodies. IL-1 or NLRP3 mRNA expressions were analyzed by real-time PCR or reverse transcription-PCR (RT-PCR) method. Results: Neither SAA nor MSU stimulation resulted in IL-1beta or interleukin-1 (IL-1 secretions and pro-IL-1beta processing in synovial fibroblasts. However, in SAA-primed synovial fibroblasts, MSU stimulation resulted in the activation of caspase-1 and production of active IL-1beta and IL-1. The effect of SAA on IL-1beta induction was impaired in cells by silencing NLRP3 using siRNA or treating with caspase-1 inhibitor. In addition, SAA induced the secretion of cathepsin B and NLRP3 mRNA expression in synovial fibroblasts. Conclusions: Our data demonstrates that exposure of human synovial fibroblasts to SAA promotes MSU-mediated caspase-1 activation and IL-1beta secretion in the absence of microbial stimulation. These findings provide insight into the molecular processes underlying the synovial inflammatory condition of gout.

Approaching the immunophysiology of steroid resistance

Rick Bucala — 2012-05-18T00:00:00Z

Wang et al. have investigated a mechanistic basis for resistance to steroid therapy in SLE patients. Their examination reveals significant differences in MIF-dependent expression of IkB, which is a critical cellular regulator of the broadly pro-inflammatory transcription factor, NF-kB. Their studies also suggest that MIF may be a clinically useful biomarker in SLE and support the therapeutic targeting of MIF as a means to reduce clinical steroid resistance.

T cell autoreactivity to citrullinated autoantigenic peptides in rheumatoid arthritis patients carrying HLA-DRB1 shared epitope alleles

Soi Law — 2012-05-17T00:00:00Z

IntroductionAnti-citrullinated peptide antibodies (ACPA) are found in rheumatoid arthritis (RA) patients with HLA-DR--chains encoding the shared epitope (SE) sequence. Citrullination can increase the immunogenicity of self-antigens, through increased binding affinity to SE-containing HLA-DR molecules. To characterize T cell autoreactivity towards citrullinated self-epitopes, we profiled responses of SE+ healthy controls and RA patients to citrullinated and unmodified epitopes of four autoantigens. Methods: We compared T cell proliferative and cytokines responses to citrullinated and native type II collagen 1237-1249, vimentin 66-78, aggrecan 84-103 and fibrinogen 79-91 in 4 SE+ healthy controls, and in 13 RA patients with disease for <1 or at least 4 years. Cytokine-producing cells were stained after incubation with peptide in the presence of Brefeldin-A. Results: Although proliferative responses were low, IL-6, IFN- and TNF were secreted by CD4+ T cells of SE+ RA patients and healthy controls, in response to citrullinated peptides. Patients with early RA were more likely to produce IL-6 in response to no epitope or to citrullinated aggrecan alone, while patients with longstanding RA were more likely to produce IL-6 to multiple epitopes. Cytokine-producing CD4+ T cells included CD45RO+ and CD45RO- and CD28+ and CD28- subsets in RA patients. Conclusions: Pro-inflammatory cytokines were produced by CD4+ T cells in SE+ individuals in response to citrullinated self-epitopes, of which citrullinated aggrecan was most immunogenic. Our data suggest that pro-inflammatory T cell responses towards citrullinated self-epitopes precede the development of ACPA, but that the T cell response matures with development of RA.

The role of Inflammation & Cardiovascular Disease Risk on Microvascular and Macrovascular Endothelial Function in Patients with Rheumatoid Arthritis: a Cross-sectional and Longitudinal Study

Aamer Sandoo — 2012-05-17T00:00:00Z

Background: Rheumatoid arthritis (RA) is associated with an increased risk of cardiovascular disease (CVD), and it has been postulated that RA disease-related inflammation contributes to endothelial dysfunction. The aim of the present work was to examine predictors (RA-related and CVD risk factors) and anti-tumour necrosis factor-alpha (anti-TNFalpha) treatment effects on endothelial function in different vascular beds. Methods: Microvascular endothelial function (Laser Doppler imaging with iontophoresis of acetylcholine and sodium-nitroprusside), and macrovascular endothelial function (flow-mediated dilatation and glyceryl-trinitrate-mediated dilatation) were analyzed in parallel with disease activity. Individual CVD risk factors and global CVD risk were assessed cross-sectionally in 99 unselected RA patients and longitudinally (baseline, 2 weeks and 3 months) in 23 RA patients commencing anti-TNFalpha therapy. Results: In this cross-sectional study, regression analyses revealed that markers of RA disease-related inflammation were not associated with microvascular or macrovascular endothelium-dependent function (P's > .05); global CVD risk inversely correlated with microvascular endothelium-dependent function (P < .01) and with macrovascular endothelium-independent function (P < .01). In the longitudinal study, only microvascular endothelium-dependent function showed an improvement following 2 weeks of anti-TNFalpha treatment when compared to baseline (437 +/- 247 vs. 319 +/- 217 (%), P = .001), but no association was evident between change in endothelial function and change in inflammatory markers. Conclusions: Classical CVD risk may influence endothelial function more than disease-related markers of inflammation in RA. Classical CVD risk factors and anti-TNFalpha medication have different effects on microvascular and macrovascular endothelial function, suggesting that combined CVD prevention approaches may be necessary. Prospective studies examining whether assessments of vascular function are predictive of long-term CV outcomes in RA are required.