The contribution of genes outside the major histocompatibility complex to susceptibility to ankylosing spondylitis

Colchicine-resistant sacroiliitis in a Japanese patient with familial Mediterranean fever

The articular involvement in patients with familial Mediterranean fever (FMF) represents a clinical characteristic of acute monoarthritis with pain and hydrarthrosis, which always resolves spontaneously. Colchicine prevents painful arthritis attacks in most FMF cases. Spondyloarthritis is rarely associated with Japanese patients with FMF. Here, we report a Japanese male patient with FMF-related axial joint involvement. A 43-year-old male Japanese patient who presented with recurrent febrile episodes with hip joint and back pain was referred to our hospital. He carried heterozygous variants in exon 2 (L110P/E148Q) of the MEFV gene. FMF was suspected, and oral administration of colchicine (1 mg/day) was initiated. Colchicine treatment improved his febrile attack with hip joint pain. He was diagnosed as having FMF based on the Tel-Hashomer diagnostic criteria for FMF since he fulfilled one major criterion (repeated febrile attack accompanied by hip joint pain) and one minor criterion (improvement with colchicine treatment). Although the human leucocyte antigen-B27 allele was not detected, sacroiliitis-related symptoms progressed despite the ongoing colchicine treatment. Salazosulphapyridine and methotrexate were administered in addition to colchicine; however, these treatments were not effective. Canakinumab treatment successfully resolved this unique aspect of sacroiliitis, and the patient was finally diagnosed with FMF-associated axial joint involvement.

Co-expression Network Analysis Reveals Key Genes Related to Ankylosing spondylitis Arthritis Disease: Computational and Experimental Validation

BACKGROUND

Ankylosing spondylitis (AS) is a type of arthritis which can cause inflammation in the vertebrae and joints between the spine and pelvis. However, our understanding of the exact genetic mechanisms of AS is still far from being clear.

OBJECTIVE

To study and find the mechanisms and possible biomarkers related to AS by surveying inter-gene correlations of networks.

MATERIALS AND METHODS

A weighted gene co-expression network was constructed among genes identified by microarray analysis, gene co-expression network analysis, and network clustering. Then receiver operating characteristic (ROC) curves were conducted to identify a significant module with the genes implicated in the AS pathogenesis. Real-time PCR was performed to validate the results of microarray analysis.

RESULTS

In the significant module obtained from the network analysis there were eight AS related genes (LSM3, MRPS11, NSMCE2, PSMA4, UBL5, RPL17, MRPL22 and RPS17) which have been reported in previous studies as hub genes. Further, in this module, eight significant enriched pathways were found with adjusted p-values < 0.001 consisting of oxidative phosphorylation, ribosome, nonalcoholic fatty liver disease, Alzheimer's, Huntington's, and Parkinson's diseases, spliceosome, and cardiac muscle contraction pathways which have been linked to AS. Furthermore, we identified nine AS related genes (UQCRB, UQCRH, UQCRHL, UQCRQ, COX7B, COX5B, COX6C, COX6A1 and COX7C) in these pathways which can play essential roles in controlling mitochondrial activity and pathogenesis of autoimmune diseases. Real-time PCR results showed that three genes including UQCRH, MRPS11, and NSMCE2 in AS patients were significantly differentially expressed compared with normal controls.

CONCLUSIONS

The results of the present study may contribute to understanding of AS molecular pathogenesis, thereby aiding the early prognosis, diagnosis, and effective therapies of the disease.

Genetically determined high activities of the TNF-alpha, IL23/IL17, and NFkB pathways were associated with increased risk of ankylosing spondylitis

Background

Ankylosing spondylitis (AS) results from the combined effects of susceptibility genes and environmental factors. Polymorphisms in genes regulating inflammation may explain part of the heritability of AS.

Methods

Using a candidate gene approach in this case-control study, 51 mainly functional single nucleotide polymorphisms (SNPs) in genes regulating inflammation were assessed in 709 patients with AS and 795 controls. Data on the patients with AS were obtained from the DANBIO registry where patients from all of Denmark are monitored in routine care during treatment with conventional and biologic disease modifying anti-rheumatic drugs (bDMARDs).

The results were analyzed using logistic regression (adjusted for age and sex).

Results

Nine polymorphisms were associated with risk of AS (p < 0.05). The polymorphisms were in genes regulating a: the TNF-α pathway (TNF -308 G > A (rs1800629), and − 238 G > A (rs361525); TNFRSF1A -609 G > T (rs4149570), and PTPN22 1858 G > A (rs2476601)), b: the IL23/IL17 pathway (IL23R G > A (rs11209026), and IL18–137 G > C (rs187238)), or c: the NFkB pathway (TLR1 743 T > C (rs4833095), TLR4 T > C (rs1554973), and LY96–1625 C > G (rs11465996)).

After Bonferroni correction the homozygous variant genotype of TLR1 743 T > C (rs4833095) (odds ratios (OR): 2.59, 95% confidence interval (CI): 1.48–4.51, p = 0.04), and TNFRSF1A -609 G > T (rs4149570) (OR: 1.79, 95% CI: 1.31–2.41, p = 0.01) were associated with increased risk of AS and the combined homozygous and heterozygous variant genotypes of TNF -308 G > A (rs1800629) (OR: 0.56, 95% CI: 0.44–0.72, p = 0.0002) were associated with reduced risk of AS.

Conclusion

We replicated associations between AS and the polymorphisms in TNF (rs1800629), TNFRSF1A (rs4149570), and IL23R (rs11209026). Furthermore, we identified novel risk loci in TNF (rs361525), IL18 (rs187238), TLR1 (rs4833095), TLR4 (rs1554973), and LY96 (rs11465996) that need validation in independent cohorts. The results suggest that genetically determined high activity of the TNF-α, IL23/IL17, and NFkB pathways increase risk of AS.

Healthcare Utilization and Direct Costs in Patients with Ankylosing Spondylitis Using a Large US Administrative Claims Database

Introduction

In addition to the considerable patient and societal burdens, the financial burdens of ankylosing spondylitis (AS) are substantial. Understanding both all-cause and AS-specific direct costs in patients with AS is important if we are to understand the financial impact on patients with AS and payers in the United States. This study assessed both all-cause and AS-specific healthcare utilization and direct costs in US patients with AS using administrative claims data.

Methods

Adults aged ≥ 18 years enrolled in the MarketScan^® Commercial and Medicare databases with ≥ 1 inpatient or ≥ 2 non-rule-out outpatient diagnoses of AS between January 1, 2013, and December 31, 2013, were included. Patients had continuous enrollment with medical and pharmacy benefits for ≥ 12 months before and after the index date (first diagnosis). Non-AS controls were matched up to 5:1 to patients with AS on age, geographic region, index calendar year, and sex. All-cause and AS-specific healthcare utilization and direct costs were measured during the follow-up period and reported as per patient per year.

Results

Patients with AS (N = 6679) had significantly higher rates of total all-cause inpatient admission (12% vs 6%), emergency department visits (23% vs 15%), nonhospital-based outpatient visits (100% vs 84%), hospital-based outpatient visits (68% vs 46%), other outpatient services (97% vs 81%), and medication use (97% vs 82%) compared with matched controls (N = 19,951). Patients with AS had approximately tenfold higher median total healthcare costs than matched controls ($24,978 vs $2139 per patient per year), largely driven by increased outpatient and pharmacy costs; P < 0.05 for all comparisons. The median (IQR) total AS-specific healthcare costs were $10,250 ($774, $28,824).

Conclusion

In this analysis of claims data, increased outpatient and pharmacy costs were key contributors to higher all-cause total healthcare costs in US patients with AS.

Funding

Novartis Pharmaceuticals Corporation, East Hanover, NJ.

Electronic supplementary material

The online version of this article (10.1007/s40744-018-0124-4) contains supplementary material, which is available to authorized users.

Evaluation of the comorbidity burden in patients with ankylosing spondylitis using a large US administrative claims data set

Comorbidities among US patients with ankylosing spondylitis (AS) are inadequately understood. This study compared the prevalence and incidence of comorbidities between patients with AS and matched controls using national claims databases. Adults enrolled in the MarketScan Commercial and Medicare databases with ≥ 1 inpatient or ≥ 2 non-rule-out outpatient diagnoses of AS between January 1, 2012 and December 31, 2014 were included. Patients had to have ≥ 1 AS diagnosis in 2013; the first AS diagnosis in 2013 was assigned as the index date. Control patients without AS were matched to AS patients on age, geographic region, index calendar year, and sex. Comorbidities were evaluated in AS patients and matched controls during the baseline and follow-up periods (before and after the index date, respectively). Hazard ratios of developing new comorbidities were estimated using Cox proportional hazard models adjusted for patients’ characteristics. A total of 6679 patients with AS were matched to 19,951 control patients. In addition to extra-articular manifestations of AS (inflammatory bowel disease [IBD], psoriasis, uveitis), a higher proportion of AS patients had asthma, cardiovascular disease, depression, dyslipidemia, gastrointestinal ulcers, malignancies, multiple sclerosis, osteoporosis, sleep apnea, and spinal fractures during the baseline period than matched controls. After AS diagnosis, a higher proportion of patients developed newly diagnosed cases of cardiovascular diseases, depression, osteoporosis, spinal fracture, IBD, psoriasis, and uveitis than matched controls. In this real-world, US claims-based study, patients with AS were shown to have significantly more comorbidities than matched controls.

Evaluation of the comorbidity burden in patients with ankylosing spondylitis treated with tumour necrosis factor inhibitors using a large administrative claims data set

Objectives

Comorbidity incidence rates among US patients with ankylosing spondylitis (AS) treated with tumour necrosis factor inhibitors (TNFis) are inadequately understood. This study compared the relative occurrence of comorbidities between patients with AS treated with TNFis and those not treated with TNFis.

Methods

Adults aged ≥18 years enrolled in the MarketScan Commercial and Medicare Supplemental databases with a diagnosis of AS between 1 January 2008 and 30 June 2015 were eligible. Patients were divided into two groups, those treated with TNFis (TNFi users) and those not treated with TNFis (TNFi nonusers) during the 12 months after the index date, defined as the date of first TNFi treatment or a randomly assigned date for TNFi nonusers. Patients had to have continuous enrolment for 24 months with no AS diagnosis or TNFi therapy pre‐index and a follow‐up period of ≥12 months postindex. The incidence of new comorbidities was evaluated in patients and adjusted for baseline characteristics.

Key findings

A total of 3077 TNFi users and 3830 TNFi nonusers were included. A higher proportion of TNFi users had a new diagnosis of inflammatory bowel disease (hazard ratio [HR], 2.00), including Crohn's disease (HR, 2.45) and ulcerative colitis (HR, 1.65), as well as uveitis (HR, 1.68) and sleep apnoea (HR, 1.21) after initiation of TNFi therapy than TNFi nonusers.

Conclusions

Patients with AS treated with TNFis had higher incidence rates of IBD, uveitis and sleep apnoea after initiation of TNFi therapy than patients not treated with TNFi therapy.

The regulatory network behind MHC class I expression

The MHC class I pathway, presenting endogenously derived peptides to T lymphocytes, is hijacked in many pathological conditions. This affects MHC class I levels and peptide presentation at the cell surface leading to immune escape of cancer cells or microbes. It is therefore important to identify the molecular mechanisms behind MHC class I expression, processing and antigen presentation. The identification of NLRC5 as regulator of MHC class I transcription was a huge step forward in understanding the transcriptional mechanism involved. Nevertheless, many questions concerning MHC class I transcription are yet unsolved. Here we illuminate current knowledge on MHC class I and NLRC5 transcription, we highlight some remaining questions and discuss the use of quickly developing high-content screening tools to reveal unknowns in MHC class I transcription in the near future.

Predicting pathway cross-talks in ankylosing spondylitis through investigating the interactions among pathways

Given that the pathogenesis of ankylosing spondylitis (AS) remains unclear, the aim of this study was to detect the potentially functional pathway cross-talk in AS to further reveal the pathogenesis of this disease. Using microarray profile of AS and biological pathways as study objects, Monte Carlo cross-validation method was used to identify the significant pathway cross-talks. In the process of Monte Carlo cross-validation, all steps were iterated 50 times. For each run, detection of differentially expressed genes (DEGs) between two groups was conducted. The extraction of the potential disrupted pathways enriched by DEGs was then implemented. Subsequently, we established a discriminating score (DS) for each pathway pair according to the distribution of gene expression levels. After that, we utilized random forest (RF) classification model to screen out the top 10 paired pathways with the highest area under the curve (AUCs), which was computed using 10-fold cross-validation approach. After 50 bootstrap, the best pairs of pathways were identified. According to their AUC values, the pair of pathways, antigen presentation pathway and fMLP signaling in neutrophils, achieved the best AUC value of 1.000, which indicated that this pathway cross-talk could distinguish AS patients from normal subjects. Moreover, the paired pathways of SAPK/JNK signaling and mitochondrial dysfunction were involved in 5 bootstraps. Two paired pathways (antigen presentation pathway and fMLP signaling in neutrophil, as well as SAPK/JNK signaling and mitochondrial dysfunction) can accurately distinguish AS and control samples. These paired pathways may be helpful to identify patients with AS for early intervention.

A Genome-Wide SNP Linkage Analysis Suggests a Susceptibility Locus on 6p21 for Ankylosing Spondylitis and Inflammatory Back Pain Trait

Objectives

To screen susceptibility loci for ankylosing spondylitis (AS) using an affected-only linkage analysis based on high-density single nucleotide polymorphisms (SNPs) in a genome-wide manner.

Patients and Methods

AS patients from ten families with Cantonese origin of China were enrolled in the study. Blood samples were genotyped using genomic DNA derived from peripheral blood leukocytes by Illumina HumanHap 610-Quad SNP Chip. Genotype data were generated using the Illumina BeadStudio 3.2 software. PLINK package was used to remove non-autosomal SNPs and to further eliminate markers of typing errors. An affected-only linkage analysis was carried out using both non-parametric and parametric linkage analyses, as implemented in MERLIN.

Result

Seventy-eight AS patients (48 males and 30 females, mean age: 39±16 years) were enrolled in the study. The mean age of onset was 23±10 years and mean duration of disease was 16.7±12.2 years. Iritis (2/76, 2.86%), dactylitis (5/78, 6.41%), hip joint involvement (9/78, 11.54%), peripheral arthritis (22/78, 28.21%), inflammatory back pain (IBP) (69/78, 88.46%) and HLA-B27 positivity (70/78, 89.74%) were observed in these patients. Using non-parameter linkage analysis, we found one susceptibility locus for AS, IBP and HLA-B27 in 6p21 respectively, spanning about 13.5Mb, 20.9Mb and 21.2Mb, respectively No significant results were found in the other clinical trait groups including dactylitis, hip involved and arthritis. The identical susceptibility locus region spanning above 9.44Mb was detected in AS IBP and HLA-B27 by the parametric linkage analysis.

Conclusion

Our genome-wide SNP linkage analysis in ten families with ankylosing spondylitis suggests a susceptibility locus on 6p21 in AS, which is a risk locus for IBP in AS patients.

New insights toward the pathogenesis of ankylosing spondylitis; genetic variations and epigenetic modifications

Ankylosing spondylitis (AS) is a chronic inflammatory autoimmune disease, characterized by typically an axial arthritis. AS is the prototype of a group of disorders called spondyloarthropathies, which is believed to have common clinical manifestations and genetic predisposition. To date, the exact etiology of AS remains unclear. Over the past few years, however, the role of genetic susceptibility and epigenetic modifications caused through environmental factors have been extensively surveyed with respect to the pathogenesis of AS, resulted in important advances. This review article focuses on the recent advances in the field of AS research, including HLA and non-HLA susceptibility genes identified in genome-wide association studies (GWAS), and aberrant epigenetic modifications of gene loci associated with AS. HLA genes most significantly linked with AS susceptibility include HLA-B27 and its subtypes. Numerous non-HLA genes such as those in ubiquitination, aminopeptidases and MHC class I presentation molecules like ERAP-1 were also reported. Moreover, epigenetic modifications occurred in AS has been summarized. Taken together, the findings presented in this review attempt to explain the circumstance by which both genetic variations and epigenetic modifications are involved in triggering and development of AS. Nonetheless, several unanswered dark sides continue to clog our exhaustive understanding of AS. Future researches in the field of epigenetics should be carried out to extend our vision of AS etiopathogenesis.

Decreased programmed death-1 expression on the T cells of patients with ankylosing spondylitis

BACKGROUND

Programmed death-1 (PD-1) plays a vital role in down-modulating immune responses and maintaining peripheral tolerance.

METHODS

The authors have investigated the inducible expression of PD-1 on activated T cells from patients with ankylosing spondylitis (AS). Thirty patients with AS and 31 unrelated healthy controls (HCs) were recruited in this study. The expression of PD-1 on T cells harvested from nonstimulated (t0) or stimulated cultures with phytohemagglutinin for 24 hours (t24) was determined by flow cytometry. The multiple levels of the PD-1 expression on stimulated and nonstimulated cells from each individual's sample (t24/t0) represented as the degree of the inducible effect on PD-1 expression.

RESULTS

The expression of PD-1 on nonstimulated T cells presented no significant difference between AS group and HC group (P > 0.05). After stimulation, the degree of effect on PD-1 expression of CD4+, CD4+CD25+, CD4+CD25 high, CD4+CD25 low and CD4+CD25- T cells were significantly lower in patients with AS than those in HC group (1.9 ± 0.9 versus 3.6 ± 2.3, 9.7 ± 7.4 versus 17.8 ± 12.6, 87.8 ± 48.6 versus 157.3 ± 117.0, 3.7 ± 1.4 versus 7.3 ± 2.4, 0.5 ± 0.3 versus 1.1 ± 0.6, respectively, P < 0.05). However, there was no significant difference of the effect on all lymphocytes and CD8+ T cells between patients with AS and HCs (P > 0.05).

CONCLUSIONS

The decreased inducible expression of PD-1 on active T lymphocytes, especially on CD4+CD25 high and CD4+CD25+ T cells, may be one of important factors involved in the development of AS.

Usage of Conventional PCR Technology for the Detection of HLA-B27 Allele: A Significant Molecular Marker of Ankylosing Spondylitis

Ankylosing spondylitis is a chronic inflammatory disease that has been linked to the human leukocyte antigen class I allele HLA-B27. More than 90 % of patients with ankylosing spondylitis possess the HLA-B27 allele, but only 1 % of people with HLA-B27 develop the disease. Ankylosing spondylitis predominately affects young males. The present study was planned to find out the involvement of HLA-B27 specific allele in relation to age and sex in symptomatic suspected patients of ankylosing spondylitis using conventional PCR technology. Forty symptomatic patients of ankylosing spondylitis were included in the present study. SSP-PCR technique was used to detect the HLA-B27 specific allele. This study showed (out of 40 symptomatic suspected cases of ankylosing spondylitis only 12 patients were detected positive with HLA-B27 allele, while remaining 28 were negative) that the positivity rate for ankylosing spondylitis with HLA-B27 allele is low. Furthermore, it was observed that the males above 50 years are more prone to develop AS with HLA-B27 specific allele. It could be concluded that the conventional PCR technology is a rapid, sensitive, and confirmatory method for the diagnosis of ankylosing spondylitis.

Genetic polymorphisms inside and outside the MHC improve prediction of AS radiographic severity in addition to clinical variables

OBJECTIVE

The aim of this study was to analyse if single nucleotide polymorphisms (SNPs) inside and outside the MHC region might improve the prediction of radiographic severity in AS.

METHODS

A cross-sectional multi-centre study was performed including 473 Spanish AS patients previously diagnosed with AS following the Modified New York Criteria and with at least 10 years of follow-up from the first symptoms of AS. Clinical variables and 384 SNPs were analysed to predict radiographic severity [BASRI-total (BASRI-t) corrected for the duration of AS since first symptoms] using multivariate forward logistic regression. Predictive power was measured by the area under the receiver operating characteristic curve (AUC), specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV).

RESULTS

The model with the best fit measured radiographic severity as the BASRI-t 60th percentile and combined eight variables: male gender, older age at disease onset and six SNPs at ADRB1 (rs1801253), NELL1 (rs8176785) and MHC (rs1634747, rs9270986, rs7451962 and rs241453) genes. The model predictive power was defined by AUC = 0.76 (95% CI 0.71, 0.80), being significantly better than the model with only clinical variables, AUC = 0.68 (95% CI 0.63, 0.73), P = 0.0004. Internal split-sample analysis proved the validation of the model. Patient genotype for SNPs outside the MHC region, inside the MHC region and clinical variables account for 26, 38 and 36%, respectively, of the explained variability on radiographic severity prediction.

CONCLUSION

Prediction of radiographic severity in AS based on clinical variables can be significantly improved by including SNPs both inside and outside the MHC region.

Blood-based biomarkers can differentiate ulcerative colitis from Crohn's disease and noninflammatory diarrhea

BACKGROUND

Blood gene expression profiling has been used in several studies to identify patients with a number of conditions and diseases. A blood test with the ability to differentiate Crohn's disease (CD) from ulcerative colitis (UC) and noninflammatory diarrhea would be useful in the clinical management of these diseases.

METHODS

Affymetrix U133Plus 2.0 GeneChip oligonucleotide arrays were used to generate whole blood gene expression profiles for 21 patients with UC, 24 patients with CD, and 10 control patients with diarrhea, but without colonic pathology.

RESULTS

A supervised learning method (logistic regression) was used to identify specific panels of probe sets which were able to discriminate between UC and CD and from controls. The UC panel consisted of the four genes, CD300A, KPNA4, IL1R2, and ELAVL1; the CD panel comprised the four genes CAP1, BID, NIT2, and NPL. These panels clearly differentiated between CD and UC.

CONCLUSIONS

Gene expression profiles from blood can differentiate patients with CD from those with UC and from noninflammatory diarrheal disorders.

Whole blood transcriptional profiling in ankylosing spondylitis identifies novel candidate genes that might contribute to the inflammatory and tissue-destructive disease aspects

INTRODUCTION

A number of genetic-association studies have identified genes contributing to ankylosing spondylitis (AS) susceptibility but such approaches provide little information as to the gene activity changes occurring during the disease process. Transcriptional profiling generates a 'snapshot' of the sampled cells' activity and thus can provide insights into the molecular processes driving the disease process. We undertook a whole-genome microarray approach to identify candidate genes associated with AS and validated these gene-expression changes in a larger sample cohort.

METHODS

A total of 18 active AS patients, classified according to the New York criteria, and 18 gender- and age-matched controls were profiled using Illumina HT-12 whole-genome expression BeadChips which carry cDNAs for 48,000 genes and transcripts. Class comparison analysis identified a number of differentially expressed candidate genes. These candidate genes were then validated in a larger cohort using qPCR-based TaqMan low density arrays (TLDAs).

RESULTS

A total of 239 probes corresponding to 221 genes were identified as being significantly different between patients and controls with a P-value <0.0005 (80% confidence level of false discovery rate). Forty-seven genes were then selected for validation studies, using the TLDAs. Thirteen of these genes were validated in the second patient cohort with 12 downregulated 1.3- to 2-fold and only 1 upregulated (1.6-fold). Among a number of identified genes with well-documented inflammatory roles we also validated genes that might be of great interest to the understanding of AS progression such as SPOCK2 (osteonectin) and EP300, which modulate cartilage and bone metabolism.

CONCLUSIONS

We have validated a gene expression signature for AS from whole blood and identified strong candidate genes that may play roles in both the inflammatory and joint destruction aspects of the disease.

ERAP1 Is Associated with Ankylosing Spondylitis in Han Chinese

Objective.

Genetic components play important roles in the incidence and development of ankylosing spondylitis (AS). Aminopeptidase regulator of tumor necrosis factor receptor shedding 1 (ERAP1) was recently found to be associated with AS in North American and British cohorts. We evaluated whether ERAP1 is associated with AS in a Chinese Han population.

Methods.

A sample of 50 patients and 50 healthy controls was recruited for preliminary screening for informative single-nucleotide polymorphisms (SNP). Then 6 SNP of suggestive significance in the initial screening were followed up in a large sample of 471 patients with AS and 456 ethnically matched controls. Diagnosis of AS followed the 1984 modified New York criteria. Linkage disequilibrium coefficient (D’ and r2) and haplotypes were estimated by Haploview.

Result.

Two SNP (rs27434, p = 0.00039, and rs27529, p = 0.0083) in ERAP1 other than that reported previously were found to be significantly associated with AS. Haplotype analysis using 5 SNP within 1 linkage disequilibrium block identified 2 risk haplotypes (GATGT and GACGT) and 1 protective haplotype (GGTGT) for AS.

Conclusion.

Our study demonstrated that 2 novel SNP in ERAP1 were associated with AS in the Han Chinese population, suggesting that ERAP1 might confer genetic risk for AS in Han Chinese through the common mechanism shared by different populations, although the AS-associated SNP in ERAP1 might be population-specific.

The genetic background of ankylosing spondylitis

It has long been known that the major histocompatibility complex (MHC) is essentially involved in genetic susceptibility to ankylosing spondylitis (AS). The HLA-B27 antigen has been accounted for 20 to 50% of the total genetic risk for this disease. However, susceptibility to AS cannot be fully explained by associations with the MHC. Recent studies including linkage analyses as well as candidate gene and, most recently, genome-wide association studies indicate significant associations of the interleukin-1 gene cluster, interleukin-23 receptor and ARTS1 genes as well as other possible loci with AS. In the murine model of proteoglycan-induced spondylitis, two susceptibility loci termed Pgis1 and Pgis2 were identified. Thus, AS is not a single-gene disease and the involvement of multiple non-MHC genes may account for the individual as well as geographical differences seen in AS.

Association ofARTS1Gene Polymorphisms with Ankylosing Spondylitis in the Hungarian Population: The rs27044 Variant Is Associated with HLA-B*2705 Subtype in Hungarian Patients with Ankylosing Spondylitis

Objective.

Associations have been found between ankylosing spondylitis (AS) and polymorphisms in the aminopeptidase regulator of TNFR1 shedding (ARTS1) gene. We studied the association of 5 polymorphisms within theARTS1gene with AS in Hungarian patients. We also investigated the prevalence of HLA-B27 subtypes in the Hungarian population.

Methods.

A case-control study including 297 patients with AS and 200 sex and ethnically matched healthy controls was performed. Patients and controls were genotyped for rs27044, rs17482078, rs10050860, rs30187, and rs2287987 single-nucleotide polymorphisms using real-time polymerase chain reaction (PCR) allelic discrimination. HLA-B27 subtypes were determined with PCR sequence-specific primer (PCR-SSP) technique.

Results.

We observed a significant increase in the minor allele frequency of rs27044 (p = 0.001) in the AS group compared to controls. The minor allele frequencies of rs10050860 (p = 0.006) and rs2287987 (p = 0.002) showed a significant decrease in AS patients compared to controls. Haplotype analysis revealed association of 2 ARTS1 haplotypes with AS in the Hungarian population. We found that HLA-B*2705 was the predominant subtype in Hungarians with AS. Carriage of the G allele of rs27044 was significantly associated with the HLA-B*2705 subtype (p = 0.009) in AS patients.

Conclusion.

We confirmed reported associations ofARTS1gene polymorphisms with AS in a Hungarian cohort study. We found HLA-B*2705 as the predominant subtype in Hungarian AS patients in accord with other studies on Caucasian populations. Our results suggest that theARTS1gene variants together with HLA-B27 strongly contribute to disease susceptibility in patients with AS.

What epidemiology has told us about risk factors and aetiopathogenesis in rheumatic diseases

This article will review how epidemiological studies have advanced our knowledge of both genetic and environmental risk factors for rheumatic diseases over the past decade. The major rheumatic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus, scleroderma, osteoarthritis, gout, and fibromyalgia, and chronic widespread pain, will be covered. Advances discussed will include how a number of large prospective studies have improved our knowledge of risk factors, including diet, obesity, hormones, and smoking. The change from small-scale association studies to genome-wide association studies using gene chips to reveal new genetic risk factors will also be reviewed.

The STAT4 gene influences the genetic predisposition to systemic sclerosis phenotype

The aim of this study was to investigate the possible role of STAT4 gene in the genetic predisposition to systemic sclerosis (SSc) susceptibility or clinical phenotype. A total of 1317 SSc patients [896 with limited cutaneous SSc (lcSSc) and 421 with diffuse cutaneous SSc (dcSSc)] and 3113 healthy controls, from an initial case-control set of Spanish Caucasian ancestry and five independent cohorts of European ancestry (The Netherlands, Germany, Sweden, Italy and USA), were included in the study. The rs7574865 polymorphism was selected as STAT4 genetic marker. We observed that the rs7574865 T allele was significantly associated with susceptibility to lcSSc in the Spanish population [P = 1.9 x 10(-5) odds ratio (OR) 1.61 95% confidence intervals (CI) 1.29-1.99], but not with dcSSc (P = 0.41 OR 0.84 95% CI 0.59-1.21). Additionally, a dosage effect was observed showing individuals with rs7574865 TT genotype higher risk for lcSSc (OR 3.34, P = 1.02 x 10(-7) 95% CI 2.11-5.31). The association of the rs7574865 T allele with lcSSc was confirmed in all the replication cohorts with different effect sizes (OR ranging between 1.15 and 1.86), as well as the lack of association of STAT4 with dcSSc. A meta-analysis to test the overall effect of the rs7574865 polymorphism showed a strong risk effect of the T allele for lcSSc susceptibility (pooled OR 1.54 95% CI 1.36-1.74; P < 0.0001). Our data show a strong and reproducible association of the STAT4 gene with the genetic predisposition to lcSSc suggesting that this gene seems to be one of the genetic markers influencing SSc phenotype.

Regulation of interleukin-12/interleukin-23 production and the T-helper 17 response in humans

Interleukin-12 (IL-12) and IL-23 share a common chain. Yet, their production in response to pathogens is differentially regulated, and their functions are distinct and often antithetic. IL-12 is involved in the induction or amplification of the T-helper (Th) type 1 response, whereas IL-23 has been associated with the generation of the Th17 response and IL-17 production. Mycobacterium tuberculosis and yeast zymosan induce IL-23, but in the absence of other stimuli, no IL-12 is induced in human dendritic cells (DCs). The stimulation of IL-23 by M. tuberculosis was mostly explained by the triggering of Toll-like receptor (TLR2) and the cytoplasmic receptor nucleotide oligomerization domain (NOD)-containing protein 2, whereas zymosan induces IL-23 primarily by stimulating the beta-glucan receptor dectin-1 alone or in combination with TLR2. IL-23, IL-6, transforming growth factor (TGF-beta1), and IL-1beta in supernatants from activated human DCs induce human naive CD4(+) T cells to produce IL-17. These data are consistent with various recent reports that TGF-beta is an inducer of IL-17 production both in human and in mouse cells. However, IL-1 is necessary in combination with some or all of the other cytokines to induce IL-17 production in human T cells. The ability of various stimuli to induce Th17 cells depends not only on their induction of IL-23, IL-6, and TGF-beta production in DCs but also on their ability to activate directly or indirectly the inflammasome and to induce IL-1beta.

GWA studies: rewriting the story of IBD

Genome-wide association (GWA) studies are substantially improving our understanding of the molecular pathways leading to inflammatory bowel diseases (IBD). This is a result of the nature of these studies, which are comprehensive - leading to a dramatic increase in the number of validated genetic risk factors - and unbiased - leading to the identification of novel pathways not previously suspected in IBD. Such discoveries are not only driving the functional studies to understand the mechanisms by which genetic variants modify an individual's susceptibility to disease, but also hold the promise of guiding the development of more effective treatment strategies. In this review, we discuss how GWA studies are enabling us to rewrite the story of IBD pathogenesis, focusing on the interleukin-23 and autophagy pathways.

Pathophysiology of ankylosing spondylitis: what's new?

Ankylosing spondylitis is a chronic inflammatory joint disease that predominantly affects the sacroiliac joints and spine. Its pathophysiology remains one of the most vexing enigmas of rheumatology. However, new insights have been provided by the recent identification of susceptibility genes other than HLA-B27; evidence of a pivotal role for several proinflammatory cytokines including interleukins 23 and 17; and the recognition that inflammation and structural progression proceed separately from each other.