Association of HLA-B27 and ERAP1 with ankylosing spondylitis susceptibility in Beijing Han Chinese

Exploring the Pathogenesis of Spondylarthritis beyond HLA-B27: A Descriptive Review

Spondylarthritis (SpA) is a chronic inflammatory condition that encompasses damage to the axial or peripheral skeleton, accompanied by specific extra-articular symptoms. Within this group, Ankylosing Spondylitis stands out as the hallmark member. Although the heritability of Ankylosing Spondylitis is estimated to be over 95%, only a portion of the heritability has been explained, with HLA-B27 accounting for 20.1% of it; therefore, ongoing research endeavors are currently concentrated on investigating the potential participation of different entities in the development of the disease. Genome-wide association studies have led to significant advances in our understanding of the genetics of SpA. In this descriptive review, we delve into the pathogenesis of Spondylarthritis beyond HLA-B27. We summarize the latest research on the potential participation of various entities in the development of the disease, including other genetic loci, immune dysregulation, microbiota, and environmental factors. The multifactorial nature of SpA and the complex interplay of genetic, immunological, and environmental factors are being increasingly recognized; therefore, it is of paramount importance to consider a holistic approach to comprehend the pathogenesis of SpA in order to identify novel therapeutic targets.

miRNAs dysregulation in ankylosing spondylitis: A review of implications for disease mechanisms, and diagnostic markers

Epigenetic processes, including non-coding RNA, histone modifications, and DNA methylation, play a vital role in connecting the environment to the development of a disorder, especially when there is a favorable genetic background. Ankylosing Spondylitis (AS) is a chronic type of spinal arthritis that highlights the significance of epigenetics in diseases related to autoimmunity and inflammation. MicroRNAs (miRNAs) are small non-coding RNAs that are involved in both normal and aberrant pathological and physiological gene expression. This study focuses on the pathophysiological pathways to clarify the role of miRNAs in AS. We have conducted a thorough investigation of the involvement of miRNAs in several processes, including inflammation, the production of new bone, T-cell activity, and the regulation of pathways such as BMP, Wnt, and TGFβ signaling. Undoubtedly, miRNAs play a crucial role in enhancing our comprehension of the pathophysiology of AS, and their promise as a therapeutic strategy is quickly expanding.

Association of a single nucleotide polymorphism (rs27434) in the ERAP1 gene with plural tissue weight

Our study was designed to examine the correlation between single nucleotide polymorphism (SNP) in the endoplasmic reticulum aminopeptidase 1 (ERAP1) gene, specifically focusing on rs27434, and plural tissue weight. We conducted this investigation using autopsy samples from the Japanese population. Blood samples were collected from 178 Japanese subjects who had undergone autopsies in Shimane Prefecture. Genomic DNA was subsequently extracted from these samples. SNP (rs27434, G＞A substitution) was analyzed by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) analysis. In the present study, rs27434 exhibited a statistically significant association with brain weight (g) in both female and male individuals. Among males, rs27434 displayed significant relationships with liver weight (g), and body surface area (m2). In females, rs27434 was significantly related to the length of the appendix. Across both genders, individuals with GA and AA genotypes tended to exhibit higher levels in these respective measurements compared to those with the GG genotype. These results suggest that genetic variant of ERAP1 gene may influence the weight of the organs. To the best of our knowledge, this is the first study investigating the interaction between the association of rs27434 in the ERAP1 gene and data routinely measured at autopsy, such as tissue weight. However, conducting further investigations with larger population samples could provide more comprehensive insights to clarify this issue.

Shedding Light on the Role of ERAP1 in Axial Spondyloarthritis

Spondyloarthritis (SpA) is a multifactorial chronic inflammatory disease affecting the axial skeleton (axSpA) and/or peripheral joints (p-SpA) and entheses. The disease's pathogenesis depends on genetic, immunological, mechanical, and environmental factors. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme that shapes the peptide repertoire presented by major histocompatibility complex (MHC) class I molecules. Genome-wide association studies (GWAS) have identified different single nucleotide polymorphisms (SNPs) in ERAP1 that are associated with several autoimmune diseases, including axSpA. Therefore, a deeper understanding of the ERAP1 role in axSpA could make it a potential therapeutic target for this disease and offer greater insight into its impact on the immune system. Here, we review the biological functions and structure of ERAP1, discuss ERAP1 polymorphisms and their association with axSpA, highlight the interaction between ERAP1 and human leukocyte antigen (HLA)-B27, and review the association between ERAP1 SNPs and axSpA clinical parameters.

Analysis of N6-Methyladenosine RNA Methylation Regulators in Diagnosis and Distinct Molecular Subtypes of Ankylosing Spondylitis

The most frequent internal modification in eukaryotic mRNA is N6-methyladenosine (m6A). However, what we know about the m6A regulators in Ankylosing spondylitis (AS) is still limited. In our study, eight distinct m6A regulators were selected utilizing Differentially Expressed Gene (DEG) analysis of the Gene Expression Omnibus GSE73754 dataset for making comparisons between AS (Ankylosing spondylitis) and non-AS patients. The random forest model and the nomogram model were used to screen the eight candidate m6A regulators and evaluate their prediction accuracy for the occurrence of AS. Furthermore, based on the selected m6A regulators, the AS patients were divided into two subgroups, and we applied principal component analysis algorithms to calculate their m6A score and evaluate the m6A patterns. Our findings revealed that patients in cluster A were linked to activated CD4 T cell immunity and activated CD8 T cell immunity. With its major contributions in the area of immunology, our research in m6A patterns may benefit the future diagnosis and treatment strategies of AS.

Spondyloarthritis: How far are we from precision medicine?

Spondyloarthritis (SpA) is a family of heterogenous diseases consisting of different phenotypes. The exact disease mechanism remains unclear but evidence shows the complex pathophysiology with interplay between genome, microbiome, and immunome. Biologic DMARDs have markedly improved patients' disease control and quality of life. However, treatment response varies among patients. There is a growing need to identify biomarkers for the diagnosis, prognosis, prevention, and treatment of SpA. Genomic studies have been the research focus in the past two decades and have identified important genes involved in SpA. In recent years, emerging evidence supports the link between gut and joint inflammation in SpA, in which the role of gut microbiome in SpA is of great interest. Herein, potential genetic and gut microbial biomarkers for predicting treatment response are discussed. Novel strategies targeting dysbiosis in SpA are also summarized. These results represent a significant step toward precision medicine for patients with SpA.

Associations between ERAP1 polymorphisms and ankylosing spondylitis susceptibility in HLA-B27 positive population: a Meta-analysis and bioinformatics analysis

Human leukocyte antigen (HLA)-B27 confers a key role in ankylosing spondylitis (AS) susceptibility. Endoplasmic reticulum aminopeptidase 1 (ERAP1) polymorphisms are associated with AS susceptibility in common population. In this study we intended to evaluate the possible association between ERAP1 polymorphisms and AS susceptibility in HLA-27 positive population. Data were collected from Pubmed, Embase, and Cochrane databases. The pooled odds ratios and 95% confidence intervals of the minor allele of each locus were calculated to appraise the associations under ERAP1 polymorphisms and AS in HLA-B27 positive population. Bioinformatics analysis was performed to explore the underlying mechanism. Four studies were included in this meta-analysis. There was a significant association between the minor allele of rs2287987 and reducing the risk of developing AS in HLA-B27 positive population. But there was no significant association between the minor allele of rs30187, rs27044, rs10050860 and rs17482078 and AS susceptibility. According to HaploReg, 5 motifs changed for rs2287987 were found. The eQTL analysis demonstrated that rs2287987 may influence ERAP1 expression. Rs2287987 in ERAP1 may have small influence on AS susceptibility in HLA-B27 positive population. Bioinformatics analysis indicated that the altered motifs and the change of EARP1 expression may influence the AS susceptibility.

Predominant frequency of HLA-B*27 in patients with ankylosing spondylitis in southeastern China

OBJECTIVES

This study was to investigate the polymorphism and distribution of alleles of HLA-B*27 in patients with ankylosing spondylitis (AS) in Han population of southeastern China.

METHODS

A total of 89 peripheral blood samples from southeastern Chinese Han patients with AS that diagnosed according to Modified New York criteria were subtyped using the high-resolution PCR-SSP.Exon 2-3 of HLA-B*27 gene was amplified and sequenced to further confirm the HLA-B*27 subtype.

RESULTS

The frequency of HLA-B*27 was 99.87% in AS patients. Three subtypes, HLA-B*2704, HLA-B*2705, and HLA-B*2706 were identified. The frequencies for these three alleles were HLA-B*2704 in 84/88 (95.46%), HLA-B*2705 in 3/88(3.41%), and HLA-B*2706 in 1/88 (1.13%) of the HLA-B*27 positive patients, respectively.

CONCLUSIONS

Our study shows that HLA-B*2704 has an overwhelming frequency in southeastern Chinese Han AS patients. A combined analysis including previous studies of HLA-B*27-subtype distributions in Chinese Han populations showed that HLA-B*2704 may originate from the southern Han and then migrate and spread to the northern areas, and HLA-B*2705 show the opposite result.

Conformational dynamics linked to domain closure and substrate binding explain the ERAP1 allosteric regulation mechanism

The endoplasmic-reticulum aminopeptidase ERAP1 processes antigenic peptides for loading on MHC-I proteins and recognition by CD8 T cells as they survey the body for infection and malignancy. Crystal structures have revealed ERAP1 in either open or closed conformations, but whether these occur in solution and are involved in catalysis is not clear. Here, we assess ERAP1 conformational states in solution in the presence of substrates, allosteric activators, and inhibitors by small-angle X-ray scattering. We also characterize changes in protein conformation by X-ray crystallography, and we localize alternate C-terminal binding sites by chemical crosslinking. Structural and enzymatic data suggest that the structural reconfigurations of ERAP1 active site are physically linked to domain closure and are promoted by binding of long peptide substrates. These results clarify steps required for ERAP1 catalysis, demonstrate the importance of conformational dynamics within the catalytic cycle, and provide a mechanism for the observed allosteric regulation and Lys/Arg528 polymorphism disease association.

Ankylosing Spondylitis

The seronegative spondyloarthropathies are a group of autoimmune inflammatory diseases lacking rheumatoid factor or antinuclear antibody in their serum. They include ankylosing spondylitis (AS), reactive arthritis, psoriatic arthritis, spondylitis associated with Crohn's disease and ulcerative colitis, and undifferentiated spondyloarthropathies. Inflammation mostly affects the axial joints, entheses, and extra-articular structures such as uveal tract, gastrointestinal tract, mucocutaneous tissue, and heart. Uveitis is the most common extra-articular manifestation. Spondyloarthropathies, especially AS, have a strong association with the presence of Human Leukocyte Antigen (HLA)-B27 gene. AS happens earlier in HLA-B27 patients and men are more prone to the disease. Uveitis, typically unilateral non-granulomatous acute anterior uveitis, occurs in up to 50% of the patients with AS. HLA-B27 positivity correlates with more frequent flare-ups. Conjunctivitis and scleritis are rare ocular manifestations of AS. To establish the diagnosis of AS, at least one clinical and one radiologic parameter are required for definitive diagnosis. Magnetic resonance imaging (MRI) or bone scan can help early detection of the axial skeleton inflammation. The course of eye and joint involvement are not correlated. Short-term treatment with topical corticosteroids and cycloplegic agents control the uveitis attack. In resistant cases, local or systemic therapy with corticosteroids are recommended. NSAIDs, disease-modifying anti-rheumatic drugs (DMARDs), methotrexate, azathioprine, anti-IL-17A monoclonal antibodies, and TNF-α antagonists are effective treatments for ocular and systemic manifestations of AS. If not treated adequately, uveitis may become recalcitrant and extend posteriorly. Functional impairment due to joint destruction can also occur as a result of under-treatment.

Research hotspots and trends analysis of ankylosing spondylitis: a bibliometric and scientometric analysis from 2009 to 2018

Background

This study utilized bibliometric analysis to qualitatively and quantitatively analyze hotspots and predict trends in the field of ankylosing spondylitis (AS) research.

Methods

Articles about AS were obtained from the Web of Science Core Collection and PubMed database, and bibliometric analysis was carried out through CiteSpace and the Online Analysis Platform of Literature Metrology and Bibliographic Item Co-Occurrence Matrix Builder (BICOMB). Then, co-word biclustering analysis was conducted to obtain research hotspots and predict trends using gCLUTO software.

Results

A total of 6,818 articles on AS from 2009 to 2018 were analyzed, showing an increasing publication trend (558 articles in 2009 to 851 articles in 2018). The Journal of Rheumatology was the leading journal in AS research, with an impact factor (IF) of 3.634 and H-index value of 49. In terms of region, the United States led the world in this field, and The University of Toronto was the leading institution for AS research. Van Der Heijde, D was the most prolific author in the field. Eight research hotspots in the field of AS were also identified.

Conclusions

Our analysis identified eight research hotspots, and predicted that surgical treatment and etiology will be the main AS research trends in the future. This study provides new directions and ideas for future research in AS.

Analysis of 47 Non-MHC Ankylosing Spondylitis Susceptibility Loci Regarding Associated Variants across Whites and Han Chinese

OBJECTIVE

To present a systematic evaluation of 47 non-MHC ankylosing spondylitis (AS) susceptibility loci that have been initially discovered through white genome-wide association studies in Han Chinese.

METHODS

Originally, 10,743 samples representing north and south Chinese in 4 datasets were obtained. After data quality control and imputation, metaanalysis results of 94,621 variants within 47 loci were extracted. Four ERAP1 single-nucleotide polymorphisms (SNP) and HLA-B27 tag SNP rs13202464 were used for interaction analysis. Population-attributable risk percentages of AS-associated variants were compared. Functional annotations of AS-associated variants were conducted using HaploReg, RegulomeDB, and rVarBase databases.

RESULTS

We revealed 16 AS-associated variants with nominal evidence in Han Chinese, including rs10865331 (p = 6.30 × 10^-10), rs10050860 (p = 4.09 × 10^-5) and rs8070463 (p = 1.03 × 10^-4). Potential susceptible SNP within these 47 loci were also identified, such as rs13024541 (2p15), rs17401719 (5q15), and rs62074054 (17q21). Epistatic interactions between 3 ERAP1 SNP (rs17401719, rs30187, and rs10050860) and HLA-B27 were confirmed. Among the 16 AS-associated variants, rs30187 showed weaker risk effect, while rs10050860 and rs12504282 seemed to attribute more risk in Han Chinese than in whites. Further genomic annotation pinpointed 35 candidate functional SNP, especially in the 2p15, ERAP1, and NPEPPS-TBKBP1 regions.

CONCLUSION

Our results provided a detailed spectrum of all the reported non-MHC AS susceptibility loci in Han Chinese, which comprehensively exhibited the ethnic heterogeneity of AS susceptibility and highlighted that 2p15, ERAP1, and NPEPPS-TBKBP1 regions may play a critical role in AS pathogenesis across diverse populations.

The roles of ERAP1 and ERAP2 in autoimmunity and cancer immunity: New insights and perspective

Autoimmunity and cancer affect millions worldwide and both, in principal, result from dysregulated immune responses. There are many well-known molecules involved in immunological process playing as a double-edged sword, by which associating autoimmune diseases and cancer. In this regard, Endoplasmic reticulum aminopeptidases (ERAP) 1, which belongs to the M1 family of aminopeptidases, plays a central role as a "molecular ruler", proteolyzing of N-terminal of the antigenic peptides before their loading onto HLA-I molecules for antigen presentation in the Endoplasmic Reticulum (ER). Several genome-wide association studies (GWAS) highlighted the significance of ERAP1 and ERAP2 in autoimmune diseases, including Ankylosing spondylitis, Psoriasis, Bechet's disease, and Birdshot chorioretinopathy, as well as in cancers. The expression of ERAP1/2 is mostly altered in different cancers compared to normal cells, but how this affects anti-cancer immune responses and cancer growth has been little explored. Recent studies on the immunological outcomes and the catalytic functions of ERAP1 and ERAP2 have provided a better understanding of their potential pathogenetic role in autoimmunity and cancer. In this review, we summarize the role of ERAP1 and ERAP2 in the autoimmune diseases and cancer immunity based on the recent advances in GWAS studies.

The relationship between CRP gene polymorphism (rs2794521, rs3091244), ASDAS-CRP and ASDAS-ESR in ankylosing spondylitis

Background: We aimed to investigate the haplotypes and alleles of two variants (rs2794521 and rs3091244) in AS patients and to examine their relationship with ASDAS-CRP and ASDAS-ESR values.Methods: We evaluated 160 AS patients diagnosed according to the ASAS criteria. ASDAS-CRP and ASDAS-ESR values were calculated. ESR and CRP were examined. The restriction fragment length polymorphism (RFLP) method was used for detecting the rs2794521 and rs3091244 regions on the CRP gene.Results: As a result of the evaluation of rs2794521 gene polymorphism using PCR, TT, TC and CC genotypes were observed in 90, 81 and 9 individuals, respectively. As a result of the evaluation of rs3091244 gene polymorphism, CC, AC and TT genotypes were observed in 104, 51 and 5 individuals, respectively. T allele and C allele were found in rs2794521 gene by 75% and 25%, respectively. In addition, T allele, C allele and A allele were found in rs3091244 gene by 80%, 17% and 3%, respectively. With the help of regression equation, ASDAS-CRP level was 0.34 units higher in cases with rs3091244 C allele than cases without rs3091244 C alleles.Conclusion: CRP rs3091244 C allele may be associated with the increased relative risk for ASDAS-CRP.

Influence of ERAP1 and ERAP2 gene polymorphisms on disease susceptibility in different populations

The endoplasmic reticulum aminopeptidases (ERAPs), ERAP1 and ERAP2, makes a role in shaping the HLA class I peptidome by trimming peptides to the optimal size in MHC-class I-mediated antigen presentation and educating the immune system to differentiate between self-derived and foreign antigens. Association studies have shown that genetic variations in ERAP1 and ERAP2 genes increase susceptibility to autoimmune diseases, infectious diseases, and cancers. Both ERAP1 and ERAP2 genes exhibit diverse polymorphisms in different populations, which may influence their susceptibly to the aforementioned diseases. In this article, we review the distribution of ERAP1 and ERAP2 gene polymorphisms in various populations; discuss the risk or protective influence of these gene polymorphisms in autoimmune diseases, infectious diseases, and cancers; and highlight how ERAP genetic variations can influence disease associations.

Associations between ERAP1 polymorphisms and susceptibility to ankylosing spondylitis: A meta-analysis of East Asian Population

BACKGROUND

The genetic factor is importantly enrolled in the pathogenesis of ankylosing spondylitis (AS) and haplotype leukocyte antigen (HLA)-B27 is the most well-known. However, only 1% to 5% of B27-positive individuals will develop AS, and it confers only 20% to 30% of the overall genetic risks, indicating more genes other than HLA-B27 may play important roles in AS pathologies. The present study aims to investigate whether the polymorphisms of endoplasmic reticulum aminopeptidase 1 (ERAP1) is associated with increased risk of AS susceptibility.

METHODS

The Cochrane library, Pubmed, and Embase databases were carefully searched for potential researches published before May 30, 2018. The title, abstract, and full text were assessed to determine whether the paper was suitable for inclusion. The pooled odds ratios (ORs) with 95% confidence intervals (CIs) were presented to assess the associations between ERAP1 polymorphisms and AS susceptibility.

RESULTS

The study finally enrolled 10 papers, 4 matched single nucleotide polymorphisms (SNPs) of ERAP1 (rs27044, rs27434, rs30187, and rs27037), and a total of 30552 patients (12492 with AS and 18060 for control). No significant difference was found between the AS susceptibility and polymorphisms of rs27044 and rs27434. However, there was a significant association between ERAP1 polymorphisms rs30187 and rs27037 (T vs C, OR, 1.322, 95% CI = 1.240-10410, P <.05; T vs G, OR, 1.247, 95% CI = 1.149-1.353; P <.05; respectively) and AS susceptibility.

CONCLUSION

There was a significant association between ERAP1 polymorphisms (rs30187 and rs27037) and increased risk of AS susceptibility.

ERAP1/ERAP2 and RUNX3 polymorphisms are not associated with ankylosing spondylitis susceptibility in Chinese Han

Previous studies show that endoplasmic reticulum‐associated aminopeptidase (ERAP1/ERAP2) and runt‐related transcription factor 3 (RUNX3) gene polymorphisms are associated with AS (ankylosing spondylitis) in European Caucasians. However, contradictory results were reported in different Asian populations. The purpose of this study was to determine whether eleven candidate single nucleotide polymorphisms (SNPs) in ERAP1/ERAP2 and six in RUNX3 genes confer susceptibility to AS with or without acute anterior uveitis (AAU) [AS⁺AAU⁺ or AS⁺AAU^–] in Chinese Han. Therefore, a case–control association study was performed in 882 AS⁺AAU^–, 884 AS⁺AAU⁺ and 1727 healthy controls. Genotyping was performed using the iPLEXGold genotyping assay. A meta‐analysis was performed to assess the association of polymorphisms of ERAP1 with AS susceptibility in Asian populations. No association was found between SNPs of ERAP1/ERAP2/RUNX3 and susceptibility of AS with or without AAU. A case–control study between patients with human leucocyte antigen HLA‐B27‐positive and healthy controls also failed to demonstrate an association of the tested SNP with AS with or without AAU. Moreover, a meta‐analysis showed that there was no association of rs30187, rs27037, rs27980, rs27434 and rs27582 in ERAP1 with AS in Chinese Han. Taken together, 17 SNPs in ERAP1/ERAP2 and RUNX3 genes did not confer disease susceptibility to AS in Chinese Han.

Association of polymorphisms in ERAP1 and risk of ankylosing spondylitis in a Chinese population

To explore the association between five polymorphisms in endoplasmic reticulum associated aminopeptidase 1 (ERAP1) gene and risk of ankylosing spondylitis (AS) in a Chinese population. A case-control study enrolled 250 AS patients and 250 healthy controls was carried out. The genotypes of involved polymorphisms (rs27037, rs27038, rs469876, rs27044 and rs27980) in ERAP1 were detected by Sequenom Mass-Array platform. There were significant differences of the level of WBC (white blood cell), Platelets, CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate) between AS patients and controls (P_all<0.05). There was statistically association between ERAP1 rs27044 polymorphism and risk of AS, and the carriers with rs27044 CG genotype have an increased the risk for AS (CG versus GG, OR=1.70, 95% CI=1.10-2.62, P=0.015). However, we found no evidence for the association of rs27037, rs469876, and rs27980 polymorphisms in ERAP1 with AS risk. Our findings indicated that ERAP1 rs27044 polymorphism was associated with the susceptibility of AS.

Bioinformatics analysis of genetic variants of endoplasmic reticulum aminopeptidase 1 in ankylosing spondylitis

According to the results of the first genome-wide association study of ankylosing spondylitis (AS), endoplasmic reticulum aminopeptidase 1 (ERAP1) may serve an important role. However, a number of case-control studies have not been able to replicate this result using the same genetic markers. In the present study, the role of common genetic variants of ERAP1 in AS was investigated using two-stage bioinformatics analysis. In the first stage, a classical meta-analysis was performed to assess AS susceptibility markers in ERAP1 using data from available published case-control association studies. The summary odds ratios for 10 single nucleotide polymorphisms (SNPs) were observed to be statistically significant in different studies. In the second stage, the functional effects of these genetic ERAP1 variants were investigated using prediction tools and structural analyses. The K528R (rs30187) substitution SNP in ERAP1 was termed as likely damaging by PolyPhen-2 software, was observed to be located close to the entrance of the substrate pocket, and was predicted to contribute to reduced ERAP1 aminopeptidase activity. In addition, the R725Q (rs17482078) SNP, which was an additional potentially damaging substitution, was suggested to decrease the enzymatic activity of ERAP1, as this substitution may lead to the loss of two hydrogen bonds between R725 and D766 and affect the stability of the C-terminus of ERAP1. In conclusion, the results of the two-stage bioinformatics analysis supported the hypothesis that ERAP1 may present an important susceptibility gene for AS. In addition, the results revealed that two functional SNPs (rs30187 and rs17482078) demonstrated the potential to decrease the enzymatic activity of ERAP1 by affecting its protein structure. Further protein structure-guided studies of the specificity and activity of these ERAP1 variants are therefore warranted.