Analysis on the interaction between IL-1F7 gene and environmental factors on patients with ankylosing spondylitis: a case-only study

Interleukin-37: associations of plasma levels and genetic variants in gout

OBJECTIVES

IL-37 is an anti-inflammatory cytokine involved in inflammatory and autoimmune diseases. We aimed to investigate the association between IL-37 genetic variants, IL-37 plasma levels, and various clinical phases of gout.

METHODS

The study included a control group with no history of primary hyperuricemia/gout, (n = 50), asymptomatic hyperuricemia (n = 74), intercritical gout (n = 200), acute gouty flare (n = 18), and chronic tophaceous gout (n = 30). Plasma IL-37 was analysed using enzyme-linked immunosorbent assay. All coding regions and intron-exon boundaries of IL-37 and exons 1-5 were amplified and sequenced.

RESULTS

Plasma levels of IL-37 were significantly higher in asymptomatic hyperuricemic (p = 0.045), intercritical gout (p = 0.001), and chronic tophaceous gout (p = 0.021) cohorts when compared to control group. The levels of IL-37 in patients with acute gouty flare were comparable to control group (p = 0.061). We identified 15 genetic variants of IL-37: eight intron (rs2708959, rs2723170, rs2708958, rs2723169 rs2466448, rs3811045, rs3811048, rs2708944) and seven non-synonymous allelic variants (rs3811046, rs3811047, rs2708943, rs2723183, rs2723187, rs2708947, rs27231927), of which rs2708959 showed an over-presentation in gouty and acute flare cohorts (p = 0.003 and 0.033, respectively) compared to European population (minor allelic frequency MAF = 0.05) but not in control and hyperuricemic cohorts (p/MAF = 0.17/0.08 and 0.71/0.05, respectively).. On the contrary, rs3811045, rs3811046, rs3811047, and rs3811048 were underrepresented among individuals with tophaceous gout (MAF = 0.57) compared to European MAF 0.70-0.71, but not compared to the control cohort (MAF = 0.67).

CONCLUSIONS

We demonstrated the up-regulation of IL-37 levels across the clinical phases of gout: asymptomatic hyperuricemia, intercritical, and chronic tophaceous gout compared to control. Moreover, 15 genetic variants of IL-37 were identified and their associations with the clinical variants of gout were evaluated.

Biology of interleukin‑37 and its role in autoimmune diseases (Review)

Autoimmune diseases (AIDs) are characterized by dysfunction and tissue destruction, and recent studies have shown that interleukin (IL)-37 expression is dysregulated in AIDs. Among cytokines of the IL-1 family, most are pro-inflammatory agents, and as an anti-inflammatory cytokine, IL-37 may have the potential to alleviate excessive inflammation and can be used as a ligand or transcription factor that is involved in regulating innate and adaptive immunity. IL-37 plays important roles in the development of AIDs. This review summarizes the biological characteristics and functions of IL-37 and discusses the potential of IL-37 as a therapeutic target for effective cytokine therapy and as a biomarker in AIDs.

The rs6427384 and rs6692977 Single Nucleotide Polymorphisms of the Fc Receptor-Like 5 (FCRL5) Gene and the Risk of Ankylosing Spondylitis: A Case Control Study in a Single Center in China

BACKGROUND The study aimed to explore the genetic association of Fc receptor-like 5 (FCRL5) gene variants (rs6427384 and rs6692977) with ankylosing spondylitis risk in Chinese Han population. MATERIAL AND METHODS Genotyping for FCRL5 gene variations rs6427384 and rs6692977 was implemented among 130 ankylosing spondylitis cases and 135 healthy persons, through polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method. Frequency dissimilarity for 2 polymorphisms was compared between 2 groups using chi-square test. The association strength of FCRL5 gene polymorphism with ankylosing spondylitis risk was estimated by odds ratios with 95% confidence intervals. RESULTS The frequencies of rs6427384 CC genotype and C allele were significantly lower in the case group than that in the control group (P<0.05), which suggested that C allele of rs6427384 polymorphism might offer protection against ankylosing spondylitis onset. Whereas only 2 genotypes of rs6692977 were detected in the control group, and no significant association was found with ankylosing spondylitis susceptibility. CONCLUSIONS FCRL5 gene polymorphism rs6427384 was correlated to ankylosing spondylitis occurrence among Chinese Han population, while rs6692977 was not.

Cynomolgus macaque IL37 polymorphism and control of SIV infection

The association between gene polymorphisms and plasma virus load at the set point (SP-PVL) was investigated in Mauritian macaques inoculated with SIV. Among 44 macaques inoculated with 50 AID50, six individuals were selected: three with SP-PVL among the highest and three with SP-PVL among the lowest. The exons of 390 candidate genes of these six animals were sequenced. Twelve non-synonymous single nucleotide polymorphisms (NS-SNPs) lying in nine genes potentially associated with PVL were genotyped in 23 animals. Three NS-SNPs with probabilities of association with PVL less than 0.05 were genotyped in a total of 44 animals. One NS-SNP lying in exon 1 of the IL37 gene displayed a significant association (p = 3.33 × 10⁻⁴) and a strong odds ratio (19.52). Multiple linear regression modeling revealed three significant predictors of SP-PVL, including the IL37 exon 1 NS-SNP (p = 0.0004) and the MHC Class IB haplotypes M2 (p = 0.0007) and M6 (p = 0.0013). These three factors in conjunction explained 48% of the PVL variance (p = 4.8 × 10⁻⁶). The potential role of IL37 in the control of SIV infection is discussed.

Ankylosing spondylitis is associated with aberrant DNA methylation of IFN regulatory factor 8 gene promoter region

OBJECTIVES

To investigate the role of methylation levels of the IFN regulatory factor 8 (IRF8) gene promoter in the development of ankylosing spondylitis (AS).

METHODS

In this study, we compared the methylation levels of the IRF8 gene promoter between 99 AS patients and 99 healthy controls using MethylTarget approach. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) was performed to compare the mRNA levels of the IRF8 gene in the other 19 AS patients and 19 healthy controls.

RESULTS

Differential methylation was found in 91 CpG sites of the IRF8 gene promoter, and 4 CpG regions were highly methylated in AS patients compared to healthy controls (p < 0.05). In the verification stage, we found that the mRNA levels of the IRF8 gene in AS patients were significantly lower than that in controls (AS 0.77 (0.39-1.74), P = 0.038). Positive correlations between methylation of the IRF8 gene and the duration of disease, BASFI, and ESR were observed in AS patients.

CONCLUSIONS

We found a significant hypermethylation of the IRF8 gene promoter and a downregulation of the mRNA levels of the IRF8 gene in AS patients. This suggests that aberrant methylation of the IRF8 gene promoter may probably contribute to the development and pathogenesis of AS through regulating the expression of mRNA.

Association between interleukin 37 (rs3811047) polymorphism and multiple autoimmune diseases in a Chinese population: A PRISMA-compliant meta-analysis

OBJECTIVE

Emerging evidence suggests that interleukin 37 (IL-37) plays an important role in the pathogenesis of several autoimmune diseases (ADs), but the correlations are still unclear. We conducted a meta-analysis to explore whether IL-37 gene (rs3811047) polymorphism was associated with susceptibility to multiple ADs in a Chinese population.

METHODS

Relevant studies were searched in the PubMed, Embase, Chinese National Knowledge Infrastructure, and Chinese Wangfang databases up to August 31, 2017. Odds ratio (OR) and its 95% confidence interval (95% CI) was used to estimate the strength of the association in different genetic models. The results of fixed or random models were adopted according to the heterogeneity. Publication bias and sensitive analysis were also performed to evaluate the reliability of results.

RESULTS

A total of 3161 patients and 4078 controls from 6 studies were included in this meta-analysis. Pooling all data together, a significant association between IL-37 gene (rs3811047 A/G) polymorphism and susceptibility to ADs in the Chinese population was found in all 4 genetic models (allelic model A vs G: OR = 0.73 95% CI = 0.67∼0.79; recessive model AA + AG vs GG: OR = 0.72, 95% CI = 0.65∼0.79; dominant model AA vs AG + GG: OR = 0.59, 95% CI = 0.45∼0.77; homozygous model AA vs GG: OR = 0.55, 95% CI = 0.42∼0.72). No heterogeneity and publication bias was detected in all models. Sensitive analysis indicated that all of the positive results are reliable.

CONCLUSION

The IL- 37 (rs3811047) polymorphism contributes to the development of ADs in a Chinese population.

Relationship between diet and ankylosing spondylitis: A systematic review

The question of whether diet plays a role in the onset of ankylosing spondylitis (AS) or can affect the course of the disease is an important one for many patients and healthcare providers. The aims of this study were to investigate whether: 1) patients with AS report different diets to those without AS; 2) amongst patients with AS, diet is related to severity; 3) persons with particular diets are less likely to develop AS; 4) specific dietary interventions improve the AS symptoms. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Medline, Embase, Cochrane Library, and reference lists of relevant articles were searched. Two authors independently selected eligible studies, assessed the quality of included trials, and extracted the data. Sixteen studies (nine observational and seven interventions) were included in the review. Due to the heterogeneity of the study designs and analyses, the results could not be aggregated. Evidence on a possible relationship between AS and diet is extremely limited and inconclusive due to the majority of included studies being small, single studies with moderate-to-high risk of bias, and insufficient reporting of results.

Suppression of innate inflammation and immunity by interleukin-37

IL-37 is unique in the IL-1 family in that unlike other members of the family, IL-37 broadly suppresses innate immunity. IL-37 can be elevated in humans with inflammatory and autoimmune diseases where it likely functions to limit inflammation. Transgenic mice expressing human IL-37 (IL37-tg) exhibit less severe inflammation in models of endotoxin shock, colitis, myocardial infarction, lung, and spinal cord injury. IL37-tg mice have reduced antigen-specific responses and dendritic cells (DCs) from these mice exhibit characteristics of tolerogenic DCs. Compared to aging wild-type (WT) mice, aging IL37-tg mice are protected against B-cell leukemogenesis and heart failure. Treatment of WT mice with recombinant human IL-37 has been shown to be protective in several models of inflammation and injury. IL-37 binds to the IL-18 receptor but then recruits the orphan IL-1R8 (formerly TIR8 or SIGIRR) in order to function as an inhibitor. Here, we review the discovery of IL-37, its production, release, and mechanisms by which IL-37 reduces inflammation and suppresses immune responses. The data reviewed here suggest a therapeutic potential for IL-37.

Genomic Variant in IL-37 Confers A Significant Risk of Coronary Artery Disease

The interleukin 1 family plays an important role in the immune and inflammatory responses. Coronary artery disease (CAD) is a chronic inflammatory disease. However, the genetic association between IL-37, the seventh member of the IL-1 family, and CAD is unknown. Here we show that a single nucleotide polymorphism in the IL-37 gene (rs3811047) confers a significant risk of CAD. We have performed an association analysis between rs3811047 and CAD in two independent populations with 2,501 patients and 3,116 controls from China. Quantitative RT-PCR analysis has been performed to determine if the IL-37 expression level is influenced by rs3811047. We show that the minor allele A of rs3811047 is significantly associated with CAD in two independent populations under a recessive model (P_adj = 5.51 × 10^-3/OR = 1.56 in the GeneID Northernern population and P_adj = 1.23 × 10^-3/OR = 1.45 in the GeneID Central population). The association became more significant in the combined population (P_adj = 9.70 × 10^-6/OR = 1.47). Moreover, the association remains significant in a CAD case control population matched for age and sex. Allele A of rs3811047 shows significant association with a decreased mRNA expression level of IL-37 (n = 168, P = 3.78 × 10^-4). These data suggest that IL37 is a new susceptibility gene for CAD, which provides a potential target for the prevention and treatment of CAD.

IL-37 Confers Protection against Mycobacterial Infection Involving Suppressing Inflammation and Modulating T Cell Activation

Interleukin-37 (IL-37), a novel member of the IL-1 family, plays fundamental immunosuppressive roles by broadly reducing both innate inflammation and acquired immunity, but whether it is involved in the pathogenesis of tuberculosis (TB) has not been clearly elucidated. In this study, single nucleotide polymorphism (SNP) analysis demonstrated an association of the genetic variant rs3811047 of IL-37 with TB susceptibility. In line with previous report, a significant elevated IL-37 abundance in the sera and increased expression of IL-37 protein in the peripheral blood mononuclear cells (PBMC) were observed in TB patients in comparison to healthy controls. Moreover, release of IL-37 were detected in either macrophages infected with Mycobacterium tuberculosis (Mtb) or the lung of BCG-infected mice, concurrent with reduced production of proinflammatory cytokines including IL-6 and TNF-α. Furthermore, in contrast to wild-type mice, BCG-infected IL-37-Tg mice manifested with reduced mycobacterial burden and tissue damage in the lung, accompanied by higher frequency of Th1 cell and less frequencies of regulatory T cells and Th17 cells in the spleen. Taken together, our findings demonstrated that IL-37 conferred resistance to Mtb infection possibly involving suppressing detrimental inflammation and modulating T cell responses. These findings implicated that IL-37 may be employed as a new molecular target for the therapy and diagnosis of TB.

Genetic analysis of innate immunity in Behcet's disease identifies an association with IL-37 and IL-18RAP

Interleukin-1 (IL-1) and the IL-1 receptor (IL-1R) family play an important role in the pathogenesis of inflammatory diseases. This study aimed to investigate the association between single nucleotide polymorphisms (SNP) of IL-1 and IL-1R family genes with Vogt-Koyanagi-Harada (VKH) and Behcet’s disease (BD) in Han Chinese. The case-control study was divided into two stages and included 419 VKH cases, 1063 BD cases and 1872 healthy controls. The MassARRAY platform (Sequenom), iPLEX Gold Assay and TaqMan SNP assays were used to score genotypes of 24 SNPs. The expression of IL-37 and IL-18Rap was measured by ELISA and real-time PCR in genotyped healthy individuals. A significantly lower frequency of the AG genotype, and a higher frequency of the GG genotype and G allele of IL-37/rs3811047 were observed in BD as compared to controls. AA genotype and A allele frequency of IL-18RAP/rs2058660 was significantly decreased in BD as compared to controls. Functional studies performed in healthy controls showed that rs3811047 AG genotype carriers had a higher IL-37 gene expression in peripheral blood mononuclear cells (PBMCs) than GG carriers. GG carriers showed a higher cytokine expression as compared to AG carriers. No association was detected between the tested SNPs and VKH.

Common genetic heterogeneity of human interleukin-37 leads to functional variance

Interleukin-37 (IL-37) is an inhibitory member of the IL-1 family of cytokines. We previously found that balanced selection maintains common variations of the human IL37 gene. However, the functional consequences of this selection have yet to be validated. Here, using cells expressing exogenous IL-37 variants, including IL-37 Ref and IL-37 Var1 and Var2, we found that the three variants of IL-37 exhibited different immunoregulatory potencies in response to immune stimulation. The protein level of IL-37 Var2 was found to be significantly less than that of IL-37 Ref or Var1, despite the comparable mRNA levels of all three variants. Further study showed that IL-37 Var2 was rapidly degraded by a proteasome-dependent mechanism mediated by enhanced polyubiquitination, leading to a transient upregulation of IL-37 Var2 after immune stimulation. Finally, when ectopically expressed in cells, human IL-37 Var2 exerted less inhibition on proinflammatory cytokine production than did other IL-37 variants. Conversely, purified extracellular IL-37 variant proteins demonstrated comparable inhibitory abilities in vitro. In conclusion, our study reveals that common genetic variants of IL37 lead to different immune-inhibitory potencies, primarily as a result of differences in IL-37 protein stability, suggesting the possible involvement of these variants in various human diseases.

Interleukin-37 gene variants segregated anciently coexist during hominid evolution

IL37 is a member of IL-1 cytokine family but conveys anti-inflammatory functions. The biological characteristic and genetic heterogeneity of IL37 are not fully understood yet. Here using the whole-genome sequencing data from 1000 Genomes Project, we performed population and evolutionary genetic analysis of human IL37 gene. First, 2184 IL37 gene sequences from different human populations were retrieved. The IL37 protein sequences were inferred from the coding DNA sequences and multiple species alignment was made. Then, the phylogenetic tree of IL37 was built and dN/dS ratios were calculated for each evolutionary branch, the classic McDonald and Kreitman test was also performed. Next, we conducted intraspecific evolutionary genetic analysis and built the genealogy network of 116 unique IL37 haplotypes through median-joining network analysis. Finally, we compared IL37 sequences between the modern and archaic humans. Our results for the first time provide solid evidence that common IL37 variants other than NCBI reference sequence are present worldwide. Our data also supports that IL37 variants are shaped and maintained by selection instead of neutral evolution. We further identified that human IL37 variants consist of two major haplogroups and their presence in archaic humans corroborates its ancient origin in hominid evolution. In conclusion, these data indicate that common IL37 variants are maintained among human populations by selective force, suggesting their potential involvements in immune regulation and human diseases. In addition, the ancient history of IL37 variants reveals interesting insight into the complicated human evolutionary history.

Association between KIR polymorphisms and ankylosing spondylitis in populations: a meta-analysis

OBJECTIVES

Published association studies of killer cell immunoglobulin-like receptors (KIRs) and ankylosing spondylitis (AS) in populations are inconsistent. The aim of this study is to determine whether the KIR polymorphisms confer susceptibility to AS in populations by conducting a meta-analysis.

METHODS

A computer search was carried out up to August 2013 for literature pertaining to AS and KIR polymorphisms. Publications addressing the association between the KIR polymorphisms and susceptibility to AS in populations were selected from the Pubmed, Elsevier Science Direct, China National Knowledge Infrastructure (CNKI) and Chinese Biomedical Literature Database (CBM) databases. The odds ratio (OR) with 95% confidence interval (95%CI) was calculated.

RESULTS

A total of 13 case-control studies in 9 articles were included in this meta-analysis. Meta-analysis results identified two positive associations of 2DS4 and 3DS1 with susceptibility to AS in populations. In subgroup analysis, there was a positive association between 2DS4 and susceptibility to AS in Asians, but not in Caucasians. And there were associations between 3DL1, 3DS1 and susceptibility to AS in Caucasians, but not in Asians. Results of subgroup analysis also showed that there were associations between 2DL5, 2DS4, 2DS5, 3DL1, 3DS1 and susceptibility to AS in HLA-B*27-positive patients and HLA-B*27-positive healthy controls.

CONCLUSIONS

This meta-analysis confirms that 2DS4 and 3DS1 might be potential risk factors for AS in populations.

Association of FCRL4 polymorphisms on disease susceptibility and severity of ankylosing spondylitis in Chinese Han population

Previous studies have found that the Fc receptor-like (FCRL) molecule, involved in controlling B cell signaling, may contribute to the autoimmune disease process. Many studies have reported the relation of FCRL gene family with SLE and RA. We hypothesized that FCRL4 may be a key gene for ankylosing spondylitis (AS) development. To test this hypothesis, we screened FCRL4 polymorphisms in the Chinese Han population. Five tag single nucleotide polymorphisms (SNPs), including rs14335, rs849826, rs10489674, rs2778003, and rs2777963, were selected. Using a case-control study, five tag SNPs, which captured the majority of known common variation within FCRL4 gene, were selected and genotyped by Multiplex Snapshot technique. We analyzed 299 patients and 300 controls from China. The genotype analysis demonstrated that one of the FCRL4 tag SNPs rs2777963 TT genotype may be a risk factor of AS (χ(2) = 7.374, p = 0.024). The haplotype analysis indicated that there were no significant differences between AS cases and controls. Patients with AS who had rs14335 AA genotype had a significantly declined visual analogue scale patient's global assessment scores compared to those with the GG genotype (31.21 ± 26.25 vs 40.54 ± 25.40, p = 0.035) and GA genotype (38.29 ± 24.94 vs 40.54 ± 25.40, p = 0.044), and in locus rs10489674, TT genotype had significantly increased Bath Ankylosing Spondylitis Disease Activity Index scores compared to those with the CC genotype (4.73 ± 2.43 vs 3.15 ± 1.61, p = 0.003) and CT genotype (4.73 ± 2.43 vs 2.97 ± 1.71, p = 0.001). The FCRL4 polymorphisms may play an important role in the susceptibility and severity of AS in the Chinese Han population.