Impact of inflammatory cytokine and adipokine gene variations in the development of HIV-associated lipodystrophy

Cytokines affect lipid and glucose metabolism and also alter the body's habitus. They play a role in the development of lipodystrophy syndrome. Adipocytes secrete the pro-inflammatory cytokines IL-1, TNF-α and IL-6. The plasma cytokine concentration is associated with the percentage and distribution of fat tissue in the body. The metabolic disturbances are strongly associated with increased levels of pro-inflammatory cytokines (IL-1, IL-6 and TNF-α). Plasma levels of cytokines such as TNF-α, IL-6 and leptin were found to be increased while plasma resistin levels were found to be variable in patients suffering from obesity and type II diabetes mellitus. Until now, limited information has been available on the polymorphism of cytokine and adipokine genes in patients of HIV-associated lipodystrophy (HIVLD), which can contribute to individual variations in susceptibility to metabolic diseases, especially to HIVLD. Hence, we studied the association of cytokine and adipokine gene polymorphisms in various diseases and their impact on HIVLD. We carry out an extensive search using several databases, including PubMed, EMBASE and Google Scholar. The distribution of cytokine and adipokine gene polymorphisms and their expression levels varied among various populations. We examined the variants of cytokine and adipokine genes, which can contribute to individual variations in susceptibility to metabolic diseases, especially to HIVLD. In the current review, we present a brief account of the risk factors of HIVLD, the pathogenesis of HIVLD and the polymorphism of cytokine and adipokine genes in various diseases with special reference to their impact on HIVLD.

Associations of Single Nucleotide Polymorphisms in IL-18 Gene with Plasmodium falciparum-Associated Malaria

Introduction

Interleukin-18 (IL-18) is a pro-inflammatory cytokine, reported to be involved in the initial immune responses against malaria. Genetic variations in the host are an important factor that influences the etiology of malaria at several disease levels. Polymorphisms within the IL-18 gene are associated with susceptibility and clinical outcome of several diseases.

Methods

We genotyped single nucleotide polymorphisms (SNPs) in IL-18 of patients infected with Plasmodium falciparum with varying extent of parasitemia and different age groups.

Results

SNPs rs5744292 (OR = 70.446; 95% CI = 4.318-1149.323; p<0.0001) and rs544354 (OR = 1.498; 95% CI = 1.088-2.063; p=0.013) were found to be significantly associated with parasitemia in P. falciparum-infected patients when compared with healthy control subjects. SNP rs5744292 (OR = 7.597; 95% CI=1.028-56.156; p=0.019) was associated with increased parasite density in infected patients. SNPs rs544354 (OR 0.407; 95% CI=0.204-0.812; p = 0.009) and rs360714 (OR of 0.256; 95% CI=0.119-0.554; p = 0.001) were significantly associated with parasite density in an age-dependent manner, with the risk alleles present more frequently among the younger (1-9 years) patients. Several haplotypes were found to have a significant association with parasitemia. In-vitro expression analysis using luciferase reporter assay showed that SNPs rs1946518 and rs187238 in the IL-18 gene promoter region and rs360728 and rs5744292 in the 3'-untranslated region of the IL-18 gene were associated with enhanced transcriptional activity.

Conclusion

Our results suggest that polymorphisms within the IL-18 gene are associated with the susceptibility to P. falciparum infection and related parasitemia among groups with different parasite density and across various age groups.

A Specific IL6 Polymorphic Genotype Modulates the Risk of Trypanosoma cruzi Parasitemia While IL18, IL17A, and IL1B Variant Profiles and HIV Infection Protect Against Cardiomyopathy in Chagas Disease

Background

Chagas disease caused by Trypanosoma cruzi (T. cruzi) affects approximately six million individuals worldwide. Clinical manifestations are expected to occur due to the parasite persistence and host immune response. Herein we investigated potential associations between IL1B, IL6, IL17A, or IL18 polymorphism profiles and cardiomyopathy or T. cruzi parasitemia, as well as the impact of HIV infection on cardiopathy.

Methods

Two hundred twenty-six patients and 90 control individuals were analyzed. IL1B rs1143627 T>C, IL6 rs1800795 C>G, IL17A rs2275913 G>A, IL18 rs187238 C>G, and IL18 rs1946518 C>A SNVs were analyzed by real-time PCR and T. cruzi parasitemia by PCR.

Results

Our data revealed association between a cytokine gene polymorphism and parasitemia never previously reported. The IL6 rs1800795 CG genotype lowered the risk of positive parasitemia (OR = 0.45, 95% CI 0.24–0.86, P = 0.015). Original findings included associations between IL17A rs2275913 AA and IL18 s1946518 AA genotypes with decreased risk of developing cardiomyopathy (OR = 0.27, 95% CI 0.07–0.97, P = 0.044; and OR = 0.35, 95% CI 0.14–0.87, P = 0.023, respectively). IL18 rs1946518 AA and IL1B rs1143627 TC were associated with reduced risk for cardiomyopathy severity, including NYHA (New York Heart Association) class ≥ 2 (OR = 0.21, 95% CI 0.06–0.68, P = 0.009; and OR = 0.48, 95% CI 0.24–0.95, P = 0.036, respectively) and LVEF (left ventricular ejection fraction) <45% for IL18 rs1946518 AA (OR = 0.22, 95% CI 0.05–0.89, P = 0.034). A novel, unexpected protective effect of HIV infection against development/progression of cardiomyopathy was identified, based on a lower risk of developing cardiopathy (OR = 0.48, 95% CI 0.23–0.96, P = 0.039), NYHA class ≥ 2 (OR = 0.15, 95% CI 0.06–0.39, P < 0.001), and LVEF < 45% (OR = 0.03, 95% CI 0.00–0.25, P = 0.001). Digestive involvement was negatively associated with NYHA ≥ 2 and LVEF < 45% (OR = 0.20, 95% CI 0.09–0.47, P < 0.001; and OR = 0.24, 95% CI 0.09–0.62, P = 0.004, respectively).

Conclusions

Our data support a protective role of IL17A AA, IL18 AA, and IL1B TC genotypes against development/progression of cardiomyopathy and a modulatory effect of the IL6 CG genotype on the risk of parasitemia in Chagas disease. Notably, HIV infection was shown to protect against development/progression of cardiopathy, potentially associated with a synergistic effect of HIV and highly active antiretroviral therapy (HAART), attenuating a Th1-mediated response in the myocardium. This proposed hypothesis requires confirmation, however, in larger and more comprehensive future studies.

Association of IL18 genetic polymorphisms with Chagas disease in Latin American populations

Host genetic factors have been suggested to play an important role in the susceptibility to Chagas disease. Given the influence of interleukin 18 (IL-18) in the development of the disease, in the present study, we analyzed three IL18 genetic variants (rs2043055, rs1946518, rs360719) regarding the predisposition to Trypanosoma cruzi infection and the development of chronic Chagas cardiomyopathy (CCC), in different Latin America populations. Genetic data of 3,608 patients from Colombia, Bolivia, Argentina, and Brazil were meta-analyzed to validate previous findings with increased statistical power. Seropositive and seronegative individuals were compared for T. cruzi infection susceptibility. In the Colombian cohort, the allelic frequencies of the three variants showed a significant association, with adjustment for sex and age, and also after applying multiple testing adjustments. Among the Colombian and Argentinean cohorts, rs360719 showed a significant genetic effect in a fixed-effects meta-analysis after a Bonferroni correction (OR: 0.76, CI: 0.66-0.89, P = 0.001). For CCC, the rs2043055 showed an association with protection from cardiomyopathy in the Colombian cohort (OR: 0.79, CI: 0.64-0.99, P = 0.037), with adjustment for sex and age, and after applying multiple testing adjustments. The meta-analysis of the CCC vs. asymptomatic patients from the four cohorts showed no evidence of association. In conclusion, our results validated the association found previously in the Colombian cohort suggesting that IL18 rs360719 plays an important role in the susceptibility to T. cruzi infection and no evidence of association was found between the IL18 genetic variants and CCC in the Latin American population studied.

Triggers of Autoimmunity: The Role of Bacterial Infections in the Extracellular Exposure of Lupus Nuclear Autoantigens

Infections are considered important environmental triggers of autoimmunity and can contribute to autoimmune disease onset and severity. Nucleic acids and the complexes that they form with proteins—including chromatin and ribonucleoproteins—are the main autoantigens in the autoimmune disease systemic lupus erythematosus (SLE). How these nuclear molecules become available to the immune system for recognition, presentation, and targeting is an area of research where complexities remain to be disentangled. In this review, we discuss how bacterial infections participate in the exposure of nuclear autoantigens to the immune system in SLE. Infections can instigate pro-inflammatory cell death programs including pyroptosis and NETosis, induce extracellular release of host nuclear autoantigens, and promote their recognition in an immunogenic context by activating the innate and adaptive immune systems. Moreover, bacterial infections can release bacterial DNA associated with other bacterial molecules, complexes that can elicit autoimmunity by acting as innate stimuli of pattern recognition receptors and activating autoreactive B cells through molecular mimicry. Recent studies have highlighted SLE disease activity-associated alterations of the gut commensals and the expansion of pathobionts that can contribute to chronic exposure to extracellular nuclear autoantigens. A novel field in the study of autoimmunity is the contribution of bacterial biofilms to the pathogenesis of autoimmunity. Biofilms are multicellular communities of bacteria that promote colonization during chronic infections. We review the very recent literature highlighting a role for bacterial biofilms, and their major components, amyloid/DNA complexes, in the generation of anti-nuclear autoantibodies and their ability to stimulate the autoreactive immune response. The best studied bacterial amyloid is curli, produced by enteric bacteria that commonly cause infections in SLE patients, including Escherichia coli and Salmonella spps. Evidence suggests that curli/DNA complexes can trigger autoimmunity by acting as danger signals, molecular mimickers, and microbial chaperones of nucleic acids.

Correlation of interleukin-18 gene polymorphism with the susceptibility of condyloma acuminatum in Chinese population

Host immunogenetic setting is involved in the regulation of human papillomavirus (HPV) infection and development of condyloma acuminatum (CA). We investigated the correlation of two common single nucleotide polymorphisms (SNPs) (−607C/A and −137G/C) of IL-18 with the susceptibility of CA in a large Chinese cohort. Out of 408 CA patients analyzed, 300 had HPV infection transmitted through sexual contact (SC) and 108 through non-sexual contact (NSC). In addition, 360 healthy volunteers were enrolled as controls. SNPs at positions −607C/A and −137G/C in IL-18 promoter were analyzed. Comparing CA patients to healthy controls, no dominant relevance was found between the IL-18 promoter −607 C/A or −137G/C polymorphisms and the CA disease either identified genotypically (p > 0.05) or by allelically (p > 0.05). However, the IL-18 promoter −137G/C polymorphism genotype and allele frequencies in the NSC CA group, but not between in the SC group, were significantly higher than in the controls. There was no dominant relevance between IL-18-607C/A polymorphism genotype and allele frequencies among SC, NSC CA patients, and controls. Our study demonstrates that polymorphism −137G/C in IL-18 promoter is significantly correlated with risk of CA in NSC patients.

Global landscape of mouse and human cytokine transcriptional regulation

Cytokines are cell-to-cell signaling proteins that play a central role in immune development, pathogen responses, and diseases. Cytokines are highly regulated at the transcriptional level by combinations of transcription factors (TFs) that recruit cofactors and the transcriptional machinery. Here, we mined through three decades of studies to generate a comprehensive database, CytReg, reporting 843 and 647 interactions between TFs and cytokine genes, in human and mouse respectively. By integrating CytReg with other functional datasets, we determined general principles governing the transcriptional regulation of cytokine genes. In particular, we show a correlation between TF connectivity and immune phenotype and disease, we discuss the balance between tissue-specific and pathogen-activated TFs regulating each cytokine gene, and cooperativity and plasticity in cytokine regulation. We also illustrate the use of our database as a blueprint to predict TF-disease associations and identify potential TF-cytokine regulatory axes in autoimmune diseases. Finally, we discuss research biases in cytokine regulation studies, and use CytReg to predict novel interactions based on co-expression and motif analyses which we further validated experimentally. Overall, this resource provides a framework for the rational design of future cytokine gene regulation studies.

Impact of functional IL-18 polymorphisms on genetic predisposition and diverse clinical manifestations of the disease in Indian SLE patients

Several studies have demonstrated associations between interleukin-18 polymorphisms and risk of systemic lupus erythematosus in different populations except one of Indian origin. We therefore investigated for the influence of interleukin-18 (-1297T/C, -607A/C, -137G/C; + 105A/C) polymorphisms on genetic susceptibility and clinical expression of the disease in Indian systemic lupus erythematosus patients. A total of 200 systemic lupus erythematosus patients and 201 controls were recruited. Genotyping of interleukin-18 polymorphisms were performed by polymerase chain reaction-restriction fragment length polymorphism. Serum interleukin-18 levels were measured by enzyme-linked immunosorbent assay. Interleukin-18 (-1297T/C; -137G/C) polymorphisms showed significant association with genetic susceptibility to the disease in our systemic lupus erythematosus cohort. Stratification analysis revealed -1297CC and -1297C associated with renal involvement (odds ratio = 3.4, correcting p value = 0.0207), (odds ratio = 2.0, correcting p value = 0.0054) respectively. Additionally, -1297C allele frequency was significantly increased in patients with anti-nucleosome antibody (odds ratio = 2.1, correcting p value = 0.0301). Haplotype analysis showed CC haplotype strongly associated with serositis (odds ratio = 9.1, correcting p values = 0.0009) and neurologic involvement (odds ratio = 9.3, correcting p value = 0.0018). We reported a 2.7-fold increase in serum interleukin-18 levels in patients (511.5 ± 242.3 pg/ml) compared to controls (189.4 ± 80.8 pg/ml) ( p < 0.0001). Furthermore, interleukin-18 levels were positively correlated with disease activity ( r = 0.548, p = 0.0001) and renal involvement in the patients with lupus nephritis ( r = 0.569, p < 0.0001). In summary, interleukin-18 polymorphisms elucidated in this study appear to confer genetic susceptibility to the disease and are associated with renal, serositis and neurologic involvement in Indian systemic lupus erythematosus patients.

Interleukin-18 in Health and Disease

Interleukin (IL)-18 was originally discovered as a factor that enhanced IFN-γ production from anti-CD3-stimulated Th1 cells, especially in the presence of IL-12. Upon stimulation with Ag plus IL-12, naïve T cells develop into IL-18 receptor (IL-18R) expressing Th1 cells, which increase IFN-γ production in response to IL-18 stimulation. Therefore, IL-12 is a commitment factor that induces the development of Th1 cells. In contrast, IL-18 is a proinflammatory cytokine that facilitates type 1 responses. However, IL-18 without IL-12 but with IL-2, stimulates NK cells, CD4⁺ NKT cells, and established Th1 cells, to produce IL-3, IL-9, and IL-13. Furthermore, together with IL-3, IL-18 stimulates mast cells and basophils to produce IL-4, IL-13, and chemical mediators such as histamine. Therefore, IL-18 is a cytokine that stimulates various cell types and has pleiotropic functions. IL-18 is a member of the IL-1 family of cytokines. IL-18 demonstrates a unique function by binding to a specific receptor expressed on various types of cells. In this review article, we will focus on the unique features of IL-18 in health and disease in experimental animals and humans.

Association of IL18 genetic polymorphisms with increased risk of Biliary atresia susceptibility in Southern Chinese children

Biliary atresia (BA) has complex genetic etiology, characterized by different levels of hepatic fibrosis after the Kasai procedure and immune responses to the bile duct. As an activator of the two most important inflammatory cells in Biliary atresia (T cells and NK cells), IL-18 is significantly increased in BA patients. This study aims to investigate the association of Interleukin 18(IL-18) with the susceptibility to BA. We examined the association of three polymorphisms (rs549908, rs187238 and rs1946518 in IL-18) and BA susceptibility in a Southern Chinese population composed of 506 cases and 1473 controls. SNP rs187238 and rs1946518 were identified as associated with BA. Interestingly, we also observed that the intragenic synergistic epistasis between SNPs rs187238 and rs1946518 boosting the risk to BA by logistic regression and Multifactor dimensionality reduction (MDR) analysis. This study provides for the first time a direct evidence to support IL-18 as a susceptibility gene for the disease in southern Chinese children.

Precision medicine in lupus nephritis: can biomarkers get us there?

Patients with systemic lupus erythematosus frequently develop lupus nephritis (LN), a condition that can lead to end-stage kidney disease. Multiple serum and urine biomarkers for LN have been proposed in recent years, yet none have become incorporated into clinical use. The majority of studies have been single center with significant variability in cohorts, assays, and sample storage, leading to inconclusive results. It has become clear that no single biomarker is likely to be sufficient to diagnose LN, identify flares, and define the response to therapy and prognosis. A more likely scenario is a panel of urine, serum, tissue, and genetic biomarkers. In this review, we summarize traditional and novel biomarkers and discuss how they may be utilized in order to bring precision medicine to clinical practice in LN.

Association of interleukin 22 gene polymorphisms and serum IL-22 level with risk of systemic lupus erythematosus in a Chinese population

The aim of this study was to investigate the association between the single-nucleotide polymorphisms (SNPs) of the interleukin 22 (IL-22) gene and systemic lupus erythematosus (SLE) in a Chinese population. Three IL-22 SNPs (rs2227485, rs2227513 and rs2227491) were genotyped using SNaPshot SNP genotyping assays and identified by sequencing in 314 SLE patients and 411 healthy controls. The IL-22 level of serum was assessed by enzyme-linked immunosorbent assay (ELISA) kits. Data were analysed by spss version 17.0 software. We found that rs2227513 was associated with an increased risk of SLE [AG versus AA: adjusted odds ratio (aOR) = 2·24, 95% confidence interval (CI) = 1·22-4·12, P = 0·010; G versus· A: adjusted OR = 2·18, 95% CI = 1·20-3·97, P = 0·011]. Further analysis in patients with SLE showed that the AG genotype and G allele were associated with an increased risk of renal disorder in SLE (G versus A: aOR = 3·09, 95% CI = 1·30-7·33, P = 0·011; AG versus· AA: aOR = 3·25, 95% CI = 1·35-7·85, P = 0·009). In addition, the concentration of IL-22 was significantly lower in the rs2227513 AG genotype compared with AA genotype (P = 0·028). These results suggest that rs2227513 polymorphism might contribute to SLE susceptibility, probably by decreasing the expression of IL-22.

NF-κB-94ins/del ATTG Genotype Contributes to the Susceptibility and Imbalanced Th17 Cells in Patients with Immune Thrombocytopenia

Background

The NLRP3 inflammasome plays important roles in the pathogenesis of autoimmune diseases. However, the role of the NLRP3 inflammasome in the pathophysiology of immune thrombocytopenia (ITP) remains unclear.

Methods

RT-PCR was used to examine the polymorphism and expression of genes involved in the NLRP3 inflammasome in ITP patients. T helper cells and apoptosis of PBMC from ITP patients were analyzed by flow cytometry. The antiplatelet autoantibodies in plasma were determined by modified monoclonal antibody-specific immobilization of platelet antigens (MAIPA).

Results

We found that the NF-κB-94ins/del ATTG genotype contributed to the susceptibility of ITP. Furthermore, the platelet counts of ITP patients with the WW genotype or WD genotype were lower than those with the DD genotype of NF-κB-94ins/del ATTG. Compared with controls, NF-κB gene expression was significantly decreased and WW or WD genotype ITP patients displayed higher mRNA expression than DD individuals. Similarly, the mRNA expression of NLRP3 was also increased in the WW genotype. There was a significant gene dose effect of the percentage of Th17 cells for the WW, WD, and DD genotypes (WW < WD < DD) in the unstimulated group and no significant difference was found after being stimulated. The activation of the NLRP3 inflammasome could upregulate Th17 in ITP patients.

Conclusion

The NF-κB-94ins/del ATTG genotype might serve as a novel biomarker and potential target for ITP.

IL18 rs360719 A>G, IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G polymorphisms and risk of gastric cardiac adenocarcinoma

The present study was conducted to investigate the association between gastric cardiac adenocarcinoma (GCA) and four functional single-nucleotide polymorphisms (SNPs), including interleukin 18 (IL18) rs360719 A>G, IL18 receptor 1 (IL18R1) rs13015714 G>T, IL18 receptor accessory protein (IL18RAP) rs917997 C>T and interleukin 28B (IL28B) rs8099917 T>G variants. A hospital-based case-control study was performed to evaluate the genetic effects of these SNPs. A total of 243 GCA cases and 476 controls were enrolled in this study. A custom-by-design 48-Plex SNPscan™ kit was used to determine the genotypes. When the IL18 rs360719 AA homozygote genotype was used as the reference group, the AG genotype was not associated with the risk for GCA; the GG genotype was also not associated with the risk for GCA. In the dominant model, the IL18 rs360719 AG/GG variants were not associated with the risk for GCA, compared with the IL18 rs360719 AA genotype. In the recessive model, when the IL18R1 rs13015714 AA/AG genotypes were used as the reference group, the GG homozygote genotype was not associated with risk for GCA. No association was observed between IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G polymorphisms and the risk for GCA. These results demonstrated that the functional polymorphisms IL18 rs360719 A>G, IL18R1 rs13015714 G>T, IL18RAP rs917997 C>T and IL28B rs8099917 T>G do not contribute to GCA susceptibility. However, as the statistical power of our study was limited, large well-designed studies and further functional investigations are required to confirm our findings.

Cell death in the pathogenesis of systemic lupus erythematosus and lupus nephritis

Nephritis is one of the most severe complications of systemic lupus erythematosus (SLE). One key characteristic of lupus nephritis (LN) is the deposition of immune complexes containing nucleic acids and/or proteins binding to nucleic acids and autoantibodies recognizing these molecules. A variety of cell death processes are implicated in the generation and externalization of modified nuclear autoantigens and in the development of LN. Among these processes, apoptosis, primary and secondary necrosis, NETosis, necroptosis, pyroptosis, and autophagy have been proposed to play roles in tissue damage and immune dysregulation. Cell death occurs in healthy individuals during conditions of homeostasis yet autoimmunity does not develop, at least in part, because of rapid clearance of dying cells. In SLE, accelerated cell death combined with a clearance deficiency may lead to the accumulation and externalization of nuclear autoantigens and to autoantibody production. In addition, specific types of cell death may modify autoantigens and alter their immunogenicity. These modified molecules may then become novel targets of the immune system and promote autoimmune responses in predisposed hosts. In this review, we examine various cell death pathways and discuss how enhanced cell death, impaired clearance, and post-translational modifications of proteins could contribute to the development of lupus nephritis.

IL18 Gene Variants Influence the Susceptibility to Chagas Disease

Chagas disease is a parasitic disorder caused by the infection with the flagellated protozoan Trypanosoma cruzi. According to the World Health Organization, more than six million people are currently infected in endemic regions. Genetic factors have been proposed to influence predisposition to infection and development of severe clinical phenotypes like chronic Chagas cardiomyopathy (CCC). Interleukin 18 (IL18) encodes a proinflammatory cytokine that has been proposed to be involved in controlling T. cruzi infection. In this study, we analyzed the possible role of six IL18 gene variants (rs5744258, rs360722, rs2043055, rs187238, rs1946518 and rs360719), which cover most of the variation within the locus, in the susceptibility to infection by T. cruzi and/or CCC. In total, 1,171 individuals from a Colombian region endemic for Chagas disease, classified as seronegative (n = 595), seropositive asymptomatic (n = 175) and CCC (n = 401), were genotyped using TaqMan probes. Significant associations with T. cruzi infection were observed when comparing seronegative and seropositive individuals for rs187238 (P = 2.18E-03, OR = 0.77), rs360719 (P = 1.49E-03, OR = 0.76), rs2043055 (P = 2.52E-03, OR = 1.29), and rs1946518 (P = 0.0162, OR = 1.22). However, dependence analyses suggested that the association was mainly driven by the polymorphism rs360719. This variant is located within the promoter region of the IL18 gene, and it has been described that it creates a binding site for the transcription factor OCT-1 affecting IL-18 expression levels. In addition, no evidence of association was observed between any of the analyzed IL18 gene polymorphisms and the development of CCC. In summary, our data suggest that genetic variation within the promoter region of IL18 is directly involved in the susceptibility to infection by T. cruzi, which provides novel insight into disease pathophysiology and adds new perspectives to achieve a more effective disease control.

Association of the interleukin-18 receptor 1 and interleukin-18 receptor accessory protein polymorphisms with the risk of esophageal cancer

Esophageal cancer is the fourth leading cause of cancer-associated fatalities and the fourth most commonly diagnosed cancer. In addition to environmental risk factors, genetic factors may have a significant role in esophageal cancer carcinogenesis. A hospital-based case-control study was conducted to evaluate the genetic effects of functional single-nucleotide polymorphisms in the interleukin-18 (IL-18), IL-18 receptor 1 protein (IL-18R1), IL-18 receptor accessory protein (IL-18RAP) and IL-28B on the development of esophageal cancer. In total, 380 esophageal squamous cell carcinoma (ESCC) cases and 380 controls were recruited for the present study. The IL-18 rs360719 A>G, IL-18R1 rs13015714 G>T, IL-18RAP rs917997 C>T and IL-28B rs8099917 T>G genotypes were determined. No association was observed between the IL-18R1 rs13015714 G>T, IL-18RAP rs917997 C>T and IL-28B rs8099917 T>G polymorphisms and the risk of ESCC. However, in stratification analyses, a significantly decreased risk of ESCC associated with the IL-18R1 rs13015714 G>T polymorphism and a significantly increased risk of ESCC associated with the IL-18RAP rs917997 C>T polymorphism was evident among male patients and patients who smoked or consumed alcohol. These findings highlighted that functional polymorphisms IL-18R1 rs13015714 G>T and IL-18RAP rs917997 C>T may contribute to ESCC susceptibility among these subgroups. However, the present results were obtained with a limited sample size and further epidemiological studies are warranted to clarify the role of IL-18R1 and IL-18RAP variants in the development of ESCC.

Ethnicity-stratified analysis of the association between IL-18 polymorphisms and systemic lupus erythematosus in a European population: a meta-analysis

We performed a meta-analysis to identify the association between polymorphisms in the promoter of interleukin-18 (IL-18) and susceptibility for systemic lupus erythematosus (SLE) . Genotype data for three single-nucleotide polymorphisms (SNPs rs360719, rs1946518, and rs187238) in the IL-18 promoter were extracted from 20 studies of three different ethnicities (European, Asian, and South American). Data from each ethnicity group and their combinations were analyzed. We found distinct evidence of an association between rs360719 and SLE (P = 0.001) in the European/South American group [odds ratio (OR) 1.31 per C allele, 95% confidence interval (CI) 1.11-1.53]. Stratification analysis by ethnicity showed a significant association between rs360719 and SLE in the European population (OR 1.33 per C allele, 95% CI 1.11-1.61, P = 0.003) and a lesser effect in the same direction in the South American population (OR 1.18). A significant association was also identified between rs1946518 and SLE in the European population (OR 1.16 per A allele, 95% CI 1.03-1.30, P = 0.017), although there was no association in the Asian or the combined European/Asian population. We also examined genome-wide association study (GWAS) data from an Asian subpopulation (Chinese) for the association between rs1946518 and SLE, but found no association (P = 0.83). The third SNP, rs187238, was not significantly associated with SLE in any of the populations examined. In summary, this study identified a significant association between SLE and two SNPs within the IL-18 gene promoter region (rs360719 and rs1946518) in a European population, but not in populations of Asian origin.

T-cell cytokine gene polymorphisms and vitamin D pathway gene polymorphisms in end-stage renal disease due to type 2 diabetes mellitus nephropathy: comparisons with health status and other main causes of end-stage renal disease

BACKGROUND

T-cell cytokine gene polymorphisms and vitamin D pathway gene polymorphisms were evaluated as possibly associated with end-stage renal disease (ESRD) resulting from type 2 diabetes mellitus (DM) nephropathy.

METHODS

Studies were conducted among hemodialysis (HD) patients with ESRD due to type 2 DM nephropathy, chronic glomerulonephritis, chronic infective tubulointerstitial nephritis, and hypertensive nephropathy as well as in healthy subjects. A frequency distribution of T-cell-related interleukin (IL) genes (IL18 rs360719, IL12A rs568408, IL12B rs3212227, IL4R rs1805015, IL13 rs20541, IL28B rs8099917, IL28B, and rs12979860) and vitamin D pathway genes (GC genes: rs2298849, rs7041, and rs1155563; VDR genes: rs2228570, rs1544410; and RXRA genes: rs10776909, rs10881578, and rs749759) was compared between groups.

RESULTS

No significant differences in a frequency distribution of tested polymorphisms were shown between type 2 DM nephropathy patients and controls. A difference was found in IL18 rs360719 polymorphic distribution between the former group and chronic infective tubulointerstitial nephritic patients (P trend = 0.033), which also differed in this polymorphism from controls (P trend = 0.005).

CONCLUSION

T-cell cytokine and vitamin D pathway gene polymorphisms are not associated with ESRD due to type 2 DM nephropathy in Polish HD patients. IL18 rs360719 is probably associated with the pathogenesis of chronic infective tubulointerstitial nephritis.

IL-18 gene polymorphisms in aphthous stomatitis vs. Behçet's disease in a cohort of Egyptian patients

OBJECTIVE

A clinical investigation of the potential correlation of two single-nucleotide polymorphisms at -137 (G/C) and -607 (C/A) in the promoter region of the IL-18 gene, with the susceptibility to aphthous stomatitis and Behçet's disease.

PATIENT AND METHODS

This study included 80 aphthous stomatitis patients and 80 patients with Behçet's disease. Eighty healthy subjects were enrolled as a control group. IL-18 single-nucleotide polymorphisms at -607 and -137 regions were analyzed using polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

The genotype and allele distributions of the two regions did not differ significantly between patients with aphthous stomatitis and controls. The genotype and allele distributions at -607 were significantly different between patients with Behçet's disease [CC (P = 0.044), C allele (P = 0.043), A allele (P = 0.043)], and controls. The frequency of the GG genotype at position -137 in patients with Behçet's disease was associated only with a higher rate of ocular manifestations (OR= 1.4, CI= 0.76-2.7, P = 0.031).

CONCLUSION

IL-18 gene polymorphisms were not associated with any susceptibility to aphthous stomatitis, while a positive association was found with patients with Behçet's disease regarding -607 promoter site. Moreover, patients with Behçet's disease carrying the GG genotype at position -137 had a higher risk of developing ocular manifestations.

Interleukin-18 gene promoter--607 A/C polymorphism and the risk of immune thrombocytopenia

Interleukin-18 (IL-18) is a T helper 1 cytokine, which is postulated to play a role in immune thrombocytopenia (ITP). The aim of this study was to determine whether IL-18 promoter gene -607 A/C polymorphism was associated with ITP. Three-hundred and fifty-four Chinese ITP patients and 300 Chinese healthy individuals were enrolled. Genomic DNA was extracted from the peripheral blood. Polymerase chain reaction-restriction fragment length polymorphism (RFLP) was used to genotype the DNA samples for single nucleotide polymorphism (SNP)-607. Allelic and genotypic frequencies were compared between the case-control groups by the chi-square test. The results showed that the frequencies of the CC, CA and AA genotypes and C and A allele were 32.4, 47.8, 19.8, 56.4 and 43.6% in ITP patients and 32.3, 50.4, 17.3, 57.5 and 42.5% in the controls, respectively. There was no significant difference in either genotypes or allelic distribution between ITP patients and the controls. Furthermore, stratified analysis by the platelet count, age and disease course including ITP with severe thrombocytopenia (sITP), non-sITP, acute adult, chronic adult, acute childhood and chronic childhood revealed no significant difference in genotype and alleles distribution. In conclusion, this polymorphism was almost equally distributed between ITP patients and the controls. These data showed that this SNP may not be used as a stratification marker to predict the susceptibility to Chinese ITP.

Absence of association of interleukin-18 gene polymorphisms with primary immune thrombocytopenia in a Chinese Han population

Interleukin-18 (IL-18) is an inflammatory cytokine that plays an important role in autoimmune disease by inducing interferon-γ secretion. Considering the abnormal serum concentration of IL-18 in primary immune thrombocytopenia (ITP) patients and the regulated effect of IL-18 gene polymorphisms on its production, the aim of this study was to investigate a possible association between the IL-18 promoter polymorphisms (-137 G/C and -607 C/A sites) and genetic susceptibility to ITP in a Chinese Han population. A total of 181 ITP patients and 163 healthy controls were included in this study; IL-18 gene promoter polymorphisms were analyzed by a polymerase chain reaction with sequence-specific primers. No significant differences in genotype (-607: χ(2)=0.307, p=0.858; -137: χ(2)=0.378, p=0.828) and allele frequencies (-607: χ(2)=0.004, p=0.949; -137: χ(2)=0.307, p=0.858) were found between total ITP patients and normal controls. We further analyzed the association of IL-18 polymorphisms with clinical parameters of ITP patients, including first onset age and clinical therapy response to glucocorticoids, and no difference was revealed. In conclusion, IL-18 promoter polymorphisms may not be associated with genetic susceptibility to ITP in a Chinese Han population.

Association of interleukin-18 (-137G/C) polymorphism with rheumatoid arthritis and systemic lupus erythematosus: a meta-analysis

BACKGROUND

Recent studies have suggested that interleukin (IL)-18 gene (-137G/C) polymorphism is associated with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, other studies did not confirm this correlation.

OBJECTIVE

The objective of this study was to evaluate the relationships of IL-18 -137G/C and RA and SLE using a meta-analysis.

METHODS

Pubmed, Embase and Cochrane library databases were systemically searched. Data were extracted by two independent reviewers and pooled odds ratio (OR) with 95% confidence interval (CI) was calculated.

RESULTS

In RA, the overall ORs and 95% CIs of -137C were 1.03, 0.88-1.22 (p=0.391); 1.22, 0.89-1.68 (p=0.020) and 1.06, 0.93-1.21 (p=0.110) in dominant, recessive, and additive models, respectively. Furthermore, in SLE, the overall ORs and 95% CIs of -137C were 1.10, 0.94-1.29 (p=0.980); 1.21, 0.91-1.60 (p=0.010) and 1.10, 0.97-1.24 (p=0.454) in dominant, recessive, and additive models, respectively. IL-18 -137G/C could increase the risk of RA and SLE. No publication bias was found in this meta-analysis. After population stratification analysis, under recessive model, the pooled ORs and 95% CIs of -137C were 1.14, 0.82-1.60 (p=0.008) and 1.01, 0.66-1.55 (p=0.004) in European RA patients and Asian SLE patients, respectively.

CONCLUSIONS

This meta-analysis showed that IL-18 -137G/C was a risk factor for RA and SLE, especially for RA in Europeans and SLE in Asians.

Association of interleukin-18 promoter polymorphisms with chronic obstructive pulmonary disease in male smokers

Chronic obstructive pulmonary disease (COPD) is considered a complex genetic disorder and it is expected that many genes play a role in the pathogenesis of this disease. Previous studies have reported that several variations within the interleukin (IL)-18 gene promoter region have been associated with different inflammatory diseases such as asthma. However, the association of IL-18 promoter polymorphisms with COPD has not been studied yet. We then performed a prospective case-control study to explore this association in male smokers of Chinese Han people. Our study recruited 112 COPD cases and 105 healthy controls matched for age. The genotyping of IL-18 promoter polymorphisms (-607 C/A and -137 G/C) was performed using TaqMan single nucleotide polymorphism genotyping assays. The frequencies of the alleles and genotypes in patients and controls were compared. We found that the frequency of IL-18 -607 C allele was significantly increased in patients with COPD (odds ratio (OR) = 1.48, 95% confidence interval (CI) = 1.01-2.15, P = 0.04). The frequency of IL-18 -607 C allele was significantly higher in the GOLD (Global initiative for Obstructive Lung Disease) 3-4 group compared with the GOLD 1-2 group (OR=2.06, 95% CI = 1.21-3.51, P = 0.01). There were no significant differences in the frequencies of the alleles and genotypes of IL-18 -137 G/C polymorphism between the patients and healthy smokers or between GOLD 3-4 group and GOLD 1-2 group. Our study revealed that the IL-18 -607 C/A polymorphism was associated with COPD susceptibility and severity of airflow limitation in male smokers of Chinese Han people.

The IL18 gene and Hashimoto thyroiditis in children

Interleukin 18 (IL18) stimulates interferon-γ production in Th1 cells which are prominent in the thyroid of Hashimoto thyroiditis (HT). We investigated the association between the IL18 gene and HT. There were 116 children with HT and 1272 controls. rs187238 and rs1946518 in the promoter region of the IL18 gene were genotyped. Differences in genotype, allele, carrier, and haplotype distributions between patients and controls were compared. A Pc value <0.05 was considered significant. The frequency of the C/G genotype of rs187238 was significantly higher in patients and conferred a risk of HT (OR, 1.96; 95% CI, 1.30-2.95; Pc, 0.0021). So did the frequencies of allele C (OR, 1.73; 95% CI, 1.22-2.44; Pc, 0.0035) and carrier C (OR, 1.96; 95% CI, 1.31-2.92; Pc, 0.0017), however the frequency of the G/G genotype was significantly lower in patients than in controls (OR, 0.51; 95% CI, 0.34-0.76; Pc, 0.0034). There was no association between HT and rs1946518. The CT haplotype was significantly more frequent in patients than in controls and conferred a risk of HT (OR, 1.76; 95% CI, 1.24-2.49; Pc, 0.0049). We concluded that the IL18 gene was associated with HT in children. The rs187238C allele and CT haplotype conferred a risk of HT.

Immunoregulatory natural killer cells suppress autoimmunity by down-regulating antigen-specific CD8+ T cells in mice

Natural killer (NK) cells belong to the innate immune system. Besides their role in antitumor immunity, NK cells also regulate the activity of other cells of the immune system, including dendritic cells, macrophages, and T cells, and may, therefore, be involved in autoimmune processes. The aim of the present study was to clarify the role of NK cells within this context. Using two mouse models for type 1 diabetes mellitus, a new subset of NK cells with regulatory function was identified. These cells were generated from conventional NK cells by incubation with IL-18 and are characterized by the expression of the surface markers CD117 (also known as c-Kit, stem cell factor receptor) and programmed death (PD)-ligand 1. In vitro analyses demonstrated a direct lysis activity of IL-18-stimulated NK cells against activated insulin-specific CD8(+) T cells in a PD-1/PD-ligand 1-dependent manner. Flow cytometry analyses revealed a large increase of splenic and lymphatic NK1.1(+)/c-Kit(+) NK cells in nonobese diabetic mice at 8 wk of age, the time point of acceleration of adaptive cytotoxic immunity. Adoptive transfer of unstimulated and IL-18-stimulated NK cells into streptozotocin-treated mice led to a delayed diabetes development and partial disease prevention in the group treated with IL-18-stimulated NK cells. Consistent with these data, mild diabetes was associated with increased numbers of NK1.1(+)/c-Kit(+) NK cells within the islets. Our results demonstrate a direct link between innate and adaptive immunity in autoimmunity with newly identified immunoregulatory NK cells displaying a potential role as immunosuppressors.

Antibodies to hepatitis B virus surface antigen and interleukin 12 and interleukin 18 gene polymorphisms in hemodialysis patients

BACKGROUND

The interleukin (IL)18 rs360719 CC genotype is associated with the development of antibodies to hepatitis B virus surface antigen (anti-HBs) in hemodialysis (HD) patients. IL18 shares biological properties with IL12 in promoting the T-hepler 1 (Th1) system. We studied whether polymorphisms in the IL12A 3` untranslated region (UTR) and IL12B 3`UTR may contribute to anti-HBs development (titre ≥ 10 IU/L) in HD patients either individually or jointly with the IL18 polymorphism.

METHODS

In 518 HD patients and 240 controls the IL12A rs568408 3'UTR G > A polymorphism was genotyped by high-resolution melting curve analysis. Polymerase chain reaction restriction fragment length polymorphism was used to detect the IL12B rs3212227 3'UTR A > C and IL18 -1297 T > C rs360719 polymorphisms. The associations between the IL12A, IL12B and IL18 genotypes and the risk of impaired anti-HBs development were estimated by computing the odds ratios and their 95% confidence intervals using logistic regression analysis.

RESULTS

In the logistic regression analysis, the higher frequency of rs360719 CC individually (2.9% in 207 patients without anti-HBs development vs 8.0% in 311 patients with anti-HBs development, p = 0.009) and of rs360719 CC combined with rs568408 GG (p = 0.048), rs568408 GA (p = 0.035), rs568408 GG/AA (p = 0.034) or rs3212227 AA (p = 0.046) was associated with an increased chance for the development of anti-HBs in HD patients. Patients bearing both rs568408 AA and rs360719 TT had a 10.9-fold or 8.9-fold lower chance, respectively, to develop anti-HBs compared with those carrying any other genotype (p = 0.005) or those who had both wild-type rs568408 GG and rs360719 TT (p = 0.011). Carriers of both rs3212227 CC and rs360719 TC had a 4.6-fold lower chance for anti-HBs development than carriers of any other genotype (p = 0.042).

CONCLUSION

Development of anti-HBs in HD patients is associated with gene polymorphisms of interleukins involved in the Th1 system.

Mechanisms of environmental influence on human autoimmunity: a National Institute of Environmental Health Sciences expert panel workshop

The mechanisms leading to autoimmune diseases remain largely unknown despite numerous lines of experimental inquiry and epidemiological evidence. The growing number of genome-wide association studies and the largely incomplete concordance for autoimmune diseases in monozygotic twins support the role of the environment (including infectious agents and chemicals) in the breakdown of tolerance leading to autoimmunity via numerous mechanisms. The present article reviews the major theories on the mechanisms of the environmental influence on autoimmunity by addressing the different degrees of confidence that characterize our knowledge. The theories discussed herein include (i) the role of innate immunity mediated by toll-like receptors in triggering the autoimmune adaptive response characterizing the observed pathology; (ii) changes in spleen marginal zone B cells in autoantibody production with particular focus on the B10 subpopulation; (iii) Th17 cell differentiation and T regulatory cells in the aryl hydrocarbon receptor model; (iv) self antigen changes induced by chemical and infectious agents which could break tolerance by post-translational modifications and molecular mimicry; and finally (v) epigenetic changes, particularly DNA methylation, that are induced by environmental stimuli and may contribute to autoimmunity initiation. We are convinced that these working hypotheses, in most cases supported by solid evidence, should be viewed in parallel with animal models and epidemiological observations to provide a comprehensive picture of the environmental causes of autoimmune diseases.

Interleukin-18 promoter polymorphism and development of antibodies to surface antigen of hepatitis B virus in hemodialysis patients

BACKGROUND

Interleukin (IL)-18 is involved in hepatitis B virus (HBV) clearance and augments antibodies against surface antigen of HBV (anti-HBsAg) production during DNA vaccination. The IL-18 -1297C>T (rs360719) polymorphism may modulate the IL-18 expression.

AIM

To determine the potential association of IL-18 -1297C>T polymorphism with development of anti-HBsAg in hemodialysis (HD) patients.

METHODS

The frequency of IL-18 -1297C>T alleles and genotypes was identified by polymerase chain reaction restriction fragment length polymorphism in 435 HD patients. Group 1 (n = 219) developed an anti-HBsAg titer >10 IU/l as a result of vaccination or HBV transmission. Group 2 (n = 216) included patients who did not develop an anti-HBsAg titer >10 IU/l in response to at least one full series of vaccination or HBV transmission. The significance of genotype frequency was tested using the Fisher exact test.

RESULTS

In group 1, the frequencies of -1297CC, -1297CT and -1297TT genotypes were 7.3, 39.7 and 53.0%, respectively, and in group 2 they were 1.9, 42.1 and 56.0%, respectively. The odds ratio for CC versus CT + TT was 0.239 (95% CI 0.079-0.728, p = 0.010), and for CC versus TT it was 0.240 (95% CI 0.078-0.738, p = 0.009).

CONCLUSION

In HD patients, the IL-18 -1297CC genotype may play a role in anti-HBsAg development in response to HBV surface antigen.

Lack of association of interleukin-18 gene promoter -607 A/C polymorphism with susceptibility to autoimmune diseases: a meta-analysis

OBJECTIVE

Published data on the association between interleukin (IL)-18 gene promoter -607 A/C polymorphism and autoimmune diseases risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed.

METHODS

A total of 17 studies, including six studies on type 1 diabetes (T1D), four on rheumatoid arthritis (RA), five on systemic lupus erythematosus (SLE), three on Crohn's Disease (CD) and three on ulcerative colitis (UC), were available for the meta-analysis. Meta-analysis was performed for genotypes A/A (recessive effect), genotypes A/A + A/C (dominant effect), and A allele in fixed or random-effects models.

RESULTS

Overall, no significantly elevated autoimmune diseases risk was found in all genetic models when all studies were pooled into the meta-analysis. The overall odds ratios (ORs) and 95% confidence intervals (CIs) for A-allele were T1D (OR = 0.938, 95% CI = 0.757-1.162), RA (OR = 0.759, 95% CI = 0.540-1.067), SLE (OR = 0.858, 95% CI = 0.609-1.208), CD (OR = 1.159, 95% CI = 0.975-1.379) and UC (OR = 1.170, 95% CI = 0.977-1.402), respectively. In the subgroup analysis by ethnicity, there was still no significant association detected in all genetic models.

CONCLUSIONS

To date, there is still not enough evidence to indicate the association of IL-18 gene promoter -607 A/C polymorphism and the development of autoimmune diseases.

Association of polymorphisms in the Interleukin-18 gene with susceptibility to biliary atresia

BACKGROUND AND OBJECTIVE

Biliary atresia (BA) is a destructive inflammatory obliterative cholangiopathy of neonates that affects both intrahepatic and extrahepatic bile ducts. Although the etiology is unknown, immunologically mediated injury of the bile ducts triggered by as yet unidentified infectious agents is likely to play a critical role. Interleukin-18 (IL-18) is a proinflammatory cytokine that plays an important role in immune, infectious, and inflammatory diseases because of its induction of interferon-gamma. In this study, we investigated whether polymorphisms of the IL18 gene were associated with susceptibility to BA.

PATIENTS AND METHODS

Genomic DNA was extracted from whole-blood samples of 50 Taiwanese children with BA and 1117 ethnically matched healthy controls. The IL18 -1297 T/C, -607 C/A, -137 G/C, and +105 A/C polymorphisms were genotyped using the TaqMan assay.

RESULTS

No statistically significant differences of genotype, allele, carrier, and haplotype frequencies of these IL18 gene variants were found between children with BA and healthy controls.

CONCLUSIONS

Our data suggest that the IL18 gene does not play a major role in BA predisposition in Taiwanese children.

Dense mapping of IL18 shows no association in SLE

Systemic lupus erythematosus (SLE) is an autoimmune disease which behaves as a complex genetic trait. At least 20 SLE risk susceptibility loci have been mapped using both candidate gene and genome-wide association strategies. The gene encoding the pro-inflammatory cytokine, IL18, has been reported as a candidate gene showing an association with SLE. This pleiotropic cytokine is expressed in a range of immune cells and has been shown to induce interferon-γ and tumour necrosis factor-α. Serum interleukin-18 has been reported to be elevated in patients with SLE. Here we aimed to densely map single nucleotide polymorphisms (SNPs) across IL18 to investigate the association across this locus. We genotyped 36 across IL18 by Illumina bead express in 372 UK SLE trios. We also genotyped these SNPs in a further 508 non-trio UK cases and were able to accurately impute a dense marker set across IL18 in WTCCC2 controls with a total of 258 SNPs. To improve the study's power, we also imputed a total of 158 SNPs across the IL18 locus using data from an SLE genome-wide association study and performed association testing. In total, we analysed 1818 cases and 10 770 controls in this study. Our large well-powered study (98% to detect odds ratio = 1.5, with respect to rs360719) showed that no individual SNP or haplotype was associated with SLE in any of the cohorts studied. We conclude that we were unable to replicate the SLE association with rs360719 located upstream of IL18. No evidence for association with any other common variant at IL18 with SLE was found.

Elevated interleukin-18 and skewed Th1:Th2 immune response in lupus nephritis

There is evidence that interleukin-18 plays a role in lupus nephritis (LN). Since interleukin -18 (IL-18) promotes polarization of the immune response toward Th1, we investigated level of IL-18 and assessed the phenotypic distribution of Th1 and Th2 type cells in LN. A predominance of Th1 type (IFN-γ+) cells and significant correlations with serum IL-18 was seen in the patients with LN compared to healthy controls. Although most patients were treated with high dosage of glucocorticoid and other immunosuppressive agents, higher level of IL-18 was found in both serum and glomeruli. However, there was no paralleled upregulation of its gene expression in peripheral blood mononuclear cells. Our findings indicate that the elevated IL-18 should be a symbol of disease activity and play a major role in the pathogenesis of LN by promoting cytokine imbalance towards Th1 type immune response. We conclude that patients with LN would benefit from it while the bioactivity of this cytokine was effectively counteracted.

Interleukin 4 and STAT6 gene polymorphisms are associated with systemic lupus erythematosus in Chinese patients

An imbalance between T Helper 1 (TH1) and T Helper 2 (TH2) cytokine production is important for the pathogenesis of systemic lupus erythematosus (SLE). We aimed to investigate gene—gene associations of TH1 and TH2 cytokines genes in Chinese patients with SLE. Twenty single nucleotide polymorphisms (SNPs) in eight cytokines genes were genotyped in 110 SLE patients and 138 healthy controls in a case—control association study. The minor allelic frequencies of interleukin4(IL4) -590 T/C, -33 T/C, 9241C/G, and IL10 -592 A/C were significantly increased in SLE patients compared with those in controls (p < 0.05). None of the separate 20 SNPs showed significant association with SLE after Bonferroni correction. An IL4 haplotype -590C/-33C/9241G/14965C was significantly associated with SLE (odds ratio 3.7, 95% confidence interval [CI] 1.5—8.9, p = 0.004, Bonferroni-corrected p = 0.024). A borderline significant three-locus gene—gene interaction among IL4 9241 C/G, IL4 -33 T/C, signal transducer and activator of transcription 6, IL4-induced (STAT6) 2892 C/T was detected by a multifactor dimensionality reduction test (p = 0.051). However, the presence of two at-risk genotypes lead to increased risk of SLE for two-locus interaction using logistic regression method. The risk of SLE increased significantly when a subject has two at-risk genotypes for IL4 -590C and STAT6 2892C (odds ratio, 3.24, 95% CI 1.5—7.0, p = 0.003, Bonferroni-corrected p = 0.009), IL4 -33C and STAT6 2892C (odds ratio 3.06, 95% CI 1.4— 6.7, p = 0.005, Bonferroni-corrected p = 0.015), as well as IL4 9241G and STAT6 2892C (odds ratio 3.34, 95% CI 1.6—7.1, p = 0.002, Bonferroni-corrected p = 0.006). Further, plasma IL-4 concentrations were significantly lower in SLE patients than in healthy controls (1.59 + 3.53 versus 5.67 + 11.28 pg/ml, p = 0.042). These results indicated that IL4 and STAT6 genes might be involved in the etiology of SLE and potentially increased SLE risk through their interaction effect in Chinese patients.

Haplotype analysis of the interleukin-18 gene in Czech patients with allergic disorders

The interleukin-18 (IL-18) gene on chromosome 11q22 has been suggested as a susceptibility factor for allergies. To test for a possible role of IL-18 polymorphisms in Czech population, case-control study including 958 subjects (633 allergic patients and 325 healthy controls) was performed. An allele-specific polymerase chain reaction was used to analyze variants at positions -607 C/A (rs1946518) and -137 G/C (rs187238) in the promoter region together with the polymerase chain reaction-restriction fragment length polymorphism method for the detection of polymorphism at position -140 C/G (previously -133 C/G, rs360721) in intron 1 of the IL-18 gene. The -1297 C/T (rs360719) polymorphism was genotyped by real-time-polymerase chain reaction, using a predevelopment TaqMan allele discrimination assay. There were no significant differences in distribution of alleles or genotypes in any of four single nucleotide polymorphisms in the IL-18 gene between controls and patients. However, subsequent analysis revealed a significant difference in haplotype frequencies between the allergic patients and healthy subjects (p < 0.01). Haplotype formed by -1297 C/-607 A/-137 C/-140 C alleles occurred significantly more frequently in patients than controls (0.0433 vs 0.0129; p < 0.0003; p(corr)< 0.01, OR = 3.37; 95% CI = 1.59-7.14). In contrast, there was no relationship among the IL-18 variants and total serum IgE level. Our results indicate that promoter polymorphisms in the IL-18 gene act in interaction and could play a role in allergic disorders.

Interleukin-18 gene polymorphism and markers of subclinical atherosclerosis. The Cardiovascular Risk in Young Finns Study

BACKGROUND AND AIM

Interleukin-18 (IL-18) is a pro-atherosclerotic cytokine. We wanted to evaluate whether IL-18 gene polymorphism associates independently of risk factors, with early subclinical markers of atherosclerosis (intima-media thickness (IMT), coronary artery compliance (CAC), and flow-mediated dilatation (FMD)) in a population of young healthy Caucasian adults.

METHODS

This study was based on the on-going Cardiovascular Risk in Young Finns Study consisting of 2260 young adults, mean age being 31.7 (range 24-39 years) (1247 women and 1013 men).

RESULTS

Five studied tagSNPs formed six major haplotypes, which accounted for 99.9% of all variation of the IL-18 gene. According to adjusted analysis of variance, the IL-18 gene polymorphism did not associate with subclinical atherosclerosis in the whole study population. However, one major haplotype associated differently among men and women with IMT (P = 0.011). Male carriers of a major CCTgT haplotype (n = 441) seemed to have a lower IMT when compared to the non-carriers (-0.016 mm, 95% confidence interval (CI) -0.028 to -0.004, P = 0.014). Among women no significant associations were observed.

CONCLUSIONS

Among all study subjects, the polymorphism of the IL-18 gene is not associated with subclinical markers of atherosclerosis. However, among men one major IL-18 haplotype seemed to associate with substantially lower IMT values.

Association between IL-18 gene polymorphisms and biopsy-proven giant cell arteritis

INTRODUCTION

The objective was to investigate the potential implication of the IL18 gene promoter polymorphisms in the susceptibility to giant-cell arteritis (GCA).

METHODS

In total, 212 patients diagnosed with biopsy-proven GCA were included in this study. DNA from patients and matched controls was obtained from peripheral blood. Samples were genotyped for the IL18-137 G>C (rs187238), the IL18-607 C>A (rs1946518), and the IL18-1297 T>C (rs360719) gene polymorphisms with polymerase chain reaction, by using a predesigned TaqMan allele discrimination assay.

RESULTS

No significant association between the IL18-137 G>C polymorphism and GCA was found. However, the IL18 -607 allele A was significantly increased in GCA patients compared with controls (47.8% versus 40.9% in patients and controls respectively; P = 0.02; OR, 1.32; 95% CI, 1.04 to 1.69). It was due to an increased frequency of homozygosity for the IL18 -607 A/A genotype in patients with GCA (20.4%) compared with controls (13.4%) (IL18 -607 A/A versus IL18 -607 A/C plus IL18 -607 C/C genotypes: P = 0.04; OR, 1.59; 95% CI, 1.02 to 2.46). Also, the IL18-1297 allele C was significantly increased in GCA patients (30.7%) compared with controls (23.0%) (P = 0.003; OR, 1.48; 95% CI, 1.13 to 1.95). In this regard, an increased susceptibility to GCA was observed in individuals carrying the IL18-1297 C/C or the IL18-1297 C/T genotypes compared with those carrying the IL18-1297 T/T genotype (IL18-1297 C/C plus IL18-1297 T/C versus IL18-1297 T/T genotype in GCA patients compared with controls: P = 0.005; OR, 1.61; 95% CI, 1.15 to 2.25). We also found an additive effect of the IL18 -1297 and -607 polymorphisms with TLR4 Asp299Gly polymorphism. The OR for GCA was 1.95 for combinations of genotypes with one or two risk alleles, whereas carriers of three or more risk alleles have an OR of 3.7.

CONCLUSIONS

Our results show for the first time an implication of IL18 gene-promoter polymorphisms in the susceptibility to biopsy-proven GCA. In addition, an additive effect between the associated IL18 and TLR4 genetic variants was observed.

High circulating levels of free interleukin-18 in patients with active SLE in the presence of elevated levels of interleukin-18 binding protein

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies particularly to nuclear antigens and by an abnormal production of proinflammatory cytokines. In the present study, we measured the levels of the proinflammatory cytokine IL-18 and its natural inhibitor, the IL-18 binding protein (IL-18BP), in sera of SLE patients at various stages of the disease. This is the first study to present IL-18BP levels in sera of SLE patients as well as the calculated, biologically active, free IL-18 concentrations that are most probably more relevant to the pathology of SLE. Sera from 48 unselective SLE patients (total of 195 samples) were obtained longitudinally with a mean follow-up period of 11.1 +/- 8.9 years and were compared to sera from 100 healthy volunteers. Circulating levels of IL-18, IL-18BP and free IL-18 in the SLE patients were significantly higher than the levels of healthy controls (5 fold, 6 fold and 3 fold for IL-18, IL-18BP and free IL-18, respectively) and correlated with disease activity as scored by SLEDAI-2K. Furthermore, these levels during active disease (SLEDAI-2K > or = 6) were higher compared to the levels measured in the sera of the same patients during remission or during mild disease (SLEDAI-2K 0-5). The high levels of IL-18 and IL-18BP in sera of active SLE patients suggest their possible role in the pathogenesis and course of the disease. However, despite the elevated levels of IL-18BP during active disease, free IL-18 remained more than 2 fold higher than the levels in healthy controls suggesting a potential benefit of administration of exogenous IL-18BP as a novel therapeutic approach for active SLE.