Differential haplotypic expression of the interleukin-18 gene

Protective effects of IL18-105G > A and IL18-137C > Ggenetic variants on severity of COVID-19

OBJECTIVE AND DESIGN

A cross-sectional study evaluated the IL18-105G > A (rs360717) and IL18-137C > G (rs187238) variants on Coronavírus Disease 2019 (COVID-19) severity.

SUBJECTS AND METHODS

528 patients with COVID-19 classifed with mild (n = 157), moderate (n = 63) and critical (n = 308) disease were genotpyed for the IL18-105G > A and IL18-137C > G variants.

RESULTS

We observed associations between severe + critical COVID-19 groups (reference group was mild COVID-19) and the IL18-105G > A (p = 0.008) and IL18-137C > G (p = 0.01) variants, which remained significant after adjusting for sex, ethnicity and age. Consequently, we have examined the associations between moderate + critical COVID-19 and the genotypes of both variants using different genetic models. The IL18-105G > A was associated with severe disease (moderate + critical), with effects of the GA genotype in the codominant [Odds ratio (OR), (95 % confidence interval) 0.55, 0.34-0.89, p = 0.015], overdominant (0.56, 0.35-0.89, p = 0.014) and dominant (0.60, 0.38-0.96, p = 0.031) models. IL18-105 GA coupled with age, chest computed tomograhy scan anormalities, body mass index, heart diseases, type 2 diabetes mellitus, hypertension, and inflammation may be used to predict the patients who develop severe disease with an accuracy of 84.3 % (sensitivity: 83.3 % and specificity: 86.5 %). Therefore, the presence of the IL18-105 A allele in homozygosis or heterozygosis conferred about 44.0 % of protection in the development of moderate and severe COVID-19. The IL18-137C > G variant was also associated with protective effects in the codominant (0.55, 0.34-0.89, p = 0.015), overdominant (0.57, 0.36-0.91, p = 0.018), and dominant models (0.59, 0.37-0.93, p = 0.025). Therefore, the IL18-137 G allele showed a protective effect against COVID-19 severity.

CONCLUSION

The IL18-105G > A and IL18-137C > Gvariants may contribute with protective effects for COVID-19 severity and the effects of IL18-137C > G may be modulating IL-18 production and Th1-mediated immune responses.

The Progress of Research on Genetic Factors of Recurrent Pregnancy Loss

Recurrent pregnancy loss (RPL) is both mental and physical health problem affecting about 1-5% of women of childbearing age. The etiology of RPL is complex, involving chromosomal abnormalities, autoimmune diseases, metabolic disorders, and endometrial dysfunction. The causes of abortion are still unknown in more than 50% of these cases. With the development of science and technology, an increasing number of scholars focus on this field and find that genetic factors may play an essential role in unexplained RPL, such as embolism-related genes, immune factor-related genes, and chromosomal numeric, and structural variation. This review summarizes the genetic factors associated with RPL, including genetic mutations and genetic polymorphisms, chromosomal variants, and chromosomal polymorphisms. Many related genetic factors have been found to be demographically and geographically relevant, some of which can be used for risk prediction or screening for the etiology of RPL. However, it is difficult to predict and prevent RPL due to uncertain pathogenesis and highly variable clinical presentation. Therefore, the genetic factors of RPL still need plentiful research to obtain a more accurate understanding of its pathogenesis and to provide more detection means for the screening and prevention of RPL.

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.

Association between Genetic Polymorphisms in Interleukin Genes and Recurrent Pregnancy Loss - A Systematic Review and Meta-Analysis

Interleukins are a group of immunomodulatory proteins that mediate a variety of immune reactions in the human body. To investigate the association between interleukin gene polymorphisms and recurrent pregnancy loss (RPL), we reviewed 21 studies from MEDLINE, EMBASE, OVID SP and PubMed to evaluate RPL-related interleukin gene polymorphisms. Meta-analysis was performed on 12 of the polymorphisms, and a review included the others. Our integrated results indicated that IL-1β (-511C/T) (P = 0.02, 95% CI 0.77[0.62,0.96]), IL-6 (-634C/G) (P<0.001, 95% CI 2.91[2.01,4.22]), IL-10 (-1082G/A, -819T/C) (P = 0.01, 95% CI 0.80[0.67,0.96]; P<0.01, 95% CI 0.66[0.49,0.89]), and IL-18 (-137G/C, -105G/A) (P<0.01, 95% CI 1.69[1.24,2.31]; P = <0.01, 95% CI 1.41[1.17,1.70]) consistently associated with RPL after meta-analysis. IL-17A rs2275913 and IL-17F rs763780, IL-21 rs2055979 and rs13143866, IL-1β (-31C/T), IL-6 (-2954G/C), and IL-10 (-536A/G) were reported only once as having a significant association with RPL. The potential mechanism underlying miscarriage and these polymorphisms and future research directions are also discussed.

Molecular Characterization of the NLRC4 Expression in Relation to Interleukin-18 Levels

BACKGROUND

Interleukin-18 (IL-18) is a pleiotropic cytokine centrally involved in the cytokine cascade with complex immunomodulatory functions in innate and acquired immunity. Circulating IL-18 concentrations are associated with type 2 diabetes mellitus, cardiovascular events, and diverse inflammatory and autoimmune disorders.

METHODS AND RESULTS

To identify causal variants affecting circulating IL-18 concentrations, we applied various omics and molecular biology approaches. By genome-wide association study, we confirmed association of IL-18 levels with a single nucleotide polymorphism in the untranslated exon 2 of the inflammasome component NLRC4 (NLR family, caspase recruitment domain-containing 4) gene on chromosome 2 (rs385076; P=2.4 × 10(-45)). Subsequent molecular analyses by gene expression analysis and reporter gene assays indicated an effect of rs385076 on NLRC4 expression and differential isoform usage by modulating binding of the transcription factor PU.1.

CONCLUSIONS

Our study provides evidence for the functional causality of single nucleotide polymorphism rs385076 within the NLRC4 gene in relation to IL-18 activation.

Interleukin-18 gene polymorphisms and risk of recurrent pregnancy loss: A systematic review and meta-analysis

Interleukin-18 (IL-18) plays a potential pathological role in recurrent pregnancy loss (RPL). The results of published studies on the relationship between IL-18 gene promoter polymorphisms (-137G/C and-607C/A) and RPL risk remain controversial. This meta-analysis was performed to evaluate the association of IL-18, -137G/C and-607C/A gene polymorphisms with the risk of RPL under recessive, dominant and additive genetic models. A literature search was conducted in Medline, Embase and Web of Science for studies that described the effect of IL-18 gene polymorphisms on RPL risk. The numbers of each -137G/C and-607C/A genotype in the case and control groups were extracted. Quality of the original studies' methodology was also assessed. Meta-analysis was performed using Stata 13.1 software and the fixed effect model was used. Five articles were included in this meta-analysis. No significant heterogeneity between the studies was noted. The IL-18 -137 G/C polymorphism was significantly associated with an increased risk of RPL under a recessive genetic model (CC vs. GG + CG: odds ratio = 1.56, 95% confidence interval = 1.13 ~ 2.15). For the -607C/A mutation, we failed to find any association under any genetic models. The Egger's regression asymmetry test showed no publication bias. Our present study indicates a positive association between the CC genotype of the IL-18 -137G/C gene and RPL risk. Future well-designed large studies are needed to validate the association between IL-18 gene polymorphisms and the risk of RPL.

Genetic variant in interleukin-18 is associated with idiopathic recurrent miscarriage in Chinese Han population

Levels of IL-18 were significantly lower in women with recurrent miscarriage (RM) than those without idiopathic RM. IL-18 promoter single nucleotide polymorphisms were previously identified to have an impact on IL18 gene transcription activity and influence the level of IL-18 protein production. The aim of this study was to evaluate whether IL-18 gene polymorphisms are risk factors for idiopathic RM in Chinese Han population. Study subjects comprised of 484 idiopathic RM patients and 468 controls. Three polymorphisms (rs360717, rs187238, rs1946518) in IL-18 gene and serum IL-18 concentrations were assessed. rs187238 variant exhibits significant association with RM in additive and recessive genetic model (additive model p = 1.05 × 10⁻⁴, dominant model p = 0.025, recessive model p = 2.43 × 10⁻⁵). In contrast, rs360717 and rs1946518 are not significantly associated with RM. Serum IL-18 levels are significantly lower in RM cases than in control (111.98 ± 93.13 versus 148.74 ± 130.51 pg/mL, p = 7.42 × 10⁻⁷). There are lower levels of serum IL-18 in rs187238 homozygous mutant (CC) than homozygous wild-type (GG) in this study population, including cases and control groups (98.31 ± 86.46 versus 131.87 ± 115.02 pg/mL, p = 0.015). These results suggest that reduced IL-18 levels and rs187238 variant may contribute to pathogenesis of idiopathic RM in Chinese Han population.

3'-UTR OLR1/LOX-1 gene polymorphism and endothelial dysfunction: molecular and vascular data in never-treated hypertensive patients

Endothelial dysfunction represents an independent predictor for clinical events. Genetic background may promote deleterious alterations of endothelial physiology. The aim of the study was to investigate the relationship between the rs1050283 polymorphism in the 3'-UTR of OLR1/LOX-1 gene and endothelial dysfunction in 178 never-treated hypertensive patients and 36 healthy subjects. The rs1050283 C/T single nucleotide polymorphism was detected, by TaqMan allelic discrimination assay. The influence of polymorphism on gene transcription rate was tested in 12 heterozygous hypertensive patients, by using an allelic imbalance assay. Forearm blood flow (FBF) was measured during intra-arterial infusion of acetylcholine (ACh), and sodium nitroprusside at increasing doses. Analysis of endothelium-dependent and endothelium-independent vasodilatation was tested according to rs1050283 polymorphism. In hypertensive patients, ACh-stimulated FBF is significantly reduced in T allele carriers (P < 0.0001), even when the allelic imbalance assay indicates an overexpression of C allele. In healthy subjects, there is no significant difference for ACh-dependent vasodilatation among genotypic groups (P = 0.660). In essential hypertensive patients, the T allele of OLR1/LOX-1 gene is strongly associated with an impaired endothelium-dependent vasodilatation, a powerful predictor of cardiovascular events.

The role of the inflammasome in cardiovascular diseases

Inflammasome is a very important signaling platform sensing a variety of triggers of the innate immune system. Inflammasome promotes the production of important pro-inflammatory cytokines such as IL-1β and IL-18. Tight control of inflammasome activity is, therefore, essential and occurs at multiple levels. The activation of inflammasome pathways is linked to the pathogenesis of various prevalent disorders including cardiovascular disease such as atherosclerosis, ischemic injury, cardiomyopathy, and Kawasaki disease. The study of the inflammasome in the cardiovascular system has led to the identification of important triggers and endogenous modulators, and to the exploration of new treatment strategies based on the inhibition of inflammasome activation or its end products, i.e., IL-1β and IL-18. In summary, the discovery of the inflammasome has greatly advanced our understanding of how the innate immune system interferes with cardiovascular disease development and progression, and targeting inflammasome provides new avenues for the treatment and management of cardiovascular diseases.

Interleukin-18 promoter polymorphisms and risk of idiopathic recurrent pregnancy loss in a Tunisian population

IL-18 is a pro-inflammatory cytokine that regulates the differentiation and effector functions of CD4+ (Th1) and CD8+ (CTL) T cells, which are implicated in the pathogenesis of recurrent pregnancy loss (RPL). We investigated the association of the IL-18 gene promoter single nucleotide polymorphisms (SNPs) -656C/A (rs1946519), -137G/C (rs187238), -119A/C (rs360718), and -105G/A (rs360717), by TaqMan assays in analysis in 470 Tunisian women comprising 235 RPL cases and 235 multi-parous controls. The association of IL-18 alleles, genotypes, and haplotypes with RPL was evaluated by Fisher's exact test and regression analysis. The frequency of minor alleles -105G/A (P<0.001) and -656C/A (P<0.001), but not -119A/C (P=0.93) or -137G/C (P=0.32), were higher in RPL cases. Significant differences were also noted in the genotype distribution of -105G/A (P<0.001) and -656C/A (P<0.001) between cases and controls. Four-locus (-656C/A, -137G/C, -119A/C, -105G/A) IL-18 haplotype analysis identified AGAA (corrected P<0.001), and CGAA (corrected P<0.001) haplotypes to be associated with increased RPL risk, after adjusting for age and BMI. These results demonstrate that -105G/A and -656C/A IL-18 variants are significantly associated with RPL.

Circulating levels of IL-18 are significantly influenced by the IL-18 +183 A/G polymorphism in coronary artery disease patients with diabetes type 2 and the metabolic syndrome: an observational study

BACKGROUND

Increased IL-18 serum levels have been associated with diabetes type 2, metabolic syndrome and the severity of atherosclerosis. The present study investigated the presence and influence of IL-18 genetic variants on gene- and protein expression in stable coronary artery disease (CAD) patients.

METHODS

The +183 A/G (rs 5744292), -137 G/C (rs 187238) and -607 C/A (rs 1946518) polymorphisms were determined in 1001 patients with angiographically verified stable CAD, and in 204 healthy controls. IL-18 gene-expression was measured in circulating leukocytes in 240 randomly selected patients. Circulating IL-18 and IL-18 binding protein levels were measured immunologically in all patients.

RESULTS

The +183 G-allele associated significantly with lower serum levels of IL-18 (p = 0.002, adjusted for age, glucose, body mass index and gender) and a 1.13- fold higher IL-18 gene-expression (p = 0.010). No influence was observed for the -137 G/C and -607 C/A polymorphisms. The IL-18 binding protein levels were not influenced by IL-18 genotypes. IL-18 levels were significantly higher in men as compared to women, and in patients with diabetes type 2 and metabolic syndrome compared to those without (p ≤ 0.001, all). The reduction in IL-18 levels according to the +183 G-allele was 3-4 fold more pronounced in diabetes and metabolic syndrome as compared to unaffected patients.Finally, the +183 AA genotype was more frequent in patients with hypertension (p = 0.042, adjusted for age, body mass index and gender).

CONCLUSION

The reduction in serum IL-18 levels across increasing numbers of +183 G-alleles was especially apparent in patient with diabetes type 2 and metabolic syndrome, suggesting a beneficial GG genotype in relation to cardiovascular outcome in these patients.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT00222261.

Genetic association analyses of atopic illness and proinflammatory cytokine genes with type 1 diabetes

BACKGROUND

The genetic basis of the autoimmune disease type 1 diabetes (T1D) has now been largely determined, so now we can compare these findings with emerging genetic knowledge of disorders and phenotypes that have been negatively or positively associated with T1D historically. Here, we assessed the role in T1D of variants previously reported to be associated with atopic diseases and epithelial barrier function, profilaggrin (FLG), and those that affect the expression levels of the proinflammatory cytokines tumour necrosis factor (TNF)-α, interleukin (IL)-1β, interferon (IFN)γ and IL-18.

METHODS

We genotyped single nucleotide polymorphisms (SNPs): -105/rs28665122 in SELS or SEPS1 (selenoprotein), three single nucleotide polymorphisms in IL18 (-105/rs360717, +183/rs5744292 and +1467/rs574456) and R501X/rs61816761 in FLG, the major locus associated with atopic dermatitis and predisposing to asthma, in a minimum of 6743 T1D cases and 7864 controls.

RESULTS

No evidence of T1D association was found for any of the SNPs we genotyped at FLG, SELS or IL18 (p≥0.03), nor with haplotypes of IL18 (p=0.82). Review of previous T1D genome-wide association results revealed that four (human leucocyte antigen (HLA), gasdermin B/ORM1 (Saccharomyces cerevisiae)-like/gasdermin B/, GSDMB/ORMDL3/GSDMA and IL2RB) of ten loci recently reported to be associated with asthma were associated with T1D (p≤0.005).

CONCLUSIONS

These results show that there are shared genetic associations for atopy-related traits and T1D, and this might help in the future to understand the mechanisms, pathways and environmental factors that underpin the rapid rise in incidence of both disorders in children.

Analysis of interleukin-18 promoter polymorphisms and changes in interleukin-18 serum levels underscores the involvement of interleukin-18 in recurrent spontaneous miscarriage

OBJECTIVE

To evaluate the association of interleukin-18 (IL-18) promoter single-nucleotide polymorphisms rs1946519 (-656C/A), rs187238 (-137G/C), rs360718 (-119A/C), and rs360717 (-105G/A) and changes in IL-18 serum levels with recurrent spontaneous miscarriage (RSM).

DESIGN

Case-control study.

SETTING

Outpatient obstetrics and gynecology clinics.

PATIENT(S)

Women with confirmed RSM (n = 282), and 283 age- and ethnically matched controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

IL-18 genotyping was accomplished by allelic discrimination assays; serum IL-18 levels were measured by ELISA.

RESULT(S)

The minor allele frequencies of rs360717 and rs1946519, but not rs360718 or rs187238, were higher in patients with RSM. Significant differences in the distribution of the rs360717 and rs1946519 genotypes were noted between patients and controls, and both rs360717 and rs1946519 IL-18 single-nucleotide polymorphisms showed significant association with RSM under additive, dominant, and recessive models. Lower serum IL-18 levels were seen between patients and controls and were more pronounced in rs360717 and rs1946519 heterozygous and homozygous genotypes. Four-locus (rs1946519/rs187238/rs360718/rs360717) IL-18 haplotype analysis identified that the AGAA (Pc<.001), CGAA (Pc<.001), and ACAG (Pc=.018) haplotypes were associated with a reduction in IL-18 secretion and with increased RSM risk, after adjustments for body mass index, menarche, and gravida.

CONCLUSION(S)

These results demonstrated that reduced IL-18 levels and rs360717 and rs1946519 IL-18 variants are significantly associated with RSM.

Interleukin 18 and coronary heart disease: prospective study and systematic review

AIM

Previous studies suggest that circulating levels of interleukin-18 (IL-18) may be prospectively related to risk of coronary heart disease (CHD) in the general population. We report new data from the largest prospective study to date, which are combined with data from all published prospective studies in a meta-analysis.

METHODS

We measured baseline IL-18 levels in stored serum samples of subjects from a case-control study nested within a prospective study of 5661 men aged 40-59 years recruited from general practices in 18 British towns in 1978-1980 and followed-up for up to 16 years (median time to event 8.4 years) for fatal CHD and non-fatal myocardial infarction (595 cases, 1238 controls).

RESULTS

IL-18 concentrations were strongly related to cigarette smoking, triglyceride, HDL-cholesterol (inversely) and to circulating levels of several inflammatory and haemostatic markers. Men in the top third of baseline IL-18 levels had an age-adjusted odds ratio (OR) for CHD of 1.55 (95% CI 1.21, 1.98) compared with those in the lowest third; this was reduced to 1.30 (95% CI 0.99, 1.69) after additional adjustment for vascular risk factors and 1.12 (95% CI 0.84, 1.49) after further adjustment for CRP and IL-6. In meta-analyses of CVD, associations (or effect sizes) were consistent between studies; RRs were 1.64 [corrected] (95% CI 1.48, 1.83) [corrected] after age adjustment, 1.39 (95% CI 1.25, [corrected] 1.55) after additional risk factor adjustment and 1.34 (95% CI 1.17, 1.53) [corrected] after additional adjustment for inflammatory markers.

CONCLUSIONS

Circulating IL-18 is prospectively and independently associated with CVD risk.

Gene-PUFA interactions and obesity risk

Although there are indications for modulatory effects of PUFA on associations between SNP and obesity risk, scientific evidence in human subjects is still scarce. The present analyses investigated interaction effects between SNP in candidate genes for obesity and PUFA in erythrocyte membranes on obesity risk. Within the second Bavarian Food Consumption Survey (cross-sectional, population-based), 568 adults provided blood samples. Fatty acid composition of erythrocyte membranes was analysed by means of GC. Genotyping was performed for twenty-one genes, including cytokines, adipokines, neurotransmitters and transcription factors. In addition, plasma IL-6 concentrations were analysed. For the statistical analysis, a logistic regression model assuming additive genetic effects was chosen. About 20 % of the study participants were classified as obese (BMI ≥ 30 kg/m(2)). Several significant gene-PUFA interactions were found, indicating regulatory effects of PUFA by gene variants of IL-2, IL-6, IL-18, TNF receptor family member 1B and 21, leptin receptor and adiponectin on obesity risk. After stratification by genotype, the strongest effects were found for rs2069779 (IL-2) and all tested PUFA as well as for rs1800795 (IL-6) and linoleic or arachidonic acid. The obesity risk of minor allele carriers significantly decreased with increasing fatty acid content. The genetic PUFA-IL-6 interaction was also reflected in plasma IL-6 concentrations. If replicated in a prospective study with sufficient statistical power, the results would indicate a beneficial effect of high PUFA supply for a substantial proportion of the population with respect to obesity risk.

Interleukin-18 promoter polymorphisms in Japanese patients with rheumatoid arthritis: protective effect of the T allele and T/T genotype at rs360722

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a strong genetic contribution to its pathogenesis. Among numerous candidate genes, cytokine gene polymorphisms have been implicated. Interleukin-18 (IL-18) induces production of tumor necrosis factor-α and promotes T helper (Th)1-type immune responses. This study investigates the association between IL-18 promoter polymorphisms and RA susceptibility. A total of 2471 Japanese case-control samples (1493 RA patients and 978 healthy controls) were examined. Three haplotype tag single-nucleotide polymorphisms, rs1946518A/C, rs360718T/G, and rs360722T/C, spanning from the 5'UTR to intron 1 were genotyped using allelic discrimination with the use of specific TaqMan probes, and three haplotypes (A-T-T, C-T-C, and A-G-C) were determined. Among these polymorphisms, the frequency of the T allele at rs360722, which tags the A-T-T haplotype, was significantly lower in the RA patient group compared with the normal subjects [0.46 versus 0.49, P = 0.0061, Fisher's exact probability test, odds ratio (OR) = 0.85, 95% confidence interval (CI) = 0.75-0.95]. Having the T/T genotype further increased the significance (0.20 versus 0.27, P = 0.0006, OR = 0.72, 95% CI = 0.58-0.86). Therefore, presence of the T allele and T/T genotype at rs360722 reduces the susceptibility of Japanese people to RA.

Evaluation of 6 candidate genes on chromosome 11q23 for coeliac disease susceptibility: a case control study

Background

Recent whole genome analysis and follow-up studies have identified many new risk variants for coeliac disease (CD, gluten intolerance). The majority of newly associated regions encode candidate genes with a clear functional role in T-cell regulation. Furthermore, the newly discovered risk loci, together with the well established HLA locus, account for less than 50% of the heritability of CD, suggesting that numerous additional loci remain undiscovered. Linkage studies have identified some well-replicated risk regions, most notably chromosome 5q31 and 11q23.

Methods

We have evaluated six candidate genes in one of these regions (11q23), namely CD3E, CD3D, CD3G, IL10RA, THY1 and IL18, as risk factors for CD using a 2-phase candidate gene approach directed at chromosome 11q. 377 CD cases and 349 ethnically matched controls were used in the initial screening, followed by an extended sample of 171 additional coeliac cases and 536 additional controls.

Results

Promotor SNPs (-607, -137) in the IL18 gene, which has shown association with several autoimmune diseases, initially suggested association with CD (P < 0.05). Follow-up analyses of an extended sample supported the same, moderate effect (P < 0.05) for one of these. Haplotype analysis of IL18-137/-607 also supported this effect, primarily due to one relatively rare haplotype IL18-607C/-137C (P < 0.0001), which was independently associated in two case-control comparisons. This same haplotype has been noted in rheumatoid arthritis.

Conclusion

Haplotypes of the IL18 promotor region may contribute to CD risk, consistent with this cytokine's role in maintaining inflammation in active CD.

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.

A functional SNP of the Interleukin-18 gene is associated with the presence of hepatocellular carcinoma in hepatitis B virus-infected patients

BACKGROUND/AIM

The natural course of hepatitis B virus (HBV) infection is likely related to host immune factors. Interleukin-18 (IL-18) plays a significant role in immune defense. This study was undertaken to determine the association between the presence of hepatocellular carcinoma (HCC) and single-nucleotide polymorphisms (SNPs) in the IL-18 gene in HBV-infected patients.

METHODS

Between March 2002 and December 2004, 730 Korean subjects were enrolled in two different groups: (1) chronic carrier without HCC (n=637) and (2) HCC (n=93). We analyzed SNPs at four polymorphic sites in the IL-18 gene at positions -667G>T, -148G>C, +8925C>G, and +13925A>C in the study subjects. To evaluate the functional significance of SNPs in the IL-18 gene promoter region, we performed a reporter gene assay in HepG2 and Hep3B cells transfected with different alleles.

RESULTS

The IL-18 -148C allele, +8925G allele, +13925C allele, and haplotype 3 (TCGC) were associated with the presence of HCC in codominant and dominant models. Furthermore, functional analyses using the reporter gene assay revealed that the -148C allele conferred significantly lower promoter activity.

CONCLUSIONS

This study indicates that the -148C, +8925G, and +13925C alleles of the IL-18 gene are associated with the presence of HCC and the 148G>C SNP is functionally important in determining disease outcome.

Interleukin-18 predicts atherosclerosis progression in SIV-infected and uninfected rhesus monkeys (Macaca mulatta) on a high-fat/high-cholesterol diet

Interleukin (IL)-18 levels have been identified as important predictors of cardiovascular mortality and are often elevated in human immunodeficiency virus (HIV)-infected individuals. To investigate a possible function for IL-18 in atherogenesis in the context of early HIV infection, we used the simian immunodeficiency model of HIV infection. Acutely simian immunodeficiency virus-infected and uninfected rhesus monkeys (Macaca mulatta) on an atherogenic diet were evaluated prospectively for atherosclerotic lesion development relative to a panel of plasma markers including IL-18, IL-8, IL-1beta, IL-6, C-reactive protein, soluble vascular cell adhesion molecule-1, soluble E-selectin, and soluble intercellular adhesion molecule-1. Although no significant differences in lesion development were identified between groups after 35 days of infection, levels of plasma IL-18 measured 1 month before virus inoculation correlated significantly with atherosclerotic plaque cross-sectional area at the carotid bifurcation (P<0.001, R=0.946), common iliac bifurcation (P<0.01, R=0.789), and cranial abdominal aorta (P<0.01, R=0.747), as well as with extent of CD3+ and CD68+ cellular infiltration in vascular lesions (both P<0.001, R>or=0.835) in both groups. Atherosclerotic plaque area at the carotid and common iliac bifurcations also showed a weaker inverse correlation with baseline IL-8 levels, as did CD68+ signal area. Results implicate a strong role for IL-18 in early atherosclerosis progression and raise the possibility that the chronically elevated IL-18 levels seen in later stages of HIV infection may contribute significantly to accelerated atherogenesis in this population.

IL18 haplotypes are associated with serum IL-18 concentrations in a population-based study and a cohort of individuals with premature coronary heart disease

BACKGROUND

Interleukin (IL)-18 is a proinflammatory cytokine that has been implicated in several diseases, including atherosclerosis, and increased circulating IL-18 concentrations increase risk of future coronary heart disease (CHD). We evaluated the effect of common variation within the IL18 gene on concentrations of circulating IL-18.

METHODS

We measured IL-18, by ELISA, in the population-based study group [Carotid Ultrasound Disease Assessment Study (CUDAS)] and a predominantly male cohort with premature cardiovascular disease [Carotid Ultrasound in Patients with Ischaemic Heart Disease (CUPID)]. Using a tagging single-nucleotide polymorphism (SNP) approach that captured >90% of genetic variation, we identified 4 common (>10%) haplotypes.

RESULTS

A common SNP was associated with differences in IL-18 concentrations; in CUDAS individuals carrying 2 copies of the rare allele, concentrations were 13% higher than in those with no copies (P = 0.002). Haplotypes were also associated with significant differences in IL-18 concentrations in CUDAS and CUPID. Haplotype GTATA (frequency 23%) was associated with significantly lower IL-18 than others. In CUDAS, those carrying 2 copies had IL-18 concentrations 15% lower than those carrying no copies (P = 0.002); in CUPID, the difference was 22% (P = 0.004). These associations remained significant after adjustment for age, sex, hypertension, HDL cholesterol, waist-to-hip ratio, and alcohol consumption. Despite being associated with differences in IL-18 concentrations, the haplotypes did not occur at different frequencies in those with or without carotid atherosclerotic plaques.

CONCLUSIONS

Variation within IL18 affects IL-18 concentrations in healthy and diseased individuals and thus may influence the pathophysiology of plaques at all stages of CHD progression.