Serum levels of interleukin-18 in patients with stable and unstable angina pectoris

Status of biomarkers for the identification of stable or vulnerable plaques in atherosclerosis

Atherosclerosis is a systemic inflammation of the arteries characterized by atherosclerotic plaque due to the accumulation of lipids, inflammatory cells, apoptotic cells, calcium and extracellular matrix (ECM) proteins. Stable plaques present a chronic inflammatory infiltration, whereas vulnerable plaques present an 'active' inflammation involved in the thinning of the fibrous cap that predisposes to plaque rupture. Several complex biological cellular processes lead plaques to evolve from stable to vulnerable predisposing them to rupture and thrombosis. In this review, we analyze some emerging circulating biomarkers related to inflammation, ECM and lipid infiltration, angiogenesis, metalloproteinases and microRNA (miRNA), as possible diagnostic and prognostic indicators of plaque vulnerability.

Hyperlipidemia Alters Regulatory T Cell Function and Promotes Resistance to Tolerance Induction Through Costimulatory Molecule Blockade

Recent work from our laboratory has shown that hyperlipidemia promotes accelerated rejection of vascularized cardiac allografts in mice by inducing anti-donor Th17 reactivity and production of IL-17. Here, we show that hyperlipidemia also affects FoxP3(+) regulatory T cells (Tregs). Hyperlipidemia promotes the development of Tregs that express low levels of CD25. Hyperlipidemia also promotes a decrease in central Tregs and an increase in effector Tregs that appears to account for the increase in the frequency of CD25(low) Tregs. Alterations in Treg subsets also appear to lead to alterations in Treg function. The ability of FoxP3(+) , CD25(high) , CD4(+) Tregs from hyperlipidemic mice to inhibit proliferation of effector T cells stimulated with anti-CD3 and CD28 was reduced when compared with Tregs from control mice. Regulatory T cells isolated from hyperlipidemic recipients exhibit increased activation of Akt, and a reduction in Bim levels that permits the expansion of FoxP3(+) CD25(low) CD4(+) T cells. Hyperlipidemic mice were also resistant to tolerance induction using costimulatory molecule blockade consisting of anti-CD154 and CTLA4Ig, a strategy that requires Tregs. Together, our data suggest that hyperlipidemia profoundly affects Treg subsets and function as well as the ability to induce tolerance.

Circulating cytokines in relation to the extent and composition of coronary atherosclerosis: results from the ATHEROREMO-IVUS study

OBJECTIVE

We investigated whether concentrations of TNF-α, TNF-β, TNF-receptor 2, interferon-γ, IL-6, IL-8, IL-10 and IL-18 are associated with extent and composition of coronary atherosclerosis determined by grayscale and virtual histology (VH)- intravascular ultrasound (IVUS).

METHODS

Between 2008 and 2011, IVUS(-VH) imaging of a non-culprit coronary artery was performed in 581 patients (stable angina pectoris (SAP), n = 261; acute coronary syndrome (ACS), n = 309) undergoing coronary angiography from the ATHEROREMO-IVUS study. Plaque burden, presence of VH-IVUS-derived thin-cap fibroatheroma (TCFA) lesions, and presence of VH-TCFA lesions with plaque burden ≥70% were assessed. Blood samples for cytokine measurement were drawn from the arterial sheath prior to the angiography procedure. We applied linear and logistic regression.

RESULTS

TNF-α levels were positively associated with plaque burden (beta (β) [95%CI]: 4.45 [0.99-7.91], for highest vs lowest TNF-α tertile) and presence of VH-TCFA lesions (odds ratio (OR) [95%CI] 2.30 (1.17-4.52), highest vs lowest TNF-α tertile) in SAP patients. Overall, an inverse association was found between IL-10 concentration and plaque burden (β [95%CI]: -1.52 [-2.49 to -0.55], per Ln (pg/mL) IL-10) as well as IL-10 and VH-TCFA lesions with plaque burden ≥70% (OR: 0.31 [0.12-0.80],highest vs lowest IL-10 tertile). These effects did not reach statistical significance in the separate SAP and ACS groups.

CONCLUSION

Higher circulating TNF-α was associated with higher plaque burden and VH-TCFA lesions in SAP patients. Lower circulating IL-10 was associated with higher plaque burden and large VH-TCFA lesions. These in-vivo findings suggest a role for these cytokines in extent and vulnerability of atherosclerosis.

Interleukin-18 Promoter Gene Polymorphisms are not Associated with Myocardial Infarction in Type 2 Diabetes in Slovenia

Type 2 diabetes is a major risk factor for myocardial infarction (MI) and chronic inflammation may play a central role in both diseases. Interleukin (IL)-18 is a potent proinflammatory cytokine, which is considered important in acute coronary syndromes and type 2 diabetes. We investigated the association of the −137 (G>C), polymorphism (rs187238) and the −607 (C>A) polymorphism (rs1946518) of the IL-18 gene promoter region in 495 Caucasians with type 2 diabetes, of whom 169 had MI and 326 subjects had no clinically evident coronary artery disease (controls). We also investigated the impact of these polymorphisms on the serum IL-18 level in subsets of both groups and in a normal group. Genotype distributions of the polymorphisms showed no significant difference between cases and controls. However, IL-18 serum levels were significantly lower in diabetics with the 137 CC genotype than in those with other genotypes (241.5 ± 132.7 ng/L vs. 340.2 ± 167.4 ng/L; p <0.05). High sensitivity C-reactive protein and IL-18 serum levels were higher in diabetics in the MI group than in the control group. We conclude that these IL-18 promoter gene polymorphisms are not risk factors for MI in Caucasians with type 2 diabetes.

IL-18 gene polymorphism, cardiovascular mortality and coronary artery disease

BACKGROUND

Interleukin 18(IL-18) is a pro-atherosclerotic cytokine. Elevated IL-18 levels and the genetic variation of the IL-18 have been previously linked with acute coronary events and cardiovascular mortality among patients with coronary artery disease (CAD). We studied the possible association between the IL-18 gene polymorphism and cardiovascular mortality during follow-up among Finnish patients who had undergone a clinical exercise stress test, in addition to the possible effect on the expression of angiography-verified CAD.

MATERIALS AND METHODS

A total of 2152 patients of the Finnish Cardiovascular Study (cohort study) were followed up for 6·3years and cardiovascular mortality was recorded. Angiography was performed on 461 patients. Genotyping of five common single nucleotide polymorphisms (SNPs) of the IL-18 gene was performed using the 5'nuclease assay for allelic discrimination with the ABI Prism 7900HT Sequence Detection System.

RESULTS

Among the study population, IL-18 gene polymorphism did not associate with cardiovascular mortality. According to adjusted binary regression analysis, the male carriers of one major haplotype (the only ones carrying the t allele of the +127 C/t SNP) had a lower occurrence rate for significant CAD defined as > 50% stenosis in at least one of the main branches of the coronary arteries (OR 0·495, 95% CI 0·862-0·284, P=0·041). No associations were observed among women. The sex-by-genotype interaction was significant (P=0·033).

CONCLUSIONS

The IL-18 gene was not found to associate significantly with mortality. Among patients who had coronary angiography, one major haplotype of the IL-18 gene has a gender-dependent different impact on the expression of CAD.

Common inflammatory mediators orchestrate pathophysiological processes in rheumatoid arthritis and atherosclerosis

RA is characterized by a systemic inflammatory state, in which immune cells and soluble mediators play a crucial role. These inflammatory processes resemble those in other chronic inflammatory diseases, such as atherosclerosis. The chronic systemic inflammation in RA can be considered as an independent risk factor for the development of atherosclerosis, and represents an important field to investigate the reasons of the increase of acute cardiovascular events in RA. In the present review, we focused on several mediators of autoimmunity, inflammation and endothelial dysfunction, which can be considered the most promising targets to prevent atherogenesis in RA. Among several mediators, the pro-inflammatory cytokine TNF-alpha has been shown as a crucial factor to induce atherosclerosis in RA patients.

Promoter polymorphism of interleukin-18 in angiographically proven coronary artery disease

Interleukin 18 (IL-18) is a pro-atherogenic cytokine associated with the occurrence of various cardiac complications. The IL-18 gene has a functional -137 G/C polymorphism (rs187238) in the promoter region. Using the ligase detection reaction-polymerase chain reaction, we genotyped a cohort of patients in Chinese Han population in Xiangfan region. Case patients of coronary artery disease and control patients were identified by coronary angiography. The plasma IL-18 concentrations were measured by ELISA. A significant increase of G allele or GG-genotype was observed in 241 case patients compared to 145 control individuals (frequency of G allele = 0.90 vs 0.83, p=0.004; frequency of GG-genotype = 0.81 vs 0.68, p = 0.005). In case patients, G allele carriers in multi-vessel disease patients had a higher occurrence rate when compared to single-vessel disease patients, but no significant difference was detected (frequency of G allele = 0.92 vs 0.88, p=0.107; frequency of GG-genotype = 0.84 vs 0.75, p = 0.089). IL-18 protein concentration of the -137GG genotype was much higher than concentration of the CG and CC genotype (case patients: 229.1+/-131.5 vs 122.7+/-73.6 pg/ml, P < 0.001; control patients: 65.9+/-31.6 vs 42.4+/-19.5 pg/ml, P < 0.001). To conclude, IL-18 promoter -137G/C polymorphism influences IL-18 levels and the occurrence of coronary artery disease, suggesting that IL-18 is causally involved in the development of atherosclerosis.

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.

Free Interleukin (IL)-18 levels, and the impact of IL18 and IL18BP genetic variation, in CHD patients and healthy men

OBJECTIVE

To investigate free interleukin-18 (fIL-18) levels, and variation within the IL-18 system genes, in heart surgery patients, and healthy men.

METHODS AND RESULTS

fIL-18 was calculated from IL-18 and IL-18 binding protein (BP) levels, in 421 healthy men and 196 post-coronary artery bypass graft (CABG) patients. After surgery, fIL-18 peaked at 6 hours (from 117 to 331 pg/mL) but fell to below presurgery levels at 24 hours (99 pg/mL), because of changes in total IL-18 and IL-18BP. fIL-18 24 hours postsurgery was significantly higher in those who suffered a major complication after surgery (125 versus 80 pg/mL, P<0.01). Baseline total IL-18 was also higher in healthy men who went on to suffer an MI over 17 years of prospective study (276 versus 240 pg/mL, P=0.01). Tagging SNPs for IL18 (n=5) and IL18BP (n=3) were determined, in both studies the IL18 HapIII haplotype (frequency 30%) was associated with 36% lower baseline fIL-18 levels before surgery (P<0.01), and 7% lower in healthy men (P=0.04). The frequency of HapIII was lower in CABG patients than in healthy men (20.7 versus 29.8%, P<0.01).

CONCLUSIONS

IL-18 levels, which are determined in part by variation in IL18, play a role in CHD development and postsurgery outcome.

Interleukin-18, the Metabolic Syndrome, and Subclinical Atherosclerosis

OBJECTIVE

Although IL-18 promotes atherogenesis in animal studies and predicts cardiovascular risk in humans, it is unknown whether elevated IL-18 levels are associated with coronary atherosclerosis in the general population.

METHODS AND RESULTS

IL-18 plasma levels were determined by ELISA in 2231 subjects from the Dallas Heart Study. In univariable analysis, IL-18 levels associated with traditional cardiovascular risk factors and particularly with components of the metabolic syndrome (MS, P<0.01 for trend across the number of MS components); IL-18 also associated with coronary artery calcium (CAC) scores measured by electron beam computed tomography and aortic plaque measured by MRI (P<0.01 for each). In multivariable analyses, IL-18 remained associated with multiple components of the MS but not with CAC or aortic plaque.

CONCLUSIONS

In a large population-based sample, elevated IL-18 plasma levels associated with risk factors for atherosclerosis and with the metabolic syndrome. The association between IL-18 and atherosclerosis diminished after accounting for traditional cardiovascular risk factors. These data suggest that IL-18 does not add independently to detection of atherosclerotic burden in asymptomatic individuals.

Interleukin-18 promoter polymorphism associates with the occurrence of sudden cardiac death among Caucasian males: the Helsinki Sudden Death Study

OBJECTIVE

The increased plasma concentrations of pro-atherogenic and cardiomyocyte hypertrophic cytokine interleukin 18 (IL-18) predict mortality in patients with coronary heart disease (CHD) in addition to predicting the outcome of heart failure. The IL-18 gene has a functional -137G/C polymorphism (rs187238) in the promoter region. The C allele carriage is associated with attenuated IL-18 production. The effect of IL-18 genotype on SCD is unknown. We studied the association of the IL-18 gene -137G/C polymorphism with the occurrence of sudden cardiac death (SCD).

METHODS

Using the TaqMan 5' nuclease assay, we genotyped two independent consecutive and prospective autopsy series which were included in the Helsinki Sudden Death Study.

RESULTS

Of the 663 men, 359 (54.1%) had the wild-type GG-genotype, 261 (39.4%) were heterozygotes (CG) and 43 (6.5%) were CC homozygotes. Compared to the GG homozygotes, the C allele carriers (i.e. subjects having CC or CG genotypes) had a lower adjusted risk for SCD from any cause (odds ratio [OR] 0.49; 95% confidence interval [CI], 0.31-0.77, p=0.002), for SCD due to CHD (OR 0.51; 95% CI, 0.32-0.82, p=0.005), and for SCD caused by non-coronary heart diseases (OR 0.34; 95% CI 0.13-0.90, p=0.030).

CONCLUSION

IL-18 promoter -137G/C polymorphism, which regulates the expression of IL-18, is an important predictor of SCD from any cause as well as SCD in patients with and without underlying CHD.

The clinical significance of interleukin 18 assessment in sarcoidosis patients

INTRODUCTION

Sarcoidosis is a multisystemic disease of unknown etiology characterized by the formation of immune granulomas in involved organs. The cytokine profile in inflamed lesions of sarcoidosis is mainly determined by T helper 1 (Th1) cells. Interleukin 18 (IL-18) is primarily a monocyte/macrophage-derived cytokine. IL-18 has been recently identified as an IFNgamma-inducing factor. The cytokine plays an important role in the induction of Th1 response and it may be responsible for sarcoidosis progression. The aim of the study was to assess the usefulness of IL-18 estimation in the sarcoidosis diagnosis and the disease course prognosis.

MATERIAL AND METHODS

The diagnosis of sarcoidosis was established in 88 patients (the mean age of 38.1+/-10.8 years). We measured IL-18 level in plasma and bronchoalveolar lavage fluid (BALF) cell culture supernatant (CCS) using the enzyme-linked immunoassay technique (ELISA). We also performed the flow cytometric analysis of BALF lymphocyte phenotype. Statistica 5.0 and non-parametric tests: the Mann-Whitney U-test and the Spearman correlation test, were used for statistical analysis.

RESULTS

The patient group consisted of 55 subjects without acute symptoms of sarcoidosis, 14 patients with acute Löfgren syndrome and 19 subjects with Löfgren syndrome in the past. Lung hilar lymphadenopathy was diagnosed in 49 patients and lung interstitial changes in 39 subjects. After 6-month-observation, 49 patients were in remission, 20 subjects manifested persistent disease and 19 patients had sarcoidosis progression. Plasma IL-18 level was significantly (P<0.0001) higher in sarcoidosis patients (383+/-250pg/ml) than in control subjects (146+/-72pg/ml). Plasma IL-18 level was similar both in subjects with Löfgren syndrome and in other patients. However, IL-18 level in BALF CCS was significantly (P<0.05) lower in Löfgren syndrome patients than in subjects without acute manifestation of the disease. The highest IL-18 level in plasma was found in patients with disease progression, in subjects with lung interstitial changes and in patients with extrapulmonary manifestation of the disease. We observed a positive correlation between plasma IL-18 level and the percentage of BALF lymphocytes (R=0.202, P=0.06) as well as the percentage of activated HLA DR+T cells (R=0.23, P<0.05). There was a negative correlation between the IL-18 level in BALF CCS and the percentage of BALF CD3-positive and CD4-positive lymphocytes (R=-0.27, -0.23, P<0.05).

CONCLUSION

IL-18 may play a significant role in the prolongation of sarcoidosis course. Its estimation may become a good prognostic factor, which should be analyzed together with other factors useful in sarcoidosis monitoring.

Increased concentrations of C-reactive protein and IL-6 but not IL-18 are independently associated with incident coronary events in middle-aged men and women: results from the MONICA/KORA Augsburg case-cohort study, 1984-2002

OBJECTIVE

We performed a prospective case-cohort study in initially healthy, middle-aged men and women from the MONICA/KORA Augsburg studies conducted between 1984 and 2002 to assess the role of IL-18 in comparison with IL-6 and CRP in the prediction of incident coronary heart disease (CHD).

METHODS AND RESULTS

Concentrations of IL-18 were measured in 382 case subjects with incident CHD and 1980 noncases. Mean follow-up was 11 years. Baseline concentrations of IL-18 were slightly higher in cases than in noncases (172.4 [1.0] versus 161.3 [1.0] pg/mL, respectively; P=0.114), but were clearly elevated for C-reactive protein (CRP) and IL-6 in cases compared with noncases. In multivariable analyses, accounting for classical cardiovascular risk factors and inflammatory markers, no statistically significant association was seen between increased concentrations of IL-18 and incident CHD both in men (hazard ratio [HR] and 95% confidence intervals [CIs] comparing extreme tertiles, 1.20; 95% CI, 0.85 to 1.69), and in women (HR, 1.25; 95% CI, 0.67 to 2.34). However, in this population increased concentrations of CRP and IL-6 were found to be independent predictors of future CHD events, even after multivariable adjustment.

CONCLUSIONS

Elevated concentrations of CRP and IL-6, but not IL-18, were independently associated with risk of CHD in subjects from an area with moderate absolute risk.

ELEVATED HIGH-MOBILITY GROUP BOX 1 LEVELS IN PATIENTS WITH CEREBRAL AND MYOCARDIAL ISCHEMIA

Cerebral and myocardial ischemia, two of the leading causes of morbidity and mortality worldwide, are associated with inflammation that can lead to multiple organ failure and death. High-mobility group box 1(HMGB1), a recently described mediator of lethal systemic inflammation, has been detected in individuals with severe sepsis and hemorrhagic shock, but its role during ischemic injury in humans is unknown. To determine whether systemic HMGB1 levels are elevated after ischemic injury, a prospective observational study was performed in subjects with a diagnosis of either Acute Coronary Syndrome (ACS) or cerebral vascular ischemia (transient ischemic attack or cerebral vascular accident). Subjects (n, 16; age [mean], 67+/-16.3 years) were enrolled in the North Shore-LIJ emergency department within 24 h of symptom onset. Blood samples were collected, and HMGB1 levels analyzed by Western blot analysis using previously described methods (Wang et al. Science. 1999). Control samples were obtained from healthy age- and sex-matched volunteers (n, 16; age [mean], 68+/-15.8 years). Here, we report that serum HMGB1 levels were significantly elevated in both myocardial ischemia subjects (myocardial control serum HMGB1, 1.94+/-2.05 ng/mL, vs. myocardial ischemia serum HMGB1, 159+/-54.3 ng/mL; P<0.001); and in cerebral ischemia subjects (cerebral control serum HMGB1, 16.8+/-10.9 ng/mL, vs. cerebral ischemia serum HMGB1, 218+/-18.8 ng/mL; P<0.001). These results suggest that systemic HMGB1 levels are elevated in human ischemic disease.