Plasma interleukin (IL)-18 concentrations is elevated in patients with previous myocardial infarction and related to severity of coronary atherosclerosis independently of C-reactive protein and IL-6

Inflammatory biomarkers and long-term outcome in young patients three months after a first myocardial infarction

BACKGROUND

Studies on predictive value of circulating inflammatory biomarkers after myocardial infarction (MI) have often been limited by blood sampling only in an acute setting and short follow-up time. We aimed to compare the long-term predictive value of nine inflammatory biomarkers, known to be involved in atherosclerosis, in young patients investigated three months after a first-time MI.

METHODS

Nine biomarkers (high-sensitivity C-reactive protein, interleukin (IL)-6, IL-18, monocyte chemoattractant protein-1, matrix metalloproteinase (MMP)-1, MMP-3, MMP-9, serum amyloid A and tumor necrosis factor-alfa) were sampled in 382 young (<60 years) patients and in age and sex-matched controls, three months after a first-time MI between 1996 and 2000. Swedish national patient registers were used to determine cardiovascular (CV) outcomes during 20 years of follow-up.

RESULTS

In cases, random forest models identified IL-6 as the most important predictor of the primary composite endpoint of death, heart failure (HF) or MI hospitalization, and the separate endpoints death and HF hospitalization. IL-18 was the most important predictor of MI hospitalization. In a Cox regression, the highest tertile of IL-6 was associated with the composite endpoint (HR (95% CI) 1.91 (1.31-2.79)), death (2.38 (1.42-3.98)) and HF hospitalization (2.70 (1.32-5.50)), when adjusting for age, sex and CV risk factors. The highest tertile of IL-18 was associated with MI hospitalization (2.31 (1.08-4.91)) when severity of coronary atherosclerosis was added to the same type of model.

CONCLUSIONS

When nine inflammatory markers involved in atherosclerosis were analyzed three months after the acute event in young MI patients, IL-6 and IL-18 were the most important biomarkers to predict long-term CV outcomes during 20 years of follow-up.

The IL-1 Family and Its Role in Atherosclerosis

The IL-1 superfamily of cytokines is a central regulator of immunity and inflammation. The family is composed of 11 cytokines (with agonist, antagonist, and anti-inflammatory properties) and 10 receptors, all tightly regulated through decoy receptor, receptor antagonists, and signaling inhibitors. Inflammation not only is an important physiological response against infection and injury but also plays a central role in atherosclerosis development. Several clinical association studies along with experimental studies have implicated the IL-1 superfamily of cytokines and its receptors in the pathogenesis of cardiovascular disease. Here, we summarize the key features of the IL-1 family, its role in immunity and disease, and how it helps shape the development of atherosclerosis.

Adipokines, adiposity, and atherosclerosis

Characterized by a surplus of whole-body adiposity, obesity is strongly associated with the prognosis of atherosclerosis, a hallmark of coronary artery disease (CAD) and the major contributor to cardiovascular disease (CVD) mortality. Adipose tissue serves a primary role as a lipid-storage organ, secreting cytokines known as adipokines that affect whole-body metabolism, inflammation, and endocrine functions. Emerging evidence suggests that adipokines can play important roles in atherosclerosis development, progression, as well as regression. Here, we review the versatile functions of various adipokines in atherosclerosis and divide these respective functions into three major groups: protective, deteriorative, and undefined. The protective adipokines represented here are adiponectin, fibroblast growth factor 21 (FGF-21), C1q tumor necrosis factor-related protein 9 (CTRP9), and progranulin, while the deteriorative adipokines listed include leptin, chemerin, resistin, Interleukin- 6 (IL-6), and more, with additional adipokines that have unclear roles denoted as undefined adipokines. Comprehensively categorizing adipokines in the context of atherosclerosis can help elucidate the various pathways involved and potentially pave novel therapeutic approaches to treat CVDs.

Serum interleukin-18 and its relationship with subclinical atherosclerosis in systemic lupus erythematosus

BACKGROUND

Interleukin-18 (IL-18) is a pro-inflammatory and pro-atherogenic factor, and its blood level has shown a direct correlation with atherosclerosis. We aimed to evaluate the serum IL-18 level in patients with systemic lupus erythematosus (SLE) and its relationship with the intima-media thickness (IMT) of the carotid artery in these patients, as an indicator of atherosclerosis.

METHODS

In this cross-sectional study, 60 patients as the patient group and 30 healthy volunteers as the control group [matched sex, age, and body mass index (BMI)] were selected, and their disease status and general data were gathered using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) form. A blood sample was also obtained from all participants to determine the serum level of IL-18 and other metrics, including high-sensitivity C-reactive protein (hs-CRP), cholesterol, triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), anti-double stranded deoxyribonucleic acid (anti-dsDNA), complement 3 (C3), and C4. The IMT of the carotid artery was calculated in both groups. We also evaluated the clinical cardiovascular manifestations.

RESULTS

The serum IL-18 levels in patients were significantly higher than in the control group (P ˂ 0.005). It had no significant correlation with disease activity (P = 0.10). The patients with SLE with high IL-18 serum levels (> 280 pg/ml) had higher SLEDAI-2K (P = 0.02) than the patients with a low level (< 280), where 280 was the median of the IL-18 levels. The serum IL-18 level had no significant correlation with the carotid artery IMT.

CONCLUSION

A high level of IL-18 reflects the disease activity, but it was not significantly correlated with subclinical atherosclerosis, denoted by the carotid artery IMT.

Multiplex Protein Biomarker Profiling in Patients with Familial Hypercholesterolemia

Familial hypercholesterolemia (FH), is an autosomal dominant disorder caused by mutations in the LDLR, APOB, PCSK9, and APOE genes and is characterized by high plasma levels of total and low-density lipoprotein (LDL) cholesterol. Our study aimed to analyze the influences of two different therapies on a wide spectrum of plasma protein biomarkers of cardiovascular diseases. Plasma from FH patients under hypolipidemic therapy (N = 18; men = 8, age 55.4 ± 13.1 years) and patients under combined long-term LDL apheresis/hypolipidemic therapy (N = 14; men = 7; age 58.0 ± 13.6 years) were analyzed in our study. We measured a profile of 184 cardiovascular disease (CVD) associated proteins using a proximity extension assay (PEA). Hypolipidemic therapy significantly (all p < 0.01) influenced 10 plasma proteins (TM, DKK1, CCL3, CD4, PDGF subunit B, AGRP, IL18, THPO, and LOX1 decreased; ST2 increased). Under combined apheresis/hypolipidemic treatment, 18 plasma proteins (LDLR, PCSK9, MMP-3, GDF2, CTRC, SORT1, VEGFD, IL27, CCL24, and KIM1 decreased; OPN, COL1A1, KLK6, IL4RA, PLC, TNFR1, GLO1, and PTX3 increased) were significantly affected (all p < 0.006). Hypolipidemic treatment mainly affected biomarkers involved in vascular endothelial maintenance. Combined therapy influenced proteins that participate in cholesterol metabolism and inflammation.

Residual inflammatory risk associated with interleukin-18 and interleukin-6 after successful interleukin-1β inhibition with canakinumab: further rationale for the development of targeted anti-cytokine therapies for the treatment of atherothrombosis

AIMS

The Canakinumab Antiinflammatory Thrombosis Outcomes Study (CANTOS) established that targeting inflammation with interleukin-1β (IL-1β) inhibition can significantly reduce cardiovascular (CV) event rates in the absence of any beneficial effects on cholesterol. Yet, CANTOS participants treated with both high-intensity statins and canakinumab remain at considerable risk for recurrent CV events. Both interleukin-18 (IL-18, which like IL-1β requires the NLRP3 inflammasome for activation) and interleukin-6 (IL-6, a pro-inflammatory cytokine downstream of IL-1) may contribute to the recurrent events that occur even on canakinumab therapy, and thus represent novel targets for treating atherothrombosis.

METHODS AND RESULTS

Plasma samples from 4848 stable post-myocardial infarction patients who were assigned to active IL-1β inhibition or placebo within CANTOS underwent measurement of IL-18 and IL-6 both before and after initiation of canakinumab using validated ELISA. All participants were followed over a median 3.7-year period (maximum 5 years) for recurrent major adverse cardiovascular events (MACE) and for all-cause mortality. Compared to placebo, canakinumab significantly reduced IL-6 levels in a dose-dependent manner yielding placebo-subtracted median percent reductions in IL-6 at 3 months of 24.8%, 36.3%, and 43.2% for the 50, 150, and 300 mg doses, respectively (all P-values <0.001). By contrast, no dose of canakinumab significantly altered IL-18 levels measured at 3 months (all effects <1%, all P-values > 0.05). Yet, despite these differential plasma effects, either baseline and on-treatment levels of IL-18 or IL-6 associated with rates of future CV events. For example, for MACE, each tertile increase in IL-18 measured 3 months after canakinumab initiation associated with a 15% increase in risk [95% confidence interval (CI) 3-29%, P = 0.016], while each tertile increase in IL-6 measured 3 months after canakinumab initiation associated with a 42% increase in risk (95% CI 26-59%, P < 0.0001). Similar effects were observed for MACE-plus, CV death, all-cause mortality, and the for the combination endpoint of all vascular events inclusive of revascularization procedures and hospitalization for congestive heart failure. In baseline as well as on-treatment analyses, risks were highest among those with the highest levels of both IL-18 and IL-6.

CONCLUSION

There remains substantial residual inflammatory risk related to both IL-18 and IL-6 after IL-1β inhibition with canakinumab These data support further pharmacologic development of therapies for atherothrombosis that target IL-18 or IL-6 signalling, or that can simultaneously inhibit both IL-1β and IL-18 (such as NLRP3 inflammasome inhibitors).

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov NCT01327846.

Endothelial Dysfunction, Inflammation and Coronary Artery Disease: Potential Biomarkers and Promising Therapeutical Approaches

Coronary artery disease (CAD) and its complications are the leading cause of death worldwide. Inflammatory activation and dysfunction of the endothelium are key events in the development and pathophysiology of atherosclerosis and are associated with an elevated risk of cardiovascular events. There is great interest to further understand the pathophysiologic mechanisms underlying endothelial dysfunction and atherosclerosis progression, and to identify novel biomarkers and therapeutic strategies to prevent endothelial dysfunction, atherosclerosis and to reduce the risk of developing CAD and its complications. The use of liquid biopsies and new molecular biology techniques have allowed the identification of a growing list of molecular and cellular markers of endothelial dysfunction, which have provided insight on the molecular basis of atherosclerosis and are potential biomarkers and therapeutic targets for the prevention and or treatment of atherosclerosis and CAD. This review describes recent information on normal vascular endothelium function, as well as traditional and novel potential biomarkers of endothelial dysfunction and inflammation, and pharmacological and non-pharmacological therapeutic strategies aimed to protect the endothelium or reverse endothelial damage, as a preventive treatment for CAD and related complications.

A novel anti-human IL-1R7 antibody reduces IL-18-mediated inflammatory signaling

Unchecked inflammation can result in severe diseases with high mortality, such as macrophage activation syndrome (MAS). MAS and associated cytokine storms have been observed in COVID-19 patients exhibiting systemic hyperinflammation. Interleukin-18 (IL-18), a proinflammatory cytokine belonging to the IL-1 family, is elevated in both MAS and COVID-19 patients, and its level is known to correlate with the severity of COVID-19 symptoms. IL-18 binds its specific receptor IL-1 receptor 5 (IL-1R5, also known as IL-18 receptor alpha chain), leading to the recruitment of the coreceptor, IL-1 receptor 7 (IL-1R7, also known as IL-18 receptor beta chain). This heterotrimeric complex then initiates downstream signaling, resulting in systemic and local inflammation. Here, we developed a novel humanized monoclonal anti-IL-1R7 antibody to specifically block the activity of IL-18 and its inflammatory signaling. We characterized the function of this antibody in human cell lines, in freshly obtained peripheral blood mononuclear cells (PBMCs) and in human whole blood cultures. We found that the anti-IL-1R7 antibody significantly suppressed IL-18-mediated NFκB activation, reduced IL-18-stimulated IFNγ and IL-6 production in human cell lines, and reduced IL-18-induced IFNγ, IL-6, and TNFα production in PBMCs. Moreover, the anti-IL-1R7 antibody significantly inhibited LPS- and Candida albicans–induced IFNγ production in PBMCs, as well as LPS-induced IFNγ production in whole blood cultures. Our data suggest that blocking IL-1R7 could represent a potential therapeutic strategy to specifically modulate IL-18 signaling and may warrant further investigation into its clinical potential for treating IL-18-mediated diseases, including MAS and COVID-19.

Biomarker profiles of endothelial activation and dysfunction in rare systemic autoimmune diseases: implications for cardiovascular risk

OBJECTIVES

Vasculopathy is an important hallmark of systemic chronic inflammatory connective tissue diseases (CICTD) and is associated with increased cardiovascular risk. We investigated disease-specific biomarker profiles associated with endothelial dysfunction, angiogenic homeostasis and (tissue) inflammation, and their relation to disease activity in rare CICTD.

METHODS

A total of 38 serum proteins associated with endothelial (dys)function and inflammation were measured by multiplex-immunoassay in treatment-naive patients with localized scleroderma (LoS, 30), eosinophilic fasciitis (EF, 8) or (juvenile) dermatomyositis (34), 119 (follow-up) samples during treatment, and 65 controls. Data were analysed by unsupervised clustering, Spearman correlations, non-parametric t test and ANOVA.

RESULTS

The systemic CICTD, EF and dermatomyositis, had distinct biomarker profiles, with 'signature' markers galectin-9 (dermatomyositis) and CCL4, CCL18, CXCL9, fetuin, fibronectin, galectin-1 and TSP-1 (EF). In LoS, CCL18, CXCL9 and CXCL10 were subtly increased. Furthermore, dermatomyositis and EF shared upregulation of markers related to interferon (CCL2, CXCL10), endothelial activation (VCAM-1), inhibition of angiogenesis (angiopoietin-2, sVEGFR-1) and inflammation/leucocyte chemo-attraction (CCL19, CXCL13, IL-18, YKL-40), as well as disturbance of the Angiopoietin-Tie receptor system and VEGF-VEGFR system. These profiles were related to disease activity, and largely normalized during treatment. However, a subgroup of CICTD patients showed continued elevation of CXCL10, CXCL13, galectin-9, IL-18, TNFR2, VCAM-1, and/or YKL-40 during clinically inactive disease, possibly indicating subclinical interferon-driven inflammation and/or endothelial dysfunction.

CONCLUSION

CICTD-specific biomarker profiles revealed an anti-angiogenic, interferon-driven environment during active disease, with incomplete normalization under treatment. This warrants further investigation into monitoring of vascular biomarkers during clinical follow-up, or targeted interventions to minimize cardiovascular risk in the long term.

NLRP3 inflammasome as a key driver of vascular disease

NLRP3 (nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3) is an intracellular innate immune receptor that recognizes a diverse range of stimuli derived from pathogens, damaged or dead cells, and irritants. NLRP3 activation causes the assembly of a large multiprotein complex termed the NLRP3 inflammasome, and leads to the secretion of bioactive interleukin (IL)-1β and IL-18 as well as the induction of inflammatory cell death termed pyroptosis. Accumulating evidence indicates that NLRP3 inflammasome plays a key role in the pathogenesis of sterile inflammatory diseases, including atherosclerosis and other vascular diseases. Indeed, the results of the Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS) trial demonstrated that IL-1β-mediated inflammation plays an important role in atherothrombotic events and suggested that NLRP3 inflammasome is a key driver of atherosclerosis. In this review, we will summarize the current state of knowledge regarding the role of NLRP3 inflammasome in vascular diseases, in particular in atherosclerosis, vascular injury, aortic aneurysm, and Kawasaki disease vasculitis, and discuss NLRP3 inflammasome as a therapeutic target for these disorders.

Association between polymorphisms in interleukin-18 promoter and risk of coronary artery disease: a meta-analysis

Background: Previous studies have explored associations between interleukin-18 (IL-18) promoter polymorphisms and coronary artery disease (CAD). However, the results were controversial. We conducted a meta-analysis to clarify the association between the two polymorphisms and CAD risk. Methods: We searched English and Chinese databases and calculated the odds ratio (OR) and 95% confidence interval (CI) to estimate whether there are genetic associations between IL-18 promoter polymorphisms and the risk of CAD. All relevant studies were screened and meta-analyzed using STATA 15.0. Results: A total of 15 studies, including 12 studies for -137 G/C and 9 studies for -607 C/A, were identified for the meta-analysis. For -137 G/C, the results showed a significantly reduced risk of CAD in the dominant model (OR = 0.85) and heterozygous model (OR = 0.88) in the overall analysis. However, in subgroup analysis, decreased CAD risks were only observed in Asian populations for heterozygous genetic models. For -607 C/A, the overall OR revealed a reduced risk of CAD in all five genetic models (allelic, OR = 0.78; recessive, OR = 0.75; dominant, OR = 0.68; homozygous, OR = 0.61; heterozygous, OR = 0.72). In subgroup analysis, reduced CAD risk was also found in five genetic models of the Asian population. We also found that the IL-18 polymorphisms were correlated with myocardial infarction (MI) and multivessel (MV) disease. Conclusion: Our results suggested that the -137 polymorphism and -607 polymorphism in the IL-18 promoter were negatively associated with CAD, especially in the Asian population. In addition, some genetic models were correlated with the severity of CAD.

UCP2, IL18, and miR-133a-3p are dysregulated in subcutaneous adipose tissue of patients with obesity

The aim of this study was to compare the expression of UCP2, NLRP3, IL1B, IL18, and miR-133a-3p in subcutaneous adipose tissue (SAT) of 61 patients divided according to BMI: Group 1 (n = 8; BMI<25.0 kg/m²), Group 2 (n = 24; BMI 30.0-39.9 kg/m²), and Group 3 (n = 29; BMI≥40.0 kg/m²). SAT biopsies were obtained from individuals who underwent bariatric surgery or elective abdominal surgery. Gene expressions were quantified using qPCR. Bioinformatics analyses were employed to investigate target genes and pathways related to miR-133a-3p. UCP2 and miR-133a-3p expressions were decreased in SAT of Groups 2 and 3 while IL18 was increased compared to Group 1. NLRP3 and IL1B expressions did not differ between groups; however, NLRP3 was positively correlated with waist circumference and excess weight. Bioinformatics analysis demonstrated that UCP2 and NLRP3 are targets of miR-133a-3p. In conclusion, UCP2 and miR-133a-3p expressions are downregulated in patients with obesity, while IL18 is upregulated. NRLP3 is correlated with waist circumference and weight excess.

Macrophages and T cells in atherosclerosis: a translational perspective

Atherosclerosis is now considered a chronic maladaptive inflammatory disease. The hallmark feature in both human and murine disease is atherosclerotic plaques. Macrophages and various T-cell lineages play a crucial role in atherosclerotic plaque establishment and disease progression. Humans and mice share many of the same processes that occur within atherogenesis. The various similarities enable considerable insight into disease mechanisms and those which contribute to cardiovascular complications. The apolipoprotein E-null and low-density lipoprotein receptor-null mice have served as the foundation for further immunological pathway manipulation to identify pro- and antiatherogenic pathways in attempt to reveal more novel therapeutic targets. In this review, we provide a translational perspective and discuss the roles of macrophages and various T-cell lineages in contrasting proatherosclerotic and atheroprotective settings.

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.

Interleukin-18: Biological properties and role in disease pathogenesis

Initially described as an interferon (IFN)γ‐inducing factor, interleukin (IL)‐18 is indeed involved in Th1 and NK cell activation, but also in Th2, IL‐17‐producing γδ T cells and macrophage activation. IL‐18, a member of the IL‐1 family, is similar to IL‐1β for being processed by caspase 1 to an 18 kDa‐biologically active mature form. IL‐18 binds to its specific receptor (IL‐18Rα, also known as IL‐1R7) forming a low affinity ligand chain. This is followed by recruitment of the IL‐18Rβ chain. IL‐18 then uses the same signaling pathway as IL‐1 to activate NF‐kB and induce inflammatory mediators such as adhesion molecules, chemokines and Fas ligand. IL‐18 also binds to the circulating high affinity IL‐18 binding protein (BP), such as only unbound free IL‐18 is active. IL‐18Rα may also bind IL‐37, another member of the IL‐1 family, but in association with the negative signaling chain termed IL‐1R8, which transduces an anti‐inflammatory signal. IL‐18BP also binds IL‐37 and this acts as a sink for the anti‐inflammatory properties of IL‐37. There is now ample evidence for a role of IL‐18 in various infectious, metabolic or inflammatory diseases such as influenza virus infection, atheroma, myocardial infarction, chronic obstructive pulmonary disease, or Crohn's disease. However, IL‐18 plays a very specific role in the pathogenesis of hemophagocytic syndromes (HS) also termed Macrophage Activation Syndrome. In children affected by NLRC4 gain‐of‐function mutations, IL‐18 circulates in the range of tens of nanograms/mL. HS is treated with the IL‐1 Receptor antagonist (anakinra) but also specifically with IL‐18BP. Systemic juvenile idiopathic arthritis or adult‐onset Still's disease are also characterized by high serum IL‐18 concentrations and are treated by IL‐18BP.

Association Between Interleukin-18 Level and Left Ventricular Mass Index in Hypertensive Patients

BACKGROUND AND OBJECTIVES

In clinical trials, hypertensive patients tend to have higher interleukin-18 (IL-18) concentrations than normotensive groups, but the relationship between IL-18 and left ventricular hypertrophy (LVH), which is a marker of end-organ damage, is not well studied. We aimed to investigate the relationship between IL-18 and LVH in apparently healthy subjects free of clinically significant atherosclerotic disease.

SUBJECTS AND METHODS

We enrolled 198 subjects (102 women and 96 men) between May 2006 and March 2007, who were free of cardiovascular or immune diseases, but were suspected to have hypertension. Twenty-four-hour ambulatory blood pressure monitoring and two-dimensional echocardiography were performed. Lipid profiles, high-sensitivity CRP (hs-CRP), IL-18, and whole blood cell counts were measured for all subjects.

RESULTS

White blood cell count, hs-CRP, left ventricular mass, left ventricular mass index (LVMI), and IL-18 were higher in the hypertensive group than in the normotensive group (p=0.045, p=0.004, p<0.0001, p=0.001, and p=0.017 respectively). Twenty-four hour day and night systolic and diastolic blood pressure averages were positively correlated with IL-18 level in the entire study population. In multivariate regression analysis, left ventricular mass index and hs-CRP level were independently associated with IL-18 level in both the hypertensive group and the entire study population (β=0.154, β=0.149 p=0.033, p=0.040 and β=0.151, β=0.155 p=0.036, p=0.032 respectively).

CONCLUSION

We found that IL-18 level independently predicted LVMI in both the general population and in newly diagnosed hypertensive patients.

NLRP3 Inflammasome Expression and Activation in Human Atherosclerosis

Background

The NLR family, pyrin domain containing 3 (NLRP3) inflammasome is an interleukin (IL)‐1β and IL‐18 cytokine processing complex that is activated in inflammatory conditions. The role of the NLRP3 inflammasome in the pathogenesis of atherosclerosis and myocardial infarction is not fully understood.

Methods and Results

Atherosclerotic plaques were analyzed for transcripts of the NLRP3 inflammasome, and for IL‐1β release. The Swedish First‐ever myocardial Infarction study in Ac‐county (FIA) cohort consisting of DNA from 555 myocardial infarction patients and 1016 healthy individuals was used to determine the frequency of 4 single nucleotide polymorphisms (SNPs) from the downstream regulatory region of NLRP3. Expression of NLRP3, Apoptosis‐associated speck‐like protein containing a CARD (ASC), caspase‐1 (CASP1), IL1B, and IL18 mRNA was significantly increased in atherosclerotic plaques compared to normal arteries. The expression of NLRP3 mRNA was significantly higher in plaques of symptomatic patients when compared to asymptomatic ones. CD68‐positive macrophages were observed in the same areas of atherosclerotic lesions as NLRP3 and ASC expression. Occasionally, expression of NLRP3 and ASC was also present in smooth muscle cells. Cholesterol crystals and ATP induced IL‐1β release from lipopolysaccharide‐primed human atherosclerotic lesion plaques. The minor alleles of the variants rs4266924, rs6672995, and rs10733113 were associated with NLRP3 mRNA levels in peripheral blood mononuclear cells but not with the risk of myocardial infarction.

Conclusions

Our results indicate a possible role of the NLRP3 inflammasome and its genetic variants in the pathogenesis of atherosclerosis.

A Study to Investigate the Efficacy and Safety of an Anti-Interleukin-18 Monoclonal Antibody in the Treatment of Type 2 Diabetes Mellitus

Objective

Evidence suggests that chronic subclinical inflammation plays an important role in the pathogenesis of type 2 diabetes (T2DM). Circulating levels of interleukin (IL)-18 appear to be associated with a number of micro- and macrovascular comorbidities of obesity and T2DM. This study was designed to investigate whether inhibition of IL-18 had any therapeutic benefit in the treatment of T2DM. Preliminary efficacy, safety and tolerability, pharmacokinetics, and pharmacodynamics of the anti-IL-18 monoclonal antibody, GSK1070806, were assessed.

Research Design and Methods

This was a multicentre, randomized, single-blind (sponsor-unblinded), placebo-controlled, parallel-group, phase IIa trial. Obese patients of either sex, aged 18–70 years, with poorly controlled T2DM on metformin monotherapy were recruited. Patients received two doses, of placebo (n = 12), GSK1070806 0.25 mg/kg (n = 13) or GSK1070806 5 mg/kg (n = 12). The primary end-point was the change from baseline in fasting plasma glucose and weighted mean glucose area under the curve (AUC)(0–4 hours) postmixed meal test on Days 29, 57, and 85.

Results

Thirty-seven patients were randomized to one of the three treatment arms. There were no statistically significant effects of GSK1070806 doses on fasting plasma glucose levels, or weighted mean glucose AUC(0–4 hours) compared with placebo.

Conclusions

GSK1070806 was well tolerated, and inhibition of IL-18 did not lead to any improvements in glucose control. However, because of study limitations, smaller, potentially clinically meaningful effects of IL-18 inhibition cannot be excluded.

Trial Registration

ClinicalTrials.gov NCT01648153

Usefulness of serum interleukin-18 in predicting cardiovascular mortality in patients with chronic kidney disease--systems and clinical approach

The aim of this study was to check if serum interleukin-18 (IL-18) predicts 2-year cardiovascular mortality in patients at various stages of chronic kidney disease (CKD) and history of acute myocardial infarction (AMI) within the previous year. Diabetes mellitus was one of the key factors of exclusion. It was found that an increase in serum concentration of IL-18 above the cut-off point (1584.5 pg/mL) was characterized by 20.63-fold higher risk of cardiovascular deaths among studied patients. IL-18 serum concentration was found to be superior to the well-known cardiovascular risk parameters, like high sensitivity C-reactive protein (hsCRP), carotid intima media thickness (CIMT), glomerular filtration rate, albumins, ferritin, N-terminal prohormone of brain natriuretic peptide (NT-proBNP) in prognosis of cardiovascular mortality. The best predictive for IL-18 were 4 variables, such as CIMT, NT-proBNP, albumins and hsCRP, as they predicted its concentration at 89.5%. Concluding, IL-18 seems to be important indicator and predictor of cardiovascular death in two-year follow-up among non-diabetic patients suffering from CKD, with history of AMI in the previous year. The importance of IL-18 in the process of atherosclerotic plaque formation has been confirmed by systems analysis based on a formal model expressed in the language of Petri nets theory.

Increased IL18 mRNA levels in peripheral artery disease and its association with triglyceride and LDL cholesterol levels: a pilot study

Peripheral artery disease (PAD) typically refers to lower limb vessel ischemia caused by atherosclerotic stenosis of lower extremity arteries. IL18 is a pleiotropic pro-inflammatory cytokine reported to function as an inflammatory biomarker in cardiovascular diseases. IL18 activity is balanced by high-affinity naturally occurring IL18-binding protein (IL18BP). This study aimed to determine whether IL18, IL18 BP mRNA levels and -137 G/C (rs187238) polymorphism, which was previously associated with IL18 gene transcriptional activity, were associated with PAD etiology. IL18, IL18BP mRNA levels from peripheral blood mononuclear cells and -137 G/C (rs187238) polymorphism were determined by quantitative real-time polymerase chain reaction (qRT-PCR) and RT-PCR, respectively, in 55 PAD patients (26 aorta-iliac, 29 femoro-popliteal) and 61 disease-free controls. IL18 mRNA levels were increased in PAD patients compared with healthy controls (p = 0.09); however, did not reach a statistical significant level, also did not significantly differ between aorta-iliac and femoro-popliteal occlusive PAD subgroups (p = 0.285). However, IL18BP mRNA levels were significantly lower in PAD group compared with controls (p < 0.001). Genotype frequencies of rs187238 polymorphism did not significantly differ between PAD patients and controls (p = 0.385). IL18 mRNA levels were significantly correlated with triglycerides and LDL cholesterol levels in PAD patients (p = 0.003, p = 0.014, respectively). HDL cholesterol levels were negatively correlated with IL18 mRNA levels in controls (p = 0.05). This report is a preliminary study to show an association between IL18, IL18BP mRNA levels and PAD and suggests that the IL18 gene may have a significant relationship with triglyceride and LDL cholesterol levels in PAD patients.

Interleukin 18 function in atherosclerosis is mediated by the interleukin 18 receptor and the Na-Cl co-transporter

Interleukin-18 (IL18) participates in atherogenesis through several putative mechanisms. Interruption of IL18 action reduces atherosclerosis in mice. Here, we show that absence of the IL18 receptor (IL18r) does not affect atherosclerosis in apolipoprotein E-deficient (Apoe(-/-)) mice, nor does it affect IL18 cell surface binding to or signaling in endothelial cells. As identified initially by co-immunoprecipitation with IL18, we found that IL18 interacts with the Na-Cl co-transporter (NCC; also known as SLC12A3), a 12-transmembrane-domain ion transporter protein preferentially expressed in the kidney. NCC is expressed in atherosclerotic lesions, where it colocalizes with IL18r. In Apoe(-/-) mice, combined deficiency of IL18r and NCC, but not single deficiency of either protein, protects mice from atherosclerosis. Peritoneal macrophages from Apoe(-/-) mice or from Apoe(-/-) mice lacking IL18r or NCC show IL18 binding and induction of cell signaling and cytokine and chemokine expression, but macrophages from Apoe(-/-) mice with combined deficiency of IL18r and NCC have a blunted response. An interaction between NCC and IL18r on macrophages was detected by co-immunoprecipitation. IL18 binds to the cell surface of NCC-transfected COS-7 cells, which do not express IL18r, and induces cell signaling and cytokine expression. This study identifies NCC as an IL18-binding protein that collaborates with IL18r in cell signaling, inflammatory molecule expression, and experimental atherogenesis.

Interleukin 18 and extracellular matrix metalloproteinase inducer cross-regulation: implications in acute myocardial infarction

Circulating interleukin-18 (IL-18) is thought to promote atherosclerosis and cardiovascular complications such as plaque rupture. Atherosclerosis is also characterized by smooth muscle cell migration, a consequence of extracellular matrix (ECM) degradation regulated by metalloproteinases (MMPs). Because extracellular matrix metalloproteinase inducer (EMMPRIN) has been shown to promote plaque instability by inducing ECM degradation and MMP synthesis, we investigated whether a cross-regulatory interaction exists between IL-18 and EMMPRIN in human monocytes. EMMPRIN levels in monocytes were markedly greater in 20 patients with acute myocardial infarction (AMI) compared with 20 patients with stable angina pectoris or 20 healthy volunteers (control group). The levels of IL-18 and MMP-9 in serum were also significantly greater in the AMI group in comparison with the other 2 groups. IL-18 levels positively correlated with increased levels of EMMPRIN in monocytes. In vitro, the expression of EMMPRIN was increased in monocytes cultured with IL-18, and IL-18 secretion was augmented in monocytes cultured with EMMPRIN. Gene silencing of EMMPRIN by small interfering RNA reduced monocyte secretion of both IL-18 and MMP-9. In the present study, cross-regulation between IL-18 and EMMPRIN in monocytes was demonstrated. This interaction may amplify the inflammatory cascade and be responsible for increased monocytic MMP-9 serum levels in atherosclerosis, contributing to atherosclerotic plaque destabilization and subsequent AMI.

Autoantibodies against basement membrane collagen type IV are associated with myocardial infarction

Background

Collagen type IV is the major constituent of basement membranes underlying endothelial cells and is important for endothelial cell attachment and function. Autoantibodies against native collagen type IV have been found in various autoimmune diseases. Oxidation of LDL in the vascular wall results in the formation of reactive aldehydes, which could modify surrounding matrix proteins. Like oxidized LDL, these modified matrix proteins are likely to induce immune responses. We examined whether autoantibodies against native or aldehyde-modified collagen type IV are associated with myocardial infarction.

Methods

IgM and IgG against native and aldehyde-modified collagen type IV were measured by ELISA in serum from 387 survivors of a first myocardial infarction and 387 age- and sex-matched controls.

Results

Post-infarction patients had significantly increased levels of IgM against native collagen type IV, and IgG against native collagen type IV was present at detectable level in 17% of patients as opposed to 7% of controls (p < 0.001). Controlling for major cardiovascular risk factors demonstrated that the presence of IgG against native collagen type IV was associated with myocardial infarction (OR 2.9 (1.6–5.4), p = 0.001). Similarly, subjects in the highest quartile of IgM against native collagen type IV had increased risk of having suffered myocardial infarction (OR 3.11 (1.8–5.4), p < 0.001) after adjusting for cardiovascular risk factors. In contrast, IgG against aldehyde-modified collagen type IV was decreased in myocardial infarction patients, but this association was not independent of established cardiovascular risk factors.

Conclusion

Autoantibodies against collagen type IV are associated with myocardial infarction independently of traditional cardiovascular risk factors.

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We measured native and MDA-collagen type IV IgM and IgG in MI patients and controls.

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Post-infarction patients had increased levels of IgM against native collagen type IV.

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Presence of IgG against native collagen type IV was associated with MI.

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In contrast, IgG against MDA-collagen type IV was decreased in MI patients.

Interleukin-18-induced atherosclerosis involves CD36 and NF-κB crosstalk in Apo E-/- mice

OBJECTIVE

Interleukin (IL)-18 is a pleotropic cytokine involved in various inflammatory disorders. The transcription factor, nuclear factor kappa-B (NF-κB), is thought to play an important role in IL-18 signaling. The present study proposes a novel role for IL-18 in cholesterol efflux and plaque stability and demonstrates that pyrrolidine dithiocarbamate (PDTC), a NF-κB inhibitor blocks IL-18 signaling in apolipoprotein (Apo) E-/- mice.

METHODS

Three groups of normal chow-diet-fed, male Apo E-/- mice, aged 12 weeks (n=6/group) were employed: Gp I, PBS (2mo); Gp II, recombinant (r)IL-18 (1mo) followed by PBS (1mo); Gp III, rIL-18 (1mo) followed by PDTC (1mo).

RESULTS

Significantly augmented expression of IL-18 receptor (R)α by fluorescence-activated cell sorting analysis and plasma IL-18 was observed in Gp II. There was a significant increase in total cholesterol and low-density lipoprotein cholesterol whereas high-density lipoprotein cholesterol was significantly decreased in Gp II. However, this pattern was reversed in Gp III. Significantly augmented mRNA expression of IL-18, CD36, matrix metalloproteinase (MMP)-9, and NF-κB was observed in Gp II but liver X receptor alpha (LXR-α) gene was significantly reduced. A significant increase in frequency of atherosclerotic lesions was observed in Gp II animals, whereas there was a significant decrease in the Gp III.

CONCLUSION

IL-18 administration initiates inflammatory cascade by binding with IL-18 Rα via NF-κB which is involved in progression and destabilization of atherosclerotic plaques in Apo E-/- mice. This study also reveals that NF-κB blockade with PDTC, blocks IL-18 signaling through down-regulation of IL-18, IL-18 Rα, CD36, and MMP-9, thus reducing inflammation and restoring plaque instability via upregulation of LXR-α.

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.

Plasma granzyme B in ST elevation myocardial infarction versus non-ST elevation acute coronary syndrome: comparisons with IL-18 and fractalkine

OBJECTIVE

The proapoptotic protein, granzyme B (GZB), was identified as a contributor to the atherosclerotic plaque instability and recently as inflammatory activator. We studied the release kinetics of GZB and other markers of inflammation such as high sensitivity C reactive protein (hsCRP), interleukin 18 (IL-18), and fractalkine (FKN) in the early phase after acute cardiac events in different ACS subgroups.

METHODS

Thirty-six nondiabetic patients with ACS were compared to 12 control subjects. According to ACS diagnosis, the patients were classified into 22 patients with ST elevation myocardial infarction (STEMI) and 14 patients with non-ST elevation myocardial infarction or unstable angina (NSTEMI/UA). Blood samples were taken on day 1 (day of onset) and day 3 to measure hsCRP, IL-18, FKN, and GZB by ELISA.

RESULTS

Patients with ACS showed significantly higher GZB, IL-18, and FKN levels than the controls. STEMI group showed significantly higher GZB levels than NSTEMI/UA group. On day 3, FKN levels displayed a significant decrease, while GZB levels were significantly increased. IL-18 levels were more or less constant. GZB levels were positively correlated with IL-18 (r = 0.416, P < 0.01) and FKN (r = 0.58, P < 0.001).

CONCLUSIONS

Unlike IL-18 and FKN, plasma GZB may be a marker of ACS disease severity.

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.

CARD8 gene encoding a protein of innate immunity is expressed in human atherosclerosis and associated with markers of inflammation

Inflammation is a key factor in the development of atherosclerotic coronary artery disease. It is promoted through the inflammasome, a molecular machine that produces IL (interleukin)-1β in response to cholesterol crystal accumulation in macrophages. The CARD8 (caspase recruitment domain 8) protein modulates this process by suppressing caspase 1 and the transcription factor NF-κB (nuclear factor κB). The expression of CARD8 mRNA was examined in atherosclerotic vascular tissue and the impact on MI (myocardial infarction) of a polymorphism in the CARD8 gene determined. CARD8 mRNA was analysed by microarray of human atherosclerotic tissue and compared with transplant donor arterial tissue. Microarray analysis was performed for proximal genes associated with the rs2043211 locus in plaque. The CARD8 rs2043211 polymorphism was analysed by genotyping of two Swedish MI cohorts, FIA (First Myocardial Infarction in Northern Sweden) and SCARF (Stockholm Coronary Atherosclerosis Risk Factor). The CRP (C-reactive protein) level was measured in both cohorts, but the levels of the pro-inflammatory cytokines IL-1β, IL-18, TNF (tumour necrosis factor) and MCP-1 (monocyte chemoattractant protein) were measured in sera available from the SCARF cohort. CARD8 mRNA was highly expressed in atherosclerotic plaques compared with the expression in transplant donor vessel (P<0.00001). The minor allele was associated with lower expression of CARD8 in the plaques, suggesting that CARD8 may promote inflammation. Carriers of the minor allele of the rs2043211 polymorphism also displayed lower circulating CRP and lower levels of the pro-atherosclerotic chemokine MCP-1. However, no significant association could be detected between this polymorphism and MI in the two cohorts. Genetic alterations in the CARD8 gene therefore seem to be of limited importance for the development of MI.

Effect of diet-induced weight loss on inflammatory cytokines in obese women

BACKGROUND

Obesity is associated with lowgrade systemic inflammation which has been linked to the increased risk of cardiovascular disease and Type 2 diabetes in obese patients.

AIM

To evaluate changes in pro/anti-inflammatory adipocytokines and metabolic profile after moderate diet-induced weight loss.

SUBJECTS AND METHODS

Twenty-nine pre-menopausal obese women (body mass index ≥30 kg/m2) aged 21 to 54 years without diabetes, hypertension, or hyperlipidemia, were enrolled in this study. We measured anthropometric parameters, lipid and glucose profiles, interleukin (IL)-6, IL-10, and IL-18 in obese women, who then entered a medically supervised program aimed at reducing body weight by 10% or more. Obese women restricted their caloric intake (by 500-1000 kcal/day) and consumed 50 g/day of a fiber supplement (Slim Last Powder) for 12 weeks.

RESULTS

By completing the dietary intervention program, weight (Δ = -10.0%, p<0.0001), body mass index, waist circumference, triceps skinfold thickness, total cholesterol, triglyceride, and fasting plasma glucose significantly decreased, while HDL-cholesterol significantly increased. While plasma levels of IL-6 and IL-18 decreased by 27% after 12 weeks, no significant change was observed in circulating levels of IL-10.

CONCLUSION

Our study suggests that an improved body composition induced by restriction of energy intake is associated with favorable serum concentrations of IL-6 and IL-18 in obese women. However, the anti-inflammatory IL-10 is not affected by a moderate weight decrease.

Value and level of plasma homocysteine in patients with angina pectoris undergoing coronary angiographic study

This study tested whether the plasma level of total homocysteine (tHcy) was predictive of obstructive coronary artery disease (CAD) and clinical outcome in patients undergoing coronary angiographic (CAG) study. From September 2002 to October 2004, 1,305 consecutive patients with angina pectoris undergoing CAG study were consecutively enrolled. Blood samples were prospectively collected to assess the plasma level of tHcy from each patient before catheterization. Of these 1305 patients, 676 (51.8%) had multivessel disease (group 1), 367 (28.1%) had single-vessel disease (group 2), and 262 (20.1%) had normal coronary artery or insignificant coronary artery disease (group 3). The plasma level of tHcy was notably higher in group 1 than in groups 2 and 3 (11.6 ± 4.4 versus 10.9 ± 4.0 versus 10.4 ± 3.8, P < 0.001). Univariate binary logistic regression analysis demonstrated that the plasma tHcy level was strongly associated with multiple-vessel disease (MVD) (defined as ≥ 2 vessel disease) (P < 0.001). Multivariate binary logistic regression analysis showed that tHcy level, fasting blood sugar, diabetes mellitus, and age were significantly and independently predictive of MVD (all P < 0.03). Univariate Cox regression analysis demonstrated that tHcy level was predictive of long-term mortality (P = 0.042). However, the tHcy level was not an independent predictor of long-term mortality on multivariate Cox regression analysis (P > 0.05). The results of our study support the hypothesis that tHcy level is an independent predictor of MVD in patients with chest pain undergoing CAG study. Conversely, our study did not support the tHcy level as an independent predictor of long-term mortality in this clinical setting.

Effects of chronic mental stress and atherogenic diet on the immune inflammatory environment in mouse aorta

Inflammation and stress are regarded as two important atherogenic factors. Because stress can affect leukocyte distribution, we hypothesized that stress-mediated leukocyte extravasation can modify the inflammatory environment of the arterial wall possibly contributing to atherogenesis. To test this hypothesis we evaluated the inflammatory environment of the aorta in C57Bl/6 mice subjected to 3 and 12 months of chronic stress and compared it to age matched non-stressed animals. Experiments were carried out in mice fed regular chow or atherogenic diets. Both treatments increased the expression of vascular and leukocyte adhesion molecules and leukocyte accumulation. At 3 months, stress but not an atherogenic diet elevated the number of CD4 cells, CD8 cells, macrophages, dendritic cells and neutrophils. These changes were associated with elevation of transcripts for ICAM-1 and VCAM-1, E-selectin and neuropeptide Y. At 12 months, stress or high cholesterol acted similarly to elevate the number of CD8 and macrophages, and synergistically on the number of all cell types investigated. At this time-point, strong synergism was also observed on the level of E-selectin and NPY in the aorta, but not in the circulation. Despite these effects, histological and morphological alterations of the arterial wall were severe in the atherogenic diet, but not in the stress groups. Thus, although stress and an atherogenic diet may both affect leukocyte accumulation in the aorta, they may contribute differently to atherogenesis.

Treatment with an oral direct thrombin inhibitor decreases platelet activity but increases markers of inflammation in patients with myocardial infarction

BACKGROUND

Thrombin has a role not only in the coagulation process but also in inflammatory responses. Oral direct thrombin inhibitors (DTIs) are currently being evaluated in patients with thromboembolic diseases.

OBJECTIVE

To investigate whether an oral DTI affects markers for platelet and inflammatory activity after myocardial infarction (MI).

METHODS

A total of 518 patients with MI were randomly assigned to ximelagatran treatment (four different dose groups) in combination with aspirin, or aspirin alone for 6 months. The levels of soluble (s) P-selectin, soluble tissue factor, C-reactive protein (CRP), interleukin (IL)-10 and IL-18 were analysed in serial blood samples.

RESULTS

sP-selectin concentration increased after 1 week and persisted at an elevated level for 6 months in all study groups (P < 0.001). In the two highest ximelagatran dose groups, there was a reduced increase in sP-selectin compared to treatment with lower doses of ximelagatran and aspirin alone (P = 0.01 and P = 0.002, respectively). IL-18 levels did not change in the aspirin alone treatment group. By contrast, there was an elevation in IL-18 level in the lower and higher ximelagatran dose groups after 6 months (P = 0.006 and P < 0.001, respectively). Ximelagatran increased IL-10 levels (P = 0.002) and reduced the decrease in CRP levels after 6 months compared to treatment with aspirin alone (P = 0.002).

CONCLUSION

A persistent elevation of platelet activity is found in patients with a recent MI after the cessation of acute antithrombotic treatment, and the addition of an oral DTI at higher doses decreases the activity. By contrast, long-term treatment with a DTI increases the levels of several markers of inflammation. Further studies with prolonged exposure of oral DTIs are needed for evaluation of the effect on inflammatory processes and to determine whether these agents influence clinical outcomes.

Effects of interleukin-18 on cardiac fibroblast function and gene expression

Fibroblasts are the primary cell type responsible for synthesis and remodeling of the extracellular matrix in the heart. A number of factors including growth factors, hormones and mechanical forces have been identified that modulate the production of extracellular matrix by cardiac fibroblasts. Inflammatory mediators including pro-inflammatory cytokines and chemokines also impact fibrosis of the heart. Recent studies have illustrated that interleukin-18 promotes a pro-fibrotic response in cardiac fibroblasts; however the effects of this cytokine on other aspects of fibroblast function have not been examined. While fibroblasts have long been known for their role in production and remodeling of the extracellular matrix, other functions of these cells are only now beginning to be appreciated. We hypothesize that exposure to interleukin-18 will stimulate other aspects of fibroblast behavior important in myocardial remodeling including proliferation, migration and collagen reorganization. Fibroblasts were isolated from adult male rat hearts and bioassays performed to determine the effects of interleukin-18 on fibroblast function. Treatment of fibroblasts with interleukin-18 (1-100ng/ml) resulted in increased production of extracellular matrix components and remodeling or contraction of three-dimensional collagen scaffolds by these cells. Furthermore, exposure to interleukin-18 stimulated fibroblast migration and proliferation. Treatment of heart fibroblasts with interleukin-18 resulted in the rapid activation of the c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase (PI3-kinase) pathways. Studies with pharmacological inhibitors illustrated that activation of these pathways is critical to interleukin-18 mediated alterations in fibroblast function. These studies illustrate that interleukin-18 plays a role in modulation of cardiac fibroblast function and may be an important component of the inflammation-fibrosis cascade during pathological myocardial remodeling.

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.

ApoE-/- PGC-1α-/- mice display reduced IL-18 levels and do not develop enhanced atherosclerosis

BACKGROUND

Atherosclerosis is a chronic inflammatory disease that evolves from the interaction of activated endothelial cells, macrophages, lymphocytes and modified lipoproteins (LDLs). In the last years many molecules with crucial metabolic functions have been shown to prevent important steps in the progression of atherogenesis, including peroxisome proliferator activated receptors (PPARs) and the class III histone deacetylase (HDAC) SIRT1. The PPARγ coactivator 1 alpha (Ppargc1a or PGC-1α) was identified as an important transcriptional cofactor of PPARγ and is activated by SIRT1. The aim of this study was to analyze total PGC-1α deficiency in an atherosclerotic mouse model.

METHODOLOGY/PRINCIPAL FINDINGS

To investigate if total PGC-1α deficiency affects atherosclerosis, we compared ApoE(-/-) PGC-1α(-/-) and ApoE(-/-) PGC-1α(+/+) mice kept on a high cholesterol diet. Despite having more macrophages and a higher ICAM-1 expression in plaques, ApoE(-/-) PGC-1α(-/-) did not display more or larger atherosclerotic plaques than their ApoE(-/-) PGC-1α(+/+) littermates. In line with the previously published phenotype of PGC-1α(-/-) mice, ApoE(-/-) PGC-1α(-/-) mice had marked reduced body, liver and epididymal white adipose tissue (WAT) weight. VLDL/LDL-cholesterol and triglyceride contents were also reduced. Aortic expression of PPARα and PPARγ, two crucial regulators for adipocyte differentiation and glucose and lipid metabolism, as well as the expression of some PPAR target genes was significantly reduced in ApoE(-/-) PGC-1α(-/-) mice. Importantly, the epididymal WAT and aortic expression of IL-18 and IL-18 plasma levels, a pro-atherosclerotic cytokine, was markedly reduced in ApoE(-/-) PGC-1α(-/-) mice.

CONCLUSIONS/SIGNIFICANCE

ApoE(-/-) PGC-1α(-/-) mice, similar as PGC-1α(-/-) mice exhibit markedly reduced total body and visceral fat weight. Since inflammation of visceral fat is a crucial trigger of atherogenesis, decreased visceral fat in PGC-1α-deficient mice may explain why these mice do not develop enhanced atherosclerosis.

Interleukin-18 as a Predictor of Future Events in Patients With Acute Coronary Syndromes

Objective— The aim of this study was to assess the short- and long-term prognostic significance of interleukin-18 (IL-18) levels in patients with acute coronary syndromes (ACS).

Methods and Results— In patients hospitalized with ACS (median age, 66 years; 30% females), we evaluated associations of serum IL-18 levels from day 1 (n=1261) with the short- (<3 months) and long-term (median, 7.6 years) risk of death, development of congestive heart failure (CHF), and myocardial infarction (MI). IL-18 was not significantly associated with short-term mortality. In the long term, IL-18 levels were significantly related to all-cause mortality, even after adjustment for clinical confounders (hazard ratio [HR], 1.19; 95% confidence interval, 1.07 to 1.33; P =0.002). Long-term, cardiovascular mortality was univariately related to IL-18, and the adjusted relation between noncardiovascular mortality and IL-18 was highly significant (HR, 1.36; 95% confidence interval, 1.11 to 1.67; P =0.003). IL-18 independently predicted CHF, MI, and cardiovascular death/CHF/MI in both the short and long term. Measurements from day 1 of ACS and 3 months after ACS had a similar power to predict late outcome.

Conclusion— The addition of the measurement of IL-18 to clinical variables improved the prediction of risk of all-cause and noncardiovascular mortality. The association between IL-18 and noncardiovascular mortality is intriguing and warrants further study.

Interleukin-18 induces EMMPRIN expression in primary cardiomyocytes via JNK/Sp1 signaling and MMP-9 in part via EMMPRIN and through AP-1 and NF-kappaB activation

IL-18 and the extracellular matrix metalloproteinase (MMP) inducer (EMMPRIN) stimulate the expression of proinflammatory cytokines and MMPs and are elevated in myocardial hypertrophy, remodeling, and failure. Here, we report several novel findings in primary cardiomyocytes treated with IL-18. First, IL-18 activated multiple transcription factors, including NF-κB (p50 and p65), activator protein (AP)-1 (cFos, cJun, and JunD), GATA, CCAAT/enhancer-binding protein, myocyte-specific enhancer-binding factor, interferon regulatory factor-1, p53, and specific protein (Sp)-1. Second, IL-18 induced EMMPRIN expression via myeloid differentiation primary response gene 88/IL-1 receptor-associated kinase/TNF receptor-associated factor-6/JNK-dependent Sp1 activation. Third, IL-18 induced a number of MMP genes, particularly MMP-9, at a rapid rate as well as tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-3 at a slower rate. Finally, the IL-18 induction of MMP-9 was mediated in part via EMMPRIN and through JNK- and ERK-dependent AP-1 activation and p38 MAPK-dependent NF-κB activation. These results suggest that the elevated expression of IL-18 during myocardial injury and inflammation may favor EMMPRIN and MMP induction and extracellular matrix degradation. Therefore, targeting IL-18 or its signaling pathways may be of potential therapeutic benefit in adverse remodeling.

Genome-wide association study identifies variants at the IL18-BCO2 locus associated with interleukin-18 levels

OBJECTIVE

Interleukin-18 (IL-18) is a proinflammatory cytokine involved in the processes of innate and acquired immunities and associated with cardiovascular disease and type 2 diabetes. We sought to identify the common genetic variants associated with IL-18 levels.

METHODS AND RESULTS

We performed a 2-stage genome-wide association study among women of European ancestry from the Nurses' Health Study (NHS) and Women's Genome Health Study (WGHS). IL-18 levels were measured by ELISA. In the discovery stage (NHS, n=1523), 7 single-nucleotide polymorphisms (SNPs) at the IL18-BCO2 locus were associated with IL-18 concentrations at the 1 x 10(-5) significance level. The strongest association was found for SNP rs2115763 in the BCO2 gene (P=6.31 x 10(-8)). In silico replication in WGHS (435 women) confirmed these findings. The combined analysis of the 2 studies indicated that SNPs rs2115763, rs1834481, and rs7106524 reached a genome-wide significance level (P<5 x 10(-8)). Forward selection analysis indicated that SNPs rs2115763 and rs1834481 were independently associated with IL-18 levels (P=0.0002 and 0.0006, respectively). The 2 SNPs together explained 2.9% of variation of plasma IL-18 levels.

CONCLUSIONS

This study identified several novel variants at the IL18-BCO2 locus associated with IL-18 levels.

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.

Circulating IL-18 and the risk of type 2 diabetes in women

AIMS/HYPOTHESIS

The pathophysiology of type 2 diabetes involves pro-inflammatory pathways. We tested the hypothesis that IL-18 predicts future diabetes cases.

METHODS

We used a nested case-control design based in the Nurses' Health Study. Baseline blood samples were collected between 1989 and 1990. Questionnaires to assess body weight, lifestyle (physical activity, diet, smoking) and diabetes diagnosis were sent out and assessed biennially (follow-up until 2002). Cases (n = 1,012) were defined as women developing type 2 diabetes at least 1 year after blood sampling. Control women (n = 1,081) were matched to cases by age, date of blood draw, fasting status and race. We calculated the RR (95% CI) of type 2 diabetes in quintiles of IL-18 using conditional logistic regression with the first quintile as referent; adjustments included matching factors, diabetes risk factors, BMI, adipokine levels (adiponectin, resistin) and inflammatory proteins (C-reactive protein, tumour necrosis factor receptor 2 (TNFalpha-R2) and IL-6).

RESULTS

Higher IL-18 levels were associated with increased risk of developing diabetes, even after adjustment for matching factors and multiple diabetes risk factors: being in the highest quintile of IL-18 was associated with a RR of 1.75 (1.41-2.18) for diabetes relative to the first quintile (p < 0.0001 for trend). Significant trends in association were still observed after adjustment for BMI (RR 1.44 [1.15-1.80], p < 0.0001 for trend) and adiponectin levels (RR 1.28 [1.02-1.60], p = 0.006 for trend). Further adjustment for inflammatory markers in a sub-sample did not significantly change the results.

CONCLUSIONS/INTERPRETATION

Elevated IL-18 levels are associated with higher risk of diabetes. This association is independent of usual risk factors, including BMI and adipokine levels.

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.