Temporal and spatial distribution of interleukin-1 beta in balloon injured porcine coronary arteries

Inflammation during Percutaneous Coronary Intervention-Prognostic Value, Mechanisms and Therapeutic Targets

Periprocedural myocardial injury and myocardial infarction (MI) are not infrequent complications of percutaneous coronary intervention (PCI) and are associated with greater short- and long-term mortality. There is an abundance of preclinical and observational data demonstrating that high levels of pre-, intra- and post-procedural inflammation are associated with a higher incidence of periprocedural myonecrosis as well as future ischaemic events, heart failure hospitalisations and cardiac-related mortality. Beyond inflammation associated with the underlying coronary pathology, PCI itself elicits an acute inflammatory response. PCI-induced inflammation is driven by a combination of direct endothelial damage, liberation of intra-plaque proinflammatory debris and reperfusion injury. Therefore, anti-inflammatory medications, such as colchicine, may provide a novel means of improving PCI outcomes in both the short- and long-term. This review summarises periprocedural MI epidemiology and pathophysiology, evaluates the prognostic value of pre-, intra- and post-procedural inflammation, dissects the mechanisms involved in the acute inflammatory response to PCI and discusses the potential for periprocedural anti-inflammatory treatment.

Targeting Residual Inflammatory Risk: A Shifting Paradigm for Atherosclerotic Disease

As biologic, epidemiologic, and clinical trial data have demonstrated, inflammation is a key driver of atherosclerosis. Circulating biomarkers of inflammation, including high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6), are associated with increased risk of cardiovascular events independent of cholesterol and other traditional risk factors. Randomized trials have shown that statins reduce hsCRP, and the magnitude of hsCRP reduction is proportional to the reduction in cardiovascular risk. Additionally, these trials have demonstrated that many individuals remain at increased risk due to persistent elevations in hsCRP despite significant reductions in low-density lipoprotein cholesterol (LDL-C) levels. This "residual inflammatory risk" has increasingly become a viable pharmacologic target. In this review, we summarize the data linking inflammation to atherosclerosis with a particular focus on residual inflammatory risk. Additionally, we detail the results of Canakinumab Anti-inflammatory Thrombosis Outcome Study (CANTOS), which showed that directly reducing inflammation with an IL-1β antagonist reduces cardiovascular event rates independent of LDL-C. These positive data are contrasted with neutral evidence from CIRT in which low-dose methotrexate neither reduced the critical IL-1β to IL-6 to CRP pathway of innate immunity, nor reduced cardiovascular event rates.

Interleukin-1 Blockade: An Update on Emerging Indications

Interleukin (IL)-1 is a pro-inflammatory cytokine that induces local and systemic inflammation aimed to eliminate microorganisms and tissue damage. However, an increasing number of clinical conditions have been identified in which IL-1 production is considered inappropriate and IL-1 is part of the disease etiology. In autoinflammatory diseases, gout, Schnitzler's syndrome, and adult-onset Still's disease, high levels of inappropriate IL-1 production have been shown to be a key process in the etiology of the disease. In these conditions, blocking IL-1 has proven very effective in clinical studies. In other diseases, IL-1 has shown to be present in disease process but is not the central driving force of inflammation. In these conditions, including type 1 and 2 diabetes mellitus, acute coronary syndrome, amyotrophic lateral sclerosis, and several neoplastic diseases, the benefits of IL-1 blockade are minimal or absent.

Suppressive activities and mechanisms of ugonin J on vascular smooth muscle cells and balloon angioplasty-induced neointimal hyperplasia

Neointimal hyperplasia (or restenosis) is primarily attributed to excessive proliferation and migration of vascular smooth muscle cells (VSMCs). In this study, we investigated the inhibitory effects and mechanisms of ugonin J on VSMC proliferation and migration as well as neointimal formation. Cell viability and the cell-cycle distribution were, respectively, analyzed using an MTT assay and flow cytometry. Cell migration was examined using a wound-healing analysis and a transwell assay. Protein expressions and gelatinase activities were, respectively, measured using Western blot and gelatin zymography. Balloon angioplasty-induced neointimal formation was induced in a rat carotid artery model and then examined using immunohistochemical staining. Ugonin J induced cell-cycle arrest at the G₀ /G₁ phase and apoptosis to inhibit VSMC growth. Ugonin J also exhibited marked suppressive activity on VSMC migration. Ugonin J significantly reduced activations of focal adhesion kinase, phosphoinositide 3-kinase, v-akt murine thymoma viral oncogene homolog 1, and extracellular signal-regulated kinase 1/2 proteins. Moreover, ugonin J obviously reduced expressions and activity levels of matrix metalloproteinase-2 and matrix metalloproteinase-9. In vivo data indicated that ugonin J prevented balloon angioplasty-induced neointimal hyperplasia. Our study suggested that ugonin J has the potential for application in the prevention of balloon injury-induced neointimal formation.

The IL-1RI Co-Receptor TILRR (FREM1 Isoform 2) Controls Aberrant Inflammatory Responses and Development of Vascular Disease

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The IL-1RI co-receptor, TILRR, is a potent amplifier of IL-1–induced responses.

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Blocking TILRR inhibits IL-1 receptor function and activation of inflammatory genes.

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TILRR expression is high in atherosclerotic lesions but low in healthy tissue, allowing distinct inhibition at sites of inflammation.

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Genetic deletion of TILRR and antibody blocking of TILRR function reduce plaque development and progression of atherosclerosis. Lesions exhibit low levels of macrophages and increased levels of smooth muscle cells and collagen, characteristics of stable plaques.

Expression of the interleukin-1 receptor type I (IL-1RI) co-receptor Toll-like and interleukin-1 receptor regulator (TILRR) is significantly increased in blood monocytes following myocardial infarction and in the atherosclerotic plaque, whereas levels in healthy tissue are low. TILRR association with IL-1RI at these sites causes aberrant activation of inflammatory genes, which underlie progression of cardiovascular disease. The authors show that genetic deletion of TILRR or antibody blocking of TILRR function reduces development of atherosclerotic plaques. Lesions exhibit decreased levels of monocytes, with increases in collagen and smooth muscle cells, characteristic features of stable plaques. The results suggest that TILRR may constitute a rational target for site- and signal-specific inhibition of vascular disease.

From C-Reactive Protein to Interleukin-6 to Interleukin-1: Moving Upstream To Identify Novel Targets for Atheroprotection

Plasma levels of the inflammatory biomarker high-sensitivity C-reactive protein (hsCRP) predict vascular risk with an effect estimate as large as that of total or high-density lipoprotein cholesterol. Further, randomized trial data addressing hsCRP have been central to understanding the anti-inflammatory effects of statin therapy and have consistently demonstrated on-treatment hsCRP levels to be as powerful a predictor of residual cardiovascular risk as on-treatment levels of low-density lipoprotein cholesterol. Yet, although hsCRP is clinically useful as a biomarker for risk prediction, most mechanistic studies suggest that CRP itself is unlikely to be a target for intervention. Moving upstream in the inflammatory cascade from CRP to interleukin (IL)-6 to IL-1 provides novel therapeutic opportunities for atheroprotection that focus on the central IL-6 signaling system and ultimately on inhibition of the IL-1β-producing NOD-like receptor family pyrin domain containing 3 inflammasome. Cholesterol crystals, neutrophil extracellular traps, atheroprone flow, and local tissue hypoxia activate the NOD-like receptor family pyrin domain containing 3 inflammasome. As such, a unifying concept of hsCRP as a downstream surrogate biomarker for upstream IL-1β activity has emerged. From a therapeutic perspective, small ischemia studies show reductions in acute-phase hsCRP production with the IL-1 receptor antagonist anakinra and the IL-6 receptor blocker tocilizumab. A phase IIb study conducted among diabetic patients at high vascular risk indicates that canakinumab, a human monoclonal antibody that targets IL-1β, markedly reduces plasma levels of IL-6, hsCRP, and fibrinogen with little change in atherogenic lipids. Canakinumab in now being tested as a method to prevent recurrent cardiovascular events in a randomized trial of 10 065 post-myocardial infarction patients with elevated hsCRP that is fully enrolled and due to complete in 2017. Clinical trials using alternative anti-inflammatory agents active against the CRP/IL-6/IL-1 axis, including low-dose methotrexate and colchicine, are being explored. If successful, these trials will close the loop on the inflammatory hypothesis of atherosclerosis and serve as examples of how fundamental biologic principles can be translated into personalized medical practice.

Neutrophil elastase promotes interleukin-1β secretion from human coronary endothelium

The endothelium is critically involved in the pathogenesis of atherosclerosis by producing pro-inflammatory mediators, including IL-1β. Coronary arteries from patients with ischemic heart disease express large amounts of IL-1β in the endothelium. However, the mechanism by which endothelial cells (ECs) release IL-1β remains to be elucidated. We investigated neutrophil elastase (NE), a potent serine protease detected in vulnerable areas of human carotid plaques, as a potential "trigger" for IL-1β processing and release. This study tested the hypothesis that NE potentiates the processing and release of IL-1β from human coronary endothelium. We found that NE cleaves the pro-isoform of IL-1β in ECs and causes significant secretion of bioactive IL-1β via extracellular vesicles. This release was attenuated significantly by inhibition of neutrophil elastase but not caspase-1. Transient increases in intracellular Ca(2+) levels were observed prior to secretion. Inside ECs, and after NE treatment only, IL-1β was detected within LAMP-1-positive multivesicular bodies. The released vesicles contained bioactive IL-1β. In vivo, in experimental atherosclerosis, NE was detected in mature atherosclerotic plaques, predominantly in the endothelium, alongside IL-1β. This study reveals a novel mechanistic link between NE expression in atherosclerotic plaques and concomitant pro-inflammatory bioactive IL-1β secretion from ECs. This could reveal additional potential anti-IL-1β therapeutic targets and provide further insights into the inflammatory process by which vascular disease develops.

The effect of interleukin-1 receptor antagonist therapy on markers of inflammation in non-ST elevation acute coronary syndromes: the MRC-ILA Heart Study

AIMS

Acute coronary syndromes (ACSs) are driven by inflammation within coronary plaque. Interleukin-1 (IL-1) has an established role in atherogenesis and the vessel-response to injury. ACS patients have raised serum markers of inflammation. We hypothesized that if IL-1 is a driving influence of inflammation in non-ST elevation ACS (NSTE-ACS), IL-1 inhibition would reduce the inflammatory response at the time of ACS.

METHODS AND RESULTS

A phase II, double-blinded, randomized, placebo-controlled, study recruited 182 patients with NSTE-ACS, presenting <48 h from onset of chest pain. Treatment was 1:1 allocation to daily, subcutaneous IL-1receptor antagonist (IL-1ra) or placebo for 14 days. Baseline characteristics were well matched. Treatment compliance was 85% at 7 days. The primary endpoint (area-under-the-curve for C-reactive protein over the first 7 days) was: IL-1ra group, 21.98 mg day/L (95%CI 16.31-29.64); placebo group, 43.5 mg day/L (31.15-60.75) (geometric mean ratio = 0.51 mg/L; 95%CI 0.32-0.79; P = 0.0028). In the IL-1ra group, 14-day achieved high-sensitive C-reactive protein (P < 0.0001) and IL-6 levels (P = 0.02) were lower than Day 1. Sixteen days after discontinuation of treatment (Day 30) high-sensitive C-reactive protein levels had risen again in the IL-1ra group [IL-1ra; 3.50 mg/L (2.65-4.62): placebo; 2.21 mg/L (1.67-2.92), P = 0.022]. MACE at Day 30 and 3 months was similar but at 1 year there was a significant excess of events in the IL-1ra group.

CONCLUSION

IL-1 drives C-reactive protein elevation at the time of NSTE-ACS. Following 14 days IL-1ra treatment inflammatory markers were reduced. These results show the importance of IL-1 as a target in ACS, but also indicate the need for additional studies with anti-IL-1 therapy in ACS to assess duration and safety.

CLINICAL TRIAL REGISTRATION EUCTR

2006-001767-31-GB: www.clinicaltrialsregister.eu/ctr-search/trial/2006-001767-31/GB.

Pressure stress reduces inducible NO synthase expression by interleukin-1β stimulation in cultured rat vascular smooth muscle cells

Elevated mechanical stress applied to vascular walls is well known to modulate vascular remodeling. We investigated the effect of pulsatile pressure stress on nitric oxide (NO) production and inducible NO synthase (iNOS) expression by interleukin-1β (IL-1β) stimulation in rat vascular smooth muscle cells (VSMCs). VSMCs were enzymatically isolated from aortic media of Wistar rats. Pulsatile pressure applied to VSMCs was repeatedly given between 80 and 160 mm Hg at a frequency of 4 cycles per min using an original apparatus. Protein expression and activation were evaluated by Western blot analysis. mRNA expression was evaluated by real-time reverse transcription-polymerase chain reaction. The pulsatile pressure reduced IL-1β-induced NO production, iNOS protein, and mRNA expression. The pressure also reduced GTP cyclohydrolase I mRNA expression. Furthermore, the pressure reduced phosphorylation of IL-1β-induced extracellular signal-regulated kinase (ERK), nuclear factor-κB (NF-κB) p65, and I-κBα. The pressure had no effect on I-κBβ degradation by IL-1β stimulation. The present study shows for the first time that pressure stress reduces IL-1β-induced iNOS expression via a mechanism involving the ERK-NF-κB signaling pathway.

From Histology and Imaging Data to Models for In-Stent Restenosis

The implantation of stents has been used to treat coronary artery stenosis for several decades. Although stenting is successful in restoring the vessel lumen and is a minimally invasive approach, the long-term outcomes are often compromised by in-stent restenosis (ISR). Animal models have provided insights into the pathophysiology of ISR and are widely used to evaluate candidate drug inhibitors of ISR. Such biological models allow the response of the vessel to stent implantation to be studied without the variation of lesion characteristics encountered in patient studies.

This paper describes the development of complementary in silico models employed to improve the understanding of the biological response to stenting using a porcine model of restenosis. This includes experimental quantification using microCT imaging and histology and the use of this data to establish numerical models of restenosis. Comparison of in silico results with histology is used to examine the relationship between spatial localization of fluid and solid mechanics stimuli immediately post-stenting. Multi-scale simulation methods are employed to study the evolution of neointimal growth over time and the variation in the extent of neointimal hyperplasia within the stented region. Interpretation of model results through direct comparison with the biological response contributes to more detailed understanding of the pathophysiology of ISR, and suggests the focus for follow-up studies.

In conclusion we outline the challenges which remain to both complete our understanding of the mechanisms responsible for restenosis and translate these models to applications in stent design and treatment planning at both population-based and patient-specific levels.

Endothelial NLRP3 inflammasome activation and enhanced neointima formation in mice by adipokine visfatin

Inflammasomes serve as an intracellular machinery to initiate inflammatory response to various danger signals. The present study tested whether an inflammasome centered on nucleotide oligomerization domain-like receptor protein 3 (NLRP3) triggers endothelial inflammatory response to adipokine visfatin, a major injurious adipokine during obesity. NLRP3 inflammasome components were abundantly expressed in cultured mouse microvascular endothelial cells, including NLRP3, apoptosis-associated speck-like protein, and caspase-1. These NLRP3 inflammasome molecules could be aggregated to form an inflammasome complex on stimulation of visfatin, as shown by fluorescence confocal microscopy and size exclusion chromatography. Correspondingly, visfatin significantly increased caspase-1 activity and IL-1β release in microvascular endothelial cells, indicating an activation of NLRP3 inflammasomes. In animal experiments, direct infusion of visfatin in mice with partially ligated left carotid artery were found to have significantly increased neointimal formation, which was correlated with increased NLRP3 inflammasome formation and IL-1β production in the intima. Further, visfatin-induced neointimal formation, endothelial inflammasome formation, and IL-1β production in mouse partially ligated left carotid artery were abolished by caspase-1 inhibition, local delivery of apoptosis-associated speck-like protein shRNA or deletion of the ASC gene. In conclusion, the formation and activation of NLRP3 inflammasomes by adipokine visfatin may be an important initiating mechanism to turn on the endothelial inflammatory response leading to arterial inflammation and endothelial dysfunction in mice during early stage obesity.

The anti-inflammatory effect of kaempferol on early atherosclerosis in high cholesterol fed rabbits

BACKGROUND

Atherosclerosis has been widely accepted as an inflammatory disease of vascular, adhesion molecules play an important role in the early progression of it. The aim of the present study was to evaluate the effect of kaempferol on the inflammatory molecules such as E-selectin (E-sel), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesionmolecule-1 (VCAM-1) and monocyte chemotactic protein-1 (MCP-1) in high cholesterol induced atherosclerosis rabbit models.

METHODS

Thirty male New Zealand white (NZW) rabbits were randomly divided into five groups, control group, model group, fenofibrate (12 mg/kg) group and kaempferol groups (150 mg/kg and 30 mg/kg). The rabbits were fed with a normal diet or a high cholesterol diet for 10 weeks. Levels of blood lipids, serum tumour-necrosis factor-alpha (TNF-α) and serum interleukin-1beta (IL-1β) were detected at the end of the sixth and tenth week. Malonaldehyde (MDA) level and superoxide dismutase (SOD) activity in serum were also determined. Lesion areas of the aorta were measured with morphometry analysis after ten weeks. Gene expression of E-sel, ICAM-1, VCAM-1 and MCP-1 in aortas was determined by RT-PCR (reverse transcription-polymerase chain reaction). Immunohistochemical staining was employed to measure protein expression of E-sel, ICAM-1, VCAM-1 and MCP-1.

RESULTS

Model rabbits fed with ten weeks of high-cholesterol diet developed significant progression of atherosclerosis. Compared with the control, levels of blood lipids, TNF-α, IL-1β and MDA increased markedly in serum of model rabbits, while SOD levels decreased. Gene and protein expressions of E-sel, ICAM-1, VCAM-1 and MCP-1 in atherosclerotic aortas increased remarkably in model group. However, comparing to the model rabbits, levels of TNF-α, IL-1β and MDA decreased significantly and serum SOD activity increased, gene and protein expressions of E-sel, ICAM-1, VCAM-1 and MCP-1 in aortas decreased significantly with the treatment of kaempferol.

CONCLUSION

Kaempferol shows anti-atherosclerotic effect by modulating the gene and protein expression of inflammatory molecules.

Systemic inflammatory response and local cytokine expression in porcine models of endocarditis

The knowledge of systemic inflammation and local cytokine expression in porcine endocarditis models is limited, though it could provide valuable information about the pathogenesis and comparability to human endocarditis. Analyses of bacteriology and hematology were performed on blood samples from pigs with non-bacterial thrombotic endocarditis (NBTE, n = 11), Staphylococcus aureus infective endocarditis (IE, n = 2), animals with S. aureus sepsis without endocarditis (n = 2) and controls (n = 2). Furthermore, immunohistochemistry was used to examine the local expression of IL-1β and IL-8. Bacterial blood cultures were continuously positive in IE pigs from inoculation to euthanasia, and negative in all other pigs at all times. The total white blood cell counts and total neutrophil counts were massively elevated in pigs with IE. Local IL-1β and IL-8 expression in IE pigs were moderate to high, and high, respectively. In addition, slight local expression of IL-1β and IL-8 was present in some NBTE pigs. In the IE model, both the systemic inflammatory response and the high local expression of IL-8 were comparable to the human disease. Furthermore, the results indicate IL-1β and IL-8 as important contributors in the endocarditis pathogenesis.

Blocking interleukin-1 as a novel therapeutic strategy for secondary prevention of cardiovascular events

The inflammatory hypothesis of atherosclerosis postulates that inflammation within the plaque promotes plaque progression and complications. Interleukin-1 (IL-1) is a key pro-inflammatory cytokine responsible for the amplification of the inflammatory response following injury. Animal studies show that IL-1 blockade is effective in limiting atherosclerosis and atherothrombosis and improving outcomes in acute myocardial infarction and ischemic stroke. Preliminary data in patients with acute myocardial infarction, ischemic stroke, and heart failure are promising. A large secondary prevention trial with canakinumab in patients with prior acute myocardial infarction is currently ongoing. Many unanswered questions remain regarding the optimal use of IL-1 blockade and the preferred agent.

Effect of interleukin 1β inhibition in cardiovascular disease

PURPOSE OF REVIEW

Atherosclerosis is greatly influenced by inflammatory mediators at all phases. Recent studies have suggested a causal role of one such mediator, interleukin 1β (IL-1β), in the development of atherosclerotic vascular disease. This review highlights recent investigation of the role of IL-1β in atherosclerosis and the potential of its inhibition as a promising therapeutic strategy for the treatment of atherosclerotic vascular disease.

RECENT FINDINGS

Studies in animals have generally shown decreased atherosclerotic plaque burden in atherosclerosis-prone mice deficient in IL-1β and increased plaque in mice exposed to excess IL-1β. In humans, IL-1β was found in greater concentrations in atherosclerotic human coronary arteries compared with normal coronary arteries. Preclinical and clinical studies of IL-1β inhibition have shown efficacy in the treatment of several inflammatory disorders, suggesting that IL-1β may be a novel therapeutic target for anti-inflammatory therapy in atherosclerosis, such as coronary artery disease (CAD).

SUMMARY

IL-1β inhibition offers an interesting and biology-based opportunity to test the potential beneficial effects of an anti-inflammatory therapeutic strategy in patients with CAD. A large clinical trial evaluating the impact of IL-1β inhibition in CAD is ongoing and will be an important test of the inflammation hypothesis in CAD.

Interleukin-1β inhibition and the prevention of recurrent cardiovascular events: rationale and design of the Canakinumab Anti-inflammatory Thrombosis Outcomes Study (CANTOS)

BACKGROUND

Inflammation contributes to all phases of the atherothrombotic process, and patients with elevated inflammatory biomarkers such as high-sensitivity C-reactive protein (hsCRP) have increased vascular risk. Yet, it remains unknown whether direct inhibition of inflammation will reduce cardiovascular event rates.

DESIGN

The CANTOS will evaluate whether interleukin-1β (IL-1β) inhibition as compared with placebo can reduce rates of recurrent myocardial infarction, stroke, and cardiovascular death among stable patients with coronary artery disease who remain at high vascular risk due to persistent elevations of hsCRP (>2 mg/L) despite contemporary secondary prevention strategies. Canakinumab is a human monoclonal antibody that selectively neutralizes IL-1β, a proinflammatory cytokine that plays multiple roles in the atherothrombotic process and that undergoes activation by the nucleotide-binding leucine-rich repeat-containing pyrin receptor 3 inflammasome, a process promoted by cholesterol crystals. Canakinumab significantly reduces systemic C-reactive protein and other inflammatory biomarker levels, is generally well tolerated, and is currently indicated for the treatment of inherited IL-1β driven inflammatory diseases such as the Muckle-Wells syndrome. In a multinational collaborative effort using an event-driven intention-to-treat protocol, CANTOS will randomly allocate 17,200 stable postmyocardial infarction patients with persistent elevation of hsCRP to either placebo or to canakinumab at doses of 50, 150, or 300 mg every 3 months, administered subcutaneously. All participants will be followed up over an estimated period of up to 4 years for the trial primary end point (nonfatal myocardial infarction, nonfatal stroke, cardiovascular death) as well as for other vascular events, total mortality, adverse events, and specific clinical end points associated with inflammation including new onset diabetes, venous thrombosis, and atrial fibrillation.

SUMMARY

If positive, CANTOS would confirm the inflammatory hypothesis of atherothrombosis and provide a novel cytokine-based therapy for the secondary prevention of cardiovascular disease and new-onset diabetes.

Multi-scale simulations of the dynamics of in-stent restenosis: impact of stent deployment and design

Neointimal hyperplasia, a process of smooth muscle cell re-growth, is the result of a natural wound healing response of the injured artery after stent deployment. Excessive neointimal hyperplasia following coronary artery stenting results in in-stent restenosis (ISR). Regardless of recent developments in the field of coronary stent design, ISR remains a significant complication of this interventional therapy. The influence of stent design parameters such as strut thickness, shape and the depth of strut deployment within the vessel wall on the severity of restenosis has already been highlighted but the detail of this influence is unclear. These factors impact on local haemodynamics and vessel structure and affect the rate of neointima formation. This paper presents the first results of a multi-scale model of ISR. The development of the simulated restenosis as a function of stent deployment depth is compared with an in vivo porcine dataset. Moreover, the influence of strut size and shape is investigated, and the effect of a drug released at the site of injury, by means of a drug-eluting stent, is also examined. A strong correlation between strut thickness and the rate of smooth muscle cell proliferation has been observed. Simulation results also suggest that the growth of the restenotic lesion is strongly dependent on the stent strut cross-sectional profile.

Histone deacetylase-1 is enriched at the platelet-derived growth factor-D promoter in response to interleukin-1beta and forms a cytokine-inducible gene-silencing complex with NF-kappab p65 and interferon regulatory factor-1

Understanding the mechanisms governing cytokine control of growth factor expression in smooth muscle cells would provide invaluable insight into the molecular regulation of vascular phenotypes and create future opportunities for therapeutic intervention. Here, we report that the proinflammatory cytokine interleukin (IL)-1beta suppresses platelet-derived growth factor (PDGF)-D promoter activity and mRNA and protein expression in smooth muscle cells. NF-kappaB p65, induced by IL-1beta, interacts with a novel element in the PDGF-D promoter and inhibits PDGF-D transcription. Interferon regulatory factor-1 (IRF-1) is also induced by IL-1beta and binds to a different element upstream in the promoter. Immunoprecipitation and chromatin immunoprecipitation experiments showed that IL-1beta stimulates p65 interaction with IRF-1 and the accumulation of both factors at the PDGF-D promoter. Mutation of the IRF-1 and p65 DNA-binding elements relieved the promoter from IL-1beta-mediated repression. PDGF-D repression by IL-1beta involves histone deacetylation and interaction of HDAC-1 with IRF-1 and p65. HDAC-1 small interfering RNA ablates complex formation with IRF-1 and p65 and abrogates IRF-1 and p65 occupancy of the PDGF-D promoter. Thus, HDAC-1 is enriched at the PDGF-D promoter in cells exposed to IL-1beta and forms a cytokine-inducible gene-silencing complex with p65 and IRF-1.

Investigation of the effect of Interleukin-1 receptor antagonist (IL-1ra) on markers of inflammation in non-ST elevation acute coronary syndromes (The MRC-ILA-HEART Study)

Background

Acute Coronary Syndromes account for 15% of deaths in the UK, and patients remain at significant risk of re-admission for future complications and death. Pathologically the underlying process of atherosclerosis is driven by inflammatory mechanisms, which are activated in ACS patients. Previous studies have investigated the role of inflammatory markers in this process, including interleukin 1 (IL-1) and C Reactive Protein (CRP). Pre-clinical studies indicate that IL-1 may be a primary driver of ACS and that the naturally occurring interleukin-1 receptor antagonist (IL-1ra) may inhibit the atherosclerotic process. This study will investigate the effects of IL-1ra on inflammatory markers in man.

Methods/design

Three centres in the UK are planning to recruit 186 Non-ST elevation myocardial infarction patients to receive either interleukin-1 receptor antagonist (Anakinra) or matching placebo. Patients will receive a daily subcutaneous injection of either study drug or placebo over a 14 day period. The primary outcome is area under the curve of high sensitivity C-Reactive Protein (CRP) over the first 7 days.

Discussion

The MRC-ILA-HEART Study is a proof of concept clinical trial investigating the effects of IL-1ra upon markers of inflammation in patients with Non-ST elevation myocardial infarction. It is hoped this will provide new and exciting information in relation to an "anti-inflammatory" strategy for patients with acute coronary syndrome.

Trial registration

ISRCTN89369318

Current challenges in coronary stenting: from bench to bedside

PCI (percutaneous coronary intervention) now outnumbers CABG (coronary artery bypass grafting) by more than 3:1 for the treatment of coronary heart disease. In this article, we discuss the current challenges faced by interventional cardiologists including restenosis and its treatment options and potential therapies for the future. The impact of stent geometry on restenosis and strategies to deal with challenging lesions such as bifurcations and lesions in the left main stem are also discussed.

P2X receptor characterization and IL-1/IL-1Ra release from human endothelial cells

BACKGROUND AND PURPOSE

The pro-inflammatory cytokine, interleukin-1beta (IL-1beta), has been implicated in the pathogenesis of atherosclerosis, potentially via its release from vascular endothelium. Endothelial cells (EC) synthesize IL-1beta in response to inflammatory stimuli, but the demonstration and mechanism of release of IL-1 from ECs remains unclear. In activated monocytes, efficient release of bioactive IL-1beta occurred via activation of ATP-gated P2X(7) receptors (P2X(7)Rs). Activation of P2X(7)R in ECs from human umbilical vein (HUVECs) released IL-1 receptor antagonist (IL-1Ra). The purpose of this study was to provide a quantitative investigation of P2XR expression and function, in parallel with IL-1beta and IL-1Ra synthesis, processing and release, in HUVECs under pro-inflammatory conditions.

EXPERIMENTAL APPROACH

Quantitative RT-PCR, immunoblotting, ELISA, flow cytometry, and whole-cell patch clamp recordings were used to determine protein expression and receptor function. IL-8-luciferase-reporter was used as an IL-1 sensitive bioassay.

KEY RESULTS

HUVECs expressed P2X(4)R and P2X(7)R subtypes and both were significantly up-regulated under inflammatory conditions. P2X(7)R currents were increased 3-fold by inflammatory stimuli, whereas no P2X(4)R-mediated currents were detected. Caspase-1, but not IL-1beta, was present intracellularly under basal conditions; inflammatory stimuli activated the synthesis of intracellular pro-IL-1beta and increased caspase-1 levels. Activation of P2X(7)Rs resulted in low-level release of bioactive IL-1beta and simultaneous release of IL-1Ra. The net biological effect of release was anti-inflammatory.

CONCLUSIONS AND IMPLICATIONS

Endothelial P2X(7)Rs induced secretion of both pro- and anti-inflammatory IL-1 receptor ligands, the balance of which may provide a means for altering the inflammatory state of the arterial vessel wall.

PKC-δ mediates activation of ERK1/2 and induction of iNOS by IL-1β in vascular smooth muscle cells

Although the inflammatory cytokine interleukin-1β (IL-β) is an important regulator of gene expression in vascular smooth muscle (VSM), the signal transduction pathways leading to transcriptional activation upon IL-1β stimulation are poorly understood. Recent studies have implicated IL-1β-mediated ERK1/2 activation in the upregulation of type II nitric oxide synthase (iNOS) in VSM. We report that these events are mediated in a phospholipase C (PLC)- and protein kinase C (PKC)-δ-dependent manner utilizing a signaling mechanism independent of p21ras (Ras) and Raf1 activation. Stimulation of rat aortic VSM cells with IL-1β activated PLC-γ and pharmacological inhibition of PLC attenuated IL-1β-induced ERK1/2 activation and subsequent iNOS expression. Stimulation with IL-1β activated PKC-α and -δ, which was blocked using the PLC inhibitor U-73122. Pharmacological studies using isoform-specific PKC inhibitors and adenoviral overexpression of constitutively active PKC-δ indicated that ERK1/2 activation was PKC-α independent and PKC-δ dependent. Similarly, adenoviral overexpression of constitutively activated PKC-δ enhanced iNOS expression. IL-1β stimulation did not induce either Ras or Raf1 activity. The absence of a functional role for Ras and Raf1 related to ERK1/2 activation and iNOS expression was further confirmed by adenoviral overexpression of dominant-negative Ras and treatment with the Raf1 inhibitor GW5074. Taken together, we have outlined a novel transduction pathway implicating PKC-δ as a critical component of the IL-1-dependent activation of ERK in VSM cells.

Interleukin-1beta and signaling of interleukin-1 in vascular wall and circulating cells modulates the extent of neointima formation in mice

Interleukin (IL)-1 is an important mediator of inflammation and cardiovascular disease. Here, we examined the role of IL-1 in arterial neointima formation. Carotid artery neointima was induced by ligation, and arteries were harvested 4 weeks after injury. The neointima/media of mice deficient in the IL-1 signaling receptor (IL-1R1(-/-)) was significantly reduced compared to IL-1R1(+/+) controls (P < 0.01). IL-1R1(+/+) mice receiving subcutaneous IL-1ra also had significantly reduced neointima/media compared with placebo (P < 0.05). IL-1beta(-/-) mice had reduced neointima/media compared to wild-type (P < 0.05), whereas IL-1alpha(-/-) mice were no different from controls. Mice deficient in the P2X(7) receptor (involved in IL-1 release) or caspase-1 (involved in IL-1 activation) did not differ in their response to carotid ligation compared to controls. To examine the site of IL-1 signaling, we generated chimeric mice. IL-1R1(+/+) mice receiving IL-1R1(-/-) marrow and IL-1R1(-/-) mice receiving IL-1R1(+/+) marrow both had significantly reduced neointima/media compared with IL-1R1(+/+) to IL-1R1(+/+) (P < 0.05) but had significantly greater neointima/media than IL-1R1(-/-) to IL-1R1(-/-) controls (P < 0.05). These data confirm the importance of IL-1beta signaling in mediating arterial neointima formation and suggest the involvement of IL-1 signaling in both circulating and arterial wall cells. Furthermore, receptor antagonism may be a better therapeutic target than interruption of IL-1beta processing or release.

Early elevation of interleukin-1beta and interleukin-6 levels after bare or drug-eluting stent implantation in patients with stable angina

INTRODUCTION

Drug-eluting stent (DES) implantation represents an important innovation in the treatment of coronary artery disease. However, inflammatory-related complications, including subacute thrombosis and in-stent restenosis, are still important limitations to percutaneous coronary intervention (PCI). The aim of this study was to compare early local release of interleukin 1beta (IL-1beta) and IL-6 proinflammatory cytokines after elective placement of either bare metal stents or DES.

MATERIALS AND METHODS

IL-1beta and IL-6 levels were assayed in plasma obtained from the coronary sinus both before and 20 min after stent implantation in 59 patients with stable angina, who were randomly assigned to receive bare, paclitaxel-, or sirolimus-eluting stents during elective PCI.

RESULTS

We found that IL-1beta and IL-6 levels were significantly increased in the coronary sinus of patients receiving either bare, paclitaxel- or sirolimus-eluting stents 20 min after stent implantation as compared with basal concentrations. The variation in the level of both cytokines was comparable among the three study groups.

CONCLUSIONS

A local release of proinflammatory cytokines occurs shortly after coronary stent placement, including DES, which is possibly related to plaque rupture and/or endothelium traumatism following the stenting procedure. This suggests that precocious anti-inflammatory treatment could be of benefit to further improve the PCI clinical outcome.

TNFα increases the inflammatory response to vascular balloon injury without accelerating neointimal formation

There is now clear evidence for a contributory role of inflammatory processes to restenosis following vascular balloon injury and stent implantation. The aim of the present study was to study the effects of TNFalpha, administered locally in vivo immediately following balloon angioplasty, on the leukocyte adhesive response and extent of neointimal formation in a rabbit model of subclavian artery injury. Initial in vitro studies were performed with normal isolated artery rings to assess the vascular adhesive response to TNFalpha or IL-1beta. Pre-incubation with either cytokine prior to addition of (51)Cr-labelled leukocytes enhanced the adhesion of leukocytes to the artery in both a time- and concentration-dependent manner. Although both cytokines induced an increase in the expression of the adhesion molecules ICAM-1 and VCAM-1, only antibodies to ICAM-1 blocked the enhanced adhesion induced by the cytokines. In artery segments retrieved from rabbits that had previously undergone subclavian artery angioplasty either 24 h or 8 days previously, there was an injury-induced increase in adhesion of leukocytes assessed ex vivo. In segments obtained from rabbits that received a 15 min local infusion of TNFalpha (2 ng/min) to the injured artery immediately after the angioplasty procedure, leukocyte adhesion assessed ex vivo was further significantly enhanced. The pro-adhesive effect of TNFalpha was associated with an increased expression of both ICAM-1 and VCAM-1. However, TNFalpha administration did not alter the extent of neointimal formation observed 8 days after injury. These findings suggest that while TNFalpha may play a role following vascular injury, it does not act alone to induce neointimal formation. Thus anti-inflammatory strategies targeted at multiple cytokines may be more appropriate than targeting a single cytokine to reduce the response to vascular injury.

Wall shear modulation of cytokines in early vein grafts

OBJECTIVE

Pro-inflammatory cytokine-driven mechanisms have been implicated in vein graft failure, though little is known about the effect of hemodynamic factors and anti-inflammatory counter-regulatory mechanisms. We hypothesized that early temporal expression of the pro-inflammatory cytokine interleukin (IL)-1 beta and the anti-inflammatory cytokine IL-10 proceeds by way of wall shear stress-dependent pathways in the arterializing vein graft.

METHODS

Rabbits (n = 27) underwent bilateral jugular vein carotid interposition grafts, and simultaneous unilateral distal carotid branch ligation, to produce both low-flow and high-flow grafts in the same animal. Vein grafts were harvested at 1, 3, 7, 14, and 28 days and were assessed for architecture, wall shear stress, and cytokine messenger RNA levels (quantitative real-time two-step reverse transcription polymerase chain reaction).

RESULTS

The model resulted in an immediate 90% flow reduction (P <.001, paired t test) in the vein graft on the ligated side, and a 36% increase (P =.01) in contralateral graft flow. This persisted as approximately 15-fold flow differential throughout the 28-day period. The construction yielded a 15-fold differential in wall shear stress between low-flow and high-flow vein grafts (P <.001, two-way repeated measures analysis of variance). Intimal hyperplasia began by day 3, and was 6-fold more in low wall shear grafts by 28 days (230.6 +/- 35.4 microm intimal thickness vs 36.1 +/- 17.6 microm for low shear versus high shear grafts; P =.001). For both cytokines time independently affected mRNA expression (P <.001, global analysis of variance). Exposure of vein grafts to the arterial circulation markedly up-regulated IL-1 beta at 1 day, with significantly more induction in the low shear setting (P =.002). IL-1 beta protein localized to the developing neointima at days 1 and 3. Conversely, IL-10 slowly increased until day 14, with significantly more expression in the high shear grafts (P <.001).

CONCLUSIONS

Vein graft adaptation induces early pro-inflammatory cytokine IL-1 beta expression and delayed protective IL-10 expression (most notable under high shear conditions), both of which are modulated by wall shear. These differential temporal windows offer strategies for appropriately timed pro-inflammatory or anti-inflammatory therapies to interrupt pathologic vein graft adaptations.

CLINICAL RELEVANCE

Neointimal hyperplasia continues to limit the durability of vein bypass grafts. Emerging evidence suggests that inflammatory mechanisms drive the neointimal hyperplasic response. This study demonstrates that specific hemodynamic forces (altered wall shear stress) differentially affect early pro-inflammatory interleukin (IL)-1 beta and delayed anti-inflammatory IL-10 signaling. These distinct temporal windows for IL-1 beta and IL-10 cytokine expression offer strategies for appropriately timed pro-inflammatory and anti-inflammatory therapies to interrupt pathologic vein graft adaptations.

Irradiation of mechanically-injured human arterial endothelial cells leads to increased gene expression and secretion of inflammatory and growth promoting cytokines

Radiation therapy is applied to inhibit neointima formation after percutaneous transluminal coronary angioplasty (PTCA). In this study, we evaluated the effect of irradiation on re-endothelialisation of circular denuded tracks made in post-confluent cultures of arterial endothelial cells (ECs) and on cellular factors involved in this process. Image analysis and time-lapse microcinematography revealed cell migration into denuded areas starting 4h after injury. Fifty percent coverage was achieved at 14.8 +/- 2.0 h. Using competitive PCR and flow cytometry techniques, no significant changes in mRNA expression of interleukin-1beta (IL-1beta), interleukin-8 (IL-8), basic fibroblast growth factor (bFGF or FGF-2), transforming growth factor-beta1 (TGF-beta1), platelet-derived growth factor A (PDGF-A), platelet-derived growth factor B (PDGF-B) and tissue factor (TF), and surface molecule expression of anti-intercellular adhesion molecule-1 (ICAM-1), anti-vascular cell adhesion molecule-1 (VCAM-1), anti-platelet/endothelial cell adhesion molecule-1 (PECAM-1), MHC-1, TF and Fas were observed. However, injury did significantly (P < 0.05) elevate the release of IL-8 and FGF-2 protein in the cell culture supernatant, as assessed by ELISA. Radiation (15Gy) given immediately after injury did not affect the kinetics of re-endothelialisation up to 48 h, in spite of the fact that no cell divisions were observed. Thereafter cell density decreased and cultures deteriorated. Compared to cultures exposed to injury alone, radiation induced significant (P < 0.05) increases in mRNA levels of IL-8 (1.35 +/- 0.10-fold increase at 4h), FGF-2 (1.62 +/- 0.10-fold at 4h; 1.76 +/- 0.33-fold at 24h) and IL-1beta (2.76 +/- 0.40-fold at 24h), whereas mRNA levels of TGF-beta1, PDGF-A and PDGF-B increased about 1.2-fold. IL-8 and FGF-2 protein concentrations in the media were higher than those observed in non-irradiated injured cell cultures; however, this difference was not significant. Radiation induced a 2.3 +/- 0.3-fold increase (P < 0.05) in Fas surface expression only. In conclusion, irradiation of mechanically-injured human EC leads to increased gene expression and protein secretion of inflammatory and growth promoting cytokines.

Interleukin-1beta inhibits PDGF-BB-induced migration by cooperating with PDGF-BB to induce cyclooxygenase-2 expression in baboon aortic smooth muscle cells

OBJECTIVE

Smooth muscle cell (SMC) migration from the media into the intima is pivotal for intimal formation after vascular injury. Platelet-derived growth factor (PDGF)-BB is a potent chemoattractant for SMCs in vitro and in vivo. We investigated whether interleukin (IL)-1beta affects migration in response to PDGF-BB. Our data suggest that IL-1beta is inhibitory and that this effect is mediated by cyclooxygenase (COX)-2. We further addressed the role of the mitogen-activated protein kinase p38, which is activated by PDGF-BB and by IL-1beta.

METHODS

Baboon aortic SMCs were prepared with the explant method. Migration was measured in a Boyden chamber assay through filters coated with monomeric collagen. COX2 expression and phosphorylation of p38 MAPK were analyzed by Western blotting.

RESULTS

PDGF-BB (10 ng/mL) stimulates migration 3.8-fold, and IL-1beta (0.1 ng/mL) reduces this response by 40%. The inhibitory effect of IL-1beta is abolished by the COX inhibitor, indomethacin (10 micromol/L), the specific COX2 inhibitor, NS398 (10 micromol/L), and the p38 MAPK inhibitor SB203580 (3 micromol/L). We found that IL-1beta and PDGF-BB synergize to stimulate COX2 expression. We further demonstrated that p38 MAPK is activated by IL-1beta and PDGF with different kinetics and that p38 MAPK is required for maximal COX2 expression in response to IL-1beta plus PDGF-BB.

CONCLUSION

IL-1beta inhibits PDGF-BB-induced migration by cooperating with PDGF-BB to induce COX2 through activation of p38 MAPK. Whether this effect of IL-1beta modulates intimal growth after vascular injury remains to be elucidated.

Expression of interleukin-1 beta and interleukin-1 receptor antagonist in oxLDL-treated human aortic smooth muscle cells and in the neointima of cholesterol-fed endothelia-denuded rabbits

The migration of vascular smooth muscle cells (VSMCs) from the media to the intima and the proliferation of intimal VSMCs are key events in restenotic lesion development. These events, which are preceded and accompanied by inflammation, are modulated by the proinflammatory cytokine, interleukin-1 beta (IL-1 beta), which induces vascular smooth muscle cells to express adhesion molecules and to proliferate. IL-1 beta action is complex and regulated, in part, by its naturally occurring inhibitor, the IL-1 receptor antagonist (IL-1ra). Whether there was a temporal and spatial correlation between IL-1 beta and IL-1ra expression in, and release by, oxidized low density lipoproteins (oxLDL)-stimulated human aortic smooth muscle cells (HASMCs) was determined by using ELISA and Western blot. In addition, IL-1 beta and IL-1ra expression was detected in the neointima of endothelia-denuded cholesterol-fed New Zealand white rabbits by immunohistochemistry and Western blot. In HASMCs, oxLDL induced IL-beta and IL-1ra expression and release in a dose- and time-dependent manner. Treatment with 20 microg/ml oxLDL resulted in increased IL-1 beta release after 6 h, which peaked at 24 h, and in increased IL-1ra release, first seen after 12 h, but continuing to increase for at least 48 h. In the cells, IL-beta expression showed a similar pattern to release, whereas IL-1ra expression was seen in unstimulated cells and was not increased by oxLDL treatment. Confocal microscopy showed colocalization of IL-beta and IL-1ra expression in oxLDL-stimulated HASMCs. oxLDL caused significant induction of nuclear factor kappa B and activator protein-1 DNA binding activity in HASMCs (6.6- and 3.3-fold, respectively). In cholesterol-fed endothelia-denuded rabbits, the notably thickened intima showed significant IL-1 beta and IL-1ra expression. These results provide further support for the role of IL-1 system in the pathogenesis of restenosis. This is the first demonstration of IL-1 beta and IL-1ra expression and secretion of oxLDL-treated HASMCs and their expression in the rabbit neointima, suggesting that the smooth muscle cells of the intima are an important source of these factors.

Effects of Ginkgo biloba extract on the proliferation of vascular smooth muscle cells in vitro and on intimal thickening and interleukin-1beta expression after balloon injury in cholesterol-fed rabbits in vivo

Restenosis may develop in response to cytokine activation and smooth muscle cell proliferation. Ginkgo biloba extract (EGb) has been used to treat cardiovascular and cerebrovascular diseases. In the present study, the effects of EGb on the growth of cultured vascular smooth muscle cells (VSMC), as well as on the expression of interleukin-1beta (IL-1beta) and the intimal response in balloon-injured arteries of cholesterol-fed rabbits, were investigated. Using bromodeoxyuridine incorporation as an index of cell proliferation, EGb was found to inhibit serum-induced mitogenesis of cultured rat aorta VSMC in a dose-dependent manner. In vivo, EGb and probucol ( positive control) reduced the atheroma area in thoracic aortas of male New Zealand white rabbits fed a 2% cholesterol diet for 6 weeks with balloon denudation of the abdominal aorta being performed at the end of the third week. Intimal hyperplasia, expressed as the intimal/medial area ratio, in the abdominal aortas was significantly inhibited in the both the EGb group (0.61 +/- 0.06) and the probucol group (0.55 +/- 0.03) compared to the C group (0.87 +/- 0.02). In the balloon-injured abdominal aorta, both EGb and probucol significantly reduced IL-1beta mRNA and protein expression and the percentage of proliferating cells. The inhibitory effects of EGb on the intimal response might be attributed to its antioxidant capacity. EGb may have therapeutic potential for the prevention of restenosis after angioplasty.

The identification of novel wound-healing genes through differential display

Effective methods to identify novel genes in complicated dynamic tissue processes are needed in molecular biology research. Traditional techniques primarily target known genes and are inefficient in the pursuit of unknown genes. Here we describe the use of a modified differential display polymerase chain reaction (DD-PCR) protocol for the identification of genes differentially expressed in wound healing. Full-thickness dorsal wounds were made on 35 adult rats, followed by wound harvest at 12 hours, 24 hours, 3 days, 5 days, 7 days, 10 days, and 14 days after injury. Modified DD-PCR was performed and gene fragments displaying definite changes during wound healing were cloned and sequenced. Gene fragments from DD-PCR were compared with available gene bank database sequences. Specific primer PCR was used to confirm DD-PCR expression patterns. As a result, over 1000 gene fragments were amplified by DD-PCR, 35 of which demonstrated distinct differences during repair. Cloning and sequencing of 13 of these gene fragments revealed that some were homologous to several characterized genes with previously unsuspected roles in repair, whereas others were completely novel genes with no known function. Specific primer PCR further confirmed expression of six of these 13 gene fragments. Only one of the 13 cloned fragments, later identified as interleukin-1beta, had well-recognized associations with tissue injury. Other fragments corresponded to various genes involved in cellular processes such as differentiation, proliferation, exocytosis, and myofibril assembly. No prior studies have linked them to wound healing. We have demonstrated that modified DD-PCR can be used to effectively identify novel genes differentially expressed during repair. Because DD-PCR allows for the simultaneous amplification of multiple arbitrary transcripts, it is a powerful genetic screening tool for complicated dynamic tissue processes, particularly when multiple, limited-sized samples are involved.

The balance between IL-1 and IL-1Ra in disease

IL-1 is an important mediator of inflammation and tissue damage in multiple organs, both in experimental animal models of disease and in human diseases. The IL-1 family consists of two agonists, IL-1alpha and IL-1beta, two receptors, biologically active IL-1RI and inert IL-1RII, and a specific receptor antagonist, IL-1Ra. The balance between IL-1 and IL-1Ra in local tissues plays an important role in the susceptibility to and severity of many diseases. An allelic polymorphism in the IL-1Ra gene has been associated with a variety of human diseases primarily of epithelial and endothelial cell origin. This association may be secondary to an imbalance in the IL-1 system with enhanced production of IL-1beta and reduced production of the major intracellular isoform of IL-1Ra. Treatment of RA with daily subcutaneous injections of recombinant IL-1Ra protein has been shown to be efficacious. Gene therapy approaches with IL-1Ra are being evaluated for the treatment of RA and other human diseases.

Macrophage depletion by clodronate-containing liposomes reduces neointimal formation after balloon injury in rats and rabbits

BACKGROUND

Inflammation is critical to vascular repair after mechanical injury. Excessive inflammation enhances neointimal formation and restenosis. We examined whether transient systemic inactivation of macrophages at the time of vascular intervention could attenuate the degree of expected restenosis.

METHODS AND RESULTS

Liposomal clodronate (LC) inhibited the growth of cultured macrophages but had no effect on endothelial or smooth muscle cells and suppressed neointimal hyperplasia in hypercholesterolemic rabbits and rats after intravenous administration of LC, with no adverse effects. LC treatment reduced the number of blood monocytes and decreased macrophage infiltration in the injured arteries as well as smooth muscle cell proliferation, interleukin-1beta transcription, and production and matrix metalloproteinase-2 activity.

CONCLUSIONS

Macrophages play a pivotal role in vascular repair after mechanical arterial injury. Systemic inactivation and depletion of monocytes and macrophages by LC reduce neointimal hyperplasia and restenosis.

Role of reactive oxygen species in IL-1 beta-stimulated sustained ERK activation and MMP-9 induction

We have recently demonstrated that interleukin-1 beta (IL-1 beta) stimulates matrix metalloproteinase-9 (MMP-9) induction. In this study we have investigated the roles of superoxide and extracellular signal-regulated kinase (ERK) activation in MMP-9 induction following exposure to IL-1 beta. IL-1 beta stimulated biphasic ERK activation in vascular smooth muscle (VSM) cells, a transient activation that reached a maximum at 15 min and declined to baseline levels within 1 h, and a second phase of sustained ERK activation lasting up to 8 h. To determine the role of ERK in IL-1 beta-stimulated MMP-9 induction, we treated cells with the specific ERK pathway inhibitor PD-98059 at different time intervals after IL-1 beta stimulation. Addition of PD-98059 up to 4 h after IL-1 beta stimulation significantly inhibited MMP-9 induction, suggesting a role for sustained ERK activation in MMP-9 induction. IL-1 beta treatment stimulated superoxide production in VSM cells that was inhibited by pretreatment of cells with the superoxide scavenger N-acetyl-L-cysteine (NAC) and also by overexpression of the human manganese superoxide dismutase (MnSOD) gene. Treatment of VSM cells with NAC selectively inhibited the sustained phase of ERK activation without influencing the transient phase, suggesting a role for reactive oxygen species in sustained ERK activation. In addition, both NAC treatment and MnSOD overexpression significantly inhibited IL-1 beta-stimulated MMP-9 induction (P < 0.05). The results demonstrate that IL-1 beta-dependent MMP-9 induction is mediated by superoxide-stimulated ERK activation.

Endogenous anti-inflammatory response after coronary injury in a porcine model

BACKGROUND

Corticotropin-releasing hormone (CRH)/adrenocorticotropic hormone (ACTH)/cortisol is the major anti-inflammatory system. After percutaneous translumenal angioplasty, an inflammatory process is triggered. We investigate whether CRH/ACTH/cortisol axis is activated after deep vessel wall injury (DVWI).

MATERIALS AND METHODS

Plasma and leukocyte CRH and ACTH, serum cortisol and IL-1beta, and leukocyte cAMP were measured (ELISA) in 16 pigs after anaesthesia (baseline), 60 min into anaesthesia without causing vascular injury and 90 min after DVWI of the left anterior descending (LAD) coronary artery induced by percutaneous directional atherectomy (Atherocath GTO 7F; DVI, Inc., Temecula, USA). Biochemical variables were also measured at baseline, 60 and 180 min into anaesthesia in six additional pigs without coronary intervention.

RESULTS

MANOVA showed that CRH/ACTH/Cortisol, cAMP and IL-1beta production was not modified during anaesthesia. Post-DVWI plasma CRH (0.077 +/- 0.046 ng mL-1), and cellular cAMP (0.14 +/- 0.067 pmol 10(-6) cells) increased significantly (P = 0.001) with respect to their baseline values (CRH = 0.036 +/- 0.013 ng mL-1; cAMP = 0.081 +/- 0.034 pmol 10-6). There was also a statistically significant increase (P = 0.02) in post-DVWI IL-1beta (from 46.6 +/- 12.8 to 64.05 +/- 13.5 pg mL-1), and in serum cortisol (P = 0.05) compared to its baseline values (8.98 +/- 3.2 microgr dL-1 vs. 6.57 +/- 2.3 microgr dL-1, respectively).

CONCLUSION

In our experimental model, coronary vessel wall injury-activated CRH/ACTH/cortisol axis caused a significant increase in plasma CRH, cortisol and cellular cAMP levels, which may influence the response of coronary arteries to injury.

Localization of c-Myb and induction of apoptosis by antisense oligonucleotide c-Myb after angioplasty of porcine coronary arteries

Previous studies have shown that inhibition of the proto-oncogene c-myb inhibits neointimal formation in various animal models. However, the temporal and spatial expression of c-Myb in the vessel wall after injury is not known, and the mechanism of action of antisense oligonucleotide (AS-ODN-c-myb) inhibition remains unclear. One potential effect of cell cycle dysregulation by inhibition of c-myb is an increase in the rates of apoptosis. In this study, c-Myb expression after percutaneous transluminal coronary angioplasty (PTCA) injury and induction of apoptosis after AS-ODN-c-myb treatment were determined. Immunohistochemistry and cellular phenotyping were used to localize c-Myb expression in porcine coronary arteries at various time intervals after PTCA. In vitro, the effects of AS-ODN-c-myb on the apoptosis of porcine vascular smooth muscle cells (PVSMCs) and endothelial cells were determined by using a cell-death ELISA and time-lapse video microscopy. In vivo, local delivery of AS-ODN-c-myb was performed after PTCA of pig coronary arteries, and apoptosis was quantified at 6 hours. c-Myb is induced in pig coronary arteries after angioplasty, with maximal expression in inflammatory cells at 18 hours and in vascular smooth muscle cells at 3 to 7 days. In vitro, AS-ODN-c-myb enhanced PVSMCs (6.8+/-0.8% [P=<0.001] versus 0.5% serum) but not endothelial cell apoptosis (1.4+/-0.5% [P=NS] versus 0.5% serum). In vivo, 6 hours after porcine coronary angioplasty and delivery of AS-ODN-c-myb, the proportion of apoptotic cells within the media was 4.2+/-0.8% (PTCA alone), 2.3+/-0.2% (PTCA+vehicle), and 9.0+/-1.1% (PTCA+AS-ODN-c-myb; P<0.05 versus PTCA alone and P<0.01 versus PTCA+saline). c-Myb is expressed after PTCA of pig coronary arteries, and AS-ODN-c-myb induces apoptosis of PVSMCs in vitro and medial cells in vivo.

Interleukin 1 receptor antagonist gene polymorphism and restenosis after coronary angioplasty

BACKGROUND

Percutaneous transluminal coronary angioplasty (PTCA) is limited by the recurrence of luminal stenosis, which occurs in up to 50% of procedures. It has been shown that patient specific factors, perhaps genes, contribute to this process.

OBJECTIVE

To determine whether completion of healing after PTCA is part of an acute self limiting inflammatory process and whether polymorphism at important inflammatory gene loci might determine susceptibility to restenosis after PTCA.

DESIGN

DNA samples were collected from 171 patients attending for elective PTCA in Sheffield (S) and Leicester (L), who were scheduled to undergo follow up angiography (at four months (L) or six months (S)) as part of other restenosis studies. At follow up angiography, the patients were separated into restenosers (> 50% luminal narrowing) and non-restenosers (< 50% luminal narrowing). Four DNA polymorphisms within interleukin 1 (IL-1) related loci (IL-1A (-889), IL-1B (-511), IL-1B (+3954), and IL-1RN intron 2 VNTR (variable number tandem repeat)) were genotyped using methods based on polymerase chain reaction. Significance was assessed by chi(2) analysis of the relevant contingency table, and the magnitude of effect was estimated by calculating odds ratios. The Mantel-Haenszel (MH) test was applied to summarise data across the two populations.

RESULTS

Allele 2 at IL-1RN (IL-1RN*2) was significantly over represented in the non-restenoser group (L+S, 34% v 23% in restenosers). Furthermore, IL-1RN*2 homozygosity was increased in the non-restenoser population compared with the restenosers (MH test: p = 0.0196 (L+S); p = 0.031 (L+S, single vessel disease only), and the effect seemed to be restricted to the single vessel disease subpopulation. For other polymorphism within IL-1 related loci no significant associations were found with either restenosis or non-restenosis.

CONCLUSIONS

IL-1RN*2 may be associated with protection from restenosis after PTCA for individuals with single vessel disease. As this polymorphism has functional significance, this finding suggests that alteration in an individual's inflammatory predisposition may modulate the blood vessel response to injury.

Mechanism of inhibition of matrix metalloproteinase-9 induction by NO in vascular smooth muscle cells

Vascular smooth muscle (VSM) cell migration is a critical step in the development of a neointima after angioplasty. Matrix metalloproteinases (MMPs) degrade the basement membrane and extracellular matrix, facilitating VSM cell migration. Recently, we demonstrated that nitric oxide (NO) inhibits interleukin-1 beta (IL-1 beta)-stimulated MMP-9 induction in rat aortic VSM cells. In this study, we examined the hypothesis that NO inhibits MMP-9 induction by attenuating superoxide generation and extracellular signal-regulated kinase (ERK) activation. Stimulation of VSM cells with IL-1 beta significantly (P < 0.05) increased superoxide production, ERK activation, and MMP-9 induction. Pretreatment of VSM cells with the NO donor DETA NONOate significantly (P < 0.05) decreased IL-1 beta-stimulated superoxide generation. In addition, pretreatment of VSM cells with a specific ERK pathway inhibitor, PD-98059, or DETA NONOate inhibited IL-1 beta-stimulated ERK activation and MMP-9 induction. Direct exposure of VSM cells to increased superoxide levels by treatment with xanthine/xanthine oxidase increased ERK activation and MMP-9 induction, whereas pretreatment of cells with PD-98059 significantly (P < 0.05) inhibited xanthine/xanthine oxidase-stimulated ERK activation and MMP-9 induction. We conclude that NO inhibits IL-1 beta-stimulated MMP-9 induction by inhibiting superoxide generation and subsequent ERK activation.

Role of p38 mitogen-activated protein kinase in neointimal hyperplasia after vascular injury

p38 mitogen-activated protein kinase (MAPK) is involved in intracellular signals that regulate a variety of cellular responses during inflammation. However, the role of p38 MAPK in atherosclerosis, a chronic inflammatory disorder, remains uncertain. The aim of the present study was to examine the role of p38 MAPK in the development of neointimal hyperplasia in balloon-injured rat carotid arteries. Immunohistochemical studies indicated that p38 MAPK was rapidly activated in the majority of medial cells in injured arterial walls. Rats treated with FR167653, a selective inhibitor of p38 MAPK, at a dosage of 10 mg x kg(-1) x d(-1), had a 29.4% lower intima-to-media ratio than the untreated controls at 14 days after balloon injury (P:<0.05). The percentage of proliferating nuclear antigen-positive cells in the media at 48 hours was significantly lower in the FR167653-treated group than in the control group. Quantitative competitive reverse transcription-polymerase chain reaction analysis revealed that interleukin-1beta mRNA expression in arteries was significantly inhibited by FR167653 (to 18.1% of control, P:<0.05) at 8 hours after balloon injury. Moreover, p38 MAPK activation and interleukin-1beta production by lipopolysaccharide-stimulated vascular smooth muscle cells were inhibited by FR167653 in a concentration-dependent manner in vitro. These results indicate that p38 MAPK is activated in vascular walls after injury and promotes neointimal formation and suggest that selective inhibition of p38 MAPK may be effective in the prevention of restenosis after percutaneous transluminal coronary angioplasty.

Expression of interleukin-1beta, interleukin-1 receptor, and interleukin-1 receptor antagonist mRNA in rat carotid artery after balloon angioplasty

Interleukin-1beta (IL-1beta) is a pleiotropic cytokine capable of inducing smooth muscle activation and leukocyte recruitment in restenosis and atherosclerosis. Our present study investigated the expression of IL-1beta, IL-1 receptor antagonist (IL-1ra), and IL-1 receptor (IL-1RI and IL-1RII) mRNA in carotid artery after balloon angioplasty using semiquantitative reverse transcription/polymerase chain reaction (RT/PCR) and Northern analysis. Time course studies revealed that IL-1beta mRNA was rapidly induced at 6 h (30-fold increase over control, P < 0.001) post balloon injury and diminished to basal levels at 24 h. The increased expression of IL-1ra mRNA was delayed, reaching a peak at 24 h (400-fold increase, P < 0.001) and sustained up to 14 days. The expression of IL-1RII mRNA was remarkably similar to that of IL-1beta, whereas the IL-1RI (the signaling receptor) mRNA expression was delayed (significantly induced at day 1; 14.2-fold increase, P < 0.01) post balloon injury. Immunohistochemical studies revealed a strong induction of IL-1beta in the area with actively proliferating and migrating smooth muscle cells (i.e., in the inner medial layer at day 1 and in neointima at day 14 after balloon injury). The differential but concomitant expression of IL-1beta, IL-1ra, IL-1RI, and IL-1RII mRNAs after balloon angioplasty suggests that each of these IL-1 system components may play a distinct role in neointima formation.