Search

Histopathological studies have revealed key processes of atherosclerotic plaque thrombosis. However, the diversity and complexity of lesion types highlight the need for improved sub- phenotyping. We hypothesized that unbiased clustering of plaques based on gene expression results in an alternative categorization of late-stage atherosclerotic lesions.We analyzed the gene expression profiles of 654 advanced human carotid plaques. The unsupervised, transcriptome-driven clustering revealed five dominant plaque types. These novel plaque phenotypes associated with clinical presentation (pIn conclusion, the definition of the plaque at risk for a thrombotic event can be fine-tuned by in- depth transcriptomic based phenotyping. These differential plaque phenotypes prove clinically relevant for both carotid and coronary artery plaques and point to differential underlying biology of symptomatic lesions.

Graphical abstract Establishment of an autoreactive B cell memory after myocardial infarction: a working hypothesis. The demise of cardiac cells leads to the release of cryptoantigens that induce a humoral immune response that leads to accumulation of immunoglobulins in plaques and eventually amplifies atherogenesis at remote sites.

The diverse leukocyte infiltrate in atherosclerotic mouse aortas was recently analyzed in 9 single-cell RNA sequencing and 2 mass cytometry studies. In a comprehensive meta-analysis, we confirm 4 known macrophage subsets—resident, inflammatory, interferon-inducible cell, and Trem2 (triggering receptor expressed on myeloid cells-2) foamy macrophages—and identify a new macrophage subset resembling cavity macrophages. We also find that monocytes, neutrophils, dendritic cells, natural killer cells, innate lymphoid cells-2, and CD (cluster of differentiation)-8 T cells form prominent and separate immune cell populations in atherosclerotic aortas. Many CD4 T cells express IL (interleukin)-17 and the chemokine receptor CXCR (C-X-C chemokine receptor)-6. A small number of regulatory T cells and T helper 1 cells is also identified. Immature and naive T cells are present in both healthy and atherosclerotic aortas. Our meta-analysis overcomes limitations of individual studies that, because of their experimental approach, over- or underrepresent certain cell populations. Mass cytometry studies demonstrate that cell surface phenotype provides valuable information beyond the cell transcriptomes. The present analysis helps resolve some long-standing controversies in the field. First, Trem2 + foamy macrophages are not proinflammatory but interferon-inducible cell and inflammatory macrophages are. Second, about half of all foam cells are smooth muscle cell-derived, retaining smooth muscle cell transcripts rather than transdifferentiating to macrophages. Third, Pf4 , which had been considered specific for platelets and megakaryocytes, is also prominently expressed in the main population of resident vascular macrophages. Fourth, a new type of resident macrophage shares transcripts with cavity macrophages. Finally, the discovery of a prominent innate lymphoid cell-2 cluster links the single-cell RNA sequencing work to recent flow cytometry data suggesting a strong atheroprotective role of innate lymphoid cells-2. This resolves apparent discrepancies regarding the role of T helper 2 cells in atherosclerosis based on studies that predated the discovery of innate lymphoid cells-2 cells.

Giant cell arteritis (GCA) is a common form of primary systemic vasculitis in adults, with no reliable indicators of prognosis or treatment responses. We used single cell technologies to comprehensively map immune cell populations in the blood of patients with GCA and identified the CD66b+CD15+CD10lo/–CD64– band neutrophils and CD66bhiCD15+CD10lo/–CD64+/bright myelocytes/metamyelocytes to be unequivocally associated with both the clinical phenotype and response to treatment. Immature neutrophils were resistant to apoptosis, remained in the vasculature for a prolonged period of time, interacted with platelets, and extravasated into the tissue surrounding the temporal arteries of patients with GCA. We discovered that immature neutrophils generated high levels of extracellular reactive oxygen species, leading to enhanced protein oxidation and permeability of endothelial barrier in an in vitro coculture system. The same populations were also detected in other systemic vasculitides. These findings link functions of immature neutrophils to disease pathogenesis, establishing a clinical cellular signature of GCA and suggesting different therapeutic approaches in systemic vascular inflammation., Bona fide immature neutrophil subsets produce unchecked extracellular ROS that contributes to vascular pathologies.

Atherosclerosis is a multifactorial chronic inflammatory disease and is largely responsible for cardiovascular disease, the most common cause of global mortality. The hallmark of atherogenesis is immune activation following lipid accumulation in the arterial wall. In particular, macrophages play a non-redundant role in both the progression and regression of inflammation in the atherosclerotic lesion. Macrophages are remarkably heterogeneous phagocytes that perform versatile functions in health and disease. Their functional diversity in vascular biology is only partially mapped. Targeting macrophages is often highlighted as a therapeutic approach for cancer, metabolic and inflammatory diseases. Future strategies for therapeutic intervention in atherosclerosis may benefit from attempts to reduce local proliferation of pro-inflammatory macrophage subsets or enhance resolution of inflammation. Thus, characterisation of macrophage subsets during atherosclerosis would empower clinical interventions. Therefore, it would be of fundamental importance to understand how pathological factors modulate macrophage activity in order to exploit their use in the treatment of atherosclerosis and other diseases.

Atherosclerosis is the major cause of cardiovascular disease (CVD), the leading cause of death worldwide. Despite much focus on lipid abnormalities in atherosclerosis, it is clear that the immune system also has important pro- and antiatherogenic functions. The enzyme indoleamine-2,3-dioxygenase (IDO) catalyses degradation of the essential amino acid tryptophan into immunomodulatory metabolites. How IDO deficiency affects immune responses during atherogenesis is unknown and we explored potential mechanisms in models of murine and human atherosclerosis. IDO deficiency in hypercholesterolemic ApoE(-/-) mice caused a significant increase in lesion size and surrogate markers of plaque vulnerability. No significant changes in cholesterol levels were observed but decreases in IL-10 production were found in the peripheral blood, spleen and lymph node B cells of IDO-deficient compared with IDO-competent ApoE(-/-) mice. 3,4,-Dimethoxycinnamoyl anthranilic acid (3,4-DAA), an orally active synthetic derivative of the tryptophan metabolite anthranilic acid, but not l-kynurenine, enhanced production of IL-10 in cultured splenic B cells. Finally, 3,4-DAA treatment reduced lesion formation and inflammation after collar-induced arterial injury in ApoE(-/-) mice, and reduced cytokine and chemokine production in ex vivo human atheroma cell cultures. Our data demonstrate that endogenous production of tryptophan metabolites via IDO is an essential feedback loop that controls atherogenesis and athero-inflammation. We show that the IDO pathway induces production of IL-10 in B cells in vivo and in vitro, suggesting that IDO may induce immunoregulatory functions of B cells in atherosclerosis. The favorable effects of anthranilic acid derivatives in atherosclerosis indicate a novel approach toward therapy of CVD.

Atherosclerosis, the major risk factor for cardiovascular disease (CVD) and the leading cause of death worldwide, is a multifactorial chronic inflammatory disease, which, clinically manifests from early lipid-rich lesions to plaque rupture and/or thrombosis in the arterial wall. The myeloid cell compartment, including macrophages and dendritic cells (DCs), is long known to contribute to the initiation and progression of atherosclerosis. However their complex phenotypic heterogeneity hampers our full understanding of their role. Here, we review the biological and functional versatility of the myeloid cells in atherosclerosis. Several distinct subsets of macrophages and myeloid cells have been identified in atherosclerotic plaques, including subsets that are specific to atherosclerosis itself. Our ability to target them therapeutically is still limited. The challenge for the future will be the definition of treatments that target specific myeloid subsets to prevent the activation of pro-atherogenic myeloid cell subsets while preserving the anti-atherogenic and repairable function of myeloid cells.

Significance: Great attention has been placed on the link between metabolism and immune function giving rise to the term “immunometabolism.” It is widely accepted that inflammation and oxidative stress are key processes that underlie metabolic complications during obesity, diabetes, and atherosclerosis. Therefore, identifying the mechanisms and mediators that are involved in the regulation of both inflammation and metabolic homeostasis is of high scientific and therapeutic interest. Recent Advances: G protein-coupled receptors (GPCRs) that signal in response to metabolites have emerged as attractive therapeutic targets in inflammatory disease. Critical Issues and Future Directions: In this review, we discuss recent findings about the physiological role of the main metabolite-sensing GPCRs, their implication in immunometabolic disorders, their principal endogenous and synthetic ligands, and their potential as drug targets in inflammation and metabolic disease.

Objective Besides functioning as an intracellular metabolite, succinate acts as a stress-induced extracellular signal through activation of GPR91 (SUCNR1) for which we lack suitable pharmacological tools. Methods and results Here we first determined that the cis conformation of the succinate backbone is preferred and that certain backbone modifications are allowed for GPR91 activation. Through receptor modeling over the X-ray structure of the closely related P2Y1 receptor, we discovered that the binding pocket is partly occupied by a segment of an extracellular loop and that succinate therefore binds in a very different mode than generally believed. Importantly, an empty side-pocket is identified next to the succinate binding site. All this information formed the basis for a substructure-based search query, which, combined with molecular docking, was used in virtual screening of the ZINC database to pick two serial mini-libraries of a total of only 245 compounds from which sub-micromolar, selective GPR91 agonists of unique structures were identified. The best compounds were backbone-modified succinate analogs in which an amide-linked hydrophobic moiety docked into the side-pocket next to succinate as shown by both loss- and gain-of-function mutagenesis. These compounds displayed GPR91-dependent activity in altering cytokine expression in human M2 macrophages similar to succinate, and importantly were devoid of any effect on the major intracellular target, succinate dehydrogenase. Conclusions These novel, synthetic non-metabolite GPR91 agonists will be valuable both as pharmacological tools to delineate the GPR91-mediated functions of succinate and as leads for the development of GPR91-targeted drugs to potentially treat low grade metabolic inflammation and diabetic complications such as retinopathy and nephropathy., Highlights • The GPR91 binding site for succinate is identified with an adjacent empty pocket. • The binding pocket structure is used to identify novel synthetic GPR91 agonists. • The non-metabolite GPR91 ligands can be used as pharmacological tools and drug leads. • Novel compounds demonstrate GPR91 control of cytokine expression in M2 macrophages.

OBJECTIVE: Identification of patients with high-risk asymptomatic carotid plaques remains an elusive but essential step in stroke prevention. Inflammation is a key process in plaque destabilization and a prelude to clinical sequelae. There are currently no clinical imaging tools to assess the inflammatory activity within plaques. This study characterized inflammation in atherosclerosis using dual-targeted microparticles of iron oxide (DT-MPIO) as a magnetic resonance imaging (MRI) probe. METHODS: DT-MPIO were used to detect and characterize inflammatory markers, vascular cell adhesion molecule 1 (VCAM-1). and P-selectin on (1) tumor necrosis factor-α-treated cells by immunocytochemistry and (2) aortic root plaques of apolipoprotein-E deficient mice by in vivo MRI. Furthermore, apolipoprotein E-deficient mice with focal carotid plaques of different phenotypes were developed by means of periarterial cuff placement to allow in vivo molecular MRI using these probes. The association between biomarkers and the magnetic resonance signal in different contrast groups was assessed longitudinally in these models. RESULTS: Immunocytochemistry confirmed specificity and efficacy of DT-MPIO to VCAM-1 and P-selectin. Using this in vivo molecular MRI strategy, we demonstrated (1) the DT-MPIO-induced magnetic resonance signal tracked with VCAM-1 (r = 0.69; P = .014), P-selectin (r = 0.65; P = .022), and macrophage content (r = 0.59; P = .045) within aortic root plaques and (2) high-risk inflamed plaques were distinguished from noninflamed plaques in the murine carotid artery within a practical clinical imaging time frame. CONCLUSIONS: These molecular MRI probes constitute a novel imaging tool for in vivo characterization of plaque vulnerability and inflammatory activity in atherosclerosis. Further development and translation into the clinical arena will facilitate more accurate risk stratification in carotid atherosclerotic disease in the future.

Smooth muscle cells (SMC) contribute to the development and stability of atherosclerotic lesions. The molecular mechanisms that mediate their properties are incompletely defined. We employed proteomics and in vitro functional assays to identify the unique characteristics of intimal SMC isolated from human carotid endarterectomy specimens and medial SMC from thoracic aortas and carotids. We verified our findings in the Tampere Vascular Study. Human atheroma-derived SMC exhibit decreased expression of mitochondrial proteins ATP Synthase subunit-beta and Aldehyde dehydrogenase 2, and decreased mitochondrial activity when compared to control SMC. Moreover, a comparison between plaque-derived SMC isolated from patients with or without recent acute cerebrovascular symptoms uncovered an increase in Annexin A1, an endogenous anti-inflammatory protein, in the asymptomatic group. The deletion of Annexin A1 or the blockade of its signaling in SMC resulted in increased cytokine production at baseline and after stimulation with the pro-inflammatory cytokine Tumor Necrosis Factor α. In summary, our proteomics and biochemical analysis revealed mitochondrial damage in human plaque-derived SMC as well as a role of Annexin A1 in reducing the production of pro-inflammatory mediators in SMC.

Although dendritic cells (DCs) are the most potent antigen-presenting cells involved in numerous physiologic and pathologic processes, little is known about the signaling pathways that regulate DC activation and antigen-presenting function. Recently, we demonstrated that nuclear factor (NF)-κB activation is central to that process, as overexpression of IκBα blocks the allogeneic mixed lymphocyte reaction (MLR), an in vitro model of T-cell activation. In this study, we investigated the role of 2 putative NF-κB–inducing components, NF-κB–inducing kinase (NIK), and IκB kinase 2 (IKK2). Using an adenoviral gene transfer method to efficiently express dominant-negative (dn) forms of these molecules in monocyte-derived DCs, we found that IKK2dn but not NIKdn inhibited the allogeneic MLR. When DCs were fixed, this inhibitory effect of IKK2dn was lost, suggesting that IKK2 is involved in T-cell–derived signals that enhance DC antigen presentation during the allogeneic MLR period and does not have an effect on viability or differentiation state of DCs prior to coculture with T cells. One such signal is likely to be CD40 ligand (CD40L), as IKK2dn blocked CD40L but not lipopolysaccharide (LPS)–induced NF-κB activation, cytokine production, and up-regulation of costimulatory molecules and HLA-DR in DCs. In summary, our results demonstrate that IKK2 is essential for DC activation induced by CD40L or contact with allogeneic T cells, but not by LPS, whereas NIK is not required for any of these signals. In addition, our results support IKK2 as a potential therapeutic target for the down-regulation of unwanted immune responses that may occur during transplantation or autoimmunity.

Background: In atherosclerosis, proteoglycan accumulation results in increased lipoprotein retention. Results: ADAMTS-5 is reduced in aortas of apolipoprotein E-null mice. ADAMTS-5 deficiency impairs processing of vascular proteoglycans, and ADAMTS-5 activity affects proteoglycan-mediated lipoprotein retention. Conclusion: ADAMTS-5 regulates vascular proteoglycan catabolism and alters lipoprotein retention. Significance: This is the first study implicating ADAMTS-5 proteolytic activity in atherosclerosis., Atherosclerosis is initiated by the retention of lipoproteins on proteoglycans in the arterial intima. However, the mechanisms leading to proteoglycan accumulation and lipoprotein retention are poorly understood. In this study, we set out to investigate the role of ADAMTS-5 (a disintegrin and metalloprotease with thrombospondin motifs-5) in the vasculature. ADAMTS-5 was markedly reduced in atherosclerotic aortas of apolipoprotein E-null (apoE−/−) mice. The reduction of ADAMTS-5 was accompanied by accumulation of biglycan and versican, the major lipoprotein-binding proteoglycans, in atherosclerosis. ADAMTS-5 activity induced the release of ADAMTS-specific versican (DPEAAE441) and aggrecan (374ALGS) fragments as well as biglycan and link protein from the aortic wall. Fibroblast growth factor 2 (FGF-2) inhibited ADAMTS-5 expression in isolated aortic smooth muscle cells and blocked the spontaneous release of ADAMTS-generated versican and aggrecan fragments from aortic explants. In aortas of ADAMTS-5-deficient mice, DPEAAE441 versican neoepitopes were not detectable. Instead, biglycan levels were increased, highlighting the role of ADAMTS-5 in the catabolism of vascular proteoglycans. Importantly, ADAMTS-5 proteolytic activity reduced the LDL binding ability of biglycan and released LDL from human aortic lesions. This study provides the first evidence implicating ADAMTS-5 in the regulation of proteoglycan turnover and lipoprotein retention in atherosclerosis.

Purpose: Atherosclerosis occurs in vascular sites subjected to complex flow, causing oscillatory shear stress (OSS) or low shear stress (LSS). Macrophages can be skewed towards a pro-inflammatory phenotype (called M1) or a regulatory one (broadly named M2) and may determine atherosclerotic plaque outcome. The aim of this study is to establish the polarisation of macrophages in different plaque phenotypes and shear stress conditions. Methods: A perivascular shear stress modifying cast was tied around a carotid artery for 6 or 9 weeks, mimicking LSS and OSS in ApoE-/- mice fed a high fat diet (HFD) from 17 weeks of age. We examined the expression of the pan-macrophage marker CD68 and polarisation markers iNOS (M1), CD206 (M2) and HO-1 (Mox subset) in the aortic root at 12, 20, 28, 35 and 53 weeks of age, and cast-treated carotid artery by Immunohistochemistry and Confocal Immunolocalisation Results: In the aortic root, most CD68+ cells stained positively for HO-1, particularly at 28 weeks (36.3±1.2% of lesion area; p

Seminal research over the past 20 years has revealed atherosclerosis to be a chronic inflammatory process that shares features with traditional inflammatory diseases including rheumatoid arthritis. More recently, emphasis has been placed on the role of innate immunity in the development and progression of atherosclerosis. In particular, pattern recognition receptors, including Toll-like receptors (TLRs), have been the focus of much attention as modulators of atherogenesis. This review provides an update on the developments in this area of research in the past 2 years, with a specific focus on the current controversies and how these may affect the design of therapeutics. Specifically, we will address the recent evidence that TLRs elicit both protective and detrimental effects in atherosclerosis and the emerging observation that the outcome of TLR signaling is dependent on the agonist and responding cell type.

Atherosclerosis is a multi-factorial inflammatory disease and is the primary initiator of coronary artery and cerebrovascular disease. Initially believed to be exclusively lipid-driven, recent evidence demonstrates that inflammation is a significant driving force of the disease. Cellular components of innate immunity, for example monocytes and macrophages, play a predominant role in atherosclerosis. Toll-like receptors (TLRs) are the most characterised innate immune receptors and recent evidence demonstrates an important role in atherogenesis. Engagement of TLRs results in the transcription of pro-inflammatory cytokines, foam cell formation and activation of adaptive immunity. Recently they have also been implicated in protection from vascular disease. In this review, we detail the role of the innate immune system, specifically macrophages and TLR signalling, in atherosclerosis and acute cardiovascular complications, and thereby identify the potential of TLRs to act as therapeutic targets.

SummaryMolecular characterisation of vulnerable atherosclerosis is necessary for targeting functional imaging and plaque-stabilising therapeutics. Inflammation has been linked to atherogenesis and the development of high-risk plaques. We set to quantify cytokine, chemokine and matrix metalloproteinase (MMP) protein production in cells derived from carotid plaques to map the inflammatory milieu responsible for instability. Carotid endarterectomies from carefully characterised symptomatic (n=35) and asymptomatic (n=32) patients were enzymatically dissociated producing mixed cell type atheroma cell suspensions which were cultured for 24 hours. Supernatants were interrogated for 45 analytes using the Luminex 100 platform. Twenty-nine of the 45 analytes were reproducibly detectable in the majority of donors. The in vitro production of a specific network of mediators was found to be significantly higher in symptomatic than asymptomatic plaques, including: tumour necrosis factor α, interleukin (IL) 1β, IL-6, granulocytemacrophage colony-stimulating factor (GM-CSF), macrophage colonystimulating factor (M-CSF), CCL5, CCL20, CXCL9, matrix metalloproteinase (MMP)-3 and MMP-9. Ingenuity pathway analysis of differentially expressed analytes between symptomatic and asymptomatic patients identified a number of key biological pathways (p > 10–25). In conclusion, the carotid artery plaque culprit of ischaemic neurological symptoms is characterised by an inflammatory milieu favouring inflammatory cell recruitment and pro-inflammatory macrophage polarisation.Supplementary Material to this article is available online at www.thrombosis-online.com.

Cognitive decline following surgery in older individuals is a major clinical problem of uncertain mechanism; a similar cognitive decline also follows severe infection, chemotherapy, or trauma and is currently without effective therapy. A variety of mechanisms have been proposed, and exploring the role of inflammation, we recently reported the role of IL-1β in the hippocampus after surgery in mice with postoperative cognitive dysfunction. Here, we show that TNF-α is upstream of IL-1 and provokes its production in the brain. Peripheral blockade of TNF-α is able to limit the release of IL-1 and prevent neuroinflammation and cognitive decline in a mouse model of surgery-induced cognitive decline. TNF-α appears to synergize with MyD88 , the IL-1/TLR superfamily common signaling pathway, to sustain postoperative cognitive decline. Taken together, our results suggest a unique therapeutic potential for preemptive treatment with anti-TNF antibody to prevent surgery-induced cognitive decline.

Inflammation drives atherosclerosis. Both immune and resident vascular cell types are involved in the development of atherosclerotic lesions. The phenotype and function of these cells are key in determining the development of lesions. Toll-like receptors are the most characterised innate immune receptors and are responsible for the recognition of exogenous conserved motifs on pathogens, and, potentially, some endogenous molecules. Both endogenous and exogenous TLR agonists may be present in atherosclerotic plaques. Engagement of toll-like receptors on immune and resident vascular cells can affect atherogenesis as signalling downstream of these receptors can elicit proinflammatory cytokine release, lipid uptake, and foam cell formation and activate cells of the adaptive immune system. In this paper, we will describe the expression of TLRs on immune and resident vascular cells, highlight the TLR ligands that may act through TLRs on these cells, and discuss the consequences of TLR activation in atherosclerosis.

Several studies support C-reactive protein (CRP) as a systemic cardiovascular risk factor. The recent detection of CRP in arterial intima suggests a dual activity in atherosclerosis as a circulating and tissue mediator on vascular and immune cells. In the present paper, we focused on the inflammatory effects of CRP on human monocytes, which were isolated by Ficoll-Percoll gradients and cultured in adherence to polystyrene, endothelial cell monolayer, or in suspension. Chemokine levels, adhesion molecule, and chemokine receptor expression were detected by ELISA, flow cytometry, and real-time RT-PCR. Migration assays were performed in a Boyden chamber. Stimulation with CRP induced release of CCL2, CCL3, and CCL4 in adherent monocytes through the binding to CD32a, CD32b, and CD64, whereas no effect was observed in suspension culture. This was associated with CRP-induced up-regulation of adhesion molecules membrane-activated complex 1 (Mac-1) and ICAM-1 on adherent monocytes. Blockade of Mac-1/ICAM-1 interaction inhibited the CRP-induced chemokine secretion. In addition, CRP reduced mRNA and surface expression of corresponding chemokine receptors CCR1, CCR2, and CCR5 in adherent monocytes. This effect was a result of chemokine secretion, as coincubation with neutralizing anti-CCL2, anti-CCL3, and anti-CCL4 antibodies reversed the effect of CRP. Accordingly, a reduced migration of CRP-treated monocytes to CCL2 and CCL3 was observed. In conclusion, our data suggest an in vitro model to study CRP activities in adherent and suspension human monocytes. CRP-mediated induction of adhesion molecules and a decrease of chemokine receptors on adherent monocytes might contribute to the retention of monocytes within atherosclerotic lesions and recruitment of other circulating cells.

Identification of subjects at increased risk for cardiovascular events plays a central role in the worldwide efforts to improve prevention, prediction, diagnosis, and prognosis of cardiovascular disease and to decrease the related costs. Despite their high predictive value on population level, traditional risk factors fail to fully predict individual risk. This position paper provides a summary of current vascular biomarkers other than the traditional risk factors with a special focus on the emerging -omics technologies. The definition of biomarkers and the identification and use of classical biomarkers are introduced, and we discuss the limitations of current biomarkers such as high sensitivity C-reactive protein (hsCRP) or N-terminal pro-brain natriuretic peptide (NT-proBNP). This is complemented by circulating plasma biomarkers, including high-density lipoprotein (HDL), and the conceptual shift from HDL cholesterol levels to HDL composition/function for cardiovascular risk assessment. Novel sources for plasma-derived markers include microparticles, microvesicles, and exosomes and their use for current omics-based analytics. Measurement of circulating micro-RNAs, short RNA sequences regulating gene expression, has attracted major interest in the search for novel biomarkers. Also, mass spectrometry and nuclear magnetic resonance spectroscopy have become key complementary technologies in the search for new biomarkers, such as proteomic searches or identification and quantification of small metabolites including lipids (metabolomics and lipidomics). In particular, pro-inflammatory lipid metabolites have gained much interest in the cardiovascular field. Our consensus statement concludes on leads and needs in biomarker research for the near future to improve individual cardiovascular risk prediction.

SummaryAuto-antibodies to apolipoprotein A-1 (anti-apoA-1 IgG) were shown to promote inflammation and atherogenesis, possibly through innate immune receptors signalling. Here, we aimed at investigating the role of Toll-like receptors (TLR) 2 and 4 on anti-apoA-1 IgG-induced athero-sclerotic plaque vulnerability, myocardial necrosis and mortality in mice. Adult male apolipoprotein E knockout (ApoE)-/- (n=72), TLR2-/-ApoE-/- (n=36) and TLR4-/-Apo-/- (n=28) mice were intravenously injected with 50 µg/mouse of endotoxin-free polyclonal anti-apoA-1 IgG or control isotype IgG (CTL IgG) every two weeks for 16 weeks. Atherosclerotic plaque size and vulnerability were assessed by histology. Myocardial ischaemia and necrosis, respectively, were determined by electrocardiographic (ECG) changes assessed by telemetry and serum troponin I (cTnI) measurements. Impact on survival was assessed by Kaplan-Meier analyses. In ApoE-/- mice, anti-apoA-1 IgG passive immunisation enhanced histological features of athero-sclerotic plaque vulnerability (increase in neutrophil and MMP-9 and reduction in collagen content), induced a substantial cTnI elevation (p=0.001), and increased mortality rate by 23 % (LogRank, p=0.04) when compared to CTL IgG. On a subgroup of ApoE-/- mice equipped with telemetry (n=4), a significant ST-segment depression was noted in anti-apoA-1 IgG-treated mice when compared to CTL IgG recipients (p< 0.001), and an acute ST-segment elevation myocardial infarction preceding mouse death was observed in one case. The deleterious effects of anti-apoA-1 IgG on atherosclerotic plaque vulnerability, myocardial necrosis and death were partially reversed in TLR2-/-ApoE-/- and TLR4-/-ApoE-/- backgrounds. In conclusion, anti-apoA-1 auto-antibodies seem to be active mediators of atherosclerotic plaque vulnerability, myocardial necrosis, and mortality in mice through TLR2- and TLR4-mediated pathways.

Nuclear factor kappa B (NF-kappa B) activation has been observed in human atherosclerotic plaques and is enhanced in unstable coronary plaques, but whether such activation has a protective or pathophysiological role remains to be determined. We addressed this question by developing a short-term culture system of cells isolated from human atherosclerotic tissue, allowing efficient gene transfer to directly investigate signaling pathways in human atherosclerosis. We found that NF-kappa B is activated in these cells and that this activity involves p65, p50, and c-Rel but not p52 or RelB. This NF-kappa B activation can be blocked by overexpression of I kappa B alpha or dominant-negative I kappa B kinase (IKK)-2 but not dominant-negative IKK-1 or NF-kappa B-inducing kinase, resulting in selective inhibition of inflammatory cytokines (tumor necrosis factor alpha, IL-6, and IL-8), tissue factor, and matrix metalloproteinases without affecting the antiinflammatory cytokine IL-10 or tissue inhibitor of matrix metalloproteinases. Our results demonstrate that the canonical pathway of NF-kappa B activation that involves p65, p50, c-Rel, and IKK-2 is activated in human atherosclerosis and results in selective up-regulation of major proinflammatory and prothrombotic mediators of the disease.

Cardiovascular diseases are the leading cause of morbidity and mortality in Western countries. Atherosclerosis, the background for many cardiovascular diseases, is characterized by the accumulation of lipid and fibrotic entities in large arteries and bears many similarities with chronic inflammatory diseases such as rheumatoid arthritis. Common features include extravasation of blood-derived leukocytes, as well as production of cytokines, chemokines and matrix-degrading enzymes. There are also many shared signaling pathways, including activation of the nuclear factor kappaB (NFkappaB) cascade. In the context of atherosclerosis, there are a range of candidate stimuli which can activate NFkappaB, including traditional risk factors, infectious agents, cytokines and cell-cell contact. Many inflammatory genes relevant to the pathogenesis of atherosclerosis are regulated by NFkappaB, the activated form of which is present in atherosclerotic plaques. Thus, it is essential to understand the role of this important signaling cascade in atherosclerosis, in a quest for more specific therapeutic targets.

Vascular endothelial growth factor (VEGF) is the most endothelial cell-specific angiogenic factor characterised to date, and it is produced by a variety of cell types. In macrophages, VEGF has been shown to be upregulated by the inflammatory mediator lipopolysaccharide (LPS) and by engagement of CD40 by CD40 ligand (CD40L). Because LPS and CD40L activate nuclear factor-kappaB (NF-kappaB) in monocytes, we investigated in this study whether VEGF production in macrophages, when stimulated with either LPS or CD40L, is NF-kappaB-dependent. We used adenoviral constructs over-expressing either IkappaBalpha (AdvIkappaBalpha), the endogenous inhibitor of NF-kappaB, or a kinase-defective mutant of IKK-2 (AdvIKK-2dn), an upstream activator of IkappaBalpha, to infect normal human monocyte-derived macrophages. We observed that LPS-induced production of VEGF in human macrophages was almost completely inhibited (>90%) following adenoviral transfer of IkappaBalpha. In addition, we observed significant inhibition of the CD40L-induced VEGF production in macrophages following infection with AdvIkappaBalpha. Expression of IKK-2dn in macrophages decreased VEGF production in response to LPS or CD40L by approximately 50%, suggesting that in addition to IKK-2, other kinases might be involved in NF-kappaB activation. These results show for the first time that VEGF production in human macrophages is NF-kappaB dependent. NF-kappaB regulates many of the genes involved in immune and inflammatory responses, and our study adds the angiogenic cytokine VEGF to the list of NF-kappaB-dependent cytokines.

Background— Patients undergoing revascularization procedures for peripheral vascular disease (PVD) have a greatly increased risk for coronary artery disease (CAD) that is predicted only partly by clinical data and cardiovascular risk factors. We investigated whether the prognostic assessment in PVD patients could be improved by preoperative measurements of C-reactive protein (CRP). Methods and Results— We assessed clinical and risk factors profiles, Eagle clinical scores, and preoperative CRP serum levels in 51 patients with PVD at Fontaine-Leriche stages II to IV without severe rest ventricular dysfunction or ischemia. During 24 months of follow-up, 17 patients (34%) had fatal (11) or nonfatal (6) myocardial infarction (MI). With univariate logistic regression analysis, only previous history of CAD, Eagle score, and CRP were independently related to MI. At multivariate logistic regression analysis, only CRP values in the upper tertile (P Conclusions— The high incidence of MI in patients with PVD severe enough to require revascularization is strongly predicted by preprocedural measurements of serum CRP, independent of previous CAD, Eagle score index, and traditional cardiovascular risk factors. These patients may benefit from therapy modulating the inflammatory response.

Thin-cap fibroatheromas (TCFAs) or vulnerable atherosclerotic plaques are considered a high-risk phenotype for acute cardiovascular events. TCFAs are identified by a thin rupture-prone fibrous cap, a large necrotic core, and a high content of leucocytes. Atherogenesis is dependent upon complex patterns of blood flow. Slow-flowing blood imposing low shear stress on the arterial wall up-regulates inflammatory signalling in endothelial cells and leucocytes, and modulates microRNAs to promote inflammation and monocyte recruitment. Hence, low shear stress is believed to promote conditions conducive to vulnerable plaque development. In this review, we explore how biomechanical factors modulate macrophage phenotype and plaque stability.

Background Takotsubo cardiomyopathy, described as transient regional contractile abnormalities limited to the apical and mid-segments of the left ventricle (LV), has also been reported to involve basal and/or mid LV segments (inverted Takotsubo); fewer reports, however, have addressed right ventricular (RV) dysfunction. Aim To assess the distribution of regional abnormalities and RV involvement in Takotsubo cardiomyopathy and compare it to the literature. Methods and Results We evaluated 23 patients with both classical and inverted presentations (19 female, aged 64 ± 19 years), including 2 recurrences, totaling 25 episodes. Classical Takotsubo was observed in 15 patients, while 10 had the inverted form. LV ejection fraction (EF) was lower for classical compared to inverted presentation (30 ± 7 vs. 45 ± 4%, P

Introduction The mechanisms regulating aberrant vascular remodelling in pulmonary arterial hypertension (PAH) are poorly understood and treatments targeted at halting or reversing this process are lacking. Toll-like receptor 3 (TLR3) is a viral sensor and more recently has been established as a sensor of endogenous damage signals, responding to mRNA released by damaged cells. TLR3 signalling induces pro- and anti-inflammatory cytokine production and regulates inflammation-associated apoptosis and tyrosine kinase signalling. In a model of systemic arterial injury, TLR3 signalling was shown to modulate neointimal remodelling in a protective manner. TLR3 is also expressed in pulmonary artery smooth muscle (PASMCs) and endothelial cells (PAECs). We therefore hypothesised that TLR3 would play roles in pulmonary vascular remodelling. Methods TLR3-deficient (TLR3−/−) or wild-type C57BL/6 (WT) mice were exposed to hypoxia (10% Oxygen) and given Sugen 5416 (weekly 20 mg/kg subcutaneous injections) or maintained in normoxic conditions for 3 weeks. Haemodynamic (cardiac catheterisation and echocardiography) and histological assessments were performed after 3 weeks. Human PASMCs were serum-starved before stimulation with PDGF or poly(I:C) and proliferation was assessed after 72 hours. Results TLR3−/− mice developed a markedly exaggerated phenotype of PAH in response to Sugen/Hypoxia with increased right ventricular systolic pressures (WT 51.6 mmHg ± 4.6 vs. TLR3−/− 73.0 mmHg ± 6.8; p Conclusions We have shown that mice deficient in TLR3 develop a markedly exaggerated haemodynamic pulmonary hypertension phenotype and human PASMC proliferation is suppressed by the TLR3 ligand, poly(I:C). Together these data imply that TLR3 signalling in disease mediates a protective phenotype in keeping with that observed in systemic vascular remodelling, and identify a protective pathway potentially amenable to therapeutic targeting.

464 STAT4 deficiency exacerbates atherosclerosis by promoting mobilization of myeloid cells, polarization of M1 macrophages and formation of foam cells {#article-title-2} Background: Atherosclerosis (AS) is a chronic inflammatory disease of large and medium size vessels. Signal transducer and activator of transcription 4 (STAT4) has been reported to regulated the proliferation and differentiation of myeloid cells. However, the role of STAT4 in atherosclerotic progression is not well defined. Methods: We constructed APOE/STAT4 double knock out (DKO) mice via hybridization of ApoE-/- and STAT4-/- mice. 10 ApoE-/- mice (control) and 10 DKO mice were challenged with high-fat diet for 12 weeks. The extent of AS was determined by oil-red staining and HE staining. Plasma cholesterol, triglyceride and cytokines were assessed by ELISA. Changes in subsets of immune cells were evaluated by flow cytometry. Microarray analysis was applied to detect gene expressions while Western blot was used to assess protein levels. Results: Genetic deletion of STAT4 significantly exacerbated AS as evidenced by markedly increased oil-red-positive lipid-rich lesion in DKO mice accompanied by reduction of collagen fiber and increase of necrotic core lesion in plaques. Higher level of TC, TG and LDL-C in the serum and more abdominal fat were detected in DKO mice. Increased percentage of CD11b+Gr-1+ myeloid cells and Ly6Chigh M1 macrophage in peripheral blood, bone marrow and spleen of DKO mice suggested that STAT4 signal may play a critical role in regulating the proliferation and mobilization of myeloid cells and polarization of macrophages. To further explore the impact of STAT4 deficiency in myeloid cells, we isolated CD11b+ myeloid cells from bone marrows of ApoE-/- and DKO mice and incubated them with GM-CSF (60ng/ml) plus ox-LDL (60ug/ml). Enhanced differentiation of CD11b+Ly6Chigh macrophage and increase formation of foam cells were detected in DKO group. IFN-γ in the supernatant increased while IL-10 decreased in DKO group, indicating enhanced polarization of M1 macrophage from CD11b+ cells of DKO mice. Meanwhile, microarray data demonstrated that STAT4 KO increased expression levels of M1-related genes such as inducible nitric oxide synthase (iNos). Mechanistically, STAT4 deficiency significantly promoted the formation of foam cells by inhibiting of phosphatidylinositol-3 kinase/ serine-threonine kinases (PI3K/AKT) signal and consequently up-regulating of the expression of acyl coenzyme A: cholesterol acyltransferase-1 (ACAT-1), an enzyme that esterifies cholesterol and promotes its storage in macrophages. Conclusions: Our studies identified STAT4 as a regulator of the proliferation and differentiation of myeloid cells and atherogenesis. PI3K/AKT/ACAT-1 signaling was the molecular mechanisms of STAT4 functioning in the process. These findings points towards the development of STAT4 as a novel pharmacotherapeutic target for the treatment of atherosclerotic diseases and ApoE/STAT4 DKO mice with hyperlipidemia and hyper-inflammation as a novel mouse model more susceptible to atherosclerosis for future study. # 465 Effects of DPP4 inhibition on cardiac regeneration and macrophage balance in a mouse model of HHT-1 {#article-title-3} Background: Hereditary Hemorrhagic Telangiectasia type 1 (HHT-1) is a genetic dominant vascular disorder caused by haploinsufficiency of the TGFβ co-receptor Endoglin. Although the pathology of HHT-1 suggests that mainly vascular endothelial cells are involved, we have previously shown dysfunctional homing of mononuclear cells (MNC) towards the infarcted myocardium (MI). This is most likely due to enhanced expression of dipeptidyl peptidase-4 (DPP4). DPP4 inactivates SDF-1α, thereby inhibiting recruitment of CXCR4 expressing cells. Purpose: Our aim is to increase homing of the HHT-1 MNC and improve cardiac recovery and function in HHT-1 mice following MI, by inhibition of DPP4 activity. Methods: MI was induced in wildtype (WT) and endoglin heterozygous (eng+/-; as a model of HHT-1) mice by ligation of the left anterior descending (LAD) coronary artery, followed by 5 days of daily treatment with the DPP4 inhibitor Diprotin A (2.5mg/kg/day). The infarcted hearts were assessed at day 4 and at day 14 post MI. Results: DPP4 inhibition restored the number of MNC present in the infarcted hearts and significantly reduced infarct size (eng+/- 46.60±9.33% vs. eng+/- treated 27.02±3.04%, P=0.03), as measured by myocardial collagen formation. Analysis of cardiac function using ultrasound demonstrated that treatment of WT mice improved ejection fraction, however showed a slightly deteriorating effect in the eng+/- animals. Investigating the infarct borderzone, the number of capillaries increased (eng+/- 61.63±1.43 vs. eng+/- treated 74.30±1.74, P=0.001) while the number of arteries decreased (eng+/- 11.88±0.63 vs. eng+/- treated 6.38±0.97, P=0.003), suggesting that angiogenesis is upregulated, though the maturation of the new vessels is still impaired. Furthermore at day 4 post-MI, during the peak of inflammatory cell influx, Eng+/- mice show a significant decrease (WT 29.88±1.52 vs. eng+/- 12.34±1.64, P

To the Editor: We read with interest the article by Dumitriu et al1 that characterized the alternative costimulatory pathways of CD4+CD28null T cells, a terminally differentiated effector T-cell population, in patients with acute coronary syndromes (ACS). In this study, a significant increase in costimulatory receptors (OX40/CD134 and 4–1IBB/CD137) was described in CD4+CD28null T cells from patients with ACS after stimulation with an anti-CD3 antibody (emulating T-cell antigen recognition). Furthermore, blocking of these costimulatory receptors was associated with reduced interferon-γ, tumor necrosis factor-α, and perforin release in CD4+CD28null T cells, thus affecting their proinflammatory and cytotoxic functions. Overall, these findings suggest a differential sensitivity to costimulation in activated CD4+CD28null T cells in the context of ACS. During ACS we recently observed that in addition to CD28 activation, the classical immunologic synapse mediated by antigen-T-cell receptor (TCR) engagement is perturbed also.2 Of the TCR subunits, the zeta (ζ) chain (CD247 or CD3ζ) has a …

Inflammation is an ancient and evolutionarily conserved process, which aims to clear the offending stimulus, and leads to resolution and healing. If excessive, inflammation is at the core of the pathogenesis of a huge number of human diseases including cancer, Alzheimer’s and atherothrombotic cardiovascular disease (CVD) [1].

The critical role of Toll-like receptors (TLRs) in mammalian host defense has been extensively explored in recent years. The capacity of about 10 TLRs to recognize conserved patterns on many bacterial and viral pathogens is remarkable. With so few receptors, cross-reactivity with self-tissue components often occurs. Previous studies have frequently assigned detrimental roles to TLRs, in particular to TLR2 and TLR4, in immune and cardiovascular disease. Using human and murine systems, we have investigated the consequence of TLR3 signaling in vascular disease. We compared the responses of human atheroma-derived smooth muscle cells (AthSMC) and control aortic smooth muscle cells (AoSMC) to various TLR ligands. AthSMC exhibited a specific increase in TLR3 expression and TLR3-dependent functional responses. Intriguingly, exposure to dsRNA in vitro and in vivo induced increased expression of both pro- and anti-inflammatory genes in vascular cells and tissues. Therefore, we sought to assess the contribution of TLR3 signaling in vivo in mechanical and hypercholesterolemia-induced arterial injury. Surprisingly, neointima formation in a perivascular collar-induced injury model was reduced by the systemic administration of the dsRNA analog Poly(I:C) in a TLR3-dependent manner. Furthermore, genetic deletion of TLR3 dramatically enhanced the development of elastic lamina damage after collar-induced injury. Accordingly, deficiency of TLR3 accelerated the onset of atherosclerosis in hypercholesterolemic ApoE −/− mice. Collectively, our data describe a protective role for TLR signaling in the vessel wall.

More than ten years ago, the “danger theory” challenged conservative immunology. At that time, the consensus was that the immune system is activated by antigens recognized as nonself. However, the self-nonself theory gave no explanation why, for example, a fetus with obvious foreign antigens does not lead to maternal immune activation whereas transplanted organs do. In an attempt to resolve these apparent paradoxes, the danger theory postulated that the immune system is triggered by “danger signals” released upon tissue injury and stress alerting the immune system that there is risk to the host [1]. The “danger theory” is supported by the growing number of endogenous ligands that can activate innate immune receptors such as toll-like receptors, RIG-I-like receptors, NOD-like receptors, and the inflammasome. However, it poses the challenge of identifying such signals and the mechanisms of their generation rigorously. Danger signals or danger associated molecular patterns (DAMPs) identified so far include factors like high-mobility group protein B1, mitochondrial DNA, heat shock protein (HSP), interleukin-1α, adenosine triphosphate, reactive oxygen intermediates, and uric acid [2]. A common feature of cardiovascular diseases, like myocardial infarction, heart failure, atherosclerosis, and so forth, is a robust inflammatory response. The reason for an immunologic reaction in mostly nonimmune diseases is not very well defined. However, the danger theory offers a good explanation: tissue damage, for example, in myocardial infarction, could lead to the release of danger signals and thereby cause an immune response. Indeed, in the current issue, several aspects of this process are highlighted: after a general introduction into DAMPs in the cardiovascular system [3], M. Ashri et al. discuss the theory of cardiotrophin-1 as a secondary DAMP in obesity “Update on the pathophysiological activities of the cardiac molecule cardiotrophin-1 in obesity,” whereas A. Schiopu et al. review S100A8 and S100A9, members of the calgranulin family, as potential DAMP in cardiovascular disease “S100A8 and S100A9: DAMPs at the crossroads between innate immunity, traditional risk factors, and cardiovascular disease.” F. van den Akker et al. highlight that danger signals might influence the phenotype of mesenchymal stem cells and secondarily outcome after myocardial infarction “Mesenchymal stem cell therapy for cardiac inflammation: immunomodulatory properties and the influence of toll-like receptors.” A few original articles deal with the role of oxidative stress as DAMP “Berberine protects against palmitate-induced endothelial dysfunction: involvements of upregulation of AMPK and eNOS and downregulation of NOX4” and “Natural antioxidant-isoliquiritigenin ameliorates contractile dysfunction of hypoxic cardiomyocytes via AMPK signaling pathway” and with actin or chitinase 3-like 1 as a trigger of immune activation in patients with advanced atherosclerotic plaques “Actin is a target of T-cell reactivity in patients with advanced carotid atherosclerotic plaques” and “Increased expression of chitinase 3-like 1 in aorta of patients with atherosclerosis and suppression of atherosclerosis in apolipoprotein E-knockout mice by chitinase 3-like 1 gene silencing” or complement factor C3 as marker of danger signal activation in patients with heart failure “Complement c3c as a biomarker in heart failure.” All manuscripts underline the importance of danger signals in cardiovascular disease in basic as well as clinical science. Clinical Implications. DAMPs may have great diagnostic, prognostic, and therapeutic potential. In theory, DAMPs may indicate active tissue injury. Since DAMP levels are related to the extent of injury, they may have prognostic implications. When DAMPs are the most important trigger for immune activation, pharmaceutical interference should allow tailoring an immune response. However, it has to be beard in mind that the activation of the immune system in the context of tissue injury makes evolutionary sense and is not necessarily negative. For example, after myocardial infarction depletion of macrophages causes the scar not to be cleared of cell debris and left ventricular thrombi to develop leading to adverse outcome in animals and potentially also in humans (Monocytes/macrophages prevent healing defects and left ventricular thrombus formation after myocardial infarction). Thus, an initial immune activation is necessary for a coordinated pathophysiologic and beneficial response to injury. However, a chronic immune activation might be detrimental, as has been shown by several groups. Therefore, timing will be crucial when interfering with DAMPs. In conclusion, a better understanding of DAMPs in cardiovascular disease might give us dual benefit: it will help us to identify and treat patients at the very core of the pathophysiological process. However, markers and potential drug targets warrant further research. Stefan Frantz Claudia Monaco Fatih Arslan

Inflammation drives atherosclerosis. Toll-like receptor-2 and -4 are so far the strongest candidates for initiating innate immune signalling in atherosclerosis. Their signalling has implications for lesion development, foam cell formation, inflammation, matrix degradation and ischemia-reperfusion. The repertoire of TLR agonists is expanding. They collectively represent a conglomerate of structurally diverse molecular patterns requiring a high level of versatility in their sensing. Such versatility is achieved through cooperation of TLR heterodimers, co-receptors, and binding proteins. Several endogenous and exogenous molecular patterns engaging TLRs are associated with atherosclerosis development and complications. In this review, I describe how such molecular patterns are sensed, how they signal and what the consequences in the atherosclerotic plaque might be. The effect of TLR antagonising compounds in human and murine atherosclerosis is also addressed. © 2012 Bentham Science Publishers.

BACKGROUND: Interleukin-6 (IL-6) and tissue factor (TF) are elevated after myocardial ischemia during dobutamine stress echo (DSE). We examined the incremental prognostic value of IL-6 or TF measured during DSE over echocardiographic and clinical factors in patients with chronic coronary artery disease (CAD). METHODS: We studied 106 patients with angiographically documented CAD. IL-6 and TF were measured at rest, peak, and during recovery. A wall motion score index was calculated. RESULTS: Fifty-seven (54%) patients had ischemia at DSE. During follow-up (63.7 +/- 20 months), 36 patients (33%) had an adverse event (12 cardiac deaths, 24 acute coronary events). Patients with events had a higher peak IL-6 (P = .02) but similar rest and recovery IL-6 than those without. Patients with peak IL-6 > or =3.14 pg/mL (upper tertile) had a hazard ratio of 2.7 (95% CI 1.44-5.37) (P < .01 for an adverse event). The addition of peak wall motion score index in a multivariable model including risk factors, ejection fraction, revascularization, and multivessel disease increased the model's c statistic from 0.66 to 0.70 (P = .04). The addition of peak IL-6 further increased the model's c statistic to 0.75 (P = .04). Tissue factor was not related with cardiac events. CONCLUSIONS: Interleuikin-6 levels measured during the peak phase of DSE incrementally contribute to risk stratification in patients with chronic CAD.

Objective— The T-cell receptor zeta (TCRζ)-chain is a master sensor and regulator of lymphocyte responses. Loss of TCRζ-chain expression has been documented during infectious and inflammatory diseases and defines a population of effector T cells (TCRζ dim T cells) that migrate to inflamed tissues. We assessed the expression and functional correlates of circulating TCRζ dim T cells in coronary artery disease. Methods and Results— We examined the expression of TCRζ-chain by flow cytometry in 140 subjects. Increased peripheral blood CD4 + TCRζ dim T cells were found in patients with acute coronary syndromes (ACS, n=66; median 5.3%, interquartile 2.6 to 9.1% of total CD4 + T cells; P dim cells were also more represented within CD8 + T cell, NK, and CD4 + CD28 null T cell subsets in ACS compared to CSA and controls. Finally, CD4 + and CD8 + TCRζ dim T cells isolated from ACS displayed an enhanced transendothelial migratory capacity. Conclusions— TCRζ dim T cells, an effector T-cell subset with transendothelial migratory ability, are increased in ACS, and may be implicated in coronary instability.

TLR3 recognizes double-stranded RNA, a product associated with viral infections. Many details of TLR3-induced mechanisms have emerged from gene-targeted mice or inhibition studies in transformed cell lines. However, the pathways activated in human immune cells or cells from disease tissue are less well understood. We have investigated TLR3-induced mechanisms of human primary cells of the innate immune system, including dendritic cells (DCs), macrophages (MØs), endothelial cells (ECs), and synovial fibroblasts isolated from rheumatoid arthritis joint tissue (RA-SFs). Here, we report that while these cells all express TLR3, they differ substantially in their response to TLR3 stimulation. The key antiviral response chemokine IP-10 was produced by all cell types, while DCs and MØs failed to produce the proinflammatory cytokines TNFα and IL-6. Unexpectedly, TNFα was found secreted by TLR3-stimulated RA-SF. Furthermore, TLR3 stimulation did not activate NFκB, MAPKs, or IRF-3 in DCs and MØs, but was able to do so in ECs and RA-SF. These findings were specific for human cells, thereby revealing a complexity not previously expected. This is the first report of such cell type– and species-specific response for any TLR stimulation and helps to explain important difficulties in correlating murine models of inflammatory diseases and human inflammation.

The T-cell receptor ζ (TCRζ) chain is a master sensor and regulator of lymphocyte responses. Loss of TCRζ expression has been documented in infectious, inflammatory, and malignant diseases, suggesting that it may serve to limit T-cell reactivity and effector responses at sites of tissue damage. These observations prompted us to explore the relationship between TCRζ expression and effector function in T cells. We report here that TCRζdim lymphocytes are enriched for antigen-experienced cells refractory to TCR-induced proliferation. Compared to their TCRζbright counterparts, TCRζdim cells share characteristics of differentiated effector T cells but use accessory pathways for transducing signals for inflammatory cytokine gene expression and cell contact-dependent pathways to activate monocytes. TCRζdim T cells accumulate in inflamed tissues in vivo and have intrinsic migratory activity in vitro. Whilst blocking leukocyte trafficking with anti-TNF therapy in vivo is associated with the accumulation of TCRζdim T cells in peripheral blood, this T-cell subset retains the capacity to migrate in vitro. Taken together, the functional properties of TCRζdim T cells make them promising cellular targets for the treatment of chronic inflammatory disease.

Reference EPFL-CONF-212220View record in Web of Science Record created on 2015-09-28, modified on 2017-05-25

In the last decade, the understanding of the molecular mechanisms of regulation of the inflammatory process in chronic inflammatory diseases has moved remarkably forward. Recent evidence in various fields has consistently indicated that T-cells play a key role in initiating and perpetuating inflammation, not only via the production of soluble mediators but also via cell/cell contact interactions with a variety of cell types through membrane receptors and their ligands. Signalling through CD40 and CD40 ligand is a versatile pathway that is potently involved in all these processes. In this article, we review how T-cells become activated by dendritic cells or inflammatory cytokines, and how these T-cells activate, in turn, monocytes/macrophages, endothelial cells, smooth muscle cells and fibroblasts to produce pro-inflammatory cytokines (tumour necrosis factor alpha, interleukin-6), chemokines (interleukin-8, monocyte chemotactic protein-1), tissue factor, the main initiator of the coagulation cascade in vivo, and finally matrix metalloproteinases, responsible for tissue destruction. Moreover, we discuss how CD40 ligand at inflammatory sites stimulates fibroblasts and tissue monocyte/macrophage production of VEGF, leading to angiogenesis, which promotes and maintains the chronic inflammatory process. This cascade of events is discussed in the context of disease initiation/progression, with particular reference to atherosclerosis and rheumatoid arthritis, and to potential novel therapeutic targets for their treatment.

How lipopolysaccharide (LPS) signals through toll-like receptors (TLRs) to induce nuclear factor (NF)–κB and inflammatory cytokines in sepsis remains unclear. Major candidates for that process are myeloid differentiation protein 88 (MyD88) and MyD88 adaptor-like/TIR domain-containing adaptor protein (Mal/TIRAP) but their role needs to be further defined. Here, we have examined the role of MyD88 and Mal/TIRAP in primary human cells of nonmyeloid and myeloid origin as physiologically relevant systems. We found that MyD88 and Mal/TIRAP are essential for LPS-induced IκBα phosphorylation, NF-κB activation, and interleukin 6 (IL-6) or IL-8 production in fibroblasts and endothelial cells in a pathway that also requires IKK2. In contrast, in macrophages neither MyD88, Mal/TIRAP, nor IκB kinase 2 (IKK2) are required for NF-κB activation or tumor necrosis factor α (TNFα), IL-6, or IL-8 production, although Mal/TIRAP is still involved in the production of interferon β (IFNβ). Differential usage of TLRs may account for that, as in macrophages but not fibroblasts or endothelial cells, TLR4 is expressed in high levels at the cell surface, and neutralization of TLR4 but not TLR2 blocks LPS signaling. These observations demonstrate for the first time the existence of 2 distinct pathways of LPS-induced NF-κB activation and cytokine production in human myeloid and nonmyeloid cells defined by selective utilization of TLR4, MyD88, Mal/TIRAP, and IKK2, and reveal a layer of complexity not previously expected.

OBJECTIVE: To investigate the potential role of IkappaB kinase 1 (IKK-1) and IKK-2 in the regulation of nuclear factor kappaB (NF-kappaB) activation and the expression of tumor necrosis factor alpha (TNFalpha), as well as interleukin-1beta (IL-1beta), IL-6, IL-8, vascular endothelial growth factor (VEGF), and matrix metalloproteinases (MMPs), in rheumatoid arthritis (RA). METHODS: Recombinant adenoviruses expressing beta-galactosidase, dominant-negative IKK-1 and IKK-2, or IkappaBalpha were used to infect ex vivo RA synovial membrane cultures and synovial fibroblasts obtained from patients with RA undergoing joint replacement surgery, or human dermal fibroblasts, human umbilical vein endothelial cells (HUVECs), and monocyte-derived macrophages from healthy volunteers. Then, their effect on the spontaneous or stimulus-induced release of inflammatory cytokines, VEGF, and MMPs from RA synovial membrane cells was examined. RESULTS: IKK-2 was not required for lipopolysaccharide (LPS)-induced NF-kappaB activation or TNFalpha, IL-6, or IL-8 production in macrophages, but was essential for this process in response to CD40 ligand, TNFalpha, and IL-1. In synovial fibroblasts, dermal fibroblasts, and HUVECs, IKK-2 was also required for LPS-induced NF-kappaB activation and IL-6 or IL-8 production. In RA synovial membrane cells, IKK-2 inhibition had no effect on spontaneous TNFalpha production but significantly reduced IL-1beta, IL-6, IL-8, VEGF, and MMPs 1, 2, 3, and 13. CONCLUSION: Our study demonstrates that IKK-2 is not essential for TNFalpha production in RA. However, because IKK-2 regulates the expression of other inflammatory cytokines (IL-1beta, IL-6, and IL-8), VEGF, and MMPs 1, 2, 3, and 13, which are involved in the inflammatory, angiogenic, and destructive processes in the RA joint, it may still be a good therapeutic target.

Adhesion of leukocytes to the vascular endothelium is an early event in inflammation. Since cell-cell signaling may be an important stimulus for endothelial activation, we focused in this study on the role of contact-mediated activation by T lymphocytes of endothelial cells (EC). T lymphocytes were cultured with anti-CD3 monoclonal antibody or in the presence of a combination of TNF-α, interleukin (IL)-6, and IL-2, prior to fixation and coculture with human umbilical vein EC. Fixed, activated (anti-CD3- or cytokine-stimulated), but not unstimulated T cells, induced release of monocyte chemotactic protein-1, IL-8, and IL-6 by EC in a contact-dependent manner. Moreover, expression of tissue-factor antigen and activity was also significantly increased. Addition of anti-CD40 ligand antibody abolished T cell-induced activation of EC. Our data suggest that contact-mediated activation of EC by T cells, involving ligand:counter ligand interactions such as CD40:CD40 ligand, may represent a novel pathogenic mechanism of progression in inflammatory diseases such as atherosclerosis or rheumatoid arthritis.

Objectives. This study sought to assess neutrophil activation in acute coronary syndromes and its relation to ischemic episodes.Background. Neutrophil activation has been reported in unstable angina and acute myocardial infarction; however, it is not clear whether it is related exclusively to ischemia-reperfusion injury.Methods. We measured the index of intracellular myeloperoxidase in 1) patients with unstable angina, myocardial infarction, variant angina and chronic stable angina and in normal subjects (protocol A); and 2) in patients with unstable angina and acute myocardial infarction during the first 4 days of the hospital period (protocol B). To assess whether neutrophil activation was triggered by ischemia, the myeloperoxidase intracellular index was analyzed before and after spontaneous ischemic episodes and before and after ischemia induced by an exercise stress test in 10 patients with chronic stable angina. In 11 patients with unstable angina, we also compared values of the myeloperoxidase intracellular index at entry with those after waning of symptoms.Results. In protocol A, the myeloperoxidase intracellular index was significantly reduced in patients with unstable angina and acute myocardial infarction compared with patients with stable and variant angina and normal subjects (p < 0.01). In protocol B, the myeloperoxidase intracellular index did not change over time in patients with unstable angina and myocardial infarction. However, in 11 patients with waning symptoms, the myeloperoxidase intracellular index was significantly higher after symptoms had waned (p < 0.05). In patients with unstable angina, 23 ischemic episodes were studied; no changes in the myeloperoxidase intracellular index were observed. In 10 patients with chronic stable angina and positive exercise stress test results, no significant differences in the myeloperoxidase intracellular index were observed after stress-induced ischemia.Conclusions. Our study confirms that neutrophils are activated in acute coronary syndromes but suggests that their activation may not be only secondary to ischemia-reperfusion injury.

The results of our study suggest that the acute phase response may be partly related to a yet unknown primary inflammatory component in unstable angina. Further studies are needed to elucidate the actual role of inflammation in unstable angina and its relation to activation of the coagulation system.