Functional profile of activated dendritic cells in unstable atherosclerotic plaque

The Evolving Role of Dendritic Cells in Atherosclerosis

Atherosclerosis, a major contributor to cardiovascular morbidity and mortality, is characterized by chronic inflammation of the arterial wall. This inflammatory process is initiated and maintained by both innate and adaptive immunity. Dendritic cells (DCs), which are antigen-presenting cells, play a crucial role in the development of atherosclerosis and consist of various subtypes with distinct functional abilities. Following the recognition and binding of antigens, DCs become potent activators of cellular responses, bridging the innate and adaptive immune systems. The modulation of specific DC subpopulations can have either pro-atherogenic or atheroprotective effects, highlighting the dual pro-inflammatory or tolerogenic roles of DCs. In this work, we provide a comprehensive overview of the evolving roles of DCs and their subtypes in the promotion or limitation of atherosclerosis development. Additionally, we explore antigen pulsing and pharmacological approaches to modulate the function of DCs in the context of atherosclerosis.

The Impact of Cytokines in Coronary Atherosclerotic Plaque: Current Therapeutic Approaches

Coronary atherosclerosis is a chronic pathological process that involves inflammation together with endothelial dysfunction and lipoprotein dysregulation. Experimental studies during the past decades have established the role of inflammatory cytokines in coronary artery disease, namely interleukins (ILs), tumor necrosis factor (TNF)-α, interferon-γ, and chemokines. Moreover, their value as biomarkers in disease development and progression further enhance the validity of this interaction. Recently, cytokine-targeted treatment approaches have emerged as potential tools in the management of atherosclerotic disease. IL-1β, based on the results of the CANTOS trial, remains the most validated option in reducing the residual cardiovascular risk. Along the same line, colchicine was also proven efficacious in preventing major adverse cardiovascular events in large clinical trials of patients with acute and chronic coronary syndrome. Other commercially available agents targeting IL-6 (tocilizumab), TNF-α (etanercept, adalimumab, infliximab), or IL-1 receptor antagonist (anakinra) have mostly been assessed in the setting of other inflammatory diseases and further testing in atherosclerosis is required. In the future, potential targeting of the NLRP3 inflammasome, anti-inflammatory IL-10, or atherogenic chemokines could represent appealing options, provided that patient safety is proven to be of no concern.

Immune and inflammatory mechanisms of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a life-threatening cardiovascular disease. Immune-mediated infiltration and a destruction of the aortic wall during AAA development plays significant role in the pathogenesis of this disease. While various immune cells had been found in AAA, the mechanisms of their activation and function are still far from being understood. A better understanding of mechanisms regulating the development of aberrant immune cell activation in AAA is essential for the development of novel preventive and therapeutic approaches. In this review we summarize current knowledge about the role of immune cells in AAA and discuss how pathogenic immune cell activation is regulated in this disease.

Urinary Proteomics Identifying Novel Biomarkers for the Diagnosis and Phenotyping of Carotid Artery Stenosis

Background: Carotid artery stenosis (CAS) is caused by the formation of atherosclerotic plaques inside the arterial wall and accounts for 20–30% of all strokes. The development of an early, noninvasive diagnostic method and the identification of high-risk patients for ischemic stroke is essential to the management of CAS in clinical practice.

Methods: We used the data-independent acquisition (DIA) technique to conduct a urinary proteomic study in patients with CAS and healthy controls. We identified the potential diagnosis and risk stratification biomarkers of CAS. And Ingenuity pathway analysis was used for functional annotation of differentially expressed proteins (DEPs). Furthermore, receiver operating characteristic (ROC) analysis was performed to evaluate the diagnostic values of DEPs.

Results: A total of 194 DEPs were identified between CAS patients and healthy controls by DIA quantification. The bioinformatics analysis showed that these DEPs were correlated with the pathogenesis of CAS. We further identified 32 DEPs in symptomatic CAS compared to asymptomatic CAS, and biological function analysis revealed that these proteins are mainly related to immune/inflammatory pathways. Finally, a biomarker panel of six proteins (ACP2, PLD3, HLA-C, GGH, CALML3, and IL2RB) exhibited potential diagnostic value in CAS and good discriminative power for differentiating symptomatic and asymptomatic CAS with high sensitivity and specificity.

Conclusions: Our study identified novel potential urinary biomarkers for noninvasive early screening and risk stratification of CAS.

A myriad of roles of dendritic cells in atherosclerosis

Atherosclerosis is an inflammatory disease with break-down of homeostatic immune regulation of vascular tissues. As a critical initiator of host immunity, dendritic cells (DCs) have also been identified in the aorta of healthy individuals and atherosclerotic patients, whose roles in regulating arterial inflammation aroused great interest. Accumulating evidence has now pointed to the fundamental roles for DCs in every developmental stage of atherosclerosis due to their myriad of functions in immunity and tolerance induction, ranging from lipid uptake, efferocytosis and antigen presentation to pro- and anti-inflammatory cytokine or chemokine secretion. In this study we provide a timely summary of the published works in this field, and comprehensively discuss both the direct and indirect roles of DCs in atherogenesis. Understanding the pathogenic roles of DCs during the development of atherosclerosis in vascular tissues would certainly help to open therapeutic avenue to the treatment of cardiovascular diseases.

Current Understanding of the Immunomodulatory Activities of High-Density Lipoproteins

Lipoproteins interact with immune cells, macrophages and endothelial cells - key players of the innate and adaptive immune system. High-density lipoprotein (HDL) particles seem to have evolved as part of the innate immune system since certain HDL subspecies contain combinations of apolipoproteins with immune regulatory functions. HDL is enriched in anti-inflammatory lipids, such as sphingosine-1-phosphate and certain saturated lysophospholipids. HDL reduces inflammation and protects against infection by modulating immune cell function, vasodilation and endothelial barrier function. HDL suppresses immune cell activation at least in part by modulating the cholesterol content in cholesterol/sphingolipid-rich membrane domains (lipid rafts), which play a critical role in the compartmentalization of signaling pathways. Acute infections, inflammation or autoimmune diseases lower HDL cholesterol levels and significantly alter HDL metabolism, composition and function. Such alterations could have a major impact on disease progression and may affect the risk for infections and cardiovascular disease. This review article aims to provide a comprehensive overview of the immune cell modulatory activities of HDL. We focus on newly discovered activities of HDL-associated apolipoproteins, enzymes, lipids, and HDL mimetic peptides.

Assessment of medullary and extramedullary myelopoiesis in cardiovascular diseases

Recruitment of innate immune cells and their accumulation in the arterial wall and infarcted myocardium has been recognized as a central feature of atherosclerosis and cardiac ischemic injury, respectively. In both, steady state and under pathological conditions, majority of these cells have a finite life span and are continuously replenished from haematopoietic stem/progenitor cell pool residing in the bone marrow and extramedullary sites. While having a crucial role in the cardiovascular disease development, proliferation and differentiation of innate immune cells within haematopoietic compartments is greatly affected by the ongoing cardiovascular pathology. In the current review, we summarize key cells, processes and tissue compartments that are involved in myelopoiesis under the steady state, during atherosclerosis development and in myocardial infarction.

The aorta can act as a site of naïve CD4+ T-cell priming

AIMS

Aortic adaptive immunity plays a role in atherosclerosis; however, the precise mechanisms leading to T-cell activation in the arterial wall remain poorly understood.

METHODS AND RESULTS

Here, we have identified naïve T cells in the aorta of wild-type and T-cell receptor transgenic mice and we demonstrate that naïve T cells can be primed directly in the vessel wall with both kinetics and frequency of T-cell activation found to be similar to splenic and lymphoid T cells. Aortic homing of naïve T cells is regulated at least in part by the P-selectin glycosylated ligand-1 receptor. In experimental atherosclerosis the aorta supports CD4+ T-cell activation selectively driving Th1 polarization. By contrast, secondary lymphoid organs display Treg expansion.

CONCLUSION

Our results demonstrate that the aorta can support T-cell priming and that naïve T cells traffic between the circulation and vessel wall. These data underpin the paradigm that local priming of T cells specific for plaque antigens contributes to atherosclerosis progression.

Functional crosstalk between T cells and monocytes in cancer and atherosclerosis

Monocytes and monocyte-derived cells, including Mϕs and dendritic cells, exhibit a diverse array of phenotypic states that are dictated by their surrounding microenvironment. These cells direct T cell activation and function via cues that range from being immunosuppressive to immunostimulatory. Solid tumors and atherosclerotic plaques represent two pathological niches with distinct immune microenvironments. While monocytes and their progeny possess a phenotypic spectrum found within both disease contexts, most within tumors are pro-tumoral and support evasion of host immune responses by tumor cells. In contrast, monocyte-derived cells within atherosclerotic plaques are usually pro-atherogenic, pro-inflammatory, and predominantly directed against self-antigens. Consequently, cancer immunotherapies strive to enhance the immune response against tumor antigens, whereas atherosclerosis treatments seek to dampen the immune response against lipid antigens. Insights into monocyte-T cell interactions within these niches could thus inform therapeutic strategies for two immunologically distinct diseases. Here, we review monocyte diversity, interactions between monocytes and T cells within tumor and plaque microenvironments, how certain therapies have leveraged these interactions, and novel strategies to assay such associations.

Pro-inflammatory Cytokines in Acute Coronary Syndromes

BACKGROUND

Over the last decades, the role of inflammation and immune system activation in the initiation and progression of coronary artery disease (CAD) has been established.

OBJECTIVES

The study aimed to present the interplay between cytokines and their actions preceding and shortly after ACS.

METHODS

We searched in a systemic manner the most relevant articles to the topic of inflammation, cytokines, vulnerable plaque and myocardial infarction in MEDLINE, COCHRANE and EMBASE databases.

RESULTS

Different classes of cytokines (intereleukin [IL]-1 family, Tumor necrosis factor-alpha (TNF-α) family, chemokines, adipokines, interferons) are implicated in the entire process leading to destabilization of the atherosclerotic plaque, and consequently, to the incidence of myocardial infarction. Especially IL-1 and TNF-α family are involved in inflammatory cell accumulation, vulnerable plaque formation, platelet aggregation, cardiomyocyte apoptosis and adverse remodeling following the myocardial infarction. Several cytokines such as IL-6, adiponectin, interferon-γ, appear with significant prognostic value in ACS patients. Thus, research interest focuses on the modulation of inflammation in ACS to improve clinical outcomes.

CONCLUSION

Understanding the unique characteristics that accompany each cytokine-cytokine receptor interaction could illuminate the signaling pathways involved in plaque destabilization and indicate future treatment strategies to improve cardiovascular prognosis in ACS patients.

Vascular Macrophages in Atherosclerosis

Atherosclerosis is the main pathological basis for the occurrence of most cardiovascular diseases, the leading global health threat, and a great burden for society. It has been well established that atherosclerosis is not only a metabolic disorder but also a chronic, sterile, and maladaptive inflammatory process encompassing both innate and adaptive immunity. Macrophages, the major immune cell population in atherosclerotic lesions, have been shown to play critical roles in all stages of atherosclerosis, including the initiation and progression of advanced atherosclerosis. Macrophages have emerged as a novel potential target for antiatherosclerosis therapy. In addition, the macrophage phenotype is greatly influenced by microenvironmental stimuli in the plaques and presents complex heterogeneity. This article reviews the functions of macrophages in different stages of atherosclerosis, as well as the phenotypes and functions of macrophage subsets. New treatment strategies based on macrophage-related inflammation are also discussed.

Immune cells in carotid artery plaques: what can we learn from endarterectomy specimens?

INTRODUCTION

Endarterectomy specimens represent a unique opportunity to study atherosclerosis. This review aims to summarize the recent knowledge of atherogenesis from studies characterizing a cellular composition of carotid endarterectomy specimens.

EVIDENCE ACQUISITION

A non-systematic literature review was carried out to summarize recent knowledge regarding ex vivo analysis of carotid artery plaque composition. Upon evaluation of their relevance, and elaborate forward and backward search, 95 articles were included in the review.

EVIDENCE SYNTHESIS

Despite the significant advancement of in vivo imaging techniques, the stroke prediction based on carotid artery plaque morphology is not reliable. Besides analyses of plaque morphology, present studies focus on precise characterization of the different immune cell types and elucidation of their role in plaque development. Plaque content analyses revealed the presence of various immune cells in carotid artery plaques. Presence of different immune cells subpopulations can be connected to some undesirable changes in plaque stability.

CONCLUSIONS

Since the destabilization of the atherosclerotic plaque is a multifactorial process, a combination of various methods should be used to characterize the unstable plaques more accurately. In this context, studies characterizing plaque content from a cellular point of view could elucidate some processes underlying the plaque progression. Together with morphological evaluation, these analyses could enable more precise assessment of plaque stability.

Using evasins to target the chemokine network in inflammation

Inflammation, is driven by a network comprising cytokines, chemokines, their target receptors and leukocytes, and is a major pathologic mechanism that adversely affects organ function in diverse human diseases. Despite being supported by substantial target validation, no successful anti-chemokine therapeutic to treat inflammatory disease has yet been developed. This is in part because of the robustness of the chemokine network, which emerges from a large total chemokine load in disease, promiscuous expression of receptors on leukocytes, promiscuous and synergistic interactions between chemokines and receptors, and feedforward loops created by secretion of chemokines by leukocytes themselves. Many parasites, including viruses, helminths and ticks, evade the chemokine network by producing proteins that bind promiscuously to chemokines or their receptors. Evasins - three small glycoproteins identified in the saliva of the brown dog tick - bind multiple chemokines, and are active in several animal models of inflammatory disease. Over 50 evasin homologs have recently been identified from diverse tick species. Characterization of the chemokine binding patterns of evasins show that several have anti-chemokine activities that extend substantially beyond those previously described. These studies indicate that evasins function at the site of the tick bite by reducing total chemokine load. This not only reduces chemokine signaling to receptors, but also interrupts feedforward loops, thus disabling the chemokine network. Taking the lead from nature, a goal for the development of new anti-chemokine therapeutics would be to reduce the total chemokine load in disease. This could be achieved by administering appropriate evasin combinations or by smaller peptides that mimic evasin action.

How Oxidized Low-Density Lipoprotein Activates Inflammatory Responses

Cardiovascular disease (CVD) is the number one cause of death in the United States and worldwide. The most common cause of cardiovascular disease is atherosclerosis, or formation of fatty plaques in the arteries. Low-density lipoprotein (LDL), termed "bad cholesterol", is a large molecule comprised of many proteins as well as lipids including cholesterol, phospholipids, and triglycerides. Circulating levels of LDL are directly associated with atherosclerosis disease severity. Once thought to simply be caused by passive retention of LDL in the vasculature, atherosclerosis studies over the past 40-50 years have uncovered a much more complex mechanism. It has now become well established that within the vasculature, LDL can undergo many different types of oxidative modifications such as esterification and lipid peroxidation. The resulting oxidized LDL (oxLDL) has been found to have antigenic potential and contribute heavily to atherosclerosis associated inflammation, activating both innate and adaptive immunity. This review discusses the many proposed mechanisms by which oxidized LDL modulates inflammatory responses and how this might modulate atherosclerosis.

Chlamydia and Lipids Engage a Common Signaling Pathway That Promotes Atherogenesis

BACKGROUND

Recent studies indicate that Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 (MyD88) signaling promote the development of high fat diet-induced atherosclerosis in hypercholesterolemic mice.

OBJECTIVES

The authors investigated the role of TLR4/MyD88 signaling in hematopoietic and stromal cells in the development and infection-mediated acceleration of atherosclerosis.

METHODS

The authors generated bone marrow chimeras between wild-type and Tlr4^-/- mice, as well as wild-type and Myd88^-/- mice. All mice were on the Apoe^-/- background and fed high fat diet. The authors infected the chimeric mice with C. pneumoniae (CP) and fed them high fat diet.

RESULTS

Aortic sinus plaques and lipid content were significantly reduced in Apoe^-/- mice that received Tlr4^-/-or Myd88^-/- bone marrow compared with control animals despite similar cholesterol levels. Similarly, Tlr4 or Myd88 deficiency in stromal cells also led to a reduction in the lesion area and lipid in aortic sinus plaques. MyD88 expression only in CD11c+ dendritic cells (myeloid cells) in cells was sufficient in otherwise MyD88-deficient mice to induce CP infection-mediated acceleration of atherosclerosis, underlining the key role of MyD88 in CD11c+ dendritic cells (myeloid cells). Whereas CP infection markedly accelerated atherosclerosis in TLR4- or MyD88-positive chimeras, CP infection had a minimal effect on atherosclerosis in TLR4- or MyD88-deficient mice (either in the hematopoietic or stromal cell compartments).

CONCLUSIONS

The authors show that both CP infection and metabolic stress associated with dyslipidemia use the same innate immune response pathway, utilizing TLR4/MyD88 signaling, with similar relative contributions in bone marrow-derived hematopoietic cells and in stromal cells. Further studies are required to understand this intricate and complex cross talk among innate and adaptive immune systems in various conditions to more effectively design dendritic cell-mediated atheroprotective vaccines and other therapeutic strategies.

The P-selectin and PSGL-1 axis accelerates atherosclerosis via activation of dendritic cells by the TLR4 signaling pathway

P-selectin and dendritic cells (DCs) are associated with atherosclerosis. However, their interactions in this setting are undefined. Herein, we investigated the role of P-selectin and its receptor P-selectin glycoprotein ligand (PSGL)-1 on atherosclerosis via activation of DCs. In the current study, a total of 34 patients with ST elevation myocardial infarction (STEMI) and 34 healthy control subjects were enrolled. Serum concentration of P-selectin was higher and the myeloid DC/plasmacytoid DC (mDC/pDC) ratio was lower in STEMI patients than in normal individuals. Interestingly, in STEMI patients, P-selectin was decreased and the mDC/pDC ratio was increased at 5–7 days after successful percutaneous coronary intervention, as compared with values on admission. Serum P-selectin was inversely correlated with the mDC/pDC ratio. Moreover, ApoE^−/−P^−/− and ApoE^−/−PSGL-1^−/− mice developed small atherosclerotic plaques after feeding of a western diet for 12 weeks and DC infiltration was significantly reduced. P-selectin stimulation markedly induced phenotypic maturation, enhanced secretion of inflammatory cytokines, communication with T cells, and the adhesion and migration of DCs. In vivo, DC maturation was significantly attenuated in P-selectin and PSGL1 knockout mice under hypercholesterolemic and inflammatory conditions. These effects were associated with the activation of myeloid differentiation primary response 88 (MYD88)-dependent and MyD88-independent Toll-like receptor 4 (TLR4) signaling pathways. Taken together, binding of P-selectin to PSGL-1 on DCs contributes to atherosclerosis progression via DC activation via the TLR4 signaling pathway.

P-Selectin Glycoprotein Ligand-1 (PSGL-1) Expressing CD4 T Cells Contribute Plaque Instability in Acute Coronary Syndrome

BACKGROUND

Adhesion molecules have essential roles in the development of atherosclerosis. We investigated whether P-selectin glycoprotein ligand-1 (PSGL-1)-expressing CD4 T cells contribute to plaque instability in acute coronary syndrome (ACS).Methods and Results:We studied the adhesion molecules on CD4 T cells from consecutive patients with ACS treated with thrombus-aspirating device and compared them with healthy controls (n=48 each). Blood, thrombi, and plaque samples from the culprit coronary arteries were collected by thrombus aspiration performed during emergency coronary artery angiography. According to flow cytometry results, peripheral CD4 T cells from ACS patients strongly expressed PSGL-1 and integrin β2 (P<0.05 for both) more than those from controls; culprit coronary arteries contained an abundance of PSGL-1⁺(P<0.001) but not integrin β2⁺CD4 T cells. In addition, immunohistochemical analysis of the thrombus-aspirating device samples revealed numerous PSGL-1⁺CD4 T cells in plaques from the culprit lesions. Results from the selectin-binding assay demonstrated that activated PSGL-1⁺CD4 T cells from ACS patients bound to P- or E-selectin after triggering the T-cell receptor, and adhered to endothelial cells under laminar flow conditions (P<0.05 and P<0.05, respectively), inducing their apoptosis (P<0.01) via activated caspase-3, which correlated with PSGL-1 expression (R=0.788, P=0.021) and was suppressed by application of a PSGL-1-specific antibody (P<0.05).

CONCLUSIONS

PSGL-1 contributed to cytotoxic CD4 T cell homing to the culprit coronary artery and promoted plaque instability in ACS.

The role of lnc-DC long non-coding RNA and SOCS1 in the regulation of STAT3 in coronary artery disease and type 2 diabetes mellitus

AIMS

Coronary artery disease (CAD) can be classified as an inflammatory disease, which affected by type 2 diabetes mellitus (T2DM). Elevated levels of many inflammatory molecules were found in the serum of patients with CAD. STAT3 molecule as a transcription factor plays an important role in the cytokines expression. Here, we examined the expression levels of STAT3 and its important regulatory genes lnc-DC and SOCS1, in patients with CAD and T2DM.

METHODS

Blood samples were obtained from 37 CAD+ and 36 CAD- patients. These patients were enrolled in this study based on angiography findings and categorized based on T2DM status. The expression levels of STAT3, lnc-DC and SOCS1 genes were examined with Real time PCR method.

RESULTS

A significant increase was observed in expression of STAT3 and lnc-DC genes but not SOCS1 in CAD+ versus CAD- patients. These results replicated partially in some groups categorized based on T2DM and CAD status. However, severity of CAD had no effect on expressions of these genes. Moreover, we found some significant correlations between expressions of lnc-DC with SOCS1 and STAT3, which confirmed by in silico analysis.

CONCLUSION

Our results shed further light to the inflammatory aspects of CAD and T2DM with emphasis to JAK/STAT pathway and the regulatory role of long non-coding RNAs in the physiopathology of these diseases.

Inflammation in human carotid atheroma plaques

Inflammation in carotid atherosclerotic plaque is linked to plaque rupture and cerebrovascular accidents. The balance between pro- and anti-inflammatory mediators governs development of the plaque, and may mediate enhancement of lesion broadening or, on the contrary, delay progression. In addition to macrophages and endothelial cells, smooth muscle cells (SMCs), which are the dominant cell subset in advanced plaques, are crucial players in carotid atherosclerosis development given their ability to differentiate into distinct phenotypes in reponse to specific signals received from the environment of the lesion. Carotid atheroma SMCs actively contribute to the inflammation in the lesion because of their acquired capacity to produce inflammatory mediators. We review the successive stages of carotid atheroma plaque formation via fatty streak early-stage toward more advanced rupture-prone lesions and document involvement of cytokines and chemokines and their cellular sources and targets in plaque progression and rupture.

Dendritic cells in atherosclerosis: Functions in immune regulation and beyond

Chronic inflammation drives the development of atherosclerosis. Dendritic cells (DCs) are known as central mediators of adaptive immune responses and the development of immunological memory and tolerance. DCs are present in non-diseased arteries, and accumulate within atherosclerotic lesions where they can be localised in close vicinity to T cells. Recent work has revealed important functions of DCs in regulating immune mechanisms in atherogenesis, and vaccination strategies using DCs have been explored for treatment of disease. However, in line with a phenotypical and functional overlap with plaque macrophages vascular DCs were also identified to engulf lipids, thus contributing to lipid burden in the vessel wall and initiation of lesion growth. Furthermore, a function of DCs in regulating cholesterol homeostasis has been revealed. Finally, phenotypically distinct plasmacytoid dendritic cells (pDCs) have been identified within atherosclerotic lesions. This review will dissect the multifaceted contribution of DCs and pDCs to the initiation and progression of atherosclerosis and the experimental approaches utilising DCs in therapeutic vaccination strategies.

Dendritic Cells and Their Role in Cardiovascular Diseases: A View on Human Studies

The antigen-presenting dendritic cells (DCs) are key to the immunological response, with different functions ascribed ranging from cellular immune activation to induction of tolerance. Such immunological responses are involved in the pathophysiological mechanisms of cardiovascular diseases, with DCs shown to play a role in atherosclerosis, hypertension, and heart failure and most notably following heart transplantation. A better understanding of the interplay between the immune system and cardiovascular diseases will therefore be critical for developing novel therapeutic treatments as well as innovative monitoring tools for disease progression. As such, the present review will provide an overview of DCs involvement in the pathophysiology of cardiovascular diseases and how targeting these cells may have beneficial effects for the prognosis of patients.

The role of toll like receptors in giant cell arteritis

GCA is a common primary systemic vasculitis that results in granulomatous inflammation of medium to large arteries. Both innate and adaptive immune mechanisms combine to drive intimal hyperplasia, luminal stenosis and ultimately occlusion. While the pathogenesis of GCA is incompletely understood, the activation of resident adventitial dendritic cells via toll like receptors (TLRs) appears to be a crucial inciting event. Here we explore the role of TLRs in the pathogenesis of GCA, including their effects on dendritic cell and T cell activation and recruitment, putative infectious triggers for GCA and the potential of TLR inhibition as a novel therapeutic strategy in GCA.

Preclinical imaging of the co-stimulatory molecules CD80 and CD86 with indium-111-labeled belatacept in atherosclerosis

Background

The inflammatory nature of atherosclerosis provides a broad range of potential molecular targets for atherosclerosis imaging. Growing interest is focused on targets related to plaque vulnerability such as the co-stimulatory molecules CD80 and CD86. We investigated in this preclinical proof-of-concept study the applicability of the CD80/CD86-binding fusion protein belatacept as a probe for atherosclerosis imaging.

Methods

Belatacept was labeled with indium-111, and the binding affinity was determined with CD80/CD86-positive Raji cells. In vivo distribution was investigated in Raji xenograft-bearing mice in single-photon emission computed tomography (SPECT)/CT scans, biodistribution, and ex vivo autoradiography studies. Ex vivo SPECT/CT experiments were performed with aortas and carotids of ApoE KO mice. Accumulation in human carotid atherosclerotic plaques was investigated by in vitro autoradiography.

Results

¹¹¹In-DOTA-belatacept was obtained in >70 % yield, >99 % radiochemical purity, and ~40 GBq/μmol specific activity. The labeled belatacept bound with high affinity to Raji cells. In vivo, ¹¹¹In-DOTA-belatacept accumulated specifically in Raji xenografts, lymph nodes, and salivary glands. Ex vivo SPECT experiments revealed displaceable accumulation in atherosclerotic plaques of ApoE KO mice fed an atherosclerosis-promoting diet. In human plaques, binding correlated with the infiltration by immune cells and the presence of a large lipid and necrotic core.

Conclusions

¹¹¹In-DOTA-belatacept accumulates in CD80/CD86-positive tissues in vivo and in vitro rendering it a research tool for the assessment of inflammatory activity in atherosclerosis and possibly other diseases. The tracer is suitable for preclinical imaging of co-stimulatory molecules of both human and murine origin. Radiolabeled belatacept could serve as a benchmark for future CD80/CD86-specific imaging agents.

Electronic supplementary material

The online version of this article (doi:10.1186/s13550-015-0157-4) contains supplementary material, which is available to authorized users.

Monocyte-Derived Dendritic Cells Upregulate Extracellular Catabolism of Aggregated Low-Density Lipoprotein on Maturation, Leading to Foam Cell Formation

OBJECTIVE

Although dendritic cells are known to play a role in atherosclerosis, few studies have examined the contribution of the wide variety of dendritic cell subsets. Accordingly, their roles in atherogenesis remain largely unknown. We investigated the ability of different dendritic cell subsets to become foam cells after contact with aggregated low-density lipoprotein (LDL; the predominant form of LDL found in atherosclerotic plaques).

APPROACH AND RESULTS

We demonstrate that both murine and human monocyte-derived dendritic cells use exophagy to degrade aggregated LDL, leading to foam cell formation, whereas monocyte-independent dendritic cells are unable to clear LDL aggregates by this mechanism. Exophagy is a catabolic process in which objects that cannot be internalized by phagocytosis (because of their size or association with extracellular structures) are initially digested in an extracellular acidic lytic compartment. Surprisingly, we found that monocyte-derived dendritic cells upregulate exophagy on maturation. This contrasts various forms of endocytic internalization in dendritic cells, which decrease on maturation. Finally, we show that our in vitro results are consistent with dendritic cell lipid accumulation in plaques of an ApoE(-/-) mouse model of atherosclerosis.

CONCLUSIONS

Our results show that monocyte-derived dendritic cells use exophagy to degrade aggregated LDL and become foam cells, whereas monocyte-independent dendritic cells are unable to clear LDL deposits. Furthermore, we find that exophagy is upregulated on dendritic cell maturation. Thus, exophagy-mediated foam cell formation in monocyte-derived dendritic cells could play a significant role in atherogenesis.

Dendritic cells in atherosclerosis: evidence in mice and humans

Atherosclerotic vascular disease is driven by chronic inflammation involving both innate and adaptive immune responses. Dendritic cells (DCs) are found in healthy arteries and accumulate in atherosclerotic lesions and engage in diverse pathogenic and protective mechanisms during atherogenesis. DCs contribute to early foam cell formation, regulate lipid metabolism, and control pro- and antiatherosclerotic T-cell responses by multifarious mechanisms. We, here, review the roles of DCs and plasmacytoid DCs in experimental models of atherosclerosis and the approaches to target DCs in therapeutic vaccination strategies. We, furthermore, discuss the evidence of the potential function of DCs in human atherosclerosis, and dissect the efforts to harness DC subsets as biomarkers of disease. Finally, we discuss necessary future steps that will help to understand the specific contribution of bona fide DCs in atherosclerosis to move toward novel therapeutic approaches.

CCL19 and CCL21 modulate the inflammatory milieu in atherosclerotic lesions

Despite advances in the pharmacologic and interventional treatment of coronary artery disease, atherosclerosis remains the leading cause of death worldwide. Atherosclerosis is a chronic inflammatory disease, and elevated expression of CCL19 and CCL21 has been observed in ruptured lesions of coronary arteries of patients with myocardial infarction and carotid plaques of patients with ischemic symptoms, as well as in plasma of coronary artery disease patients. However, the exact role of CCL19 and CCL21 in atherosclerosis remains unknown. In order to identify CCL19 and CCL21 as a novel therapeutic target, we performed bone marrow transplantation as an immunomodulatory treatment concept. Bone marrow of plt/plt mice (lacking CCL19 and CCL21-Ser) was transplanted into atherogenic Ldlr(-/-) mice. The study demonstrated a significantly increased inflammatory cellular infiltration into the lesions of plt/plt/Ldlr(-/-) mice versus controls. Although the level of chemoattraction was increased, messenger ribonucleic acid and protein levels in thoracic aorta and serum of several proinflammatory cytokines (TNFα, IFNγ, IL-6, IL-12, and IL-17) were significantly reduced in plt/plt/Ldlr(-/-) versus control mice. Increased influx, accompanied by reduced activation of leukocytes in atherosclerotic lesion, was accompanied by increased plaque stability but unchanged lesion development. In conclusion, modulation of the chemokines CCL19 and CCL21 represents a potent immunoregulatory treatment approach, and thus represents a novel therapeutic target to stabilize atherosclerotic lesions.

Plasmacytoid dendritic cells: development, functions, and role in atherosclerotic inflammation

Plasmacytoid dendritic cells (pDCs) are a specialized subset of DCs that links innate and adaptive immunity. They sense viral and bacterial pathogens and release high levels of Type I interferons (IFN-I) in response to infection. pDCs were shown to contribute to inflammatory responses in the steady state and in pathology. In atherosclerosis, pDCs are involved in priming vascular inflammation and atherogenesis through production of IFN-I and chemokines that attract inflammatory cells to inflamed sites. pDCs also contribute to the proinflammatory activation of effector T cells, cytotoxic T cells, and conventional DCs. However, tolerogenic populations of pDCs are found that suppress atherosclerosis-associated inflammation through down-regulation of function and proliferation of proinflammatory T cell subsets and induction of regulatory T cells with potent immunomodulatory properties. Notably, atheroprotective tolerogenic DCs could be induced by certain self-antigens or bacterial antigens that suggests for great therapeutic potential of these DCs for development of DC-based anti-atherogenic vaccines.

Dendritic cells in atherosclerotic inflammation: the complexity of functions and the peculiarities of pathophysiological effects

Atherosclerosis is considered as a chronic disease of arterial wall, with a strong contribution of inflammation. Dendritic cells (DCs) play a crucial role in the initiation of proatherogenic inflammatory response. Mature DCs present self-antigens thereby supporting differentiation of naïve T cells to effector cells that further propagate atherosclerotic inflammation. Regulatory T cells (Tregs) can suppress proinflammatory function of mature DCs. In contrast, immature DCs are able to induce Tregs and prevent differentiation of naïve T cells to proinflammatory effector T cells by initiating apoptosis and anergy in naïve T cells. Indeed, immature DCs showed tolerogenic and anti-inflammatory properties. Thus, DCs play a double role in atherosclerosis: mature DCs are proatherogenic while immature DCs appear to be anti-atherogenic. Tolerogenic and anti-inflammatory capacity of immature DCs can be therefore utilized for the development of new immunotherapeutic strategies against atherosclerosis.

Inhibition of B7-1 (CD80) by RhuDex® reduces lipopolysaccharide-mediated inflammation in human atherosclerotic lesions

Background

Atherosclerosis is based on a chronic inflammatory process including the innate and adaptive immune response. Costimulatory molecules and their receptors provide decisive signals for antigen-specific cell activation. The contribution of B7-related pathways to atherosclerosis has hardly been explored.

Methods

In the present study, we investigated the contribution of B7-1 to inflammation and tissue injury in the human plaque microenvironment in order to identify possible target structures of future therapeutic agents ex vivo and in vitro.

Results

Carotid artery plaque stimulation with lipopolysaccharides (LPS) could be significantly inhibited by RhuDex^®, a specific inhibitor of the costimulatory molecule B7-1 ex vivo (P<0.001). Coculture of antigen-presenting cells with T-cells demonstrated that the inhibitory effects of RhuDex^® derived from reduced T-cell activation. In addition, incubation of monocytes/macrophages with LPS and RhuDex^® resulted in an inhibitory negative feedback on antigen-presenting cells. Signaling pathways affected by RhuDex^® seem to be nuclear transcription factor kappa B, activator protein-1, and extracellular signal-regulated kinase 1/2.

Conclusion

The present data support B7-1 alone as an important costimulatory molecule in the context of LPS-mediated inflammation in atherosclerotic lesions. Due to its marked inhibitory effects, RhuDex^® may be a useful therapy to modulate the inflammatory milieu in atherosclerosis.

A human ex vivo atherosclerotic plaque model to study lesion biology

Atherosclerosis is a chronic inflammatory disease of the vasculature. There are various methods to study the inflammatory compound in atherosclerotic lesions. Mouse models are an important tool to investigate inflammatory processes in atherogenesis, but these models suffer from the phenotypic and functional differences between the murine and human immune system. In vitro cell experiments are used to specifically evaluate cell type-dependent changes caused by a substance of interest, but culture-dependent variations and the inability to analyze the influence of specific molecules in the context of the inflammatory compound in atherosclerotic lesions limit the impact of the results. In addition, measuring levels of a molecule of interest in human blood helps to further investigate its clinical relevance, but this represents systemic and not local inflammation. Therefore, we here describe a plaque culture model to study human atherosclerotic lesion biology ex vivo. In short, fresh plaques are obtained from patients undergoing endarterectomy or coronary artery bypass grafting and stored in RPMI medium on ice until usage. The specimens are cut into small pieces followed by random distribution into a 48-well plate, containing RPMI medium in addition to a substance of interest such as cytokines or chemokines alone or in combination for defined periods of time. After incubation, the plaque pieces can be shock frozen for mRNA isolation, embedded in Paraffin or OCT for immunohistochemistry staining or smashed and lysed for western blotting. Furthermore, cells may be isolated from the plaque for flow cytometry analysis. In addition, supernatants can be collected for protein measurement by ELISA. In conclusion, the presented ex vivo model opens the possibility to further study inflammatory lesional biology, which may result in identification of novel disease mechanisms and therapeutic targets.

Dendritic cells in atherosclerosis

Atherosclerosis is a chronic inflammatory disease with activation of both the innate and adaptive arms of the immune system. Dendritic cells (DCs) are potent activators of adaptive immunity and have been identified in the normal arterial wall and within atherosclerotic lesions. Recent evidence points to a functional role for DCs in all stages of atherosclerosis because of their myriad functions including lipid uptake, antigen presentation, efferocytosis, and inflammation resolution. Moreover, DC-based vaccination strategies are currently being developed for the treatment of atherosclerosis. This review will focus on the current evidence as well as the proposed roles for DCs in the pathogenesis of atherosclerosis and discuss future therapeutic strategies.

Inflammation and immune system interactions in atherosclerosis

Cardiovascular disease (CVD) is the leading cause of mortality worldwide, accounting for 16.7 million deaths each year. The underlying cause of the majority of CVD is atherosclerosis. In the past, atherosclerosis was considered to be the result of passive lipid accumulation in the vessel wall. Today's picture is far more complex. Atherosclerosis is considered a chronic inflammatory disease that results in the formation of plaques in large and mid-sized arteries. Both cells of the innate and the adaptive immune system play a crucial role in its pathogenesis. By transforming immune cells into pro- and anti-inflammatory chemokine- and cytokine-producing units, and by guiding the interactions between the different immune cells, the immune system decisively influences the propensity of a given plaque to rupture and cause clinical symptoms like myocardial infarction and stroke. In this review, we give an overview on the newest insights in the role of different immune cells and subtypes in atherosclerosis.

Decrease in dendritic cells in endomyocardial biopsies of human dilated cardiomyopathy

AIMS

Dendritic cells (DCs) are sentinels of the immune system-their role in myocardial disease is unknown as yet. We investigated their myocardial presence in human dilated cardiomyopathy (DCM).

METHODS AND RESULTS

Endomyocardial biopsies from 72 patients with DCM (EF ∼30%), as well as myocardial specimens from 18 suicide or accident victims were immunohistochemically analysed for myeloid and plasmacytoid DCs, antigen-presenting cells (APCs), and other leucocytes; also tissue fibrosis and apoptosis were histologically quantified. The myocardial viral genome was identified through polymerase chain reaction, and patients underwent clinical follow-up in 3-6 months. We found myocardial DCs of all examined subtypes and maturation stages (fascin, CD11c, CD209, CD83, and CD304), as well as markers for APCs (HLA-DR and CD40) and T-cell activation (CD69) to be significantly decreased in DCM compared with controls. In contrast, regulatory T cells (the GITR epitope), apoptosis (by TUNEL reaction and immunostaining with BCL-2), and a DC chemokine receptor (CCR7) were overexpressed, while no significant differences were observed for macrophages (CD68). Immature myeloid and plasmacytoid DCs strongly correlated with endothelial progenitor cells (CD34), which were similarly reduced in DCM, and inversely correlated with fibrosis. Myeloid DCs were especially reduced in virus-positive biopsies, and their numbers correlated with positive change in EF (ΔEF) at follow-up.

CONCLUSION

Myocardial DCs are reduced in heart biopsies of symptomatic DCM patients. Such a reduction correlates with an unfavourable short-term outcome in terms of EF, and could result from myocardial tissue damage, cellular death, and insufficient vascularization in chronic heart failure.

WITHDRAWN: Dendritic cells: A double-edge sword in atherosclerotic inflammation

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Neuroimmunology of the atherosclerotic plaque: a morphological approach

Atherosclerosis is a chronic inflammatory process, lasting for several decades until the onset of its clinical manifestations. The progression of the atherosclerotic lesion to a stable fibrotic plaque, narrowing the vascular lumen, or to a vulnerable plaque leading to main vascular complications, is associated to the involvement of several cell subpopulations of the innate as well as of the adaptive immunity, and to the release of chemokines and pro-inflammatory cytokines. Emerging evidence outlines that the cardiovascular risk is dependent on stress-mediators influencing cell migration and vascular remodeling. The view that atherosclerosis is initiated by monocytes and lymphocytes adhering to dysfunctional endothelial cells is substantiated by experimental and clinical observations. Macrophages, dendritic cells, T and B lymphocytes, granulocytes accumulating into the subendothelial space secrete and are stimulated by soluble factors, including peptides, proteases and cytokines acting synergistically. The final step of the disease, leading to plaque destabilization and rupture, is induced by the release, at the level of the fibrous cap, of metalloproteinases and elastases by the activated leukocytes which accumulate locally. Recruitment of specific cell subpopulations as well as the progression of atherosclerotic lesions towards a stable or an unstable phenotype, are related to the unbalance between pro-atherogenic and anti-atherogenic factors. In this connection stress hormones deserve particular attention, since their role in vascular remodeling, via vascular smooth cell proliferation, as well as in neoangiogenesis, via stimulation of endothelial cell proliferation and migration, has been already established.

Dynamic T cell-APC interactions sustain chronic inflammation in atherosclerosis

Atherosclerosis is a chronic inflammatory disease of large and medium-sized arteries characterized by leukocyte accumulation in the vessel wall. Both innate and adaptive immune responses contribute to atherogenesis, but the identity of atherosclerosis-relevant antigens and the role of antigen presentation in this disease remain poorly characterized. We developed live-cell imaging of explanted aortas to compare the behavior and role of APCs in normal and atherosclerotic mice. We found that CD4+ T cells were capable of interacting with fluorescently labeled (CD11c-YFP+) APCs in the aortic wall in the presence, but not the absence, of cognate antigen. In atherosclerosis-prone Apoe-/-CD11c-YFP+ mice, APCs extensively interacted with CD4+ T cells in the aorta, leading to cell activation and proliferation as well as secretion of IFN-γ and TNF-α. These cytokines enhanced uptake of oxidized and minimally modified LDL by macrophages. We conclude that antigen presentation by APCs to CD4+ T cells in the arterial wall causes local T cell activation and production of proinflammatory cytokines, which promote atherosclerosis by maintaining chronic inflammation and inducing foam cell formation.

Do we know enough about the immune pathogenesis of acute coronary syndromes to improve clinical practice?

Morbidities related to atherosclerosis, such as acute coronary syndromes (ACS) including unstable angina and myocardial infarction, remain leading causes of mortality. Unstable plaques are inflamed and infiltrated with macrophages and T lymphocytes. Activated dendritic cells interact with T cells, yielding predominantly Th1 responses involving interferon-gamma (IFN-γ) and tumour necrosis factor-alpha (TNF-α), while the role of interleukin 17 (IL-17) is questionable. The expansion of CD28nullCD4 or CD8 T cells as well as pattern recognition receptors activation (especially Toll-like receptors; TLR2 and TLR4) is characteristic for unstable plaque. Inflammation modifies platelet and fibrin clot characteristics, which are critical for ACS. Understanding of the inflammatory mechanisms of atherothrombosis, bridging inflammation, oxidative stress and immune regulation, will allow for the detection of subjects at risk, through the use of novel biomarkers and imaging techniques including intravascular ultrasound, molecular targeting, magnetic resonance imaging (MRI) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET). Moreover, understanding the specific inflammatory pathways of plaque rupture and atherothrombosis may allow for immunomodulation of ACS. Statins and anti-platelet drugs are anti-inflammatory, but importance of immune events in ACS warrants the introduction of novel, specific treatments directed either on cytokines, TLRs or inflammasomes. While the prime time for the introduction of immunologically inspired diagnostic tests and treatments for atherosclerosis have not come yet, we are closer than ever before to finally being able to benefit from this vast body of experimental and clinical evidence. This paper provides a comprehensive review of the role of the immune system and inflammation in ACS.

Role of Peroxisome Proliferator-Activated Receptor-γ in Vascular Inflammation

Vascular inflammation plays a crucial role in atherosclerosis, and its regulation is important to prevent cerebrovascular and coronary artery disease. The inflammatory process in atherogenesis involves a variety of immune cells including monocytes/macrophages, lymphocytes, dendritic cells, and neutrophils, which all express peroxisome proliferator-activated receptor-γ (PPAR-γ). PPAR-γ is a nuclear receptor and transcription factor in the steroid superfamily and is known to be a key regulator of adipocyte differentiation. Increasing evidence from mainly experimental studies has demonstrated that PPAR-γ activation by endogenous and synthetic ligands is involved in lipid metabolism and anti-inflammatory activity. In addition, recent clinical studies have shown a beneficial effect of thiazolidinediones, synthetic PPAR-γ ligands, on cardiovascular disease beyond glycemic control. These results suggest that PPAR-γ activation is an important regulator in vascular inflammation and is expected to be a therapeutic target in the treatment of atherosclerotic complications. This paper reviews the recent findings of PPAR-γ involvement in vascular inflammation and the therapeutic potential of regulating the immune system in atherosclerosis.

Macrophages, dendritic cells, and regression of atherosclerosis

Atherosclerosis is the number one cause of death in the Western world. It results from the interaction between modified lipoproteins and cells such as macrophages, dendritic cells (DCs), T cells, and other cellular elements present in the arterial wall. This inflammatory process can ultimately lead to the development of complex lesions, or plaques, that protrude into the arterial lumen. Ultimately, plaque rupture and thrombosis can occur leading to the clinical complications of myocardial infarction or stroke. Although each of the cell types plays roles in the pathogenesis of atherosclerosis, the focus of this review will be primarily on the macrophages and DCs. The role of these two cell types in atherosclerosis is discussed, with a particular emphasis on their involvement in atherosclerosis regression.

Elevated circulating interleukin-27 in patients with coronary artery disease is associated with dendritic cells, oxidized low-density lipoprotein, and severity of coronary artery stenosis

Coronary artery disease (CAD) is an immune-mediated chronic inflammatory disease mainly caused by atherosclerosis. The aims of this study were to investigate the role of interleukin-27 (IL-27) in patients with CAD and the severity of coronary artery lesions, which was evaluated by Gensini score and to investigate the biosynthesis of IL-27 and oxidized low-density lipoprotein (ox-LDL) in vitro using monocyte-derived dendritic cells (DCs). To this aim, plasma levels of IL-27, ox-LDL, and Gensini score were analyzed in patients with CAD (n = 136) and normal subjects (controls, n = 29). IL-27 concentration of the supernatant and the mRNA expression levels of p28 and ebi3, subunits of IL-27, from cultured immature DCs incubated with different concentrations of ox-LDL for 24 h were also analyzed. We found that circulating IL-27 levels were significantly elevated in patients with CAD than in controls (P < 0.01), and positively correlated to ox-LDL and Gensini score. ox-LDL dose-dependently upregulated expression of both IL-27 protein and IL-27 (p28 and EBI3) mRNA in vitro, indicating that ox-LDL can stimulate DCs to produce IL-27. These results demonstrate that IL-27 might regulate the network of immunity and inflammation in the pathogenesis of atherosclerosis.

Marked acceleration of atherosclerosis after Lactobacillus casei-induced coronary arteritis in a mouse model of Kawasaki disease

OBJECTIVE

The purpose of this study was to investigate whether Lactobacillus casei cell wall extract-induced Kawasaki disease (KD) accelerates atherosclerosis in hypercholesterolemic mice. Method and Results- Apolipoprotein E knockout or low-density lipoprotein receptor knockout mice were injected with Lactobacillus casei cell wall extract (KD mice) or PBS, fed high-fat diet for 8 weeks, and atherosclerotic lesions in aortic sinuses, arch (AC), and whole aorta were assessed. KD mice had larger, more complex aortic lesions with abundant collagen, and both extracellular and intracellular lipid and foam cells, compared with lesions in control mice despite similar cholesterol levels. Both apolipoprotein E knockout KD and low-density lipoprotein receptor knockout KD mice showed dramatic acceleration in atherosclerosis versus controls, with increases in en face aortic atherosclerosis and plaque size in both the aortic sinuses and AC plaques. Accelerated atherosclerosis was associated with increased circulating interleukin-12p40, interferon-γ, tumor necrosis factor-α, and increased macrophage, dendritic cell, and T-cell recruitment in lesions. Furthermore, daily injections of the interleukin-1Ra, which inhibits Lactobacillus casei cell wall extract-induced KD vasculitis, prevented the acceleration of atherosclerosis.

CONCLUSIONS

Our results suggest an important pathophysiologic link between coronary arteritis/vasculitis in the KD mouse model and subsequent atherosclerotic acceleration, supporting the concept that a similar relation may also be present in KD patients. These results also suggest that KD in childhood may predispose to accelerated and early atherosclerosis as adults.