Monaco, Claudia

Introduction: V-domain Immunoglobulin Suppressor of T-cell Activation (VISTA), a co-inhibitory immune checkpoint protein, is known for regulating adaptive immune responses. Here, we investigated the role of VISTA in atherosclerosis. Hypothesis: VISTA is constitutively expressed on hematopoietic cells, particularly T cells. VISTA functions as both a ligand and receptor to maintain T cell quiescence. We hypothesize that VISTA expression is protective against plaque formation by inhibiting CD4 + T cell activation. Methods: Cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) was performed on aortic CD45 + cells of HCD fed ApoE-/- mice. Spatial transcriptomics (VISIUM) was performed on carotid plaques from patients with either asymptomatic or symptomatic cerebrovascular disease. Plaque burden, characterization, and flow cytometry of blood and lymphoid organs were performed on VISTA -/- ApoE -/- (VISTA KO) and VISTA +/+ ApoE -/- (WT) mice that were fed a HCD for 10 weeks. ApoE -/- mice treated with VISTA agonist 8G8 or IgG control (200ug, intra-peritoneal, 3 times per week for the last 6/10 weeks of HCD feeding). In vitro proliferation, migration, and functional T cell assays were performed. Results: We found that VISTA is expressed on plaque T cell populations, particularly regulatory T cells, gamma-delta T cells, and naïve T cells. In humans, individuals with symptomatic CVD have significantly reduced VISTA gene expression in carotid plaques. VISTA KO mice have increased total plaque area and necrotic core area compared to littermate WT controls. VISTA KO mice have increased peripheral CD4 + and CD8 + effector memory T (T EM ) cells with a corresponding decrease in CD4 + and CD8 + naïve T (T N ) cells and CD4 + regulatory T (T reg ) cells. Further, VISTA KO mice have a higher frequency of CD4 + T H 1 (T-bet + IFNy + ) cells and lower frequencies of IL-10 + CD4 + T cells and CD4 + T H 2 (GATA-3 + IL-13 + ) cells. In vitro assays showed that VISTA suppresses CD4 + T cell proliferation, IFNγ production, and migration. Finally, VISTA agonist treatment significantly decreased plaque and necrotic core areas in atherosclerotic mice. Conclusion: Our data reveals a novel role for VISTA in reducing plaque development and in suppressing T cell activation, proliferation, and migration. Further characterization of T-cell specific VISTA-deficient mouse models and mechanistic insights into how VISTA modulates T cells are currently being investigated.

Cardiovascular disease is the global #1 cause of mortality and morbidity. The majority of cardiovascular diseases is caused by atherosclerosis, a lipid-driven, inflammatory disease of the middle- and large-sized arteries. The disease is characterized by the formation of atherosclerotic plaques throughout the arterial tree. Over the years, insights into the pathogenesis of atherosclerosis have shifted from a ‘lipid-driven’ model to a ‘response-to-injury’ perspective, and more recently to a ‘lipid-driven inflammatory disease’ viewpoint. We are now aware that a network of multiple immune cell-types and -subsets of the innate and adaptive immune system inhabit our arteries. Intricate interactions between these immune cellsubsets, non-immune cells, and local environmental substances such as lipids, cell debris and calcium cause a fluidic balance of pro-inflammatory and regulatory responses. A dysregulation of this balance towards a pro-inflammatory milieu drives atherosclerotic disease progression. Although we have acknowledged that atherosclerosis is an inflammatory disease, state-of-theart treatments are still based on lipid lowering, anti-hypertensive and lifestyle-changing strategies. In the past decade, clinical phase I, II and III trials targeting the immune system revealed that patients tolerate immunotherapy, show decreased inflammation and/or had a reduction in cardiovascular endpoints. However, the search for novel immunotherapeutic targets and treatment regimens as well as stratification of patients who would benefit from such treatments to combat atherosclerotic cardiovascular disease is only just beginning. In this review article, we will highlight the newest insights on the different cell subsets and components of the immune system in atherosclerosis and elaborate on current and future immunotherapeutics to treat atherosclerotic cardiovascular disease.

Abstract Introduction Immune checkpoint (IC) targeting is an attractive way to combat atherosclerosis, since ICs regulate the immune response by activating or inhibiting inflammatory pathways. We have shown that ICs exert cell-divergent functions and that cell-specific IC-based treatments can limit immune-related side effects. To design tailored IC-based immunotherapies for atherosclerosis, a detailed single-cell atlas of IC expression during atherogenesis is required. Purpose To obtain cell-type- and atherosclerosis-stage-specific expression profiles of ICs and assess the transcriptome of IC+ cells during atherosclerosis. Methods ApoE-/- mice were fed normal chow diet (NCD) for 10, 20 or 30 weeks, or high-cholesterol diet (HCD) for 6, 10, 14 (study 1) or 20 weeks (study 2). Using mass-cytometry by time of flight (CyTOF), we assessed the cell-type-specific aortic expression of ICs during atheroprogression (study 1). Using cellular indexing of transcriptomes and epitopes by sequencing (CITE-Seq), we assessed the transcriptome of aortic IC+ and IC- cells (study 2). Results Using CyTOF, we identified 21 immune cell clusters, including T and B cells, Ly6C- and Ly6C+ monocytes and macrophage (mφ) subsets. On T cell subsets, IC expression remained relatively constant in early plaques independent of the type of diet, apart from an increase in CD40-CD40L and decrease in CD28 and PD-L1 in HCD-fed mice. In advanced plaques from NCD-fed mice, most T cell subsets showed increased PD-L1, GITRL and CD27, while in HCD-fed mice, CD40L was decreased and PD-L1, PD-L2, CD27, CD86-CD28 and GITR-GITRL were induced on these T cell subsets. On myeloid cells, IC expression changed during early atherogenesis. Specifically, in NCD-fed mice, CD11c+MHCII+ mφ upregulated CD40 and PD-L1 and downregulated CD27 and PD-L2, while dendritic cells increased GITR and decreased PD-L2. Additional ICs, such as GITRL, CD40L and CD86-CD28, were induced in advanced plaques from NCD-fed mice. In HCD-fed mice, numerous ICs, i.e. CD40-CD40L, GITR-GITRL, CD86-CD28 and PD-L2, were increased in myeloid subsets in both early and advanced plaques. Using CITE-Seq, we further studied ICs that were strongly regulated during atherogenesis, e.g. GITR. Gene Ontology enrichment analysis of GITR+ and GITR- cells within the myeloid and T cell subsets identified the regulation of various pathways: When compared to their GITR- counterparts, both CD25- and CD25+ CD4+GITR+ T cell subsets showed upregulated pathways of death receptor activity, while CD25+ cells also showed induction of pathways involved in transmembrane lipid transporter activity. In mφ, GITR+ mφ showed upregulated pathways of cell adhesion and cytokine activity compared to GITR- mφ. Conclusion We have identified the expression pattern of numerous ICs on aortic immune cell subsets at various atherosclerosis stages. These data will pave the way towards the development of selective IC-based therapies to combat atherosclerosis.

Abstract Aims Recent studies have revealed a close connection between cellular metabolism and the chronic inflammatory process of atherosclerosis. While the link between systemic metabolism and atherosclerosis is well established, the implications of altered metabolism in the artery wall are less understood. Pyruvate dehydrogenase kinase (PDK)-dependent inhibition of pyruvate dehydrogenase (PDH) has been identified as a major metabolic step regulating inflammation. Whether the PDK/PDH axis plays a role in vascular inflammation and atherosclerotic cardiovascular disease remains unclear. Methods and results Gene profiling of human atherosclerotic plaques revealed a strong correlation between PDK1 and PDK4 transcript levels and the expression of pro-inflammatory and destabilizing genes. Remarkably, the PDK1 and PDK4 expression correlated with a more vulnerable plaque phenotype, and PDK1 expression was found to predict future major adverse cardiovascular events. Using the small-molecule PDK inhibitor dichloroacetate (DCA) that restores arterial PDH activity, we demonstrated that the PDK/PDH axis is a major immunometabolic pathway, regulating immune cell polarization, plaque development, and fibrous cap formation in Apoe−/− mice. Surprisingly, we discovered that DCA regulates succinate release and mitigates its GPR91-dependent signals promoting NLRP3 inflammasome activation and IL-1β secretion by macrophages in the plaque. Conclusions We have demonstrated for the first time that the PDK/PDH axis is associated with vascular inflammation in humans and particularly that the PDK1 isozyme is associated with more severe disease and could predict secondary cardiovascular events. Moreover, we demonstrate that targeting the PDK/PDH axis with DCA skews the immune system, inhibits vascular inflammation and atherogenesis, and promotes plaque stability features in Apoe−/− mice. These results point toward a promising treatment to combat atherosclerosis.

Abstract The advent of single-cell biology opens a new chapter for understanding human biological processes and for diagnosing, monitoring, and treating disease. This revolution now reaches the field of cardiovascular disease (CVD). New technologies to interrogate CVD samples at single-cell resolution are allowing the identification of novel cell communities that are important in shaping disease development and direct towards new therapeutic strategies. These approaches have begun to revolutionize atherosclerosis pathology and redraw our understanding of disease development. This review discusses the state-of-the-art of single-cell analysis of atherosclerotic plaques, with a particular focus on human lesions, and presents the current resolution of cellular subpopulations and their heterogeneity and plasticity in relation to clinically relevant features. Opportunities and pitfalls of current technologies as well as the clinical impact of single-cell technologies in CVD patient care are highlighted, advocating for multidisciplinary and international collaborative efforts to join the cellular dots of CVD.

Background Adolescents with chronic disease are often exposed to inflammatory, metabolic, and hemodynamic risk factors for early atherosclerosis. Since postmortem studies have shown that atherogenesis starts in the aorta, the CDACD (Cardiovascular Disease in Adolescents with Chronic Disease) study investigated preclinical aortic atherosclerosis in these adolescents. Methods and Results The cross‐sectional CDACD study enrolled 114 adolescents 12 to 18 years old with chronic disorders including juvenile idiopathic arthritis, cystic fibrosis, obesity, corrected coarctation of the aorta, and healthy controls with a corrected atrial septal defect. Cardiovascular magnetic resonance was used to assess aortic pulse wave velocity and aortic wall thickness, as established aortic measures of preclinical atherosclerosis. Cardiovascular magnetic resonance showed a higher aortic pulse wave velocity, which reflects aortic stiffness, and higher aortic wall thickness in all adolescent chronic disease groups, compared with controls ( P <0.05). Age (β=0.253), heart rate (β=0.236), systolic blood pressure (β=−0.264), and diastolic blood pressure (β=0.365) were identified as significant predictors for aortic pulse wave velocity, using multivariable linear regression analysis. Aortic wall thickness was predicted by body mass index (β=0.248) and fasting glucose (β=0.242), next to aortic lumen area (β=0.340). Carotid intima‐media thickness was assessed using ultrasonography, and was only higher in adolescents with coarctation of the aorta, compared with controls ( P <0.001). Conclusions Adolescents with chronic disease showed enhanced aortic stiffness and wall thickness compared with controls. The enhanced aortic pulse wave velocity and aortic wall thickness in adolescents with chronic disease could indicate accelerated atherogenesis. Our findings underscore the importance of the aorta for assessment of early atherosclerosis, and the need for tailored cardiovascular follow‐up of children with chronic disease.

Abstract Aims CD40 and its ligand, CD40L, play a critical role in driving atherosclerotic plaque development. Disrupted CD40-signalling reduces experimental atherosclerosis and induces a favourable stable plaque phenotype. We recently showed that small molecule-based inhibition of CD40-tumour necrosis factor receptor associated factor-6 interactions attenuates atherosclerosis in hyperlipidaemic mice via macrophage-driven mechanisms. The present study aims to detail the function of myeloid CD40 in atherosclerosis using myeloid-specific CD40-deficient mice. Method and Results Cd40flox/flox and LysM-cre Cd40flox/flox mice on an Apoe−/− background were generated (CD40wt and CD40mac−/−, respectively). Atherosclerotic lesion size, as well as plaque macrophage content, was reduced in CD40mac−/− compared to CD40wt mice, and their plaques displayed a reduction in necrotic core size. Transcriptomics analysis of the CD40mac−/− atherosclerotic aorta revealed downregulated pathways of immune pathways and inflammatory responses. Loss of CD40 in macrophages changed the representation of aortic macrophage subsets. Mass cytometry analysis revealed a higher content of a subset of alternative or resident-like CD206+CD209b− macrophages in the atherosclerotic aorta of CD40mac−/− compared to CD40wt mice. RNA-sequencing of bone marrow-derived macrophages of CD40mac−/− mice demonstrated upregulation of genes associated with alternatively activated macrophages (including Folr2, Thbs1, Sdc1, and Tns1). Conclusions We here show that absence of CD40 signalling in myeloid cells reduces atherosclerosis and limits systemic inflammation by preventing a shift in macrophage polarization towards pro-inflammatory states. Our study confirms the merit of macrophage-targeted inhibition of CD40 as a valuable therapeutic strategy to combat atherosclerosis.