Bosmans, Laura A.

Abstract Background Patients with cancer treated with immune checkpoint inhibitors are at increased risk of myocardial infarction and ischemic stroke. The mechanism is incompletely understood but may involve accelerated atherosclerosis due to plaque inflammation. Pre-clinical studies may provide insight in these mechanisms. Aim To assess the effects of modulating co-inhibitory immune checkpoint proteins on atherosclerosis progression in animal models. Methods A systematic review was performed in MEDLINE, Embase, Web of Science, and Scopus up to September 2023. Animal studies were included if the effect of modulation of programmed cell death protein 1 (PD-1), programmed death-ligand 1 (PD-L1), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), and/or lymphocyte-activation gene 3 (LAG-3) on atherosclerotic plaque size was evaluated. Secondary outcomes were plaque composition and systemic inflammation. The ratios of means (RoM) across the studies were pooled in a random effects meta-analysis. Results 1,655 studies were identified of which twelve were included. All studies used an atherosclerotic mouse model (Apoe-/-, Ldlr-/-, or ApoE3*Leiden) and either evaluated pharmacological or genetic modulation of co-inhibitory immune checkpoint proteins. Upon inhibition, atherosclerotic plaque size in the aorta was 49% higher in exposed mice compared to control mice (RoM, 1.49; 95% CI, 1.12-1.82; I2=86%). Plaque composition was predominantly characterized by a greater abundance of CD4+ T cells, CD8+ T cells, and macrophages. Studies stimulating co-inhibitory immune checkpoint proteins corroborated these findings and demonstrated that atherosclerotic plaque size was reduced by 28% in treated mice compared to controls (RoM, 0.72; 95% CI, 0.65-0.80; I2=85%). This reduction was paralleled by a decrease in the number of macrophages and T cells in plaques. Conclusion Immune checkpoint inhibition leads to plaque inflammation and a significant increase in murine atherosclerotic plaque size. These changes may reflect the cause of the increased risk of myocardial infarction and ischemic stroke in patients treated with immune checkpoint inhibitors.

Background Atherosclerosis is highly prevalent in people with chronic kidney disease (CKD), including those receiving peritoneal dialysis (PD). Although it is lifesaving, PD induces profound systemic inflammation, which may aggravate atherosclerosis. Therefore, the hypothesis is that this PD‐induced inflammation aggravates atherosclerosis via immune cell activation. Methods and Results ApoE −/− mice were subjected to a 5/6 nephrectomy to induce CKD. Three weeks later, mice were fed a high‐cholesterol diet. Half of the nephrectomized mice then received daily peritoneal infusions of 3.86% Physioneal for 67 further days (CKD+PD) until the end of the experiment, and were compared with mice without CKD. Sham operated and PD‐only mice were additional controls. CKD+PD mice displayed more severe atherosclerotic disease than control mice. Plaque area increased, and plaques were more advanced with a vulnerable phenotype typified by decreased collagen content and decreased fibrous cap thickness. Increased CD3 + T‐cell numbers were present in plaques and perivascular adipose tissue of CKD and CKD+PD mice. Plaques of CKD+PD mice contained more iNOS + immune cells. Spleens of CKD+PD mice showed more CD4 + central memory, terminally differentiated type 1 T‐helper (Th1), Th17, and CX3C motif chemokine receptor 1 + (CX3CR1) CD4 + T‐cells with less regulatory and effector T‐cells. Conclusions PD‐fluid exposure in uremic mice potentiates systemic and vascular T‐cell‐driven inflammation and aggravates atherosclerosis. PD polarized CD4 + T‐cells toward an inflammatory Th1/Th17 phenotype, and increased CX3CR1 + CD4 + T‐cells, which are associated with vascular homing in CKD‐associated atherosclerosis. Targeting CD4 + T‐cell activation and CX3CR1 + polarization has the potential to attenuate atherosclerosis in PD patients.

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 Background Atherosclerosis is a chronic inflammatory disease, characterized by the formation of luminal plaques in arteries. Atheroprogression is accompanied by strong immune activation, during which T cells play a pivotal role. Genes driving T-cell activation are regulated by the polycomb repressive complex 2(PRC2), whose major component is the Enhancer of Zeste Homolog 2(EZH2), responsible for the methylation of Histone 3 Lysine 27(H3K27me3) epigenetic mark. Purpose We hypothesize that EZH2 mediates T-cell activation and modulates T-helper (Th) cell polarization, thus atherogenesis. Methods To study the effect of EZH2 in atherosclerosis, we backcrossed mice with Ezh2 flanked by loxP-sites sensitive to Cre-mediated inactivation in T cells to apolipoprotein E (Apoe-/-)mice and fed a high cholesterol diet to have hyperlipidemic Ezh2fl/flCd4CreApoe-/-mice and controls. Atherosclerotic plaque progression and immune cell phenotyping were assessed by histology, flow cytometry (FC), gene and protein expression analysis and single cell (sc)RNA-sequencing (Seq) as well as by functional in vitro assays. Results T cell-specific EZH2 deficiency resulted in a significant reduction in H3K27me3 in T-cells. Female Ezh2fl/flCd4Cre mice developed 34% less atherosclerotic plaques in the aortic root compared to wildtype (WT) littermates. FC analysis of spleen and lymph nodes of Ezh2fl/flCd4Cre mice revealed a shift from naive to effector CD4+ T cells, and the majority were Th2 cells (p<0.0001). Accordingly, plasma levels of lL4 and aortic IL4 transcripts were increased in Ezh2fl/flCd4Cre mice(p=0.05 and p=0.0079, respectively). Functional analysis revealed that splenic CD4+ T cells from Ezh2fl/flCd4Cre mice showed decreased migratory capacity towards the chemokines CXCL10, CCL17, CCL22, CCL19. To unravel mechanisms driving the type 2 immune response, bulk RNA-Seq of CD4+ T cells and scRNA-Seq of splenic CD3+ T cells from Ezh2fl/flCd4Cre and WT mice revealed that CD4+ T cell EZH2 deficiency caused upregulation of promyelocytic leukemia zinc finger (Plzf), a transcription factor of NKT cells of the NKT2 subtype, characterized by high IL4 production. Via FC we confirmed the increase in splenic NKT cells in Ezh2fl/flCd4Cre mice. Likewise, Plzf aortic mRNA levels were also significantly increased(p=0.002). To exploit the translational potential of T cell-specific EZH2 targeting, we treated Jurkat T cells with EZH2 inhibitors, the FDA-approved drug Tazemetostat and GSK126. Corroborating our in vivo data, EZH2 inhibitor-treated cells showed decreased H3K27me3 and 70% reduced migration towards the chemokine CXCL12. Conclusions Our study demonstrates that CD4+ T-cell specific EZH2 deficiency impairs T cell-migration and skews the immune response towards a type 2 response, resulting in protection against atherosclerosis. We aim at investigating whether the epigenetic mark H3K27me3 in T cells may be a promising therapeutic target for future cardiovascular immunotherapies.

Abstract Background and Aims Inflammation is an established contributor to accelerated atherosclerosis, which is highly prevalent in people with chronic kidney disease (CKD) and even more so in those treated with peritoneal dialysis (PD). We therefore hypothesised that PD-induced systemic inflammation is essential in the development of atherosclerosis. To study this we developed a novel mouse model of CKD and PD accelerated atherosclerosis. Method We performed a 5/6ths nephrectomy in ApoE deficient “black 6” mice, fed these mice a high-cholesterol diet (HCD), and intraperitoneally administered 3.86% Physioneal daily for 67 days. There were three groups of mice: control (HCD-only), CKD+HCD, and CKD+HCD+PD, with relevant shams. Tissues were harvested twelve weeks after the nephrectomy. Assessments of residual kidney function, atherosclerotic plaque pathology and immunology, and systemic immune responses were performed. Results Atherosclerotic plaque size in the aortic arch was larger in the PD group compared to the control, increasing from 83,779 μm2 ±18,430 to 109,973 μm2 ±25,602 (p = 0.0349), whilst plaque size was unchanged in the CKD group. In contrast, both the CKD and PD groups displayed altered plaque stability. There was less collagen in the plaque vs control, decreasing from 43.54% ±10.65 to 29.71% ±9.43 and 29.73% ±10.18 respectively. Additionally, fibrous cap thickness decreased in both groups vs control. The plaques from only the PD group showed infiltration by T-cells compared to control, with no changes in macrophage content in either the CKD or PD group. In the spleen in the CKD and PD groups, naïve CD4 cells increased and effector CD4 cells decreased compared to control, with the latter change also occurring in the circulation. Central memory CD4 cells, terminally differentiated Th1 cells, Th17 cells, and ‘vascular homing’ cells all increased in the PD group compared to control mice. These homing cells also increased in circulation. The PD group showed decreases in the spleen of regulatory T-cells, effector Th1 cells, and effector CD8 cells. Notably, all of these changes were absent from the mesenteric lymph node. There was a large drop in monocytes in the spleen and a loss of immature and mature dendritic cells in the PD group. Conclusion Combining CKD, a high-cholesterol diet, and exposure to PD fluids in ApoE−/-mice successfully generated a new model for cardiovascular disease in human PD patients. This new model is in a widespread and well-understood mouse line representative of human atherosclerosis. Here we demonstrate the pronounced effects of CKD and PD on the innate and adaptive immune response which increases atherosclerotic burden and leads to larger more vulnerable plaques

Abstract Aims Hyperlipidemia and T cell driven inflammation are important drivers of atherosclerosis, the main underlying cause of cardiovascular disease. Here, we detailed the effects of hyperlipidemia on T cells. Methods and results In vitro, exposure of human and murine CD4+ T cells to very low-density lipoprotein (VLDL), but not to low-density lipoprotein (LDL) resulted in upregulation of Th1 associated pathways. VLDL was taken up via a CD36-dependent pathway and resulted in membrane stiffening and a reduction in lipid rafts. To further detail this response in vivo, T cells of mice lacking the LDL receptor (LDLr), which develop a strong increase in VLDL cholesterol and triglyceride levels upon high cholesterol feeding were investigated. CD4+ T cells of hyperlipidemic Ldlr-/- mice exhibited an increased expression of the C-X-C-chemokine receptor 3 (CXCR3) and produced more interferon-γ (IFN-γ). Gene set enrichment analysis identified IFN-γ-mediated signaling as the most upregulated pathway in hyperlipidemic T cells. However, the classical Th1 associated transcription factor profile with strong upregulation of Tbet and Il12rb2 was not observed. Hyperlipidemia did not affect levels of the CD4+ T cell's metabolites involved in glycolysis or other canonical metabolic pathways but enhanced amino acids levels. However, CD4+ T cells of hyperlipidemic mice showed increased cholesterol accumulation and an increased arachidonic acid (AA) to docosahexaenoic acid (DHA) ratio, which was associated with inflammatory T cell activation. Conclusions Hyperlipidemia, and especially its VLDL component induces an atypical Th1 response in CD4+ T cells. Underlying mechanisms include CD36 mediated uptake of VLDL, and an altered AA/DHA ratio.

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.

Abstract Background Galectins have numerous cellular functions in immunity and inflammation. Short-term galectin-2 (Gal-2) blockade in ischemia-induced arteriogenesis shifts macrophages to an anti-inflammatory phenotype and improves perfusion. Gal-2 may also affect other macrophage-related cardiovascular diseases. Objectives This study aims to elucidate the effects of Gal-2 inhibition in atherosclerosis. Methods ApoE −/− mice were given a high-cholesterol diet (HCD) for 12 weeks. After 6 weeks of HCD, intermediate atherosclerotic plaques were present. To study the effects of anti-Gal-2 nanobody treatment on the progression of existing atherosclerosis, treatment with two llama-derived anti-Gal-2 nanobodies (clones 2H8 and 2C10), or vehicle was given for the remaining 6 weeks. Results Gal-2 inhibition reduced the progression of existing atherosclerosis. Atherosclerotic plaque area in the aortic root was decreased, especially so in mice treated with 2C10 nanobodies. This clone showed reduced atherosclerosis severity as reflected by a decrease in fibrous cap atheromas in addition to decreases in plaque size.The number of plaque resident macrophages was unchanged; however, there was a significant increase in the fraction of CD206+ macrophages. 2C10 treatment also increased plaque α-smooth muscle content, and Gal-2 may have a role in modulating the inflammatory status of smooth muscle cells. Remarkably, both treatments reduced serum cholesterol concentrations including reductions in very low-density lipoprotein, low-density lipoprotein, and high-density lipoprotein while triglyceride concentrations were unchanged. Conclusion Prolonged and frequent treatment with anti-Gal-2 nanobodies reduced plaque size, slowed plaque progression, and modified the phenotype of plaque macrophages toward an anti-inflammatory profile. These results hold promise for future macrophage modulating therapeutic interventions that promote arteriogenesis and reduce atherosclerosis.