The Prognostic, Diagnostic, and Therapeutic Potential of TRAIL Signalling in Cardiovascular Diseases.

TNF-related apoptosis-inducing ligand (TRAIL) was originally discovered, almost 20 years ago, for its ability to kill cancer cells. More recent evidence has described pleiotropic functions, particularly in the cardiovascular system. There is potential for TRAIL concentrations in the circulation to act as prognostic and/or diagnostic factors for cardiovascular diseases (CVD). Pre-clinical studies also describe the therapeutic capacity for TRAIL signals, particularly in the context of atherosclerotic disease and diseases of the myocardium. Because diabetes mellitus significantly contributes to the progression and pathogenesis of CVDs, in this review we highlight recent evidence for the prognostic, diagnostic, and therapeutic potential of TRAIL signals in CVDs, and where relevant, the impact of diabetes mellitus. A greater understanding of how TRAIL signals regulate cardiovascular protection and pathology may offer new diagnostic and therapeutic avenues for patients suffering from CVDs.

Sex, Endothelial Cell Functions, and Peripheral Artery Disease.

Peripheral artery disease (PAD) is caused by blocked arteries due to atherosclerosis and/or thrombosis which reduce blood flow to the lower limbs. It results in major morbidity, including ischemic limb, claudication, and amputation, with patients also suffering a heightened risk of heart attack, stroke, and death. Recent studies suggest women have a higher prevalence of PAD than men, and with worse outcomes after intervention. In addition to a potential unconscious bias faced by women with PAD in the health system, with underdiagnosis, and lower rates of guideline-based therapy, fundamental biological differences between men and women may be important. In this review, we highlight sexual dimorphisms in endothelial cell functions and how they may impact PAD pathophysiology in women. Understanding sex-specific mechanisms in PAD is essential for the development of new therapies and personalized care for patients with PAD.

Vascular transcriptome landscape of Trail-/- mice: Implications and therapeutic strategies for diabetic vascular disease.

Circulating plasma TRAIL levels are suppressed in patients with cardiovascular and diabetic diseases. To identify novel targets in vascular metabolic diseases, genome-wide transcriptome of aortic tissue from Trail-/- versus Trail+/+ mice were interrogated. We found 861 genes differentially expressed with TRAIL deletion. Gene enrichment analyses showed many of these genes were related to inflammation, cell-to-cell cytoskeletal interactions, and transcriptional modulation. We identified vascular protective and pathological gene clusters, with Ifi205 as the most significantly reduced vascular protective gene, whereas Glut1, the most significantly increased pathological gene with TRAIL deletion. We hypothesized that therapeutic targets could be devised from such integrated analysis and validated our findings from vascular tissues of diabetic mice. From the differentially expressed gene targets, enriched transcription factor (TF) and microRNA binding motifs were identified. The top two TFs were Elk1 and Sp1, with enrichment to eight gene targets common to both. miR-520d-3p and miR-377-3p were the top enriched microRNAs with TRAIL deletion; with four overlapping genes enriched for both microRNAs. Our findings offer an alternate in silico approach for therapeutic target identification and present a deeper understanding of gene signatures and pathways altered with TRAIL suppression in the vasculature.

A "Western Diet" promotes symptoms of hepatic steatosis in spontaneously hypertensive rats.

Systemic hypertension, characterized by elevated blood pressure ≥140/90 mm Hg, is a major modifiable risk factor for cardiovascular disease. Hypertension also associates with non-alcoholic fatty liver disease (NAFLD), which is becoming common due to a modern diet and lifestyle. The aim of the present study was to examine whether a high-fat "Western" diet had effects on hypertension and associated NAFLD. Normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) were placed on a normal chow or high-fat diet for 8 weeks; blood pressure was measured fortnightly and body weight recorded weekly. As expected, SHR had elevated blood pressure compared to WKY. Diet did not influence blood pressure. Compared to SHR, WKY rats gained more weight, associating with increased white adipose tissue weight. Normotensive rats also had higher plasma cholesterol and triglycerides in response to a "Western" diet, with no changes in plasma glucose levels. Neither strain developed atherosclerosis. Interestingly, high-fat diet-fed SHR had increased liver weight, associating with a significant level of hepatic lipid accumulation not observed in WKY. Further, they exhibited hepatocellular ballooning and increased hepatic inflammation, indicative of steatohepatitis. These findings suggest that a high-fat "Western" diet promotes features of NAFLD in SHR, but not WKY rats. Importantly, the high-fat diet had no effect on blood pressure.

Broad-spectrum chemokine inhibition blocks inflammation-induced angiogenesis, but preserves ischemia-driven angiogenesis.

M3 is a broad-spectrum chemokine-binding protein that inactivates inflammatory chemokines, including CCL2, CCL5, and CX3CL1. The aim of this study was to compare whether M3 could inhibit angiogenesis driven by inflammation or ischemia. Here, apolipoprotein E-/- mice were injected with adenoviral M3 (AdM3) or control adenoviral green fluorescent protein (AdGFP) 3 d prior to stimulating angiogenesis using 2 established models that distinctly represent inflammatory or ischemia-driven angiogenesis, namely the periarterial femoral cuff and hind limb ischemia. AdM3 reduced intimal thickening, adventitial capillary density, and macrophage accumulation in femoral arteries 21 d after periarterial femoral cuff placement compared with AdGFP-treated mice (P < 0.05). AdM3 also reduced mRNA expression of proangiogenic VEGF, inflammatory markers IL-6 and IL-1ß, and vascular smooth muscle cell (VSMC)-activated synthetic markers Krüppel-like family of transcription factor 4 (KLF4) and platelet-derived growth factor receptor ß (PDGFRß) in the inflammatory cuff model. In contrast, capillary density, VSMC content, blood flow perfusion, and VEGF gene expression were unaltered between groups in skeletal muscle following hind limb ischemia. In vitro, AdM3 significantly reduced human microvascular endothelial cell 1 proliferation, migration, and tubule formation by ∼17, 71.3, and 8.7% (P < 0.05) in macrophage-conditioned medium associating with reduced VEGF and hypoxia-inducible factor 1α mRNA but not in hypoxia (1% O2). Compared with AdGFP, AdM3 also inhibited VSMC proliferation and migration and reduced mRNA expression of KLF4 and PDGFRß under inflammatory conditions. In contrast, AdM3 had no effect on VSMC processes in response to hypoxia in vitro. Our findings show that broad-spectrum inhibition of inflammatory chemokines by M3 inhibits inflammatory-driven but not ischemia-driven angiogenesis, presenting a novel strategy for the treatment of diseases associated with inflammatory-driven angiogenesis.-Ravindran, D., Cartland, S. P., Bursill, C. A., Kavurma, M. M. Broad-spectrum chemokine inhibition blocks inflammation-induced angiogenesis, but preserves ischemia-driven angiogenesis.

HDL particle size is a critical determinant of ABCA1-mediated macrophage cellular cholesterol export.

RATIONALE: High-density lipoprotein (HDL) is a heterogeneous population of particles. Differences in the capacities of HDL subfractions to remove cellular cholesterol may explain variable correlations between HDL-cholesterol and cardiovascular risk and inform future targets for HDL-related therapies. The ATP binding cassette transporter A1 (ABCA1) facilitates cholesterol efflux to lipid-free apolipoprotein A-I, but the majority of apolipoprotein A-I in the circulation is transported in a lipidated state and ABCA1-dependent efflux to individual HDL subfractions has not been systematically studied. OBJECTIVE: Our aims were to determine which HDL particle subfractions are most efficient in mediating cellular cholesterol efflux from foam cell macrophages and to identify the cellular cholesterol transporters involved in this process. METHODS AND RESULTS: We used reconstituted HDL particles of defined size and composition, isolated subfractions of human plasma HDL, cell lines stably expressing ABCA1 or ABCG1, and both mouse and human macrophages in which ABCA1 or ABCG1 expression was deleted. We show that ABCA1 is the major mediator of macrophage cholesterol efflux to HDL, demonstrating most marked efficiency with small, dense HDL subfractions (HDL3b and HDL3c). ABCG1 has a lesser role in cholesterol efflux and a negligible role in efflux to HDL3b and HDL3c subfractions. CONCLUSIONS: Small, dense HDL subfractions are the most efficient mediators of cholesterol efflux, and ABCA1 mediates cholesterol efflux to small dense HDL and to lipid-free apolipoprotein A-I. HDL-directed therapies should target increasing the concentrations or the cholesterol efflux capacity of small, dense HDL species in vivo.

Comparative Evaluation of TRAIL, FGF-2 and VEGF-A-Induced Angiogenesis In Vitro and In Vivo.

Tumor necrosis-factor-related apoptosis-inducing ligand (TRAIL) has been implicated in angiogenesis; the growth of new blood vessels from an existing vessel bed. Our aim was to compare pro-angiogenic responses of TRAIL, vascular endothelial growth-factor-A (VEGF-A) and fibroblast growth-factor-2 (FGF-2) either separately (10 ng/mL) or in combination, followed by the assessment of proliferation, migration and tubule formation using human microvascular endothelial-1 (HMEC-1) cells in vitro. Angiogenesis was also measured in vivo using the Matrigel plug assay. TRAIL and FGF-2 significantly augmented HMEC-1 cell proliferation and migration, with combination treatment having an enhanced effect on cell migration only. In contrast, VEGF-A did not stimulate HMEC-1 migration at 10 ng/mL. Tubule formation was induced by all three factors, with TRAIL more effective compared to VEGF-A, but not FGF-2. TRAIL at 400 ng/mL, but not VEGF-A, promoted CD31-positive staining into the Matrigel plug. However, FGF-2 was superior, stimulating cell infiltration and angiogenesis better than TRAIL and VEGF-A in vivo. These findings demonstrate that each growth factor is more effective at different processes of angiogenesis in vitro and in vivo. Understanding how these molecules stimulate different processes relating to angiogenesis may help identify new strategies and treatments aimed at inhibiting or promoting dysregulated angiogenesis in people.

Cholesterol through the looking glass: ability of its enantiomer also to elicit homeostatic responses.

How cholesterol is sensed to maintain homeostasis has been explained by direct binding to a specific protein, Scap, or through altering the physical properties of the membrane. The enantiomer of cholesterol (ent-cholesterol) is a valuable tool in distinguishing between these two models because it shares nonspecific membrane effects with native cholesterol (nat-cholesterol), but not specific binding interactions. This is the first study to compare ent- and nat-cholesterol directly on major molecular parameters of cholesterol homeostasis. We found that ent-cholesterol suppressed activation of the master transcriptional regulator of cholesterol metabolism, SREBP-2, almost as effectively as nat-cholesterol. Importantly, ent-cholesterol induced a conformational change in the cholesterol-sensing protein Scap in isolated membranes in vitro, even when steps were taken to eliminate potential confounding effects from endogenous cholesterol. Ent-cholesterol also accelerated proteasomal degradation of the key cholesterol biosynthetic enzyme, squalene monooxygenase. Together, these findings provide compelling evidence that cholesterol maintains its own homeostasis not only via direct protein interactions, but also by altering membrane properties.

Endothelial cell dysfunction: Implications for the pathogenesis of peripheral artery disease.

Peripheral artery disease (PAD) is caused by occluded or narrowed arteries that reduce blood flow to the lower limbs. The treatment focuses on lifestyle changes, management of modifiable risk factors and vascular surgery. In this review we focus on how Endothelial Cell (EC) dysfunction contributes to PAD pathophysiology and describe the largely untapped potential of correcting endothelial dysfunction. Moreover, we describe current treatments and clinical trials which improve EC dysfunction and offer insights into where future research efforts could be made. Endothelial dysfunction could represent a target for PAD therapy.

HDL Improves Cholesterol and Glucose Homeostasis and Reduces Atherosclerosis in Diabetes-Associated Atherosclerosis.

BACKGROUND AND AIMS: Apolipoprotein A-I (ApoA-I), the main component of high-density lipoprotein (HDL), not only promotes reverse cholesterol transport (RCT) in atherosclerosis but also increases insulin secretion in pancreatic ß-cells, suggesting that interventions which raise HDL levels may be beneficial in diabetes-associated cardiovascular disease (CVD). Previously, we showed that TNF-related apoptosis-inducing ligand (TRAIL) deletion in Apolipoprotein Eknockout (Apoe-/- ) mice results in diabetes-accelerated atherosclerosis in response to a "Western" diet. Here, we sought to identify whether reconstituted HDL (rHDL) could improve features of diabetes-associated CVD in Trail-/-Apoe-/- mice. METHODS AND RESULTS: Trail-/-Apoe-/- and Apoe-/- mice on a "Western" diet for 12 weeks received 3 weekly infusions of either PBS (vehicle) or rHDL (containing ApoA-I (20 mg/kg) and 1-palmitoyl-2-linoleoyl phosphatidylcholine). Administration of rHDL reduced total plasma cholesterol, triglyceride, and glucose levels in Trail-/-Apoe-/- but not in Apoe-/- mice, with no change in weight gain observed. rHDL treatment also improved glucose clearance in response to insulin and glucose tolerance tests. Immunohistological analysis of pancreata revealed increased insulin expression/production and a reduction in macrophage infiltration in mice with TRAIL deletion. Furthermore, atherosclerotic plaque size in Trail-/-Apoe-/- mice was significantly reduced associating with increased expression of the M2 macrophage marker CD206, suggesting HDL's involvement in the polarization of macrophages. rHDL also increased vascular mRNA expression of RCT transporters, ABCA1 and ABCG1, in Trail-/-Apoe-/- but not in Apoe-/- mice. Conclusions. rHDL improves features of diabetes-associated atherosclerosis in mice. These findings support the therapeutic potential of rHDL in the treatment of atherosclerosis and associated diabetic complications. More studies are warranted to understand rHDL's mechanism of action.

ß 3 Adrenergic Receptor Stimulation Promotes Reperfusion in Ischemic Limbs in a Murine Diabetic Model.

Aims/Hypothesis: Peripheral arterial disease (PAD) is a major burden, resulting in limb claudication, repeated surgical interventions and amputation. There is an unmet need for improved medical management of PAD that improves quality of life, maintains activities of daily life and reduces complications. Nitric oxide (NO)/redox balance is a key regulator of angiogenesis. We have previously shown beneficial effects of a ß 3 adrenergic receptor (ß 3AR) agonist on NO/redox balance. We hypothesized that ß 3AR stimulation would have therapeutic potential in PAD by promoting limb angiogenesis. Methods: The effect of the ß 3AR agonist CL 316,243 (1-1,000 nmol/L in vitro, 1 mg/kg/day s. c) was tested in established angiogenesis assays with human endothelial cells and patient-derived endothelial colony forming cells. Post-ischemia reperfusion was determined in streptozotocin and/or high fat diet-induced diabetic and non-diabetic mice in vivo using the hind limb ischemia model. Results: CL 316,243 caused accelerated recovery from hind limb ischemia in non-diabetic and type 1 and 2 diabetic mice. Increased eNOS activity and decreased superoxide generation were detected in hind limb ischemia calf muscle from CL 316, 243 treated mice vs. controls. The protective effect of CL 316,243 in diabetic mice was associated with >50% decreases in eNOS glutathionylation and nitrotyrosine levels. The ß 3AR agonist directly promoted angiogenesis in endothelial cells in vitro. These pro-angiogenic effects were ß 3AR and NOS-dependent. Conclusion/Interpretation: ß 3AR stimulation increased angiogenesis in diabetic ischemic limbs, with demonstrable improvements in NO/redox balance and angiogenesis elicited by a selective agonist. The orally available ß 3AR agonist, Mirabegron, used for overactive bladder syndrome, makes translation to a clinical trial by repurposing of a ß 3AR agonist to target PAD immediately feasible.

Smart tissue culture: in situ monitoring of the activity of protease enzymes secreted from live cells using nanostructured photonic crystals.

Monitoring enzyme secretion in tissue culture has proved challenging because to date the activity cannot be continuously measured in situ. In this Letter, we present a solution using biopolymer loaded photonic crystals of anodized silicon. Shifts in the optical response by proteolytic degradation of the biopolymer provide label-free sensing with unprecedented low detection limits (1 pg) and calculation of kinetic parameters. The enhancement in sensitivity relative to previous photonic crystal sensors constitutes a change in the sensing paradigm because here the entire pore space is responsive to the secreted enzyme rather than just the pore walls. In situ monitoring is demonstrated by detecting secretion of matrix metalloprotease 9 from stimulated human macrophages.

TRAIL signals, extracellular matrix and vessel remodelling.

The extracellular matrix (ECM) is an essential part of the vasculature, not only providing structural support to the blood vessel wall, but also in its ability to interact with cells to regulate cell phenotype and function including proliferation, migration, differentiation and death - processes important in vascular remodelling. Increasing evidence implicates TNF-related apoptosis-inducing ligand (TRAIL) signalling in the modulation of vascular cell function and remodelling under normal and pathological conditions such as in atherosclerosis. TRAIL can also stimulate synthesis of multiple ECM components within blood vessels. This review explores the relationship between TRAIL signals, the ECM, and its implications in vessel remodelling in cardiovascular disease.

Selenomethionine supplementation reduces lesion burden, improves vessel function and modulates the inflammatory response within the setting of atherosclerosis.

Atherosclerosis is a chronic inflammatory disease of the vasculature characterised by the infiltration of activated neutrophils and macrophages at sites of damage within the vessel wall, which contributes to lesion formation and plaque progression. Selenomethionine (SeMet) is an organic form of selenium (Se), an essential trace element that functions in the regulation of the immune response by both bolstering the endogenous thioredoxin and glutathione antioxidant defence systems and by directly scavenging damaging oxidant species. This study evaluated the effect of dietary SeMet supplementation within a high fat diet fed apolipoprotein E deficient (ApoE-/-) mouse model of atherosclerosis. Dietary supplementation with SeMet (2 mg/kg) increased the tissue concentration of Se, and the expression and activity of glutathione peroxidase, compared to non-supplemented controls. Supplementation with SeMet significantly reduced atherosclerotic plaque formation in mouse aortae, resulted in a more stable lesion phenotype and improved vessel function. Concurrent with these results, SeMet supplementation decreased lesion accumulation of M1 inflammatory type macrophages, and decreased the extent of extracellular trap release from phorbol myristate acetate (PMA)-stimulated mouse bone marrow-derived cells. Importantly, these latter results were replicated within ex-vivo experiments on cultured neutrophils isolated from acute coronary syndrome patients, indicating the ability of SeMet to alter the acute inflammatory response within a clinically-relevant setting. Together, these data highlight the potential beneficial effect of SeMet supplementation as a therapeutic strategy for atherosclerosis.

Caveolin-1-dependent and -independent membrane domains.

Lipid rafts defined as cholesterol- and sphingomyelin-rich domains have been isolated from different cell types that vary greatly in their lipid profiles. Here, we investigated the contribution of the structural protein caveolin-1 (Cav1) to the overall lipid composition and domain abundance in mouse embryonic fibroblasts (MEFs) from wild-type (WT) or Cav1-deficient (Cav1(-/-)) animals. Our findings show that Cav1 expression had no effect on free (membrane-associated) cholesterol levels. However, Cav1(-/-)-deficient cells did have a higher proportion of sphingomyelin, decreased abundance of unsaturated phospholipids, and a trend toward shorter fatty acid chains in phosphatidylcholine. We isolated detergent-resistant membranes (DRMs), nondetergent raft domains (NDR), and cholesterol oxidase (CO)-sensitive domains and assessed the abundance of ordered domains in intact cells using the fluorescent dye Laurdan. Despite differences in phospholipid composition, we found that cholesterol levels in DRMs, NDR, and CO-sensitive domains were similar in both cell types. The data suggest that Cav1 is not required to target cholesterol to lipid rafts and that CO does not specifically oxidize caveolar cholesterol. In contrast, the abundance of ordered domains in adherent cells is reduced in Cav1(-/-) compared with WT MEFs, suggesting that cell architecture is critical in maintaining Cav1-induced lipid rafts.

Tumour necrosis factor superfamily members in ischaemic vascular diseases.

Current treatment of ischaemic vascular diseases such as coronary and peripheral artery disease includes angioplasty and bypass grafting, as well as lipid lowering therapies and control of other cardiovascular risk factors. Numerous members of the tumour necrosis factor superfamily (TNFSF) have recently shown emerging roles in both the protection and progression of such diseases. Understanding the role TNFSF members play in ischaemic vascular disease may provide insight into the development of novel therapeutics to prevent or treat diseases relating to atherosclerosis and ischaemia. This review summarizes the most recent findings relating to TNFSF members and the mechanisms that precede ischaemic vascular disease progression, particularly endothelial dysfunction, chronic inflammation, and atherosclerotic plaque development. This review also explores recent translational research on the role of TNFSF therapies in cardiovascular disease.

Microglia in the RVLM of SHR have reduced P2Y12R and CX3CR1 expression, shorter processes, and lower cell density.

The RVLM of spontaneously hypertensive rats (SHR) contains over-active C1 neurons, which model the pathology of essential hypertension. Hypertension involves chronic low-grade neuroinflammation. Inflammation in the brain is produced and maintained primarily by microglia. We assessed microglial gene expression (P2Y12R and CX3CR1) and morphology in the RVLM of SHR compared to normotensive Wistar-Kyoto rats (WKY). The gene expression of the metabotropic purinergic receptor P2Y12 and the fractalkine receptor CX3CR1 was downregulated in the RVLM of SHR compared to WKY (by 37.3% and 30.9% respectively). P2Y12R and CX3CR1 are required for normal microglial function, and reduced P2Y12R expression is associated with changes in microglial activity. Histological analysis showed a 22.9% reduction in microglial cell density, along with 18.7% shorter microglial processes, a phenotypic indicator of activation, in the RVLM of SHR compared to WKY. These results indicate a subtle loss of function, or a mild state of inflammation, in the RVLM microglia of SHR.

Colchicine as a Novel Therapy for Suppressing Chemokine Production in Patients With an Acute Coronary Syndrome: A Pilot Study.

PURPOSE: Existing literature reports that colchicine inhibits inflammasome activation and downstream inflammatory cytokine production and stabilizes coronary plaque. However, colchicine's effect on chemokines, which orchestrate multiple atheroinflammatory pathways, is unknown. METHODS: Patients with acute coronary syndrome (ACS) were randomly assigned to colchicine (1.5 mg PO) (n = 12; mean age, 65.2 years) or no treatment (n = 13; mean age, 62.2 years). Blood samples were collected during cardiac catheterization within 24 hours of colchicine administration from the coronary sinus, aortic root, and right atrium. Patients with colchicine-naive stable angina (SAP) (n = 13; mean age, 66.8 years) were additionally sampled. Serum chemokine levels were analyzed with ELISA. In parallel, monocytes from healthy donors were isolated and subjected to colchicine treatment. FINDINGS: Transcoronary (TC) levels of chemokine ligand 2 (CCL2) and C-X3-C motif chemokine ligand 1 (CX3CL1) were significantly elevated in patients with ACS versus patients with SAP (P < 0.01). TC chemokine ligand 5 (CCL5) levels were not significantly (P = 0.084) elevated in patients with ACS versus patients with SAP. Colchicine treatment markedly reduced TC levels of CCL2, CCL5, and CX3CL1 in patients with ACS (P < 0.05). In vitro colchicine suppressed CCL2 gene expression in stimulated monocytes (P < 0.05). Colchicine treatment reduced the intracellular concentration of all 3 chemokines (P < 0.01) and impaired monocyte chemotaxis (P < 0.05). IMPLICATIONS: Here, we report for the first time that short-term colchicine therapy significantly reduces the local production of coronary chemokines, in part by attenuating production of these mediators by monocytes. These data provide further evidence of colchicine's beneficial role in patients with ACS.

A Nanoparticle-Based Affinity Sensor that Identifies and Selects Highly Cytokine-Secreting Cells.

We developed a universal method termed OnCELISA to detect cytokine secretion from individual cells by applying a capture technology on the cell membrane. OnCELISA uses fluorescent magnetic nanoparticles as assay reporters that enable detection on a single-cell level in microscopy and flow cytometry and fluorimetry in cell ensembles. This system is flexible and can be modified to detect different cytokines from a broad range of cytokine-secreting cells. Using OnCELISA we have been able to select and sort highly cytokine-secreting cells and identify cytokine-secreting expression profiles of different cell populations in vitro and ex vivo. We show that this system can be used for ultrasensitive monitoring of cytokines in the complex biological environment of atherosclerosis that contains multiple cell types. The ability to identify and select cell populations based on their cytokine expression characteristics is valuable in a host of applications that require the monitoring of disease progression.

TRAIL-Expressing Monocyte/Macrophages Are Critical for Reducing Inflammation and Atherosclerosis.

Circulating tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) levels are reduced in patients with cardiovascular disease, and TRAIL gene deletion in mice exacerbates atherosclerosis and inflammation. How TRAIL protects against atherosclerosis and why levels are reduced in disease is unknown. Here, multiple strategies were used to identify the protective source of TRAIL and its mechanism(s) of action. Samples from patients with coronary artery disease and bone-marrow transplantation experiments in mice lacking TRAIL revealed monocytes/macrophages as the main protective source. Accordingly, deletion of TRAIL caused a more inflammatory macrophage with reduced migration, displaying impaired reverse cholesterol efflux and efferocytosis. Furthermore, interleukin (IL)-18, commonly increased in plasma of patients with cardiovascular disease, negatively regulated TRAIL transcription and gene expression, revealing an IL-18-TRAIL axis. These findings demonstrate that TRAIL is protective of atherosclerosis by modulating monocyte/macrophage phenotype and function. Manipulating TRAIL levels in these cells highlights a different therapeutic avenue in the treatment of cardiovascular disease.