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

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

Organ weights, blood and urine measurements from ApoE^-/- and TRAIL^-/-ApoE^-/- mice after 20 w HFD.

<p>Measurements are from n = 7–11 mice per group. Results are expressed as mean ± SEM, *p< 0.05 and **p<0. 01, by Mann-Whitney U test.</p

Body weights, plasma glucose and insulin levels in HFD-fed ApoE^-/- and TRAIL^-/-ApoE^-/- mice.

<p>Measurements are from n = 5–11 mice per group. Results are expressed as mean ± SEM, *p<0.05 and ****p<0. 0001, by Mann-Whitney U test.</p

TRAIL Deficiency Contributes to Diabetic Nephropathy in Fat-Fed ApoE^-/- Mice

<div><p>Background</p><p>We recently demonstrated that TNF-related apoptosis-inducing ligand (TRAIL) is protective of diet-induced diabetes in mice. While TRAIL has been implicated in chronic kidney disease, its role <i>in vivo</i> in diabetic nephropathy is not clear. The present study investigated the role of TRAIL in the pathogenesis of diabetic nephropathy using TRAIL^-/-ApoE^-/- mice.</p><p>Methods</p><p>TRAIL^-/-ApoE^-/- and ApoE^-/- mice were fed a high fat diet for 20 w. Plasma glucose and insulin levels were assessed over 0, 5, 8 and 20 w. At 20 w, markers of kidney function including creatinine, phosphate, calcium and cystatin C were measured. Changes in mRNA expression of MMPs, TIMP-1, IL-1β and IL-18 were assessed in the kidney. Functional and histological changes in kidneys were examined. Glucose and insulin tolerance tests were performed.</p><p>Results</p><p>TRAIL^-/-ApoE^-/- mice had significantly increased urine protein, urine protein:creatinine ratio, plasma phosphorous, and plasma cystatin C, with accelerated nephropathy. Histologically, increased extracellular matrix, mesangial expansion and mesangial cell proliferation in the glomeruli were observed. Moreover, TRAIL^-/-ApoE^-/- kidneys displayed loss of the brush border and disorganisation of tubular epithelium, with increased fibrosis. TRAIL-deficient kidneys also had increased expression of MMPs, TIMP-1, PAI-1, IL-1β and IL-18, markers of renal injury and inflammation. Compared with ApoE^-/- mice, TRAIL^-/-ApoE^-/- mice displayed insulin resistance and type-2 diabetic features with reduced renal insulin-receptor expression.</p><p>Conclusions</p><p>Here, we show that TRAIL-deficiency in ApoE^-/- mice exacerbates nephropathy and insulin resistance. Understanding TRAIL signalling in kidney disease and diabetes, may therefore lead to novel strategies for the treatment of diabetic nephropathy.</p></div

Kidneys from TRAIL^-/-ApoE^-/- mice have increased expression of genes indicative of fibrosis.

<p>mRNA expression for (a) fibronectin, (b) PAI-1, (c) TIMP-1, (d) MMP-2 and (e) MMP-9 from kidneys. All levels were normalized to β-actin; n = 6/ genotype. Results are expressed as mean ± SEM, *p<0.05 and **p<0.01 by Mann-Whitney U test.</p

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

TRAIL^-/-ApoE^-/- mice have increased macrophage infiltration and genes of inflammation.

<p>Representative sections (40X magnification) of mouse kidney after 20 w HFD stained for the pan macrophage marker (a) F4/80. Kidney mRNA expression for (b) IL-1β, (c) IL-18, (d) osteopontin (e) PPAR-γ and (f) TNF-α. All levels were normalized to β-actin; n = 5-6/genotype. Results expressed as mean ± SEM, *p<0.05, **p<0.01 and ****p<0.0001 by Mann-Whitney U test.</p