Fatty acid binding protein 4 in circulating leucocytes reflects atherosclerotic lesion progression in Apoe(-/-) mice

Biopharmaceutic

Subclinical leaflet thrombosis after transcatheter aortic valve implantation: no association with left ventricular reverse remodeling at 1-year follow-up

Hypo-attenuated leaflet thickening (HALT) of transcatheter aortic valves is detected on multidetector computed tomography (MDCT) and reflects leaflet thrombosis. Whether HALT affects left ventricular (LV) reverse remodeling, a favorable effect of LV afterload reduction after transcatheter aortic valve implantation (TAVI) is unknown. The aim of this study was to examine the association of HALT after TAVI with LV reverse remodeling. In this multicenter case-control study, patients with HALT on MDCT were identified, and patients without HALT were propensity matched for valve type and size, LV ejection fraction (LVEF), sex, age and time of scan. LV dimensions and function were assessed by transthoracic echocardiography before and 12 months after TAVI. Clinical outcomes (stroke or transient ischemic attack, heart failure hospitalization, new-onset atrial fibrillation, all-cause mortality) were recorded. 106 patients (age 81 +/- 7 years, 55% male) with MDCT performed 37 days [IQR 32-52] after TAVI were analyzed (53 patients with HALT and 53 matched controls). Before TAVI, all echocardiographic parameters were similar between the groups. At 12 months follow-up, patients with and without HALT showed a significant reduction in LV end-diastolic volume, LV end-systolic volume and LV mass index (from 125 +/- 37 to 105 +/- 46 g/m(2), p = 0.001 and from 127 +/- 35 to 101 +/- 27 g/m(2), p < 0.001, respectively, p for interaction = 0.48). Moreover, LVEF improved significantly in both groups. In addition, clinical outcomes were not statistically different. Improvement in LVEF and LV reverse remodeling at 12 months after TAVI were not limited by HALT.Cardiolog

Deficiency of the T cell regulator Casitas B-cell lymphoma-B aggravates atherosclerosis by inducing CD8+ T cell-mediated macrophage death

The E3-ligase CBL-B (Casitas B-cell lymphoma-B) is an important negative regulator of T cell activation that is also expressed in macrophages. T cells and macrophages mediate atherosclerosis, but their regulation in this disease remains largely unknown; thus, we studied the function of CBL-B in atherogenesis.The expression of CBL-B in human atherosclerotic plaques was lower in advanced lesions compared with initial lesions and correlated inversely with necrotic core area. Twenty weeks old Cblb−/−Apoe−/− mice showed a significant increase in plaque area in the aortic arch, where initial plaques were present. In the aortic root, a site containing advanced plaques, lesion area rose by 40%, accompanied by a dramatic change in plaque phenotype. Plaques contained fewer macrophages due to increased apoptosis, larger necrotic cores, and more CD8+ T cells. Cblb−/−Apoe−/− macrophages exhibited enhanced migration and increased cytokine production and lipid uptake. Casitas B-cell lymphoma-B deficiency increased CD8+ T cell numbers, which were protected against apoptosis and regulatory T cell-mediated suppression. IFNγ and granzyme B production was enhanced in Cblb−/−Apoe−/− CD8+ T cells, which provoked macrophage killing. Depletion of CD8+ T cells in Cblb−/−Apoe−/− bone marrow chimeras rescued the phenotype, indicating that CBL-B controls atherosclerosis mainly through its function in CD8+ T cells. Casitas B-cell lymphoma-B expression in human plaques decreases during the progression of atherosclerosis. As an important regulator of immune responses in experimental atherosclerosis, CBL-B hampers macrophage recruitment and activation during initial atherosclerosis and limits CD8+ T cell activation and CD8+ T cell-mediated macrophage death in advanced atherosclerosis, thereby preventing the progression towards high-risk plaques.Biopharmaceutic

Phenotypic Modulation of Smooth Muscle Cells in Atherosclerosis is Associated with Downregulation of LMOD1, SYNPO2, PDLIM7, PLN, and SYNM

Objective-Key augmented processes in atherosclerosis have been identified, whereas less is known about downregulated pathways. Here, we applied a systems biology approach to examine suppressed molecular signatures, with the hypothesis that they may provide insight into mechanisms contributing to plaque stability. Approach and Results-Muscle contraction, muscle development, and actin cytoskeleton were the most downregulated pathways (false discovery rate=6.99e-21, 1.66e-6, 2.54e-10, respectively) in microarrays from human carotid plaques (n=177) versus healthy arteries (n=15). In addition to typical smooth muscle cell (SMC) markers, these pathways also encompassed cytoskeleton-related genes previously not associated with atherosclerosis. SYNPO2, SYNM, LMOD1, PDLIM7, and PLN expression positively correlated to typical SMC markers in plaques (Pearson r>0.6, P0.8, P<0.0001). By immunohistochemistry, the proteins were expressed in SMCs in normal vessels, but largely absent in human plaques and intimal hyperplasia. Subcellularly, most proteins localized to the cytoskeleton in cultured SMCs and were regulated by active enhancer histone modification H3K27ac by chromatin immunoprecipitationsequencing. Functionally, the genes were downregulated by PDGFB (platelet-derived growth factor beta) and IFNg (interferron gamma), exposure to shear flow stress, and oxLDL (oxidized low-density lipoprotein) loading. Genetic variants in PDLIM7, PLN, and SYNPO2 loci associated with progression of carotid intima-media thickness in high-risk subjects without symptoms of cardiovascular disease (n=3378). By eQTL (expression quantitative trait locus), rs11746443 also associated with PDLIM7 expression in plaques. Mechanistically, silencing of PDLIM7 in vitro led to downregulation of SMC markers and disruption of the actin cytoskeleton, decreased cell spreading, and increased proliferation. Conclusions-We identified a panel of genes that reflect the altered phenotype of SMCs in vascular disease and could be early sensitive markers of SMC dedifferentiation

Vascular Remodeling in Health and Disease

The term vascular remodeling is commonly used to define the structural changes in blood vessel geometry that occur in response to long-term physiologic alterations in blood flow or in response to vessel wall injury brought about by trauma or underlying cardiovascular diseases.1, 2, 3, 4 The process of remodeling, which begins as an adaptive response to long-term hemodynamic alterations such as elevated shear stress or increased intravascular pressure, may eventually become maladaptive, leading to impaired vascular function. The vascular endothelium, owing to its location lining the lumen of blood vessels, plays a pivotal role in regulation of all aspects of vascular function and homeostasis.5 Thus, not surprisingly, endothelial dysfunction has been recognized as the harbinger of all major cardiovascular diseases such as hypertension, atherosclerosis, and diabetes.6, 7, 8 The endothelium elaborates a variety of substances that influence vascular tone and protect the vessel wall against inflammatory cell adhesion, thrombus formation, and vascular cell proliferation.8, 9, 10 Among the primary biologic mediators emanating from the endothelium is nitric oxide (NO) and the arachidonic acid metabolite prostacyclin [prostaglandin I2 (PGI2)], which exert powerful vasodilatory, antiadhesive, and antiproliferative effects in the vessel wall

Blocking cysteinyl leukotriene signalling ameliorates myocardial hypoxia in chronic ischemic heart disease

Background: The involvement of cysteinyl leukotrienes (cys-LTs) and their receptors (CysLTs receptor) in the pathologic response to chronic cardiac ischemia and during bouts of ischemia remains an unresolved question. Objective: We investigated the expression of cys-LT pathway components in normal and ischemic myocardium and the potential benefits of interrupting cys-LT signalling during bouts of ischemia. Methods and Results: Heart biopsies were collected from C57BL/6J control mice and Apoe-/- mice fed a hypercholesterolemic diet for 1 year and subjected to an hypoxic stimulus for 30 minutes. Contribution of leukotriene signalling to cardiac ischemia induced by hypoxia was evaluated by administration of montelukast, a selective CysLT1 receptor antagonist. We also used a unique collection of human heart biopsies obtained from normal and chronic ischemic areas of the myocardium of 14 patients with chronic coronary artery disease. Here we report that in myocardium of Apoe-/- mice, leukotriene C4 synthase (LTC4S) and CysLT1 are upregulated compared to C57BL/6J. Acute hypoxia further induced LTC4S expression and enzyme activity along with increased CysLT1 expression. Similar mRNA expression patterns of LTC4S and CysLT1 were observed in non-ischemic versus chronic ischemic human myocardium. Treatment of Apoe-/- mice with montelukast, during acute hypoxic stress, ameliorated myocardial hypoxic load to levels equal to those observed under normoxia. Conclusions: The data show an increased leukotriene signalling in chronic ischemic myocardium. In an experimental Apoe-/- model of ischemic cardiomyopathy, inhibition of leukotriene signalling ameliorates hypoxic damage to the myocardium suggesting a possible beneficial effect of antileukotriene drugs on the ischemic heart. Figure 1: LTC4S and CysLT1 are upregulated in cardiac tissue of Apoe-/- mice In the -/-Apoe-/- heart levels of LTC4S and CysLT1 are significantly upregulated as compared to control C57BL/6J mice (Panel A). Acute hypoxic stress in Apoe-/- mice increases the cardiac expression of LTC4S (p<0.05) and CysLT1 (p=0.06) compared to normoxic conditions (Panel B). Each experiment was run in duplicate and changes in mRNA levels were expressed as \u394\u394Ct values. Values are mean \ub1 SD. *, p<0.05; **, p<0.01. References. [1] Gabrielsen A, Lawler PR, Yongzhong W, et al., Gene expression signals involved in ischemic injury, extracellular matrix composition and fibrosis defined by global mRNA profiling of the human left ventricular myocardium. J Mol Cell Cardiol. 42, 870-83, 2007. [2] Steffens S, Montecucco F, Mach F., The inflammatory response as a target to reduce myocardial ischaemia and reperfusion injury. Thromb Haemost,102, 240-7, 2009