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Preview: Arteriosclerosis, Thrombosis, and Vascular Biology recent issues

Arteriosclerosis, Thrombosis, and Vascular Biology recent issues



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Endothelial Functions [Recent Highlights of ATVB]

2017-08-23T12:44:27-07:00

The endothelium plays important roles in modulating vascular tone by synthesizing and releasing a variety of endothelium-derived relaxing factors, including vasodilator prostaglandins, NO, and endothelium-dependent hyperpolarization factors, as well as endothelium-derived contracting factors. Endothelial dysfunction is mainly caused by reduced production or action of these relaxing mediators. Accumulating evidence has demonstrated that endothelial functions are essential to ensure proper maintenance of vascular homeostasis and that endothelial dysfunction is the hallmark of a wide range of cardiovascular diseases associated with pathological conditions toward vasoconstriction, thrombosis, and inflammatory state. In the clinical settings, evaluation of endothelial functions has gained increasing attention in view of its emerging relevance for cardiovascular disease. Recent experimental and clinical studies in the vascular biology field have demonstrated a close relationship between endothelial functions and cardiovascular disease and the highlighted emerging modulators of endothelial functions, new insight into cardiovascular disease associated with endothelial dysfunction, and potential therapeutic and diagnostic targets with major clinical implications. We herein will summarize the current knowledge on endothelial functions from bench to bedside with particular focus on recent publications in Arteriosclerosis, Thrombosis, and Vascular Biology.






Deletion of Fstl1 (Follistatin-Like 1) From the Endocardial/Endothelial Lineage Causes Mitral Valve Disease [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Fstl1 (Follistatin-like 1) is a secreted protein that is expressed in the atrioventricular valves throughout embryonic development, postnatal maturation, and adulthood. In this study, we investigated the loss of Fstl1 in the endocardium/endothelium and their derived cells.Approach and Results—We conditionally ablated Fstl1 from the endocardial lineage using a transgenic Tie2-Cre mouse model. These mice showed a sustained Bmp and Tgfβ signaling after birth. This resulted in ongoing proliferation and endocardial-to-mesenchymal transition and ultimately in deformed nonfunctional mitral valves and a hypertrophic dilated heart. Echocardiographic and electrocardiographic analyses revealed that loss of Fstl1 leads to mitral regurgitation and left ventricular diastolic dysfunction. Cardiac function gradually deteriorated resulting in heart failure with preserved ejection fraction and death of the mice between 2 and 4 weeks after birth.Conclusions—We report on a mouse model in which deletion of Fstl1 from the endocardial/endothelial lineage results in deformed mitral valves, which cause regurgitation, heart failure, and early cardiac death. The findings provide a potential molecular target for the clinical research into myxomatous mitral valve disease.



Recommendation on Design, Execution, and Reporting of Animal Atherosclerosis Studies: A Scientific Statement From the American Heart Association [AHA Scientific Statements]

2017-08-23T12:44:27-07:00

Animal studies are a foundation for defining mechanisms of atherosclerosis and potential targets of drugs to prevent lesion development or reverse the disease. In the current literature, it is common to see contradictions of outcomes in animal studies from different research groups, leading to the paucity of extrapolations of experimental findings into understanding the human disease. The purpose of this statement is to provide guidelines for development and execution of experimental design and interpretation in animal studies. Recommendations include the following: (1) animal model selection, with commentary on the fidelity of mimicking facets of the human disease; (2) experimental design and its impact on the interpretation of data; and (3) standard methods to enhance accuracy of measurements and characterization of atherosclerotic lesions.









Fueling Platelets [Editorial]

2017-08-23T12:44:27-07:00







Procoagulant Platelets [Editorial]

2017-08-23T12:44:27-07:00




Tracking Adventitial Fibroblast Contribution to Disease [ATVB in Focus: Identification of Vascular Cell Types: Strengths and Weaknesses of Available Cre-Recombinase Mouse Lines]

2017-08-23T12:44:27-07:00

Cells present in the adventitia, or outermost layer of the blood vessel, contribute to the progression of vascular diseases, such as atherosclerosis, hypertension, and aortic dissection. The adventitial fibroblast of the aorta is the prototypic perivascular fibroblast, but the adventitia is composed of multiple distinct cell populations. Therefore, methods for uniquely identifying the fibroblast are critical for a better understanding of how these cells contribute to disease processes. A popular method for distinguishing adventitial cell types relies on the use of genetic tools in the mouse to trace and manipulate these cells. Because lineage tracing relying on Cre-recombinase expressing mice is used more frequently in studies of vascular disease, it is important to outline the advantages and limitations of these genetic tools. The purpose of this article is to provide an overview of the various genetic tools available in the mouse for the study of resident adventitial fibroblasts.



The Involvement of miRNA in Carotid-Related Stroke [Brief Reviews]

2017-08-23T12:44:27-07:00

Cardiovascular disease is the leading cause of morbidity and mortality in developed countries. Stroke is associated with a marked disability burden and has a major economic impact; this is especially true for carotid artery stroke. Major advances in primary and secondary prevention during the last few decades have helped to tackle this public health problem. However, better knowledge of the physiopathology of stroke and its underlying genetic mechanisms is needed to improve diagnosis and therapy. miRNAs are an important, recently identified class of post-transcriptional regulators of gene expression and are known to be involved in cerebrovascular disease. These endogenous, small, noncoding RNAs may have applications as noninvasive biomarkers and therapeutic tools in practice. Here, we review the involvement of several miRNAs in cell-based and whole-animal models of stroke, with a focus on human miRNA profiling studies of carotid artery stroke. Lastly, we describe the miRNAs’ potential role as a biomarker of stroke.



Stasis Promotes Erythrocyte Adhesion to von Willebrand Factor [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Venous thromboembolism is a major contributor to global disease burden. Leukocytes and platelets initiate thrombogenesis on blood stasis and initiate the formation of a fibrin, VWF (von Willebrand factor), and neutrophil extracellular trap scaffold for erythrocytes. However, there is little knowledge on how erythrocytes become stably incorporated into this scaffold. Recently, we described the adhesion of calcium-loaded erythrocytes to endothelial-derived VWF strings. Because VWF is part of the scaffold of venous thrombi, we questioned whether reduced flow or stasis promotes the adhesion of normal erythrocytes to VWF and whether venous thrombi show evidence of erythrocyte–VWF interactions.Approach and Results—In the present work, we perfused, under controlled shear conditions, washed, normal erythrocytes over surface-immobilized plasma and extracellular matrix proteins and showed that normal erythrocytes specifically bind to VWF. The interaction between erythrocytes and VWF significantly increased when the wall shear stress was reduced. Next, we investigated whether erythrocyte–VWF interactions support the structure of venous thrombi. High-resolution immunofluorescence imaging of human venous thrombi showed a striking pattern between erythrocytes, VWF, and fibrin, which suggests that VWF plays a supporting role, linking erythrocytes to fibrin in the thrombus.Conclusions—Our data suggest that erythrocyte retention in venous thrombi is mediated by erythrocyte–VWF or erythrocyte–VWF–fibrin interactions. Targeting erythrocyte retention could be a new strategy in the treatment or prevention of venous thrombosis.



Glucose Transporter 3 Potentiates Degranulation and Is Required for Platelet Activation [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—On activation, platelets increase glucose uptake, glycolysis, and glucose oxidation and consume stored glycogen. This correlation between glucose metabolism and platelet function is not well understood and even less is known about the role of glucose metabolism on platelet function in vivo. For glucose to enter a cell, it must be transported through glucose transporters. Here we evaluate the contribution of GLUT3 (glucose transporter 3) to platelet function to better understand glucose metabolism in platelets.Approach and Results—Platelet-specific knockout of GLUT3 was generated by crossing mice harboring GLUT3 floxed allele to a PF4 (platelet factor 4)-driven Cre recombinase. In platelets, GLUT3 is localized primarily on α-granule membranes and under basal conditions facilitates glucose uptake into α-granules to be used for glycolysis. After activation, platelets degranulate and GLUT3 translocates to the plasma membrane, which is responsible for activation-mediated increased glucose uptake. In vivo, loss of GLUT3 in platelets increased survival in a collagen/epinephrine model of pulmonary embolism, and in a K/BxN model of autoimmune inflammatory disease, platelet-specific GLUT3 knockout mice display decreased disease progression. Mechanistically, loss of GLUT3 decreased platelet degranulation, spreading, and clot retraction. Decreased α-granule degranulation is due in part to an impaired ability of GLUT3 to potentiate exocytosis.Conclusions—GLUT3-mediated glucose utilization and glycogenolysis in platelets promotes α-granule release, platelet activation, and postactivation functions.



Ly6Chigh Monocytes Oscillate in the Heart During Homeostasis and After Myocardial Infarction—Brief Report [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Circadian regulation of neutrophil homeostasis affects myocardial infarction (MI) healing. It is unknown whether diurnal variations of monocyte counts exist in the heart and whether this affects their cardiac infiltration in response to MI.Approach and Results—Murine blood and organs were harvested at distinct times of day and analyzed by flow cytometry. Ly6Chigh monocyte surface expression levels of chemokine receptors (CCR) were ≈2-fold higher at the beginning of the active phase, Zeitgeber Time (ZT) 13 compared with ZT5. This was because of enhanced receptor surface expression at ZT13, whereas no significant changes in total cellular protein levels were found. Most blood Ly6Chigh monocytes were CCR2high, whereas only a minority was CCR1high and CCR5high. We also found diurnal changes of classical monocyte blood counts in humans, being higher in the evening, while exhibiting enhanced CCR2 surface expression in the morning. In support of monocyte oscillations between blood and tissue, murine cardiac Ly6Chigh monocyte counts were highest at ZT13, accompanied by an upregulation of cardiac CC chemokine ligand 2 mRNA. Mice subjected to MI at ZT13 had an even higher upregulation of CCR2 surface expression on circulating monocytes compared with noninfarcted mice and more elevated cardiac CC chemokine ligand 2 protein expression and more pronounced Ly6Chigh monocyte infiltration compared with ZT5-infarcted mice. Concomitantly, CCR2 antagonism only inhibited the excessive cardiac Ly6Chigh monocyte infiltration after ZT13 MI but not ZT5 MI.Conclusions—CCR2 surface expression on Ly6Chigh monocytes changes in a time-of-day–dependent manner, which crucially affects cardiac monocyte recruitment after an acute ischemic event.



Endothelial Cell Autophagy Maintains Shear Stress-Induced Nitric Oxide Generation via Glycolysis-Dependent Purinergic Signaling to Endothelial Nitric Oxide Synthase [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Impaired endothelial cell (EC) autophagy compromises shear stress–induced nitric oxide (NO) generation. We determined the responsible mechanism.Approach and Results—On autophagy compromise in bovine aortic ECs exposed to shear stress, a decrease in glucose uptake and EC glycolysis attenuated ATP production. We hypothesized that decreased glycolysis-dependent purinergic signaling via P2Y1 (P2Y purinoceptor 1) receptors, secondary to impaired autophagy in ECs, prevents shear-induced phosphorylation of eNOS (endothelial nitric oxide synthase) at its positive regulatory site S1117 (p-eNOSS1177) and NO generation. Maneuvers that restore glucose transport and glycolysis (eg, overexpression of GLUT1 [glucose transporter 1]) or purinergic signaling (eg, addition of exogenous ADP) rescue shear-induced p-eNOSS1177 and NO production in ECs with impaired autophagy. Conversely, inhibiting glucose transport via GLUT1 small interfering RNA, blocking purinergic signaling via ectonucleotidase-mediated ATP/ADP degradation (eg, apyrase), or inhibiting P2Y1 receptors using pharmacological (eg, MRS2179 [2′-deoxy-N6-methyladenosine 3′,5′-bisphosphate tetrasodium salt]) or genetic (eg, P2Y1-receptor small interfering RNA) procedures inhibit shear-induced p-eNOSS1177 and NO generation in ECs with intact autophagy. Supporting a central role for PKCδT505 (protein kinase C delta T505) in relaying the autophagy-dependent purinergic-mediated signal to eNOS, we find that (1) shear stress–induced activating phosphorylation of PKCδT505 is negated by inhibiting autophagy, (2) shear-induced p-eNOSS1177 and NO generation are restored in autophagy-impaired ECs via pharmacological (eg, bryostatin) or genetic (eg, constitutively active PKCδ) activation of PKCδT505, and (3) pharmacological (eg, rottlerin) and genetic (eg, PKCδ small interfering RNA) PKCδ inhibition prevents shear-induced p-eNOSS1177 and NO generation in ECs with intact autophagy. Key nodes of dysregulation in this pathway on autophagy compromise were revealed in human arterial ECs.Conclusions—Targeted reactivation of purinergic signaling and PKCδ has strategic potential to restore compromised NO generation in pathologies associated with suppressed EC autophagy.



mTOR (Mechanistic Target of Rapamycin) Inhibition Decreases Mechanosignaling, Collagen Accumulation, and Stiffening of the Thoracic Aorta in Elastin-Deficient Mice [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Elastin deficiency because of heterozygous loss of an ELN allele in Williams syndrome causes obstructive aortopathy characterized by medial thickening and fibrosis and consequent aortic stiffening. Previous work in Eln-null mice with a severe arterial phenotype showed that inhibition of mTOR (mechanistic target of rapamycin), a key regulator of cell growth, lessened the aortic obstruction but did not prevent early postnatal death. We investigated the effects of mTOR inhibition in Eln-null mice partially rescued by human ELN that manifest a less severe arterial phenotype and survive long term.Approach and Results—Thoracic aortas of neonatal and juvenile mice with graded elastin deficiency exhibited increased signaling through both mTOR complex 1 and 2. Despite lower predicted wall stress, there was increased phosphorylation of focal adhesion kinase, suggestive of greater integrin activation, and increased transforming growth factor-β–signaling mediators, associated with increased collagen expression. Pharmacological blockade of mTOR by rapalogs did not improve luminal stenosis but reduced mechanosignaling (in delayed fashion after mTOR complex 1 inhibition), medial collagen accumulation, and stiffening of the aorta. Rapalog administration also retarded somatic growth, however, and precipitated neonatal deaths. Complementary, less-toxic strategies to inhibit mTOR via altered growth factor and nutrient responses were not effective.Conclusions—In addition to previously demonstrated therapeutic benefits of rapalogs decreasing smooth muscle cell proliferation in the absence of elastin, we find that rapalogs also prevent aortic fibrosis and stiffening attributable to partial elastin deficiency. Our findings suggest that mTOR-sensitive perturbation of smooth muscle cell mechanosensing contributes to elastin aortopathy.



Targeted Disruption of JCAD (Junctional Protein Associated With Coronary Artery Disease)/KIAA1462, a Coronary Artery Disease-Associated Gene Product, Inhibits Angiogenic Processes In Vitro and In Vivo [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Recent genome-wide association studies newly identified the human KIAA1462 gene as a new locus for coronary artery disease. However, the function of the gene product, named JCAD (junctional protein associated with coronary artery disease), is unknown. Because JCAD is expressed at cell–cell junctions in endothelial cells, we hypothesized and tested whether JCAD regulates angiogenic processes in vitro and in vivo.Approach and Results—Cell culture experiments revealed impaired angiogenic ability (proliferation, migration, and cord formation) by the knockdown of JCAD with siRNA (P<0.05 versus control siRNA). We have generated mice lacking JCAD (mKIAA1462−/−) by gene-targeted deletion of JCAD to address in vivo angiogenic function. mKIAA1462−/− mice did not show morphological differences in development of retinal vasculature. Ex vivo aortic ring model demonstrated impaired neovascularization in aorta from mKIAA1462−/− mice than control wild-type mice (P<0.05). Tumor growth was assessed by monitoring tumor volume after the subcutaneous injection of melanoma, LLC (Lewis lung carcinoma), and E0771 cells into the mice. mKIAA1462−/− mice exhibited significantly smaller tumor volume compared with wild-type mice (P<0.001). Histological assessment of the tumor exhibited less smooth muscle actin–positive neovascularization determined by CD31-positive vascular structure in tumor of mKIAA1462−/− mice than wild-type mice, indicating that knockdown of JCAD inhibited the vascular maturation in pathological angiogenic process.Conclusions—These in vitro and in vivo studies suggest that JCAD has a redundant functional role in physiological angiogenesis but serves a pivotal role in pathological angiogenic process after birth.



BRG1 (Brahma-Related Gene 1) Promotes Endothelial Mrtf Transcription to Establish Embryonic Capillary Integrity [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—The chromatin remodeling enzyme BRG1 (brahma-related gene 1) transcriptionally regulates target genes important for early blood vessel development and primitive hematopoiesis. However, because Brg1 deletion in vascular progenitor cells results in lethal anemia by embryonic day 10.5 (E10.5), roles for BRG1 in embryonic vascular development after midgestation are unknown. In this study, we sought to determine whether endothelial cell BRG1 regulates genes important for vascular development or maintenance later in embryonic development.Approach and Results—Using mice with temporally inducible deletion of endothelial BRG1 (Brg1fl/fl;Cdh5(PAC)-CreERT2), we found that Brg1 excision between E9.5 and 11.5 results in capillary dilation and lethal hemorrhage by E14.5. This phenotype strongly resembles that seen when the SRF (serum response factor) transcription factor is deleted from embryonic endothelial cells. Although expression of Srf and several of its known endothelial cell target genes are downregulated in BRG1-depleted endothelial cells, we did not detect binding of BRG1 at these gene promoters, indicating that they are not direct BRG1 target genes. Instead, we found that BRG1 binds to the promoters of the SRF cofactors Mrtfa and Mrtfb (myocardin-related transcription factors A and B) in endothelial cells, and these genes are downregulated in Brg1-deficient endothelial cells.Conclusions—BRG1 promotes transcription of endothelial Mrtfa and Mrtfb, which elevates expression of SRF and SRF target genes that establish embryonic capillary integrity. These data highlight a new and temporally specific role for BRG1 in embryonic vasculature and provide novel information about epigenetic regulation of Mrtf expression and SRF signaling in developing blood vessels.



Selective Deletion of Leptin Signaling in Endothelial Cells Enhances Neointima Formation and Phenocopies the Vascular Effects of Diet-Induced Obesity in Mice [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Obesity is associated with elevated circulating leptin levels and hypothalamic leptin resistance. Leptin receptors (LepRs) are expressed on endothelial cells, and leptin promotes neointima formation in a receptor-dependent manner. Our aim was to examine the importance of endothelial LepR (End.LepR) signaling during vascular remodeling and to determine whether the cardiovascular consequences of obesity are because of hyperleptinemia or endothelial leptin resistance.Approach and Results—Mice with loxP-flanked LepR alleles were mated with mice expressing Cre recombinase controlled by the inducible endothelial receptor tyrosine kinase promoter. Obesity was induced with high-fat diet. Neointima formation was examined after chemical carotid artery injury. Morphometric quantification revealed significantly greater intimal hyperplasia, neointimal cellularity, and proliferation in End.LepR knockout mice, and similar findings were obtained in obese, hyperleptinemic End.LepR wild-type animals. Analysis of primary endothelial cells confirmed abrogated signal transducer and activator of transcription-3 phosphorylation in response to leptin in LepR knockout and obese LepR wild-type mice. Quantitative PCR, ELISA, and immunofluorescence analyses revealed increased expression and release of endothelin-1 in End.LepR-deficient and LepR-resistant cells, and ET receptor A/B antagonists abrogated their paracrine effects on murine aortic smooth muscle cell proliferation. Reduced expression of peroxisome proliferator-activated receptor-γ and increased nuclear activator protein-1 staining was observed in End.LepR-deficient and LepR-resistant cells, and peroxisome proliferator-activated receptor-γ antagonization increased endothelial endothelin-1 expression.Conclusions—Our findings suggest that intact endothelial leptin signaling limits neointima formation and that obesity represents a state of endothelial leptin resistance. These observations and the identification of endothelin-1 as soluble mediator of the cardiovascular risk factor obesity may have relevant therapeutic implications.



CYLD Deubiquitinates Nicotinamide Adenine Dinucleotide Phosphate Oxidase 4 Contributing to Adventitial Remodeling [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Transdifferentiation of adventitial fibroblasts (AFs) into myofibroblasts plays a critical role during the vascular remodeling that occurs during atherosclerosis, restenosis, and aortic aneurysm. The ubiquitination/deubiquitination regulatory system is essential for the quality control of proteins. The involvement of ubiquitination/deubiquitination during AF transdifferentiation remains largely unknown. In this study, we determined the role of cylindromatosis (CYLD), a deubiquitinase, in the process of AF differentiation and activation in vitro and in vivo.Approach and Results—Transforming growth factor-β1 and homocysteine, 2 known inducers of AF transdifferentiation, greatly upregulated CYLD expression in a time- and dose-dependent manner. The silencing of CYLD significantly inhibited AF transdifferentiation and activation as evidenced by the expression of contractile proteins, the production of the proinflammatory cytokines MCP-1 (monocyte chemotactic protein 1) and IL-6 (interleukin-6), the deposition of extracellular matrix, and cell migration. We further asked whether CYLD mediates AF activation via the regulation of nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) as it is an essential factor during AF transdifferentiation. Indeed, the silencing of CYLD repressed transforming growth factor-β1–induced and homocysteine-induced Nox4 upregulation and reactive oxygen species production, whereas Nox4 overexpression greatly rescued the inhibitory effect on AF activation by CYLD silencing. Most interestingly, transforming growth factor-β1 and homocysteine repressed Nox4 ubiquitination and prolonged the half-life of Nox4. Moreover, Nox4 was deubiquitinated via a direct interaction with the ubiquitin-specific protease domain of CYLD. In accordance, hyperhomocysteinemia significantly increased adventitial CYLD and Nox4 expression, promoted AF transdifferentiation, and aggravated CaPO4-induced abdominal aortic aneurysm in mice. These effects were abolished in CYLD−/− mice.Conclusions—CYLD contributes to the transdifferentiation of AFs via deubiquitinating Nox4 and may play a role in vascular remodeling.



Sema3F (Semaphorin 3F) Selectively Drives an Extraembryonic Proangiogenic Program [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Molecular pathways governing blood vessel patterning are vital to vertebrate development. Because of their ability to counteract proangiogenic factors, antiangiogenic secreted Sema3 (class 3 semaphorins) control embryonic vascular morphogenesis. However, if and how Sema3 may play a role in the control of extraembryonic vascular development is presently unknown.Approach and Results—By characterizing genetically modified mice, here, we show that surprisingly Sema3F acts instead as a selective extraembryonic, but not intraembryonic proangiogenic cue. Both in vivo and in vitro, in visceral yolk sac epithelial cells, Sema3F signals to inhibit the phosphorylation-dependent degradation of Myc, a transcription factor that drives the expression of proangiogenic genes, such as the microRNA cluster 17/92. In Sema3f-null yolk sacs, the transcription of Myc-regulated microRNA 17/92 cluster members is impaired, and the synthesis of Myc and microRNA 17/92 foremost antiangiogenic target Thbs1 (thrombospondin 1) is increased, whereas Vegf (vascular endothelial growth factor) signaling is inhibited in yolk sac endothelial cells. Consistently, exogenous recombinant Sema3F inhibits the phosphorylation-dependent degradation of Myc and the synthesis of Thbs1 in mouse F9 teratocarcinoma stem cells that were in vitro differentiated in visceral yolk sac epithelial cells. Sema3f−/− mice placentas are also highly anemic and abnormally vascularized.Conclusions—Sema3F functions as an unconventional Sema3 that promotes extraembryonic angiogenesis by inhibiting the Myc-regulated synthesis of Thbs1 in visceral yolk sac epithelial cells.



Smooth Muscle Cells Derived From Second Heart Field and Cardiac Neural Crest Reside in Spatially Distinct Domains in the Media of the Ascending Aorta—Brief Report [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Smooth muscle cells (SMCs) of the proximal thoracic aorta are embryonically derived from the second heart field (SHF) and cardiac neural crest (CNC). However, distributions of these embryonic origins are not fully defined. The regional distribution of SMCs of different origins is speculated to cause region-specific aortopathies. Therefore, the aim of this study was to determine the distribution of SMCs of SHF and CNC origins in the proximal thoracic aorta.Approach and Results—Mice with repressed LacZ in the ROSA26 locus were bred to those expressing Cre controlled by either the Wnt1 or Mef2c (myocyte-specific enhancer factor 2c) promoter to trace CNC- and SHF-derived SMCs, respectively. Thoracic aortas were harvested, and activity of β-galactosidase was determined. Aortas from Wnt1-Cre mice had β-galactosidase–positive areas throughout the region from the proximal ascending aorta to just distal of the subclavian arterial branch. Unexpectedly, β-galactosidase–positive areas in Mef2c-Cre mice extended from the aortic root throughout the ascending aorta. This distribution occurred independent of sex and aging. Cross and sagittal aortic sections demonstrated that CNC-derived cells populated the inner medial aspect of the anterior region of the ascending aorta and transmurally in the media of the posterior region. Interestingly, outer medial cells throughout anterior and posterior ascending aortas were derived from the SHF. β-Galactosidase–positive medial cells of both origins colocalized with an SMC marker, α-actin.Conclusions—Both CNC- and SHF-derived SMCs populate the media throughout the ascending aorta. The outer medial cells of the ascending aorta form a sleeve populated by SHF-derived SMCs.



Sox10+ Cells Contribute to Vascular Development in Multiple Organs—Brief Report [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—Previous genetic lineage tracing studies showed that Sox10+ cells differentiate into vascular mural cells, limited to neural crest–derived blood vessels in craniofacial tissues, aortic arch, pulmonary arch arteries, brachiocephalic, carotid arteries, and thymus. The purpose of this study was to investigate the contribution of Sox10+ cells to the vascular development in other tissues and organs and their relationship with neural crest.Approach and Results—Using genetic lineage tracing technique based on Cre/LoxP system, we examined blood vessels in the adult organs of the mice expressing Sox10-Cre/Rosa-LoxP-red fluorescent protein or Wnt1-Cre/Rosa-LoxP-red fluorescent protein by immunohistological analysis. In addition to previously reported tissues and organs derived from neural crest, we showed that Sox10+ cells also contributed to vascular mural cells in the lung, spleen, and kidney, which are derived from non-neural crest origin as evidenced by red fluorescent protein-negative blood vessels in these 3 organs of Wnt1-Cre/Rosa-LoxP-red fluorescent protein mice.Conclusions—This study demonstrates that Sox10+ cells contribute to pericytes and smooth muscle cells in most parts of the body, including those from neural crest and non-neural crest, which has significant implications in vascular remodeling under physiological and pathological conditions.



Dachsous1-Fat4 Signaling Controls Endothelial Cell Polarization During Lymphatic Valve Morphogenesis—Brief Report [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—The purpose of this study was to investigate the role of Fat4 and Dachsous1 signaling in the lymphatic vasculature.Approach and Results—Phenotypic analysis of the lymphatic vasculature was performed in mice lacking functional Fat4 or Dachsous1. The overall architecture of lymphatic vasculature is unaltered, yet both genes are specifically required for lymphatic valve morphogenesis. Valve endothelial cells (Prox1high [prospero homeobox protein 1] cells) are disoriented and failed to form proper valve leaflets. Using Lifeact-GFP (green fluorescent protein) mice, we revealed that valve endothelial cells display prominent actin polymerization. Finally, we showed the polarized recruitment of Dachsous1 to membrane protrusions and cellular junctions of valve endothelial cells in vivo and in vitro.Conclusions—Our data demonstrate that Fat4 and Dachsous1 are critical regulators of valve morphogenesis. This study highlights that valve defects may contribute to lymphedema in Hennekam syndrome caused by Fat4 mutations.



A Novel Single-Domain Antibody Against von Willebrand Factor A1 Domain Resolves Leukocyte Recruitment and Vascular Leakage During Inflammation—Brief Report [Basic Sciences]

2017-08-23T12:44:27-07:00

Objective—von Willebrand factor (VWF) is crucial to hemostasis, but also plays a role in inflammatory processes. Unfortunately, no proper monoclonal antibodies to study VWF function in mice are currently available. We therefore aimed to generate single-domain antibodies (sdAbs) recognizing murine VWF and blocking its function in vivo.Approach and Results—Llama-derived sdAbs recognizing both human and murine VWF were isolated via phage display technology. One of them (designated KB-VWF-006) recognized the VWF A1 domain with picomolar affinity. This sdAb avidity was strongly enhanced via dimerization using a triple Ala linker (KB-VWF-006bi). When administered in vivo to wild-type mice, KB-VWF-006bi dose dependently induced bleeding in a tail clip model. In 2 distinct models of inflammation, KB-VWF-006bi efficiently interfered with leukocyte recruitment and vascular leakage.Conclusions—KB-VWF-006bi is an sdAb recognizing the A1 domain of human VWF and murine VWF that interferes with VWF–platelet interactions in vivo. By using this sdAb, we now also show that the A1 domain is pertinent to the participation of VWF in the inflammatory response.



In Vivo Base Editing of PCSK9 (Proprotein Convertase Subtilisin/Kexin Type 9) as a Therapeutic Alternative to Genome Editing [Translational Sciences]

2017-08-23T12:44:27-07:00

Objective—High-efficiency genome editing to disrupt therapeutic target genes, such as PCSK9 (proprotein convertase subtilisin/kexin type 9), has been demonstrated in preclinical animal models, but there are safety concerns because of the unpredictable nature of cellular repair of double-strand breaks, as well as off-target mutagenesis. Moreover, precise knock-in of specific nucleotide changes—whether to introduce or to correct gene mutations—has proven to be inefficient in nonproliferating cells in vivo. Base editors comprising CRISPR-Cas9 (clustered regularly interspaced short palindromic repeats [CRISPR]-CRISPR-associated 9) fused to a cytosine deaminase domain can effect the alteration of cytosine bases to thymine bases in genomic DNA in a sequence-specific fashion, without the need for double-strand DNA breaks. The efficacy of base editing has not been established in vivo. The goal of this study was to assess whether in vivo base editing could be used to modify the mouse Pcsk9 gene in a sequence-specific fashion in the liver in adult mice.Approach and Results—We screened base editors for activity in cultured cells, including human-induced pluripotent stem cells. We then delivered a base editor into the livers of adult mice to assess whether it could introduce site-specific nonsense mutations into the Pcsk9 gene. In adult mice, this resulted in substantially reduced plasma PCSK9 protein levels (>50%), as well as reduced plasma cholesterol levels (≈30%). There was no evidence of off-target mutagenesis, either cytosine-to-thymine edits or indels.Conclusions—These results demonstrate the ability to precisely introduce therapeutically relevant nucleotide variants into the genome in somatic tissues in adult mammals, as well as highlighting a potentially safer alternative to therapeutic genome editing.



Expression of ADAMTS13 in Normal and Abnormal Placentae and Its Potential Role in Angiogenesis and Placenta Development [Translational Sciences]

2017-08-23T12:44:27-07:00

Objective—ADAMTS13 (a disintegrin and metalloproteinase with thrombospondin type 1 repeats, member 13) is primarily synthesized in liver. The biosynthesis of ADAMTS13 and its physiological role in placenta are not known.Approach and Results—We used real-time polymerase chain reaction, immunohistochemistry, and Western blotting analyses, as well as proteolytic cleavage of FRETS (fluorescent resonance energy transfers)-VWF73, to determine ADAMTS13 expression in placenta and trophoblasts obtained from individuals with normal pregnancy and patients with severe preeclampsia. We also determined the role of ADAMTS13 in extravillous trophoblasts using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, wound scratch assay, transwell migration assay, tube formation assay, and tissue outgrowth assays. We showed that full-length and proteolytically active ADAMTS13 was expressed in normal human placenta, primarily in the trophoblasts and villous core fetal vessel endothelium during pregnancy. Placental expression of ADAMTS13 mRNA, protein, and proteolytic activity was at the highest levels during the first trimester and significantly reduced at the term of gestation. Additionally, significantly reduced levels of placental ADAMTS13 expression was detected under hypoxic conditions and in patients with preeclampsia. In addition, recombinant ADAMTS13 protease stimulated proliferation, migration, invasion, and network formation of trophoblastic cells in culture. Finally, knockdown of ADAMTS13 expression attenuated the ability of tube formation in trophoblast (HTR-8/SVNEO) cells and the extravillous trophoblast outgrowth in placental explants.Conclusions—Our results demonstrate for the first time the expression of ADAMTS13 mRNA and protein in normal and abnormal placental tissues and its role in promoting angiogenesis and trophoblastic cell development. The findings support the potential role of the ADAMTS13–von Willebrand factor pathway in normal pregnancy and pathogenesis of preeclampsia.



Association of Coronary Perivascular Adipose Tissue Inflammation and Drug-Eluting Stent-Induced Coronary Hyperconstricting Responses in Pigs [Translational Sciences]

2017-08-23T12:44:27-07:00

Objective—Although coronary perivascular adipose tissue (PVAT) may play important roles as a source of inflammation, the association of coronary PVAT inflammation and coronary hyperconstricting responses remains to be examined. We addressed this important issue in a porcine model of coronary hyperconstricting responses after drug-eluting stent implantation with 18F-fluorodeoxyglucose (18F-FDG) positron emission tomographic imaging.Approach and Results—An everolimus-eluting stent (EES) was randomly implanted in pigs into the left anterior descending or the left circumflex coronary artery while nonstented coronary artery was used as a control. After 1 month, coronary vasoconstricting responses to intracoronary serotonin (10 and 100 μg/kg) were examined by coronary angiography in vivo, followed by in vivo and ex vivo 18F-FDG positron emission tomographic/computed tomographic imaging. Coronary vasoconstricting responses to serotonin were significantly enhanced at the EES edges compared with the control site (P<0.01; n=40). Notably, in vivo and ex vivo 18F-FDG positron emission tomographic/computed tomographic imaging and autoradiography showed enhanced 18F-FDG uptake and its accumulation in PVAT at the EES edges compared with the control site, respectively (both P<0.05). Furthermore, histological and reverse transcription polymerase chain reaction analysis showed that inflammatory changes of coronary PVAT were significantly enhanced at the EES edges compared with the control site (all P<0.01). Importantly, Rho-kinase expressions (ROCK1/ROCK2) and Rho-kinase activity (phosphorylated myosin phosphatase target subunit-1) at the EES edges were significantly enhanced compared with the control site.Conclusions—These results indicate for the first time that inflammatory changes of coronary PVAT are associated with drug-eluting stent–induced coronary hyperconstricting responses in pigs in vivo and that 18F-FDG positron emission tomographic imaging is useful for assessment of coronary PVAT inflammation.



APOL1 Risk Variants and Cardiovascular Disease [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—Among African Americans, the apolipoprotein L1 (APOL1) risk variants have been associated with various types of kidney disease and chronic kidney disease progression. We aimed to determine whether these same risk variants also confer an increased risk for cardiovascular disease.Approach and Results—In a cohort of African Americans with hypertension-attributed chronic kidney disease followed for up to 12 years, we used Cox proportional hazards models to estimate the relative hazard of a composite cardiovascular disease outcome (cardiovascular death or hospitalization for myocardial infarction, cardiac revascularization procedure, heart failure, or stroke) for the APOL1 high- (2 risk variants) versus low-risk (0–1 risk variant) genotypes. We adjusted for age, sex, ancestry, smoking, heart disease history, body mass index, cholesterol, randomized treatment groups, and baseline and longitudinal estimated glomerular filtration rate, systolic blood pressure, and proteinuria. Among 693 participants with APOL1 genotyping available (23% high risk), the high-risk group had lower mean estimated glomerular filtration rate (44.7 versus 50.1 mL/min per 1.73 m2) and greater proteinuria (median 0.19 versus 0.06) compared with the low-risk group at baseline. There was no significant association between APOL1 genotypes and the composite cardiovascular disease outcome in both unadjusted (hazard ratio=1.23; 95% confidence interval: 0.83–1.81) and fully adjusted (hazard ratio=1.16; 95% confidence interval: 0.77–1.76) models; however, in using an additive model, APOL1 high-risk variants were associated with increased cardiovascular mortality.Conclusions—Among African Americans with hypertension-attributed chronic kidney disease, APOL1 risk variants were not associated with an overall risk for cardiovascular disease although some signals for cardiovascular mortality were noted.



CETP (Cholesteryl Ester Transfer Protein) Inhibition With Anacetrapib Decreases Production of Lipoprotein(a) in Mildly Hypercholesterolemic Subjects [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—Lp(a) [lipoprotein (a)] is composed of apoB (apolipoprotein B) and apo(a) [apolipoprotein (a)] and is an independent risk factor for cardiovascular disease and aortic stenosis. In clinical trials, anacetrapib, a CETP (cholesteryl ester transfer protein) inhibitor, causes significant reductions in plasma Lp(a) levels. We conducted an exploratory study to examine the mechanism for Lp(a) lowering by anacetrapib.Approach and Results—We enrolled 39 participants in a fixed-sequence, double-blind study of the effects of anacetrapib on the metabolism of apoB and high-density lipoproteins. Twenty-nine patients were randomized to atorvastatin 20 mg/d, plus placebo for 4 weeks, and then atorvastatin plus anacetrapib (100 mg/d) for 8 weeks. The other 10 subjects were randomized to double placebo for 4 weeks followed by placebo plus anacetrapib for 8 weeks. We examined the mechanisms of Lp(a) lowering in a subset of 12 subjects having both Lp(a) levels >20 nmol/L and more than a 15% reduction in Lp(a) by the end of anacetrapib treatment. We performed stable isotope kinetic studies using 2H3-leucine at the end of each treatment to measure apo(a) fractional catabolic rate and production rate. Median baseline Lp(a) levels were 21.5 nmol/L (interquartile range, 9.9–108.1 nmol/L) in the complete cohort (39 subjects) and 52.9 nmol/L (interquartile range, 38.4–121.3 nmol/L) in the subset selected for kinetic studies. Anacetrapib treatment lowered Lp(a) by 34.1% (P≤0.001) and 39.6% in the complete and subset cohort, respectively. The decreases in Lp(a) levels were because of a 41% reduction in the apo(a) production rate, with no effects on apo(a) fractional catabolic rate.Conclusions—Anacetrapib reduces Lp(a) levels by decreasing its production.Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT00990808.



Effects of Intranasal Insulin on Triglyceride-Rich Lipoprotein Particle Production in Healthy Men [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—Insulin administered directly into the brain acutely suppresses hepatic glucose production and triglyceride-rich lipoprotein (TRL) secretion in rodents. In addition, intranasally administered insulin, which selectively raises cerebrospinal fluid insulin concentration, suppresses hepatic glucose production in humans; however, its effect on TRL secretion in humans has not previously been examined. In this study, we examined whether intranasal insulin, administered at a dose that has previously been shown to suppress hepatic glucose production, modulates TRL particle secretion by the liver and intestine in humans.Approach and Results—Nine healthy, normolipidemic, and normoglycemic men participated in a study consisting of 2 randomized study arms. Subjects received intranasal lispro insulin (40 IU) or placebo. Because intranasal insulin results in a rapid and transient increase in systemic insulin concentration after administration, we matched systemic insulin concentrations in the 2 study arms by infusing lispro insulin intravenously for 30 minutes together with intranasal placebo administration. Apo (apolipoprotein) B100–containing (hepatically derived) and apoB48-containing (intestinally derived) TRL lipoprotein particle turnover were measured for the ensuing 10 hours under pancreatic clamp conditions and constant fed state, using stable isotope enrichment techniques and multicompartmental modeling. Under these experimental conditions, no significant effects of intranasal insulin versus placebo on TRL apoB100 or B48 concentrations, fractional catabolic rates, or production rates were observed.Conclusions—Insulin delivered intranasally at a dose that has been shown to raise cerebrospinal fluid insulin concentration and suppress hepatic glucose production does not affect TRL particle production by the liver and intestine in healthy men.Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT03141827.



Subcutaneous Adipocyte Lipolysis Contributes to Circulating Lipid Levels [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—Fatty acids released via fat cell lipolysis can affect circulating lipid levels. However, the contribution of different lipolysis measures in adipose tissue is unknown and was presently examined in isolated subcutaneous adipocytes.Approach and Results—One thousand and sixty-six men and women were examined for lipolysis regulation in subcutaneous abdominal fat cells. Results were compared with fasting plasma levels of total cholesterol, high-density lipoprotein (HDL) cholesterol (HDL-C) and triglycerides. Spontaneous (basal) lipolysis and the effects of the major hormones stimulating (catecholamines and natriuretic peptides) and inhibiting lipolysis (insulin) were examined. Several statistically significant (P<0.0001) correlations between the different lipolysis parameters and plasma lipids were observed. However, physiologically relevant correlations (adjusted r2≥0.05) were only evident between basal or insulin-inhibited lipolysis and plasma triglycerides or HDL-C. Together, these lipolysis measures explained 14% of the variation in triglycerides or HDL-C, respectively. In comparison, a combination of established factors associated with variations in plasma lipids, that is, age; body mass index; waist circumference; waist-to-hip ratio; sex; nicotine use; fat cell volume; and pharmacotherapy against diabetes mellitus; hypertension; or hyperlipidemia explained 17% and 28%, respectively, of the variations in plasma triglycerides and HDL-C.Conclusions—Subcutaneous fat cell lipolysis is an important independent contributor to interindividual variations in plasma lipids. High spontaneous lipolysis activity and resistance to the antilipolytic effect of insulin associate with elevated triglyceride and low HDL-C concentrations. Thus, although several other factors also play a role, subcutaneous adipose tissue may have a causal influence on dyslipidemia.



The Effect of Iron Status on Risk of Coronary Artery Disease [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—Iron status is a modifiable trait that has been implicated in cardiovascular disease. This study uses the Mendelian randomization technique to investigate whether there is any causal effect of iron status on risk of coronary artery disease (CAD).Approach and Results—A 2-sample Mendelian randomization approach is used to estimate the effect of iron status on CAD risk. Three loci (rs1800562 and rs1799945 in the HFE gene and rs855791 in TMPRSS6) that are each associated with serum iron, transferrin saturation, ferritin, and transferrin in a pattern suggestive of an association with systemic iron status are used as instruments. SNP (single-nucleotide polymorphism)-iron status association estimates are based on a genome-wide association study meta-analysis of 48 972 individuals. SNP-CAD estimates are derived by combining the results of a genome-wide association study meta-analysis of 60 801 CAD cases and 123 504 controls with those of a meta-analysis of 63 746 CAD cases and 130 681 controls obtained from Metabochip and genome-wide association studies. Combined Mendelian randomization estimates are obtained for each marker by pooling results across the 3 instruments. We find evidence of a protective effect of higher iron status on CAD risk (iron odds ratio, 0.94 per SD unit increase; 95% confidence interval, 0.88–1.00; P=0.039; transferrin saturation odds ratio, 0.95 per SD unit increase; 95% confidence interval, 0.91–0.99; P=0.027; log-transformed ferritin odds ratio, 0.85 per SD unit increase; 95% confidence interval, 0.73–0.98; P=0.024; and transferrin odds ratio, 1.08 per SD unit increase; 95% confidence interval, 1.01–1.16; P=0.034).Conclusions—This Mendelian randomization study supports the hypothesis that higher iron status reduces CAD risk. These findings may highlight a therapeutic target.



Short-Term Exposure to Ambient Air Pollution and Biomarkers of Systemic Inflammation [Clinical and Population Studies]

2017-08-23T12:44:27-07:00

Objective—The objective of this study is to examine associations between short-term exposure to ambient air pollution and circulating biomarkers of systemic inflammation in participants from the Framingham Offspring and Third Generation cohorts in the greater Boston area.Approach and Results—We included 3996 noncurrent smoking participants (mean age, 53.6 years; 54% women) who lived within 50 km from a central air pollution monitoring site in Boston, MA, and calculated the 1- to 7-day moving averages of fine particulate matter (diameter<2.5 µm), black carbon, sulfate, nitrogen oxides, and ozone before the examination visits. We used linear mixed effects models for C-reactive protein and tumor necrosis factor receptor 2, which were measured up to twice for each participant; we used linear regression models for interleukin-6, fibrinogen, and tumor necrosis factor α, which were measured once. We adjusted for demographics, socioeconomic position, lifestyle, time, and weather. The 3- to 7-day moving averages of fine particulate matter (diameter<2.5 µm) and sulfate were positively associated with C-reactive protein concentrations. A 5 µg/m3 higher 5-day moving average fine particulate matter (diameter<2.5 µm) was associated with 4.2% (95% confidence interval: 0.8, 7.6) higher circulating C-reactive protein. Positive associations were also observed for nitrogen oxides with interleukin-6 and for black carbon, sulfate, and ozone with tumor necrosis factor receptor 2. However, black carbon, sulfate, and nitrogen oxides were negatively associated with fibrinogen, and sulfate was negatively associated with tumor necrosis factor α.Conclusions—Higher short-term exposure to relatively low levels of ambient air pollution was associated with higher levels of C-reactive protein, interleukin-6, and tumor necrosis factor receptor 2 but not fibrinogen or tumor necrosis factor α in individuals residing in the greater Boston area.



Macrophages [Recent Highlights of ATVB]

2017-07-26T12:43:42-07:00




Mitochondrial Oxidative Stress Promotes Atherosclerosis and Neutrophil Extracellular Traps in Aged MiceHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Rationale—Mitochondrial oxidative stress (mitoOS) has been shown to be increased in various cell types in human atherosclerosis and with aging. However, the role of cell type–specific mitoOS in atherosclerosis in the setting of advanced age and the molecular mechanisms remains to be determined in vivo.Objective—The aim of this study was to examine the role of myeloid cell mitoOS in atherosclerosis in aged mice.Approach and Results—Lethally irradiated low-density lipoprotein receptor–deficient mice (Ldlr−/−) were reconstituted with bone marrow from either wild-type or mitochondrial catalase (mCAT) mice. mCAT transgenic mice contain ectopically expressed human catalase gene in mitochondria, which reduces mitoOS. Starting at the age of 36 weeks, mice were fed the Western-type diet for 16 weeks. We found that mitoOS in lesional myeloid cells was suppressed in aged mCAT→Ldlr−/− chimeric mice compared with aged controls, and this led to a significant reduction in aortic root atherosclerotic lesion area despite higher plasma cholesterol levels. Neutrophil extracellular traps (NETs), a proinflammatory extracellular structure that contributes to atherosclerosis progression, were significantly increased in the lesions of aged mice compared with lesions of younger mice. Aged mCAT→Ldlr−/− mice had less lesional neutrophils and decreased NETs compared with age-matched wild-type→Ldlr−/− mice, whereas young mCAT→ and wild-type→Ldlr−/− mice had comparable numbers of neutrophils and similar low levels of lesional NETs. Using cultured neutrophils, we showed that suppression of mitoOS reduced 7-ketocholesterol–induced NET release from neutrophils of aged but not younger mice.Conclusions—MitoOS in lesional myeloid cells enhanced atherosclerosis development in aged mice, and this enhancement was associated with increased lesional NETs. Thus, mitoOS-induced NET formation is a potentially new therapeutic target to prevent atherosclerosis progression during aging.



By CyTOF [Editorial]

2017-07-26T12:43:42-07:00




OxPL [Editorial]

2017-07-26T12:43:42-07:00







Magnesium Counteracts Vascular CalcificationHighlights [Brief Review]

2017-07-26T12:43:42-07:00

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate–buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells.



Plasminogen Activator Inhibitor-1 Is a Marker and a Mediator of SenescenceHighlights [Brief Review]

2017-07-26T12:43:42-07:00

PAI-1 (plasminogen activator inhibitor-1) is a member of the evolutionarily conserved serine protease inhibitor family and a potent and rapid-acting inhibitor of both of the mammalian plasminogen activators. Organismal homeostasis requires physiological levels of endogenous PAI-1, and increased PAI-1 production guides the onset and progression of numerous human diseases and contributes to the multimorbidity of aging. Both chronological and stress-induced accelerated aging are associated with cellular senescence and accompanied by marked increases in PAI-1 expression in tissues. Recent studies suggest that PAI-1 is not only a marker but also a key mediator of cellular senescence and organismal aging. Here, we review the significance of PAI-1 as a bonafide marker, as well as a critical mediator, of cellular senescence associated with aging and aging-related pathologies.









NLRP3 Inflammasome Inhibition by MCC950 Reduces Atherosclerotic Lesion Development in Apolipoprotein E-Deficient Mice—Brief ReportHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Inflammasomes are multiprotein complexes, and their activation has been associated with cardiovascular disease. Inflammasome activation leads to secretion of caspase-1 by innate immune cells, resulting in the activation of interleukin-1β. Recently, a potent and selective inhibitor of the NLRP3 inflammasome, MCC950, was described. In this study, we investigated the effect of MCC950 on atherosclerotic lesion development in apoE−/− mice.Approach and Results—First, we determined the efficacy of MCC950 in vitro. Bone marrow–derived macrophages and dendritic cells were stimulated with lipopolysaccharide and cholesterol crystals resulting in high levels of interleukin-1β release, which was inhibited by MCC950. In vivo MCC950 treatment reduced lipopolysaccharide–induced interleukin-1β secretion, without affecting the tumor necrosis factor-α response. Subsequently, atherosclerotic plaques were induced in Western-type diet fed apoE−/− mice by semiconstrictive perivascular collar placement at the carotid arteries, after which the mice received MCC950 (10 mg/kg) or vehicle control 3× per week intraperitoneally for 4 weeks. After euthanize, atherosclerotic plaque size and volume were quantified in hematoxylin-eosin–stained 10-µm cryosections throughout the artery. MCC950 treatment significantly reduced the development of atherosclerotic lesions as determined by maximal stenosis, average plaque size, and plaque volume. Although the amount of collagen and the necrotic core size were not affected, the number of macrophages in the plaque was significantly reduced on treatment. In addition, VCAM-1 (vascular cell adhesion molecule 1) and ICAM-1 (intercellular adhesion molecule 1) mRNA expression was significantly reduced in the carotids of MCC950-treated mice.Conclusions—These findings show that specific inhibition of the NLRP3 inflammasome using MCC950 can be a promising therapeutic approach to inhibit atherosclerotic lesion development.



Cardiotonic Steroids Stimulate Macrophage Inflammatory Responses Through a Pathway Involving CD36, TLR4, and Na/K-ATPaseHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Circulating levels of cardiotonic steroids (CTS) are elevated in various chronic inflammatory conditions, but the role of CTS in inflammation remains largely unknown. We have previously shown that the CTS ouabain stimulates proinflammatory responses in murine macrophages. In this study, we aim to explore the mechanism how CTS induce proinflammatory responses in primary murine and human macrophages.Approach and Results—Using both murine peritoneal macrophages and human monocyte–derived macrophages, we demonstrated that ouabain activated NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells), leading to proinflammatory cytokine (eg, MCP-1 [monocyte chemotactic protein 1], TNF-α [tumor necrosis factor-α], IL-1β [interleukin-1β], and IL-6) production. By applying siRNA techniques and murine peritoneal macrophages isolated from genetically modified mice, we showed that macrophages partially deficient in Na/K-ATPase, the receptor for CTS, or fully deficient in the scavenger receptor CD36 or TLR4 (Toll-like receptor) were resistant to ouabain-induced NF-κB activation, suggesting an indispensable role of these 3 receptors in this pathway. Mechanistically, this effect of ouabain was independent of the ion transport function of the Na/K-ATPase. Instead, ouabain stimulated a signaling complex, including Na/K-ATPase, CD36, and TLR4. Subsequently, TLR4 recruited MyD88 adaptor protein for NF-κB activation. Furthermore, intraperitoneal injection of ouabain into mice specifically recruited Ly6C+CCR2+ monocyte subtypes to the peritoneal cavities, indicating that the CTS ouabain triggers inflammation in vivo.Conclusions—CTS activate NF-κB leading to proinflammatory cytokine production in primary macrophages through a signaling complex, including CD36, TLR4, and Na/K-ATPase. These findings warrant further studies on endogenous CTS in chronic inflammatory diseases, such as atherosclerosis.



Mediator 1 Is Atherosclerosis Protective by Regulating Macrophage PolarizationHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—MED1 (mediator 1) interacts with transcription factors to regulate transcriptional machinery. The role of MED1 in macrophage biology and the relevant disease state remains to be investigated.Approach and Results—To study the molecular mechanism by which MED1 regulates the M1/M2 phenotype switch of macrophage and the effect on atherosclerosis, we generated MED1/apolipoprotein E (ApoE) double-deficient (MED1ΔMac/ApoE−/−) mice and found that atherosclerosis was greater in MED1ΔMac/ApoE−/− mice than in MED1fl/fl/ApoE−/− littermates. The gene expression of M1 markers was increased and that of M2 markers decreased in both aortic wall and peritoneal macrophages from MED1ΔMac/ApoE−/− mice, whereas MED1 overexpression rectified the changes in M1/M2 expression. Moreover, LDLR (low-density lipoprotein receptor)–deficient mice received bone marrow from MED1ΔMac mice showed greater atherosclerosis. Mechanistically, MED1 ablation decreased the binding of PPARγ (peroxisome proliferator–activated receptor γ) and enrichment of H3K4me1 and H3K27ac to upstream region of M2 marker genes. Furthermore, interleukin 4 induction of PPARγ and MED1 increased the binding of PPARγ or MED1 to the PPAR response elements of M2 marker genes.Conclusions—Our data suggest that MED1 is required for the PPARγ-mediated M2 phenotype switch, with M2 marker genes induced but M1 marker genes suppressed. MED1 in macrophages has an antiatherosclerotic role via PPARγ-regulated transactivation.



Farnesoid X Receptor and Liver X Receptor Ligands Initiate Formation of Coated PlateletsHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objectives—The liver X receptors (LXRs) and farnesoid X receptor (FXR) have been identified in human platelets. Ligands of these receptors have been shown to have nongenomic inhibitory effects on platelet activation by platelet agonists. This, however, seems contradictory with the platelet hyper-reactivity that is associated with several pathological conditions that are associated with increased circulating levels of molecules that are LXR and FXR ligands, such as hyperlipidemia, type 2 diabetes mellitus, and obesity.Approach and Results—We, therefore, investigated whether ligands for the LXR and FXR receptors were capable of priming platelets to the activated state without stimulation by platelet agonists. Treatment of platelets with ligands for LXR and FXR converted platelets to the procoagulant state, with increases in phosphatidylserine exposure, platelet swelling, reduced membrane integrity, depolarization of the mitochondrial membrane, and microparticle release observed. Additionally, platelets also displayed features associated with coated platelets such as P-selectin exposure, fibrinogen binding, fibrin generation that is supported by increased serine protease activity, and inhibition of integrin αIIbβ3. LXR and FXR ligand-induced formation of coated platelets was found to be dependent on both reactive oxygen species and intracellular calcium mobilization, and for FXR ligands, this process was found to be dependent on cyclophilin D.Conclusions—We conclude that treatment with LXR and FXR ligands initiates coated platelet formation, which is thought to support coagulation but results in desensitization to platelet stimuli through inhibition of αIIbβ3 consistent with their ability to inhibit platelet function and stable thrombus formation in vivo.



Cre/lox Studies Identify Resident Macrophages as the Major Source of Circulating Coagulation Factor XIII-AHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—To establish the cellular source of plasma factor (F)XIII-A.Approach and Results—A novel mouse floxed for the F13a1 gene, FXIII-Aflox/flox (Flox), was crossed with myeloid- and platelet-cre–expressing mice, and cellular FXIII-A mRNA expression and plasma and platelet FXIII-A levels were measured. The platelet factor 4-cre.Flox cross abolished platelet FXIII-A and reduced plasma FXIII-A to 23±3% (P<0.001). However, the effect of platelet factor 4-cre on plasma FXIII-A was exerted outside of the megakaryocyte lineage because plasma FXIII-A was not reduced in the Mpl−/− mouse, despite marked thrombocytopenia. In support of this, platelet factor 4-cre depleted FXIII-A mRNA in brain, aorta, and heart of floxed mice, where FXIII-Apos cells were identified as macrophages as they costained with CD163. In the integrin αM-cre.Flox and the double copy lysozyme 2-cre.cre.Flox crosses, plasma FXIII-A was reduced to, respectively, 75±5% (P=0.003) and 30±7% (P<0.001), with no change in FXIII-A content per platelet, further consistent with a macrophage origin of plasma FXIII-A. The change in plasma FXIII-A levels across the various mouse genotypes mirrored the change in FXIII-A mRNA expression in aorta. Bone marrow transplantation of FXIII-A+/+ bone marrow into FXIII-A−/− mice both restored plasma FXIII-A to normal levels and replaced aortic and cardiac FXIII-A mRNA, while its transplantation into FXIII-A+/+ mice did not increase plasma FXIII-A levels, suggesting that a limited population of niches exists that support FXIII-A-releasing cells.Conclusions—This work suggests that resident macrophages maintain plasma FXIII-A and exclude the platelet lineage as a major contributor.



Inner Mitochondrial Membrane Disruption Links Apoptotic and Agonist-Initiated Phosphatidylserine Externalization in PlateletsHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Phosphatidylserine exposure mediates platelet procoagulant function and regulates platelet life span. Apoptotic, necrotic, and integrin-mediated mechanisms have been implicated as intracellular determinants of platelet phosphatidylserine exposure. Here, we investigate (1) the role of mitochondrial events in platelet phosphatidylserine exposure initiated by these distinct stimuli and (2) the cellular interactions of the procoagulant platelet in vitro and in vivo.Approach and Results—Key mitochondrial events were examined, including cytochrome c release and inner mitochondrial membrane (IMM) disruption. In both ABT-737 (apoptotic) and agonist (necrotic)-treated platelets, phosphatidylserine externalization was temporally correlated with IMM disruption. Agonist stimulation resulted in rapid cyclophilin D–dependent IMM disruption that coincided with phosphatidylserine exposure. ABT-737 treatment caused rapid cytochrome c release, eventually followed by caspase-dependent IMM disruption that again closely coincided with phosphatidylserine exposure. A nonmitochondrial and integrin-mediated mechanism has been implicated in the formation of a novel phosphatidylserine-externalizing platelet subpopulation. Using image cytometry, this subpopulation is demonstrated to be the result of the interaction of an aggregatory platelet and a procoagulant platelet rather than indicative of a novel intracellular mechanism regulating platelet phosphatidylserine externalization. Using electron microscopy, similar interactions between aggregatory and procoagulant platelets are demonstrated in vitro and in vivo within a mesenteric vein hemostatic thrombus.Conclusions—Platelet phosphatidylserine externalization is closely associated with the mitochondrial event of IMM disruption identifying a common pathway in phosphatidylserine-externalizing platelets. The limited interaction of procoagulant platelets and integrin-active aggregatory platelets identifies a potential mechanism for procoagulant platelet retention within the hemostatic thrombus.



Implication of Inflammation and Epigenetic Readers in Coronary Artery Remodeling in Patients With Pulmonary Arterial HypertensionHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Pulmonary arterial hypertension (PAH) is a vascular disease not restricted to the lungs. Many signaling pathways described in PAH are also of importance in other vascular remodeling diseases, such as coronary artery disease (CAD). Intriguingly, CAD is 4× more prevalent in PAH compared with the global population, suggesting a link between these 2 diseases. Both PAH and CAD are associated with sustained inflammation and smooth muscle cell proliferation/apoptosis imbalance and we demonstrated in PAH that this phenotype is, in part, because of the miR-223/DNA damage/Poly[ADP-ribose] polymerase 1/miR-204 axis activation and subsequent bromodomain protein 4 (BRD4) overexpression. Interestingly, BRD4 is also a trigger for calcification and remodeling processes, both of which are important in CAD. Thus, we hypothesize that BRD4 activation in PAH influences the development of CAD.Approach and Results—PAH was associated with significant remodeling of the coronary arteries in both human and experimental models of the disease. As observed in PAH distal pulmonary arteries, coronary arteries of patients with PAH also exhibited increased DNA damage, inflammation, and BRD4 overexpression. In vitro, using human coronary artery smooth muscle cells from PAH, CAD and non-PAH–non-CAD patients, we showed that both PAH and CAD smooth muscle cells exhibited increased proliferation and suppressed apoptosis in a BRD4-dependent manner. In vivo, improvement of PAH by BRD4 inhibitor was associated with a reduction in coronary remodeling and interleukin-6 expression.Conclusions—Overall, this study demonstrates that increased BRD4 expression in coronary arteries of patient with PAH contributes to vascular remodeling and comorbidity development.



LRP1-Dependent BMPER Signaling Regulates Lipopolysaccharide-Induced Vascular InflammationHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Bacterial endotoxin (lipopolysaccharide)-mediated sepsis involves dysregulated systemic inflammation, which injures the lung and other organs, often fatally. Vascular endothelial cells act as both targets and mediators of lipopolysaccharide-induced inflammatory responses. Dysfunction of endothelium results in increases of proinflammatory cytokine production and permeability leakage. BMPER (bone morphogenetic protein–binding endothelial regulator), an extracellular modulator of bone morphogenetic protein signaling, has been identified as a vital component in chronic endothelial inflammatory responses and atherosclerosis. However, it is unclear whether BMPER also regulates inflammatory response in an acute setting such as sepsis. To address this question, we investigated the role of BMPER during lipopolysaccharide-induced acute lung injury.Approach and Results—Mice missing 1 allele of BMPER (BMPER+/− mice used in the place of BMPER−/− mice that die at birth) were used for lipopolysaccharide challenge. Lipopolysaccharide-induced pulmonary inflammation and injury was reduced in BMPER+/− mice as shown by several measures, including survival rate, infiltration of inflammatory cells, edema, and production of proinflammatory cytokines. Mechanistically, we have demonstrated that BMPER is required and sufficient for the activation of nuclear factor of activated T cells c1. This BMPER-induced nuclear factor of activated T cells activation is coordinated by multiple signaling pathways, including bone morphogenetic protein–independent low-density lipoprotein receptor–related protein 1-extracellular signal-regulated kinase activation, calcineurin signaling, and low-density lipoprotein receptor–related protein 1β–mediated nuclear factor 45 nuclear export in response to BMPER treatment.Conclusions—We conclude that BMPER plays a pivotal role in pulmonary inflammatory response, which provides new therapeutic options against sepsis shock. The new signaling pathway initiated by BMPER/low-density lipoprotein receptor–related protein 1 axis broadens our understanding about BMPER’s role in vascular homeostasis.



Ager Deletion Enhances Ischemic Muscle Inflammation, Angiogenesis, and Blood Flow Recovery in Diabetic MiceHighlights [Basic Sciences]

2017-07-26T12:43:42-07:00

Objective—Diabetic subjects are at higher risk of ischemic peripheral vascular disease. We tested the hypothesis that advanced glycation end products (AGEs) and their receptor (RAGE) block angiogenesis and blood flow recovery after hindlimb ischemia induced by femoral artery ligation through modulation of immune/inflammatory mechanisms.Approach and Results—Wild-type mice rendered diabetic with streptozotocin and subjected to unilateral femoral artery ligation displayed increased accumulation and expression of AGEs and RAGE in ischemic muscle. In diabetic wild-type mice, femoral artery ligation attenuated angiogenesis and impaired blood flow recovery, in parallel with reduced macrophage content in ischemic muscle and suppression of early inflammatory gene expression, including Ccl2 (chemokine [C-C motif] ligand-2) and Egr1 (early growth response gene-1) versus nondiabetic mice. Deletion of Ager (gene encoding RAGE) or transgenic expression of Glo1 (reduces AGEs) restored adaptive inflammation, angiogenesis, and blood flow recovery in diabetic mice. In diabetes mellitus, deletion of Ager increased circulating Ly6Chi monocytes and augmented macrophage infiltration into ischemic muscle tissue after femoral artery ligation. In vitro, macrophages grown in high glucose display inflammation that is skewed to expression of tissue damage versus tissue repair gene expression. Further, macrophages grown in high versus low glucose demonstrate blunted macrophage–endothelial cell interactions. In both settings, these adverse effects of high glucose were reversed by Ager deletion in macrophages.Conclusions—These findings indicate that RAGE attenuates adaptive inflammation in hindlimb ischemia; underscore microenvironment-specific functions for RAGE in inflammation in tissue repair versus damage; and illustrate that AGE/RAGE antagonism may fill a critical gap in diabetic peripheral vascular disease.



Human Blood Monocyte SubsetsHighlights [Translational Sciences]

2017-07-26T12:43:42-07:00

Objective—Human monocyte subsets are defined as classical (CD14++CD16−), intermediate (CD14++CD16+), and nonclassical (CD14+CD16+). Alterations in monocyte subset frequencies are associated with clinical outcomes, including cardiovascular disease, in which circulating intermediate monocytes independently predict cardiovascular events. However, delineating mechanisms of monocyte function is hampered by inconsistent results among studies.Approach and Results—We use cytometry by time-of-flight mass cytometry to profile human monocytes using a panel of 36 cell surface markers. Using the dimensionality reduction approach visual interactive stochastic neighbor embedding (viSNE), we define monocytes by incorporating all cell surface markers simultaneously. Using viSNE, we find that although classical monocytes are defined with high purity using CD14 and CD16, intermediate and nonclassical monocytes defined using CD14 and CD16 alone are frequently contaminated, with average intermediate and nonclassical monocyte purity of ≈86.0% and 87.2%, respectively. To improve the monocyte purity, we devised a new gating scheme that takes advantage of the shared coexpression of cell surface markers on each subset. In addition to CD14 and CD16, CCR2, CD36, HLA-DR, and CD11c are the most informative markers that discriminate among the 3 monocyte populations. Using these additional markers as filters, our revised gating scheme increases the purity of both intermediate and nonclassical monocyte subsets to 98.8% and 99.1%, respectively. We demonstrate the use of this new gating scheme using conventional flow cytometry of peripheral blood mononuclear cells from subjects with cardiovascular disease.Conclusions—Using cytometry by time-of-flight mass cytometry, we have identified a small panel of surface markers that can significantly improve monocyte subset identification and purity in flow cytometry. Such a revised gating scheme will be useful for clinical studies of monocyte function in human cardiovascular disease.



Codependence of Bone Morphogenetic Protein Receptor 2 and Transforming Growth Factor-{beta} in Elastic Fiber Assembly and Its Perturbation in Pulmonary Arterial HypertensionHighlights [Translational Sciences]

2017-07-26T12:43:42-07:00

Objective—We determined in patients with pulmonary arterial (PA) hypertension (PAH) whether in addition to increased production of elastase by PA smooth muscle cells previously reported, PA elastic fibers are susceptible to degradation because of their abnormal assembly.Approach and Results—Fibrillin-1 and elastin are the major components of elastic fibers, and fibrillin-1 binds bone morphogenetic proteins (BMPs) and the large latent complex of transforming growth factor-β1 (TGFβ1). Thus, we considered whether BMPs like TGFβ1 contribute to elastic fiber assembly and whether this process is perturbed in PAH particularly when the BMP receptor, BMPR2, is mutant. We also assessed whether in mice with Bmpr2/1a compound heterozygosity, elastic fibers are susceptible to degradation. In PA smooth muscle cells and adventitial fibroblasts, TGFβ1 increased elastin mRNA, but the elevation in elastin protein was dependent on BMPR2; TGFβ1 and BMP4, via BMPR2, increased extracellular accumulation of fibrillin-1. Both BMP4- and TGFβ1-stimulated elastic fiber assembly was impaired in idiopathic (I) PAH-PA adventitial fibroblast versus control cells, particularly those with hereditary (H) PAH and a BMPR2 mutation. This was related to profound reductions in elastin and fibrillin-1 mRNA. Elastin protein was increased in IPAH PA adventitial fibroblast by TGFβ1 but only minimally so in BMPR2 mutant cells. Fibrillin-1 protein increased only modestly in IPAH or HPAH PA adventitial fibroblasts stimulated with BMP4 or TGFβ1. In Bmpr2/1a heterozygote mice, reduced PA fibrillin-1 was associated with elastic fiber susceptibility to degradation and more severe pulmonary hypertension.Conclusions—Disrupting BMPR2 impairs TGFβ1- and BMP4-mediated elastic fiber assembly and is of pathophysiologic significance in PAH.



Oxidized Phospholipids and Risk of Calcific Aortic Valve DiseaseHighlights [Clinical and Population Studies]

2017-07-26T12:43:42-07:00

Objective—Lipoprotein(a) is causally associated with calcific aortic valve disease (CAVD). Lipoprotein(a) carries proinflammatory and procalcific oxidized phospholipids (OxPL). We tested whether the CAVD risk is mediated by the content of OxPL on lipoprotein(a).Approach and Results—A case–control study was performed within the Copenhagen General Population Study (n=87 980), including 725 CAVD cases (1977–2013) and 1413 controls free of cardiovascular disease. OxPL carried by apoB (apolipoprotein B-100; OxPL-apoB) or apolipoprotein(a) (OxPL-apo(a)) containing lipoproteins, lipoprotein(a) levels, LPA kringle IV type 2 repeat, and rs10455872 genetic variants were measured. OxPL-apoB and OxPL-apo(a) levels correlated with lipoprotein(a) levels among cases (r=0.75 and r=0.95; both P<0.001) and controls (r=0.65 and r=0.93; both P<0.001). OxPL-apoB levels associated with risk of CAVD with odds ratios of 1.2 (95% confidence interval [CI]:1.0–1.6) for 34th to 66th percentile levels, 1.6 (95% CI, 1.2–2.1) for 67th to 90th percentile levels, 2.0 (95% CI, 1.3–3.0) for 91st to 95th percentile levels, and 3.4 (95% CI, 2.1–5.5) for levels >95th percentile, versus levels <34th percentile (trend, P<0.001). Corresponding odds ratios for OxPL-apo(a) were 1.2 (95% CI, 1.0–1.5), 1.2(95% CI, 0.9–1.6), 2.1(95% CI, 1.4–3.1), and 2.9(95% CI, 1.9–4.5; trend, P<0.001) and were similar for lipoprotein(a). LPA genotypes associated with OxPL-apoB, OxPL-apo(a), and lipoprotein(a) levels and explained 34%, 46%, and 39%, respectively, of the total variation in levels. LPA genotypes associated with risk of CAVD; a doubling in genetically determined OxPL-apoB, OxPL-apo(a), and lipoprotein(a) levels associated with odds ratio of CAVD of 1.18 (95% CI, 1.10–1.27), 1.09 (95% CI, 1.05–1.13), and 1.09 (95% CI, 1.05–1.14), respectively, comparable to the corresponding observational estimates of 1.27 (95% CI, 1.16–1.39), 1.13 (95% CI, 1.08–1.18), and 1.11 (95% CI, 1.06–1.17).Conclusions—OxPL-apoB and OxPL-apo(a) are novel genetic and potentially causal risk factors for CAVD and may explain the association of lipoprotein(a) with CAVD.



Blood Pressure and Heart Rate Measures Associated With Increased Risk of Covert Brain Infarction and Worsening Leukoaraiosis in Older AdultsHighlights [Clinical and Population Studies]

2017-07-26T12:43:42-07:00

Objective—In people without previous stroke, covert findings on serial magnetic resonance imaging (MRI) of incident brain infarcts and worsening leukoaraiosis are associated with increased risk for ischemic stroke and dementia. We evaluated whether various measures of blood pressure (BP) and heart rate are associated with these MRI findings.Approach and Results—In the CHS (Cardiovascular Health Study), a longitudinal cohort study of older adults, we used relative risk regression to assess the associations of mean, variability, and trend in systolic BP, diastolic BP, and heart rate measured at 4 annual clinic visits between 2 brain MRIs with incident covert brain infarction and worsening white matter grade (using a 10-point scale to characterize leukoaraiosis). We included participants who had both brain MRIs, no stroke before the follow-up MRI, and no change in antihypertensive medication status during follow-up. Among 878 eligible participants, incident covert brain infarction occurred in 15% and worsening white matter grade in 27%. Mean systolic BP was associated with increased risk for incident covert brain infarction (relative risk per 10 mm Hg, 1.28; 95% confidence interval, 1.12–1.47), and mean diastolic BP was associated with increased risk for worsening white matter grade (relative risk per 10 mm Hg, 1.45; 95% confidence interval, 1.24–1.69). These findings persisted in secondary and sensitivity analyses.Conclusions—Elevated mean systolic BP is associated with increased risk for covert brain infarction, and elevated mean diastolic BP is associated with increased risk for worsening leukoaraiosis. These findings reinforce the importance of hypertension in the development of silent cerebrovascular diseases, but the pathophysiologic relationships to BP for each may differ.









DBA/2J Haplotype on Distal Chromosome 2 Reduces Mertk Expression, Restricts Efferocytosis, and Increases Susceptibility to AtherosclerosisHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Arch atherosclerosis 4 (Aath4) is a quantitative trait locus for atherosclerotic plaque formation in the inner curve of the aortic arch previously identified in an F2 cross of Apoe−/− mice on DBA/2J and 129S6 backgrounds. C-mer proto-oncogene tyrosine kinase (Mertk), coding for a ligand-activated transmembrane tyrosine kinase, is a candidate gene within the same chromosomal region. Our objective was to determine whether strain differences in Mertk influence plaque formation.Approach and Results—To dissect the strain effects of Mertk on atherosclerosis, we first established a congenic mouse line (Aath4aDBA/DBA) in which a 5′ region of Aath4 of DBA/2J, including Mertk, was backcrossed onto a 129S6-Apoe−/− background. The resulting Aath4aDBA/DBA male mice developed significantly larger plaques compared with control mice (Aath4a129/129), proving that the DBA/2J allele of Aath4a is proatherogenic. Thioglycollate-elicited peritoneal macrophages from Aath4aDBA/DBA mice express less than 50% of Mertk mRNA and cell-surface MERTK protein compared with those from the control mice. Moreover, both large and small peritoneal Aath4aDBA/DBA macrophages showed reduced phagocytosis of apoptotic cells. When Mertk cDNAs from 129S6 and DBA/2J mice were overexpressed in HEK293T (human embryonic kidney 293T) cells, phagocytosis of apoptotic cells was equally enhanced in direct proportion to Mertk levels, indicating that phagocytosis is modulated by the amount of MERTK, but that it is not affected by MERTK amino acid differences between 129S6 and DBA/2J.Conclusions—Reduced transcription of Mertk, rather than differences in MERTK protein structure, determines the reduced efficiency of apoptotic cell clearance in the Aath4aDBA/DBA mice, which, in turn, contributes to their increased susceptibility to atherosclerosis.



A Game of Unknowns [Editorial]

2017-06-21T12:43:28-07:00




GAS6 [Editorial]

2017-06-21T12:43:28-07:00




Charming the Snake [Editorial]

2017-06-21T12:43:28-07:00










iNOS-Derived Nitric Oxide Induces Integrin-Linked Kinase Endocytic Lysosome-Mediated Degradation in the Vascular EndotheliumHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—ILK (integrin-linked kinase) plays a key role in controlling vasomotor tone and is decreased in atherosclerosis. The objective of this study is to test whether nitric oxide (NO) regulates ILK in vascular remodeling.Approach and Results—We found a striking correlation between increased levels of inducible nitric oxide and decreased ILK levels in human atherosclerosis and in a mouse model of vascular remodeling (carotid artery ligation) comparing with iNOS (inducible NO synthase) knockout mice. iNOS induction produced the same result in mouse aortic endothelial cells, and these effects were mimicked by an NO donor in a time-dependent manner. We found that NO decreased ILK protein stability by promoting the dissociation of the complex ILK/Hsp90 (heat shock protein 90)/eNOS (endothelial NO synthase), leading to eNOS uncoupling. NO also destabilized ILK signaling platform and lead to decreased levels of paxillin and α-parvin. ILK phosphorylation of its downstream target GSK3-β (glycogen synthase kinase 3 beta) was decreased by NO. Mechanistically, NO increased ILK ubiquitination mediated by the E3 ubiquitin ligase CHIP (C terminus of HSC70-interacting protein), but ILK ubiquitination was not followed by proteasome degradation. Alternatively, NO drove ILK to degradation through the endocytic-lysosomal pathway. ILK colocalized with the lysosome marker LAMP-1 (lysosomal-associated membrane protein 1) in endothelial cells, and inhibition of lysosome activity with chloroquine reversed the effect of NO. Likewise, ILK colocalized with the early endosome marker EEA1 (early endosome antigen 1). ILK endocytosis proceeded via dynamin because a specific inhibitor of dynamin (Dyngo 4a) was able to reverse ILK endocytosis and its lysosome degradation.Conclusions—Endocytosis regulates ILK signaling in vascular remodeling where there is an overload of inducible NO, and thus its inhibition may represent a novel target to fight atherosclerotic disease.



Increased Hepatic Expression of Endothelial Lipase Inhibits Cholesterol Diet-Induced Hypercholesterolemia and Atherosclerosis in Transgenic RabbitsHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Endothelial lipase (EL) is a key determinant in plasma high-density lipoprotein-cholesterol. However, functional roles of EL on the development of atherosclerosis have not been clarified. We investigated whether hepatic expression of EL affects plasma lipoprotein metabolism and cholesterol diet–induced atherosclerosis.Approach and Results—We generated transgenic (Tg) rabbits expressing the human EL gene in the liver and then examined the effects of EL expression on plasma lipids and lipoproteins and compared the susceptibility of Tg rabbits with cholesterol diet–induced atherosclerosis with non-Tg littermates. On a chow diet, hepatic expression of human EL in Tg rabbits led to remarkable reductions in plasma levels of total cholesterol, phospholipids, and high-density lipoprotein-cholesterol compared with non-Tg controls. On a cholesterol-rich diet for 16 weeks, Tg rabbits exhibited significantly lower hypercholesterolemia and less atherosclerosis than non-Tg littermates. In Tg rabbits, gross lesion area of aortic atherosclerosis was reduced by 52%, and the lesions were characterized by fewer macrophages and smooth muscle cells compared with non-Tg littermates.Conclusions—Increased hepatic expression of EL attenuates cholesterol diet–induced hypercholesterolemia and protects against atherosclerosis.



Activation of Adiponectin Receptor Regulates Proprotein Convertase Subtilisin/Kexin Type 9 Expression and Inhibits Lesions in ApoE-Deficient MiceHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—The reduced adiponectin levels are associated with atherosclerosis. Adiponectin exerts its functions by activating adiponectin receptor (AdipoR). Proprotein convertase subtilisin kexin type 9 (PCSK9) degrades LDLR protein (low-density lipoprotein receptor) to increase serum LDL-cholesterol levels. PCSK9 expression can be regulated by PPARγ (peroxisome proliferator–activated receptor γ) or SREBP2 (sterol regulatory element-binding protein 2). The effects of AdipoR agonists on PCSK9 and LDLR expression, serum lipid profiles, and atherosclerosis remain unknown.Approach and Results—At cellular levels, AdipoR agonists (ADP355 and AdipoRon) induced PCSK9 transcription/expression that solely depended on activation of PPAR-responsive element in the PCSK9 promoter. AdipoR agonists induced PPARγ expression; thus, the AdipoR agonist-activated PCSK9 expression/production was impaired in PPARγ deficient hepatocytes. Meanwhile, AdipoR agonists transcriptionally activated LDLR expression by activating SRE in the LDLR promoter. Moreover, AMP-activated protein kinase α (AMPKα) was involved in AdipoR agonist-activated PCSK9 expression. In wild-type mice, ADP355 increased PCSK9 and LDLR expression and serum PCSK9 levels, which was associated with activation of PPARγ, AMPKα and SREBP2 and reduction of LDL-cholesterol levels. In contrast, ADP355 reduced PCSK9 expression/secretion in apoE-deficient (apoE−/−) mice, but it still activated hepatic LDLR, PPARγ, AMPKα, and SREBP2. More importantly, ADP355 inhibited lesions in en face aortas and sinus lesions in aortic root in apoE−/− mice with amelioration of lipid profiles.Conclusions—Our study demonstrates that AdipoR activation by agonists regulated PCSK9 expression differently in wild-type and apoE−/− mice. However, ADP355 activated hepatic LDLR expression and ameliorated lipid metabolism in both types of mice and inhibited atherosclerosis in apoE−/− mice.



Apolipoprotein A-I Mimetic PeptidesHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Apolipoprotein A-I (apoA-I) mimetic peptides have antiatherogenic properties of high-density lipoprotein in vitro and have been shown to inhibit atherosclerosis in vivo. It is unclear, however, if each in vitro antiatherogenic property of these peptides translates to a corresponding activity in vivo, and if so, which of these contributes most to reduce atherosclerosis.Approach and Results—The effect of 7 apoA-I mimetic peptides, which were developed to selectively reproduce a specific component of the antiatherogenic properties of apoA-I, on the development of atherosclerosis was investigated in apolipoprotein E–deficient mice fed a high-fat diet for 4 or 12 weeks. The peptides include those that selectively upregulate cholesterol efflux, or are anti-inflammatory, or have antioxidation properties. All the peptides studied effectively inhibited the in vivo development of atherosclerosis in this model to the same extent. However, none of the peptides had the same selective effect in vivo as they had exhibited in vitro. None of the tested peptides affected plasma lipoprotein profile; capacity of plasma to support cholesterol efflux was increased modestly and similarly for all peptides.Conclusions—There is a discordance between the selective in vitro and in vivo functional properties of apoA-I mimetic peptides, and the in vivo antiatherosclerotic effect of apoA-I-mimetic peptides is independent of their in vitro functional profile. Comparing the properties of apoA-I mimetic peptides in plasma rather than in the lipid-free state is better for predicting their in vivo effects on atherosclerosis.



Trowaglerix Venom Polypeptides As a Novel Antithrombotic Agent by Targeting Immunoglobulin-Like Domains of Glycoprotein VI in PlateletHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Currently prescribed antiplatelet drugs have 1 common side effect—an increased risk of hemorrhage and thrombocytopenia. On the contrary, bleeding defects associated with glycoprotein VI (GPVI) expression deficiency are usually slightly prolonged bleeding times. However, GPVI antagonists are lacking in clinic.Approach and Results—Using reverse-phase high-performance liquid chromatography and sequencing, we revealed the partial sequence of trowaglerix α subunit, a potent specific GPVI-targeting snaclec (snake venom C-type lectin protein). Hexapeptide (Troα6 [trowaglerix a chain hexapeptide, CKWMNV]) and decapeptide (Troα10) derived from trowaglerix specifically inhibited collagen-induced platelet aggregation through blocking platelet GPVI receptor. Computational peptide design helped to design a series of Troα6/Troα10 peptides. Protein docking studies on these decapeptides and GPVI suggest that Troα10 was bound at the lower surface of D1 domain and outer surface of D2 domain, which was at the different place of the collagen-binding site and the scFv (single-chain variable fragment) D2-binding site. The newly discovered site was confirmed by inhibitory effects of polyclonal antibodies on collagen-induced platelet aggregation. This indicates that D2 domain of GPVI is a novel and important binding epitope on GPVI-mediated platelet aggregation. Troα6/Troα10 displayed prominent inhibitory effect of thrombus formation in fluorescein sodium-induced platelet thrombus formation of mesenteric venules and ferric chloride-induced carotid artery injury thrombosis model without prolonging the in vivo bleeding time.Conclusions—We develop a novel antithrombotic peptides derived from trowaglerix that acts through GPVI antagonism with greater safety—no severe bleeding. The binding epitope of polypeptides on GPVI is novel and important. These hexa/decapeptides have therapeutic potential for developing ideal small-mass GPVI antagonists for arterial thrombogenic diseases.



Gas6 Promotes Inflammatory (CCR2hiCX3CR1lo) Monocyte Recruitment in Venous ThrombosisHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Coagulation and inflammation are inter-related. Gas6 (growth arrest–specific 6) promotes venous thrombosis and participates to inflammation through endothelial-innate immune cell interactions. Innate immune cells can provide the initiating stimulus for venous thrombus development. We hypothesize that Gas6 promotes monocyte recruitment during venous thrombosis.Approach and Results—Deep venous thrombosis was induced in wild-type and Gas6-deficient (−/−) mice using 5% FeCl3 and flow reduction in the inferior vena cava. Total monocyte depletion was achieved by injection of clodronate before deep venous thrombosis. Inflammatory monocytes were depleted using an anti–C-C chemokine receptor type 2 (CCR2) antibody. Similarly, injection of an anti–chemokine ligand 2 (CCL2) antibody induced CCL2 depletion. Flow cytometry and immunofluorescence were used to characterize the monocytes recruited to the thrombus. In vivo, absence of Gas6 was associated with a reduction of monocyte recruitment in both deep venous thrombosis models. Global monocyte depletion by clodronate leads to smaller thrombi in wild-type mice. Compared with wild type, the thrombi from Gas6−/− mice contain less inflammatory (CCR2hiCX3CR1lo) monocytes, consistent with a Gas6-dependent recruitment of this monocyte subset. Correspondingly, selective depletion of CCR2hiCX3CR1lo monocytes reduced the formation of venous thrombi in wild-type mice demonstrating a predominant role of the inflammatory monocytes in thrombosis. In vitro, the expression of both CCR2 and CCL2 were Gas6 dependent in monocytes and endothelial cells, respectively, impacting monocyte migration. Moreover, Gas6-dependent CCL2 expression and monocyte migration were mediated via JNK (c-Jun N-terminal kinase).Conclusions—This study demonstrates that Gas6 specifically promotes the recruitment of inflammatory CCR2hiCX3CR1lo monocytes through the regulation of both CCR2 and CCL2 during deep venous thrombosis.



Tissue Factor Prothrombotic Activity Is Regulated by Integrin-arf6 TraffickingHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Coagulation initiation by tissue factor (TF) is regulated by cellular inhibitors, cell surface availability of procoagulant phosphatidylserine, and thiol-disulfide exchange. How these mechanisms contribute to keeping TF in a noncoagulant state and to generating prothrombotic TF remain incompletely understood.Approach and Results—Here, we study the activation of TF in primary macrophages by a combination of pharmacological, genetic, and biochemical approaches. We demonstrate that primed macrophages effectively control TF cell surface activity by receptor internalization. After cell injury, ATP signals through the purinergic receptor P2rx7 induce release of TF+ microvesicles. TF cell surface availability for release onto microvesicles is regulated by the GTPase arf6 associated with integrin α4β1. Furthermore, microvesicles proteome analysis identifies activation of Gαi2 as a participating factor in the release of microvesicles with prothrombotic activity in flowing blood. ATP not only prevents TF and phosphatidylserine internalization but also induces TF conversion to a conformation with high affinity for its ligand, coagulation factor VII. Although inhibition of dynamin-dependent internalization also exposes outer membrane procoagulant phosphatidylserine, the resulting TF+ microvesicles distinctly lack protein disulfide isomerase and high affinity TF and fail to produce fibrin strands typical for microvesicles generated by thrombo-inflammatory P2rx7 activation.Conclusions—These data show that procoagulant phospholipid exposure is not sufficient and that TF affinity maturation is required to generate prothrombotic microvesicles from a variety of cell types. These findings are significant for understanding TF-initiated thrombosis and should be considered in designing functional microvesicles-based diagnostic approaches.



ADAMTS13 Retards Progression of Diabetic Nephropathy by Inhibiting Intrarenal Thrombosis in MiceHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—ADAMTS13 (a disintegrin and metalloprotease with thrombospondin type I repeats-13) prevents microvascular thrombosis by cleaving prothrombogenic ultralarge von Willebrand factor (VWF) multimers. Clinical studies have found association between reduced ADAMTS13-specific activity, ultralarge VWF multimers, and thrombotic angiopathy in patients with diabetic nephropathy. It remains unknown, however, whether ADAMTS13 deficiency or ultralarge VWF multimers have a causative effect in diabetic nephropathy.Approach and Results—The extent of renal injury was evaluated in wild-type (WT), Adamts13−/− and Adamts13−/−Vwf−/− mice after 26 weeks of streptozotocin-induced diabetic nephropathy. We found that WT diabetic mice exhibited low plasma ADAMTS13-specific activity and increased VWF levels (P<0.05 versus WT nondiabetic mice). Adamts13−/− diabetic mice exhibited deterioration of kidney function (increased albuminuria, plasma creatinine, and urea; P<0.05 versus WT diabetic mice), independent of hyperglycemia and hypertension. Deterioration of kidney function in Adamts13−/− diabetic mice was concomitant with aggravated intrarenal thrombosis (assessed by plasminogen activator inhibitor, VWF, fibrin(ogen), and CD41-positive microthrombi), increased mesangial cell expansion, and extracellular matrix deposition (P<0.05 versus WT diabetic mice). Genetic deletion of VWF in Adamts13−/− diabetic mice improved kidney function, inhibited intrarenal thrombosis, and alleviated histological changes in glomeruli, suggesting that exacerbation of diabetic nephropathy in the setting of ADAMTS13 deficiency is VWF dependent.Conclusions—ADAMTS13 retards progression of diabetic nephropathy, most likely by inhibiting VWF-dependent intrarenal thrombosis. Alteration in ADAMTS13–VWF balance may be one of the key pathophysiological mechanisms of thrombotic angiopathy in diabetes mellitus.



ADAMTS5 Deficiency in Calcified Aortic Valves Is Associated With Elevated Pro-Osteogenic Activity in Valvular Interstitial CellsHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Extracellular matrix proteinases are implicated in the pathogenesis of calcific aortic valve disease. The ADAMTS5 (a disintegrin and metalloproteinase with thrombospondin motifs 5) enzyme is secreted, matrix-associated metalloendopeptidase, capable of degrading extracellular matrix proteins, particularly matrilin 2. We sought to determine the role of the ADAMTS5/matrilin 2 axis in mediating the phenotype transition of valvular interstitial cells (VICs) associated with calcific aortic valve disease.Approach and Results—Levels of ADAMTS5, matrilin 2, and α-SMA (α-smooth muscle actin) were evaluated in calcified and normal human aortic valve tissues and VICs. Calcified aortic valves have reduced levels of ADAMTS5 and higher levels of matrilin 2 and α-SMA. Treatment of normal VICs with soluble matrilin 2 caused an increase in α-SMA level through Toll-like receptors 2 and 4, which was accompanied by upregulation of runt-related transcription factor 2 and alkaline phosphatase. In addition, ADAMTS5 knockdown in normal VICs enhanced the effect of matrilin 2. Matrilin 2 activated nuclear factor (NF) κB and NF of activated T cells complex 1 and induced the interaction of these 2 NFs. Inhibition of either NF-κB or NF of activated T cells complex 1 suppressed matrilin 2’s effect on VIC phenotype change. Knockdown of α-SMA reduced and overexpression of α-SMA enhanced the expression of pro-osteogenic factors and calcium deposit formation in human VICs.Conclusions—Matrilin 2 induces myofibroblastic transition and elevates pro-osteogenic activity in human VICs via activation of NF-κB and NF of activated T cells complex 1. Myofibroblastic transition in human VICs is an important mechanism of elevating the pro-osteogenic activity. Matrilin 2 accumulation associated with relative ADAMTS5 deficiency may contribute to the mechanism underlying calcific aortic valve disease progression.



Janus Kinase 3, a Novel Regulator for Smooth Muscle Proliferation and Vascular RemodelingHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Vascular remodeling because of smooth muscle cell (SMC) proliferation is a common process occurring in several vascular diseases, such as atherosclerosis, aortic aneurysm, post-transplant vasculopathy, restenosis after angioplasty, etc. The molecular mechanism underlying SMC proliferation, however, is not completely understood. The objective of this study is to determine the role and mechanism of Janus kinase 3 (JAK3) in vascular remodeling and SMC proliferation.Approach and Results—Platelet-derived growth factor-BB, an SMC mitogen, induces JAK3 expression and phosphorylation while stimulating SMC proliferation. Janex-1, a specific inhibitor of JAK3, or knockdown of JAK3 by short hairpin RNA, inhibits the SMC proliferation. Conversely, ectopic expression of JAK3 promotes SMC proliferation. Mechanistically, JAK3 promotes the phosphorylation of signal transducer and activator of transcription 3 and c-Jun N-terminal kinase in SMC, 2 signaling pathways known to be critical for SMC proliferation and vascular remodeling. Blockade of these 2 signaling pathways by their inhibitors impeded the JAK3-mediated SMC proliferation. In vivo, knockdown of JAK3 attenuates injury-induced neointima formation with attenuated neointimal SMC proliferation. Knockdown of JAK3 also induces neointimal SMC apoptosis in rat carotid artery balloon injury model.Conclusions—Our results demonstrate that JAK3 mediates SMC proliferation and survival during injury-induced vascular remodeling, which provides a potential therapeutic target for preventing neointimal hyperplasia in proliferative vascular diseases.



Serotonin Signaling Through the 5-HT1B Receptor and NADPH Oxidase 1 in Pulmonary Arterial HypertensionHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Serotonin can induce human pulmonary artery smooth muscle cell (hPASMC) proliferation through reactive oxygen species (ROS), influencing the development of pulmonary arterial hypertension (PAH). We hypothesize that in PASMCs, serotonin induces oxidative stress through NADPH-oxidase–derived ROS generation and reduced Nrf-2 (nuclear factor [erythroid-derived 2]-like 2) antioxidant systems, promoting vascular injury.Approach and Results—HPASMCs from controls and PAH patients, and PASMCs from Nox1−/− mice, were stimulated with serotonin in the absence/presence of inhibitors of Src kinase, the 5-HT1B receptor, and NADPH oxidase 1 (Nox1). Markers of fibrosis were also determined. The pathophysiological significance of our findings was examined in vivo in serotonin transporter overexpressing female mice, a model of pulmonary hypertension. We confirmed thatserotonin increased superoxide and hydrogen peroxide production in these cells. For the first time, we show that serotonin increased oxidized protein tyrosine phosphatases and hyperoxidized peroxiredoxin and decreased Nrf-2 and catalase activity in hPASMCs. ROS generation was exaggerated and dependent on cellular Src-related kinase, 5-HT1B receptor, and the serotonin transporter in human pulmonary artery smooth muscle cells from PAH subjects. Proliferation and extracellular matrix remodeling were exaggerated in human pulmonary artery smooth muscle cells from PAH subjects and dependent on 5-HT1B receptor signaling and Nox1, confirmed in PASMCs from Nox1−/− mice. In serotonin transporter overexpressing mice, SB216641, a 5-HT1B receptor antagonist, prevented development of pulmonary hypertension in a ROS-dependent manner.Conclusions—Serotonin can induce cellular Src-related kinase–regulated Nox1-induced ROS and Nrf-2 dysregulation, contributing to increased post-translational oxidative modification of proteins and activation of redox-sensitive signaling pathways in hPASMCs, associated with mitogenic responses. 5-HT1B receptors contribute to experimental pulmonary hyperte[...]



Neutrophil Extracellular Traps Drive Endothelial-to-Mesenchymal TransitionHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—An excessive release and impaired degradation of neutrophil extracellular traps (NETs) leads to the continuous exposure of NETs to the endothelium in a variety of hematologic and autoimmune disorders, including lupus nephritis. This study aims to unravel the mechanisms through which NETs jeopardize vascular integrity.Approach and Results—Microvascular and macrovascular endothelial cells were exposed to NETs, and subsequent effects on endothelial integrity and function were determined in vitro and in vivo. We found that endothelial cells have a limited capacity to internalize NETs via the receptor for advanced glycation endproducts. An overflow of the phagocytic capacity of endothelial cells for NETs resulted in the persistent extracellular presence of NETs, which rapidly altered endothelial cell–cell contacts and induced vascular leakage and transendothelial albumin passage through elastase-mediated proteolysis of the intercellular junction protein VE-cadherin. Furthermore, NET-associated elastase promoted the nuclear translocation of junctional β-catenin and induced endothelial-to-mesenchymal transition in cultured endothelial cells. In vivo, NETs could be identified in kidney samples of diseased MRL/lpr mice and patients with lupus nephritis, in whom the glomerular presence of NETs correlated with the severity of proteinuria and with glomerular endothelial-to-mesenchymal transition.Conclusions—These results indicate that an excess of NETs exceeds the phagocytic capacity of endothelial cells for NETs and promotes vascular leakage and endothelial-to-mesenchymal transition through the degradation of VE-cadherin and the subsequent activation of β-catenin signaling. Our data designate NET-associated elastase as a potential therapeutic target in the prevention of endothelial alterations in diseases characterized by aberrant NET release.



Endothelial Myocyte Enhancer Factor 2c Inhibits Migration of Smooth Muscle Cells Through Fenestrations in the Internal Elastic LaminaHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Laminar flow activates myocyte enhancer factor 2 (MEF2) transcription factors in vitro to induce expression of atheroprotective genes in the endothelium. Here we sought to establish the role of Mef2c in the vascular endothelium in vivo.Approach and Results—To study endothelial Mef2c, we generated endothelial-specific deletion of Mef2c using Tie2-Cre or Cdh5-Cre-ERT2 and examined aortas and carotid arteries by en face immunofluorescence. We observed enhanced actin stress fiber formation in the Mef2c-deleted thoracic aortic endothelium (laminar flow region), similar to those observed in normal aortic inner curvature (disturbed flow region). Furthermore, Mef2c deletion resulted in the de novo formation of subendothelial intimal cells expressing markers of differentiated smooth muscle in the thoracic aortas and carotids. Lineage tracing showed that these cells were not of endothelial origin. To define early events in intimal development, we induced endothelial deletion of Mef2c and examined aortas at 4 and 12 weeks postinduction. The number of intimal cell clusters increased from 4 to 12 weeks, but the number of cells within a cluster peaked at 2 cells in both cases, suggesting ongoing migration but minimal proliferation. Moreover, we identified cells extending from the media through fenestrations in the internal elastic lamina into the intima, indicating transfenestral smooth muscle migration. Similar transfenestral migration was observed in wild-type carotid arteries ligated to induce neointimal formation.Conclusions—These results indicate that endothelial Mef2c regulates the endothelial actin cytoskeleton and inhibits smooth muscle cell migration into the intima.



Oligogalacturonic Acid Inhibits Vascular Calcification by Two MechanismsHighlights [Basic Sciences]

2017-06-21T12:43:28-07:00

Objective—Cardiovascular diseases constitute the leading cause of mortality worldwide. Calcification of the vessel wall is associated with cardiovascular morbidity and mortality in patients having many diseases, including diabetes mellitus, atherosclerosis, and chronic kidney disease. Vascular calcification is actively regulated by inductive and inhibitory mechanisms (including vascular smooth muscle cell adaptation) and results from an active osteogenic process. During the calcification process, extracellular vesicles (also known as matrix vesicles) released by vascular smooth muscle cells interact with type I collagen and then act as nucleating foci for calcium crystallization. Our primary objective was to identify new, natural molecules that inhibit the vascular calcification process.Approach and Results—We have found that oligogalacturonic acids (obtained by the acid hydrolysis of polygalacturonic acid) reduce in vitro inorganic phosphate–induced calcification of vascular smooth muscle cells by 80% and inorganic phosphate–induced calcification of isolated rat aortic rings by 50%. A specific oligogalacturonic acid with a degree of polymerization of 8 (DP8) was found to inhibit the expression of osteogenic markers and, thus, prevent the conversion of vascular smooth muscle cells into osteoblast-like cells. We also evidenced in biochemical and immunofluorescence assays a direct interaction between matrix vesicles and type I collagen via the GFOGER sequence (where single letter amino acid nomenclature is used, O=hydroxyproline) thought to be involved in interactions with several pairs of integrins.Conclusions—DP8 inhibits vascular calcification development mainly by inhibition of osteogenic marker expression but also partly by masking the GFOGER sequence—thereby, preventing matrix vesicles from binding to type I collagen.



Circulating MicroRNA-125b Predicts the Presence and Progression of Uremic Vascular CalcificationHighlights [Translational Sciences]

2017-06-21T12:43:28-07:00

Objective—Vascular calcification (VC) is a major cause of mortality in patients with end-stage renal diseases. Biomarkers to predict the progression of VC early are in urgent demand.Approach and Results—We identified circulating, cell-free microRNAs as potential biomarkers using in vitro VC models in which both rat and human aortic vascular smooth muscle cells were treated with high levels of phosphate to mimic uremic hyperphosphatemia. Using an Affymetrix microRNA array, we found that miR-125b and miR-382 expression levels declined significantly as biomineralization progressed, but this decline was only observed for miR-125b in the culture medium. A time-dependent decrease in aortic tissue and serum miR-125b levels was also found in both ex vivo and in vivo renal failure models. We examined the levels of circulating, cell-free miR-125b in sera from patients with end-stage renal diseases (n=88) and found an inverse association between the severity of VC and the circulating miR-125b level, irrespective of age or mineral-related hormones (odds ratio, 0.71; P=0.03). Furthermore, serum miR-125b levels on enrollment can predict VC progression years later (for high versus low, odds ratio, 0.14; P<0.01; for the highest versus lowest tertile and middle versus lowest tertile, odds ratio, 0.55 and 0.13; P=0.3 and <0.01, respectively). The uremic VC prediction efficacy using circulating miR-125b levels was also observed in an independent cohort (n=135).Conclusions—The results suggest that serum miR-125b levels are associated with VC severity and serve as a novel predictive marker for the risk of uremia-associated calcification progression.



Statin Pretreatment and Microembolic Signals in Large Artery AtherosclerosisHighlights [Clinical and Population Studies]

2017-06-21T12:43:28-07:00

Objective—Although statin pretreatment (SP) is associated with better outcomes in patients with acute cerebral ischemia after an ischemic stroke/transient ischemic attack, data on the underlying mechanism of this beneficial effect are limited.Approach and Results—We sought to evaluate the potential association between SP and microembolic signal (MES) burden in acute cerebral ischemia because of large artery atherosclerosis (LAA). We prospectively evaluated consecutive patients with first-ever acute cerebral ischemia because of LAA in 3 tertiary stroke centers over a 2-year period. All patients underwent continuous 1-hour transcranial Doppler monitoring of the relevant vessel at baseline (≤24 hours). SP was recorded and dichotomized as high dose or low-to-moderate dose. SP was documented in 43 (41%) of 106 LAA patients (mean age, 65.4±10.3 years; 72% men; low-to-moderate dose, 32%; high dose, 8%). There was a significant (P=0.022) dose-dependent effect between SP and MES prevalence: no SP (37%), SP with low-to-moderate dose (18%), and SP with high dose (0%). Similarly, a significant (P=0.045) dose-dependent effect was documented between SP and MES burden: no SP (1.1±1.8), SP with low-to-moderate dose (0.7±1.6), and SP with high dose (0±0). In multivariable logistic regression analysis adjusting for demographics, vascular risk factors, location of LAA, stroke severity, and other prevention therapies, SP was associated with lower likelihood of MES presence (odds ratio, 0.29; 95% confidence interval, 0.09–0.92; P=0.036). In addition, SP was found also to be independently related to higher odds of functional improvement (common odds ratio, 3.33; 95% confidence interval, 1.07–10.0; P=0.037).Conclusions—We found that SP in patients with acute LAA is related with reduced MES presence and lower MES burden with an apparently dose-dependent association.















Apolipoprotein C-III [Editorial]

2017-05-24T12:43:10-07:00







Quality Versus Quantity [Editorial]

2017-05-24T12:43:10-07:00







Circadian Control of Inflammatory Processes in Atherosclerosis and Its ComplicationsHighlights [Brief Review]

2017-05-24T12:43:10-07:00

Physiological cardiovascular functions show daily diurnal variations, which are synchronized by intrinsic molecular clocks and environment-driven cues. The clinical manifestation of cardiovascular disease also exhibits diurnal variation, with an increased incidence in the early morning. This coincides with circadian oscillations of circulating parameters, such as hormones and leukocyte counts. We are just at the beginning of understanding how circadian rhythms of immune functions are related to cardiovascular disease progression and outcome after an acute ischemic event. Here, we briefly summarize clinical data on oscillations of circulating inflammatory parameters, as well as experimental evidences for the role of circadian clocks in atherosclerosis, postmyocardial infarction inflammatory responses, and cardiac healing.



Molecular Imaging of Atherothrombotic DiseasesHighlights [Brief Review]

2017-05-24T12:43:10-07:00

Molecular imaging, with major advances in the development of both innovative targeted contrast agents/particles and radiotracers, as well as various imaging technologies, is a fascinating, rapidly growing field with many preclinical and clinical applications, particularly for personalized medicine. Thrombosis in either the venous or the arterial system, the latter typically caused by rupture of unstable atherosclerotic plaques, is a major determinant of mortality and morbidity in patients. However, imaging of the various thrombotic complications and the identification of plaques that are prone to rupture are at best indirect, mostly unreliable, or not available at all. The development of molecular imaging toward diagnosis and prevention of thrombotic disease holds promise for major advance in this clinically important field. Here, we review the medical need and clinical importance of direct molecular imaging of thrombi and unstable atherosclerotic plaques that are prone to rupture, thereby causing thrombotic complications such as myocardial infarction and ischemic stroke. We systematically compare the advantages/disadvantages of the various molecular imaging modalities, including X-ray computed tomography, magnetic resonance imaging, positron emission tomography, single-photon emission computed tomography, fluorescence imaging, and ultrasound. We further systematically discuss molecular targets specific for thrombi and those characterizing unstable, potentially thrombogenic atherosclerotic plaques. Finally, we provide examples for first theranostic approaches in thrombosis, combining diagnosis, targeted therapy, and monitoring of therape[...]









Deficiency of LRP1 in Mature Adipocytes Promotes Diet-Induced Inflammation and Atherosclerosis—Brief ReportHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Mice with adipocyte-specific inactivation of low-density lipoprotein receptor–related protein-1 (LRP1) are resistant to diet-induced obesity and hyperglycemia because of compensatory thermogenic response by muscle. However, the physiological function of LRP1 in mature adipocytes and its role in cardiovascular disease modulation are unknown. This study compared perivascular adipose tissues (PVAT) from wild-type (adLrp1+/+) and adipocyte-specific LRP1 knockout (adLrp1−/−) mice in modulation of atherosclerosis progression.Approach and Results—Analysis of adipose tissues from adLrp1+/+ and adLrp1−/− mice after Western diet feeding for 16 weeks revealed that, in comparison to adLrp1+/+ mice, the adipocytes in adLrp1−/− mice were smaller, but their adipose tissues were more inflamed with increased monocyte–macrophage infiltration and inflammatory gene expression. The transplantation of PVAT from chow-fed adLrp1+/+ and adLrp1−/− mice into the area surrounding the carotid arteries of Ldlr−/− mice before feeding the Western diet revealed a contributory role of PVAT toward hypercholesterolemia-induced atherosclerosis. Importantly, recipients of adLrp1−/− PVAT displayed a 3-fold increase in atherosclerosis compared with adLrp1+/+ PVAT recipients. The increased atherosclerosis invoked by LRP1-deficient PVAT was associated with elevated monocyte–macrophage infiltration and inflammatory cytokine expression in the transplanted fat.Conclusions—PVAT provide outside-in signals through the adventitia to modulate atherosclerotic le[...]



Coronary Artery Disease-Associated LIPA Coding Variant rs1051338 Reduces Lysosomal Acid Lipase Levels and Activity in LysosomesHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Genome-wide association studies have linked variants at chromosome 10q23 with increased coronary artery disease risk. The disease-associated variants fall in LIPA, which encodes lysosomal acid lipase (LAL), the enzyme responsible for lysosomal cholesteryl ester hydrolysis. Loss-of-function mutations in LIPA result in accelerated atherosclerosis. Surprisingly, the coronary artery disease variants are associated with increased LIPA expression in some cell types. In this study, we address this apparent contradiction.Approach and Results—We investigated a coding variant rs1051338, which is in high linkage disequilibrium (r2=0.89) with the genome-wide association study lead–associated variant rs2246833 and causes a nonsynonymous threonine to proline change within the signal peptide of LAL. Transfection of allele-specific expression constructs showed that the risk allele results in reduced lysosomal LAL protein (P=0.004) and activity (P=0.005). Investigation of LAL localization and turnover showed the risk LAL protein is degraded more quickly. This mechanism was confirmed in disease-relevant macrophages from individuals homozygous for either the nonrisk or risk allele. There was no difference in LAL protein or activity in whole macrophage extracts; however, we found reduced LAL protein (P=0.02) and activity (P=0.026) with the risk genotype in lysosomal extracts, suggesting that the risk genotype affects lysosomal LAL activity. Inhibition of the proteasome resulted in equal amounts of lysosomal LAL protein in risk and non[...]



microRNA-33 Regulates Macrophage Autophagy in AtherosclerosisHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Defective autophagy in macrophages leads to pathological processes that contribute to atherosclerosis, including impaired cholesterol metabolism and defective efferocytosis. Autophagy promotes the degradation of cytoplasmic components in lysosomes and plays a key role in the catabolism of stored lipids to maintain cellular homeostasis. microRNA-33 (miR-33) is a post-transcriptional regulator of genes involved in cholesterol homeostasis, yet the complete mechanisms by which miR-33 controls lipid metabolism are unknown. We investigated whether miR-33 targeting of autophagy contributes to its regulation of cholesterol homeostasis and atherogenesis.Approach and Results—Using coherent anti-Stokes Raman scattering microscopy, we show that miR-33 drives lipid droplet accumulation in macrophages, suggesting decreased lipolysis. Inhibition of neutral and lysosomal hydrolysis pathways revealed that miR-33 reduced cholesterol mobilization by a lysosomal-dependent mechanism, implicating repression of autophagy. Indeed, we show that miR-33 targets key autophagy regulators and effectors in macrophages to reduce lipid droplet catabolism, an essential process to generate free cholesterol for efflux. Notably, miR-33 regulation of autophagy lies upstream of its known effects on ABCA1 (ATP-binding cassette transporter A1)-dependent cholesterol efflux, as miR-33 inhibitors fail to increase efflux upon genetic or chemical inhibition of autophagy. Furthermore, we find that miR-33 inhibits apoptotic cell clearanc[...]



Deficiency of Cholesteryl Ester Transfer Protein Protects Against Atherosclerosis in RabbitsHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—CETP (cholesteryl ester transfer protein) plays an important role in lipoprotein metabolism; however, whether inhibition of CETP activity can prevent cardiovascular disease remains controversial.Approach and Results—We generated CETP knockout (KO) rabbits by zinc finger nuclease gene editing and compared their susceptibility to cholesterol diet–induced atherosclerosis to that of wild-type (WT) rabbits. On a chow diet, KO rabbits showed higher plasma levels of high-density lipoprotein (HDL) cholesterol than WT controls, and HDL particles of KO rabbits were essentially rich in apolipoprotein AI and apolipoprotein E contents. When challenged with a cholesterol-rich diet for 18 weeks, KO rabbits not only had higher HDL cholesterol levels but also lower total cholesterol levels than WT rabbits. Analysis of plasma lipoproteins revealed that reduced plasma total cholesterol in KO rabbits was attributable to decreased apolipoprotein B–containing particles, while HDLs remained higher than that in WT rabbits. Both aortic and coronary atherosclerosis was significantly reduced in KO rabbits compared with WT rabbits. Apolipoprotein B–depleted plasma isolated from CETP KO rabbits showed significantly higher capacity for cholesterol efflux from macrophages than that from WT rabbits. Furthermore, HDLs isolated from CETP KO rabbits suppressed tumor necrosis factor-α–induced vascular cell adhesion molecule 1 and E-selectin expression in cultured endothelial cells.Conclusi[...]



Maturation of Platelet Function During Murine Fetal Development In VivoHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Platelet function has been intensively studied in the adult organism. However, little is known about the function and hemostatic capacity of platelets in the developing fetus as suitable in vivo models are lacking.Approach and Results—To examine fetal platelet function in vivo, we generated a fetal thrombosis model and investigated light/dye-induced thrombus formation by intravital microscopy throughout gestation. We observed that significantly less and unstable thrombi were formed at embryonic day (E) 13.5 compared with E17.5. Flow cytometry revealed significantly lower platelet counts in E13.5 versus E17.5 fetuses versus adult controls. In addition, fetal platelets demonstrated changed activation responses of surface adhesion molecules and reduced P-selectin content and mobilization. Interestingly, we also measured reduced levels of the integrin-activating proteins Kindlin-3, Talin-1, and Rap1 during fetal development. Consistently, fetal platelets demonstrated diminished spreading capacity compared with adults. Transfusion of adult platelets into the fetal circulation led to rapid platelet aggregate formation even in young fetuses. Yet, retrospective data analysis of a neonatal cohort demonstrated no correlation of platelet transfusion with closure of a persistent ductus arteriosus, a process reported to be platelet dependent.Conclusions—Taken together, we demonstrate an ontogenetic regulation of platelet function in vivo with phys[...]



Gain-of-Function Mutation in Filamin A Potentiates Platelet Integrin {alpha}IIb{beta}3 ActivationHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Dominant mutations of the X-linked filamin A (FLNA) gene are responsible for filaminopathies A, which are rare disorders including brain periventricular nodular heterotopia, congenital intestinal pseudo-obstruction, cardiac valves or skeleton malformations, and often macrothrombocytopenia.Approach and Results—We studied a male patient with periventricular nodular heterotopia and congenital intestinal pseudo-obstruction, his unique X-linked FLNA allele carrying a stop codon mutation resulting in a 100–amino acid–long FLNa C-terminal extension (NP_001447.2: p.Ter2648SerextTer101). Platelet counts were normal, with few enlarged platelets. FLNa was detectable in all platelets but at 30% of control levels. Surprisingly, all platelet functions were significantly upregulated, including platelet aggregation and secretion, as induced by ADP, collagen, or von Willebrand factor in the presence of ristocetin, as well as thrombus formation in blood flow on a collagen or on a von Willebrand factor matrix. Most importantly, patient platelets stimulated with ADP exhibited a marked increase in αIIbβ3 integrin activation and a parallel increase in talin recruitment to β3, contrasting with normal Rap1 activation. These results are consistent with the mutant FLNa affecting the last step of αIIbβ3 activation. Overexpression of mutant FLNa in the HEL megakaryocytic cell line correlated with an increase (compared with wild-[...]



CMTM3 (CKLF-Like Marvel Transmembrane Domain 3) Mediates Angiogenesis by Regulating Cell Surface Availability of VE-Cadherin in Endothelial Adherens JunctionsHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Decrease in VE-cadherin adherens junctions reduces vascular stability, whereas disruption of adherens junctions is a requirement for neovessel sprouting during angiogenesis. Endocytosis plays a key role in regulating junctional strength by altering bioavailability of cell surface proteins, including VE-cadherin. Identification of new mediators of endothelial endocytosis could enhance our understanding of angiogenesis. Here, we assessed the function of CMTM3 (CKLF-like MARVEL transmembrane domain 3), which we have previously identified as highly expressed in Flk1+ endothelial progenitor cells during embryonic development.Approach and Results—Using a 3-dimensional coculture of human umbilical vein endothelial cells-GFP (green fluorescent protein) and pericytes-RFP (red fluorescent protein), we demonstrated that siRNA-mediated CMTM3 silencing in human umbilical vein endothelial cells impairs angiogenesis. In vivo CMTM3 inhibition by morpholino injection in developing zebrafish larvae confirmed that CMTM3 expression is required for vascular sprouting. CMTM3 knockdown in human umbilical vein endothelial cells does not affect proliferation or migration. Intracellular staining demonstrated that CMTM3 colocalizes with early endosome markers EEA1 (early endosome marker 1) and Clathrin+ vesicles and with cytosolic VE-cadherin in human umbilical vein endothelial cells. Adenovirus-mediated CMTM[...]



Endoglin Mediates Vascular Maturation by Promoting Vascular Smooth Muscle Cell Migration and SpreadingHighlights [Basic Sciences]

2017-05-24T12:43:10-07:00

Objective—Endoglin, a transforming growth factor-β superfamily coreceptor, is predominantly expressed in endothelial cells and has essential roles in vascular development. However, whether endoglin is also expressed in vascular smooth muscle cells (VSMCs), especially in vivo, remains controversial. Furthermore, the roles of endoglin in VSMC biology remain largely unknown. Our objective was to examine the expression and determine the function of endoglin in VSMCs during angiogenesis.Approach and Results—Here, we determine that endoglin is robustly expressed in VSMCs. Using CRISPR/CAS9 knockout and short hairpin RNA knockdown in the VSMC/endothelial coculture model system, we determine that endoglin in VSMCs, but not in endothelial cells, promotes VSMCs recruitment by the endothelial cells both in vitro and in vivo. Using an unbiased bioinformatics analysis of RNA sequencing data and further study, we determine that, mechanistically, endoglin mediates VSMC recruitment by promoting VSMC migration and spreading on endothelial cells via increasing integrin/FAK pathway signaling, whereas endoglin has minimal effects on VSMC adhesion to endothelial cells. In addition, we further determine that loss of endoglin in VSMCs inhibits VSMC recruitment in vivo.Conclusions—These studies demonstrate that endoglin has an important role in VSMC recruitment and blood vessel maturati[...]