Coronary Artery Disease Associated Transcription Factor TCF21 Regulates Smooth Muscle Precursor Cells That Contribute to the Fibrous Cap.

Recent genome wide association studies have identified a number of genes that contribute to the risk for coronary heart disease. One such gene, TCF21, encodes a basic-helix-loop-helix transcription factor believed to serve a critical role in the development of epicardial progenitor cells that give rise to coronary artery smooth muscle cells (SMC) and cardiac fibroblasts. Using reporter gene and immunolocalization studies with mouse and human tissues we have found that vascular TCF21 expression in the adult is restricted primarily to adventitial cells associated with coronary arteries and also medial SMC in the proximal aorta of mouse. Genome wide RNA-Seq studies in human coronary artery SMC (HCASMC) with siRNA knockdown found a number of putative TCF21 downstream pathways identified by enrichment of terms related to CAD, including "vascular disease," "disorder of artery," and "occlusion of artery," as well as disease-related cellular functions including "cellular movement" and "cellular growth and proliferation." In vitro studies in HCASMC demonstrated that TCF21 expression promotes proliferation and migration and inhibits SMC lineage marker expression. Detailed in situ expression studies with reporter gene and lineage tracing revealed that vascular wall cells expressing Tcf21 before disease initiation migrate into vascular lesions of ApoE-/- and Ldlr-/- mice. While Tcf21 lineage traced cells are distributed throughout the early lesions, in mature lesions they contribute to the formation of a subcapsular layer of cells, and others become associated with the fibrous cap. The lineage traced fibrous cap cells activate expression of SMC markers and growth factor receptor genes. Taken together, these data suggest that TCF21 may have a role regulating the differentiation state of SMC precursor cells that migrate into vascular lesions and contribute to the fibrous cap and more broadly, in view of the association of this gene with human CAD, provide evidence that these processes may be a mechanism for CAD risk attributable to the vascular wall.

Phenotypic Modulation of Smooth Muscle Cells in Atherosclerosis Is Associated With Downregulation of LMOD1, SYNPO2, PDLIM7, PLN, and SYNM.

OBJECTIVE: Key augmented processes in atherosclerosis have been identified, whereas less is known about downregulated pathways. Here, we applied a systems biology approach to examine suppressed molecular signatures, with the hypothesis that they may provide insight into mechanisms contributing to plaque stability. APPROACH AND RESULTS: Muscle contraction, muscle development, and actin cytoskeleton were the most downregulated pathways (false discovery rate=6.99e-21, 1.66e-6, 2.54e-10, respectively) in microarrays from human carotid plaques (n=177) versus healthy arteries (n=15). In addition to typical smooth muscle cell (SMC) markers, these pathways also encompassed cytoskeleton-related genes previously not associated with atherosclerosis. SYNPO2, SYNM, LMOD1, PDLIM7, and PLN expression positively correlated to typical SMC markers in plaques (Pearson r>0.6, P<0.0001) and in rat intimal hyperplasia (r>0.8, P<0.0001). By immunohistochemistry, the proteins were expressed in SMCs in normal vessels, but largely absent in human plaques and intimal hyperplasia. Subcellularly, most proteins localized to the cytoskeleton in cultured SMCs and were regulated by active enhancer histone modification H3K27ac by chromatin immunoprecipitation-sequencing. Functionally, the genes were downregulated by PDGFB (platelet-derived growth factor beta) and IFNg (interferron gamma), exposure to shear flow stress, and oxLDL (oxidized low-density lipoprotein) loading. Genetic variants in PDLIM7, PLN, and SYNPO2 loci associated with progression of carotid intima-media thickness in high-risk subjects without symptoms of cardiovascular disease (n=3378). By eQTL (expression quantitative trait locus), rs11746443 also associated with PDLIM7 expression in plaques. Mechanistically, silencing of PDLIM7 in vitro led to downregulation of SMC markers and disruption of the actin cytoskeleton, decreased cell spreading, and increased proliferation. CONCLUSIONS: We identified a panel of genes that reflect the altered phenotype of SMCs in vascular disease and could be early sensitive markers of SMC dedifferentiation.

E-NTPDase1/CD39 modulates renin release from heart mast cells during ischemia/reperfusion: a novel cardioprotective role.

Ischemia/reperfusion (I/R) elicits renin release from cardiac mast cells (MC), thus activating a local renin-angiotensin system (RAS), culminating in ventricular fibrillation. We hypothesized that in I/R, neurogenic ATP could degranulate juxtaposed MC and that ecto-nucleoside triphosphate diphosphohydrolase 1/CD39 (CD39) on MC membrane could modulate ATP-induced renin release. We report that pharmacological inhibition of CD39 in a cultured human mastocytoma cell line (HMC-1) and murine bone marrow-derived MC with ARL67156 (100 µM) increased ATP-induced renin release (≥2-fold), whereas purinergic P2X7 receptors (P2X7R) blockade with A740003 (3 µM) prevented it. Likewise, CD39 RNA silencing in HMC-1 increased ATP-induced renin release (≥2-fold), whereas CD39 overexpression prevented it. Acetaldehyde, an I/R product (300 µM), elicited an 80% increase in ATP release from HMC-1, in turn, causing an autocrine 20% increase in renin release. This effect was inhibited or potentiated when CD39 was overexpressed or silenced, respectively. Moreover, P2X7R silencing prevented ATP- and acetaldehyde-induced renin release. I/R-induced RAS activation in ex vivo murine hearts, characterized by renin and norepinephrine overflow and ventricular fibrillation, was potentiated (∼2-fold) by CD39 inhibition, an effect prevented by P2X7R blockade. Our data indicate that by regulating ATP availability at the MC surface, CD39 modulates local renin release and thus, RAS activation, ultimately exerting a cardioprotective effect.

IgE receptor-mediated mast-cell renin release.

Renin is a newly discovered constituent of mast cells. Given that mast cells play a major role in IgE-mediated allergic hypersensitivity, we investigated whether activation of the high-affinity IgE receptor FcεRI elicits release of mast-cell renin. Cross-linking of FcεRI on the surface of mature bone marrow-derived mast cells elicited release of enzymatically active renin protein. The angiotensin I-forming activity of the renin protein was completely blocked by the selective renin inhibitor BILA 2157, which excludes formation of angiotensin I by proteases other than renin. FcεRI-mediated mast-cell renin release was inhibited by dexamethasone and potentiated by the proinflammatory mediator PGE2. Furthermore, cross-linking of mast-cell FcεRI in ex vivo murine hearts passively sensitized with monoclonal anti-DNP IgE also resulted in mast-cell degranulation and overflow of renin. Our findings indicate that IgE-mediated allergic hypersensitivity provokes release of renin from both cultured and resident cardiac mast cells, a process likely to be exacerbated in a chronic inflammatory background. Given the widespread distribution of mast cells, and the presence of angiotensinogen and angiotensin-converting enzyme in many tissues, renin release in immediate hypersensitivity reactions could result in local angiotensin II generation and multiorgan dysfunctions.

Histamine H4-receptors inhibit mast cell renin release in ischemia/reperfusion via protein kinase C ε-dependent aldehyde dehydrogenase type-2 activation.

Renin released by ischemia/reperfusion (I/R) from cardiac mast cells (MCs) activates a local renin-angiotensin system (RAS) causing arrhythmic dysfunction. Ischemic preconditioning (IPC) inhibits MC renin release and consequent activation of this local RAS. We postulated that MC histamine H4-receptors (H4Rs), being Gαi/o-coupled, might activate a protein kinase C isotype-ε (PKCε)-aldehyde dehydrogenase type-2 (ALDH2) cascade, ultimately eliminating MC-degranulating and renin-releasing effects of aldehydes formed in I/R and associated arrhythmias. We tested this hypothesis in ex vivo hearts, human mastocytoma cells, and bone marrow-derived MCs from wild-type and H4R knockout mice. We found that activation of MC H4Rs mimics the cardioprotective anti-RAS effects of IPC and that protection depends on the sequential activation of PKCε and ALDH2 in MCs, reducing aldehyde-induced MC degranulation and renin release and alleviating reperfusion arrhythmias. These cardioprotective effects are mimicked by selective H4R agonists and disappear when H4Rs are pharmacologically blocked or genetically deleted. Our results uncover a novel cardioprotective pathway in I/R, whereby activation of H4Rs on the MC membrane, possibly by MC-derived histamine, leads sequentially to PKCε and ALDH2 activation, reduction of toxic aldehyde-induced MC renin release, prevention of RAS activation, reduction of norepinephrine release, and ultimately to alleviation of reperfusion arrhythmias. This newly discovered protective pathway suggests that MC H4Rs may represent a new pharmacologic and therapeutic target for the direct alleviation of RAS-induced cardiac dysfunctions, including ischemic heart disease and congestive heart failure.

Oxygen governs Galß1-3GalNAc epitope in human placenta.

It is becoming increasingly apparent that the dynamics of glycans reflect the physiological state of cells involved in several cell functions including growth, response to signal molecules, migration, as well as adhesion to, interaction with, and recognition of other cells. The presence of glycoconjugates in human placenta suggests their major role in maternal-fetal exchanges, intercellular adhesion, cellular metabolism, and villous vessel branching. Although several studies have described glycoconjugate distribution in the human placenta descriptions of their physiological function and control mechanisms during placental development are lacking. In this study we investigated the developmental distribution and regulation of placental core 1 O- and N-glycans focusing on early and late first trimester human pregnancy. To define the control mechanisms of the oligosaccharide chains during early placentation process, chorionic villous explants and human trophoblast cell lines were exposed to various oxygen levels. We found that oxygen tension regulates changes in core-1 O-glycan (the disaccharide Galß1-3GalNAc) epitope expression levels. Moreover, by double affinity chromatography and subsequent analysis with mass spectrometry, we identified in the heat shock protein 90-α (HSP90α) a good candidate as carrier of the Galß1-3GalNAc epitope at low oxygen tension. Our results support a fundamental role of oxygen tension in modulating glycosylation of proteins during placental development.

RNA-mediated gene silencing of FUT1 and FUT2 influences expression and activities of bovine and human fucosylated nucleolin and inhibits cell adhesion and proliferation.

In a previous article, we demonstrated the existence of fucosyl-containing O-glycans forms of nucleolin in bovine post-capillary venular endothelial cells (CVEC) and malignant cultured human A431 cells. The tool for this discovery was an antibody found to interact strongly and exclusively with nucleolin in total protein extracts. The antibody was originally raised against a mollusc glycoprotein and was demonstrated to be directed against its O-glycans, recently found to belong prevalently to the blood group H-antigen type with fucose linked in alpha1, 2 to galactose. Here, we show that si-RNA induced down-regulation of the expression of FUT1 and FUT2, the fucosyltransferases required for the biosynthesis of the terminal glycan motif Fucalpha-2-Galbeta-R, reduced expression of the fucosylated nucleolin glycoforms and their exposure at the cell surface in CVEC. Treatment of the cells with FUT1/2 siRNA also reduced their ability to bind and internalize endostatin and their adhesion efficiency and inhibited cell growth. Expression of FUT1, FUT2, and FUT6 was also analyzed in serum-stimulated versus serum-starved cells and in cells treated with FUT1 and FUT2 siRNA. A reduced expression of fucosylated nucleolin and inhibition of cell growth by suppressing FUT1/2 expression was also tested and shown to be exhibited in human A431 cells.

Synthesis of an Array of Triple-Helical Peptides from Type II Collagen for Multiplex Analysis of Autoantibodies in Rheumatoid Arthritis.

Type II collagen (CII) is the most abundant protein in joint cartilage. Antibodies to CII appear around the clinical onset of the autoimmune disease rheumatoid arthritis (RA) in a subset of patients. They target specific epitopes on CII and can be pathogenic or protective. Assays for early detection of such autoantibodies may provide new opportunities for selecting effective treatment strategies of RA. We report the efficient and reproducible assembly of an array of covalently branched native and citrullinated triple helical peptides (THPs) from CII that contain defined autoantibody epitopes. Both monoclonal antibodies and sera from experimental mouse models show a unique reactivity toward the THPs, compared to cyclic peptides containing the epitopes, revealing the importance that the epitopes are displayed in a triple-helical conformation. Importantly, antibodies against three of the THPs that contain major CII epitopes were found to be increased in sera from patients with RA, compared to control persons. These results indicate that such synthetic THPs should be included in multiplex analysis of autoantibodies that are uniquely occurring in individuals with early RA, to provide valuable information on disease prognosis and on what type of therapy should be chosen for individual patients.

A fucose-containing O-glycoepitope on bovine and human nucleolin.

In this paper, we demonstrate the existence and localization of fucosyl-containing O-glycoforms of nucleolin in cultured bovine endothelial cells (CVEC) and malignant cultured human A431 cells. The tool for this discovery was an antibody raised against gp273, a glycoprotein ligand for the sperm-egg interaction in the mollusc bivalve Unio elongatulus. The function and immunological properties of gp273 mainly depend on clustered Lewis-like, fucose-containing O-glycans. Here an anti-gp273 antibody was used to evaluate whether glycoepitopes similar to those of gp273 are part of potential ligands of selectins in endothelial cells. We found that anti-gp273 strongly and exclusively interacted with a 110 kDa protein in CVEC and A431 tumor cells. After partial purification, mass spectrometry identified the protein as nucleolin. This was confirmed by comparing anti-gp273 and anti-nucleolin antibody immunoblotting after nucleolin depletion. We confirmed that anti-gp273 binding to nuclear and extranuclear nucleolin was against a fucose-containing O-glycoepitope by immunoblot analysis of the protein after chemically removing O-glycans and by lectin-blot analysis of control and nucleolin-depleted samples. Using anti-gp273 IgG, we detected nucleolin on the plasma membrane and cytoplasm. O-Glycosylation may regulate the plethora of functions in which nucleolin is involved.

Human serum albumin-based probes for molecular targeting of macrophage scavenger receptors.

Background: Inflammation and accumulation of macrophages are key features of unstable atherosclerotic plaques. The ability of macrophages to take up molecular probes can be exploited in new clinical imaging methods for the detection of unstable atherosclerotic lesions. We investigated whether modifications of human serum albumin (HSA) could be used to target macrophages efficiently in vitro. Materials and methods: Maleylated and aconitylated HSA were compared with unmodified HSA. Fluorescent or radiolabeled (89Zr) modified HSA was used in in vitro experiments to study cellular uptake by differentiated THP-1 cells and primary human macrophages. The time course of uptake was evaluated by flow cytometry, confocal microscopy, real-time microscopy and radioactivity measurements. The involvement of scavenger receptors (SR-A1, SR-B2, LOX-1) was assessed by knockdown experiments using RNA interference, by blocking experiments and by assays of competition by modified low-density lipoprotein. Results: Modified HSA was readily taken up by different macrophages. Uptake was mediated nonexclusively via the scavenger receptor SR-A1 (encoded by the MSR1 gene). Knockdown of CD36 and ORL1 had no influence on the uptake. Modified HSA was preferentially taken up by human macrophages compared with other vascular cell types such as endothelial cells and smooth muscle cells. Conclusions: Modified 89Zr-labeled HSA probes were recognized by different subsets of polarized macrophages, and maleylated HSA may be a promising radiotracer for radionuclide imaging of macrophage-rich inflammatory vascular diseases.

Molecular Imaging of a New Multimodal Microbubble for Adhesion Molecule Targeting.

INTRODUCTION: Inflammation is an important risk-associated component of many diseases and can be diagnosed by molecular imaging of specific molecules. The aim of this study was to evaluate the possibility of targeting adhesion molecules on inflammation-activated endothelial cells and macrophages using an innovative multimodal polyvinyl alcohol-based microbubble (MB) contrast agent developed for diagnostic use in ultrasound, magnetic resonance, and nuclear imaging. METHODS: We assessed the binding efficiency of antibody-conjugated multimodal contrast to inflamed murine or human endothelial cells (ECs), and to peritoneal macrophages isolated from rats with peritonitis, utilizing the fluorescence characteristics of the MBs. Single-photon emission tomography (SPECT) was used to illustrate 99mTc-labeled MB targeting and distribution in an experimental in vivo model of inflammation. RESULTS: Flow cytometry and confocal microscopy showed that binding of antibody-targeted MBs to the adhesion molecules ICAM-1, VCAM-1, or E-selectin, expressed on cytokine-stimulated ECs, was up to sixfold higher for human and 12-fold higher for mouse ECs, compared with that of non-targeted MBs. Under flow conditions, both VCAM-1- and E-selectin-targeted MBs adhered more firmly to stimulated human ECs than to untreated cells, while VCAM-1-targeted MBs adhered best to stimulated murine ECs. SPECT imaging showed an approximate doubling of signal intensity from the abdomen of rats with peritonitis, compared with healthy controls, after injection of anti-ICAM-1-MBs. CONCLUSIONS: This novel multilayer contrast agent can specifically target adhesion molecules expressed as a result of inflammatory stimuli in vitro, and has potential for use in disease-specific multimodal diagnostics in vivo using antibodies against targets of interest.

Dual roles of heparanase in human carotid plaque calcification.

BACKGROUND AND AIMS: Calcification is a hallmark of advanced atherosclerosis and an active process akin to bone remodeling. Heparanase (HPSE) is an endo-ß-glucuronidase, which cleaves glycosaminoglycan chains of heparan sulfate proteoglycans. The role of HPSE is controversial in osteogenesis and bone remodeling while it is unexplored in vascular calcification. Previously, we reported upregulation of HPSE in human carotid endarterectomies from symptomatic patients and showed correlation of HPSE expression with markers of inflammation and increased thrombogenicity. The present aim is to investigate HPSE expression in relation to genes associated with osteogenesis and osteolysis and the effect of elevated HPSE expression on calcification and osteolysis in vitro. METHODS: Transcriptomic and immunohistochemical analyses were performed using the Biobank of Karolinska Endarterectomies (BiKE). In vitro calcification and osteolysis were analysed in human carotid smooth muscle cells overexpressing HPSE and bone marrow-derived osteoclasts from HPSE-transgenic mice respectively. RESULTS: HPSE expression correlated primarily with genes coupled to osteoclast differentiation and function in human carotid atheromas. HPSE was expressed in osteoclast-like cells in atherosclerotic lesions, and HPSE-transgenic bone marrow-derived osteoclasts displayed a higher osteolytic activity compared to wild-type cells. Contrarily, human carotid SMCs with an elevated HPSE expression demonstrated markedly increased mineralization upon osteogenic differentiation. CONCLUSIONS: We suggest that HPSE may have dual functions in vascular calcification, depending on the stage of the disease and presence of inflammatory cells. While HPSE plausibly enhances mineralization and osteogenic differentiation of vascular smooth muscle cells, it is associated with inflammation-induced osteoclast differentiation and activity in advanced atherosclerotic plaques.

Integrated Human Evaluation of the Lysophosphatidic Acid Pathway as a Novel Therapeutic Target in Atherosclerosis.

Variants in the PLPP3 gene encoding for lipid phosphate phosphohydrolase 3 have been associated with susceptibility to atherosclerosis independently of classical risk factors. PLPP3 inactivates lysophosphatidic acid (LPA), a pro-inflammatory, pro-thrombotic product of phospholipase activity. Here we performed the first exploratory analysis of PLPP3, LPA, and LPA receptors (LPARs 1-6) in human atherosclerosis. PLPP3 transcript and protein were repressed when comparing plaques versus normal arteries and plaques from symptomatic versus asymptomatic patients, and they were negatively associated with risk of adverse cardiovascular events. PLPP3 localized to macrophages, smooth muscle, and endothelial cells (ECs) in plaques. LPAR 2, 5, and especially 6 showed increased expression in plaques, with LPAR6 localized in ECs and positively correlated to PLPP3. Utilizing in situ mass spectrometry imaging, LPA and its precursors were found in the plaque fibrous cap, co-localizing with PLPP3 and LPAR6. In vitro, PLPP3 silencing in ECs under LPA stimulation resulted in increased expression of adhesion molecules and cytokines. LPAR6 silencing inhibited LPA-induced cell activation, but not when PLPP3 was silenced simultaneously. Our results show that repression of PLPP3 plays a key role in atherosclerosis by promoting EC activation. Altogether, the PLPP3 pathway represents a suitable target for investigations into novel therapeutic approaches to ameliorate atherosclerosis.

Identification of a novel, alpha2-fucosylation-dependent uptake system in highly proliferative cells.

In this paper we describe a new structure present in highly proliferative cells and absent in cells with normal growth potential. We used cultured bovine venular endothelial cells (CVEC) as examples of high proliferation, and dermal fibroblasts of a primary culture as examples of normal proliferation. The structure, consisting of tubules radiating from the nuclear region to the tips of cell protrusions, was revealed by its strong positivity to the fucose-binding lectin from Lotus (LTL) that prefers glycans with alpha-1,2-linked fucose. Another fucose-binding lectin that prefers glycans with alpha-1,6-linked fucose was instead found to localize glycans exclusively in Golgi complexes. LTL binding sites were also found at the surface of CVEC in a restricted region close to the nucleus. The role of alpha-1,2-linked fucose in forming or maintaining the tubules was confirmed by the fact that down-regulation of the fucosyltransferases FUT1 and FUT2 resulted in disappearance of the tubular structure. LTL also proved able to penetrate the cells through the tubular structures up to the nuclear region and to inhibit proliferation. Endostatin was also found to massively penetrate the cells in the tubular structures in control cells but not in FUT1/2 depleted cells. In cells of a first passage primary culture of dermal fibroblasts the tubular LTL-positive structure was absent as well as the LTL-positive sites at the external surface, and both fucose-binding lectins were found to exclusively localize glycans in Golgi complexes. Tubules were again found progressively in fibroblasts derived from repeated passages, where faster growing cells predominate. Disappearance of LTL-positivity in Golgi complexes paralleled appearance of LTL-positive tubules. The role of Golgi complexes in forming the tubules is discussed.

Expression of CD52 mRNA in the rat embryo.

CD52 is a leukocyte differentiation antigen first discovered in humans as expressed on the surface of lymphocytes, monocytes and eosinophils. The human CD52 is found on chromosome 1, and two alleles are both known to be reasonably common. A closely homologous gene has been identified in the cynomologous monkey and related genes have been found in mouse, rat and dog. The role of CD52 in lymphocyte is still unclear but the anti-CD52 antibodies named CAMPATH-1 antibodies are largely used for therapy where depletion of lymphocytes is required. In the past expression of the antigen on progenitors of leukocytes in bone marrow had been excluded, but recent work indicates CD52 is highly expressed on cells with colony-forming and NOD/SCID (non-obese diabetic-severe combined immunodeficiency)-engrafting capacities, both at the mRNA and membrane protein level. We have investigated CD52 expression during development in rat embryos by in situ hybridization. We report here that the antigen is highly expressed in the liver that is the major organ where multipotent hematopietic stem cells differentiate but also in the splancnopleuric mesoderm, at early stages of embryo differentiation, where hematopietic stem cells are suggested to arise. CD52+ cells were found in areas active in vasculogenesis at early embryo stages and in the walls of the vessels in the liver at mid gestation. CD52+ cells were also found to emerge among c-Kit positive cells.