Gemma Vilahur

Atherosclerosis, platelets and thrombosis in acute ischaemic heart disease.

Atherosclerosis is the underlying reason for nearly all causes of coronary artery disease and peripheral arterial disease and many cases of stroke. Atherosclerosis is a systemic inflammatory process characterised by the accumulation of lipids and macrophages/lymphocytes within the intima of large arteries. The deposition of these blood borne materials and the subsequent thickening of the wall often significantly compromise the residual lumen leading to ischaemic events distal to the arterial stenosis. However, these initial fatty streak lesions may also evolve into vulnerable plaques susceptible to rupture or erosion. Plaque disruption initiates both platelet adhesion and aggregation on the exposed vascular surface and the activation of the clotting cascade leading to the so-called atherothrombotic process. Yet, platelets have also been shown to be transporters of regulatory molecules (micro-RNA), to drive the inflammatory response and mediate atherosclerosis progression. Here we discuss our current understanding of the pathophysiological mechanisms involved in atherogenesis – from fatty streaks to complex and vulnerable atheromas – and highlight the molecular machinery used by platelets to regulate the atherogenic process, thrombosis and its clinical implications.

The subcutaneous adipose tissue reservoir of functionally active stem cells is reduced in obese patients

It has been demonstrated that the adipose tissue, a highly functional metabolic tissue, is a reservoir of mesenchymal stem cells. The potential use of adipose‐derived stem cells (ADSCs) from white adipose tissue (WAT) for organ repair and regeneration has been considered because of their obvious benefits in terms of accessibility and quantity of available sample. However, the functional capability of ADSCs from subjects with different adiposity has not been investigated. It has been our hypothesis that ADSCs from adipose tissue of patients with metabolic syndrome and high adiposity may be functionally impaired. We report that subcutaneous WAT stromal vascular fraction (SVF) from nonobese individuals had a significantly higher number of CD90+ cells than SVF from obese patients. The isolated ADSCs from WAT of obese patients had reduced differentiation potential and were less proangiogenic. Therefore, ADSCs in adipose tissue of obese patients have lower capacity for spontaneous or therapeutic repair than ADSCs from nonobese metabolically normal individuals.—Oñate, B., Vilahur, G., Ferrer‐Lorente, R., Ybarra, J., Díez‐Caballero, A., Ballesta‐López, C., Moscatiello, F., Herrero, J., Badimon, L. The subcutaneous adipose tissue reservoir of functionally active stem cells is reduced in obese patients. FASEB J. 26, 4327–4336 (2012). www.fasebj.org

Lipoproteínas, plaquetas y aterotrombosis

La aterosclerosis y los procesos tromboticos asociados a la rotura de placas vulnerables son la principal causa de eventos cardiovasculares incluyendo los sindromes coronarios agudos. Las lipoproteinas de baja densidad (LDL) desempenan un papel clave en la patogenia del proceso aterotrombotico. Las LDL no solo inducen una alteracion en las propiedades antitromboticas derivadas del endotelio vascular y en las propiedades contractiles del vaso como resultado de una disminucion en la disponibilidad de oxido nitrico endotelial y una activacion de las vias de senalizacion proinflamatorias, sino que tambien afectan a la funcion e interaccion de las celulas presentes en la lesion aterosclerotica, tanto derivadas de la sangre como residentes en la pared vascular. De hecho, las LDL infiltradas en el vaso sufren modificaciones (oxidaciones, agregacion, glucosilacion, etc.) que potencian sus propiedades aterogenicas. Una vez modificadas, las LDL intravasculares facilitan la formacion de celulas espumosas derivadas de celulas musculares lisas y macrofagos y acrecientan la vulnerabilidad de las placas ateroscleroticas. Asimismo aumentan la trombogenicidad de las placas y la de la sangre, esto ultimo asociado a un aumento en los niveles de factor tisular circulante y en la reactividad de las plaquetas. Esta revision se centra en la importancia de las LDL, nativas y modificadas, en la patogenia de la aterotrombosis. Aborda estudios actuales sobre las LDL y su efecto en la funcion de celulas sanguineas, especialmente plaquetas y celulas vasculares, asi como sobre potenciales nuevas dianas terapeuticas.

Enfermedad aterotrombótica coronaria: avances en el tratamiento antiplaquetario

La plaqueta ha asumido un papel preponderante en la medicina cardiovascular gracias a la comprension del syndrome coronario agudo (SCA) como un proceso aterotrombotico. Esto ha establecido el uso generalizado de agentes antiplaquetarios, como la aspirina, las tienopiridinas y los antagonistas de los receptores de la glucoproteina IIb/IIIa, en la prevencion de las enfermedades isquemicas coronarias. Sin embargo, hay evidencias recientes de que no todos los pacientes reciben el tratamiento antiplaquetario adecuado, ya sea por el fenomeno de la «resistencia » o «respuesta variable» al farmaco o por un aumento en el riesgo de sangrado. Es mas, la falta de eficacia de la combinacion aspirina-clopidogrel en la prevencion primaria ha cuestionado el concepto de «a mayor inhibicion, mayor eficacia». Actualmente, los esfuerzos se centran en la mejora de los tratamientos antiplaquetarios en uso a fin de mejorar su efectividad y su seguridad. Se estan desarrollando antagonistas alternativos de los receptors del ADP (prasugrel, AZD6140 y cangrelor) y de la trombina (E555 y SCH530348) que podrian ofrecer mas inhibicion de las plaquetas, mas rapida y constante. Asimismo, el avance en el conocimiento de la estructura de la plaqueta y los mecanismos implicados en la formacion del trombo puede dar lugar al descubrimiento de nuevas dianas terapeuticas. Este articulo revisa el papel fisiopatologico de las plaquetas en el proceso aterotrombotico, evalua lo mas actual del arsenal antiplaquetario actualmente en uso y comenta nuevas aproximaciones terapeuticas.

Qualitative and quantitative accuracy of ultrasound-based virtual histology for detection of necrotic core in human coronary arteries

The aim was to test the accuracy of virtual histology (VH) for detecting necrotic core (NC) in an ex vivo human model of coronary arteries as compared to real histology (RH). A total of nine consecutive explanted hearts were included in the study. Coronary segments, clearly identified by anatomical landmarks, were analyzed by intravascular ultrasound (IVUS-VH) immediately after heart collection and thereafter by RH. NC was expressed as absolute (total amount) and relative (corrected for plaque area) values. Correlation analysis was performed using linear regression models at cross-section level, with correction for repeated measurements per patient, and at segment level. Receiver operator curves (ROC) were developed for testing accuracy of VH in detecting RH-NC. Overall, 321xa0mm were analyzed corresponding to 642 IVUS-VH frames and corresponding histological slices. VH and RH-NC areas were 0.24xa0±xa00.43 and 0.16xa0±xa00.43xa0mm2, respectively (pxa0<xa00.001). At cross-section level, the correlation between VH and RH-NC was moderate in absolute (rxa0=xa00.50, pxa0<xa00.001) and poor in relative values (rxa0=xa00.43, pxa0=xa00.120). At the segment level, this correlation improves in terms of absolute values (rxa0=xa00.80, pxa0=xa00.01), but was not significant in terms of relative values (rxa0=xa00.43, pxa0=xa00.25). The ROC curve showed a C-statistics of 0.904 (pxa0<xa00.001) with high sensitivity (94xa0%), but low specificity (53xa0%) and low positive predictive value (48xa0%). Although VH has a high sensitivity in identifying RH-NC, it has a low specificity and low positive predictive value. In addition, it is not able to accurately quantify its size within the corresponding histological specimen.

Coronary Atherothrombotic Disease: Progress in Antiplatelet Therapy

Platelets are now regarded as playing a dominant role in cardiovascular medicine since our recent understanding of acute coronary syndrome as an atherothrombotic process. This development has led to the widespread use of antiplatelet agents, such as aspirin, thienopyridines and glycoprotein-IIb/IIIa receptor blockers, for the prevention of ischemic heart disease. Nevertheless, recent evidence suggests that not all patients receive appropriate antiplatelet therapy because there may be resistance or a variable response to the drug used or because of an increased risk of hemorrhage. Moreover, the reported lack of efficacy of the combination of clopidogrel and aspirin when used for primary prevention has raised concerns about the general concept that greater inhibition implies greater efficacy. At present, research efforts are focused on improving current antiplatelet treatment with the aim of increasing efficacy and safety. Alternative ADP-receptor antagonists (e.g., prasugrel, cangrelor and AZD6140) and thrombin-receptor antagonists (e.g., E5555 and SCH 530348) are being developed. They may provide faster, more potent and more stable platelet inhibition. In addition, new insights into platelet structure and into the mechanisms underlying thrombus formation could lead to the discovery of new therapeutic targets. This article reviews what is known about the pathophysiological role of platelets in the atherothrombotic process, considers the current state of the art in antiplatelet therapy, and provides a commentary on new therapeutic approaches.

New insights into the role of adipose tissue in thrombosis

Central obesity is independently associated with an elevated risk of cardiovascular disease, particularly thrombotic complications. Increasing data supports a link between excess body weight and the risk to suffer acute myocardial infarction, stent thrombosis after percutaneous interventions, ischemic stroke and vein thrombosis. Experimental and in vitro data have provided insights as to the mechanisms currently presumed to increase the thrombotic risk in obese subjects. Obesity is characterized by a chronic low grade inflammation and systemic oxidative stress that eventually damage the endothelium losing its antithrombotic properties. Obesity also stimulates the expression of leptin and attenuates adiponectin release, a protective adipokine. Although the contribution of adipokines to thrombosis has been questioned, recent work has suggested that they enhance platelet activation and, although to a lesser extent, induce the coagulation cascade through tissue factor (TF) expression. Increased body weight also impairs platelet sensitivity to insulin signaling and enhances the production of bioactive isoprostanes further promoting platelet reactivity. Finally, obese subjects have shown elevated circulating levels of von Willebrand factor, TF, factor VII and VIII, and fibrinogen, favoring a mild-to-moderate hypercoagulable state, and, on the other hand, increased secretion of plasminogen activator inhibitor (PAI)-1 and thrombin activatable fibrinolysis inhibitor (TAFI) contributing to impair the fibrinolytic system. In the present review, we provide an overview of the impact of excess body weight on thrombosis. We will focus on the link between dysfunctional adipose tissue and endothelial damage, platelet reactivity, enhanced coagulation and impaired fibrinolysis; mechanisms currently recognized to increase arterial thrombotic risk in obese subjects.

Detrimental Effect of Hypercholesterolemia on High-Density Lipoprotein Particle Remodeling in Pigs

BACKGROUNDnBeneficial effects of high-density lipoproteins (HDL) seem altered in patients with symptomatic cardiovascular disease. We recently demonstrated in a swine model of ischemia-reperfusion (IR) that hypercholesterolemia abolishes HDL-related cardioprotection.nnnOBJECTIVESnThis study sought to investigate, using the same animal model, whether the reported impairment of HDL cardioprotective function was associated with alterations in HDL remodeling and functionality.nnnMETHODSnPigs were fed a normocholesterolemic (NC) or hypercholesterolemic (HL) diet for 10xa0days, reaching non-HDL cholesterol concentrations of 38.2 ± 3.5xa0mg/dl and 218.6 ± 27.6xa0mg/dl, respectively (pxa0< 0.0001). HDLs were isolated,xa0and lipidomics and differential proteomics tests were performed to determine HDL molecular changes. HDL functionality and particle size were determined.nnnRESULTSnUsing principal component analysis, we identified 255 molecular lipid species differentially clustered in NC-HDL and HL-HDL. Ninety lipid metabolites were differentially expressed, and 50 showed at least 1.5-fold variation (false discovery rate adjustment q valuexa0<0.05). HL-HDLs presented a core enriched in cholesteryl esters and a surface depleted of phosphatidylcholine species containing polyunsaturated and long-chain fatty acids, indicating the presence of mature HDL particles with low surface fluidity. Hypercholesterolemia induced an important change in HDL-transported proteins (576 spots in HL-HDL vs. 621 spots in NC-HDL). HL-HDLs showed a reduced content of lipocalin retinol binding protein 4 and apolipoprotein M and in the retinoic acid-transporter cellular retinoic acid binding protein 1 (pxa0<xa00.05 vs. NC-HDL). No changes were observed in apolipoprotein A-I content and profile. Functionally, HL-HDL showed lower antioxidant activity (-35%) and a reduced capacity to efflux cholesterol (-60%) compared to NC-HDL (pxa0< 0.05). Hypercholesterolemia induced larger HDL particles.nnnCONCLUSIONSnWe demonstrate that hypercholesterolemia induces HDL lipidomic changes, losing phosphatidylcholine-lipid species and gaining cholesteryl esters, and proteomic changes, with losses in cardioprotective proteins. These remodelingxa0changesxa0shifted HDL particles toward a dysfunctional state.

Intracellular platelet signalling as a target for drug development

Platelets are endowed with a repertoire of surface receptors that enable them to adhere, activate and aggregate upon vascular injury. Platelet adhesion is governed by the interaction between vascular collagen and GPIb-IX-V and GPVI-FcRγ complexes. Platelet kinases downstream 14-3-3ζ-bound GPIb and the FcRγ ITAM domain enable the activation of PLC-γ2 whereas the engagement of soluble agonists (predominantly ADP, TXA2 and thrombin) with Gq-protein coupled receptor trigger PLC-β activation. Once activated, PLC-γ2/β induces the generation of second messengers IP3 and DAG. IP3 is involved in Ca2+ cytosolic release from the dense tubular system whereas DAG induces PKC activation. CalDAG-GEFI sensors Ca2+ mobilization and, through activation of the small GTPase Rap1, induces cytoskeleton re-arrangements, extrusion of platelet granules and conversion of integrin αIIbβ3 into a high-affinity state (inside-out signalling). These events are found to be reinforced by PKC, MAPK, and ROS-dependent GPVI pathways. Finally, ligand-interaction with αIIbβ3 bridges platelets together and triggers outside-in signalling that orchestrates cytoskeletal rearrangements for platelet spreading and clot stabilization through the PI3K/PDK1/Akt/GSK3 axis. Understanding the platelet signalling machinery involved in thrombus formation is necessary to identify potential targets for the development of new antiplatelet agents.

P2Y12 antagonists and cardiac repair post-myocardial infarction: global and regional heart function analysis and molecular assessments in pigs

AimsnP2Y12 antagonists are the standard in antiplatelet therapy but their potential effects on functional myocardial recovery and cardioprotection post-myocardial infarction (MI) are unknown. We investigated in a preclinical model of MI whether ticagrelor and clopidogrel differently affect cardiac repair post-MI.nnnMethods and resultsnPigs either received: (i) clopidogrel (600u2009mg; 75u2009mg/qd); (ii) ticagrelor (180u2009mg; 90u2009mg/bid); and (iii) placebo control. MI was induced by mid-left anterior descending coronary artery balloon occlusion (60u2009min) and animals received the maintenance doses for the following 42u2009days. Serial cardiac magnetic resonance was performed at Day 3 and Day 42 for the assessment of global and regional cardiac parameters. We determined cardiac AMP-activated protein kinase (AMPK), Akt/PKB, aquaporin-4, vascular density, and fibrosis. In comparison to controls, both P2Y12 antagonists limited infarct expansion at Day 3, although ticagrelor induced a further 5% reduction (Pu2009<u20090.05 vs. clopidogrel) whereas oedema was only reduced by ticagrelor (≈23% Pu2009<u20090.05). Scar size decreased at Day 42 in ticagrelor-treated pigs vs. controls but not in clopidogrel-treated pigs. Left ventricular ejection fraction was higher 3u2009days post-MI in ticagrelor-treated pigs and persisted up to Day 42 (Pu2009<u20090.05 vs. post-MI). Regional analysis revealed that control and clopidogrel-treated pigs had severe and extensive wall motion abnormalities in the jeopardized myocardium and a reduced myocardial viability that was not as evident in ticagrelor-treated pigs (χ2Pu2009<u20090.05 vs. ticagrelor). Only ticagrelor enhanced myocardial AMPK and Akt/PKB activation and reduced aquaporin-4 levels (Pu2009<u20090.05 vs. control and clopidogrel). No differences were observed in vessel density and fibrosis markers among groups.nnnConclusionsnTicagrelor is more efficient than clopidogrel in attenuating myocardial structural and functional alterations post-MI and in improving cardiac healing. These benefits are associated with persistent AMPK and Akt/PKB activation.