Soumaya Ben-Aicha

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.

Silybum marianum provides cardioprotection and limits adverse remodeling post-myocardial infarction by mitigating oxidative stress and reactive fibrosis

AIMSnMilk thistle (Silybum marianum; SM) is an herb commonly used for hepatoprotection with antioxidant and antifibrotic properties. We investigated in pigs the cardiac effects of SM intake during the acute phase of myocardial infarction (MI) and remodeling period post-MI.nnnMETHODSnStudy-1 tested the effect of SM use on the acute phase of MI. Hence, animals were distributed to a control group or to receive SM prior infarction (1.5u202fh ischemia). Animals were sacrificed after 2.5u202fh of reperfusion. Study-2 tested the effect of SM use in the cardiac remodeling phase. Accordingly, animals received for 10u202fd dietu202f±u202fSM prior MI and followed the same regime for 3u202fweeks and then sacrificed. Study-3 tested the effect of SM in a non-infarcted heart; therefore, animals received for 10u202fd dietu202f±u202fSM and then sacrificed.nnnRESULTSnAnimals taking SM before MI showed a reduction in cardiac damage (decreased oxidative damage, ROS production and xanthine oxidase levels; preserved mitochondrial function; and increased myocardial salvage; pu202f<u202f0.05) versus controls. Animals that remained on chronic SM intake post-MI improved left ventricular remodeling. This was associated with the attenuation of the TGFß1/TßRs/SMAD2/3 signaling, lower myofibroblast transdifferentiation and collagen content in the border zone (pu202f<u202f0.05 vs. all other groups). Cardiac contractility improved in animals taking SM (pu202f<u202f0.05 vs. post-MI-control). No changes in cardiac function or fibrosis were detected in animals on SM but without MI.nnnCONCLUSIONnIntake of SM protects the heart against the deleterious effects of an MI and favors cardiac healing. These benefits may be attributed to the antioxidant and antifibrotic properties of SM.

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.

Phytosterols and Inflammation

Besides the well-characterized effect of foods and supplements enriched with plant sterols/stanols on serum LDL-C concentrations, evidence is now emerging that phytosterols exert beneficial effects on non-lipid variables such as inflammatory and oxidative stress markers, coagulation parameters and endothelial function. This makes sterols and stanols an attractive alternative for dietary interventions in cardiovascular disease prevention, particularly in populations at low or medium risk. This review aims to summarize the current knowledge derived from experimental studies and human data on the anti-inflammatory effects of phytosterols/stanols and their relevance in promoting atheroprotection and preventing cardiovascular disease. The anti-inflammatory effects induced by plant sterols/stanols have been demonstrated in in vitro studies and in experimental animal models. However, not all the beneficial effects seen at an experimental level have translated into clinical benefit. Indeed, clinical studies that evaluate the association between phytosterols consumption and inflammatory variables (CRP and cytokines) are inconsistent and have not yet provided a solid answer. Plant sterols have been proposed as useful adjuncts to statin therapy to further reduce the risk of cardiovascular disease. However, there is limited available data and more research needs to be done.

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.