Inhibitory mechanisms of very low-dose rivaroxaban in non-ST-elevation myocardial infarction.

Very low-dose (VLD) factor Xa (FXa) inhibition, in combination with acetylsalicylic acid (ASA) and clopidogrel, is associated with improved outcomes in patients with acute coronary syndrome (ACS) with a tolerable bleeding risk profile. To date, there are no data documenting platelet inhibition and the anticoagulatory effects of VLD FXa inhibition on top of guideline-adherent dual-antiplatelet therapy (DAPT) in patients with ACS. Patients with non-ST-elevation myocardial infarction (NSTEMI) receiving oral DAPT (ASA + clopidogrel, n = 20; or ASA + ticagrelor, n = 20) were prospectively enrolled in a nonrandomized study.

Tetraspanin CD9 regulates cell contraction and actin arrangement via RhoA in human vascular smooth muscle cells.

The most prevalent cardiovascular diseases arise from alterations in vascular smooth muscle cell (VSMC) morphology and function. Tetraspanin CD9 has been previously implicated in regulating vascular pathologies; however, insight into how CD9 may regulate adverse VSMC phenotypes has not been provided. We utilized a human model of aortic smooth muscle cells to understand the consequences of CD9 deficiency on VSMC phenotypes.

Tetraspanin CD9 modulates human lymphoma cellular proliferation via histone deacetylase activity.

Non-Hodgkin Lymphoma (NHL) is a type of hematological malignancy that affects two percent of the overall population in the United States. Tetraspanin CD9 is a cell surface protein that has been thoroughly demonstrated to be a molecular facilitator of cellular phenotype. CD9 expression varies in two human lymphoma cell lines, Raji and BJAB.

Pro-MMP-9 upregulation in HT1080 cells expressing CD9 is regulated by epidermal growth factor receptor.

Degradation of the surrounding extracellular matrix (ECM) by matrix metalloproteinases (MMPs) drives invasion and metastasis of cancer cells. We previously demonstrated that tetraspanin CD9 expression upregulates pro-MMP-9 expression and release and promotes cellular invasion in a human fibrosarcoma cell line (HT1080). These events were dependent upon the highly functional second extracellular loop of CD9.

Tetraspanin CD9 promotes the invasive phenotype of human fibrosarcoma cells via upregulation of matrix metalloproteinase-9.

Tumor cell metastasis, a process which increases the morbidity and mortality of cancer patients, is highly dependent upon matrix metalloproteinase (MMP) production. Small molecule inhibitors of MMPs have proven unsuccessful at reducing tumor cell invasion in vivo. Therefore, finding an alternative approach to regulate MMP is an important endeavor.

Elevating local concentrations of GPIIb-IIIa antagonists counteracts platelet thrombus stability.

Glycoprotein IIb-IIIa (GPIIb-IIIa) antagonists have the capacity to destabilize coronary thrombi and restore vessel patency. Antagonist concentration and residence time, which can be increased by local intracoronary (LIC) administration, and thrombus age may be key factors that influence thrombus stability. Light transmission aggregometry was used to examine the effects of exposing human platelet aggregates to extremely high local levels of GPIIb-IIIa antagonists versus conventional therapeutic levels in vitro.

Pharmacodynamic effects of clopidogrel in pediatric cardiac patients: a comparative study of platelet aggregation response.

Little data on pediatric percent platelet aggregation (%PA) exist in the literature, particularly in cardiac patients and in response to clopidogrel. The objectives were to estimate the %PA range expected in pediatric patients and to measure the clopidogrel effect on %PA in the PICOLO (Platelet Inhibition in Children on Clopidogrel) trial. To estimate a neonatal/infant %PA response range, %PA induced by 5 µM adenosine diphosphate (ADP) was assessed using light transmission aggregometry in 16 cord and 11 normal adult blood samples and prior to clopidogrel therapy in 49 neonatal and 49 infant/toddler cardiac patients enrolled in PICOLO.

Variability of platelet aggregate dispersal with glycoprotein IIb-IIIa antagonists eptifibatide and abciximab.

Background: Utilization of glycoprotein IIb-IIIa (GPIIb-IIIa) inhibitors improves outcomes of patients with acute coronary syndromes (ACS), including those undergoing percutaneous coronary intervention (PCI). These results may be related to the ability of the inhibitors to destabilize coronary thrombi, reduce microembolization, and restore vessel patency.

Objective: To evaluate in vitro the ability of GPIIb-IIIa antagonists, abciximab and eptifibatide, to promote the disaggregation of platelet-rich thrombus.

Variability in platelet response to the antiplatelet agents aspirin and clopidogrel: mechanisms, measurement, and clinical relevance.

Platelet reactivity (eg, platelet adhesion, activation, aggregation) is the underlying pathology for atherothrombotic processes and subsequent ischemic complications. Antiplatelet drugs, including aspirin, dipyridamole, thienopyridines (clopidogrel and ticlopidine), and glycoprotein IIb/IIIa antagonists, have proven efficacy in atherothrombotic event prevention. However, variability of platelet response measured in the laboratory has been reported and is a subject of keen interest.

Tetraspanins and vascular functions.

Tetraspanins are multiple membrane-spanning proteins that likely function as the organizers of membrane microdomains. Tetraspanins associate with other membrane-bound molecules such as cell-adhesion proteins, growth factor receptors, and Ig superfamily members and regulate key cellular processes such as adhesion, migration, and fusion. Tetraspanins are widely expressed in vascular and haematopoietic cells and are involved in both physiological and pathological processes related to angiogenesis, vascular injury, thrombosis, and haemostasis.

Role of platelets in atherothrombosis.

Platelets play a pivotal role in atherothrombosis and therefore are primary targets of antithrombotic therapy. They release an array of agonists, such as adenosine diphosphate (ADP); adhesive molecules, such as P-selectin, thrombospondin, fibrinogen, and von Willebrand factor; coagulation factors; and growth factors. In turn, they present transmembrane receptors for a plethora of agonists and ligands.

Functional relevance of tetraspanin CD9 in vascular smooth muscle cell injury phenotypes: a novel target for the prevention of neointimal hyperplasia.

Vascular smooth muscle cell (VSMC) migration and proliferation are critical events in the development of neointima following vascular injury. In this study, we found that CD9 is constitutively expressed in the VSMC of the neointima of injured carotid arteries. The in vitro migration and proliferation of human coronary artery smooth muscle (hCASM) cells were reduced by 40% and 63%, respectively, by treatment with a CD9 specific monoclonal antibody mAb7 when compared to control antibody treatment.

Antiplatelet and anticoagulant agents: key differences in mechanisms of action, clinical application, and therapeutic benefit in patients with non-ST-segment-elevation acute coronary syndromes.

Purpose Of Review: Platelet activation and aggregation are important pathophysiologic elements of both non-ST-elevation acute coronary syndromes and the ischemic complications of percutaneous coronary intervention, making antiplatelet agents necessary components of the pharmacotherapeutic treatment paradigm for these patients. This review evaluates and interprets the role of oral antiplatelet agents, glycoprotein IIb-IIIa inhibitors, and bivalirudin in the context of current clinical evidence and practice.

Recent Findings: The current standard of care for patients with non-ST-elevation acute coronary syndromes--aspirin, clopidogrel, and glycoprotein IIb-IIIa inhibitors for the majority of patients--is being challenged by recent clinical trials (Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment, Intracoronary Stenting and Antithrombotic Regimen: Rapid Early Action for Coronary Treatment 2, Randomized Evaluation of Percutaneous coronary intervention Linking Angiomax to Reduced Clinical Events-2, Acute Catheterization and Urgent Intervention Triage StrategY), raising important questions regarding the value of glycoprotein IIb-IIIa inhibitors as accompaniments of high-dose clopidogrel pretreatment and increased use of the anticoagulant bivalirudin.

Tetraspanin CD9 regulates beta 1 integrin activation and enhances cell motility to fibronectin via a PI-3 kinase-dependent pathway.

Tetraspanin CD9 regulates cell motility and other adhesive processes in a variety of tissue types. Using transfected Chinese Hamster Ovary cells as our model system, we examined the cellular pathways critical for CD9 promoted cell migration. alpha 5 beta 1 integrin was directly involved as CD9 enhanced migration was abolished by the alpha 5 beta 1 blocking antibody PB1.

Detergent and detergent-free methods to define lipid rafts and caveolae.

Lipid rafts and their related membrane vesicular structures, caveolae, are cholesterol- and sphingolipid-rich microdomains of the plasma membrane that have attracted considerable interest because of their ability to concentrate numerous signaling proteins. Efforts to define the proteins that reside in lipid rafts and caveolae as well as investigations into the functional role of these microdomains in signaling, endocytosis, and other cellular processes have led to the hypothesis that they compartmentalize or prearrange molecules involved in regulating these pathways. This chapter describes biochemical approaches for defining lipid rafts and caveolae.

cAMP inhibits transforming growth factor-beta-stimulated collagen synthesis via inhibition of extracellular signal-regulated kinase 1/2 and Smad signaling in cardiac fibroblasts.

Cardiac fibroblasts produce and degrade extracellular matrix and are critical in regulating cardiac remodeling and hypertrophy. Cytokines such as transforming growth factor-beta (TGF-beta) play a fundamental role in the development of tissue fibrosis by stimulating matrix deposition and other profibrotic responses, but less is known about pathways that might inhibit fibrosis. Increased cAMP formation inhibits myofibroblast differentiation and collagen production by cardiac fibroblasts, but the mechanism of this inhibition is not known.

Methods for the study of signaling molecules in membrane lipid rafts and caveolae.

Lipid rafts and caveolae are cholesterol- and sphingolipid-rich microdomains of the plasma membrane that concentrate components of certain signal transduction pathways. Interest in and exploration of these microdomains has grown in recent years, especially after the discovery of the biochemical marker of caveolae, caveolin, and the recognition that caveolin interacts with many different signaling molecules via its scaffolding domain. There are three major types of caveolins (1, 2, and 3), with some selectivity in their expression in different tissues.

Current strategies with eptifibatide and other antiplatelet agents in percutaneous coronary intervention and acute coronary syndromes.

Antiplatelet and anticoagulation therapies are essential for the prevention of thromboembolic-induced myocardial ischaemia in non-ST-elevation acute coronary syndromes and the ischaemic complications of percutaneous coronary intervention. Although heparin, direct thrombin inhibitors and oral platelet activation inhibitors provide substantial benefit, only glycoprotein (GP) IIb/IIIa inhibitors block the final common pathway leading to platelet aggregation, and the American College of Cardiology/American Heart Association guidelines recommend GP IIb/IIIa inhibitors as an integral component of care in these patients. Abciximab, eptifibatide and tirofiban all act through the GP IIb/IIIa receptor; however, variations in clinical outcomes among patients receiving these agents may be related to their structural and pharmacological differences, as well as to patient demographics.

The use of the point of care Helena ICHOR/Plateletworks and the Accumetrics Ultegra RPFA for assessment of platelet function with GPIIB-IIIa antagonists.

Objective: To evaluate a newly modified rapid platelet function analysis system (ICHOR/ Plateletworks) and to compare the results obtained with those of traditional light transmission aggregometry (LTA), and the Ultegra/RPFA system.

Background: Anti-platelet therapy is standard of care for patients as an adjunct to percutaneous coronary intervention (PCI) or for medical management of non-ST elevation acute coronary syndromes (NSTE ACS). Recent clinical trial results suggest that the three currently approved platelet GPIIb-IIIa receptor antagonists, eptifibatide, tirofiban and abciximab, may vary in extent of inhibition of platelet aggregation (IPA) at the approved doses.

Leukocyte-derived myeloperoxidase amplifies high-glucose--induced endothelial dysfunction through interaction with high-glucose--stimulated, vascular non--leukocyte-derived reactive oxygen species.

Vascular non-leukocyte-derived reactive oxygen species (ROS), such as superoxide and hydrogen peroxide (H(2)O(2)), have emerged as important molecules in diabetic endothelial dysfunction. In addition, leukocyte-derived myeloperoxidase (MPO) has been implicated in vascular injury, and its injury response is H(2)O(2) dependent. It is well known that MPO can use leukocyte-derived H(2)O(2); however, it is unknown whether the vascular-bound MPO can use high-glucose-stimulated, vascular non-leukocyte-derived H(2)O(2) to induce diabetic endothelial dysfunction.

The evolving role of lipid rafts and caveolae in G protein-coupled receptor signaling: implications for molecular pharmacology.

The many components of G-protein-coupled receptor (GPCR) signal transduction provide cells with numerous combinations with which to customize their responses to hormones, neurotransmitters, and pharmacologic agonists. GPCRs function as guanine nucleotide exchange factors for heterotrimeric (alpha, beta, gamma) G proteins, thereby promoting exchange of GTP for GDP and, in turn, the activation of 'downstream' signaling components. Recent data indicate that individual cells express mRNA for perhaps over 100 different GPCRs (out of a total of nearly a thousand GPCR genes), several different combinations of G-protein subunits, multiple regulators of G-protein signaling proteins (which function as GTPase activating proteins), and various isoforms of downstream effector molecules.

Lysophosphatidic acid induces neointima formation through PPARgamma activation.

Neointimal lesions are characterized by accumulation of cells within the arterial wall and are a prelude to atherosclerotic disease. Here we report that a brief exposure to either alkyl ether analogs of the growth factor-like phospholipid lysophosphatidic acid (LPA), products generated during the oxidative modification of low density lipoprotein, or to unsaturated acyl forms of LPA induce progressive formation of neointima in vivo in a rat carotid artery model. This effect is completely inhibited by the peroxisome proliferator-activated receptor (PPAR)gamma antagonist GW9662 and mimicked by PPARgamma agonists Rosiglitazone and 1-O-hexadecyl-2-azeleoyl-phosphatidylcholine.

Nitric oxide inhibition of adenylyl cyclase type 6 activity is dependent upon lipid rafts and caveolin signaling complexes.

Several cell types, including cardiac myocytes and vascular endothelial cells, produce nitric oxide (NO) via both constitutive and inducible isoforms of NO synthase. NO attenuates cardiac contractility and contributes to contractile dysfunction in heart failure, although the precise molecular mechanisms for these effects are poorly defined. Adenylyl cyclase (AC) isoforms type 5 and 6, which are preferentially expressed in cardiac myocytes, may be inhibited via a direct nitrosylation by NO.

Interaction of myeloperoxidase with vascular NAD(P)H oxidase-derived reactive oxygen species in vasculature: implications for vascular diseases.

Vascular NAD(P)H oxidase-derived reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) have emerged as important molecules in the pathogenesis of atherosclerosis, hypertension, and diabetic vascular complications. Additionally, myeloperoxidase (MPO), a transcytosable heme protein that is derived from leukocytes, is also believed to play important roles in the above-mentioned inflammatory vascular diseases. Previous studies have shown that MPO-induced vascular injury responses are H2O2 dependent.

Role of in vitro cholesterol depletion in mediating human platelet aggregation.

We investigated the direct role of cholesterol lowering on human platelet aggregation by in vitro cholesterol depletion using methyl-beta-cyclodextrin. Collagen and thrombin receptor agonist peptide induced maximal aggregation was significantly decreased in cholesterol depleted platelets. In contrast, anti-CD9 antibody, mAb7, or anti-beta(3) antibody, D3, induced percent maximal aggregation was unaffected by cholesterol depletion.