Background: Clinical trials demonstrate either no benefit or increased risk of cardiovascular events and mortality in patients with chronic kidney disease (CKD) targeted for higher hemoglobin levels, who are treated with erythropoiesis-stimulating agents (ESAs). The mechanism underlying this observation remains unexplained. Methods and Results: We assessed platelet activation by measuring ...

BACKGROUND: In the SToP platelet dose study, the World Health Organization (WHO) bleeding grade was assigned using adjudication. This study describes the challenges associated with adjudicating bleeding events and compares the adjudicated and bedside results for bleeding grade. STUDY DESIGN AND METHODS: To categorize bleeding, the following information was provided ...

Bovine topical thrombin is commonly used for local hemostasis in pediatric surgery. Acquired inhibitors to coagulation factors, particularly to factor V and bovine thrombin, have been infrequently reported in the pediatric population. We report a 3-year-old male who developed a coagulopathy and clinical bleeding after cardiothoracic surgery, during which bovine ...

The platelet P2Y12 ADP receptor is a well-known target of thienopyridine-type antiplatelet drugs. This study is the first to describe increased transcriptional expression of a functionally active P2Y12 in response to thrombin in human vascular smooth muscle cells (SMC). On exposure to thrombin, P2Y12 mRNA was transiently increased, whereas total ...

Thrombin exosite-1 mediates the specific binding of thrombin with fibrinogen and protease-activated receptor (PAR) 1. Exosite-1 inhibitors have been shown to effectively decrease the clotting activity of thrombin, while their antiplatelet effects are relatively weak. In the present study, the inhibitory effects of two exosite-1 inhibitors, hirugen and HD1, but ...

Despite the availability of dual antiplatelet therapy comprised of aspirin and clopidogrel, there is still significant unmet medical need for treating and preventing arterial thrombotic diseases. To achieve further reduction of cardiovascular events without exceeding bleeding tolerability and safety limits, novel antiplatelet strategies might need to trade in antiplatelet efficacy ...

Thrombomodulin (TM) is a cofactor for thrombin-mediated activation of protein C and thrombin-activatable fibrinolysis inhibitor (TAFI) and thereby helps coordinate coagulation, anticoagulation, fibrinolysis, and inflammation. Platelet factor 4 (PF4), a platelet α-granule protein and a soluble cofactor for TM-dependent protein C activation, stimulates protein C activation in vitro and in ...

The main question concerning the mechanism of a-thrombin binding to platelet membrane glycoprotein (GP)Ib is whether it involves both thrombin exosite I and exosite II. The solution of two independent crystal structures suggests alternative explanations that may actually reflect different modes of binding with distinct pathophysiological significance. With respect to ...

To determine factors regulating human aortic smooth muscle cells (HASMC) supported tissue factor-induced thrombin generation. The addition of nonlipidated tissue factor and Ca(2+) to HASMCs maintained in reptilase-treated platelet-poor plasma resulted in the robust formation of thrombin after a lag phase of approximately 6 minutes. Pretreatment with low concentrations of ...

Toward understanding their redundancies and interactions in hemostasis and thrombosis, we examined the roles of thrombin receptors (protease-activated receptors, PARs) and the ADP receptor P2RY12 (purinergic receptor P2Y G protein-coupled 12) in human and mouse platelets ex vivo and in mouse models. Par3(-/-) and Par4(+/-) mouse platelets showed partially decreased ...

Platelet activation, achieved through a variety of surface receptors and biochemical mediators, represents a key event in the pathogenesis of atherothrombosis and its clinical manifestations. The major pathways involved in platelet activation are triggered by thromboxane A(2), adenosine diphosphate and thrombin, with the latter being the most potent of these ...

Activation of human platelets by thrombin is mediated predominately through two proteinase-activated receptors (PARs), PAR1 and PAR4. Phosphatidylinositol 3-kinase (PI3K) inhibition leads to reversible PAR1-mediated platelet aggregation, but has no effect on the stability of platelet aggregation induced by thrombin. In the present study, the molecular mechanisms underlying this difference ...

Thrombosis is a major cause of morbidity and mortality, and thrombin is a major inducer of thrombus formation. Thus, several antithrombotic agents targeting thrombin have been developed. We previously reported on a thrombin derivative prepared by dual chemical modifications designated as 'M-anhydrothrombin', which possessed both anticoagulant and antiplatelet properties. In ...

In addition to a recognized role in the coagulation cascade and haemostasis, thrombin is known to have multiple functions. We hypothesized that protracted intravenous infusion of thrombin at steady state will allow to study isolated thrombin effects in vivo. Thrombin (0.05-0.9U/kg/min) was continuously infused in Sprague Dawley rats over five ...

Calibrated automated thrombin generation assay was adapted to measure thrombin generation in platelet rich plasma from mice. Vena cava phlebotomy appeared the best technique for blood sampling. The concentration-effect curves of tissue factor and platelet count have been determined. Corn trypsin inhibitor 2μM inhibits contact activation effectively. Recombinant human thrombomodulin ...

A dermatan sulfate isolated from the shark Scyliorhinus canicula skin by enzymatic digestion followed by purification with anion exchange chromatography was identified by chondroitinase and nitrous acid treatment and partially characterized by Fourier-transform infrared spectroscopy. Dermatan sulfate was the major glycosaminoglycan and represented 75% of the polysaccharide fraction in the ...

Three different surface receptors mediate thrombin-induced activation and aggregation of human blood platelets: the protease activated receptors 1 and 4 (PAR1 and PAR4), and the glycoprotein (GP) Ibalpha of the GPIb-IX-V complex. However, their relative contribution in the stimulation of specific intracellular signaling pathways by thrombin remains largely controversial. In ...

Hydroxysafflor Yellow A has been demonstrated to attenuate pressure overloaded hypertrophy in rats and inhibit platelet aggregation. Herein we found that Hydroxysafflor Yellow A prevented cerebral ischemia-reperfusion injury by inhibition of thrombin generation. In addition, treatment with Hydroxysafflor Yellow A significantly inhibited NF-kappaB p65 nuclear translation and p65 binding activity, ...

A highly sensitive and selective electrochemiluminescence biosensor for detection of thrombin based on the strategy of target-induced conjunction of split aptamer fragments was developed.

In platelets, STIM1 has been recognized as the key regulatory protein in store-operated Ca(2+) entry (SOCE) with Orai1 as principal Ca(2+) entry channel. Both proteins contribute to collagen-dependent arterial thrombosis in mice in vivo. It is unclear whether STIM2 is involved. A key platelet response relying on Ca(2+) entry is ...

Thrombin generation is thought to be mediated predominantly by the tissue factor or ''extrinsic'' coagulation pathway. An alternate pathway to thrombin generation (the ''intrinsic'' pathway or contact system) has been observed when blood or plasma comes in contact with artificial surfaces. Here we present evidence for a new route to ...

Despite major advances in antiplatelet therapies, recurrent cardiovascular events remain high after acute coronary syndrome. Furthermore, incremental benefits achieved in the reduction of atherothrombotic events have almost always been at the expense of hemorrhagic side effects. Thrombin is the most potent platelet activating factor known and it makes important interactions ...

Hirudin is a direct thrombin inhibitor that has potential mechanistic advantages over indirect inhibitors. Peptides containing the RGD motif competitively inhibit binding of fibrinogen to glycoprotein IIb/IIIa on platelets, thus inhibiting platelet aggregation. A novel hirudin derivative, recombinant RGD-hirudin (r-RGD-hirudin), was engineered by fusing the tripeptide RGD sequence to the ...

Activated platelets become procoagulant and efficiently promote the conversion of prothrombin to thrombin. A role of the GPIb-V-IX complex has long been postulated in view of the decreased prothrombin consumption in Bernard-Soulier patients. We evaluated the impact of GPIb-V-IX deficiency and the requirement for the GPIbalpha extracellular domain. In GPIbbeta(-/-) ...

The dermatan sulfate (DS) isolated from the ray skin Raja montagui was identified and characterized. Its average molecular weight (Mw) and sulfate content were 39 kDa and 25% w/w, respectively. This DS prolonged thrombin time and activated partial thromboplastin time and inhibited the thrombin generation in a concentration-dependent manner whereas ...

Platelets play an important role in hemostasis by forming a thrombotic plug that seals the vessel wall and promotes vascular healing. After platelets adhere and aggregate at the wound site, their next step is to generate contractile forces through the coordination of physicochemical interactions between actin, myosin, and alpha(IIb)beta(3) integrin ...

Venous and arterial thromboembolic diseases are still the most frequent causes of death and disability in high-income countries. Clinical anticoagulants are inhibitors of enzymes involved in the coagulation pathway, such as thrombin and factor X(a). Thrombin is a key enzyme of blood coagulation system, activating the platelets, converting the fibrinogen ...

Newborn platelets show in vitro hypoaggregability to thrombin. Sensitivity of platelets to such a potent agonist is crucial for a functional clot formation. Nevertheless, newborns have an excellent hemostasis. We wanted to investigate the reason for this impairment by comparatively analysing levels of receptors known to be involved in thrombin ...

Platelets bind annexin V when stimulated with combinations of platelet agonists such as collagen and thrombin. Previous studies have demonstrated significant heterogeneity of platelets binding annexin V. The relative role of the thrombin protease-activated receptors (PARs), PAR1 and PAR4, together with different methods of platelet preparation on annexin V binding ...

The platelet glycoprotein receptor regulates the adhesion of blood platelets to damaged blood vessel walls and the subsequent platelet aggregation. One of the subunits, platelet glycoprotein Ibalpha (GpIbalpha), binds thrombin, a serine protease with both procoagulant and anticoagulant activities. Two groups reported the crystal structures of the complex between thrombin ...

The kinetics of thrombin inhibition by irons ions was studied in the thrombin time test with normal plasma. The kinetic and concentration characteristics for recovery of thrombin activity by desferal were evaluated at various periods of thrombin incubation with iron ions. The thrombin time test showed that incubation of thrombin ...

Coagulation factor V (FV), present in plasma and platelets, is indispensable to thrombin formation, yet patients with undetectable plasma FV seldom experience major bleeding. We used thrombin generation assays to explore the role of platelet FV in 4 patients with severe congenital FV deficiency (3 with plasma FV clotting activity ...

Protease nexin-1 (PN-1) is a serpin that inhibits plasminogen activators, plasmin, and thrombin. PN-1 is barely detectable in plasma but is expressed by platelets. Here, we studied platelet PN-1 in resting and activated conditions and its function in thrombosis. Studies on human platelets from healthy donors and from patients with ...

BACKGROUND AND PURPOSE: The modulation by flavonoids of platelet responses induced by thrombin has been little investigated, and the antiplatelet activity, as well as possible inhibitory mechanisms of these compounds on thrombin signalling, has not yet been elucidated. We explored whether flavonoids affect platelet signalling pathways triggered by thrombin and ...

Platelet stimulation with thrombin induces an elevation in cytoplasmic free Ca(2+) concentration ([Ca(2+)]c) due to Ca(2+) release from intracellular stores and entry from the extracellular medium. Two different intracellular Ca(2+) stores have been described in human platelets: the dense tubular system and the lysosomal-like acidic stores. In the present study, ...

HD1, a DNA aptamer, binds exosite 1 on thrombin and blocks its clotting activity. Because HD1 also binds prothrombin and inhibits its activation by prothrombinase, we hypothesised that HD1 would be a more potent inhibitor of coagulation than other exosite 1-directed ligands, such as Hir(54-65)(SO(3)(-)). Supporting this concept, the effect ...

SCH 530348, a synthetic tricyclic 3-phenylpyridine, is an orally active fourth generation himbacine-based antagonist of the protease-activated receptor (PAR)-1, the primary receptor for thrombin on platelets in humans. SCH 530348 is the first in a new class of compounds that inhibit thrombin-mediated platelet aggregation without affecting the enzymatic activity of ...

Human platelets are differentially activated by varying concentrations of alpha-thrombin or by beta- and gamma-thrombin via three thrombin receptors, PAR-1, PAR-4 and GPIbalpha.It is likely that the development of a normal or abnormal hemostatic event in humans is dictated, in part, by the selective activation of these receptors. The ability ...

BACKGROUND: Concentrations of inflammatory and hemostatic variables are influenced by biological variation, which is the natural within-subject variation over time. OBJECTIVES: The aim of this study was to determine fibrinogen, C-reactive protein (CRP), platelet aggregation, thrombin generation and prothrombin time (PT): (i) the number of repeated measurements needed to obtain ...

BACKGROUND: Demineralized bone matrix is an osteoinductive and osteoconductive material that is often used in orthopaedic surgery to induce bone formation. Autologous platelet-rich plasma, which contains proliferative and chemoattractant growth factors, has been used as a demineralized bone matrix adjuvant with mixed results. One variable during clinical use appears to ...

AZD0837 is in development as a new oral anticoagulant for use in thromboembolic disorders. In vivo, AZD0837 is converted to AR-H067637, a selective and reversible direct thrombin inhibitor. Established biochemical methods were used to assess and measure the biochemical and pharmacological properties of AR-H067637. Both direct Biacore binding studies of ...

PURPOSE: Peeling of the internal limiting membrane is the treatment of choice for macular holes. Fresh platelet suspension (PS) is used to support wound healing in persistent macular holes. The concentration of growth factors in fresh, frozen, and thrombin-activated PSs were compared, to optimize their trophic potential and examine their ...

Platelet activation due to vascular injury is essential for hemostatic plug formation, and is mediated by agonists, such as thrombin, which trigger distinct receptor-coupled signaling pathways. Thrombin is a coagulation protease, which activates G protein-coupled protease-activated receptors (PARs) on the surface of platelets. We found that C57BL/6J and BALB/C mice ...

The REG1 system consists of factor IXa inhibitor, RB006, an aptamer-based anticoagulant and its antidote, RB007. The optimal use of RB006 can be facilitated by understanding its effect on the formation of thrombin and fibrin, and other standard tests of coagulation. Blood from consented volunteers was drawn into 3.2% citrate ...

The current study systematically evaluates the in vitro effect of eptifibatide, a GPIIb/IIIa blocker, on various responses of porcine platelets evoked by principal physiological stimulators. Eptifibatide at concentrations up to 40 mg/mL did not affect the calcium signal produced by thrombin, partly reduced the procoagulant response evoked by collagen, and ...

During surface-initiated blood coagulation in vitro, activated factor XII (fXIIa) converts factor XI (fXI) to fXIa. Whereas fXI deficiency is associated with a hemorrhagic disorder, factor XII deficiency is not, suggesting that fXI can be activated by other mechanisms in vivo. Thrombin activates fXI, and several studies suggest that fXI ...

In addition to its established roles in the haemostatic system, thrombin is an intriguing coagulation protease demonstrating an array of effects on endothelial cells, vascular smooth muscle cells (VSMC), monocytes, and platelets, all of which are involved in the pathophysiology of atherosclerosis. There is mounting evidence that thrombin acts as ...

Anti-platelet integrin GPIIIa49-66 antibody (Ab) induces complement-independent platelet oxidative fragmentation and death by generation of platelet peroxide following NADPH oxidase activation. A C-terminal 385-amino acid fragment of ADAMTS-18 (a disintegrin metalloproteinase with thrombospondin motifs produced in endothelial cells) induces oxidative platelet fragmentation in an identical kinetic fashion as anti-GPIIIa49-66 Ab. ...

Thrombin plays an important role in hemostasis through its multiple functions across blood coagulation, platelet activation, and fibrinolysis. The measurement of thrombin generation is therefore viewed as a potentially useful test that could be applied to the screening, monitoring, and/or diagnosis of hemostatic abnormalities. Indeed, advances in thrombin generation assays ...

Platelet activation has long been postulated to contribute to the development of atherosclerotic plaques, although the mechanism by which this might occur remains unknown. Thrombin is a potent platelet activator and transfusion of thrombin-activated platelets into mice increases plaque formation, suggesting that thrombin-induced platelet activation might contribute to platelet-dependent atherosclerosis. ...