Target For Antithrombotic Drugs Research Articles

Purification and characterisation of the platelet-activating GPVI/FcRγ complex in SMALPs

The collagen/fibrin(ogen) receptor, glycoprotein VI (GPVI), is a platelet activating receptor and a promising anti-thrombotic drug target. However, while agonist-induced GPVI clustering on platelet membranes has been shown to be essential for its activation, it is unknown if GPVI dimerisation represents a unique conformation for ligand binding. Current GPVI structures all contain only the two immunoglobulin superfamily (IgSF) domains in the GPVI extracellular region, so lacking the mucin-like stalk, transmembrane, cytoplasmic tail of GPVI and its associated Fc receptor γ (FcRγ) homodimer signalling chain, and provide contradictory insights into the mechanisms of GPVI dimerisation. Here, we utilised styrene maleic-acid lipid particles (SMALPs) to extract GPVI in complex with its two associated FcRγ chains from transfected HEK-293T cells, together with the adjacent lipid bilayer, then purified and characterised the GPVI/FcRγ-containing SMALPs, to enable structural insights into the full-length GPVI/FcRγ complex. Using size exclusion chromatography followed by a native polyacrylamide gel electrophoresis (PAGE) method, SMA-PAGE, we revealed multiple sizes of the purified GPVI/FcRγ SMALPs, suggesting the potential existence of GPVI oligomers. Importantly, GPVI/FcRγ SMALPs were functional as they could bind collagen. Mono-dispersed GPVI/FcRγ SMALPs could be observed under negative stain electron microscopy. These results pave the way for the future investigation of GPVI stoichiometry and structure, while also validating SMALPs as a promising tool for the investigation of human membrane protein interactions, stoichiometry and structure.

Identification of Potential Drug Targets for Antiplatelet Therapy Specifically Targeting Platelets of Old Individuals through Proteomic Analysis.

Aging is a growing problem worldwide, and the prevalence and mortality of arterial and venous thromboembolism (VTE) are higher in the elderly than in the young population. To address this issue, various anticoagulants have been used. However, no evidence can confirm that antithrombotic agents are suitable for the elderly. Therefore, this study aims to investigate the platelet proteome of aged mice and identify antithrombotic drug targets specific to the elderly. Based on the proteome analysis of platelets from aged mice, 308 increased or decreased proteins were identified. Among these proteins, three targets were selected as potential antithrombotic drug targets. These targets are membrane proteins or related to platelet function and include beta-2-glycoprotein 1 (β2GP1, ApolipoproteinH (ApoH)), alpha-1-acid glycoprotein2 (AGP2, Orosomucoid-2 (Orm2)), and Ras-related protein (Rab11a).

Phosphoinositides take a central stage in regulating blood platelet production and function

Blood platelets are produced by megakaryocytes through a complex program of differentiation and play a critical role in hemostasis and thrombosis. These anucleate cells are the target of antithrombotic drugs that prevent them from clumping in cardiovascular disease conditions. Platelets also significantly contribute to various aspects of physiopathology, including interorgan communications, healing, inflammation, and thromboinflammation. Their production and activation are strictly regulated by highly elaborated mechanisms. Among them, those involving inositol lipids have drawn the attention of researchers. Phosphoinositides represent the seven combinatorially phosphorylated forms of the inositol head group of inositol lipids. They play a crucial role in regulating intracellular mechanisms, such as signal transduction, actin cytoskeleton rearrangements, and membrane trafficking, either by generating second messengers or by directly binding to specific domains of effector proteins. In this review, we will explore how phosphoinositides are implicated in controlling platelet production by megakaryocytes and in platelet activation processes. We will also discuss the diversity of phosphoinositides in platelets, their role in granule biogenesis and maintenance, as well as in integrin signaling. Finally, we will address the discovery of a novel pool of phosphatidylinositol 3-monophosphate in the outerleaflet of the plasma membrane of human and mouse platelets.

RJararacin, a recombinant disintegrin from Bothrops jararaca venom: Exploring its effects on hemostasis and thrombosis

Integrins are a family of heterodimeric transmembrane receptors which link the extracellular matrix to the cell cytoskeleton. These receptors play a role in many cellular processes: adhesion, proliferation, migration, apoptosis, and platelet aggregation, thus modulating a wide range of scenarios in health and disease. Therefore, integrins have been the target of new antithrombotic drugs. Disintegrins from snake venoms are recognized by the ability to modulate the activity of integrins, such as integrin αIIbβ3, a fundamental platelet glycoprotein, and αvβ3 expressed on tumor cells. For this reason, disintegrins are unique and potential tools for examining integrin-matrix interaction and the development of novel antithrombotic agents. The present study aims to obtain the recombinant form of jararacin and evaluate the secondary structure and its effects on hemostasis and thrombosis. rJararacin was expressed in the Pichia pastoris (P. pastoris) expression system and purified the recombinant protein with a yield of 40 mg/L of culture. The molecular mass (7722 Da) and internal sequence were confirmed by mass spectrometry. Structure and folding analysis were obtained by Circular Dichroism and 1H Nuclear Magnetic Resonance spectra. Disintegrin structure reveals properly folded with the presence of β-sheet structure. rJararacin significantly demonstrated inhibition of the adhesion of B16F10 cells and platelets to the fibronectin matrix under static conditions. rJararacin inhibited platelet aggregation induced by ADP (IC50 95 nM), collagen (IC50 57 nM), and thrombin (IC50 22 nM) in a dose-dependent manner. This disintegrin also inhibited 81% and 94% of the adhesion of platelets to fibrinogen and collagen under continuous flow, respectively. In addition, rjararacin efficaciously prevents platelet aggregation in vitro and ex vivo with rat platelets and thrombus occlusion at an effective dose (5 mg/kg). The data here provides evidence that rjararacin possesses the potential as an αIIbβ3 antagonist, capable of preventing arterial thrombosis.

Coagulation Factor XII Is Activated Via Noncanonical Binding to Platelet Integrin αIIbβ3

Coagulation factor XII (FXII) has attracted significant interest as a potentially transformative antithrombotic drug target, with preclinical models consistently showing that FXII deletion or blockade protects against thrombosis without causing hemorrhage. A long-standing observation has been that stimulated platelets can support activation of FXII, thereby linking platelet function to FXIIa generation and thrombus formation. However, the mechanism by which FXII is recruited and activated at the platelet surface remains unclear and a source of considerable controversy. In order to explore the FXII-platelet interaction, we performed a mass spectrometry-based proteomic screen of potential FXII binding partners in the solubilized membrane fraction of SFLLRN-activated platelets. FXII co-immunoprecipitated with integrins αIIb and β3, with strong signals also observed for several integrin-associated proteins. These results were corroborated by Western blot of FXII co-immunoprecipitation with washed stimulated platelets and pulldown of FXII from dilute human plasma by beads coated with activated integrin αIIbβ3. Using inactive integrin from resting platelet lysate, we found that only by inducing the activated conformation of αIIbβ3 with MnCl2 could the receptor bind FXII. When flow cytometry was performed on K562 cell lines stably transfected with integrin αIIbβ3, αvβ3, or αvβ1, only those expressing αIIbβ3 in the presence of MnCl2 supported binding of FXII-FITC (Figure 1). We next evaluated the need for αIIbβ3 to support platelet-dependent FXIIa generation. Platelets from integrin β3 knockout mice (ITGB3-/-) demonstrated significantly decreased binding to FXII-FITC by flow cytometry, and ITGB3-/- platelet-rich plasma (PRP) stimulated with PAR4 agonist peptide failed to generate FXIIa in a chromogenic assay compared to PRP from wild-type littermate controls. Similarly, platelets from a patient with congenital biallelic loss of integrin αIIb (Glanzmann's thrombasthenia) also failed to bind or activate FXII compared to platelets from healthy donors. To further interrogate the role of αIIbβ3 in FXII activation, we recombinantly generated the soluble αIIbβ3 ectodomain (rED). Bio-layer interferometry (Octet) steady state analysis showed that FXII bound the rED with KD=16 nM. We found that rED greatly enhanced the rate of FXIIa generation in solution (Figure 2), with an increase of 133-fold in Kcat/Km and 203-fold in Vmax measured for FXII catalytic activity. Further, when rED was added to FXII in the presence of factor XI (FXI), we found a significant enhancement in FXIIa-dependent activation of FXI. All known physiologic ligands of αIIbβ3 contain an RGD motif, which is required for binding to the integrin. However, FXII does not have an RGD or equivalent sequence. We sought to better understand the potentially non-canonical nature of FXII-αIIbβ3 binding. We found that PAC-1 antibody, which blocks RGD-dependent macromolecular ligand binding to αIIbβ3, inhibited binding of fibrinogen-FITC to activated human platelets but failed to block FXII-FITC binding. We next studied the impact of two αIIbβ3 inhibitors on the FXII-integrin interaction. Eptifibatide blocks RGD-dependent ligand binding to αIIbβ3 and induces a large structural change in the receptor, causing it to assume an "extended open" conformation. By contrast, antibody 10E5 blocks ligand binding without inducing a conformational change in αIIbβ3. In a solid-phase assay, 10E5 did not inhibit binding of FXII to αIIbβ3, whereas eptifibatide partially blocked binding, consistent with an allosteric effect mediated by the transition to the extended open conformation. Likewise, eptifibatide partially inhibited FXIIa generation by stimulated PRP and by purified αIIbβ3, while 10E5 had no effect in either assay. Our data are consistent with a model in which non-canonical binding of FXII to integrin αIIbβ3 is responsible for FXII activation at the platelet surface. Future studies will be directed at dissecting the molecular mechanism of FXII activation by αIIbβ3 and determining whether non-RGD dependent binding may generalize to other ligands of the integrin. Taken together, our work contributes to a novel understanding of pathologic FXIIa generation during platelet activation and thrombus formation. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Identification of linoleic acid as an antithrombotic component of Wenxin Keli via selective inhibition of p-selectin-mediated platelet activation

Atrial fibrillation significantly increases the risk of thromboembolism and stroke. Wenxin Keli (WXKL) is a widely used Chinese patent medicine against arrhythmia but if it has antithrombotic activity is unknown. Since platelet activation is a critical factor in thrombosis and the key target for many antithrombotic drugs, this study aims to demonstrate the antithrombotic efficacy of WXKL. In vitro platelet activation experiments showed that WXKL significantly inhibited platelet adhesion and aggregation. The potential active monomers in WXKL were screened by in silico prediction and in vitro platelet aggregation/adhesion assays. From WXKL chemical fractions and more than 40 monomers, linoleic acid (LA) was identified as the strongest antiplatelet compound. Oral administration of WXKL (1.2 g/kg/day) and LA (50 mg/kg/day) for 7 days significantly improved FeCl3-induced carotid thrombus formation in ICR mice without prolonging bleeding time. Flow cytometry showed that both WXKL and LA inhibited the release of p-selectin after platelet activation. ELISA showed that WXKL and LA also inhibited the expression of 6-Keto-PGF1α in plasma of mice with thrombus, but had no obvious effect on the expression of TXB2. WXKL inhibited platelet activation by broadly inhibiting the phosphorylation of protein kinase B (Akt), mitogen-activated protein kinases (MAPKs) and phospholipase C (PLC) β3. In contrast, LA only inhibited the phosphorylation of PLCβ3. In conclusion, WXKL and its active component LA showed good antiplatelet and antithrombotic efficacy in vivo and in vitro. Mechanistically, the multicomponent Chinese medicine WXKL acts on multiple targets in the platelet activation pathway whereas its active monomer linoleic acid acts specifically on phospholipase C β3.

A Factor XIa Inhibitor Engineered from Banded Krait Venom Toxin: Efficacy and Safety in Rodent Models of Arterial and Venous Thrombosis.

Activated factor XI (FXIa) is an important antithrombotic drug target. Clinical and pre-clinical data have demonstrated that its inhibition attenuates thrombosis with minimal risk of excessive bleeding. We isolated Fasxiator from the venom of banded krait Bungarus fasciatus and subsequently engineered FasxiatorN17R,L19E, with improved affinity (Ki = 0.9 nM) and selectivity towards FXIa. Here, we assess the in vivo efficacy and bleeding risk of rFasxiatorN17R, L19E in pre-clinical animal models. Rats injected intravenously (i.v.) with bolus rFasxiatorN17R, L19E showed the specific in vivo attenuation of the intrinsic coagulation pathway, lasting for at least 60 min. We performed the in vivo dose-ranging experiments for rFasxiatorN17R, L19E as follows: FeCl3-induced carotid artery occlusion in rats (arterial thrombosis); inferior vena cava ligation in mice (venous thrombosis); tail bleeding time in both rats and mice (bleeding risk). Head-to-head comparisons were made using therapeutic dosages of unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) for arterial and venous thrombosis, respectively. In the arterial thrombosis model, 2 mg/kg i.v. rFasxiatorN17R,L19E achieved a similar antithrombotic efficacy to that of UFH, with >3-fold lower bleeding time. In the venous thrombosis model, the 10 mg/kg subcutaneous (s.c.) injection of rFasxiatorN17R,L19E achieved similar efficacy and bleeding levels to those of LMWH enoxaparin. Overall, rFasxiatorN17R,L19E represents a promising molecule for the development of FXIa-targeting anticoagulants.

Prenylcysteine Oxidase 1 (PCYOX1), a New Player in Thrombosis.

Prenylcysteine Oxidase 1 (PCYOX1) is an enzyme involved in the degradation of prenylated proteins. It is expressed in different tissues including vascular and blood cells. We recently showed that the secretome from Pcyox1-silenced cells reduced platelet adhesion both to fibrinogen and endothelial cells, suggesting a potential contribution of PCYOX1 into thrombus formation. Here, we show that in vivo thrombus formation after FeCl3 injury of the carotid artery was delayed in Pcyox1−/− mice, which were also protected from collagen/epinephrine induced thromboembolism. The Pcyox1−/− mice displayed normal blood cells count, vascular procoagulant activity and plasma fibrinogen levels. Deletion of Pcyox1 reduced the platelet/leukocyte aggregates in whole blood, as well as the platelet aggregation, the alpha granules release, and the αIIbβ3 integrin activation in platelet-rich plasma, in response to adenosine diphosphate (ADP) or thrombin receptor agonist peptide (TRAP). Washed platelets from the Pcyox1−/− and WT animals showed similar phosphorylation pathway activation, adhesion ability and aggregation. The presence of Pcyox1−/− plasma impaired agonist-induced WT platelet aggregation. Our findings show that the absence of PCYOX1 results in platelet hypo-reactivity and impaired arterial thrombosis, and indicates that PCYOX1 could be a novel target for antithrombotic drugs.

Microscale Parallel Synthesis of Acylated Aminotriazoles Enabling the Development of Factor XIIa and Thrombin Inhibitors.

Herein we report a microscale parallel synthetic approach allowing for rapid access to libraries of N‐acylated aminotriazoles and screening of their inhibitory activity against factor XIIa (FXIIa) and thrombin, which are targets for antithrombotic drugs. This approach, in combination with post‐screening structure optimization, yielded a potent 7 nM inhibitor of FXIIa and a 25 nM thrombin inhibitor; both compounds showed no inhibition of the other tested serine proteases. Selected N‐acylated aminotriazoles exhibited anticoagulant properties in vitro influencing the intrinsic blood coagulation pathway, but not extrinsic coagulation. Mechanistic studies of FXIIa inhibition suggested that synthesized N‐acylated aminotriazoles are covalent inhibitors of FXIIa. These synthesized compounds may serve as a promising starting point for the development of novel antithrombotic drugs.

Knockdown screening of chromatin binding and regulatory proteins in zebrafish identified Suz12b as a regulator of tfpia and an antithrombotic drug target

Tissue factor pathway inhibitor (TFPI) is an anticoagulant protein that inhibits factor VIIa and Xa in the coagulation cascade. It has been shown that forkhead box P3 protein is a TFPI transcriptional repressor. However, there are no studies on chromatin remodeling that control TFPI expression. We hypothesized that the genome-wide knockdowns of the chromatin binding and regulatory proteins (CBRPs) in zebrafish could identify novel tfpia gene regulators. As an initial step, we selected 69 CBRP genes from the list of zebrafish thrombocyte-expressed genes. We then performed a 3-gene piggyback knockdown screen of these 69 genes, followed by quantification of tfpia mRNA levels. The results revealed that knockdown of brd7, ing2, ing3, ing4, and suz12b increased tfpia mRNA levels. The simultaneous knockdown of these 5 genes also increased tfpia mRNA levels. We also performed individual gene and simultaneous 5-gene knockdowns on the 5 genes in zebrafish larvae. We found that after laser injury, it took a longer time for the formation of the thrombus to occlude the caudal vessel compared to the control larvae. We then treated the larvae and adults with a chemical UNC6852 known to proteolytically degrade polycomb repressor complex 2, where SUZ12 is a member, and observed prolongation of time to occlude (TTO) the caudal vein after laser injury and increased tfpia mRNA levels in larvae and adults, respectively. In summary, our results have identified novel epigenetic regulators for tfpia and exploited this information to discover a drug that enhances tfpia mRNA levels and prolongation of TTO. This discovery provides the basis for testing whether UNC6852 could be used as an antithrombotic drug. This approach could be used to study the regulation of other plasma proteins, including coagulant and anticoagulant factors.

Improved efficacy/safety profile of factor XIa inhibitor BMS‐724296 versus factor Xa inhibitor apixaban and thrombin inhibitor dabigatran in cynomolgus monkeys

BackgroundInhibition of activated factor XI (FXIa) is a promising antithrombotic drug target. BMS‐724296 is a selective, reversible, small‐molecule inhibitor of human FXIa (Ki 0.3 nM). ObjectivesThis study assessed effects of BMS‐724296 versus standard‐of‐care oral anticoagulants apixaban (activated factor X inhibitor) and dabigatran (thrombin inhibitor) on arterial thrombosis, kidney bleeding time (KBT), and clotting time (CT) in nonhuman primate (NHP) cynomolgus monkey models. MethodsCarotid artery thrombosis was produced by electrical stimulation in anesthetized NHPs. Hemostasis was assessed with a provoked KBT model. Thrombosis, KBT, and CT were monitored. Vehicle and various doses of BMS‐724296, apixaban, and dabigatran were administered as bolus (intravenous [i.v.]) followed by infusion starting 30 minutes before initiation of thrombosis and continued until the experiment’s end (n = 3‐8/group). Primary end points included thrombus weight reduction (TWR), KBT, and CT (activated partial thromboplastin time [aPTT], prothrombin time [PT], and thrombin time [TT]). ResultsBMS‐724296 at 0.025 + 0.05, 0.05 + 0.1, 0.102 + 0.2, and 0.4 + 0.8 mg/kg+mg/kg/h i.v. (bolus + infusion) reduced thrombus weight by 0 ± 0, 35 ± 7*, 72 ± 4*, and 86 ± 4%*, respectively (*P< .05 vs vehicle; n = 5‐6/group). BMS‐724296 at the highest dose (0.4 + 0.8 mg/kg+mg/kg/h) did not increase KBT compared to vehicle (109 ± 6 vs 113 ± 20 seconds, respectively) and increased ex vivo aPTT by 2.9 ± 0.1‐fold without changing PT and TT. In companion NHP studies, high doses of apixaban and dabigatran produced similar TWR as BMS‐724296, but increased KBT 4.3 ± 0.5‐fold and 5.8 ± 0.5‐fold, respectively (n = 3‐4/group). ConclusionsBMS‐724296 produced similar antithrombotic efficacy as apixaban and dabigatran but with no increase in KBT in NHPs. These findings suggest that FXIa inhibitors may provide safe and effective antithrombotic therapy.

Gain-of-Function Variant p.Pro2555Arg of von Willebrand Factor Increases Aggregate Size through Altering Stem Dynamics.

The multimeric plasma glycoprotein (GP) von Willebrand factor (VWF) is best known for recruiting platelets to sites of injury during primary hemostasis. Generally, mutations in the VWF gene lead to loss of hemostatic activity and thus the bleeding disorder von Willebrand disease. By employing cone and platelet aggregometry and microfluidic assays, we uncovered a platelet GPIIb/IIIa-dependent prothrombotic gain of function (GOF) for variant p.Pro2555Arg, located in the C4 domain, leading to an increase in platelet aggregate size. We performed complementary biophysical and structural investigations using circular dichroism spectra, small-angle X-ray scattering, nuclear magnetic resonance spectroscopy, molecular dynamics simulations on the single C4 domain, and dimeric wild-type and p.Pro2555Arg constructs. C4-p.Pro2555Arg retained the overall structural conformation with minor populations of alternative conformations exhibiting increased hinge flexibility and slow conformational exchange. The dimeric protein becomes disordered and more flexible. Our data suggest that the GOF does not affect the binding affinity of the C4 domain for GPIIb/IIIa. Instead, the increased VWF dimer flexibility enhances temporal accessibility of platelet-binding sites. Using an interdisciplinary approach, we revealed that p.Pro2555Arg is the first VWF variant, which increases platelet aggregate size and shows a shear-dependent function of the VWF stem region, which can become hyperactive through mutations. Prothrombotic GOF variants of VWF are a novel concept of a VWF-associated pathomechanism of thromboembolic events, which is of general interest to vascular health but not yet considered in diagnostics. Thus, awareness should be raised for the risk they pose. Furthermore, our data implicate the C4 domain as a novel antithrombotic drug target.

FEIBA® and Novoseven® Neutralize the Anticoagulant Effects of a Novel Small Molecule FXIa Inhibitor BMS-986177/JNJ-70033093 in Human Plasma and Whole Blood in Vitro

Background: FXIa inhibition is a promising antithrombotic drug target. BMS-986177/JNJ-70033093 (BMS-177/JNJ-3093) is a novel small molecular inhibitor of FXIa currently in Phase II clinical trials with the potential for reduced bleeding risk as compared to the currently approved oral anticoagulantsHowever, reversal of anticoagulation may still be required in patients who have uncontrolled or life-threatening bleeding or need an urgent surgical procedure. Aim: To evaluate the ability of nonspecific reversal agents (NSRAs) FEIBA®, NovoSeven®, Kcentra®, Profilnine®, BeneFix®, Novoeight®, and Cyklokapron® to neutralize the anticoagulation of BMS-177/JNJ-3093 in the activated partial thromboplastin time (aPTT), thromboelastography (TEG) and thrombin generation assay (TGA) in vitro using human plasma or whole blood. Method: aPTT and TEG were performed in human plasma and whole blood, respectively, using standard assay procedures. TGA was performed in human plasma using diluted kaolin aPTT reagent (1:10,000). JNJ-3093 was evaluated at different concentrations (0.3 -10 µM) to cover the anticipated exposures in the Phase II clinical trials. The NSRAs were evaluated at the anticipated concentrations according to the dosing information in their respective labels. Results: BMS-177/JNJ-3093 produced concentration dependent increases in aPTT (up to 4.4x at 10 μM); prolongations of lag time in TEG (2.6X); prolongations of lag time (3X) as well as reductions in peak thrombin generation (70%) in TGA. FEIBA® effectively neutralized the anticoagulant effects of JNJ-3093 in aPTT, TEG and TGA. NovoSeven® neutralized the BMS-177/JNJ-3093-induced prolongations in aPTT, prolongations in lag time in TEG and TGA assays and partially restored the peak thrombin generation in TGA. In contrast, all other NSRAs tested had negligible effects or did not show neutralization of anticoagulation induced by BMS-177/JNJ-3093 in the referenced assays Conclusion: These results demonstrate that FEIBA® and NovoSeven® can effectively neutralize the anticoagulant effects of BMS-177/JNJ-3093 in vitro. A clinical study is required to determine if these agents can reverse the anticoagulant effects of BMS-177/JNJ-3093 in patients. Table Disclosures Bunce: Johnson &amp; Johnson: Current Employment, Current equity holder in publicly-traded company. Huang Devine:Johnson &amp; Johnson: Current Employment, Current equity holder in publicly-traded company. Chintala:Johnson &amp; Johnson: Current Employment, Current equity holder in publicly-traded company. OffLabel Disclosure: FEIBA: hemophilia A and B patients with inhibitors for: control and prevention of bleeding episodes; use around the time of surgery; routine prophylaxis to prevent or reduce the frequency of bleeding episodes NovoSeven: Treatment of bleeding and prevention of bleeding for surgeries and procedures in adults and children with hemophilia A or B with inhibitors, congenital Factor VII (FVII) deficiency, and Glanzmanns thrombasthenia with a decreased or absent response to platelet transfusions; treatment of bleeding and prevention of bleeding for surgeries and procedures in adults with acquired hemophilia Kcentra: urgent reversal of acquired coagulation factor deficiency induced by vitamin K antagonist therapy in adult patients with need for urgent surgery/invasive procedure or acute major bleeding Profilnine: prevention and control of bleeding in patients with Factor IX deficiency due to hemophilia B BeneFix: control and prevention of bleeding episodes or peri-operative management in adult and pediatric patients with hemophilia B Novoeight: for use in adults and children with hemophilia A for control and prevention of bleeding, perioperative management, and routine prophylaxis to prevent or reduce the frequency of bleeding episodes Cyklokapron: patients with hemophilia for short-term use to reduce or prevent hemorrhage and reduce the need for replacement therapy during and following tooth extraction)

Analysis of platelets from a diet-induced obesity rat model: elucidating platelet dysfunction in obesity

Obesity is one of the main health problems in industrialized countries. The contribution of multiple factors developed in obesity can hardly be modeled in vitro. In this context, the development of animal models mimicking human obesity could be essential. The aim of the present study was to compare platelets from a diet-induced obesity (DIO) rat model with their lean control group in order to elucidate platelet dysfunction mechanisms in obesity and correlate the results with previous data from morbid obese patients. In parallel, we also established a blood collection and platelet isolation methodology to study the DIO rat model at biochemical and functional level. Optimal blood collection was obtained from vena cava and platelet isolation was based on a serial of centrifugations avoiding platelet activation. Our results show that the DIO rat model simulate obesity pathologically since weight gain, fasting glucose and platelet counts are increased in obese rats. Interestingly, platelet levels of the active form of Src (pTyr419) showed a tendency to increase in DIO rats pointing towards a potential dysfunction in Src family kinases-related signalling pathways in obesity. Moreover, platelets from DIO rats adhere more to collagen compared with the control group, pointing towards Glycoprotein VI (GPVI) as one of the dysregulated receptors in obesity, in agreement with our recent studies in humans. These results confirm that obesity, in line with human studies, present a platelet dysregulation, and highlight the relevance of considering novel antithrombotic drug targets in these patients, such as GPVI.

Platelet Aggregation Activities of Vietnamese Medicinal Plants: Anti-Thrombolytic Potentials?

Blood coagulant, an important physiological process, underlines pathology of various diseases. Thrombosis caused by activated platelets in blood stream can lead to narrowing or blocking the blood flow, which results in stroke or ischemic conditions. The number of human deaths caused by coronary disease or stroke has been increasing rapidly over the last few years in Vietnam. Many anti-thrombosis and anti-platelet aggregation drugs have been discovered and applied in treatment. However, these drugs have many side effects such as bleeding, stomach lesion, etc. Vietnam is a tropical country with plenty of medicinal plants, from which a potential drug for anti-thrombolytic activities can be prepared. 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P2Y12 Inhibition beyond Thrombosis: Effects on Inflammation.

The P2Y12 receptor is a key player in platelet activation and a major target for antithrombotic drugs. The beneficial effects of P2Y12 receptor antagonists might, however, not be restricted to the primary and secondary prevention of arterial thrombosis. Indeed, it has been established that platelet activation also has an essential role in inflammation. Additionally, nonplatelet P2Y12 receptors present in immune cells and vascular smooth muscle cells might be effective players in the inflammatory response. This review will investigate the biological and clinical impact of P2Y12 receptor inhibition beyond its platelet-driven antithrombotic effects, focusing on its anti-inflammatory role. We will discuss the potential molecular and cellular mechanisms of P2Y12-mediated inflammation, including cytokine release, platelet–leukocyte interactions and neutrophil extracellular trap formation. Then we will summarize the current evidence on the beneficial effects of P2Y12 antagonists during various clinical inflammatory diseases, especially during sepsis, acute lung injury, asthma, atherosclerosis, and cancer.

Cobalt hematoporphyrin inhibits CLEC-2–podoplanin interaction, tumor metastasis, and arterial/venous thrombosis in mice

AbstractThe platelet activation receptor C-type lectin-like receptor 2 (CLEC-2) interacts with podoplanin on the surface of certain types of tumor cells, and this interaction facilitates tumor metastasis. CLEC-2 is also involved in thrombus formation and its stabilization. Because CLEC-2–depleted mice are protected from experimental lung metastasis and thrombus formation and do not show increased bleeding time, CLEC-2 may serve as a good target for antimetastatic or antithrombotic drugs. We screened 6770 compounds for their capability to inhibit CLEC-2–podoplanin binding using an enzyme-linked immunosorbent assay. In the first screening round, 63 compounds were identified and further evaluated by flow cytometry using CLEC-2–expressing cells. We identified protoporphyrin IX (H2-PP) as the most potent inhibitor and modified its hematoporphyrin moiety to be complexed with cobalt (cobalt hematoporphyrin [Co-HP]), which resulted in an inhibitory potency much stronger than that of H2-PP. Surface plasmon resonance analysis and molecular docking study showed that Co-HP binds directly to CLEC-2 at N120, N210, and K211, previously unknown podoplanin-binding sites; this binding was confirmed by analysis of CLEC-2 mutants with alterations in N120 and/or K211. Co-HP at a concentration of 1.53 μM inhibited platelet aggregation mediated through CLEC-2, but not that mediated through other receptors. IV administration of Co-HP to mice significantly inhibited hematogenous metastasis of podoplanin-expressing B16F10 cells to the lung as well as in vivo arterial and venous thrombosis, without a significant increase in tail-bleeding time. Thus, Co-HP may be a promising molecule for antimetastatic and antiplatelet treatment that does not cause bleeding tendency.

Molecular Docking of Ferulic Acid Derivatives on P2Y12 Receptor and their ADMET Prediction

P2Y12 is a platelet receptor that is involved in ADP signal transduction and is an attractive target for antithrombotic drugs. The side effects of antithrombotic drugs are not pleasant for the patient, so research into the development of new antithrombotic agents is still necessary. Evaluation of absorption, distribution, metabolism, elimination, and the toxicity profile of candidate drugs is an important step in drug development. The aim of this study was to predict the potency of ferulic acid (FA) and its derivatives (FA1-24) as antiplatelet drugs by a docking study on the P2Y12 receptor (PDB ID: 4PXZ) and their ADMET performance. The docking study was performed using Molegro Virtual Docker, version 5.5. ADMET prediction of FA was conducted using the pkCSM online tool. The results of the in silico study showed that FA-19 had the lowest MolDock score (MDS), which means that this compound is predicted to have the greatest activity. FA-19 is also predicted to be practically non-toxic. It is expected that FA-19 will have good intestinal absorption and is similarly distributed in the intestine and in the blood plasma. Its penetration in the blood-brain barrier is moderate but does not inhibit the CYP2D6 and CYP3A4 enzymes.

A function-blocking PAR4 antibody is markedly antithrombotic in the face of a hyperreactive PAR4 variant

AbstractThrombin activates human platelets via 2 protease-activated receptors (PARs), PAR1 and PAR4, both of which are antithrombotic drug targets: a PAR1 inhibitor is approved for clinical use, and a PAR4 inhibitor is in trial. However, a common sequence variant in human PAR4 (rs773902, encoding Thr120 in place of Ala120) renders the receptor more sensitive to agonists and less sensitive to antagonists. Here, we develop the first human monoclonal function-blocking antibody to human PAR4 and show it provides equivalent efficacy against the Ala120 and Thr120 PAR4 variants. This candidate was generated from a panel of anti-PAR4 antibodies, was found to bind PAR4 with affinity (KD ≈ 0.4 nM) and selectivity (no detectable binding to any of PAR1, PAR2, or PAR3), and is capable of near-complete inhibition of thrombin cleavage of either the Ala120 or Thr120 PAR4 variant. Platelets from individuals expressing the Thr120 PAR4 variant exhibit increased thrombin-induced aggregation and phosphatidylserine exposure vs those with the Ala120 PAR4 variant, yet the PAR4 antibody inhibited these responses equivalently (50% inhibitory concentration, 4.3 vs 3.2 µg/mL against Ala120 and Thr120, respectively). Further, the antibody significantly impairs platelet procoagulant activity in an ex vivo thrombosis assay, with equivalent inhibition of fibrin formation and overall thrombus size in blood from individuals expressing the Ala120 or Thr120 PAR4 variant. These findings reveal antibody-mediated inhibition of PAR4 cleavage and activation provides robust antithrombotic activity independent of the rs773902 PAR4 sequence variant and provides rationale for such an approach for antithrombotic therapy targeting this receptor.

Mechanisms of Hirudo in promoting blood circulation and removing stasis based on network pharmacology

The study aims to analyze the mechanisms of Hirudo in promoting blood circulation and removing blood stasis based on network pharmacology. A database of chemical components of Hirudo was established through literature retrieval. The targets were predicted by using the reverse pharmacophore matching method and screened according to the antithrombotic and anticoagulant drug targets approved by FDA in the DrugBank database. Then, the targets were analyzed by KEGG pathway analysis, the protein interactions were analyzed by using BioGrid database, and the active constituents-target-pathway network model of Hirudo was established to study the mechanisms of Hirudo in promoting blood circulation and removing blood stasis. This study collected 49 chemical components of Hirudo, including amino acid, polypeptide, fatty acid ester, alkaloid, glycosides, and steroid. Totally 376 targets were predicted, and 5 critical targets related to the effects of Hirudo in promoting blood circulation and removing blood stasis were screened, including fibrinogen gamma chain, plasminogen, prothrombin, Urokinase-type plasminogen activator and coagulation factor X. The potential regulatory pathways included complement and coagulation cascades, platelet activation, VEGF signaling pathway, focal adhesion. This study reflects the multi-component, multi-target and multi-pathway features of Hirudo, and provides a scientific basis for elucidating the mechanisms of action of Hirudo in promoting blood circulation and removing blood stasis, as well as a reference for the study of mechanisms of traditional Chinese medicine.