The Inhibitory Effect of Protamine on Platelets is Attenuated by Heparin without Inducing Thrombocytopenia in Rodents

Protamine sulfate (PS) is a polycationic protein drug obtained from the sperm of fish, and is used to reverse the anticoagulant effect of unfractionated heparin (UFH). However, the interactions between PS, UFH, and platelets are still not clear. We measured the platelet numbers and collagen-induced aggregation, P-selectin, platelet factor 4, β-thromboglobulin, prostacyclin metabolite, D-dimers, activated partial thromboplastin time, prothrombin time, anti-factor Xa, fibrinogen, thrombus weight and megakaryocytopoiesis in blood collected from mice and rats in different time points.. All of the groups were treated intravenously with vehicle, UFH, PS, or UFH with PS. We found a short-term antiplatelet activity of PS in mice and rats, and long-term platelet-independent antithrombotic activity in rats with electrically-induced thrombosis. The antiplatelet and antithrombotic potential of PS may contribute to bleeding risk in PS-overdosed patients. The inhibitory effect of PS on the platelets was attenuated by UFH without inducing thrombocytopenia. Treatment with UFH and PS did not affect the formation, number, or activation of platelets, or the thrombosis development in rodents.

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Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159412 ◽

1990 ◽

Vol 48 (3) ◽

pp. 374-375

Author(s):

D.E. Loudy ◽

J. Sprinkle-Cavallo ◽

J.T. Yarrington ◽

F.Y. Thompson ◽

J.P. Gibson

Keyword(s):

Antidepressant Drug ◽

Beagle Dogs ◽

Long Term Effects ◽

Short Term ◽

Platelet Counts ◽

Toxicological Studies ◽

Induced Aggregation ◽

Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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The Venous Antithrombotic Profile of Naroparcil in the Rabbit

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648977 ◽

1994 ◽

Vol 72 (06) ◽

pp. 874-879 ◽

Cited By ~ 11

Author(s):

Jean Millet ◽

Jocelyne Theveniaux ◽

Neil L Brown

Keyword(s):

Oral Administration ◽

Bleeding Time ◽

Dermatan Sulfate ◽

Factor Xa ◽

Bleeding Risk ◽

Thrombin Time ◽

Heparin Cofactor Ii ◽

Antithrombotic Activity ◽

Thrombin Inhibition ◽

Maximal Reduction

SummaryThe venous antithrombotic profile of naroparcil or (4-[4-cyanoben-zoyl]-phenyl)-1.5-dithio-β-D-xylopyranoside was investigated in the rabbit following single i. v. and oral administration. Naroparcil attenuated thrombus development in a Wessler stasis model of venous thrombosis (jugular vein) employing bovine factor Xa as a thrombogenic stimulus giving ED50 values of 21.9 mg/kg and 36.0 mg/kg after respectively i. v. and oral administration. Venous antithrombotic activity was maximal 2-3 h after i. v. administration and 4-8 h after oral administration. Four hours after the oral administration of maximal antithrombotic (Wessler model, factor Xa) doses (100 and 400 mg/kg), naroparcil had no significant effect on bleeding time. In platelet poor plasma obtained from animals treated 4 h previously with various doses (25 to 400 mg/kg) of naroparcil, there was no detectable anti-factor Xa nor antithrombin activity. Similarly, naroparcil had no effect on APTT nor on thrombin time. A sensitized thrombin time (to about 35 s) was modestly but significantly increased following oral administration of the compound at 400 mg/kg. However, thrombin generation by the intrinsic pathway was reduced in a dose-related manner, maximal reduction being 65% at 400 mg/kg. The same doses of naroparcil enhanced the formation of thrombin/heparin cofactor II complexes at the expense of thrombin/antithrombin III complexes in plasma incubated with (125I)-human a-thrombin and induced the appearance of dermatan sulfate-like material in the plasma of treated rabbits, as measured by a heparin cofactor II-mediated thrombin inhibition assay. The results suggest that naroparcil could have a safe venous antithrombotic profile following oral administration (antithrombotic effect compared to bleeding risk). It is probable that part of the mechanism of action of the β-D-xyloside, naroparcil, is due to the induction of chondroitin sulfate-like glycosaminoglycan biosynthesis, this material being detectable in the plasma.

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Complicated Long Term Vaccine Induced Thrombotic Immune Thrombocytopenia—A Case Report

Vaccines ◽

10.3390/vaccines9111344 ◽

2021 ◽

Vol 9 (11) ◽

pp. 1344

Author(s):

Albrecht Günther ◽

Dirk Brämer ◽

Mathias W. Pletz ◽

Thomas Kamradt ◽

Sabine Baumgart ◽

...

Keyword(s):

Intracranial Hemorrhage ◽

Sinus Thrombosis ◽

Immunosuppressive Treatment ◽

Bleeding Risk ◽

Term Therapy ◽

Repeated Treatment ◽

Laboratory Findings ◽

Platelet Factor ◽

Sagittal Sinus

Background and Objectives: Vaccine induced thrombotic thrombocytopenia (VITT) may occur after COVID-19 vaccination with recombinant adenoviral vector-based vaccines. VITT can present as cerebral sinus and venous thrombosis (CSVT), often complicated by intracranial hemorrhage. Today it is unclear, how long symptomatic VITT can persist. Here, we report the complicated long-term course of a VITT patient with extremely high titers of pathogenic anti-platelet factor 4 (PF4)-IgG antibodies. Methods: Clinical and laboratory findings are presented, including the course of platelet counts, D-Dimer levels, clinical presentation, imaging, SARS-CoV-2-serological and immunological, platelet activating anti-PF4-IgG, as well as autopsy findings. Results: The patient presented with extended superior sagittal sinus thrombosis with accompanying bifrontal intracerebral hemorrhage. Repeated treatment with intravenous immune globuline (IVIG) resolved recurrent episodes of thrombocytopenia. Moreover, the patient’s serum remained strongly positive for platelet-activating anti-PF4-IgG over three months. After a period of clinical stabilization, the patient suffered a recurrent and fatal intracranial hemorrhage. Conclusions: Complicated VITT with extremely high anti-PF4-IgG titers over three months can induce recurrent thrombocytopenia despite treatment with IVIG and anticoagulation. Plasma exchange, immunoadsorption, and /or immunosuppressive treatment may be considered in complicated VITT to reduce extraordinarily high levels of anti-PF4-IgG. Long-term therapy in such cases must take the individual bleeding risk and CSVT risk into account.

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Congenital Deficiency of Alpha-2-Adrenoceptors on Human Platelets : Description of Two Cases

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646046 ◽

1987 ◽

Vol 58 (04) ◽

pp. 1012-1016 ◽

Cited By ~ 24

Author(s):

Giacomo Tamponi ◽

Antonella Pannocchia ◽

Carlo Arduino ◽

Mario Bazzan ◽

Nadine Della Dora ◽

...

Keyword(s):

Radioligand Binding ◽

Adenine Nucleotides ◽

Thromboxane A2 ◽

Inhibitory Effect ◽

Human Platelets ◽

Platelet Factor ◽

Congenital Deficiency ◽

Normal Limits ◽

Flux Aggregation ◽

Induced Aggregation

SummaryThe biochemistry and functionality of platelets from two related subjects (mother and son) with alpha-2-adrenoceptor-deficient platelets has been evaluated. Radioligand binding experimentes with the specific alpha-2-adrenergic-receptor antagonist, 3H-yohimbine, showed a drastic reduction of alpha-2-adrenoceptors in platelets from both subjects in comparison with the control values. Electron microscopy studies revealed a normal morphology and a normal number of alpha granules and dense bodies. Levels of adenine nucleotides; 5-hydroxytryptamine; B-thromboglobulin; platelet-factor-4 and thromboxane A2 production were within normal limits.Platelet aggregation and 5-hydroxytryplamine production in response to adrenalin (at concentrations up to 50 μM) were absent, whereas ADP, AA, PAF, collagen and thrombin-induced aggregation, secretion, Ca++ flux and thromboxane A2 production were normal.The inhibitory effect caused by different concentrations of prostacyclin on Ca++ flux, aggregation, secretion and thromboxane A2 production of platelet functionally lacking of alpha-2-adrenoceptor was not distinguishable from control platelets and platelets preincubated with yohimbine.

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Combination of FXI Antisense Oligonucleotide and Plavix® Treatment Results in Enhanced Antithrombotic Activity without Increased Risk of Bleeding in Mouse Models of Thrombosis.

Blood ◽

10.1182/blood.v114.22.4173.4173 ◽

2009 ◽

Vol 114 (22) ◽

pp. 4173-4173

Author(s):

Dacao Gao ◽

Jeff Crosby ◽

Robert MacLeod ◽

Gourab Bhattacharjee ◽

Ester C Lowenberg ◽

...

Keyword(s):

Mouse Models ◽

Antisense Oligonucleotide ◽

Factor Xa ◽

Bleeding Risk ◽

Fibrin Clot ◽

Bleeding Tendency ◽

Loss Of Function ◽

Factor Xi ◽

Antithrombotic Activity ◽

Increased Risk

Abstract Abstract 4173 Factor XI (FXI) is a serine protease produced in the liver that contributes to thrombin generation via the intrinsic coagulation pathway. Also, it is a key component of an amplification pathway that is thought to sustain thrombin production at a wound site to maintain fibrin clot integrity. Loss of function mutations in the human FXI gene results in FXI deficiency, a disorder which is associated with only mild bleeding. In addition, high levels of FXI are a risk factor for thrombosis. We have previously presented the antithrombotic efficacy and safety of antisense oligonucleotide (ASO) mediated FXI depletion in various animal models of thrombosis. We have demonstrated that in combination with Lovenox®, FXI ASO treatment increases antithrombotic activity but does not increase bleeding risk. The purpose of the current study was to evaluate the relative risk/benefit of ASO mediated Factor XI depletion in combination with the platelet antagonist Plavix®. The “risk” component was bleeding tendency as measured by blood volume loss following tail nick, and the “benefit” component was antithrombotic effect in arterial and venous mouse models of thrombosis. Our study investigated a 20 mg/kg dose of FXI ASO in combination with a dose response of Plavix® and indicates that antisense mediated FXI depletion provides enhanced antithrombotic protection when given in combination with Plavix®. The combination of FXI ASO and Plavix® did not result in increased bleeding tendency. In contrast, treatment with a small molecule inhibitor of factor Xa in combination with Plavix® significantly increased bleeding. The approach used in this study is being used to define the ability of FXI ASO to combine with standard of care agents for the treatment of thrombosis. Disclosures: Gao: Isis Pharmaceuticals, Inc.: Employment. Crosby:Isis Pharmaceuticals, Inc.: Employment. MacLeod:Isis Pharmaceuticals: Employment. Bhattacharjee:Isis Pharmaceuticals, Inc.: Employment. Lowenberg:Isis Pharmaceuticals, Inc.: Consultancy. Levi:Isis Pharmaceuticals, Inc.: Consultancy. Monia:Isis Pharmaceuticals, Inc.: Employment.

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Reactivation of cytoplasmic actomyosin in Physarum plasmodia extracted with glycerol and dimethylsulphoxide

Journal of Cell Science ◽

10.1242/jcs.87.2.231 ◽

1987 ◽

Vol 87 (2) ◽

pp. 231-239

Author(s):

R. Bell ◽

F. Achenbach

Keyword(s):

Calcium Sensitivity ◽

Inhibitory Effect ◽

Prolonged Treatment ◽

Short Term ◽

Extraction Procedures ◽

Term Extraction ◽

Cytoplasmic Actomyosin ◽

Structural Preservation ◽

Physarum Plasmodia

Thin-spread plasmodia of Physarum were subjected to extraction procedures using 50% glycerol or DMSO (dimethylsulphoxide) followed by labelling of actin with fluorescent phallotoxins. During the reactivation of the actomyosin system by 2 mM-MgATP fluorescent actin fibres contract isotonically, which results in numerous fluorescent ‘contraction beads’. After short-term extraction 1 mM-Ca2+ has an inhibitory effect on the reactivation. This calcium sensitivity is abolished after long-term extraction with glycerol. Calcium at 10 mM irreversibly inhibits reactivation, irrespective of the duration of extraction. The inhibitory effect of 10 mM-calcium is prevented by phallotoxin labelling prior to incubation in Ca2+. The DMSO model shows an improvement in structural preservation when compared with the glycerol models. However, reactivation is inhibited by prolonged treatment with DMSO.

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Oxidized high-density lipoprotein inhibits platelet activation and aggregation via scavenger receptor BI

Blood ◽

10.1182/blood-2007-08-107813 ◽

2008 ◽

Vol 111 (4) ◽

pp. 1962-1971 ◽

Cited By ~ 69

Author(s):

Manojkumar Valiyaveettil ◽

Niladri Kar ◽

Mohammad Z. Ashraf ◽

Tatiana V. Byzova ◽

Maria Febbraio ◽

...

Keyword(s):

High Density Lipoprotein ◽

Platelet Activation ◽

Scavenger Receptor ◽

Density Lipoprotein ◽

Inhibitory Effect ◽

High Density ◽

Type I ◽

Antithrombotic Activity ◽

Atheromatous Plaques ◽

Induced Aggregation

Numerous studies have reported the presence of oxidatively modified high-density lipoprotein (OxHDL) within the intima of atheromatous plaques as well as in plasma; however, its role in the pathogenesis of thrombotic disease is not established. We now report that OxHDL, but not native HDL, is a potent inhibitor of platelet activation and aggregation induced by physiologic agonists. This antithrombotic effect was concentration and time dependent and positively correlated with the degree of lipoprotein oxidation. Oxidized lipoproteins are known ligands for scavenger receptors type B, CD36 and scavenger receptor B type I (SR-BI), both of which are expressed on platelets. Studies using murine CD36−/− or SR-BI−/− platelets demonstrated that the antithrombotic activity of OxHDL depends on platelet SR-BI but not CD36. Binding to SR-BI was required since preincubation of human and murine platelets with anti–SR-BI blocking antibody abrogated the inhibitory effect of OxHDL. Agonist-induced aggregation of platelets from endothelial nitric oxide synthase (eNOS)−/−, Akt-1−/−, and Akt-2−/− mice was inhibited by OxHDL to the same degree as platelets from wild-type (WT) mice, indicating that the OxHDL effect is mediated by a pathway different from the eNOS/Akt pathway. These novel findings suggest that contrary to the prothrombotic activity of oxidized low-density lipoprotein (OxLDL), HDL upon oxidation acquires antithrombotic activity that depends on platelet SR-BI.

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Non-steroidal factors in bovine follicular fluid inhibit or facilitate the action of pulsatile administration of GnRH on LH release in the female rat

Journal of Endocrinology ◽

10.1677/joe.0.1610237 ◽

1999 ◽

Vol 161 (2) ◽

pp. 237-243 ◽

Cited By ~ 1

Author(s):

JA van Dieten ◽

MN Helder ◽

C van den Oever ◽

J de Koning

Keyword(s):

Follicular Fluid ◽

Inhibitory Effect ◽

Female Rats ◽

Minor Effect ◽

Female Rat ◽

Short Term ◽

Ovx Rats ◽

Lh Release ◽

Intact Rats

Using steroid-free bovine follicular fluid (bFF), we studied the action of gonadotrophin surge-inhibiting factor/attenuating factor (GnSIF/AF) on GnRH-induced self-priming in phenobarbital-blocked female rats. For the experiments we used intact rats, short-term (4 h) ovariectomized (OVX) rats and long-term (14 days) OVX rats. In the latter case the rats were injected with 17beta-oestradiol benzoate (OB, 40 micrograms) or vehicle only, 2 or 48 h before the experiment. GnRH (10-50 pmol/kg body weight) was injected intra-arterially in 5 or 15 pulses, respectively 60 or 20 min apart, starting 1 or 4 h after injection of bFF (0.5 or 1.0 ml). In response to 25 pmol/kg GnRH pulses (1/h), we observed no effect in the long-term OVX rats, a minor effect in the intact rats and an enhanced self-priming effect in the short-term OVX rats. Administration of bFF attenuated or even completely inhibited the self-priming process. However, in the case of long-term OVX rats LH release was inhibited only after long-term OB priming. Furthermore, 4 h after administration of bFF, LH release in response to 25 pmol/kg GnRH pulses (3/h) was inhibited transiently in intact rats and long-term OVX rats. The results support the hypothesis of a functional antagonistic action between GnRH and GnSIF/AF. However, when injected 1 h before, bFF facilitated the initial release of the surge-like LH pattern in intact rats in response to 3 pulses/h of GnRH. These results are consistent with an important role of GnSIF/AF and other non-steroidal ovarian factors in the control of both low LH concentrations and the generation of the LH surge. Some genomic action of oestradiol might be a prerequisite for the inhibitory effect of GnSIF/AF on GnRH-induced LH release.

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Design, Synthesis, and Docking Studies of Arylhydrazone Compounds and Evaluation of Their Platelet Aggregation Inhibitory Effect and Cytotoxicity

10.21203/rs.3.rs-1204698/v1 ◽

2022 ◽

Author(s):

Maryam H. Klidsar ◽

Marjan Esfahanizadeh ◽

Pantea Haghverdi ◽

Salimeh Amidi ◽

Farzad Kobarfard

Keyword(s):

Isonicotinic Acid ◽

Catalytic Amount ◽

Adenosine Diphosphate ◽

Inhibitory Effect ◽

Docking Studies ◽

Antiplatelet Activity ◽

Toxicity Assay ◽

Phenyl Hydrazine ◽

Design Synthesis ◽

Induced Aggregation

Abstract In view of proven antiplatelet activity of hydrazone group containing compounds, two series of hydrazone derivatives were synthesized by coupling appropriate aldehydes with phenyl hydrazine and Isonicotinic acid in the presence of distilled water and a catalytic amount of glacial acetic acid. All synthesized compounds were screened for their antiplatelet activity against induced aggregation by adenosine diphosphate (ADP) and arachidonic acid (AA). The results indicate that compounds in arylhydrazone group had shown satisfactory activity. Among them, 1-(3-methoxybenzylidene)-2-phenylhydrazine (1c), 2-methoxy-4-(2-phenylhydrazono) methyl phenol (1g), and 2-((2-phenylhydrazono) methyl)-1H-pyrrole (1h) were found to be the most potent antiplatelet compounds with IC50 less than 39 μM. Furthermore, the cell toxicity assay, (MTT test) indicates their noncytotoxic in various cell lines. None of the synthesized N-isonicotinohydrazide derivatives in this study excreted sufficient antiplatelet activity.

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Intracranial haemorrhage in patients with atrial fibrillation on anticoagulants

ESC CardioMed ◽

10.1093/med/9780198784906.003.0233 ◽

2018 ◽

pp. 976-978

Author(s):

Heinrich Mattle ◽

Marcel Arnold ◽

Urs Fischer

Keyword(s):

Risk Factors ◽

Intracranial Haemorrhage ◽

Early Recognition ◽

Vitamin K Antagonists ◽

Factor Xa ◽

Bleeding Risk ◽

Risk Of Bleeding ◽

Anticoagulation Treatment ◽

Life Saving

Anticoagulants increase the risk of bleeding. Rarely, they become devastating instead of preventing thrombosis and embolism. Intracranial haemorrhagic complications in particular can be disabling or fatal. Careful monitoring of anticoagulation and treatment of risk factors are important to reduce the bleeding risk and, if haemorrhage occurs nonetheless, early recognition and management can be life-saving and reduce long-term sequelae. Controlling the intensity of anticoagulation, treatment of hypertension, avoiding concomitant use of other antithrombotic drugs, and observing drug–drug interactions minimize the bleeding risk of anticoagulants. In case of anticoagulation-related intracranial haemorrhage, immediate normalization of coagulation is the cornerstone of treatment in addition to general measures. Prothrombin complex concentrate serves as the best antidote against vitamin K antagonists, idarucizumab to reverse the effect of dabigatran, and andexanet alfa to antagonize the inhibition of factor Xa.

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