Human recombinant non pancreatic secreted platelet phospholipase A2 has anticoagulant activity in vitro on human plasma

Abstract Apixaban, previously known as BMS-562247, is a high affinity, highly selective, orally-active, reversible inhibitor of coagulation factor Xa (fXa), in clinical studies as a therapeutic agent for prevention and treatment of thromboembolic diseases. The in vitro characteristics of apixaban were evaluated in purified systems and in human blood from healthy volunteers. Detailed kinetic analysis of apixaban inhibition of human fXa showed that it is a readily reversible, potent and competitive inhibitor versus a synthetic tripeptide substrate with a Ki of 0.08 nM, an association rate of 2 × 107 M−1s−1and a dissociation half life of 3.4 min. Weak affinity (Ki ~3 μM) is observed for thrombin, plasma kallikrein, and chymotrypsin. Affinity for trypsin and all other serine proteases tested is negligible with Ki > 15 μM. Apixaban is an effective inhibitor of free fXa and of prothrombinase, in buffer, platelet poor plasma, and whole blood. The anticoagulant activity of apixaban was determined in platelet-poor human plasma. Apixaban causes concentration dependent prolongation of the fXa mediated clotting assays. The human plasma concentration required to produce a doubling of the clotting time is 3.6 μM for prothrombin time, 7.4 μM for activated partial thromboplastin time and 0.4 μM for HepTest. To support preclinical efficacy and safety studies purified fXa from rabbit, dog and rat plasma was also found to be inhibited by apixaban (0.17, 2.6, and 1.3 nM, respectively). In summary the in vitro properties of apixaban show that it is a highly selective and potentially potent antithrombotic agent for venous and arterial thrombotic diseases.

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The in Vitro Anticoagulant Activity of Human Plasma Lipids

Thrombosis and Haemostasis ◽

10.1055/s-0038-1656298 ◽

1965 ◽

Vol 13 (02) ◽

pp. 531-542

Author(s):

J Cohen ◽

C. F Reed ◽

S. B Troup

Keyword(s):

Human Plasma ◽

Inhibitory Activity ◽

Plasma Lipids ◽

Present Report ◽

Anticoagulant Activity ◽

Lipid Fraction ◽

Plasma Lipid ◽

Lipid Mixture ◽

Platelet Poor Plasma

SummaryThe present report describes the in vitro inhibition of prothrombin consumption by lipid extracted from normal human platelet-poor plasma. Pro-coagulant lipids and the test plasma lipids were dissolved in the same solvent and evaporated to dryness. The dried lipid mixture was emulsified in platelet-poor plasma, and the plasma clotted by recalcification. Inhibition of prothrombin consumption by plasma lipid was observed when the ratio of plasma lipid to procoagulant lipid equaled or exceeded 5:1. The inhibitory effect of plasma lipid on prothrombin consumption was not observed when procoagulant activity was provided by intact platelets or platelet granules.Human plasma lipids have been fractionated on silicic acid columns to permit identification of the plasma lipid component responsible for the inhibition of prothrombin consumption. The inhibitory activity is present in a lipid fraction which is 95% lecithin. Other plasma lipid components exhibit little or no inhibitory activity.

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THE EFFECT OF THE VENOM OF THE ORIENTAL HORNET ON COAGULATION FACTORS

10.1055/s-0038-1644338 ◽

1987 ◽

Author(s):

A Kornberg ◽

S Kaufman ◽

L Silber ◽

J Ishay

Keyword(s):

Human Plasma ◽

Degradation Products ◽

Anticoagulant Activity ◽

Coagulation Factors ◽

Plasma Fibrinogen ◽

Thrombin Time ◽

Clotting Factors ◽

Viii And Ix

The extract from the venom sac of Vespa orientalis (VSE) inactivates exogenous and endogenous thromboplastin (Joshua and Ishay, Toxicon, 13:11-20,1975). The prolongation of both prothrombin time (PT) and recalcification time suggests inactivation of other factors. The aim of the present study is to investigate the effect of VSE on clotting factors. A lyophilized VSE with protein concentration of 5 mg/ml was used. Studies were performed in vitro with human plasma and in vivo in cats. Routine methods were employed for the assay of PT, activated tissue thromboplastin (APTT), thrombin time (TT), fibrinogen degradation products (FDP), fibrinogen and factors V,VII,VIII,IX,X. Human plasma was incubated with various concentrations of VSE (0,1,5,10,50,100 μg/ml) for 60 min and for various incubation times (0,5,15,30,+ 60,90,120 min) with 50 μg/ml VSE (n=8). 1 μg/ml VSE prolonged PT from 13.5 to 16 sec (p<0.05) and APTT from 62 to 180 sec. PT was maximal (17.7 sec) with 10 μg/ml and APTT (442 sec) with 50 μg/ml VSE. Factors V,VII,X decreased gradually from 94-105% to 11%,11% and 29% with 100 μg/ml VSE and VIII and IX to 1% even with 1 μg/ml VSE. After 5 min with constant concentration of VSE (50 μg/ml) PT was 14.9 sec (normal 13 sec) and APTT 165 sec (normal 54 sec). Both were maximal (17.5 and 298 sec) after 60 min. Factors VII and X decreased to 13% and 32% and VIII and IX to >1% after 60 min of incubation. Injection of 5 mg/kg VSE to cats (n=6-8) resulted in prolongation of PT from 9.4 to 11.2 sec and of APTT from 19.5 to 63 sec after 5 min. Both were maximal after 90 min (12.3 and 127 sec). Factors V,VII and X decreased from 100% to 7.6%, 13% and 37% and VIII and IX to 1% after 10 min. In all experiments TT and plasma fibrinogen were not affected and FDP were normal. Heating of VSE for 5 min at 80°C abolished completely the anticoagulant activity but dialysis for 24 hr at 4°C had no effect on it. The activity was eluted on Sephadex-25 both in void and post void volumes. The results show that VSE has a potent anticoagulant activity against various factors. Factors VIII and IX are markedly decreased. The effect on V, VII and X is moderate. Plasma fibrinogen is not affected. The nature and clinical significance of the anticoagulant activity merit further investigation.

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Lipoprotein-Associated Phospholipase A2 Activity Is a Marker of Small, Dense LDL Particles in Human Plasma

Clinical Chemistry ◽

10.1373/clinchem.2005.058404 ◽

2005 ◽

Vol 51 (12) ◽

pp. 2264-2273 ◽

Cited By ~ 129

Author(s):

Irene Gazi ◽

Evangelia S Lourida ◽

Theodosios Filippatos ◽

Vasilis Tsimihodimos ◽

Moses Elisaf ◽

...

Keyword(s):

Phospholipase A2 ◽

Human Plasma ◽

Polyacrylamide Gel Electrophoresis ◽

Serum Triglyceride ◽

Total Plasma ◽

Pla2 Activity ◽

Ldl Particles ◽

Mass Proportion ◽

Ldl Subfractions

Abstract Background: Recent clinical studies showed that lipoprotein-associated phospholipase A2 (Lp-PLA2) is a predictor for incident atherosclerotic disease. We have previously shown that among the LDL subfractions, Lp-PLA2 activity is preferentially associated with the atherogenic small, dense (sdLDL) particles in vitro. We investigated whether Lp-PLA2 could be a marker of sdLDL in human plasma. Methods: One hundred and seventy-six individuals participated in the study. LDL subclass analysis was performed by polyacrylamide gel electrophoresis. Lp-PLA2 activity and mass were determined in total plasma and in apolipoprotein B-depleted plasma (HDL-Lp-PLA2). Non–HDL-Lp-PLA2 activity and mass were calculated by subtracting the HDL-Lp-PLA2 from total plasma Lp-PLA2. Results: On the basis of the LDL subclass analysis, participants were categorized into phenotype A and non-A (total cholesterol mass of the sdLDL subfractions ≤0.155 and >0.155 mmol/L, respectively). Unlike total plasma Lp-PLA2 mass, total plasma Lp-PLA2 activity and non–HDL-Lp-PLA2 activity and mass were significantly higher in persons with phenotype non-A compared with persons with phenotype A, whereas HDL-Lp-PLA2 activity and mass were lower in persons with phenotype non-A compared with phenotype A. Total plasma activity and non–HDL-Lp-PLA2 activity and mass, but not Lp-PLA2 mass, were correlated with sdLDL-cholesterol mass, proportion, and mean LDL particle size. In multiple regression analysis, total plasma and non–HDL-Lp-PLA2 activities were the second best predictors of the presence of sdLDL particles in human plasma after serum triglyceride concentrations. At serum triglyceride concentrations >1.356 mmol/L, total plasma and non–HDL-Lp-PLA2 activity added significantly to the prediction of the presence of sdLDL in plasma. Conclusions: Lp-PLA2 activity, but not the enzyme mass, is a marker of sdLDL in human plasma.

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Abstract 18218: In Vitro Characterization of Andexanet Alfa (PRT064445), a Specific fXa Inhibitor Antidote versus Aripazine (PER977), a Non-specific Reversal Agent

Circulation ◽

10.1161/circ.130.suppl_2.18218 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Genmin Lu ◽

Jayaprakash Kotha ◽

Juan M Cardenas ◽

Michael J Herr ◽

Anjali Pandey ◽

...

Keyword(s):

Human Plasma ◽

Anticoagulant Activity ◽

Procoagulant Activity ◽

Thrombin Inhibitors ◽

Molar Ratio ◽

Buffer System ◽

Reversal Agent ◽

Fxa Inhibitor ◽

Andexanet Alfa

New oral fXa inhibitors have been increasingly adopted for VTE or AF treatment in the outpatient setting instead of warfarin. Andexanet alfa (AnXa) is a modified, recombinant human fXa molecule developed as a specific antidote to reverse anticoagulant activity of fXa inhibitors during episodes of serious bleeding or before urgent surgery. PER977, a small molecule under development by Perosphere, Inc., is reported to reverse the effect of a broad range of anticoagulants (fXa and thrombin inhibitors, LMWH). In order to compare AnXa and PER977 mechanisms of action, we studied the in vitro activity of both agents in the presence or absence of fXa inhibitors rivaroxaban, apixaban, edoxaban or enoxaparin. In a buffer system containing purified human fXa with physiologic Ca 2+ (5 mM), AnXa dose-dependently reversed oral fXa inhibitor activity. Reversal activity was not observed for any fXa inhibitor with PER977 over a wide concentration range (≤2 mM). In human plasma, AnXa reversed both direct and ATIII-dependent fXa inhibitors, whereas no reversal effect by PER977 was detected. In the absence of a fXa inhibitor, PER977 potentiated fX activation by fIXa in a buffer system (purified human fX, fIXa and 5mM Ca 2+ ). Similar cofactor activity was observed with polylysine, indicating that PER977 may have properties similar to poly-cationic molecules. Procoagulant activity was observed in human plasma with PER977 at low concentrations (≤100 μM) as measured by clotting (aPTT) or thrombin generation, but inhibition in these assays was seen at higher concentrations ( ~1 mM). PER977 also potentiated human platelet activation as determined by P-selectin expression induced by 10 μM ADP. Platelet aggregation, whole blood hemolysis, or complement activation testing showed no effect with either AnXa or PER977. These data indicate that PER977 does not reverse the anticoagulant activity of a direct or indirect fXa inhibitor in vitro. Its observed in vivo effect on blood loss in animals may not be mediated by direct interaction of PER977 with the inhibitor, but may be in part attributed to an off-target effect, suggested by its potential procoagulant activity. In contrast, AnXa acts as a specific antidote to fXa inhibitors by sequestering them with a defined stoichiometry (1:1 molar ratio).

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Compound heterozygous protein C deficiency resulting in the presence of only the beta-form of protein C in plasma

Blood ◽

10.1182/blood.v88.6.2101.bloodjournal8862101 ◽

1996 ◽

Vol 88 (6) ◽

pp. 2101-2108 ◽

Cited By ~ 13

Author(s):

P Simioni ◽

M Kalafatis ◽

DS Millar ◽

SC Henderson ◽

S Luni ◽

...

Keyword(s):

Human Plasma ◽

Protein C ◽

Anticoagulant Activity ◽

Active Form ◽

Compound Heterozygous ◽

In Vitro Mutagenesis ◽

Protein C Deficiency ◽

Beta Form ◽

Factor Va

About 30% of human plasma protein C (PC) is of lower molecular weight than the predominant alpha-form. The minor beta-form arises as a consequence of the lack of glycosylation at Asn329. Although the functional role of Asn329 has been investigated by in vitro mutagenesis, until now no naturally occurring mutations have been reported at this site. We describe here the case of two identical twin sisters compound heterozygous for two novel PC mutations: Cys78-->Stop inherited from the maternal side and Asn329-->Thr inherited from the paternal side, associated with the presence of only the beta-form of PC in plasma. The Cys78-->Stop substitution is predicted to abolish PC synthesis from one allele, whereas the Asn329-->Thr substitution results in the reduced synthesis of a beta PC variant with decreased functional activity. PCN329T from the two monovular twin sisters was purified and its active form APCN329T was assessed for its ability to inactivate factor Va. Whereas no differences were observed between the activation rates of normal PC and PCN329T, APCN329T inactivated human factor Va with a rate slower than the normal APC. This is the first report of a PC defect involving glycosylation of the molecule. This defect results in the presence of only the beta-form of PC in human plasma and is responsible for the reduced anticoagulant activity observed.

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Dermatan Sulfate and LMW Heparin Enhance the Anticoagulant Action of Activated Protein C

Thrombosis and Haemostasis ◽

10.1055/s-0037-1614856 ◽

1999 ◽

Vol 82 (11) ◽

pp. 1462-1468 ◽

Cited By ~ 22

Author(s):

José Fernández ◽

Jari Petäjä ◽

John Griffin

Keyword(s):

Molecular Weight ◽

Unfractionated Heparin ◽

Protein C ◽

Dermatan Sulfate ◽

Anticoagulant Activity ◽

Activated Protein C ◽

Factor V ◽

Factor Va ◽

Anticoagulant Action

SummaryUnfractionated heparin potentiates the anticoagulant action of activated protein C (APC) through several mechanisms, including the recently described enhancement of proteolytic inactivation of factor V. Possible anticoagulant synergism between APC and physiologic glycosaminoglycans, pharmacologic low molecular weight heparins (LMWHs), and other heparin derivatives was studied. Dermatan sulfate showed potent APC-enhancing effect. Commercial LMWHs showed differing abilities to promote APC activity, and the molecular weight of LMWHs correlated with enhancement of APC activity. Degree of sulfation of the glycosaminoglycans influenced APC enhancement. However, because dextran sulfates did not potentiate APC action, the presence of sulfate groups per se on a polysaccharide is not sufficient for APC enhancement. As previously for unfractionated heparin, APC anticoagulant activity was enhanced by glycosaminoglycans when factor V but not factor Va was the substrate. Thus, dermatan sulfate and LMWHs exhibit APC enhancing activity in vitro that could be of physiologic and pharmacologic significance.

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Assays for Phospholipid-Dependent Formation of Thrombin and Xa: A Potential Method for Quantifying Lupus Anticoagulant Activity

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646437 ◽

1991 ◽

Vol 66 (04) ◽

pp. 453-458 ◽

Cited By ~ 15

Author(s):

John T Brandt

Keyword(s):

Specific Activity ◽

Anticoagulant Activity ◽

Factor Xa ◽

Clinical Importance ◽

Potential Method ◽

Quantitative Expression ◽

Increased Risk ◽

Apparent Association

SummaryLupus anticoagulants (LAs) are antibodies which interfere with phospholipid-dependent procoagulant reactions. Their clinical importance is due to their apparent association with an increased risk of thrombo-embolic disease. To date there have been few assays for quantifying the specific activity of these antibodies in vitro and this has hampered attempts to purify and characterize these antibodies. Methods for determining phospholipid-dependent generation of thrombin and factor Xa are described. Isolated IgG fractions from 7 of 9 patients with LAs were found to reproducibly inhibit enzyme generation in these assay systems, permitting quantitative expression of inhibitor activity. Different patterns of inhibitory activity, based on the relative inhibition of thrombin and factor Xa generation, were found, further substantiating the known heterogeneity of these antibodies. These systems may prove helpful in further purification and characterization of LAs.

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The Anticoagulant Properties of a Modified Form of Protein S

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647048 ◽

1988 ◽

Vol 60 (02) ◽

pp. 298-304 ◽

Cited By ~ 17

Author(s):

C A Mitchell ◽

S M Kelemen ◽

H H Salem

Keyword(s):

Monoclonal Antibody ◽

Anticoagulant Activity ◽

Activated Protein C ◽

Factor Xa ◽

Protein S ◽

Human Neutrophil Elastase ◽

Factor X ◽

Sds Page

SummaryProtein S (PS) is a vitamin K-dependent anticoagulant that acts as a cofactor to activated protein C (APC). To date PS has not been shown to possess anticoagulant activity in the absence of APC.In this study, we have developed monoclonal antibody to protein S and used to purify the protein to homogeneity from plasma. Affinity purified protein S (PSM), although identical to the conventionally purified protein as judged by SDS-PAGE, had significant anticoagulant activity in the absence of APC when measured in a factor Xa recalcification time. Using SDS-PAGE we have demonstrated that prothrombin cleavage by factor X awas inhibited in the presence of PSM. Kinetic analysis of the reaction revealed that PSM competitively inhibited factor X amediated cleavage of prothrombin. PS preincubated with the monoclonal antibody, acquired similar anticoagulant properties. These results suggest that the interaction of the monoclonal antibody with PS results in an alteration in the protein exposing sites that mediate the observed anticoagulant effect. Support that the protein was altered was derived from the observation that PSM was eight fold more sensitive to cleavage by thrombin and human neutrophil elastase than conventionally purified protein S.These observations suggest that PS can be modified in vitro to a protein with APC-independent anticoagulant activity and raise the possibility that a similar alteration could occur in vivo through the binding protein S to a cellular or plasma protein.

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Potentially Thrombogenic Materials in Factor IX Concentrates

Thrombosis and Haemostasis ◽

10.1055/s-0038-1647857 ◽

1975 ◽

Vol 33 (03) ◽

pp. 617-631 ◽

Cited By ~ 47

Author(s):

H. S Kingdon ◽

R. L Lundblad ◽

J. J Veltkamp ◽

D. L Aronson

Keyword(s):

Human Plasma ◽

Antithrombin Iii ◽

Factor Ix ◽

In Vitro Assays ◽

Substantial Agreement ◽

Coefficient Of Correlation

SummaryFactor IX concentrates manufactured from human plasma and intended for therapeutic infusion in man have been suspected for some time of being potentially thrombogenic. In the current studies, assays were carried out in vitro and in vivo for potentially thrombogenic materials. It was possible to rank the various materials tested according to the amount of thrombogenic material detected. For concentrates not containing heparin, there was substantial agreement between the in vivo and in vitro assays, with a coefficient of correlation of 0.77. There was no correlation between the assays for thrombogenicity and the antithrombin III content. We conclude that many presently available concentrates of Factor IX contain substantial amounts of potentially thrombogenic enzymes, and that this fact must be considered in arriving at the decision whether or not to use them therapeutically.

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