Activation of human prothrombin by highly purified human factors V and X-a in presence of human antithrombin

Clinical, Laboratory, Molecular, and Reproductive Aspects of Combined Deficiency of Factors V and VIII

Congenital combined deficiency of factor V (FV) and factor VIII (FVIII; F5F8D, OMIM 227300) is a rare hereditary coagulopathy and accounts for approximately 3% of cases of rare coagulation disorders. The prevalence of this disease in the general population is estimated to be 1:1,000,000 and is significantly higher in regions where consanguineous marriages are permitted, such as the Mideast and South Asia. The disease has an autosomal recessive mode of inheritance and therefore occurs with an equal incidence among males and females. Heterozygous mutation carriers usually do not have clinical manifestations. The molecular basis of this disease differs from that of stand-alone congenital deficiencies of FVIII and FV. F5F8D is caused by mutations in either LMAN1 or MCFD2, which encode components of a cargo receptor complex for endoplasmic reticulum to Golgi transport of FV and FVIII, leading to defects in an intracellular transport pathway shared by these two coagulation factors. Congenital combined deficiency of FV and FVIII is characterized by decreased activities of both FV and FVIII in plasma, usually to 5 to 30% of normal. Clinical manifestations in most cases are represented by mild or moderate hemorrhagic syndrome. The simultaneous decreases of two coagulation factors present complications in the diagnosis and management of the disease. In female patients, the disease requires a special approach for family planning, pregnancy management, and parturition. This review summarizes recent progress in clinical, laboratory, and molecular understanding of this disorder.

Novel 2-aminobenzamides as potential orally active antithrombotic agents

In an effort to develop potent antithrombotic agents, a series of novel 2-aminobenzamide derivatives were synthesized and screened for their in vivo antithrombotic activity. Among the 23 compounds tested, compound (8g) showed the most promising antithrombotic activity, which was comparable with clinically used aspirin or warfarin, but at variance with these standard drugs, 8g did not exhibit the increased bleeding time, suggesting its potential as a novel antithrombotic agent.

Synthesis and Evaluation of 1-Arylsulfonyl-3-piperazinone Derivatives as Factor Xa Inhibitors VI. A Series of New Derivatives Containing N,S- and N,SO2-Spiro Acetal Scaffolds

In the course of development of factor Xa (FXa) inhibitors, we have found unique compounds containing an N,O- and an N,N-spiro acetal structure. It appeared that the difference in overall conformation due to the N,X-spiro acetal structure might be important for FXa inhibitory activity. Therefore, other N,X-spiro acetal structures, an N,S- and an N,SO2-spiro acetal, were developed as analogues of the N,X-spiro acetal structure. Compound 7b (N,S-spiro acetal structure) was found to have the strongest activity in these series of N,X-spiro acetal compounds, which had ever been synthesized.(4,5)).

Synthesis and Evaluation of 1-Arylsulfonyl-3-piperazinone Derivatives as Factor Xa Inhibitors V. A Series of New Derivatives Containing a Spiro[imidazo[1,2-a]pyrazine-2(3H),4'-piperidin]-5(1H)-one Scaffold

We have already reported unique compounds containing a N,O-spiro acetal structure as an orally active factor Xa (FXa) inhibitor. This time, we described a N,N-spiro acetal structure as an analogue of the N,O-spiro acetal structure for an orally active FXa inhibitor. The synthesis of these analogues could be achieved in a similar fashion to the N,O-spiro acetal synthesis. Consequently, FXa inhibitory activity was increased and more active compounds could be found (M58163: IC50 = 0.61 nM, M58169: IC50 = 0.58 nM). Additionally, the absolute configuration could be determined by X-ray crystallography analysis (M58169: (R)-config.).

Synthesis and biological activity of novel 1,2-disubstituted benzene derivatives as factor Xa inhibitors

Factor Xa (fXa) is a serine protease that plays a pivotal role in the coagulation cascade. High-throughput screening of the Yamanouchi compound library yielded lead compound 1 with the ability to inhibit fXa at micromolar concentrations. To improve its fXa inhibitory activity and its oral anticoagulant activity, the linker between benzamidine and the central benzene ring was modified and a carboxyl group was introduced at the central benzene ring. The resulting compounds 40b (YM-203552), 41a (YM-202054), and 41c (YM-203558) exhibited potent fXa inhibitory activity and oral anticoagulant activity. In particular, YM-203558 exhibited the most potent oral anticoagulant activity, prolonging PT more than 3-fold at 0.5 and 2.0 h. Additionally, these compounds showed a high degree of selectivity for other serine proteases.

Synthesis and biological activity of novel 1,4-diazepane derivatives as factor Xa inhibitor with potent anticoagulant and antithrombotic activity

Factor Xa (fXa) is a serine protease involved in the coagulation cascade, which has received great interest as a potential target for the development of new antithrombotic drugs. Herein we report a novel series of fXa inhibitors in which the 1,4-diazepane moiety was designed to interact with the S4 aryl-binding domain of the fXa active site. Compound 13 (YM-96765) showed potent fXa inhibitory activity (IC(50) = 6.8 nM) and effective antithrombotic activity without prolonging bleeding time.

Synthesis and Evaluation of 1-Arylsulfonyl-3-piperazinone Derivatives as Factor Xa Inhibitors IV. A Series of New Derivatives Containing a Spiro[5H-oxazolo[3,2-a]pyrazine-2(3H),4'-piperidin]-5-one Skeleton

In the course of development of factor Xa (FXa) inhibitor in an investigation involving the synthesis of 1-arylsulfonyl-3-piperazinone derivatives, we found new compounds containing a unique spiro skeleton. Among such compounds, (-)-7-[(6-chloro-2-naphthalenyl)sulfonyl]tetrahydro-8a-(methoxymethyl)-1'-(4-pyridinyl)-spiro[5H-oxazolo[3,2-a]pyrazine-2(3H),4'-piperidin]-5-one (28, M55529) had activity more favorable than those of previously reported compounds. The inhibitory activity of M55529 for FXa is IC(50)=2 nM, with high selectivity for FXa over thrombin and trypsin.

Synthesis and Evaluation of 1-Arylsulfonyl-3-piperazinone Derivatives as Factor Xa Inhibitors III. Effect of Ring Opening of Piperazinone Moiety on Inhibition

Compounds containing an ethylenediamine structure in place of the piperazine ring of M55113 (1) and M55551 (2) were synthesized to investigate the effects of a piperazine moiety and evaluated for activity as factor Xa (FXa) inhibitors. Most such compounds, however, exhibited lower activity (1/10-1/100) than that of M55113 and M55551 as FXa inhibitors.

Discovery of 3-amino-4-chlorophenyl P1 as a novel and potent benzamidine mimic via solid-phase synthesis of an isoxazoline library

In an effort to identify orally bioavailable factor Xa inhibitors, two isoxazolines libraries were prepared to scan for novel P1 ligands. From this work, 4-chloro-3-aniline was identified as a novel and potent benzamidine mimic.

Disseminated intravascular coagulation current concepts of etiology, pathophysiology, diagnosis, and treatment

The pathophysiologic mechanisms and clinical and laboratory manifestations of DIC are complex, partly because of inter-relationships within the hemostasis system. Only by clearly understanding these extraordinarily complex pathophysiologic inter-relationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often-confusing clinical and laboratory findings in patients with DIC. Many therapeutic decisions to be made are controversial and lack validation. Nevertheless, newer antithrombotic agents and agents that can block, blunt, or modify cytokine activity and the activity of vasoactive substances seem to be of value. The complexity and variable degree of clinical expression suggest that therapy should be individualized depending on the nature of DIC, the patient's age, etiology of DIC, site and severity of hemorrhage or thrombosis, and hemodynamics and other appropriate clinical parameters.

Synthesis and evaluation of 1-arylsulfonyl-3-piperazinone derivatives as a factor Xa inhibitor II. Substituent effect on biological activities

Intravascular clot formation is an important event in a number of cardiovascular diseases. The prevention of blood coagulation has become a major target for new therapeutic agents. Factor Xa (FXa) is a trypsin-like serine protease that plays a key role in the blood coagulation cascade and represents an attractive target for anticoagulant drug development. We have investigated substituents in the central part of a lead compound (3: M55113), and discovered that compound M55551 (34: (R)-4-[(6-Chloro-2-naphthalenyl)sulfonyl]-6-oxo-1-[[1-(4-pyridinyl)-4-piperidinyl]methyl]-2-piperazinecarboxylic acid) is a potent inhibitor of FXa (IC(50)=0.006 microM), with high selectivity for FXa over trypsin and thrombin. The activity of this compound is ten times more powerful than the lead compound.

Disseminated intravascular coagulation: a review of etiology, pathophysiology, diagnosis, and management: guidelines for care

The pathophysiologic mechanisms, clinical, and laboratory manifestations of DIC are complex in part due to interrelationships within the hemostasis system. Only by clearly understanding these extraordinarily complex pathophysiologic interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Many therapeutic decisions to be made are controversial and lack validation. Nevertheless, newer antithrombotic agents, and agents that can block, blunt, or modify cytokine activity and the activity of vasoactive substances appear to be of value. The complexity and variable degree of clinical expression suggests that therapy should be individualized depending on the nature of DIC, age, etiology of DIC, site and severity of hemorrhage or thrombosis and hemodynamics and other appropriate clinical parameters. At present, treatment of the triggering event, low-dose heparin or antithrombin concentrate and wise choice of components when indicated appear to be the most effective modes of therapy.

Syndromes of disseminated intravascular coagulation in obstetrics, pregnancy, and gynecology. Objective criteria for diagnosis and management

This article presents current understanding of the causes, pathophysiology, clinical, and laboratory diagnosis, and management of fulminant and low-grade DIC, as they apply to obstetric, pregnant, and gynecologic patients. General medical complications leading to DIC, which may often be seen in these patients, are also discussed. Considerable attention has been given to interrelationships within the hemostasis system. Only by clearly understanding these pathophysiologic interrelationships can the obstetrician/gynecologist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. Objective clinical and laboratory criteria for diagnosis of DIC have been outlined to eliminate unnecessary confusion and the need to make empiric decisions regarding the diagnosis. Particularly in the obstetric patient, if a condition is observed that is associated with DIC, or if any suspicion of DIC arises from either clinical or laboratory findings, it is imperative to monitor the patient carefully with clinical and laboratory tools to assess any progression to a catastrophic event. In most instances of DIC in obstetric patients, the disease can be ameliorated easily at early stages. Many therapeutic decisions are straightforward, particularly in obstetric and gynecologic patients. For more serious and complicated cases of DIC in these patients, however, efficacy and choices of therapy will remain unclear until more information is published regarding response rates and survival patterns. Also, therapy must be highly individualized according to the nature of DIC, patient's age, origin of DIC, site and severity of hemorrhage or thrombosis, and hemodynamic and other clinical parameters. Finally, many syndromes that are often categorized as organ-specific disorders and are sometimes identified as independent disease entities, such as AFE syndrome, HELLP syndrome, adult shock lung syndrome, eclampsia, and many others, either share common pathophysiology with DIC or are simply a form of DIC. These entities represent the varied modes of clinical expression of DIC and illustrate the diverse clinical and anatomic manifestations of this syndrome.

Comparison of the anticoagulant and antithrombotic effects of YM-75466, a novel orally-active factor Xa inhibitor, and warfarin in mice

The anticoagulant and antithrombotic effects of YM-75466 (N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-naph thyl)methyl]sulfamoyl acetic acid monomethanesulfonate), a novel orally-active factor Xa (FXa) inhibitor, and warfarin were compared in mice. Both agents were orally administered in all studies. In ex vivo studies, the peak effects of YM-75466 occurred 1 hr after administration while the peak of warfarin activity occurred 18 hr after administration. At each peak, both YM-75466 and warfarin prolonged coagulation time dose-dependently. The dose response curve of warfarin for prothrombin time was steeper than that of YM-75466. In a thromboplastin-induced thromboembolism model, administration of 30 mg/kg YM-75466 or 3 mg/kg warfarin significantly improved the lethality ratio. In blood loss studies, YM-75466 did not increase blood loss from the tail even at 30 mg/kg, while warfarin markedly increased blood loss at 3 mg/kg. Agents that interfere with warfarin action did not interfere with YM-75466 action. In conclusion, this study shows that YM-75466 has advantages over warfarin: i) rapid onset of anticoagulant activity, ii) wide therapeutic range, iii) little effect on bleeding and iv) lack of drug interaction with agents that interfere with warfarin. These results suggest that YM-75466 may be promising as a novel oral anticoagulant agent.

Antithrombotic effect of YM-75466 is separated from its effect on bleeding time and coagulation time

The antithrombotic effects of YM-75466 ([N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-nap hthyl)methyl]sulfamoyl]acetic acid monomethane sulfonate), a novel orally-active factor Xa inhibitor, and its effects on bleeding time and coagulation time were studied in rats and compared with those of warfarin. Both agents were orally administered. In the venous thrombosis model, YM-75466 and warfarin inhibited thrombus formation dose-dependently, with ID50 values of 3.3 and 0.56 mg/kg, respectively. Ex vivo study showed that both YM-75466 and warfarin prolonged prothrombin time dose-dependently, with doses, causing a two-fold prolongation of prothrombin time in the control group, of 89 and 0.38 mg/kg, respectively. In bleeding time studies, YM-75466 and warfarin prolonged bleeding time dose-dependently, with doses, causing a two-fold prolongation of bleeding time in the control group, of > 100 and 0.43 mg/kg, respectively. These results show that the antithrombotic effects of YM-75466 are markedly separate from its effects on bleeding time and coagulation time compared with warfarin.

Antithrombotic effects of YM-60828 in three thrombosis models in guinea pigs

The antithrombotic effects of a novel factor Xa inhibitor, YM-60828 ([N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-nap hthyl)methyl]sulfamoyl]acetic acid dihydrochloride), in three thrombosis models in guinea pigs were studied in comparison with its effect on bleeding time. The antithrombotic effects of YM-60828 were most pronounced in the venous thrombosis and the arterio-venous shunt models but YM-60828 showed 10-fold weaker effects in the carotid thrombosis model. However, YM-60828 prolonged bleeding time at a much higher dose than that required in all thrombosis models. In conclusion, YM-60828 exerted its antithrombotic effects without prolonging bleeding time in all thrombosis models and may be of clinical value not only in venous thrombosis but also in arterial thrombosis.

Relationship between the antithrombotic effect of YM-75466, a novel factor Xa inhibitor, and coagulation parameters in rats

The relationship between the antithrombotic effects of intravenous infusions of YM-75466 [N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-naph thyl)methyl] sulfamoyl]acetic acid monomethanesulfonate), a novel factor Xa (FXa) inhibitor, and various coagulation parameters (prothrombin time, activated partial thromboplastin time, thrombin-antithrombin III complex (TAT), anti-FXa activity and anti-thrombin activity) in rats was studied and compared with results for heparin. In the arterio-venous shunt model, both agents exerted antithrombotic effects in a dose-dependent manner. Coagulation parameters were studied simultaneously with antithrombotic effects. YM-75466 did not prolong coagulation time even at the dose which exerted significant antithrombotic effects, while it decreased TAT level in plasma in a dose-dependent manner. YM-75466 exerted anti-FXa activity but not anti-thrombin activity. In contrast, heparin prolonged activated partial thromboplastin time in a dose-dependent manner and decreased TAT level in plasma with increasing inhibition of thrombus formation. Heparin exerted both anti-FXa and anti-thrombin activity in a dose-dependent manner. These results suggest that TAT is a suitable parameter for monitoring the antithrombotic effect of YM-75466 in the arterio-venous shunt model in rats and that YM-75466, unlike heparin, exerts its antithrombotic effect through specific inhibition of FXa without any effect on thrombin.

Antithrombotic effects of YM-60828, a newly synthesized factor Xa inhibitor, in rat thrombosis models and its effects on bleeding time

1. The effects of YM-60828, a newly synthesized factor Xa inhibitor, were investigated to analyse the relationship between its antithrombotic effects and its prolongation of template bleeding time in rats. YM-60828 was compared with argatroban, heparin and dalteparin. All agents were intravenously administered as a bolus. 2. In ex vivo studies, YM-60828 and argatroban prolonged both prothrombin time and activated partial thromboplastin time in a dose-dependent manner, while heparin and dalteparin prolonged only activated partial thromboplastin time. 3. In a venous thrombosis model, all agents exerted antithrombotic effects in a dose-dependent manner. The ID50 values of YM-60828, argatroban, heparin and dalteparin were 0.0081 mg kg(-1), 0.011 mg kg(-1), 6.3 iu kg(-1) and 4.7 iu kg(-1), respectively. 4. In an arterio-venous shunt model, all agents exerted antithrombotic effects in a dose-dependent manner. The ID50 values of YM-60828, argatroban, heparin and dalteparin were 0.010 mg kg(-1), 0.011 mg kg(-1), 10 iu kg(-1) and 4.2 iu kg(-1), respectively. 5. In bleeding time studies, all agents prolonged template bleeding time in a dose-dependent manner. ED2 values, the doses causing a 2 fold prolongation of bleeding time in the saline group, of YM-60828, argatroban, heparin and dalteparin were 0.76 mg kg(-1), 0.081 mg kg(-1), 18 iu kg(-1) and 25 iu kg(-1), respectively. 6. The ratio (ED2/ID50) of YM-60828 was more than 30 fold greater than that of heparin and more than 10 fold greater than those of argatroban and dalteparin. 7. These data show that YM-60828 can exert its antithrombotic effects with little prolongation of bleeding time compared with the other currently used anticoagulant agents.

YM-60828, a novel factor Xa inhibitor: separation of its antithrombotic effects from its prolongation of bleeding time

The antithrombotic effects of intravenous infusions of YM-60828 ([N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-nap hthyl)methyl]sulfamoyl]acetic acid dihydrochloride), a novel factor Xa inhibitor, argatroban, heparin and dalteparin in an arterio-venous shunt model were studied in comparison with their effects on template bleeding time. In an arterio-venous shunt model, all agents exerted antithrombotic effects in a dose-dependent manner. ID50 values of YM-60828, argatroban, heparin and dalteparin were 0.0087 mg/kg/h. 0.027 mg/kg/h, 22 IU/kg/h and 11 IU/kg/h, respectively. In bleeding time studies, all agents prolonged bleeding time in a dose-dependent manner. Doses (ED2) of YM-60828, argatroban, heparin and dalteparin, which caused 2-fold prolongation of bleeding time in the saline group, were 3.0 mg/kg/h, 0.25 mg/kg/h, 18 IU/kg/h and 26 IU/kg/h. respectively. The risk-benefit ratio (ED2/ID50) of YM-60828 was much greater than that of the other agents. These data suggest that the antithrombotic effect of YM-60828 is separate from its prolongation of bleeding time and that YM-60828 is much safer than conventional anticoagulant agents.

Congenital factor VII deficiency presenting as delayed bleeding following dental extraction. A review of the role of factor VII in coagulation

Recent updated models of the coagulation mechanism suggest that factor VII/thromboplastin complex is the main initiator or trigger of coagulation. Factor VII activation of factor IX is likely to be an important activation pathway. Inhibition of factor VII by tissue factor pathway inhibitor may have a regulatory role in the initiation of coagulation. Defining factor VII's interactions in coagulation physiology may lead to answers for some clinical problems in both hemostasis and thrombosis. We describe a 15-year-old Chinese boy with factor VII deficiency and a factor VII level of 0.08 U/ml. His symptoms were recurrent epistaxis and moderate delayed bleeding post-dental extraction. Such specific symptoms have been reported previously in a study of 40 European patients. It is one diagnosis to consider if a patients main symptom is significant post-dental bleeding. It is possible that there is requirement for higher levels of factor VII at these anatomical sites making them the common sites for symptoms in patients with moderate deficiency. Case reports of rare clotting factor deficiencies will illustrate what may be important in vitro functions of clotting proteins. Therefore reporting should be encouraged, especially during review and reconsideration of models of the coagulation mechanism.

Purification and characterization of a variant of human prothrombin: prothrombin Segovia

A dysprothrombin designated prothrombin Segovia was isolated from the plasma of an individual with normal prothrombin antigen and prothrombin activity lesser than 25% of the control prothrombin activity. Activation by prothrombinase complex showed a lower amidolytic than clotting activity, which suggests a lesser generation of active intermediates than normal prothrombin. When prothrombin Segovia was activated by prothrombinase complex in the absence of factor Va, no thrombin formation was found by functional activities. SDS-PAGE analysis of the molecules derived by activation with prothrombinase complex, Taipan snake venom and Echis carinatus venom showed an accumulation of molecules not cleaved at bond Arg320-Ile321. This was more evident with Echis carinatus venom, which only acts on this bond. Our data suggest that the alteration of prothrombin Segovia impairs the scission of bond Arg320-Ile321.

Disseminated intravascular coagulation. Objective criteria for diagnosis and management

Current concepts of the cause, pathophysiology, clinical and laboratory diagnosis, and management of fulminant and low-grade DIC have been presented. Considerable attention has been devoted to interrelationships within the hemostasis system. Only by clearly understanding these pathophysiological interrelationships can the clinician and laboratory scientist appreciate the divergent and wide spectrum of often confusing clinical and laboratory findings in patients with DIC. In this discussion, objective clinical and laboratory criteria for a diagnosis of DIC have been delineated, thus eradicating unnecessary confusion and empirical decisions regarding the diagnosis. Many therapeutic decisions to be made are controversial and will remain so until more is published about specific therapeutic modalities and survival patterns. Also, therapy must be highly individualized depending on the nature of DIC, age, cause of DIC, site and severity of hemorrhage or thrombosis, and hemodynamic and other clinical parameters. Also presented are clear criteria for severity of DIC and objective criteria for defining a response to therapy. Also, because it is often difficult for the individual physician to decide when to stop often extensive therapy, objective criteria whereby therapy may be stopped, as continuation is likely fruitless, have been presented as a guideline. Lastly, it should be appreciated that many syndromes that are often organ specific share common pathophysiology with DIC but are typically identified as an independent disease entity, such as hemolytic uremic syndrome, adult shock lung syndrome, eclampsia, and many other isolated organ-specific disorders.

Rapid purification of factor IX, factor X and prothrombin by immunoaffinity and ion exchange chromatography

This study describes a rapid purification of factor IX, factor X and prothrombin by immunoaffinity and ion exchange chromatography. Human factor IX was purified from plasma in 34% yield using barium sulfate adsorption and immunoaffinity purification. The specific clotting activity of purified factor IX was 269 units/mg, with an apparent molecular weight of 57,000 in the presence of sodium dodecyl sulfate on polyacrylamide gels. The immunodepleted, factor-IX deficient plasma was chromatographed on a dextran sulfate agarose column which resolved prothrombin and factor X in highly purified states and with approximately 50% yield. The specific activities of prothrombin and factor X obtained by this procedure were 24 units/mg and 147 units/mg respectively. Both proteins isolated by this method showed a single component on SDS gel electrophoresis and the molecular weights of intact prothrombin and factor X were 72,000 and 67,000 respectively.

Conformational changes in human prothrombin as detected by antibody populations

The amino-terminal peptides of human prothrombin corresponding to residues 1-51 and 52-156 have been isolated from a thrombin digest of prothrombin fragment 1. The products of digestion were purified by means of barium citrate and ammonium sulfate precipitations, followed by gel filtration and hydroxyapatite chromatographies. They were identified by their molecular sizes as well as their amino acid compositions. Peptides 1-51 (F1A) and 52-156 (F1B) were used as affinity ligands for the isolation of antibody populations from antisera that were elicited against human prothrombin or prothrombin fragment 1. These antibody populations displayed restricted specificity for the respective ligands as shown by competitive radioimmunoassays. They were used to study the conformational changes in prothrombin and fragment 1. The F1A-specific antibody populations detected a conformational change which is stabilized by calcium ions and which has a transition midpoint at approximately 0.2 mM calcium ion concentration. The F1B-specific antibody populations identified a different conformational change which is destabilized by calcium ions and which has a transition midpoint at approximately 0.5 mM calcium.

Antiproliferative effects of heparin on vascular smooth muscle cells are reversed by epidermal growth factor

Heparin and related glycosaminoglycans are potent inhibitors of both in vivo and in vitro smooth muscle cell (SMC) proliferation. We have found that epidermal growth factor (EGF) reverses the antiproliferative effects of heparin. Other known SMC mitogens, including platelet-derived growth factor (PDGF), insulin-like growth factor-1 (IGF-1), and thrombin, were unable to prevent heparin action. The EGF specificity was further demonstrated by developing a biological growth assay in which EGF or PDGF, at concentrations as low as 1 ng/ml, stimulated SMC growth in the absence of other serum components. Under these conditions, EGF, but not PDGF, suppressed heparin inhibition as well. The ability of EGF to reverse heparin inhibition was only observed when mitogen and glycosaminoglycan were added to SMC at similar times. If SMC were pretreated with heparin for 48 hours prior to EGF addition, the protective effects of EGF were lost. Heparin did not directly prevent 125I-EGF or platelet-derived EGF-like peptides from binding to the EGF receptor on SMC. However, cultures that were pretreated with heparin for 48 hours bound 49% less 125I-EGF than cultures that had been pretreated with the mucopolysaccharide for only 2 hours or that had not been preexposed to heparin. In previous studies, we have established that heparin exerts its maximal inhibitory activity after a 48-hour treatment of SMC (Reilly et al. 1986). Taken together, these data suggest that heparin may exert its antiproliferative potential by slowly and specifically altering SMC response to EGF-like mitogens of platelet origin.

Human factor VIII: purification from commercial factor VIII concentrate, characterization, identification and radiolabeling

Human factor VIII was purified from commercial factor VIII concentrate with a 12% yield. The specific coagulant activity of purified factor VIII was 8,000 units/mg. In the presence of SDS the purified factor VIII consisted of a variety of polypeptides on polyacrylamide gels, ranging between Mr 80,000 and Mr 208,000. In the absence of SDS the purified factor VIII showed an apparent molecular weight of 270,000 upon Sephadex G200 gel-filtration. The purified factor VIII could be activated by thrombin, which resulted in the disappearance of Mr 108,000-208,000 polypeptides in favor of an Mr 92,000 polypeptide. Treatment with factor Xa also activated factor VIII, whereas treatment with activated protein C resulted in the inactivation of coagulant activity. Coagulant-active 125I-factor VIII was prepared using a lactoperoxidase radioiodination procedure. This 125I-factor had the same characteristics as unlabeled factor VIII. All polypeptides could be precipitated with monoclonal antibodies directed against factor VIII. With 125I-factor VIII a pIapp of 5.7 was found in the presence of urea.

Anticoagulantly active heparin-like molecules from cultured fibroblasts

Heparin-like molecules, isolated from cultured rat and human skin fibroblasts, accelerated the inactivation of purified human thrombin via purified human antithrombin. Only 15% of the biologic activity of the complex carbohydrates derived from human skin fibroblasts was expressed when the heparin-binding domain an antithrombin was chemically modified at the Trp 49 residue. Human skin fibroblasts were metabolically labeled with [35S]Na2SO4, and radiolabeled heparin-like molecules were isolated utilizing ion-exchange chromatography and fractionated into two separate populations employing immobilized antithrombin. The species which bound with high avidity to the affinity matrix represented about 12% of the radiolabeled heparin-like molecules, accounted for almost 95% of the initial anticoagulant activity, and exhibited a specific activity of 3.98 USP units/10(6) 35S-cpm.

Anticoagulantly active heparin from clam (Mercenaria mercenaria)

Heparin was isolated from Mercenaria mercenaria by ion-exchange chromatography and was fractionated into two distinct populations with immobilized antithrombin. The high-affinity glycosaminoglycan accelerated dramatically the inhibition of purified human factors IIa and Xa via purified human antithrombin. Specific anti-factor IIa and anti-factor Xa activities were 363 and 348 U.S.P. units/mg, respectively. The highly active clam heparin exhibited a molecular weight of approximately 18,000 and contained approximately 2.5 sulfate groups per disaccharide. The intrinsic fluorescence of purified human antithrombin was enhanced in the presence of the high-affinity invertebrate glycosaminoglycan to an extent comparable to the level induced by vertebrate heparin. In addition, the critical tetrasaccharides containing 3-O-sulfated glucosamine residues, which constitute part of the unique antithrombin-binding domain of mammalian heparin, were also detected in high-affinity Mercenaria heparin.

Heparinlike molecules with anticoagulant activity are synthesized by cultured endothelial cells

Cultured microvascular endothelial cells isolated from rat epididymal fat pads produce glycosaminoglycans that accelerate thrombin-antithrombin complex formation. The heparinlike nature of these macromolecules was established by complete destruction of their anticoagulant activity employing purified Flavobacterium heparinase. Only 15% of the biologic activity of these complex carbohydrates was expressed when the heparin binding domain on the protease inhibitor was chemically modified at the Trp 49 residue. The anticoagulantly active species contains disaccharides which constitute the unique antithrombin binding region of the mucopolysaccharide. Removal of the biologically active heparinlike components from endothelial cells with 0.05% trypsin suggests that these molecular species are present on the cell surface.