Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:4.2.2.7 (heparinase)
 1,270 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Basic fibroblast growth factor (bFGF) and its specific receptors have diverse roles on a variety of cell types, such as the induction of vascular smooth-muscle cell proliferation which contributes to restenosis after coronary balloon angioplasty. bFGF is also known to interact with heparan sulphate proteoglycans present on the cell surface or in the extracellular matrix. In this study, the binding of 125I-bFGF to human aortic smooth-muscle cells was investigated. 125I-bFGF binding to these cells was reversible and saturable. Scatchard analysis revealed the presence of two distinct binding sites: a high-affinity receptor (Kd=38+/-7 pM; 1480+/-220 sites/cell) and a low-affinity non-saturable binding site (Kd=8. 0+/-2.0 nM). Pretreatment of the cells with heparinase resulted in a large reduction of 125I-bFGF binding to its low-affinity receptors, suggesting that they are heparin-like molecules. The specificity of the low- and high-affinity binding sites for bFGF was determined with acidic FGF, platelet-derived growth factor-BB and epidermal growth factor, which did not compete for 125I-bFGF binding. Expression of FGF receptor isoforms analysed by reverse transcriptase-PCR revealed the presence of only the type-1 receptor. Binding to low-affinity binding sites was antagonized by heparin, suramin, protamine sulphate and platelet factor 4. Unexpectedly, these molecules also reduced the binding of 125I-bFGF to its high-affinity sites. Consistent with these results, heparin, suramin, protamine sulphate and platelet factor 4 inhibited bFGF-induced proliferation of human aortic smooth-muscle cells. Heparin abrogated bFGF-induced release of tissue-type plasminogen activator by these cells. These observations suggest that the interaction of bFGF with human aortic smooth-muscle cells is different from that described for other cells such as endothelial cells, in which heparin acts as a potentiating factor of the mitogenic activity of bFGF.
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PMID:Heparin inhibits the binding of basic fibroblast growth factor to cultured human aortic smooth-muscle cells. 930 14

Low molecular weight heparins (LMWHs) are obtained from unfractionated heparin by diverse chemical and enzymatic processes and findings with one LMWH cannot be extrapolated to another. Functional assays performed in vitro, evaluating antiprotease activity mediated via antithrombin III, heparin cofactor II interactions, antithrombin III binding, and plasma protein binding, showed wide variations between LMWHs, indicating that compositional differences among the LMWHs have a major impact on function. Evaluation in vitro showed varying potency in United States Pharmacopeia (USP) and anti-Xa assays. LMWHs tested at anti-Xa-adjusted concentrations exhibited varying potencies with anti-IIa, Heptest, and activated partial thromboplastin time (APTT) assays. Evaluation of these assays showed differences between LMWHs and a link with molecular weight. Each LMWH also varied in the in vitro neutralization by platelet factor 4, thrombin, and heparinase. LMWHs also varied in platelet interactions as assessed by whole blood clotting, thromboelastography and P-selectin expression, and in tissue factor pathway inhibitor release in cell culture. It was concluded that compositional variations in LMWHs give each product a unique biochemical profile. This profile, plus varying endogenous interactions and pharmacokinetic profiles may give rise to the clinical differences observed with LMWHs in specific indications.
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PMID:In vitro studies on the biochemistry and pharmacology of low molecular weight heparins. 1054 13

Heparin-induced thrombocytopenia represents one of the most severe drug-induced disorders of platelets. This syndrome is believed to be mediated through antibodies generated against a heparin-platelet factor 4 complex. Complexation of a sulfated mucopolysaccharide chain of heparin with a platelet granular protein (platelet factor 4) produces an allosteric modification of platelet factor 4 resulting in neoepitope formation and the generation of antiheparin-platelet factor 4 antibodies. These antibodies are capable of activating platelets by binding to heparin, platelet factor 4 and the Fc receptor on platelets, resulting in a complex pathophysiology involving ischemic, thrombotic, and inflammatory processes. To characterize this antibody, IgG fractions were obtained from the serum of patients with heparin-induced thrombocytopenia using ammonium sulphate precipitation and heparin-platelet factor 4-sepharose 4B affinity chromatography methods. With the affinity purification, two major components, peaks I and II, with high antiheparin-platelet factor 4 antibody titers were eluted. The purity of all the fractionated immunoglobulins was established by sodium dodecylsulphate-polyacrylamide gel electrophoretic analyses. While peak I did not induce 14C-serotonin release from platelets in the heparin-dependent assay for heparin-induced thrombocytopenia antibodies (14C-serotonin release assay), peak II and the IgGs obtained with the ammonium sulphate precipitation method exhibited a strong and concentration-dependent activation in the presence and absence of heparin and low molecular weight heparin. These immunoglobulins were treated with heparinase, a cationic ion-exchange resin (Heparsorb), or dialyzed to remove traces of heparin, and when tested in the 14C-serotonin release assay, showed the same high degree of activity. These data are suggestive of the generation of heparin-induced thrombocytopenia antibodies capable of activating platelets directly in a nonheparin-dependent manner. These observations underscore the complex pathophysiology of heparin-induced thrombocytopenia syndrome and suggest that the severity of this syndrome in some patients may be due to the generation of "super-active" heparin-induced thrombocytopenia antibodies capable of activating platelets without the requirement of heparin. This could explain why the cessation of heparin in patients does not necessarily correct the symptoms of heparin-induced thrombocytopenia or associated thrombosis.
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PMID:Functional heterogeneity of antiheparin-platelet factor 4 antibodies: implications in the pathogenesis of the HIT syndrome. 1072 34

Thromboelastography (TEG) has been used increasingly as an intraoperative hemostasis monitoring device. Low-molecular-weight heparins are given increasingly to reduce the development of antibodies against the heparin-platelet factor 4 complex, and heparinoids are given to patients who have developed the antibody. We studied the effect of unfractionated heparin, a low-molecular-weight heparin (enoxaparin sodium [Lovenox]), and a heparinoid (danaparoid sodium [Orgaran]) on blood clotting assayed with TEG (TEG clotting) in vitro and the efficacy of protamine sulfate and heparinase for reversing the effect. Heparin, enoxaparin, and danaparoid all caused a dose-dependent inhibition of TEG clotting of normal blood. Concentrations of enoxaparin and danaparoid that totally inhibited TEG clotting only minimally prolonged the activated partial thromboplastin time. While inhibition of TEG clotting by heparin and enoxaparin was reversed by protamine sulfate and heparinase, inhibition by danaparoid was reversed only by heparinase. Abnormal TEG clotting was observed in patients receiving enoxaparin whose plasma level of the drug was more than 0.1 antiXa U/mL. However, the degree of TEG abnormality did not always coincide with plasma levels of the drug.
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PMID:Effects of unfractionated heparin, low-molecular-weight heparin, and heparinoid on thromboelastographic assay of blood coagulation. 1080 Apr 6

Heparinomimetic mannopentaose phosphate sulfate (PI-88) (Progen Industries Ltd. Brisbane, Australia), currently developed as an anticoagulant and antiproliferative agent, mainly is composed of a pentomannan. However, tetrasaccharide and disaccharide components are also present. The molecular profile and the anticoagulant potency of PI-88 are investigated in this study. Gel permeation chromatography and polyacrylamide gel electrophoresis analyses were carried out to determine the molecular profile and separation of components of PI-88, respectively. Potentiation of antithrombin III (ATIII) and heparin cofactor-II (HC-II) activity were measured using chromogenic substrate assay. In order to determine anticoagulant and antiprotease effects of PI-88, various global anticoagulant tests, such as the prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), Hep-test (Haemachem Inc., St. Louis), ecarin clotting time (ECT), activated clotting time (ACT), and thromboelastography (TEG) were used. Anti-Xa and anti-IIa activities also were measured. The effect of PI-88 on the release of tissue factor pathway inhibitor (TFPI) was performed in nonhuman primates who received PI-88 and in endothelial cell culture systems. The relative susceptibility of PI-88 to heparinase I, protamine sulfate (PS), and platelet factor 4 (PF4) also was evaluated. The high-performance liquid chromatography profiles of PI-88 showed that its average molecular weight is approximately 2300 Da. Separation and gradient electrophoretic patterns of PI-88 showed that it is composed of five different fractions. This agent activates HC-II through inhibiting the thrombin generation but not inhibiting ATIII. Although PI-88 produced a concentration-dependent prolongation of all of the clotting tests, ECT gave the best correlation in the dose-response curve (ECT, r2 = 0.94; TT, r2 = 0.84; APTT, r2 = 0.69). Heparinomimetic mannopentaose phosphate sulfate (PI-88) exhibited marked inhibition of FIIa, but not of FXa. Heparinase I failed to produce significant neutralization of PI-88 in all the assays used, whereas PS and PF4 partially neutralized the effects of this compound. Heparinomimetic mannopentaose phosphate sulfate (PI-88) produced fivefold increase in the TFPI levels at 15 minutes after intravenous (IV) injection to primates. The incubation of PI-88 in endothelial cell culture system also showed a strong effect on TFPI release. These results suggest that PI-88 exhibited strong antithrombotic and anticoagulant activity in addition to its known antiproliferative properties. Because of the molecular characteristics and the dual nature of the pharmacologic action of PI-88, this agent represents an attractive pharmacologic agent for the control of thrombotic and proliferative disorders.
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PMID:Anticoagulant and antiprotease profiles of a novel natural heparinomimetic mannopentaose phosphate sulfate (PI-88). 1129 91


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