Anticoagulant and antiprotease effects of a novel heparinlike compound from shrimp (Penaeus brasiliensis) and its neutralization by heparinase I

Isolation and Characterization of Heparin From Tuna Skins

This study characterized heparin isolated from tuna skins. Glycosaminoglycans were isolated from tuna skin after digestion using anion exchange resin. Heparin was eluted from the resin by sodium chloride gradient and was further fractionated by acetone fractionation. Anticoagulant activity was determined using the activated partial thromboplastin time and Heptest assays. Potency was determined using amidolytic antifactor IIa and antifactor Xa assays. The presence of heparin in the extracted tuna skin glycosaminoglycans was confirmed using13C-nuclear magnetic resonance. The activated partial thromboplastin time and Heptest clotting times were doubled at concentrations of about 4 and 1 µg/mL, respectively. The clotting time prolongation and antiprotease activity induced by tuna heparin was readily neutralized by 25 µg/mL protamine sulfate. These results demonstrate that biologically active heparin with properties similar to clinical grade heparin can be derived from tuna skin, a raw material with otherwise relatively little economic value.

Unique extracellular matrix heparan sulfate from the bivalve Nodipecten nodosus (Linnaeus, 1758) safely inhibits arterial thrombosis after photochemically induced endothelial lesion

Heparin-like glycans with diverse disaccharide composition and high anticoagulant activity have been described in several families of marine mollusks. The present work focused on the structural characterization of a new heparan sulfate (HS)-like polymer isolated from the mollusk Nodipecten nodosus (Linnaeus, 1758) and on its anticoagulant and antithrombotic properties. Total glycans were extracted from the mollusk and fractionated by ethanol precipitation. The main component (>90%) was identified as HS-like glycosaminoglycan, representing approximately 4.6 mg g(-1) of dry tissue. The mollusk HS resists degradation with heparinase I but is cleaved by nitrous acid. Analysis of the mollusk glycan by one-dimensional (1)H, two-dimensional correlated spectroscopy, and heteronuclear single quantum coherence nuclear magnetic resonance revealed characteristic signals of glucuronic acid and glucosamine residues. Signals corresponding to anomeric protons of nonsulfated, 3- or 2-sulfated glucuronic acid as well as N-sulfated and/or 6-sulfated glucosamine were also observed. The mollusk HS has an anticoagulant activity of 36 IU mg(-1), 5-fold lower than porcine heparin (180 IU mg(-1)), as measured by the activated partial thromboplastin time assay. It also inhibits factor Xa (IC(50) = 0.835 microg ml(-1)) and thrombin (IC(50) = 9.3 microg ml(-1)) in the presence of antithrombin. In vivo assays demonstrated that at the dose of 1 mg kg(-1), the mollusk HS inhibited thrombus growth in photochemically injured arteries. No bleeding effect, factor XIIa-mediated kallikrein activity, or toxic effect on fibroblast cells was induced by the invertebrate HS at the antithrombotic dose.

Isolation and characterization of a heparin with low antithrombin activity from the body of Styela plicata (Chordata-Tunicata). Distinct effects on venous and arterial models of thrombosis

INTRODUCTION

A heparin preparation with low antithrombin activity and different disaccharide composition than mammalian heparin was isolated from the body of the ascidian Styela plicata (Chordata-Tunicata). The disaccharide composition and the effect of the invertebrate glycan on venous and arterial models of thrombosis was investigated.

METHODS AND RESULTS

High performance liquid chromatography of the products formed by a mixture of heparin lyases showed that the ascidian heparin is composed mainly by delta UA(2SO4)-1-->4-beta-d-GlcN(SO4) (47.5%), delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(6SO4) (38.3%) disaccharides and smaller amounts of the disaccharides delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4)(6SO4) (2.8%) and delta UA(2SO4)-1-->4-beta-d-GlcN(SO4)(3SO4) (8.0%). The invertebrate heparin has an aPTT activity of 18 IU/mg and an antithrombin-mediated antithrombin and anti-factor Xa activities 10-fold lower than that of mammalian heparin. In a venous model of thrombosis in the vena cava, S. plicata heparin inhibits only 80% of thrombosis at a dose 10-fold higher than that of the mammalian heparin that inhibits 100% of thrombosis. However, in an arterio-shunt model of arterial thrombosis, both S. plicata and mammalian heparin possess equivalent antithrombotic activities. It is also shown that at equivalent doses, ascidian heparin has a lower bleeding effect than mammalian heparin.

CONCLUSION

The antithrombin-mediated anticoagulant activity of heparin polymers is not directly related to antithrombotic potency in the arterio-venous shunt. The results of the present work suggest that heparin preparations obtained from the body of S. plicata may have a safer therapeutic action in the treatment of arterial thrombosis than mammalian heparin.

The Hemolymph of the Ascidian Styela plicata (Chordata-Tunicata) Contains Heparin inside Basophil-like Cells and a Unique Sulfated Galactoglucan in the Plasma

The hemolymph of ascidians (Chordata-Tunicata) contains different types of hemocytes embedded in a liquid plasma. In the present study, heparin and a sulfated heteropolysaccharide were purified from the hemolymph of the ascidian Styela plicata. The heteropolysaccharide occurs free in the plasma, is composed of glucose ( approximately 60%) and galactose ( approximately 40%), and is highly sulfated. Heparin, on the other hand, occurs in the hemocytes, and high performance liquid chromatography of the products formed by degradation with specific lyases revealed that it is composed mainly by the disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4)) (39.7%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(6SO(4)) (38.2%). Small amounts of the 3-O-sulfated disaccharides DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4)) (9.8%) and DeltaUA(2SO(4))-1-->4-beta-d-GlcN(SO(4))(3SO(4))(6SO(4)) (3.8%) were also detected. These 3-O-sulfated disaccharides were demonstrated to be essential for the binding of the hemocyte heparin to antithrombin III. Electron microscopy techniques were used to characterize the ultrastructure of the hemocytes and to localize heparin and histamine in these cells. At least five cell types were recognized and classified as univacuolated and multivacuolated cells, amebocytes, hemoblasts, and granulocytes. Immunocytochemistry showed that heparin and histamine co-localize in intracellular granules of only one type of hemocyte, the granulocyte. These results show for the first time that in ascidians, a sulfated galactoglucan circulates free in the plasma, and heparin occurs as an intracellular product of a circulating basophil-like cell.

The 'precautionary principle' as a guide for future drug development

During the last decade, the 'precautionary principle' health has gained importance. It is an approach to manage uncertain risks and to prevent any damage to the environment or human. A key element is to take action, even if some cause and effect relationships are not fully established scientifically. Although there are also critics of this principle, it is meanwhile, also increasingly implemented in medicine. An important subject is medicinal products of human or animal origin. Manifold official precaution-guided regulations have been stated to improve their safety, particularly to avoid any infection by viruses and pathogens causing transmissible spongiform encephalopathies. In addition to numerous regulations and decisions, it is generally recommended to substitute animal and human-derived products with adequate alternatives wherever possible. This is a great challenge for research and drug development. One option is recombinant proteins, which however, are not generally free of any risk of contamination. Therefore, the best strategy might be the development of synthetic, specifically acting drugs. The most widely used medicinal product of animal origin at present is heparin. Although there has been no indication of any viral contamination, many other reasons suggest its substitution by alternative antithrombotics. These actually promoted the research on new anticoagulants. With the approval of fondaparinux, the first synthetic, selective factor Xa, a first alternative to the porcine-derived heparin has become available. In addition, other synthetic antithrombotics are currently in clinical development. In principle, it is thus possible that the prophylaxis and therapy of thromboembolic diseases will become completely independent of animal-derived drugs, which would be in line with the precautionary principle.

From heparins to factor Xa inhibitors and beyond

Despite some disadvantages, unfractionated heparin (UFH) and oral anticoagulants have been the only anticoagulants for prophylaxis and therapy of thromboembolic disorders for several decades. Based on the increasing knowledge of the structure and pharmacology of heparin, low molecular weight heparins (LMWH) have been developed in the 1980s. Compared to UFH, their advantages are mainly based on their reduced nonspecific binding to proteins and cells resulting in improved pharmacokinetics. In 1991, LMWH were declared as the most efficient prophylaxis in high-risk patients. Although the use of LMWH is increasing and they are today also applied for therapy and in other indications like acute coronary syndrome, they are considered not optimal concerning efficacy and safety. With the approval of fondaparinux for the prevention of venous thromboembolic disease in high-risk orthopedic patients, there might be a paradigm shift in the field of anticoagulants. Fondaparinux, a synthetic, chemically defined pentasaccharide, is the first selective inhibitor of factor Xa. By its highly specific binding to antithrombin, it selectively inhibits factor Xa and consequently prevents thrombin generation. In contrast to UFH and LMWH, it does not bind to any other cells and other proteins than antithrombin. This leads to a favourable linear pharmacokinetic profile, allowing once-daily subcutaneous application of a fixed dose without monitoring in thromboembolism prophylaxis. In addition to the evaluation of fondaparinux for further indications, chemical modifications of this pentasaccharide such as the long-acting idraparinux are currently under investigation.