Anticoagulant properties of semisynthetic polysaccharide sulfates

State-of-the-Art Review: Usefulness of Laboratory Techniques for Evaluating Antithrombotic Efficacy of New Therapeutic Strategies

New drugs and new therapeutic strategies are being introduced for the prevention and the management of cardiovascular and thromboembolic disorders. Extensive clinical studies and large-scale epidemiological investigations are conducted to demonstrate the efficacy of these therapeutic approaches. Laboratory assays are invaluable tools for this exploration. We discuss how the new understanding concerning the regulation of the coagulolytic equilibrium offers novel investigation tools. Parameters reflecting the activities of new drugs targeted to their impact site and presenting few side effects are available. In addition to global clotting methods and chromogenic substrate-based assays, introduction of immunoassays has allowed measurement of most of the molecular markers of hemostatic activation. We recommend use of a panel of markers exploring the endothelial damage, the blood cell involvement, the early coagulant pathways' activation (XIIa and VIIa), the thrombin-formation pathways, the fibrin formation, and the evaluation of the global fibrinolytic capacity. When related to the clinical end points, all these laboratory assays offer useful and reliable monitoring of new drugs. They contribute to the establishment of new therapeutic strategies. Key Words: Hemostasis—Activation—Antithrombotic—Therapy— Laboratory monitoring.

Charge-directed fiber surface modification by molecular assemblies of functional polysaccharides

Molecular assemblies, namely, polyelectrolyte complexes (PECs) composed of negatively charged xylan-based derivatives and a novel positively charged cellulose derivative (CN(+)), were used for interfacial modification of wood fibers by charge directed self-assembly. The adsorption process was studied using polyelectrolyte titration and elemental analysis. X-ray spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used as advanced techniques for the characterization of the modified fiber surfaces. The measurements revealed an intense interaction between the pulp fibers and PECs, and provided essential information for a better understanding of the adsorption process. The information gathered on this paper might contribute to the basis for the development of new value added products by the use of underutilized biomass.

Effect of oversulfated chondroitin-6-sulfate or oversulfated fucoidan in the activation of glutamic plasminogen by tissue plasminogen activator: role of lysine and cyanogen bromide-fibrinogen

Fucoidan and chondroitin-6-sulfate were oversulfated using chlorosulfonic acid-pyridine complex and were isolated as the sodium salt. Infrared analysis of oversulfated compounds showed introduction of sulfate groups in new positions, and in-vitro studies of the compounds showed a significant increase in the anticoagulant property. Addition of 28.6 microg/ml oversulfated compound gave a two-fold to four-fold increase in the rate of enhancement of activation of glutamic plasminogen by tissue plasminogen activator using 0.05 mol/l Tris buffer (pH 7.35) containing physiological concentrations of NaCl (0.9%). Under these conditions, unfractionated heparin was not active and the native compounds gave less than 30% enhancement. In the present study, the effect of lysine or cyanogen bromide-treated fibrinogen, alone or in combination with the oversulfated compounds, on the activation of glutamic plasminogen by tissue plasminogen activator was investigated. Addition of 16.2 mmol/l L-lysine gave three-fold to four-fold enhancement of activation, which was further enhanced to five-fold to six-fold by addition of 2.86 microg/ml oversulfated chondroitin-6-sulfate or oversulfated fucoidan. Cyanogen bromide-treated fibrinogen (50 microg/ml) gave a 10-fold enhancement of activation by itself, and addition of 2.86 microg/ml oversulfated compounds amplified this to 15-fold. A 25-fold to 35-fold enhancement of activation of glutamic plasminogen was obtained when 2.86 microg/ml oversulfated compounds were combined with 16.2 mmol/l lysine and 50 microg/ml cyanogen bromide-treated fibrinogen. Dilution studies showed that the amplification of the enhancement of lysine by 2.86 microg/ml oversulfated compound was related to interaction of the cofactors with both glutamic plasminogen and tissue plasminogen activator.

Anticoagulant and antithrombotic activities of a chemically sulfated galactoglucomannan obtained from the lichen Cladonia ibitipocae

A galactoglucomannan (GGM), isolated from the lichen Cladonia ibitipocae, consisted of a (1-->6)-linked main chain of alpha-mannopyranose units, substituted by alpha- and beta-D-galacto (alpha- and beta-D-Galp)-, beta-D-gluco (beta-D-Glcp)- and alpha-D-mannopyranosyl (alpha-D-Manp) groups, and was sulfated giving a sulfated polysaccharide (GGM-SO4) with 42.2% sulfate corresponding to a degree of substitution of 1.29. NMR studies indicated that after sulfation, the OH-6 groups of galactopyranosyl and mannopyranosyl units were preferentially substituted. GGM-SO4 was investigated in terms of its in vitro anticoagulant and in vivo antithrombotic properties. Those of the former were evaluated by its activated partial thromboplastin (APTT) and thrombin time (TT), using pooled normal human plasma, and compared with that of 140 USP units mg(-1) for a porcine intestinal mucosa heparin. Anticoagulant activity was detected in GGM-SO4, but not in GGM. The in vivo antithrombotic properties of GGM-SO4 were evaluated using a stasis thrombosis model in Wistar rats, intravenous administration of 2 mg kg(-1) body weight totally inhibiting thrombus formation. It caused dose-dependent increases in tail transection bleeding time. The results obtained showed that this sulfated polysaccharides is a promising anticoagulant and antithrombotic agent.

Anticoagulant activity of immobilized heparin on the polypropylene nonwoven fabric surface depending upon the pH of processing environment

Antenna coupling microwave plasma enables a highly oxidative treatment of the outmost surface of polypropylene (PP) nonwoven fabric within a short time period. Subsequently, grafting copolymerization with acrylic acid (AAc) makes the plasma-treated fabric durably hydrophilic and excellent in water absorbency. With high grafting density and strong water affinity, the pAAc-grafted support greatly becomes feasible as an intensive absorbent and as a support to promote heparin immobilization through amide bonds. For heparin immobilized in acidic condition, the carbonate groups of the molecule tend to dissolve and passive encapsulation of the molecule prevents its functional groups from bonding with the carboxylic acid of pAAc. This effect leads to inhibit the immobilization process and consequently reduces the quantity as well as the bioactivity of the immobilized heparin. In alkaline processing environment, the oxidized uronic acid residues in heparin-related glycans are presumably cleaved and the removal of some oxidized residuals before immobilization process is likely to reduce the chain length of heparin. In the latter case, anticoagulant Factors X and XII, but not thrombin, are unaffected. Anticoagulant activity test using activated partial thromboplastin time (aPTT) is more sensitive in assessing heparin-immobilized surfaces, since it corresponds to Factor X and initiates the inhibition of Factor XII and thrombin. Likewise, platelets adhesion on the surfaces decreases as the process shifted from acidic to alkaline condition, whereas the hydrophilic character of the grafted pAAc markedly contributes to extend physical insertion of platelets. The immobilized heparin has a great part of original bioactivity, depending on the pH of the processing environment and the immobilized quantity. Relative bioactivity based upon aPTT tests is partially held longer than 90 days for the sample prepared in the alkaline or neutral environment.

Fluorescence and circular dichroism studies during the interactions of sulfated polysaccharides with antithrombin III

The changes in relative fluorescence of antithrombin III (AT-III) during its interaction with sulfated xylans were compared with that of sulfated glycosaminoglycans by measuring the ratio of the increase in fluorescence of AT-III in the presence of sulfated polysaccharide to the fluorescence of AT-III alone for various mass ratios. Interactions of corn cob xylan sulfate (CCXS) and sodium pentosan polysulfate (SP-54) with AT-III resulted in enhancements of relative fluorescence which were lower than commercial heparin. At mass ratios below 1, heparan sulfate and low molecular weight heparin (LMWH) gave increases in the relative fluorescence higher than that of commercial heparin, while highly sulfated semisynthetic chondroitin sulfates A and C gave much smaller increases. The relative fluorescence enhancements of AT-III by heparan sulfate, commercial heparin, LMWH and heparin derived pentasaccharide (HDP) increased with increasing mass ratios while the enhancements by CCXS, SP-54 and the highly sulfated chondroitin sulfates A and C were reversed at higher mass ratios. The estimated dissociation constants (kd) for the interaction of AT-III and the heparin-related compounds showed that heparin sulfate and LMWH gave the lowest kd values indicating a higher affinity for AT-III while commercial heparin and HDP gave higher kd values, indicating a lower affinity for AT-III. SP-54 gave a kd value lower than CCXS, indicating a greater affinity for AT-III. A comparison of the near ultraviolet (UV) circular dichroism (CD) spectrum of AT-III alone and during its interaction with oat spelts xylan sulfate (OSXS) showed enhancements of the two aromatic amino acid regions corresponding to phenylalanine and tryptophan.

Effect of sulfated xylans during the interaction of [125I]-thrombin with antithrombin III or heparin cofactor II of human plasma

[125I]-Labeled thrombin was incubated with human plasma and its interactions with the two plasma protease inhibitors antithrombin III (AT-III) or heparin cofactor II (HC-II) were investigated in the presence of oat spelts xylan sulfate (OSXS), sodium pentosan polysulfate (SP-54), and the results were compared with heparin and dermatan sulfate. Addition of OSXS or SP-54 enhanced the complexation of thrombin with HC-II or with both AT-III and HC-II depending upon the concentration and the duration of the interactions of the sulfated compounds with plasma. During the 30 s interaction, OSXS and SP-54 enhanced both AT-III-thrombin and HC-II-thrombin interaction while heparin was more selective and enhanced only the AT-III-thrombin interaction. However after a 2 min interaction, heparin showed an increase in the HC-II-thrombin interaction at higher concentrations. The complexations of AT-III-thrombin and HC-II-thrombin were reversed in the presence of 200 micrograms/ml of SP-54 during a 30 s interaction or in presence of 100 micrograms/ml of OSXS during a 2 min interaction. The Western blotting method of detecting thrombin showed that during the 10 s interaction, heparin enhanced the thrombin-AT-III complex formation while OSXS enhanced the thrombin-HC-II complex formation.