Comparative anticoagulant activity and influence on thrombin generation of dextran derivatives and of a fucoidan fraction

Abstract

CMDBS compounds are synthetic dextran derivatives with a random distribution of glucosylunits substituted with carboxymethyl, benzylamide, sulfonate, and sulfate groups. Fucoidans are sulfatedpolysaccharides extracted from brown seaweeds. CMDBS and fucoidans exhibit anticoagulant activitywhich depends on their chemical composition and molecular weight. Tested with purified proteins,these compounds catalyse thrombin (EC 3.4.21.5) inhibition mainly via heparin cofactor II (HCII). Weinvestigated the mechanism involved in the anticoagulant activity of these polysaccharides relative to thatof heparin. Three CMDBS with different chemical compositions were studied to evaluate the effect ofsulfate and sulfonate groups on the anticoagulant activity. The fucoidan fraction was extracted fromthe brown seaweed Ascophylum nodosum. The clotting assays (activated partial thromboplastin time,thrombin time, prothrombin time) were significantly prolonged in the presence of CMDBS and fucoidan,which were less active than heparin. To investigate the action mechanism of these polysaccharides,thrombin generation tests (TGT) were performed on human plasma in the presence of several CMDBSand a fucoidan fraction. The results showed an inhibition of thrombin generation in contact-activatedplasma in the presence of both polysaccharides, with a prolonged lag phase preceding the burst ofthrombin generation. In thromboplastin-activated plasma, thrombin generation was inhibited by CMDBSand fucoidan, with a prolonged lag phase only in the presence of CMDBS. The data obtained with eachpolysaccharide, compared to those obtained with heparin (our study) and hirudin (published data), ledto hypothesize that fucoidan could act, like heparin, by forming complexes with the inhibitor (althoughantithrombin (AT) in the case of heparin, and HCII for fucoidan), while CMDBS could act, like hirudin,by forming complexes with thrombin.