Galactana sulfatada da alga vermelha Acanthophora muscoides: potencial anticoagulante e antitrombótico.

Abstract

Currently available anticoagulants have significant limitations, which demonstrate the necessity of alternative agents. Sulfated polysaccharides from marine algae with anticoagulant and/or antithrombotic activities open new perspectives in the treatment of thromboembolic disorders. In the present study, we analyzed the anticoagulant and the antithrombotic activities of a sulfated galactan from the marine red alga Acanthophora muscoides (AmII). The anticoagulant activity was analyzed using the aPTT, the aPTT ex vivo and the recalcification time assays. In addition, specific proteases (IIa or Xa) and coagulation inhibitors (AT or HCII) were used to further investigate the anticoagulant activity. Experimental models of venous and arterial thrombosis were used to investigate the antithrombotic potential of the sulfated galactan. The factor XII activation assay was also performed. The AmII-antithrombin interaction was analyzed by measures of fluorescence emissions. Furthermore, AmII was used in ADP or collagen-induced platelet aggregation assays. The sulfated galactan from A. muscoides presented a lower anticoagulant activity on aPTT, the aPTT ex vivo and the recalcification time assays when compared with heparin. The sulfated galactan only enhanced the thrombin inhibition mediated by AT or HCII at high concentrations. In contrast, when factor Xa was used as the target protease, the sulfated galactan from A. muscoides presented a potent anticoagulant effect, similar to heparin. In addition, the sulfated galactan was shown to be a very potent antithrombotic agent in low doses (up to 0.5 mg/kg body weight), on venous thrombosis model, but these effects were reduced in higher doses. In the arterial experimental thrombosis, the sulfated galactan had antithrombotic effect similar to heparin at all doses tested. In contrast with heparin, the sulfated galactan activated factor XII, but the sulfated galactan did not present hemorrhagic effect in rats. In addition, AmII had no effect on platelet aggregation, and AmII together with antithrombin did not alter the fluorescence emission, indicating that this interaction might occur by a different mechanism than heparin-antithrombin interaction. The sulfated galactan from alga Acanthophora muscoides presented low anticoagulant potential and potent antithrombotic effect. These results suggest that this sulfated galactan opens new perspectives for a possible development of new antithrombotic drugs.