Home About us Contact
|
Home About us Contact | ||
|
|
||
Heparin Cofactor II (heparin + cofactor_ii)
Selected AbstractsTyrosine sulfation and N-glycosylation of human heparin cofactor II from plasma and recombinant Chinese hamster ovary cells and their effects on heparin bindingFEBS JOURNAL, Issue 3 2002Christoph Böhme The structure of post-translational modifications of human heparin cofactor II isolated from human serum and from recombinant Chinese hamster ovary cells and their effects on heparin binding have been characterized. Oligosaccharide chains were found attached to all three potential N-glycosylation sites in both protein preparations. The carbohydrate structures of heparin cofactor II circulating in blood are complex-type diantennary and triantennary chains in a ratio of 6 : 1 with the galactose being > 90% sialylated with ,2,6 linked N-acetylneuraminic acid. About 50% of the triantennary structures contain one sLex motif. Proximal ,1,6 fucosylation of oligosacharides from Chinese hamster ovary cell-derived HCII was detected in >,90% of the diantennary and triantennary glycans, the latter being slightly less sialylated with exclusively ,2,3-linked N -acetylneuraminic acid units. Applying the ESI-MS/ MS-MS technique, we demonstrate that the tryptic peptides comprising tyrosine residues in positions 60 and 73 were almost completely sulfated irrespective of the protein's origin. Treatment of transfected Chinese hamster ovary cells with chlorate or tunicamycin resulted in the production of heparin cofactor II molecules that eluted with higher ionic strength from heparin,Sepharose, indicating that tyrosine sulfation and N-linked glycans may affect the inhibitor's interaction with glycosaminoglycans. [source] A comparison of the , -D-xyloside, odiparcil, to warfarin in a rat model of venous thrombosisJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 9 2006J. R. TOOMEY Summary,Background:,A significant need exists for new chronic oral anticoagulation therapies to replace warfarin. Previous studies have shown that , -D-xylosides, which prime glycosaminoglycan (GAG) synthesis, have antithrombin and antithrombotic activity. In the following report, a new orally active , -D-xyloside (odiparcil) has been characterized in a rat model of venous thrombosis and its efficacy and bleeding liability compared to warfarin. Additionally, studies were conducted to investigate odiparcil's ex vivo antithrombin and antiplatelet activity, and also to explore the potential utility of protamine sulfate as a neutralizing agent. Methods and results:,In vivo thrombosis studies were conducted in a rat inferior vena cava model, and bleeding studies in a rat tail transection model. Following oral dosing, warfarin and odiparcil produced dose-related suppression of thrombus formation. A therapeutically relevant dose of warfarin in this model (international normalized ratio; INR 3.0) achieved ,65% inhibition of thrombus formation. Warfarin caused dose-related significant increases in bleeding indices. Odiparcil antithrombotic activity was limited by its mechanism to a maximum suppression of thrombus formation of 65,70%, and did not prolong bleeding indices. Additionally, odiparcil-induced heparin cofactor II (HCII)-dependent antithrombin activity was shown to be a function of dermatan sulfate-like GAG production. Other than thrombin-related effects, no odiparcil effects on platelet function were observed. In antidote studies, it was demonstrated that odiparcil-induced antithrombotic activity could be partially neutralized by protamine sulfate. Conclusions:,These experiments suggest that an antithrombotic approach based upon xyloside induction of circulating GAGs may have the potential to approximate the efficacy of warfarin and yet with a reduced risk to hemostasis. [source] Beta2 -glycoprotein I protects thrombin from inhibition by heparin cofactor II: Potentiation of this effect in the presence of anti,,2 -glycoprotein I autoantibodiesARTHRITIS & RHEUMATISM, Issue 4 2008Soheila Rahgozar Objective Beta2 -glycoprotein I (,2GPI) is an important autoantigen in the antiphospholipid syndrome (APS). In vitro studies suggest that it may have multifaceted physiologic functions, since it displays both anticoagulant and procoagulant properties. We have previously reported that ,2GPI can directly bind thrombin, a key serine protease in the coagulation pathway. The present study was undertaken to examine the influence of ,2GPI on thrombin inactivation by the serpin heparin cofactor II (HCII). The effect of anti-,2GPI antibodies was also examined. Methods HCII inactivation of thrombin was assessed using chromogenic and various platelet functional assays. The influence of intact and proteolytically cleaved ,2GPI and anti-,2GPI antibodies was determined in these systems. Results ,2GPI protected thrombin against inactivation by HCII/heparin. Cleavage of ,2GPI at Lys317,Thr318 abrogated its protective effect. Patient polyclonal IgG and murine monoclonal anti-,2GPI antibodies potentiated the procoagulant influence of ,2GPI in this system. Conclusion These novel findings suggest that ,2GPI may regulate thrombin inactivation by HCII/heparin. The observation that anti-,2GPI antibodies potentiate the protective effect of ,2GPI on thrombin in this system, thereby promoting a procoagulant response, may potentially delineate one of the pathophysiologic mechanisms contributing to the prothrombotic tendency in patients with APS. [source] | ||||||||||