Profibrinolytic activities of chemically modified heparins with very low anticoagulant activities

Depolymerized holothurian glycosaminoglycan (DHG), a novel alternative anticoagulant for hemodialysis, is safe and effective in a dog renal failure model

BACKGROUND

Depolymerized holothurian glycosaminoglycan (DHG) is a new agent with anticoagulant properties quite different from those of unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) in terms of antithrombin III-dependency, and exerts an antithrombotic effect with less bleeding than UFH and LMWH in vivo. In this study, the anticoagulant and hemorrhagic effects of DHG were investigated on hemodialysis in a dog model of renal failure and compared with those of UFH, LMWH, and nafamostat mesilate (FUT).

METHODS

The dog renal failure model was prepared by 7/8 renal artery ligation. Effectiveness was based on completion of 3-hour hemodialysis, no marked clot deposition in the extracorporeal circuit, and permeability of blood urea nitrogen (BUN) and creatinine. Template bleeding was measured by determining the hemoglobin content of the blood from the wound.

RESULTS

DHG induced no major bleeding or clot formation during 3-hour hemodialysis, in contrast to UFH and LMWH, each of which induced marked bleeding. These glycosaminoglycans (GAGs) were equally effective in decreasing plasma levels of BUN and creatinine. On the other hand, dogs treated with FUT failed to complete 3-hour hemodialysis. These anticoagulants prolonged activated partial thromboplastin time (APTT) to different extents and GAGs prolonged thrombin clotting time markedly but FUT did not.

CONCLUSION

Our findings suggest that thrombin clotting time prolongation can contribute to prevention of clot formation in extracorporeal circuits, and the non-antithrombin III-dependent activities of DHG may be related to its low risk of hemorrhage for hemodialysis. DHG appears to be promising as an alternative anticoagulant with low risk of hemorrhage for hemodialysis.

Effects of heparan sulfate analogue or other sulfated polysaccharides on the activation of plasminogen by t-PA or u-PA

Effects of heparan sulfate analogue (HHS-5) and other sulfated polysaccharides on the fibrinolytic system were investigated. Activation rate of native plasminogen (Glu-plg) by tissue plasminogen activator (t-PA), urinary plasminogen activator (u-PA) and single-chain u-PA (scu-PA) was enhanced in the presence of HHS-5 dose dependently up to 10 micrograms/ml. Activation rate of Glu-plg by sct-PA was more enhanced than that by tct-PA in its presence. HHS-5 enhanced the activation of Glu-plg by t-PA or u-PA compared to the activation of Lys-plg. SDS-PAGE confirmed that the enhancement of the hydrolysis of S-2251 by the mixture of Glu-plg, sct-PA and HHS-5 was due to the facilitation of the conversion of Glu-plg to plasmin. HHS-5 only slightly enhanced the amidolytic activity of sct-PA or tct-PA. The enhancement of the activation of plasminogen by t-PA or u-PA was more significant in the presence of HHS-5 than in the presence of chondroitin sulfate C, dextran sulfate or heparin. It is possible that the enhancement of the activation of Glu-plg by activators in the presence of HHS-5 was due to the conformational change of Glu-plg upon interaction with HHS-5.