Macromolecular ensembles of internal and external fibrinolysis: the resources for enhancement of thrombolysis efficacy.

The results of the search for new plasminogen activators for thrombolytic therapy have been reviewed with analysis of slowdown in this process. The reserves of increasing the effectiveness of thrombolysis are considered and the mechanisms underlying the interactions between plasminogen and its activators with fibrin are described. The domain composition of the fibrinolytic agents and the functional role of their structural elements in fibrinolytic interactions are discussed. The action of fibrin-specific and fibrin-nonspecific plasminogen activators in fibrinolysis has been evaluated. The necessity of the investigation of the regularities of internal and external fibrinolysis has been substantiated. The internal fibrinolysis became the resource for enhancement of thrombolysis efficacy. The approaches to the use of internal fibrinolysis to increase the effectiveness of enzyme therapy (monotherapy with plasminogen or new-made plasminogen activator as well as polytherapy with combination of different plasminogen activators /thrombolysis trigger plus third-generation plasminogen activator of prolonged action/) have been outlined and the relationship between this research and the current tendencies in the improvement of clinical thrombolysis (dose reduction, adjacent therapy, etc.) has been discussed.

The combination of modified antioxidant enzymes for anti-thrombotic protection of the vascular wall: the significance of covalent connection of superoxide dismutase and catalase activities.

Vascular wall protection can be achieved by preventive attachment to the vascular wall of antioxidants and elimination/neutralization of toxic products after their disproportioning. For this purpose we have prepared covalent conjugates between the vascular wall glycosaminglycan chondroitin sulfate (CHS) and the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). The following conjugates were obtained: SOD-CHS, CAT-CHS and SOD-CHS-CAT. Their anti-thrombotic activity was compared in a rat model of arterial thrombosis by measuring the time of occlusion emergence and thrombus mass. It is noteworthy that the effectiveness of single bolus injections of SOD-CHS/CAT-CHS mixture was much lower than that of the bienzymic SOD-CHS-CAT conjugate. The conjugate SOD-CHS-CAT proved to be anti-thrombotically effective in doses two orders of magnitude lower than the native biocatalysts and an order of magnitude lower than SOD-CHS and CAT-CHS derivatives. For effective anti-thrombotic protection in oxidative conditions it is important to maintain the stable connection of SOD and CAT activity on the vascular wall and the large size of these conjugates. Covalent conjugate SOD-CHS-CAT is the best prospect for pharmaceutical development.

Catalase and chondroitin sulfate derivatives against thrombotic effect induced by reactive oxygen species in a rat artery.

Antithrombotic activity of catalase (CAT) and chondroitin sulfate (CHS) preparations was studied in a rat model of arterial injury induced by ferrous chloride. Equal doses (according to catalytically active CAT) were used to examine the effect of native CAT, CAT-CHS covalent conjugate and mixture of native CAT and free CHS in a ratio corresponding to their contents in the conjugate. The antithrombotic activity of the derivatives was determined by the time during which arterial occlusion developed (occlusion time) and by the mass of the formed thrombus. The antithrombotic activities of the conjugate and mixture were similar and markedly higher than that of native CAT. The conjugate was more effective with respect to deceleration and prevention of arterial occlusion. Small doses of the preparations altered the structure of the formed thrombus, promoting sustained blood flow. Further investigations of the antithrombotic activity of CAT, superoxide dismutase and CHS derivatives have been outlined.