The fibrinolytic cascade functions to remove blood clots through the enzyme plasmin,which is generated as needed in a controlled fashion by a complex series of reactions. The proposed workis designed to provide a fuller, more quantitative understanding of the properties of the cascade and how itsactivity is regulated. The project is intimately related to the mission of the NIH because it is directed atobtaining a better understanding of the mechanisms which, when improperly regulated, underlie a good dealof the morbidity and mortality that afflict western society and manifest as heart attacks, stokes and otherthrombotic pathologies.
SPECIFIC AIMS :
The specific aims of the project are:(1) To determine thedynamics of the interactions between fibrin, tPA and plasminogen .involved in plasminogen activation; (2) Toinvestigate the enzymology of key reactions in the fibrinolytic cascade including: a) the fibrin dependentconversion of glu plasminogen to lys plasminogen by plasmin with and without TAFIa, b) the down regulationby fibrin of the inhibition of one and two chain tPA by PAI-1 with and without TAFIa, c) the activation of lysplasminogen by tPA on plasmin modified fibrin with and without TAFIa, and d) the plasmin catalyzeddigestion of fibrin; (3) To determine the effects of TAFIa on components and reactions of the coagulationcascade; (4) To determine the effect of chronic TAFI activation on clot lysis; (5) To investigate the inhibitionof fibrinolysis by platelets and study fibrinolysis in whole blood; (6) To determine the time courses andextents of TAFI activation in normal and factor VIII deficient whole blood and plasmas; and (7) To continuethe development of the Lys Speed computer model of the fibrinolytic cascade. RESEARCH DESIGN ANDMETHODS:
The first aim will be accomplished by measuring the dynamics of the interactions by which thetPA-fibrin-plasminogen complex is assembled; the second will be accomplished by standard measurementsof steady-state kinetics; the third, in collaboration with Dr. Mann, by exposing the clotting factors to TAFIaand assessing functional consequences; the forth by chronically generating TAFIa and monitoring clot lysis;the fifth, in collaboration with Drs. Tracy and Samis, by measuring lysis in the presence of platelets, wholeblood, and other blood cells; the sixth, in collaboration with Dr. Brummel-Ziedins by measuring TAFIaactivation and clot lysis in normal and factor VIIl-deficient whole blood or plasma; and the seventh by refiningand validating the computer model of the fibrinolytic cascade.
The relevance of this work topublic health is that it will lead to a better understanding of the means by which blood clots are removed andtherefore to a better understanding of pathologies associated with improperly balanced fibrin deposition andremoval such as venous thrombosis, pulmonary embolism, heart attack and stroke. In so doing, this workmay contribute to better means to diagnose, treat and prevent these maladies.
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