Recent in vivo studies from several laboratories have challenged the paradigm that tissue factor is solely responsible for triggering blood clotting in thrombotic disease, by showing that blocking the function of coagulation factor XII (which is essential for the contact pathway of blood clotting) significantly decreases thrombosis in animal models. However, for many years it has been unclear how the contact pathway is initiated in vivo. Recent work from our laboratory has identified inorganic polyphosphate as the long-sought (patho) physiologic activator of the contact pathway. Polyphosphate is secreted from activated platelets and accumulates in infectious microorganisms;we propose that it is an important triggering agent at the nexus of prothrombotic and pro-inflammatory pathways. Our studies have now shown that, in addition to being an extremely potent initiator of the contact pathway, polyphosphate also accelerates factor V activation and enhances fibrin clot structure, leading to thicker fibrin fibrils that are more resistant to fibrinolysis. Because the ability of polyphosphate to modulate blood clotting has only recently been discovered, we still do not understand mechanistically how polyphosphate exerts its effects on coagulation. Similarly, many questions remain regarding where, when and how if functions in vivo. These questions will be addressed in three aims, which focus on: understanding how polyphosphate triggers the contact pathway of clotting;understanding how polyphosphate accelerates factor V activation;and understanding how polyphosphate functions in vivo. The work outlined in this grant proposal will therefore provide a mechanistic understanding of how polyphosphate functions in hemostasis, thrombosis and inflammation. These studies are designed to identify novel drug targets for interrupting thrombotic and inflammatory pathways with minimized risk of bleeding side effects. They are also designed to develop novel hemostatic agents for treating bleeding.
Our laboratory has recently identified a substance - polyphosphate - which is released by certain human cells, and which regulates the blood clotting system. We are investigating how polyphosphate accomplishes this, which can lead to new insights into thrombotic diseases such as heart attack and stroke. These studies may also allow us to develop new methods that could eventually be used to treat bleeding episodes in patients.
|Gajsiewicz, Joshua M; Smith, Stephanie A; Morrissey, James H (2017) Polyphosphate and RNA Differentially Modulate the Contact Pathway of Blood Clotting. J Biol Chem 292:1808-1814|
|Smith, Stephanie A; Baker, Catherine J; Gajsiewicz, Joshua M et al. (2017) Silica particles contribute to the procoagulant activity of DNA and polyphosphate isolated using commercial kits. Blood 130:88-91|
|Kalathottukaren, Manu Thomas; Abraham, Libin; Kapopara, Piyushkumar R et al. (2017) Alteration of blood clotting and lung damage by protamine are avoided using the heparin and polyphosphate inhibitor UHRA. Blood 129:1368-1379|
|Sylman, Joanna L; Daalkhaijav, Uranbileg; Zhang, Ying et al. (2017) Differential Roles for the Coagulation Factors XI and XII in Regulating the Physical Biology of Fibrin. Ann Biomed Eng 45:1328-1340|
|Puy, Cristina; Tucker, Erik I; Ivanov, Ivan S et al. (2016) Platelet-Derived Short-Chain Polyphosphates Enhance the Inactivation of Tissue Factor Pathway Inhibitor by Activated Coagulation Factor XI. PLoS One 11:e0165172|
|Wijeyewickrema, Lakshmi C; Lameignere, Emilie; Hor, Lilian et al. (2016) Polyphosphate is a novel cofactor for regulation of complement by a serpin, C1 inhibitor. Blood 128:1766-76|
|Zilberman-Rudenko, Jevgenia; Itakura, Asako; Wiesenekker, Chantal P et al. (2016) Coagulation Factor XI Promotes Distal Platelet Activation and Single Platelet Consumption in the Bloodstream Under Shear Flow. Arterioscler Thromb Vasc Biol 36:510-7|
|Hassanian, S M; Dinarvand, P; Smith, S A et al. (2015) Inorganic polyphosphate elicits pro-inflammatory responses through activation of the mammalian target of rapamycin complexes 1 and 2 in vascular endothelial cells. J Thromb Haemost 13:860-71|
|Travers, R J; Smith, S A; Morrissey, J H (2015) Polyphosphate, platelets, and coagulation. Int J Lab Hematol 37 Suppl 1:31-5|
|Smith, Stephanie A; Morrissey, James H (2015) 2013 scientific sessions Sol Sherry distinguished lecture in thrombosis: polyphosphate: a novel modulator of hemostasis and thrombosis. Arterioscler Thromb Vasc Biol 35:1298-305|
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