Cellular cooperation in endothelial cell thromboplastin synthesis

Abstract

Endothelial cells from human umbilical veins produce a procoagulant identified as thromboplastin (tissue factor, factor III) when stimulated with the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA), phytohaemagglutinin (PHA) or endotoxin, Inducible thromboplastin synthesis (i.e. synthesis of the protein component of thromboplastin, apoprotein III) was totally inhibited by cycloheximide and actinomycin D, indicating that de novo protein and RNA syntheses are necessary. Serum enhanced the induced apoprotein synthesis. Of the total thromboplastin activity in homogenates of stimulated endothelial cells, about 50--70% was available on the cell surface for interaction with other coagulation factors, inactivation by trypsin and neutralization with antiserum against apoprotein III. Induced synthesis of thromboplastin in endothelial cells was 2--7-fold enhanced by the presence of several other cell types in optimal ratio 4--10 cells per endothelial cell. Some of these cell types were themselves thromboplstin producers (U-937, U-937-4), some were not inducible (lymphocytes, granulocytes and the lymphoblast lines Daudi and Molt 4). This enhancing effect was also seen with cell-free culture supernatants, but these were generally somewhat less effective than the intact cells. Supernatants derived from cells cultured in the presence of TPA, PHA or endotoxin were in most cases more effective than supernatants from unstimulated cells.

Tissue factor-expressing monocytes inhibit fibrinolysis through a TAFI-mediated mechanism, and make clots resistant to heparins

“…In fact, the antifibrinolytic activity of LPS-MNC could be virtually abolished by an anti-TF monoclonal antibody, by an antibody preventing thrombin-mediated TAFI activation, as well as by the direct TAFIa inhibitor, PTCI. Considering that the monocyte is the only blood mononuclear cell capable of producing TF 19,25 and that the lysis time was prolonged also by a monocyte-enriched preparation, it can be safely concluded that the inhibition of fibrinolysis is ascribable to TF-expressing monocytes. These findings, coupled with the observation that soluble TF also prolonged fibrinolysis time and that the conditioned medium of LPS-MNC failed to inhibit fibrinolysis, makes it unlikely that other cell-derived fibrinolysis inhibitors 22 could have contributed appreciably to the prolongation of lysis time.…”

“…19,25 In vivo, under a variety of pathophysiological conditions, fibrin formation is induced by TFexpressing monocytes/macrophages adhering to the extracellular matrix. [15][16][17] To see whether adherent activated monocytes influence fibrinolysis we tested monocyte-enriched preparations isolated by adherence to plastic.…”

A coagulation pathway on bovine aortic segments leading to generation of Factor Xa and thrombin.

“…Endothelial cells inhibit thrombosis by synthesis of prostacyclin (1), plasminogen activator (2), and thrombomodulin (3), and by the presence of antithrombin III cofactor activity (4); they have the potential to support coagulation by generation of tissue factor (5), von Willebrand factor (VWF)' (6), and thromboxane (7). Recently, there has been increased interest in clot-promoting activities of endothelium, and we and other groups reported that Factors IX, IXa, X, and Xa bind to bovine aortic endothelial cells in culture (8)(9)(10)(11)(12)(13).…”

Prediction of Disseminated Intravascular Coagulation in Patients with Leukemia.

“…Wehave reported previously that the severity of DIC in patients with acute leukemia is correlated to the TF activity of bone marrowcells on admission (9). Lyberg and associates (10) (1 1, 12). In the present study, in order to investigate leukemic cells mainly belonging to the second category, we assessed the response ofleukemic cell TF activity to endotoxin in 43 patients with various types of leukemia, and evaluated the clinical implications with regard to the development of DIC.…”