Identification of an endothelial cell cofactor for thrombin-catalyzed activation of protein C.

Esmon, Charles T.; Owen, Whyte G.

doi:10.1073/pnas.78.4.2249

Cited by 909 publications

(623 citation statements)

References 14 publications

Supporting

Mentioning

611

Contrasting

Unclassified

Order By: Relevance

“…Anticoagulant heparan sulphate proteoglycan, which like heparin can bind antithrombin and thereby potentiate their effect, are localised to the endothelial surface [59]. Another important anti-coagulant molecule on the endothelium is TM, which is constitutively expressed in most vascular beds [60]. TM is a cell surface proteoglycan that binds thrombin, which then alters substrate specificity from fibrinogen to proCPU and protein C.…”

Section: Endothelial Cellsmentioning

confidence: 99%

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

Björkman

Abrahamsson

Nerme

et al. 2005

Thrombosis Research

View full text Add to dashboard Cite

The physiologically most important activator of intravascular fibrinolysis is tissue-type plasminogen activator (t-PA) released from endothelial cells. In man, sympathomimetic drugs increase the systemic concentration of t-PA. It is therefore of interest to investigate whether cardiac sympathetic activation can induce a local t-PA release, which could counteract intra-coronary clot formation.Thrombolytic therapy with recombinant t-PA (rt-PA) is effective in acute myocardial infarction, but the treatment is limited by a fairly slow reperfusion rate and frequent early reocclusions. A potential mechanism behind early reocclusions might be that active thrombin is released from the thrombus during thrombolytic therapy. Thrombin has recently been shown to activate procarboxypeptidase U, which in its active form (CPU) down-regulates endogenous fibrinolysis. Therefore, one way of improving thrombolytic efficacy may be to combine rt-PA with a lowmolecular weight direct thrombin inhibitor, which theoretically could have a pro-fibrinolytic effect, either by inhibition of fibrin-bound thrombin and/or by inhibition of CPU activation. An alternative way may be direct inhibition of CPU.In a porcine model, experimental activation of cardiac sympathetic nerves by electrical stimulation at 1 and 8 Hz induced 5-and 20-fold increase in the release of both total and active t-PA together with frequency-dependent increases in heart rate, blood pressure, and coronary blood flow. The t-PA release was independent of the heart rate and coronary flow response, but local infusion of isoprenaline suggested that part of the t-PA response was mediated by stimulation of β-adrenergic receptors. Next, we studied the combined effect of rt-PA and thrombin inhibitors (melagatran, hirudin and heparin) in a canine model of copper coil-induced coronary thrombosis. The profibrinolytic effect of rt-PA, either measured as patency rate or time-to-patency, was significantly enhanced with the low-molecular weight direct thrombin inhibitor melagatran, but to a lesser degree by hirudin and heparin. In the same model it was shown that active CPU is produced locally in the coronary vascular bed during both thrombus formation and clot lysis. Inhibition of thrombin attenuated CPU formation and improved patency. A similar effect was obtained with a direct inhibitor of CPU.In conclusion, the coronary t-PA response to sympathetic stimulation may constitute a thromboprotective defence mechanism to counteract its prothrombotic effects on the systemic level. Furthermore, direct thrombin and/or CPU inhibition may be potential targets for prevention of thrombus formation via facilitation of the endogenous fibrinolytic system.

show abstract

Section: Endothelial Cellsmentioning

confidence: 99%

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

Björkman

Abrahamsson

Nerme

et al. 2005

Thrombosis Research

View full text Add to dashboard Cite

show abstract

“…On the other hand, the biosynthesis of a structurally heterogeneous glycosaminoglycan seems to result from a series of incomplete enzymatic reactions, raising concern about the genetic control of glycosaminoglycan fine structure (6). At least one protein, antithrombin III (AT-III), binds to a specific sequence present in some Hep molecules but not in others (1)(2)(3). Other proteins, such as the FGFs bind to Hep with surprisingly high affinity; however, attempts to identify specific binding sites in Hep for different growth factors have given inconclusive and sometimes conflicting results.…”

mentioning

confidence: 99%

“…Because of the microheterogeneity of the sulfate substitutions of the polysaccharides, it has been speculated that specific monosaccharide sequences in Hep bind to selective domains in target proteins (1)(2)(3)(4)(5). A Hep hexasaccharide can theoretically occur in Ͼ10 5 different structural forms, which allows for sufficient structural variations, expected for an information molecule.…”

mentioning

confidence: 99%

A heparin-binding synthetic peptide of heparin/heparan sulfateinteracting protein modulates blood coagulation activities

Liu¹,

Zhou²,

Höök³

et al. 1997

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

We have previously identified and characterized a heparin-binding cell surface protein (heparin͞heparan sulfate-interacting protein, or HIP) present on epithelial and endothelial cells. A synthetic peptide mimicking a heparinbinding domain of HIP is now shown to bind a small subset of heparin molecules with high affinity and, therefore, presumably recognizes a specific structural motif in the heparin molecule. Further analyses revealed that the heparin molecules exhibiting a high affinity for the HIP peptide also show an extremely high affinity for antithrombin III (AT-III), a cofactor required for heparin's anticoagulant activity. The HIP peptide was shown to compete with AT-III for binding to heparin and to neutralize the anticoagulant activity of heparin in blood plasma assays. Furthermore, the heparin subfraction that binds to the HIP peptide with high affinity exhibits an extremely high anticoagulant activity. We conclude that although the HIP peptide shows no sequence similarity with AT-III, the two proteins recognize the same or similar structural motifs in heparin.

show abstract

“…Address Thrombomodulin CTM) Immunofluorescence Anti-TM antiserum was prepared by immunizing a goat with TM isolated from rabbit lungs and purified by published methods (9). The IgG fraction of the goat antithrombomodulin serum was affinity purified on a TMaffigel column.…”

Section: Cell Lines and Mediamentioning

confidence: 99%

The relationship between thrombomodulin expression and cell cycle stages in cultured rabbit endothelial cells

DeBault

Esmon

1984

Cytometry

View full text Add to dashboard Cite

Cultured rabbit endothelial cells have significant but variable amounts of thrombomodulin (TM), both on their surface as well as inside the cell. To determine if variations in TM antigen is cell cycle related, cells with very high levels of TM antigen were identified and staged according to the intracellular distribution and relative amounts of the antigen, using immunofluorescence techniques. After staging, the nuclear DNA content of each of these cells was determined by measuring the propidium iodide (PI) fluorescence intensity cytophotometrically. Stages 1,2, and 3, which exhibited TM immunofluorescence in the golgi area, clustered to the GI phase of the cell cycle. Cells without discernible golgi fluorescence (stages 4 and 5) but with variable amounts of cytoplasmic and surface fluorescence appeared to have little or no relationship to the cell cycle.Key terms: Thrombomodulin, vascular endothelium, cell cycle, cytophotometry, tissue culture Thrombomodulin (TM) is a cell surface protein found on endothelial cells (7,15) that binds thrombin and increases thrombin's ability to activate Protein C, a serine protease zymogen. Once activated, Protein C becomes a potent anticoagulant that selectively inactivates Factors Va and VIIIa (16,18,19) and appears to modulate the fibrinolytic system as well (1). For further background on the relationship between TM, thrombin and Protein C, see the comprehensive review by C.T. Esmon (6).Using a bioassay for TM (8) on intact, living cells, we were able to show that cultured rabbit endothelium has significant but variable amounts of surface TM activity (3,8). Immunofluorescence studies, using a goat antiserum against the purified TM antigen, indicated there is a significant quantity of TM antigen located within these endothelial cells in addition to the surface TM measured in the bioassay (3). The immunofluorescence studies also revealed that a variable percentage of the cells were very bright relative to the other cells in the cultures. These observations are interpreted as the expression of very high levels of the TM antigen by some but not all cells. This phenomenon appears to occur spontaneously in culture, though the biological activity and number of very bright cells increase in postconfluent cultures. The objective of the present study is to determine if the expression of the TM antigen is a cellcycle-related event. MATERIALS AND METHODS Cell Lines and MediaWhite New Zealand rabbits (Me1 Wishard, Sand Springs, OK) were used as the tissue source for isolating microvascular and macrovascular endothelium as well as leukocytes for DNA standards. Endothelial cells were isolated or derived from rabbit aorta (lo), fat microvessels (8,171, and brain microvessels (43). The cells were maintained in M-199 medium (Gibco) with Hanks' Salts and supplemented with 15% fetal bovine serum, 100 U/ ml penicillin-G and 100 kg/ml streptomycin. Experimental cultures were set up by seeding cells on glass cover slips in six-well cluster dishes (well diameter = 35 mm) (Costar, Cambridge, MA). For...

show abstract

Identification of an endothelial cell cofactor for thrombin-catalyzed activation of protein C.

Cited by 909 publications

References 14 publications

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

Inhibition of carboxypeptidase U (TAFIa) activity improves rt-PA induced thrombolysis in a dog model of coronary artery thrombosis

A heparin-binding synthetic peptide of heparin/heparan sulfateinteracting protein modulates blood coagulation activities

The relationship between thrombomodulin expression and cell cycle stages in cultured rabbit endothelial cells

Contact Info

Product

Resources

About