title: The effect of active site-inhibited factor VIIa on tissue factor-initiated coagulation using platelets before and after aspirin administration.
abstract: Active site-inactivated factor VIIa has potential as an antithrombotic agent. The effects of D-Phe-L-Phe-L-Arg-chloromethyl ketone-treated factor VIIa (FFR-FVIIa) were evaluated in a cell-based system mimicking in vivo initiation of coagulation. FFR-FVIIa inhibited platelet activation (as measured by expression of P-selectin) and subsequent large-scale thrombin generation in a dose-dependent manner with IC50 values of 1.4 +/- 0.8 nM (n = 8) and 0.9 +/- 0.7 nM (n = 7), respectively. Kd for factor VIIa binding to monocytes and Ki for FFR-FVIIa competing with factor VIIa were similar (11.4 +/- 0.8 pM and 10.6 +/- 1.1 pM, respectively), showing that FFR-FVIIa binds to tissue factor in the tenase complex with the same affinity as factor VIIa. Using platelets from volunteers before and after ingestion of aspirin (1.3 g), there were no significant differences in the IC50 values of FFR-FVIIa [after aspirin ingestion, the IC50 values were 1.7 +/- 0.9 nM (n = 8) for P-selectin expression, p = 0.37, and 1.4 +/- 1.3 nM (n = 7) for thrombin generation, p = 0.38]. This shows that aspirin treatment of platelets does not influence the inhibition of tissue factor-initiated coagulation by FFR-FVIIa, probably because thrombin activation of platelets is not entirely dependent upon expression of thromboxane A2.
authors.affiliation: Center for Thrombosis and Hemostasis, University of North Carolina at Chapel Hill, USA. mkja@novo.dk
authors.forename: M
authors.initials: M
authors.lastname: Kjalke
authors.forename: J A
authors.initials: JA
authors.lastname: Oliver
authors.forename: D M
authors.initials: DM
authors.lastname: Monroe
authors.forename: M
authors.initials: M
authors.lastname: Hoffman
authors.forename: M
authors.initials: M
authors.lastname: Ezban
authors.forename: U
authors.initials: U
authors.lastname: Hedner
authors.forename: H R
authors.initials: HR
authors.lastname: Roberts
mesh_terms: D000328:Adult; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology*; D001665:Binding Sites; D001667:Binding, Competitive; D001777:Blood Coagulation / Q000187:drug effects*; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004334:Drug Administration Schedule; D004347:Drug Interactions; D005167:Factor VII / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D015942:Factor VIIa; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000378:metabolism; D019007:P-Selectin / Q000378:metabolism; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D011485:Protein Binding; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000494:pharmacology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013917:Thrombin / Q000096:biosynthesis; D013925:Thromboplastin / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D016861:Cyclooxygenase Inhibitors; D005343:Fibrinolytic Agents; D008070:Lipopolysaccharides; D019007:P-Selectin; D010975:Platelet Aggregation Inhibitors; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; C027587:phenylalanyl-phenylalanyl-arginine chloromethyl ketone; D005167:Factor VII; D013925:Thromboplastin; C103587:recombinant FVIIa; D015942:Factor VIIa; D013917:Thrombin; D001241:Aspirin; D002118:Calcium