title: The hemostatic agent ethamsylate enhances P-selectin membrane expression in human platelets and cultured endothelial cells.
abstract: Ethamsylate possesses antihemorrhagic properties, but whether or not it directly activates blood platelets is unclear. Here we investigated the platelet activation potential of ethamsylate, by measuring membrane P-selectin expression with flow cytometry in human whole blood and also by immunofluorescence imaging of isolated human platelets. Moreover, we measured membrane P-selectin expression in the SV40-transformed aortic rat endothelial cell line (SVAREC) and 14C-ethamsylate membrane binding and/or uptake in platelets and endothelial cells. Whole blood flow cytometry showed a modest, but statistically significant increase by ethamsylate in the percentage of platelets expressing P-selectin (from 2% to 4-5%, p < 0.05). Immunofluorescence showed a sizable (39%) and significant (p < 0.01) enhancement of P-selectin expression at the lowest concentration of ethamsylate tested (1 microM), with maximal enhancement of P-selectin expression (75-90%) at 10 microM ethamsylate. Similar results were obtained in SVAREC endothelial cells. 14C-ethamsylate specifically bound to platelets and endothelial cell membranes, without significant uptake into the cell interior. In conclusion, ethamsylate enhances membrane P-selectin expression in human platelets and in cultured endothelial cells. Ethamsylate specifically binds to some protein receptor in platelet and endothelial cell membranes, receptor which can signal for membrane P-selectin expression. These results support the view that ethamsylate acts on the first step of hemostasis, by improving platelet adhesiveness and restoring capillary resistance.
authors.affiliation: INSERM U400, Faculté de Médecine, 8 rue du Général Sarrail, 94010 Créteil Cédex, France.
authors.forename: Miriam
authors.initials: M
authors.lastname: Alvarez-Guerra
authors.forename: Maria Rosa
authors.initials: MR
authors.lastname: Hernandez
authors.forename: Ginés
authors.initials: G
authors.lastname: Escolar
authors.forename: Carlo
authors.initials: C
authors.lastname: Chiavaroli
authors.forename: Ricardo P
authors.initials: RP
authors.lastname: Garay
authors.forename: Patrick
authors.initials: P
authors.lastname: Hannaert
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism*; D004979:Ethamsylate / Q000494:pharmacology*; D005434:Flow Cytometry; D006490:Hemostatics / Q000494:pharmacology*; D006801:Humans; D008856:Microscopy, Fluorescence; D019007:P-Selectin / Q000378:metabolism*; D015539:Platelet Activation / Q000187:drug effects*; D051381:Rats
chemical_list: D006490:Hemostatics; D019007:P-Selectin; D004979:Ethamsylate