title: Differences in intracellular calcium dynamics cause differences in α-granule secretion and phosphatidylserine expression in platelets adhering on glass and TiO2.
abstract: In this study, the activation of purified human platelets due to their adhesion on glass and TiO2 in the absence of extracellular calcium was investigated. Differences in α-granule secretion between platelets adhering on the two surfaces were detected by examining the expression and secretion of the α-granule markers P-selectin (CD62P) and β-thromboglobulin. Similarly, differences in the expression of phosphatidylserine (PS), and in the activation of the major integrin GPIIb/IIIa, on the surfaces of the adhering platelets, were also observed. While all of these activation markers were expressed in platelets adhering on glass, the surface markers were not expressed in platelets adhering on TiO2, and β-thromboglobulin secretion levels were substantially reduced. Differences in marker expression and secretion correlated with differences in the intracellular calcium dynamics. Calcium ionophore treatment triggered α-granule secretion and PS expression in TiO2-adhering platelets but had no effect on the activation of GPIIb/IIIa. These results demonstrate specificity in the way surfaces of artificial materials activate platelets, link differences in the intracellular calcium dynamics observed in the platelets adhering on the two surfaces to the differences in some of the platelet responses (α-granule secretion and PS expression), but also highlight the involvement of synergistic, calcium-independent pathways in platelet activation. The ability to control activation in surface-adhering platelets makes this an attractive model system for studying platelet signaling pathways and for tissue engineering applications.
authors.affiliation: Biosurfaces, CIC biomaGUNE, Paseo Miramón 182, San Sebastián 20009, Spain and Department of Biochemistry and Molecular Biology, University of the Basque Country, 28940 Leioa, Spain.
authors.forename: Swati
authors.initials: S
authors.lastname: Gupta
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
authors.forename: Alessia
authors.initials: A
authors.lastname: Donati
authors.affiliation: Institute of Functional Interfaces (IFG), Karlsruhe Institute of Technology (KIT), Hermann-von Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany and Department of Bioengineering, University of Washington, Seattle, Washington 98105.
authors.forename: Ilya
authors.initials: I
authors.lastname: Reviakine
mesh_terms: D001792:Blood Platelets / Q000737:chemistry / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002448:Cell Adhesion; D005898:Glass; D006801:Humans; D016023:Integrins / Q000032:analysis; D019007:P-Selectin / Q000032:analysis; D010718:Phosphatidylserines / Q000378:metabolism*; D015539:Platelet Activation; D022142:Secretory Vesicles / Q000378:metabolism; D014025:Titanium; D001620:beta-Thromboglobulin / Q000032:analysis
chemical_list: D016023:Integrins; D019007:P-Selectin; C061615:PPBP protein, human; D010718:Phosphatidylserines; C546937:SELP protein, human; D001620:beta-Thromboglobulin; C009495:titanium dioxide; D014025:Titanium; D002118:Calcium