title: Fibrillar type I collagens enhance platelet-dependent thrombin generation via glycoprotein VI with direct support of alpha2beta1 but not alphaIIbbeta3 integrin.
abstract: The role of collagens and collagen receptors was investigated in stimulating platelet-dependent thrombin generation. Fibrillar type-I collagens, including collagen from human heart, were most potent in enhancing thrombin generation, in a way dependent on exposure of phosphatidylserine (PS) at the platelet surface. Soluble, non-fibrillar type-I collagen required pre-activation of integrin alpha2beta1 with Mn2+ for enhancement of thrombin generation. With all preparations, blocking of glycoprotein VI (GPVI) with 9O12 antibody abrogated the collagen-enhanced thrombin generation, regardless of the alpha2beta 1 activation state. Blockade of alpha2beta1 alone or antagonism of autocrine thromboxane A2 and ADP were less effective. Blockade of alphaIIbbeta3 with abciximab suppressed thrombin generation in platelet-rich plasma, but this did not abolish the enhancing effect of collagens. The high activity of type-I fibrillar collagens in stimulating GPVI-dependent procoagulant activity was confirmed in whole-blood flow studies, showing that these collagens induced relatively high expression of PS. Together, these results indicate that: i) fibrillar type-I collagen greatly enhances thrombin generation, ii) GPVI-induced platelet activation is principally responsible for the procoagulant activity of fibrillar and non-fibrillar collagens, iii) alpha2beta1 and signaling via autocrine mediators facilitate and amplify this GPVI activity, and iv) alphaIIbbeta3 is not directly involved in the collagen effect.
authors.affiliation: Department Biochemistry, CARIM, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands.
authors.forename: Christelle
authors.initials: C
authors.lastname: Lecut
authors.forename: Marion A H
authors.initials: MA
authors.lastname: Feijge
authors.forename: Judith M E M
authors.initials: JM
authors.lastname: Cosemans
authors.forename: Martine
authors.initials: M
authors.lastname: Jandrot-Perrus
authors.forename: Johan W M
authors.initials: JW
authors.lastname: Heemskerk
mesh_terms: D000925:Anticoagulants / Q000737:chemistry; D001792:Blood Platelets / Q000378:metabolism*; D003094:Collagen / Q000737:chemistry; D024042:Collagen Type I / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D038982:Integrin alpha2beta1 / Q000378:metabolism*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D013917:Thrombin / Q000378:metabolism*; D013927:Thrombosis / Q000378:metabolism; D013997:Time Factors
chemical_list: D000925:Anticoagulants; D024042:Collagen Type I; D038982:Integrin alpha2beta1; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D010980:Platelet Membrane Glycoproteins; C098341:platelet membrane glycoprotein VI; D003094:Collagen; D013917:Thrombin