The Impact of Shear Stress On the Interaction of Human Platelet Integrin αIIbβ3 with Fibrinogen

• Published in: Blood 2012-11, Vol.120 (21), p.2167-2167
• Main Authors: Gyenes, Marianna, Stoldt, Volker R., Huynh, Khon C., Scharf, Rüdiger E.
• Format: Article
• Language: English
• ISSN: 0006-4971; 1528-0020
• DOI: 10.1182/blood.V120.21.2167.2167

Abstract 2167 Shear stress can activate platelets resulting in subsequent platelet aggregation. The so-called “shear-induced platelet aggregation” (SIPA) contributes to various vascular diseases (Speich et al., Am J Physiol Cell Physiol 2008). Several signaling pathways were proposed to be involved in this process, e.g., αIIbβ3-mediated signaling (Feng et al., Am J Physiol Cell Physiol 2006). We investigated the impact of shear stress on the αIIbβ3–ligand interaction in human platelets adherent onto fibrinogen. Platelets on immobilized fibrinogen were exposed to various shear rates and signaling of Src and FAK tyrosine kinases, both essential in the integrin downstream signaling pathways, were examined. Specifically, we analyzed the role of αIIbβ3 in shear-induced platelet signaling (i) by comparing the Src Y418 and FAK Y397 phosphorylation activities between platelets on immobilized fibrinogen and platelets on BSA matrix in response to shear stress, and (ii) by performing experiments in the presence of the αIIbβ3 antagonist abciximab. Human washed platelets were incubated on immobilized fibrinogen 100 μg/ml or 1% BSA either under static conditions or exposed to shear rates of 500 s−1 or 5000 s−1, respectively. Specific phosphorylation of Src (pY418) and FAK (pY397) was determined by Western blot and quantified densitometrically. Experiments under flow conditions were performed in a cone-plate viscometer. Both Src and FAK exhibited phosphorylation under static conditions on immobilized fibrinogen after 2 min of adhesion. A shear rates of 500 s−1 did not increase the phosphorylation activities. By contrast, high shear rates (5000 s−1) significantly enhanced both Src and FAK phosphorylations in fibrinogen-adherent platelets (3-fold increase each, p