Page 202 - Haematologica - Vol. 105 n. 6 - June 2020

Platelet Biology & its Disorders
Ferrata Storti Foundation
Haematologica 2020 Volume 105(6):1660-1666
Glycoprotein Ib clustering in platelets can be inhibited by α-linolenic acid as revealed by cryo-electron tomography
Simona Stivala,1* Simona Sorrentino,2* Sara Gobbato,1 Nicole R. Bonetti,1,3 Giovanni G. Camici,1,4,5 Thomas F. Lüscher,1 Ohad Medalia2,6 and Jürg H. Beer1,3
1Laboratory for Platelet Research, Center for Molecular Cardiology, University of Zurich, Zurich, Switzerland; 2Department of Biochemistry, University of Zurich, Zurich, Switzerland; 3Internal Medicine, Cantonal Hospital of Baden, Baden, Switzerland; 4University Heart Center, University Hospital Zurich, Zurich, Switzerland; 5Department of Research and Education, University Hospital Zurich, Zurich, Switzerland and 6Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University, Beer-Sheva, Israel
*SSt and SSo contributed equally as co-first authors
ABSTRACT
Platelet adhesion to the sub-endothelial matrix and damaged endotheli- um occurs through a multi-step process mediated in the initial phase by glycoprotein Ib binding to von Willebrand factor (vWF), which leads to the subsequent formation of a platelet plug. The plant-derived ω-3 fatty acid α-linolenic acid is an abundant alternative to fish-derived n-3 fatty acids and has anti-inflammatory and antithrombotic properties. In this study, we investigated the impact of α-linolenic acid on human platelet binding to vWF under high-shear flow conditions (mimicking blood flow in stenosed arter- ies). Pre-incubation of fresh human blood from healthy donors with α- linolenic acid at dietary relevant concentrations reduced platelet binding and rolling on vWF-coated microchannels at a shear rate of 100 dyn/cm2. Depletion of membrane cholesterol by incubation of platelet-rich plasma with methyl-β cyclodextrin abrogated platelet rolling on vWF. Analysis of glycoprotein Ib by applying cryo-electron tomography to intact platelets revealed local clusters of glycoprotein Ib complexes upon exposure to shear force: the formation of these complexes could be prevented by treatment with α-linolenic acid. This study provides novel findings on the rapid local rearrangement of glycoprotein Ib complexes in response to high-shear flow and highlights the mechanism of in vitro inhibition of platelet binding to and rolling on vWF by α-linolenic acid.
Introduction
The first event leading to the formation of a platelet plug is mediated by the gly- coprotein Ib-IX complex (GpIb-IX), the second most-abundant platelet receptor after the integrin αIIbβ3.1-3 Platelet binding to von Willebrand factor (vWF) is tight- ly controlled in order to occur only at sites of bleeding but not in the normal circu- lation, where it would cause thrombosis. This regulation involves activation of vWF only at high flow rates and binding of GpIb to the A1 domain of vWF through a two-step mechanism, in which a vWF multimer first elongates, then the A1 domain transitions to a high-affinity state.4-6 The role of high-shear flow in the pathogenesis of thrombosis is particularly relevant under pathological conditions such as in stenosed, atherosclerotic arteries, where shear stress can increase above 100 dyn/cm2 (shear rate >4000/s).7,8 Because of its pivotal role in initiating platelet adhesion, GpIb represents a promising antithrombotic target.
Omega-3 fatty acids (n-3 FA) are a class of naturally occurring polyunsaturated fatty acids that include the plant-derived α-linolenic acid (ALA), whose cardiopro- tective effects have been shown by us and others,9-12 which is readily available and marine-derived n-3 FA, whose use is restricted by limited fishery resources and sea pollution.13-15 n-3 FA modulate cellular responses through incorporation into plasma
Correspondence:
JÜRG H. BEER
hansjuerg.beer@ksb.ch
Received: March 5, 2019. Accepted: August 14, 2019. Pre-published: August 22, 2019.
doi:10.3324/haematol.2019.220988
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/6/1660
©2020 Ferrata Storti Foundation
Material published in Haematologica is covered by copyright. All rights are reserved to the Ferrata Storti Foundation. Use of published material is allowed under the following terms and conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode. Copies of published material are allowed for personal or inter- nal use. Sharing published material for non-commercial pur- poses is subject to the following conditions: https://creativecommons.org/licenses/by-nc/4.0/legalcode, sect. 3. Reproducing and sharing published material for com- mercial purposes is not allowed without permission in writing from the publisher.
1660
haematologica | 2020; 105(6)
ARTICLE