Page 253 - Haematologica April 2020

Platelet Biology & its Disorders
Mechanisms of increased mitochondria-dependent necrosis in Wiskott-Aldrich syndrome platelets
Sergey I. Obydennyi,1,2 Elena O. Artemenko,1,2 Anastasia N. Sveshnikova,1,2,3,4 Anastasia A. Ignatova,1,2 Tatiana V. Varlamova,1 Stepan Gambaryan,5 Galina Y. Lomakina,6,7 Natalia N. Ugarova,6 Igor I. Kireev,8 Fazoil I. Ataullakhanov,1,2,3,9 Galina A. Novichkova,1 Aleksey A. Maschan,1 Anna Shcherbina1 and Mikhail Panteleev1,2,3,9
1National Scientific and Practical Center of Pediatric Hematology, Oncology and Immunology named after Dmitry Rogachev, Moscow; 2Center for Theoretical Problems of Physicochemical Pharmacology, Moscow; 3Faculty of Physics, Lomonosov Moscow State University, Moscow; 4I.M. Sechenov First Moscow State Medical University, Moscow; 5Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St Petersburg, 6Department of Chemistry, Lomonosov Moscow State University, Moscow; 7Bauman Moscow State Technical University, Moscow; 8Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow and 9Faculty of Biological and Medical Physics, Moscow Institute of Physics and Technology, Dolgoprudny, Russia
ABSTRACT
Wiskott-Aldrich syndrome (WAS) is associated with thrombocy- topenia of unclear origin. We investigated real-time cytosolic cal- cium dynamics, mitochondrial membrane potential and phos- phatidylserine (PS) exposure in single fibrinogen-bound platelets using con- focal microscopy. The WAS platelets had higher resting calcium levels, more frequent spikes, and their mitochondria more frequently lost mem- brane potential followed by PS exposure (in 22.9% of platelets vs. 3.9% in controls; P<0.001) after the collapse of the last mitochondria. This phenom- enon was inhibited by the mitochondrial permeability transition pore inhibitor cyclosporine A, as well by xestospongin C and lack of extracellular calcium. Thapsigargin by itself caused accelerated cell death in the WAS platelets. The number of mitochondria was predictive of PS exposure: 33% of platelets from WAS patients with fewer than five mitochondria exposed PS, while only 12% did among those that had five or more mitochondria. Interestingly, healthy donor platelets with fewer mitochondria also more readily became procoagulant upon PAR1/PAR4 stimulation. Collapse of sin- gle mitochondria led to greater cytosolic calcium increase in WAS platelets if they had one to three mitochondria compared with platelets containing higher numbers. A computer systems biology model of platelet calcium homeostasis showed that smaller platelets with fewer mitochondria could have impaired calcium homeostasis because of higher surface-to-volume ratio and greater metabolic load, respectively. There was a correlation (C=0.81, P<0.02) between the mean platelet size and platelet count in the WAS patients. We conclude that WAS platelets readily expose PS via a mitochondria-dependent necrotic mechanism caused by their smaller size, which could contribute to the development of thrombocytopenia.
Introduction
Wiskott-Aldrich syndrome (WAS) is an X-linked disorder classically character- ized by thrombocytopenia, immunodeficiency and eczema.1 Its pathophysiological mechanisms relate to defective actin polymerization and abnormal signal-mediated cytoskeleton rearrangements in hematopoietic cells as a result of deficient or dys- regulated activity of the WAS protein that belongs to a distinct family of proteins involved in the transduction of signals from the cell surface to the actin cytoskele-
Ferrata Storti Foundation
Haematologica 2020 Volume 105(4):1095-1106
Correspondence:
MIKHAIL A. PANTELEEV
mapanteleev@yandex.ru
Received: December 18, 2018. Accepted: July 4, 2019. Pre-published: July 5, 2019.
doi:10.3324/haematol.2018.214460
Check the online version for the most updated information on this article, online supplements, and information on authorship & disclosures: www.haematologica.org/content/105/4/1095
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