Gerd Schmitz
University of Regensburg, Germany
Title: Addition of high-density lipoprotein3 and Apo A-I antagonize the platelet storage lesion and the release of platelet extracellular vesicles
Biography
Biography: Gerd Schmitz
Abstract
During activation and senescence, platelets release increased amounts of platelet extracellular vesicles (PL-EVs). We established an in vitro model for size, proteomic, lipidomic and transcriptomic characterization of PL-EVs over 5 days in platelet concentrates to better understand the platelet storage lesion. After 5 days standard blood banking, PL-EVs were isolated by filtration and differential gradient ultracentrifugation into 5 platelet microvesicle subfractions (PL-MV F1-F5) and platelet exosomes (PL-EXs) and subjected to Nanoparticle Tracking Analysis, Flow Cytometry, proteomic/lipidomic mass spectrometry, miRNA-microarray profiling and deep sequencing. PL-EVs showed overlapping particle mean sizes of 180-260 nm, but differed significantly in composition. Less dense (F1-3), intermediate and dense (F5-EX) PL-EVs, are enriched in lipidomic and proteomic markers for plasma membrane, intracellular membranes/platelet granules and mitochondria. F1-F4 is enriched in free cholesterol, sphingomyelin(SM), dihydroSM and glycerophospholipids. F4-F5 are enriched with phosphatidylinositol, ceramides, lysophosphatidic acid, phosphatidylserine and cardiolpin species. Alpha-synuclein (81% of total expression) accumulated in F1-F2, amyloid beta precursor protein in F3-F4 (84%) and ApoE (88%) and ApoJ (92%) in F3-5. PL-EXs are enriched in lipid-raft and adhesion markers. During platelet senescence, HDL3/apoA-I significantly reduce PL-EVs by 62%, and the decrease correlates with the concentration of added apoA-I, and is mediated by SRB-I and CD36. Compared to platelets, PL-EVs enriched miRNAs related to neurodegenerative diseases. Different lipid and protein compositions of PL-EVs suggest their unique cellular origins, partly overlapping with platelet granule secretion. Dense PL-EVs might represent autophagic vesicles released during platelet activation/apoptosis and PL-EXs resemble lipid rafts, with a possible role in platelet coagulation and immunology. Segregation of alpha-synuclein and amyloid beta precursor protein, ApoE/J into less dense and dense PL-MVs, respectively, show their differential carrier role of neurological disease-related cargo. HDL3/apoA-I influences membrane homeostasis of platelets by reduction of PL-EV release during platelet senescence, improving intracellular lipid processing/vesicle transport and increasing cholesterol CE-efflux.