Inner Mitochondrial Membrane Disruption Links Apoptotic and Agonist-Initiated Phosphatidylserine Externalization in Platelets

• Type of Material: Article
• Authors: Hyojung Choo, Emory University; Andaleb Kholmukhamedov, Blood Center of Wisconsin; ChengZing Zhou, Emory University; Shawn Jobe, Blood Center of Wisconsin
• Language: English
• Date: 2017-08-01
• Publisher: American Heart Association
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2017 American Heart Association, Inc.
• Final Published Version (URL): http://dx.doi.org/10.1161/ATVBAHA.117.309473
• Title of Journal or Parent Work: Arteriosclerosis, Thrombosis, and Vascular Biology
• ISSN: 1079-5642
• Volume: 37
• Issue: 8
• Start Page: 1503
• End Page: 1512
• Grant/Funding Information: This work was supported by Grant HL095858 from the National Institutes of Health; The data described here was gathered on the JEOL JEM-1400 120kV TEM supported by a National Institutes of Health Grant S10 RR025679.; Additional support was provided by the National Center for Advancing Translational Sciences of the National Institutes of Health under award number UL1TR000454.
• Keywords: Nitrophenols; Biphenyl Compounds; Cyclophilins; Integrins; Kinetics; Mice, Knockout; Apoptosis; bcl-2-Associated X Protein; bcl-2 Homologous Antagonist-Killer Protein; Mitochondrial Membranes; Piperazines; blood platelet; Caspases; Blood Coagulation; Disease Models, Animal; Genotype; Phosphatidylserines; Necrosis; Phenotype; Lectins, C-Type; Sulfonamides; Platelet Aggregation; Venous Thrombosis; Blood Platelets; cytosol; Mitochondria; Animals; Crotalid Venoms; cell death; Signal Transduction; phosphatidylserine; Thrombin; mitochondrial membrane; Cytochromes c
• Research Categories: Health Sciences, Pathology; Health Sciences, Medicine and Surgery

Abstract

Objective - Phosphatidylserine exposure mediates platelet procoagulant function and regulates platelet life span. Apoptotic, necrotic, and integrin-mediated mechanisms have been implicated as intracellular determinants of platelet phosphatidylserine exposure. Here, we investigate (1) the role of mitochondrial events in platelet phosphatidylserine exposure initiated by these distinct stimuli and (2) the cellular interactions of the procoagulant platelet in vitro and in vivo. Approach and Results - Key mitochondrial events were examined, including cytochrome c release and inner mitochondrial membrane (IMM) disruption. In both ABT-737 (apoptotic) and agonist (necrotic)-treated platelets, phosphatidylserine externalization was temporally correlated with IMM disruption. Agonist stimulation resulted in rapid cyclophilin D-dependent IMM disruption that coincided with phosphatidylserine exposure. ABT-737 treatment caused rapid cytochrome c release, eventually followed by caspase-dependent IMM disruption that again closely coincided with phosphatidylserine exposure. A nonmitochondrial and integrin-mediated mechanism has been implicated in the formation of a novel phosphatidylserine-externalizing platelet subpopulation. Using image cytometry, this subpopulation is demonstrated to be the result of the interaction of an aggregatory platelet and a procoagulant platelet rather than indicative of a novel intracellular mechanism regulating platelet phosphatidylserine externalization. Using electron microscopy, similar interactions between aggregatory and procoagulant platelets are demonstrated in vitro and in vivo within a mesenteric vein hemostatic thrombus. Conclusions - Platelet phosphatidylserine externalization is closely associated with the mitochondrial event of IMM disruption identifying a common pathway in phosphatidylserine-externalizing platelets. The limited interaction of procoagulant platelets and integrin-active aggregatory platelets identifies a potential mechanism for procoagulant platelet retention within the hemostatic thrombus.