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Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration.

ABSTRACT: There is a growing appreciation for the contribution of platelets to immunity; however, our knowledge mostly relies on platelet functions associated with vascular injury and the prevention of bleeding. Circulating immune complexes (ICs) contribute to both chronic and acute inflammation in a multitude of clinical conditions. Herein, we scrutinized platelet responses to systemic ICs in the absence of tissue and endothelial wall injury. Platelet activation by circulating ICs through a mechanism requiring expression of platelet Fc? receptor IIA resulted in the induction of systemic shock. IC-driven shock was dependent on release of serotonin from platelet-dense granules secondary to platelet outside-in signaling by ?IIb?3 and its ligand fibrinogen. While activated platelets sequestered in the lungs and leaky vasculature of the blood-brain barrier, platelets also sequestered in the absence of shock in mice lacking peripheral serotonin. Unexpectedly, platelets returned to the blood circulation with emptied granules and were thereby ineffective at promoting subsequent systemic shock, although they still underwent sequestration. We propose that in response to circulating ICs, platelets are a crucial mediator of the inflammatory response highly relevant to sepsis, viremia, and anaphylaxis. In addition, platelets recirculate after degranulation and sequestration, demonstrating that in adaptive immunity implicating antibody responses, activated platelets are longer lived than anticipated and may explain platelet count fluctuations in IC-driven diseases.

SUBMITTER: Cloutier N

PROVIDER: S-EPMC5816207 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration.

Cloutier Nathalie N Allaeys Isabelle I Marcoux Genevieve G Machlus Kellie R KR Mailhot Benoit B Zufferey Anne A Levesque Tania T Becker Yann Y Tessandier Nicolas N Melki Imene I Zhi Huiying H Poirier Guy G Rondina Matthew T MT Italiano Joseph E JE Flamand Louis L McKenzie Steven E SE Cote Francine F Nieswandt Bernhard B Khan Waliul I WI Flick Matthew J MJ Newman Peter J PJ Lacroix Steve S Fortin Paul R PR Boilard Eric E

Proceedings of the National Academy of Sciences of the United States of America 20180131 7

There is a growing appreciation for the contribution of platelets to immunity; however, our knowledge mostly relies on platelet functions associated with vascular injury and the prevention of bleeding. Circulating immune complexes (ICs) contribute to both chronic and acute inflammation in a multitude of clinical conditions. Herein, we scrutinized platelet responses to systemic ICs in the absence of tissue and endothelial wall injury. Platelet activation by circulating ICs through a mechanism req ...[more]

PMID: 29386381

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Project description:Platelet aggregation in the bloodstream is tightly associated with the secretory function of platelets based on several types of cytoplasmic secretory granules, each sequestering distinct chemical messenger species. Dense-body granules are one prominent type of secretory granule responsible for storing small molecule chemical messengers. Upon platelet activation, the timely and rapid release of these small molecules is critical in facilitating platelet aggregation. Therefore, techniques capable of measuring real-time granule content release are needed to understand the fundamental properties of platelet secretion and aggregation. Existing techniques lack adequate time resolution or require potentially toxic exogenous reagents for real-time measurement of granule content release. Herein, we demonstrate a label-free electrochemical method based on the endogenous electroactive chemical messenger serotonin (5-hydroxytryptamine or 5-HT) for the real-time measurement of dense-body granule secretion from platelet suspensions; fast-scan cyclic voltammetry (FSCV) using carbon-fiber microelectrodes was chosen on the basis of its excellent temporal resolution, high sensitivity, and the ability to provide the electrochemical signature cyclic voltammograms for molecular identification. Real-time serotonin release from thrombin-stimulated human platelet suspensions was successfully measured, and the amount and time course of the bulk serotonin release were found to agree well with data obtained from single platelet measurements, thus confirming accurate characterization of granular secretion. Furthermore, this electrochemical method was applied to study the stimulation-secretion coupling in platelets, serotonin storage and release dynamics with applied pharmacological agents, and chemical messenger storage deficiency in Hermansky-Pudlak Syndrome (HPS) platelets, and the potential of this method to reveal secretion behavior in both normal and diseased platelets has clearly been demonstrated.

Project description:Sonodynamic therapy (SDT) has aroused great interest for its potential in the treatment of glioblastoma (GBM). SDT relies on tumor-selective accumulation of a sonosensitizer that is activated by ultrasound irradiation (UI) to generate cytotoxic actions. The efficacy of GBM-SDT depends on sufficient sonosensitizer buildup in the tumor, which is, however, seriously hampered by the anatomical and biochemical barriers of the GBM. To overcome this difficulty, we herein propose a delivery strategy of 'platelets with ultrasound-triggered release property', which takes advantage of 1) the platelets' ability to carry cargo and release cargo upon activation, and 2) the ROS-generating property of SDT. To provide proof of concept for the strategy, we first stably loaded platelets with IOPD-Ce6, a nano-formed sonosensitizer consisting of iron oxide nanoparticles coated with polyglycerol and doxorubicin and loaded with chlorine e6. UI of the IOPD-Ce6-loaded platelets (IOPD-Ce6@Plt) elicited ROS generation in the IOPD-Ce6@Plt, which were immediately activated to release IOPD-Ce6 into GBM cells in co-culture which, when subjected to a second time of UI, exhibited pronounced ROS production, DNA injury, viability loss, and cell death in the GBM cells. In the in vivo experiments, mice bearing intracranial GBM grafts exhibited substantial tumor distribution of IOPD-Ce6 following intravenous injection of IOPD-Ce6@Plt and subsequent UI at the tumor site. The GBM grafts then exhibited pronounced cell injury and death after another round of UI of the tumors. Finally, the growth of intra-cranial GBM grafts was significantly slowed when an SDT protocol consisting of an intravenous IOPD-Ce6@Plt injection followed by multiple times of tumor UI had been applied twice to the mice. Our results are strong evidence for the idea that platelets are sound and amenable carriers to deliver sonosensitizers in the GBM in an ultrasound-triggered manner and thus to produce highly targeted and effective SDT of GBM.

Project description:In addition to haemostasis, platelets mediate inflammation and clearance of bacteria from the bloodstream. As with platelet-platelet interactions, platelet-bacteria interactions involve cytoskeletal rearrangements and release of granular content. Stimulation of the immune Toll-like receptor 2 (TLR2) on the platelet surface, activates phosphoinositide-3-kinase (PI3K) and causes platelet activation and platelet-dependent thrombosis. It remains unknown if platelet activation by immune versus thrombotic pathways leads to the differential regulation of signal transduction, protein-protein interactions, and alpha-granule release, and the physiological relevance of these potential differences. We investigated these processes after immune versus thrombotic platelet stimulation. We examined selected signalling pathways and found that phosphorylation kinetics of Akt, ERK1/2 and p38 differed dramatically between agonists. Next, we investigated platelet protein-protein interactions by mass spectrometry (MS)-based proteomics specifically targeting cytosolic factor XIIIa (FXIIIa) because of its function as a cytoskeleton-crosslinking protein whose binding partners have limited characterisation. Four FXIIIa-binding proteins were identified, two of which are novel interactions: FXIIIa-focal adhesion kinase (FAK) and FXIIIa-gelsolin. The binding of FAK to FXIIIa was found to be altered differentially by immune versus thrombotic stimulation. Lastly, we studied the effect of thrombin versus Pam(3)CSK(4) stimulation on alpha-granule release and observed differential release patterns for selected granule proteins and decreased fibrin clot formation compared with thrombin. The inhibition of PI3K caused a decrease in protein release after Pam(3)CSK(4)- but not after thrombin-stimulation. In summary, stimulation of platelets by either thrombotic or immune receptors leads to markedly different signalling responses and granular protein release consistent with differential contribution to coagulation and thrombosis.

Dataset Information

Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration.

Publications

Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration.

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