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Blood May 2013The effects of phosphoinositide-dependent protein kinase 1 (PDK1), a master kinase in the phosphoinositide 3-kinase/Akt pathway, on platelet activation are unknown....
The effects of phosphoinositide-dependent protein kinase 1 (PDK1), a master kinase in the phosphoinositide 3-kinase/Akt pathway, on platelet activation are unknown. Accordingly, platelet-specific PDK1-deficient mice were characterized to elucidate the platelet-related function(s) of PDK1. We found that PDK1 deficiency caused mild thrombocytopenia. The aggregation of PDK1(-/-) platelets was diminished in response to low levels of thrombin, U46619, and adenosine 5'-diphosphate. Further results demonstrated that PDK1 regulates thrombin-induced platelet activation by affecting αIIbβ3-mediated outside-in signaling. This result provided an explanation for the diminished spreading of PDK1(-/-) platelets on immobilized fibrinogen (Fg) and the decreased rate of clot retraction in platelet-rich plasma (PRP) containing PDK1(-/-) platelets. PDK1 deficiency diminished agonist-induced Akt Ser473 phosphorylation and thoroughly abolished Akt Thr308 and Gsk3β Ser9 phosphorylation in response to agonist treatment and platelet spreading, respectively. A Gsk3β inhibitor fully restored the aggregation of PDK1(-/-) platelets in response to low levels of thrombin, normal spreading of PDK1(-/-) platelets on Fg, and normal clot retraction in PRP containing PDK1(-/-) platelets. Those results indicated that Gsk3β is one of the major downstream effectors of PDK1 in thrombin-induced platelet activation and αIIbβ3-mediated outside-in signaling. In addition, in vivo data demonstrated that PDK1 is an important regulator in arterial thrombosis formation.
Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adenosine Diphosphate; Animals; Arteries; Blood Platelets; Clot Retraction; Mice; Mice, Inbred C57BL; Mice, Knockout; Platelet Activation; Protein Serine-Threonine Kinases; Pyruvate Dehydrogenase Acetyl-Transferring Kinase; Thrombin; Thrombosis; Vasoconstrictor Agents
PubMed: 23444402
DOI: 10.1182/blood-2012-10-461897 -
Journal of Thrombosis and Haemostasis :... Jul 2009Platelet aggregation and thrombus formation at sites of atherosclerotic plaque rupture is a dynamic process that can lead to intermittent or permanent obstruction to... (Review)
Review
Platelet aggregation and thrombus formation at sites of atherosclerotic plaque rupture is a dynamic process that can lead to intermittent or permanent obstruction to blood flow, resulting in ischemic tissue injury and organ dysfunction. There is a growing body of evidence suggesting that the dynamics of platelet aggregation and initial thrombus development are regulated by two distinct, complementary processes, involving: (i) rheological (biomechanical) and (ii) soluble-agonist-dependent mechanisms. Rheological-dependent platelet aggregation occurs between discoid platelets and requires the biomechanical adhesive and signaling function (mechanotransduction) of the major platelet adhesion receptors, GPIb and integrin alpha(IIb)beta3. Soluble agonists further potentiate platelet activation, stimulating global platelet shape change and degranulation, and play a major role in stabilizing formed aggregates. Unraveling the dynamics of platelet aggregation and thrombus formation in vivo requires consideration of the cooperative interplay between rheological- and soluble agonist-dependent platelet aggregation mechanisms.
Topics: Blood Platelets; Humans; Platelet Activation; Platelet Aggregation; Thrombosis
PubMed: 19630759
DOI: 10.1111/j.1538-7836.2009.03401.x -
Biological Chemistry Jul 2013Platelet activation at sites of vascular injury leads to the formation of a hemostatic plug and is crucial for hemostasis. However, uncontrolled platelet activation may... (Review)
Review
Platelet activation at sites of vascular injury leads to the formation of a hemostatic plug and is crucial for hemostasis. However, uncontrolled platelet activation may lead to the formation of occlusive thrombi. Several soluble or matricellular proteins can activate platelets. In this article, we review recent advances in knowledge of the role of galectins in platelet physiology. In soluble or immobilized form, these endogenous glycan-binding proteins trigger platelet activation through the modulation of discrete signaling pathways. We discuss the role of platelet-galectin interactions not only in hemostasis, but also in chronic inflammation, atherosclerosis and cancer.
Topics: Animals; Blood Platelets; Galectins; Hemostasis; Humans; Platelet Activation; Platelet Adhesiveness
PubMed: 23509216
DOI: 10.1515/hsz-2013-0108 -
Frontiers in Immunology 2023
Topics: Humans; COVID-19; Platelet Activation
PubMed: 37818358
DOI: 10.3389/fimmu.2023.1285355 -
Journal of Thrombosis and Haemostasis :... May 2016The role of platelets in hemostasis and thrombosis is dependent on a complex balance of activatory and inhibitory signaling pathways. Inhibitory signals released from... (Review)
Review
The role of platelets in hemostasis and thrombosis is dependent on a complex balance of activatory and inhibitory signaling pathways. Inhibitory signals released from the healthy vasculature suppress platelet activation in the absence of platelet receptor agonists. Activatory signals present at a site of injury initiate platelet activation and thrombus formation; subsequently, endogenous negative signaling regulators dampen activatory signals to control thrombus growth. Understanding the complex interplay between activatory and inhibitory signaling networks is an emerging challenge in the study of platelet biology, and necessitates a systematic approach to utilize experimental data effectively. In this review, we will explore the key points of platelet regulation and signaling that maintain platelets in a resting state, mediate activation to elicit thrombus formation, or provide negative feedback. Platelet signaling will be described in terms of key signaling molecules that are common to the pathways activated by platelet agonists and can be described as regulatory nodes for both positive and negative regulators.
Topics: Animals; Antigens, CD; Apyrase; Cell Adhesion Molecules; Cyclic GMP-Dependent Protein Kinases; Gene Expression Regulation; Hemostasis; Humans; Integrins; Models, Biological; Platelet Activation; Receptors, Cell Surface; Signal Transduction; Thrombosis; Thromboxane A2; Type C Phospholipases
PubMed: 26929147
DOI: 10.1111/jth.13302 -
Blood Cells, Molecules & Diseases May 2024Extracellular vesicles (EVs) as membrane-bound particles released by various cells are potential tools for diagnosis and treatment. Blood cells, particularly platelets,...
UNLABELLED
Extracellular vesicles (EVs) as membrane-bound particles released by various cells are potential tools for diagnosis and treatment. Blood cells, particularly platelets, are the source of circulating EVs.
MATERIAL
EVs were enriched with gradient ultracentrifugation and measured by nanoparticle tracking assay. A flow cytometric multiplex assay was used for cellular source determination. Activation of platelets was measured as a percentage of CD62p+/CD61+ platelets and correlated with the concentration and size of released EVs.
RESULTS
In general there was no statistically significant correlation between EVs` concentration and degree of platelet activation. EVs from different cellular sources were detected. Comparing different needle thicknesses, there was a decrease in the EVs concentration for the 16G needle versus the 21G needle, but no difference was observed for EVs` size and phenotype or platelets activation. During blood storage, platelet activation increased, but there was no effect on the EVs` concentration, size, or phenotype.
CONCLUSIONS
Preanalytical factors like needle thickness and storage time can affect the MVs' properties. Activation of platelets during blood collection or blood storage occurs; however, it is difficult to determine its effect on the physiological properties of EVs since the mechanisms of EVs` biogenesis and especially clearness are not precisely known.
Topics: Humans; Platelet Activation; Extracellular Vesicles; Blood Platelets; Blood Coagulation; Blood Preservation
PubMed: 38492545
DOI: 10.1016/j.bcmd.2024.102842 -
International Journal of Molecular... Apr 2017The three major blood cell types, i.e., platelets, erythrocytes and leukocytes, are all produced in the bone marrow. While red blood cells are the most numerous and... (Review)
Review
The three major blood cell types, i.e., platelets, erythrocytes and leukocytes, are all produced in the bone marrow. While red blood cells are the most numerous and white cells are the largest, platelets are small fragments and account for a minor part of blood volume. However, platelets display a crucial function by preventing bleeding. Upon vessel wall injury, platelets adhere to exposed extracellular matrix, become activated, and form a platelet plug preventing hemorrhagic events. However, when platelet activation is exacerbated, as in rupture of an atherosclerotic plaque, the same mechanism may lead to acute thrombosis causing major ischemic events such as myocardial infarction or stroke. In the past few years, major progress has been made in understanding of platelet function modulation. In this respect, membrane channels formed by connexins and/or pannexins are of particular interest. While it is still not completely understood whether connexins function as hemichannels or gap junction channels to inhibit platelet aggregation, there is clear-cut evidence for a specific implication of pannexin1 channels in collagen-induced aggregation. The focus of this review is to summarize current knowledge of the role of connexins and pannexins in platelet aggregation and to discuss possible pharmacological approaches along with their limitations and future perspectives for new potential therapies.
Topics: Animals; Blood Platelets; Carrier Proteins; Cell Communication; Connexins; Gap Junctions; Humans; Intracellular Space; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Protein Binding; Signal Transduction; Thrombosis
PubMed: 28420171
DOI: 10.3390/ijms18040850 -
PloS One 2018Cutibacterium (Propionibacterium) acnes, considered a part of the skin microbiota, is one of the most commonly isolated anaerobic bacteria from medical implants in...
Cutibacterium (Propionibacterium) acnes, considered a part of the skin microbiota, is one of the most commonly isolated anaerobic bacteria from medical implants in contact with plasma. However, the precise interaction of C. acnes with blood cells and plasma proteins has not been fully elucidated. Herein, we have investigated the molecular interaction of C. acnes with platelets and plasma proteins. We report that the ability of C. acnes to aggregate platelets is dependent on phylotype, with a significantly lower ability amongst type IB isolates, and the interaction of specific donor-dependent plasma proteins (or concentrations thereof) with C. acnes. Pretreatment of C. acnes with plasma reduces the lag time before aggregation demonstrating that pre-deposition of plasma proteins on C. acnes is an important step in platelet aggregation. Using mass spectrometry we identified several plasma proteins deposited on C. acnes, including IgG, fibrinogen and complement factors. Inhibition of IgG, fibrinogen or complement decreased C. acnes-mediated platelet aggregation, demonstrating the importance of these plasma proteins for aggregation. The interaction of C. acnes and platelets was visualized using fluorescence microscopy, verifying the presence of IgG and fibrinogen as components of the aggregates, and co-localization of C. acnes and platelets in the aggregates. Here, we have demonstrated the ability of C. acnes to activate and aggregate platelets in a bacterium and donor-specific fashion, as well as added mechanistic insights into this interaction.
Topics: Blood Proteins; Humans; Mass Spectrometry; Microscopy, Fluorescence; Platelet Activation; Platelet Aggregation; Propionibacterium acnes
PubMed: 29385206
DOI: 10.1371/journal.pone.0192051 -
Nature Communications Jul 2020Genetic factors contribute to the risk of thrombotic diseases. Recent genome wide association studies have identified genetic loci including SLC44A2 which may regulate...
Genetic factors contribute to the risk of thrombotic diseases. Recent genome wide association studies have identified genetic loci including SLC44A2 which may regulate thrombosis. Here we show that Slc44a2 controls platelet activation and thrombosis by regulating mitochondrial energetics. We find that Slc44a2 null mice (Slc44a2(KO)) have increased bleeding times and delayed thrombosis compared to wild-type (Slc44a2(WT)) controls. Platelets from Slc44a2(KO) mice have impaired activation in response to thrombin. We discover that Slc44a2 mediates choline transport into mitochondria, where choline metabolism leads to an increase in mitochondrial oxygen consumption and ATP production. Platelets lacking Slc44a2 contain less ATP at rest, release less ATP when activated, and have an activation defect that can be rescued by exogenous ADP. Taken together, our data suggest that mitochondria require choline for maximum function, demonstrate the importance of mitochondrial metabolism to platelet activation, and reveal a mechanism by which Slc44a2 influences thrombosis.
Topics: Adenosine Triphosphate; Animals; Blotting, Western; Disease Models, Animal; Genome-Wide Association Study; Male; Mass Spectrometry; Membrane Transport Proteins; Mice; Mice, Knockout; Mitochondria; Platelet Activation; Platelet Aggregation; Real-Time Polymerase Chain Reaction; Thrombosis
PubMed: 32661250
DOI: 10.1038/s41467-020-17254-w -
Seminars in Thrombosis and Hemostasis Apr 2016Flow cytometry enables studies of several different aspects of platelet function in response to a variety of platelet agonists. This can be done using only a small... (Review)
Review
Flow cytometry enables studies of several different aspects of platelet function in response to a variety of platelet agonists. This can be done using only a small volume of whole blood, and also in blood with low platelet counts. These properties, together with the increasing number of flow cytometers available in hospitals worldwide, make flow cytometry an interesting option for laboratories interested in studies of platelet function in different clinical settings. This review focuses on practical issues regarding the use of flow cytometry for platelet function testing. It provides an overview of available activation markers, platelet agonists, and experimental setup issues. The review summarizes previous experience and factors important to consider to perform high-quality platelet function testing by flow cytometry. It also discusses its current use and possibilities and challenges for future use of flow cytometry in clinical settings.
Topics: Blood Platelet Disorders; Blood Platelets; Flow Cytometry; Humans; Platelet Activation; Platelet Aggregation; Platelet Function Tests; Reproducibility of Results; Sensitivity and Specificity; Thrombosis
PubMed: 26886398
DOI: 10.1055/s-0035-1570082