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Cardiovascular Research Dec 2017In addition to maintaining haemostasis, circulating blood platelets are the cellular culprits that form occlusive thrombi in arteries and veins. Compared to blood... (Review)
Review
AIMS
In addition to maintaining haemostasis, circulating blood platelets are the cellular culprits that form occlusive thrombi in arteries and veins. Compared to blood leucocytes, which exist as functionally distinct subtypes, platelets are considered to be relatively simple cell fragments that form vascular system plugs without a differentially regulated cellular response. Hence, investigation into platelet subpopulations with distinct functional roles in haemostasis/thrombosis has been limited. In our present study, we investigated whether functionally distinct platelet subpopulations exist based on their ability to generate and respond to nitric oxide (NO), an endogenous platelet inhibitor.
METHODS AND RESULTS
Utilizing highly sensitive and selective flow cytometry protocols, we demonstrate that human platelet subpopulations exist based on the presence and absence of endothelial nitric oxide synthase (eNOS). Platelets lacking eNOS (approximately 20% of total platelets) fail to produce NO and have a down-regulated soluble guanylate cyclase-protein kinase G (sGC-PKG)-signalling pathway. In flow chamber and aggregation experiments eNOS-negative platelets primarily initiate adhesion to collagen, more readily activate integrin αIIbβ3 and secrete matrix metalloproteinase-2, and form larger aggregates than their eNOS-positive counterparts. Conversely, platelets having an intact eNOS-sGC-PKG-signalling pathway (approximately 80% of total platelets) form the bulk of an aggregate via increased thromboxane synthesis and ultimately limit its size via NO generation.
CONCLUSION
These findings reveal previously unrecognized characteristics and complexity of platelets and their regulation of adhesion/aggregation. The identification of platelet subpopulations also has potentially important consequences to human health and disease as impaired platelet NO-signalling has been identified in patients with coronary artery disease.
Topics: Animals; Blood Platelets; Humans; Matrix Metalloproteinase 2; Nitric Oxide; Nitric Oxide Synthase Type III; Platelet Aggregation; Platelet Aggregation Inhibitors
PubMed: 29016749
DOI: 10.1093/cvr/cvx179 -
Blood Mar 2022
Topics: Blood Platelets; Humans; Inflammation; Platelet Aggregation
PubMed: 35323878
DOI: 10.1182/blood.2021015118 -
Veterinary Medicine and Science Nov 2021Pentoxifylline can decrease platelet function in humans, but the anti-platelet effects of pentoxifylline in dogs is unknown. The addition of a luciferin-luciferase...
BACKGROUND
Pentoxifylline can decrease platelet function in humans, but the anti-platelet effects of pentoxifylline in dogs is unknown. The addition of a luciferin-luciferase reagent during platelet aggregometry can induce a dose-dependent potentiation of platelet aggregation.
OBJECTIVE
To determine if exposure to pentoxifylline, without the addition of a luciferin-luciferase reagent during aggregometry, causes canine platelet dysfunction. Our hypotheses were that pentoxifylline would inhibit platelet function, and that the addition of a luciferin-luciferase reagent would obscure detection of pentoxifylline-induced platelet dysfunction as measured via aggregometry.
METHODS
Seven healthy Walker hound dogs. Platelet-rich plasma (PRP) and whole blood were treated for 30 minutes with pentoxifylline: 0 (control), 1 and 2 μg/mL. The platelet aggregation was determined using optical (maximum amplitude) and impedance (ohms) aggregometry using collagen as the agonists, with and without a luciferin-luciferase reagent. Four samples were analysed per concentration and the results were averaged.
RESULTS
Based on optical aggregometry, there was no difference (p = 0.964) in the mean maximum amplitude at any pentoxifylline concentration, with and without the luciferin-luciferase reagent. During impedance aggregometry, the addition of a luciferin-luciferase reagent was associated with significantly (p < 0.001) greater platelet aggregation in response to a collagen agonist, regardless of the presence or absence of pentoxifylline.
CONCLUSIONS
Pentoxifylline does not exert an in vitro anti-platelet effect on canine platelet aggregation when collagen is used as an agonist, but it is unknown if long-term oral drug administration will inhibit platelet aggregation. The addition of a luciferin-luciferase reagent during platelet aggregometry can artificially enhance canine platelet aggregation.
Topics: Animals; Blood Platelets; Dogs; Electric Impedance; Pentoxifylline; Platelet Aggregation; Platelet Function Tests
PubMed: 34358418
DOI: 10.1002/vms3.595 -
PloS One 2021Galectin-1 (gal-1) is a carbohydrate-binding lectin with important functions in angiogenesis, immune response, hemostasis and inflammation. Comparable functions are...
Galectin-1 (gal-1) is a carbohydrate-binding lectin with important functions in angiogenesis, immune response, hemostasis and inflammation. Comparable functions are exerted by platelet factor 4 (CXCL4), a chemokine stored in the α-granules of platelets. Previously, gal-1 was found to activate platelets through integrin αIIbβ3. Both gal-1 and CXCL4 have high affinities for polysaccharides, and thus may mutually influence their functions. The aim of this study was to investigate a possible synergism of gal-1 and CXCL4 in platelet activation. Platelets were treated with increasing concentrations of gal-1, CXCL4 or both, and aggregation, integrin activation, P-selectin and phosphatidyl serine (PS) exposure were determined by light transmission aggregometry and by flow cytometry. To investigate the influence of cell surface sialic acid, platelets were treated with neuraminidase prior to stimulation. Gal-1 and CXCL4 were found to colocalize on the platelet surface. Stimulation with gal-1 led to integrin αIIbβ3 activation and to robust platelet aggregation, while CXCL4 weakly triggered aggregation and primarily induced P-selectin expression. Co-incubation of gal-1 and CXCL4 potentiated platelet aggregation compared with gal-1 alone. Whereas neither gal-1 and CXCL4 induced PS-exposure on platelets, prior removal of surface sialic acid strongly potentiated PS exposure. In addition, neuraminidase treatment increased the binding of gal-1 to platelets and lowered the activation threshold for gal-1. However, CXCL4 did not affect binding of gal-1 to platelets. Taken together, stimulation of platelets with gal-1 and CXCL4 led to distinct and complementary activation profiles, with additive rather than synergistic effects.
Topics: Blood Platelets; Galectin 1; Humans; N-Acetylneuraminic Acid; Platelet Activation; Platelet Aggregation; Platelet Factor 4; Platelet Glycoprotein GPIIb-IIIa Complex; Signal Transduction
PubMed: 33411760
DOI: 10.1371/journal.pone.0244736 -
Journal of Thrombosis and Haemostasis :... Oct 2021Platelets are now recognized as immunological sentries in the first line of defense that participate in the detection and response to pathogens. This frequently results...
BACKGROUND
Platelets are now recognized as immunological sentries in the first line of defense that participate in the detection and response to pathogens. This frequently results in a decrease in the number of circulating platelets. Different mechanisms have been hypothesized to explain the thrombocytopenia in patients with severe dengue, one of them is the participation of the non-structural protein 1 (NS1) of dengue virus (DENV), which can be secreted into circulation during DENV infection and promotes a more efficient infection.
OBJECTIVE
The present study aimed to investigate the ability of platelet response to stimulation with full-length DENV NS1 protein and its domains.
METHODS
DENV NS1 plasmid was transfected into HEK-293T. Proteins were purified by Niquel Sepharose affinity chromatography. Secreted proteins were assessed by sodium dodecylsulfate polyacrylamide gel electrophoresis, Coomassie staining and western blot. Platelet-rich plasma was directly incubated with DENV NS1 proteins. Platelet activation was confirmed by expression of αIIbβIII and P-selectin by flow cytometry. Platelet aggregation was also assessed using DENV NS1 protein and its individual domains as agonists.
RESULTS
DENV NS1 protein and its domains induce P-selectin and αIIbβ3 complex expression on platelet surfaces. DENV NS1 induce a stable platelet aggregation after the addition of a minimal dose of adenosine diphosphate (ADP), epinephrine (EPI), or collagen. Interestingly, only EPI could induce the formation of platelet aggregates after incubation with the protein domains of NS1.
CONCLUSION
Our results suggest that the full DENV NS1 protein and also its domains promote platelet recognition, activation, and aggregation.
Topics: Blood Platelets; Dengue; Dengue Virus; Humans; Platelet Aggregation; Viral Nonstructural Proteins
PubMed: 34160117
DOI: 10.1111/jth.15431 -
British Journal of Clinical Pharmacology Nov 2014Platelets play an important role in cardiovascular disease, and β-blockers are often prescribed for cardiovascular disease prevention. β-Blockers may directly affect... (Meta-Analysis)
Meta-Analysis Review
AIMS
Platelets play an important role in cardiovascular disease, and β-blockers are often prescribed for cardiovascular disease prevention. β-Blockers may directly affect platelet aggregation, because β-adrenergic receptors are present on platelets. There is uncertainty about the existence and magnitude of an effect of β-blockers on platelet aggregation. The aim of this study was to perform a systematic review and meta-analysis of the effect of β-blockers on platelet aggregation.
METHODS
MEDLINE and EMBASE were searched until April 2014. Two reviewers independently performed data extraction and risk of bias assessment. Type of β-blocker, population, treatment duration and platelet aggregation were extracted. Standardized mean differences were calculated for each study and pooled in a random-effects meta-analysis.
RESULTS
We retrieved 31 studies (28 clinical trials and three observational studies). β-Blockers decreased platelet aggregation (standardized mean difference -0.54, 95% confidence interval -0.85 to -0.24, P < 0.0001). This corresponds to a reduction of 13% (95% confidence interval 8-17%). Nonselective lipophilic β-blockers decreased platelet aggregation more than selective nonlipophilic β-blockers.
CONCLUSIONS
Clinically used β-blockers significantly reduce platelet aggregation. Nonselective lipophilic β-blockers seem to reduce platelet aggregation more effectively than selective nonlipophilic β-blockers. These findings may help to explain why some β-blockers are more effective than others in preventing cardiovascular disease.
Topics: Adrenergic beta-Antagonists; Cardiovascular Diseases; Clinical Trials as Topic; Humans; Observational Studies as Topic; Platelet Aggregation
PubMed: 24730697
DOI: 10.1111/bcp.12404 -
Arteriosclerosis, Thrombosis, and... Oct 2014
Topics: Animals; Blood Platelets; Carotid Stenosis; Emergency Medical Services; Fibrinolytic Agents; Humans; Male; Myocardial Infarction; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Pyrimidinones; Thiadiazoles; Thrombosis
PubMed: 25231635
DOI: 10.1161/ATVBAHA.114.304486 -
BioMed Research International 2015As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD.... (Review)
Review
As platelet activation is closely related to the liberation of growth factors and inflammatory mediators, platelets play a central role in the development of CVD. Virtually all cardiovascular risk factors favor platelet hyperreactivity and, accordingly, also physical (in)activity affects platelet function. Within this paper, we will summarize and discuss the current knowledge on the impact of acute and habitual exercise on platelet function. Although there are apparent discrepancies regarding the reported effects of acute, strenuous exercise on platelet activation, a deeper analysis of the available literature reveals that the applied exercise intensity and the subjects' cardiorespiratory fitness represent critical determinants for the observed effects. Consideration of these factors leads to the summary that (i) acute, strenuous exercise can lead to platelet activation, (ii) regular physical activity and/or physical fitness diminish or prevent platelet activation in response to acute exercise, and (iii) habitual physical activity and/or physical fitness also favorably modulate platelet function at physical rest. Notably, these effects of exercise on platelet function show obvious similarities to the well-recognized relation between exercise and the risk for cardiovascular events where vigorous exercise transiently increases the risk for myocardial infarction and a physically active lifestyle dramatically reduces cardiovascular mortality.
Topics: Blood Platelets; Cardiovascular Diseases; Humans; Motor Activity; Platelet Activation; Platelet Aggregation; Risk Factors; Sedentary Behavior
PubMed: 26557653
DOI: 10.1155/2015/165078 -
Cellular and Molecular Life Sciences :... Jan 2015Hemostasis and pathological thrombus formation are dynamic processes that require multiple adhesive receptor-ligand interactions, with blood platelets at the heart of... (Review)
Review
Hemostasis and pathological thrombus formation are dynamic processes that require multiple adhesive receptor-ligand interactions, with blood platelets at the heart of such events. Many studies have contributed to shed light on the importance of von Willebrand factor (VWF) interaction with its platelet receptors, glycoprotein (GP) Ib-IX-V and αIIbβ3 integrin, in promoting primary platelet adhesion and aggregation following vessel injury. This review will recapitulate our current knowledge on the subject from the rheological aspect to the spatio-temporal development of thrombus formation. We will also discuss the signaling events generated by VWF/GPIb-IX-V interaction, leading to platelet activation. Additionally, we will review the growing body of evidence gathered from the recent development of pathological mouse models suggesting that VWF binding to GPIb-IX-V is a promising target in arterial and venous pathological thrombosis. Finally, the pathological aspects of VWF and its impact on platelets will be addressed.
Topics: Animals; Glycoproteins; Hemostasis; Mice; Models, Biological; Platelet Adhesiveness; Platelet Aggregation; Protein Structure, Tertiary; Thrombosis; von Willebrand Factor
PubMed: 25297919
DOI: 10.1007/s00018-014-1743-8 -
Blood Advances Sep 2021Brain-derived neurotrophic factor (BDNF) has both autocrine and paracrine roles in neurons, and its release and signaling mechanisms have been extensively studied in the...
Brain-derived neurotrophic factor (BDNF) has both autocrine and paracrine roles in neurons, and its release and signaling mechanisms have been extensively studied in the central nervous system. Large quantities of BDNF have been reported in circulation, essentially stored in platelets with concentrations reaching 100- to 1000-fold those of neurons. Despite this abundance, the function of BDNF in platelet biology has not been explored. At low concentrations, BDNF primed platelets, acting synergistically with classical agonists. At high concentrations, BDNF induced complete biphasic platelet aggregation that in part relied on amplification from secondary mediators. Neurotrophin-4, but not nerve growth factor, and an activating antibody against the canonical BDNF receptor tropomyosin-related kinase B (TrkB) induced similar platelet responses to BDNF, suggesting TrkB could be the mediator. Platelets expressed, both at their surface and in their intracellular compartment, a truncated form of TrkB lacking its tyrosine kinase domain. BDNF-induced platelet aggregation was prevented by inhibitors of Ras-related C3 botulinum toxin substrate 1 (Rac1), protein kinase C, and phosphoinositide 3-kinase. BDNF-stimulated platelets secreted a panel of angiogenic and inflammatory cytokines, which may play a role in maintaining vascular homeostasis. Two families with autism spectrum disorder were found to carry rare missense variants in the BDNF gene. Platelet studies revealed defects in platelet aggregation to low concentrations of collagen, as well as reduced adenosine triphosphate secretion in response to adenosine diphosphate. In summary, circulating BDNF levels appear to regulate platelet activation, aggregation, and secretion through activation of a truncated TrkB receptor and downstream kinase-dependent signaling.
Topics: Autism Spectrum Disorder; Brain-Derived Neurotrophic Factor; Humans; Phosphatidylinositol 3-Kinases; Platelet Activation; Platelet Aggregation
PubMed: 34546355
DOI: 10.1182/bloodadvances.2020004098