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Platelets Apr 2021The core structure of the extracellular basement membrane is made up of self-assembling networks of collagen and laminin which associate with each other through the...
The core structure of the extracellular basement membrane is made up of self-assembling networks of collagen and laminin which associate with each other through the bridging adapter proteins including the sulfated monomeric glycoprotein nidogen. While collagen and laminin are known to support platelet adhesion and activation via β1 integrins and glycoprotein (GP) VI, respectively, whether nidogen contributes to platelet activation and hemostasis is unknown. In this study, we demonstrate that recombinant human nidogen-1 supports platelet adhesion and stimulates platelet activation in a phospholipase-C γ-2 (PLCγ2), Src and Syk kinase-dependent manner downstream. Platetet adhesion to nidogen-1 was inhibited by blocking the platelet receptors GPVI and β1 integrins. Platelet adhesion to nidogen-1 activated the IκB kinase (IKK) complex, while pharmacological inhibition of IKK blocked platelet spreading on nidogen. Taken together our results suggest that nidogen may play a redundant role in hemostasis by activating platelets downstream of GPVI.
Topics: Humans; Membrane Glycoproteins; Platelet Activation; Platelet Adhesiveness
PubMed: 32233694
DOI: 10.1080/09537104.2020.1745170 -
Pharmacology & Therapeutics Jan 2021Subendothelial collagen exposed to platelets after rupture of atherosclerotic plaques is the main trigger of platelet activation und acute arterial thrombotic occlusion... (Review)
Review
Subendothelial collagen exposed to platelets after rupture of atherosclerotic plaques is the main trigger of platelet activation und acute arterial thrombotic occlusion leading to myocardial infarction or ischemic stroke. An efficacious antiplatelet therapy is essential to prevent atherothrombotic events. However, increasing potency of antiplatelet treatment is associated with an increased risk of bleeding limiting the clinical benefit for the patient since current antiplatelet strategies concomitantly affect hemostasis. Therefore, an unmet clinical need remains to develop antiplatelet strategies that selectively inhibit atherothrombosis without interfering with control of bleeding. Platelet glycoprotein VI (GPVI) plays a crucial role in collagen-induced activation and aggregation of platelets. Since GPVI is platelet-specific and strongly involved in the pathogenesis of arterial thrombosis without great impact on normal hemostasis, GPVI moved into the focus of novel approaches of antithrombotic therapy strategies. This review summarizes ligands, properties, function and downstream signaling of GPVI and discusses the potential of GPVI as target for novel therapeutic strategies in thrombotic and inflammatory diseases on the basis of recent scientific findings and currently ongoing clinical phase I and phase II trials.
Topics: Animals; Atherosclerosis; Biomarkers; Blood Platelets; Collagen; Hemorrhage; Humans; Ligands; Neoplasms; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Membrane Glycoproteins; Signal Transduction; Thrombosis
PubMed: 32681846
DOI: 10.1016/j.pharmthera.2020.107630 -
Cells Apr 2022Dysregulation of platelet function is causally connected to thrombus formation and cardiovascular diseases. Therefore, assessing platelet reactivity is crucial. However,...
Dysregulation of platelet function is causally connected to thrombus formation and cardiovascular diseases. Therefore, assessing platelet reactivity is crucial. However, current platelet function tests come with pitfalls, limiting clinical use. Plasma miRNA signatures have been suggested as novel biomarkers for predicting/diagnosing cardiovascular diseases and monitoring antiplatelet therapy. Here, we provide results from a comprehensive study on the feasibility of using circulatory platelet miRNAs as surrogate markers of platelet activation. We performed small RNA-Seq on different blood cell types to confirm known and identify novel platelet-enriched miRNAs and validated a panel of 16 miRNAs using RT-qPCR. To identify the main carrier of these blood-based platelet miRNAs, we enriched and analyzed distinct microvesicle populations. Platelets were stimulated with GPVI and P2Y12 agonists in vitro to monitor the release of the selected miRNAs following activation. Finally, the miRNA panel was also measured in plasma from mice undergoing the Folts intervention (recurrent thrombus formation in the carotid artery). Applying an unbiased bioinformatics-supported workflow to our NGS data, we were able to confirm a panel of previously established miRNA biomarker candidates and identify three new candidates (i.e., miR-199a-3p, miR-151a-5p, and miR-148b-3p). Basal levels of platelet-derived miRNAs in plasma were mainly complexed with proteins, not extracellular vesicles. We show that changes in miRNA levels due to platelet activation are detectable using RT-qPCR. In addition, we highlight limitations of studying the in vitro release of miRNAs from platelets. In vivo thrombosis resulted in significant elevations of platelet-derived miRNA levels in mice. In conclusion, we provide in-depth evidence that activated platelets release miRNAs, resulting in measurable changes in circulatory miRNA levels, rendering them promising biomarker candidates.
Topics: Animals; Biomarkers; Blood Platelets; Cardiovascular Diseases; Mice; MicroRNAs; Platelet Activation
PubMed: 35455934
DOI: 10.3390/cells11081254 -
PloS One 2021Atrial fibrillation (AF) comes along with high risk of stroke. This risk continues even after re-establishing sinus rhythm with cardioversion. Aim of this study is to...
INTRODUCTION
Atrial fibrillation (AF) comes along with high risk of stroke. This risk continues even after re-establishing sinus rhythm with cardioversion. Aim of this study is to evaluate the contribution of electric cardioversion (EC) to platelet activation and procoagulatory tendency.
METHODS
Extent of platelet activation before and after electric cardioversion was quantified using flow cytometry, impedance aggregation measurements with Multiplate®, and quantification of serum levels of platelet factor 4 (PF4) and ß-thromboglobulin (ß-TG) in patients with AF (N = 10).
RESULTS
No significant differences were observed in any of the measured parameters comparing the values from before and after cardioversion. Geometric means of P-selectin expression and integrin αIIbβ3 activation were 0.27 (+/- 0.07) and 2.30 (+/- 2.61) before EC and 0.28 (+/- 0.17) and 1.67 (+/- 1.82) after EC. Levels of ß-TG were 110.11 ng/ml (+/- 3.78) before and 110.51 ng/ml (+/- 2.56) after EC, levels of PF4 were 35.64 ng/ml (+/- 12.94) before and 32.40 ng/ml (+/- 4.95) after EC. Platelet aggregation triggered with adenosine diphosphate (ADP), arachidonic acid, collagen, Ristocetin, or thrombin receptor activating peptide (TRAP) revealed results within the normally expected ranges without significant changes before and after EC.
DISCUSSION
Electric cardioversion has no influence on platelet activation markers which is in agreement with other studies reporting electrical cardioversion to be safe.
Topics: Adenosine Diphosphate; Adult; Aged; Arachidonic Acid; Atrial Fibrillation; Blood Coagulation; Collagen; Electric Countershock; Female; Humans; Male; Middle Aged; Peptide Fragments; Platelet Activation; Platelet Aggregation; Platelet Factor 4; Platelet Function Tests; Ristocetin; Treatment Outcome
PubMed: 33886660
DOI: 10.1371/journal.pone.0250353 -
Hamostaseologie Nov 2019Platelets play a crucial role in haemostasis and several pathophysiological processes. Collagen is a main initiator for platelet activation and aggregation. Given that...
Platelets play a crucial role in haemostasis and several pathophysiological processes. Collagen is a main initiator for platelet activation and aggregation. Given that Wnt signalling negatively regulates platelet function, and IWR-1 (a small molecule inhibitor for Wnt signalling) has the potential of inhibiting collagen synthesis, it is essential to investigate whether IWR-1 regulates collagen-induced platelet activation and protects against thrombogenesis. In the present study we found that IWR-1 pretreatment effectively suppressed collagen-induced platelet aggregation in a dose-dependent manner. In addition, IWR-1 also resulted in a decrease of P-selectin and phosphatidylserine surface exposure using fluorescence-activated cell sorting analysis. In vitro studies further revealed that IWR-1 had a negative effect on integrin a2β1 activation and platelet spreading. More importantly, the results from in vivo studies showed that IWR-1 exhibited a robust bleeding diathesis in the tail-bleeding assay and a prolonged occlusion time in the FeCl3-induced carotid injury model. Taken together, current results demonstrate that IWR-1 could effectively block collagen-induced platelet activity in vitro and in vivo, and suggest its candidacy as a new antiplatelet agent.
Topics: Animals; Blood Platelets; Collagen; Humans; Imides; Mice; Platelet Activation; Quinolines
PubMed: 30849780
DOI: 10.1055/s-0038-1676822 -
Current Protocols Jun 2021Platelets are small but very abundant blood cells that play a key role in hemostasis, contributing to thrombus formation at sites of injury. The ability of platelets to...
Platelets are small but very abundant blood cells that play a key role in hemostasis, contributing to thrombus formation at sites of injury. The ability of platelets to perform this function, as well as functions in immunity and inflammation, is dependent on the presence of cell surface glycoproteins and changes in their quantity and conformation after platelet stimulation. In this article, we describe the characterization of platelet surface markers and platelet function using platelet-specific fluorescent probes and flow cytometry. Unlike traditional platelet tests, immunophenotypic analysis of platelets by flow cytometry allows the analysis of platelet function in samples with very low platelet counts as often encountered in clinical situations. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Immunophenotyping of platelet surface receptors Alternate Protocol: Fix-first method for immunophenotyping of platelet surface receptors Basic Protocol 2: Determination of platelet activation using P-selectin expression and/or PAC1 binding Basic Protocol 3: Determination of procoagulant platelets using annexin V binding or antibodies specific for coagulation factor V/Va or X/Xa Support Protocol: Preparation of isolated platelets.
Topics: Blood Platelets; Factor Va; Flow Cytometry; Immunophenotyping; Platelet Activation
PubMed: 34170638
DOI: 10.1002/cpz1.178 -
Journal of Thrombosis and Haemostasis :... Mar 2021The effects of docosahexaenoic acid (DHA) on cardiovascular disease are controversial and a mechanistic understanding of how this omega-3 polyunsaturated fatty acid...
BACKGROUND
The effects of docosahexaenoic acid (DHA) on cardiovascular disease are controversial and a mechanistic understanding of how this omega-3 polyunsaturated fatty acid (ω-3 PUFA) regulates platelet reactivity and the subsequent risk of a thrombotic event is warranted. In platelets, DHA is oxidized by 12-lipoxygenase (12-LOX) producing the oxidized lipids (oxylipins) 11-HDHA and 14-HDHA. We hypothesized that 12-LOX DHA-oxylipins may be involved in the beneficial effects observed in dietary supplemental treatment with ω-3 PUFAs or DHA itself.
OBJECTIVES
To determine the effects of DHA, 11-HDHA, and 14-HDHA on platelet function and thrombus formation, and to elucidate the mechanism by which these ω-3 PUFAs regulate platelet activation.
METHODS AND RESULTS
DHA, 11-HDHA, and 14-HDHA attenuated collagen-induced human platelet aggregation, but only the oxylipins inhibited ⍺IIbβ3 activation and decreased ⍺-granule secretion. Furthermore, treatment of whole blood with DHA and its oxylipins impaired platelet adhesion and accumulation to a collagen-coated surface. Interestingly, thrombus formation was only diminished in mice treated with 11-HDHA or 14-HDHA, and mouse platelet activation was inhibited following acute treatment with these oxylipins or chronic treatment with DHA, suggesting that under physiologic conditions, the effects of DHA are mediated through its oxylipins. Finally, the protective mechanism of DHA oxylipins was shown to be mediated via activation of protein kinase A.
CONCLUSIONS
This study provides the first mechanistic evidence of how DHA and its 12-LOX oxylipins inhibit platelet activity and thrombus formation. These findings support the beneficial effects of DHA as therapeutic intervention in atherothrombotic diseases.
Topics: Animals; Docosahexaenoic Acids; Mice; Oxylipins; Platelet Activation; Signal Transduction; Thrombosis
PubMed: 33222370
DOI: 10.1111/jth.15184 -
Blood Advances Mar 2021Ischemic stroke is a leading cause of morbidity and mortality worldwide and, despite reperfusion either via thrombolysis or thrombectomy, stroke patients often suffer... (Review)
Review
Ischemic stroke is a leading cause of morbidity and mortality worldwide and, despite reperfusion either via thrombolysis or thrombectomy, stroke patients often suffer from lifelong disabilities. These persistent neurological deficits may be improved by treating the ischemia/reperfusion (I/R) injury that occurs following ischemic stroke. There are currently no approved therapies to treat I/R injury, and thus it is imperative to find new targets to decrease the burden of ischemic stroke and related diseases. Platelets, cell fragments from megakaryocytes, are primarily known for their role in hemostasis. More recently, investigators have studied the nonhemostatic role of platelets in inflammatory pathologies, such as I/R injury after ischemic stroke. In this review, we seek to provide an overview of how I/R can lead to platelet activation and how activated platelets, in turn, can exacerbate I/R injury after stroke. We will also discuss potential mechanisms by which platelets may ameliorate I/R injury.
Topics: Blood Platelets; Humans; Ischemia; Platelet Activation; Reperfusion Injury; Stroke
PubMed: 33687431
DOI: 10.1182/bloodadvances.2020002888 -
Physiological Research Mar 2022Exposure to high altitudes and exercise alters body's physiology and may cause acute cardiovascular events. Platelet activation is one of the key players in these...
Exposure to high altitudes and exercise alters body's physiology and may cause acute cardiovascular events. Platelet activation is one of the key players in these events. Therefore, we investigated the effect of vigorous exercise at higher altitude (2650 m) on platelet aggregation and serum markers of platelet activation. 14 healthy subjects performed a step incremental ergometer test until exhaustion at the Environmental Research Station (UFS, 2650 m) at Zugspitze. Platelet aggregation and serum levels of endothelin-1, soluble p-selectin, platelet factor 4 and Chromogranin A were measured. Platelet activation was significantly enhanced after exercise at high altitude compared to measures immediately prior exercise. We detected significantly enhanced serum levels of endothelin-1 and soluble p-selectin whereas chromogranin A and platelet factor 4 remained unchanged. This effect might be due to increased endothelin-1 levels causing pulmonary vasoconstriction, rheological changes and direct platelet activation. This might be of clinical relevance, especially in patients with pre-existing diseases.
Topics: Altitude; Exercise; Humans; P-Selectin; Platelet Activation; Platelet Aggregation
PubMed: 35043652
DOI: 10.33549/physiolres.934768 -
International Journal of Cardiology Nov 2023
Topics: Humans; Platelet Activation; Syndrome; Takotsubo Cardiomyopathy
PubMed: 37586422
DOI: 10.1016/j.ijcard.2023.131256