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Annual International Conference of the... 2015Mechanical circulatory support (MCS) devices, such as ventricular assist devices and the total artificial heart, have emerged as a vital therapy for advanced and...
Mechanical circulatory support (MCS) devices, such as ventricular assist devices and the total artificial heart, have emerged as a vital therapy for advanced and end-stage heart failure. However, MCS patients face life-long antiplatelet and anticoagulant therapy to minimize thrombotic complications resulting from the dynamic and supraphysiologic device-associated shear stress conditions, whose effect on platelet activation is poorly understood. We repeatedly exposed platelets to average shear stresses up to 1000 dyne/cm(2) for as short as 25 ms in the "platelet hammer," a syringe-capillary viscometer. Platelet activation state was measured using a modified prothrombinase assay and morphological changes analyzed using scanning electron microscopy. An increase in stress accumulation (SA), the product of shear stress and exposure time, led to an increase in the platelet activation state and post-high shear platelet activation rate, or sensitization. A significant increase in platelet activation state was observed beyond an SA of 1500 dyne-s/cm(2), with a marked increase in pseudopod length visible beyond an SA of 1000 dyne-s/cm(2). The platelet hammer may be used to study other shear-dependent pathologies and may ultimately enhance the safety and effectiveness of MCS devices and objective antithrombotic pharmacotherapy management.
Topics: Adult; Blood Platelets; Female; Heart-Assist Devices; Humans; Male; Microscopy, Electron, Scanning; Platelet Activation; Stress, Mechanical; Thrombosis
PubMed: 26736250
DOI: 10.1109/EMBC.2015.7318350 -
Clinical Hemorheology and... 2019Circulating blood cells are prone to varying flow conditions when contacting cardiovascular devices. For a profound understanding of the complex interplay between the...
Circulating blood cells are prone to varying flow conditions when contacting cardiovascular devices. For a profound understanding of the complex interplay between the blood components/cells and cardiovascular implant surfaces, testing under varying shear conditions is required. Here, we study the influence of arterial and venous shear conditions on the in vitro evaluation of the thrombogenicity of polymer-based implant materials.Medical grade poly(dimethyl siloxane) (PDMS), polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) films were included as reference materials. The polymers were exposed to whole blood from healthy humans. Blood was agitated orbitally at low (venous shear stress: 2.8 dyne · cm-2) and high (arterial shear stress: 22.2 dyne · cm-2) agitation speeds in a well-plate based test system. Numbers of non-adherent platelets, platelet activation (P-Selectin positive platelets), platelet function (PFA100 closure times) and platelet adhesion (laser scanning microscopy (LSM)) were determined.Microscopic data and counting of the circulating cells revealed increasing numbers of material-surface adherent platelets with increasing agitation speed. Also, activation of the platelets was substantially increased when tested under the high shear conditions (P-Selectin levels, PFA-100 closure times). At low agitation speed, the platelet densities did not differ between the three materials. Tested at the high agitation speed, lowest platelet densities were observed on PDMS, intermediate levels on PET and highest on PTFE. While activation of the circulating platelets was affected by the implant surfaces in a similar manner, PFA closure times did not reflect this trend.Differences in the thrombogenicity of the studied polymers were more pronounced when tested at high agitation speed due to the induced shear stresses. Testing under varying shear stresses, thus, led to a different evaluation of the implant thrombogenicity, which emphasizes the need for testing under various flow conditions. Our data further confirmed earlier findings where the same reference implants were tested under static (and not dynamic) conditions and with fresh human platelet rich plasma instead of whole blood. This supports that the application of common reference materials may improve inter-study comparisons, even under varying test conditions.
Topics: Biocompatible Materials; Humans; Platelet Activation; Platelet Adhesiveness; Stress, Mechanical
PubMed: 30584128
DOI: 10.3233/CH-189410 -
Cephalalgia : An International Journal... Jul 2005As migraine is the result of an inflammatory mechanism with serotonergic signalling, leucocyte function, platelet function and intercellular communication between those... (Clinical Trial)
Clinical Trial
As migraine is the result of an inflammatory mechanism with serotonergic signalling, leucocyte function, platelet function and intercellular communication between those cells is likely to be connected to the final pathway of the disease. We examined P-selectin expression on platelets (platelet activation) and leucocyte-platelet aggregate formation in 72 migraine patients during their attack-free interval and controls using a flow cytometric assay. Patients suffering from migraine without aura had a significantly increased platelet activation and leucocyte-platelet aggregation compared with the control group, unlike the migraine patients with aura. Patients who had taken a triptan within 3 days prior to the investigation showed platelet activation values similar to the control group. The variations in platelet activation patterns of migraine subgroups could indicate different pathomechanisms. Even outside an attack, migraine patients, particularly those without aura, show an increased level of platelet activation which seems to be down-regulated by triptans. This mechanism may account for the triptan-induced increases in headache frequency. The involvement of proinflammatory platelet-leucocyte cross-talk suggests a possible therapeutic strategy using anti-inflammatory drugs.
Topics: Female; Humans; Male; Middle Aged; Migraine with Aura; Migraine without Aura; Neutrophil Activation; Platelet Activation; Platelet Aggregation; Tryptamines
PubMed: 15955041
DOI: 10.1111/j.1468-2982.2005.00916.x -
Biomaterials Nov 2021Major blood loss still is a risk factor during surgery. Electrocauterization often is used for necrotizing the tissue and thereby halts bleeding (hemostasis). However,...
Major blood loss still is a risk factor during surgery. Electrocauterization often is used for necrotizing the tissue and thereby halts bleeding (hemostasis). However, the carbonized tissue is prone to falling off, putting patients at risk of severe side effects, such as dangerous internal bleeding many hours after surgery. We have developed a medical gas plasma jet technology as an alternative to electrocauterization and investigated its hemostatic (blood clotting) effects and mechanisms of action using whole human blood. The gas plasma efficiently coagulated anticoagulated donor blood, which resulted from the local lysis of red blood cells (hemolysis). Image cytometry further showed enhanced platelet aggregation. Gas plasmas release reactive oxygen species (ROS), but neither scavenging of long-lived ROS nor addition of chemically-generated ROS were able to abrogate or recapitulate the gas plasma effect, respectively. However, platelet activation was markedly impaired in platelet-rich plasma when compared to gas plasma-treated whole blood that moreover contained significant amounts of hemoglobin indicative of red blood cell lysis (hemolysis). Finally, incubation of whole blood with concentration-matched hemolysates phenocopied the gas plasmas-mediated platelet activation. These results will spur the translation of plasma systems for hemolysis into clinical practice.
Topics: Blood Coagulation; Blood Platelets; Hemostasis; Hemostatics; Humans; Platelet Activation; Platelet Aggregation
PubMed: 34562836
DOI: 10.1016/j.biomaterials.2020.120433 -
Circulation Research Jul 2019
Topics: Cerebellum; Conditioning, Classical; Platelet Activation; Platelet Aggregation; Reward; Rivaroxaban; Thromboxane A2
PubMed: 31268853
DOI: 10.1161/CIRCRESAHA.119.315453 -
Clinical Hemorheology and... 2017Interaction of von Willebrand factor (VWF) with circulating platelets is the trigger for thrombosis in a region of arterial stenosis. These events are typically studied...
BACKGROUND
Interaction of von Willebrand factor (VWF) with circulating platelets is the trigger for thrombosis in a region of arterial stenosis. These events are typically studied in vitro under conditions where platelets adhere to a VWF-coated surface. Our approach assesses platelet responses in the absence of adhesion.
OBJECTIVE
To characterize extent of platelet activation and erythrocyte lysis in an artificial stenosis model.
METHODS
Whole blood is perfused through a length of polyetheretherketone tubing that includes an artificial stenosis, comprising narrow-bore (89-381 μm) tubing. Secretion of [14C] serotonin and hemoglobin release was measured to evaluate platelet activation and hemolysis respectively at various perfusion rates and different stenosis dimensions.
RESULTS
Platelet activation and erythrocyte lysis increased progressively with increasing perfusion rate and decreasing stenosis diameter; the length of the stenosis had negligible influence. Modest platelet activation (5-10% secretion of [14C] serotonin) occurred without significant erythrocyte lysis under a limited range of perfusion conditions (4-6 mL/min flow through a 127 μm stenosis).
CONCLUSIONS
Our experimental approach mimics conditions in severe arterial stenosis or a mechanical heart valve. It could be a valuable aid in the development of novel drugs to treat arterial thrombosis and in the design of heart valves.
Topics: Blood Chemical Analysis; Blood Platelets; Erythrocytes; Humans; Platelet Activation; Platelet Adhesiveness; Stress, Mechanical
PubMed: 28800323
DOI: 10.3233/CH-170256 -
Thrombosis Research Nov 2017Neuromedin U (NmU) is a pleiotropic hypothalamic neuropeptide involved in the gut-brain axis. It acts via both a Gαq/11-coupled receptor (NMUR1) and a Gαi-coupled...
Neuromedin U (NmU) is a pleiotropic hypothalamic neuropeptide involved in the gut-brain axis. It acts via both a Gαq/11-coupled receptor (NMUR1) and a Gαi-coupled receptor (NMUR2) in different cell types. Expression of both receptors was reported in platelets, but their significance for NmU signaling remains elusive. We studied the potential effects of NmU on human platelet activation. In platelet-rich plasma (PRP), NmU alone (up to 10μM) did not induce any measurable aggregation, but at nanomolar concentrations, it potentiated platelet aggregation by low (mean 0.47μM) ADP concentrations (from 25.9±3.6% to 74.8±2.7% maximal aggregation for ADP vs. ADP+NmU, 100nM, mean±SEM, n=13), accompanied by platelet P-selectin expression and intracellular calcium mobilization. Accordingly, platelet preincubation with NmU for 2min sensitized platelets for subsequent activation by ADP. When P2Y was inactivated by 50μM MRS2179, NmU comparably potentiated ADP-induced PRP aggregation, suggestive of cooperative activation with Gαi-coupled P2Y. Likewise, NmU potentiated platelet aggregation by Gαi-operated epinephrine at subthreshold concentrations (99ng/ml, mean), but not that by Gαq-dependent serotonin (20μM). Platelet aggregation by NmU/epinephrine combination was fully inhibited by the Gαq inhibitor YM-254890 (1μM). qPCR detection and western blot analysis substantiated platelet expression of NMUR1 in different donors, a finding collectively complying with functionally relevant Gαq/11-mediated activation of platelet NMUR1 by NmU. Our findings advocate further studies on platelet sensitization by NmU, released during vascular activation and injury, to define its role as a modifier of platelet responsiveness to the physiological activation signals, operational in cardiovascular health and disease.
Topics: Humans; Neuropeptides; Platelet Activation; Signal Transduction
PubMed: 29078099
DOI: 10.1016/j.thromres.2017.09.027 -
Hormone Molecular Biology and Clinical... Apr 2014Platelets and their activation/inhibition mechanisms play a central role in haemostasis. It is well known agonists and antagonists of platelet activation; however,... (Review)
Review
Platelets and their activation/inhibition mechanisms play a central role in haemostasis. It is well known agonists and antagonists of platelet activation; however, during the last years novel evidences of hormone effects on platelet activation have been reported. Platelet functionality may be modulated by the interaction between different hormones and their platelet receptors, contributing to sex differences in platelet function and even in platelet-mediated vascular damage. It has suggested aspects that apparently are well established should be reviewed. Hormones effects on platelet activity are included among them. This article tries to review knowledge about the involvement of hormones in platelet biology and activity.
Topics: Catecholamines; Estrogens; Female; Gonadal Steroid Hormones; Hormones; Humans; Male; Platelet Activation; Platelet Aggregation; Platelet Aggregation Inhibitors; Sex Factors
PubMed: 25389998
DOI: 10.1515/hmbci-2013-0055 -
Coronary Artery Disease Dec 1995
Review
Topics: Animals; Constriction, Pathologic; Fibrinolytic Agents; Hemostasis; Humans; Platelet Activation; Recurrence; Streptokinase; Thrombolytic Therapy; Thrombosis; Urokinase-Type Plasminogen Activator
PubMed: 8723013
DOI: No ID Found -
Rinsho Byori. the Japanese Journal of... Sep 1999Platelet membrane glycoproteins such as GPIb and GPIa/IIa play important roles in platelet functional responses. They are the receptors for specific ligands (GPIb for... (Review)
Review
Platelet membrane glycoproteins such as GPIb and GPIa/IIa play important roles in platelet functional responses. They are the receptors for specific ligands (GPIb for von Willebrand factors, and GPIa/IIa for collagen), and the ligand-receptor interaction is the first step that elicits downstream intracellular activation signals which finally culminate in platelet aggregation. Although a variety of signal transduction pathways may be involved, tyrosine kinases appear to be most closely related to platelet activation mediated by membrane glycoproteins. Since its discovery in early 1980's, protein tyrosine phosphorylation catalyzed by tyrosine kinases has been recognized to play a role in regulating the cell function of various cells. Platelets have several Src family tyrosine kinases with an SH2 domain and an SH3 domain. Syk with two SH2 domains also appears to play an important role in platelet activation, especially in its early phase. The SH2 domain binds to a phosphorylated tyrosine residue of other proteins, and the SH3 domain recognizes proline-rich domains of target proteins, thus providing the anchoring sites for protein-protein interactions. In this article, some of the recent developments in the signal transduction pathways related with tyrosine kinases are introduced. Several signaling molecules involved in GPIb- or GPIa/IIa-mediated platelet activation have been identified. Interestingly, the members participating in these processes are distinct, suggesting a diversity of signal transduction mechanisms.
Topics: Animals; Membrane Glycoproteins; Platelet Activation; Protein-Tyrosine Kinases; Signal Transduction
PubMed: 10518415
DOI: No ID Found