Agonist-induced rises in cytosolic Ca control most platelet responses in thrombosis and hemostasis. In human platelets, we earlier demonstrated that the ORAI1-STIM1 pathway is a major component of extracellular Ca entry, in particular when induced via the ITAM-linked collagen receptor, glycoprotein VI (GPVI). In the present article, using functionally defective platelets from patients with a loss-of-function mutation in ORAI1 or STIM1, we show that Ca entry induced by the endoplasmic reticulum ATPase inhibitor, thapsigargin, fully relies on this pathway.
View Article and Find Full Text PDFThe anucleate human platelets contain a broad pattern of mRNAs and other RNA transcripts. The high quantitative similarity of mRNAs in megakaryocytes and platelets from different sources points to a common origin, and suggests a random redistribution of mRNA species upon proplatelet formation. A comparison of the classified platelet transcriptome (17.
View Article and Find Full Text PDFPlatelets are small anucleate cell fragments (2-4 μm in diameter) in the blood, which play an essential role in thrombosis and hemostasis. Genetic or acquired platelet dysfunctions are linked to bleeding, increased risk of thromboembolic events and cardiovascular diseases. Advanced proteomic approaches may pave the way to a better understanding of the roles of platelets in hemostasis, and pathophysiological processes such as inflammation, metastatic spread and thrombosis.
View Article and Find Full Text PDFIntegrin αIIbβ3 activation is essential for platelet aggregation and, accordingly, for hemostasis and arterial thrombosis. The αIIbβ3 integrin is highly expressed on platelets and requires an activation step for binding to fibrinogen, fibrin or von Willebrand factor (VWF). A current model assumes that the process of integrin activation relies on actomyosin force-dependent molecular changes from a bent-closed and extended-closed to an extended-open conformation.
View Article and Find Full Text PDFBMC Cancer
June 2022
Background: Tyrosine kinase inhibitors (TKIs), such as sunitinib, are used for cancer treatment, but may also affect platelet count and function with possible hemostatic consequences. Here, we investigated whether patient treatment with the TKI sunitinib affected quantitative and qualitative platelet traits as a function of the sunitinib level and the occurrence of bleeding.
Methods: Blood was collected from 20 metastatic renal cell carcinoma (mRCC) patients before treatment, and at 2 weeks, 4 weeks and 3 months after sunitinib administration.
Background: Prothrombin complex concentrate (PCC) is a human plasma-derived mixture of partially purified vitamin K-dependent coagulation factors (VKCF). Current therapeutic indication is treatment and perioperative prophylaxis of bleeding in acquired VKCF deficiency. Off-label uses include treatment of direct factor Xa- or thrombin inhibitor-associated bleeds, treatment of trauma-induced coagulopathy, and hemorrhagic complications in patients with liver disease.
View Article and Find Full Text PDFJ Proteome Res
April 2022
Fibrinogen γ' accounts for 3% to 40% of plasma fibrinogen. Earlier studies indicated that fibrinogen γ' forms altered fibrin clots under static conditions, whereas clinically, altered plasma γ' levels are associated with arterial and venous thrombosis. However, the effects of static vs flow conditions on the role of γ' throughout the pathophysiological range is unknown.
View Article and Find Full Text PDFNovel platelet and megakaryocyte transcriptome analysis allows prediction of the full or theoretical proteome of a representative human platelet. Here, we integrated the established platelet proteomes from six cohorts of healthy subjects, encompassing 5.2 k proteins, with two novel genome-wide transcriptomes (57.
View Article and Find Full Text PDFIntroduction: Current developments to assess qualitative and quantitative platelet traits in flowed whole-blood are based on microfluidic devices that mostly operate at room temperature. However, operation at physiological temperature (37 °C) may increase the assay's sensitivity, and facilitates the comparison to other platelet function tests of the diagnostic laboratory.
Materials And Methods: We adapted the conventional microspot-based microfluidic device with a simple thermo-coupled pre-heating module.
Background: Polycythaemia vera is a myeloproliferative neoplasm characterised by a high incidence of thrombosis. The contribution of platelets, key players in haemostasis, in this setting is still unclear. So far, the majority of studies have been focussed on specific platelet abnormalities but not on their actual capacity to form thrombi.
View Article and Find Full Text PDFHyperlipidemia is a well-established risk factor for cardiovascular diseases. Millions of people worldwide display mildly elevated levels of plasma lipids and cholesterol linked to diet and life-style. While the prothrombotic risk of severe hyperlipidemia has been established, the effects of moderate hyperlipidemia are less clear.
View Article and Find Full Text PDFObjective: Fibrin is considered to strengthen thrombus formation via integrin αIIbβ3, but recent findings indicate that fibrin can also act as ligand for platelet glycoprotein VI. Approach and Results: To investigate the thrombus-forming potential of fibrin and the roles of platelet receptors herein, we generated a range of immobilized fibrin surfaces, some of which were cross-linked with factor XIIIa and contained VWF-BP (von Willebrand factor-binding peptide). Multicolor microfluidics assays with whole-blood flowed at high shear rate (1000 s) indicated that the fibrin surfaces, regardless of the presence of factor XIIIa or VWF-BP, supported platelet adhesion and activation (P-selectin expression), but only microthrombi were formed consisting of bilayers of platelets.
View Article and Find Full Text PDFPatients diagnosed with pseudohypoparathyroidism type Ia (PHP Ia) suffer from hormonal resistance and abnormal postural features, in a condition classified as Albright hereditary osteodystrophy (AHO) syndrome. This syndrome is linked to a maternally inherited mutation in the GNAS complex locus, encoding for the GTPase subunit Gsα. Here, we investigated how platelet phenotype and omics analysis can assist in the often difficult diagnosis.
View Article and Find Full Text PDFMicrofluidic assays are versatile tests which, using only small amounts of blood, enable high throughput analyses of platelet function in several minutes. In combination with fluorescence microscopy, these flow tests allow real-time visualisation of platelet activation with the possibility of examining combinatorial effects of wall shear rate, coagulation and modulation by endothelial cells. In particular, the ability to use blood and blood cells from healthy subjects or patients makes this technology promising, both for research and (pre)clinical diagnostic purposes.
View Article and Find Full Text PDFAntithrombotic therapies reduce cardiovascular diseases by preventing arterial thrombosis and thromboembolism, but at expense of increased bleeding risks. Arterial thrombosis studies using genetically modified mice have been invaluable for identification of new molecular targets. Because of low sample sizes and heterogeneity in approaches or methodologies, a formal meta-analysis to compare studies of mice with single-gene defects encountered major limitations.
View Article and Find Full Text PDFThe platelet receptors glycoprotein Ibα (GPIbα) and GPVI are known to be cleaved by members of a disintegrin and metalloprotease (ADAM) family (ADAM10 and ADAM17), but the mechanisms and consequences of this shedding are not well understood. Our results revealed that (1) glycoprotein shedding is confined to distinct platelet populations showing near-complete shedding, (2) the heterogeneity between (non)shed platelets is independent of agonist type but coincides with exposure of phosphatidylserine (PS), and (3) distinct pathways of shedding are induced by elevated Ca, low Ca protein kinase C (PKC), or apoptotic activation. Furthermore, we found that receptor shedding reduces binding of von Willebrand factor, enhances binding of coagulation factors, and augments fibrin formation.
View Article and Find Full Text PDFRes Pract Thromb Haemost
July 2018
Platelets interact with the coagulation system in a multitude of ways, not only during the phases of thrombus formation, but also in specific areas within a formed thrombus. This review discusses current concepts of platelet control of thrombin generation, fibrin formation and structure, and anticoagulation. Indicated are how combined signalling via the platelet receptors for collagen (glycoprotein VI) and thrombin induces the secretion of (anti)coagulation factors, as well as surface exposure of phosphatidylserine, thereby catalysing thrombin generation.
View Article and Find Full Text PDFAMP-activated protein kinase (AMPK) α1 is activated in platelets on thrombin or collagen stimulation, and as a consequence, phosphorylates and inhibits acetyl-CoA carboxylase (ACC). Because ACC is crucial for the synthesis of fatty acids, which are essential for platelet activation, we hypothesized that this enzyme plays a central regulatory role in platelet function. To investigate this, we used a double knock-in (DKI) mouse model in which the AMPK phosphorylation sites Ser79 on ACC1 and Ser212 on ACC2 were mutated to prevent AMPK signaling to ACC.
View Article and Find Full Text PDFSevere thrombocytopenia (≤50×10 platelets/L) due to hematological malignancy and intensive chemotherapy is associated with an increased risk of clinically significant bleeding. Since the bleeding risk is not linked to the platelet count only, other hemostatic factors must be involved. We studied platelet function in 77 patients with acute leukemia, multiple myeloma or malignant lymphoma, who experienced chemotherapy-induced thrombocytopenia.
View Article and Find Full Text PDFPlatelets are the smallest cells within the circulating blood with key roles in physiological hemostasis and pathological thrombosis regulated by the onset of activating/inhibiting processes via receptor responses and signaling cascades. Areas covered: Proteomics as well as genomic approaches have been fundamental in identifying and quantifying potential targets for future diagnostic strategies in the prevention of bleeding and thrombosis, and uncovering the complexity of platelet functions in health and disease. In this article, we provide a critical overview on current functional tests used in diagnostics and the future perspectives for platelet proteomics in clinical applications.
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