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Nagy M, van Geffen JP, Stegner D, Adams DJ, Braun A, de Witt SM, Elvers M, Geer MJ, Kuijpers MJE, Kunzelmann K, Mori J, Oury C, Pircher J, Pleines I, Poole AW, Senis YA, Verdoold R, Weber C, Nieswandt B, Heemskerk JWM, Baaten CCFMJ. Comparative Analysis of Microfluidics Thrombus Formation in Multiple Genetically Modified Mice: Link to Thrombosis and Hemostasis. Front Cardiovasc Med 2019; 6:99. [PMID: 31417909 PMCID: PMC6682619 DOI: 10.3389/fcvm.2019.00099] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Accepted: 07/03/2019] [Indexed: 12/15/2022] Open
Abstract
Genetically modified mice are indispensable for establishing the roles of platelets in arterial thrombosis and hemostasis. Microfluidics assays using anticoagulated whole blood are commonly used as integrative proxy tests for platelet function in mice. In the present study, we quantified the changes in collagen-dependent thrombus formation for 38 different strains of (genetically) modified mice, all measured with the same microfluidics chamber. The mice included were deficient in platelet receptors, protein kinases or phosphatases, small GTPases or other signaling or scaffold proteins. By standardized re-analysis of high-resolution microscopic images, detailed information was obtained on altered platelet adhesion, aggregation and/or activation. For a subset of 11 mouse strains, these platelet functions were further evaluated in rhodocytin- and laminin-dependent thrombus formation, thus allowing a comparison of glycoprotein VI (GPVI), C-type lectin-like receptor 2 (CLEC2) and integrin α6β1 pathways. High homogeneity was found between wild-type mice datasets concerning adhesion and aggregation parameters. Quantitative comparison for the 38 modified mouse strains resulted in a matrix visualizing the impact of the respective (genetic) deficiency on thrombus formation with detailed insight into the type and extent of altered thrombus signatures. Network analysis revealed strong clusters of genes involved in GPVI signaling and Ca2+ homeostasis. The majority of mice demonstrating an antithrombotic phenotype in vivo displayed with a larger or smaller reduction in multi-parameter analysis of collagen-dependent thrombus formation in vitro. Remarkably, in only approximately half of the mouse strains that displayed reduced arterial thrombosis in vivo, this was accompanied by impaired hemostasis. This was also reflected by comparing in vitro thrombus formation (by microfluidics) with alterations in in vivo bleeding time. In conclusion, the presently developed multi-parameter analysis of thrombus formation using microfluidics can be used to: (i) determine the severity of platelet abnormalities; (ii) distinguish between altered platelet adhesion, aggregation and activation; and (iii) elucidate both collagen and non-collagen dependent alterations of thrombus formation. This approach may thereby aid in the better understanding and better assessment of genetic variation that affect in vivo arterial thrombosis and hemostasis.
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van Geffen JP, Brouns SLN, Batista J, McKinney H, Kempster C, Nagy M, Sivapalaratnam S, Baaten CCFMJ, Bourry N, Frontini M, Jurk K, Krause M, Pillitteri D, Swieringa F, Verdoold R, Cavill R, Kuijpers MJE, Ouwehand WH, Downes K, Heemskerk JWM. High-throughput elucidation of thrombus formation reveals sources of platelet function variability. Haematologica 2018; 104:1256-1267. [PMID: 30545925 PMCID: PMC6545858 DOI: 10.3324/haematol.2018.198853] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 12/05/2018] [Indexed: 01/25/2023] Open
Abstract
In combination with microspotting, whole-blood microfluidics can provide high-throughput information on multiple platelet functions in thrombus formation. Based on assessment of the inter- and intra-subject variability in parameters of microspot-based thrombus formation, we aimed to determine the platelet factors contributing to this variation. Blood samples from 94 genotyped healthy subjects were analyzed for conventional platelet phenotyping: i.e. hematologic parameters, platelet glycoprotein (GP) expression levels and activation markers (24 parameters). Furthermore, platelets were activated by ADP, CRP-XL or TRAP. Parallel samples were investigated for whole-blood thrombus formation (6 microspots, providing 48 parameters of adhesion, aggregation and activation). Microspots triggered platelet activation through GP Ib-V-IX, GPVI, CLEC-2 and integrins. For most thrombus parameters, inter-subject variation was 2-4 times higher than the intra-subject variation. Principal component analyses indicated coherence between the majority of parameters for the GPVI-dependent microspots, partly linked to hematologic parameters, and glycoprotein expression levels. Prediction models identified parameters per microspot that were linked to variation in agonist-induced αIIbβ3 activation and secretion. Common sequence variation of GP6 and FCER1G, associated with GPVI-induced αIIbβ3 activation and secretion, affected parameters of GPVI-and CLEC-2-dependent thrombus formation. Subsequent analysis of blood samples from patients with Glanzmann thrombasthenia or storage pool disease revealed thrombus signatures of aggregation-dependent parameters that were subject-dependent, but not linked to GPVI activity. Taken together, this high-throughput elucidation of thrombus formation revealed patterns of inter-subject differences in platelet function, which were partly related to GPVI-induced activation and common genetic variance linked to GPVI, but also included a distinct platelet aggregation component.
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Tullemans BME, Nagy M, Sabrkhany S, Griffioen AW, Oude Egbrink MGA, Aarts M, Heemskerk JWM, Kuijpers MJE. Tyrosine Kinase Inhibitor Pazopanib Inhibits Platelet Procoagulant Activity in Renal Cell Carcinoma Patients. Front Cardiovasc Med 2018; 5:142. [PMID: 30460241 PMCID: PMC6232667 DOI: 10.3389/fcvm.2018.00142] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 09/24/2018] [Indexed: 01/03/2023] Open
Abstract
Pazopanib is an angiostatic tyrosine kinase inhibitor (TKI) presently used for cancer treatment, particularly in patients with renal cell carcinoma (RCC). This treatment can be accompanied by mild bleeding as an adverse effect. Given the role of protein tyrosine kinases in platelet activation processes, we investigated whether and how pazopanib can affect platelet functions in purified systems and during treatment of advanced RCC patients. In isolated platelets from healthy volunteers, pazopanib dose-dependently reduced collagen-induced integrin activation and secretion, as well as platelet aggregation. Pazopanib addition diminished glycoprotein (GP) VI-dependent tyrosine phosphorylation of multiple platelet proteins, including the tyrosine kinase Syk. Furthermore, pazopanib inhibited GPVI-induced Ca2+ elevation, resulting in reduced exposure of the procoagulant phospholipid phosphatidylserine (PS). Upon perfusion of control blood over a collagen surface, pazopanib inhibited thrombus size as well as PS exposure. Blood samples from 10 RCC patients were also analyzed before and after 14 days of pazopanib treatment as monotherapy. This treatment caused an overall lowering in platelet count, with 3 out of 10 patients experiencing mild bleeding. Platelets isolated from pazopanib-treated patients showed a significant lowering of PS exposure upon activation. In addition, platelet procoagulant activity was inhibited in thrombi formed under flow conditions. Control experiments indicated that higher pazopanib concentrations were required to inhibit GPVI-mediated PS exposure in the presence of plasma. Together, these results indicated that pazopanib suppresses GPVI-induced platelet activation responses in a way partly antagonized by the presence of plasma. In treated cancer patients, pazopanib effects were confined to a reduction in GPVI-dependent PS exposure. Together with the reduced platelet count, this may explain the mild bleeding tendency observed in pazopanib-treated patients.
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Tullemans BME, Heemskerk JWM, Kuijpers MJE. Acquired platelet antagonism: off-target antiplatelet effects of malignancy treatment with tyrosine kinase inhibitors. J Thromb Haemost 2018; 16:1686-1699. [PMID: 29975003 DOI: 10.1111/jth.14225] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2018] [Indexed: 12/26/2022]
Abstract
Platelets can contribute to tumor progression and metastasis. Cancer patients are at increased risk of thrombosis, and advanced stages of cancer are associated with thrombocytosis or increased platelet reactivity. Tyrosine kinase inhibitors (TKIs) are widely used as a targeted strategy for cancer treatment, with the aim of prolonging progression-free survival of the patients. Because of their broad kinase target spectrum, most TKIs inevitably have off-target effects. Platelets rely on tyrosine kinase activity for their activation. Frequently observed side effects are lowering of platelet count and inhibition of platelet functions, whether or not accompanied by an increased bleeding risk. In this review, we aim to give insights into: (i) 38 TKIs that are currently used for the treatment of different types of cancer, either on the market or in clinical trials; (ii) how distinct TKIs can inhibit activation mechanisms in platelets; and (iii) the clinical consequences of the antiplatelet effects of TKI treatment. For several TKIs, the knowledge on affinity for their targets does not align with the published effects on platelets and reported bleeding events. This review should raise awareness of the potential antiplatelet effects of several TKIs, which will be enhanced in the presence of antithrombotic drugs.
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Sabrkhany S, Kuijpers MJE, Knol JC, Olde Damink SWM, Dingemans AMC, Verheul HM, Piersma SR, Pham TV, Griffioen AW, Oude Egbrink MGA, Jimenez CR. Exploration of the platelet proteome in patients with early-stage cancer. J Proteomics 2018; 177:65-74. [PMID: 29432918 DOI: 10.1016/j.jprot.2018.02.011] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 12/29/2017] [Accepted: 02/05/2018] [Indexed: 02/07/2023]
Abstract
Platelets play an important role in tumor growth and, at the same time, platelet characteristics are affected by cancer presence. Therefore, we investigated whether the platelet proteome harbors differentially expressed proteins associated with early-stage cancer. For this proof-of-concept study, patients with early-stage lung (n = 8) or head of pancreas cancer (n = 4) were included, as were healthy sex- and age-matched controls for both subgroups. Blood samples were collected from controls and from patients before surgery. Furthermore, from six of the patients, a second sample was collected two months after surgery. NanoLC-MS/MS-based proteomics of gel-fractionated platelet proteins was used for comparative spectral count analyses of patients to controls and before to after surgery samples. The total platelet proteome dataset included 4384 unique proteins of which 85 were significantly (criteria Fc > 1.5 and p < 0.05) changed in early-stage cancer compared to controls. In addition, the levels of 81 platelet proteins normalized after tumor resection. When filtering for the most discriminatory proteins, we identified seven promising platelet proteins associated with early-stage cancer. In conclusion, this pioneering study on the platelet proteome in cancer patients clearly identifies platelets as a new source of candidate protein biomarkers of early-stage cancer. BIOLOGICAL SIGNIFICANCE Currently, most blood-based diagnostics/biomarker research is performed in serum or plasma, while the content of blood cells is usually neglected. It is known that especially blood platelets, which are the main circulating pool of many bioactive proteins, such as growth factors, chemokines, and cytokines, are a potentially rich source of biomarkers. The current study is the first to measure the effect of early-stage cancer on the platelet proteome of patients. Our study demonstrates that the platelet proteome of patients with early-stage lung or head of pancreas cancer differs considerably compared to that of healthy individuals of matched sex and age. In addition, the platelet proteome of cancer patients normalized after surgical resection of the tumor. Exploiting platelet proteome differences linked to both tumor presence and disease status, we were able to demonstrate that the platelet proteome can be mined for potential biomarkers of cancer.
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Sabrkhany S, Griffioen AW, Pineda S, Sanders L, Mattheij N, van Geffen JP, Aarts MJ, Heemskerk JWM, Oude Egbrink MGA, Kuijpers MJE. Sunitinib uptake inhibits platelet function in cancer patients. Eur J Cancer 2016; 66:47-54. [PMID: 27525572 DOI: 10.1016/j.ejca.2016.07.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 06/09/2016] [Accepted: 07/05/2016] [Indexed: 12/14/2022]
Abstract
BACKGROUND Sunitinib is an oral tyrosine kinase inhibitor used for cancer treatment. Patients treated with sunitinib are at higher bleeding risk. As tyrosine kinases are essential for platelet signalling, the effects of sunitinib on platelet function in vitro and in cancer patients on treatment were investigated. PATIENTS AND METHODS Blood samples were collected from eight healthy volunteers and eight patients diagnosed with metastatic renal cell cancer (RCC) before and 2 weeks on treatment with sunitinib. Platelets from 15 additional healthy individuals were preincubated with sunitinib or vehicle to perform in vitro experiments. Immunofluorescence imaging, western blotting, light transmission aggregometry, whole blood perfusion over collagen, flow cytometry and ELISA were performed. RESULTS Confocal microscopy indicated that platelets sequester sunitinib in vitro and in patients. In platelets from healthy controls, tyrosine phosphorylation was inhibited by sunitinib. Also, sunitinib dose dependently reduced collagen- and ADP-induced aggregation, collagen-dependent thrombus formation and collagen-induced secretion of platelet-derived growth factor and β-thromboglobulin. In blood from RCC patients before treatment, thrombus formation and procoagulant activity under flow were 47% and 80% higher than in healthy controls. After 14 d of sunitinib treatment, platelet count was moderately, but significantly decreased (from 243 to 144 × 10(9)/l). At the same time, collagen-induced platelet aggregation as well as thrombus formation and phosphatidylserine exposure under flow were significantly reduced (by 45%, 16% and 61%, respectively). CONCLUSIONS Sunitinib uptake by platelets inhibits collagen receptor-induced aggregation and thrombus formation via reduction of protein tyrosine phosphorylation and α-granule secretion. This dysfunction may contribute to the higher bleeding tendency observed in sunitinib-treated patients.
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Mattheij NJA, Braun A, van Kruchten R, Castoldi E, Pircher J, Baaten CCFMJ, Wülling M, Kuijpers MJE, Köhler R, Poole AW, Schreiber R, Vortkamp A, Collins PW, Nieswandt B, Kunzelmann K, Cosemans JMEM, Heemskerk JWM. Survival protein anoctamin-6 controls multiple platelet responses including phospholipid scrambling, swelling, and protein cleavage. FASEB J 2016; 30:727-37. [PMID: 26481309 DOI: 10.1096/fj.15-280446] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2015] [Accepted: 10/05/2015] [Indexed: 11/11/2022]
Abstract
Scott syndrome is a rare bleeding disorder, characterized by altered Ca(2+)-dependent platelet signaling with defective phosphatidylserine (PS) exposure and microparticle formation, and is linked to mutations in the ANO6 gene, encoding anoctamin (Ano)6. We investigated how the complex platelet phenotype of this syndrome is linked to defective expression of Anos or other ion channels. Mice were generated with heterozygous of homozygous deficiency in Ano6, Ano1, or Ca(2+)-dependent KCa3.1 Gardos channel. Platelets from these mice were extensively analyzed on molecular functions and compared with platelets from a patient with Scott syndrome. Deficiency in Ano1 or Gardos channel did not reduce platelet responses compared with control mice (P > 0.1). In 2 mouse strains, deficiency in Ano6 resulted in reduced viability with increased bleeding time to 28.6 min (control 6.4 min, P < 0.05). Platelets from the surviving Ano6-deficient mice resembled platelets from patients with Scott syndrome in: 1) normal collagen-induced aggregate formation (P > 0.05) with reduced PS exposure (-65 to 90%); 2) lowered Ca(2+)-dependent swelling (-80%) and membrane blebbing (-90%); 3) reduced calpain-dependent protein cleavage (-60%); and 4) moderately affected apoptosis-dependent PS exposure. In conclusion, mouse deficiency of Ano6 but not of other channels affects viability and phenocopies the complex changes in platelets from hemostatically impaired patients with Scott syndrome.
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Gerdes N, Seijkens T, Lievens D, Kuijpers MJE, Winkels H, Projahn D, Hartwig H, Beckers L, Megens RTA, Boon L, Noelle RJ, Soehnlein O, Heemskerk JWM, Weber C, Lutgens E. Platelet CD40 Exacerbates Atherosclerosis by Transcellular Activation of Endothelial Cells and Leukocytes. Arterioscler Thromb Vasc Biol 2016; 36:482-90. [PMID: 26821950 DOI: 10.1161/atvbaha.115.307074] [Citation(s) in RCA: 79] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 01/06/2016] [Indexed: 12/22/2022]
Abstract
OBJECTIVE Beyond their eminent role in hemostasis and thrombosis, platelets are recognized as mediators of inflammation. Platelet cluster of differentiation 40 (CD40) ligand (CD40L and CD154) plays a key role in mediating platelet-induced inflammation in atherosclerosis. CD40, the receptor for CD40L, is present on platelets; however, the role of CD40 on this cell type is until now undefined. APPROACH AND RESULTS We found that in both mice and humans, platelet CD40 mediates the formation of platelet-leukocyte aggregates and the release of chemokine (C-X-C motif) ligand 4. Leukocytes were also less prone to adhere to CD40-deficient thrombi. However, platelet CD40 was not involved in platelet aggregation. Activated platelets isolated from Cd40(-/-)Apoe(-/-) mice adhered less to the endothelium upon injection into Apoe(-/-) mice when compared with CD40-sufficient platelets. Furthermore, lack of CD40 on injected platelets led to reduced leukocyte recruitment to the carotid artery as assayed by intravital microscopy. This was accompanied by a decrease in endothelial vascular cell adhesion molecule-1, platelet endothelial cell adhesion molecule, VE-cadherin, and P-selectin expression. To investigate the effect of platelet CD40 in atherosclerosis, Apoe(-/-) mice received thrombin-activated Apoe(-/-) or Cd40(-/-)Apoe(-/-) platelets every 5 days for 12 weeks, starting at the age of 17 weeks, when atherosclerotic plaques had already formed. When compared with mice that received Apoe(-/-) platelets, those receiving Cd40(-/-)Apoe(-/-) platelets exhibited a >2-fold reduction in atherosclerosis. Plaques of mice receiving CD40-deficient platelets were less advanced, contained less macrophages, neutrophils, and collagen, and displayed smaller lipid cores. CONCLUSIONS Platelet CD40 plays a crucial role in inflammation by stimulating leukocyte activation and recruitment and activation of endothelial cells, thereby promoting atherosclerosis.
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Sabrkhany S, Kuijpers MJE, Verheul HMW, Griffioen AW, oude Egbrink MGA. Platelets: an unexploited data source in biomarker research. LANCET HAEMATOLOGY 2015; 2:e512-3. [DOI: 10.1016/s2352-3026(15)00225-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 10/12/2015] [Accepted: 10/15/2015] [Indexed: 10/22/2022]
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Swieringa F, Kuijpers MJE, Lamers MME, van der Meijden PEJ, Heemskerk JWM. Rate-limiting roles of the tenase complex of factors VIII and IX in platelet procoagulant activity and formation of platelet-fibrin thrombi under flow. Haematologica 2015; 100:748-56. [PMID: 25769543 DOI: 10.3324/haematol.2014.116863] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Accepted: 03/10/2015] [Indexed: 11/09/2022] Open
Abstract
The importance of factor Xa generation in thrombus formation has not been studied extensively so far. Here, we used mice deficient in either factor VIII or factor IX to determine the role of platelet-stimulated tenase activity in the formation of platelet-fibrin thrombi on collagen. With tissue factor present, deficiency in factor VIII or IX markedly suppressed thrombus growth, fibrin formation and platelet procoagulant activity (phosphatidylserine exposure). In either case, residual fibrin formation was eliminated in the absence of tissue factor. Effects of factor deficiencies were antagonized by supplementation of the missing coagulation factor. In wild-type thrombi generated under flow, phosphatidylserine-exposing platelets bound (activated) factor IX and factor X, whereas factor VIII preferentially co-localized at sites of von Willebrand factor binding. Furthermore, proteolytic activity of the generated activated factor X and thrombin was confined to the sites of phosphatidylserine exposure. With blood from a hemophilia A or B patient, the formation of platelet-fibrin thrombi was greatly delayed and reduced, even in the presence of high concentrations of tissue factor. A direct activated factor X inhibitor, rivaroxaban, added to human blood, suppressed both thrombin and fibrin formation. Together, these data point to a potent enforcement loop in thrombus formation due to factor X activation, subsequent thrombin and fibrin generation, causing activated factor X-mediated stimulation of platelet phosphatidylserine exposure. This implies that the factor VIII/factor IX-dependent stimulation of platelet procoagulant activity is a limiting factor for fibrin formation under flow conditions, even at high tissue factor concentrations.
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van Montfoort ML, Kuijpers MJE, Knaup VL, Bhanot S, Monia BP, Roelofs JJTH, Heemskerk JWM, Meijers JCM. Factor XI regulates pathological thrombus formation on acutely ruptured atherosclerotic plaques. Arterioscler Thromb Vasc Biol 2014; 34:1668-73. [PMID: 24947525 DOI: 10.1161/atvbaha.114.303209] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
OBJECTIVE Coagulation factor XI is proposed as therapeutic target for anticoagulation. However, it is still unclear whether the antithrombotic properties of factor XI inhibitors influence atherosclerotic disease and atherothrombosis. Our aim is to investigate whether factor XI antisense oligonucleotides could prevent thrombus formation on acutely ruptured atherosclerotic plaques. APPROACH AND RESULTS Atherosclerotic plaques in the carotid arteries of Apoe(-/-) mice were acutely ruptured using ultrasound. The subsequent thrombus formation was visualized and quantified by intravital microscopy and immunohistochemistry. Mice were pretreated with either factor XI antisense or nonsense oligonucleotides (50 mg/kg) to lower factor XI plasma levels. A tail bleeding assay was used to determine the safety. On plaque rupture, initial platelet adhesion and platelet plug formation were not impaired in animals treated with factor XI antisense oligonucleotides. However, the ensuing thrombus formation and fibrin deposition were significantly lower after 5 to 10 minutes (P<0.05) in factor XI antisense oligonucleotide-treated animals without inducing a bleeding tendency. Furthermore, thrombi from antisense-treated animals were less stable than thrombi from placebo-treated animals. Moreover, macrophage infiltration and collagen deposition were lower in the carotid arteries of factor XI antisense-treated animals. No neutrophils were present. CONCLUSIONS Factor XI antisense oligonucleotides safely prevent thrombus formation on acutely ruptured atherosclerotic plaques in mice. Furthermore, perturbed carotid arteries from factor XI antisense-treated animals show a less severe inflammatory response.
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Kuijpers MJE, van der Meijden PEJ, Feijge MAH, Mattheij NJA, May F, Govers-Riemslag J, Meijers JCM, Heemskerk JWM, Renné T, Cosemans JMEM. Factor XII regulates the pathological process of thrombus formation on ruptured plaques. Arterioscler Thromb Vasc Biol 2014; 34:1674-80. [PMID: 24855058 DOI: 10.1161/atvbaha.114.303315] [Citation(s) in RCA: 97] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Atherothrombosis is the main cause of myocardial infarction and ischemic stroke. Although the extrinsic (tissue factor-factor VIIa [FVIIa]) pathway is considered as a major trigger of coagulation in atherothrombosis, the role of the intrinsic coagulation pathway via coagulation FXII herein is unknown. Here, we studied the roles of the extrinsic and intrinsic coagulation pathways in thrombus formation on atherosclerotic plaques both in vivo and ex vivo. APPROACH AND RESULTS Plaque rupture after ultrasound treatment evoked immediate formation of subocclusive thrombi in the carotid arteries of Apoe(-/-) mice, which became unstable in the presence of structurally different FXIIa inhibitors. In contrast, inhibition of FVIIa reduced thrombus size at a more initial stage without affecting embolization. Genetic deficiency in FXII (human and mouse) or FXI (mouse) reduced ex vivo whole-blood thrombus and fibrin formation on immobilized plaque homogenates. Localization studies by confocal microscopy indicated that FXIIa bound to thrombi and fibrin particularly in luminal-exposed thrombus areas. CONCLUSIONS The FVIIa- and FXIIa-triggered coagulation pathways have distinct but complementary roles in atherothrombus formation. The tissue factor-FVIIa pathway contributes to initial thrombus buildup, whereas FXIIa bound to thrombi ensures thrombus stability.
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van Kruchten R, Braun A, Feijge MAH, Kuijpers MJE, Rivera-Galdos R, Kraft P, Stoll G, Kleinschnitz C, Bevers EM, Nieswandt B, Heemskerk JWM. Antithrombotic potential of blockers of store-operated calcium channels in platelets. Arterioscler Thromb Vasc Biol 2012; 32:1717-23. [PMID: 22580895 DOI: 10.1161/atvbaha.111.243907] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Platelet Orai1 channels mediate store-operated Ca(2+) entry (SOCE), which is required for procoagulant activity and arterial thrombus formation. Pharmacological blockage of these channels may provide a novel way of antithrombotic therapy. Therefore, the thromboprotective effect of SOCE blockers directed against platelet Orai1 is determined. METHODS AND RESULTS Candidate inhibitors were screened for their effects on SOCE in washed human platelets. Tested antagonists included the known compounds, SKF96365, 2-aminoethyl diphenylborate, and MRS1845 and the novel compounds, Synta66 and GSK-7975A. The potency of SOCE inhibition was in the order of Synta66>2-aminoethyl diphenylborate>GSK-7975A>SKF96365>MRS1845. The specificity of the first 3 compounds was verified with platelets from Orai1-deficient mice. Inhibitory activity on procoagulant activity and high-shear thrombus formation was assessed in plasma and whole blood. In the presence of plasma, all 3 compounds suppressed platelet responses and restrained thrombus formation under flow. Using a murine stroke model, arterial thrombus formation was provoked in vivo by transient middle cerebral artery occlusion. Postoperative administration of 2-aminoethyl diphenylborate markedly diminished brain infarct size. CONCLUSIONS Plasma-soluble SOCE blockers such as 2-aminoethyl diphenylborate suppress platelet-dependent coagulation and thrombus formation. The platelet Orai1 channel is a novel target for preventing thrombotic events causing brain infarction.
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Kuijpers MJE, Heemskerk JWM. Intravital imaging of thrombus formation in small and large mouse arteries: experimentally induced vascular damage and plaque rupture in vivo. Methods Mol Biol 2012; 788:3-19. [PMID: 22130696 DOI: 10.1007/978-1-61779-307-3_1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Intravital fluorescence microscopy is increasingly used to measure experimental arterial thrombosis in large and small arteries of mice in vivo. This chapter describes protocols for applying this technology to detect and measure thrombi formed by: (1) ultrasound-induced rupture of an atherosclerotic plaque in the carotid artery of adult Apoe (-/-) mice; (2) FeCl(3) or ligation in the carotid artery of nonatherosclerotic mice; and (3) FeCl(3) in the mesenteric venules and arterioles of young mice. In addition, we describe a protocol using two-photon laser scanning microscopy for intraluminal scanning of thrombi formed in the carotid artery. These approaches provide important information that cannot be obtained with ex vivo methods and thus are likely to lead to new insights into the complex process of thrombosis.
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Kuijpers MJE, Megens RTA, Nikookhesal E, Feijge MAH, De Mey JGR, oude Egbrink MGA, van Giezen JJJ, Heemskerk JWM. Role of newly formed platelets in thrombus formation in rat after clopidogrel treatment: comparison to the reversible binding P2Y₁₂ antagonist ticagrelor. Thromb Haemost 2011; 106:1179-88. [PMID: 22071958 DOI: 10.1160/th11-04-0252] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2011] [Accepted: 09/12/2011] [Indexed: 01/29/2023]
Abstract
Platelet P2Y₁₂ receptors play an important role in arterial thrombosis by stimulating thrombus growth. Both irreversibly (clopidogrel) and reversibly binding (ticagrelor, AZD6140) P2Y₁₂ antagonists are clinically used for restricted periods, but possible differences in platelet function recovery after drug cessation have not been investigated. We treated WKY rats with a single, high dose of 200 mg/kg clopidogrel or 40 mg/kg ticagrelor. Blood was collected at different time points after treatment. Flow cytometry confirmed full platelet protection against ADP-induced αIIbβ₃ activation shortly after clopidogrel or ticagrelor treatment. At later time points after clopidogrel treatment, a subpopulation of juvenile platelets appeared that was fully responsive to ADP. Addition of ticagrelor to clopidogrel-treated blood reduced αIIbβ₃ activation of the unprotected platelets. In contrast, at later time points after ticagrelor treatment, all platelets gradually lost their protection against ADP activation. Perfusion experiments showed abolishment of thrombus formation shortly after clopidogrel or ticagrelor treatment. Thrombus formation on collagen was determined under high shear flow conditions. At later time points, large thrombi formed in the clopidogrel but not in the ticagrelor group, and unprotected, juvenile platelets preferentially incorporated into the formed thrombi. However, platelets from both groups were still similarly reduced in assays of whole blood aggregation. Conclusively, recovery of rat platelet function after ticagrelor differs mechanistically from that after clopidogrel. This difference is masked by conventional platelet aggregation methods, but is revealed by thrombus formation measurement under flow. Juvenile platelets formed at later time points after clopidogrel treatment promoted thrombus formation.
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Nergiz-Unal R, Lamers MME, Van Kruchten R, Luiken JJ, Cosemans JMEM, Glatz JFC, Kuijpers MJE, Heemskerk JWM. Signaling role of CD36 in platelet activation and thrombus formation on immobilized thrombospondin or oxidized low-density lipoprotein. J Thromb Haemost 2011; 9:1835-46. [PMID: 21696539 DOI: 10.1111/j.1538-7836.2011.04416.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND AND OBJECTIVE Platelets abundantly express glycoprotein CD36 with thrombospondin-1 (TSP1) and oxidized low-density lipoprotein (oxLDL) as proposed ligands. How these agents promote platelet activation is still poorly understood. METHODS AND RESULTS Both TSP1 and oxLDL caused limited activation of platelets in suspension. However, immobilized TSP1 and oxLDL, but not LDL, strongly supported platelet adhesion and spreading with a major role of CD36. Platelet spreading was accompanied by potent Ca(2+) rises, and resulted in exposure of P-selectin and integrin activation, all in a CD36-dependent manner with additional contributions of α(IIb) β(3) and ADP receptor stimulation. Signaling responses via CD36 involved activation of the protein tyrosine kinase Syk. In whole blood perfusion, co-coating of TSP1 or oxLDL with collagen enhanced thrombus formation at high-shear flow conditions, with increased expression on platelets of activated α(IIb) β(3), P-selectin and phosphatidylserine, again in a CD36-dependent way. CONCLUSIONS Immobilized TSP1 and oxLDL activate platelets partly via CD36 through a Syk kinase-dependent Ca(2+) signaling mechanism, which enhances collagen-dependent thrombus formation under flow. These findings provide novel insight into the role of CD36 in hemostasis.
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Gilio K, van Kruchten R, Braun A, Berna-Erro A, Feijge MAH, Stegner D, van der Meijden PEJ, Kuijpers MJE, Varga-Szabo D, Heemskerk JWM, Nieswandt B. Roles of platelet STIM1 and Orai1 in glycoprotein VI- and thrombin-dependent procoagulant activity and thrombus formation. J Biol Chem 2010; 285:23629-38. [PMID: 20519511 DOI: 10.1074/jbc.m110.108696] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In platelets, STIM1 has been recognized as the key regulatory protein in store-operated Ca(2+) entry (SOCE) with Orai1 as principal Ca(2+) entry channel. Both proteins contribute to collagen-dependent arterial thrombosis in mice in vivo. It is unclear whether STIM2 is involved. A key platelet response relying on Ca(2+) entry is the surface exposure of phosphatidylserine (PS), which accomplishes platelet procoagulant activity. We studied this response in mouse platelets deficient in STIM1, STIM2, or Orai1. Upon high shear flow of blood over collagen, Stim1(-/-) and Orai1(-/-) platelets had greatly impaired glycoprotein (GP) VI-dependent Ca(2+) signals, and they were deficient in PS exposure and thrombus formation. In contrast, Stim2(-/-) platelets reacted normally. Upon blood flow in the presence of thrombin generation and coagulation, Ca(2+) signals of Stim1(-/-) and Orai1(-/-) platelets were partly reduced, whereas the PS exposure and formation of fibrin-rich thrombi were normalized. Washed Stim1(-/-) and Orai1(-/-) platelets were deficient in GPVI-induced PS exposure and prothrombinase activity, but not when thrombin was present as co-agonist. Markedly, SKF96365, a blocker of (receptor-operated) Ca(2+) entry, inhibited Ca(2+) and procoagulant responses even in Stim1(-/-) and Orai1(-/-) platelets. These data show for the first time that: (i) STIM1 and Orai1 jointly contribute to GPVI-induced SOCE, procoagulant activity, and thrombus formation; (ii) a compensating Ca(2+) entry pathway is effective in the additional presence of thrombin; (iii) platelets contain two mechanisms of Ca(2+) entry and PS exposure, only one relying on STIM1-Orai1 interaction.
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Elvers M, Pozgaj R, Pleines I, May F, Kuijpers MJE, Heemskerk JMW, Yu P, Nieswandt B. Platelet hyperreactivity and a prothrombotic phenotype in mice with a gain-of-function mutation in phospholipase Cgamma2. J Thromb Haemost 2010; 8:1353-63. [PMID: 20230420 DOI: 10.1111/j.1538-7836.2010.03838.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Agonist-induced platelet activation involves different signaling pathways leading to the activation of phospholipase C (PLC) beta or PLCgamma2. Activated PLC produces inositol 1,4,5-trisphosphate and diacylglycerol, which trigger Ca(2+) mobilization and the activation of protein kinase C, respectively. PLCbeta is activated downstream of Gq-coupled receptors for soluble agonists with only short interaction times in flowing blood. In contrast, PLCgamma2 becomes activated downstream of receptors that interact with immobilized ligands such as the collagen receptor glycoprotein (GP) VI or activated integrins. OBJECTIVE AND METHODS We speculated that PLCgamma2 activity might be optimized for sustained but submaximal signaling to control relatively slow platelet responses. To test this hypothesis, we analyzed platelets from mice heterozygous for a gain-of-function mutation in the Plcg2 gene (Plcg2(Ali5/+)). RESULTS Plcg2(Ali5/+) platelets showed enhanced Ca(2+) mobilization, integrin activation, granule secretion and phosphatidylserine exposure upon GPVI or C-type lectin-like receptor-2 stimulation. Furthermore, integrin alpha(IIb)beta(3) outside-in signaling was markedly enhanced in the mutant platelets, as shown by accelerated spreading on different matrices and faster clot retraction. These defects translated into virtually unlimited thrombus formation on collagen under flow in vitro and a prothrombotic phenotype in vivo. CONCLUSIONS These results demonstrate that the enzymatic activity of PLCgamma2 is tightly regulated to ensure efficient but limited platelet activation at sites of vascular injury.
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Nergiz-Unal R, Cosemans JMEM, Feijge MAH, van der Meijden PEJ, Storey RF, van Giezen JJJ, oude Egbrink MGA, Heemskerk JWM, Kuijpers MJE. Stabilizing role of platelet P2Y(12) receptors in shear-dependent thrombus formation on ruptured plaques. PLoS One 2010; 5:e10130. [PMID: 20405028 PMCID: PMC2853564 DOI: 10.1371/journal.pone.0010130] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 03/12/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND In most models of experimental thrombosis, healthy blood vessels are damaged. This results in the formation of a platelet thrombus that is stabilized by ADP signaling via P2Y(12) receptors. However, such models do not predict involvement of P2Y(12) in the clinically relevant situation of thrombosis upon rupture of atherosclerotic plaques. We investigated the role of P2Y(12) in thrombus formation on (collagen-containing) atherosclerotic plaques in vitro and in vivo, by using a novel mouse model of atherothrombosis. METHODOLOGY Plaques in the carotid arteries from Apoe(-/-) mice were acutely ruptured by ultrasound treatment, and the thrombotic process was monitored via intravital fluorescence microscopy. Thrombus formation in vitro was assessed in mouse and human blood perfused over collagen or plaque material under variable conditions of shear rate and coagulation. Effects of two reversible P2Y(12) blockers, ticagrelor (AZD6140) and cangrelor (AR-C69931MX), were investigated. PRINCIPAL FINDINGS Acute plaque rupture by ultrasound treatment provoked rapid formation of non-occlusive thrombi, which were smaller in size and unstable in the presence of P2Y(12) blockers. In vitro, when mouse or human blood was perfused over collagen or atherosclerotic plaque material, blockage or deficiency of P2Y(12) reduced the thrombi and increased embolization events. These P2Y(12) effects were present at shear rates >500 s(-1), and they persisted in the presence of coagulation. P2Y(12)-dependent thrombus stabilization was accompanied by increased fibrin(ogen) binding. CONCLUSIONS/SIGNIFICANCE Platelet P2Y(12) receptors play a crucial role in the stabilization of thrombi formed on atherosclerotic plaques. This P2Y(12) function is restricted to high shear flow conditions, and is preserved in the presence of coagulation.
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Kuijpers MJE, Gilio K, Reitsma S, Nergiz-Unal R, Prinzen L, Heeneman S, Lutgens E, van Zandvoort MAMJ, Nieswandt B, Egbrink MGAO, Heemskerk JWM. Complementary roles of platelets and coagulation in thrombus formation on plaques acutely ruptured by targeted ultrasound treatment: a novel intravital model. J Thromb Haemost 2009; 7:152-61. [PMID: 18983512 DOI: 10.1111/j.1538-7836.2008.03186.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
BACKGROUND Atherothrombosis is a major cause of cardiovascular events. However, animal models to study this process are scarce. OBJECTIVES We describe the first murine model of acute thrombus formation upon plaque rupture to study atherothrombosis by intravital fluorescence microscopy. METHODS Localized rupture of an atherosclerotic plaque in a carotid artery from Apoe(-/-) mice was induced in vivo using ultrasound. Rupture of the plaque and formation of localized thrombi were verified by two-photon laser scanning microscopy (TPLSM) in isolated arteries, and by immunohistochemistry. The thrombotic reaction was quantified by intravital fluorescence microscopy. RESULTS Inspection of the ultrasound-treated plaques by histochemistry and TPLSM demonstrated local damage, collagen exposure, luminal thrombus formation as well as intra-plaque intrusion of erythrocytes and fibrin. Ultrasound treatment of healthy carotid arteries resulted in endothelial damage and limited platelet adhesion. Real-time intravital fluorescence microscopy demonstrated rapid platelet deposition on plaques and formation of a single thrombus that remained subocclusive. The thrombotic process was antagonized by thrombin inhibition, or by blocking of collagen or adenosine diphosphate receptor pathways. Multiple thrombi were formed in 70% of mice lacking CD40L. CONCLUSIONS Targeted rupture of murine plaques results in collagen exposure and non-occlusive thrombus formation. The thrombotic process relies on platelet activation as well as on thrombin generation and coagulation, and is sensitive to established and novel antithrombotic medication. This model provides new possibilities to study atherothrombosis in vivo.
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Kuijpers MJE, Pozgajova M, Cosemans JMEM, Munnix ICA, Eckes B, Nieswandt B, Heemskerk JWM. Role of murine integrin alpha2beta1 in thrombus stabilization and embolization: contribution of thromboxane A2. Thromb Haemost 2007; 98:1072-1080. [PMID: 18000613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Platelets stably interact with collagen via glycoprotein (GP)VI and alpha2beta1integrin. With alpha2-null mice, we investigated the role of alpha2beta1 in thrombus formation and stability in vivo and in vitro. Using a FeCl(3)-induced thrombosis model, in arteries from alpha2-null mice smaller thrombi were formed with more embolization compared to vessels from wild-type mice. Aspirin treatment of wild-type mice causes similar effects, while the thromboxane A(2) analogue U46619 was borderline effective in suppressing the embolisation in alpha2-null mice. In vitro, perfusion of alpha2-null blood over collagen resulted in formation of thrombi that were smaller and looser in appearance, regardless of the presence or absence of coagulation. Aspirin treatment or blockage of thromboxane receptors provoked embolus formation in wildtype blood, while U46619 normalized thrombus formation in blood from alpha2-null mice. We conclude that integrin alpha2beta1 plays a role in stabilizing murine thrombi, likely by enhancing GPVI activation and thromboxane A(2) release. The increased embolization in alpha2-null mice may argue against the use of alpha2beta1 integrin inhibitors for antithrombotic therapy.
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Munnix ICA, Kuijpers MJE, Auger J, Thomassen CMLGD, Panizzi P, van Zandvoort MAM, Rosing J, Bock PE, Watson SP, Heemskerk JWM. Segregation of platelet aggregatory and procoagulant microdomains in thrombus formation: regulation by transient integrin activation. Arterioscler Thromb Vasc Biol 2007; 27:2484-90. [PMID: 17761939 PMCID: PMC2376762 DOI: 10.1161/atvbaha.107.151100] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Platelets play a dual role in thrombosis by forming aggregates and stimulating coagulation. We investigated the commitment of platelets to these separate functions during collagen-induced thrombus formation in vitro and in vivo. METHODS AND RESULTS High-resolution 2-photon fluorescence microscopy revealed that in thrombus formation under flow, fibrin(ogen)-binding platelets assembled into separate aggregates, whereas distinct patches of nonaggregated platelets exposed phosphatidylserine. The latter platelet population had inactivated alphaIIb beta3 integrins and displayed increased binding of coagulation factors. Coated platelets, expressing serotonin binding sites, were not identified as a separate population. Thrombin generation and coagulation favored the transformation to phosphatidylserine-exposing platelets with inactivated integrins and reduced adhesion. Prolonged tyrosine phosphorylation in vitro resulted in secondary downregulation of active alphaIIb beta3. CONCLUSIONS These results lead to a new spatial model of thrombus formation, in which aggregated platelets ensure thrombus stability, whereas distinct patches of nonaggregated platelets effectuate procoagulant activity and generate thrombin and fibrin. Herein, the hemostatic activity of a developing thrombus is determined by the balance in formation of proaggregatory and procoagulant platelets. This balance is influenced by antiplatelet and anticoagulant medication.
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Megens RTA, Oude Egbrink MGA, Cleutjens JPM, Kuijpers MJE, Schiffers PHM, Merkx M, Slaaf DW, van Zandvoort MAMJ. Imaging collagen in intact viable healthy and atherosclerotic arteries using fluorescently labeled CNA35 and two-photon laser scanning microscopy. Mol Imaging 2007; 6:247-60. [PMID: 17711780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023] Open
Abstract
We evaluated CNA35 as a collagen marker in healthy and atherosclerotic arteries of mice after both ex vivo and in vivo administration and as a molecular imaging agent for the detection of atherosclerosis. CNA35 conjugated with fluorescent Oregon Green 488 (CNA35/OG488) was administered ex vivo to mounted viable muscular (uterine), elastic (carotid), and atherosclerotic (carotid) arteries and fresh arterial rings. Two-photon microscopy was used for imaging. CNA35/OG488 labeling in healthy elastic arteries was compared with collagen type I, III, and IV antibody labeling in histologic sections. For in vivo labeling experiments, CNA35/OG488 was injected intravenously in C57BL6/J and apolipoprotein E(-/-) mice. Ex vivo CNA35/OG488 strongly labeled collagen in the tunica adventitia, media, and intima of muscular arteries. In healthy elastic arteries, tunica adventitia was strongly labeled, but labeling in tunica media and intima was prevented by endothelium and elastic laminae. Histology confirmed the affinity of CNA35 for type I, III, and IV collagen in arteries. Strong CNA35/OG488 labeling was found in atherosclerotic plaques. In vivo applied CNA35/OG488 minimally labeled the tunica intima of healthy carotid arteries. Atherosclerotic plaques in apolipoprotein E(-/-) mice exhibited large uptake. CNA35/OG488 imaging in organs revealed endothelium as a limiting barrier for in vivo uptake. CNA35/OG488 is a good molecular imaging agent for atherosclerosis.
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Strehl A, Munnix ICA, Kuijpers MJE, van der Meijden PEJ, Cosemans JMEM, Feijge MAH, Nieswandt B, Heemskerk JWM. Dual Role of Platelet Protein Kinase C in Thrombus Formation. J Biol Chem 2007; 282:7046-55. [PMID: 17210570 DOI: 10.1074/jbc.m611367200] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Protein kinase C (PKC) isoforms regulate many platelet responses in a still incompletely understood manner. Here we investigated the roles of PKC in the platelet reactions implicated in thrombus formation as follows: secretion aggregate formation and coagulation-stimulating activity, using inhibitors with proven activity in plasma. In human and mouse platelets, PKC regulated aggregation by mediating secretion and contributing to alphaIIbbeta3 activation. Strikingly, PKC suppressed Ca(2+) signal generation and Ca(2+)-dependent exposure of procoagulant phosphatidylserine. Furthermore, under coagulant conditions, PKC suppressed the thrombin-generating capacity of platelets. In flowing human and mouse blood, PKC contributed to platelet adhesion and controlled secretion-dependent thrombus formation, whereas it down-regulated Ca(2+) signaling and procoagulant activity. In murine platelets lacking G(q)alpha, where secretion reactions were reduced in comparison with wild type mice, PKC still positively regulated platelet aggregation and down-regulated procoagulant activity. We conclude that platelet PKC isoforms have a dual controlling role in thrombus formation as follows: (i) by mediating secretion and integrin activation required for platelet aggregation under flow, and (ii) by suppressing Ca(2+)-dependent phosphatidylserine exposure, and consequently thrombin generation and coagulation. This platelet signaling protein is the first one identified to balance the pro-aggregatory and procoagulant functions of thrombi.
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Munnix ICA, Strehl A, Kuijpers MJE, Auger JM, van der Meijden PEJ, van Zandvoort MAM, oude Egbrink MGA, Nieswandt B, Heemskerk JWM. The Glycoprotein VI-Phospholipase Cγ2 Signaling Pathway Controls Thrombus Formation Induced by Collagen and Tissue Factor In Vitro and In Vivo. Arterioscler Thromb Vasc Biol 2005; 25:2673-8. [PMID: 16254207 DOI: 10.1161/01.atv.0000193568.71980.4a] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Objective—
Both collagen and tissue factor can be initiating factors in thrombus formation. We investigated the signaling pathway of collagen-induced platelet activation in interaction with tissue factor–triggered coagulation during the thrombus-forming process.
Methods and Results—
In murine blood flowing over collagen, platelet exposure of phosphatidylserine and procoagulant activity, but not adhesion, completely relied on each of the following signaling modules: glycoprotein VI (GPVI), FcR γ-chain, Src kinases, adaptor protein LAT, and phospholipase Cγ2 (PLCγ2). On flow in the presence of tissue factor, these signaling components were essential for platelet aggregation and greatly enhanced fibrin clot formation. Collagen-stimulated thrombin generation relied on the presence and activity of GPVI, FcR γ-chain, Src kinase, LAT, and PLCγ2. The physiological importance of this GPVI pathway was shown in a FeCl
3
-induced in vivo murine thrombosis model. In both venules and arterioles, signaling through GPVI, FcR γ-chain, and Src kinases enhanced the formation of phosphatidylserine-exposing and fibrin-rich thrombi.
Conclusions—
The GPVI-PLCγ2 activation pathway regulates collagen-dependent coagulation in venous and arterial thrombus formation.
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