scholarly journals The calcium sensor STIM1 is an essential mediator of arterial thrombosis and ischemic brain infarction

2008 ◽  
Vol 205 (7) ◽  
pp. 1583-1591 ◽  
Author(s):  
David Varga-Szabo ◽  
Attila Braun ◽  
Christoph Kleinschnitz ◽  
Markus Bender ◽  
Irina Pleines ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Arterial Thrombosis ◽  
Thrombus Formation ◽  
Brain Infarction ◽  
Major Pathway ◽  
Ischemic Brain ◽  
Exact Function ◽  
Sarcoplasmatic Reticulum ◽  
Ischemic Brain Infarction

Platelet activation and aggregation are essential to limit posttraumatic blood loss at sites of vascular injury but also contributes to arterial thrombosis, leading to myocardial infarction and stroke. Agonist-induced elevation of [Ca2+]i is a central step in platelet activation, but the underlying mechanisms are not fully understood. A major pathway for Ca2+ entry in nonexcitable cells involves receptor-mediated release of intracellular Ca2+ stores, followed by activation of store-operated calcium (SOC) channels in the plasma membrane. Stromal interaction molecule 1 (STIM1) has been identified as the Ca2+ sensor in the endoplasmic reticulum (ER) that activates Ca2+ release–activated channels in T cells, but its role in mammalian physiology is unknown. Platelets express high levels of STIM1, but its exact function has been elusive, because these cells lack a normal ER and Ca2+ is stored in a tubular system referred to as the sarcoplasmatic reticulum. We report that mice lacking STIM1 display early postnatal lethality and growth retardation. STIM1-deficient platelets have a marked defect in agonist-induced Ca2+ responses, and impaired activation and thrombus formation under flow in vitro. Importantly, mice with STIM1-deficient platelets are significantly protected from arterial thrombosis and ischemic brain infarction but have only a mild bleeding time prolongation. These results establish STIM1 as an important mediator in the pathogenesis of ischemic cardio- and cerebrovascular events.

Orai1 (CRACM1) is the platelet SOC channel and essential for pathological thrombus formation

Blood ◽  
2009 ◽  
Vol 113 (9) ◽  
pp. 2056-2063 ◽  
Author(s):  
Attila Braun ◽  
David Varga-Szabo ◽  
Christoph Kleinschnitz ◽  
Irina Pleines ◽  
Markus Bender ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Thrombus Formation ◽  
Brain Infarction ◽  
Direct Consequence ◽  
Primary Hemostasis ◽  
Cerebrovascular Events ◽  
Store Operated Calcium Entry ◽  
Crac Channel ◽  
Ischemic Brain Infarction

Abstract Platelet activation and aggregation at sites of vascular injury are essential for primary hemostasis, but are also major pathomechanisms underlying myocardial infarction and stroke. Changes in [Ca2+]i are a central step in platelet activation. In nonexcitable cells, receptor-mediated depletion of intracellular Ca2+ stores triggers Ca2+ entry through store-operated calcium (SOC) channels. STIM1 has been identified as an endoplasmic reticulum (ER)–resident Ca2+ sensor that regulates store-operated calcium entry (SOCE) in immune cells and platelets, but the identity of the platelet SOC channel has remained elusive. Orai1 (CRACM1) is the recently discovered SOC (CRAC) channel in T cells and mast cells but its role in mammalian physiology is unknown. Here we report that Orai1 is strongly expressed in human and mouse platelets. To test its role in blood clotting, we generated Orai1-deficient mice and found that their platelets display severely defective SOCE, agonist-induced Ca2+ responses, and impaired activation and thrombus formation under flow in vitro. As a direct consequence, Orai1 deficiency in mice results in resistance to pulmonary thromboembolism, arterial thrombosis, and ischemic brain infarction, but only mild bleeding time prolongation. These results establish Orai1 as the long-sought platelet SOC channel and a crucial mediator of ischemic cardiovascular and cerebrovascular events.

scholarly journals Annexin A7 is a critical regulator of Ca2+ mobilization and lipid metabolism during platelet activation and arterial thrombosis

2020 ◽  
Vol 41 (Supplement_2) ◽  
Author(s):  
O Borst ◽  
S Geue ◽  
M.C Manke ◽  
B Peng ◽  
P Muenzer ◽  
...  
Keyword(s):  
Lipid Metabolism ◽  
Platelet Activation ◽  
Arterial Thrombosis ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Vascular Occlusion ◽  
Funding Source ◽  
Annexin A7

Abstract Background Platelet activation after contact to subendothelial collagen following atherosclerotic plaque rupture can lead to arterial thrombosis with acute thrombotic vascular occlusion. Annexin A7 (AnxA7) is an intracellular Ca2+- and phospholipid-binding protein that participates in the regulation of prostaglandin production in inflammatory diseases, but also in cell survival and tumor growth. Objective In the present study, we aimed to determine the role of AnxA7 for platelet Ca2+ signaling and lipid metabolism in platelet activation and arterial thrombosis in gene-targeted mice lacking annexin A7 (Anxa7−/−). Results AnxA7 is strongly expressed in platelets of platelet-rich human coronary thrombi aspirated from patients with acute ST elevation myocardial infarction. Functionally, platelet aggregation and dense granule secretion were significantly abrogated in Anxa7−/− platelets as compared to wildtype platelets (Anxa7+/+) after activation with collagen or collagen-related peptide (CRP), a specific agonist of the major platelet collagen receptor glycoprotein VI (GPVI). Further, in vitro thrombus formation on a collagen-coated surface under high arterial shear rates was significantly diminished in Anxa7-deficient platelets, and thrombotic vascular occlusion after FeCl3-induced injury in vivo was blunted in Anxa7−/−bone marrow chimeric mice, but no prolongation of bleeding time was observed. Moreover, Anxa7−/− platelets showed a significant reduction of IP3 production due to an abolished phospholipase C (PLC) gamma2 phosphorylation resulting in an abolished increase of [Ca2+]i after platelet activation with CRP. Moreover, we could show by quantitative lipidomics analysis that annexin A7 critically affects platelet oxylipid metabolism following activation of GPVI-dependent platelet signalling since Anxa7−/− platelets showed a significant reduction of the bioactive metabolites thromboxane A2 and 12(S)-hydroxy-eicosatetraenoic acid (12(S)-HETE) levels as well as significantly reduced levels of several other prostaglandins following stimulation with collagen or CRP. Finally, defective PLCgamma2 phosphorylation, IP1 production and blunted increase of [Ca2+]i in Anxa7−/− platelets could be rescued by exogenous addition of 12(S)-HETE indicating that AnxA7 is a critical regulator of the platelet oxygenase 12-lipoxygenase (12-LOX) in GPVI-dependent platelet Ca2+ signalling during arterial thrombosis following activation by collagen. Conclusions The present study reveals annexin A7 as a critical regulator of oxylipid metabolism and Ca2+ signaling in GPVI-dependent platelet activation. Anxa7-deficiency further results in decreased in vitro and in vivo thrombus formation, but does not affect bleeding time. In conclusion, annexin A7 plays an important role in platelet signaling during arterial thrombosis and thus, may reflect a promising target for novel antiplatelet strategies. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): German Research Foundation (Deutsche Forschungsgemeinschaft, DFG)

scholarly journals Rivaroxaban Reduces Arterial Thrombosis by Inhibition of FXa-Driven Platelet Activation via Protease Activated Receptor-1

2020 ◽  
Vol 126 (4) ◽  
pp. 486-500 ◽  
Author(s):  
Tobias Petzold ◽  
Manuela Thienel ◽  
Lisa Dannenberg ◽  
Philipp Mourikis ◽  
Carolin Helten ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Platelet Activation ◽  
Arterial Thrombosis ◽  
Platelet Reactivity ◽  
Thrombus Formation ◽  
Vitamin K Antagonists ◽  
Factor Xa ◽  
Antiplatelet Effect ◽  
Protease Activated Receptor 1

Rationale: A reduced rate of myocardial infarction has been reported in patients with atrial fibrillation treated with FXa (factor Xa) inhibitors including rivaroxaban compared with vitamin K antagonists. At the same time, low-dose rivaroxaban has been shown to reduce mortality and atherothrombotic events in patients with coronary artery disease. Yet, the mechanisms underlying this reduction remain unknown. Objective: In this study, we hypothesized that rivaroxaban’s antithrombotic potential is linked to a hitherto unknown rivaroxaban effect that impacts on platelet reactivity and arterial thrombosis. Methods and Results: In this study, we identified FXa as potent, direct agonist of the PAR-1 (protease-activated receptor 1), leading to platelet activation and thrombus formation, which can be inhibited by rivaroxaban. We found that rivaroxaban reduced arterial thrombus stability in a mouse model of arterial thrombosis using intravital microscopy. For in vitro studies, atrial fibrillation patients on permanent rivaroxaban treatment for stroke prevention, respective controls, and patients with new-onset atrial fibrillation before and after first intake of rivaroxaban (time series analysis) were recruited. Platelet aggregation responses, as well as thrombus formation under arterial flow conditions on collagen and atherosclerotic plaque material, were attenuated by rivaroxaban. We show that rivaroxaban’s antiplatelet effect is plasma dependent but independent of thrombin and rivaroxaban’s anticoagulatory capacity. Conclusions: Here, we identified FXa as potent platelet agonist that acts through PAR-1. Therefore, rivaroxaban exerts an antiplatelet effect that together with its well-known potent anticoagulatory capacity might lead to reduced frequency of atherothrombotic events and improved outcome in patients.

scholarly journals SLAP/SLAP2 prevent excessive platelet (hem)ITAM signaling in thrombosis and ischemic stroke in mice

Blood ◽  
2015 ◽  
Vol 125 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Deya Cherpokova ◽  
Markus Bender ◽  
Martina Morowski ◽  
Peter Kraft ◽  
Michael K. Schuhmann ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Thrombus Formation ◽  
Brain Infarction ◽  
Ischemic Brain ◽  
Key Points ◽  
Ischemic Brain Infarction ◽  
Redundant Functions

Key Points SLAP and SLAP2 have redundant functions in the regulation of platelet (hem)ITAM signaling. SLAP and SLAP2 in platelets limit occlusive thrombus formation and ischemic brain infarction.

scholarly journals Only severe thrombocytopenia results in bleeding and defective thrombus formation in mice

Blood ◽  
2013 ◽  
Vol 121 (24) ◽  
pp. 4938-4947 ◽  
Author(s):  
Martina Morowski ◽  
Timo Vögtle ◽  
Peter Kraft ◽  
Christoph Kleinschnitz ◽  
Guido Stoll ◽  
...  
Keyword(s):  
Platelet Count ◽  
Thrombus Formation ◽  
Brain Infarction ◽  
Severe Thrombocytopenia ◽  
Ischemic Brain ◽  
Platelet Counts ◽  
Key Points ◽  
Ischemic Brain Infarction

Key Points Hemostasis, thrombosis, and ischemic brain infarction efficiently occur at unexpectedly low platelet counts in mice. The threshold platelet count required for occlusive thrombus formation differs between thrombosis models.

scholarly journals Layer-by-layer coating of stainless steel plates mediated by surface priming treatment to improve antithrombogenic properties

2016 ◽  
Author(s):  
Irene Carmagnola ◽  
Tiziana Nardo ◽  
Francesca Boccafoschi ◽  
Valeria Chiono
Keyword(s):  
Stainless Steel ◽  
Surface Modification ◽  
Platelet Activation ◽  
Colorimetric Assay ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Steel Plates ◽  
Blue Dye ◽  
Layer By Layer

The stainless steel (SS) stents have been used in clinics since 1994. However, typical drawbacks are restenosis and thrombus formation due to limited endothelialisation and hemocompatibility. Surface modification is a smart strategy to enhance antithrombogenicity by promoting endothelialisation. In this work, the layer-by-layer (LbL) technique was applied for coating SS model substrates, after surface priming by functionalisation with 3-aminopropyl triethoxysilane (APTES). A LbL coating made of 14 layers of poly(styrene sulfonate)/poly(diallyldimethylammonium chloride) and heparin as last layer was deposited. FTIR-ATR analysis and contact angle measurements showed that LbL was an effective method to prepare nanostructured coatings. XPS analysis and colorimetric assay employing 1,9-dimethylmethylene blue dye to detect -COOH groups confirmed the successful polyelectrolyte deposition on the coated samples. Preliminary in vitro cell tests, using whole blood and human platelets, were performed to evaluate how surface modification affects platelet activation. Results showed that SS and SS-APTES surfaces induced platelet activation, as indicated by platelet spreading and filopodia formation. After surface modification by LbL coating, the platelets assumed a round shape and no fibrin nets were detected. Data demonstrated that LbL coating is a promising technique to fabricate antithrombogenic surface.

Supplemental Fibrinogen Restores Platelet Inhibitor-Induced Reduction in Thrombus Formation without Altering Platelet Function: An In Vitro Study

2020 ◽  
Vol 120 (11) ◽  
pp. 1548-1556
Author(s):  
Thomas Bärnthaler ◽  
Elisabeth Mahla ◽  
Gabor G. Toth ◽  
Rufina Schuligoi ◽  
Florian Prüller ◽  
...  
Keyword(s):  
Antiplatelet Therapy ◽  
Platelet Activation ◽  
Platelet Function ◽  
Dual Antiplatelet Therapy ◽  
Thrombus Formation ◽  
In Vitro Study ◽  
Coronary Intervention ◽  
Calcium Flux ◽  
Major Surgery

Abstract Background For patients treated with dual antiplatelet therapy, standardized drug-specific 3-to-7 day cessation is recommended prior to major surgery to reach sufficient platelet function recovery. Here we investigated the hypothesis that supplemental fibrinogen might mitigate the inhibitory effects of antiplatelet therapy. Methods and Results To this end blood from healthy donors was treated in vitro with platelet inhibitors, and in vitro thrombus formation and platelet activation were assessed. Ticagrelor, acetylsalicylic acid, the combination of both, and tirofiban all markedly attenuated the formation of adherent thrombi, when whole blood was perfused through collagen-coated microchannels at physiological shear rates. Addition of fibrinogen restored in vitro thrombus formation in the presence of antiplatelet drugs and heparin. However, platelet activation, as investigated in assays of P-selectin expression and calcium flux, was not altered by fibrinogen supplementation. Most importantly, fibrinogen was able to restore in vitro thrombogenesis in patients on maintenance dual antiplatelet therapy after percutaneous coronary intervention. Conclusion Thus, our in vitro data support the notion that supplementation of fibrinogen influences the perioperative hemostasis in patients undergoing surgery during antiplatelet therapy by promoting thrombogenesis without significantly interfering with platelet activation.

scholarly journals IκB kinase 2 is not essential for platelet activation

2020 ◽  
Vol 4 (4) ◽  
pp. 638-643
Author(s):  
Manuel Salzmann ◽  
Sonja Bleichert ◽  
Bernhard Moser ◽  
Marion Mussbacher ◽  
Mildred Haase ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Active Site ◽  
Bleeding Time ◽  
Thrombus Formation ◽  
Human Platelets ◽  
Iκb Kinase ◽  
Specific Deletion

Abstract Platelets are small anucleate cells that release a plethora of molecules to ensure functional hemostasis. It has been reported that IκB kinase 2 (IKK2), the central enzyme of the inflammatory NF-κB pathway, is involved in platelet activation, because megakaryocyte/platelet-specific deletion of exons 6 and 7 of IKK2 resulted in platelet degranulation defects and prolonged bleeding. We aimed to investigate the role of IKK2 in platelet physiology in more detail, using a platelet-specific IKK2 knockout via excision of exon 3, which makes up the active site of the enzyme. We verified the deletion on genomic and transcriptional levels in megakaryocytes and were not able to detect any residual IKK2 protein; however, platelets from these mice did not show any functional impairment in vivo or in vitro. Bleeding time and thrombus formation were not affected in platelet-specific IKK2-knockout mice. Moreover, platelet aggregation, glycoprotein GPIIb/IIIa activation, and degranulation were unaltered. These observations were confirmed by pharmacological inhibition of IKK2 with TPCA-1 and BMS-345541, which did not affect activation of murine or human platelets over a wide concentration range. Altogether, our results imply that IKK2 is not essential for platelet function.

scholarly journals Mumefural Improves Blood Flow in a Rat Model of FeCl3-Induced Arterial Thrombosis

Nutrients ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3795
Author(s):  
Jihye Bang ◽  
Won Kyung Jeon
Keyword(s):  
Blood Flow ◽  
Blood Vessels ◽  
Rat Model ◽  
Arterial Thrombosis ◽  
Thrombus Formation ◽  
Sprague Dawley ◽  
Fiber Damage ◽  
Sprague Dawley Rats ◽  
Related Proteins

Mumefural (MF), a bioactive component of the processed fruit of Prunus mume Sieb. et Zucc, is known to inhibit platelet aggregation induced by agonists in vitro. In this study, we investigated the anti-thrombotic effects of MF using a rat model of FeCl3-induced arterial thrombosis. Sprague–Dawley rats were intraperitoneally injected with MF (0.1, 1, or 10 mg/kg) 30 min before 35% FeCl3 treatment to measure the time to occlusion using a laser Doppler flowmeter and to assess the weight of the blood vessels containing thrombus. MF treatment significantly improved blood flow by inhibiting occlusion and thrombus formation. MF also prevented collagen fiber damage in injured vessels and inhibited the expression of the platelet activation-related proteins P-selectin and E-selectin. Moreover, MF significantly reduced the increased inflammatory signal of nuclear factor (NF)-κB, toll-like receptor 4 (TLR4), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in blood vessels. After administration, MF was detected in the plasma samples of rats with a bioavailability of 36.95%. Therefore, we suggest that MF may improve blood flow as a candidate component in dietary supplements for improving blood flow and preventing blood circulation disorders.

scholarly journals Noncanonical Effects of Oral Thrombin and Factor Xa Inhibitors in Platelet Activation and Arterial Thrombosis

2020 ◽  
Author(s):  
Amin Polzin ◽  
Lisa Dannenberg ◽  
Manuela Thienel ◽  
Martin Orban ◽  
Georg Wolff ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Arterial Thrombosis ◽  
Thrombus Formation ◽  
Vitamin K Antagonists ◽  
Oral Anticoagulants ◽  
Direct Oral Anticoagulants ◽  
Factor Xa ◽  
Coagulation Cascade ◽  
Platelet Activity ◽  
Vein Thrombosis

AbstractNonvitamin K oral anticoagulants (NOACs) or direct oral anticoagulants comprise inhibitors of factor Xa (rivaroxaban, apixaban, edoxaban) or factor IIa (dabigatran). Both classes efficiently interfere with the final or penultimate step of the coagulation cascade and showed superior net clinical benefit compared with vitamin K antagonists for prevention of thromboembolic events in patients with AF and for prevention and therapy of deep vein thrombosis and pulmonary embolism. None the less, accumulating data suggested, that there may be differences regarding the frequency of atherothrombotic cardiovascular events between NOACs. Thus, the optimal individualized NOAC for each patient remains a matter of debate. Against this background, some basic and translational analyses emphasized NOAC effects that impact on platelet activity and arterial thrombus formation beyond inhibition of plasmatic coagulation. In this review, we will provide an overview of the available clinical and translational evidence for so-called noncanonical NOAC effects on platelet activation and arterial thrombosis.

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