thrombin receptor
Recently Published Documents


TOTAL DOCUMENTS

731
(FIVE YEARS 31)

H-INDEX

70
(FIVE YEARS 3)

Author(s):  
Maria V Selvadurai ◽  
Moeen Riaz ◽  
Sophia Xie ◽  
Andrew Tonkin ◽  
John J McNeil ◽  
...  

Background: Protease-activated receptor 4 (PAR4) is a platelet thrombin receptor important for thrombosis and a target of anti-platelet drug development. A frequently occurring single nucleotide polymorphism (SNP; rs773902) causes a PAR4 sequence variant (NC_000019.10:p.Ala120Thr) whereby platelets from Thr120-expressing individuals are hyper-responsive to PAR4 agonists versus platelets from Ala120-expressing individuals. However, whether this enhanced platelet responsiveness translates to increased thrombotic risk or decreased bleeding risk remains unknown. Objectives: To examine the association of rs773902 with adjudicated cardiovascular events and aspirin use in a randomized trial population of healthy older individuals. Patients/Methods: We analyzed 13,547 participants in the ASPirin in Reducing Events in the Elderly (ASPREE) trial. Participants had no previous cardiovascular events at enrollment and were randomized to either 100 mg daily aspirin or placebo for a median follow-up of 4.7 years. Total genotypes were 8,761 (65%) GG (Ala120 variant), 4,303 (32%) heterozygotes, and 483 (4%) AA (Thr120 variant). Cox proportional hazard regression tested the relationship between rs773902 and thrombotic events (major adverse cardiovascular events [MACE] and ischemic stroke [IS]) and bleeding (major hemorrhage [MHEM] and intracranial bleeding [ICB]). Results: No statistically significant association was observed overall or by treatment group between rs773902 and any thrombotic or bleeding event examined. Further, there was no significant interaction between rs773902 and treatment for any of MACE, IS, MHEM, or ICB. Conclusions: This post-hoc analysis of a prospective cohort study suggests that, despite sensitizing platelet activation, the rs773902 PAR4 variant is not associated with thrombotic cardiovascular or bleeding events in a healthy older population.


Author(s):  
Daisuke Mizutani ◽  
Haruhiko Tokuda ◽  
Takashi Onuma ◽  
Kodai Uematsu ◽  
Daiki Nakashima ◽  
...  

Abstract Amyloid β protein deposition in cerebral vessels, a characteristic of Alzheimer's disease, is a risk factor for intracerebral hemorrhage. Amyloid β protein directly modulates human platelet function; however, the exact mechanism of action is unclear. Therefore, we investigated the effects of amyloid β protein on human platelet activation using an aggregometer with laser scattering. Amyloid β protein decreased platelet aggregation induced by thrombin receptor-activating protein, but not by collagen and ADP. Amyloid β protein also suppressed platelet aggregation induced by SCP0237 and A3227. Platelet-derived growth factor-AB secretion and phosphorylated-heat shock protein 27 release by thrombin receptor-activating protein were inhibited by amyloid β protein. Additionally, thrombin receptor-activating protein-induced phosphorylation of JNK and p38 MAP kinase was reduced by amyloid β protein. Collectively, our results strongly suggest that amyloid β protein negatively regulates protease-activated receptor-elicited human platelet activation. These findings may indicate a cause of intracerebral hemorrhage due to amyloid β protein.


2021 ◽  
pp. 116498
Author(s):  
Daisuke Asai ◽  
Naoko Inoue ◽  
Makiko Sugiyama ◽  
Tsugumi Fujita ◽  
Yutaka Matsuyama ◽  
...  

2021 ◽  
Vol 5 (20) ◽  
pp. 3986-4002
Author(s):  
Lorena Buitrago ◽  
Samuel Lefkowitz ◽  
Ohad Bentur ◽  
Julio Padovan ◽  
Barry Coller

Abstract The molecular basis of platelet-fibrin interactions remains poorly understood despite the predominance of fibrin in thrombi. We have studied the interaction of platelets with polymerizing fibrin by adding thrombin to washed platelets in the presence of the peptide RGDW, which inhibits the initial platelet aggregation mediated by fibrinogen binding to αIIbβ3 but leaves intact a delayed increase in light transmission (delayed wave; DW) as platelets interact with the polymerizing fibrin. The DW was absent in platelets from a patient with Glanzmann thrombasthenia, indicating a requirement for αIIbβ3. The DW required αIIbb3 activation and it was inhibited by the αIIbβ3 antagonists eptifibatide and the monoclonal antibody (mAb) 7E3, but only at much higher concentrations than needed to inhibit platelet aggregation initiated by a thrombin receptor activating peptide (T6). Surface plasmon resonance and scanning electron microscopy studies both supported fibrin having greater avidity for αIIbβ3 than fibrinogen rather than greater affinity, consistent with fibrin’s multivalency. mAb 10E5, a potent inhibitor of T6-induced platelet aggregation, did not inhibit the DW, suggesting that fibrin differs from fibrinogen in its mechanism of binding. Inhibition of factor XIII–mediated fibrin cross-linking by >95% reduced the DW by only 32%. Clot retraction showed a pattern of inhibition similar to that of the DW. We conclude that activated αIIbβ3 is the primary mediator of platelet-fibrin interactions leading to clot retraction, and that the interaction is avidity driven, does not require fibrin cross-linking, and is mediated by a mechanism that differs subtly from that of the interaction of αIIbβ3 with fibrinogen.


2021 ◽  
Vol 42 (Supplement_1) ◽  
Author(s):  
D Bongiovanni ◽  
M Klug ◽  
O Lazareva ◽  
K Kirmes ◽  
M Biasi ◽  
...  

Abstract Background Reticulated platelets (RPs) are young, hyper-reactive thrombocytes that contain more RNA compared with mature platelets (MPs). The measurement of RPs level in peripheral blood with point-of-care systems is fast, reproducible, and inexpensive. Elevated RPs in peripheral blood predict adverse events in patients with acute and chronic coronary syndrome through unknown mechanisms. Preliminary transcriptome analyses reported an enrichment of pro-thrombotic transcripts. However, proteomic analyses are not available, and the biological features of RPs are largely unknown. Purpose We aimed to perform the largest proteomic characterization of RPs using mass cytometry with single-cell resolution in patients with chronic coronary syndrome (CCS) undergoing dual antiplatelet therapy (DAPT). Methods Thrombocytes from peripheral blood of CCS patients were isolated, prepared for mass cytometry (CyTOF) and stained with a custom-made CyTOF-panel of 20 antibodies targeting important transmembrane proteins (anti-CD9, anti-CD29, anti-CD31, anti-CD36-, anti-CD40, anti-CD41, anti-CD42a, anti-CD42b-, anti-CD47, anti-CD61, anti-CD62P-, anti-CD63, anti-CD69, anti-CD107a, anti-CD154, anti-GPVI, antiGPIIb/GPIIIa complex, anti-Par1, anti-PEAR-1 and the negative control anti-CD3 coupled with different metal isotopes). Two samples were prepared from each donor: one baseline sample (non-stimulated platelets) and one sample stimulated with 10 μM thrombin receptor-activating peptide (TRAP). According to previous experiences and common practice, we detected RPs and MPs based on their RNA content. We analyzed the results with a custom bioinformatic pipeline. Results 13 patients with CCS on DAPT were included in this study. Mass cytometry highlighted an expression heterogeneity of relevant transmembrane proteins in thrombocytes of CCS patients (Figure 1A-B colored according to expression level: from blue-low to red-high). CyTOF detected an upregulation of important transmembrane receptors in RPs compared to MPs in quiescent platelets: GPVI (p<0.0001), PAR-1 (p<0.0001), GPIX (p<0.0001), and GPIbα (p<0.0001, Figure 1C). After TRAP-stimulation, RPs expressed higher levels of the activation markers P-Selectin (p=0.0016) and LAMP-3 (CD63, p<0.0001) compared to MPs confirming RPs hyperactivity (Figure 1D). Conclusion We here describe the first biological proteomic characterization with single-cell resolution of RPs biology in CCS patients. The upregulation of the activation markers P-Selectin and LAMP-3 as well as of specific transmembrane proteins as the collagen receptor GPVI and the thrombin receptor PAR-1 in patients treated with DAPT (schematic overview in Figure 2) provides the first solid biomolecular explanation of RPs hyper-reactivity and involvement in cardiovascular disease. Moreover, these results offer unexplored therapeutic targets to tailor antiplatelet therapy based on platelet protein expression in patients with elevated RPs FUNDunding Acknowledgement Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Center for Cardiovascular Research (DZHK) Figure 1. Platelet expression Figure 2. Schematic overview


Author(s):  
Gabrielle J. Pennings ◽  
Caroline J. Reddel ◽  
Mathew Traini ◽  
Magdalena Lam ◽  
Maaike Kockx ◽  
...  

Abstract Objective Platelets are critical in mediating both rapid responses to injury and the development and progression of coronary disease. Several studies have shown that, after prolonged exposure to agonists, they produce and release inflammatory mediators including interleukin-1β (IL-1β), via the classical pathway (NLRP3 inflammasome and caspase-1 cleavage to release active IL-1β) as described for leukocytes. This study aimed to determine whether there is rapid release of IL-1β in response to soluble platelet agonists and whether such rapid release is NLRP3- and caspase-1-dependent. Methods and Results Using flow cytometry to detect platelet activation (and release of α and dense granule contents) and the combination of Western blotting, enzyme-linked-immunosorbent assay, and immunogold labeling transmission electron and immunofluorescence microscopy, we identified that resting human platelets contain mature IL-1β. Platelets release IL-1β within minutes in response to adenosine diphosphate (ADP), collagen, and thrombin receptor agonists, but not in response to conventional NLRP3 inflammasome agonists—lipopolysaccharide and adenosine triphosphate. The rapid release of IL-1β in response to ADP and thrombin receptor agonists was independent of caspases (including caspase-1) and NLRP3. Immature and mature IL-1β were identified as low-abundance proteins on transmission electron microscopy of human platelets, and were localized to the platelet cytosol, open canalicular system, and the periphery of α granules. Conclusion Unlike monocytes and neutrophils, human platelets are capable of rapid agonist- and time-dependent release of IL-1β by a mechanism which is independent of caspase-1 and NLRP3.


PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250353
Author(s):  
Harald Haidl ◽  
Johanna Gaugler ◽  
Gerhard Cvirn ◽  
Hildegard Jasser-Nitsche ◽  
Wolfgang Schwinger ◽  
...  

Introduction Atrial fibrillation (AF) comes along with high risk of stroke. This risk continues even after re-establishing sinus rhythm with cardioversion. Aim of this study is to evaluate the contribution of electric cardioversion (EC) to platelet activation and procoagulatory tendency. Methods Extent of platelet activation before and after electric cardioversion was quantified using flow cytometry, impedance aggregation measurements with Multiplate®, and quantification of serum levels of platelet factor 4 (PF4) and ß-thromboglobulin (ß-TG) in patients with AF (N = 10). Results No significant differences were observed in any of the measured parameters comparing the values from before and after cardioversion. Geometric means of P-selectin expression and integrin αIIbβ3 activation were 0.27 (+/- 0.07) and 2.30 (+/- 2.61) before EC and 0.28 (+/- 0.17) and 1.67 (+/- 1.82) after EC. Levels of ß-TG were 110.11 ng/ml (+/- 3.78) before and 110.51 ng/ml (+/- 2.56) after EC, levels of PF4 were 35.64 ng/ml (+/- 12.94) before and 32.40 ng/ml (+/- 4.95) after EC. Platelet aggregation triggered with adenosine diphosphate (ADP), arachidonic acid, collagen, Ristocetin, or thrombin receptor activating peptide (TRAP) revealed results within the normally expected ranges without significant changes before and after EC. Discussion Electric cardioversion has no influence on platelet activation markers which is in agreement with other studies reporting electrical cardioversion to be safe.


Glia ◽  
2021 ◽  
Author(s):  
Ha Neui Kim ◽  
Erin M. Triplet ◽  
Maja Radulovic ◽  
Samantha Bouchal ◽  
Laurel S. Kleppe ◽  
...  

2021 ◽  
Author(s):  
Daisuke Mizutani ◽  
Haruhiko Tokuda ◽  
Takashi Onuma ◽  
Kodai Uematsu ◽  
Daiki Nakashima ◽  
...  

Abstract Background: Amyloid β protein (Aβ) is the main product derived from amyloid precursor protein (APP) by sequential enzymatic actions. Deposition of Aβ in the brain parenchyma or cerebral vessels is a primary morphological feature of Alzheimer’s disease (AD). In addition, abnormal accumulation of Aβ in the cerebral vessels is known as cerebral amyloid angiopathy (CAA), which is considered a risk factor for intracerebral hemorrhage, particularly in the elderly. CAA reportedly contributes to the development of vascular cognitive decline in addition to AD. On the other hand, human platelets are recognized as the principal components affecting the onset and progression of AD. Although there are several studies showing that Aβ directly modulates human platelet functions, the exact mechanism underlying the Aβ effects on human platelets remains to be elucidated.Methods: The present study investigated the effects of Aβ on human platelet activation using a platelet aggregometer with laser scattering, followed by western blot analysis and ELISA.Results: Aβ at doses up to 7 µM alone failed to affect platelet aggregation or platelet-derived growth factor (PDGF)-AB secretion. On the other hand, Aβ decreased the platelet aggregation induced by thrombin receptor-activating protein (TRAP), but not collagen or ADP. Aβ also suppressed platelet aggregation induced by SCP0237, a selective protease-activated receptor (PAR)-1 agonist, and A3227, a selective PAR-4 agonist. The PDGF-AB secretion and the phosphorylated-heat shock protein (HSP)27 release by TRAP were inhibited by Aβ. In addition, the TRAP-induced phosphorylation of JNK and the phosphorylation of p38 MAP kinase followed by phosphorylation of HSP27 were reduced by Aβ.Conclusion: The results of the present study strongly suggest that Aβ negatively regulates PAR-elicited human platelet activation. These findings may indicate one of the causes of intracerebral hemorrhage due to CAA.


Sign in / Sign up

Export Citation Format

Share Document