Jurk K, Kehrel BE. Platelets: physiology and biochemistry

Department of Anaesthesiology and Intensive Care, Experimental and Clinical Haemostasis, University-Hospital Münster, Münster, Germany.
Seminars in Thrombosis and Hemostasis (Impact Factor: 3.88). 02/2005; 31(4):381-92. DOI: 10.1055/s-2005-916671
Source: PubMed


Platelets are specialized blood cells that play central roles in physiologic and pathologic processes of hemostasis, inflammation, tumor metastasis, wound healing, and host defense. Activation of platelets is crucial for platelet function that includes a complex interplay of adhesion and signaling molecules. This article gives an overview of the activation processes involved in primary and secondary hemostasis, for example, platelet adhesion, platelet secretion, platelet aggregation, microvesicle formation, and clot retraction/stabilization. In addition, activated platelets are predominantly involved in cross talk to other blood and vascular cells. Stimulated "sticky" platelets enable recruitment of leukocytes at sites of vascular injury under high shear conditions. Platelet-derived microparticles as well as soluble adhesion molecules, sP-selectin and sCD40L, shed from the surface of activated platelets, are capable of activating, in turn, leukocytes and endothelial cells. This article focuses further on the new view of receptor-mediated thrombin generation of human platelets, necessary for the formation of a stable platelet-fibrin clot during secondary hemostasis. Finally, special emphasis is placed on important stimulatory and inhibitory signaling pathways that modulate platelet function.

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Available from: Beate E Kehrel, Aug 23, 2015
    • "P latelets (PLTs) are key contributors to coagulation and wound healing, as well as providing a significant contribution to inflammation and innate immune responses ( Jurk and Kehrel 2005). Transfusion of platelet concentrates (PCs) is standard in the treatment of thrombocytopenia and severe trauma (Hunt 1998; Sahler and others 2012). "
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    ABSTRACT: The transfusion of platelet concentrates (PCs) is widely used to treat thrombocytopenia and severe trauma. Ex vivo storage of PCs is associated with a storage lesion characterized by partial platelet activation and the release of soluble mediators, such as soluble CD40 ligand (sCD40L), RANTES, and interleukin (IL)-8. An in vitro whole blood culture transfusion model was employed to assess whether mediators present in PC supernatants (PC-SNs) modulated dendritic cell (DC)-specific inflammatory responses (intracellular staining) and the overall inflammatory response (cytometric bead array). Lipopolysaccharide (LPS) was included in parallel cultures to model the impact of PC-SNs on cell responses following toll-like receptor-mediated pathogen recognition. The impact of both the PC dose (10%, 25%) and ex vivo storage period was investigated [day 2 (D2), day 5 (D5), day 7 (D7)]. PC-SNs alone had minimal impact on DC-specific inflammatory responses and the overall inflammatory response. However, in the presence of LPS, exposure to PC-SNs resulted in a significant dose-associated suppression of the production of DC IL-12, IL-6, IL-1α, tumor necrosis factor-α (TNF-α), and macrophage inflammatory protein (MIP)-1β and storage-associated suppression of the production of DC IL-10, TNF-α, and IL-8. For the overall inflammatory response, IL-6, TNF-α, MIP-1α, MIP-1β, and inflammatory protein (IP)-10 were significantly suppressed and IL-8, IL-10, and IL-1β significantly increased following exposure to PC-SNs in the presence of LPS. These data suggest that soluble mediators present in PCs significantly suppress DC function and modulate the overall inflammatory response, particularly in the presence of an infectious stimulus. Given the central role of DCs in the initiation and regulation of the immune response, these results suggest that modulation of the DC inflammatory profile is a probable mechanism contributing to transfusion-related complications.
    Journal of interferon & cytokine research: the official journal of the International Society for Interferon and Cytokine Research 10/2015; 35(10):821-830. DOI:10.1089/jir.2015.0029 · 2.00 Impact Factor
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    • "The relation between platelets and cancer progression suggests a possible role that extends beyond their hemostatic function [14,15]. More recently, platelets have been recognized as mediators of other regulatory functions in physiology such as angiogenesis, wound healing and immunomodulation [15]. "
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    ABSTRACT: Background Head and neck squamous cell carcinoma (HNSCC) mortality rates have not shown significant reduction in decades. Platelets are being implicated in having cancer-promoting roles, an observation supported by the adverse outcomes in many malignancies associated with thrombocytosis. However, the prognostic significance of platelet counts in HNSCC is unknown. Here, we comprehensively investigate the predictive value of platelet counts at diagnosis and post-diagnosis antiplatelet treatment in the overall survival of HNSCC patients.Methods The study population consists of 1051 pathologically confirmed HNSCC cases diagnosed between years 2000 and 2012 in a tertiary medical center. Platelet count was investigated as a predictor of survival by fitting Cox Proportional Hazards (CPH) regression models to generate Hazard Ratios (HR) and 95% confidence intervals (CI), while adjusting for age, sex, race, stage, treatment and smoking status. Finally, we evaluated the association between overall survival and antiplatelet medication intake after diagnosis.ResultsMultivariable analysis showed an increased death rate in patients with thromobocytosis [HR 2.37, 95% CI 1.60-3.50)] and high normal platelet counts [HR 2.20, 95% CI 1.58-3.05] compared to the reference middle normal group. Post-diagnosis treatment with antiplatelet medications was inversely associated with death rate [HR 0.76, 95% CI 0.58-0.99].Conclusions Higher platelet counts were associated with poorer prognosis in HNSCC patients, whereas antiplatelet agents were associated with better prognosis. Antiplatelet agents warrant evaluation in preclinical and clinical settings as a way to improve survival in HNSCC.
    Journal of Hematology & Oncology 09/2014; 7(1):65. DOI:10.1186/s13045-014-0065-5 · 4.81 Impact Factor
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    • "In the platelet plug formation are two stages: Firstly apposition and platelet adhesion and secondly platelet aggregation and secretion (4-6). "
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    ABSTRACT: The hemostasis alterations, either congenital or hereditary origin, and acquired, are circumstances that hinder oral care to patients who suffer them and also generates in the professional who has to attend, high stress. Bleeding control once established and dental treatment planning, both in the aspect of preparation, as the realization of the odonto-stomatological therapeutic, has suffered updates that do need to remember certain aspects of the care of these patients. But we must not forget that the hematologist or internist who controls the patient’s medical condition, is a cornerstone for the planning and implementation of treatment plans. We must also remember that, in certain circumstances, treatment should be performed in a hospital setting. In this review, we aim to provide the odonto-stomatologist guidance on how to address the problem and provide simple and updated guidelines to apply in the treatment of these people. Key words:Hemostasis disorder, oral care protocols, haemorrhagic and thrombotic disorders, haemophilia, von willebrand disease, desmopressin, purple, thrombocytopenia, thrombocytopathies.
    Medicina oral, patologia oral y cirugia bucal 10/2013; 19(3). DOI:10.4317/medoral.19560 · 1.17 Impact Factor
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