Science.gov

Sample records for platelets induces rejection

  1. Platelets in Early Antibody-Mediated Rejection of Renal Transplants

    PubMed Central

    Kuo, Hsiao-Hsuan; Fan, Ran; Dvorina, Nina; Chiesa-Vottero, Andres

    2015-01-01

    Antibody-mediated rejection is a major complication in renal transplantation. The pathologic manifestations of acute antibody-mediated rejection that has progressed to functional impairment of a renal transplant have been defined in clinical biopsy specimens. However, the initial stages of the process are difficult to resolve with the unavoidable variables of clinical studies. We devised a model of renal transplantation to elucidate the initial stages of humoral rejection. Kidneys were orthotopically allografted to immunodeficient mice. After perioperative inflammation subsided, donor-specific alloantibodies were passively transferred to the recipient. Within 1 hour after a single transfer of antibodies, C4d was deposited diffusely on capillaries, and von Willebrand factor released from endothelial cells coated intravascular platelet aggregates. Platelet-transported inflammatory mediators platelet factor 4 and serotonin accumulated in the graft at 100- to 1000-fold higher concentrations compared with other platelet-transported chemokines. Activated platelets that expressed P-selectin attached to vascular endothelium and macrophages. These intragraft inflammatory changes were accompanied by evidence of acute endothelial injury. Repeated transfers of alloantibodies over 1 week sustained high levels of platelet factor 4 and serotonin. Platelet depletion decreased platelet mediators and altered the accumulation of macrophages. These data indicate that platelets augment early inflammation in response to donor-specific antibodies and that platelet-derived mediators may be markers of evolving alloantibody responses. PMID:25145937

  2. Platelet-collagen adhesion enhances platelet aggregation induced by binding of VWF to platelets

    SciTech Connect

    Laduca, F.M.; Bell, W.R.; Bettigole, R.E. State Univ. of New York, Buffalo )

    1987-11-01

    Ristocetin-induced platelet aggregation (RIPA) was evaluated in the presence of platelet-collagen adhesion. RIPA of normal donor platelet-rich plasma (PRP) demonstrated a primary wave of aggregation mediated by the binding of von Willebrand factor (VWF) to platelets and a secondary aggregation wave, due to a platelet-release reaction, initiated by VWF-platelet binding and inhibitable by acetylsalicylic acid (ASA). An enhanced RIPA was observed in PRP samples to which collagen had been previously added. These subthreshold concentrations of collagen, which by themselves were insufficient to induce aggregation, caused measurable platelet-collagen adhesion. Subthreshold collagen did not cause microplatelet aggregation, platelet release of ({sup 3}H)serotonin, or alter the dose-responsive binding of {sup 125}I-labeled VWF to platelets, which occurred with increasing ristocetin concentrations. However, ASA inhibition of the platelet release reaction prevented collagen-enhanced RIPA. These results demonstrate that platelet-collagen adhesion altered the platelet-release reaction induced by the binding of VWF to platelets causing a platelet-release reaction at a level of VWF-platelet binding not normally initiating a secondary aggregation. These findings suggest that platelet-collagen adhesion enhances platelet function mediated by VWF.

  3. Thrombospondin-induced adhesion of human platelets.

    PubMed Central

    Tuszynski, G P; Kowalska, M A

    1991-01-01

    Washed human unactivated platelets attached and spread on thrombospondin (TSP)-coated microtiter plates. Platelet adhesion was promoted by divalent cations Mn2+, Mg2+, and Ca2+ as compared to buffer having all divalent cations complexed with EDTA. TSP-dependent adhesion was inhibited by anti-TSP fab fragments, an anti-TSP monoclonal antibody, an RGD-containing peptide, complex-specific anti-glycoprotein (GP)IIb-IIIa monoclonal antibodies (A2A9 or AP-2) and anti-VLA-2 monoclonal antibodies (6F1 and Gi9), but not by rabbit preimmune fab fragments, mouse IgG, an anti-GPIIIa monoclonal antibody, or monoclonal antibodies against either the human vitronectin receptor, glycocalicin, or GPIV. At saturating concentrations, anti-GPIIb-IIIa inhibited adhesion by 40-60%. Glanzman's thrombasthenic platelets, which lack GPIIb-IIIa, adhered to TSP to the same extent as anti-GPIIb-IIIa-treated normal platelets or 40-60% as well as untreated normal platelets. Antibody 6F1 (5-10 micrograms/ml) inhibited platelet adhesion of both normal and thrombasthenic platelets by 84-100%. Both VLA-2 antibodies also inhibited collagen-induced platelet adhesion, but had no effect on fibronectin-induced adhesion of normal platelets. These data indicate that platelets specifically adhere to TSP and that this adhesion is mediated through GPIIb-IIIa and/or VLA-2. Images PMID:2010551

  4. Reactions Induced by Platelet Transfusions

    PubMed Central

    Kiefel, Volker

    2008-01-01

    Summary Platelet transfusions play a central role in therapeutic regimens for patients with hematologic/oncologic diseases who develop severe thrombocytopenia either in the course of their disease or following cytostatic therapy. Like other blood components, platelet transfusions have achieved a high degree of safety as far as transmission of viral diseases is concerned. However, transfusion of platelet concentrates is accompanied by a high frequency of febrile and anaphylactoid reactions. In rare cases, recipients of platelet concentrates are threatened by severe reactions as septic complications due to bacterial contamination of platelet concentrates, transfusion-related acute lung injury and severe anaphylactic episodes. PMID:21512624

  5. Early diagnosis of acute postoperative renal transplant rejection by indium-111-labeled platelet scintigraphy

    SciTech Connect

    Tisdale, P.L.; Collier, B.D.; Kauffman, H.M.; Adams, M.B.; Isitman, A.T.; Hellman, R.S.; Hoffmann, R.G.; Rao, S.A.; Joestgen, T.; Krohn, L.

    1986-08-01

    A prospective evaluation of /sup 111/In-labeled platelet scintigraphy (IPS) for the early diagnosis of acute postoperative renal transplant rejection (TR) was undertaken. The results of IPS were compared with in vitro biochemical tests, the clinical finding of graft tenderness, and combined (/sup 99m/Tc)DTPA and (/sup 131/I)orthoiodohippurate scintigraphy. With a sensitivity of 0.93 and a specificity of 0.95, IPS provided otherwise unavailable diagnostic information. Furthermore, postoperative IPS was a good predictor of long-term allograft survival.

  6. Accurate diagnosis of renal transplant rejection by indium-111 platelet imaging despite postoperative cyclosporin therapy

    SciTech Connect

    Collier, B.D.; Adams, M.B.; Kauffman, H.M.; Trembath, L.; Hoffmann, R.G.; Tisdale, P.L.; Rao, S.A.; Hellman, R.S.; Isitman, A.T.

    1988-08-01

    Previous reports indicate that In-111 platelet scintigraphy (IPS) is a reliable test for the early diagnosis of acute post-operative renal transplant rejection (TR). However, the recent introduction of cyclosporin for post-transplantation immunosuppression requires that the diagnostic efficacy of IPS once again be established. Therefore, a prospective IPS study of 73 post-operative renal transplant recipients was conducted. Fourty-nine patients received cyclosporin and 24 patients did not receive this drug. Between these two patient groups, there were no significant differences in the diagnostic sensitivities (0.86 vs 0.80) and specificities (0.93 vs 0.84) with which TR was identified. We conclude that during the first two weeks following renal transplantation the cyclosporin treatment regimen used at our institution does not limit the reliability of IPS as a test for TR.

  7. CD8+ T cells induce platelet clearance in the liver via platelet desialylation in immune thrombocytopenia

    PubMed Central

    Qiu, Jihua; Liu, Xuena; Li, Xiaoqing; Zhang, Xu; Han, Panpan; Zhou, Hai; Shao, Linlin; Hou, Yu; Min, Yanan; Kong, Zhangyuan; Wang, Yawen; Wei, Yu; Liu, Xinguang; Ni, Heyu; Peng, Jun; Hou, Ming

    2016-01-01

    In addition to antiplatelet autoantibodies, CD8+ cytotoxic T lymphocytes (CTLs) play an important role in the increased platelet destruction in immune thrombocytopenia (ITP). Recent studies have highlighted that platelet desialylation leads to platelet clearance via hepatocyte asialoglycoprotein receptors (ASGPRs). Whether CD8+ T cells induce platelet desialylation in ITP remains unclear. Here, we investigated the cytotoxicity of CD8+ T cells towards platelets and platelet desialylation in ITP. We found that the desialylation of fresh platelets was significantly higher in ITP patients with positive cytotoxicity of CD8+ T cells than those without cytotoxicity and controls. In vitro, CD8+ T cells from ITP patients with positive cytotoxicity induced significant platelet desialylation, neuraminidase-1 expression on the platelet surface, and platelet phagocytosis by hepatocytes. To study platelet survival and clearance in vivo, CD61 knockout mice were immunized and their CD8+ splenocytes were used. Platelets co-cultured with these CD8+ splenocytes demonstrated decreased survival in the circulation and increased phagocytosis in the liver. Both neuraminidase inhibitor and ASGPRs competitor significantly improved platelet survival and abrogated platelet clearance caused by CD8+ splenocytes. These findings suggest that CD8+ T cells induce platelet desialylation and platelet clearance in the liver in ITP, which may be a novel mechanism of ITP. PMID:27321376

  8. Transfusion Induced Bone Marrow Transplant Rejection Due to Minor Histocompatibility Antigens

    PubMed Central

    Patel, Seema R; Zimring, James C

    2014-01-01

    Traditionally, alloimmunization to transfused blood products has focused exclusively upon recipient antibodies recognizing donor alloantigens present on the cell surface. Accordingly, the immunological sequelae of alloimmunization have been antibody mediated effects (i.e. hemolytic transfusion reactions, platelet refractoriness, anti-HLA and anti-HNA effects, etc.). However, in addition to the above sequelae, there is also a correlation between the number of antecedent transfusions in humans and the rate of bone marrow transplant (BMT) rejection - under reduced intensity conditioning with HLA matched or HLA identical marrow. BMT of this nature is the only existing cure for a series of non-malignant hematological diseases (e.g. sickle cell disease, thalassemias, etc.); however, rejection remains a clinical problem. It has been hypothesized that transfusion induces subsequent BMT rejection through immunization. Studies in animal models have observed the same effect and have demonstrated that transfusion induced BMT rejection can occur in response to alloimmunization. However, unlike traditional antibody responses, sensitization in this case results in cellular immune effects, involving populations such as T cell or NK cells. In this case, rejection occurs in the absence of alloantibodies, and would not be detected by existing immune-hematological methods. We review human and animal studies in light of the hypothesis that, for distinct clinical populations, enhanced rejection of BMT may be an unappreciated adverse consequence of transfusion which current blood bank methodologies are unable to detect. PMID:24090731

  9. Function of eltrombopag-induced platelets compared to platelets from control patients with immune thrombocytopenia.

    PubMed

    Haselboeck, Johanna; Kaider, Alexandra; Pabinger, Ingrid; Panzer, Simon

    2013-04-01

    Data on the in vivo function of platelets induced by the thrombopoietin receptor agonist eltrombopag are scarce. To assess a possible influence of eltrombopag we compared platelet function of eltrombopag-treated immune thrombocytopenia (ITP) patients (group 1; n=10) after treatment response to that from control ITP patients (group 2; n=12). We further analysed platelet function at baseline and after one, three, and four weeks of eltrombopag treatment and estimated daily changes of platelet function during the eltrombopag-induced platelet rise. The formation of platelet-monocyte aggregates (PMA), P-selectin expression [MFI], and platelet adhesion under high shear conditions (surface coverage, SC) in vivo and after in vitro addition of agonists (ADP, TRAP-6, Collagen) were similar between both groups after response to eltrombopag treatment. Only TRAP-6 induced a lower SC in the eltrombopag group (p=0.03). All platelet function parameters except for Collagen-induced P-selectin expression changed significantly during treatment with eltrombopag. PMA, naïve and after addition of ADP or TRAP-6 increased with increasing platelet counts. P-selectin expression decreased, when measured without and upon addition of ADP, increased in the presence of TRAP-6, and remained unchanged after addition of Collagen. SC increased during the eltrombopag-induced platelet rise. All significant changes of platelet function correlated to changes in platelet counts. Two patients developed venous thromboses during eltrombopag treatment, but no association with any distinct single platelet function parameter or combinations thereof was identifiable. Thus, eltrombopag-induced platelets function similar to those from control ITP patients without discernible increased hyper-reactivity.

  10. A simple method for activating the platelets used in microfluidic platelet aggregation tests: Stirring-induced platelet activation

    PubMed Central

    Lee, Hoyoon; Kim, Gyehyu; Lim, Chaeseung; Lee, ByoungKwon; Shin, Sehyun

    2016-01-01

    High-shear stimulation is well known as one of the key factors affecting platelet activation and aggregation, which can lead to the formation of a thrombus. In one of our previous studies, we introduced migration distance-based platelet function analysis in a microfluidic system. In this study, we set out to examine the effects of stirring on shear-induced platelet activation and aggregation in a chamber system by using a rotating stirrer. We found that the rotating stirrer caused not only rotational shear flow but also a strong radial secondary flow. The latter flow led to efficient mixing in the chamber. Moreover, the rotational flow led to the generation of shear stress, the magnitude of which can be controlled to activate the platelets. Activated platelets tend to aggregate themselves. The maximum platelet aggregation was observed at a critical shear rate of 3100 s−1, regardless of the stirrer shape. Furthermore, the time taken to attain maximum aggregation was significantly shortened when using a wide stirrer (30 s) instead of a narrow one (180 s). When using a flat stirrer, the non-uniform shear field in the chamber system was resolved with the radial secondary flow-induced mixing; thus, most of the platelets were homogenously activated. The stirring-induced platelet activation mechanism was experimentally confirmed in a microfluidic system for a platelet aggregation test while monitoring the migration distance until the microfluidic channel is occluded. Our findings indicate that the present system, consisting of a rotating stirrer and a confined chamber, provides effective shear stimulation for activating platelets and inducing platelet aggregates. PMID:28058084

  11. A simple method for activating the platelets used in microfluidic platelet aggregation tests: Stirring-induced platelet activation.

    PubMed

    Lee, Hoyoon; Kim, Gyehyu; Lim, Chaeseung; Lee, ByoungKwon; Shin, Sehyun

    2016-11-01

    High-shear stimulation is well known as one of the key factors affecting platelet activation and aggregation, which can lead to the formation of a thrombus. In one of our previous studies, we introduced migration distance-based platelet function analysis in a microfluidic system. In this study, we set out to examine the effects of stirring on shear-induced platelet activation and aggregation in a chamber system by using a rotating stirrer. We found that the rotating stirrer caused not only rotational shear flow but also a strong radial secondary flow. The latter flow led to efficient mixing in the chamber. Moreover, the rotational flow led to the generation of shear stress, the magnitude of which can be controlled to activate the platelets. Activated platelets tend to aggregate themselves. The maximum platelet aggregation was observed at a critical shear rate of 3100 s(-1), regardless of the stirrer shape. Furthermore, the time taken to attain maximum aggregation was significantly shortened when using a wide stirrer (30 s) instead of a narrow one (180 s). When using a flat stirrer, the non-uniform shear field in the chamber system was resolved with the radial secondary flow-induced mixing; thus, most of the platelets were homogenously activated. The stirring-induced platelet activation mechanism was experimentally confirmed in a microfluidic system for a platelet aggregation test while monitoring the migration distance until the microfluidic channel is occluded. Our findings indicate that the present system, consisting of a rotating stirrer and a confined chamber, provides effective shear stimulation for activating platelets and inducing platelet aggregates.

  12. Increased platelet adhesion under flow conditions is induced by both thalassemic platelets and red blood cells.

    PubMed

    Goldschmidt, Neta; Spectre, Galia; Brill, Alexander; Zelig, Orly; Goldfarb, Ada; Rachmilewitz, Eliezer; Varon, David

    2008-11-01

    Thromboembolic complications are not uncommon in thalassemia. Previous studies suggest increased platelet aggregation and a potential role of pathological changes in the red blood cell (RBC) lipid membrane, induced by oxidative stress. In the present study, platelet adhesion and the effect of thalassemic RBC on platelet adhesion under flow conditions were evaluated, using the Cone and Plate (let) Analyzer(CPA). Twenty-two beta-thalassemia patients and 22 blood type-matched healthy controls were studied. An increased platelet adhesion (% surface coverage, SC), was observed in patients as compared to controls (p < 0.05). When platelet count and haematocrit were normalized by autologous reconstitution, a significant increase in platelet aggregation (average size, AS) was observed (p < 0.05). Increased platelet adhesion (SC and AS), was demonstrated in six patients with a history of thrombosis as compared to 16 patients without any history of thrombosis (p < or = 0.007) and in 17 splenectomized patients as compared to five non-splenectomized patients (p = 0.003). In reconstitution studies, thalassemic RBC mixed with normal platelet-rich plasma significantly increased platelet adhesion compared to normal RBC (SC p < 0.03, AS p < 0.02). Thalassemic platelets reconstituted with normal RBC, had increased aggregation (AS, p < 0.004) in comparison with normal platelets. The results indicate that increased platelet adhesion in beta-thalassemia is induced by both platelets and RBC. Increased platelet adhesion correlated with clinical thrombotic events and thus may suggest a mechanism of thrombosis in thalassemic patients. The potential application of the CPA in identifying thalassemic patients with high risk for thrombosis should be studied prospectively in a larger cohort of patients.

  13. Radiation-induced volatile hydrocarbon production in platelets

    SciTech Connect

    Radha, E.; Vaishnav, Y.N.; Kumar, K.S.; Weiss, J.F.

    1989-01-01

    Generation of volatile hydrocarbons (ethane, pentane) as a measure of lipid peroxidation was followed in preparations from platelet-rich plasma irradiated in vitro. The hydrocarbons in the headspace of sealed vials containing irradiated and nonirradiated washed platelets, platelet-rich plasma, or platelet-poor plasma increased with time. The major hydrocarbon, pentane, increased linearly and significantly with increasing log radiation dose, suggesting that reactive oxygen species induced by ionizing radiation result in lipid peroxidation. Measurements of lipid peroxidation products may give an indication of suboptimal quality of stored and/or irradiated platelets.

  14. Effects of Suilysin on Streptococcus suis-Induced Platelet Aggregation

    PubMed Central

    Zhang, Shengwei; Wang, Junping; Chen, Shaolong; Yin, Jiye; Pan, Zhiyuan; Liu, Keke; Li, Lin; Zheng, Yuling; Yuan, Yuan; Jiang, Yongqiang

    2016-01-01

    Blood platelets play important roles during pathological thrombocytopenia in streptococcal toxic shock syndrome (STSS). Streptococcus suis (S. suis) an emerging human pathogen, can cause STSS similarly to S. pyogenes. However, S. suis interactions with platelets are poorly understood. Here, we found that suilysin (SLY), different from other bacterial cholesterol-dependent cytolysins (CDCs), was the sole stimulus that induced platelet aggregation. Furthermore, the inside-out activation of GPIIb/IIIa of platelets mediated SLY-induced platelet aggregation. This process was triggered by Ca2+ influx that depend on the pore forming on platelets by SLY. Additionally, although SLY induced α-granule release occurred via the MLCK-dependent pathway, PLC-β-IP3/DAG-MLCK and Rho-ROCK-MLCK signaling were not involved in SLY-induced platelet aggregation. Interestingly, the pore dependent Ca2+ influx was also found to participate in the induction of platelet aggregation with pneumolysin (PLY) and streptolysin O (SLO), two other CDCs. It is possible that the CDC-mediated platelet aggregation we observed in S. suis is a similar response mechanism to that used by a wide range of bacteria. These findings might lead to the discovery of potential therapeutic targets for S. suis-associated STSS. PMID:27800304

  15. Platelets protect lung from injury induced by systemic inflammatory response

    PubMed Central

    Luo, Shuhua; Wang, Yabo; An, Qi; Chen, Hao; Zhao, Junfei; Zhang, Jie; Meng, Wentong; Du, Lei

    2017-01-01

    Systemic inflammatory responses can severely injure lungs, prompting efforts to explore how to attenuate such injury. Here we explored whether platelets can help attenuate lung injury in mice resulting from extracorporeal circulation (ECC)-induced systemic inflammatory responses. Mice were subjected to ECC for 30 min, then treated with phosphate-buffered saline, platelets, the GPIIb/IIIa inhibitor Tirofiban, or the combination of platelets and Tirofiban. Blood and lung tissues were harvested 60 min later, and lung injury and inflammatory status were assessed. As expected, ECC caused systemic inflammation and pulmonary dysfunction, and platelet transfusion resulted in significantly milder lung injury and higher lung function. It also led to greater numbers of circulating platelet-leukocyte aggregates and greater platelet accumulation in the lung. Platelet transfusion was associated with higher production of transforming growth factor-β and as well as lower levels of tumour necrosis factor-α and neutrophil elastase in plasma and lung. None of these platelet effects was observed in the presence of Tirofiban. Our results suggest that, at least under certain conditions, platelets can protect lung from injury induced by systemic inflammatory responses. PMID:28155889

  16. Radiation-induced volatile hydrocarbon production in platelets. Scientific report

    SciTech Connect

    Radha, E.; Vaishnav, Y.N.; Kumar, K.S.; Weiss, J.F.

    1989-01-01

    Thrombocytopenia plays an important role in the development of the post-irradiation hemorrhagic syndrome. Although destruction of platelet precursors in bone marrow is a major effect of high-dose radiation exposure, the effects of radiation on preformed platelets are unclear. The latter is also of concern with respect to blood-banking practices since platelets are often irradiated at doses in the range of 20-50 Gy before transfusions to prevent graft-versus-host disease. With increasing emphasis on allogenic and autologous bone-marrow transplantation, transfusions of irradiated platelets are likely to rise. Generation of volatile hydrocarbons (ethane, pentane) as a measure of lipid peroxidation was followed in preparations from platelet-rich plasma irradiated in vitro. The hydrocarbons in the headspace of sealed vials containing irradiated and nonirradiated washed platelets, platelet-rich plasma, or platelet-poor plasma increased with time. The major hydrocarbon, pentane, increased linearly and significantly with increasing log radiation dose, suggesting that reactive oxygen species induced by ionizing radiation result in lipid peroxidation. Measurements of lipid peroxidation products may give an indication of suboptimal quality of stored and/or irradiated platelets.

  17. Generation of functional platelets from canine induced pluripotent stem cells.

    PubMed

    Nishimura, Toshiya; Hatoya, Shingo; Kanegi, Ryoji; Sugiura, Kikuya; Wijewardana, Viskam; Kuwamura, Mitsuru; Tanaka, Miyuu; Yamate, Jyoji; Izawa, Takeshi; Takahashi, Masahiro; Kawate, Noritoshi; Tamada, Hiromichi; Imai, Hiroshi; Inaba, Toshio

    2013-07-15

    Thrombocytopenia (TTP) is a blood disease common to canines and human beings. Currently, there is no valid therapy for this disease except blood transfusion. In this study, we report the generation of canine induced pluripotent stem cells (ciPSCs) from canine embryonic fibroblasts, and a novel protocol for creating mature megakaryocytes (MKs) and functional platelets from ciPSCs. The ciPSCs were generated using lentiviral vectors, and differentiated into MKs and platelets on OP9 stromal cells supplemented with growth factors. Our ciPSCs presented in a tightly domed shape and showed expression of a critical pluripotency marker, REX1, and normal karyotype. Additionally, ciPSCs differentiated into cells derived from three germ layers via the formation of an embryoid body. The MKs derived from ciPSCs had hyperploidy and transformed into proplatelets. The proplatelets released platelets early on that expressed specific MK and platelet marker CD41/61. Interestingly, these platelets, when activated with adenosine diphosphate or thrombin, bind to fibrinogen. Moreover, electron microscopy showed that the platelets had the same ultrastructure as peripheral platelets. Thus, we have demonstrated for the first time the generation of ciPSCs that are capable of differentiating into MKs and release functional platelets in vitro. Our system for differentiating ciPSCs into MKs and platelets promises a critical therapy for canine TTP and appears to be extensible in principle to resolve human TTP.

  18. Creatine kinase inhibits ADP-induced platelet aggregation

    PubMed Central

    Horjus, D. L.; Nieuwland, R.; Boateng, K. B.; Schaap, M. C. L.; van Montfrans, G. A.; Clark, J. F.; Sturk, A.; Brewster, L. M.

    2014-01-01

    Bleeding risk with antiplatelet therapy is an increasing clinical challenge. However, the inter-individual variation in this risk is poorly understood. We assessed whether the level of plasma creatine kinase, the enzyme that utilizes ADP and phosphocreatine to rapidly regenerate ATP, may modulate bleeding risk through a dose-dependent inhibition of ADP-induced platelet activation. Exogenous creatine kinase (500 to 4000 IU/L, phosphocreatine 5 mM) added to human plasma induced a dose-dependent reduction to complete inhibition of ADP-induced platelet aggregation. Accordingly, endogenous plasma creatine kinase, studied in 9 healthy men (mean age 27.9 y, SE 3.3; creatine kinase 115 to 859 IU/L, median 358), was associated with reduced ADP-induced platelet aggregation (Spearman's rank correlation coefficient, −0.6; p < 0.05). After exercise, at an endogenous creatine kinase level of 4664, ADP-induced platelet aggregation was undetectable, normalizing after rest, with a concomitant reduction of creatine kinase to normal values. Thus, creatine kinase reduces ADP-induced platelet activation. This may promote bleeding, in particular when patients use platelet P2Y12 ADP receptor inhibitors. PMID:25298190

  19. High shear flow induces migration of adherent human platelets.

    PubMed

    Kraemer, Bjoern F; Schmidt, Christine; Urban, Benjamin; Bigalke, Boris; Schwanitz, Laura; Koch, Miriam; Seizer, Peter; Schaller, Martin; Gawaz, Meinrad; Lindemann, Stephan

    2011-01-01

    Shear forces are generated in all parts of the vascular system and contribute directly and indirectly to vascular disease progression. Endothelial cells are able to adapt to flow conditions, and are known to polarize and migrate in response to shear forces. Platelets exposed to shear stress are activated and release bioactive molecules from their alpha granules. So far, platelets have been considered to be static cells that do not leave the site of tight adhesion. However, we have recently been able to demonstrate the capacity of platelets to migrate in response to stromal derived factor-1 (SDF-1). In this project, we have demonstrated that platelets accumulate in areas with a high concentration of SDF-1 under flow conditions and respond to high shear stress by cellular polarization, cytoskeletal reorganisation, and flow-directed migration. In this context, we have shown increased Wiskott-Aldrich Syndrome protein (WASP) phosphorylation and intracellular redistribution of focal adhesion kinase (FAK) under high-shear stress conditions. The effect of flow-induced platelet migration has not previously been recognized and offers a new role for platelets as mobile cells. Their migratory potential may enable platelets to cover intimal lesions and contribute to vascular repair.

  20. Transgenic, inducible RNAi in megakaryocytes and platelets in mice

    PubMed Central

    TAKIGUCHI, M.; JAMES, C.; JOSEFSSON, E. C.; CARMICHAEL, C. L.; PREMSRIRUT, P. K.; LOWE, S. W.; HAMILTON, J. R.; HUANG, D. C. S.; KILE, B. T.; DICKINS, R. A.

    2012-01-01

    Summary Background RNA interference (RNAi) is a powerful tool for suppressing gene function. The tetracycline (tet)-regulated expression system has recently been adapted to allow inducible RNAi in mice, however its efficiency in a particular cell type in vivo depends on a transgenic tet transactivator expression pattern and is often highly variable. Objective We aimed to establish a transgenic strategy that allows efficient and inducible gene knockdown in particular hematopoietic lineages in mice. Methods and results Using a tet-regulated reporter gene strategy, we found that transgenic mice expressing the rtTA (tet-on) transactivator under control of the cytomegalovirus (CMV) promoter (CMV-rtTA mice) display inducible reporter gene expression with unusual and near-complete efficiency in megakaryocytes and platelets. To test whether the CMV-rtTA transgene can drive inducible and efficient gene knockdown within this lineage, we generated a novel mouse strain harboring a tet-regulated short hairpin RNA (shRNA) targeting Bcl-xL, a pro-survival Bcl-2 family member known to be essential for maintaining platelet survival. Doxycycline treatment of adult mice carrying both transgenes induces shRNA expression, depletes Bcl-xL in megakaryocytes and triggers severe thrombocytopenia, whereas doxycycline withdrawal shuts off shRNA expression, normalizes Bcl-xL levels and restores platelet numbers. These effects are akin to those observed with drugs that target Bcl-xL, clearly demonstrating that this transgenic system allows efficient and inducible inhibition of genes in megakaryocytes and platelets. Conclusions We have established a novel transgenic strategy for inducible gene knockdown inmegakaryocytes and platelets that will be useful for characterizing genes involved in platelet production and function in adult mice. PMID:21138522

  1. Serum-induced platelet procoagulant activity: an assay for the characterization of prothrombotic disorders.

    PubMed

    Warner, M N; Pavord, S; Moore, J C; Warkentin, T E; Hayward, C P; Kelton, J G

    1999-02-01

    Platelets contribute to hemostasis by forming a platelet plug and by providing a procoagulant surface for the assembly and activation of the coagulation factors. The contribution of platelets to prothrombotic disorders has been difficult to analyze. Recently an assay was reported that measured the procoagulant activity of test platelets by making the platelet lipid surface the limiting factor in the production of thrombin. In this report we describe a novel technique, based on this assay, that we used to study patient serum factors that activate control platelets and in turn initiate measurable procoagulant activity. Using this assay we investigated a group of patients with prothrombotic disorders. The patient test serum was incubated with normal platelets in the presence of activated factor Xa. The resultant thrombin was measured in a chromogenic assay. The rate-limiting step was the presence of any potential platelet-activating factors, such as antibodies in the heat-treated test serum, that would allow the Xa to bind to the platelet phospholipid surface. Serum samples from patients with heparin-induced thrombocytopenia (HIT) and the anti-phospholipid antibody syndrome enhanced platelet procoagulant activity, while samples from patients with idiopathic thrombocytopenic purpura and disseminated intravascular coagulation (DIC) did not. HIT serum samples also induced platelet activation, as measured by platelet microparticle shedding, carbon 14-labeled serotonin release, and platelet aggregation. The measurement of serum-induced platelet procoagulant activity provides a method for the investigation of circulating platelet agonists in prothrombotic disorders.

  2. Peer Rejection Cues Induce Cardiac Slowing after Transition into Adolescence

    ERIC Educational Resources Information Center

    Gunther Moor, Bregtje; Bos, Marieke G. N.; Crone, Eveline A.; van der Molen, Maurits W.

    2014-01-01

    The present study examined developmental and gender differences in sensitivity to peer rejection across the transition into adolescence by examining beat-by-beat heart rate responses. Children between the ages of 8 and 14 years were presented with unfamiliar faces of age-matched peers and were asked to predict whether they would be liked by the…

  3. Mechanism of platelet activation induced by endocannabinoids in blood and plasma.

    PubMed

    Brantl, S Annette; Khandoga, Anna L; Siess, Wolfgang

    2014-01-01

    Platelets play a central role in atherosclerosis and atherothrombosis, and circulating endocannabinoids might modulate platelet function. Previous studies concerning effects of anandamide (N-arachidonylethanolamide) and 2-arachidonoylglycerol (2-AG) on platelets, mainly performed on isolated cells, provided conflicting results. We therefore investigated the action of three main endocannabinoids [anandamide, 2-AG and virodhamine (arachidonoylethanolamine)] on human platelets in blood and platelet-rich plasma (PRP). 2-AG and virodhamine induced platelet aggregation in blood, and shape change, aggregation and adenosine triphosphate (ATP) secretion in PRP. The EC50 of 2-AG and virodhamine for platelet aggregation in blood was 97 and 160 µM, respectively. Lower concentrations of 2-AG (20 µM) and virodhamine (50 µM) synergistically induced aggregation with other platelet stimuli. Platelet activation induced by 2-AG and virodhamine resembled arachidonic acid (AA)-induced aggregation: shape change, the first platelet response, ATP secretion and aggregation induced by 2-AG and virodhamine were all blocked by acetylsalicylic acid (ASA) or the specific thromboxane A2 (TXA2) antagonist daltroban. In addition, platelet activation induced by 2-AG and virodhamine in blood and PRP were inhibited by JZL184, a selective inhibitor of monoacylglycerol lipase (MAGL). In contrast to 2-AG and virodhamine, anandamide, a substrate of fatty acid amidohydrolase, was inactive. Synthetic cannabinoid receptor subtype 1 (CB1) and 2 (CB2) agonists lacked stimulatory as well as inhibitory platelet activity. We conclude that 2-AG and virodhamine stimulate platelets in blood and PRP by a MAGL-triggered mechanism leading to free AA and its metabolism by platelet cyclooxygenase-1/thromboxane synthase to TXA2. CB1, CB2 or non-CB1/CB2 receptors are not involved. Our results imply that ASA and MAGL inhibitors will protect platelets from activation by high endocannabinoid levels, and that

  4. An atypical IgM class platelet cold agglutinin induces GPVI-dependent aggregation of human platelets.

    PubMed

    Sánchez Guiu, I M; Martínez-Martinez, I; Martínez, C; Navarro-Fernandez, J; García-Candel, F; Ferrer-Marín, F; Vicente, V; Watson, S P; Andrews, R K; Gardiner, E E; Lozano, M L; Rivera, J

    2015-08-01

    Platelet cold agglutinins (PCA) cause pseudothrombocytopenia, spurious thrombocytopenia due to ex vivo platelet clumping, complicating clinical diagnosis, but mechanisms and consequences of PCA are not well defined. Here, we characterised an atypical immunoglobulin (Ig)M PCA in a 37-year-old woman with lifelong bleeding and chronic moderate thrombocytopenia, that induces activation and aggregation of autologous or allogeneic platelets via interaction with platelet glycoprotein (GP)VI. Patient temperature-dependent pseudothrombocytopenia was EDTA-independent, but was prevented by integrin αIIbβ3 blockade. Unstimulated patient platelets revealed elevated levels of bound IgM, increased expression of activation markers (P-selectin and CD63), low GPVI levels and abnormally high thromboxane (TX)A2 production. Patient serum induced temperature- and αIIbβ3-dependent decrease of platelet count in allogeneic donor citrated platelet-rich plasma (PRP), but not in PRP from Glanzmann's thrombasthenia or afibrinogenaemia patients. In allogeneic platelets, patient plasma induced shape change, P-selectin and CD63 expression, (14)C-serotonin release, and TXA2 production. Activation was not inhibited by aspirin, cangrelor or blocking anti-Fc receptor (FcγRIIA) antibody, but was abrogated by inhibitors of Src and Syk, and by a soluble GPVI-Fc fusion protein. GPVI-deficient platelets were not activated by patient plasma. These data provide the first evidence for an IgM PCA causing platelet activation/aggregation via GPVI. The PCA activity persisted over a five-year follow-up period, supporting a causative role in patient chronic thrombocytopenia and bleeding.

  5. Dabigatran and rivaroxaban do not affect AA- and ADP-induced platelet aggregation in patients receiving concomitant platelet inhibitors.

    PubMed

    Olivier, Christoph B; Weik, Patrick; Meyer, Melanie; Weber, Susanne; Diehl, Philipp; Bode, Christoph; Moser, Martin; Zhou, Qian

    2016-08-01

    Dabigatran and rivaroxaban are novel, vitamin K-independent oral anticoagulants (NOACs) and act via antagonism of the coagulation factor (F) IIa (dabigatran) or FXa (rivaroxaban), respectively. Compared to vitamin-K-antagonists, NOACs have shown non-inferiority of risk and benefit in patients with non valvular atrial fibrillation (AF). In clinical practice there is increasing use of NOACs combined with platelet inhibitors in patients with AF and coronary artery disease. However, whether NOACs affect the function of platelet inhibitors remains incompletely known. This observational study aimed to assess the platelet function in patients receiving dabigatran or rivaroxaban and concomitant platelet inhibitors. A single centre observational study was performed analysing the platelet aggregation of patients treated with dabigatran or rivaroxaban with or without concomitant platelet inhibitors. Measurements before the initiation of NOAC therapy served as the respective control group. Platelet aggregation was measured by multiple electrode aggregometry and was induced with adenosine diphosphate (ADP, 6.5 µM) and arachidonic acid (AA, 0.5 mM), respectively. In order to evaluate whether NOACs interact with platelet inhibition by ASA or the P2Y12-antagonist clopidogrel, 87 patients were grouped according to their concomitant antiplatelet medication. Comparing the ADP- and AA-induced platelet aggregation in patients without concomitant platelet inhibitors (n = 45) no significant differences under therapy with dabigatran (d) or rivaroxaban (r) compared to the control group (c) were observed. In patients taking clopidogrel as a concomitant platelet inhibitor (n = 21), neither dabigatran nor rivaroxaban affected the ADP-induced platelet aggregation (c 20 ± 11, d 21 ± 14, r 18 ± 8 AU*min, p = 0.200). Patients receiving dabigatran or rivaroxaban in combination with ASA (n = 42; 21 ASA only, 21 ASA + clopidogrel) showed no significant differences of the AA-induced

  6. Alloantibody induced platelet responses in transplants: potent mediators in small packages.

    PubMed

    Kuo, Hsiao-Hsuan; Morrell, Craig N; Baldwin, William M

    2012-12-01

    The early histological studies of organ allografts noted platelets attached to vascular endothelium. Platelets adhere to vessels before any morphological evidence of endothelial injury. Subsequently, in vitro and in vivo experiments have demonstrated that alloantibodies can induce exocytosis of von Willebrand factor and P-selectin from endothelial cells and attachment of platelets within minutes. Platelets also adhere to and stimulate leukocytes. These interactions are increased by complement activation. After attachment platelets degranulate, releasing preformed mediators. Some chemokines stored together in platelet granules can form heteromers with synergistic functions. Heteromers containing platelet factor 4 (PF4; CXCL4) are specific to platelets and provide insights to unique platelet functions and opportunities for therapeutic intervention.

  7. In vitro platelet activation, aggregation and platelet-granulocyte complex formation induced by surface modified single-walled carbon nanotubes.

    PubMed

    Fent, János; Bihari, Péter; Vippola, Minnamari; Sarlin, Essi; Lakatos, Susan

    2015-08-01

    Surface modification of single-walled carbon nanotubes (SWCNTs) such as carboxylation, amidation, hydroxylation and pegylation is used to reduce the nanotube toxicity and render them more suitable for biomedical applications than their pristine counterparts. Toxicity can be manifested in platelet activation as it has been shown for SWCNTs. However, the effect of various surface modifications on the platelet activating potential of SWCNTs has not been tested yet. In vitro platelet activation (CD62P) as well as the platelet-granulocyte complex formation (CD15/CD41 double positivity) in human whole blood were measured by flow cytometry in the presence of 0.1mg/ml of pristine or various surface modified SWCNTs. The effect of various SWCNTs was tested by whole blood impedance aggregometry, too. All tested SWCNTs but the hydroxylated ones activate platelets and promote platelet-granulocyte complex formation in vitro. Carboxylated, pegylated and pristine SWCNTs induce whole blood aggregation as well. Although pegylation is preferred from biomedical point of view, among the samples tested by us pegylated SWCNTs induced far the most prominent activation and a well detectable aggregation of platelets in whole blood.

  8. Platelet size and density affect shear-induced thrombus formation in tortuous arterioles

    NASA Astrophysics Data System (ADS)

    Chesnutt, Jennifer K. W.; Han, Hai-Chao

    2013-10-01

    Thrombosis accounts for 80% of deaths in patients with diabetes mellitus. Diabetic patients demonstrate tortuous microvessels and larger than normal platelets. Large platelets are associated with increased platelet activation and thrombosis, but the physical effects of large platelets in the microscale processes of thrombus formation are not clear. Therefore, the objective of this study was to determine the physical effects of mean platelet volume (MPV), mean platelet density (MPD) and vessel tortuosity on platelet activation and thrombus formation in tortuous arterioles. A computational model of the transport, shear-induced activation, collision, adhesion and aggregation of individual platelets was used to simulate platelet interactions and thrombus formation in tortuous arterioles. Our results showed that an increase in MPV resulted in a larger number of activated platelets, though MPD and level of tortuosity made little difference on platelet activation. Platelets with normal MPD yielded the lowest amount of mural thrombus. With platelets of normal MPD, the amount of mural thrombus decreased with increasing level of tortuosity but did not have a simple monotonic relationship with MPV. The physical mechanisms associated with MPV, MPD and arteriole tortuosity play important roles in platelet activation and thrombus formation.

  9. Clinical application of radiolabelled platelets

    SciTech Connect

    Kessler, C. )

    1990-01-01

    This book presents papers on the clinical applications of radiolabelled platelets. The papers are grouped into six sections on platelet labelling techniques, radiolabelled platelets in cardiology, monitoring of antiplatelet therapy, platelet scintigraphy in stroke patients, platelet scintigraphy in angiology, and platelet scintigraphy in hematology and other clinical applications, including renal transplant rejection.

  10. Reversibility of thrombin-induced decrease in platelet glycoprotein Ib function.

    PubMed

    Lu, H; Menashi, S; Garcia, I; Cramer, E M; Li, H; Tenza, D; De Romeuf, C; Soria, J; Soria, C

    1993-09-01

    Thrombin induces a redistribution of glycoprotein (GP) Ib/GP IX complex from the platelet surface into the surface connected canalicular system (SCCS). This redistribution results in a reduced interaction of platelet GP Ib with von Willebrand factor (vWF) bound to subendothelium leading to impaired platelet adhesion. In this study we show that the platelet aggregation and degranulation require concentrations of thrombin above 0.05 U/ml, while the decrease in GP Ib function (about 50% of control value), as determined by ristocetin induced platelet agglutination, can be induced by lower concentrations (0.01-0.04 U/ml). Moreover, we show that when adding thrombin inhibitors to the platelets preincubated with < 0.04 U/ml thrombin for 5 min, their agglutinability by ristocetin was gradually recovered within 30 min, indicating that in these conditions the decrease in platelet adhesiveness is reversible. Immuno-electromicroscopic study showed that this restoration of platelet GP Ib function was associated with a reversed translocation of GP Ib from the SCCS to the plasma membrane. The data obtained from counting gold particles showed that the ratio of GP Ib immunolabelling on the external membrane versus that on the SCCS was 3.31 +/- 0.90 for resting platelets, down-regulated to 0.84 +/- 0.13 (P < 0.05 versus resting platelets) for the platelets treated with 0.04 U/ml thrombin and returned to 2.63 +/- 2.21 (P > 0.05 versus resting platelets) after incubation for 30 min with hirudin. However, the translocation of GP Ib was poorly reversed by thrombin inhibitors when higher concentrations of thrombin were used which induced platelet aggregation and large extent of degranulation. We conclude that thrombin affects platelets in a dose dependent manner, and that at low concentrations the decrease in platelet GP Ib related function is a reversible phenomenon.

  11. Crocin prevents sesamol-induced oxidative stress and apoptosis in human platelets.

    PubMed

    Thushara, Ram M; Hemshekhar, Mahadevappa; Paul, Manoj; Shanmuga Sundaram, Mahalingam; Shankar, Rohith L; Kemparaju, Kempaiah; Girish, Kesturu S

    2014-10-01

    Recent studies have reported the platelet proapoptotic propensity of plant-derived molecules such as, resveratrol, thymoquinone, andrographolide and gossypol. Meanwhile, there were also reports of phytochemicals such as cinnamtannin B1, which shows antiapoptotic effect towards platelets. Platelets are mainly involved in hemostasis, thrombosis and wound healing. However, altered platelet functions can have serious pathological outcomes that include cardiovascular diseases. Platelets are sensitive to external and internal stimuli including therapeutic and dietary components. The anuclear platelets do undergo apoptosis via mitochondrial pathway. However, exaggerated rate of platelet apoptosis could lead to thrombocytopenia and other bleeding disorders. The present study deals with ameliorative efficacy of crocin on sesamol-induced platelet apoptosis. The antiapoptotic property of crocin and the proapoptotic tendency of sesamol in platelets were previously demonstrated. Therefore, it was interesting to see how these two compounds would interact and wield their effects on human platelets. Crocin effectively inhibited sesamol-induced oxidative stress on platelets, which was evidenced by the measurement of endogenously generated reactive oxygen species, particularly hydrogen peroxide, and changes in thiol levels. Further, crocin abrogated sesamol-induced biochemical events of apoptosis in platelets, which include intracellular calcium mobilization, changes in mitochondrial membrane integrity, cytochrome c release, caspase activity and phosphatidylserine externalization. Even though sesamol has proapoptotic effects on platelets, its anti-platelet activity cannot be neglected. Thus, the study proposes that sesamol could be supplemented with crocin, an approach that could not only abolish the toxic effects of sesamol on platelets, but also enhance the quality of treatment due to their synergistic action.

  12. Targeting factor VIII expression to platelets for hemophilia A gene therapy does not induce an apparent thrombotic risk in mice.

    PubMed

    Baumgartner, C K; Mattson, J G; Weiler, H; Shi, Q; Montgomery, R R

    2017-01-01

    Essentials Platelet-Factor (F) VIII gene therapy is a promising treatment in hemophilia A. This study aims to evaluate if platelet-FVIII expression would increase the risk for thrombosis. Targeting FVIII expression to platelets does not induce or elevate thrombosis risk. Platelets expressing FVIII are neither hyper-activated nor hyper-responsive.

  13. Scalable generation of universal platelets from human induced pluripotent stem cells.

    PubMed

    Feng, Qiang; Shabrani, Namrata; Thon, Jonathan N; Huo, Hongguang; Thiel, Austin; Machlus, Kellie R; Kim, Kyungho; Brooks, Julie; Li, Feng; Luo, Chenmei; Kimbrel, Erin A; Wang, Jiwu; Kim, Kwang-Soo; Italiano, Joseph; Cho, Jaehyung; Lu, Shi-Jiang; Lanza, Robert

    2014-11-11

    Human induced pluripotent stem cells (iPSCs) provide a potentially replenishable source for the production of transfusable platelets. Here, we describe a method to generate megakaryocytes (MKs) and functional platelets from iPSCs in a scalable manner under serum/feeder-free conditions. The method also permits the cryopreservation of MK progenitors, enabling a rapid "surge" capacity when large numbers of platelets are needed. Ultrastructural/morphological analyses show no major differences between iPSC platelets and human blood platelets. iPSC platelets form aggregates, lamellipodia, and filopodia after activation and circulate in macrophage-depleted animals and incorporate into developing mouse thrombi in a manner identical to human platelets. By knocking out the β2-microglobulin gene, we have generated platelets that are negative for the major histocompatibility antigens. The scalable generation of HLA-ABC-negative platelets from a renewable cell source represents an important step toward generating universal platelets for transfusion as well as a potential strategy for the management of platelet refractoriness.

  14. Scalable Generation of Universal Platelets from Human Induced Pluripotent Stem Cells

    PubMed Central

    Feng, Qiang; Shabrani, Namrata; Thon, Jonathan N.; Huo, Hongguang; Thiel, Austin; Machlus, Kellie R.; Kim, Kyungho; Brooks, Julie; Li, Feng; Luo, Chenmei; Kimbrel, Erin A.; Wang, Jiwu; Kim, Kwang-Soo; Italiano, Joseph; Cho, Jaehyung; Lu, Shi-Jiang; Lanza, Robert

    2014-01-01

    Summary Human induced pluripotent stem cells (iPSCs) provide a potentially replenishable source for the production of transfusable platelets. Here, we describe a method to generate megakaryocytes (MKs) and functional platelets from iPSCs in a scalable manner under serum/feeder-free conditions. The method also permits the cryopreservation of MK progenitors, enabling a rapid “surge” capacity when large numbers of platelets are needed. Ultrastructural/morphological analyses show no major differences between iPSC platelets and human blood platelets. iPSC platelets form aggregates, lamellipodia, and filopodia after activation and circulate in macrophage-depleted animals and incorporate into developing mouse thrombi in a manner identical to human platelets. By knocking out the β2-microglobulin gene, we have generated platelets that are negative for the major histocompatibility antigens. The scalable generation of HLA-ABC-negative platelets from a renewable cell source represents an important step toward generating universal platelets for transfusion as well as a potential strategy for the management of platelet refractoriness. PMID:25418726

  15. FcγRIIa ligation induces platelet hypersensitivity to thrombotic stimuli.

    PubMed

    Berlacher, Mark D; Vieth, Joshua A; Heflin, Brittany C; Gay, Steven R; Antczak, Adam J; Tasma, Brian E; Boardman, Holly J; Singh, Navinderjit; Montel, Angela H; Kahaleh, M Bashar; Worth, Randall G

    2013-01-01

    Platelets are known for their important role in hemostasis, however their significance in other functions, including inflammation and infection, are becoming more apparent. Patients with systemic lupus erythematosus (SLE) are known to have circulating IgG complexes in their blood and are highly susceptible to thrombotic events. Because platelets express a single receptor for IgG, we tested the hypothesis that ligation of this receptor (FcγRIIa) induces platelet hypersensitivity to thrombotic stimuli. Platelets from SLE patients were considerably more sensitive to thrombin compared to healthy volunteers, and this correlated with elevated levels of surface IgG on SLE platelets. To test whether FcγRIIa ligation stimulated thrombin hypersensitivity, platelets from healthy volunteers were incubated with buffer or heat-aggregated IgG, then stimulated with increasing concentrations of thrombin. Interestingly, heat-aggregated IgG-stimulated platelets, but not buffer-treated platelets, were hypersensitive to thrombin, and hypersensitivity was blocked by an anti-FcγRIIa monoclonal antibody (mAb). Thrombin hypersensitivity was not due to changes in thrombin receptor expression (GPIbα or PAR1) but is dependent on activation of shared signaling molecules. These observations suggest that ligation of platelet FcγRIIa by IgG complexes induces a hypersensitive state whereby small changes in thrombotic stimuli may result in platelet activation and subsequent vascular complications such as transient ischemic attacks or stroke.

  16. Platelet–cancer interactions: mechanisms and pharmacology of tumour cell-induced platelet aggregation

    PubMed Central

    Jurasz, Paul; Alonso-Escolano, David; Radomski, Marek W

    2004-01-01

    During haematogenous metastasis, cancer cells migrate to the vasculature and interact with platelets resulting in tumour cell-induced platelet aggregation (TCIPA). We review: The biological and clinical significance of TCIPA; Molecular mechanisms involved in platelet aggregation by cancer cells; Strategies for pharmacological regulation of these interactions. We conclude that pharmacological regulation of platelet–cancer cell interactions may reduce the impact of TCIPA on cancer biology. PMID:15492016

  17. Hyaluronic acid influence on platelet-induced airway smooth muscle cell proliferation

    SciTech Connect

    Svensson Holm, Ann-Charlotte B.; Bengtsson, Torbjoern; Grenegard, Magnus; Lindstroem, Eva G.

    2012-03-10

    Hyaluronic acid (HA) is one of the main components of the extracellular matrix (ECM) and is expressed throughout the body including the lung and mostly in areas surrounding proliferating and migrating cells. Furthermore, platelets have been implicated as important players in the airway remodelling process, e.g. due to their ability to induce airway smooth muscle cell (ASMC) proliferation. The aim of the present study was to investigate the role of HA, the HA-binding surface receptor CD44 and focal adhesion kinase (FAK) in platelet-induced ASMC proliferation. Proliferation of ASMC was measured using the MTS-assay, and we found that the CD44 blocking antibody and the HA synthase inhibitor 4-Methylumbelliferone (4-MU) significantly inhibited platelet-induced ASMC proliferation. The interaction between ASMC and platelets was studied by fluorescent staining of F-actin. In addition, the ability of ASMC to synthesise HA was investigated by fluorescent staining using biotinylated HA-binding protein and a streptavidin conjugate. We observed that ASMC produced HA and that a CD44 blocking antibody and 4-MU significantly inhibited platelet binding to the area surrounding the ASMC. Furthermore, the FAK-inhibitor PF 573228 inhibited platelet-induced ASMC proliferation. Co-culture of ASMC and platelets also resulted in increased phosphorylation of FAK as detected by Western blot analysis. In addition, 4-MU significantly inhibited the increased FAK-phosphorylation. In conclusion, our findings demonstrate that ECM has the ability to influence platelet-induced ASMC proliferation. Specifically, we propose that HA produced by ASMC is recognised by platelet CD44. The platelet/HA interaction is followed by FAK activation and increased proliferation of co-cultured ASMC. We also suggest that the mitogenic effect of platelets represents a potential important and novel mechanism that may contribute to airway remodelling.

  18. Extracellular matrix metalloproteinase inducer (CD147) is a novel receptor on platelets, activates platelets, and augments nuclear factor kappaB-dependent inflammation in monocytes.

    PubMed

    Schmidt, Roland; Bültmann, Andreas; Fischel, Sina; Gillitzer, Angelika; Cullen, Paul; Walch, Axel; Jost, Philipp; Ungerer, Martin; Tolley, Neal D; Lindemann, Stephan; Gawaz, Meinrad; Schömig, Albert; May, Andreas E

    2008-02-15

    In atherosclerosis, circulating platelets interact with endothelial cells and monocytes, leading to cell activation and enhanced recruitment of leukocytes into the vascular wall. The invasion of monocytes is accompanied by overexpression of matrix metalloproteinases (MMPs), which are thought to promote atherosclerosis and trigger plaque rupture. Following interaction with itself, the extracellular matrix metalloproteinase inducer (EMMPRIN) induces MMP synthesis via a little-known intracellular pathway. Recently, we showed upregulation of EMMPRIN on monocytes during acute myocardial infarction. EMMPRIN also stimulates secretion of MMP-9 by monocytes and of MMP-2 by smooth muscle cells, indicating that it may be an important regulator of MMP activity. Expression of EMMPRIN on platelets has not been described until now. Here, we demonstrate that resting platelets show low surface expression of EMMPRIN, which is upregulated by various platelet stimulators (flow cytometry). EMMPRIN is located in the open canalicular system and in alpha granules of platelets (according to electron microscopy and sucrose gradient ultracentrifugation). Platelet stimulation with recombinant EMMPRIN-Fc induced surface expression of CD40L and P-selectin (according to flow cytometry), suggesting that EMMPRIN-EMMPRIN interaction activates platelets. Coincubation of platelets with monocytes induced EMMPRIN-mediated nuclear factor kappaB activation (according to Western blot) in monocytes with increased MMP-9 (zymography), interleukin-6, and tumor necrosis factor-alpha secretion (according to ELISA) by monocytes. In conclusion, EMMPRIN displays a new platelet receptor that is upregulated on activated platelets. Binding of EMMPRIN to platelets fosters platelet degranulation. Platelet-monocyte interactions via EMMPRIN stimulate nuclear factor kappaB-driven inflammatory pathways in monocytes, such as MMP and cytokine induction. Thus, EMMPRIN may represent a novel target to diminish the burden of

  19. Sunlight suppressing rejection of 280- to 320-nm UV-radiation-induced skin tumors in mice

    SciTech Connect

    Morison, W.L.; Kelley, S.P.

    1985-02-01

    Repeated exposure of female C3H/HeNCR- mice to sunlight prevented the normal immunologic rejection of a UV-induced tumor. This systemic immunologic alteration was transferred to syngeneic lethally X-irradiated animals with lymphoid cells from mice exposed to sunlight. The lymphoid cells also were able to suppress the capacity of lymphoid cells from normal animals to reject a UV-induced tumor. The 295- to 320-nm wave band appeared to be responsible for this immunosuppressive effect of sunlight because suppression was prevented by filtration of the radiation through Mylar and by application of a sunscreen containing para-aminobenzoic acid. These observations may have importance in understanding the pathogenesis of sunlight-induced skin cancer in humans.

  20. Immune response to UV-induced tumors: mediation of progressor tumor rejection by natural killer cells

    SciTech Connect

    Streeter, P.R.; Fortner, G.W.

    1986-03-01

    Skin tumors induced in mice by chronic ultraviolet (UV) irradiation are highly antigenic and can induce a state of transplantation immunity in syngeneic animals. In the present study, the authors compared the in vitro cytolytic activity of splenic lymphocytes from mice immunized with either regressor or progressor UV-tumors. The results of this comparison implicated tumor-specific cytolytic T (Tc) lymphocytes in rejection of regressor UV-tumors, and revealed that immunization with the progressor UV-tumor 2237 failed to elicit detectable levels of progressor tumor-specific Tc cells even as the tumors rejected. Following in vitro resensitization of spleen cells from either regressor or progressor tumor immune animals, the authors found NK-like lymphocytes with anti-tumor activity. As the authors had not detected cells with this activity in splenic lymphocyte preparations prior to in vitro resensitization, the authors examined lymphocytes from the local tumor environment during the course of progressor tumor rejection for this activity. This analysis revealed NK lymphocytes exhibiting significant levels of cytolytic activity against UV-tumors. These results implicate NK cells as potential effector cells in the rejection of progressor UV-tumors by immune animals, and suggests that these cells may be regulated by T lymphocytes.

  1. Platelet activation during exercise induced asthma: effect of prophylaxis with cromoglycate and salbutamol.

    PubMed Central

    Johnson, C E; Belfield, P W; Davis, S; Cooke, N J; Spencer, A; Davies, J A

    1986-01-01

    Peak expiratory flow (PEF) and plasma concentrations of platelet factor 4 and beta thromboglobulin were measured before and after exercise in nine asthmatic patients and 12 non-asthmatic volunteers. Exercise was preceded by administration in random order of either placebo, salbutamol 200 micrograms, or sodium cromoglycate 2 mg from a pressurised inhaler. In control subjects there were minimal changes in PEF and plasma concentrations of platelet factor 4 and beta thromboglobulin. In the asthmatic patients the typical changes in PEF were seen on exercise; plasma concentrations of platelet factor 4 and beta thromboglobulin rose significantly in parallel, the rise preceding the fall in PEF. The changes in peak flow and platelet activation induced by exercise were attenuated by prior administration of salbutamol or cromoglycate. These results indicate that exercise induced asthma is associated with a rise in platelet release products similar to that observed in antigen induced asthma. PMID:2943049

  2. Platelet clearance via shear-induced unfolding of a membrane mechanoreceptor

    PubMed Central

    Deng, Wei; Xu, Yan; Chen, Wenchun; Paul, David S.; Syed, Anum K.; Dragovich, Matthew A.; Liang, Xin; Zakas, Philip; Berndt, Michael C.; Di Paola, Jorge; Ware, Jerry; Lanza, Francois; Doering, Christopher B.; Bergmeier, Wolfgang; Zhang, X. Frank; Li, Renhao

    2016-01-01

    Mechanisms by which blood cells sense shear stress are poorly characterized. In platelets, glycoprotein (GP)Ib–IX receptor complex has been long suggested to be a shear sensor and receptor. Recently, a relatively unstable and mechanosensitive domain in the GPIbα subunit of GPIb–IX was identified. Here we show that binding of its ligand, von Willebrand factor, under physiological shear stress induces unfolding of this mechanosensory domain (MSD) on the platelet surface. The unfolded MSD, particularly the juxtamembrane ‘Trigger' sequence therein, leads to intracellular signalling and rapid platelet clearance. These results illustrate the initial molecular event underlying platelet shear sensing and provide a mechanism linking GPIb–IX to platelet clearance. Our results have implications on the mechanism of platelet activation, and on the pathophysiology of von Willebrand disease and related thrombocytopenic disorders. The mechanosensation via receptor unfolding may be applicable for many other cell adhesion receptors. PMID:27670775

  3. Activated platelets release sphingosine 1-phosphate and induce hypersensitivity to noxious heat stimuli in vivo

    PubMed Central

    Weth, Daniela; Benetti, Camilla; Rauch, Caroline; Gstraunthaler, Gerhard; Schmidt, Helmut; Geisslinger, Gerd; Sabbadini, Roger; Proia, Richard L.; Kress, Michaela

    2015-01-01

    At the site of injury activated platelets release various mediators, one of which is sphingosine 1-phosphate (S1P). It was the aim of this study to explore whether activated human platelets had a pronociceptive effect in an in vivo mouse model and whether this effect was based on the release of S1P and subsequent activation of neuronal S1P receptors 1 or 3. Human platelets were prepared in different concentrations (105/μl, 106/μl, 107/μl) and assessed in mice with different genetic backgrounds (WT, S1P1fl/fl, SNS-S1P1−/−, S1P3−/−). Intracutaneous injections of activated human platelets induced a significant, dose-dependent hypersensitivity to noxious thermal stimulation. The degree of heat hypersensitivity correlated with the platelet concentration as well as the platelet S1P content and the amount of S1P released upon platelet activation as measured with LC MS/MS. Despite the significant correlations between S1P and platelet count, no difference in paw withdrawal latency (PWL) was observed in mice with a global null mutation of the S1P3 receptor or a conditional deletion of the S1P1 receptor in nociceptive primary afferents. Furthermore, neutralization of S1P with a selective anti-S1P antibody did not abolish platelet induced heat hypersensitivity. Our results suggest that activated platelets release S1P and induce heat hypersensitivity in vivo. However, the platelet induced heat hypersensitivity was caused by mediators other than S1P. PMID:25954148

  4. Induced pluripotent stem cell-derived gamete-associated proteins incite rejection of induced pluripotent stem cells in syngeneic mice.

    PubMed

    Kim, Eun-Mi; Manzar, Gohar; Zavazava, Nicholas

    2017-02-10

    The safety of induced pluripotent stem cells (iPSCs) in autologous recipients has been questioned after iPSCs, but not embryonic stem cells (ESCs), were reported to be rejected in syngeneic mice. This important topic has remained controversial because there has not been a mechanistic explanation for this phenomenon. Here, we hypothesize that iPSCs, but not ESCs, readily differentiate into gamete-forming cells that express meiotic antigens normally found in immune-privileged gonads. Because peripheral blood T cells are not tolerized to these antigens in the thymus, gamete-associated-proteins (GAPs) sensitize T cells leading to rejection. Here, we provide evidence that GAPs expressed in iPSC teratomas, but not in ESC teratomas, are responsible for the immunological rejection of iPSCs. Furthermore, silencing the expression of Stra8, 'the master regulator of meiosis', in iPSCs, using short hairpin RNA led to significant abrogation of the rejection of iPSCs, supporting our central hypothesis that GAPs expressed after initiation of meiosis in iPSCs were responsible for rejection. In contrast to iPSCs, iPSC-derivatives, such as haematopoietic progenitor cells, are able to engraft long-term into syngeneic recipients because they no longer express GAPs. Our findings, for the first time, provide a unifying explanation of why iPSCs, but not ESCs, are rejected in syngeneic recipients, ending the current controversy on the safety of iPSCs and their derivatives.

  5. Nanomolar concentrations of adrenaline induce platelet adhesion in vitro.

    PubMed

    Eriksson, Andreas C; Whiss, Per A

    2013-01-01

    Adrenaline is a platelet activator having a resting plasma concentration of <1 nmol/l that increases to a few nmol/l during stress. However, most in vitro assays only detect effects of adrenaline in micromolar concentrations. This makes it difficult to estimate the relevance of in vitro data for the in vivo situation. The aim of this study was to investigate experimental conditions in vitro that could detect platelet effects of adrenaline in nanomolar concentrations. Platelet adhesion to albumin and collagen was evaluated with a static platelet adhesion assay. Our results show that 10 nmol/l adrenaline induced platelet adhesion to albumin in platelet-rich plasma (PRP) prepared at 140 × g, while 100 nmol/l was necessary in order to increase adhesion of platelets prepared at 220 × g. The mean platelet volume was increased after preparation at 140 × g, suggesting that large reactive platelets contributed to the increased adrenaline sensitivity. At optimal Mg(2+)-concentration, adhesion to collagen was increased by 10 nmol/l adrenaline irrespective of centrifugal force applied during PRP preparation. More specifically, we defined two populations where adhesion to collagen was increased by 10 nmol/l adrenaline either upon centrifugation at 140 × g but not 220 × g or vice versa. In some experiments, platelet adhesion to collagen was induced by 3 nmol/l adrenaline, which corresponds to concentrations achieved during stress in vivo. In summary, the static adhesion assay is able to detect platelet activating effects of adrenaline very close to physiological concentrations. This is rare for in vitro assays and motivates further research about adrenergic signalling in platelets.

  6. Selective deficiency in collagen-induced platelet aggregation during L-asparaginase therapy.

    PubMed

    Shapiro, R S; Gerrard, J M; Ramsay, N K; Nesbit, M E; Coccia, P F; Stoddard, S F; Plow, E F; White, J G; Krivit, W

    1980-01-01

    Platelet aggregation studies were performed on 10 pediatric patients with acute lymphoblastic leukemia (ALL) receiving induction therapy with vincristine, prednisone, and L-asparaginase. An isolated abnormality in platelet aggregation in response to collagen was found in all patients during the course of therapy. Platelet aggregation in response to collagen normalized following the discontinuation of L-asparaginase, while patients were still on vincristine and prednisone. In contrast to the abnormal collagen response, platelet aggregation induced by epinephrine, arachidonic acid, adenosine diphosphate (ADP), and thrombin were normal both during and following therapy. In the one patient with a normal platelet count before therapy, aggregation induced by all agents was normal. This selective abnormality in collagen aggregation therefore appears to result from therapy, with the use of L-asparaginase in particular being implicated.

  7. Activation induced morphological changes and integrin αIIbβ3 activity of living platelets.

    PubMed

    Posch, Sandra; Neundlinger, Isabel; Leitner, Michael; Siostrzonek, Peter; Panzer, Simon; Hinterdorfer, Peter; Ebner, Andreas

    2013-04-01

    Platelets are essential in hemostasis. Upon activation they undergo a shape-change accompanied with receptor presentation. Atomic force microscopy (AFM) imaging and single molecule force spectroscopy (SMFS) were used as powerful tools for exploring morphological changes as well as receptor activities of platelets. Imaging time series was accomplished with and without fixation steps at the single platelet level. Hereby the response of mechanical stimulation of the platelet by the AFM cantilever tip was directly observed. We demonstrate that living and fixed platelets develop filopodia after a short activation time followed by their disappearance including cellular bleb formation. Thereafter a second filopodia formation (filopodia extrusion) was observed; those filopodia subsequently disappeared again, and finally platelets detached from the support due to cell death. We determined the influence of mechanical stress on the chronology of morphological changes of platelets and demonstrated shear force induced filopodia formation. Through recordings over several hours, topographical AFM images over the full platelet lifetime - from early activation up to apoptosis - are presented. SMFS measurements on living platelets allowed determining the activation state of the most prominent membrane receptor integrin αIIbβ3 at all different phases of activation. αIIbβ3 was fully activated, independent of the morphological state.

  8. Platelet-activating factor-induced increases in glucose kinetics

    SciTech Connect

    Lang, C.H.; Dobrescu, C.; Hargrove, D.M.; Bagby, G.J.; Spitzer, J.J. )

    1988-02-01

    Platelet-activating factor (PAF) is a postulated mediator of many of the early hemodynamic effects of endotoxin. The aim of the present study was to determine whether in vivo administration of PAF could produce alterations in whole-body glucose metabolism that would mimic those seen during endotoxemia. Glucose kinetics were assessed in chronically catheterized conscious rats by the constant infusion of (6-{sup 3}H)- and (U-{sup 14}C)glucose before and for 4 h after either a bolus injection or a constant infusion of PAF. The bolus injection of PAF elevated the rate of glucose appearance (R{sub a}; 44%) for 1.5 h. The lower PAF infusion rate decreased blood pressure 11% to 104 mmHg, whereas the higher infusion rate decreased pressure 34% to 77 mmHg. Both PAF infusion rates produced elevations in plasma glucose and glucose R{sub a} throughout the 4-h infusion period in a dose-related manner. The PAF infusions also induced dose-related increases in plasma glucagon and catecholamine levels throughout the infusion period. Because the constant infusion of PAF did stimulate many of the hemodynamic and metabolic alterations produced by endotoxin, this study provides additional support for the potential importance of PAF as a mediator of the early hemodynamic and metabolic sequela of endotoxin shock. Furthermore, the PAF-induced changes in glucose metabolism appear to be mediated by the resultant elevation in plasma catecholamines.

  9. Effect of resveratrol, a natural polyphenolic compound, on platelet activation induced by endotoxin or thrombin.

    PubMed

    Olas, Beata; Wachowicz, Barbara; Saluk-Juszczak, Joanna; Zieliński, Tomasz

    2002-08-15

    Resveratrol (3, 4', 5-trihydroxystilbene), a natural polyphenol, is found in some plants that are used in human nutrition. Grapes are a major source for resveratrol, and a significant amount can also be found in red wine. Several experimental studies have demonstrated biological properties of resveratrol, especially its anti-inflammatory, antioxidant, anti-platelet and antitumor effects. In the present study, we investigated the first step of platelet activation-platelet adhesion stimulated by lipopolysaccharide (LPS) from Proteus mirabilis (weak stimulator) and thrombin (strong activator) in the presence of resveratrol. Our studies show that endotoxin (0.3 microg/10(8) platelets), like thrombin (0.2 U/10(8) platelets), induced the adhesion of platelets (expressed as absorbance of cell attached proteins) to collagen and fibrinogen. Preincubation of washed platelets with resveratrol at physiological plasma concentrations (25-100 microg/ml, 30 min, 37 degrees C) had an inhibitory effect on adhesion of platelets to collagen after activation by LPS alone or LPS with thrombin. The strongest effect on this process was caused by resveratrol at the concentration of 100 microg/ml. Pretreatment of platelets with resveratrol (25-100 microg/ml, 30 min, 37 degrees C) had also inhibitory effects on adhesion of platelets to fibrinogen after stimulation of these cells by LPS alone or by LPS with thrombin at the same concentration. In conclusion, we suggest that resveratrol present in human diet may be an important compound responsible for the reduction of platelet adhesion and changed reactivity of blood platelets in inflammatory process.

  10. Bacteria differentially induce degradation of Bcl-xL, a survival protein, by human platelets

    PubMed Central

    Kraemer, Bjoern F.; Campbell, Robert A.; Schwertz, Hansjörg; Franks, Zechariah G.; Vieira de Abreu, Adriana; Grundler, Katharina; Kile, Benjamin T.; Dhakal, Bijaya K.; Rondina, Matthew T.; Kahr, Walter H. A.; Mulvey, Matthew A.; Blaylock, Robert C.; Zimmerman, Guy A.

    2012-01-01

    Bacteria can enter the bloodstream in response to infectious insults. Bacteremia elicits several immune and clinical complications, including thrombocytopenia. A primary cause of thrombocytopenia is shortened survival of platelets. We demonstrate that pathogenic bacteria induce apoptotic events in platelets that include calpain-mediated degradation of Bcl-xL, an essential regulator of platelet survival. Specifically, bloodstream bacterial isolates from patients with sepsis induce lateral condensation of actin, impair mitochondrial membrane potential, and degrade Bcl-xL protein in platelets. Bcl-xL protein degradation is enhanced when platelets are exposed to pathogenic Escherichia coli that produce the pore-forming toxin α-hemolysin, a response that is markedly attenuated when the gene is deleted from E coli. We also found that nonpathogenic E coli gain degrading activity when they are forced to express α-hemolysin. Like α-hemolysin, purified α-toxin readily degrades Bcl-xL protein in platelets, as do clinical Staphylococcus aureus isolates that produce α-toxin. Inhibition of calpain activity, but not the proteasome, rescues Bcl-xL protein degradation in platelets coincubated with pathogenic E coli including α-hemolysin producing strains. This is the first evidence that pathogenic bacteria can trigger activation of the platelet intrinsic apoptosis program and our results suggest a new mechanism by which bacterial pathogens might cause thrombocytopenia in patients with bloodstream infections. PMID:23086749

  11. Sirtuin Inhibition Induces Apoptosis-like Changes in Platelets and Thrombocytopenia.

    PubMed

    Kumari, Sharda; Chaurasia, Susheel N; Nayak, Manasa K; Mallick, Ram L; Dash, Debabrata

    2015-05-08

    Sirtuins are evolutionarily conserved NAD(+)-dependent acetyl-lysine deacetylases that belong to class III type histone deacetylases. In humans, seven sirtuin isoforms (Sirt1 to Sirt7) have been identified. Sirtinol, a cell-permeable lactone ring derived from naphthol, is a dual Sirt1/Sirt2 inhibitor of low potency, whereas EX-527 is a potent and selective Sirt1 inhibitor. Here we demonstrate that Sirt1, Sirt2, and Sirt3 are expressed in enucleate platelets. Both sirtinol and EX-527 induced apoptosis-like changes in platelets, as revealed by enhanced annexin V binding, reactive oxygen species production, and drop in mitochondrial transmembrane potential. These changes were associated with increased phagocytic clearance of the platelets by macrophages. Expression of acetylated p53 and the conformationally active form of Bax were found to be significantly higher in both sirtinol- and EX-527-treated platelets, implicating the p53-Bax axis in apoptosis induced by sirtuin inhibitors. Administration of either sirtinol or EX-527 in mice led to a reduction in both platelet count and the number of reticulated platelets. Our results, for the first time, implicate sirtuins as a central player in the determination of platelet aging. Because sirtuin inhibitors are being evaluated for their antitumor activity, this study refocuses attention on the potential side effect of sirtuin inhibition in delimiting platelet life span and management of thrombosis.

  12. The influence of erythrocyte aggregation on induced platelet aggregation.

    PubMed

    Ott, C; Lardi, E; Schulzki, T; Reinhart, W H

    2010-01-01

    Red blood cells (RBCs) affect platelet aggregation in flowing blood (primary hemostasis). We tested the hypothesis that RBC aggregation could influence platelet aggregation. RBC aggregation was altered in vitro by: (i) changing plasma aggregatory properties with 3.7 g% dextran 40 (D40), 3.0 g% dextran 70 (D70) or 1.55 g% dextran 500 (D500); (ii) changing RBC aggregatory properties by incubating RBCs in 50 mU/ml neuraminidase for 60 min (reduction of the surface sialic acid content, thus reducing electrostatic repulsion) and subsequent RBC resuspension in platelet rich plasma (PRP) containing 1 g% dextran 70. RBC aggregation was assessed with the sedimentation rate (ESR). Platelet aggregation was measured: (i) in flowing whole blood with a platelet function analyzer PFA-100(R), which simulates in vivo conditions with RBCs flowing in the center and platelets along the wall, where they adhere to collagen and aggregate; and (ii) in a Chrono-log 700 Aggregometer, which measures changes of impedance by platelet aggregation in whole blood or changes in light transmission in PRP. We found that RBC aggregation increased with increasing molecular weight of dextran (ESR: 4 +/- 3 mm/h, 34 +/- 14 mm/h and 89 +/- 23 mm/hfor D40, D70 and D500, respectively, p < 0.0001) and with neuraminidase-treated RBCs (76 +/- 27 mm/h vs 27 +/- 8 mm/h, respectively, p < 0.0001). Platelet aggregation measured in whole blood under flow conditions (PFA-100) and without flow (Chronolog Aggregometer) was not affected by RBC aggregation. Our data suggest that RBC aggregation does not affect platelet aggregation in vitro and plays no role in primary hemostasis.

  13. Platelets play an important role in TNF-induced microvascular endothelial cell pathology.

    PubMed Central

    Lou, J.; Donati, Y. R.; Juillard, P.; Giroud, C.; Vesin, C.; Mili, N.; Grau, G. E.

    1997-01-01

    Tumor necrosis factor-alpha (TNF) is known to be an important mediator in the pathogenesis of several inflammatory diseases. Vascular endothelial cells represent a major target of TNF effects. Platelet sequestration has been found in brain microvessels during experimental cerebral malaria and lung in experimental pulmonary fibrosis, implying that it may participate in TNF-dependent microvascular pathology. In this study, we investigated the mechanisms of platelet-endothelial interaction, using co-cultures between platelets and TNF-activated mouse brain microvascular endothelial cells (MVECs). Adhesion and fusion of platelets to MVECs was evidenced by electron microscopy, dye transfer, and flow cytometry. It was induced by TNF and interferon-gamma and depended on LFA-1 expressed on the platelet surface and ICAM-1 expressed on MVECs. The adhesion and fusion also led to the transfer of platelet markers on the MVEC surface, rendering these more adherent for leukocytes, and to an enhanced MVEC sensitivity to TNF-induced injury. These results suggest that platelets can participate in TNF-induced microvascular pathology. Images Figure 2 Figure 3 Figure 6 PMID:9358766

  14. Time-dependent inhibitory effects of cGMP-analogues on thrombin-induced platelet-derived microparticles formation, platelet aggregation, and P-selectin expression

    SciTech Connect

    Nygaard, Gyrid; Herfindal, Lars; Kopperud, Reidun; Aragay, Anna M.; Holmsen, Holm; Døskeland, Stein Ove; Kleppe, Rune; Selheim, Frode

    2014-07-04

    Highlights: • We investigated the impact of cyclic nucleotide analogues on platelet activation. • Different time dependence were found for inhibition of platelet activation. • Additive effect was found using PKA- and PKG-activating analogues. • Our results may explain some of the discrepancies reported for cNMP signalling. - Abstract: In platelets, nitric oxide (NO) activates cGMP/PKG signalling, whereas prostaglandins and adenosine signal through cAMP/PKA. Cyclic nucleotide signalling has been considered to play an inhibitory role in platelets. However, an early stimulatory effect of NO and cGMP-PKG signalling in low dose agonist-induced platelet activation have recently been suggested. Here, we investigated whether different experimental conditions could explain some of the discrepancy reported for platelet cGMP-PKG-signalling. We treated gel-filtered human platelets with cGMP and cAMP analogues, and used flow cytometric assays to detect low dose thrombin-induced formation of small platelet aggregates, single platelet disappearance (SPD), platelet-derived microparticles (PMP) and thrombin receptor agonist peptide (TRAP)-induced P-selectin expression. All four agonist-induced platelet activation phases were blocked when platelets were costimulated with the PKG activators 8-Br-PET-cGMP or 8-pCPT-cGMP and low-doses of thrombin or TRAP. However, extended incubation with 8-Br-PET-cGMP decreased its inhibition of TRAP-induced P-selectin expression in a time-dependent manner. This effect did not involve desensitisation of PKG or PKA activity, measured as site-specific VASP phosphorylation. Moreover, PKG activators in combination with the PKA activator Sp-5,6-DCL-cBIMPS revealed additive inhibitory effect on TRAP-induced P-selectin expression. Taken together, we found no evidence for a stimulatory role of cGMP/PKG in platelets activation and conclude rather that cGMP/PKG signalling has an important inhibitory function in human platelet activation.

  15. Minor histocompatibility antigens on transfused leukoreduced units of red blood cells induce bone marrow transplant rejection in a mouse model.

    PubMed

    Desmarets, Maxime; Cadwell, Chantel M; Peterson, Kenneth R; Neades, Renee; Zimring, James C

    2009-09-10

    When successful, human leukocyte antigen (HLA)-matched bone marrow transplantation with reduced-intensity conditioning is a cure for several nonmalignant hematologic disorders that require chronic transfusion, such as sickle cell disease and aplastic anemia. However, there are unusually high bone marrow transplant (BMT) rejection rates in these patients. Rejection correlates with the number of transfusions before bone marrow transplantation, and it has been hypothesized that preimmunization to antigens on transfused blood may prime BMT rejection. Using a novel mouse model of red blood cell (RBC) transfusion and major histocompatibility complex-matched bone marrow transplantation, we report that transfusion of RBC products induced BMT rejection across minor histocompatibility antigen (mHA) barriers. It has been proposed that contaminating leukocytes are responsible for transfusion-induced BMT rejection; however, filter leukoreduction did not prevent rejection in the current studies. Moreover, we generated a novel transgenic mouse with RBC-specific expression of a model mHA and demonstrated that transfusion of RBCs induced a CD8(+) T-cell response. Together, these data suggest that mHAs on RBCs themselves are capable of inducing BMT rejection. Cellular immunization to mHAs is neither monitored nor managed by current transfusion medicine practice; however, the current data suggest that mHAs on RBCs may represent an unappreciated and significant consequence of RBC transfusion.

  16. Platelet factors induce chemotactic migration of murine mammary adenocarcinoma cells with different metastatic capabilities.

    PubMed Central

    Sarach, M. A.; Rovasio, R. A.; Eynard, A. R.

    1993-01-01

    The chemotactic response of neoplastic cells (NC) induced by soluble platelet factors was investigated. NC suspensions isolated from murine mammary gland adenocarcinomas having different metastatic capabilities were incubated in Boyden's chambers and challenged with (1) 'Early Platelet Factors' (EP), obtained from the soluble fraction of recently collagen-activated human platelets, and (2) 'Late Platelet Factors' (LP), isolated after 24 hours incubation of the platelet aggregates. Chemotaxis was expressed as the distance travelled by NC through nitrocellulose filters. NC isolated from M3, the tumour line having the stronger metastatic potential, showed a significant chemotactic response towards LP factors, whereas NC from the M2 line exhibiting the lower metastatic behaviour, showed a chemotactic response towards EP factors. Both tumour cell lines lacked motion capability towards the well known chemoattractant peptide N-f-Met-Leu-Phe-Phe as well as to serum, plasma, collagen type I or culture medium. The different chemotactic response of both tumour lines when they were challenged by concentration gradients of factors released by early or late collagen-activated human platelets, confirm a relationship between platelet activity and metastatic capabilities and suggests that platelet chemoattractants might play a role in the metastatic dissemination of these mammary gland adenocarcinomas. Images Figure 1 PMID:8217786

  17. Heparin-induced thrombocytopenia: the role of platelets genetic polymorphisms.

    PubMed

    Pamela, Scarparo; Anna Maria, Lombardi; Elena, Duner; Giovanni, Malerba; Emanuele, Allemand; Silvia, Vettore; Carmen, Blumentritt; Andreas, Greinacher; Fabrizio, Fabris

    2013-01-01

    Heparin-induced thrombocytopenia (HIT) is a severe complication of heparin therapy, characterized by thrombocytopenia and an increased risk for thrombotic complications secondary to the formation of IgG antibodies (Ab), recognizing a complex of heparin (H) and PF4. Using the 4T clinical score for HIT and the presence of heparin-associated Ab assayed by enzyme-linked immunosorbent assay and heparin-induced platelet aggregation, we define the phenotype of three groups of patients: 51 H/PF4/Ab patients with antibodies and without thrombocytopenia; 50 patients with thrombocytopenia (HIT) and 53 patients with thrombosis (HITT). In these patients we studied four polymorphisms: FcγRIIA-H131R, GpIIb/IIIa-HP-1, PECAM1-L125V (in linkage-disequilibrium with S563N and R670G), and FcγRIIIA-F158V, to understand if these variations may influence the different phenotypes of the patients. There were no difference in genotype or allele frequencies between controls and the three groups of patients. Afterward, we created a genotype score for multiple risk alleles for thrombosis considering as risk genotype FcγRIIA R/R131, HPA-1a/b, and PECAM1-V/V125. These polymorphisms were overrepresented in HITT patients, ascertained by a permutation test (10 000 replicates) p = 0.0198 for the two-single-nucleotide polymorphism (SNP) model and p = 0.0119 for the three-SNP model. The calculated odds ratio for thrombosis was 4.01[CI: 2.30-6.96] in the case of the presence of two at risk genotypes and 8.002 [CI: 4.59-13.93] if all the three at risk genotypes were present. In conclusion these polymorphisms could contribute to the risk of thrombotic complications in HIT.

  18. Platelet functional and transcriptional changes induced by intralipid infusion.

    PubMed

    Beaulieu, Lea M; Vitseva, Olga; Tanriverdi, Kahraman; Kucukural, Alper; Mick, Eric; Hamburg, Naomi; Vita, Joseph; Freedman, Jane E

    2016-06-02

    Multiple studies have shown the effects of long-term exposure to high-fat or western diets on the vascular system. There is limited knowledge on the acute effects of high circulating fat levels, specifically on platelets, which have a role in many processes, including thrombosis and inflammation. This study investigated the effects of acute, high-fat exposure on platelet function and transcript profile. Twenty healthy participants were given an intravenous infusion of 20% Intralipid emulsion and heparin over 6 hours. Blood samples were taken prior to and the day after infusion to measure platelet function and transcript expression levels. Platelet aggregation was not significantly affected by Intralipid infusion, but, when mitochondria function was inhibited by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) or oligomycin, platelet aggregation was higher in the post-infusion state compared to baseline. Through RNA sequencing, and verified by RT-qPCR, 902 miRNAs and 617 mRNAs were affected by Intralipid infusion. MicroRNAs increased include miR-4259 and miR-346, while miR-517b and miR-517c are both decreased. Pathway analysis identified two clusters significantly enriched, including cell motility. In conclusion, acute exposure to high fat affects mitochondrial-dependent platelet function, as well as the transcript profile.

  19. Red cabbage anthocyanins as inhibitors of lipopolysaccharide-induced oxidative stress in blood platelets.

    PubMed

    Saluk, Joanna; Bijak, Michal; Posmyk, Malgorzata M; Zbikowska, Halina M

    2015-09-01

    LPS is a Gram-negative bacteria endotoxin, which is an important pro-inflammatory agent. Blood platelets take part both in inflammatory processes and in pathogenesis of septic shock following accumulation of LPS. As a platelet agonist LPS causes the intraplatelet overproduction of ROS/RNS that are responsible for adverse modifications in the structure of platelet compounds being associated with a development of platelet-dependent diseases. Existing evidence suggests that anthocyanins (ATH) are able to protect the circulatory system. The antioxidative properties of ATH are believed to be mainly responsible for their positive health effects. The main goal of the present in vitro study was to investigate the potential protective properties of red cabbage ATH against oxidative damage induced by LPS in blood platelets. Exposure of platelets to LPS resulted in carbonyl group increase, 3-nitrotyrosine formation, lipid peroxidation and O2(•-) generation. We have shown that ATH extract effectively decreased oxidative stress induced by LPSs. The in silico analysis demonstrated that both cyanin and LPS were located at the same region of human TLR4-MD-2 complex. Our findings suggest that there could be two-way ATH platelet protection mechanism, by their antioxidant properties and directly by binding with TLRs.

  20. Platelet adhesion and degranulation induce pro-survival and pro-angiogenic signalling in ovarian cancer cells.

    PubMed

    Egan, Karl; Crowley, Darragh; Smyth, Paul; O'Toole, Sharon; Spillane, Cathy; Martin, Cara; Gallagher, Michael; Canney, Aoife; Norris, Lucy; Conlon, Niamh; McEvoy, Lynda; Ffrench, Brendan; Stordal, Britta; Keegan, Helen; Finn, Stephen; McEneaney, Victoria; Laios, Alex; Ducrée, Jens; Dunne, Eimear; Smith, Leila; Berndt, Michael; Sheils, Orla; Kenny, Dermot; O'Leary, John

    2011-01-01

    Thrombosis is common in ovarian cancer. However, the interaction of platelets with ovarian cancer cells has not been critically examined. To address this, we investigated platelet interactions in a range of ovarian cancer cell lines with different metastatic potentials [HIO-80, 59M, SK-OV-3, A2780, A2780cis]. Platelets adhered to ovarian cancer cells with the most significant adhesion to the 59M cell line. Ovarian cancer cells induced platelet activation [P-selectin expression] in a dose dependent manner, with the most significant activation seen in response to the 59M cell line. The platelet antagonists [cangrelor, MRS2179, and apyrase] inhibited 59M cell induced activation suggesting a P2Y12 and P2Y1 receptor mediated mechanism of platelet activation dependent on the release of ADP by 59M cells. A2780 and 59M cells potentiated PAR-1, PAR-4, and TxA2 receptor mediated platelet activation, but had no effect on ADP, epinephrine, or collagen induced activation. Analysis of gene expression changes in ovarian cancer cells following treatment with washed platelets or platelet releasate showed a subtle but valid upregulation of anti-apoptotic, anti-autophagy pro-angiogenic, pro-cell cycle and metabolic genes. Thus, ovarian cancer cells with different metastatic potential adhere and activate platelets differentially while both platelets and platelet releasate mediate pro-survival and pro-angiogenic signals in ovarian cancer cells.

  1. SIRT1 prevents pulmonary thrombus formation induced by arachidonic acid via downregulation of PAF receptor expression in platelets.

    PubMed

    Kim, Yun Hak; Bae, Jin Ung; Kim, In Suk; Chang, Chulhun L; Oh, Sae Ock; Kim, Chi Dae

    2016-12-01

    SIRT1, a class III histone deacetylase, is critically involved in cellular response to stress and modulates cardiovascular risk factors. However, its role in thrombus formation is largely unknown. Thus, this study investigated the effect of SIRT1 on pulmonary thrombus formation, and then identified its role in the modulation of platelet aggregation. In isolated human platelets, cell aggregation was increased by various platelet activators, such as platelet activating factor (PAF), arachidonic acid (AA), ADP, and thrombin. AA- and PAF-mediated platelet aggregations were suppressed by WEB2086, a PAF receptor (PAFR) antagonist. Pulmonary thrombus formation induced by PAF or AA was also attenuated by WEB2086, suggesting that PAFR plays a key role in AA-induced platelet aggregation. In platelets isolated from SIRT1-TG mice as well as in platelets treated with resveratrol or reSIRT1, PAFR expression was decreased, whereas this expressional downregulation by SIRT1 activators was inhibited in platelets treated with MG132 (a proteasome inhibitor) or NH4Cl (a lysosome inhibitor). Furthermore, platelet aggregation induced by AA was markedly attenuated by resveratrol and reSIRT1. Likewise, the increased pulmonary thrombus formation in mice treated with AA was also attenuated by SIRT1 activators. In line with these results, pulmonary thrombus formation was markedly attenuated in SIRT1-TG mice. Taken together, this study showed that SIRT1 downregulates PAFR expression on platelets via proteasomal and lysosomal pathways, and that this downregulation inhibits platelet aggregation in vitro and pulmonary thrombus formation in vivo.

  2. Duration of exposure to high fluid shear stress is critical in shear-induced platelet activation-aggregation.

    PubMed

    Zhang, Jian-ning; Bergeron, Angela L; Yu, Qinghua; Sun, Carol; McBride, Latresha; Bray, Paul F; Dong, Jing-fei

    2003-10-01

    Platelet functions are increasingly measured under flow conditions to account for blood hydrodynamic effects. Typically, these studies involve exposing platelets to high shear stress for periods significantly longer than would occur in vivo. In the current study, we demonstrate that the platelet response to high shear depends on the duration of shear exposure. In response to a 100 dyn/cm2 shear stress for periods less than 10-20 sec, platelets in PRP or washed platelets were aggregated, but minimally activated as demonstrated by P-selectin expression and binding of the activation-dependent alphaIIbbeta3 antibody PAC-1 to sheared platelets. Furthermore, platelet aggregation under such short pulses of high shear was subjected to rapid disaggregation. The disaggregated platelets could be re-aggregated by ADP in a pattern similar to unsheared platelets. In comparison, platelets that are exposed to high shear for longer than 20 sec are activated and aggregated irreversibly. In contrast, platelet activation and aggregation were significantly greater in whole blood with significantly less disaggregation. The enhancement is likely via increased collision frequency of platelet-platelet interaction and duration of platelet-platelet association due to high cell density. It may also be attributed to the ADP release from other cells such as red blood cells because increased platelet aggregation in whole blood was partially inhibited by ADP blockage. These studies demonstrate that platelets have a higher threshold for shear stress than previously believed. In a pathologically relevant timeframe, high shear alone is likely to be insufficient in inducing platelet activation and aggregation, but acts synergistically with other stimuli.

  3. Atherosclerosis proceeds independently of thrombin-induced platelet activation in ApoE-/- mice

    PubMed Central

    Hamilton, J.R.; Cornelissen, I.; Mountford, J.K.; Coughlin, S.R.

    2009-01-01

    Platelet activation has long been postulated to contribute to the development of atherosclerotic plaques, although the mechanism by which this might occur remains unknown. Thrombin is a potent platelet activator and transfusion of thrombin-activated platelets into mice increases plaque formation, suggesting that thrombin-induced platelet activation might contribute to platelet-dependent atherosclerosis. Platelets from protease-activated receptor 4-deficient (Par4-/-) mice fail to respond to thrombin. To determine whether thrombin-activated platelets play a necessary role in a model of atherogenesis, we compared plaque formation and progression in Par4+/+ and Par4-/- mice in the atherosclerosis-prone apolipoprotein E-deficient (ApoE-/-) background. Littermate Par4+/+ and Par4-/- mice, all ApoE-/-, were placed on a Western diet (21% fat, 0.15% cholesterol) for 5 or 10 weeks. The percent of aortic lumenal surface covered by plaques in Par4+/+ and Par4-/- mice was not different at either time point (2.2 ± 0.3% vs. 2.5 ± 0.2% and 5.1 ± 0.4% vs. 5.6 ± 0.4% after 5 and 10 weeks, respectively). Further, no differences were detected in the cross-sectional area of plaques measured at the aortic root (1.53 ± 0.17 vs. 1.66 ± 0.16 × 105 μm2 and 12.56 ± 1.23 vs. 13.03 ± 0.55 × 105 μm2 after 5 and10 weeks, respectively). These findings indicate that thrombin-mediated platelet activation is not required for the early development of atherosclerotic plaques in the ApoE-/- mouse model and suggest that, if platelet activation is required for plaque formation under these experimental conditions, platelet activators other than thrombin suffice. PMID:19217621

  4. Piperlongumine Blocks JAK2-STAT3 to Inhibit Collagen-Induced Platelet Reactivity Independent of Reactive Oxygen Species†

    PubMed Central

    Yuan, Hengjie; Houck, Katie L.; Tian, Ye; Bharadwaj, Uddalak; Hull, Ken; Zhou, Zhou; Zhou, Mingzhao; Wu, Xiaoping; Tweardy, David J.; Romo, Daniel; Fu, Xiaoyun; Zhang, Yanjun; Zhang, Jianning; Dong, Jing-fei

    2015-01-01

    Background Piperlongumine (PL) is a compound isolated from the piper longum plant. It possesses anti-cancer activities through blocking the transcription factor STAT3 and by inducing reactive oxygen species (ROS) in cancer, but not normal cells. It also inhibits platelet aggregation induced by collagen, but the underlying mechanism is not known. Objective We conducted in vitro experiments to test the hypothesis that PL regulates a non-transcriptional activity of STAT3 to specifically reduce the reactivity of human platelets to collagen. Results PL dose-dependently blocked collagen-induced platelet aggregation, calcium influx, CD62p expression and thrombus formation on collagen with a maximal inhibition at 100 μM. It reduced platelet microvesiculation induced by collagen. PL blocked the activation of JAK2 and STAT3 in collagen-stimulated platelets. This inhibitory effect was significantly reduced in platelets pretreated with a STAT3 inhibitor. Although PL induced ROS production in platelets; quenching ROS using excessive reducing agents: 20 μM GSH and 0.5 mM L-Cysteine, did not block the inhibitory effects. The NADPH oxidase inhibitor Apocynin also had no effect. Conclusions PL inhibited collagen-induced platelet reactivity by targeting the JAK2-STAT3 pathway. We also provide experimental evidence that PL and collagen induce different oxidants that have differential effects on platelets. Studying these differential effects may uncover new mechanisms of regulating platelet functions by oxidants in redox signals. PMID:26645674

  5. Platelet Aggregation and Mental Stress Induced Myocardial Ischemia: Results from the REMIT Study

    PubMed Central

    Jiang, Wei; Boyle, Stephen H.; Ortel, Thomas L.; Samad, Zainab; Velazquez, Eric J.; Harrison, Robert W.; Wilson, Jennifer; Kuhn, Cynthia; Williams, Redford B.; O’Connor, Christopher M.; Becker, Richard C.

    2015-01-01

    BACKGROUND Mental stress-induced myocardial ischemia (MSIMI) is common in patients with ischemic heart disease (IHD) and associated with a poorer cardiovascular prognosis. Platelet hyperactivity is an important factor in acute coronary syndrome. This study examined associations between MSIMI and resting and mental stress-induced platelet activity. METHODS Eligible patients with clinically stable IHD underwent a battery of 3 mental stress tests during the recruitment phase of REMIT (Responses of Myocardial Ischemia to Escitalopram Treatment) study. MSIMI was assessed by echocardiography and electrocardiography. Ex vivo platelet aggregation in response to ADP, epinephrine, collagen, serotonin, and combinations of serotonin plus ADP, epinephrine, and collagen were evaluated as was platelet serotonin transporter expression. RESULTS Of the 270 participants who completed mental stress testing, and had both resting and post-stress platelet aggregation evaluation, 43.33% (N=117) met criteria for MSIMI and 18.15% (N=49) had normal left ventricular response to stress (NLVR). The MSIMI group, relative to the NLVR groups, demonstrated heightened mental stress-induced aggregation responses, as measured by area under the curve, to collagen 10 μM (6.95[5.54] vs. −14.23[8.75].; p=0.045), epinephrine 10 μM (12.84[4.84] vs. −6.40[7.61].; p=0.037) and to serotonin 10 μM plus ADP 1 μM (6.64[5.29] vs. −27.34[8.34]; p < .001). The resting platelet aggregation and serotonin transporter expression, however, were not different between the two groups. CONCLUSIONS These findings suggest that the dynamic change of platelet aggregation caused by mental stress may underlie MSIMI. While the importance of these findings requires additional investigation, they raise concern given the recognized relationship between mental stress-induced platelet hyperactivity and cardiovascular events in patients with IHD. PMID:25819856

  6. Platelet-rich fibrin matrix improves wound angiogenesis via inducing endothelial cell proliferation.

    PubMed

    Roy, Sashwati; Driggs, Jason; Elgharably, Haytham; Biswas, Sabyasachi; Findley, Muna; Khanna, Savita; Gnyawali, Urmila; Bergdall, Valerie K; Sen, Chandan K

    2011-11-01

    The economic, social, and public health burden of chronic ulcers and other compromised wounds is enormous and rapidly increasing with the aging population. The growth factors derived from platelets play an important role in tissue remodeling including neovascularization. Platelet-rich plasma (PRP) has been utilized and studied for the last four decades. Platelet gel and fibrin sealant, derived from PRP mixed with thrombin and calcium chloride, have been exogenously applied to tissues to promote wound healing, bone growth, hemostasis, and tissue sealing. In this study, we first characterized recovery and viability of as well as growth factor release from platelets in a novel preparation of platelet gel and fibrin matrix, namely platelet-rich fibrin matrix (PRFM). Next, the effect of PRFM application in a delayed model of ischemic wound angiogenesis was investigated. The study, for the first time, shows the kinetics of the viability of platelet-embedded fibrin matrix. A slow and steady release of growth factors from PRFM was observed. The vascular endothelial growth factor released from PRFM was primarily responsible for endothelial mitogenic response via extracellular signal-regulated protein kinase activation pathway. Finally, this preparation of PRFM effectively induced endothelial cell proliferation and improved wound angiogenesis in chronic wounds, providing evidence of probable mechanisms of action of PRFM in healing of chronic ulcers.

  7. Stacking fault induced tunnel barrier in platelet graphite nanofiber

    SciTech Connect

    Lan, Yann-Wen E-mail: ywlan@phys.sinica.edu.tw; Chang, Yuan-Chih; Chang, Chia-Seng; Chen, Chii-Dong E-mail: ywlan@phys.sinica.edu.tw; Chang, Wen-Hao; Li, Yuan-Yao

    2014-09-08

    A correlation study using image inspection and electrical characterization of platelet graphite nanofiber devices is conducted. Close transmission electron microscopy and diffraction pattern inspection reveal layers with inflection angles appearing in otherwise perfectly stacked graphene platelets, separating nanofibers into two domains. Electrical measurement gives a stability diagram consisting of alternating small-large Coulomb blockade diamonds, suggesting that there are two charging islands coupled together through a tunnel junction. Based on these two findings, we propose that a stacking fault can behave as a tunnel barrier for conducting electrons and is responsible for the observed double-island single electron transistor characteristics.

  8. Cholesterol-induced stimulation of platelet aggregation is prevented by a hempseed-enriched diet.

    PubMed

    Prociuk, M A; Edel, A L; Richard, M N; Gavel, N T; Ander, B P; Dupasquier, C M C; Pierce, G N

    2008-04-01

    Hypercholesterolemia indirectly increases the risk for myocardial infarction by enhancing the ability of platelets to aggregate. Diets enriched with polyunsaturated fatty acids (PUFAs) have been shown to reduce the detrimental effects of cholesterol on platelet aggregation. This study investigated whether dietary hempseed, a rich source of PUFAs, inhibits platelet aggregation under normal and hypercholesterolemic conditions. Male New Zealand white rabbits were fed one of 6 dietary interventions: regular control diet (RG); control diet + 10% hempseed (HP); control diet + 10% partially delipidated hempseed (DHP); control diet + 0.5% cholesterol (OL); control diet + 0.5% cholesterol + 10% hempseed (OLHP); control diet + 5% coconut oil (CO). After 8 weeks, blood was collected to measure ADP- and collagen-induced platelet aggregation and plasma levels of fatty acids, cholesterol, and triglycerides. The hempseed-fed animals (HP and OLHP) displayed elevated plasma levels of PUFAs and a prominent enhancement in 18:3n-6 (gamma-linolenic acid, GLA) levels, a unique PUFA found in hempseed. The cholesterol-supplemented groups (OL and OLHP) had significantly elevated plasma levels of cholesterol and triglycerides, but platelet aggregation was significantly augmented only in the OL group. The addition of hempseed to this diet (OLHP) normalized aggregation. The direct addition of GLA to the OL platelet samples blocked the cholesterol-induced stimulation of platelet aggregation. The results of this study demonstrate that when hempseed is added to a cholesterol-enriched diet, cholesterol-induced platelet aggregation returns to control levels. This normalization is not due to a reduction in plasma cholesterol levels, but may be partly due to increased levels of plasma GLA.

  9. Constitutively activated phosphatidylinositol 3-kinase primes platelets from patients with chronic myelogenous leukemia for thrombopoietin-induced aggregation.

    PubMed

    Kubota, Y; Tanaka, T; Ohnishi, H; Kitanaka, A; Okutani, Y; Taminato, T; Ishida, T; Kamano, H

    2004-06-01

    In this study, we examined the effect of thrombopoietin (TPO) on the aggregation of platelets from 40 patients with myeloproliferative disorders (MPDs), including 17 patients with chronic myelogenous leukemia in the chronic phase (CML-CP), 10 with polycythemia vera, 10 with essential thrombocythemia, and three with myelofibrosis. TPO by itself dose-dependently induced the aggregation of platelets from patients with CML-CP but not from those with other MPDs or with CML-CP in cytogenetical complete remission. The expression of CD63 in CML-CP platelets was induced by TPO treatment. Phosphatidylinositol 3-kinase (PI3-kinase) was constitutively activated in CML-CP platelets. Pretreatment with PI3-kinase inhibitors (wortmannin and LY294002) dose-dependently inhibited TPO-induced aggregation of CML-CP platelets. The Abl kinase inhibitor imatinib mesylate and the Jak inhibitor AG490 suppressed TPO-induced aggregation of CML-CP platelets. Pretreatment with imatinib mesylate, but not with AG490, inhibited the activity of PI3-kinase in CML-CP platelets. In addition, tyrosine phosphorylation of Jak2 was undetected in CML-CP platelets before TPO treatment. These findings indicate that the constitutive activation of PI3-kinase primes CML-CP platelets for the aggregation induced by TPO, and that Bcr-Abl, but not Jak family protein tyrosine kinases, are involved in the constitutive activation of PI3-kinase in CML-CP platelets.

  10. Prevention of ischemia-induced myocardial platelet deposition by exogenous prostacyclin

    SciTech Connect

    Aherne, T.; Price, D.C.; Yee, E.S.; Hsieh, W.R.; Ebert, P.A.

    1986-07-01

    The antithrombotic effects of prostacyclin infusion on myocardial platelet deposition were studied in a canine model during and after global ischemia. Eleven isolated heart preparations were subjected to 1 hour of cardioplegic arrest under moderate hypothermia (27 to 28/sup 0/C), including a control group (n = 7) and a prostacyclin-treated group (n = 4). The hearts of four other dogs were continuously perfused for 180 minutes. Platelet deposition was measured at 15 minute intervals throughout the 3 hour study. Serial full-thickness myocardial biopsy specimens were analyzed for activity of /sup 111/In-labeled platelets with /sup 99m/Tc-labeled erythrocyte correction for tissue blood content. The pattern of platelet distribution was determined by scintiscans of each heart, taken with a gamma camera at the end of the 60 minute reperfusion period. Substantial myocardial platelet deposition was found in the control hearts after ischemia but not in the prostacyclin-treated group (p less than 0.05). Furthermore, prostacyclin infusion had a significant disaggregatory effect on intracoronary platelet deposits when the precardioplegic and postcardioplegic biopsy specimens were analyzed (p less than 0.05). Three hours of continuous perfusion did not increase tissue /sup 111/In-labeled platelet activity. Ex vivo images showed platelet deposition to be a diffuse patchy process with significantly more /sup 111/In activity in the endocardium than in the epicardium after global ischemia (p less than 0.05). These data show the potent antithrombotic properties of prostacyclin in preventing and disaggregating ischemia-induced intracoronary platelet deposition during and after cardioplegic arrest.

  11. Resveratrol protects against peroxynitrite-induced thiol oxidation in blood platelets.

    PubMed

    Olas, Beata; Nowak, Paweł; Wachowicz, Barbara

    2004-01-01

    The peroxynitrite anion (ONOO-) is a reactive species produced in the reaction between the superoxide anion (O2*-) and nitric oxide (*NO). ONOO- is involved in several pathological conditions such as inflammation, arteriosclerosis, and neurodegenerative and cardiovascular disorders. Our earlier results showed that ONOO- inhibits different steps of blood platelet activation and causes the depletion of platelet thiols. In this study, we investigated the effects of resveratrol (3, 4', 5-trihydroxystilbene) and other antioxidants (uric acid and deferoxamine (DFO)) on the level of low molecular thiols such as glutathione, cysteine and cysteinylglycine (in reduced and oxidized form) in blood platelets treated with ONOO-. Our results showed that ONOO- (100 microM, 2 min) induces changes in these thiols (measured by HPLC method); these changes are diminished in the presence of resveratrol. Preincubation of human platelets with resveratrol at a concentration of 100 microM (30 min) has a protective effect against the oxidation of platelet thiols induced by ONOO- or its intermediate. The other tested antioxidants also have a protectory action. In conclusion, we suggest that the resveratrol present in the human diet may partially protect -SH groups from oxidation and may be responsible for redox regulation and control in platelets.

  12. Direct Adaptive Rejection of Vortex-Induced Disturbances for a Powered SPAR Platform

    NASA Technical Reports Server (NTRS)

    VanZwieten, Tannen S.; Balas, Mark J.; VanZwieten, James H.; Driscoll, Frederick R.

    2009-01-01

    The Rapidly Deployable Stable Platform (RDSP) is a novel vessel designed to be a reconfigurable, stable at-sea platform. It consists of a detachable catamaran and spar, performing missions with the spar extending vertically below the catamaran and hoisting it completely out of the water. Multiple thrusters located along the spar allow it to be actively controlled in this configuration. A controller is presented in this work that uses an adaptive feedback algorithm in conjunction with Direct Adaptive Disturbance Rejection (DADR) to mitigate persistent, vortex-induced disturbances. Given the frequency of a disturbance, the nominal DADR scheme adaptively compensates for its unknown amplitude and phase. This algorithm is extended to adapt to a disturbance frequency that is only coarsely known by including a Phase Locked Loop (PLL). The PLL improves the frequency estimate on-line, allowing the modified controller to reduce vortex-induced motions by more than 95% using achievable thrust inputs.

  13. Identification of a novel platelet antagonist that binds to CLEC-2 and suppresses podoplanin-induced platelet aggregation and cancer metastasis

    PubMed Central

    Chang, Yu-Tsui; Lu, Meng-Hong; Huang, Tur-Fu; Chong, Kowit-Yu; Liao, Hsiang-Ruei; Cheng, Ju-Chien; Tseng, Ching-Ping

    2015-01-01

    Podoplanin (PDPN) enhances tumor metastases by eliciting tumor cell-induced platelet aggregation (TCIPA) through activation of platelet C-type lectin-like receptor 2 (CLEC-2). A novel and non-cytotoxic 5-nitrobenzoate compound 2CP was synthesized that specifically inhibited the PDPN/CLEC-2 interaction and TCIPA with no effect on platelet aggregation stimulated by other platelet agonists. 2CP possessed anti-cancer metastatic activity in vivo and augmented the therapeutic efficacy of cisplatin in the experimental animal model without causing a bleeding risk. Analysis of the molecular action of 2CP further revealed that Akt1/PDK1 and PKCμ were two alternative CLEC-2 signaling pathways mediating PDPN-induced platelet activation. 2CP directly bound to CLEC-2 and, by competing with the same binding pocket of PDPN in CLEC-2, inhibited PDPN-mediated platelet activation. This study provides evidence that 2CP is the first defined platelet antagonist with CLEC-2 binding activity. The augmentation in the therapeutic efficacy of cisplatin by 2CP suggests that a combination of a chemotherapeutic agent and a drug with anti-TCIPA activity such as 2CP may prove clinically effective. PMID:26528756

  14. Synthesis of huaicarbon A/B and their activating effects on platelet glycoprotein VI receptor to mediate collagen-induced platelet aggregation

    PubMed Central

    Yu, Hongli; Chen, Yeqing; Wu, Hao; Wang, Kuilong; Liu, Liping; Zhang, Xingde

    2017-01-01

    Quercetin and rhamnose were efficiently converted into huaicarbon A/B by heating at 250°C for 10-15 min or at 200°C for 25-30 min. With the optimum molar ratio of quercetin/rhamnose (1:3), huaicarbon A and B yields reached 25% and 16% respectively after heating at 250°C, with 55% quercetin conversion. Huaicarbon A/B both promoted washed platelet aggregation dose-dependently, which was antagonized by an inhibitor of glycoprotein VI (GPVI) receptor. Similarly, they both promoted collagen-induced platelet aggregation in platelet-rich plasma in dose-dependent manners. According to the S type dose-response model, EC50 values of huaicarbon A and huaicarbon B were calculated as 33.48 μM and 48.73 μM respectively. They induced intracellular Ca2+ accumulation that was specifically blocked by GPVI antagonist. Huaicarbon A/B enhanced intracellular Ca2+ accumulation and facilitated collagen-induced platelet aggregation, which were blocked by GPVI antagonist. They were conducive to collagen-induced platelet aggregation by activating platelet GPVI receptor. PMID:28337278

  15. DPIV prediction of flow induced platelet activation-comparison to numerical predictions.

    PubMed

    Raz, Sagi; Einav, Shmuel; Alemu, Yared; Bluestein, Danny

    2007-04-01

    Flow induced platelet activation (PA) can lead to platelet aggregation, deposition onto the blood vessel wall, and thrombus formation. PA was thoroughly studied under unidirectional flow conditions. However, in regions of complex flow, where the platelet is exposed to varying levels of shear stress for varying durations, the relationship between flow and PA is not well understood. Numerical models were developed for studying flow induced PA resulting from stress histories along Lagrangian trajectories in the flow field. However, experimental validation techniques such as Digital Particle Image Velocimetry (DPIV) were not extended to include such models. In this study, a general experimental tool for PA analysis by means of continuous DPIV was utilized and compared to numerical simulation in a model of coronary stenosis. A scaled up (5:1) 84% eccentric and axisymetric coronary stenosis model was used for analysis of shear stress and exposure time along particle trajectories. Flow induced PA was measured using the PA State (PAS) assay. An algorithm for computing the PA level in pertinent trajectories was developed as a tool for extracting information from DPIV measurements for predicting the flow induced thrombogenic potential. CFD, DPIV and PAS assay results agreed well in predicting the level of PA. In addition, the same trend predicted by the DPIV was measured in vitro using the Platelet Activity State (PAS) assay, namely, that the symmetric stenosis activated the platelets more as compared to the eccentric stenosis.

  16. Collagen-induced binding to human platelets of platelet-derived growth factor leading to inhibition of P43 and P20 phosphorylation

    SciTech Connect

    Bryckaert, M.C.; Rendu, F.; Tobelem, G.; Wasteson, A.

    1989-03-15

    Platelet-derived growth factor (PDGF) is known to inhibit collagen-induced platelet aggregation. Collagen-induced binding of /sup 125/I-PDGF to human washed platelets was therefore investigated. It was found to be time-dependent, reaching a plateau at 20 degrees C after 30 min, collagen concentration-dependent, specifically inhibited by unlabeled PDGF, and saturable. Scatchard plot analysis showed a single class of sites with 3000 +/- 450 molecules bound/cell and an apparent KD of 1.2 +/- 0.2 10(-8) M. The effects of PDGF on collagen-induced phosphoinositide breakdown and protein phosphorylation were also investigated. At 50 ng/ml PDGF, a concentration which completely inhibited collagen-induced aggregation, the breakdown of (/sup 32/P)phosphatidylinositol 4,5-biphosphate (PIP2) and (/sup 32/P)phosphatidylinositol 4-phosphate (PIP) was observed, but the subsequent replenishment of (/sup 32/P)PIP2 was inhibited. The same PDGF concentration totally inhibited collagen-induced phosphatidic acid formation. PDGF also completely prevented phosphorylation of P43 and P20, as a result of protein kinase C activation consecutive to phosphoinositide metabolism. These results suggest that a specific PDGF receptor can be induced by collagen, and PDGF can effect the early events of collagen-induced platelet activation by inhibiting PIP2 resynthesis and P43 and P20 phosphorylation. It is concluded that PDGF might be involved in a negative feed-back control of platelet activation.

  17. Reduced platelet-mediated and enhanced leukocyte-mediated fibrinolysis in experimentally induced diabetes in rats

    SciTech Connect

    Winocour, P.D.; Colwell, J.A.

    1985-05-01

    Studies of fibrinolytic activity in diabetes mellitus have produced conflicting results. This may be a result of methodologic insensitivity or of variable contributions of the different blood components to whole blood fibrinolysis. To explore these two possibilities, the authors used a sensitive solid-phase radiometric assay to examine the fibrinolytic activity of whole blood, platelet-rich plasma, leukocytes, and platelet- and leukocyte-poor plasma prepared from control rats and rats with streptozocin-induced diabetes at various times after induction of diabetes. Fibrinolytic activity of whole blood from diabetic rats after 7 days was significantly reduced, and remained reduced after longer durations of diabetes up to 28 days. Platelet-rich plasma from diabetic rats had decreased fibrinolytic activity, which followed the same time course of changes as in whole blood. The platelet contribution to whole blood fibrinolysis was further reduced in vivo after 14 days of diabetes by a reduced whole blood platelet count. In contrast, fibrinolytic activity of leukocytes from diabetic rats became enhanced after 7 days of diabetes. After 49 days of diabetes, the whole blood leukocyte count was reduced, and in vivo would offset the enhanced activity. Plasma fibrinolytic activity was small compared with that of whole blood and was unaltered in diabetic rats. The authors conclude that altered platelet function contributes to decreased fibrinolytic activity of whole blood in diabetic rats, and that this may be partially offset by enhanced leukocyte-mediated fibrinolysis.

  18. The effect of shear on in vitro platelet and leukocyte material-induced activation.

    PubMed

    Chang, Xiaojian; Gorbet, Maud

    2013-09-01

    The failure to understand the mechanisms of biomaterial-associated thrombosis prevents us from improving the blood compatibility of stents and mechanical heart valves. Blood-material interactions trigger a complex series of events and anticoagulant and anti-platelet therapies are needed to reduce the risks of thrombotic complications with most cardiovascular materials. While material interaction with platelets has been widely studied, little is currently known on material-induced leukocyte activation in the presence of shear. In vitro experiments were performed to assess the effect of flow on blood cell activation induced by medical grade metals, ST316L and TiAl6V4. Blood was circulated in flow chambers preloaded with or without metal wires at shear rates of 100, 500, and 1500 s⁻¹. Platelet and leukocyte activation, leukocyte-platelet aggregation, and tissue factor expression on monocytes were measured by flow cytometry. Metal surfaces were characterized by scanning electron microscopy. Under physiological shear rates, no significant platelet microparticle formation was observed. However, significant CD11b up-regulation, leukocyte-platelet aggregates, and tissue factor expression were observed at 100 s⁻¹. As shear rate increased to 1500 s⁻¹, leukocyte activation reduced to control values. TiAl6V4-induced leukocyte activation was generally lower than that of ST316L. Adhesion significantly decreased with increasing shear rate to 1500 s⁻¹. In blood, increase within physiological shear rates led to a significant reduction in in vitro material-induced leukocyte activation, suggesting that difference between material biocompatibility may be better identified at low shear rates or under pathological shear conditions.

  19. Streptococcus sanguis-Induced Platelet Clotting in Rabbits and Hemodynamic and Cardiopulmonary Consequences

    PubMed Central

    Meyer, Maurice W.; Gong, Ke; Herzberg, Mark C.

    1998-01-01

    By mimicking hemostatic structural domains of collagen, Streptococcus sanguis (aggregation-positive phenotype; Agg+) induces platelets to aggregate in vitro. To test the hypothesis that aggregation occurs in vivo, S. sanguis (Agg+ or Agg− suspension) was infused intravenously into rabbits. The extent of hemodynamic and cardiopulmonary changes and the fate of circulating platelets were Agg+ strain dose dependent. Within 45 to 50 s of the start of infusion, 40 × 108 CFU of the Agg+ strain caused increased blood pressure. Thirty seconds after infusion, other changes occurred. Intermittent electrocardiographic abnormalities (13 of 15 rabbits), ST-segment depression (10 of 15 rabbits), and preventricular contractions (7 of 15 rabbits) manifested at 3 to 7 min, with frequencies dose dependent. Respiratory rate and cardiac contractility increased during this phase. Blood catecholamine concentration, thrombocytopenia, accumulation of 111Indium-labeled platelets in the lungs, and ventricular axis deviation also showed dose dependency. Rabbits were unaffected by inoculation of an Agg− strain. Therefore, Agg+ S. sanguis induced platelet aggregation in vitro. Platelet clots caused hemodynamic changes, acute pulmonary hypertension, and cardiac abnormalities, including ischemia. PMID:9826372

  20. Platelet participation in the pathogenesis of dermonecrosis induced by Loxosceles gaucho venom.

    PubMed

    Tavares, F L; Peichoto, M E; Marcelino, J R; Barbaro, K C; Cirillo, M C; Santoro, M L; Sano-Martins, I S

    2016-06-01

    Loxosceles gaucho spider venom induces in vitro platelet activation and marked thrombocytopenia in rabbits. Herein, we investigated the involvement of platelets in the development of the dermonecrosis induced by L. gaucho venom, using thrombocytopenic rabbits as a model. L. gaucho venom evoked a drop in platelet and neutrophil counts 4 h after venom injection. Ecchymotic areas at the site of venom inoculation were noticed as soon as 4 h in thrombocytopenic animals but not in animals with initial normal platelet counts. After 5 days, areas of scars in thrombocytopenic animals were also larger, evidencing the marked development of lesions in the condition of thrombocytopenia. Histologically, local hemorrhage, collagen fiber disorganization, and edema were more severe in thrombocytopenic animals. Leukocyte infiltration, predominantly due to polymorphonuclears, was observed in the presence or not of thrombocytopenia. Thrombus formation was demonstrated by immunohistochemistry at the microvasculature, and it occurred even under marked thrombocytopenia. Taken together, platelets have an important role in minimizing not only the hemorrhagic phenomena but also the inflammatory and wound-healing processes, suggesting that cutaneous loxoscelism may be aggravated under thrombocytopenic conditions.

  1. Mouse model of alloimmune-induced vascular rejection and transplant arteriosclerosis.

    PubMed

    Enns, Winnie; von Rossum, Anna; Choy, Jonathan

    2015-05-17

    Vascular rejection that leads to transplant arteriosclerosis (TA) is the leading representation of chronic heart transplant failure. In TA, the immune system of the recipient causes damage of the arterial wall and dysfunction of endothelial cells and smooth muscle cells. This triggers a pathological repair response that is characterized by intimal thickening and luminal occlusion. Understanding the mechanisms by which the immune system causes vasculature rejection and TA may inform the development of novel ways to manage graft failure. Here, we describe a mouse aortic interposition model that can be used to study the pathogenic mechanisms of vascular rejection and TA. The model involves grafting of an aortic segment from a donor animal into an allogeneic recipient. Rejection of the artery segment involves alloimmune reactions and results in arterial changes that resemble vascular rejection. The basic technical approach we describe can be used with different mouse strains and targeted interventions to answer specific questions related to vascular rejection and TA.

  2. Dual role of the p38 MAPK/cPLA2 pathway in the regulation of platelet apoptosis induced by ABT-737 and strong platelet agonists

    PubMed Central

    Rukoyatkina, N; Mindukshev, I; Walter, U; Gambaryan, S

    2013-01-01

    p38 Mitogen-activated protein (MAP) kinase is involved in the apoptosis of nucleated cells. Although platelets are anucleated cells, apoptotic proteins have been shown to regulate platelet lifespan. However, the involvement of p38 MAP kinase in platelet apoptosis is not yet clearly defined. Therefore, we investigated the role of p38 MAP kinase in apoptosis induced by a mimetic of BH3-only proteins, ABT-737, and in apoptosis-like events induced by such strong platelet agonists as thrombin in combination with convulxin (Thr/Cvx), both of which result in p38 MAP kinase phosphorylation and activation. A p38 inhibitor (SB202190) inhibited the apoptotic events induced by ABT-737 but did not influence those induced by Thr/Cvx. The inhibitor also reduced the phosphorylation of cytosolic phospholipase A2 (cPLA2), an established p38 substrate, induced by ABT-737 or Thr/Cvx. ABT-737, but not Thr/Cvx, induced the caspase 3-dependent cleavage and inactivation of cPLA2. Thus, p38 MAPK promotes ABT-737-induced apoptosis by inhibiting the cPLA2/arachidonate pathway. We also show that arachidonic acid (AA) itself and in combination with Thr/Cvx or ABT-737 at low concentrations prevented apoptotic events, whereas at high concentrations it enhanced such events. Our data support the hypothesis that the p38 MAPK-triggered arachidonate pathway serves as a defense mechanism against apoptosis under physiological conditions. PMID:24263105

  3. Bcl-xL-inhibitory BH3 mimetics can induce a transient thrombocytopathy that undermines the hemostatic function of platelets.

    PubMed

    Schoenwaelder, Simone M; Jarman, Kate E; Gardiner, Elizabeth E; Hua, My; Qiao, Jianlin; White, Michael J; Josefsson, Emma C; Alwis, Imala; Ono, Akiko; Willcox, Abbey; Andrews, Robert K; Mason, Kylie D; Salem, Hatem H; Huang, David C S; Kile, Benjamin T; Roberts, Andrew W; Jackson, Shaun P

    2011-08-11

    BH3 mimetics are a new class of proapo-ptotic anticancer agents that have shown considerable promise in preclinical animal models and early-stage human trials. These agents act by inhibiting the pro-survival function of one or more Bcl-2-related proteins. Agents that inhibit Bcl-x(L) induce rapid platelet death that leads to thrombocytopenia; however, their impact on the function of residual circulating platelets remains unclear. In this study, we demonstrate that the BH3 mimetics, ABT-737 or ABT-263, induce a time- and dose-dependent decrease in platelet adhesive function that correlates with ectodomain shedding of the major platelet adhesion receptors, glycoprotein Ibα and glycoprotein VI, and functional down-regulation of integrin α(IIb)β(3). Analysis of platelets from mice treated with higher doses of BH3 mimetics revealed the presence of a subpopulation of circulating platelets undergoing cell death that have impaired activation responses to soluble agonists. Functional analysis of platelets by intravital microscopy revealed a time-dependent defect in platelet aggregation at sites of vascular injury that correlated with an increase in tail bleeding time. Overall, these studies demonstrate that Bcl-x(L)-inhibitory BH3 mimetics not only induce thrombocytopenia but also a transient thrombocytopathy that can undermine the hemostatic function of platelets.

  4. PLATELET-ASSOCIATED NAD(P)H OXIDASE CONTRIBUTES TO THE THROMBOGENIC PHENOTYPE INDUCED BY HYPERCHOLESTEROLEMIA

    PubMed Central

    Stokes, Karen Y.; Russell, Janice M.; Jennings, Merilyn H.; Alexander, J. Steven; Granger., D. Neil

    2007-01-01

    Elevated cholesterol levels promote pro-inflammatory and prothrombogenic responses in venules and impaired endothelium-dependent arteriolar dilation. Although NAD(P)H oxidase-derived superoxide has been implicated in the altered vascular responses to hypercholesterolemia, it remains unclear whether this oxidative pathway mediates the associated arteriolar dysfunction and platelet adhesion in venules. Platelet and leukocyte adhesion in cremasteric postcapillary venules, and arteriolar dilation responses to acetylcholine were monitored in wild-type (WT), Cu,Zn-superoxide dismutase transgenic (SOD-TgN) and NAD(P)H oxidase-knockout (gp91phox-/-) mice placed on normal (ND) or high cholesterol (HC) diet for 2 wk. HC elicited increased platelet and leukocyte adhesion in WT mice, versus ND. Cytosolic subunits of NAD(P)H oxidase (p47phox and p67phox) were expressed in platelets. This was not altered by hypercholesterolemia, however platelets and leukocytes from HC mice exhibited elevated generation of reactive oxygen species when compared to ND mice. Hypercholesterolemia-induced leukocyte recruitment was attenuated in SOD-TgN-HC and gp91phox-/--HC mice. Recruitment of platelets derived from WT-HC mice in venules of SOD-TgN-HC or gp91phox-/--HC recipients was comparable to ND levels. Adhesion of SOD-TgN-HC platelets paralleled the leukocyte response and was attenuated in SOD-TgN-HC recipients, but not in WT-HC recipients. However, gp91phox-/--HC platelets exhibited low levels of adhesion comparable to WT-ND in both hypercholesterolemic gp91phox-/- and WT recipients. Arteriolar dysfunction was evident in WT-HC mice, compared to WT-ND. Overexpression of SOD or, to a lesser extent, gp91phox deficiency, restored arteriolar vasorelaxation responses towards WT-ND levels. These findings reveal a novel role for platelet-associated NAD(P)H oxidase in producing the thrombogenic phenotype in hypercholesterolemia and demonstrate that NAD(P)H oxidase-derived superoxide mediates the HC-induced

  5. Plasma concentrations of endotoxin and platelet activation in the developmental stage of oligofructose-induced laminitis.

    PubMed

    Bailey, S R; Adair, H S; Reinemeyer, C R; Morgan, S J; Brooks, A C; Longhofer, S L; Elliott, J

    2009-06-15

    The link between the fermentation of carbohydrate in the equine large intestine and the development of acute laminitis is poorly understood. Absorption of endotoxin (lipopolysaccharide; LPS) into the plasma has been observed in one experimental model of laminitis, but does not cause laminitis when administered alone. Thus, the potential role of endotoxin is unclear. Platelet activation has previously been demonstrated in the developmental stage of laminitis. Equine platelets are more sensitive than leukocytes to activation by endotoxin, and can be activated directly by LPS in the low pg/ml range, activating p38 MAP kinase and releasing serotonin (5-HT) and thromboxane. The objectives of this study were firstly to determine whether endotoxin and platelet activation could be measured in the plasma of horses in the developmental phase of laminitis induced with oligofructose. Secondly, the time course of events involving platelet activation and platelet-derived vasoactive mediator production was investigated. Laminitis was induced in six Standardbred horses by the administration of 10 g/kg bwt of oligofructose. Plasma samples were obtained every 4h, and platelet pellets were obtained by centrifugation. LPS was measured using a kinetic limulus amebocyte lysate assay, and platelet activation was assessed by Western blotting for the phosphorylated form of p38 MAP kinase. Plasma 5-HT was assayed by HPLC with electrochemical detection and thromboxane B(2) was measured by radioimmunoassay. Clinical signs of laminitis and histopathologic changes were observed in lamellar sections from five of the six horses. Onset of lameness was between 20 and 30 h after the administration of oligofructose. LPS increased above the limit of detection (0.6 pg/ml) to reach a peak of 2.4+/-1.0 pg/ml at 8 h. TNFalpha was also detectable in the plasma from 12 to 24 h. There was a time-dependent increase in platelet p38 MAPK phosphorylation, which peaked at approximately 12 h (3.8+/-1.3 fold

  6. High Fat Diet Induces Adhesion of Platelets to Endothelium in Two Models of Dyslipidemia

    PubMed Central

    Gonzalez, Jaime; Donoso, Wendy; Díaz, Natalia; Albornoz, María Eliana; Huilcaman, Ricardo; Morales, Erik

    2014-01-01

    Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE−/− mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE−/− mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cells in vivo. These findings support studying the participation of platelets in the formation of atheromatous plate. PMID:25328689

  7. High fat diet induces adhesion of platelets to endothelium in two models of dyslipidemia.

    PubMed

    Gonzalez, Jaime; Donoso, Wendy; Díaz, Natalia; Albornoz, María Eliana; Huilcaman, Ricardo; Morales, Erik; Moore-Carrasco, Rodrigo

    2014-01-01

    Cardiovascular diseases (CVD) represent about 30% of all global deaths. It is currently accepted that, in the atherogenic process, platelets play an important role, contributing to endothelial activation and modulation of the inflammatory phenomenon, promoting the beginning and formation of lesions and their subsequent thrombotic complications. The objective of the present work was to study using immunohistochemistry, the presence of platelets, monocytes/macrophages, and cell adhesion molecules (CD61, CD163, and CD54), in two stages of the atheromatous process. CF-1 mice fed a fat diet were used to obtain early stages of atheromatous process, denominated early stage of atherosclerosis, and ApoE(-/-) mice fed a fat diet were used to observe advanced stages of atherosclerosis. The CF-1 mice model presented immunostaining on endothelial surface for all three markers studied; the advanced atherosclerosis model in ApoE(-/-) mice also presented granular immunostaining on lesion thickness, for the same markers. These results suggest that platelets participate in atheromatous process from early stages to advance d stages. High fat diet induces adhesion of platelets to endothelial cells in vivo. These findings support studying the participation of platelets in the formation of atheromatous plate.

  8. Functional Comparison of Induced Pluripotent Stem Cell- and Blood-Derived GPIIbIIIa Deficient Platelets

    PubMed Central

    Haas, Jessica; Sandrock-Lang, Kirstin; Gärtner, Florian; Jung, Christian Billy; Zieger, Barbara; Parrotta, Elvira; Kurnik, Karin; Sinnecker, Daniel; Wanner, Gerhard; Laugwitz, Karl-Ludwig; Massberg, Steffen; Moretti, Alessandra

    2015-01-01

    Human induced pluripotent stem cells (hiPSCs) represent a versatile tool to model genetic diseases and are a potential source for cell transfusion therapies. However, it remains elusive to which extent patient-specific hiPSC-derived cells functionally resemble their native counterparts. Here, we generated a hiPSC model of the primary platelet disease Glanzmann thrombasthenia (GT), characterized by dysfunction of the integrin receptor GPIIbIIIa, and compared side-by-side healthy and diseased hiPSC-derived platelets with peripheral blood platelets. Both GT-hiPSC-derived platelets and their peripheral blood equivalents showed absence of membrane expression of GPIIbIIIa, a reduction of PAC-1 binding, surface spreading and adherence to fibrinogen. We demonstrated that GT-hiPSC-derived platelets recapitulate molecular and functional aspects of the disease and show comparable behavior to their native counterparts encouraging the further use of hiPSC-based disease models as well as the transition towards a clinical application. PMID:25607928

  9. Beta-lactam antibiotic-induced platelet dysfunction: Evidence for irreversible inhibition of platelet activation in vitro and in vivo after prolonged exposure to penicillin

    SciTech Connect

    Burroughs, S.F.; Johnson, G.J. )

    1990-04-01

    beta-Lactam antibiotics cause platelet dysfunction with bleeding complications. Previous in vitro studies documented reversible inhibition of agonist-receptor interaction. This mechanism is inadequate to explain the effect of beta-lactam antibiotics in vivo. Platelet function does not return to normal immediately after drug treatment, implying irreversible inhibition of platelet function. We report here evidence of irreversible platelet functional and biochemical abnormalities after in vitro and in vivo exposure to beta-lactam antibiotics. Irreversible binding of (14C)-penicillin (Pen) occurred in vitro. After 24 hours' in vitro incubation with 10 to 20 mmol/L Pen, or ex vivo after antibiotic treatment, irreversible functional impairment occurred; but no irreversible inhibition of alpha 2 adrenergic receptors, measured with (3H)-yohimbine, or high-affinity thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors, measured with agonist (3H)-U46619 and antagonist (3H)-SQ29548, occurred. However, low-affinity platelet TXA2/PGH2 receptors were decreased 40% after Pen exposure in vitro or in vivo, indicating irreversible membrane alteration. Two postreceptor biochemical events were irreversibly inhibited in platelets incubated with Pen for 24 hours in vitro or ex vivo after antibiotic treatment. Thromboxane synthesis was inhibited 28.3% to 81.7%. Agonist-induced rises in cytosolic calcium ((Ca2+)i) were inhibited 40.1% to 67.5% in vitro and 26.6% to 52.2% ex vivo. Therefore, Pen binds to platelets after prolonged exposure, resulting in irreversible dysfunction attributable to inhibition of TXA2 synthesis and impairment of the rise in (Ca2+)i. The loss of low-affinity TXA2/PGH2 receptors suggests that the primary site of action of these drugs is on the platelet membrane.

  10. Shape changes induced by biologically active peptides and nerve growth factor in blood platelets of rabbits.

    PubMed

    Gudat, F; Laubscher, A; Otten, U; Pletscher, A

    1981-11-01

    1 Nerve growth factor (NGF), substance P (SP) and thymopoietin all caused shape change reactions of rapid onset in rabbit platelets. NGF had the highest maximal effect, and SP the lowest EC50 (concentration causing half maximal shape change). The action of SP was reversible within 5 min, whereas that of NGF lasted for at least 1 h. A series of other peptides were inactive. 2 After preincubation of platelets with SP, a second application of SP no longer caused a shape change reaction, whereas the effect of NGF was not influenced. 3 An oxidized NGF-derivative without biological activity did not cause a shape change reaction, neither did epidermal growth factor. 4 Prostaglandin E1 (PGE1) and pretreatment of the platelets with 3% butanol, which counteract the shape changes caused by 5-hydroxytryptamine (5-HT) and adenosine 3',5'-diphosphate, also antagonized those induced by NGF and SP. Neither heparin nor methysergide, an antagonist of 5-HT-receptors, influenced the shape change induced by NGF or SP. The action of NGF was also antagonized by a specific antibody to NGF. 5 Thymopoietin, like the basic polypeptide polyornithine (mol. wt. 40,000) was not antagonized by PGE1 and butanol. Heparin, which counteracted the effect of polyornithine, did not influence that of thymopoietin. 6 In conclusion, different modes of action are involved in the shape change of blood platelets induced by polypeptides and proteins. SP and NGF may act by stimulating specific membrane receptors.

  11. The Role of Platelet Factor 4 in Radiation-Induced Thrombocytopenia

    SciTech Connect

    Lambert, Michele P.; Xiao Liqing; Nguyen, Yvonne; Kowalska, M. Anna; Poncz, Mortimer

    2011-08-01

    Purpose: Factors affecting the severity of radiation-induced thrombocytopenia (RIT) are not well described. We address whether platelet factor 4 (PF4; a negative paracrine for megakaryopoiesis) affects platelet recovery postradiation. Methods and Materials: Using conditioned media from irradiated bone marrow (BM) cells from transgenic mice overexpressing human (h) PF4 (hPF4+), megakaryocyte colony formation was assessed in the presence of this conditioned media and PF4 blocking agents. In a model of radiation-induced thrombocytopenia, irradiated mice with varying PF4 expression levels were treated with anti-hPF4 and/or thrombopoietin (TPO), and platelet count recovery and survival were examined. Results: Conditioned media from irradiated BM from hPF4+ mice inhibited megakaryocyte colony formation, suggesting that PF4 is a negative paracrine released in RIT. Blocking with an anti-hPF4 antibody restored colony formation of BM grown in the presence of hPF4+ irradiated media, as did antibodies that block the megakaryocyte receptor for PF4, low-density lipoprotein receptor-related protein 1 (LRP1). Irradiated PF4 knockout mice had higher nadir platelet counts than irradiated hPF4+/knockout litter mates (651 vs. 328 x 106/mcL, p = 0.02) and recovered earlier (15 days vs. 22 days, respectively, p <0.02). When irradiated hPF4+ mice were treated with anti-hPF4 antibody and/or TPO, they showed less severe thrombocytopenia than untreated mice, with improved survival and time to platelet recovery, but no additive effect was seen. Conclusions: Our studies show that in RIT, damaged megakaryocytes release PF4 locally, inhibiting platelet recovery. Blocking PF4 enhances recovery while released PF4 from megakaryocytes limits TPO efficacy, potentially because of increased release of PF4 stimulated by TPO. The clinical value of blocking this negative paracrine pathway post-RIT remains to be determined.

  12. Imaging the elastic modulus of human platelets during thrombin-induced activation using scanning ion conductance microscopy.

    PubMed

    Rheinlaender, Johannes; Vogel, Sebastian; Seifert, Jan; Schächtele, Marc; Borst, Oliver; Lang, Florian; Gawaz, Meinrad; Schäffer, Tilman E

    2015-02-01

    Platelet activation plays a critical role in haemostasis and thrombosis. It is well-known that platelets generate contractile forces during activation. However, their mechanical material properties have rarely been investigated. Here, we use scanning ion conductance microscopy (SICM) to visualise morphological and mechanical properties of live human platelets at high spatial resolution. We found that their mean elastic modulus decreases during thrombin-induced activation by about a factor of two. We observed a similar softening of platelets during cytochalasin D-induced cytoskeleton depolymerisation. However, thrombin-induced temporal and spatial modulations of the elastic modulus were substantially different from cytochalasin D-mediated changes. We thereby provide new insights into the mechanics of haemostasis and establish SICM as a novel imaging platform for the ex vivo investigation of the mechanical properties of live platelets.

  13. [Neurologic complications induced by the treatment of the acute renal allograft rejection with the monoclonal antibody OKT3].

    PubMed

    Fernández, O; Romero, F; Bravo, M; Burgos, D; Cabello, M; González-Molina, M

    1993-10-01

    The treatment of the acute renal allograft rejection with the monoclonal antibody orthoclone OKT3 produces both systemic and neurologic alterations. In a series of 21 patients with an acute renal allograft rejection treated with this monoclonal antibody, 20 with a renal allograft transplantation and one with a renal and pancreatic allograft transplantation, 29% referred headache associated with fever and vomiting, and 14.2% presented severe neurological alterations induced by the treatment. We stress the need to know these secondary effects to differentiate them from other central nervous system disorders, particularly those of infectious origin.

  14. Inhibition of glutamate receptors reduces the homocysteine-induced whole blood platelet aggregation but does not affect superoxide anion generation or platelet membrane fluidization.

    PubMed

    Karolczak, Kamil; Pieniazek, Anna; Watala, Cezary

    2017-01-01

    Homocysteine (Hcy) is an excitotoxic amino acid. It is potentially possible to prevent Hcy-induced toxicity, including haemostatic impairments, by antagonizing glutaminergic receptors. Using impedance aggregometry with arachidonate and collagen as platelet agonists, we tested whether the blockade of platelet NMDA (N-methyl-D-aspartate), AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and kainate receptors with their inhibitors: MK-801 (dizocilpine hydrogen maleate, [5R,10S]-[+]-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine), CNQX (7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile) and UBP-302 (2-{[3-[(2S)-2-amino-2-carboxyethyl]-2,6-dioxo-3,6-dihydropyrimidin 1(2H)-yl]methyl}benzoic acid) may hamper Hcy-dependent platelet aggregation. All the tested compounds significantly inhibited Hcy-augmented aggregation of blood platelets stimulated either with arachidonate or collagen. Hcy stimulated the generation of superoxide anion in whole blood samples in a concentration-dependent manner; however, this process appeared as independent on ionotropic glutamate receptors, as well as on NADPH oxidase and protein kinase C, and was not apparently associated with the extent of either arachidonate- or collagen-dependent platelet aggregation. Moreover, Hcy acted as a significant fluidizer of surface (more hydrophilic) and inner (more hydrophobic) regions of platelet membrane lipid bilayer, when used at the concentration range from 10 to 50 µmol/l. However, this effect was independent on the Hcy action through glutamate ionotropic receptors, since there was no effects of MK-801, CNQX or UBP-302 on Hcy-mediated membrane fluidization. In conclusion, Hcy-induced changes in whole blood platelet aggregation are mediated through the ionotopic excitotoxic receptors, although the detailed mechanisms underlying such interactions remain to be elucidated.

  15. Effector Mechanisms of Rejection

    PubMed Central

    Moreau, Aurélie; Varey, Emilie; Anegon, Ignacio; Cuturi, Maria-Cristina

    2013-01-01

    Organ transplantation appears today to be the best alternative to replace the loss of vital organs induced by various diseases. Transplants can, however, also be rejected by the recipient. In this review, we provide an overview of the mechanisms and the cells/molecules involved in acute and chronic rejections. T cells and B cells mainly control the antigen-specific rejection and act either as effector, regulatory, or memory cells. On the other hand, nonspecific cells such as endothelial cells, NK cells, macrophages, or polymorphonuclear cells are also crucial actors of transplant rejection. Last, beyond cells, the high contribution of antibodies, chemokines, and complement molecules in graft rejection is discussed in this article. The understanding of the different components involved in graft rejection is essential as some of them are used in the clinic as biomarkers to detect and quantify the level of rejection. PMID:24186491

  16. Effect of the crude extract of Cestrum parqui on carrageenin-induced rat paw oedema and aggregation of human blood platelets.

    PubMed

    Shehnaz, D; Hamid, F; Baqai, F T; Uddin Ahmad, V

    1999-08-01

    An extract of Cestrum parqui aerial parts in methanol:water (1:1) showed inhibition of carrageenin-induced oedema. The aggregation of human blood platelets induced by adenosine diphosphate and platelet activating factor was also inhibited (IC(50)s were 3 and 2 mg/mL, respectively). On the contrary, the extract did not inhibit arachidonic acid-mediated platelet aggregation.

  17. Resveratrol may reduce oxidative stress induced by platinum compounds in human plasma, blood platelets and lymphocytes.

    PubMed

    Olas, Beata; Wachowicz, Barbara; Majsterek, Ireneusz; Blasiak, Janusz

    2005-07-01

    Resveratrol (trans-3,4',5-trihydroxystilbene), a polyphenolic compound found in grapes and wine, has been shown to have anti-inflammatory, anti-oxidant, anti-tumor and anti-platelet activities. Using different methods, we show that resveratrol reduces oxidative stress induced by cisplatin (cis-diamminedichloroplatinum II) and selenium-cisplatin conjugate ([NH(3)](2)Pt(SeO(3)), Se-Pt) in human blood platelets, lymphocytes and plasma. Resveratrol decreased the production of 8-epi-prostaglandin F(2) (a biomarker of lipid peroxidation) in control blood platelets and platelets treated with platinum compounds (10 microg/ml), and markedly reduced activities of different anti-oxidative enzymes (glutathione peroxidase, superoxide dismutase and catalase) in these cells. A combined action of resveratrol and Se-Pt evoked a significant decrease of DNA damage (measured by comet assay) in lymphocytes compared with cells treated with Se-Pt only. Resveratrol also caused a distinct reduction of total anti-oxidant level in plasma after incubation with platinum compounds. Therefore, anti-oxidative activity of resveratrol may diminish oxidative stress and damage to cellular biomolecules (lipids, proteins and DNA) induced by platinum compounds.

  18. Abacavir induces platelet-endothelium interactions by interfering with purinergic signalling: A step from inflammation to thrombosis.

    PubMed

    Alvarez, Angeles; Rios-Navarro, Cesar; Blanch-Ruiz, Maria Amparo; Collado-Diaz, Victor; Andujar, Isabel; Martinez-Cuesta, Maria Angeles; Orden, Samuel; Esplugues, Juan V

    2017-05-01

    The controversy connecting Abacavir (ABC) with cardiovascular disease has been fuelled by the lack of a credible mechanism of action. ABC shares structural similarities with endogenous purines, signalling molecules capable of triggering prothrombotic/proinflammatory programmes. Platelets are leading actors in the process of thrombosis. Our study addresses the effects of ABC on interactions between platelets and other vascular cells, while exploring the adhesion molecules implicated and the potential interference with the purinergic signalling pathway. The effects of ABC on platelet aggregation and platelet-endothelium interactions were evaluated, respectively, with an aggregometer and a flow chamber system that reproduced conditions in vivo. The role of adhesion molecules and purinergic receptors in endothelial and platelet populations was assessed by selective pre-incubation with specific antagonists and antibodies. ABC and carbovir triphosphate (CBT) levels were evaluated by HPLC. The results showed that ABC promoted the adherence of platelets to endothelial cells, a crucial step for the formation of thrombi. This was not a consequence of a direct effect of ABC on platelets, but resulted from activation of the endothelium via purinergic ATP-P2X7 receptors, which subsequently triggered an interplay between P-selectin and ICAM-1 on endothelial cells with constitutively expressed GPIIb/IIIa and GPIbα on platelets. ABC did not induce platelet activation (P-selectin expression or Ca(2+) mobilization) or aggregation, even at high concentrations. CBT levels in endothelial cells were lower than those required to induce platelet-endothelium interactions. Thus, ABC interference with endothelial purinergic signalling leads to platelet recruitment. This highlights the endothelium as the main cell target of ABC in this interaction, which is in line with previous experimental evidence that ABC induces manifestations of vascular inflammation.

  19. A continuous infusion of a minor histocompatibility antigen-immunodominant peptide induces a delay of male skin graft rejection.

    PubMed

    Sireci, Guido; Barera, Annalisa; Macaluso, Pasquale; Di Sano, Caterina; Bonanno, Cesira T; Pio La Manna, Marco; Di Liberto, Diana; Dieli, Francesco; Salerno, Alfredo

    2009-01-01

    We previously reported that an inhibition of antigen-specific Interferon-gamma release and cytotoxicity occurs after a continuous infusion of an HY immunodominant peptide although this treatment is not able to cause a significant delay of male skin grafts rejection. In vivo administration of high doses of an HY peptide, through mini-osmotic pumps, in naïve female mice was used to study the effects on the male skin grafts rejection. A continuous infusion of 1mg of an HY peptide induces a significant delay of male skin graft rejection. In vitro HY-specific Interferon-gamma release was inhibited adding peptide-specific suppressor cells: the ability to inhibit Interferon-gamma release was evident when two HY peptides were present on the same dendritic cells indicating that the suppressor cells exert "linked-suppression". The phenotype of the suppressor cells is CD8(+)CD28(-) and these cells express more CD62 ligand and FOXP3 than controls. Suppressor cells were able to cause a significant delay of rejection of male skin grafts when injected in naive female mice. The inhibitory effects of these suppressor cells seem to be due to the impairment of antigen presentation; down-regulation of B7 molecules on dendritic cells occurred. Taken all together, our data demonstrate that a continuous infusion of an immunodominant HY peptide induces a T CD8 suppressor subset able to inhibit immune responses to male tissues and cells.

  20. Single platelets seal neutrophil-induced vascular breaches via GPVI during immune-complex-mediated inflammation in mice.

    PubMed

    Gros, Angèle; Syvannarath, Varouna; Lamrani, Lamia; Ollivier, Véronique; Loyau, Stéphane; Goerge, Tobias; Nieswandt, Bernhard; Jandrot-Perrus, Martine; Ho-Tin-Noé, Benoît

    2015-08-20

    Platelets protect vascular integrity during inflammation. Recent evidence suggests that this action is independent of thrombus formation and requires the engagement of glycoprotein VI (GPVI), but it remains unclear how platelets prevent inflammatory bleeding. We investigated whether platelets and GPVI act primarily by preventing detrimental effects of neutrophils using models of immune complex (IC)-mediated inflammation in mice immunodepleted in platelets and/or neutrophils or deficient in GPVI. Depletion of neutrophils prevented bleeding in thrombocytopenic and GPVI(-/-) mice during IC-mediated dermatitis. GPVI deficiency did not modify neutrophil recruitment, which was reduced by thrombocytopenia. Neutrophil cytotoxic activities were reduced in thrombocytopenic and GPVI(-/-) mice during IC-mediated inflammation. Intravital microscopy revealed that in this setting, intravascular binding sites for platelets were exposed by neutrophils, and GPVI supported the recruitment of individual platelets to these spots. Furthermore, the platelet secretory response accompanying IC-mediated inflammation was partly mediated by GPVI, and blocking of GPVI signaling impaired the vasculoprotective action of platelets. Together, our results show that GPVI plays a dual role in inflammation by enhancing neutrophil-damaging activities while supporting the activation and hemostatic adhesion of single platelets to neutrophil-induced vascular breaches.

  1. Dynamic redistribution of major platelet surface receptors after contact-induced platelet activation and spreading. An immunoelectron microscopy study.

    PubMed Central

    Kieffer, N.; Guichard, J.; Breton-Gorius, J.

    1992-01-01

    The authors used an immunogold labeling procedure to investigate the redistribution of platelet receptors and their ligands on the surface of contact-activated adherent platelets before and after thrombin stimulation. During the initial stage of platelet adhesion, a typical segregation of receptors occurred. Gold particles identifying glycoprotein (GP) Ib (CD42b) and GPIIb-IIIa (CD41a) remained distributed over the entire platelet surface, whereas gold particles identifying GPIa-IIa (CDw 49b) and GPIV (CD36) were found essentially overlying the granulomere; p24 (CD9) was present at the peripheral platelet rim and over the cell body. An increased labeling of GPIIb-IIIa, GPIV and p24 was also observed on pseudopods, with GPIIb-IIIa and GPIV concentrated at the enlarged extremities and at sites of contact between two platelets, whereas GPIb was absent from pseudopods. After thrombin stimulation of adherent platelets, GPIb underwent a relocation to the cell center, in contrast to GPIIb-IIIa which still remained randomly distributed over the cell body. To investigate whether ligand distribution paralleled this receptor segregation, platelet released von Willebrand factor (vWF), fibrinogen (Fg) and thrombospondin (TSP) were visualized. During the early stages of platelet activation, surface labeling for all three adhesive proteins was minimal and almost undetectable. Occasionally, intragranular Fg and vWF was accessible to gold-coupled antibodies, with vWF exhibiting the typical eccentric alpha-granular localization. At later stages of activation and especially after thrombin stimulation, no surface labeling for vWF was observed, whereas immunogold particles identifying vWF were still present inside enlarged clear vacuoles. In contrast, labeling of Fg and TSP was increased over the granulomere and extended to the cell periphery and the pseudopods, but was absent from the hyalomere, despite the presence of GPIIb-IIIa molecules. Double labeling experiments showed

  2. Effect of diltiazem and low-dose aspirin on platelet aggregation and ATP release induced by paired agonists.

    PubMed

    Zucker, M L; Budd, S E; Dollar, L E; Chernoff, S B; Altman, R

    1993-08-02

    The authors studied the effects of diltiazem, administered alone and together with low-dose aspirin, on the platelet response to paired agonists. After a baseline period, 25 healthy volunteers were given oral diltiazem for 1 week (120, 240, or 360 mg/day), and then crossed over randomly between 1 week on diltiazem plus aspirin (81 mg/day), and 1 week on aspirin (81 mg/day) alone. Platelet function was tested on 2 consecutive days in each period. Synergistic platelet aggregation and ATP release were obtained at baseline using a subthreshold concentration of arachidonic acid combined with platelet activating factor, ADP, or epinephrine. Diltiazem resulted in significant decrease from baseline in platelet aggregation and ATP release using the arachidonic acid-epinephrine combination (35% and 40% decrease, respectively, p < 0.01) and a significant decrease in aggregation using the arachidonic acid-ADP combination (22% decrease, p < 0.01). The effects were neither dose-related, nor accompanied by any significant change in serum thromboxane B2 levels or bleeding times. There was no significant difference between the effects of aspirin alone and aspirin plus diltiazem on the synergistic platelet aggregation and ATP release induced by the paired agonists, or on thromboxane B2 levels or bleeding times. Diltiazem administered in vivo partially inhibits the synergistic platelet aggregation and ATP release induced by paired agonists; however, in contrast to a previous in vitro study it does not potentiate the platelet-inhibitory effect of aspirin.

  3. Three-dimentional simulation of flow-induced platelet activation in artificial heart valves

    NASA Astrophysics Data System (ADS)

    Hedayat, Mohammadali; Asgharzadeh, Hafez; Borazjani, Iman

    2015-11-01

    Since the advent of heart valve, several valve types such as mechanical and bio-prosthetic valves have been designed. Mechanical Heart Valves (MHV) are durable but suffer from thromboembolic complications that caused by shear-induced platelet activation near the valve region. Bio-prosthetic Heart Valves (BHV) are known for better hemodynamics. However, they usually have a short average life time. Realistic simulations of heart valves in combination with platelet activation models can lead to a better understanding of the potential risk of thrombus formation in such devices. In this study, an Eulerian approach is developed to calculate the platelet activation in three-dimensional simulations of flow through MHV and BHV using a parallel overset-curvilinear immersed boundary technique. A curvilinear body-fitted grid is used for the flow simulation through the anatomic aorta, while the sharp-interface immersed boundary method is used for simulation of the Left Ventricle (LV) with prescribed motion. In addition, dynamics of valves were calculated numerically using under-relaxed strong-coupling algorithm. Finally, the platelet activation results for BMV and MHV are compared with each other.

  4. Effect of diabetic duration on hemorheological properties and platelet aggregation in streptozotocin-induced diabetic rats

    PubMed Central

    Yeom, Eunseop; Byeon, Hyeokjun; Lee, Sang Joon

    2016-01-01

    Diabetes mellitus with abnormal glucose concentration is associated with changes in hemorheological properties, endothelial function, and platelets hyperactivity. Disturbances may significantly be responsible for diabetes-related vascular complications. In this study, hemorheological and hemodynamic properties were measured according to diabetic duration after streptozotocin treatment in rats. For ex vivo measurements, an extracorporeal model was adopted. Flow rate and blood viscosity were measured using a microfluidic device. Erythrocyte aggregation and morphological parameters of erythrocytes were measured by modified erythrocyte sedimentation rate and the phase-contrast holography under in vitro conditions. The platelet aggregation and mean pressure in the femoral artery were estimated under ex vivo conditions. Hemorheological properties including blood viscosity, erythrocyte aggregation and shape parameters for the control group are significantly different with those for diabetic groups. The changes with respect to diabetic duration were relatively unnoticeable. However, the platelet aggregation is strongly dependent on the diabetic duration. Based on these results, hyperglycemia exposure may induce hemorheological variations in early stages of diabetes mellitus. High platelet aggregation may become more pronounced according to the diabetic duration caused by variations in hemorheological properties resulting in endothelial dysfunction. This study would be helpful in understanding the effects of diabetic duration on biophysical properties. PMID:26898237

  5. Platelet lysate induces in vitro wound healing of human keratinocytes associated with a strong proinflammatory response.

    PubMed

    El Backly, Rania; Ulivi, Valentina; Tonachini, Laura; Cancedda, Ranieri; Descalzi, Fiorella; Mastrogiacomo, Maddalena

    2011-07-01

    Platelet lysates (PL), which are derived from platelets, are cocktails of growth factors and cytokines that can promote tissue regeneration. Until today, most studies have focused on growth factor content of platelets rather than on their potential as a reservoir of mediators and cytokines. Taking advantage of an in vitro scratch assay performed under both normal and inflammatory conditions, in the present work, we report that at physiologic concentrations, PL enhanced wound closure rates of NCTC 2544 human keratinocytes. This effect was clearly detectable 6 h after wounding. Moreover, PL induced a strong cell actin cytoskeletal re-organization that persisted up to 24 h. The accelerated wound closure promoted by PL, in either presence or absence of serum, was associated with a high expression of the inflammatory cytokine interleukin-8. Further, after 24 h PL treatment, confluent keratinocytes also expressed low amounts of interleukin-8 and of the antimicrobial peptide neutrophil gelatinase-associated lipocalin, which dramatically increased under inflammatory conditions. These effects were associated with activation of the inflammatory pathways, p38 mitogen-activated protein kinase, and NF-κB. Our findings support the concept that platelet-derived preparations could accelerate regeneration of difficult-to-heal wounds by triggering an inflammatory cascade and having an antimicrobial role.

  6. Inability of probiotic bacterial strains Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 to induce human platelet aggregation in vitro.

    PubMed

    Zhou, J S; Rutherfurd, K J; Gill, H S

    2005-11-01

    Platelet aggregation contributes to the pathogenesis of infective endocarditis, and aggregation of platelets induced by lactobacilli is thought to be an important contributory factor in the development and progression of Lactobacillus endocarditis. The main purpose of this study was to examine the effect of immunity-enhancing probiotic strains Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 on the activation and aggregation of human blood platelets. Whole blood samples from healthy individuals were incubated in vitro with HN001 or HN019 and subsequently labeled with platelet-specific monoclonal antibodies, fluorescein isothiocyanate-conjugated anti-CD41a (expressed on normal platelets), and phycoerythrin-streptavidin-conjugated anti-CD62p (expressed on activated platelets) before analysis by flow cytometry. Platelet-rich plasma was used to assist the gating of the platelet cluster. ADP and epinephrine were used as the physiological platelet activation agonists. Platelet aggregation-inducing strain Streptococcus sanguis 133-79 was used as a positive control strain. The mean fluorescence intensity of phycoerythrin and the percentage of platelets expressing the CD62p marker were used to assess the degree of platelet activation. The percentage of CD62p-positive platelets and the light scatter profiles of the agonist-activated platelets were used to identify the occurrence and degree of platelet aggregation. HN001 and HN019 had no effect on spontaneous platelet activation and aggregation; they also failed to exacerbate the platelet aggregation activity induced by ADP and epinephrine. Therefore, these test probiotic strains HN001 and HN019 are less likely to participate in the pathogenesis of infective endocarditis or other thrombotic disorders with regard to platelet aggregation factors.

  7. Suppression of Aggrus/podoplanin-induced platelet aggregation and pulmonary metastasis by a single-chain antibody variable region fragment.

    PubMed

    Miyata, Kenichi; Takagi, Satoshi; Sato, Shigeo; Morioka, Hiroshi; Shiba, Kiyotaka; Minamisawa, Tamiko; Takami, Miho; Fujita, Naoya

    2014-12-01

    Almost all highly metastatic tumor cells possess high platelet aggregating abilities, thereby form large tumor cell-platelet aggregates in the microvasculature. Embolization of tumor cells in the microvasculature is considered to be the first step in metastasis to distant organs. We previously identified the platelet aggregation-inducing factor expressed on the surfaces of highly metastatic tumor cells and named as Aggrus. Aggrus was observed to be identical to the marker protein podoplanin (alternative names, T1α, OTS-8, and others). Aggrus is frequently overexpressed in several types of tumors and enhances platelet aggregation by interacting with the platelet receptor C-type lectin-like receptor 2 (CLEC-2). Here, we generated a novel single-chain antibody variable region fragment (scFv) by linking the variable regions of heavy and light chains of the neutralizing anti-human Aggrus monoclonal antibody MS-1 with a flexible peptide linker. Unfortunately, the generated KM10 scFv failed to suppress Aggrus-induced platelet aggregation in vitro. Therefore, we performed phage display screening and finally obtained a high-affinity scFv, K-11. K-11 scFv was able to suppress Aggrus-induced platelet aggregation in vitro. Moreover, K-11 scFv prevented the formation of pulmonary metastasis in vivo. These results suggest that K-11 scFv may be useful as metastasis inhibitory scFv and is expected to aid in the development of preclinical and clinical examinations of Aggrus-targeted cancer therapies.

  8. Transfusion of Human Platelets Treated with Mirasol Pathogen Reduction Technology Does Not Induce Acute Lung Injury in Mice.

    PubMed

    Caudrillier, Axelle; Mallavia, Beñat; Rouse, Lindsay; Marschner, Susanne; Looney, Mark R

    2015-01-01

    Pathogen reduction technology (PRT) has been developed in an effort to make the blood supply safer, but there is controversy as to whether it may induce structural or functional changes to platelets that could lead to acute lung injury after transfusion. In this study, we used a commercial PRT system to treat human platelets that were then transfused into immunodeficient mice, and the development of acute lung injury was determined. P-selectin expression was higher in the Mirasol PRT-treated platelets compared to control platelets on storage day 5, but not storage day 1. Transfusion of control vs. Mirasol PRT-treated platelets (day 5 of storage, 109 platelets per mouse) into NOD/SCID mice did not result in lung injury, however transfusion of storage day 5 platelets treated with thrombin receptor-activating peptide increased both extravascular lung water and lung vascular permeability. Transfusion of day 1 platelets did not produce lung injury in any group, and LPS priming 24 hours before transfusion had no effect on lung injury. In a model of transfusion-related acute lung injury, NOD/SCID mice were susceptible to acute lung injury when challenged with H-2Kd monoclonal antibody vs. isotype control antibody. Using lung intravital microscopy, we did not detect a difference in the dynamic retention of platelets in the lung circulation in control vs. Mirasol PRT-treated groups. In conclusion, Mirasol PRT produced an increase in P-selectin expression that is storage-dependent, but transfusion of human platelets treated with Mirasol PRT into immunodeficient mice did not result in greater platelet retention in the lungs or the development of acute lung injury.

  9. Fps/Fes and Fer non-receptor protein-tyrosine kinases regulate collagen- and ADP-induced platelet aggregation.

    PubMed

    Senis, Y A; Sangrar, W; Zirngibl, R A; Craig, A W B; Lee, D H; Greer, P A

    2003-05-01

    Fps/Fes and Fer proto-oncoproteins are structurally related non-receptor protein-tyrosine kinases implicated in signaling downstream from cytokines, growth factors and immune receptors. We show that Fps/Fes and Fer are expressed in human and mouse platelets, and are activated following stimulation with collagen and collagen-related peptide (CRP), suggesting a role in GPVI receptor signaling. Fer was also activated following stimulation with thrombin and a protease-activated receptor4 (PAR4)-activating peptide, suggesting a role in signaling downstream from the G protein-coupled PAR4. There were no detectable perturbations in CRP-induced activation of Syk, PLCgamma2, cortactin, Erk, Jnk, Akt or p38 in platelets from mice lacking Fps/Fes, Fer, or both kinases. Platelets lacking Fps/Fes, from a targeted fps/fes null strain of mice, showed increased rates and amplitudes of collagen-induced aggregation, relative to wild-type platelets. P-Selectin expression was also elevated on the surface of Fps/Fes-null platelets in response to CRP. Fer-deficient platelets, from mice targeted with a kinase-inactivating mutation, disaggregated more rapidly than wild-type platelets in response to ADP. This report provides the first evidence that Fps/Fes and Fer are expressed in platelets and become activated downstream from the GPVI collagen receptor, and that Fer is activated downstream from a G-protein coupled receptor. Furthermore, using targeted mouse models we show that deficiency in Fps/Fes or Fer resulted in disregulated platelet aggregation and disaggregation, demonstrating a role for these kinases in regulating platelet functions.

  10. Effects of oral contraceptives, or lanosterol, on ADP-induced aggregation and binding of /sup 125/I-fibrinogen to rat platelets

    SciTech Connect

    McGregor, L.; Toor, B.; McGregor, J.L.; Renaud, S.; Clemetson, K.J.

    1984-03-01

    The aggregation to ADP and the binding of /sup 125/I-fibrinogen to platelets from rats treated with oral contraceptives or normal platelets treated in vitro with lanosterol were compared to their respective controls. Both types of platelets showed a significant increase in ADP-induced aggregation and in binding of fibrinogen, indicating that the effect of oral contraceptives could be partly due to increased levels of lanosterol in platelet membrane.

  11. Estriol-induced fibrinolysis due to the activation of plasminogen to plasmin by nitric oxide synthesis in platelets.

    PubMed

    Jana, Pradipta; Maiti, Smarajit; Kahn, Nighat N; Sinha, Asru K

    2015-04-01

    Estriol, an oestrogen, at 0.6 nmol/l was reported to inhibit ADP-induced platelet aggregation through nitric oxide synthesis. As nitric oxide has been reported to cause fibrinolysis due to the activation of plasminogen to plasmin, the role of estriol as a fibrinolytic agent was investigated. Also, the mechanism of estriol-induced nitric oxide synthesis in anucleated platelets was investigated. The estriol-induced lysis of platelet-rich plasma (PRP) clot was determined by photography of the clot lysis and by the assay of fibrin degradation products in the lysate and was obtained by SDS-PAGE. Nitric oxide was determined by methemoglobin method. The platelet membrane protein was isolated from the platelets by using Triton X-100 (0.05% v/v). The binding of estriol to the protein was determined by Scatchard plot by using an ELISA for estriol. Estriol at 0.6 nmol/l was found to lyse the clotted PRP due to fibrinolysis that produced fibrin degradation products in the lysate. The amino acid analysis of the platelet membrane protein, which resembles with nitric oxide synthase (NOS) activity, was activated nearly 10-fold over the control in the presence of estriol and was identified to be a human serum albumin precursor (Mr. 69 kDa) that binds to estriol with Kd1 of 6.0 × 10 mol/l and 39 ± 2 molecules of estriol bound the NOS molecule. The estriol-induced nitric oxide is capable of inducing fibrinolysis of the clotted PRP. The binding of estriol to platelet membrane NOS activated the enzyme in the absence of DNA in the platelet.

  12. Alleviation of viper venom induced platelet apoptosis by crocin (Crocus sativus): implications for thrombocytopenia in viper bites.

    PubMed

    Santhosh, M Sebastin; Thushara, R M; Hemshekhar, M; Sunitha, K; Devaraja, S; Kemparaju, K; Girish, K S

    2013-11-01

    Viper envenomations are characterized by prominent local and systemic manifestations including hematological alterations. Snake venom metalloproteinases (SVMPs) and phospholipase A2 (PLA2) plays crucial role in the pathophysiology of hemorrhage by targeting/altering the platelets function which may result in thrombocytopenia. Platelets undergo the classic events of mitochondria-mediated apoptotic pathway due to augmented endogenous reactive oxygen species (ROS) levels. The observed anticoagulant effects during viper envenomations could be due to exacerbated platelet apoptosis and thrombocytopenia. Moreover, antivenin treatments are ineffective against the venom-induced oxidative stress; therefore, it necessitates an auxiliary therapy involving antioxidants which can effectively scavenge the endothelium-generated/endogenous ROS and protect the platelets. The present study explored the effects of viper venom on platelet apoptosis and its amelioration by a phytochemical crocin. The study evaluated the Vipera russelli venom-induced apoptotic events including endogenous ROS generation, intracellular Ca(2+) mobilization, mitochondrial membrane depolarization, cyt-c translocation, caspase activation and phosphatidylserine externalization which were effectively mitigated when the venom was pre-treated with crocin. The study highlights one of the less studied features of venom-induced secondary complications i.e. platelet apoptosis and sheds light on the underlying basis for venom-induced thrombocytopenia, systemic hemorrhage and in vivo anticoagulant effect.

  13. Platelet adhesion and protein adsorption on silicone rubber surface by ozone-induced grafted polymerization with carboxybetaine monomer.

    PubMed

    Zhou, Jun; Yuan, Jiang; Zang, Xiaopeng; Shen, Jian; Lin, Sicong

    2005-03-10

    Platelet adhesion and protein adsorption on the silicone rubber film grafted with N,N'-dimethyl-N-methacryloyloxyethyl-N-(2-carboxyethyl) ammonium (DMMCA) was studied. The grafting was carried out by means of ozone-induced method and was confirmed by ATR-FTIR and XPS investigations. The grafted films possessed relatively hydrophilic surface revealed by contact angle measurement. The blood compatibility of the grafted film was evaluated in vitro by platelet adhesion in platelet-rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG) using silicone film as the reference. No substantial platelet adhesion was observed for the grafted films incubated in PRP for 60 and 180 min. The protein absorption was also significantly reduced after incubated in bovine fibrinogen for 60 min. Both the results indicated that the blood compatibility of silicone rubber was greatly improved by ozone-induced grafting of carboxybetaine zwitterionic polymer onto its surface.

  14. Vancomycin-induced Immune Thrombocytopenia Proven by the Detection of Vancomycin-dependent Anti-platelet Antibody with Flow Cytometry

    PubMed Central

    Yamanouchi, Jun; Hato, Takaaki; Shiraishi, Sanshiro; Takeuchi, Kazuto; Yakushijin, Yoshihiro; Yasukawa, Masaki

    2016-01-01

    Vancomycin-induced thrombocytopenia is a rare adverse reaction that may be overlooked because no specific diagnostic test is currently available. We herein report a patient with vancomycin-induced immune thrombocytopenia who was diagnosed by the detection of vancomycin-dependent anti-platelet antibody with flow cytometry. An IgG antibody in the patient's serum reacted with platelets only in the presence of vancomycin. Severe thrombocytopenia gave rise to life-threatening gastrointestinal bleeding, which was quickly resolved after effective platelet transfusion following the cessation of vancomycin administration. This report suggests that the flow cytometric test is useful for the differential diagnosis of thrombocytopenia and platelet transfusion should be performed after the cessation of vancomycin administration. PMID:27746445

  15. AMP-activated protein kinase (AMPK) regulates the insulin-induced activation of the nitric oxide synthase in human platelets.

    PubMed

    Fleming, Ingrid; Schulz, Christian; Fichtlscherer, Birgit; Kemp, Bruce E; Fisslthaler, Beate; Busse, Rudi

    2003-11-01

    Little is known about the signaling cascades that eventually regulate the activity of the endothelial nitric oxide synthase (eNOS) in platelets. Here, we investigated the effects of insulin on the phosphorylation and activation of eNOS in washed human platelets and in endothelial cells. Insulin activated the protein kinase Akt in cultured endothelial cells and increased the phosphorylation of eNOS on Ser(1177) but failed to increase endothelial cyclic GMP levels or to elicit the relaxation of endothelium-intact porcine coronary arteries. In platelets, insulin also elicited the activation of Akt as well as the phosphorylation of eNOS and initiated NO production which was associated with increased cyclic GMP levels and the inhibition of thrombin-induced aggregation. The insulin-induced inhibition of aggregation was accompanied by a decreased Ca(2+) response to thrombin and was also prevented by N(omega) nitro-L-arginine. In platelets, but not in endothelial cells, insulin induced the activation of the AMP-activated protein kinase (AMPK), a metabolic stress-sensing kinase which was sensitive to the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin and the AMPK inhibitor iodotubercidin. Moreover, the insulin-mediated inhibition of thrombin-induced aggregation was prevented by iodotubercidin. Insulin-independent activation of the AMPK using 5-aminoimidazole-4-carboxamide ribonucleoside, increased platelet eNOS phosphorylation, increased cyclic GMP levels and attenuated platelet aggregation. These results highlight the differences in the signal transduction cascade activated by insulin in endothelial cells and platelets, and demonstrate that insulin stimulates the formation of NO in human platelets, in the absence of an increase in Ca(2+), by acti-vating PI3-K and AMPK which phosphorylates eNOS on Ser(1177).

  16. Protein kinase A mediates inhibition of the thrombin-induced platelet shape change by nitric oxide.

    PubMed

    Jensen, Baard Olav; Selheim, Frode; Døskeland, Stein Ove; Gear, Adrian R L; Holmsen, Holm

    2004-11-01

    The thrombin-induced platelet shape change was blocked by nitric oxide (NO), as revealed by scanning electron microscopy, light transmission, and resistive-particle volume determination. The inhibitory effect of NO was accompanied by an increase in levels of both cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) and phosphorylation of the vasodilator-stimulated phosphoprotein (VASP). However, the inhibition of the shape change was only mimicked by cAMP analogs (Sp-5,6-DClcBIMPS, 8-AHA-cAMP, and 8-CPT-cAMP) and not by cGMP analogs (8-Br-PET-cGMP, 8-Br-cGMP, and 8-pCPT-cGMP). The effect of NO on the thrombin-induced shape change was prevented by the protein kinase A (PKA) antagonists Rp-8-Br-cAMPS and Rp-cAMPS. The protein kinase G (PKG) antagonist Rp-8-CPT-cGMPS strongly inhibited PKG-mediated 46-kDa VASP Ser239 phosphorylation, but did not inhibit the thrombin-induced shape change or the PKA-mediated VASP Ser157 phosphorylation. Whereas an inhibitor of cyclic nucleotide phosphodiesterase (PDE) 3A (milrinone) mimicked the effect of NO, inhibitors of PDE2 (erythro-9-(2-hydroxy-3-nonyl)adenine) and PDE5 (dipyridamole) were poorly effective. We concluded that (1) NO was a potent and reversible inhibitor of the platelet shape change, (2) the shape change was reversible, (3) the inhibitory effect of NO was mediated through activation of PKA, (4) the onset of the NO effect coincided with VASP Ser157 phosphorylation, and (5) removal of NO and platelet shape change coincided with VASP Ser157 dephosphorylation. These findings are compatible with elevation of cGMP by NO in a compartment close to PDE3A, PKA, and VASP, leading to a local increase of cAMP able to block thrombin-induced shape change.

  17. Inducible costimulatory molecule deficiency induced imbalance of Treg and Th17/Th2 delays rejection reaction in mice undergoing allogeneic tracheal transplantation

    PubMed Central

    Xu, Jingsong; Wu, Yu; Wang, Guifang; Qin, Yanghua; Zhu, Li; Tang, Gusheng; Shen, Qian

    2014-01-01

    Objective: This study aimed to investigate the role of inducible costimulatory molecule (ICOS) pathway in the rejection reaction of mice undergoing allogeneic tracheal transplantation. Methods: The bronchus was separated from wide-type (WT) BalB/c mice and transplanted into WT BalB/c mice, C57 mice and icos-/- mice to prepare the obliterative bronchiolitis (OB) animal model. The transplanted bronchus was pathologically examined; flow cytometry was done to detect the T cell subsets and activity of the bronchus and spleen of recipient mice. Results: 21 d after transplantation, evident rejection reaction was observed and the proportion of Th2 and Th17 cells increased significantly in the bronchus and spleen in C57 mice receiving allogeneic tracheal transplantation when compared with mice with autologous transplantation, but the proportion of Treg cells was comparable between them. When compared with WT BalB/c mice, the proportion of Th2, Th17 and Treg cells reduced markedly and rejection reaction was attenuated in icos-/- mice receiving tracheal transplantation, although rejection reaction was still noted. Conclusion: icos knockout may delay the rejection reaction after tracheal transplantation, which might be ascribed to the imbalance among Th2, Th17 and Treg cells. PMID:25628788

  18. Platelet PlA2 Polymorphism and the risk for thrombosis in heparin-induced thrombocytopenia.

    PubMed

    Harris, Kenneth; Nguyen, Phan; Van Cott, Elizabeth M

    2008-02-01

    Platelet glycoprotein (GP) IIb/IIIa has an important role in platelet aggregation. A polymorphism of platelet GPIIIa (PlA2, also called HPA1b) has been associated with a higher risk of thrombosis, but its implication in heparin-induced thrombocytopenia (HIT) is unclear. To investigate the hypothesis that the PlA2 polymorphism influences the prothrombotic effects of HIT, we conducted a prospective study of 66 consecutive patients with a laboratory diagnosis of HIT. The end point of the study was the diagnosis of a thrombus within 30 days of the positive HIT test result. The Diagnostica Stago (Asnières, France) enzyme-linked immunosorbent assay was used to detect HIT antibodies, and a polymerase chain reaction assay was used to detect the PlA2 polymorphism. Of the 66 patients, thrombotic complications developed in 27 (41%). Patients with the PlA2 allele demonstrated a significantly higher thrombosis risk than did patients without (69% vs 32%; P = .0088; odds ratio, 4.68; 95% confidence interval, 1.39-15.72). The risk was stronger for arterial thrombosis and for patients 60 years or older. There was a significant association between the PlA2 polymorphism of GPIIIa and the risk of thrombosis in patients with HIT antibodies.

  19. Chronic lead treatment accelerates photochemically induced platelet aggregation in cerebral microvessels of mice, in vivo

    SciTech Connect

    Al Dhaheri, A.H.; El-Sabban, F.; Fahim, M.A.

    1995-04-01

    Effects of two chronic treatment levels with lead on platelet aggregation in cerebral (pial) microcirculation of the mouse were investigated. Exposure to lead was made by subcutaneous injections for 7 days of lead acetate dissolved in 5% glucose solution, vehicle. Two doses of lead were used, a low dose of 0.1 mg/kg and a high dose of 1.0 mg/kg. Adult male mice were divided into three groups, 10 each; one group was injected with vehicle (control), another was injected with the low dose, and the third was injected with the high dose. Additional mice were used for the determination of hematological parameters and for the lead level in serum of the three groups. On the eighth day, platelet aggregation in pial microvessels of these groups of mice was carried out in vivo. Animals were anesthetized (urethane, 1-2 mg/g, ip), the trachea was intubated, and a craniotomy was performed. Platelet aggregation in pial microvessels was induced photochemically, by activation of circulating sodium fluorescein (0.1 mg/25 g, iv) with an intense mercury light. The time required for the first platelet aggregate to appear in pial arterioles was significantly shorter in the lead-treated mice than in control. This effect was in a dose-dependent manner; 113 {+-} 44 sec for low dose and 71 {+-} 18 sec for high dose vs 155 {+-} 25 sec for control, P < 0.02 and P < 0.001, respectively. Between the two lead-treated groups, the high dose significantly (P < 0.05) shortened the time to first aggregate. These data evidenced an increased susceptibility to cerebrovascular thrombosis as a result of exposure to lead. 26 refs., 4 figs., 2 tabs.

  20. A severe Mycoplasma pneumoniae pneumonia inducing an acute antibody-mediated pulmonary graft rejection

    PubMed Central

    Démir, Sarah; Saison, Julien; Sénéchal, Agathe; Mornex, Jean-Francois

    2017-01-01

    A 40-year-old cystic fibrosis woman with a history of double-lung transplantation 2 years previously was admitted for a progressive respiratory distress. Physical examination revealed fever (39°C) and diffuse bilateral lung crackles. Laboratory findings included severe hypoxemia and inflammatory syndrome. Bronchoalveolar lavage and serological test were positive for mycoplasma pneumonia. As the patient did not improve after 3 days of antibiotics and donor-specific HLA antibodies had been detected, an acute antibody-mediated graft rejection was treated with high-dose corticosteroids, plasma exchange, intravenous immunoglobulin, and rituximab. The patient rapidly improved. Unfortunately, 6 months after this episode, she developed a bronchiolitis obliterans syndrome with a dependence to noninvasive ventilator leading to the indication of retransplantation. This case illustrates the possible relationship between infection and humoral rejection. These two diagnoses should be promptly investigated and systematically treated in lung transplant recipients. PMID:28144069

  1. Foraging leaf-cutting ants learn to reject Vitis vinifera ssp. vinifera plants that emit herbivore-induced volatiles.

    PubMed

    Thiele, Theresa; Kost, Christian; Roces, Flavio; Wirth, Rainer

    2014-06-01

    Leaf-cutting ants (LCAs) are dominant herbivores of the Neotropics, as well as economically important pests. Their foraging ecology and patterns/mechanisms of food selection have received considerable attention. Recently, it has been documented that LCAs exhibit a delayed rejection of previously accepted food plants following treatment with a fungicide that makes the plants unsuitable as substrate for their symbiotic fungus. Here, we investigated whether LCAs similarly reject plants with induced chemical defenses, by combining analysis of volatile emissions with dual-choice bioassays that used LCA subcolonies (Atta sexdens L.). On seven consecutive days, foraging ants were given the choice between leaf disks from untreated control plants and test plants of Vitis vinifera ssp. vinifera L. treated with the phytohormone jasmonic acid (JA) to mimic herbivore attack. Chemical analysis revealed the emission of a characteristic set of herbivore-induced volatile organic compounds (VOC) from JA-induced plants. Dual-choice experiments indicated that workers did not show any preference initially, but that they avoided JA-treated plants from day five onwards. Our finding that A. sexdens foragers learn to avoid VOC-emitting plants, which are likely detrimental to their symbiotic fungus, represents the first evidence for avoidance learning in attine ants toward plants with induced defenses.

  2. Serotonin-induced mate rejection in the female cabbage butterfly, Pieris rapae crucivora

    NASA Astrophysics Data System (ADS)

    Obara, Yoshiaki; Fukano, Yuya; Watanabe, Kenta; Ozawa, Gaku; Sasaki, Ken

    2011-11-01

    Virgin female cabbage butterflies, Pieris rapae crucivora, accept and mate with courting males, whereas mated females reject them and assume the "mate refusal posture". This study tested whether the biogenic amines, serotonin (5HT), dopamine (DA), and octopamine (OA), were responsible for this change in behavior. The results showed that 2-3-day-old virgin females fed with 5HT rejected courting males significantly more frequently compared with controls fed on sucrose. In contrast, the proportions of courting males rejected by virgin females fed with either DA or OA did not differ from sucrose-fed controls. Oral application of each amine resulted in significantly increased levels of the amine applied (or its metabolite) in the brain. The results strongly suggest that 5HT or a 5HT metabolite may be responsible for the post-mating change in behavioral response of 2-3-day-old virgin females to courting males. Similar effects of 5HT treatment were observed in 6-8-day-old virgin females, but in this case the results were only marginally different from the controls, suggesting that the effect may decline with increasing female age.

  3. Collagen-induced platelet activation mainly involves the protein kinase C pathway.

    PubMed Central

    Karniguian, A; Grelac, F; Levy-Toledano, S; Legrand, Y J; Rendu, F

    1990-01-01

    This study analyses early biochemical events in collagen-induced platelet activation. An early metabolic event occurring during the lag phase was the activation of PtdIns(4,5)P2-specific phospholipase C. Phosphatidic acid (PtdOH) formation, phosphorylation of P43 and P20, thromboxane B2 (TXB2) synthesis and platelet secretion began after the lag phase, and were similarly time-dependent, except for TXB2 synthesis, which was delayed. Collagen induced extensive P43 phosphorylation, whereas P20 phosphorylation was weak and always lower than with thrombin. The dose-response curves of P43 phosphorylation and granule secretion were similar, and both reached a peak at 7.5 micrograms of collagen/ml, a dose which induced half-maximal PtdOH and TXB2 formation. Sphingosine, assumed to inhibit protein kinase C, inhibited P43 phosphorylation and secretion in parallel. However, sphingosine was not specific for protein kinase C, since a 15 microM concentration, which did not inhibit P43 phosphorylation, blocked TXB2 synthesis by 50%. Sphingosine did not affect PtdOH formation at all, even at 100 microM, suggesting that collagen itself induced this PtdOH formation, independently of TXB2 generation. The absence of external Ca2+ allowed the cleavage of polyphosphoinositides and the accumulation of InsP3 to occur, but impaired P43 phosphorylation, PtdOH and TXB2 formation, and secretion; these were only restored by adding 0.11 microM-Ca2+. In conclusion, stimulation of platelet membrane receptors for collagen initiates a PtdInsP2-specific phospholipase C activation, which is independent of external Ca2+, and might be the immediate receptor-linked response. A Ca2+ influx is indispensable to the triggering of subsequent platelet responses. This stimulation predominantly involves the protein kinase C pathway associated with secretion, and appears not to be mediated by TXB2, at least during its initial stage. Images Fig. 6. PMID:2163606

  4. The platelet fibrinogen receptor: an immunogold-surface replica study of agonist-induced ligand binding and receptor clustering

    PubMed Central

    1987-01-01

    Platelet aggregation requires the binding of fibrinogen to its receptor, a heterodimer consisting of the plasma-membrane glycoproteins (GP) IIb and IIIa. Although the GPIIb-IIIa complex is present on the surface of unstimulated platelets, it binds fibrinogen only after platelet activation. We have used an immunogold-surface replica technique to study the distribution of GPIIb-IIIa and bound fibrinogen over broad areas of surface membranes in unstimulated, as well as thrombin-activated and ADP-activated human platelets. We found that the immunogold-labeled GPIIb-IIIa was monodispersed over the surface of unstimulated platelets, although the cell surface lacked immunoreactive fibrinogen. On thrombin-stimulated platelets, approximately 65% of the GPIIb-IIIa molecules were in clusters within the plane of the membrane. Fibrinogen, which had been released from the alpha-granules of these cells, bound to GPIIb-IIIa on the cell surface and was similarly clustered. To determine whether the receptors clustered before ligand binding, or as a consequence thereof, we studied the surface distribution of GPIIb-IIIa after stimulation with ADP, which causes activation of the fibrinogen receptor function of GPIIb-IIIa without inducing the release of fibrinogen. In the absence of added fibrinogen, the unoccupied, yet binding-competent receptors on ADP-stimulated platelets were monodispersed. The addition of fibrinogen caused the GPIIb-IIIa molecules to cluster on the cell surface. Clustering was also induced by the addition of the GPIIb-IIIa-binding domains of fibrinogen, namely the tetrapeptide Arg-Gly-Asp-Ser on the alpha-chain or the gamma-chain decapeptide gamma 402-411. These results show that receptor occupancy causes clustering of GPIIb-IIIa in activated platelets. PMID:3584243

  5. Selective Inhibition of ADAM17 Efficiently Mediates Glycoprotein Ibα Retention During Ex Vivo Generation of Human Induced Pluripotent Stem Cell-Derived Platelets.

    PubMed

    Hirata, Shinji; Murata, Takahiko; Suzuki, Daisuke; Nakamura, Sou; Jono-Ohnishi, Ryoko; Hirose, Hidenori; Sawaguchi, Akira; Nishimura, Satoshi; Sugimoto, Naoshi; Eto, Koji

    2017-03-01

    Donor-independent platelet concentrates for transfusion can be produced in vitro from induced pluripotent stem cells (iPSCs). However, culture at 37°C induces ectodomain shedding on platelets of glycoprotein Ibα (GPIbα), the von Willebrand factor receptor critical for adhesive function and platelet lifetime in vivo, through temperature-dependent activation of a disintegrin and metalloproteinase 17 (ADAM17). The shedding can be suppressed by using inhibitors of panmetalloproteinases and possibly of the upstream regulator p38 mitogen-activated protein kinase (p38 MAPK), but residues of these inhibitors in the final platelet products may be accompanied by harmful risks that prevent clinical application. Here, we optimized the culture conditions for generating human iPSC-derived GPIbα(+) platelets, focusing on culture temperature and additives, by comparing a new and safe selective ADAM17 inhibitor, KP-457, with previous inhibitors. Because cultivation at 24°C (at which conventional platelet concentrates are stored) markedly diminished the yield of platelets with high expression of platelet receptors, 37°C was requisite for normal platelet production from iPSCs. KP-457 blocked GPIbα shedding from iPSC platelets at a lower half-maximal inhibitory concentration than panmetalloproteinase inhibitor GM-6001, whereas p38 MAPK inhibitors did not. iPSC platelets generated in the presence of KP-457 exhibited improved GPIbα-dependent aggregation not inferior to human fresh platelets. A thrombus formation model using immunodeficient mice after platelet transfusion revealed that iPSC platelets generated with KP-457 exerted better hemostatic function in vivo. Our findings suggest that KP-457, unlike GM-6001 or p38 MAPK inhibitors, effectively enhances the production of functional human iPSC-derived platelets at 37°C, which is an important step toward their clinical application. Stem Cells Translational Medicine 2017;6:720-730.

  6. Protein Kinase C isoform epsilon (ε) negatively regulates ADP-induced calcium mobilization and thromboxane generation in platelets

    PubMed Central

    Bynagari-Settipalli, Yamini S; Lakhani, Parth; Jin, Jianguo; Bhavaraju, Kamala; Rico, Mario C.; Kim, Soochong; Woulfe, Donna; Kunapuli, Satya P

    2012-01-01

    Objective Members of Protein Kinase C (PKC) family are shown to positively and negatively regulate platelet activation. Although positive regulatory roles are extensively studied, negative regulatory roles of PKCs are poorly understood. In this study we investigated the mechanism and specific isoforms involved in PKC-mediated negative regulation of ADP-induced functional responses. Methods and Results A pan-PKC inhibitor GF109203X potentiated ADP-induced cPLA2 phosphorylation and thromboxane generation, as well as ERK activation and intracellular calcium (Ca2+i) mobilization, two signaling molecules, upstream of cPLA2 activation. Thus, PKCs inhibit cPLA2 activation by inhibiting ERK and Ca2+i mobilization. Since, the inhibitor of Classical PKC isoforms, GO-6976 did not affect ADP-mediated thromboxane generation, we investigated the role of novel class of PKC isoforms. ADP- induced thromboxane generation, calcium mobilization and ERK phosphorylation were potentiated in PKCε null murine platelets compared to platelets from wild type (WT) littermates. Interestingly, when thromboxane release is blocked, ADP-induced aggregation in PKCε KO and WT was similar, suggesting that PKCε does not affect ADP-induced aggregation directly. PKCε knockout mice exhibited shorter times to occlusion in FeCl3-induced arterial injury model and shorter bleeding times in tail bleeding experiments. Conclusion We conclude that PKCε negatively regulates ADP-induced thromboxane generation in platelets and offers protection against thrombosis. PMID:22362759

  7. Regulation of hormone-induced Ca sup 2+ mobilization in the human platelets

    SciTech Connect

    Crouch, M.F.; Lapetina, E.G. )

    1990-03-01

    {alpha}-Thrombin, {gamma}-thrombin, and platelet-activating factor each stimulated the mobilization of intracellular Ca{sup 2+} stores in aspirin-treated human platelets. This was followed by desensitization of the receptors, as shown by the return of the Ca{sup 2+} level to basal values and by the fact that a subsequent addition of a second different agonist, but not the same agonist, could again elicit a response. Epinephrine, acting on {alpha}{sub 2}-adrenergic receptors, was by itself ineffective at mobilizing Ca{sup 2+} stores. However, when added after the thrombin-induced response, epinephrine could evoke a considerable release of Ca{sup 2+} from cellular stores. This appeared to be due to epinephrine recoupling thrombin receptors to phospholipase C. In support of this, epinephrine was able to induce the formation of inositol triphosphate when added after the response to thrombin had also become desensitized. Alone, epinephrine was without effect. Pre-activation of protein kinase C with the phorbol ester abolished these effects of epinephrine, suggesting that epinephrine was working by activating a protein which could be inactivated by phosphorylation. The current work is to characterize this protein that may be a member of the G{sub i}, GTP-binding protein family.

  8. Hydroxyapatite formed on/in agarose gel induces activation of blood coagulation and platelets aggregation.

    PubMed

    Arimura, Shin-ichiro; Kawahara, Ko-ichi; Biswas, Kamal Krishna; Abeyama, Kazuhiro; Tabata, Masashi; Shimoda, Toru; Ogomi, Daisuke; Matsusaki, Michiya; Kato, Shinya; Ito, Takashi; Sugihara, Kazumasa; Akashi, Mitsuru; Hashiguchi, Teruto; Maruyama, Ikuro

    2007-05-01

    We reported earlier that hydroxyapatite (HA) formed on/in agarose gels (HA/agarose) produced by alternate soaking process is a bone-filling material possessing osteoconductive and hemostatic effects. This process could allow us to make bone-like apatite that was formed on/in organic polymer hydrogel matrices. Here, we investigated the mechanism of hemostasis induced by HA/agarose and found that HA/agarose, but not agarose or HA powder, significantly shortened activated partial thromboplastin time (APTT). While HA/agarose did not show significant platelet aggregation, it markedly enhanced adenosine diphosphate (ADP)-induced platelet aggregation. Moreover, Western blot analysis revealed selective adsorption of vitronectin onto HA/agarose. We also observed marked differences between HA powder and HA/agarose in their XRD patterns. The crystallinity of HA powder was much higher compared to that of HA/agarose. Furthermore, 50-100 nm of tube-form aggregations was observed in HA powder on the other hand 100-200 nm of particles was observed in HA/agarose by SEM observation. Thus 100-200 nm of low crystallized particles on the surface structure of HA/agarose may play an important role in hemostasis. Our results demonstrated a crucial role of HA/agarose in the mechanism of hemostasis and suggested a potential role for HA/agarose as a bone-grafting material.

  9. Membrane-associated 41-kDa GTP-binding protein in collagen-induced platelet activation

    SciTech Connect

    Walker, G.; Bourguignon, L.Y. )

    1990-08-01

    Initially we established that the binding of collagen to human blood platelets stimulates both the rapid loss of PIP2 and the generation of inositol-4,5-bisphosphate (IP2) and inositol-1,4,5-triphosphate (IP3). These results indicate that the binding of collagen stimulates inositol phospholipid-specific phospholipase C during platelet activation. The fact that GTP or GTP-gamma-S augments, and pertussis toxin inhibits, collagen-induced IP3 formation suggests that a GTP-binding protein or (or proteins) may be directly involved in the regulation of phospholipase C-mediated phosphoinositide turnover in human platelets. We have used several complementary techniques to isolate and characterize a platelet 41-kDa polypeptide (or polypeptides) that has a number of structural and functional similarities to the regulatory alpha i subunit of the GTP-binding proteins isolated from bovine brain. This 41-kDa polypeptide (or polypeptides) is found to be closely associated with at least four membrane glycoproteins (e.g., gp180, gp110, gp95, and gp75) in a 330-kDa complex that can be dissociated by treatment with high salt plus urea. Most important, we have demonstrated that antilymphoma 41-kDa (alpha i subunit of GTP-binding proteins) antibody cross-reacts with the platelet 41-kDa protein (or proteins) and the alpha i subunit of bovine brain Gi alpha proteins, and blocks GTP/collagen-induced IP3 formation. These data provide strong evidence that the 41-kDa platelet GTP-binding protein (or proteins) is directly involved in collagen-induced signal transduction during platelet activation.

  10. Prostaglandin E1-induced deconsolidation of thrombin-activated platelet aggregates I: ultrastructure-computer image analysis.

    PubMed

    Salganicoff, L; Russo, M A; Sevy, R W

    1999-06-15

    We have compared, at an ultrastructural-computer image morphometric level, the relaxation induced by Mg-ethylene-bis-oxyethylenenitrilo-tetracetic acid and prostaglandin E1 on a model of a thrombin-activated platelet aggregate. Mg-ethylene-bisoxyethylenenitrilo-tetracetic acid produced a small increase of 5.0% of the intercellular space over the control levels, and a decrease of 10.0+/-1.3% of the cross-sectional area of the platelets, with no apparent cytoskeletal alterations. In contrast, the prostaglandin El-treated preparation shows a 360% increase in the intercellular space and a decrease of the average platelet cross-sectional area of 30.0+/-2.0% with marked cytoskeletal alterations. We use the term "deconsolidation" to describe this effect. The enlargement of the intercellular space allows the observation of two types of contacts: (1) a type S (segmental) complex, of approximately 200-nm length that maintains a narrow interplatelet gap of 20-30 nm, filled with a dense intercellular material, and (2) a type R (reticular) complex, formed by scant focal regions of the plasma membrane from opposing platelets that are connected through a mesh of fibrillar or granular material contained within a variable-size space. We hypothesize that deconsolidation is caused by fluid loss from the platelets into the intercellular space. As a result, platelet volume decreases and intercellular space increases.

  11. Phage-Derived Protein Induces Increased Platelet Activation and Is Associated with Mortality in Patients with Invasive Pneumococcal Disease

    PubMed Central

    Cremers, Amelieke J.; van der Gaast-de Jongh, Christa E.; Ferwerda, Gerben; Meis, Jacques F.; Roeleveld, Nel; Bentley, Stephen D.; Pastura, Alexander S.; van Hijum, Sacha A. F. T.; van der Ven, Andre J.; de Mast, Quirijn; Zomer, Aldert

    2017-01-01

    ABSTRACT To improve our understanding about the severity of invasive pneumococcal disease (IPD), we investigated the association between the genotype of Streptococcus pneumoniae and disease outcomes for 349 bacteremic patients. A pneumococcal genome-wide association study (GWAS) demonstrated a strong correlation between 30-day mortality and the presence of the phage-derived gene pblB, encoding a platelet-binding protein whose effects on platelet activation were previously unknown. Platelets are increasingly recognized as key players of the innate immune system, and in sepsis, excessive platelet activation contributes to microvascular obstruction, tissue hypoperfusion, and finally multiorgan failure, leading to mortality. Our in vitro studies revealed that pblB expression was induced by fluoroquinolones but not by the beta-lactam antibiotic penicillin G. Subsequently, we determined pblB induction and platelet activation by incubating whole blood with the wild type or a pblB knockout mutant in the presence or absence of antibiotics commonly administered to our patient cohort. pblB-dependent enhancement of platelet activation, as measured by increased expression of the α-granule protein P-selectin, the binding of fibrinogen to the activated αIIbβ3 receptor, and the formation of platelet-monocyte complex occurred irrespective of antibiotic exposure. In conclusion, the presence of pblB on the pneumococcal chromosome potentially leads to increased mortality in patients with an invasive S. pneumoniae infection, which may be explained by enhanced platelet activation. This study highlights the clinical utility of a bacterial GWAS, followed by functional characterization, to identify bacterial factors involved in disease severity. PMID:28096486

  12. Differential Inhibition of Human Atherosclerotic Plaque–Induced Platelet Activation by Dimeric GPVI-Fc and Anti-GPVI Antibodies

    PubMed Central

    Jamasbi, Janina; Megens, Remco T.A.; Bianchini, Mariaelvy; Münch, Götz; Ungerer, Martin; Faussner, Alexander; Sherman, Shachar; Walker, Adam; Goyal, Pankaj; Jung, Stephanie; Brandl, Richard; Weber, Christian; Lorenz, Reinhard; Farndale, Richard; Elia, Natalie; Siess, Wolfgang

    2015-01-01

    Background Glycoprotein VI (GPVI) is the essential platelet collagen receptor in atherothrombosis, but its inhibition causes only a mild bleeding tendency. Thus, targeting this receptor has selective antithrombotic potential. Objectives This study sought to compare compounds interfering with platelet GPVI–atherosclerotic plaque interaction to improve current antiatherothrombotic therapy. Methods Human atherosclerotic plaque–induced platelet aggregation was measured in anticoagulated blood under static and arterial flow conditions (550/s, 1,100/s, and 1,500/s). Inhibition by dimeric GPVI fragment crystallizable region of IgG (Fc) masking GPVI binding sites on collagen was compared with that of 3 anti-GPVI antibodies: BLO8-1, a human domain antibody; 5C4, a fragment antigen-binding (Fab fragment) of monoclonal rat immunoglobulin G; and m-Fab-F, a human recombinant sFab against GPVI dimers. Results GPVI-Fc reduced plaque-triggered platelet aggregation in static blood by 51%, BLO8-1 by 88%, and 5C4 by 93%. Under arterial flow conditions, BLO8-1 and 5C4 almost completely inhibited platelet aggregation while preserving platelet adhesion on plaque. Inhibition by GPVI-Fc, even at high concentrations, was less marked but increased with shear rate. Advanced optical imaging revealed rapid persistent GPVI-Fc binding to collagen under low and high shear flow, upstream and downstream of plaque fragments. At low shear particularly, platelets adhered in plaque flow niches to GPVI-Fc–free segments of collagen fibers and recruited other platelets onto aggregates via ADP and TxA2 release. Conclusions Anti-GPVI antibodies inhibit atherosclerotic plaque-induced platelet aggregation under static and flow conditions more effectively than GPVI-Fc. However, potent platelet inhibition by GPVI-Fc at a higher shear rate (1,500/s) suggests localized antithrombotic efficacy at denuded or fissured stenotic high-risk lesions without systemic bleeding. The compound-specific differences

  13. Kaempferol suppresses collagen-induced platelet activation by inhibiting NADPH oxidase and protecting SHP-2 from oxidative inactivation.

    PubMed

    Wang, Su Bin; Jang, Ji Yong; Chae, Yun Hee; Min, Ji Hyun; Baek, Jin Young; Kim, Myunghee; Park, Yunjeong; Hwang, Gwi Seo; Ryu, Jae-Sang; Chang, Tong-Shin

    2015-06-01

    Reactive oxygen species (ROS) generated upon collagen stimulation act as second messengers to propagate various platelet-activating events. Among the ROS-generating enzymes, NADPH oxidase (NOX) plays a prominent role in platelet activation. Thus, NOX has been suggested as a novel target for anti-platelet drug development. Although kaempferol has been identified as a NOX inhibitor, the influence of kaempferol on the activation of platelets and the underlying mechanism have never been investigated. Here, we studied the effects of kaempferol on NOX activation, ROS-dependent signaling pathways, and functional responses in collagen-stimulated platelets. Superoxide anion generation stimulated by collagen was significantly inhibited by kaempferol in a concentration-dependent manner. More importantly, kaempferol directly bound p47(phox), a major regulatory subunit of NOX, and significantly inhibited collagen-induced phosphorylation of p47(phox) and NOX activation. In accordance with the inhibition of NOX, ROS-dependent inactivation of SH2 domain-containing protein tyrosine phosphatase-2 (SHP-2) was potently protected by kaempferol. Subsequently, the specific tyrosine phosphorylation of key components (Syk, Vav1, Btk, and PLCγ2) of collagen receptor signaling pathways was suppressed by kaempferol. Kaempferol also attenuated downstream responses, including cytosolic calcium elevation, P-selectin surface exposure, and integrin-αIIbβ3 activation. Ultimately, kaempferol inhibited platelet aggregation and adhesion in response to collagen in vitro and prolonged in vivo thrombotic response in carotid arteries of mice. This study shows that kaempferol impairs collagen-induced platelet activation through inhibition of NOX-derived ROS production and subsequent oxidative inactivation of SHP-2. This effect suggests that kaempferol has therapeutic potential for the prevention and treatment of thrombovascular diseases.

  14. Transient activation of c-MYC expression is critical for efficient platelet generation from human induced pluripotent stem cells

    PubMed Central

    Takayama, Naoya; Nishimura, Satoshi; Nakamura, Sou; Shimizu, Takafumi; Ohnishi, Ryoko; Endo, Hiroshi; Yamaguchi, Tomoyuki; Otsu, Makoto; Nishimura, Ken; Nakanishi, Mahito; Sawaguchi, Akira; Nagai, Ryozo; Takahashi, Kazutoshi; Yamanaka, Shinya; Nakauchi, Hiromitsu

    2010-01-01

    Human (h) induced pluripotent stem cells (iPSCs) are a potentially abundant source of blood cells, but how best to select iPSC clones suitable for this purpose from among the many clones that can be simultaneously established from an identical source is not clear. Using an in vitro culture system yielding a hematopoietic niche that concentrates hematopoietic progenitors, we show that the pattern of c-MYC reactivation after reprogramming influences platelet generation from hiPSCs. During differentiation, reduction of c-MYC expression after initial reactivation of c-MYC expression in selected hiPSC clones was associated with more efficient in vitro generation of CD41a+CD42b+ platelets. This effect was recapitulated in virus integration-free hiPSCs using a doxycycline-controlled c-MYC expression vector. In vivo imaging revealed that these CD42b+ platelets were present in thrombi after laser-induced vessel wall injury. In contrast, sustained and excessive c-MYC expression in megakaryocytes was accompanied by increased p14 (ARF) and p16 (INK4A) expression, decreased GATA1 expression, and impaired production of functional platelets. These findings suggest that the pattern of c-MYC expression, particularly its later decline, is key to producing functional platelets from selected iPSC clones. PMID:21098095

  15. Xanthohumol from hop cones (Humulus lupulus L.) prevents ADP-induced platelet reactivity.

    PubMed

    Luzak, Boguslawa; Kassassir, Hassan; Rój, Edward; Stanczyk, Lidia; Watala, Cezary; Golanski, Jacek

    2017-02-01

    Hop cones (Humulus lupulus L.), very rich source of phenolic compounds, possessing anticancer, antioxidant and anti-inflammatory activities, are considered as beneficial diet ingredients improving human health. In this study, the antiplatelet action of xanthohumol (XN), the principal flavonoid in hop cones, was investigated. XN significantly attenuated ADP-induced blood platelet aggregation (97.2 ± 35.7 AU for 6 μg/ml of XN vs. 120.4 ± 30.1 AU for 0.17% dimethyl sulfoxide (DMSO), p < 0.001) and significantly reduced the expression of fibrinogen receptor (activated form of GPIIbIIIa) on platelets' surface (47.6 ± 15.8 for 1.5 μg/ml XN, 44.6 ± 17.3% for 3 μg/ml XN vs. 54.5 ± 19.2% for control or 43.3 ± 18.4% for 6 μg/ml XN vs. 49.7 ± 19.4% for 0.17% DMSO, p < 0.05 or less). These findings suggest that the phenolic compounds originating from hops (XN) have a novel role as antiplatelet agents and can likely be used as dietary supplements in prophylactic approaches.

  16. Alloimmune refractoriness to platelet transfusions.

    PubMed

    Sandler, S G

    1997-11-01

    Patients who are transfused on multiple occasions with red cells or platelets may develop platelet-reactive alloantibodies and experience decreased clinical responsiveness to platelet transfusion. This situation, conventionally described as "refractoriness to platelet transfusions," is defined by an unsatisfactory low post-transfusion platelet count increment. If antibodies to HLAs are detected, improved clinical outcomes may result from transfusions of HLA-matched or donor-recipient cross-matched platelets. Because refractoriness is an expected, frequently occurring phenomenon, prevention of HLA alloimmunization is an important management strategy. Prevention strategies include efforts to decrease the number of transfusions, filtration of cellular components to reduce the number of HLA-bearing leukocytes, or pretransfusion ultraviolet B irradiation of cellular components to decrease their immunogenicity. Other investigational approaches include reducing the expression of HLAs on transfused platelets, inducing a transient reticuloendothelial system blockade by infusions of specialized immunoglobulin products, or transfusing semisynthetic platelet substitutes (thromboerythrocytes, thrombospheres) or modified platelets (infusible platelet membranes, lyophilized platelets).

  17. Inducible expression of indoleamine 2,3-dioxygenase attenuates acute rejection of tissue-engineered lung allografts in rats.

    PubMed

    Ebrahimi, Ammar; Kardar, Gholam Ali; Teimoori-Toolabi, Ladan; Toolabi, LadanTeimoori; Ghanbari, Hossein; Sadroddiny, Esmaeil

    2016-01-15

    Lung disease remains one of the principal causes of death worldwide and the incidence of pulmonary diseases is increasing. Complexity in treatments and shortage of donors leads us to develop new ways for lung disease treatment. One promising strategy is preparing engineered lung for transplantation. In this context, employing new immunosuppression strategies which suppresses immune system locally rather than systemic improves transplant survival. This tends to reduce the difficulties in transplant rejection and the systemic impact of the use of immunosuppressive drugs which causes side effects such as serious infections and malignancies. In our study examining the immunosuppressive effects of IDO expression, we produced rat lung tissues with the help of decellularized tissue, differentiating medium and rat mesenchymal stem cells. Transduction of these cells by IDO expressing lentiviruses provided inducible and local expression of this gene. To examine immunosuppressive properties of IDO expression by these tissues, we transplanted these allografts into rats and, subsequently, evaluated cytokine expression and histopathological properties. Expression of inflammatory cytokines IFNγ and TNFα were significantly downregulated in IDO expressing allograft. Moreover, acute rejection score of this experimental group was also lower comparing other two groups and mRNA levels of FOXP3, a regulatory T cell marker, upregulated in IDO expressing group. However, infiltrating lymphocyte counting did not show significant difference between groups. This study demonstrates that IDO gene transfer into engineered lung allograft tissues significantly attenuates acute allograft damage suggesting local therapy with IDO as a strategy to reduce the need for systemic immunosuppression and, thereby, its side effects.

  18. The Heparin-Induced Thrombocytopenia and Thrombosis Syndrome: Treatment with Intraarterial Urokinase and Systemic Platelet Aggregation Inhibitors

    SciTech Connect

    Murphy, Kenneth D.; McCrohan, Gerard; DeMarta, Deborah A.; Shirodkar, Nitin B.; Kwon, Oun J.; Chopra, Paramjit S.

    1996-03-15

    We report a case of the heparin-induced thrombocytopenia and thrombosis syndrome presenting with acute ischemia of a lower limb. The patient was successfully treated by withdrawal of heparin products, intraarterial urokinase, and platelet anti-aggregation therapy consisting of Dextran and aspirin.

  19. In vitro shear stress-induced platelet activation: sensitivity of human and bovine blood.

    PubMed

    Lu, Qijin; Hofferbert, Bryan V; Koo, Grace; Malinauskas, Richard A

    2013-10-01

    As platelet activation plays a critical role in physiological hemostasis and pathological thrombosis, it is important in the overall hemocompatibility evaluation of new medical devices and biomaterials to assess their effects on platelet function. However, there are currently no widely accepted in vitro test methods to perform this assessment. In an effort to develop effective platelet tests for potential use in medical device evaluation, this study compared the sensitivity of platelet responses to shear stress stimulation of human and bovine blood using multiple platelet activation markers. Fresh whole blood samples anticoagulated with heparin or anticoagulant citrate dextrose, solution A (ACDA) were exposed to shear stresses up to 40 Pa for 2 min using a cone-and-plate rheometer model. Platelet activation was characterized by platelet counts, platelet surface P-selectin expression, and serotonin release into blood plasma. The results indicated that exposure to shear stresses above 20 Pa caused significant changes in all three of the platelet markers for human blood and that the changes were usually greater with ACDA anticoagulation than with heparin. In contrast, for bovine blood, the markers did not change with shear stress stimulation except for plasma serotonin in heparin anticoagulated blood. The differences observed between human and bovine platelet responses suggest that the value of using bovine blood for in vitro platelet testing to evaluate devices may be limited.

  20. Giant Platelets in Platelet Donors – A Blessing in Disguise?

    PubMed Central

    Choudhury, Nabajyoti; Ray, Deepanjan

    2015-01-01

    Introduction Inherited thrombocytopenias, including inherited giant platelet disorders (IGPD) are relatively rare, but their prevalence is probably underestimated. Harris platelet syndrome, the most common IGPD reported from Indian subcontinent, mostly from eastern part, is characterised by a low platelet count, high mean platelet volume (MPV) and absence of bleeding. Aim A short study was conducted to assess the prevalence of giant platelets in voluntary donors of single donor platelets (SDP) and analyse the effect of transfusion of such SDPs in patients. Materials and Methods Voluntary donors of SDPs were screened as per standard guidelines prior to the procedure. A complete blood count (including MPV) along with a peripheral smear was done. A total of 45 donors were screened for plateletpheresis. Following plateletpheresis from these donors, a platelet count from the collection bag was done after one hour. The SDP was transfused as a single unit or divided into two and transfused to the same patient at two different occasions, as per clinical need. Platelet counts on pateints were done after one hour and the platelet recovery was noted. Results Out of the 45 donors who were screened, 30 (66.67%) were found to have giant platelets. It was observed that the pre procedure platelet counts in donors having giant platelets were relatively low (1.5 -1.7 lacs) and so also the platelet yield (2.7-3x1011) compared to donors who did not, but the post transfusion platelet recovery was greater. Conclusion Since presence of giant platelets has been seen to be common in the Eastern part of India, a peripheral smear examination should always be considered during screening of plateletpheresis donors to avoid rejecting donors with giant platelets whose platelet counts are given falsely low by autoanalysers. PMID:26266124

  1. Hodgkin lymphoma cell lines bind to platelets. Incubation with platelets induces CD15 and P-selectin dependent adhesion of the cell lines to Human Umbilical Vein Endothelial cells (HUVEC)

    PubMed Central

    Ohana, Ofra Malka; Ozer, Janet; Prinsloo, Isebrand; Benharroch, Daniel; Gopas, Jacob

    2015-01-01

    Hodgkin's lymphoma is believed to spread in an orderly fashion within the lymphatic compartment. In a minority of cases, after reaching the spleen, the neoplasm disseminates, reminiscent of metastasis. In the spleen, the Hodgkin-Reed-Sternberg tumor cells come across platelets in the blood vessels and mainly in the splenic red pulp. Based on this knowledge, we investigated the possibility of platelets inducing cell adhesion in Hodgkin's lymphoma cell lines. We showed that L428 and KMH-2 cells strongly adhere to thrombin-activated platelets. Cell adhesion to platelets is partially dependent on CD15 antigens (LewisX), mainly sialyl-CD15, and P-selectin. KMH-2, as compared to L428 cells, showed increased binding due to its differential high expression of the sialyl-CD15. As a consequence of incubation with platelets, KMH-2 cells also produced increased amounts of tumor necrosis factors α (TNFα) followed by enhanced binding to human vascular endothelial cells (HUVEC). Incubation of both cell lines with activated platelets also induced activation of AP-1 transcription complex. Our findings are consistent with the concept that platelets play a critical role in the dissemination of HRS cells in HL, predominantly in the spleen, by increasing cell adhesion and thus promoting their proliferative and migratory properties beyond the lymphatic system. PMID:26418972

  2. Hodgkin lymphoma cell lines bind to platelets. Incubation with platelets induces CD15 and P-selectin dependent adhesion of the cell lines to Human Umbilical Vein Endothelial cells (HUVEC).

    PubMed

    Ohana, Ofra Malka; Ozer, Janet; Prinsloo, Isebrand; Benharroch, Daniel; Gopas, Jacob

    2015-01-01

    Hodgkin's lymphoma is believed to spread in an orderly fashion within the lymphatic compartment. In a minority of cases, after reaching the spleen, the neoplasm disseminates, reminiscent of metastasis. In the spleen, the Hodgkin-Reed-Sternberg tumor cells come across platelets in the blood vessels and mainly in the splenic red pulp. Based on this knowledge, we investigated the possibility of platelets inducing cell adhesion in Hodgkin's lymphoma cell lines. We showed that L428 and KMH-2 cells strongly adhere to thrombin-activated platelets. Cell adhesion to platelets is partially dependent on CD15 antigens (Lewis(X)), mainly sialyl-CD15, and P-selectin. KMH-2, as compared to L428 cells, showed increased binding due to its differential high expression of the sialyl-CD15. As a consequence of incubation with platelets, KMH-2 cells also produced increased amounts of tumor necrosis factors α (TNFα) followed by enhanced binding to human vascular endothelial cells (HUVEC). Incubation of both cell lines with activated platelets also induced activation of AP-1 transcription complex. Our findings are consistent with the concept that platelets play a critical role in the dissemination of HRS cells in HL, predominantly in the spleen, by increasing cell adhesion and thus promoting their proliferative and migratory properties beyond the lymphatic system.

  3. Rejected applications

    PubMed Central

    2014-01-01

    Objective: To review membership application materials (especially rejected applications) to the American Academy of Neurology (AAN) during its formative years (1947–1953). Methods: Detailed study of materials in the AAN Historical Collection. Results: The author identified 73 rejected applications. Rejected applicants (71 male, 2 female) lived in 25 states. The largest number was for the Associate membership category (49). These were individuals “in related fields who have made and are making contributions to the field of neurology.” By contrast, few applicants to Active membership or Fellowship status were rejected. The largest numbers of rejectees were neuropsychiatrists (19), neurosurgeons (16), and psychiatrists (14). Conclusion: The AAN, established in the late 1940s, was a small and politically vulnerable organization. A defining feature of the fledgling society was its inclusiveness; its membership was less restrictive than that of the older American Neurological Association. At the same time, the society needed to preserve its core as a neurologic society rather than one of psychiatry or neurosurgery. Hence, the balance between inclusiveness and exclusive identity was a difficult one to maintain. The Associate membership category, more than any other, was at the heart of this issue of self-definition. Associate members were largely practitioners of psychiatry or neurosurgery. Their membership was a source of consternation and was to be carefully been held in check during these critical formative years. PMID:24944256

  4. Effects of Platelet-Rich Plasma on Kidney Regeneration in Gentamicin-Induced Nephrotoxicity

    PubMed Central

    2017-01-01

    Platelet-rich plasma (PRP) as a source of growth factors may induce tissue repairing and improve fibrosis. This study aimed to assess the effects of PRP on kidney regeneration and fibrosis in gentamicin (GM)-induced nephrotoxicity rat model by stereological study. Thirty-two male rats were selected. Nephrotoxicity was induced in animals by administration of GM (80 mg/kg/daily, intraperitoneally [IP], 8 day) and animals were treated by PRP (100 µL, intra-cortical injection using surgical microscopy, single dose). Blood samples were collected for determine blood urea nitrogen (BUN) and creatinine (Cr) before and after PRP therapy. At the end of experiment, right kidneys were sectioned by Isotropic Uniform Random (IUR) method and stained with H & E and Masson’s Trichrome. The stereological methods were used for estimating the changes in different structures of kidney. PRP increased the number of epithelial cells in convoluted tubules, and decreased the volume of connective tissue, renal corpuscles and glomeruli in GM-treated animals (P < 0.05). Our findings indicate that PRP had beneficial effects on proliferation of epithelial cells in convoluted tubules and ameliorated GM-induced fibrosis. PMID:27914126

  5. Cystamine immobilization on TiO 2 film surfaces and the influence on inhibition of collagen-induced platelet activation

    NASA Astrophysics Data System (ADS)

    Zhou, Yujuan; Weng, Yajun; Zhang, Liping; Jing, Fengjuan; Huang, Nan; Chen, Junying

    2011-12-01

    Poor haemocompatibility is a main issue of artificial cardiovascular materials in clinical application. Nitric oxide (NO), produced by vascular endothelial cells, is a well known inhibitor of platelet adhesion and activation. Thus, NO-releasing biomaterials are beneficial for improving haemocompatibility of blood-contacting biomedical devices. In this paper, a novel method was developed for enhancement of haemocompatibility by exploiting endogenous NO donors. TiO 2 films were firstly synthesized on Si (1 0 0) wafers via unbalanced magnetron sputtering technology, and then polydopamine was grafted on TiO 2 films and used as a linker for further immobilization of cystamine. The obtained surfaces were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. NO generation is evaluated by saville-griess reagents, and it shows that cystamine immobilized samples are able to catalytically generate NO by decomposing endogenous S-nitrosothiols (RSNO). In vitro platelet adhesion results reveal that cystamine modified surfaces can inhibit collagen-induced platelet activation. ELISA analysis reveals that cGMP in platelets obviously increases on cystamine immobilized surface, which suggests the reducing of platelet activation is through NO/cGMP signal channel. It can be concluded that cystamine immobilized surface shows better blood compatibility by catalyzing NO release from the endogenous NO donor. It may be a promising method for improvement of haemocompatibility of blood-contacting implants.

  6. Modeling HIV-1 Induced Neuroinflammation in Mice: Role of Platelets in Mediating Blood-Brain Barrier Dysfunction

    PubMed Central

    Jones, Letitia D.; Jackson, Joseph W.; Maggirwar, Sanjay B.

    2016-01-01

    The number of HIV-1 positive individuals developing some form of HIV-associated neurocognitive disorder (HAND) is increasing. In these individuals, the integrity of the blood-brain barrier (BBB) is compromised due to an increase in exposure to pro-inflammatory mediators, viral proteins, and virus released from infected cells. It has been shown that soluble CD40L (sCD40L) is released upon platelet activation and is an important mediator of the pathogenesis of HAND but the underlying mechanisms are unclear, emphasizing the need of an effective animal model. Here, we have utilized a novel animal model in which wild-type (WT) mice were infected with EcoHIV; a derivative of HIV-1 that contains a substitution of envelope protein gp120 with that of gp80 derived from murine leukemia virus-1 (MuLV-1). As early as two-weeks post-infection, EcoHIV led to increased permeability of the BBB associated with decreased expression of tight junction protein claudin-5, in CD40L and platelet activation-dependent manner. Treatment with an antiplatelet drug, eptifibatide, in EcoHIV-infected mice normalized BBB function, sCD40L release and platelet activity, thus implicating platelet activation and platelet-derived CD40L in virally induced BBB dysfunction. Our results also validate and underscore the importance of EcoHIV infection mouse model as a tool to explore therapeutic targets for HAND. PMID:26986758

  7. Circulating primers enhance platelet function and induce resistance to antiplatelet therapy

    PubMed Central

    Blair, T A; Moore, S F; Hers, I

    2015-01-01

    Background Aspirin and P2Y12 antagonists are antiplatelet compounds that are used clinically in patients with thrombosis. However, some patients are ‘resistant’ to antiplatelet therapy, which increases their risk of developing acute coronary syndromes. These patients often present with an underlying condition that is associated with altered levels of circulating platelet primers and platelet hyperactivity. Platelet primers cannot stimulate platelet activation, but, in combination with physiologic stimuli, significantly enhance platelet function. Objectives To explore the role of platelet primers in resistance to antiplatelet therapy, and to evaluate whether phosphoinositide 3-kinase (PI3K) contributes to this process. Methods and Results We used platelet aggregation, thromboxane A2 production and ex vivo thrombus formation as functional readouts of platelet activity. Platelets were treated with the potent P2Y12 inhibitor AR-C66096, aspirin, or a combination of both, in the presence or absence of the platelet primers insulin-like growth factor-1 (IGF-1) and thrombopoietin (TPO), or the Gz-coupled receptor ligand epinephrine. We found that platelet primers largely overcame the inhibitory effects of antiplatelet compounds on platelet functional responses. IGF-1-mediated and TPO-mediated, but not epinephrine-mediated, enhancements in the presence of antiplatelet drugs were blocked by the PI3K inhibitors wortmannin and LY294002. Conclusions These results demonstrate that platelet primers can contribute to antiplatelet resistance. Furthermore, our data demonstrate that there are PI3K-dependent and PI3K-independent mechanisms driving primer-mediated resistance to antiplatelet therapy. PMID:26039631

  8. Platelet-Activating Factor Induces Epigenetic Modifications in Human Mast Cells.

    PubMed

    Damiani, Elisabetta; Puebla-Osorio, Nahum; Gorbea, Enrique; Ullrich, Stephen E

    2015-12-01

    UV radiation-induced systemic immune suppression is a major risk factor for skin cancer induction. The migration of dermal mast cells from the skin to the draining lymph nodes has a prominent role in activating systemic immune suppression. UV-induced keratinocyte-derived platelet-activating factor (PAF) activates mast cell migration, in part by upregulating the expression of CXCR4 on the surface of mast cells. Others have indicated that epigenetic mechanisms regulate CXCR4 expression; therefore, we asked whether PAF activates epigenetic mechanisms in mast cells. Human mast cells were treated with PAF, and the effect on DNA methylation and/or acetylation was measured. PAF suppressed the expression of DNA methyltransferase (DNMT) 1 and 3b. On the other hand, PAF increased p300 histone acetyltransferase expression, and the acetylation of histone H3, which coincided with a decreased expression of the histone deacetylase HDAC2. Chromatin immunoprecipitation assays indicated that PAF treatment activated the acetylation of the CXCR4 promoter. Finally, inhibiting histone acetylation blocked p300 upregulation and suppressed PAF-induced surface expression of CXCR4. Our findings suggest a novel molecular mechanism for PAF, activation of epigenetic modifications. We suggest that PAF may serve as an endogenous molecular mediator that links the environment (UV radiation) with the epigenome.

  9. Platelet activating factor-induced expression of p21 is correlated with histone acetylation.

    PubMed

    Damiani, Elisabetta; Puebla-Osorio, Nahum; Lege, Bree M; Liu, Jingwei; Neelapu, Sattva S; Ullrich, Stephen E

    2017-02-03

    Ultraviolet (UV)-irradiated keratinocytes secrete the lipid mediator of inflammation, platelet-activating factor (PAF). PAF plays an essential role in UV-induced immune suppression and skin cancer induction. Dermal mast cell migration from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced PAF activates mast cell migration by up-regulating mast cell CXCR4 surface expression. Recent findings indicate that PAF up-regulates CXCR4 expression via histone acetylation. UV-induced PAF also activates cell cycle arrest and disrupts DNA repair, in part by increasing p21 expression. Do epigenetic alterations play a role in p21 up-regulation? Here we show that PAF increases Acetyl-CREB-binding protein (CBP/p300) histone acetyltransferase expression in a time and dose-dependent fashion. Partial deletion of the HAT domain in the CBP gene, blocked these effects. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the p21 promoter. PAF-treatment had no effect on other acetylating enzymes (GCN5L2, PCAF) indicating it is not a global activator of histone acetylation. This study provides further evidence that PAF activates epigenetic mechanisms to affect important cellular processes, and we suggest this bioactive lipid can serve as a link between the environment and the epigenome.

  10. Platelet activating factor-induced expression of p21 is correlated with histone acetylation

    PubMed Central

    Damiani, Elisabetta; Puebla-Osorio, Nahum; Lege, Bree M.; Liu, Jingwei; Neelapu, Sattva S.; Ullrich, Stephen E.

    2017-01-01

    Ultraviolet (UV)-irradiated keratinocytes secrete the lipid mediator of inflammation, platelet-activating factor (PAF). PAF plays an essential role in UV-induced immune suppression and skin cancer induction. Dermal mast cell migration from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced PAF activates mast cell migration by up-regulating mast cell CXCR4 surface expression. Recent findings indicate that PAF up-regulates CXCR4 expression via histone acetylation. UV-induced PAF also activates cell cycle arrest and disrupts DNA repair, in part by increasing p21 expression. Do epigenetic alterations play a role in p21 up-regulation? Here we show that PAF increases Acetyl-CREB-binding protein (CBP/p300) histone acetyltransferase expression in a time and dose-dependent fashion. Partial deletion of the HAT domain in the CBP gene, blocked these effects. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the p21 promoter. PAF-treatment had no effect on other acetylating enzymes (GCN5L2, PCAF) indicating it is not a global activator of histone acetylation. This study provides further evidence that PAF activates epigenetic mechanisms to affect important cellular processes, and we suggest this bioactive lipid can serve as a link between the environment and the epigenome. PMID:28157211

  11. Platelet-Activating Factor Induces Epigenetic Modifications in Human Mast Cells

    PubMed Central

    Gorbea, Enrique; Ullrich, Stephen E.

    2015-01-01

    Ultraviolet (UV) radiation-induced systemic immune suppression is a major risk factor for skin cancer induction. The migration of dermal mast cells from the skin to the draining lymph nodes plays a prominent role in activating systemic immune suppression. UV-induced keratinocyte-derived platelet-activating factor (PAF) activates mast cell migration, in part by up regulating the expression of CXCR4 on the surface of mast cells. Others have indicated that epigenetic mechanisms regulate CXCR4 expression, so we asked whether PAF activates epigenetic mechanisms in mast cells. Human mast cells were treated with PAF and the effect on DNA methylation and/or acetylation was measured. PAF suppressed the expression of DNA methyltransferase (DNMT) 1 and 3b. On the other hand, PAF increased p300 histone acetyltransferase expression, and the acetylation of histone H3, which coincided with a decreased expression of the histone deacetylase HDAC2. Chromatin immunoprecipitation assays indicated that PAF-treatment activated the acetylation of the CXCR4 promoter. Finally, inhibiting histone acetylation blocked p300 up-regulation and suppressed PAF-induced surface expression of CXCR4. Our findings suggest a novel molecular mechanism for PAF, activation of epigenetic modifications. We suggest that PAF may serve as an endogenous molecular mediator that links the environment (UV radiation) with the epigenome. PMID:26316070

  12. Platelet interaction with polymerizing fibrin.

    PubMed

    Niewiarowski, S; Regoeczi, E; Stewart, G J; Senyl, A F; Mustard, J F

    1972-03-01

    Interaction of washed pig, rabbit, or human platelets with fibrinogen was studied during its transition to fibrin using photometric, isotopic, and electron microscopic techniques. Untreated fibrinogen and fully polymerized fibrin had no detectable effect on platelets. Fibrinogen, incubated with low concentrations of reptilase or thrombin, formed intermediate products which readily became associated with platelets and caused their aggregation. Neutralization of the thrombin did not prevent this interaction. In the absence of fibrinogen, reptilase did not affect platelets. The interaction of polymerizing fibrin with platelets was accompanied by small losses of platelet constituents (serotonin, adenine nucleotides, platelet factor 4, and lactic dehydrogenase). This loss did not appear to be the result of the platelet release reaction. Inhibitors of the release reaction or of adenosine diphosphate (ADP)-induced aggregation did not prevent the interaction of platelets with polymerizing fibrin. Apyrase or prostaglandin E(1) (PGE(1)) reduced the extent of platelet aggregation by polymerizing fibrin, but the amount of protein associated with platelets was slightly increased. The interaction of polymerizing fibrin with platelets was completely inhibited by ethylenediaminetetraacetate (EDTA) or ethylene glycol bis (beta-aminoethyl ether) N, N,N',N'-tetraacetic acid (EGTA).Fibers formed in solutions of polymerizing fibrin were larger in the presence than in the absence of washed platelets, suggesting that platelets affect fibrin polymerization. The adherence of platelets to polymerizing fibrin may be responsible for the establishment of links between platelets and fibrin in hemostatic plugs and thrombi.

  13. Teratocarcinomas Arising from Allogeneic Induced Pluripotent Stem Cell-Derived Cardiac Tissue Constructs Provoked Host Immune Rejection in Mice

    PubMed Central

    Kawamura, Ai; Miyagawa, Shigeru; Fukushima, Satsuki; Kawamura, Takuji; Kashiyama, Noriyuki; Ito, Emiko; Watabe, Tadashi; Masuda, Shigeo; Toda, Koichi; Hatazawa, Jun; Morii, Eiichi; Sawa, Yoshiki

    2016-01-01

    Transplantation of induced pluripotent stem cell-derived cardiac tissue constructs is a promising regenerative treatment for cardiac failure: however, its tumourigenic potential is concerning. We hypothesised that the tumourigenic potential may be eliminated by the host immune response after allogeneic cell transplantation. Scaffold-free iPSC-derived cardaic tissue sheets of C57BL/6 mouse origin were transplanted into the cardiac surface of syngeneic C57BL/6 mice and allogeneic BALB/c mice with or without tacrolimus injection. Syngeneic mice and tacrolimus-injected immunosuppressed allogeneic mice formed teratocarcinomas with identical phenotypes, characteristic, and time courses, as assessed by imaging tools including 18F-fluorodeoxyglucose-positron emission tomography. In contrast, temporarily immunosuppressed allogeneic mice, following cessation of tacrolimus injection displayed diminished progression of the teratocarcinoma, accompanied by an accumulation of CD4/CD8-positive T cells, and finally achieved complete elimination of the teratocarcinoma. Our results indicated that malignant teratocarcinomas arising from induced pluripotent stem cell-derived cardiac tissue constructs provoked T cell-related host immune rejection to arrest tumour growth in murine allogeneic transplantation models. PMID:26763872

  14. Tumor necrosis factor alpha-induced angiogenesis depends on in situ platelet-activating factor biosynthesis

    PubMed Central

    1994-01-01

    Tumor necrosis factor (TNF) alpha, a potent inhibitor of endothelial cell growth in vitro, is angiogenic in vivo. Therefore, it was suggested that the angiogenic properties of this agent might be consequent to the production of secondary mediators. Since TNF-alpha stimulates the synthesis of platelet-activating factor (PAF) by monocytes and endothelial cells, we investigated the possible involvement of PAF in the angiogenic effect of TNF-alpha. Angiogenesis was studied in a murine model in which Matrigel was used as a vehicle for the delivery of mediators. In this model the angiogenesis induced by TNF-alpha was shown to be inhibited by WEB 2170, a specific PAF receptor antagonist. Moreover, in mice injected with TNF-alpha, PAF was detected within the Matrigel, 6 and 24 h after TNF-alpha injection. The synthesis of PAF within the Matrigel was concomitant with the early migration of endothelial cells and infiltration of monocytes. No infiltration of lymphocytes or polymorphonuclear leukocytes was observed. Synthetic PAF as well as PAF extracted and purified from mice challenged with TNF-alpha induced a rapid angiogenic response, inhibited by WEB 2170. These results suggest that the angiogenic effect of TNF-alpha is, at least in part, mediated by PAF synthesized from monocytes and/or endothelial cells infiltrating the Matrigel plug. PMID:7516414

  15. Investigating the fluid mechanics behind red blood cell-induced lateral platelet motion

    NASA Astrophysics Data System (ADS)

    Crowl Erickson, Lindsay; Fogelson, Aaron

    2009-11-01

    Platelets play an essential role in blood clotting; they adhere to damaged tissue and release chemicals that activate other platelets. Yet in order to adhere, platelets must first come into contact with the injured vessel wall. Under arterial flow conditions, platelets have an enhanced concentration near blood vessel walls. This non-uniform cell distribution depends on the fluid dynamics of blood as a heterogeneous medium. We use a parallelized lattice Boltzmann-immersed boundary method to solve the flow dynamics of red cells and platelets in a periodic 2D vessel with no-slip boundary conditions. Red cells are treated as biconcave immersed boundary objects with isotropic Skalak membrane tension and an internal viscosity five times that of the surrounding plasma. Using this method we analyze the influence of shear rate, hematocrit, and red cell membrane properties on lateral platelet motion. We find that the effective diffusion of platelets is significantly lower near the vessel wall compared to the center of the vessel. Insight gained from this work could lead to significant improvements to current models for platelet adhesion where the presence of red blood cells is neglected due to computational intensity.

  16. Lectin-induced activation of platelets may require only limited phosphorylation of the 47K protein

    SciTech Connect

    Ganguly, C.; Chelladurai, M.; Ganguly, P.

    1986-05-01

    Wheat germ agglutinin (WGA) is an N-acetylglucosamine (Glc-NAc) specific lectin which can activate platelets. Like thrombin, stimulation of platelets by WGA is accompanied by enhanced phosphorylation of two polypeptides of M/sub r/ 47K and 20K. Addition of GlcNAc at different time intervals arrested that aggregation of platelets by WGA and paralleled the modification of phosphorylation of the 47K polypeptide. So, the phosphorylation of the 47K polypeptide may regulate the WGA-receptor mediated stimulation of platelets. However, the ratio of phosphoserine to phosphothreonine in the 47K protein was markedly different in WGA-activated than thrombin-stimulated platelets. Thus, the molecular mechanism of action of thrombin and WGA could be different. To explore this idea, /sup 32/P/sub i/-labeled platelets were stimulated with WGA and the activation arrested with N-acetyl-glucosamine at different times. Two-dimensional gel electrophoresis of total protein at 5s showed only two phosphorylated species of 47K protein. At 60s, maximally four phosphorylated species were noted. In contrast, with thrombin using the same technique, seven to nine phosphorylated components have been reported. These results suggest that the different activators of platelets may act by different mechanisms. In addition, activation of platelets may require only limited levels of phosphorylation of the 47K polypeptide.

  17. [Platelet count in the cat].

    PubMed

    Moritz, A; Hoffmann, C

    1997-11-01

    The technique of collecting blood samples is primarily responsible for the appearance of platelet-agglomeration in cats. Blood obtained by the conventional way ("one syringe technology", drips of blood) caused in 52% of the cases an activation of the large and therefore active thrombocytes however. Rejection of the first 2-5 ml blood for the platelet count ("two syringe technology") reduced the rate of platelet-agglomeration significantly. No big differences in platelet-agglomeration were found with regard to the place used for collecting blood (V. cephalica antebrachii/V. jugularis). Platelet-agglutination was observed with Li-Heparin, K-EDTA, Na-Citrat or ACD anticoagulated blood samples. Citrat (Na-Citrat, ACD) seemed to have a stabilizing effect on feline thrombocytes as has been described for human thrombocytes. The platelet count in cats should be performed within 30 minutes.

  18. CdTe quantum dots induce activation of human platelets: implications for nanoparticle hemocompatibility.

    PubMed

    Samuel, Stephen P; Santos-Martinez, Maria J; Medina, Carlos; Jain, Namrata; Radomski, Marek W; Prina-Mello, Adriele; Volkov, Yuri

    2015-01-01

    New nanomaterials intended for systemic administration have raised concerns regarding their biocompatibility and hemocompatibility. Quantum dots (QD) nanoparticles have been used for diagnostics, and recent work suggests their use for in vivo molecular and cellular imaging. However, the hemocompatibility of QDs and their constituent components has not been fully elucidated. In the present study, comprehensive investigation of QD-platelet interactions is presented. These interactions were shown using transmission electron microscopy. The effects of QDs on platelet function were investigated using light aggregometry, quartz crystal microbalance with dissipation, flow cytometry, and gelatin zymography. Platelet morphology was also analyzed by phase-contrast, immunofluorescence, atomic-force and transmission electron microscopy. We show that the QDs bind to platelet plasma membrane with the resultant upregulation of glycoprotein IIb/IIIa and P-selectin receptors, and release of matrix metalloproteinase-2. These findings unravel for the first time the mechanism of functional response of platelets to ultrasmall QDs in vitro.

  19. Suilysin-induced Platelet-Neutrophil Complexes Formation is Triggered by Pore Formation-dependent Calcium Influx

    PubMed Central

    Zhang, Shengwei; Zheng, Yuling; Chen, Shaolong; Huang, Shujing; Liu, Keke; Lv, Qingyu; Jiang, Yongqiang; Yuan, Yuan

    2016-01-01

    Platelet activation and platelet–neutrophil interactions have been found to be involved in inflammation, organ failure and soft-tissue necrosis in bacterial infections. Streptococcus suis, an emerging human pathogen, can cause streptococcal toxic-shock syndrome (STSS) similarly to Streptococcus pyogenes. Currently, S. suis–platelet interactions are poorly understood. Here, we found that suilysin (SLY), the S. suis cholesterol-dependent cytolysin (CDC), was the sole stimulus of S. suis that induced platelet-neutrophil complexes (PNC) formation. Furthermore, P-selectin released in α-granules mediated PNC formation. This process was triggered by the SLY-induced pore forming-dependent Ca2+ influx. Moreover, we demonstrated that the Ca2+ influx triggered an MLCK-dependent pathway playing critical roles in P-selectin activation and PNC formation, however, PLC-β-IP3/DAG-MLCK and Rho-ROCK-MLCK signalling were not involved. Additionally, the “outside-in” signalling had a smaller effect on the SLY-induced P-selectin release and PNC formation. Interestingly, other CDCs including pneumolysin and streptolysin O have also been found to induce PNC formation in a pore forming-dependent Ca2+ influx manner. It is possible that the bacterial CDC-mediated PNC formation is a similar response mechanism used by a wide range of bacteria. These findings may provide useful insight for discovering potential therapeutic targets for S. suis-associated STSS. PMID:27830834

  20. Differential effect of the inhibition of Grb2-SH3 interactions in platelet activation induced by thrombin and by Fc receptor engagement.

    PubMed Central

    Saci, Abdelhafid; Liu, Wang-Qing; Vidal, Michel; Garbay, Christiane; Rendu, Francine; Bachelot-Loza, Christilla

    2002-01-01

    The adaptor protein Grb2 (growth factor receptor-bound protein 2) is involved in cell proliferation via the Ras signalling pathway. In order to study the role of Grb2 in blood platelet responses, we used a peptide containing two proline-rich sequences derived from Sos (peptidimer), which binds to Grb2-Src homology 3 domain (SH3) with a high affinity, and hence inhibits Grb2-SH3-mediated protein interactions. Platelet aggregation and 5-hydroxytryptamine (serotonin) release measured in the presence of the peptidimer were: (i) significantly decreased when induced by thrombin; and (ii) potentiated when induced by the engagement of the Fc receptor. In thrombin-activated platelets, the Grb2-SH2 domain formed an association with the beta3 subunit of the alphaIIb-beta3 integrin (GPIIb-IIIa), Shc, Syk, Src and SHP1 (SH2-containing phosphotyrosine phosphatase 1), whereas these associations did not occur after the engagement of the receptor for the Fc domain of IgG (FcgammaRIIa) or in resting platelets. Grb2-SH3 domains formed an association with the proline-rich sequences of Sos and Cbl in both resting and activated platelets, since the peptidimer abolished these associations. Inhibition of both fibrinogen binding and platelet aggregation by the peptide RGDS (Arg-Gly-Asp-Ser) had no effect on thrombin-induced Grb2-SH2 domain association with the aforementioned signalling molecules, indicating that these associations occurred during thrombin-induced 'inside-out' signalling. Platelet aggregation induced by direct activation via alphaIIb-beta3 ('outside-in' signalling) was potentiated by the peptidimer. The results show that inhibition of Grb2-SH3 interactions with signal-transduction proteins down-regulates thrombin-induced platelet activation, but also potentiates Fc receptor- and alphaIIb-beta3-mediated platelet activation. PMID:11964172

  1. Binding of /sup 125/I-labeled endotoxin to bovine, canine, and equine platelets and endotoxin-induced agglutination of canine platelets

    SciTech Connect

    Meyers, K.M.; Boehme, M.; Inbar, O.

    1982-10-01

    Endotoxin from Escherichia coli O127:B8, Salmonella abortus-equi and S minnesota induced clumping of some canine platelets (PLT) at a final endotoxin concentration of 1 microgram/ml. Endotoxin-induced clumping of canine PLT was independent of PLT energy-requiring processes, because clumping was observed with canine PLT incubated with 2-deoxy-D-glucose and antimycin A. The PLT responded to adenosine diphosphate before, but not after, incubation with the metabolic inhibitors. Endotoxin induced a slight and inconsistant clumping of bovine and equine PLT at high (mg/ml) endotoxin concentration. High-affinity binding sites could not be demonstrated on canine, bovine, and equine PLT, using /sup 125/I-labeled E coli O127:B8 endotoxin. Nonspecific binding was observed and appeared to be due primarily to an extraneous coat on the PLT surface that was removed by gel filtration. The endotoxin that was bound to PLT did not appear to modify PLT function. An attempt to identify plasma proteins that bound physiologically relevant amounts of endotoxin was not successful. The significance of the endotoxin-induced clumping or lack of it on the pathophysiology of endotoxemia is discussed.

  2. High Residual Collagen-Induced Platelet Reactivity Predicts Development of Restenosis in the Superficial Femoral Artery After Percutaneous Transluminal Angioplasty in Claudicant Patients

    SciTech Connect

    Gary, Thomas; Prüller, Florian Raggam, Reinhard; Mahla, Elisabeth; Eller, Philipp Hafner, Franz Brodmann, Marianne

    2016-02-15

    PurposeAlthough platelet reactivity is routinely inhibited with aspirin after percutaneous angioplasty (PTA) in peripheral arteries, the restenosis rate in the superficial femoral artery (SFA) is high. Interaction of activated platelets and the endothelium in the region of intervention could be one reason for this as collagen in the subendothelium activates platelets.Materials and MethodsA prospective study evaluating on-site platelet reactivity during PTA and its influence on the development of restenosis with a total of 30 patients scheduled for PTA of the SFA. Arterial blood was taken from the PTA site after SFA; platelet function was evaluated with light transmission aggregometry. After 3, 6, 12, and 24 months, duplex sonography was performed and the restenosis rate evaluated.ResultsEight out of 30 patients developed a hemodynamically relevant restenosis (>50 % lumen narrowing) in the PTA region during the 24-month follow-up period. High residual collagen-induced platelet reactivity defined as AUC >30 was a significant predictor for the development of restenosis [adjusted odds ratio 11.8 (9.4, 14.2); P = .04].ConclusionsHigh residual collagen-induced platelet reactivity at the interventional site predicts development of restenosis after PTA of the SFA. Platelet function testing may be useful for identifying patients at risk.

  3. SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation

    PubMed Central

    Hayashi, Moyuru; Kaneda, Mizuho; Iida, Kazuko; Shimonaka, Motoyuki; Hara, Takahiko; Arai, Morio; Koike, Yuichi; Yamamoto, Naomasa; Kasahara, Kohji

    2017-01-01

    Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation. PMID:28072855

  4. SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation.

    PubMed

    Ohtsuka, Hiroko; Iguchi, Tomohiro; Hayashi, Moyuru; Kaneda, Mizuho; Iida, Kazuko; Shimonaka, Motoyuki; Hara, Takahiko; Arai, Morio; Koike, Yuichi; Yamamoto, Naomasa; Kasahara, Kohji

    2017-01-01

    Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation.

  5. Platelet preservation: agitation and containers.

    PubMed

    van der Meer, Pieter F; de Korte, Dirk

    2011-06-01

    For platelets to maintain their in vitro quality and in vivo effectiveness, they need to be stored at room temperature with gentle agitation in gas-permeable containers. The mode of agitation affects the quality of the platelets, and a gentle method of agitation, either a circular or a flat bed movement, provides the best results. Tumblers or elliptical agitators induce platelet activation and subsequent damage. As long as the platelets remain in suspension, the agitation speed is not important. Agitation of the platelet concentrates ensures that the platelets are continuously oxygenated, that sufficient oxygen can enter the storage container and that excess carbon dioxide can be expelled. During transportation of platelet concentrates, nowadays over long distances where they are held without controlled agitation, platelets may tolerate a certain period without agitation. However, evidence is accumulating that during the time without agitation, local hypoxia surrounding the platelets may induce irreversible harm to the platelets. Over the decades, more gas-permeable plastics have been used to manufacture platelet containers. The use of different plastics and their influence on the platelet quality both in vitro and in vivo is discussed. The improved gas-permeability has allowed the extension of platelet storage from 3 days in the early 1980s, to currently at least 7 days. In the light of new developments, particularly the introduction of pathogen reduction techniques, the use of platelet additive solutions and the availability of improved automated separators, further (renewed) research in this area is warranted.

  6. Platelet activating factor produced in vitro by Kaposi's sarcoma cells induces and sustains in vivo angiogenesis.

    PubMed Central

    Bussolino, F; Arese, M; Montrucchio, G; Barra, L; Primo, L; Benelli, R; Sanavio, F; Aglietta, M; Ghigo, D; Rola-Pleszczynski, M R

    1995-01-01

    Imbalance in the network of soluble mediators may play a pivotal role in the pathogenesis of Kaposi's sarcoma (KS). In this study, we demonstrated that KS cells grown in vitro produced and in part released platelet activating factor (PAF), a powerful lipid mediator of inflammation and cell-to-cell communication. IL-1, TNF, and thrombin enhanced the synthesis of PAF. PAF receptor mRNA and specific, high affinity binding site for PAF were present in KS cells. Nanomolar concentration of PAF stimulated the chemotaxis and chemokinesis of KS cells, endothelial cells, and vascular smooth muscle cells. The migration response to PAF was inhibited by WEB 2170, a hetrazepinoic PAF receptor antagonist. Because neoangiogenesis is essential for the growth and progression of KS and since PAF can activate vascular endothelial cells, we examined the potential role of PAF as an instrumental mediator of angiogenesis associated with KS. Conditioned medium (CM) from KS cells (KS-CM) or KS cells themselves induced angiogenesis and macrophage recruitment in a murine model in which Matrigel was injected subcutaneously. These effects were inhibited by treating mice with WEB 2170. Synthetic PAF or natural PAF extracted from plasma of patients with classical KS also induced angiogenesis, which in turn was inhibited by WEB 2170. The action of PAF was amplified by expression of other angiogenic factors and chemokines: these included basic and acidic fibroblast growth factor, placental growth factor, vascular endothelial growth factor and its specific receptor flk-1, hepatocyte growth factor, KC, and macrophage inflammatory protein-2. Treatment with WEB 2170 abolished the expression of the transcripts of these molecules within Matrigel containing KS-CM. These results indicate that PAF may cooperate with other angiogenic molecules and chemokines in inducing vascular development in KS. Images PMID:7543496

  7. Proteomic analysis of the porcine platelet proteome and alterations induced by thrombin activation.

    PubMed

    Esteso, Gloria; Mora, María Isabel; Garrido, Juan José; Corrales, Fernando; Moreno, Angela

    2008-12-02

    Platelets are enucleated cells derived from bone marrow megakaryocytes and defects in platelet functions could be involved in many cardiovascular diseases. Proteomics can be used to provide a new insight in the study of these platelet functions and can help to identify the biochemical events underlying platelet activation. In this study, we have obtained a reference 2-DE map of porcine platelet proteins. A large number of cytoskeletal and metabolic proteins were found as well as some proteins related to cell mobility and immunological functions. Other proteins implicated in the cell signalling process, transport or apoptosis were also identified. Moreover, we have analysed, by 2D-DIGE methodology, quantitative modifications of platelet proteins following their activation by thrombin. 26 spots exhibited statistically significant differences, and a total of 16 spots corresponding to 13 different proteins were successfully identified. Using Ingenuity Pathway Analysis, the association of the deregulated proteins with canonical pathways highlighted two major pathways; coagulation system and integrin signalling. These results confirm that this proteomic approach (based on 2D-DIGE, mass spectrometry and bioinformatic and pathway databases) has proved to be a powerful tool when applied to studying signalling pathways that could play a relevant role in the activation of platelets.

  8. Statin-induced changes in mitochondrial respiration in blood platelets in rats and human with dyslipidemia.

    PubMed

    Vevera, J; Fišar, Z; Nekovářová, T; Vrablík, M; Zlatohlávek, L; Hroudová, J; Singh, N; Raboch, J; Valeš, K

    2016-11-23

    3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) are widely used drugs for lowering blood lipid levels and preventing cardiovascular diseases. However, statins can have serious adverse effects, which may be related to development of mitochondrial dysfunctions. The aim of study was to demonstrate the in vivo effect of high and therapeutic doses of statins on mitochondrial respiration in blood platelets. Model approach was used in the study. Simvastatin was administered to rats at a high dose for 4 weeks. Humans were treated with therapeutic doses of rosuvastatin or atorvastatin for 6 weeks. Platelet mitochondrial respiration was measured using high-resolution respirometry. In rats, a significantly lower physiological respiratory rate was found in intact platelets of simvastatin-treated rats compared to controls. In humans, no significant changes in mitochondrial respiration were detected in intact platelets; however, decreased complex I-linked respiration was observed after statin treatment in permeabilized platelets. We propose that the small in vivo effect of statins on platelet energy metabolism can be attributed to drug effects on complex I of the electron transport system. Both intact and permeabilized platelets can be used as a readily available biological model to study changes in cellular energy metabolism in patients treated with statins.

  9. Hyperglycaemia-induced reciprocal changes in miR-30c and PAI-1 expression in platelets

    PubMed Central

    Luo, Mao; Li, Rong; Ren, Meiping; Chen, Ni; Deng, Xin; Tan, Xiaoyong; Li, Yongjie; Zeng, Min; Yang, Yan; Wan, Qin; Wu, Jianbo

    2016-01-01

    Type 2 diabetic mellitus (DM2) is associated with accelerated thrombotic complications and is characterized by high levels of plasminogen activator inhibitor-1 (PAI-1). Recent studies show that human platelets have high levels of miR-30c and synthesize considerable active PAI-1. The underlying mechanism of how PAI-1 expression is upregulated in DM2 is poorly understood. We now report that hyperglycaemia-induced repression of miR-30c increases PAI-1 expression and thrombus formation in DM2. Bioinformatic analysis and identification of miRNA targets were assessed using luciferase assays, quantitative real-time PCR and western blots in vitro and in vivo. The changes in miR-30c and PAI-1 levels were identified in platelets from healthy and diabetic individuals. We found that miR-30c directly targeted the 3′ UTR of PAI-1 and negatively regulated its expression. miR-30c was negatively correlated with glucose and HbA1c levels in DM2. In HFD-fed diabetic mice, increasing miR-30c expression by lenti-miR-30c significantly decreased the PAI-1 expression and prolonged the time to occlusion in an arterial thrombosis model. Platelet depletion/reinfusion experiments generating mice with selective ablation of PAI-1 demonstrate a major contribution by platelet-derived PAI-1 in the treatment of lenti-miR-30c to thrombus formation. These results provide important implications regarding the regulation of fibrinolysis by platelet miRNA under diabetic mellitus. PMID:27819307

  10. Trivalent methylated arsenical-induced phosphatidylserine exposure and apoptosis in platelets may lead to increased thrombus formation

    SciTech Connect

    Bae, Ok-Nam; Lim, Kyung-Min; Chung, Jin-Ho

    2009-09-01

    Trivalent methylated metabolites of arsenic, monomethylarsonous acid (MMA{sup III}) and dimethylarsinous acid (DMA{sup III}), have been found highly reactive and toxic in various cells and in vivo animal models, suggesting their roles in the arsenic-associated toxicity. However, their effects on cardiovascular system including blood cells, one of the most important targets for arsenic toxicity, remain poorly understood. Here we found that MMA{sup III} and DMA{sup III} could induce procoagulant activity and apoptosis in platelets, which play key roles in the development of various cardiovascular diseases (CVDs) through excessive thrombus formation. In freshly isolated human platelets, treatment of MMA{sup III} resulted in phosphatidylserine (PS) exposure, a hallmark of procoagulant activation, accompanied by distinctive apoptotic features including mitochondrial membrane potential disruption, cytochrome c release, and caspase-3 activation. These procoagulant activation and apoptotic features were found to be mediated by the depletion of protein thiol and intracellular ATP, and flippase inhibition by MMA{sup III}, while the intracellular calcium increase or reactive oxygen species generation was not involved. Importantly, increased platelet procoagulant activity by MMA{sup III} resulted in enhanced blood coagulation and excessive thrombus formation in a rat in vivo venous thrombosis model. DMA{sup III} also induced PS-exposure with apoptotic features mediated by protein thiol depletion, which resulted in enhanced thrombin generation. In summary, we believe that this study provides an important evidence for the role of trivalent methylated arsenic metabolites in arsenic-associated CVDs, giving a novel insight into the role of platelet apoptosis in toxicant-induced cardiovascular toxicity.

  11. Effects of platelet-rich plasma on liver regeneration in CCl4-induced hepatotoxicity model.

    PubMed

    Mafi, Afsaneh; Dehghani, Farzaneh; Moghadam, Abbas; Noorafshan, Ali; Vojdani, Zahra; Talaei-Khozani, Tahereh

    2016-12-01

    Numerous bioactive growth factors and cytokines in platelet-rich plasma (PRP) have recently made it an attractive biomaterial for therapeutic purposes. These growth factors have the potential to regenerate the injured tissues. The aim of this study was to investigate the therapeutic effects of PRP in hepatotoxic animal model. Hepatotoxicity was induced in rats by oral administration of 4 mL/kg/week of CCl4 diluted 1:1 in corn oil for 10 weeks. To confirm the hepatotoxicity, 24 h after the last CCl4 administration, blood samples were collected via cardiac puncture to assess the serum levels of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, albumin, total protein, and total bilirubin. Twenty-four hours after blood collection, the experimental animals received a single injection of PRP (1 mL) via the anterior mesenteric vein. One week later, all biochemical tests were performed again, and the rats were scarified and their livers were removed, prepared histologically, and stained. The stereological analyses were performed to evaluate the effects of PRP on histopathological features of CCl4-treated livers. The results were compared statistically with the corresponding control and CCl4+normal saline (NS)-treated animals. A significant decrease in the number and volume of hepatocytes (p = 0.01), and also a reduction in the volume of sinusoids (p = 0.001) and connective tissue (p = 0.04), were observed in the PRP-treated animals compared with the CCl4+NS-treated ones. Our findings demonstrated that application of PRP had beneficial effects on CCl4-induced fibrosis; however, it had detrimental effects on the total number of hepatocytes and the volume of hepatocytes and sinusoidal spaces.

  12. Enhanced Shear-induced Platelet Aggregation Due to Low-temperature Storage

    DTIC Science & Technology

    2013-07-01

    rheometer. PLT aggregation was measured using a flow cytometer as an increase in the forward scatter-side scatter population which is bigger and...500, 2500, or 10,000/second for 120 seconds at 37°C, and PLT aggregation was measured. (A) Flow cytometric plots for the measurement of PLT...platelet aggregation and microaggregate formation in whole blood by flow cytometry. Platelets 2004;15:85-93. 26. Shankaran H, Alexandridis P

  13. Venous hypertension induces increased platelet reactivity and accumulation in patients with chronic venous insufficiency.

    PubMed

    Lu, Xinwu; Chen, Yujie; Huang, Yin; Li, Weimin; Jiang, Mier

    2006-01-01

    The objective of this study was to determine whether there are changes in platelet activation and rheology in patients with chronic venous insufficiency (CVI) and what their impact is on this disease. Anticoagulated peripheral venous blood collected from 21 patients with CVI and 13 normal control subjects in different bodily positions was incubated either with 0.5 mumol/L adenosine diphosphate (ADP) or without agonist and analyzed by whole blood flow cytometry. Soluble P-selectin was analyzed in obtained sera by enzyme-linked immunosorbent assay. Platelet count was determined by a whole blood analyzer. Circulating platelets were more reactive to stimulation with 0.5 mumol/L ADP in patients with CVI compared with control subjects. There was no statistically significant change in platelet activation without ADP and the level of soluble P-selectin as a function of posture. Under simulated venous hypertension, platelet accumulation was observed in patients with CVI. Patients with CVI had increased platelet reactivity and accumulation during orthostasis, suggesting this might be a contributory factor to CVI pathogenesis.

  14. Thrombin-induced lysosomal exocytosis in human platelets is dependent on secondary activation by ADP and regulated by endothelial-derived substances.

    PubMed

    Södergren, Anna L; Svensson Holm, Ann-Charlotte B; Ramström, Sofia; Lindström, Eva G; Grenegård, Magnus; Öllinger, Karin

    2016-01-01

    Exocytosis of lysosomal contents from platelets has been speculated to participate in clearance of thrombi and vessel wall remodelling. The mechanisms that regulate lysosomal exocytosis in platelets are, however, still unclear. The aim of this study was to identify the pathways underlying platelet lysosomal secretion and elucidate how this process is controlled by platelet inhibitors. We found that high concentrations of thrombin induced partial lysosomal exocytosis as assessed by analysis of the activity of released N-acetyl-β-glucosaminidase (NAG) and by identifying the fraction of platelets exposing the lysosomal-associated membrane protein (LAMP)-1 on the cell surface by flow cytometry. Stimulation of thrombin receptors PAR1 or PAR4 with specific peptides was equally effective in inducing LAMP-1 surface expression. Notably, lysosomal exocytosis in response to thrombin was significantly reduced if the secondary activation by ADP was inhibited by the P2Y12 antagonist cangrelor, while inhibition of thromboxane A2 formation by treatment with acetylsalicylic acid was of minor importance in this regard. Moreover, the NO-releasing drug S-nitroso-N-acetyl penicillamine (SNAP) or the cyclic AMP-elevating eicosanoid prostaglandin I2 (PGI2) significantly suppressed lysosomal exocytosis. We conclude that platelet inhibitors that mimic functional endothelium such as PGI2 or NO efficiently counteract lysosomal exocytosis. Furthermore, we suggest that secondary release of ADP and concomitant signaling via PAR1/4- and P2Y12 receptors is important for efficient platelet lysosomal exocytosis by thrombin.

  15. Early storage lesions in apheresis platelets are induced by the activation of the integrin αIIbβ₃ and focal adhesion signaling pathways.

    PubMed

    Thiele, Thomas; Iuga, Cristina; Janetzky, Susann; Schwertz, Hansjorg; Gesell Salazar, Manuela; Fürll, Birgit; Völker, Uwe; Greinacher, Andreas; Steil, Leif

    2012-12-05

    Production and storage of platelet concentrates (PC) induce protein changes in platelets leading to impaired platelet function. This study aimed to identify signaling pathways involved in the development of early platelet storage lesions in apheresis-PCs stored in plasma or additive solution (PAS). Apheresis-PCs from four donors were stored in plasma or in PAS at 22°C (n=4 each). Platelets were analyzed at day 0 (production day) and after 1, 6 and 9 days of storage. Platelet response to agonists (TRAP, collagen, ADP) and to hypotonic shock decreased, CD62P expression increased in both storage media over time. Using DIGE 1550 protein spots were monitored and compared to baseline values at day 0. Platelets in plasma displayed changes in 352 spots (166/day 1, 263/day 6 and 201/day 9); in PAS 325 spots changed (202/day 1, 221/day 6, 200/day 9). LC-ESI-MS/MS analysis of 405 platelet proteins revealed 32 proteins changed during storage in plasma (9/day 1, 15/day 6 and 26/day 9) and 28 in PAS (5/day 1, 20/day 6, 26/day 9). Ingenuity pathway analysis found integrin-αII(b)β(3) and focal adhesion signaling pathways involved in early alterations, being confirmed by Western blotting. Corresponding mRNAs in platelets were identified by next generation sequencing for 84 changed proteins. Integrin-αII(b)β(3) and focal adhesion signaling cause irreversible early storage lesions in apheresis platelets. This article is part of a Special Issue entitled: Integrated omics.

  16. Platelet-activating factor: a candidate human immunodeficiency virus type 1-induced neurotoxin.

    PubMed Central

    Gelbard, H A; Nottet, H S; Swindells, S; Jett, M; Dzenko, K A; Genis, P; White, R; Wang, L; Choi, Y B; Zhang, D

    1994-01-01

    The pathogenesis of central nervous system disease during human immunodeficiency virus type 1 (HIV-1) infection revolves around productive viral infection of brain macrophages and microglia. Neuronal losses in the cortex and subcortical gray matter accompany macrophage infection. The question of how viral infection of brain macrophages ultimately leads to central nervous system (CNS) pathology remains unanswered. Our previous work demonstrated high-level production of tumor necrosis factor alpha, interleukin 1 beta, arachidonic acid metabolites, and platelet-activating factor (PAF) from HIV-infected monocytes and astroglia (H. E. Gendelman, P. Genis, M. Jett, and H. S. L. M. Nottet, in E. Major, ed., Technical Advances in AIDS Research in the Nervous System, in press; P. Genis, M. Jett, E. W. Bernton, H. A. Gelbard, K. Dzenko, R. Keane, L. Resnick, D. J. Volsky, L. G. Epstein, and H. E. Gendelman, J. Exp. Med. 176:1703-1718, 1992). These factors, together, were neurotoxic. The relative role(s) of each of these candidate neurotoxins in HIV-1-related CNS dysfunction was not unraveled by these initial experiments. We now report that PAF is produced during HIV-1-infected monocyte-astroglia interactions. PAF was detected at high levels in CSF of HIV-1-infected patients with immunosuppression and signs of CNS dysfunction. The biologic significance of the results for neurological disease was determined by addition of PAF to cultures of primary human fetal cortical or rat postnatal retinal ganglion neurons. Here, PAF at concentrations of > or = 300 pg/ml produced neuronal death. The N-methyl-D-aspartate receptor antagonist MK-801 or memantine partially blocked the neurotoxic effects of PAF. The identification of PAF as an HIV-1-induced neurotoxin provides new insights into how HIV-1 causes neurological impairment and how it may ultimately be ameliorated. PMID:8207837

  17. Platelet-derived growth factor induces phosphorylation of a 64-kDa nuclear protein

    SciTech Connect

    Shawver, L.K.; Pierce, G.F.; Kawahara, R.S.; Deuel, T.F.

    1989-01-15

    The platelet-derived growth factor (PDGF) stimulated the phosphorylation of a nuclear protein of 64 kDa (pp64) in nuclei of nontransformed normal rat kidney (NRK) cells. Low levels of phosphorylation of pp64 were observed in nuclei of serum-starved NRK cells. Fetal calf serum (FCS), PDGF, and homodimeric v-sis and PDGF A-chain protein enhanced the incorporation of 32P into pp64 over 4-fold within 30 min and over 8-fold within 2 h of exposure of NRK cells to the growth factors. In contrast, constitutive phosphorylation of 32P-labeled pp64 in nuclei of NRK cells transformed by the simian sarcoma virus (SSV) was high and only minimally stimulated by PDGF and FCS. 32P-Labeled pp64 was isolated from nuclei of PDGF-stimulated nontransformed NRK cells; the 32P of pp64 was labile in 1 M KOH, and pp64 was not significantly recognized by anti-phosphotyrosine antisera, suggesting that the PDGF-induced phosphorylation of pp64 occurred on serine or on threonine residues. However, pp64 from SSV-transformed NRK cell nuclei was significantly stable to base hydrolysis and was immunoprecipitated with anti-phosphotyrosine antisera, suggesting that pp64 from SSV-transformed cell nuclei is phosphorylated also on tyrosine. FCS, PDGF, and PDGF A- and B-chain homodimers thus stimulate the rapid time-dependent phosphorylation of a 64-kDa nuclear protein shortly after stimulation of responsive cells. The growth factor-stimulated phosphorylation of pp64 and the constitutive high levels of pp64 phosphorylation in cells transformed by SSV suggest important roles for pp64 and perhaps regulated nuclear protein kinases and phosphatases in cell division and proliferation.

  18. Low Molecular Weight Heparin Induced Skin Necrosis without Platelet Fall Revealing Immunoallergic Heparin Induced Thrombocytopenia

    PubMed Central

    Godet, Thomas; Perbet, Sébastien; Lebreton, Aurélien; Gayraud, Guillaume; Cayot, Sophie; Tremblay, Aymeric; Ravinet, Aurélie; Christophe, Sébastien; Guérin, Renaud; Pascal, Julien; Jabaudon, Matthieu; Hassan, Amr; Sapin, Anne-Françoise; Bazin, Jean-Etienne; Constantin, Jean-Michel

    2013-01-01

    Low molecular weight heparins (LMWH) are commonly used in the ICU setting for thromboprophylaxis as well as curative decoagulation as required during renal replacement therapy (RRT). A rare adverse event revealing immunoallergic LMWH induced thrombopenia (HIT) is skin necrosis at injection sites. We report the case of a patient presenting with skin necrosis witnessing an HIT after RRT, without thrombocytopenia. The mechanism remains unclear. Anti-PF4/heparin antibodies, functional tests (HIPA and/or SRA), and skin biopsy are of great help to evaluate differential diagnosis with a low pretest probability 4T's score. PMID:24307958

  19. Activation of human platelets by antibodies to thymocytes and beta 2-microglobulin. I. Qualitative and quantitative aspects of the platelet aggregation induced by HATG and SA beta 2mG.

    PubMed Central

    Csákó, G; Suba, E A; Wistar, R

    1980-01-01

    The platelet effect of antibody preparations known to have immunosuppressive action was investigated by a turbidimetric method in vitro. Both horse anti-human thymocyte globulin (HATG) and sheep anti-human beta 2-microglobulin IgG (SA beta 2mG) caused the platelets to aggregate in all human platelet-rich plasmas (PRP) tested. The aggregation was usually irreversible and characterized by a sigmoid curve. The action is specific for the antibodies in HATG and SA beta 2mG because control preparations (horse normal IgG and IgG fractions of sheep normal, anti-dog IgG and anti-human IgA sera) were ineffective; further, heating (30 min at 56 degrees C) and BaSO4 or Al(OH)3 adsorption of HATG and SA beta 2mG did not alter their aggregating capability. When HATG and SA beta 2mG were added together to PRP, they induced aggregation in a simple additive manner. High antibody doses tended to decrease the extent of aggregation. The effect of platelet count on aggregation varied with both the dose level ('low' or 'high') and type (HATG or SA beta 2mG) of the inducer antibody. Using fixed submaximal doses, four main aggregation patterns could be recognized among 60 PRP: (i) high responses to both HATG and SA beta 2mG; (ii) high to HATG, low to SA beta 2mG; (iii) low to HATG, high to SA beta 2mG; and (iv) low to both. The results provide guidelines for quantitative aggregation studies with platelet antibodies and suggest that HATG and SA beta 2mG act through distinct platelet membrane components, the receptor for the latter being the best characterized protein of the mammalian cell membrane. PMID:6156042

  20. Thrombin-induced translocation of GLUT3 glucose transporters in human platelets.

    PubMed Central

    Sorbara, L R; Davies-Hill, T M; Koehler-Stec, E M; Vannucci, S J; Horne, M K; Simpson, I A

    1997-01-01

    Platelets derive most of their energy from anaerobic glycolysis; during activation this requirement rises approx. 3-fold. To accommodate the high glucose flux, platelets express extremely high concentrations (155+/-18 pmol/mg of membrane protein) of the most active glucose transporter isoform, GLUT3. Thrombin, a potent platelet activator, was found to stimulate 2-deoxyglucose transport activity 3-5-fold within 10 min at 25 degrees C, with a half-time of 1-2 min. To determine the mechanism underlying the increase in glucose transport activity, an impermeant photolabel, [2-3H]2N-4-(1-azi-2,2,2-trifluoethyl)benzoyl-1,3, -bis-(d-mannose-4-ylozy)-2-propylamine, was used to covalently bind glucose transporters accessible to the extracellular milieu. In response to thrombin, the level of transporter labelling increased 2.7-fold with a half-time of 1-2 min. This suggests a translocation of GLUT3 transporters from an intracellular site to the plasma membrane in a manner analogous to that seen for the translocation of GLUT4 in insulin-stimulated rat adipose cells. To investigate whether a similar signalling pathway was involved in both systems, platelets and adipose cells were exposed to staurosporin and wortmannin, two inhibitors of GLUT4 translocation in adipose cells. Thrombin stimulation of glucose transport activity in platelets was more sensitive to staurosporin inhibition than was insulin-stimulated transport activity in adipose cells, but it was totally insensitive to wortmannin. This indicates that the GLUT3 translocation in platelets is mediated by a protein kinase C not by a phosphatidylinositol 3-kinase mechanism. In support of this contention, the phorbol ester PMA, which specifically activates protein kinase C, fully stimulated glucose transport activity in platelets and was equally sensitive to inhibition by staurosporin. This study provides a cellular mechanism by which platelets enhance their capacity to import glucose to fulfil the increased energy demands

  1. Cisplatin triggers platelet activation.

    PubMed

    Togna, G I; Togna, A R; Franconi, M; Caprino, L

    2000-09-01

    Clinical observations suggest that anticancer drugs could contribute to the thrombotic complications of malignancy in treated patients. Thrombotic microangiopathy, myocardial infarction, and cerebrovascular thrombotic events have been reported for cisplatin, a drug widely used in the treatment of many solid tumours. The aim of this study is to explore in vitro cisplatin effect on human platelet reactivity in order to define the potentially active role of platelets in the pathogenesis of cisplatin-induced thrombotic complications. Our results demonstrate that cisplatin increases human platelet reactivity (onset of platelet aggregation wave and thromboxane production) to non-aggregating concentrations of the agonists involving arachidonic acid metabolism. Direct or indirect activation of platelet phospholipase A(2) appears to be implicated. This finding contributes to a better understanding of the pathogenesis of thrombotic complications occurring during cisplatin-based chemotherapy.

  2. Platelet Donation

    MedlinePlus

    ... donating platelets, can I still donate blood? What blood types should donate platelets? Can I donate plasma at ... Community Learn About Blood Blood Facts and Statistics Blood Types Blood Components What Happens to Donated Blood Blood ...

  3. The Platelet Function Defect of Cardiopulmonary Bypass.

    DTIC Science & Technology

    1992-11-24

    fibrinolytic and coagulation systems occur during CPB,1 a platelet function defect is generally considered to be the primary CPB-induced hemostatic...platelets.39 OKM5 (provided by Dr. Patricia Rao, Ortho Diagnostic Systems , Raritan, NJ) is directed against platelet membrane GPIV.40 Flow Cytometric...22 after degranulation.7-14-16-18 Utilizing washed platelet systems , Nieuwenhuis et al.14 found a modest increase during CPB of the platelet

  4. Arachidonic Acid Metabolite 19(S)-HETE Induces Vasorelaxation and Platelet Inhibition by Activating Prostacyclin (IP) Receptor

    PubMed Central

    Chennupati, Ramesh; Nüsing, Rolf M.; Offermanns, Stefan

    2016-01-01

    19(S)-hydroxy-eicosatetraenoic acid (19(S)-HETE) belongs to a family of arachidonic acid metabolites produced by cytochrome P450 enzymes, which play critical roles in the regulation of cardiovascular, renal and pulmonary functions. Although it has been known for a long time that 19(S)-HETE has vascular effects, its mechanism of action has remained unclear. In this study we show that 19(S)-HETE induces cAMP accumulation in the human megakaryoblastic leukemia cell line MEG-01. This effect was concentration-dependent with an EC50 of 520 nM, insensitive to pharmacological inhibition of COX-1/2 and required the expression of the G-protein Gs. Systematic siRNA-mediated knock-down of each G-protein coupled receptor (GPCR) expressed in MEG-01 followed by functional analysis identified the prostacyclin receptor (IP) as the mediator of the effects of 19(S)-HETE, and the heterologously expressed IP receptor was also activated by 19(S)-HETE in a concentration-dependent manner with an EC50 of 567 nM. Pretreatment of isolated murine platelets with 19(S)-HETE blocked thrombin-induced platelets aggregation, an effect not seen in platelets from mice lacking the IP receptor. Furthermore, 19(S)-HETE was able to relax mouse mesenteric artery- and thoracic aorta-derived vessel segments. While pharmacological inhibition of COX-1/2 enzymes had no effect on the vasodilatory activity of 19(S)-HETE these effects were not observed in vessels from mice lacking the IP receptor. These results identify a novel mechanism of action for the CYP450-dependent arachidonic acid metabolite 19(S)-HETE and point to the existence of a broader spectrum of naturally occurring prostanoid receptor agonists. PMID:27662627

  5. Unfractionated and Low-Molecular-Weight Heparin and the Phosphodiesterase Inhibitors, IBMX and Cilostazol, Block Ex Vivo Equid Herpesvirus Type-1-Induced Platelet Activation.

    PubMed

    Stokol, Tracy; Serpa, Priscila Beatriz da Silva; Zahid, Muhammad N; Brooks, Marjory B

    2016-01-01

    Equid herpes virus type-1 (EHV-1) is a major pathogen of horses, causing abortion storms and outbreaks of herpes virus myeloencephalopathy. These clinical syndromes are partly attributed to ischemic injury from thrombosis in placental and spinal vessels. The mechanism of thrombosis in affected horses is unknown. We have previously shown that EHV-1 activates platelets through virus-associated tissue factor-initiated thrombin generation. Activated platelets participate in thrombus formation by providing a surface to localize coagulation factor complexes that amplify and propagate thrombin generation. We hypothesized that coagulation inhibitors that suppress thrombin generation (heparins) or platelet inhibitors that impede post-receptor thrombin signaling [phosphodiesterase (PDE) antagonists] would inhibit EHV-1-induced platelet activation ex vivo. We exposed platelet-rich plasma (PRP) collected from healthy horses to the RacL11 abortigenic and Ab4 neuropathogenic strains of EHV-1 at 1 plaque-forming unit/cell in the presence or absence of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) or the PDE inhibitors, 3-isobutyl-1methylxanthine (IBMX), and cilostazol. We assessed platelet activation status in flow cytometric assays by measuring P-selectin expression. We found that all of the inhibitors blocked EHV-1- and thrombin-induced platelet activation in a dose-dependent manner. Platelet activation in PRP was maximally inhibited at concentrations of 0.05 U/mL UFH and 2.5 μg/mL LMWH. These concentrations represented 0.1-0.2 U/mL anti-factor Xa activity measured in chromogenic assays. Both IBMX and cilostazol showed maximal inhibition of platelet activation at the highest tested concentration of 50 μM, but inhibition was lower than that seen with UFH and LMWH. Our results indicate that heparin anticoagulants and strong non-selective (IBMX) or isoenzyme-3 selective (cilostazol) PDE antagonists inhibit ex vivo EHV-1-induced platelet activation

  6. Unfractionated and Low-Molecular-Weight Heparin and the Phosphodiesterase Inhibitors, IBMX and Cilostazol, Block Ex Vivo Equid Herpesvirus Type-1-Induced Platelet Activation

    PubMed Central

    Stokol, Tracy; Serpa, Priscila B. S.; Zahid, Muhammad N.; Brooks, Marjory B.

    2016-01-01

    Equid herpes virus type-1 (EHV-1) is a major pathogen of horses, causing abortion storms and outbreaks of herpes virus myeloencephalopathy. These clinical syndromes are partly attributed to ischemic injury from thrombosis in placental and spinal vessels. The mechanism of thrombosis in affected horses is unknown. We have previously shown that EHV-1 activates platelets through virus-associated tissue factor-initiated thrombin generation. Activated platelets participate in thrombus formation by providing a surface to localize coagulation factor complexes that amplify and propagate thrombin generation. We hypothesized that coagulation inhibitors that suppress thrombin generation (heparins) or platelet inhibitors that impede post-receptor thrombin signaling [phosphodiesterase (PDE) antagonists] would inhibit EHV-1-induced platelet activation ex vivo. We exposed platelet-rich plasma (PRP) collected from healthy horses to the RacL11 abortigenic and Ab4 neuropathogenic strains of EHV-1 at 1 plaque-forming unit/cell in the presence or absence of unfractionated heparin (UFH), low-molecular-weight heparin (LMWH) or the PDE inhibitors, 3-isobutyl-1methylxanthine (IBMX), and cilostazol. We assessed platelet activation status in flow cytometric assays by measuring P-selectin expression. We found that all of the inhibitors blocked EHV-1- and thrombin-induced platelet activation in a dose-dependent manner. Platelet activation in PRP was maximally inhibited at concentrations of 0.05 U/mL UFH and 2.5 μg/mL LMWH. These concentrations represented 0.1–0.2 U/mL anti-factor Xa activity measured in chromogenic assays. Both IBMX and cilostazol showed maximal inhibition of platelet activation at the highest tested concentration of 50 μM, but inhibition was lower than that seen with UFH and LMWH. Our results indicate that heparin anticoagulants and strong non-selective (IBMX) or isoenzyme-3 selective (cilostazol) PDE antagonists inhibit ex vivo EHV-1-induced platelet activation

  7. The 20S proteasome core, active within apoptotic exosome-like vesicles, induces autoantibody production and accelerates rejection.

    PubMed

    Dieudé, Mélanie; Bell, Christina; Turgeon, Julie; Beillevaire, Deborah; Pomerleau, Luc; Yang, Bing; Hamelin, Katia; Qi, Shijie; Pallet, Nicolas; Béland, Chanel; Dhahri, Wahiba; Cailhier, Jean-François; Rousseau, Matthieu; Duchez, Anne-Claire; Lévesque, Tania; Lau, Arthur; Rondeau, Christiane; Gingras, Diane; Muruve, Danie; Rivard, Alain; Cardinal, Héloise; Perreault, Claude; Desjardins, Michel; Boilard, Éric; Thibault, Pierre; Hébert, Marie-Josée

    2015-12-16

    Autoantibodies to components of apoptotic cells, such as anti-perlecan antibodies, contribute to rejection in organ transplant recipients. However, mechanisms of immunization to apoptotic components remain largely uncharacterized. We used large-scale proteomics, with validation by electron microscopy and biochemical methods, to compare the protein profiles of apoptotic bodies and apoptotic exosome-like vesicles, smaller extracellular vesicles released by endothelial cells downstream of caspase-3 activation. We identified apoptotic exosome-like vesicles as a central trigger for production of anti-perlecan antibodies and acceleration of rejection. Unlike apoptotic bodies, apoptotic exosome-like vesicles triggered the production of anti-perlecan antibodies in naïve mice and enhanced anti-perlecan antibody production and allograft inflammation in mice transplanted with an MHC (major histocompatibility complex)-incompatible aortic graft. The 20S proteasome core was active within apoptotic exosome-like vesicles and controlled their immunogenic activity. Finally, we showed that proteasome activity in circulating exosome-like vesicles increased after vascular injury in mice. These findings open new avenues for predicting and controlling maladaptive humoral responses to apoptotic cell components that enhance the risk of rejection after transplantation.

  8. Attenuation of Folic Acid-Induced Renal Inflammatory Injury in Platelet-Activating Factor Receptor-Deficient Mice

    PubMed Central

    Doi, Kent; Okamoto, Koji; Negishi, Kousuke; Suzuki, Yoshifumi; Nakao, Akihide; Fujita, Toshiro; Toda, Akiko; Yokomizo, Takehiko; Kita, Yoshihiro; Kihara, Yasuyuki; Ishii, Satoshi; Shimizu, Takao; Noiri, Eisei

    2006-01-01

    Platelet-activating factor (PAF), a potent lipid mediator with various biological activities, plays an important role in inflammation by recruiting leukocytes. In this study we used platelet-activating factor receptor (PAFR)-deficient mice to elucidate the role of PAF in inflammatory renal injury induced by folic acid administration. PAFR-deficient mice showed significant amelioration of renal dysfunction and pathological findings such as acute tubular damage with neutrophil infiltration, lipid peroxidation observed with antibody to 4-hydroxy-2-hexenal (day 2), and interstitial fibrosis with macrophage infiltration associated with expression of monocyte chemoattractant protein-1 and tumor necrosis factor-α in the kidney (day 14). Acute tubular damage was attenuated by neutrophil depletion using a monoclonal antibody (RB6-8C5), demonstrating the contribution of neutrophils to acute phase injury. Macrophage infiltration was also decreased when treatment with a PAF antagonist (WEB2086) was started after acute phase. In vitro chemotaxis assay using a Boyden chamber demonstrated that PAF exhibits a strong chemotactic activity for macrophages. These results indicate that PAF is involved in pathogenesis of folic acid-induced renal injury by activating neutrophils in acute phase and macrophages in chronic interstitial fibrosis. Inhibiting the PAF pathway might be therapeutic to kidney injury from inflammatory cells. PMID:16651609

  9. Regulation of murine megakaryocyte size and ploidy by non-platelet-dependent mechanisms in radiation-induced megakaryocytopenia

    SciTech Connect

    Ebbe, S. )

    1991-09-01

    Megakaryocytic macrocytosis was evaluated in mice after irradiation with 6.5 Gy 60Co gamma rays. During the second and third months after sublethal irradiation, one or more of the following abnormalities of thrombocytopoiesis was present: thrombocytopenia, megakaryocytopenia, macromegakaryocytosis, a shift to higher ploidies, and enlargement of cells within ploidy groups. After transfusion-induced thrombocytosis, reductions in megakaryocyte size were delayed or absent relative to non-irradiated mice, and there was more of a tendency to shift to lower values for megakaryocyte ploidy. Mice with radiation-induced megakaryocytopenia failed to show rebound thrombocytosis during recovery from immunothrombocytopenia, in spite of further increases in megakaryocyte size and ploidy. The findings support the hypotheses that numbers of megakaryocytes may influence the regulation of megakaryocytopoiesis even when there is an excess of platelets and that ploidy distribution is not the sole determinant of the average size of a population of megakaryocytes. After irradiation, persistent megakaryocytopenia may not severely affect platelet production under steady-state conditions, but the ability of the marrow to respond to homeostatic regulation is compromised.

  10. Coronary vasoconstriction in the rat, isolated perfused heart induced by platelet-activating factor is mediated by leukotriene C4.

    PubMed Central

    Piper, P. J.; Stewart, A. G.

    1986-01-01

    Platelet-activating factor (Paf, 0.04-4.50 nmol) dose-dependently induced coronary vasoconstriction and decreased cardiac contractility in rat, isolated perfused hearts and concomitantly released leukotriene-like bioactivity into the cardiac effluent. Platelet-activating factor (0.9 nmol) induced an increase in 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), PGF2 alpha, PGE2 and thromboxane B2 (TXB2) measured by radioimmunoassay (RIA) of cardiac effluents following partial purification using C18 Sep-Paks. The leukotriene-like bioactivity released by Paf was identified as leukotriene C4 (LTC4) using a combination of isolation on reverse phase-h.p.l.c. (r.p.h.p.l.c.) and quantitation by RIA. In addition, LTB4 was also identified by r.p.h.p.l.c. and the levels, determined by RIA, were within the range having biological activity. The release of cyclo-oxygenase products by Paf was prevented by indomethacin (2.8 microM), markedly attenuated by diethylcarbamazine (7.7 mM) but unaffected by FPL 55712 (1.9 microM)-pretreatment. Furthermore, LTC4 (50 pmol) did not increase the release of the cyclo-oxygenase products measured. The release of LTB4 and LTC4 appeared to be unaffected by indomethacin pretreatment whereas diethylcarbamazine-pretreatment markedly inhibited release. The coronary vasoconstriction induced by Paf (0.9 nmol) was attenuated by pretreatment with indomethacin or diethylcarbamazine, whereas FPL 55712 caused a marked inhibition of the response. In contrast, the decrease in cardiac contractility was prevented by indomethacin or diethylcarbamazine and unaffected by FPL 55712 pretreatment. It is concluded that LTC4 may be largely responsible for the coronary vasoconstriction induced by Paf with cyclo-oxygenase products having a possible modulatory role whereas the latter appear to be involved in the Paf-induced decrease in cardiac contractility. PMID:3091131

  11. Immune complex induced pancreatitis: effect of BN 52021, a selective antagonist of platelet-activating factor.

    PubMed

    Jancar, S; De Giaccobi, G; Mariano, M; Mencia-Huerta, J M; Sirois, P; Braquet, P

    1988-05-01

    A model of acute pancreatitis was developed by induction of an immune complex mediated hypersensitivity reaction in rats. This acute inflammatory reaction was characterized by intense interstitial edema, neutrophil infiltration and margination, and congestion of small vessels whereas serum amylase levels remained unchanged. Microscopic examination of the pancreatic tissue revealed the presence of immune complex deposition around blood vessels and ducts. Vascular permeability, as measured by Evan's blue extravasation increased by 6 fold. In addition, circulating platelets dropped to 50% of normal levels. Injection of platelet-activating factor (PAF) in the peritoneal cavity of rats also produced an increase in vascular permeability in the pancreas. A selective PAF-antagonist, BN 52021 reduced by approximately 50% the increase in vascular permeability produced by immune complex in the pancreas as well as that elicited by intraperitoneal injection of PAF. These results suggest that PAF plays a role in the pathological manifestations of immune complex-mediated pancreatitis.

  12. Alterations in the extracellular catabolism of nucleotides and platelet aggregation induced by high-fat diet in rats: effects of α-tocopherol.

    PubMed

    Gutierres, Jessié M; Carvalho, Fabiano B; Schetinger, Maria Rosa C; Rodrigues, Marília V; Vieira, Juliano M; Maldonado, Paula; Araújo, Maria do Carmo S; Schmatz, Roberta; Stefanello, Naiara; Jaques, Jeandre A S; Costa, Marcio; Morsch, Vera; Mazzanti, Cinthia M; Pimentel, Victor; Lopes, Sonia Terezinha A; Spanevello, Roselia M

    2014-06-01

    The aim of this study was to assess whether α-tocopherol administration prevented alterations in the ectonucleotidase activities and platelet aggregation induced by high-fat diet in rats. Thus, we examined four groups of male rats which received standard diet, high-fat diet (HFD), α-tocopherol (α-Toc), and high-fat diet plus α-tocopherol. HFD was administered ad libitum and α-Toc by gavage using a dose of 50 mg/kg. After 3 months of treatment, animals were submitted to euthanasia, and blood samples were collected for biochemical assays. Results demonstrate that NTPDase, ectonucleotide pyrophosphatase/phosphodiesterase, and 5'-nucleotidase activities were significantly decreased in platelets of HFD group, while that adenosine deaminase (ADA) activity was significantly increased in this group in comparison to the other groups (P < 0.05). When rats that received HFD were treated with α-Toc, the activities of these enzymes were similar to the control, but ADA activity was significantly increased in relation to the control and α-Toc group (P < 0.05). HFD group showed an increased in platelet aggregation in comparison to the other groups, and treatment with α-Toc significantly reduced platelet aggregation in this group. These findings demonstrated that HFD alters platelet aggregation and purinergic signaling in the platelets and that treatment with α-Toc was capable of modulating the adenine nucleotide hydrolysis in this experimental condition.

  13. Nitric oxide mediates angiogenesis induced in vivo by platelet-activating factor and tumor necrosis factor-alpha.

    PubMed Central

    Montrucchio, G.; Lupia, E.; de Martino, A.; Battaglia, E.; Arese, M.; Tizzani, A.; Bussolino, F.; Camussi, G.

    1997-01-01

    We evaluated the role of an endogenous production of nitric oxide (NO) in the in vitro migration of endothelial cells and in the in vivo angiogenic response elicited by platelet-activating factor (PAF), tumor necrosis factor-alpha (TNF), and basic fibroblast growth factor (bFGF). The NO synthase inhibitor, N omega-nitro-L-arginine-methyl ester (L-NAME), but not its enantiomer D-NAME, prevented chemotaxis of endothelial cells induced in vitro by PAF and by TNF. The motogenic activity of TNF was also inhibited by WEB 2170, a specific PAF-receptor antagonist. In contrast, chemotaxis induced by bFGF was not prevented by L-NAME or by WEB 2170. Angiogenesis was studied in vivo in a murine model in which Matrigel was used as a vehicle for the delivery of mediators. In this model, the angiogenesis induced by PAF and TNF was inhibited by WEB 2170 and L-NAME but not by D-NAME. In contrast, angiogenesis induced by bFGF was not affected by L-NAME or by WEB 2170. TNF, but not bFGF, induced PAF synthesis within Matrigel. These results suggest that NO mediates the angiogenesis induced by PAF as well as that induced by TNF, which is dependent on the production of PAF. In contrast, the angiogenic effect of bFGF appears to be both PAF and NO independent. Images Figure 3 Figure 4 PMID:9250168

  14. Effect of some cyclooxygenase inhibitors on the increase in guanosine 3′:5′-cyclic monophosphate induced by NO-donors in human whole platelets

    PubMed Central

    Failli, Paola; Cecchi, Enrica; Tosti-Guerra, Cristina; Mugelli, Alessandro; Laffi, Giacomo; Zilletti, Lucilla; Giotti, Alberto

    1998-01-01

    The effect of the NSAIDs indomethacin, indoprofen, diclofenac and acetylsalicylic acid on the increase in guanosine 3′:5′-cyclic monophosphate (cyclic GMP) induced by nitric oxide-donor agents was tested in human whole platelets and in platelet crude homogenate.In whole platelets, indomethacin reduced the increase in cyclic GMP induced by the nitric oxide-donors (NO-donors) sodium nitroprusside (NaNP) and S-nitroso-N-acetylpenicillamine (SNAP) in a dose-dependent way, its IC50 being 13.7 μM and 15.8 μM, respectively.Of the other cyclooxygenase inhibitors tested, only indoprofen reduced the increase in cyclic GMP induced by both NO-donors in a dose-dependent way (IC50=32.7 μM, NaNP and 25.0 μM, SNAP), while acetylsalicylic acid (up to 1000 μM) and diclofenac (up to 100 μM) were ineffective.However, in platelet crude homogenate neither indomethacin nor indoprofen reduced the cyclic GMP production.Indomethacin (10 μM), indoprofen (30 μM), diclofenac (100 μM) and acetylsalicylic acid (1000 μM) showed a comparable efficacy in inhibiting platelet thromboxane B2 (TXB2) production, suggesting that the inhibitory effect of indomethacin and indoprofen on the increase in cyclic GMP induced by both NO-donors was not mediated by inhibition of cyclooxygenase.In vitro, the NSAIDs analysed did not interfere with nitrite production of SNAP.The unhomogeneous behaviour of NSAIDs on the increase in cyclic GMP induced by NO-donors in whole platelets may contribute to the different pharmacological and toxicological characteristics of the drugs, providing new knowledge on the effect of indomethacin and indoprofen. PMID:9579743

  15. Variability of the thrombin- and ADP-induced Ca2+ response among human platelets measured using fluo-3 and fluorescent videomicroscopy.

    PubMed

    Tao, J; Rose, B; Haynes, D H

    1996-05-28

    The intracellular free Ca2+ concentration ([Ca2+]cyt) of individual human platelets localized between siliconized glass cover slips was determined at rest and after stimulation with thrombin and ADP using the Ca2+ indicator fluo-3 (0.97 +/- 0.30 mmol/l cell volume) with fluorescence video microscopy. Resting [Ca2+]cyt in the presence of 2 mM external Ca2+ showed only small inter-platelet variability ([Ca2+]cyt = 86 +/- 30 (S.D.) nM). Resting [Ca2+]cyt of individual fluo-3-loaded platelets measured as a function of time had a S.D. of 10 nM or 12% (S.D./mean). Individual platelets showed no affinity for the siliconized support and their [Ca2+]cyt showed no tendency to oscillate in either the resting or in the activated state. When 0.2 U/ml thrombin or 20 microM ADP were added, all platelets showed a characteristic Ca2+ transient whereby [Ca2+]cyt increased to peak values within 8-12 sec and then declined. The Ca2+ transients measured with fluo-3 were in approximate synchrony but peak [Ca2+]cyt values showed large inter-platelet variability. The ensemble average peak [Ca2+]cyt for thrombin and ADP were 672 +/- 619 (S.D.) nM and 640 +/- 642 (S.D.) nM, respectively. Thus inter-platelet variations (S.D./mean) were 92% or 100% as large as the average measured values. Mathematically-constructed averages of the single platelet experiments agreed reasonably well with platelet-averaged values obtained in parallel experiments with stirred platelet suspensions in a plastic cuvette, measured with a conventional spectrofluorometer. Peak [Ca2+]cyt values reflecting dense tubular Ca2+ release alone (external Ca2+ removed) also showed large interplatelet variation (171 +/- 105 (S.D.) nM with thrombin and 183 +/- 134 (S.D.) nM with ADP). Dense tubular Ca2+ release induced by cyclopiazonic acid (a dense tubular Ca2+-ATPase inhibitor) gave peak [Ca2+]cyt of 289 +/- 170 nM. Thus the size of the dense tubular Ca2+ pool has an inter-platelet variation of 59% (S.D./mean). Variability of

  16. Quantification of the Blood Platelet Reactivity in the ADP-Induced Model of Non-Lethal Pulmonary Thromboembolism in Mice with the Use of Laser Doppler Flowmetry

    PubMed Central

    Przygodzki, Tomasz; Talar, Marcin; Blazejczyk, Agnieszka; Kalchenko, Vyacheslav; Watala, Cezary

    2016-01-01

    Introduction The paper describes an alternative method for quantification of in vivo ADP-induced thromboembolism. The aim of the studies was to develop a method of quantification which would not require either extravasation or labelling of platelets. Our proposed approach is based on the monitoring of changes of blood flow with the use of laser Doppler flowmetry. Materials and Methods Mice of C57Bl strain were used in the study. ADP was injected to the vena cava and blood flow was monitored with the use of a laser Doppler flowmeter in the mesentery. Measurements in platelet-depleted mice, mice pretreated with cangrelor, an ADP receptor antagonist, and eptifibatide, a blocker of fibrinogen binding to GPIIbIIIa, were conducted as the proof-of-concept in the performed experiments. Intravital microscopy and ex vivo imaging of organs was performed to identify the sites of aggregate formation resulting from ADP injection. Results The injection of ADP resulted in a dose-dependent reduction of the blood flow in the mesentery. These responses were fully attributable to blood platelet aggregation, as shown by the lack of the effect in platelet-depleted mice, and significantly reduced responses in mice pretreated with cangrelor and eptifibatide. No platelet aggregate formation in mesenteric vessels was revealed by intravital microscopy, while ex vivo imaging showed accumulation of fluorescent labelled platelets in the lung. Conclusions Injection of ADP to the venous system results in the formation of platelet aggregates predominantly in the lung. This results in reversible blood flow cessation in peripheral blood vessels. The measurement of this blood flow cessation in the mesentery allows indirect measurement of ADP-induced pulmonary thromboembolism. We suggest that this approach can be useful for in vivo screening for antiplatelet drug candidates. PMID:26751810

  17. Surface proteome analysis identifies platelet derived growth factor receptor-alpha as a critical mediator of transforming growth factor-beta-induced collagen secretion.

    PubMed

    Heinzelmann, Katharina; Noskovičová, Nina; Merl-Pham, Juliane; Preissler, Gerhard; Winter, Hauke; Lindner, Michael; Hatz, Rudolf; Hauck, Stefanie M; Behr, Jürgen; Eickelberg, Oliver

    2016-05-01

    Fibroblasts are extracellular matrix-producing cells in the lung. Fibroblast activation by transforming growth factor-beta leads to myofibroblast-differentiation and increased extracellular matrix deposition, a hallmark of pulmonary fibrosis. While fibroblast function with respect to migration, invasion, and extracellular matrix deposition has been well-explored, little is known about the surface proteome of lung fibroblasts in general and its specific response to fibrogenic growth factors, in particular transforming growth factor-beta. We thus performed a cell-surface proteome analysis of primary human lung fibroblasts in presence/absence of transforming growth factor-beta, followed by characterization of our findings using FACS analysis, Western blot, and siRNA-mediated knockdown experiments. We identified 213 surface proteins significantly regulated by transforming growth factor-beta, platelet derived growth factor receptor-alpha being one of the top down-regulated proteins. Transforming growth factor beta-induced downregulation of platelet derived growth factor receptor-alpha induced upregulation of platelet derived growth factor receptor-beta expression and phosphorylation of Akt, a downstream target of platelet derived growth factor signaling. Importantly, collagen type V expression and secretion was strongly increased after forced knockdown of platelet derived growth factor receptor-alpha, an effect that was potentiated by transforming growth factor-beta. We therefore show previously underappreciated cross-talk of transforming growth factor-beta and platelet derived growth factor signaling in human lung fibroblasts, resulting in increased extracellular matrix deposition in a platelet derived growth factor receptor-alpha dependent manner. These findings are of particular importance for the treatment of lung fibrosis patients with high pulmonary transforming growth factor-beta activity.

  18. Heterogenous graft rejection pathways in class I major histocompatibility complex-disparate combinations and their differential susceptibility to immunomodulation induced by intravenous presensitization with relevant alloantigens

    PubMed Central

    1991-01-01

    The present study investigates the heterogeneity of graft rejection pathways in class I major histocompatibility complex (MHC)-disparate combinations and the susceptibility of each pathway to immunomodulation induced by intravenous presensitization with alloantigens. Depletion of CD8+ T cells was induced by repeated administration of anti-CD8 monoclonal antibody. CD8+ T cell-depleted mice failed to generate anti- allo class I MHC cytotoxic T cell (CTL) responses but exhibited anti- allo class I MHC T cell responses, such as mixed lymphocyte reaction (MLR)/IL-2 production, that were induced by CD4+ T cells. In contrast, donor-specific intravenous presensitization (DSP), as a model of donor- specific transfusion, induced almost complete elimination of CD4+ and CD8+ T cell-mediated MLR/IL-2 production, whereas this regimen did not affect the generation of CTL responses induced by DSP-resistant elements (CD8+ CTL precursors and CD4+ CTL helpers). Prolongation of skin graft survival was not induced by either of the above two regimens alone, but by the combination of these. Prolonged graft survival was obtained irrespective of whether the administration of anti-CD8 antibody capable of eliminating CTL was started before or after DSP. The combination of DSP with injection of anti-CD4 antibody also effectively prolonged graft survival. However, this was the case only when the injection of antibody was started before DSP, because such antibody administration was capable of inhibiting the generation of CTL responses by eliminating DSP-resistant CD4+ CTL helpers. These results indicate that (a) the graft rejection in class I-disparate combinations is induced by CD8+ CTL-involved and -independent pathways that are resistant and susceptible to DSP, respectively; (b) DSP contributes to, but is not sufficient for, the prolongation of graft survival; and (c) the suppression of graft rejection requires an additional treatment for reducing DSP-resistant CTL responses. The results are

  19. Spontaneous heparin-induced thrombocytopenia syndrome without any proximate heparin exposure, infection, or inflammatory condition: Atypical clinical features with heparin-dependent platelet activating antibodies.

    PubMed

    Okata, Takuya; Miyata, Shigeki; Miyashita, Fumio; Maeda, Takuma; Toyoda, Kazunori

    2015-01-01

    Recent studies suggest that a thromboembolic disorder resembling heparin-induced thrombocytopenia (HIT), so-called spontaneous HIT syndrome, can occur in patients without any history of heparin exposure. It is likely due to anti-platelet factor 4 (PF4)/polyanion antibodies induced by other polyanions, such as bacterial surfaces and nucleic acids. We describe an atypical case of spontaneous HIT syndrome. A 70-year-old man suddenly presented with acute cerebral sinus thrombosis (CST). Soon after the initiation of unfractionated heparin (UFH) for the treatment of CST, his platelet count fell precipitously and he developed deep vein thrombosis, a clinical picture consistent with rapid-onset HIT but without any proximate episodes of heparin exposure, infection, trauma, surgery, or other acute illness. Antigen assays and a washed platelet activation assay indicated that the patient already possessed anti-PF4/heparin IgG antibodies with heparin-dependent platelet activation properties on admission. Cessation of UFH and initiation of argatroban resulted in prompt recovery of his platelet count without further thromboembolic events. We identified two similar cases in the literature. However, these patients do not meet the recently proposed criteria for spontaneous HIT syndrome. Even in atypical cases, however, inappropriate or delayed diagnosis of HIT appears to be associated with worse outcomes. We propose that these atypical cases should be included in the category of spontaneous HIT syndrome.

  20. Detection of cardiac transplant rejection with radiolabeled lymphocytes. [Rats

    SciTech Connect

    Bergmann, S.R.; Lerch, R.A.; Carlson, E.M.; Saffitz, J.E.; Sobel, B.E.

    1982-03-01

    To determine whether rejections of cardiac transplants could be detected specifically and non-invasively by lymphocytes labeled with indium-111 (111In), we studied 36 allogeneic and 14 isogeneic heterotopic cardiac transplants in rats. Allogeneic grafts accumulated autologous 111In-lymphocytes, detectable scintigraphically 24 hours after i.v. injection of the labeled cells. At the time of peak histologic rejection, the allogeneic grafts accumulated 92. +/- 4.8 times more activity than the native hearts (determined by well counting). The tissue-to-blood ratio in the rejecting transplants was 3.7 +/- 2.2; total uptake by the graft was 2.9 +/- 2.1% of the injected dose. Autoradiography confirmed that graft radioactivity was associated with labeled lymphocytes. In contrast, isogeneic grafts showed no signs of rejection and did not accumulate radioactivity. Because conventionally isolated and labeled lymphocytes are often contaminated with platelets, we prepared both 111In-platelets and purified 111In-lymphocytes for use in additional experiments. Allogeneic grafts accumulated platelets and purified lymphocytes independently. Thus, deposition of immunologically active cells in the rejecting graft representing specific pathophysiologic events can be detected. The results suggest that rejection of cardiac transplants can be detected noninvasively, potentially facilitating objective early clinical detection of rejection and titration of antirejection therapy.

  1. Early diagnosis of acute postoperative renal transplant rejection

    SciTech Connect

    Tisdale, P.L.; Collier, B.D.; Kauffman, H.M.; Adams, M.B.; Isitman, A.T.; Hellman, R.S.; Rao, S.A.; Joestgen, T.; Krohn, L.

    1985-05-01

    A prospective evaluation of In-111 labeled autologous platelet scintigraphy for the early diagnosis of acute postoperative renal transplant rejection was undertaken. To date, 28 consecutive patients between 7 and 14 days post-op have been injected with 500..mu..Ci of In-111 platelets followed by imaging at 24 and 48 hours. Activity within the renal transplant exceeding activity in the adjacent iliac vessels was considered to be evidence of rejection, and both chemical evidence and clinical impression of rejection at 5 days after completion of imaging was accepted as proof of ongoing or incipient rejection at the time of scintigraphy. In addition, to visual inspection, independent quantitative analysis compared the area-normalized activity over the transplant with the adjacent iliac vessels (normal <1.0). For 5 patients, positive In-111 scintigraphy was present before convincing clinical evidence of rejection. In-111 platelet scintigraphy is useful not only to confirm the clinical diagnosis of rejection but also to establish the early, pre-clinical diagnosis of incipient acute postoperative renal transplant rejection.

  2. Oxidative response of neutrophils to platelet-activating factor is altered during acute ruminal acidosis induced by oligofructose in heifers

    PubMed Central

    Concha, Claudia; Carretta, María Daniella; Alarcón, Pablo; Conejeros, Ivan; Gallardo, Diego; Hidalgo, Alejandra Isabel; Tadich, Nestor; Cáceres, Dante Daniel; Hidalgo, María Angélica

    2014-01-01

    Reactive oxygen species (ROS) production is one of the main mechanisms used to kill microbes during innate immune response. D-lactic acid, which is augmented during acute ruminal acidosis, reduces platelet activating factor (PAF)-induced ROS production and L-selectin shedding in bovine neutrophils in vitro. This study was conducted to investigate whether acute ruminal acidosis induced by acute oligofructose overload in heifers interferes with ROS production and L-selectin shedding in blood neutrophils. Blood neutrophils and plasma were obtained by jugular venipuncture, while ruminal samples were collected using rumenocentesis. Lactic acid from plasma and ruminal samples was measured by HPLC. PAF-induced ROS production and L-selectin shedding were measured in vitro in bovine neutrophils by a luminol chemiluminescence assay and flow cytometry, respectively. A significant increase in ruminal and plasma lactic acid was recorded in these animals. Specifically, a decrease in PAF-induced ROS production was observed 8 h after oligofructose overload, and this was sustained until 48 h post oligofructose overload. A reduction in PAF-induced L-selectin shedding was observed at 16 h and 32 h post oligofructose overload. Overall, the results indicated that neutrophil PAF responses were altered in heifers with ruminal acidosis, suggesting a potential dysfunction of the innate immune response. PMID:25013355

  3. Oxidative response of neutrophils to platelet-activating factor is altered during acute ruminal acidosis induced by oligofructose in heifers.

    PubMed

    Concha, Claudia; Carretta, María Daniella; Alarcón, Pablo; Conejeros, Ivan; Gallardo, Diego; Hidalgo, Alejandra Isabel; Tadich, Nestor; Cáceres, Dante Daniel; Hidalgo, María Angélica; Burgos, Rafael Agustín

    2014-01-01

    Reactive oxygen species (ROS) production is one of the main mechanisms used to kill microbes during innate immune response. D-lactic acid, which is augmented during acute ruminal acidosis, reduces platelet activating factor (PAF)-induced ROS production and L-selectin shedding in bovine neutrophils in vitro. This study was conducted to investigate whether acute ruminal acidosis induced by acute oligofructose overload in heifers interferes with ROS production and L-selectin shedding in blood neutrophils. Blood neutrophils and plasma were obtained by jugular venipuncture, while ruminal samples were collected using rumenocentesis. Lactic acid from plasma and ruminal samples was measured by HPLC. PAF-induced ROS production and L-selectin shedding were measured in vitro in bovine neutrophils by a luminol chemiluminescence assay and flow cytometry, respectively. A significant increase in ruminal and plasma lactic acid was recorded in these animals. Specifically, a decrease in PAF-induced ROS production was observed 8 h after oligofructose overload, and this was sustained until 48 h post oligofructose overload. A reduction in PAF-induced L-selectin shedding was observed at 16 h and 32 h post oligofructose overload. Overall, the results indicated that neutrophil PAF responses were altered in heifers with ruminal acidosis, suggesting a potential dysfunction of the innate immune response.

  4. A Histologically Distinctive Interstitial Pneumonia Induced by Overexpression of the Interleukin 6, Transforming Growth Factor β1, or Platelet-Derived Growth Factor B Gene

    NASA Astrophysics Data System (ADS)

    Yoshida, Mitsuhiro; Sakuma, Junko; Hayashi, Seiji; Abe, Kin'ya; Saito, Izumu; Harada, Shizuko; Sakatani, Mitsunoir; Yamamoto, Satoru; Matsumoto, Norinao; Kaneda, Yasufumi; Kishmoto, Tadamitsu

    1995-10-01

    Interstitial pneumonia is characterized by alveolitis with resulting fibrosis of the interstitium. To determine the relevance of humoral factors in the pathogenesis of interstitial pneumonia, we introduced expression vectors into Wistar rats via the trachea to locally overexpress humoral factors in the lungs. Human interleukin (IL) 6 and IL-6 receptor genes induced lymphocytic alveolitis without marked fibroblast proliferation. In contrast, overexpression of human transforming growth factor β1 or human platelet-derived growth factor B gene induced only mild or apparent cellular infiltration in the alveoli, respectively. However, both factors induced significant proliferation of fibroblasts and deposition of collagen fibrils. These histopathologic changes induced by the transforming growth factor β1 and platelet-derived growth factor B gene are partly akin to those changes seen in lung tissues from patients with pulmonary fibrosis and markedly contrast with the changes induced by overexpression of the IL-6 and IL-6 receptor genes that mimics lymphocytic interstitial pneumonia.

  5. Impact of reticulated platelets on antiplatelet response to thienopyridines is independent of platelet turnover.

    PubMed

    Stratz, Christian; Nührenberg, Thomas; Amann, Michael; Cederqvist, Marco; Kleiner, Pascal; Valina, Christian M; Trenk, Dietmar; Neumann, Franz-Josef; Hochholzer, Willibald

    2016-10-28

    Reticulated platelets are associated with impaired antiplatelet response to thienopyridines. It is uncertain whether this interaction is caused by a decreased drug exposure due to high platelet turnover reflected by elevated levels of reticulated platelets or by intrinsic properties of reticulated platelets. This study sought to investigate if the impact of reticulated platelets on early antiplatelet response to thienopyridines is mainly caused by platelet turnover as previously suggested. Elective patients undergoing coronary intervention were randomised to loading with clopidogrel 600 mg or prasugrel 60 mg (n=200). Adenosine diphosphate (ADP)-induced platelet reactivity was determined by impedance aggregometry before, at 30, 60, 90, and 120 minutes and at day 1 after loading. Immature platelet count was assessed as marker of reticulated platelets by flow cytometry. Platelet reactivity increased with rising levels of immature platelet count in both groups. This effect was more distinctive in patients on clopidogrel as compared to patients on prasugrel. Overall, immature platelet count correlated well with on-treatment platelet reactivity at all time-points (p < 0.001). These correlations did not change over time in the entire cohort as well as in patients treated with clopidogrel or prasugrel indicating an effect independent of platelet turnover (comparison of correlations 120 minutes/day 1: p = 0.64). In conclusion, the association of immature platelet count with impaired antiplatelet response to thienopyridines is similar early and late after loading. This finding suggests as main underlying mechanism another effect of reticulated platelets on thienopyridines than platelet turnover.

  6. Thrombin-activated platelets induce proliferation of human skin fibroblasts by stimulating autocrine production of insulin-like growth factor-1.

    PubMed

    Giacco, Ferdinando; Perruolo, Giuseppe; D'Agostino, Elio; Fratellanza, Giorgio; Perna, Enzo; Misso, Saverio; Saldalamacchia, Gennaro; Oriente, Francesco; Fiory, Francesca; Miele, Claudia; Formisano, Salvatore; Beguinot, Francesco; Formisano, Pietro

    2006-11-01

    Platelet components have found successful clinical utilization to initiate or to accelerate tissue-repair mechanisms. However, the molecular pathways by which platelet factors contribute to tissue regeneration have not been fully elucidated. We have studied the effect of thrombin-activated platelets (TAPs) on cell growth in vivo and in cultured cell systems. Application of TAPs to ulcerative skin lesions of diabetic patients induced local activation of ERK1/2 and Akt/PKB. Moreover, when applied to cultured human skin fibroblasts, TAPs promoted cell growth and DNA synthesis and activated platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF)-1 receptor tyrosine kinases. PDGF was released by TAPs and rapidly achieved a plateau. At variance, the release of IGF-1 was mainly provided by the TAPs-stimulated fibroblasts and progressively increased up to 48 h. The PDGF-R blocker Ag1296 reduced the activation of Akt/PKB and, at a lesser extent, of ERK1/2. Conversely, inhibition of IGF-1 signaling by Ag1024 and expression of a dominant-negative IGF-1R mutant selectively reduced the stimulation of ERK1/2 by TAPs and fibroblast-released factors, with minor changes of Akt/PKB activity. Thus, platelet factors promote fibroblast growth by acutely activating Akt/PKB and ERK1/2. Sustained activation of ERK1/2, however, requires autocrine production of IGF-1 by TAPs-stimulated fibroblasts.

  7. [Stereological analysis of the degranulation and the contraction of platelets. Application to the ultrastructural study of thrombin induced excretion in vitro].

    PubMed

    Bryon, P A; Lagarde, M; Dechavanne, M

    1975-12-01

    A stereological model, which provides quantitative information on the morphology of the platelet release reaction as isolated from platelet aggregation, was developed for the human platelets separated from blood by Mustard's procedure. Three morphologically defined spaces (granules, surface-connected canalicular system S.C.S., cytoplasm) were used to characterize platelet degranulation (with the variation of the volume density of the granules) and contraction (with the variation of the volume density of both granules and S.C.S.). This model was applied to the evaluation of ultrastructural changes associated with the thrombin-induced release reaction. Degranulation and contraction were associated in the platelets which had been allowed to release for 1,5 and 150 sec. Under conditions of the study, prostaglandins E1 (10(-7) M) inhibited both degranulation and contraction (p less than 0,001). Aspirin (10(-4) M) only inhibited contraction (p less than 0.01) and dibutyryl-AMPc (10(-4)) only inhibited granulation (p less than 0,001).

  8. Typing for human platelet alloantigens.

    PubMed

    Juji, T; Saji, H; Satake, M; Tokunaga, K

    1999-01-01

    Antibodies to platelet alloantigens, and sometimes to isoantigens, induce severe clinical problems such as neonatal alloimmune thrombocytopenia (NAIT), post-transfusion purpura (PTP) and refractoriness to platelet transfusions (PTR). For example, NAIT affects approximately 1 in 5,000 live births. It is essential, therefore, to screen pregnant women for platelet antibodies in order to save babies' lives. Almost 40 years ago, two platelet alloantigen systems were discovered using relatively simple methods, namely the platelet agglutination test and the complement fixation test. However, these methods were not sensitive enough to identify all antibodies in mothers and patients, even in those with severe clinical problems. Tremendous effort has been devoted to establish more sensitive and reliable methods. In recent years, excellent new serological and immunochemical methods have been established and several new platelet antigen systems have been discovered. Simultaneously, newly developed molecular genetic techniques have been introduced for the typing and analysis of human platelet alloantigen systems. These methods allow DNA typing for cases in which serological typing is not available. In this article, the history of studies on human platelet alloantigen systems and isoantigens, the nomenclature of platelet alloantigen systems and their alleles, the present status of antibody detection and typing techniques and, finally, ethnic variations in platelet antigen profiles are reviewed.

  9. Resveratrol inhibits collagen-induced platelet stimulation through suppressing NADPH oxidase and oxidative inactivation of SH2 domain-containing protein tyrosine phosphatase-2.

    PubMed

    Jang, Ji Yong; Min, Ji Hyun; Wang, Su Bin; Chae, Yun Hee; Baek, Jin Young; Kim, Myunghee; Ryu, Jae-Sang; Chang, Tong-Shin

    2015-12-01

    Reactive oxygen species (ROS) produced upon collagen stimulation are implicated in propagating various platelet-activating pathways. Among ROS-producing enzymes, NADPH oxidase (NOX) is largely responsible for collagen receptor-dependent ROS production. Therefore, NOX has been proposed as a novel target for the development of antiplatelet agent. We here investigate whether resveratrol inhibits collagen-induced NOX activation and further examine the effects of resveratrol on ROS-dependent signaling pathways in collagen-stimulated platelets. Collagen-induced superoxide anion production in platelets was inhibited by resveratrol. Resveratrol suppressed collagen-induced phosphorylation of p47(phox), a major regulatory subunit of NOX. Correlated with the inhibitory effects on NOX, resveratrol protected SH2 domain-containing protein tyrosine phosphatase-2 (SHP-2) from ROS-mediated inactivation and subsequently attenuated the specific tyrosine phosphorylation of key components (spleen tyrosine kinase, Vav1, Bruton's tyrosine kinase, and phospholipase Cγ2) for collagen receptor signaling cascades. Resveratrol also inhibited downstream responses such as cytosolic calcium elevation, P-selectin surface exposure, and integrin-αIIbβ3 activation. Furthermore, resveratrol inhibited platelet aggregation and adhesion in response to collagen. The antiplatelet effects of resveratrol through the inhibition of NOX-derived ROS production and subsequent oxidative inactivation of SHP-2 suggest that resveratrol is a potential compound for prevention and treatment of thrombovascular diseases.

  10. The effect of polyphenolic-polysaccharide conjugates from selected medicinal plants of Asteraceae family on the peroxynitrite-induced changes in blood platelet proteins.

    PubMed

    Saluk-Juszczak, Joanna; Pawlaczyk, Izabela; Olas, Beata; Kołodziejczyk, Joanna; Ponczek, Michal; Nowak, Pawel; Tsirigotis-Wołoszczak, Marta; Wachowicz, Barbara; Gancarz, Roman

    2010-12-01

    Lots of plants belonging to Asteraceae family are very popular in folk medicine in Poland. These plants are also known as being rich in acidic polysaccharides, due to the presence of hexuronic acids or its derivatives. Our preliminary experiments have shown that the extract from Conyza canadensis L. possesses various biological activity, including antiplatelet, antiocoagulant and antioxidant properties. The aim of our study was to assess if macromolecular glycoconjugates from selected herbal plants of Asteraceae family: Achillea millefolium L., Arnica montana L., Echinacea purpurea L., Solidago virgaurea L., Chamomilla recutita (L.) Rauschert., and Conyza canadensis L. protect platelet proteins against nitrative and oxidative damage induced by peroxynitrite, which is responsible for oxidative/nitrative modifications of platelet proteins: the formation of 3-nitrotyrosine and carbonyl groups. These modifications may lead to changes of blood platelet functions and can have pathological consequences. The role of these different medicinal plants in the defence against oxidative/nitrative stress in human platelets is still unknown, therefore the oxidative damage to platelet proteins induced by peroxynitrite and protectory effects of tested conjugates by the estimation of carbonyl group level and nitrotyrosine formation (a marker of protein nitration) were studied in vitro. The antioxidative properties of the polyphenolic-polysaccharide conjugates from selected tested medicinal plants were also compared with the action of a well characterized antioxidative commercial polyphenol - resveratrol (3,4',5-trihydroxystilbene). The obtained results demonstrate that the compounds from herbal plants: A. millefolium, A. montana, E. purpurea, C. recutita, S. virgaurea, possess antioxidative properties and protect platelet proteins against peroxynitrite toxicity in vitro, similar to the glycoconjugates from C. canadensis. However, in the comparative studies, the polyphenolic

  11. Combination of monoclonal antibodies with DST inhibits accelerated rejection mediated by memory T cells to induce long-lived heart allograft acceptance in mice.

    PubMed

    Shao, Wei; Chen, Jibing; Dai, Helong; Peng, Yuanzheng; Wang, Feng; Xia, Junjie; Thorlacius, Henrik; Zhu, Qi; Qi, Zhongquan

    2011-08-30

    Donor-reactive memory T cells mediated accelerated rejection is known as a barrier to the survival of transplanted organs. We investigated the combination of different monoclonal antibodies (mAbs) and donor-specific transfusion (DST) in memory T cells-based adoptive mice model. In the presence of donor-reactive memory T cells, the mean survival time (MST) of grafts in the anti-CD40L/LFA-1/DST group was 49.8d. Adding anti-CD44/CD70 mAbs to anti-CD40L/LFA-1/DST treatment. The MST was more than 100 d (MST>100 d). Compared with anti-CD40L/LFA-1/DST group, anti-CD40L/LFA-1/CD44/CD70/DST group notably reduced the expansion of memory T cells, enhanced the proportion of CD4+Foxp3+ regulatory T cells (Tregs) and suppressed donor-specific responses. Our data suggest that anti-CD40L/LFA-1/CD44/CD70mAbs and DST can synergistically inhibit accelerated rejection mediated by memory T cells to induce long-lived heart allograft acceptance in mice.

  12. Acetal phosphatidic acids: novel platelet aggregating agents.

    PubMed

    Brammer, J P; Maguire, M H; Walaszek, E J; Wiley, R A

    1983-05-01

    1 Palmitaldehyde, olealdehyde and linolealdehyde acetal phosphatidic acids induced rapid shape change and dose-dependent biphasic aggregation of human platelets in platelet-rich plasma; aggregation was reversible at low doses and irreversible at high doses of the acetal phosphatidic acids. The palmitaldehyde congener elicited monophasic dose-dependent aggregation of sheep platelets in platelet-rich plasma.2 The threshold concentration for palmitaldehyde acetal phosphatidic acid (PGAP)-induced platelet aggregation was 2.5-5 muM for human platelets and 0.25-0.5 muM for sheep platelets. PGAP was 4-5 times as potent versus human platelets as the olealdehyde and linolealdehyde acetal phosphatidic acids, which were equipotent.3 PGAP-induced irreversible aggregation of [(14)C]-5-hydroxytryptamine ([(14)C]-5-HT)-labelled human platelets in platelet-rich plasma was accompanied by release of 44.0+/-2.4% (s.e.) of the platelet [(14)C]-5-HT; reversible aggregation was not associated with release. In contrast, PGAP-induced release of [(14)C]-5-HT-labelled sheep platelets was dose-dependent.4 The adenosine diphosphate (ADP) antagonist, 2-methylthio-AMP, and the cyclo-oxygenase inhibitor, aspirin, abolished PGAP-induced second phase aggregation and release in human platelets but did not affect the first, reversible, phase of aggregation. Both the first and second phases of PGAP-induced aggregation were abolished by chlorpromazine, by the phospholipase A(2) inhibitor, mepacrine, and by nmolar concentrations of prostaglandin E(1) (PGE(1)); these agents abolished the second, but not the first phase of ADP-induced aggregation.5 The related phospholipids, lecithin, lysolecithin and phosphatidic acid, at <100 muM, neither induced aggregation of human platelets in platelet-rich plasma, nor modified PGAP-induced aggregation; 1-palmityl lysophosphatidic acid elicited aggregation of human platelets at a threshold concentration of 100 muM.6 It is concluded that the acetal phosphatidic acids

  13. Dengue platelets meet Sir Arthur Conan Doyle.

    PubMed

    Bray, Paul F

    2013-11-14

    In this issue of Blood, Hottz et al provide compelling evidence that dengue virus (DV) induces (1) platelet synthesis of interleukin-1b (IL-1b); (2) platelet-derived IL-1b–containing microvesicles (MVs) that increase vascular permeability; and (3) DV-triggered inflammasome activation in platelets.

  14. Protective effect of platelet activating factor antagonists on cultured endothelial cell lysis induced by elastase or activated neutrophils.

    PubMed Central

    Renesto, P.; Vicart, P.; Paulin, D.; Chignard, M.

    1996-01-01

    1. The mechanism(s) responsible for injury of endothelial cells induced by human leukocyte elastase (HLE) was investigated in an immortalized venous human endothelial cell line (IVEC). 2. First, the proteinase concentrations and incubation delays necessary to trigger a significant IVEC cytotoxicity were determined by chromium assays. Thus, exposure of IVEC for 6 h to 10 micrograms ml-1 HLE resulted in 22 +/- 2.8% lysis and 36.4 +/- 5.4% detachment (mean +/- s.e. mean; n = 4; P < 0.05). 3. WEB 2086, a specific platelet-activating factor (PAF) receptor antagonist, induced a significant concentration-dependent decrease of such a lysis (39.6 +/- 7.7% protection at 100 microM; n = 4). This potential role for PAF was confirmed with two other antagonists of this lipid mediator, i.e., BN 52021 and RP 48740. 4. Finally, we demonstrated that pretreatment of IVEC with WEB 2086 protected significantly against cell lysis induced by stimulated human neutrophils, an experimental model in which HLE participates. PMID:8851508

  15. Rejection of partial-discharge-induced pulses in fission chambers designed for sodium-cooled fast reactors

    NASA Astrophysics Data System (ADS)

    Hamrita, H.; Jammes, C.; Galli, G.; Laine, F.

    2017-03-01

    Under given temperature and bias voltage conditions, partial discharges can create pulses in fission chambers. Based on experimental results, this phenomenon is in-depth investigated and discussed. A pulse-shape-analysis technique is proposed to discriminate neutron-induced pulses from partial-discharge-induced ones.

  16. Oxygen free-radical scavengers and immune destruction of murine islets in allograft rejection and multiple low-dose streptozocin-induced insulitis.

    PubMed

    Mendola, J; Wright, J R; Lacy, P E

    1989-03-01

    We examined the effects of desferrioxamine (DFX), a potent inhibitor of the formation of oxygen-derived hydroxyl radicals, and nicotinamide (NIC), a poly(ADP-ribose) synthetase inhibitor and a weak free-radical scavenger, on two models of immune destruction of murine islets [i.e., allograft rejection and multiple low-dose streptozocin (STZ)-induced insulitis]. Freshly isolated or low-temperature-cultured BALB/cJ islets were transplanted beneath the kidney capsules of C57BL/6J recipients. The recipients were treated with NIC alone (500 mg.kg-1.day-1), DFX alone (4.2 mg/day x 14 days), or NIC + DFX. Only recipients treated with NIC + DFX, receiving cultured islets, showed a mean graft survival time significantly longer than control mice receiving freshly isolated or cultured islets. Control CD-1 mice treated with multiple low doses of STZ developed insulitis and diabetes. Treatment with NIC alone, DFX alone, or NIC + DFX decreased the severity of hyperglycemia relative to the controls. Treatment with DFX alone was more effective than NIC alone or NIC + DFX. Only the group treated with DFX alone had a lower incidence of diabetes (mean plasma glucose level greater than 200 mg/dl) than the controls after 4 wk. Histologically, islets from control mice showed severe insulitis, islet destruction, and absence of stainable insulin, whereas islets from DFX-treated mice showed only mild peri-insulitis and a relative preservation of beta-cell granulation. Our study showed that NIC and DFX partially protect islets from immune destruction in allograft rejection and in low-dose STZ-induced insulitis. Apparently, hydroxyl radicals play important roles in both of these models.

  17. [Polyserositic syndromes and/or sectorial dysventilation with platelet activation induced by immunoallergic etiopathogenesis].

    PubMed

    De Luca, L

    1989-01-01

    The author from a study of 5 dysventilatorial syndromes (bronchiolitis-PNX, pneumomediastinal aerial cystis of lung) and 5 polysierositic syndromes pleuritis and peritonitis) evices that all these syndromes show in the anamnesis or in present a viral infection from influenzal virus or rubeola. In addition to that, the Authors shows the presence of a food allergy asserted by RAST and/or Skin Prick Tests or FBST (Food Bronchostimulation test) and the introduction of a food allergen during the viral infection, and a great platelet's activation. The Author, besides, shows the association normal VES and normal neutrophil cells in the dysventilatorial syndrome and high VES, and high neutrophil cells in the polysierositic syndromes; in all cases the negativity of culture exams. Starting from these points she worked out a new etiopathogenetic theory: the viral localization on the Peyer's plates cause the expression on the epithelial surface of the gut's cells of SELF HLA II type recognition. The food allergens' introduction causes a great reaction of II, III, IV, VI type which involves the bronchus, alveolus, and the serous epithelium by PAF activation, in all cases and in the polisierositic syndrome a neutrophil activation as well. The author advices to prize the importance of cortisone therapy and of exclusion of food allergen by diet, besides advices the antibiotic therapy for covering only.

  18. Effect of sildenafil on platelet function and platelet cGMP of patients with erectile dysfunction.

    PubMed

    Akand, M; Gencer, E; Yaman, Ö; Erişgen, G; Tekin, D; Özdiler, E

    2015-12-01

    To investigate the effect of sildenafil on platelet function and cyclic guanosine monophosphate (cGMP) levels in patients with erectile dysfunction, we evaluated the association between erectile function and platelet responses after administration of 100 mg sildenafil. Erectile responses were monitored after 8 daily doses of the drug. Adenosine diphosphate (ADP) and collagen-induced platelet aggregation and simultaneous adenosine triphosphate (ATP) release and cGMP levels were determined before and after sildenafil therapy. Basal levels for platelet aggregation, ATP release and cGMP were compared with age-matched controls. There was no difference among basal levels of platelet responses between patients and controls, except for ADP-induced platelet aggregation (P = 0.04). It was significantly higher in the patient group. Analysis of the responses to sildenafil revealed that for the patients who showed a positive erectile response, there was a significant increase in platelet cGMP (P = 0.028) and a decrease in ADP-induced platelet aggregation (P = 0.04). However, for those who showed a negative or poor erectile response, there was no change in platelet cGMP levels and platelet functions. Sildenafil did not affect collagen-induced platelet responses although cGMP levels of the responders increased. It is concluded that sildenafil increases platelet cGMP in the patients with positive erectile response. Therefore, it has been speculated that platelet cGMP may be used as an index for erectile response.

  19. Contact- and agonist-regulated microvesiculation of human platelets.

    PubMed

    Zhang, Yanjun; Liu, Xiao; Liu, Li; Zaske, Ana-Maria; Zhou, Zhou; Fu, Yuanyuan; Yang, Xi; Conyers, Jodie L; Li, Min; Dong, Jing-fei; Zhang, Jianning

    2013-08-01

    After exposure to an agonist, platelets are activated and become aggregated. They also shed membrane microparticles that participate in the pathogenesis of thrombosis, hyper-coagulation and inflammation. However, microvesiculation can potentially disrupt the integrity of platelet aggregation by shedding the membrane receptors and phosphatidylserine critical for forming and stabilising a platelet clot. We tested the hypothesis that adhesion and microvesiculation are functions of different subsets of platelets at the time of haemostasis by real-time monitoring of agonist-induced morphological changes and microvesiculation of human platelets.We identified two types of platelets that are adherent to fibrinogen: a high density bubble shape (HDBS) and low-density spread shape (LDSS). Adenosine diphosphate (ADP) predominantly induced HDBS platelets to vesiculate, whereas LDSS platelets were highly resistant to such vesiculation. Thrombin-receptor activating peptide (TRAP) stabilised platelets against microvesiculation by promoting a rapid HDBS-to-LDSS morphological transition. These activities of ADP and TRAP were reversed for platelets in suspension, independent of an engagement integrin αIIbβ3. As the result of membrane contact, LDSS platelets inhibited the microvesiculation of HDBS platelets in response to ADP. Aspirin and clopidogrel inhibited ADP-induced microvesiculation through different mechanisms. These results suggest that platelet aggregation and microvesiculation occur in different subsets of platelets and are differently regulated by agonists, platelet-platelets and platelet-fibrinogen interactions.

  20. Prevotella intermedia induces severe bacteremic pneumococcal pneumonia in mice with upregulated platelet-activating factor receptor expression.

    PubMed

    Nagaoka, Kentaro; Yanagihara, Katsunori; Morinaga, Yoshitomo; Nakamura, Shigeki; Harada, Tatsuhiko; Hasegawa, Hiroo; Izumikawa, Koichi; Ishimatsu, Yuji; Kakeya, Hiroshi; Nishimura, Masaharu; Kohno, Shigeru

    2014-02-01

    Streptococcus pneumoniae is the leading cause of respiratory infection worldwide. Although oral hygiene has been considered a risk factor for developing pneumonia, the relationship between oral bacteria and pneumococcal infection is unknown. In this study, we examined the synergic effects of Prevotella intermedia, a major periodontopathic bacterium, on pneumococcal pneumonia. The synergic effects of the supernatant of P. intermedia (PiSup) on pneumococcal pneumonia were investigated in mice, and the stimulation of pneumococcal adhesion to human alveolar (A549) cells by PiSup was assessed. The effects of PiSup on platelet-activating factor receptor (PAFR) transcript levels in vitro and in vivo were analyzed by quantitative real-time PCR, and the differences between the effects of pneumococcal infection induced by various periodontopathic bacterial species were verified in mice. Mice inoculated with S. pneumoniae plus PiSup exhibited a significantly lower survival rate, higher bacterial loads in the lungs, spleen, and blood, and higher inflammatory cytokine levels in the bronchoalveolar lavage fluid (macrophage inflammatory protein 2 and tumor necrosis factor alpha) than those infected without PiSup. In A549 cells, PiSup increased pneumococcal adhesion and PAFR transcript levels. PiSup also increased lung PAFR transcript levels in mice. Similar effects were not observed in the supernatants of Porphyromonas gingivalis or Fusobacterium nucleatum. Thus, P. intermedia has the potential to induce severe bacteremic pneumococcal pneumonia with enhanced pneumococcal adhesion to lower airway cells.

  1. Interdependence of Platelet-Derived Growth Factor and Estrogen-Signaling Pathways in Inducing Neonatal Rat Testicular Gonocytes Proliferation1

    PubMed Central

    Thuillier, Raphael; Mazer, Monty; Manku, Gurpreet; Boisvert, Annie; Wang, Yan; Culty, Martine

    2010-01-01

    We previously found that platelet-derived growth factor (PDGF) and 17beta-estradiol stimulate gonocyte proliferation in a dose-dependent, nonadditive manner. In the present study, we report that gonocytes express RAF1, MAP2K1, and MAPK1/3. Inhibition of RAF1 and MAP2K1/2, but not phosphoinositide-3-kinase, blocked PDGF-induced proliferation. AG-370, an inhibitor of PDGF receptor kinase activity, suppressed not only PDGF-induced proliferation but also that induced by 17beta-estradiol. In addition, RAF1 and MAP2K1/2 inhibitors blocked 17beta-estradiol-activated proliferation. The estrogen receptor antagonist ICI 182780 inhibited both the effects of 17beta-estradiol and PDGF. PDGF lost its stimulatory effect when steroid-depleted serum or no serum was used. Similarly, 17beta-estradiol did not induce gonocyte proliferation in the absence of PDGF. The xenoestrogens genistein, bisphenol A, and DES, but not coumestrol, stimulated gonocyte proliferation in a dose-dependent and PDGF-dependent manner similarly to 17beta-estradiol. Their effects were blocked by ICI 182780, suggesting that they act via the estrogen receptor. AG-370 blocked genistein and bisphenol A effects, demonstrating their requirement of PDGF receptor activation in a manner similar to 17beta-estradiol. These results demonstrate the interdependence of PDGF and estrogen pathways in stimulating in vitro gonocyte proliferation, suggesting that this critical step in gonocyte development might be regulated in vivo by the coordinated action of PDGF and estrogen. Thus, the inappropriate exposure of gonocytes to xenoestrogens might disrupt the crosstalk between the two pathways and potentially interfere with gonocyte development. PMID:20089883

  2. Protein kinase A regulates 3-phosphatidylinositide dynamics during platelet-derived growth factor-induced membrane ruffling and chemotaxis.

    PubMed

    Deming, Paula B; Campbell, Shirley L; Baldor, Linda C; Howe, Alan K

    2008-12-12

    Spatial regulation of the cAMP-dependent protein kinase (PKA) is required for chemotaxis in fibroblasts; however, the mechanism(s) by which PKA regulates the cell migration machinery remain largely unknown. Here we report that one function of PKA during platelet-derived growth factor (PDGF)-induced chemotaxis was to promote membrane ruffling by regulating phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) dynamics. Inhibition of PKA activity dramatically altered membrane dynamics and attenuated formation of peripheral membrane ruffles in response to PDGF. PKA inhibition also significantly decreased the number and size of PIP(3)-rich membrane ruffles in response to uniform stimulation and to gradients of PDGF. This ruffling defect was quantified using a newly developed method, based on computer vision edge-detection algorithms. PKA inhibition caused a marked attenuation in the bulk accumulation of PIP(3) following PDGF stimulation, without effects on PI3-kinase (PI3K) activity. The deficits in PIP(3) dynamics correlated with a significant inhibition of growth factor-induced membrane recruitment of endogenous Akt and Rac activation in PKA-inhibited cells. Simultaneous inhibition of PKA and Rac had an additive inhibitory effect on growth factor-induced ruffling dynamics. Conversely, the expression of a constitutively active Rac allele was able to rescue the defect in membrane ruffling and restore the localization of a fluorescent PIP(3) marker to membrane ruffles in PKA-inhibited cells, even in the absence of PI3K activity. These data demonstrate that, like Rac, PKA contributes to PIP(3) and membrane dynamics independently of direct regulation of PI3K activity and suggest that modulation of PIP(3)/3-phosphatidylinositol (3-PI) lipids represents a major target for PKA in the regulation of PDGF-induced chemotactic events.

  3. Cholesterol synthesis inhibitors protect against platelet-activating factor-induced neuronal damage

    PubMed Central

    Bate, Clive; Rumbold, Louis; Williams, Alun

    2007-01-01

    Background Platelet-activating factor (PAF) is implicated in the neuronal damage that accompanies ischemia, prion disease and Alzheimer's disease (AD). Since some epidemiological studies demonstrate that statins, drugs that reduce cholesterol synthesis, have a beneficial effect on mild AD, we examined the effects of two cholesterol synthesis inhibitors on neuronal responses to PAF. Methods Primary cortical neurons were treated with cholesterol synthesis inhibitors (simvastatin or squalestatin) prior to incubation with different neurotoxins. The effects of these drugs on neuronal cholesterol levels and neuronal survival were measured. Immunoblots were used to determine the effects of simvastatin or squalestatin on the distribution of the PAF receptor and an enzyme linked immunoassay was used to quantify the amounts of PAF receptor. Results PAF killed primary neurons in a dose-dependent manner. Pre-treatment with simvastatin or squalestatin reduced neuronal cholesterol and increased the survival of PAF-treated neurons. Neuronal survival was increased 50% by 100 nM simvastatin, or 20 nM squalestatin. The addition of mevalonate restored cholesterol levels, and reversed the protective effect of simvastatin. Simvastatin or squalestatin did not affect the amounts of the PAF receptor but did cause it to disperse from within lipid rafts. Conclusion Treatment of neurons with cholesterol synthesis inhibitors including simvastatin and squalestatin protected neurons against PAF. Treatment caused a percentage of the PAF receptors to disperse from cholesterol-sensitive domains. These results raise the possibility that the effects of statins on neurodegenerative disease are, at least in part, due to desensitisation of neurons to PAF. PMID:17233902

  4. Effect of photodynamic therapy on mouse platelets

    NASA Astrophysics Data System (ADS)

    Zhou, Chuannong; Chi, Shunji; Deng, Jinsheng; Zhang, Hua; Liang, Junlin; Ha, Xian-wen

    1993-06-01

    Normal mice received hematoporphyrin derivative (HpD) i.v. prior to red light irradiation and the platelet-rich plasma was prepared and irradiated by red light. The platelets were processed for EM examination and stereological analysis. It was shown the 16 hrs after irradiation almost all platelets were necrotized; 8 hours after irradiation about one fourth of the platelets were necrotized and the remaining were considerably damaged. Immediately after irradiation a small number of platelets became necrotic and most other platelets were swollen and deformated, showing significantly increased mean area, perimeter and short axis, and mean cell volume and cell surface area. The findings indicate that platelets are highly sensitive to PDT action and can be directly and rapidly damaged by PDT even in the absence of vascular endothelial cells. The early platelet photoactivation may play an important role in the initiation of early vascular damage and microcirculatory alterations induced by PDT in vivo.

  5. Platelet Activating Factor-Induced Ceramide Micro-Domains Drive Endothelial NOS Activation and Contribute to Barrier Dysfunction

    PubMed Central

    Predescu, Sanda; Knezevic, Ivana; Bardita, Cristina; Neamu, Radu Florin; Brovcovych, Viktor; Predescu, Dan

    2013-01-01

    The spatial and functional relationship between platelet activating factor-receptor (PAF-R) and nitric oxide synthase (eNOS) in the lateral plane of the endothelial plasma membrane is poorly characterized. In this study, we used intact mouse pulmonary endothelial cells (ECs) as well as endothelial plasma membrane patches and subcellular fractions to define a new microdomain of plasmalemma proper where the two proteins colocalize and to demonstrate how PAF-mediated nitric oxide (NO) production fine-tunes ECs function as gatekeepers of vascular permeability. Using fluorescence microscopy and immunogold labeling electron microscopy (EM) on membrane patches we demonstrate that PAF-R is organized as clusters and colocalizes with a subcellular pool of eNOS, outside recognizable vesicular profiles. Moreover, PAF-induced acid sphingomyelinase activation generates a ceramide-based microdomain on the external leaflet of plasma membrane, inside of which a signalosome containing eNOS shapes PAF-stimulated NO production. Real-time measurements of NO after PAF-R ligation indicated a rapid (5 to 15 min) increase in NO production followed by a > 45 min period of reduction to basal levels. Moreover, at the level of this new microdomain, PAF induces a dynamic phosphorylation/dephosphorylation of Ser, Thr and Tyr residues of eNOS that correlates with NO production. Altogether, our findings establish the existence of a functional partnership PAF-R/eNOS on EC plasma membrane, at the level of PAF-induced ceramide plasma membrane microdomains, outside recognized vesicular profiles. PMID:24086643

  6. Splenic release of platelets contributes to increased circulating platelet size and inflammation after myocardial infarction.

    PubMed

    Gao, Xiao-Ming; Moore, Xiao-Lei; Liu, Yang; Wang, Xin-Yu; Han, Li-Ping; Su, Yidan; Tsai, Alan; Xu, Qi; Zhang, Ming; Lambert, Gavin W; Kiriazis, Helen; Gao, Wei; Dart, Anthony M; Du, Xiao-Jun

    2016-07-01

    Acute myocardial infarction (AMI) is characterized by a rapid increase in circulating platelet size but the mechanism for this is unclear. Large platelets are hyperactive and associated with adverse clinical outcomes. We determined mean platelet volume (MPV) and platelet-monocyte conjugation (PMC) using blood samples from patients, and blood and the spleen from mice with AMI. We further measured changes in platelet size, PMC, cardiac and splenic contents of platelets and leucocyte infiltration into the mouse heart. In AMI patients, circulating MPV and PMC increased at 1-3 h post-MI and MPV returned to reference levels within 24 h after admission. In mice with MI, increases in platelet size and PMC became evident within 12 h and were sustained up to 72 h. Splenic platelets are bigger than circulating platelets in normal or infarct mice. At 24 h post-MI, splenic platelet storage was halved whereas cardiac platelets increased by 4-fold. Splenectomy attenuated all changes observed in the blood, reduced leucocyte and platelet accumulation in the infarct myocardium, limited infarct size and alleviated cardiac dilatation and dysfunction. AMI-induced elevated circulating levels of adenosine diphosphate and catecholamines in both human and the mouse, which may trigger splenic platelet release. Pharmacological inhibition of angiotensin-converting enzyme, β1-adrenergic receptor or platelet P2Y12 receptor reduced platelet abundance in the murine infarct myocardium albeit having diverse effects on platelet size and PMC. In conclusion, AMI evokes release of splenic platelets, which contributes to the increase in platelet size and PMC and facilitates myocardial accumulation of platelets and leucocytes, thereby promoting post-infarct inflammation.

  7. [STRUCTURAL CHARACTERIZATION OF PLATELETS AND PLATELET-DERIVED MICROVESICLES].

    PubMed

    Ponomareva, A A; Nevzorova, T A; Mordakhanova, E R; Andrianova, I A; Litvinov, R I

    2016-01-01

    Platelets are the anucleated blood cells, wich together with the fibrin stop bleeding (hemostasis). Cellular microvesicles are membrane-surrounded microparticles released into extracellular space upon activation and/or apoptosis of various cells. Platelet-derived macrovesicles from the major population of circulating blood microparticles that play an important role in hemostasis and thrombosis. Despite numerous studies on the pathophysiology of platelet-derived macrovesicles, mechanisms of their formation and structural details remain poorly understood. Here we investigated the ultrastructure of parental platelets and platelet-derived microvesicles formed in vitro by quiescent cells as well as by cells stimulated with one of the following activators: arachidonic acid, ADP, thrombin, calcium ionophore A23187. Using transmission electron microscopy of human platelets and isolated microvesicles, we analyzed the intracellular origin, steps of formation, structural diversity, and size distributions of the subcellular particles. We have revealed that thrombin, unlike other stimuli, not only induced vesiculation of the plasma membrane but also caused break-up of the cells followed by formation of microparticles that are comparable with microvesicles by size. A fraction of these microparticles contained cellular organelles surrounded by a thin membrane. The size of platelet-derived macrovesicles varied from 30 nm to 500 nm, however, the size distributions depended on the nature of a cell-activating stimulus. The results obtained provide new information about the formation of platelet-derived macrovesicles and their structural diversity, wich is important to understand their multiple functions in normal and disease states.

  8. Autologous leukocyte-reduced platelet-rich plasma therapy for Achilles tendinopathy induced by collagenase in a rabbit model.

    PubMed

    González, Juan C; López, Catalina; Álvarez, María E; Pérez, Jorge E; Carmona, Jorge U

    2016-01-19

    Leukocyte-reduced platelet-rich plasma (LR-PRP) is a therapy for tendinopathy of the Achilles tendon (TAT); however, there is scarce information regarding LR-PRP effects in rabbit models of TAT. We compared, at 4 and 12 weeks (w), the LR-PRP and placebo (PBS) effects on ultrasonography, histology and relative gene expression of collagen types I (COL1A1) and III (COL3A1) and vascular endothelial growth factor (VEGF) in 24 rabbits with TAT induced by collagenase. The rabbits (treated with both treatments) were euthanatised after either 4 or 12 w. A healthy group (HG (n = 6)) was included. At 4 and 12 w, the LR-PRP group had a no statistically different histology score to the HG. At w 4, the COL1A1 expression was significantly higher in the LR-PRP group when compared to HG, and the expression of COL3A1 from both LR-PRP and PBS-treated tendons was significantly higher when compared to the HG. At w 12, the expression of COL3A1 remained significantly higher in the PBS group in comparison to the LR-PRP group and the HG. At w 4, the LR-PRP group presented a significantly higher expression of VEGF when compared to the PBS group and the HG. In conclusion, LR-PRP treatment showed regenerative properties in rabbits with TAT.

  9. Autologous leukocyte-reduced platelet-rich plasma therapy for Achilles tendinopathy induced by collagenase in a rabbit model

    PubMed Central

    González, Juan C.; López, Catalina; Álvarez, María E.; Pérez, Jorge E.; Carmona, Jorge U.

    2016-01-01

    Leukocyte-reduced platelet-rich plasma (LR-PRP) is a therapy for tendinopathy of the Achilles tendon (TAT); however, there is scarce information regarding LR-PRP effects in rabbit models of TAT. We compared, at 4 and 12 weeks (w), the LR-PRP and placebo (PBS) effects on ultrasonography, histology and relative gene expression of collagen types I (COL1A1) and III (COL3A1) and vascular endothelial growth factor (VEGF) in 24 rabbits with TAT induced by collagenase. The rabbits (treated with both treatments) were euthanatised after either 4 or 12 w. A healthy group (HG (n = 6)) was included. At 4 and 12 w, the LR-PRP group had a no statistically different histology score to the HG. At w 4, the COL1A1 expression was significantly higher in the LR-PRP group when compared to HG, and the expression of COL3A1from both LR-PRP and PBS-treated tendons was significantly higher when compared to the HG. At w 12, the expression of COL3A1 remained significantly higher in the PBS group in comparison to the LR-PRP group and the HG. At w 4, the LR-PRP group presented a significantly higher expression of VEGF when compared to the PBS group and the HG. In conclusion, LR-PRP treatment showed regenerative properties in rabbits with TAT. PMID:26781753

  10. Signaling during platelet adhesion and activation

    PubMed Central

    Li, Zhenyu; Delaney, M. Keegan; O’Brien, Kelly A.; Du, Xiaoping

    2011-01-01

    Upon vascular injury, platelets are activated by adhesion to adhesive proteins like von Willebrand factor and collagen, or by soluble platelet agonists like ADP, thrombin, and thromboxane A2. These adhesive proteins and soluble agonists induce signal transduction via their respective receptors. The various receptor-specific platelet activation signaling pathways converge into common signaling events, which stimulate platelet shape change, granule secretion, and ultimately induce the “inside-out” signaling process leading to activation of the ligand binding function of integrin αIIbβ3. Ligand binding to integrin αIIbβ3 mediates platelet adhesion and aggregation and triggers “outside-in” signaling, resulting in platelet spreading, additional granule secretion, stabilization of platelet adhesion and aggregation, and clot retraction. It has become increasingly evident that agonist-induced platelet activation signals also crosstalk with integrin “outside-in” signals to regulate platelet responses. Platelet activation involves a series of rapid positive feedback loops that greatly amplify initial activation signals, and enable robust platelet recruitment and thrombus stabilization. Recent studies have provided novel insight into the molecular mechanisms of these processes. PMID:21071698

  11. Platelets and angiogenesis in malignancy.

    PubMed

    Sierko, Ewa; Wojtukiewicz, Marek Z

    2004-02-01

    There is increasing evidence that platelets play an important role in the process of tumor angiogenesis. Thrombocytosis is a frequent finding in cancer patients (10-57%). Although the mechanisms underlying thrombocytosis are not yet fully elucidated, tumor-derived factors with thrombopoietin-like activity and growth factors, platelet-derived microparticles, and factors secreted from bone marrow endothelial cells, as well as growth factors released by megakaryocytes (acting via an autocrine loop), are postulated to influence this process. The progression of cancer is associated with hypercoagulability, which results from direct influences of tumor cells and diverse indirect mechanisms. Activated platelets serve as procoagulant surfaces amplifying the coagulation reactions. It is well known that hemostatic proteins are involved in different steps of the angiogenic process. Furthermore, platelets adhering to endothelium facilitate adhesion of mononuclear cells (which exert various proangiogenic activities) to endothelial cells and their transmigration to the extravascular space. It was also documented that platelets induce angiogenesis in vivo. Platelets are a rich source of proangiogenic factors. They also store and release angiogenesis inhibitors. In addition, platelets express surface growth factor receptors, which may regulate the process of angiogenesis. Platelets also contribute directly to the process of basement membrane and extracellular matrix proteolysis by releasing proteinases, or indirectly via inducing endothelial cells and tumor cells to release proteolytic enzymes, as well as through the proteolytic activities of platelet-derived growth factors. The multidirectional activities of platelets in the process of new blood vessel formation during tumor development and metastasis formation may create the possibility of introducing antiplatelet agents for antiangiogenic therapy in cancer patients. Thus far experimental studies employing inhibitors of

  12. Hemolysis after ABO-incompatible platelet transfusions.

    PubMed

    Chow, M P; Yung, C H; Hu, H Y; Tzeng, C H

    1991-08-01

    An 18 year old girl, with acute myeloid leukemia, developed progressive hemolysis after receiving multiple transfusions with ABO-incompatible platelets. It was caused by passive transfusion of anti-A and -B isoagglutinin from the donor plasma. Her hemoglobin level returned to normal after giving group compatible or pooled and reduced volume platelet concentrates. Transfusing group-incompatible platelets is not contraindicated, but donor plasma reduction should be considered for those patients who need prolonged platelet support. Testing for isoagglutinin titer in group O donors is an alternate method to reduce the incidence of plasma-induced hemolysis in group-incompatible platelet transfusions.

  13. Biologic nanoparticles and platelet reactivity

    PubMed Central

    Miller, Virginia M; Hunter, Larry W; Chu, Kevin; Kaul, Vivasvat; Squillace, Phillip D; Lieske, John C; Jayachandran, Muthuvel

    2009-01-01

    Aim Nanosized particles (NPs) enriched in hydroxyapatite and protein isolated from calcified human tissue accelerate occlusion of endothelium-denuded arteries when injected intravenously into rabbits. Since platelet aggregation and secretory processes participate in normal hemostasis, thrombosis and vascular remodeling, experiments were designed to determine if these biologic NPs alter specific platelet functions in vitro. Methods Platelet-rich plasma was prepared from citrate anticoagulated human blood. Platelet aggregation and ATP secretion were monitored in response to thrombin receptor agonists peptide (10 μM) or convulxin (50 μg/ml) prior to and following 15 min incubation with either control solution, human-derived NPs, bovine-derived NPs or crystals of hydroxyapatite at concentrations of 50 and 150 nephelometric turbidity units. Results Incubation of platelets for 15 min with either human- or bovine-derived NPs reduced aggregation induced by thrombin receptor activator peptide and convulxin in a concentration-dependent manner. Hydroxyapatite caused a greater inhibition than either of the biologically derived NPs. Human-derived NPs increased ATP secretion by unstimulated platelets during the 15 min incubation period. Conclusion Effects of bovine-derived and hydroxyapatite NPs on basal release of ATP were both time and concentration dependent. These results suggest that biologic NPs modulate both platelet aggregation and secretion. Biologically derived NPs could modify platelet responses within the vasculature, thereby reducing blood coagulability and the vascular response to injury. PMID:19839809

  14. Identification of key genes induced by platelet-rich plasma in human dermal papilla cells using bioinformatics methods

    PubMed Central

    Shen, Haiyan; Cheng, Hanxiao; Chen, Haihua; Zhang, Jufang

    2016-01-01

    Dermal papilla cells (DPCs) are located at the base of hair follicles, and are known to induce hair follicle regeneration. Platelet-rich plasma (PRP) functions in hair follicle regeneration. To investigate the influence of PRP on DPCs, the present study analyzed RNA-seq data of human hair dermal papilla cells (HHDPCs) that were treated or untreated by PRP. The data included in the RNA-seq were from two normal and two treated HHDPC samples. Following identification by Cuffdiff software, differentially expressed genes (DEGs) underwent enrichment analyses, and protein-protein interaction networks were constructed using Cytoscape software. Additionally, transcription factor (TF)-DEG and TF-long non-coding RNA (lncRNA) regulatory networks were constructed. A total of 178 differentially expressed lncRNA were screened, 365 were upregulated and 142 were downregulated. Notably, upregulated cyclin dependent kinase 1 (CDK1) (degree=76), polo-like kinase 1 (PLK1) (degree=65), cell division cycle 20 (degree=50), cyclin B1 (degree=49), aurora kinase B (degree=47), cyclin dependent kinase 2 (degree=46) and downregulated v-myc avian myelocytomatosis viral oncogene homolog (MYC) (degree=12) had higher degrees in networks. In addition, CCAAT/enhancer binding protein β, E2F transcription factor 1 (E2F1), early growth response 1 and MYC may be key TFs for their target genes, and were enriched in pathways associated with the cell cycle. They may also be involved in cell proliferation via various interactions with other genes, for example CDK1-PLK1 and E2F1→CDK1. These dysregulated genes induced by PRP may affect proliferation of HHDPCs. PMID:27922680

  15. A myocardial ischemia- and reperfusion-induced injury is mediated by reactive oxygen species released from blood platelets.

    PubMed

    Seligmann, Christian; Prechtl, Gerald; Kusus-Seligmann, Magda; Daniel, Werner G

    2013-01-01

    In recent experimental studies, blood platelets have been found to exhibit some cardiodepressive effects in ischemic and reperfused guinea pig hearts independent of thrombus formation. These effects seemed to be mediated by reactive oxygen species (ROS). However, the source of these ROS - platelets or heart - remained still unknown. Isolated, buffer-perfused and pressure-volume work performing guinea pig hearts were exposed to a low-flow ischemia (1 ml/min) of 30 min duration and reperfused at a constant flow of 5 ml/min. Human thrombocytes were administered as 1 min bolus (20 000 thrombocytes/µl perfusion buffer) in the 15th min of ischemia or in the 1st or 5th min of reperfusion in the presence of thrombin (0.3 U/ml perfusion buffer). Recovery of external heart work (REHW) was expressed as ratio between postischemic and preischemic EHW in percent. Intracoronary platelet retention (RET) was quantified as percent of platelets applied. In a second set of experiments, thrombocytes were incubated with 10 µM of the irreversible NADPH oxidase blocker diphenyliodonium chloride and washed twice, thereafter, and administered according to the same protocol as described above. Hearts exposed to ischemia and reperfusion in the presence of thrombin but without application of platelets served as controls. Controls without application of platelets did not reveal a severe compromisation of myocardial function (REHW 85.5 ± 1%). However, addition of platelets during ischemia or in the 1st or 5th min of reperfusion led to a significant reduction of REHW as compared with controls (REHW 62.4 ± 6, 53.9 ± 3, 40.5 ± 3, respectively). Application of platelets pretreated with diphenyliodonium chloride did not reveal any cardiodepressive effects being significantly different from controls without platelet application. Moreover, treatment of platelets with diphenyliodonium chloride did not significantly decrease intracoronary platelet retention. In conclusion, these results demonstrate

  16. Reversible Hypothermia-Induced Inhibition of Human Platelet Activation in Whole Blood in Vitro and in Vivo

    DTIC Science & Technology

    2007-11-02

    IX complex (the von Willebrand factor receptor) (12), thromboxane Bj generation (the stable metabolite of thromboxane A2) (13), platelet aggregate...6D1 (provided by Dr. Barry S. Coller, SUNY, Stony Brook) is directed against the von Willebrand factor receptor on the glycocalicin portion of the a...Fig 1, panel A) and, after a delay of approximately 20 seconds, downregulation of the platelet surface expression of GPIb (the von Willebrand factor

  17. [Platelet hyperreactivity and antiaggregatory properties of nootropic drugs under conditions of alloxan-induced diabetes in rats].

    PubMed

    Zhiliuk, V I; Levykh, A É; Mamchur, V I

    2012-01-01

    The effects of nootropic drugs (noopept, pentoxifylline, piracetam, pramiracetam, Ginkgo biloba extract, entrop, cerebrocurin and citicoline) on platelet aggregation in rats with experimental diabetes have been studied. It is established that all these drugs exhibit an inhibitory action of various degrees against platelet hyperreactivity under conditions of chronic hyperglycemia. The maximum universality of the antiaggregatory action is characteristic of pramiracetam, entrop and Ginkgo biloba extract.

  18. Platelet Supernatant Suppresses LPS-Induced Nitric Oxide Production from Macrophages Accompanied by Inhibition of NF-κB Signaling and Increased Arginase-1 Expression

    PubMed Central

    2016-01-01

    We previously reported that mouse bone marrow-derived macrophages (BMDMs) that had been co-cultured with platelets exhibited lower susceptibility to bacterial lipopolysaccharide (LPS) and produced lower levels of nitric oxide (NO) and inflammatory cytokines including TNF-α and IL-6. The suppression of macrophage responses was mediated, at least in part, by platelet supernatant. In the present study, we assessed phenotypic changes of BMDMs induced by incubation with the supernatant from thrombin-activated platelets (PLT-sup) and found that BMDMs cultured with PLT-sup (PLT-BMDMs) expressed a lower level of inducible NO synthase (iNOS) and a higher level of arginase-1, both of which are involved in the L-arginine metabolism, upon stimulation with LPS or zymosan. We also examined possible modulation of the NF-κB signaling pathway and observed suppression of IκBα phosphorylation and a decrease of NF-κB p65 expression in LPS-stimulated PLT-BMDMs. These results suggest that PLT-sup suppresses inflammatory responses of BMDMs via negative regulation of NF-κB signaling leading to lowered expression of iNOS and enhanced L-arginine catabolism by arginase-1. PMID:27588757

  19. Heparin Causes Platelet Dysfunction and Induces Fibrinolysis Before the Institution of Cardiopulmonary Bypass

    DTIC Science & Technology

    2007-11-02

    Anesthesia was induced with fentanyl and lidocaine and maintained with fentanyl and halothane. After an initial heparin dose of 4 mg/kg, cardiopulmonary...multimer distribution was not altered in patients after infusion of heparin, as measured by visual inspection of vWF antigen on autoradiographs (Figure...Autoradiograph of vWF in normal pool plasma (N), and from three representative patients out of 15, before (A) and after (B) infusion of heparin. Note no

  20. Platelet 5-hydroxytryptamine (5-HT) transporter and 5-HT2A receptor binding after chronic hypercorticosteronemia, (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane administration or neurotoxin-induced depletion of central nervous system 5-HT in the rat.

    PubMed

    Owens, M J; Ballenger, C A; Knight, D L; Nemeroff, C B

    1996-09-01

    There is considerable evidence that the number of platelet 5-hydroxytryptamine (5-HT) transporter binding sites, as measured by [3H]imipramine binding, are significantly decreased, and platelet 5-HT2 receptor density is increased, in drug-free patients with major depression. To investigate whether these changes in the platelet 5-HT transporter or 5-HT2 receptor sites resulted from known or hypothesized biochemical changes observed in major depression, we examined, in the rat, whether a chronic hyperglucocorticoid state, or decreases or increases in central nervous system 5-HT neurotransmission, altered binding of the selective ligands [3H]citalopram and [125I] (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane to platelet and brain 5-HT transporters and 5-HT2 receptors, respectively. Chronic (6 weeks) hypercorticosteronemia did not alter either brain or platelet 5-HT transporter or 5-HT2A receptor binding. Similarly, 8-week administration of the 5-HT2A/5-HT2C agonist (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane, at a dose which down-regulates brain 5-HT2A/2C receptors, did not alter brain or platelet 5-HT transporters or platelet 5-HT2A receptors. Additionally, para-chloroamphetamine-(11 weeks) or fenfluramine-induced chronic (1.5-10 weeks) depletion of central nervous system 5-HT did not alter platelet 5-HT transporter or 5-HT2A receptor binding. Finally, there was no correlation between the number of 5-HT transporters in brain and platelets in any of the control or treatment groups. These findings suggest that the observed changes in platelet 5-HT transporter and 5-HT2A receptor binding in depressed patients are more apt to be of genetic origin (i.e., trait-dependent) rather than an epiphenomenon of hypercortisolemia or altered central nervous system 5-HT status.

  1. Complexes of heparin and platelet factor 4 specifically stimulate T cells from patients with heparin-induced thrombocytopenia/thrombosis.

    PubMed

    Bacsi, S; De Palma, R; Visentin, G P; Gorski, J; Aster, R H

    1999-07-01

    Heparin-induced thrombocytopenia with thrombosis (HITT) is associated with antibodies specific for complexes consisting of heparin and platelet factor 4 (PF4). Studies in individual patients with HITT have demonstrated immunoglobulin (Ig) class switching from IgM to the IgG or IgA isotypes. This transition is thought to require helper T cells, but no studies of the cellular or molecular basis of this process have yet been reported. To characterize T-cell involvement in HITT, peripheral blood mononuclear cells (PBMC) from two patients with classical HITT obtained shortly after the acute episode were restimulated with heparin:PF4 complexes, PF4 alone, heparin alone, and medium alone in the presence of autologous antigen-presenting cells (APC). Responding T cells were then examined using the technique of "spectratyping," in which sequences encoding CDR3 domains of individual V beta (BV) families are amplified and separated by gel electrophoresis. After 14 days in culture with antigen (heparin:PF4 complexes), but not after culture with PF4, heparin, or medium alone, patient cells, but not cells from normal subjects, preferentially expressed T-cell receptor (TCR)-containing beta chains of the BV 5.1 family. Nucleotide sequencing of BV 5.1 TCR CDR3 showed that each patient had a personal repertoire, but also shared a tetrapeptide motif (PGTG). These findings provide evidence that the humoral immune response associated with HITT is driven by helper T cells that presumably recognize peptides derived from PF4. Identification of a common beta-chain CDR3 motif in responding T cells from each of two patients suggests that a limited number of helper TCRs may be used to mount an antibody response to heparin:PF4 complexes. TCR spectratyping appears to offer a new way to examine the molecular basis of pathologic immune responses and may be useful in further studies of HITT and other immune-mediated hematologic disorders.

  2. Desmopressin (DDAVP) improves recruitment of activated platelets to collagen but simultaneously increases platelet endothelial interactions in vitro.

    PubMed

    Calmer, Simone; Ferkau, Annika; Larmann, Jan; Johanning, Kai; Czaja, Eliana; Hagl, Christian; Echtermeyer, Frank; Goudeva, Lilia; Heuft, Hans-Gert; Theilmeier, Gregor

    2014-01-01

    Platelet dysfunction can cause clinically relevant bleeding. Treatment with DDAVP is advocated for this condition. DDAVP increases von Willebrand factor (VWF) on endothelial cells (ECs) and in plasma. VWF could facilitate platelet deposition on subendothelial collagen. VWF also facilitates platelet/EC interactions. Therefore DDAVP could precipitate thromboembolic events. We used a flow chamber model to study in vitro and ex vivo if DDAVP alters recruitment of platelets to EC and collagen. Resting or TRAP-activated platelets and EC were treated individually or simultaneously with 0.4 ng/ml DDAVP. Fluorophor-labeled platelets (10(6)/ml) were resuspended in reconstituted blood and superfused across EC and collagen in an in vitro flow chamber model at arterial shear (320 s(-1)). Adhesion of platelets to the respective surface was recorded fluorescence microscopically and platelet covered area was assessed. TRAP significantly induced adhesiveness of platelets for collagen and EC. DDAVP pretreatment of platelets did not affect adhesiveness of resting or TRAP-activated platelets for collagen or EC. Adhesiveness of resting but not TRAP-activated platelets was induced on DDAVP-treated EC. DDAVP-conditioned EC supernatant contained vWF and significantly increased platelet deposition on collagen. Platelets from patients with clinically suspected platelet dysfunction undergoing aortic valve replacement exhibited decreased platelet deposition on collagen surfaces. In summary, our data confirm that DDAVP can induce release of platelet adhesion promoting factors from EC, which is most likely vWF. DDAVP has no direct effect on platelets. Blood samples from DDAVP-treated patients do not exhibit significantly augmented platelet deposition on collagen ex vivo. This influence of released promoting factors might cause an increase of undesirable interactions of platelets with EC.

  3. O-linked carbohydrate of recombinant von Willebrand factor influences ristocetin-induced binding to platelet glycoprotein 1b.

    PubMed Central

    Carew, J A; Quinn, S M; Stoddart, J H; Lynch, D C

    1992-01-01

    By transfecting the full-length cDNA for human von Willebrand factor (vWf) into a line of Chinese hamster ovary cells with a defect in carbohydrate metabolism, we have prepared recombinant vWf specifically lacking O-linked carbohydrates. We have compared this under-glycosylated protein to fully glycosylated recombinant vWf with respect to several structural and binding properties. vWf deficient in O-linked glycans was synthesized, assembled into multimers, and secreted in an apparently normal manner and was not prone to degradation in the extracellular milieu. It did not differ from fully glycosylated vWf in ability to bind to heparin or to collagen type I but did interact less well with glycoprotein 1b on formalin-fixed platelets. This decreased interaction was evidenced in both a lessened overall binding to platelets and in diminished capacity to promote platelet agglutination, in the presence of ristocetin. In contrast, no difference was seen in platelet binding in the presence of botrocetin. These data indicate a possible role for O-linked carbohydrates in the vWf-glycoprotein 1b interaction promoted by ristocetin and suggest that abnormalities in carbohydrate modification might contribute to the altered ristocetin-dependent reactivity between vWf and platelets described for some variant forms of von Willebrand disease. Images PMID:1469086

  4. Response of Northern Elephant Seal platelets to pressure and temperature changes: a comparison with human platelets.

    PubMed

    Field, Cara L; Tablin, Fern

    2012-08-01

    Mammalian blood platelets are activated by physiological agonists such as collagen or thrombin, or by physical stimuli such as cold temperatures and rapid decompression. Marine mammals regularly experience cold temperatures, high pressures and rapid decompression while diving, yet do not appear to suffer from thrombotic events during routine dive activity. We evaluated the effects of cold temperature and high pressure excursions on Northern Elephant Seal (NES) platelets and compared NES platelet response to that of human platelets subjected to identical stimuli. NES platelets undergo cold-induced activation when chilled to 4 °C, and 3 distinct phase transitions can be measured using Fourier Transform Infrared Spectroscopy. NES platelet membrane lipid composition was determined using thin layer chromatography and NES platelets were found to have three times the amount of cholesterol (21% by weight) as human platelets. When exposed to high pressure-rapid decompression excursion, NES platelets did not undergo morphological shape change nor bind increased amounts of fibrinogen, while human platelets were significantly activated by the same excursion. These results demonstrate that while NES platelets are activated by the physical stimulus of cold temperatures, they are resistant to decompression-induced activation. We suggest that the composition of NES platelet membranes may play an important role in preventing pressure-related activation.

  5. Blood platelets in the progression of Alzheimer's disease.

    PubMed

    Gowert, Nina S; Donner, Lili; Chatterjee, Madhumita; Eisele, Yvonne S; Towhid, Seyda T; Münzer, Patrick; Walker, Britta; Ogorek, Isabella; Borst, Oliver; Grandoch, Maria; Schaller, Martin; Fischer, Jens W; Gawaz, Meinrad; Weggen, Sascha; Lang, Florian; Jucker, Mathias; Elvers, Margitta

    2014-01-01

    Alzheimer's disease (AD) is characterized by neurotoxic amyloid-ß plaque formation in brain parenchyma and cerebral blood vessels known as cerebral amyloid angiopathy (CAA). Besides CAA, AD is strongly related to vascular diseases such as stroke and atherosclerosis. Cerebrovascular dysfunction occurs in AD patients leading to alterations in blood flow that might play an important role in AD pathology with neuronal loss and memory deficits. Platelets are the major players in hemostasis and thrombosis, but are also involved in neuroinflammatory diseases like AD. For many years, platelets were accepted as peripheral model to study the pathophysiology of AD because platelets display the enzymatic activities to generate amyloid-ß (Aß) peptides. In addition, platelets are considered to be a biomarker for early diagnosis of AD. Effects of Aß peptides on platelets and the impact of platelets in the progression of AD remained, however, ill-defined. The present study explored the cellular mechanisms triggered by Aß in platelets. Treatment of platelets with Aß led to platelet activation and enhanced generation of reactive oxygen species (ROS) and membrane scrambling, suggesting enhanced platelet apoptosis. More important, platelets modulate soluble Aß into fibrillar structures that were absorbed by apoptotic but not vital platelets. This together with enhanced platelet adhesion under flow ex vivo and in vivo and platelet accumulation at amyloid deposits of cerebral vessels of AD transgenic mice suggested that platelets are major contributors of CAA inducing platelet thrombus formation at vascular amyloid plaques leading to vessel occlusion critical for cerebrovascular events like stroke.

  6. Platelets effects on tumor growth.

    PubMed

    Goubran, Hadi A; Stakiw, Julie; Radosevic, Mirjana; Burnouf, Thierry

    2014-06-01

    Unlike other blood cells, platelets are small anucleate structures derived from marrow megakaryocytes. Thought for almost a century to possess solely hemostatic potentials, platelets, however, play a much wider role in tissue regeneration and repair and interact intimately with tumor cells. On one hand, tumor cells induce platelet aggregation (TCIPA), known to act as the trigger of cancer-associated thrombosis. On the other hand, platelets recruited to the tumor microenvironment interact, directly, with tumor cells, favoring their proliferation, and, indirectly, through the release of a wide palette of growth factors, including angiogenic and mitogenic proteins. In addition, the role of platelets is not solely confined to the primary tumor site. Indeed, they escort tumor cells, helping their intravasation, vascular migration, arrest, and extravasation to the tissues to form distant metastasis. As expected, nonspecific or specific inhibition of platelets and their content represents an attractive novel approach in the fight against cancer. This review illustrates the role played by platelets at primary tumor sites and in the various stages of the metastatic process.

  7. Platelets in inflammation and infection.

    PubMed

    Jenne, Craig N; Kubes, Paul

    2015-01-01

    Although platelets are traditionally recognized for their central role in hemostasis, many lines of research clearly demonstrate these rather ubiquitous blood components are potent immune modulators and effectors. Platelets have been shown to directly recognize, sequester and kill pathogens, to activated and recruit leukocytes to sites of infection and inflammation, and to modulate leukocyte behavior, enhancing their ability to phagocytose and kill pathogens and inducing unique effector functions, such as the production of Neutrophil Extracellular Traps (NETs). This multifaceted response to infection and inflammation is due, in part, to the huge array of soluble mediators and cell surface molecules expressed by platelets. From their earliest origins as primordial hemocytes in invertebrates to their current form as megakaryocyte-derived cytoplasts, platelets have evolved to be one of the key regulators of host intravascular immunity and inflammation. In this review, we present the diverse roles platelets play in immunity and inflammation associated with autoimmune diseases and infection. Additionally, we highlight recent advances in our understanding of platelet behavior made possible through the use of advanced imaging techniques that allow us to visualize platelets and their interactions, in real-time, within the intact blood vessels of a living host.

  8. A randomized, controlled study on the influence of acetaminophen, diclofenac, or naproxen on aspirin-induced inhibition of platelet aggregation.

    PubMed

    Galliard-Grigioni, Katja S; Reinhart, Walter H

    2009-05-01

    Nonsteroidal anti-inflammatory drugs (NSAID) may interfere with aspirin (acetylsalicylic acid) and increase the risk for cardiovascular events. The clinical relevance is uncertain. The aim of this study was to analyse the influence of a co-administration of aspirin and NSAID on platelet aggregation. In a randomized, placebo controlled trial, eleven healthy volunteers were studied during 4 separate study periods of 4 days each. Individuals were treated on each occasion with 100 mg aspirin daily in combination with either 3 x 1 g acetaminophen, 3 x 50 mg diclofenac, 3 x 250 mg naproxen, or 3 x 1 placebo. Primary hemostasis was assessed with a platelet function analyser (PFA-100), which measures the closure time (CT) of a collagen- and epinephrine-coated pore by aggregating platelets in flowing blood. Naproxen enhanced the anti-aggregatory action of aspirin after 24 h (CT rising from 104+/-16 s at baseline to 212+/-69 s at 24 h, P<0.001), which was not seen with any other drug combination. Diclofenac reduced the anti-aggregatory action of aspirin in the first two days, since the CT did not rise significantly (109+/-19 s, 148+/-56 s, and 168+/-66 s at 0 h, 24 h, 48 h, respectively, P>0.05). Acetaminophen had no effect compared with placebo. After 4 days of treatment platelet aggregation was similarly inhibited by all combinations. We conclude that a co-administration of NSAID and aspirin may interfere with platelet inhibition at the beginning of a treatment with an increase of naproxen and a decrease of diclofenac. This effect is lost after 4 days, suggesting that a regular daily co-administration of NSAID does not have an influence on platelet inhibition by aspirin.

  9. THE EFFECT OF ACETYLSALICYLIC ACID ON PLATELET FUNCTION

    PubMed Central

    Evans, Geoffrey; Packham, Marian A.; Nishizawa, Edward E.; Mustard, James F.; Murphy, Edmund A.

    1968-01-01

    Acetylsalicylic acid (ASA, aspirin) and sodium salicylate inhibit platelet aggregation induced by collagen, antigen-antibody complexes, gamma globulin-coated particles or thrombin. These compounds suppress the release of platelet constituents, such as adenosine diphosphate (ADP) and serotonin, induced by such stimuli. Since ASA and sodium salicylate do not inhibit ADP-induced platelet aggregation, it appears that their effect on the action of the other stimuli is due to a decrease in the amount of ADP released. The administration of ASA to rabbits (in doses which inhibited collagen-induced platelet aggregation) impaired hemostasis, prolonged platelet survival, and diminished the amount of deposit formed in an extracorporeal shunt. PMID:4176225

  10. Enhanced pyrite rejection in coal flotation

    SciTech Connect

    Tao, D.P.; Lu, M.X.; Richardson, P.E.; Luttrell, G.H.; Adel, G.T.; Yoon, R.H.

    1994-12-31

    Difficulties in rejecting pyrite from coal by flotation primarily result from two mechanisms of particle recovery: attachment and middlings. Attachment of pyrite is the consequence of surface hydrophobicity induced by superficial oxidation; middlings that can float readily are caused by incomplete liberation of pyrite from coal. New flotation schemes have been developed to enhance pyrite rejection. They are referred to as Electrochemically-Enhanced Sulfur Rejection (EESR) and Polymer-Enhanced Sulfur Rejection (PESR) processes. In the EESR process, the formation of hydrophobic products is prevented by electrochemical techniques in which active metals are used as sacrificial anodes to cathodically protect pyrite from oxidation; in the PESR process, hydrophilic polymers is used to mask coal in middlings by specific adsorption on pyrite, and thus depress coal-pyrite middlings.

  11. Paying To Belong: When Does Rejection Trigger Ingratiation?

    PubMed Central

    Romero-Canyas, Rainer; Downey, Geraldine; Reddy, Kavita S.; Rodriguez, Sylvia; Cavanaugh, Timothy J.; Pelayo, Rosemary

    2010-01-01

    Societies and social scientists have long held the belief that exclusion induces ingratiation and conformity, an idea in contradiction with robust empirical evidence linking rejection with hostility and aggression. The classic literatures on ingratiation and conformity help resolve this contradiction by identifying circumstances under which rejection may trigger efforts to ingratiate. Jointly, findings from these literatures suggest that when people are given an opportunity to impress their rejecters, ingratiation is likely after rejection experiences that are harsh and that occur in important situations that threaten the individual’s self-definition. Four studies tested the hypothesis that people high in rejection sensitivity, and therefore dispositionally concerned about rejection, will utilize opportunities to ingratiate after harsh rejection in situations that are self-defining. In three studies of situations that are particularly self-defining for men, rejection predicted ingratiation among men (but not women) who were high in rejection sensitivity. In a fourth study, harsh rejection in a situation particularly self-defining for women predicted ingratiation among highly rejection-sensitive women (but not men). These findings help identify the specific circumstances under which people are willing to act in socially desirable ways toward those who have rejected them harshly. PMID:20649367

  12. Late acute humoral rejection in low-risk renal transplant recipients induced with an interleukin-2 receptor antagonist and maintained with standard therapy: preliminary communication.

    PubMed

    Morales, J; Contreras, L; Zehnder, C; Pinto, V; Elberg, M; Araneda, S; Herzog, C; Calabran, L; Aguiló, J; Ferrario, M; Buckel, E; Fierro, J A

    2011-01-01

    Low-risk renal transplant recipients treated with standard immunosuppressive therapy including interleukin-2 receptor (IL-2R) antagonist show a low incidence of early rejection episodes but few reports have examined the incidence and severity of late rejection processes. This study evaluated retrospectively cellular and antibody-mediated rejection (AMR) among 42 recipients selected because they showed low panel-reactive-antibodies, short cold ischemia time, no delayed graft function, and therapy including basiliximab (Simulect) induction. The mean observation time was 6.6 years. Sixty-seven percent of donors were deceased. Ten-year patient and death-censored graft survivals were 81% and 78%, respectively. Seven patients lost their kidneys due to nonimmunologic events. The seven recipients who experienced cellular rejection episodes during the first posttransplant year had them reversed with steroids. Five patients displayed late acute AMR causing functional deterioration in four cases including 1 graft loss. De novo sensitization occurred in 48% of recipients including patients without clinical rejection. In conclusion, long-term follow-up of kidney transplant recipients selected by a low immunologic risk showed a persistent risk of de novo sensitization evolving to acute AMR in 11% of cases. Although immunologic events were related to late immunosuppressive reduction, most graft losses were due to nonimmunologic factors.

  13. Platelet associated antibodies

    MedlinePlus

    ... medlineplus.gov/ency/article/003552.htm Platelet-associated antibodies blood test To use the sharing features on ... JavaScript. This blood test shows if you have antibodies against platelets in your blood. Platelets are a ...

  14. The proteolytic processing of pro-platelet-derived growth factor-A at RRKR(86) by members of the proprotein convertase family is functionally correlated to platelet-derived growth factor-A-induced functions and tumorigenicity.

    PubMed

    Siegfried, Géraldine; Khatib, Abdel-Majid; Benjannet, Suzanne; Chrétien, Michel; Seidah, Nabil G

    2003-04-01

    Although altered expression of platelet-derived growth factor (PDGF)-A is a hallmark of many cancers, the importance of pro-PDGF-A conversion to PDGF-A in tumorigenesis and the cognate protease(s) is unknown. Pro-PDGF-A processing occurs at pairs of basic residues, likely involving the proprotein convertases (PCs). In the colon carcinoma cell line LoVo, we found that Furin is the most potent PDGF-A convertase. Mutation of the PC-site RRKR(86) to ARKA(86) inhibited pro-PDGF-A processing, its receptor tyrosine phosphorylation, and cell proliferation. This processing is also blocked by the PC preprosegments (pps) ppFurin, ppPC5, and ppPACE4, and by the Furin-variants of alpha2-macroglobulin and alpha1-antitrypsin. Chinese hamster ovary cells overexpressing pro-PDGF-A (ARKA(86)) failed to induce tumors in nude mice. Thus, PC-directed inhibitors might represent new agents for therapy in neoplasia induced by PDGF-A.

  15. Blood platelet kinetics and platelet transfusion.

    PubMed

    Aster, Richard H

    2013-11-01

    The discovery of citrate anticoagulant in the 1920s and the development of plastic packs for blood collection in the 1960s laid the groundwork for platelet transfusion therapy on a scale not previously possible. A major limitation, however, was the finding that platelet concentrates prepared from blood anticoagulated with citrate were unsuitable for transfusion because of platelet clumping. We found that this could be prevented by simply reducing the pH of platelet-rich plasma to about 6.5 prior to centrifugation. We used this approach to characterize platelet kinetics and sites of platelet sequestration in normal and pathologic states and to define the influence of variables such as anticoagulant and ABO incompatibility on post-transfusion platelet recovery. The "acidification" approach enabled much wider use of platelet transfusion therapy until alternative means of producing concentrates suitable for transfusion became available.

  16. The relationship between platelet endothelial cell adhesion molecule-1 and paraquat-induced lung injury in rabbits

    PubMed Central

    Shi, Jing; Hu, Chun-lin; Gao, Yu-feng; Liao, Xiao-xing; Xu, Hope

    2012-01-01

    BACKGROUND: Platelet endothelial cell adhesion molecule-1 (PECAM-1), also known as CD31, is mainly distributed in vascular endothelial cells. Studies have shown that PECAM-1 is a very significant indicator of angiogenesis, and has been used as an indicator for vascular endothelial cells. The present study aimed to explore the relationship between the expression of PECAM-1 and the degree of acute lung injury (ALI) and fibrosis in paraquat (PQ) induced lung injury in rabbits. METHODS: Thirty-six adult New Zealand rabbits were randomly divided into three groups (12 rabbits in each group) according to PQ dosage: 8 mg/kg (group A), 16 mg/kg (group B), and 32 mg/kg (group C). After PQ infusion, the rabbits were monitored for 7 days and then euthanized. The lungs were removed for histological evaluation. Masson staining was used to determine the degree of lung fibrosis (LF), and semi-quantitative immune-histochemistry analysis to determine the expression of PECAM-1. Pearson’s product-moment correlation analysis was performed to evaluate the relationship between the expression of PECAM-1 and the extent of lung injuries expressed by ALI score and degree of LF. RESULTS: Rabbits in the three groups showed apparent poisoning. The rabbits survived longer in group A than in groups B and C (6.47±0.99 days vs. 6.09±1.04 days vs. 4.77±2.04 days) (P<0.05). ALI score was lower in group A than in groups B and C (8.33±1.03 vs. 9.83±1.17 vs. 11.50±1.38) (P<0.05), and there was statistically significant difference between group B and group C (P=0.03). LF was slighter in group A than in groups B and C (31.09%±2.05 % vs. 34.37%±1.62 % vs. 36.54%±0.44%) (P<0.05), and there was statistically significant difference between group B and group C (P=0.026). The PEACAM-1 expression was higher in group A than in groups B and C (20.31%±0.70% vs. 19.34%±0.68% vs. 18.37%±0.46%) (P<0.05), and there was statistically significant difference between group B and group C (P=0.017). Pearson

  17. A role for platelet-derived growth factor in drug-induced chronic ergotism? A case report.

    PubMed

    Pietrogrande, F; Caenazzo, A; Dazzi, F; Polato, G; Girolami, A

    1995-07-01

    Generalized vasoconstriction in chronic ergot poisoning is attributed both to the ergotamine activity on alpha-adrenergic receptors and to its direct action on vascular smooth muscle cells. The authors propose that endothelial wall, chronically damaged by ergot alkaloids, releases platelet-derived growth factor (PDGF), which contributes to vasoconstriction and promotes further arterial obstruction. Their hypothesis is supported by the increased PDGF activity found in plasma of a patient suffering from chronic ergotism.

  18. Platelet-induced thrombin generation by the calibrated automated thrombogram assay is increased in patients with essential thrombocythemia and polycythemia vera.

    PubMed

    Panova-Noeva, Marina; Marchetti, Marina; Spronk, Henri Maria; Russo, Laura; Diani, Erika; Finazzi, Guido; Finazzi, Good; Salmoiraghi, Silvia; Rambaldi, Alessandro; Rambaldi, Aueesandrd; Barbui, Tiziano; Barbui, Titiano; Ten Cate, Hugo; Ten Cate, Huao; Falanga, Anna

    2011-04-01

    The platelet contribution to the thrombophilic state of patients with myeloproliferative neoplasms (MPNs), i.e., essential thrombocythemia (ET) and polycythemia vera (PV), remains uncertain. In this study we aimed to characterize the thrombin generation (TG) potential expressed by platelets from these subjects, compare it to normal platelets, and identify what factors might be responsible for platelet TG. In a group of 140 MPN patients (80 ET and 60 PV) and 72 healthy subjects, we measured the global procoagulant potential of platelet-rich plasma (PRP) utilizing the TG assay by the calibrated automated thrombogram (CAT). To characterize the procoagulant contribution of platelets in PRP, the TG of both isolated platelets and platelet-poor plasma was measured, and the platelet surface expression of TF was determined. Finally, the activation status of platelets was assessed by the levels of P-selectin expressed on platelet surface. MPN patients had significantly increased PRP and isolated platelet TG potential compared to controls. This was associated to the occurrence of platelet activation. Patients carriers of the JAK2V617F mutation showed the highest values of TG and platelet surface TF and P-selectin. Platelet TG potential was significantly lower in hydroxyurea(HU) compared to non-HU-treated patients and was lowest in HU-treated JAK2V617F carriers. In subjects not receiving HU, platelet TG significantly increased by JAK2V617F allele burden increment (P < 0.05).This study demonstrates a platelet-dependent form of hypercoagulability in MPN patients, particularly in those carriers of the JAK2V617F mutation. The cytoreductive therapy with HU significantly affects this prothrombotic phenotype.

  19. LC-MS/MS Analysis and Comparison of Oxidative Damages on Peptides Induced by Pathogen Reduction Technologies for Platelets

    NASA Astrophysics Data System (ADS)

    Prudent, Michel; Sonego, Giona; Abonnenc, Mélanie; Tissot, Jean-Daniel; Lion, Niels

    2014-04-01

    Pathogen reduction technologies (PRT) are photochemical processes that use a combination of photosensitizers and UV-light to inactivate pathogens in platelet concentrates (PCs), a blood-derived product used to prevent hemorrhage. However, different studies have questioned the impact of PRT on platelet function and transfusion efficacy, and several proteomic analyses revealed possible oxidative damages to proteins. The present work focused on the oxidative damages produced by the two main PRT on peptides. Model peptides containing residues prone to oxidation (tyrosine, histidine, tryptophane, and cysteine) were irradiated with a combination of amotosalen/UVA (Intercept process) or riboflavin/UVB (Mirasol-like process). Modifications were identified and quantified by liquid chromatography coupled to tandem mass spectrometry. Cysteine-containing peptides formed disulfide bridges (R-SS-R, -2 Da; favored following amotosalen/UVA), sulfenic and sulfonic acids (R-SOH, +16 Da, R-SO3H, +48 Da, favored following riboflavin/UVB) upon treatment and the other amino acids exhibited different oxidations revealed by mass shifts from +4 to +34 Da involving different mechanisms; no photoadducts were detected. These amino acids were not equally affected by the PRT and the combination riboflavin/UVB generated more oxidation than amotosalen/UVA. This work identifies the different types and sites of peptide oxidations under the photochemical treatments and demonstrates that the two PRT may behave differently. The potential impact on proteins and platelet functions may thus be PRT-dependent.

  20. Clovamide-rich extract from Trifolium pallidum reduces oxidative stress-induced damage to blood platelets and plasma.

    PubMed

    Kolodziejczyk, Joanna; Olas, Beata; Wachowicz, Barbara; Szajwaj, Barbara; Stochmal, Anna; Oleszek, Wieslaw

    2011-09-01

    Numerous plants (including clovers) have been widely used in folk medicine for the treatment of different disorders. This in vitro study was designed to examine the antioxidative effects of the clovamide-rich fraction, obtained from aerial parts of Trifolium pallidum, in the protection of blood platelets and plasma against the nitrative and oxidative damage, caused by peroxynitrite (ONOO(-)). Carbonyl groups and 3-nitrotyrosine in blood platelet and plasma proteins were determined by ELISA tests. Thiol groups level was estimated by using 5,5'-dithio-bis(2-nitro-benzoic acid, DTNB). Plasma lipid peroxidation was measured spectrophotometrically as the production of thiobarbituric acid reactive substances. The results from our work indicate that clovamide-rich T. pallidum extract may reveal the protective properties in the prevention against oxidative stress. The presence of clovamide-rich T. pallidum extract (12.5-100 μg/ml) partly inhibited ONOO(-)-mediated protein carbonylation and nitration. All the used concentrations of T. pallidum extract reduced lipid peroxidation in plasma. The antioxidative action of the tested extract in the protection of blood platelet lipids was less effective; the extract at the lowest final concentration (12.5 μg/ml) had no protective effect against lipid peroxidation. The present results indicate that the extract from T. pallidum is likely to be a source of compounds with the antioxidative properties, useful in the prevention against the oxidative stress-related diseases.

  1. Platelet dynamics in three-dimensional simulation of whole blood.

    PubMed

    Vahidkhah, Koohyar; Diamond, Scott L; Bagchi, Prosenjit

    2014-06-03

    A high-fidelity computational model using a 3D immersed boundary method is used to study platelet dynamics in whole blood. We focus on the 3D effects of the platelet-red blood cell (RBC) interaction on platelet margination and near-wall dynamics in a shear flow. We find that the RBC distribution in whole blood becomes naturally anisotropic and creates local clusters and cavities. A platelet can enter a cavity and use it as an express lane for a fast margination toward the wall. Once near the wall, the 3D nature of the platelet-RBC interaction results in a significant platelet movement in the transverse (vorticity) direction and leads to anisotropic platelet diffusion within the RBC-depleted zone or cell-free layer (CFL). We find that the anisotropy in platelet motion further leads to the formation of platelet clusters, even in the absence of any platelet-platelet adhesion. The transverse motion, and the size and number of the platelet clusters are observed to increase with decreasing CFL thickness. The 3D nature of the platelet-RBC collision also induces fluctuations in off-shear plane orientation and, hence, a rotational diffusion of the platelets. Although most marginated platelets are observed to tumble just outside the RBC-rich zone, platelets further inside the CFL are observed to flow with an intermittent dynamics that alters between sliding and tumbling, as a result of the off-shear plane rotational diffusion, bringing them even closer to the wall. To our knowledge, these new findings are based on the fundamentally 3D nature of the platelet-RBC interaction, and they underscore the importance of using cellular-scale 3D models of whole blood to understand platelet margination and near-wall platelet dynamics.

  2. Expansion of the neonatal platelet mass is achieved via an extension of platelet lifespan

    PubMed Central

    Liu, Zhi-Jian; Hoffmeister, Karin M.; Hu, Zhongbo; Mager, Donald E.; Ait-Oudhia, Sihem; Debrincat, Marlyse A.; Pleines, Irina; Josefsson, Emma C.; Kile, Benjamin T.; Italiano, Joseph; Ramsey, Haley; Grozovsky, Renata; Veng-Pedersen, Peter; Chavda, Chaitanya

    2014-01-01

    The fetal/neonatal hematopoietic system must generate enough blood cells to meet the demands of rapid growth. This unique challenge might underlie the high incidence of thrombocytopenia among preterm neonates. In this study, neonatal platelet production and turnover were investigated in newborn mice. Based on a combination of blood volume expansion and increasing platelet counts, the platelet mass increased sevenfold during the first 2 weeks of murine life, a time during which thrombopoiesis shifted from liver to bone marrow. Studies applying in vivo biotinylation and mathematical modeling showed that newborn and adult mice had similar platelet production rates, but neonatal platelets survived 1 day longer in circulation. This prolonged lifespan fully accounted for the rise in platelet counts observed during the second week of murine postnatal life. A study of pro-apoptotic and anti-apoptotic Bcl-2 family proteins showed that neonatal platelets had higher levels of the anti-apoptotic protein Bcl-2 and were more resistant to apoptosis induced by the Bcl-2/Bcl-xL inhibitor ABT-737 than adult platelets. However, genetic ablation or pharmacologic inhibition of Bcl-2 alone did not shorten neonatal platelet survival or reduce platelet counts in newborn mice, indicating the existence of redundant or alternative mechanisms mediating the prolonged lifespan of neonatal platelets. PMID:24599546

  3. Expansion of the neonatal platelet mass is achieved via an extension of platelet lifespan.

    PubMed

    Liu, Zhi-Jian; Hoffmeister, Karin M; Hu, Zhongbo; Mager, Donald E; Ait-Oudhia, Sihem; Debrincat, Marlyse A; Pleines, Irina; Josefsson, Emma C; Kile, Benjamin T; Italiano, Joseph; Ramsey, Haley; Grozovsky, Renata; Veng-Pedersen, Peter; Chavda, Chaitanya; Sola-Visner, Martha

    2014-05-29

    The fetal/neonatal hematopoietic system must generate enough blood cells to meet the demands of rapid growth. This unique challenge might underlie the high incidence of thrombocytopenia among preterm neonates. In this study, neonatal platelet production and turnover were investigated in newborn mice. Based on a combination of blood volume expansion and increasing platelet counts, the platelet mass increased sevenfold during the first 2 weeks of murine life, a time during which thrombopoiesis shifted from liver to bone marrow. Studies applying in vivo biotinylation and mathematical modeling showed that newborn and adult mice had similar platelet production rates, but neonatal platelets survived 1 day longer in circulation. This prolonged lifespan fully accounted for the rise in platelet counts observed during the second week of murine postnatal life. A study of pro-apoptotic and anti-apoptotic Bcl-2 family proteins showed that neonatal platelets had higher levels of the anti-apoptotic protein Bcl-2 and were more resistant to apoptosis induced by the Bcl-2/Bcl-xL inhibitor ABT-737 than adult platelets. However, genetic ablation or pharmacologic inhibition of Bcl-2 alone did not shorten neonatal platelet survival or reduce platelet counts in newborn mice, indicating the existence of redundant or alternative mechanisms mediating the prolonged lifespan of neonatal platelets.

  4. Transfusion of ABO-mismatched platelets leads to early platelet refractoriness.

    PubMed

    Carr, R; Hutton, J L; Jenkins, J A; Lucas, G F; Amphlett, N W

    1990-07-01

    Forty-three consecutive patients previously unexposed to platelets and undergoing treatment for acute leukaemia or autografting for relapsed Hodgkin's lymphoma were randomized to receive transfused platelets of either their own ABO group (OG) or of a major mismatched group (MMG). The 26 evaluable patients were equally distributed between the two study groups. Nine of 13 (69%) MMG patients became refractory with a median onset at transfusion 7 (15 d), compared with only one of 13 (8%) OG patients (P = 0.001). Refractoriness was associated with the formation of high titre isoagglutinins, anti-HLA and platelet specific antibodies. In one patient refractoriness appeared to be due to high titre isoagglutinins alone. Six other patients developed an increase in isoagglutinin titre sufficient to adversely affect platelet increments. Patients receiving ABO-mismatched platelets had a higher incidence of anti-HLA antibodies (5 v. 1) and platelet specific antibodies (4 v. 1). ABO-mismatched platelets transfused prior to the onset of refractoriness resulted in increments similar to those achieved by ABO-matched platelets. The study demonstrates that ABO-mismatched platelets are as effective as matched platelets in patients with low titre isoagglutinins requiring only few transfusions. However, the greater incidence of early refractoriness induced in MMG patients indicates that ABO-mismatched platelets should not be given to patients with marrow failure requiring long-term support.

  5. Reelin is a platelet protein and functions as a positive regulator of platelet spreading on fibrinogen.

    PubMed

    Tseng, Wei-Lien; Huang, Chien-Ling; Chong, Kowit-Yu; Liao, Chang-Huei; Stern, Arnold; Cheng, Ju-Chien; Tseng, Ching-Ping

    2010-02-01

    Abnormalities of platelet functions have been linked to reelin-impaired neuronal disorders. However, little attention has been given to understanding the interplay between reelin and platelet. In this study, reelin was found to present in the human platelets and megakaryocyte-like leukemic cells. Reelin-binding assays revealed that extracellular reelin can interact with platelets through the receptor belonging to the low density lipoprotein receptor gene family. The reelin-to-platelet interactions enhance platelet spreading on fibrinogen concomitant with the augmentation of lamellipodia formation and F-actin bundling. In contrast, reelin has no effect on integrin alphaIIbbeta3 activation and agonist-induced platelet aggregation. Molecular analysis revealed that the up-regulation of Rac1 activity and the inhibition of protein kinase C delta-Thr505 phosphorylation are important for reelin-mediated enhancement of platelet spreading on fibrinogen. These findings demonstrate for the first time that reelin is present in platelets and the reelin-to-platelet interactions play a novel role in platelet signaling and functions.

  6. Platelet-cytokine Complex Suppresses Tumour Growth by Exploiting Intratumoural Thrombin-dependent Platelet Aggregation

    PubMed Central

    Li, Yu-Tung; Nishikawa, Tomoyuki; Kaneda, Yasufumi

    2016-01-01

    Tumours constitute unique microenvironments where various blood cells and factors are exposed as a result of leaky vasculature. In the present study, we report that thrombin enrichment in B16F10 melanoma led to platelet aggregation, and this property was exploited to administer an anticancer cytokine, interferon-gamma induced protein 10 (IP10), through the formation of a platelet-IP10 complex. When intravenously infused, the complex reached platelet microaggregates in the tumour. The responses induced by the complex were solely immune-mediated, and tumour cytotoxicity was not observed. The complex suppressed the growth of mouse melanoma in vivo, while both platelets and the complex suppressed the accumulation of FoxP3+ regulatory T cells in the tumour. These results demonstrated that thrombin-dependent platelet aggregation in B16F10 tumours defines platelets as a vector to deliver anticancer cytokines and provide specific treatment benefits. PMID:27117228

  7. Daily prickly pear consumption improves platelet function.

    PubMed

    Wolfram, R; Budinsky, A; Efthimiou, Y; Stomatopoulos, J; Oguogho, A; Sinzinger, H

    2003-07-01

    Prickly pear is traditionally used by Pima Indians as a dietary nutrient against diabetes mellitus. We examined the effect of daily consumption of 250 g in 8 healthy volunteers and 8 patients with mild familial heterozygous hypercholesterolemia on various parameters of platelet function. Beside its action on lipids and lipoproteins, prickly pear consumption significantly reduced the platelet proteins (platelet factor 4 and beta-thromboglobulin), ADP-induced platelet aggregation and improved platelet sensitivity (against PGI2 and PGE1) in volunteers as well as in patients. Also plasma 11-DH-TXB2 and the WU-test showed a significant improvement in both patients and volunteers. In contrast, collagen-induced platelet aggregation and the number of circulating endothelial cells showed a significant response in patients only. No influence of prickly pear ingestion on peripheral platelet count was monitored. The dietary run-in period did not influence any of the parameters of haemostasis examined. No sex difference was seen. Prickly pear may induce at least part of its beneficial actions on the cardiovascular system via decreasing platelet activity and thereby improving haemostatic balance.

  8. Inhibition of platelet-activating factor- and zymosan-activated serum-induced chemotaxis of human neutrophils by nedocromil sodium, BN 52021 and sodium cromoglycate.

    PubMed Central

    Bruijnzeel, P. L.; Warringa, R. A.; Kok, P. T.

    1989-01-01

    1. Inflammatory cells such as eosinophils and neutrophils are thought to contribute actively to the pathogenesis of asthma since they infiltrate into the lung tissue. These cells are mobilized by lipid-like and protein-like chemotactic factors. As illustrative examples of both groups, platelet-activating-factor (Paf) and zymosan-activated-serum (ZAS) were used in this study. The inhibitory effects of nedocromil sodium, the Paf antagonist BN 52021 and sodium cromoglycate on Paf- and ZAS-induced neutrophil chemotaxis were evaluated. 2. All tested drugs inhibited Paf-induced neutrophil chemotaxis with approximately the same potency (IC50 approximately 1 nM). 3. Nedocromil sodium and sodium cromoglycate were equally potent in inhibiting ZAS-induced neutrophil chemotaxis (IC50 = 0.1-1 microM), whereas BN 52021 was considerably less potent (IC30 = 10 microM). 4. To find out whether the drugs tested could inhibit early events in cell activation, their capacity to inhibit Paf- and ZAS-induced cytosolic free Ca2+-mobilization was investigated. BN 52021, at a concentration of 100 microM, completely inhibited Paf-induced Ca2+-mobilization and inhibited ZAS-induced Ca2+-mobilization by about 50%. Nedocromil sodium and sodium cromoglycate were ineffective. PMID:2551444

  9. CD8+ T cells mediate antibody-independent platelet clearance in mice.

    PubMed

    Arthur, Connie M; Patel, Seema R; Sullivan, H Cliff; Winkler, Annie M; Tormey, Chris A; Hendrickson, Jeanne E; Stowell, Sean R

    2016-04-07

    Platelet transfusion provides an important therapeutic intervention in the treatment and prevention of bleeding. However, some patients rapidly clear transfused platelets, preventing the desired therapeutic outcome. Although platelet clearance can occur through a variety of mechanisms, immune-mediated platelet removal often plays a significant role. Numerous studies demonstrate that anti-platelet alloantibodies can induce significant platelet clearance following transfusion. In fact, for nearly 50 years, anti-platelet alloantibodies were considered to be the sole mediator of immune-mediated platelet clearance in platelet-refractory individuals. Although nonimmune mechanisms of platelet clearance can often explain platelet removal in the absence of anti-platelet alloantibodies, many patients experience platelet clearance following transfusion in the absence of a clear mechanism. These results suggest that other processes of antibody-independent platelet clearance may occur. Our studies demonstrate that CD8(+)T cells possess the unique ability to induce platelet clearance in the complete absence of anti-platelet alloantibodies. These results suggest a previously unrecognized form of immune-mediated platelet clearance with significant implications in the appropriate management of platelet-refractory individuals.

  10. Interaction of a Monoclonal Antibody to Glycoprotein IV (CD36) with Human Platelets and its Effect on Platelet Function.

    PubMed

    Legrand, C; Pidard, D; Beiso, P; Tenza, D; Edelman, L

    1991-01-01

    FA6-152, a monoclonal antibody to platelet membrane glycoprotein IV (CP IV), was used to quantify the expression of this glycoprotein on platelets, as well as to evaluate its role in platelet aggregation. On resting platelets, 19 400 ± 7700 molecules of the (125)I-labelled IgC could bind per platelet (n = 20). Binding was not modified following stimulation of the platelets with ADP (10 µmol/l) or thrombin (0.1 U/ml). Fab fragments prepared from the antibody by papain digestion also bound to the platelet surface in a saturable manner. Both the intact IgC and its Fab fragments were found to inhibit platelet aggregation and secretion induced by ADP or collagen in platelet-rich plasma and by thrombin in platelet suspensions. Under nonstirred conditions, whereby the release reaction was only minimally affected, the antibody markedly inhibited thrombin-induced surface expression of α-granule thrombospondin (TSP), whereas it did not alter the concomitant expression of α-granule fibrinogen. In addition, electron microscopy revealed a predominant distribution of TSP and T;P IV on pseudopodia and between adherent cells on thrombin-stimulated platelets. These findings thus support the hypothesis that the interaction of TSP with GP IV on the platelet surface is required for an optimal platelet aggregation/secretion process to occur.

  11. Platelet-adenovirus vs. inert particles interaction: effect on aggregation and the role of platelet membrane receptors.

    PubMed

    Gupalo, Elena; Kuk, Cynthia; Qadura, Mohammad; Buriachkovskaia, Liudmila; Othman, Maha

    2013-01-01

    Platelets are involved in host defense via clearance of bacteria from the circulation, interaction with virus particles, and uptake of various size particulates. There is a growing interest in micro- and nanoparticles for drug delivery and there is evidence that the properties of these particles critically influence their interaction and uptake by various tissues and cells including platelets. Virus mediated gene therapy applications are still challenged by the resultant thrombocytopenia and the mechanism(s) of platelet-foreign particles interaction remains unclear. We studied the specifics of platelet interaction with an active biological agent (adenovirus) and inert latex microspheres (MS) and investigated the role of platelet proteins in this interaction. We show that activated and not resting platelets internalize MS, without influencing platelet aggregation. In contrast, adenovirus induces and potentiates ADP-induced platelet aggregation and results in rapid expression of P-selectin. Platelets then internalize adenovirus and viral particles appear inside the open canalicular system. Inhibition of platelet αIIbβ3, GPIbα, and P-selectin decreases both platelet aggregation and internalization of MS. Inhibition of αIIbβ3 and αVβ3 does not abolish adenovirus platelet internalization and adenovirus-induced platelet activation is maintained. Our study demonstrates that platelets react differentially with foreign particles and that αIIbβ3 is a key player in platelet engulfing of foreign particles but not in mediating adenovirus internalization. Other platelet candidate molecules remain to be investigated as potential targets for management of adenovirus-induced thrombocytopenia.

  12. The potential of GMP-compliant platelet lysate to induce a permissive state for cardiovascular transdifferentiation in human mediastinal adipose tissue-derived mesenchymal stem cells.

    PubMed

    Siciliano, Camilla; Chimenti, Isotta; Bordin, Antonella; Ponti, Donatella; Iudicone, Paola; Peruzzi, Mariangela; Rendina, Erino Angelo; Calogero, Antonella; Pierelli, Luca; Ibrahim, Mohsen; De Falco, Elena

    2015-01-01

    Human adipose tissue-derived mesenchymal stem cells (ADMSCs) are considered eligible candidates for cardiovascular stem cell therapy applications due to their cardiac transdifferentiation potential and immunotolerance. Over the years, the in vitro culture of ADMSCs by platelet lysate (PL), a hemoderivate containing numerous growth factors and cytokines derived from platelet pools, has allowed achieving a safe and reproducible methodology to obtain high cell yield prior to clinical administration. Nevertheless, the biological properties of PL are still to be fully elucidated. In this brief report we show the potential ability of PL to induce a permissive state of cardiac-like transdifferentiation and to cause epigenetic modifications. RTPCR results indicate an upregulation of Cx43, SMA, c-kit, and Thy-1 confirmed by immunofluorescence staining, compared to standard cultures with foetal bovine serum. Moreover, PL-cultured ADMSCs exhibit a remarkable increase of both acetylated histones 3 and 4, with a patient-dependent time trend, and methylation at lysine 9 on histone 3 preceding the acetylation. Expression levels of p300 and SIRT-1, two major regulators of histone 3, are also upregulated after treatment with PL. In conclusion, PL could unravel novel biological properties beyond its routine employment in noncardiac applications, providing new insights into the plasticity of human ADMSCs.

  13. Short-term exposure of platelets to glucose impairs inhibition of platelet aggregation by cyclooxygenase inhibitors.

    PubMed

    Kobzar, Gennadi; Mardla, Vilja; Samel, Nigulas

    2011-01-01

    Aspirin treatment reduces cardiovascular events and deaths in high-risk non-diabetic patients, but not in patients suffering from diabetes. In these patients, hyperglycemia has been found to cause reduced platelet sensitivity to aspirin. It is supposed that long-term exposure of platelets to glucose leads to non-enzymatic glycosylation and impairs aspirin inhibition of platelet aggregation. On the other hand, short-term exposure of platelets to glucose also attenuates the effect of aspirin on platelets. The aim of the present work was to analyse the effect of short-term exposure of glucose on the inhibition of platelet aggregation by aspirin and other cyclooxygenase (COX) inhibitors. Already a 15 min exposure of platelets to glucose impaired aspirin inhibition of the platelet aggregation induced by collagen, thrombin, adenosine diphosphate (ADP), and arachidonic acid (AA). Aspirin inhibition of platelet aggregation in platelet-rich plasma (PRP) was attenuated by 5.6, 11.2, 16.8, and 22.4 mM of glucose in a concentration-dependent way. The same effect was observed with indomethacin and acetaminophen used as cyclooxygenase inhibitors instead of aspirin. N-methyl-L-arginine, an inhibitor of nitric oxide synthase, prevented the effect of glucose on aspirin, indomethacin and acetaminophen inhibition of platelet aggregation. Other monosaccharides, for example fructose and galactose, impaired aspirin inhibition as did glucose. Lactic acid (0.1, 0.2, 0.4, 0.8 mM), the end product of anaerobic glycolysis in platelets, impaired the inhibition of platelet aggregation with aspirin in a concentration-dependent way but did not affect indomethacin. It is suggested that lactic acid might be a mediator of the effect of glucose on aspirin inhibition in platelets.

  14. Soothing the Sting of Rejection.

    ERIC Educational Resources Information Center

    Campbell, Joan Daniels

    1990-01-01

    Preventing rejection of a student by his/her peers and helping the child to cope with such rejection are ever-present challenges for teachers. Suggestions are given by teachers who have successfully dealt with students who were rejected by classmates. (IAH)

  15. Cancer and Thrombosis: The Platelet Perspective

    PubMed Central

    Meikle, Claire K. S.; Kelly, Clare A.; Garg, Priyanka; Wuescher, Leah M.; Ali, Ramadan A.; Worth, Randall G.

    2017-01-01

    Platelets are critical to hemostatic and immunological function, and are key players in cancer progression, metastasis, and cancer-related thrombosis. Platelets interact with immune cells to stimulate anti-tumor responses and can be activated by immune cells and tumor cells. Platelet activation can lead to complex interactions between platelets and tumor cells. Platelets facilitate cancer progression and metastasis by: (1) forming aggregates with tumor cells; (2) inducing tumor growth, epithelial-mesenchymal transition, and invasion; (3) shielding circulating tumor cells from immune surveillance and killing; (4) facilitating tethering and arrest of circulating tumor cells; and (5) promoting angiogenesis and tumor cell establishment at distant sites. Tumor cell-activated platelets also predispose cancer patients to thrombotic events. Tumor cells and tumor-derived microparticles lead to thrombosis by secreting procoagulant factors, resulting in platelet activation and clotting. Platelets play a critical role in cancer progression and thrombosis, and markers of platelet-tumor cell interaction are candidates as biomarkers for cancer progression and thrombosis risk. PMID:28105409

  16. Effect of photodynamic therapy on mouse platelets

    NASA Astrophysics Data System (ADS)

    Zhou, Chuannong; Chi, Shunji; Deng, Jinsheng; Zhang, Hua; Liang, Junlin; Ha, Xian-wen

    1993-03-01

    Normal mice received hematoporphyrin derivative (10 mg/kg iv) immediately, 24 or 48 hrs prior to red light irradiation. The blood was collected and the platelet-rich plasma was irradiated by red light (100 J/cm2). The platelets were fixed immediately, 8 or 16 hrs after irradiation, and processed for EM examination. In comparison with those of control mice, the platelets of all experimental mice showed structural changes: 16 hrs after irradiation all platelets were necrotized; 8 hrs after irradiation almost one fourth of the platelets were necrotized and the remaining were considerably damaged; immediately after irradiation a small number of platelets became necrotic and most other platelets were swollen and deformed, often with many cytoplasmic projections and considerable dilatation of the canalicular membrane system. Our findings provided a clear evidence that platelets are highly sensitive to PDT action and can be directly and rapidly injured by PDT even in the absence of vascular endothelial cells. Our results give firm support to the hypothesis that both endothelial cells and platelets may play an important role in the initiation of early vascular damage and microcirculatory alterations induced by PDT in vivo.

  17. [In vitro platelet production].

    PubMed

    Dunois-Lardé, C; Baruch, D

    2011-04-01

    This review aims at presenting a state of the art on platelet functions, not only in well-characterized hemostasis and thrombosis, but also in various domains such as inflammation, immunity, angiogenesis, source of growth factors, metastasis and vascular remodelling. This multivalent phenotype of platelets suggests new potential applications of platelets. The second objective is to present new advances in platelet formation from megakaryocytes and direct platelet release, as initially shown by our group and more recently by others.

  18. Platelet-activating factor in Iberian pig spermatozoa: receptor expression and role as enhancer of the calcium-induced acrosome reaction.

    PubMed

    Bragado, M J; Gil, M C; Garcia-Marin, L J

    2011-12-01

    Platelet-activating factor (PAF) is a phospholipid involved in reproductive physiology. PAF receptor is expressed in some mammalian spermatozoa species where it plays a role in these germ-cell-specific processes. The aim of this study is to identify PAF receptor in Iberian pig spermatozoa and to evaluate PAF's effects on motility, viability and acrosome reaction. Semen samples from Iberian boars were used. PAF receptor identification was performed by Western blotting. Spermatozoa motility was analysed by computer-assisted sperm analysis system, whereas spermatozoa viability and acrosome reaction were evaluated by flow cytometry. Different PAF concentrations added to non-capacitating medium during 60 min have no effect on any spermatozoa motility parameter measured. Acrosome reaction was rapid and potently induced by 1 μm calcium ionophore A23187 showing an effect at 60 min and maximum at 240 min. PAF added to a capacitating medium is not able to induce spermatozoa acrosome reaction at any time studied. However, PAF, in the presence of A23187, significantly accelerates and enhances the calcium-induced acrosome reaction in a concentration-dependent manner in Iberian boar spermatozoa. Exogenous PAF does not affect at all spermatozoa viability, whereas slightly exacerbated the A23187-induced loss in viability. This work demonstrates that PAF receptor is expressed in Iberian pig spermatozoa and that its stimulation by PAF regulates the calcium-induced acrosome reaction. This work contributes to further elucidate the physiological regulation of the most relevant spermatozoa functions for successful fertilization: acrosome reaction.

  19. Platelet function in the postprandial period

    PubMed Central

    2012-01-01

    Background Postprandial hyperlipidemia and hyperglycemia have been related to cardiovascular events. Among different underlying mechanisms platelet activation seems to be responsible too. No comparable data between various tests in normo- vs. hyperlipidemics before and at different time intervals are available after a fat meal. We aimed to compare 9 of them within the same patients at several time points in postprandial hyperlipidemia. Results For some tests baseline values between the groups were significantly different (TXB2, platelet sensitivity, sedimentation and WU-test). However, hyperlipidemia revealed a variable influence on the tests examined. Some of the available tests apparently sensitive to show platelet activation reflect the increase in triglycerides (TG), such as the sedimentation index. ADP-induced platelet aggregatory activity in count adjusted washed isolated platelet samples during postprandial hyperlipidemia indicates mildly enhanced platelet activity, but does not seem to induce significant changes in aggregation. In patients with severe hypertriglyceridemia (> 400 mg/dl fasting) changes in platelet function are more pronounced due to delayed decay and may last up to 16 hours paralleling TG reaching the prevalue. The overwhelming majority of platelet function tests do not significantly respond to postprandial hyperlipidemia. The correlation between the tests applied is poor. For standardization purpose, platelet aggregation tests, aimed to examine proaggregatory capacity in atherosclerosis, should only be performed at the same time of the day after a fasting period > 6 hours. The great variation in preanalytical work-up on comparison of various tests, large number of platelet tests available and their respective potential value are discussed. Conclusions At present, the suspicion that platelet function is significantly activated in the postprandial period cannot be supported by any of the tests used. The information provided is valuable to

  20. Evaluation of platelet turnover by flow cytometry.

    PubMed

    Salvagno, G L; Montagnana, M; Degan, M; Marradi, P L; Ricetti, M M; Riolfi, P; Poli, G; Minuz, P; Santonastaso, C L; Guidi, G C

    2006-05-01

    The number of circulating newly produced platelets depends on the thrombopoietic capacity of bone marrow as well as platelet removal from the bloodstream. Flow cytometric analysis with thiazole orange (TO), a fluorescent dye that crosses platelet membranes and binds intracellular RNA, has been used to measure circulating reticulated platelets (RPs) with high RNA content as an index of platelet turnover. We first assessed the specificity of TO flow cytometry and then applied this method in the diagnosis of thrombocytopenia caused by impaired platelet production or increased destruction. We also explored the utility of TO flow cytometry to predict thrombocytopoiesis after chemotherapy-induced bone marrow aplasia. Venous blood, anticoagulated with K(2)EDTA, was incubated with 0.6 microg/ml TO plus an anti-GPIIIa monoclonal antibody. The mean percentage of RPs in control subjects (n = 23) was 6.13 +/- 3.09%. RPs were 10.41 +/- 9.02% in patients (n = 10) with hematological malignancies during aplasia induced by chemotherapy and a significant increase in RPs (35.45 +/- 6.11%) was seen in the recovery phase. In 10 patients with idiopathic thrombocytopenic purpura, the percentage of TO positive platelets was 67.81 +/- 18.79 (P < 0.001 vs. controls). In patients with thrombocytopenia associated with hepatic cirrhosis (n = 21; 21.04 +/- 16.21%, P < 0.001 vs. controls) or systemic lupus erythematosus (n = 6, 29.08 +/- 15.57%; P < 0.001 vs. controls) increases in TO-stained platelets were also observed. Measurement of TO positive platelets may be a reliable tool for the laboratory identification of platelet disorders, with a higher sensitivity than measurement of platelet volume. Measurement of RPs may also prove useful to recognize the underlying pathogenetic mechanisms in thrombocytopenia.

  1. Monitoring Pharmacologically Induced Immunosuppression by Immune Repertoire Sequencing to Detect Acute Allograft Rejection in Heart Transplant Patients: A Proof-of-Concept Diagnostic Accuracy Study

    PubMed Central

    Valantine, Hannah A.; Penland, Lolita; Luikart, Helen; Strehl, Calvin; Cohen, Garrett; Khush, Kiran K.; Quake, Stephen R.

    2015-01-01

    Background It remains difficult to predict and to measure the efficacy of pharmacological immunosuppression. We hypothesized that measuring the B-cell repertoire would enable assessment of the overall level of immunosuppression after heart transplantation. Methods and Findings In this proof-of-concept study, we implemented a molecular-barcode-based immune repertoire sequencing assay that sensitively and accurately measures the isotype and clonal composition of the circulating B cell repertoire. We used this assay to measure the temporal response of the B cell repertoire to immunosuppression after heart transplantation. We selected a subset of 12 participants from a larger prospective cohort study (ClinicalTrials.gov NCT01985412) that is ongoing at Stanford Medical Center and for which enrollment started in March 2010. This subset of 12 participants was selected to represent post-heart-transplant events, with and without acute rejection (six participants with moderate-to-severe rejection and six without). We analyzed 130 samples from these patients, with an average follow-up period of 15 mo. Immune repertoire sequencing enables the measurement of a patient’s net state of immunosuppression (correlation with tacrolimus level, r = −0.867, 95% CI −0.968 to −0.523, p = 0.0014), as well as the diagnosis of acute allograft rejection, which is preceded by increased immune activity with a sensitivity of 71.4% (95% CI 30.3% to 94.9%) and a specificity of 82.0% (95% CI 72.1% to 89.1%) (cell-free donor-derived DNA as noninvasive gold standard). To illustrate the potential of immune repertoire sequencing to monitor atypical post-transplant trajectories, we analyzed two more patients, one with chronic infections and one with amyloidosis. A larger, prospective study will be needed to validate the power of immune repertoire sequencing to predict rejection events, as this proof-of-concept study is limited to a small number of patients who were selected based on several

  2. Platelet Disorders: MedlinePlus Health Topic

    MedlinePlus

    ... disorders depends on the cause. NIH: National Heart, Lung, and Blood Institute Start Here Platelets (University of Oklahoma Health ... the Signs and Symptoms of Thrombocytopenia? (National Heart, Lung, and Blood Institute) Diagnosis and Tests Heparin-Induced Thrombocytopenia Antibody ...

  3. Platelet factor XIII increases the fibrinolytic resistance of platelet-rich clots by accelerating the crosslinking of alpha 2-antiplasmin to fibrin

    NASA Technical Reports Server (NTRS)

    Reed, G. L.; Matsueda, G. R.; Haber, E.

    1992-01-01

    Platelet clots resist fibrinolysis by plasminogen activators. We hypothesized that platelet factor XIII may enhance the fibrinolytic resistance of platelet-rich clots by catalyzing the crosslinking of alpha 2-antiplasmin (alpha 2AP) to fibrin. Analysis of plasma clot structure by polyacrylamide gel electrophoresis and immunoblotting revealed accelerated alpha 2AP-fibrin crosslinking in platelet-rich compared with platelet-depleted plasma clots. A similar study of clots formed with purified fibrinogen (depleted of factor XIII activity), isolated platelets, and specific factor XIII inhibitors indicated that this accelerated crosslinking was due to the catalytic activity of platelet factor XIII. Moreover, when washed platelets were aggregated by thrombin, there was evidence of platelet factor XIII-mediated crosslinking between platelet alpha 2AP and platelet fibrin(ogen). Specific inhibition (by a monoclonal antibody) of the alpha 2AP associated with washed platelet aggregates accelerated the fibrinolysis of the platelet aggregate. Thus in platelet-rich plasma clots, and in thrombin-induced platelet aggregates, platelet factor XIII actively formed alpha 2AP-fibrin crosslinks, which appeared to enhance the resistance of platelet-rich clots to fibrinolysis.

  4. Interactions of human blood-platelets with vaccinia

    SciTech Connect

    Vernon, C.E.B.

    1989-01-01

    These investigations were conducted to determine whether vaccinia (strain WR) adsorbs to the human platelet and alters specific platelet activities, namely, the uptake of {sup 14}C-serotonin, the release of {sup 14}C-serotonin and also the release of {sup 14}C-serotonin stimulated by thrombin. Vaccinia did not alter the platelet uptake of {sup 14}C-serotonin. To determine if vaccinia induces a release of {sup 14}C-serotonin from platelets, vaccinia was added to washed or unwashed {sup 14}C-serotonin labeled platelets, and the release of {sup 14}C-Serotonin into the supernatant was measured. Less than 8% of the {sup 14}C-Serotonin was released. The action of vaccinia to alter the platelet release of {sup 14}C-serotonin induced by thrombin was monitored by measuring the radioactivity released from thrombin stimulated {sup 14}C-serotonin labeled platelets incubated with or without vaccinia. Vaccinia inhibited the thrombin induced release of {sup 14}C-serotonin from platelets at a virus to platelet ratios of 5 through 80 plaque forming units (p.f.u.)/platelet. The inhibition was dose dependent. The binding of virus to platelets was determined by a plaque assay of a washed mixture of vaccinia virus and platelets. After inoculation of mixture onto a monolayer of BSC40 cells at a virus to platelet ratio of 0.1 p.f.u./platelet, 50 cell-bound-virus per 130,000-150,000 platelets were enumerated. Vaccinia was observed to inhibit the thrombin induced clot formation of plasma by a thrombin clotting time test. Scanning electron micrographs of the clot formed in the presence of vaccinia revealed a close packed fibrous structure lacking the cross-linked mesh-like pattern seen in a normal clot. Transmission electron micrographs showed an increase in the length and a close packing of the fibrin threads.

  5. Rejection of deeply implanted foreign body induced by acupuncture treatment in patient suffering intractable pains lasting ten years following traumatic injury to the left scapular region during a road accident.

    PubMed

    Sternfeld, M; Hod, I

    1986-01-01

    Upper back pains lasting ten years were promptly improved in a 63 year old woman following the rejection of a forgotten foreign glass body, through a scar located over the left scapula, and treated by acupuncture. The patient insisted on having this treatment after unsuccessful prolonged and multi-disciplinary formal medical interventions culminating in preparations for exploratory surgery. The acupuncture directed to the scar induced an inflammatory reaction characterized by a sterile granulomatous reaction which surrounded a large piece of glass, apparently implanted in the soft tissue of the suprascapular area during a severe road accident which occurred ten years previously. The surgical intervention was avoided.

  6. Alteration of the platelet transcriptome in chronic kidney disease.

    PubMed

    Plé, Hélène; Maltais, Manon; Corduan, Aurélie; Rousseau, Guy; Madore, François; Provost, Patrick

    2012-10-01

    Bleeding and thrombotic disorders are major complications affecting patients with chronic kidney disease (CKD). Exposure of circulating platelets to uraemic toxins and contact with artificial surfaces during dialysis induce platelet abnormalities and alter the platelet proteome. We hypothesised that these changes may be subsequent to changes in the composition and/or regulation of the platelet transcriptome. In this study, we investigated the circulating platelets of 10 CKD patients (i.e. five chronic haemodialysis patients and five stage 4 CKD uraemic patients) and five age- and sex-matched healthy subjects. We observed an alteration of the platelet messenger RNA (mRNA) and microRNA transcriptome in CKD patients. Impaired in uraemic platelets, the levels of some mRNAs and of most microRNAs appeared to be corrected by dialysis, which is consistent with a beneficial effect of dialysis and a mRNA regulatory role of platelet microRNAs. Reduced in platelets of uraemic patients, phosphatidylcholine transfer protein (PCTP) and WD repeat-containing protein 1 (WDR1) were found to be regulated by microRNAs, the latter of which involving hsa-miR-19b, a microRNA increased in platelets of uraemic patients and involved in platelet reactivity. These results suggest that an alteration of microRNA-based mRNA regulatory mechanisms may underlie the platelet response to uremia and entail the development of platelet-related complications in CKD.

  7. Heat rejection system

    DOEpatents

    Smith, Gregory C.; Tokarz, Richard D.; Parry, Jr., Harvey L.; Braun, Daniel J.

    1980-01-01

    A cooling system for rejecting waste heat consists of a cooling tower incorporating a plurality of coolant tubes provided with cooling fins and each having a plurality of cooling channels therein, means for directing a heat exchange fluid from the power plant through less than the total number of cooling channels to cool the heat exchange fluid under normal ambient temperature conditions, means for directing water through the remaining cooling channels whenever the ambient temperature rises above the temperature at which dry cooling of the heat exchange fluid is sufficient and means for cooling the water.

  8. Isoform-Specific Modulation of Inflammation Induced by Adenoviral Mediated Delivery of Platelet-Derived Growth Factors in the Adult Mouse Heart

    PubMed Central

    Ylä-Herttuala, Seppo; Betsholtz, Christer; Andrae, Johanna

    2016-01-01

    Platelet-derived growth factors (PDGFs) are key regulators of mesenchymal cells in vertebrate development. To what extent PDGFs also exert beneficial homeostatic or reparative roles in adult organs, as opposed to adverse fibrogenic responses in pathology, are unclear. PDGF signaling plays critical roles during heart development, during which forced overexpression of PDGFs induces detrimental cardiac fibrosis; other studies have implicated PDGF signaling in post-infarct myocardial repair. Different PDGFs may exert different effects mediated through the two PDGF receptors (PDGFRα and PDGFRβ) in different cell types. Here, we assessed responses induced by five known PDGF isoforms in the adult mouse heart in the context of adenovirus vector-mediated inflammation. Our results show that different PDGFs have different, in some cases even opposing, effects. Strikingly, whereas the major PDGFRα agonists (PDGF-A and -C) decreased the amount of scar tissue and increased the numbers of PDGFRα-positive fibroblasts, PDGFRβ agonists either induced large scars with extensive inflammation (PDGF-B) or dampened the adenovirus-induced inflammation and produced a small and dense scar (PDGF-D). These results provide evidence for PDGF isoform-specific inflammation-modulating functions that may have therapeutic implications. They also illustrate a surprising complexity in the PDGF-mediated pathophysiological responses. PMID:27513343

  9. The platelet-activating factor acetylhydrolase gene derived from Trichoderma harzianum induces maize resistance to Curvularia lunata through the jasmonic acid signaling pathway.

    PubMed

    Yu, Chuanjin; Fan, Lili; Gao, Jinxin; Wang, Meng; Wu, Qiong; Tang, Jun; Li, Yaqian; Chen, Jie

    2015-01-01

    Platelet-activating factor acetylhydrolase (PAF-AH) derived from Trichoderma harzianum was upregulated by the interaction of T. harzianum with maize roots or the foliar pathogen Curvularia lunata. PAF-AH was associated with chitinase and cellulase expressions, but especially with chitinase, because its activity in the KO40 transformant (PAF-AH disruption transformant) was lower, compared with the wild-type strain T28. The result demonstrated that the colonization of maize roots by T. harzianum induced systemic protection of leaves inoculated with C. lunata. Such protection was associated with the expression of inducible jasmonic acid pathway-related genes. Moreover, the data from liquid chromatography-mass spectrometry confirmed that the concentration of jasmonic acid in maize leaves was associated with the expression level of defense-related genes, suggesting that PAF-AH induced resistance to the foliar pathogen. Our findings showed that PAF-AH had an important function in inducing systemic resistance to maize leaf spot pathogen.

  10. Pharmacokinetic Properties of Single and Repeated Injection of Liposomal Platelet Substitute in a Rat Model of Red Blood Cell Transfusion-Induced Dilutional Thrombocytopenia.

    PubMed

    Hashimoto, Mai; Taguchi, Kazuaki; Ogaki, Shigeru; Watanabe, Hiroshi; Kinoshita, Manabu; Nishikawa, Kahoko; Takeoka, Shinji; Ikeda, Yasuo; Handa, Makoto; Otagiri, Masaki; Maruyama, Toru

    2015-11-01

    A preclinical study of dodecapeptide ((400)HHLGGAKQAGDV(411)) (H12)-(adenosine diphosphate, ADP)-liposomes for use as a synthetic platelet (PLT) substitute under conditions of red blood cell (RBC) transfusion-induced dilutional thrombocytopenia is limited to pharmacological effect. In this study, the pharmacokinetics of H12-(ADP)-liposomes in RBC transfusion-induced dilutional thrombocytopenic rats were evaluated. As evidenced by the use of (14) C, (3) H double-radiolabeled H12-(ADP)-liposomes in which the encapsulated ADP and liposomal membrane were labeled with (14) C and (3) H, respectively, the H12-(ADP)-liposomes remained intact in the blood circulation for up to 3 h after injection, and were mainly distributed to the liver and spleen. The encapsulated ADP was mainly eliminated in the urine, whereas the outer membrane was mainly eliminated in the feces. These successive pharmacokinetic properties of the H12-(ADP)-liposomes in RBC transfusion-induced dilutional thrombocytopenic rats were similar to those in healthy rats, except for the shorter retention time in the circulation. When H12-(ADP)-liposomes were repeatedly injected into RBC transfusion-induced dilutional thrombocytopenic rats at intervals of 5 days at a dose of 10 mg lipids/kg, the second dose of injected H12-(ADP)-liposomes were rapidly cleared from the circulation, namely, via the accelerated blood clearance phenomenon. These novel pharmacokinetic findings provide useful information for the further development of H12-(ADP)-liposomes as a PLT substitute.

  11. Geldanamycin disrupts platelet-membrane structure, leading to membrane permeabilization and inhibition of platelet aggregation.

    PubMed Central

    Suttitanamongkol, S; Gear, A R; Polanowska-Grabowska, R

    2000-01-01

    Geldanamycin (GA), a benzoquinoid ansamycin antibiotic, has been used as a tyrosine kinase inhibitor and an anti-tumour agent and is known to bind to heat-shock protein 90. In the present study on human platelets we have found that GA inhibited platelet aggregation induced by ADP, thrombin and the thrombin-receptor-activating peptide and caused platelet plasma-membrane damage, detected by leakage of adenine nucleotides as well as serotonin. Scanning electron microscopy (SEM) revealed that platelet exposure to GA led to the formation of holes or fenestrations in the platelet plasma membrane, confirming GA's ability to initiate membrane damage. In addition, GA itself caused both the dephosphorylation and phosphorylation of proteins in resting platelets and prevented agonist-induced phosphorylation of pleckstrin, the 20-kDa myosin light chain and other proteins. Another ansamycin, herbimycin A, also inhibited platelet aggregation, but caused minimal membrane permeabilization, as detected by (3)H release from platelets labelled previously with [(3)H]adenine, and much less membrane damage, revealed by SEM. Overall, GA is able to disrupt membrane structure and inhibit platelet aggregation, an ability which may be linked to alterations in the activity of protein kinases and phosphatases. PMID:10620508

  12. Anti-β2 glycoprotein I antibodies in complex with β2 glycoprotein I induce platelet activation via two receptors: apolipoprotein E receptor 2' and glycoprotein I bα.

    PubMed

    Zhang, Wenjing; Gao, Fei; Lu, Donghe; Sun, Na; Yin, Xiaoxue; Jin, Meili; Liu, Yanhong

    2016-03-01

    Anti-β2 glycoprotein I (anti-β2GPI ) antibodies are important contributors to thrombosis, especially in patients with antiphospholipid syndrome (APS). However, the mechanism by which anti-β2GPI antibodies are involved in the pathogenesis of thrombosis is not fully understood. In this report, we investigated the role of anti- β2GPI antibodies in complexes with β2GPI as mediators of platelet activation, which can serve as a potential source contributing to thrombosis. We examined the involvement of the apolipoprotein E receptor 2' (apoER2') and glycoprotein I ba (GP I ba) in platelet activation induced by the anti-β2GPI /β2GPI complex. The interaction between the anti-β2GPI /β2GPI complex and platelets was examined using in vitro methods, in which the Fc portion of the antibody was immobilized using protein A coated onto a microtiter plate. Platelet activation was assessed by measuring GPII b/III a activation and P-selectin expression and thromboxane B2 production as well as p38 mitogen-activated protein kinase phosphorylation. Our results revealed that the anti-β2GPI /β2GPI complex was able to activate platelets, and this activation was inhibited by either the anti-GP I bα antibody or the apoER2' inhibitor. Results showed that the anti-β2GPI /β2GPI complex induced platelet activation via GPI ba and apoER2', which may then contribute to the prothrombotic tendency in APS patients.

  13. Transcellular activation of platelets and endothelial cells by bioactive lipids in platelet microparticles.

    PubMed Central

    Barry, O. P.; Pratico, D.; Lawson, J. A.; FitzGerald, G. A.

    1997-01-01

    Microparticles are released during platelet activation in vitro and have been detected in vivo in syndromes of platelet activation. They have been reported to express both pro- and anticoagulant activities. Nevertheless, their functional significance has remained unresolved. To address the mechanism(s) of cellular activation by platelet microparticles, we examined their effects on platelets and endothelial cells. Activation of human platelets by diverse stimuli (thrombin, 0.1 U/ml; collagen, 4 microg/ml; and the calcium ionophore A23187, 1 microM) results in shedding of microparticles. Pretreatment of these particles, but not membrane fractions from resting platelets, with (s)PLA2 evokes a dose-dependent increase in platelet aggregation, intracellular [Ca2+] movement, and inositol phosphate formation. These effects localize to the arachidonic acid fraction of the microparticles and are mimicked by arachidonic acid isolated from them. However, platelet activation requires prior metabolism of microparticle arachidonic acid to thromboxane A2. Thus, pretreatment of platelets with the cyclooxygenase (COX) inhibitor, indomethacin (20 microM), the thromboxane antagonist SQ29,548 (1 microM), or the protein kinase C inhibitor GF109203X (5 microM) prevents platelet activation by microparticles. However, platelet microparticles fail to evoke an inositol phosphate response directly, via either of the cloned thromboxane receptor isoforms stably expressed in human embryonic kidney (HEK) 293 cells. Prelabeling platelets with [2H(8)] arachidonate was used to demonstrate platelet metabolism of the microparticle-derived substrate to thromboxane. Platelet microparticles can also induce expression of COX-2 and prostacyclin (PGI2) production, but not expression of COX-1, in human endothelial cells. These effects are prevented by pretreatment with actinomycin D (12 microM) or cycloheximide (5 microg/ml). Expression of COX-2 is again induced by the microparticle arachidonate fraction

  14. Acetylglyceryl ether phosphorylcholine (AGEPC; platelet-activating factor)-induced stimulation of rabbit platelets: correlation between phosphatidic acid level, 45Ca2+ uptake, and (3H)serotonin secretion

    SciTech Connect

    Shukla, S.D.; Hanahan, D.J.

    1984-08-01

    When 32P-labeled rabbits platelet were incubated with 5 X 10(-10) M 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), either in the presence or absence (0.1 mM EGTA) of added Ca2+, there was a three- to five-fold increase in the (32P)phosphatidic acid (PA) pool within 15 to 20 s. This event was followed by a gradual decrease in the (32P)PA level to near basal level in 5 min. AGEPC effected this change in (32P)PA in a characteristic dose- and time-dependent manner. Polar head group analogs of AGEPC, such as AGEDME and AGEMME, also effected an increase in PA labeling at levels comparable to those previously reported for their activity toward rabbit platelets. Other analogs, i.e., lysoGEPC and the enantiomer, sn-1-AGEPC, which are inactive toward rabbit platelets, also showed no effect on the level of (32P)PA. The finding that the PA level in rabbit platelets could be manipulated by the addition of AGEPC, without any added Ca2+, provided an excellent model system for establishing a correlation between the uptake of Ca2+, serotonin release, and PA level. Thus, PA must be regarded as a sensitive indicator of a reaction mechanism important to the platelet response to AGEPC, and could be the focal point in promoting calcium uptake during the stimulation process.

  15. Expression and function of purinergic receptors in platelets from apheresis-derived platelet concentrates

    PubMed Central

    Koessler, Juergen; Weber, Katja; Koessler, Angela; Yilmaz, Pinar; Boeck, Markus; Kobsar, Anna

    2016-01-01

    Background The storage of platelets affects platelet integrity and functionality, a process named platelet storage lesion (PSL). Reduced adenosine diphosphate (ADP)-induced platelet aggregation is a typical manifestation of PSL. However, the role of ADP receptors in this context has not been evaluated yet. The aim of this study was, therefore, to investigate surface expression and function of the purinergic receptors P2Y1, P2Y12 and P2X1 in stored platelet concentrates. Material and methods Platelets were obtained from venous whole blood and from apheresis-derived platelet concentrates stored for 0, 2 and 5 days. Purinergic receptor expression was measured by flow cytometry and western blot analysis. Receptor function was determined by calcium-induced fluorescence (P2Y1 and P2X1) or by flow cytometric measurement of the platelet reactivity index (P2Y12). Results The basal surface expression and total content of purinergic receptors remained unchanged throughout storage. After an initial reduction during apheresis, P2X1-mediated calcium flux was maintained, whereas the P2Y1-mediated increase of calcium flux gradually decreased during the course of storage. In contrast, the platelet reactivity index was comparable in freshly obtained and stored platelets. Discussion The function of the P2Y12 receptor is maintained during storage of apheresis-derived platelet concentrates. However, the impairment of P2X1 and especially of P2Y1 receptor function indicated by decreased receptor-mediated calcium flux is an important mechanism contributing to reduced ADP responsiveness of stored platelets. PMID:26674810

  16. Revascularization Induced Maturogenesis of Non-Vital Immature Permanent Tooth Using Platelet-Rich-Fibrin: A Case Report.

    PubMed

    Nagaveni, N B; Pathak, Sidhant; Poornima, P; Joshi, Jooie S

    2016-01-01

    The aim of this report is to describe a novel method of revascularization therapy done in a non-vital, immature permanent tooth using Platelet-rich fibrin (PRF),in a recently developed scaffold material to overcome limitations associated with the traditional method of revascularization using natural blood clot. PRF prepared from autologous blood was placed in the root canal and patient was followed up regularly at one, three, six, nine and 12 months for detailed clinical and radiographic evaluation. At 12 months, radiographic examination revealed root elongation, root end closure, continued thickening of the root dentinal walls, obliteration of root canal space, and normal periradicular anatomy. However, more long term prospective trials and histological studies are highly needed before to testify PRF a panacea for the regenerative endodontic therapy in children.

  17. Diltiazem potentiates the inhibitory effect of aspirin on platelet aggregation.

    PubMed

    Altman, R; Scazziota, A; Dujovne, C

    1988-09-01

    Platelet aggregation in vivo occurs through the combined effects of many agonists. Aspirin inhibits platelet aggregation but its antiaggregate effects can be overcome by the synergistic action of sodium arachidonate (AA) plus platelet activating factor (PAF). We tested the effect of a calcium entry-blocking agent, diltiazem, on AA-PAF-induced platelet aggregation in platelet-rich plasma from seven healthy volunteers. The studies were done before and after aspirin (100 mg/day) administration for 7 to 10 days. Stimulation of platelet was done in vitro by AA, PAF, or both. Before aspirin treatment, diltiazem (2 micrograms/ml) added in vitro to the platelet-rich plasma inhibited platelet aggregation induced by AA (0.75 mmol/L) by 50%. When PAF was used the inhibition of aggregation was obtained at a lower concentration of diltiazem (0.4 to 1 microgram/ml). After aspirin treatment, AA-induced aggregation was inhibited, and PAF alone (30 nmol/L) produced a first-wave aggregation followed by complete disaggregation. When AA and PAF were added together a full aggregation of postaspirin treatment platelets was obtained. Diltiazem added in vitro at the clinically attainable concentration of 0.1 microgram/ml produced a complete inhibition of this AA-PAF synergism on platelet aggregation. These results suggest that administration of a combination of low-dose aspirin and diltiazem may be of greater benefit than aspirin alone for prophylaxis of cardiovascular diseases where platelets are involved in the pathogenesis.

  18. Unaltered Angiogenesis-Regulating Activities of Platelets in Mild Type 2 Diabetes Mellitus despite a Marked Platelet Hyperreactivity

    PubMed Central

    Miao, Xinyan; Zhang, Wei; Huang, Zhangsen

    2016-01-01

    Type 2 diabetes mellitus (T2DM) is associated with platelet dysfunction and impaired angiogenesis. Aim of the study is to investigate if platelet dysfunction might hamper platelet angiogenic activities in T2DM patients. Sixteen T2DM patients and gender/age-matched non-diabetic controls were studied. Flow cytometry and endothelial colony forming cell (ECFC) tube formation on matrigel were used to assess platelet reactivity and angiogenic activity, respectively. Thrombin receptor PAR1-activating peptide (PAR1-AP) induced higher platelet P-selectin expression, and evoked more rapid and intense platelet annexin V binding in T2DM patients, seen as a more rapid increase of annexin V+ platelets (24.3±6.4% vs 12.6±3.8% in control at 2 min) and a higher elevation (30.9±5.1% vs 24.3±3.0% at 8 min). However, PAR1-AP and PAR4-AP induced similar releases of angiogenic regulators from platelets, and both stimuli evoked platelet release of platelet angiogenic regulators to similar extents in T2DM and control subjects. Thus, PAR1-stimulated platelet releasate (PAR1-PR) and PAR4-PR similarly enhanced capillary-like network/tube formation of ECFCs, and the enhancements did not differ between T2DM and control subjects. Direct supplementation of platelets to ECFCs at the ratio of 1:200 enhanced ECFC tube formation even more markedly, leading to approximately 100% increases of the total branch points of ECFC tube formation, for which the enhancements were also similar between patients and controls. In conclusion, platelets from T2DM subjects are hyperreactive. Platelet activation induced by high doses of PAR1-AP, however, results in similar releases of angiogenic regulators in mild T2DM and control subjects. Platelets from T2DM and control subjects also demonstrate similar enhancements on ECFC angiogenic activities. PMID:27612088

  19. Platelets and their role in cancer evolution and immune system.

    PubMed

    Karachaliou, Niki; Pilotto, Sara; Bria, Emilio; Rosell, Rafael

    2015-12-01

    Platelets are anucleate fragments formed from the cytoplasm of megakaryocytes and represent the smallest circulating hematopoietic cells. Thought for almost a century to possess solely hemostatic potentials, platelets actually play a much wider role in tissue regeneration and repair and interact intimately with tumor cells. On the one hand, tumor cells induce platelet aggregation, known to act as the trigger of cancer-associated thrombosis and on the other hand, platelets recruited to the tumor microenvironment interact directly with tumor cells favoring proliferation, and indirectly through the release of angiogenic and mitogenic proteins. Furthermore, platelets are immunosuppressive cells that protect metastatic cancer cells from surveillance by killer cells, nullifying the effects of immunotherapy.

  20. Role of platelets in the pathogenesis of canine endotoxin shock.

    PubMed Central

    From, A H; Fong, J S; Chiu, T; Good, R A

    1976-01-01

    Endotoxin-platelet interactions are thought to be of major importance in the response of dogs and other species to bacterial endotoxin; the mechanisms postulated are: (i) the release of vasoactive substances, (ii) the formation of occlusive platelet aggregates, and (iii) induction of intravascular coagulation. The role of platelets in canine endotoxin shock was examined in animals with thrombocytopenia induced by estrogen pretreatment (less than 10,000 platelets/mm3) and in controls. After intravenously administered endotoxin, the hemodynamic responses, mortality, and gross necropsy findings were similar in both groups. These data indicate that endotoxin-platelet interactions are not determinative in the pathogenesis of canine endotoxin shock. PMID:786877

  1. Effects of pathogen reduction systems on platelet microRNAs, mRNAs, activation, and function.

    PubMed

    Osman, Abdimajid; Hitzler, Walter E; Meyer, Claudius U; Landry, Patricia; Corduan, Aurélie; Laffont, Benoit; Boilard, Eric; Hellstern, Peter; Vamvakas, Eleftherios C; Provost, Patrick

    2015-01-01

    Pathogen reduction (PR) systems for platelets, based on chemically induced cross-linking and inactivation of nucleic acids, potentially prevent transfusion transmission of infectious agents, but can increase clinically significant bleeding in some clinical studies. Here, we documented the effects of PR systems on microRNA and mRNA levels of platelets stored in the blood bank, and assessed their impact on platelet activation and function. Unlike platelets subjected to gamma irradiation or stored in additive solution, platelets treated with Intercept (amotosalen+ ultraviolet-A [UVA] light) exhibited significantly reduced levels of 6 of the 11 microRNAs, and 2 of the 3 anti-apoptotic mRNAs (Bcl-xl and Clusterin) that we monitored, compared with platelets stored in plasma. Mirasol (riboflavin+ UVB light) treatment of platelets did not produce these effects. PR neither affected platelet microRNA synthesis or function nor induced cross-linking of microRNA-sized endogenous platelet RNA species. However, the reduction in the platelet microRNA levels induced by Intercept correlated with the platelet activation (p < 0.05) and an impaired platelet aggregation response to ADP (p < 0.05). These results suggest that Intercept treatment may induce platelet activation, resulting in the release of microRNAs and mRNAs from platelets. The clinical implications of this reduction in platelet nucleic acids secondary to Intercept remain to be established.

  2. Effects of pathogen reduction systems on platelet microRNAs, mRNAs, activation, and function

    PubMed Central

    Osman, Abdimajid; Hitzler, Walter E.; Meyer, Claudius U.; Landry, Patricia; Corduan, Aurélie; Laffont, Benoit; Boilard, Eric; Hellstern, Peter; Vamvakas, Eleftherios C.

    2015-01-01

    Pathogen reduction (PR) systems for platelets, based on chemically induced cross-linking and inactivation of nucleic acids, potentially prevent transfusion transmission of infectious agents, but can increase clinically significant bleeding in some clinical studies. Here, we documented the effects of PR systems on microRNA and mRNA levels of platelets stored in the blood bank, and assessed their impact on platelet activation and function. Unlike platelets subjected to gamma irradiation or stored in additive solution, platelets treated with Intercept (amotosalen + ultraviolet-A [UVA] light) exhibited significantly reduced levels of 6 of the 11 microRNAs, and 2 of the 3 anti-apoptotic mRNAs (Bcl-xl and Clusterin) that we monitored, compared with platelets stored in plasma. Mirasol (riboflavin + UVB light) treatment of platelets did not produce these effects. PR neither affected platelet microRNA synthesis or function nor induced cross-linking of microRNA-sized endogenous platelet RNA species. However, the reduction in the platelet microRNA levels induced by Intercept correlated with the platelet activation (p < 0.05) and an impaired platelet aggregation response to ADP (p < 0.05). These results suggest that Intercept treatment may induce platelet activation, resulting in the release of microRNAs and mRNAs from platelets. The clinical implications of this reduction in platelet nucleic acids secondary to Intercept remain to be established. PMID:24749844

  3. Escaping from Rejection

    PubMed Central

    Lynch, Raymond J.; Platt, Jeffrey L.

    2009-01-01

    Summary Those engaged in clinical transplantation and transplantation immunology have always taken as a central objective the elucidation of means to prevent graft rejection by the recipient immune system. Conceptually, such mechanisms stem from the concept of Paul Ehrlich that all organisms can selectively avoid autotoxicity; i.e. they exhibit horror autotoxicus. Some mechanisms of horror autotoxicus now understood. T lymphocytes and B lymphocytes recognize foreign antigens but not some auto-antigens. Clonal deletion generates lacunae in what is otherwise a virtually limitless potential to recognize antigens. We call this mechanism structural tolerance. Where imperfections in structural tolerance allow self-recognition, the full activation of lymphocytes and generation of effector activity depends on delivery of accessory signals generated by infection and/or injury. The absence of accessory signals prevents or even suppresses immunological responses. We call this dichotomy of responsiveness conditional tolerance. When, despite structural and conditional tolerance, effector activity perturbs autologous cells, metabolism changes in ways that protect against injury. We use the term accommodation to refer to this acquired protection against injury. Structural and conditional tolerance and accommodation overlap in such a way that potentially toxic products can be generated to control microorganisms and neutralize toxins without overly damaging adjacent cells. The central challenge in transplantation, then, should be the orchestration of structural and conditional tolerance and accommodation in such a way that toxic products can still be generated for defense while preserving graft function and survival. Since the earliest days of transplantation, immunobiologists have sought means by which to prevent recognition and rejection of foreign tissue. The goal of these strategies is the retention of recipient immune function while selectively avoiding graft injury. While

  4. Electrospun silk fibroin/poly (L-lactide-ε-caplacton) graft with platelet-rich growth factor for inducing smooth muscle cell growth and infiltration

    PubMed Central

    Yin, Anlin; Bowlin, Gary L.; Luo, Rifang; Zhang, Xingdong; Wang, Yunbing; Mo, Xiumei

    2016-01-01

    The construction of a smooth muscle layer for blood vessel through electrospinning method plays a key role in vascular tissue engineering. However, smooth muscle cells (SMCs) penetration into the electrospun graft to form a smooth muscle layer is limited due to the dense packing of fibers and lack of inducing factors. In this paper, silk fibroin/poly (L-lactide-ε-caplacton) (SF/PLLA-CL) vascular graft loaded with platelet-rich growth factor (PRGF) was fabricated by electrospinning. The in vitro results showed that SMCs cultured in the graft grew fast, and the incorporation of PRGF could induce deeper SMCs infiltrating compared to the SF/PLLA-CL graft alone. Mechanical properties measurement showed that PRGF-incorporated graft had proper tensile stress, suture retention strength, burst pressure and compliance which could match the demand of native blood vessel. The success in the fabrication of PRGF-incorporated SF/PLLA-CL graft to induce fast SMCs growth and their strong penetration into graft has important application for tissue-engineered blood vessels. PMID:27482466

  5. miR-503 inhibits platelet-derived growth factor-induced human aortic vascular smooth muscle cell proliferation and migration through targeting the insulin receptor.

    PubMed

    Bi, Rui; Ding, Fangbao; He, Yi; Jiang, Lianyong; Jiang, Zhaolei; Mei, Ju; Liu, Hao

    2016-12-01

    Abnormal proliferation and migration of vascular smooth muscle cells (VSMC) is a common feature of disease progression in atherosclerosis. Here, we investigated the potential role of miR-503 in platelet-derived growth factor (PDGF)-induced proliferation and migration of human aortic smooth muscle cells and the underlying mechanisms of action. miR-503 expression was significantly downregulated in a dose- and time-dependent manner following PDGF treatment. Introduction of miR-503 mimics into cultured SMCs significantly attenuated cell proliferation and migration induced by PDGF. Bioinformatics analyses revealed that the insulin receptor (INSR) is a target candidate of miR-503. miR-503 suppressed luciferase activity driven by a vector containing the 3'-untranslated region of INSR in a sequence-specific manner. Downregulation of INSR appeared critical for miR-503-mediated inhibitory effects on PDGF-induced cell proliferation and migration in human aortic SMCs. Based on the collective data, we suggest a novel role of miR-503 as a regulator of VSMC proliferation and migration through modulating INSR.

  6. The poly-γ-d-glutamic acid capsule surrogate of the Bacillus anthracis capsule induces nitric oxide production via the platelet activating factor receptor signaling pathway.

    PubMed

    Lee, Hae-Ri; Jeon, Jun Ho; Park, Ok-Kyu; Chun, Jeong-Hoon; Park, Jungchan; Rhie, Gi-Eun

    2015-12-01

    The poly-γ-d-glutamic acid (PGA) capsule, a major virulence factor of Bacillus anthracis, confers protection of the bacillus from phagocytosis and allows its unimpeded growth in the host. PGA capsules released from B. anthracis are associated with lethal toxin in the blood of experimentally infected animals and enhance the cytotoxic effect of lethal toxin on macrophages. In addition, PGA capsule itself activates macrophages and dendritic cells to produce proinflammatory cytokine such as IL-1β, indicating multiple roles of PGA capsule in anthrax pathogenesis. Here we report that PGA capsule of Bacillus licheniformis, a surrogate of B. anthracis capsule, induces production of nitric oxide (NO) in RAW264.7 cells and bone marrow-derived macrophages. NO production was induced by PGA in a dose-dependent manner and was markedly reduced by inhibitors of inducible NO synthase (iNOS), suggesting iNOS-dependent production of NO. Induction of NO production by PGA was not observed in macrophages from TLR2-deficient mice and was also substantially inhibited in RAW264.7 cells by pretreatment of TLR2 blocking antibody. Subsequently, the downstream signaling events such as ERK, JNK and p38 of MAPK pathways as well as NF-κB activation were required for PGA-induced NO production. In addition, the induced NO production was significantly suppressed by treatment with antagonists of platelet activating factor receptor (PAFR) or PAFR siRNA, and mediated through PAFR/Jak2/STAT-1 signaling pathway. These findings suggest that PGA capsule induces NO production in macrophages by triggering both TLR2 and PAFR signaling pathways which lead to activation of NF-kB and STAT-1, respectively.

  7. Jet Transport Rejected Takeoffs.

    DTIC Science & Technology

    1977-02-01

    r _ _ _ _ _ _ N AD—A05 6 032 FEDERAL AVIATIO N ADMINISTRATION WASHINGTON 0 C FLIGHT—ETC FIG 1/2 ~,JET TRANSPORT REJECTED TAKEOFFS • (U)FED 77 0 S...AF~~16O-77-2 FOR FURTHER IRAN JET TRANSPORT R&JECTED TAKEDFFS DAVID W. OSTROWSKILI~~ H c ,~ ~~~~ C ...) ~~~~ O~ —1 w DDU FEB~JARY 1977U... FINAL...Pag. .po ,t No. 2 C.o.,,nm.rr, A c c . s s on No . 3. R.c ,pr. ns s Cat alog No. AFS-16~~-77-2_ j

  8. Biochemical and functional abnormalities in hypercholesterolemic rabbit platelets

    SciTech Connect

    Dalal, K.B.; Ebbe, S.; Mazoyer, E.; Carpenter, D.; Yee, T. )

    1990-02-01

    This study was designed to elucidate changes in rabbit platelet lipids induced by a cholesterol rich diet and to explore the possible correlation of these lipid changes with platelet abnormalities. Pronounced biochemical alterations were observed when serum cholesterol levels of 700-1000 mg% were reached. Hypercholesterolemic (HC) platelets contained 37% more neutral lipids and 16% less phospholipids than the controls. Lysolecithin, cholesterol esters and phosphatidylinositol (PI) levels were increased in HC platelets, and the levels of phosphatidylcholine (PC) were decreased. The cholesterol/phospholipid molar ratio of lipidemic platelets increased from 0.55 +/- 0.011 to 0.89 +/- 0.016 (P less than 0.01) in eight weeks. HC platelets had 90% more arachidonic acid (AA) in the PI than normal platelets. No significant changes in AA of PC were observed. Platelet function was monitored by the uptake and release of (14C)serotonin in platelet rich plasma (PRP), using varying concentrations of collagen as an aggregating agent. The uptake of (14C)serotonin in HC and normal platelets ranged from 78-94%. The percent of (14C)serotonin released from normal and HC platelets was proportional to the concentration of collagen. However, lipidemic platelets were hyperreactive to low concentrations of collagen. Incorporation of 50 microM acetylsalicylic acid into the aggregating medium suppressed the release of (14C)serotonin in normal PRP by more than 90%, but had only a partial effect on lipidemic PRP.

  9. Platelet cytosolic 44-kDa protein is a substrate of cholera toxin-induced ADP-ribosylation and is not recognized by antisera against the. alpha. subunit of the stimulatory guanine nucleotide-binding regulatory protein

    SciTech Connect

    Molina Y Vedia, L.M.; Reep, B.R.; Lapetina, E.G. )

    1988-08-01

    ADP-ribosylation induced by cholera toxin and pertussis toxin was studied in particulate and cytosolic fractions of human platelets. Platelets were disrupted by a cycle of freezing and thawing in the presence of a hyposmotic buffer containing protease inhibitors. In both fractions, the A subunit of cholera toxin ADP-ribosylates two proteins with molecular masses of 42 and 44 kDa, whereas pertussis toxin ADP-ribosylates a 41-kDa polypeptide. Two antisera against the {alpha} subunit of the stimulatory guanine nucleotide-binding regulatory protein recognize only the 42-kDa polypeptide. Cholera toxin-induced ADP-ribosylation of the 42- and 44-kDa proteins is reduced by pretreatment of platelets with iloprost, a prostacyclin analog. The 44-kDa protein, which is substrate of cholera toxin, could be extracted completely from the membrane and recovered in the cytosolic fraction when the cells were disrupted by Dounce homogenization and the pellet was extensively washed. A 44-kDa protein can also be labeled with 8-azidoguanosine 5{prime}-({alpha}-{sup 32}P)triphosphate in the cytosol and membranes. These finding indicate that cholera and pertussis toxins produced covalent modifications of proteins present in particulate and cytosolic platelet fractions. Moreover, the 44-kDa protein might be an {alpha} subunit of a guanine nucleotide-binding regulatory protein that is not recognized by available antisera.

  10. Glutamate Receptor Interacting Protein 1 Mediates Platelet Adhesion and Thrombus Formation

    PubMed Central

    Modjeski, Kristina L.; Ture, Sara K.; Field, David J.; Cameron, Scott J.; Morrell, Craig N.

    2016-01-01

    Thrombosis-associated pathologies, such as myocardial infarction and stroke, are major causes of morbidity and mortality worldwide. Because platelets are necessary for hemostasis and thrombosis, platelet directed therapies must balance inhibiting platelet function with bleeding risk. Glutamate receptor interacting protein 1 (GRIP1) is a large scaffolding protein that localizes and organizes interacting proteins in other cells, such as neurons. We have investigated the role of GRIP1 in platelet function to determine its role as a molecular scaffold in thrombus formation. Platelet-specific GRIP1-/- mice were used to determine the role of GRIP1 in platelets. GRIP1-/- mice had normal platelet counts, but a prolonged bleeding time and delayed thrombus formation in a FeCl3-induced vessel injury model. In vitro stimulation of WT and GRIP1-/- platelets with multiple agonists showed no difference in platelet activation. However, in vivo platelet rolling velocity after endothelial stimulation was significantly greater in GRIP1-/- platelets compared to WT platelets, indicating a potential platelet adhesion defect. Mass spectrometry analysis of GRIP1 platelet immunoprecipitation revealed enrichment of GRIP1 binding to GPIb-IX complex proteins. Western blots confirmed the mass spectrometry findings that GRIP1 interacts with GPIbα, GPIbβ, and 14-3-3. Additionally, in resting GRIP1-/- platelets, GPIbα and 14-3-3 have increased interaction compared to WT platelets. GRIP1 interactions with the GPIb-IX binding complex are necessary for normal platelet adhesion to a stimulated endothelium. PMID:27631377

  11. Induction of platelet formation from megakaryocytoid cells by nitric oxide.

    PubMed

    Battinelli, E; Willoughby, S R; Foxall, T; Valeri, C R; Loscalzo, J

    2001-12-04

    Although the growth factors that regulate megakaryocytopoiesis are well known, the molecular determinants of platelet formation from mature megakaryocytes remain poorly understood. Morphological changes in megakaryocytes associated with platelet formation and removal of senescent megakaryocytes are suggestive of an apoptotic process. Previously, we have established that nitric oxide (NO) can induce apoptosis in megakaryocytoid cell lines. To determine whether there is an association between NO-induced apoptosis and platelet production, we exposed Meg-01 cells to S-nitrosoglutathione (GSNO) with or without thrombopoeitin (TPO) pretreatment and used flow cytometry and electron microscopy to assess platelet-sized particle formation. Meg-01 cells treated with TPO alone produced few platelet-sized particles (<3% of total counts), whereas treatment with GSNO alone produced a significant percentage of platelet-sized particles (22 +/- 4% of total counts); when combined with TPO pretreatment, however, GSNO led to a marked increase in platelet-sized particle production (48 +/- 3% of total counts). Electron microscopy confirmed that Meg-01 cells treated with TPO and GSNO yielded platelet-sized particles with morphological features specific for platelet forms. The platelet-sized particle population appears to be functional, because addition of calcium, fibrinogen, and thrombin receptor-activating peptide led to aggregation. These results demonstrate that NO facilitates platelet production, thereby establishing the essential role of NO in megakaryocyte development and thrombopoiesis.

  12. Superoxide dismutase abolishes the platelet-derived growth factor-induced release of prostaglandin E2 by blocking induction of nitric oxide synthase: role of superoxide.

    PubMed

    Kelner, M J; Uglik, S F

    1995-09-10

    The ability of platelet-derived growth factor (PDGF) to induce prostaglandin E2 (PGE2) release in fibroblasts is abolished when copper-zinc superoxide dismutase activity is increased by transfection of an expression vector. The effect is specific to copper-zinc superoxide dismutase as glutathione peroxidase-overexpressing NIH3T3 cells, again produced by transfection of an expression vector, retain the ability to release PGE2 in response to growth factor stimulation. The defect in PDGF-induced PGE2 release occurs prior to action of prostaglandin H synthase/cyclooxygenase as release of arachadonic acid (in response to PDGF) does not occur in the superoxide dismutase-overexpressing clones. The defect in PDGF-induced release of PGE2 in superoxide dismutase-overexpressing clones differs from the defect found in pEJ-ras-transformed clones. The parent cells, the glutathione peroxidase-expressing cells, and the superoxide dismutase-overexpressing cells all release PGE2 in response to exogenous nitric oxide, whereas the pEJ-ras-transformed cells do not. The glutathione peroxidase-expressing cells also retained the ability to release nitrite in response to PDGF, whereas the superoxide dismutase-expressing clones do not. PDGF stimulates nitric oxide synthase activity in NIH3T3 cells, but not in the superoxide dismutase-expressing clones. These results indicate that superoxide dismutase overexpression blocks the PDGF-induced release of PGE2 by blocking induction of nitric oxide synthase. This indicates that the increase of nitric oxide synthase induced by PDGF is mediated in part by production of superoxide. These findings link cellular oxygen radical homeostasis to three different classes of messenger molecules (growth factors, nitric oxide, and prostaglandins).

  13. Platelet Integrin αIIbβ3 Inhibitor Rescues Progression of Apoptosis in Human Platelets

    PubMed Central

    Zhu, Jie; Wang, Qinghang; Nie, Yumei; Yan, Rong; Dai, Kesheng; Zhou, Birong

    2016-01-01

    Background Apoptosis plays an important role in the physiology of platelet function. We aimed to detect the effect of the platelet integrin αIIbβ3 inhibitor, tirofiban, on apoptotic events, including mitochondrial inner-membrane potential (ΔΨm), phosphatidylserine (PS) exposure on platelet surface, and the generation of reactive oxygen species (ROS), when washed platelets were stimulated with thrombin. Material/Methods The study included washed platelets from healthy humans, divided into 4 groups: vehicle, and tirofiban (0.05 μg/ml, 0.25 μg/ml, and 0.5 μg/ml). Platelets were pretreated with vehicle or tirofiban and incubated at 37°C with agitation for 6 h and 24 h. Before thrombin addition, the vehicle group divided into 2 equal groups. Except one vehicle group, the other 4 groups were all stimulated with thrombin (1 U/ml) for 30 min at 37°C. Using flow cytometry, we studied the ΔΨm and PS exposure on platelet surfaces, and the generation of ROS in platelets. Results We observed that at the time of 6 h and 24 h, thrombin-stimulated vehicle platelets induced significant depolarization of ΔΨm, higher PS exposure, and increased ROS production compared with the vehicle group (P<0.01). However, the tirofiban group had significantly more recovery of ΔΨm, PS exposure, and ROS production compared with the thrombin group (P<0.01). Conclusions The platelet integrin αIIbβ3 inhibitor, tirofiban, inhibits the depolarization of ΔΨm, PS exposure on platelet surface, and ROS production when stimulated with thrombin. These results suggest that αIIbβ3 inhibitor inhibits the initiation of apoptosis in platelets, showing a potential clinical application of tirofiban as an apoptosis inhibitor. PMID:27827357

  14. Increased platelet reactivity in patients with late-stage metastatic cancer

    PubMed Central

    Cooke, Niamh M; Egan, Karl; McFadden, Siobhan; Grogan, Liam; Breathnach, Oscar S; O'Leary, John; Hennessy, Bryan T; Kenny, Dermot

    2013-01-01

    Abstract Platelet hyperreactivity is associated with an increased risk of thrombosis. Cancer patients are at an increased risk of thrombosis, a risk that increases with disease progression. While cancer patients show evidence of platelet activation in vivo, few studies have extensively assessed whether these patients display platelet hyperreactivity. We hypothesized that patients with metastatic cancer would display platelet hyperreactivity, reflecting their associated high risk of thrombosis. In a cohort of patients with metastatic cancer (n = 13), we assessed platelet function using well-established assays of platelet reactivity (agonist-induced platelet aggregation, spontaneous platelet aggregation, and agonist-induced P-selectin expression). In comparison with healthy controls (n = 10), patients with metastatic cancer displayed global platelet hyperreactivity. Agonist-induced platelet aggregation responses to ADP (adenosine diphosphate), epinephrine, collagen, arachidonic acid, and PAR-1 (protease-activated receptor-1) activating peptide, as well as spontaneous platelet aggregation, were significantly increased in patients with metastatic cancer. Furthermore, agonist-induced platelet P-selectin expression was also significantly increased within the patient cohort. We demonstrate that patients with metastatic cancer are characterized by global platelet hyperreactivity, a factor that may contribute to their increased risk of thrombosis. We assessed platelet function in a cohort of patients with metastatic cancer (n = 13) using well-established assays of platelet reactivity. Agonist-induced platelet aggregation and activation in response to platelet agonists, as well as spontaneous platelet aggregation, was significantly increased in cancer patients compared with healthy controls. We demonstrate that patients with metastatic cancer are characterized by global platelet hyperreactivity, a factor that may contribute to their increased risk of thrombosis. PMID

  15. Background Rejection in the ARA Experiment

    NASA Astrophysics Data System (ADS)

    Pfendner, Carl

    2017-03-01

    The Askaryan Radio Array (ARA) is a radio frequency observatory under construction at the South Pole that is searching for ultrahigh energy neutrinos via the Askaryan effect. Thermal fluctuations currently dominate the trigger-level background for the observatory and anthropogenic sources also introduce a significant source of noise. By taking advantage of the observatory's regular geometry and the expected coincident nature of the RF signals arriving from neutrino-induced events, this background can be filtered efficiently. This contribution will discuss techniques developed for the ARA analyses to reject these thermal signals, to reject anthropogenic backgrounds, and to search for neutrino-induced particle showers in the Antarctic ice. The results of a search for neutrinos from GRBs using the prototype station using some of these techniques will be presented.

  16. Platelet-rich plasma induces mixed osteogenic/osteoclastogenic phenotype in osteosarcoma SaOS-2 cells: role of TGF-beta.

    PubMed

    Martinotti, Simona; Mazzucco, Laura; Balbo, Valeria; Patrone, Mauro; Mozzati, Marco; Ranzato, Elia; Burlando, Bruno

    2014-01-01

    Platelet-rich plasma (PRP) is widely used to promote tissue repair and accelerate osteogenesis, but there is no agreement about its mechanism of action. We characterized the modulatory effect of PRP on the in vitro osteoblast model SaOS-2, by using cell motility/chemoattraction and osteogenesis/mineralization assays, and a series of osteogenic/ osteoclastogenic genomic markers. Scratch wound assay showed that PRP stimulates cell motility, while transwell assay revealed a strong chemoattraction. Alkaline phosphatase (ALP) and alizarin red-S assays showed that PRP induces slight, but significant, stimulations of ALP activity and mineralization. The TGF-β inhibitor SB431542 reversed these effects, showing a main role for TGF-β1 released by PRP. Analyses of gene expression by qRT-PCR, showed the upregulation of osteocalcin, osteopontin, osteoprotegerin, receptor activator of NFκB (RANK), and runt-related transcription factor 2 (RUNX2) genes, with a total reversion by SB431542 for osteoprotegerin and RANK, and a partial reversion for ostecalcin, osteopontin, and RUNX2. The use of PCR array technique revealed the upregulation of the cathepsin K gene. These data show that PRP induces the development of mixed osteogenic/osteoclastogenic traits in the SaOS-2 model. Such a behavior may favour in vivo bone resorption and reconstitution at post-surgery or post-traumatic sites.

  17. UAP56 is an important mediator of Angiotensin II/platelet derived growth factor induced vascular smooth muscle cell DNA synthesis and proliferation

    SciTech Connect

    Sahni, Abha; Wang, Nadan; Alexis, Jeffrey

    2013-02-15

    Highlights: ► Knockdown of UAP56 inhibits Angiotensin II/PDGF induced vascular smooth muscle cell proliferation. ► UAP56 is a positive regulator of E2F transcriptional activation. ► UAP56 is present in the vessel wall of low flow carotid arteries. -- Abstract: Angiotensin (Ang) II and platelet-derived growth factor (PDGF) are important mediators of pathologic vascular smooth muscle cell (VSMC) proliferation. Identifying downstream mediators of Ang II and PDGF signaling may provide insights for therapies to improve vascular proliferative diseases. We have previously demonstrated that breakpoint cluster region (Bcr) is an important mediator of Ang II/PDGF signaling in VSMC. We have recently reported that the DExD/H box protein UAP56 is an interacting partner of Bcr in regulating VSMC DNA synthesis. We hypothesized that UAP56 itself is an important regulator of VSMC proliferation. In this report we demonstrate that knockdown of UAP56 inhibits Ang II/PDGF induced VSMC DNA synthesis and proliferation, and inhibits E2F transcriptional activity. In addition, we demonstrate that UAP56 is present in the vessel wall of low-flow carotid arteries. These findings suggest that UAP56 is a regulator of VSMC proliferation and identify UAP56 as a target for preventing vascular proliferative disease.

  18. Comparative proteome approach demonstrates that platelet-derived growth factor C and D efficiently induce proliferation while maintaining multipotency of hMSCs

    SciTech Connect

    Sotoca, Ana M.; Roelofs-Hendriks, Jose; Boeren, Sjef; Kraan, Peter M. van der; Vervoort, Jacques; Zoelen, Everardus J.J. van; Piek, Ester

    2013-10-15

    This is the first study that comprehensively describes the effects of the platelet-derived growth factor (PDGF) isoforms C and D during in vitro expansion of human mesenchymal stem cells (hMSCs). Our results show that PDGFs can enhance proliferation of hMSCs without affecting their multipotency. It is of great value to culture and expand hMSCs in a safe and effective manner without losing their multipotency for manipulation and further development of cell-based therapies. Moreover, differential effects of PDGF isoforms have been observed on lineage-specific differentiation induced by BMP2 and Vitamin D3. Based on label-free LC-based quantitative proteomics approach we have furthermore identified specific pathways induced by PDGFs during the proliferation process, showing the importance of bioinformatics tools to study cell function. - Highlights: • PDGFs (C and D) significantly increased the number of multipotent undifferentiated hMSCs. • Enhanced proliferation did not impair the ability to undergo lineage-specific differentiation. • Proteomic analysis confirmed the overall signatures of the ‘intact’ cells.

  19. The omnipotent platelet.

    PubMed

    Steinberg, L A

    1996-03-01

    This information was derived from the increase in platelets of patients following fractures and/or bone surgery and in conjunction with a vast amount of published literature. The increase in numbers of platelets reflects the extent of bone involvement, especially noted in the hip, knee, post-coronary artery bypass graft, and multiple fractures. The role of the platelet in any and all tissues, i.e. soft tissue or bone, whether beneficial or detrimental, is multifunctional. The platelet responds to all physiologic and pathologic states and, if tissue involved is sufficient, the role of the platelet becomes obvious.

  20. Aspirin decreases platelet uptake on Dacron vascular grafts in baboons

    SciTech Connect

    Mackey, W.C.; Connolly, R.J.; Callow, A.D.; Keough, E.M.; Ramberg-Laskaris, K.; McCullough, J.L.; O'Donnell, T.F. Jr.; Melaragno, A.; Valeri, C.R.; Weiblen, B.

    1984-07-01

    The influence of a single dose of aspirin (5.4-7.4 mg/kg) on platelet uptake on 4-mm Dacron interposition grafts was studied in a baboon model using gamma camera scanning for 111-Indium labeled platelets. In vitro assessment of platelet function after aspirin administration revealed that in the baboon, as in the human, aspirin abolished arachidonic acid-induced platelet aggregation, prolonged the lag time between exposure to collagen and aggregation, and decreased plasma thromboxane B2 levels. Aspirin also prolonged the template bleeding time. Scans for 111-Indium labeled platelets revealed that pretreatment with a single dose of aspirin decreased platelet uptake on 4-mm Dacron carotid interposition grafts. This decrease in platelet uptake was associated with a significant improvement in 2-hour graft patency and with a trend toward improved 2-week patency.

  1. The role of platelets and megakaryocytes in bone metastasis.

    PubMed

    Leblanc, Raphael; Peyruchaud, Olivier

    2016-09-01

    Blood platelets have been known for more than a century as important partners for successful metastatic dissemination of solid tumors. Cancer cell-induced platelet activation is a key event responsible for prometastatic activity of platelets. Blocking platelet aggregation inhibits the progression of skeletal metastases through mechanisms that are not fully understood. The establishment and progression of bone metastases are strongly influenced by the bone remodeling process. Growth factors and cytokines released upon platelet activation may contribute to both skeletal tumor growth and osteolytic lesions. Megakaryocytes are platelet precursors located in the bone marrow that control bone mass through direct stimulation of osteoblast functions and indirect inhibition of osteoclast activities. Considering growing evidence for their role in the metastatic cascade, platelets and/or megakaryocytes may provide new therapeutic opportunities to help limit bone metastases.

  2. Uptake of donor lymphocytes treated with 8-methoxypsoralen and ultraviolet A light by recipient dendritic cells induces CD4{sup +}CD25{sup +}Foxp3{sup +} regulatory T cells and down-regulates cardiac allograft rejection

    SciTech Connect

    Zheng, De-Hua; Dou, Li-Ping; Wei, Yu-Xiang; Du, Guo-Sheng; Zou, Yi-Ping; Song, Ji-Yong; Zhu, Zhi-Dong; Cai, Ming; Qian, Ye-Yong; Shi, Bing-Yi

    2010-05-14

    Extracorporeal photopheresis (ECP) is an effective immunomodulatory therapy and has been demonstrated to be beneficial for graft-vs-host disease and solid-organ allograft rejection. ECP involves reinfusion of a patient's autologous peripheral blood leukocytes treated ex vivo with 8-methoxypsoralen and UVA light radiation (PUVA). Previous studies focused only on ECP treatment of recipient immune cells. Our study is the first to extend the target of ECP treatment to donor immune cells. The results of in vitro co-culture experiments demonstrate uptake of donor PUVA-treated splenic lymphocytes (PUVA-SPs) by recipient immature dendritic cells (DCs). Phagocytosis of donor PUVA-SPs does not stimulate phenotype maturation of recipient DCs. In the same co-culture system, donor PUVA-SPs enhanced production of interleukin-10 and interferon-{gamma} by recipient DCs and impaired the subsequent capability of recipient DCs to stimulate recipient naive T cells. Phagocytosis of donor PUVA-SP (PUVA-SP DCs) by recipient DCs shifted T-cell responses in favor of T helper 2 cells. Infusion of PUVA-SP DCs inhibited cardiac allograft rejection in an antigen-specific manner and induced CD4{sup +}CD25{sup high}Foxp3{sup +} regulatory T cells. In conclusion, PUVA-SP DCs simultaneously deliver the donor antigen and the regulatory signal to the transplant recipient, and thus can be used to develop a novel DC vaccine for negative immune regulation and immune tolerance induction.

  3. Protein Kinase A Regulates 3-Phosphatidylinositide Dynamics during Platelet-derived Growth Factor-induced Membrane Ruffling and Chemotaxis*S⃞

    PubMed Central

    Deming, Paula B.; Campbell, Shirley L.; Baldor, Linda C.; Howe, Alan K.

    2008-01-01

    Spatial regulation of the cAMP-dependent protein kinase (PKA) is required for chemotaxis in fibroblasts; however, the mechanism(s) by which PKA regulates the cell migration machinery remain largely unknown. Here we report that one function of PKA during platelet-derived growth factor (PDGF)-induced chemotaxis was to promote membrane ruffling by regulating phosphatidylinositol 3,4,5-trisphosphate (PIP3) dynamics. Inhibition of PKA activity dramatically altered membrane dynamics and attenuated formation of peripheral membrane ruffles in response to PDGF. PKA inhibition also significantly decreased the number and size of PIP3-rich membrane ruffles in response to uniform stimulation and to gradients of PDGF. This ruffling defect was quantified using a newly developed method, based on computer vision edge-detection algorithms. PKA inhibition caused a marked attenuation in the bulk accumulation of PIP3 following PDGF stimulation, without effects on PI3-kinase (PI3K) activity. The deficits in PIP3 dynamics correlated with a significant inhibition of growth factor-induced membrane recruitment of endogenous Akt and Rac activation in PKA-inhibited cells. Simultaneous inhibition of PKA and Rac had an additive inhibitory effect on growth factor-induced ruffling dynamics. Conversely, the expression of a constitutively active Rac allele was able to rescue the defect in membrane ruffling and restore the localization of a fluorescent PIP3 marker to membrane ruffles in PKA-inhibited cells, even in the absence of PI3K activity. These data demonstrate that, like Rac, PKA contributes to PIP3 and membrane dynamics independently of direct regulation of PI3K activity and suggest that modulation of PIP3/3-phosphatidylinositol (3-PI) lipids represents a major target for PKA in the regulation of PDGF-induced chemotactic events. PMID:18936099

  4. Rhesus monkey platelets

    SciTech Connect

    Harbury, C.B.

    1986-03-01

    The purpose of this abstract is to describe the adenine nucleotide metabolism of Rhesus monkey platelets. Nucleotides are labelled with /sup 14/C-adenine and extracted with EDTA-ethanol (EE) and perchlorate (P). Total platelet ATP and ADP (TATP, TADP) is measured in the Holmsen Luciferase assay, and expressed in nanomoles/10/sup 8/ platelets. TR=TATP/TADP. Human platelets release 70% of their TADP, with a ratio of released ATP/ADP of 0.7. Rhesus platelets release 82% of their TADP, with a ratio of released ATP/ADP of 0.33. Thus, monkey platelets contain more ADP than human platelets. Thin layer chromatography of EE gives a metabolic ratio of 11 in human platelets and 10.5 in monkey platelets. Perchlorate extracts metabolic and actin bound ADP. The human and monkey platelets ratios were 5, indicating they contain the same proportion of actin. Thus, the extra ADP contained in monkey platelets is located in the secretory granules.

  5. Emotional responses to interpersonal rejection

    PubMed Central

    Leary, Mark R.

    2015-01-01

    A great deal of human emotion arises in response to real, anticipated, remembered, or imagined rejection by other people. Because acceptance by other people improved evolutionary fitness, human beings developed biopsychological mechanisms to apprise them of threats to acceptance and belonging, along with emotional systems to deal with threats to acceptance. This article examines seven emotions that often arise when people perceive that their relational value to other people is low or in potential jeopardy, including hurt feelings, jealousy, loneliness, shame, guilt, social anxiety, and embarrassment. Other emotions, such as sadness and anger, may occur during rejection episodes, but are reactions to features of the situation other than low relational value. The article discusses the evolutionary functions of rejection-related emotions, neuroscience evidence regarding the brain regions that mediate reactions to rejection, and behavioral research from social, developmental, and clinical psychology regarding psychological and behavioral concomitants of interpersonal rejection. PMID:26869844

  6. Emotional responses to interpersonal rejection.

    PubMed

    Leary, Mark R

    2015-12-01

    A great deal of human emotion arises in response to real, anticipated, remembered, or imagined rejection by other people. Because acceptance by other people improved evolutionary fitness, human beings developed biopsychological mechanisms to apprise them of threats to acceptance and belonging, along with emotional systems to deal with threats to acceptance. This article examines seven emotions that often arise when people perceive that their relational value to other people is low or in potential jeopardy, including hurt feelings, jealousy, loneliness, shame, guilt, social anxiety, and embarrassment. Other emotions, such as sadness and anger, may occur during rejection episodes, but are reactions to features of the situation other than low relational value. The article discusses the evolutionary functions of rejection-related emotions, neuroscience evidence regarding the brain regions that mediate reactions to rejection, and behavioral research from social, developmental, and clinical psychology regarding psychological and behavioral concomitants of interpersonal rejection.

  7. The Platelet Proteome

    PubMed Central

    Senzel, Lisa; Gnatenko, Dmitri V.; Bahou, Wadie F.

    2010-01-01

    Purpose of review The proteome is the pool of proteins expressed at a given time and circumstance. The word “proteomics” summarizes several technologies for visualization, quantitation and identification of these proteins. Recent advances in these techniques are helping to elucidate platelet processes which are relevant to bleeding and clotting disorders, transfusion medicine and regulation of angiogenesis. Recent findings Over 1100 platelet proteins have been identified using proteomic techniques. Various subproteomes have been characterized, including platelet releasates (the “secretome”), alpha and dense granules, membrane and cytoskeletal proteins, platelet-derived microparticles, and the platelet “phosphoproteome”. Proteomic data about platelets have become increasingly available in integrated databases. Summary Proteomic experiments in resting and activated platelets have identified novel signaling pathways and secreted proteins which may represent therapeutic targets, as well as potential cancer biomarkers. PMID:19550320

  8. Betaine (N,N,N-trimethylglycine) averts photochemically-induced thrombosis in pial microvessels in vivo and platelet aggregation in vitro.

    PubMed

    Nemmar, Abderrahim; Yuvaraju, Priya; Beegam, Sumaya; Ali, Badreldin H

    2015-07-01

    Betaine (N,N,N-trimethylglycine) is an important food component with established health benefits through its homocysteine-lowering effects, and is used to lower total homocysteine concentration in plasma of patients with homocystinuria. It is well established that hyperhomocysteinemia is an established risk factor for cardiovascular disease and stroke. However, the possible protective effect of betaine on coagulation events in vivo and in vitro has thus far not been studied. Betaine was given to mice at oral doses of either 10 mg/kg (n = 6) or 40 mg/kg (n = 6) for seven consecutive days, and control mice (n = 6) received water only. The thrombotic occlusion time in photochemically induced thrombosis in pial arterioles was significantly delayed in mice pretreated with betaine at doses of 10 mg/kg (P < 0.001) and 40 mg/kg (P < 0.01). Similar effects were observed in pial venules with 10 mg/kg (P < 0.05) and 40 mg/kg (P < 0.05) betaine. In vitro, in whole blood samples collected from untreated mice (n = 3-5), betaine (0.01-1 mg/mL) significantly reversed platelet aggregation induced by adenosine diphosphate (5 µM). The number of circulating platelets and plasma concentration of fibrinogen in vivo were not significantly affected by betaine pretreament compared with the control group. Lipid peroxidation (LPO) in mice pretreated with betaine was significantly reduced compared with the control group. Moreover, betaine (0.01-1 mg/mL) caused a dose-dependent and significant prolongation of PT (n = 5) and aPTT (n = 4-6). In conclusion, our data show that betaine protected against coagulation events in vivo and in vitro and decreased LPO in plasma.

  9. Abnormal megakaryocyte development and platelet function in Nbeal2(-/-) mice.

    PubMed

    Kahr, Walter H A; Lo, Richard W; Li, Ling; Pluthero, Fred G; Christensen, Hilary; Ni, Ran; Vaezzadeh, Nima; Hawkins, Cynthia E; Weyrich, Andrew S; Di Paola, Jorge; Landolt-Marticorena, Carolina; Gross, Peter L

    2013-11-07

    Gray platelet syndrome (GPS) is an inherited bleeding disorder associated with macrothrombocytopenia and α-granule-deficient platelets. GPS has been linked to loss of function mutations in NEABL2 (neurobeachin-like 2), and we describe here a murine GPS model, the Nbeal2(-/-) mouse. As in GPS, Nbeal2(-/-) mice exhibit splenomegaly, macrothrombocytopenia, and a deficiency of platelet α-granules and their cargo, including von Willebrand factor (VWF), thrombospondin-1, and platelet factor 4. The platelet α-granule membrane protein P-selectin is expressed at 48% of wild-type levels and externalized upon platelet activation. The presence of P-selectin and normal levels of VPS33B and VPS16B in Nbeal2(-/-) platelets suggests that NBEAL2 acts independently of VPS33B/VPS16B at a later stage of α-granule biogenesis. Impaired Nbeal2(-/-) platelet function was shown by flow cytometry, platelet aggregometry, bleeding assays, and intravital imaging of laser-induced arterial thrombus formation. Microscopic analysis detected marked abnormalities in Nbeal2(-/-) bone marrow megakaryocytes, which when cultured showed delayed maturation, decreased survival, decreased ploidy, and developmental abnormalities, including abnormal extracellular distribution of VWF. Our results confirm that α-granule secretion plays a significant role in platelet function, and they also indicate that abnormal α-granule formation in Nbeal2(-/-) mice has deleterious effects on megakaryocyte survival, development, and platelet production.

  10. Platelet function, activation and apoptosis during and after apheresis.

    PubMed

    Bakry, Rania; Sayed, Douaa; Galal, Hanan; Shaker, Sanaa

    2010-10-01

    Platelets are known to undergo shape change, activation, release reaction and apoptosis/necrosis during processing and storage. Apheresis may have a deleterious impact on platelet achievability and functional integrity. Platelet concentrates from 50 male volunteers obtained by COBE spectra were screened for platelet activation (CD62 and CD154) and apoptosis (phosphatidylserine detected by Annexin V). Donor samples before separation, during apheresis and at the third day of storage were used as baseline donor samples. Platelet aggregation to adenosine diphosphate (ADP) and collagen was performed. There was a statistically significant increase in the expression of activation markers in two different samples (during separation samples and third day samples). Although the increase in Annexin V expression was not so observable, it showed a significant increase also. There was marked decline in the platelet aggregation. The correlations between the values of CD62, CD154 and Annexin V were detected in baseline samples and increased during separation and at the third day of platelets storage. Correlation between values of platelet aggregation to collagen and Annexin V was relevant only in the baseline samples. No other correlations were encountered between platelet aggregation and markers of activation and apoptosis during apheresis and storage. Initial platelet activation induced by apheresis may have an impact on phosphatidylserine expression with no impact on aggregation function of platelets during storage.

  11. Platelet antibody: review of detection methods

    SciTech Connect

    Schwartz, K.A.

    1988-10-01

    The driving force behind development of in vitro methods for platelet antibodies is identification of plasma factors causing platelet destruction. Early methods relied on measurement of platelet activation. Current methods are more specific and use a purified antibody against immunoglobulin or complement, which is usually labeled with /sup 125/I or tagged with an enzyme or fluorescein. Comparisons of quantitation of platelet-associated IgG show wide variability between different methods. The disparate results can be related both to differences in binding of secondary antibodies to immunoglobulin in solution compared to immunoglobulins attached to platelets and to the improper assumption that the binding ratio between the secondary detecting and primary antiplatelet antibody is one. Most assays can 1) identify neonatal isoimmune thrombocytopenia and posttransfusion purpura, 2) help to differentiate between immune and nonimmune thrombocytopenias, 3) help to sort out the offending drug when drug-induced thrombocytopenia is suspected, and 4) identify platelet alloantibodies and potential platelet donors via a cross match assay for refractory patients. However, the advantages of quantitative assays over qualitative methods with respect to predictions of patients clinical course and response to different treatments remain to be investigated. 61 references.

  12. Complement Activation Alters Platelet Function

    DTIC Science & Technology

    2015-12-01

    2004; Danese et al., 2003). Recent studies have demonstrated a role for platelets in the development of both innate and adaptive immune responses...mediated modulation of adaptive immunity. A communication link between innate and adaptive immune compartments. Immunity 19:9-19. 4. Fleming, S.D., M...Monestier, and G.C. Tsokos. 2004. Accelerated ischemia/reperfusion- induced injury in autoimmunity-prone mice. Journal of immunology 173:4230-4235

  13. [Mechanism of cooked blanched garlic leaves against platelet aggregation].

    PubMed

    Wang, Xin-Hua; Di, Yan-Hui

    2014-06-01

    This study was purposed to explore the mechanism of cooked blanched garlic leave juice against platelet aggregation. The juice of blanched garlic leaves was mixed with platelet rich plasma (PRP), the human platelet aggregation, the activation of human platelets induced by adenosine diphosphate (ADP) and collagen were observed; the expression levels of the activated platelets (Fib-R) and P-selectin (CD62P), and the amount of platelet fibrinogen binding were detected by flow cytometry; 10 rabbits were randomly divided into two groups, in addition to the normal diet, they were fed with physiologic saline and cooked blanched garlic leave juice respectively. After 1, 3, 5 , 8 weeks, the maximum ratio of rabbit platelet aggregation induced by ADP and collagen were observed . The results showed that the cooked blanched garlic leave juice could significantly inhibit human platelet aggregation induced by ADP and collagen (P < 0.05), the inhibitory ratio were 87.37% and 86.24% respectively; the juice could not inhibit activated platelets Fib-R and CD62P expression levels (P > 0.05), but was able to inhibit platelet fibrinogen binding capacity (P < 0.05); the rabbit platelet aggregation rate in the group given cooked blanched garlic leave juice was significantly lower than that in control group (P < 0.05). It is concluded that the cooked blanched garlic leave juice can inhibit platelet aggregation in vitro and in vivo, the inhibition of aggregation pathway mainly is blocking the combination of fibrinogen with Fib-R, which finally results in the inhibition of platelet aggregation. Therefore, regular consumption of cooked blanched garlic leaves may prevent cardiovascular thrombotic diseases.

  14. High glucose concentration induces the overexpression of transforming growth factor-beta through the activation of a platelet-derived growth factor loop in human mesangial cells.

    PubMed Central

    Di Paolo, S.; Gesualdo, L.; Ranieri, E.; Grandaliano, G.; Schena, F. P.

    1996-01-01

    High glucose concentration has been shown to induce the overexpression of transforming growth factor (TGF)-beta 1 mRNA and protein in different cell types, including murine mesangial cells, thus possibly accounting for the expansion of mesangial extracellular matrix observed in diabetic glomerulopathy. In the present study, we evaluated platelet-derived growth factor (PDGF) B-chain and PDGF-beta receptor gene expression in human mesangial cells (HMCs) exposed to different concentrations of glucose and then sought a possible relationship between a PDGF loop and the modulation of TGF-beta 1 expression. HMC [3H]thymidine incorporation was upregulated by 30 mmol/L glucose (HG) up to 24 hours, whereas it was significantly inhibited at later time points. Neutralizing antibodies to PDGF BB abolished the biphasic response to HG, whereas anti-TGF-beta antibodies reversed only the late inhibitory effect of hyperglycemic medium. HG induced an early and persistent increase of PDGF B-chain gene expression, as evaluated by reverse transcriptase polymerase chain reaction, whereas PDGF-beta receptor mRNA increased by twofold after 6 hours, thereafter declining at levels 70% lower than in controls after 24 hours. 125I-Labeled PDGF BB binding studies in HMCs exposed to HG for 24 hours confirmed the decrease of PDGF-beta receptor expression. TGF-beta 1-specific transcripts showed 43 and 78% increases after 24 and 48 hours of incubation in HG, respectively, which was markedly diminished by anti-PDGF BB neutralizing antibodies or suramin. We conclude that HG induces an early activation of a PDGF loop that, in turn, causes an increase of TGF-beta 1 gene expression, thus modulating both HMC proliferation and mesangial matrix production. Images Figure 2 Figure 3 Figure 4 Figure 5 PMID:8952542

  15. Contrasting role of phospholipase C-{gamma}1 in the expression of immediate early genes induced by epidermal or platelet-derived growth factors

    SciTech Connect

    Liao Hongjun; Santos, Josue de los; Carpenter, Graham . E-mail: graham.carpenter@vanderbilt.edu

    2006-04-01

    While significant progress has been achieved in identifying the signal transduction elements that operate downstream of activated receptor tyrosine kinases, it remains unclear how different receptors utilize these signaling elements to achieve a common response. This study compares the capacity of epidermal growth factor (EGF) and platelet-derived growth factor (PDGF) to elicit the induction of immediate early gene (IEG) mRNAs in the presence or absence of phospholipase C-{gamma}1 (PLC-{gamma}1). The results show that while PDGF induction of nearly all IEG mRNAs is abrogated in plcg1 null cells, EGF induction of the same genes is variable in the null cells and exhibits three distinct responses. Five IEG mRNAs (Nup475, Cyr61, TF, Gly, TS7) are completely inducible by EGF in the presence or absence of PLC-{gamma}1, while three others (JE, KC, FIC) exhibit a stringent requirement for the presence of PLC-{gamma}1. The third type of response is exhibited by c-fos and COX-2. While these mRNAs are completely induced by EGF in the absence of PLC-{gamma}1, the time course of their accumulation is significantly delayed. No IEG was identified as completely inducible by EGF and PDGF in the absence of PLC-{gamma}1. Electrophoretic mobility shift assays (EMSA) demonstrate that PLC-{gamma}1 is necessary for nuclear extracts from PDGF-treated cells, but not EGF-treated cells, to interact with probes for AP-1 or NF-{kappa}B.

  16. Private Information and Insurance Rejections

    PubMed Central

    Hendren, Nathaniel

    2013-01-01

    Across a wide set of non-group insurance markets, applicants are rejected based on observable, often high-risk, characteristics. This paper argues that private information, held by the potential applicant pool, explains rejections. I formulate this argument by developing and testing a model in which agents may have private information about their risk. I first derive a new no-trade result that theoretically explains how private information could cause rejections. I then develop a new empirical methodology to test whether this no-trade condition can explain rejections. The methodology uses subjective probability elicitations as noisy measures of agents beliefs. I apply this approach to three non-group markets: long-term care, disability, and life insurance. Consistent with the predictions of the theory, in all three settings I find significant amounts of private information held by those who would be rejected; I find generally more private information for those who would be rejected relative to those who can purchase insurance; and I show it is enough private information to explain a complete absence of trade for those who would be rejected. The results suggest private information prevents the existence of large segments of these three major insurance markets. PMID:24187381

  17. Rejected by peers-attracted to antisocial media content: rejection-based anger impairs moral judgment among adolescents.

    PubMed

    Plaisier, Xanthe S; Konijn, Elly A

    2013-06-01

    Adolescence is an important developmental stage during which both peers and the media have a strong influence. Both peer rejection and the use of morally adverse media are associated with negative developmental outcomes. This study examines processes by which peer rejection might drive adolescents to select antisocial media content by tying together developmental research on peer rejection and research on media effects. Assumed underlying mechanisms are rejection-based anger and frustration and the adolescent's moral judgment. A between-participants experimental design manipulated peer rejection versus acceptance in adolescents (Mage = 13.88 years; N = 74) and young adults (Mage = 21.37 years; N = 75), applying the Cyberball paradigm. Measures included the State Anger Inventory (STAXI) to assess feelings of rejection and the newly devised Media, Morals, and Youth Questionnaire (MMaYQue) to assess media preferences and moral judgment of media content. Using bootstrapping analyses, a double mediation was established: Higher levels of state anger in peer-rejected adolescents induced more tolerable moral judgments of antisocial media content, subsequently instigating a preference for antisocial media content. In contrast, the young adult sample showed no relations between peer rejection and antisocial media preference. Results are discussed within a downward spiral framework of combined peer and media influences.

  18. Reversible translocation of glycoprotein Ib in plasmin-treated platelets: consequences for platelet function.

    PubMed

    Lu, H; Soria, C; Soria, J; De Romeuf, C; Perrot, J Y; Tenza, D; Garcia, I; Caen, J P; Cramer, E M

    1993-12-01

    Understanding the effect of fibrinolysis on platelet function is of clinical importance. Plasmin is recognized to affect platelet adhesive function by reducing the interaction of platelet glycoprotein (GP) Ib with von Willebrand factor (vWF) bound to the subendothelium. This platelet function is commonly explored in vitro by the ristocetin-induced agglutination test. Our previous study demonstrated a plasmin-induced redistribution of GP Ib molecules from the platelet surface to the linings of the surface-connected canalicular system (SCCS), a critical mechanism for understanding plasmin-induced GP Ib dysfunction. Here, we demonstrate that neutralization of plasmin by its inhibitors, aprotinin or tripeptide Val-Phe-Lys-CH2Cl, permits a time dependent recovery (within 30 min) of ristocetin-induced agglutination in the platelets which were stimulated by plasmin at < 1 CU ml-1. This functional recovery was accompanied with a restoration of a normal amount of GP Ib on the platelet surface, as measured by the binding of both monoclonal anti-GP Ib antibody SZ 2 and 125I-labelled vWF to the platelets. Cytochalasin D did not inhibit this recovery, suggesting that this process may be due to passive actin depolymerization. These findings were further confirmed by immunoelectron microscopic study. Utilizing the platelets pre-labelled with anti-GP Ib antibody prior to plasmin stimulation, it was demonstrated that the observed recovery is due to a reverse translocation from the SCCS to the plasma membrane of the same GP Ib molecules which were present initially at the cell surface.(ABSTRACT TRUNCATED AT 250 WORDS)

  19. Platelets: handle with care.

    PubMed

    Thomas, S

    2016-10-01

    Platelets are delicate cells that require careful handling between collection, preparation and transfusion. This review addresses practical questions relating to platelet concentration, resting time after collection, total time and number of periods without agitation and temperature. The bags in which platelets are stored are made from gas-permeable plastic to allow sufficient oxygen for the platelets to maintain aerobic respiration. Manufacturers have assigned limits for platelet content and concentration, and these must not be exceeded. There is no strong evidence for or against the resting of platelets post-collection and pre-agitation, but platelets should not be over-wrapped during this period as this compromises gas exchange; a short rest period of up to 1 h may allow the separation of minor aggregates. It is necessary to transport platelet concentrates (e.g. from manufacturing site to hospital), but these periods without gas exchange must be limited to avoid excessive damage to the platelets. Current data support a total of 24 h of transportation per component but with no individual period lasting more than 8 h. Platelets need to be stored at 20-24 °C based on evidence that colder storage leads to irreversible changes on the platelet membrane, resulting in phagocytosis of the platelets following transfusion. Storage at warmer temperatures may lead to an increase in bacterial risk. On the basis of this review, the UK Guidelines for Blood Transfusion Services have been updated to ensure that platelets are handled in the most appropriate way to ensure that efficacious components are provided for patients.

  20. Genetic engineering of platelets to neutralize circulating tumor cells.

    PubMed

    Li, Jiahe; Sharkey, Charles C; Wun, Brittany; Liesveld, Jane L; King, Michael R

    2016-04-28

    Mounting experimental evidence demonstrates that platelets support cancer metastasis. Within the circulatory system, platelets guard circulating tumor cells (CTCs) from immune elimination and promote their arrest at the endothelium, supporting CTC extravasation into secondary sites. Neutralization of CTCs in blood circulation can potentially attenuate metastases to distant organs. Therefore, extensive studies have explored the blockade of platelet-CTC interactions as an anti-metastatic strategy. Such an intervention approach, however, may cause bleeding disorders since the platelet-CTC interactions inherently rely on the blood coagulation cascade including platelet activation. On the other hand, platelets have been genetically engineered to correct inherited bleeding disorders in both animal models and human clinical trials. In this study, inspired by the physical association between platelets and CTCs, platelets were genetically modified to express surface-bound tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), a cytokine known to induce apoptosis specifically in tumor cells. The TRAIL-expressing platelets were demonstrated to kill cancer cells in vitro and significantly reduce metastases in a mouse model of prostate cancer metastasis. Our results suggest that using platelets to produce and deliver cancer-specific therapeutics can provide a Trojan-horse strategy of neutralizing CTCs to attenuate metastasis.

  1. Role of Siglec-7 in Apoptosis in Human Platelets

    PubMed Central

    Nguyen, Kim Anh; Hamzeh-Cognasse, Hind; Palle, Sabine; Anselme-Bertrand, Isabelle; Arthaud, Charles-Antoine; Chavarin, Patricia; Pozzetto, Bruno; Garraud, Olivier; Cognasse, Fabrice

    2014-01-01

    Background Platelets participate in tissue repair and innate immune responses. Sialic acid-binding immunoglobulin-like lectins (Siglecs) are well-characterized I-type lectins, which control apoptosis. Methodology/Principal Findings We characterized the expression of Siglec-7 in human platelets isolated from healthy volunteers using flow cytometry and confocal microscopy. Siglec-7 is primarily expressed on α granular membranes and colocalized with CD62P. Siglec-7 expression was increased upon platelet activation and correlated closely with CD62P expression. Cross-linking Siglec-7 with its ligand, ganglioside, resulted in platelet apoptosis without any significant effects on activation, aggregation, cell morphology by electron microscopy analysis or secretion. We show that ganglioside triggered four key pathways leading to apoptosis in human platelets: (i) mitochondrial inner transmembrane potential (ΔΨm) depolarization; (ii) elevated expression of pro-apoptotic Bax and Bak proteins with reduced expression of anti-apoptotic Bcl-2 protein; (iii) phosphatidylserine exposure and (iv), microparticle formation. Inhibition of NAPDH oxidase, PI3K, or PKC rescued platelets from apoptosis induced by Siglec-7 recruitment, suggesting that the platelet receptors P2Y1 and GPIIbIIIa are essential for ganglioside-induced platelet apoptosis. Conclusions/Significance The present work characterizes the role of Siglec-7 and platelet receptors in regulating apoptosis and death. Because some platelet pathology involves apoptosis (idiopathic thrombocytopenic purpura and possibly storage lesions), Siglec-7 might be a molecular target for therapeutic intervention/prevention. PMID:25230315

  2. Autoantibodies to Vimentin Cause Accelerated Rejection of Cardiac Allografts

    PubMed Central

    Mahesh, Balakrishnan; Leong, Hon-Sing; McCormack, Ann; Sarathchandra, Padmini; Holder, Angela; Rose, Marlene L.

    2007-01-01

    Autoimmune responses to vimentin occur after solid organ transplantation, but their pathogenic effects are unclear. The aim of these studies was to investigate the effects of vimentin preimmunization on allogeneic and isografted hearts in a murine transplant model. Immunization of C57BL/6 mice with murine vimentin in complete Freund’s adjuvant resulted in anti-vimentin antibodies and vimentin-reactive Th-1 cells. Transplantation of 129/sv hearts into vimentin-immunized C57BL/6 recipients resulted in accelerated rejection (8.4 ± 1.5 days; n = 18), compared with hen egg lysozyme-immunized C57BL/6 (13.3 ± 2.2 days; n = 10; P < 0.0001, log-rank test). In contrast, isografts continued to beat beyond 90 days. Immunohistochemical analysis of allografts from vimentin/complete Freund’s adjuvant mice demonstrated increased numbers of T cells and enhanced microvascular deposition of C3d, CD41, and P-selectin compared with controls. Antibodies were necessary for accelerated rejection, shown by the fact that vimentin-immunized B-cell-deficient IgH6 mice did not show accelerated rejection of 129/sv allografts, but rejection was restored by adoptive transfer of serum containing anti-vimentin antibodies. Eluates from donor hearts placed in vimentin/complete Freund’s adjuvant recipients contained anti-vimentin antibodies, shown by Western blotting. Confocal imaging of rejected hearts demonstrated presence of vimentin and C3d on apoptosed leukocytes, endothelial cells, and platelet/leukocyte conjugates. These results demonstrate that autoantibodies to vimentin, in conjunction with the alloimmune response, have a pathogenic role in allograft rejection. PMID:17392180

  3. Targeted gene correction of RUNX1 in induced pluripotent stem cells derived from familial platelet disorder with propensity to myeloid malignancy restores normal megakaryopoiesis.

    PubMed

    Iizuka, Hiromitsu; Kagoya, Yuki; Kataoka, Keisuke; Yoshimi, Akihide; Miyauchi, Masashi; Taoka, Kazuki; Kumano, Keiki; Yamamoto, Takashi; Hotta, Akitsu; Arai, Shunya; Kurokawa, Mineo

    2015-10-01

    Familial platelet disorder with propensity to acute myeloid leukemia (FPD/AML) is an autosomal dominant disease associated with a germline mutation in the RUNX1 gene and is characterized by thrombocytopenia and an increased risk of developing myeloid malignancies. We generated induced pluripotent stem cells (iPSCs) from dermal fibroblasts of a patient with FPD/AML possessing a nonsense mutation R174X in the RUNX1 gene. Consistent with the clinical characteristics of the disease, FPD iPSC-derived hematopoietic progenitor cells were significantly impaired in undergoing megakaryocytic differentiation and subsequent maturation, as determined by colony-forming cell assay and surface marker analysis. Notably, when we corrected the RUNX1 mutation using transcription activator-like effector nucleases in conjunction with a donor plasmid containing normal RUNX1 cDNA sequences, megakaryopoiesis and subsequent maturation were restored in FPD iPSC-derived hematopoietic cells. These findings clearly indicate that the RUNX1 mutation is robustly associated with thrombocytopenia in patients with FPD/AML, and transcription activator-like effector nuclease-mediated gene correction in iPSCs generated from patient-derived cells could provide a promising clinical application for treatment of the disease.

  4. Hypothermia-induced platelet aggregation in human blood in an in vitro model: the dominant role of blood-material interactions.

    PubMed

    Hall, Matthew W; Solen, Kenneth A

    2002-03-05

    Hypothermia-induced platelet aggregation (HIPA) with or without neutrophil involvement may cause neurologic dysfunction during hypothermic surgery. We report the use of a previously developed model to study the contributions of several surfaces, surface area, shear rate, and blood-material exposure time to HIPA. Heparinized (1.5 u/mL) human blood was quenched to 24 degrees C and passed (0.5 mL/min) through a 75-cm long 1/32" ID tubing of polyvinylchloride (PVC), polyethylene (PE), polyurethane (PU), Teflon-FEP, or heparin (Duraflo)-coated PVC. The number of aggregates was measured by a light-scattering method, and the concentration of occlusive aggregates was assessed using constant-pressure filtration (50 mmHg). No differences were seen among PVC, PE, PU, or Teflon-FEP. The heparin-coated PVC tubing produced fewer occlusive aggregates, and heparin leaching from the coating was not the cause of the decrease in occlusive aggregates. Increasing surface area increased the number of aggregates, and increasing shear rates decreased the occlusiveness of those aggregates.

  5. Understanding the connection between platelet-activating factor, a UV-induced lipid mediator of inflammation, immune suppression and skin cancer.

    PubMed

    Damiani, Elisabetta; Ullrich, Stephen E

    2016-07-01

    Lipid mediators of inflammation play important roles in several diseases including skin cancer, the most prevalent type of cancer found in the industrialized world. Ultraviolet (UV) radiation is a complete carcinogen and is the primary cause of skin cancer. UV radiation is also a potent immunosuppressive agent, and UV-induced immunosuppression is a well-known risk factor for skin cancer induction. An essential mediator in this process is the glyercophosphocholine 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine commonly referred to as platelet-activating factor (PAF). PAF is produced by keratinocytes in response to diverse stimuli and exerts its biological effects by binding to a single specific G-protein-coupled receptor (PAF-R) expressed on a variety of cells. This review will attempt to describe how this lipid mediator is involved in transmitting the immunosuppressive signal from the skin to the immune system, starting from its production by keratinocytes, to its role in activating mast cell migration in vivo, and to the mechanisms involved that ultimately lead to immune suppression. Recent findings related to its role in regulating DNA repair and activating epigenetic mechanisms, further pinpoint the importance of this bioactive lipid, which may serve as a critical molecular mediator that links the environment (UVB radiation) to the immune system and the epigenome.

  6. Supplementation of bone marrow aspirate-derived platelet-rich plasma for treating radiation-induced ulcer after cardiac fluoroscopic procedures: A preliminary report

    PubMed Central

    Nishimoto, Soh; Fukuda, Kenji; Kawai, Kenichiro; Fujiwara, Toshihiro; Tsumano, Tomoko; Fujita, Kazutoshi; Kakibuchi, Masao

    2012-01-01

    Background: The frequency of encountering radiodermatitis caused by X-ray fluoroscopic procedures for ischaemic heart disease is increasing. In severe cases, devastating ulcers with pain, for which conservative therapy is ineffective, emerge. Radiation-induced ulcers are notorious for being difficult to treat. Simple skin grafting often fails because of the poor state of the wound bed. A vascularized flap is a very good option. However, the non-adherence of the well-vascularized flap with the irradiated wound bed is frequently experienced. Aim: To ameliorate the irradiated wound bed, bone marrow-derived platelet-rich plasma (bm-PRP) was delivered during the surgery. Materials and Methods: Four patients with severe cutaneous radiation injury accompanied by unbearable pain after multiple fluoroscopic procedures for ischaemic heart disease were treated. Wide excision of the lesion and coverage with a skin flap supplemented with bm-PRP injection was performed. Results: All patients obtained wound closure and were relieved from pain. No complication concerning the bone marrow aspiration and delivery of bm-PRP was observed. Conclusions: Supplementation of bm-PRP can be an option without major complications, time, and cost to improve the surgical outcome for irradiated wounds. PMID:22754164

  7. The influence of prostaglandin G2 on platelet ultrastructure and platelet secretion.

    PubMed Central

    Gerrard, J. M.; Townsend, D.; Stoddard, S.; Witkop, C. J.; White, J. G.

    1977-01-01

    Prostaglandin G2 (PGG2) is a labile endoperoxide produced physiologically following exposure of platelets to aggregating agents. We report here studies using isolated PGG2. This agent stimulates a concentration-dependent internal platelet contraction very similar to that produced by the calcium ionophore A23187. EDTA prevented platelet aggregation but did not prevent PGG2-stimulated internal contraction or secretion. In contrast, prostaglandin E1 and dibutyryl cyclic AMP inhich selectively labilizes platelet granules, was added to platelets together with PGG2 there was a superadditive effect on platelet secretion. Thus, granule labilization induced by PMA is a separable phenomenon and complementary to the effect of PGG2 on contraction. The ultimate degree of secretion is dependent on both processes. Studies using additional inhibitors supported the hypothesis that PGG2 activates platelets (either directly or following conversion to thromboxane A2) by transporting calcium from an intracellular store to the cytoplasmic site of the platelet contractile proteins. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 PMID:188341

  8. Propranolol modifies platelet serotonergic mechanisms in rats.

    PubMed

    Zółtowski, R; Pawlak, R; Matys, T; Pietraszek, M; Buczko, W

    2002-06-01

    Though the mechanisms for the vascular actions of vasodilatory beta-blockers are mostly determined, some of their interactions with monoaminergic systems are not elucidated. Because there are evidences supporting a possible involvement of serotonin (5-HT) in the actions of beta-blockers, we studied the effect of propranolol on peripheral serotonergic mechanisms in normotensive and Goldblatt two-kidney - one clip (2K1C) hypertensive rats. In both groups of animals propranolol decreased systolic blood pressure, significantly increased whole blood serotonin concentration and at the same time it decreased platelet serotonin level. The uptake of the amine by platelets from hypertensive animals was lower than that of normotensive animals and it was decreased by propranolol only in the latter. In both groups propranolol inhibited potentiation of ADP-induced platelet aggregation by serotonin. In conclusion, this study provides evidence that propranolol modifies platelet serotonergic mechanisms in normotensive and renal hypertensive rats.

  9. [Blood platelets and asthma caused by aspirin].

    PubMed

    Joseph, M; Capron, A; Ameisen, J C; Martinot, J B; Tonnel, A B

    1987-10-01

    Platelets isolated from patients with aspirin-induced asthma (ASA patients) react abnormally in vitro to aspirin and to non-steroid anti-inflammatory drugs (NSAID), by generating cytocidal molecules, that can kill parasitic larvae and to oxygen-dependent free radicles, which may be detected by chemiluminescence, although these drugs do not have a similar effect on platelets from normal donors or allergic asthmatics. The abnormality appears to be associated with the inhibiting properties of NSAID and aspirin on the cyclo-oxygenase pathway, that leads to a defect of the binding of prostaglandin endoperoxide PGH2 to its receptors on the platelet membrane. In addition, another metabolite from the lipoxygenase pathway which is at present poorly defined seems to participate in the anomaly. Sodium salicylate, a naturally produced catabolite of aspirin, that is well-tolerated by ASA patients, inhibits the abnormal response of the platelets and this opens new perspectives in the management of aspirin-sensitive intolerance.

  10. Platelet function and fibrinolytic activity following distance running.

    PubMed

    Knudsen, J B; Brodthagen, U; Gormsen, J; Jordal, R; Nørregaard-Hansen, K; Paulev, P E

    1982-11-01

    6 long distance runners from the Danish marathon elite and 6 non-runners completed test runs of 28 and 12 km, respectively. Distance runners and non-runners showed the same responses in platelet function. We found a significant decrease in ADP induced platelet aggregability, a decreased serotonin release induced by ADP and collagen and an increase in platelet factor 4 immediately following the run. The antithrombin III levels remained constant. Euglobulin lysis time was shortened (by approximately 50%) and the plasminogen levels significantly increased. The last 2 findings indicate an equal increase in fibrinolytic activity during distance running in both groups. While short term, strenuous exercise induces platelet hyperaggregation, long term distance running induces a state of exhaustion of platelet aggregation capacity.

  11. Fusaric acid, a mycotoxin, and its influence on blood coagulation and platelet function.

    PubMed

    Devaraja, Sannaningaiah; Girish, Kesturu S; Santhosh, Martin S; Hemshekhar, Mahadevappa; Nayaka, Siddaiah C; Kemparaju, Kempaiah

    2013-06-01

    The current study intended to explore the effect of fusaric acid on blood coagulation including plasma coagulation and platelet aggregation. Fusaric acid exhibited biphasic effects on citrated human plasma recalcification time. At concentrations below 50 ng, fusaric acid decreased the clotting time of plasma dose-dependently from 130 ± 3s control value to 32 ± 3s; however, above 50 ng, fusaric acid increased the clotting time from 32 ± 3s and reached a maximum of 152 s at 100 ng and remained unaltered thereafter for the increased dose of fusaric acid. Fusaric acid without damaging red blood cells and platelets, inhibited agonists such as collagen, ADP, thrombin, and epinephrine-induced aggregation of both platelet-rich plasma (PRP) and washed platelets preparations of human. Interestingly, fusaric acid showed biphasic effects only in thrombin-induced platelet aggregation of washed platelets, and at lower concentration (below 900 ng) it activated platelet aggregation; however, in increased concentration (above 900 ng) it inhibited the platelet aggregation of washed platelets. In addition, fusaric acid also inhibited the agonist ADP-induced platelet aggregation of washed platelet suspension but did not show biphasic effect. Further, fusaric acid did not induce the platelets to generate reactive oxygen species (ROS) that clearly suggests that the induction of platelet function could be the result of the fusaric acid-mediated receptor interaction but not through the morphological shape change.

  12. Do Scientists Really Reject God?

    ERIC Educational Resources Information Center

    Scott, Eugenie C.

    1998-01-01

    Suggests that the title of the recent Larson and Witham article in the journal Nature, "Leading Scientists Still Reject God", is premature and without reliable data upon which to base it. (Author/CCM)

  13. Space vehicle thermal rejection system

    NASA Technical Reports Server (NTRS)

    Tanzer, Herbert J. (Inventor)

    1989-01-01

    A space vehicle thermal heat rejection system 10 utilizing separate optimized heat pipe components for the functions of heat acquisition, heat transport, and heat rejection. A honeycomb panel heat pipe evaporator section 20 performs the function of heat acquisition, and forms a closed thermodynamic system with a dual channel heat pipe transport section 30, which performs the function of heat transport. A plurality of truss or channel core heat pipe rejection fins 41 form the condenser section 40, which performs the function of heat rejection. A common wall 32 separates the condenser section 40 from the transport section 30. Using the above heat pipe components and having efficient interfacing between them results in high performance factors for the overall system.

  14. Endotoxin Interactions with Platelets

    DTIC Science & Technology

    1985-01-01

    irreversible aggregation of human platelets (Hamberg and Sainuelsson 1974; Hlamberg et al 1975). Acetylsalicylic acid , an inhibitor of cyclooxygenase aud...exposure to endotoxin (100 ttg/nil). To simulate the lipopolysac- charide of endotoxin, several different fatty acids were added individually to platelet...platelet lytic capability. Similarity, iflegaradt doses of ganima radiation 6wCo destroy fatty acid groups on lipid A (L. Bertok, personal communication

  15. Functional fractionation of platelets.

    PubMed

    Haver, V M; Gear, A R

    1981-02-01

    Studies of platelet populations suggest that they are heterogeneous in size, age, and metabolic parameters. In an attempt to correlate these parameters with efficiency of aggregation, a new technique, functional fractionation, was developed. Platelet populations are separated by their differential reactivity to aggregating agents. For example, low doses of ADP (0.1 to 0.7 microM) are added to stirred PRP, after which gentle centrifugation is used to remove aggregates from single unreacted platelets. The loose aggregates can be readily dispersed for comparison of the physical or biochemical properties of the reacted versus unreacted platelets. It was found that reactive platelets were larger (6.5 micrometer3) than unreacted platelets (5.51 micrometer3). No significant difference in density existed between the two populations, and no release of [14C]serotonin from prelabeled platelets occurred during functional fractionation. Scanning and transmission electron microscopy confirmed the size difference and revealed that in both populations platelets were structurally intact with a normal discoid shape and no significant difference in organelle content. Human platelets most reactive to ADP were also enriched in glycogen (3.6-fold), ATP (1.6-fold), and ADP (twofold), compared with less reactive cells. These "reactive" cells took up more 51[Cr] and contained 1.9 times more surface sialic acid. In an in vivo aging experiment, rats were injected with 75[Se]methionine. Shortly after labeling (1 day), the most reactive platelets possessed the highest amount of 75[Se]. These results reveal that functionally active platelets, which are also larger, are more active metabolically than less reactive platelets, possess a higher negative surface charge, and may be a younger population.

  16. Platelet-derived growth factor-BB induces cystathionine γ-lyase expression in rat mesangial cells via a redox-dependent mechanism

    PubMed Central

    Hassan, Mohamed I; Boosen, Meike; Schaefer, Liliana; Kozlowska, Jowita; Eisel, Florian; von Knethen, Andreas; Beck, Martina; Hemeida, Ramadan A M; El-Moselhy, Mohamed A M; Hamada, Farid M A; Beck, Karl-Friedrich; Pfeilschifter, Josef

    2012-01-01

    BACKGROUND AND PURPOSE So far, there is only limited information about the regulation of the endogenous synthesis of hydrogen sulfide (H2S), an important gaseous signalling molecule. This study was done to evaluate the redox-dependent signalling events that regulate the expression of the H2S synthesising enzyme cystathionine-γ-lyase (CSE) in rat mesangial cells. EXPERIMENTAL APPROACH The effects of platelet-derived growth factor (PDGF)-BB and antioxidants on CSE expression and activity in cultured rat renal mesangial cells were assessed. Activity of nuclear factor erythroid-2-related factor-2 (Nrf2) was measured as the binding capacity to a radiolabelled consensus element by electrophoretic mobility shift assay (EMSA). Furthermore, CSE and Nrf2 expression was analysed in a rat model of anti-Thy-1-induced glomerulonephritis by immunohistochemistry. KEY RESULTS Treatment of mesangial cells with PDGF-BB resulted in a marked time- and dose-dependent up-regulation of CSE mRNA and protein levels, as well as CSE activity accompanied with increased formation of reactive oxygen species. Remarkably, co-administration of antioxidants, such as N-acetylcysteine, ebselen or diphenylene iodonium chloride, drastically reduced PDGF-BB-induced CSE expression. PDGF-BB induced binding of Nrf2 to a corresponding consensus antioxidant element in a redox-dependent manner. Furthermore, PDGF-BB-induced CSE expression in mouse mesangial cells was completely abolished in Nrf2 knockout mice compared with wild-type mice. In a rat model of anti-Thy-1-induced proliferative glomerulonephritis, we observed a marked up-regulation of CSE protein paralleled by a stabilization of Nrf2 protein. CONCLUSIONS AND IMPLICATIONS PDGF-BB regulated CSE via a redox-mediated activation of Nrf2. Such action would aid the resolution of glomerular inflammatory diseases. LINKED ARTICLE This article is commented on by Gallyas, pp. 2228–2230 of this issue. To view this commentary visit http://dx.doi.org/10.1111/j

  17. Endocannabinoids Control Platelet Activation and Limit Aggregate Formation under Flow

    PubMed Central

    De Angelis, Valentina; Koekman, Arnold C.; Weeterings, Cees; Roest, Mark; de Groot, Philip G.; Herczenik, Eszter; Maas, Coen

    2014-01-01

    Background The endocannabinoid system has previously been implicated in the regulation of neurons and inflammatory cells. Additionally, it has been reported that endocannabinoid receptors are present on circulating platelets, but there has been conflicting evidence on their contribution to platelet function. Objectives Our aim was to examine the role of endocannabinoids in platelet function in vitro and in vivo. Methods and Results We studied the effects of the well-characterized endogenous endocannabinoid anandamide on platelet aggregation in suspension, α-granule release, calcium mobilization, Syk phosphorylation, as well as platelet spreading and aggregate formation under flow. Anandamide inhibits platelet aggregation and α-granule release by collagen, collagen-derived peptide CRP-XL, ADP, arachidonic acid and thromboxane A2 analogue U46619. However, activation via thrombin receptor PAR-1 stays largely unaffected. Calcium mobilization is significantly impaired when platelets are stimulated with collagen or CRP-XL, but remains normal in the presence of the other agonists. In line with this finding, we found that anandamide prevents collagen-induced Syk phosphorylation. Furthermore, anandamide-treated platelets exhibit reduced spreading on immobilized fibrinogen, have a decreased capacity for binding fibrinogen in solution and show perturbed platelet aggregate formation under flow over collagen. Finally, we investigated the influence of Cannabis sativa consumption by human volunteers on platelet activation. Similar to our in vitro findings with anandamide, ex vivo collagen-induced platelet aggregation and aggregate formation on immobilized collagen under flow were impaired in whole blood of donors that had consumed Cannabis sativa. Conclusions Endocannabinoid receptor agonists reduce platelet activation and aggregate formation both in vitro and ex vivo after Cannabis sativa consumption. Further elucidation of this novel regulatory mechanism for platelet function

  18. Effect of intravascular neutrophil chemotactic factors on blood neutrophil and platelet kinetics

    SciTech Connect

    Issekutz, A.C.; Ripley, M.

    1986-02-01

    Intravenous infusion of an analogue (f-met-leu-phe (FMLP)) of a bacterial-derived polymorphonuclear leukocyte (PMNL) chemotactic factor, or of the complement-derived chemotactic stimulus, zymosan-activated plasma (ZAP, containing C5ades Arg) into rabbits induces acute PMNL margination in the pulmonary vasculature. The pulmonary PMNL sequestration is accompanied by thrombocytopenia. Because of the role platelets and PMNLs play in hemostasis and defense against infection, we studied the fate of these blood elements following sequestration induced by chemotactic factors. By employing 111In-labelled platelets and external radioisotope scanning, platelets were found to sequester in the pulmonary vasculature during FMLP infusion. Simultaneous 51Cr PMNL and 111In-platelet studies showed that following sequestration, PMNLs returned to the circulation and disappeared with a normal half-life (T1/2) whereas the T1/2 of the platelets was markedly shortened (T1/2 of control = 49 +/- 3.0 hr; FMLP or ZAP infused T1/2 = 27 +/- 2.7 hr). Infusion of platelet-activating factor (PAF) induced PMN and platelet sequestration with similar abnormalities in platelet kinetics. Studies with 51Cr- and 14C-serotonin-labelled platelets showed that platelets did not release serotonin during FMLP, ZAP, or low dose PAF-induced sequestration. In contrast to platelet survival, platelet size, platelet aggregation responses, and platelet glycoproteins were not affected by transient sequestration. These results indicate that during PMNL margination induced by relatively pure PMNL stimuli such as FMLP, platelets may reversibly marginate and subsequently be cleared at an accelerated rate. The reason for accelerated platelet clearance is not a result of circulating platelet aggregates or detectable proteolytic modification of membrane glycoproteins.

  19. The inhibitory effect of dexamethasone on platelet-derived growth factor-induced vascular smooth muscle cell migration through up-regulating PGC-1{alpha} expression

    SciTech Connect

    Xu, Wei; Guo, Ting; Zhang, Yan; Jiang, Xiaohong; Zhang, Yongxian; Zen, Ke; Yu, Bo; Zhang, Chen-Yu

    2011-05-01

    Dexamethasone has been shown to inhibit vascular smooth muscle cell (VSMC) migration, which is required for preventing restenosis. However, the mechanism underlying effect of dexamethasone remains unknown. We have previously demonstrated that peroxisome proliferator-activated receptor gamma (PPAR{gamma}) coactivator-1 alpha (PGC-1{alpha}) can inhibit VSMC migration and proliferation. Here, we investigated the role of PGC-1{alpha} in dexamethasone-reduced VSMC migration and explored the possible mechanism. We first examined PGC-1{alpha} expression in cultured rat aortic VSMCs. The results revealed that incubation of VSMCs with dexamethasone could significantly elevate PGC-1{alpha} mRNA expression. In contrast, platelet-derived growth factor (PDGF) decreased PGC-1{alpha} expression while stimulating VSMC migration. Mechanistic study showed that suppression of PGC-1{alpha} by small interfering RNA strongly abrogated the inhibitory effect of dexamethasone on VSMC migration, whereas overexpression of PGC-1{alpha} had the opposite effect. Furthermore, an analysis of MAPK signal pathways showed that dexamethasone inhibited ERK and p38 MAPK phosphorylation in VSMCs. Overexpression of PGC-1{alpha} decreased both basal and PDGF-induced p38 MAPK phosphorylation, but it had no effect on ERK phosphorylation. Finally, inhibition of PPAR{gamma} activation by a PPAR{gamma} antagonist GW9662 abolished the suppressive effects of PGC-1{alpha} on p38 MAPK phosphorylation and VSMC migration. These effects of PGC-1{alpha} were enhanced by a PPAR{gamma} agonist troglitazone. Collectively, our data indicated for the first time that one of the anti-migrated mechanisms of dexamethasone is due to the induction of PGC-1{alpha} expression. PGC-1{alpha} suppresses PDGF-induced VSMC migration through PPAR{gamma} coactivation and, consequently, p38 MAPK inhibition.

  20. High glucose induces platelet-derived growth factor-C via carbohydrate response element-binding protein in glomerular mesangial cells.

    PubMed

    Kitsunai, Hiroya; Makino, Yuichi; Sakagami, Hidemitsu; Mizumoto, Katsutoshi; Yanagimachi, Tsuyoshi; Atageldiyeva, Kuralay; Takeda, Yasutaka; Fujita, Yukihiro; Abiko, Atsuko; Takiyama, Yumi; Haneda, Masakazu

    2016-03-01

    Persistent high concentration of glucose causes cellular stress and damage in diabetes via derangement of gene expressions. We previously reported high glucose activates hypoxia-inducible factor-1αand downstream gene expression in mesangial cells, leading to an extracellular matrix expansion in the glomeruli. A glucose-responsive transcription factor carbohydrate response element-binding protein (ChREBP) is a key mediator for such perturbation of gene regulation. To provide insight into glucose-mediated gene regulation in mesangial cells, we performed chromatin immunoprecipitation followed byDNAmicroarray analysis and identified platelet-derived growth factor-C (PDGF-C) as a novel target gene of ChREBP In streptozotocin-induced diabetic mice, glomerular cells showed a significant increase inPDGF-C expression; the ratio ofPDGF-C-positive cells to the total number glomerular cells demonstrated more than threefold increase when compared with control animals. In cultured human mesangial cells, high glucose enhanced expression ofPDGF-C protein by 1.9-fold. Knock-down of ChREBPabrogated this induction response. UpregulatedPDGF-C contributed to the production of typeIVand typeVIcollagen, possibly via an autocrine mechanism. Interestingly, urinaryPDGF-C levels in diabetic model mice were significantly elevated in a fashion similar to urinary albumin. Taken together, we hypothesize that a high glucose-mediated induction ofPDGF-C via ChREBPin mesangial cells contributes to the development of glomerular mesangial expansion in diabetes, which may provide a platform for novel predictive and therapeutic strategies for diabetic nephropathy.

  1. Abnormal phosphoinositide metabolism and protein phosphorylation in platelets from a patient with the grey platelet syndrome.

    PubMed

    Rendu, F; Marche, P; Hovig, T; Maclouf, J; Lebret, M; Tenza, D; Levy-Toledano, S; Caen, J P

    1987-10-01

    Washed platelets isolated from one patient suffering from the inherited grey platelet syndrome were studied during thrombin-induced activation. The agonist-induced changes in (i) morphology, (ii) typical functional cell responses, (iii) membrane phospholipid metabolism and protein phosphorylation were studied and compared with the changes obtained with normal platelets. The morphology of the platelets as visualized by electron microscopy confirmed the almost total absence of intracellular alpha-granules and marked vacuolization. During thrombin stimulation the morphological changes were clearly delayed as compared to normal platelets, the granule centralization and aggregation occurred only 15 s after thrombin addition instead of 5 s in normal platelets. After 15 s, however, even though no alpha-granules were observed, a ring-like structure occurred centrally, indicating that they are not a prerequisite for this reaction. The whole release reaction, i.e. liberation of [14C]serotonin from dense granules and beta-N-acetylglucosaminidase activity from lysosomes, and the thromboxane synthesis were delayed and remained lower than in normal platelets. No thrombin-induced phosphatidyl 4,5-bisphosphate breakdown was measurable on 32P-prelabelled platelets although [32P]phosphatidate formation occurred normally. Phosphorylation time courses of myosin light chain (P20) and of protein P43 (mol wt 43,000) markedly differed from those of controls, being less than half of the normal during the first 15 s and remaining subnormal even after complete aggregation. These results suggest that in platelets devoid of alpha-granules a deficient transmembrane signalling system is likely responsible for the impaired physiological responses.

  2. Platelet size in man.

    PubMed

    Paulus, J M

    1975-09-01

    The shape and parameters of platelet size distributions were studied in 50 normal persons and 97 patients in order to test the proposed thesis that platelet size heterogeneity results mainly from aging in the circulation. This thesis was contradicted (1) by size distributions of age-homogeneous, newly-born cell populations which were lognormal with increased (instead of decreased) dispersion of volumes and (2) by the macrothrombocytosis found in some populations with normal age distribution. For these reasons, thrombocytopoiesis appeared to play the major role in determining platelet size. A model was built in which the volume variation of platelet territories due to megakaryocyte growth and membrane demarcation at each step of maturation was a random proportion of the previous value of the volume. This model explains the lognormal shape of both newborn and circulating platelet size distributions. It also implies that (1) the mean and standard deviation of platelet logvolumes depend on the rates of volume change of the individual platelet territories (growth rate minus demarcation rate) as well as on megakaryocyte maturation time; (2) platelet hyperdestruction causes an increase in the mean and dispersion of the rates of territory volume change; (3) Mediterranean macrothrombocytosis and some hereditary macrothrombocytotic thrombocytopenias or dysthrombocytopoieses reflect a diminished rate of territory demarcation, and (4) platelet size heterogeneity is caused mainly by the variations in territory growth and demarcation and not by aging in the circulation.

  3. Membrane rejection of nitrogen compounds

    NASA Technical Reports Server (NTRS)

    Lee, S.; Lueptow, R. M.

    2001-01-01

    Rejection characteristics of nitrogen compounds were examined for reverse osmosis, nanofiltration, and low-pressure reverse osmosis membranes. The rejection of nitrogen compounds is explained by integrating experimental results with calculations using the extended Nernst-Planck model coupled with a steric hindrance model. The molecular weight and chemical structure of nitrogen compounds appear to be less important in determining rejection than electrostatic properties. The rejection is greatest when the Donnan potential exceeds 0.05 V or when the ratio of the solute radius to the pore radius is greater than 0.8. The transport of solute in the pore is dominated by diffusion, although convective transport is significant for organic nitrogen compounds. Electromigration contributes negligibly to the overall solute transport in the membrane. Urea, a small organic compound, has lower rejection than ionic compounds such as ammonium, nitrate, and nitrite, indicating the critical role of electrostatic interaction in rejection. This suggests that better treatment efficiency for organic nitrogen compounds can be obtained after ammonification of urea.

  4. Platelets enhance neutrophil transendothelial migration

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Platelets are increasingly recognized as important mediators of inflammation in addition to thrombosis. While platelets have been shown to promote neutrophil (PMN) adhesion to endothelium in various inflammatory models, it is unclear whether platelets enhance neutrophil transmigration across inflame...

  5. Ultraviolet irradiation of platelet concentrate abrogates lymphocyte activation without affecting platelet function in vitro

    SciTech Connect

    Kahn, R.A.; Duffy, B.F.; Rodey, G.G.

    1985-11-01

    We studied the effect of ultraviolet (UV) radiation on platelet concentrates. Samples irradiated at 310 mm for 30 minutes at a dose of 1782 J per m2 showed no loss of platelet function in vitro as determined by adenosine diphosphate, collagen, or ristocetin-induced aggregation. Lymphocytes isolated from irradiated units were unable to act as responders or stimulators in a mixed-lymphocyte reaction. These data suggest that UV radiation of platelet concentrates may result in a cell suspension that is unable to evoke an immunological response.

  6. Platelet-like Nanoparticles: Mimicking Shape, Flexibility, and Surface Biology of Platelets To Target Vascular Injuries

    PubMed Central

    2015-01-01

    Targeted delivery of therapeutic and imaging agents in the vascular compartment represents a significant hurdle in using nanomedicine for treating hemorrhage, thrombosis, and atherosclerosis. While several types of nanoparticles have been developed to meet this goal, their utility is limited by poor circulation, limited margination, and minimal targeting. Platelets have an innate ability to marginate to the vascular wall and specifically interact with vascular injury sites. These platelet functions are mediated by their shape, flexibility, and complex surface interactions. Inspired by this, we report the design and evaluation of nanoparticles that exhibit platelet-like functions including vascular injury site-directed margination, site-specific adhesion, and amplification of injury site-specific aggregation. Our nanoparticles mimic four key attributes of platelets, (i) discoidal morphology, (ii) mechanical flexibility, (iii) biophysically and biochemically mediated aggregation, and (iv) heteromultivalent presentation of ligands that mediate adhesion to both von Willebrand Factor and collagen, as well as specific clustering to activated platelets. Platelet-like nanoparticles (PLNs) exhibit enhanced surface-binding compared to spherical and rigid discoidal counterparts and site-selective adhesive and platelet-aggregatory properties under physiological flow conditions in vitro. In vivo studies in a mouse model demonstrated that PLNs accumulate at the wound site and induce ∼65% reduction in bleeding time, effectively mimicking and improving the hemostatic functions of natural platelets. We show that both the biochemical and biophysical design parameters of PLNs are essential in mimicking platelets and their hemostatic functions. PLNs offer a nanoscale technology that integrates platelet-mimetic biophysical and biochemical properties for potential applications in injectable synthetic hemostats and vascularly targeted payload delivery. PMID:25318048

  7. Chorein sensitivity of cytoskeletal organization and degranulation of platelets.

    PubMed

    Schmidt, Eva-Maria; Schmid, Evi; Münzer, Patrick; Hermann, Andreas; Eyrich, Ann-Kathrin; Russo, Antonella; Walker, Britta; Gu, Shuchen; vom Hagen, Jennifer Müller; Faggio, Caterina; Schaller, Martin; Föller, Michael; Schöls, Ludger; Gawaz, Meinrad; Borst, Oliver; Storch, Alexander; Stournaras, Christos; Lang, Florian

    2013-07-01

    Chorea-acanthocytosis (ChAc), a lethal disease caused by defective chorein, is characterized by neurodegeneration and erythrocyte acanthocytosis. The functional significance of chorein in other cell types remained ill-defined. The present study revealed chorein expression in blood platelets. As compared to platelets from healthy volunteers, platelets from patients with ChAc displayed a 47% increased globular/filamentous actin ratio, indicating actin depolymerization. Moreover, phosphoinositide-3-kinase subunit p85 phosphorylation, p21 protein-activated kinase (PAK1) phosphorylation, as well as vesicle-associated membrane protein 8 (VAMP8) expression were significantly reduced in platelets from patients with ChAc (by 17, 22, and 39%, respectively) and in megakaryocytic (MEG-01) cells following chorein silencing (by 16, 54, and 11%, respectively). Activation-induced platelet secretion from dense granules (ATP release) and α granules (P-selectin exposure) were significantly less (by 55% after stimulation with 1 μg/ml CRP and by 33% after stimulation with 5 μM TRAP, respectively) in ChAc platelets than in control platelets. Furthermore, platelet aggregation following stimulation with different platelet agonists was significantly impaired. These observations reveal a completely novel function of chorein, i.e., regulation of secretion and aggregation of blood platelets.

  8. The platelet Fc receptor, FcγRIIa.

    PubMed

    Qiao, Jianlin; Al-Tamimi, Mohammad; Baker, Ross I; Andrews, Robert K; Gardiner, Elizabeth E

    2015-11-01

    Human platelets express FcγRIIa, the low-affinity receptor for the constant fragment (Fc) of immunoglobulin (Ig) G that is also found on neutrophils, monocytes, and macrophages. Engagement of this receptor on platelets by immune complexes triggers intracellular signaling events that lead to platelet activation and aggregation. Importantly these events occur in vivo, particularly in response to pathological immune complexes, and engagement of this receptor on platelets has been causally linked to disease pathology. In this review, we will highlight some of the key features of this receptor in the context of the platelet surface, and examine the functions of platelet FcγRIIa in normal hemostasis and in response to injury and infection. This review will also highlight pathological consequences of engagement of this receptor in platelet-based autoimmune disorders. Finally, we present some new data investigating whether levels of the extracellular ligand-binding region of platelet glycoprotein VI which is rapidly shed upon engagement of platelet FcγRIIa by autoantibodies, can report on the presence of pathological anti-heparin/platelet factor 4 immune complexes and thus identify patients with pathological autoantibodies who are at the greatest risk of developing life-threatening thrombosis in the setting of heparin-induced thrombocytopenia.

  9. [The usefulness of platelet function evaluation in clinical practice].

    PubMed

    Elalamy, Ismail; Gkalea, Vasiliki; Gerotziafas, Grigorios; Ketatni, Hela; Hatmi, Mohamed

    2013-11-01

    Platelets play a pivotal role in the regulation of both thrombosis and haemostasis. Functional testing of platelet response has been exclusively used in the diagnosis and management of bleeding disorders. Recent advances of light transmission aggregometry and development of more useful devices have demonstrated the clinical utility to enlarge platelet function testing in patients with cardiovascular disease. The ex vivo measurement of residual platelet response seems, with some assays, predictive of adverse clinical events. Still a debate, it represents an emerging area of interest for both the clinician and the basic scientist. Heparin-induced thrombocytopenia diagnosis is also difficult and a functional assay is now available for an easier and rapid method to rule out such a life-threatening situation. This review article will describe the available methods of measuring platelet response and will discuss both the limitations and emerging data supporting the role of platelet function studies in clinical practice.

  10. Effect of BN 52021, a specific antagonist of platelet activating factor (PAF-acether), on calcium movements and phosphatidic acid production induced by PAF-acether in human platelets

    SciTech Connect

    Simon, M.F.; Chap, H.; Braquet, P.; Douste-Blazy, L.

    1987-02-15

    /sup 32/P-labelled human platelets loaded with quin 2 and pretreated with aspirin were stimulated with 1-100 nM platelet activating factor (PAF-acether or 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in a medium containing the ADP-scavenging system creatine phosphate/creatine phosphokinase. Under these conditions, PAF-acether evoked a characteristic fluorescence change allowing to quantify elevations in cytoplasmic free Ca/sup 2 +/ from internal stores (Ca/sup 2 +/ mobilization) or from external medium (Ca/sup 2 +/ influx), as well as an increased production of phosphatidic acid, reflecting phospholipase C activation. These effects, which can be attributed to PAF-acether only and not to released products such as ADP or thromboxane A2, were strongly inhibited in a dose-dependent manner by BN 52021, a specific antagonist of PAF-acether isolated from Ginkgo biloba. As the drug remained inactive against the same effects elicited by thrombin, it is concluded that BN 52021 does not interfere directly with the mechanism of transmembrane signalling involving inositol-phospholipids or (and) some putative receptor-operated channels, but rather acts on the binding of PAF-acether to its presumed membrane receptor.

  11. Hypervigilance to Rejecting Stimuli in Rejection Sensitive Individuals: Behavioral and Neurocognitive Evidence.

    PubMed

    Ehrlich, Katherine B; Gerson, Sarah A; Vanderwert, Ross E; Cannon, Erin N; Fox, Nathan A

    2015-10-01

    Individuals who are high in rejection sensitivity are vigilant toward social cues that signal rejection, and they exhibit attention biases towards information that confirms expectations of rejection. Little is known, however, about the neural correlates of rejection sensitivity. The present study examined whether rejection sensitivity is associated with individuals' neural responses to rejection-relevant information. Female participants, classified as high or average in rejection sensitivity, completed a modified dot-probe task in which a neutral face was paired with either another neutral face or a gaze-averted ("rejecting") face while EEG was collected and ERP components were computed. Behavioral results indicated that average rejection sensitive participants showed an attention bias away from rejecting faces, while high rejection sensitive participants were equally vigilant to neutral and rejecting faces. High rejection sensitivity was associated with ERP components signaling elevated attention and arousal to faces. These findings suggest that rejection sensitivity shapes behavioral and neurocognitive responses to faces.

  12. Platelet additive solution - electrolytes.

    PubMed

    Azuma, Hiroshi; Hirayama, Junichi; Akino, Mitsuaki; Ikeda, Hisami

    2011-06-01

    Recent attention to solutions that replace most or all plasma in platelet concentrates, while maintaining satisfactory platelet function, is motivated by the potential of plasma reduction or depletion to mitigate various transfusion-related adverse events. This report considers the electrolytic composition of previously described platelet additive solutions, in order to draw general conclusions about what is required for platelet function and longevity. The optimal concentrations of Na(+) and Cl(-) are 69-115 mM. The presence of both K(+) and Mg(2+) in platelet suspension at nearly physiological concentrations (3-5mM and 1.5-3mM, respectively) is indispensable for good preservation capacity because both electrolytes are required to prevent platelet activation. In contrast to K(+) and Mg(2+), Ca(2+) may not be important because no free Ca(2+) is available in M-sol, which showed excellent platelet preservation capacity at less than 5% plasma concentration. The importance of bicarbonate (approximately 40 mM) can be recognized when the platelets are suspended in additive solution under less than 5% residual plasma concentration.

  13. Platelet Function Tests.

    PubMed

    Lordkipanidzé, Marie

    2016-04-01

    Traditionally developed for diagnosis of bleeding disorders, platelet function assays have become increasingly used in basic research on platelet physiology, in phenotype-genotype associations in bleeding disorders, in drug development as surrogate endpoints of efficacy of new antiplatelet therapy, and to an extent, in the monitoring of antiplatelet therapy in clinical practice to predict thrombotic and bleeding risk. A multiplicity of platelet function assays is available to measure the level of platelet activity in various settings. These include assays that are restricted to a specialized laboratory as well as point-of-care instruments meant to investigate platelet function at patient bedside. Unlike tests that determine a defined quantity or measurement of a clinical biomarker (e.g., cholesterol or blood pressure), platelet function testing assesses the dynamics of living cells, which immediately presents a series of unique problems to any laboratory or clinic. This article presents currently used platelet function assays and discusses important variables to take into account when performing these assays, including preanalytical issues and difficulties in interpreting platelet function test results.

  14. Irisin reverses platelet derived growth factor-BB-induced vascular smooth muscle cells phenotype modulation through STAT3 signaling pathway.

    PubMed

    Song, Haibo; Xu, Jia; Lv, Nan; Zhang, Yuzhu; Wu, Fei; Li, Huanjie; Shao, Lei; Mu, Qian; Wang, Fang; Tang, Dongqi; Fang, Xu

    2016-10-14

    Vascular smooth muscle cells (VSMCs) phenotype modulation toward a synthetic phenotype is the main cause of cardiovascular disease. As a newly discovered myokine, Irisin is thought to be a promising candidate for the treatment of metabolic disturbances, as well as cardiovascular disease. However, no evidence has been shown for the direct effect of Irisin on VSMCs phenotype modulation and its underling mechanisms. The aim of this study was to explore the effect of Irisin on VSMCs phenotype modulation and the mechanisms involved. In the present study, it was found that Irisin restored the PDGF-BB-induced VSMCs phenotype modulation which exhibited down-regulation of smooth muscle cells (SMC) expression and up-regulation of matrix synthesis related marker expression, as well as proliferative phenotype. Moreover, our research demonstrated that Irisin further activated STAT3 signaling pathways. Finally, by applying an STAT3 inhibitor, WP1066, we revealed the roles of STAT3 in the PDGF-BB-induced VSMCs phenotype modulation when they were treated with Irisin. Taken together, these results demonstrated that Irisin may play a crucial role in regulating VSMCs phenotype modulation via the STAT3 signaling pathway.

  15. DNA Vaccine Encoding HPV16 Oncogenes E6 and E7 Induces Potent Cell-mediated and Humoral Immunity Which Protects in Tumor Challenge and Drives E7-expressing Skin Graft Rejection

    PubMed Central

    Chandra, Janin; Dutton, Julie L.; Li, Bo; Woo, Wai-Ping; Xu, Yan; Tolley, Lynn K.; Yong, Michelle; Wells, James W.; R. Leggatt, Graham; Finlayson, Neil

    2017-01-01

    We have previously shown that a novel DNA vaccine technology of codon optimization and the addition of ubiquitin sequences enhanced immunogenicity of a herpes simplex virus 2 polynucleotide vaccine in mice, and induced cell-mediated immunity when administered in humans at relatively low doses of naked DNA. We here show that a new polynucleotide vaccine using the same technology and encoding a fusion protein of the E6 and E7 oncogenes of high-risk human papillomavirus type 16 (HPV16) is immunogenic in mice. This vaccine induces long-lasting humoral and cell-mediated immunity and protects mice from establishment of HPV16-E7-expressing tumors. In addition, it suppresses growth of readily established tumors and shows enhanced efficacy when combined with immune checkpoint blockade targeted at PD-L1. This vaccine also facilitates rejection of HPV16-E7-expressing skin grafts that demonstrate epidermal hyperplasia with characteristics of cervical and vulvar intraepithelial neoplasia. Clinical studies evaluating the efficacy of this vaccine in patients with HPV16+ premalignancies are planned. PMID:28166181

  16. Function of platelet 47K protein phosphorylation

    SciTech Connect

    Imaoka, T.

    1987-05-01

    To provide insight into the biochemical pathway of platelet activation, they purified both unphosphorylated and phosphorylated P47 to homogeneity from human platelets. This study represents the first demonstration of a change of physiological action of P47 in response to phosphorylation in platelet activation. SVI labelled unphosphorylated P47 had an ability to bind with platelet membrane fraction in the presence of phosphatidylserine. Effect of diacylglycerol was inhibitory in this PS dependent P47 binding with membrane. Unphosphorylated P47 had an inhibitory activity in platelet actin polymerization. Molar ratio to inhibit actin polymerization was 1:8 (P47:actin). These activities were Ca independent. Purified TSP-labelled P47 lost the binding ability with membrane, also the inhibitory activity in actin polymerization. Therefore, they propose the hypothesis that unphosphorylated P47 may loosely bind with the inside of plasma membrane of platelet and inhibit actin polymerization as a modulator, when stimulated, protein Kinase C rapidly phosphorylate P47 and induce the activation of cytoskeletal network and subsequently release reaction.

  17. Isolation and characterization of two disintegrins inhibiting ADP-induced human platelet aggregation from the venom of Crotalus scutulatus scutulatus (Mohave Rattlesnake)

    SciTech Connect

    Sanchez, Elda E.; Galan, Jacob A.; Russell, William K.; Soto, Julio G.; Russell, David H.; Perez, John C. . E-mail: kfjcp00@tamuk.edu

    2006-04-01

    Disintegrins and disintegrin-like proteins are molecules found in the venom of four snake families (Atractaspididae, Elapidae, Viperidae, and Colubridae). The disintegrins are nonenzymatic proteins that inhibit cell-cell interactions, cell-matrix interactions, and signal transduction, and may have potential in the treatment of strokes, heart attacks, cancers, and osteoporosis. Prior to 1983, the venom of Crotalus scutulatus scutulatus (Mohave Rattlesnake) was known to be only neurotoxic; however, now there is evidence that these snakes can contain venom with: (1) neurotoxins; (2) hemorrhagins; and (3) both neurotoxins and hemorrhagins. In this study, two disintegrins, mojastin 1 and mojastin 2, from the venom of a Mohave rattlesnake collected in central Arizona (Pinal County), were isolated and characterized. The disintegrins in these venoms were identified by mass-analyzed laser desorption ionization/time-of-flight/time-of-flight (MALDI/TOF/TOF) mass spectrometry as having masses of 7.436 and 7.636 kDa. Their amino acid sequences are similar to crotratroxin, a disintegrin isolated from the venom of the western diamondback rattlesnake (C. atrox). The amino acid sequence of mojastin 1 was identical to the amino acid sequence of a disintegrin isolated from the venom of the Timber rattlesnake (C. horridus). The disintegrins from the Mohave rattlesnake venom were able to inhibit ADP-induced platelet aggregation in whole human blood both having IC{sub 5}s of 13.8 nM, but were not effective in inhibiting the binding of human urinary bladder carcinoma cells (T24) to fibronectin.

  18. Topical application of a platelet activating factor receptor agonist suppresses phorbol ester-induced acute and chronic inflammation and has cancer chemopreventive activity in mouse skin.

    PubMed

    Sahu, Ravi P; Rezania, Samin; Ocana, Jesus A; DaSilva-Arnold, Sonia C; Bradish, Joshua R; Richey, Justin D; Warren, Simon J; Rashid, Badri; Travers, Jeffrey B; Konger, Raymond L

    2014-01-01

    Platelet activating factor (PAF) has long been associated with acute edema and inflammatory responses. PAF acts by binding to a specific G-protein coupled receptor (PAF-R, Ptafr). However, the role of chronic PAF-R activation on sustained inflammatory responses has been largely ignored. We recently demonstrated that mice lacking the PAF-R (Ptafr-/- mice) exhibit increased cutaneous tumorigenesis in response to a two-stage chemical carcinogenesis protocol. Ptafr-/- mice also exhibited increased chronic inflammation in response to phorbol ester application. In this present study, we demonstrate that topical application of the non-hydrolysable PAF mimetic (carbamoyl-PAF (CPAF)), exerts a potent, dose-dependent, and short-lived edema response in WT mice, but not Ptafr -/- mice or mice deficient in c-Kit (c-KitW-sh/W-sh mice). Using an ear inflammation model, co-administration of topical CPAF treatment resulted in a paradoxical decrease in both acute ear thickness changes associated with a single PMA application, as well as the sustained inflammation associated with chronic repetitive PMA applications. Moreover, mice treated topically with CPAF also exhibited a significant reduction in chemical carcinogenesis. The ability of CPAF to suppress acute and chronic inflammatory changes in response to PMA application(s) was PAF-R dependent, as CPAF had no effect on basal or PMA-induced inflammation in Ptafr-/- mice. Moreover, c-Kit appears to be necessary for the anti-inflammatory effects of CPAF, as CPAF had no observable effect in c-KitW-sh/W-sh mice. These data provide additional evidence that PAF-R activation exerts complex immunomodulatory effects in a model of chronic inflammation that is relevant to neoplastic development.

  19. Anti-platelet factor 4/heparin antibodies from patients with heparin-induced thrombocytopenia provoke direct activation of microvascular endothelial cells.

    PubMed

    Blank, Miri; Shoenfeld, Yehuda; Tavor, Sigal; Praprotnik, Sonja; Boffa, Marie Claire; Weksler, Babette; Walenga, M Jeanine; Amiral, Jean; Eldor, Amiram

    2002-02-01

    Heparin-induced thrombocytopenia (HIT) is a serious complication that occurs in approximately 1-5% of patients treated with heparin and may be associated with severe thrombotic events. HIT is mediated by antibodies directed mostly to epitope(s) formed by complexes between heparin or other anionic mucopolysaccharides and platelet factor 4 (PF4). Anti-PF4/heparin IgG antibodies from six patients with HIT were affinity purified and assessed for interaction with human microvascular and macrovascular endothelial cells (EC). The antibodies directly activated primary cultures of human bone marrow microvascular EC (HBMEC) and SV40 immortalized HBMEC (TrHBMEC) only in the presence of PF4, but did not activate macrovascular human umbilical vein EC (HUVEC) under the same conditions. These antibodies were found to bind to TrHBMEC through the F(ab)(2) portion of the anti-PF4/heparin IgG. TrHBMEC activation was characterized by an augmented release of IL-6, von Willebrand factor, soluble thrombomodulin, and by an elevated expression of the adhesion molecules P-selectin, E-selectin and vascular cellular endothelial molecule-I to different degrees. Enhanced monocyte adhesion to PF4/heparin antibody-treated TrHBMEC (33-72% adhesion) was also observed. None of these effects occurred with unstimulated HUVEC. However, pre-treatment of HUVEC with tumor necrosis factor-alpha resulted in the same changes observed with microvascular EC exposed to the HIT antibodies. Our findings indicate that anti-PF4/heparin antibodies directly activate microvascular EC while interaction with macrovascular EC requires pre-activation. These results may explain some of the specific clinical manifestations in HIT.

  20. The sticky platelet syndrome.

    PubMed

    Moncada, Benjamín; Ruíz-Arguelles, Guillermo J; Castillo-Martínez, Claudio

    2013-07-01

    The sticky platelets syndrome (SPS) is a procoagulant condition based on either arterial, venous, or capillary thrombi caused by hyperesponsive and hyperaggregable platelets. This is a frequent disease, which often remains clinically inapparent, until stressful events or combination with other factors increase the risk of developing SPS. The condition is due to a congenital platelet defect with autosomal dominant characteristics, leading to the increased platelet aggregability when they are challenged with epinephrine and adenosine diphosphate. Nowadays classification of this disorder is based on platelet reactivity to both ADP and epinephrine (SPS type 1), epinephrine alone (SPS type 2), and ADP alone (SPS type 3). The diagnoses of the syndrome depend on the functional aggregometer assay. This condition should be taken into account whenever a patient with thrombophilia is considered.

  1. Procoagulant activity induced by transcatheter closure of atrial septal defects is associated with exposure of phosphatidylserine on microparticles, platelets and red blood cells.

    PubMed

    Ding, Wenbo; Kou, Junjie; Meng, Huan; Kou, Yan; He, Zhangxiu; Cao, Muhua; Wang, Lixiu; Bi, Yayan; Thatte, Hemant S; Shi, Jialan

    2015-08-01

    The mechanism of hypercoagulable state following transcatheter closure of atrial septal defects (ASDs) remains unclear. We evaluated the exposure of phosphatidylserine (PS) on released microparticles (MPs) and also the cells of their origin from peripheral blood, and the associated increase in procoagulant activity (PCA) following transcatheter ASD closure. We demonstrate that PS(+) MP levels were elevated immediately after device implantation (P <0.002), peaked at 24hour (P <0.002), and persisted at high levels for 1-week post procedure (P <0.002). Flow cytometry analysis indicated that PS(+) MPs were mainly derived from platelets, endothelial cells, and the red blood cells (RBCs). Concomittantly, PS(+) platelet and RBC count also increased after transcatheter closure of ASDs, while PS(+) leukocytes levels remained the same. Compared to the baseline, coagulation time of PS(+) MPs, platelets, and RBCs at 24hours post procedure decreased by about 18.7% (P <0.004), 21.5% (P <0.001), and 26.8% (P <0.001), respectively. Intrinsic factor Xa and prothrombinase were produced abundantly by platelets, RBCs, and MPs leading to materialization of fibrin by 24hours. Additionally, Xase complex formation and thrombin generation was inhibited by about 74% by the addition of lactadherin to the assays. Our results thus demonstrate that PS exposure on MPs, platelets, and RBCs play an important role in hypercoagulability following transcatheter ASD closure.

  2. Antioxidant and antiaggregatory effects of an extract from Conyza canadensis on blood platelets in vitro.

    PubMed

    Olas, Beata; Saluk-Juszczak, Joanna; Pawlaczyk, Izabela; Nowak, Pawel; Kolodziejczyk, Joanna; Gancarz, Roman; Wachowicz, Barbara

    2006-09-01

    The antioxidative activity of the polysaccharide extract from Conyza canadensis in blood platelets treated with peroxynitrite (ONOO-) was studied. Peroxynitrite as a strong biological oxidant has toxic effects on blood platelets and induces the oxidation of thiols, carbonylation and nitration of platelet proteins and lipid peroxidation. Therefore, the aim of our study was to assess if the natural extract from herbal plant, Conyza Canadensis, may protect platelet proteins against nitrative and oxidative damage induced by ONOO-. In our study we measured oxidative damage of platelet proteins induced by peroxynitrite and protectory effects of this extract by estimation of the level of carbonyl groups and nitrotyrosine (a marker of platelet protein nitration). We also used cytochrome c reduction method to test the ability of this extract to change O2-* generation in platelets. Moreover, we determined the effects of the extract on blood platelet aggregation induced by ADP. We observed that the extract from Conyza canadensis distinctly reduced oxidation and nitration of proteins in blood platelets treated with ONOO-(0.1mM) and O2-* production in these cells. The extract from Conyza canadensis also inhibited platelet aggregation. The ability of the extract to decrease O2-* generation in blood platelets supports the importance of free radicals in platelet functions, including aggregation process. The present study suggests that the natural polysaccharide extract from Conyza canadensis has antiaggregatory and antioxidative activities, and therefore may be beneficial in the prevention of peroxynitrite-related diseases, such as cardiovascular or inflammatory diseases.

  3. Platelet Activation and Biofilm Formation by Aerococcus urinae, an Endocarditis-Causing Pathogen▿

    PubMed Central

    Shannon, Oonagh; Mörgelin, Matthias; Rasmussen, Magnus

    2010-01-01

    The Gram-positive bacterium Aerococcus urinae can cause infectious endocarditis (IE) in older persons. Biofilm formation and platelet aggregation are believed to contribute to bacterial virulence in IE. Five A. urinae isolates from human blood were shown to form biofilms in vitro, and biofilm formation was enhanced by the presence of human plasma. Four of the A. urinae isolates caused platelet aggregation in platelet-rich plasma from healthy donors. The Au3 isolate, which induced platelet aggregation in all donors, also activated platelets, as determined by flow cytometry. Platelet aggregation was dependent on bacterial protein structures and on platelet activation since it was sensitive to both trypsin and prostaglandin E1. Plasma proteins at the bacterial surface were needed for platelet aggregation; and roles of the complement system, fibrinogen, and immunoglobulin G were demonstrated. Complement-depleted serum was unable to support platelet aggregation by Au3 and complement blockade using compstatin-inhibited platelet activation. Platelet activation by Au3 was inhibited by blocking of the platelet fibrinogen receptor, and this isolate was also shown to bind to radiolabeled fibrinogen. Removal of IgG from platelet-rich plasma by a specific protease inhibited the platelet aggregation induced by A. urinae, and blockade of the platelet FcRγIIa hindered platelet activation induced by Au3. Convalescent-phase serum from a patient with A. urinae IE transferred the ability of the bacterium to aggregate platelets in an otherwise nonresponsive donor. Our results show that A. urinae exhibits virulence strategies of importance for IE. PMID:20696834

  4. The Platelet Actin Cytoskeleton Associates with SNAREs and Participates in α-Granule Secretion†

    PubMed Central

    Woronowicz, Kamil; Dilks, James R.; Rozenvayn, Nataliya; Dowal, Louisa; Blair, Price S.; Peters, Christian G.; Woronowicz, Lucyna; Flaumenhaft, Robert

    2010-01-01

    Following platelet activation, platelets undergo a dramatic shape change mediated by the actin cytoskeleton and accompanied by secretion of granule contents. While the actin cytoskeleton is thought to influence platelet granule secretion, the mechanism for this putative regulation is not known. We found that disruption of the actin cytoskeleton by latrunculin A inhibited α-granule secretion induced by several different platelet agonists without significantly affecting activation-induced platelet aggregation. In a cell-free secretory system, platelet cytosol was required for α-granule secretion. Inhibition of actin polymerization prevented α-granule secretion in this system and purified platelet actin could substitute for platelet cytosol to support α–granule secretion. To determine whether SNAREs physically associate with the actin cytoskeleton, we isolated the Triton X-100 insoluble actin cytoskeleton from platelets. VAMP-8 and syntaxin-2 associated only with actin cytoskeletons of activated platelets. Syntaxin-4 and SNAP-23 associated with cytoskeletons isolated from either resting or activated platelets. When syntaxin-4 and SNAP-23 were tested for actin binding in a purified protein system, only syntaxin-4 associated directly with polymerized platelet actin. These data show that the platelet cytoskeleton interacts with select SNAREs and that actin polymerization facilitates α-granule release. PMID:20429610

  5. Hypervigilance to Rejecting Stimuli in Rejection Sensitive Individuals: Behavioral and Neurocognitive Evidence

    PubMed Central

    Ehrlich, Katherine B.; Gerson, Sarah A.; Vanderwert, Ross E.; Cannon, Erin N.; Fox, Nathan A.

    2015-01-01

    Individuals who are high in rejection sensitivity are vigilant toward social cues that signal rejection, and they exhibit attention biases towards information that confirms expectations of rejection. Little is known, however, about the neural correlates of rejection sensitivity. The present study examined whether rejection sensitivity is associated with individuals’ neural responses to rejection-relevant information. Female participants, classified as high or average in rejection sensitivity, completed a modified dot-probe task in which a neutral face was paired with either another neutral face or a gaze-averted (“rejecting”) face while EEG was collected and ERP components were computed. Behavioral results indicated that average rejection sensitive participants showed an attention bias away from rejecting faces, while high rejection sensitive participants were equally vigilant to neutral and rejecting faces. High rejection sensitivity was associated with ERP components signaling elevated attention and arousal to faces. These findings suggest that rejection sensitivity shapes behavioral and neurocognitive responses to faces. PMID:26213434

  6. Pathogen-Reduced, Platelet Additive Solution, Extended Stored Platelets (PREPS)

    DTIC Science & Technology

    2015-10-01

    trauma patients. References: 1. Slichter SJ, Harker LA. Preparation and storage of platelet concentrates . II. Storage variables influencing ...Storage variables influencing platelet viability and function. Br J Haematol 1976;34(3):403-419. 2. Becker GA, Tuccelli M, Kunicki T, et al. Studies of...platelet additive solution (PAS) to extend the life of stored platelets. Our project also aims to determine how long acceptable platelet viability can be

  7. Ligustrazine attenuates oxidative stress-induced activation of hepatic stellate cells by interrupting platelet-derived growth factor-β receptor-mediated ERK and p38 pathways

    SciTech Connect

    Zhang, Feng; Ni, Chunyan; Kong, Desong; Zhang, Xiaoping; Zhu, Xiaojing; Chen, Li; Lu, Yin; Zheng, Shizhong

    2012-11-15

    Hepatic fibrosis represents a frequent event following chronic insult to trigger wound healing reactions with accumulation of extracellular matrix (ECM) in the liver. Activation of hepatic stellate cells (HSCs) is the pivotal event during liver fibrogenesis. Compelling evidence indicates that oxidative stress is concomitant with liver fibrosis irrespective of the underlying etiology. Natural antioxidant ligustrazine exhibits potent antifibrotic activities, but the mechanisms are poorly understood. Our studies were to investigate the ligustrazine effects on HSC activation stimulated by hydrogen peroxide (H{sub 2}O{sub 2}), an in vitro model mimicking the oxidative stress in liver fibrogenesis, and to elucidate the possible mechanisms. Our results demonstrated that H{sub 2}O{sub 2} at 5 μM significantly stimulated HSC proliferation and expression of marker genes of HSC activation; whereas ligustrazine dose-dependently suppressed proliferation and induced apoptosis in H{sub 2}O{sub 2}-activated HSCs, and attenuated expression of fibrotic marker genes. Mechanistic investigations revealed that ligustrazine reduced platelet-derived growth factor-β receptor (PDGF-βR) expression and blocked the phosphorylation of extracellular regulated protein kinase (ERK) and p38 kinase, two downstream effectors of PDGF-βR. Further molecular evidence suggested that ligustrazine interruption of ERK and p38 pathways was dependent on the blockade of PDGF-βR and might be involved in ligustrazine reduction of fibrotic marker gene expression under H{sub 2}O{sub 2} stimulation. Furthermore, ligustrazine modulated some proteins critical for HSC activation and ECM homeostasis in H{sub 2}O{sub 2}-stimulated HSCs. These data collectively indicated that ligustrazine could attenuate HSC activation caused by oxidative stress, providing novel insights into ligustrazine as a therapeutic option for hepatic fibrosis. Highlights: ► Ligustrazine inhibits oxidative stress-induced HSC activation.

  8. Platelet Adhesion under Flow

    PubMed Central

    Ruggeri, Zaverio M.

    2011-01-01

    Platelet adhesive mechanisms play a well-defined role in hemostasis and thrombosis, but evidence continues to emerge for a relevant contribution to other pathophysiological processes including inflammation, immune-mediated responses to microbial and viral pathogens, and cancer metastasis. Hemostasis and thrombosis are related aspects of the response to vascular injury, but the former protects from bleeding after trauma while the latter is a disease mechanism. In either situation, adhesive interactions mediated by specific membrane receptors support the initial attachment of single platelets to cellular and extracellular matrix constituents of the vessel wall and tissues. In the subsequent steps of thrombus growth and stabilization, adhesive interactions mediate platelet to platelet cohesion (aggregation) and anchoring to the fibrin clot. A key functional aspect of platelets is their ability to circulate in a quiescent state surveying the integrity of the inner vascular surface, coupled to a prompt reaction wherever alterations are detected. In many respects, therefore, platelet adhesion to vascular wall structures, to one another or to other blood cells are facets of the same fundamental biological process. The adaptation of platelet adhesive functions to the effects of blood flow is the main focus of this review. PMID:19191170

  9. Platelets in Critical Illness.

    PubMed

    Levi, Marcel

    2016-04-01

    In patients with critical illness, thrombocytopenia is a frequent laboratory abnormality. However frequent this may occur, a low platelet count is not an epiphenomenon, but a marker with further significance. It is always important to assess the proper cause for thrombocytopenia in critically ill patients because different underlying disorders may precipitate different diagnostic and therapeutic management strategies. Platelets are part of the first-line defense of the body against bleeding; hence, thrombocytopenia may increase the risk of hemorrhage. In case of systemic inflammatory syndromes, such as the response to sepsis, disseminated intravascular platelet activation may occur. This will contribute to microvascular failure and thereby play a role in the development of organ dysfunction. Platelets are circulating blood cells that will normally not interact with the intact vessel wall but that may swiftly respond to endothelial disruption (which is often part of the pathogenesis of critical illness) by adhering to subendothelial structures, followed by interaction with each other, thereby forming a platelet aggregate. The activated platelet (phospholipid) membrane may form a suitable surface on which further coagulation activation may occur. A low platelet count is a strong and independent predictor of an adverse outcome in critically ill patients, thereby facilitating a simple and practically risk assessment in these patients and potentially guiding the use of complex or expensive treatment strategies.

  10. Resistance of platelet proteins to effects of ionizing radiation

    SciTech Connect

    Prodouz, K.N.; Habraken, J.W.; Moroff, G. )

    1990-12-01

    Gamma irradiation of blood components prevents lymphocyte-induced graft-versus-host disease after transfusion in immunocompromised individuals. In this report we demonstrate the resistance of blood platelet proteins to gamma radiation-induced protein cleavage and aggregate formation when platelet concentrates were treated with a dose of 5000 rad. Results of one- and two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total platelet protein and cytoskeletal protein preparations indicate that platelet proteins are neither cleaved nor cross-linked under these conditions of irradiation. These results support those of a previous study that documented the lack of any adverse effect of 5000 rad gamma radiation on in vitro platelet properties.

  11. Echicetin coated polystyrene beads: a novel tool to investigate GPIb-specific platelet activation and aggregation.

    PubMed

    Navdaev, Alexey; Subramanian, Hariharan; Petunin, Alexey; Clemetson, Kenneth J; Gambaryan, Stepan; Walter, Ulrich

    2014-01-01

    von Willebrand factor/ristocetin (vWF/R) induces GPIb-dependent platelet agglutination and activation of αIIbβ3 integrin, which also binds vWF. These conditions make it difficult to investigate GPIb-specific signaling pathways in washed platelets. Here, we investigated the specific mechanisms of GPIb signaling using echicetin-coated polystyrene beads, which specifically activate GPIb. We compared platelet activation induced by echicetin beads to vWF/R. Human platelets were stimulated with polystyrene beads coated with increasing amounts of echicetin and platelet activation by echicetin beads was then investigated to reveal GPIb specific signaling. Echicetin beads induced αIIbβ3-dependent aggregation of washed platelets, while under the same conditions vWF/R treatment led only to αIIbβ3-independent platelet agglutination. The average distance between the echicetin molecules on the polystyrene beads must be less than 7 nm for full platelet activation, while the total amount of echicetin used for activation is not critical. Echicetin beads induced strong phosphorylation of several proteins including p38, ERK and PKB. Synergistic signaling via P2Y12 and thromboxane receptor through secreted ADP and TxA2, respectively, were important for echicetin bead triggered platelet activation. Activation of PKG by the NO/sGC/cGMP pathway inhibited echicetin bead-induced platelet aggregation. Echicetin-coated beads are powerful and reliable tools to study signaling in human platelets activated solely via GPIb and GPIb-triggered pathways.

  12. Common variants in the human platelet PAR4 thrombin receptor alter platelet function and differ by race

    PubMed Central

    Edelstein, Leonard C.; Simon, Lukas M.; Lindsay, Cory R.; Kong, Xianguo; Teruel-Montoya, Raúl; Tourdot, Benjamin E.; Chen, Edward S.; Ma, Lin; Coughlin, Shaun; Nieman, Marvin; Holinstat, Michael; Shaw, Chad A.

    2014-01-01

    Human platelets express 2 thrombin receptors: protease-activated receptor (PAR)-1 and PAR4. Recently, we reported 3.7-fold increased PAR4-mediated aggregation kinetics in platelets from black subjects compared with white subjects. We now show that platelets from blacks (n = 70) express 14% more PAR4 protein than those from whites (n = 84), but this difference is not associated with platelet PAR4 function. Quantitative trait locus analysis identified 3 common single nucleotide polymorphisms in the PAR4 gene (F2RL3) associated with PAR4-induced platelet aggregation. Among these single nucleotide polymorphisms, rs773902 determines whether residue 120 in transmembrane domain 2 is an alanine (Ala) or threonine (Thr). Compared with the Ala120 variant, Thr120 was more common in black subjects than in white subjects (63% vs 19%), was associated with higher PAR4-induced human platelet aggregation and Ca2+ flux, and generated greater inositol 1,4,5-triphosphate in transfected cells. A second, less frequent F2RL3 variant, Phe296Val, was only observed in blacks and abolished the enhanced PAR4-induced platelet aggregation and 1,4,5-triphosphate generation associated with PAR4-Thr120. PAR4 genotype did not affect vorapaxar inhibition of platelet PAR1 function, but a strong pharmacogenetic effect was observed with the PAR4-specific antagonist YD-3 [1-benzyl-3(ethoxycarbonylphenyl)-indazole]. These findings may have an important pharmacogenetic effect on the development of new PAR antagonists. PMID:25293779

  13. Cordycepin-Enriched WIB801C from Cordyceps militaris Inhibits Collagen-Induced [Ca(2+)]i Mobilization via cAMP-Dependent Phosphorylation of Inositol 1, 4, 5-Trisphosphate Receptor in Human Platelets.

    PubMed

    Lee, Dong-Ha; Kim, Hyun-Hong; Cho, Hyun-Jeong; Yu, Young-Bin; Kang, Hyo-Chan; Kim, Jong-Lae; Lee, Jong-Jin; Park, Hwa-Jin

    2014-05-01

    In this study, we prepared cordycepin-enriched (CE)-WIB801C, a n-butanol extract of Cordyceps militaris-hypha, and investigated the effect of CE-WIB801C on collagen-induced human platelet aggregation. CE-WIB801C dose-dependently inhibited collagen-induced platelet aggregation, and its IC50 value was 175 μg/ml. CE-WIB801C increased cAMP level more than cGMP level, but inhibited collagen-elevated [Ca(2+)]i mobilization and thromboxane A2 (TXA2) production. cAMP-dependent protein kinase (A-kinase) inhibitor Rp-8-Br-cAMPS increased the CE-WIB801C-downregulated [Ca(2+)]i level in a dose dependent manner, and strongly inhibited CE-WIB801C-induced inositol 1, 4, 5-trisphosphate receptor (IP3R) phosphorylation. These results suggest that the inhibition of [Ca(2+)]i mobilization by CE-WIB801C is resulted from the cAMP/A-kinase-dependent phosphorylation of IP3R. CE-WIB801C suppressed TXA2 production, but did not inhibit the activities of cyclooxygenase-1 (COX-1) and TXA2 synthase (TXAS). These results suggest that the inhibition of TXA2 production by WIB801C is not resulted from the direct inhibition of COX-1 and TXAS. In this study, we demonstrate that CE-WIB801C with cAMP-dependent Ca(2+)-antagonistic antiplatelet effects may have preventive or therapeutic potential for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease.

  14. Cordycepin-Enriched WIB801C from Cordyceps militaris Inhibits Collagen-Induced [Ca2+]i Mobilization via cAMP-Dependent Phosphorylation of Inositol 1, 4, 5-Trisphosphate Receptor in Human Platelets

    PubMed Central

    Lee, Dong-Ha; Kim, Hyun-Hong; Cho, Hyun-Jeong; Yu, Young-Bin; Kang, Hyo-Chan; Kim, Jong-Lae; Lee, Jong-Jin; Park, Hwa-Jin

    2014-01-01

    In this study, we prepared cordycepin-enriched (CE)-WIB801C, a n-butanol extract of Cordyceps militaris-hypha, and investigated the effect of CE-WIB801C on collagen-induced human platelet aggregation. CE-WIB801C dose-dependently inhibited collagen-induced platelet aggregation, and its IC50 value was 175 μg/ml. CE-WIB801C increased cAMP level more than cGMP level, but inhibited collagen-elevated [Ca2+]i mobilization and thromboxane A2 (TXA2) production. cAMP-dependent protein kinase (A-kinase) inhibitor Rp-8-Br-cAMPS increased the CE-WIB801C-downregulated [Ca2+]i level in a dose dependent manner, and strongly inhibited CE-WIB801C-induced inositol 1, 4, 5-trisphosphate receptor (IP3R) phosphorylation. These results suggest that the inhibition of [Ca2+]i mobilization by CE-WIB801C is resulted from the cAMP/A-kinase-dependent phosphorylation of IP3R. CE-WIB801C suppressed TXA2 production, but did not inhibit the activities of cyclooxygenase-1 (COX-1) and TXA2 synthase (TXAS). These results suggest that the inhibition of TXA2 production by WIB801C is not resulted from the direct inhibition of COX-1 and TXAS. In this study, we demonstrate that CE-WIB801C with cAMP-dependent Ca2+-antagonistic antiplatelet effects may have preventive or therapeutic potential for platelet aggregation-mediated diseases, such as thrombosis, myocardial infarction, atherosclerosis, and ischemic cerebrovascular disease. PMID:25009703

  15. Augmented orbiter heat rejection study

    NASA Technical Reports Server (NTRS)

    Hixon, C. W.

    1981-01-01

    Spacecraft radiator concepts are presented that relieve attitude restrictions required by the shuttle orbiter space radiator for baseline and extended capability STS missions. Cost effective heat rejection kits are considered which add additional capability in the form of attached spacelab radiators or a deployable radiator module.

  16. Thrombin Increases Expression of Fibronectin Antigen on the Platelet Surface

    NASA Astrophysics Data System (ADS)

    Ginsberg, Mark H.; Painter, Richard G.; Forsyth, Jane; Birdwell, Charles; Plow, Edward F.

    1980-02-01

    Fibronectins (fn) are adhesive glycoproteins which bind to collagen and to fibrin and appear to be important in cellular adhesion to other cells or surfaces. Fn-related antigen is present in human platelets, suggesting a possible role for fn in the adhesive properties of platelets. We have studied the localization of fn in resting and thrombin-stimulated platelets by immunofluorescence and quantitative binding of radiolabeled antibody. In resting fixed platelets, variable light surface staining for fn was observed. When these cells were made permeable to antibody with detergent, staining for fn was markedly enhanced and was present in a punctate distribution, suggesting intracellular localization. Stimulation with thrombin, which is associated with increased platelet adhesiveness, resulted in increased staining for fn antigen on intact platelets. These stimulated cells did not leak 51Cr nor did they stain for F-actin, thus documenting that the increased fn staining was not due to loss of plasma membrane integrity. The thrombin-induced increase in accessible platelet fn antigen was confirmed by quantitative antibody binding studies in which thrombin-stimulated platelets specifically bound 15 times as much radiolabeled F(ab')2 anti-fn as did resting cells. Thus, thrombin stimulation results in increased expression of fn antigen on the platelet surface. Here it may participate in interactions with fibrin, connective tissue, or other cells.

  17. Modifications of blood platelet proteins of patients with schizophrenia.

    PubMed

    Dietrich-Muszalska, Anna; Olas, Beata

    2009-03-01

    Oxidative damage to lipids in plasma, blood platelets and neurons in patients with schizophrenia was described. The aim of our present study was to evaluate oxidative/nitrative modifications of blood platelets proteins by measurement the level of biomarkers of oxidative stress such as carbonyl groups, thiol groups and 3-nitrotyrosine in proteins in patients with schizophrenia and compare with a control group. Levels of carbonyl groups and 3-nitrotyrosine residues in platelet proteins were measured by ELISA and competition ELISA, respectively. The method with 5,5'-dithio-bis(2-nitro-benzoic acid) has been used to analyse thiol groups in platelet proteins. We demonstrated for the first time in platelet proteins from patients with schizophrenia a statistically significant increase of the level of biomarkers of oxidative/nitrative stress such as carbonyl groups or 3-nitrotyrosine; in schizophrenic patients the amount of thiol groups in platelet proteins was lower than in platelets from healthy subjects. Our results strongly indicate that in patients with schizophrenia reactive oxygen species and reactive nitrogen species induce not only peroxidation of lipids, but also may stimulate oxidative/nitrative modifications of platelet proteins. The consequence of these modifications may be the alteration of platelet protein structure and function.

  18. Abnormal T-cell reactivity against paternal antigens in spontaneous abortion: adoptive transfer of pregnancy-induced CD4+CD25+ T regulatory cells prevents fetal rejection in a murine abortion model.

    PubMed

    Zenclussen, Ana Claudia; Gerlof, Katrin; Zenclussen, Maria Laura; Sollwedel, André; Bertoja, Annarosa Zambon; Ritter, Thomas; Kotsch, Katja; Leber, Joachim; Volk, Hans-Dieter

    2005-03-01

    Mammalian pregnancy is thought to be a state of immunological tolerance. The mechanisms underlying this phenomenon are still poorly understood. Here, we determined whether an inappropriate function of T regulatory (Treg) cells is involved in the pathogenesis of spontaneous abortion. We evaluated spleen and decidual lymphocytes from CBA/J mice undergoing immunological abortion (DBA/2J-mated) or having normal pregnancy (BALB/c-mated) on day 14 of gestation for ex vivo cytokine production after PMA or paternal antigen (alloantigen) stimulation. Treg activity was characterized by quantifying CD4(+)CD25(+) cells, foxp3 expression, and interleukin-10 secretion. Decidual lymphocytes from abortion CBA/J mice contained a significantly higher frequency of interferon-gamma-producing T cells specific for paternal antigens compared to those from normal pregnancy (7.8% versus 2.7%, P < 0.05). Compared to virgin CBA/J females, normal pregnant mice showed strongly elevated numbers of CD4(+)CD25(+) and interleukin-10(+) Treg cells in the thymus whereas significantly lower frequencies of Treg cells were observed in abortion mice. Very interestingly, CD4(+)CD25(+) Treg cells from normal pregnant and nonpregnant CBA/J mice could inhibit both proliferation and interferon-gamma secretion of lymphocytes from abortion mice in vitro whereas in vivo prevention of fetal rejection could only be achieved after adoptive transfer of Treg cells from normal pregnant mice. Our data suggest that pregnancy-induced Treg cells play a vital role in maternal tolerance to the allogeneic fetus.

  19. Application of an optimized flow cytometry-based quantification of Platelet Activation (PACT): Monitoring platelet activation in platelet concentrates

    PubMed Central

    Roest, Mark; Henskens, Yvonne M. C.; de Laat, Bas; Huskens, Dana

    2017-01-01

    Background Previous studies have shown that flow cytometry is a reliable test to quantify platelet function in stored platelet concentrates (PC). It is thought that flow cytometry is laborious and hence expensive. We have optimized the flow cytometry-based quantification of agonist induced platelet activation (PACT) to a labor, time and more cost-efficient test. Currently the quality of PCs is only monitored by visual inspection, because available assays are unreliable or too laborious for use in a clinical transfusion laboratory. Therefore, the PACT was applied to monitor PC activation during storage. Study design and methods The optimized PACT was used to monitor 5 PCs during 10 days of storage. In brief, optimized PACT uses a ready-to-use reaction mix, which is stable at -20°C. When needed, a test strip is thawed and platelet activation is initiated by mixing PC with PACT. PACT was based on the following agonists: adenosine diphosphate (ADP), collagen-related peptide (CRP) and thrombin receptor-activating peptide (TRAP-6). Platelet activation was measured as P-selectin expression. Light transmission aggregometry (LTA) was performed as a reference. Results Both PACT and LTA showed platelet function decline during 10-day storage after stimulation with ADP and collagen/CRP; furthermore, PACT showed decreasing TRAP-induced activation. Major differences between the two tests are that PACT is able to measure the status of platelets in the absence of agonists, and it can differentiate between the number of activated platelets and the amount of activation, whereas LTA only measures aggregation in response to an agonist. Also, PACT is more time-efficient compared to LTA and allows high-throughput analysis. Conclusion PACT is an optimized platelet function test that can be used to monitor the activation of PCs. PACT has the same accuracy as LTA with regard to monitoring PCs, but it is superior to both LTA and conventional flow cytometry based tests with regard to labor

  20. Heparin-induced platelet aggregation (H-IPA): dose/response relationship for two low molecular weight (LMW) heparin preparations (CY 216 and CY 222)

    SciTech Connect

    Brace, L.D.; Fareed, J.

    1986-03-01

    The authors have previously demonstrated that heparin and a LMW heparin derivative (PK 10169) causes platelet aggregation in a dose-dependent manner that can be inhibited by antagonists of the thromboxane pathway. Using fractions of these agents separated on the basis of molecular weight (MW) by gel permeation chromatography, the authors showed that H-IPA was directly dependent upon the MW of the agents tested. In order to further examine this MW dependence, the authors tested two other LMW heparin preparations, CY 216 and CY 222 and subfractions of these agents separated on the basis of MW. Citrate anticoagulated whole blood was drawn from drug-free normal healthy donors whose platelets aggregated when heparin was added to their platelet-rich plasma (PRP). PRP was prepared, various concentrations of the agents or their subfractions were added and aggregation was monitored for 40 minutes at 37/sup 0/C. The results demonstrate that like heparin and PK 10169, CY 216 and CY 222 caused platelet aggregation in a dose and MW dependent manner. Fractions with MW less than 2500 daltons caused aggregation only at concentrations exceeding the therapeutic range of the agents. The authors conclude that the ability to cause H-IPA is an inherent property of heparin and its fractions.

  1. Effects of alcohol ingestion post-exercise on platelet aggregation.

    PubMed

    El-Sayed, Mahmoud S

    2002-01-15

    The present study examined the influence of ingesting a moderate dose of alcohol on platelet count and platelet aggregation during recovery following exercise. Nineteen subjects (11 male and 8 female) were studied immediately after a standardised cycle ergometer test and during the 24-h period of recovery. In random order, alcohol (0.7 g/kg body mass) was given 1 h after exercise on one test occasion, while an equal volume of alcohol-free solution was administered on the other. Venous blood samples were obtained at baseline, post-exercise, and at 1, 5, and 22 h post-alcohol ingestion. Blood alcohol level increased significantly 1 h after the ingestion of alcohol, but decreased and returned to the resting baseline level at 5 h during recovery. Males and females subjects exhibited similar mean values of platelet count, platelet aggregation, and beta-thromboglobulin concentration at rest and following exercise and recovery. A significant increase in platelet count and a decrease in platelet aggregation using adenosine diphosphate (ADP) was found following exercise. Although plasma beta-thromboglobulin level (pooled data for males and females) showed an increase by 26.0% (from a mean pre-exercise value of 22.3-28.1 IU/ml), this rise was not significant (P>.05). The post-exercise increase in platelet count was mainly due to exercise-induced plasma volume loss. During recovery, while the increase in platelet count post-exercise returned to the baseline level in control and alcohol trials, the optical density of platelet aggregation remained significantly depressed at 5-h during recovery in the alcohol trial but not in the normal control condition. It is concluded that exercise induces significant reduction in platelet aggregation and the consumption of alcohol after physical exercise delays the normal return of platelet aggregation to the resting baseline levels during recovery.

  2. Platelet-delivered therapeutics.

    PubMed

    Lyde, R; Sabatino, D; Sullivan, S K; Poncz, M

    2015-06-01

    We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches.

  3. Platelet aggregation test

    MedlinePlus

    ... disorders Uremia (a result of kidney failure ) Von Willebrand disease (a bleeding disorder) Risks There is very little ... vasculitis Platelet count Polycythemia vera Prerenal azotemia Von Willebrand disease Review Date 1/27/2015 Updated by: Yi- ...

  4. Platelet aggregability in relation to impaired consciousness after head injury.

    PubMed Central

    Vecht, C J; Minderhoud, J M; Sibinga, C T

    1975-01-01

    ADP-induced platelet aggregation was studied for up to six weeks in 34 patients with head injuries. The patients were divided into three groups according to the degree of impaired consciousness assessed by a clinical coma scale, and change in platelet aggregation was related to the coma score. Platelet aggregation was markedly reduced in all eight patients dying within 24 hours of injury. All 17 patients who remained unconscious for four days or more showed decreased platelet aggregation up to nine days after admission, the most marked effect being on the second day. Platelet function in this group returned to normal within 16 days. Nine patients with only slightly impaired consciousness also showed subnormal platelet aggregation during the first few days with a return to normal by the fourth day. Platelet counts remained within normal limits in all groups. We suggest that during coma following head injury brainstem dysfunction induces neurohumoral changes in the blood which are responsible for a decrease in platelet function. PMID:1214015

  5. Synthetic polyphosphate inhibits endogenous coagulation and platelet aggregation in vitro

    PubMed Central

    Yang, Xiaoyang; Wan, Mengjie; Liang, Ting; Peng, Minyuan; Chen, Fangping

    2017-01-01

    Platelet-derived polyphosphate has previously been indicated to induce coagulation. However, industrially synthesized polyphosphate has been found to have different effects from those of the platelet-derived form. The present study investigated whether synthetic sodium polyphosphate inhibits coagulation using routine coagulation tests and thromboelastography. Synthetic polyphosphate was found to inhibit adenosine diphosphate-, epinephrine-, arachidonic acid-, ristocetin-, thrombin-, oxytocin- and pituitrin-induced platelet aggregation. The effects of synthetic polyphosphate in clotting inhibition were revealed by the analysis of clotting factor activity and platelet aggregation tests. Synthetic polyphosphate may inhibit platelet aggregation by reducing platelet calcium levels, as indicated by the results of flow cytometric analysis and high-throughput fluorescent screening. Furthermore, analysis of thromboxane (TX)B2 by ELISA indicated that synthetic polyphosphate reduces platelet aggregation by inhibiting the TXA2 signaling pathway. In conclusion, synthetic polyphosphate inhibits clotting factor activity and endogenous coagulation by reducing the levels of calcium ions and TXA2 to curb platelet aggregation. PMID:28123708

  6. HMGB1 binds to activated platelets via the receptor for advanced glycation end products and is present in platelet rich human coronary artery thrombi.

    PubMed

    Ahrens, Ingo; Chen, Yung-Chih; Topcic, Danijal; Bode, Michael; Haenel, David; Hagemeyer, Christoph E; Seeba, Hannah; Duerschmied, Daniel; Bassler, Nicole; Jandeleit-Dahm, Karin A; Sweet, Matthew J; Agrotis, Alex; Bobik, Alex; Peter, Karlheinz

    2015-11-01

    High mobility group box 1 (HMGB1) acts as both a nuclear protein that regulates gene expression, as well as a pro-inflammatory alarmin that is released from necrotic or activated cells. Recently, HMGB1-expression in human atherosclerotic plaques was identified. Therapeutic blockade of HMGB1 reduced the development of diet-induced atherosclerosis in ApoE knockout mice. Thus, we hypothesised an interaction between HMGB1 and activated platelets. Binding of recombinant HMGB1 to platelets was assessed by flow cytometry. HMGB1 bound to thrombin-activated human platelets (MFI 2.49 vs 25.01, p=0.0079). Blood from wild-type, TLR4 and RAGE knockout mice was used to determine potential HMGB1 receptors on platelets. HMGB1 bound to platelets from wild type C57Bl6 (MFI 2.64 vs 20.3, p< 0.05), and TLR4-/- mice (MFI 2.11 vs 25.65, p< 0.05) but failed to show binding to platelets from RAGE-/- mice (p > 0.05). RAGE expression on human platelets was detected by RT-PCR with mRNA extracted from highly purified platelets and confirmed by Western blot and immunofluorescence microscopy. Platelet activation increased RAGE surface expression (MFI 4.85 vs 6.74, p< 0.05). Expression of HMGB1 in human coronary artery thrombi was demonstrated by immunohistochemistry and revealed high expression levels. Platelets bind HMGB1 upon thrombin-induced activation. Platelet specific expression of RAGE could be detected at the mRNA and protein level and is involved in the binding of HMGB1. Furthermore, platelet activation up-regulates platelet surface expression of RAGE. HMGB1 is highly expressed in platelet-rich human coronary artery thrombi pointing towards a central role for HMGB1 in atherothrombosis, thereby suggesting the possibility of platelet targeted anti-inflammatory therapies for atherothrombosis.

  7. Platelets amplify inflammation in arthritis via collagen-dependent microparticle production.

    PubMed

    Boilard, Eric; Nigrovic, Peter A; Larabee, Katherine; Watts, Gerald F M; Coblyn, Jonathan S; Weinblatt, Michael E; Massarotti, Elena M; Remold-O'Donnell, Eileen; Farndale, Richard W; Ware, Jerry; Lee, David M

    2010-01-29

    In addition to their pivotal role in thrombosis and wound repair, platelets participate in inflammatory responses. We investigated the role of platelets in the autoimmune disease rheumatoid arthritis. We identified platelet microparticles--submicrometer vesicles elaborated by activated platelets--in joint fluid from patients with rheumatoid arthritis and other forms of inflammatory arthritis, but not in joint fluid from patients with osteoarthritis. Platelet microparticles were proinflammatory, eliciting cytokine responses from synovial fibroblasts via interleukin-1. Consistent with these findings, depletion of platelets attenuated murine inflammatory arthritis. Using both pharmacologic and genetic approaches, we identified the collagen receptor glycoprotein VI as a key trigger for platelet microparticle generation in arthritis pathophysiology. Thus, these findings demonstrate a previously unappreciated role for platelets and their activation-induced microparticles in inflammatory joint diseases.

  8. Equid herpesvirus type 1 activates platelets.

    PubMed

    Stokol, Tracy; Yeo, Wee Ming; Burnett, Deborah; DeAngelis, Nicole; Huang, Teng; Osterrieder, Nikolaus; Catalfamo, James

    2015-01-01

    Equid herpesvirus type 1 (EHV-1) causes outbreaks of abortion and neurological disease in horses. One of the main causes of these clinical syndromes is thrombosis in placental and spinal cord vessels, however the mechanism for thrombus formation is unknown. Platelets form part of the thrombus and amplify and propagate thrombin generation. Here, we tested the hypothesis that EHV-1 activates platelets. We found that two EHV-1 strains, RacL11 and Ab4 at 0.5 or higher plaque forming unit/cell, activate platelets within 10 minutes, causing α-granule secretion (surface P-selectin expression) and platelet microvesiculation (increased small events double positive for CD41 and Annexin V). Microvesiculation was more pronounced with the RacL11 strain. Virus-induced P-selectin expression required plasma and 1.0 mM exogenous calcium. P-selectin expression was abolished and microvesiculation was significantly reduced in factor VII- or X-deficient human plasma. Both P-selectin expression and microvesiculation were re-established in factor VII-deficient human plasma with added purified human factor VIIa (1 nM). A glycoprotein C-deficient mutant of the Ab4 strain activated platelets as effectively as non-mutated Ab4. P-selectin expression was abolished and microvesiculation was significantly reduced by preincubation of virus with a goat polyclonal anti-rabbit tissue factor antibody. Infectious virus could be retrieved from washed EHV-1-exposed platelets, suggesting a direct platelet-virus interaction. Our results indicate that EHV-1 activates equine platelets and that α-granule secretion is a consequence of virus-associated tissue factor triggering factor X activation and thrombin generation. Microvesiculation was only partly tissue factor and thrombin-dependent, suggesting the virus causes microvesiculation through other mechanisms, potentially through direct binding. These findings suggest that EHV-1-induced platelet activation could contribute to the thrombosis that occurs in

  9. Equid Herpesvirus Type 1 Activates Platelets

    PubMed Central

    Stokol, Tracy; Yeo, Wee Ming; Burnett, Deborah; DeAngelis, Nicole; Huang, Teng; Osterrieder, Nikolaus; Catalfamo, James

    2015-01-01

    Equid herpesvirus type 1 (EHV-1) causes outbreaks of abortion and neurological disease in horses. One of the main causes of these clinical syndromes is thrombosis in placental and spinal cord vessels, however the mechanism for thrombus formation is unknown. Platelets form part of the thrombus and amplify and propagate thrombin generation. Here, we tested the hypothesis that EHV-1 activates platelets. We found that two EHV-1 strains, RacL11 and Ab4 at 0.5 or higher plaque forming unit/cell, activate platelets within 10 minutes, causing α-granule secretion (surface P-selectin expression) and platelet microvesiculation (increased small events double positive for CD41 and Annexin V). Microvesiculation was more pronounced with the RacL11 strain. Virus-induced P-selectin expression required plasma and 1.0 mM exogenous calcium. P-selectin expression was abolished and microvesiculation was significantly reduced in factor VII- or X-deficient human plasma. Both P-selectin expression and microvesiculation were re-established in factor VII-deficient human plasma with added purified human factor VIIa (1 nM). A glycoprotein C-deficient mutant of the Ab4 strain activated platelets as effectively as non-mutated Ab4. P-selectin expression was abolished and microvesiculation was significantly reduced by preincubation of virus with a goat polyclonal anti-rabbit tissue factor antibody. Infectious virus could be retrieved from washed EHV-1-exposed platelets, suggesting a direct platelet-virus interaction. Our results indicate that EHV-1 activates equine platelets and that α-granule secretion is a consequence of virus-associated tissue factor triggering factor X activation and thrombin generation. Microvesiculation was only partly tissue factor and thrombin-dependent, suggesting the virus causes microvesiculation through other mechanisms, potentially through direct binding. These findings suggest that EHV-1-induced platelet activation could contribute to the thrombosis that occurs in

  10. Platelets and diabetes mellitus.

    PubMed

    Santilli, Francesca; Simeone, Paola; Liani, Rossella; Davì, Giovanni

    2015-07-01

    Platelet activation plays a key role in atherothrombosis in type 2 diabetes mellitus (T2DM) and increased in vivo platelet activation with enhanced thromboxane (TX) biosynthesis has been reported in patients with impairment of glucose metabolism even in the earlier stages of disease and in the preclinical phases. In this regards, platelets appear as addresses and players carrying and transducing metabolic derangement into vascular injury. The present review critically addresses key pathophysiological aspects including (i) hyperglycemia, glycemic variability and insulin resistance as determinants and predictors of platelet activation, (ii) inflammatory mediators derived from platelets, such as soluble CD40 ligand, soluble CD36, Dickkopf-1 and probably soluble receptor for advanced glycation-end-products (sRAGE), which expand the functional repertoire of platelets from players of hemostasis and thrombosis to powerful amplifiers of inflammation by promoting the release of cytokines and chemokines, cell activation, and cell-cell interactions; (iii) molecular mechanisms underpinning the less-than-expected antithrombotic protection by aspirin (ASA), despite regular antiplatelet prophylaxis at the standard dosing regimen, and (iv) stratification of patients deserving different antiplatelet strategies, based on the metabolic phenotype. Taken together, these pathophysiological aspects may contribute to the development of promising mechanism-based therapeutic strategies to reduce the progression of atherothrombosis in diabetic subjects.

  11. Platelets and wound healing.

    PubMed

    Nurden, Alan T; Nurden, Paquita; Sanchez, Mikel; Andia, Isabel; Anitua, Eduardo

    2008-05-01

    Platelets help prevent blood loss at sites of vascular injury. To do this, they adhere, aggregate and form a procoagulant surface favoring thrombin generation and fibrin formation. In addition, platelets express and release substances that promote tissue repair and influence processes such as angiogenesis, inflammation and the immune response. They contain large secretable pools of biologically active proteins, while newly synthesized active metabolites are also released. Although anucleate, activated platelets possess a spliceosome and can synthesize tissue factor and interleukin-1beta. The binding of secreted proteins within a developing fibrin mesh or to the extracellular matrix can create chemotactic gradients favoring the recruitment of stem cells, stimulating cell migration and differentiation, and promoting repair. The therapeutic use of platelets in a fibrin clot has a positive influence in clinical situations requiring rapid healing. Dental implant surgery, orthopaedic surgery, muscle and tendon repair, skin ulcers, hole repair in eye surgery and cardiac surgery are situations where the use of autologous platelets accelerates healing. We now review the ways in which platelets participate in these processes.

  12. "Message in the platelet"--more than just vestigial mRNA!

    PubMed

    Harrison, Paul; Goodall, Alison H

    2008-09-01

    Although mammalian platelets are anucleated cells, a number of studies have shown that they retain a pool of messenger RNA (mRNA) carried over from the megakaryocyte during thrombopoiesis. Platelet mRNA was originally thought to be relatively unstable and short-lived within the youngest cells and has been used as a potential marker of platelet turnover. In this article we will discuss both theoretical and methodological issues related to the measurement of these younger, "reticulated platelets". A key question relating to platelet mRNA is also whether it has any functional relevance other than a marker of platelet immaturity. Evidence going back more than 30 years suggests that platelets can biosynthesize proteins. However, it is only very recently that the nature and specificity of platelet mRNA has been examined in any detail. Difficulties in obtaining pure platelet mRNA, free of contamination from other cells has added to the complexity of unravelling this story. However, there is now clear evidence that platelets contain small but significant levels of message for a variety of proteins. The platelet mRNA pool is much richer and more diverse than previously thought and recent data suggests that regulated synthesis of a selected number of proteins can be induced on platelet activation. The full complexity of the platelet genome is now just being revealed and may open the possibility for improved diagnosis and therapy of many haemostatic and thrombotic disorders.

  13. Nitric oxide released from activated platelets inhibits platelet recruitment.

    PubMed Central

    Freedman, J E; Loscalzo, J; Barnard, M R; Alpert, C; Keaney, J F; Michelson, A D

    1997-01-01

    Vessel injury and thrombus formation are the cause of most ischemic coronary syndromes and, in this setting, activated platelets stimulate platelet recruitment to the growing thrombus. Recently, a constitutive nitric oxide synthase (NOS) has been identified in human platelets. To further define the capacity of platelets to produce nitric oxide (NO), as well as to study the role of this NO in platelet recruitment, we adapted a NO-selective microelectrode for use in a standard platelet aggregometer, thereby permitting simultaneous measurement of platelet aggregation and NO production. Treatment of platelets with the NO synthase inhibitor -NG-nitroarginine methyl ester (L-NAME), reduced NO production by 92+/-8% in response to 5 microM ADP compared to control but increased aggregation by only 15+/-2%. In contrast, L-NAME had a more pronounced effect on platelet recruitment as evidenced by a 35+/-5% increase in the extent of aggregation, a 33+/-3% decrease in cyclic GMP content, and a 31+/-5% increase in serotonin release from a second recruitable population of platelets added to stimulated platelets at the peak of NO production. To study platelet recruitment accurately, we developed an assay that monitors two platelet populations simultaneously. Nonbiotinylated platelets were incubated with L-NAME or vehicle and activated with ADP. At peak NO production, biotinylated platelets were added. As measured by three-color flow cytometry, there was a 56+/-11% increase in the number of P selectin- positive platelets in the nonbiotinylated population treated with L-NAME as compared to control. When biotinylated platelets were added to the L-NAME-treated nonbiotinylated population, the number of P selectin positive biotinylated plate-lets increased by 180+/-32% as compared to biotinylated platelets added to the control. In summary, stimulated platelets produce NO that modestly inhibits platelet activation but markedly inhibits additional platelet recruitment. These data suggest

  14. Granulocyte colony-stimulating factor increases the platelet volume in peripheral stem cell apheresis donors.

    PubMed

    Ihara, Akihiro; Matsui, Keiko; Minami, Ryouta; Uchida, Shuzou; Ueda, Shuji; Nishiura, Tetsuo

    2008-01-01

    We investigated the short-term influence of granulocyte colony-stimulating factor (G-CSF) administration on platelet counts and platelet indices in 12 donors (8 males and 4 females; median age 34 years, range 16-49) for peripheral stem cell transplantation using an automated blood cell analyzer. On day 3 (D3) compared with D0, 11 donors with normal laboratory and physical findings showed increases in platelet indices (chi(2) = 12.0, p = 0.0025). Furthermore, mean platelet volume (MPV) was significantly increased (p = 0.04). Also, platelet count decreased, and platelet distribution width and platelet-large cell ratio were increased, but these were not significant. On the contrary, 1 donor with abnormal laboratory findings who had large platelets (MPV 11.4 fl) before G-CSF administration showed decreases in platelet indices (MPV 10.3 fl) on D3, although platelet count (18.2 x 10(4)/microl) decreased after G-CSF administration. G-CSF administration induces an inflammatory process with endothelial cell activation. This is probably the reason why platelet volume increases after G-CSF use. This is the first report showing that G-CSF administration immediately induces increases in large platelets in peripheral stem cell transplant donors before harvest.

  15. Human platelet aggregation inhibitors from thyme (Thymus vulgaris L.).

    PubMed

    Okazaki, Kenji; Kawazoe, Kazuyoshi; Takaishi, Yoshihisa

    2002-06-01

    Two antiaggregant compounds, thymol (compound 1) and 3,4,3',4'-tetrahydroxy-5,5'-diisopropyl-2,2'-dimethylbiphenyl (compound 2) were isolated from the leaves of thyme (Thymus vulgaris L.). The structures were determined by (1)H-, (13)C-NMR and mass spectra (MS) studies. These compounds inhibited platelet aggregation induced by collagen, ADP, arachidonic acid (AA) and thrombin except that compound 2 did not inhibit platelet aggregation induced by thrombin.

  16. Formaldehyde-fixation of platelets for flow cytometric measurement of phosphatidylserine exposure is feasible.

    PubMed

    Rochat, Sophie; Alberio, Lorenzo

    2015-01-01

    Strong platelet activation results in a redistribution of negatively charged phospholipids from the cytosolic to the outer leaflet of the cellular membrane. Annexin V has a high affinity to negatively charged phospholipids and can be used to identify procoagulant platelets. Formaldehyde fixation can cause factitious Annexin V binding. Our aim was to evaluate a method for fixing platelets avoiding additional Annexin V binding. We induced expression of negatively charged phospholipids on the surface of a fraction of platelets by combined activation with convulxin and thrombin in the presence of Annexin V-fluorescein isothiocyanate and calcium. Aliquots of resting and activated platelets were fixed with a low concentration, calcium-free formaldehyde solution. Both native platelets and fixed platelets were analyzed by flow cytometry immediately and after a 24-h storage at 4°C. We observed that the percentage of Annexin V positive resting platelets ranged from 1.5 to 9.3% for the native samples and from 0.4 to 12.8% for the fixed samples (P=0.706, paired t-test). The amount of Annexin V positive convulxin/thrombin activated platelets varied from 12.9 to 35.4% without fixation and from 15.3 to 36.3% after formalin fixation (P=0.450). After a 24-h storage at 4°C, Annexin V positive platelets significantly increased both in the resting and in the convulxin/thrombin activated samples of native platelets (both P<0.001), while results for formalin fixed platelets did not differ from baseline values (P=0.318 for resting fixed platelets; P=0.673 for activated fixed platelets). We conclude that platelet fixation with a low concentration, calcium-free formaldehyde solution does not alter the proportion of Annexin V positive platelets. This method can be used to investigate properties of procoagulant platelets by multicolor flow-cytometric analysis requiring fixation steps.

  17. GPS antenna multipath rejection performance

    NASA Astrophysics Data System (ADS)

    Dinius, A. M.

    1995-08-01

    A GPS antenna multipath rejection performance evaluation was conducted. Ground reference station antennas and aviation patches were tested for their ability to reject a multipath signal. Different types of ground plane structures were used such as choke rings, ground planes, and mock sections of fuselage. Frequencies transmitted were L1 (1575 MHz), L2 (1227 MHz), and the median GLONASS frequency (1609 MHz). Receive amplitude and phase were measured on each antenna. Subsequently, these data were converted to absolute gain for a right hand and left hand circularly polarized signal as a function of satellite elevation angle. Two types of multipath signals were considered: ground bounce multipath and building or structure bounce multipath. Ground bounce multipath typically occurs at low satellite elevation angles while structure bounce multipath can occur at any satellite elevation angle. Separate analysis methods were used to assess an antenna's ability to reject either type of multipath. This report describes the data collection methods, data reduction and analysis, and the results.

  18. Clinical uses of radiolabeled platelets

    SciTech Connect

    Datz, F.L.; Christian, P.E.; Baker, W.J.

    1985-12-01

    Platelets were first successfully radiolabeled in 1953. At that time, investigators were primarily interested in developing a technique to accurately measure platelet life span in both normal and thrombocytopenic patients. Studies using platelets labeled with /sup 51/Cr have shown shortened platelet survival times in a number of diseases including idiopathic thrombocytopenic purpura, coronary artery disease, and diabetes mellitus. More recently, labels such as /sup 111/In have been developed that allow in vivo imaging of platelets. Indium-111 platelets are being used to better understand the pathophysiology of atherosclerosis, thrombophlebitis, pulmonary embolism and clotting disorders, and to improve the clinical diagnosis of these diseases.

  19. Platelets and their role in cancer evolution and immune system

    PubMed Central

    Karachaliou, Niki; Pilotto, Sara; Bria, Emilio

    2015-01-01

    Platelets are anucleate fragments formed from the cytoplasm of megakaryocytes and represent the smallest circulating hematopoietic cells. Thought for almost a century to possess solely hemostatic potentials, platelets actually play a much wider role in tissue regeneration and repair and interact intimately with tumor cells. On the one hand, tumor cells induce platelet aggregation, known to act as the trigger of cancer-associated thrombosis and on the other hand, platelets recruited to the tumor microenvironment interact directly with tumor cells favoring proliferation, and indirectly through the release of angiogenic and mitogenic proteins. Furthermore, platelets are immunosuppressive cells that protect metastatic cancer cells from surveillance by killer cells, nullifying the effects of immunotherapy. PMID:26798580

  20. Anti-apoptotic role of sonic hedgehog on blood platelets.

    PubMed

    Kumari, Sharda; Chaurasia, Susheel N; Kumar, Kailash; Dash, Debabrata

    2014-12-01

    Sonic hedgehog (Shh) is an essential morphogen involved in vertebrate organogenesis. Perturbation of Hh signaling is associated with pathological consequences like tumor formation and chronic lung fibrosis. Platelets are highly sensitive circulating blood cells responsible for hemostasis, while hyperactivity of these cells lead to morbidities like ischemic heart diseases and stroke. Despite being terminally differentiated cells with life span of 10-12 days, platelets have recently been shown to respond to Wnt ligand, another developmental signal similar to Shh. In this study, we demonstrate that components of Shh signaling, Patched and Gli3, are expressed in human platelets consistent with existence of functional Hedgehog signaling in these cells. Shh had potent inhibitory effect on platelet apoptosis induced by ABT-737 or thrombin through attenuation of caspase-3 activity. The Shh-mediated pathway may thus represent a novel endogenous mechanism for regulating platelet activity and life span.

  1. Comparative studies on homocysteine and its metabolite-homocysteine thiolactone action in blood platelets in vitro.

    PubMed

    Olas, B; Kedzierska, M; Wachowicz, B

    2008-11-01

    Homocysteine (Hcy), an intermediate formed during the catabolism of the essential dietary amino acid methionine, and its cyclic thioester, homocysteine thiolactone (TL) formed from Hcy in plasma, may be implicated in pathological haemostasis and atherosclerosis. The mechanism by which TL exerts the prothrombotic effect and influences blood platelets remains unclear. Activation of blood platelets plays an important role in prothrombotic events. The aim of our study was to establish and compare the influence of a reduced form of homocysteine (at final doses of 10-100 microM) and its cyclic thioester, homocysteine thiolactone (0.1-1 microM), on platelet activation induced by thrombin (platelet aggregation), on platelet protein modifications (determined by parameters such as level of protein carbonyl groups, 3-nitrotyrosine residues in proteins) and on superoxide anion radicals ( O2-*) generation using the model system in vitro. We have observed that TL, like its precursor, Hcy, stimulates the generation of O2* in platelets and causes an augmentation of platelet aggregation induced by thrombin. Our present results in vitro also demonstrate that Hcy (10-100 microM) and TL at lower doses than Hcy (0.1-1 microM) cause modification of platelet proteins: diminished formation of carbonyl groups and distinctly decreased tyrosine nitration in platelet proteins after thrombin stimulation, but increased platelet aggregation induced by thrombin. TL like Hcy (at concentrations corresponding to concentrations in blood during hyperhomocysteinemia) modifies platelet responses to an important physiological agonist--thrombin.

  2. Platelets and Infections – Complex Interactions with Bacteria

    PubMed Central

    Hamzeh-Cognasse, Hind; Damien, Pauline; Chabert, Adrien; Pozzetto, Bruno; Cognasse, Fabrice; Garraud, Olivier

    2015-01-01

    Platelets can be considered sentinels of vascular system due to their high number in the circulation and to the range of functional immunoreceptors they express. Platelets express a wide range of potential bacterial receptors, including complement receptors, FcγRII, Toll-like receptors but also integrins conventionally described in the hemostatic response, such as GPIIb–IIIa or GPIb. Bacteria bind these receptors either directly, or indirectly via fibrinogen, fibronectin, the first complement C1q, the von Willebrand Factor, etc. The fate of platelet-bound bacteria is questioned. Several studies reported the ability of activated platelets to internalize bacteria such as Staphylococcus aureus or Porphyromonas gingivalis, though there is no clue on what happens thereafter. Are they sheltered from the immune system in the cytoplasm of platelets or are they lysed? Indeed, while the presence of phagolysosome has not been demonstrated in platelets, they contain antimicrobial peptides that were shown to be efficient on S. aureus. Besides, the fact that bacteria can bind to platelets via receptors involved in hemostasis suggests that they may induce aggregation; this has indeed been described for Streptococcus sanguinis, S. epidermidis, or C. pneumoniae. On the other hand, platelets are able to display an inflammatory response to an infectious triggering. We, and others, have shown that platelet release soluble immunomodulatory factors upon stimulation by bacterial components. Moreover, interactions between bacteria and platelets are not limited to only these two partners. Indeed, platelets are also essential for the formation of neutrophil extracellular traps by neutrophils, resulting in bacterial clearance by trapping bacteria and concentrating antibacterial factors but in enhancing thrombosis. In conclusion, the platelet–bacteria interplay is a complex game; its fine analysis is complicated by the fact that the inflammatory component adds to the aggregation response

  3. 7 CFR 58.136 - Rejected milk.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 3 2013-01-01 2013-01-01 false Rejected milk. 58.136 Section 58.136 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Milk § 58.136 Rejected milk. A plant shall reject specific milk from a producer if the milk fails...

  4. 7 CFR 58.136 - Rejected milk.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 3 2014-01-01 2014-01-01 false Rejected milk. 58.136 Section 58.136 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Milk § 58.136 Rejected milk. A plant shall reject specific milk from a producer if the milk fails...

  5. 7 CFR 58.136 - Rejected milk.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 3 2012-01-01 2012-01-01 false Rejected milk. 58.136 Section 58.136 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Milk § 58.136 Rejected milk. A plant shall reject specific milk from a producer if the milk fails...

  6. Peer Group Rejection and Children's Outgroup Prejudice

    ERIC Educational Resources Information Center

    Nesdale, Drew; Durkin, Kevin; Maass, Anne; Kiesner, Jeff; Griffiths, Judith; Daly, Josh; McKenzie, David

    2010-01-01

    Two simulation studies examined the effect of peer group rejection on 7 and 9 year old children's outgroup prejudice. In Study 1, children (n = 88) pretended that they were accepted or rejected by their assigned group, prior to competing with a lower status outgroup. Results indicated that rejected versus accepted children showed increased…

  7. 7 CFR 58.136 - Rejected milk.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Rejected milk. 58.136 Section 58.136 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Milk § 58.136 Rejected milk. A plant shall reject specific milk from a producer if the milk fails...

  8. 7 CFR 58.136 - Rejected milk.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 3 2011-01-01 2011-01-01 false Rejected milk. 58.136 Section 58.136 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards... Milk § 58.136 Rejected milk. A plant shall reject specific milk from a producer if the milk fails...

  9. Anti-platelet effects of yuzu extract and its component.

    PubMed

    Yu, Hye Yon; Park, Se Won; Chung, Ill Min; Jung, Yi-Sook

    2011-12-01

    In this study, we investigated whether the methanolic extract of yuzu (yuzu ME) and its components hesperidin and naringin, have anti-platelet activities. Yuzu ME and hesperidin inhibited collagen-, arachidonic acid (AA)-, ADP- and thrombin-induced rat platelet aggregation in vitro and ex vivo. Naringin also inhibited platelet aggregation induced by collagen, AA, or thrombin, but not aggregation induced by ADP. The oral administration of yuzu ME or hesperidin prolonged mouse tail vein bleeding time in a dose-dependent manner in vivo. These results suggest that yuzu ME and hesperidin have anti-platelet activity, and that intake of yuzu, which includes various flavonoids such as hesperidin, may be beneficial for individuals at high risk of cardiovascular diseases.

  10. In vitro canine platelet aggregation caused by Dirofilaria immitis extract

    PubMed Central

    TAKASHIMA, Yasuhiro; ONODA, Isako; CHIOU, Shin-Pin; KITOH, Katsuya

    2016-01-01

    Platelet function hyper-activity has been reported in Dirofilaria immitis (heartworm, HW)-infected dogs. Although the mechanism of increased platelet hyper-activity has not yet been elucidated, it is suggested to be mediated by unknown factors, which may be related to adult HW components. This study aims to determine whether adult male HW whole body extract induces canine platelet aggregation in vitro. The results indicate that HW extract caused an aggregation of canine platelets in a concentration-dependent manner. This aggregation ability of the HW extract was not mediated by the adenosine diphosphate receptor. In addition, the mechanisms of aggregation did not require cyclooxygenase-dependent pathways, and the aggregating activity of substances contained in the HW extract was heat stable; therefore, the active substances may be different from collagen. Furthermore, the platelet aggregating activity remained within the molecular weight (MW)≥100,000 fraction obtained by ultrafiltrating the HW extract. In contrast, the MW <100,000 fraction also had a platelet aggregation ability, but the aggregation pattern was reversible and the maximum extent decreased, compared with the MW≥100,000 fraction response. Our experiments have been conducted using a whole body extract from adult HWs to determine with certainty the aggregating activity of HW elements on canine platelets. More studies are necessary to evaluate the effects of the metabolic products released from live adult worms in pulmonary arteries and the symbiont bacterium Wolbachia-derived antigens on canine platelet aggregation. PMID:28049921

  11. BCL-2 is dispensable for thrombopoiesis and platelet survival

    PubMed Central

    Debrincat, M A; Pleines, I; Lebois, M; Lane, R M; Holmes, M L; Corbin, J; Vandenberg, C J; Alexander, W S; Ng, A P; Strasser, A; Bouillet, P; Sola-Visner, M; Kile, B T; Josefsson, E C

    2015-01-01

    Navitoclax (ABT-263), an inhibitor of the pro-survival BCL-2 family proteins BCL-2, BCL-XL and BCL-W, has shown clinical efficacy in certain BCL-2-dependent haematological cancers, but causes dose-limiting thrombocytopaenia. The latter effect is caused by Navitoclax directly inducing the apoptotic death of platelets, which are dependent on BCL-XL for survival. Recently, ABT-199, a selective BCL-2 antagonist, was developed. It has shown promising anti-leukaemia activity in patients whilst sparing platelets, suggesting that the megakaryocyte lineage does not require BCL-2. In order to elucidate the role of BCL-2 in megakaryocyte and platelet survival, we generated mice with a lineage-specific deletion of Bcl2, alone or in combination with loss of Mcl1 or Bclx. Platelet production and platelet survival were analysed. Additionally, we made use of BH3 mimetics that selectively inhibit BCL-2 or BCL-XL. We show that the deletion of BCL-2, on its own or in concert with MCL-1, does not affect platelet production or platelet lifespan. Thrombocytopaenia in Bclx-deficient mice was not affected by additional genetic loss or pharmacological inhibition of BCL-2. Thus, BCL-2 is dispensable for thrombopoiesis and platelet survival in mice. PMID:25880088

  12. BCL-2 is dispensable for thrombopoiesis and platelet survival.

    PubMed

    Debrincat, M A; Pleines, I; Lebois, M; Lane, R M; Holmes, M L; Corbin, J; Vandenberg, C J; Alexander, W S; Ng, A P; Strasser, A; Bouillet, P; Sola-Visner, M; Kile, B T; Josefsson, E C

    2015-04-16

    Navitoclax (ABT-263), an inhibitor of the pro-survival BCL-2 family proteins BCL-2, BCL-XL and BCL-W, has shown clinical efficacy in certain BCL-2-dependent haematological cancers, but causes dose-limiting thrombocytopaenia. The latter effect is caused by Navitoclax directly inducing the apoptotic death of platelets, which are dependent on BCL-XL for survival. Recently, ABT-199, a selective BCL-2 antagonist, was developed. It has shown promising anti-leukaemia activity in patients whilst sparing platelets, suggesting that the megakaryocyte lineage does not require BCL-2. In order to elucidate the role of BCL-2 in megakaryocyte and platelet survival, we generated mice with a lineage-specific deletion of Bcl2, alone or in combination with loss of Mcl1 or Bclx. Platelet production and platelet survival were analysed. Additionally, we made use of BH3 mimetics that selectively inhibit BCL-2 or BCL-XL. We show that the deletion of BCL-2, on its own or in concert with MCL-1, does not affect platelet production or platelet lifespan. Thrombocytopaenia in Bclx-deficient mice was not affected by additional genetic loss or pharmacological inhibition of BCL-2. Thus, BCL-2 is dispensable for thrombopoiesis and platelet survival in mice.

  13. In vitro canine platelet aggregation caused by Dirofilaria immitis extract.

    PubMed

    Takashima, Yasuhiro; Onoda, Isako; Chiou, Shin-Pin; Kitoh, Katsuya

    2017-02-28

    Platelet function hyper-activity has been reported in Dirofilaria immitis (heartworm, HW)-infected dogs. Although the mechanism of increased platelet hyper-activity has not yet been elucidated, it is suggested to be mediated by unknown factors, which may be related to adult HW components. This study aims to determine whether adult male HW whole body extract induces canine platelet aggregation in vitro. The results indicate that HW extract caused an aggregation of canine platelets in a concentration-dependent manner. This aggregation ability of the HW extract was not mediated by the adenosine diphosphate receptor. In addition, the mechanisms of aggregation did not require cyclooxygenase-dependent pathways, and the aggregating activity of substances contained in the HW extract was heat stable; therefore, the active substances may be different from collagen. Furthermore, the platelet aggregating activity remained within the molecular weight (MW)≥100,000 fraction obtained by ultrafiltrating the HW extract. In contrast, the MW <100,000 fraction also had a platelet aggregation ability, but the aggregation pattern was reversible and the maximum extent decreased, compared with the MW≥100,000 fraction response. Our experiments have been conducted using a whole body extract from adult HWs to determine with certainty the aggregating activity of HW elements on canine platelets. More studies are necessary to evaluate the effects of the metabolic products released from live adult worms in pulmonary arteries and the symbiont bacterium Wolbachia-derived antigens on canine platelet aggregation.

  14. Platelets and platelet-like particles mediate intercellular RNA transfer

    PubMed Central

    Risitano, Antonina; Beaulieu, Lea M.; Vitseva, Olga

    2012-01-01

    The role of platelets in hemostasis and thrombosis is clearly established; however, the mechanisms by which platelets mediate inflammatory and immune pathways are less well understood. Platelets interact and modulate the function of blood and vascular cells by releasing bioactive molecules. Although the platelet is anucleate, it conta