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Sample records for facilitating platelet aggregation

  1. Activation of Protein Kinase G (PKG) Reduces Neointimal Hyperplasia, Inhibits Platelet Aggregation, and Facilitates Re-endothelialization

    PubMed Central

    Kim, Ju-Young; Yang, Han-Mo; Lee, Joo-Eun; Kim, Baek-Kyung; Jin, Sooryeonhwa; Lee, Jaewon; Park, Kyung-Woo; Cho, Hyun-Jai; Kwon, Yoo-Wook; Lee, Hae-Young; Kang, Hyun-Jae; Oh, Byung-Hee; Park, Young-Bae; Kim, Hyo-Soo

    2016-01-01

    In spite of its great success in reducing restenosis, drug-eluting stent (DES) has unfavorable aspects such as stent thrombosis and delayed re-endothelialization. We examined the effects of PKG activation by Exisulind on neointimal formation, platelet aggregation, and re-endothelialization. Exisulind significantly reduced VSMCs viability, cell cycle progression, migration, and neointimal hyperplasia after vascular injury in rat carotid arteries. Interestingly, in contrast to the effect on VSMC viability, Exisulind did not reduce the viability of endothelial cells. Increased PKG activity by Exisulind inhibited PDGF-stimulated phenotype change of VSMCs from a contractile to a synthetic form. Conversely, the use of PKG inhibitor or gene transfer of dominant-negative PKG reversed the effects of Exisulind, resulting in the increased viability of VSMCs and neointimal formation. In addition, Exisulind facilitated the differentiation of peripheral blood mononuclear cells to endothelial lineage via PKG pathway, while inhibiting to VSMCs lineage, which was correlated with the enhanced re-endothelialization in vivo. Finally, Exisulind reduced platelet aggregation, which was mediated via PKG activation. This study demonstrated that Exisulind inhibits neointimal formation and platelet aggregation while increasing re-endothelialization via PKG pathway. These findings suggest that Exisulind could be a promising candidate drug of DES for the prevention of restenosis without other complications. PMID:27833146

  2. 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- ...

  3. 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

  4. Blood platelet aggregation and personality traits.

    PubMed

    Jenkins, C D; Thomas, G; Olewine, D; Zyzanski, S J; Simpson, M T; Hames, C G

    1975-12-01

    Changes in blood platelet aggregation may precipitate episodes of arterial occlusive diseases. Little is known, however, regarding the influence of psychological traits, emotional states and other behavioral stressors on platelet aggregation phenomena. This study examined 46 healthy college men at rest and after submaximal treadmill exercise. Associations were found between the duration of platelet aggregation and a number of scores from the California Psychological Inventory and self-administered anxiety scales. The more socially adequate, poised and dominant persons--those with more mature ego development and less overt anxiety--had platelets with more prolonged aggregation reactions to the in vitro introduction of noradrenalin. Irreversible aggregation of platelets occurred more regularly to lower in vitro concentrations of noradrenalin in platelet samples drawn from subjects who were less anxious and tended to be more rigidly defensive. It is premature to attempt to derive clinical implications from this exploratory work, but some implications for the design of future research are discussed.

  5. Labile aggregation stimulating substance, free fatty acids, and platelet aggregation.

    PubMed

    Gerrard, J M; White, J G; Krivit, W

    1976-01-01

    Labile aggregation stimulating substance (LASS), an intermediate produced during platelet biosynthesis of PGE2 and PGF2alpha, acts as a physiologic intercellular messenger to promote platelet aggregation and the release reaction. The activity is formed by intact cells after physiologic stimulation or can be generated from platelet membrane fractions after combination with arachidonate. In the present investigation, small amounts of polyunsaturated fatty acids added to an incubation mixture of platelet microsomes and arachidonate were found to significantly inhibit subsequent platelet aggregation. Saturated and mono-unsaturated fatty acids in the same concentrations were without effect. However, in higher concentrations mono-unsaturated fatty acids were found to be inhibitory and stearic acid was found to enhance subsequent platelet aggregation. The inhibition caused by the polyunsaturated fatty acid, linoleate, was shown to be the result of an effect on the production of LASS through an interaction with the platelet enzyme responsible for conversion of arachidonate to LASS. In contrast, stearic acid was found to enhance platelet aggregation by acting on the platelets and not directly on LASS production. The results suggest that small changes in the fatty acid composition of platelet phospholipids could significantly influence platelet reactivity.

  6. 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.

  7. 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.

  8. Acid soluble, pepsin resistant platelet aggregating material

    SciTech Connect

    Schneider, M.D.

    1982-08-31

    Disclosed is an acid soluble, pepsin resistant, platelet aggregating material isolated from equine arterial tissue by extraction with dilute aqueous acid. The method of isolation and use to control bleeding are described. 4 figs.

  9. In vitro model of platelet aggregation in stenotic arteries

    SciTech Connect

    Morley, D.; Santamore, W.P.

    1988-07-01

    Clinical and experimental evidence suggest a strong relationship between arterial stenosis, platelet aggregation, and subsequent thrombus formation. To facilitate the study of platelet accumulation in stenotic arteries, we developed an in vitro preparation. Arterial segments were perfused with whole citrated blood. A stenosis was created by applying an external plastic constrictor to the artery. Platelet accumulation within the stenosis was assessed by scanning electron microscopy and by radioactive counts from Indium-111 labeled platelets. Utilizing this preparation, 30 carotid arterial segments from 10 mongrel dogs were perfused at 100 mmHg for 15 min. In 10 arteries without a stenosis, scanning electron microscopy and radioactive counts demonstrated little platelet accumulation. In contrast, extensive platelet aggregation was observed in 10 arteries with stenoses. Moreover, in 10 stenotic arteries exposed to the thromboxane mimetic, U46619 (Upjohn Diagnostic Group), scanning electron microscopy and radioactive counts demonstrated a significant increase in platelet deposition. Conversely, we demonstrated a dimunition of platelet accumulation in stenosed arterial segments exposed to the prostacyclin analogue platelet inhibitor, Iloprost. The in vitro preparation allows precise control of hemodynamic variables and makes it possible to perform multiple tests on segments of the same vessel from the same animal.

  10. 21 CFR 864.5700 - Automated platelet aggregation system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... addition of an aggregating reagent to a platelet-rich plasma. (b) Classification. Class II (performance... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Automated platelet aggregation system. 864.5700... § 864.5700 Automated platelet aggregation system. (a) Identification. An automated platelet...

  11. 21 CFR 864.5700 - Automated platelet aggregation system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... addition of an aggregating reagent to a platelet-rich plasma. (b) Classification. Class II (performance... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Automated platelet aggregation system. 864.5700... § 864.5700 Automated platelet aggregation system. (a) Identification. An automated platelet...

  12. Analysis of aggregation of platelets in thrombosis

    NASA Astrophysics Data System (ADS)

    Ahuja, Suresh

    Platelets are key players in thrombus formation by first rolling over collagen bound von Willebrand factor followed by formation of a stable interaction with collagen. The first adhered platelets bind additional platelets until the whole injury is sealed off by a platelet aggregate. The coagulation system stabilizes the formed platelet plug by creating a tight fibrin network, and then wound contraction takes place because of morphological changes in platelets. Coagulation takes place by platelet activation and aggregation mainly through fibrinogen polymerization into fibrin fibers. The process includes multiple factors, such as thrombin, plasmin, and local shear-rate which regulate and control the process. Coagulation can be divided into two pathways: the intrinsic pathway and the extrinsic pathway. The intrinsic pathway is initiated by the exposure of a negatively charged. It is able to activate factor XII, using a complex reaction that includes prekallikrein and high-molecular-weight kininogen as cofactors.. Thrombin is the final enzyme that is needed to convert fibrinogen into fibrin. The extrinsic pathway starts with the exposure of tissue factor to the circulating blood, which is the major initiator of coagulation. There are several feedback loops that reinforce the coagulation cascade, resulting in large amounts of thrombin. It is dependent on the presence of pro-coagulant surfaces of cells expressing negatively charged phospholipids--which include phosphatidylserine (PS)--on their outer membrane. PS-bearing surfaces are able to increase the efficiency of the reactions by concentrating and co-localizing coagulation factors.. Aggregation of platelets are analyzed and compared to adhesion of platelet to erythrocyte and to endothelial cells. This abstract is replacing MAR16-2015-020003.

  13. Platelet aggregating material from equine arterial tissue

    SciTech Connect

    Schneider, M.D.

    1983-02-22

    Novel hemostatic agent comprises equine arterial fibrillar collagen in a carrier. The agent is useful for the aggregation of platelets for clinical diagnostic tests and for the clotting of blood, such as for controlling bleeding in warm blooded species. The fibrillar collagen is obtained by extracting homogenized equine arterial tissue with aqueous solutions followed by extensive dialysis. No Drawings

  14. Platelet aggregating material from equine arterial tissue

    DOEpatents

    Schneider, Morris D.

    1983-02-22

    Novel hemostatic agent comprises equine arterial fibrillar collagen in a carrier. The agent is useful for the aggregation of platelets for clinical diagnostic tests and for the clotting of blood, such as for controlling bleeding in warm blooded species. The fibrillar collagen is obtained by extracting homogenized equine arterial tissue with aqueous solutions followed by extensive dialysis.

  15. Platelet aggregation Inhibitors from Hametophagous Animals

    PubMed Central

    Francischetti, Ivo M. B.

    2010-01-01

    Salivary glands from blood-sucking animals (e.g., mosquitoes, bugs, sandflies, fleas, ticks, leeches, hookworms, bats) are a rich source of bioactive molecules that counteract hemostasis in a redundant and synergistic manner. This review discusses recent progress in the identification of salivary inhibitors of platelet aggregation, their molecular characterization, and detailed mechanism of action. Diversity of inhibitors is remarkable, with distinct families of proteins characterized as apyrases that enzymatically degrade ADP or as collagen-binding proteins that prevent its interaction with vWF, or platelet integrin α2β1 or GPVI. Molecules that bind ADP, TXA2, epinephrine, or serotonin with high affinity have also been cloned, expressed, and their structure determined. In addition, a repertoire of antithrombins and an increasingly number of RGD and non-RGD disintegrins targeting platelet αIIbβ3 have been reported. Moreover, metalloproteases with fibrinogen(olytic) activity and PAF phosphorylcholine hydrolase are enzymes that have been recruited to the salivary gland to block platelet aggregation. Platelet inhibitory prostaglandins, lysophosphatydilcholine, adenosine, and nitric oxide (NO)-carrying proteins are other notable examples of molecules from hematophagous salivary secretions (herein named sialogenins) with antihemostatic properties. Sialogenins have been employed as tools in biochemistry and cell biology and also display potential therapeutic applications. PMID:20035779

  16. Platelet aggregation in the formation of tumor metastasis

    PubMed Central

    Tsuruo, Takashi; Fujita, Naoya

    2008-01-01

    Metastasis is the major cause of death from cancer, yet the optimal strategy against it remains uncertain. The pathogenesis of hematogenous metastasis is dynamic and consists of the following steps: 1) detachment of tumor cells from the primary site, 2) invasion into the host’s blood vessels, 3) migration in the host’s blood stream, 4) transport along the circulation, 5) arrest in or adhesion to the capillary in a distant organ, 6) extravasation, and 7) proliferation within the foreign tissues. A key to successful hematogenous metastasis is tumor survival in the bloodstream because most circulating tumor cells are rapidly destroyed by the shear forces or are attacked by the immune system. Less than 0.01% of these cells result in metastasis. Tumor cell–induced platelet aggregation has been reported to facilitate hematogenous metastasis by increasing the arrest of tumor cell emboli in the microcirculation. Platelet aggregation is also believed to protect tumor cells from immunological assault in the circulation. We have identified Aggrus as a platelet–aggregating factor expressed on a number of human cancers. Because hematogenous metastasis is reduced when neutralizing antibodies or eliminating carbohydrates attenuates Aggrus function, Aggrus’s main contribution to hematogenous metastasis of Aggrus–expressing cells, then, is by promoting platelet aggregation. Aggrus could serve as an ideal target for drug development to block metastasis. PMID:18941298

  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. Platelet aggregation associated with ethanol intoxication

    SciTech Connect

    Volk, S.; Walenga, J.; Fareed, J.; Schumacher, H. )

    1989-02-09

    Alcohol is known to produce profound effects on blood; during chronic intoxication, prolongation of bleeding time has been reported. Utilizing human platelet rich plasma, we have studied the effect of alcohol on epinephrine, arachidonic acid and ADP induced aggregation. Control responses were obtained with saline from which the relative inhibition by alcohol was calculated. These studies were carried out at a concentration of 1.25-5.0 mg/ml which represents 0.125-0.5% alcohol blood levels. From 25 normal male and female volunteers, without prior hemostatic defects or drug ingestion, a dose-dependent inhibition by alcohol of all three agonist induced aggregations was noted. Alcohol itself did not produce any aggregation response. These studies demonstrate that alcohol at levels which are reached during intoxication is capable of impairing platelet function. The implication of this finding on the bleeding complications in healthy intoxicated patients may be significant during traumatic events, and individuals taking antiplatelet drugs may present a more serious hemostatic deficit during alcohol intoxication.

  19. 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

  20. 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.

  1. [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.

  2. Effects of hormones on platelet aggregation.

    PubMed

    Farré, Antonio López; Modrego, Javier; Zamorano-León, José J

    2014-04-01

    Platelets and their activation/inhibition mechanisms play a central role in haemostasis. It is well known agonists and antagonists of platelet activation; however, during the last years novel evidences of hormone effects on platelet activation have been reported. Platelet functionality may be modulated by the interaction between different hormones and their platelet receptors, contributing to sex differences in platelet function and even in platelet-mediated vascular damage. It has suggested aspects that apparently are well established should be reviewed. Hormones effects on platelet activity are included among them. This article tries to review knowledge about the involvement of hormones in platelet biology and activity.

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. Acid soluble platelet aggregating material isolated from human umbilical cord

    SciTech Connect

    Schneider, M.D.

    1983-12-27

    An acid soluble, pepsin sensitive platelet aggregating material is isolated from human umbilical cord tissue by extraction with dilute aqueous acid. The method of isolation is disclosed and its use to control bleeding is described. 2 figs.

  10. [Changes of platelet aggregation function of apheresis collected platelets and soluble P-selectin during storage].

    PubMed

    Xie, Zuo-Ting; Yang, Li-Hong; Tao, Zhi-Hua; Wang, Ming-Shan; Hong, Jun-Ying; Zhou, Wu; Chen, Zeng-Qiang; Dai, Mei-Jie

    2008-10-01

    The objective of this study was to explore the changes of aggregation function of apheresis platelets and soluble P-selectin (sP-selectin) during storage. 20 samples of apheresis platelets were collected, and the aggregation function were examined by function test and the level of sP-selectin every day in storage of 5 days. The results showed that the aggregation function of platelets declined obviously during storage, there were significant differences between the first-day group and any of the other groups (p < 0.01). The max platelet aggregation rate was < or = 3% in the fourth-day group; sP-selectin level in plasma increased with prolong of storage time; there were significant differences between the first-day group and any of the other groups (p < 0.05). In conclusion, platelets were activated continuously during storage, while its aggregation function declines significantly. The ability of platelet aggregation to response to ADP loses almost completely since the fourth day during platelet storage. It should be paid more attention to the damage of apheresis collected platelets during storage.

  11. 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.

  12. Lysophosphatidic acids. Influence on platelet aggregation and intracellular calcium flux.

    PubMed Central

    Gerrard, J. M.; Kindom, S. E.; Peterson, D. A.; Peller, J.; Krantz, K. E.; White, J. G.

    1979-01-01

    Decanoyl-, palmitoyl-, and oleoyl-lysophosphatidic acid (LPA) were studied for their effects on platelet aggregation and intracellular calcium flux. Palmitoyl-LPA and oleoyl-LPA both caused a concentration-dependent aggregation of human blood platelets at concentrations of 12--300 microM. Aggregation by adenosine diphosphate (ADP) was enhanced at slightly lower concentrations. First-wave aggregation induced by these LPAs was not blocked by aspirin, indomethacin, or heparin, suggesting similarities to ADP aggregation. However, in washed platelets with a high calcium concentration, no serotonin secretion was observed, even though full aggregation occurred, suggesting that aggregation was not due to released ADP. This concept was supported by studies of platelets deficient in the storage pool of ADP and serotonin, which had a normal first-wave aggregation response to palmitoyl-LPA. Aggregation induced by palmitoyl LPA was inhibited by prostaglandin E1 (PGE1), theophylline, and ethylenediaminotetraacetate (EDTA), though in the presence of EDTA shape change occurred. Aggregation stimulated by palmitoyl-LPA or oleoyl-LPA was characterized by changes in the shape of the platelets with development of pseudopods and centralization of granules closely surrounded by contractile microfilaments and supporting microtubules. The addition of palmitoyl-LPA and oleoyl-LPA, but not decanoyl-LPA, caused the release of calcium from a platelet membrane fraction that contains elements of the intracellular calcium storage system and actively concentrates this cation in the presence of adenosine triphosphate (ATP) and magnesium. It is suggested that LPAs cause aggregation by stimulating the release of calcium intracellularly. Images Figure 1 Figure 2 Figure 3 Figure 4 Text-Figure 6 PMID:112871

  13. 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

  14. 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.

  15. Inhibition of rat platelet aggregation by Urtica dioica leaves extracts.

    PubMed

    El Haouari, Mohammed; Bnouham, Mohamed; Bendahou, Mourad; Aziz, Mohammed; Ziyyat, Abderrahim; Legssyer, Abdelkhaleq; Mekhfi, Hassane

    2006-07-01

    Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was undertaken to investigate the effects of different extracts of Urtica dioica leaves on platelet aggregation. Rat platelets were prepared and incubated in vitro with different concentrations of the tested extracts and aggregation was induced by different agonists including thrombin (0.5 U/mL), ADP (10 microm), epinephrine (100 microm) and collagen (5 mg/mL). The crude aqueous extract inhibited thrombin-induced platelet aggregation in a dose-dependent manner. At 1 mg/mL, the percent inhibition was 17.1 +/- 4.2%. Soxhlet extraction of the plant leaves with different successive solvents showed that the ethyl acetate extract exhibited the most antiaggregant effect with an inhibition of 76.8 +/- 6.1% at 1 mg/mL. Flavonoids isolated from the plant leaves, produced a strong inhibitory effect on thrombin-induced platelet aggregation with an IC(50) of 0.25 +/- 0.05 and 0.40 +/- 0.04 mg/mL for genins and heterosidic flavonoids, respectively. Flavonoids also markedly inhibited platelet aggregation induced by ADP, collagen and epinephrine. It is concluded that Urtica dioica has an antiplatelet action in which flavonoids are mainly implicated. These results support the traditional use of Urtica dioica in the treatment and/or prevention of cardiovascular disease.

  16. 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

  17. 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

  18. Enhancement of Platelet Aggregation by Ursolic Acid and Oleanolic Acid

    PubMed Central

    Kim, Mikyung; Han, Chang-ho; Lee, Moo-Yeol

    2014-01-01

    The pentacyclic triterpenoid ursolic acid (UA) and its isomer oleanolic acid (OA) are ubiquitous in food and plant medicine, and thus are easily exposed to the population through natural contact or intentional use. Although they have diverse health benefits, reported cardiovascular protective activity is contentious. In this study, the effect of UA and OA on platelet aggregation was examined on the basis that alteration of platelet activity is a potential process contributing to cardiovascular events. Treatment of UA enhanced platelet aggregation induced by thrombin or ADP, which was concentration-dependent in a range of 5–50 μM. Quite comparable results were obtained with OA, in which OA-treated platelets also exhibited an exaggerated response to either thrombin or ADP. UA treatment potentiated aggregation of whole blood, while OA failed to increase aggregation by thrombin. UA and OA did not affect plasma coagulation assessed by measuring prothrombin time and activated partial thromboplastin time. These results indicate that both UA and OA are capable of making platelets susceptible to aggregatory stimuli, and platelets rather than clotting factors are the primary target of them in proaggregatory activity. These compounds need to be used with caution, especially in the population with a predisposition to cardiovascular events. PMID:25009707

  19. Development of a method to quantify platelet adhesion and aggregation under static conditions

    PubMed Central

    Baker-Groberg, Sandra M.; Cianchetti, Flor A.; Phillips, Kevin G.; McCarty, Owen J.T.

    2014-01-01

    Platelets are important players in hemostasis and thrombosis. Thus, accurate assessment of platelet function is crucial for identifying platelet function disorders and measuring the efficacy of antiplatelet therapies. We have developed a novel platelet aggregation technique that utilizes the physical parameter of platelet concentration in conjunction with volume and mass measurements to evaluate platelet adhesion and aggregation. Platelet aggregates were formed by incubating purified platelets on fibrinogen- or fibrillar collagen-coated surfaces at platelet concentrations ranging from 20,000 to 500,000 platelets/ L. Platelets formed aggregates under static conditions in a platelet concentration-dependent manner, with significantly greater mean volume and mass at higher platelet concentrations ( 400,000 platelets/ L). We show that a platelet glycoprotein IIb/IIIa inhibitor abrogated platelet-platelet aggregation, which significantly reduced the volume and mass of the platelets on the collagen surface. This static platelet aggregation technique is amenable to standardization and represents a useful tool to investigate the mechanism of platelet activation and aggregation under static conditions. PMID:24883127

  20. Platelets and atherogenesis: Platelet anti-aggregation activity and endothelial protection from tomatoes (Solanum lycopersicum L.)

    PubMed Central

    PALOMO, IVÁN; FUENTES, EDUARDO; PADRÓ, TERESA; BADIMON, LINA

    2012-01-01

    In recent years, it has been shown that platelets are not only involved in the arterial thrombotic process, but also that they play an active role in the inflammatory process of atherogenesis from the beginning. The interaction between platelets and endothelial cells occurs in two manners: activated platelets unite with intact endothelial cells, or platelets in resting adhere to activated endothelium. In this context, inhibition of the platelet function (adhesion/aggregation) could contribute to the prevention of atherothrombosis, the leading cause of cardiovascular morbidity. This can be achieved with antiplatelet agents. However, at the public health level, the level of primary prevention, a healthy diet has also been shown to exert beneficial effects. Among those elements of a healthy diet, the consumption of tomatoes (Solanum lycopersicum L.) stands out for its effect on platelet anti-aggregation activity and endothelial protection, which may be beneficial for cardiovascular health. This article briefly discusses the involvement of platelets in atherogenesis and the possible mechanisms of action provided by tomatoes for platelet anti-aggregation activity and endothelial protection. PMID:22969932

  1. 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

  2. Cardamom extract as inhibitor of human platelet aggregation.

    PubMed

    Suneetha, W Jessie; Krishnakantha, T P

    2005-05-01

    The inhibitory activity of cardamom extract was studied on human platelets. Platelet aggregation and lipid peroxidation were evaluated with platelet rich plasma (PRP) and platelet membranes, respectively, obtained from blood of healthy volunteers. Human platelets were subjected to stimulation with a variety of agonists including ADP (2.5 mM), epinephrine (2.5 mM), collagen (10 mM), calcium ionophore A 23187 (6 microM) and ristocetin (1.25 microg/mL). The IC50 were 0.49, 0.21, 0.55 and 0.59 mg with ADP, epinephrine, collagen and calcium ionophore A 23187, respectively, and no inhibition with ristocetin. The inhibitory effect was dose dependent with concentrations varying between 0.14 and 0.70 mg and time dependent at IC50. Lipid peroxidation induced by iron--ascorbic acid system in platelet membranes was analysed with malondialdehyde (MDA) as an index. An increase in concentration of cardamom has decreased the MDA formation significantly. Hence, it may be said that aqueous extract of cardamom may have component(s), which protect platelets from aggregation and lipid peroxidation.

  3. Sustained increase in platelet aggregation after the cessation of clopidogrel.

    PubMed

    Djukanovic, Nina; Todorovic, Zoran; Zamaklar-Trifunovic, Danijela; Protic, Dragana; Dzudovic, Boris; Ostojic, Miodrag; Obradovic, Slobodan

    2016-02-01

    This study shows that the abrupt cessation of one-year clopidogrel treatment was not associated with thrombotic events in a prospective, multicentre study that enrolled 200 patients subjected to coronary stent implantation and treated with aspirin + clopidogrel 1 year after the stent placement. The aim of the study was to investigate the causes of a sustained increase of platelet aggregability, considering that the values of platelet aggregation stimulated with ADP + PGE1 (ADPHS values) significantly increased 10-90 days after the cessation of clopidogrel. Values of platelet aggregation induced by thrombin receptor activating peptide (TRAP values) and arachidonic acid (ASPI values) were divided into quartiles on the basis of ADPHS values 10 days after stopping clopidogrel (ADPHS10 ). There was a significant difference between TRAP values divided into quartiles according to ADPHS10 , 10, 45 and 90 days after stopping clopidogrel (P < 0.001, all), and ASPI values across the same quartiles 10 and 45 days after the cessation of clopidogrel (P = 0.028 and 0.003). The results of the study indicate that patients with early pronounced rebound phenomena to clopidogrel termination have a long-term (at least 90 days) increased platelet aggregation to other agonists such as thrombin-related activated protein and arachidonic acid, suggesting the complex mutual relationship of various factors/agonists influencing the function of platelets.

  4. Effects of tomato extract on human platelet aggregation in vitro.

    PubMed

    Dutta-Roy, A K; Crosbie, L; Gordon, M J

    2001-06-01

    Among all fruits tested in vitro for their anti-platelet property, tomato had the highest activity followed by grapefruit, melon, and strawberry, whereas pear and apple had little or no activity. Tomato extract (20-50 microl of 100% juice) inhibited both ADP- and collagen-induced aggregation by up to 70% but could not inhibit arachidonic acid-induced platelet aggregation and concomitant thromboxane synthesis under similar experimental conditions. The anti-platelet components (MW <1000 Da) in tomatoes are water soluble, heat stable and are concentrated in the yellow fluid around the seeds. The active fractions were separated using gel filtration and HPLC. The aqueous fraction (110 000 xg supernatant) of tomatoes containing anti-platelet activity was subjected to gel filtration column chromatography (Biogel P2 column). The activity was fractionated into two peaks, peak-3 and peak-4 (major peak). Subsequently, peak-4 was further purified by HPLC using a reversed-phase column. NMR and mass spectroscopy studies indicated that peak F2 (obtained from peak 4) contained adenosine and cytidine. Deamination of peak F2 with adenosine deaminase almost completely abolished its anti-platelet activity, confirming the presence of adenosine in this fraction. In comparison, deamination of peak-4 resulted in only partial loss of inhibitory activity while the activity of peak-3 remained unaffected. These results indicate that tomatoes contain anti-platelet compounds in addition to adenosine. Unlike aspirin, the tomato-derived compounds inhibit thrombin-induced platelet aggregation. All these data indicate that tomato contains very potent anti-platelet components, and consuming tomatoes might be beneficial both as a preventive and therapeutic regime for cardiovascular disease.

  5. New platelet aggregation inhibitors based on pyridazinone moiety.

    PubMed

    Costas, Tamara; Costas-Lago, María Carmen; Vila, Noemí; Besada, Pedro; Cano, Ernesto; Terán, Carmen

    2015-04-13

    New series of pyridazinone derivatives (4, 5 and 6) were synthesized in good yields following a synthetic strategy based on singlet oxygen oxidation of alkyl furans, in which a suitable β(α)-substituted γ-hydroxybutenolide (10 or 11) or a bicyclic lactone (12 or 13) was the key intermediate. The synthesized compounds were tested in vitro as antiplatelet agents and some of them (compounds 4b, 4d and 5b) exhibited potent inhibitory effects on collagen-induced platelet aggregation with IC50 values in the low μM range. Studies performed with the most active compound of these series (4b) demonstrated its lack of activity as inhibitor of platelet aggregation induced by other agonists as thrombin, ionomycin or U-46619 suggesting a selective action on the biochemical mechanisms triggered by collagen in the platelets.

  6. 21 CFR 864.5700 - Automated platelet aggregation system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Automated platelet aggregation system. 864.5700 Section 864.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology...

  7. 21 CFR 864.5700 - Automated platelet aggregation system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Automated platelet aggregation system. 864.5700 Section 864.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology...

  8. 21 CFR 864.5700 - Automated platelet aggregation system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Automated platelet aggregation system. 864.5700 Section 864.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Automated and Semi-Automated Hematology...

  9. Reduced platelet aggregation in a boy with scurvy.

    PubMed

    Dey, F; Möller, A; Kemkes-Matthes, B; Wilbrand, J-F; Krombach, G A; Neubauer, B; Hahn, A

    2012-11-01

    Pediatric scurvy is a rare condition characterized by perifollicular petechiae and bruising, hemorrhagic gingivitis and musculoskeletal symptoms, all assumed to be predominantly related to abnormal collagen structure. We report on a 9-year-old autistic boy with vitamin C deficiency due to a highly limited food range presenting with multiple petechiae, gum bleeding and debilitating bone pain, in whom platelet aggregometry revealed a distinctly reduced thrombocyte aggregation, normalizing after vitamin C supplementation. This observation indicates that platelet dysfunction may additionally contribute to the hemorrhagic diathesis in scurvy, and demonstrates that ascorbic acid deficiency should be considered in children with an otherwise unexplained acquired thrombocytopathy.

  10. Dose response of surfactants to attenuate gas embolism related platelet aggregation

    NASA Astrophysics Data System (ADS)

    Eckmann, David M.; Eckmann, Yonaton Y.; Tomczyk, Nancy

    2014-03-01

    Intravascular gas embolism promotes blood clot formation, cellular activation, and adhesion events, particularly with platelets. Populating the interface with surfactants is a chemical-based intervention to reduce injury from gas embolism. We studied platelet activation and platelet aggregation, prominent adverse responses to blood contact with bubbles. We examined dose-response relationships for two chemically distinct surfactants to attenuate the rise in platelet function stimulated by exposure to microbubbles. Significant reduction in platelet aggregation and platelet activation occurred with increasing concentration of the surfactants, indicating presence of a saturable system. A population balance model for platelet aggregation in the presence of embolism bubbles and surfactants was developed. Monte Carlo simulations for platelet aggregation were performed. Results agree qualitatively with experimental findings. Surfactant dose-dependent reductions in platelet activation and aggregation indicate inhibition of the gas/liquid interface's ability to stimulate cellular activation mechanically.

  11. Substituted pyrazolylhydrazones: a new class of platelet aggregation inhibitors.

    PubMed

    Silveira, I A; Paulo, L G; Miranda, A L; Rocha, S O; Freitas, A C; Barreiro, E J

    1991-01-01

    A series of 5-pyrazolylhydrazone derivatives (I) were designed to be mixed hybrid isosteres of both BW-755C and CBS-1108 which belong to the class of dual cyclooxygenase and 5-lipoxygenase inhibitors. Pharmacological evaluation of some members of this series (Ia, 1-formyl-3,4-methylenedioxy-6-nitrobenzene-5-(1-phenyl-3-methyl-4-nit ropyrazolyl)hydrazone; Ib, 2-formylfurane-5-(1-phenyl-3-methyl-4-nitropyrazolyl)hydr azo ne;Ic, (E)-2-(formylethenylfurane)-5-(1-phenyl-3-methyl-4-nitropyrazol yl)hydrazone showed that they inhibit the in vitro platelet aggregation of citrated platelet-rich rabbit plasma induced by ADP (5 microM), collagen (5 micrograms/ml) and arachidonic acid (100 microM). Compounds Ia and Ic at 100 microM concentration showed 49% and 58% inhibition, respectively, of ADP-induced aggregation. In the arachidonic acid-induced aggregation, compounds Ia and Ib at 100 microM concentration fully inhibited platelet aggregation. All compounds significantly inhibited the collagen-induced aggregation. In contrast, indomethacin (10 microM) showed 100% and 85% aggregation inhibition against arachidonic acid and collagen, respectively, and was inactive in the ADP-induced aggregation test. These results suggest that the structure-activity relationship in this series of compounds is dependent on the hydrazone moiety at position 5 of the pyrazole ring and on the distance between the aryl ring and the pyrazole ring and that the 2-furyl ring is at the optimal distance for the maximal activity.

  12. 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

  13. Effects of argon laser on in vitro aggregation of platelets in platelet rich plasma and whole blood

    SciTech Connect

    Doerger, P.T.; Glueck, H.I.; McGill, M.

    1988-06-01

    The effects of an Argon laser on platelet aggregation were studied, since platelets may be exposed to laser energy when used intravascularly. Various preparations of platelets in platelet rich plasma (PRP) and whole blood, with or without aspirin, were tested with the aggregating agents ADP, collagen, thrombin, and epinephrine. Simultaneous release of ATP was also measured in PRP. At relatively low levels of irradiation, platelet aggregation was potentiated. Enhancement was evidenced by an increase in percent aggregation, earlier onset of the reaction, and reduction in the amount of aggregating agent required. In PRP, the mechanism of laser potentiation appeared to be the release of endogenous ATP from platelets. At relatively high levels of irradiation, platelets were destroyed and aggregation abolished. In whole blood, the mechanism was somewhat more complicated since release of ATP occurred from RBCs as well as platelets. Spontaneous aggregation following laser treatment occurred in isolated instances in PRP and in every trial in whole blood preparations. Aspirin ingestion inhibited the laser's effects in PRP but not in whole blood. These results may have important clinical implications for laser angioplasty, and the potentiated aggregation response may prove useful in laboratory studies of platelet function.

  14. The automation of routine light transmission platelet aggregation

    PubMed Central

    Lawrie, A S; Kobayashi, K; Lane, P J; Mackie, I J; Machin, S J

    2014-01-01

    Introduction The investigation of platelet function by aggregometry requires specialist equipment and is labour intensive. We have developed an automated platelet aggregation method on a routine coagulation analyser. Methods We used a CS-2000i (Sysmex) with prototype software to perform aggregation in platelet-rich plasma (PRP), using the following agonists: ADP (0.5–10 μm), epinephrine (0.5–10 μm), collagen (0.5–10 mg/μL), ristocetin (0.75–1.25 mg/mL) and arachidonic acid (0.12–1.0 mm). Platelet agonists were from Hyphen Biomed, and an AggRAM aggregometer (Helena Biosciences) was used as the reference instrument. Results CS-2000i reaction cuvette stirrer speed was found to influence reaction sensitivity and was optimized to 800 rpm. There were no clinically significant changes in aggregation response when the PRP platelet count was 150–480 x 109/L, but below this there were changes in the maximum amplitude (MA) and slope (rate). Dose response with each of the agonists was comparable between CS-2000i and an AggRAM aggregometer and normal subjects receiving antiplatelet drugs. Aggregation imprecision was similar on both the CS-2000i and AggRAM systems, with a cv for 2–5 μm ADP MA and slope varying between 3–12%. Conclusion Our preliminary studies indicated that optimal sensitivity using the CS-2000i was obtained with a reaction cuvette stirrer speed of 800 rpm and a PRP platelet count of 200–300 x 109/L; aggregation with a PRP count <100 x 109/L showed poor sensitivity. Imprecision and detection of antiplatelet drug effects was similar between the CS-2000i and AggRAM. These data demonstrate that CS-2000i is comparable to a stand-alone aggregometer, although CS-2000i has the advantages of walk-away technology and also required a smaller sample volume than the AggRAM (44% less). PMID:24237750

  15. Platelet anti-aggregation activities of compounds from Cinnamomum cassia.

    PubMed

    Kim, Sun Young; Koo, Yean Kyoung; Koo, Ja Yong; Ngoc, Tran Minh; Kang, Sam Sik; Bae, KiHwan; Kim, Yeong Sik; Yun-Choi, Hye Sook

    2010-10-01

    Cinnamomum cassia is a well-known traditional medicine for improvement of blood circulation. An extract of this plant showed both platelet anti-aggregation and blood anti-coagulation effects in preliminary testing. Among the 13 compounds obtained from this plant, eugenol (2), amygdalactone (4), cinnamic alcohol (5), 2-hydroxycinnamaldehyde (7), 2-methoxycinnamaldehyde (8), and coniferaldehyde (9) showed 1.5-73-fold greater inhibitory effects than acetylsalicylic acid (ASA) on arachidonic acid (AA)-induced aggregation (50% inhibitory concentration [IC₅₀] = 3.8, 5.16, 31.2, 40.0, 16.9, and 0.82 μM, respectively, vs. 60.3 μM) and 6.3-730-fold stronger effect than ASA on U46619 (a thromboxane A₂ mimic)-induced aggregation (IC₅₀ = 3.51, 33.9, 31.0, 51.3, 14.6, and 0.44 μM, respectively, vs. 321 μM). The other compounds, coumarin (3), cinnamaldehyde (6), cinnamic acid (10), icariside DC (11), and dihydrocinnacasside (12), also inhibited (2.5 to four times greater than ASA) U46619-induced aggregation. In addition, compounds 2, 4, 5, 6, 7, 8, and 9 were 1.3-87 times more effective than ASA against epinephrine-induced aggregation (IC₅₀ = 1.86, 1.10, 37.7, 25.0, 16.8, 15.3, and 0.57 μM, respectively, vs. 50.0 μM). However, the 13 compounds were only very mildly effective against blood coagulation, if at all. In conclusion, compounds 2, 4, 8, and 9 showed stronger inhibitory potencies than others on AA-, U46619-, and epinephrine-induced platelet aggregation. Eugenol (2) and coniferaldehyde (9) were the two of the most active anti-platelet constituents of C. cassia.

  16. Platelet anti-aggregant property of some Moroccan medicinal plants.

    PubMed

    Mekhfi, Hassane; El Haouari, Mohammed; Legssyer, Abdelkhaleq; Bnouham, Mohammed; Aziz, Mohammed; Atmani, Fouad; Remmal, Adnane; Ziyyat, Abderrahim

    2004-10-01

    It is known that blood platelets may present some dysfunction linked to cardiovascular pathologies such as arterial hypertension. The aim of this work is to examine the in vitro anti-aggregant effect of five medicinal plants among which three were reported as antihypertensive in oriental Morocco: Arbutus unedo (Ericaceae), Urtica dioïca (Urticaceae), and Petroselinum crispum (Apiaceae). The two other plants were Cistus ladaniferus (Cistaceae) and Equisetum arvense (Equisetaceae). The results obtained showed that all extracts produced a dose-dependent inhibition of thrombin and ADP-induced aggregation. The calculated IC50 (half-maximal inhibition of thrombin and ADP-induced aggregation) was found to be identical in all plant extracts while Urtica dioïca had a higher IC50 value. The effect of plants could be related in part to the polyphenolic compounds present in their extracts suggesting their involvement in the treatment or prevention of platelet aggregation complications linked to cardiovascular diseases. Phytochemical separation must be carried out to identify the active principles responsible for the anti-aggregant effect and elucidate their mechanisms of action.

  17. Abnormal platelet aggregation in patients with Raynaud's phenomenon.

    PubMed Central

    Biondi, M L; Marasini, B

    1989-01-01

    Platelet aggregation in vitro to several aggregating agents (serotonin (5-HT), adenosine diphosphate, adrenaline and collagen) was studied in 16 patients with primary and secondary Raynaud's phenomenon and compared with that in 13 normal volunteers. Platelets from patients with Raynaud's phenomenon had significantly greater responses to all the 5-HT concentrations tested (p less than 0.001 for 10 microM; p less than 0.01 for 1 microM; p less than 0.05 for 0.1 microM; p less than 0.02 for 0.025 microM) and to low doses of adenosine diphosphate (p less than 0.01 for 1 microM; p less than 0.02 for 0.5 microM) but normal responses to collagen, adrenaline, and high doses of adenosine diphosphate. Patients with secondary Raynaud's phenomenon were significantly more hypersensitive to 0.5 microM adenosine diphosphate than patients with primary Raynaud's phenomenon. In patients with secondary Raynaud's phenomenon there was a significant correlation between the extent of 5-HT aggregation and the duration of the disease. The finding that platelets from patients with Raynaud's phenomenon have enhanced responses to 5-HT and adenosine diphosphate, but normal responses to adrenaline and collagen, is consistent with a role for 5-HT in this disease. PMID:2760232

  18. The effect of urethane and thiopental sodium on platelet aggregation in vitro and in vivo.

    PubMed

    Evangelista, S; Abelli, L; Maggi, C A; Meli, A

    1984-09-01

    The potential in vitro (heparinized or citrated PRP) and in vivo effects of urethane and thiopental sodium on arachidonic acid, collagen, or ADP-induced rat platelet aggregation has been investigated. Both anesthetics antagonized platelet aggregation in vitro at concentrations higher than those found in plasma during anesthesia. Neither anesthetic altered the piastrinopenia induced by intravenous administration of these aggregating agents. These findings suggest that both anesthetics are suitable for in vivo platelet aggregation studies.

  19. Quantitative analysis of platelets aggregates in 3D by digital holographic microscopy

    PubMed Central

    Boudejltia, Karim Zouaoui; Ribeiro de Sousa, Daniel; Uzureau, Pierrick; Yourassowsky, Catherine; Perez-Morga, David; Courbebaisse, Guy; Chopard, Bastien; Dubois, Frank

    2015-01-01

    Platelet spreading and retraction play a pivotal role in the platelet plugging and the thrombus formation. In routine laboratory, platelet function tests include exhaustive information about the role of the different receptors present at the platelet surface without information on the 3D structure of platelet aggregates. In this work, we develop, a method in Digital Holographic Microscopy (DHM) to characterize the platelet and aggregate 3D shapes using the quantitative phase contrast imaging. This novel method is suited to the study of platelets physiology in clinical practice as well as the development of new drugs. PMID:26417523

  20. In vitro effects of ethanol on the pathways of platelet aggregation

    SciTech Connect

    Rand, M.L.; Kinlough-Rathbone, R.L.; Packham, M.A.; Mustard, J.F.

    1986-03-01

    Ethanol is reported to inhibit platelet aggregation in vivo and in vitro, but the mechanisms of its action on stimulus-response coupling in platelets is unknown. Platelet aggregation to thrombin occurs through at least three pathways: released ADP; thromboxane A/sub 2/ (TXA/sub 2/); and a third pathway(s). Aggregation of rabbit platelets in citrated platelet-rich plasma (PRP) or washed suspensions to ADP (0.5-10 ..mu..M) was not affected by ethanol, at concentrations up to 5 mg/ml (lethal). Primary ADP-induced (5 ..mu..M) aggregation of human platelets in PRP was also unaffected by ethanol, but secondary aggregation and release of /sup 14/C-serotonin, due to TXA/sub 2/ formation, was inhibited by ethanol (2 and 4 mg/ml). Since arachidonate (AA)-induced (25-250 ..mu..M) aggregation and release by washed rabbit platelets was unaltered by ethanol, it may inhibit mobilization of AA from platelet membrane phospholipids. Ethanol (2-4 mg/ml) inhibited rabbit platelet aggregation and release to low concentrations of thrombin (< 10 mU/ml) or collagen, and also inhibited aggregation and release of aspirin-treated (500 ..mu.. M) rabbit platelets (that cannot form TXA/sub 2/) to low concentrations of thrombin (< 10 mU/ml). Thus, ethanol does not inhibit the mobilization of AA, and partially inhibits the third pathway(s) of platelet aggregation.

  1. Engineering Factor Xa Inhibitor with Multiple Platelet-Binding Sites Facilitates its Platelet Targeting

    NASA Astrophysics Data System (ADS)

    Zhu, Yuanjun; Li, Ruyi; Lin, Yuan; Shui, Mengyang; Liu, Xiaoyan; Chen, Huan; Wang, Yinye

    2016-07-01

    Targeted delivery of antithrombotic drugs centralizes the effects in the thrombosis site and reduces the hemorrhage side effects in uninjured vessels. We have recently reported that the platelet-targeting factor Xa (FXa) inhibitors, constructed by engineering one Arg-Gly-Asp (RGD) motif into Ancylostoma caninum anticoagulant peptide 5 (AcAP5), can reduce the risk of systemic bleeding than non-targeted AcAP5 in mouse arterial injury model. Increasing the number of platelet-binding sites of FXa inhibitors may facilitate their adhesion to activated platelets, and further lower the bleeding risks. For this purpose, we introduced three RGD motifs into AcAP5 to generate a variant NR4 containing three platelet-binding sites. NR4 reserved its inherent anti-FXa activity. Protein-protein docking showed that all three RGD motifs were capable of binding to platelet receptor αIIbβ3. Molecular dynamics simulation demonstrated that NR4 has more opportunities to interact with αIIbβ3 than single-RGD-containing NR3. Flow cytometry analysis and rat arterial thrombosis model further confirmed that NR4 possesses enhanced platelet targeting activity. Moreover, NR4-treated mice showed a trend toward less tail bleeding time than NR3-treated mice in carotid artery endothelium injury model. Therefore, our data suggest that engineering multiple binding sites in one recombinant protein is a useful tool to improve its platelet-targeting efficiency.

  2. New pyrazolylhydrazone derivatives as inhibitors of platelet aggregation.

    PubMed

    da Silveira, I A; Paulo, L G; de Miranda, A L; Rocha, S O; Freitas, A C; Barreiro, E J

    1993-07-01

    A series of 5-pyrazolylhydrazone derivatives was designed to be mixed hybrid isosteres of both BW755C and CBS-1108, which belong to the class of dual cyclo-oxygenase and 5-lipoxygenase inhibitors. Some derivatives of this series inhibit the in-vitro platelet aggregation of citrated platelet-rich rabbit plasma induced by ADP (5 microM), collagen (5 micrograms mL-1) and arachidonic acid (100 microM). The structure-activity relationships of this class of compounds were determined from these results. When ADP is used as the aggregation inducer, the presence of free oxygenated substituents at the p-position in the phenyl subunit of the hydrazone moiety favours inhibitory activity; p-methoxyformylbenzene-5-(1-phenyl-3-methyl-4-nitropyrazolyl )hydrazone (100 microM), which has a methoxy group at this position was the most active with 62.8% inhibition of aggregation. In contrast, substitution in the aryl ring does not affect the aggregation induced by collagen, whereas the non-substituted compound, formylbenzene-5-(1-phenyl-3-methyl-4-nitropyrazolyl)hydra zon e, showed similar activity to those of substituted derivatives. In the arachidonic acid assays, the presence of an aryl ring linked to the hydrazone moiety, with an adequate electronic density at the ring due to the nature of its substituents, is an important structural requirement for inhibitory activity.

  3. 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.

  4. Platelets aggregation in pathological conditions: role of local shear rates and platelet activation delay time.

    NASA Astrophysics Data System (ADS)

    Li, He; Zarif Khalili Yazdani, Alireza; Karniadakis, George

    2015-11-01

    Platelets play an essential role in the initiation and formation of a thrombus, however their detailed motion in blood vessels with complex geometries, such as in the aneurysmal vessel or stenotic vessel in atherosclerosis, has not been studied systematically. Here, we perform spectral element simulations (NEKTAR code) to obtain the 3D flow field in blood vessel with cavities, and we apply the force coupling method (FCM) to simulate the motion of platelets in blood flow. Specifically, simulations of platelets are performed in a 0.25 mm diameter circular blood vessel with 1 mm length. Corresponding coarse-grained molecular dynamics simulations are employed to provide input to the NEKTAR-FCM code. Simulations are conducted at several different Reynolds numbers (Re). An ellipsoid-shaped cavity is selected to intersect with the middle part of the circular vessel to represent the aneurysmal part of the blood vessel. Based on the simulation results, we quantify how the platelets motion and aggregation in the blood vessel cavities depend on Re, platelet activation delay time, and the geometry of the cavities.

  5. [Effect of magnesium, acetylsalicilic acid and emoxypine on aggregation of platelets].

    PubMed

    Loznikova, S Zh; Sukhodola, A A; Shcharbina, N Iu; Shcharbin, D G

    2014-01-01

    The thrombin-induced platelet aggregation was studied in the absence and presence of magnesium sulfate, acetylsalicylic acid and emoxypine. It was found that all the preparations studied were able separately to decrease platelet aggregation. In contrast, their joint action was not able to affect the aggregation of platelets. The data obtained can be used to choose the treatment strategy for patients with ischemic stroke.

  6. Effect of the Garlic Pill in comparison with Plavix on Platelet Aggregation and Bleeding Time

    PubMed Central

    Fakhar, H; Hashemi Tayer, A

    2012-01-01

    Introduction Platelet aggregation plays a significant role in the etiology of cardiovascular diseases. Therefore, treatments to inhibit platelet aggregation can reduce the risk of coronary thrombosis. Several studies indicated that garlic can inhibit platelet aggregation. This study aimed to determine the effect of garlic in comparison with Plavix on platelet aggregation. Materials and Methods In this randomized clinical trial, platelet aggregation and bleeding time was obtained from 36 healthy volunteers. Volunteers were randomly divided into 4 groups. The first, second and third groups respectively received 600, 1200 and 2400 mg garlic and the fourth group received 75 mg Plavix for three weeks. Afterwards, platelet aggregation and bleeding time were both evaluated and the results before and after the study were compared. Data were analyzed using SPSS software version 16. Results Platelet aggregation induced by adenosine diphosphate and arachidonic acid agonists decreased in the groups that used 1200 or 2400 mg garlic. This difference was statistically significant (p<0.05). As compared to the other groups, the bleeding time also increased in those received 2400 mg garlic pill. Conclusion Since garlic can inhibit platelet aggregation, it is suggested to use it as a supplementary treatment to reduce platelet aggregation is highly recommended. PMID:24575255

  7. Imperanene, a novel phenolic compound with platelet aggregation inhibitory activity from Imperata cylindrica.

    PubMed

    Matsunaga, K; Shibuya, M; Ohizumi, Y

    1995-01-01

    Imperanene, a novel phenolic compound [1] has been isolated from Imperata cylindrica. Its structure was elucidated by spectroscopic evidence. Imperanene showed platelet aggregation inhibitory activity.

  8. Platelet 5-hydroxytryptamine release and aggregation promoted by cotton bracts tannin.

    PubMed

    Rohrbach, M S; Rolstad, R A; Tracy, P B; Russell, J A

    1984-01-01

    The effect of aqueous extracts of cotton bract (CBE) on platelet secretion and aggregation was examined by using washed bovine and human platelets. The CBE promoted the release of 75% to 90% of the 5-hydroxytryptamine (5-HT) stored in both human and bovine platelets in a dose-dependent manner. This release reaction occurred without the lysis of the platelets and was not inhibited by indomethacin, 2-deoxyglucose, or KCN. Fractionation of the CBE indicated that the platelet secretagogue present in the CBE was the condensed polyphenol, tannin. In addition to promoting the secretion of 5-HT, tannin also aggregated the platelets in a dose-dependent manner. We conclude that the secretion of platelet 5-HT and the aggregation of platelets by tannin could potentially contribute to the pulmonary symptoms associated with byssinosis.

  9. L-4F Alters Hyperlipidemic (but not Normal) Mouse Plasma to Reduce Platelet Aggregation

    PubMed Central

    Buga, Georgette M.; Navab, Mohamad; Imaizumi, Satoshi; Reddy, Srinivasa T.; Yekta, Babak; Hough, Greg; Chanslor, Shawn; Anantharamaiah, G.M.; Fogelman, Alan M.

    2010-01-01

    Objective Hyperlipidemia is associated with platelet hyper-reactivity. We hypothesized that L-4F, an apoA-I mimetic peptide, would inhibit platelet aggregation in hyperlipidemic mice. Methods and Results Injecting L-4F into apoE null and LDL receptor null mice resulted in a significant reduction in platelet aggregation in response to agonists but there was no reduction in platelet aggregation after injection of L-4F into wild-type (WT) mice. Consistent with these results, injection of L-4F into apoE null mice prolonged bleeding time but not in WT mice. Incubating L-4F in vitro with apoE null platelet rich plasma also resulted in decreased platelet aggregation. However, incubating washed platelets from either apoE null or WT mice with L-4F did not alter aggregation. Compared to wild-type mice, unstimulated platelets from apoE null mice contained significantly more 12-HETE, thromboxane A2 (TXA2), prostaglandins D2 (PGD2) and E2 (PGE2). In response to agonists, platelets from L-4F treated apoE null mice formed significantly less TXA2, PGD2 PGE2, and 12-HETE. Conclusions By binding plasma oxidized lipids that cause platelet hyper-reactivity in hyperlipidemic mice, L-4F decreases platelet aggregation. PMID:19965777

  10. 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.

  11. 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

  12. In vitro effects of mercury on platelet aggregation, thromboxane and vascular prostacyclin production.

    PubMed

    Caprino, L; Togna, A R; Cebo, B; Dolci, N; Togna, G

    1983-01-01

    Mercuric chloride [25-50 micrograms/ml platelet-rich plasma (PRP)] lowers the threshold concentration of arachidonic acid (AA) required for triggering rabbit platelet aggregation and causes a marked increase of thromboxane production. The metal, added as HgCl2, does not modify (50 micrograms/ml PRP) or block (100 micrograms/ml PRP) the platelet aggregation wave induced by a normal aggregating dose of AA. Whether or not AA-induced platelet aggregation takes place, a large increase in thromboxane production is observed. Methyl mercury, assayed as reference drug, induces platelet aggregation and a significant increase of thromboxane levels. Finally, HgCl2 and methyl mercury, in a concentration range of 0.125-0.5 micrograms/microliters in the incubation liquid, induce an increased prostacyclin release from rat aortic tissue.

  13. [Mechanism of action of biogenic chloramines and hypochlorite on initial aggregation of blood platelets].

    PubMed

    Murina, M A; Savel'eva, E L; Roshchupkin, D I

    2006-01-01

    The antiaggregant action of two reactive oxidants N,N-dichlorotaurine (chloramine of biogenic type) and sodium hypochlorite on the initial ADP-induced aggregation of rabbit blood platelets has been studied. Platelet aggregation in the reconstructed platelet-rich plasma (PRP) was measured by the nephelometric method, and the aggregation index was an increase in the intensity of small-angle light scattering. The introduction of chloramine at comparatively small concentrations (no greater than 1 mM active chlorine) directly into the reconstructed platelet-rich plasma induces the suppression of the initial aggregation (formation of small aggregates) several times stronger than in the case of its preliminary incubation with plasma alone. This suggests that N,N-dichlorotaurine exerts its antiaggeregant action on the platelet-rich plasma by direct interaction with cells. The effects of the inhibition of platelet aggregation in two variants of introduction of high concentrations of N,N-dichlorotaurine do not significantly differ. In this case a great amount of residual chloramine remains in the plasma, which just induces the suppression of platelet aggregation during subsequent reconstruction of the platelet-rich plasma. Similar data have been obtained in the study of the antiaggregant action of hypochlorite. N,N-Dichlorotaurine and hypochlorite at final concentrations of 0.2-0.3 and 0.15 mM, respectively, inhibit strongly the initial aggregation of isolated platelets (approximately 2 x 10(8) cells in 1 ml) preliminarily activated for 1.5 min by the addition of 100-500 nM ADP. However, the antiaggregants show a more profound suppression of aggregation of unstimulated platelets. The antiaggregant effects of N,N-dichlorotaurine and hypochlorite are probably due to the oxidative modification of sulfur-containing groups in platelet plasmatic membrane.

  14. Spice active principles as the inhibitors of human platelet aggregation and thromboxane biosynthesis.

    PubMed

    Raghavendra, R H; Naidu, K Akhilender

    2009-07-01

    Spice active principles are reported to have anti-diabetic, anti-hypercholesterolemic, antilithogenic, anti-inflammatory, anti-microbial and anti-cancer properties. In our previous report we have shown that spices and their active principles inhibit 5-lipoxygenase and also formation of leukotriene C4. In this study, we report the modulatory effect of spice active principles viz., eugenol, capsaicin, piperine, quercetin, curcumin, cinnamaldehyde and allyl sulphide on in vitro human platelet aggregation. We have demonstrated that spice active principles inhibit platelet aggregation induced by different agonists, namely ADP (50microM), collagen (500microg/ml), arachidonic acid (AA) (1.0mM) and calcium ionophore A-23187 (20microM). Spice active principles showed preferential inhibition of arachidonic acid-induced platelet aggregation compared to other agonists. Among the spice active principles tested, eugenol and capsaicin are found to be most potent inhibitors of AA-induced platelet aggregation with IC50 values of 0.5 and 14.6microM, respectively. The order of potency of spice principles in inhibiting AA-induced platelet aggregation is eugenol>capsaicin>curcumin>cinnamaldehyde>piperine>allyl sulphide>quercetin. Eugenol is found to be 29-fold more potent than aspirin in inhibiting AA-induced human platelet aggregation. Eugenol and capsaicin inhibited thromboxane B2 (TXB2) formation in platelets in a dose-dependent manner challenged with AA apparently by the inhibition of the cyclooxygenase (COX-1). Eugenol-mediated inhibition of platelet aggregation is further confirmed by dose-dependent decrease in malondialdehyde (MDA) in platelets. Further, eugenol and capsaicin inhibited platelet aggregation induced by agonists-collagen, ADP and calcium ionophore but to a lesser degree compared to AA. These results clearly suggest that spice principles have beneficial effects in modulating human platelet aggregation.

  15. Inhalation of Whole Diesel Exhaust but not Gas-Phase Components Affects In Vitro Platelet Aggregation in Hypertensive Rats

    EPA Science Inventory

    Rationale: Intravascular thrombosis and platelet aggregation are enhanced following exposure to diesel exhaust (DE) and other respirable particulate matter; however, the roles of endothelial and circulating mediators on platelet aggregation remain unclear. We hypothesized that ad...

  16. Parsley extract inhibits in vitro and ex vivo platelet aggregation and prolongs bleeding time in rats.

    PubMed

    Gadi, Dounia; Bnouham, Mohamed; Aziz, Mohammed; Ziyyat, Abderrahim; Legssyer, Abdelkhaleq; Legrand, Chantal; Lafeve, Françoise Fauvel; Mekhfi, Hassane

    2009-08-17

    Many cardiovascular diseases are associated with an increase in blood platelet activity. In Morocco, parsley (Petroselinum crispum, Apiaceae) is one of the medicinal herbs used to treat cardiovascular diseases such as arterial hypertension. In this study, crude aqueous extract (CAE) of parsley was evaluated for its anti-platelet activity in experimental animals on platelet aggregation in vitro and ex vivo; and on bleeding time in vivo. The in vitro aggregation was monitored after pre-incubation of platelets with CAE. The bleeding time and ex vivo aggregation were performed after oral treatment. CAE inhibited dose dependently platelet aggregation in vitro induced by thrombin, ADP, collagen and epinephrine. The oral administration of CAE (3g/kg) inhibited significantly (p<0.001) platelet aggregation ex vivo and prolonged bleeding time (p<0.001) without changes in the platelet amount. The prolongation of bleeding time by CAE may be attributed to the observed inhibition of platelet aggregation. These effects could be related in part to the polyphenolic compounds present in the extract. These results support the hypothesis that the dietary intake of parsley may be benefit in the normalization of platelet hyperactivation, in the nutritional prevention of cardiovascular diseases and are potentially interesting in the development of new prevention strategies.

  17. Effects of acute and chronic psychological stress on platelet aggregation in mice.

    PubMed

    Matsuhisa, Fumikazu; Kitamura, Nobuo; Satoh, Eiki

    2014-03-01

    Although psychological stress has long been known to alter cardiovascular function, there have been few studies on the effect of psychological stress on platelets, which play a pivotal role in cardiovascular disease. In the present study, we investigated the effects of acute and chronic psychological stress on the aggregation of platelets and platelet cytosolic free calcium concentration ([Ca(2+)]i). Mice were subjected to both transportation stress (exposure to novel environment, psychological stress) and restraint stress (psychological stress) for 2 h (acute stress) or 3 weeks (2 h/day) (chronic stress). In addition, adrenalectomized mice were subjected to similar chronic stress (both transportation and restraint stress for 3 weeks). The aggregation of platelets from mice and [Ca(2+)]i was determined by light transmission assay and fura-2 fluorescence assay, respectively. Although acute stress had no effect on agonist-induced platelet aggregation, chronic stress enhanced the ability of the platelet agonists thrombin and ADP to stimulate platelet aggregation. However, chronic stress failed to enhance agonist-induced increase in [Ca(2+)]i. Adrenalectomy blocked chronic stress-induced enhancement of platelet aggregation. These results suggest that chronic, but not acute, psychological stress enhances agonist-stimulated platelet aggregation independently of [Ca(2+)]i increase, and the enhancement may be mediated by stress hormones secreted from the adrenal glands.

  18. [Effect of dauricine on rat and human platelet aggregation and metabolism of arachidonic acid in washed rat platelets].

    PubMed

    Tong, L; Yue, T L

    1989-01-01

    Dauricine (Dau), an isoquinoline alkaloid extracted from the roots of Menispermum dauricum D. C. and used as an antiarrhythmic agent in China recently, was shown to inhibit rat platelet aggregation induced by arachidonic acid (AA) and ADP, as well as human platelet aggregation induced by AA, ADP and adrenaline (Adr) in vitro in a dose-dependent manner. The concentration of Dau required for 50% inhibition (IC50) of rat platelet aggregation induced by AA and ADP was 26 and 37 mumol/L, respectively. For human platelet aggregation induced by AA, ADP and Adr the IC50 of Dau was found to be 39, 55 and 43 mumol/L, respectively. Dau inhibited the cyclooxygenase pathway metabolites of AA (TXB2 and HHT) in washed intact rat platelets. The production of TXB2 and HHT was reduced by 26% and 19%, respectively, when the Dau concentration was 50 mumol/L and by 46 and 45%, respectively, when the concentration of Dau was 100 mumol/L. The formation of 12-HETE was also inhibited at 100 mumol/L of Dau. The inhibitory effect of Dau on AA metabolism may be one of the mechanisms related to its inhibition of platelet aggregation.

  19. COX, LOX and platelet aggregation inhibitory properties of Lauraceae neolignans.

    PubMed

    Coy, Ericsson David; Cuca, Luis Enrique; Sefkow, Michael

    2009-12-15

    The anti-inflammatory potential of 26 neolignans (14 of the bicyclooctane-type and 12 of the benzofuran-type), isolated from three Lauraceae species (Pleurothyrium cinereum, Ocotea macrophylla and Nectandra amazonum), was evaluated in vitro through inhibition of COX-1, COX-2, 5-LOX and agonist-induced aggregation of rabbit platelets. Benzofuran neolignans were found to be selective COX-2 inhibitors, whereas bicyclooctane neolignans inhibit selectively the PAF-action as well as COX-1 and 5-LOX. The neolignan 9-nor-7,8-dehydro-isolicarin B 15 and cinerin C 7 were found to be the most potent COX-2 inhibitor and PAF-antagonist, respectively. Nectamazin C 10 exhibited dual 5-LOX/COX-2 inhibition.

  20. Role of red cells in preventing the growth of platelet aggregation.

    PubMed

    Machi, J; Sigel, B; Ramos, J R; Justin, J R; Feinberg, H; LeBreton, G C; Robertson, A L

    1984-10-01

    Using high-resolution real-time two-dimensional ultrasound, we have investigated the role of red cells in the growth of already established platelet aggregates under controlled flow conditions. Platelet rich plasma (PRP) was circulated in vitro in horizontally and vertically arranged tubing at mean shear rate ranging from 60 to 0 sec-1, and adenosine diphosphate (ADP) was used to induce platelet aggregation. ADP-induced platelet aggregates grew in size and tended to sediment as shear rate decreased, in particular, below 10 sec-1. At 0 sec-1 (stasis), large clusters of platelet aggregates formed. The addition of washed red cells to produce a hematocrit of only 2% significantly interfered with the growth and sedimentation of platelet aggregates as shear rate was reduced. Formaldehyde-hardened erythrocytes had a similar effect in preventing the growth of platelet aggregates, suggesting that mechanical collision of red cells with platelet aggregates may be the cause of growth inhibition. Therefore, the thrombotic process may be enhanced in red cell poor zones in circulation resulting from flow disturbances associated with vascular stenosis or within artificial organs and extracorporeal systems. The present study also suggested that red cell free PRP should be carefully administered therapeutically.

  1. 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

  2. Effect of coffee drinking on platelets: inhibition of aggregation and phenols incorporation.

    PubMed

    Natella, F; Nardini, M; Belelli, F; Pignatelli, P; Di Santo, S; Ghiselli, A; Violi, F; Scaccini, C

    2008-12-01

    Epidemiological studies indicate a J-shaped relationship linking coffee consumption and cardiovascular risk, suggesting that moderate coffee consumption can be beneficial. Platelet aggregation is of critical importance in thrombotic events, and platelets play a major role in the aetiology of several CVD. The aim of this study was to evaluate the effect of coffee drinking on platelet aggregation ex vivo, using caffeine as control. A crossover study was performed on ten healthy subjects. In two different sessions, subjects drank 200 ml coffee, containing 180 mg caffeine, or a capsule of caffeine (180 mg) with 200 ml water. Platelets were separated from plasma at baseline and 30 and 60 min after coffee drinking. Platelet aggregation was induced with three different agonists: collagen, arachidonic acid and ADP. Coffee drinking inhibited collagen (P < 0.05 from baseline at time 30 min) and arachidonic acid (P < 0.05 from baseline at time 60 min) induced platelet aggregation. Caffeine intake did not affect platelet aggregation induced by the three agonists. Coffee consumption induced a significant increase of platelet phenolic acids (likely present as glucuronate and sulphate derivatives), caffeic acid, the principal phenolic acid in coffee, raising from 0.3 (SEM 0.1) to 2.4 (SEM 0.6) ng/mg (P < 0.01). Caffeine was not detectable in platelets. Coffee drinking decreases platelet aggregation, and induces a significant increase in phenolic acid platelet concentration. The antiplatelet effect of coffee is independent from caffeine and could be a result of the interaction of coffee phenolic acids with the intracellular signalling network leading to platelet aggregation.

  3. Molecular determinants of the platelet aggregation inhibitory activity of carbamoylpiperidines.

    PubMed

    Feng, Z; Gollamudi, R; Dillingham, E O; Bond, S E; Lyman, B A; Purcell, W P; Hill, R J; Korfmacher, W A

    1992-08-07

    A series of alpha,alpha'-bis[3-(N,N-dialkylcarbamoyl)piperidino]-p- xylenes were synthesized and tested for their inhibitory activity on ADP-induced aggregation of human platelets. A parabolic curve was obtained when log 1/C (activity) was plotted against log P (octanol/water partition coefficient). Using this as a model, a new analogue, alpha,alpha'-bis-[3-(N-methyl-N-butylcarbamoyl)piperidino]-p-xylen e (3g), was synthesized with a predicted IC50 of 25 microM. When this compound was subsequently evaluated, the IC50 was 22.1 +/- 5.5 microM, demonstrating the applicability of this model. The amide oxygen of the carbamoyl substituent appeared necessary for activity. Thus, for example, when the amide carbonyl group of 3a (IC50 = 44.5 microM) was reduced to CH2, the resulting compound 4 had a dramatically reduced activity, IC50 = 1565 microM. Compound 3a was resolved into (+) and (-) enantiomers and a meso (0) diastereomer using fractional crystallization, diastereomeric tartrate formation, and chiral HPLC. Compared to (-)-3a, the (+) isomer was 15 times more potent when ADP was the agonist and 19 times more active when collagen was used as the agonist. Molecular modeling of R,R- and S,S-3a using the SYBYL program was used to examine their interactions with phosphatidylinositol (PI). There was a better fit between PI and the R,R-3a with the energy of interaction being 17.6 kcal/mol less than that of the S,S-3a/PI complex. Although the absolute stereochemistry of individual enantiomers is not known, this study shows that R,R-3a interacts more favorably with PI than does S,S-3a and that (+)-3a is a more potent inhibitor of human platelet aggregation than (-)-3a. It is postulated that because of their lipophilicity, these compounds penetrate the platelet membrane and are then protonated at the pH of the cytosol. The protonated N then neutralizes the anionic charge on the membrane phosphoinositides, thereby rendering them less susceptible to hydrolysis by phospholipase C

  4. pA2 values for antagonists of platelet activating factor on aggregation of rabbit platelets.

    PubMed Central

    O'Donnell, S. R.; Barnett, C. J.

    1988-01-01

    1. The relative potencies, and equilibrium dissociation constants, for nine antagonists of platelet activating factor (Paf) have been determined on rabbit platelets (in diluted platelet-rich plasma (PRP)) in experiments in which the aggregatory response to Paf was measured. 2. Log concentration-response (% maximum) curves to Paf were obtained in the absence (controls) and presence of different concentrations of each Paf antagonist drug. The antagonists shifted the Paf curves to a higher concentration range and the slopes of the Schild plots, constructed from these data, suggested that the drugs were competitive antagonists of Paf. The slopes of the Schild plots for CV-3988 and SRI 63-119 were greater than 1. 3. The pA2 values (pKB values in parentheses) were: WEB 2086 7.31 (7.63); SRI 63-119 6.95; L-652,731 6.71 (6.73); BN 52021 6.38 (6.47); SRI 63-072 6.36 (6.43); CV-3988 5.87; 48740 RP 4.97 (5.07); ketotifen 4.94 (4.95); thiazinamium 4.73 (4.76). 4. This study provides, for the first time, some functional response data for Paf antagonists (pKB values) which are in an appropriate form for use in classifying putative Paf receptors. The study also provides the comparative potencies of these Paf antagonists in inhibiting Paf-induced platelet aggregation. WEB 2086 was the most potent of the drugs examined. PMID:3293683

  5. 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

  6. Hemolysate-mediated platelet aggregation: an additional risk mechanism contributing to thrombosis of continuous flow ventricular assist devices.

    PubMed

    Tran, Phat L; Pietropaolo, Maria-Grazia; Valerio, Lorenzo; Brengle, William; Wong, Raymond K; Kazui, Toshinobu; Khalpey, Zain I; Redaelli, Alberto; Sheriff, Jawaad; Bluestein, Danny; Slepian, Marvin J

    2016-07-01

    Despite the clinical success and growth in the utilization of continuous flow ventricular assist devices (cfVADs) for the treatment of advanced heart failure, hemolysis and thrombosis remain major limitations. Inadequate and/or ineffective anticoagulation regimens, combined with high pump speed and non-physiological flow patterns, can result in hemolysis which often is accompanied by pump thrombosis. An unexpected increase in cfVADs thrombosis was reported by multiple major VAD implanting centers in 2014, highlighting the association of hemolysis and a rise in lactate dehydrogenase (LDH) presaging thrombotic events. It is well established that thrombotic complications arise from the abnormal shear stresses generated by cfVADs. What remains unknown is the link between cfVAD-associated hemolysis and pump thrombosis. Can hemolysis of red blood cells (RBCs) contribute to platelet aggregation, thereby, facilitating prothrombotic complications in cfVADs? Herein, we examine the effect of RBC-hemolysate and selected major constituents, i.e., lactate dehydrogenase (LDH) and plasma free hemoglobin (pHb) on platelet aggregation, utilizing electrical resistance aggregometry. Our hypothesis is that elements of RBCs, released as a result of shear-mediated hemolysis, will contribute to platelet aggregation. We show that RBC hemolysate and pHb, but not LDH, are direct contributors to platelet aggregation, posing an additional risk mechanism for cfVAD thrombosis.

  7. PKC and AKT Modulate cGMP/PKG Signaling Pathway on Platelet Aggregation in Experimental Sepsis

    PubMed Central

    Lopes-Pires, M. Elisa; Naime, Ana C. Antunes; Almeida Cardelli, Nádia J.; Anjos, Débora J.; Antunes, Edson; Marcondes, Sisi

    2015-01-01

    Sepsis severity has been positively correlated with platelet dysfunction, which may be due to elevations in nitric oxide (NO) and cGMP levels. Protein kinase C, Src kinases, PI3K and AKT modulate platelet activity in physiological conditions, but no studies evaluated the role of these enzymes in platelet aggregation in sepsis. In the present study we tested the hypothesis that in sepsis these enzymes positively modulate upstream the NO-cGMP pathway resulting in platelet inhibition. Rats were injected with lipopolysaccharide (LPS, 1 mg/kg, i.p.) and blood was collected after 6 h. Platelet aggregation was induced by ADP (10 μM). Western blotting assays were carried out to analyze c-Src and AKT activation in platelets. Intraplatelet cGMP levels were determined by enzyme immunoassay kit. Phosphorylation of c-SRC at Tyr416 was the same magnitude in platelets of control and LPS group. Incubation of the non-selective Src inhibitor PP2 (10 μM) had no effect on platelet aggregation of LPS-treated rats. LPS increased intraplatelet cGMP levels by 5-fold compared with control group, which was accompanied by 76% of reduction in ADP-induced platelet aggregation. The guanylyl cyclase inhibitor ODQ (25 μM) and the PKG inhibitor Rp-8-Br-PET-cGMPS (25 μM) fully reversed the inhibitory effect of LPS on platelet aggregation. Likewise, the PKC inhibitor GF109203X (10 μM) reversed the inhibition by LPS of platelet aggregation and decreased cGMP levels in platelets. AKT phosphorylation at Thr308 was significantly higher in platelets of LPS compared with control group, which was not reduced by PI3K inhibition. The AKT inhibitor API-1 (20 μM) significantly increased aggregation and reduced cGMP levels in platelets of LPS group. However, the PI3K inhibitor wortmannin and LY29004 had no effect on platelet aggregation of LPS-treated rats. Therefore, inhibition of ADP-induced platelet aggregation after LPS injection is mediated by cGMP/PKG-dependent mechanisms, and PKC and AKT act

  8. Evidence for a Structural Requirement for the Aggregation of Platelets by Collagen

    PubMed Central

    Jaffe, Russell; Deykin, Daniel

    1974-01-01

    This study investigates whether soluble collagen can initiate platelet aggregation or whether a higher degree of polymerization is required. Purified rat skin collagen was prepared in four states. Soluble monomeric collagen, containing 2 μM calcium chloride, was maintained at 4°C until use. A previously uncharacterized form of collagen, soluble microfibrillar collagen, was prepared from monomeric collagen containing calcium chloride by allowing it to polymerize at 23°C. Viscometric and electron microscopic characterization of microfibrillar collagen indicated polymerization to ordered native filaments. Particulate native macrofibrillar collagen was prepared from monomeric collagen by allowing it to polymerize at 37°C in the absence of calcium. Particulate collagen, in which the fibers were randomly associated, was prepared by salt precipitation of calcium-free monomeric collagen. Microfibrillar and native macrofibrillar collagen initiated platelet aggregation, with a lag phase of approximately 60 s. Monomeric collagen initiated aggregation with a lag phase of approximately 180 s. The duration of the lag phase for platelet aggregation initiated by monomeric collagen was independent of the dose. Salt-precipitated particulate collagen did not initiate platelet aggregation. Agents which prolong the transition from monomeric collagen to fibrillar collagen (urea, arginine) retarded or prevented the aggregation of platelets by monomeric collagen. Sodium borohydride, which stabilizes the intraand intermolecular cross-links of collagen did not affect platelet aggregation. Penicillamine, which displaces the intermolecular cross-links and binds the intramolecular cross-links of collagen, did not prevent platelet aggregation. The data suggest that an architectural requirement exists for the initiation of self-perpetuating platelet aggregation; that tropocollagen units do not fulfill this requirement; that a soluble collagen preparation, microfibrillar collagen, contains

  9. Licochalcones extracted from Glycyrrhiza inflata inhibit platelet aggregation accompanied by inhibition of COX-1 activity

    PubMed Central

    Okuda-Tanino, Asa; Sugawara, Daiki; Tashiro, Takumi; Iwashita, Masaya; Obara, Yutaro; Moriya, Takahiro; Tsushima, Chisato; Saigusa, Daisuke; Tomioka, Yoshihisa; Ishii, Kuniaki; Nakahata, Norimichi

    2017-01-01

    Licochalcones extracted from Glycyrrhiza inflata are known to have a variety of biological properties such as anti-inflammatory, anti-bacterial, and anti-tumor activities, but their action on platelet aggregation has not yet been reported. Therefore, in this study we investigated the effects of licochalcones on platelet aggregation. Collagen and U46619, a thromboxane A2 receptor agonist, caused rabbit platelet aggregation, which was reversed by pretreatment with licochalcones A, C and D in concentration-dependent manners. Among these compounds, licochalcone A caused the most potent inhibitory effect on collagen-induced platelet aggregation. However, the licochalcones showed marginal inhibitory effects on thrombin or ADP-induced platelet aggregation. In addition to rabbit platelets, licochalcone A attenuated collagen-induced aggregation in human platelets. Because licochalcone A also inhibited arachidonic acid-induced platelet aggregation and production of thromboxane A2 induced by collagen in intact platelets, we further examined the direct interaction of licochalcone A with cyclooxygenase (COX)-1. As expected, licochalcone A caused an inhibitory effect on both COX-1 and COX-2 in vitro. Regarding the effect of licochalcone A on COX-1 enzyme reaction kinetics, although licochalcone A showed a stronger inhibition of prostaglandin E2 synthesis induced by lower concentrations of arachidonic acid, Vmax values in the presence or absence of licochalcone A were comparable, suggesting that it competes with arachidonic acid at the same binding site on COX-1. These results suggest that licochalcones inhibit collagen-induced platelet aggregation accompanied by inhibition of COX-1 activity. PMID:28282426

  10. Licochalcones extracted from Glycyrrhiza inflata inhibit platelet aggregation accompanied by inhibition of COX-1 activity.

    PubMed

    Okuda-Tanino, Asa; Sugawara, Daiki; Tashiro, Takumi; Iwashita, Masaya; Obara, Yutaro; Moriya, Takahiro; Tsushima, Chisato; Saigusa, Daisuke; Tomioka, Yoshihisa; Ishii, Kuniaki; Nakahata, Norimichi

    2017-01-01

    Licochalcones extracted from Glycyrrhiza inflata are known to have a variety of biological properties such as anti-inflammatory, anti-bacterial, and anti-tumor activities, but their action on platelet aggregation has not yet been reported. Therefore, in this study we investigated the effects of licochalcones on platelet aggregation. Collagen and U46619, a thromboxane A2 receptor agonist, caused rabbit platelet aggregation, which was reversed by pretreatment with licochalcones A, C and D in concentration-dependent manners. Among these compounds, licochalcone A caused the most potent inhibitory effect on collagen-induced platelet aggregation. However, the licochalcones showed marginal inhibitory effects on thrombin or ADP-induced platelet aggregation. In addition to rabbit platelets, licochalcone A attenuated collagen-induced aggregation in human platelets. Because licochalcone A also inhibited arachidonic acid-induced platelet aggregation and production of thromboxane A2 induced by collagen in intact platelets, we further examined the direct interaction of licochalcone A with cyclooxygenase (COX)-1. As expected, licochalcone A caused an inhibitory effect on both COX-1 and COX-2 in vitro. Regarding the effect of licochalcone A on COX-1 enzyme reaction kinetics, although licochalcone A showed a stronger inhibition of prostaglandin E2 synthesis induced by lower concentrations of arachidonic acid, Vmax values in the presence or absence of licochalcone A were comparable, suggesting that it competes with arachidonic acid at the same binding site on COX-1. These results suggest that licochalcones inhibit collagen-induced platelet aggregation accompanied by inhibition of COX-1 activity.

  11. Effect of evening primrose oil on platelet aggregation in rabbits fed an atherogenic diet.

    PubMed

    De La Cruz, J P; Martín-Romero, M; Carmona, J A; Villalobos, M A; Sánchez de la Cuesta, F

    1997-07-01

    Evening primrose oil (Oenothera biennis) is a rich source of omega-6 series fatty acids. We report here the effects of dietary supplementation with evening primrose oil (EPO) on platelet aggregation as the main factor in arterial thrombus formation in an experimental model of atherogenesis in rabbits. A total of 40 male white New Zealand rabbits were divided into four groups (n = 10 animals/group): 1: normal diet, 2: atherogenic diet (ATD), 3: normal diet enriched with 15% EPO, 4: ATD + EPO. Each group was kept on the diet for 6 weeks. We determined serum lipid profile, platelet aggregation in whole blood, platelet thromboxane B2 production and platelet lipid peroxides. The atherogenic diet increased platelet aggregation (135% when ADP was used, and 185% when collagen was used as the inducer). Evening primrose oil reduced hyperaggregation to the values obtained in rabbits fed with the normal diet. Thromboxane synthesis was increased from 0.18 to 2.28 nmol/10(9) platelets); EPO reduced this value to 1.38 nmol/10(9) platelets. Lipid peroxides were increased by ATD from 0.27 to 0.81 nmol/10(8) platelets; EPO prevented this increase (0.35 nmol/10(8) platelets). In conclusion, EPO reduced platelet hyperaggregability in rabbits fed an atherogenic diet.

  12. Platelet concentrates transfusion in cardiac surgery in relation to preoperative point-of-care assessment of platelet adhesion and aggregation.

    PubMed

    Solomon, Cristina; Hartmann, Jennifer; Osthaus, Alexander; Schöchl, Herbert; Raymondos, Kostas; Koppert, Wolfgang; Rahe-Meyer, Niels

    2010-01-01

    Platelet dysfunction is an important cause of bleeding early after cardiac surgery. Whole-blood multiple electrode aggregometry (MEA), investigating the adhesion and aggregation of activated platelets onto metal electrodes, has shown correlations with platelet concentrates transfusion in this setting. Platelet activity in vivo is dependent on shear stress, an aspect that cannot be investigated with MEA, but with the cone and plate(let) analyzer (CPA) Impact-R that measures the interaction of platelets and von Willebrand factor (vWF) in whole blood under shear. We hypothesized that preoperative CPA may show better correlation with platelet concentrates transfusion post-cardiac surgery than MEA, since it is dependent on both platelet activity and platelet interaction with vWF multimers. Blood was obtained preoperatively from 30 patients undergoing aorto-coronary bypass (ACB) and 20 patients with aortic valve (AV) surgery. MEA was performed in hirudin-anticoagulated blood. The Impact-R analyses were performed in blood anticoagulated with hirudin, heparin or the standard anticoagulant citrate. For the light microscopy images obtained, the parameter surface coverage (SC) was calculated. Preoperative Impact-R results were abnormally decreased in AV patients and significantly lower than in ACB patients. For the Impact-R analysis performed in citrated blood, no correlation with platelet concentrates transfusion was observed. In contrast, MEA was comparable between the groups and correlated significantly with intraoperative platelet concentrates transfusion in both groups (rho between -0.47 and -0.62, p < 0.05). Multiple electrode aggregometry appeared more useful and easier to apply than CPA for preoperatively identifying patients with platelet concentrates transfusion in cardiac surgery.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. The role of von Willebrand factor and fibrinogen in platelet aggregation under varying shear stress.

    PubMed Central

    Ikeda, Y; Handa, M; Kawano, K; Kamata, T; Murata, M; Araki, Y; Anbo, H; Kawai, Y; Watanabe, K; Itagaki, I

    1991-01-01

    Exposure of platelets to shear stress leads to aggregation in the absence of exogenous agonists. We have now found that different adhesive proteins and platelet membrane glycoproteins are involved in aggregation depending on the shear stress conditions and the concentration of divalent cations in the medium. When blood is collected with trisodium citrate as anticoagulant, which causes a decrease in the levels of external ionized calcium ([Ca2+]o), platelet aggregation can be induced under low shear force (12 dyn/cm2) and is mediated by fibrinogen binding to the glycoprotein IIb-IIIa complex. Aggregates formed under these conditions are not stable, and when shear force is increased to 68 dyn/cm2, disaggregation results. By contrast, platelets from blood collected with hirudin as anticoagulant, wherein [Ca2+]o is within normal plasma levels, do not undergo low shear-induced aggregation; however, after exposure to a shear force above 80 dyn/cm2, aggregation is observed but only when von Willebrand factor is present and can interact with both its platelet binding sites, glycoprotein Ib-IX and glycoprotein IIb-IIIa. Fibrinogen is not involved in high shear-induced aggregation which, in fact, occurs normally in patients with severe afibrinogenemia. Thus, von Willebrand factor in the absence of exogenous agonists can mediate platelet aggregation in experimental conditions that may mimic the hemorheological situation of partially occluded arteries. This pathway of platelet aggregation involving only one adhesive ligand and two membrane adhesion receptors may play a relevant role in thrombogenesis. PMID:2010539

  18. 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.

  19. Measurement of platelet aggregation functions using whole blood migration ratio in a microfluidic chip.

    PubMed

    Seo, Hong Seog; Choi, Sung Hyuk; Han, Miran; Kim, Kyeong Ah; Cho, Chi Hyun; An, Seong Soo A; Lim, Chae Seung; Shin, Sehyun

    2016-01-01

    Platelets play a major role in maintaining endothelial integrity and hemostasis. Of the various soluble agonists, ADP is an important in vivo stimulus for inducing platelet aggregation. In this study, a simple, rapid, and affordable method was designed for testing bleeding time (BT) and platelet aggregation with a two-channel microfluidic chip. Whole blood migration ratio (MR) from a microchip system was evaluated in comparison to the closure time (CT) from PFA-100 assays (Siemens, Germany) and CD62P expression on platelets. To induce platelet aggregation, a combination of collagen (1.84 mg/ml) and ADP (37.5 mg/ml) were used as agonists. After adding the agonists to samples, whole blood MR from the microchip system was measured. The outcome of the assessment depended on reaction time and agonist concentration. MR of whole blood from the microchip system was significantly correlated with CT from PFA-100 (r = 0.61, p <  0.05, n = 60). In addition, MR was negatively correlated with CD62P expression (r =-0.95, p <  0.05, n = 60). These results suggest that the measurement of MR using agonists is an easy, simple and efficient method for monitoring platelet aggregation in normal and ADP-receptors defective samples, along with the BT test. Thus, usage of the current microfluidic method could expand to diverse applications, including efficacy assessments in platelet therapy.

  20. Perilla oil improves blood flow through inhibition of platelet aggregation and thrombus formation

    PubMed Central

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang-Sei; Lee, Sung-Pyo; Kang, Myung-Hwa; Choi, Ehn-Kyoung

    2014-01-01

    The inhibitory effects of perilla oil on the platelet aggregation in vitro and thrombosis in vivo were investigated in comparison with aspirin, a well-known blood flow enhancer. Rabbit platelet-rich plasma was incubated with perilla oil and aggregation inducers collagen or thrombin, and the platelet aggregation rate was analyzed. Perilla oil significantly inhibited both the collagen- and thrombin-induced platelet aggregations, in which the thromboxane B2 formation from collagen-activated platelets were reduced in a concentration-dependent manner. Rats were administered once daily by gavage with perilla oil for 1 week, carotid arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Perilla oil delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 0.5 mL/kg. In addition, a high dose (2 mL/kg) of perilla oil greatly prevented the occlusion, comparable to the effect of aspirin (30 mg/kg). The results indicate that perilla oil inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is proposed that perilla oil could be a good candidate without adverse effects for the improvement of blood flow. PMID:24707301

  1. Nattokinase improves blood flow by inhibiting platelet aggregation and thrombus formation

    PubMed Central

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang Sei; Park, Sung Kyeong; Lee, Sung-Pyo; Choi, Ehn-Kyoung

    2013-01-01

    The effects of nattokinase on the in vitro platelet aggregation and in vivo thrombosis were investigated in comparison with aspirin. Rabbit platelet-rich plasma was incubated with nattokinase and aggregation inducers collagen and thrombin, and the platelet aggregation rate was analyzed. Nattokinase significantly inhibited both the collagen- and thrombin-induced platelet aggregations. Nattokinase also reduced thromboxane B2 formation from collagen-activated platelets in a concentration-dependent manner. Rats were orally administered with nattokinase for 1 week, and their carotid arteries were exposed. Arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Nattokinase delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 160 mg/kg. In addition, a high dose (500 mg/kg) of nattokinase fully prevented the occlusion, as achieved with aspirin (30 mg/kg). The results indicate that nattokinase extracted from fermented soybean inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is suggested that nattokinase could be a good candidate without adverse effects for the improvement of blood flow. PMID:24396387

  2. Nattokinase improves blood flow by inhibiting platelet aggregation and thrombus formation.

    PubMed

    Jang, Ja-Young; Kim, Tae-Su; Cai, Jingmei; Kim, Jihyun; Kim, Youngeun; Shin, Kyungha; Kim, Kwang Sei; Park, Sung Kyeong; Lee, Sung-Pyo; Choi, Ehn-Kyoung; Rhee, Man Hee; Kim, Yun-Bae

    2013-12-01

    The effects of nattokinase on the in vitro platelet aggregation and in vivo thrombosis were investigated in comparison with aspirin. Rabbit platelet-rich plasma was incubated with nattokinase and aggregation inducers collagen and thrombin, and the platelet aggregation rate was analyzed. Nattokinase significantly inhibited both the collagen- and thrombin-induced platelet aggregations. Nattokinase also reduced thromboxane B2 formation from collagen-activated platelets in a concentration-dependent manner. Rats were orally administered with nattokinase for 1 week, and their carotid arteries were exposed. Arterial thrombosis was induced by applying 35% FeCl3-soaked filter paper for 10 min, and the blood flow was monitored with a laser Doppler probe. Nattokinase delayed the FeCl3-induced arterial occlusion in a dose-dependent manner, doubling the occlusion time at 160 mg/kg. In addition, a high dose (500 mg/kg) of nattokinase fully prevented the occlusion, as achieved with aspirin (30 mg/kg). The results indicate that nattokinase extracted from fermented soybean inhibit platelet aggregation by blocking thromboxane formation, and thereby delay thrombosis following oxidative arterial wall injury. Therefore, it is suggested that nattokinase could be a good candidate without adverse effects for the improvement of blood flow.

  3. Hydrodynamic effects and receptor interactions of platelets and their aggregates in linear shear flow.

    PubMed Central

    Tandon, P; Diamond, S L

    1997-01-01

    We have modeled platelet aggregation in a linear shear flow by accounting for two body collision hydrodynamics, platelet activation and receptor biology. Considering platelets and their aggregates as unequal-sized spheres with DLVO interactions (psi(platelet) = -15 mV, Hamaker constant = 10(-19) J), detailed hydrodynamics provided the flow field around the colliding platelets. Trajectory calculations were performed to obtain the far upstream cross-sectional area and the particle flux through this area provided the collision frequency. Only a fraction of platelets brought together by a shearing fluid flow were held together if successfully bound by fibrinogen cross-bridging GPIIb/IIIa receptors on the platelet surfaces. This fraction was calculated by modeling receptor-mediated aggregation using the formalism of Bell (Bell, G. I. 1979. A theoretical model for adhesion between cells mediated by multivalent ligands. Cell Biophys. 1:133-147) where the forward rate of bond formation dictated aggregation during collision and was estimated from the diffusional limited rate of lateral association of receptors multiplied by an effectiveness factor, eta, to give an apparent rate. For a value of eta = 0.0178, we calculated the overall efficiency (including both receptor binding and hydrodynamics effects) for equal-sized platelets with 50,000 receptors/platelet to be 0.206 for G = 41.9 s(-1), 0.05 for G = 335 s(-1), and 0.0086 for G = 1920 s(-1), values which are in agreement with efficiencies determined from initial platelet singlet consumption rates in flow through a tube. From our analysis, we predict that bond formation proceeds at a rate of approximately 0.1925 bonds/microm2 per ms, which is approximately 50-fold slower than the diffusion limited rate of association. This value of eta is also consistent with a colloidal stability of unactivated platelets at low shear rates. Fibrinogen was calculated to mediate aggregation quite efficiently at low shear rates but not at

  4. Influence of combinations of acetylsalicylic acid, acetaminophen, and diclofenac on platelet aggregation.

    PubMed

    Galliard-Grigioni, Katja S; Fehr, Martin; Reinhart, Walter H

    2008-10-24

    Acetylsalicylic acid (aspirin) is often given together with other nonsteroidal anti-inflammatory drugs and acetaminophen. The latter have been accused in epidemiologic studies to cause an increased cardiovascular risk. We have, therefore, analysed the influence of various such drug combinations on platelet aggregation in vitro. Citrated blood was incubated with either 25 microg/ml acetaminophen, 0.5 microg/ml aspirin, 0.04 microg/ml diclofenac, or buffer; followed by a second of the above-mentioned solutions. After a 20 min incubation, platelet aggregation was assessed with a platelet function analyser (PFA-100), which measures the pore closure time (CT) by aggregating platelets. The length of CT reflects the degree of platelet inhibition. Acetaminophen alone did not affect platelet aggregation. Aspirin and diclofenac both increased CT (184+/-69 s, P<0.01 and 196+/-54 s, P<0.001; control 120+/-13 s). Combinations of either aspirin and diclofenac, aspirin and acetaminophen, or diclofenac and acetaminophen increased CT further (290+/-22 s, 281+/-36 s, 288+/-25 s, respectively, P<0.001). The time sequence of drug application was important: when diclofenac or acetaminophen was added before aspirin, platelet aggregation was less inhibited than when given in opposite order, i.e. aspirin prior to diclofenac or acetaminophen. We conclude that acetaminophen by itself does not affect platelet aggregation, but potentiates the antiaggregatory effect of aspirin or diclofenac. Aspirin given before acetaminophen or diclofenac had a more potent antiaggregatory effect than vice versa. These observations may have clinical implications.

  5. The effect of ex vivo anticoagulants on whole blood platelet aggregation.

    PubMed

    Kalb, Madeleine L; Potura, Lukasz; Scharbert, Gisela; Kozek-Langenecker, Sibylle A

    2009-02-01

    Pre- and intraoperative platelet function monitoring is increasingly recommended in order to detect risk factors for bleeding and to target coagulation management. The ideal anticoagulant for accurate platelet aggregometry remains controversial. The aim of this experimental trial was to compare platelet aggregability in whole blood stored in citrate, heparin and direct thrombin inhibitors. Whole blood was drawn from 11 healthy adult volunteers who had not taken any medication in the previous 14 days. Blood was stored in trisodium citrate, unfractionated heparin, melagatran, lepirudin and argatroban. Platelet aggregation was performed using the impedance aggregometer Multiplate (Dynabyte, Munich, Germany) with adenosine diphosphate (ADP), thrombin receptor activating peptide (TRAP), collagen, arachidonic acid and ristocetin as agonists. Samples were analysed immediately after blood sampling (baseline), as well as 30 and 120 min afterwards. At baseline there were no significant differences in aggregability between samples containing direct thrombin inhibitors and heparin. In contrast, aggregation in response to all agonists except for ristocetin was significantly impaired in citrated blood. During storage the response to arachidonic acid and collagen was maintained by direct thrombin inhibitors and heparin, whereas ADP-, TRAP- and ristocetin-induced aggregation varied considerably over time in all ex vivo anticoagulants tested. Pre-analytical procedures should be standardized because storage duration and anticoagulants significantly affect platelet aggregability in whole blood. For point-of-care monitoring with immediate analysis after blood withdrawal all tested direct thrombin inhibitors as well as unfractionated heparin can be used as anticoagulants whereas citrate is not recommended.

  6. Paraphenylene diamine exacerbates platelet aggregation and thrombus formation in response to a low dose of collagen.

    PubMed

    Zaid, Younes; Marhoume, Fatimazahra; Senhaji, Nezha; Kojok, Kevin; Boufous, Hicham; Naya, Abdallah; Oudghiri, Mounia; Darif, Youssef; Habti, Norddine; Zouine, Soukaina; Mohamed, Fekhaoui; Chait, Abderahmane; Bagri, Abdellah

    2016-02-01

    Paraphenylene daimine (PPD) is an aromatic amine that is widely used in several industrial products; however, its toxicity has been reported in several cases of cardiac arrests. As platelets play a key role in cardiovascular diseases, we aimed to determine the impact of PPD in vitro and in vivo on platelet function. Our findings demonstrated that platelet activation and aggregation were strongly enhanced by PPD. Treatment with PPD primed human platelets that became more reactive in response to low doses of collagen. Furthermore, PPD exacerbated thrombus formation in rats in comparison with those untreated. Our results suggest that PPD is an important platelet primer predisposing platelets to promote thrombus formation in response to vascular injury. This should prompt the authorities to consider controlling the marketing of this product.

  7. The passage of a hemodialysis filter affects hemorheology, red cell shape, and platelet aggregation.

    PubMed

    Reinhart, W H; Cagienard, F; Schulzki, T; Venzin, R M

    2014-01-01

    We investigated the influence of the passage of a hemodialysis filter on red blood cells (RBCs), platelets, and hemorheological parameters. After one hour of hemodialysis, blood was drawn from 15 patients immediately ahead and behind the dialysis filter. RBCs were fixed for morphological analysis. Blood viscosity was measured with a Couette viscometer (LS-30, Contraves), RBC aggregation with a Myrenne aggregometer, platelet aggregation in flowing whole blood and in platelet rich plasma. The passage of the hemodialysis filter increased the hematocrit from 34.0 ± 3.8 to 44.6 ± 8.7% (p < 0.01). Discocytes decreased from 73 ± 9 to 60 ± 15%, while echinocytes/knizocytes were more abundant 24 ± 9% and 38 ± 15%, respectively, p < 0.01). Blood viscosity increased from 3.77 ± 0.52 to 6.75 ± 2.21 mPa.s (p < 0.01). The RBC aggregation index decreased from 25.8 ± 5.0 to 20.9 ± 5.6 (p < 0.05). These changes were less pronounced when the blood flow rate was reduced from 350 to 100 ml/min. Platelet aggregation was slightly increased in flowing whole blood, but decreased in platelet rich plasma. At the end of hemodialysis, a small increase in abnormally shaped RBCs, hematocrit, and whole blood viscosity persisted; platelet aggregation in flowing whole blood was reduced in all patients. We conclude that the passage of a hemodialysis filter induced RBC shape changes, increased the hematocrit, whole blood and plasma viscosity, decreased RBC aggregation, and affected platelet aggregation.

  8. Comparison of different procedures to prepare platelet-rich plasma for studies of platelet aggregation by light transmission aggregometry.

    PubMed

    Femia, Eti Alessandra; Pugliano, Mariateresa; Podda, Gianmarco; Cattaneo, Marco

    2012-01-01

    Light transmission aggregometry (LTA), the gold standard for the study of patients with defects of platelet function, is a poorly standardized technique. The guidelines that have been produced so far are largely based on consensus of experts, due to the absence of studies directly comparing different procedures. Therefore, ad hoc studies are needed to gather scientific evidence on how to choose the most appropriate procedures for LTA measurement. In this study, we aimed at evaluating the most appropriate conditions for preparing samples of platelet-rich plasma (PRP) for studies of platelet aggregation by LTA. Citrate-anticoagulated blood from 32 individuals was centrifuged at 150, 200, 250 or 300×g at room temperature for 10 min. Red blood cells contamination was highest in PRP prepared at 150×g; mean platelet volume (MPV) was lowest in PRP prepared at 300×g. The extent of platelet aggregation measured by LTA was lower and more variable in PRP prepared at 300×g. Therefore, centrifugation of blood at 200×g or 250×g for 10 min appears to be the best condition for preparing PRP for LTA studies.

  9. Platelet-aggregating activity of released factor(s) from Trypanosoma brucei brucei.

    PubMed

    Nwagwu, M; Inyang, A L; Molokwu, R I; Essien, E M

    1989-12-01

    The effect of factors derived from Trypanosoma brucei brucei on rat platelets was studied. T. brucei at a concentration of 4 X 10(9) trypanosomes/ml phosphate saline glucose (PSG) was stored at -20 degrees C for 18 h, thawed, and a supernatant fraction, trypanosome-derived supernatant (TDS) was obtained by spinning the sample at 3000 g for 10 min at 20 degrees C. Normal rat platelets, prepared as platelet-rich plasma (PRP), were then incubated with TDS in the absence or presence of ADP (0.05-0.1 microM). The results showed that approximately 83% platelet aggregation was induced by addition of TDS (50 microliters; 113 micrograms protein) to 100 microliters PRP with a platelet count of 10(6). simultaneous addition of ADP and TDS to PRP produced a synergistic effect. It was also shown that a supernatant fraction, obtained by incubating live T. brucei (4 X 10(9)/microliters PSG) at 0 degrees C 1 h and spinning down the trypanosomes (3000 g for 10 min), also induced platelet aggregation. The nature of the factor(s) derived from, or released by, T. brucei inducing platelet aggregation is being investigated but it has been shown not to be ADP.

  10. Effects of nitroblue tetrazolium and vitamin E on platelet ultrastructure, aggregation, and secretion

    PubMed Central

    White, James G.; Rao, Gundu H. R.; Gerrard, Jonathan M.

    1977-01-01

    All agents capable of triggering the platelet release reaction also stimulate prostaglandin biosynthesis in these cells. Information concerning the endoperoxides, thromboxanes, and more stable metabolites generated by the action of cyclooxygenase and lipoxygenase on arachidonic acid has accumulated rapidly, but little is known about the preliminary steps in the cleavage and preparation of arachidonic acid for insertion into the enzymatic pathways of prostaglandin synthesis. Studies in this laboratory have shown that the combination of nitroblue tetrazolium (NBT) and vitamin E which prevents oxygenation of arachidonic acid to a free radical also blocks platelet prostaglandin biosynthesis. The present study has evaluated the influence of NBT, vitamin E, and the combination of NBT and vitamin E on the fine structure and biochemistry of platelets during incubation, and the effects of these compounds on the aggregation and secretion of platelets stimulated by collagen, thrombin, epinephrine, and ADP. Results of the study demonstrate that NBT and vitamin E, rather than injuring platelets, appear to protect them during incubation. Together NBT and vitamin E blocked aggregation by epinephrine, collagen, and thrombin, but permitted a small first wave stimulated by ADP. Both ADP and thrombin induced shape change, pseudopod formation, and limited degrees of internal contraction in vitamin E-NBT-treated platelets, whereas epinephrine and collagen failed to significantly alter discoid form. This pattern of response to aggregating agents was identical to reactions observed in platelets pretreated with aspirin and indomethacin, both potent inhibitors of platelet prostaglandin synthesis. In addition, NBT-vitamin E virtually blocked the first wave of aggregation which is not affected by aspirin and indomethacin. The findings support the concept that conversion of arachidonic acid to an activated state is an important step in prostaglandin synthesis and that electron transfer or

  11. Angiotensin II AT1 receptor antagonists inhibit platelet adhesion and aggregation by nitric oxide release.

    PubMed

    Kalinowski, Leszek; Matys, Tomasz; Chabielska, Ewa; Buczko, Włodzimierz; Malinski, Tadeusz

    2002-10-01

    This study investigated the process of nitric oxide (NO) release from platelets after stimulation with different angiotensin II type 1 (AT1)-receptor antagonists and its effect on platelet adhesion and aggregation. Angiotensin II AT1-receptor antagonist-stimulated NO release in platelets was compared with that in human umbilical vein endothelial cells by using a highly sensitive porphyrinic microsensor. In vitro and ex vivo effects of angiotensin II AT1-receptor antagonists on platelet adhesion to collagen and thromboxane A2 analog U46619-induced aggregation were evaluated. Losartan, EXP3174, and valsartan alone caused NO release from platelets and endothelial cells in a dose-dependent manner in the range of 0.01 to 100 micro mol/L, which was attenuated by NO synthase inhibitor N(G)-nitro-L-arginine methyl ester. The angiotensin II AT1-receptor antagonists had more than 70% greater potency in NO release in platelets than in endothelial cells. The degree of inhibition of platelet adhesion (collagen-stimulated) and aggregation (U46619-stimulated) elicited by losartan, EXP3174, and valsartan, either in vitro or ex vivo, closely correlated with the NO levels produced by each of these drugs alone. The inhibiting effects of angiotensin II AT1-receptor antagonists on collagen-stimulated adhesion and U46619-stimulated aggregation of platelets were significantly reduced by pretreatment with N(G)-nitro-L-arginine methyl ester. Neither the AT2 receptor antagonist PD123319, the cyclooxygenase synthase inhibitor indomethacin, nor the selective thromboxane A2/prostaglandin H2 receptor antagonist SQ29,548 had any effect on angiotensin II AT1-receptor antagonist-stimulated NO release in platelets and endothelial cells. The presented studies clearly indicate a crucial role of NO in the arterial antithrombotic effects of angiotensin II AT1-receptor antagonists.

  12. Platelet calcium and quenched-flow aggregation kinetics in essential hypertension.

    PubMed

    Taylor, M A; Ayers, C R; Gear, A R

    1989-06-01

    Abnormal platelet function may contribute to the complications of essential hypertension. We have studied the kinetics of platelet aggregation induced by adenosine diphosphate (ADP) or epinephrine, plasma beta-thromboglobulin, and basal, cytosolic, and free calcium, as correlates of platelet function. Fifteen untreated patients with essential hypertension and without detectable atherosclerosis, 18-40 years old, were compared with 30 matched normotensive control subjects. Maximal rates of platelet aggregation (Vmax) with ADP and epinephrine were significantly higher in patients than in control subjects (p less than 0.03), as assessed by quenched-flow aggregometry. However, significance was lost when Vmax was corrected for the platelet count. Paradoxically, the activation constants (Ka) for ADP were higher in patients than in control subjects (p less than 0.03). With ADP as the inducing agent, onset time (t) or lag period before aggregation begins was longer in patients than in control subjects (p less than 0.02). beta-thromboglobulin levels, an index of in vivo platelet activation, were not significantly different between the two groups (p = 0.13). The mean platelet cytosolic free calcium concentration was higher in patients (213 +/- 19 nM) than in control subjects (172 +/- 14 nM), but this difference was not statistically significant (p = 0.07). However, there was a close correlation between the free calcium level and systolic, diastolic, and mean blood pressure (p less than 0.003, p less than 0.04, p less than 0.004, respectively). No difference in platelet volume between the two groups was found. Our data suggest that platelets in the early stages of essential hypertension display an overall increased aggregation potential but a diminished sensitivity to ADP.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. 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

  14. Palmitic acid-labeled lipids selectively incorporated into platelet cytoskeleton during aggregation

    SciTech Connect

    Packham, M.A.; Guccione, M.A.; Bryant, N.L.; Livne, A. )

    1990-07-01

    Previous experiments showed that during the early stages (20-30 seconds) of aggregation induced by adenosine diphosphate (ADP, 2 microM) or thrombin (0.1 U/mL) of rabbit or human platelets prelabeled with (3H)palmitic acid, labeled lipid became associated with the cytoskeleton isolated after lysis with 1% Triton X-100, 5 mM EGTA (ethylene glycol-bis-(beta-aminoethyl ether))-N,N,N',N'-tetra-acetic acid. The association appeared to be related to the number of sites of contact and was independent of the release of granule contents. We have now investigated the nature of the labeled lipids by thin-layer and column chromatography and found differences between the distribution of the label in intact platelets (both stimulated and unstimulated) and the isolated cytoskeletons. In both species, and with either ADP or thrombin as aggregating agent, 70-85% of the label in both intact platelets and in the cytoskeletons was in phospholipids. The distribution of label among the phospholipids in the cytoskeletons was similar to that in intact platelets except that the percentage of label in phosphatidylcholine was significantly higher in the cytoskeletons of human platelets than in the intact platelets, and the percentage of label in phosphatidylserine/phosphatidylinositol was significantly lower in the cytoskeletons of rabbit platelets and thrombin-aggregated human platelets than in intact platelets. The cytoskeletons contained a lower percentage of label in triacylglycerol, diacylglycerol, and cholesterol ester than the intact platelets. Contrary to a report in the literature, we found no evidence for the incorporation of diacylglycerol and palmitic acid into the cytoskeleton.

  15. Syntaxin 8 Regulates Platelet Dense Granule Secretion, Aggregation, and Thrombus Stability*

    PubMed Central

    Golebiewska, Ewelina M.; Harper, Matthew T.; Williams, Christopher M.; Savage, Joshua S.; Goggs, Robert; Fischer von Mollard, Gabriele; Poole, Alastair W.

    2015-01-01

    Platelet secretion not only drives thrombosis and hemostasis, but also mediates a variety of other physiological and pathological processes. The ubiquitous SNARE machinery and a number of accessory proteins have been implicated in regulating secretion in platelet. Although several platelet SNAREs have been identified, further members of the SNARE family may be needed to fine-tune platelet secretion. In this study we identified expression of the t-SNARE syntaxin 8 (STX8) (Qc SNARE) in mouse and human platelets. In mouse studies, whereas STX8 was not essential for α-granule or lysosome secretion, Stx8−/− platelets showed a significant defect in dense granule secretion in response to thrombin and CRP. This was most pronounced at intermediate concentrations of agonists. They also showed an aggregation defect that could be rescued with exogenous ADP and increased embolization in Stx8−/− mice in vivo consistent with an important autocrine and paracrine role for ADP in aggregation and thrombus stabilization. STX8 therefore specifically contributes to dense granule secretion and represents another member of a growing family of genes that play distinct roles in regulating granule release from platelets and thus platelet function in thrombosis and hemostasis. PMID:25404741

  16. Evaluation of Anti-Platelet Aggregation Effect of Some Allium Species

    PubMed Central

    Lorigooini, Zahra; Ayatollahi, Seyed Abdolmajid; Amidi, Salimeh; Kobarfard, Farzad

    2015-01-01

    Epidemiologic studies show that the cardiovascular diseases are associated with multiple factors such as raised serum total cholesterol, increased LDL, increased platelet aggregation, hypertension and smoking. In-vitro studies have confirmed the ability of some plants of Allium species to reduce these parameters. Therefore, we evaluated anti-platelet aggregation effect of some Allium species (Allium ampeloprasum, A. hirtifolium, A. haemanthoides, A. vavillovi, A. atroviolaceum, A. jesdianum, A. shelkovnikovii) using arachidonic acid (AA) and adenosine diphosphate (ADP) as platelet aggregation inducers. The screening results for methanolic extract of Allium species showed that the maximum effect of anti-platelet aggregation was related to A. atroviolaceum. This extract inhibited the in-vitro platelet aggregation induced by AA and ADP with IC50 values of 0.4881 (0.4826-0.4937) mg/ml and 0.4945 (0.4137-0.5911) mg/ml respectively. These results support the hypothesis that the dietary intake of Allium could be beneficial for prevention of cardiovascular diseases. PMID:26664390

  17. Keishibukuryogan, a Traditional Japanese Medicine, Inhibits Platelet Aggregation in Guinea Pig Whole Blood

    PubMed Central

    Terawaki, Kiyoshi; Noguchi, Masamichi; Yuzurihara, Mitsutoshi; Omiya, Yuji; Ikarashi, Yasushi; Kase, Yoshio

    2015-01-01

    Effects of keishibukuryogan (KBG) on platelet aggregation were investigated. To ensure the specificity of KBG, tokishakuyakusan (TSS) and kamisyoyosan (KSS), which are known to have platelet aggregation-inhibiting effects, and rikkunshito (RKT) and shakuyakukanzoto (SKT), which are considered to be devoid of such effects, were used for comparison. The platelet aggregation of each test drug was measured by the screen filtration pressure method using whole blood of guinea pigs and expressed as a collagen-induced pressure rate (%) or a collagen concentration required for 50% increase in the pressure rate (PATI value). KBG suppressed the collagen-induced whole blood pressure rate increase and increased the PATI value, like TSS and KSS. Neither RKT nor SKT showed these effects. The Moutan cortex and Cinnamomi cortex, the constituent crude drugs of KBG, showed KBG-like pressure rate suppression and PATI-increasing effects. Furthermore, paeonol, a representative component of Moutan cortex, and aspirin which is known to have platelet aggregation-inhibiting activity (COX-1 inhibitor) also showed similar effects. These results suggest that the platelet aggregation-inhibiting activity of the constituent crude drugs Moutan cortex and Cinnamomi cortex is involved in the improving effects of KBG on impaired microcirculation and that paeonol plays a role in these effects. PMID:26379740

  18. Platelet aggregation and serum adenosine deaminase (ADA) activity in pregnancy associated with diabetes, hypertension and HIV.

    PubMed

    Leal, Claudio A M; Leal, Daniela B R; Adefegha, Stephen A; Morsch, Vera M; da Silva, José E P; Rezer, João F P; Schrekker, Clarissa M L; Abdalla, Faida H; Schetinger, Maria R C

    2016-07-01

    Platelet aggregation and adenosine deaminase (ADA) activity were evaluated in pregnant women living with some disease conditions including hypertension, diabetes mellitus and human immunodeficiency virus infection. The subject population is consisted of 15 non-pregnant healthy women [control group (CG)], 15 women with normal pregnancy (NP), 7 women with hypertensive pregnancy (HP), 10 women with gestational diabetes mellitus (GDM) and 12 women with human immunodeficiency virus-infected pregnancy (HIP) groups. The aggregation of platelets was checked using an optical aggregometer, and serum ADA activity was determined using the colorimetric method. After the addition of 5 µM of agonist adenosine diphosphate, the percentage of platelet aggregation was significantly (p < 0·05) increased in NP, HP, GDM and HIP groups when compared with the CG, while the addition of 10 µM of the same agonist caused significant (p < 0·05) elevations in HP, GDM and HIP groups when compared with CG. Furthermore, ADA activity was significantly (p < 0·05) enhanced in NP, HP, GDM and HIP groups when compared with CG. In this study, the increased platelet aggregation and ADA activity in pregnancy and pregnancy-associated diseases suggest that platelet aggregation and ADA activity could serve as peripheral markers for the development of effective therapy in the maintenance of homeostasis and some inflammatory process in these pathophysiological conditions. Copyright © 2016 John Wiley & Sons, Ltd.

  19. Mathematical model and numerical method for studying platelet adhesion and aggregation during blood clotting

    SciTech Connect

    Fogelson, A.L.

    1984-10-01

    The repair of small blood vessels and the pathological growth of internal blood clots involve the formation of platelet aggregates adhering to portions of the vessel wall. Our microscopic model represents blood by a suspension of discrete massless platelets in a viscous incompressible fluid. Platelets are initially noncohesive; however, if stimulated by an above-threshold concentration of the chemical ADP or by contact with the adhesive injured region of the vessel wall, they become cohesive and secrete more ADP into the fluid. Cohesion between platelets and adhesion of a platelet to the injured wall are modeled by creating elastic links. Repulsive forces prevent a platelet from coming too close to another platelet or to the wall. The forces affect the fluid motion in the neighborhood of an aggregate. The platelets and secreted ADP both move by fluid advection and diffusion. The equations of the model are studied numerically in two dimensions. The platelet forces are calculated implicitly by minimizing a nonlinear energy function. Our minimization scheme merges Gill and Murray's (Math. Programming 7 (1974), 311) modified Newton's method with elements of the Yale sparse matix package. The stream-function formulation of the Stokes' equations for the fluid motion under the influence of platelet forces is solved using Bjorstad's biharmonic solver (''Numerical Solution of the Biharmonic Equation,'' Ph.D. Thesis, Stanford University, 1980). The ADP transport equation is solved with an alternating-direction implicit scheme. A linked-list data structure is introduced to keep track of changing platelet states and changing configurations of interplatelet links.

  20. Inhibition of Platelet Aggregation by Supernates from Stored Red Blood Cells

    DTIC Science & Technology

    2010-04-01

    platelet aggregates in fresh whole blood.[10] In those experiments , we observed that platelets in blood incubated with supernates from stored RBC...volumes in sterile cryovials, and the vials were stored at -80C. For each experiment , aliquots were thawed quickly in a 37°C water bath just before...The final ratio of whole blood to supernate was 2:1. For each experiment , blood was collected first into one red top Vacutainer tube (no anti

  1. Inhibitory effects of yuzu and its components on human platelet aggregation.

    PubMed

    Kim, Tae-Ho; Kim, Hye-Min; Park, Se Won; Jung, Yi-Sook

    2015-03-01

    Our previous study demonstrated that yuzu has an anti-platelet effect in rat blood. In the present study, we examined whether the anti-platelet effect of yuzu can be extended to human blood by investigating its ability to inhibit aggregations induced by various agonists in human platelet rich plasma (PRP). This study also investigated the underlying mechanism of yuzu focusing on ADP granule secretion, TXB2 formations, and PLCγ/Akt signaling. The results from this study showed that ethanolic yuzu extract (YE), and its components, hesperidin and naringin, inhibited human platelet aggregation in a concentration-dependent manner. YE, hesperidin and naringin also inhibited TXB2 formation and ADP release. The phosphorylation of PLCγ and Akt was significantly inhibited by YE, heperidin and naringin. Furthermore, we demonstrated that YE, heperidin and naringin has anti-platelet effects in rat ex vivo studies, and lower side effects in mice tail bleeding time studies. The results from this study suggest that YE, hesperidin and naringin can inhibit human platelet aggregation, at least partly through the inhibition of PLCγ and Akt, leading to a decrease in TXB2 formation and granule secretion.

  2. Inhibitory Effects of Yuzu and Its Components on Human Platelet Aggregation

    PubMed Central

    Kim, Tae-Ho; Kim, Hye-Min; Park, Se Won; Jung, Yi-Sook

    2015-01-01

    Our previous study demonstrated that yuzu has an anti-platelet effect in rat blood. In the present study, we examined whether the anti-platelet effect of yuzu can be extended to human blood by investigating its ability to inhibit aggregations induced by various agonists in human platelet rich plasma (PRP). This study also investigated the underlying mechanism of yuzu focusing on ADP granule secretion, TXB2 formations, and PLCγ/Akt signaling. The results from this study showed that ethanolic yuzu extract (YE), and its components, hesperidin and naringin, inhibited human platelet aggregation in a concentration-dependent manner. YE, hesperidin and naringin also inhibited TXB2 formation and ADP release. The phosphorylation of PLCγ and Akt was significantly inhibited by YE, heperidin and naringin. Furthermore, we demonstrated that YE, heperidin and naringin has anti-platelet effects in rat ex vivo studies, and lower side effects in mice tail bleeding time studies. The results from this study suggest that YE, hesperidin and naringin can inhibit human platelet aggregation, at least partly through the inhibition of PLCγ and Akt, leading to a decrease in TXB2 formation and granule secretion. PMID:25767683

  3. Computational analysis of platelet adhesion and aggregation under stagnation point flow conditions.

    PubMed

    Reininger, C B; Lasser, R; Rumitz, M; Böger, C; Schweiberer, L

    1999-01-01

    The clinical relevance of platelet function assessment with stagnation point flow adhesio-aggregometry (SPAA) has been verified. Quantitative analysis of platelet adhesion and aggregation is possible by means of mathematical analysis of the dark-field, light intensity curves (growth curves) obtained during the SPAA experiment. We present a computational procedure for evaluating these curves, which was necessitated by, and is based on, actual clinical application. A qualitative growth curve classification, corresponding to a basic and distinct pattern of platelet deposition and characteristic of a regularly occurring clinical state is also presented.

  4. Persistent aggregates in apheresis platelet concentrates are commonly collected from donors with a history of aggregate donation.

    PubMed

    Feys, H B; Pottel, H; Coene, J; Vandewalle, G; Vandekerckhove, P; Compernolle, V

    2016-11-01

    Platelet apheresis sometimes causes persistent aggregates (PA). This study (n = 211) shows that changing the apheresis settings to reach fixed product volumes instead of yields does not influence PA incidence, even though PA products on average contain more platelets than controls. Furthermore, logistic regression was used to model if PA can be predicted on the basis of certain predonation parameters. PA donation history was the only parameter retained, proving a strong determinant of predictability [AUC = 0.735 (SE = 0.022)]. Consequently, donations from a donor with previous PA history are 7.8 times more likely to contain PA than from a donor without preceding history.

  5. Inhibition of bovine platelets aggregation in response to Hyalomma anatolicum salivary gland proteins/peptides

    PubMed Central

    Surbhi; Sangwan, Nirmal; Sangwan, Arun K.; Singh, Vijender; Kumar, Ankit

    2016-01-01

    Aim: Ticks are obligate ectoparasites that have an impact on wide range of vertebrates and also act as a potential vector for the transmission of tropical theileriosis, babesiosis, etc., causing significant loss to livestock production worldwide. While feeding, they introduce their saliva containing different bioactive molecules into the host. These molecules have the capability to counteract the host hemostatic mechanism to suck host blood successfully. Therefore, the study was aimed to isolate anti-platelet aggregating peptides from salivary gland extract (SGE) of Hyalomma anatolicum ticks, a commonly available tick in India. Materials and Methods: Female H. anatolicum salivary glands were dissected out and SGE was prepared by homogenizing it in a suitable buffer under ice. Extract so obtained was fractionated by gel filtration chromatography using Sephacryl S-200 column. Total protein concentration in fractions was estimated and bovine platelets were isolated, stimulated with thrombin (positive control), treated with Gly-Pro-Arg-Pro amide (negative control) and with salivary gland fractions for identification of proteins/peptides having anti-platelet aggregating activities. Results: Proteins/peptides present in various salivary gland fractions inhibited the bovine platelet aggregation and the percent inhibition ranged between 33% and 35.8%. Conclusion: The results suggests that the fractions of H. anatolicum salivary glands possess thrombin-induced anti-platelet aggregating activity and which could be further exploited for raising anti-tick vaccine and also for therapeutic purpose. PMID:27956779

  6. Platelet hemostasis in patients with metabolic syndrome and type 2 diabetes mellitus: cGMP- and NO-dependent mechanisms in the insulin-mediated platelet aggregation.

    PubMed

    Suslova, Tatiana E; Sitozhevskii, Alexei V; Ogurkova, Oksana N; Kravchenko, Elena S; Kologrivova, Irina V; Anfinogenova, Yana; Karpov, Rostislav S

    2014-01-01

    Patients with metabolic syndrome (MetS) and type 2 diabetes mellitus (T2DM) have high risk of microcirculation complications and microangiopathies. An increase in thrombogenic risk is associated with platelet hyperaggregation, hypercoagulation, and hyperfibrinolysis. Factors leading to platelet activation in MetS and T2DM comprise insulin resistance, hyperglycemia, non-enzymatic glycosylation, oxidative stress, and inflammation. This review discusses the role of nitric oxide (NO) in the regulation of platelet adhesion and aggregation processes. NO is synthesized both in endotheliocytes, smooth muscle cells, macrophages, and platelets. Modification of platelet NO-synthase (NOS) activity in MetS patients can play a central role in the manifestation of platelet hyperactivation. Metabolic changes, accompanying T2DM, can lead to an abnormal NOS expression and activity in platelets. Hyperhomocysteinemia, often accompanying T2DM, is a risk factor for cardiovascular accidents. Homocysteine can reduce NO production by platelets. This review provides data on the insulin effects in platelets. Decrease in a number and sensitivity of the insulin receptors on platelets in T2DM can cause platelet hyperactivation. Various intracellular mechanisms of anti-aggregating insulin effects are discussed. Anti-aggregating effects of insulin are mediated by a NO-induced elevation of cGMP and upregulation of cAMP- and cGMP-dependent pathways. The review presents data suggesting an ability of platelets to synthesize humoral factors stimulating thrombogenesis and inflammation. Proinflammatory cytokines are considered as markers of T2DM and cardiovascular complications and are involved in the development of dyslipidemia and insulin resistance. The article provides an evaluation of NO-mediated signaling pathway in the effects of cytokines on platelet aggregation. The effects of the proinflammatory cytokines on functional activity of platelets are demonstrated.

  7. [Effect of acetylsalicylic acid in complex with lipid nanostructures of various compositions on human platelet aggregation].

    PubMed

    Suslina, Z A; Prokhorov, D I; Shilova, A G; Kaplun, A P; Ionova, V G; Seĭfulla, R D

    2011-01-01

    The effect of lipid nanocomplexes loaded with acetylsalicylic acid (aspirin) on platelet aggregation in vitro was investigated. The antithrombotic effect of aspirin in complex with liposomes prepared from pig brain glycosphingolipids is not only significantly higher compared to control, but also accompanied by leveling of the development of proaggregant effects. It was shown that ADP-induced platelet aggregation is reduced by the introduction of electrostatic charge in the structure of lipid bilayer of liposomes. The effect achieved for the liposomes possessing a negative charge was more pronounced in comparison to the effect of positively charged liposomes.

  8. Inhibitory effects of in vivo oxidized high-density lipoproteins on platelet aggregation: evidence from patients with abetalipoproteinemia.

    PubMed

    Calzada, Catherine; Véricel, Evelyne; Colas, Romain; Guillot, Nicolas; El Khoury, Graziella; Drai, Jocelyne; Sassolas, Agnès; Peretti, Noël; Ponsin, Gabriel; Lagarde, Michel; Moulin, Philippe

    2013-07-01

    There is evidence that high-density lipoproteins (HDLs) may regulate platelet function, but disparate results exist regarding the effects of oxidized HDLs on platelets. The objective of our study was to determine the role of in vivo oxidized HDLs on platelet aggregation. Platelet aggregation and redox status were investigated in 5 patients with abetalipoproteinemia (ABLP) or homozygous hypobetalipoproteinemia, two rare metabolic diseases characterized by the absence of apolipoprotein B-containing lipoproteins, compared to 5 control subjects. Platelets isolated from plasma of patients with ABLP aggregated 4 to 10 times more than control platelets, depending on the agonist. By contrast, no differences in the extent of platelet aggregation were observed between ABLP platelet-rich plasma (PRP) and control PRP, suggesting the presence of a protective factor in ABLP plasma. ABLP HDLs inhibited agonist-induced platelet aggregation by binding to SR-BI, while control HDLs had no effect. On the other hand, lipoprotein-deficient plasma from patients with ABLP did not inhibit platelet aggregation. Severe oxidative stress was evidenced in patients with ABLP. Compared to control HDLs, ABLP HDLs showed a 40% decrease of α-tocopherol and an 11-fold increased malondialdehyde concentration. These results demonstrate that in vivo oxidized HDLs do not lose their antiaggregatory properties despite oxidation.

  9. 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

  10. Modification of Platelet Proteins by 4-hydroxynonenal: Potential Mechanisms for Inhibition of Aggregation and Metabolism

    PubMed Central

    Ravi, Saranya; Johnson, Michelle S.; Chacko, Balu K.; Kramer, Philip A.; Sawada, Hirotaka; Locy, Morgan L.; Wilson, Landon. S.; Barnes, Stephen; Marques, Marisa B.; Darley-Usmar, Victor M.

    2015-01-01

    Platelet aggregation is an essential response to tissue injury and is associated with activation of pro-oxidant enzymes, such as cyclooxygenase, and is also a highly energetic process. The two central energetic pathways in the cell, glycolysis and mitochondrial oxidative phosphorylation, are susceptible to damage by reactive lipid species. Interestingly, how platelet metabolism is affected by the oxidative stress associated with aggregation is largely unexplored. To address this issue, we examined the response of human platelets to 4-hydroxynonenal (4-HNE), a reactive lipid species which is generated during thrombus formation and during oxidative stress. Elevated plasma 4-HNE has been associated with renal failure, septic shock and cardiopulmonary bypass surgery. In this study, we found that 4-HNE decreased thrombin stimulated platelet aggregation by approximately 60%. The metabolomics analysis demonstrated that underlying our previous observation of a stimulation of platelet energetics by thrombin glycolysis and TCA (Tricarboxylic acid) metabolites were increased. Next, we assessed the effect of both 4-HNE and alkyne HNE (A-HNE) on bioenergetics and targeted metabolomics, and found a stimulatory effect on glycolysis, associated with inhibition of bioenergetic parameters. In the presence of HNE and thrombin glycolysis was further stimulated but the levels of the TCA metabolites were markedly suppressed. Identification of proteins modified by A-HNE followed by click chemistry and mass spectrometry revealed essential targets in platelet activation including proteins involved in metabolism, adhesion, cytoskeletal reorganization, aggregation, vesicular transport, protein folding, antioxidant proteins, and small GTPases. In summary, the biological effects of 4-HNE can be more effectively explained in platelets by the integrated effects of the modification of an electrophile responsive proteome rather than the isolated effects of candidate proteins. PMID:26475426

  11. [Mean platelet volume: interactions with platelet aggregation activity and glycoprotein IIb-IIIa and Ib expression levels].

    PubMed

    Khaspekova, S G; Ziuriaev, I T; Iakushkin, V V; Naĭmushin, Ia A; Sirotkina, O V; Zaĭtseva, N O; Ruda, M Ia; Mazurov, A V

    2014-01-01

    Increased mean platelet volume (MPV) is an independent risk factor of thrombotic events in patients with cardiovascular diseases. Interactions of MPV with platelet aggregation activity and contents of glycoprotein (GP) IIb-IIIa (alphaIIb/beta3 integrin, fibrinogen receptor) and GP Ib (von Willebrand factor receptor) were investigated in this study. Investigation was performed in a group of healthy volunteers (n = 38) and in a group of patients with acute coronary syndrome (ACS). In patients blood was collected at days 1, 3-5 and 8-12 after ACS development. As an antiaggregant therapy all patients received acetylsalicylic acid (ASA, inhibitor of thromboxane A2 synthesis) and most of them--clopidogrel (ADP receptor antagonist) with the exception of part of the patients (n = 44) at day 1 who had not taken clopidogrel before first blood collection. In volunteers platelet aggregation was stimulated by 1.25, 2.5, 5 and 20 M ADP, and in patients--by 5 and 20 M ADP. GP IIb-IIIa and GP Ib content on platelet surface was measured using 125I-labelled monoclonal antibodies. GP IIb-IIIa and GP Ib genetic polymorphisms were determined in ACS patients. In healthy donors significant correlations between MPV and aggregation levels were revealed at 1.25 and 2.5 M ADP (coefficients of correlation (r)--0.396 and 0.373, p < 0.05) and at 5 and 20 those interactions did not reach significant level (r--0.279 and 0.205, p > 0.05). Correlations between MPV and aggregation levels were observed at day 1 of ACS in a subgroup of patients who received ASA but had not started clopidogrel treatment (r--0.526, p < 0.01 and 0.368, p < 0.05 for 5 and 20 M ADP respectively). Interactions between these parameters were not registered upon combined treatment with ASA and clopidogrel. Strong direct correlations between MPV and GP IIb-IIIa and GP Ib contents were detected in healthy donors and ACS patients (at all time points) -r from 0.439 to 0.647 (p < or = 0.001 for all correlations). Genetic

  12. Acetaminophen and meloxicam inhibit platelet aggregation and coagulation in blood samples from humans.

    PubMed

    Martini, Angela K; Rodriguez, Cassandra M; Cap, Andrew P; Martini, Wenjun Z; Dubick, Michael A

    2014-12-01

    Acetaminophen (Ace) and meloxicam (Mel) are the two types of analgesic and antipyretic medications. This study investigated the dose responses of acetaminophen and meloxicam on platelet aggregation and coagulation function in human blood samples. Blood samples were collected from six healthy humans and processed to make platelet-adjusted (100 × 10 cells/μl) blood samples. Acetaminophen (Tylenol, Q-PAP, 100 mg/ml) was added at the doses of 0 μg/ml (control), 214 μg/ml (the standard dose, 1 ×), 4 ×, 8 ×, 10 ×, 12 ×, 16 ×, and 20 ×. Similarly, meloxicam (Metacam, 5 mg/ml) was added at doses of 0 μg/ml (control), 2.85 μg/ml (the standard dose, 1 ×), 4 ×, 8 ×, 10 ×, 12 ×, 16 ×, and 20 ×. Fifteen minutes after the addition of acetaminophen and/or meloxicam, platelet aggregation was stimulated with collagen (2 μg/ml) or arachidonic acid (0.5 mmol/l) and assessed using a Chrono-Log 700 aggregometer. Coagulation function was assessed by prothrombin time (PT), activated partial thromboplastin time (aPTT), and using Rotem thrombelastogram. A robust inhibition by acetaminophen and/or meloxicam was observed in arachidonic acid-stimulated platelet aggregation starting at 1 × dose. Collagen-stimulated platelet aggregation was inhibited by ACE starting at 1 × (78 ± 10% of control), and by meloxicam starting at 4 × (72 ± 5% of control, both P < 0.05). The inhibitions by acetaminophen and meloxicam combined were similar to those by acetaminophen or meloxicam. aPTT was prolonged by meloxicam starting at 4 ×. No changes were observed in PT or any of Rotem measurements by acetaminophen and/or meloxicam. Acetaminophen and meloxicam compromised platelet aggregation and aPTT. Further effort is warranted to characterize the effects of acetaminophen and meloxicam on bleeding in vivo.

  13. 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.

  14. Further insights into the anti-aggregating activity of NMDA in human platelets

    PubMed Central

    Franconi, Flavia; Miceli, Mauro; Alberti, Luisa; Seghieri, Giuseppe; De Montis, M Graziella; Tagliamonte, Alessandro

    1998-01-01

    In the present study the effect of N-methyl-D-aspartate (NMDA) on thromboxane B2 synthesis and on [Ca2+]i was studied in human platelets.NMDA (10−7 M) completely inhibited the synthesis of thromboxane B2 from exogenous arachidonic acid (AA), while it did not interfere with the aggregating effect of the thromboxane A2 receptor agonist U-46619.NMDA (0.1 μM–10 μM) dose-dependently increased intracellular calcium in washed platelets pre-loaded with fura 2 AM, and this effect was not additive with that of AA.NMDA shifted the dose-response curve of AA to the right. At the highest AA concentrations platelet aggregation was not inhibited.The antiaggregating effect of NMDA was not antagonized by NG-monomethyl-L-arginine (L-NMMA), a nitric oxide synthase (NOS) inhibitor.Finally, NMDA (0.01 nM–100 nM) associated with either aspirin or indomethacin significantly potentiated the antiaggregating activity of both cyclo-oxygenase inhibitors.It was concluded that NMDA is a potent inhibitor of platelet aggregation and thromboxane B2 synthesis in human platelet rich plasma (PRP). PMID:9630340

  15. Modulation of P-selection and platelet aggregation in chronic periodontitis: A clinical study

    PubMed Central

    Perumal, Ramesh; Rajendran, Maheashwari; Krishnamurthy, Malathi; Ganji, Kiran Kumar; Pendor, Sunil Dattuji

    2014-01-01

    Background: The primary etiologic factor of periodontitis is the subgingival infection with a group of Gram negative pathogens. Transient bacteremia in periodontitis patients underlie chronic production and systemic increases of various proinflammatory mediators, including Interleukin (IL)-1α, IL-6, C-reactive protein and Tumor necrosis factor (TNF)-α. P- selectin is a member of selectin family of cell surface receptor which is located in the membrane of the secretory granules (alpha granules) of platelets and in the membrane of the Weibel-Palade bodies of the vascular endothelial cells. P selectin redistributes from the membrane of the granules to the plasma membrane when platelets and endothelial cells are activated and thus degranulated. Aim: To compare the level of platelet activation, soluble P Selectin level and morphological changes and aggregation of platelets in patients in periodontitis patients compared to healthy controls. Materials and Methods: 80 patients were included in the study with the age group of 35-60. The patients were divided into 2 groups, 40 subjects with generalized chronic periodontitis and 40 healthy subjects taken as control. Periodontal Examination using clinical parameters namely, Bleeding Index, Plaque Index, Probing Pocket Depth and Clinical Attachment Level were recorded. Collection of blood samples for estimation of serum soluble P- selectin level by ELISA method. Evaluation of Platelet morphology and grading the platelet aggregation. Results: P-selectin expression shows that the mean value for control group is 4.97 ± 16.56 ng/mL and study group 13.05 ± 29.94 ng/mL which was significantly higher than control group with P value 0.001. Platelet morphological changes shows small form – mean value for control group is 75.83% ± 14.24% while for study group is 39.08%. ± 21.59; Big form – mean value for control group 0.80% ± 0.35% while for study group 0.48% ± 1.3%and Spider form- mean value for control group 23.88% ± 14

  16. Substituted alpah-methylbenzyl and tricyclic arylalkyl lactamimides as inhibitors of blood platelet aggregation.

    PubMed

    Grisar, J M; Claxton, G P; MacKenzie, R D

    1976-04-01

    N-[1-(p-Phenoxyphenyl)ethyl]hexahydro-2H-azepin-2-imine hydrochloride (10) and N-[1-(2-dibenzothienyl)-ethyl]hexahydro-2H-azepin-2-imine hydrochloride (22) were found to inhibit in vitro aggregation of human blood platelets induced by ADP with minimal release of procoagulant platelet factor 3. The compounds were selected from a series of substituted alpha-methylbenzyl and tricyclic arylalkyl lactamimides that were free of hypoglycemic and diuretic effects. Compounds 10 and 22, as well as N-[1-(1-naphthyl)ethyl]hexahydro-2H-azepin-2-imine hydrochloride (I) and N-(2,2-diphenylpentyl)hexahydro-2H-azepin-2-imine hydrochloride (II), were evaluated for effects on ADP-induced platelet aggregation after repeated oral administration to guinea pigs. Compound II (RMI 12,366A) showed in vivo activity in this system 2 h after the last of four daily doses of 100 mg/kg po.

  17. Validity of Particle-Counting Method Using Laser-Light Scattering for Detecting Platelet Aggregation in Diabetic Patients

    NASA Astrophysics Data System (ADS)

    Nakadate, Hiromichi; Sekizuka, Eiichi; Minamitani, Haruyuki

    We aimed to study the validity of a new analytical approach that reflected the phase from platelet activation to the formation of small platelet aggregates. We hoped that this new approach would enable us to use the particle-counting method with laser-light scattering to measure platelet aggregation in healthy controls and in diabetic patients without complications. We measured agonist-induced platelet aggregation for 10 min. Agonist was added to the platelet-rich plasma 1 min after measurement started. We compared the total scattered light intensity from small aggregates over a 10-min period (established analytical approach) and that over a 2-min period from 1 to 3 min after measurement started (new analytical approach). Consequently platelet aggregation in diabetics with HbA1c ≥ 6.5% was significantly greater than in healthy controls by both analytical approaches. However, platelet aggregation in diabetics with HbA1c < 6.5%, i.e. patients in the early stages of diabetes, was significantly greater than in healthy controls only by the new analytical approach, not by the established analytical approach. These results suggest that platelet aggregation as detected by the particle-counting method using laser-light scattering could be applied in clinical examinations by our new analytical approach.

  18. Dauricoside, a new glycosidal alkaloid having an inhibitory activity against blood-platelet aggregation.

    PubMed

    Hu, S M; Xu, S X; Yao, X S; Cui, C B; Tezuka, Y; Kikuchi, T

    1993-10-01

    Dauricoside (1), a new glycosidal alkaloid, was isolated from the rhizomes of Menispermum dauricum DC. along with dauricine (2), daurisoline (3), dauriporphine (4), menisporphine (5), and 6-O-demethylmenisporphine (6), and its structure was determined by means of spectroscopic methods. Compounds 1, 2, and 3 inhibited blood-platelet aggregation induced by adenosine 5'-diphosphate (ADP).

  19. Effect of n-tyrosol on blood viscosity and platelet aggregation.

    PubMed

    Plotnikov, M B; Chernysheva, G A; Smol'yakova, V I; Maslov, M Yu; Cherkashina, I V; Krysin, A P; Sorokina, I V; Tolstikova, T G

    2007-01-01

    Experiments on rats showed that n-tyrosol limited the increase in blood viscosity during thermal exposure at a shear rate of 5-300 sec(-1) and inhibited ADP-induced platelet aggregation. The effects of n-tyrosol are comparable to that of pentoxyphylline.

  20. Uridine Triphosphate Thio Analogues Inhibit Platelet P2Y12 Receptor and Aggregation

    PubMed Central

    Gündüz, Dursun; Tanislav, Christian; Sedding, Daniel; Parahuleva, Mariana; Santoso, Sentot; Troidl, Christian; Hamm, Christian W.; Aslam, Muhammad

    2017-01-01

    Platelet P2Y12 is an important adenosine diphosphate (ADP) receptor that is involved in agonist-induced platelet aggregation and is a valuable target for the development of anti-platelet drugs. Here we characterise the effects of thio analogues of uridine triphosphate (UTP) on ADP-induced platelet aggregation. Using human platelet-rich plasma, we demonstrate that UTP inhibits P2Y12 but not P2Y1 receptors and antagonises 10 µM ADP-induced platelet aggregation in a concentration-dependent manner with an IC50 value of ~250 µM. An eight-fold higher platelet inhibitory activity was observed with a 2-thio analogue of UTP (2S-UTP), with an IC50 of 30 µM. The 4-thio analogue (4S-UTP) with an IC50 of 7.5 µM was 33-fold more effective. A three-fold decrease in inhibitory activity, however, was observed by introducing an isobutyl group at the 4S- position. A complete loss of inhibition was observed with thio-modification of the γ phosphate of the sugar moiety, which yields an enzymatically stable analogue. The interaction of UTP analogues with P2Y12 receptor was verified by P2Y12 receptor binding and cyclic AMP (cAMP) assays. These novel data demonstrate for the first time that 2- and 4-thio analogues of UTP are potent P2Y12 receptor antagonists that may be useful for therapeutic intervention. PMID:28146050

  1. Reduction of Platelet Aggregation From Ingestion of Oleic and Linoleic Acids Found in Vitis vinifera and Arachis hypogaea Oils.

    PubMed

    Bazán-Salinas, Irma Leticia; Matías-Pérez, Diana; Pérez-Campos, Eduardo; Pérez-Campos Mayoral, Laura; García-Montalvo, Iván Antonio

    The purpose of this study was to evaluate the effect of the consumption of seed oils from Vitis vinifera and Arachis hypogaea in platelet aggregation. The initial hypothesis suggested that subjects who have consumed these seed oils undergo modified platelet aggregation. This study was performed using a pre-post test design, with a control group, and double blind. The effects of the consumption of grape seed and peanut oils were measured for platelet aggregation in clinical and laboratory tests in 30 healthy subjects. In addition to this group, a control group of 4 health subjects received no treatment with oils, just 500 mg oral administration acetylsalicylic acid for 7 days. Platelet aggregation was assessed by the Born turbidimetric method, using 3 different concentrations of adenosine diphosphate as agonists (2, 54; 1, 17; and 0, 58 μM). The study subjects had very similar results; both oils were shown to have a significant reduction in platelet aggregation. Grape seed oil showed a decrease of 8.4 ± 1% in aggregation, compared with peanut oil, which decreased aggregation by 10.4 ± 1%. The control group, taking 500 mg OD aspirin for 7 days, showed a significant decrease in platelet aggregation, similar to that of oil ingestion. Each of the oils was analyzed for fatty acids, to determine which particular acids were presents in greater levels, which could explain the reduction in platelet aggregation. The oil found to be most abundant in grape seeds was linoleic acid (omega-6), and in peanuts, it was oleic acid (omega-9). However, in fact, both acids reduced platelet aggregation. Consumption of plant oils from grape seeds and peanuts had a lowering effect on platelet aggregation, in addition to containing a high content of unsaturated fatty acids. However, omega-3, omega-6, and omega-9 fatty acids were not specifically responsible for the reductions mentioned above.

  2. Effects of heparin on platelet aggregation and release and thromboxane A2 production

    SciTech Connect

    Mohammad, S.F.; Anderson, W.H.; Smith, J.B.; Chuang, H.Y.; Mason, R.G.

    1981-08-01

    Heparin, when added to citrated platelet-rich plasma (PRP), caused potentiation of platelet aggregation and the release reaction induced by the aggregating agents adenosine diphosphate (ADP), arachidonic acid, collagen, and epinephrine. At low concentrations (4.7 x 10(-5) M) arachidonic acid failed to cause aggregation of platelets in citrated PRP. However, in the presence of heparin, the same concentration of arachidonic acid caused aggregation. Examination of PRP for the presence of thromboxane A2 (TxA2) by use of a bioassay revealed that heparin also stimulated release of TxA2. This finding indicated that platelets released more TxA2 when they were challenged by low concentrations of arachidonic acid in the presence of heparin than in its absence. Platelets were labeled with /sup 3/H-arachidonic acid and /sup 14/C-serotonin, and attempts were made to determine whether heparin stimulated the platelet release reaction first with subsequent increased production of TxA2, or alternatively, whether heparin stimulated TxA2 production first with subsequent enhancement of the release reaction. In view of the demonstrated simultaneous release of /sup 14/C-serotonin and /sup 3/H-arachidonic acid metabolites, it appeared that either release of /sup 14/C and /sup 3/H occurs concurrently or, even if one of these events is dependent on the other, both events take place in rapid succession. Timed sequential studies revealed that in the presence of arachidonic acid, the addition of heparin hastened the apparently simultaneous release of both /sup 14/C and /sup 3/H.

  3. [Recurrent idiopathic cerebral infarction in a 5-year-old boy, with emphasis on the importance of platelet aggregation analysis for appropriate selection of anti-platelet drugs].

    PubMed

    Sugiyama, Nobuyoshi; Matsuda, Shin-ichi; Shimizu, Mie; Obara, Saori; Ikegami, Mariko; Yokoyama, Jyun-ichi; Miyashita, Yoshihiro; Takizawa, Shyunya; Takagi, Shigeharu

    2009-01-01

    We present a 5-year-old boy with recurrent idiopathic cerebral infarction in which analysis of platelet hyperaggregability was useful in choosing appropriate anti-platelet drugs. The patient presented with gait disturbance at the age of 5 years and 1 month. Brain MRI demonstrated multiple infarctions in the right thalamus and left cerebellum. There were no apparent underlying diseases including hematological, cardiac and vascular abnormalities. He was diagnosed as idiopathic cerebral infarction. First, we administered ticlopidine and he remained stable with persistent mild intention tremor in the left upper extremity for 4 months. Then he developed the second stroke at the age of 5 years and 5 months, and multiple infarctions in the right celebellum and cerebellar vermis were demonstrated. On platelet aggregation analysis, adenosine diphosphate (ADP)-induced aggregation was inhibited, probably due to ticlopidine administration. Collagen- and epinephrine-induced platelet aggregation showed hyperaggregation, so we started to administer cilostazol, which inhibits only epinephrine-induced hyperaggregation. We also added aspirin, which inhibits collagen-induced hyperaggregation. The combination of anti-platelet drugs inhibited epinephrine-, collagen- and ADP-induced hyperaggregation in this patient. He has been stable on the triple combination of anti-platelet drugs without further episodes of cerebral infarction or transient ischemic attack for 4 years to date. Appropriate selection of anti-platelet therapy was achieved by the simple and repeatable platelet aggregation analyses, which must be considered even in pediatric patients with cerebral infarction.

  4. Enhancement of platelet response to immune complexes and IgG aggregates by lipid A-rich bacterial lipopolysaccharides

    PubMed Central

    1978-01-01

    The effect of the common lipid moiety of bacterial LPS on secretion from washed human platelets has been studied. The lipid A-rich LPS of S. minnesota R595 and a lipid A preparation both potentiated platelet serotonin secretion in response to IgG aggregates or immune complexes up to 50-fold but had little effect in the absence of IgG. Lipid A has been shown to bind immune aggregates, raising the possibility that its mechanism of action involved effective enlargement or insolubilization of the aggregates. IgG aggregates of dimer to tetramer size were shown to be platelet simuli, equivalent on a weight basis to larger soluble aggregates. The effect of both sizes of aggregates on platelets were equally enhanced by the LPS, indicating that increased size of aggregates alone could not account for the effect of LPS. Similarly, because lipid A-rich LPS enhanced platelet response to already insoluble immune complexes, its mechanism of action cannot simply be insolubilization of immune aggregates. These LPS did not enhance platelet stimulation by antiplatelet antibody, monosodium urate crystals, or thrombin and only slightly enhanced stimulation by insoluble human skin collagen. This indicates some stimulus specificity in the ability of LPS to increase platelet secretion. The enhancement of cell response to immune complexes by the common lipid region of LPS may represent a mechanism for the diverse effects of LPS in vivo and in vitro. PMID:627836

  5. Warm-up exercise suppresses platelet-eosinophil/neutrophil aggregation and platelet-promoted release of eosinophil/neutrophil oxidant products enhanced by severe exercise in men.

    PubMed

    Wang, Jong-Shyan; Yen, Hsiang-Ling; Yang, Chuen-Mao

    2006-03-01

    Heterotypic platelet-eosinophil/neutrophil aggregation and subsequent release of eosinophil/neutrophil oxidant products contribute to pathogenesis of conditions such as asthma and inflammatory bowel diseases. This study investigates whether warmup exercise (WUE) affects platelet-eosinophil/neutrophil interaction mediated by high-intensity exercise (HIE). Twenty-three healthy sedentary men performed on three occasions light-intensity exercise (LIE, 40%VO(2 max) for 40 min) and HIE (80%VO(2 max) for 40 min) with and without WUE (40%VO(2 max) for 20 min). Before and immediately after exercise, platelet-eosinophil and platelet-neutrophil aggregation (PEA and PNA), reactive oxygen species production of eosinophils and neutrophils (EROS and NROS) enhanced by platelets, and adhesion molecule expression on platelets, eosinophils, and neutrophils were measured. The results of this study demonstrated that HIE enhanced PEA, PNA, and platelet-induced EROS and NROS, was accompanied by increased expressions of Mac-1 on eosinophils and neutrophils and P-selectin on platelets at 5 dyne/cm(2) of shear stress, 100 microg/ml lipopolysaccharide, and 1 microM N-formylmethionyl- leucyl-phenylalanine treatments, whereas the enhancement of HIE on platelet-eosinophil/neutrophil interaction was suppressed by WUE. Conversely, LIE significantly reduced PEA and PNA, suppressed platelet-induced EROS and NROS, and down-regulated eosinophil/neutrophil Mac-1 and platelet P-selectin expressions under various stimuli and shear flow conditions. Moreover, these effects were more pronounced in platelet interaction with eosinophils than with neutrophils. It is concluded that HIE enhances hetero-aggregation, adhesion molecules expressions, and subsequent oxidative bursts mediated by platelets and eosinophils/neutrophils, this effect diminishes after WUE. However, LIE minimizes the risk of thromboinflammation.

  6. Responses to aggregating agents after cleavage of GPIb of human platelets by the O-sialoglycoprotein endoprotease from Pasteurella haemolytica- potential surrogates for Bernard-Soulier platelets?

    PubMed

    Kinlough-Rathbone, R L; Perry, D W; Rand, M L; Packham, M A

    2000-07-15

    Most proteolytic enzymes that cleave glycoprotein lb (GPlb) also cleave other glycoproteins or receptors on the surface of platelets. We have used an O-sialoglycoprotein endoprotease from Pasteurella haemolytica that selectively cleaves the heavily O-glycosylated GPlb, but does not cleave N-linked glycoproteins or unglycosylated proteins. Isolated, [14C]serotonin-labeled platelets in Tyrode-albumin solution were incubated with 10 microg/mL endoprotease for 60 minutes at 37 degrees C. These platelets did not release [14C]serotonin, had no detectable GPIb, and were unresponsive to ristocetin/von Willebrand factor. Compared with control platelets, aggregation and release of [14C]serotonin by the endoprotease-pretreated platelets were inhibited in response to low concentrations of thrombin, SFLLRN (the PAR-1-activating peptide), collagen, and U46619 (a thromboxane A(2) mimetic); aggregates were smaller in size. The presence of fibrinogen overcame the inhibition of responses induced by SFLLRN, collagen, and U46619. With fibrinogen, primary ADP-induced aggregation was scarcely affected by pretreatment with the endoprotease. Thus, the PAR-1 receptor for thrombin, and receptors for collagen, thromboxane A(2), fibrinogen (GPIIb/IIIa), and ADP appear to function normally on the endoprotease-pretreated platelets. Since only GPIb is cleaved by the endoprotease, these platelets seem to provide potential surrogates for Bernard-Soulier syndrome platelets for further studies of platelet functions in this condition.

  7. The effect of naloxone and cyproheptadine on pulmonary platelet trapping, hypotension, and platelet aggregability in traumatized dogs

    SciTech Connect

    Almqvist, P.; Kuenzig, M.; Schwartz, S.I.

    1983-05-01

    Adult respiratory distress syndrome (ARDS) is a serious complication of trauma and sepsis. We have earlier shown naloxone, an opiate antagonist, and cyproheptadine, an antiserotonin drug, to be effective in reducing pulmonary platelet trapping (PPT), which is thought to play an important role in the evolution of ARDS in endotoxin-shocked dogs. Endorphins are implicated as pathophysiologic factors in shock, and serotonin is a possible mediator of their action. The present study shows naloxone and cyproheptadine to be equally effective in protecting against PPT in dogs subjected to trauma, and when naloxone is given before the trauma it also obviates the hypotension associated with trauma. In addition, the naloxone- and cyproheptadine-treated animals did not show the increased platelet aggregability usually seen in traumatized dogs.

  8. Effect of dietary copper on platelet volume and aggregation in men

    SciTech Connect

    Milne, D.B.; Gallagher, S.K. )

    1991-03-15

    A study conducted in the authors' laboratory indicated that mean platelet (PLT) volume (MPV) in rats was affected by dietary copper. They suggested that PLT aggregation may also be affected. Ten men aged 19 to 39 yrs, who lived in a metabolic unit, participated in a study that was divided into four six-week dietary periods in a 2 {times} 2 factorial design with 0.65 and 2.65 mg Cu/d and 0.75 and 2.75 g cystine/d as variables. Plasma copper was not significantly affected by the dietary manipulations, but enzymatically measured ceruloplasmin (Cp) was significantly depressed during low copper intake. Maximum 5 {mu}M ADP-stimulated PLT aggregation in platelet rich plasma was significantly greater during low copper intake than during high Cu intake. Total platelet count and collagen or epinephrine stimulated PLT aggregation were not significantly affected by dietary treatment. Four men who responded to low copper intake with elevated serum cholesterol and depressed specific activity of Cp had significantly elevated MPV and maximum ADP-stimulated PLT aggregation during low Cu intake. The other six men exhibited only increased PLT aggregation during only the low copper, low cystine dietary period. These data indicate that dietary copper is a factor in PLT function in humans.

  9. Thrombotic thrombocytopenic purpura: from platelet aggregates to plasma.

    PubMed

    Marques, Marisa B; Mayfield, Charles A; Blackall, Douglas P

    2004-06-01

    Thrombotic thrombocytopenic purpura (TTP) is a syndrome of severe thrombocytopenia and microangiopathic hemolytic anemia without an alternative explanation. Although some patients also have a combination of fever and neurologic and/or renal manifestations, these are not required for the diagnosis. Thus, plasmapheresis should start as soon as TTP is placed high in the differential diagnosis to prevent significant mortality. Histopathologically, TTP is characterized by widespread platelet thrombi in the microcirculation. Ultralarge von Willebrand factor (vWf) multimers found in the patient's plasma are the basis for the platelet thrombi. Recent evidence has linked the abnormal fragments of vWf with deficiency of a plasma enzyme named vWf-cleaving protease, or ADAMTS-13. While a small percentage of patients with TTP have a constitutional defect in this enzyme, many with the acute idiopathic form have an antibody to ADAMTS-13, affecting its ability to cleave vWf. The determination of the enzyme activity and the presence of its inhibitor have emerged as a potential tool in the diagnosis and prognosis of TTP. Furthermore, it helps to differentiate TTP from the hemolytic uremic syndrome, in which the level of ADAMTS-13 is expected to be normal or only slightly decreased.

  10. Platelet factor XIIIa release during platelet aggregation and plasma clot strength measured by thrombelastography in patients with coronary artery disease treated with clopidogrel.

    PubMed

    Kreutz, Rolf P; Owens, Janelle; Lu, Deshun; Nystrom, Perry; Jin, Yan; Kreutz, Yvonne; Desta, Zeruesenay; Flockhart, David A

    2015-01-01

    It has been estimated that up to half of circulating factor XIIIa (FXIIIa) is stored in platelets. The release of FXIIIa from platelets upon stimulation with adenosine diphosphate (ADP) in patients with coronary artery disease treated with dual antiplatelet therapy has not been previously examined. Samples from 96 patients with established coronary artery disease treated with aspirin and clopidogrel were examined. Platelet aggregation was performed by light transmittance aggregometry in platelet-rich plasma (PRP), with platelet-poor plasma (PPP) as reference, and ADP 5 µM as agonist. Kaolin-activated thrombelastography (TEG) was performed in citrate PPP. PRP after aggregation was centrifuged and plasma supernatant (PSN) collected. FXIIIa was measured in PPP and PSN. Platelet aggregation after stimulation with ADP 5 µM resulted in 24% additional FXIIIa release in PSN as compared to PPP (99.3 ± 27 vs. 80.3 ± 24%, p < 0.0001). FXIIIa concentration in PSN correlated with maximal plasma clot strength (TEG-G) (r = 0.48, p < 0.0001), but not in PPP (r = 0.15, p = 0.14). Increasing quartiles of platelet-derived FXIIIa were associated with incrementally higher TEG-G (p = 0.012). FXIIIa release was similar between clopidogrel responders and non-responders (p = 0.18). In summary, platelets treated with aspirin and clopidogrel release a significant amount of FXIIIa upon aggregation by ADP. Platelet-derived FXIIIa may contribute to differences in plasma TEG-G, and thus, in part, provide a mechanistic explanation for high clot strength observed as a consequence of platelet activation. Variability in clopidogrel response does not significantly influence FXIIIa release from platelets.

  11. Platelet activation, adhesion, inflammation, and aggregation potential are altered in the presence of electronic cigarette extracts of variable nicotine concentrations.

    PubMed

    Hom, Sarah; Chen, Li; Wang, Tony; Ghebrehiwet, Berhane; Yin, Wei; Rubenstein, David A

    2016-11-01

    Tobacco smoke extracts prepared from both mainstream and sidestream smoking have been associated with heightened platelet activation, aggregation, adhesion, and inflammation. Conversely, it has been shown that pure nicotine inhibits similar platelet functions. In this work, we 1) evaluated the effects of e-cigarette extracts on platelet activities and 2) elucidated the differences between the nicotine-dependent and non-nicotine dependent (e.g. fine particulate matter or toxic compounds) effects of tobacco and e-cigarette products on platelet activities. To accomplish these goals, platelets from healthy volunteers (n = 50) were exposed to tobacco smoke extracts, e-cigarette vapor extracts, and pure nicotine and changes in platelet activation, adhesion, aggregation, and inflammation were evaluated, using optical aggregation, flow cytometry, and ELISA methods. Interestingly, the exposure of platelets to e-vapor extracts induced a significant up-regulation in the expression of the pro-inflammatory gC1qR and cC1qR and induced a marked increase in the deposition of C3b as compared with traditional tobacco smoke extracts. Similarly, platelet activation, as measured by a prothrombinase based assay, and platelet aggregation were also significantly enhanced after exposure to e-vapor extracts. Finally, platelet adhesion potential toward fibrinogen, von Willebrand factor, and other platelets was also enhanced after exposure to e-cigarette vapor extracts. In the presence of pure nicotine, platelet functions were observed to be inhibited, which further suggests that other constituents of tobacco smoke and electronic vapor can antagonize platelet functions, however, the presence of nicotine in extracts somewhat perpetuated the platelet functional changes in a dose-dependent manner.

  12. C-phycocyanin, a very potent and novel platelet aggregation inhibitor from Spirulina platensis.

    PubMed

    Hsiao, George; Chou, Po-Hsiu; Shen, Ming-Yi; Chou, Duen-Suey; Lin, Chien-Huang; Sheu, Joen-Rong

    2005-10-05

    The aim of this study was to systematically examine the inhibitory mechanisms of C-phycocyanin (C-PC), one of the major phycobiliproteins of Spirulina platensis (a blue-green alga), in platelet activation. In this study, C-PC concentration-dependently (0.5-10 nM) inhibited platelet aggregation stimulated by agonists. C-PC (4 and 8 nM) inhibited intracellular Ca2+ mobilization and thromboxane A2 formation but not phosphoinositide breakdown stimulated by collagen (1 microg/mL) in human platelets. In addition, C-PC (4 and 8 nM) markedly increased levels of cyclic GMP and cyclic GMP-induced vasodilator-stimulated phosphoprotein (VASP) Ser(157) phosphorylation. Rapid phosphorylation of a platelet protein of Mw 47,000 (P47), a marker of protein kinase C activation, was triggered by phorbol-12,13-dibutyrate (150 nM). This phosphorylation was markedly inhibited by C-PC (4 and 8 nM). In addition, C-PC (4 and 8 nM) markedly reduced the electron spin resonance (ESR) signal intensity of hydroxyl radicals in collagen (1 microg/mL)-activated platelets. The present study reports on a novel and very potent (in nanomolar concentrations) antiplatelet agent, C-PC, which is involved in the following inhibitory pathways: (1) C-phycocyanin increases cyclic GMP/VASP Ser157 phosphorylation and subsequently inhibits protein kinase C activity, resulting in inhibition of both P47 phosphorylation and intracellular Ca2+ mobilization, and (2) C-PC may inhibit free radicals (such as hydroxyl radicals) released from activated platelets, which ultimately inhibits platelet aggregation. These results strongly indicate that C-PC appears to represent a novel and potential antiplatelet agent for treatment of arterial thromboembolism.

  13. Inhibition of Platelet Aggregation by the Leaf Extract of Carica papaya During Dengue Infection: An In Vitro Study.

    PubMed

    Chinnappan, Shobia; Ramachandrappa, Vijayakumar Shettikothanuru; Tamilarasu, Kadhiravan; Krishnan, Uma Maheswari; Pillai, Agiesh Kumar Balakrishna; Rajendiran, Soundravally

    2016-04-01

    Dengue cases were reported to undergo platelet activation and thrombocytopenia by a poorly understood mechanism. Recent studies suggested that Carica papaya leaf extract could recover the platelet count in dengue cases. However, no studies have attempted to unravel the mechanism of the plant extract in platelet recovery. Since there are no available drugs to treat dengue and considering the significance of C. papaya in dengue treatment, the current study aimed to evaluate two research questions: First one is to study if the C. papaya leaf extract exerts its action directly on platelets and second one is to understand if the extract can specifically inhibit the platelet aggregation during dengue viral infection. Sixty subjects with dengue positive and 60 healthy subjects were recruited in the study. Platelet-rich plasma (PRP) and platelet-poor plasma were prepared from both the dengue-infected and healthy control blood samples. Effect of the leaf extract obtained from C. papaya leaves was assessed on plasma obtained as well as platelets collected from both healthy and dengue-infected individuals. Platelet aggregation was significantly reduced when leaf extract preincubated with dengue plasma was added into control PRP, whereas no change in aggregation when leaf extract incubated-control plasma was added into control PRP. Upon direct addition of C. papaya leaf extract, both dengue PRP and control PRP showed a significant reduction in platelet aggregation. Within the dengue group, PRP from severe and nonsevere cases showed a significant decrease in aggregation without any difference between them. From the study, it is evident that C. papaya leaf extract can directly act on platelet. The present study, the first of its kind, found that the leaf extract possesses a dengue-specific neutralizing effect on dengue viral-infected plasma that may exert a protective role on platelets.

  14. 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.

  15. 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.

  16. Effects of ethanol on aggregation, serotonin release, and amyloid precursor protein processing in rat and human platelets.

    PubMed

    Ehrlich, Daniela; Humpel, Christian

    2014-01-01

    It is known that oxidative stress leads to amyloid precursor protein (APP) dysregulation in platelets. Ethanol (EtOH) is a vascular risk factor and induces oxidative stress. The aim of the present study was thus to investigate whether EtOH affects APP processing in rat and human platelets. Platelets were exposed to 50 mM EtOH with and without 2 mM calcium-chloride (CaCl₂) for 20 or 180 minutes at 37°C. Platelet aggregation, serotonin release and APP isoforms 130 and 106/110 kDa were analyzed. As a control, 100 mM H₂O₂ was tested in rat platelets. Our data show that EtOH alone did not affect any of the analyzed parameters, whereas CaCl₂ significantly increased aggregation of rat and human platelets. In addition, CaCl₂ alone enhanced serotonin release in rat platelets. EtOH counteracted CaCl₂-induced aggregation and serotonin release. In the presence of CaCl₂, EtOH reduced the 130 kDa APP isoform in rat and human platelets. In conclusion, this study shows that in the presence of CaCl₂, EtOH affects the platelet function and APP processing in rat and human platelets.

  17. 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.

  18. Dietary calcium attenuates platelet aggregation and intracellular Ca2+ mobilization in spontaneously hypertensive rats

    NASA Technical Reports Server (NTRS)

    Otsuka, K.; Watanabe, M.; Yue, Q.; McCarron, D. A.; Hatton, D.

    1997-01-01

    Spontaneously hypertensive rats (SHR) are known to be blood pressure sensitive to dietary calcium. The effects of dietary calcium on platelet aggregation and intracellular Ca2+ mobilization were assessed by turbidimetric methods and fura-2 methods, respectively, in washed platelets of SHR. Ca2+ ATPase activity was examined in aortic membrane fractions. Six weeks of dietary calcium supplementation attenuated the increase of systolic blood pressure (SBP 199 +/- 16 v 170 +/- 9 mm Hg, P < .001) and thrombin-induced platelet aggregation (84.5 +/- 3.7 v 73.7 +/- 7.4%, P < .004) at 9 weeks of age. The ionomycin-induced intracellular calcium ([Ca2+]i) peak in the absence of external Ca2+, which reflects [Ca2+]i storage size, and thrombin-evoked [Ca2+]i release from [Ca2+]i storage were decreased by 2.0% Ca diet (472 +/- 55 v 370 +/- 23 nmol/L, P < .001, 339 +/- 29 v 278 +/- 33 nmol/L, P < .002). In addition, SBP was positively correlated with platelet aggregation (r = 0.703, P = .0088), thrombin-evoked [Ca2+]i (r = 0.739, P = .0044), and ionomycin-induced [Ca2+]i (r = 0.591, P = .0415), respectively. However, there was no significant effect of dietary calcium on Ca2+-ATPase activity in aortic membranes. These results suggest that dietary calcium supplementation had a beneficial effect on platelets of SHR by attenuating [Ca2+]i mobilization from [Ca2+]i storage. The hypotensive effect of dietary calcium might be associated with attenuated [Ca2+]i mobilization in SHR.

  19. Anti-platelet aggregation triterpene saponins from the galls of Sapindus mukorossi.

    PubMed

    Huang, Hui-Chi; Tsai, Wei-Jern; Liaw, Chia-Ching; Wu, Shih-Hsiung; Wu, Yang-Chang; Kuo, Yao-Haur

    2007-09-01

    Bioassay-directed fractionation of an ethanolic extract of the galls of Sapindus mukorossi has resulted in the isolation of two new tirucallane-type triterpenoid saponins, sapinmusaponins Q (1) and R (2), along with three known oleanane-type triterpenoid saponins (3-5). Their structures were elucidated on the basis of spectroscopic analysis and chemical hydrolysis. Biological evaluation showed that both sapinmusaponins Q and R demonstrated more potent anti-platelet aggregation activity than aspirin.

  20. Coherent Plasmon-Exciton Coupling in Silver Platelet-J-aggregate Nanocomposites

    DTIC Science & Technology

    2015-02-27

    plexcitons, which may result in unusual light-matter interactions. We report the formation of a transparency dip in the visible spectra of colloidal ...visible spectra of colloidal suspensions containing silver nanoplatelets and a cyanine dye, 1,1?-diethyl-2,2?-cyanine iodide (PIC). PIC was...highest reported for colloidal nanoparticles. The optical properties of the silver platelet-J-aggregate nanocomposites were supported numerically and

  1. Effects of ergotamine and methysergide on blood platelet aggregation responses of migrainous subjects

    PubMed Central

    Hilton, Barbara P.; Zilkha, K. J.

    1974-01-01

    Platelet aggregation responses to 5-hydroxytryptamine (5-HT) were measured in plasma from migrainous subjects taking either methysergide maleate or ergotamine tartrate and were found to be reduced. Blood 5-HT levels of subjects free of headache were not affected by these drugs. The results support the hypothesis that methysergide and ergotamine act by occupying 5-HT uptake sites in vessel walls, leaving 5-HT molecules available to occupy receptors concerned with vasoconstriction. PMID:4836755

  2. The influence of Rubus idaeus and Rubus caesius leaf extracts on platelet aggregation in whole blood. Cross-talk of platelets and neutrophils.

    PubMed

    Dudzinska, Dominika; Bednarska, Katarzyna; Boncler, Magdalena; Luzak, Boguslawa; Watala, Cezary

    2016-07-01

    Recently, polyphenols have gained attention as potential natural cardioprotective therapeutics, due to their antiplatelet, anti-inflammatory and anticoagulant activity. Species belonging to the genus Rubus sp. have been reported to be a source of polyphenolic compounds with antioxidative proprieties and beneficial biological activities. This study investigates the effects of leaf extracts obtained from red raspberry (Rubus idaeus L.) and European dewberry (Rubus caesius L.) on the reactivity of blood platelets. In ADP-stimulated blood, raspberry and dewberry extracts (15 µg/ml) markedly decreased platelet surface membrane expression of activated GPIIbIIIa receptor by 16% and 21%, respectively (P < 0.01) and significantly inhibited platelet aggregation (by 31-41% for raspberry and by 38-55% for dewberry, P < 0.01). In platelet-rich plasma (PRP), the extracts had no effect on ADP-induced platelet aggregation. The effectiveness of the extracts in whole blood and the lack of their activity in PRP indicate that leukocytes are likely to participate in the platelet response to the extracts. Our experiments show that the extracts significantly reduced the amount of free radicals released by activated neutrophils in whole blood (P < 0.001), as well as in suspensions of isolated neutrophils (P < 0.05). Moreover, the reduced number of neutrophils leads to the decreased efficiency of the extracts in the inhibition of platelet aggregation. In summary, our findings show that the raspberry and dewberry leaf extracts considerably modulated blood platelet reactivity in whole blood: they influenced blood platelet aggregation, possibly via the modulation of the redox status dependent on the oxidative activity of neutrophils.

  3. Release of Phosphorylated HSP27 (HSPB1) from Platelets Is Accompanied with the Acceleration of Aggregation in Diabetic Patients.

    PubMed

    Tokuda, Haruhiko; Kuroyanagi, Gen; Tsujimoto, Masanori; Enomoto, Yukiko; Matsushima-Nishiwaki, Rie; Onuma, Takashi; Kojima, Akiko; Doi, Tomoaki; Tanabe, Kumiko; Akamatsu, Shigeru; Iida, Hiroki; Ogura, Shinji; Otsuka, Takanobu; Iwama, Toru; Tanikawa, Takahisa; Ishikawa, Kei; Kojima, Kumi; Kozawa, Osamu

    2015-01-01

    We investigated the relationship between HSP27 phosphorylation and collagen-stimulated activation of platelets in patients with diabetes mellitus (DM). Platelet-rich plasma was prepared from blood of type 2 DM patients. The platelet aggregation was analyzed in size of aggregates by an aggregometer using a laser scattering method. The protein phosphorylation was analyzed by Western blotting. Phosphorylated-HSP27 and PDGF-AB released from platelets were measured by ELISA. The phosphorylated-HSP27 levels at Ser-78 and Ser-82 induced by collagen were directly proportional to the platelet aggregation. Total HSP27 levels in platelets were decreased concomitantly with the phosphorylation. The released HSP27 levels were significantly correlated with the phosphorylated levels of HSP27 in the platelets stimulated by 0.3 μg/ml collagen. The low dose collagen-stimulated release of HSP27 was detected but relatively small in healthy donors. The released levels of PDGF-AB were in parallel with the levels of released HSP27. Area under the curve (AUC) of small aggregation (9-25 μm) induced by 0.3 μg/ml collagen was inversely proportional to the levels of released HSP27. AUC of large aggregation (50-70 μm) was directly proportional to the levels of released HSP27. Exogenous recombinant phosphorylated- HSP27 hardly affected the aggregation or the released levels of PDGF-AB induced by collagen. These results strongly suggest that HSP27 is released from human platelets accompanied with its phosphorylation induced by collagen, which is correlated with the acceleration of platelet aggregation in type 2 DM patients.

  4. Response to platelet-activating factor in human platelets stored and aged in plasma. Decrease in aggregation, phosphoinositide turnover, and receptor affinity

    SciTech Connect

    Shukla, S.D.; Morrison, W.J.; Klachko, D.M.

    1989-07-01

    Human platelet concentrates were stored in polyolefin bags at 22 to 24 degrees C on a horizontal shaker for up to 8 days. At different intervals, aliquots of platelet-rich plasma (PRP) were removed aseptically and five variables, i.e., platelet counts, morphology, platelet-activating factor (PAF)-stimulated aggregation, phosphoinositide turnover, and (3H)PAF binding to platelet receptors, were studied. The number of platelets did not change during the 8 days of storage. Scanning electron microscopy of the platelets revealed a gradual morphologic change from biconcave flat discs to irregular, crenated forms. The PAF-induced aggregation of platelets declined with time of storage. A decrease to 50 percent of the Day 1 aggregatory response to PAF was evident on Day 2, and there was a further decline to about 20 percent by Day 6. Similarly, PAF receptor-coupled phosphoinositide turnover, as monitored by 32P incorporation into individual phosphoinositides, decreased dramatically with storage. After 2 to 3 days of storage, the phosphoinositide turnover was reduced to 50 percent of the original response, and it continued to decline to about 25 percent of original response by Day 5 or 6. The binding of (3H)PAF to washed human platelets indicated subtle changes between Days 2 and 4, which became more noticeable by Day 6. These results have raised the possibility of changes in the number of the receptors and/or their affinity for the ligand during storage. We conclude that although the number of platelets was maintained during storage for 8 days, a general deterioration of their responses to PAF occurred at the levels of cell surface receptor, transmembrane signaling (phosphoinositide turnover), and response (aggregation).

  5. 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.

  6. 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.

  7. Platelet response to increased aspirin dose in patients with persistent platelet aggregation while treated with aspirin 81 mg.

    PubMed

    Gengo, Fran; Westphal, Erica S; Rainka, Michelle M; Janda, Maria; Robson, Matthew J; Hourihane, J Maurice; Bates, Vernice

    2016-04-01

    This study demonstrates that patients who are taking 81 mg of aspirin and are nonresponsive benefit from a dose of 162 mg or greater vs a different antiplatelet therapy. We identified 100 patients who were nonresponsive to aspirin 81 mg via whole blood aggregometry and observed how many patients became responsive at a dose of 162 mg or greater. Platelet nonresponsiveness was defined as >10 Ω of resistance to collagen 1 µg/mL and/or an ohms ratio of collagen 1 µg/mL to collagen 5 µg/mL >0.5 and/or >6 Ω to arachidonate. Borderline response was defined as an improvement in 1 but not both of the above criteria. Of the initial 100 patients who were nonresponsive to an aspirin dose of 81 mg, 79% became responsive at a dose of 162 mg or >162 mg. Only 6% did not respond to any increase in dose. We believe that patients treated with low-dose aspirin who have significant risk for secondary vascular events should be individually assessed to determine their antiplatelet response. Those found to have persistent platelet aggregation despite treatment with 81 mg of aspirin have a higher likelihood of obtaining an adequate antiplatelet response at a higher aspirin dose.

  8. Treatment of experimental furcation perforations with mineral trioxide aggregate, platelet rich plasma or platelet rich fibrin in dogs' teeth.

    PubMed

    Tawfik, Hosam E; Abu-Seida, Ashraf M; Hashem, Ahmed A; El-Khawlani, Mohammed M

    2016-06-01

    This work evaluates the effect of mineral trioxide aggregate (MTA), platelet rich plasma (PRP) or platelet rich fibrin (PRF) on healing of non-contaminated and contaminated furcation perforations. A total of 192 teeth of 12 dogs was divided into three equal groups according to evaluation period. Each group was further subdivided into MTA, PRP, PRF, negative and positive control subgroups. Each experimental subgroup was further subdivided according to perforation status into non-contaminated and contaminated subdivisions. Root canal therapy was carried out and furcation perforation was made in all teeth except in negative control subgroup. The furcation perforation was repaired immediately in subdivision (1) and after 4 weeks in subdivision (2). The change in vertical bone loss was measured by radiography. Inflammatory cell count, cemental deposition, new bone formation, bone resorption and epithelial proliferation were assessed. Both PRP and PRF demonstrated statistically significant reduction in vertical bone loss and inflammatory cell count than MTA. No significant difference was found between MTA, PRP and PRF in cemental deposition, new bone formation, bone resorption and epithelial proliferation. The non-contaminated teeth demonstrated better treatment outcomes than the contaminated teeth. In conclusion, PRP and PRF are successful treatment options for repairing of furcation perforation in both non-contaminated and contaminated teeth in dogs with superior outcomes in non contaminated teeth.

  9. 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

  10. The effects of 7.5% NaCl/6% dextran 70 on coagulation and platelet aggregation in humans

    NASA Technical Reports Server (NTRS)

    Hess, J. R.; Dubick, M. A.; Summary, J. J.; Bangal, N. R.; Wade, C. E.

    1992-01-01

    The combination solution of 7.5% NaCl/6% dextran 70 (HSD) administered IV gives hemodynamic improvement in the treatment of hemorrhagic hypotension. Since earlier dextran solutions were reported to interfere with blood coagulation, the effects of HSD on the prothrombin time (PT), the activated partial thromboplastin time (APTT), platelet aggregation, and platelet concentration were studied. The HSD mixed with human plasma (1:5 and 1:10) slightly prolonged PT, but had no effect on the APTT, compared with saline controls. The HSD also decreased human platelet aggregation at the 1:5 dilution. In separate mixing studies, the hypertonic saline component of HSD was associated with the prolongation of PT and decreased platelet aggregation. The data from these studies indicate that at its proposed therapeutic dose, HSD is expected to have minimal effect on blood coagulation.

  11. Red Wine Inhibits Aggregation and Increases ATP-diphosphohydrolase (CD39) Activity of Rat Platelets in Vitro.

    PubMed

    Caiazzo, Elisabetta; Tedesco, Idolo; Spagnuolo, Carmela; Russo, Gian Luigi; Ialenti, Armando; Cicala, Carla

    2016-06-01

    Moderate consumption of red wine has been shown to exert a peculiar cardioprotective effect compared with other alcoholic beverages; inhibition of platelet aggregation seems to be one of the mechanisms underlying this beneficial effect. CD39/ATP-diphosphohydrolase is an integral membrane glycoprotein metabolizing ATP and ADP to AMP; in concert with CD73/ecto-5'-nucleotidase, it contributes to extracellular adenosine accumulation. CD39 is considered a key modulator of thrombus formation; it inhibits platelet aggregation by promoting ADP hydrolysis. There is evidence that red wine consumption increases CD39 activity in platelets from streptozotocin-induced diabetic rats. Here we show that two kinds of Aglianico red wines inhibit aggregation and increase ATP--and ADPase activity in rat platelets.

  12. [The effects of ticlopidine and nifedipine on platelet aggregation in patients with obliterating arteriopathy of the lower limbs].

    PubMed

    Hevia Alonso, A; Gago Angelino, J; López-Valpuesta, F J; Serrano Molina, J S; Fernández-Sanz, S

    1992-04-01

    This paper evaluates the antiaggregant action of ticlopidine and nifedipine in patients with obliterate arteriopathy in inferior limbs of arteriosclerotic etiology (OAIL). They were established 4 study groups: control, with health volunteers without treatment (N = 10); patients treated with placebo (n = 11); patients treated with 500 mg/day of ticlopidine (n = 12) and treated with 30 mg/day of nifedipine (n = 12). The last 3 groups the treatment duration was 30 days. It was studied the platelet aggregatory activity against ADP and collagen, before drug administration and at 15 and 30 days post-treatment. Our results suggest that: Platelet aggregation is increased in patients with AOMI compared with that observed in the control group. Ticlopidine inhibits platelet aggregation induced by ADP, but not that induced by collagen. Nifedipine doesn't produce any effect on platelet aggregation.

  13. 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.

  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. 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.

  16. Investigation of piperidine derivatives in ex vivo models of pain and platelet aggregation.

    PubMed

    Saify, Zafar Saeed; Rasheed, Huma; Mushtaq, Nousheen; Nisa, Mehrun; Haider, Shazia; Naz, Afshan; Azhar, Kaniz Fizza; Miana, Ghulam Abbas

    2012-11-01

    Piperidine derivatives are known to exhibit analgesic activities and are likely to possess the ability to block the effects of prostaglandins through inhibition of downstream signaling pathways. The present study investigated the activity of five derivatives (PD2-6) of 4-(4'-bromophenyl)-4-piperidinol (PD1), against pain and platelet aggregation mediated by the release of prostaglandins and thromboxane A2, respectively. The results showed that compound PD1 and its two phenacyl derivatives PD3 and PD5 exhibited a highly significant analgesic effect (p < 0.01), whereas PD4 and PD6 also showed significant activity. PD3, the most active analgesic compound when docked to the opioid receptor, had interactions between the oxygen of its nitro group and the amino group of ARG 573, indicating a distance of 1.2563 Å. The antiplatelet data showed that compound PD5 (4-(4'-bromo-phenyl)-4-hydroxy-1-[2-(2″,4″-dimethoxyphenyl)-2-oxo-ethyl]-piperidinium bromide) had an IC(50) = 0.06 mM, which was the most active compound, whereas PD3 was the second most active compound against platelet aggregating factor-induced aggregation with an IC(50) = 80 mM. Acetyl salicylic acid (IC(50) = 150 μM) was used as a positive control.

  17. Detection of Platelet-Monocyte Aggregates by the ADAM® Image Cytometer

    PubMed Central

    Jung, Bo Kyeung; Cho, Chi Hyun; Moon, Kyung Chul; sung Hur, Dae; Yoon, Jeong-Ah; Yoon, Soo-Young

    2014-01-01

    Background: Inappropriate platelet activation is known to be associated with various thrombotic disorders. Platelet-monocyte aggregates (PMAs), whose formation is mediated by platelet surface P-selectin (CD62P), can be used as a reliable marker to detect platelet activation. Previous studies have generally detected PMAs through flow cytometry-based approaches. Recently, the ADAM® image cytometer (Nanoentek Inc., Seoul, Korea) was developed for image-based cellular analysis. In this study, we detected PMAs with the ADAM® cytometer, evaluated the reproducibility of the measurements made by the ADAM® cytometer, and compared the abilities of the ADAM® cytometer and a flow cytometric assay to detect PMAs. Methods: Whole blood samples were collected from patients. Within 5 minutes of collection, anticoagulated whole blood samples were fixed in 10% paraformaldehyde and 5% glyoxal. Nineteen clinical specimens were collected; each was analyzed three times with the ADAM® cytometer in order to assess the reproducibility of its measurements. To compare the ability of the ADAM® cytometer with that of a flow cytometer to detect PMAs, each cytometer was used for 23 clinical samples and the correlation of the measurements was determined. Results: The PMA measurements made by the ADAM® cytometer showed good reproducibility (CV < 10% for all specimens). Moreover, the PMA measurements made by the ADAM® cytometer exhibited a high correlation with those made by a flow cytometric assay (R = 0.944). Conclusions: The ADAM® cytometer is a suitable alternative method to the flow cytometry-based assays. Since the ADAM cytometer does not need specialized instrument knowledge or software proficiency (unlike flow cytometry), the ADAM® cytometer can be used as a rapid and reliable POCT device to measure platelet activation in peripheral blood. This, in turn, will provide valuable information regarding patient propensities to thrombotic diseases. PMID:25317068

  18. Structure, Sulfatide Binding Properties, and Inhibition of Platelet Aggregation by a Disabled-2 Protein-derived Peptide*

    PubMed Central

    Xiao, Shuyan; Charonko, John J.; Fu, Xiangping; Salmanzadeh, Alireza; Davalos, Rafael V.; Vlachos, Pavlos P.; Finkielstein, Carla V.; Capelluto, Daniel G. S.

    2012-01-01

    Disabled-2 (Dab2) targets membranes and triggers a wide range of biological events, including endocytosis and platelet aggregation. Dab2, through its phosphotyrosine-binding (PTB) domain, inhibits platelet aggregation by competing with fibrinogen for αIIbβ3 integrin receptor binding. We have recently shown that the N-terminal region, including the PTB domain (N-PTB), drives Dab2 to the platelet membrane surface by binding to sulfatides through two sulfatide-binding motifs, modulating the extent of platelet aggregation. The three-dimensional structure of a Dab2-derived peptide encompassing the sulfatide-binding motifs has been determined in dodecylphosphocholine micelles using NMR spectroscopy. Dab2 sulfatide-binding motif contains two helices when embedded in micelles, reversibly binds to sulfatides with moderate affinity, lies parallel to the micelle surface, and when added to a platelet mixture, reduces the number and size of sulfatide-induced aggregates. Overall, our findings identify and structurally characterize a minimal region in Dab2 that modulates platelet homotypic interactions, all of which provide the foundation for rational design of a new generation of anti-aggregatory low-molecular mass molecules for therapeutic purposes. PMID:22977233

  19. Recombinant albumins containing additional peptide sequences smaller than barbourin retain the ability of barbourin-albumin to inhibit platelet aggregation.

    PubMed

    Sheffield, William P; Wilson, Brianna; Eltringham-Smith, Louise J; Gataiance, Sharon; Bhakta, Varsha

    2005-05-01

    The previously described fusion protein BLAH(6) (Marques JA et al.,Thromb Haemost 2001; 86: 902-8) is a recombinant protein that combines the small disintegrin barbourin with hexahistidine-tagged rabbit serumalbumin (RSA) produced in Pichia pastoris yeast. We sought to determine: (1) if BLAH(6) was immunogenic; and (2) if its barbourin domain could be productively replaced with smaller peptides. Purified BLAH(6) was injected into rabbits, and anti-barbourin antibodies were universally detected in plasma 28 days later; BLAH(6) was, however, equally effective in reducing platelet aggregation in both naive and pre-treated rabbits. Thrombocytopenia was not observed, and complexing BLAH(6) to alpha(IIb)beta(3) had no effect on antibody detection. The barbourin moiety of BLAH(6) was replaced with each of four sequences: Pep I (VCKGDWPC); PepII (VCRGDWPC); PepIII (bar-bourin 41-54); and PepIV (LPSPGDWR). The corresponding fusion proteins were tested for their ability to inhibit ADP-induced platelet aggregation. PepIII-LAH(6) inhibited neither rabbit nor human platelets. PepI-LAH(6) and PepIV-LAH(6) inhibited rabbit platelet aggregation as effectively as BLAH(6), but PepIV-LAH(6) did not inhibit human platelet aggregation. PepI-LAH(6) and PepIILAH(6) inhibited human platelet aggregation with IC(50)s 10- and 20-fold higher than BLAH(6). Cross-immunoprecipitation assays with human platelet lysates confirmed that all proteins and peptides interacted with the platelet integrin alpha(IIb)beta(3), but with greatly varying affinities. Our results suggest that the antiplatelet activity of BLAH(6) can be retained in albumin fusion proteins in which smaller peptides replace the barbourin domain; these proteins may be less immunogenic than BLAH(6).

  20. 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.

  1. An ultrastructural analysis of endothelial change paralleling platelet aggregation in a light/dye model of microvascular insult.

    PubMed Central

    Povlishock, J. T.; Rosenblum, W. I.; Sholley, M. M.; Wei, E. P.

    1983-01-01

    Those microvascular endothelial events that parallel the evolution of platelet aggregation were evaluated in a well-controlled animal model. Cat pial microvessels were observed through a cranial window while local platelet aggregation was produced by intravenous injection of sodium fluorescein and simultaneous exposure of the pial vessels to light from a filtered mercury lamp that excited the fluorescein. The vessels were fixed in situ when the in vivo observations of a preselected vessel indicated early, intermediate, or advanced aggregation in that vessel. The preselected vessel was then harvested for ultrastructural study together with adjacent vessels from the illuminated field. These vessels and appropriate controls were compared in semiserial thin sections. The onset of platelet aggregation in both venules and arterioles was accompanied by focal endothelial lucency, vacuole formation, luminal membrane rupture, and swelling of the nuclear envelope. These changes were not found in control material. With intermediate aggregation these changes were more common, while with advanced aggregation these abnormalities occurred together with focal endothelial denudation. Thus, in this model denudation occurred only with advanced aggregation and was not a prerequisite for aggregation. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 PMID:6824062

  2. Aggregation and disaggregation kinetics of human blood platelets: Part I. Development and validation of a population balance method.

    PubMed Central

    Huang, P Y; Hellums, J D

    1993-01-01

    Hydrodynamic shear stress of sufficient intensity is known to cause platelet activation and aggregation and to alter the effects of biochemical platelet agonists and antagonists. In this work, a population balance equation (PBE) model is developed for analysis of platelet aggregation and disaggregation kinetics under the influence of a shear field. The model incorporates both aggregation and disaggregation by splitting and/or erosion mechanisms. This paper, the first of a series of three, deals with the formulation, simplification, and validation of the PBE and with the estimation of parameters involved in the PBE. These population parameters include collision efficiency, void fraction (related to the particle collision diameter), and the breakage rate coefficient. The platelet particle size distribution is determined experimentally, both initially and at some later times. The PBE can then be used to match satisfactorily the observed particle histograms, by appropriate choice of parameters of the model as functions of time, platelet size, and magnitude of physical or chemical stimuli. Besides providing information on adhesive forces and on the rates of aggregation and disaggregation, these parameters infer the physical properties of platelets and platelet aggregates. These properties are of potential value in increasing our understanding of the processes involved in thrombotic disease and/or therapy. A numerical procedure for solving the PBE is validated by application to simple cases for which analytical solutions are available. The model is applied to analysis of experiments, and parameter sensitivity studies are used to order the importance of the parameters and to reduce the complexity of the model. The simplified model is shown to give good agreement with experimental observations. PMID:8369441

  3. [Efficacy of clopidogrel as ADP-dependent platelet aggregation inhibitor. Study on individuals with coronary artery disease].

    PubMed

    Izaguirre Avila, R; de la Peña, A; González Pacheco, H; Ramírez Gutiérrez, A; González Valdez, H; Quiroz, A; Cortina, E; Huerta, M; Lupi, E

    2000-01-01

    Acetyl-salicylic acid inhibits thromboxane A2 production and reduces the risk of vascular occlusive events by 20 to 25%. Ticlopidine inhibits ADP-dependent platelet aggregation and reduces the same risk by 30 to 35%, but produces some adverse effects. Clopidogrel is a ticlopidin-derived antiplatelet-drug, with the same mechanism of action; reduces the expression of the glycoprotein IIb/IIIa, the fibrinogen receptor on the platelet surface. Clopidogrel has the same clinical efficacy of ticlopidin and lowers the incidence of adverse effects. In this study, we evaluated the effects of one daily dosis of 75 mg of clopidogrel on platelet function in 33 subjects with coronary artery disease. Before treatment and after the 6th and 12th week, the following parameters were evaluated: 5 microM-ADP and 20 micrograms/mL collagen-induced platelet aggregation, bleeding time and fibrinogen concentration. In basal and in the 6th and 12th week samples, ADP-induced platelet aggregation was 90.7% +/- 13.2, 54.6% +/- 23.2 and 49.2% +/- 23.7 respectively, that represents a significant reduction of 38.6% and 44.4%. Reduction of collagen-induced platelet aggregation was not significative. Plasmatic fibrinogen did not suffer variation during treatment. Bleeding time was significant prolonged from 4.1 minutes to 15.4 and 14.6 minutes (3.7-3.5 times compared with the test before treatment). There were no haemorrhagic complications, only digestive discomfort in fewer than 3% of patients. We concluded that clopidogrel is a safe and efficacious drug for patients, it efficiently reduces ADP-induced platelet aggregation and prolongs bleeding time.

  4. Investigation of platelet aggregation inhibitory activity by phenyl amides and esters of piperidinecarboxylic acids.

    PubMed

    de Candia, Modesto; Summo, Luciana; Carrieri, Antonio; Altomare, Cosimo; Nardecchia, Adele; Cellamare, Saverio; Carotti, Angelo

    2003-04-03

    A series of anilides and phenyl esters of piperidine-3-carboxylic acid (nipecotic acid) were synthesized and tested for the ability to inhibit aggregation of human platelet rich-plasma triggered by adenosine 5'-diphosphate (ADP) and adrenaline. As a rule, amides were about two times more active than the corresponding esters, and derivatives bearing substituents at the para position of the phenyl ring were significantly more active than the meta-substituted ones. Among the tested compounds, 4-hexyloxyanilide of nipecotic acid (18a) was found to be the most active one, its IC(50) value being close to that of the most active bis-3-carbamoylpiperidines reported in literature (ca. 40 micro M) and aspirin (ca. 60 microM) in ADP- and adrenaline-induced aggregation, respectively. Compared with the isomeric 4-hexyloxyanilides of piperidine-2-carboxylic (pipecolinic) and piperidine-4-carboxylic (isonipecotic) acids, compound 18a showed higher activity, and a Hansch-type quantitative structure-activity relationship (QSAR) study highlighted lipophilicity and increase in electron density of the phenyl ring as the properties which mainly increase the antiplatelet activity (r(2)=0.74, q(2)=0.64). The interaction of nipecotoyl anilides with phosphatidylinositol, a major component of the inner layer of the platelet membranes, was investigated by means of flexible docking calculation methods to give an account of a key event underlying their biological action.

  5. 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.

  6. Purification and characterization of BmooAi: a new toxin from Bothrops moojeni snake venom that inhibits platelet aggregation.

    PubMed

    de Queiroz, Mayara Ribeiro; Mamede, Carla Cristine N; de Morais, Nadia Cristina G; Fonseca, Kelly Cortes; de Sousa, Bruna Barbosa; Migliorini, Thaís M; Pereira, Déborah Fernanda C; Stanziola, Leonilda; Calderon, Leonardo A; Simões-Silva, Rodrigo; Soares, Andreimar Martins; de Oliveira, Fábio

    2014-01-01

    In this paper, we describe the purification/characterization of BmooAi, a new toxin from Bothrops moojeni that inhibits platelet aggregation. The purification of BmooAi was carried out through three chromatographic steps (ion-exchange on a DEAE-Sephacel column, molecular exclusion on a Sephadex G-75 column, and reverse-phase HPLC chromatography on a C2/C18 column). BmooAi was homogeneous by SDS-PAGE and shown to be a single-chain protein of 15,000 Da. BmooAi was analysed by MALDI-TOF Spectrometry and revealed two major components with molecular masses 7824.4 and 7409.2 as well as a trace of protein with a molecular mass of 15,237.4 Da. Sequencing of BmooAi by Edman degradation showed two amino acid sequences: IRDFDPLTNAPENTA and ETEEGAEEGTQ, which revealed no homology to any known toxin from snake venom. BmooAi showed a rather specific inhibitory effect on platelet aggregation induced by collagen, adenosine diphosphate, or epinephrine in human platelet-rich plasma in a dose-dependent manner, whereas it had little or no effect on platelet aggregation induced by ristocetin. The effect on platelet aggregation induced by BmooAi remained active even when heated to 100°C. BmooAi could be of medical interest as a new tool for the development of novel therapeutic agents for the prevention and treatment of thrombotic disorders.

  7. Purification and Characterization of BmooAi: A New Toxin from Bothrops moojeni Snake Venom That Inhibits Platelet Aggregation

    PubMed Central

    Ribeiro de Queiroz, Mayara; Mamede, Carla Cristine N.; de Morais, Nadia Cristina G.; Cortes Fonseca, Kelly; Barbosa de Sousa, Bruna; Migliorini, Thaís M.; Pereira, Déborah Fernanda C.; Stanziola, Leonilda; Calderon, Leonardo A.; Simões-Silva, Rodrigo; Martins Soares, Andreimar; de Oliveira, Fábio

    2014-01-01

    In this paper, we describe the purification/characterization of BmooAi, a new toxin from Bothrops moojeni that inhibits platelet aggregation. The purification of BmooAi was carried out through three chromatographic steps (ion-exchange on a DEAE-Sephacel column, molecular exclusion on a Sephadex G-75 column, and reverse-phase HPLC chromatography on a C2/C18 column). BmooAi was homogeneous by SDS-PAGE and shown to be a single-chain protein of 15,000 Da. BmooAi was analysed by MALDI-TOF Spectrometry and revealed two major components with molecular masses 7824.4 and 7409.2 as well as a trace of protein with a molecular mass of 15,237.4 Da. Sequencing of BmooAi by Edman degradation showed two amino acid sequences: IRDFDPLTNAPENTA and ETEEGAEEGTQ, which revealed no homology to any known toxin from snake venom. BmooAi showed a rather specific inhibitory effect on platelet aggregation induced by collagen, adenosine diphosphate, or epinephrine in human platelet-rich plasma in a dose-dependent manner, whereas it had little or no effect on platelet aggregation induced by ristocetin. The effect on platelet aggregation induced by BmooAi remained active even when heated to 100°C. BmooAi could be of medical interest as a new tool for the development of novel therapeutic agents for the prevention and treatment of thrombotic disorders. PMID:24971359

  8. The effect of physical exercise on the daily rhythm of platelet aggregation and body temperature in horses.

    PubMed

    Piccione, Giuseppe; Grasso, Fortunata; Fazio, Francesco; Giudice, Elisabetta

    2008-05-01

    The goal of this study was to investigate the influence of physical activity on the daily rhythm of platelet aggregation and body temperature in horses. Blood samples from 12 Thoroughbred horses, six sedentary animals and six athletes (studied both before and after a period of inactivity) were collected at 4h intervals for 48h via an intravenous cannula inserted into the jugular vein. Body temperature was recorded every 4h for 48h with a rectal probe. Platelet aggregation was measured with an aggregometer. Collagen was used to test the aggregation of the plasma samples. Statistical analysis of the data was performed by one-way repeated-measures analysis of variance (ANOVA) and by single cosinor method. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. On each single day, there was a highly significant effect of time in all the horses, with P values <0.05. Temperature rhythms were unaffected by exercise. Platelet aggregation in exercising horses differed from the sedentary horses, and this difference disappeared after a 2-week period of rest. The results could be interpreted as indicating that physical exercise has an influence on the daily rhythm of platelet aggregation in horses.

  9. Design of Synthetic Polymer Nanoparticles That Facilitate Resolubilization and Refolding of Aggregated Positively Charged Lysozyme.

    PubMed

    Nakamoto, Masahiko; Nonaka, Tadashi; Shea, Kenneth J; Miura, Yoshiko; Hoshino, Yu

    2016-04-06

    Designed polymer hydrogel nanoparticles (NPs) capable of facilitating resolubilization and refolding of an aggregated protein, positively charged lysozyme, are prepared. NPs designed to interact strongly with denatured lysozyme and relatively weakly with native lysozyme, facilitated resolubilization and refolding of aggregated lysozyme. Such NPs could be prepared by copolymerizing optimized combinations and populations of functional monomers. The refolded lysozyme showed native conformation and enzymatic activity. Eleven grams of aggregated protein was refolded by 1 g of NPs. However, NPs having low affinity to denatured lysozyme and NPs having high affinity to both denatured and native lysozyme showed relatively low facilitation activity. Our results suggest a potential strategy for the design of artificial chaperones with high facilitating activity.

  10. Venous levels of shear support neutrophil-platelet adhesion and neutrophil aggregation in blood via P-selectin and beta2-integrin

    NASA Technical Reports Server (NTRS)

    Konstantopoulos, K.; Neelamegham, S.; Burns, A. R.; Hentzen, E.; Kansas, G. S.; Snapp, K. R.; Berg, E. L.; Hellums, J. D.; Smith, C. W.; McIntire, L. V.; Simon, S. I.

    1998-01-01

    BACKGROUND: After activation, platelets adhere to neutrophils via P-selectin and beta2-integrin. The molecular mechanisms and adhesion events in whole blood exposed to venous levels of hydrodynamic shear in the absence of exogenous activation remain unknown. METHODS AND RESULTS: Whole blood was sheared at approximately 100 s(-1). The kinetics of neutrophil-platelet adhesion and neutrophil aggregation were measured in real time by flow cytometry. P-selectin was upregulated to the platelet surface in response to shear and was the primary factor mediating neutrophil-platelet adhesion. The extent of neutrophil aggregation increased linearly with platelet adhesion to neutrophils. Blocking either P-selectin, its glycoprotein ligand PSGL-1, or both simultaneously by preincubation with a monoclonal antibody resulted in equivalent inhibition of neutrophil-platelet adhesion (approximately 30%) and neutrophil aggregation (approximately 70%). The residual amount of neutrophil adhesion was blocked with anti-CD11b/CD18. Treatment of blood with prostacyclin analogue ZK36374, which raises cAMP levels in platelets, blocked P-selectin upregulation and neutrophil aggregation to baseline. Complete abrogation of platelet-neutrophil adhesion required both ZK36374 and anti-CD18. Electron microscopic observations of fixed blood specimens revealed that platelets augmented neutrophil aggregation both by forming bridges between neutrophils and through contact-mediated activation. CONCLUSIONS: The results are consistent with a model in which venous levels of shear support platelet adherence to neutrophils via P-selectin binding PSGL-1. This interaction alone is sufficient to mediate neutrophil aggregation. Abrogation of platelet adhesion and aggregation requires blocking Mac-1 in addition to PSGL-1 or P-selectin. The described mechanisms are likely of key importance in the pathogenesis and progression of thrombotic disorders that are exacerbated by leukocyte-platelet aggregation.

  11. Extract from Aronia melanocarpa fruits potentiates the inhibition of platelet aggregation in the presence of endothelial cells

    PubMed Central

    Luzak, Boguslawa; Golanski, Jacek; Rozalski, Marek; Krajewska, Urszula; Olas, Beata

    2010-01-01

    Introduction Some polyphenolic compounds extracted from Aronia melanocarpa fruits (AM) have been reported to be cardioprotective agents. In this study we evaluated the ability of AM extract to increase the efficacy of human umbilical vein endothelial cells (HUVECs) to inhibit platelet functions in vitro. Material and methods This study encompasses two models of monitoring platelet reactivity: optical aggregation and platelet degranulation (monitored as the surface CD62P expression) in PRP upon the stimulation with ADP. Results We observed that only at low concentrations (5 µg/ml) did AM extract significantly improve antiplatelet action of HUVECs towards ADP-activated platelets in the aggregation test. Conclusions It is concluded that the potentiating effect of AM extract on the endothelial cell-mediated inhibition of platelet aggregation clearly depends on the used concentrations of Aronia-derived active compounds. Therefore, despite these encouraging preliminary outcomes on the beneficial effects of AM extract polyphenols, more profound dose-effect studies should certainly be considered before the implementation of Aronia-originating compounds in antiplatelet therapy and the prevention of cardiovascular diseases. PMID:22371737

  12. First total synthesis of antrocamphin A and its analogs as anti-inflammatory and anti-platelet aggregation agents.

    PubMed

    Lee, Chia-Lin; Huang, Chi-Huan; Wang, Hui-Chun; Chuang, Da-Wei; Wu, Ming-Jung; Wang, Sheng-Yang; Hwang, Tsong-Long; Wu, Chin-Chung; Chen, Yeh-Long; Chang, Fang-Rong; Wu, Yang-Chang

    2011-01-07

    Naturally occurring antrocamphin A (1) is a potent anti-inflammatory compound from the edible fungus Antrodia camphorata (Taiwanofungus camphoratus), whose wild fruiting body is used as a valuable folk medicine in Taiwan. This study is the first total synthesis of antrocamphin A (1) and its analogs. Their inhibition ability on NO release, superoxide anion generation, elastase release and platelet aggregation are reported herein.

  13. 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.

  14. Extracts from Trifolium pallidum and Trifolium scabrum aerial parts as modulators of blood platelet adhesion and aggregation.

    PubMed

    Kolodziejczyk-Czepas, Joanna; Olas, Beata; Malinowska, Joanna; Wachowicz, Barbara; Szajwaj, Barbara; Kowalska, Iwona; Oleszek, Wieslaw; Stochmal, Anna

    2013-01-01

    A growing number of reports indicate that some species of clover (Trifolium) may have remarkable medical importance; however, the effects of these plants on blood platelets and hemostasis are inadequately recognized. This work was designed to study the effects of Trifolium pallidum and Trifolium scabrum extracts on the functions of human blood platelets in vitro. Platelet suspensions were preincubated with extracts from aerial parts of T. pallidum (phenolic fraction and clovamide fraction) and T. scabrum (phenolic fraction) at the final concentrations of 12.5, 25, and 50 µg/ml. Then, for platelet activation thrombin (0.1 U/ml), thrombin receptor activating peptide (TRAP; 20 µM), or adenosine diphosphate (ADP; 1 µM) were used. The effects of Trifolium extracts on adhesion of blood platelets to fibrinogen and collagen were determined by enzyme-linked immunosorbent assay (ELISA) method. Platelet aggregation was monitored on a dual-channel Chronolog aggregometer. In these studies, we also compared the action of tested plant extracts with the effects of another antiplatelet plant-derived compound - resveratrol (3,4',5-trihydroxystilbene). The performed assays demonstrated that the tested extracts might influence the platelet functions in vitro. The inhibitory, concentration-dependent effects of all tested extracts on adhesion of thrombin-stimulated platelets to collagen was found. Both extracts from T. pallidum and from T. scabrum reduced the thrombin-induced platelet adhesion to fibrinogen. Furthermore, in the presence of all three extracts, the platelet aggregation induced by thrombin was slightly inhibited. Our results also indicate that the tested plant extracts (at the highest concentrations used of 50 µg/ml), similar to purified resveratrol, inhibit selected steps of platelet activation stimulated by both proteolytic (thrombin) and nonproteolytic agonists (TRAP or ADP). In the comparative studies, T. pallidum and T. scabrum extracts was not found

  15. Procoagulant platelets form an α-granule protein-covered "cap" on their surface that promotes their attachment to aggregates.

    PubMed

    Abaeva, Anastasia A; Canault, Matthias; Kotova, Yana N; Obydennyy, Sergey I; Yakimenko, Alena O; Podoplelova, Nadezhda A; Kolyadko, Vladimir N; Chambost, Herve; Mazurov, Aleksei V; Ataullakhanov, Fazoil I; Nurden, Alan T; Alessi, Marie-Christine; Panteleev, Mikhail A

    2013-10-11

    Strongly activated "coated" platelets are characterized by increased phosphatidylserine (PS) surface expression, α-granule protein retention, and lack of active integrin αIIbβ3. To study how they are incorporated into thrombi despite a lack of free activated integrin, we investigated the structure, function, and formation of the α-granule protein "coat." Confocal microscopy revealed that fibrin(ogen) and thrombospondin colocalized as "cap," a single patch on the PS-positive platelet surface. In aggregates, the cap was located at the point of attachment of the PS-positive platelets. Without fibrin(ogen) retention, their ability to be incorporated in aggregates was drastically reduced. The surface fibrin(ogen) was strongly decreased in the presence of a fibrin polymerization inhibitor GPRP and also in platelets from a patient with dysfibrinogenemia and a fibrinogen polymerization defect. In contrast, a fibrinogen-clotting protease ancistron increased the amount of fibrin(ogen) and thrombospondin on the surface of the PS-positive platelets stimulated with collagen-related peptide. Transglutaminases are also involved in fibrin(ogen) retention. However, platelets from patients with factor XIII deficiency had normal retention, and a pan-transglutaminase inhibitor T101 had only a modest inhibitory effect. Fibrin(ogen) retention was normal in Bernard-Soulier syndrome and kindlin-3 deficiency, but not in Glanzmann thrombasthenia lacking the platelet pool of fibrinogen and αIIbβ3. These data show that the fibrin(ogen)-covered cap, predominantly formed as a result of fibrin polymerization, is a critical mechanism that allows coated (or rather "capped") platelets to become incorporated into thrombi despite their lack of active integrins.

  16. Effects of the glycoprotein IIb/IIIa receptor antagonist c7E3 Fab and anticoagulants on platelet aggregation and thrombin potential under high coagulant challenge in vitro.

    PubMed

    Koestenberger, M; Gallistl, S; Cvirn, G; Roschitz, B; Muntean, W

    2000-07-01

    The present study was performed to investigate the combined effects of the platelet glycoprotein IIb/IIIa receptor antagonist c7E3 Fab (abciximab) and the anticoagulants unfractionated heparin (UH), low molecular weight heparin (LMWH), and recombinant hirudin (rH) on platelet aggregation and thrombin generation under high coagulant challenge by extrinsic activation of platelet-rich plasma. Platelet aggregation and thrombin generation were assessed simultaneously in the presence of different concentrations of abciximab and anticoagulants. Increasing concentrations of abciximab resulted in a dose-dependent anti-aggregating effect with a maximum at 20 microg/ml. Doses of 5, 10, and 20 microg/ml abciximab prolonged the lag phase until the onset of platelet aggregation, but this effect was independent of the dosage used. Abciximab had no influence on the thrombin potential under our high coagulant challenge. UH, LMWH, and rH showed a dose-dependent prolongation of the lag phase until the onset of platelet aggregation and decreased the thrombin potential. Addition of anticoagulants did not contribute to further inhibition of platelet aggregation in the presence of abciximab, but the combination of abciximab and anticoagulants exhibited an additive effect on prolongation of the lag phase until the onset of platelet aggregation. Addition of abciximab to anticoagulants did not result in further decrease of the thrombin potential. Our study demonstrates the respective specific effects of abciximab and anticoagulants on platelet aggregation and thrombin potential under high coagulant challenge, and also an additive effect of abciximab and the anticoagulants UH, LMWH, and rH on the lag phase until the onset of platelet aggregation.

  17. The pyrrolidinoindoline alkaloid Psm2 inhibits platelet aggregation and thrombus formation by affecting PI3K/Akt signaling

    PubMed Central

    Su, Xing-li; Su, Wen; Wang, Ying; Wang, Yue-hu; Ming, Xin; Kong, Yi

    2016-01-01

    Aim: Psm2, one of the pyrrolidinoindoline alkaloids isolated from whole Selaginella moellendorffii plants, has shown a potent antiplatelet activity. In this study, we further evaluated the antiplatelet effects of Psm2, and elucidated the underlying mechanisms. Methods: Human platelet aggregation in vitro and rat platelet aggregation ex vivo were investigated. Agonist-induced platelet aggregation was measured using a light transmission aggregometer. The antithrombotic effects of Psm2 were evaluated in arteriovenous shunt thrombosis model in rats. To elucidate the mechanisms underlying the antiplatelet activity of Psm2, ELISAs, Western blotting and molecular docking were performed. The bleeding risk of Psm2 administration was assessed in a mouse tail cutting model, and the cytotoxicity of Psm2 was measured with MTT assay in EA.hy926 cells. Results: Psm2 dose-dependently inhibited human platelet aggregation induced by ADP, U4619, thrombin and collagen with IC50 values of 0.64, 0.37, 0.35 and 0.87 mg/mL, respectively. Psm2 (1, 3, 10 mg/kg) administered to rats significantly inhibited platelet aggregation ex vivo induced by ADP. Psm2 (1, 3, 10 mg/mL, iv) administered to rats with the A–V shunt dose-dependently decreased the thrombus formation. Psm2 inhibited platelet adhesion to fibrinogen and collagen with IC50 values of 84.5 and 96.5 mg/mL, respectively, but did not affect the binding of fibrinogen to GPIIb/IIIa. Furthermore, Psm2 inhibited AktSer473 phosphorylation, but did not affect MAPK signaling and Src kinase activation. Molecular docking showed that Psm2 bound to phosphatidylinositol 3-kinase β (PI3Kβ) with a binding free energy of −13.265 kcal/mol. In addition, Psm2 did not cause toxicity in EA.hy926 cells and produced only slight bleeding in a mouse tail cutting model. Conclusion: Psm2 inhibits platelet aggregation and thrombus formation by affecting PI3K/Akt signaling. Psm2 may be a lead compound or drug candidate that could be developed for the

  18. Platelet adhesiveness and aggregation in congenital afibrinogenemia. An investigation of three patients with post-transfusion, cross-correction studies between two of them.

    PubMed

    Girolami, A; De Marco, L; Virgolini, L; Peruffo, R; Fabris, F

    1975-02-01

    Platelet adhesiveness and aggregation were studied in three patients with congenital afibrinogenemia. The results obtained may be summarized as follows: The retention of platelets to a glass-bead filter determined with the Salzman method was significantly decreased; it was normal after fibrinogen infusion. With a modification of the Hellem test the values obtained were slightly decreased. Adrenalin-induced aggregation was absent whereas ADP-and collagen-induced aggregation was near normal or slightly decreased. Thrombofax aggregation was absent in citrated plasma. The abnormalities of platelet aggregation were corrected after fibrinogen infusion or after addition in vitro of fibrinogen, hemofilia A plasma and PPP obtained from an afibrinogenemic patient after fibrinogen infusion. The abnormalities of platelet aggregation were corrected well by ADP, collagen and Thrombofax in heparinized blood, but only a slight correction of adrenalin-induced aggregation was noted. Thrombin aggregation proved to be normal with the higher concentrations, whereas it was defective with the lower ones. Ristocetin aggregation was normal in citrated plasma at the concentration of 1.5 mg per ml but it was absent at the lower concentration (1.0 mg per ml). Ristocetin aggregation was, on the other hand absent in heparinized blood regardless of the concentration. These findings are in agreement with the presence of a prolonged bleeding time in congenital afibrinogenemia and suggest that fibrinogen plays an important role in platelet aggregation and adhesiveness.

  19. 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.

  20. Effects of calcium antagonists on serotonin-dependent aggregation and serotonin transport in platelets of patients with migraine.

    PubMed

    Pukhal'skaya, T G; Kolosova, O A; Men'shikov, M Y; Vein, A M

    2000-07-01

    Flunarizine and cinnarizine (IC50 6.8x10(-6) and 2.8x10(-5) M, respectively) inhibited 3H-serotonin uptake by platelets. In higher doses, they blocked serotonin-induced platelet aggregation and stimulated 3H-serotonin release from these cells. Imipramine did not affect serotonin-releasing effects of preparations. In all patients cinnarizine was more potent in inhibiting serotonin uptake, and in half of the patients cinnarizine displayed higher activity as an inductor of serotonin release.

  1. 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.

  2. Genetic Variation in the Platelet Endothelial Aggregation Receptor 1 Gene Results in Endothelial Dysfunction.

    PubMed

    Fisch, Adam S; Yerges-Armstrong, Laura M; Backman, Joshua D; Wang, Hong; Donnelly, Patrick; Ryan, Kathleen A; Parihar, Ankita; Pavlovich, Mary A; Mitchell, Braxton D; O'Connell, Jeffrey R; Herzog, William; Harman, Christopher R; Wren, Jonathan D; Lewis, Joshua P

    2015-01-01

    Platelet Endothelial Aggregation Receptor 1 (PEAR1) is a newly identified membrane protein reported to be involved in multiple vascular and thrombotic processes. While most studies to date have focused on the effects of this receptor in platelets, PEAR1 is located in multiple tissues including the endothelium, where it is most highly expressed. Our first objective was to evaluate the role of PEAR1 in endothelial function by examining flow-mediated dilation of the brachial artery in 641 participants from the Heredity and Phenotype Intervention Heart Study. Our second objective was to further define the impact of PEAR1 on cardiovascular disease computationally through meta-analysis of 75,000 microarrays, yielding insights regarding PEAR1 function, and predictions of phenotypes and diseases affected by PEAR1 dysregulation. Based on the results of this meta-analysis we examined whether genetic variation in PEAR1 influences endothelial function using an ex vivo assay of endothelial cell migration. We observed a significant association between rs12041331 and flow-mediated dilation in participants of the Heredity and Phenotype Intervention Heart Study (P = 0.02). Meta-analysis results revealed that PEAR1 expression is highly correlated with several genes (e.g. ANG2, ACVRL1, ENG) and phenotypes (e.g. endothelial cell migration, angiogenesis) that are integral to endothelial function. Functional validation of these results revealed that PEAR1 rs12041331 is significantly associated with endothelial migration (P = 0.04). Our results suggest for the first time that genetic variation of PEAR1 is a significant determinant of endothelial function through pathways implicated in cardiovascular disease.

  3. Genetic Variation in the Platelet Endothelial Aggregation Receptor 1 Gene Results in Endothelial Dysfunction

    PubMed Central

    Fisch, Adam S.; Yerges-Armstrong, Laura M.; Backman, Joshua D.; Wang, Hong; Donnelly, Patrick; Ryan, Kathleen A.; Parihar, Ankita; Pavlovich, Mary A.; Mitchell, Braxton D.; O’Connell, Jeffrey R.; Herzog, William; Harman, Christopher R.; Wren, Jonathan D.; Lewis, Joshua P.

    2015-01-01

    Platelet Endothelial Aggregation Receptor 1 (PEAR1) is a newly identified membrane protein reported to be involved in multiple vascular and thrombotic processes. While most studies to date have focused on the effects of this receptor in platelets, PEAR1 is located in multiple tissues including the endothelium, where it is most highly expressed. Our first objective was to evaluate the role of PEAR1 in endothelial function by examining flow-mediated dilation of the brachial artery in 641 participants from the Heredity and Phenotype Intervention Heart Study. Our second objective was to further define the impact of PEAR1 on cardiovascular disease computationally through meta-analysis of 75,000 microarrays, yielding insights regarding PEAR1 function, and predictions of phenotypes and diseases affected by PEAR1 dysregulation. Based on the results of this meta-analysis we examined whether genetic variation in PEAR1 influences endothelial function using an ex vivo assay of endothelial cell migration. We observed a significant association between rs12041331 and flow-mediated dilation in participants of the Heredity and Phenotype Intervention Heart Study (P = 0.02). Meta-analysis results revealed that PEAR1 expression is highly correlated with several genes (e.g. ANG2, ACVRL1, ENG) and phenotypes (e.g. endothelial cell migration, angiogenesis) that are integral to endothelial function. Functional validation of these results revealed that PEAR1 rs12041331 is significantly associated with endothelial migration (P = 0.04). Our results suggest for the first time that genetic variation of PEAR1 is a significant determinant of endothelial function through pathways implicated in cardiovascular disease. PMID:26406321

  4. Pharmacological assessment of ibuprofen arginate on platelet aggregation and colon cancer cell killing.

    PubMed

    Ahmetaj-Shala, B; Tesfai, A; Constantinou, C; Leszczynski, R; Chan, M V; Gashaw, H; Galaris, G; Mazi, S; Warner, T D; Kirkby, N S; Mitchell, J A

    2017-03-18

    Nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen, are amongst the most commonly used medications and produce their anti-inflammatory and analgesic benefits by blocking cyclooxygenase (COX)-2. These drugs also have the potential to prevent and treat cancer and some members of the class including ibuprofen can produce anti-platelet effects. Despite their utility, all NSAIDs are associated with increased risk of cardiovascular side effects which our recent work suggests could be mediated by increased levels of the endogenous NO synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA) leading to reduced endothelial NOS activity and associated endothelial cell dysfunction. ADMA is a cardiotoxic hormone and biomarker of cardiovascular risk whose effects can be prevented by l-arginine. The ibuprofen salt, ibuprofen arginate (Spididol(®)) was created to increase drug solubility but we have previously established that it not only effectively blocks COX-2 but also provides an arginine source able to reverse the effects of ADMA in vitro and in vivo. Here we have gone on to explore whether the formulation of ibuprofen with arginine influences the potency and efficacy of the parent molecule using a range of simple in vitro assays designed to test the effects of NSAIDs on (i) platelet aggregation and (iii) colon cancer cell killing. Our findings demonstrate that ibuprofen arginate retains these key functional effects of NSAIDs with similar or increased potency compared to ibuprofen sodium, further illustrating the potential of ibuprofen arginate as an efficacious drug with the possibility of improved cardiovascular safety.

  5. Comparative evaluation of antiplatelet effect of lycopene with aspirin and the effect of their combination on platelet aggregation: An in vitro study

    PubMed Central

    Sawardekar, Swapna B.; Patel, Tejal C.; Uchil, Dinesh

    2016-01-01

    Introduction: The objective was to compare antiplatelet effect of lycopene with aspirin and to study effect of combination of the two on platelet aggregation in vitro, using platelets from healthy volunteers. Materials and Methods: Platelets were harvested; platelet count of platelet-rich plasma adjusted to 2.5 Χ 105/μL. Aspirin (140 μmol/L) and lycopene (4, 6, 8, 10, and 12 μmol/L) were studied in vitro against adenosine-5’- diphosphate (ADP) (2.5 μM/L) and collagen Results: All the concentrations of lycopene (4–12 μmol/L) exhibited reduction in maximum platelet aggregation induced by aggregating agents ADP and collagen (P < 0.01 vs. vehicle) and were comparable with aspirin. Lycopene at concentration 10 μmol/L showed maximum platelet inhibition (47.05% ± 19.56%) against ADP, whereas lycopene at concentration 8 μmol/L showed maximum platelet inhibition (54.26% ± 30.71%) against collagen. Four μmol/L of lycopene combined with 140 μmol/L and 70 μmol/L aspirin showed greater inhibition of platelets as compared to aspirin 140 μmol/L alone, against both ADP and collagen. Conclusion: The study favorably compares lycopene and aspirin with respect to their antiplatelet activities against ADP and collagen. Lycopene can be considered as a potential target for modifying the thrombotic and pro-inflammatory events associated with platelet activation. PMID:26997718

  6. Extracts from two frequently consumed spices--cumin (Cuminum cyminum) and turmeric (Curcuma longa)--inhibit platelet aggregation and alter eicosanoid biosynthesis in human blood platelets.

    PubMed

    Srivastava, K C

    1989-07-01

    In the traditional Indian system of medicine, Ayurveda, several spices and herbs are claimed to possess medicinal properties, such as being antithrombotic, antiatherosclerotic, hypolipidemic, anti-inflammatory etc. Earlier we have reported that extracts from several spices behave as antiaggregatory agents and inhibit eicosanoid synthesis. Similar studies with extracts prepared from cumin (Cuminum cyminum) and turmeric (Curcuma longa) were undertaken. Ethereal extract of both cumin and turmeric inhibited arachidonate-induced platelet aggregation. Extracts from these spices inhibited thromboxane B2 production from exogenous (14C) arachidonic acid (AA) in washed platelets; a simultaneous increase in the formation of lipoxygenase-derived products was observed. Less TxB2 was produced in blood samples treated with turmeric extract when they were allowed to clot. Turmeric extract inhibited incorporation of (14C)AA into platelet phospholipids and deacylation of AA-labelled phospholipids on stimulation with calcium ionophore A23187. Cumin extract was devoid of such effects. Extracts from the two spices reduced the formation of (14C)TxB2 from AA-labelled platelets when they were challenged with A23187. The anti-inflammatory property of turmeric may, in part, be explained by its effect on eicosanoid biosynthesis.

  7. Evaluation of antiplatelet effects of a modified protocol by platelet aggregation in patients undergoing "one-stop" hybrid coronary revascularization.

    PubMed

    Gao, Peixian; Xiong, Hui; Zheng, Zhe; Li, Lihuan; Gao, Runlin; Hu, Sheng-Shou

    2010-01-01

    "One-stop" hybrid coronary revascularization has emerged to be a reliable and attractive alternative for selected patients with multivessel coronary artery disease. However, the optimal antiplatelet regimen of the one-stop hybrid procedure still remains controversial. We modified the antiplatelet protocol in order to reduce the risk of perioperative bleeding and maximally inhibit platelet activity. This study sought to investigate whether the inhibition of platelet activity by this modified antiplatelet protocol is comparable with the conventional protocol widely used and recommended in percutaneous coronary interventions (PCI). Twenty three patients undergoing one-stop hybrid procedure and 20 patients undergoing conventional PCI were enrolled in this prospective study. The modified antiplatelet protocol included perioperative use of aspirin; clopidogrel was administered immediately before PCI with a 300 mg loading dose, followed by a maintenance dose of 75 mg/day for 12 months. Blood samples were obtained before the operation and 2 hours, day 1 and day 3 after operation. Platelet aggregation was induced with: 1) arachidonic acid (AA) (final concentration 0.5 mmol/L) to assess the efficacy of aspirin; 2) adenosine diphosphate (ADP) (final concentration 10 micromol/L) to assess the specific efficacy of clopidogrel. Platelet counts were statistically lower in the hybrid group than in the PCI control group (p = 0.0018) on day 1 after operation. AA-induced platelet aggregation increased significantly in comparison with the preoperative baseline values (p = 0.0079) and the PCI control group (p = 0.0023) on day 1 after operation. ADP-induced platelet aggregation gradually decreased in the hybrid group, and achieved similar platelet inhibition with the PCI group on 2 hours and day 1 after operation. No major adverse clinical events such as death, perioperative myocardial infarction, stent thrombosis or reoperation for bleeding occurred in both groups within 30 days after

  8. Aggregation of human platelets by endotoxic glycolipid-bearing Salmonella minnesota Re595 is prevented by synthetic peptide analogs of cell adhesion sites of fibrinogen and fibronectin

    SciTech Connect

    Timmons, S.; Grabarek, J.; Kloczewiak, M.; Hawiger, J.

    1986-03-01

    Thrombocytopenia often accompanies sepsis due to endotoxin producing gram-negative bacteria. The authors have observed that mutant Re595 of S. minnesota induced aggregation of human platelets separated from plasma fibrinogen (Theta) and other proteins. This aggregation is dependent on ADP secreted from storage granules in response to mutant Re595. Platelet aggregation induced by mutant Re595 was prevented by simultaneously added EDTA and EGTA (5mM), whereas secretion of /sup 14/C-serotonin was maintained. Preincubation of platelets with chelators (1 hr, 37/sup 0/C), known to dissociate irreversibly the platelet membrane glycoprotein IIb x IIIa complex, abolished aggregation while serotonin secretion was decreased by only one fourth. Since the GPIIb x IIIa complex constitutes the receptor for Theta, its role was examined using synthetic peptide analogs of sites on gamma and alpha chains of Theta. Gamma 400-411 (225 ..mu..M) inhibited platelet aggregation induced by mutant Re595 while serotonin secretion was unaffected. Alpha 572-575 (RGDS; 100 ..mu..M), analogous to cell adhesion site of fibronectin, also prevented aggregation induced by mutant Re595. Thus, mutant Re595 causes platelet aggregation which is divalent cation-dependent and proceeds via receptor pathway for secreted adhesive macromolecules.

  9. Metalloproteases Affecting Blood Coagulation, Fibrinolysis and Platelet Aggregation from Snake Venoms: Definition and Nomenclature of Interaction Sites

    PubMed Central

    Kini, R. Manjunatha; Koh, Cho Yeow

    2016-01-01

    Snake venom metalloproteases, in addition to their contribution to the digestion of the prey, affect various physiological functions by cleaving specific proteins. They exhibit their activities through activation of zymogens of coagulation factors, and precursors of integrins or receptors. Based on their structure–function relationships and mechanism of action, we have defined classification and nomenclature of functional sites of proteases. These metalloproteases are useful as research tools and in diagnosis and treatment of various thrombotic and hemostatic conditions. They also contribute to our understanding of molecular details in the activation of specific factors involved in coagulation, platelet aggregation and matrix biology. This review provides a ready reference for metalloproteases that interfere in blood coagulation, fibrinolysis and platelet aggregation. PMID:27690102

  10. Platelet-mediated adhesion facilitates leukocyte sequestration in hypoxia-reoxygenated microvessels.

    PubMed

    Zheng, Senfeng; Cao, Yanting; Zhang, Wenjian; Liu, Honglin; You, Jia; Yin, Yiqing; Lou, Jinning; Li, Chenghui

    2016-03-01

    Leukocyte transendothelial migration and sequestration are two distinct outcomes following leukocyte adhesion to endothelium during ischemia-reperfusion injury, in which platelets may play a pivotal role. In the present study, we established an in vitro hypoxia-reoxygenation model to mimic ischemia-reperfusion injury and found platelet pre-incubation significantly increased leukocyte adhesion to endothelial cells after hyoxia-reoxygenation (over 67%). Blockade of endothelial-cell-expressed adhesion molecules inhibited leukocyte direct adhesion to endothelial cells, while platelet-mediated leukocyte adhesion was suppressed by blockade of platelet-expressed adhesion molecules. Further experiments revealed platelets acted as a bridge to mediate leukocyte adhesion, and platelet-mediated adhesion was the predominant pattern in the presence of platelets. However, platelet pre-incubation significantly suppressed leukocyte transendothelial migration after hypoxia-reoxygenation (over 31%), which could be aggravated by blockade of endothelial-cell-expressed adhesion molecules, but alleviated by blockade of platelet- expressed adhesion molecules. This would indicate that platelet-mediated adhesion disrupted leukocyte transendothelial migration. An in vivo mesenteric ischemia-reperfusion model demonstrated leukocyte transfusion alone caused mild leukocyte adhesion to reperfused vessels and subsequent leukocyte infiltration, while simultaneous leukocyte and platelet transfusion led to massive leukocyte adhesion and sequestration within reperfused microvessels. Our studies revealed platelets enhanced leukocyte adhesion to endothelial cells, but suppressed leukocyte transendothelial migration. Overall, this leads to leukocyte sequestration in hypoxia-reoxygenated microvessels.

  11. Schisandra chinensis and Morus alba Synergistically Inhibit In Vivo Thrombus Formation and Platelet Aggregation by Impairing the Glycoprotein VI Pathway

    PubMed Central

    Sung, Yoon-Young; Kim, Seung Hyung; Park, Sun Haeng

    2017-01-01

    Morus alba L. (MAL) extract has been used in traditional medicine for its cardioprotective and antiplatelet effects, while another herbal remedy, Schisandra chinensis (SCC), has been reported to have anti-inflammatory and antioxidant properties. We evaluated underlying cellular changes exerted by extracts of these plants on platelet function and effects of SCC + MAL on in vivo thrombus formation using AV shunt and tail thrombosis-length models in rats. In vitro platelet aggregation, granule secretion, and [Ca2+]i release assays were carried out. The activation of integrin αIIbβ3 and phosphorylation of downstream signaling molecules, including MAPK and Akt, were investigated using cytometry and immunoblotting, respectively. Scanning electron microscopy (SEM) was used to evaluate changes in platelet shape and HPLC analysis was carried out to identify the marker compounds in SCC + MAL mixture. In vivo thrombus weight and average length of tail thrombosis were significantly decreased by SCC + MAL. In vitro platelet aggregation, granule secretion, [Ca2+]i release, and integrin αIIbβ3 activation were notably inhibited. SCC + MAL markedly reduced the phosphorylation of MAPK pathway factors along with Akt. HPLC analysis identified four marker compounds: isoquercitrin, astragalin, schizandrol A, and gomisin A. The extracts exerted remarkable synergistic effects as natural antithrombotic and antiplatelet agent and a potent drug candidate for treating cardiovascular diseases. PMID:28194217

  12. Platelet aggregation but not activation and degranulation during the acute post-ischemic reperfusion phase in livers with no underlying disease

    PubMed Central

    van Golen, Rowan F.; Stevens, Katarzyna M.; Colarusso, Pina; Jaeschke, Hartmut; Heger, Michal

    2016-01-01

    Background Platelets and P-selectin (CD62P) play an unequivocal role in the pathology of hepatic ischemia/reperfusion (I/R) injury. Inhibition or knock-out of P-selectin or immunodepletion of platelets results in amelioration of post-ischemic inflammation, reduced hepatocellular damage, and improved survival. However, P-selectin expression on platelets and endothelial cells, which concurs with platelet activation, has never been clearly demonstrated in I/R-subjected livers. Aims To determine whether platelets become activated and degranulate in the acute phase of liver I/R and whether the platelets interact with neutrophils. Methods Hepatic I/R was induced in male C57BL/6J mice (N = 12) using 37.5-min ischemia time. Platelets, endothelial cells, and neutrophils were fluorescently labeled by systemic administration of non-blocking antibodies. Cell kinetics were monitored by intravital spinning disk confocal microscopy during 90 min of reperfusion. Image analysis and quantification was performed with dedicated software. Results Platelets adhered to sinusoids more extensively in post-ischemic livers compared to livers not subjected to I/R and formed aggregates, which occurred directly after ischemia. Platelets and endothelial cells did not express P-selectin in post-ischemic livers. There was no interaction between platelets and neutrophils. Conclusions Platelets aggregate but do not become activated and do not degranulate in post-ischemic livers. There is no platelet-neutrophil interplay during the early reperfusion phase in a moderate model of hepatic I/R injury. The mechanisms underlying the biological effects of platelets and P-selectin in this setting warrant further investigation. Relevance for patients I/R in surgical liver patients may compromise outcome due to post-ischemic oxidative stress and sterile inflammation. Both processes are mediated in part by platelets. Understanding platelet function during I/R is key to developing effective interventions for I

  13. Evening primrose oil ameliorates platelet aggregation and improves cardiac recovery in myocardial-infarct hypercholesterolemic rats

    PubMed Central

    Abo-Gresha, Noha M; Abel-Aziz, Eman Z; Greish, Sahar M

    2014-01-01

    Omega-6 polyunsaturated fatty acids (n-6 PUFA) are well known for their role in cardiovascular disease (CVD). We proposed that Evening prime rose oil (EPO) can improve the outcome of a heart with myocardial infarction (MI) in the presence of diet-induced hyperaggregability. This study was designed to examine its cholesterol lowering, antithrombotic and anti-inflammatory effects. High fat diet was administered for 4 weeks then MI was induced by isoproterenol (85 mg/kg/s.c./24 h). Treatment with EPO (5 or 10 gm/kg/day) for 6 weeks improved the electrocardiographic pattern, serum lipid profile, cardiac biomarkers as well as Platelet aggregation percent. We reported decreased serum level of TNF-α, IL-6 and COX-2 with attenuation of TNF-α and TGF-β in the cardiac homogenate. Moreover, histopathology revealed marked amelioration. Finally, we provide evidence that EPO improve cardiac recovery in hypercholesterolemic myocardial infarct rats. These effects are attributed to direct hypocholesterolemic effect and indirect effect on the synthesis of eicosanoids (prostaglandins, cytokines). PMID:24665356

  14. Effects of smoking on prostacyclin formation and platelet aggregation in users of oral contraceptives.

    PubMed

    Roy, S

    1999-06-01

    This review covers 10 articles published during 1981-96 to determine which subgroups within the population of smokers and oral contraceptive (OC) users are at especially elevated risk for thromboembolic events. It was found that the thrombogenic effects of smoking are mediated by two pathways: 1) increased biosynthesis of thromboxane, which promotes platelet aggregation; 2) degenerative changes in the vascular endothelium leading to the formation of atheromas and necrotic plaque, which in turn results in formation of thrombi. There was evidence showing that cardiovascular disease associated with OC use is due to thrombosis rather than atherosclerosis. The effects of smoking, resulting in an increase in arterial wall stiffness and changes in the patterns of arterial blood flow, would lead to formation of thrombi. However, there was an inconsistency in the data presented; studies revealed that smoking alone constitutes greater cardiovascular risk. Cigarette smoking and OC use can act synergistically to favor the formation of thrombi and increase the risk of thromboembolic events. Heavy smoking, a longer history of smoking, and inhaling smoke in association with OC use increases the risk of thrombosis.

  15. ACE and platelet aggregation inhibitors from Tamarix hohenackeri Bunge (host plant of Herba Cistanches) growing in Xinjiang

    PubMed Central

    Xing, Yachao; Liao, Jing; Tang, Yingzhan; Zhang, Peng; Tan, Chengyu; Ni, Hui; Wu, Xueqin; Li, Ning; Jia, Xiaoguang

    2014-01-01

    Background: Tamarix hohenackeri Bunge is a salt cedar that grows widespread in the desert mountains in Xinjiang. T. hohenackeri has not been investigated earlier, although there are many reports of phytochemical work on other Tamarix species. Materials and Methods: To find out natural angiotensin-converting enzyme (ACE) inhibitor and platelet aggregation inhibitors, the bioactive extract (ethyl acetate [EtOAc] fraction) from the dried aerial parts of T. hohenackeri were investigated. The active fraction was purified by repeated column chromatography, including silica gel, Sephadex LH-20 column, medium-pressure liquid chromatography (MPLC) (polyamide column) and high-performance liquid chromatography (HPLC). The isolated major constituents were tested for their anti-platelet aggregation activity. Results: Bioassay-directed separation of the EtOAc fraction of the 70% ethanol extract from the air-dried aerial parts of T. hohenackeri led to the isolation of a new triterpenoid lactone (1), together with 13 known compounds (2-14). It was the first time to focus on screening bioactive constituents for this plant. The chemical structures were established on the basis of spectral data (ESI-MS and NMR). The results showed that the flavonoid compounds (7 and 8) and phenolic compounds (9, 10, 11, and 14) were potential ACE inhibitors. And the flavonoid compounds (5 and 7) showed significant anti-platelet aggregation activities. Conclusion: On the basis of the chemical and biological data, the material basis of ACE inhibitory activity for the active part was the phenolic constituents. However, the flavonoid compounds were responsible for the anti-platelet aggregation. The primary structure and activity relationship were also discussed respectively. PMID:24914275

  16. Inhibition of the activation of Hageman factor (factor XII) and of platelet aggregation by extracts of Brugia malayi microfilariae.

    PubMed

    Foster, C B; Flanigan, T P; Kazura, J W; Dumenco, L L; Ratnoff, O D

    1991-05-01

    In human filariasis, large numbers of blood-borne microfilariae circulate unimpeded through the blood stream. How intravascular filarial parasites avoid precipitating thrombosis has not been studied in detail. We hypothesized that extracts of Brugia malayi microfilariae would contain factors that inhibit activation of hemostatic mechanisms. Initial studies demonstrated an inhibitor specific for the intrinsic coagulation cascade. The addition of microfilarial extracts to human plasma prolonged the activated partial thromboplastin time in a dose-dependent fashion but did not prolong the prothrombin, thrombin, or Russell's viper venom times. Microfilarial extracts (0.1 mg/ml) completely inhibited activation of Hageman factor (factor XII, at 0.05 U/ml) as measured in an amidolytic assay. Hageman factor previously activated by ellagic acid (factor XIIa) retained full enzymatic activity in the presence of microfilarial extract (0.1 mg/ml). The presence of inhibitory activity in the culture medium of live parasites raises the possibility that microfilariae secrete an inhibitory protein into their local environment. Microfilarial extracts at a final concentration of 0.1 mg/ml also inhibited collagen- and adenosine diphosphate-induced platelet aggregation. Arachidonic acid-induced platelet aggregation was inhibited by microfilarial extracts at a final concentration of 0.6 mg/ml. These results suggest that microfilariae of Brugia malayi, a human filarial parasite, may avoid initiating thrombosis through inhibition of the intrinsic coagulation pathway and platelet aggregation.

  17. A Novel Direct Factor Xa Inhibitory Peptide with Anti-Platelet Aggregation Activity from Agkistrodon acutus Venom Hydrolysates

    PubMed Central

    Chen, Meimei; Ye, Xiaohui; Ming, Xin; Chen, Yahui; Wang, Ying; Su, Xingli; Su, Wen; Kong, Yi

    2015-01-01

    Snake venom is a natural substance that contains numerous bioactive proteins and peptides, nearly all of which have been identified over the last several decades. In this study, we subjected snake venom to enzymatic hydrolysis to identify previously unreported bioactive peptides. The novel peptide ACH-11 with the sequence LTFPRIVFVLG was identified with both FXa inhibition and anti-platelet aggregation activities. ACH-11 inhibited the catalytic function of FXa towards its substrate S-2222 via a mixed model with a Ki value of 9.02 μM and inhibited platelet aggregation induced by ADP and U46619 in a dose-dependent manner. Furthermore, ACH-11 exhibited potent antithrombotic activity in vivo. It reduced paralysis and death in an acute pulmonary thrombosis model by 90% and attenuated thrombosis weight in an arterio-venous shunt thrombosis model by 57.91%, both at a dose of 3 mg/kg. Additionally, a tail cutting bleeding time assay revealed that ACH-11 did not prolong bleeding time in mice at a dose of 3 mg/kg. Together, our results reveal that ACH-11 is a novel antithrombotic peptide exhibiting both FXa inhibition and anti-platelet aggregation activities, with a low bleeding risk. We believe that it could be a candidate or lead compound for new antithrombotic drug development. PMID:26035670

  18. Effect of GABA derivatives on the rate of thrombus formation, platelet aggregation, and plasma coagulation capacity in rats with experimental gestosis.

    PubMed

    Tyurenkov, I N; Perfilova, V N; Karamysheva, V I; Reznikova, L B; Mokrousov, I S; Mikhailova, L I; Berestovitskaya, V M; Vasil'eva, O S

    2014-12-01

    Experimental gestosis induced by replacement of drinking water with 1.8% NaCl promoted hypercoagulation, increased the rate and degree of platelet aggregation, and reduced clotting time in pregnant females. GABA derivatives, compounds RGPU-151, RGPU-152, and phenibut normalized parameters of hemostasis and platelet aggregation and the rate of thrombus formation in the animals. The efficiency of the test substances did not significantly differ from that of the reference drug sulodexide.

  19. Platelet Aggregation Unchanged by Lipoprotein-Associated Phospholipase A2 Inhibition: Results from an In Vitro Study and Two Randomized Phase I Trials

    PubMed Central

    Shaddinger, Bonnie C.; Xu, Yanmei; Roger, James H.; Macphee, Colin H.; Handel, Malcolm; Baidoo, Charlotte A.; Magee, Mindy; Lepore, John J.; Sprecher, Dennis L.

    2014-01-01

    Background We explored the theorized upregulation of platelet-activating factor (PAF)– mediated biologic responses following lipoprotein-associated phospholipase A2 (Lp-PLA2) inhibition using human platelet aggregation studies in an in vitro experiment and in 2 clinical trials. Methods and Results Full platelet aggregation concentration response curves were generated in vitro to several platelet agonists in human plasma samples pretreated with rilapladib (selective Lp-PLA2 inhibitor) or vehicle. This was followed by a randomized, double-blind crossover study in healthy adult men (n = 26) employing a single-agonist dose assay of platelet aggregation, after treatment of subjects with 250 mg oral rilapladib or placebo once daily for 14 days. This study was followed by a second randomized, double-blind parallel-group trial in healthy adult men (n = 58) also treated with 250 mg oral rilapladib or placebo once daily for 14 days using a full range of 10 collagen concentrations (0–10 µg/ml) for characterizing EC50 values for platelet aggregation for each subject. Both clinical studies were conducted at the GlaxoSmithKline Medicines Research Unit in the Prince of Wales Hospital, Sydney, Australia. EC50 values derived from multiple agonist concentrations were compared and no pro-aggregant signals were observed during exposure to rilapladib in any of these platelet studies, despite Lp-PLA2 inhibition exceeding 90%. An increase in collagen-mediated aggregation was observed 3 weeks post drug termination in the crossover study (15.4% vs baseline; 95% confidence interval [CI], 3.9–27.0), which was not observed during the treatment phase and was not observed in the parallel-group study employing a more robust EC50 examination. Conclusions Lp-PLA2 inhibition does not enhance platelet aggregation. Trial Registration 1) Study 1: ClinicalTrials.gov NCT01745458 2) Study 2: ClinicalTrials.gov NCT00387257 PMID:24475026

  20. Attenuation of Thrombosis by Crude Rice (Oryza sativa) Bran Policosanol Extract: Ex Vivo Platelet Aggregation and Serum Levels of Arachidonic Acid Metabolites

    PubMed Central

    Ismail, Maznah; Tohit, Eusni Rahayu Mohd; Abdullah, Rasedee; Zhang, Yi-Da

    2016-01-01

    Background. Vascular occlusion or thrombosis was often attributed to uncontrolled platelet activation. Influence of sugarcane policosanol extract on platelet was reported but little was known of rice bran policosanol, particularly its mechanisms of actions on platelet activities. Objective. Antiplatelet mechanisms of rice bran policosanol extract (RBE) were studied using hyperlipidemic Sprague Dawley rats. Ex vivo platelet aggregation, platelet count (PC), bleeding time (BT), and coagulation time were assayed. Serum eicosanoids and other aggregation-related metabolites levels were quantified. Design. Rats were divided into 6 groups for comparisons (vehicle control Tween 20/H2O, high dose policosanol 500 mg/kg, middle dose policosanol 250 mg/kg, low dose policosanol 100 mg/kg, and positive control aspirin 30 mg/kg). Results. Low dose 100 mg/kg of RBE inhibited aggregation by 42.32 ± 4.31% and this was comparable with the effect of 30 mg/kg aspirin, 43.91 ± 5.27%. Results showed that there were no significant differences in PC, BT, and coagulation time among various groups after RBE treatment. Serum thromboxane A2 was attenuated while prostacyclin level increased upon RBE treatment. Conclusions. RBE reduced ex vivo ADP-induced platelet aggregation without giving adverse effects. No changes in full blood count suggested that rice bran policosanol did not disturb biological blood cell production and destruction yet it reduced aggregation through different mechanisms. PMID:27800004

  1. 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

  2. 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.

  3. Bioequivalence and tolerability study of two brands of clopidogrel tablets, using inhibition of platelet aggregation and pharmacodynamic measures☆

    PubMed Central

    Rao, Takallapalli Ramesh Kumar; Usha, P.Rani; Naidu, M.U.R; Gogtay, J.A; Meena, Matthew

    2003-01-01

    Background The role of platelets in acute cardiovascular atherothrombotic events has been well established and attention has focused on platelet inhibition therapy. Clopidogrel is a novel thienopyridine inhibitor of adenosine diphosphate–induced platelet activation. Recent studies have shown that in the setting of coronary angioplasty/stenting, a loading dose of 300 mg followed by 75 mg once daily is required for optimum benefit. Objective This study assessed the bioequivalence and tolerability of 2 oral formulations of clopidogrel 75-mg tablets. Methods This 10-day, open-label, randomized, parallel-group, comparative bioequivalence and tolerability study was carried out in the Department of Clinical Pharmacology and Therapeutics, Nizam's Institute of Medical Sciences (Hyderabad, India). Young healthy male volunteers were enrolled. Subjects were randomized to receive one of two 75-mg tablet formulations of clopidogrel (Clopivas® [test formulation] or Plavix® [reference formulation]). Subjects first received a 300-mg loading dose (four 75-mg tablets) on day 1, followed by 75 mg (1 tablet) at 8:00 AM daily for the next 6 days. Inhibition of platelet aggregation, which is the pharmacologic basis for the therapeutic efficacy of antiplatelet agents, and the effect on bleeding time were used as the pharmacodynamic assessment criteria. Pharmacodynamic variables included mean of maximum activity of percentage of inhibition of platelet aggregation (Emax), mean time to reach Emax (tmax), and mean area under the activity–time curve from time 0 to 168 hours (AUC0–168). Tolerability assessments included blood pressure and heart rate measurements before and at regular intervals (every hour for 12 hours and then at 24 hours) over a 24-hour period after drug administration. Clinical tolerability was assessed using adverse effects, platelet count (assessed on days 3, 6, and 10 after first-dose administration), and neutrophil count (assessed on day 10 after first

  4. 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

  5. Platelet-Monocyte Aggregates and C-Reactive Protein are Associated with VTE in Older Surgical Patients

    PubMed Central

    Shih, Lauren; Kaplan, David; Kraiss, Larry W.; Casper, T. Charles; Pendleton, Robert C.; Peters, Christopher L.; Supiano, Mark A.; Zimmerman, Guy A.; Weyrich, Andrew S.; Rondina, Matthew T.

    2016-01-01

    Emerging evidence implicates platelets as key mediators of venous thromboembolism (VTE). Nevertheless, the pathways by which platelets and circulating procoagulant proteins synergistically orchestrate VTE remain incompletely understood. We prospectively determined whether activated platelets and systemic procoagulant factors were associated with VTE in 32 older orthopedic surgery patients. Circulating platelet-monocyte aggregates (PMAs), p-selectin expression (P-SEL), and integrin αIIbβ3 activation (PAC-1 binding) were assessed pre-operatively and 24 hours post-operatively. The proinflammatory and procoagulant molecule C-reactive protein (CRP), which induces PMA formation in vitro, along with plasma d-dimer and fibrinogen levels were also measured. The primary outcome was VTE occurring within 30 days post-operatively. Overall, 40.6% of patients developed VTE. Patients with VTE had a significant increase in circulating PMAs and CRP post-operatively, compared to those without VTE. Changes in PMA and CRP in VTE patients were significantly correlated (r2 = 0.536, p = 0.004). In contrast, P-SEL expression and PAC-1 binding, fibrinogen levels, and d-dimers were not associated with VTE. This is the first study to identify that increased circulating PMAs and CRP levels are early markers associated with post-surgical VTE. Our findings also provide new clinical evidence supporting the interplay between PMAs and CRP in patients with VTE. PMID:27270163

  6. Enhancement of platelet aggregation and thrombus formation by arsenic in drinking water: a contributing factor to cardiovascular disease.

    PubMed

    Lee, Moo-Yeol; Bae, Ok-Nam; Chung, Seung-Min; Kang, Kyu-Tae; Lee, Joo-Young; Chung, Jin-Ho

    2002-03-01

    Arsenic in drinking water is a worldwide health problem that is associated with cardiovascular disease, but the cause is currently unknown. Arsenic effects on platelets, which are important in development of cardiovascular disease, were examined in vitro and in a drinking water study using a rat animal model. Trivalent inorganic arsenic (arsenite) induced in vitro aggregation when platelets were exposed to subthreshold challenge by thrombin and several other agonists in a concentration-dependent manner, with arsenite being the most potent form tested. Arsenite also induced significant increases in serotonin secretion, thromboxane A(2) formation, and adhesion protein expression in platelets. Consistent with the in vitro studies, 4-week ingestion of arsenite-contaminated drinking water resulted in enhanced arterial thrombosis. Human platelets showed similar responses, suggesting that the effects seen in animal experiments are applicable to humans. These results will provide new insights into the mechanism of arsenic-induced cardiovascular disease. They will also allow regulatory agencies to estimate risk from arsenic-induced cardiovascular disease and to determine if drinking water regulatory levels based on human cancer studies will protect against noncancer effects associated with cardiovascular disease.

  7. Synthesis of sFlt-1 by platelet-monocyte aggregates contributes to the pathogenesis of preeclampsia

    PubMed Central

    Major, Heather D.; Cambell, Robert A.; Silver, Robert M.; Branch, D. Ware; Weyrich, Andrew S.

    2014-01-01

    Objective Soluble fms-like tyrosine kinase (sFlt-1) is an important mediator in the pathogenesis of preeclampsia. We sought to determine if platelet-monocyte aggregates (PMAs) produced sFlt-1 and if PMAs contributed to sFlt-1 production in preeclampsia. Study Design Case-control study of sFlt-1 release from PMAs using blood samples from women with preeclampsia matched by gestational age to pregnant controls. A third group of nonpregnant, reproductive-age women comprised an additional control group. Experiments were also performed using blood from non-pregnant women to elucidate if inducing PMAs could stimulate sFlt-1 production, and if so, to determine the necessary receptors and pathways. Results Women with preeclampsia had increased total Flt-1 concentrations in platelets and monocytes at baseline compared to pregnant controls (25 vs. 10 pg/ml, p=0.0003). sFlt-1 production was elicited from monocytes incubated with thrombin-activated platelets from non-pregnant women. sFlt-1 production was regulated at the transcriptional level by p38 and NF-κB dependent pathways. Conclusion Activated platelets in preeclampsia bind monocytes to generate sFlt-1. PMAs are a previously unrecognized source of sFlt-1 that may contribute to endothelial dysfunction and systemic inflammation commonly observed in preeclampsia. PMID:24440566

  8. Purification and characterization of L-amino acid oxidase from king cobra (Ophiophagus hannah) venom and its effects on human platelet aggregation.

    PubMed

    Li, Z Y; Yu, T F; Lian, E C

    1994-11-01

    Venoms of several snake species contain large amounts of L-amino acid oxidase but its effects on human plasma coagulation and platelet aggregation have not been explored. We have purified L-amino acid oxidase from king cobra venom through CM-Sephadex C-25, Sephadex G-100 and DEAE Sephadex A-50 chromatographies. The purified enzyme has a mol. wt of 135,000 as determined by gel filtration and 65,000 by SDS-PAGE under non-reducing and reducing conditions. Incubation of plasma with L-amino acid oxidase at 200 micrograms/ml did not affect prothrombin time, activated partial thromboplastin time, or thrombin time. Upon addition of L-amino acid oxidase, platelets in platelet-rich plasma were aggregated. The enzyme-induced aggregation was abolished by catalase. The aggregation was also inhibited by indomethacin, aspirin, ethylenediaminetetraacetate, sodium nitroprusside, prostaglandin E1, mepacrine and verapamil, but not by heparin, hirudin, creatine phosphate/creatine phosphokinase or antimycin/2-deoxy-D-glucose. These results suggest that L-amino acid oxidase induces human platelet aggregation through the formation of H2O2, and subsequent thromboxane A2 synthesis requiring Ca2+ but independent of ADP release. The platelet aggregation caused by L-amino acid oxidase is likely to contribute to toxicity inflicted by cobra venom.

  9. Use of selective-serotonin reuptake inhibitors and platelet aggregation inhibitors among individuals with co-occurring atherosclerotic cardiovascular disease and depression or anxiety

    PubMed Central

    Thornton, J Douglas; Agarwal, Parul; Sambamoorthi, Usha

    2016-01-01

    Objective: Medications commonly used to treat heart disease, anxiety, and depression can interact resulting in an increased risk of bleeding, warranting a cautious approach in medical decision making. This retrospective, descriptive study examined the prevalence and the factors associated with the use of both selective-serotonin reuptake inhibitor and platelet aggregation inhibitor among individuals with co-occurring atherosclerotic cardiovascular disease and anxiety or depression. Methods: Respondents aged 22 years and older, alive throughout the study period, and diagnosed with co-occurring atherosclerotic cardiovascular disease and anxiety or depression (n = 1507) in years 2007 through 2013 of the Medical Expenditures Panel Survey were included. The use of treatment was grouped as follows: selective-serotonin reuptake inhibitor and platelet aggregation inhibitor, selective-serotonin reuptake inhibitor or platelet aggregation inhibitor, and neither selective-serotonin reuptake inhibitor nor platelet aggregation inhibitor. Results: Overall, 16.5% used both selective-serotonin reuptake inhibitor and platelet aggregation inhibitor, 61.2% used selective-serotonin reuptake inhibitor or platelet aggregation inhibitor, and 22.3% used neither selective-serotonin reuptake inhibitor nor platelet aggregation inhibitor. Respondents aged over 65 years (adjusted odds ratio = 1.93 (95% confidence interval = 1.08–3.45)) and having a diagnosis of diabetes (adjusted odds ratio = 1.63 (95% confidence interval = 1.15–2.31)) and hypertension (adjusted odds ratio = 1.84 (95% confidence interval = 1.04–3.27)) were more likely to be prescribed the combination. Conclusion: The drug interaction was prevalent in patients who are already at higher risk of health disparities and worse outcomes thus requiring vigilant evaluation. PMID:28348738

  10. Relation between clopidogrel active metabolite levels and different platelet aggregation methods in patients receiving clopidogrel and aspirin.

    PubMed

    Liang, Yan; Johnston, Marilyn; Hirsh, Jack; Pare, Guillaume; Li, Chunjian; Mehta, Shamir; Teo, Koon K; Sloane, Debi; Yi, Qilong; Zhu, Jun; Eikelboom, John W

    2012-11-01

    Clopidogrel is a prodrug that undergoes bioconversion via cytochrome P450 system to form an active metabolite (AM) that binds to the platelet ADP receptor. The antiplatelet effect of clopidogrel is commonly assessed by measuring the aggregatory response to 5 μM ADP by light transmission aggregation (LTA) or multiple electrode aggregometry (MEA) or by the vasodilator-stimulated phosphoprotein platelet reactivity index (VASP-PRI). To determine which of these three tests of platelet ADP receptor pathway inhibition most closely correlates with clopidogrel AM levels. We analyzed blood samples from 82 patients with coronary artery disease who were randomized to receive double-dose or standard dose clopidogrel for 2 weeks. We measured peak clopidogrel AM levels, platelet aggregation in response to ADP and VASP-PRI on days 1, and repeated all the measures on days 7 and 14. Linear regression analysis was used to examine the correlation between clopidogrel AM and LTA, MEA and VASP-PRI. Bland-Altman plots were used to explore the agreement between tests of the antiplatelet effects of clopidogrel. Clopidogrel AM on day 1 correlated most closely with VASP-PRI (r = -0.5767) and demonstrated weaker correlations with LTA (r = -0.4656) and MEA (r = -0.3384) (all p < 0.01). Intra-class correlation (ICC) between VASP-PRI and LTA was 0.6446; VASP-PRI and MEA was 0.4720; and LTA and MEA was 0.4693. Similar results were obtained on days 7 and 14. Commonly used pharmacodynamic measures of clopidogrel response are only moderately correlated with clopidogrel AM levels and may not be suitable to measure the adequacy of clopidogrel therapy.

  11. Abciximab treatment in vitro after aspirin treatment in vivo has additive effects on platelet aggregation, ATP release, and P-selectin expression.

    PubMed

    Scazziota, A; Altman, R; Rouvier, J; Gonzalez, C; Ahmed, Z; Jeske, W P; Walenga, J M; Fareed, J

    2000-12-15

    To prevent arterial thrombosis, abciximab is administered together with aspirin. However, whether or not there are benefits to combine abciximab with aspirin is not yet well defined. Healthy volunteers were studied for the effect of aspirin + abciximab using sodium arachidonate and adenosine diphosphate (ADP) alone or in combination to induce platelet activation/aggregation. Abciximab produced complete inhibition of platelet aggregation induced with ADP but only 40% inhibition of aggregation induced by 0.75-mmol/l sodium arachidonate. Abciximab added in vitro to platelet-rich plasma (PRP) from platelets from aspirin-treated donors produced an almost complete inhibition of platelet aggregation. Aspirin, and abciximab alone, did not inhibit adenosine triphosphate (ATP) release as thoroughly as aspirin + abciximab did. Abciximab (3-5 microg/ml) produced inhibition of P-selectin expression induced with 5 (from 46.2 +/- 6.0% to 27.4 +/- 7.0%, P=0.002) and 20-micromol/l ADP (from 53.1 +/- 8.1% to 35.1 +/- 11.0%, P=0.019), but no effect was observed when 0.75-mmol/l sodium arachidonate was used (P=0.721). Aspirin diminished P-selectin expression in sodium arachidonate-stimulated platelets (from 77.7 +/- 11.8% to 40.2 +/- 3.6%, P<0.0001) in non-aspirinated and platelets from aspirin-treated donors, respectively. Abciximab (3, 4, and 5 microg/ml) added to platelets from aspirin-treated donors decreased P-selectin expression in platelets stimulated with sodium arachidonate from 40.2 +/- 8.6% to 25.6 +/- 11.5% (P=0.027), to 20.5 +/- 3.5% (P<0.0001), and to 22.5 +/- 1.8% (P<0.0001). We concluded that the antiplatelet effect of abciximab is greatly increased by aspirin.

  12. Effects of ticlopidine or ticlopidine plus aspirin on platelet aggregation and ATP release in normal volunteers: why aspirin improves ticlopidine antiplatelet activity.

    PubMed

    Altman, R; Scazziota, A; Rouvier, J; Gonzalez, C

    1999-10-01

    Aspirin and ticlopidine are used to prevent arterial thrombosis. In some clinical settings ticlopidine is administered with aspirin for improving antithrombotic effect. We administered aspirin (100 mg/day), ticlopidine (500 mg/day), or ticlopidine and aspirin for 7 days to healthy volunteers. Platelet aggregation and ATP release induced by sodium arachidonate, ADP, or a combination of both were measured. Sodium arachidonate (0.25 mmol/L), which produces no platelet aggregation, combined with adenosine diphosphate (1 mumol/L), which produced a reversible platelet aggregation of 20% after ticlopidine, resulted in a synergistic platelet aggregation response in normal (74.6 +/- 9.2%) and in ticlopidine platelet-rich plasma (59.1% +/- 14.9%, p < 0.0001). Synergism after sodium arachidonate (0.75 mmol/L) plus adenosine diphosphate (4 mumol/L) fell from 75.8% +/- 11.0% and 59.1% +/- 15.6% after ticlopidine or aspirin, respectively, to 14.8% +/- 18.0% (p < 0.0001) after ticlopidine plus aspirin. Aspirin and ticlopidine alone did not inhibit adenosine triphosphate release as thoroughly as did aspirin plus ticlopidine. Aspirin or ticlopidine does not adequately prevent platelet activity as ticlopidine plus aspirin do. Addition of aspirin to treatment with ticlopidine improves their antiplatelet activity and better results could be obtained in arterial thrombotic prevention strategies.

  13. 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.

  14. Isolation of microtubule coils from platelets after exposure to aggregating agents.

    PubMed Central

    White, J. G.; Krumwiede, M.; Burris, S. M.; Heagan, B.

    1986-01-01

    The discoid shape of human blood platelets is supported by a circumferential microtubule (MT) organized in many loops or coils. A recent study reported from the authors' laboratory demonstrated that significant numbers of MT rings could be isolated from resting platelets by simultaneous exposure to detergent and a small amount of fixative. This method has been used in the present investigation to determine the number of MT coils obtained from platelets after activation by ADP, thrombin, and the calcium ionophore, A23187. Concentrations of the agonists that caused shape change and internal transformation in parallel samples did not influence the frequency of MT rings present in activated samples after treatment with fixative and detergent. As many or more MT coils were present 5, 15, 30, 60, 90, and 120 seconds after addition of an agonist as from the control. Statistical analysis revealed no significant difference between the number of isolated coils from controls and activated platelets at any time during early activation. Immunofluorescence microscopic examination of platelets stained with a monoclonal antibody to tubulin at intervals of 5, 15, 30, 60, 90, and 120 seconds after activation on glass surfaces confirmed the suggestion that platelet MTs are resistant to disassembly during the early response to stimulation. Images Figure 1 Figure 7 and 8 Figure 9-14 PMID:3098108

  15. [Platelet aggregation inhibitors and vitamin K antagonists in stomatology and maxillo-facial surgery].

    PubMed

    Lévesque, H; Péron, J-M

    2003-04-01

    Anti-thrombin, anti-platelet and anti-vitamin K agents are common treatments given for the prevention of thrombotic or embolic events. In oral or maxillofacial surgery, the question is whether oral anticoagulants or anti-platelets should be discontinued or not: temporary interruption could limit the risk of bleeding, but would increase the risk of thrombosis, and inversely. The best risk/benefit ratio must be achieved, but in many cases anti-platelet agents or even anti-vitamin K agents can be continued. In case of "potentially hemorrhagic" oral surgery, anti-platelet agents should be interrupted about ten days before the intervention. Anti-vitamin K agents should be interrupted four days before surgery and if required, replaced by low-molecular weight heparin at preventive or curative doses. In the very large majority of patients however, surgery (avulsion for example) can be performed without interrupting anticoagulation. Data in the literature have demonstrated that despite the theoretical risk of hemorrhage, bleeding is minimal and can be easily controlled by local treatments; the risk of thrombotic or thromboembolic events after discontinuing anticoagulation is much greater. A close collaboration between the dentist, the stomatologist, and the clinician is required to determine whether anti-thrombosis prevention should be continued and whether the anticoagulation level is adapted to the thrombotic risk. Good surgical technique and local anti-hemorrhagic treatment are essential in oral surgery, particularly in patients taking anti-platelets or oral anticoagulants.

  16. Experimental Trypanosoma cruzi cardiomyopathy in BALB/c mice. The potential role of intravascular platelet aggregation in its genesis.

    PubMed Central

    Rossi, M. A.; Gonçalves, S.; Ribeiro-dos-Santos, R.

    1984-01-01

    In male BALB/c mice aged 5-6 weeks inoculated three times at intervals of 15 days with 1 X 10(7) epimastigote forms of the PF strain of Trypanosoma cruzi and challenged 30 days after the last inoculation with 2 X 10(4) trypomastigote forms of the Colombia strain of T cruzi (the mice were sacrificed 80-100 days after the challenge) a cardiomyopathy very similar to that observed in the chronic phase of Chagas' disease in man develops. The cardiac syndrome is characterized grossly by cardiomegaly with hypertrophy, dilatation of ventricular chambers, and thinning of the apex of the left ventricle (apical aneurysm) and microscopically by focal areas of myocytolytic necrosis and myocardial degeneration with an inflammatory response composed of mononuclear cells (predominantly macrophages and a few lymphocytes) with concurrent interstitial fibrosis and occasional myofibers containing pseudocysts. In addition, aggregated platelets and occlusive thrombi were found in small epicardial and intramyocardial vessels of infected mice as compared with controls. The potential role of intravascular platelet aggregation in the causation of focal myocardial necrosis and degeneration and apical aneurysm in experimental T cruzi cardiomyopathy in BALB/c mice is discussed. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 PMID:6230012

  17. A Novel Pentapeptide Targeting Integrin β3-Subunit Inhibits Platelet Aggregation and Its Application in Rat for Thrombosis Prevention

    PubMed Central

    Qu, Qingrong; Liu, Yamin; Yan, Xuejiao; Fan, Xiaobo; Liu, Naifeng; Wu, Guoqiu

    2016-01-01

    Background: Antiplatelet therapy plays a pivotal role in the prevention and treatment of thrombotic diseases. We reported the screening of P1C as a novel integrin-binding peptide from the C-terminal of connective tissue growth factor. Primary study indicated that P1C has potential against platelet aggregation. Objectives: We aimed to find the shortest active unit from the P1C fragments and explore its in vivo and in vitro activities. Methods: A series of truncated P1C fragments was prepared and screened for antiplatelet activity. The most active fragment was evaluated using coagulation assays. Flow cytometry and confocal microscopy were used to determine the interaction between the peptide and the integrin. The in vivo potential was further explored using two types of rat models. Results: From a series of truncated P1C forms, a so-called P1Cm peptide of 5-amino acids, namely, IRTPK was screened out as the shortest active unit with superior activity. Coagulation experiments and an in vivo toxicity assay demonstrated that P1Cm is safe in vivo and inhibits ADP- and TH-induced human platelet aggregation in vitro in a concentration-dependent manner. Furthermore, it has limited effect on the coagulation parameters. Flow cytometry and confocal microscopy experiments consistently indicated that the peptide specifically binds the β3-subunit of integrin on platelets. Further experiments using rat models of artery-vein shunt and carotid arterial thrombosis illustrated that P1Cm can effectively prevent thrombosis formation. Conclusion: P1Cm may be a new, promising antithrombotic alternative to currently available antiplatelet treatments. PMID:27014063

  18. Hemostatic markers and platelet aggregation factors as predictive markers for type of stroke and neurological disability following cerebral infarction.

    PubMed

    Tombul, Temel; Atbas, Cigdem; Anlar, Omer

    2005-05-01

    We investigated the plasma levels of D-dimer, fibrinogen, beta-thromboglobulin (BTG) and platelet factor-4 (PF-4), indices of the occurrence of platelet activation in vivo, to find out their role in pathophysiology of ischemic stroke and whether or not such a role has any effect on the disability and the prognosis of stroke patients. A total of 76 patients with AIS aged from 26 to 85 (32 men, 44 women) and 30 cases as controls with similar age (18 men, 12 women) were included in the study. The plasma levels of D-dimer, BTG and PF-4 were measured by ELISA method using a special commercial kit. The cases were allocated into two groups as non-embolic (NEI) and cardioembolic stroke (CEI). The D-dimer levels in 76% of 42 patients in NEI group (p<0.05) and 85.2% of 34 patients in CEI group (p<0.05) were outside the confidence interval (CI) defined for the control group. The levels of BTG were elevated in 81% of 42 cases with NEI (p<0.05) and in 76% of 34 cases with CEI, with reference to CI of control group. The levels of PF-4 were significantly increased in 86% of cases with NEI (p<0.05) and in 88% of cases with CEI than controls (p<0.05). It was observed that the cases with high Rankin scores had higher levels of D-dimer (p<0.005), BTG (p<0.01) and PF-4 (p<0.01) than those with lower scores. There was a correlation between hemostatic markers, platelet activation and functional disability. D-dimer levels were an important marker that determined to degree of the activation of hemostatic system, especially in CEI subtype. The platelet aggregation had an important role in pathophysiology of ischemic stroke and this condition is significant in NEI subgroup and subjects with large infarcts and high disability scores.

  19. Structure and oxidation capacity of amino acid chloramine derivatives and their effects on platelet aggregation.

    PubMed

    Murina, M A; Chudina, N A; Roshchupkin, D I; Belakina, N S; Sergienko, V I

    2004-12-01

    Comparison of antiaggregation capacity of N-chloramine acids with different position of the chloramine group in the molecule showed that in the most efficient compounds the distance between the chloramine and carboxyl groups was 3-5 carbon atoms. This feature of antiaggregation activity was not related to the difference in oxidation capacity of N-chloramine acids. It was hypothesized that the revealed structural dependence of antiaggregation activity of N-chloramine acids is determined by the structure of platelet membrane, in particular, the presence of a negatively charged group near the site of interaction between N-chloramine acids and platelet membrane.

  20. [The relationship between lipid peroxidation and platelet aggregation in atherosclerotic patients].

    PubMed

    Gómez Calviño, C; Simón Carballo, R; Coma Alfonso, C; Sánchez de León, T; Montero Pacheco, E; Rodríguez Piloto, R

    1991-01-01

    We studied 58 patients with arterial esteno-occlusive disease, 32 diabetics and 26 nondiabetics. Some parameters of lipid metabolism and platelet function were evaluated. We show the correlations founded among these parameters and we offer a possible explanation which support this behaviour.

  1. 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.

  2. 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.

  3. Chemical synthesis and structural characterization of the RGD-protein decorsin: a potent inhibitor of platelet aggregation.

    PubMed Central

    Polverino de Laureto, P.; Scaramella, E.; De Filippis, V.; Marin, O.; Doni, M. G.; Fontana, A.

    1998-01-01

    Decorsin is a 39-residue RGD-protein crosslinked by three disulfide bridges isolated from the leech Macrobdella decora belonging to the family of GPIIb-IIIa antagonists and acting as a potent inhibitor of platelet aggregation. Here we report the solid-phase synthesis of decorsin using the Fmoc strategy. The crude polypeptide was purified by reverse-phase HPLC in its reduced form and allowed to refold in the presence of glutathione. The homogeneity of the synthetic oxidized decorsin was established by reverse-phase HPLC and capillary zone electrophoresis. The results of amino acid analysis after acid hydrolysis of the synthetic protein, NH2-terminal sequencing and mass determination (4,377 Da) by electrospray mass spectrometry were in full agreement with this theory. The correct pairing of the three disulfide bridges in synthetic decorsin was determined by a combined approach of both peptide mapping using proteolytic enzymes and analysis of the disulfide chirality by CD spectroscopy in the near-UV region. Synthetic decorsin inhibited human platelet aggregation with an IC50 of approximately 0.1 microM, a figure quite similar to that determined utilizing decorsin from natural source. In particular, the synthetic protein was 2,000-fold more potent than a model RGD-peptide (e.g., Arg-Gly-Asp-Ser) in inhibiting platelet aggregation. Thermal denaturation experiments of synthetic decorsin, monitored by CD spectroscopy, revealed its high thermal stability (Tm approximately 74 degrees C). The features of the oxidative refolding process of reduced decorsin, as well as the thermal stability of the oxidized species, were compared with those previously determined for the NH2-terminal core domain fragment 1-41 or 1-43 from hirudin. This fragment shows similarity in size, pairing of the three disulfides and three-dimensional structure with those of decorsin, even if very low sequence similarity. It is suggested that the less efficient oxidative folding and the enhanced thermal

  4. Purification and characterization of a platelet aggregation inhibitor and anticoagulant Cc 5_NTase, CD 73-like, from Cerastes cerastes venom.

    PubMed

    Saoud, Samah; Chérifi, Fatah; Benhassine, Traki; Laraba-Djebari, Fatima

    2016-12-07

    The present study is the first attempt to report the characterization of a nucleotidase from Cerastes cerastes venom. A 70 kDa 5'-nucleotidase (Cc-5'NTase) was purified to homogeneity. The amino acid sequence of Cc-5'NTase displayed high homology with many nucleotidases. Its activity was optimal at pH 7 with a specific hydrolytic activity toward mono-, di-, and triphosphate adenylated nucleotides. Cc-5'NTase preferentially hydrolyzed ADP and obeyed Michaelis-Menten kinetics. Among the metals and inhibitors tested, Ni(2+) and Mg(2+) completely potentiated enzyme activity, whereas EGTA, PMSF, iodoacetamide, vanillic acid, vanillyl mandelic acid, and 1,10-phenanthroline partially abolished its activity. Cc-5'NTase was not lethal for mice at 5 mg/kg and exhibited in vivo anticoagulant effect. It also dose-dependently inhibited adenosine diphosphate-induced platelet aggregation by converting adenosine diphosphate to adenosine and prohibited arachidonic acid-induced aggregation but was not effective on fibrinogen-induced aggregation. Cc-5'NTase could be a good tool as pharmacological molecule in thrombosis diagnostic and/or therapy.

  5. The effect of different doses and different routes of acetylsalicylic acid administration on platelet aggregation in healthy volunteers and ischemic stroke patients.

    PubMed

    Chýlová, Miroslava; Moťovská, Zuzana; Osmančík, Pavel; Procházka, Bohumír; Kalvach, Pavel

    2015-04-01

    The purpose was to assess the effect of different doses and different routes of acetylsalicylic acid (ASA) administration on platelet aggregation and the comparison between platelet aggregation after the single and the repetitive administration of ASA in healthy individuals and in patients after ischemic stroke. The study group consists of 22 healthy individuals and 30 patients with documented ischemic stroke. Platelet aggregation was measured in healthy individuals: (a) twice before ASA and (b) 2 h after different single doses and different routes of ASA administration-(b1) 500 mg orally, (b2) 500 mg intravenously, and (b3) 100 mg orally. We measured aggregability in healthy individuals after five consecutive days of 100 mg of ASA q.d. and in patients on chronic ASA 100 mg q.d. The VerifyNow was used with results expressed in aspirin reaction units (ARU). In healthy individuals, the dose-(b1) 500 mg orally-reduced the aggregability to mean (SD) 392 (36) ARU (p < 0.001), (b2) 500 mg intravenously to 428 (46) (p < 0.001) and (b3) 100 mg orally to 460 (76) (p < 0.001). The suppression of aggregation after 500 mg was (p = 0.029) higher after the oral compared to intravenous administration, and the same is true for the suppression after single dose of 500 mg orally and 100 mg orally (p = 0.011). Oral dose 100 mg for 5 days in healthy individuals reduced aggregation to 405 (37) and in post-stroke patients to 433 (54). All doses of ASA, both orally and intravenously, have produced a significant reduction of platelet aggregation. Preference of the parenteral to oral application has not been established.

  6. Circulating complexes in leprosy studied by the platelet aggregation test. The platelet aggregation test and its relation to the rubino test and other sero-immunological parameters in 135 patients with leprosy

    PubMed Central

    Wager, O.; Penttinen, K.; Almeida, J. D.; Opromolla, D. V. A.; Godal, T.; Kronvall, G.

    1978-01-01

    Sera from 135 patients with leprosy were tested by the platelet aggregation test (PAT), by the Rubino test and by other sero-immunological assays. PAT positivity (titre≥10) was 53% in the lepromatous subgroups and 5% in the tuberculoid subgroups (P<0·005). The higher PAT titres and Rubino titres clustered significantly (P<0·0005) toward the lepromatous end of the disease spectrum. A statistically significant correlation was found between the PAT and the Rubino titres (0·05>P>0·025). Removal of the effect of the disease spectrum, however, resulted in a partial correlation between the PAT and the Rubino titres that was not significant (P>0·1), suggesting different basic mechanisms for the platelet aggregation (PA) and the Rubino activity of the lepromatous sera. The correlation between the PAT titres and twenty-nine other sero-immunological parameters was calculated, and a highly significant correlation was found between the PAT and the IgG level (P<0·005) and between the PAT and the antistaphylolysin-α titre (P<0·005). The PA activity in most lepromatous sera studied sedimented in the heavy (>19S) fractions and was inhibitable by IgM rheumatoid factor. It thus fulfilled the criteria for IgG complexes as defined in previous studies with known model Ag/Ab complexes and with sera from patients with immune complex states. The addition of an excess of soluble mycobacterial antigens affected the PA activity of some lepromatous sera, which suggests that the putative complexes were composed of mycobacterial antigens complexed with corresponding IgG antibody. It was concluded that the PAT is a sensitive detector of IgG complexes peculiar to the lepromatous leprosy. In leprosy the discriminatory power of the PAT seems to be superior to that of other immune complex tests recently applied for the analysis of leprosy series. ImagesFIG. 1 PMID:369750

  7. Analogues of diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) as potential anti-platelet-aggregation agents.

    PubMed Central

    Zamecnik, P C; Kim, B; Gao, M J; Taylor, G; Blackburn, G M

    1992-01-01

    Dense granules of platelets contain a high content of diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A). We have previously demonstrated an antithrombotic effect of this compound in a live rabbit model. In the present study we find that certain synthetic Ap4A analogues are superior to Ap4A in inhibiting ADP-induced aggregation of human platelets. Analogues having a P--C--P bridge located in the P2,P3 position of Ap4A are the most potent inhibitors. These analogues are also resistant to hydrolytic enzymes. Analogues having the above characteristics exhibit competitive inhibition with ADP in the ADP-induced platelet aggregation reaction. These compounds, such as AppCHFppA, may be useful as antithrombotic agents. The analogues ApSppSpA and ApSpCHFpSpA also showed good inhibitory effects on ADP-induced platelet aggregation. In addition, this action of Ap4A and its analogues provides an example of a dinucleotide inducing an antagonistic effect by occupying an extracellular mononucleotide binding site on platelets. It calls attention to the possibility that Ap4A and its analogues may act in a similar way in whole organisms, triggering effector or inhibitory responses in any one of a variety of cells. PMID:1549600

  8. Combined administration of 5-HT2 and thromboxane A2 antagonists: effects on platelet aggregation and isolated cardiac muscle

    PubMed Central

    Shaw, Linda A; Batey, Andrew J; Coker, Susan J

    1997-01-01

    To investigate possible mechanisms underlying the ability of combined administration of a 5-hydroxytryptamine2 (5-HT2) antagonist and a thromboxane A2 antagonist to reduce reperfusion-induced arrhythmias, the effects of these drugs alone and in combination on platelet aggregation and on cardiac muscle were determined. Platelet aggregation was measured in whole blood obtained from anaesthetized rats. Concentrations of 5-HT (10 μM) and the thromboxane A2 mimetic U46619 (1 μM) which did not cause aggregation themselves, enhanced the responses to ADP (0.1 μM) and to collagen (1 μg ml−1). For example, the response of 1.0±0.5 Ω to ADP alone was increased significantly to 6.4±1.0 Ω by 5-HT, 15.5±2.8 Ω by U46619, and 17.3±1.3 Ω when U46619, 5-HT and ADP were added together. In further experiments blood was obtained from rats which had received either the 5-HT2 antagonist, ICI 170,809 (1 mg kg−1), or the thromboxane A2 antagonist, ICI 192,605 (1 mg kg−1 min−1), or both in combination. When ADP was used as the primary aggregating agent, the ability of U46619 alone, or together with 5-HT, to enhance responses was reduced significantly by ICI 192,605 alone and in combination with ICI 170,809. Similar results were obtained with lower doses of ICI 170,809 (0.3 mg kg−1) and ICI 192,605 (0.3 mg kg−1 min−1). When collagen was used as the primary aggregating agent ICI 170,809 (1 mg kg−1) reduced the response to 5-HT (5.0±0.8 Ω versus 10.9±1.2 Ω in controls), and ICI 192,605 (1 mg kg−1 min−1) reduced the response to U46619 (6.8±2.5 Ω versus 11.2±2.2 Ω in control). The greatest reduction of platelet aggregation was seen in blood from rats which had received both antagonists, with the response to U46619 plus 5-HT plus collagen being 2.7± 0.6 Ω compared to 14.2±1.7 Ω in controls. In contrast, there was no significant attenuation of platelet aggregation in blood from rats which had received the lower

  9. Effects of simvastatin/ezetimibe on microparticles, endothelial progenitor cells and platelet aggregation in subjects with coronary heart disease under antiplatelet therapy

    PubMed Central

    Camargo, L.M.; França, C.N.; Izar, M.C.; Bianco, H.T.; Lins, L.S.; Barbosa, S.P.; Pinheiro, L.F.; Fonseca, F.A.H.

    2014-01-01

    It is not known whether the addition of ezetimibe to statins adds cardiovascular protection beyond the expected changes in lipid levels. Subjects with coronary heart disease were treated with four consecutive 1-week courses of therapy (T) and evaluations. The courses were: T1, 100 mg aspirin alone; T2, 100 mg aspirin and 40 mg simvastatin/10 mg ezetimibe; T3, 40 mg simvastatin/10 mg ezetimibe, and 75 mg clopidogrel (300 mg initial loading dose); T4, 75 mg clopidogrel alone. Platelet aggregation was examined in whole blood. Endothelial microparticles (CD51), platelet microparticles (CD42/CD31), and endothelial progenitor cells (CD34/CD133; CDKDR/CD133, or CD34/KDR) were quantified by flow cytometry. Endothelial function was examined by flow-mediated dilation. Comparisons between therapies revealed differences in lipids (T2 and T3T1 and T4, P=0.001). Decreased platelet aggregation was observed after aspirin (arachidonic acid, T1platelet aggregation, the amount of circulating endothelial and platelet microparticles, or endothelial progenitor cells. Cardiovascular protection following therapy with simvastatin/ezetimibe seems restricted to lipid changes and improvement of endothelial function not affecting the release of microparticles, mobilization of endothelial progenitor cells or decreased platelet aggregation. PMID:24760119

  10. The effect of a prostaglandin DP-receptor partial agonist (192C86) on platelet aggregation and the cardiovascular system in healthy volunteers.

    PubMed

    Gray, S J; Giles, H; Posner, J

    1992-10-01

    1. PGD2 (DP)-receptors mediate inhibition of platelet aggregation and vasodilatation. If receptor reserve were greater on platelets it might be possible to separate these effects. To determine whether such a difference in receptor reserve exists, we have examined the effects of a highly selective DP-receptor partial agonist 192C86 on platelet aggregation and the cardiovascular system in healthy volunteers. 2. Using an open, dose-escalating study design, four male volunteers received constant rate intravenous infusions of 192C86 for up to 60 min. Ex vivo platelet aggregation to ADP and collagen in platelet-rich plasma (PRP) and whole blood (WB) was studied at baseline, after 15, 30 and 60 min of each infusion and at 180 min post-infusion. Heart rate (HR), systolic and diastolic (DBP) blood pressure were measured at frequent intervals. Adverse experiences were monitored by checklist. Facial flushing was assessed by the volunteer using a visual analogue scale, by an observer using a numerical scale and by full-face colour photographs. Blood was taken for assay of plasma 192C86 concentrations by radio-immunoassay (r.i.a.). 3. 192C86 (0.007-0.058 micrograms kg-1 min-1) inhibited platelet aggregation to ADP and collagen both in PRP and WB in a dose-dependent manner. However, this was always accompanied by a decrease in DBP, increase in HR and facial flushing. Plasma concentrations of 192C86 were at or below the limits of sensitivity of the r.i.a. (0.5 ng ml-1). 4. The highest infusion rate was stopped after 20 min due to symptomatic hypotension on standing.(ABSTRACT TRUNCATED AT 250 WORDS)

  11. Validation of a P2Y12-receptor specific whole blood platelet aggregation assay.

    PubMed

    Amann, Michael; Ferenc, Miroslaw; Valina, Christian M; Bömicke, Timo; Stratz, Christian; Leggewie, Stefan; Trenk, Dietmar; Neumann, Franz-Josef; Hochholzer, Willibald

    2016-11-01

    Testing of P2Y12-receptor antagonist effects can support clinical decision-making. However, most platelet function assays use only ADP as agonist which is not P2Y12-receptor specific. For this reason P2Y12-receptor specific assays have been developed by adding prostaglandin E1 (PGE1) to reduce ADP-induced platelet activation via the P2Y1-receptor. The present study sought to evaluate a P2Y12-receptor specific assay for determination of pharmacodynamic and clinical outcomes. This study enrolled 400 patients undergoing coronary stenting after loading with clopidogrel or prasugrel. ADP-induced platelet reactivity was assessed by whole blood aggregometry at multiple time points with a standard ADP assay (ADPtest) and a P2Y12-receptor specific assay (ADPtest HS, both run on Multiplate Analyzer, Roche Diagnostics). Patients were clinically followed for 1 month and all events adjudicated by an independent committee. In total, 2084 pairs of test results of ADPtest and ADPtest HS were available showing a strong correlation between results of both assays (r = 0.96, p < 0.001). These findings prevailed in multiple prespecified subgroups (e.g., age; body mass index; diabetes). Calculated cutoffs for ADPtest HS and the established cutoffs of ADPtest showed a substantial agreement for prediction of ischemic and hemorrhagic events with a Cohen's κ of 0.66 and 0.66, respectively. The P2Y12-receptor specific ADPtest HS assay appears similarly predictive for pharmacodynamic and clinical outcomes as compared to the established ADPtest assay indicating its applicability for clinical use. Further evaluation in large cohorts is needed to determine if P2Y12-receptor specific testing offers any advantage for prediction of clinical outcome.

  12. Morphologies developed by the drying of droplets containing dispersed and aggregated layered double hydroxide platelets.

    PubMed

    Zhang, Yan; Evans, Julian R G

    2013-04-01

    Despite much interest in the structures formed from droplets of suspension as they dry, there are few studies involving plate-like particles. Layered double hydroxide suspensions were prepared with pH adjusted to give well-dispersed and flocculated variants that were characterised by sedimentation and rheology measurements. In the well-dispersed suspension, the three-phase boundary was pinned and radial flow created a peripheral wall. The platelet structure involved local flat packing but was replete with scrolls that result from the recirculation flows in the droplets as they dry. In contrast, the flocculating suspension produced flatter droplet relics and the microstructure consisted of ordered domains which were disoriented with respect to each other. Although of scientific interest, the control of these structures will make it possible to use direct ink-jet printing to build 3D shapes for the preparation of aligned, ordered nanocomposites based on plate-like particles in which platelet preferred orientation mimics the structures found in nacre.

  13. Platelet leukocyte gel facilitates bone substitute growth and autologous bone growth in a goat model.

    PubMed

    Everts, Peter A M; Delawi, Diyar; Mahoney, Christine Brown; van Erp, Albert; Overdevest, Eddy P; van Zundert, André; Knape, Johannes T A; Dhert, Wouter J A

    2010-02-01

    The aim of this study is to evaluate multiple conditions on the formation of bone growth in a goat model. We prepared from a unit of whole blood, platelet-leukocyte gel (PLG) to stimulate bone formation, based on the release of platelet growth factors. Two 3-compartment cages containing autologous bone, calcium phosphate, and trabecular metal were implanted onto goat spinal transverse processes. One cage was treated with PLG, prepared according to a standardized protocol. An untreated cage served as a control. To monitor bone formation overtime, fluorochrome markers were administered at 2, 3, and 5 weeks. Animals were sacrificed at 9 weeks after implantation. Bone growth in these 3-compartments cages was examined by histology and histomorphometry of nondecalcified sections using traditional light and epifluorescent microscopy. Compared to the control samples, bone growth in the PLG-treated autologous bone and calcium phosphate samples was significantly more. Fairly little bone growth was seen in PLG treated or untreated trabecular metal scaffolds. The results obtained from this goat model suggest a potential role for the application of autologous PLG during surgeries in which autologous bone grafts or calcium phosphate scaffolds are used.

  14. Horse chestnut extract contracts bovine vessels and affects human platelet aggregation through 5-HT(2A) receptors: an in vitro study.

    PubMed

    Felixsson, Emma; Persson, Ingrid A-L; Eriksson, Andreas C; Persson, Karin

    2010-09-01

    Extract from seeds and bark of horse chestnut (Aesculus hippocastanum L) is used as an herbal medicine against chronic venous insufficiency. The effect and mechanism of action on veins, arteries, and platelets are not fully understood. The aim of this study was to investigate the effects and mechanisms of action of horse chestnut on the contraction of bovine mesenteric veins and arteries, and human platelet aggregation. Contraction studies showed that horse chestnut extract dose-dependently contracted both veins and arteries, with the veins being the most sensitive. Contraction of both veins and arteries were significantly inhibited by the 5-HT(2A) receptor antagonist ketanserin. No effect on contraction was seen with the cyclooxygenase inhibitor indomethacin, the alpha(1) receptor antagonist prazosin or the angiotensin AT(1) receptor antagonist saralasin neither in veins nor arteries. ADP-induced human platelet aggregation was significantly reduced by horse chestnut. A further reduction was seen with the extract in the presence of ketanserin. In conclusion, horse chestnut contraction of both veins and arteries is, at least partly, mediated through 5-HT(2A) receptors. Human platelet aggregation is reduced by horse chestnut. The clinical importance of these findings concerning clinical use, possible adverse effects, and drug interactions remains to be investigated.

  15. AgfC and AgfE facilitate extracellular thin aggregative fimbriae synthesis in Salmonella enteritidis.

    PubMed

    Gibson, D L; White, A P; Rajotte, C M; Kay, W W

    2007-04-01

    Salmonella thin aggregative fimbriae (Tafi; curli) are important in pathogenesis and biofilm formation; however, less is known of their structure and morphogenesis. In the Salmonella agfBAC Tafi operon, the transcription and role of agfC have been elusive. In this study, agfBAC transcripts were detected using a sensitive reverse transcriptase technique. Native AgfC was not detected using polyclonal antibodies generated against purified hexahistidine-tagged AgfC; however, in trans expression revealed that AgfC was localized to the periplasm as a mature form. An isogenic DeltaagfC mutant displayed an abundance of 20 nm fibres, in addition to native Tafi (5-7 nm), and had an increase in cell surface hydrophobicity. Purified 20 nm fibres were depolymerized under exceptionally stringent conditions to release what proved to be AgfA subunits. This revealed that the 20 nm fibres represented a different form of Tafi. The role of AgfC in Tafi assembly was investigated further using an antibody-capture assay of isogenic Deltaagf mutants. A soluble antibody-accessible form of AgfA was captured in wild-type (wt), DeltaagfB and DeltaagfF strains, in support of the extracellular nucleation-precipitation pathway of Tafi assembly, but not in DeltaagfC or DeltaagfE mutants. This indicates that AgfC and AgfE are important for AgfA extracellular assembly, facilitating the synthesis of Tafi.

  16. Encapsulation of eptifibatide in RGD-modified nanoliposomes improves platelet aggregation inhibitory activity.

    PubMed

    Bardania, Hassan; Shojaosadati, Seyed Abbas; Kobarfard, Farzad; Dorkoosh, Farid; Zadeh, Marjan Esfahani; Naraki, Mahmoud; Faizi, Mehrdad

    2017-02-01

    Eptifibatide is an antiplatelet drug used for the treatment of thrombosis. However, as a result of its accumulation in non-targeted tissues and short half-life, it has a limited efficacy. In this study, RGD-modified nano-liposomes (RGD-MNL) were prepared as carriers for the targeted delivery of eptifibatide to activated platelets. The nano-liposomes were about 90 ± 10 nm in size, with an encapsulation efficiency of 37 ± 5 % and a good stability during 21 days, with a negligible change in the size of nanoliosomes. The in vitro cytotoxicity of nanoliposomes was examined using MTT assay. The results obtained from the ex vivo study showed that the antiplatelet activity of eptifibatide encapsulated nanoliposomes was higher in comparison with the free drug (81.63 vs. 46.17 % for RGD-MNL) and (66.67 vs. 46.17 % for UNL), and this increase was more significant for nanoliposomes targeted with RGD peptide (81.63 %; p < 0.05). The results indicated that RGD-MNL encapsulated eptifibatide had no significant cytotoxic effect on cells. In conclusion, the present nanoliposome formulation can be regarded as a new delivery system for protection and enhancement of the antiplatelet activity of eptifibatide.

  17. 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

  18. von Willebrand factor fibers promote cancer-associated platelet aggregation in malignant melanoma of mice and humans

    PubMed Central

    Bauer, Alexander T.; Suckau, Jan; Frank, Kathrin; Desch, Anna; Goertz, Lukas; Wagner, Andreas H.; Hecker, Markus; Goerge, Tobias; Umansky, Ludmila; Beckhove, Philipp; Utikal, Jochen; Gorzelanny, Christian; Diaz-Valdes, Nancy; Umansky, Viktor

    2015-01-01

    Tumor-mediated procoagulatory activity leads to venous thromboembolism and supports metastasis in cancer patients. A prerequisite for metastasis formation is the interaction of cancer cells with endothelial cells (ECs) followed by their extravasation. Although it is known that activation of ECs and the release of the procoagulatory protein von Willebrand factor (VWF) is essential for malignancy, the underlying mechanisms remain poorly understood. We hypothesized that VWF fibers in tumor vessels promote tumor-associated thromboembolism and metastasis. Using in vitro settings, mouse models, and human tumor samples, we showed that melanoma cells activate ECs followed by the luminal release of VWF fibers and platelet aggregation in tumor microvessels. Analysis of human blood samples and tumor tissue revealed that a promoted VWF release combined with a local inhibition of proteolytic activity and protein expression of ADAMTS13 (a disintegrin-like and metalloproteinase with thrombospondin type I repeats 13) accounts for this procoagulatory milieu. Blocking endothelial cell activation by the low-molecular-weight heparin tinzaparin was accompanied by a lack of VWF networks and inhibited tumor progression in a transgenic mouse model. Our findings implicate a mechanism wherein tumor-derived vascular endothelial growth factor-A (VEGF-A) promotes tumor progression and angiogenesis. Thus, targeting EC activation envisions new therapeutic strategies attenuating tumor-related angiogenesis and coagulation. PMID:25977583

  19. Sequential sup 1 H NMR assignments of kistrin, a potent platelet aggregation inhibitor and glycoprotein IIb-IIIa antagonist

    SciTech Connect

    Adler, M.; Wagner, G. )

    1992-02-04

    Sequence-specific nuclear magnetic resonances assignments have been obtained for the protons of kistrin. Kistrin is a small naturally occurring snake venom protein that inhibits platelet aggregation by blocking the interaction of fibrinogen with the membrane-bound glycoprotein IIb-IIIa (GP IIb-IIIa), a receptor from the integrin family. Kistrin has an Arg-Gly-Asp sequence which is believed to form an adhesion recognition sequence that is essential for activity. Therefore, the interaction between kistrin and GP IIb-IIIa may provide important information on the motif used by integrins to recognize their target proteins which bear RGD sequences. Kistrin consists of 68 residues and contains six intramolecular disulfide bonds. Although one-third of the amide protons are protected from exchange with the solvent, there appears to be little or no regular secondary structure. The large number of NOE's between residues separated by two and three positions in the sequence indicates that the protein contains a large number of tightly packed loops. Along with the sequential assignments, this paper also discusses the construction and use of computerized data bases for manipulating NMR results. A strategy for computer-assisted sequential resonance using these data bases is also presented.

  20. 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.

  1. Adenosine diphosphate receptors on blood platelets: potential new targets for antiplatelet therapy.

    PubMed

    Rozalski, Marcin; Nocun, Marek; Watala, Cezary

    2005-01-01

    Platelets play a key role not only in physiological haemostasis, but also under pathological conditions such as thrombosis. Platelet activation may be initiated by a variety of agonists including thrombin, collagen, thromboxane or adenosine diphosphate (ADP). Although ADP is regarded as a weak agonist of blood platelets, it remains an important mediator of platelet activation evoked by other agonists, which induce massive ADP release from dense granules, where it occurs in molar concentrations. Thus, ADP action underlies a positive feedback that facilitates further platelet aggregation and leads to platelet plug formation. Additionally, ADP acts synergistically to other, even weak, agonists such as serotonin, adrenaline or chemokines. Blood platelets express two types of P2Y ADP receptors: P2Y(1) and P2Y(12). ADP-dependent platelet aggregation is initiated by the P2Y1 receptor, whereas P2Y(12) receptor augments the activating signal and promotes platelet release reaction. Stimulation of P2Y(12) is also essential for ADP-mediated complete activation of GPIIb-IIIa and GPIa-IIa, and further stabilization of platelet aggregates. The crucial role in blood platelet biology makes P2(Y12) an ideal candidate for pharmacological approaches for anti-platelet therapy.

  2. Enzymatic biofilm digestion in soil aggregates facilitates the release of particulate organic matter by sonication

    NASA Astrophysics Data System (ADS)

    Büks, Frederick; Kaupenjohann, Martin

    2016-10-01

    The stability of soil aggregates against shearing and compressive forces as well as water-caused dispersion is an integral marker of soil quality. High stability results in less compaction and erosion and has been linked to enhanced water retention, dynamic water transport and aeration regimes, increased rooting depth, and protection of soil organic matter (SOM) against microbial degradation. In turn, particulate organic matter is supposed to support soil aggregate stabilization. For decades the importance of biofilm extracellular polymeric substances (EPSs) regarding particulate organic matter (POM) occlusion and aggregate stability has been canonical because of its distribution, geometric structure and ability to link primary particles. However, experimental proof is still missing. This lack is mainly due to methodological reasons. Thus, the objective of this work is to develop a method of enzymatic biofilm detachment for studying the effects of EPSs on POM occlusion. The method combines an enzymatic pre-treatment with different activities of α-glucosidase, β-galactosidase, DNAse and lipase with a subsequent sequential ultrasonic treatment for disaggregation and density fractionation of soils. POM releases of treated samples were compared to an enzyme-free control. To test the efficacy of biofilm detachment the ratio of bacterial DNA from suspended cells and the remaining biofilm after enzymatic treatment were measured by quantitative real-time PCR. Although the enzyme treatment was not sufficient for total biofilm removal, our results indicate that EPSs may attach POM within soil aggregates. The tendency to additional POM release with increased application of enzymes was attributed to a slight loss in aggregate stability. This suggests that an effect of agricultural practices on soil microbial populations could influence POM occlusion/aggregate stability and thereby carbon cycle/soil quality.

  3. The effects of aspirin and fish oil consumption on lysophosphatidylcholines and lysophosphatidic acids and their correlates with platelet aggregation in adults with diabetes mellitus

    PubMed Central

    Abdolahi, Amir; Georas, Steve N; Brenna, J. Thomas; Cai, Xueya; Thevenet-Morrison, Kelly; Phipps, Richard P; Lawrence, Peter; Mousa, Shaker A; Block, Robert C

    2014-01-01

    Many diabetics are insensitive to aspirin's platelet anti-aggregation effects. The influence of co-administration of aspirin and fish oil (FO) on plasma lysophospholipids in subjects with diabetes is poorly characterized. Thirty adults with type 2 diabetes mellitus were treated with aspirin (81 mg/day) for seven days, then with FO (4 g/day) for 28 days, then in combination for another seven days. Lysophospholipids and platelet measures were determined after acute (4 hours) and chronic (7 days) ingestion of aspirin, FO, or both in combination. FO ingestion reduced all lysophosphatidic acid (LPA) concentrations, while EPA (20:5n-3) and DHA (22:6n-3) lysophosphatidylcholine (LPC) concentrations significantly increased after FO alone and in combination with aspirin. In vitro arachidonic acid-induced platelet aggregation was most strongly correlated with palmitoleic (16:1) and oleic (18:1) LPA and LPC concentrations at all time points. The ingestion of these agents may reduce cardiovascular disease risk in diabetic adults, with a disrupted lipid milieu, via lysolipid mediated mechanisms. PMID:24373610

  4. Platelet-mimetic strategies for modulating the wound environment and inflammatory responses

    PubMed Central

    Nandi, Seema

    2016-01-01

    Platelets closely interface with the immune system to fight pathogens, target wound sites, and regulate tissue repair. Natural platelet levels within the body can be depleted for a variety of reasons, including excessive bleeding following traumatic injury, or diseases such as cancer and bacterial or viral infections. Platelet transfusions are commonly used to improve platelet count and hemostatic function in these cases, but transfusions can be complicated by the contamination risks and short storage life of donated platelets. Lyophilized platelets that can be freeze-dried and stored for longer periods of time and synthetic platelet-mimetic technologies that can enhance or replace the functions of natural platelets, while minimizing adverse immune responses have been explored as alternatives to transfusion. Synthetic platelets typically comprise nanoparticles surface-decorated with peptides or ligands to recreate specific biological characteristics of platelets, including targeting of wound and disease sites and facilitating platelet aggregation. Recent efforts in synthetic platelet design have additionally focused on matching platelet shape and mechanics to recreate the marginalization and clot contraction capabilities of natural platelets. The ability to specifically tune the properties of synthetic platelet-mimetic materials has shown utility in a variety of applications including hemostasis, drug delivery, and targeted delivery of cancer therapeutics. PMID:27190260

  5. Management of pulpal floor perforation and grade II Furcation involvement using mineral trioxide aggregate and platelet rich fibrin: A clinical report.

    PubMed

    Bains, Rhythm; Bains, Vivek K; Loomba, Kapil; Verma, Kavita; Nasir, Afreena

    2012-09-01

    To report the management of an iatrogenic perforation of pulpal floor in the furcation of mandibular first molar, using Mineral Trioxide Aggregate (MTA) and platelet rich fibrin (PRF). Unpredictable endodontic root/pulp chamber floor perforations resulting in unacceptable high rate of clinical failure has now been a lesser threat with the advent of new technologies and biocompatible materials that utilize the applications of basic research along with tissue engineering concept in clinical practice. Present case report illustrates the use of MTA and platelet rich fibrin (PRF) for the repair of the perforation defect and regeneration of the lost periodontium in furcation area. Although, histologic events and reaction of MTA with PRF is not studied so far, however, the autologous and biocompatible nature of the components used for present treatment modalities seems to be beneficial for the long term clinical results obtained in our case.

  6. Management of pulpal floor perforation and grade II Furcation involvement using mineral trioxide aggregate and platelet rich fibrin: A clinical report

    PubMed Central

    Bains, Rhythm; Bains, Vivek K.; Loomba, Kapil; Verma, Kavita; Nasir, Afreena

    2012-01-01

    To report the management of an iatrogenic perforation of pulpal floor in the furcation of mandibular first molar, using Mineral Trioxide Aggregate (MTA) and platelet rich fibrin (PRF). Unpredictable endodontic root/pulp chamber floor perforations resulting in unacceptable high rate of clinical failure has now been a lesser threat with the advent of new technologies and biocompatible materials that utilize the applications of basic research along with tissue engineering concept in clinical practice. Present case report illustrates the use of MTA and platelet rich fibrin (PRF) for the repair of the perforation defect and regeneration of the lost periodontium in furcation area. Although, histologic events and reaction of MTA with PRF is not studied so far, however, the autologous and biocompatible nature of the components used for present treatment modalities seems to be beneficial for the long term clinical results obtained in our case. PMID:23230369

  7. Surface modification of CoCr alloy using varying concentrations of phosphoric and phosphonoacetic acids: albumin and fibrinogen adsorption, platelet adhesion, activation, and aggregation studies.

    PubMed

    Thiruppathi, Eagappanath; Larson, Mark K; Mani, Gopinath

    2015-01-01

    CoCr alloy is commonly used in various cardiovascular medical devices for its excellent physical and mechanical properties. However, the formation of blood clots on the alloy surfaces is a serious concern. This research is focused on the surface modification of CoCr alloy using varying concentrations (1, 25, 50, 75, and 100 mM) of phosphoric acid (PA) and phosphonoacetic acid (PAA) to generate various surfaces with different wettability, chemistry, and roughness. Then, the adsorption of blood plasma proteins such as albumin and fibrinogen and the adhesion, activation, and aggregation of platelets with the various surfaces generated were investigated. Contact angle analysis showed PA and PAA coatings on CoCr provided a gradient of hydrophilic surfaces. FTIR showed PA and PAA were covalently bound to CoCr surface and formed different bonding configurations depending on the concentrations of coating solutions used. AFM showed the formation of homogeneous PA and PAA coatings on CoCr. The single and dual protein adsorption studies showed that the amount of albumin and fibrinogen adsorbed on the alloy surfaces strongly depend on the type of PA and PAA coatings prepared by different concentrations of coating solutions. All PA coated CoCr showed reduced platelet adhesion and activation when compared to control CoCr. Also, 75 and 100 mM PA-CoCr showed reduced platelet aggregation. For PAA coated CoCr, no significant difference in platelet adhesion and activation was observed between PAA coated CoCr and control CoCr. Thus, this study demonstrated that CoCr can be surface modified using PA for potentially reducing the formation of blood clots and improving the blood compatibility of the alloy.

  8. The functional role of platelets in the regulation of angiogenesis.

    PubMed

    Walsh, Tony G; Metharom, Pat; Berndt, Michael C

    2015-01-01

    Functionally, platelets are primarily recognized as key regulators of thrombosis and hemostasis. Upon vessel injury, the typically quiescent platelet interacts with subendothelial matrix to regulate platelet adhesion, activation and aggregation, with subsequent induction of the coagulation cascade forming a thrombus. Recently, however, newly described roles for platelets in the regulation of angiogenesis have emerged. Platelets possess an armory of pro- and anti-angiogenic proteins, which are actively sequestered and highly organized in α-granule populations. Platelet activation facilitates their release, eliciting potent angiogenic responses through mechanisms that appear to be tightly regulated. In conjunction, the release of platelet-derived phospholipids and microparticles has also earned merit as synergistic regulators of angiogenesis. Consequently, platelets have been functionally implicated in a range of angiogenesis-dependent processes, including physiological roles in wound healing, vascular development and blood/lymphatic vessel separation, whilst facilitating aberrant angiogenesis in a range of diseases including cancer, atherosclerosis and diabetic retinopathy. Whilst the underlying mechanisms are only starting to be elucidated, significant insights have been established, suggesting that platelets represent a promising therapeutic strategy in diseases requiring angiogenic modulation. Moreover, anti-platelet therapies targeting thrombotic complications also exert protective effects in disorders characterized by persistent angiogenesis.

  9. Spirostanol saponins derivated from the seeds of Trigonella foenum-graecum by β-glucosidase hydrolysis and their inhibitory effects on rat platelet aggregation.

    PubMed

    Pang, Xu; Cong, Yue; Yu, He-Shui; Kang, Li-Ping; Feng, Bing; Han, Bing-Xing; Zhao, Yang; Xiong, Cheng-Qi; Tan, Da-Wei; Song, Wei; Liu, Bin; Cong, Yu-Wen; Ma, Bai-Ping

    2012-02-01

    Nine spirostanol saponins (1-9) and seven mixtures of 25 R and 25 S spirostanol saponin isomers (10-16) were obtained from the seeds of Trigonella foenum-graecum after enzymatic hydrolysis of the furostanol saponin fraction by β-glucosidase. Their structures were determined by NMR and MS spectroscopy. Among them, 1- 4, 6, 8, and 9 were new compounds and five, 11B, 12A, 13B, 14A, and 14B, were new structures observed from seven mixtures. In addition, the inhibitory effects of all saponins on rat platelet aggregation were evaluated.

  10. 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.

  11. One-step apexification in immature tooth using grey mineral trioxide aggregate as an apical barrier and autologus platelet rich fibrin membrane as an internal matrix

    PubMed Central

    Rudagi, Kavitarani B; Rudagi, BM

    2012-01-01

    Immature teeth with necrotic pulp and periapical lesion are difficult to treat via conventional endodontic therapy. Numerous procedures and materials have been utilized to induce root-end barrier formation. Traditionally, calcium hydroxide has been the material of choice for the apexification of immature permanent teeth; however, Mineral Trioxide Aggregate holds significant promise as an alternative to multiple treatments with calcium hydroxide. One of the technical problems associated with the placement of the restorative materials used as artificial barrier is to prevent overfill and underfill. Using a matrix avoids the extrusion of the material into the periodontal tissues. This case report presents the successful healing and apexification with combined use of Mineral Trioxide Aggregate as an apical barrier, and autologus platelet rich fibrin membrane as an internal matrix. PMID:22557824

  12. Platelets and cancer: a casual or causal relationship: revisited.

    PubMed

    Menter, David G; Tucker, Stephanie C; Kopetz, Scott; Sood, Anil K; Crissman, John D; Honn, Kenneth V

    2014-03-01

    Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as "First Responders" during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy.

  13. Platelets and cancer: a casual or causal relationship: revisited

    PubMed Central

    Menter, David G.; Tucker, Stephanie C.; Kopetz, Scott; Sood, Anil K.; Crissman, John D.; Honn, Kenneth V.

    2014-01-01

    Human platelets arise as subcellular fragments of megakaryocytes in bone marrow. The physiologic demand, presence of disease such as cancer, or drug effects can regulate the production circulating platelets. Platelet biology is essential to hemostasis, vascular integrity, angiogenesis, inflammation, innate immunity, wound healing, and cancer biology. The most critical biological platelet response is serving as “First Responders” during the wounding process. The exposure of extracellular matrix proteins and intracellular components occurs after wounding. Numerous platelet receptors recognize matrix proteins that trigger platelet activation, adhesion, aggregation, and stabilization. Once activated, platelets change shape and degranulate to release growth factors and bioactive lipids into the blood stream. This cyclic process recruits and aggregates platelets along with thrombogenesis. This process facilitates wound closure or can recognize circulating pathologic bodies. Cancer cell entry into the blood stream triggers platelet-mediated recognition and is amplified by cell surface receptors, cellular products, extracellular factors, and immune cells. In some cases, these interactions suppress immune recognition and elimination of cancer cells or promote arrest at the endothelium, or entrapment in the microvasculature, and survival. This supports survival and spread of cancer cells and the establishment of secondary lesions to serve as important targets for prevention and therapy. PMID:24696047

  14. VerifyNow and VASP phosphorylation assays give similar results for patients receiving clopidogrel, but they do not always correlate with platelet aggregation.

    PubMed

    Bidet, Audrey; Jais, Catherine; Puymirat, Etienne; Coste, Pierre; Nurden, Alan; Jakubowski, Joseph; Nurden, Paquita

    2010-01-01

    Point-of-care testing permits an evaluation of the efficacy of drugs used in the treatment of acute coronary syndromes (ACS). An increased risk of thrombosis after coronary stenting for ACS patients treated with aspirin and clopidogrel has been linked to high platelet reactivity and, for certain patients, poor drug response. The objective of our study was to compare the VerifyNow-P2Y12 device with the VASP (vasodilator-stimulated phosphoprotein) phosphorylation assay and ADP-induced platelet aggregation as assessed by light transmission aggregometry in a group of 81 ACS patients (100 tests) treated in our hospital. There was a good correlation between VerifyNow-P2Y12 and VASP especially during the chronic phase of one month or more after the ischemic event, whereas discordance was sometimes seen with platelet aggregometry. The rapidity and ease of use of the VerifyNow device suggests that it has a valuable place in point-of-care testing of ACS patients.

  15. Comparison of modified Thrombelastograph and Plateletworks whole blood assays to optical platelet aggregation for monitoring reversal of clopidogrel inhibition in elective surgery patients.

    PubMed

    Craft, Robert M; Chavez, Jack J; Snider, Carolyn C; Muenchen, Robert A; Carroll, Roger C

    2005-06-01

    Clinically monitoring recovery from clopidogrel and nonsteroidal anti-inflammatory drug (NSAID) inhibition requires whole blood assays corresponding to a standard methodology such as platelet-rich plasma aggregation monitored optically (OPA). We compared OPA, using an ED 50 dose of adenosine diphosphate activation, with 2 whole blood assays, Plateletworks (PWA) and modified Thrombelastograph (TEG). Two sets of assays were performed on 43 surgery patients while on clopidogrel and off clopidogrel to determine the reversal of absolute and relative inhibition. The modified TEG had Spearman correlations with OPA for absolute (rho = .424; P = .006) and relative inhibition (rho = .742; P < .0001). PWA correlations with OPA gave absolute (rho = .28; P = .08) and relative inhibition (rho = .46; P = .004) values. Bland-Altman analysis indicated agreement of both tests with OPA, showing constant biases of about 18% and some dependency on mean magnitude error. Cohen effect size thresholds defined nonresponders as < 7.7% clopidogrel inhibition relative to baseline recovery of full platelet function. Apparent nonresponse to clopidogrel or lack of platelet recovery did not correlate with statin or NSAID therapies. These PWA and modified TEG whole blood assays could prove useful for monitoring the reversal of clopidogrel and NSAID inhibition before surgery. More important, these assays done at baseline and after beginning clopidogrel therapy could monitor the effectiveness for the individual patients with cardiovascular disease and help identify the need for alternative therapies.

  16. Improving Patient Care by Unshackling Telemedicine: Adaptively Aggregating Wireless Networks to Facilitate Continuous Collaboration

    PubMed Central

    Qureshi, Asfandyar; Shih, Eugene; Fan, Irene; Carlisle, Jennifer; Brezinski, Donna; Kleinman, Monica; Guttag, John

    2010-01-01

    Telemedicine has had a positive impact on some aspects of patient care. However, existing telemedicine systems that use high-quality video are inflexible, requiring investment in fixed infrastructure. We have overcome a number of technical challenges to build a mobile telemedicine system that can reliably deliver high-quality video from both stationary sites and moving vehicles. Our system is constructed using custom software and off-the-shelf hardware, and opportunistically aggregates wireless data connections from different providers. We have evaluated the communication capabilities of our system in a number of realistic experiments. We are about to launch an evaluation of the clinical utility of our system. The system will be used to allow neonatal specialists to participate in the care of critically ill infants at remote sites and during transport. PMID:21347061

  17. Rapid Purification and Procoagulant and Platelet Aggregating Activities of Rhombeobin: A Thrombin-Like/Gyroxin-Like Enzyme from Lachesis muta rhombeata Snake Venom

    PubMed Central

    Torres-Huaco, Frank Denis; Werneck, Cláudio C.; Vicente, Cristina Pontes; Vassequi-Silva, Talita; Nery-Diez, Ana Cláudia Coelho; Mendes, Camila B.; Antunes, Edson; Marangoni, Sérgio; Damico, Daniela C. S.

    2013-01-01

    We report a rapid purification method using one-step chromatography of SVSP Rhombeobin (LMR-47) from Lachesis muta rhombeata venom and its procoagulant activities and effects on platelet aggregation. The venom was fractionated by a single chromatographic step in RP-HPLC on a C8 Discovery BIO Wide Pore, showing high degree of molecular homogeneity with molecular mass of 47035.49 Da. Rhombeobin showed amidolytic activity upon BAρNA, with a broad optimum pH (7–10) and was stable in solution up to 60°C. The amidolytic activity was inhibited by serine proteinase inhibitors and reducing agents, but not chelating agents. Rhombeobin showed high coagulant activity on mice plasma and bovine fibrinogen. The deduced amino acid sequence of Rhombeobin showed homology with other SVSPs, especially with LM-TL (L. m. muta) and Gyroxin (C. d. terrificus). Rhombeobin acts, in vitro, as a strong procoagulant enzyme on mice citrated plasma, shortening the APTT and PT tests in adose-dependent manner. The protein showed, “ex vivo”, a strong defibrinogenating effect with 1 µg/animal. Lower doses activated the intrinsic and extrinsic coagulation pathways and impaired the platelet aggregation induced by ADP. Thus, this is the first report of a venom component that produces a venom-induced consumptive coagulopathy (VICC). PMID:24058917

  18. Isolation of intact megakaryocytes from guinea pig femoral marrow. Successful harvest made possible with inhibitions of platelet aggregation; enrichment achieved with a two-step separation technique

    PubMed Central

    1976-01-01

    Methods have been devised to harvest megakaryocytes from guinea pig femoral marrow and to isolate them in high yield. When marrow tissue was disaggregated the megakaryocytes underwent degenerative changes characterized by the loss of cytoplasmic granules and alterations in membrane topography, similar to the changes seen in aggregating platelets. These morphologic changes were interpreted to mean that megakaryocytes possessed functional attributes of platelets. The use of agents which inhibit platelt aggregation (0.38% sodium citrate. 10(-3) M adenosine, and 2 x 10(-3) M theophylline) in a medium free of bivalent cations prevented these changes. This solution resulted in both an excellent morphologic preservation and a significantly increased recovery of megakaryocytes from marrow tissue. A two-step purification of the intact megakaryocytes was carried out on the basis of their low density and large size, with equilibrium density gradient centrifugation followed by velocity sedimentation. This sequence gave approximately a 100-fold enrichment of megakaryocytes, significantly better than that achieved with either method alone. These techniques for harvesting and concentrating megakaryocytes make it possible for the first time to study megakaryocytes in vitro. PMID:3509

  19. Acetylsalicylic Acid Daily vs Acetylsalicylic Acid Every 3 Days in Healthy Volunteers: Effect on Platelet Aggregation, Gastric Mucosa, and Prostaglandin E2 Synthesis.

    PubMed

    Ferreira, Plinio Minghin Freitas; Gagliano-Jucá, Thiago; Zaminelli, Tiago; Sampaio, Marinalva Ferreira; Blackler, Rory Willian; Trevisan, Miriam da Silva; Novaes Magalhães, Antônio Frederico; De Nucci, Gilberto

    2016-07-01

    Substantial platelet inhibition was observed 3 days after a single administration of acetylsalicylic acid 81 mg to healthy volunteers. Here we investigate prostaglandin E2 (PGE2 ) antrum concentrations and gastrointestinal symptoms in two treatment groups: one receiving losartan and acetylsalicylic acid every day and the other receiving losartan every day and acetylsalicylic acid every 3 days. Twenty-eight healthy volunteers from both sexes received either 50 mg losartan and acetylsalicylic acid 81 mg daily or 50 mg losartan and acetylsalicylic acid 81 every 3 days with placebo on the other days. Therapy was delivered for 30 days for both groups. Gastric endoscopy was performed before and after treatment period. Biopsies were collected for PGE2 quantification. Platelet function tests were carried out before and during treatment and TXB2 release on platelet rich plasma was measured. The every 3 day low-dose acetylsalicylic acid regimen produced complete inhibition of platelet aggregation compared to the daily treatment. Thromboxane B2 release was substantially abolished for both groups during treatment. There was no significant difference on the endoscopic score of both treatment groups after the 30-day treatment (P = .215). There was over 50% suppression of antrum PGE2 content on volunteers receiving acetylsalicylic acid daily (P = .0016), while for the every 3 day dose regimen there was no significant difference between pre and post-treatment antrum PGE2 dosages (P = .4193). Since PGE2 is involved in gastric healing, we understand that this new approach could be safer and as efficient as the standard daily therapy on a long-term basis.

  20. 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.

  1. 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

  2. Identification of the platelet ADP receptor targeted by antithrombotic drugs.

    PubMed

    Hollopeter, G; Jantzen, H M; Vincent, D; Li, G; England, L; Ramakrishnan, V; Yang, R B; Nurden, P; Nurden, A; Julius, D; Conley, P B

    2001-01-11

    Platelets have a crucial role in the maintenance of normal haemostasis, and perturbations of this system can lead to pathological thrombus formation and vascular occlusion, resulting in stroke, myocardial infarction and unstable angina. ADP released from damaged vessels and red blood cells induces platelet aggregation through activation of the integrin GPIIb-IIIa and subsequent binding of fibrinogen. ADP is also secreted from platelets on activation, providing positive feedback that potentiates the actions of many platelet activators. ADP mediates platelet aggregation through its action on two G-protein-coupled receptor subtypes. The P2Y1 receptor couples to Gq and mobilizes intracellular calcium ions to mediate platelet shape change and aggregation. The second ADP receptor required for aggregation (variously called P2Y(ADP), P2Y(AC), P2Ycyc or P2T(AC)) is coupled to the inhibition of adenylyl cyclase through Gi. The molecular identity of the Gi-linked receptor is still elusive, even though it is the target of efficacious antithrombotic agents, such as ticlopidine and clopidogrel and AR-C66096 (ref. 9). Here we describe the cloning of this receptor, designated P2Y12, and provide evidence that a patient with a bleeding disorder has a defect in this gene. Cloning of the P2Y12 receptor should facilitate the development of better antiplatelet agents to treat cardiovascular diseases.

  3. Lower-Extremity Functional Electrical Stimulation Decreases Platelet Aggregation and Blood Coagulation in Persons With Chronic Spinal Cord Injury: A Pilot Study

    PubMed Central

    Kahn, Nighat N; Feldman, Susan P; Bauman, William A

    2010-01-01

    Background: Individuals with spinal cord injury (SCI) develop premature cardiovascular disease. Regular exercise reduces the incidence and symptoms of cardiovascular disease in able-bodied individuals; these salutary effects of exercise have not been documented in persons with SCI. Objective: To evaluate the effects of functional electrical stimulation leg cycle ergometry (FES-LCE) exercise training on platelet aggregation and blood coagulation in persons with SCI. Participants: Subjects (n  =  14) with stable chronic (>1 year) paraplegia (T1–T10) or tetraplegia (C4–C8). Methods: Blood samples were collected before and after the first and eighth sessions (2 sessions per week for 4 weeks) of FES exercise. Results: Platelet aggregation was inhibited by 20% after the first session and by 40% (P < 0.001) after the eighth session. Thrombin activity was unchanged after the first session (10.7 ± 0.85 s to 10.43 ± 0.56 s) and decreased after the eighth session (12.5 ± 1.98 s to 11.1 ± 1.7 s; P < 0.0003). Antithrombin III activity increased after the first (103.8% ± 8.9% to 110% ± 6.9%; P < 0.0008) and eighth sessions (107.8% ± 12.1% to 120.4% ± 13.1%; P < 0.0001). Cyclic adenosine monophosphate increased after the first (9.9% ± 2.5% to 15.8% ± 3%; P < 0.001) and eighth sessions (17.8% ± 4.2% to 36.5% ± 7.6%; P < 0.0001). After the eighth session, factors V and X increased significantly (88% ± 27% to 103% ± 23%, P < 0.0001; 100% ± 40% to 105% ± 7%, P < 0.01, respectively); factors VII and VIII and fibrinogen did not change significantly. A significant reduction in platelet activation/aggregation was demonstrated in response to FES-LCE. The decrease in thrombin level was caused by the simultaneous increase in antithrombin activity. Conclusion: These findings provide new insight into the potential protective effects of FES-LCE against the risk of cardiovascular disease. PMID:20486534

  4. SDF-1α is a novel autocrine activator of platelets operating through its receptor CXCR4.

    PubMed

    Walsh, Tony G; Harper, Matthew T; Poole, Alastair W

    2015-01-01

    Platelets store and secrete the chemokine stromal cell-derived factor (SDF)-1α upon platelet activation, but the ability of platelet-derived SDF-1α to signal in an autocrine/paracrine manner mediating functional platelet responses relevant to thrombosis and haemostasis is unknown. We sought to explore the role of platelet-derived SDF-1α and its receptors, CXCR4 and CXCR7 in facilitating platelet activation and determine the mechanism facilitating SDF-1α-mediated regulation of platelet function. Using human washed platelets, CXCR4 inhibition, but not CXCR7 blockade significantly abrogated collagen-mediated platelet aggregation, dense granule secretion and thromboxane (Tx) A2 production. Time-dependent release of SDF-1α from collagen-activated platelets supports a functional role for SDF-1α in this regard. Using an in vitro whole blood perfusion assay, collagen-induced thrombus formation was substantially reduced with CXCR4 inhibition. In washed platelets, recombinant SDF-1α in the range of 20-100 ng/mL(-1) could significantly enhance platelet aggregation responses to a threshold concentration of collagen. These enhancements were completely dependent on CXCR4, but not CXCR7, which triggered TxA2 production and dense granule secretion. Rises in cAMP were significantly blunted by SDF-1α, which could also enhance collagen-mediated Ca2+ mobilisation, both of which were mediated by CXCR4. This potentiating effect of SDF-1α primarily required TxA2 signalling acting upstream of dense granule secretion, whereas blockade of ADP signalling could only partially attenuate SDF-1α-induced platelet activation. Therefore, this study supports a potentially novel autocrine/paracrine role for platelet-derived SDF-1α during thrombosis and haemostasis, through a predominantly TxA2-dependent and ADP-independent pathway.

  5. Inhibitory effects of Tabebuia impetiginosa inner bark extract on platelet aggregation and vascular smooth muscle cell proliferation through suppressions of arachidonic acid liberation and ERK1/2 MAPK activation.

    PubMed

    Son, Dong-Ju; Lim, Yong; Park, Young-Hyun; Chang, Sung-Keun; Yun, Yeo-Pyo; Hong, Jin-Tae; Takeoka, Gary R; Lee, Kwang-Geun; Lee, Sung-Eun; Kim, Mi-Ran; Kim, Jeong-Han; Park, Byeoung-Soo

    2006-11-03

    The antiplatelet and antiproliferative activities of extract of Tabebuia impetiginosa inner bark (taheebo) were investigated using washed rabbit platelets and cultured rat aortic vascular smooth muscle cells (VSMCs) in vitro. n-Hexane, chloroform and ethyl acetate fractions showed marked and selective inhibition of platelet aggregation induced by collagen and arachidonic acid (AA) in a dose-dependent manner. These fractions, especially the chloroform fraction, also significantly suppressed AA liberation induced by collagen in [(3)H]AA-labeled rabbit platelets. The fractions, especially the chloroform fraction, potently inhibited cell proliferation and DNA synthesis induced by platelet derived growth factor (PDGF)-BB, and inhibited the levels of phosphorylated extracellular signal regulated kinase (ERK1/2) mitogen activated protein kinase (MAPK) stimulated by PDGF-BB, in the same concentration range that inhibits VSMC proliferation and DNA synthesis.

  6. The P2Y12 antagonists, 2-methylthioadenosine 5'-monophosphate triethylammonium salt and cangrelor (ARC69931MX), can inhibit human platelet aggregation through a Gi-independent increase in cAMP levels.

    PubMed

    Srinivasan, Subhashini; Mir, Fozia; Huang, Jin-Sheng; Khasawneh, Fadi T; Lam, Stephen C-T; Le Breton, Guy C

    2009-06-12

    ADP plays an integral role in the process of hemostasis by signaling through two platelet G-protein-coupled receptors, P2Y1 and P2Y12. The recent use of antagonists against these two receptors has contributed a substantial body of data characterizing the ADP signaling pathways in human platelets. Specifically, the results have indicated that although P2Y1 receptors are involved in the initiation of platelet aggregation, P2Y12 receptor activation appears to account for the bulk of the ADP-mediated effects. Based on this consideration, emphasis has been placed on the development of a new class of P2Y12 antagonists (separate from clopidogrel and ticlopidine) as an approach to the treatment of thromboembolic disorders. The present work examined the molecular mechanisms by which two of these widely used adenosine-based P2Y12 antagonists (2-methylthioadenosine 5'-monophosphate triethylammonium salt (2MeSAMP) and ARC69931MX), inhibit human platelet activation. It was found that both of these compounds raise platelet cAMP to levels that substantially inhibit platelet aggregation. Furthermore, the results demonstrated that this elevation of cAMP did not require Gi signaling or functional P2Y12 receptors but was mediated through activation of a separate G protein-coupled pathway, presumably involving Gs. However, additional experiments revealed that neither 2MeSAMP nor ARC69931MX (cangrelor) increased cAMP through activation of A2a, IP, DP, or EP2 receptors, which are known to couple to Gs. Collectively, these findings indicate that 2MeSAMP and ARC69931MX interact with an unidentified platelet G protein-coupled receptor that stimulates cAMP-mediated inhibition of platelet function. This inhibition is in addition to that derived from antagonism of P2Y12 receptors.

  7. A Pilot Study on the Effect of Angiotensin Receptor Blockers on Platelet Aggregation in Hypertensive Patients- A Prospective Observational Study

    PubMed Central

    Sanji, Narendranath; Kamath, Pallavi Mahadeva; Devendrappa, Srinivas Lokikere; Hanumanthareddy, Shashikala Gowdara; Maniyar, Imran; Rudrappa, Suresh Surappla

    2016-01-01

    Introduction Thrombosis is an invariable component contributing to cardiovascular events in patients with hypertension. One of the risk factors of cardiovascular disease is increased platelet activity. One among the widely used antihypertensive agents are Angiotensin II type 1 Receptor Blockers (ARBs). Even though there are many studies involving antihypertensive agents, their antithrombotic properties remain elusive and not fully characterized. Aim To evaluate the anti-aggregatory effect of ARBs on platelets in-vivo. Materials and Methods A total of 60 subjects were included in this observational pilot study conducted in the medicine out patient department of JJM Hospital, Davanagere, Karnataka, India. Among them, 30 patients with essential hypertension attending Medicine OPD of a tertiary care hospital, who were on ARB for at least one month, were enrolled into study group. The control group consisted of 30 normotensive subjects who were not on any drug affecting platelet function. The Bleeding Time (BT) was evaluated for both the groups using Duke method of BT estimation. Data was analysed using SPSS software version 20. The test group was compared with control group using student’s unpaired t-test. Results The mean BT of study group was 2.488 minutes ± 0.0361 Standard Error of Mean (SEM) and that of control group was 1.998 minutes ± 0.0362 SEM. The result was statistically significant (p<0.001). The average duration of treatment was 2.933 years. Conclusion ARB have antiplatelet activity. Increase in BT in ARB group when compared with that of control group is a reflection of antiplatelet activity. PMID:28050394

  8. 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

  9. 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.

  10. Platelets are versatile cells: New discoveries in hemostasis, thrombosis, immune responses, tumor metastasis and beyond.

    PubMed

    Xu, Xiaohong Ruby; Zhang, Dan; Oswald, Brigitta Elaine; Carrim, Naadiya; Wang, Xiaozhong; Hou, Yan; Zhang, Qing; Lavalle, Christopher; McKeown, Thomas; Marshall, Alexandra H; Ni, Heyu

    2016-12-01

    Platelets are small anucleate blood cells generated from megakaryocytes in the bone marrow and cleared in the reticuloendothelial system. At the site of vascular injury, platelet adhesion, activation and aggregation constitute the first wave of hemostasis. Blood coagulation, which is initiated by the intrinsic or extrinsic coagulation cascades, is the second wave of hemostasis. Activated platelets can also provide negatively-charged surfaces that harbor coagulation factors and markedly potentiate cell-based thrombin generation. Recently, deposition of plasma fibronectin, and likely other plasma proteins, onto the injured vessel wall has been identified as a new "protein wave of hemostasis" that may occur even earlier than the first wave of hemostasis, platelet accumulation. Although no experimental evidence currently exists, it is conceivable that platelets may also contribute to this protein wave of hemostasis by releasing their granule fibronectin and other proteins that may facilitate fibronectin self- and non-self-assembly on the vessel wall. Thus, platelets may contribute to all three waves of hemostasis and are central players in this critical physiological process to prevent bleeding. Low platelet counts in blood caused by enhanced platelet clearance and/or impaired platelet production are usually associated with hemorrhage. Auto- and allo-immune thrombocytopenias such as idiopathic thrombocytopenic purpura and fetal and neonatal alloimmune thrombocytopenia may cause life-threatening bleeding such as intracranial hemorrhage. When triggered under pathological conditions such as rupture of an atherosclerotic plaque, excessive platelet activation and aggregation may result in thrombosis and vessel occlusion. This may lead to myocardial infarction or ischemic stroke, the major causes of mortality and morbidity worldwide. Platelets are also involved in deep vein thrombosis and thromboembolism, another leading cause of mortality. Although fibrinogen has been

  11. Simplagrin, a Platelet Aggregation Inhibitor from Simulium nigrimanum Salivary Glands Specifically Binds to the Von Willebrand Factor Receptor in Collagen and Inhibits Carotid Thrombus Formation In Vivo

    PubMed Central

    Chagas, Andrezza C.; McPhie, Peter; San, Hong; Narum, David; Reiter, Karine; Tokomasu, Fuyuki; Brayner, Fabio A.; Alves, Luiz C.; Ribeiro, José M. C.; Calvo, Eric

    2014-01-01

    Background Among the several challenges faced by bloodsucking arthropods, the vertebrate hemostatic response against blood loss represents an important barrier to efficient blood feeding. Here we report the first inhibitor of collagen-induced platelet aggregation derived from the salivary glands of a black fly (Simulium nigrimanum), named Simplagrin. Methods and Findings Simplagrin was expressed in mammalian cells and purified by affinity-and size-exclusion chromatography. Light-scattering studies showed that Simplagrin has an elongated monomeric form with a hydrodynamic radius of 5.6 nm. Simplagrin binds to collagen (type I-VI) with high affinity (2–15 nM), and this interaction does not involve any significant conformational change as determined by circular dichroism spectroscopy. Simplagrin-collagen interaction is both entropically and enthalpically driven with a large negative ΔG, indicating that this interaction is favorable and occurs spontaneously. Simplagrin specifically inhibits von Willebrand factor interaction with collagen type III and completely blocks platelet adhesion to collagen under flow conditions at high shear rates; however, Simplagrin failed to block glycoprotein VI and Iα2β1 interaction to collagen. Simplagrin binds to RGQOGVMGF peptide with an affinity (KD 11 nM) similar to that of Simplagrin for collagen. Furthermore, Simplagrin prevents laser-induced carotid thrombus formation in vivo without significant bleeding in mice and could be useful as an antithrombotic agent in thrombosis related disease. Conclusion Our results support the orthology of the Aegyptin clade in bloodsucking Nematocera and the hypothesis of a faster evolutionary rate of salivary function of proteins from blood feeding arthropods. PMID:24921659

  12. Association of MicroRNAs and YRNAs with Platelet Function

    PubMed Central

    Bender, Lukas H.; Barwari, Temo; Willeit, Peter; Pechlaner, Raimund; Sunderland, Nicholas P.; Willeit, Karin; Morton, Allison C.; Armstrong, Paul C.; Chan, Melissa V.; Lu, Ruifang; Yin, Xiaoke; Gracio, Filipe; Dudek, Katarzyna; Langley, Sarah R.; Zampetaki, Anna; de Rinaldis, Emanuele; Ye, Shu; Warner, Timothy D.; Saxena, Alka; Kiechl, Stefan; Storey, Robert F.; Mayr, Manuel

    2016-01-01

    Rationale Platelets shed microRNAs (miRNAs). Plasma miRNAs change upon platelet inhibition. It is unclear if plasma miRNA levels correlate with platelet function. Objective To link small RNAs to platelet reactivity. Methods and Results Next-generation sequencing of small RNAs in plasma revealed two peaks at 22-23 and 32-33 nucleotides corresponding to miRNAs and YRNAs, respectively. Among YRNAs, predominantly fragments of RNY4 and RNY5 were detected. Plasma miRNAs and YRNAs were measured in 125 patients with a history of ACS who had undergone detailed assessment of platelet function 30 days after the acute event. Using quantitative real-time polymerase chain reactions, 92 miRNAs were assessed in ACS patients on different anti-platelet therapies. Key platelet-related miRNAs and YRNAs were correlated with platelet function tests. MiR-223 (rp=0.28, n=121, P=0.002), miR-126 (rp=0.22, n=121, P=0.016), other abundant platelet miRNAs and YRNAs showed significant positive correlations with the vasodilator-stimulated phosphoprotein phosphorylation assay. YRNAs, miR-126 and miR-223 were also among the small RNAs showing the greatest dependency on platelets, and strongly correlated with plasma levels of P-selectin, platelet factor 4 and platelet basic protein in the population-based Bruneck study (n=669). A single nucleotide polymorphism that facilitates processing of pri-miR-126 to mature miR-126 accounted for a rise in circulating platelet activation markers. Inhibition of miR-126 in mice reduced platelet aggregation. MiR-126 directly and indirectly affects ADAM9 and P2Y12 receptor expression. Conclusions Levels of platelet-related plasma miRNAs and YRNAs correlate with platelet function tests in ACS patients and platelet activation markers in the general population. Alterations in miR-126 affect platelet reactivity. PMID:26646931

  13. Molecular techniques in ecohealth research toolkit: facilitating estimation of aggregate gastroenteritis burden in an irrigated periurban landscape.

    PubMed

    Tserendorj, Ariuntuya; Anceno, Alfredo J; Houpt, Eric R; Icenhour, Crystal R; Sethabutr, Orntipa; Mason, Carl S; Shipin, Oleg V

    2011-09-01

    Assessment of microbial hazards associated with certain environmental matrices, livelihood strategies, and food handling practices are constrained by time-consuming conventional microbiological techniques that lead to health risk assessments of narrow geographic or time scope, often targeting very few pathogens. Health risk assessment based on one or few indicator organisms underestimates true disease burden due a number of coexisting causative pathogens. Here, we employed molecular techniques in a survey of Cryptosporidium parvum, Giardia lamblia, Campylobacter jejuni, Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Shigella spp., Vibrio cholera, and Rotavirus A densities in canal water with respect to seasonality and spatial distribution of point-nonpoint pollution sources. Three irrigational canals stretching across nearly a 150-km(2) periurban landscape, traditionally used for agricultural irrigation but function as vital part of municipal wastewater stabilization in recent years, were investigated. Compiled stochastic data (pathogen concentration, susceptible populations) and literature-obtained deterministic data (pathogen dose-response model parameter values) were used in estimating waterborne gastroenteritis burden. Exposure scenarios include swimming or fishing, consuming canal water-irrigated vegetables, and ingesting or inhaling water aerosols while working in canal water-irrigated fields. Estimated annual gastroenteritis burden due individual pathogens among the sampling points was -10.6log(10) to -2.2log(10) DALYs. Aggregated annual gastroenteritis burden due all the target pathogens per sampling point was -3.1log(10) to -1.9log(10) DALYs, far exceeding WHO acceptable limit of -6.0log(10) DALYs. The present approach will facilitate the comprehensive collection of surface water microbiological baseline data and setting of benchmarks for interventions aimed at reducing microbial hazards in similar landscapes worldwide.

  14. 21 CFR 864.6675 - Platelet aggregometer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... shape and platelet aggregation following the addition of an aggregating reagent to a platelet rich... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Platelet aggregometer. 864.6675 Section 864.6675...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6675...

  15. 21 CFR 864.6675 - Platelet aggregometer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... shape and platelet aggregation following the addition of an aggregating reagent to a platelet rich... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Platelet aggregometer. 864.6675 Section 864.6675...) MEDICAL DEVICES HEMATOLOGY AND PATHOLOGY DEVICES Manual Hematology Devices § 864.6675...

  16. 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.

  17. Local shear conditions and platelet aggregates regulate the incorporation and activity of circulating tissue factor in ex-vivo thrombi.

    PubMed

    Balasubramanian, Viji; Vele, Oana; Nemerson, Yale

    2002-11-01

    The presence of thrombogenic blood-borne or circulating tissue factor (cTF) has recently been demonstrated. These observations have implicated cTF to be a key determinant of thrombus propagation by depositing on platelets in nascent thrombi. Previously, we detected cTF by detergent solubilization and addition of phospholipids. We now report the direct demonstration of TF activity in ex-vivo thrombi. Collagen-coated substrates were exposed to native blood at shear rates of 0, 650, and 2,000 s(-1) for 10 min in a modified rotating Teflon cone and plate viscometer. Substrates were then gently rinsed to remove 'loose' (unadherent) components of blood. cTF activity was measured by adding a solution containing 10 nM FVIIa, 100 nM FX, and 5 mM CaCl(2) to the substrates exposed to blood. Samples of this mixture were obtained at intervals for 30 min and the amount of Xa generated was quantified by adding a chromogenic substrate, Spectrozyme Xa, and measuring the increase in OD at 405 nm. Our studies show that a minimal amount of generated Xa (approximately 1nM) can be measured from ex-vivo thrombi. Static and shear samples generated the same amount of Xa, with the exception of blood subjected to 650 s(-1) shear. At 650 s(-1) shear rate, the amount of Xa generated reached a maximum of 4 nM at 5 min and then decreased to approximately 1 nM. Immunohistological stains and fluorescent images demonstrate the presence of cTF antigen at 650 s(-1) wall shear rate.

  18. Supplementation of a Standardized Extract from Phyllanthus emblica Improves Cardiovascular Risk Factors and Platelet Aggregation in Overweight/Class-1 Obese Adults

    PubMed Central

    Khanna, Savita; Das, Amitava; Spieldenner, James; Rink, Cameron

    2015-01-01

    Abstract The objective of this study (clinicaltrials.gov NCT01858376) was to determine the effect of oral supplementation of a standardized extract of Phyllanthus emblica (CAPROS®) on cardiovascular disease (CVD) risk factors in overweight adult human subjects from the US population. Overweight/Class-1 obese (body–mass index: 25–35) adult subjects received 500 mg of CAPROS supplement b.i.d for 12 weeks. The study design included two baseline visits followed by 12 weeks of supplementation and then 2 weeks of washout. At all visits, peripheral venous blood was collected in sodium citrate tubes. Lipid profile measurements demonstrated a significant decrease in calculated low-density lipoprotein cholesterol and total cholesterol/high-density lipoprotein following 12 weeks of CAPROS supplementation when compared to averaged baseline visits. Circulatory high-sensitivity C reactive protein (hs-CRP) levels were significantly decreased after 12 weeks of supplementation. In addition, both ADP- and collagen-induced platelet aggregation was significantly downregulated following 12 weeks of supplementation. Overall, the study suggests that oral CAPROS supplementation may provide beneficial effects in overweight/Class-1 obese adults by lowering multiple global CVD risk factors. PMID:25756303

  19. Effect of Sclerovit on endothelial dysfunction, hemorheological parameters, platelet aggregation, plasma concentration of homocysteine and progression of atherosclerosis in patients with vascular diseases.

    PubMed

    Horvath, Beata; Szapary, Laszlo; Debreceni, Laszlo; Feher, Gergely; Kenyeres, Peter; Fulop, Adrienn; Battyani, Istvan; Toth, Kalman

    2009-01-01

    In our prospective study the effect of Sclerovit (0.8 mg folic acid, 20 mug vitamin B12,5 mg vitamin B6,100 mg vitamin E) on inflammatory markers, hemorheological parameters, platelet aggregation, von Willebrand factor activity as a marker of endothelium dysfunction, plasma lipids, plasma levels of folic acid, vitamin B12 and homocysteine (hcy), flow mediated vasodilatation (FMD) and thickness of carotis intima-media after 1 and 6 months of treatment in patients with vascular diseases (10 patients took 1 capsule, 10 patients 2 capsules of Sclerovit and 10 patients placebo) was determined.Plasma level of vitamin B12, folic acid and elongation index of red blood cells (RBC) increased significantly (p<0.05-0.001), hcy and triglyceride concentrations decreased significantly (p<0.05-0.001) in patients taking Sclerovit. HDL-cholesterol, RBC count, hematocrit, plasma and whole blood viscosity increased significantly (p<0.05-0.001) both in patients taking placebo or vitamins. Fibrinogen and CRP showed a significant (p<0.05-0.01) increase in patients on placebo, but did not change in patients on Sclerovit therapy. FMD showed a significant (p<0.05) amelioration in patients on 1 capsule of Sclerovit.Beside the favorable effects of Sclerovit on some of the measured parameters, the observed deterioration in hemorheological parameters can correlate with the contradictory results of large prospective studies with vitamins.

  20. Crystallization and preliminary X-ray diffraction studies of BmooPLA2-I, a platelet-aggregation inhibitor and hypotensive phospholipase A2 from Bothrops moojeni venom

    PubMed Central

    Salvador, Guilherme H. M.; Marchi-Salvador, Daniela P.; Silveira, Lucas B.; Soares, Andreimar M.; Fontes, Marcos R. M.

    2011-01-01

    Phospholipases A2 (PLA2s) are enzymes that cause the liberation of fatty acids and lysophospholipids by the hydrolysis of membrane phospholipids. In addition to their catalytic action, a wide variety of pharmacological activities have been described for snake-venom PLA2s. BmooPLA2-I is an acidic, nontoxic and catalytic PLA2 isolated from Bothrops moojeni snake venom which exhibits an inhibitory effect on platelet aggregation, an immediate decrease in blood pressure, inducing oedema at a low concentration, and an effective bactericidal effect. BmooPLA2-I has been crystallized and X-ray diffraction data have been collected to 1.6 Å resolution using a synchrotron-radiation source. The crystals belonged to space group C2221, with unit-cell parameters a = 39.7, b = 53.2, c = 89.2 Å. The molecular-replacement solution of BmooPLA2-I indicated a monomeric conformation, which is in agreement with nondenaturing electrophoresis and dynamic light-scattering experiments. A comparative study of this enzyme with the acidic PLA2 from B. jararacussu (BthA-I) and other toxic and nontoxic PLA2s may provide important insights into the functional aspects of this class of proteins. PMID:21821890

  1. Supplementation of a standardized extract from Phyllanthus emblica improves cardiovascular risk factors and platelet aggregation in overweight/class-1 obese adults.

    PubMed

    Khanna, Savita; Das, Amitava; Spieldenner, James; Rink, Cameron; Roy, Sashwati

    2015-04-01

    The objective of this study (clinicaltrials.gov NCT01858376) was to determine the effect of oral supplementation of a standardized extract of Phyllanthus emblica (CAPROS(®)) on cardiovascular disease (CVD) risk factors in overweight adult human subjects from the US population. Overweight/Class-1 obese (body-mass index: 25-35) adult subjects received 500 mg of CAPROS supplement b.i.d for 12 weeks. The study design included two baseline visits followed by 12 weeks of supplementation and then 2 weeks of washout. At all visits, peripheral venous blood was collected in sodium citrate tubes. Lipid profile measurements demonstrated a significant decrease in calculated low-density lipoprotein cholesterol and total cholesterol/high-density lipoprotein following 12 weeks of CAPROS supplementation when compared to averaged baseline visits. Circulatory high-sensitivity C reactive protein (hs-CRP) levels were significantly decreased after 12 weeks of supplementation. In addition, both ADP- and collagen-induced platelet aggregation was significantly downregulated following 12 weeks of supplementation. Overall, the study suggests that oral CAPROS supplementation may provide beneficial effects in overweight/Class-1 obese adults by lowering multiple global CVD risk factors.

  2. 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

  3. Methodology and outcomes of platelet aggregation testing in Australia, New Zealand and the Asia-Pacific region: results of a survey from the Royal College of Pathologists of Australasia Haematology Quality Assurance Program.

    PubMed

    Duncan, E M; Bonar, R; Rodgers, S E; Favaloro, E J; Marsden, K

    2009-08-01

    Platelet aggregometry is widely used to investigate platelet function but its performance is poorly standardized between laboratories. The aim of this work was to document the platelet aggregation methods used in specialist laboratories enrolled in the Haematology Quality Assurance Program of the Royal College of Pathologists of Australasia. A questionnaire requesting many details of methodology was distributed and from the responses, we determined a consensus view. Consensus was defined here as >70% agreement among respondents in answer to a question and this was seen for a number of aspects of the preanalytical, analytical and interpretive phases. However, for many questions there was a wide variation in responses. Sixteen laboratories provided a breakdown of the types of abnormal results typically seen in a 12-month period. In these laboratories a total of 1400 patients were tested and 390 (27%) had abnormal platelet function. Although it was common to diagnose the cause as aspirin or an aspirin-like defect or a release/storage pool disorder, the range of experience was wide and other rare defects were reported. We conclude that whilst there are a number of points of agreement between laboratories in platelet function testing, standardization could be improved.

  4. 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.

  5. 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.

  6. Comparative evaluation of platelet-rich fibrin, mineral trioxide aggregate, and calcium hydroxide as pulpotomy agents in permanent molars with irreversible pulpitis: A randomized controlled trial

    PubMed Central

    Kumar, Varun; Juneja, Ruchi; Duhan, Jigyasa; Sangwan, Pankaj; Tewari, Sanjay

    2016-01-01

    Background: Pulpotomy has been proposed as an alternative for the management of irreversible pulpitis in permanent molars with closed apices. Aim: To compare the performances of calcium hydroxide (CH), mineral trioxide aggregate (MTA), and platelet-rich fibrin (PRF) as pulpotomy agents in mature permanent molars with irreversible pulpitis. Materials and Methods: Fifty-four permanent mandibular molars with carious exposure and symptoms of irreversible pulpitis were randomly allocated to three groups, and full pulpotomy was performed using CH, MTA, or PRF as pulpotomy agents. Pain intensity was recorded using numeric rating scale score at baseline, 24 h, 7 days, 6 months, and 1 year. Clinical and radiographic assessments were done at 6 months and 1 year. Statistical Analysis: Kruskal–Wallis test and Friedman test were used for intergroup and intragroup comparison of pain scores, respectively. The radiographic outcomes between the three study arms were compared using Chi-square test. Results: Clinical success rate was 94.4% at 7 days, which dropped to 85.4% at 12 months. All three agents were equally effective in providing pain relief at all the intervals tested, with no significant difference between them (P > 0.05 at all intervals). However, at 6 months and 12 months, 26.2% and 52.4% teeth depicted slight widening of periodontal ligament space. No significant difference was observed between the radiographic success rates observed with the three groups (P = 0.135 at 6 months, 0.717 at 12 months). Conclusion: Pulpotomy exhibited a high clinical success rate in mature molars with irreversible pulpitis and selection of biomaterial did not affect its outcome. PMID:27994420

  7. 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.

  8. Immunohistochemical Evaluation of Fibronectin and Tenascin Following Direct Pulp Capping with Mineral Trioxide Aggregate, Platelet-Rich Plasma and Propolis in Dogs’ Teeth

    PubMed Central

    Moradi, Saeed; Saghravanian, Nasrollah; Moushekhian, Siavash; Fatemi, Samar; Forghani, Maryam

    2015-01-01

    Introduction: The aim of the present study was to evaluate the expression of fibronectin (FN) and tenascin (TN) after direct pulp capping (DPC) in dogs’ teeth with either mineral trioxide aggregate (MTA), Propolis or Platelet-rich plasma (PRP), by means of immunohistochemistry. Methods and Materials: A total of 48 sound molars and premolars with mature apices from four dogs, were included. The teeth were randomly divided into 4 groups according to the material used for DPC: PRP, Propolis, MTA, and glass-ionomer (as the negative control group). Each group was divided into two 7-day and 30-day subgroups. The teeth were restored at the same session. The animals were sacrificed at the mentioned time intervals and the expression of FN and TN in each test group and between each time intervals was assessed with Wilcoxon and Mann-Whitney U tests, respectively. The Kruskal-Wallis test was used to compare FN and TN staining among the test groups. The significance level was set at 0.05. Results: The amount of FN in the MTA group in the 30-day interval was significantly higher than the 7-day interval; however, there were no significant differences among the other groups. The amount of TN in the MTA and Propolis groups in the 30-day interval was significantly higher than that in the 7-day interval; no recognizable difference was observed in the other groups. Moreover, the difference in expression of FN and TN in the 7-day interval was not significant in the experimental groups. Nevertheless, the difference was significant in the 30-day interval, with the highest and lowest expressions belonging to the MTA and glass-ionomer groups, respectively. Conclusion: Based on the results of the present animal study, MTA is still a better choice for direct pulp capping PMID:26213542

  9. Detection of platelet alloimmunity with a platelet-associated IgG assay

    SciTech Connect

    Myers, T.J.; Kim, B.K.; Steiner, M.; Bishop, J.; Baldini, M.G.

    1981-06-01

    A quantitative immunofluorescence PA-IgG assay was used to detect alloimmunity to platelets. The assay identified serum alloantibodies in 10 out of 14 multitransfused patients and for two of three infants with neonatal thrombocytopenia. The correct separation of all multitransfused patients into alloimmune and nonalloimmune groups by the PA-IgG assay was substantiated with chromium-51-labeled platelet survival studies. The allogeneic nature of the serum antibodies was demonstrated by progressive absorption of the antibody with increasing numbers of allogeneic platelets but not with autologous platelets. The sensitivity of the PA-IgG assay for detection of serum alloantibodies was superior to that of platelet aggregation, platelet serotonin release, and lymphocytotoxicity testing. In dilution experiments with alloimmune serum, elevated levels of serum PA-IgG could still be detected on donor platelets when platelet aggregation and serotonin release tests became negative. Platelet survival studies with selected platelets performed in the 10 alloimmunized, multitransfused patients confirmed the results of the PA-IgG assays, predicting alloimmunity to the donor platelets. In contrast, platelet aggregation, platelet serotonin release, and lymphocytotoxicity testing indicated alloimmunity for 50% or less of the patients. Reduced platelet survival times were also seen with HLA A- and HLA B-matched donor platelets when donor-recipient incompatibility was demonstrated by the PA-IgG assay. Thus the PA-IgG assay provides a sensitive method to detect serum platelet alloantibodies and may offer a technique in platelet crossmatching.

  10. The effects of two synthetic glycoprotein IIb/IIIa antagonists, Ro 43-8857 and L-700,462, on platelet aggregation and bleeding in guinea-pigs and dogs: evidence that Ro 43-8857 is orally active.

    PubMed

    Cook, N S; Bruttger, O; Pally, C; Hagenbach, A

    1993-11-15

    In vitro platelet aggregation studies in whole blood were used to define the species-specificity profile of two synthetic GP-IIb/IIIa antagonists, Ro 43-8857 and L-700,462. Aggregation of rhesus monkey platelets was inhibited with a similar potency to human platelets, whereas both compounds were poor antagonists in mini-pig, rabbit or hamster blood. Compared to human platelets, Ro 43-8857 was 2-3-fold less active as an inhibitor of dog and guinea-pig platelet aggregation, whereas L-700,462 was, respectively, 4- and 14-fold less active in these species. In vivo investigations with these two compounds were performed in anesthetized guinea-pigs and conscious dogs, with bleeding times measured on small mesenteric arteries or on the inner jowl respectively. Ex vivo ADP-induced whole blood platelet aggregation was completely inhibited in guinea-pigs by Ro 43-8857 following intravenous administration of 0.1 mg/kg and intraduodenal administration of 3 mg/kg, with a duration of action exceeding 5 hours. Mesenteric bleeding times were prolonged by Ro 43-8857 only at doses causing supra-maximal inhibition of aggregation, suggesting these two effects could be partially dissociated. L-700,462 (3 mg/kg i.v.) was shorter acting than Ro 43-8857 in guinea-pigs (duration approximately 1 hour) and the anti-aggregatory effect was accompanied by mesenteric bleeding time prolongations. In conscious dogs, ex vivo aggregation was inhibited to approximately 80% by Ro 43-8857 (0.3 mg/kg i.v. or 10 mg/kg p.o.) and L-700,462 (1 mg/kg i.v.). However, bleeding time prolongations accompanied these anti-aggregatory effects with both compounds. In conclusion, we have shown clear differences between two synthetic GP-IIb/IIIa antagonists, both in terms of their species-specificity in vitro and in terms of their in vivo profile, and in particular the propensity to promote bleeding from mesenteric arteries in guinea-pigs. However, the ability of Ro 43-8857 to discriminate between anti-aggregatory and

  11. 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.

  12. The fibril core of transforming growth factor beta-induced protein (TGFBIp) facilitates aggregation of corneal TGFBIp

    PubMed Central

    Sørensen, Charlotte S.; Runager, Kasper; Scavenius, Carsten; Jensen, Morten M.; Nielsen, Nadia S.; Christiansen, Gunna; Petersen, Steen V.; Karring, Henrik; Sanggaard, Kristian W.; Enghild, Jan J.

    2016-01-01

    Mutations in the transforming growth factor beta-induced (TGFBI) gene result in a group of hereditary diseases of the cornea that are collectively known as TGFBI corneal dystrophies. These mutations translate into amino acid substitutions mainly within the fourth fasciclin 1 domain (FAS1-4) of the transforming growth factor beta-induced protein (TGFBIp) and cause either amyloid or non-amyloid protein aggregates in the anterior and central parts of the cornea, depending on the mutation. The A546T substitution in TGFBIp causes lattice corneal dystrophy (LCD), which manifests as amyloid-type aggregates in the corneal stroma. We previously showed that the A546T substitution renders TGFBIp and the FAS1-4 domain thermodynamically less stable compared with the wild-type (WT) protein, and the mutant FAS1-4 is prone to amyloid formation in vitro. In the present study, we identified the core of A546T FAS1-4 amyloid fibrils. Significantly, we identified the Y571-R588 region of TGFBIp, which we previously found to be enriched in amyloid deposits in LCD patients. We further found that the Y571-R588 peptide seeded fibrillation of A546T FAS1-4 and, more importantly, we demonstrated that native TGFBIp aggregates in the presence of fibrils formed by the core peptide. Collectively, these data suggest an involvement of the Y571-R588 peptide in LCD pathophysiology. PMID:25910219

  13. A Computer-Assisted 3D Model for Analyzing the Aggregation of Tumorigenic Cells Reveals Specialized Behaviors and Unique Cell Types that Facilitate Aggregate Coalescence

    PubMed Central

    Scherer, Amanda; Kuhl, Spencer; Wessels, Deborah; Lusche, Daniel F.; Hanson, Brett; Ambrose, Joseph; Voss, Edward; Fletcher, Emily; Goldman, Charles; Soll, David R.

    2015-01-01

    We have developed a 4D computer-assisted reconstruction and motion analysis system, J3D-DIAS 4.1, and applied it to the reconstruction and motion analysis of tumorigenic cells in a 3D matrix. The system is unique in that it is fast, high-resolution, acquires optical sections using DIC microscopy (hence there is no associated photoxicity), and is capable of long-term 4D reconstruction. Specifically, a z-series at 5 μm increments can be acquired in less than a minute on tissue samples embedded in a 1.5 mm thick 3D Matrigel matrix. Reconstruction can be repeated at intervals as short as every minute and continued for 30 days or longer. Images are converted to mathematical representations from which quantitative parameters can be derived. Application of this system to cancer cells from established lines and fresh tumor tissue has revealed unique behaviors and cell types not present in non-tumorigenic lines. We report here that cells from tumorigenic lines and tumors undergo rapid coalescence in 3D, mediated by specific cell types that we have named “facilitators” and “probes.” A third cell type, the “dervish”, is capable of rapid movement through the gel and does not adhere to it. These cell types have never before been described. Our data suggest that tumorigenesis in vitro is a developmental process involving coalescence facilitated by specialized cells that culminates in large hollow spheres with complex architecture. The unique effects of select monoclonal antibodies on these processes demonstrate the usefulness of the model for analyzing the mechanisms of anti-cancer drugs. PMID:25790299

  14. A novel family of RGD-containing disintegrin (Tablysin-15) from the salivary gland of the horsefly Tabanus yao targets integrins αIIbβ3 and αVβ3 and inhibits platelet aggregation and angiogenesis

    PubMed Central

    Ma, Dongying; Xu, Xueqing; An, Su; Liu, Huan; Yang, Xuening; Andersen, John F.; Wang, Yipeng; Tokumasu, Fuyuki; Ribeiro, José M. C.; Francischetti, Ivo M. B.; Lai, Ren

    2012-01-01

    A novel family of RGD-containing molecule (Tablysin-15) has been molecularly characterized from the salivary gland of the hematophagous horsefly Tabanus yao. Tablysin-15 does not share primary sequence homology to any disintegrin discovered so far, and displays an RGD motif in the N-terminus of the molecule. It is also distinct from disintegrins from Viperidae since its mature form is not released from a metalloproteinase precursor. Tablysin-15 exhibits high affinity for platelet αIIbβ3 and endothelial cell αvβ3 integrins, but not for α5β1 or α2β1. Accordingly, it blocks endothelial cell adhesion to vitronectin (IC50 ~ 1 nM) and marginally to fibronectin (IC50 ~ 1 µM), but not to collagen. It also inhibits FGF-induced endothelial cell proliferation, and attenuates tube formation in vitro. In platelets, Tablysin-15 inhibits aggregation induced by collagen, ADP and convulxin, and prevents static platelet adhesion to immobilized fibrinogen. In addition, solid-phase assays and flow cytometry demonstrates that αIIbβ3 binds to Tablysin-15. Moreover, immobilized Tablysin-15 supports platelet adhesion by a mechanism which was blocked by anti-integrin αIIbβ3 monoclonal antibody (e.g. abciximab) or by EDTA. Furthermore, Tablysin-15 dose-dependently attenuates thrombus formation to collagen under flow, without affecting platelet adhesion to collagen fibrils. Consistent with these findings, Tablysin-15 displays antithrombotic properties in vivo suggesting that it is a useful tool to block αIIbβ3, or as a prototype to develop antithrombotics. The RGD motif in the unique sequence of Tablysin-15 represents a novel template for studying the structure-function relationship of the disintegrin family of inhibitors. PMID:21475772

  15. The Kinetics of Circulating Monocyte Subsets and Monocyte-Platelet Aggregates in the Acute Phase of ST-Elevation Myocardial Infarction

    PubMed Central

    Zhou, Xin; Liu, Xin-Lin; Ji, Wen-Jie; Liu, Jun-Xiang; Guo, Zhao-Zeng; Ren, Dong; Ma, Yong-Qiang; Zeng, Shan; Xu, Zhong-Wei; Li, Hong-Xia; Wang, Peizhong Peter; Zhang, Zhuoli; Li, Yu-Ming; Benefield, Brandon C.; Zawada, Adam M.; Thorp, Edward B.; Lee, Daniel C.; Heine, Gunnar H.

    2016-01-01

    Abstract In experimental myocardial infarction (MI), a rise in cell counts of circulating monocyte subsets contributes to impaired myocardial healing and to atherosclerotic plaque destabilization. In humans, the prognostic role of monocyte subsets in patients suffering ST-elevation MI (STEMI) is still unclear. In the present study, we aimed to determine the kinetics of the 3 monocyte subsets (classical CD14++CD16–, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes), as well as the subset-specific monocyte–platelet aggregates (MPA), in acute STEMI followed by primary percutaneous coronary intervention (PCI), and their relationships with cardiovascular outcomes during a 2-year follow-up. Monocyte subsets and MPA were measured in 100 STEMI patients receiving primary PCI on days 1, 2, 3, 5, and 7 of symptom onset, which were compared with 60 stable coronary heart disease patients and 35 healthy volunteers. From day 1 to day 7, significant increases in the counts of CD14++CD16+ monocytes and CD14++CD16+ MPA were observed, with peak levels on day 2. During a median follow-up of 2.0 years, 28 first cardiovascular events (defined as cardiovascular death, nonfatal ischemic stroke, recurrent MI, need for emergency or repeat revascularization, and rehospitalization for heart failure) were recorded. After adjustment for confounders, CD14++CD16+ monocytosis (day 1 [HR: 3.428; 95% CI: 1.597–7.358; P = 0.002], day 2 [HR: 4.835; 95% CI: 1.106–21.13; P = 0.04], day 3 [HR: 2.734; 95% CI: 1.138–6.564; P = 0.02], and day 7 [HR: 2.647; 95% CI: 1.196–5.861; P = 0.02]), as well as increased levels of CD14++CD16+ MPA measured on all time points (days 1, 2, 3, 5, and 7), had predictive values for adverse cardiovascular events. In conclusion, our data show the expansion of the CD14++CD16+ monocyte subset during acute phase of STEMI has predictive values for 2-year adverse cardiovascular outcomes in patients treated with primary PCI. Future studies

  16. The Kinetics of Circulating Monocyte Subsets and Monocyte-Platelet Aggregates in the Acute Phase of ST-Elevation Myocardial Infarction: Associations with 2-Year Cardiovascular Events.

    PubMed

    Zhou, Xin; Liu, Xin-Lin; Ji, Wen-Jie; Liu, Jun-Xiang; Guo, Zhao-Zeng; Ren, Dong; Ma, Yong-Qiang; Zeng, Shan; Xu, Zhong-Wei; Li, Hong-Xia; Wang, Peizhong Peter; Zhang, Zhuoli; Li, Yu-Ming; Benefield, Brandon C; Zawada, Adam M; Thorp, Edward B; Lee, Daniel C; Heine, Gunnar H

    2016-05-01

    In experimental myocardial infarction (MI), a rise in cell counts of circulating monocyte subsets contributes to impaired myocardial healing and to atherosclerotic plaque destabilization. In humans, the prognostic role of monocyte subsets in patients suffering ST-elevation MI (STEMI) is still unclear. In the present study, we aimed to determine the kinetics of the 3 monocyte subsets (classical CD14++CD16-, intermediate CD14++CD16+, and nonclassical CD14+CD16++ monocytes), as well as the subset-specific monocyte-platelet aggregates (MPA), in acute STEMI followed by primary percutaneous coronary intervention (PCI), and their relationships with cardiovascular outcomes during a 2-year follow-up.Monocyte subsets and MPA were measured in 100 STEMI patients receiving primary PCI on days 1, 2, 3, 5, and 7 of symptom onset, which were compared with 60 stable coronary heart disease patients and 35 healthy volunteers. From day 1 to day 7, significant increases in the counts of CD14++CD16+ monocytes and CD14++CD16+ MPA were observed, with peak levels on day 2. During a median follow-up of 2.0 years, 28 first cardiovascular events (defined as cardiovascular death, nonfatal ischemic stroke, recurrent MI, need for emergency or repeat revascularization, and rehospitalization for heart failure) were recorded. After adjustment for confounders, CD14++CD16+ monocytosis (day 1 [HR: 3.428; 95% CI: 1.597-7.358; P = 0.002], day 2 [HR: 4.835; 95% CI: 1.106-21.13; P = 0.04], day 3 [HR: 2.734; 95% CI: 1.138-6.564; P = 0.02], and day 7 [HR: 2.647; 95% CI: 1.196-5.861; P = 0.02]), as well as increased levels of CD14++CD16+ MPA measured on all time points (days 1, 2, 3, 5, and 7), had predictive values for adverse cardiovascular events.In conclusion, our data show the expansion of the CD14++CD16+ monocyte subset during acute phase of STEMI has predictive values for 2-year adverse cardiovascular outcomes in patients treated with primary PCI. Future studies will be warranted to

  17. 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

  18. Drosophila UNC-45 prevents heat-induced aggregation of skeletal muscle myosin and facilitates refolding of citrate synthase

    SciTech Connect

    Melkani, Girish C.; Lee, Chi F.; Cammarato, Anthony; Bernstein, Sanford I.

    2010-05-28

    UNC-45 belongs to the UCS (UNC-45, CRO1, She4p) domain protein family, whose members interact with various classes of myosin. Here we provide structural and biochemical evidence that Escherichia coli-expressed Drosophila UNC-45 (DUNC-45) maintains the integrity of several substrates during heat-induced stress in vitro. DUNC-45 displays chaperone function in suppressing aggregation of the muscle myosin heavy meromyosin fragment, the myosin S-1 motor domain, {alpha}-lactalbumin and citrate synthase. Biochemical evidence is supported by electron microscopy, which reveals the first structural evidence that DUNC-45 prevents inter- or intra-molecular aggregates of skeletal muscle heavy meromyosin caused by elevated temperatures. We also demonstrate for the first time that UNC-45 is able to refold a denatured substrate, urea-unfolded citrate synthase. Overall, this in vitro study provides insight into the fate of muscle myosin under stress conditions and suggests that UNC-45 protects and maintains the contractile machinery during in vivo stress.

  19. How do the full-generation poly(amido)amine (PAMAM) dendrimers activate blood platelets? Activation of circulating platelets and formation of "fibrinogen aggregates" in the presence of polycations.

    PubMed

    Watala, Cezary; Karolczak, Kamil; Kassassir, Hassan; Talar, Marcin; Przygodzki, Tomasz; Maczynska, Katarzyna; Labieniec-Watala, Magdalena

    2016-04-30

    Direct use of poly(amido)amine (PAMAM) dendrimers as drugs may be limited, due to uncertain (cyto)toxicity. Peripheral blood components, which constitute the first line of a contact with administered pharmaceuticals, may become vastly affected by PAMAM dendrimers. The aim of this study was to explore how PAMAMs' polycationicity might affect blood platelet activation and reactivity, and thus trigger various haemostatic events. We monitored blood platelet reactivity in rats with experimental diabetes upon a long-term administration of the unmodified PAMAM dendrimers. In parallel, the effects on blood flow in a systemic circulation was recorded intravitally in mice administered with PAMAM G2, G3 or G4. Compounding was the in vitro approach to monitor the impact of PAMAM dendrimers on blood platelet activation and reactivity and on selected haemostatic and protein conformation parameters. We demonstrated the activating effects of polycations on blood platelets. Some diversity of the revealed outcomes considerably depended on the used approach and the particular technique employed to monitor blood platelet function. We discovered undesirable impact of plain PAMAM dendrimers on primary haemostasis and their prothrombotic influence. We emphasize the need of a more profound verifying of all the promising findings collected for PAMAMs with the use of well-designed in vivo preclinical studies.

  20. 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.

  1. Effects of LY117018 and the estrogen analogue, 17alpha-ethinylestradiol, on vascular reactivity, platelet aggregation, and lipid metabolism in the insulin-resistant JCR:LA-cp male rat: role of nitric oxide.

    PubMed

    Russell, J C; McKendrick, J D; Dubé, P J; Dolphin, P J; Radomski, M W

    2001-01-01

    The JCR:LA-cp rat is obese and insulin resistant and develops a major vasculopathy, with associated ischemic damage to the heart. Male rats were treated with 17alpha-ethinylestradiol (EE), LY117018, and/or the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME). LY117018 decreased plasma cholesterol esters, with a 40% reduction in total cholesterol. EE increased triglyceride levels and modestly decreased cholesterol esters. L-NAME increased blood pressure and aortic contractile sensitivity to phenylephrine and inhibited acetylcholine-induced relaxation. LY117018 decreased the force of contraction. The L-NAME-mediated increase in force of contraction and decrease in response to acetylcholine was inhibited by LY117018. L-NAME-induced hypertension was prevented by LY117018. Platelet aggregation was not different between obese and lean rats and was unaffected by L-NAME. LY117018, both in the absence and presence of L-NAME, inhibited platelet aggregation. The effects of LY117018 are apparently mediated through both NO-dependent and -independent mechanisms. The changes induced by EE and LY117018 may reflect the activation of multiple mechanisms, both estrogen receptor-dependent and -independent. The changes induced by LY117018 are significant and may prove to be cardioprotective in the presence of the insulin resistance syndrome.

  2. Expression, purification, and analysis of three recombinant ECD disintegrins (r-colombistatins) from P-III class snake venom metalloproteinases affecting platelet aggregation and SK-MEL-28 cell adhesion

    PubMed Central

    Suntravat, Montamas; Helmke, Thomas J.; Atphaisit, Chairat; Cuevas, Esteban; Lucena, Sara E.; Uzcátegui, Nestor L.; Sánchez, Elda E.; Rodriguez-Acosta, Alexis

    2016-01-01

    Crotalid venoms are rich sources of components that affect the hemostatic system. Snake venom metalloproteinases are zinc-dependent enzymes responsible for hemorrhage that also interfere with hemostasis. The disintegrin domain is a part of snake venom metalloproteinases, which involves the binding of integrin receptors. Integrins play an essential role in cancer survival and invasion, and they have been major targets for drug development and design. Both native and recombinant disintegrins have been widely investigated for their anti-cancer activities in biological systems as well as in vitro and in vivo systems. Here, three new cDNAs encoding ECD disintegrin-like domains of metalloproteinase precursor sequences obtained from a Venezuelan mapanare (Bothrops colombiensis) venom gland cDNA library have been cloned. Three different N- and C-terminal truncated ECD disintegrin-like domains of metalloproteinases named colombistatins 2, 3, and 4 were amplified by PCR, cloned into a pGEX-4T-1 vector, expressed in Escherichia coli BL21, and tested for inhibition of platelet aggregation and inhibition of adhesion of human skin melanoma (SK-Mel-28) cancer cell lines on collagen I. Purified recombinant colombistatins 2, 3, and 4 were able to inhibit ristocetin- and collagen-induced platelet aggregation. r-Colombistatins 2 showed the most potent inhibiting SK-Mel-28 cancer cells adhesion to collagen. These results suggest that colombistatins may have utility in the development of therapeutic tools in the treatment of melanoma cancers and also thrombotic diseases. PMID:27641750

  3. Identification of membrane proteins mediating the interaction of human platelets

    PubMed Central

    Phillips, D; Jennings, L; Edwards, H

    1980-01-01

    Membrane glycoproteins that mediate platelet-platelet interactions were investigated by identifying those associated with the cytoskeletal structures from aggregated platelets. The cytoskeletal structures from washed platelets, thrombin-activated platelets (platelets incubated with thrombin in the presence of mM EDTA to prevent aggregation) and thrombin- aggregated platelets (platelets activated in the presence of mM Ca(++) were prepared by first treating platelet suspensions with 1 percent Triton X-100 and 5 mM EGTA and then isolating the insoluble residue by centrifugation. The readily identifiable structures in electron micrographs of the residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue from washed platelets had the shape and dimensions of actin filaments. Analysis of this residue by SDS gel electrophoresis showed that it consisted primarily of three proteins: actin (mol wt = 43,000), myosin (mol wt = 200,000) and a high molecular weight polypeptide (mol wt = 255,000) which had properties indentical to actin-binding protein (filamin). When platelets are activated with thrombin in the presence of EDTA to prevent aggregation, there was a marked increase in the amount of insoluble precipitate in the subsequent Triton extraction. Transmission electron microscopy showed that this residue not only contained the random array of actin filaments as seen above, but also organized structures from individual platelets which appeared as balls of electron-dense filamentous material approximately 1mum in diameter. SDS polyacrylamide gel analysis of the Triton residue of activated platelets showed that this preparation contained more actin, myosin and actin-binding protein than that from washed platelets plus polypeptides with mol wt of 56,000 and 90,000 and other minor polypeptides. Thus, thrombin activation appeared to increase polymerization of actin in association with other cytoskeletal proteins into structures that

  4. Salivary Antigen-5/CAP Family Members Are Cu2+-dependent Antioxidant Enzymes That Scavenge O2⨪ and Inhibit Collagen-induced Platelet Aggregation and Neutrophil Oxidative Burst*

    PubMed Central

    Assumpção, Teresa C. F.; Ma, Dongying; Schwarz, Alexandra; Reiter, Karine; Santana, Jaime M.; Andersen, John F.; Ribeiro, José M. C.; Nardone, Glenn; Yu, Lee L.; Francischetti, Ivo M. B.

    2013-01-01

    The function of the antigen-5/CAP family of proteins found in the salivary gland of bloodsucking animals has remained elusive for decades. Antigen-5 members from the hematophagous insects Dipetalogaster maxima (DMAV) and Triatoma infestans (TIAV) were expressed and discovered to attenuate platelet aggregation, ATP secretion, and thromboxane A2 generation by low doses of collagen (<1 μg/ml) but no other agonists. DMAV did not interact with collagen, glycoprotein VI, or integrin α2β1. This inhibitory profile resembles the effects of antioxidants Cu,Zn-superoxide dismutase (Cu,Zn-SOD) in platelet function. Accordingly, DMAV was found to inhibit cytochrome c reduction by O2⨪ generated by the xanthine/xanthine oxidase, implying that it exhibits antioxidant activity. Moreover, our results demonstrate that DMAV blunts the luminescence signal of O2⨪ generated by phorbol 12-myristate 13-acetate-stimulated neutrophils. Mechanistically, inductively coupled plasma mass spectrometry and fluorescence spectroscopy revealed that DMAV, like Cu,Zn-SOD, interacts with Cu2+, which provides redox potential for catalytic removal of O2⨪. Notably, surface plasmon resonance experiments (BIAcore) determined that DMAV binds sulfated glycosaminoglycans (e.g. heparin, KD ∼100 nmol/liter), as reported for extracellular SOD. Finally, fractions of the salivary gland of D. maxima with native DMAV contain Cu2+ and display metal-dependent antioxidant properties. Antigen-5/CAP emerges as novel family of Cu2+-dependent antioxidant enzymes that inhibit neutrophil oxidative burst and negatively modulate platelet aggregation by a unique salivary mechanism. PMID:23564450

  5. 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

  6. 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.

  7. Platelet function in Takotsubo cardiomyopathy.

    PubMed

    Núñez-Gil, Iván J; Bernardo, Esther; Feltes, Gisela; Escaned, Javier; Mejía-Rentería, Hernán D; De Agustín, José Alberto; Vivas, David; Nombela-Franco, Luis; Jiménez-Quevedo, Pilar; Macaya, Carlos; Fernández-Ortiz, Antonio

    2015-05-01

    Takotsubo cardiomyopathy (TK) includes a transient left ventricular dysfunction without obstructive coronary disease, sometimes after stressful situations with elevated cathecolamines. Since catecholamines activate platelets we aimed to study the platelet influence in a TK setting. We included 32 patients with a TK diagnosis, 13 with an acute coronary syndrome (ACS) and 18 healthy volunteers. Once consent informed was obtained, blood samples were extracted and processed (at admission and after 3 months follow-up). Clinical, ecg, echocardiographic and angiographic features were thoroughly recorded.Previous treatment before admission was similar between groups. No differences were observed in clinical features or any of the acute markers studied regarding platelet reactivity between TK compared to ACS. After follow-up, aggregation levels and platelet reactivity showed differences, mainly due to the antithrombotic therapy prescribed at discharge, but similar to volunteers. Circulating epinephrine during the acute phase was significantly higher in TK (p < 0.001). Patients with higher levels of epinephrine had elevated platelet activation and aggregation after 3 months. No differences were observed in Takotsubo acute platelet aggregation compared to patients with ACS, in spite of higher blood levels of adrenaline. Takotsubo patients had elevated platelet aggregation and activation compared with ACS patients at 3 months follow-up because they were less frequently on chronic clopidogrel and ASA. However, they had similar platelet aggregation and activation levels to healthy volunteers despite treatment with low-dose ASA. Takotsubo patients who had higher levels of adrenaline in the acute phase displayed increased platelet reactivity during follow-up.

  8. Platelet function tests: a comparative review.

    PubMed

    Paniccia, Rita; Priora, Raffaella; Liotta, Agatina Alessandrello; Abbate, Rosanna

    2015-01-01

    In physiological hemostasis a prompt recruitment of platelets on the vessel damage prevents the bleeding by the rapid formation of a platelet plug. Qualitative and/or quantitative platelet defects promote bleeding, whereas the high residual reactivity of platelets in patients on antiplatelet therapies moves forward thromboembolic complications. The biochemical mechanisms of the different phases of platelet activation - adhesion, shape change, release reaction, and aggregation - have been well delineated, whereas their complete translation into laboratory assays has not been so fulfilled. Laboratory tests of platelet function, such as bleeding time, light transmission platelet aggregation, lumiaggregometry, impedance aggregometry on whole blood, and platelet activation investigated by flow cytometry, are traditionally utilized for diagnosing hemostatic disorders and managing patients with platelet and hemostatic defects, but their use is still limited to specialized laboratories. To date, a point-of-care testing (POCT) dedicated to platelet function, using pertinent devices much simpler to use, has now become available (ie, PFA-100, VerifyNow System, Multiplate Electrode Aggregometry [MEA]). POCT includes new methodologies which may be used in critical clinical settings and also in general laboratories because they are rapid and easy to use, employing whole blood without the necessity of sample processing. Actually, these different platelet methodologies for the evaluation of inherited and acquired bleeding disorders and/or for monitoring antiplatelet therapies are spreading and the study of platelet function is strengthening. In this review, well-tried and innovative platelet function tests and their methodological features and clinical applications are considered.

  9. Platelet function tests: a comparative review

    PubMed Central

    Paniccia, Rita; Priora, Raffaella; Alessandrello Liotta, Agatina; Abbate, Rosanna

    2015-01-01

    In physiological hemostasis a prompt recruitment of platelets on the vessel damage prevents the bleeding by the rapid formation of a platelet plug. Qualitative and/or quantitative platelet defects promote bleeding, whereas the high residual reactivity of platelets in patients on antiplatelet therapies moves forward thromboembolic complications. The biochemical mechanisms of the different phases of platelet activation – adhesion, shape change, release reaction, and aggregation – have been well delineated, whereas their complete translation into laboratory assays has not been so fulfilled. Laboratory tests of platelet function, such as bleeding time, light transmission platelet aggregation, lumiaggregometry, impedance aggregometry on whole blood, and platelet activation investigated by flow cytometry, are traditionally utilized for diagnosing hemostatic disorders and managing patients with platelet and hemostatic defects, but their use is still limited to specialized laboratories. To date, a point-of-care testing (POCT) dedicated to platelet function, using pertinent devices much simpler to use, has now become available (ie, PFA-100, VerifyNow System, Multiplate Electrode Aggregometry [MEA]). POCT includes new methodologies which may be used in critical clinical settings and also in general laboratories because they are rapid and easy to use, employing whole blood without the necessity of sample processing. Actually, these different platelet methodologies for the evaluation of inherited and acquired bleeding disorders and/or for monitoring antiplatelet therapies are spreading and the study of platelet function is strengthening. In this review, well-tried and innovative platelet function tests and their methodological features and clinical applications are considered. PMID:25733843

  10. 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.

  11. 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

  12. Overview of platelet physiology and laboratory evaluation of platelet function.

    PubMed

    Rodgers, G M

    1999-06-01

    Appropriate laboratory testing for the platelet-type bleeding disorders hinges on an adequate assessment in the history and physical examination. Patients with histories and screening laboratory results consistent with coagulation disorders (hemophilia, disseminated intravascular coagulation) are not appropriate candidates for platelet function testing. In contrast, patients with a lifelong history of platelet-type bleeding symptoms and perhaps a positive family history of bleeding would be appropriate for testing. Figure 6 depicts one strategy to evaluate these patients. Platelet morphology can easily be evaluated to screen for two uncommon qualitative platelet disorders: Bernard-Soulier syndrome (associated with giant platelets) and gray platelet syndrome, a subtype of storage pool disorder in which platelet granulation is morphologically abnormal by light microscopy. If the bleeding disorder occurred later in life (no bleeding with surgery or trauma early in life), the focus should be on acquired disorders of platelet function. For those patients thought to have an inherited disorder, testing for vWD should be done initially because approximately 1% of the population has vWD. The complete vWD panel (factor VIII coagulant activity, vWf antigen, ristocetin cofactor activity) should be performed because many patients will have abnormalities of only one particular panel component. Patients diagnosed with vWD should be classified using multimeric analysis to identify the type 1 vWD patients likely to respond to DDAVP. If vWD studies are normal, platelet aggregation testing should be performed, ensuring that no antiplatelet medications have been ingested at least 1 week before testing. If platelet aggregation tests are normal and if suspicion for an inherited disorder remains high, vWD testing should be repeated. The evaluation of thrombocytopenia may require bone marrow examination to exclude primary hematologic disorders. If future studies with thrombopoietin assays

  13. Phytohemagglutinin facilitates the aggregation of blastomere pairs from Day 5 donor embryos with Day 4 host embryos for chimeric bovine embryo multiplication.

    PubMed

    Simmet, Kilian; Reichenbach, Myriam; Reichenbach, Horst-Dieter; Wolf, Eckhard

    2015-12-01

    Multiplication of bovine embryos by the production of aggregation chimeras is based on the concept that few blastomeres of a donor embryo form the inner cell mass (ICM) and thus the embryo proper, whereas cells of a host embryo preferentially contribute to the trophectoderm (TE), the progenitor cells of the embryonic part of the placenta. We aggregated two fluorescent blastomeres from enhanced green fluorescent protein (eGFP) transgenic Day 5 morulae with two Day 4 embryos that did not complete their first cleavage until 27 hours after IVF and tested the effect of phytohemagglutinin-L (PHA) on chimeric embryo formation. The resulting blastocysts were characterized by differential staining of cell lineages using the TE-specific factor CDX2 and confocal laser scanning microscopy to facilitate the precise localization of eGFP-positive cells. The proportions of blastocyst development of sandwich aggregates with (n = 99) and without PHA (n = 46) were 85.9% and 54.3% (P < 0.05), respectively. Epifluorescence microscopy showed that the proportion of blastocysts with eGFP-positive cells in the ICM was higher in the PHA group than in the no-PHA group (40% vs. 16%; P < 0.05). Confocal laser scanning microscopy revealed that the total cell numbers of blastocysts from the PHA group of aggregation chimeras (n = 17; 207.8 ± 67.3 [mean ± standard deviation]) were higher (P < 0.05) than those of embryos without ZP and exposed to PHA (n = 30; 159.6 ± 42.2) and of handling control embryos (n = 19; 176.9 ± 53.3). The same was true for ICM cell counts (56.5 ± 22.0 vs. 37.7 ± 14.2 and 38.7 ± 12.4) and TE cell counts (151.2 ± 58.0 vs. 121.9 ± 37.4 and 138.3 ± 53.0), whereas the ICM/total cell number ratio was not different between the groups. Of the 17 chimeric blastocysts analyzed by confocal laser scanning microscopy, nine had eGFP-positive cells (three of them in the ICM, three in the TE, and three in both lineages). When integration in

  14. 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 ...

  15. Endodontic management of nonvital permanent teeth having immature roots with one step apexification, using mineral trioxide aggregate apical plug and autogenous platelet-rich fibrin membrane as an internal matrix: Case series

    PubMed Central

    Sharma, Vivek; Sharma, Sarang; Dudeja, Pooja; Grover, Shibani

    2016-01-01

    A tooth with blunderbuss canal and open apex can be an endodontic challenge because of difficulty in obtaining an apical seal, and existing thin radicular walls which are susceptible to fracture. To overcome the limitations of traditional long-term calcium hydroxide apexification procedures, nonsurgical one step apexification using an array of materials such as mineral trioxide aggregate (MTA) has been suggested. However, adequate compaction of MTA in teeth with wide open apices can be an arduous task, and an internal matrix is required for controlled placement of MTA against which obturating material can be condensed. Platelet-rich fibrin (PRF), a second generation platelet concentrate containing several growth factors that promotes hard and soft-tissue healing, has been used as an internal matrix to create an apical plug of MTA and hence prevent extrusion of filling materials. This case series presents the endodontic management of immature permanent teeth with open apices using internal matrix of autologous PRF membrane and one step apical barrier placement of MTA. PMID:27041904

  16. Ramipril and Losartan Exert a Similar Long-Term Effect upon Markers of Heart Failure, Endogenous Fibrinolysis, and Platelet Aggregation in Survivors of ST-Elevation Myocardial Infarction: A Single Centre Randomized Trial

    PubMed Central

    Marinšek, Martin; Sinkovič, Andreja

    2016-01-01

    Introduction. Blocking the renin-angiotensin-aldosterone system in ST-elevation myocardial infarction (STEMI) patients prevents heart failure and recurrent thrombosis. Our aim was to compare the effects of ramipril and losartan upon the markers of heart failure, endogenous fibrinolysis, and platelet aggregation in STEMI patients over the long term. Methods. After primary percutaneous coronary intervention (PPCI), 28 STEMI patients were randomly assigned ramipril and 27 losartan, receiving therapy for six months with dual antiplatelet therapy (DAPT). We measured N-terminal proBNP (NT-proBNP), ejection fraction (EF), plasminogen-activator-inhibitor type 1 (PAI-1), and platelet aggregation by closure times (CT) at the baseline and after six months. Results. Baseline NT-proBNP ≥ 200 pmol/mL was observed in 48.1% of the patients, EF < 55% in 49.1%, and PAI-1 ≥ 3.5 U/mL in 32.7%. Six-month treatment with ramipril or losartan resulted in a similar effect upon PAI-1, NT-proBNP, EF, and CT levels in survivors of STEMI, but in comparison to control group, receiving DAPT alone, ramipril or losartan treatment with DAPT significantly increased mean CT (226.7 ± 80.3 sec versus 158.1 ± 80.3 sec, p < 0.05). Conclusions. Ramipril and losartan exert a similar effect upon markers of heart failure and endogenous fibrinolysis, and, with DAPT, a more efficient antiplatelet effect in long term than DAPT alone. PMID:27064499

  17. Genetic Polymorphism of CYP2C19 and Inhibitory Effects of Ticagrelor and Clopidogrel Towards Post-Percutaneous Coronary Intervention (PCI) Platelet Aggregation in Patients with Acute Coronary Syndromes

    PubMed Central

    Dong, Peng; Yang, Xinchun; Bian, Suyan

    2016-01-01

    Background The aim of this study was to observe the effects of genetic polymorphism of CYP2C19 on inhibitory effects of ticagrelor (Tic) and clopidogrel (Clo) towards post-percutaneous coronary intervention (PCI) platelet aggregation (IPA) and major cardiovascular events (MACE) in patients with acute coronary syndromes (ACS). Material/Methods From August 2013 to March 2014, 166 patients with ACS undergoing PCI were selected. The patients were randomly grouped into the Tic group and the Clo group. IPA was detected by thromboelastography (TEG) at 1 week after taking the pills. Genotyping of CYP2C19 gene was determined by analysis of gene sequence detection. Patients were followed up for 1 month and MACE was observed. Results The total IPA in the Clo group was significantly increased compared with the Tic group (P<0.05). The IPAs in the 3 subgroups of Clo group were all significantly increased compared with the 3 subgroups of the Tic group (all P<0.05). MACE was not significantly different between Clo and Tic groups (P>0.05). MACE had no significant difference among the 3 subgroups of the Tic group (P>0.05). MACE in the low metabolism subgroup of the Clo group was significantly increased compared with the fast metabolism subgroup and middle metabolism subgroup of Clo group (P<0.05). MACE was not significant different between the fast metabolism subgroup and the middle metabolism subgroup of the Clo group (P>0.05). MACE in the low metabolism subgroup of the Tic group was significantly decreased compared with the low metabolism subgroup of the Clo group (P<0.05). Conclusions Ticagrelor has a better effect on inhibition platelet aggregation than Clopidogrel in ACS patients undergoing PCI. PMID:27977637

  18. Modulatory effect of coffee on platelet function.

    PubMed

    Bhaskar, Shobha; Rauf, Arun A

    2010-01-01

    Blood platelets play a major role in cardiovascular disease (CVD) and thrombosis. Conflicting information exists regarding the effect of coffee consumption on the cardiovascular system. We have investigated whether the consumption of moderate amount of coffee affect platelet functions and primary hemostasis in vivo in normal and high fat diet fed rats. Coffee fed group showed significant (P < 0.05) decrease in mean platelet volume, platelet crit and platelet distribution width as compared to high fat diet (HFD) group. The concentration of malondialdehyde in platelets increased in atherosclerotic group indicates the increased thromboxane A2 (TXA2) production from membrane arachidonic acid and it was decreased in coffee treated group. Platelet aggregation studies with ADP, collagen, arachidonic acid and epinephrine showed significant (P < 0.05) decrease in aggregation in coffee fed group. Scanning electron microscopic studies revealed that platelet aggregation tendency increased in HFD group and was reduced in coffee fed group. These results indicate that coffee is active in inhibiting platelet aggregation, a critical step involved in thrombosis.

  19. Tryptic digestion of human GPIIIa. Isolation and biochemical characterization of the 23 kDa N-terminal glycopeptide carrying the antigenic determinant for a monoclonal antibody (P37) which inhibits platelet aggregation.

    PubMed Central

    Calvete, J J; Rivas, G; Maruri, M; Alvarez, M V; McGregor, J L; Hew, C L; Gonzalez-Rodriguez, J

    1988-01-01

    Early digestion of pure human platelet glycoprotein IIIa (GPIIIa) leads to a single cleavage of the molecule at 23 kDa far from one of the terminal amino acids. Automated Edman degradation demonstrates that GPIIIa and the smaller (23 kDa) tryptic fragment share the same N-terminal amino acid sequence. A further cleavage occurs in the larger fragment (80 kDa), reducing its apparent molecular mass by 10 kDa. The 23 kDa fragment remains attached to the larger ones in unreduced samples. Stepwise reduction of early digested GPIIIa with dithioerythritol selectively reduces the single disulphide bond joining the smaller (23 kDa) to the larger (80/70 kDa) fragments. Two fractions were obtained by size-exclusion chromatography of early digested GPIIIa after partial or full reduction and alkylation. The larger-size fraction contains the 80/70 kDa fragments, while the 23 kDa fragment is isolated in the smaller. The amino acid compositions of these fractions do not differ very significantly from the composition of GPIIIa; however the 23 kDa fragment contains only 10.2% by weight of sugars and is richer in neuraminic acid. Disulphide bonds are distributed four in the 23 kDa glycopeptide and 20-21 in the 80/70 kDa glycopeptide. The epitope for P37, a monoclonal antibody which inhibits platelet aggregation [Melero & González-Rodríguez (1984) Eur. J. Biochem. 141, 421-427] is situated within the first 17 kDa of the N-terminal region of GPIIIa, which gives a special functional interest to this extracellular region of GPIIIa. On the other hand, the epitopes for GPIIIa-specific monoclonal antibodies, P6, P35, P40 and P97, which do not interfere with platelet aggregation, are located within the larger tryptic fragment (80/70 kDa). Thus, the antigenic areas available in the extracellular surface of GPIIIa for these five monoclonal antibodies are now more precisely delineated. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. PMID:2455507

  20. Rupture Forces among Human Blood Platelets at different Degrees of Activation

    PubMed Central

    Nguyen, Thi-Huong; Palankar, Raghavendra; Bui, Van-Chien; Medvedev, Nikolay; Greinacher, Andreas; Delcea, Mihaela

    2016-01-01

    Little is known about mechanics underlying the interaction among platelets during activation and aggregation. Although the strength of a blood thrombus has likely major biological importance, no previous study has measured directly the adhesion forces of single platelet-platelet interaction at different activation states. Here, we filled this void first, by minimizing surface mediated platelet-activation and second, by generating a strong adhesion force between a single platelet and an AFM cantilever, preventing early platelet detachment. We applied our setup to measure rupture forces between two platelets using different platelet activation states, and blockade of platelet receptors. The rupture force was found to increase proportionally to the degree of platelet activation, but reduced with blockade of specific platelet receptors. Quantification of single platelet-platelet interaction provides major perspectives for testing and improving biocompatibility of new materials; quantifying the effect of drugs on platelet function; and assessing the mechanical characteristics of acquired/inherited platelet defects. PMID:27146004

  1. 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.

  2. 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

  3. Cyclophilin A is an important mediator of platelet function by regulating integrin αIIbβ3 bidirectional signalling.

    PubMed

    Wang, Lian; Soe, Nwe Nwe; Sowden, Mark; Xu, Yingqian; Modjeski, Kristina; Baskaran, Padmamalini; Kim, Yeonghwan; Smolock, Elaine M; Morrell, Craig N; Berk, Bradford C

    2014-05-05

    Cyclophilin A (CyPA) is an important mediator in cardiovascular diseases. It possesses peptidyl-prolyl cis-trans isomerase activity (PPIase) and chaperone functions, which regulate protein folding, intracellular trafficking and reactive oxygen species (ROS) production. Platelet glycoprotein receptor αIIbβ3 integrin activation is the common pathway for platelet activation. It was our objective to understand the mechanism by which CyPA-regulates αIIbβ3 activation in platelets. Mice deficient for CyPA (CyPA-/-) had prolonged tail bleeding time compared to wild-type (WT) controls despite equivalent platelet numbers. In vitro studies revealed that CyPA-/- platelets exhibited dramatically decreased thrombin-induced platelet aggregation. In vivo, formation of occlusive thrombi following FeCl3 injury was also significantly impaired in CyPA-/- mice compared with WT-controls. Furthermore, CyPA deficiency inhibited flow-induced thrombus formation in vitro. Flow cytometry demonstrated that thrombin-induced ROS production and αIIbβ3 activation were reduced in CyPA-/- platelets. Coimmunoprecipitation studies showed ROS-dependent increased association of CyPA and αIIbβ3. This association was dependent upon the PPIase activity of CyPA. Significantly, fibrinogen-platelet binding, platelet spreading and cytoskeleton reorganisation were also altered in CyPA-/- platelets. Moreover, CyPA deficiency prevented thrombin-induced αIIbβ3 and cytoskeleton association. In conclusion, CyPA is an important mediator in platelet function by regulation of αIIbβ3 bidirectionalsignalling through increased ROS production and facilitating interaction between αIIbβ3 and the cell cytoskeleton.

  4. Human podoplanin-positive monocytes and platelets enhance lymphangiogenesis through the activation of the podoplanin/CLEC-2 axis.

    PubMed

    Hur, Jin; Jang, Jae Hee; Oh, Il-Young; Choi, Jae-Il; Yun, Ji-Yeon; Kim, Joonoh; Choi, Young-Eun; Ko, Seung-Bum; Kang, Jin-A; Kang, Jeehoon; Lee, Sang Eun; Lee, Hwan; Park, Young-Bae; Kim, Hyo-Soo

    2014-08-01

    Emerging studies suggested that murine podoplanin-positive monocytes (PPMs) are involved in lymphangiogenesis. The goal of this study was to demonstrate the therapeutic lymphangiogenesis of human PPMs by the interaction with platelets. Aggregation culture of human peripheral blood mononuclear cells (PBMCs) resulted in cellular aggregates termed hematospheres. During 5-day culture, PPMs expanded exponentially and expressed several lymphatic endothelial cell-specific markers including vascular endothelial growth factor receptor (VEGFR)-3 and well-established lymphangiogenic transcription factors. Next, we investigated the potential interaction of PPMs with platelets that had C-type lectin-like receptor-2 (CLEC-2), a receptor of podoplanin. In vitro coculture of PPMs and platelets stimulated PPMs to strongly express lymphatic endothelial markers and upregulate lymphangiogenic cytokines. Recombinant human CLEC-2 also stimulated PPMs through Akt and Erk signaling. Likewise, platelets in coculture with PPMs augmented secretion of a lymphangiogenic cytokine, interleukin (IL)-1-β, via podoplanin/CLEC-2 axis. The supernatant obtained from coculture was able to enhance the migration, viability, and proliferation of lymphatic endothelial cell. Local injection of hematospheres with platelets significantly increased lymphatic neovascularization and facilitated wound healing in the full-thickness skin wounds of nude mice. Cotreatment with PPMs and platelets augments lymphangiogenesis through podoplanin/CLEC-2 axis, which thus would be a promising novel strategy of cell therapy to treat human lymphatic vessel disease.

  5. Platelet reactions to modified surfaces under dynamic conditions.

    PubMed

    Rhodes, N P; Shortland, A P; Rattray, A; Williams, D F

    1998-12-01

    The influence of surfaces on the reactions of platelets in whole blood under laminar flow was investigated in a cone and plate viscometer. Citrated whole blood was exposed to steel, PMMA and PMMA modified with PEO at low (500 s(-1)) and high (4000 s(-1)) wall shear rates at room temperature for a period of 100 s. Treated blood samples were fixed with paraformaldehyde, stained with a monoclonal antibody for CD41 (platelet GPIIb/IIIa) conjugated with phycoerythrin and analyzed by flow cytometry. The reactions of platelets (microparticle generation and formation of platelet-platelet, platelet-red blood cell and red blood cell-microparticle aggregates) to these environments were quantified. Additionally, the size of platelet-platelet aggregates was assessed. The percentage platelet aggregation and numbers of microparticles generated were independent of surface type at any shear rate. The composition of the aggregates formed was influenced by the surface: at low and high shear rates PMMA caused the generation of platelet-platelet aggregates of the greatest size. The numbers of red blood cell-platelet and red blood cell-microparticle aggregates also varied depending on the surface. Fewer red blood cell-platelet aggregates were formed at higher shear rates, whereas the reverse was true for red blood cell-microparticle aggregates. It is concluded that these variations may help to explain the differential effects of surfaces to the induction of distant thrombotic events: microparticles may be protected from loss from the blood stream by their association with red blood cells at high shear rates.

  6. Effect of serotonin on platelet function in cocaine exposed blood

    PubMed Central

    Ziu, Endrit; Hadden, Coedy; Li, Yicong; Lowery, Curtis Lee; Singh, Preeti; Ucer, Serra S.; Mercado, Charles P.; Gu, Howard H.; Kilic, Fusun

    2014-01-01

    5-hydroxytryptamine (5-HT) reuptake inhibitors counteract the pro-thrombotic effect of elevated plasma 5-HT by down-regulating the 5-HT uptake rates of platelets. Cocaine also down-regulates the platelet 5-HT uptake rates but in contrast, the platelets of cocaine-injected mice show a much higher aggregation rate than the platelets of control mice. To examine the involvement of plasma 5-HT in cocaine-mediated platelet aggregation, we studied the function of platelets isolated from wild-type and transgenic, peripheral 5-HT knock-out (TPH1-KO) mice, and cocaine-insensitive dopamine transporter knock in (DAT-KI) mice. In cocaine-injected mice compared to the control mice, the plasma 5-HT level as well as the surface level of P-selectin was elevated; in vitro platelet aggregation in the presence of type I fibrillar collagen was enhanced. However, cocaine injection lowered the 5-HT uptake rates of platelets and increased the plasma 5-HT levels of the DAT-KI mice but did not change their platelets aggregation rates further which are already hyper-reactive. Furthermore, the in vitro studies supporting these in vivo findings suggest that cocaine mimics the effect of elevated plasma 5-HT level on platelets and in 5-HT receptor- and transporter-dependent pathways in a two-step process propagates platelet aggregation by an additive effect of 5-HT and nonserotonergic catecholamine. PMID:25091505

  7. 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.

  8. Platelets can enhance vascular permeability.

    PubMed

    Cloutier, Nathalie; Paré, Alexandre; Farndale, Richard W; Schumacher, H Ralph; Nigrovic, Peter A; Lacroix, Steve; Boilard, Eric

    2012-08-09

    Platelets survey blood vessels, searching for endothelial damage and preventing loss of vascular integrity. However, there are circumstances where vascular permeability increases, suggesting that platelets sometimes fail to fulfill their expected function. Human inflammatory arthritis is associated with tissue edema attributed to enhanced permeability of the synovial microvasculature. Murine studies have suggested that such vascular leak facilitates entry of autoantibodies and may thereby promote joint inflammation. Whereas platelets typically help to promote microvascular integrity, we examined the role of platelets in synovial vascular permeability in murine experimental arthritis. Using an in vivo model of autoimmune arthritis, we confirmed the presence of endothelial gaps in inflamed synovium. Surprisingly, permeability in the inflamed joints was abrogated if the platelets were absent. This effect was mediated by platelet serotonin accumulated via the serotonin transporter and could be antagonized using serotonin-specific reuptake inhibitor antidepressants. As opposed to the conventional role of platelets to microvascular leakage, this demonstration that platelets are capable of amplifying and maintaining permeability adds to the rapidly growing list of unexpected functions for platelets.

  9. Pathogen-Reduced, Plasmalyte-Extended Stored Platelets (PREPS)

    DTIC Science & Technology

    2013-10-01

    regulatory document developed Laboratory equipment and reagents purchased Test methodology refined for cold stored platelet radiolabeling, aggregation and...STUDY SCHEMA 11 FIGURE 2. FLOW OF STUDY PROCEDURES 17 Puget Sound Blood Center Protocol: 12-1, Revision 7/17/2013...provide RBCs , plasma and platelets in forward combat situations without the need to separate the blood into components. Therefore these platelets need

  10. [Activation and inhibitory mechanisms of blood platelets].

    PubMed

    Suzuki-Inoue, Katsue

    2014-07-01

    Exposure of platelets to subendothelial matrices initiates physiological hemostasis and pathological thrombosis. Under high shear stress, von Willebrand factor bridges newly exposed collagen to glycoprotein (GP) Ib on platelets. This initial tethering facilitates association between the collagen receptor GPVI and collagen, which generates tyrosine kinase-dependent activation signals, followed by release of secondary mediators and integrin activation. Activated integrin can bind to their ligands including fibrinogen. The released secondary mediators, ADP and thromboxane A2, activate integrin of flowing platelets, which enables formation of platelet thrombi by binding of activated flowing platelets and adhered platelets to collagen via binding between activated aIIbbeta3 integrin and fibrinogen. Platelets also have inhibitory mechanisms, which help to prevent unwanted platelet activation in vivo.

  11. Influence of Oxidative Stress on Stored Platelets

    PubMed Central

    2016-01-01

    Platelet storage and its availability for transfusion are limited to 5-6 days. Oxidative stress (OS) is one of the causes for reduced efficacy and shelf-life of platelets. The studies on platelet storage have focused on improving the storage conditions by altering platelet storage solutions, temperature, and materials. Nevertheless, the role of OS on platelet survival during storage is still unclear. Hence, this study was conducted to investigate the influence of storage on platelets. Platelets were stored for 12 days at 22°C. OS markers such as aggregation, superoxides, reactive oxygen species, glucose, pH, lipid peroxidation, protein oxidation, and antioxidant enzymes were assessed. OS increased during storage as indicated by increments in aggregation, superoxides, pH, conjugate dienes, and superoxide dismutase and decrements in glucose and catalase. Thus, platelets could endure OS till 6 days during storage, due to the antioxidant defense system. An evident increase in OS was observed from day 8 of storage, which can diminish the platelet efficacy. The present study provides an insight into the gradual changes occurring during platelet storage. This lays the foundation towards new possibilities of employing various antioxidants as additives in storage solutions. PMID:26949396

  12. Oral contraceptive use alters the balance of platelet prostaglandin and thromboxane synthesis.

    PubMed

    Schorer, A E; Gerrard, J M; White, J G; Krivit, W

    1978-07-01

    The ability of platelet microsomes to generate platelet aggregating activity on addition of arachidonic acid was evaluated in women taking oral contraceptives and in controls taking no medication but matched for age, sex, and family history. Oral contraceptive users generated significantly more platelet aggregating activity per 100 ug of platelet microsomal protein than controls. Variation in generation of platelet aggregating activity during the menstrual cycle was also observed with highest activity during the third week. These studies show an altered balance of platelet prostaglandin and thromboxane synthesis in oral contraceptive users which may contribute to their increased incidence of thromboembolic phenomena.

  13. Dynamic light scattering can determine platelet function

    NASA Astrophysics Data System (ADS)

    Lee, Nathan

    2011-10-01

    Platelet transfusions are life-saving procedures for patients who are bleeding or undergoing chemotherapy. The effectiveness of transfusions depends on the number of platelets transfused and the platelet function. Platelet function correlates with proportion of discoid to activated platelets, morphology response to temperature stress, and inversely correlates with microparticle content. ThromboLUX is a novel device that determines platelet function by measuring all of these characteristics using dynamic light scattering (DLS). During periods of stress, such as decreased temperature, cytoskeletal rearrangements will cause normal, discoid platelets to activate and become spiny spheres. The formation of pseudopods of various lengths facilitates the clotting cascade and also increases the apparent size of platelets. ThromboLUX uses a 37-20-37 C temperature cycle that mimics the bleeding, storage, and transfusion process. As the temperature fluctuates, DLS will measure the changing platelet hydrodynamic radius and the size of any microparticles present. ThromboLUX analysis of platelet concentrates in vitro would allow determination of high platelet function units before transfusion and would therefore improve transfusion outcomes and patient safety. This study examined how DLS is able to distinguish between discoid and activated platelets as well as measure the parameters that contribute to high platelet function.

  14. 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.

  15. 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.

  16. Activity of platelet hemostasis in children with spinal deformities.

    PubMed

    Medvedev, I N; Lapshina, E V; Zavalishina, S Yu

    2010-10-01

    An increase of adhesion and aggregation functions of platelets in vivo and in vitro was detected in 5-6-year-old children with scoliosis. These disorders were caused by hyperproduction of von Willebrand's factor in the vascular wall and intensification of thromboxane production in blood platelets. Activation of thromboxane formation is the main cause of platelet hyperactivity in children with scoliosis. Correction of platelet hemostasis may include pathogenetically substantiated complex of therapeutic exercises, swimming, and massage.

  17. [Cardiology. Platelet function testing for clinicians].

    PubMed

    Pellaton, Cyril; Eeckhout, Eric; Silvain, Johanne; Montalescot, Gilles; Collet, Jean-Phillipe

    2014-01-15

    Platelet P2YI2 receptor inhibition with clopidogrel, prasugrel or ticagrelor plays a key role to prevent recurrent ischaemic events after percutaneous coronary intervention in acute coronary syndromes or elective settings. The degree of platelet inhibition depends on the antiplatelet medication used and is influenced by clinical and genetic factors. A concept of therapeutic window exists. On one side, efficient anti-aggregation is required in order to reduce cardio-vascular events. On the other side, an excessive platelet inhibition represents a risk of bleeding complications. This article describes the current knowledge about some platelet function tests and genetic tests and summarises their role in the clinical practice.

  18. In vitro inhibition of platelet aggregation by peptides derived from oat (Avena sativa L.), highland barley (Hordeum vulgare Linn. var. nudum Hook. f.), and buckwheat (Fagopyrum esculentum Moench) proteins.

    PubMed

    Yu, Guoyong; Wang, Feng; Zhang, Bolin; Fan, Junfeng

    2016-03-01

    Bioactive compounds present in foods could have beneficial effects on human health. In this study, we report the capacity of peptides released from oat, highland barley, and buckwheat proteins after enzymatic digestion to inhibit platelet aggregation in vitro. All hydrolysates showed high antiplatelet activity, with IC50 values of 0.282mg/ml (oat flour gastrointestinal hydrolysate, 6h) to 2.496mg/ml (highland barley glutelin tryptic hydrolysate, 14h) in a dose-dependent manner. Thirty-eight peptides with more than seven residues were identified in the tryptic hydrolysates of oat globulin. Results of computational modeling revealed that nine peptides, including ALPIDVLANAYR, EFLLAGNNKR, GEEFGAFTPK, QLAQIPR, LQAFEPLR, ALPVDVLANAYR, GEEFDAFTPK, QKEFLLAGNNK, and TNPNSMVSHIAGK bound the cyclooxygenase-1 active centers with low binding energy (-6.5 to -7.5kcal/mol). This is the first report to identify antiplatelet peptides from grain hydrolysates and the binding modes at the molecular level, leading to their possible use as functional food ingredients to prevent thrombosis.

  19. 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.

  20. 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.

  1. Platelet-derived CXCL12 regulates monocyte function, survival, differentiation into macrophages and foam cells through differential involvement of CXCR4–CXCR7

    PubMed Central

    Chatterjee, M; von Ungern-Sternberg, S N I; Seizer, P; Schlegel, F; Büttcher, M; Sindhu, N A; Müller, S; Mack, A; Gawaz, M

    2015-01-01

    Platelets store and release CXCL12 (SDF-1), which governs differentiation of hematopoietic progenitors into either endothelial or macrophage-foam cells. CXCL12 ligates CXCR4 and CXCR7 and regulates monocyte/macrophage functions. This study deciphers the relative contribution of CXCR4–CXCR7 in mediating the effects of platelet-derived CXCL12 on monocyte function, survival, and differentiation. CXCL12 and macrophage migration inhibitory factor (MIF) that ligate CXCR4–CXCR7 induced a dynamic bidirectional trafficking of the receptors, causing CXCR4 internalization and CXCR7 externalization during chemotaxis, thereby influencing relative receptor availability, unlike MCP-1. In vivo we found enhanced accumulation of platelets and platelet-macrophage co-aggregates in peritoneal fluid following induction of peritonitis in mice. The relative surface expression of CXCL12, CXCR4, and CXCR7 among infiltrated monocytes was also enhanced as compared with peripheral blood. Platelet-derived CXCL12 from collagen-adherent platelets and recombinant CXCL12 induced monocyte chemotaxis specifically through CXCR4 engagement. Adhesion of monocytes to immobilized CXCL12 and CXCL12-enriched activated platelet surface under static and dynamic arterial flow conditions were mediated primarily through CXCR7 and were counter-regulated by neutralizing platelet-derived CXCL12. Monocytes and culture-derived-M1–M2 macrophages phagocytosed platelets, with the phagocytic potential of culture-derived-M1 macrophages higher than M2 involving CXCR4–CXCR7 participation. CXCR7 was the primary receptor in promoting monocyte survival as exerted by platelet-derived CXCL12 against BH3-mimetic induced apoptosis (phosphatidylserine exposure, caspase-3 activation, loss of mitochondrial transmembrane potential). In co-culture experiments with platelets, monocytes predominantly differentiated into CD163+ macrophages, which was attenuated upon CXCL12 neutralization and CXCR4/CXCR7 blocking antibodies

  2. 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

  3. Survival and function of transfused platelets. Studies in two patients with congenital deficiencies of platelet membrane glycoproteins.

    PubMed

    Cesar, Jesus M; Vecino, Ana M

    2009-05-01

    Platelets of patients suffering from Glanzmann's thrombasthenia (GT) and Bernard Soulier Syndrome (BSS) are defective in different membrane glycoproteins. Since these integrins can be identified by monoclonal antibodies, normal infused platelets could be distinguished from defective platelets and followed by using flow cytometry (FC). We studied this aspect in two recipients suffering, one from GT and the other one, who underwent splenectomy, from BSS. One hour after transfusion, normal platelets comprised 17% of the total platelet population in the patient with GT. Aggregation tests detected a measurable response to collagen (increase of 15% of transmittance). The presence of transfused platelets decreased progressively to 0.8% on day 4, which corresponded with a half-life of 2.6 days. Studies performed in the patient suffering from BSS found that 1 hour after transfusion, 53% of the platelet population corresponded to normal platelets. There was a progressive decay until day 6, which corresponded to a half-life of 4.6 days. Aggregation tests also detected a platelet response to ristocetin from 1 hour after transfusion (47% increase of transmittance) to day 3. FC is useful to measure platelet lifespan in these kinds of patients. We also report the first studies of platelet aggregation after platelet transfusion.

  4. 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.

  5. 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

  6. Thrombocytopenia and platelet transfusion in the neonate.

    PubMed

    Cremer, Malte; Sallmon, Hannes; Kling, Pamela J; Bührer, Christoph; Dame, Christof

    2016-02-01

    Neonatal thrombocytopenia is widespread in preterm and term neonates admitted to neonatal intensive care units, with up to one-third of infants demonstrating platelet counts <150 × 10(9)/L. Thrombocytopenia may arise from maternal, placental or fetal/neonatal origins featuring decreased platelet production, increased consumption, or both mechanisms. Over the past years, innovations in managing neonatal thrombocytopenia were achieved from prospectively obtained clinical data on thrombocytopenia and bleeding events, animal studies on platelet life span and production rate and clinical use of fully automated measurement of reticulated platelets (immature platelet fraction). This review summarizes the pathophysiology of neonatal thrombocytopenia, current management including platelet transfusion thresholds and recent developments in megakaryopoietic agents. Furthermore, we propose a novel index score for bleeding risk in thrombocytopenic neonates to facilitate clinician's decision-making when to transfuse platelets.

  7. Platelet interaction with modified articular cartilage. Its possible relevance to joint repair.

    PubMed Central

    Zucker-Franklin, D; Drosenberg, L

    1977-01-01

    During studies concerned with the platelet-collagen interaction, it was observed that platelets did not adhere to bovine or human articular cartilage and that cartilage did not induce platelet aggregation in vivo or in vitro. To study the mechanism responsible for this observation, the role of proteoglycans was examined. Purified cartilage collagen proved to be fully active as a platelet aggregant. Addition of small amounts of proteoglycan subunit (PGS) blocked platelet aggregation, whereas chondroitin sulfate, a major glycosaminoglycan component of cartilage matrix, impaired platelet aggregation only at concentrations which resulted in a marked increase in viscosity. Moreover, PGS abolished aggregation of platelets by polylysine but did not prevent aggregation by ADP, suggesting that PGS may block strategically placed lysine sites on the collagen molecule. Treatment of fresh articular cartilage with proteolytic enzymes rendered the tissue active as a platelet aggregant. In vivo experiments demonstrated that surgical scarification of rabbit articular cartilage does not result in adhesion of autologous platelets. Treatment of rabbit knee joints with intraarticular trypsin 1 wk before the injection of blood resulted in adhesion and aggregation of platelets on the surface of the lesions. Since there is evidence from other studies that some degree of cartilage healing may take place after initiation of an inflammatory response, it is postulated that induction of platelet-cartilage interaction may eventuate in cartilage repair. Images PMID:557500

  8. Hypersensitivity to thrombin of platelets from hypercholesterolemic rats

    SciTech Connect

    Winocour, P.D.; Rand, M.L.; Kinlough-Rathbone, R.L.; Mustard, J.F.

    1986-03-01

    Hypersensitivity of platelets to thrombin has been associated with hypercholesterolemia. The authors have examined the mechanisms involved in this hypersensitivity. Rats were given diets rich in milk fat and containing added cholesterol and taurocholate to produce hypercholesterolemia (HC) (262 +/- 25 mg%) or added sitosterol as a normocholesterolemic control (NC) (89 +/- 6 mg%). Washed platelets were prelabelled with /sup 14/C-serotonin. In the presence of acetylsalicyclic acid (ASA) (to inhibit thromboxane A/sub 2/ (TXA/sub 2/) formation) and creatine phosphate/creatine phosphokinase (CP/CPK) (to remove released ADP), HC platelets aggregated more (26 +/- 1%) and released more /sup 14/C (9.1 +/- 2.0%) than NC platelets (aggregation: 0%, p < 0.001; /sup 14/C release: 1.5 +/- 0.5%, p < 0.002) in response to thrombin (0.075 U/ml). Thus, a pathway independent of released ADP or TXA/sub 2/ formation is involved in the hypersensitivity of HC platelets to thrombin. Total binding of /sup 125/I-thrombin to HC platelets was less than that to NC platelets but HC platelets were smaller and had less protein than NC platelets; the thrombin binding per mg platelet protein was the same for HC and NC platelets, indicating that hypersensitivity to thrombin of HC platelets does not result from increased thrombin binding. Thus, hypersensitivity of HC platelets to thrombin is not due to TXA/sub 2/ formation, the action of released ADP or increased thrombin binding.

  9. 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

  10. Platelet Function Tests in Bleeding Disorders.

    PubMed

    Lassila, Riitta

    2016-04-01

    Functional disorders of platelets can involve any aspect of platelet physiology, with many different effects or outcomes. These include platelet numbers (thrombocytosis or thrombocytopenia); changes in platelet production or destruction, or capture to the liver (Ashwell receptor); altered adhesion to vascular injury sites and/or influence on hemostasis and wound healing; and altered activation or receptor functions, shape change, spreading and release reactions, procoagulant and antifibrinolytic activity. Procoagulant membrane alterations, and generation of thrombin and fibrin, also affect platelet aggregation. The above parameters can all be studied, but standardization and quality control of assay methods have been limited despite several efforts. Only after a comprehensive clinical bleeding assessment, including family history, information on drug use affecting platelets, and exclusion of coagulation factor, and tissue deficits, should platelet function testing be undertaken to confirm an abnormality. Current diagnostic tools include blood cell counts, platelet characteristics according to the cell counter parameters, peripheral blood smear, exclusion of pseudothrombocytopenia, whole blood aggregometry (WBA) or light transmission aggregometry (LTA) in platelet-rich plasma, luminescence, platelet function analysis (PFA-100) for platelet adhesion and deposition to collagen cartridges under blood flow, and finally transmission electron microscopy to exclude rare structural defects leading to functional deficits. The most validated test panels are included in WBA, LTA, and PFA. Because platelets are isolated from their natural environment, many simplifications occur, as circulating blood and interaction with vascular wall are omitted in these assays. The target to reach a highly specific platelet disorder diagnosis in routine clinical management can be exhaustive, unless needed for genetic counseling. The elective overall assessment of platelet function disorder

  11. 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.

  12. Platelet fibrinogen binding in Basset Hound Hereditary Thrombopathy

    SciTech Connect

    Patterson, W.; Estry, D.; Schwartz, K.; Bell, T.

    1986-03-01

    Platelets from dogs with Basset Hound Hereditary Thrombopathy (BHT) display a thrombasthenia-like aggregation defect but have been shown to have normal amounts of platelet membrane glycoproteins IIb and IIIa (GP IIb-IIIa). In order to investigate the possibility of a functionally abnormal GPIIb-IIIa complex, which might be unable to bind fibrinogen after stimulation, fibrinogen binding in BHT was evaluated. Two canine fibrinogen preparations were used, one from BHT dogs and one from normal control dogs, as well as a human fibrinogen preparation. Platelets from BHT and normal dogs were activated with 1 x 10/sup -5/M ADP in the presence of /sup 125/I-labeled fibrinogen and the surface bound radioactivity quantitated. For all fibrinogen preparations, the amount of fibrinogen bound by BHT platelets was not significantly different than that bound by normal dog platelets. BHT platelets bound 23,972 +/- 3612 and normal dog platelets bound 23,033 +/- 3971 molecules of fibrinogen per platelet. The BHT platelet aggregation defect does not seem to be caused by a functionally abnormal GP IIb-IIIa complex, since BHT platelets bind normal amounts of fibrinogen. The results suggest that fibrinogen binding is not sufficient for platelet aggregation, and other factors, perhaps receptor mobility and membrane phospholipid content should be investigated in BHT.

  13. 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.

  14. Platelets and viruses: an ambivalent relationship.

    PubMed

    Flaujac, Claire; Boukour, Siham; Cramer-Bordé, Elisabeth

    2010-02-01

    Thrombocytopenia is a frequent complication of viral infections providing evidence that interaction of platelets with viruses is an important pathophysiological phenomenon. Multiple mechanisms are involved depending on the nature of the viruses involved. These include immunological platelet destruction, inappropriate platelet activation and consumption, and impaired megakaryopoiesis. Viruses bind platelets through specific receptors and identified ligands, which lead to mutual alterations of both the platelet host and the viral aggressor. We have shown that HIV-1 viruses are internalized specifically in platelets and megakaryocytes, where they can be either sheltered, unaltered (with potential transfer of the viruses into target organs), or come in contact with platelet secretory products leading to virus destruction and facilitated platelet clearance. In this issue, we have reviewed the various pathways that platelets use in order to interact with viruses, HIV and others. This review also shows that more work is still needed to precisely identify platelet roles in viral infections, and to answer the challenge of viral safety in platelet transfusion.

  15. 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.

  16. Cryopreservation of buffy-coat-derived platelet concentrates in dimethyl sulfoxide and platelet additive solution.

    PubMed

    Johnson, L N; Winter, K M; Reid, S; Hartkopf-Theis, T; Marks, D C

    2011-04-01

    Platelets prepared in plasma can be frozen in 6% dimethyl sulfoxide (Me(2)SO) and stored for extended periods at -80°C. The aim of this study was to reduce the plasma present in the cryopreserved product, by substituting plasma with platelet additive solution (PAS; SSP+), whilst maintaining in vitro platelet quality. Buffy coat-derived pooled leukoreduced platelet concentrates were frozen in a mixture of SSP+, plasma and 6% Me(2)SO. The platelets were concentrated, to avoid post-thaw washing, and frozen at -80°C. The cryopreserved platelet units (n=9) were rapidly thawed at 37°C, reconstituted in 50% SSP+/plasma and stored at 22°C. Platelet recovery and quality were examined 1 and 24h post-thaw and compared to the pre-freeze samples. Upon thawing, platelet recovery ranged from 60% to 80%. However, there were differences between frozen and liquid-stored platelets, including a reduction in aggregation in response to ADP and collagen; increased CD62P expression; decreased viability; increased apoptosis and some loss of mitochondrial membrane integrity. Some recovery of these parameters was detected at 24h post-thaw, indicating an extended shelf-life may be possible. The data suggests that freezing platelets in 6% Me(2)SO and additive solution produces acceptable in vitro platelet quality.

  17. 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.

  18. 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.

  19. Resveratrol preserves the function of human platelets stored for transfusion.

    PubMed

    Lannan, Katie L; Refaai, Majed A; Ture, Sara K; Morrell, Craig N; Blumberg, Neil; Phipps, Richard P; Spinelli, Sherry L

    2016-03-01

    Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for 5 d released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol's beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function.

  20. Resveratrol preserves the function of human platelets stored for transfusion

    PubMed Central

    Lannan, Katie L; Refaai, Majed A; Ture, Sara K; Morrell, Craig N; Blumberg, Neil; Phipps, Richard P; Spinelli, Sherry L

    2015-01-01

    Summary Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for five days released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol’s beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function. PMID:26683619

  1. 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

  2. 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

  3. Simulation of Polymer Physical Gel With Platelet Fillers

    NASA Astrophysics Data System (ADS)

    Xu, Di; Gerssape, Dilip

    Platelet filler such as clays have superior effects on the properties of polymer gels. We used molecular dynamic simulations to study platelet filled composite gels system, in which small hexagonal disks simulate the platelets and gelation is due to short-range attraction between end-monomers and platelets. The properties of platelet filled composites are studied as a function of filler concentration. The mechanism of gelation was found similar to those of pure polymer gels; the polymers and platelets formed organic-inorganic networks, which percolate at high enough filler concentration. It was observed platelets aggregated into local intercalation structure, which significantly differs from typical spherical fillers. This unique intercalation structure is examined by radial distribution function and ordering parameters. We discussed how intercalation would affect the properties of the platelet composites by comparing them with spherical fillers.

  4. New trends in bioanalytical microdevices to assess platelet function.

    PubMed

    Basabe-Desmonts, Lourdes; Meade, Gerardene; Kenny, Dermot

    2010-10-01

    Cardiovascular disease is the major cause of mortality globally. The role of platelets and antiplatelet drugs in the treatment of cardiovascular disease is widely appreciated. Platelets have a less well-known role in cancer and inflammation and as the role of platelets in cancer and inflammation is increasingly understood, there is a compelling need to develop diagnostic assays of platelet function to guide clinical management. Most current platelet-function tests are focused on platelet aggregation, are cumbersome, require dedicated laboratory personnel, measure a single response to a single agonist and artificially separate platelets from blood, thus, these assays do not reflect the pathophysiolgical environment of complex disease states. New technology platforms are emerging that address the physiological adhesive function of platelets to vascular-specific matrices using small volumes of whole blood, giving rapid results. These technologies will guide therapy in the prevention of cardiovascular disease and probably in risk management in both cancer and atherosclerosis.

  5. 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.

  6. 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

  7. [Glycoproteins, inherited diseases of platelets, and the role of platelets in wound healing].

    PubMed

    Nurden, Alan T; Nurden, Paquita

    2013-02-01

    Recognition that platelets have a glycocalyx rich in membrane glycoproteins prompted the discovery in France that inherited bleeding syndromes due to defects of platelet adhesion and aggregation were caused by deficiencies in major receptors at the platelet surface. Identification of the alpha IIb beta3 integrin prompted the development of powerful anti-thrombotic drugs that have gained worldwide use. Since these discoveries, the genetic causes of many other defects of platelet function and production have been elucidated, with the identification of an ADP receptor, P2 Y12, another widespread target for anti-thrombotic drugs. Discovery of the molecular basis of a rare disease of storage of biologically active proteins in platelet alpha-granules has been accompanied by the recognition of the roles of platelets in inflammation, the innate immune system and tissue repair, opening new avenues for therapeutic advances.

  8. Evaluation of electrical aggregometry: comparison with optical aggregometry, secretion of ATP, and accumulation of radiolabeled platelets

    SciTech Connect

    Ingerman-Wojenski, C.; Smith, J.B.; Silver, M.J.

    1983-01-01

    Platelet aggregation has been most commonly studied in vitro by measuring increases in light transmission as platelets aggregate in PRP (platelet-rich plasma). Recently, an electrical impedance method for measuring platelet aggregation has been introduced. This method can be used with either PRP or whole blood and measures an increase in impedance across electrodes placed in the blood samples as platelets accumulate on them. Results obtained by the two methods were compared using ADP and collagen as aggregating agents, and also have measured the secretion of platelet ATP simultaneously. Although the aggregometry results were similar, recordings obtained by the electrical method did not distinguish two waves of platelet aggregation or correlate with secretion as well as recordings obtained by the optical method. When PGI/sub 2/ (prostacyclin) or PGE/sub 1/ (prostaglandin E/sub 1/) was added to the PRP, both the rate and extent of the increase in light transmittance were inhibited, but the main effect on the increase in impedance was a decrease in its rate and not in its extent. Increases in impedance and secretion of ATP were also measured in whole blood after the platelets had been labeled with a /sup 125/I-containing antibody specific for platelet surface glycoproteins. It appeared that the increases in impedance lagged several minutes behind the formation of platelet aggregates and the secretion of platelet ATP.

  9. Human platelet heparanase: purification, characterization and catalytic activity.

    PubMed Central

    Freeman, C; Parish, C R

    1998-01-01

    Heparan sulphate (HS) is an important component of the extracellular matrix (ECM) and the vasculature basal lamina (BL) which functions as a barrier to the extravasation of metastatic and inflammatory cells. Platelet-tumour cell aggregation at the capillary endothelium results in activation and degranulation of platelets. Cleavage of HS by endoglycosidase or heparanase activity produced in relatively large amounts by the platelets and the invading cells may assist in the disassembly of the ECM and BL, and thereby facilitate cell migration. Using a recently published rapid, quantitative assay for heparanase activity towards HS [Freeman, C. and Parish, C.R. (1997), Biochem. J., 325, 229-237], human platelet heparanase has now been purified 1700-fold to homogeneity in 19% yield by a five column procedure, which consists of concanavalin A-Sepharose, Zn2+-chelating-Sepharose, Blue A-agarose, octyl-agarose and gel filtration chromatography. The enzyme, which was shown to be an endoglucuronidase that degrades both heparin and HS, has a native molecular mass of 50 kDa when analysed by gel filtration chromatography and by SDS/PAGE. Platelet heparanase degraded porcine mucosal HS in a stepwise fashion from a number average molecular mass of 18.5 to 13, to 8 and finally to 4.5 kDa fragments as determined by gel filtration analysis. Bovine lung heparin was degraded from 8.9 to 4.8 kDa while porcine mucosal heparin was degraded from 8.1 kDa to 3.8 and finally to 2.9 kDa fragments. Studies of the enzyme's substrate specificity using modified heparin analogues showed that substrate cleavage required the presence of carboxyl groups, but O- and N-sulphation were not essential. Inhibition studies demonstrated an absolute requirement for the presence of O-sulphate groups. Platelet heparanase was inhibited by heparin analogues which also inhibited tumour heparanase, suggesting that sulphated polysaccharides which inhibit tumour metastasis may act to prevent both tumour cell and

  10. 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.

  11. Inhibitory effect of trichothecene mycotoxins on bovine platelets stimulated by platelet activating factor.

    PubMed Central

    Gentry, P A; Ross, M L; Bondy, G S

    1987-01-01

    Several species of fungi, which infect cereals and grains, can produce a class of compounds, known as trichothecene mycotoxins, which is characterized by a substituted epoxy-trichothecene ring structure. Cattle are susceptible to intoxication from feeds contaminated with T-2 toxin, one of the more potent trichothecene mycotoxins, while swine refuse to ingest feed contaminated with T-2 toxin. The bovine platelet has been used as a model cell system to evaluate the effects of T-2 toxin and its natural metabolites, HT-2 toxin and T-2 tetraol, on cell function in vitro. Due to the lipophilic nature of these mycotoxins, a biologically active phospholipid was used to stimulate the platelets in the presence and absence of the toxins. The mycotoxin T-2 toxin and its major metabolite HT-2 toxin inhibited platelet activating factor-stimulated bovine platelets, suspended in homologous plasma, in a concentration but not time dependent manner. Significant inhibition of platelet function (p less than 0.01) occurred with 135 ng T-2 toxin per 10(6) platelets and with 77 ng HT-2 toxin per 10(6) platelets. These mycotoxins exerted an additive inhibitory effect on the platelet aggregation response. In contrast, the minor metabolite T-2 tetraol had no inhibitory effect on platelet function and had no influence on the responses of T-2 toxin or HT-2 toxin when the mycotoxins were present together in the platelet suspensions.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3453270

  12. Plasma protein regulation of platelet function and metabolism.

    PubMed

    Hansen, M S; Bang, N U

    1979-04-02

    This reviews summarizes our evidence suggesting that the plasma protein enviroment influences platelet aggregation potential and metabolic activity. Cationic proteins are capable of restoring the aggreation potential of washed human platelets. The aggregation restoring effect of gamma globulin is inhibited by more anionic proteins in subfractions of Cohn fraction IV and fractions V and VI. Artificial enhancement of the net negative charge of plasma proteins through acylation produces derivatives capable of inhibiting platelet rich plasma. The oxygen consumption of washed human platelets is lower than in platelet rich plasma while the lactate production is identical. Autologus plasma, albumin or IgG immunoglobulin restores the oxygen consumption of washed platelets to values comparable to those obtained for platelet rich plasma, while the lactate production is unaffected. Fibrinogen on IgA myeloma protein increases the lactate production, but not the oxygen consumption. Cyclic AMP levels are considerably lower in washed platelets than in platelet rich plasma. Gamma globulin and albumin causes a futher decrease, which is progressive with time. Fibrinogen causes no change in platelet cyclic AMP content. It is suggested that these observations may in part be explained by the equilibriun between anionic and cationic proteins in the platelet microenvironment. This hypothesis appears applicable in certain situations.

  13. Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus), Prevents Platelet Activation in Human Platelets.

    PubMed

    Lee, Ye-Ming; Hsieh, Kuo-Hsien; Lu, Wan-Jung; Chou, Hsiu-Chu; Chou, Duen-Suey; Lien, Li-Ming; Sheu, Joen-Rong; Lin, Kuan-Hung

    2012-01-01

    Xanthohumol is the principal prenylated flavonoid in the hop plant (Humulus lupulus L.). Xanthohumol was found to be a very potent cancer chemopreventive agent through regulation of diverse mechanisms. However, no data are available concerning the effects of xanthohumol on platelet activation. The aim of this paper was to examine the antiplatelet effect of xanthohumol in washed human platelets. In the present paper, xanthohumol exhibited more-potent activity in inhibiting platelet aggregation stimulated by collagen. Xanthohumol inhibited platelet activation accompanied by relative [Ca(2+)](i) mobilization, thromboxane A(2) formation, hydroxyl radical (OH(●)) formation, and phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), and Akt phosphorylation. Neither SQ22536, an inhibitor of adenylate cyclase, nor ODQ, an inhibitor of guanylate cyclase, reversed the xanthohumol-mediated inhibitory effect on platelet aggregation. Furthermore, xanthohumol did not significantly increase nitrate formation in platelets. This study demonstrates for the first time that xanthohumol possesses potent antiplatelet activity which may initially inhibit the PI3-kinase/Akt, p38 MAPK, and PLCγ2-PKC cascades, followed by inhibition of the thromboxane A(2) formation, thereby leading to inhibition of [Ca(2+)](i) and finally inhibition of platelet aggregation. Therefore, this novel role of xanthohumol may represent a high therapeutic potential for treatment or prevention of cardiovascular diseases.

  14. Xanthohumol, a Prenylated Flavonoid from Hops (Humulus lupulus), Prevents Platelet Activation in Human Platelets

    PubMed Central

    Lee, Ye-Ming; Hsieh, Kuo-Hsien; Lu, Wan-Jung; Chou, Hsiu-Chu; Chou, Duen-Suey; Lien, Li-Ming; Sheu, Joen-Rong; Lin, Kuan-Hung

    2012-01-01

    Xanthohumol is the principal prenylated flavonoid in the hop plant (Humulus lupulus L.). Xanthohumol was found to be a very potent cancer chemopreventive agent through regulation of diverse mechanisms. However, no data are available concerning the effects of xanthohumol on platelet activation. The aim of this paper was to examine the antiplatelet effect of xanthohumol in washed human platelets. In the present paper, xanthohumol exhibited more-potent activity in inhibiting platelet aggregation stimulated by collagen. Xanthohumol inhibited platelet activation accompanied by relative [Ca2+]i mobilization, thromboxane A2 formation, hydroxyl radical (OH●) formation, and phospholipase C (PLC)γ2, protein kinase C (PKC), mitogen-activated protein kinase (MAPK), and Akt phosphorylation. Neither SQ22536, an inhibitor of adenylate cyclase, nor ODQ, an inhibitor of guanylate cyclase, reversed the xanthohumol-mediated inhibitory effect on platelet aggregation. Furthermore, xanthohumol did not significantly increase nitrate formation in platelets. This study demonstrates for the first time that xanthohumol possesses potent antiplatelet activity which may initially inhibit the PI3-kinase/Akt, p38 MAPK, and PLCγ2-PKC cascades, followed by inhibition of the thromboxane A2 formation, thereby leading to inhibition of [Ca2+]i and finally inhibition of platelet aggregation. Therefore, this novel role of xanthohumol may represent a high therapeutic potential for treatment or prevention of cardiovascular diseases. PMID:22611436

  15. A factor VIII-derived peptide enables von Willebrand factor (VWF)-binding of artificial platelet nanoconstructs without interfering with VWF-adhesion of natural platelets

    NASA Astrophysics Data System (ADS)

    Haji-Valizadeh, Hassan; Modery-Pawlowski, Christa L.; Sen Gupta, Anirban

    2014-04-01

    There is substantial clinical interest in synthetic platelet analogs for potential application in transfusion medicine. To this end, our research is focused on self-assembled peptide-lipid nanoconstructs that can undergo injury site-selective adhesion and subsequently promote site-directed active platelet aggregation, thus mimicking platelet's primary hemostatic actions. For injury site-selective adhesion, we have utilized a coagulation factor FVIII-derived VWF-binding peptide (VBP). FVIII binds to VWF's D'-D3 domain while natural platelet GPIbα binds to VWF's A1 domain. Therefore, we hypothesized that the VBP-decorated nanoconstructs will adhere to VWF without mutual competition with natural platelets. We further hypothesized that the adherent VBP-decorated constructs can enhance platelet aggregation when co-decorated with a fibrinogen-mimetic peptide (FMP). To test these hypotheses, we used glycocalicin to selectively block VWF's A1 domain and, using fluorescence microscopy, studied the binding of fluorescently labeled VBP-decorated nanoconstructs versus platelets to ristocetin-treated VWF. Subsequently, we co-decorated the nanoconstructs with VBP and FMP and incubated them with human platelets to study construct-mediated enhancement of platelet aggregation. Decoration with VBP resulted in substantial construct adhesion to ristocetin-treated VWF even if the A1-domain was blocked by glycocalicin. In comparison, such A1-blocking resulted in significant reduction of platelet adhesion. Without A1-blocking, the VBP-decorated constructs and natural platelets could adhere to VWF concomitantly. Furthermore, the constructs co-decorated with VBP and FMP enhanced active platelet aggregation. The results indicate significant promise in utilizing the FVIII-derived VBP in developing synthetic platelet analogs that do not interfere with VWF-binding of natural platelets but allow site-directed enhancement of platelet aggregation when combined with FMP.There is substantial

  16. Functional platelet defects in children with severe chronic ITP as tested with 2 novel assays applicable for low platelet counts.

    PubMed

    van Bladel, Esther R; Laarhoven, Annemieke G; van der Heijden, Laila B; Heitink-Pollé, Katja M; Porcelijn, Leendert; van der Schoot, C Ellen; de Haas, Masja; Roest, Mark; Vidarsson, Gestur; de Groot, Philip G; Bruin, Marrie C A

    2014-03-06

    Immune thrombocytopenia (ITP) is an autoimmune disease with a complex heterogeneous pathogenesis and a bleeding phenotype that is not necessarily correlated to platelet count. In this study, the platelet function was assessed in a well-defined cohort of 33 pediatric chronic ITP patients. Because regular platelet function test cannot be performed in patients with low platelet counts, 2 new assays were developed to determine platelet function: first, the microaggregation test, measuring in platelets isolated from 10 mL of whole blood the platelet potential to form microaggregates in response to an agonist; second, the platelet reactivity assay, measuring platelet reactivity to adenosine diphosphate (ADP), convulxin (CVX), and thrombin receptor activator peptide in only 150 μL of unprocessed whole blood. Patients with a severe bleeding phenotype demonstrated a decreased aggregation potential upon phorbol myristate acetate stimulation, decreased platelet degranulation following ADP stimulation, and a higher concentration of ADP and CVX needed to activate the glycoprotein IIbIIIa complex compared with patients with a mild bleeding phenotype. In conclusion, here we have established 2 functional tests that allow for evaluation of platelet function in patients with extremely low platelet counts (<10(9)). These tests show that platelet function is related to bleeding phenotype in chronic ITP.

  17. 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

  18. Synthetic materials for platelet quality control.

    PubMed

    Lott, J A; Hartzell, R K; Longberry, J

    1983-01-01

    At present, the quality control of platelet counting by semi-automated and automated methods does not meet ideal standards. Controls prepared from human or animal platelets have limited stability, and some synthetic platelet controls that are available do not have the size distribution of fresh platelets. The platelet control materials described here are wholly synthetic; however, their particle size distribution is like that of normal human platelets, and the dispersing medium has the viscosity and surface tension of plasma. Two types of products are described. The first type are dilutions of the synthetic platelets which are handled like 3000-fold dilutions of platelet-rich plasma and are intended for direct use on instruments like the Coulter ZBI. The two dilution levels gave counts of about 50,000 and 200,000/microL on the Coulter ZBI and were found to be stable for at least 30 days at - 20C, 4C, and 37C, and at least eight months at 25C. The second type of product is handled like whole blood and is intended for direct use on instruments like the Coulter Model S-Plus. This product gave counts of about 200,000/microL and was found to be stable for at least 120 days at - 20C, 4C, 25C, and 37C. Freezing at - 20C produced some aggregates that dispersed after thawing and standing for several days prior to testing.

  19. 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 ...

  20. Hereditary sideroblastic anemia with associated platelet abnormalities.

    PubMed

    Soslau, G; Brodsky, I

    1989-12-01

    A 62 year old male (R.H.) presented with a mild anemia (Hb 11-12 gm%) and a history of multiple hemorrhagic episodes. The marrow had 40-50% sideroblasts. Marrow chromosomes were normal. His wife was hematologically normal, while one daughter, age 30 years, had a sideroblastic anemia (Hb 11-12 gm%) with 40-50% sideroblasts in the marrow. Her anemia was first noted at age 15 years. Administration of vitamin B6 did not correct the anemia in either the father or daughter. Platelet abnormalities inherited jointly with this disorder are described for the first time. Both R.H. and his daughter had prolonged bleeding times, with normal PTT, PT times, fVIII:C, fVIII:Ag levels, and vWF multimers, which may rule out a von Willebrand's disease. They have normal platelet numbers but abnormally low platelet adhesiveness and greatly depressed ADP, collagen, and epinephrine responsiveness. Response to ristocetin was in the low normal range, and aggregation with thrombin was normal. While desmopressin completely normalized R.H.'s bleeding time, none of these platelet parameters were improved. No differences in the SDS PAGE protein patterns of RH platelets could be detected in comparison to normal samples. His platelets took up and released serotonin (5HT) normally, and electron micrographs defined no morphological abnormalities. However, no ATP was released from platelets activated with collagen, and when followed by thrombin about fourfold greater ATP was released by control platelets as compared to RH platelets. The dense granule fraction derived from RH platelets contained about 20% the level of ATP, 40% the level of ADP, and 50% the level of 5HT detected in a normal sample. The results indicate that the bleeding disorder is related to a non-classical heritable storage pool defect. The connection between the inherited sideroblastic anemia and platelet defects is obscure.

  1. 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

  2. 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.

  3. 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.

  4. Grow with the flow: a spatial–temporal model of platelet deposition and blood coagulation under flow

    PubMed Central

    Leiderman, Karin; Fogelson, Aaron L.

    2011-01-01

    The body's response to vascular injury involves two intertwined processes: platelet aggregation and coagulation. Platelet aggregation is a predominantly physical process, whereby platelets clump together, and coagulation is a cascade of biochemical enzyme reactions. Thrombin, the major product of coagulation, directly couples the biochemical system to platelet aggregation by activating platelets and by cleaving fibrinogen into fibrin monomers that polymerize to form a mesh that stabilizes platelet aggregates. Together, the fibrin mesh and the platelet aggregates comprise a thrombus that can grow to occlusive diameters. Transport of coagulation proteins and platelets to and from an injury is controlled largely by the dynamics of the blood flow. To explore how blood flow affects the growth of thrombi and how the growing masses, in turn, feed back and affect the flow, we have developed the first spatial–temporal mathematical model of platelet aggregation and blood coagulation under flow that includes detailed descriptions of coagulation biochemistry, chemical activation and deposition of blood platelets, as well as the two-way interaction between the fluid dynamics and the growing platelet mass. We present this model and use it to explain what underlies the threshold behaviour of the coagulation system's production of thrombin and to show how wall shear rate and near-wall enhanced platelet concentrations affect the development of growing thrombi. By accounting for the porous nature of the thrombus, we also demonstrate how advective and diffusive transport to and within the thrombus affects its growth at different stages and spatial locations. PMID:20439306

  5. 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.

  6. Platelet lipidomics: a modern day perspective on lipid discovery and characterization in platelets

    PubMed Central

    O’Donnell, Valerie B; Murphy, Robert C.; Watson, Steve P

    2014-01-01

    Lipids are diverse families of biomolecules that perform essential structural and signaling roles in platelets. Their formation and metabolism is tightly controlled by enzymes and signal transduction pathways, and their dysregulation leads to significant defects in platelet function and disease. Platelet activation is associated with significant changes to membrane lipids, and formation of diverse bioactive lipids that play essential roles in hemostasis. In recent years, new generation mass spectrometry analysis of lipids (termed “lipidomics”) has begun to alter our understanding of how these molecules participate in key cellular processes. While, the application of lipidomics to platelet biology is still in its infancy, seminal earlier studies have shaped our knowledge of how lipids regulate key aspects of platelet biology, including aggregation, shape change, coagulation and degranulation, as well as how lipids generated by platelets influence other cells, such as leukocytes and the vascular wall, and thus how they regulate hemostasis, vascular integrity and inflammation, as well as contribute to pathologies including arterial/deep vein thrombosis and atherosclerosis. This review will provide a brief historical perspective on the characterization of lipids in platelets, then an overview of the new generation lipidomic approaches, their recent application to platelet biology, and future perspectives for research in this area. The major platelet-regulatory lipid families, their formation, metabolism, and their role in health and disease, will be summarized. PMID:24677238

  7. Optimized preparation method of platelet-concentrated plasma and noncoagulating platelet-derived factor concentrates: maximization of platelet concentration and removal of fibrinogen.

    PubMed

    Araki, Jun; Jona, Masahiro; Eto, Hitomi; Aoi, Noriyuki; Kato, Harunosuke; Suga, Hirotaka; Doi, Kentaro; Yatomi, Yutaka; Yoshimura, Kotaro

    2012-03-01

    Platelet-rich plasma (PRP) has been clinically used as an easily prepared growth factor cocktail that can promote wound healing, angiogenesis, and tissue remodeling. However, the therapeutic effects of PRP are still controversial, due partly to the lack of optimized and standardized preparation protocols. We used whole blood (WB) samples to optimize the preparation protocols for PRP, white blood cell-containing (W-PRP), platelet-concentrated plasma (PCP), and noncoagulating platelet-derived factor concentrate (PFC). PRP and W-PRP were most efficiently collected by 10 min centrifugation in a 15-mL conical tube at 230-270 g and 70 g, respectively. To prepare PCP, platelets were precipitated by centrifugation of PRP at >2300 g, 90% of supernatant plasma was removed, and the platelets were resuspended. For preparation of noncoagulating PFC, the supernatant was replaced with one-tenth volume of saline, followed by platelet activation with thrombin. Platelet (before activation) and platelet-derived growth factor (PDGF)-BB (after activation) concentrations in PCP were approximately 20 times greater than those in WB, whereas PFC contained a 20-times greater concentration of platelets before platelet activation and a 50-times greater concentration of PDGF-BB without formation of a fibrin gel after platelet activation than WB. Surprisingly, total PDGF-BB content in the PFC was twice that of activated WB, which suggested that a substantial portion of the PDGF-BB became trapped in the fibrin glue, and replacement of plasma with saline is crucial for maximization of platelet-derived factors. As an anticoagulant, ethylene di-amine tetra-acetic acid disodium inhibited platelet aggregation more efficiently than acid citrate dextrose solution, resulting in higher nonaggregated platelet yield and final PDGF-BB content. These results increase our understanding of how to optimize and standardize preparation of platelet-derived factors at maximum concentrations.

  8. Assessment of platelet function in healthy sedated cats using three whole blood platelet function tests.

    PubMed

    Ho, Kimberly K; Abrams-Ogg, Anthony C G; Wood, R Darren; O'Sullivan, M Lynne; Kirby, Gordon M; Blois, Shauna L

    2015-05-01

    The objectives of this study were to establish feline references intervals for 3 commercial whole blood platelet function test analyzer systems: Multiplate analyzer (MP; Roche Diagnostics International Ltd., Rotkreuz, Switzerland), Platelet Function Analyzer-100 (PF: Siemens Canada, Mississauga, Ontario, Canada), and Plateletworks Combo-25 kit (PW; Helena Laboratories, Beaumont, TX). Venipuncture was performed on 55 healthy sedated cats, and platelet aggregation in response to adenosine diphosphate (ADP), collagen (COL), and arachidonic acid (AA; MP only) was assessed using citrated blood. For the MP analyzer, median (95% confidence intervals [CIs]) area under curve (Units) for ADP, COL, and AA agonists were 87 (11-176), 81 (32-129), and 91 (59-129), respectively. For the PF analyzer, median (95% CIs) closure time, using COL-ADP cartridges, was 69 (46-89) sec. For the PW assay, median (95% CIs) percent aggregations for ADP and COL agonists were 71 (18-92) and 49 (9-96), respectively, using impedance hematology analyzer platelet counts, and 94 (25-98) and 68 (14-119), respectively, using flow cytometry hematology analyzer platelet counts. There were low correlations between the PF analyzer (COL-ADP cartridge) and MP analyzer (COL agonist; ρ = 0.11), and between the PF analyzer (COL-ADP cartridge) and PW assay (COL agonist using impedance platelet counts; ρ = 0.14). The PW assay percent aggregations using impedance and flow cytometric platelet counts were correlated for both ADP (ρ = 0.64) and COL (ρ = 0.64) agonists. Platelet function testing using these tests are feasible in cats, but 95% CIs are wide, so single results may be difficult to interpret. Platelet counting by impedance or flow cytometry may be used for the PW assay but are not interchangeable.

  9. 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.

  10. Platelet-derived microparticles and platelet function profile in children with congenital heart disease.

    PubMed

    Ismail, Eman Abdel Rahman; Youssef, Omneya Ibrahim

    2013-01-01

    Platelet microparticles (PMPs) and function profile in children with congenital heart disease (CHD) have not been widely explored. We investigated platelet aggregation, flow cytometric platelet surface receptors (P-selectin and glycoprotein (GP) IIb/IIIa) and PMPs in 23 children with cyanotic CHD (CCHD), 30 children with acyanotic CHD (ACHD) and 30 healthy controls correlating these variables to hematological and coagulation parameters including von Willebrand factor antigen (vWF Ag) as a marker of endothelial dysfunction. Hemoglobin, hematocrit (HCT), D-dimer, and vWF Ag were significantly higher in CCHD than ACHD group. Platelet MPs and P-selectin expression were increased in patients than controls, particularly in CCHD and positively correlated to HCT, D-dimer, and vWF Ag while platelet count, aggregation, and GP IIb/IIIa expression were decreased in CCHD compared with ACHD group and negatively correlated to HCT. The overproduction of PMPs and platelet activation with suppressed aggregation may be implicated in the pathogenesis of coagulation/hemostatic abnormalities in children with CCHD.

  11. Platelets possess functional TGF-beta receptors and Smad2 protein.

    PubMed

    Lev, P R; Salim, J P; Marta, R F; Osorio, M J Mela; Goette, N P; Molinas, F C

    2007-02-01

    TGF-beta1 plays a main role in tissue repair by regulating extracellular matrix production and tissue granulation. Platelets are one of the main sources of this cytokine in the circulation. The aim of this study was to evaluate the presence of the TGF-beta receptors on platelets, the effect of TGF-beta1 on platelet aggregation and the underlying intracellular mechanisms. TGF-beta receptors on platelets were studied by flow cytometry and their mRNA by PCR. Platelet aggregation was assessed by turbidimetric methods and intracellular pathways by Western blot. TGF-beta receptor type II and mRNA codifying for TbetaRI and TbetaRII were found in platelets. We demonstrated that TGF-beta1 did not trigger platelet aggregation by itself but had a modulating effect on ADP-induced platelet aggregation. Either inhibition or increase in platelet aggregation, depending on the exposure time to TGF-beta1 and the ADP concentration used, were shown. We found that platelets possess Smad2 protein and that its phosphorylation state is increased after exposure to TGF-beta1. Besides, TGF-beta1 modified the pattern of ADP-induced tyrosine phosphorylation. Increased phosphorylation levels of 64-, 80- and 125-kDa proteins during short time incubation with TGF-beta1 and increased phosphorylation of 64- and 125-kDa proteins after longer incubation were observed. The modulating effect of TGF-beta1 on platelet aggregation could play a role during pathological states in which circulating TGF-beta1 levels are increased and intravascular platelet activation is present, such as myeloproliferative disorders. In vascular injury, in which platelet activation followed by granule release generates high local ADP concentrations, it could function as a physiological mechanism of platelet activation control.

  12. Platelet Dysfunction in Patients with Chronic Myeloid Leukemia: Does Imatinib Mesylate Improve It?

    PubMed Central

    Akay, Olga Meltem; Mutlu, Fezan; Gülbaş, Zafer

    2016-01-01

    Objective: The aim of this study was to investigate the effects of imatinib mesylate on platelet aggregation and adenosine triphosphate (ATP) release in chronic myeloid leukemia patients. Materials and Methods: Platelet aggregation and ATP release induced by 5.0 mM adenosine diphosphate, 0.5 mM arachidonic acid, 1.0 mg/mL ristocetin, and 2 µg/mL collagen were studied by whole blood platelet lumi-aggregometer in 20 newly diagnosed chronic myeloid leukemia patients before and after imatinib mesylate treatment. Results: At the time of diagnosis, 17/20 patients had abnormal platelet aggregation results; 8 (40%) had hypoactivity, 6 (30%) had hyperactivity, and 3 (15%) had mixed hypo- and hyperactivity. Repeat platelet aggregation studies were performed after a mean of 19 months (min: 5 months-max: 35 months) in all patients who received imatinib mesylate during this period. After therapy, 18/20 (90%) patients had abnormal laboratory results; 12 (60%) had hypoactive platelets, 4 (20%) had mixed hypo- and hyperactive platelets, and 2 (10%) had hyperactive platelets. Three of the 8 patients with initial hypoactivity remained hypoactive, while 2 developed a mixed picture, 2 became hyperactive, and 1 normalized. Of the 6 patients with initial hyperactivity, 4 became hypoactive and 2 developed a mixed pattern. All of the 3 patients with initial hypo- and hyperactivity became hypoactive. Finally, 2 of the 3 patients with initial normal platelets became hypoactive while 1 remained normal. There was a significant decrease in ristocetin-induced platelet aggregation after therapy (p<0.001), while platelet aggregation and secretion induced by other agonists showed no difference after treatment (p>0.05). Conclusion: These findings indicate that a significant proportion of chronic myeloid leukemia patients have different patterns of platelet function abnormalities and imatinib mesylate has no effect on these abnormalities, with a significant impairment in ristocetin-induced platelet

  13. 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

  14. 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.

  15. 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

  16. 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

  17. External quality assessment of platelet disorder investigations: results of international surveys on diagnostic tests for dense granule deficiency and platelet aggregometry interpretation.

    PubMed

    Hayward, Catherine P M; Moffat, Karen A; Plumhoff, Elizabeth; Timleck, Marnie; Hoffman, Suzanne; Spitzer, Ernie; Van Cott, Elizabeth M; Meijer, Piet

    2012-09-01

    The quality of platelet aggregation and dense granule deficiency testing is important for diagnosing platelet function disorders. After a successful pilot exercise on diagnosing platelet dense granule deficiency by electron microscopy (EM), the North American Specialized Coagulation Laboratory Association (NASCOLA) has launched regular external quality assurance (EQA) for dense granule EM, as well as for the interpretation of platelet aggregation findings. EQA records were analyzed to assess performance. For EM EQA, between 2009 and 2011, there was excellent performance in distinguishing normal from dense granule-deficient samples and good (>70%) agreement on classifying most electron dense structures in platelets. For aggregation EQA, some normal variants were misclassified and overall case interpretations were more acceptable for rare disorders than for common findings. NASCOLA experiences with these EQAs indicate that there is a need to improve the quality of platelet disorder evaluations. For aggregometry interpretations, deficits in performance could be addressed by translating guideline recommendations into practice.

  18. A colorimetric method for the measurement of platelet adhesion in microtiter plates.

    PubMed

    Bellavite, P; Andrioli, G; Guzzo, P; Arigliano, P; Chirumbolo, S; Manzato, F; Santonastaso, C

    1994-02-01

    A procedure for the determination of the adhesion of human platelets to protein-coated culture microwells was developed. The number of platelets was quantitated by measuring the activity of acid phosphatase, a platelet enzyme whose activity is stable independently of platelet stimulation and is not released. Isolated and washed platelets were incubated in 96-well microtiter plates with flat-bottom wells that had been precoated with various compounds, including collagen, fibrinogen, human plasma, and human albumin. At the end of incubation (optimal time: 40-60 min), nonadherent platelets were washed out, adherent platelets were solubilized with Triton X-100, and the acid phosphatase activity was measured by using the substrate p-nitrophenyl phosphate. The p-nitrophenol produced was measured with a microplate reader at 405 nm and the percentage of adhesion was calculated with reference to known platelet standards. ADP and thrombin stimulated platelet adhesion in a dose-dependent manner to fibrinogen and human plasma, but not to human albumin. Platelets adhered to collagen even in the absence of stimulants. Simultaneous evaluation of adhesion and aggregation demonstrated that with ADP as stimulus, but not with thrombin, the two platelet responses were dissociated. Microscopic examination of culture wells showed that most of platelets adhered as single cells and not as aggregates. The sensitivity of this method allowed the assay of platelet adhesion by using only 2.5 x 10(5) platelets/well.

  19. Cangrelor attenuates coated-platelet formation.

    PubMed

    Norgard, Nicholas B; Hann, Callie L; Dale, George L

    2009-01-01

    P2Y(12) inhibitors were introduced clinically as effective inhibitors of adenosine-5'-diphosphate (ADP) mediated platelet activation and aggregation. This class of pharmacological agents has enjoyed considerable success. Cangrelor is a recently developed P2Y(12) inhibitor that has the advantage of being an active drug not requiring metabolic conversion, although it is not orally available. Coated-platelets are a subclass of activated platelets generated on dual agonist activation with collagen plus thrombin; the primary hallmark of coated-platelets is their ability to support prothrombinase activity. Interestingly, we recently observed that the relatively weak agonist ADP potentiates the production of coated-platelets by the very strong agonists collagen plus thrombin, a previously unknown role for ADP. The authors sought in this study to determine if P2Y(12) inhibitors, such as cangrelor, were capable of attenuating this augmentation of coated-platelet generation. Cangrelor, at physiologically relevant concentrations, was able to eliminate the ADP-dependent increase in coated-platelet production with an IC(50) of 1.4 nM. Cangrelor, however, had no effect on thrombin-dependent platelet activation as measured by P-selectin expression. Although this in vitro study does not address the question of whether the effectiveness of cangrelor in vivo is partially due to an attenuation of coated-platelet production in addition to its documented antiaggregatory effects, it does reveal an unexpected action of cangrelor. Additional studies will be required to determine if all P2Y(12) inhibitors are equally effective in attenuating coated-platelet production.

  20. Novel mutations in RASGRP2, which encodes CalDAG-GEFI, abrogate Rap1 activation, causing platelet dysfunction.

    PubMed

    Lozano, María Luisa; Cook, Aaron; Bastida, José María; Paul, David S; Iruin, Gemma; Cid, Ana Rosa; Adan-Pedroso, Rosa; Ramón González-Porras, José; Hernández-Rivas, Jesús María; Fletcher, Sarah J; Johnson, Ben; Morgan, Neil; Ferrer-Marin, Francisca; Vicente, Vicente; Sondek, John; Watson, Steve P; Bergmeier, Wolfgang; Rivera, José

    2016-09-01

    In addition to mutations in ITG2B or ITGB3 genes that cause defective αIIbβ3 expression and/or function in Glanzmann's thrombasthenia patients, platelet dysfunction can be a result of genetic variability in proteins that mediate inside-out activation of αIIbβ3 The RASGRP2 gene is strongly expressed in platelets and neutrophils, where its encoded protein CalDAG-GEFI facilitates the activation of Rap1 and subsequent activation of integrins. We used next-generation sequencing (NGS) and whole-exome sequencing (WES) to identify 2 novel function-disrupting mutations in RASGRP2 that account for bleeding diathesis and platelet dysfunction in 2 unrelated families. By using a panel of 71 genes, we identified a homozygous change (c.1142C>T) in exon 10 of RASGRP2 in a 9-year-old child of Chinese origin (family 1). This variant led to a p.Ser381Phe substitution in the CDC25 catalytic domain of CalDAG-GEFI. In 2 Spanish siblings from family 2, WES identified a nonsense homozygous variation (c.337C>T) (p.Arg113X) in exon 5 of RASGRP2 CalDAG-GEFI expression was markedly reduced in platelets from all patients, and by using a novel in vitro assay, we found that the nucleotide exchange activity was dramatically reduced in CalDAG-GEFI p.Ser381Phe. Platelets from homozygous patients exhibited agonist-specific defects in αIIbβ3 integrin activation and aggregation. In contrast, α- and δ-granule secretion, platelet spreading, and clot retraction were not markedly affected. Integrin activation in the patients' neutrophils was also impaired. These patients are the first cases of a CalDAG-GEFI deficiency due to homozygous RASGRP2 mutations that are linked to defects in both leukocyte and platelet integrin activation.

  1. Novel mutations in RASGRP2, which encodes CalDAG-GEFI, abrogate Rap1 activation, causing platelet dysfunction

    PubMed Central

    Lozano, María Luisa; Cook, Aaron; Bastida, José María; Paul, David S.; Iruin, Gemma; Cid, Ana Rosa; Adan-Pedroso, Rosa; Ramón González-Porras, José; Hernández-Rivas, Jesús María; Fletcher, Sarah J.; Johnson, Ben; Morgan, Neil; Ferrer-Marin, Francisca; Vicente, Vicente; Sondek, John; Watson, Steve P.; Bergmeier, Wolfgang

    2016-01-01

    In addition to mutations in ITG2B or ITGB3 genes that cause defective αIIbβ3 expression and/or function in Glanzmann’s thrombasthenia patients, platelet dysfunction can be a result of genetic variability in proteins that mediate inside-out activation of αIIbβ3. The RASGRP2 gene is strongly expressed in platelets and neutrophils, where its encoded protein CalDAG-GEFI facilitates the activation of Rap1 and subsequent activation of integrins. We used next-generation sequencing (NGS) and whole-exome sequencing (WES) to identify 2 novel function-disrupting mutations in RASGRP2 that account for bleeding diathesis and platelet dysfunction in 2 unrelated families. By using a panel of 71 genes, we identified a homozygous change (c.1142C>T) in exon 10 of RASGRP2 in a 9-year-old child of Chinese origin (family 1). This variant led to a p.Ser381Phe substitution in the CDC25 catalytic domain of CalDAG-GEFI. In 2 Spanish siblings from family 2, WES identified a nonsense homozygous variation (c.337C>T) (p.Arg113X) in exon 5 of RASGRP2. CalDAG-GEFI expression was markedly reduced in platelets from all patients, and by using a novel in vitro assay, we found that the nucleotide exchange activity was dramatically reduced in CalDAG-GEFI p.Ser381Phe. Platelets from homozygous patients exhibited agonist-specific defects in αIIbβ3 integrin activation and aggregation. In contrast, α- and δ-granule secretion, platelet spreading, and clot retraction were not markedly affected. Integrin activation in the patients’ neutrophils was also impaired. These patients are the first cases of a CalDAG-GEFI deficiency due to homozygous RASGRP2 mutations that are linked to defects in both leukocyte and platelet integrin activation. PMID:27235135

  2. Role of oxidative stress on platelet hyperreactivity during aging.

    PubMed

    Fuentes, Eduardo; Palomo, Iván

    2016-03-01

    Thrombotic events are common causes of morbidity and mortality in the elderly. Age-accelerated vascular injury is commonly considered to result from increased oxidative stress. There is abundant evidence that oxidative stress regulate several components of thrombotic processes, including platelet activation. Thus oxidative stress can trigger platelet hyperreactivity by decreasing nitric oxide bioavailability. Therefore oxidative stress measurement may help in the early identification of asymptomatic subjects at risk of thrombosis. In addition, oxidative stress inhibitors and platelet-derived nitric oxide may represent a novel anti-aggregation/-activation approach. In this article the relative contribution of oxidative stress and platelet activation in aging is explored.

  3. 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.

  4. Effects of drugs on platelet function.

    PubMed

    Morse, E E

    1977-01-01

    Numerous drugs and chemicals affect the function of human blood platelets. The mechanism of action of some medications is partly understood. Aspirin is the most frequently involved drug. It appears to interfere with the platelet release reaction by acetylation of a platelet membrane protein which may be involved in the synthesis of prostaglandins. Other anti-inflammatory drugs, including indomethacin, phenylbutazone, ibuprophen (Motrin) and clonixin, also interfere with the release reaction but have a shorter acting course than aspirin. Some drugs stimulate adenylcyclase (gliclazide) or block phosphodiesterase, (dipyridamole, caffeine) both of which actions lead to an increase in adenosine cyclic 3':5' monophosphate (cAMP) and decrease aggregation by adenosine diphosphate (ADP). These interactions should be known to clinical scientists since patients using these medicaments may manifest abnormal platelet function tests in the laboratory and mild hemorrhagic syndromes in the clinic.

  5. Microfluidics for simultaneous quantification of platelet adhesion and blood viscosity

    PubMed Central

    Yeom, Eunseop; Park, Jun Hong; Kang, Yang Jun; Lee, Sang Joon

    2016-01-01

    Platelet functions, including adhesion, activation, and aggregation have an influence on thrombosis and the progression of atherosclerosis. In the present study, a new microfluidic-based method is proposed to estimate platelet adhesion and blood viscosity simultaneously. Blood sample flows into an H-shaped microfluidic device with a peristaltic pump. Since platelet aggregation may be initiated by the compression of rotors inside the peristaltic pump, platelet aggregates may adhere to the H-shaped channel. Through correlation mapping, which visualizes decorrelation of the streaming blood flow, the area of adhered platelets (APlatelet) can be estimated without labeling platelets. The platelet function is estimated by determining the representative index IA·T based on APlatelet and contact time. Blood viscosity is measured by monitoring the flow conditions in the one side channel of the H-shaped device. Based on the relation between interfacial width (W) and pressure ratio of sample flows to the reference, blood sample viscosity (μ) can be estimated by measuring W. Biophysical parameters (IA·T, μ) are compared for normal and diabetic rats using an ex vivo extracorporeal model. This microfluidic-based method can be used for evaluating variations in the platelet adhesion and blood viscosity of animal models with cardiovascular diseases under ex vivo conditions. PMID:27118101

  6. 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.

  7. Modified expression of surface glyconjugates in stored human platelets

    SciTech Connect

    Dhar, A.; Ganguly, P.

    1987-05-01

    Platelets are anucleated cells which play an important part in blood coagulation and thrombosis. These cells may be stored in the blood bank for only 4/5 days. In order to improve the storage of platelets, it is essential to first understand the changes in these cells due to storage. In this work, human platelets were stored in autologous plasma at 4/sup 0/ or 22/sup 0/ and their surface changes were monitored with three lectins - wheat germ afflutinin (WGA), concanavalin A (Con A) and lentil lectin (LL). Blood was drawn from healthy donors and platelet rich plasma (PRP) was collected by slow speed centrifugation. Platelets stored at either temperature for different times showed increased sensitivity to agglutination by WGA after 34-48 hrs. Lectins, Con A and LL, which were not agglutinating to fresh platelets readily caused agglutination after 48-72 hrs. The platelets stored for 25 hrs or longer period were insensitive to thrombin but showed enhanced aggregation with WGA. Labelling of surface glycoconjugates of stored platelets with /sup 3/H-boro-hydride revealed progressive loss of a glycoprotein of Mr 150,000 (GPIb infinity) together with the appearance of components of Mr 69,000; Mr 60,000; Mr 25,000. New high molecular weight glycoproteins were also detected only in stored platelets. The author studies clearly indicate that modification or altered expression of platelets surface glycoproteins may be one factor of storage related dysfunction of platelets.

  8. 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.

  9. Influence of gold nanoparticles on platelets functional activity in vitro

    NASA Astrophysics Data System (ADS)

    Akchurin, Garif G.; Akchurin, George G.; Ivanov, Alexey N.; Kirichuk, Vyacheslav F.; Terentyuk, George S.; Khlebtsov, Boris N.; Khlebtsov, Nikolay G.

    2008-02-01

    Now in the leading biomedical centers of the world approved new technology of laser photothermal destruction of cancer cells using plasmon gold nanoparticles. Investigations of influence of gold nanoparticles on white rat platelets aggregative activity in vitro have been made. Platelet aggregation was investigated in platelet rich plasma (PRP) with help of laser analyzer 230 LA <>, Russia). Aggregation inductor was ADP solution in terminal concentration 2.5 micromole (<>, Russia). Gold nanoshells soluted in salt solution were used for experiments. Samples of PRP were incubated with 50 or 100 μl gold nanoshells solution in 5 minute, after that we made definition ADP induced platelet aggregation. We found out increase platelet function activity after incubation with nanoparticles solution which shown in maximum ADP-induced aggregation degree increase. Increase platelet function activity during intravenous nanoshells injection can be cause of thrombosis on patients. That's why before clinical application of cancer cell destruction based on laser photothermal used with plasmon gold nanoparticles careful investigations of thrombosis process and detail analyze of physiological blood parameters are very necessary.

  10. 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.

  11. [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.

  12. Macrothrombocytopenia: investigating the ultrastructure of platelets and fibrin networks using scanning and transmission electron microscopy.

    PubMed

    Pretorius, Etheresia; Oberholzer, Hester M; van der Spuy, Wendy J; Meiring, Johannes H

    2009-10-01

    Macrothrombocytopenia is a rare condition where large, circulating platelets ranging between approximately 5 and 20 microm are found (typically platelets size range from 1.5 to 2.5 microm). The condition is also characterized by the prevalence of decreased numbers of circulating platelets, bleeding, short circulating times in blood, as well as abnormal platelet destruction. The current research investigates the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of platelet aggregates and fibrin networks of a family diagnosed with macrothrombocytopenia. Although TEM analysis of macrothrombocytopenia is not novel, little is known regarding the SEM analysis of platelet aggregates and fibrin networks. Here the authors show that macrothrombocytopenia have two different variations of giant platelet aggregates: a bulbous, giant aggregate that is very similar to control aggregates, and a giant flattened aggregate, with a compressed outer rim and a centrally placed area that forms a bulbous pseudopodia-like core. TEM micrographs of controls showed that, as previously seen in the literature, an aggregate contains dense bodies and alpha granules that carry, among other compounds, fibrinogen. TEM micrographs of the individuals with macrothrombocytopenia revealed aggregates with large vacuoles and areas mostly devoid of dense bodies and alpha granules. An interesting observation was that, in the presence of added human thrombin (to initially form the clot), fibrin fiber networks, comparable to that of control fibrin networks, were formed. This might be of clinical interest in the treatment regime and should be investigated further.

  13. Thrombotic thrombocytopenic purpura: a syndrome of intravascular platelet consumption.

    PubMed Central

    Neame, P. B.; Hirsh, J.; Browman, G.; Denburg, J.; D'Souza, T. J.; Gallus, A.; Brain, M. C.

    1976-01-01

    In four of five patients with thrombotic thrombocytopenic purpura (TTP) in whom serial tests of hemostatic function were performed, severe thrombocytopenia, normal plasma fibrinogen concentrations and mildly increased concentrations of fibrinogen/fibrin degradation products were observed. Widespread platelet thrombi were found in arterioles and capillaries. Fibrin could be seen around some of the platelet clumps and was the main component in a small number of the thrombi in two patients. The observations show that TTP is a disorder in which intravascular platelet consumption results in disseminated platelet thrombosis. The coagulation system is apparently activated secondarily to platelet aggregation and variable quantities of fibrin are incorporated into the thrombi. Clinical improvement resulted from combined therapy with corticosteroids, heparin and drugs that suppress platelet function. Images FIG. 3 FIG. 4 FIG. 5 FIG. 6 PMID:1084215

  14. 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.

  15. Nonmuscle Myosin IIA Regulates Platelet Contractile Forces Through Rho Kinase and Myosin Light-Chain Kinase.

    PubMed

    Feghhi, Shirin; Tooley, Wes W; Sniadecki, Nathan J

    2016-10-01

    Platelet contractile forces play a major role in clot retraction and help to hold hemostatic clots against the vessel wall. Platelet forces are produced by its cytoskeleton, which is composed of actin and nonmuscle myosin filaments. In this work, we studied the role of Rho kinase, myosin light-chain kinase, and myosin in the generation of contractile forces by using pharmacological inhibitors and arrays of flexible microposts to measure platelet forces. When platelets were seeded onto microposts, they formed aggregates on the tips of the microposts. Forces produced by the platelets in the aggregates were measured by quantifying the deflection of the microposts, which bent in proportion to the force of the platelets. Platelets were treated with small molecule inhibitors of myosin activity: Y-27632 to inhibit the Rho kinase (ROCK), ML-7 to inhibit myosin light-chain kinase (MLCK), and blebbistatin to inhibit myosin ATPase activity. ROCK inhibition reduced platelet forces, demonstrating the importance of the assembly of actin and myosin phosphorylation in generating contractile forces. Similarly, MLCK inhibition caused weaker platelet forces, which verifies that myosin phosphorylation is needed for force generation in platelets. Platelets treated with blebbistatin also had weaker forces, which indicates that myosin's ATPase activity is necessary for platelet forces. Our studies demonstrate that myosin ATPase activity and the regulation of actin-myosin assembly by ROCK and MLCK are needed for the generation of platelet forces. Our findings illustrate and explain the importance of myosin for clot compaction in hemostasis and thrombosis.

  16. 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 signif