Journal articles on the topic 'Platelet aggregation'
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1
Sugiyama, T., M. Okuma, F. Ushikubi, S. Sensaki, K. Kanaji, and H. Uchino. "A novel platelet aggregating factor found in a patient with defective collagen-induced platelet aggregation and autoimmune thrombocytopenia." Blood 69, no. 6 (June 1, 1987): 1712–20. http://dx.doi.org/10.1182/blood.v69.6.1712.1712.
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Abstract We found a novel platelet aggregating factor in a patient with steroid- responsive immune thrombocytopenic purpura that is associated with defective collagen-induced platelet functions. The aggregating factor and platelet functions were analyzed. The patient, a 58-year-old female, had purpura and prolonged bleeding time despite adequate platelet counts (greater than 140,000/microL) after steroid therapy. The patient's platelets responded normally to all agonists except collagen. Platelet adhesion to collagen fibrils was decreased. The patient's plasma induced irreversible aggregation and ATP release in normal platelet-rich plasma (PRP). This platelet aggregating factor was found in F(ab')2 fragments of the patient's IgG, which caused thromboxane B2 synthesis, elevation of cytoplasmic Ca2+ levels, and phosphorylation of 40 kDa protein in normal platelets. Platelet aggregation by the patient's IgG was inhibited by prostacyclin, dibutyryl cAMP, diltiazem, disodium ethylenediaminetetraacetate, and antimycin A plus iodoacetate, but ADP scavengers, cyclo-oxygenase inhibitors, and heparin had little or no effect. The aggregating activity of the patient's IgG absorbed to and eluted from normal platelets. The patient's Fab fragments did not induce platelet aggregation in eight of ten normal PRP but specifically inhibited aggregation induced by collagen and by the patient's IgG. The major component of an immunoprecipitate made with the patient's IgG from radiolabeled membrane proteins of normal platelet extract had a 62 kDa mol wt, while no such precipitate appeared in extracts of the patient's platelets. These results indicated that platelet aggregation by the patient's IgG was induced by the reaction of an antibody with a specific antigen on the normal platelet membrane through stimulus- response coupling. This antigen may be a collagen receptor on the platelet, most likely a polypeptide of 62 kDa under reducing condition. The defect of collagen-induced aggregation of the patient's platelets seemed to be due to alteration of the membrane protein related to this putative collagen receptor.
2
Sugiyama, T., M. Okuma, F. Ushikubi, S. Sensaki, K. Kanaji, and H. Uchino. "A novel platelet aggregating factor found in a patient with defective collagen-induced platelet aggregation and autoimmune thrombocytopenia." Blood 69, no. 6 (June 1, 1987): 1712–20. http://dx.doi.org/10.1182/blood.v69.6.1712.bloodjournal6961712.
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We found a novel platelet aggregating factor in a patient with steroid- responsive immune thrombocytopenic purpura that is associated with defective collagen-induced platelet functions. The aggregating factor and platelet functions were analyzed. The patient, a 58-year-old female, had purpura and prolonged bleeding time despite adequate platelet counts (greater than 140,000/microL) after steroid therapy. The patient's platelets responded normally to all agonists except collagen. Platelet adhesion to collagen fibrils was decreased. The patient's plasma induced irreversible aggregation and ATP release in normal platelet-rich plasma (PRP). This platelet aggregating factor was found in F(ab')2 fragments of the patient's IgG, which caused thromboxane B2 synthesis, elevation of cytoplasmic Ca2+ levels, and phosphorylation of 40 kDa protein in normal platelets. Platelet aggregation by the patient's IgG was inhibited by prostacyclin, dibutyryl cAMP, diltiazem, disodium ethylenediaminetetraacetate, and antimycin A plus iodoacetate, but ADP scavengers, cyclo-oxygenase inhibitors, and heparin had little or no effect. The aggregating activity of the patient's IgG absorbed to and eluted from normal platelets. The patient's Fab fragments did not induce platelet aggregation in eight of ten normal PRP but specifically inhibited aggregation induced by collagen and by the patient's IgG. The major component of an immunoprecipitate made with the patient's IgG from radiolabeled membrane proteins of normal platelet extract had a 62 kDa mol wt, while no such precipitate appeared in extracts of the patient's platelets. These results indicated that platelet aggregation by the patient's IgG was induced by the reaction of an antibody with a specific antigen on the normal platelet membrane through stimulus- response coupling. This antigen may be a collagen receptor on the platelet, most likely a polypeptide of 62 kDa under reducing condition. The defect of collagen-induced aggregation of the patient's platelets seemed to be due to alteration of the membrane protein related to this putative collagen receptor.
3
Teng, Che-Ming, Ya-Fei Kang, Ya-Ling Chang, Feng-Nien Ko, Shu-Chen Yang, and Feng-Lin Hsu. "ADP-mimicking Platelet Aggregation Caused by Rugosin E, an Ellagitannin Isolated from Rosa rugosa Thunb." Thrombosis and Haemostasis 77, no. 03 (1997): 555–61. http://dx.doi.org/10.1055/s-0038-1656005.
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SummaryAmong the nine ellagitannins, rugosin E was the most potent platelet aggregating agent with an EC50 of 1.5 ± 0.1 µM in rabbit platelets and 3.2 ±0.1 µM in human platelets. The aggregations caused by rugosin E and ADP were inhibited by EGTA, PGE1, mepacrine, sodium nitroprusside and neomycin, but not by indomethacin, verapamil, TMB-8, BN52021 and GR32191B. Rugosin E-induced thromboxane formation was suppressed by indomethacin, EGTA, PGE,, verapamil, mepacrine, TMB-8 and neomycin. ADP-scavenging agents, such as CP/CPK and apyrase inhibited concentration-dependently ADP (20 εM)-, but not rugosin E (5 εM)-induced platelet aggregation. In thrombin (0.1 U/ml)-treated and degranulated platelets, rugosin E and ADP still caused 63.5 ± 3.0% and 61.2 ± 3.5% of platelet aggregation, respectively. Selective ADP receptor antagonists, ATP and FSBA inhibited rugosin E- and ADP-induced platelet aggregations in a concentration-dependent manner. Both rugosin E and ADP did not induce platelet aggregation in ADP (1 mM)-desensitized platelets. In contrast to ADP, rugosin E did not decrease cAMP formation in washed rabbit platelets. Both rugosin E and ADP did not cause phosphoinositide breakdown in [3H]myo-inositol-labeled rabbit platelets. In fura-2/AM- load platelets, both rugosin E and ADP induced increase in intracellular calcium concentration and these responses were inhibited by ATP and PGEj. All these data suggest that rugosin E may be an ADP receptor agonist in rabbit platelets.
4
Higashihara, M., H. Maeda, Y. Shibata, S. Kume, and T. Ohashi. "A monoclonal anti-human platelet antibody: a new platelet aggregating substance." Blood 65, no. 2 (February 1, 1985): 382–91. http://dx.doi.org/10.1182/blood.v65.2.382.382.
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Abstract A monoclonal anti-human platelet antibody, TP82, is described, which caused irreversible aggregation of platelets in association with the release of adenosine triphosphate or [14C] serotonin, and which inhibited ristocetin-induced agglutination. Immunofluorescence assay showed that the antibody binds to platelets, megakaryocytes, and common acute lymphoblastic leukemia cells. The antibody (IgG1) immunoprecipitated a polypeptide of 23,000 daltons with an isoelectric point of about 7.0. The aggregation induced by the purified antibody and/or F(ab')2 fragments occurred in platelet-rich plasma and with washed platelets, but not with formalin-fixed washed platelets. TP82- induced aggregation was completely inhibited by disodium ethylendiaminotetraacetate, diltiazem, W-7, PGE1, and several metabolic inhibitors. At a concentration of apyrase or CP/CPK, which inhibited adenosine 5-diphosphate-induced aggregation. TP82-induced aggregation was only partially affected. Thrombin was not required for the antibody- mediated effects, since two thrombin inhibitors failed to block the reaction. The antibody, at least at a high concentration, induced platelet aggregation by a mechanism almost independent of thromboxane A2 formation, since cyclooxygenase inhibitors had little inhibitory effect on aggregation. TP82 monoclonal antibody is a new platelet- aggregating substance that interacts with a low-molecular-weight binding site on the platelet membrane.
5
Higashihara, M., H. Maeda, Y. Shibata, S. Kume, and T. Ohashi. "A monoclonal anti-human platelet antibody: a new platelet aggregating substance." Blood 65, no. 2 (February 1, 1985): 382–91. http://dx.doi.org/10.1182/blood.v65.2.382.bloodjournal652382.
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A monoclonal anti-human platelet antibody, TP82, is described, which caused irreversible aggregation of platelets in association with the release of adenosine triphosphate or [14C] serotonin, and which inhibited ristocetin-induced agglutination. Immunofluorescence assay showed that the antibody binds to platelets, megakaryocytes, and common acute lymphoblastic leukemia cells. The antibody (IgG1) immunoprecipitated a polypeptide of 23,000 daltons with an isoelectric point of about 7.0. The aggregation induced by the purified antibody and/or F(ab')2 fragments occurred in platelet-rich plasma and with washed platelets, but not with formalin-fixed washed platelets. TP82- induced aggregation was completely inhibited by disodium ethylendiaminotetraacetate, diltiazem, W-7, PGE1, and several metabolic inhibitors. At a concentration of apyrase or CP/CPK, which inhibited adenosine 5-diphosphate-induced aggregation. TP82-induced aggregation was only partially affected. Thrombin was not required for the antibody- mediated effects, since two thrombin inhibitors failed to block the reaction. The antibody, at least at a high concentration, induced platelet aggregation by a mechanism almost independent of thromboxane A2 formation, since cyclooxygenase inhibitors had little inhibitory effect on aggregation. TP82 monoclonal antibody is a new platelet- aggregating substance that interacts with a low-molecular-weight binding site on the platelet membrane.
6
Burgess-Wilson, ME, SR Cockbill, GI Johnston, and S. Heptinstall. "Platelet aggregation in whole blood from patients with Glanzmann's thrombasthenia." Blood 69, no. 1 (January 1, 1987): 38–42. http://dx.doi.org/10.1182/blood.v69.1.38.38.
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Abstract We examined platelet aggregation in platelet-rich plasma (PRP) and in whole blood from two patients with Glanzmann's thrombasthenia. In PRP, aggregation was measured by monitoring the changes in light absorbance that occurred in response to aggregating agents; to measure platelet aggregation in whole blood, we used a platelet counting technique. In PRP, the patients' platelets showed defective aggregation in response to ADP, adrenaline, arachidonic acid (AA), and collagen, but normal agglutination occurred in response to ristocetin. In whole blood, however, platelet aggregation in response to the aggregating agents appeared to be either very similar to that which occurred in blood from normal subjects or only slightly reduced. There was a reduced response to all concentrations of ADP and to low concentrations of collagen but a normal response to all concentrations of adrenaline, AA, and higher concentrations of collagen. Conversely, there seemed to be an increased agglutination response to ristocetin. The abnormality in our two patients with Glanzmann's thrombasthenia probably lies in the inability of their platelets to form large, macroscopic aggregates rather than in platelet aggregation per se.
7
Burgess-Wilson, ME, SR Cockbill, GI Johnston, and S. Heptinstall. "Platelet aggregation in whole blood from patients with Glanzmann's thrombasthenia." Blood 69, no. 1 (January 1, 1987): 38–42. http://dx.doi.org/10.1182/blood.v69.1.38.bloodjournal69138.
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We examined platelet aggregation in platelet-rich plasma (PRP) and in whole blood from two patients with Glanzmann's thrombasthenia. In PRP, aggregation was measured by monitoring the changes in light absorbance that occurred in response to aggregating agents; to measure platelet aggregation in whole blood, we used a platelet counting technique. In PRP, the patients' platelets showed defective aggregation in response to ADP, adrenaline, arachidonic acid (AA), and collagen, but normal agglutination occurred in response to ristocetin. In whole blood, however, platelet aggregation in response to the aggregating agents appeared to be either very similar to that which occurred in blood from normal subjects or only slightly reduced. There was a reduced response to all concentrations of ADP and to low concentrations of collagen but a normal response to all concentrations of adrenaline, AA, and higher concentrations of collagen. Conversely, there seemed to be an increased agglutination response to ristocetin. The abnormality in our two patients with Glanzmann's thrombasthenia probably lies in the inability of their platelets to form large, macroscopic aggregates rather than in platelet aggregation per se.
8
Refaai, Majed A., Kelly F. Henrichs, Sherry L. Spinelli, Richard P. Phipps, Edward Masel, Brian H. Smith, Charles W. Francis, and Neil Blumberg. "Platelet Activation Following Exposure to Anti-ABO Antibodies— An In Vitro Study." Oncology & Hematology Review (US) 07, no. 01 (2011): 72. http://dx.doi.org/10.17925/ohr.2011.07.1.72.
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Since platelets possess A and B antigen, mismatched ABO platelets could, theoretically, become activated or hypofunctional by exposure to anti-A or anti-B antibodies found in transfused or recipient plasma. Following normal baseline platelet aggregation to adenosine diphosphate (ADP), platelets from normal donors of different blood types were incubated at 37°C for 10 minutes with 50μl of normal saline (NS), O plasma, or AB plasma. Aggregation was then induced with ADP. No significant changes from baseline were seen in platelet aggregation studies following incubation with NS. However, platelet aggregations of type A and type B platelets were significantly inhibited when incubated with O plasma (mean of 41 and 22%, respectively). Our findings indicate that mediators in group O plasma, very likely anti-A and anti-B antibodies, cause impaired platelet aggregation of ABO non-identical platelets.
9
Chiang, T. M., A. Jin, and A. H. Kang. "Platelet-collagen interaction. Inhibition by a monoclonal antibody raised against collagen receptor." Journal of Immunology 139, no. 3 (August 1, 1987): 887–92. http://dx.doi.org/10.4049/jimmunol.139.3.887.
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Abstract Monoclonal antibodies to the purified platelet type I collagen receptor were produced to study platelet receptor function. The antibody specifically reacted with the platelet receptor in immunoblot experiments. The IgG purified from the monoclonal antibodies and isolated Fab' fragments inhibited the binding of radiolabeled alpha 1(I) chain to washed platelets competitively. Soluble and fibrillar type I collagen-induced platelet aggregations were inhibited by purified IgG suggesting that soluble and fibrillar collagens shared a common receptor. The adhesion of platelets to an artificial collagen matrix was also inhibited by the monoclonal antibody. However, adenosine diphosphate-induced platelet aggregation was not inhibited by the same amount of IgG that inhibited collagen-induced platelet aggregation. The results suggest that collagen-induced platelet aggregation is mediated through the interaction of collagen with the platelet receptor.
10
Cimminiello, C., M. Milani, T. Uberti, G. Arpaia, and G. Bonfardeci. "Effects of Ticlopidine and Indobufen on Platelet Aggregation Induced by A23187 and Adrenaline in the Presence of Different Anticoagulants." Journal of International Medical Research 17, no. 6 (November 1989): 514–20. http://dx.doi.org/10.1177/030006058901700603.
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As Ca2+ is known to play a fundamental role in platelet function, the effect of combining two platelet aggregating agents (adrenaline and the ionophore A23187) with different effects on Ca2+ was studied at levels subthreshold for aggregation using platelet-rich plasma from eight atherosclerotic patients. Adrenaline lowered the A23187 threshold required to induce aggregation. The effects of treating patients with the antiplatelet agents, indobufen and ticlopidine, on A23187 and adrenaline induced aggregation of platelets prepared in hirudin or sodium citrate was also evaluated. Aggregation was also studied using platelets resuspended in Ca2+-free and Ca2+-enriched Tyrode solution. Before treatment hirudin treated platelet-rich plasma, which has physiological extraplatelet Ca2+ levels, was more sensitive to A23187 and adrenaline than was citrated platelet-rich plasma, which has suppressed Ca2+ levels. Ticlopidine significantly raised the concentration of A23187 required to induce aggregation in citrated but not hirudin treated platelet-rich plasma. Indobufen did not significantly affect A23187 induced aggregation. Ticlopidine acts by inhibiting the glycoprotein IIb – IIIa complex on the platelet membranes. Low levels of extracellular Ca2+ and ticlopidine may act synergistically to reduce the aggregatory response of stimulated platelets.
11
Salvemini, Daniela, Gilberto de Nucci, and John R. Vane. "Superoxide Dismutase Cooperates with Prostacyclin to Inhibit Platelet Aggregation: a Comparative Study in Washed Platelets and Platelet Rich Plasma." Thrombosis and Haemostasis 65, no. 04 (1991): 421–24. http://dx.doi.org/10.1055/s-0038-1648164.
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SummaryThe role of superoxide anions (O2 −) in human platelet aggregation in Krebs’ buffer or plasma was investigated. In indome thacin (10 μM)-treated washed platelets superoxide dismutase (SOD; 60 U/ml) or ferricytochrome c (FCC; 70 μM) inhibited platelet aggregation by thrombin but not that by collagen or ADP. In addition, in indomethacin (10 μM)-treated washed platelets, SOD significantly potentiated the anti-aggregatory activity of prostacyclin (PGI2) or iloprost when thrombin but not collagen was used as the aggregating agent. In platelet rich plasma, SOD (60 U/ml) did not inhibit platelet aggregation nor did it potentiate the anti-aggregatory activity of iloprost when ADP, collagen or thrombin were used as aggregating agents. Thus, O2 − participate in the aggregatory activity of thrombin but not collagen or ADP and PGI2 or iloprost, by reducing the sensitivity of platelets to thrombin, co-operate with SOD to inhibit thrombin-induced platelet aggregationThe interpretation of the use of SOD in experiments involving endothelium-derived relaxing factor (NO) is discussed
12
Huang, T. F., C. Z. Liu, and S. H. Yang. "Aggretin, a novel platelet-aggregation inducer from snake (Calloselasma rhodostoma) venom, activates phospholipase C by acting as a glycoprotein Ia/IIa agonist." Biochemical Journal 309, no. 3 (August 1, 1995): 1021–27. http://dx.doi.org/10.1042/bj3091021.
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A potent platelet aggregation inducer, aggretin, was purified from Malayan-pit-viper (Calloselasma rhodostoma) venom by ionic-exchange chromatography, gel-filtration chromatography and HPLC. It is a heterodimeric protein (29 kDa) devoid of esterase, phospholipase A and thrombin-like activity. Aggretin (> 5 nM) elicited platelet aggregation with a lag period in both human platelet-rich plasma and washed platelet suspension. EDTA (5 mM), prostaglandin E1 (1 microM) and 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (‘TMB-8’; 100 microM) abolished its aggregating activity, indicating that exogenous bivalent cations and intracellular Ca2+ mobilization are essential for aggretin-induced platelet aggregation. Neomycin (4 mM) and mepacrine (50 microM) completely inhibited aggretin (33 nM)-induced aggregation; however, creatine phosphate/creatine phosphokinase (5 mM, 5 units/ml) and indomethacin (50 microM) did not significantly affect its aggregating activity. Aggretin caused a significant increase of [3H]InsP formation in [3H]Ins-loaded platelets, intracellular Ca2+ mobilization and thromboxane B2 formation. Neomycin, a phospholipase C inhibitor, completely inhibited both the increase of [3H]InsP and intracellular Ca2+ mobilization of platelets stimulated by aggretin. A monoclonal antibody (6F1) directed against glycoprotein Ia/IIa inhibited platelet shape change and aggregation induced by aggretin. 125I-aggretin bound to platelets with a high affinity (Kd = 4.0 +/- 1.1 nM), and the number of binding sites was estimated to be 2119 +/- 203 per platelet. It is concluded that aggretin may act as a glycoprotein Ia/IIa agonist to elicit platelet aggregation through the activation of endogenous phospholipase C, leading to hydrolysis of phosphoinositides and subsequent intracellular Ca2+ mobilization.
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Tuszynski, GP, VL Rothman, A. Murphy, K. Siegler, and KA Knudsen. "Thrombospondin promotes platelet aggregation." Blood 72, no. 1 (July 1, 1988): 109–15. http://dx.doi.org/10.1182/blood.v72.1.109.109.
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Abstract Thrombospondin (TSP), isolated from human platelets, promotes aggregation of both nonstimulated platelets and platelets stimulated with thrombin or ADP. The TSP-promoted aggregation is specific since a monoclonal antibody against TSP inhibits the effect of exogenously added TSP and inhibits thrombin-induced platelet aggregation in the absence of added TSP. Several lines of evidence suggest that TSP mediates its effect on aggregation of nonstimulated and stimulated platelets through different platelet-surface receptor systems. The TSP- promoted aggregation of nonstimulated platelets was inhibited by a monoclonal antibody to platelet glycoprotein IV (GPIV), but not by a monoclonal antibody to the fibrinogen receptor, GPIIb-IIIa. In contrast, the antibody to GPIIb-IIIa totally inhibited the TSP- potentiated aggregation of thrombin-stimulated platelets, whereas the antibody to GPIV has no effect. Thus, these studies suggest that TSP promotes platelet aggregation by at least two mechanisms--one dependent on and one independent of the platelet fibrinogen receptor system.
14
Tuszynski, GP, VL Rothman, A. Murphy, K. Siegler, and KA Knudsen. "Thrombospondin promotes platelet aggregation." Blood 72, no. 1 (July 1, 1988): 109–15. http://dx.doi.org/10.1182/blood.v72.1.109.bloodjournal721109.
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Thrombospondin (TSP), isolated from human platelets, promotes aggregation of both nonstimulated platelets and platelets stimulated with thrombin or ADP. The TSP-promoted aggregation is specific since a monoclonal antibody against TSP inhibits the effect of exogenously added TSP and inhibits thrombin-induced platelet aggregation in the absence of added TSP. Several lines of evidence suggest that TSP mediates its effect on aggregation of nonstimulated and stimulated platelets through different platelet-surface receptor systems. The TSP- promoted aggregation of nonstimulated platelets was inhibited by a monoclonal antibody to platelet glycoprotein IV (GPIV), but not by a monoclonal antibody to the fibrinogen receptor, GPIIb-IIIa. In contrast, the antibody to GPIIb-IIIa totally inhibited the TSP- potentiated aggregation of thrombin-stimulated platelets, whereas the antibody to GPIV has no effect. Thus, these studies suggest that TSP promotes platelet aggregation by at least two mechanisms--one dependent on and one independent of the platelet fibrinogen receptor system.
15
CALZADA, Catherine, Evelyne VERICEL, and Michel LAGARDE. "Low concentrations of lipid hydroperoxides prime human platelet aggregation specifically via cyclo-oxygenase activation." Biochemical Journal 325, no. 2 (July 15, 1997): 495–500. http://dx.doi.org/10.1042/bj3250495.
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There is mounting evidence that lipid peroxides contribute to pathophysiological processes and can modulate cellular functions. The aim of the present study was to investigate the effects of lipid hydroperoxides on platelet aggregation and arachidonic acid (AA) metabolism. Human platelets, isolated from plasma, were incubated with subthreshold (i.e. non-aggregating) concentrations of AA in the absence or presence of hydroperoxyeicosatetraenoic acids (HPETEs). Although HPETEs alone had no effect on platelet function, HPETEs induced the aggregation of platelets co-incubated with non-aggregating concentrations of AA, HPETEs being more potent than non-eicosanoid peroxides. The priming effect of HPETEs on platelet aggregation was associated with an increased formation of cyclo-oxygenase metabolites, in particular thromboxane A2, and was abolished by aspirin, suggesting an activation of cyclo-oxygenase by HPETEs. It was not receptor-mediated because the 12-HPETE-induced enhancement of AA metabolism was sustained in the presence of SQ29,548 or RGDS, which blocked the aggregation. These results indicate that physiologically relevant concentrations of HPETEs potentiate platelet aggregation, which appears to be mediated via a stimulation of cyclo-oxygenase activity.
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Jurasz, Paul, David Alonso, Susana Castro-Blanco, Ferid Murad, and Marek W. Radomski. "Generation and role of angiostatin in human platelets." Blood 102, no. 9 (November 1, 2003): 3217–23. http://dx.doi.org/10.1182/blood-2003-02-0378.
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AbstractPlatelets regulate new blood vessel growth, because they contain a number of angiogenesis promoters and inhibitors. Additionally, platelets contain matrix metalloproteinases (MMPs), which when released mediate platelet adhesion and aggregation, and plasminogen, a fibrinolytic system enzyme that serves to limit blood clot formation. Enzymatic cleavage of plasminogen by MMPs generates angiostatin, an angiogenesis inhibitor. Therefore, we examined whether platelets generate angiostatin during aggregation in vitro. Platelets were isolated from healthy human donors and then aggregated with collagen, thrombin, or HT-1080 fibrosarcoma cells. Angiostatin was detected by Western blot analysis in the platelet releasates of all blood donors irrespective of the aggregating agent used. Platelet pellet homogenates showed the presence of angiostatin in all donors, which was released upon aggregation. Furthermore, platelet-derived angiostatin was isolated and purified by lysine-Sepharose affinity chromatography from collagen-aggregated platelet releasates. Bioassay of platelet-derived angiostatin showed that it inhibited the formation of capillary structures by human umbilical vein endothelial cells (HUV-EC-Cs) in an in vitro angiogenesis model. Inhibition of angiostatin in platelet releasates promoted the formation of capillary structures by HUV-EC-Cs. We conclude that healthy human platelets contain angiostatin, which is released in active form during platelet aggregation, and platelet-derived angiostatin has the capacity to inhibit angiogenesis.
17
Parbtani, Anwar, William F. Clark, Anita Caveney, and Bruce Reid. "Binding of Aggregated Immunoglobulins to the Human Platelet Fc Receptors: A Mechanism of Platelet to Platelet Bridging." Thrombosis and Haemostasis 58, no. 04 (1987): 966–70. http://dx.doi.org/10.1055/s-0038-1646038.
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SummaryAggregated immunoglobulins react with human platelets by occupying the Fc receptors present on their surface, inducing aggregation and the release reaction. We studied the effect of heat aggregated gammaglobulins (HAGG) on ADP-induced aggregation of platelets. We used the minimum concentration of ADP required to induce a reversible aggregation of platelets without any substantial amount of serotonin (14C 5HT) release. EDTA (5 mM) added at the peak of platelet aggregation resulted in rapid deaggrcgation ot these platelets. However, incubation of platelets with HAGG at a dose that did not by itself induce any aggregation or release reaction, followed by ADP addition resulted in an irreversible platelet aggregation of greater magnitude accompanied by a substantial release of 14C-5HT. The addition of EDTA at the peak of platelet aggregation failed to deaggregate these platelets. To determine whether the augmented aggregation response and the inhibition of deaggiega-tion was due to HAGG or a consequence of platelet release products, we used thrombin-degranulated platelets. The augmented aggregation response and the inhibition of deaggregation due to HAGG and ADP could be demonstrated using these platelets. To confirm that the binding of HAGG to the platelet Pc receptors was responsible for these observations, we incubated platelets with an excess of Fc fragments of IgG prior to the addition of HAGG and ADP. This abolished the aggregation response observed previously. From this study we conclude that interplatelet bridging by HAGG renders the platelets hyperag-gregable and appears to be a mechanism involved in maintaining platelet aggregates.
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POLGÁR, János, Ruth M. KRAMER, Suzane L. UM, Joseph A. JAKUBOWSKI, and Kenneth J. CLEMETSON. "Human group II 14 kDa phospholipase A2 activates human platelets." Biochemical Journal 327, no. 1 (October 1, 1997): 259–65. http://dx.doi.org/10.1042/bj3270259.
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Recombinant human group II phospholipase A2 (sPLA2) added to human platelets in the low μg/ml range induced platelet activation, as demonstrated by measurement of platelet aggregation, thromboxane A2 generation and influx of intracellular free Ca2+ concentration and by detection of time-dependent tyrosine phosphorylation of platelet proteins. The presence of Ca2+ at low millimolar concentrations is a prerequisite for the activation of platelets by sPLA2. Mg2+ cannot replace Ca2+. Mg2+, given in addition to the necessary Ca2+, inhibits sPLA2-induced platelet activation. Pre-exposure to sPLA2 completely blocked the aggregating effect of a second dose of sPLA2. Albumin or indomethacin inhibited sPLA2-induced aggregation, similarly to the inhibition of arachidonic acid-induced aggregation. Platelets pre-treated with heparitinase or phosphatidylinositol-specific phospholipase C lost their ability to aggregate in response to sPLA2, although they still responded to other agonists. This suggests that a glycophosphatidylinositol-anchored platelet-membrane heparan sulphate proteoglycan is the binding site for sPLA2 on platelets. Previous reports have stated that sPLA2 is unable to activate platelets. The inhibitory effect of albumin and Mg2+, frequently used in aggregation studies, and the fact that isolated platelets lose their responsiveness to sPLA2 relatively quickly, may explain why the platelet-activating effects of sPLA2 have not been reported earlier.
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Shi, Quanwei, Zhicheng Wang, Rong Yan, Juan Du, Jun Liu, Changgeng Ruan, and Kesheng Dai. "The Effects of Hyperthermia On Platelet Physiology." Blood 114, no. 22 (November 20, 2009): 2422. http://dx.doi.org/10.1182/blood.v114.22.2422.2422.
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Abstract Abstract 2422 Poster Board II-399 Introduction: In some patients with fever or hyperthermia, hemorrhage is a significant pathological feature, which incurs severe or even fatal consequence. Although the mechanisms of hemorrhage in patients with hyperthermia or fever have been though to be complex, whether there is an association between hemorrhage and hyperthermia or fever is not well understood. Platelets play a central role in maintaining integrity of endothelium and biological hemostasis. Platelet count obviously reduces in most of patients with dengue fever or heatstroke, and reduced platelet aggregations have been found in patients with hemorrhage fever, raising the possibility that fever or hyperthermia incurs reduction of platelet count or function leading to hemorrhage. Methods and Results: To explore the effect of hyperthermia on platelet function, platelet-rich plasma (PRP) was isolated and incubated at hypothermia (22 degrees C), normothermia (37 degrees C) or hyperthermia (40 and 42 degrees C) for 1 or 2 hours, and then induced to aggregation by ADP. Platelet aggregation was significantly reduced with the growth of temperature in a time-dependent manner. To exclude the possible interference from plasma proteins, and to further investigate the effects of hyperthermia on platelet function, alpha-thrombin induced platelet aggregations were examined in washed platelets incubated at different temperatures for 1 or 2 hours. Washed platelets presented normal aggregation response to alpha-thrombin in platelets incubated at hypothermia, whereas alpha-thrombin induced platelet aggregations reduced gradually with the increase of temperature and time duration. Next, we investigated whether the reductions of platelet aggregation were resulted from platelet apoptosis under high temperature conditions. Hyperthermia gradually induced apoptotic events in platelets with the increase of temperature and time duration, including depolarization of mitochondrial inner transmembrane potential (ΔΨm), gelsolin cleavage, and phosphatidylserine (PS) exposure. Furthermore, hyperthermia incurs platelet glycoprotein (GP) Ibalpha ectodomain shedding. Conclusions: These results indicate that hyperthermia induces platelet apoptosis, thus suggesting the possible reason why platelet count or function was reduced in some patients with fever or hyperthermia. These findings not only have important implications for the pathogenesis of hemorrhage in some fever or hyperthermia-related diseases, but also suggest that attentions should be paid on platelet apoptosis under relative high temperature conditions, such as during hyperthermia therapy or platelet storage. Disclosures: No relevant conflicts of interest to declare.
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Natella, F., M. Nardini, F. Belelli, P. Pignatelli, S. Di Santo, A. Ghiselli, F. Violi, and C. Scaccini. "Effect of coffee drinking on platelets: inhibition of aggregation and phenols incorporation." British Journal of Nutrition 100, no. 6 (December 2008): 1276–82. http://dx.doi.org/10.1017/s0007114508981459.
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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 aggregationex 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 (sem0·1) to 2·4 (sem0·6) 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.
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Sils, D., S. E. Rodgers, J. V. Lloyd, K. M. Wilson, D. M. Siebert, and F. Bochner. "Inhibition of platelet aggregation and thromboxane production by low concentrations of aspirin in vitro." Clinical Science 74, no. 5 (May 1, 1988): 491–97. http://dx.doi.org/10.1042/cs0740491.
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1. The aspirin concentrations previously reported to inhibit platelet aggregation in vitro (40–500 μmol/l) are much greater than those required in vivo in man (5 μmol/l). 2. Human platelet-rich plasma was incubated with buffer or various aspirin concentrations at 37°C for up to 4.5 h. Platelet aggregation and thromboxane generation were measured in response to collagen (0.4–6.3 μg/ml) and adenosine 5′-pyrophosphate (0.5–4 μmol/l). 3. The concentration of aspirin needed to inhibit platelet aggregation in response to a critical concentration of aggregating agent (lowest concentration to cause greater than 50% aggregation) was lower than that required for higher concentrations of aggregating agent. 4. With more prolonged incubation times with aspirin, lower concentrations of aspirin inhibited platelet aggregation. 5. Inhibition of platelet aggregation and thromboxane formation by 10 μmol/l aspirin was maximal by 90 min. There was progressive inhibition by 3 μmol/l aspirin during incubation for 270 min. By the end of this time there was also significant inhibition by 1 μmol/l aspirin. 6. The apparent discrepancy between inhibitory aspirin concentrations in vivo and those observed in vitro in previous studies appears to have been resolved by extending the incubation time of platelets with low aspirin concentrations, thus mimicking the conditions in vivo.
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McMahon, Greg S., Chris I. Jones, Paul D. Hayes, A. Ross Naylor, and Alison H. Goodall. "Transient heparin-induced platelet activation linked to generation of platelet 12-lipoxygenase." Thrombosis and Haemostasis 109, no. 06 (2013): 1099–107. http://dx.doi.org/10.1160/th12-11-0793.
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SummaryPreviously we demonstrated that heparin administration during carotid endarterectomy (CEA) caused a marked, but transient increase in platelet aggregation to arachidonic acid (AA) and adenosine diphosphate (ADP), despite effective platelet cyclo-oxygenase-1 (COX-1) inhibition with aspirin. Here we investigated the metabolism of AA via platelet 12-lipoxygenase (12-LOX) as a possible mediator of the observed transient aspirin resistance, and compared the effects of unfractionated (UFH) and low-molecular-weight (LMWH) heparin. A total of 43 aspirinated patients undergoing CEA were randomised in the trial to 5,000 IU UFH (n=22) or 2,500 IU LMWH (dalteparin, n=21). Platelet aggregation to AA (4×10–3) and ADP (3×10–6) was determined, and the products of the COX-1 and 12-LOX pathways; thromboxane B2 (TXB2) and 12-hydroxyeicosatretraenoic acid (12-HETE) were measured in plasma, and in material released from aggregating platelets. Aggregation to AA increased significantly (∼10-fold) following heparinisation (p<0.0001), irrespective of heparin type (p=0.33). Significant, but smaller (∼2-fold) increases in aggregation to ADP were also seen, which were significantly lower in the platelets of patients randomised to LMWH (p<0.0001). Plasma levels of TxB2 did not rise following heparinisation (p=0.93), but 12-HETE increased significantly in the patients’ plasma, and released from platelets stimulated in vitro with ADP, with both heparin types (p<0.0001). The magnitude of aggregation to ADP correlated with 12-HETE generation (p=0.03). Heparin administration during CEA generates AA that is metabolised to 12-HETE via the 12-LOX pathway, possibly explaining the phenomenon of transient heparin-induced platelet activation. LMWH has less effect on aggregation and 12-HETE generation than UFH when the platelets are stimulated with ADP.
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Zhang, Yun-Xiang, Ting-Ting Yang, Liu Xia, Wei-Fen Zhang, Jia-Fu Wang, and Ya-Ping Wu. "Inhibitory Effect of Propolis on Platelet Aggregation In Vitro." Journal of Healthcare Engineering 2017 (2017): 1–6. http://dx.doi.org/10.1155/2017/3050895.
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Platelet hyperactivity plays an important role in arterial thrombosis and atherosclerosis. The present study was aimed to investigate the effects of different extracts of propolis and components of flavonoids on platelet aggregation. Platelet-rich plasma was prepared and incubated in vitro with different concentrations of the tested extracts and components of flavonoids. Platelets aggregation was induced by different agonists including adenosine diphosphate (ADP, 10 μM), thrombin receptor activator peptide (TRAP, 50 μM), and collagen (5 μg/mL). At 25 mg/L to 300 mg/mL, the water extract propolis (WEP) inhibited three agonists-induced platelet aggregations in a dose-dependent manner. The flavonoids isolated from the propolis also showed markedly inhibited platelet aggregation induced by collagen, ADP, and TRAP, respectively. The components including caffeic acid phenethyl ester (CAPE), galangin, apigenin, quercetin, kaempferol, ferulic acid, rutin, chrysin, pinostrobin, and pinocembrin and their abilities of inhibiting platelet aggregation were studied. It was concluded that propolis had an antiplatelet action in which flavonoids were mainly implicated.
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Del Zar, María de las M., Marta Martinuzzo, Daniel P. Cardinali, Luis O. Carreras, and María I. Vacas. "Diurnal variation in melatonin effect on adenosine triphosphate and serotonin release by human platelets." Acta Endocrinologica 123, no. 4 (October 1990): 453–58. http://dx.doi.org/10.1530/acta.0.1230453.
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Abstract. The effect of the pineal hormone melatonin on adenosine diphosphate-induced human platelet aggregation and adenosine triphosphate release was assessed in platelet-rich plasma obtained from normal volunteers at 08.30 and 20.30 h. In 10−7-10−5 mol/l concentrations melatonin inhibited ADP-induced platelet aggregation only in the evening (p<0.05). ADP-induced ATP release, an index of platelet secretory processes, showed a generally greater, dose-dependent inhibition after adding melatonin (10−9-10−5 mol/l) at 20.30 h as compared with 08.30 h. The inhibitory activity of melatonin (10−9-10−5 mol/l) on [3H]serotonin release elicited by thrombin in washed human platelets obtained from normal volunteers was dose-dependent; the effect was generally greater at 20.30 h. The activity of the potent platelet anti-aggregating agent prostacyclin did not exhibit diurnal differences with respect to impairing ADP-induced platelet-rich plasma aggregation. These results indicate the existence of a diurnal variation of sensitivity to melatonin in human platelets.
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Csako, Gyorgy, Eva A. Suba, and Ronald J. Elin. "Endotoxin-Induced Platelet Activation in Human Whole Blood In Vitro." Thrombosis and Haemostasis 59, no. 03 (1988): 378–82. http://dx.doi.org/10.1055/s-0038-1647499.
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SummaryThe effect of purified bacterial endotoxin was studied on human platelets in vitro. In adding up to 1 μg/mL of a highly purified endotoxin, we found neither aggregation nor ATP release in heparinized or citrated human platelet-rich plasma. On the other hand, endotoxin at concentrations as low as a few ng/mL (as may be found in septic patients) caused platelet aggregation in both heparinized and citrated human whole blood, as monitored by change in impedance, free platelet count, and size. Unlike collagen, the platelet aggregation with endotoxin occurred after a long lag phase, developed slowly, and was rarely coupled with measurable release of ATP. The platelet aggregating effect of endotoxin was dose-dependent and modified by exposure of the endotoxin to ionizing radiation. Thus, the activation of human platelets by “solubilized” endotoxin in plasma requires the presence of other blood cells. We propose that the platelet effect is mediated by monocytes and/or neutrophils stimulated by endotoxin.
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Packham, Marian A. "Role of platelets in thrombosis and hemostasis." Canadian Journal of Physiology and Pharmacology 72, no. 3 (March 1, 1994): 278–84. http://dx.doi.org/10.1139/y94-043.
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Platelet aggregates, stabilized by fibrin, rapidly form hemostatic plugs when blood vessels are severed or arterial thrombi at sites of vessel injury, such as ruptured atherosclerotic plaques, or regions where blood flow is disturbed, such as at stenoses. These thrombi cause the thromboembolic complications of atherosclerosis: heart attacks, strokes, and peripheral vascular disease. Platelet adhesion to subendothelial components such as collagen activates signalling pathways that lead to thromboxane A2 formation and secretion of platelet granule contents, including ADP. Both these substances cause platelet aggregation, a process in which the integrin, glycoprotein IIb/IIIa, becomes a receptor for fibrinogen, which forms bridges between adjacent platelets. On the surface of stimulated platelets, coagulation is accelerated and thrombin is generated; it is a potent inducer of platelet aggregation and secretion and also causes fibrin to form around the aggregates, stabilizing them. There are receptors on the platelet surface for thrombin, thromboxane A2, collagen, ADP, platelet-activating factor, fibrinogen, von Willebrand factor, and other ligands. Agents that inhibit platelet aggregation and the signalling pathways that are activated by the various aggregating agents are under intensive investigation in many laboratories.Key words: platelets, hemostasis, arterial thrombosis, thrombin.
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Krishnamurthi, S., and V. V. Kakkar. "Studies on the Effect of Platelet Inhibitors on Platelet Adhesion to Collagen and Collagen-Induced Human Platelet Activation." Thrombosis and Haemostasis 53, no. 03 (1985): 337–42. http://dx.doi.org/10.1055/s-0038-1661310.
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SummaryThe effect of pyridoxal 5’-phosphate (PALP) and trifluoperazine (TFPZ), the calmodulin antagonist, on in vitro platelet adhesion to collagen and collagen-induced platelet activation was studied using platelet-rich-plasma (PRP) or washed platelets (WPL). Platelet aggregation and [14C]-5HT release induced by “threshold” or low concentrations of collagen (0.6 μg/ ml) in PRP were completely abolished by PALP (24 mM), TFPZ (250 μM) as well as indomethacin (10 μM). At higher concentrations of collagen (10–15 μg/ml) in PRP and WPL, the use of stirred and unstirred platelets treated with collagen enabled a distinction to be made between aggregation and adhesion- mediated release reaction. Platelet aggregation and the aggregation-mediated release reaction induced by these concentrations of collagen in stirred platelets were completely abolished by PALP, TFPZ and indomethacin although neither adhesion to collagen nor the adhesion-mediated release reaction of unstirred platelets was significantly affected by these inhibitors. Interestingly, both adhesion and the adhesion-mediated release reaction were abolished by concentrations of PALP 10–40 fold higher than those required to abolish aggregation. Collagen-induced platelet aggregation, but not platelet adhesion, was inhibited in resuspended platelets pretreated with PALP and NaBH4 indicating a separation in the membrane sites involved in aggregation and adhesion. The results further emphasize the distinction between adhesion and aggregation-mediated events with regards to collagen with the latter being more susceptible to inhibition by antiplatelet agents such as PALP and TFPZ.
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Yang, Hong, Adili Reheman, Pingguo Chen, Richard O. Hynes, John Freedman, Denisa D. Wagner, and Heyu Ni. "Fibrinogen and von Willebrand Factor-Independent Platelet Aggregation: The Essential Roles of β3 Integrin, Thrombin, and Divalent Ca2+ Cations." Blood 106, no. 11 (November 16, 2005): 2651. http://dx.doi.org/10.1182/blood.v106.11.2651.2651.
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Abstract It has been documented that fibrinogen (Fg) is required for platelet aggregation. However, we recently found that platelet rich thrombi still formed in mice lacking either Fg (Fg−/−) or both Fg and vWF (Fg/vWF−/−) (Ni et al, JCI106:385–392, 2000). To explore the potential mechanisms of Fg/vWF-independent platelet aggregation, we studied platelet aggregation in vitro in platelet rich plasma (PRP). We found no platelet aggregation in Fg−/− or Fg/vWF−/− PRP induced by adenosine diphosphate (ADP) in the presence of anticoagulant reagents including divalent cation chelators (ACD, sodium citrate, and EDTA), and thrombin inhibitors (heparin, hirudin, PPACK). Since no fibrin formation occurs in Fg/vWF−/− plasma, we then induced Fg/vWF−/− platelet aggregation in non-anticoagulated platelet poor plasma (PPP). Surprisingly, robust aggregation occurred after ADP treatment. We further demonstrated that directly triggering the thrombin receptor PAR4 with thrombin receptor activation peptide (TRAP, AYPGKF-NH2) induced platelet aggregation in thrombin-inhibitor treated Fg/vWF−/− PRP and gel-filtered Fg/vWF-platelets in 1mM Ca2+ PIPES buffer. Thus Fg/vWF-independent aggregation can be induced in vitro and both divalent cations and thrombin are required for this novel platelet aggregation pathway. It is likely that ADP induced thrombin generation in Fg/vWF-/- PRP. Considering platelet aggregation has been observed in type I Glanzmann Thrombasthenic patients lacking αIIbβ3 protein, we hypothesized that Fg/vWF−/− platelet aggregation may occur in either a β3 integrin-dependent or β3 integrin independent manners. To test this hypothesis, β3 integrin deficient (β3−/−) platelets were added into the same non-anticoagulated Fg/vWF−/− plasma and no aggregation was observed after ADP treatment. β3−/− platelets also did not co-aggregate with Fg/vWF−/− platelets in vitro in aggregation assays, which were analyzed by flow cytometry with an anti-CD61 (anti-β3 integrin) antibody. Furthermore, when fluorescently labeled β3−/− platelets were injected into Fg/vWF−/− mice, β3−/− platelets did not significantly incorporate into Fg/vWF−/− thrombi under confocal intravital microscopy. The inability of β3−/− platelets to aggregate is not due to a deficiency in other adhesive receptors, since no reduction of GPIbα, β1 integrins, and P-selectin was observed on β3−/− platelets. Thus, although the GPIb complex, P-selectin, and β1 integrins may be involved in platelet aggregation, β3 integrin is essential for this Fg/vWF-independent platelet aggregation pathway. This also indicates that other alternative ligands of β3 integrin from either the plasma or platelet granules are capable of mediating platelet aggregation independent of both Fg and vWF under more physiologically relevant conditions (i.e. non anti-coagulated blood) where divalent cations and thrombin are present.
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Duarte, A. Torres, Z. Zukowska-Grojec, and A. K. Myers. "Agonist-Induced Release of Neuropeptide Y by Platelets." International Journal of Immunopathology and Pharmacology 9, no. 1 (January 1996): 1–8. http://dx.doi.org/10.1177/039463209600900101.
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Neuropeptide Y (NPY) is a multi-functional peptide localized in a number of tissues besides the brain, and its expression is high in strains of mice with autoimmune disease. Functionally, along with its neurotransmitter role, NPY has multiple effects on both vascular tissues and tissues involved in immune responses. Previous studies demonstrated that immunoreactive NPY (i-NPY) exists in large quantities in platelets and bone marrow of some species, and suggested its release during platelet aggregation by collagen. Because NPY has been hypothesized to have a role in a number of pathophysiological states in which platelets are involved, including immune responses, hypertension and vascular smooth muscle proliferation, we sought to further characterize platelet i-NPY content and release by a diverse group of physiological platelet agonists. Platelet rich plasma and gel filtered platelets were prepared from citrated whole blood of male Sprague Dawley rats. Platelet content and concentration of i-NPY were quantified by RIA. Platelet aggregation responses (turbidometric method) and release of i-NPY were measured in rat platelet preparations stimulated by a thromboxane agonist (U44069), collagen, thrombin and ADP. All agents induced dose-dependent aggregation, although ADP and U44069 were weak agonists in citrated platelet rich plasma, ADP only inducing primary aggregation. Total i-NPY content in platelet rich plasma of Sprague-Dawley rats was 32.1±3.8 pmol/ml; more than 20 pmol/ml was released into supernatant of aggregating platelets stimulated with high dose thrombin or collagen during secondary, irreversible aggregation. Although U44069 and ADP both stimulated i-NPY release in a dose-dependent manner, release was substantially lower than with the other agonists. We conclude that i-NPY release from rat platelets is associated mainly with secondary, irreversible aggregation, and can be produced by a variety of platelet stimulating agents as part of the platelet release reaction. The present study and other recent studies demonstrate wide variability in platelet i-NPY content between and within species. Investigation of the genetic regulation of i-NPY content in platelets could offer new insights into the relationship between NPY and pathophysiology of the immune and cardiovascular systems.
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Maloney, James P., Christopher C. Silliman, Daniel R. Ambruso, Jun Wang, Rubin M. Tuder, and Norbert F. Voelkel. "In vitro release of vascular endothelial growth factor during platelet aggregation." American Journal of Physiology-Heart and Circulatory Physiology 275, no. 3 (September 1, 1998): H1054—H1061. http://dx.doi.org/10.1152/ajpheart.1998.275.3.h1054.
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Platelet aggregation is a cardinal feature of both vascular repair and vascular disease. During aggregation platelets release a variety of vasoactive substances; some of these promote angiogenesis, endothelial permeability, and endothelial growth, actions shared by vascular endothelial growth factor (VEGF). This study was undertaken to investigate the hypothesis that VEGF is released by aggregating platelets. We found that VEGF was secreted during the in vitro aggregation of platelet-rich plasma induced by thrombin, collagen, epinephrine, and ADP (range 23–518 pg VEGF/ml). Furthermore, serum VEGF levels were elevated compared with plasma (230 ± 63 vs. 38 ± 8 pg VEGF/ml), indicative of VEGF release during whole blood coagulation. Lysates of apheresed, leukocyte-poor platelet units contained significant amounts of VEGF (2.4 ± 0.8 pg VEGF/mg protein). VEGF message and protein were also present in a megakaryocytic cell line (Dami cell). These results suggest constitutive roles for platelet VEGF in the repair of intimal vessel injury and in the altered permeability and intimal proliferation seen at sites of platelet aggregation and thrombosis.
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Cortelazzo, Sergio, Monica Galli, Donatella Castagna, Piera Viero, Giovanni de Gaetano, and Tiziano Barbui. "Increased Response to Arachidonic Acid and U-46619 and Resistance to Inhibitory Prostaglandins in Patients with Chronic Myeloproliferative Disorders." Thrombosis and Haemostasis 59, no. 01 (1988): 073–76. http://dx.doi.org/10.1055/s-0038-1642568.
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SummaryIn patients with myeloproliferative disorders (MPD) a group of related diseases of the bone marrow stem cell and recurrent haemorrhagic and/or thrombotic complications, the production of aggregating prostaglandins (PGs) may be normal or slightly reduced, while PGI2 production is normal. However, MPD platelet sensitivity to antiaggregatory PGs is still unknown.We studied the potency of PGD2, PGI2 and PGEi as inhibitors of platelet aggregation induced by threshold aggregating concentrations of arachidonic acid and U-46619-analogue of the cyclic endoperoxide PGH2 in 20 patients with MPD in comparison with healthy controls, with the aim of evaluating the sensitivity of MPD platelets to antiaggregatory PGs. In these patients platelet prostanoid metabolism was normal. However, the functional response of platelets to aggregating and antiaggregating prostanoids was shifted towards potentially increased platelet aggregation response. These findings could have a clinical relevance in view of the haemostatic and thrombotic complications so frequent in MPD.
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ZHOU, J. S., K. J. RUTHERFURD, and H. S. GILL. "Inability of Probiotic Bacterial Strains Lactobacillus rhamnosus HN001 and Bifidobacterium lactis HN019 To Induce Human Platelet Aggregation In Vitro." Journal of Food Protection 68, no. 11 (November 1, 2005): 2459–64. http://dx.doi.org/10.4315/0362-028x-68.11.2459.
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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.
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Ezzeroug Ezzraimi, Amina, Jean-Pierre Baudoin, Antoine Mariotti, and Laurence Camoin-Jau. "Microscopic Description of Platelet Aggregates Induced by Escherichia coli Strains." Cells 11, no. 21 (November 4, 2022): 3495. http://dx.doi.org/10.3390/cells11213495.
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In addition to their role in haemostasis, platelets are also involved in the inflammatory and antimicrobial process. Interactions between pathogens and platelets, mediated by receptors can lead to platelet activation, which may be responsible for a granular secretion process or even aggregation, depending on the bacterial species. Granular secretion releases peptides with bactericidal activity as well as aggregating factors. To our knowledge, these interactions have been poorly studied for Escherichia coli (E. coli). Few studies have characterised the cellular organization of platelet-E. coli aggregates. The objective of our study was to investigate the structure of platelet aggregates induced by different E. coli strains as well as the ultrastructure of platelet-E. coli mixtures using a scanning and transmission electron microscopy (SEM and TEM) approach. Our results show that the appearance of platelet aggregates is mainly dependent on the strain used. SEM images illustrate the platelet activation and aggregation and their colocalisation with bacteria. Some E. coli strains induce platelet activation and aggregation, and the bacteria are trapped in the platelet magma. However, some strains do not induce significant platelet activation and are found in close proximity to the platelets. The structure of the E. coli strains might explain the results obtained.
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Starovoitov, A. G., A. L. Lipnitski, and А. V. Marochkov. "ANALYSIS OF PLATELET AGGREGATION IN DONORS OF BLOOD COMPONENTS." Journal of the Grodno State Medical University 19, no. 6 (December 27, 2021): 646–51. http://dx.doi.org/10.25298/2221-8785-2021-19-6-646-651.
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The functional state of platelets can be determined using the method of platelet aggregation. The aim of our study was to investigate platelet aggregation in donors of blood components and to identify the features of the reactions of these platelets with the most common inducers of aggregation. Material and methods. 31 donors of fresh frozen plasma and platelet concentrate were included in the study. The study of platelet aggregation was carried out by the turbidimetric method with AP2110 analyzer (SOLAR, Minsk, Republic of Belarus). Results. A total of 33 studies of platelet aggregation in donors were carried out before the collection of blood components. Normal platelet aggregation was found in 10 cases (30.3%), hypoaggregation in 15 cases (45.5%), and hyperaggregation in 8 studies. (24.2%). Thus, in 23 (69.7%) cases, platelet aggregation disorders were found in donors. Statistical analysis showed that the incidence of platelet aggregation disorders (hypo- or hyperaggregation) was high in donors who had undergone COVID-19 infection (5 - hypoaggregation, 4 - hyperaggregation). In donors with no history of this infection, the incidence of platelet aggregation disorders was statistically significantly lower - 63.6% (in 10 - hypoaggregation, in 4 - hyperaggregation), p=0.04. A history of previous COVID-19 infection in the donor is an independent predictor of platelet aggregation disorder (Chi-square=7.24, p=0.007). Conclusion. When preparing platelet mass, it is necessary to first monitor platelet aggregation, especially in donors with a previous COVID-19 infection, and take into account the results obtained to predict the therapeutic effect of using platelet concentrate in clinical practice. Keywords: platelet aggregation, platelets, blood component donor, platelet concentrate, novel coronavirus infection, COVID-19.
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Laduca, F. M., W. R. Bell, and R. E. Bettigole. "Platelet-collagen adhesion enhances platelet aggregation induced by binding of VWF to platelets." American Journal of Physiology-Heart and Circulatory Physiology 253, no. 5 (November 1, 1987): H1208—H1214. http://dx.doi.org/10.1152/ajpheart.1987.253.5.h1208.
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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 [3H]serotonin, or alter the dose-responsive binding of 125I-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.
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Nemmar, Abderrahim, and Marc F. Hoylaerts. "Neutrophil Cathepsin G Enhances Thrombogenicity of Mildly Injured Arteries via ADP-Mediated Platelet Sensitization." International Journal of Molecular Sciences 23, no. 2 (January 11, 2022): 744. http://dx.doi.org/10.3390/ijms23020744.
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Inhalation of particulate matter in polluted air causes direct, size-restricted passage in the circulation and pronounced lung inflammation, provoking platelet activation and (non)-fatal cardiovascular complications. To determine potency and mechanism of platelet sensitization via neutrophil enzymes, we performed in vitro aggregation studies in washed human platelets and in murine and human blood, in the presence of elastase, cathepsin G and regular platelet agonists, present in damaged arteries. The impact of both enzymes on in vivo thrombogenicity was studied in the same thrombosis mouse model, previously having demonstrated that neutrophil activation enhances peripheral thrombogenicity. At 0.05 U/mL, cathepsin G activated washed human platelets via PAR1, whereas at 0.35 U/mL, aggregation occurred via PAR4. In Swiss mouse platelet-rich plasma no aggregation occurred by cathepsin G at 0.4 U/mL. In human and murine blood, aggregations by 0.05–0.1 U/mL cathepsin G were similar and not PAR-mediated, but platelet aggregation was inhibited by ADP antagonists, advocating cathepsin G-released ADP in blood as the true agonist of sustained platelet activation. In the mouse thrombosis model, cathepsin G and elastase amplified mild thrombogenicity at blood concentrations that activated platelets in vitro. This study shows that cathepsin G and elastase secreted in the circulation during mild air pollution-induced lung inflammation lyse red blood cell membrane proteins, leading to ADP-leakage into plasma, sensitizing platelets and amplifying their contribution to cardiovascular complications of ambient particle inhalation.
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Miajlovic, Helen, Anthony Loughman, Marian Brennan, Dermot Cox, and Timothy J. Foster. "Both Complement- and Fibrinogen-Dependent Mechanisms Contribute to Platelet Aggregation Mediated by Staphylococcus aureus Clumping Factor B." Infection and Immunity 75, no. 7 (April 16, 2007): 3335–43. http://dx.doi.org/10.1128/iai.01993-06.
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ABSTRACT Staphylococcus aureus can stimulate activation and aggregation of platelets, which are thought to be factors in the development of infective endocarditis. Previous studies have identified clumping factor A (ClfA) and fibronectin binding proteins A and B (FnBPA and FnBPB) as potent platelet aggregators. These proteins are able to stimulate rapid platelet aggregation by either a fibrinogen- or a fibronectin-dependent process which also requires antibodies specific to each protein. Slower aggregation has been seen in other systems where specific fibrinogen binding ligands are absent and platelet aggregation is mediated by complement and specific antibodies. Bacteria expressing ClfB aggregate platelets with a longer lag time than ClfA or FnBPA and FnBPB. In order to investigate whether ClfB causes platelet aggregation in a complement- or fibrinogen-dependent manner, a non-fibrinogen-binding mutant of ClfB (ClfB Q235A) was constructed. Lactococcus lactis expressing ClfB Q235A was able to stimulate platelet aggregation in platelet-rich plasma without a significant increase in lag time. The requirements for platelet aggregation were investigated using gel-filtered platelets. Fibrinogen and specific anti-ClfB antibodies were found to be sufficient to allow platelet aggregation mediated by the wild-type ClfB protein. It seems that ClfB causes platelet aggregation by a fibrinogen-dependent mechanism. The non-fibrinogen-binding ClfB mutant was unable to stimulate platelet aggregation under these conditions. However, bacteria expressing ClfB Q235A caused platelet aggregation in a complement-dependent manner which required specific anti-ClfB antibodies.
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Cattaneo, Marco, J. Fraser Mustard, Maria T. Canciani, Mary Richardson, Augusto B. Federici, and Pier Mannuccio Mannucci. "Conditions Influencing the Interaction of Asialo von Willebrand Factor with Human Platelets – The Effects of External Ionized Calcium Concentration and the Role of Arachidonate Pathway." Thrombosis and Haemostasis 60, no. 02 (1988): 280–88. http://dx.doi.org/10.1055/s-0038-1647045.
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SummaryWe have studied the interaction of ASvWf with human platelets in PRP and in suspensions of washed platelets containing either physiological or low external ionized calcium concentration [Ca2+]0. In hirudin-PRP or in washed platelets in 1.5-2 mM CaCl2, ASvWf up to 50 μg/ml does not induce platelet aggregation or the release reaction. When [Ca2+]c is decreased by addition of citrate to hirudin-PRP or when no CaCl2 is added to washed platelet suspensions, ASvWf does induce platelet aggregation and the release reaction. In low [Ca2+]0, ASvWf interacts with platelet GPIb to cause primary aggregation of disc-shaped platelets to each other through GPIIb/IIIa, with or without added fibrinogen. This primary platelet aggregation leads to thromboxane A2 formation and secondary aggregation and the release reaction. With [Ca2+]0 in the physiological range, there is less ASvWf interaction with GPIb, no primary platelet aggregation and no thromboxane A2 formation. The ASvWf-platelet interaction at physiological [Ca2+]0, however, enhances the platelet response to collagen or epinephrine.
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Kazes, Isabelle, Ismaı̈l Elalamy, Jean-Daniel Sraer, Mohamed Hatmi, and Geneviève Nguyen. "Platelet release of trimolecular complex components MT1-MMP/TIMP2/MMP2: involvement in MMP2 activation and platelet aggregation." Blood 96, no. 9 (November 1, 2000): 3064–69. http://dx.doi.org/10.1182/blood.v96.9.3064.
Full textAbstract:
Abstract Matrix metalloproteinase 2 (MMP2) has been reported to be secreted by collagen-stimulated platelets, and active MMP2 has been shown to play a role in platelet aggregation. It has been demonstrated that MMP2 activation is dependent on the complex (membrane type 1 [MT1]-MMP/tissue inhibitor of MMP2 [TIMP2]) receptor and MMP2. We have investigated human platelets as a possible source of MT1-MMP, and we have studied its role in MMP2 activation and in platelet aggregation. Gelatin zymograms showed the existence of MMP2 at proforms (68 kd) and activated-enzyme forms (62-59 kd) in supernatants of resting and activated platelets, respectively. No gelatinolytic activity was associated with the platelet pellet after aggregation, suggesting a total release of MMP2 during cell activation. By Western blot analysis in nonreduced conditions, MT1-MMP was found on resting platelet membranes in 2 forms–the inactive 45-kd form and an apparent 89-kd form, which totally disappeared under reduced conditions. After platelet degranulation, only the 45-kd form was detected. Reverse transcription–polymerase chain reaction experiments showed the expression in platelets of messenger RNA encoding for MMP2, MT1-MMP, and TIMP2. Flow cytometry analysis showed that MT1-MMP, MMP2, and TIMP2 expressions were enhanced at the activated platelet surface. MMP inhibitors, recombinant TIMP2, and synthetic BB94 inhibited collagen-induced platelet aggregation in a concentration-dependent manner, indicating the role of activated MT1-MMP in the modulation of platelet function. In conclusion, our results demonstrate the expression of the trimolecular complex components (MT1-MMP/TIMP2/MMP2) by blood platelets as well as the ability of MMP inhibitors to modulate the aggregating response.
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Kazes, Isabelle, Ismaı̈l Elalamy, Jean-Daniel Sraer, Mohamed Hatmi, and Geneviève Nguyen. "Platelet release of trimolecular complex components MT1-MMP/TIMP2/MMP2: involvement in MMP2 activation and platelet aggregation." Blood 96, no. 9 (November 1, 2000): 3064–69. http://dx.doi.org/10.1182/blood.v96.9.3064.h8003064_3064_3069.
Full textAbstract:
Matrix metalloproteinase 2 (MMP2) has been reported to be secreted by collagen-stimulated platelets, and active MMP2 has been shown to play a role in platelet aggregation. It has been demonstrated that MMP2 activation is dependent on the complex (membrane type 1 [MT1]-MMP/tissue inhibitor of MMP2 [TIMP2]) receptor and MMP2. We have investigated human platelets as a possible source of MT1-MMP, and we have studied its role in MMP2 activation and in platelet aggregation. Gelatin zymograms showed the existence of MMP2 at proforms (68 kd) and activated-enzyme forms (62-59 kd) in supernatants of resting and activated platelets, respectively. No gelatinolytic activity was associated with the platelet pellet after aggregation, suggesting a total release of MMP2 during cell activation. By Western blot analysis in nonreduced conditions, MT1-MMP was found on resting platelet membranes in 2 forms–the inactive 45-kd form and an apparent 89-kd form, which totally disappeared under reduced conditions. After platelet degranulation, only the 45-kd form was detected. Reverse transcription–polymerase chain reaction experiments showed the expression in platelets of messenger RNA encoding for MMP2, MT1-MMP, and TIMP2. Flow cytometry analysis showed that MT1-MMP, MMP2, and TIMP2 expressions were enhanced at the activated platelet surface. MMP inhibitors, recombinant TIMP2, and synthetic BB94 inhibited collagen-induced platelet aggregation in a concentration-dependent manner, indicating the role of activated MT1-MMP in the modulation of platelet function. In conclusion, our results demonstrate the expression of the trimolecular complex components (MT1-MMP/TIMP2/MMP2) by blood platelets as well as the ability of MMP inhibitors to modulate the aggregating response.
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Chung, Jun, Xue-Qing Wang, Frederik P. Lindberg, and William A. Frazier. "Thrombospondin-1 Acts Via IAP/CD47 to Synergize With Collagen in 2β1-Mediated Platelet Activation." Blood 94, no. 2 (July 15, 1999): 642–48. http://dx.doi.org/10.1182/blood.v94.2.642.
Full textAbstract:
Abstract Integrin-associated protein (IAP; or CD47) is a receptor for the cell binding domain (CBD) of thrombospondin-1 (TS1). In platelets, IAP associates with and regulates the function of IIbβ3 integrin (Chung et al, J Biol Chem 272:14740, 1997). We test here the possibility that CD47 may also modulate the function of platelet integrin 2β1, a collagen receptor. The CD47 agonist peptide, 4N1K (KRFYVVMWKK), derived from the CBD, synergizes with soluble collagen in aggregating platelet-rich plasma. 4N1K and intact TS1 also induce the aggregation of washed, unstirred platelets on immobilized collagen with a rapid increase in tyrosine phosphorylation. The effects of TS1 and 4N1K on platelet aggregation are absolutely dependent on IAP, as shown by the use of platelets from IAP−/− mice. Prostaglandin E1 (PGE1) prevents 4N1K-dependent aggregation on immobilized collagen but does not inhibit the 4N1K peptide stimulation of 2β1-dependent platelet spreading. Finally, a detergent-stable, physical association of IAP and 2β1 integrin is detected by coimmunoprecipitation. These results imply a role for IAP and TS1 in the early activation of platelets upon adhesion to collagen.
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Chung, Jun, Xue-Qing Wang, Frederik P. Lindberg, and William A. Frazier. "Thrombospondin-1 Acts Via IAP/CD47 to Synergize With Collagen in 2β1-Mediated Platelet Activation." Blood 94, no. 2 (July 15, 1999): 642–48. http://dx.doi.org/10.1182/blood.v94.2.642.414k35_642_648.
Full textAbstract:
Integrin-associated protein (IAP; or CD47) is a receptor for the cell binding domain (CBD) of thrombospondin-1 (TS1). In platelets, IAP associates with and regulates the function of IIbβ3 integrin (Chung et al, J Biol Chem 272:14740, 1997). We test here the possibility that CD47 may also modulate the function of platelet integrin 2β1, a collagen receptor. The CD47 agonist peptide, 4N1K (KRFYVVMWKK), derived from the CBD, synergizes with soluble collagen in aggregating platelet-rich plasma. 4N1K and intact TS1 also induce the aggregation of washed, unstirred platelets on immobilized collagen with a rapid increase in tyrosine phosphorylation. The effects of TS1 and 4N1K on platelet aggregation are absolutely dependent on IAP, as shown by the use of platelets from IAP−/− mice. Prostaglandin E1 (PGE1) prevents 4N1K-dependent aggregation on immobilized collagen but does not inhibit the 4N1K peptide stimulation of 2β1-dependent platelet spreading. Finally, a detergent-stable, physical association of IAP and 2β1 integrin is detected by coimmunoprecipitation. These results imply a role for IAP and TS1 in the early activation of platelets upon adhesion to collagen.
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Sawicki, Grzegorz, Esmond Sanders, Eduardo Salas, Mieczyslaw Wozniak, Jose Rodrigo, and Marek Radomski. "Localization and Translocation of MMP-2 during Aggregation of Human Platelets." Thrombosis and Haemostasis 80, no. 11 (1998): 836–39. http://dx.doi.org/10.1055/s-0037-1615367.
Full textAbstract:
SummaryWe have previously shown that human platelets express matrix metalloproteinase-2 (MMP-2) and that the release of this enzyme during platelet activation mediates the ADP- and thromboxane-independent part of aggregation. We have now used immunogold electron microscopy, flow cytometry, Western blot analysis and zymography methods to study the ultrastructural localization of MMP-2 in human washed platelets. Platelet aggregation was stimulated by collagen and the MMP-2 immunoreactivity of platelets was followed during various stages of aggregation. In resting platelets, MMP-2 was randomly distributed in the platelet cytosol without detectable association with platelet granules. Platelet aggregation caused the translocation of MMP-2 from the cytosol to the extracellular space. During the early stages of aggregation, MMP-2 remained in close association with the platelet plasma membrane. We conclude that the interactions of MMP-2 with platelet surface membranes mediate the aggregatory response induced by this enzyme.
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Yang, Linlin, Roger Ottenheijm, Paul Worley, Marc Freichel, and Juan E. Camacho Londoño. "Reduction in SOCE and Associated Aggregation in Platelets from Mice with Platelet-Specific Deletion of Orai1." Cells 11, no. 20 (October 14, 2022): 3225. http://dx.doi.org/10.3390/cells11203225.
Full textAbstract:
Calcium signalling in platelets through store operated Ca2+ entry (SOCE) or receptor-operated Ca2+ entry (ROCE) mechanisms is crucial for platelet activation and function. Orai1 proteins have been implicated in platelet’s SOCE. In this study we evaluated the contribution of Orai1 proteins to these processes using washed platelets from adult mice from both genders with platelet-specific deletion of the Orai1 gene (Orai1flox/flox; Pf4-Cre termed as Orai1Plt-KO) since mice with ubiquitous Orai1 deficiency show early lethality. Platelet aggregation as well as Ca2+ entry and release were measured in vitro following stimulation with collagen, collagen related peptide (CRP), thromboxane A2 analogue U46619, thrombin, ADP and the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) inhibitor thapsigargin, respectively. SOCE and aggregation induced by Thapsigargin up to a concentration of 0.3 µM was abrogated in Orai1-deficient platelets. Receptor-operated Ca2+-entry and/or platelet aggregation induced by CRP, U46619 or thrombin were partially affected by Orai1 deletion depending on the gender. In contrast, ADP-, collagen- and CRP-induced aggregation was comparable in Orai1Plt-KO platelets and control cells over the entire concentration range. Our results reinforce the indispensability of Orai1 proteins for SOCE in murine platelets, contribute to understand its role in agonist-dependent signalling and emphasize the importance to analyse platelets from both genders.
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Gordy, Dominique, and Elizabeth Stone. "Mouse Model for Platelet Aggregation using Flow Cytometry." American Journal of Clinical Pathology 158, Supplement_1 (November 1, 2022): S8—S9. http://dx.doi.org/10.1093/ajcp/aqac126.014.
Full textAbstract:
Abstract Platelets play crucial roles in hemostasis, bleeding, and thrombosis. Within the United States, an estimated 7,000 platelet units are transfused daily. The gold standard to measure platelet survival in humans is to determine post-transfusion recovery after an autologous transfusion of radiolabeled platelet units, however, the ability to detect platelets circulating after transfusion does not provide information on how well these platelets function in hemostasis. Clinically, platelet unit function is routinely measured using aggregometry, which requires large volumes of platelet concentrates and normal platelet counts. While the clinical demand for platelets continues to increase with advances in medical care, there remains a lack of in vitro measures to properly assess platelet function in animal models. Here we outline an in vitro method for characterizing platelet function using flow cytometry to assess platelet activation and aggregation simultaneously in a mouse model. Using two commercially available transgenic mouse lines, one with platelets expressing red fluorescent protein (RFP) and the other with platelets expressing green fluorescent protein (GFP), whole blood is collected from each transgenic mouse line by aseptic cardiac puncture, and leukocyte-reduced platelet rich plasma (LRPRP) is isolated after two consecutive centrifuge spins and leukocyte reduction. RFP- and GFP-labeled platelets can be visually separated by flow cytometry. Platelets are activated after incubation with 4 mM GPRP peptide followed by exposure to 0.5U/mL high activity bovine thrombin for 2 minutes. Platelets are then stained with anti-CD41a, labelling all platelets, and anti-CD62P, labelling activated platelets; these platelet populations can be analyzed by flow cytometry. When RFP- and GFP-LRPRP are combined prior to activation with thrombin, RFP- and GFP-labeled platelet aggregation can be measured as the number of cells doubly expressing RFP and GFP by flow cytometry. Thrombin stimulation activated 93.31% of the total number of RFP- and GFP-platelets. Of the activated, CD62P-positive platelets, 11.03% expressed both RFP and GFP, indicating that these platelets were aggregated. Of the inactivated, CD62P-negative platelets, 0.81% expressed both RFP and GFP. These results suggest that thrombin exposure activates platelets and causes platelet aggregation, while <1% of inactivated platelets aggregate. Additionally, platelet aggregation is easily measured by flow without differentially labeling the two separate platelet populations. These data indicate that our model is a viable measure of platelet function in vitro. Our model of platelet activation and aggregation provides a baseline measure of in vitro platelet function in RFP and GFP mice. This in vitro method of assessing platelet function can be applied to various experimental populations and used to quantify the effects of experimental conditions on platelet function in mice. Using this model of platelet function, factors influencing platelet storage can be characterized and ultimately used to improve platelet transfusion therapies.
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González, Roxana Elizabeth, Verónica Carolina Soto, María Mirta Sance, and Claudio Rómulo Galmarini. "Garlic inhibitory effect on platelet activity induced by different agonists." Revista de la Facultad de Ciencias Agrarias UNCuyo 53, no. 1 (July 7, 2021): 46–54. http://dx.doi.org/10.48162/rev.39.005.
Full textAbstract:
Platelets are essential elements of human blood. In addition to their normal role, platelets are involved in causing myocardial infarction, stroke and other thrombotic disorders. Platelet activation in vivo, probably involves a combination of agonists. Garlic has beneficial effects due to its ability to inhibit platelet aggregation and thromboxane formation. The aim of this work was to evaluate the ability of garlic extracts to inhibit platelet aggregation induced by different agonists and their mixtures in different donors. Significant differences were found in platelet aggregation in response to each agonist (P ≤ 0.05). The highest antiaggregatory effect was observed with arachidonic acid and the lowest effect with collagen-arachidonic acid mixture. Interaction effects between donor and agonist (or mixtures) were detected. The study showed the potential of aqueous garlic extracts to prevent platelet aggregation induced by different agonist.
Highlights
Platelets play a central role in the progression of atherosclerotic lesions.
Blood from nine non-smoker healthy donors was used for in vitro platelet aggregation study.
Significant differences were found in platelet aggregation in response to each agonist.
Aqueous garlic extracts could prevent platelet aggregation induced by different agonist.
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Starovoitov, A. G., A. L. Lipnitski, and A. V. Marochkov. "PLATELET AGGREGATION IN DONORS OF PLATELET MASS AND FRESH FROZEN PLASMA." Vestnik of Vitebsk State Medical University 20, no. 5 (October 11, 2021): 42–48. http://dx.doi.org/10.22263/2312-4156.2021.5.42.
Full textAbstract:
Currently, the most common method in clinical practice, that enables the determination of the functional state of platelets, is the method of platelet aggregation. Objectives. To study the aggregation of platelets in donors of platelet mass and fresh frozen plasma. Material and methods. The study included 31 donors of fresh frozen plasma and platelet mass. The study of platelet aggregation was carried out by the turbidimetric measurement technique on the AP2110 analyzer (ZAO «SOLAR», Minsk, Republic of Belarus) with an inductor: ADP (concentrations of 0.3 μg/ml, 0.6 μg/ml, 1.25 μg/ml and 2.5 μg/ml were used), epinephrine (concentrations of 2.5 μM and 5.0 μM were used), collagen (concentration of 2 mg/ml). Results. 33 analysis of platelet aggregation were performed in donors prior to collection of platelet mass and fresh frozen plasma. Only in 10 cases (30.3%) donors had normal platelet aggregation, hypoaggregation was detected in 15 cases (45.5%) and hyperaggregation - in 8 studies (24.2%). Impaired platelet aggregation was detected in all donors who had COVID-19 infection in their anamnesis (in 5 - hypoaggregation, in 4 - hyperaggregation). In donors who didn’t have this infection in their anamnesis, the incidence of platelet aggregation disorders was statistically significantly lower - 63.6% (in 10 - hypoaggregation, in 4 - hyperaggregation), p=0.04. The presence of COVID-19 infection in the donor’s anamnesis is an independent predictor of impaired platelet aggregation (Chi-square=7.24, p=0.007). Conclusions. The study of platelet aggregation must be mandatory before collecting platelet mass in all donors.
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Minamoto, Yoko, Takaaki Hato, Shingo Nakatani, and Shigeru Fujita. "Detection of Platelet Adhesion/Aggregation to Immobilized Ligands on Microbeads by an Aggregometer." Thrombosis and Haemostasis 76, no. 06 (1996): 1072–79. http://dx.doi.org/10.1055/s-0038-1650708.
Full textAbstract:
SummaryPlatelet aggregation is believed to follow platelet adhesion to vascular injury sites. We have developed a turbidimetric assay for platelet aggregation following platelet adhesion to immobilized ligands using an aggregometer. The addition of polystyrene beads coated with von Willebrand factor (vWF) or fibrinogen (Fg) to platelet suspensions caused prompt aggregation of beads and platelets, which was detected as an increase in light transmission. Electron microscopic analysis revealed that platelets adhered to the bead surfaces and that additional platelets adhered to already adhering platelets, leading to the formation of platelet aggregates. vWF-coated beads induced larger aggregates than Fg-coated beads. The interaction of vWF-coated beads with platelets was abolished by both GPIb and GPIIb-IIIa blockers, while that of Fg-coated beads was abolished by GPIIb-IIIa blockers. vWF-coated beads induced modest secretion of granules from platelets but no thromboxane B2 synthesis. Fg-coated beads induced neither reaction. However, pleckstrin phosphorylation and protein tyrosine phosphorylation was induced by both types of bead. Platelet aggregation following platelet adhesion to both types of bead was inhibited by ADP scavengers, a protein kinase C inhibitor and a tyrosine kinase inhibitor, but not by aspirin. These findings suggest that vWF- and Fg-coated beads can induce platelet aggregation following platelet adhesion through specific ligand-receptor interactions and intracellular signaling. Our simple assay using these beads may represent a useful test for immobilized ligand-induced platelet adhesion and aggregation.
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Heyns A du, P., A. Eldor, R. Yarom, and G. Marx. "Zinc-induced platelet aggregation is mediated by the fibrinogen receptor and is not accompanied by release or by thromboxane synthesis." Blood 66, no. 1 (July 1, 1985): 213–19. http://dx.doi.org/10.1182/blood.v66.1.213.bloodjournal661213.
Full textAbstract:
We demonstrate that zinc (0.1 to 0.3 mmol/L) induces aggregation of washed platelet suspensions. Higher concentrations (1 to 3 mmol/L) of zinc were needed to aggregate platelets in platelet-rich plasma obtained from blood anticoagulated with low-molecular-weight heparin, probably due to the binding of zinc to the plasma proteins. Zinc- induced aggregation of normal washed platelets required added fibrinogen and no aggregation occurred with thrombasthenic platelets or with normal platelets pretreated with a monoclonal antibody (10E5) that blocks the platelet fibrinogen receptor. These data indicate that the platelet membrane fibrinogen receptor-glycoproteins IIb and IIIa mediate the effect of zinc. Zinc-induced aggregation was blocked by the agent TMB-8, which interferes with the internal calcium flux, and by prostacyclin, which elevates platelet cyclic adenosine monophosphate levels. Zinc-induced aggregation was not accompanied by thromboxane synthesis or by the secretion of dense-body serotonin and was not affected by preexposure of platelets to acetylsalicylic acid. Experiments with creatine phosphate/creatine phosphokinase showed that the zinc effect on platelets was independent of extracellular adenosine diphosphate (ADP). Zinc had an additive effect when platelet aggregation was stimulated with subthreshhold concentrations of collagen or ADP. Together with the known effects of nutritional zinc on in vivo bleeding, on platelet aggregation, and on lipid metabolism, the results suggest that zinc may have an important bearing on normal hemostasis, thrombosis, and atherosclerosis.
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Nanda, Nisha, Patrick Andre, Ming Bao, Karl Clauser, Francis Deguzman, Duncan Howie, Pamela B. Conley, Cox Terhorst, and David R. Phillips. "Platelet aggregation induces platelet aggregate stability via SLAM family receptor signaling." Blood 106, no. 9 (November 1, 2005): 3028–34. http://dx.doi.org/10.1182/blood-2005-01-0333.
Full textAbstract:
AbstractPlatelet aggregation is a dynamic entity, capable of directing its own growth and stability via the activation of signaling cascades that lead to the expression and secretion of various secondary agonists. Here we show that the signaling pathways triggered during platelet aggregation include an intrinsic pro-thrombotic activity mediated by 2 homophilic adhesion molecules, CD84 and CD150 (SLAM [signaling lymphocyte activation molecule]), which are tyrosine phosphorylated in a platelet aggregation–dependent fashion. The 2 CD84/SLAM adapter proteins, SAP (SLAM-associated protein) and EAT-2 (EWS-activated transcript-2), were found in platelets; only SAP, however, was found to immunoprecipitate with tyrosine-phosphorylated SLAM. The immobilized extracellular domain of CD84 promoted microaggregate formation, while SAP-deficient platelets demonstrated defective spreading on immobilized CD84, demonstrating a functional role in platelets for SLAM family interactions. Finally, analysis of SLAM-deficient mice revealed an overall defect in platelet aggregation in vitro and a delayed arterial thrombotic process in vivo. The data indicate that signaling of the adhesion molecules in the SLAM family, activated by proximity during aggregation, further stabilize platelet-platelet interactions in thrombosis.