Platelet Apoptosis and Agonist Mediated Activation In Myelodysplastic Syndromes

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 1866-1866
Author(s):  
Nora V. Butta ◽  
Raquel de Paz ◽  
Mónica Martín Salces ◽  
Ihosvany Fernández Bello ◽  
Elena G. Arias Salgado ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Myelodysplastic Syndromes ◽  
Surface Expression ◽  
Refractory Anemia ◽  
Control Group ◽  
Western Blots ◽  
Platelet Surface ◽  
Fibrinogen Receptor ◽  
Bax Protein

Abstract Abstract 1866 Myelodysplastic syndromes (MDS) comprise distinct disorders characterized by dysplastic and ineffective hematopoiesis that seems to be related to an increased apoptosis of bone marrow cells (Nimer, Blood 111: 4841, 2008). Clinical manifestations in MDS range from a diverse degree of anemias, leuko- or thrombocytopenias to severe transfusion-dependent peripheral pancytopenias. Thrombocytopenia and platelet dysfunction contribute to hemorrhagic complications observed in MDS. Many of the features of apoptosis such as membrane fragmentation, microvesiculation and phosphatidylserine (PS) exposure are observed during platelet activation to a procoagulant state, raising the possibility that apoptosis may regulate platelet function. The aim of this work was to determine whether a correlation exists between apoptosis and activation processes in platelets from MDS patients. Twenty six patients diagnosed MDS and classified according to WHO-2008 were included: 6 with refractory anemia (RA), 7 with RA with ringed sideroblasts (RARS), 6 with refractory RA with excess blasts-1 (RAEB-1) and 7 with cytopenia with multilineage dysplasia (RCMD) associated with isolated 5q deletion. Twenty six healthy donors were included as control group. Apoptosis was determined by flow cytometry analysis through FITC-annexin V binding to platelet membrane PS exposed under basal conditions and after stimulation with a PAR-1 receptor agonist (TRAP, SFLLRN, thrombin receptor-activating peptide 6). Levels of pro- apoptotic Bax and anti-apoptotic Bcl-2 proteins were determined by densitometric analysis of western blots performed with platelet lysates. Platelet activation was determined through FITC-fibrinogen, FITC-PAC-1 (a mAb that recognizes activated conformation of fibrinogen receptor) and FITC-P-selectin mAb binding to quiescent and 100 mM TRAP activated platelets by flow cytometry. Surface expression of fibrinogen receptor (aIIb and b3 subunits) was determined by flow cytometry with specific mAbs. Platelets from RA, RARS and RCMD patients expressed more PS than control ones under basal conditions (p<0.05) as well as after 100 mM TRAP stimulation (p<0.05). Moreover, platelets from these MDS patients expressed more Bax protein than control group (p<0.05). On the other hand, PS exposure and Bax content in platelets from RAEB-1 patients were similar to controls, but they expressed a higher amount of Bcl-2 (p<0.05). No correlation was observed between PS exposure or Bax expression and platelet number. Platelets from all MDS patients showed an impaired activation by TRAP, even when PS exposure was higher than in control group. This diminished response to TRAP was not due to a reduction in surface expression of fibrinogen receptor in platelets from MDS patients. Our results suggest that platelets from RA, RARS and RCMD patients are more apoptotic than control ones and that a correlation between platelet surface PS and activation does not seem to exist. Moreover, dissimilarity in expression pattern of apoptotic proteins among MDS types indicates differences in the intracellular mechanisms underlying these pathologies. Disclosures: No relevant conflicts of interest to declare.

Platelet Functions and Risk Prognosis in Myelodysplastic Syndromes,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3806-3806
Author(s):  
Nora V. Butta ◽  
Mónica Martín Salces ◽  
Raquel de Paz ◽  
Elena G. Arias Salgado ◽  
Ihosvany Fernández Bello ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
High Risk ◽  
Myelodysplastic Syndromes ◽  
Surface Expression ◽  
Low Risk ◽  
Control Group ◽  
Platelet Surface ◽  
High Risk Patients ◽  
Fibrinogen Receptor ◽  
Risk Patients

Abstract Abstract 3806 The myelodysplastic syndromes (MDS) are a heterogenous group of clonal stem cell disorders with peripheral cytopenias and increased incidence of leukemic transformation. The prognosis of MDS is determined by several factors, including the presence of specific cytogenetic abnormalities, the percentage of blastoid cells in bone marrow and peripheral blood, the number of affected cell lineages, and transfusion dependency. The most commonly used risk stratification system is the International Prognostic Scoring System (IPSS). This score divides patients into a lower risk subset (low and intermediate-1) and a higher risk subset (intermediate-2 and high). Patients with MDS may have hemorrhagic complications with serious outcomes that are among the major causes of death in this population. These bleeding episodes that are often related to thrombocytopenia also occur in MDS patients with normal platelet count. The aim of this work was to study functional characteristics of platelets in MDS patients and their relationship to risk evaluated as indicated by IPSS. Eighty diagnosed MDS patients risk-stratified according to IPSS were included: 40 with low-risk, 29 with intermediate-1-risk (I-1), 8 with intermediate-2-risk (I-2) and 3 with high-risk. Eighty healthy donors were included as control group. Platelet-related primary haemostasis was evaluated with an automated platelet function analyzer (PFA-100®, Siemens Healthcare Diagnostics). Samples of citrated blood were aspirated under a shear rate of 4,000–5,000/s through a 150-μm aperture cut into a collagen-ADP (COL-ADP) or collagen-epinephrine (COL-EPI) coated membrane. The platelet haemostatic capacity is indicated by the time required for the platelet plug to occlude the aperture (closure time, CT), which is expressed in seconds. Platelet activation was determined through FITC-PAC-1 (a mAb that recognizes activated conformation of fibrinogen receptor) and FITC-P-selectin mAb binding to quiescent and 100 μM TRAP activated platelets by flow cytometry. Surface expression of fibrinogen receptor (αIIb and β3 subunits) was determined by flow cytometry with specific mAbs. Apoptosis was determined by flow cytometry analysis through FITC-annexin V binding to platelet membrane phosphatidylserine (PS) exposed in basal conditions. I-2 and high-risk patients were gathered together in a high-risk group in order to analyze experimental results. Statistical analysis was performed with one-way ANOVA and Tukey test. CTs obtained with COL-EPI and COL-ADP cartridges in controls and low risk patients were similar and significantly shorter than CTs observed in I-1-risk and high-risk MDS patients (p<0.05). Platelets from all MDS patients showed a reduced capability for being activated by 100 μM TRAP. This impairment was more evident in I-1-risk and high-risk patients: PAC-1 binding, in arbitrary units (AU), was 11368±1017 in controls; 7849±789 in low-risk MDS (p<0.05); 4161±591 in I-1-risk MDS (p<0.01 versus control and p<0.05 versus low-risk) and 492±184 in high-risk MDS (p<0.01 versus control and p<0.05 versus low-risk). The platelet surface expression of P-selectin induced by 100 μM TRAP was also reduced: 5102±340 AU in controls, 3318±400 AU in low-risk MDS (p<0.05); 1880 ±197 AU in I-1-risk MDS (p<0.05 versus control and versus low-risk), and 1211±130 AU in high-risk MDS (p<0.05 versus control and versus low-risk). Diminished responses to TRAP were not due to a reduction in surface expression of fibrinogen receptor in platelets from MDS patients. Platelets from MDS patients expressed more PS than controls under basal conditions. Mean fluorescence values for FITC-annexin binding were: 383±16 in controls; 444±21 in low-risk (p<0.05); 575±52 in I-1-risk MDS (p<0.05 versus control and versus low-risk); 611±17 in high-risk MDS (p<0.05 versus control and versus low-risk). Our results indicated that platelets from MDS patients had less ability to be activated and were more apoptotic than control ones. These dysfunctions were more pronounced when the risk of the disease was higher according to IPSS. Disclosures: No relevant conflicts of interest to declare.

scholarly journals von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2011-2021 ◽  
Author(s):  
P Hourdille ◽  
HR Gralnick ◽  
E Heilmann ◽  
A Derlon ◽  
AM Ferrer ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Immunogold Staining ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin- induced platelet activation is a potential mechanism for regulating platelet adhesivity.

A Study of Platelet Activation during Human Cardiopulmonary Bypass and the Effect of S-Nitrosoglutathione

1997 ◽  
Vol 78 (06) ◽  
pp. 1516-1519 ◽  
Author(s):  
Edward J Langford ◽  
Andrew Parfitt ◽  
Adam J de Beider ◽  
Michael T Marrinan ◽  
John F Martin
Keyword(s):  
Nitric Oxide ◽  
Flow Cytometry ◽  
Cardiac Surgery ◽  
Cardiopulmonary Bypass ◽  
Platelet Activation ◽  
Surface Expression ◽  
Platelet Inhibition ◽  
Nitric Oxide Donor ◽  
Platelet Dysfunction ◽  
Platelet Surface

SummaryCardiac surgery is complicated by the occurrence of post-operative bleeding due to platelet dysfunction. This is largely caused by platelet activation and consumption during cardiopulmonary bypass. Patients undergoing cardiac surgery requiring cardiopulmonary bypass were studied to determine whether early platelet changes due to bypass could be inhibited using the platelet-selective nitric oxide donor S-nitroso-glutathione (GSNO). Flow cytometry was used to measure platelet surface expression of P-selectin (an α-granule protein) and glycoproteins (GP) IIb/IIIa and Ib (mediators of aggregation and adhesion) before and 5 and 10 min after commencing cardiopulmonary bypass, in 6 controls and 6 patients receiving GSNO 50 μg/min. Platelet P-selectin expression increased during bypass both in controls and patients receiving GSNO. Glycoproteins IIb/IIIa and Ib fell during bypass in control and GSNO-treated patients. There was no difference between control and GSNO-treated groups. Thus no significant platelet inhibition by S-nitrosoglutathione was demonstrated under these conditions.

Multicolour Flow Cytometric Finetuning of the Classification of Myelodysplastic Syndromes.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2614-2614
Author(s):  
Arjan A. van de Loosdrecht ◽  
Theresia M. Westers ◽  
Guus Westra ◽  
Angelica Draeger ◽  
Vincent H. Van der Velden ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Myelodysplastic Syndromes ◽  
Surface Expression ◽  
New Drugs ◽  
Refractory Anemia ◽  
Aberrant Expression ◽  
Clinical Behaviour ◽  
Flow Cytometric ◽  
Hla Dr

Abstract The WHO classification of myeloid disorders contribute to a more refined classification and prognostication of myelodysplastic syndromes (MDS). The considerable differences in clinical behaviour of pure refractory anemia (RA) versus refractory cytopenia with multilineage dysplasia (RCMD) with or without ringsideroblasts are of importance in the management of patients with MDS. Flow cytometry may add additional diagnostic criteria to adequately discriminate RA from RCMD (+/− ringsideroblasts; (RS)) and may contribute in identifying Idiopathic Cytopenia of Undetermined Significance. We developed a 4-colour flow-cytometric procedure that comprises all differentiation stages of granulocytic, monocytic and erythroid lineages, instrumental for the recognition of various subpopulations within all three lineages in normal bone marrow samples. In 43 evaluable patients with MDS (RA, RARS, RCMD, RCMD-RS, MDS-U, RAEB-1 and 2), aberrant expression of differentiation antigens were demonstrated in 1 or more lineages. Flow-cytometry identified aberrancies in granulopoiesis and monocytopoiesis in 93% and 74% of the cases, respectively. In the majority of cases abnormal relations between CD13, CD16, CD11b, CD15 and HLA-DR were prominent in the granulopoiesis. In 34% of the cases a striking monocytopenia was detected, whereas in 59% abnormal surface expression of CD14, CD36 and CD33 indicating aberrant differentiation of monocytes. We defined aberrant myeloid blasts by a leukaemia associated phenotype (LAP) according to the definitions used in acute myeloid leukaemia. In 47% of the patients a LAP was detectable by demonstrating co-expression of CD5, CD7, CD19 and CD56 on CD34+ myeloid blasts. In all patients diagnosed as RA/RARS and MDS-U (n=12) according to WHO criteria, additional flow aberrancies were identified including a leukaemia associated phenotype of myeloid blasts in 41% of the cases. Only in 3 out of 28 cases with RCMD/RCMD-RS no erythroid aberrancies were detectable by flow-cytometry. In 9 normal control BM samples, no flow-cytometric abnormalities were present. It is concluded that flow-cytometry in MDS identifies aberrancies in the granulocytic and monocytic lineages and may classify patients with multi-lineage aberrancies not otherwise determined by cytology (WHO). Flow-cytometry may discriminate pure RA or MDS-U from RCMD. Since new drugs are emerging in low-risk MDS, the value of flow-cytometry might be of importance to further refine the classification in MDS. The exact role of these aberrant differentiation patterns on IPSS, clinical behaviour, impact on treatment decisions and as tool in disease monitoring have to be determined in future prospective studies.

scholarly journals von Willebrand factor bound to glycoprotein Ib is cleared from the platelet surface after platelet activation by thrombin

Blood ◽  
1992 ◽  
Vol 79 (8) ◽  
pp. 2011-2021
Author(s):  
P Hourdille ◽  
HR Gralnick ◽  
E Heilmann ◽  
A Derlon ◽  
AM Ferrer ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Platelet Activation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Surface Expression ◽  
Von Willebrand Disease ◽  
Platelet Surface ◽  
Immunogold Staining ◽  
Von Willebrand ◽  
Willebrand Factor

We recently reported that after activation of human platelets by thrombin, glycoprotein (GP) Ib-IX complexes are translocated to the surface-connected canalicular system (SCCS) (Blood 76:1503, 1990). As GPIb is a major receptor for von Willebrand factor (vWF) in platelet adhesion, we have now examined the consequences of thrombin activation on the organization of vWF bound to GPIb on the platelet surface. Studies were performed using monoclonal or polyclonal antibodies in either immunogold staining and electron microscopy (Au-EM) or in flow cytometry. When unstirred platelet-rich plasma was incubated with ristocetin, bound vWF was located by Au-EM as discrete masses regularly distributed over the cell surface. Platelets from a patient with Glanzmann's thrombasthenia, lacking GPIIb-IIIa complexes, gave a similar pattern, confirming that this represented binding to GPIb. That ristocetin was not precipitating vWF before their binding to the platelets was shown by the detection of similar masses on the surface of platelets of a patient with type IIB von Willebrand disease. Experiments were continued using washed normal platelets incubated in Tyrode-EDTA, the purpose of the EDTA being to limit the surface expression of endogenous vWF after platelet stimulation. Under these conditions, platelets were treated with ristocetin for 5 minutes at 37 degrees C in the presence of increasing amounts of purified vWF. This was followed by incubation with thrombin (0.5 U/mL) for periods of up to 10 minutes. Flow cytometry showed a time-dependent loss in the surface expression of vWF bound to GPIb and these changes were confirmed by Au-EM. In particular, immunogold staining performed on ultrathin sections showed that the bulk of the vWF was being cleared to internal membrane systems. Surface clearance of vWF during thrombin- induced platelet activation is a potential mechanism for regulating platelet adhesivity.

Platelet apoptosis and agonist-mediated activation in myelodysplastic syndromes

2013 ◽  
Vol 109 (05) ◽  
pp. 909-919 ◽  
Author(s):  
Víctor Jiménez-Yuste ◽  
Ihosvany Bello ◽  
Elena García Salgado ◽  
María Álvarez ◽  
Mónica Martín ◽  
...  
Keyword(s):  
Platelet Count ◽  
Platelet Activation ◽  
Myelodysplastic Syndromes ◽  
Thrombin Generation ◽  
Procoagulant Activity ◽  
Control Group ◽  
Bleeding Tendency ◽  
Western Blots ◽  
Platelet Apoptosis ◽  
Generation Capacity

SummaryPatients with myelodysplastic syndromes (MDS) have a defect in the differentiation of bone marrow multipotent progenitor cells. Thrombocytopenia in MDS patients may be due to premature megakaryocyte death, but platelet apoptotic mechanisms may also occur. This study aimed to study function and apoptotic state of platelets from MDS patients with different platelet count. Reticulated platelets, platelet activation, activated caspases and annexin-V binding were evaluated by flow cytometry. Pro-apoptotic Bax and Bak proteins were determined by western blots and plasma thrombopoietin by ELISA. Microparticle-associated procoagulant activity and thrombin generation capacity of plasma were determined by an activity kit and calibrated automated thrombography, respectively. High plasma thrombopoietin levels and low immature circulating platelet count showed a pattern of hypoplastic thrombocytopenia in MDS patients. Platelets from MDS patients showed reduced activation capacity and more apoptosis signs than controls. Patients with the lowest platelet count showed less platelet activation and the highest extent of platelet apoptosis. On this basis, patients with thrombocytopenia should suffer more haemorrhagic episodes than is actually observed. Consequently, we tested whether there were some compensatory mechanisms to counteract their expected bleeding tendency. Microparticle-associated procoagulant activity was enhanced in MDS patients with thrombocytopenia, whereas their plasma thrombin generation capacity was similar to control group. This research shows a hypoplastic thrombocytopenia that platelets from MDS patients possess an impaired ability to be stimulated and more apoptosis markers than those from healthy controls, indicating that MDS is a stem cell disorder, and then, both number and function of progeny cells, might be affected.

scholarly journals Platelet and Immune Characteristics of Patients with Immune Thrombocytopaenia Non Responders to Therapeutic Treatments

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1089-1089
Author(s):  
Elena Monzón Manzano ◽  
Raul Justo Sanz ◽  
Diana Hernández ◽  
Teresa Álvarez Roman ◽  
Ihosvany Fernandez-Bello ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Immune Response ◽  
Sialic Acid ◽  
Research Funding ◽  
Caspase 3 ◽  
Mononuclear Cells ◽  
Ricinus Communis ◽  
The Other ◽  
Control Group ◽  
Platelet Surface

Introduction: Mechanisms leading to diminished platelet counts in immune thrombocytopaenia (ITP) appear to be multifactorial: autoantibodies, autoreactive CD8+ cytotoxic T cells, enhanced apoptosis and loss of sialic acid which mediates platelet clearance through the Ashwell-Morell receptors present in hepatocytes. Differential involvement of each of them might condition the ability of patients with ITP to respond to treatments. We aimed to examine platelet features and the immunological state of patients with ITP who do not respond to any treatment to detect the unique characteristics of this group. Methods: This was an observational, prospective and transversal study. Patients with chronic primary ITP were included: 28 ITP patients without treatment for at least 6 months (UT-ITP); 36 responders to agonists of thrombopoietin receptors (TPO-RA); and 14 ITP patients who did not respond to first- and second-line treatments (NR-ITP). A healthy control group (n=104) was also included in the study. Active caspase-3, -7, -8 or -9 were determined by flow cytometry using CaspaTag kits (Millipore, Madrid, Spain) in PRP diluted with HEPES-buffer containing 2 mM Ca2+ and 2 mM Gly-Pro-Arg-Pro (Sigma-Aldrich, Madrid, Spain) to prevent fibrin formation . Platelet surface glycan exposure was analysed by determining the binding of lectins by flow cytometry. To do so, washed platelets were incubated with 1 μg/ml Alexa fluor 488-conjugated wheat germ agglutinin lectin (WGA, Invitrogen, Spain) or with 1 μg/ml FITC-conjugated Ricinus communis agglutinin (RCA, Vector Labs, UK). WGA binds to sialic acid and N-acetylglucosaminyl residues, and RCA is a galactose-specific legume lectin which binding serves as an indirect measurement of the loss of sialic acid. Peripheral blood mononuclear cells (PBMCs) subsets were analysed by flow cytometry using specific antibodies. Experimental data was analysed using SPSS 9.0 software (SPSS Inc., Chicago, IL). Results: Platelets from TPO-RA treated and from NR-ITP patients had increased caspase-3, -7, -8 and -9 activities (Figure 1A). Platelets from NR-ITP patients exposed less sialic acid and more N-acetylglucosaminyl residues than the other groups (Figure 1B). Binding of WGA and RCA correlated with caspase activities (Table 1). Distribution of lymphocytes, monocytes and natural killer cells is shown in Table 1. NR-ITP patients had an increased proportion of B lymphocyte (LB), maybe due to a significant rise in the fraction of naive LB cells, and a diminution in LTreg subset. Whereas classical monocytes was increased, nonclassical monocyte fraction was decreased in the UT-ITP and NR-ITP groups. NR-ITP patients also presented an increased CD16+CD56bright cells fraction and a diminished NK CD16+CD56dim subset. TPO-RA-treated patients seemed to recover an immune homeostasis similar to healthy controls (monocyte and NK cells subset distribution and LTreg count similar to control group). It is of interest to note the relationship between loss of sialic acid from platelet surface glycans and Tregs count: the most reduced surface exposure of sialic acid, the less Treg count (Figure 2). Conclusions: Platelets from NR-ITP patients had more signs of apoptosis and a different composition of surface glycans, accompanied by a diminished LTreg population, a higher LB naïve percentage, and an increased CD16+CD56bright cells fraction in circulation, indicating a severe deregulation of the immune system. Since an inverse correlation was observed between loss of sialic acid and LTreg count, a potential relationship between glycan composition on the platelet surface and immune response is suggested, positing terminal sugar moieties of the glycan chains as aetiopathogenic agents in ITP. On the other hand, TPO-RA appears to have a beneficial effect on immune response. Nevertheless, one of the limitations of our study was that patients were recruited once the response to TPO-RA was achieved; therefore, a longitudinal study would provide more information regarding TPO-RA effects. This work was supported by grants from the FIS-FONDOS FEDER (PI15/01457, NB). NVB holds a Miguel Servet tenure track grant from FIS-FONDOS FEDER (CP14/00024). Disclosures Álvarez Roman: Roche: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Bayer: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Consultancy, Speakers Bureau; Takeda: Research Funding; NovoNordisk: Consultancy, Speakers Bureau; CSL Behring: Consultancy, Speakers Bureau; Sobi: Consultancy, Speakers Bureau. Fernandez-Bello:Novartis, Pfizer, ROCHE, Stago: Speakers Bureau. Martín:SOBI: Research Funding; Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau. Rivas Pollmar:Novartis, Pfizer, ROCHE, Novo Nordisk: Speakers Bureau; SOBI: Research Funding. Canales:Novartis: Honoraria; Takeda: Speakers Bureau; iQone: Honoraria; Sandoz: Honoraria; Celgene: Honoraria; SOBI: Research Funding; Karyopharm: Honoraria; F. Hoffmann-La Roche Ltd: Honoraria, Speakers Bureau; Gilead: Honoraria; Janssen: Honoraria, Speakers Bureau. Jimenez-Yuste:Bayer, CSL Behring, Grifols, Novo Nordisk, Octapharma, Pfizer, Roche, Sobi, Shire: Consultancy, Honoraria, Other: reimbursement for attending symposia/congresses , Research Funding, Speakers Bureau. Butta:Novartis: Consultancy; Roche, Pfizer: Speakers Bureau.

scholarly journals Factor XIIIa binding to activated platelets is mediated through activation of glycoprotein IIb-IIIa

Blood ◽  
1994 ◽  
Vol 83 (4) ◽  
pp. 1006-1016 ◽  
Author(s):  
AD Cox ◽  
DV Devine
Keyword(s):  
Monoclonal Antibody ◽  
Flow Cytometry ◽  
Platelet Activation ◽  
Factor Xiiia ◽  
Cross Linking ◽  
Platelet Surface ◽  
Activated Platelets ◽  
Fibrinogen Binding ◽  
A Chain ◽  
Functional Receptor

Abstract Stabilization of a clot is dependent on fibrin cross-linking mediated by the transglutaminase, factor XIIIa (FXIIIa). In addition to fibrin stabilization, FXIIIa acts on a number of platelet-reactive proteins, including fibronectin and vitronectin, as well as the platelet proteins, glycoprotein (GP) IIb-IIIa, myosin, and actin. However, conditions inducing the platelet-activation dependent binding of FXIIIa have not been characterized nor have the sites mediating FXIIIa binding been identified. The generation of FXIIIa and consequent detection of FXIIIa on the platelet surface were compared with other thrombin- induced activation events; the rate at which FXIIIa bound to activated platelets was much slower than platelet degranulation or fibrin(ogen) binding. Whereas platelets could be rapidly induced to express a functional receptor for FXIIIa, the rate of FXIIIa binding to platelets is limited by the rate of conversion of FXIII to FXIIIa. Immunoprecipitation of radiolabeled platelets using polyclonal anti- FXIII A-chain antibody identified two proteins corresponding to GPIIb and GPIIIa. Preincubation of intact platelets with 7E3, a monoclonal antibody that blocks the fibrinogen binding site, or GRGDSP peptide inhibited FXIIIa binding by about 95% when measured by flow cytometry; FXIIIa binding to purified GPIIb-IIIa was also inhibited by 7E3. The binding of FXIIIa to purified GPIIb-IIIa was enhanced by the addition of fibrinogen, but not by that of fibronectin or thrombospondin, suggesting that FXIIIa also binds to fibrinogen associated with the complex. These observations suggest that activated platelets bearing FXIIIa may enhance stabilization of platelet-rich thrombi through surface-localized cross-linking events.

A novel homozygous mutation (1619delC) in GPIIb gene associated with Glanzmann thrombasthenia, the decay of GPIIb-mRNA and the synthesis of a truncated GPIIb unable to form complex with GPIIIa

2005 ◽  
Vol 93 (05) ◽  
pp. 904-909 ◽  
Author(s):  
Gergely Losonczy ◽  
Nurit Rosenberg ◽  
Csongor Kiss ◽  
János Kappelmayer ◽  
György Vereb ◽  
...  
Keyword(s):  
Stop Codon ◽  
Flow Cytometric Analysis ◽  
Surface Expression ◽  
Homozygous Deletion ◽  
Homozygous Mutation ◽  
Truncated Form ◽  
Platelet Surface ◽  
Form Complex ◽  
Glanzmann Thrombasthenia ◽  
Fibrinogen Receptor

SummaryThe absence of agonist-induced platelet aggregation and the lack of fibrinogen receptor (GPIIb/IIIa) on the platelet surface demonstrated that the severe hemorrhagic complications of a child of Romany descent were caused by Glanzmann thrombasthenia. DNA sequencing revealed a novel homozygous deletion of a cytosine (1619delC) in the GPIIb gene causing a frameshift and predicting a novel stop codon at position 533 following 24 altered amino acids. Both parents possessed the same deletion in heterozygous form. The amount of GPIIb mRNA in the patient’s platelets was 0.06% of the amount measured in control platelets. Neither GPIIb nor its truncated form could be detected in the platelets of the patient by Western blotting, while a small amount of GPIIIa was demonstrated. Quantitative flow cytometric analysis showed an elevated number of vitronectin receptors, a component of which is GPIIIa, on the patient’s platelets. The surface expression of vitronectin receptor on thrombasthenic, but not on normal platelets was further increased by activation with thrombin receptor agonist peptide. BHK cells transfected with wild type GPIIIa and mutated GPIIb failed to express any mature GPIIb or pro-GPIIb. Immunoprecipitation with a polyclonal antibody recognizing both GPIIb and GPIIIa recovered a 60 kDa truncated form of GPIIb. This band was absent when immunoprecipitation was carried out with an antibody recognizing GPIIIa, suggesting that the truncated protein, lacking calf-1, calf-2 domains and major part of the thigh domain, is unable to form complex with GPIIIa.

DETECTION OF ACTIVATED PLATELETS IN WHOLE BLOOD BY FLOW CYTOMETRY

1987 ◽  
Author(s):  
S J Shattil ◽  
J A Hoxie ◽  
M Cunningham ◽  
C S Abrahms ◽  
J O’Brien ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Monoclonal Antibodies ◽  
Platelet Activation ◽  
Whole Blood ◽  
Thrombus Formation ◽  
Membrane Surface ◽  
White Blood Cells ◽  
Color Flow ◽  
Platelet Surface ◽  
Activated Platelets

Platelets may become activated in a number of clinical disorders and participate in thrombus formation. We have developed a direct test for activated platelets in whole blood that utilizes dual-color flow cytometry and requires no washing steps. Platelets were distinguished from erythrocytes and white blood cells in the flow cytometer by labeling the platelets with biotin-AP1, an antibody specific for membrane glycoprotein lb, and analyzing the cells for phycoerythrin-streptavidin fluorescence. Membrane surface changes resulting from platelet activation were detected with three different FITC-labeled monoclonal antibodies: 1) PAC1, an antibody specific for the fibrinogen receptor on activated platelets; 2) 9F9, which binds to the D-domain of fibrinogen and detects platelet-bound fibrinogen; and 3) S12, which binds to an alpha-granule membrane protein that associates with the platelet surface during secretion. Unstimulated platelets demonstrated no PAC1, 9F9, or S12-specific fluorescence, indicating that they did not bind these antibodies. Upon stimulation with agonists, however, the platelets demonstrated a dose-dependent increase in FITC-fluorescence. The binding of 9F9 to activated platelets required fibrinogen. Low concentrations of ADP and epinephrine, which induce fibrinogen receptors but little secretion, stimulated near-maximal PAC1 or 9F9 binding but little S12 binding. On the other hand, a concentration of phorbol myristate acetate that evokes full platelet aggregation and secretion induced maximal binding of all three antibodies. When blood samples containing activated and non-activated platelets were mixed, as few as 0.8% activated platelets could be detected by this technique. There was a direct correlation between ADP-induced FITC-PAC1 binding and binding determined in a conventional 125I-PAC1 binding assay (r = 0.99; p < 0.001). These studies demonstrate that activated platelets can be reliably detected in whole blood using activation-dependent monoclonal antibodies and flow cytometry. This method may be useful to assess the degree of platelet activation and the efficacy platelet inhibitor therapy in thrombotic disorders.

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