Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:Q9UE34 (fibrinogen)
 30,244 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cigarette smoking is a risk factor for the development of atherosclerosis. Possible mechanisms for this include leucocytes and platelet activation, and/or damage to the endothelium, any of which may contribute to changes in thrombosis and haemostasis. We examined the acute effects of smoking on these systems by obtaining blood before, immediately after, and at 10 and 30 min after the rapid smoking of two cigarettes in sequence by 20 smokers. Blood samples taken at the same time points from ten non-smokers acted as control material. In the smokers there was a transient rise in leucocyte count and neutrophil activation, but von Willebrand factor (VWF--marking endothelial damage) increased steadily at each time point (P <0.05). There were no changes in neutrophil elastase, soluble intercellular adhesion molecule-1 (sICAM-1 normally increased in smokers), fibrinogen, platelet count or soluble P-selectin (marking platelet activation, also normally increased in smokers). We conclude that the acute smoking of two cigarettes in succession will activate leucocytes and cause endothelial cell damage, but will not immediately influence platelet activity.
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PMID:The influence of acute smoking on leucocytes, platelets and the endothelium. 986 46

We compared several responses in thrombin-stimulated and collagen (type I)-stimulated platelets with and without forskolin and inhibitors of autocrine stimulation (IAS: an ADP-removing system of creatine phosphate/creatine phosphokinase, Arg-Gly-Asp-Ser peptide to prevent fibrinogen/fibronectin binding to GPIIb/IIIa, SQ 29.548 as a thromboxane A2 receptor antagonist, cyproheptadine as a serotonin receptor antagonist, BN 52021 as a platelet-activating factor receptor antagonist). The pattern of tyrosine-phosphorylated proteins, the phosphorylation of lipids in the polyphosphoinositide cycle and phosphorylation of pleckstrin (P47) were studied as markers for signal-transducing responses, exposure of CD62 (P-selectin) and CD63 (Glycoprotein 53), as well as secretion of ADP + ATP and beta-N-acetyl-glycosaminidase were studied as final activation responses. Clear differences between thrombin-stimulated and collagen-stimulated platelets were observed. First, practically all protein-tyrosine phosphorylation induced by thrombin was inhibited by IAS, while a partial inhibition was observed for collagen; the phosphorylation due to collagen alone was apparently stimulated by elevation of cAMP. Secondly, the other responses to thrombin were inhibited by increased levels of cAMP, independent of autocrine stimulation. In contrast, only the autocrine part of the collagen-induced responses was inhibited by elevation of cAMP. Thus, the inhibition by elevated cAMP seen in collagen-stimulated platelets seems to be due to removal of the G-protein-mediated activation from secreted autocrine stimulators either by IAS or forskolin. The remaining activity is a pure collagen effect which is not affected by elevated levels of cAMP.
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PMID:Role of autocrine stimulation on the effects of cyclic AMP on protein and lipid phosphorylation in collagen-activated and thrombin-activated platelets. 1009 87

Dual color flow cytometric techniques were applied to micro-aliquots of whole blood obtained from bleeding time (BT) wounds. Modifications in platelet activation markers (P-selectin [CD62P]) and lysosomal related protein (UMPS [CD63]), presence of membrane glycoproteins (GPIb [CD42b], GPIIb-IIIa [CD41a], GDIV [CD36], binding of von Willebrand factor (vWF), fibrinogen (Fg) and factor V [FV]) were analyzed in normal donors (n = 10) and in a severe von Willebrand patient (type 3) von Willebrand disease [vWD]). Samples of blood (20 microl) were sequentially removed from BT wound edges for up to 5 min and fixed with paraformaldehyde. Antigens were detected using the corresponding tagged monoclonal antibodies (moAbs) and quantitative results were referred to those found on platelet samples obtained from venous blood obtained from the same individuals. A progressive increase in % of platelets positive for activation dependent antigens (CD62 from 7 +/- 2 to 48 +/- 19% and CD63 from 9 +/- 1 to 44 +/- 8%; initial vs. 4 min) was observed. Accessibility of GPIIb-IIIa epitopes on platelets from BT wounds remained slightly above levels observed in venous blood platelets, despite a progressive increase in the presence of platelets positive for Fgn. Binding of MoAb to GPIV increased at late stages of BT. A moderate decrease in the binding of a moAb to GPIb was observed on platelets obtained at late stages of the BT (14 +/- 9% and 20 +/- 6% at 4 and 5 min, respectively). This apparent decrease in GPIb epitopes paralleled an increased presence of platelets positive for vWF (26 +/- 12 and 38 +/- 15%). Binding of moAb to GPIb always remained above basal levels in platelets obtained from BTs performed in the patient with type 3 vWD. FV levels on platelets coming from the BT persisted at background levels in all the individuals and at all times studied.
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PMID:Modifications in accessibility of membrane glycoproteins, binding of specific ligands and coagulation factor V during the activation of platelets in blood emerging from bleeding time wounds. 1020 98

Systemic thromboembolism is a major complication in patients with mitral stenosis, especially in those who have atrial fibrillation (AF). It has been suggested that there may be increased regional left atrial coagulation activity in such patients, despite normal systemic coagulation activity on peripheral blood sampling. Our aim was to investigate whether there were significant differences between intracardiac versus peripheral indexes of hypercoagulability in 25 patients (5 men; mean age 60 years) with mitral stenosis who were undergoing percutaneous balloon mitral valvuloplasty and who were all in chronic AF. Two days after halting warfarin therapy, intracardiac (right and left atria) and peripheral (venous and arterial) blood samples from patients were obtained and compared with levels in matched healthy controls in sinus rhythm. Thrombogenicity was assessed by levels of fibrin D-dimer, fibrinogen, indexes of platelet activation (soluble P-selectin and beta thromboglobulin [betaTG]) and indexes of endothelial dysfunction (soluble thrombomodulin [sTM] and von Willebrand factor [vWF]). There were no statistically significant differences in the various markers between the femoral vein and artery, left and right atria, and between the femoral vein and both atria (all p = NS). Plasma fibrinogen, vWf (both p <0.005), and D-dimer (p = 0.011) were significantly higher and levels of sP-selectin and sTM were lower (both p <0.005) in patients when compared with controls. There was no significant difference in plasma betaTG levels. Our results suggest that there is no significant variation in indexes of thrombogenesis, platelet activation, and endothelial dysfunction between left atrium, right atrium, and the peripheral artery or vein. Peripheral samples therefore do reflect atrial coagulation, platelet, and endothelial activities.
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PMID:Indexes of hypercoagulability measured in peripheral blood reflect levels in intracardiac blood in patients with atrial fibrillation secondary to mitral stenosis. 1042 53

Vasodilator-stimulated phosphoprotein (VASP), a substrate of cAMP- and cGMP-dependent protein kinases, is associated with focal adhesions, cell-cell contacts, microfilaments, and highly dynamic membrane regions. VASP, which is expressed in most cell types and in particularly high levels in human platelets, binds to profilin, zyxin, vinculin, F-actin, and the Listeria monocytogenes surface protein ActA. VASP is a member of the enabled (Ena)/VASP protein family and is thought to be involved in actin filament formation and integrin alphaIIbbeta3 inhibition in human platelets. To gain further insight into the in vivo function of this protein, VASP-deficient mice were generated by homologous recombination. VASP-/- mice demonstrated hyperplasia of megakaryocytes in bone marrow and spleen but exhibited no other macroscopic or microscopic abnormalities. Activation of platelets with thrombin induced a more than 2-fold higher surface expression of P-selectin and fibrinogen binding in VASP-deficient platelets in comparison to wild type. These data support the concept that VASP is a negative modulator of platelet and integrin alphaIIbbeta3 activation. Although the limited phenotypic differences between wild-type and VASP-/- mice suggested functional compensation of VASP by members of the Ena/VASP family, alterations in the expression levels of mammalian enabled (Mena) and Ena-VASP-like (Evl) protein were not detected. VASP-deficient mice may provide an interesting model system for diseases in which enhanced platelet activation plays a major role.
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PMID:Megakaryocyte hyperplasia and enhanced agonist-induced platelet activation in vasodilator-stimulated phosphoprotein knockout mice. 1039 58

Platelet activation has been a focus of numerous studies in normal and abnormal states. Morphological changes and calcium signals found with activated platelets in vitro have been well characterized. However, the rate of cell spreading on substrates and the frequency of calcium oscillation within individual platelets upon activation have not yet been reported. In this study, we first examined the ability of a recombinant fusion protein of rhodostomin (GST-rhodostomin), a snake disintegrin containing an Arg-Gly-Asp (RGD) motif, to activate platelets when GST-rhodostomin served as a substrate. Four aspects of platelet activities induced by immobilized GST-rhodostomin and fibrinogen were analyzed in parallel. Examinations of (1) translocation of P-selectin from intracellular compartments to the plasma membrane, (2) platelet adhesion to and spreading on substrates, (3) platelet contact pattern on substrates, and (4) the degree of phosphorylation of focal adhesion kinase in platelets indicated that GST-rhodostomin was a better substrate for platelet activation than fibrinogen. Analysis of the rate of platelet spreading on GST-rhodostomin was examined by time-lapsed video microscopy. The spreading rate averaged 0.43 micrometer/minute, while cell spreading averaged 0.22 micrometer/minute when platelets were plated on fibrinogen and treated with thrombin. A newly developed method, using time-lapsed microscopy and the Metamorph program, was used to analyze calcium signals within platelets. We found that platelets on GST-rhodostomin evoked calcium oscillation at a frequency of 4.77 spike/cell/minute vs 2.76 spike/cell/minute on fibrinogen. The results of cell spreading and calcium oscillation were consistent with the results of microscopic and biochemical assays. We therefore conclude that the determination of the rate of platelet spreading and the frequency of calcium oscillation within platelets performed in this study provides more quantitative parameters for measuring platelet activities. Our results also suggest that GST-rhodostomin might potentially be used as a probe to dissect the molecular mechanisms underlying the kinetic processes of platelet activation.
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PMID:Recombinant rhodostomin substrates induce transformation and active calcium oscillation in human platelets. 1041 93

Increased platelet reactivity is a descriptor of the risk of cardiovascular events in healthy men and in patients with overt coronary artery disease. We sought to determine if differential thresholds exist for activation of platelets with respect to alpha-granule degranulation and fibrinogen binding in healthy volunteers and in patients with acute coronary syndromes. We also sought to characterize the effect of aspirin on activation. Platelet activation was assessed with flow cytometry in whole blood anticoagulated with corn trypsin inhibitor and incubated with fluorescein isothiocyanate conjugated fibrinogen (to define activation of glycoprotein IIb-IIIa), a phycoerythrin conjugated antibody to P-selectin (a marker of alpha-granule degranulation), and selected concentrations of adenosine diphosphate (ADP) or thrombin receptor agonist peptide. ADP-induced fibrinogen binding was found to be a low threshold activation event (40% of platelets bound fibrinogen in response to 0.2 microM ADP). Alpha-granule degranulation was a higher threshold event (33% of platelets expressed P-selectin in response to 1.0 microM ADP). Intra- and interindividual variability were most apparent with low concentrations of agonist (0.2 microM ADP). Patients with acute coronary syndromes (on aspirin) had significantly increased P-selectin expression in response to ADP compared with healthy subjects (on aspirin), but no difference in ADP-induced fibrinogen binding was observed. Daily ingestion of 325 mg of aspirin had no effect on either P-selectin expression or fibrinogen binding in healthy subjects. Analysis of platelet reactivity with flow cytometry characterizes activation with respect to specific components of the process and should facilitate development and optimal titration of antiplatelet therapy.
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PMID:Differences between activation thresholds for platelet P-selectin glycoprotein IIb-IIIa expression and their clinical implications. 1041 96

Antiplatelet therapy with glycoprotein IIb-IIIa inhibitors reduces the incidence of cardiac events in patients with acute coronary syndromes. A lack of universal efficacy may result from interindividual variation in the inhibition of fibrinogen binding after exposure to tirofiban and eptifibatide. Accordingly, accurate monitoring of platelet function in individual subjects may be needed. To assess this possibility, blood was drawn from 15 healthy volunteers into syringes containing corn trypsin inhibitor (an anticoagulant that is a specific inhibitor of factor XIIa) and selected concentrations of tirofiban and eptifibatide. Platelets were then activated with adenosine diphosphate (ADP) and thrombin receptor agonist peptide. Flow cytometry was used to assess activation with respect to glycoprotein IIb-IIIa activation as reflected by fibrinogen binding and alpha-granule degranulation as reflected by P-selectin expression. In platelets activated with 1 microM ADP, clinically relevant concentrations of tirofiban caused inhibition of fibrinogen binding ranging from 17% to 88%. Similarly, eptifibatide caused inhibition of fibrinogen binding ranging from 32% to 74%. The highest concentration of eptifibatide tested enhanced agonist-induced degranulation, an effect not seen with tirofiban at concentrations tested. Flow cytometry in minimally altered whole blood can discriminate variation in the response to glycoprotein IIb-IIIa inhibitors with respect to specific components of platelet activation. Thus, the approach developed should facilitate definition of optimal platelet inhibition and individualized tailoring of therapy to induce optimal effects.
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PMID:Variable responses to inhibition of fibrinogen binding induced by tirofiban and eptifibatide in blood from healthy subjects. 1042 41

Cryopreservation of platelets is of great interest since it could extend to years the shelf life of therapeutic platelet concentrates (PCs) and facilitate stockpiling and inventory control in blood banking. We have compared the cryopreservation of PCs by the standard method using 6% Me(2)SO as cryoprotectant with the method of freezing employing low concentrations of Me(2)SO (2%) plus ThromboSol, a mixture of second-messenger effectors that protect platelets from cold damage. PC pools were treated either with 6% Me(2)SO or with ThromboSol and 2% Me(2)SO and then placed directly in a -80 degrees C freezer or in the vapor phase of a liquid nitrogen freezer (-120 degrees C). After storage for 1 week or for 3 months, samples were removed, thawed, and analyzed. Measurements included cell recovery, biochemical parameters, membrane glycoproteins (GPs), platelet aggregation, and binding of radiolabeled von Willebrand factor (vWF) and fibrinogen. PCs cryopreserved with ThromboSol and 2% Me(2)SO displayed a platelet recovery (90%) equivalent to those frozen with 6% Me(2)SO. Following either cryopreservation procedure, platelets showed increased surface expression of P-selectin and moderate loss of GP Ibalpha in comparison to fresh platelets. The aggregatory response to ristocetin and the binding of vWF were similar in platelets frozen by either procedure. Finally, both methods promoted comparable impairment of the reactivity of platelets to thrombin, aggregation and binding of fibrinogen and vWF, compared to that of fresh platelets. In summary, cryopreservation of PCs using reduced Me(2)SO concentration and ThromboSol yields platelets with in vitro functional characteristics equivalent to those of cells frozen with the conventional method using 6% Me(2)SO.
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PMID:Platelet cryopreservation using a reduced dimethyl sulfoxide concentration and second-messenger effectors as cryopreserving solution. 1045 97

Experimental models have indicated prothrombotic effects of inhibition of nitric oxide (NO) production, and anti-thrombotic effects of inhaled NO, but the influence of NO on platelet function in vivo in humans is not well established. We therefore investigated the effects of systemic inhibition of NO synthesis by N(G)-monomethyl-L-arginine (L-NMMA) and of NO inhalation on platelet function in vivo. On two occasions, L-NMMA (13.5 mg/kg) or saline infusion was administered to 14 healthy volunteers in a double-blind cross-over study. After a 30 min infusion of L-NMMA or placebo, NO inhalation (30 p.p.m) was added during the remaining 30 min of infusion, on both occasions. Measurements included filtragometry ex vivo (reflecting platelet aggregability), flow-cytometric evaluation of platelets in whole blood (fibrinogen binding and P-selectin expression), plasma beta-thromboglobulin (reflecting platelet secretion), cGMP in platelets and plasma, thrombin generation markers (thrombin fragment 1+2 and thrombin-antithrombin complexes) in plasma, and bleeding time. L-NMMA increased blood pressure and decreased heart rate. NO inhalation did not influence blood pressure or heart rate, but caused a 3-fold elevation in plasma cGMP levels (P<0.001). Neither L-NMMA nor NO influenced filtragometry readings or flow-cytometric determinations of platelet fibrinogen binding and P-selectin expression. Furthermore, plasma beta-thromboglobulin, platelet cGMP and thrombin generation markers were not influenced by either treatment. Bleeding time was not influenced by L-NMMA compared with placebo, but was increased by approximately 25% during NO inhalation (P<0.01), whether NO synthesis had been inhibited or not. The prolongation of bleeding time by inhaled NO was not accompanied by any effect on the platelet variables assessed. The present results indicate that circulating platelets are not influenced by endogenous or inhaled NO, presumably due to the rapid inactivation of NO in the blood. This does not exclude possible effects of endothelial NO in the interface between the blood and the vessel wall.
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PMID:Neither endogenous nor inhaled nitric oxide influences the function of circulating platelets in healthy volunteers. 1046 60


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