Effect of nitroxyl on human platelets function

2005 ◽  
Vol 94 (09) ◽  
pp. 578-584 ◽  
Author(s):  
Emilse Bermejo ◽  
Fabiana Alberto ◽  
Ruth E. Rosenstein ◽  
Sara E. Bari ◽  
María A. Lazzari ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Functional Role ◽  
Human Platelet ◽  
Atp Release ◽  
Human Platelets ◽  
Angeli's Salt ◽  
Human Platelet Aggregation ◽  
Platelets Function ◽  
Platelet Physiology

SummaryThere is a growing body of evidence on the role of nitric oxide (NO) in human platelet physiology regulation. Recently, interest has developed in the functional role of an alternative redox form of NO, namely nitroxyl (HNO/NO-), because it is formed by a number of diverse biochemical reactions. The aim of the present study was to comparatively analyze the effect of HNO and NO on several functional parameters of human platelets. For this purpose, sodium trioxodinitrate (Angeli’s salt, AS) and sodium nitroprusside (SNP) were used as HNO and NO releasers, respectively. Both AS and SNP significantly inhibited platelet aggregation and ATP release induced by different agonists and adrenaline. AS or SNP did not modify the expression of platelet glycoproteins (Ib, IIb-IIIa, Ia-IIa, IV), whereas they substantially decreased the levels of CD62P, CD63 and of PAC-1 (a platelet activated glycoprotein IIb/IIIa epitope) after the stimulation with ADP. AS and SNP significantly increased cGMP accumulation in a 1H-[1,2,4]oxadiazolo [4,3-a] quinoxalin-1-one (ODQ)-sensitive manner. However, while L-cysteine reduced the effect of AS, it increased the effect of SNP on this parameter. Accordingly, a differential effect of L-cysteine was observed on the antiaggregatory effect of both compounds. In summary, these results indicate that HNO is an effective inhibitor of human platelet aggregation.

Human Platelet Aggregation Without Thromboxane (Tx) Formation

1981 ◽  
Author(s):  
J Westwick ◽  
J B Smith ◽  
V V Kakkar
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Human Platelets ◽  
Synthesis Inhibitor ◽  
Thromboxane Receptor ◽  
Human Platelet Aggregation ◽  
Thromboxane Receptor Antagonist ◽  
Induced Aggregation ◽  
Carbocyclic Thromboxane A2

It is not known whether PG endoperoxides have to be converted to TxA2 in order to induce aggregation and secretion We have examined this crucial question by measuring human platelet aggregation, 14C-5HT release and TxB2 formation induced by collagen, arachidonic acid (AA), adrenaline, U46619 and PGH2 in presence of either 1) 1-2-(4-carboxy-phenoxy) ethyl imidazole hydrochloride, a potent and selective thromboxane synthesis inhibitor (TSI) or a carbocyclic thromboxane A2 (CTA) - a so called thromboxane receptor antagonist. TSI, 1.5 to 75μM produced a dose related inhibition (IC50 5μM n=5) of Tx and elevation of PGE2 synthesis in adrenaline (8μM) and collagen (1.5μg/ml) stimulated platelets. When 14C-SHT labelled platelets were stimulated with 4.5μM adrenaline in the presence of 0, 2.5, 15 and 300μM TSI a 35±2.8, 27±0.5, 24.5±5.0% release of 14C-5HT release resulted and a 10014, 9612, 9711 and 9114% of control aggregation occurred. Similarly when human platelets were stimulated with 0.8mMAA a 51±1.4% (mean ±SE) release of 14C-5HT occurred, while in the presence of 15, 75 and 300μM of UK, a 42±0.4, 32±1, 33±3% of 14C-5HT release resulted. Aggregation induced by the PG endoperoxide analogue U46619 (lμM) was not inhibited by 300μM TSI or l00μM indomethacin, although 99.5% inhibition of Tx formation resulted, and 50 to 60% inhibition of 14C-5HT release was produced both by TSI and indomethacin. However CTA (l-3±M) produced a dose related inhibition of both aggregation and release induced by U46619. CTA (l-10μM) was found to produce superimposable dose related inhibition of collagen induced aggregation and secretion of platelets, whether the platelets were pretreated with 300μM TSI, or not.These results suggest that Tx formation is not necessary for human platelet aggregation, although is contributory to 14C-5HT release induced by collagen, adrenaline, AA and U46619.Also caution must be employed when CTA is used to elucidate the role of TxA2, as it appears to be an effective PG endoperoxide antagonist.

Differential Ability of Agonists to Express Distinct Pools of Fibrinogen (Gpllb/llla) Receptors which Can Mediate the Aggregation of Human Platelets

1989 ◽  
Vol 62 (03) ◽  
pp. 955-961 ◽  
Author(s):  
Ian S Watts ◽  
Rebecca J Keery ◽  
Philip Lumley
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Surface Membrane ◽  
Blood Platelet ◽  
Human Platelets ◽  
Membrane Glycoprotein ◽  
Platelet Surface ◽  
Human Platelet Aggregation ◽  
Differential Ability ◽  
Blood Platelet Aggregation

SummaryWe have investigated the effect of two procedures that modify human platelet surface membrane glycoprotein (Gp) IIb and IIIa complexes upon whole blood platelet aggregation to a range of agonists. (A) Irreversible disruption of complexes by temporary (30 min) Ca2+-deprivation with EGTA at 37° C. (B) Binding of a monoclonal antibody M148 to the complex. EGTA exposure abolished aggregation to ADP, adrenaline and PAF. In contrast, full aggregation curves to collagen and U-46619 could still be established. EGTA exposure reduced M148 binding to platelets by 80%. Excess M148 abolished aggregation to ADP, PAF, collagen and U-46619. However, upon removal of unbound antibody from platelets full aggregation curves to collagen and U-46619 but not to ADP and PAF could be re-established. Thus human platelet aggregation to ADP, PAF and adrenaline appears absolutely dependent upon surface membrane GpIIb/IIIa complexes. In contrast, collagen and U-46619 cause expression of an additional distinct pool of Gp complexes inaccessible to EGTA and M148 in unstimulated platelets which is intimately involved in aggregation to these agonists.

Collagen-Induced Platelet Aggregation: -Evidence Against the Essential Role of Platelet Adenosine Diphosphate

1979 ◽  
Vol 42 (04) ◽  
pp. 1193-1206 ◽  
Author(s):  
Barbara Nunn
Keyword(s):  
Platelet Aggregation ◽  
Time Course ◽  
Essential Role ◽  
Atp Release ◽  
Adenosine Diphosphate ◽  
Human Platelets ◽  
High Doses ◽  
Induced Aggregation

SummaryThe hypothesis that platelet ADP is responsible for collagen-induced aggregation has been re-examined. It was found that the concentration of ADP obtaining in human PRP at the onset of aggregation was not sufficient to account for that aggregation. Furthermore, the time-course of collagen-induced release in human PRP was the same as that in sheep PRP where ADP does not cause release. These findings are not consistent with claims that ADP alone perpetuates a collagen-initiated release-aggregation-release sequence. The effects of high doses of collagen, which released 4-5 μM ADP, were not inhibited by 500 pM adenosine, a concentration that greatly reduced the effect of 300 μM ADP. Collagen caused aggregation in ADP-refractory PRP and in platelet suspensions unresponsive to 1 mM ADP. Thus human platelets can aggregate in response to collagen under circumstances in which they cannot respond to ADP. Apyrase inhibited aggregation and ATP release in platelet suspensions but not in human PRP. Evidence is presented that the means currently used to examine the role of ADP in aggregation require investigation.

Endotoxin-Induced Platelet Activation in Human Whole Blood In Vitro

1988 ◽  
Vol 59 (03) ◽  
pp. 378-382 ◽  
Author(s):  
Gyorgy Csako ◽  
Eva A Suba ◽  
Ronald J Elin
Keyword(s):  
Platelet Aggregation ◽  
Whole Blood ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Atp Release ◽  
Human Platelets ◽  
Lag Phase ◽  
Human Whole Blood ◽  
Dose Dependent

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.

Inhibition of Human Platelet Aggregation by the Proteolytic Effect of Streptokinase Role of the Human Factor-VIII-Related Protein

1976 ◽  
Vol 5 (5) ◽  
pp. 306-317
Author(s):  
Ricardo Castillo ◽  
Santiago Maragall ◽  
Javier Alvarez Guisasola ◽  
Francisco Casals ◽  
Juan Profitós ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Factor Viii ◽  
Human Factor ◽  
Human Platelet ◽  
Related Protein ◽  
Human Platelet Aggregation ◽  
Human Factor Viii

59 Role of phosphatidylinositol 3-kinase in human platelet aggregation

1997 ◽  
Vol 25 (4) ◽  
pp. S600-S600 ◽  
Author(s):  
BUKHTIAR H. SHAH ◽  
SHEIKH A. SAEED ◽  
GAZALA SHAMIM ◽  
ZAFAR NAWAZ ◽  
ANWAR H. GILANI
Keyword(s):  
Platelet Aggregation ◽  
Human Platelet ◽  
Phosphatidylinositol 3 Kinase ◽  
Human Platelet Aggregation ◽  
Phosphatidylinositol 3

Functional role of a polymorphism in the Pannexin1 gene in collageninduced platelet aggregation

2015 ◽  
Vol 114 (08) ◽  
pp. 325-336 ◽  
Author(s):  
Filippo Molica ◽  
Jean-François Denis ◽  
Paul Bradfield ◽  
Silvia Penuela ◽  
Anne Zufferey ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Platelet Reactivity ◽  
Critical Role ◽  
Atp Release ◽  
Human Platelets ◽  
Immune Synapse ◽  
Cardiovascular Patients ◽  
Exogenous Expression ◽  
First Time

SummaryPannexin1 (Panx1) forms ATP channels that play a critical role in the immune response by reinforcing purinergic signal amplification in the immune synapse. Platelets express Panx1 and given the importance of ATP release in platelets, we investigated Panx1 function in platelet aggregation and the potential impact of genetic polymorphisms on Panx1 channels. We show here that Panx1 forms ATP release channels in human platelets and that inhibiting Panx1 channel function with probenecid, mefloquine or specific 10Panx1 peptides reduces collagen-induced platelet aggregation but not the response induced by arachidonic acid or ADP. These results were confirmed using Panx1-/- platelets. Natural variations have been described in the human Panx1 gene, which are predicted to induce non-conservative amino acid substitutions in its coding sequence. Healthy subjects homozygous for Panx1–400C, display enhanced platelet reactivity in response to collagen compared with those bearing the Panx1–400A allele. Conversely, the frequency of Panx1–400C homozygotes was increased among cardiovascular patients with hyper-reactive platelets compared with patients with hypo-reactive platelets. Exogenous expression of polymorphic Panx1 channels in a Panx-deficient cell line revealed increased basal and stimulated ATP release from cells transfected with Panx1–400C channels compared with Panx1–400A expressing transfectants. In conclusion, we demonstrate a specific role for Panx1 channels in the signalling pathway leading to collagen-induced platelet aggregation. Our study further identifies for the first time an association between a Panx1–400A>C genetic polymorphism and collagen-induced platelet reactivity. The Panx1–400C variant encodes for a gain-of-function channel that may adversely affect atherothrombosis by specifically enhancing collagen-induced ATP release and platelet aggregation.

Role of Caspase in a Subset of Human Platelet Activation Responses

Blood ◽  
1999 ◽  
Vol 93 (12) ◽  
pp. 4222-4231 ◽  
Author(s):  
Anna Shcherbina ◽  
Eileen Remold-O’Donnell
Keyword(s):  
Platelet Activation ◽  
Caspase 3 ◽  
Human Platelet ◽  
Thrombus Formation ◽  
Shape Change ◽  
Vascular Wall ◽  
Human Platelets ◽  
Granule Secretion ◽  
Platelets Function

Abstract Platelets function to protect the integrity of the vascular wall. A subset of platelet activation responses that are especially important for thrombus formation include exposure of phosphatidylserine and release of microparticles, which generate procoagulant surfaces. The resemblance of these platelet activation processes to events occurring in nucleated cells undergoing apoptosis suggests a possible role for caspases, which are major effector enzymes of nucleated cell apoptosis. We demonstrate here the presence of caspase-3 in human platelets and its activation by physiological platelet agonists. Using cell-permeable specific inhibitors, we demonstrate a role for a caspase-3–like protease in the agonist-induced (collagen plus thrombin or Ca2+ ionophore) platelet activation events of phosphatidylserine exposure, microparticle release, and cleavage of moesin, a cytoskeletal-membrane linker protein. The role of caspase-3 in platelet activation is restricted rather than global, because other activation responses,  granule secretion, shape change, and aggregation were unaffected by caspase-3 inhibitors. Experiments with two classes of protease inhibitors show that caspase-3 function is distinct from that of calpain, which is also involved in late platelet activation events. These findings show novel functions of caspase and provide new insights for understanding of platelet activation.

scholarly journals Human platelet aggregation by murine monoclonal antiplatelet antibodies is subtype-dependent

Blood ◽  
1993 ◽  
Vol 81 (7) ◽  
pp. 1792-1800 ◽  
Author(s):  
S De Reys ◽  
C Blom ◽  
B Lepoudre ◽  
PJ Declerck ◽  
M De Ley ◽  
...  
Keyword(s):  
Monoclonal Antibodies ◽  
Platelet Aggregation ◽  
Platelet Activation ◽  
Human Platelet ◽  
Human Platelets ◽  
Antigen Recognition ◽  
Metabolic Inhibitors ◽  
Antigen Binding ◽  
Human Platelet Aggregation ◽  
Murine Monoclonal Antibodies

Abstract Twenty murine monoclonal antibodies (MoAbs) generated against different human platelet antigens induced clumping of human platelets in plasma and buffer. Whereas one MoAb could agglutinate platelets, clumping for 19 MoAbs was blocked by metabolic inhibitors, indicating that these induce platelet activation. Fifteen MoAbs were of IgG1, two of IgG2a, and two of IgG2b subtype. F(ab')2 fragments of these did not evoke an aggregatory response, but specifically inhibited aggregations by and binding of their respective intact MoAbs to platelets. Single-platelet counting technology indicated that the MoAbs bind through their antigen- binding and Fc domains mainly to the surface of the same platelet, rather than cause interplatelet-binding. Despite these similarities, the mechanism of action was nevertheless subtype-dependent. Aggregation induced by all IgG1 antibodies could consistently be prevented by blocking the Fc gamma II-receptor, whereas aggregations induced by all IgG2 antibodies still occurred with blocked Fc-receptor, provided functional complement was present. We therefore conclude that platelet activation by MoAb-binding is initiated by antigen recognition followed by an Fc domain-dependent step, which involves the Fc gamma II-receptor for IgG1-type MoAbs and complement-binding for IgG2-type MoAbs. Thus, antibodies of different subtypes can aggregate platelets via different pathways.

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