Low concentrations of lipid hydroperoxides prime human platelet aggregation specifically via cyclo-oxygenase activation

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

Thrombosis and Haemostasis ◽

10.1055/s-0038-1651035 ◽

1989 ◽

Vol 62 (03) ◽

pp. 955-961 ◽

Cited By ~ 4

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.

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Low concentrations of reactive γ-ketoaldehydes prime thromboxane-dependent human platelet aggregation via p38-MAPK activation

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids ◽

10.1016/j.bbalip.2009.02.003 ◽

2009 ◽

Vol 1791 (4) ◽

pp. 307-313 ◽

Cited By ~ 19

Author(s):

Nathalie Bernoud-Hubac ◽

Denise Al Alam ◽

Jennifer Lefils ◽

Sean S. Davies ◽

Venkataraman Amarnath ◽

...

Keyword(s):

Platelet Aggregation ◽

P38 Mapk ◽

Human Platelet ◽

Mapk Activation ◽

Human Platelet Aggregation ◽

Low Concentrations

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Potentiation of Adrenaline-Induced Platelet Aggregation by Angiotensin II

Thrombosis and Haemostasis ◽

10.1055/s-0038-1660105 ◽

1985 ◽

Vol 54 (03) ◽

pp. 717-720 ◽

Cited By ~ 32

Author(s):

Yu-An Ding ◽

D Euan MacIntyre ◽

Christopher J Kenyon ◽

Peter F Semple

Keyword(s):

Platelet Aggregation ◽

Angiotensin Ii ◽

Human Platelet ◽

Inhibitory Effect ◽

Facilitatory Effect ◽

Ang Ii ◽

Human Platelet Aggregation ◽

Low Concentrations ◽

High Concentrations ◽

Stimulation Of

SummaryThe effects of angiotensin II (ANG II) alone and in combination with other agonists on human platelet aggregation, thromboxane B2 (TxB2) and cytosolic [Ca2+]i were investigated. ANG II (10™11 - 10™7 M) alone had no direct effect on aggregation, TxB2 production or [Ca2+]i after short- (<2 min) or longterm (30 min) incubation. In contrast, low concentrations of ANG II (10™11 M) enhanced adrenaline-induced platelet aggregation but high concentrations (10™7 M) had an inhibitory effect. Moreover, ANG II (10™11 - 10™7 M) augmented platelet responses to the TxA2 mimetic, U44069. Pretreatment of platelets with flurbiprofen abolished this facilitatory effect of ANG II on adrenaline- but not on U44069-induced platelet aggregation. These results suggest that ANG II stimulation of agonist-induced platelet activation may be due to potentiation of the effects rather than the synthesis of TxA2

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Human Platelet Aggregation and Release Reaction Induced by Platelet Activating Factor (PAF-Acether) – Effects of Acetylsalicylic Acid and External Ionized Calcium

Thrombosis and Haemostasis ◽

10.1055/s-0038-1661279 ◽

1985 ◽

Vol 53 (02) ◽

pp. 221-224 ◽

Cited By ~ 12

Author(s):

Marco Cattaneo ◽

Maria Teresa Canciani ◽

Pier Mannuccio Mannucci

Keyword(s):

Platelet Aggregation ◽

Acetylsalicylic Acid ◽

Human Platelet ◽

Platelet Rich Plasma ◽

Normal Subjects ◽

Human Platelet Aggregation ◽

Low Concentrations ◽

Before And After ◽

Platelet Secretion

SummaryThe effects of the cyclo-oxygenase inhibition on PAF-acether- induced human platelet aggregation and secretion are controversial. We studied the above parameters on citrated platelet-rich plasma of 12 normal subjects before and after the in vivo administration of acetylsalicylic acid (ASA). Individual sensitivities to PAF-acether were highly variable. ASA completely inhibited the platelet secretion induced by low concentrations of PAF-acether, but caused only partial inhibition when platelets were exposed to high concentrations of PAF-acether. The concentration of PAF-acether which overcame the cyclo-oxygenase inhibition varied substantially, depending on the individual sensitivity of the platelets to it. The addition of CaCl2 2 mM to the samples did not affect the extent of the platelet secretion, but increased irreversible aggregation in samples taken both before and after the ASA administration. These data suggest that low concentrations of PAF-acether stimulate the human platelet secretion by activating the cyclo-oxygenase pathway, whereas higher concentrations also trigger other mechanism(s) that suffice to induce human platelet secretion and full aggregation.

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Prostaglandins (PG) Inhibit Human Platelet Aggregation by PG Receptor Antagonism as well as Adenylate Cyclase Stimulation

10.1055/s-0039-1684546 ◽

1979 ◽

Author(s):

D.E. MacIntyre ◽

E.W. Salzman

Keyword(s):

Platelet Aggregation ◽

Adenylate Cyclase ◽

Human Platelet ◽

High Ratio ◽

Receptor Antagonism ◽

Human Platelet Aggregation ◽

Alkyl Groups ◽

Low Concentrations ◽

Alkyl Substitution ◽

Adenylate Cyclase Stimulation

11-Deoxy and/or 15 or 16 alkyl substitution confer platelet aggregating activity to bis-enoic PG's: e.g., 11-deoxy-PGE2 (threshold (T)-5μM); ll-deoxy-15(S)-15-methyl-PGE2 (T=0.1μM);ll-deoxy-15(S)-16-methyl-PGE2(T=0.1μM). Responses induced by such PG’s mimic those induced by PGH2 and PGH2 analogues (e.g., U44069). N0164 competitively inhibits aggregation induced by PG’s and suppresses “secondary” responses induced by low concentrations of ADP or arachidonic acid, suggesting involvement of a specific PG stimulatory receptor in platelet aggregation. We compared non-aggregatory PG’s as inhibitors of pri mary aggregation induced by ADP or U44069. PG’s containing 11-deoxy and/or 16-alkyl groups selectively inhibited aggregation induced by U44069. Mean I50 values (n-4) against ADP and U44069 respectively were PGA2 (>100μM; 0.3μM); PGB2 (>100μM; 5μM); PGD2 (6nM; 2nM); PGE1(10nM; 5nM); 11-deoxy PGE1 (60μM; 2μM); ll-deoxy-15-(R)-16-methyl (100μM; 2μM); 13,14-dihydro-16-methyl-PGE2 methyl ester(750nM; 15nM). A low ADP: 406 I50 ratio (e.g., PGD2) indicates that inhibition is mainly due to adenylate cyclase stim ulation, and a high ratio (e.g., PGA2) that inhibition is mainly due to PG receptor antagonism. We have demonstrated a PG stimulatory receptor on the platelet, and its involvement in “secondary” aggregation. PG’s inhibit aggregation by combining with this receptor and/or by stimulating adenylate cyclase.

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

Blood ◽

10.1182/blood.v81.7.1792.1792 ◽

1993 ◽

Vol 81 (7) ◽

pp. 1792-1800 ◽

Cited By ~ 28

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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Adenosine 5’-O-(2-Thiodiphosphate) (ADP-β-S) Is A Partial Agonist At The ADP Receptor Of Human Platelets

10.1055/s-0038-1652016 ◽

1981 ◽

Author(s):

N J Cusack ◽

S M O Hourani

Keyword(s):

Platelet Aggregation ◽

Adenylate Cyclase ◽

Human Platelet ◽

Partial Agonist ◽

Human Platelets ◽

Simultaneous Addition ◽

Prostaglandin Receptor ◽

Human Platelet Aggregation ◽

Adp Receptor ◽

Stimulation Of

ADP induces human platelet aggregation and inhibits the stimulation of platelet adenylate cyclase by prostaglandin E1 (PGE1), but analogues of ADP in which the diphosphate group is modified retain only weak aggregating activity. However, ADP-β-S, an ADP analogue in which a terminal phosphate oxygen is replaced by sulphur, is known to be equipotent with ADP as an inhibitor of PGE1-stimulated adenylate cyclase in purified human platelet membranes. We therefore tested ADP-β-S on intact human platelets. ADP-β-S induced human platelet aggregation and inhibited PGE1-stimulated adenylate cyclase, but in botn cases was less potent than ADP and only achieved 75% and 50% respectively of the maximal effects of ADP. Aggregation induced by ADP-β-S was competitively inhibited by ATP (50 μM), a known ADP antagonist.Both these actions of ADP could be inhibited by the simultaneous addition of ADP-β-S (50 μM). Aggregation induced by a stable endoperoxide analogue (11 ,9 -epoxymethano PGH2), which acts at a prostaglandin receptor rather than at an ADP receptor, was not inhibited by the simultaneous addition of ADP-β-S (50 μM). The behaviour of ADP-β-S towards human platelets is therefore tnat of a partial agonist at the ADP receptor.

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Thromboxane A2-Stimulated Human Platelet Aggregation Is Potentiated By Epinephrine Acting VIA Alpha Adrenergic Receptors

10.1055/s-0038-1653296 ◽

1981 ◽

Author(s):

G J Johnson ◽

G H R Rao ◽

J G White

Keyword(s):

Platelet Aggregation ◽

Adrenergic Receptors ◽

Human Platelet ◽

Thromboxane A2 ◽

Human Platelets ◽

Adrenergic Agents ◽

Alpha Adrenergic Receptors ◽

Human Platelet Aggregation ◽

Induced Aggregation

Epinephrine (E) potentiates arachidonate (A)-induced aggregation of human platelets. A-insensitive dog platelets (AIP), that form thromboxane A2 (T) but do not aggregate when stirred with A alone, aggregate when exposed to E + A. Therefore, we studied the effect of E on T-stimu- lated human platelet aggregation. AIP stirred with A formed T which was confirmed by TLC. 1/100 to 1/200 volume of AIP was removed 30 sec. after A, and transferred to gel- filtered, aspirin-incubated human platelets. Recipient platelet aggregation was proportional to the volume of AIP transferred. The addition of the thromboxane synthetase inhibitor, Azo Analog I, abolished the aggregating activity of AIP. Transfer of an aliquot of AIP that was inadequate to aggregate human gel-filtered, aspirin-incubated platelets resulted in irreversible aggregation in the presence of ≥0.5nM E. E potentiated aggregation when added 3 min. before but not 3 min. after aliquot transfer. T-stimulated aggregation was abolished by the T-antagonist, 13 azapro- stenoic acid (APA), but E added after APA and before T restored aggregation. E potentiation of T-stimulated aggregation was abolished by prior exposure to equimolar yohimbine, dihydroergocryptine and phentolamine, agents that bind to alpha2 adrenergic receptors, but not by prazosin an alpha1 antagonist. Higher concentrations of E reversed the inhibitory effects of the alpha2 adrenergic agents. All of these agents in higher concentrations (1-100μM) also blocked aggregation induced by T alone. Therefore T-induced platelet aggregation is potentiated by E, in concentrations attained in vivo, by a mechanism linked to platelet alpha adrenergic receptors. Platelet alpha2 receptors have a close functional relationship to the postulated T receptor. E may initiate platelet aggregation in vivo when T is formed in quantities inadequate to alone induce aggregation.

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Impairment of Human Platelet Aggregation and Serotonin Release Caused in Vitro by Echis Colorata Venom

Thrombosis and Haemostasis ◽

10.1055/s-0038-1649116 ◽

1973 ◽

Vol 30 (01) ◽

pp. 191-198 ◽

Cited By ~ 2

Author(s):

Haim Biran ◽

Alexander Dvilansky ◽

Ilana Nathan ◽

Avinoam Livne

Keyword(s):

Platelet Aggregation ◽

Functional Impairment ◽

Human Platelet ◽

Human Platelets ◽

Endothelial Damage ◽

Serotonin Release ◽

Bleeding Tendency ◽

Human Platelet Aggregation

SummaryAggregation of washed human platelets, induced by either ADP, thrombin or collagen, was decreased by Echis colorata venom (EVC). With ADP as an inducer, the inhibition of aggregation was proportional to the venom concentration, starting from 0.27 μg/ml and attaining full inhibition with venom concentration of 9 μg/ml. Higher concentrations were required for comparable venom effects when collagen or thrombin were used as inducers. Based on serotonin release measurements and platelet counting, it is concluded that the ECV-diminished aggregation is not due to platelet lysis. Thrombin-dependent serotonin release was inhibited by the venom to an extent proportional to the log ECV concentration at a range of 0.27 to 90 μg/ml. ECV effeces on serotonin release are apparently independent on its effects on aggregation, since similar results were obtained either with or without EDTA.Endothelial damage and defibrination are already known to be associated with the bleeding tendency caused by ECV. The present data disclose a functional impairment of platelets as an additional antihemostatic effect of this venom.

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Prostaglandins (PG) Inhibit Human Platelet Aggregation By PG Receptor Antagonism as well as Adenylate Cyclase Stimulation

10.1055/s-0038-1665818 ◽

1979 ◽

Author(s):

D. E. Macfarlane ◽

E. W. Salzman

Keyword(s):

Platelet Aggregation ◽

Adenylate Cyclase ◽

Human Platelet ◽

High Ratio ◽

Receptor Antagonism ◽

Human Platelet Aggregation ◽

Alkyl Groups ◽

Low Concentrations ◽

Alkyl Substitution ◽

Adenylate Cyclase Stimulation

11-Deoxy and/or 15 or 16 alkyl substitution confer platelet aggregating activity to bis-enoic PG’s: e.g., ll-deoxy-PGE2(threshold (T)-5μM); ll-deoxy-15(S)-15-methyl-PGE2(T= O.lμM); ll-deoxy-15(S)-16-methyl-PGE2(T=0.1μM). Responses induced by such PG’s mimic those induced by PGH2 and PGH2 analogues (e.g., U44069). N0164 competitively inhibits aggregation induced by PG’s and suppresses “secondary” responses induced by low concentrations of ADP or arachidonic acid, suggesting involvement of a specific PG stimulatory receptor in platelet aggregation. We compared non-aggregatory PG’s as inhibitors of primary aggregation induced by ADP or U44069. PG’s containing 11-deoxy and/or 16-alkyl groups selectively inhibited aggregation induced by U44069. Mean I50 values (n=4) against ADP and U44069 respectively were PGA2(>100μM; 0.3μM); PGB2(>100μM; 5μM). PGE1(60μM; 2μM); PGE1(10nM; 5nM); 11-deoxy PGEX (60μM; 2μM); ll-deoxy-15-(R)-16-methyl PGE1(lOOμM; 2μM); 13,14-dihydro-16-methyl-PGE2 methyl ester (750nM; 15nM). A low ADP: U4406 I50 ratio (e.g., PGD2) indicates that inhibition is mainly due to adenylate cyclase stim ulation, and a high ratio (e.g., PGA2) that inhibition is mainly due to PG receptor antagonism. We have demonstrated a PG stimulatory receptor on the platelet, and its involvement in “secondary”aggregation. PG’s inhibit aggregation by combining with this receptor and/or by stimulating adenylate cyclase.

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