scholarly journals The inhibition of platelet-activating factor-induced platelet activation by oleic acid is associated with a decrease in polyphosphoinositide metabolism.

1990 ◽  
Vol 265 (30) ◽  
pp. 18330-18338 ◽  
Author(s):  
D Nunez ◽  
J Randon ◽  
C Gandhi ◽  
A Siafaka-Kapadai ◽  
M S Olson ◽  
...  
Keyword(s):  
Oleic Acid ◽  
Platelet Activation ◽  
Platelet Activating Factor ◽  
Polyphosphoinositide Metabolism

Platelet-Activating Factor (PAF) in Internal Jugular Venous Blood of Migraine without aura Patients Assessed during Migraine Attacks

Cephalalgia ◽  
2004 ◽  
Vol 24 (8) ◽  
pp. 623-630 ◽  
Author(s):  
P Sarchielli ◽  
A Alberti ◽  
F Coppola ◽  
A Baldi ◽  
B Gallai ◽  
...  
Keyword(s):  
Platelet Activation ◽  
High Performance ◽  
Neurogenic Inflammation ◽  
Venous Blood ◽  
Platelet Activating Factor ◽  
Catheter Insertion ◽  
Reverse Phase Hplc ◽  
Opposite Trend ◽  
Serial Samples ◽  
Radioimmunoassay Method

The aim of the study was to verify the production of PAF and the activity of PAF acetyl-hydrolase (PAF-AH), the enzyme involved in the catabolism of this phospholipid mediator, in migraine attacks. Their levels were determined during migraine crises in serial samples of internal jugular venous blood taken from five migraine patients without aura, who were admitted to the hospital during the crises. Internal jugular venous blood samples were taken immediately after catheter insertion at 1, 2, and 4 h after attack onset, and within 2 h from its cessation. PAF was purified by high-performance liquid chromatography (HPLC) and determined by radioimmunoassay method. The enzymatic activity of PAF-AH was measured by reverse-phase HPLC, based on the derivatization with 7-diethylaminocoumarin-3-carbonylazide. In the internal jugular venous blood of migraine patients without aura (MO), an increase was observed in PAF levels, which was already evident at the time of catheter insertion (885.6 ± 82.8) and at the first hour (868.4 ± 65.24) (ANOVA: P < 0.0001). PAF levels remained elevated through the second (746.8 ± 82.95), fourth (700.6 ± 34.93) and sixth hours (644.4 ± 42.85), and then decreased at the end of the attack, reaching levels significantly lower than those measured at the time of catheter insertion (565.5 ± 38.34). The activity of PAF-AH showed an opposite trend with higher values at the first hour and significantly lower values at the second and fourth hours from the beginning of the migraine attack (ANOVA: P < 0.02). The increased production of PAF may account for persistent platelet activation during migraine crises, even in the presence of an increased production of nitric oxide (NO) end-products which, on the other hand, should instead intervene in counteracting and limiting platelet activation. Potential sources of PAF production are the endothelial cells from cerebral vessels, stimulated by trigeminal neuropeptides, platelets themselves, and mast cells, as suggested by the neurogenic inflammation model.

Inhibition by cardiolipins of platelet-activating factor-induced rabbit platelet activation

Lipids ◽  
1993 ◽  
Vol 28 (12) ◽  
pp. 1119-1124 ◽  
Author(s):  
Demokritos Tsoukatos ◽  
Constantinos A. Demopoulos ◽  
Alexandros D. Tselepis ◽  
Michael C. Moschidis ◽  
Andreas Donos ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Platelet Activating Factor ◽  
Rabbit Platelet

scholarly journals Alteration of platelet function in dogs mediated by interleukin-6

Blood ◽  
1994 ◽  
Vol 83 (2) ◽  
pp. 398-403
Author(s):  
J Peng ◽  
P Friese ◽  
JN George ◽  
GL Dale ◽  
SA Burstein
Keyword(s):  
Monoclonal Antibody ◽  
Platelet Activation ◽  
Platelet Function ◽  
Interleukin 6 ◽  
Platelet Activating Factor ◽  
Platelet Surface ◽  
Thrombin Activation ◽  
Dog Blood ◽  
And Control ◽  
Twofold Decrease

To determine if interleukin-6 (IL-6) administration influences platelet function, platelet activation was analyzed sequentially in IL-6-treated (80 micrograms/kg/d) and control dogs. Platelet activation was determined in whole blood by flow cytometry by quantitating the binding of a monoclonal antibody to platelet surface P-selectin after stimulation with graded doses of thrombin. Administration of IL-6 resulted in a twofold decrease in the thrombin concentration required for induction of half-maximal P-selectin expression (ED50) compared with control animals. The ED50 returned to normal after cessation of IL- 6 administration. As measured by P-selectin expression, enhanced responsiveness to the strong agonist platelet activating factor (PAF) was also observed in the IL-6-treated dogs. IL-6 had no effect on the susceptibility of platelets to thrombin activation when incubated with anticoagulated dog blood. The data show that, in addition to augmenting the platelet count in normal dogs, IL-6 enhances the sensitivity of platelets to activation in response to thrombin and PAF.

Neutrophil but not Monocyte Activation Inhibits P-Selectin-Mediated Platelet Adhesion

1994 ◽  
Vol 72 (05) ◽  
pp. 750-756 ◽  
Author(s):  
Henry M Rinder ◽  
Jayne L Tracey ◽  
Christine S Rinder ◽  
David Leitenberg ◽  
Brian R Smith
Keyword(s):  
Platelet Activation ◽  
Whole Blood ◽  
Platelet Adhesion ◽  
Platelet Activating Factor ◽  
Leukocyte Activation ◽  
Monocyte Activation ◽  
Activated Platelets ◽  
Simultaneous Activation ◽  
Cell Fractions

SummarySelectins are Ca2+-dependent glycoprotein receptors that mediate the adhesion of activated platelets or endothelial cells to unstimulated leukocytes. Using purified cell fractions, we examined activated neutrophil adhesion to P-selectin-expressing platelets and found that phorbol 12-myristate 13-acetate (PMA), platelet activating factor C16 (PAF), and n-formyl-met-leu-phe (fMLP) pretreatment of neutrophils inhibited activated platelet adhesion. Furthermore, PMA and PAF were capable of dissociating established resting neutrophil-activated platelet conjugates. Since L-selectin is downregulated after leukocyte activation and has been postulated as a ligand for P-selectin, we preincubated resting neutrophils with Dreg-2 and Dreg-56, blocking monoclonal antibodies (MoAb) to L-selectin; these MoAb failed to inhibit activated platelet adhesion. To more closely approximate in vivo conditions of leukocyte and platelet activation, we also employed a whole blood (WB) model of leukocyte-platelet adhesion. We found that simultaneous activation of both platelets and leukocytes by PMA caused an immediate rise in the % of P-selectin-positive platelets accompanied by a rapid increase in monocyte-platelet and neutrophil-platelet conjugates; however, the % of neutrophil-platelet conjugates subsequently declined over 30-60 min to baseline levels while monocyte-platelet adhesion remained elevated over 90 min. By contrast, selective platelet activation in WB by thrombin resulted in an increase in platelet P-selectin expression accompanied by a sustained (90 min) elevation in both monocyte- and neutrophil-platelet conjugates. This increase in leukocyte-platelet conjugates after thrombin was not inhibited by preincubation of WB with Dreg-2 or Dreg-56. We conclude that neutrophil activation decreases the expression of the ligand for platelet P-selectin within 30-60 min resulting in inhibition of neutrophil-platelet adhesion and dissociation of existing neutrophil-platelet conjugates. By contrast, monocyte activation over 90 min does not affect monocyte adhesion to activated platelets in whole blood.

Regulation of platelet activating factor-induced equine platelet activation by intracellular kinases

2009 ◽  
Vol 32 (2) ◽  
pp. 189-196 ◽  
Author(s):  
A. C. BROOKS ◽  
N. J. MENZIES-GOW ◽  
C. P. D. WHEELER-JONES ◽  
S. R. BAILEY ◽  
J. ELLIOTT ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Platelet Activating Factor

scholarly journals Role of platelet-activating factor in hypotension and platelet activation induced by infusion of thrombolytic agents in rabbits.

1993 ◽  
Vol 72 (3) ◽  
pp. 658-670 ◽  
Author(s):  
G Montrucchio ◽  
G Alloatti ◽  
F Mariano ◽  
E Lupia ◽  
P G Lucchina ◽  
...  
Keyword(s):  
Platelet Activation ◽  
Platelet Activating Factor ◽  
Thrombolytic Agents

scholarly journals Platelet-activating factor (PAF-acether) induces high- and low-affinity binding of fibrinogen to human platelets via independent mechanisms

1986 ◽  
Vol 240 (2) ◽  
pp. 403-412 ◽  
Author(s):  
E Kloprogge ◽  
J W Akkerman
Keyword(s):  
Platelet Activation ◽  
Binding Sites ◽  
Platelet Activating Factor ◽  
Human Platelets ◽  
Affinity Binding ◽  
Binding Studies ◽  
High Affinity Binding ◽  
High Affinity ◽  
Fibrinogen Binding ◽  
A Minor

When human platelets are incubated with 500 nM-PAF-acether (platelet-activating factor. 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) under equilibrium conditions (60 min, 22 degrees C, non-stirred suspensions), two classes of fibrinogen binding sites are exposed: one class with a high affinity [Kd (7.2 +/- 2.1) X 10(-8) M, 2367 +/- 485 sites/platelet, n = 9] and one class with a low affinity [Kd (5.9 +/- 2.4) X 10(-7) M, 26972 +/- 8267 sites/platelet]. Preincubation with inhibitors of cyclo-oxygenase (acetylsalicylic acid, indomethacin) or thromboxane synthetase (UK 38.485) completely abolishes high-affinity binding, leaving low-affinity binding unchanged. In contrast, ADP scavengers (phosphocreatine/creatine kinase or phosphoenol pyruvate/pyruvate kinase) completely prevent low-affinity binding, leaving high-affinity binding unaltered. Initial binding studies (2-10 min incubation) confirm these findings with a major part of the binding being sensitive to ADP scavengers, a minor part sensitive to indomethacin and complete blockade with both inhibitors. Increasing the temperature to 37 degrees C decreases the number of low affinity-binding sites 6-fold without changing high-affinity binding. Aggregation, measured as the rate of single platelet disappearance, then depends on high-affinity binding at 10 nM-fibrinogen or less, whereas at 100 nM-fibrinogen or more low-affinity binding becomes predominant. These findings point at considerable platelet activation during binding experiments. However, arachidonate metabolism [(3H]arachidonate mobilization and thromboxane synthesis) and secretion [(14C]serotonin and beta-thromboglobulin) are about 10% or less of the amounts found under optimal conditions (5 units of thrombin/ml 37 degrees C, stirring). We conclude that PAF-acether induces little platelet activation under binding conditions. The amounts of thromboxane A2 and secreted ADP, however, are sufficient for initiating high- and low-affinity fibrinogen binding via mutually independent mechanisms.

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