Inhibition of thromboxane A2 production by trapidil and trapidil derivatives in the arachidonic acid-injected rat

1987 ◽  
Vol 30 (2-3) ◽  
pp. 87-92 ◽  
Author(s):  
Ingrid Heinroth-Hoffmann ◽  
A. Hauser ◽  
H.-J. Mest
Keyword(s):  
Arachidonic Acid ◽  
Thromboxane A2

In Vitro Incorporation and Metabolism of Icosapentaenoic and Docosahexaenoic Acids in Human Platelets - Effect on Aggregation

1986 ◽  
Vol 56 (01) ◽  
pp. 057-062 ◽  
Author(s):  
Martine Croset ◽  
M Lagarde
Keyword(s):  
Arachidonic Acid ◽  
Fatty Acid ◽  
Platelet Aggregation ◽  
Fatty Acid Distribution ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Aggregation Response ◽  
Docosahexaenoic Acids ◽  
Membrane Level

SummaryWashed human platelets were pre-loaded with icosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or EPA + DHA and tested for their aggregation response in comparison with control platelets. In fatty acid-rich platelets, an inhibition of the aggregation could be observed when induced by thrombin, collagen or U-46619. The strongest inhibition was observed with DHA-rich platelets and it was reduced when DHA was incorporated in the presence of EPA.Study of fatty acid distribution in cell lipids after loading showed that around 90% of EPA or DHA taken up was acylated into phospholipids and a very small amount (less than 2%) remained in their free and hydroxylated forms. DHA was more efficiently acylated into phosphatidylethanolamine (PE) than into phosphatidylinositol (PI) in contrast to what observed with EPA, and both acids were preferentially incorporated into phosphatidylcholine (PC). EPA inhibited total incorporation of DHA and increased its relative acylation into PE at the expense of PC. In contrast, DHA did not affect the acylation of EPA. Upon stimulation with, thrombin, EPA was liberated from phospholipids and oxygenated (as judged by the formation of its monohydroxy derivative) whereas DHA was much less metabolized, although consistently transferred into PE.It is concluded that EPA and DHA might affect platelet aggregation via different mechanisms when pre-loaded in phospholipids. Whereas EPA is known to alter thromboxane A2 metabolism from endogenous arachidonic acid, by competing with it, DHA might act directly at the membrane level for inhibiting aggregation.

scholarly journals Lipid peroxidation, prostacyclin and thromboxane A2 in pigs depleted of vitamin E and selenium and supplemented with linseed oil

1995 ◽  
Vol 74 (3) ◽  
pp. 369-380 ◽  
Author(s):  
Maeve R. Nolan ◽  
Seamus Kennedy ◽  
W. John Blanchflower ◽  
D. Glenn Kennedy
Keyword(s):  
Lipid Peroxidation ◽  
Arachidonic Acid ◽  
Vitamin E ◽  
Platelet Aggregation ◽  
Plasma Concentration ◽  
Linseed Oil ◽  
Thromboxane A2 ◽  
Dietary Factors ◽  
Biochemical Effects ◽  
Skeletal Myopathy

In a 2×2 balanced factorial experiment the biochemical effects on pigs of two dietary factors were investigated. The first factor was α-tocopherol and Se supplementation and the second factor was supplementation with α-tocopherol-stripped linseed oil. In pigs fed on diets depleted of α-tocopherol and Se, increases in concentrations of markers of lipid peroxidation (4-hydroxynonenal and hexanal) were observed. However, skeletal myopathy was only observed in those pigs fed on diets depleted of α-tocopherol and Se and supplemented with oil. In those pigs, increased lipid peroxidation was observed in heart and supraspinatus muscle. The plasma concentration of thromboxane B2 was increased in pigs fed on diets depleted of α-tocopherol and Se, suggesting an increased tendency towards platelet aggregation. However, this change was reversed in pigs depleted of α-tocopherol and Se, but supplemented with oil. This may have been a consequence of loss of arachidonic acid, the substrate for thromboxane formation, as a result of lipid peroxidation.

Diabetic Retinopathy And Thromboxane Like Substance

1981 ◽  
Author(s):  
M A Lazzari ◽  
M Gimeno ◽  
N M Sutton ◽  
J R Lopez
Keyword(s):  
Diabetes Mellitus ◽  
Arachidonic Acid ◽  
Diabetic Retinopathy ◽  
Risk Factor ◽  
Platelet Aggregation ◽  
Platelet Rich Plasma ◽  
Thromboxane A2 ◽  
Initial Step ◽  
Platelet Activity

Diabetes Mellitus (DM) is a risk factor in the development of vasculopathies and its complications. It produces also its own microangiopathy. Evidence was reported of increased platelet activity in DM in different assays. Platelets aggregation and the arachidonic cycle could play a key role in the increased tendency to thrombosis. A disorder of ratio TXA2/PGI2, two opposing prostaglandin derivatives, could be the initial step. We intended to evaluate a thromboxane like substance (TLS) produced from platelet rich plasma (PRP) and to compare between normals and diabetic retinopathy (DR) patients. TLS was measured in 16 controls and 16 patients. Assay was done with the aggregating activity developed in PRP (considered TLS) after addition of arachidonic acid (f.c. 2 mM). The supernatant of the PRP (100 μl) was taken 40 sec. after the aggregation started and were added to a normal PRP treated with aspirin (f.c. 40 μl/ml) adjusted to 250.000 - 300.000 pl/μl and the degree of platelet aggregation measured in a Chrono Log Aggregometer. TLS was inactivated after its incubation during 2 min. at 37°C. This finding suggests this activity is due to TXA2.The results obtained (expressed in % of platelet aggregation) were: controls x 16.37% ± 6.28 and DR x 36.00% ± 9.72.The increase detected in the DR group supports previous experimental reports suggesting the role of the thromboxane A2 in vaso occlusive complication of diabetes mellitus.

Lack Of Inhibition Of Thromboxane Production Despite Inhibition Of Platelet Function By 1,3-Bis(2 Chloroethyl)-1-Nitrosourea (BCNU)

1981 ◽  
Author(s):  
R McKenna ◽  
T Ahmad ◽  
A Prancan ◽  
D Simon ◽  
H Frischer
Keyword(s):  
Arachidonic Acid ◽  
Oxygen Consumption ◽  
Platelet Aggregation ◽  
Acetylsalicylic Acid ◽  
Platelet Function ◽  
Human Platelet ◽  
Thromboxane A2 ◽  
Rabbit Aorta ◽  
Thromboxane Production ◽  
Platelet Thromboxane

We have previously shown that BCNU inhibits human platelet glutathione reductase (GSSG-R) prior to inhibiting platelet function; since thromboxane production is important in platelet function, we evaluated the effect of BCNU induced inhibition of GSSG-R on platelet thromboxane production.Control platelet GSSG-R activity was 0.091 ]jmoles NAD(P)H oxidized min-1lmg-1 protein at 37°C (±0.015 S.D.; n=9); inhibition was detectable at 10-7M% BCNU (70% of control) with a >90% inhibition at and above 10-5M BCNU. Platelet aggregation in response to 1.5×10-3M Arachidonic acid (AA), 10 μM epinephrine, 6 μg/ml equine collagen and 3 μM ADP were inhibited at 10-5M BCNU and abolished at 10-4 BCNU.BCNU (10-3M) did not affect the increase in oxygen consumption induced by AA. Using the rabbit aorta superfusion bioassay for thromboxane A2 (TXA2), threshold concentrations of AA in 10-5 and 10-4 BCNU platelets resulted in an increased measure of aortic tension 13.5 ± 9.4 mm S.D. (n=6) and 23.2 ± 9.5 mm respectively, compared with control values of 4.5 ± 2.4. Acetylsalicylic acid (5 × l0-4M) inhibited the contraction: 1.7 ± 1.1 (n=5). The conversion of 14C AA to thromboxane B2 (TXB2) and PGE2, as measured by radio TLC, was not decreased in BCNU treated platelets. There is a significant increase in TXB2 (p<0.05;n=4) and in the ratio of TXB2:PGE2 in platelets treated with 10-4M BCNU and 10-3M imidazole when compared to platelets treated with imidazole alone.In conclusion BCNU induced inhibition of platelet GSSG-R and platelet function occurs despite preservation of thromboxane production

Aspirin Does Not Affect the Flow Cytometric Detection of Fibrinogen Binding to, or Release of α-Granules or Lysosomes from, Human Platelets

1994 ◽  
Vol 87 (5) ◽  
pp. 575-580 ◽  
Author(s):  
Nicolas A. F. Chronos ◽  
Darren J. Wilson ◽  
Sarah L. Janes ◽  
Ronald A. Hutton ◽  
Nigel P. Buller ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Arachidonic Acid ◽  
Thromboxane A2 ◽  
Normal Subjects ◽  
Human Platelets ◽  
Aspirin Therapy ◽  
Flow Cytometric Assay ◽  
Blood Samples ◽  
Flow Cytometric ◽  
Fibrinogen Binding

1. Aspirin inhibits the conversion of arachidonic acid to thromboxane A2 which reinforces the effects of weak agonists such as ADP in platelets. 2. In this study the effect of aspirin (300 mg/day) on platelet agonist response was measured by whole blood flow cytometry of unfixed blood samples from normal subjects (n = 10), an assay that investigates aggregation-independent changes in the platelet. 3. Fibrinogen binding to unstimulated platelets or to platelets stimulated with ADP or thrombin was unaffected by aspirin. 4. Under the conditions of this assay, platelets undergo a partial degranulation of α-granules and lysosomes (evidenced by expression of P-selectin and CD63, respectively) in response to ADP, and full degranulation in response to thrombin. P-selectin expression was paralleled by release of β-thromboglobulin. None of these events was affected by aspirin. 5. Thromboxane formation was totally prevented by the aspirin treatment, as shown by Born aggregometry in which the platelet aggregatory response to arachidonic acid was abolished and secondary aggregation by ADP was inhibited. 6. The flow cytometric assay can therefore be used to investigate platelets in patients, regardless of aspirin therapy. 7. These findings suggest that platelet fibrinogen binding and the release of platelet α-granule and lysosomal contents, in response to stimulation with physiological agonists, can continue in patients despite aspirin therapy. This may help to explain why aspirin is only partially effective in preventing thrombotic events.

Marked Temperature Dependence of the Platelet Calcium Signal Induced by Human von Willebrand Factor

Blood ◽  
1999 ◽  
Vol 94 (1) ◽  
pp. 199-207 ◽  
Author(s):  
John C. Kermode ◽  
Qi Zheng ◽  
Elizabeth P. Milner
Keyword(s):  
Arachidonic Acid ◽  
Temperature Dependence ◽  
Von Willebrand Factor ◽  
Thromboxane A2 ◽  
Underlying Mechanism ◽  
Calcium Signal ◽  
Free Calcium ◽  
Strong Temperature Dependence ◽  
Von Willebrand ◽  
Willebrand Factor

Interaction of von Willebrand factor (vWF) with the platelet is essential to hemostasis when vascular injury occurs. This interaction elevates the intracellular free calcium concentration ([Ca2+]i) and promotes platelet activation. The present study investigated the temperature dependence of vWF-induced [Ca2+]i signaling in human platelets. The influence of temperature can provide invaluable insight into the underlying mechanism. Platelet [Ca2+]i was monitored with Fura-PE3. Ristocetin-mediated binding of vWF induced a transient platelet [Ca2+]i increase at 37°C, but no response at lower temperatures (20°C to 25°C). This temperature dependence could not be attributed to a reduction in vWF binding, as ristocetin-mediated platelet aggregation and agglutination were essentially unaffected by temperature. Most other platelet agonists (U-46619, -thrombin, and adenosine 5′-diphosphate [ADP]) induced a [Ca2+]isignal whose amplitude did not diminish at lower temperatures. The [Ca2+]i signal in response to arachidonic acid, however, showed similar temperature dependence to that seen with vWF. Assessment of thromboxane A2 production showed a strong temperature dependence for metabolism of arachidonic acid by the cyclo-oxygenase pathway. vWF induced thromboxane A2production in the platelet. Aspirin treatment abolished the vWF-induced [Ca2+]i signal. These observations suggest that release of arachidonic acid and its conversion to thromboxane A2 play a central role in vWF-mediated [Ca2+]i signaling in the platelet at physiological temperatures.

ADRENALINE (ADR) INTERACTIONS WITH THROMBIN AND COLLAGEN -EFFECTS ON PLATELET ARACHIDONATE RELEASE AND 5HT SECRETION AND ROLE OF ENDOGENOUSLY FORMED THROMBOXANE A2 (TxA2)

1987 ◽  
Author(s):  
Y Patel ◽  
S Krishnamurthi ◽  
V V Kakkar
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Adenylate Cyclase ◽  
Synergistic Effects ◽  
Thromboxane A2 ◽  
Human Platelets ◽  
Presence And Absence ◽  
Pre Treatment ◽  
Arachidonate Release

We have examined the effect of combinations of ADR + thrombin (T) and ADR + collagen (C) on platelet arachidonate release and 5HT secretion, and assessed the role of endogenously formed TxA2 on these responses using indomethacin (I). Washed, human platelets prelabelled with [3H]-arachidonic acid (AA) or [14C]-5HT were used, ADR was added 10 sec before T or C and the reaction was terminated 3 min later. In the range 1-100μM, ADR induced no detectable aggregation or 5HT secretion but potentiated platelet aggregation when added with sub-threshold concentrations of T or C, which on their own induced no aggregation. At 2-4 fold higher concentrations of T and C (threshold for 5HT secretion), 5HT secretion and AA/TXB2 release were also potentiated by ADR (1-10μM) by 30-50%. Pre-treatment of platelets with I (10μM) abolished threshold T and C-induced 5HT secretion, as well as its potentiation by ADR. However, approximately 2-fold and 5-fold higher concentrations of T and C respectively were able to induce 'I-insensitive'secretion, which was further potentiated by ADR. In I-treated platelets, C-induced AA release and its potentiation by ADR were also abolished suggesting a role for endogenously formed TxA2 This was confirmed by addition of the TxA2 mimetic, U46619 (0.3μM), which potentiated C-induced AA release in the presence and absence of ADR, even though it induced no AA release on its own or, in combination with ADR alone in the absence of collagen. The latter suggests agonist specificity regarding the ability of TxA2 to synergistically stimulate AA release. Finally, unstirred platelets in PRP pre-incubated with ADR (10μM) for 120 min lost their responsiveness to ADR, when eventually stirred; however, these 'ADR-desensitised' platelets when washed and resuspended, were able to demonstrate synergistic effects on secretion when stimulated with ADR+T or ADR+C. This is analogous to the previously demonstrated ability of ADR to inhibit adenylate cyclase even in 'ADR-desensitised' platelets and re-inforces the separation regarding the mechanisms underlying the various effects of ADR on platelets.

scholarly journals Endothelial-secreted arachidonic acid metabolites modulate polymorphonuclear leukocyte chemotaxis and diapedesis in vitro

Blood ◽  
1988 ◽  
Vol 71 (3) ◽  
pp. 771-779 ◽  
Author(s):  
J Doukas ◽  
HB Hechtman ◽  
D Shepro
Keyword(s):  
Arachidonic Acid ◽  
Polymorphonuclear Leukocyte ◽  
Thromboxane A2 ◽  
In Vitro Assays ◽  
General Effect ◽  
Random Motility ◽  
Acid Metabolites ◽  
Leukocyte Chemotaxis ◽  
High Doses

Abstract The influence of endothelial cells (ECs) on polymorphonuclear leukocyte (PMN) motility was examined using in vitro assays of PMN diapedesis and chemotaxis. ECs are seen to release arachidonic acid (20:4) metabolites that directly increase or decrease PMN movement, with their general effect being enhanced motility. This effect can be increased or decreased by treating ECs with stimulators or inhibitors of 20:4 metabolism, respectively. The metabolites include thromboxane B2, which increases PMN random motility, chemotaxis, and diapedesis in a dose- responsive manner and which acts as a chemoattractant; 6-keto-PGF1 alpha, which increases chemotaxis and diapedesis at high doses but decreases these responses at low doses; and a lipoxygenase-derived metabolite, suggested to be 5-hydroxyeicosatetraenoic acid, which increases chemotaxis and diapedesis. Thromboxane A2 and prostacyclin mimetics also affect chemotaxis in qualitatively similar manners as TxB2 and 6-keto-PGF1 alpha, respectively, but display greater potency. EC release of these metabolites is also seen to be substratum modulated, with an increased production by cells cultured on extracellular matrices. These results suggest that ECs are capable of modulating PMN motility and suggest a role for ECs in the control of PMN diapedesis.

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