Glutathione Peroxidase And Malondialdehyde Production In The Arachidonic Acid Metabolism Of Human Platelets

1981 ◽  
Author(s):  
G C Guidi ◽  
R Schiavon ◽  
G L Avventi ◽  
G Perona
Keyword(s):  
Arachidonic Acid ◽  
Glutathione Peroxidase ◽  
Peroxidase Activity ◽  
Acid Metabolism ◽  
Inverse Correlation ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Glutathione Peroxidase Activity ◽  
Physiological Variations

A series of functional parameters, including the aggregability triggered by various agents, the in vitro malondialdehyde production and the glutathio ne peroxidase activity, has been investigated in platelets from normal blood donors.Glutathione peroxidase activity assays showed a significant inverse correlation with malondialdehyde induced by arachidonic acid but not with aggregation data and malondialdehyde induced by thrombin. Moreover, arachidonic acid generates in human platelets lysates large amounts of hydrogen acceptor substrate(s) for the glutathione peroxidase with peculiar kinetic features. These are related to ma londialdehyde production and to partial inhibition by acetyl-salicilic acid and are likely connected with prostaglandin metabolism.Our data suggest that physiological variations in glutathione peroxidase activity are important in human platelet arachidonic acid metabolism, because they modulate the biosynthesis of key end-products, as thromboxane A2, whose malondialdehyde is an inde.

Evidence for the presence of phospholipid hydroperoxide glutathione peroxidase in human platelets: implications for its involvement in the regulatory network of the 12-lipoxygenase pathway of arachidonic acid metabolism

2000 ◽  
Vol 353 (1) ◽  
pp. 91-100 ◽  
Author(s):  
Mark SUTHERLAND ◽  
Pattabhiraman SHANKARANARAYANAN ◽  
Tankred SCHEWE ◽  
Santosh NIGAM
Keyword(s):  
Arachidonic Acid ◽  
Glutathione Peroxidase ◽  
Regulatory Network ◽  
Acid Metabolism ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Phospholipid Hydroperoxide Glutathione Peroxidase ◽  
Lipoxygenase Pathway ◽  
Phospholipid Hydroperoxide ◽  
12 Lipoxygenase

The 12-lipoxygenase pathway of arachidonic acid metabolism in platelets and other cells is bifurcated into a reduction route yielding 12-hydroxyeicosatetraenoic acid (12-HETE) and an isomerization route forming hepoxilins. Here we show for the first time the presence of phospholipid hydroperoxide glutathione peroxidase (PHGPx) protein and its activity in platelets. The ratio of the activity of PHGPx to that of cytosolic glutathione peroxidase (GPx-1) was consistently found to be approx. 1:60 in platelets and UT7 megakaryoblasts. Moreover, short-lived PHGPx mRNA was detected in megakaryocytes but not in platelets. Carboxymethylation of selenium-containing glutathione peroxidases by iodoacetate, which results in the inactivation of PHGPx and GPx-1 without inhibition of 12-lipoxygenase, markedly altered the pattern of arachidonic acid metabolism in human platelets. Whereas the formation of 12-HETE was inhibited by 80%, a concomitant accumulation of 12-hydroperoxyeicosatetraenoic acid (12-HpETE) by two orders of magnitude as well as the formation of hepoxilins A3 and B3 were observed. The formation of hepoxilins also occurred when 12-HpETE was added to untreated platelets. In selenium-deficient UT7 cells, which were devoid of GPx-1 but not of PHGPx, the reduction of 12-HPETE was retained, albeit with a lower rate than in control cells containing GPx-1. We therefore believe that both GPx-1 and PHGPx are involved in the regulatory network of the 12-lipoxygenase pathway in platelets and other mammalian cells. Moreover, the diminution of hydroperoxide tone in platelets incubated with arachidonic acid leads primarily to the formation of 12-HETE, whereas the increase in hydroperoxide tone (a situation found under oxidative stress or selenium deficiency or on incubation with 12-HPETE) partly diverts the 12-lipoxygenase pathway from the reduction route to the isomerization route, thus resulting in the formation of hepoxilins.

Aspirin Preferentially Inhibits Arachidonic Acid Metabolism In Collagen Vs. Thrombin-Stimulated Platelets

1981 ◽  
Author(s):  
D Deykin ◽  
R Vaillancourt
Keyword(s):  
High Performance Liquid Chromatography ◽  
Arachidonic Acid ◽  
Liquid Chromatography ◽  
High Performance ◽  
Acid Metabolism ◽  
Gel Filtration ◽  
Human Platelets ◽  
Arachidonic Acid Metabolism ◽  
Selective Effect ◽  
Oxygenase Activity

The purpose of this study was to compare the effect of aspirin on the release of metabolites of arachidonic acid from thrombin and collagen stimulated platelets. Human platelets were incubated with tritium-labeled arachidonic acid and then isolated by gel filtration. The labeled platelets were stimulated with varied doses of either thrombin or collagen for 15 minutes. The platelets were then pelleted and the released metabolites of arachidonic acid were separated by high-performance liquid chromatography. In experiments with aspirin, the aspirin was added 5 minutes before either thrombin or collagen. The total release of radioactivity was comparable at 15 μg/ml of collagen and 1.0 units/ml of thrombin (approximately 10% of the total) and at 100 μg/ml of collagen and 5 units/ml of thrombin (approximately 30%). Aspirin (25 μg/ml) preferentially inhibited collagen-stimulated release of radioactivity (62% inhibition of release with 15 μg/ml of collagen vs. 25% inhibition of release with 1.0 units/ml of thrombin; 54% inhibition of release with 100 μg/ml of collagen vs. 8% inhibition of release with 5.0 units/ml of thrombin). At all concentrations of collagen or thrombin, cyclo-oxygenase activity was markedly reduced by aspirin. The selective effect of aspirin on collagen reflects primarily preferential suppression of HETE formation. We conclude that aspirin inhibits the formation of both lipoxygenase and cyclooxygenase-derived products in collagen-stimulated platelets.

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