INVOLVEMENT OF LIPID-PEROXIDATION IN PLATELET SIGNALING

A well-known signalling pathway in blood platelets consists in the rel ease of arachidonic acid (AA) from membrane phospholipids and its spec ific oxygenation into bioactive derivatives. In particular, cyclic pro staglandin endoperoxides and thromboxane A(2) are potent inducers of p latelet functions and are produced in greater amounts when the level o f lipid hydroperoxides is higher than normal, as 'physiological concen trations' of such peroxides activate the cyclooxygenation of AA. In th is context, a lower activity of platelet glutathione peroxidase (GPx), the key-enzyme for the degradation of lipid hydroperoxides, has been reported in aging, which will ensure a longer life span to those perox ides. Accordingly, the biosynthesis of pro-aggregatory prostanoids is elevated in platelets from the elderly. On the other hand, fatty acids from marine origin have been recognized as inhibitors of platelet fun ctions, and they may alter the redox status of cells. They may for ins tance increase the platelet GPx activity, an effect that can be preven ted by antioxidants. Overall, these data point out the relevance of th e redox status in platelet functions.