The generation of superoxide anion radicals (O2*-) and the other reactive oxygen species (ROS) was estimated by means of cytochrome c reduction and chemiluminescence, as well in resting blood platelets and in platelets stimulated by thrombin in the presence or absence of some inhibitors of pathways involved in platelet activation. We used allopurinol (xanthine oxidase inhibitor), wortmannin (PI 3-kinase inhibitor) and staurosporine (protein kinase C inhibitor). To determine the involvement of the glutathione in ROS generation, we used L-buthionine sulfoximine (BSO) which blocks GSH synthesis. Our results confirmed that thrombin stimulates the production of ROS concomitant with metabolism of arachidonate and production of malonyldialdehyde (MDA) in blood platelets (P < 0.05) and showed that, in the presence of inhibitors, the generation of ROS in platelets (resting and stimulated) was reduced. This indicates that xanthine oxidase, PI 3-kinase or protein kinase C take part in the formation of ROS in blood platelets. Moreover, adhesion of platelets to fibrinogen and secretion of adenine nucleotides from platelets after wortmannin and staurosporine action was also inhibited. BSO not only decreased GSH level, but also reduced the amount of ROS; a correlation between the depletion of GSH and the decrease of ROS was observed (R = -0.987; P < 0.02). It is concluded that in blood platelets, ROS are produced in the receptor-mediated signaling pathways and platelet activation (arachidonic acid metabolism, the glutathione cycle, metabolism of phosphoinositoides and due to xanthine oxidase). Our results support the importance of ROS in platelet function.

The main purpose of this article is to provide an overview of the currently available evidence of antiplatelet properties of resveratrol (3,4('),5-trihydroxystilbene). Resveratrol, a phenolic compound found naturally in fruits, nuts, flowers, seeds and bark of different plants is integral part of human diet. It exhibits a wide range of biological effects, including antiplatelet, anti-inflammatory, anticancer, antimutagenic and antifungal properties. It is also a potent antioxidant, reactive oxygen species scavenger and metal chelators. Resveratrol reduces lipid peroxidation, oxidation and nitration of platelet and plasma proteins. This review article describes the chemical structure of resveratrol, its biological activity, the effects on blood platelet functions and the mechanisms involved in its action on blood platelets, the cells which play an important role not only in the haemostatic process, but also in pathogenesis of cardiovascular diseases.

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The aim of the present study was to investigate and compare the anti-platelet action of extracts from three different plants: bark of Yucca schidigera, seeds of grape and berries of Aronia melanocarpa (chokeberry). Anti-platelet action of tested extracts was compared with action of well characterized antioxidative and anti-platelet commercial monomeric polyphenol-resveratrol. The effects of extracts on platelet adhesion to collagen, collagen-induced platelet aggregation and on the production of O2-* in resting platelets and platelets stimulated by a strong platelet agonist-thrombin were studied. The in vitro experiments have shown that all three tested extracts (5-50 microg/ml) rich in polyphenols reduce platelet adhesion, aggregation and generation of O2-* in blood platelets. Comparative studies indicate that all three plant extracts were found to be more reactive in reduction of platelet processes than the solution of pure resveratrol. The tested extracts due to their anti-platelet effects may play an important role as components of human diet in prevention of cardiovascular or inflammatory diseases, where blood platelets are involved.

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Blood platelets, in analogy to other circulating blood cells, can generate reactive oxygen/nitrogen species (ROS/RNS) that may behave as second messengers and may regulate platelet functions. Accumulating evidence suggest a role of ROS/RNS in platelet activation. On the other hand, an increased production of ROS/RNS causes oxidative stress, and thus, may contribute to the development of different diseases, including vascular complications, inflammatory and psychiatric illnesses. Oxidative stress in platelets leads to chemical changes in a wide range of their components, and platelet proteins may be initial targets of ROS/RNS action. It has been demonstrated that reaction of proteins with ROS/RNS results in the oxidation and nitration of some amino acid residues, formation of aggregates or fragmentation of proteins. In oxidized proteins new carbonyl groups and protein hydroperoxides are also formed. In platelets, low molecular weight thiols such as glutathione (GSH), cysteine and cysteinylglycine and protein thiols may be also target for ROS/RNS action. This review describes the chemical structure and biological activities of reactive nitrogen species, mainly nitric oxide ((*)NO) and peroxynitrite (ONOO(-)) and their effects on blood platelet functions, and the mechanisms involved in their action on platelets.