Taurine in Lower Concentration Attenuates Platelet Activity

The ex vivo antiplatelet activation potential of fruit phenolic metabolite hippuric acid

Active metabolite of polyphenol intake, hippuric acid, reduces platelet activation-related conformational change and de-granulationex vivothereby alleviating thrombogenesis.

Bilirubin, platelet activation and heart disease: a missing link to cardiovascular protection in Gilbert's syndrome?

Gilbert's syndrome (GS) is a relatively common condition, inducing a benign, non-hemolytic, unconjugated hyperbilirubinemia. Gilbert's Syndrome is associated with mutation in the Uridine Glucuronosyl Transferase 1A1 (UGT1A1) gene promoter, reducing UGT1A1 activity, which normally conjugates bilirubin allowing its elimination from the blood. Individuals with GS demonstrate mildly elevated plasma antioxidant capacity caused by elevated levels of unconjugated bilirubin (UCB), reduced thiols and glutathione. Interestingly, the development of, and risk of mortality from, cardiovascular disease is remarkably reduced in GS individuals. An explanation for this protection may be explained by bilirubin's ability to inhibit multiple processes that induce platelet hyper-reactivity and thrombosis, thus far under-appreciated in the literature. Reactive oxygen species are produced continuously via metabolic processes and have the potential to oxidatively modify proteins and lipids within cell membranes, which may encourage the development of thrombosis and CVDs. Oxidative stress induced platelet hyper-reactivity significantly increases the risk of thrombosis, which can potentially lead to tissue infarction. Here, we discuss the possible mechanisms by which increased antioxidant status might influence platelet function and link this to cardiovascular protection in GS. In summary, this is the first article to discuss the possible role of bilirubin as an anti-thrombotic agent, which inhibits platelet activation and potentially, organ infarction, which could contribute to the reduced mortality rate in mildly hyperbilirbinemic individuals.

A review of the mechanisms and effectiveness of dietary polyphenols in reducing oxidative stress and thrombotic risk

Dietary sources of polyphenols, which are derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, possess antioxidant properties and therefore might be important in preventing oxidative-stress-induced platelet activation and attenuating adverse haemostatic function. Free radicals, including reactive oxygen and nitrogen species, promote oxidative stress, leading to platelet hyperactivation and the risk of thrombosis. The consumption of antioxidant/polyphenol rich foods might therefore impart anti-thrombotic and cardiovascular protective effects via their inhibition of platelet hyperactivation or aggregation. Most commonly-used anti-platelet drugs such as aspirin block the cyclooxygenase (COX)-1 pathway of platelet activation, similar to the action of antioxidants with respect to neutralising hydrogen peroxide (H2 O2 ), with a similar effect on thromboxane production via the COX-1 pathway. Polyphenols also target various additional platelet activation pathways (e.g. by blocking platelet-ADP, collagen receptors); thus alleviating fibrinogen binding to platelet surface (GPIIb-IIIa) receptors, reducing further platelet recruitment for aggregation and inhibiting platelet degranulation. As a result of the ability of polyphenols to target additional pathways of platelet activation, they may have the potential to substitute or complement currently used anti-platelet drugs in sedentary, obese, pre-diabetic or diabetic populations who can be resistant or sensitive to pharmacological anti-platelet therapy.