Vascular protection of tea and grape-derived polyphenols: in vitro and in vivo evidence

Epidemiological studies have indicated that regular intake of polyphenol rich sources such as vegetables, fruit, red wine and tea is associated with a decreased risk of coronary diseases. The protective effect of polyphenols on the vascular system has been attributable in part to their direct action on endothelial cells resulting in an enhanced formation of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF), two factors playing a major role in the control of vascular homeostasis. Indeed, tea and grape-derived polyphenols cause pronounced endothelium-dependent relaxations of isolated arteries, which are mediated by NO and, also in some arteries, by EDHF. The increased formation of NO is initiated by a pro-oxidant response in endothelial cells, which triggers activation of Src kinase with the subsequent activation of the PI3-kinase/Akt pathway resulting in the activation of endothelial NO synthase following its phosphorylation on Ser1177. Intake of red wine polyphenols in the drinking water is also able to prevent the development of an endothelial dysfunction and hypertension induced by infusion of angiotensin II to rats, and also of an endothelial dysfunction in ageing. The protective effect of polyphenols involves their ability to prevent the excessive oxidative stress, the arachidonic acid-derived formation of endothelium-dependent contracting factors, and to regulate the local angiotensin II system in the pathologic artery. Thus, polyphenols induce a great variety of effects on both endothelial cells and vascular smooth muscle cells to protect blood vessels.