Protection of endothelial function: targets for nutritional and pharmacological interventions

The vascular endothelium synthesizes and releases a spectrum of vasoactive substances and therefore plays a fundamental role in the basal and dynamic regulation of the circulation. Nitric oxide (NO)-originally described as endothelium-derived relaxing factor-is released from endothelial cells in response to shear stress produced by blood flow, and in response to activation of a variety of receptors. After diffusion from endothelial to vascular smooth muscle cells, NO increases intracellular cyclic guanosine-monophosphate concentrations by activation of the enzyme guanylate cyclase leading to relaxation of the smooth muscle cells. NO has also antithrombogenic, antiproliferative, leukocyte-adhesion inhibiting effects, and influences myocardial contractility. Endothelium-derived NO-mediated vascular relaxation is impaired in spontaneously hypertensive animals. NO decomposition by free oxygen radicals is a major mechanism of impaired NO bioavailability. The resulting imbalance of endothelium-derived relaxing and contracting substances disturbs the normal function of the vascular endothelium. Endothelin acts as the natural counterpart to endothelium-derived NO. Besides its arterial blood pressure rising effect in humans, endothelin-1 induces vascular and myocardial hypertrophy, which are independent risk factors for cardiovascular morbidity and mortality. Current therapeutic strategies concentrate mainly on lowering low-density lipoprotein cholesterol and an impressive reduction in the risk for cardiovascular morbidity and mortality has been achieved. Inflammatory mechanisms play an important role in vascular disease and inflammatory plasma markers correlate with prognosis. The production of reactive oxygen species under pathological conditions may represent an important inflammatory trigger. Novel therapeutic strategies specifically targeting inflammation thus bear great potential for the prevention and treatment of atherosclerotic vascular disease. In this context, the vascular actions of flavanol-rich cocoa, particularly with regard to enhanced NO synthesis and endothelial function observed in humans following consumption, warrants further attention. This review discusses pharmacological and dietary intervention.