Endothelial dysfunction in the pathogenesis of atherosclerosis.
Healthy endothelium plays a central role in cardiovascular control. Therefore, endothelial dysfunction (ED), which is characterized by an imbalance between relaxing and contracting factors, procoagulant and anticoagulant substances, and between proinflammatory and antiinflammatory mediators, may play a particularly significant role in the pathogenesis of atherosclerosis. Endothelial dysfunction is closely related to different risk factors of atherosclerosis, and to their intensity and duration. The involvement of risk factors in ED is also supported by results of interventions studies that showed regression of ED with treatment of risk factors. Because risk factors are commonly accompanied by decreased bioavailability of nitric oxide, the common denominator whereby different risk factors cause ED is most probably increased oxidative stress. Endothelial dysfunction may promote atherogenesis through different mechanisms such as increased adherence of monocytes, macrophages, and enhanced permeability of the endothelial layer. Further, ED probably plays an important role in the growth of atherosclerotic lesions and in the development of thrombotic complications in late stages of the disease. Because ED is a key underlying factor in the atherosclerotic process, markers of endothelial abnormalities have been sought. Detection of ED is based on tests of endothelium-dependent vasomotion (dilation capability of peripheral and coronary arteries) and on circulating markers of endothelial function (endothelin-1, von Willebrand factor, tissue plasminogen activator, plasminogen activator inhibitor, and adhesion molecules). Using these tests it is possible to follow the dose response of harmful effects of risk factors, and the effects of preventive procedures on vessel wall function.