Endothelial dysfunction is a physiological dysfunction of normal biochemical processes carried out by the endothelium, the cells that line the inner surface of all blood vessels including arteries and veins (as well as the innermost lining of the heart and lymphatics.) Compromise of normal function of endothelial cells is characteristic of endothelial dysfunction. Normal functions of endothelial cells include mediation of coagulation, platelet adhesion, immune function, control of volume and electrolyte content of the intravascular and extravascular spaces. Endothelial dysfunction can result from disease processes, as occurs in septic shock, hypertension, hypercholesterolaemia, diabetes as well as from environmental factors, such as from smoking tobacco products.
Endothelial dysfunction as a result of von Willebrand factor and E selectin dysfunction Source: D'Adamo, P. IfHI 2003, Tempe AZ
Endothelial dysfunction is thought to be a key event in the development of atherosclerosis and predates clinically obvious vascular pathology by many years. Endothelial dysfunction has also been shown to be of prognostic significance in predicting vascular events including stroke and heart attacks.
A key feature of endothelial dysfunction is the inability of arteries and arterioles to dilate fully in response to an appropriate stimulis. This can be tested by a variety of methods including iontophoresis of acetylcholine, intra-arterial administration of various vasoactive agents, localised heating of the skin and temporary arterial occlusion by inflating a blood pressure cuff to high pressures. Testing can also take place in the coronary arteries themselves but this is invasive and not normally conducted unless there is a clinal reason for intracoronary catheterisation. These techniques are thought to stimulate the endothelium to release nitric oxide (NO) and possibly some other agents, which diffuse into the surrounding vascular smooth muscle causing vasodilation.
Dysfunctional endothelial cells are unable to produce NO to the same extent (or there is increased and rapid destruction of NO) as healthy endothelial cells and therefore vasodilatation is reduced. This creates a detectable difference in subjects with endothelial dysfunction verses a normal, healthy endothelium.
Unfortunately the variability in such tests means that no technique has yet been identified that would allow endothelial testing to attain routine clinical significance.
Endothelial function can be improved significantly by exercise and improved diet. Other factors have been identified as improving endothelial function and include cessation of smoking, loss of weight and treatment of hypertension and hypercholesterolemia amongst other things.
The influence of advanced glycation endproducts (AGE) on the expression of human endothelial adhesion molecules
Exp Clin Endocrinol Diabetes. 1998;106(3):183-8
Kunt T, Forst T, Harzer O, Buchert G, Pfutzner A, Lobig M, Zschabitz A, Stofft E, Engelbach M, Beyer J.
- Advanced glycation endproducts (AGEs) possibly play a dominant role in the pathogenesis of macrovascular disease in diabetes. Recent studies could demonstrate that glycated albumin (AGE-BSA) was able to stimulate vascular cell adhesion molecule-1 (VCAM.1) on endothelial cells. The aim of this study was to find out if AGE-BSA was not only able to enhance the expression of vascular cell adhesion molecule-1, but also of intercellular adhesion molecule-1 (ICAM-1) and E-Selectin on human endothelial cells. Stimulation of endothelial cells with AGE-BSA for six hours predominantly increased the expression of VCAM-1, but ICAM-1 and E-Selectin were also upregulated as shown by immunoilluminometric assay (ILMA)