Pathobiology of atherosclerosis and plaque complications.

To understand the process of atherosclerosis, the homeostatic and protective functions of the endothelium must be considered. The endothelium serves as the interface between blood flow and the vascular tissues. It normally regulates vascular tone and structure through the release of vasoactive substances and maintenance of a nonthrombogenic surface. Endothelial dysfunction, which results from biochemical and hemodynamic stresses associated with cardiovascular risk factors, causes an imbalance in the expression of vasodilating and vasoconstricting substances, as well as excess production of chemoattractant molecules and growth factors. Endothelial dysfunction in the presence of elevated cholesterol levels fosters the development of fatty streaks, which represent the early stage of atherosclerotic plaque. The unstable progression of atherosclerosis can be interrupted and even reversed in both animals and humans, although the exact clinical correlates of progression and regression are not fully understood.