The endothelium and lipoproteins: Insights from recent cell biology and animal studies

Both lipoproteins and the endothelium play critical roles in the initiation and progression of atherosclerosis. An understanding of the interactions b etween lipoproteins and the endothelium facilitates our understanding of at herogenesis and could suggest new therapeutic targets. Lipoproteins have im portant effects on endothelial cells. Atherogenic lipoproteins such as remn ants, low-density lipoprotein (LDL), and oxidized LDL act on endothelial ce lls to cause upregulation of endothelial adhesion molecules and selectins, promotion of oxygen radicals, increased apoptosis, and reduced endothelium- dependent relaxation. Antiatherogenic lipoproteins such as HDL protect endo thelial cells from oxidative stress and apoptosis and reduce adhesion molec ule expression. Conversely, the endothelium has major effects on lipoprotei n metabolism and function. Several lipases, including lipoprotein lipase, h epatic lipase, endothelial lipase, and secretory phospholipase A2, are boun d to the endothelial cell matrix and have the ability to hydrolyze lipoprot ein triglycerides and phospholipids. Furthermore, endothelial cells express a variety of lipoprotein receptors including the VLDL receptor, scavenger receptor A, SR-BI, CD36, and LOX-1, although little is known about their fu nction on endothelial cells. Although a great deal is known about endotheli al-lipoprotein interactions, more research is needed in this important area .