Scavenger receptors and oxidized low density lipoproteins

Oxidized LDL has been shown to exhibit a number of potentially proatherogen ic actions and properties, including receptor-mediated uptake and lipid acc umulation within macrophages. It has been postulated that rapid, unregulate d uptake of oxidatively modified LDL could account for the transformation o f monocyte-derived macrophages to foam cells in atherosclerotic lesions. In support of this hypothesis, oxidized LDL and lipid peroxidation products h ave been shown to exist in atheromas in vivo. Furthermore, a number of cell membrane proteins that can bind oxidized LDL with high affinity have been identified on the surface of macrophages, endothelial cells and smooth musc le cells. One characteristic that almost all of these 'scavenger receptors' share is the ability to bind with high affinity to a broad spectrum of str ucturally unrelated Ligands. Of all of the different classes of scavenger r eceptors that have been identified, the scavenger receptor class A type I/I I (SR-AI/II) has received the most attention. Studies with macrophages from mice deficient in the gene for SR-AI/II provide direct evidence that a rec eptor other than the SR-AI/II is responsible for most of the uptake of oxid ized LDL in murine macrophages. This article provides an overview of the ch aracterization and functions of the scavenger receptors that have been show n to interact with oxidized LDL, including SR-AI/II, CD36, SR-BI, macrosial in/CD68, LOX-1, and SREC. Isolation and characterization of these and other scavenger receptors has increased our understanding of their role in the u ptake of oxidized LDL and the pathogenesis of atherosclerosis. (C) 1999 Els evier Science BN. All rights reserved.