Lipoproteins in normal and atherosclerotic aorta.

Each method used for the extraction and isolation of intimal lipoproteins has advantages and disadvantages. Gentle extraction methods are needed to characterize subtle modifications in the structure and biologic properties of the lipoproteins, whereas more aggressive methods are needed if the goal is to maximize the yield of lipoproteins from atherosclerotic arteries. The present paper evaluates different methods used for the isolation of intimal lipoproteins. Normal intima contains remnant-like and low density lipoprotein (LDL)-like particles that more strongly stimulate cholesterol esterification in macrophages than do control plasma LDL. Both fractions contain apolipoprotein (apo) E but neither shows clear signs of oxidative modification. LDL-like particles from atherosclerotic lesions, on the other hand, contain malondialdehyde- and 4-hydroxynonenal-lysine adducts in apo B, are chemotactic for monocytes and show increased degradation in macrophages, a process that oxidized LDL prepared in vitro can compete with. The findings support the conclusion that at least a portion of the LDL isolated from atherosclerotic lesions is similar, if not identical, to oxidatively modified LDL.