Effect of High Density Lipoproteins Modified with Dilinoleoylphosphatidylcholine Vesicles on [³H]Cholesterol Release from Macrophages

Abstract

High density lipoprotein 3 (HDL₃=1.12<d<1.21) was modified with dilinoleoylphosphatidylcholine, and the effects of these modified HDL₃ on the removal of [³H]cholesterol from rat peritoneal macrophages were studied. On incubation of HDL₃ with polyenephosphatidylcholine (PPC) vesicles, phospholipid-rich high density lipoproteins (1.18<d<1.24) were formed. The apolipoprotein AI (apo AI) and AII (apo AII) contents of these modified HDL₃ were about 3 to 40% of those of native HDL₃. Removal of [³H]cholesterol from macrophages was investigated using rat peritoneal macrophages prelabeled with [³H]cholesterol emulsion or with [³H]cholesterol oleate-labeled acetylated low density lipoproteins (1.019<d<1.063). The modified HDL₃s facilitated the removal of [³H]cholesterol from macrophages. The extent of removal of [³H]cholesterol from macrophages was higher with modified HDL₃ than with native HDL₃, and among modified HDL₃ subfractions, fractions IV and V, whose ratio of apo AI to phospholipid (AI/PL) were 0.44 and 0.58, respectively, were more efficient [³H]cholesterol acceptors than native HDL₃ (AI/PL=1.46). These results indicate that the effectiveness of HDL₃ in removing [³H]cholesterol from macrophages was enhanced by modification with PPC.