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

Abstract

SummaryHigh 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 All (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.