Lysophosphatidylcholine promotes cholesterol efflux from mouse macrophage foam cells

We examined the effects of lysophosphatidylcholine (lyse-PC) on promoting cholesterol efflux from macrophage foam cells. Mouse peritoneal macrophages were converted to foam cells by incubation with [H-3]cholesteryl linolaate-labeled or unlabeled acetyl-LDL. When these cells were incubated with lyso-PC, [H-3]cholesterol release was promoted in relation to both dose and time, and cellular cholesterol mass was decreased, while medium cholesterol mass was increased. These cholesterol efflux-promotive effects of lyse-PC were confirmed by the fact that the lyse-PC-treated cells showed less oil red O Staining than the control cells. ApoE secretion, estimated by Western blotting of the medium, was also augmented by lyse-PC. Both the cholesterol and apoE released by Ipso-PC treatment were floated by ultracentrifugation of the medium after its density had been adjusted to 1.210 g/mL. By electron microscopic analysis, vesicular lipoproteins were observed in ultracentrifugally concentrated conditioned medium of lyse-PC. Monensin, a protein secretion inhibitor, effectively inhibited [H-3]cholesterol release induced by lyse-PC but not by apoA-I. These results suggest that lyso-PC map inhibit the development of atherosclerosis or enhance its regression by stimulating cholesterol efflux from macrophage foam cells.