Intracellular transport of cholesteryl esters from lysosomes to cytoplasm in macrophages.

The mechanism through which nonmembranous lipid inclusion bodies consisting of cholesteryl esters accumulate in the cytoplasm was studied. Most lipid inclusion bodies in macrophages after 24 h incubation with anisotropic cholesteryl oleate liquid crystals were surrounded by a limiting membrane. The limiting membrane, however, could not be observed after further incubation for 48 h in the presence of esterastin, which is known to be an inhibitor of lipase and esterase. Under these conditions, the levels of hydrolysis and re-esterification of cholesteryl esters were less than 15% and 5% of the control ones, respectively. These results suggest that the inclusion bodies were transferred from lysosomes to the cytoplasm, with partial hydrolysis of cholesteryl esters, in addition to through the pathway via microsomes.