Failure of exogenous apoprotein E-3 to enhance cholesterol egress from J-774 murine macrophages in culture Original Research Article

HDL has been shown to enhance the removal of cholesterol from cultured fibroblasts, smooth muscle cells and macrophages, but fails to stimulate cholesterol removal from J-774 macrophages. Since J-774 macrophages do not synthesize or secrete apolipoprotein E, the effect of exogenous apolipoprotein E on HDL-mediated cellular cholesterol efflux was studied in this cell line. In cholesterol loaded J-774 macrophages total cellular cholesterol increased up to 6–7-fold, mainly cholesteryl esters. HDL3 removed up to 30% of total cellular cholesterol with a decrease in cholesteryl ester levels while free cholesterol levels remained unchanged. HDL3 was slightly superior to albumin in promoting cellular cholesterol removal. Exogenous apo E, over a wide range of apo E concentrations, did not enhance the ability of HDL3 to remove cellular cholesterol from cholesterol loaded J-774 cells. Exogenous apo E did not promote HDL-mediated cholesterol efflux from cells, thus suggesting a possible role for the intracellular route of newly synthesized apo E in these processes.