NET TRANSPORT OF CHOLESTEROL FROM CELLS OF THE HUMAN EA-HY-926 ENDOTHELIAL-CELL LINE TO HIGH-DENSITY-LIPOPROTEINS

EA.hy 926 cells, a human endothelial cell line, show characteristics o f differentiated endothelial cells. The cells express saturable bindin g of apo E-free I-125-high density lipoprotein3 (HDL3). B(max) increas ed from 71 to 226 ng HDL3 bound/mg cell protein after cholesterol load ing of the confluent endothelial cells with cationized low density lip oprotein (LDL). The affinity did not change after cholesterol enrichme nt (K(d) was 37 mug HDL3 protein/ml for control cells and 31 mug/ml fo r loaded cells). Incubation of cholesterol-loaded EA.hy 926 cells with native HDL and LDL had different effects on cellular cholesterol leve ls. Incubation with HDL decreased both esterified and unesterified cel lular cholesterol, but LDL did not change total cellular cholesterol. However, LDL tended to increase cellular cholesteryl esters, with a co ncomitant decrease of unesterified cellular cholesterol. Incubation of endothelial cells with both HDL and LDL also resulted in decreased to tal cellular cholesterol levels. These data show that cationized LDL-l oaded human endothelial EA.hy 926 cells can be used to study the net t ransport of cellular cholesterol to HDL, the first step in reverse cho lesterol transport.