Cholesterol Efflux from Cells in Culture: Studies with Lipid-Free Acceptors, Reconstituted Particles and Whole Serum
The movement of cholesterol from cells to acceptor lipoproteins is the first step in the process of reverse cholesterol transport. Both cellular factors and the characteristics of the acceptors modulate the rate at which the cholesterol molecules leave the cell and are picked up by the extracellular acceptors. To gain more information on the factors that influence the efficiency of various acceptors we have conducted a series of studies using acceptor particles of increasing complexity. The simplest system consisted of lipid-free apolipoprotein (apo) Al or synthetic peptides. Increasing complexity was produced when these peptides were reconstituted into disc-like structures composed of phospholipid and the different peptides. The last, and most complex, experimental cholesterol efflux system was one in which whole human serum was added to cells. In all of the studies we have quantitated the release of radiolabeled cholesterol from the cells. In the studies using lipid-free peptides or reconstituted particles the release of the labeled cholesterol reflects the net movement of cholesterol from cells to acceptors, since the acceptors were initially free of cholesterol and no significant cholesterol influx could occur. In the studies using whole serum, the quantitation of labeled cholesterol efflux does not predict the net change in cell cholesterol content since influx would be occurring from a variety of lipoproteins in the serum.
KeywordsCholesterol Foam Amide Proline Acetyl
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