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.
KeywordsFree Cholesterol Cholesterol Efflux Reverse Cholesterol Transport Small Unilamellar Vesicle Cell Cholesterol
Unable to display preview. Download preview PDF.
- 3.Venkatachalapathi YV, Phillips MC, Epand RM, Epand RF, Tytler EM, Segrest JP, Anantharamaiah GM. Effect of end group blockage on the properties of a class A amphipathic helical peptide. Proteins 1993;15:349359.Google Scholar
- 4.Sokoloff L, Rothblat GH. Regulation of sterol synthesis in L-cells: steady-state and transitional responses. Biochim. Biophys. Acta 1972;280:171181.Google Scholar
- 6.Francone OL, Fielding CJ. Initial steps in reverse cholesterol transport: the role of short-lived cholesterol acceptors. Eur. Heart J. 1990;11:218224.Google Scholar
- 8.de la Llera Moya M, Atger V, Paul JL, Fournier N, Moatti N, Giral P, Friday KE, Rothblat GH. A cell culture system for screening human serum for ability to promote cellular cholesterol efflux: relationships between serum compnents and efflux, esterification and transfer. Arterioscier. Thromb. 1994;In PressGoogle Scholar
- 9.Bates SR, Rothblat GH. Regulation of cellular sterol flux and synthesis by human serum lipoproteins. Biochim. Biophys. Acta 1974;360:39–55.Google Scholar