Stimulated Release of
Cholesterol from Liposomal Membranes
by a PEGylated Phospholipid
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Abstract
PEGylated phospholipids are commonly used to increase
the blood-circulation
time of liposomes by providing a steric barrier around them. This
paper documents a fundamentally new property of these lipidsan
ability to stimulate the release of cholesterol from phospholipid
membranes. Evidence for such stimulation has been obtained by measuring
the transport of dehydroergosterol (DHE), a fluorescent simulant of
cholesterol, from donor liposomes made from 1-palmitoyl-2-oleoyl-<i>sn</i>-glycero-3-phosphocholine (POPC), 1,2-distearoyl-<i>sn</i>-glycero-3-phosphoethanolamine-<i>N</i>-[methoxy(polyethylene
glycol)-2000 (DSPE-PEG<sub>2000</sub>), and DHE to acceptor liposomes
made from POPC, 1-palmitoyl-2-oleoyl-<i>sn</i>-glycero-3-phosphoglycerol
(POPG), and cholesterol. The potential of PEGylated lipids to serve
as novel cholesterol-lowering agents is briefly discussed