Analysis of the 22-NBD-cholesterol transfer between liposome membranes and its relation to the intermembrane exchange of 25-hydroxycholesterol.
The transfer of 22-NBD-cholesterol (22-(N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3-ol) between two liposome membranes was quantitatively analyzed by using the fluorescence resonance energy transfer (FRET) method. Liposomes labeled with both 22-NBD-cholesterol and a rhodamine-labeled phosphatidylethanolamine (Rh-DHPE) were used as donor liposomes, and the 22-NBD-cholesterol transfer from these donor liposomes to acceptor liposomes prepared from same type of phosphatidylcholine was monitored. The transfer kinetics was found to be composed of a fast and a slow phase, and all kinetic measurements could be fitted with a bi-exponential model. The results obtained indicate that the 22-NBD-cholesterol transfer kinetics between liposome membranes depends on the fluidity of the liposome used and that the curvature may affect the kinetics. Furthermore, the behavior of 22-NBD-cholesterol in lipid membrane is similar to that of the oxysterol 25-hydroxycholesterol rather than cholesterol. It is proposed that 22-NBD-cholesterol can be a useful fluorescent probe to mimic the intermembrane transfer of oxidized cholesterols like 25-hydroxycholesterol, rather than that of cholesterol itself.
Ishii
Haruyuki
H
Department of Chemical Science and Engineering, Osaka University, Toyonaka, Japan.
Shimanouchi
Toshinori
T
Umakoshi
Hiroshi
H
Walde
Peter
P
Kuboi
Ryoichi
R
D002784:Cholesterol / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D006888:Hydroxycholesterols / Q000737:chemistry*; D007700:Kinetics; D008081:Liposomes; D008567:Membranes, Artificial; D013050:Spectrometry, Fluorescence
D006888:Hydroxycholesterols; D008081:Liposomes; D008567:Membranes, Artificial; C007997:25-hydroxycholesterol; D002784:Cholesterol