Susceptibilities of phospholipid vesicles containing different sterols to amphotericin B-loaded lysophosphatidylcholine micelles.
To investigate the susceptibilities of fungal and mammalian cells to amphotericin B (AmB), AmB-loaded lysophosphatidylcholine (LPC)micelles as drug delivery vehicles were incubated at 37 degrees C with phosphatidylcholine vesicles containing different sterols as model systems for fungal and mammalian cells. The binding and kinetics of AmB to sterols in the membranes were judged by UV-visible spectroscopy. In the 91% monomeric form, AmB interacted rapidly with ergosterol and slowly with 7-dehydrocholesterol (7-DHC), while it did not interact with cholesterol. In the 50% monomeric form, AmB formed complexes more rapidly with ergosterol or 7-DHC than in the monomeric form, whereas it did not still interact with cholesterol. The interaction was also characterized by resonance energy transfer between the fluorescent probe trimethylammonium diphenylhexatriene (TMA-DPH) and AmB. In the 91% monomeric form, AmB caused initial fluorescence quenching in bilayer membranes containing any sterol as well as sterol-free bilayer membranes due to the release of AmB and its incorporation within the membranes. However, a second phase of increasing fluorescence was found in the case of ergosterol alone. On the other hand, in the 47% monomeric form, AmB gave a biphasic intensity profile in membranes containing any sterol as well as sterol-free membranes. However, the extent of the second phase of increasing fluorescence intensity was markedly dependent upon sterol composition. Studies using sterol-containing vesicles provide important insights into the role of the aggregation state of AmB in its effects on cells.
Onda
Maki
M
Department of Environmental Sciences, Faculty of Science, Osaka Women's University, 2-1 Daisen-cho, Sakai, Osaka 590-0035.
Inoue
Yukari
Y
Kawabata
Manami
M
Mita
Tomoyoshi
T
D000666:Amphotericin B / Q000737:chemistry*; D002784:Cholesterol / Q000737:chemistry; D003684:Dehydrocholesterols / Q000737:chemistry; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry; D004875:Ergosterol / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry*; D008244:Lysophosphatidylcholines / Q000737:chemistry*; D008823:Micelles; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013261:Sterols / Q000737:chemistry*
D003684:Dehydrocholesterols; D004337:Drug Carriers; D008081:Liposomes; D008244:Lysophosphatidylcholines; D008823:Micelles; D013261:Sterols; D000666:Amphotericin B; D002784:Cholesterol; C016705:7-dehydrocholesterol; D004134:Dimyristoylphosphatidylcholine; D004875:Ergosterol