Comparison of the capacity of beta-cyclodextrin derivatives and cyclophanes to shuttle cholesterol between cells and serum lipoproteins

Previous studies from this laboratory have demonstrated that low concentrat ions of cyclodextrins (<1.0 mM), when added to serum, act catalytically as cholesterol shuttles to accelerate the exchange of free cholesterol between cells and serum lipoproteins, As cholesterol shuttles, cyclodextrins have the potential to serve as pharmacological agents for modifying cholesterol metabolism, In the present study, we have quantitated the cholesterol-shutt ling capacity of a series of newly synthesized beta-cyclodextrin derivative s (beta CDs), with varying structure, and two double-decker cyclophanes, Th e general protocol is as follows. [H-3]cholesterol-labeled CHOK1 cells are incubated for 2 h with the test compounds alone or together with 5% human s erum, and efflux of the cellular [H-3]cholesterol is measured, As methyl be ta-cyclodextrin (M beta CD) served as the basis for comparison, initial exp eriments were conducted that demonstrated there was a dose-dependent stimul ation of cell cholesterol efflux as the concentration of M beta CD increase d, with an EC50 that was calculated to be 0.05 mM. To determine the cholest erol-shuttling capacity of the newly synthesized compounds, cell cholestero l efflux is measured when the compounds are present alone, at a concentrati on of 0.05 mM, or together with 5% human serum. Our results demonstrate tha t the double-decker cyclophanes are the most efficient cholesterol shuttles . Under our experimental conditions, methyl beta-cyclodextrin (M beta CD) a pproximately doubles the efflux of cell cholesterol to serum, whereas one o f the double-decker cyclophanes produces a 4-fold stimulation in efflux, Fo ur of the beta-cyclodextrin derivatives (beta CDs) display shuttling abilit y similar to that of M beta CD, Furthermore, there does not appear to be a structural pattern among the other beta CDs which could explain their shutt ling capacity.