Effect of 6-O-α-maltosyl-β cyclodextrin and its cholesterol inclusion complex on cellular cholesterol levels and ABCA1 and ABCG1 expression in mouse mastocytoma P-815 cells.

We have previously described 6-O-α-maltosyl-β cyclodextrin (Mal-βCD), which forms soluble inclusion complex with cholesterol. Here we further investigated the effect of Mal-βCD and cholesterol/Mal-βCD inclusion complex (CLM) on cellular cholesterol levels in a mouse mast cell line, mastocytoma P-815 cells (P-815 cells). Mal-βCD removes cellular cholesterol forming inclusion complexes, while Mal-βCD-induced lack of cellular cholesterol was replenished by the addition of CLM without cytotoxicity. Reduction and replenishment of cellular cholesterol in Mal-βCD- and/or CLM-treated P-815 cells, respectively, were demonstrated by LC/MS and fluorescence microscopy with filipin III. CLM rather than free Mal-βCD and free cholesterol was efficiently incorporated into P-815 cells and its incorporation was inhibited by incubation at low temperature, or with sodium azide and cytochalasin D. P-815 cells have been confirmed to express ATP-binding cassette (ABC) transporters, ABCA1, ABCG1, and P-glycoprotein (P-gp), by Western blot and mRNA analysis. Cholesterol reduction by Mal-βCD abolishes the mRNA and protein expression of ABCA1 and ABCG1, but not of P-gp. Cholesterol loading by CLM restores the diminished ABCA1 and ABCG1 mRNA expression in Mal-βCD-treated P-815 cells. However, both Mal-βCD and CLM had no effect on P-gp activity measured by the rhodamine 123 efflux assay. These results indicate that alteration of cholesterol levels with Mal-βCD or CLM led to down- or up-regulation of ABCA1 and ABCG1 expression in P-815 cells.