USE OF THE INTESTINAL BILE-ACID TRANSPORTER FOR THE UPTAKE OF CHOLIC-ACID CONJUGATES WITH HIV-1 PROTEASE INHIBITORY ACTIVITY

Purpose. To investigate the ability of the human intestinal bile acid transporter to transport cholic acid conjugates with potential HIV-1 p rotease inhibitory activity. Methods. Cholic acid was conjugated at th e 24 position of the sterol nucleus with various amino acids and amino acid analogs. The CaCo-2 cell. line was used as a model to investigat e the interaction of these bile acid conjugates with the human intesti nal bile acid transporter. Interaction between the carrier and the con jugates was quantified by inhibition of taurocholic acid transport and confirmed by transport of radiolabelled conjugates in this cell line. Results. The highest interaction with the transporter, as quantified by inhibition of taurocholic acid transport, occurred when a single ne gative charge was present around the 24 to 29 region of the sterol nuc leus. A second negative charge or a positive charge significantly redu ced the interaction. Transport of radiolabelled cholyl-L-Lys-epsilon-t BOC ester and cholyl-D-Asp-beta-benzyl ester was inhibited by taurocho lic acid. Of all tested compounds, only cholyl-D-Asp-beta-benzyl ester showed modest HIV-1 protease inhibitory activity with an IC50 of 125 mu M. Conclusions, Cholic acid-amino acid conjugates with appropriate stereochemistry are recognized and transported by the human bile acid transporter and show modest HIV-1 protease inhibitory activity. Transp ort of these conjugates by the bile acid carrier is influenced by char ge and hydrophobicity around the 24 position of the sterol nucleus.