title: Dipeptide model prodrugs for the intestinal oligopeptide transporter. Affinity for and transport via hPepT1 in the human intestinal Caco-2 cell line.
abstract: The human intestinal di/tri-peptide carrier, hPepT1, has been suggested as a drug delivery target via increasing the intestinal transport of low permeability compounds by designing peptidomimetic prodrugs. Model ester prodrugs using the stabilized dipeptides D-Glu-Ala and D-Asp-Ala as pro-moieties for benzyl alcohol have been shown to maintain affinity for hPepT1. The primary aim of the present study was to investigate if modifications of the benzyl alcohol model drug influence the corresponding D-Glu-Ala and D-Asp-Ala model prodrugs' affinity for hPepT1 in Caco-2 cells. A second aim was to investigate the transepithelial transport and hydrolysis parameters for D-Asp(BnO)-Ala and D-Glu(BnO)-Ala across Caco-2 cell monolayers. In the present study, all investigated D-Asp-Ala and D-Glu-Ala model prodrugs retained various degrees of affinity for hPepT1 in Caco-2 cells. These affinities are used to establish a QSAR of our benzyl alcohol modified model prodrugs, aided at elucidating the observed differences in model prodrug affinity for hPepT1; additionally, these data suggest that the hydrophobicity of the side-chain model drug is the major determinant in the compounds affinity for hPepT1. Transepithelial transport studies performed using Caco-2 cells of D-Asp(BnO)-Ala and D-Glu(BnO)-Ala showed that the K(m) for transepithelial transport was not significantly different for the two compounds. The maximal transport rate of the carrier-mediated flux component does not differ between the two model prodrugs either. The transepithelial transport of D-Asp(BnO)-Ala and D-Glu(BnO)-Ala follows simple kinetics, and the release of benzyl alcohol is pH-dependent, but unaffected by 1 mM of the esterase inhibitor Paraoxon in 80% human plasma and Caco-2 cell homogenate.
authors.affiliation: Department of Pharmaceutics, The Royal Danish School of Pharmacy, 2 Universitetsparken, DK-2100, Copenhagen, Denmark.
authors.forename: C U
authors.initials: CU
authors.lastname: Nielsen
authors.forename: R
authors.initials: R
authors.lastname: Andersen
authors.forename: B
authors.initials: B
authors.lastname: Brodin
authors.forename: S
authors.initials: S
authors.lastname: Frokjaer
authors.forename: M E
authors.initials: ME
authors.lastname: Taub
authors.forename: B
authors.initials: B
authors.lastname: Steffansen
mesh_terms: D018938:Caco-2 Cells; D002352:Carrier Proteins / Q000378:metabolism*; D004151:Dipeptides / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000074011:Peptide Transporter 1; D011355:Prodrugs / Q000378:metabolism*; D021281:Quantitative Structure-Activity Relationship; D027981:Symporters
chemical_list: D002352:Carrier Proteins; D004151:Dipeptides; D000074011:Peptide Transporter 1; D011355:Prodrugs; C082186:SLC15A1 protein, human; D027981:Symporters