Exploring the role of different drug transport routes in permeability screening.
ABSTRACT The influence of different drug transport routes in intestinal drug permeability screening assays was studied. Three experimental models were compared: the small-intestine-like 2/4/A1 cell model, which has a leaky paracellular pathway, the Caco-2 cell model, which has a tighter paracellular pathway, and artificial hexadecane membranes (HDMs), which exclusively model the passive transcellular pathway. The models were investigated regarding their ability to divide passively and actively transported compounds into two permeability classes and to rank compounds according to human intestinal absorption. In silico permeability models based on two-dimensional (2D) and three-dimensional (3D) molecular descriptors were also developed and validated using external test sets. The cell-based models classified 80% of the acceptably absorbed compounds (FA >/= 30%) correctly, compared to 60% correct classifications using the HDM model. The best compound ranking was obtained with 2/4/A1 (r(s) = 0.74; r(s) = 0.95 after removing actively transported outliers). The in silico model based on 2/4/A1 permeability gave results of similar quality to those obtained when using experimental permeability, and it was also better than the experimental HDM model at compound ranking (r(s) = 0.85 and 0.47, respectively). We conclude that the paracellular transport pathway present in the cell models plays a significant role in models used for intestinal permeability screening and that 2/4/A1 in vitro and in silico models are promising alternatives for drug discovery permeability screening.
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ABSTRACT: Objectives: There are several approaches to gain early information regarding the intestinal permeability and potential for intestinal absorption of drugs. Thus in the present work, different methods available in scientific sources are reviewed. Methods: several models gathered from literature, then their use, advantages and limitations were evaluated. Results: The review indicates that the models are categorized into five classes including human perfusion studies, animal studies (using isolated tissue and/or intestinal perfusion), cell culture techniques, immobilized artificial membrane columns and in silico models. Conclusion: Introduced models could be used in different phases of drug discovery and development, however in silico models are the only one that can help optimizing chemical synthesis since the absorption potential is predicted based on structural characteristics only. Key words: intestinal permeability, absorption, in vivo, in vitro, in silico, cell culture.
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ABSTRACT: Adult intestinal stem cells (ISC) possess both a long-term proliferation ability and differentiation capability into enterocytes. As a novel in vitro system for the evaluation of drug absorption, we characterized a human small intestinal epithelial cell (HIEC) monolayer that differentiated from adult ISC. Continuous proliferation/differentiation from ISC consistently conferred the capability of maturation of enterocytes to HIEC over 25 passages. The morphologically-matured HIEC monolayer consisted of polarized columnar epithelia with dense microvilli, tight junctions, and desmosomes 8 days after seeding onto culture inserts. Transepithelial electrical resistance across the monolayer was 9-fold lower in HIEC (98.9 ω×cm(2)) than in Caco-2 cells (900 ω×cm(2)), which indicated that the looseness of the tight junctions in the HIEC monolayer was similar to that in the human small intestine (~40 ω×cm(2)). No significant differences were observed in the overall gene expression patterns of the major drug metabolizing enzymes and transporters between the HIEC and Caco-2 cells monolayers. Furthermore, the functions of P-glycoprotein and BCRP in the HIEC monolayer were confirmed by the vectorial transport of marker substrates and their disappearance in the presence of specific inhibitors. The Papp values of paracellularly transported compounds (fluorescein isothiocyanate-dextran 4000, atenolol, and terbutaline) and nucleoside transporter substrates (ribavirin and doxifluridine) in the HIEC monolayer were markedly higher than those of Caco-2 cells, while transcellularly transported drugs (pindolol and midazolam) were equally well permeated. In conclusion, the HIEC monolayer can serve as a novel and superior alternative to the conventional Caco-2 cell monolayer for predicting oral absorption in humans.Drug metabolism and disposition: the biological fate of chemicals 09/2014; 42(11). · 3.74 Impact Factor
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ABSTRACT: The formal [3+3]cyclization of 3-arylthio-1-silyloxy-1,3-butadienes with 2-aryldiazenyl-3-silyloxy-2-en-1-ones afforded a variety of 2-arylthio-5-aryldiazenylbenzoates.Phosphorus Sulfur and Silicon and the Related Elements 01/2014; 189(2). · 0.83 Impact Factor