Intestinal transport of TRH analogs through PepT1: the role of in silico and in vitro modeling |
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Authors: | Chhuttan Lal Meena Arvind K Bansal Rahul Jain Kulbhushan Tikoo Abhay T Sangamwar |
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Institution: | 1. Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), Mohali, Punjab, India;2. Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Mohali, Punjab, India;3. Department of Pharmacology and Toxicology, National Institute of Pharmaceutical Education and Research (NIPER), Mohali, Punjab, India;4. Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER), Mohali, Punjab, India |
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Abstract: | The present study involves molecular docking, molecular dynamics (MD) simulation studies, and Caco‐2 cell monolayer permeability assay to investigate the effect of structural modifications on PepT1‐mediated transport of thyrotropin releasing hormone (TRH) analogs. Molecular docking of four TRH analogs was performed using a homology model of human PepT1 followed by subsequent MD simulation studies. Caco‐2 cell monolayer permeability studies of four TRH analogs were performed at apical to basolateral and basolateral to apical directions. Inhibition experiments were carried out using Gly‐Sar, a typical PepT1 substrate, to confirm the PepT1‐mediated transport mechanism of TRH analogs. Papp of the four analogs follows the order: NP‐1894 < NP‐2378 < NP‐1896 < NP‐1895. Higher absorptive transport was observed in the case of TRH analogs, indicating the possibility of a carrier‐mediated transport mechanism. Further, the significant inhibition of the uptake of Gly‐Sar by TRH analogs confirmed the PepT1‐mediated transport mechanism. Glide docking scores of all the four analogues were in good agreement with their transport rates, suggesting the role of substrate binding affinity in the PepT1‐mediated transport of TRH analogs. MD simulation studies revealed that the polar interactions with amino acid residues present in the active site are primarily responsible for substrate binding, and a downward trend was observed with the increase in bulkiness at the N‐histidyl moiety of TRH analogs. Copyright © 2014 John Wiley & Sons, Ltd. |
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Keywords: | Caco‐2 cells TRH analogs molecular dynamics molecular docking PepT1‐mediated transport GastroPlus |
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