title: Intestinal transport of TRH analogs through PepT1: the role of in silico and in vitro modeling.
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.
authors.affiliation: Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Sector-67, S.A.S. Nagar, Mohali, Punjab, 160062, India.
authors.forename: Pravin
authors.initials: P
authors.lastname: Bagul
authors.forename: Kailas S
authors.initials: KS
authors.lastname: Khomane
authors.forename: Siddharth S
authors.initials: SS
authors.lastname: Kesharwani
authors.forename: Preeti
authors.initials: P
authors.lastname: Pragyan
authors.forename: Prajwal P
authors.initials: PP
authors.lastname: Nandekar
authors.forename: Chhuttan Lal
authors.initials: CL
authors.lastname: Meena
authors.forename: Arvind K
authors.initials: AK
authors.lastname: Bansal
authors.forename: Rahul
authors.initials: R
authors.lastname: Jain
authors.forename: Kulbhushan
authors.initials: K
authors.lastname: Tikoo
authors.forename: Abhay T
authors.initials: AT
authors.lastname: Sangamwar
mesh_terms: D001665:Binding Sites; D001692:Biological Transport; D018938:Caco-2 Cells; D002851:Chromatography, High Pressure Liquid; D019295:Computational Biology; D003198:Computer Simulation; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D000074011:Peptide Transporter 1; D010539:Permeability; D027981:Symporters / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives / Q000737:chemistry* / Q000493:pharmacokinetics
chemical_list: D000074011:Peptide Transporter 1; D027981:Symporters; D013973:Thyrotropin-Releasing Hormone
keywords: Caco-2 cells; GastroPlus; PepT1-mediated transport; TRH analogs; molecular docking; molecular dynamics