Effect of Structural Modification of α-Aminoxy Peptides on Their Intestinal Absorption and Transport Mechanism

Abstract

A representative α-aminoxy peptide 1 has been demonstrated to have a potential for the treatment of human diseases associated with Cl(-) channel dysfunctions. However, its poor intestinal absorption was determined. The purpose of this study was to delineate the transport mechanism responsible for its poor absorption and also to prepare peptide analogues by structural modifications of 1 at its isobutyl side chains without changing the α-aminoxy core for retaining biological activity to improve the intestinal absorption. The poor intestinal absorption of 1 was proved to be due to the P-glycoprotein (P-gp) mediated efflux transport in Caco-2 cell monolayer, intestinal segments in Ussing chamber and rat single pass intestinal perfusion models. Four analogues with propionic acid (2), butanamine (3), methyl (4) and hydroxymethyl side chains (5) were synthesized and tested using the same models. Except for the permeability of 2, the absorbable permeability of the modified peptides in Caco-2 cell monolayer and their intestinal absorption in rats were significantly improved to 7-fold (3), 4-fold (4), 11-fold (5) and 36-fold (2), 42-fold (3), 55-fold (4), 102-fold (5), respectively, compared with 1 (P(app), 0.034 ± 0.003 × 10(-6) cm/s; P(blood), 1.61 ± 0.807 × 10(-6) cm/s). More interestingly, the structural modification remarkably altered transport mechanism of the peptides, leading to the conversion of the active transport via P-gp mediation (1, 2), to MRP mediation (3), MRP plus BCRP mediation (4) or a passive diffusion (5). Furthermore, P-gp mediated efflux transport of 1 and 2 was demonstrated to not alter the P-gp expression, while 1 but not 2 exhibited uncompetitive inhibitory effect on P-gp ATPase. The results demonstrated that intestinal absorption and transport mechanism of the α-aminoxy peptides varied significantly with different structures, and their absorption can be dramatically improved by structural modifications, which allow us to further design and prepare better α-aminoxy peptide candidates with appropriate pharmacokinetic fates, including intestinal absorption, for potential clinical use.

Applications of Supramolecular Anion Recognition

“…Channel formation by 310 was suggested based on patch clamp experiments on giant unilamellar vesicles, but the mechanism of this channel formation has not yet been reported. Interestingly, Yang and co-workers also published a series of papers about the biological activity of 310 , including a report suggesting that the chloride transport activity of this compound is able to restore chloride conductance across cystic fibrosis epithelial cells. ,− …”

Investigation of Transport Mechanism of Exendin-4 across Madin Darby Canine Kidney Cell Monolayers

“…However, some peptides can also be absorbed through intestine via active transports. 14) We sought to confirm which premise are true in the case of exendine-4. The objectives of this study were: (1) to determine whether exendin-4 is absorbed by passive or active way; (2) if passive way, to confirm the contributions of transcellular and paracellular pathway mainly involved in exendin-4 transport; (3) the effect of absorption enhancers, chitosan, sodium decanoate and ethylenediaminetetraacetic acid (EDTA) on the transport of exendin-4.…”