Abstract
The present study analyzed the transepithelial transport of the dietary anti-inflammatory peptide, γ-glutamyl valine (γ-EV). γ-EV is naturally found in dry edible beans. Our previous study demonstrated the anti-inflammatory potency of γ-EV against vascular inflammation at a concentration of 1mM, and that it can transport with the apparent permeability coefficient (Papp) of 1.56 × 10−6 ± 0.7 × 10−6 cm/s across the intestinal Caco-2 cells. The purpose of the current study was to explore whether the permeability of the peptide could be enhanced and to elucidate the mechanism of transport of γ-EV across Caco-2 cells. The initial results indicated that γ-EV was nontoxic to the Caco-2 cells up to 5 mM concentration and could be transported across the intestinal cells intact. During apical-to-basolateral transport, a higher peptide dose (5 mM) significantly (p < 0.01) enhanced the transport rate to 2.5 × 10−6 ± 0.6 × 10−6 cm/s. Cytochalasin-D disintegrated the tight-junction proteins of the Caco-2 monolayer and increased the Papp of γ-EV to 4.36 × 10−6 ± 0.16 × 10−6 cm/s (p < 0.001), while theaflavin 3′-gallate and Gly-Sar significantly decreased the Papp (p < 0.05), with wortmannin having no effects on the peptide transport, indicating that the transport route of γ-EV could be via both PepT1-mediated and paracellular.
Highlights
Dietary bioactive peptides have been shown to exhibit numerous health-modulating, beneficial biological activities, such as anti-inflammatory, antioxidant, antihypertensive, immunomodulatory, anticancer, and antithrombotic activities [1]
The first barrier is to survive the extensive hydrolysis in the gastrointestinal tract (GIT), and the second is to overcome the permeability across the intestinal epithelium [2]
Bioactive peptides may range from 2 to 20 amino acid residues, and their transepithelial transport route depends upon their overall charge, molecular mass, hydrophobicity, and tendency to aggregate [5]
Summary
Dietary bioactive peptides have been shown to exhibit numerous health-modulating, beneficial biological activities, such as anti-inflammatory, antioxidant, antihypertensive, immunomodulatory, anticancer, and antithrombotic activities [1]. To exert such health-beneficial activities, these food-derived bioactive peptides must overcome two critical physiological barriers in order to be absorbed in the blood circulation intact. A monolayer of human intestinal carcinoma-derived cell line, Caco-2, is generally used for transport and permeability studies of various drugs and peptides across the intestinal epithelium, as it mimics the human GIT in terms of the microvilli structure, tight junctions, and overall biological functions [3,4]. Numerous studies on the transport of food-derived bioactive peptides have been reported, and they may all have different transport mechanisms
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