Transport of soybean protein-derived antihypertensive peptide LSW across Caco-2 monolayers

The purpose of this study was to study the transport mechanism of LSW (Leu-Ser-Trp), an angiotensin I-converting enzyme inhibitory tripeptide derived from soybean proteins, using Caco-2 cell monolayers. Antihypertensive peptide LSW at a concentration of 5 or 10 mM had no cytotoxicity on cells, and could be intact transported across Caco-2 monolayers (apparent permeability coefficient: (11.53 ± 1.82) × 10−8 cm/s), and was resistant to the peptidases in apical sides. In addition, LSW transport was significantly increased by cytochalasin D (a tight junction expander), and decreased by theaflavin-3′-O-gallate (a tight junction enhancer), but not by wortmannin (a transcytosis inhibitor). Furthermore, knockdown of peptide transporter 1 (PepT1) expression by siRNA significantly decreased LSW transport. The LSW transport from apical to basolateral side was significantly higher than that of the reverse direction. In conclusion, antihypertensive tripeptide LSW was transported intact across Caco-2 monolayers by paracellular diffusion via TJ and PepT1 pathway, but not by transcytosis pathway.