Lipoxidized Protein Digests Alter Caco-2 Redox Homeostasis and Transepithelial Peptide Transport

This study examined how lipoxidized myofibrillar protein digests affect intestinal epithelial redox homeostasis and peptide transport using Caco-2 cell and monolayer models. Oxidation-then-digestion products (ODPs) were generated from proteins oxidized by 4-hydroxy-2-nonenal (HNE), lipoxygenase (LOX), or lipoxygenase-linoleic acid (LOX-LA), and then applied to Caco-2 cells and monolayers. Exposure to ODPs, relative to unoxidized digestion products (UDPs), increased intracellular lipid oxidation, as evidenced by elevated HNE and malondialdehyde (MDA) levels, and promoted intracellular HNE-protein adduct formation. High-dose ODP-HNE increased lactate dehydrogenase (LDH) release from 22.12 ± 1.00 to 37.13 ± 0.44 mU (P < 0.05), indicating weakened membrane integrity. ODP treatments altered glutathione peroxidase (GPx) and catalase (CAT) activities and increased several epithelial cytokine levels. LC–MS/MS analysis showed that lipoxidation increased peptide molecular size and diversified peptide modifications. These changes were accompanied by altered apical and basolateral peptide distributions, suggesting modified epithelial handling of oxidized peptides.