Antioxidant Peptides from Skipjack tuna: Ameliorate Function on Cigarette Smoke Extract-Induced COPD in Cell Model by Targeting Oxidative Stress, Inflammation and Apoptosis

peptides against in vitro cigarette smoke extract (CSE)-induced chronic obstructive pulmonary disease (COPD). The results demonstrated that tuna peptides DVGRG (S1), PHPR (S5), GRVPR (S6), and SVTEV (S7) significantly enhanced the activities of SOD, CAT, and GSH-Px by upregulating the mRNA transcription levels of Keap1 and Nrf2, consequently reducing ROS and MDA levels in CSE-induced COPD model of MLE-12 cells. Molecular docking analysis revealed that S1, S6, and S7 competitively inhibited the Keap1-Nrf2 interaction by binding to the Kelch domain of Keap1, whereas S5 operated through a non-competitive mechanism. These peptides also downregulated p65 mRNA expression and upregulated IκBα mRNA expression, leading to a significant reduction in inflammatory cytokines of IL-1β, IL-6, and TNF-α, thereby alleviating inflammatory responses. Furthermore, these peptides significantly inhibited CSE-induced apoptosis by restoring mitochondrial membrane potential and upregulating the Bcl-2/Bax ratio. Additionally, S1, S5, S6, and S7 promoted MLE-12 cell migration in a concentration-dependent manner, suggesting a role in lung epithelial repair and regeneration. In conclusion, tuna peptides S1, S5, S6, and S7 exert antioxidant, anti-inflammatory, anti-apoptotic, and cell migration-promoting effects through the regulation of the Keap1/Nrf2 and NF-κB signaling pathways, as well as Bcl-2/Bax apoptotic balance, providing a promising strategy for mitigating CSE-induced lung injury.