Antioxidant activity and protective effect of wheat germ peptides in an in vitro celiac disease model via Keap1/Nrf2 signaling pathway

Celiac disease (CD) is an allergic intestinal disease caused primarily by gliadin and is widespread in the population. Alpha gliadin peptide causes cellular damage by substantially increasing cellular reactive oxygen species (ROS) levels. In this study, we examined the protective effect of 25 wheat germ peptides (WGPs) on the ɑ-gliadin peptide (P31-43)-treated Caco-2 cells. The experimental results showed that three peptides, WGP2, WGP7, and WGP11, significantly promoted cell viability and greatly alleviated the damage of Caco-2 cells by P31-43. According the assay of ROS, The three WGPS significantly reduced ROS to normal levels, which were elevated by P31-43 peptide. The results in terms of antioxidant-related enzymes showed that WGPs significantly increased catalase (CAT), Glutathione Reductases (GR), Glutathione peroxidase (GPx), and Glutathione (GSH)/ oxidized Glutathione (GSSG) levels, thus significantly enhancing the antioxidant level of cells. By studying the key protein expression levels of the Kelch-like ECH-associated protein 1 (Keap1)/NF-E2-related factor 2 (Nrf2) pathway, the results show that WGPs could activate Nrf2 and glutamate-cysteine ligase catalytic subunit (GCLC) up-regulation. For glutamate-cysteine ligase modifier (GCLM), WGP2 and WGP7 lead to its down-regulation, while WGP11 leads to its significant up-regulation.The present study found that peptides from wheat germ can effectively mitigate the cellular damage induced by the ɑ-gliadin peptide, which provides a new perspective for the prevention and treatment of CD.