Nrf2-Activating Bioactive Peptides Exert Anti-Inflammatory Activity through Inhibition of the NF-κB Pathway

Abstract

Redox status and inflammation are related to the pathogenesis of the majority of diseases. Therefore, understanding the role of specific food-derived molecules in the regulation of their specific pathways is a relevant issue. Our previous studies indicated that <b>K-8-K</b> and <b>S-10-S</b>, milk and soy-derived bioactive peptides, respectively, exert antioxidant effects through activation of the Keap1/Nrf2 pathway. A crosstalk between Nrf2 and NF-κB, mediated by the action of heme oxygenase (HO-1), is well known. On this basis, we studied if these peptides, in addition to their antioxidant activity, could exert anti-inflammatory effects in human cells. First, we observed an increase of HO-1 expression in Caco-2 cells treated with <b>K-8-K</b> and <b>S-10-S</b>, following the activation of the Keap1/Nrf2 pathway. Moreover, when cells are treated with the two peptides and stimulated by TNF-α, the levels of NF-κB in the nucleus decreased in comparison with TNF-α alone. In the same conditions, we observed the downregulation of the gene expression of proinflammatory cytokines (<i>IL1B</i>, <i>IL6</i>, and <i>TNF</i>), while the anti-inflammatory cytokine gene, <i>IL1RN</i>, was upregulated in Caco-2 cells processed as reported above. Then, when the cells were pretreated with the two peptides and stimulated with LPS, a different proinflammatory factor, (TNF-α) was estimated to have a lower secretion in the supernatant of cells. In conclusion, these observations confirmed that Nrf2-activating bioactive peptides, <b>K-8-K</b> and <b>S-10-S</b>, exerted anti-inflammatory effects by inhibiting the NF-κB pathway.