Screening of the AhR- and Nrf2-linked transcriptional activities of some cruciferous vegetables and nuts in human intestinal epithelial cells as foods containing endogenous AhR ligand precursors

ABSTRACT Cruciferous vegetables and nuts are rich in indole-3-carbinol (I3C) and L-tryptophan (L-Trp), respectively, which can be converted upon ingestion into AhR ligands. Activation of AhR by dietary ligands contributes to unlocking its therapeutic potential in gastrointestinal homeostasis. In this study, some cruciferous vegetables (cabbage (red and white), cauliflower) and nuts (sunflower seed kernel, pistachio, cashew, walnut) were investigated for their effects on AhR- and Nrf2-mediated gene expression by using an in vitro digestion/Caco-2 cell culture model. Nuts induced AhR-pathway in a directly proportional manner with their L-Trp contents (sunflower induced the highest (5.3-fold) CYP1A1 expression). Nuts also showed Nrf2-dependent activities, although L-Trp standard did not. Vegetables activated only AhR-pathway, same with I3C standard, and red cabbage induced the highest CYP1A1 expression (9.6-fold). Results suggested the contribution of L-Trp and I3C in AhR-dependent activities of nuts and vegetables, respectively, although there appeared other bioactives to be identified in overall health aspects of these foods.