Regulation of the intestinal immune system by flavonoids and its utility in chronic inflammatory bowel disease

Figure 1 Simplified scheme of the gene regulation by the aryl hydrocarbon receptor. Flavonoids bind to the toll-like receptor in the lumen and get internalized to the cytosol. Then the complex functions as a ligand for the Ah receptor, which results in the release of associated proteins and translocation to the nucleus followed by dimerization with Arnt. The Ahr/Arnt complex binds the AhRE promoting target gene transcription like upregulation of IL-22, cytochrome P-450 and PERM activity as well as downregulation of STAT3 and NF-κB. The ligands can also exert their effects in the cytoplasm through AhR-associated protein kinases to alter the function of a variety of proteins through a cascade of protein phosphorylation. Ahr: Aryl hydrocarbon receptor; Arnt: Ahr nuclear translocator; Ah: Aryl hydrocarbon.