Phytochemical-Mediated Ah Receptor Activity Is Dependent on Dietary Context

Area of Science:

• Nutrition Science
• Molecular Biology
• Immunology

Background:

• The aryl hydrocarbon receptor (AHR) is crucial for intestinal homeostasis.
• AHR ligands include plant phytochemicals and tryptophan metabolites.
• Previous studies showed AHR ligands in foods but lacked in vivo validation.

Purpose of the Study:

• To determine if dietary phytochemicals activate the AHR in vivo.
• To investigate the role of CYP1A1 activity in AHR activation by food components.

Main Methods:

• Mice were fed diets containing various freeze-dried vegetables (15% w/w).
• CYP1A1 microsomal assays identified specific phytochemical substrates.
• Expression of the AHR target gene Cyp1a1 was measured in mouse tissues.

Main Results:

• Broccoli, onion, and carrots upregulated Cyp1a1 in the duodenum.
• Broccoli induced indolo[3,2-b]carbazole (ICZ), an AHR ligand and CYP1A1 substrate.
• Parsley (containing apigenin) enhanced broccoli-mediated Cyp1a1 induction in multiple organs.

Conclusions:

• Dietary phytochemicals activate the AHR in vivo.
• Competition for AHR binding and CYP1A1 metabolism influences systemic AHR activity.
• Specific food components can modulate AHR-mediated responses.