AHR and Alzheimer disease: We and other researchers have demonstrated that tar derived from coal or soybeans clinically used in Japan upregulates FLG via AHR activation, contributing to improvement of the barrier function in AD.7, 21 It has been shown in AHR knockdown NHEKs21 that an AHR-binding site (xenobiotic response element) in the FLG promoter region has an important role in the upregulation of FLG induced by AHR activation.