Increased expression of the aryl hydrocarbon receptor in patients with chronic inflammatory skin diseases

Polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are major environmental pollutants, and their effects on the human body critically depend on the aryl hydrocarbon receptor (AhR). The aim of this study was to evaluate the significance of the AhR and its ligands in chronic inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis. Expression of AhR-related mRNA was increased in lesional skin from patients with AD and psoriasis compared to those of normal skin from healthy controls. The AhR and aryl hydrocarbon receptor nuclear translocator were colocalized in the nuclei of keratinocytes at the lower epidermis of psoriatic lesions, which suggested activation of the AhR pathway. After treatment of normal human epidermal keratinocytes with TCDD or PCBs, IL-6 and IL-8 production were increased. The results of this study suggest that AhR is highly expressed in the acute lesional skin of patients with AD and psoriasis, and the AhR pathway is activated especially in psoriasis.