Melanocortin receptor type 2 (MC2R, ACTH receptor) expression in patients with alopecia areata.

Human skin expresses elements of the hypothalamo-pituitary-adrenal (HPA) axis that function as a local stress response system. Because adrenocorticotropic hormone (ACTH) is an intermediate in the HPA axis from corticotropin-releasing hormone (CRH) signal to cortisol secretion, MC2R that binds only ACTH may be important in the stress response of skin. We investigated the local expression of MC2R by immunohistochemistry to identify the role of ACTH/MC2R in stress-associated alopecia areata (AA). MC2R appeared to be highly compartmentalized in scalp skin including the epidermal cells of hair follicles and epidermis, sebaceous and eccrine glands, as well as dermal fibroblasts. The expression of MC2R was lower in AA lesions than in normal scalp tissue in almost all scalp skin cells, especially in epithelial cells. These findings demonstrate that MC2R expression is aberrant in AA and suggest a deficit in ACTH/MC2R activity may play an important role in the pathophysiology of AA.