Expression of the corticotropin‐releasing hormone–proopiomelanocortin axis in the various clinical types of psoriasis

Abstract: Psychological stress is known to aggravate inflammatory skin diseases such as atopic dermatitis, psoriasis and contact sensitivity by altering the cellular constituents of the immune system. The skin appendages function dually as prominent targets and sources of the peripheral corticotropin‐releasing hormone–proopiomelanocortin (CRH‐POMC) axis. In this study, we examined the expression level of CRH‐POMC axis constituents in psoriasis, a well‐known stress‐related inflammatory skin disease. The 15 psoriasis patients and six normal controls were retrospectively selected after extensive review of their clinical records and skin biopsy specimens. We immunohistochemically analysed the expressivity of CRH, adrenocorticotrophic hormone (ACTH) and α ‐melanocyte‐stimulating hormone ( α ‐MSH) in various types of psoriatic lesions and control skin. A significant increase of CRH expression was observed in psoriatic lesions, which involved the entire epidermis (upper layer in particular), hair follicles and sweat glands compared with controls. Expression of ACTH and α ‐MSH was clearly stimulated in a subset of psoriasis patients compared with controls, but on the whole, lacked statistical significance. The immunoreactivity of CRH, ACTH and α ‐MSH in psoriasis was not dependent on its clinical subtype, duration or number of previous treatments. Compared with the definite increase of CRH expression in psoriasis, the expression of the POMC peptides was heterogenous with no overall significance. From the findings, we suggest that CRH, a key stress hormone, may play an important role in the pathomechanism of psoriasis.