Abstract

Ultraviolet (UV) light is one of the most crucial environmental factors with regard to its capacity to induce skin cancer, premature aging of the skin, and immunosuppression. Although UV directly affects the function of epidermal cells, many of these effects are mediated by the induction of cytokines, growth factors, and neuropeptides such as α‐melanocyte‐stimulating hormone (α‐MSH). Recently, in addition to its well‐known pigmentation inducing activity, a strong anti‐inflammatory as well as an immunomodulatory potential of α‐MSH has been recognized. The aim of this study was to determine whether UV irradiation affects the expression of both α‐MSH and the melanocortin‐1 receptor (MC‐1R) in human epidermis in vivo . The volar aspects of the forearms were exposed to twice the minimal erythema dose of solar simulating radiation (SSR). Three, 6, and 24 h after irradiation, the pro‐opiomelanocortin (POMC) and interleukin‐10 (IL‐10) mRNA levels in suction blister‐induced epidermal sheets were considerably upregulated as detected by semiquantitative RT‐PCR. Furthermore, α‐MSH and IL‐10 protein levels in blister fluids were significantly increased 24 h after UV irradiation, an effect which could be abolished by the application of the broadspectrum sunscreen AnthéliosXL ® prior to UV (SSR) exposure. In addition, enhanced MC‐1R mRNA and receptor protein expression upon SSR was ascertained by RT‐PCR and immunohistochemistry of the epidermal sheets, respectively. POMC‐derived neuropeptides such as α‐MSH may therefore play an important role in modulating UV‐induced inflammation.