α-MSH regulates interleukin-10 expression by human keratinocytes

Abstract Normal human keratinocytes (HKC) are able to synthesize α-MSH. Because the production of α-MSH by HKC is induced significantly by ultraviolet B radiation, the involvement of keratinocyte-derived α-MSH in UV-induced immunosuppression has been suggested. The induction of the antiinflammatory cytokine IL-10 in monocytes is a major mechanism in the antiinflammatory actions of α-MSH. In the present study, HKC were investigated for their ability to produce IL-10 after α-MSH stimulation. HKC were obtained from the skin of human female breast sections and either left untreated or treated with 0.01 or 0.1 μg/ml α-MSH for different times. Using RT-PCR, HKC were shown to express IL-10 mRNA even under basal conditions, and treatment with α-MSH increased expression. Only minimal concentrations of IL-10 protein were detected in supernatants from the α-MSH-stimulated cultures. To the best of our knowledge this is the first report of IL-10 expression by cultured HKC after α-MSH stimulation. Further studies are needed to determine the biological and therapeutic relevance of these findings.