Alpha-melanocyte-stimulating hormone.: Its relevance for dermatology

Alpha-melanocyte-stimulating hormone (alpha-MSH) is a tridecapeptide that was originally characterized as a neuropeptide derived from the pituitary gland. alpha-MSH is synthesized from proopiomelanocortin (POMC) by the action of specific prohormone convertases which cleave POW into alpha-MSH, adrenocorticotropin and beta-endorphin. The various effects of alpha-MSH are mediated via melanocortin receptors. The skin as well as the majority of cutaneous cell types express POMC. Proinflammatory stimuli such as ultraviolet (UV) light induce POMC expression and alpha-MSH secretion. Receptors for alpha-MSH are not only expressed by melanocytes, where they mediate melanogenesis and proliferation, but also by virtually every cutaneous cell type. Accordingly, alpha-MSH elicits a plethora of biological actions in these cell types including immunomodulation, protection from oxidative stress and UV-induced apoptosis, modulation of secretory epithelial function and regulation of extracellular matrix composition. These actions may be exploited in future by using superpotent and truncated MSH peptides for the treatment of various skin disorders including inflammatory dermatoses.