ALPHA-MSH IS EXPRESSED IN CULTURED HUMAN MELANOCYTES AND KERATINOCYTES

The melanotropic peptide alpha-MSH is known to originate from the prec ursor protein pro-opio-melanocortin (POMC). Although the main source o f alpha-MSH is the pituitary gland, recent findings also suggest its s ynthesis in nonpituitary tissues. This study investigated alpha-MSH sy nthesis in vitro, in human epidermal keratinocytes (HaCaT) and melanoc ytes. We demonstrated the presence of alpha-MSH in a radio-immuno-assa y (RIA) of homogenates of human keratinocytes and melanocytes. In addi tion we detected the expression of exon 2 and 3 of the POMC-gene using a RT-PCR. After reverse transcription of the total RNA, PCR performed with a set of primers specific for sequences within the POMC gene gav e positive results for keratinocytes and melanocytes. Our data provide strong evidence for the production of POMC-peptides - especially alph a-MSH - in keratinocyts and melanocytes. This is of particular interes t as alpha-MSH has also an immunomodulatory potency and has to be seen in the context of the skin immune system.