The Role of Proopiomelanocortin‐Derived Peptides in Skin Fibroblast and Mast Cell Functions

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Abstract
We have previously described proopiomelanocortin (POMC) gene‐expression in human normal cultured dermal fibroblasts, and its dose‐ and time‐dependent modulation by transforming growth factor‐β (TGF‐β) and tumor necrosis factor‐α (TNF‐α). The aim of the work described here was to investigate POMC‐derived peptide release in vitro by cultured fibroblasts following incubation with different concentrations of both TNF‐α and TGF‐β for 24 hours (1, 5, and 10 ng/ml). The effect of simultaneous addition of both TNF‐α and TGF‐β (10 ng/ml) was also evaluated. Culture supernatants of human skin fibroblasts were collected to detect adrenocorticotropin hormone (ACTH), α‐melanotropin (α‐MSH), and β‐endorphin (β‐EP) levels by specific immunoenzymatic assay. We investigated the in vitro histamine‐releasing activity of the POMC‐derived peptides, α‐MSH and β‐EP, on human foreskin mast cells. Detection of cleavage products in supernatants from cultured normal human dermal fibroblasts indicated intracellular processing by POMC protein. We were able to measure detectable levels of all peptides in basal conditions. TNF‐α addition resulted in an increase in β‐EP and ACTH levels. TGF‐β‐stimulated fibroblasts showed no alteration in β‐EP and α‐MSH levels, whereas ACTH release was significantly enhanced. Both α‐MSH and β‐EP induced histamine release from human foreskin mast cells in vitro with β‐EP‐induced histamine levels as high as those observed with the calcium ionophore, ionomycin. Our data document fibroblast POMC‐derived peptide release and modulation by cytokines, suggesting that they have a possible role in extracellular matrix deposit regulation and skin inflammation.