Expression of MC‐R, POMC and POMC peptides and evidence for a immunoregulatory role of α‐MSH in human dermal papilla cells

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Abstract
Pro‐opiomelanocortin (POMC)‐derived peptides are well‐known regulators of pigmentation and proliferation of epidermal and hair follicle‐derived melanocytes. We demonstrated that human dermal papilla cells (DPCs), a distinct myofibroblastic cell population of the hair follicle, participate in the cutaneous POMC system. DPCs in vitro and in situ expressed the melanocortin receptor‐1 (MC‐1R) as well as MC‐4R as shown by RT‐PCR, immunofluorescence and immunohistochemistry. Expression of POMC but not agouti signalling protein, a natural MC‐1R/MC‐4R antagonist, was also detectable in DPC. Generation of POMC peptides by DPCs in vitro was demonstrated by immunofluorescence and ELISA studies revealing the expression of both adrenocorticotropin and β‐endorphin. To investigate the functional relevance of MC‐R expression in DPCs, we examined the effect of α‐MSH on interferon‐γ (IFN‐γ)‐induced expression of intercellular adhesion molecule‐1 (ICAM‐1), an adhesion molecule upregulated in inflammatory disorders of the hair follicle such as alopecia areata. α‐MSH markedly suppressed the IFN‐γ‐mediated upregulation of ICAM‐1 in DPCs as shown by real‐time PCR studies, while α‐MSH alone did not have any effect. Our data suggest that melanocortins such as α‐MSH mediate paracrine and autocrine effect in the dermal papilla whose disruption may contribute to inflammatory diseases of the hair follicle.

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