Detection of Functionally Active Melanocortin Receptors and Evidence for an Immunoregulatory Activity of α-Melanocyte-Stimulating Hormone in Human Dermal Papilla Cells

Abstract

Proopiomelanocortin (POMC)-derived peptides and their receptors have been identified in many peripheral organs including the skin in which they exert a diversity of biological actions. We investigated the expression and potential role of the POMC system in human dermal papilla cells (DPCs), a specialized cutaneous mesenchymal cell type regulating hair follicle activity. In culture, these cells expressed POMC and displayed immunoreactivity for ACTH, alphaMSH, and beta-endorphin. Among the prohormone convertases (PCs) tested, only PC2, its chaperone 7B2, and furin convertase but not PC1 and paired basic amino acid cleaving enzyme 4 gene were detected. Human DPCs in vitro expressed both the melanocortin-1 receptor (MC-1R) and MC-4R, and immunoreactivity for these receptors was also present in cells of the human dermal papilla in situ. In contrast to the dermal papilla of agouti mice, agouti signaling protein, a natural and highly selective MC-1R and MC-4R antagonist, was undetectable in human DPCs. The MC-Rs detected in human DPCs were functionally active because alphaMSH increased intracellular cAMP and calcium. Preincubation of the cells with a synthetic peptide corresponding to the C-terminal domain of agouti signaling protein abrogated cAMP induction by alphaMSH. Furthermore, alphaMSH was capable of antagonizing the expression of intercellular adhesion molecule-1 induced by the proinflammatory cytokine interferon-gamma. Our data suggest a regulatory function of alphaMSH within the dermal papilla whose disruption may lead to deregulation of immune and inflammatory responses of the hair follicle, thereby possibly contributing to the development of inflammatory forms of alopecia.

α‐melanocyte–stimulating hormone suppresses bleomycin‐induced collagen synthesis and reduces tissue fibrosis in a mouse model of scleroderma: Melanocortin peptides as a novel treatment strategy for scleroderma?

“…With regard to the detected expression of POMC in the skin of SSc patients, it should be noted that normal human skin and various cutaneous cell types in vitro express POMC autonomously and have the full capacity to make melanocortin peptides (10,11,43,44). POMC expression per se does not impair the response of skin cells to ␣-MSH (9-13).…”

“…Total RNA (1 g) was reverse-transcribed with a RevertAid First-Strand cDNA Synthesis kit (Fermentas, St. Leon-Rot, Germany) using oligo(dT) primers. Semiquantitative RT-PCR for POMC and MC-1R was performed as described previously (9,10). Primers against the housekeeping gene product ␤-actin were 5Ј-CGTCATACTCCTGCTTGCTGATCCACATCTGC-3Ј (sense) and 5Ј-ATCTGGCACCACACCTTCTACAATGAGCTGC-G-3Ј (antisense).…”

“…Cell extracts were prepared by hot lysis using 2ϫ Laemmli sample buffer followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoprobing as previously described (10). Antibodies were obtained from the following sources: anti-type I collagen from DPC Biermann (Bad Nauheim, Germany), anti-HO-1 from StressGen (Ann Arbor, MI), anti-SOD2 from R&D Systems (Minneapolis, MN), antiSmad2/3 from BD Biosciences (Heidelberg, Germany), and anti-phosphoserine 433/435 Smad3 from CalbiochemNovabiochem.…”

“…We recently reported that fibroblastic cells in the skin, such as human dermal fibroblasts (HDFs) and dermal papilla cells, express functional melanocortin 1 receptors (MC-1R) (9,10) that bind the neuropeptide ␣-melanocyte-stimulating hormone (␣-MSH) with high affinity. Alpha-melanocyte-stimulating hormone is derived from pro-opiomelanocortin (POMC), both of which are produced by the skin itself (11).…”

Differential expression of HPA axis homolog in the skin

“…The skin also contains the full machinery for POMC processing (PC1, PC2 convertases and 7B2 protein) with generation of ACTH or α-MSH, and β-LPH or β-endorphin as final products, depending on the cellular compartment and cell type (Bohm et al, 2005;Luger et al, 1999;Paus et al, 1999;Slominski et al, 1999b;Slominski et al, 2004b;Slominski and Wortsman, 2000;Slominski et al, 2000d;Wintzen and Gilchrest, 1996). In human skin, the process can be upregulated by UVR and factors increasing cAMP levels, while it is inhibited by several growth factors (Luger et al, 1999;Slominski and Pawelek, 1998;Slominski et al, 2004b;Slominski et al, 2000d).…”