Neuropeptides: a new strategy for skin care

The melanin production pathway in melanocytes is regulated by the interaction between steroid hormones and its respective melanocortin receptors (MCRs). The usage of synthetic peptides allows it to mimic that effect. The chemical synthesis of these compounds allows modifying or introducing changes that increase the affinity to these receptors and modulate melanin production. In the present work we present a new synthetic peptide for cosmetic application, which allows melanogenesis via MCRs activation. The new peptide developed by Infinitec Activos enables the formulation of a natural sunscreen without UV exposure and prevents possible skin damage.

 Human skin exists in a wide range of different colours and gradations, ranging from white to brown and black. This is due to the presence of a chemically inert and stable pigment known as melanin, which is produced deep inside the skin but is displayed as a mosaic at the surface of the body. Melanin is therefore responsible for the most striking polymorphic traits of humans and for the most obvious and thoroughly discussed aspect of human geographical variability: skin colour. Besides its role in defining ethnicity, melanin plays an essential role in defending the body against harmful ultraviolet (UV) light and other environmental challenges. Minor changes in the physiological status of the human body or exposure to harmful external factors can affect pigmentation patterns either in transitory (such as in pregnancy) or permanent (e.g. age spots) manners.1,2 Today there is compelling evidence that pro-opiomelanocortin (POMC) peptides are implicated in the regulation of skin colour in humans.3 Moreover, it has been shown that the skin and the hair follicle are the local sources and targets for POMC-derived peptides including adrenocorticotrophin (ACTH), ?- and ?-melanocyte-stimulating hormone (?-MSH) and ?-endorphin.4,5,6,7 The involvement of ACTH or ?- and ?-MSH in human skin pigmentation was first recognised upon systemic application onto human volunteers where these peptides induced noticeable skin darkening.8,9,10 Later, it was shown that ACTH, ?-MSH and ?-endorphin could stimulate melanogenesis and proliferation of epidermal and hair follicle melanocytes and modulate cell dendricity.11 Both ?-MSH and ACTH are proposed to be the key players in pigmentation via the melanocortin-1- receptor (MC1R)/cAMP second messenger system.5,6 A number of approaches to stimulate pigmentation have been tried, including activation of MC1R by agonists and bioactive derivatives, such as topical application of factors that bypass the MC1R, factors to stimulate TYR function or factors to increase melanosome transfer. Most of those experiments have met with limited or no success, in part because of the challenge in penetrating the skin barrier and in part because of the quest for specificity, i.e. to stimulate melanocyte function without affecting other types of cells in the skin. Interested readers are referred to a recent review examining approaches to up-regulating skin pigmentation.12 One major determinant of pigment phenotype of the skin is the melanocortin 1 receptor (MC1R), a G-protein coupled receptor that regulates the quantity and quality of melanins produced.13 MC1R function is controlled by the agonists ?-melanocyte-stimulating hormone (?-MSH) and adrenocorticotropic hormone (ACTH) and by an antagonist, Agouti signalling protein (ASP). Activation of the MC1R by an agonist stimulates the expression of the melanogenic cascade and thus the synthesis of eumelanin, whereas ASP can reverse those effects and elicit the production of pheomelanin. MSH and ACTH can also up-regulate expression of the MC1R gene, thus acting in a positive feedback loop. MC1R function controls the switch to produce eu- versus pheomelanin, but the mechanism(s) underlying that switch remains unknown.14 Our work here shows the capability of synthetic peptides developed by Infinitec Activos, which can increase melanogenesis upon cAMP elevation.

Materials and methods