A Comprehensive Review of Mammalian Pigmentation: Paving the Way for Innovative Hair Colour-Changing Cosmetics

Abstract

The natural colour of hair shafts is formed at the bulb of hair follicles, and it is coupled to the hair growth cycle. Three critical processes must happen for efficient pigmentation: (1) melanosome biogenesis in neural crest-derived melanocytes, (2) the biochemical synthesis of melanins (melanogenesis) inside melanosomes, and (3) the transfer of melanin granules to surrounding pre-cortical keratinocytes for their incorporation into nascent hair fibres. All these steps are under complex genetic control. The array of natural hair colour shades are ascribed to polymorphisms in several pigmentary genes. A myriad of factors acting via autocrine, paracrine, and endocrine mechanisms also contributes for hair colour diversity. Given the enormous social and cosmetic importance attributed to hair colour, hair dyeing is today a common practice. Nonetheless, the adverse effects of the long-term usage of such cosmetic procedures demand the development of new methods for colour change. In this context, case reports of hair lightening, darkening and repigmentation as a side-effect of the therapeutic usage of many drugs substantiate the possibility to tune hair colour by interfering with the biology of follicular pigmentary units. By scrutinizing mammalian pigmentation, this review pinpoints key targetable processes for the development of innovative cosmetics that can safely change the hair colour from the inside out.

Afamelanotide in protoporphyria and other skin diseases: a review

“…It exhibits vast amounts of activities within the skin including anti-inflammatory and immunosuppressive effects. As an endogenous peptide (compound of 13 amino acids) with paracrine and autocrine effects on melanocytes, it may stimulate melanogenesis via the melanocortin-1 receptor (MCR1) as well as tyrosinase activation, leading to skin-darkening by eumelanin synthesis [ 1 , 2 ]. This brown-black pigment presents a photoprotective effect, while pheomelanin – a yellow-red pigment – contributes to UV-skin damage by generation of free radicals.…”

Malignant Melanoma: An Overview, New Perspectives, and Vitamin D Signaling

“…Intracellular regulatory proteins include transporter proteins, such as solute carrier family 45 member 2 (SLC45A2) and SLC24A5, which is also involved in regulation of intramelanosomal pH in which mutations lead to OCA4 and OCA6, respectively [ 112 , 114 ], oculocutaneous albinism 2 protein/P protein (OCA2) that assists in the trafficking and processing of TYR, tyrosine transport, the regulation of melanosomal pH, glutathione metabolism, and anion transport [ 112 ]. Others include leucine-rich melanocyte differentiation associated (LRMDA) (OCA7), G protein-coupled receptor 143 (GP143), and RAB27A [ 111 , 112 , 327 ].…”

“…Other important regulators include transient receptor potential cation channel, subfamily M, member 1 (TRPM-1) which also inhibits melanoma progression [ 340 , 341 ], and KIT protein representing tyrosine kinase receptor important for melanocyte development and distribution in the skin, which plays a role in melanoma development [ 332 , 342 ]. There are also other receptors activated by different signaling molecules, including histamine, serotonin, melatonin, acetylcholine, steroids, and cytokines, which can be involved in the positive or negative regulation of melanin pigmentation and are reviewed in [ 3 , 82 , 83 , 98 , 112 , 275 , 316 , 327 , 343 , 344 , 345 , 346 , 347 ].…”

Establishment of a synchronized tyrosinase transport system revealed a role of Tyrp1 in efficient melanogenesis by promoting tyrosinase targeting to melanosomes

“…Although the melanin whose synthesis is catalyzed by Tyr is crucial in achieving photoprotection, abnormal melanin accumulation causes hyperpigmentation disorders such as melasma, senile lentigo, and freckles 5 . Thus, inhibiting the enzymatic activity of Tyr has often been used as a major strategy for skin whitening in the cosmetic industry 6 .…”