The potential depigmenting activity of retinaldehyde.
BACKGROUND
Retinoids have been reported to exert depigmenting activity. Unlike most depigmenting agents that target tyrosinase, they are not phenolic agents and may act via different mechanisms.


OBJECTIVE
We analysed the properties of retinaldehyde (RAL), a precursor of retinoic acid (RA), as a skin-lightening agent in various models.


METHODS
The viability and the depigmenting properties of RAL were assessed in murine melanocytes, in human reconstructed epidermis, and in mice and guinea pigs. The melanin content and cytotoxicity were assessed in melanocytes; in 3-dimensional models, the melanin concentration and the number of active melanocytes were determined.


RESULTS
RAL was taken up by melanocytes and mostly metabolised to retinol and retinyl esters, and to a lesser extent to RA. RAL decreased the melanin concentration of guinea pig ears and mouse tails by 54 and 74%, respectively, and decreased the number of active melanocytes by 42 and 77%, respectively. In reconstructed epidermis the melanin concentration was increased by 52%, whereas the number of active melanocytes decreased by 44%.


CONCLUSIONS
RAL exerts a significant depigmenting activity with a mode of action that looks different from that of RA. Our data suggest a skin-lightening effect related to a melanolytic action (i.e. a decrease in melanin concentration, whatever the mechanism) rather than to melanocytotoxicity, besides other still unknown actions of RAL on melanocytes.
Swiss Centre for Applied Human Toxicology, University of Geneva, Geneva, Switzerland.
O
O
Sorg
B
B
Kasraee
D
D
Salomon
J-H
JH
Saurat
D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004817:Epidermis / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008543:Melanins / Q000378:metabolism*; D008544:Melanocytes / Q000201:enzymology; D051379:Mice; D008810:Mice, Inbred C57BL; D014442:Monophenol Monooxygenase / Q000378:metabolism; D012172:Retinaldehyde / Q000378:metabolism / Q000494:pharmacology*; D062327:Skin Lightening Preparations / Q000378:metabolism / Q000494:pharmacology*; D012880:Skin Pigmentation / Q000187:drug effects*
D008543:Melanins; D062327:Skin Lightening Preparations; D014442:Monophenol Monooxygenase; D012172:Retinaldehyde