PHEOMELANIN/EUMELANIN RATIO AS A BIOCHEMICAL INDICATOR OF UV SUSCEPTIBILITY
M.R. Vincensi*, M. dIschia*, A. Napolitano*, E.M. Procaccini**, G. Riccio**, G. Monfrecola**, G. Prota*
* Istituto di Biochimica - University "Federico II" - Naples - Italy
** Clinica Dermatologica - University "Federico II" - Naples - Italy
Uncontrolled sun exposure and certain host characteristics, including primarily red hair and a fair complexion, are generally recognised as a primary risk factors for skin cancers. Unfortunately, however, accuracy in predicting high risk individuals, is currently beset by the lack of clear cut correlation between phenotypic characteristics and solar sensitivity.
The UV sensitivity differences are related to cutaneous levels of dark eumelanin pigments, generally regarded as the main photoprotective pigments in the epidermis. The sulphur containing pheomelanins are considerably photolabile and may produce upon photoexcitation highly cytotoxic and mutagenic free radical species which would account for the greater proclivity of red-haired Celtic-type populations to sunburn and skin cancer.
The red colour is not always indicative of truly pheomelanic hair, because of the existence of lighter variants of eumelanin pigments which may afford a different degree of photoprotection.
The relationship between phenotypic characteristics, melanin pigmentation and sun sensitivity is less obvious than generally accepted.
The relationship between phenotypic characteristics for the UV susceptibility trait, hair melanin composition and the Minimal Erythema Dose (MED) were investigated in a group of 15 healthy red-haired subjects, in comparison with suitable age-matched subjects with blond, brown or black hair.