Melanocytes from dark and light skin respond differently after ultraviolet B irradiation: effect of keratinocyte-conditioned medium.
OBJECTIVE
The response to the damage provoked by exposure to UV radiation is mediated by melanocytes and a network of paracrine factors produced by keratinocytes, and it varies among individuals of different geographical origin and skin colour. The mechanisms underlying this differential response, however, have not been completely elucidated.


METHODS
We characterized the differential behaviour of melanocytes (proliferation and differentiation/melanogenesis) from both dark- and light-skinned individuals in response to ultraviolet B (UVB) irradiation, cultured with and without keratinocyte-conditioned medium (KCM). ELISA assays and real-time quantitative PCR were used to assess the production of keratinocyte-derived factors.


RESULTS
After UVB irradiation, dark melanocytes showed a decreased proliferation consistent with the highly differentiated state inferred by the increased dendricity of the cells and higher levels of melanogenic genes expression, whereas light melanocytes showed an increase in proliferation in accord with a less differentiated state and decreased melanogenesis levels. KCM induced melanogenesis in dark melanocytes after UVB irradiation, but not in light-pigmented melanocytes.


CONCLUSIONS
Proliferation and differentiation are coordinated in response to UVB. A lower proliferative rate and a higher differentiation state in dark melanocytes could account for more effective photoprotective mechanisms that would prevent from cell damage against UVB irradiation.
Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country UPV/EHU, Leioa, Bizkaia, Spain.
Saioa
S
López
Santos
S
Alonso
Alicia
A
García de Galdeano
Isabel
I
Smith-Zubiaga
D000328:Adult; D017077:Culture Media, Conditioned / Q000494:pharmacology*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008544:Melanocytes / Q000166:cytology / Q000378:metabolism*; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D014466:Ultraviolet Rays
D017077:Culture Media, Conditioned
Melanocyte; UV irradiation; keratinocyte; melanogenesis; pigmentation