Ultraviolet (UV)A- and UVB-induced redox alterations and activation of nuclear factor-kappaB in human melanocytes-protective effects of alpha-tocopherol.
BACKGROUND
Despite compelling evidence that ultraviolet (UV) irradiation causes melanoma the knowledge concerning reaction pathways and signalling transduction in melanocytes is still limited.


OBJECTIVE
To evaluate the protective capacity of alpha-tocopherol and beta-carotene during UVA and UVB irradiation of human melanocytes in vitro.


METHODS
Primary cultures of normal human melanocytes were irradiated by different wavelengths within the UV spectrum (UVA 6 J cm(-2), UVB 60 mJ cm(-2)). Redox alterations and apoptosis were studied and the protective potential of alpha-tocopherol and beta-carotene was evaluated.


RESULTS
UVA and UVB irradiation decreased the intracellular concentration of reduced glutathione and activated the transcription factor nuclear factor (NF)-kappaB, detected as the increased level of the p65 subunit and translocation to the nucleus. This coincided with a rise in the level of gamma-glutamyl-cysteine-synthetase, the rate-limiting enzyme of the glutathione synthesis. UVA and UVB caused apoptotic cell death as detected by nuclear fragmentation and caspase activation 24 h postirradiation. Pretreatment with alpha-tocopherol prevented UVA- and UVB-induced glutathione loss, NF-kappaB translocation and diminished apoptosis, but beta-carotene did not show a similar protective capacity. Further, exposure to alpha-tocopherol by itself reduced cell proliferation rate.


CONCLUSIONS
UVA and UVB irradiation affected the intracellular redox state and increased the frequency of apoptosis in human melanocytes in vitro. alpha-Tocopherol might be a useful substance in protecting melanocytes from UV-induced damage.
Larsson
P
P
Department of Biomedicine and Surgery Division of Dermatology, Faculty of Health Sciences, Linköping University, S-581 85 Linköping, Sweden. perla@ibk.liu.se
Ollinger
K
K
Rosdahl
I
I
D000975:Antioxidants / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000528:radiation effects; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008544:Melanocytes / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D016328:NF-kappa B / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects / Q000528:radiation effects; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D014466:Ultraviolet Rays; D024502:alpha-Tocopherol / Q000494:pharmacology*; D019207:beta Carotene / Q000494:pharmacology
D000975:Antioxidants; D016328:NF-kappa B; D011837:Radiation-Protective Agents; D019207:beta Carotene; D024502:alpha-Tocopherol