UVA1 Impairs the Repair of UVB-Induced DNA Damage in Normal Human Melanocytes

Abstract

The exact correlation between melanoma and sun light is still a controversially debated issue. Although natural sunlight contains various ratios of UVA and UVB, most investigators so far focused on the effects of single solar wavebands and neglected possible interactions. Therefore, in the present study primary human melanocytes of three donors were simultaneously exposed to physiologic doses of UVA1 and UVB. Effects on apoptosis were analyzed using Annexin V assays and cell death ELISAs, effects on DNA damage were investigated using Southwestern slot blots. While UVA1 did not influence UVB-induced apoptosis, UVA1 impaired the repair of UVB-induced Cyclobutane Pyrimidine Dimers (CPD) as the amount of CPD was 1.8 higher in UVA1+UVB than in UVB only exposed melanocytes six hours after irradiation. We conclude that UVA1 might contribute to melanomagenesis since it partially inhibits the repair of UVB-induced CPDs in human melanocytes while it does not affect UVB-mediated apoptosis.

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