Abstract
Purpose :
Exposure to solar ultraviolet radiation (UVR) is a major environmental risk factor causing skin cancer, especially Basal Cell Carcinoma, which is the most common malignancy in the eyelid. UVRs are classified according to the wavelength: UVA (315-400 nm), UVB (280-315 nm), and UVC (100- 280 nm). The ozone layer filters out UVC, only UVA and UVB are known to cause a toxic effect towards the DNA of the cells, which may produce skin cancer. In this study, we assessed the capacity to damage the DNA of cells found in the skin epidermis and dermis, by energies contained in the spectrum of sunlight wavelengths ranging from 300 to 1800 nm.
Methods :
Two cell types of human origin were used: primary epidermal keratinocytes (normal adult; HEka) and normal diploid fibroblasts (Malme-3). Keratinocytes were grown in cell medium containing keratinocyte growth factor, glutamine, hydrocortisone, TGFα, insulin, epinephrine, and antibiotics. The fibroblasts were maintained in RPMI-1640 with 10% FBS, insulin, HEPES, glutamine, and antibiotics. The cells were exposed to germicidal light (UVC) for 4 min or to a Tri-Sol Solar Simulator for 40 min on ice (300-1800 nm). DNA damage was assessed through the accumulation of cyclobutane pyrimidines dimers (CPDs) by ELISA. The CCK8 assay was used to assess cell viability.
Results :
In response to UVC exposure, keratinocytes and fibroblasts formed CPDs when compared to cells not exposed to the germicidal light. The DNA damage induced by UVC caused a decrease in the viability of both cell types. When keratinocytes and fibroblasts were exposed to the energy of a solar simulator (excluding UVC), the formation of CPDs in both cell types was detected. The blockage of the artificial sunlight spectrum using filters ranging from 355 to 400 nm prevented the formation of CPDs. The damage caused by the energy of the artificial sun decreased the viability of fibroblasts but not keratinocytes.
Conclusions :
DNA damaging capacity of UVA and UVB was confirmed. The sunlight-containing wavelengths ranging from 300 to 1800 nm are sufficient to damage the DNA by forming CPDs in both keratinocytes and fibroblasts. Whereas the toxicity of the artificial sun diminished the viability of fibroblasts, it did not do so in keratinocytes. Our data suggests that two cell types encountered within the skin respond to sunlight induced DNA damage in a differential manner likely because of differential DNA repair capacity.
This is a 2020 ARVO Annual Meeting abstract.