In vitro Method to Quantify UV Mediated DNA Damage
The gel-based electrophoretic assay described in this study measures the levels of DNA damage caused by ultraviolet (UV) light, particularly UVB radiation, directly, in the absence of any possibility for DNA repair. The correlation between exposure to UV light, particularly UVB radiation, and increased skin cancer risk has necessitated the ability to easily assess DNA damage and the protective effects of certain UV absorbing chemicals. UV exposure followed by alkali treatment and gel electrophoresis reveals the extent of DNA Damage to be directly correlated with gel mobility. To enhance the sensitivity of the assay, T4 Endonuclease V was used to induce strand breaks at positions of cyclobutane dimmer formation. The potential utility of this assay in assessing the ability of sunscreen reagents to protect against DNA damage was demonstrated by examining the impact of UV-absorbing chemicals PABA and HMBS at different doses of UVB light. When these chemicals were included during irradiation of DNA protection was demonstrated in a dose-dependent manner. The assay described in this study provides a simple and rapid measure of DNA damage with the potential application to quantify the level of protection afforded by various chemicals.