Group Award for Leveraging Activities - 2001 FDA Science Forum

Board B04

The role of racial/ethnic origin in determining individual UV sensitivity remains unclear. We are evaluating usefulness of various biomarker methods for measuring UV responses in human skin, and we are analyzing UV-induced DNA damage and repair within different racial/ethnic groups. This study will involve 110 subjects representing different UV sensitivities with six racial/ethnic groups. Minimal Erythema Dose (MED) of each individual was determined to assess the sensitivity for UV irradiation before biopsies. Shave biopsies are taken before exposure, immediately after exposure to approximately 1 MED of UV, and then 1 day and 7 days later. Induction of DNA damage (cyclobutane pyrimidine dimers, CPD) is detected in sections by indirect immunofluorescence using a monoclonal antibody (TDM-2) specific for CPD and the fluorescein isothiocyanate (FITC). Nuclear DNA is counterstained with propidium iodide (PI). DNA damage is expressed as the ratio of the intensities of the FITC fluorescence for CPD and that of the PI fluorescence for DNA. The available data show that DNA damage measured by CPD is most significant immediately following UV exposure, but is repaired more than 50 % within 1 day. However, melanin contents measured by Fontana-Masson staining do not change consistently with UV exposure.

This study will eventually compare the immediate DNA damage, the repair efficiency and the degree of photoprotection afforded in the skins of individuals from different racial/ethnic origins and phototypes 1-6.