According to Yale-led research, published in the online edition of the journal, Science, on February 19, the skin damage caused by ultraviolet radiation (UV) occurs hours after sun exposure.
Any type of exposure to UV radiation, either directly from the sun or tanning beds, damage the DNA present in melanocytes, the cell that produces melanin and gives the skin its color, and is the major cause of skin cancer, the most common cancer in the United States.
In this study, Douglas E. Brash, clinical professor of therapeutic radiology and dermatology at Yale School of Medical, and his co-authors, through their experiments discovered that melanin had both carcinogenic and protective effects.
The team first exposed mouse and human melanocyte cells to radiation from a UV lamp. The radiation caused a type of DNA damage known as a cyclobutane dimer (CPD), in which two DNA ‘letters’ attach and bend the DNA, preventing the information it contains from being read correctly. To the researchers’ surprise, the melanocytes not only generated CPDs immediately but continued to do so hours after UV exposure ended. Cells without melanin generated CPDs only during the UV exposure. The researchers next tested the extent of damage that occurred after sun exposure by preventing normal DNA repair in mouse samples. They found that half of the CPDs in melanocytes were ‘dark CPDs’ or CPDs created in the dark.
This new discovery will help researchers understand the factors affecting skin damage and develop better skin treatments.