Stepping under the shade of a parasol after soaking in some sun may feel like an instant fresh, but your skin cells have postsunshine hangover that lasts for hours. In fact, the molecules excited by the ultraviolet (UV) radiation continue to DNA damage in the cells of the skin, even in complete darkness, the researchers found. The discovery could lead to a new generation of preventive of skin cancer that are applied after a day in the sun and block these delayed effects.
"This is an interesting new mechanism, unexpected, and very important to skin damage by UV radiation," says dermatologist David Fisher Massachusetts General Hospital in Boston, who has not participated.
When UV light or sunlight bed tanning skin cells affected the genes of damages of radiation, causing additional chemical bonds to form between the building blocks of DNA. Over time, these genetic changes accumulate and can make cells more prone to melanoma skin cancer. But when Douglas Brash radiology researcher at Yale University has kept pace with these genetic changes in cells isolated from the skin, it was found that the additional bonds in the DNA did not stop forming when UV rays arrested. For more than 3 hours after the cells were exposed to UV light, the DNA damage continued to increase.
"This means that we have been underestimating the amount of DNA damage that people receive from UV exposure," Brash said.
He and his colleagues went on to show in both mouse cells and human skin, that persistent harmful effects of UV rays were dependent melanin, the pigment that gives skin its color . high melanin levels in people with dark skin are generally associated with protection against melanoma, because melanin absorbs UV energy, preventing it from causing damage to DNA. But Brash has found a new role for the pigment. When UV rays strike the cells of the skin, they cause a cascade reaction that puts the melanin in an excited state. For hours after, even if the cells are in the dark, the energy of the excited melanin can keep DNA damage, scientists report online today in Science .
The new document is "extremely important and elegantly done," said Frank Meyskens, melanoma researcher at the University of California, Irvine. He finally explains clinical observation that long puzzled researchers, he said. why black African albinos have melanoma rates low Without melanin in their skin, they do not get the protective effects of pigment, but they do not also have the long-term damage after exposure to the sun comes with excited melanin.
the research also suggests a new way to prevent melanoma. "If we can divert energy melanin excited before it is transferred, we may be able intervene, "said Brash. In the new study, his group found that vitamin E lotion reduced some delayed effects of UV rays, but he suspects that there are other compounds that might work even better. "If you look over there data on current sunscreens and prevention of skin cancer, it is not so great," said Fisher. "But this new discovery could really give us new opportunities to improve."
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