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Sunbathers can experience cancer-causing DNA damage
hours after they’ve left the beach or the tanning
bed, a new study finds, and the skin pigment melanin
appears to be the culprit in this delayed reaction.
Melanin is usually thought of as a protective
pigment, blocking the UV radiation that damages DNA
and contributes to skin cancer.
The process starts when the radiation causes lesions
or breaks in DNA that may lead to cancer-causing
mutations, and these lesions usually appear within
less than a second after UV exposure.
But Sanjay Premi and colleagues now show in mouse
and human cells that these lesions can appear in
melanin-producing cells more than three hours after
exposure to UVA radiation -- a major part of the
radiation from sunlight and tanning beds.
The researchers think that the UV radiation produces
reactive oxygen and nitrogen that energize an
electron in melanin, and this released energy in
turn causes the DNA lesions.
Premi and colleagues suggest that researchers should
look at adding “quenching” compounds that suppress
this high-energy state as part of an “evening-after”
sunscreen. John-Stephen Taylor discusses the results
in a related Perspective.
For more information
"Chemiexcitation of melanin derivatives induces DNA
photoproducts long after UV exposure," by S. Premi;
S. Wallisch; C.M. Mano; A.B. Weiner; A. Bacchiocchi;
R. Halaban; D.E. Brash at Yale University School of
Medicine in New Haven, CT; C.M. Mano; E.J.H. Bechara
at Universidade de São Paulo in São Paulo, Brazil;
K. Wakamatsu at Fujita Health University School of
Health Sciences in Toyoake, Japan; E.J.H. Bechara at
Universidade Federal de São Paulo in São Paulo,
Brazil; T. Douki at Université Joseph Fourier
Grenoble in Grenoble, France; T. Douki at
Commissariat à l’Energie Atomique (CEA) in Grenoble,
France; A.B. Weiner at University of Chicago in
Chicago, IL.
http://www.sciencemag.org/content/347/6224/842
"The dark side of sunlight and melanoma," by J.-S.
Taylor at Washington University in St. Louis, MO.
http://www.sciencemag.org/content/347/6224/824.summary
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