Can Your Skin “See” UV Rays?
Saturday, November 05, 2011
For most people, tanning seems a simple proposition. A naturally light-skinned person lies in the sun for hours and ends up as bronzed as a Jersey Shore star. To scientists, though, the reaction of skin to ultraviolet light is more mysterious. A new study from Brown University demonstrates that your skin detects UVA radiation using a light-sensitive receptor previously found only in the eye and that this starts melanin production within a couple of hours. Until now, scientists only knew that melanin production occurred days after UVB radiation had already begun damaging DNA.
In other words, your skin "sees" those rays and steps up its melanin to protect itself.
“As soon as you step out into the sun, your skin knows that it is exposed to UV radiation,” said senior author Elena Oancea, assistant professor of biology in the Department of Molecular Pharmacology, Physiology, and Biotechnology at Brown University. “This is a very fast process, faster than anything that was known before.”
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Scientists believe that melanin protects the DNA in skin cells against damage from UVB rays by absorbing the incoming radiation. It isn’t perfect, which is why people must use sun block. But the Brown study, now appearing in the journal Current Biology, shows that the body mounts its defense much sooner, well before it becomes apparent in the form of a tan.
In lab experiments with human melanin-producing skin cells called melanocytes, Oancea, graduate student Nadine Wicks, and their team discovered that the cells contain rhodopsin, a photosensitive receptor used by the eye to detect light. Moreover, they traced the steps of how rhodopsin unleashes calcium ion signals that instigate melanin production.
A healthy glow
As much as they learned, Oancea and Wicks still have some questions. One is whether rhodopsin is acting alone or in concert with another yet undiscovered receptor. Another question is whether melanocytes immediately begin exporting melanin to other kinds of skin cells for protection or whether they keep the early supply for themselves.
Just because scientists are learning more about how the skin responds to and protects itself against UV radiation, Oancea said, that’s no reason for people to change what they do to protect themselves. “This doesn’t say, ‘Don’t use sunscreen’,” Oancea said.
Brown University, the National Institutes of Health, and the Natural Sciences and Engineering Research Council of Canada supported the research.
