It's not just your eyes that sense the light. Your skin contains photoreceptors like those in the retina, allowing it to mount an immediate defence against damaging ultraviolet radiation.A light-sensitive receptor (rhodopsis) previously thought to exist only in the eye has been found in human skin cells, detecting certain wavelengths of ultraviolet light to protect DNA from damage. Skin cells, called malanocyte, send out calcium ion signals to produce the pigment melanin. Until now, scientists knew only that melanin production occurred days after UVB radiation had already begun damaging DNA.
“As soon as you step out into the sun, your skin knows that it is exposed to UV radiation,” said 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.”
In lab experiments with melanocytes, researchers discovered that the cells contain rhodopsin, which unleash calcium ion signals that instigate melanin production. The team first looked to see whether UV light instigated a calcium signaling response. They found nothing. But guessing that the skin might sense light in the same way that the eyes do, they added retinal, a co-factor of opsin receptors including rhodopsin.
However,there are still some questions,One is whether rhodopsin is acting alone or in concert with another yet undiscovered receptor. Another is whether melanocytes immediately begin exporting melanin to other kinds of skin cells for protection or whether they keep the early supply for themselves.
Rick Sturm at the University of Queensland in Brisbane, Australia, isn't convinced that "seeing" the light offers the skin much protection against damage, though. "Immediate tanning does not protect against UV-induced sunburn or DNA damage," he says.
No comments:
Post a Comment