November 4, 2011
Skin And Eyes Use Similar Mechanism For Sun Protection
A group of scientists at Brown University in Rhode Island discovered that the skin and eyes use the same molecular mechanism to protect themselves from the UV light. The discovery was reported in the journal Current Biology.
The scientists discovered that the cells that create melanin - melanocytes - contain rhodopsin, a photosensitive receptor used in the eye to detect light. They also discovered that the body produces melanin to protect the cells much quicker than previously suspected. Melanin production happens immediately in order to help protect the DNA from damaging UV (Ultraviolet) radiation.Elena Oancea of Brown University, the senior author of the study says, “As soon as you step into the sun, your skin knows that it is exposed to UV radiation. This is a very fast process, faster than anything that was know before.”
At first the scientists suspected that UV light triggered a calcium signaling response, a common intercellular response mechanism, but found nothing. In the next phase they added retinal, a co-factor of opsin receptors including rhodopsin which is found in the retina.
Graduate student Nadine Wicks said: “When we did that, we saw an immediate and massive calcium response.”
The scientists found after several investigations that the skin cells contained rhodopsin RNA and protein. They reduced the rhodopsin levels under UV light and the calcium signaling response was reduced. Melanin production stopped completely after starving the cells of retinal. They also discovered that melanocytes created rhodopsin with UVA light rather than UVB.
After several experiments they were able to trace the process: When UVA strikes the rhodopsin receptors with retinal, calcium signals are triggered within a few seconds. After an hour, small amounts of melanin accumulate but not in the quantities that build up within 24 hours.
The scientists warn that this is not an excuse not to use sunscreen when out in the sun.
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