The findings by researchers at University of Michigan Medical School highlighted the need for better sunscreens to protect against these damaging rays, and prevent the process that can cause skin to look old, wrinkled and sagging prematurely.
The researchers showed that damage starts after just two daily exposures to a low amount of ultraviolet A1, or UVA1, light- which makes up most of the UV light we are exposed to throughout the day, and tanning bed light too.
By showing that repeated exposure to the type of UVA1 light that we typically experience on a sunny day causes these damaging processes in the skin, the researchers hope it will lead to the development of new protective ingredients in sunscreens, and more caution about routine sun exposure throughout the day.
The researchers were able to measure the effects of UVA1 at the molecular level using advanced gene expression analysis of skin samples from human volunteers.
The researchers shined a low level of pure UVA1 rays, as might be encountered in daily life, on small areas of 22 volunteers' buttocks. A day later, they measured changes in skin pigmentation. Then, they took tiny samples of skin, in order to detect which genes had been 'turned on' by the light exposure. They repeated this process three more times on each participant.
After just two exposures, UVA1 rays caused skin cells to make molecules that break down the protein called collagen, which makes skin firm, smooth, and youthful in appearance.
The UVA1 also caused the skin to darken a little with each exposure, but this tan didn't protect against further production of the collagen-destroying molecule, called matrix metalloproteinase 1 or MMP1, when the skin was exposed to more doses of UVA1.
"There is very little UVB in sunlight, and most UVB exposure is at midday. During the rest of the day it's mostly UVA, with UVA1 being the majority. UVA1 is also the main component of tanning booth light. So, we wanted to look at whether it can predispose skin to premature aging by simulating repetitive daily exposure. And we found that it can. Furthermore, the mild tanning that occurs does not seem to protect against damage from additional exposures," first author Frank Wang said.
The study was published in journal JAMA Dermatology.
--ANI (Posted on 05-12-2013)