Featured Research

from universities, journals, and other organizations

UV Skin Damage In A Different Light

Date:
September 3, 1998
Source:
NIH-National Institute Of General Medical Sciences
Summary:
Despite all the warnings to avoid exposure to the sun and to wear sunscreen, scientists don't really know how the sun damages our skin. Now, they're a bit closer to the answer.

Despite all the warnings to avoid exposure to the sun and to wear sunscreen, scientists don't really know how the sun damages our skin. Now, they're a bit closer to the answer.

Two scientists recently discovered that sunlight triggers a harmful reaction when it strikes a molecule in our skin--ironically a molecule once thought to be "nature's sunscreen." The work suggests the science behind the sagging, leathery skin typical of long-term sun worshipers, and may also shed light on how ultraviolet light causes skin cancer.

"We studied a natural component of human skin exposed to ultraviolet light and uncovered a new chemical reaction that may contribute to aging [of the skin] and cancer," said Dr. John Simon, who led the study.

The research will appear in the September 1 issue of the Proceedings of the National Academy of Sciences. The work was conducted at the University of California, San Diego by Dr. John D. Simon (who is now at Duke University), and his graduate student Kerry Hanson (who is now a postdoctoral fellow at the University of Illinois at Urbana-Champaign).

The sun's harmful rays come in two flavors: ultraviolet A and ultraviolet B. Evidence mounts that ultraviolet A and B both play a role in causing skin cancer and photoaging, which is characterized by deep, premature wrinkles, thickened skin, and age spots.

Time, gravity, and heredity notwithstanding, "something like 90 percent of all the visible signs of aging are from ultra-violet sources," said Dr. Kerry Hanson. "Photoaging is not just a cosmetic effect. It destroys the integrity of your skin."

The focus of this study is the sun-sensitive molecule called trans-urocanic acid (t-UA). Formed in the top layer of the skin, t-UA molecules cover our bodies, acting like antennae for light. In the 1950s, urocanic acid was hailed as a "natural sunscreen" because it absorbs ultraviolet B light. It was thus thought to protect against damage by such rays, which can potentially lead to skin cancer. For a time, the pigment was even added to sunscreens and skin lotions.

When exposed to ultraviolet rays, trans-UA buckles in upon itself to form cis-UA. Most theories about urocanic acid's action focus on this structural flip and subsequent chemical reactions. But the data didn't seem to fit--urocanic acid was absorbing almost three times more energy than could be accounted for by its twist into its cis form. It must undergo some additional chemical reaction, the scientists reasoned. So they investigated the molecule in a different light--literally. What they found revealed not only the molecule's additional maneuver, but its sinister consequences.

Using a cutting-edge technique called photoacoustic spectroscopy, Drs. Hanson and Simon studied urocanic acid's activity when exposed to light near the tail end of the ultraviolet A range, where the molecule's reactivity was thought to be harmless. They discovered that when this type of light strikes t-UA, it zaps the molecule into an excited "triplet" state that sparks the creation of oxygen radicals.

Oxygen radicals are chemical rogues blamed not only for premature aging, but also for damaging DNA, suppressing the immune system, and causing some respiratory problems.

"The results certainly surprised us," said Dr. Simon. "We never expected to see [any] process that allowed oxygen to get sensitized" because the study was conducted under ultraviolet light much different than that which most excites t-UA. "It's a real serendipity case."

"What it means is that you have to be more concerned about protecting yourself from ultraviolet A radiation," he continued. "We should probably use sunscreens that block all the way out to 400 nm [the end of the ultraviolet A region]."

The SPF (solar or sun protection factor) in sunscreen refers to its ability to protect against the burning rays of ultraviolet B light. But currently there are no world-wide standards to measure protection against ultraviolet A, which accounts for 95 percent of sunlight that reaches the earth.

The work may also change the way researchers approach similar projects. Instead of studying a biological molecule exclusively under the type of light that it absorbs most, Dr. Simon suggested that scientists may need to expose the molecule to a whole spectrum of light, slice by slice, to fully understand the molecule's physiological effects.

Reference

Hanson K, Simon J. Epidermal trans-Urocanic Acid and the UV-A Induced Photoaging of the Skin. Proc. Natl. Acad. Sci. USA 1998;95(18):10576-10578.


Story Source:

The above story is based on materials provided by NIH-National Institute Of General Medical Sciences. Note: Materials may be edited for content and length.


Cite This Page:

NIH-National Institute Of General Medical Sciences. "UV Skin Damage In A Different Light." ScienceDaily. ScienceDaily, 3 September 1998. <www.sciencedaily.com/releases/1998/09/980903090954.htm>.
NIH-National Institute Of General Medical Sciences. (1998, September 3). UV Skin Damage In A Different Light. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/1998/09/980903090954.htm
NIH-National Institute Of General Medical Sciences. "UV Skin Damage In A Different Light." ScienceDaily. www.sciencedaily.com/releases/1998/09/980903090954.htm (accessed July 25, 2014).

Share This




More Health & Medicine News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Beatings and Addiction: Pakistan Drug 'clinic' Tortures Patients

Beatings and Addiction: Pakistan Drug 'clinic' Tortures Patients

AFP (July 24, 2014) A so-called drugs rehab 'clinic' is closed down in Pakistan after police find scores of ‘patients’ chained up alleging serial abuse. Duration 03:05 Video provided by AFP
Powered by NewsLook.com
Too Few Teens Receiving HPV Vaccination, CDC Says

Too Few Teens Receiving HPV Vaccination, CDC Says

Newsy (July 24, 2014) The Centers for Disease Control and Prevention is blaming doctors for the low number of children being vaccinated for HPV. Video provided by Newsy
Powered by NewsLook.com
New Painkiller Designed To Discourage Abuse: Will It Work?

New Painkiller Designed To Discourage Abuse: Will It Work?

Newsy (July 24, 2014) The FDA approved Targiniq ER on Wednesday, a painkiller designed to keep users from abusing it. Like any new medication, however, it has doubters. Video provided by Newsy
Powered by NewsLook.com
Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Newsy (July 24, 2014) Sheik Umar Khan has treated many of the people infected in the Ebola outbreak, and now he's become one of them. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

    Health News

      Environment News

        Technology News



          Save/Print:
          Share:

          Free Subscriptions


          Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

          Get Social & Mobile


          Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

          Have Feedback?


          Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
          Mobile: iPhone Android Web
          Follow: Facebook Twitter Google+
          Subscribe: RSS Feeds Email Newsletters
          Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins