Sunlight continues to damage skin in the dark
Much of the damage that ultraviolet radiation (UV) does to skin occurs hours after sun exposure, a team of Yale-led researchers concluded in a study that was published by the journal Science.
Exposure to UV light from the sun or from tanning beds can damage the DNA in melanocytes, the cells that make the melanin that gives skin its color. This damage is a major cause of skin cancer, the most common form of cancer in the United States. In the past, experts believed that melanin protected the skin by blocking harmful UV light. But there was also evidence from studies suggesting that melanin was associated with skin cell damage.
In the current study, Douglas E. Brash, clinical professor of therapeutic radiology and dermatology at Yale School of Medical, and his co-authors first exposed mouse and human melanocyte cells to radiation from a UV lamp. The radiation caused a type of DNA damage known as a cyclobutane dimer (CPD), in which two DNA "letters" attach and bend the DNA, preventing the information it contains from being read correctly. To the researchers' surprise, the melanocytes not only generated CPDs immediately but continued to do so hours after UV exposure ended. Cells without melanin generated CPDs only during the UV exposure.
This finding showed that melanin had both carcinogenic and protective effects. "If you look inside adult skin, melanin does protect against CPDs. It does act as a shield," said Brash, also a member of Yale Cancer Center. "But it is doing both good and bad things."
The researchers next tested the extent of damage that occurred after sun exposure by preventing normal DNA repair in mouse samples. They found that half of the CPDs in melanocytes were "dark CPDs" -- CPDs created in the dark.
In searching for an explanation of these results, Sanjay Premi, associate research scientist in the Brash laboratory, discovered that the UV light activated two enzymes that combined to "excite" an electron in melanin. The energy generated from this process - known as chemiexcitation - was transferred to DNA in the dark, creating the same DNA damage that sunlight caused in daytime. Chemiexcitation has previously been seen only in lower plants and animals.
While noting that news of the carcinogenic effect of melanin is disconcerting, the researchers also pointed to a ray of hope: The slowness of chemiexcitation may allow time for new preventive tools, such as an "evening-after" sunscreen designed to block the energy transfer.
Veterans returning from Middle East face higher skin cancer risk
Soldiers who served in the glaring desert sunlight of Iraq and Afghanistan returned home with an increased risk of skin cancer, due not only to the desert climate, but also a lack of sun protection, Vanderbilt dermatologist Jennifer Powers, M.D., reports in a study published in the Journal of Investigative Dermatology.
"The past decade of United States combat missions, including operations in Iraq and Afghanistan, have occurred at a more equatorial latitude than the mean center of the United States population, increasing the potential for ultraviolet irradiance and the development of skin cancer," Powers said.
There were several factors contributing to the increased risk, including not only the desert and more equatorial latitudes, but also the length of sunlight exposure day to day, and, among many service members, a lack of training regarding the dangers of sun exposure and limited access to sunscreen.
For the study, Powers and her colleagues analyzed anonymous survey data from 212 veterans regarding sun exposure and protection during their last deployment.
Only 13 percent of participants said they routinely used sunscreen, while 87 percent reported their sunscreen use as "sporadic" or "sometimes." Moreover, only 23 percent of veterans indicated the military had made them very aware of the risks of skin cancer.
The authors found that 77 percent of respondents spent four or more hours per day working in bright sun and 63 percent had at least one sunburn during deployment.
The authors also assessed the availability of sun protection gear, including sunscreen, shade structures, hats and sunglasses, from which they calculated a Sun Protection Availability Score. They found that working more than six hours in the sun was associated with lower Sun Protection Availability Scores.
While military personnel deployed overseas may often have survival priorities other than avoiding sun exposure, Powers notes that the study indicates a potential deficiency for access to sun protection that could translate to long-term health risks.
"Our study has identified factors that put veterans at risk for skin cancer, including melanoma, but we need to better understand the 'why' of sun protection in the field," Powers said. "There is a suggestion that there are times when the lack of availability was associated with lack of use. Understanding how to provide practical and effective sun protection to servicemen and women in warm climates is the next step.
"This study demonstrates room for improvement for skin cancer prevention and early detection in the military population, including possible screening of higher-risk personnel," she said.
The authors note that 80 percent of responses to the survey relied on recall of events that occurred over a year ago. As a majority of the participants were Army veterans, they also suggest that future studies should include national samples representing other military branches.
Nanomaterials in sunscreens and boats leave marine life vulnerable
Nanomaterials commonly used in sunscreens and boat-bottom paints are making sea urchin embryos more vulnerable to toxins, according to a study from the University of California, Davis. The authors said this could pose a risk to coastal, marine and freshwater environments.
The study, published in the journal Environmental Science and Technology, is the first to show that the nanomaterials work as chemosensitizers. In cancer treatments, a chemosensitizer makes tumor cells more sensitive to the effects of chemotherapy.
Similarly, nanozinc and nanocopper made developing sea urchin embryos more sensitive to other chemicals, blocking transporters that would otherwise defend them by pumping toxins out of cells.
Stop being defensive: Nanozinc and nanocopper
Nanozinc oxide is used as an additive in cosmetics such as sunscreens, toothpastes and beauty products. Nanocopper oxide is often used for electronics and technology, but also for antifouling paints, which prevent things like barnacles and mussels from attaching to boats.
“At low levels, both of these nanomaterials are nontoxic,” said co-author Gary Cherr, professor and interim director of the UC Davis Bodega Marine Laboratory, and an affiliate of the UC Davis Coastal Marine Sciences Institute. “However, for sea urchins in sensitive life stages, they disrupt the main defense mechanism that would otherwise protect them from environmental toxins.”
Science for safe design
Nanomaterials are tiny chemical substances measured in nanometers, which are about 100,000 times smaller than the diameter of a human hair. Nano-sized particles can enter the body through the skin, ingestion, or inhalation. They are being rapidly introduced across the fields of electronics, medicine and technology, where they are being used to make energy efficient batteries, clean up oil spills, and fight cancer, among many other uses. However, relatively little is known about nanomaterials with respect to the environment and health.
This research is part of the University of California Center for the Environmental Implications of Nanotechnology and supported by the National Science Foundation and the Environmental Protection Agency.
“The hope is the science will try to stay abreast of the use of nanomaterials so there actually can be safe design,” Cherr said. “The nanotechnology industry wants to come up with designs that are practical but still safe for the environment and human health. The UC center is trying to help fine-tune this.”
The study’s other authors include Bing Wu, Cristina Torres-Duarte and Bryan Cole, all from the UC Davis Bodega Marine Laboratory. Wu is also affiliated with Nanjing University in China.
Action spectrum of sun skin damage documented
Scientists at Newcastle University have documented for the first time the DNA damage, which can occur to skin across the full range of ultraviolet radiation from the sun providing an invaluable tool for sun-protection and the manufacturers of sunscreen.
Testing on human skin cell lines, this study published today in The Society for Investigative Dermatology, documents the action spectrum of ultraviolet damage in cells derived from both the upper layer (dermis) and lower layer (epidermis) of the skin.
This will allow manufacturers of sunscreen to develop and test products so that they can provide protection to both layers.
Our skin ages due to the constant exposure to sunlight as ultraviolet radiation comprising UVA and UVB rays from the sun penetrates cells and increases the number of damaging free radicals, especially the reactive oxygen species. Too many reactive oxygen species can be harmful because they can damage the DNA within our cells.
Over time, this can lead to the accumulation of DNA damage, particularly in mitochondria - the batteries of the cells - which speed up ageing and destroy the skin's supportive fibres, collagen and elastin, leading to wrinkles. Studies strongly suggest the damage caused by reactive oxygen species may also initiate and exacerbate the development of skin cancers.
Professor Mark Birch-Machin, Professor of Molecular Dermatology at Newcastle University said: "Because we were able to analyse the full spectrum of UVA and UVB induced sunburnt DNA damage in the batteries of human skin cells this is an invaluable tool for the cosmetic and pharmaceutical industries and for anti-ageing studies."
The Engineering and Physical Sciences Research Council funded Dr Jennifer Latimer as a CASE PhD Student at Newcastle University for the work alongside a funding award for the collaboration with Proctor and Gamble.
Dr Latimer said: "It is satisfying to think that four years of scientific research has resulted in an outcome that is potentially beneficial, not only to the scientific community but also to industry and the general public."
Sunscreen confusion may burn shoppers
Consumers may need more help navigating the sunscreen aisle. A new Northwestern Medicine study found that many people seem to be confused by sunscreen terminology.
Only 43 percent of people surveyed understood the definition of sun factor protection (SPF) and only seven percent knew what to look for on a label if they wanted a sunscreen that offers protection against early skin aging.
Details of the study were published in the journal JAMA Dermatology.
"We need to do a better job of educating people about sun protection and make it easier for them to understand labels," said Dr. Roopal Kundu, lead author of the study.
Kundu is an associate professor in dermatology at Northwestern University Feinberg School of Medicine and a dermatologist at Northwestern Memorial Hospital.
Sunscreens with SPF help protect the skin from ultraviolet B (UV-B) rays. UV-B rays are the main cause of sunburns. However, research has shown that both ultraviolet A (UV-A) and UV-B can contribute to premature skin aging and skin cancers.
In 2011, the Food and Drug Administration announced new regulations for sunscreen labels to emphasize the importance of 'broad spectrum protection' sunscreen that protects the skin from both UV-A and UV-B rays.
"We recommend you buy a sunscreen lotion labeled 'broad spectrum protection' -- which helps to protect against both types of UV rays -- with an SPF of 30 or higher that is also water resistant," Kundu said. "SPF 30 blocks 97 percent of the UVB radiation. But, you need to reapply it every two hours, using about a shot glass full of lotion over your exposed skin, for the best results."
To assess how well consumers understand new sunscreen labels and evaluate how much they know about sun protection, Kundu and colleagues surveyed 114 participants who attended the Northwestern Medicine dermatology clinic during the summer of 2014.
About 80 percent of those surveyed had purchased sunscreen in 2013, and 75 percent said preventing sunburn was a top reason they wore sunscreen, followed by preventing skin cancer (almost 66 percent). The three top factors influencing their decisions to purchase a particular sunscreen were highest SPF value, sensitive skin formulation and water and sweat resistance.
Almost half reported buying sunscreen with the highest SPF value available. This overreliance on high SPF values is a concern, Kundu said.
"Just because you buy SPF 100 doesn't mean you are 100 percent protected," Kundu said. "Staying out of the sun is the only way to guarantee 100 percent protection."
To assess knowledge of sunscreen labels, participants were shown an image of the front and back of a common sunscreen with a SPF of 30. Many had trouble identifying sunscreen terminology on the label.
• Just 38 percent correctly identified terminology associated with skin cancer protection
• About 23 percent were able to correctly identify how well the sunscreen protected against sun burn
• Only seven percent were able to correctly identify how well the sunscreen protected against early skin aging
"A lot of people seem unsure about the definition of SPF, too," Kundu said. "Only 43 percent understood that if you apply SPF 30 sunscreen to skin 15 minutes before going outdoors, you can stay outside 30 times longer without getting a sunburn."
The study participants were shown another sunscreen label where UV-A protection was designated as a star rating (out of four stars) and UV-B protection as an SPF value. Nearly 80 percent were able to determine the level of UV-A protection and close to 90 percent could determine UV-B protection. This could be a promising new approach to improve customer understanding of labels, Kundu said.
Licorice extract protects the skin from UV-induced stress
The skin is constantly challenged, and very often harmed, by environmental stressors such as UV radiation and chemicals. To cope with UV radiation, various skin cells have evolved a complex protective antioxidant defense system. New research published in Experimental Dermatology introduces a new plant-derived agent which protects skin from the harmful effects of UV irradiation.
"We found out that the antioxidant active Licochalcone A, which is the main component of the root extract of the plant Glycyrrhiza inflata (Chinese Licorice), is able to protect the skin from subsequent UV irradiation damage from within by strengthening the skin's own defense systems. Thus plant extracts with the described profile are able to provide a protective shield from sun exposure supporting and going beyond the action of sunscreens regarding sun protection," said Gitta Neufang, a researcher involved in the work from Beiersdorf AG, Hamburg, Germany.
In order to test the effects of the plant-derived active Licochalcone A in cell culture, Neufang and colleagues isolated human skin cells and irradiated them with solar simulated light mimicking sun exposure. They were able to show that skin cells pretreated with Licochalcone A produced a higher amount of 'self-protecting', antioxidant molecules. Consequently, significantly less harmful radicals were detected in Licochalone A treated human skin cells. In addition, they also conducted a study with healthy volunteers demonstrating that the application of a lotion containing Licochalcone A-rich root extract on the inner forearms for two weeks protected the skin from damage after UV irradiation.
These findings show that the skin´s own defense system can be stimulated by the application of licorice extract. In combination with UV-filters this approach therefore might provide superior sun protection by not only offering physical but also biological sun protection. "Even with the best sun-protecting filter system (SPF50+) 2% of UV-rays still reach the skin and cause damage. We hope that our study helps to improve the effectiveness of sunscreens to protect from the harmful aspects of sun exposure." concluded Gitta Neufang.