July 9, 2012
Researchers Describe Cellular Processes That Result In Sunburns
With scorching heat affecting much of the United States in recent weeks, sunburn undoubtedly has become a concern to many, and now researchers say that they have discovered the biological mechanism that causes the painful, reddish response to excessive UV radiation exposure.
As it turns out, sunburn is the result of RNA damage to skin cells, researchers at the University of California, San Diego (UCSD) School of Medicine, Rutgers University, and the Miami Veterans Affairs Medical Center report in a new study appearing Sunday in the Advance Online Publication of Nature Medicine. The discovery could open the door for the development of a way to block or treat the condition, the researchers said.
"For example, diseases like psoriasis are treated by UV light, but a big side effect is that this treatment increases the risk of skin cancer," Dr. Richard L. Gallo, principal investigator and a professor of medicine at the UCSD School of Medicine and the Veterans Affairs San Diego Healthcare System, said in a statement.
"Our discovery suggests a way to get the beneficial effects of UV therapy without actually exposing our patients to the harmful UV light. Also, some people have excess sensitivity to UV light, patients with lupus, for example. We are exploring if we can help them by blocking the pathway we discovered," he added.
Gallo and his colleagues used both actual human skin cells and a mouse model, and discovered that UVB radiation fractures and entangles elements of a special type of non-protein-producing RNA in the cells known as non-coding micro-RNA.
When cells become irradiated, they release this special type of RNA, which causes healthy, neighboring cells to launch a process resulting in an inflammatory response designed to remove those sun-damaged cells, the researchers reported in a UCSD press release.
"The inflammatory response is important to start the process of healing after cell death," Gallo said. "We also believe the inflammatory process may clean up cells with genetic damage before they can become cancer. Of course, this process is imperfect and with more UV exposure, there is more chance of cells becoming cancerous."
"Genetics is closely linked to the ability to defend against UV damage and develop skin cancers," he added, noting that he and his colleagues are still not sure how a person's gender, skin pigmentation and individual genetics impact the entire process. "We know in our mouse genetic models that specific genes will change how the mice get sunburn.
Humans have similar genes, but it is not known if people have mutations in these genes that affect their sun response."