'Rewrite the textbooks': We've been wrong about what causes sunburn, experts say
"I think most people associate sunburn with DNA damage; it is established knowledge."
New research out of the University of Copenhagen and Singapore's Nanyang Technological University (NTU) suggests we've been wrong about what causes sunburn.
It turns out the immediate effects are driven by RNA damage, not DNA damage, as originally thought.
The findings appear in the journal Molecular Cell.
The study's authors say their work could one day aid in the development of better treatments for sunburns and other conditions exacerbated by sun exposure.
The research team found exposure to UV radiation damages RNA, triggering an inflammatory response in the skin, a process orchestrated by a protein called ZAK-alpha, which detects RNA damage and signals the immune system, leading to redness, irritation, and cell death.
“Sunburn damages the DNA, leading to cell death and inflammation. So the textbooks say. But in this study we were surprised to learn that this is a result of damage to the RNA, not the DNA that causes the acute effects of sunburn,” Assistant Professor Anna Constance Vind from the Department of Cellular and Molecular Medicine, who is one of the researchers responsible for the new study, says in a statement.
RNA is similar to DNA, the statement goes on to say, but while DNA is long-lasting, RNA is more temporary. One type, messenger RNA (mRNA), acts as a go-between, carrying genetic instructions from DNA to produce proteins—the essential components of cells.
“DNA damage is serious as the mutations will get passed down to progenies of the cells, RNA damage happens all the time and does not cause permanent mutations. Therefore, we used to believe that the RNA is less important, as long as the DNA is intact. But in fact, damages to the RNA are the first to trigger a response to UV radiation,” Professor Vind explains.
Conducted on both mice and human skin cells, the research reveals a new layer of the body's response to UV radiation.
The role of ZAK-alpha
When UV radiation damages messenger RNA (mRNA), it triggers a response in ribosomes (protein-building structures in cells), a process controlled by a protein called ZAK-alpha, which acts as an internal "surveillance system."
It detects RNA damage and triggers inflammation, recruiting immune cells to the skin.
“We found that the first thing the cells respond to after being exposed to UV radiation is damage to the RNA and that this is what triggers cell death and inflammation of the skin,” says Professor Simon Bekker-Jensen in a statement.
“In mice exposed to UV radiation, we found responses such as inflammation and cell death, but when we removed the ZAK gene, these responses disappeared, which means that ZAK plays a key role in the skin’s response to UV-induced damage.”
Researchers tested this mechanism on mice and human skin cells, and in all instances, once the ZAK gene was removed, sunburn responses disappeared.
“This new knowledge turns things upside down. I think most people associate sunburn with DNA damage; it is established knowledge," Bekker-Jensen says.
"But now we need to rewrite the textbooks, and it will affect future research on the effects of UV radiation on the skin.”
Header image: Cheryl Santa Maria for The Weather Network. Graphics via Canva Pro.