For sun worshipers, the sting of the sunburn is sometimes the price of bronzed skin, but it doesn't have to be that way, according to researchers.
Wolfgang Liedtke, a Duke University neurologist, and scientists from Rockefeller University and the University of California San Francisco discovered that by blocking a molecule called TRPV4, they can eliminate the chain of events that result in the pain caused by sunburn.
Most sunburns are triggered by ultraviolet B rays (UVB) that damage the skin's outermost layer, which can result in redness and burning. In moderate amounts, exposure to UVB rays can be beneficial, launching the body's vitamin D-making processes. But with intense exposure, UVB rays can contribute to skin cancer and accelerate skin aging as well. In their findings, published in the Proceedings of the National Academy of Sciences (PNAS), Liedtke and his colleagues showed they could halt the process by which UVB rays irritate skin cells in both mice and people.
UVB rays activate TRPV4 to allow calcium ions into skin cells, and lead to secretion and increased production of another molecule called endothelin, which causes pain and itching. The researchers identified this pathway after they bred mice that were missing TRPV4 in the outer layer of the skin on their hind paws, which resembles human skin. When their paws were exposed to UVB rays, the mice showed little change or pain to their skin, while normal mice with TRPV4 developed blisters and redness.
Liedtke saw similar increases in TRPV4 and endothelin in biopsy specimen of human skin, which suggests the same pathway is involved in people's responses to UVB rays.
But most importantly, he and his team also showed that by blocking the activity of TRPV4 with a solution containing an experimental agent that inhibits TRPV4 that was applied to the hind paws of the normal mice, the mice showed little adverse reaction to the UVB exposure and were significantly less affected by pain.
The researchers are still unsure whether the process actually protects the skin from long-term UVB exposure damage–or if it simply blocks the sensation for pain. That's important, since sunburn and the pain associated with it are signals that skin has reached its limit of sun exposure — and for people, that's an alert to get out of the sun and into the shade.
"[TRPV4 inhibitors] will have to be used together with sunscreen because of the yet unknown issue of the long-term damage by UV rays on cell growth and on the damage it can have on DNA and the DNA structure," says Liedtke. "We need to look into whether and how much the calcium influx through the TRPV4 channel is linked to that type of damage. It's possible the calcium influx makes defense mechanisms stronger, or weaker. It could also be that the calcium accelerates the damage."
So for now, the researchers envision that TRPV4 blockers would be used in tandem with sunblock. According to the International Business Times, there are quite a few pharmaceutical companies that are already producing TRPV4 blockers:
But even if the inhibitors don't prove helpful in protecting against sunburn pain after exposure, they will likely work preventively Liedtke says the results highlight the role that skin may play in other pain-related reactions. "This plays into a direction that some research has taken in implicating the skin as having a more proactive role in pain symptoms — for instance, skin inflammations, in which skin cells are obvious contributors to the pain response. But there has also been research suggesting that even [in] bone fractures where the bone is close to the skin, the pain of that is modulated and enhanced by the skin cells," says Liedtke.
There won't be a solution to sunburn pain in time for the last sunny days of summer, but the findings could pave the way for soothing treatments in summers to come. In the meantime, the best way to treat sunburn pain is to avoid inflaming the skin in the first place — wear sunscreen and avoid the sun's most intense UV rays, between 10am and 4pm.