If you've ever been sunburned, you've experienced the dreaded pain of putting on a shirt the next day. Fabric that should feel soft turns into a layer of painful pressure. That kind of pain-from what should feel like a gentle touch-is called allodynia, and it's a fact of life for many people who suffer from chronic conditions, such as fibromyalgia or nerve damage from chemotherapy. There are limited options to help these patients.

Now scientists in 2 different studies have identified the molecule in neurons responsible for tactile allodynia, a protein called PIEZO2. The new studies are published in the journal Science Translational Medicine and one of the studies showed that Piezo2 is also responsible for allodynia in humans.

For both studies, the researchers induced allodynia using various methods including application of capsaicin, the irritating molecule active in chili peppers, to areas of the skin. Capsaicin is known to sensitize neurons, causing inflammation similar to a sunburn.

Researchers looked at how mice reacted to gentle touch after they were exposed to capsaicin. While normal mice experienced allodynia, the mice with PIEZO2 "knocked out" did not react. The same held true when they tested humans with mutations that inactivated their PIEZO2.

"It was very gratifying to see this in both studies," says one of the authors. "It usually takes years to confirm if results observed in mice hold true in humans, so I think it was mutually exciting for both groups."
Going forward, the researchers want to understand exactly how inflammation interferes with normal touch signals. They are also interested in identifying small molecules that block PIEZO2. Topical application of such PIEZO2 blockers could be beneficial for patients suffering from neuropathic pain.

https://www.scripps.edu/news-and-events/press-room/2018/20181010-pain-allodynia-patapoutian.html

http://stm.sciencemag.org/content/10/462/eaat9897