To itch or not to itch? It’s in the genes

GRPR codes for a receptor found in a small group of spinal cord nerve cells where pain and itch signals are transmitted from the skin to the brain. Mice who do not have this gene scratch less in the presence of known itch-inducers, the researchers found.

Chronic itching is a widespread problem. Skin disorders such as eczema, illnesses such as kidney failure or liver disease, and cancer therapies and powerful painkillers such as morphine can all lead to itchiness. For some people, itching is bad enough to interfere with sleep or result in scarring from scratching. Effective treatment options for itchy patients are limited.

Writing in the July 25 online issue of Nature, lead researcher Zhou-Feng Chen describe research that came about as a result of an effort to find genes in the pain pathway. “Many genes have been identified in the pain pathway,” said Chen. “But itch research has lived in the shadow of pain research, and no one knew which gene was responsible for itching.”

They identified GRPR as a potential candidate and performed studies on mice missing GRPR. Although they saw no difference between the mice in terms of pain response, they found a striking change when the mice were presented with itchy substances. While normal mice scratched vigorously, those lacking GRPR scratched little if at all.

The researchers also injected a substance that stimulates the GRPR gene and witnessed an increase in scratching behavior. In the long term, the research results suggest a way to develop anti-itch medication that does not dull pain response. The researchers noted that there are already pharmaceuticals in the pipeline that could help ease itching.