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See Inside July 2011

Questions for the Itch Doctor

The head of a new center that focuses on itch explains the sensation's biological roots and what we still don't know about it



Courtesy of Elisa Yin

NAME: Zhou-Feng Chen
TITLE: Director, Center for the Study of Itch at the Washington University School of Medicine
LOCATION: St. Louis, Mo.

Why do we need a research center dedicated to itch?
First, chronic itch is a major underreported disease. Many patients—as many as 17 percent of adults, according to one study—suffer from it, and many of them never seek medical help. They think they can scratch it away. Because it’s not cancer, you don’t die from it, so people don’t take it seriously. But a majority of chronic itch is resistant to treatment.

What causes it?
It can be associated with a skin condition such as psoriasis, or it can stem from a systemic disease, such as kidney or liver failure. It can also be a side effect of chemotherapy. Other times it is caused by a deregulation of the nervous system: something is wrong with the nervous system and the itch pathway is activated.

Tell me about your current research.
We are trying to understand how our nervous system transmits the itch signal. Three years ago we identified a subset of neurons in the mouse spinal cord through which all itch sensations pass. This raises very interesting possibilities. If those same kinds of neurons exist in the human spinal cord, and if you could block that molecular signaling pathway, you might stop itch transmission and greatly improve someone’s quality of life.

What is the relation between itch and pain?
For a long time, people thought itch and pain were transmitted through the same pathway, that itch was just a weaker form of pain. But now we know that they are transmitted through separate pathways and that they also antagonize each other: when you create pain, you can suppress itch, like when you scratch.

Also, their biological functions are different. When you feel pain, you withdraw to protect yourself. But when you feel an itch, you move your hands toward it. If something attaches itself to your skin, like a mosquito, you want to remove it. So it is possible that the body’s warning system is telling you that something is happening to your skin and that you’d better get rid of it.

What are the main unanswered questions in your field?
We want to know how the itch sensation is caused in the first place. Our discovery of an itch receptor called GRPR and itch-specific neurons was just the first step. The system is so complex that we still don’t know how this information flows in the body, and we also don’t know how different kinds of diseases activate the itch receptor. There are receptors located in the skin, in the brain and in the spinal cord, so it’s extremely complicated. That’s why we need more scientists in different areas working together.

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