Alzheimer drug helps mice recover some hearing

A drug developed for Alzheimer's disease can partially reverse hearing loss caused by exposure to extremely loud sounds, an international team reports in the journal Neuron.

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Loud noises cause hearing loss by injuring or killing hair cells, cells in the inner ear that transform sounds into electrical signals that are sent to the brain.

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Hair cells can be lost to diseases, after taking certain medications, or as a part of normal aging. And hearing specialists are seeing a new group of relatively young people who have lost hair cells, Edge says.

"What's important in our society right now are a lot of the soldiers coming back from overseas who have been exposed to even a single loud noise which can seriously damage hearing," he says.

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Next, the team administered an experimental drug known as a gamma secretase inhibitor to the inner ear. Gamma secretase inhibitors were developed to treat Alzheimer's disease, but haven't worked out for that purpose. The drugs never made it to the market for humans — or mice — so you can't go ask your doctor for a presciption.

These drugs have an interesting side effect, though, Edge says. In mice, they can cause so-called support cells from the inner ear to transform into hair cells.

"And to our delight these hair cells were functioning hair cells that improved the hearing of the animal," he says.

Edge says this shows it IS possible to grow new hair cells in a mammal. And because mice and humans have very similar hearing systems, he says, the approach is likely to work in people too.

It's not a complete cure, though. The mice got only about 20 percent of their hearing back, and still couldn't hear certain sound frequencies, Edge says.