Zinc provides new clue for why loud noise causes hearing loss

Exposure to loud noises can affect us. Hearing By disrupting zinc levels in our inner ears, a study in mice suggests. Antidepressants can also be used to treat or prevent such damage, for example if taken before a rock concert.

May cause loud noise. Cells in the inner ear to die. It has long been known to affect hearing, but the mechanism behind it is less clear.

Thanos Zounopoulos at the University of Pittsburgh, Pennsylvania, suspected it might have something to do with free-moving zinc, which plays an important role in the neural communication of our senses.

Most of the body’s zinc is bound to proteins, Tzounopoulos says, but serves as a communication signal between other organs, especially the brain. The highest concentration of free zinc in the body is in the cochlea, the snail-shaped structure in the inner ear that converts vibrations into electrical signals, which are then interpreted. the sound.

To learn more, Tzounopoulos and colleagues tested free zinc levels in young mice that had been genetically modified to produce biomarkers that indicate free zinc transport throughout the body. .

Tzounopoulos says that after listening to sounds of 100 decibels — as loud as a bulldozer or motorcycle — for 2 hours, the rats’ hearing decreased significantly within the next 24 hours.

The researchers found that these mice had higher amounts of free zinc in and around the cells of their cochlea after the sound blast than before, as compared to a group of control mice exposed to loud sounds. Didn’t hear.

“There is a very strong upgradation of zinc in terms of quantity, but also in terms of the spatial coverage of the area,” he says. “It goes everywhere.”

Tzounopoulos says zinc appears to be released from certain cells in the cochlea after it detaches from the proteins that normally bind it. Free zinc eventually damages the cell and disrupts normal communication between cells, he says.

To see if lowering free zinc levels might protect hearing, Tzounopoulos and his team treated another group of mice with a zinc-trapping compound, either injected into their stomachs. or by placing a slow-release implant in their inner ears. The mice then listened to the same loud noise for 2 hours. Both groups experienced much less hearing loss.

With more research, zinc-trapping tablets, drops or slow-release implants may one day help prevent or treat inner ear damage from noise trauma, Tzounopoulos says.

“You can go to a concert or a fight and you can get shot,” he says. “Or you might have an accident, and they might put these compounds in the ER. [emergency room] To help you minimize the damage.”

Future studies should also determine how long people can benefit from such zinc-trapping therapy after noise exposure, the team member says. Amantha ThatiaAlso at the University of Pittsburgh.