Exposure to loud noises can disrupt zinc levels in the inner ear, potentially affecting hearing, a study in mice suggests. Treatments that reduce this could be used to treat or prevent such damage, for example, if taken before a rock concert.
Loud noises can cause cells in the inner ear die. Although it has long been known that this affects hearing, the mechanisms behind it are less clear.
Thanos Tsonopoulos Researchers at the University of Pittsburgh, Pennsylvania, thought it might have something to do with free-moving zinc, which plays an important role in the neurotransmission of our senses.
Most of the zinc in the body is bound to proteins, but the rest acts as communication signals between organs, especially the brain, Tsonopoulos says. 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 as sound.
To learn more, Tzounopoulos and colleagues tested free zinc levels in young mice that had been genetically engineered to produce biological markers that indicate the transport of free zinc throughout the body.
Tsonopoulos said mice exposed to 100 decibels of noise, about the same level as a bulldozer or motorcycle, for two hours straight developed significant hearing loss within the next 24 hours.
The researchers found that these mice had higher amounts of free zinc between and around the cells of the cochlea after the blast compared to before the blast and compared to a group of control mice that did not hear the loud noise. I discovered that
“There is a very strong upregulation of zinc, not only in terms of quantity but also in terms of regional spatial extent,” he says. “It goes everywhere.”
Tsonopoulos said the zinc appears to be released from specific cells in the cochlea after it is separated from the proteins to which it is normally bound. Free zinc ultimately causes cell damage and disrupts normal communication between cells, he says.
To see if lowering free zinc levels could protect hearing, Tsonopoulos and his team injected another group of mice with a compound that scavenged zinc into their abdomens or administered a slow-release drug into the inner ear. It was treated by placing an implant. The mice then listened to the same loud sound for two hours. Both groups experienced significant reductions in hearing loss.
With further research, zinc-capturing tablets, IV drugs, or slow-release implants could one day help prevent or treat inner ear damage caused by noise trauma, Tsonopoulos says.
“You can go to concerts, you can go to battle, you can take drugs,” he says. “Or, if you have an accident, you might have these compounds in your ER. [emergency room] We will give it to you to reduce the damage. ”
Future research should also determine how long after exposure to noise people can benefit from such zinc trap therapy, team members say. Amantha Satyaalso at the University of Pittsburgh.