Scientists discover biological mechanism of hearing loss caused by loud noise and find a way to prevent it

Anyone who has ever been to a loud concert knows the feeling of ringing in the ears. Some people experience temporary or even permanent hearing loss or drastic changes in their perception of sound after loud noises stop. Thanos Tzounopoulos, Ph.D., director of the Pittsburgh Hearing Research Center at the University of Pittsburgh School of Medicine, has focused his scientific career on studying how hearing works and developing ways to treat tinnitus and hearing loss.

In an article published in the Proceedings of the National Academy of Sciences, Tzounopoulos and his Pitt collaborators, Amantha Thathiah, Ph.D., and Chris Cunningham, Ph.D., have discovered a molecular mechanism of noise-induced hearing loss and show that it could be alleviated by medication.

The study showed that noise-induced hearing loss, which affects millions of Americans, stems from cellular damage in the inner ear associated with excess free-floating zinc, a mineral essential for proper cellular function and hearing. Experiments on mice have shown that drugs that act as molecular sponges trapping excess zinc can help restore hearing loss or, if given before loud sound exposure, can protect against hearing loss.

“Noise-induced hearing loss impairs millions of lives, but because the biology of hearing loss is not fully understood, preventing hearing loss is an ongoing challenge,” said lead author Thanos Tzounopoulos, Ph.D., Endowed Professor and Vice President. of research in otolaryngology at Pitt.

While some experience noise-induced hearing loss following an acute traumatic injury to the ear, others notice sudden hearing loss after being continually exposed to loud noise, such as on a battlefield or on a construction site. Others notice a deterioration in their hearing after attending a loud music performance.

Researchers say such noise-induced hearing loss can be debilitating. Some people begin to hear sounds that are not there, developing a condition called tinnitus, which seriously affects a person’s quality of life.

Tzounopoulos’ research, which focuses on the biology of hearing, tinnitus and hearing loss, has worked to determine the mechanistic underpinnings of the disease with the goal of laying the foundation for the development of effective and minimal treatments. -invasive in the future.

By performing experiments on mice and isolated cells from the inner ear, the researchers found that a few hours after the mice were exposed to loud noise, the zinc level in their inner ear increased. Exposure to loud noise causes a strong release of zinc into the extra- and intracellular space, which ultimately leads to cellular damage and disrupts normal cell-to-cell communication.

Fortunately, this discovery opens the door to a possible solution. Experiments showed that mice treated with a slow-release compound that trapped excess free zinc were less prone to hearing loss and were protected from noise-induced damage.

Researchers are now developing a treatment that will be tested in preclinical safety studies with the goal of making it available as a simple, over-the-counter option to protect against hearing loss.

The study’s other authors are first author Brandon Bizup, Ph.D., and co-author Sofie Brutsaert, both of Pitt.