Pitt researchers discovered a way to prevent hearing loss caused by loud noise

Anyone who has been to a loud concert knows the feeling of ringing ears. Some people experience temporary or even permanent hearing loss or drastic changes in their perception of sound after the loud noises stop.

In a paper published today in the Proceedings of the National Academy of Sciences, a team of University of Pittsburgh researchers announced the discovery of a molecular mechanism for this kind of hearing loss and showed that it could be mitigated with medication.

The team found that noise-induced hearing loss, which affects millions of Americans, stems from cellular damage in the inner ear that is associated with an excess of free-floating zinc — a mineral that is essential for proper cellular function and hearing. Experiments in mice showed drugs that sponge up excess zinc can help restore lost hearing or, if administered before an expected loud sound exposure, can protect from hearing loss. 

“Noise-induced hearing loss impairs millions of lives but, because the biology of hearing loss is not fully understood, preventing hearing loss has been an ongoing challenge,” said senior author Thanos Tzounopoulos, director of the Pittsburgh Hearing Research Center at Pitt’s School of Medicine.

While some experience noise-induced hearing loss from an acute traumatic injury to the ear, others notice a sudden hearing impairment after being continuously exposed to loud noise, in a battlefield or at a construction site, for example. Others notice their hearing deteriorating after attending a loud music show. 

Researchers say such noise-induced hearing loss can be debilitating. Some people start hearing sounds that aren’t there, a condition called tinnitus, which can severely affect their quality of life.  

Tzounopoulos, also an endowed professor and vice chair of research in the Department of Otolaryngology, has focused his scientific career on investigating how hearing works and developing ways to treat tinnitus and hearing loss. He sought to determine the mechanism behind the condition to lay the groundwork for effective and minimally invasive treatments.

By performing experiments in mice and on isolated cells of the inner ear, the team found zinc levels in the inner ear spike hours after exposure to a loud noise. The exposure, they found, causes a robust release of zinc into spaces within and between cells, which ultimately leads to cellular damage and disrupts normal cell-to-cell communication.

This discovery opens the doors to a possible solution. Experiments showed mice treated with a slow-releasing compound that traps excess free zinc were less prone to hearing loss and were protected from noise-induced damage.  

“This exciting discovery was only possible thanks to the collaboration and complementary scientific expertise of our colleagues in the School of Medicine”: Amantha Thathiah of the Department of Neurobiology and Chris Cunningham of the Department of Otolaryngology, said Tzounopoulos. He added that Thathiah’s expertise in the mechanisms by which cells degenerate and Cunningham’s expertise in the biology of cochlear cells were essential for the project.

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

Other authors of the study are School of Medicine PhD student Brandon Bizup and undergraduate Sofie Brutsaert.

— Anastasia Gorelova, photography by Joshua Franzos