Many people have experienced ringing ears after a loud concert. Some people suffer from temporary or even permanent hearing loss or drastic changes in their sound perception after exposure to loud noise.
Thanos Tzounopoulos, Ph.D., director of the Pittsburgh Hearing Research Center at the University of Pittsburgh School of Medicine, has dedicated his scientific career to investigating how hearing works and developing ways to treat tinnitus and hearing loss.
In a paper published on Monday in the Proceedings of the National Academy of Sciences, Tzounopoulos and his Pitt collaborators Amantha Thathiah, Ph.D., and Chris Cunningham, Ph.D., discovered a molecular mechanism of noise-induced hearing loss and showed that it could be treated with medication.
The study revealed that noise-induced hearing loss, which affects millions of Americans, results from cellular damage in the inner ear that is linked to the excess of free-floating zinc – a mineral that is vital for proper cellular function and hearing. Experiments in mice showed that drugs that act as molecular sponges to trap excess zinc can help restore lost hearing or, if given before an expected loud noise 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, Ph.D., endowed professor and vice-chair of research of otolaryngology at Pitt.
Some people experience noise-induced hearing loss as a result of a sudden traumatic injury to the ear, while others notice a sudden hearing impairment after being exposed to loud noise for a long time, for example in a battlefield or at a construction site. Others notice their hearing worsening after attending a loud music show.
Researchers say that noise-induced hearing loss can be debilitating. Some people start hearing sounds that aren’t there, developing a condition called tinnitus, which severely affects their quality of life.
Tzounopoulos’ research, which focuses on the biology of hearing, tinnitus and hearing loss, aimed to determine the mechanistic basis of the condition in order to lay the groundwork for the development of effective and minimally invasive treatments in the future.
By performing experiments in mice and on isolated cells of the inner ear, researchers found that hours after mice are exposed to loud noise, their inner ear zinc level spikes. Loud noise exposure 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 doors for a possible solution. Experiments showed that mice who were treated with a slow-releasing compound that trapped excess free zinc were less likely to suffer from hearing loss and were protected from noise-induced damage.
Researchers are currently developing a treatment to be tested in preclinical safety studies with the goal of making it available as a simple, over-the-counter option to protect oneself from hearing loss.