A team of researchers from the University of Pittsburgh has made a significant breakthrough in understanding the molecular mechanism behind noise-induced hearing loss (NIHL). The findings, published in the Proceedings of the National Academy of Sciences, could pave the way for new treatments and preventive measures.
The study revealed that NIHL, which affects millions of Americans, is caused by cellular damage in the inner ear associated with an excess of free-floating zinc. This mineral is essential for proper cellular function and hearing. Experiments on mice showed that drugs capable of absorbing excess zinc can help restore lost hearing or protect against hearing loss if administered before exposure to loud noises.
"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.
Noise-induced hearing loss can occur due to acute traumatic injury to the ear or continuous exposure to loud noise such as in a battlefield or construction site. Some people also experience deteriorating hearing after attending loud music shows. Such impairment can be debilitating and may lead to tinnitus, a condition where people start hearing sounds that aren't there, severely affecting their quality of life.
Tzounopoulos and his team performed experiments on mice and isolated cells from the inner ear. They discovered that zinc levels in the inner ear spike hours after exposure to loud noise. This release leads to cellular damage and disrupts normal cell-to-cell communication.
The team's discovery could potentially lead to a solution for NIHL. 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.
The researchers are now 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 include School of Medicine PhD student Brandon Bizup and undergraduate Sofie Brutsaert.
