Developing An Over The Counter Hearing Loss Drug

The study published in the Proceedings of the National Academy of Sciences describes the discovery of a molecular mechanism behind hearing loss caused by loud noise and shows how it could be mitigated with medication. This study is part of the career-long investigation of Tzounopoulos to discover how hearing works and develop ways to treat tinnitus and hearing loss by determining the mechanism(s) behind the conditions to lay the foundation for effective and minimally invasive treatments.

This kind of hearing loss affects millions of Americans, and it stems from cellular damage in the inner ear that is associated with an excess of free-floating zinc (zinc is essential for proper cellular function and hearing). The researchers demonstrated in mice experiments that drugs are able to sponge up the excess zinc to help restore lost hearing, or if administered before loud sound exposure can help to protect against hearing loss. 

Some people experience noise-induced hearing loss from an acute or traumatic injury to the ear, but others experience a sudden hearing impairment from being continuously exposed to loud noise such as at a construction site, at a battlefield, or airport. Additionally, others may notice that their hearing has deteriorated after mowing their lawn or attending a drag race or loud music show. Noise-induced hearing loss can become debilitating, some people even begin to hear sounds that aren’t there, which is a condition called tinnitus that can severely affect quality of life. 

In experiments with mice, the researchers isolated cells of the inner ear, which led to finding zinc levels in the inner ear remained spiked hours after exposure to a loud noise. Exposure to loud noise was found to cause a robust release of zinc into spaces within the cells which leads to cellular damage and disrupts normal cell to cell communication. 

Further experiments with mice treated with a slow releasing compound that traps excess free zinc demonstrated that the animals were less prone to hearing loss and they were protected from noise induced hearing damage. 

Next steps are to develop a treatment that could be tested in preclinical studies, with the goal of making the treatment available as a simple over the counter option for hearing loss prevention. 

“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.