Your mother was right when she warned you that loud music could damage your hearing, but now scientists have discovered exactly what gets damaged and how. In a research report published in the September 2013 issue of The FASEB Journal, scientists describe exactly what type of damage noise does to the inner ear, and provide insights into a compound that may prevent noise-related damage.
"Noise-induced hearing loss, with accompanying tinnitus and sound hypersensitivity is a common condition which leads to communication problems and social isolation," said Xiaorui Shi, M.D., Ph.D., study author from the Department of Otolaryngology/Head and Neck Surgery at the Oregon Hearing Research Center at Oregon Health and Science University in Portland, Oregon. "The goal of our study is to understand the molecular mechanisms well enough to mitigate damage from exposure to loud sound."
To make this discovery, Shi and colleagues used three groups of 6 - 8 week old mice, which consisted of a control group, a group exposed to broadband noise at 120 decibels for three hours a day for two days, and a third group given single-dose injections of pigment epithelium-derived factor (PEDF) prior to noise exposure. PEDF is a protein found in vertebrates that is currently being researched for the treatment of diseases like heart disease and cancer. The cells that secrete PEDF in control animals showed a characteristic branched morphology, with the cells arranging in a self-avoidance pattern which provided good coverage of the capillary wall. The morphology of the same cells in the animals exposed to wide-band noise, however, showed clear differences—noise exposure caused changes in melanocytes located in the inner ear.
"Hearing loss over time robs people of their quality of life," said Gerald Weissmann, M.D., Editor-in-Chief of The FASEB Journal. "It's easy to say that we should avoid loud noises, but in reality, this is not always possible. Front-line soldiers or first responders do not have time to worry about the long-term effects of loud noise when they are giving their all. If, however, a drug could be developed to minimize the negative effects of loud noises, it would benefit one and all."
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Fei Zhang, Min Dai, Lingling Neng, Jin Hui Zhang, Zhongwei Zhi, Anders Fridberger, and Xiaorui Shi. Perivascular macrophage-like melanocyte responsiveness to acoustic trauma—a salient feature of strial barrier associated hearing loss. FASEB J September 2013 27:3730-3740, DOI: 10.1096/fj.13-232892