Protecting the Inner Ear from Acoustic Trauma.

Calcium activated proteases, or calpains, play an important role in neurodegeneration. In some cases, neural degeneration can be significantly reduced by leupeptin, a potent calpain inhibitor. To determine if leupeptin could protect against noise-induced hearing loss and hair cell loss, we infused leupeptin into scala tympani of one cochlea before, during and after a 14-day exposure to a 100 dB SPL, octave band noise centered at 4.0 kHz. Hearing loss, assessed with the auditory evoked response, was less in the leupeptin-treated ear than in the control ear during the early stage of recovery from acoustic trauma. In addition, hair cell loss in the leupeptin-treated ear was significantly less than in the control ear. These preliminary results suggest that leupeptin may protect against noise-induced hearing loss.