Noise-induced time-dependent changes in oxidative stress in the mouse cochlea and attenuation by d-methionine

• DOI: 10.1016/j.neuroscience.2007.11.015
• Publication Date: 2007-11-20T12:20:48Z
• Authors: J. Samson; A. Wiktorek-Smagur; P. Politanski; E. Rajkowska; M. Pawlaczyk-Lusz...; A. Dudarewicz; S.-H. Sha; J. Schacht; M. Sliwinska-Kowa...
• Keywords: Superoxide Dismutase; Catalase; Cochlea; Time; Mice, Inbred C57BL; Mice; Oxidative Stress; 03 medical and health sciences; Methionine; 0302 clinical medicine; Acoustic Stimulation; Hearing Loss, Noise-Induced; Evoked Potentials, Auditory, Brain Stem; Animals; Lipid Peroxidation; Noise

Oxidative stress in the cochlea is considered to play an important role in noise-induced hearing loss. This study determined changes in superoxide dismutase (SOD), catalase, lipid peroxidation (LPO) and the auditory brainstem response (ABR) in the cochlea of C57BL/6 mice prior to and immediately, 1, 3, 7, 10, 14 and 21 days after noise exposure (4 kHz octave band at the intensity of 110 dB SPL for 4 h). A significant increase in SOD activity immediately and on 1st day after noise exposure, without a concomitant increase in catalase activity suggested a difference in the time dependent changes in the scavenging enzymes, which facilitates the increase in LPO observed on day 7. The ABR indicated significant noise-induced functional deficits which stabilized in 2 weeks with a permanent threshold shift (PTS) of 15 dB at both 4 kHz and 8 kHz. The antioxidant D-methionine (D-Met) reversed the noise-induced changes in LPO levels and enzyme activities. It also significantly reduced the PTS observed on the 14th day from 15 dB to 5 dB for 4 kHz. In summary, the findings indicate that time-dependent alterations in scavenging enzymes facilitate the production of reactive oxygen species and that D-met effectively attenuates noise-induced oxidative stress and the associated functional loss in the mouse cochlea.