Noise-induced time-dependent changes in oxidative stress in the mouse cochlea and attenuation by D-methionine.
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.
Samson
J
J
Nofer Institute of Occupational Medicine, 8 Teresy Street, 91-348 Lodz, Poland.
Wiktorek-Smagur
A
A
Politanski
P
P
Rajkowska
E
E
Pawlaczyk-Luszczynska
M
M
Dudarewicz
A
A
Sha
S H
SH
Schacht
J
J
Sliwinska-Kowalska
M
M
D000161:Acoustic Stimulation; D000818:Animals; D002374:Catalase / Q000187:drug effects / Q000378:metabolism; D003051:Cochlea / Q000187:drug effects* / Q000473:pathology*; D016057:Evoked Potentials, Auditory, Brain Stem; D006317:Hearing Loss, Noise-Induced / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008715:Methionine / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009622:Noise / Q000009:adverse effects*; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology*; D013482:Superoxide Dismutase / Q000187:drug effects / Q000378:metabolism; D013995:Time
D008715:Methionine; D002374:Catalase; D013482:Superoxide Dismutase