Protective effects of N-acetylcysteine on noise-induced hearing loss in guinea pigs.
Increasing evidence suggests the involvement of oxidative stress in noise-induced hearing loss. The present study analysed, in an animal experimental model, the time course of the pathogenic mechanisms of noise-induced cochlear damage and the efficacy of the antioxidant drug N-acetylcysteine in reducing noise ototoxicity. Animals were divided into two groups, exposed to noise one treated with N-acetylcysteine for 3 days and one (the control group) with saline. Acoustic trauma was induced by a continuous pure tone of 6 kHz, at 120 dB SPL for 30 minutes. Electrocochleographic recordings were made from an implanted round window electrode and the compound action potentials were measured daily at 2-16 kHz for 7 days. Morphological changes were analysed by scanning electron microscopy. The acoustic threshold measured 1 hour after acoustic trauma was elevated in the control group to 70-90 dB in the higher frequencies of the compound action potential audiogram, with a maximum threshold elevation ranging between 12 and 16 kHz. During the first 24 h, following acoustic trauma, there was a partial recovery of compound action potential thresholds of about 20 dB to reach a final threshold elevation of about 50-70 dB; there was no further improvement over the remaining experimental week. Animals treated with N-acetylcysteine showed a similar temporary threshold shift but a clear improvement in the recovery of compound action potential thresholds, with significantly reduced permanent threshold shift and hair cell loss. These data suggest that N-acetylcysteine is able to attenuate the toxic effect of acoustic trauma and could represent an interesting molecule for preventing inner ear injuries.
Fetoni
A R
AR
Institutes of Otolaryngology, Catholic University of Rome, Italy. afetoni@rm.unicatt.it
Ralli
M
M
Sergi
B
B
Parrilla
C
C
Troiani
D
D
Paludetti
G
G
D000111:Acetylcysteine / Q000627:therapeutic use*; D000818:Animals; D005260:Female; D016166:Free Radical Scavengers / Q000627:therapeutic use*; D006168:Guinea Pigs; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*
D016166:Free Radical Scavengers; D000111:Acetylcysteine