Long-term white noise exposure-induced mtDNA deletion in the auditory system

Conclusion. Long-term exposure to broadband noise can lead to increased levels of mtDNA4834 deletion in the auditory system in rats. Objective. This study aimed to determine if long-term noise exposure induces mtDNA deletion in the auditory system. Materials and methods. Wistar rats aged 3 months (n = 20) were exposed to 110 dB SPL white noise, 4 h per day, for 20 consecutive days. The control group included Wistar rats of the same age (n = 20) with no noise exposure. Auditory brainstem responses (ABRs) were tested as an indicator of hearing function. The cochlea, cochlear nucleus, temporal lobe brain tissue, and blood specimens were collected for DNA extraction. The mtDNA was amplified to identify the highly conserved ND1 segment, as well as mtDNA4834 deletion. Results. Animals in the noise-exposed group demonstrated permanent loss of auditory sensitivity following noise exposure compared with the control animals (p < 0.01). The majority of animals in the noise-exposed group demonstrated mtDNA4834 deletion in cochlea, cochlear nucleus and temporal lobe brain tissues, while only a few in the control group showed such deletion (p < 0.01). In contrast, mtDNA4834 deletion in blood specimens was identified at an extremely low rate in both the noise-exposed and the control groups.