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Modified Experimental Conditions for Noise-Induced Hearing Loss in Mice and Assessment of Hearing Function and Outer Hair Cell Damage
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Modified Experimental Conditions for Noise-Induced Hearing Loss in Mice and Assessment of Hearing Function and Outer Hair Cell Damage

Published on: February 10, 2023

Bcl-2 genes regulate noise-induced hearing loss

Daisuke Yamashita1, Shujiro B Minami, Sho Kanzaki

  • 1Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan 48109-0506, USA.

Journal of Neuroscience Research
|October 19, 2007
PubMed

Insights

The Bcl-2 family proteins, Bcl-xL and Bak, play key roles in preventing or causing sensory cell death after noise exposure. Bcl-xL protects cells from temporary hearing loss, while Bak triggers cell death during permanent hearing loss.

Area of Science:

  • Oto-neuroscience
  • Molecular biology
  • Cellular biology

Background:

  • Proteins of the Bcl-2 family regulate apoptosis, a process involved in neuronal cell death.
  • Noise-induced hearing loss is a significant health concern linked to neuronal cell death pathways.
  • The roles of specific Bcl-2 family proteins in noise-induced hearing loss are not fully understood.

Purpose of the Study:

  • To investigate the expression of anti-apoptotic Bcl-xL and pro-apoptotic Bak following noise exposures causing temporary threshold shift (TTS) and permanent threshold shift (PTS).
  • To determine the involvement of Bcl-xL and Bak in sensory cell survival or death after intense noise exposure.

Main Methods:

  • Animals were exposed to either 100 dB SPL, 4 kHz OBN for 1 hr (TTS) or 120 dB SPL, 4 kHz OBN for 5 hr (PTS).
  • Auditory brainstem responses (ABRs) were measured at 4, 8, and 16 kHz before and after noise exposure.
  • Immunohistochemical analysis was performed to assess Bcl-xL and Bak expression in cochlear tissues.

Main Results:

  • Both TTS and PTS noise exposures increased ABR thresholds.
  • ABR thresholds fully recovered after TTS exposure.
  • PTS exposure resulted in significant permanent threshold shifts and outer hair cell loss.
  • Bcl-xL was highly expressed in outer hair cells after TTS exposure.
  • Bak expression was observed following PTS exposure, correlating with cell death.

Conclusions:

  • Bcl-2 family proteins are crucial in modulating sensory cell fate following intense noise.
  • Bcl-xL is essential for preventing sensory cell death after TTS-inducing noise levels.
  • PTS-inducing noise exposure activates Bak, leading to sensory cell death.

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