Photobiomodulation rescues the cochlea from noise-induced hearing loss via upregulating nuclear factor κB expression in rats

Brain Res. 2016 Sep 1:1646:467-474. doi: 10.1016/j.brainres.2016.06.031. Epub 2016 Jun 21.


Photobiomodulation (PBM) is a noninvasive treatment that can be neuroprotective, although the underlying mechanisms remain unclear. In the present study, we assessed the mechanism of PBM as a novel treatment for noise-induced hearing loss, focusing on the nuclear factor (NF)-κB signaling pathway. Sprague-Dawley rats were exposed to 1-octave band noise centered at 4kHz for 5h (121dB). After noise exposure, their right ears were irradiated with an 808nm diode laser beam at an output power density of 165mW/cm(2) for 30min a day for 5 consecutive days. Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with PBM compared with the non-treatment group at 4, 7, and 14 days after noise exposure. Immunofluorescent image analysis for inducible nitric oxide synthase and cleaved caspase-3 showed lesser immunoreactivities in outer hair cells in the PBM group compared with the non-treatment group. However, immunofluorescent image analysis for NF-κB, an upstream protein of inducible nitric oxide synthase, revealed greater activation in the PBM group compared with the naïve and non-treatment groups. Western blot analysis for NF-κB also showed stronger activation in the cochlear tissues in the PBM group compared with the naïve and non-treatment groups (p<0.01, each). These data suggest that PBM activates NF-κB to induce protection against inducible nitric oxide synthase-triggered oxidative stress and caspase-3-mediated apoptosis that occur following noise-induced hearing loss.

Keywords: Cleaved caspase-3; Inducible nitric oxide synthase; Noise-induced hearing loss; Nuclear factor κB; Photobiomodulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Caspase 3 / metabolism
  • Cochlea / metabolism*
  • Evoked Potentials, Auditory, Brain Stem
  • Hearing Loss, Noise-Induced / metabolism*
  • Hearing Loss, Noise-Induced / therapy
  • Low-Level Light Therapy*
  • Male
  • NF-kappa B / metabolism*
  • Nitric Oxide Synthase Type II / metabolism
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Up-Regulation


  • NF-kappa B
  • Nitric Oxide Synthase Type II
  • Nos2 protein, rat
  • Proto-Oncogene Proteins c-akt
  • Caspase 3