Low-level laser therapy for prevention of noise-induced hearing loss in rats.

Abstract

Noninvasive low-level laser therapy (LLLT) is neuroprotective, but the mechanism of this effect is not fully understood. In this study, the use of LLLT as a novel treatment for noise-induced hearing loss (NIHL) is investigated. Sprague-Dawley rats were exposed to intense noise and their right ears were irradiated with an 808nm diode laser at an output power density of 110 or 165mW/cm(2) for a 30min period for 5 consecutive days. Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with LLLT compared with the non-treatment group at days 2, 4, 7 and 14 after noise exposure. Morphological observations also revealed a significantly higher outer hair cell survival rate in the LLLT groups. Immunohistochemical analyses for inducible nitric oxide synthase (iNOS) and cleaved caspase-3 were used to examine oxidative stress and apoptosis. Strong immunoreactivities were observed in the inner ear tissues of the non-treatment group, whereas these signals were decreased in the LLLT group at 165mW/cm(2) power density. Our findings suggest that LLLT has cytoprotective effects against NIHL via the inhibition of iNOS expression and apoptosis.

• Authors: Atsushi Tamura, Takeshi Matsunobu, Kunio Mizutari, Katsuki Niwa, Takaomi Kurioka, Satoko Kawauchi, Shunichi Satoh, Sadayuki Hiroi, Yasushi Satoh, Masashi Nibuya, Risa Tamura, Akihiro Shiotani
• Journal: Neuroscience letters (Neurosci Lett) Vol. 595 Pg. 81-6 (May 19 2015) ISSN: 1872-7972 [Electronic] Ireland
• PMID: 25797186 (Publication Type: Journal Article)
• Copyright: Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Nitric Oxide Synthase Type II
• Caspase 3

Topics

• Animals
• Apoptosis (radiation effects)
• Caspase 3 (metabolism)
• Evoked Potentials, Auditory, Brain Stem
• Hair Cells, Auditory, Outer (pathology, radiation effects)
• Hearing Loss (etiology, pathology, physiopathology, prevention & control)
• Low-Level Light Therapy
• Male
• Nitric Oxide Synthase Type II (metabolism)
• Noise (adverse effects)
• Oxidative Stress (radiation effects)
• Rats, Sprague-Dawley