Low-level laser therapy for prevention of noise-induced hearing loss in rats. (19th May 2015)

• Record Type: Journal Article
• Authors: Tamura, Atsushi; Matsunobu, Takeshi; Mizutari, Kunio; Niwa, Katsuki; Kurioka, Takaomi; Kawauchi, Satoko; Satoh, Shunichi; Hiroi, Sadayuki; Satoh, Yasushi; Nibuya, Masashi; Tamura, Risa; Shiotani, Akihiro
• Is Part Of: Neuroscience letters. Volume 595(2015)
• Page Start: 81
• Page End: 86
• Publication Date: 2015-05-19
• Subjects: LLLT low-level laser therapy -- NIHL noise-induced hearing loss -- ABR auditory brainstem response -- OHC outer hair cell -- iNOS inducible nitric oxide synthase -- ROS reactive oxygen species -- RNS reactive nitrogen species; Low-level laser therapy -- Noise-induced hearing loss -- Inducible nitric oxide synthase -- Cleaved caspase-3; Neurology -- Periodicals; Neurology -- Periodicals; Research -- Periodicals; Neurologie -- Périodiques; Neuroanatomie -- Périodiques; Neuropharmacologie -- Périodiques; Neurophysiologie -- Périodiques; Neurology; Periodicals; Electronic journals; 617.48
• DOI: 10.1016/j.neulet.2015.03.031
• Languages: English
• ISSNs: 0304-3940

Abstract

Highlights: LLLT was performed in rats after noise exposure. ABR measurement revealed that LLLT accelerated recovery of auditory function. Outer hair cell survival rates were significantly elevated in the LLLT group compared to the non-LLLT group. Immunoreactivities against iNOS and cleaved-caspase 3 were decreased in the LLLT group compared to the non-LLLT group. 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 808 nm diode laser at an output power density of 110 or 165 mW/cm 2 for a 30 min 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 165 mW/cm 2 power density. Our findings suggest that LLLT has cytoprotective effects against NIHL via the inhibition of iNOS expression and apoptosis.