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Biochem Biophys Res Commun. 2017 Nov 18;493(2):894-900. doi: 10.1016/j.bbrc.2017.09.124. Epub 2017 Sep 23.

Macrophage recruitment, but not interleukin 1 beta activation, enhances noise-induced hearing damage.

Author information

1
Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Japan.
2
Department of Otolaryngology and Head and Neck Surgery, Faculty of Medicine, University of Tokyo, Japan. Electronic address: tyamasoba-tky@umin.ac.jp.

Abstract

It has been suggested that macrophages or inflammatory monocytes participate in the pathology of noise-induced hearing loss (NIHL), but it is unclear how extensively these cells contribute to the development of temporary and/or permanent NIHL. To address this question, we used clodronate liposomes to deplete macrophages and monocytes. After clodronate liposome injection, mice were exposed to 4-kHz octave band noise at 121 dB for 4 h. Compared to vehicle-injected controls, clodronate-treated mice exhibited significantly reduced permanent threshold shifts at 4 and 8 kHz and significantly smaller outer hair cell losses in the lower-apical cochlear turn. Following noise exposure, the stria vascularis had significantly more cells expressing the macrophage-specific protein F4/80, and this effect was significantly suppressed by clodronate treatment. These F4/80-positive cells expressed interleukin 1 beta (IL-1β), which noise exposure activated. However, IL-1β deficient mice did not exhibit significant resistance to intense noise when compared to wild-type mice. These findings suggest that macrophages that enter the cochlea after noise exposure are involved in NIHL, whereas IL-1β inhibition does not reverse this cochlear damage. Therefore, macrophages may be a promising therapeutic target in human sensorineural hearing losses such as NIHL.

KEYWORDS:

Clodronate liposomes; F4/80; Interleukin 1 beta; Macrophages; Noise-induced hearing loss; Permanent threshold shift

PMID:
28951212
DOI:
10.1016/j.bbrc.2017.09.124
[Indexed for MEDLINE]

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