Heat shock pathway activation by TRC051384 protects spiral ganglion neurons from noise-induced hearing loss
Jintao Yu, Miguel A. Ramirez, Yi-Zhi Wang, Seby Edassery, Maxwell Shramuk, SangEun Yeom, Casey Jiaxi Li, Yuvraj Joshi, Mary Ann Cheatham, Mark A. Rutherford, Leah J. Welty, Jeffrey N. Savas
Jintao Yu, Miguel A. Ramirez, Yi-Zhi Wang, Seby Edassery, Maxwell Shramuk, SangEun Yeom, Casey Jiaxi Li, Yuvraj Joshi, Mary Ann Cheatham, Mark A. Rutherford, Leah J. Welty, Jeffrey N. Savas
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Research Article Aging Neuroscience Otology

Heat shock pathway activation by TRC051384 protects spiral ganglion neurons from noise-induced hearing loss

Abstract

Noise-induced hearing loss (NIHL) is a major public health problem caused by damage to cochlear hair cells, synapses, and spiral ganglion neurons (SGNs). Since effective treatments are lacking, we investigated cellular stress responses induced by moderate and loud noise in a mouse model of cochlear synaptopathy. RNA-seq and spatial transcriptomics revealed that noise exposure elicited a robust but transient upregulation of endoplasmic reticulum chaperones and proteasome subunits in SGNs and their supporting cells. To target this response, we administered TRC051384, a small-molecule activator of the heat shock transcription factor Hsf1, prior to noise exposure. TRC051384 crossed the blood-labyrinth barrier and reached the cochlea, induced heat shock protein gene expression, and restored ubiquitin-proteasome function in SGNs. Notably, TRC051384 treatment enhanced auditory brainstem response threshold recovery, preserved Wave I amplitudes, and maintained ribbon synapse density. Together with the existing literature, these findings identify proteotoxic stress in SGNs as a contributor to noise-induced hearing loss and support pharmacological activation of HSF1 as a promising therapeutic strategy.

Authors

Jintao Yu, Miguel A. Ramirez, Yi-Zhi Wang, Seby Edassery, Maxwell Shramuk, SangEun Yeom, Casey Jiaxi Li, Yuvraj Joshi, Mary Ann Cheatham, Mark A. Rutherford, Leah J. Welty, Jeffrey N. Savas

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Figure 4

Prophylactic TRC051384 administration attenuates proteasomal impairments in C57BL/6NJ mice after 105 dB SPL noise exposure for 2 hours.

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Prophylactic TRC051384 administration attenuates proteasomal impairments...
(A–C) Representative fluorescent images from 12 μm cochlear sections near the mid-modiolar plane from P60 Tg(CAG-Ub*G76V/GFP)1Dant mice exposed for 2 hours to 70 dB SPL (ambient), 94 dB SPL, or 105 dB SPL noise, followed by a 2-hour postexposure interval. (D) Representative fluorescent images from 12 μm cochlear sections near the mid-modiolar plane from mice pretreated with TRC051384 and subsequently exposed to 105 dB SPL noise for 2 hours, followed by a 2-hour post-exposure interval. Arrows indicate the spiral ganglion region, highlighting GFP-positive signal. (E) Representative fluorescent images from 12 μm sections near the mid-modiolar plane, focusing on the spiral ganglion of P60 Tg(CAG-Ub*G76V/GFP)1Dant mice. As expected, noise exposure markedly increased the intensity and abundance of GFP signals within spiral ganglion neurons that were NF200+. Prophylactic administration of TRC051384 noticeably reduced both the size and abundance of GFP+ clusters. (F) Quantification of GFP puncta intensity from E shows that noise exposure markedly increased puncta intensity compared with unexposed cochleae (ambient: 0.08 ± 0.024; 105 dB SPL: 0.34 ± 0.11). Prophylactic administration of TRC051384 significantly reduced GFP puncta accumulation following noise exposure, as evidenced by the lower GFP signal in the Noise + TRC051384 group (0.19 ± 0.09). (G) Western blot analysis of GFP protein levels in cochlear extracts from mice treated with TRC051384, with or without 105 dB SPL noise exposure for 2 hours. The upper panel shows GFP signal intensity, and the lower panel shows GAPDH as a loading control. (H) Quantification of G GFP levels normalized to the GAPDH loading control to determine relative GFP signal intensity. TRC051384 treatment alone did not significantly alter GFP abundance compared with uninjected mice (TRC051384: 1.83 ± 0.013; Uninjected: 1.77 ± 0.016). However, TRC051384 significantly reduced GFP abundance following 105 dB SPL noise exposure compared with untreated noise-exposed mice (TRC051384 + Noise: 1.82 ± 0.002; Uninjected + Noise: 2.17 ± 0.031). (F) n = 4 P60–P65 mice of mixed sex per condition. (G) n = 3 P60–P65 mice of mixed sex per condition. Data are represented as mean ± SD, *P < 0.05, ***P < 0.001 by 1-way ANOVA determined significance with Tukey’s post hoc correction. Scale bar: 25 μm (A–D); 15 μm (E).