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Zhao HB, Liu LM, Mei L, Quinonez AT, Roberts RA, Lu X. Prevention and treatment of noise-induced hearing loss and cochlear synapse degeneration by potassium channel blockers in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.04.597382. [PMID: 38895254 PMCID: PMC11185602 DOI: 10.1101/2024.06.04.597382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Noise can induce hearing loss. In particularly, noise can induce cochlear synapse degeneration leading to hidden hearing loss, which is the most common type of hearing disorders in the clinic. Currently, there is no pharmacological treatment, particularly, no post-exposure (i.e., therapeutic) treatment available in the clinic. Here, we report that systematic administration of K + channel blockers before or after noise exposure could significantly attenuate NIHL and synapse degeneration. After systematic administration of a general K-channel blocker tetraethylammonium (TEA), the elevation of auditory brainstem response (ABR) thresholds after noise-exposure significantly reduced, and the active cochlear mechanics significantly improved. The therapeutic effect was further improved as the post-exposure administration time extending to 3 days. BK channel is a predominant K + channel in the inner hair cells. Systematic administration of a BK channel blocker GAL-021 after noise exposure also ameliorated hearing loss and improved hearing behavioral responses tested by acoustic startle response (ASR). Finally, both TEA and GAL-021 significantly attenuated noise-induced ribbon synapse degeneration. These data demonstrate that K + -channel blockers can prevent and treat NIHL and cochlear synapse degeneration. Our finding may aid in developing therapeutic strategies for post-exposure treatment of NIHL and synapse degeneration. Significance Statement Noise is a common deafness factor affecting more 100 million people in the United States. So far, there is no pharmacological treatment available. We show here that administration of K + channel blockers after noise exposure could attenuate noise-induced hearing loss and synapse degeneration, and improved behavioral responses. This is the first time to real the K + channel blockers that could treat noise-induced hearing loss and cochlear synaptopathy after noise exposure.
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Ding F, Sun Q, Long C, Rasmussen RN, Peng S, Xu Q, Kang N, Song W, Weikop P, Goldman SA, Nedergaard M. Dysregulation of extracellular potassium distinguishes healthy ageing from neurodegeneration. Brain 2024; 147:1726-1739. [PMID: 38462589 PMCID: PMC11068329 DOI: 10.1093/brain/awae075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 02/15/2024] [Accepted: 02/18/2024] [Indexed: 03/12/2024] Open
Abstract
Progressive neuronal loss is a hallmark feature distinguishing neurodegenerative diseases from normal ageing. However, the underlying mechanisms remain unknown. Extracellular K+ homeostasis is a potential mediator of neuronal injury as K+ elevations increase excitatory activity. The dysregulation of extracellular K+ and potassium channel expressions during neurodegeneration could contribute to this distinction. Here we measured the cortical extracellular K+ concentration ([K+]e) in awake wild-type mice as well as murine models of neurodegeneration using K+-sensitive microelectrodes. Unexpectedly, aged wild-type mice exhibited significantly lower cortical [K+]e than young mice. In contrast, cortical [K+]e was consistently elevated in Alzheimer's disease (APP/PS1), amyotrophic lateral sclerosis (ALS) (SOD1G93A) and Huntington's disease (R6/2) models. Cortical resting [K+]e correlated inversely with neuronal density and the [K+]e buffering rate but correlated positively with the predicted neuronal firing rate. Screening of astrocyte-selective genomic datasets revealed a number of potassium channel genes that were downregulated in these disease models but not in normal ageing. In particular, the inwardly rectifying potassium channel Kcnj10 was downregulated in ALS and Huntington's disease models but not in normal ageing, while Fxyd1 and Slc1a3, each of which acts as a negative regulator of potassium uptake, were each upregulated by astrocytes in both Alzheimer's disease and ALS models. Chronic elevation of [K+]e in response to changes in gene expression and the attendant neuronal hyperexcitability may drive the neuronal loss characteristic of these neurodegenerative diseases. These observations suggest that the dysregulation of extracellular K+ homeostasis in a number of neurodegenerative diseases could be due to aberrant astrocytic K+ buffering and as such, highlight a fundamental role for glial dysfunction in neurodegeneration.
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Affiliation(s)
- Fengfei Ding
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
- Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Qian Sun
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
- Department of Pharmacology, Shanghai Medical College, Fudan University, Shanghai, 200032, China
| | - Carter Long
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Rune Nguyen Rasmussen
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, Neurology Department, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Sisi Peng
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Qiwu Xu
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Ning Kang
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Wei Song
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Pia Weikop
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, Neurology Department, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Steven A Goldman
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, Neurology Department, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY 14642, USA
- Center for Basic and Translational Neuroscience, Faculty of Health and Medical Sciences, Neurology Department, University of Copenhagen, 2200 Copenhagen, Denmark
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Yu C, He Y, Liu Q, Qian X, Gao X, Yang D, Yang Y, Wan G. Thyroid hormone controls the timing of cochlear ribbon synapse maturation. Biochem Biophys Res Commun 2024; 704:149704. [PMID: 38430700 DOI: 10.1016/j.bbrc.2024.149704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 01/25/2024] [Accepted: 02/20/2024] [Indexed: 03/05/2024]
Abstract
Ribbon synapses in the cochlear hair cells are subject to extensive pruning and maturation processes before hearing onset. Previous studies have highlighted the pivotal role of thyroid hormone (TH) in this developmental process, yet the detailed mechanisms are largely unknown. In this study, we found that the thyroid hormone receptor α (Thrα) is expressed in both sensory epithelium and spiral ganglion neurons in mice. Hypothyroidism, induced by Pax8 gene knockout, significantly delays the synaptic pruning during postnatal development in mice. Detailed spatiotemporal analysis of ribbon synapse distribution reveals that synaptic maturation involves not only ribbon pruning but also their migration, both of which are notably delayed in the cochlea of Pax8 knockout mice. Intriguingly, postnatal hyperthyroidism, induced by intraperitoneal injections of liothyronine sodium (T3), accelerates the pruning of ribbon synapses to the mature state without affecting the auditory functions. Our findings suggest that thyroid hormone does not play a deterministic role but rather controls the timing of cochlear ribbon synapse maturation.
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Affiliation(s)
- Chaorong Yu
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; MOE Key Laboratory of Model Animal for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, National Resource Center for Mutant Mice of China, Nanjing University, Nanjing, 210061, China
| | - Yihan He
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; MOE Key Laboratory of Model Animal for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, National Resource Center for Mutant Mice of China, Nanjing University, Nanjing, 210061, China
| | - Qing Liu
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; MOE Key Laboratory of Model Animal for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, National Resource Center for Mutant Mice of China, Nanjing University, Nanjing, 210061, China; Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210061, China
| | - Xiaoyun Qian
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210061, China
| | - Xia Gao
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210061, China
| | - Deye Yang
- Department of Cardiology, The Affiliated Hospital of Hangzhou Normal University, Hangzhou, Zhejiang, 310000, China.
| | - Ye Yang
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210061, China.
| | - Guoqiang Wan
- State Key Laboratory of Pharmaceutical Biotechnology, Department of Otolaryngology Head and Neck Surgery, Jiangsu Provincial Key Medical Discipline (Laboratory), The Affiliated Drum Tower Hospital of Medical School, Model Animal Research Center of Medical School, Nanjing University, Nanjing, 210061, China; MOE Key Laboratory of Model Animal for Disease Study, Jiangsu Key Laboratory of Molecular Medicine, National Resource Center for Mutant Mice of China, Nanjing University, Nanjing, 210061, China; Research Institute of Otolaryngology, No. 321 Zhongshan Road, Nanjing, 210061, China.
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Ismail Mohamad N, Santra P, Park Y, Matthews IR, Taketa E, Chan DK. Synaptic ribbon dynamics after noise exposure in the hearing cochlea. Commun Biol 2024; 7:421. [PMID: 38582813 PMCID: PMC10998851 DOI: 10.1038/s42003-024-06067-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 03/18/2024] [Indexed: 04/08/2024] Open
Abstract
Moderate noise exposure induces cochlear synaptopathy, the loss of afferent ribbon synapses between cochlear hair cells and spiral ganglion neurons, which is associated with functional hearing decline. Prior studies have demonstrated noise-induced changes in the distribution and number of synaptic components, but the dynamic changes that occur after noise exposure have not been directly visualized. Here, we describe a live imaging model using RIBEYE-tagRFP to enable direct observation of pre-synaptic ribbons in mature hearing mouse cochleae after synaptopathic noise exposure. Ribbon number does not change, but noise induces an increase in ribbon volume as well as movement suggesting unanchoring from synaptic tethers. A subgroup of basal ribbons displays concerted motion towards the cochlear nucleus with subsequent migration back to the cell membrane after noise cessation. Understanding the immediate dynamics of synaptic damage after noise exposure may facilitate identification of specific target pathways to treat cochlear synaptopathy.
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Affiliation(s)
- Noura Ismail Mohamad
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Peu Santra
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Yesai Park
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Ian R Matthews
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Emily Taketa
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA
| | - Dylan K Chan
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco, San Francisco, CA, USA.
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Liu LM, Liang C, Chen J, Fang S, Zhao HB. Cx26 heterozygous mutations cause hyperacusis-like hearing oversensitivity and increase susceptibility to noise. SCIENCE ADVANCES 2023; 9:eadf4144. [PMID: 36753545 PMCID: PMC9908021 DOI: 10.1126/sciadv.adf4144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 01/10/2023] [Indexed: 06/18/2023]
Abstract
Gap junction gene GJB2 (Cx26) mutations cause >50% of nonsyndromic hearing loss. Its recessive hetero-mutation carriers, who have no deafness, occupy ~10 to 20% of the general population. Here, we report an unexpected finding that these heterozygote carriers have hearing oversensitivity, and active cochlear amplification increased. Mouse models show that Cx26 hetero-deletion reduced endocochlear potential generation in the cochlear lateral wall and caused outer hair cell electromotor protein prestin compensatively up-regulated to increase active cochlear amplification and hearing sensitivity. The increase of active cochlear amplification also increased sensitivity to noise; exposure to daily-level noise could cause Cx26+/- mice permanent hearing threshold shift, leading to hearing loss. This study demonstrates that Cx26 recessive heterozygous mutations are not "harmless" for hearing as previously considered and can cause hyperacusis-like hearing oversensitivity. The data also indicate that GJB2 hetero-mutation carriers are vulnerable to noise and should avoid noise exposure in daily life.
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Affiliation(s)
- Li-Man Liu
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
- Department of Surgery–Otolaryngology, Yale University Medical School, 310 Cedar Street, New Haven, CT 06510, USA
| | - Chun Liang
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
- Hearing Function Testing Center, Shenzhen Maternity and Child Healthcare Hospital, 3012 Fuqiang Road, Shenzhen 518017, China
| | - Jin Chen
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
| | - Shu Fang
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
| | - Hong-Bo Zhao
- Department of Otolaryngology, University of Kentucky Medical Center, 800 Rose Street, Lexington, KY 40536, USA
- Department of Surgery–Otolaryngology, Yale University Medical School, 310 Cedar Street, New Haven, CT 06510, USA
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6
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Barnes CC, Yee KT, Vetter DE. Conditional Ablation of Glucocorticoid and Mineralocorticoid Receptors from Cochlear Supporting Cells Reveals Their Differential Roles for Hearing Sensitivity and Dynamics of Recovery from Noise-Induced Hearing Loss. Int J Mol Sci 2023; 24:3320. [PMID: 36834731 PMCID: PMC9961551 DOI: 10.3390/ijms24043320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 02/01/2023] [Accepted: 02/03/2023] [Indexed: 02/11/2023] Open
Abstract
Endogenous glucocorticoids (GC) are known to modulate basic elements of cochlear physiology. These include both noise-induced injury and circadian rhythms. While GC signaling in the cochlea can directly influence auditory transduction via actions on hair cells and spiral ganglion neurons, evidence also indicates that GC signaling exerts effects via tissue homeostatic processes that can include effects on cochlear immunomodulation. GCs act at both the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR). Most cell types in the cochlea express both receptors sensitive to GCs. The GR is associated with acquired sensorineural hearing loss (SNHL) through its effects on both gene expression and immunomodulatory programs. The MR has been associated with age-related hearing loss through dysfunction of ionic homeostatic balance. Cochlear supporting cells maintain local homeostatic requirements, are sensitive to perturbation, and participate in inflammatory signaling. Here, we have used conditional gene manipulation techniques to target Nr3c1 (GR) or Nr3c2 (MR) for tamoxifen-induced gene ablation in Sox9-expressing cochlear supporting cells of adult mice to investigate whether either of the receptors sensitive to GCs plays a role in protecting against (or exacerbating) noise-induced cochlear damage. We have selected mild intensity noise exposure to examine the role of these receptors related to more commonly experienced noise levels. Our results reveal distinct roles of these GC receptors for both basal auditory thresholds prior to noise exposure and during recovery from mild noise exposure. Prior to noise exposure, auditory brainstem responses (ABRs) were measured in mice carrying the floxed allele of interest and the Cre recombinase transgene, but not receiving tamoxifen injections (defined as control (no tamoxifen treatment), versus conditional knockout (cKO) mice, defined as mice having received tamoxifen injections. Results revealed hypersensitive thresholds to mid- to low-frequencies after tamoxifen-induced GR ablation from Sox9-expressing cochlear supporting cells compared to control (no tamoxifen) mice. GR ablation from Sox9-expressing cochlear supporting cells resulted in a permanent threshold shift in mid-basal cochlear frequency regions after mild noise exposure that produced only a temporary threshold shift in both control (no tamoxifen) f/fGR:Sox9iCre+ and heterozygous f/+GR:Sox9iCre+ tamoxifen-treated mice. A similar comparison of basal ABRs measured in control (no tamoxifen) and tamoxifen-treated, floxed MR mice prior to noise exposure indicated no difference in baseline thresholds. After mild noise exposure, MR ablation was initially associated with a complete threshold recovery at 22.6 kHz by 3 days post-noise. Threshold continued to shift to higher sensitivity over time such that by 30 days post-noise exposure the 22.6 kHz ABR threshold was 10 dB more sensitive than baseline. Further, MR ablation produced a temporary reduction in peak 1 neural amplitude one day post-noise. While supporting cell GR ablation trended towards reducing numbers of ribbon synapses, MR ablation reduced ribbon synapse counts but did not exacerbate noise-induced damage including synapse loss at the experimental endpoint. GR ablation from the targeted supporting cells increased the basal resting number of Iba1-positive (innate) immune cells (no noise exposure) and decreased the number of Iba1-positive cells seven days following noise exposure. MR ablation did not alter innate immune cell numbers at seven days post-noise exposure. Taken together, these findings support differential roles of cochlear supporting cell MR and GR expression at basal, resting conditions and especially during recovery from noise exposure.
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Affiliation(s)
- Charles C. Barnes
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS 39216, USA
| | - Kathleen T. Yee
- Department of Otolaryngology–Head and Neck Surgery, University of Mississippi Medical Center, Jackson, MS 39216, USA
| | - Douglas E. Vetter
- Graduate Program in Neuroscience, University of Mississippi Medical Center, Jackson, MS 39216, USA
- Department of Otolaryngology–Head and Neck Surgery, University of Mississippi Medical Center, Jackson, MS 39216, USA
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Yu YC, Wang TC, Shih TC. A comprehensive finite-element human ear model to estimate noise-induced hearing loss associated with occupational noise exposure. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 226:107179. [PMID: 36306646 DOI: 10.1016/j.cmpb.2022.107179] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 09/17/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
BACKGROUND AND OBJECTIVE Noise is a common occupational and environmental hazard; however, little is known about the use of computational tools to quantitively analyze data on basilar membrane (BM) damage in noise-induced hearing loss (NIHL). Here, we established a comprehensive three-dimensional finite-element human ear model to quantify the impact of noise exposure on BM and perilymph fluid. METHODS We used auditory risk units (ARUs) to evaluate the BM damage for subjects (3 men and 5 women; mean age, 32.75 ± 8.86 years; age range, 24-44 years). A 90-dB sound pressure level (SPL) was normally applied at the external auditory canal (EAC) entrance to simulate sound transmission from the EAC to the cochlea at frequencies of 0.2-10.0 kHz. RESULTS The pressure distribution of perilymph fluid is totally different on frequency responses under low and high sound-evoked (0.013-10.0 kHz). The highest ARUs were 18.479% at the distance of 1 mm from the base, and the second-highest to fourth-highest ARUs occurred at distances of 5-7 mm from the base, where their ARUs were 9.749%, 9.176%, and 11.231%. The total of the ARUs reached 81.956% at external frequencies' sounds of 3.2-5.0 kHz. Among these, the 3.8-kHz and 3.6-kHz frequencies yielded the highest and second-highest ARUs of 20.325% and 19.873%, respectively. CONCLUSIONS This study would inform our understanding of NIHL associated with occupational noise exposure. We present a FE modelling and describe how it might provide a unique way to unravel mechanisms that drive NIHL due to loud noises.
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Affiliation(s)
- You-Cheng Yu
- Department of Biomedical Imaging and Radiological Science, College of Medicine, China Medical University, Taichung 406040, Taiwan
| | - Tang-Chuan Wang
- School of Medicine, College of Medicine, China Medical University, Taichung 406040, Taiwan; Department of Public Health, College of Public Health, China Medical University, Taichung 406040, Taiwan; Department of Otolaryngology-Head and Neck Surgery, China Medical University Hsinchu Hospital, Zhubei City, Hsinchu County 302056, Taiwan
| | - Tzu-Ching Shih
- Department of Biomedical Imaging and Radiological Science, College of Medicine, China Medical University, Taichung 406040, Taiwan; The PhD Program for Medical Engineering and Rehabilitation Science, College of Biomedical Engineering, China Medical University, Taichung 406040, Taiwan.
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8
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Paik CB, Pei M, Oghalai JS. Review of blast noise and the auditory system. Hear Res 2022; 425:108459. [PMID: 35181171 PMCID: PMC9357863 DOI: 10.1016/j.heares.2022.108459] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 02/03/2022] [Accepted: 02/07/2022] [Indexed: 11/22/2022]
Abstract
The auditory system is particularly vulnerable to blast injury due to the ear's role as a highly sensitive pressure transducer. Over the past several decades, studies have used a variety of animal models and experimental procedures to recreate blast-induced acoustic trauma. Given the developing nature of this field and our incomplete understanding of molecular mechanisms underlying blast-related auditory disturbances, an updated discussion about these studies is warranted. Here, we comprehensively review well-established blast-related auditory pathology including tympanic membrane perforation and hair cell loss. In addition, we discuss important mechanistic studies that aim to bridge gaps in our current understanding of the molecular and microstructural events underlying blast-induced cochlear, auditory nerve, brainstem, and central auditory system damage. Key findings from the recent literature include the association between endolymphatic hydrops and cochlear synaptic loss, blast-induced neuroinflammatory markers in the peripheral and central auditory system, and therapeutic approaches targeting biochemical markers of blast injury. We conclude that blast is an extreme form of noise exposure. Blast waves produce cochlear damage that appears similar to, but more extreme than, the standard noise exposure protocols used in auditory research. However, experimental variations in studies of blast-induced acoustic trauma make it challenging to compare and interpret data across studies.
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Affiliation(s)
- Connie B Paik
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA USA
| | - Michelle Pei
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA USA
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA USA.
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9
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Zhao HB, Liu LM, Yu N, Zhu Y, Mei L, Chen J, Liang C. Efferent neurons control hearing sensitivity and protect hearing from noise through the regulation of gap junctions between cochlear supporting cells. J Neurophysiol 2022; 127:313-327. [PMID: 34907797 PMCID: PMC8759971 DOI: 10.1152/jn.00468.2021] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
It is critical for hearing that the descending cochlear efferent system provides a negative feedback to hair cells to regulate hearing sensitivity and protect hearing from noise. The medial olivocochlear (MOC) efferent nerves project to outer hair cells (OHCs) to regulate OHC electromotility, which is an active cochlear amplifier and can increase hearing sensitivity. Here, we report that the MOC efferent nerves also could innervate supporting cells (SCs) in the vicinity of OHCs to regulate hearing sensitivity. MOC nerve fibers are cholinergic, and acetylcholine (ACh) is a primary neurotransmitter. Immunofluorescent staining showed that MOC nerve endings, presynaptic vesicular acetylcholine transporters (VAChTs), and postsynaptic ACh receptors were visible at SCs and in the SC area. Application of ACh in SCs could evoke a typical inward current and reduce gap junctions (GJs) between them, which consequently enhanced the direct effect of ACh on OHCs to shift but not eliminate OHC electromotility. This indirect, GJ-mediated inhibition had a long-lasting influence. In vivo experiments further demonstrated that deficiency of this GJ-mediated efferent pathway decreased the regulation of active cochlear amplification and compromised the protection against noise. In particular, distortion product otoacoustic emission (DPOAE) showed a delayed reduction after noise exposure. Our findings reveal a new pathway for the MOC efferent system via innervating SCs to control active cochlear amplification and hearing sensitivity. These data also suggest that this SC GJ-mediated efferent pathway may play a critical role in long-term efferent inhibition and is required for protection of hearing from noise trauma.NEW & NOTEWORTHY The cochlear efferent system provides a negative feedback to control hair cell activity and hearing sensitivity and plays a critical role in noise protection. We reveal a new efferent control pathway in which medial olivocochlear efferent fibers have innervations with cochlear supporting cells to control their gap junctions, therefore regulating outer hair cell electromotility and hearing sensitivity. This supporting cell gap junction-mediated efferent control pathway is required for the protection of hearing from noise.
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10
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Badash I, Quiñones PM, Oghalai KJ, Wang J, Lui CG, Macias-Escriva F, Applegate BE, Oghalai JS. Endolymphatic Hydrops is a Marker of Synaptopathy Following Traumatic Noise Exposure. Front Cell Dev Biol 2021; 9:747870. [PMID: 34805158 PMCID: PMC8602199 DOI: 10.3389/fcell.2021.747870] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 10/20/2021] [Indexed: 12/28/2022] Open
Abstract
After acoustic trauma, there can be loss of synaptic connections between inner hair cells and auditory neurons in the cochlea, which may lead to hearing abnormalities including speech-in-noise difficulties, tinnitus, and hyperacusis. We have previously studied mice with blast-induced cochlear synaptopathy and found that they also developed a build-up of endolymph, termed endolymphatic hydrops. In this study, we used optical coherence tomography to measure endolymph volume in live CBA/CaJ mice exposed to various noise intensities. We quantified the number of synaptic ribbons and postsynaptic densities under the inner hair cells 1 week after noise exposure to determine if they correlated with acute changes in endolymph volume measured in the hours after the noise exposure. After 2 h of noise at an intensity of 95 dB SPL or below, both endolymph volume and synaptic counts remained normal. After exposure to 2 h of 100 dB SPL noise, mice developed endolymphatic hydrops and had reduced synaptic counts in the basal and middle regions of the cochlea. Furthermore, round-window application of hypertonic saline reduced the degree of endolymphatic hydrops that developed after 100 dB SPL noise exposure and partially prevented the reduction in synaptic counts in the cochlear base. Taken together, these results indicate that endolymphatic hydrops correlates with noise-induced cochlear synaptopathy, suggesting that these two pathologic findings have a common mechanistic basis.
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Affiliation(s)
- Ido Badash
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Patricia M Quiñones
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Kevin J Oghalai
- Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
| | - Juemei Wang
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Christopher G Lui
- Department of Otolaryngology-Head and Neck Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, United States
| | - Frank Macias-Escriva
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States
| | - Brian E Applegate
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States.,Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
| | - John S Oghalai
- Caruso Department of Otolaryngology-Head and Neck Surgery, Keck School of Medicine of the University of Southern California, Los Angeles, CA, United States.,Viterbi School of Engineering, University of Southern California, Los Angeles, CA, United States
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