scholarly journals Cochlear Synaptopathy and Noise-Induced Hidden Hearing Loss

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Lijuan Shi ◽  
Ying Chang ◽  
Xiaowei Li ◽  
Steve Aiken ◽  
Lijie Liu ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Noise Exposure ◽  
Human Subjects ◽  
Spiral Ganglion ◽  
Nerve Fibers ◽  
Type I ◽  
Functional Deficits ◽  
Ganglion Neurons ◽  
Hidden Hearing Loss ◽  
Signal Coding

Recent studies on animal models have shown that noise exposure that does not lead to permanent threshold shift (PTS) can cause considerable damage around the synapses between inner hair cells (IHCs) and type-I afferent auditory nerve fibers (ANFs). Disruption of these synapses not only disables the innervated ANFs but also results in the slow degeneration of spiral ganglion neurons if the synapses are not reestablished. Such a loss of ANFs should result in signal coding deficits, which are exacerbated by the bias of the damage toward synapses connecting low-spontaneous-rate (SR) ANFs, which are known to be vital for signal coding in noisy background. As there is no PTS, these functional deficits cannot be detected using routine audiological evaluations and may be unknown to subjects who have them. Such functional deficits in hearing without changes in sensitivity are generally called “noise-induced hidden hearing loss (NIHHL).” Here, we provide a brief review to address several critical issues related to NIHHL: (1) the mechanism of noise induced synaptic damage, (2) reversibility of the synaptic damage, (3) the functional deficits as the nature of NIHHL in animal studies, (4) evidence of NIHHL in human subjects, and (5) peripheral and central contribution of NIHHL.

scholarly journals Spatiotemporal Developmental Upregulation of Prestin Correlates With the Severity and Location of Cyclodextrin-Induced Outer Hair Cell Loss and Hearing Loss

2021 ◽  
Vol 9 ◽  
Author(s):  
Dalian Ding ◽  
Haiyan Jiang ◽  
Senthilvelan Manohar ◽  
Xiaopeng Liu ◽  
Li Li ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Hair Cells ◽  
Auditory Nerve ◽  
High Frequency ◽  
Spiral Ganglion ◽  
Low Frequency ◽  
Nerve Fibers ◽  
Spiral Ganglion Neurons ◽  
Auditory Nerve Fibers ◽  
Ganglion Neurons

2-Hyroxypropyl-beta-cyclodextrin (HPβCD) is being used to treat Niemann-Pick C1, a fatal neurodegenerative disease caused by abnormal cholesterol metabolism. HPβCD slows disease progression, but unfortunately causes severe, rapid onset hearing loss by destroying the outer hair cells (OHC). HPβCD-induced damage is believed to be related to the expression of prestin in OHCs. Because prestin is postnatally upregulated from the cochlear base toward the apex, we hypothesized that HPβCD ototoxicity would spread from the high-frequency base toward the low-frequency apex of the cochlea. Consistent with this hypothesis, cochlear hearing impairments and OHC loss rapidly spread from the high-frequency base toward the low-frequency apex of the cochlea when HPβCD administration shifted from postnatal day 3 (P3) to P28. HPβCD-induced histopathologies were initially confined to the OHCs, but between 4- and 6-weeks post-treatment, there was an unexpected, rapid and massive expansion of the lesion to include most inner hair cells (IHC), pillar cells (PC), peripheral auditory nerve fibers, and spiral ganglion neurons at location where OHCs were missing. The magnitude and spatial extent of HPβCD-induced OHC death was tightly correlated with the postnatal day when HPβCD was administered which coincided with the spatiotemporal upregulation of prestin in OHCs. A second, massive wave of degeneration involving IHCs, PC, auditory nerve fibers and spiral ganglion neurons abruptly emerged 4–6 weeks post-HPβCD treatment. This secondary wave of degeneration combined with the initial OHC loss results in a profound, irreversible hearing loss.

scholarly journals Autophagy Regulates the Survival of Hair Cells and Spiral Ganglion Neurons in Cases of Noise, Ototoxic Drug, and Age-Induced Sensorineural Hearing Loss

2021 ◽  
Vol 15 ◽  
Author(s):  
Lingna Guo ◽  
Wei Cao ◽  
Yuguang Niu ◽  
Shuangba He ◽  
Renjie Chai ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Sensorineural Hearing Loss ◽  
Hair Cells ◽  
Noise Exposure ◽  
Spiral Ganglion ◽  
Sensorineural Hearing ◽  
Spiral Ganglion Neurons ◽  
Core Components ◽  
Spontaneous Regeneration ◽  
Ganglion Neurons

Inner ear hair cells (HCs) and spiral ganglion neurons (SGNs) are the core components of the auditory system. However, they are vulnerable to genetic defects, noise exposure, ototoxic drugs and aging, and loss or damage of HCs and SGNs results in permanent hearing loss due to their limited capacity for spontaneous regeneration in mammals. Many efforts have been made to combat hearing loss including cochlear implants, HC regeneration, gene therapy, and antioxidant drugs. Here we review the role of autophagy in sensorineural hearing loss and the potential targets related to autophagy for the treatment of hearing loss.

scholarly journals Impulse Noise Induced Hidden Hearing Loss, Hair Cell Ciliary Changes and Oxidative Stress in Mice

Antioxidants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 1880
Author(s):  
Paul Gratias ◽  
Jamal Nasr ◽  
Corentin Affortit ◽  
Jean-Charles Ceccato ◽  
Florence François ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Hearing Loss ◽  
Hair Cells ◽  
Impulse Noise ◽  
Noise Exposure ◽  
Morphological Changes ◽  
Nerve Fibers ◽  
Outer Hair Cells ◽  
Hidden Hearing Loss ◽  
The Impact

Recent studies demonstrated that reversible continuous noise exposure may induce a temporary threshold shift (TTS) with a permanent degeneration of auditory nerve fibers, although hair cells remain intact. To probe the impact of TTS-inducing impulse noise exposure on hearing, CBA/J Mice were exposed to noise impulses with peak pressures of 145 dB SPL. We found that 30 min after exposure, the noise caused a mean elevation of ABR thresholds of ~30 dB and a reduction in DPOAE amplitude. Four weeks later, ABR thresholds and DPOAE amplitude were back to normal in the higher frequency region (8–32 kHz). At lower frequencies, a small degree of PTS remained. Morphological evaluations revealed a disturbance of the stereociliary bundle of outer hair cells, mainly located in the apical regions. On the other hand, the reduced suprathreshold ABR amplitudes remained until 4 weeks later. A loss of synapse numbers was observed 24 h after exposure, with full recovery two weeks later. Transmission electron microscopy revealed morphological changes at the ribbon synapses by two weeks post exposure. In addition, increased levels of oxidative stress were observed immediately after exposure, and maintained for a further 2 weeks. These results clarify the pathology underlying impulse noise-induced sensory dysfunction, and suggest possible links between impulse-noise injury, cochlear cell morphology, metabolic changes, and hidden hearing loss.

scholarly journals The Physiological Bases of Hidden Noise-Induced Hearing Loss: Protocol for a Functional Neuroimaging Study (Preprint)

2017 ◽  
Author(s):  
Rebecca Susan Dewey ◽  
Deborah A Hall ◽  
Hannah Guest ◽  
Garreth Prendergast ◽  
Christopher J Plack ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Noise Exposure ◽  
Functional Neuroimaging ◽  
Nerve Fibers ◽  
High Threshold ◽  
Hearing Level ◽  
Noise Induced Hearing Loss ◽  
Brainstem Response ◽  
Neuroimaging Study ◽  
Hidden Hearing Loss

BACKGROUND Rodent studies indicate that noise exposure can cause permanent damage to synapses between inner hair cells and high-threshold auditory nerve fibers, without permanently altering threshold sensitivity. These demonstrations of what is commonly known as hidden hearing loss have been confirmed in several rodent species, but the implications for human hearing are unclear. OBJECTIVE Our Medical Research Council–funded program aims to address this unanswered question, by investigating functional consequences of the damage to the human peripheral and central auditory nervous system that results from cumulative lifetime noise exposure. Behavioral and neuroimaging techniques are being used in a series of parallel studies aimed at detecting hidden hearing loss in humans. The planned neuroimaging study aims to (1) identify central auditory biomarkers associated with hidden hearing loss; (2) investigate whether there are any additive contributions from tinnitus or diminished sound tolerance, which are often comorbid with hearing problems; and (3) explore the relation between subcortical functional magnetic resonance imaging (fMRI) measures and the auditory brainstem response (ABR). METHODS Individuals aged 25 to 40 years with pure tone hearing thresholds ≤20 dB hearing level over the range 500 Hz to 8 kHz and no contraindications for MRI or signs of ear disease will be recruited into the study. Lifetime noise exposure will be estimated using an in-depth structured interview. Auditory responses throughout the central auditory system will be recorded using ABR and fMRI. Analyses will focus predominantly on correlations between lifetime noise exposure and auditory response characteristics. RESULTS This paper reports the study protocol. The funding was awarded in July 2013. Enrollment for the study described in this protocol commenced in February 2017 and was completed in December 2017. Results are expected in 2018. CONCLUSIONS This challenging and comprehensive study will have the potential to impact diagnostic procedures for hidden hearing loss, enabling early identification of noise-induced auditory damage via the detection of changes in central auditory processing. Consequently, this will generate the opportunity to give personalized advice regarding provision of ear defense and monitoring of further damage, thus reducing the incidence of noise-induced hearing loss.

Morphology Changes in the Cochlea of Impulse Noiseinduced Hidden Hearing Loss

2021 ◽  
Author(s):  
Guo-wei Qi ◽  
Lei Shi ◽  
Han-dai Qin ◽  
Yuhua Zhu ◽  
Qing-qing Jiang ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Guinea Pigs ◽  
Impulse Noise ◽  
Noise Exposure ◽  
Nerve Fibers ◽  
Basement Membranes ◽  
Time Interval ◽  
Noise Induced Hearing Loss ◽  
Hidden Hearing Loss ◽  
Morphology Changes

Abstract Objectives: This study was designed to determine the morphology changes of noise-induced hidden hearing loss (NIHHL). Method: Fifteen guinea pigs were divided into three groups: noise-induced hidden hearing loss (NIHHL) group, noise-induced hearing loss (NIHL) group, and normal control group. For the noise-induced hidden hearing loss group, the guinea pigs were exposed to 15 times of impulse noise at one time. For the noise-induced hearing loss group, the animals were exposed to a total of 200 times of impulse noise in two times, and the time interval is 24 hours. Auditory brain response (ABR) was tested before, immediately, 24h, 1week, and one month after noise exposure to evaluate cochlear physiology changes. One month after noise exposure, all guinea pigs in three groups were sacrificed, and basement membranes were carefully dissected immediately after ABR tests. The cochlea samples were observed by transmission electron microscopy (TEM) to found out the monograph changes. Result: The ABR results showed that 15 times of impulse noise exposure could cause NIHHL in guinea pigs and 200 times could cause completely hearing loss. Impulse noise exposure could cause a dramatic increase in chondriosome in the inner hair cell. The structures of ribbon synapses and heminodes were also obviously impaired compared to the normal group. The nerve fibers and myelin sheaths remained intact after impulse noise exposure. Conclusion: This research revealed for the first time that impulse noise could cause hidden hearing loss, and the changes in inner hair cells, ribbon synapse, and heminode all played a vital role in the pathogenesis of hidden hearing loss.

scholarly journals Effect of Electroacupuncture on Noise-Induced Hearing Loss in Rats

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Chia-Hao Chang ◽  
Chia-Der Lin ◽  
Ching-Liang Hsieh
Keyword(s):  
Hearing Loss ◽  
Noise Exposure ◽  
Histopathological Examination ◽  
Spiral Ganglion ◽  
Auditory Brainstem ◽  
Auditory Threshold ◽  
Auditory Brainstem Responses ◽  
Control Group ◽  
Noise Induced Hearing Loss ◽  
Ganglion Neurons

Acupuncture has long been used to relieve some inner ear diseases such as deafness and tinnitus. The present study examined the effect of electroacupuncture (EA) on noise-induced hearing loss (NIHL) in animals. A NIHL rat model was established. Electroacupuncture pretreatment at 2 Hz or posttreatment at the right Zhongzhu (TE3) acupoint was applied for 1 hour. Auditory thresholds were measured using auditory brainstem responses (ABRs), and histopathology of the cochlea was examined. The results indicated that the baseline auditory threshold of ABR was not significantly different between the control (no noise), EA-only (only EA without noise), noise (noise exposure only), pre-EA (pretreating EA then noise), and post-EA (noise exposure then posttreating with EA) groups. Significant auditory threshold shifts were found in the noise, pre-EA, and post-EA groups in the immediate period after noise exposure, whereas auditory recovery was better in the pre-EA and post-EA groups than that in the noise group at the three days, one week (W1), two weeks (W2), three weeks (W3), and four weeks(W4) after noise stimulation. Histopathological examination revealed greater loss of the density of spiral ganglion neurons in the noise group than in the control group at W1 and W2. Although significant loss of spiral ganglion loss happened in pre-EA and post-EA groups, such loss was less than the loss of the noise group, especially W1. These results indicate that either pretreatment or posttreatment with EA may facilitate auditory recovery after NIHL. The detailed mechanism through which EA alleviates NIHL requires further study.

scholarly journals Type 1 Diabetes Induces Hearing Loss: Functional and Histological Findings in An Akita Mouse Model

Biomedicines ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 343
Author(s):  
Yun Yeong Lee ◽  
Yeon Ju Kim ◽  
Eun Sol Gil ◽  
Hantai Kim ◽  
Jeong Hun Jang ◽  
...  
Keyword(s):  
Type 1 Diabetes ◽  
Hearing Loss ◽  
Spiral Ganglion ◽  
Spiral Ganglion Neurons ◽  
Blood Capillary ◽  
Spiral Ligament ◽  
Type I ◽  
Ganglion Neurons ◽  
Akita Mice

The relationship between type 1 diabetes and hearing loss is not well known, although based on many pathological studies, type 2 diabetes induced hearing loss is associated with microcirculation problems in the inner ear. The purpose of this study was to investigate the correlation between type 1 diabetes and hearing loss through hearing function and immunohistochemical analyses using type 1 diabetic Akita or wild-type (WT) mice. The Akita mice had a significant increase in hearing thresholds, blood glucose, and insulin tolerance compared to WT mice. Histological analysis showed that the loss of cells and damage to mitochondria in the spiral ganglion neurons of Akita mice were significantly increased compared to WT. Also, the stria vascularis showed decreased thickness, loss of intermediate cells, and disturbance in blood capillary shape in the Akita mice. Moreover, a reduction in type I, II, and IV fibrocytes and Na+/K+-ATPase α1 expression in spiral ligament was also observed. Cleaved caspase-3 expression was highly expressed in spiral ganglion neurons. In conclusion, hearing loss in type 1 diabetes is caused not only by ion imbalance and blood flow disorders of cochlear endolymph, but through the degenerative nervous system via apoptosis-mediated cell death.

scholarly journals Protection of Cochlear Ribbon Synapses and Prevention of Hidden Hearing Loss

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Mei Wei ◽  
Wei Wang ◽  
Yao Liu ◽  
Xiang Mao ◽  
Tai Sheng Chen ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Molecular Mechanisms ◽  
Spiral Ganglion ◽  
Structural Features ◽  
Auditory Neuropathy ◽  
Synapse Loss ◽  
Ribbon Synapses ◽  
Ganglion Neurons ◽  
Hidden Hearing Loss ◽  
Therapeutic Research

In the auditory system, ribbon synapses are vesicle-associated structures located between inner hair cells (IHCs) and spiral ganglion neurons that are implicated in the modulation of trafficking and fusion of synaptic vesicles at the presynaptic terminals. Synapse loss may result in hearing loss and difficulties with understanding speech in a noisy environment. This phenomenon happens without permanent hearing loss; that is, the cochlear synaptopathy is “hidden.” Recent studies have reported that synapse loss might be critical in the pathogenesis of hidden hearing loss. A better understanding of the molecular mechanisms of the formation, structure, regeneration, and protection of ribbon synapses will assist in the design of potential therapeutic strategies. In this review, we describe and summarize the following aspects of ribbon synapses: (1) functional and structural features, (2) potential mechanisms of damage, (3) therapeutic research on protecting the synapses, and (4) the role of synaptic regeneration in auditory neuropathy and the current options for synapse rehabilitation.

scholarly journals Molecular Mechanisms and Biological Functions of Autophagy for Genetics of Hearing Impairment

Genes ◽  
2020 ◽  
Vol 11 (11) ◽  
pp. 1331
Author(s):  
Ken Hayashi ◽  
Yuna Suzuki ◽  
Chisato Fujimoto ◽  
Sho Kanzaki
Keyword(s):  
Cell Death ◽  
Hearing Loss ◽  
Inner Ear ◽  
Hearing Impairment ◽  
Cell Fate ◽  
Molecular Mechanisms ◽  
Noise Exposure ◽  
Spiral Ganglion ◽  
Eukaryotic Cell ◽  
Ganglion Neurons

The etiology of hearing impairment following cochlear damage can be caused by many factors, including congenital or acquired onset, ototoxic drugs, noise exposure, and aging. Regardless of the many different etiologies, a common pathologic change is auditory cell death. It may be difficult to explain hearing impairment only from the aspect of cell death including apoptosis, necrosis, or necroptosis because the level of hearing loss varies widely. Therefore, we focused on autophagy as an intracellular phenomenon functionally competing with cell death. Autophagy is a dynamic lysosomal degradation and recycling system in the eukaryotic cell, mandatory for controlling the balance between cell survival and cell death induced by cellular stress, and maintaining homeostasis of postmitotic cells, including hair cells (HCs) and spiral ganglion neurons (SGNs) in the inner ear. Autophagy is considered a candidate for the auditory cell fate decision factor, whereas autophagy deficiency could be one of major causes of hearing impairment. In this paper, we review the molecular mechanisms and biologic functions of autophagy in the auditory system and discuss the latest research concerning autophagy-related genes and sensorineural hearing loss to gain insight into the role of autophagic mechanisms in inner-ear disorders.

scholarly journals Physiopathological Relevance of D-Serine in the Mammalian Cochlea

2021 ◽  
Vol 15 ◽  
Author(s):  
Jing Wang ◽  
Nicolas Serratrice ◽  
Cindy J. Lee ◽  
Florence François ◽  
Jonathan V. Sweedler ◽  
...  
Keyword(s):  
Hearing Loss ◽  
Nmda Receptors ◽  
Guinea Pigs ◽  
Stria Vascularis ◽  
Spiral Ganglion ◽  
Nerve Fibers ◽  
Inner Hair Cell ◽  
Ganglion Neurons

NMDA receptors (NMDARs) populate the complex between inner hair cell (IHC) and spiral ganglion neurons (SGNs) in the developing and mature cochlea. However, in the mature cochlea, activation of NMDARs is thought to mainly occur under pathological conditions such as excitotoxicity. Ototoxic drugs such as aspirin enable cochlear arachidonic-acid-sensitive NMDAR responses, and induced chronic tinnitus was blocked by local application of NMDAR antagonists into the cochlear fluids. We largely ignore if other modulators are also engaged. In the brain, D-serine is the primary physiological co-agonist of synaptic NMDARs. Whether D-serine plays a role in the cochlea had remained unexplored. We now reveal the presence of D-serine and its metabolic enzymes prior to, and at hearing onset, in the sensory and non-neuronal cells of the cochlea of several vertebrate species. In vivo intracochlear perfusion of D-serine in guinea pigs reduces sound-evoked activity of auditory nerve fibers without affecting the receptor potentials, suggesting that D-serine acts specifically on the postsynaptic auditory neurons without altering the functional state of IHC or of the stria vascularis. Indeed, we demonstrate in vitro that agonist-induced activation of NMDARs produces robust calcium responses in rat SGN somata only in the presence of D-serine, but not of glycine. Surprisingly, genetic deletion in mice of serine racemase (SR), the enzyme that catalyzes D-serine, does not affect hearing function, but offers protection against noise-induced permanent hearing loss as measured 3 months after exposure. However, the mechanisms of activation of NMDA receptors in newborn rats may be different from those in adult guinea pigs. Taken together, these results demonstrate for the first time that the neuro-messenger D-serine has a pivotal role in the cochlea by promoting the activation of silent cochlear NMDAR in pathological situations. Thus, D-serine and its signaling pathway may represent a new druggable target for treating sensorineural hearing disorders (i.e., hearing loss, tinnitus).

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