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Chen HK, Wang YH, Lei CS, Guo YR, Tang MC, Tsai TF, Chen YF, Wang CH. Loss of Cisd2 Exacerbates the Progression of Age-Related Hearing Loss. Aging Dis 2024:AD.2024.1036. [PMID: 39226169 DOI: 10.14336/ad.2024.1036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2024] [Accepted: 08/24/2024] [Indexed: 09/05/2024] Open
Abstract
Age-related hearing loss (ARHL) is a disease that impacts human quality of life and contributes to the progression of other neuronal problems. Various stressors induce an increase in free radicals, destroy mitochondria to further contribute to cellular malfunction, and compromise cell viability, ultimately leading to functional decline. Cisd2, a master gene for Marfan syndrome, plays an essential role in maintaining mitochondrial integrity and functions. As shown by our data, specific deletion of Cisd2 in the cochlea exacerbated the hearing impairment of ARHL in C57BL/6 mice. Increased defects in mitochondrial function, potassium homeostasis and synapse activity were observed in the Cisd2-deleted mouse models. These mechanistic phenotypes combined with oxidative stress contribute to cell death in the whole cochlea. Human patients with obviously deteriorated ARHL had low Cisd2 expression; therefore, Cisd2 may be a potential target for designing therapeutic methods to attenuate the disease progression of ARHL.
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Affiliation(s)
- Hang-Kang Chen
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114201, Taiwan
- Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei 114201, Taiwan
- Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114202, Taiwan
| | - Yen-Hsin Wang
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Cing-Syuan Lei
- Ph.D. Program for Cancer Molecular Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University and Academia Sinica, Taipei 11031, Taiwan
| | - Yu-Ru Guo
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Ming-Chi Tang
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Ting-Fen Tsai
- Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Taipei 11221, Taiwan
- Brain Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Aging and Health Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Genome Research Center, National Yang-Ming University, Taipei 11221, Taiwan
- Institute of Molecular and Genomic Medicine, National Health Research Institutes, Zhunan 35053, Taiwan
| | - Yi-Fan Chen
- Graduate Institute of Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan
- Master Program in Clinical Genomics and Proteomics, School of Pharmacy, Taipei Medical University, Taipei 11031, Taiwan
- International Ph.D. Program for Translational Science, College of Medical Science and Technology, Taipei Medical University, Taipei 11031, Taiwan
- The Ph.D. Program for Translational Medicine, Taipei Medical University, Taipei 11031, Taiwan
| | - Chih-Hung Wang
- Graduate Institute of Medical Sciences, National Defense Medical Center, Taipei 114201, Taiwan
- Graduate Institute of Microbiology and Immunology, National Defense Medical Center, Taipei 114201, Taiwan
- Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei 114202, Taiwan
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2
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Yeo XY, Kwon S, Rinai KR, Lee S, Jung S, Park R. A Consolidated Understanding of the Contribution of Redox Dysregulation in the Development of Hearing Impairment. Antioxidants (Basel) 2024; 13:598. [PMID: 38790703 PMCID: PMC11118506 DOI: 10.3390/antiox13050598] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 04/26/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The etiology of hearing impairment is multifactorial, with contributions from both genetic and environmental factors. Although genetic studies have yielded valuable insights into the development and function of the auditory system, the contribution of gene products and their interaction with alternate environmental factors for the maintenance and development of auditory function requires further elaboration. In this review, we provide an overview of the current knowledge on the role of redox dysregulation as the converging factor between genetic and environmental factor-dependent development of hearing loss, with a focus on understanding the interaction of oxidative stress with the physical components of the peripheral auditory system in auditory disfunction. The potential involvement of molecular factors linked to auditory function in driving redox imbalance is an important promoter of the development of hearing loss over time.
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Affiliation(s)
- Xin Yi Yeo
- Department of Psychological Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore;
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Soohyun Kwon
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
- Department of BioNanotechnology, Gachon University, Seongnam 13120, Republic of Korea
| | - Kimberley R. Rinai
- Department of Life Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Sungsu Lee
- Department of Otolaryngology-Head and Neck Surgery, Chonnam National University Hospital and Medical School, Gwangju 61469, Republic of Korea;
| | - Sangyong Jung
- Department of Medical Science, College of Medicine, CHA University, Seongnam 13488, Republic of Korea;
| | - Raekil Park
- Department of Biomedical Science and Engineering, Gwangju Institute of Science & Technology (GIST), Gwangju 61005, Republic of Korea
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3
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Tan WJT, Song L. Role of mitochondrial dysfunction and oxidative stress in sensorineural hearing loss. Hear Res 2023; 434:108783. [PMID: 37167889 DOI: 10.1016/j.heares.2023.108783] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 04/19/2023] [Accepted: 04/28/2023] [Indexed: 05/13/2023]
Abstract
Sensorineural hearing loss (SNHL) can either be genetically inherited or acquired as a result of aging, noise exposure, or ototoxic drugs. Although the precise pathophysiological mechanisms underlying SNHL remain unclear, an overwhelming body of evidence implicates mitochondrial dysfunction and oxidative stress playing a central etiological role. With its high metabolic demands, the cochlea, particularly the sensory hair cells, stria vascularis, and spiral ganglion neurons, is vulnerable to the damaging effects of mitochondrial reactive oxygen species (ROS). Mitochondrial dysfunction and consequent oxidative stress in cochlear cells can be caused by inherited mitochondrial DNA (mtDNA) mutations (hereditary hearing loss and aminoglycoside-induced ototoxicity), accumulation of acquired mtDNA mutations with age (age-related hearing loss), mitochondrial overdrive and calcium dysregulation (noise-induced hearing loss and cisplatin-induced ototoxicity), or accumulation of ototoxic drugs within hair cell mitochondria (drug-induced hearing loss). In this review, we provide an overview of our current knowledge on the role of mitochondrial dysfunction and oxidative stress in the development of SNHL caused by genetic mutations, aging, exposure to excessive noise, and ototoxic drugs. We also explore the advancements in antioxidant therapies for the different forms of acquired SNHL that are being evaluated in preclinical and clinical studies.
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Affiliation(s)
- Winston J T Tan
- Department of Surgery (Otolaryngology), Yale University School of Medicine, New Haven, CT, 06510, USA; Department of Physiology, Faculty of Medical and Health Sciences, The University of Auckland, Auckland, 1023, New Zealand.
| | - Lei Song
- Department of Surgery (Otolaryngology), Yale University School of Medicine, New Haven, CT, 06510, USA; Department of Otolaryngology - Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, 200125, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, 200125, China.
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4
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Du P, Liu T, Luo P, Li H, Tang W, Zong S, Xiao H. SIRT3/GLUT4 signaling activation by metformin protect against cisplatin-induced ototoxicity in vitro. Arch Toxicol 2023; 97:1147-1162. [PMID: 36800006 DOI: 10.1007/s00204-023-03457-9] [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: 12/11/2022] [Accepted: 02/02/2023] [Indexed: 02/18/2023]
Abstract
Cisplatin is highly effective for killing tumor cells. However, as one of its side effects, ototoxicity limits the clinical application of cisplatin. The mechanisms of cisplatin-induced ototoxicity have not been fully clarified yet. SIRT3 is a deacetylated protein mainly located in mitochondria, which regulates a variety of physiological processes in cells. The role of SIRT3 in cisplatin-induced hair cell injury has not been founded. In this study, primary cultured cochlear explants exposed to 5 μM cisplatin, as well as OC-1 cells exposed to 10 μM cisplatin, were used to establish models of cisplatin-induced ototoxicity in vitro. We found that when combined with cisplatin, metformin (75 μM) significantly up-regulated the expression of SIRT3 and alleviated cisplatin-induced apoptosis of hair cells. We regulated the expression of SIRT3 to explore the role of SIRT3 in cisplatin-induced auditory hair cell injury. Overexpression of SIRT3 promoted the survival of auditory hair cells and alleviated the apoptosis of auditory hair cells. In contrast, knockdown of SIRT3 impaired the protective effect of metformin and exacerbated cisplatin injury. In addition, we found that the protective effect of SIRT3 may be achieved by regulating GLUT4 translocation and rescuing impaired glucose uptake caused by cisplatin. Our study confirmed that upregulation of SIRT3 may antagonize cisplatin-induced ototoxicity, and provided a new perspective for the study of cisplatin-induced ototoxicity.
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Affiliation(s)
- Peiyu Du
- Department of Otolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Tianyi Liu
- Department of Otolaryngology-Head and Neck Surgery, Renmin Hospital of Wuhan University, Wuhan, China
| | - Pan Luo
- Department of Otolaryngology-Head and Neck Surgery, Wuhan Central Hospital, Wuhan, China
| | - Hejie Li
- Department of Otolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Wei Tang
- Department of Otolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China
| | - Shimin Zong
- Department of Otolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
| | - Hongjun Xiao
- Department of Otolaryngology-Head and Neck Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
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5
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McQuate A, Knecht S, Raible DW. Activity regulates a cell type-specific mitochondrial phenotype in zebrafish lateral line hair cells. eLife 2023; 12:e80468. [PMID: 36912880 PMCID: PMC10129330 DOI: 10.7554/elife.80468] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 03/10/2023] [Indexed: 03/14/2023] Open
Abstract
Hair cells of the inner ear are particularly sensitive to changes in mitochondria, the subcellular organelles necessary for energy production in all eukaryotic cells. There are over 30 mitochondrial deafness genes, and mitochondria are implicated in hair cell death following noise exposure, aminoglycoside antibiotic exposure, as well as in age-related hearing loss. However, little is known about the basic aspects of hair cell mitochondrial biology. Using hair cells from the zebrafish lateral line as a model and serial block-face scanning electron microscopy, we have quantifiably characterized a unique hair cell mitochondrial phenotype that includes (1) a high mitochondrial volume and (2) specific mitochondrial architecture: multiple small mitochondria apically, and a reticular mitochondrial network basally. This phenotype develops gradually over the lifetime of the hair cell. Disrupting this mitochondrial phenotype with a mutation in opa1 impacts mitochondrial health and function. While hair cell activity is not required for the high mitochondrial volume, it shapes the mitochondrial architecture, with mechanotransduction necessary for all patterning, and synaptic transmission necessary for the development of mitochondrial networks. These results demonstrate the high degree to which hair cells regulate their mitochondria for optimal physiology and provide new insights into mitochondrial deafness.
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Affiliation(s)
- Andrea McQuate
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Department of Otolaryngology-HNS, University of WashingtonSeattleUnited States
| | - Sharmon Knecht
- Department of Biological Structure, University of WashingtonSeattleUnited States
| | - David W Raible
- Department of Biological Structure, University of WashingtonSeattleUnited States
- Department of Otolaryngology-HNS, University of WashingtonSeattleUnited States
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6
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Finding the balance: The elusive mechanisms underlying auditory hair cell mitochondrial biogenesis and mitophagy. Hear Res 2023; 428:108664. [PMID: 36566644 DOI: 10.1016/j.heares.2022.108664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 11/23/2022] [Accepted: 12/07/2022] [Indexed: 12/13/2022]
Abstract
In all cell types, mitochondrial biogenesis is balanced with mitophagy to maintain a healthy mitochondrial pool that sustains specific energetic demands. Cell types that have a higher energetic burden, such as skeletal muscle cells and cardiomyocytes, will subsequently develop high mitochondrial volumes. In these cells, calcium influx during activity triggers cascades leading to activation of the co-transcriptional regulation factor PGC-1α, a master regulator of mitochondrial biogenesis, in a well-defined pathway. Despite the advantages in ATP production, high mitochondrial volumes might prove to be perilous, as it increases exposure to reactive oxygen species produced during oxidative phosphorylation. Mechanosensory hair cells are highly metabolically active cells, with high total mitochondrial volumes to meet that demand. However, the mechanisms leading to expansion and maintenance of the hair cell mitochondrial pool are not well defined. Calcium influx during mechanotransduction and synaptic transmission regulate hair cell mitochondria, leading to a possibility that similar to skeletal muscle and cardiomyocytes, intracellular calcium underlies the expansion of the hair cell mitochondrial volume. This review briefly summarizes the potential mechanisms underlying mitochondrial biogenesis in other cell types and in hair cells. We propose that hair cell mitochondrial biogenesis is primarily product of cellular differentiation rather than calcium influx, and that the hair cell high mitochondrial volume renders them more susceptible to reactive oxygen species increased by calcium flux than other cell types.
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Lysakowski A, Govindaraju AC, Raphael RM. Structural and functional diversity of mitochondria in vestibular/cochlear hair cells and vestibular calyx afferents. Hear Res 2022; 426:108612. [PMID: 36223702 DOI: 10.1016/j.heares.2022.108612] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2022] [Revised: 07/21/2022] [Accepted: 09/19/2022] [Indexed: 11/30/2022]
Abstract
Mitochondria supply energy in the form of ATP to drive a plethora of cellular processes. In heart and liver cells, mitochondria occupy over 20% of the cellular volume and the major need for ATP is easily identifiable - i.e., to drive cross-bridge recycling in cardiac cells or biosynthetic machinery in liver cells. In vestibular and cochlear hair cells the overall cellular mitochondrial volume is much less, and mitochondria structure varies dramatically in different regions of the cell. The regional demands for ATP and cellular forces that govern mitochondrial structure and localization are not well understood. Below we review our current understanding of the heterogeneity of form and function in hair cell mitochondria. A particular focus of this review will be on regional specialization in vestibular hair cells, where large mitochondria are found beneath the cuticular plate in close association with the striated organelle. Recent findings on the role of mitochondria in hair cell death and aging are covered along with potential therapeutic approaches. Potential avenues for future research are discussed, including the need for integrated computational modeling of mitochondrial function in hair cells and the vestibular afferent calyx.
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Affiliation(s)
- Anna Lysakowski
- Department of Anatomy and Cell Biology, University of Illinois at Chicago, 808 S. Wood St., M/C 512, Chicago, IL 60605, USA.
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8
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Approaches to Mitigate Mitochondrial Dysfunction in Sensorineural Hearing Loss. Ann Biomed Eng 2022; 50:1762-1770. [PMID: 36369597 DOI: 10.1007/s10439-022-03103-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 10/18/2022] [Indexed: 11/13/2022]
Abstract
Mitochondria are highly dynamic multifaceted organelles with various functions including cellular energy metabolism, reactive oxygen species (ROS) generation, calcium homeostasis, and apoptosis. Because of these diverse functions, mitochondria are key regulators of cell survival and death, and their dysfunction is implicated in numerous diseases, particularly neurodegenerative disorders such as Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease. One of the most common neurodegenerative disorders is sensorineural hearing loss (SNHL). SNHL primarily originates from the degenerative changes in the cochlea, which is the auditory portion of the inner ear. Many cochlear cells contain an abundance of mitochondria and are metabolically highly active, rendering them susceptible to mitochondrial dysfunction. Indeed, the causal role of mitochondrial dysfunction in SNHL progression is well established, and therefore, targeted for treatment. In this review, we aim to compile the emerging findings in the literature indicating the role of mitochondrial dysfunction in the progression of sensorineural hearing loss and highlight potential therapeutics targeting mitochondrial dysfunction for hearing loss treatment.
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9
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Holmgren M, Sheets L. Influence of Mpv17 on Hair-Cell Mitochondrial Homeostasis, Synapse Integrity, and Vulnerability to Damage in the Zebrafish Lateral Line. Front Cell Neurosci 2021; 15:693375. [PMID: 34413725 PMCID: PMC8369198 DOI: 10.3389/fncel.2021.693375] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 06/16/2021] [Indexed: 01/27/2023] Open
Abstract
Noise exposure is particularly stressful to hair-cell mitochondria, which must produce enough energy to meet high metabolic demands as well as regulate local intracellular Ca2+ concentrations. Mitochondrial Inner Membrane Protein 17 (Mpv17) functions as a non-selective cation channel and plays a role in maintaining mitochondrial homeostasis. In zebrafish, hair cells in mpv17a9/a9 mutants displayed elevated levels of reactive oxygen species (ROS), elevated mitochondrial calcium, hyperpolarized transmembrane potential, and greater vulnerability to neomycin, indicating impaired mitochondrial function. Using a strong water current to overstimulate hair cells in the zebrafish lateral line, we observed mpv17a9/a9 mutant hair cells were more vulnerable to morphological disruption than wild type (WT) siblings simultaneously exposed to the same stimulus. To determine the role of mitochondrial homeostasis on hair-cell synapse integrity, we surveyed synapse number in mpv17a9/a9 mutants and WT siblings as well as the sizes of presynaptic dense bodies (ribbons) and postsynaptic densities immediately following stimulus exposure. We observed mechanically injured mpv17a9/a9 neuromasts were not more vulnerable to synapse loss; they lost a similar number of synapses per hair cell relative to WT. Additionally, we quantified the size of hair cell pre- and postsynaptic structures following stimulation and observed significantly enlarged WT postsynaptic densities, yet relatively little change in the size of mpv17a9/a9 postsynaptic densities following stimulation. These results suggest chronically impaired hair-cell mitochondrial activity influences postsynaptic size under homeostatic conditions but does not exacerbate synapse loss following mechanical injury.
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Affiliation(s)
- Melanie Holmgren
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Lavinia Sheets
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, United States
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10
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Holmgren M, Sheets L. Using the Zebrafish Lateral Line to Understand the Roles of Mitochondria in Sensorineural Hearing Loss. Front Cell Dev Biol 2021; 8:628712. [PMID: 33614633 PMCID: PMC7892962 DOI: 10.3389/fcell.2020.628712] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 12/23/2020] [Indexed: 01/05/2023] Open
Abstract
Hair cells are the mechanosensory receptors of the inner ear and can be damaged by noise, aging, and ototoxic drugs. This damage often results in permanent sensorineural hearing loss. Hair cells have high energy demands and rely on mitochondria to produce ATP as well as contribute to intracellular calcium homeostasis. In addition to generating ATP, mitochondria produce reactive oxygen species, which can lead to oxidative stress, and regulate cell death pathways. Zebrafish lateral-line hair cells are structurally and functionally analogous to cochlear hair cells but are optically and pharmacologically accessible within an intact specimen, making the zebrafish a good model in which to study hair-cell mitochondrial activity. Moreover, the ease of genetic manipulation of zebrafish embryos allows for the study of mutations implicated in human deafness, as well as the generation of transgenic models to visualize mitochondrial calcium transients and mitochondrial activity in live organisms. Studies of the zebrafish lateral line have shown that variations in mitochondrial activity can predict hair-cell susceptibility to damage by aminoglycosides or noise exposure. In addition, antioxidants have been shown to protect against noise trauma and ototoxic drug–induced hair-cell death. In this review, we discuss the tools and findings of recent investigations into zebrafish hair-cell mitochondria and their involvement in cellular processes, both under homeostatic conditions and in response to noise or ototoxic drugs. The zebrafish lateral line is a valuable model in which to study the roles of mitochondria in hair-cell pathologies and to develop therapeutic strategies to prevent sensorineural hearing loss in humans.
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Affiliation(s)
- Melanie Holmgren
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
| | - Lavinia Sheets
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States.,Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO, United States
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11
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Perkins G, Lee JH, Park S, Kang M, Perez-Flores MC, Ju S, Phillips G, Lysakowski A, Gratton MA, Yamoah EN. Altered Outer Hair Cell Mitochondrial and Subsurface Cisternae Connectomics Are Candidate Mechanisms for Hearing Loss in Mice. J Neurosci 2020; 40:8556-8572. [PMID: 33020216 PMCID: PMC7605424 DOI: 10.1523/jneurosci.2901-19.2020] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 09/21/2020] [Accepted: 09/24/2020] [Indexed: 11/21/2022] Open
Abstract
Organelle crosstalk is vital for cellular functions. The propinquity of mitochondria, ER, and plasma membrane promote regulation of multiple functions, which include intracellular Ca2+ flux, and cellular biogenesis. Although the purposes of apposing mitochondria and ER have been described, an understanding of altered organelle connectomics related to disease states is emerging. Since inner ear outer hair cell (OHC) degeneration is a common trait of age-related hearing loss, the objective of this study was to investigate whether the structural and functional coupling of mitochondria with subsurface cisternae (SSC) was affected by aging. We applied functional and structural probes to equal numbers of male and female mice with a hearing phenotype akin to human aging. We discovered the polarization of cristae and crista junctions in mitochondria tethered to the SSC in OHCs. Aging was associated with SSC stress and decoupling of mitochondria with the SSC, mitochondrial fission/fusion imbalance, a remarkable reduction in mitochondrial and cytoplasmic Ca2+ levels, reduced K+-induced Ca2+ uptake, and marked plasticity of cristae membranes. A model of structure-based ATP production predicts profound energy stress in older OHCs. This report provides data suggesting that altered membrane organelle connectomics may result in progressive hearing loss.
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Affiliation(s)
- Guy Perkins
- National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California 92093
| | | | | | | | | | - Saeyeon Ju
- National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California 92093
| | - Grady Phillips
- Washington University School of Medicine, St. Louis, Missouri 63110
| | - Anna Lysakowski
- Departments of Anatomy and Cell Biology and Otolaryngology, University of Illinois at Chicago, Chicago, Illinois 60612
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12
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Murakami K, Yurgel ME, Stahl BA, Masek P, Mehta A, Heidker R, Bollinger W, Gingras RM, Kim YJ, Ja WW, Suter B, DiAngelo JR, Keene AC. translin Is Required for Metabolic Regulation of Sleep. Curr Biol 2016; 26:972-980. [PMID: 27020744 DOI: 10.1016/j.cub.2016.02.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Revised: 12/13/2015] [Accepted: 02/03/2016] [Indexed: 01/28/2023]
Abstract
Dysregulation of sleep or feeding has enormous health consequences. In humans, acute sleep loss is associated with increased appetite and insulin insensitivity, while chronically sleep-deprived individuals are more likely to develop obesity, metabolic syndrome, type II diabetes, and cardiovascular disease. Conversely, metabolic state potently modulates sleep and circadian behavior; yet, the molecular basis for sleep-metabolism interactions remains poorly understood. Here, we describe the identification of translin (trsn), a highly conserved RNA/DNA binding protein, as essential for starvation-induced sleep suppression. Strikingly, trsn does not appear to regulate energy stores, free glucose levels, or feeding behavior suggesting the sleep phenotype of trsn mutant flies is not a consequence of general metabolic dysfunction or blunted response to starvation. While broadly expressed in all neurons, trsn is transcriptionally upregulated in the heads of flies in response to starvation. Spatially restricted rescue or targeted knockdown localizes trsn function to neurons that produce the tachykinin family neuropeptide Leucokinin. Manipulation of neural activity in Leucokinin neurons revealed these neurons to be required for starvation-induced sleep suppression. Taken together, these findings establish trsn as an essential integrator of sleep and metabolic state, with implications for understanding the neural mechanism underlying sleep disruption in response to environmental perturbation.
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Affiliation(s)
- Kazuma Murakami
- Department of Biology, University of Nevada, Reno, NV 89557.,Department of Biological Sciences, Florida Atlantic University, John D MacArthur Campus, Jupiter, FL, USA
| | - Maria E Yurgel
- Department of Biology, University of Nevada, Reno, NV 89557.,Department of Biological Sciences, Florida Atlantic University, John D MacArthur Campus, Jupiter, FL, USA
| | - Bethany A Stahl
- Department of Biological Sciences, Florida Atlantic University, John D MacArthur Campus, Jupiter, FL, USA
| | - Pavel Masek
- Department of Biology, SUNY Binghamton, Binghamton, NY 13902
| | - Aradhana Mehta
- Department of Biology, University of Nevada, Reno, NV 89557
| | | | - Wesley Bollinger
- Department of Biology, University of Nevada, Reno, NV 89557.,Department of Biological Sciences, Florida Atlantic University, John D MacArthur Campus, Jupiter, FL, USA
| | | | - Young-Joon Kim
- School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, South Korea
| | - William W Ja
- Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL 33458
| | - Beat Suter
- University of Bern, Institute of Cell Biology, Bern, Switzerland, CH-3012
| | - Justin R DiAngelo
- Department of Biology, Hofstra University, Hempstead, NY, 11549.,Division of Science, Penn State Berks, Reading, PA 19610
| | - Alex C Keene
- Department of Biology, University of Nevada, Reno, NV 89557.,Department of Biological Sciences, Florida Atlantic University, John D MacArthur Campus, Jupiter, FL, USA
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13
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Neuroglobin Expression in the Mammalian Auditory System. Mol Neurobiol 2015; 53:1461-1477. [PMID: 25636685 DOI: 10.1007/s12035-014-9082-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Accepted: 12/29/2014] [Indexed: 01/07/2023]
Abstract
The energy-yielding pathways that provide the large amounts of metabolic energy required by inner ear sensorineural cells are poorly understood. Neuroglobin (Ngb) is a neuron-specific hemoprotein of the globin family, which is suggested to be involved in oxidative energy metabolism. Here, we present quantitative real-time reverse transcription PCR, in situ hybridization, immunohistochemical, and Western blot evidence that neuroglobin is highly expressed in the mouse and rat cochlea. For primary cochlea neurons, Ngb expression is limited to the subpopulation of type I spiral ganglion cells, those which innervate inner hair cells, while the subpopulation of type II spiral ganglion cells which innervate the outer hair cells do not express Ngb. We further investigated Ngb distribution in rat, mouse, and human auditory brainstem centers, and found that the cochlear nuclei and superior olivary complex (SOC) also express considerable amounts of Ngb. Notably, the majority of olivocochlear neurons, those which provide efferent innervation of outer hair cells as identified by neuronal tract tracing, were Ngb-immunoreactive. We also observed that neuroglobin in the SOC frequently co-localized with neuronal nitric oxide synthase, the enzyme responsible for nitric oxide production. Our findings suggest that neuroglobin is well positioned to play an important physiologic role in the oxygen homeostasis of the peripheral and central auditory nervous system, and provides the first evidence that Ngb signal differentiates the central projections of the inner and outer hair cells.
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14
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Zampini V, Johnson SL, Franz C, Knipper M, Holley MC, Magistretti J, Russo G, Marcotti W, Masetto S. Fine Tuning of CaV1.3 Ca2+ channel properties in adult inner hair cells positioned in the most sensitive region of the Gerbil Cochlea. PLoS One 2014; 9:e113750. [PMID: 25409445 PMCID: PMC4237458 DOI: 10.1371/journal.pone.0113750] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 10/28/2014] [Indexed: 01/15/2023] Open
Abstract
Hearing relies on faithful signal transmission by cochlear inner hair cells (IHCs) onto auditory fibres over a wide frequency and intensity range. Exocytosis at IHC ribbon synapses is triggered by Ca2+ inflow through CaV1.3 (L-type) Ca2+ channels. We investigated the macroscopic (whole-cell) and elementary (cell-attached) properties of Ca2+ currents in IHCs positioned at the middle turn (frequency ∼2 kHz) of the adult gerbil cochlea, which is their most sensitive hearing region. Using near physiological recordings conditions (body temperature and a Na+ based extracellular solution), we found that the macroscopic Ca2+ current activates and deactivates very rapidly (time constant below 1 ms) and inactivates slowly and only partially. Single-channel recordings showed an elementary conductance of 15 pS, a sub-ms latency to first opening, and a very low steady-state open probability (Po: 0.024 in response to 500-ms depolarizing steps at ∼−18 mV). The value of Po was significantly larger (0.06) in the first 40 ms of membrane depolarization, which corresponds to the time when most Ca2+ channel openings occurred clustered in bursts (mean burst duration: 19 ms). Both the Po and the mean burst duration were smaller than those previously reported in high-frequency basal IHCs. Finally, we found that middle turn IHCs are likely to express about 4 times more Ca2+ channels per ribbon than basal cells. We propose that middle-turn IHCs finely-tune CaV1.3 Ca2+ channel gating in order to provide reliable information upon timing and intensity of lower-frequency sounds.
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Affiliation(s)
- Valeria Zampini
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Stuart L. Johnson
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Christoph Franz
- Department of Otolaryngology, Tübingen Hearing Research Centre, Laboratory of Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Marlies Knipper
- Department of Otolaryngology, Tübingen Hearing Research Centre, Laboratory of Molecular Physiology of Hearing, University of Tübingen, Tübingen, Germany
| | - Matthew C. Holley
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Jacopo Magistretti
- Department of Biology and Biotechnology “Lazzaro Spallanzani”, University of Pavia, Pavia, Italy
| | - Giancarlo Russo
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
| | - Walter Marcotti
- Department of Biomedical Science, University of Sheffield, Sheffield, United Kingdom
| | - Sergio Masetto
- Department of Brain and Behavioral Sciences, University of Pavia, Pavia, Italy
- * E-mail:
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15
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ATP hydrolysis is critically required for function of CaV1.3 channels in cochlear inner hair cells via fueling Ca2+ clearance. J Neurosci 2014; 34:6843-8. [PMID: 24828638 DOI: 10.1523/jneurosci.4990-13.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Sound encoding is mediated by Ca(2+) influx-evoked release of glutamate at the ribbon synapse of inner hair cells. Here we studied the role of ATP in this process focusing on Ca(2+) current through CaV1.3 channels and Ca(2+) homeostasis in mouse inner hair cells. Patch-clamp recordings and Ca(2+) imaging demonstrate that hydrolyzable ATP is essential to maintain synaptic Ca(2+) influx in inner hair cells via fueling Ca(2+)-ATPases to avoid an increase in cytosolic [Ca(2+)] and subsequent Ca(2+)/calmodulin-dependent inactivation of CaV1.3 channels.
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16
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Daniel SJ, McIntosh M, Akinpelu OV, Rohlicek CV. Hearing outcome of early postnatal exposure to hypoxia in Sprague-Dawley rats. J Laryngol Otol 2014; 128:1-5. [PMID: 24735907 DOI: 10.1017/s002221511300265x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Objective: To determine the effect of experimentally induced hypoxia, in the first 10 days of life, on physiological hearing in a Sprague-Dawley rat model. Methods: A prospective, controlled animal study was carried out using 22 male rat pups. The rats in the hypoxic group (n = 12) were reared in hypoxia for the first 10 days of life, and subsequently reared in normoxia, while those in the control group (n = 10) were reared in normoxia for the duration of the experiment. Hearing was assessed using auditory brainstem response testing at approximately 72 days of age. Results: The hypoxia group had higher auditory brainstem response thresholds for all frequencies tested (more pronounced at 16 kHz), compared with controls. Wave I-V inter-peak latencies were more prolonged in the hypoxic rats, while both groups had similar wave I latencies. Conclusion: Chronic postnatal hypoxia induced permanent hearing loss in this Sprague-Dawley rat model. Prolonged wave I-V inter-peak latencies suggested functional abnormality in the central auditory pathway.
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Affiliation(s)
- S J Daniel
- Department of Otolaryngology - Head and Neck Surgery, Montreal Children's Hospital - McGill University Health Centre, Quebec, Canada
| | - M McIntosh
- Division of Cardiology, Montreal Children's Hospital - McGill University Health Centre, Quebec, Canada
| | - O V Akinpelu
- McGill Auditory Sciences Laboratory, Montreal Children's Hospital - McGill University Health Centre, Quebec, Canada
| | - C V Rohlicek
- Division of Cardiology, Montreal Children's Hospital - McGill University Health Centre, Quebec, Canada
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17
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The mitochondrion: a perpetrator of acquired hearing loss. Hear Res 2013; 303:12-9. [PMID: 23361190 DOI: 10.1016/j.heares.2013.01.006] [Citation(s) in RCA: 142] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Revised: 12/22/2012] [Accepted: 01/06/2013] [Indexed: 02/01/2023]
Abstract
Age, drugs, and noise are major causes of acquired hearing loss. The involvement of reactive oxygen species (ROS) in hair cell death has long been discussed, but there is considerably less information available as to the mechanisms underlying ROS formation. Most cellular ROS arise in mitochondria and this review will evaluate evidence for mitochondrial pathology in general and dysfunction of the mitochondrial respiratory chain in particular in acquired hearing loss. We will discuss evidence that different pathways can lead to the generation of ROS and that oxidative stress might not necessarily be causal to all three pathologies. Finally, we will detail recent advances in exploiting knowledge of aminoglycoside-mitochondria interactions for the development of non-ototoxic antibacterials. This article is part of a Special Issue entitled "Annual Reviews 2013".
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18
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Ritterson Lew C, Tolan DR. Targeting of several glycolytic enzymes using RNA interference reveals aldolase affects cancer cell proliferation through a non-glycolytic mechanism. J Biol Chem 2012; 287:42554-63. [PMID: 23093405 DOI: 10.1074/jbc.m112.405969] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In cancer, glucose uptake and glycolysis are increased regardless of the oxygen concentration in the cell, a phenomenon known as the Warburg effect. Several (but not all) glycolytic enzymes have been investigated as potential therapeutic targets for cancer treatment using RNAi. Here, four previously untargeted glycolytic enzymes, aldolase A, glyceraldehyde 3-phosphate dehydrogenase, triose phosphate isomerase, and enolase 1, are targeted using RNAi in Ras-transformed NIH-3T3 cells. Of these enzymes, knockdown of aldolase causes the greatest effect, inhibiting cell proliferation by 90%. This defect is rescued by expression of exogenous aldolase. However, aldolase knockdown does not affect glycolytic flux or intracellular ATP concentration, indicating a non-metabolic cause for the cell proliferation defect. Furthermore, this defect could be rescued with an enzymatically dead aldolase variant that retains the known F-actin binding ability of aldolase. One possible model for how aldolase knockdown may inhibit transformed cell proliferation is through its disruption of actin-cytoskeleton dynamics in cell division. Consistent with this hypothesis, aldolase knockdown cells show increased multinucleation. These results are compared with other studies targeting glycolytic enzymes with RNAi in the context of cancer cell proliferation and suggest that aldolase may be a useful target in the treatment of cancer.
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19
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Jacobs PG, Konrad-Martin D, McMillan GP, McDermott D, Fausti SA, Kagen D, Wan EA. Influence of acute hyperglycemia on otoacoustic emissions and the medial olivocochlear reflex. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2012; 131:1296-1306. [PMID: 22352503 PMCID: PMC3292605 DOI: 10.1121/1.3676609] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/16/2011] [Accepted: 12/20/2011] [Indexed: 05/29/2023]
Abstract
Stimulus-frequency (SF) otoacoustic emission (OAE) amplitude and the amplitude of medial olivocochlear (MOC) inhibition of SF OAEs for ipsilateral, contralateral and bilateral MOC reflex elicitors were recorded in six subjects with type 2 diabetes during a glucose tolerance test (GTT). Five of the six subjects were tested twice for a total of 11 trials and three subjects were tested in a control experiment. During the GTT experiment, the subjects' blood glucose was elevated from a euglycemic level below 150 mg/dL to a hyperglycemic level above 160 mg/dL following the consumption of a bolus of 80 g of sugar. A subset of three subjects were tested in a control experiment during which SF OAE and MOC reflex measurements were made while blood sugar levels remained constant within the euglycemic region. Mean SF OAE amplitudes were elevated following glucose consumption. A statistically significant increase in MOC inhibition amplitude was observed during elevated sugar levels for the 11 GTT trials. Maximum inhibition occurred about an hour after glucose consumption when blood glucose levels peaked. Results indicate that acute hyperglycemia influences efferent control of the cochlea in people with type 2 diabetes.
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Affiliation(s)
- Peter G Jacobs
- VA RR&D National Center for Rehabilitative Auditory Research, Portland VA Medical Center, 3710 SW U.S. Veterans Hospital Road, Portland, Oregon 97239, USA.
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20
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Hu BH, Henderson D, Yang WP. The impact of mitochondrial energetic dysfunction on apoptosis in outer hair cells of the cochlea following exposure to intense noise. Hear Res 2007; 236:11-21. [PMID: 18082984 DOI: 10.1016/j.heares.2007.11.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2007] [Revised: 10/11/2007] [Accepted: 11/08/2007] [Indexed: 01/11/2023]
Abstract
Previous studies have shown that exposure to intense noise causes outer hair cells (OHCs) to die, primarily through the process of apoptotic degeneration. The current study was designed to examine the regulatory role of mitochondrial bioenergetic function in controlling the initiation and execution of the apoptotic process of OHCs. Chinchilla cochleae were treated with 3-nitropropionic acid (3-NP, 20 or 50mM), an irreversible inhibitor of succinate dehydrogenase (SDH), to inhibit the mitochondrial energy production before and after exposure to 75 pairs of impulses at 155dB pSPL. Comparison of the noise-exposed cochleae treated with and without 3-NP revealed that the inhibition of SDH activity delayed nuclear degradation in apoptotic OHCs. However, the initiation of apoptosis appeared to be undeterred. There was no major shift of cell death pathways from apoptosis to necrosis, although a small portion of OHCs showed signs of secondary necrosis. Collectively, the results of the study suggest that, while the mitochondrial energetic function plays an important role in regulating the apoptotic process, its dysfunction has a limited influence on the suppression of apoptotic induction in OHCs following exposure to intense noise.
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Affiliation(s)
- Bo Hua Hu
- Center for Hearing and Deafness, State University of New York at Buffalo, 137 Cary Hall, 3435 Main Street, Buffalo NY 14214, USA.
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21
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Mazurek B, Haupt H, Georgiewa P, Klapp BF, Reisshauer A. A model of peripherally developing hearing loss and tinnitus based on the role of hypoxia and ischemia. Med Hypotheses 2006; 67:892-9. [PMID: 16757123 DOI: 10.1016/j.mehy.2006.03.040] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2006] [Accepted: 03/30/2006] [Indexed: 10/24/2022]
Abstract
The incidence of sensorineural hearing loss often caused by direct damage to the cochlear hair cells is by far more frequent and more serious than disorders affecting the external ear or the middle ear. Mechanisms that are discussed to be relevant for the genesis of tinnitus and acquired hearing impairment are hair cell loss, signal transduction disturbances in the region of the outer and inner hair cells and the spiral ganglion, impairment of cochlear blood flow, mechanical disturbance, and hypoxia and ischemia. The present model surveys the possible cellular and molecular biological causes of peripherally developing hearing loss and tinnitus. In particular, the paper discusses the roles of hypoxia and ischemia in the cochlea and in the etiology of the neurosensory types of tinnitus. Peripheral origins of hearing disturbances and tinnitus may be: (a) damage to the stereocilia and the tip links, (b) dysfunction of potassium channels or (c) modification of the glutamate release. Moreover, the hypoxia inducible factor-1 may have an important role to play as a key transcription factor in the cells' adaptation to hypoxia and ischemia. An impairment of the cochlear blood flow may be induced by the expression of target genes like nitrogen monoxide synthase and endothelin-1 resulting in tinnitus. The paper discusses consequences resulting from the present model for the medical treatment of peripherally developing tinnitus and hearing loss.
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MESH Headings
- Cochlea/blood supply
- Cochlea/innervation
- Cochlea/pathology
- Cochlea/physiopathology
- Ganglia, Spinal/pathology
- Ganglia, Spinal/physiopathology
- Hair Cells, Auditory, Inner/pathology
- Hair Cells, Auditory, Inner/physiopathology
- Hair Cells, Auditory, Outer/pathology
- Hair Cells, Auditory, Outer/physiopathology
- Hearing Loss, Sensorineural/etiology
- Hearing Loss, Sensorineural/physiopathology
- Humans
- Hypoxia/complications
- Hypoxia/metabolism
- Hypoxia-Inducible Factor 1/metabolism
- Ischemia/complications
- Ischemia/metabolism
- Models, Biological
- Signal Transduction
- Tinnitus/etiology
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Affiliation(s)
- Birgit Mazurek
- Molecular Biological Research Laboratory and Tinnitus Center, Department of Otorhinolaryngology, Charité-University Medicine Berlin, Campus Charité Mitte, Schumannstrasse 20/21, 10117 Berlin, Germany.
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22
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Bittar RSM, Bottino MA, Simoceli L, Venosa AR. Labirintopatia secundária aos distúrbios do metabolismo do açúcar: realidade ou fantasia? ACTA ACUST UNITED AC 2004. [DOI: 10.1590/s0034-72992004000600016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
As vestibulopatias atribuídas aos distúrbios do metabolismo do açúcar são ainda hoje um tema controverso na literatura pela falta de demonstração objetiva que relacione causa e efeito. OBJETIVO: Nosso objetivo é relatar os resultados seriados do Teste de Integração Sensorial no acompanhamento dos pacientes portadores de DMA tratados com dieta fracionada e restrição de glicose. FORMA DE ESTUDO: Retrospectivo, inclui um desenho de descrição de casos. MÉTODO: Foram avaliadas as respostas de 21 pacientes portadores de distúrbios do metabolismo do açúcar e tontura submetidos à dieta fracionada com restrição de glicose. A medição objetiva do equilíbrio corporal dos pacientes foi feita pela Posturografia Dinâmica Computadorizada, utilizando-se o protocolo do Teste de Integração Sensorial. RESULTADOS: Após a instituição da dieta, observou-se melhora objetiva significante nas condições que retratam a função vestibular e o equilíbrio corporal dos indivíduos estudados. CONCLUSÃO: Concluímos que o Teste de Integração Sensorial demonstrou ser uma ferramenta útil na documentação da melhora do equilíbrio corporal de pacientes portadores de DMA submetidos à dieta fracionada com restrição de glicose.
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23
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Mazurek B, Winter E, Fuchs J, Haupt H, Gross J. Susceptibility of the hair cells of the newborn rat cochlea to hypoxia and ischemia. Hear Res 2003; 182:2-8. [PMID: 12948595 DOI: 10.1016/s0378-5955(03)00134-5] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hypoxia and ischemia are thought to be important pathogenetic factors in bringing about hearing loss. In order to study the effect of these determinants on the loss of inner and outer hair cells (IHCs/OHCs), we used an in vitro hypoxia and ischemia model of the newborn rat cochlea. The specimens of the organ of Corti were exposed either to hypoxia (10-20 mm Hg) or to normoxic glucose deprivation or to both (ischemia) in artificial perilymph for different exposure periods. The number of IHCs and OHCs was counted and the hair cell loss was compared to controls. Normoxic aglycemia did not cause significant hair cell loss as compared to controls. Hypoxia and ischemia led to hair cell loss in a dose-dependent manner, with the loss in the ischemia groups found to be markedly higher than that in the hypoxia groups. Hypoxia resulted in a mean loss of 8% OHC and of 14% IHC after an 8-h exposure. Ischemia increased the loss to 19% OHC and 39% IHC after the same exposure period of 8 h. Our findings suggest that IHCs are more susceptible to hypoxia/ischemia than OHCs.
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Affiliation(s)
- Birgit Mazurek
- Molecular-Biological Research Laboratory, Department of Otorhinolaryngology, Charité Hospital, Humboldt University, Spandauer Damm 130, Bld. 31, 14050 Berlin, Germany
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24
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Armour G, Mhaskar Y, Rybak L, Dunaway G. Alteration of 6-phosphofructo-1-kinase subunits during neonatal maturation of the rat cochlear cells. Hear Res 2001; 151:149-156. [PMID: 11124462 DOI: 10.1016/s0378-5955(00)00222-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
During postnatal development of rat cochlear cells and the onset of hearing (10-23 days), the increasing endocochlear potential and energy requirements are largely provided by increased glucose utilization. It is well established that the ability of maturing rat tissues to use glucose is directly related to alteration of 6-phosphofructo-1-kinase (PFK) subunits. To gain insight into the alteration of PFK subunit levels in the cochlea from 6 to 60 days of age, PFK subunit types were measured in sections of paraffin-embedded temporal bone using IgG specific for each type of PFK subunit and quantified by computer image analysis. Although the L-type and C-type subunits did not exhibit statistically significant changes in the cochlear structures during maturation, the levels of M-type subunit in the stria vascularis cells, spiral ligament cell types I, II, and III, outer hair cells, inner hair cells, and support cells significantly increased. Also, the type IV and V spiral ligament fibrocytes during this period did not exhibit significant alterations of the M-type subunit. These data suggest that during neonatal development of the cochlear, the elevated levels of the M-type subunit are associated with increased glucose utilization and the onset of hearing.
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MESH Headings
- Animals
- Animals, Newborn
- Cochlea/cytology
- Cochlea/enzymology
- Cochlea/growth & development
- Energy Metabolism
- Glucose/metabolism
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/growth & development
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Outer/cytology
- Hair Cells, Auditory, Outer/growth & development
- Hair Cells, Auditory, Outer/metabolism
- Hearing/physiology
- Immunohistochemistry
- Phosphofructokinase-1/chemistry
- Phosphofructokinase-1/metabolism
- Protein Subunits
- Rats
- Rats, Inbred F344
- Stria Vascularis/cytology
- Stria Vascularis/metabolism
- Tissue Distribution
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Affiliation(s)
- G Armour
- Department of Pharmacology, Division of Otolaryngology, Southern Illinois University School of Medicine, Springfield 62794-9629, USA
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25
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Lamm K, Arnold W. The effect of blood flow promoting drugs on cochlear blood flow, perilymphatic pO(2) and auditory function in the normal and noise-damaged hypoxic and ischemic guinea pig inner ear. Hear Res 2000; 141:199-219. [PMID: 10713508 DOI: 10.1016/s0378-5955(00)00005-8] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The effect of blood flow promoting drugs, such as hydroxyethyl starch (HES) either of low or high molecular weight (HES 70, HES 200), pentoxifylline, ginkgo biloba, naftidrofuryl and betahistine, and various combinations of the drugs was studied in unexposed and noise-exposed (broad-band noise, bandwidth 1-12 kHz, 106 dB SPL, 30 min) guinea pigs. The results were compared without therapy and placebo (isotonic saline, NaCl). The cochlear blood flow (CoBF) and the partial pressure of oxygen in the perilymph (PL-pO(2)) were continuously and simultaneously recorded over a period of 210 min. In addition, cochlear microphonics (CMs), compound action potentials of the auditory nerve (CAPs) and auditory brain stem responses (ABRs) were registered. Noise-induced hearing loss (NIHL) paralleled a decrease of PL-pO(2). Both were found to occur before evidence of reduced CoBF. PL-pO(2) and CoBF declined progressively post-exposure, while CMs, CAPs and ABRs showed no further deterioration or signs of recovery up to 180 min after cessation of noise. Treatment started 60 min post-exposure, respectively after 90 min, without manipulation in unexposed animals, and was then studied for a further 120 min. In unexposed animals, CoBF increased significantly during infusion of HES 70, HES 200, pentoxifylline and betahistine. NaCl, ginkgo biloba and naftidrofuryl did not alter CoBF. PL-pO(2) decreased significantly during infusion of all administered drugs and combinations, except for NaCl. CMs, CAPs and ABRs remained constant, with the exception of increased ABRs after infusion of HES 70 and HES 200. In noise-exposed animals, a sustained therapeutic effect on cochlear ischemia was achieved only by HES 200 and pentoxifylline. HES 70, betahistine and ginkgo biloba compensated cochlear ischemia only during infusion; however, 30-60 min after termination of therapy, no significant difference of values for CoBF was observed compared to the untreated noise-exposed groups. NaCl and naftidrofuryl showed no effect on CoBF. None of the applied drugs had a sustained compensatory effect on cochlear hypoxia. CMs, CAPs and ABRs improved significantly after HES 70, HES 200 and betahistine, resulting in partial recovery of CMs, and partial (betahistine) or even full (HES 70 and HES 200) recovery of CAPs and ABRs. In contrast, NaCl, pentoxifylline, ginkgo biloba and naftidrofuryl had no therapeutic effect on NIHL.
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Affiliation(s)
- K Lamm
- Department of Otolaryngology, Head and Neck Surgery, Klinikum rechts der Isar, Technical University of Munich, Ismaninger Str. 22, D-81675, Munich, Germany.
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26
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Abstract
The mechanosensitive transducer channels of hair cells have long been proposed to be gated directly by tension in the tip links. These are thin, elastic extracellular elements connecting the tips of adjacent stereocilia located on the apical surface of the cell. If this hypothesis is true, the channels should close after destruction of tip links. The hypothesis was tested pharmacologically using receptor currents obtained in response to mechanical stimulation of the stereociliary bundle of outer hair cells isolated from the adult guinea pig cochlea. Application of elastase (20 U/ml) or 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetra-acetic acid (BAPTA; 5 mM), both of which are known to disrupt tip links in other hair-cell preparations, led to the expected irreversible loss of receptor currents. However, the cells then displayed a maintained inward current, implying that channels were left permanently open. This current was similar in magnitude to the receptor current before treatment and was reduced reversibly by known blockers of mechanosensitive channels, namely, dihydrostreptomycin (100 microM), amiloride (300 microM), and gadolinium ions (1 mM). These observations suggest that the maintained current flows through the mechanosensitive channels. Electron microscopical analysis of isolated hair cells, exposed to the same concentrations of elastase or BAPTA as in the electrophysiological experiments, demonstrated an almost total loss of tip links in hair bundles that showed no evidence of other mechanical damage. It is concluded that although the tip links are required for mechanoelectrical transduction, the channels are not gated directly by the tip links.
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