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Lu M, Xian F, Jin X, Hong G, Fu X, Wang S, Li X, Yang H, Li H, Zhang H, Yang Y, Xiao J, Dong H, Liu Y, Shen H, Lv P. Upregulation of the Ca v1.3 channel in inner hair cells by interleukin 6-dependent inflammaging contributes to age-related hearing loss. Aging Cell 2024:e14305. [PMID: 39148148 DOI: 10.1111/acel.14305] [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: 01/17/2024] [Revised: 07/02/2024] [Accepted: 07/24/2024] [Indexed: 08/17/2024] Open
Abstract
Age-related hearing loss (AHL) is the most common sensory disorder amongst the older population. Inflammaging is a ≈chronic low-grade inflammation that worsens with age and is an early sign of AHL; however, the underlying mechanisms remain unclear. We used electrophysiological and genetic approaches to establish the importance of interleukin 6 (IL-6)-dependent inflammation in AHL. Elevated IL-6 in the cochlea enhanced Cav1.3 calcium channel function in the inner hair cell (IHC) synapse in mice with AHL. IL-6 upregulated the Cav1.3 channel via the Janus kinase-mitogen activated kinase pathway, causing neurotransmitter excitotoxicity and synapse impairment; IL-6 deficiency or the administration of a Cav1.3 channel blocker attenuated this age-related damage, and rescued hearing loss. Thus, IL-6-dependent inflammaging upregulated the Cav1.3 channel in IHCs, contributing to AHL. Our findings could help the comprehensive understanding of inflammaging's effects on AHL, aiding in early intervention to protect against hearing decline.
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Affiliation(s)
- Mingshun Lu
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Fuyu Xian
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xishuo Jin
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Guodong Hong
- Medical Science and Technology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, China
| | - Xiaolong Fu
- Shandong Provincial Hospital, Medical Science and Technology Innovation Center, College of Clinical and Basic Medicine, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong, China
- Department of Neurology, Aerospace Center Hospital, School of Life Science, Beijing Institute of Technology, Beijing, China
| | - Shengnan Wang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Xinyu Li
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Haichao Yang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Hongchen Li
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Haiwei Zhang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yuxin Yang
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Jundan Xiao
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
| | - Hui Dong
- Department of Neurology, The Second Hospital of Hebei Medical University, The Key Laboratory of Neurology, Ministry of Education, Hebei Medical University, Neurological Laboratory of Hebei Province, Shijiazhuang, Hebei, China
| | - Yaling Liu
- Department of Neurology, The Second Hospital of Hebei Medical University, The Key Laboratory of Neurology, Ministry of Education, Hebei Medical University, Neurological Laboratory of Hebei Province, Shijiazhuang, Hebei, China
| | - Haitao Shen
- Lab of Pathology, Hebei Medical University,, Shijiazhuang, Hebei, China
- Hebei Collaborative Innovation Center of Tumor Microecological Metabolism Regulation, Affiliated Hospital of Hebei University, Baoding, Hebei, China
| | - Ping Lv
- Department of Pharmacology, The Key Laboratory of Neural and Vascular Biology, Ministry of Education, The Key Laboratory of New Drug Pharmacology and Toxicology, The Hebei Collaboration Innovation Center for Mechanism, Diagnosis and Treatment of Neurological and Psychiatric Disease, Hebei Medical University, Shijiazhuang, Hebei, China
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Lee JH, Park S, Perez-Flores MC, Chen Y, Kang M, Choi J, Levine L, Gratton MA, Zhao J, Notterpek L, Yamoah EN. Demyelination and Na + Channel Redistribution Underlie Auditory and Vestibular Dysfunction in PMP22-Null Mice. eNeuro 2024; 11:ENEURO.0462-23.2023. [PMID: 38378628 PMCID: PMC11059428 DOI: 10.1523/eneuro.0462-23.2023] [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: 11/05/2023] [Revised: 12/14/2023] [Accepted: 12/15/2023] [Indexed: 02/22/2024] Open
Abstract
Altered expression of peripheral myelin protein 22 (PMP22) results in demyelinating peripheral neuropathy. PMP22 exhibits a highly restricted tissue distribution with marked expression in the myelinating Schwann cells of peripheral nerves. Auditory and vestibular Schwann cells and the afferent neurons also express PMP22, suggesting a unique role in hearing and balancing. Indeed, neuropathic patients diagnosed with PMP22-linked hereditary neuropathies often present with auditory and balance deficits, an understudied clinical complication. To investigate the mechanism by which abnormal expression of PMP22 may cause auditory and vestibular deficits, we studied gene-targeted PMP22-null mice. PMP22-null mice exhibit an unsteady gait, have difficulty maintaining balance, and live for only ∼3-5 weeks relative to unaffected littermates. Histological analysis of the inner ear revealed reduced auditory and vestibular afferent nerve myelination and profound Na+ channel redistribution without PMP22. Yet, Na+ current density was unaltered, in stark contrast to increased K+ current density. Atypical postsynaptic densities and a range of neuronal abnormalities in the organ of Corti were also identified. Analyses of auditory brainstem responses (ABRs) and vestibular sensory-evoked potential (VsEP) revealed that PMP22-null mice had auditory and vestibular hypofunction. These results demonstrate that PMP22 is required for hearing and balance, and the protein is indispensable for the formation and maintenance of myelin in the peripheral arm of the eighth nerve. Our findings indicate that myelin abnormalities and altered signal propagation in the peripheral arm of the auditory nerve are likely causes of auditory deficits in patients with PMP22-linked neuropathies.
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Affiliation(s)
- Jeong Han Lee
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Seojin Park
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
- Prestige BioPharma, Busan 67264, South Korea
| | - Maria C Perez-Flores
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Yingying Chen
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Mincheol Kang
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
- Prestige BioPharma, Busan 67264, South Korea
| | - Jinsil Choi
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Lauren Levine
- Program in Audiology and Communication Sciences, Washington University, St. Louis 63110, Missouri
| | | | - Jie Zhao
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Lucia Notterpek
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno 89557, Nevada
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3
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Ranjdoost F, Ghaffari ME, Azimi F, Mohammadi A, Fouladi-Fard R, Fiore M. Association between air pollution and sudden sensorineural hearing loss (SSHL): A systematic review and meta-analysis. ENVIRONMENTAL RESEARCH 2023; 239:117392. [PMID: 37838197 DOI: 10.1016/j.envres.2023.117392] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 09/23/2023] [Accepted: 10/11/2023] [Indexed: 10/16/2023]
Abstract
Recent studies have indicated that air pollution (AP) has harmful effects on hearing and ear diseases such as Sudden Sensorineural Hearing Loss (SSHL). The purpose of this study was to evaluate the impact of exposure to AP on SSHL incidence. Valid electronic databases were searched to retrieve studies published until December 1, 2022, using appropriate keywords. The result of the search was 1146 studies, and after screening according to the defined criteria, in total 8 studies were obtained. The risk of bias (ROB) in the studies and their quality were assessed. Finally, the meta-analysis with a significance level of 5% was performed. The findings revealed that the mean level of SO2, CO, NO2, and PM10 in the patient group was more than that of the control group, and p-values were 0.879, 0.144, 0.077, and 0.138, respectively. There was an indirect relation between air pollutants and SSHL, and PM2.5 showed a significant effect (p < 0.05). Given the limited research and the use of different statistical methods, more research is suggested to confirm this association and to determine the mechanisms by which AP exposure may cause SSHL.
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Affiliation(s)
- Fatemeh Ranjdoost
- Research Center for Environmental Pollutants, Department of Environmental Health Engineering, Faculty of Health, Qom University of Medical Sciences, Qom, Iran.
| | - Mohammad-Ebrahim Ghaffari
- Department of Epidemiology and Biostatistics, Faculty of Health, Qom University of Medical Sciences, Qom, Iran.
| | - Faramarz Azimi
- Environmental Health Research Center, School of Health and Nutrition, Lorestan University of Medical Sciences, Khorramabad, Iran.
| | - Amir Mohammadi
- Social Determinants of Health Research Center, Clinical Research Institute, Urmia University of Medical Sciences, Urmia, Iran; Department of Environmental Health Engineering, School of Public Health, Urmia University of Medical Sciences, Urmia, Iran.
| | - Reza Fouladi-Fard
- Research Center for Environmental Pollutants, Department of Environmental Health Engineering, Faculty of Health, Qom University of Medical Sciences, Qom, Iran; Environmental Health Research Center, School of Health and Nutrition, Lorestan University of Medical Sciences, Khorramabad, Iran.
| | - Maria Fiore
- Department of Medical, Surgical and Advanced Technologies "G.F. Ingrassia", University of Catania, 87-95123, Catania, Italy.
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Iyer MR, Ventura C, Bronson D, Nowak N, Regalado K, Kalluri R. Isolating and Culturing Vestibular and Spiral Ganglion Somata from Neonatal Rodents for Patch-Clamp Recordings. J Vis Exp 2023:10.3791/64908. [PMID: 37154564 PMCID: PMC11020343 DOI: 10.3791/64908] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023] Open
Abstract
The compact morphology of isolated and cultured inner ear ganglion neurons allows for detailed characterizations of the ion channels and neurotransmitter receptors that contribute to cell diversity across this population. This protocol outlines the steps necessary for successful dissecting, dissociating, and short-term culturing of the somata of inner ear bipolar neurons for the purpose of patch-clamp recordings. Detailed instructions for preparing vestibular ganglion neurons are provided with the necessary modifications needed for plating spiral ganglion neurons. The protocol includes instructions for performing whole-cell patch-clamp recordings in the perforated-patch configuration. Example results characterizing the voltage-clamp recordings of hyperpolarization-activated cyclic nucleotide-gated (HCN)-mediated currents highlight the stability of perforated-patch recording configuration in comparison to the more standard ruptured-patch configuration. The combination of these methods, isolated somata plus perforated-patch-clamp recordings, can be used to study cellular processes that require long, stable recordings and the preservation of intracellular milieu, such as signaling through G-protein coupled receptors.
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Affiliation(s)
- Megana R Iyer
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California
| | - Christopher Ventura
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California
| | - Daniel Bronson
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California
| | - Nathaniel Nowak
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California
| | - Katherine Regalado
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California
| | - Radha Kalluri
- Caruso Department of Otolaryngology Head & Neck Surgery, Zilkha Neurogenetics Institute, Hearing and Communications Neuroscience Training Program, University of Southern California;
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5
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Zhang H, Li H, Lu M, Wang S, Ma X, Wang F, Liu J, Li X, Yang H, Zhang F, Shen H, Buckley NJ, Gamper N, Yamoah EN, Lv P. Repressor element 1-silencing transcription factor deficiency yields profound hearing loss through K v7.4 channel upsurge in auditory neurons and hair cells. eLife 2022; 11:76754. [PMID: 36125121 PMCID: PMC9525063 DOI: 10.7554/elife.76754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Accepted: 09/16/2022] [Indexed: 11/23/2022] Open
Abstract
Repressor element 1-silencing transcription factor (REST) is a transcriptional repressor that recognizes neuron-restrictive silencer elements in the mammalian genomes in a tissue- and cell-specific manner. The identity of REST target genes and molecular details of how REST regulates them are emerging. We performed conditional null deletion of Rest (cKO), mainly restricted to murine hair cells (HCs) and auditory neurons (aka spiral ganglion neurons [SGNs]). Null inactivation of full-length REST did not affect the development of normal HCs and SGNs but manifested as progressive hearing loss in adult mice. We found that the inactivation of REST resulted in an increased abundance of Kv7.4 channels at the transcript, protein, and functional levels. Specifically, we found that SGNs and HCs from Rest cKO mice displayed increased Kv7.4 expression and augmented Kv7 currents; SGN’s excitability was also significantly reduced. Administration of a compound with Kv7.4 channel activator activity, fasudil, recapitulated progressive hearing loss in mice. In contrast, inhibition of the Kv7 channels by XE991 rescued the auditory phenotype of Rest cKO mice. Previous studies identified some loss-of-function mutations within the Kv7.4-coding gene, Kcnq4, as a causative factor for progressive hearing loss in mice and humans. Thus, the findings reveal that a critical homeostatic Kv7.4 channel level is required for proper auditory functions.
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Affiliation(s)
- Haiwei Zhang
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Hongchen Li
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Mingshun Lu
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Shengnan Wang
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Xueya Ma
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Fei Wang
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Jiaxi Liu
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Xinyu Li
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Haichao Yang
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Fan Zhang
- Department of Pharmacology, Hebei Medical University, Hebei, China
| | - Haitao Shen
- Laboratory of Pathology, Hebei Medical University, Hebei, China
| | - Noel J Buckley
- Department of Psychiatry, University of Oxford, Oxford, United Kingdom
| | - Nikita Gamper
- Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, University of Nevada Reno, Reno, United States
| | - Ping Lv
- Department of Pharmacology, Hebei Medical University, Hebei, China
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Sharma K, Kang KW, Seo YW, Glowatzki E, Yi E. Low-voltage Activating K + Channels in Cochlear Afferent Nerve Fiber Dendrites. Exp Neurobiol 2022; 31:243-259. [PMID: 36050224 PMCID: PMC9471414 DOI: 10.5607/en22013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/18/2022] [Accepted: 07/29/2022] [Indexed: 11/19/2022] Open
Abstract
Cochlear afferent nerve fibers (ANF) are the first neurons in the ascending auditory pathway. We investigated the low-voltage activating K+ channels expressed in ANF dendrites using isolated rat cochlear segments. Whole cell patch clamp recordings were made from the dendritic terminals of ANFs. Outward currents activating at membrane potentials as low as -64 mV were observed in all dendrites studied. These currents were inhibited by 4-aminopyridine (4-AP), a blocker known to preferentially inhibit low-voltage activating K+ currents (IKL) in CNS auditory neurons and spiral ganglion neurons. When the dendritic IKL was blocked by 4-AP, the EPSP decay time was significantly prolonged, suggesting that dendritic IKL speeds up the decay of EPSPs and likely modulates action potentials of ANFs. To reveal molecular subtype of dendritic IKL, α-dendrotoxin (α-DTX), a selective inhibitor for Kv1.1, Kv1.2, and Kv1.6 containing channels, was tested. α-DTX inhibited 23±9% of dendritic IKL. To identify the α-DTXsensitive and α-DTX-insensitive components of IKL, immunofluorescence labeling was performed. Strong Kv1.1- and Kv1.2-immunoreactivity was found at unmyelinated dendritic segments, nodes of Ranvier, and cell bodies of most ANFs. A small fraction of ANF dendrites showed Kv7.2- immunoreactivity. These data suggest that dendritic IKL is conducted through Kv1.1and Kv1.2 channels, with a minor contribution from Kv7.2 and other as yet unidentified channels.
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Affiliation(s)
- Kushal Sharma
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Kwon Woo Kang
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
| | - Young-Woo Seo
- KBSI Gwangju Center, Korea Basic Science Institute, Gwangju 61186, Korea
| | - Elisabeth Glowatzki
- Department of Otolaryngology-Head and Neck Surgery and Neuroscience, The Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
| | - Eunyoung Yi
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, Muan 58554, Korea
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7
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Perez-Flores MC, Verschooten E, Lee JH, Kim HJ, Joris PX, Yamoah EN. Intrinsic mechanical sensitivity of mammalian auditory neurons as a contributor to sound-driven neural activity. eLife 2022; 11:74948. [PMID: 35266451 PMCID: PMC8942473 DOI: 10.7554/elife.74948] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 03/09/2022] [Indexed: 11/18/2022] Open
Abstract
Mechanosensation – by which mechanical stimuli are converted into a neuronal signal – is the basis for the sensory systems of hearing, balance, and touch. Mechanosensation is unmatched in speed and its diverse range of sensitivities, reaching its highest temporal limits with the sense of hearing; however, hair cells (HCs) and the auditory nerve (AN) serve as obligatory bottlenecks for sounds to engage the brain. Like other sensory neurons, auditory neurons use the canonical pathway for neurotransmission and millisecond-duration action potentials (APs). How the auditory system utilizes the relatively slow transmission mechanisms to achieve ultrafast speed, and high audio-frequency hearing remains an enigma. Here, we address this paradox and report that the mouse, and chinchilla, AN are mechanically sensitive, and minute mechanical displacement profoundly affects its response properties. Sound-mimicking sinusoidal mechanical and electrical current stimuli affect phase-locked responses. In a phase-dependent manner, the two stimuli can also evoke suppressive responses. We propose that mechanical sensitivity interacts with synaptic responses to shape responses in the AN, including frequency tuning and temporal phase locking. Combining neurotransmission and mechanical sensation to control spike patterns gives the mammalian AN a secondary receptor role, an emerging theme in primary neuronal functions.
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Affiliation(s)
| | - Eric Verschooten
- Laboratory of Auditory Neurophysiology, University of Leuven, Leuven, Belgium
| | | | | | - Philip X Joris
- Laboratory of Auditory Neurophysiology, University of Leuven, Leuven, Belgium
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8
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Geng Q, Li H, Zhang H, Lu M, Liu J, Wang F, Shen H, Yamoah EN, Jia Z, Lv P. Association between Ca v3 channel upregulation in spiral ganglion neurons and age-dependent hearing loss. Exp Gerontol 2021; 151:111429. [PMID: 34052348 DOI: 10.1016/j.exger.2021.111429] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2020] [Revised: 05/09/2021] [Accepted: 05/26/2021] [Indexed: 01/12/2023]
Abstract
Cav3 channels play a critical role in maintaining calcium homeostasis, and its dysregulation is related to age-related diseases, such as age-related hearing loss (AHL). However, the underlying mechanism of the Cav3 channels involved in AHL remains unknown. Previous studies have shown that the degeneration of spiral ganglion neurons (SGNs) plays a critical role in AHL. Here, we explored the involvement of Cav3 channels in the dysregulation of SGNs in AHL. We used C57BL/6 mice as the AHL mouse model and found that the expression of Cav3 channels was increased in SGNs associated with age. The three subtypes of Cav3 channels were present in the apical, middle, and basal SGNs from young and older (AHL) mice. The immunostaining data suggest that Cav3.1 and Cav3.2 may contribute to Cav3 upregulation in SGNs of AHL mice. Additionally, we found that calpain-2 and apoptosis-inducing factor (AIF) were activated in SGNs from AHL mice. The inhibition of Cav3 channels or calpain-2 reduced AIF-activation in SGNs may affect neuronal survival. In conclusion, the findings suggest that Cav3 channels are upregulated in SGNs from AHL mice that may contribute to the degeneration of SGNs through the calpain-2-AIF apoptosis pathway in AHL mice.
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Affiliation(s)
- Qiaowei Geng
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Hongchen Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Haiwei Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Mingshun Lu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Jiaxi Liu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Fei Wang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Haitao Shen
- Lab of Pathology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, Reno, NV 89557, United States
| | - Zhanfeng Jia
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
| | - Ping Lv
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, Hebei 050017, PR China; Center for Innovative Drug Research and Evaluation, Institute of Medical Science and Health, Hebei Medical University, Shijiazhuang, Hebei Province 050017, PR China
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9
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Abstract
Kv7.1-Kv7.5 (KCNQ1-5) K+ channels are voltage-gated K+ channels with major roles in neurons, muscle cells and epithelia where they underlie physiologically important K+ currents, such as neuronal M current and cardiac IKs. Specific biophysical properties of Kv7 channels make them particularly well placed to control the activity of excitable cells. Indeed, these channels often work as 'excitability breaks' and are targeted by various hormones and modulators to regulate cellular activity outputs. Genetic deficiencies in all five KCNQ genes result in human excitability disorders, including epilepsy, arrhythmias, deafness and some others. Not surprisingly, this channel family attracts considerable attention as potential drug targets. Here we will review biophysical properties and tissue expression profile of Kv7 channels, discuss recent advances in the understanding of their structure as well as their role in various neurological, cardiovascular and other diseases and pathologies. We will also consider a scope for therapeutic targeting of Kv7 channels for treatment of the above health conditions.
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10
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Bachmann M, Li W, Edwards MJ, Ahmad SA, Patel S, Szabo I, Gulbins E. Voltage-Gated Potassium Channels as Regulators of Cell Death. Front Cell Dev Biol 2020; 8:611853. [PMID: 33381507 PMCID: PMC7767978 DOI: 10.3389/fcell.2020.611853] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/23/2020] [Indexed: 12/11/2022] Open
Abstract
Ion channels allow the flux of specific ions across biological membranes, thereby determining ion homeostasis within the cells. Voltage-gated potassium-selective ion channels crucially contribute to the setting of the plasma membrane potential, to volume regulation and to the physiologically relevant modulation of intracellular potassium concentration. In turn, these factors affect cell cycle progression, proliferation and apoptosis. The present review summarizes our current knowledge about the involvement of various voltage-gated channels of the Kv family in the above processes and discusses the possibility of their pharmacological targeting in the context of cancer with special emphasis on Kv1.1, Kv1.3, Kv1.5, Kv2.1, Kv10.1, and Kv11.1.
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Affiliation(s)
- Magdalena Bachmann
- Department of Biology, University of Padova, Padua, Italy.,Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Weiwei Li
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Michael J Edwards
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Syed A Ahmad
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Sameer Patel
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States
| | - Ildiko Szabo
- Department of Biology, University of Padova, Padua, Italy.,Consiglio Nazionale delle Ricerche Institute of Neuroscience, Padua, Italy
| | - Erich Gulbins
- Department of Surgery, Medical School, University of Cincinnati, Cincinnati, OH, United States.,Department of Molecular Biology, University of Duisburg-Essen, Essen, Germany
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11
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Markowitz AL, Kalluri R. Gradients in the biophysical properties of neonatal auditory neurons align with synaptic contact position and the intensity coding map of inner hair cells. eLife 2020; 9:e55378. [PMID: 32639234 PMCID: PMC7343388 DOI: 10.7554/elife.55378] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 06/24/2020] [Indexed: 02/07/2023] Open
Abstract
Sound intensity is encoded by auditory neuron subgroups that differ in thresholds and spontaneous rates. Whether variations in neuronal biophysics contributes to this functional diversity is unknown. Because intensity thresholds correlate with synaptic position on sensory hair cells, we combined patch clamping with fiber labeling in semi-intact cochlear preparations in neonatal rats from both sexes. The biophysical properties of auditory neurons vary in a striking spatial gradient with synaptic position. Neurons with high thresholds to injected currents contact hair cells at synaptic positions where neurons with high thresholds to sound-intensity are found in vivo. Alignment between in vitro and in vivo thresholds suggests that biophysical variability contributes to intensity coding. Biophysical gradients were evident at all ages examined, indicating that cell diversity emerges in early post-natal development and persists even after continued maturation. This stability enabled a remarkably successful model for predicting synaptic position based solely on biophysical properties.
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Affiliation(s)
- Alexander L Markowitz
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
| | - Radha Kalluri
- Neuroscience Graduate Program, University of Southern CaliforniaLos AngelesUnited States
- Department of Otolaryngology, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
- Zilkha Neurogenetic Institute, Keck School of Medicine, University of Southern CaliforniaLos AngelesUnited States
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12
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Increased Risk of Sensorineural Hearing Loss as a Result of Exposure to Air Pollution. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2020; 17:ijerph17061969. [PMID: 32192124 PMCID: PMC7143358 DOI: 10.3390/ijerph17061969] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 03/03/2020] [Accepted: 03/11/2020] [Indexed: 12/12/2022]
Abstract
Whether exposure to air pollution is associated with developing sensorineural hearing loss (SHL) remains controversial. Using data from the National Health Insurance Research Database, we recruited a total of 75,767 subjects aged older than 20 years with no history of SHL from 1998 to 2010, and they were followed up until SHL was observed, they withdrew from the National Health Insurance program, or the study ended. The subjects were evenly exposed to low-level, mid-level, and high-level carbon monoxide (CO) and nitrogen dioxide (NO2). The incidence rate ratio of SHL for patients exposed to high-level CO was 1.24 (95% confidence interval (CI) = 1.14–1.36). The NO2 pollutants increased the incidence rate ratios of SHL in mid-level NO2 and high-level NO2 exposures by 1.10 (95% CI = 1.10–1.32) and 1.36 (95% CI = 1.24–1.49) times, respectively. The adjusted hazard ratio (adj. HR) of SHL in patients exposed to high-level CO was 1.45 (95% CI = 1.31–1.59), relative to that of patients exposed to low-level CO. Compared to patients exposed to low-level NO2, patients exposed to mid-level NO2 (adj. HR = 1.40, 95% CI = 1.27–1.54) and high-level NO2 (adj. HR = 1.63, 95% CI = 1.48–1.81) had a higher risk of developing SHL. The increased risk of SHL following the increased concentrations of air pollutants (CO and NO2) was statistically significant in this study. In conclusion, the subjects’ exposure to air pollution exhibited a significantly higher risk of developing SHL in Taiwan.
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13
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Lee JH, Kang M, Park S, Perez-Flores MC, Zhang XD, Wang W, Gratton MA, Chiamvimonvat N, Yamoah EN. The local translation of KNa in dendritic projections of auditory neurons and the roles of KNa in the transition from hidden to overt hearing loss. Aging (Albany NY) 2019; 11:11541-11564. [PMID: 31812952 PMCID: PMC6932877 DOI: 10.18632/aging.102553] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 11/20/2019] [Indexed: 02/07/2023]
Abstract
Local and privileged expression of dendritic proteins allows segregation of distinct functions in a single neuron but may represent one of the underlying mechanisms for early and insidious presentation of sensory neuropathy. Tangible characteristics of early hearing loss (HL) are defined in correlation with nascent hidden hearing loss (HHL) in humans and animal models. Despite the plethora of causes of HL, only two prevailing mechanisms for HHL have been identified, and in both cases, common structural deficits are implicated in inner hair cell synapses, and demyelination of the auditory nerve (AN). We uncovered that Na+-activated K+ (KNa) mRNA and channel proteins are distinctly and locally expressed in dendritic projections of primary ANs and genetic deletion of KNa channels (Kcnt1 and Kcnt2) results in the loss of proper AN synaptic function, characterized as HHL, without structural synaptic alterations. We further demonstrate that the local functional synaptic alterations transition from HHL to increased hearing-threshold, which entails changes in global Ca2+ homeostasis, activation of caspases 3/9, impaired regulation of inositol triphosphate receptor 1 (IP3R1), and apoptosis-mediated neurodegeneration. Thus, the present study demonstrates how local synaptic dysfunction results in an apparent latent pathological phenotype (HHL) and, if undetected, can lead to overt HL. It also highlights, for the first time, that HHL can precede structural synaptic dysfunction and AN demyelination. The stepwise cellular mechanisms from HHL to canonical HL are revealed, providing a platform for intervention to prevent lasting and irreversible age-related hearing loss (ARHL).
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Affiliation(s)
- Jeong Han Lee
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
| | - Mincheol Kang
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
| | - Seojin Park
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
| | - Maria C Perez-Flores
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
| | - Xiao-Dong Zhang
- Department of Internal Medicine, Division of Cardiology, University of California Davis, Davis, CA 95616, USA
| | - Wenying Wang
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
| | - Michael Anne Gratton
- Department of Otolaryngology, Head and Neck Surgery, Washington University St. Louis, St. Louis, MO 63110, USA
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiology, University of California Davis, Davis, CA 95616, USA
| | - Ebenezer N Yamoah
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada Reno, Reno, NV 89557, USA
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14
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Lu J, Liu H, Lin S, Li C, Wu H. Electrophysiological characterization of acutely isolated spiral ganglion neurons in neonatal and mature sonic hedgehog knock-in mice. Neurosci Lett 2019; 714:134536. [PMID: 31589904 DOI: 10.1016/j.neulet.2019.134536] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Revised: 09/04/2019] [Accepted: 10/01/2019] [Indexed: 12/18/2022]
Abstract
Spiral ganglion neurons (SGNs) are primary afferent auditory neurons activated by inner hair cells in mammalian cochlea. Here, for the convenience of SGN studies such as patch-clamp or single cell RNA-sequence studies, a knock-in mouse (ShhCreEGFP/+; Rosa26-Tdtomatoloxp/+) was generated for the purpose of obtaining fluorescence SGNs. Auditory brainstem response (ABR) and Tuj1 immunohistochemistry staining were performed to verify the hearing function and the morphological characteristics. The results showed that there was no significant difference between shh and wild type mice. In electrophysiological studies, we verified a series of electrophysiological characteristics including the amplitude of sodium and potassium currents and action potential characteristics of shh and wild type mice and no significant differences were found either. From the above, shh mice have the same cell function and morphology as their littermate control wild type mice and could be used as an ideal tool to study the function and characteristics of spiral ganglion neurons. Potassium channels of SGNs play an important role in resolving time accuracy. We obtained similar amplitude of IK+ in neonatal and mature mice in the aging competition experiment, however, the density of IK+ from mature mice were significantly different from those of neonatal mice, a phenomenon that may play a key role in the nervous system. Potassium channels have been shown to contribute to apoptosis induced by cisplatin administration in various cell lines. Here we used cisplatin administration to study the ototoxicity and found that the effects of a low dose of cisplatin (0.5 mM correspond to therapeutic doses) causes a decrease in currents and is reversible after a short administration time. Moreover, we propose the activated state of potassium channels has changed but the characteristic and number remain still after cisplatin administration. The excess potassium ions may accumulate in the cell body, which had affected the firing properties and induce cytotoxicity and apoptosis. We suggest that the electrophysiological properties of acutely isolated SGNs may support further research on the mechanics of auditory propagation and ion channel pharmacology.
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Affiliation(s)
- Jiawen Lu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Huihui Liu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Shanshan Lin
- College of Medical Technology, Zhejiang Chinese Medical University, Hangzhou, China
| | - Chao Li
- Institute of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Shanghai Institutes for Biological Sciences, China
| | - Hao Wu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Ear Institute, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China.
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15
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Early functional alterations in membrane properties and neuronal degeneration are hallmarks of progressive hearing loss in NOD mice. Sci Rep 2019; 9:12128. [PMID: 31431657 PMCID: PMC6702171 DOI: 10.1038/s41598-019-48376-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 08/05/2019] [Indexed: 11/24/2022] Open
Abstract
Presbycusis or age-related hearing loss (ARHL) is the most common sensory deficit in the human population. A substantial component of the etiology stems from pathological changes in sensory and non-sensory cells in the cochlea. Using a non-obese diabetic (NOD) mouse model, we have characterized changes in both hair cells and spiral ganglion neurons that may be relevant for early signs of age-related hearing loss (ARHL). We demonstrate that hair cell loss is preceded by, or in parallel with altered primary auditory neuron functions, and latent neurite retraction at the hair cell-auditory neuron synapse. The results were observed first in afferent inner hair cell synapse of type I neurites, followed by type II neuronal cell-body degeneration. Reduced membrane excitability and loss of postsynaptic densities were some of the inaugural events before any outward manifestation of hair bundle disarray and hair cell loss. We have identified profound alterations in type I neuronal membrane properties, including a reduction in membrane input resistance, prolonged action potential latency, and a decrease in membrane excitability. The resting membrane potential of aging type I neurons in the NOD, ARHL model, was significantly hyperpolarized, and analyses of the underlying membrane conductance showed a significant increase in K+ currents. We propose that attempts to alleviate some forms of ARHL should include early targeted primary latent neural degeneration for effective positive outcomes.
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16
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Carignano C, Barila EP, Rías EI, Dionisio L, Aztiria E, Spitzmaul G. Inner Hair Cell and Neuron Degeneration Contribute to Hearing Loss in a DFNA2-Like Mouse Model. Neuroscience 2019; 410:202-216. [PMID: 31102762 DOI: 10.1016/j.neuroscience.2019.05.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2018] [Revised: 04/03/2019] [Accepted: 05/07/2019] [Indexed: 01/19/2023]
Abstract
DFNA2 is a progressive deafness caused by mutations in the voltage-activated potassium channel KCNQ4. Hearing loss develops with age from a mild increase in the hearing threshold to profound deafness. Studies using transgenic mice for Kcnq4 expressed in a mixed background demonstrated the implication of outer hair cells at the initial phase. However, it could not explain the last phase mechanisms of the disease. Genetic backgrounds are known to influence disease expressivity. To unmask the cause of profound deafness phenotype, we backcrossed the Kcnq4 knock-out allele to the inbred strain C3H/HeJ and investigated inner and outer hair cell and spiral ganglion neuron degeneration across the lifespan. In addition to the already reported outer hair cell death, the C3H/HeJ strain also exhibited inner hair cell and spiral ganglion neuron death. We tracked the spatiotemporal survival of cochlear cells by plotting cytocochleograms and neuronal counts at different ages. Cell loss progressed from basal to apical turns with age. Interestingly, the time-course of cell degeneration was different for each cell-type. While for outer hair cells it was already present by week 3, inner hair cell and neuronal loss started 30 weeks later. We also established that outer hair cell loss kinetics slowed down from basal to apical regions correlating with KCNQ4 expression pattern determined in wild-type mice. Our findings indicate that KCNQ4 plays differential roles in each cochlear cell-type impacting in their survival ability. Inner hair cell and spiral ganglion neuron death generates severe hearing loss that could be associated with the last phase of DFNA2.
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Affiliation(s)
- Camila Carignano
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina
| | - Esteban Pablo Barila
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina
| | - Ezequiel Ignacio Rías
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina.; Departamento de Biología, Bioquímica y Farmacia (BByF)-UNS, San Juan 670, 8000 Bahía Blanca, Argentina
| | - Leonardo Dionisio
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina.; Departamento de Biología, Bioquímica y Farmacia (BByF)-UNS, San Juan 670, 8000 Bahía Blanca, Argentina
| | - Eugenio Aztiria
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina.; Departamento de Biología, Bioquímica y Farmacia (BByF)-UNS, San Juan 670, 8000 Bahía Blanca, Argentina
| | - Guillermo Spitzmaul
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)-Universidad Nacional del Sur (UNS), Camino La Carrindanga Km 7, B8000FWB, Bahía Blanca, Argentina.; Departamento de Biología, Bioquímica y Farmacia (BByF)-UNS, San Juan 670, 8000 Bahía Blanca, Argentina..
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17
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Sodium-activated potassium channels shape peripheral auditory function and activity of the primary auditory neurons in mice. Sci Rep 2019; 9:2573. [PMID: 30796290 PMCID: PMC6384918 DOI: 10.1038/s41598-019-39119-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/17/2019] [Indexed: 11/08/2022] Open
Abstract
Potassium (K+) channels shape the response properties of neurons. Although enormous progress has been made to characterize K+ channels in the primary auditory neurons, the molecular identities of many of these channels and their contributions to hearing in vivo remain unknown. Using a combination of RNA sequencing and single molecule fluorescent in situ hybridization, we localized expression of transcripts encoding the sodium-activated potassium channels KNa1.1 (SLO2.2/Slack) and KNa1.2 (SLO2.1/Slick) to the primary auditory neurons (spiral ganglion neurons, SGNs). To examine the contribution of these channels to function of the SGNs in vivo, we measured auditory brainstem responses in KNa1.1/1.2 double knockout (DKO) mice. Although auditory brainstem response (wave I) thresholds were not altered, the amplitudes of suprathreshold responses were reduced in DKO mice. This reduction in amplitude occurred despite normal numbers and molecular architecture of the SGNs and their synapses with the inner hair cells. Patch clamp electrophysiology of SGNs isolated from DKO mice displayed altered membrane properties, including reduced action potential thresholds and amplitudes. These findings show that KNa1 channel activity is essential for normal cochlear function and suggest that early forms of hearing loss may result from physiological changes in the activity of the primary auditory neurons.
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18
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Wong VSC, Meadows M, Goldberg D, Willis DE. Semaphorin 3A induces acute changes in membrane excitability in spiral ganglion neurons in vitro. Eur J Neurosci 2019; 50:1741-1758. [PMID: 30706560 DOI: 10.1111/ejn.14360] [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: 07/20/2018] [Revised: 01/10/2019] [Accepted: 01/23/2019] [Indexed: 11/29/2022]
Abstract
The development and survival of spiral ganglion neurons (SGNs) are dependent on multiple trophic factors as well as membrane electrical activity. Semaphorins (Sema) constitute a family of membrane-associated and secreted proteins that have garnered significant attention as a potential SGN "navigator" during cochlea development. Previous studies using mutant mice demonstrated that Sema3A plays a role in the SGN pathfinding. The mechanisms, however, by which Sema3A shapes SGNs firing behavior are not known. In these studies, we found that Sema3A plays a novel role in regulating SGN resting membrane potential and excitability. Using dissociated SGN from pre-hearing (P3-P5) and post-hearing mice (P12-P15), we recorded membrane potentials using whole-cell patch clamp recording techniques in apical and basal SGN populations. Recombinant Sema3A was applied to examine the effects on intrinsic membrane properties and action potentials evoked by current injections. Apical and basal SGNs from newborn mice treated with recombinant Sema3A (100 ng/ml) displayed a higher resting membrane potential, higher threshold, decreased amplitude, and prolonged latency and duration of spikes. Although a similar phenomenon was observed in SGNs from post-hearing mice, the resting membrane potential was essentially indistinguishable before and after Sema3A exposure. Sema3A-mediated changes in membrane excitability were associated with a significant decrease in K+ and Ca2+ currents. Sema3A acts through linopirdine-sensitive K+ channels in apical, but not in the basal SGNs. Therefore, Sema3A induces differential effects in SGN membrane excitability that are dependent on age and location, and constitutes an additional early and novel effect of Sema3A SGNs in vitro.
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Affiliation(s)
| | - Marc Meadows
- The Vollum Institute, Oregon Health and Science University, Portland, Oregon
| | - David Goldberg
- The Burke Neurological Institute, White Plains, New York
| | - Dianna E Willis
- The Burke Neurological Institute, White Plains, New York.,Brain and Mind Research Institute, Weill Cornell Medicine, New York, New York
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19
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Yu Y, Hu B, Bao J, Mulvany J, Bielefeld E, Harrison RT, Neton SA, Thirumala P, Chen Y, Lei D, Qiu Z, Zheng Q, Ren J, Perez-Flores MC, Yamoah EN, Salehi P. Otoprotective Effects of Stephania tetrandra S. Moore Herb Isolate against Acoustic Trauma. J Assoc Res Otolaryngol 2018; 19:653-668. [PMID: 30187298 PMCID: PMC6249158 DOI: 10.1007/s10162-018-00690-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/08/2018] [Indexed: 01/10/2023] Open
Abstract
Noise is the most common occupational and environmental hazard, and noise-induced hearing loss (NIHL) is the second most common form of sensorineural hearing deficit. Although therapeutics that target the free-radical pathway have shown promise, none of these compounds is currently approved against NIHL by the United States Food and Drug Administration. The present study has demonstrated that tetrandrine (TET), a traditional Chinese medicinal alkaloid and the main chemical isolate of the Stephania tetrandra S. Moore herb, significantly attenuated NIHL in CBA/CaJ mice. TET is known to exert antihypertensive and antiarrhythmic effects through the blocking of calcium channels. Whole-cell patch-clamp recording from adult spiral ganglion neurons showed that TET blocked the transient Ca2+ current in a dose-dependent manner and the half-blocking concentration was 0.6 + 0.1 μM. Consistent with previous findings that modulations of calcium-based signaling pathways have both prophylactic and therapeutic effects against neural trauma, NIHL was significantly diminished by TET administration. Importantly, TET has a long-lasting protective effect after noise exposure (48 weeks) in comparison to 2 weeks after noise exposure. The otoprotective effects of TET were achieved mainly by preventing outer hair cell damage and synapse loss between inner hair cells and spiral ganglion neurons. Thus, our data indicate that TET has great potential in the prevention and treatment of NIHL.
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Affiliation(s)
- Yan Yu
- The First People’s Hospital of Zhangjiagang, 68 W Jiyang Road, Zhangjiagang City, 215600 Jiangsu China
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
| | - Bing Hu
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106 USA
- Department of Otolaryngology Head and Neck Surgery, The Second Xiangya Hospital of Central South University, Changsha, 440011 Hunan China
| | - Jianxin Bao
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
- Department of Research and Development, Gateway Biotechnology Inc., Rootstown, OH 44272 USA
| | - Jessica Mulvany
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
- Department of Research and Development, Gateway Biotechnology Inc., Rootstown, OH 44272 USA
| | - Eric Bielefeld
- Department of Speech and Hearing Science, Ohio State University, Columbus, OH 43210 USA
| | - Ryan T. Harrison
- Department of Speech and Hearing Science, Ohio State University, Columbus, OH 43210 USA
| | - Sarah A. Neton
- Department of Speech and Hearing Science, Ohio State University, Columbus, OH 43210 USA
| | - Partha Thirumala
- The University of Pittsburgh Medical Center, Suite B-400, 200 Lothrop Street, Pittsburgh, PA 15213 USA
| | - Yingying Chen
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
| | - Debin Lei
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
| | - Ziyu Qiu
- Department of Research and Development, Gateway Biotechnology Inc., Rootstown, OH 44272 USA
| | - Qingyin Zheng
- Department of Otolaryngology-Head and Neck Surgery, Case Western Reserve University School of Medicine, Cleveland, OH 44106 USA
| | - Jihao Ren
- Department of Otolaryngology Head and Neck Surgery, The Second Xiangya Hospital of Central South University, Changsha, 440011 Hunan China
| | - Maria Cristina Perez-Flores
- Department of Physiology and Cell Biology, University of Nevada Reno, 1664 North Virginia St, Reno, NV 89557 USA
| | - Ebenezer N. Yamoah
- Department of Physiology and Cell Biology, University of Nevada Reno, 1664 North Virginia St, Reno, NV 89557 USA
| | - Pezhman Salehi
- Translational Research Center, Northeast Ohio Medical University, Rootstown, OH 44272 USA
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20
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Whole-exome sequencing identifies two novel mutations in KCNQ4 in individuals with nonsyndromic hearing loss. Sci Rep 2018; 8:16659. [PMID: 30413759 PMCID: PMC6226507 DOI: 10.1038/s41598-018-34876-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 10/27/2018] [Indexed: 11/09/2022] Open
Abstract
Mutations in potassium voltage-gated channel subfamily Q member 4 (KCNQ4) are etiologically linked to a type of nonsyndromic hearing loss, deafness nonsyndromic autosomal dominant 2 (DFNA2). We performed whole-exome sequencing for 98 families with hearing loss and found mutations in KCNQ4 in five families. In this study, we characterized two novel mutations in KCNQ4: a missense mutation (c.796G>T; p.Asp266Tyr) and an in-frame deletion mutation (c.259_267del; p.Val87_Asn89del). p.Asp266Tyr located in the channel pore region resulted in early onset and moderate hearing loss, whereas p.Val87_Asn89del located in the N-terminal cytoplasmic region resulted in late onset and high frequency-specific hearing loss. When heterologously expressed in HEK 293 T cells, both mutant proteins did not show defects in protein trafficking to the plasma membrane or in interactions with wild-type (WT) KCNQ4 channels. Patch-clamp analysis demonstrated that both p.Asp266Tyr and p.Val87_Asn89del mutant channels lost conductance and were completely unresponsive to KCNQ activators, such as retigabine, zinc pyrithione, and ML213. Channels assembled from WT-p.Asp266Tyr concatemers, like those from WT-WT concatemers, exhibited conductance and responsiveness to KCNQ activators. However, channels assembled from WT-p.Val87_Asn89del concatemers showed impaired conductance, suggesting that p.Val87_Asn89del caused complete loss-of-function with a strong dominant-negative effect on functional WT channels. Therefore, the main pathological mechanism may be related to loss of K+ channel activity, not defects in trafficking.
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Shen H, Liu W, Geng Q, Li H, Lu M, Liang P, Zhang B, Yamoah EN, Lv P. Age-Dependent Up-Regulation of HCN Channels in Spiral Ganglion Neurons Coincide With Hearing Loss in Mice. Front Aging Neurosci 2018; 10:353. [PMID: 30459593 PMCID: PMC6232381 DOI: 10.3389/fnagi.2018.00353] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Accepted: 10/17/2018] [Indexed: 01/05/2023] Open
Abstract
Age-related hearing loss (AHL) is the most common sensory disorder in the elderly population, and the etiologies are diverse. To understand the underlying mechanisms of AHL, one strategy is to identify correlates of the disease for comprehensive evaluation of treatment approaches. Dysfunction and degeneration of spiral ganglion neurons (SGNs) are major contributors to AHL. Previously, we showed that one of the changes in the aging auditory system is SGN excitability increase in mice. Since hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play important roles in determining neuronal excitability, we predicted that HCN channels in SGNs are involved in AHL. To investigate the contribution of HCN channels to AHL, we examined the expression and biophysical properties of HCN channels in SGNs from adult (2–3 months) and 11–12-month-old mice. We report a dramatic increase of HCN channel current (Ih) in SGNs in old mice (11–12 months old). The results matched well with increased expression of HCN1 and HCN2 subunits, suggesting that upregulation of HCN channels in SGNs is one of the important facets of the aging SGNs. Moreover, the activity of Ih produced a major impact on the firing properties of SGNs in older mice. The upregulation of Ih may contribute to AHL by regulating SGN excitability. We assessed whether increased SGNs excitability dovetail with neurodegeneration. Apoptosis-inducing factor (AIF)-mediated apoptosis in SGNs was observed in old mice and activation of HCN channels mediates AIF activation. Thus, these findings demonstrate stark correlation between age-dependent increased expression of HCN channels and Ih, and apoptosis in SGNs, which may contribute towards the varied mechanisms of AHL.
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Affiliation(s)
- Haitao Shen
- Laboratory of Pathology, Hebei Medical University, Shijiazhuang, China
| | - Weilin Liu
- Division of Cardiovascular Medicine, Hebei Province Geriatric Hospital, Shijiazhuang, China
| | - Qiaowei Geng
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Hongchen Li
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Mingshun Lu
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Peng Liang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Bo Zhang
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
| | - Ebenezer N Yamoah
- Department of Physiology, School of Medicine, University of Nevada, Reno, NV, United States
| | - Ping Lv
- Department of Pharmacology, Hebei Medical University, Shijiazhuang, China
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22
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Reijntjes DO, Pyott SJ. The afferent signaling complex: Regulation of type I spiral ganglion neuron responses in the auditory periphery. Hear Res 2016; 336:1-16. [DOI: 10.1016/j.heares.2016.03.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 02/12/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022]
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Phosphoinositide Modulation of Heteromeric Kv1 Channels Adjusts Output of Spiral Ganglion Neurons from Hearing Mice. J Neurosci 2015; 35:11221-32. [PMID: 26269632 DOI: 10.1523/jneurosci.0496-15.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
UNLABELLED Spiral ganglion neurons (SGNs) relay acoustic code from cochlear hair cells to the brainstem, and their stimulation enables electrical hearing via cochlear implants. Rapid adaptation, a mechanism that preserves temporal precision, and a prominent feature of auditory neurons, is regulated via dendrotoxin-sensitive low-threshold voltage-activated (LVA) K(+) channels. Here, we investigated the molecular physiology of LVA currents in SGNs cultured from mice following the onset of hearing (postnatal days 12-21). Kv1.1- and Kv1.2-specific toxins blocked the LVA currents in a comparable manner, suggesting that both subunits contribute to functional heteromeric channels. Confocal immunofluorescence in fixed cochlear sections localized both Kv1.1 and Kv1.2 subunits to specific neuronal microdomains, including the somatic membrane, juxtaparanodes, and the first heminode, which forms the spike initiation site of the auditory nerve. The spatial distribution of Kv1 immunofluorescence appeared mutually exclusive to that of Kv3.1b subunits, which mediate high-threshold voltage-activated currents. As Kv1.2-containing channels are positively modulated by membrane phosphoinositides, we investigated the influence of phosphatidylinositol-4,5-bisphosphate (PIP2) availability on SGN electrophysiology. Reducing PIP2 production using wortmannin, or sequestration of PIP2 using a palmitoylated peptide (PIP2-PP), slowed adaptation rate in SGN populations. PIP2-PP specifically inhibited the LVA current in SGNs, an effect reduced by intracellular dialysis of a nonhydrolysable analog of PIP2. PIP2-PP also inhibited heterologously expressed Kv1.1/Kv1.2 channels, recapitulating its effect in SGNs. Collectively, the data identify Kv1.1/Kv1.2 heteromeric channels as key regulators of action potential initiation and propagation in the auditory nerve, and suggest that modulation of these channels by endogenous phosphoinositides provides local control of membrane excitability. SIGNIFICANCE STATEMENT Rapid spike adaptation is an important feature of auditory neurons that preserves temporal precision. In spiral ganglion neurons, the primary afferents in the cochlea, adaptation is regulated by heteromeric ion channels composed of Kv1.1 and Kv1.2 subunits. These subunits colocalize to common functional microdomains, such as juxtaparanodes and the somatic membrane. Activity of the heteromeric channels is controlled by cellular availability of PIP2, a membrane phospholipid. This mechanism provides an intrinsic regulation of output from the auditory nerve, which could be targeted for therapeutic adjustment of hearing sensitivity.
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24
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Sihn CR, Kim HJ, Woltz RL, Yarov-Yarovoy V, Yang PC, Xu J, Clancy CE, Zhang XD, Chiamvimonvat N, Yamoah EN. Mechanisms of Calmodulin Regulation of Different Isoforms of Kv7.4 K+ Channels. J Biol Chem 2015; 291:2499-509. [PMID: 26515070 DOI: 10.1074/jbc.m115.668236] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Indexed: 01/17/2023] Open
Abstract
Calmodulin (CaM), a Ca(2+)-sensing protein, is constitutively bound to IQ domains of the C termini of human Kv7 (hKv7, KCNQ) channels to mediate Ca(2+)-dependent reduction of Kv7 currents. However, the mechanism remains unclear. We report that CaM binds to two isoforms of the hKv7.4 channel in a Ca(2+)-independent manner but that only the long isoform (hKv7.4a) is regulated by Ca(2+)/CaM. Ca(2+)/CaM mediate reduction of the hKv7.4a channel by decreasing the channel open probability and altering activation kinetics. We took advantage of a known missense mutation (G321S) that has been linked to progressive hearing loss to further examine the inhibitory effects of Ca(2+)/CaM on the Kv7.4 channel. Using multidisciplinary techniques, we demonstrate that the G321S mutation may destabilize CaM binding, leading to a decrease in the inhibitory effects of Ca(2+) on the channels. Our study utilizes an expression system to dissect the biophysical properties of the WT and mutant Kv7.4 channels. This report provides mechanistic insights into the critical roles of Ca(2+)/CaM regulation of the Kv7.4 channel under physiological and pathological conditions.
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Affiliation(s)
- Choong-Ryoul Sihn
- From the Department of Physiology and Cell Biology, Program in Communication Science, School of Medicine, University of Nevada, Reno, Reno, Nevada 85997
| | - Hyo Jeong Kim
- the Department of Internal Medicine, Division of Cardiovascular Medicine
| | - Ryan L Woltz
- the Department of Internal Medicine, Division of Cardiovascular Medicine
| | - Vladimir Yarov-Yarovoy
- Department of Physiology and Membrane Biology, and the Northern California Health Care System, Department of Veterans Affairs, Mather, California 95655, and
| | - Pei-Chi Yang
- Department of Pharmacology, University of California, Davis, Davis, California 95616
| | - Jun Xu
- the Department of Engineering Technology, College of Science and Technology, Tarleton State University, Stephenville, Texas 76402
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Davis, California 95616
| | - Xiao-Dong Zhang
- the Department of Internal Medicine, Division of Cardiovascular Medicine, the Northern California Health Care System, Department of Veterans Affairs, Mather, California 95655, and
| | - Nipavan Chiamvimonvat
- the Department of Internal Medicine, Division of Cardiovascular Medicine, the Northern California Health Care System, Department of Veterans Affairs, Mather, California 95655, and
| | - Ebenezer N Yamoah
- From the Department of Physiology and Cell Biology, Program in Communication Science, School of Medicine, University of Nevada, Reno, Reno, Nevada 85997,
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25
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Akil O, Rouse SL, Chan DK, Lustig LR. Surgical method for virally mediated gene delivery to the mouse inner ear through the round window membrane. J Vis Exp 2015:52187. [PMID: 25867531 PMCID: PMC4401361 DOI: 10.3791/52187] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Gene therapy, used to achieve functional recovery from sensorineural deafness, promises to grant better understanding of the underlying molecular and genetic mechanisms that contribute to hearing loss. Introduction of vectors into the inner ear must be done in a way that widely distributes the agent throughout the cochlea while minimizing injury to the existing structures. This manuscript describes a post-auricular surgical approach that can be used for mouse cochlear therapy using molecular, pharmacologic, and viral delivery to mice postnatal day 10 and older via the round window membrane (RWM). This surgical approach enables rapid and direct delivery into the scala tympani while minimizing blood loss and avoiding animal mortality. This technique involves negligible or no damage to essential structures of the inner and middle ear as well as neck muscles while wholly preserving hearing. To demonstrate the efficacy of this surgical technique, the vesicular glutamate transporter 3 knockout (VGLUT3 KO) mice will be used as an example of a mouse model of congenital deafness that recovers hearing after delivery of VGLUT3 to the inner ear using an adeno-associated virus (AAV-1).
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Affiliation(s)
- Omar Akil
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco;
| | - Stephanie L Rouse
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco
| | - Dylan K Chan
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco
| | - Lawrence R Lustig
- Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco
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26
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Zhang XD, Lee JH, Lv P, Chen WC, Kim HJ, Wei D, Wang W, Sihn CR, Doyle KJ, Rock JR, Chiamvimonvat N, Yamoah EN. Etiology of distinct membrane excitability in pre- and posthearing auditory neurons relies on activity of Cl- channel TMEM16A. Proc Natl Acad Sci U S A 2015; 112:2575-80. [PMID: 25675481 PMCID: PMC4345570 DOI: 10.1073/pnas.1414741112] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The developmental rehearsal for the debut of hearing is marked by massive changes in the membrane properties of hair cells (HCs) and spiral ganglion neurons (SGNs). Whereas the underlying mechanisms for the developing HC transition to mature stage are understood in detail, the maturation of SGNs from hyperexcitable prehearing to quiescent posthearing neurons with broad dynamic range is unknown. Here, we demonstrated using pharmacological approaches, caged-Ca(2+) photolysis, and gramicidin patch recordings that the prehearing SGN uses Ca(2+)-activated Cl(-) conductance to depolarize the resting membrane potential and to prime the neurons in a hyperexcitable state. Immunostaining of the cochlea preparation revealed the identity and expression of the Ca(2+)-activated Cl(-) channel transmembrane member 16A (TMEM16A) in SGNs. Moreover, null deletion of TMEM16A reduced the Ca(2+)-activated Cl(-) currents and action potential firing in SGNs. To determine whether Cl(-) ions and TMEM16A are involved in the transition between pre- and posthearing features of SGNs we measured the intracellular Cl(-) concentration [Cl(-)]i in SGNs. Surprisingly, [Cl(-)]i in SGNs from prehearing mice was ∼90 mM, which was significantly higher than posthearing neurons, ∼20 mM, demonstrating discernible altered roles of Cl(-) channels in the developing neuron. The switch in [Cl(-)]i stems from delayed expression of the development of intracellular Cl(-) regulating mechanisms. Because the Cl(-) channel is the only active ion-selective conductance with a reversal potential that lies within the dynamic range of SGN action potentials, developmental alteration of [Cl(-)]i, and hence the equilibrium potential for Cl(-) (ECl), transforms pre- to posthearing phenotype.
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Affiliation(s)
- Xiao-Dong Zhang
- Department of Internal Medicine, Division of Cardiovascular Medicine, School of Medicine, University of California, Davis, CA 95616
| | - Jeong-Han Lee
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Ping Lv
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557; Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Wei Chun Chen
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Hyo Jeong Kim
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Dongguang Wei
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Wenying Wang
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Choong-Ryoul Sihn
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Karen Jo Doyle
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557
| | - Jason R Rock
- Department of Anatomy, School of Medicine, University of California, San Francisco, CA 94143; and
| | - Nipavan Chiamvimonvat
- Department of Internal Medicine, Division of Cardiovascular Medicine, School of Medicine, University of California, Davis, CA 95616; Department of Veterans Affairs, Northern California Health Care System, Mather, CA 95655
| | - Ebenezer N Yamoah
- Program in Communication Science, Department of Physiology, School of Medicine, University of Nevada, Reno, Reno NV 89557;
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27
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Davis RL, Crozier RA. Dynamic firing properties of type I spiral ganglion neurons. Cell Tissue Res 2015; 361:115-27. [PMID: 25567109 DOI: 10.1007/s00441-014-2071-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 11/17/2014] [Indexed: 10/24/2022]
Abstract
Spiral ganglion neurons, the first neural element in the auditory system, possess complex intrinsic properties, possibly required to process frequency-specific sensory input that is integrated with extensive efferent regulation. Together with their tonotopically-graded sizes, the somata of these neurons reveal a sophisticated electrophysiological profile. Type I neurons, which make up ~95 % of the ganglion, have myriad voltage-gated ion channels that not only vary along the frequency contour of the cochlea, but also can be modulated by regulators such as voltage, calcium, and second messengers. The resultant developmentally- and tonotopically-regulated neuronal firing patterns conform to three distinct response modes (unitary, rapid, and slow) based on threshold and accommodation. This phenotype, however, is not static for any individual type I neuron. Recent observations have shown that, as neurons become less excitable with age, they demonstrate enhanced plasticity enabling them to change from one response mode to another depending upon resting membrane potential and the presence of neurotrophin-3. Thus, the primary auditory afferents utilized to encode dynamic acoustic stimuli possess the intrinsic specializations that allow them dynamically to alter their firing pattern.
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Affiliation(s)
- Robin L Davis
- Department of Cell Biology and Neuroscience, Nelson Laboratories, Rutgers University, 604 Allison Road, Piscataway, NJ 08854, USA,
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28
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Genetic, cellular, and functional evidence for Ca2+ inflow through Cav1.2 and Cav1.3 channels in murine spiral ganglion neurons. J Neurosci 2014; 34:7383-93. [PMID: 24849370 DOI: 10.1523/jneurosci.5416-13.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Spiral ganglion neurons (SGNs) of the eighth nerve serve as the bridge between hair cells and the cochlear nucleus. Hair cells use Cav1.3 as the primary channel for Ca(2+) inflow to mediate transmitter release. In contrast, SGNs are equipped with multiple Ca(2+) channels to mediate Ca(2+)-dependent functions. We examined directly the role of Cav1.3 channels in SGNs using Cav1.3-deficient mice (Cav1.3(-/-)). We revealed a surprising finding that SGNs functionally express the cardiac-specific Cav1.2, as well as neuronal Cav1.3 channels. We show that evoked action potentials recorded from SGNs show a significant decrease in the frequency of firing in Cav1.3(-/-) mice compared with wild-type (Cav1.3(+/+)) littermates. Although Cav1.3 is the designated L-type channel in neurons, whole-cell currents recorded in isolated SGNs from Cav1.3(-/-) mice showed a surprising remnant current with sensitivity toward the dihydropyridine (DHP) agonist and antagonist, and a depolarization shift in the voltage-dependent activation compared with that in the Cav1.3(+/+) mice. Indeed, direct measurement of the elementary properties of Ca(2+) channels, in Cav1.3(+/+) neurons, confirmed the existence of two DHP-sensitive single-channel currents, with distinct open probabilities and conductances. We demonstrate that the DHP-sensitive current in Cav1.3(-/-) mice is derived from Cav1.2 channel activity, providing for the first time, to our knowledge, functional data for the expression of Cav1.2 currents in neurons. Finally, using shRNA gene knockdown methodology, and histological analyses of SGNs from Cav1.2(+/-) and Cav1.3(+/-) mice, we were able to establish the differential roles of Cav1.2 and Cav1.3 in SGNs.
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Moya A, Mínguez JJ, Martorell J, Gallinato MJ, Recio A. Congenital Peripheral Vestibular Syndrome in a Domestic Ferret ( Mustela putorius furo). J Exot Pet Med 2014; 23:287-293. [PMID: 32362793 PMCID: PMC7185825 DOI: 10.1053/j.jepm.2014.06.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
A 3-month-old intact female ferret (Mustela putorius furo) was presented with a 2-month history of ataxia. On physical examination, the ferret had difficulty standing upright. During the neurologic examination, the patient had a left head tilt and positional strabismus, circled to the left, and was ataxic. Results of the complete blood count were consistent with a mild normocytic normochromic anemia. Initial treatment was supportive. Magnetic resonance imaging was performed and revealed an asymmetry of the inner ears. A brainstem auditory evoked response test was also performed. History, clinical signs, and diagnostic test results indicated that the ferret was suffering from congenital peripheral vestibular syndrome and left-sided deafness. Congenital disease should be considered in the differential diagnosis of young ferrets with peripheral vestibular syndrome. Supportive care and physiotherapy can improve balance and motor function, leading to an acceptable quality of life.
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Affiliation(s)
| | | | - Jaime Martorell
- Departament de Medicina i Cirurgia Animals, Facultat de Veterinaria, Universitat Autònoma de Barcelona, Barcelona, Spain
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30
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Oak MH, Yi E. Voltage-gated K(+) channels contributing to temporal precision at the inner hair cell-auditory afferent nerve fiber synapses in the mammalian cochlea. Arch Pharm Res 2014; 37:821-33. [PMID: 24925343 DOI: 10.1007/s12272-014-0411-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 05/09/2014] [Indexed: 12/16/2022]
Abstract
To perform auditory tasks such as sound localization in the space, auditory neurons in the brain must distinguish sub-millisecond temporal differences in signals from two ears. Such high temporal resolution is possible when each neuron in the ascending auditory pathway fires brief action potential at very accurate timing. Various pre- and postsynaptic machineries ensuring such high temporal precision of auditory synaptic transmission have been identified. Of particular, in this review, the role of K(+) channels in shortening the duration of synaptic potentials will be discussed. First, the contribution of K(+) channels to AP firing of general auditory neurons will be discussed. Then, the focus will be moved to the inner hair cell (IHC)-auditory afferent nerve fiber (ANF) synapses, the first synapses of ascending auditory pathway. Molecular and immunohistological techniques have revealed various K(+) channels in the cell bodies and their processes of ANFs. Since the development of patch-clamp recordings from the ANF dendrites in 2002, it became possible to monitor the IHC-ANF synaptic transmission in greater detail. As revealed in brain auditory synapses, several different K(+) channels appear to participate in reducing the duration of synaptic potentials at the IHC-ANF synapses. In addition, K(+) channels at the ANF dendrites might act as potential targets of efferent feedback from the brain. The hypothesis is that, upon loud sound exposure, efferent neurotransmitters released onto the ANF dendrites activate certain K(+) channels and prevent excitotoxicity of ANFs. Therefore, K(+) channels of the ANF dendrites might provide potential sites of pharmacological actions to prevent noise-induced hearing loss.
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Affiliation(s)
- Min-Ho Oak
- College of Pharmacy and Natural Medicine Research Institute, Mokpo National University, 1666 Yeongsan-ro, Cheonggye-Myeon, Muan, Jeonnam, 534-729, Republic of Korea
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31
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Kim YH, Holt JR. Functional contributions of HCN channels in the primary auditory neurons of the mouse inner ear. ACTA ACUST UNITED AC 2014; 142:207-23. [PMID: 23980193 PMCID: PMC3753603 DOI: 10.1085/jgp.201311019] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The hyperpolarization-activated current, Ih, is carried by members of the Hcn channel family and contributes to resting potential and firing properties in excitable cells of various systems, including the auditory system. Ih has been identified in spiral ganglion neurons (SGNs); however, its molecular correlates and their functional contributions have not been well characterized. To investigate the molecular composition of the channels that carry Ih in SGNs, we examined Hcn mRNA harvested from spiral ganglia of neonatal and adult mice using quantitative RT-PCR. The data indicate expression of Hcn1, Hcn2, and Hcn4 subunits in SGNs, with Hcn1 being the most highly expressed at both stages. To investigate the functional contributions of HCN subunits, we used the whole-cell, tight-seal technique to record from wild-type SGNs and those deficient in Hcn1, Hcn2, or both. We found that HCN1 is the most prominent subunit contributing to Ih in SGNs. Deletion of Hcn1 resulted in reduced conductance (Gh), slower activation kinetics (τfast), and hyperpolarized half-activation (V1/2) potentials. We demonstrate that Ih contributes to SGN function with depolarized resting potentials, depolarized sag and rebound potentials, accelerated rebound spikes after hyperpolarization, and minimized jitter in spike latency for small depolarizing stimuli. Auditory brainstem responses of Hcn1-deficient mice showed longer latencies, suggesting that HCN1-mediated Ih is critical for synchronized spike timing in SGNs. Together, our data indicate that Ih contributes to SGN membrane properties and plays a role in temporal aspects of signal transmission between the cochlea and the brain, which are critical for normal auditory function.
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Affiliation(s)
- Ye-Hyun Kim
- Neuroscience Graduate Program, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
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32
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Wang W, Kim HJ, Lee JH, Wong V, Sihn CR, Lv P, Perez Flores MC, Mousavi-Nik A, Doyle KJ, Xu Y, Yamoah EN. Functional significance of K+ channel β-subunit KCNE3 in auditory neurons. J Biol Chem 2014; 289:16802-13. [PMID: 24727472 DOI: 10.1074/jbc.m113.545236] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The KCNE3 β-subunit interacts with and regulates the voltage-dependent gating, kinetics, and pharmacology of a variety of Kv channels in neurons. Because a single neuron may express multiple KCNE3 partners, it is impossible to predict the overall functional relevance of the single transmembrane domain peptide on the pore-forming K(+) channel subunits with which it associates. In the inner ear, the role of KCNE3 is undefined, despite its association with Meniere disease and tinnitus. To gain insights on the functional significance of KCNE3 in auditory neurons, we examined the properties of spiral ganglion neurons (SGNs) in Kcne3 null mutant neurons relative to their age-matched controls. We demonstrate that null deletion of Kcne3 abolishes characteristic wide variations in the resting membrane potentials of SGNs and yields age-dependent alterations in action potential and firing properties of neurons along the contour of the cochlear axis, in comparison with age-matched wild-type neurons. The properties of basal SGNs were markedly altered in Kcne3(-/-) mice compared with the wild-type controls; these include reduced action potential latency, amplitude, and increased firing frequency. Analyses of the underlying conductance demonstrate that null mutation of Kcne3 results in enhanced outward K(+) currents, which is sufficient to explain the ensuing membrane potential changes. Additionally, we have demonstrated that KCNE3 may regulate the activity of Kv4.2 channels in SGNs. Finally, there were developmentally mediated compensatory changes that occurred such that, by 8 weeks after birth, the electrical properties of the null mutant neurons were virtually indistinguishable from the wild-type neurons, suggesting that ion channel remodeling in auditory neurons progresses beyond hearing onset.
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Affiliation(s)
- Wenying Wang
- From the Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang 050017, China, the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Hyo Jeong Kim
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Jeong-Han Lee
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Victor Wong
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Choong-Ryoul Sihn
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Ping Lv
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and the Department of Pharmacology, Hebei Medical University, Shijiazhuang 050017, China
| | - Maria Cristina Perez Flores
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Atefeh Mousavi-Nik
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Karen Jo Doyle
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
| | - Yanfang Xu
- From the Key Laboratory of Neural and Vascular Biology, Ministry of Education, Hebei Medical University, Shijiazhuang 050017, China,
| | - Ebenezer N Yamoah
- the Department of Anesthesiology and Pain Medicine, Program in Communication and Sensory Sciences, University of California at Davis School of Medicine, Davis, California 95618, and
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Abstract
Cell shrinkage is a hallmark and contributes to signaling of apoptosis. Apoptotic cell shrinkage requires ion transport across the cell membrane involving K(+) channels, Cl(-) or anion channels, Na(+)/H(+) exchange, Na(+),K(+),Cl(-) cotransport, and Na(+)/K(+)ATPase. Activation of K(+) channels fosters K(+) exit with decrease of cytosolic K(+) concentration, activation of anion channels triggers exit of Cl(-), organic osmolytes, and HCO3(-). Cellular loss of K(+) and organic osmolytes as well as cytosolic acidification favor apoptosis. Ca(2+) entry through Ca(2+)-permeable cation channels may result in apoptosis by affecting mitochondrial integrity, stimulating proteinases, inducing cell shrinkage due to activation of Ca(2+)-sensitive K(+) channels, and triggering cell-membrane scrambling. Signaling involved in the modification of cell-volume regulatory ion transport during apoptosis include mitogen-activated kinases p38, JNK, ERK1/2, MEKK1, MKK4, the small G proteins Cdc42, and/or Rac and the transcription factor p53. Osmosensing involves integrin receptors, focal adhesion kinases, and tyrosine kinase receptors. Hyperosmotic shock leads to vesicular acidification followed by activation of acid sphingomyelinase, ceramide formation, release of reactive oxygen species, activation of the tyrosine kinase Yes with subsequent stimulation of CD95 trafficking to the cell membrane. Apoptosis is counteracted by mechanisms involved in regulatory volume increase (RVI), by organic osmolytes, by focal adhesion kinase, and by heat-shock proteins. Clearly, our knowledge on the interplay between cell-volume regulatory mechanisms and suicidal cell death is still far from complete and substantial additional experimental effort is needed to elucidate the role of cell-volume regulatory mechanisms in suicidal cell death.
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Affiliation(s)
- Florian Lang
- Institute of Physiology, University of Tübingen, Tübingen, Germany
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34
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Evolutionary analysis of voltage-gated potassium channels by Bayes method. J Mol Neurosci 2013; 53:41-9. [PMID: 24318840 DOI: 10.1007/s12031-013-0192-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 11/12/2013] [Indexed: 10/25/2022]
Abstract
Voltage-gated potassium channels (VGPCs) are among the most complex families of ion channels. VGPCs are distributed widely among species but their biological roles remain unclear. In this study, the evolution of VGPCs and the functions of ancestral families are determined according to phylogenetic studies. We downloaded 127 genomic data of alpha subunits and 38 genomic data of beta subunits including those from human, rat, mice, Drosophila and Puccinellia tenuiflora. The genetic neighborhood of subfamily genes was determined by neighbor-joining, minimum evolution, maximum parsimony, and Bayes methods. Data was presented as phylogenetic trees. We also detected positive selection sites by site model. New insights into the evolutionary history of the VGPC family are provided. Our assumptions are as follows: (a) KCNH subfamily is likely the most original subfamily in alpha subunit; (b) VGPCs are related to neural and cardiac systems at the earliest time; (c) KCNA4 and KCNF1 may be as ancestors; (d) abnormality in one gene may cause both cardiac and neural diseases; and (e) abnormalities in KCNH6 and KCNQ7 are more likely to cause cardiac diseases.
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35
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Wang W, Kim HJ, Lv P, Tempel B, Yamoah EN. Association of the Kv1 family of K+ channels and their functional blueprint in the properties of auditory neurons as revealed by genetic and functional analyses. J Neurophysiol 2013; 110:1751-64. [PMID: 23864368 DOI: 10.1152/jn.00290.2013] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Developmental plasticity in spiral ganglion neurons (SGNs) ensues from profound alterations in the functional properties of the developing hair cell (HC). For example, prehearing HCs are spontaneously active. However, at the posthearing stage, HC membrane properties transition to graded receptor potentials. The dendrotoxin (DTX)-sensitive Kv1 channel subunits (Kv1.1, 1.2, and 1.6) shape the firing properties and membrane potential of SGNs, and the expression of the channel undergoes developmental changes. Because of the stochastic nature of Kv subunit heteromultimerization, it has been difficult to determine physiologically relevant subunit-specific interactions and their functions in the underlying mechanisms of Kv1 channel plasticity in SGNs. Using Kcna2 null mutant mice, we demonstrate a surprising paradox in changes in the membrane properties of SGNs. The resting membrane potential of Kcna2(-/-) SGNs was significantly hyperpolarized compared with that of age-matched wild-type (WT) SGNs. Analyses of outward currents in the mutant SGNs suggest an apparent approximately twofold increase in outward K(+) currents. We show that in vivo and in vitro heteromultimerization of Kv1.2 and Kv1.4 α-subunits underlies the striking and unexpected alterations in the properties of SGNs. The results suggest that heteromeric interactions of Kv1.2 and Kv1.4 dominate the defining features of Kv1 channels in SGNs.
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Affiliation(s)
- Wenying Wang
- Program in Communication Science, Center for Neuroscience, University of California, Davis, School of Medicine, Davis, California
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36
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Posthearing Ca(2+) currents and their roles in shaping the different modes of firing of spiral ganglion neurons. J Neurosci 2013; 32:16314-30. [PMID: 23152615 DOI: 10.1523/jneurosci.2097-12.2012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Whereas prehearing spiral ganglion neurons (SGNs) rely faithfully on outputs from spontaneously active developing hair cells, the electrical phenotypes of posthearing neurons are shaped by distinct rapid and graded receptor potentials from hair cells. To date, technical difficulties in isolation of fragile posthearing neurons from the rigid bony labyrinth of the inner ear have hindered analyses of the electrical phenotype of SGNs. Therefore, we have recently developed new strategies to isolate posthearing mouse SGNs for functional analyses. Here, we describe the coarse and fine properties of Ca(2+) currents, which sculpt the firing properties of posthearing SGNs. Murine SGNs express multiple Ca(2+) channel currents to enable diverse functions. We have demonstrated that suppression of Ca(2+) currents results in significant hyperpolarization of the resting membrane potential (rmp) of basal SGNs, suggesting that Ca(2+) influx primes rmp for excitation. In contrast, removal of external Ca(2+) has modest effects on rmp of apical SGNs. The blockade of Ca(2+) currents with a mixture of specific blockers attenuates spontaneously active SGNs. Paradoxically, different subtypes of Ca(2+) currents, such as R-type currents, may activate resting outward conductances since blockage of the current results in depolarization of rmp. In keeping with whole-cell current data, single-channel records revealed multiple diverse Ca(2+) channels in SGNs. Additionally, there were differential expressions of distinct Ca(2+) current densities in the apicobasal contour of the adult cochlea. This report provides invaluable insights into Ca(2+)-dependent processes in adult SGNs.
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37
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Abstract
Conductive deafness, caused by outer or middle ear obstruction, may be corrected, whereas sensorineural deafness cannot. Most deafness in dogs is congenital sensorineural hereditary deafness, associated with the genes for white pigment: piebald or merle. The genetic cause has not yet been identified. Dogs with blue eyes have a greater likelihood of hereditary deafness than brown-eyed dogs. Other common forms of sensorineural deafness include presbycusis, ototoxicity, noise-induced hearing loss, otitis interna, and anesthesia. Definitive diagnosis of deafness requires brainstem auditory evoked response testing.
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Affiliation(s)
- George M Strain
- Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
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38
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Purcell EK, Yang A, Liu L, Velkey JM, Morales MM, Duncan RK. BDNF profoundly and specifically increases KCNQ4 expression in neurons derived from embryonic stem cells. Stem Cell Res 2012; 10:29-35. [PMID: 23089626 DOI: 10.1016/j.scr.2012.08.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 08/15/2012] [Accepted: 08/27/2012] [Indexed: 01/10/2023] Open
Abstract
Neurons resembling the spiral ganglion neurons (SGNs) of the auditory nerve can be generated from embryonic stem cells through induced overexpression of the transcription factor Neurogenin-1 (Neurog1). While recapitulating this developmental pathway produces glutamatergic, bipolar neurons reminiscent of SGNs, these neurons are functionally immature, being characterized by a depolarized resting potential and limited excitability. We explored the effects of two neurotrophins known to be present in the inner ear, brain derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), on the electrophysiology of neurons following Neurog1 induction. Our data reveal a significant reduction in resting membrane potential (RMP) following neurotrophin exposure, with BDNF producing a more robust effect than NT-3. This effect was accompanied by a profound and specific upregulation of the KCNQ4 subtype, where a 9-fold increase was observed with quantitative PCR. The other neuronally expressed KCNQ subtypes (2, 3, and 5) exhibited upregulation which was 3-fold or less in magnitude. Quantitative immunohistochemistry confirmed the increase in KCNQ4 expression at the protein level. The present data show a novel link between BDNF and KCNQ4 expression, yielding insight into the restricted expression pattern of a channel known to play special roles in setting the resting potential of auditory cells and in the etiology of progressive high-frequency hearing loss.
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39
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Xia L, Yin S, Wang J. Inner ear gene transfection in neonatal mice using adeno-associated viral vector: a comparison of two approaches. PLoS One 2012; 7:e43218. [PMID: 22912830 PMCID: PMC3422324 DOI: 10.1371/journal.pone.0043218] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2012] [Accepted: 07/18/2012] [Indexed: 01/06/2023] Open
Abstract
Local gene transfection is a promising technique for the prevention and/or correction of inner ear diseases, particularly those resulting from genetic defects. Adeno-associated virus (AAV) is an ideal viral vector for inner ear gene transfection because of its safety, stability, long-lasting expression, and its high tropism for many different cell types. Recently, a new generation of AAV vectors with a tyrosine mutation (mut-AAV) has demonstrated significant improvement in transfection efficiency. A method for inner ear gene transfection via the intact round window membrane (RWM) has been developed in our laboratory. This method has not been tested in neonatal mice, an important species for the study of inherited hearing loss. Following a preliminary study to optimize the experimental protocol in order to reduce mortality, the present study investigated inner ear gene transfection in mice at postnatal day 7. We compared transfection efficiency, the safety of the scala tympani injection via RWM puncture, and the trans-RWM diffusion following partial digestion with an enzyme technique. The results revealed that approximately 47% of inner hair cells (IHCs) and 17% of outer hair cells (OHCs) were transfected via the trans-RWM approach. Transfection efficiency via RWM puncture (58% and 19% for IHCs and OHCs, respectively) was slightly higher, but the difference was not significant.
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Affiliation(s)
- Li Xia
- Department of Otolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiao Tong University, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Shankai Yin
- Department of Otolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiao Tong University, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
- * E-mail: (SY); (JW)
| | - Jian Wang
- Department of Otolaryngology, Affiliated Sixth People's Hospital of Shanghai Jiao Tong University, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
- School of Human Communication Disorder, Dalhousie University, Halifax, Nova Scotia, Canada
- * E-mail: (SY); (JW)
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40
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Leitner MG, Feuer A, Ebers O, Schreiber DN, Halaszovich CR, Oliver D. Restoration of ion channel function in deafness-causing KCNQ4 mutants by synthetic channel openers. Br J Pharmacol 2012; 165:2244-59. [PMID: 21951272 DOI: 10.1111/j.1476-5381.2011.01697.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE DFNA2 is a frequent hereditary hearing disorder caused by loss-of-function mutations in the voltage-gated potassium channel KCNQ4 (Kv7.4). KCNQ4 mediates the predominant K(+) conductance, I(K,n) , of auditory outer hair cells (OHCs), and loss of KCNQ4 function leads to degeneration of OHCs resulting in progressive hearing loss. Here we explore the possible recovery of channel activity of mutant KCNQ4 induced by synthetic KCNQ channel openers. EXPERIMENTAL APPROACH Whole cell patch clamp recordings were performed on CHO cells transiently expressing KCNQ4 wild-type (wt) and DFNA2-relevant mutants, and from acutely isolated OHCs. KEY RESULTS Various known KCNQ channel openers robustly enhanced KCNQ4 currents. The strongest potentiation was observed with a combination of zinc pyrithione plus retigabine. A similar albeit less pronounced current enhancement was observed with native I(K,n) currents in rat OHCs. DFNA2 mutations located in the channel's pore region abolished channel function and these mutant channels were completely unresponsive to channel openers. However, the function of a DFNA2 mutation located in the proximal C-terminus was restored by the combined application of both openers. Co-expression of wt and KCNQ4 pore mutants suppressed currents to barely detectable levels. In this dominant-negative situation, channel openers essentially restored currents back to wt levels, most probably through strong activation of only the small fraction of homomeric wt channels. CONCLUSIONS AND IMPLICATIONS Our data suggest that by stabilizing the KCNQ4-mediated conductance in OHCs, chemical channel openers can protect against OHC degeneration and progression of hearing loss in DFNA2.
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Affiliation(s)
- Michael G Leitner
- Department of Neurophysiology, Philipps-University Marburg, Marburg, Germany
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41
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Spike encoding of neurotransmitter release timing by spiral ganglion neurons of the cochlea. J Neurosci 2012; 32:4773-89. [PMID: 22492033 DOI: 10.1523/jneurosci.4511-11.2012] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Mammalian cochlear spiral ganglion neurons (SGNs) encode sound with microsecond precision. Spike triggering relies upon input from a single ribbon-type active zone of a presynaptic inner hair cell (IHC). Using patch-clamp recordings of rat SGN postsynaptic boutons innervating the modiolar face of IHCs from the cochlear apex, at room temperature, we studied how spike generation contributes to spike timing relative to synaptic input. SGNs were phasic, firing a single short-latency spike for sustained currents of sufficient onset slope. Almost every EPSP elicited a spike, but latency (300-1500 μs) varied with EPSP size and kinetics. When current-clamp stimuli approximated the mean physiological EPSC (≈300 pA), several times larger than threshold current (rheobase, ≈50 pA), spikes were triggered rapidly (latency, ≈500 μs) and precisely (SD, <50 μs). This demonstrated the significance of strong synaptic input. However, increasing EPSC size beyond the physiological mean resulted in less-potent reduction of latency and jitter. Differences in EPSC charge and SGN baseline potential influenced spike timing less as EPSC onset slope and peak amplitude increased. Moreover, the effect of baseline potential on relative threshold was small due to compensatory shift of absolute threshold potential. Experimental first-spike latencies in response to a broad range of stimuli were predicted by a two-compartment exponential integrate-and-fire model, with latency prediction error of <100 μs. In conclusion, the close anatomical coupling between a strong synapse and spike generator along with the phasic firing property lock SGN spikes to IHC exocytosis timing to generate the auditory temporal code with high fidelity.
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42
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Tune in to KCNQ. Nat Neurosci 2011; 15:8-10. [PMID: 22193251 DOI: 10.1038/nn.3012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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43
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Klinger F, Gould G, Boehm S, Shapiro MS. Distribution of M-channel subunits KCNQ2 and KCNQ3 in rat hippocampus. Neuroimage 2011; 58:761-9. [PMID: 21787867 DOI: 10.1016/j.neuroimage.2011.07.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 06/17/2011] [Accepted: 07/04/2011] [Indexed: 11/29/2022] Open
Abstract
Neuronal M-channels are low threshold, slowly activating and non-inactivating, voltage dependent K(+) channels that play a crucial role in controlling neuronal excitability. The native M-channel is composed of heteromeric or homomeric assemblies of subunits belonging to the Kv7/KCNQ family, with KCNQ2/3 heteromers being the most abundant form. KCNQ2 and KCNQ3 subunits have been found to be expressed in various neurons in the central and peripheral nervous system of rodents and humans. Previous evidence shows preferential localization of both subunits to axon initial segments, somata and nodes of Ranvier. In this work, we show the distribution and co-localization of KCNQ2 and KCNQ3 subunits throughout the hippocampal formation, via immunostaining experiments on unfixed rat brain slices and confocal microscopy. We find intense localization and colocalization to the axonal initial segment in several regions of the hippocampus, as well as staining for non-neuronal cells in the area of the lateral ventricle. We did not observe colocalization of KCNQ2 or KCNQ3 with the presynaptic protein, synaptophysin.
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Affiliation(s)
- Felicia Klinger
- Department of Physiology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
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44
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Kim HJ, Lv P, Sihn CR, Yamoah EN. Cellular and molecular mechanisms of autosomal dominant form of progressive hearing loss, DFNA2. J Biol Chem 2010; 286:1517-27. [PMID: 20966080 DOI: 10.1074/jbc.m110.179010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Despite advances in identifying deafness genes, determination of the underlying cellular and functional mechanisms for auditory diseases remains a challenge. Mutations of the human K(+) channel hKv7.4 lead to post-lingual progressive hearing loss (DFNA2), which affects world-wide population with diverse racial backgrounds. Here, we have generated the spectrum of point mutations in the hKv7.4 that have been identified as diseased mutants. We report that expression of five point mutations in the pore region, namely L274H, W276S, L281S, G285C, and G296S, as well as the C-terminal mutant G321S in the heterologous expression system, yielded non-functional channels because of endoplasmic reticulum retention of the mutant channels. We mimicked the dominant diseased conditions by co-expressing the wild-type and mutant channels. As compared with expression of wild-type channel alone, the blend of wild-type and mutant channel subunits resulted in reduced currents. Moreover, the combinatorial ratios of wild type:mutant and the ensuing current magnitude could not be explained by the predictions of a tetrameric channel and a dominant negative effect of the mutant subunits. The results can be explained by the dependence of cell surface expression of the mutant on the wild-type subunit. Surprisingly, a transmembrane mutation F182L, which has been identified in a pre-lingual progressive hearing loss patient in Taiwan, yielded cell surface expression and functional features that were similar to that of the wild type, suggesting that this mutation may represent redundant polymorphism. Collectively, these findings provide traces of the cellular mechanisms for DFNA2.
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Affiliation(s)
- Hyo Jeong Kim
- Department of Anesthesiology and Pain Medicine, Program in Communication Science, School of Medicine, University of California, Davis, California 95618, USA
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