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Zong L, Zhao J, Wu W, Wang J, Huang D, Liu M. AIF knockdown induce apoptosis and mitochondrial dysfunction in cochlear spiral ganglion neurons in vitro. Mol Med Rep 2020; 21:1910-1920. [PMID: 32319616 PMCID: PMC7057812 DOI: 10.3892/mmr.2020.10970] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 01/14/2020] [Indexed: 12/14/2022] Open
Abstract
The underlying mechanism involved in auditory neuropathy spectrum disorder (ANSD) remains largely unclear. It has been previously reported that mutations in the apoptosis-inducing factor (AIF) gene are associated with auditory neuropathy and delayed peripheral neuropathy, which can eventually cause ANSD. In the present study, the regulatory effects of AIF knockdown on the cellular functions of spiral ganglion neurons (SNGs) and the molecular mechanism(s) of AIF knockdown in inducing cell apoptosis in SGNs were further investigated. The results showed that the AIF knockdown via siRNA transfection resulted in high levels of oxidative stress, and impaired mitochondrial respiration activity and membrane potential in SGNs. Western blotting further proved that the knockdown of AIF can decrease the content of anti-apoptotic and anti-oxidative proteins, as well as mitochondrial respiratory chain Complex I proteins. The present experimental data suggested that the abnormal expression of AIF may affect SGNs cellular function, and may contribute to the progress of ANSD.
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Affiliation(s)
- Liang Zong
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
| | - Jiandong Zhao
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
| | - Wenming Wu
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
| | - Jialing Wang
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
| | - Deliang Huang
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
| | - Mingbo Liu
- Department of Otolaryngology‑Head and Neck Surgery, Institute of Otolaryngology, PLA General Hospital, Beijing 100853, P.R. China
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Stolle M, Schulze J, Roemer A, Lenarz T, Durisin M, Warnecke A. Human Plasma Rich in Growth Factors Improves Survival and Neurite Outgrowth of Spiral Ganglion Neurons In Vitro. Tissue Eng Part A 2017; 24:493-501. [PMID: 28610547 DOI: 10.1089/ten.tea.2017.0120] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Platelet-rich and platelet-poor plasma (PRP and PPP) are autologous preparations from peripheral blood and contain several growth factors and cytokines involved in tissue repair. Although their neuroprotective and neuroregenerative properties have been already described, little is known about their effects in the inner ear. We, therefore, examined the effects of PRP and PPP on spiral ganglion neurons (SGN) in vitro. RESULTS For all experiments, spiral ganglia were isolated from neonatal rats and were cultured in serum-free medium. PRP from human venous blood was added to dissociated SGN. Treatment with PRP (1:10, 1:50) significantly increased the neuronal survival and the neuronal outgrowth of SGN. This effect was completely reversed by the addition of Bay 11 (nuclear factor kappa B-inhibitor) and SB203580 (p38 mitogen-activated protein kinase [p38MAPK]-inhibitor). Furthermore, PPP was used as a cell-free matrix for the attachment of spiral ganglion explants. Coating with activated PPP improved the adhesion and neurite outgrowth of spiral ganglia explants. Therefore, activated PPP is a promising alternative for poly d/l-ornithine and laminin coating due to the gelatinous composition through the activation of PPP with calcium gluconate. PRP promotes neuroprotective and neuroregenerative effects on SGN when administered in adequate concentrations. These beneficial effects seem to be depending on NF-κB and the p38MAPK pathways. CONCLUSION Preparations from autologous whole blood (PRP and PPP, respectively) present an interesting alternative for pharmacological intervention to the inner ear since they contain a balanced and natural composition of trophic factors.
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Affiliation(s)
- Michael Stolle
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany
| | - Jennifer Schulze
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany .,2 Cluster of Excellence of the German Research Foundation (DFG; "Deutsche Forschungsgemeinschaft") "Hearing4all", Hannover, Germany
| | - Ariane Roemer
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany
| | - Thomas Lenarz
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany .,2 Cluster of Excellence of the German Research Foundation (DFG; "Deutsche Forschungsgemeinschaft") "Hearing4all", Hannover, Germany
| | - Martin Durisin
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany
| | - Athanasia Warnecke
- 1 Department of Otolaryngology, Hannover Medical School , Hannover, Germany .,2 Cluster of Excellence of the German Research Foundation (DFG; "Deutsche Forschungsgemeinschaft") "Hearing4all", Hannover, Germany
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Chen Y, Chuan HL, Yu SY, Li CZ, Wu ZB, Li GL, Zhang YZ. A Novel Invasive-Related Biomarker in Three Subtypes of Nonfunctioning Pituitary Adenomas. World Neurosurg 2017; 100:514-521. [PMID: 28093347 DOI: 10.1016/j.wneu.2017.01.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 01/02/2017] [Accepted: 01/03/2017] [Indexed: 01/03/2023]
Abstract
OBJECTIVE To identify biomarkers key to invasiveness of the 3 subtypes of nonfunctioning pituitary adenomas (NFPAs) and provide a guidance for therapeutic decision making and identification of potential adjuvant drugs. METHODS Fifty NFPA tumor tissues obtained from transsphenoidal surgery were used in the study. Three invasive NFPAs and 4 noninvasive NFPAs were used for gene expression microarray analyses. In addition, there are 5 invasive NFPAs and 4 noninvasive NFPAs used for proteomic analyses. Invasive-related biomarkers were identified by bioinformatics analysis by integrating the transcriptomics and proteomics data sets. All 3 subtypes of NFPAs (null cell adenomas, oncocytomas, and gonadotroph adenomas) were used to validate differentially expressed candidate biomarkers by means of quantitative real-time reverse transcription polymerase chain reaction and Western blot. The level of EZR was downregulated in pituitary adenoma cell line GH3 to investigate the invasive effect of EZR on GH3 cells by using the RNA interference technique. RESULTS Eight genes involved in the invasion function were found by bioinformatics analysis, and the EZR gene was identified as a novel invasive-related biomarker in the 3 subtypes of NFPAs. The expression level of EZR was found higher in terms of invasiveness than the noninvasive ones of the 3 subtypes of NFPAs. Moreover, the knockdown of EZR inhibited the invasion of GH3 cells in vitro. CONCLUSIONS EZR is a novel biomarker in terms of invasion among the 3 subtypes of NFPAs, and it is a promising guide for therapeutic decision making as well.
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Affiliation(s)
- Yong Chen
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Hong-Li Chuan
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Sheng-Yuan Yu
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Chu-Zhong Li
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China
| | - Zhe-Bao Wu
- Department of Neurosurgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Gui-Lin Li
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
| | - Ya-Zhuo Zhang
- Beijing Neurosurgical Institute, Beijing Tiantan Hospital, Beijing Institute for Brain Disorders Brain Tumor Center, China National Clinical Research Center for Neurological Diseases, Capital Medical University, Beijing, China.
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Pramanik S, Sulistio YA, Heese K. Neurotrophin Signaling and Stem Cells-Implications for Neurodegenerative Diseases and Stem Cell Therapy. Mol Neurobiol 2016; 54:7401-7459. [PMID: 27815842 DOI: 10.1007/s12035-016-0214-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Accepted: 10/11/2016] [Indexed: 02/07/2023]
Abstract
Neurotrophins (NTs) are members of a neuronal growth factor protein family whose action is mediated by the tropomyosin receptor kinase (TRK) receptor family receptors and the p75 NT receptor (p75NTR), a member of the tumor necrosis factor (TNF) receptor family. Although NTs were first discovered in neurons, recent studies have suggested that NTs and their receptors are expressed in various types of stem cells mediating pivotal signaling events in stem cell biology. The concept of stem cell therapy has already attracted much attention as a potential strategy for the treatment of neurodegenerative diseases (NDs). Strikingly, NTs, proNTs, and their receptors are gaining interest as key regulators of stem cells differentiation, survival, self-renewal, plasticity, and migration. In this review, we elaborate the recent progress in understanding of NTs and their action on various stem cells. First, we provide current knowledge of NTs, proNTs, and their receptor isoforms and signaling pathways. Subsequently, we describe recent advances in the understanding of NT activities in various stem cells and their role in NDs, particularly Alzheimer's disease (AD) and Parkinson's disease (PD). Finally, we compile the implications of NTs and stem cells from a clinical perspective and discuss the challenges with regard to transplantation therapy for treatment of AD and PD.
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Affiliation(s)
- Subrata Pramanik
- Graduate School of Biomedical Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 133-791, Republic of Korea
| | - Yanuar Alan Sulistio
- Graduate School of Biomedical Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 133-791, Republic of Korea
| | - Klaus Heese
- Graduate School of Biomedical Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 133-791, Republic of Korea.
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Smith FL, Davis RL. Organ of Corti explants direct tonotopically graded morphology of spiral ganglion neurons in vitro. J Comp Neurol 2016; 524:2182-207. [PMID: 26663318 DOI: 10.1002/cne.23940] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2014] [Revised: 11/12/2015] [Accepted: 11/30/2015] [Indexed: 01/25/2023]
Abstract
The spiral ganglion is a compelling model system to examine how morphological form contributes to sensory function. While the ganglion is composed mainly of a single class of type I neurons that make simple one-to-one connections with inner hair cell sensory receptors, it has an elaborate overall morphological design. Specific features, such as soma size and axon outgrowth, are graded along the spiral contour of the cochlea. To begin to understand the interplay between different regulators of neuronal morphology, we cocultured neuron explants with peripheral target tissues removed from distinct cochlear locations. Interestingly, these "hair cell microisolates" were capable of both increasing and decreasing neuronal somata size, without adversely affecting survival. Moreover, axon characteristics elaborated de novo by the primary afferents in culture were systematically regulated by the sensory endorgan. Apparent peripheral nervous system (PNS)-like and central nervous system (CNS)-like axonal profiles were established in our cocultures allowing an analysis of putative PNS/CNS axon length ratios. As predicted from the in vivo organization, PNS-like axon bundles elaborated by apical cocultures were longer than their basal counterparts and this phenotype was methodically altered when neuron explants were cocultured with microisolates from disparate cochlear regions. Thus, location-dependent signals within the organ of Corti may set the "address" of neurons within the spiral ganglion, allowing them to elaborate the appropriate tonotopically associated morphological features in order to carry out their signaling function. J. Comp. Neurol. 524:2182-2207, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Felicia L Smith
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
| | - Robin L Davis
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, New Jersey, USA
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Zhang W, Sun JZ, Han Y, Chen J, Liu H, Wang Y, Yue B, Chen Y. CXCL12/CXCR4 signaling pathway regulates cochlear development in neonatal mice. Mol Med Rep 2016; 13:4357-64. [PMID: 27052602 DOI: 10.3892/mmr.2016.5085] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 03/17/2016] [Indexed: 11/06/2022] Open
Abstract
Chemotactic cytokines (chemokines) are a highly conserved class of secreted signaling molecules that are important in various cellular processes. CXC chemokine ligand 12 (CXCL12) and its receptor, CXC chemokine receptor 4 (CXCR4) have been previously reported to be crucial for the establishment of neural networks in different neuronal systems. However, it is unclear whether the CXCL12/CXCR4 signaling pathway regulates the development of the cochlea. The current study investigated the effects of the CXCL12/CXCR4 signaling pathway on cochlear development in neonatal mice. The expression levels of CXCL12 and CXCR4 were detected using immunofluorescence, reverse transcription‑quantitative polymerase chain reaction and western blot analysis demonstrating that CXCL12 and CXCR4 expression were significantly increased during cochlear development in neonatal mice. Treatment of spiral ganglion neurons with CXCL12 significantly decreased the protein expression levels of caspase‑3 and cleaved caspase‑3, indicating that CXCL12/CXCR4 signaling increased cell survival of spiral ganglion neurons. Furthermore, CXCL12 treatment significantly increased the number and length of neurites extending from spiral ganglion neurons. By contrast, the in vitro effects of CXCL12 were significantly abrogated by AMD100, a CXCR4 antagonist. Additionally, inhibiting CXCL12/CXCR4 signaling in neonatal mice significantly reduced the cell number and altered the morphology of spiral ganglion neurons in vivo. Thus, the present study indicates that the CXCL12/CXCR4 signaling pathway is important during the development of cochleae in neonatal mice.
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Affiliation(s)
- Wen Zhang
- Department of Otolaryngology, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi 710068, P.R. China
| | - Ji-Zhou Sun
- Department of Otolaryngology, Xi'an XD Group Hospital, Xi'an, Shaanxi 710077, P.R. China
| | - Yu Han
- Department of Otolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Jun Chen
- Department of Otolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Hui Liu
- Department of Otolaryngology, Shaanxi Provincial People's Hospital, Xi'an, Shaanxi 710068, P.R. China
| | - Ye Wang
- Department of Otolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Bo Yue
- Department of Otolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
| | - Yang Chen
- Department of Otolaryngology, Xijing Hospital, Fourth Military Medical University, Xi'an, Shaanxi 710032, P.R. China
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Simvastatin Results in a Dose-Dependent Toxic Effect on Spiral Ganglion Neurons in an In Vitro Organotypic Culture Assay. BIOMED RESEARCH INTERNATIONAL 2016; 2016:3580359. [PMID: 27051663 PMCID: PMC4808657 DOI: 10.1155/2016/3580359] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2016] [Accepted: 02/14/2016] [Indexed: 12/20/2022]
Abstract
Statins are inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase, an enzyme necessary for the production of mevalonate. They are widely used as cholesterol-lowering drugs. However, conflicting data about the effect of statins on neuronal cells has been published. To explore the effect of simvastatin on spiral ganglion neurons (SGNs), SG explants of 5-day-old rats were treated with increasing concentrations of simvastatin. In addition, SG explants were treated with mevalonate and with the combination of simvastatin and mevalonate. SGN number, length of the neurites, area of nonneuronal supporting cells, and neuronal survival were analyzed. Simvastatin treatment results in a significant dose-dependent decrease of SG neurite number, length of neurites, area of supporting cells, and SG neuronal survival compared to control. Interestingly, treatment with mevalonate in addition to simvastatin increased SG neuronal survival compared to simvastatin treatment only. However, treatment with mevalonate in addition to simvastatin did not influence SG neurite number, length of neurites, and area of supporting cells compared to simvastatin treatment only. Our results suggest a neurotoxic effect of simvastatin on SGNs in vitro. Neurotoxicity seems to be at least partially mediated by the mevalonate pathway. Therefore, caution is warranted to use simvastatin as a potential otoprotective drug.
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The Three-Dimensional Culture System with Matrigel and Neurotrophic Factors Preserves the Structure and Function of Spiral Ganglion Neuron In Vitro. Neural Plast 2016; 2016:4280407. [PMID: 27057364 PMCID: PMC4736769 DOI: 10.1155/2016/4280407] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 11/10/2015] [Indexed: 02/06/2023] Open
Abstract
Whole organ culture of the spiral ganglion region is a resourceful model system facilitating manipulation and analysis of live sprial ganglion neurons (SGNs). Three-dimensional (3D) cultures have been demonstrated to have many biomedical applications, but the effect of 3D culture in maintaining the SGNs structure and function in explant culture remains uninvestigated. In this study, we used the matrigel to encapsulate the spiral ganglion region isolated from neonatal mice. First, we optimized the matrigel concentration for the 3D culture system and found the 3D culture system protected the SGNs against apoptosis, preserved the structure of spiral ganglion region, and promoted the sprouting and outgrowth of SGNs neurites. Next, we found the 3D culture system promoted growth cone growth as evidenced by a higher average number and a longer average length of filopodia and a larger growth cone area. 3D culture system also significantly elevated the synapse density of SGNs. Last, we found that the 3D culture system combined with neurotrophic factors had accumulated effects in promoting the neurites outgrowth compared with 3D culture or NFs treatment only groups. Together, we conclude that the 3D culture system preserves the structure and function of SGN in explant culture.
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Novel High Content Screen Detects Compounds That Promote Neurite Regeneration from Cochlear Spiral Ganglion Neurons. Sci Rep 2015; 5:15960. [PMID: 26521685 PMCID: PMC4629150 DOI: 10.1038/srep15960] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 10/06/2015] [Indexed: 12/21/2022] Open
Abstract
The bipolar spiral ganglion neurons (SGN) carry sound information from cochlear hair cells to the brain. After noise, antibiotic or toxic insult to the cochlea, damage to SGN and/or hair cells causes hearing impairment. Damage ranges from fiber and synapse degeneration to dysfunction and loss of cells. New interventions to regenerate peripheral nerve fibers could help reestablish transfer of auditory information from surviving or regenerated hair cells or improve results from cochlear implants, but the biochemical mechanisms to target are largely unknown. Presently, no drugs exist that are FDA approved to stimulate the regeneration of SGN nerve fibers. We designed an original phenotypic assay to screen 440 compounds of the NIH Clinical Collection directly on dissociated mouse spiral ganglia. The assay detected one compound, cerivastatin, that increased the length of regenerating neurites. The effect, mimicked by other statins at different optimal concentrations, was blocked by geranylgeraniol. These results demonstrate the utility of screening small compound libraries on mixed cultures of dissociated primary ganglia. The success of this screen narrows down a moderately sized library to a single compound which can be elevated to in-depth in vivo studies, and highlights a potential new molecular pathway for targeting of hearing loss drugs.
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Inhibition of mTOR by Rapamycin Results in Auditory Hair Cell Damage and Decreased Spiral Ganglion Neuron Outgrowth and Neurite Formation In Vitro. BIOMED RESEARCH INTERNATIONAL 2015; 2015:925890. [PMID: 25918725 PMCID: PMC4395993 DOI: 10.1155/2015/925890] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/10/2015] [Accepted: 03/11/2015] [Indexed: 12/21/2022]
Abstract
Rapamycin is an antifungal agent with immunosuppressive properties. Rapamycin inhibits the mammalian target of rapamycin (mTOR) by blocking the mTOR complex 1 (mTORC1). mTOR is an atypical serine/threonine protein kinase, which controls cell growth, cell proliferation, and cell metabolism. However, less is known about the mTOR pathway in the inner ear. First, we evaluated whether or not the two mTOR complexes (mTORC1 and mTORC2, resp.) are present in the mammalian cochlea. Next, tissue explants of 5-day-old rats were treated with increasing concentrations of rapamycin to explore the effects of rapamycin on auditory hair cells and spiral ganglion neurons. Auditory hair cell survival, spiral ganglion neuron number, length of neurites, and neuronal survival were analyzed in vitro. Our data indicates that both mTOR complexes are expressed in the mammalian cochlea. We observed that inhibition of mTOR by rapamycin results in a dose dependent damage of auditory hair cells. Moreover, spiral ganglion neurite number and length of neurites were significantly decreased in all concentrations used compared to control in a dose dependent manner. Our data indicate that the mTOR may play a role in the survival of hair cells and modulates spiral ganglion neuronal outgrowth and neurite formation.
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Riecken LB, Tawamie H, Dornblut C, Buchert R, Ismayel A, Schulz A, Schumacher J, Sticht H, Pohl KJ, Cui Y, Reis A, Morrison H, Abou Jamra R. Inhibition of RAS Activation Due to a Homozygous Ezrin Variant in Patients with Profound Intellectual Disability. Hum Mutat 2015; 36:270-8. [DOI: 10.1002/humu.22737] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 12/01/2014] [Indexed: 01/19/2023]
Affiliation(s)
- Lars Björn Riecken
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | - Hasan Tawamie
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Carsten Dornblut
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | - Rebecca Buchert
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Amina Ismayel
- Praxis of Pediatrics; Jesser El Sheghour; Idlib Syria
| | - Alexander Schulz
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | | | - Heinrich Sticht
- Bioinformatics; Institute of Biochemistry; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Katja J. Pohl
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | - Yan Cui
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | - André Reis
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
| | - Helen Morrison
- Leibniz Institute for Age Research; Fritz Lipmann Institute; Jena Germany
| | - Rami Abou Jamra
- Institute of Human Genetics; Friedrich-Alexander-Universität Erlangen-Nürnberg; Erlangen Germany
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12
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Neural cell adhesion molecule NrCAM is expressed in the mammalian inner ear and modulates spiral ganglion neurite outgrowth in an in vitro alternate choice assay. J Mol Neurosci 2014; 55:836-44. [PMID: 25407819 DOI: 10.1007/s12031-014-0436-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 09/30/2014] [Indexed: 12/17/2022]
Abstract
Neuron-glial-related cell adhesion molecule (NrCAM) is a neuronal cell adhesion molecule involved in neuron-neuron and neuron-glial adhesion as well as directional signaling during axonal cone growth. NrCAM has been shown to be involved in several cellular processes in the central and peripheral nervous systems, including neurite outgrowth, axonal pathfinding and myelination, fasciculation of nerve fibers, and cell migration. This includes sensory systems such as the eye and olfactory system. However, there are no reports on the expression/function of NrCAM in the auditory system. The aim of the present study was to elucidate the occurrence of NrCAM in the mammalian cochlea and its role in innervation of the auditory end organ. Our work indicates that NrCAM is highly expressed in the developing mammalian cochlea (position consistent with innervation). Moreover, we found that NrCAM, presented in stripe micropatterns, provide directional cues to neonatal rat inner ear spiral ganglion neurites in vitro. Our results are consistent with a role for NrCAM in the pathfinding of spiral ganglion dendrites toward their hair cell targets in the sensory epithelium.
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Wanakhachornkrai O, Pongrakhananon V, Chunhacha P, Wanasuntronwong A, Vattanajun A, Tantisira B, Chanvorachote P, Tantisira MH. Neuritogenic effect of standardized extract of Centella asiatica ECa233 on human neuroblastoma cells. Altern Ther Health Med 2013; 13:204. [PMID: 23915016 PMCID: PMC3750251 DOI: 10.1186/1472-6882-13-204] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 07/31/2013] [Indexed: 12/28/2022]
Abstract
BACKGROUND In order to gain insight into neuroprotective effects of ECa 233, a standardized extract of Centella asiatica, previously demonstrated in animal models of memory impairment induced by transient global ischemia or intracerebroventricular injection of β-amyloid, the effect of ECa 233 on neurite outgrowth of human IMR-32 neuroblastoma cell line was investigated. METHODS Cells were seeded and incubated with various concentrations of ECa 233. Morphometric analysis was carried out by a measurement of the longest neurite growth of cells at 24 and 48 h. Contributing signaling pathways possibly involved were subsequently elucidated by western blot analysis. RESULTS While ECa 233 had only limited effects on cell viability, it significantly enhanced neurite outgrowth of IMR-32 cells at the concentrations of 1-100 μg/ml. Western blot analysis revealed that ECa 233 significantly upregulated the level of activated ERK1/2 and Akt of the treated cells suggesting their involvement in the neuritogenic effect observed, which was subsequently verified by the finding that an addition of their respective inhibitors could reverse the effect of ECa 233 on these cells. CONCLUSIONS The present study clearly demonstrated neurite outgrowth promoting activity of ECa 233. ERK1/2 and Akt signaling pathways seemed to account for the neurotrophic effect observed. In conjunction with in vivo neuroprotective effect of ECa 233 previously reported, the results obtained support further development of ECa 233 for clinical use in neuronal injury or neurodegenerative diseases.
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14
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Shah SM, Patel CH, Feng AS, Kollmar R. Lithium alters the morphology of neurites regenerating from cultured adult spiral ganglion neurons. Hear Res 2013; 304:137-44. [PMID: 23856237 DOI: 10.1016/j.heares.2013.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2012] [Revised: 06/23/2013] [Accepted: 07/01/2013] [Indexed: 01/13/2023]
Abstract
The small-molecule drug lithium (as a monovalent ion) promotes neurite regeneration and functional recovery, is easy to administer, and is approved for human use to treat bipolar disorder. Lithium exerts its neuritogenic effect mainly by inhibiting glycogen synthase kinase 3, a constitutively-active serine/threonine kinase that is regulated by neurotrophin and "wingless-related MMTV integration site" (Wnt) signaling. In spiral ganglion neurons of the cochlea, the effects of lithium and the function of glycogen synthase kinase 3 have not been investigated. We, therefore, set out to test whether lithium modulates neuritogenesis from adult spiral ganglion neurons. Primary cultures of dissociated spiral ganglion neurons from adult mice were exposed to lithium at concentrations between 0 and 12.5 mM. The resulting neurite morphology and growth-cone appearance were measured in detail by using immunofluorescence microscopy and image analysis. We found that lithium altered the morphology of regenerating neurites and their growth cones in a differential, concentration-dependent fashion. Low concentrations of 0.5-2.5 mM (around the half-maximal inhibitory concentration for glycogen synthase kinase 3 and the recommended therapeutic serum concentration for bipolar disorder) enhanced neurite sprouting and branching. A high concentration of 12.5 mM, in contrast, slowed elongation. As the lithium concentration rose from low to high, the microtubules became increasingly disarranged and the growth cones more arborized. Our results demonstrate that lithium selectively stimulates phases of neuritogenesis that are driven by microtubule reorganization. In contrast, most other drugs that have previously been tested on spiral ganglion neurons are reported to inhibit neurite outgrowth or affect only elongation. Lithium sensitivity is a necessary, but not sufficient condition for the involvement of glycogen synthase kinase 3. Our results are, therefore, consistent with, but do not prove lithium inhibiting glycogen synthase kinase 3 activity in spiral ganglion neurons. Experiments with additional drugs and molecular-genetic tools will be necessary to test whether glycogen synthase kinase 3 regulates neurite regeneration from spiral ganglion neurons, possibly by integrating neurotrophin and Wnt signals at the growth cone.
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Affiliation(s)
- S M Shah
- Department of Molecular and Integrative Physiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Neuroscience Graduate Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA; Medical Scholars Program, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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Brand Y, Sung M, Chavez E, Wei E, Pak KK, Housley GD, Bodmer D, Ryan AF. Neural cell adhesion molecule L1 modulates type I but not type II inner ear spiral ganglion neurite outgrowth in an in vitro alternate choice assay. J Mol Neurosci 2013; 51:663-70. [PMID: 23760987 DOI: 10.1007/s12031-013-0040-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2013] [Accepted: 05/27/2013] [Indexed: 12/17/2022]
Abstract
L1, a neural cell adhesion molecule of the immunoglobulin superfamily, is widely expressed in the nervous system and important in axonal outgrowth, guidance, synapse formation, and signaling. Gene deletion studies emphasize the significance of L1 during development of the central nervous system and L1 is crucial for the topographic targeting of retinal axons. In contrast to the brain and retina, the role of L1 in the inner ear is largely unknown. While previous studies have localized L1 in the developing inner ear of the chicken and mouse, its function during the innervation of the cochlea still remains largely unclear. We therefore investigated the functional role of L1 in the mammalian inner ear. Our aim was to determine whether or not L1 can modulate type I and/or type II spiral ganglion neuron outgrowth using an in vitro alternate choice assay. We found that L1, presented in stripe micropatterns, provide directional cues to neonatal rodent type I but not type II inner ear spiral ganglion neurites. The results suggest that L1 may play a role in axonal pathfinding of type I spiral ganglion dendrites toward their inner hair cell targets but not of type II toward the outer hair cells.
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Affiliation(s)
- Yves Brand
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA, 92093, USA
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16
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Kondo K, Pak K, Chavez E, Mullen L, Euteneuer S, Ryan AF. Changes in responsiveness of rat spiral ganglion neurons to neurotrophins across age: differential regulation of survival and neuritogenesis. Int J Neurosci 2013; 123:465-75. [PMID: 23301942 DOI: 10.3109/00207454.2013.764497] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Developmental changes in responsiveness of rat spiral ganglion neurons (SGNs) to neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF) were examined using an explant culture system. Spiral ganglion (SG) explants at embryonic Day 18 (E18), postnatal Day 0 (P0), P5, P10 and P20 were cultured with the addition of either NT-3 or BDNF at various concentrations (0.1-100 ng/ml) and analyzed the dose-response characteristics of three parameters: SGN survival, the number of neurites emanating from the explants and the length of neurite extension. In E18 cultures, SGN survival and neurite number were enhanced more strongly by NT-3 than by the BDNF. As the explants became more mature, the effects of NT-3 decreased, whereas those of BDNF increased, peaking at P0. Although the intrinsic capacity of SGNs to produce and extend neurites declined considerably by P20, they still retained the capacity to respond to both NT-3 and BDNF. These temporal patterns in responsiveness of SGNs to neurotrophins correspond well to the expression pattern of the two neurotrophins in cochlear sensory epithelium in vivo and also correlate with the time course of developmental events in SGNs such as cell death and the establishment of mature hair cell innervation patterns.
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Affiliation(s)
- Kenji Kondo
- Division of Otolaryngology and Neurosciences, Department of Surgery and Veterans Administration Medical Center, University of California, San Diego School of Medicine, La Jolla, CA 92093, USA
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Jin Y, Kondo K, Ushio M, Kaga K, Ryan AF, Yamasoba T. Developmental changes in the responsiveness of rat spiral ganglion neurons to neurotrophic factors in dissociated culture: differential responses for survival, neuritogenesis and neuronal morphology. Cell Tissue Res 2012; 351:15-27. [PMID: 23149719 DOI: 10.1007/s00441-012-1526-1] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Accepted: 10/24/2012] [Indexed: 12/26/2022]
Abstract
The way that the development of the inner ear innervation is regulated by various neurotrophic factors and/or their combinations at different postnatal developmental stages remains largely unclear. Moreover, survival and neuritogenesis in deafferented adult neurons is important for cochlear implant function. To address these issues, developmental changes in the responsiveness of postnatal rat spiral ganglion neurons (SGNs) to neurotrophin-3 (NT-3), brain-derived neurotrophic factor (BDNF) and leukemia inhibitory factor (LIF) were examined by using a dissociated cell culture system. SGNs at postnatal day (P) 0, P5 and P20 (young adult) were cultured with the addition of NT-3, BDNF, or LIF or of a combination of NT-3 and BDNF (N + B) or of NT-3, BDNF and LIF (ALL factors). SGNs were analyzed for three parameters: survival, longest neurite length (LNL) and neuronal morphology. At P0, SGNs required exposure to N + B or ALL factors for enhanced survival and the ALL factors combination showed a synergistic effect much greater than the sum of the individual factors. At P5, SGNs responded to a wider range of treatment conditions for enhanced survival and combinations showed only an additive improvement over individual factors. The survival percentage of untreated SGNs was highest at P20 but combinations of neurotrophic factors were no more effective than individual factors. LNL of each SGN was enhanced by LIF alone or ALL factors at P0 and P5 but was suppressed by NT-3, BDNF and N + B at P5 in a dose-dependent manner. The LNL at P20 was enhanced by ALL factors and suppressed by N + B. Treatment with ALL factors increased the proportion of SGNs that had two or more primary neurites in all age groups. These findings suggest that NT-3, BDNF, LIF and their combinations predominantly support different ontogenetic events at different developmental stages in the innervation of the inner ear.
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Affiliation(s)
- Yulian Jin
- Department of Otolaryngology and Head and Neck Surgery, Graduate School of Medicine, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
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Green SH, Bailey E, Wang Q, Davis RL. The Trk A, B, C's of Neurotrophins in the Cochlea. Anat Rec (Hoboken) 2012; 295:1877-95. [DOI: 10.1002/ar.22587] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 07/24/2012] [Indexed: 12/20/2022]
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Mullen LM, Pak KK, Chavez E, Kondo K, Brand Y, Ryan AF. Ras/p38 and PI3K/Akt but not Mek/Erk signaling mediate BDNF-induced neurite formation on neonatal cochlear spiral ganglion explants. Brain Res 2012; 1430:25-34. [PMID: 22119396 PMCID: PMC3242932 DOI: 10.1016/j.brainres.2011.10.054] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 10/06/2011] [Accepted: 10/30/2011] [Indexed: 01/08/2023]
Abstract
Neurotrophins participate in regulating the survival, differentiation, and target innervation of many neurons, mediated by high-affinity Trk and low-affinity p75 receptors. In the cochlea, spiral ganglion (SG) neuron survival is strongly dependent upon neurotrophic input, including brain-derived neurotrophic factor (BDNF), which increases the number of neurite outgrowth in neonatal rat SG in vitro. Less is known about signal transduction pathways linking the activation of neurotrophin receptors to SG neuron nuclei. In particular, the p38 and cJUN Kinase (JNK), mitogen-activated protein kinase (MAPK) pathways, which participate in JNK signaling in other neurons, have not been studied. We found that inhibition of Ras, p38, phosphatidyl inositol 3 kinase (PI3K) or Akt signaling reduced or eliminated BDNF mediated increase in number of neurite outgrowth, while inhibition of Mek/Erk had no influence. Inhibition of Rac/cdc42, which lies upstream of JNK, modestly enhanced BDNF induced formation of neurites. Western blotting implicated p38 and Akt signaling, but not Mek/Erk. The results suggest that the Ras/p38 and PI3K/Akt are the primary pathways by which BDNF promotes its effects. Activation of Rac/cdc42/JNK signaling by BDNF may reduce the formation of neurites. This is in contrast to our previous results on NT-3, in which Mek/Erk signaling was the primary mediator of SG neurite outgrowth in vitro. Our data on BDNF agree with prior results from others that have implicated PI3K/Akt involvement in mediating the effects of BDNF on SG neurons in vitro, including neuronal survival and neurite extension. However, the identification of p38 and JNK involvement is entirely novel. The results suggest that neurotrophins can exert opposing effects on SG neurons, the balance of competing signals influencing the generation of neurites. This competition could provide a potential mechanism for the control of neurite number during development.
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Affiliation(s)
- Lina M. Mullen
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
| | - Kwang K. Pak
- San Diego VA Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161
| | - Eduardo Chavez
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
| | - Kenji Kondo
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
| | - Yves Brand
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
- Department of Biomedicine and Clinic of Otolaryngology, Head and Neck Surgery, University Hospital Basel, Hebelstrasse 20, 4031 Basel, Switzerland
| | - Allen F. Ryan
- San Diego VA Medical Center, 3350 La Jolla Village Drive, San Diego, CA 92161
- Department of Surgery/Otolaryngology, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
- Department of Neurosciences, UCSD School of Medicine, 9500 Gilman Drive MC0666, La Jolla, CA 92093
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20
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Xu N, Engbers J, Khaja S, Xu L, Clark JJ, Hansen MR. Influence of cAMP and protein kinase A on neurite length from spiral ganglion neurons. Hear Res 2011; 283:33-44. [PMID: 22154930 DOI: 10.1016/j.heares.2011.11.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 11/15/2011] [Accepted: 11/22/2011] [Indexed: 12/17/2022]
Abstract
Regrowth of peripheral spiral ganglion neuron (SGN) fibers is a primary objective in efforts to improve cochlear implant outcomes and to potentially reinnervate regenerated hair cells. Cyclic adenosine monophosphate (cAMP) regulates neurite growth and guidance via activation of protein kinase A (PKA) and Exchange Protein directly Activated by Cylic AMP (Epac). Here we explored the effects of cAMP signaling on SGN neurite length in vitro. We find that the cAMP analog, cpt-cAMP, exerts a biphasic effect on neurite length; increasing length at lower concentrations and reducing length at higher concentrations. This biphasic response occurs in cultures plated on laminin, fibronectin, or tenascin C suggesting that it is not substrate dependent. cpt-cAMP also reduces SGN neurite branching. The Epac-specific agonist, 8-pCPT-2'-O-Me-cAMP, does not alter SGN neurite length. Constitutively active PKA isoforms strongly inhibit SGN neurite length similar to higher levels of cAMP. Chronic membrane depolarization activates PKA in SGNs and also inhibits SGN neurite length. However, inhibition of PKA fails to rescue neurite length in depolarized cultures implying that activation of PKA is not necessary for the inhibition of SGN neurite length by chronic depolarization. Expression of constitutively active phosphatidylinositol 3-kinase, but not c-Jun N-terminal kinase, isoforms partially rescues SGN neurite length in the presence of activated PKA. Taken together, these results suggest that activation of cAMP/PKA represents a potential strategy to enhance SGN fiber elongation following deafness; however such therapies will likely require careful titration so as to promote rather than inhibit nerve fiber regeneration.
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Affiliation(s)
- Ningyong Xu
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa, IA 52242, USA
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Renton JP, Xu N, Clark JJ, Hansen MR. Interaction of neurotrophin signaling with Bcl-2 localized to the mitochondria and endoplasmic reticulum on spiral ganglion neuron survival and neurite growth. J Neurosci Res 2010; 88:2239-51. [PMID: 20209634 DOI: 10.1002/jnr.22381] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Enhanced spiral ganglion neuron (SGN) survival and regeneration of peripheral axons following deafness will likely enhance the efficacy of cochlear implants. Overexpression of Bcl-2 prevents SGN death but inhibits neurite growth. Here we assessed the consequences of Bcl-2 targeted to either the mitochondria (GFP-Bcl-2-Maob) or the endoplasmic reticulum (ER, GFP-Bcl-2-Cb5) on cultured SGN survival and neurite growth. Transfection of wild-type GFP-Bcl-2, GFP-Bcl-2-Cb5, or GFP-Bcl-2-Maob increased SGN survival, with GFP-Bcl-2-Cb5 providing the most robust response. Paradoxically, expression of GFP-Bcl-2-Maob results in SGN death in the presence of neurotrophin-3 (NT-3) and brain-derived neurotrophic factor (BDNF), neurotrophins that independently promote SGN survival via Trk receptors. This loss of SGNs is associated with cleavage of caspase 3 and appears to be specific for neurotrophin signaling, insofar as coexpression of constitutively active mitogen-activated kinase kinase (MEKDeltaEE) or phosphatidyl inositol-3 kinase (P110), but not other prosurvival stimuli (e.g., membrane depolarization), also results in the loss of SGNs expressing GFP-Bcl-2-Maob. MEKDeltaEE and P110 promote SGN survival, whereas P110 promotes neurite growth to a greater extent than NT-3 or MEKDeltaEE. However, wild-type GFP-Bcl-2, GFP-Bcl-2-Cb5, and GFP-Bcl-2-Maob inhibit neurite growth even in the presence of neurotrophins, MEKDeltaEE, or P110. Historically, Bcl-2 has been thought to act primarily at the mitochondria to prevent neuronal apoptosis. Nevertheless, our data show that Bcl-2 targeted to the ER is more effective at rescuing SGNs in the absence of trophic factors. Additionally, Bcl-2 targeted to the mitochondria results in SGN death in the presence of neurotrophins. (c) 2010 Wiley-Liss, Inc.
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Affiliation(s)
- John P Renton
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa
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22
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Defective cAMP generation underlies the sensitivity of CNS neurons to neurofibromatosis-1 heterozygosity. J Neurosci 2010; 30:5579-89. [PMID: 20410111 DOI: 10.1523/jneurosci.3994-09.2010] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Individuals with the neurofibromatosis type 1 (NF1) inherited cancer syndrome exhibit neuronal dysfunction that predominantly affects the CNS. In this report, we demonstrate a unique vulnerability of CNS neurons, but not peripheral nervous system (PNS) neurons, to reduced Nf1 gene expression. Unlike dorsal root ganglion neurons, Nf1 heterozygous (Nf1+/-) hippocampal and retinal ganglion cell (RGC) neurons have decreased growth cone areas and neurite lengths, and increased apoptosis compared to their wild-type counterparts. These abnormal Nf1+/- CNS neuronal phenotypes do not reflect Ras pathway hyperactivation, but rather result from impaired neurofibromin-mediated cAMP generation. In this regard, elevating cAMP levels with forskolin or rolipram treatment, but not MEK (MAP kinase kinase) or PI3-K (phosphatidylinositol 3-kinase) inhibition, reverses these abnormalities to wild-type levels in vitro. In addition, Nf1+/- CNS, but not PNS, neurons exhibit increased apoptosis in response to excitotoxic or oxidative stress in vitro. Since children with NF1-associated optic gliomas often develop visual loss and Nf1 genetically engineered mice with optic glioma exhibit RGC neuronal apoptosis in vivo, we further demonstrate that RGC apoptosis resulting from optic glioma in Nf1 genetically engineered mice is attenuated by rolipram treatment in vivo. Similar to optic glioma-induced RGC apoptosis, the increased RGC neuronal death in Nf1+/- mice after optic nerve crush injury is also attenuated by rolipram treatment in vivo. Together, these findings establish a distinctive role for neurofibromin in CNS neurons with respect to vulnerability to injury, define a CNS-specific neurofibromin intracellular signaling pathway responsible for neuronal survival, and lay the foundation for future neuroprotective glioma treatment approaches.
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Seira O, Gavín R, Gil V, Llorens F, Rangel A, Soriano E, del Río JA. Neurites regrowth of cortical neurons by GSK3beta inhibition independently of Nogo receptor 1. J Neurochem 2010; 113:1644-58. [PMID: 20374426 DOI: 10.1111/j.1471-4159.2010.06726.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Lesioned axons do not regenerate in the adult mammalian CNS, owing to the over-expression of inhibitory molecules such as myelin-derived proteins or chondroitin sulphate proteoglycans. In order to overcome axon inhibition, strategies based on extrinsic and intrinsic treatments have been developed. For myelin-associated inhibition, blockage with NEP1-40, receptor bodies or IN-1 antibodies has been used. In addition, endogenous blockage of cell signalling mechanisms induced by myelin-associated proteins is a potential tool for overcoming axon inhibitory signals. We examined the participation of glycogen synthase kinase 3beta (GSK3beta) and extracellular-related kinase (ERK) 1/2 in axon regeneration failure in lesioned cortical neurons. We also investigated whether pharmacological blockage of GSK3beta and ERK1/2 activities facilitates regeneration after myelin-directed inhibition in two models: (i) cerebellar granule cells and (ii) lesioned entorhino-hippocampal pathway in slice cultures, and whether the regenerative effects are mediated by Nogo Receptor 1 (NgR1). We demonstrate that, in contrast to ERK1/2 inhibition, the pharmacological treatment of GSK3beta inhibition strongly facilitated regrowth of cerebellar granule neurons over myelin independently of NgR1. Finally, these regenerative effects were corroborated in the lesioned entorhino-hippocampal pathway in NgR1-/- mutant mice. These results provide new findings for the development of new assays and strategies to enhance axon regeneration in injured cortical connections.
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Affiliation(s)
- Oscar Seira
- Molecular and Cellular Neurobiotechnology, Institute for Bioengineering of Catalonia, Barcelona, Spain
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Hearing development and spiral ganglion neurite growth in VASP deficient mice. Brain Res 2007; 1178:73-82. [PMID: 17920567 DOI: 10.1016/j.brainres.2007.06.041] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 04/27/2007] [Accepted: 06/07/2007] [Indexed: 10/23/2022]
Abstract
Vasodilator-stimulated phosphoprotein (VASP) has been found to be involved in intracellular signalling pathways and to play an important role in the actin associated organization and formation of the cytoskeleton. Since differential VASP expression was noted in inner ear tissues, the present study was performed to investigate the hearing development in VASP deficient mice. Hearing development in VASP-/- mice and wild type animals was investigated by auditory brain stem (ABR) measurements. In addition, inner ear tissues of wild type animals were tested for VASP expression using PCR, Western blot analysis, in situ hybridisation, and immunohistochemistry. To compare spiral ganglion (SG) neurite growth, SG explants from VASP-/- and wild type mice were analyzed under cell culture conditions. The electroacoustical results of the present study indicate that VASP deficient mice present with a later onset of hearing during postnatal development compared to wild type animals. Transient VASP expression was detected in neonatal SG of wild type mice. Tissue culture experiments with SG explants from VASP-/- animals revealed significant alterations in SG neurite extension compared to wild types. The present findings suggest a role for VASP during neonatal development of the mammalian cochlea and allow speculation on a possible delayed innervation of cochlear hair cells due to changes in SG neurite growth in VASP-deficient mice. Temporary VASP deficits in the neonatal inner ear may be compensated by related proteins like MENA leading to a delayed but complete development of hearing function in VASP-/- animals.
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Greenwood D, Jagger DJ, Huang LC, Hoya N, Thorne PR, Wildman SS, King BF, Pak K, Ryan AF, Housley GD. P2X receptor signaling inhibits BDNF-mediated spiral ganglion neuron development in the neonatal rat cochlea. Development 2007; 134:1407-17. [PMID: 17329369 DOI: 10.1242/dev.002279] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Type I and type II spiral ganglion neurons (SGN) innervate the inner and outer hair cells of the cochlea, respectively. This neural system is established by reorganization of promiscuous innervation of the hair cells, immediately before hearing is established. The mechanism for this synaptic reorganization is unresolved but probably includes regulation of trophic support between the hair cells and the neurons. We provide evidence that P2X receptors (ATP-gated ion channels) contribute such a mechanism in the neonatal rat cochlea. Single-cell quantitative RT-PCR identified the differential expression of two P2X receptor subunits, splice variant P2X(2)(-3) and P2X(3), in a 1:2 transcript ratio. Downregulation of this P2X(2-3/3) receptor coincided with maturation of the SGN innervation of the hair cells. When the P2X(2-3) and P2X(3) subunits were co-expressed in Xenopus oocytes, the resultant P2X receptor properties corresponded to the SGN phenotype. This included enhanced sensitivity to ATP and extended agonist action. In P4 spiral ganglion explants, activation of the P2X receptor signaling pathway by ATPgammaS or alpha,betaMeATP inhibited BDNF-induced neurite outgrowth and branching. These findings indicate that P2X receptor signaling provides a mechanism for inhibiting neurotrophin support of SGN neurites when synaptic reorganization is occurring in the cochlea.
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Affiliation(s)
- Denise Greenwood
- Department of Physiology, University of Auckland, Private Bag 92019, Auckland, New Zealand
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26
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Abstract
The innervation of the cochlear sensory epithelium is intricately organized, allowing the tonotopy established by the auditory hair cells to be maintained along the ascending auditory pathways. These auditory projections are patterned by several gene families that regulate neurite attraction and repulsion, known as axon guidance cues. In this review, the roles of various axon guidance molecules, including fibroblast growth factor, ephs, semaphorins, netrins and slits, are examined in light of their known contribution to auditory development. Additionally, morphogens are discussed in the context of their recently described influence on axonal pathfinding in other sensory systems. The elucidation of these various mechanisms may guide the development of therapies aimed at maximizing the connectivity of auditory neurons in the context of congenital or acquired sensorineural hearing loss, especially as pertains to cochlear implants. Further afield, improved understanding of the molecular processes which regulate innervation of the organ of Corti during normal development may prove useful in connecting regenerated hair cells to the central nervous system.
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Affiliation(s)
- Audra Webber
- Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Anderson M, Boström M, Pfaller K, Glueckert R, Schrott-Fischer A, Gerdin B, Rask-Andersen H. Structure and locomotion of adult in vitro regenerated spiral ganglion growth cones – A study using video microscopy and SEM. Hear Res 2006; 215:97-107. [PMID: 16684592 DOI: 10.1016/j.heares.2006.03.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Revised: 03/06/2006] [Accepted: 03/09/2006] [Indexed: 11/16/2022]
Abstract
Neuronal development and neurite regeneration depends on the locomotion and navigation of nerve growth cones (GCs). There are few detailed descriptions of the GC function and structure in the adult auditory system. In this study, GCs of adult dissociated and cultured spiral ganglion (SG) neurons were analyzed in vitro utilizing combined high resolution scanning electron microscopy (SEM) and time lapse video microscopy (TLVM). Axon kinesis was assessed on planar substratum with growth factors BDNF, NT-3 and GDNF. At the nano-scale level, lamellipodial abdomen of the expanding GC was found to be decorated with short surface specializations, which at TLVM were considered to be related to their crawling capacity. Filopodia were devoid of these surface structures, supporting its generally described sensory role. Microspikes appearing on lamellipodia and axons, showed circular adhesions, which at TLVM were found to provide anchorage of the navigating and turning axon. Neurons and GCs expressed the DCC-receptor for the guidance molecule netrin-1. Asymmetric ligand-based stimulation initiated turning responses suggest that this attractant cue influences steering of GC in adult regenerating auditory neurites. Hopefully, these findings may be used for ensuing tentative navigation of spiral ganglion neurons to induce regenerative processes in the human ear.
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Affiliation(s)
- Malin Anderson
- Department of Surgical Sciences, Unit of Otosurgery, Uppsala University Hospital, Uppsala, Sweden.
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28
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Cui Q. Actions of neurotrophic factors and their signaling pathways in neuronal survival and axonal regeneration. Mol Neurobiol 2006; 33:155-79. [PMID: 16603794 DOI: 10.1385/mn:33:2:155] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Revised: 11/30/1999] [Accepted: 08/15/2005] [Indexed: 02/05/2023]
Abstract
Adult axons in the mammalian central nervous system do not elicit spontaneous regeneration after injury, although many affected neurons have survived the neurotrauma. However, axonal regeneration does occur under certain conditions. These conditions include: (a) modification of regrowth environment, such as supply of peripheral nerve bridges and transplantation of Schwann cells or olfactory ensheathing glia to the injury site; (b) application of neurotrophic factors at the cell soma and axon tips; (c) blockade of growth-inhibitory molecules such as Nogo-A, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein; (d) prevention of chondroitin-sulfate-proteoglycans-related scar tissue formation at the injury site using chondroitinase ABC; and (e) elevation of intrinsic growth potential of injured neurons via increasing intracellular cyclic adenosine monophosphate level. A large body of evidence suggests that these conditions achieve enhanced neuronal survival and axonal regeneration through sometimes overlapping and sometimes distinct signal transduction mechanisms, depending on the targeted neuronal populations and intervention circumstances. This article reviews the available information on signal transduction pathways underlying neurotrophic-factor-mediated neuronal survival and neurite outgrowth/axonal regeneration. Better understanding of signaling transduction is important in helping us develop practical therapeutic approaches for encouraging neuronal survival and axonal regeneration after traumatic injury in clinical context.
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Affiliation(s)
- Qi Cui
- Laboratory for Neural Repair, Shantou University Medical College, China.
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Soumyanath A, Zhong YP, Gold SA, Yu X, Koop DR, Bourdette D, Gold BG. Centella asiatica accelerates nerve regeneration upon oral administration and contains multiple active fractions increasing neurite elongation in-vitro. J Pharm Pharmacol 2006; 57:1221-9. [PMID: 16105244 DOI: 10.1211/jpp.57.9.0018] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Axonal regeneration is important for functional recovery following nerve damage. Centella asiatica Urban herb, also known as Hydrocotyle asiatica L., has been used in Ayurvedic medicine for centuries as a nerve tonic. Here, we show that Centella asiatica ethanolic extract (100 microg mL-1) elicits a marked increase in neurite outgrowth in human SH-SY5Y cells in the presence of nerve growth factor (NGF). However, a water extract of Centella was ineffective at 100 microg mL-1. Sub-fractions of Centella ethanolic extract, obtained through silica-gel chromatography, were tested (100 microg mL-1) for neurite elongation in the presence of NGF. Greatest activity was found with a non-polar fraction (GKF4). Relatively polar fractions (GKF10 to GKF13) also showed activity, albeit less than GKF4. Thus, Centella contains more than one active component. Asiatic acid (AA), a triterpenoid compound found in Centella ethanolic extract and GKF4, showed marked activity at 1 microM (microg mL-1). AA was not present in GKF10 to GKF13, further indicating that other active components must be present. Neurite elongation by AA was completely blocked by the extracellular-signal-regulated kinase (ERK) pathway inhibitor PD 098059 (10 microM). Male Sprague-Dawley rats given Centella ethanolic extract in their drinking water (300-330 mg kg-1 daily) demonstrated more rapid functional recovery and increased axonal regeneration (larger calibre axons and greater numbers of myelinated axons) compared with controls, indicating that the axons grew at a faster rate. Taken together, our findings indicate that components in Centella ethanolic extract may be useful for accelerating repair of damaged neurons.
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Affiliation(s)
- Amala Soumyanath
- Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland OR 97239, USA
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Abstract
PURPOSE OF REVIEW Degeneration of spiral ganglion neurons following hair cell loss carries critical implications for efforts to rehabilitate severe cases of hearing loss with cochlear implants or hair cell regeneration. This review considers recently identified neurotrophic factors and therapeutic strategies which promote spiral ganglion neuron survival and neurite growth. Replacement of these factors may help preserve or regenerate the auditory nerve in patients with extensive hair cell loss. RECENT FINDINGS Spiral ganglion neurons depend on neurotrophic factors supplied by hair cells and other targets for their development and continued survival. Loss of this trophic support leads to spiral ganglion neuron death via apoptosis. Hair cells support spiral ganglion neuron survival by producing several peptide neurotrophic factors such as neurotrophin-3 and glial derived neurotrophic factor. In addition, neurotransmitter release from the hair cells drives membrane electrical activity in spiral ganglion neurons which also supports their survival. In animal models, replacement of peptide neurotrophic factors or electrical stimulation with an implanted electrode attenuates spiral ganglion neuron degeneration following deafferentation. Cell death inhibitors can also preserve spiral ganglion neuron populations. Preliminary studies show that transfer of stem cells or neurons from other ganglia are two potential strategies to replace lost spiral ganglion neurons. Inducing the regrowth of spiral ganglion neuron peripheral processes to approximate or contact cochlear implant electrodes may help optimize signaling from a diminished population of neurons. SUMMARY Recent studies of spiral ganglion neuron development and survival have identified several trophic and neuritogenic factors which protect these specialized cells from degeneration following hair cell loss. While still preliminary, such strategies show promise for future clinical applications.
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Affiliation(s)
- Pamela C Roehm
- Department of Otolaryngology-Head and Neck Surgery, University of Iowa, Iowa City, Iowa 52242, USA
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Ryan AF, Wittig J, Evans A, Dazert S, Mullen L. Environmental Micropatterning for the Study of Spiral Ganglion Neurite Guidance. ACTA ACUST UNITED AC 2006; 11:134-43. [PMID: 16439836 DOI: 10.1159/000090686] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The projection of neuronal processes is guided by a variety of soluble and insoluble factors, which are sensed by a fiber's growth cone. It is the differential distribution of such guidance cues that determine the direction in which neurites grow. The growth cone senses these cues on a fine scale, using extensible filopodia that range from a few to tens of mum in length. In order to study the effects of guidance cues on spiral ganglion (SG) neurites, we have used methods for distributing both soluble and insoluble cues on a scale appropriate for sensing by growth filopodia. The scale of these methods are at the micro, rather than nano, level to match the sensing range of the growth cone. Microfluidics and transfected cells were used to spatially localize tropic factors within the fluid environment of extending neurites. Micro-patterning was used to present neurites with stripes of insoluble factors. The results indicate that differentially distributed permissive, repulsive and stop signals can control the projection of SG neurites. Implications for future micro-patterning studies, for SG development and for the growth of deafferented SG dendrites toward a cochlear implant are discussed.
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Affiliation(s)
- Allen F Ryan
- Department of Surgery/Otolaryngology, UCSD School of Medicine, La Jolla, CA 92093, USA.
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32
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Shepherd RK, Coco A, Epp SB, Crook JM. Chronic depolarization enhances the trophic effects of brain-derived neurotrophic factor in rescuing auditory neurons following a sensorineural hearing loss. J Comp Neurol 2005; 486:145-58. [PMID: 15844207 PMCID: PMC1831822 DOI: 10.1002/cne.20564] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The development and maintenance of spiral ganglion neurons (SGNs) appears to be supported by both neural activity and neurotrophins. Removal of this support leads to their gradual degeneration. Here, we examined whether the exogenous delivery of the neurotrophin brain-derived neurotrophic factor (BDNF) in concert with electrical stimulation (ES) provides a greater protective effect than delivery of BDNF alone in vivo. The left cochlea of profoundly deafened guinea pigs was implanted with an electrode array and drug-delivery system. BDNF or artificial perilymph (AP) was delivered continuously for 28 days. ES induced neural activity in two cohorts (BDNF/ES and AP/ES), and control animals received BDNF or AP without ES (BDNF/- and AP/-). The right cochleae of the animals served as deafened untreated controls. Electrically evoked auditory brainstem responses (EABRs) were recorded immediately following surgery and at completion of the drug-delivery period. AP/ES and AP/- cohorts showed an increase in EABR threshold over the implantation period, whereas both BDNF cohorts exhibited a reduction in threshold (P < 0.001, t-test). Changes in neural sensitivity were complemented by significant differences in both SGN survival and soma area. BDNF cohorts demonstrated a significant trophic or survival advantage and larger soma area compared with AP-treated and deafened control cochleae; this advantage was greatest in the base of the cochlea. ES significantly enhanced the survival effects of BDNF throughout the majority of the cochlea (P < 0.05, Bonferroni's t-test), although there was no evidence of trophic support provided by ES alone. Cotreatment of SGNs with BDNF and ES provides a substantial functional and trophic advantage; this treatment may have important implications for neural prostheses.
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MESH Headings
- Animals
- Brain-Derived Neurotrophic Factor/pharmacology
- Brain-Derived Neurotrophic Factor/therapeutic use
- Cell Survival/drug effects
- Cell Survival/physiology
- Cochlea/drug effects
- Cochlea/physiology
- Cochlear Implants/standards
- Cochlear Implants/trends
- Disease Models, Animal
- Electric Stimulation Therapy/instrumentation
- Electric Stimulation Therapy/methods
- Electrodes, Implanted
- Evoked Potentials, Auditory, Brain Stem/drug effects
- Evoked Potentials, Auditory, Brain Stem/physiology
- Guinea Pigs
- Hearing Loss, Sensorineural/pathology
- Hearing Loss, Sensorineural/physiopathology
- Hearing Loss, Sensorineural/therapy
- Membrane Potentials/physiology
- Nerve Degeneration/drug therapy
- Nerve Degeneration/physiopathology
- Nerve Degeneration/prevention & control
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Organ of Corti/injuries
- Organ of Corti/physiopathology
- Recovery of Function/drug effects
- Recovery of Function/physiology
- Spiral Ganglion/drug effects
- Spiral Ganglion/physiology
- Treatment Outcome
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Affiliation(s)
- Robert K Shepherd
- The Bionic Ear Institute, Department of Otolaryngology, University of Melbourne, East Melbourne, Victoria 3002, Australia.
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Wittig JH, Ryan AF, Asbeck PM. A reusable microfluidic plate with alternate-choice architecture for assessing growth preference in tissue culture. J Neurosci Methods 2005; 144:79-89. [PMID: 15848242 DOI: 10.1016/j.jneumeth.2004.10.010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 10/15/2004] [Accepted: 10/15/2004] [Indexed: 11/30/2022]
Abstract
We present the design of a chamber to evaluate in vitro how species and concentrations of soluble molecules control features of cell growth-potentially including cell proliferation, cell motility, process extension, and process termination. We have created a reusable cell culture plate that integrates a microfluidic media delivery network with standard cell culture environment. The microfluidic network delivers a stream of cell culture media with a step-like concentration gradient down a 50-100 microm wide microchannel called the presentation region. Migrating cells or growing cell processes freely choose between the two distinct chemical environments in the presentation region, but they are forced to exclusively choose either one environment or the other when they grow past a physical barrier acting as a decision point. Our fabrication technique requires little specialized equipment, and can be carried out in approximately 4 days per plate. We demonstrate the effectiveness of our plates as neurites from spiral ganglion explants preferentially grow in media containing neurotrophin-3 (NT-3) as opposed to media without NT-3. Our design could be used without modification to study dissociated cell responses to soluble growth cues, and for behavioral screening of small motile organisms.
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Affiliation(s)
- John H Wittig
- Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, CA 92093-0407, USA.
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Heffron DS, Mandell JW. Opposing roles of ERK and p38 MAP kinases in FGF2-induced astroglial process extension. Mol Cell Neurosci 2005; 28:779-90. [PMID: 15797724 DOI: 10.1016/j.mcn.2004.12.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2004] [Revised: 11/23/2004] [Accepted: 12/21/2004] [Indexed: 11/28/2022] Open
Abstract
The stellate processes of astroglial cells undergo extensive remodeling in response to neural injury. Little is known about intracellular signaling mechanisms controlling process extension. We tested roles for the ERK and p38 MAP kinase pathways in a simplified culture model. FGF2-induced process extension was preceded by a strong and transient phosphorylation of ERK, and a modest activation of p38 MAP kinase, which exhibited significant basal activity. Phosphorylated ERK was found predominantly in the cytoplasm, whereas activated p38 MAP kinase was nuclear. Process extension was completely blocked by the specific MEK inhibitor U0126. Conversely, inhibition of the p38 MAP kinase pathway with SB202190 stimulated spontaneous process growth and greatly potentiated FGF2-induced process extension. The p38 inhibitor effect was reproduced with an adenovirus expressing dominant-negative p38 MAP kinase. Selective pharmacological blockade of MAP kinase pathways may enable modulation of the astroglial response to injury so as to promote neural regeneration.
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Affiliation(s)
- Daniel S Heffron
- Department of Pathology, University of Virginia Health System, PO Box 800904, Charlottesville, VA 22908, USA
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Thompson J, Dolcet X, Hilton M, Tolcos M, Davies AM. HGF promotes survival and growth of maturing sympathetic neurons by PI-3 kinase- and MAP kinase-dependent mechanisms. Mol Cell Neurosci 2004; 27:441-52. [PMID: 15555922 DOI: 10.1016/j.mcn.2004.07.007] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2004] [Revised: 07/26/2004] [Accepted: 07/27/2004] [Indexed: 11/16/2022] Open
Abstract
Hepatocyte growth factor (HGF) is a pleiotrophic factor whose many functions include promoting neuronal survival and growth. Hitherto, these effects have been observed in the presence of other neurotrophic factors like NGF and CNTF, and this requirement for an accessory factor has made it difficult to elucidate the signaling pathways that mediate its survival and growth-enhancing effects. Here, we show that HGF promotes the survival of mature sympathetic neurons of the superior cervical ganglion (SCG) grown at low density in defined medium lacking other neurotrophic factors. This effect was first clearly observed in cultures established from postnatal day 20 (P20) mice and became maximal by P40. HGF also enhanced the growth of neurite arbors from neurons throughout postnatal development and in the adult. HGF treatment resulted in phosphorylation of Akt and ERK1/ERK2. Preventing Akt activation with the phosphatidylinositol-3 (PI-3) kinase inhibitor LY294002 blocked the HGF survival response, and inhibition of ERK activation with the MEK inhibitors PD98059 or U0126 reduced the HGF survival response and the neurite growth-promoting effects of HGF. These results indicate that HGF promotes the survival and growth of maturing sympathetic neurons by both PI-3 kinase- and MAP kinase-dependent mechanisms.
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Affiliation(s)
- Jane Thompson
- Department of Preclinical Veterinary Sciences, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh EH9 1QH, Scotland, United Kingdom.
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Gold BG, Udina E, Bourdette D, Navarro X. Neuroregenerative and neuroprotective actions of neuroimmunophilin compounds in traumatic and inflammatory neuropathies. Neurol Res 2004; 26:371-80. [PMID: 15198862 DOI: 10.1179/016164104225013734] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
FK506 (tacrolimus, Prograf is an immunosuppressant drug that also has profound neuroregenerative and neuroprotective actions independent of its immunosuppressant activity. The separation of these properties has led to the development of non-immunosuppressant derivatives that retain the neurotrophic activity. This review focuses on the peripheral nerve actions of these compounds following mechanical injury (nerve crush or transection with graft repair) and in models of inflammatory neuropathies. Whereas FK506 may be indicative for the treatment of inflammatory neuropathies where its immunosuppressive action would be advantageous, non-immunosuppressant derivatives represent a new class of potential therapeutic agents for the treatment of human neurological conditions in general. Moreover, these studies have led to the discovery of a novel mechanism whereby these compounds activate intrinsic neuroregenerative and neuroprotective pathways in the neuron.
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Affiliation(s)
- Bruce G Gold
- Center for Research on Occupational and Environmental Toxicology (CROET), Oregon Health & Science University, Portland, OR 97201-3098, USA.
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Battaglia A, Pak K, Brors D, Bodmer D, Frangos JA, Ryan AF. Involvement of ras activation in toxic hair cell damage of the mammalian cochlea. Neuroscience 2004; 122:1025-35. [PMID: 14643769 DOI: 10.1016/j.neuroscience.2003.08.041] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To identify possible intracellular mediators of hair cell (HC) death due to ototoxins, we treated basal-turn, neonatal, rat HCs in vitro with several intracellular signaling inhibitors, prior to and during gentamicin exposure. The general guanine nucleotide-binding protein (G-protein) inhibitor, GDP-betaS (1 mM), provided potent HC protection, suggesting involvement of G-proteins in the intracellular pathway linking gentamicin exposure to HC death. ADP-betaS had minimal effect, indicating that the protection is specific to guanosine diphosphate (GDP)-binding, rather than a general reaction to nucleotides. Azido-GTP(32) photolabeling and gel electrophoresis indicated activation of an approximately 21 kDa G-protein in HCs after exposure to gentamicin. Spectroscopic analysis of peptide fragments from this band matched its sequence with H-Ras. The Ras inhibitors B581 (50 microM) and FTI-277 (10 microM) provided potent protection against damage and reduced c-Jun activation in HC nuclei, suggesting that activation of Ras is functionally involved in damage to these cells due to gentamicin.
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Affiliation(s)
- A Battaglia
- Department of Surgery, University of California, San Diego, School of Medicine, 9500 Gilman Drive 0666, La Jolla, CA 92093-0666, USA
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Brors D, Bodmer D, Pak K, Aletsee C, Schäfers M, Dazert S, Ryan AF. EphA4 provides repulsive signals to developing cochlear ganglion neurites mediated through ephrin-B2 and -B3. J Comp Neurol 2003; 462:90-100. [PMID: 12761826 DOI: 10.1002/cne.10707] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ephrins and Eph receptors make up two large families of bi-directional signaling molecules that are known to play a role in the development of the nervous system. Recently, expression of EphA4 in the developing cochlea was shown, with strong expression in cells lining the osseous spiral lamina (OSL) through which afferent dendrites must pass to reach the organ of Corti (OC). It was also demonstrated that ephrin-B2 and -B3, both of which are known to interact with EphA4, are expressed by spiral ganglion (SG) neurons. To investigate the functional role of EphA4 in the development of inner ear neurons, neonatal rat SG explants were cultured for 72 hours on uniformly coated surfaces or near stripes of EphA4/IgG-Fc-chimera. Control explants were cultured on or near IgG-Fc and EphA1/IgG-Fc-chimera. To assess the roles of ephrin-B2 and -B3 in EphA4 signaling, SG explants were cultured with or without anti-ephrin-B2 and/or -B3 blocking antibodies. Growth patterns of SG neurites at the border of EphA4 receptor stripes showed repulsion, characterized by turning, stopping and/or reversal. In the case of IgG-Fc and EphA1, the neurites grew straight onto the stripes. Treatment with either anti-ephrin-B2 or -B3 blocking antibodies significantly reduced the repulsive effect of an EphA4 stripe. Moreover, when both antibodies were used together, neurites crossed onto EphA4 stripes with no evidence of repulsion. The results suggest that EphA4 provides repulsive signals to SG neurites in the developing cochlea, and that ephrin-B2 and -B3 together mediate this response.
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Affiliation(s)
- Dominik Brors
- Department of Surgery, Division Otolaryngology and Neurosciences, University of California, San Diego School of Medicine and Veterans Administration Medical Center, La Jolla 92093, USA
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39
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Affiliation(s)
- Allen F Ryan
- Department of Surgery/Otolaryngology, University of California San Diego School of Medicine and San Diego Veterans Administration Medical Center, La Jolla, California 92093, USA
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Bodmer D, Gloddek B, Ryan AF, Huverstuhl J, Brors D. Inhibition of the c-Jun N-terminal kinase signaling pathway influences neurite outgrowth of spiral ganglion neurons in vitro. Laryngoscope 2002; 112:2057-61. [PMID: 12439181 DOI: 10.1097/00005537-200211000-00028] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Inhibitors of the c-Jun N-terminal kinase (JNK) signaling pathway have been demonstrated to protect hair cells of the auditory system and different types of neurons from various insults, and their use for future therapeutic applications has been proposed. In the study, we evaluated the effects of inhibition of the JNK pathway on process outgrowth from spiral ganglion neurons. METHODS Spiral ganglion explants from rats (postnatal days 3-5) that were cultured on laminin were treated with neurotrophin-3 and/or the JNK signaling pathway inhibitor CEP-11004. Both neurite length and number of the explants were evaluated and statistically analyzed by analysis of variance. RESULTS Inhibition of the JNK signaling pathway reduced process outgrowth from spiral ganglion explants. The reduction, both in length and number of neurites, was reversed by the application of neurotrophin-3. CONCLUSIONS The results indicate that an intact JNK signaling pathway is important for process outgrowth of spiral ganglion neurons. However, neurotrophin-3 stimulates process extension by a JNK independent pathway. Our results demonstrate that inhibition of the JNK pathway can have adverse effects on the extension of spiral ganglion neurons, but that the negative effects can be ameliorated by appropriate treatment.
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Affiliation(s)
- Daniel Bodmer
- Division of Otolaryngology, Department of Surgery, University of California San Diego School of Medicine, Veterans Affairs Medical Center, La Jolla 92093, USA
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