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Ohlemiller KK, Dwyer N, Henson V, Fasman K, Hirose K. A critical evaluation of "leakage" at the cochlear blood-stria-barrier and its functional significance. Front Mol Neurosci 2024; 17:1368058. [PMID: 38486963 PMCID: PMC10937559 DOI: 10.3389/fnmol.2024.1368058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 02/16/2024] [Indexed: 03/17/2024] Open
Abstract
The blood-labyrinth-barrier (BLB) is a semipermeable boundary between the vasculature and three separate fluid spaces of the inner ear, the perilymph, the endolymph and the intrastrial space. An important component of the BLB is the blood-stria-barrier, which shepherds the passage of ions and metabolites from strial capillaries into the intrastrial space. Some investigators have reported increased "leakage" from these capillaries following certain experimental interventions, or in the presence of inflammation or genetic variants. This leakage is generally thought to be harmful to cochlear function, principally by lowering the endocochlear potential (EP). Here, we examine evidence for this dogma. We find that strial capillaries are not exclusive, and that the asserted detrimental influence of strial capillary leakage is often confounded by hair cell damage or intrinsic dysfunction of the stria. The vast majority of previous reports speculate about the influence of strial vascular barrier function on the EP without directly measuring the EP. We argue that strial capillary leakage is common across conditions and species, and does not significantly impact the EP or hearing thresholds, either on evidentiary or theoretical grounds. Instead, strial capillary endothelial cells and pericytes are dynamic and allow permeability of varying degrees in response to specific conditions. We present observations from mice and demonstrate that the mechanisms of strial capillary transport are heterogeneous and inconsistent among inbred strains.
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Affiliation(s)
- Kevin K. Ohlemiller
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
- Program in Communication Sciences and Audiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Noël Dwyer
- Program in Communication Sciences and Audiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Veronica Henson
- Program in Communication Sciences and Audiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Kaela Fasman
- Program in Communication Sciences and Audiology, Washington University School of Medicine, St. Louis, MO, United States
| | - Keiko Hirose
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO, United States
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2
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Hosoya M, Iwabu K, Kitama T, Nishiyama T, Oishi N, Okano H, Ozawa H. Development of cochlear spiral ligament fibrocytes of the common marmoset, a nonhuman model animal. Sci Rep 2023; 13:11789. [PMID: 37479821 PMCID: PMC10362005 DOI: 10.1038/s41598-023-39003-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 07/18/2023] [Indexed: 07/23/2023] Open
Abstract
Spiral ligament fibrocytes generate potassium gradients, which hair cells require to convert mechanical sound waves into electrical palsy. Together with the stria vascularis, they regulate endolymph electrolyte homeostasis. Developing spiral ligament fibrocytes and generating endocochlear potential with an appropriate endolymph ion composition are essential for hearing. Understanding spiral ligament fibrocyte development is useful for studying age-related and genetic hearing loss, as well as for regenerative therapy and cochlear immunology. Despite interspecies differences, most studies of cochlear development have been conducted in rodent models due to the difficulty of using human fetal samples. This study investigated the cochlear development of spiral ligament fibrocytes in a small New World monkey species, the common marmoset (Callithrix jacchus). We examined the developmental expression of specific genes in spiral ligament fibrocytes, including those essential for the generation of endolymphatic potential. Our results showed that this animal model of spiral ligament fibrocyte development is similar to that of humans and is a suitable alternative for the analysis of human cochlear development. The time course established in this study will be useful for studying the primate-specific developmental biology of the inner ear, which may lead to novel treatment strategies for human hearing loss.
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Affiliation(s)
- Makoto Hosoya
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan.
| | - Kaho Iwabu
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Tsubasa Kitama
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Takanori Nishiyama
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Naoki Oishi
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Hideyuki Okano
- Department of Physiology, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
- Laboratory for Marmoset Neural Architecture, Center for Brain Science, RIKEN, 2-1 Hirosawa Wako, Saitama, 351-0193, Japan
| | - Hiroyuki Ozawa
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi Shinjuku-ku, Tokyo, 160-8582, Japan
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3
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Hosoya M, Kitama T, Iwabu K, Nishiyama T, Oishi N, Okano H, Ozawa H. Development of the stria vascularis in the common marmoset, a primate model. Sci Rep 2022; 12:19811. [PMID: 36396805 PMCID: PMC9672111 DOI: 10.1038/s41598-022-24380-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/15/2022] [Indexed: 11/18/2022] Open
Abstract
Stria vascularis is a structure that generates potassium gradients in the cochlea, which is vital for hair cells to convert mechanical sound waves into electrical pulses. The precise development of the stria vascularis and subsequent generation of endocochlear potential are thus essential for hearing. Understanding the development of the stria vascularis is valuable for studying hearing loss caused by aging or genetics and designing regenerative therapy. Although inter-species differences have been reported between rodents and humans, most of our current knowledge regarding cochlear development has been obtained from rodent models because of the difficulty in using human fetal samples in this field of research. Therefore, we investigated the development of the cochlear stria vascularis in the common marmoset (Callithrix jacchus), a small monkey species native to the New World. Our study confirms that stria vascularis development in the common marmoset is similar to that in humans and is suitable for furthering our understanding of human cochlear development. The time course established in this report will aid in studying the primate-specific developmental biology of the inner ear, which could eventually lead to new treatment strategies for hearing loss in humans.
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Affiliation(s)
- Makoto Hosoya
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
| | - Tsubasa Kitama
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
| | - Kaho Iwabu
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
| | - Takanori Nishiyama
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
| | - Naoki Oishi
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
| | - Hideyuki Okano
- grid.26091.3c0000 0004 1936 9959Department of Physiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan ,grid.7597.c0000000094465255Laboratory for Marmoset Neural Architecture, Center for Brain Science, RIKEN, 2-1 Hirosawa, Wako, Saitama, 351-0193 Japan
| | - Hiroyuki Ozawa
- grid.26091.3c0000 0004 1936 9959Department of Otorhinolaryngology, Head and Neck Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-Ku, Tokyo, 160-8582 Japan
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4
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Huerzeler N, Petkovic V, Sekulic-Jablanovic M, Kucharava K, Wright MB, Bodmer D. Insulin Receptor and Glucose Transporters in the Mammalian Cochlea. Audiol Neurootol 2019; 24:65-76. [PMID: 31117067 DOI: 10.1159/000499561] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 03/07/2019] [Indexed: 11/19/2022] Open
Abstract
Insulin receptors are expressed on nerve cells in the mammalian brain, but little is known about insulin signaling and the expression of the insulin receptor (IR) and glucose transporters in the cochlea. We performed immunohistochemistry and gene/protein expression analysis to characterize the expression pattern of the IR and glucose transporters in the mouse organ of Corti (OC). We also performed glucose uptake assays to explore the action of insulin and the effects of pioglitazone, an insulin sensitizer, on glucose transport in the OC. Western blots of protein extracts from OCs showed high expression of IR and glucose transporter 3 (GLUT3). Immunohistochemistry demonstrated that the IR is specifically expressed in the supporting cells of the OC. GLUT3 was found in outer and inner hair cells, in the basilar membrane (BM), the stria vascularis (SV), Reissner's membrane and spiral ganglion neurons (SGN). Glucose transporter 1 (GLUT1) was detected at low levels in the BM, SV and Reissner's membrane, and showed high expression in the SGN. Fluorescence glucose uptake assays revealed that hair cells take up glucose and that addition of insulin (10 nM or 1 µM) approximately doubled the rate of uptake. Pioglitazone conferred a small but nonsignificant potentiation of glucose uptake at the highest concentration of insulin. Gene expression analysis confirmed expression of IR, GLUT1 and GLUT3 mRNA in the OC. Pioglitazone significantly upregulated IR and GLUT1 mRNA expression, which was further increased by insulin. Together, these data show that insulin-stimulated glucose uptake occurs in the OC and may be associated with upregulation of both the IR and GLUT1.
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Affiliation(s)
- Nathan Huerzeler
- Department of Biomedicine, University of Basel, Basel, Switzerland,
| | - Vesna Petkovic
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | | | | | | | - Daniel Bodmer
- Department of Biomedicine, University of Basel, Basel, Switzerland.,Clinic for Otorhinolaryngology, Head and Neck Surgery, University Hospital Basel, Basel, Switzerland
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5
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Modulation of Glucose Takeup by Glucose Transport on the Isolated OHCs. Neural Plast 2018; 2018:7513217. [PMID: 29849567 PMCID: PMC5907477 DOI: 10.1155/2018/7513217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2018] [Accepted: 03/03/2018] [Indexed: 12/02/2022] Open
Abstract
Glucose is a fundamental source of energy for mammalian cells; however, whether glucose is taken up through the lateral walls of cochlear outer hair cells (OHCs) is unknown. The OHC lateral wall is complex, composed of a plasma membrane, cortical lattice, and subsurface cisternae. This study assessed the uptake of glucose by OHCs using live-cell microscopy and examined the distribution of glucose transporter isoforms by immunohistochemistry. We found that glucose transporter-4 was mostly expressed on the lateral wall of OHCs. Glucose crossed the lateral walls of OHCs via glucose transporters-4 mainly, and this process could be modulated. These results suggest that the lateral walls are involved in modulating energy transport into OHCs.
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6
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Differential localizations of the myo-inositol transporters HMIT and SMIT1 in the cochlear stria vascularis. Neurosci Lett 2018; 674:88-93. [PMID: 29551423 DOI: 10.1016/j.neulet.2018.03.028] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 02/28/2018] [Accepted: 03/13/2018] [Indexed: 11/22/2022]
Abstract
The cochlear stria vascularis produces endolymph and thereby plays an active role in inner ear homeostasis. We recently reported that the H+/myo-inositol cotransporter (HMIT) gene is expressed in the stria vascularis. Here, we examined the protein localization of HMIT and Na+/myo-inositol cotransporter 1 (SMIT1) in the stria vascularis by immunohistochemistry. HMIT and SMIT1 were detected in the lateral wall of the cochlear duct. HMIT was widely detected throughout the stria vascularis, while SMIT1 was enriched in the strial basal cells. To examine the localization of HMIT in the stria vascularis in more detail, dissociated strial cells were immunostained, which resulted in the detection of HMIT immunoreactivity in marginal cells. These results indicate that HMIT is expressed in marginal cells and basal cells of the stria vascularis, while SMIT1 expression is enriched in basal cells. We speculate that HMIT and SMIT1 may play important roles in the homeostasis of cochlear fluids, for example by participating in pH regulation and osmoregulation.
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7
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Sato MP, Higuchi T, Nin F, Ogata G, Sawamura S, Yoshida T, Ota T, Hori K, Komune S, Uetsuka S, Choi S, Masuda M, Watabe T, Kanzaki S, Ogawa K, Inohara H, Sakamoto S, Takebayashi H, Doi K, Tanaka KF, Hibino H. Hearing Loss Controlled by Optogenetic Stimulation of Nonexcitable Nonglial Cells in the Cochlea of the Inner Ear. Front Mol Neurosci 2017; 10:300. [PMID: 29018325 PMCID: PMC5616010 DOI: 10.3389/fnmol.2017.00300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 09/06/2017] [Indexed: 01/22/2023] Open
Abstract
Light-gated ion channels and transporters have been applied to a broad array of excitable cells including neurons, cardiac myocytes, skeletal muscle cells and pancreatic β-cells in an organism to clarify their physiological and pathological roles. Nonetheless, among nonexcitable cells, only glial cells have been studied in vivo by this approach. Here, by optogenetic stimulation of a different nonexcitable cell type in the cochlea of the inner ear, we induce and control hearing loss. To our knowledge, deafness animal models using optogenetics have not yet been established. Analysis of transgenic mice expressing channelrhodopsin-2 (ChR2) induced by an oligodendrocyte-specific promoter identified this channel in nonglial cells—melanocytes—of an epithelial-like tissue in the cochlea. The membrane potential of these cells underlies a highly positive potential in a K+-rich extracellular solution, endolymph; this electrical property is essential for hearing. Illumination of the cochlea to activate ChR2 and depolarize the melanocytes significantly impaired hearing within a few minutes, accompanied by a reduction in the endolymphatic potential. After cessation of the illumination, the hearing thresholds and potential returned to baseline during several minutes. These responses were replicable multiple times. ChR2 was also expressed in cochlear glial cells surrounding the neuronal components, but slight neural activation caused by the optical stimulation was unlikely to be involved in the hearing impairment. The acute-onset, reversible and repeatable phenotype, which is inaccessible to conventional gene-targeting and pharmacological approaches, seems to at least partially resemble the symptom in a population of patients with sensorineural hearing loss. Taken together, this mouse line may not only broaden applications of optogenetics but also contribute to the progress of translational research on deafness.
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Affiliation(s)
- Mitsuo P Sato
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Department of Otolaryngology, Kindai University Faculty of MedicineOsaka, Japan
| | - Taiga Higuchi
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan
| | - Fumiaki Nin
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Center for Transdisciplinary Research, Niigata UniversityNiigata, Japan
| | - Genki Ogata
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Center for Transdisciplinary Research, Niigata UniversityNiigata, Japan
| | - Seishiro Sawamura
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan
| | - Takamasa Yoshida
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Center for Transdisciplinary Research, Niigata UniversityNiigata, Japan.,Department of Otorhinolaryngology, Graduate School of Medical Sciences, Kyushu UniversityFukuoka, Japan
| | - Takeru Ota
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan
| | - Karin Hori
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan
| | - Shizuo Komune
- Division of Otolaryngology-Head and Neck Surgery, Yuaikai Oda HospitalSaga, Japan
| | - Satoru Uetsuka
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School of Medicine, Osaka UniversityOsaka, Japan
| | - Samuel Choi
- Department of Electrical and Electronics Engineering, Niigata UniversityNiigata, Japan.,AMED-CREST, AMEDNiigata, Japan
| | - Masatsugu Masuda
- Department of Otolaryngology, Kyorin University School of MedicineTokyo, Japan
| | - Takahisa Watabe
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of MedicineTokyo, Japan
| | - Sho Kanzaki
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of MedicineTokyo, Japan
| | - Kaoru Ogawa
- Department of Otolaryngology, Head and Neck Surgery, Keio University School of MedicineTokyo, Japan
| | - Hidenori Inohara
- Department of Otorhinolaryngology-Head and Neck Surgery, Graduate School of Medicine, Osaka UniversityOsaka, Japan
| | - Shuichi Sakamoto
- Department of Mechanical and Production Engineering, Niigata UniversityNiigata, Japan
| | - Hirohide Takebayashi
- Division of Neurobiology and Anatomy, Graduate School of Medical and Dental Sciences, Niigata UniversityNiigata, Japan
| | - Katsumi Doi
- Department of Otolaryngology, Kindai University Faculty of MedicineOsaka, Japan
| | - Kenji F Tanaka
- Department of Neuropsychiatry, Keio University School of MedicineTokyo, Japan
| | - Hiroshi Hibino
- Department of Molecular Physiology, Niigata University School of MedicineNiigata, Japan.,Center for Transdisciplinary Research, Niigata UniversityNiigata, Japan.,AMED-CREST, AMEDNiigata, Japan
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8
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Jiang M, Karasawa T, Steyger PS. Aminoglycoside-Induced Cochleotoxicity: A Review. Front Cell Neurosci 2017; 11:308. [PMID: 29062271 PMCID: PMC5640705 DOI: 10.3389/fncel.2017.00308] [Citation(s) in RCA: 171] [Impact Index Per Article: 24.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/15/2017] [Indexed: 12/20/2022] Open
Abstract
Aminoglycoside antibiotics are used as prophylaxis, or urgent treatment, for many life-threatening bacterial infections, including tuberculosis, sepsis, respiratory infections in cystic fibrosis, complex urinary tract infections and endocarditis. Although aminoglycosides are clinically-essential antibiotics, the mechanisms underlying their selective toxicity to the kidney and inner ear continue to be unraveled despite more than 70 years of investigation. The following mechanisms each contribute to aminoglycoside-induced toxicity after systemic administration: (1) drug trafficking across endothelial and epithelial barrier layers; (2) sensory cell uptake of these drugs; and (3) disruption of intracellular physiological pathways. Specific factors can increase the risk of drug-induced toxicity, including sustained exposure to higher levels of ambient sound, and selected therapeutic agents such as loop diuretics and glycopeptides. Serious bacterial infections (requiring life-saving aminoglycoside treatment) induce systemic inflammatory responses that also potentiate the degree of ototoxicity and permanent hearing loss. We discuss prospective clinical strategies to protect auditory and vestibular function from aminoglycoside ototoxicity, including reduced cochlear or sensory cell uptake of aminoglycosides, and otoprotection by ameliorating intracellular cytotoxicity.
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Affiliation(s)
- Meiyan Jiang
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, United States
| | - Takatoshi Karasawa
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, United States
| | - Peter S Steyger
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, United States.,National Center for Rehabilitative Auditory Research, Portland VA Medical Center (VHA), Portland, OR, United States
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9
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Wangemann P, Marcus DC. Ion and Fluid Homeostasis in the Cochlea. UNDERSTANDING THE COCHLEA 2017. [DOI: 10.1007/978-3-319-52073-5_9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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Meehan DT, Delimont D, Dufek B, Zallocchi M, Phillips G, Gratton MA, Cosgrove D. Endothelin-1 mediated induction of extracellular matrix genes in strial marginal cells underlies strial pathology in Alport mice. Hear Res 2016; 341:100-108. [PMID: 27553900 PMCID: PMC5086449 DOI: 10.1016/j.heares.2016.08.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/21/2016] [Accepted: 08/15/2016] [Indexed: 12/20/2022]
Abstract
Alport syndrome, a type IV collagen disorder, manifests as glomerular disease associated with hearing loss with thickening of the glomerular and strial capillary basement membranes (SCBMs). We have identified a role for endothelin-1 (ET-1) activation of endothelin A receptors (ETARs) in glomerular pathogenesis. Here we explore whether ET-1 plays a role in strial pathology. Wild type (WT) and Alport mice were treated with the ETAR antagonist, sitaxentan. The stria vascularis was analyzed for SCBM thickness and for extracellular matrix (ECM) proteins. Additional WT and Alport mice were exposed to noise or hypoxia and the stria analyzed for hypoxia-related and ECM genes. A strial marginal cell line cultured under hypoxic conditions, or stimulated with ET-1 was analyzed for expression of hypoxia-related and ECM transcripts. Noise exposure resulted in significantly elevated ABR thresholds in Alport mice relative to wild type littermates. Alport stria showed elevated expression of collagen α1(IV), laminin α2, and laminin α5 proteins relative to WT. SCBM thickening and elevated ECM protein expression was ameliorated by ETAR blockade. Stria from normoxic Alport mice and hypoxic WT mice showed upregulation of hypoxia-related, ECM, and ET-1 transcripts. Both ET-1 stimulation and hypoxia up-regulated ECM transcripts in cultured marginal cells. We conclude that ET-1 mediated activation of ETARs on strial marginal cells results in elevated expression of ECM genes and thickening of the SCBMs in Alport mice. SCBM thickening results in hypoxic stress further elevating ECM and ET-1 gene expression, exacerbating strial pathology.
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Affiliation(s)
| | | | - Brianna Dufek
- Boys Town National Research Hospital, Omaha, NE, USA
| | | | | | | | - Dominic Cosgrove
- Boys Town National Research Hospital, Omaha, NE, USA; University of Nebraska Medical Center, Omaha, NE, USA.
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11
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Partial corrosion casting to assess cochlear vasculature in mouse models of presbycusis and CMV infection. Hear Res 2016; 332:95-103. [DOI: 10.1016/j.heares.2015.11.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 10/21/2015] [Accepted: 11/23/2015] [Indexed: 12/20/2022]
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12
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Carraro M, Harrison RV. Degeneration of stria vascularis in age-related hearing loss; a corrosion cast study in a mouse model. Acta Otolaryngol 2016; 136:385-90. [PMID: 26824717 DOI: 10.3109/00016489.2015.1123291] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Conclusion With age, in a mouse model, degenerative changes to the capillaries of the stria vascularis are observed. These range from a narrowing of vessel lumen to complete degeneration of strial vessels. Other vascular beds in the cochlea are relatively unchanged with age. Strial capillaries at the cochlear base are significantly more affected than those in mid-apical turns. Objectives Previous work suggests that age-related hearing loss is associated with degenerative changes to cochlear vasculature; the term strial presbyacusis is often cited. This study reports on vascular changes observed in a murine model of presbyacusis, analyzed using corrosion cast techniques. Methods A novel corrosion cast technique was developed to compare cochlear vasculature in control mice (non-presbycusic, CD1) and old (> 6 months) C57BL/6 animals. ABR measures indicated a significant age-related threshold elevation in the C57BL/6 mice. Cochlear vascular casts were imaged using scanning electron microscopy, and vessel degeneration was quantified by measuring capillary diameters. Results Corrosion casts of cochlear vasculature in 6-12 month old C57BL/6 mice reveal significant degeneration of stria vascularis. Other capillary beds (spiral ligament and the spiral limbus) appear unchanged. Comparison of strial capillary diameters reveals significantly more damage in basal/lower-turn regions compared with the cochlear mid-turn.
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Abstract
BACKGROUND The pathologic changes that occur as a result of diabetic microangiopathy have been well described for the kidneys and the eyes. Although many studies suggest an association between diabetes mellitus and hearing loss, the pathologic changes in the cochlea in association with the diabetic state remain to be clarified. AIM/OBJECTIVE The aim of this review is to determine the effects of diabetes mellitus on cochlear morphology. METHOD A comprehensive search for relevant articles was carried out on electronic databases of Ovid Medline, Ovid Medline in Process, PubMed, Ovid Embase,or Biosis Preview, The Cochrane Library, ISI Web of Science, and Scopus. Articles published in English between 1940 and June 2010 were eligible to be reviewed. Using predefined inclusion criteria, published articles on histologic changes occurring in the cochlea due to diabetes mellitus were selected and reviewed, and their findings were synthesized. RESULTS Changes were observed in the basement membrane of the capillaries of the stria vascularis and in the basilar membrane, which was remarkably thickened, giving rise to diabetic microangiopathy. Loss of spiral ganglion neurons, organ of Corti cells, and atrophic changes in the stria vascularis were varied and infrequent. CONCLUSION There seems to be variable vulnerability of different cochlear cell types to the DM state. Further studies are required to determine the factors responsible for the differences in the histopathologic observations of cochlear tissues.
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Sodium-glucose transporter-2 (SGLT2; SLC5A2) enhances cellular uptake of aminoglycosides. PLoS One 2014; 9:e108941. [PMID: 25268124 PMCID: PMC4182564 DOI: 10.1371/journal.pone.0108941] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 08/26/2014] [Indexed: 12/20/2022] Open
Abstract
Aminoglycoside antibiotics, like gentamicin, continue to be clinically essential worldwide to treat life-threatening bacterial infections. Yet, the ototoxic and nephrotoxic side-effects of these drugs remain serious complications. A major site of gentamicin uptake and toxicity resides within kidney proximal tubules that also heavily express electrogenic sodium-glucose transporter-2 (SGLT2; SLC5A2) in vivo. We hypothesized that SGLT2 traffics gentamicin, and promotes cellular toxicity. We confirmed in vitro expression of SGLT2 in proximal tubule-derived KPT2 cells, and absence in distal tubule-derived KDT3 cells. D-glucose competitively decreased the uptake of 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG), a fluorescent analog of glucose, and fluorescently-tagged gentamicin (GTTR) by KPT2 cells. Phlorizin, an SGLT2 antagonist, strongly inhibited uptake of 2-NBDG and GTTR by KPT2 cells in a dose- and time-dependent manner. GTTR uptake was elevated in KDT3 cells transfected with SGLT2 (compared to controls); and this enhanced uptake was attenuated by phlorizin. Knock-down of SGLT2 expression by siRNA reduced gentamicin-induced cytotoxicity. In vivo, SGLT2 was robustly expressed in kidney proximal tubule cells of heterozygous, but not null, mice. Phlorizin decreased GTTR uptake by kidney proximal tubule cells in Sglt2+/− mice, but not in Sglt2−/− mice. However, serum GTTR levels were elevated in Sglt2−/− mice compared to Sglt2+/− mice, and in phlorizin-treated Sglt2+/− mice compared to vehicle-treated Sglt2+/− mice. Loss of SGLT2 function by antagonism or by gene deletion did not affect gentamicin cochlear loading or auditory function. Phlorizin did not protect wild-type mice from kanamycin-induced ototoxicity. We conclude that SGLT2 can traffic gentamicin and contribute to gentamicin-induced cytotoxicity.
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Cura AJ, Carruthers A. Role of monosaccharide transport proteins in carbohydrate assimilation, distribution, metabolism, and homeostasis. Compr Physiol 2013; 2:863-914. [PMID: 22943001 DOI: 10.1002/cphy.c110024] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The facilitated diffusion of glucose, galactose, fructose, urate, myoinositol, and dehydroascorbicacid in mammals is catalyzed by a family of 14 monosaccharide transport proteins called GLUTs. These transporters may be divided into three classes according to sequence similarity and function/substrate specificity. GLUT1 appears to be highly expressed in glycolytically active cells and has been coopted in vitamin C auxotrophs to maintain the redox state of the blood through transport of dehydroascorbate. Several GLUTs are definitive glucose/galactose transporters, GLUT2 and GLUT5 are physiologically important fructose transporters, GLUT9 appears to be a urate transporter while GLUT13 is a proton/myoinositol cotransporter. The physiologic substrates of some GLUTs remain to be established. The GLUTs are expressed in a tissue specific manner where affinity, specificity, and capacity for substrate transport are paramount for tissue function. Although great strides have been made in characterizing GLUT-catalyzed monosaccharide transport and mapping GLUT membrane topography and determinants of substrate specificity, a unifying model for GLUT structure and function remains elusive. The GLUTs play a major role in carbohydrate homeostasis and the redistribution of sugar-derived carbons among the various organ systems. This is accomplished through a multiplicity of GLUT-dependent glucose sensing and effector mechanisms that regulate monosaccharide ingestion, absorption,distribution, cellular transport and metabolism, and recovery/retention. Glucose transport and metabolism have coevolved in mammals to support cerebral glucose utilization.
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Affiliation(s)
- Anthony J Cura
- Department of Biochemistry & Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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Edamatsu M, Kondo Y, Ando M. Multiple expression of glucose transporters in the lateral wall of the cochlear duct studied by quantitative real-time PCR assay. Neurosci Lett 2010; 490:72-7. [PMID: 21182893 DOI: 10.1016/j.neulet.2010.12.029] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Revised: 12/02/2010] [Accepted: 12/11/2010] [Indexed: 11/20/2022]
Abstract
We have investigated the gene expression of the facilitated glucose transporter (GLUT), H+-coupled myo-inositol cotransporter (HMIT), and Na+ glucose cotransporter (SGLT) in the lateral wall of the cochlear duct by conventional RT-PCR and quantitative real-time PCR. The isoforms GLUT1, -3, -4, -5, -8, -10, -12 and HMIT were detected in both the stria vascularis and the spiral ligament, whereas no SGLT isoforms could be detected in these tissues. Quantitative real-time PCR analysis revealed significant differences in the gene expression of GLUT1, -4, -5, -10, and HMIT isoforms between the stria vascularis and the spiral ligament. This result reflects the tissue-dependent distributions of GLUT isoforms. These findings strongly suggest that a number of GLUT isoforms participate in glucose transport in the stria vascularis and the spiral ligament.
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Affiliation(s)
- Midori Edamatsu
- Laboratory of Cell Physiology, Department of Science Education, Graduate School of Education, Okayama University, Okayama 700-8530, Japan
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Roles of gap junctions in glucose transport from glucose transporter 1-positive to -negative cells in the lateral wall of the rat cochlea. Histochem Cell Biol 2008; 131:89-102. [PMID: 18787834 DOI: 10.1007/s00418-008-0502-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/26/2008] [Indexed: 01/23/2023]
Abstract
Despite the importance of glucose metabolism for auditory function, the mechanisms of glucose transport in the cochlea are not completely understood. We hypothesized that gap junctions mediate intercellular glucose transport in the cochlea in cooperation with facilitative glucose transporter 1 (GLUT1). Immunohistochemistry showed that GLUT1 and the tight junction protein occludin were expressed in blood vessels, and GLUT1, the gap junction proteins connexin26 and connexin30, and occludin were also present in strial basal cells in the lateral wall of the rat cochlea. Gap junctions were found among not only these GLUT1-positive strial basal cells but also GLUT1-negative fibrocytes in the spiral ligaments and strial intermediate cells. Glucose imaging using 6-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-6-deoxyglucose (6-NBDG, MW 342) together with Evans Blue Albumin (EBA, MW 68,000) showed that 6-NBDG was rapidly distributed throughout the stria vascularis and spiral ligament, whereas EBA was localized only in the vessels. The gap junctional uncouplers heptanol and carbenoxolone inhibited the distribution of 6-NBDG in the spiral ligament without decreasing the fluorescence of EBA in the blood vessels. These findings suggest that gap junctions mediate glucose transport from GLUT1-positive cells (strial basal cells) to GLUT1-negative cells (fibrocytes in the spiral ligament and strial intermediate cells) in the cochlea.
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