1
|
He C, Gai H, Zhao W, Zhang H, Lai L, Ding C, Chen L, Ding J. Advances in the Study of Etiology and Molecular Mechanisms of Sensorineural Hearing Loss. Cell Biochem Biophys 2024:10.1007/s12013-024-01344-3. [PMID: 38849694 DOI: 10.1007/s12013-024-01344-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/29/2024] [Indexed: 06/09/2024]
Abstract
Sensorineural hearing loss (SNHL), a multifactorial progressive disorder, results from a complex interplay of genetic and environmental factors, with its underlying mechanisms remaining unclear. Several pathological factors are believed to contribute to SNHL, including genetic factors, ion homeostasis, cell apoptosis, immune inflammatory responses, oxidative stress, hormones, metabolic syndrome, human cytomegalovirus infection, mitochondrial damage, and impaired autophagy. These factors collectively interact and play significant roles in the onset and progression of SNHL. The present review offers a comprehensive overview of the various factors that contribute to SNHL, emphasizes recent developments in understanding its etiology, and explores relevant preventive and intervention measures.
Collapse
Affiliation(s)
- Cairong He
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Hongcun Gai
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Wen Zhao
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Haiqin Zhang
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Lin Lai
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Chenyu Ding
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Lin Chen
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China
| | - Jie Ding
- Key laboratory of Plant Resource Conservation and Germplasm Innovation in Mountainous Region (Ministry of Education), College of Life Sciences/Institute of Agro-bioengineering, Guizhou University, Guiyang, 550025, Guizhou, China.
| |
Collapse
|
2
|
Rivetti S, Romano A, Mastrangelo S, Attinà G, Maurizi P, Ruggiero A. Aminoglycosides-Related Ototoxicity: Mechanisms, Risk Factors, and Prevention in Pediatric Patients. Pharmaceuticals (Basel) 2023; 16:1353. [PMID: 37895824 PMCID: PMC10610175 DOI: 10.3390/ph16101353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2023] [Revised: 09/17/2023] [Accepted: 09/21/2023] [Indexed: 10/29/2023] Open
Abstract
Aminoglycosides are broad-spectrum antibiotics largely used in children, but they have potential toxic side effects, including ototoxicity. Ototoxicity from aminoglycosides is permanent and is a consequence of its action on the inner ear cells via multiple mechanisms. Both uncontrollable risk factors and controllable risk factors are involved in the pathogenesis of aminoglycoside-related ototoxicity and, because of the irreversibility of ototoxicity, an important undertaking for preventing ototoxicity includes antibiotic stewardship to limit the use of aminoglycosides. Aminoglycosides are fundamental in the treatment of numerous infectious conditions at neonatal and pediatric age. In childhood, normal auditory function ensures adequate neurocognitive and social development. Hearing damage from aminoglycosides can therefore strongly affect the normal growth of the child. This review describes the molecular mechanisms of aminoglycoside-related ototoxicity and analyzes the risk factors and the potential otoprotective strategies in pediatric patients.
Collapse
Affiliation(s)
- Serena Rivetti
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
| | - Alberto Romano
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
| | - Stefano Mastrangelo
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
- Dipartimento di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Giorgio Attinà
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
| | - Palma Maurizi
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
- Dipartimento di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| | - Antonio Ruggiero
- Pediatric Oncology Unit, Fondazione Policlinico Universitario Agostino Gemelli IRCCS, 00168 Rome, Italy; (S.R.); (A.R.); (S.M.); (G.A.); (P.M.)
- Dipartimento di Scienze della Vita e Sanità Pubblica, Università Cattolica del Sacro Cuore, 00168 Rome, Italy
| |
Collapse
|
3
|
Kim J, Hemachandran S, Cheng AG, Ricci AJ. Identifying targets to prevent aminoglycoside ototoxicity. Mol Cell Neurosci 2022; 120:103722. [PMID: 35341941 PMCID: PMC9177639 DOI: 10.1016/j.mcn.2022.103722] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 03/14/2022] [Accepted: 03/19/2022] [Indexed: 12/21/2022] Open
Abstract
Aminoglycosides are potent antibiotics that are commonly prescribed worldwide. Their use carries significant risks of ototoxicity by directly causing inner ear hair cell degeneration. Despite their ototoxic side effects, there are currently no approved antidotes. Here we review recent advances in our understanding of aminoglycoside ototoxicity, mechanisms of drug transport, and promising sites for intervention to prevent ototoxicity.
Collapse
Affiliation(s)
- Jinkyung Kim
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Sriram Hemachandran
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Alan G Cheng
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA.
| | - Anthony J Ricci
- Department of Otolaryngology-Head and Neck Surgery, Stanford University School of Medicine, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
| |
Collapse
|
4
|
Steyger PS. Mechanisms of Aminoglycoside- and Cisplatin-Induced Ototoxicity. Am J Audiol 2021; 30:887-900. [PMID: 34415784 PMCID: PMC9126111 DOI: 10.1044/2021_aja-21-00006] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 04/30/2021] [Accepted: 05/14/2021] [Indexed: 12/11/2022] Open
Abstract
Purpose This review article summarizes our current understanding of the mechanisms underlying acquired hearing loss from hospital-prescribed medications that affects as many as 1 million people each year in Western Europe and North America. Yet, there are currently no federally approved drugs to prevent or treat the debilitating and permanent hearing loss caused by the life-saving platinum-based anticancer drugs or the bactericidal aminoglycoside antibiotics. Hearing loss has long-term impacts on quality-of-life measures, especially in young children and older adults. This review article also highlights some of the current knowledge gaps regarding iatrogenic causes of hearing loss. Conclusion Further research is urgently needed to further refine clinical practice and better ameliorate iatrogenic drug-induced hearing loss.
Collapse
Affiliation(s)
- Peter S. Steyger
- Translational Hearing Center, Creighton University, Omaha, NE
- National Center for Rehabilitative Auditory Research, VA Portland Health Care System, OR
| |
Collapse
|
5
|
Abstract
Hearing loss is often caused by death of sensory hair cells (HCs) in the inner ear. HCs are vulnerable to some ototoxic drugs, such as aminoglycosides(AGs) and the cisplatin.The most predominant form of drug-induced cell death is apoptosis. Many efforts have been made to protect HCs from cell death after ototoxic drug exposure. These mechanisms and potential targets of HCs protection will be discussed in this review.And we also propose further investigation in the field of HCs necrosis and regeneration, as well as future clinical utilization.
Collapse
|
6
|
Chai Y, He W, Yang W, Hetrick AP, Gonzalez JG, Sargsyan L, Wu H, Jung TTK, Li H. Intratympanic Lipopolysaccharide Elevates Systemic Fluorescent Gentamicin Uptake in the Cochlea. Laryngoscope 2021; 131:E2573-E2582. [PMID: 33956344 PMCID: PMC8453712 DOI: 10.1002/lary.29610] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/09/2021] [Accepted: 04/26/2021] [Indexed: 12/20/2022]
Abstract
Objectives/Hypothesis Lipopolysaccharide (LPS), a key component of bacterial endotoxins, activates macrophages and triggers the release of inflammatory cytokines in mammalian tissues. Recent studies have shown that intratympanic injection of LPS simulates acute otitis media (AOM) and results in morphological and functional changes in the inner ear. Here we established an AOM mouse model with LPS to investigate the uptake of ototoxic gentamicin in the inner ear, and elucidated the underlying mechanism by focusing on cochlear inflammation as a result of AOM. Study Design Preclinical rodent animal model. Methods Fluorescently tagged gentamicin (GTTR) was systemically administered to mice with AOM. Iba1‐positive macrophage morphology and inner ear cytokine profile were evaluated by immunofluorescence technique and a mouse cytokine array kit, respectively. Results We observed characteristic symptoms of AOM in the LPS‐treated ears with elevated hearing thresholds indicating a conductive hearing loss. More importantly, the LPS‐induced AOM activated cochlear inflammatory responses, manifested by macrophage infiltration, particularly in the organ of Corti and the spiral ligament, in addition to the up‐regulation of proinflammatory cytokines. Meanwhile, GTTR uptake in the stria vascularis and sensory hair cells from all the LPS‐treated ears was significantly enhanced at 24, 48, and 72‐hour post‐treatment, as the most prominent enhancement was observed in the 48‐hour group. Conclusion In summary, this study suggests that the pathological cochlea is more susceptible to ototoxic drugs, including aminoglycosides, and justified the clinical concern of aminoglycoside ototoxicity in the AOM treatment. Laryngoscope, 131:E2573–E2582, 2021
Collapse
Affiliation(s)
- Yongchuan Chai
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A.,Department of Otolaryngology Head and Neck Surgery, Shanghai Ninth People's Hospital Affiliated Shanghai Jiaotong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China.,Department of Otolaryngology Head and Neck Surgery, Loma Linda University Health, Loma Linda, California, U.S.A
| | - Weiwei He
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A.,Department of Otolaryngology Head and Neck Surgery, Shanghai Ninth People's Hospital Affiliated Shanghai Jiaotong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China.,Department of Otolaryngology Head and Neck Surgery, Loma Linda University Health, Loma Linda, California, U.S.A
| | - Weiqiang Yang
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A.,Department of Otolaryngology Head and Neck Surgery, Loma Linda University Health, Loma Linda, California, U.S.A
| | - Alisa P Hetrick
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A
| | - Jessica G Gonzalez
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A
| | - Liana Sargsyan
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A
| | - Hao Wu
- Department of Otolaryngology Head and Neck Surgery, Shanghai Ninth People's Hospital Affiliated Shanghai Jiaotong University School of Medicine, Shanghai, China.,Ear Institute, Shanghai Jiaotong University School of Medicine, Shanghai, China
| | - Timothy T K Jung
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A.,Department of Otolaryngology Head and Neck Surgery, Loma Linda University Health, Loma Linda, California, U.S.A
| | - Hongzhe Li
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, U.S.A.,Department of Otolaryngology Head and Neck Surgery, Loma Linda University Health, Loma Linda, California, U.S.A
| |
Collapse
|
7
|
Qian X, He Z, Wang Y, Chen B, Hetrick A, Dai C, Chi F, Li H, Ren D. Hair cell uptake of gentamicin in the developing mouse utricle. J Cell Physiol 2020; 236:5235-5252. [PMID: 33368220 DOI: 10.1002/jcp.30228] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 11/27/2020] [Accepted: 12/08/2020] [Indexed: 12/27/2022]
Abstract
Intratympanic injection of gentamicin has proven to be an effective therapy for intractable vestibular dysfunction. However, most studies to date have focused on the cochlea, so little is known about the distribution and uptake of gentamicin by the counterpart of the auditory system, specifically vestibular hair cells (HCs). Here, with a combination of in vivo and in vitro approaches, we used a gentamicin-Texas Red (GTTR) conjugate to investigate the mechanisms of gentamicin vestibulotoxicity in the developing mammalian utricular HCs. In vivo, GTTR fluorescence was concentrated in the apical cytoplasm and the cellular membrane of neonatal utricular HCs, but scarce in the nucleus of HCs and supporting cells. Quantitative analysis showed the GTTR uptake by striolar HCs was significantly higher than that in the extrastriola. In addition, the GTTR fluorescence intensity in the striola was increased gradually from 1 to 8 days, peaking at 8-9 days postnatally. In vitro, utricle explants were incubated with GTTR and candidate uptake conduits, including mechanotransduction (MET) channels and endocytosis in the HC, were inhibited separately. GTTR uptake by HCs could be inhibited by quinine, a blocker of MET channels, under both normal and stressed conditions. Meanwhile, endocytic inhibition only reduced GTTR uptake in the CoCl2 hypoxia model. In sum, the maturation of MET channels mediated uptake of GTTR into vestibular HCs. Under stressed conditions, MET channels play a pronounced role, manifested by channel-dependent stress enhanced GTTR permeation, while endocytosis participates in GTTR entry in a more selective manner.
Collapse
Affiliation(s)
- Xiaoqing Qian
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Ziyu He
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Yanmei Wang
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Binjun Chen
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Alisa Hetrick
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, USA
| | - Chunfu Dai
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Fanglu Chi
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| | - Hongzhe Li
- Research Service, VA Loma Linda Healthcare System, Loma Linda, California, USA.,Department of Otolaryngology-Head and Neck Surgery, Loma Linda University School of Medicine, Loma Linda, California, USA
| | - Dongdong Ren
- ENT Institute and Department of Otorhinolaryngology, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Hearing Medicine (Fudan University), Shanghai, China
| |
Collapse
|
8
|
|
9
|
Kros CJ, Steyger PS. Aminoglycoside- and Cisplatin-Induced Ototoxicity: Mechanisms and Otoprotective Strategies. Cold Spring Harb Perspect Med 2019; 9:cshperspect.a033548. [PMID: 30559254 DOI: 10.1101/cshperspect.a033548] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ototoxicity refers to damage of inner ear structures (i.e., the cochlea and vestibule) and their function (hearing and balance) following exposure to specific in-hospital medications (i.e., aminoglycoside antibiotics, platinum-based drugs), as well as a variety of environmental or occupational exposures (e.g., metals and solvents). This review provides a narrative derived from relevant papers describing factors contributing to (or increasing the risk of) aminoglycoside and cisplatin-induced ototoxicity. We also review current strategies to protect against ototoxicity induced by these indispensable pharmacotherapeutic treatments for life-threatening infections and solid tumors. We end by highlighting several interventional strategies that are currently in development, as well as the diverse challenges that still need to be overcome to prevent drug-induced hearing loss.
Collapse
Affiliation(s)
- Corné J Kros
- Sussex Neuroscience, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9QG, United Kingdom
| | - Peter S Steyger
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon 97239.,National Center for Rehabilitative Auditory Research, VA Portland Health Care System, Portland, Oregon 97239
| |
Collapse
|
10
|
Jiang M, Li H, Johnson A, Karasawa T, Zhang Y, Meier WB, Taghizadeh F, Kachelmeier A, Steyger PS. Inflammation up-regulates cochlear expression of TRPV1 to potentiate drug-induced hearing loss. SCIENCE ADVANCES 2019; 5:eaaw1836. [PMID: 31328162 PMCID: PMC6636990 DOI: 10.1126/sciadv.aaw1836] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2018] [Accepted: 06/13/2019] [Indexed: 05/26/2023]
Abstract
Aminoglycoside antibiotics are essential for treating life-threatening bacterial infections, despite the risk of lifelong hearing loss. Infections induce inflammation and up-regulate expression of candidate aminoglycoside-permeant cation channels, including transient receptor potential vanilloid-1 (TRPV1). Heterologous expression of TRPV1 facilitated cellular uptake of (fluorescently tagged) gentamicin that was enhanced by agonists, and diminished by antagonists, of TRPV1. Cochlear TRPV1 was immunolocalized near the apical membranes of sensory hair cells, adjacent supporting cells, and marginal cells in the stria vascularis. Exposure to immunostimulatory lipopolysaccharides, to simulate of bacterial infections, increased cochlear expression of TRPV1 and hair cell uptake of gentamicin. Lipopolysaccharide exposure exacerbated aminoglycoside-induced auditory threshold shifts and loss of cochlear hair cells in wild-type, but not in heterozygous Trpv1+/- or Trpv1 knockout, mice. Thus, TRPV1 facilitates cochlear uptake of aminoglycosides, and bacteriogenic stimulation upregulates TRPV1 expression to exacerbate cochleotoxicity. Furthermore, loss-of-function polymorphisms in Trpv1 can protect against immunogenic exacerbation of aminoglycoside-induced cochleotoxicity.
Collapse
Affiliation(s)
- Meiyan Jiang
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Hongzhe Li
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Anastasiya Johnson
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Takatoshi Karasawa
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Yuan Zhang
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - William B. Meier
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Farshid Taghizadeh
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Allan Kachelmeier
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
| | - Peter S. Steyger
- Oregon Hearing Research Center, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA
- National Center for Rehabilitative Auditory Research, VA Portland Health Care System, Portland, OR 97239, USA
| |
Collapse
|
11
|
Mahendrasingam S, Furness DN. Ultrastructural localization of the likely mechanoelectrical transduction channel protein, transmembrane-like channel 1 (TMC1) during development of cochlear hair cells. Sci Rep 2019; 9:1274. [PMID: 30718571 PMCID: PMC6362151 DOI: 10.1038/s41598-018-37563-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 12/05/2018] [Indexed: 01/27/2023] Open
Abstract
Transmembrane channel like protein 1 (TMC1) is likely to be a pore-forming subunit of the transduction channel of cochlear hair cells that is mechanically gated by tension on tip links in the stereocilia bundle. To localise TMC1 precisely, we labelled mice cochleae of different ages using custom-made polyclonal antibodies to TMC1 for light and transmission electron microscopy (TEM). Immunofluorescence revealed stereocilia labelling at P9 but not at P3 in apical hair cells. Immunogold labelling for TEM confirmed that labelling was absent at P3, and showed weak labelling at P6 with no stereocilia tip labelling, increasing at P9, with specific tip labelling on shorter stereocilia and some throughout the bundle. At P12 and P21, labelling was refined mostly to stereocilia tips. Quantification showed that labelling overall reached maximum by P12, labelling per tip was relatively constant from P9 to P21, but percent tips labelled was reduced from 16% to 8%. Tmc1−/− showed no labelling. Thus TMC1 occurs at the lower end of the tip link, supporting its presence in the MET complex and likely the channel. Tip localisation from P9 onwards coincides with lipoma HMGIC fusion partner-like 5 (LHFPL5), a protein that may be involved in acquiring/maintaining TMC1 localisation.
Collapse
Affiliation(s)
| | - David N Furness
- School of Life Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK.
| |
Collapse
|
12
|
Konrad-Martin D, Poling GL, Garinis AC, Ortiz CE, Hopper J, Bennett KO, Dille MF. Applying U.S. national guidelines for ototoxicity monitoring in adult patients: perspectives on patient populations, service gaps, barriers and solutions. Int J Audiol 2018; 57:S3-S18. [PMID: 29157038 PMCID: PMC6450095 DOI: 10.1080/14992027.2017.1398421] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2017] [Revised: 10/05/2017] [Accepted: 10/20/2017] [Indexed: 02/07/2023]
Abstract
OBJECTIVES To promote establishment of effective ototoxicity monitoring programs (OMPs), this report reviews the U.S. national audiology guidelines in relation to "real world" OMP application. Background is provided on the mechanisms, risks and clinical presentation of hearing loss associated with major classes of ototoxic medications. DESIGN This is a non-systematic review using PubMed, national and international agency websites, personal communications between ototoxicity experts, and results of unpublished research. Examples are provided of OMPs in various healthcare settings within the U.S. civilian sector, Department of Defense (DoD), and Department of Veterans Affairs (VA). STUDY SAMPLE The five OMPs compared in this report represent a convenience sample of the programs with which the authors are affiliated. Their opinions were elicited via two semi-structured teleconferences on barriers and facilitators of OMP, followed by a self-administered questionnaire on OMP characteristics and practices, with responses synthesized herein. Preliminary results are provided from an ongoing VA clinical trial at one of these OMP sites. Participants were 40 VA patients who received cisplatin chemotherapy in 2014-2017. The study arms contrast access to care for OMP delivered on the treatment unit versus usual care as provided in the audiology clinic. RESULTS Protocols of the OMPs examined varied, reflecting their diverse settings. Service delivery concerns included baseline tests missed or completed after the initial treatment, and monitoring tests done infrequently or only after cessation of treatment. Perceived barriers involved logistics related to accessing and testing patients, such as a lack of processes to help patients enter programs, patients' time and scheduling constraints, and inconvenient audiology clinic locations. Use of abbreviated or screening methods facilitated monitoring. CONCLUSIONS The most effective OMPs integrated audiological management into care pathways of the clinical specialties that prescribe ototoxic medications. More OMP guidance is needed to inform evaluation schedules, outcome reporting, and determination of actionable ototoxic changes. Guidance is also lacking on the use of hearing conservation approaches suitable for the mass testing needed to support large-scale OMP efforts. Guideline adherence might improve with formal endorsement from organizations governing the medical specialty stakeholders in OMP such as oncologists, pulmonologists, infectious disease specialists, ototolaryngologists and pharmacists.
Collapse
Affiliation(s)
- Dawn Konrad-Martin
- VA Portland Health Care System, VA National Center for Rehabilitative Auditory Research, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health & Science University, Portland, OR
| | - Gayla L. Poling
- Mayo Clinic, Department of Otorhinolaryngology, Division of Audiology, Rochester, MN
| | - Angela C. Garinis
- VA Portland Health Care System, VA National Center for Rehabilitative Auditory Research, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health & Science University, Portland, OR
| | - Candice E. Ortiz
- Walter Reed National Military Medical Center, National Military Audiology and Speech Pathology Center, Bethesda, MD
| | - Jennifer Hopper
- Department of Otolaryngology, Yale University School of Medicine, New Haven, CT
| | - Keri O’Connell Bennett
- VA Portland Health Care System, VA National Center for Rehabilitative Auditory Research, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health & Science University, Portland, OR
| | - Marilyn F. Dille
- VA Portland Health Care System, VA National Center for Rehabilitative Auditory Research, Portland, OR
- Department of Otolaryngology/Head and Neck Surgery, Oregon Health & Science University, Portland, OR
| |
Collapse
|
13
|
Edderkaoui B, Sargsyan L, Hetrick A, Li H. Deficiency of Duffy Antigen Receptor for Chemokines Ameliorated Cochlear Damage From Noise Exposure. Front Mol Neurosci 2018; 11:173. [PMID: 29899689 PMCID: PMC5988871 DOI: 10.3389/fnmol.2018.00173] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 05/08/2018] [Indexed: 01/06/2023] Open
Abstract
Cochlear inflammatory response to various environmental insults, including acoustic and ototoxic overexposures, has been increasingly become a topic of interest. As the immune response is associated with both pathology and protection, targeting specific components of the immune response is expected to dissect the relationships between cellular damage and inflammation-associated protection and repair in the cochlea. Duffy antigen receptor for chemokines (DARC) is a member of a group of atypical chemokine receptors, and essential for chemokine-regulated leukocyte/neutrophil trafficking during inflammation. Previous studies have reported that Darc deficiency alters chemokine bioavailability and leukocyte homeostasis, leading to significant anti-inflammatory effects in tissues following injury. In this study, we have used Darc knockout mice to determine the impact of a deficiency in this gene on cochlear development, as well as function in cochlea subjected to various stresses. We observed that DARC is not required for normal development of cochlear function, as evidenced by typical hearing sensitivity in juvenile Darc-KO mice, as compared to wild type (WT) C57BL/6 mice. However, Darc-KO mice exhibited improved hearing recovery after intense noise exposure when compared to wild-type. The auditory brainstem response (ABR) threshold shift between KO and WT mice was most obvious at 1-week post-noise exposure. At cochlear locations above the frequency range of the energy band of damaging noise, both hair cell survival and ribbon synapse density were improved in Darc deficient animals. In addition, the mRNA levels of some major inflammatory effectors, including Mcp-1 and Gdf15, were altered in Darc-KO mice compared to control mice at 1, 3 and 7 days post-noise exposure. These data collectively suggest that the normal Darc-dependent inflammatory response slows down the process of hearing recovery, and exacerbates cellular damage in the cochlea after noise exposure.
Collapse
Affiliation(s)
- Bouchra Edderkaoui
- Research Service, VA Loma Linda Healthcare System, Loma Linda, CA, United States.,Loma Linda University School of Medicine, Loma Linda, CA, United States
| | - Liana Sargsyan
- Research Service, VA Loma Linda Healthcare System, Loma Linda, CA, United States
| | - Alisa Hetrick
- Research Service, VA Loma Linda Healthcare System, Loma Linda, CA, United States
| | - Hongzhe Li
- Research Service, VA Loma Linda Healthcare System, Loma Linda, CA, United States.,Loma Linda University School of Medicine, Loma Linda, CA, United States.,Department of Otolaryngology-Head and Neck Surgery, Loma Linda University School of Medicine, Loma Linda, CA, United States
| |
Collapse
|
14
|
Tompkins N, Spinelli KJ, Choi D, Barr-Gillespie PG. A Model for Link Pruning to Establish Correctly Polarized and Oriented Tip Links in Hair Bundles. Biophys J 2017; 113:1868-1881. [PMID: 29045880 DOI: 10.1016/j.bpj.2017.08.029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/14/2017] [Accepted: 08/21/2017] [Indexed: 10/18/2022] Open
Abstract
Tip links are thought to gate the mechanically sensitive transduction channels of hair cells, but how they form during development and regeneration remains mysterious. In particular, it is unclear how tip links are strung between stereocilia so that they are oriented parallel to a single axis; why their polarity is uniform despite their constituent molecules' intrinsic asymmetry; and why only a single tip link is present at each tip-link position. We present here a series of simple rules that reasonably explain why these phenomena occur. In particular, our model relies on each of the two ends of the tip link having distinct Ca2+-dependent stability and being connected to different motor complexes. A simulation employing these rules allowed us to explore the parameter space for the model, demonstrating the importance of the feedback between transduction channels and angled links, links that are 60° off-axis with respect to mature tip links. We tested this key aspect of the model by examining angled links in chick cochlea hair cells. As implied by the assumptions used to generate the model, we found that angled links were stabilized if there was no tip link at the tip of the upper stereocilium, and appeared when transduction channels were blocked. The model thus plausibly explains how tip-link formation and pruning can occur.
Collapse
Affiliation(s)
- Nathan Tompkins
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon
| | - Kateri J Spinelli
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon
| | - Dongseok Choi
- School of Public Health, Oregon Health and Science University, Portland, Oregon; Graduate School of Dentistry, Kyung Hee University, Seoul, South Korea
| | - Peter G Barr-Gillespie
- Oregon Hearing Research Center and Vollum Institute, Oregon Health and Science University, Portland, Oregon.
| |
Collapse
|
15
|
Jiang M, Taghizadeh F, Steyger PS. Potential Mechanisms Underlying Inflammation-Enhanced Aminoglycoside-Induced Cochleotoxicity. Front Cell Neurosci 2017; 11:362. [PMID: 29209174 PMCID: PMC5702304 DOI: 10.3389/fncel.2017.00362] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/03/2017] [Indexed: 12/20/2022] Open
Abstract
Aminoglycoside antibiotics remain widely used for urgent clinical treatment of life-threatening infections, despite the well-recognized risk of permanent hearing loss, i.e., cochleotoxicity. Recent studies show that aminoglycoside-induced cochleotoxicity is exacerbated by bacteriogenic-induced inflammation. This implies that those with severe bacterial infections (that induce systemic inflammation), and are treated with bactericidal aminoglycosides are at greater risk of drug-induced hearing loss than previously recognized. Incorporating this novel comorbid factor into cochleotoxicity risk prediction models will better predict which individuals are more predisposed to drug-induced hearing loss. Here, we review the cellular and/or signaling mechanisms by which host-mediated inflammatory responses to infection could enhance the trafficking of systemically administered aminoglycosides into the cochlea to enhance the degree of cochleotoxicity over that in healthy preclinical models. Once verified, these mechanisms will be potential targets for novel pharmacotherapeutics that reduce the risk of drug-induced hearing loss (and acute kidney damage) without compromising the life-saving bactericidal efficacy of aminoglycosides.
Collapse
Affiliation(s)
- Meiyan Jiang
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, OR, United States
| | - Farshid Taghizadeh
- 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, VA Portland Health Care System, Portland, OR, United States
| |
Collapse
|
16
|
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.
Collapse
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
| |
Collapse
|
17
|
Garinis AC, Kemph A, Tharpe AM, Weitkamp JH, McEvoy C, Steyger PS. Monitoring neonates for ototoxicity. Int J Audiol 2017; 57:S41-S48. [PMID: 28949262 DOI: 10.1080/14992027.2017.1339130] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Neonates admitted to the neonatal intensive care unit (NICU) are at greater risk of permanent hearing loss compared to infants in well mother and baby units. Several factors have been associated with this increased prevalence of hearing loss, including congenital infections (e.g. cytomegalovirus or syphilis), ototoxic drugs (such as aminoglycoside or glycopeptide antibiotics), low birth weight, hypoxia and length of stay. The aetiology of this increased prevalence of hearing loss remains poorly understood. DESIGN Here we review current practice and discuss the feasibility of designing improved ototoxicity screening and monitoring protocols to better identify acquired, drug-induced hearing loss in NICU neonates. STUDY SAMPLE A review of published literature. CONCLUSIONS We conclude that current audiological screening or monitoring protocols for neonates are not designed to adequately detect early onset of ototoxicity. This paper offers a detailed review of evidence-based research, and offers recommendations for developing and implementing an ototoxicity monitoring protocol for young infants, before and after discharge from the hospital.
Collapse
Affiliation(s)
- Angela C Garinis
- a Oregon Hearing Research Center, Otolaryngology , Oregon Health & Science University , Portland , OR , USA.,b National Center for Rehabilitative Auditory Research , VA Portland Health Care System , Portland , OR , USA
| | - Alison Kemph
- c Hearing and Speech Sciences , Vanderbilt University School of Medicine , Nashville , TN , USA
| | - Anne Marie Tharpe
- c Hearing and Speech Sciences , Vanderbilt University School of Medicine , Nashville , TN , USA
| | | | - Cynthia McEvoy
- e Neonatology, Pediatrics , Oregon Health & Science University , Portland , OR , USA
| | - Peter S Steyger
- a Oregon Hearing Research Center, Otolaryngology , Oregon Health & Science University , Portland , OR , USA.,b National Center for Rehabilitative Auditory Research , VA Portland Health Care System , Portland , OR , USA
| |
Collapse
|
18
|
Garinis AC, Liao S, Cross CP, Galati J, Middaugh JL, Mace JC, Wood AM, McEvoy L, Moneta L, Lubianski T, Coopersmith N, Vigo N, Hart C, Riddle A, Ettinger O, Nold C, Durham H, MacArthur C, McEvoy C, Steyger PS. Effect of gentamicin and levels of ambient sound on hearing screening outcomes in the neonatal intensive care unit: A pilot study. Int J Pediatr Otorhinolaryngol 2017; 97:42-50. [PMID: 28483249 PMCID: PMC5439527 DOI: 10.1016/j.ijporl.2017.03.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Revised: 03/16/2017] [Accepted: 03/18/2017] [Indexed: 11/29/2022]
Abstract
OBJECTIVE Hearing loss rates in infants admitted to neonatal intensive care units (NICU) run at 2-15%, compared to 0.3% in full-term births. The etiology of this difference remains poorly understood. We examined whether the level of ambient sound and/or cumulative gentamicin (an aminoglycoside) exposure affect NICU hearing screening results, as either exposure can cause acquired, permanent hearing loss. We hypothesized that higher levels of ambient sound in the NICU, and/or gentamicin dosing, increase the risk of referral on the distortion product otoacoustic emission (DPOAE) assessments and/or automated auditory brainstem response (AABR) screens. METHODS This was a prospective pilot outcomes study of 82 infants (<37 weeks gestational age) admitted to the NICU at Oregon Health & Science University. An ER-200D sound pressure level dosimeter was used to collect daily sound exposure in the NICU for each neonate. Gentamicin dosing was also calculated for each infant, including the total daily dose based on body mass (mg/kg/day), as well as the total number of treatment days. DPOAE and AABR assessments were conducted prior to discharge to evaluate hearing status. Exclusion criteria included congenital infections associated with hearing loss, and congenital craniofacial or otologic abnormalities. RESULTS The mean level of ambient sound was 62.9 dBA (range 51.8-70.6 dBA), greatly exceeding American Academy of Pediatrics (AAP) recommendation of <45.0 dBA. More than 80% of subjects received gentamicin treatment. The referral rate for (i) AABRs, (frequency range: ∼1000-4000 Hz), was 5%; (ii) DPOAEs with a broad F2 frequency range (2063-10031 Hz) was 39%; (iii) DPOAEs with a low-frequency F2 range (<4172 Hz) was 29%, and (iv) DPOAEs with a high-frequency F2 range (>4172 Hz) was 44%. DPOAE referrals were significantly greater for infants receiving >2 days of gentamicin dosing compared to fewer doses (p = 0.004). The effect of sound exposure and gentamicin treatment on hearing could not be determined due to the low number of NICU infants without gentamicin exposure (for control comparisons). CONCLUSION All infants were exposed to higher levels of ambient sound that substantially exceed AAP guidelines. More referrals were generated by DPOAE assessments than with AABR screens, with significantly more DPOAE referrals with a high-frequency F2 range, consistent with sound- and/or gentamicin-induced cochlear dysfunction. Adding higher frequency DPOAE assessments to existing NICU hearing screening protocols could better identify infants at-risk for ototoxicity.
Collapse
Affiliation(s)
- Angela C. Garinis
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Selena Liao
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Campbell P. Cross
- School of Medicine, Oregon Health & Science University, Portland, Oregon,Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| | - Johnathan Galati
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| | - Jessica L. Middaugh
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Jess C. Mace
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Anna-Marie Wood
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| | - Lindsey McEvoy
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| | - Lauren Moneta
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Troy Lubianski
- Oregon Clinical and Translational Research Institute, Oregon Health & Science University, Portland, Oregon
| | - Noe Coopersmith
- Oregon Clinical and Translational Research Institute, Oregon Health & Science University, Portland, Oregon
| | - Nicholas Vigo
- School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Christopher Hart
- School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Artur Riddle
- School of Medicine, Oregon Health & Science University, Portland, Oregon
| | - Olivia Ettinger
- Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| | - Casey Nold
- Oregon Clinical and Translational Research Institute, Oregon Health & Science University, Portland, Oregon
| | - Heather Durham
- Child Development and Research Center, Oregon Health & Science University, Portland, Oregon
| | - Carol MacArthur
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon
| | - Cynthia McEvoy
- Department of Neonatology, Oregon Health & Science University, Portland, Oregon
| | - Peter S. Steyger
- Department of Otolaryngology, Oregon Health & Science University, Portland, Oregon,Oregon Hearing Research Center, Oregon Health & Science University, Portland, Oregon
| |
Collapse
|
19
|
Pathophysiology of the cochlear intrastrial fluid-blood barrier (review). Hear Res 2016; 338:52-63. [PMID: 26802581 DOI: 10.1016/j.heares.2016.01.010] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Revised: 01/11/2016] [Accepted: 01/14/2016] [Indexed: 12/20/2022]
Abstract
The blood-labyrinth barrier (BLB) in the stria vascularis is a highly specialized capillary network that controls exchanges between blood and the intrastitial space in the cochlea. The barrier shields the inner ear from blood-born toxic substances and selectively passes ions, fluids, and nutrients to the cochlea, playing an essential role in the maintenance of cochlear homeostasis. Anatomically, the BLB is comprised of endothelial cells (ECs) in the strial microvasculature, elaborated tight and adherens junctions, pericytes (PCs), basement membrane (BM), and perivascular resident macrophage-like melanocytes (PVM/Ms), which together form a complex "cochlear-vascular unit" in the stria vascularis. Physical interactions between the ECs, PCs, and PVM/Ms, as well as signaling between the cells, is critical for controlling vascular permeability and providing a proper environment for hearing function. Breakdown of normal interactions between components of the BLB is seen in a wide range of pathological conditions, including genetic defects and conditions engendered by inflammation, loud sound trauma, and ageing. In this review, we will discuss prevailing views of the structure and function of the strial cochlear-vascular unit (also referred to as the "intrastrial fluid-blood barrier"). We will also discuss the disrupted homeostasis seen in a variety of hearing disorders. Therapeutic targeting of the strial barrier may offer opportunities for improvement of hearing health and amelioration of auditory disorders. This article is part of a Special Issue entitled <Annual Reviews 2016>.
Collapse
|