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Tian C, Yang Y, Wang R, Li Y, Sun F, Chen J, Zha D. Norepinephrine protects against cochlear outer hair cell damage and noise-induced hearing loss via α 2A-adrenergic receptor. BMC Neurosci 2024; 25:5. [PMID: 38291397 PMCID: PMC10829207 DOI: 10.1186/s12868-024-00845-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 01/16/2024] [Indexed: 02/01/2024] Open
Abstract
BACKGROUND The cochlear sympathetic system plays a key role in auditory function and susceptibility to noise-induced hearing loss (NIHL). The formation of reactive oxygen species (ROS) is a well-documented process in NIHL. In this study, we aimed at investigating the effects of a superior cervical ganglionectomy (SCGx) on NIHL in Sprague-Dawley rats. METHODS We explored the effects of unilateral and bilateral Superior Cervical Ganglion (SCG) ablation in the eight-ten weeks old Sprague-Dawley rats of both sexes on NIHL. Auditory function was evaluated by auditory brainstem response (ABR) testing and Distortion product otoacoustic emissions (DPOAEs). Outer hair cells (OHCs) counts and the expression of α2A-adrenergic receptor (AR) in the rat cochlea using immunofluorescence analysis. Cells culture and treatment, CCK-8 assay, Flow cytometry staining and analysis, and western blotting were to explore the mechanisms of SCG fibers may have a protective role in NIHL. RESULTS We found that neither bilateral nor unilateral SCGx protected the cochlea against noise exposure. In HEI-OC1 cells, H2O2-induced oxidative damage and cell death were inhibited by the application of norepinephrine (NE). NE may prevent ROS-induced oxidative stress in OHCs and NIHL through the α2A-AR. CONCLUSION These results demonstrated that sympathetic innervation mildly affected cochlear susceptibility to acoustic trauma by reducing oxidative damage in OHCs through the α2A-AR. NE may be a potential therapeutic strategy for NIHL prevention.
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Affiliation(s)
- Chaoyong Tian
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Yang Yang
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Renfeng Wang
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Yao Li
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Fei Sun
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Jun Chen
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China
| | - Dingjun Zha
- Department of Otolaryngology Head and Neck Surgery, Xijing Hospital, Air Force Medical University, Xi'an, Shaanxi, 710032, China.
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Rose KP, Manilla G, Milon B, Zalzman O, Song Y, Coate TM, Hertzano R. Spatially distinct otic mesenchyme cells show molecular and functional heterogeneity patterns before hearing onset. iScience 2023; 26:107769. [PMID: 37720106 PMCID: PMC10502415 DOI: 10.1016/j.isci.2023.107769] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 06/29/2023] [Accepted: 08/25/2023] [Indexed: 09/19/2023] Open
Abstract
The cochlea consists of diverse cellular populations working in harmony to convert mechanical stimuli into electrical signals for the perception of sound. Otic mesenchyme cells (OMCs), often considered a homogeneous cell type, are essential for normal cochlear development and hearing. Despite being the most numerous cell type in the developing cochlea, OMCs are poorly understood. OMCs are known to differentiate into spatially and functionally distinct cell types, including fibrocytes of the lateral wall and spiral limbus, modiolar osteoblasts, and specialized tympanic border cells of the basilar membrane. Here, we show that OMCs are transcriptionally and functionally heterogeneous and can be divided into four distinct populations that spatially correspond to OMC-derived cochlear structures. We also show that this heterogeneity and complexity of OMCs commences during early phases of cochlear development. Finally, we describe the cell-cell communication network of the developing cochlea, inferring a major role for OMC in outgoing signaling.
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Affiliation(s)
- Kevin P. Rose
- Neurotology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Gabriella Manilla
- Neurotology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Beatrice Milon
- Neurotology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ori Zalzman
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Yang Song
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Thomas M. Coate
- Department of Biology, Georgetown University, Washington, DC 20007, USA
| | - Ronna Hertzano
- Neurotology Branch, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD 21201, USA
- Department of Otorhinolaryngology Head and Neck Surgery, University of Maryland School of Medicine, Baltimore, MD 21201, USA
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3
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Shi X. Research advances in cochlear pericytes and hearing loss. Hear Res 2023; 438:108877. [PMID: 37651921 PMCID: PMC10538405 DOI: 10.1016/j.heares.2023.108877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 08/03/2023] [Accepted: 08/18/2023] [Indexed: 09/02/2023]
Abstract
Pericytes are specialized mural cells surrounding endothelial cells in microvascular beds. They play a role in vascular development, blood flow regulation, maintenance of blood-tissue barrier integrity, and control of angiogenesis, tissue fibrosis, and wound healing. In recent decades, understanding of the critical role played by pericytes in retina, brain, lung, and kidney has seen significant progress. The cochlea contains a large population of pericytes. However, the role of cochlear pericytes in auditory pathophysiology is, by contrast, largely unknown. The present review discusses recent progress in identifying cochlear pericytes, mapping their distribution, and defining their role in regulating blood flow, controlling the blood-labyrinth barrier (BLB) and angiogenesis, and involvement in different types of hearing loss.
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Affiliation(s)
- Xiaorui Shi
- Department of Otolaryngology/Head & Neck Surgery, Oregon Hearing Research Center (NRC04), Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA.
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4
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Xu K, Xu B, Gu J, Wang X, Yu D, Chen Y. Intrinsic mechanism and pharmacologic treatments of noise-induced hearing loss. Theranostics 2023; 13:3524-3549. [PMID: 37441605 PMCID: PMC10334830 DOI: 10.7150/thno.83383] [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: 02/09/2023] [Accepted: 06/12/2023] [Indexed: 07/15/2023] Open
Abstract
Noise accounts for one-third of hearing loss worldwide. Regretfully, noise-induced hearing loss (NIHL) is deemed to be irreversible due to the elusive pathogenic mechanisms that have not been fully elucidated. The complex interaction between genetic and environmental factors, which influences numerous downstream molecular and cellular events, contributes to the NIHL. In clinical settings, there are no effective therapeutic drugs other than steroids, which are the only treatment option for patients with NIHL. Therefore, the need for treatment of NIHL that is currently unmet, along with recent progress in our understanding of the underlying regulatory mechanisms, has led to a lot of new literatures focusing on this therapeutic field. The emergence of novel technologies that modify local drug delivery to the inner ear has led to the development of promising therapeutic approaches, which are currently under clinical investigation. In this comprehensive review, we focus on outlining and analyzing the basics and potential therapeutics of NIHL, as well as the application of biomaterials and nanomedicines in inner ear drug delivery. The objective of this review is to provide an incentive for NIHL's fundamental research and future clinical translation.
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Affiliation(s)
- Ke Xu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Baoying Xu
- Materdicine Lab, School of Life Sciences, Shanghai University, Shanghai, China
| | - Jiayi Gu
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Xueling Wang
- Department of Otolaryngology-Head and Neck Surgery, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Ear Institute, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
- Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, Shanghai, China
| | - Dehong Yu
- Materdicine Lab, School of Life Sciences, Shanghai University, Shanghai, China
| | - Yu Chen
- Materdicine Lab, School of Life Sciences, Shanghai University, Shanghai, China
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5
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Bae SH, Yoo JE, Choe YH, Kwak SH, Choi JY, Jung J, Hyun YM. Neutrophils infiltrate into the spiral ligament but not the stria vascularis in the cochlea during lipopolysaccharide-induced inflammation. Am J Cancer Res 2021; 11:2522-2533. [PMID: 33456557 PMCID: PMC7806478 DOI: 10.7150/thno.49121] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 12/06/2020] [Indexed: 12/16/2022] Open
Abstract
It has been challenging to apply intravital imaging for monitoring the inner ear, as the anatomical location and intricate structure hamper the access of imaging instruments to the inner ear of live mice. By employing intravital imaging of the cochlea in live mice with two-photon microscopy, we investigated neutrophil infiltration into the cochlea tissue and its characteristics under a lipopolysaccharide (LPS)-induced inflammatory state. Methods: Cochlea inflammation was induced by LPS injection to the middle ear. Using two-photon intravital microscopy with specifically designed surgical exteriorization of the cochlea in live mice, we investigated the dynamic features of neutrophils in the lateral wall of the cochlea. The molecular expression pattern of the cochlea lateral wall was also investigated during the LPS-induce inflammation. Results: Despite the contention of whether neutrophils are recruited to the spiral ligament (SL) during inflammation, we observed that LPS-induced inflammation of the middle ear, which mimics acute otitis media, triggered neutrophil migration to the SL in the lateral wall. Notably, massive neutrophil infiltration to the SL occurred 2 days after LPS inoculation, but there was no neutrophil infiltration into the stria vascularis (SV) region. At 1 day after LPS-induced cochlear inflammation, increased mRNA expression of interleukin-1β, interleukin-6 were identified in both the SL and SV, while the ICAM-1 mRNA expression increased only in the SL. The differential reactivity of ICAM-1 is likely responsible for the different neutrophil recruitment pattern in the cochlea. Conclusion: Intravital imaging of the cochlea revealed that neutrophil recruitment and infiltration during inflammation are spatially controlled and exclusively observed in the SL but not in the SV and organ of Corti.
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6
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Chen D, Li Z, Zhou Q, Chen Y, Yang L, Tan J, Zeng X, Li P. Impacts of different methylprednisolone administration routes in patients with sudden hearing loss or Meniere's disease. J Otol 2020; 15:149-154. [PMID: 33293916 PMCID: PMC7691840 DOI: 10.1016/j.joto.2020.08.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Evidence suggests that glucocorticoids are important in the treatment of sudden hearing loss (SHL) and Meniere's disease (MD). However, different glucocorticoid administration methods may have a significant impact on treatment outcomes. OBJECTIVE This study aimed to investigate effects of different glucocorticoid administration methods on sudden hearing loss and Meniere's disease. METHODS In this study, glucocorticoids were administered orally in 18 patients, by retroauricular injection in 15 patients and by intratympanic injection in 15 patients. White blood cell (WBC) count, serum K+, fasting plasma glucose (FPG), body temperature, heart rate and blood pressure were used to evaluate effects of glucocorticoids on patients with hearing loss. Visual analog scale (VAS) of pain and sleep disorders were also surveyed, and pure tone audiometry (PTA) results were compared among groups to evaluate efficacy of different glucocorticoids administration methods. RESULT WBC count, heart rate and blood pressure were higher in patients taking oral glucocorticoids, while body temperature, serum K+ and FPG levels did not change in all three groups. However, patients who received intratympanic injection of glucocorticoids experienced more pain, while those taking oral glucocorticoids reported more sleep impairment. Treatment efficacy on hearing loss was not significantly different among the three groups. CONCLUSION These findings suggest that systemic glucocorticoid administration can result in greater whole body responses than local administration, but with similar hearing treatment efficacy.
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Affiliation(s)
- Dan Chen
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Zhipeng Li
- Department of Emergency, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Qilin Zhou
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Yubin Chen
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Luoying Yang
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Jingqian Tan
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Xiangli Zeng
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
| | - Peng Li
- Department of Otolaryngology, Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong, 510630, PR China
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8
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Peeleman N, Verdoodt D, Ponsaerts P, Van Rompaey V. On the Role of Fibrocytes and the Extracellular Matrix in the Physiology and Pathophysiology of the Spiral Ligament. Front Neurol 2020; 11:580639. [PMID: 33193034 PMCID: PMC7653186 DOI: 10.3389/fneur.2020.580639] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 09/10/2020] [Indexed: 12/19/2022] Open
Abstract
The spiral ligament in the cochlea has been suggested to play a significant role in the pathophysiology of different etiologies of strial hearing loss. Spiral ligament fibrocytes (SLFs), the main cell type in the lateral wall, are crucial in maintaining the endocochlear potential and regulating blood flow. SLF dysfunction can therefore cause cochlear dysfunction and thus hearing impairment. Recent studies have highlighted the role of SLFs in the immune response of the cochlea. In contrast to sensory cells in the inner ear, SLFs (more specifically type III fibrocytes) have also demonstrated the ability to regenerate after different types of trauma such as drug toxicity and noise. SLFs are responsible for producing proteins, such as collagen and cochlin, that create an adequate extracellular matrix to thrive in. Any dysfunction of SLFs or structural changes to the extracellular matrix can significantly impact hearing function. However, SLFs may prove useful in restoring hearing by their potential to regenerate cells in the spiral ligament.
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Affiliation(s)
- Noa Peeleman
- Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium
| | - Dorien Verdoodt
- Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.,Laboratory of Experimental Hematology, Vaccine and Infectious Disease Institute (Vaxinfectio), University of Antwerp, Antwerp, Belgium
| | - Peter Ponsaerts
- Laboratory of Experimental Hematology, Vaccine and Infectious Disease Institute (Vaxinfectio), University of Antwerp, Antwerp, Belgium
| | - Vincent Van Rompaey
- Department of Translational Neurosciences, Faculty of Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium.,Department of Otorhinolaryngology and Head and Neck Surgery, Antwerp University Hospital, Edegem, Belgium
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9
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Burwood GWS, Dziennis S, Wilson T, Foster S, Zhang Y, Liu G, Yang J, Elkins S, Nuttall AL. The mechanoelectrical transducer channel is not required for regulation of cochlear blood flow during loud sound exposure in mice. Sci Rep 2020; 10:9229. [PMID: 32514013 PMCID: PMC7280509 DOI: 10.1038/s41598-020-66192-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2020] [Accepted: 05/12/2020] [Indexed: 01/03/2023] Open
Abstract
The mammalian cochlea possesses unique acoustic sensitivity due to a mechanoelectrical ‘amplifier’, which requires the metabolic support of the cochlear lateral wall. Loud sound exposure sufficient to induce permanent hearing damage causes cochlear blood flow reduction, which may contribute to hearing loss. However, sensory epithelium involvement in the cochlear blood flow regulation pathway is not fully described. We hypothesize that genetic manipulation of the mechanoelectrical transducer complex will abolish sound induced cochlear blood flow regulation. We used salsa mice, a Chd23 mutant with no mechanoelectrical transduction, and deafness before p56. Using optical coherence tomography angiography, we measured the cochlear blood flow of salsa and wild-type mice in response to loud sound (120 dB SPL, 30 minutes low-pass filtered noise). An expected sound induced decrease in cochlear blood flow occurred in CBA/CaJ mice, but surprisingly the same sound protocol induced cochlear blood flow increases in salsa mice. Blood flow did not change in the contralateral ear. Disruption of the sympathetic nervous system partially abolished the observed wild-type blood flow decrease but not the salsa increase. Therefore sympathetic activation contributes to sound induced reduction of cochlear blood flow. Additionally a local, non-sensory pathway, potentially therapeutically targetable, must exist for cochlear blood flow regulation.
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Affiliation(s)
- George W S Burwood
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Suzan Dziennis
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Teresa Wilson
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Sarah Foster
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Yuan Zhang
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Gangjun Liu
- Shenzhen Bay laboratory, 5F, No.9 Duxue Rd., Nanshan District, Shenzhen, Guangdong, China
| | - Jianlong Yang
- Ningbo Institute of Materials Technology and Engineering, No. 1219 Zhongguan West Road Zhenhai District, Ningbo City, Zhejiang Province, 315201, P.R. China
| | - Sean Elkins
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA
| | - Alfred L Nuttall
- Oregon Hearing Research Center, Dept. of Otolaryngology / HNS, Oregon Health & Science University, 3250S.W. Sam Jackson Park Rd., Portland, OR, 97239, USA.
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10
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Nyberg S, Abbott NJ, Shi X, Steyger PS, Dabdoub A. Delivery of therapeutics to the inner ear: The challenge of the blood-labyrinth barrier. Sci Transl Med 2020; 11:11/482/eaao0935. [PMID: 30842313 DOI: 10.1126/scitranslmed.aao0935] [Citation(s) in RCA: 150] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 12/01/2017] [Accepted: 03/22/2018] [Indexed: 12/20/2022]
Abstract
Permanent hearing loss affects more than 5% of the world's population, yet there are no nondevice therapies that can protect or restore hearing. Delivery of therapeutics to the cochlea and vestibular system of the inner ear is complicated by their inaccessible location. Drug delivery to the inner ear via the vasculature is an attractive noninvasive strategy, yet the blood-labyrinth barrier at the luminal surface of inner ear capillaries restricts entry of most blood-borne compounds into inner ear tissues. Here, we compare the blood-labyrinth barrier to the blood-brain barrier, discuss invasive intratympanic and intracochlear drug delivery methods, and evaluate noninvasive strategies for drug delivery to the inner ear.
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Affiliation(s)
- Sophie Nyberg
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada
| | - N Joan Abbott
- Institute of Pharmaceutical Science, King's College London, London SE1 9NH, UK
| | - Xiaorui Shi
- Oregon Hearing Research Center, Department of Otolaryngology, Head & Neck Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Peter S Steyger
- Oregon Hearing Research Center, Department of Otolaryngology, Head & Neck Surgery, Oregon Health & Science University, Portland, OR 97239, USA
| | - Alain Dabdoub
- Biological Sciences, Sunnybrook Research Institute, Toronto, ON M4N 3M5, Canada. .,Department of Otolaryngology-Head & Neck Surgery, University of Toronto, Toronto, ON M5G 2C4, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON M5G 2C4, Canada
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11
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Dos Santos JC, Musso F, Mayer WP, Baptista JDS. Descriptive and topographical analysis of the labyrinthine artery in human fetuses. Anat Sci Int 2020; 95:374-380. [PMID: 32062763 DOI: 10.1007/s12565-020-00531-5] [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: 10/24/2019] [Accepted: 02/04/2020] [Indexed: 11/24/2022]
Abstract
Hearing or/and balance impairments may be caused by disorders of the labyrinthine artery (LA) and their branches. Most findings regarding the LA anatomy have been acquired through investigation of the cerebellopontine angle (CPA) in animal or adult human specimens. Eighty-eight CPAs and LAs of human fetuses were investigated using angio-techniques and microdissections. We found 15 intricate forms of distribution of LA. The LA usually originated from the extra-meatus loop in the anterior inferior cerebellar artery (AICA). The distribution of its terminal branches was 53.42% uni-arterial, 44.31% bi-arterial, and 2.27% tri-arterial systems. In the uni-arterial system, the LA described an anterior superior path to the cochlear nerve (CN) and originated its terminal branches in the gap between CN and the inferior part of the vestibular nerve. In the bi-arterial system, the anterior LA was located anterior and superior to the CN while the posterior LA appeared posterosuperior to the superior part of the vestibular nerve. In the tri-arterial system, the terminal branches originated directly from the AICA loop. Our results provide anatomical support to explain how compressions in the LA branches inside the internal acoustic meatus, as evoked by Schwannomas in the VII and VIII nerves, can lead to hearing and balance loss. The zone of the posterior vestibular nerve appeared to be a "safe area" for invasive procedures in these specimens.
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Affiliation(s)
| | - Fernando Musso
- Escola Superior de Ciencias da Santa Casa de Misericórdia de Vitoria, Vitoria, Brazil
| | - William Paganini Mayer
- Department of Medical Neuroscience at Dalhousie Medicine New Brunswick, Saint John, NB, Canada
| | - Josemberg Da Silva Baptista
- Laboratory of Applied Morphology (LEMA), Universidade Federal Do Espirito Santo, Marechal Campos Avenue, 1468, Maruipe, Vitoria, Espirito Santo, 29043-900, Brazil.
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12
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Furness DN. Forgotten Fibrocytes: A Neglected, Supporting Cell Type of the Cochlea With the Potential to be an Alternative Therapeutic Target in Hearing Loss. Front Cell Neurosci 2019; 13:532. [PMID: 31866825 PMCID: PMC6908467 DOI: 10.3389/fncel.2019.00532] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/15/2019] [Indexed: 12/31/2022] Open
Abstract
Cochlear fibrocytes are a homeostatic supporting cell type embedded in the vascularized extracellular matrix of the spiral ligament, within the lateral wall. Here, they participate in the connective tissue syncytium that enables potassium recirculation into the scala media to take place and ensures development of the endolymphatic potential that helps drive current into hair cells during acoustic stimulation. They have also been implicated in inflammatory responses in the cochlea. Some fibrocytes interact closely with the capillaries of the vasculature in a way which suggests potential involvement, together with the stria vascularis, also in the blood-labyrinth barrier. Several lines of evidence suggests that pathology of the fibrocytes, along with other degenerative changes in this region, contribute to metabolic hearing loss (MHL) during aging that is becoming recognized as distinct from, and potentially a precursor for, sensorineural hearing loss (SNHL). This pathology may underlie a significant proportion of cases of presbycusis. Some evidence points also to an association between fibrocyte degeneration and Ménière’s disease (MD). Fibrocytes are mesenchymal; this characteristic, and their location, make them amenable to potential cell therapy in the form of cell replacement or genetic modification to arrest the process of degeneration that leads to MHL. This review explores the properties and roles of this neglected cell type and suggests potential therapeutic approaches, such as cell transplantation or genetic engineering of fibrocytes, which could be used to prevent this form of presbycusis or provide a therapeutic avenue for MD.
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Affiliation(s)
- David N Furness
- School of Life Sciences, Keele University, Keele, United Kingdom
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13
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Ishiyama G, Wester J, Lopez IA, Beltran-Parrazal L, Ishiyama A. Oxidative Stress in the Blood Labyrinthine Barrier in the Macula Utricle of Meniere's Disease Patients. Front Physiol 2018; 9:1068. [PMID: 30233382 PMCID: PMC6129601 DOI: 10.3389/fphys.2018.01068] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Accepted: 07/17/2018] [Indexed: 12/13/2022] Open
Abstract
The blood labyrinthine barrier (BLB) is critical in the maintenance of inner ear ionic and fluid homeostasis. Recent studies using imaging and histopathology demonstrate loss of integrity of the BLB in the affected inner ear of Meniere's disease (MD) patients. We hypothesized that oxidative stress is involved in the pathogenesis of BLB degeneration, and to date there are no studies of oxidative stress proteins in the human BLB. We investigated the ultrastructural and immunohistochemical changes of the BLB in the vestibular endorgan, the macula utricle, from patients with MD (n = 10), acoustic neuroma (AN) (n = 6) and normative autopsy specimens (n = 3) with no inner ear disease. Each subject had a well-documented clinical history and audiovestibular testing. Utricular maculae were studied using light and transmission electron microscopy and double labeling immunofluorescence. Vascular endothelial cells (VECs) were identified using isolectin B4 (IB4) and glucose-transporter-1 (GLUT-1). Pericytes were identified using alpha smooth muscle actin (αSMA) and phalloidin. IB4 staining of VECS was consistently seen in both AN and normative. In contrast, IB4 was nearly undetectable in all MD specimens, consistent with the significant VEC damage confirmed on transmission electron microscopy. GLUT-1 was present in MD, AN, and normative. αSMA and phalloidin were expressed consistently in the BLB pericytes in normative, AN specimen, and Meniere's specimens. Endothelial nitric oxide synthase (eNOS), inducible nitric oxide synthase (iNOS), and nitrotyrosine were used as markers of oxidative stress. The VECs of the BLB in Meniere's had significantly higher levels of expression of iNOS and nitrotyrosine compared with normative and AN specimen. eNOS-IF staining showed similar patterns in normative and Meniere's specimens. Microarray-based gene expression profiling confirmed upregulation of iNOS mRNA from the macula utricle of Meniere's patients compared with AN. Nitrotyrosine, a marker recognized as a hallmark of inflammation, especially when seen in association with an upregulation of iNOS, was detected in the epithelial and stromal cells in addition to VECs in MD. Immunohistochemical and ultrastructural degenerative changes of the VEC suggest that these cells are the primary targets of oxidative stress, and pericyte pathology including degeneration and migration, likely also plays a role in the loss of integrity of the BLB and triggering of inflammatory pathways in MD. These studies advance our scientific understanding of oxidative stress in the human inner ear BLB and otopathology.
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Affiliation(s)
- Gail Ishiyama
- Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Jacob Wester
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Ivan A. Lopez
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
| | - Luis Beltran-Parrazal
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
- Centro de Investigaciones Cerebrales, Universidad Veracruzana, Xalapa, Mexico
| | - Akira Ishiyama
- Department of Head and Neck Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
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Mei X, Atturo F, Wadin K, Larsson S, Agrawal S, Ladak HM, Li H, Rask-Andersen H. Human inner ear blood supply revisited: the Uppsala collection of temporal bone-an international resource of education and collaboration. Ups J Med Sci 2018; 123:131-142. [PMID: 30204028 PMCID: PMC6198224 DOI: 10.1080/03009734.2018.1492654] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND The Uppsala collection of human temporal bones and molds is a unique resource for education and international research collaboration. Micro-computerized tomography (micro-CT) and synchrotron imaging are used to investigate the complex anatomy of the inner ear. Impaired microcirculation is etiologically linked to various inner ear disorders, and recent developments in inner ear surgery promote examination of the vascular system. Here, for the first time, we present three-dimensional (3D) data from investigations of the major vascular pathways and corresponding bone channels. METHODS We used the archival Uppsala collection of temporal bones and molds consisting of 324 inner ear casts and 113 macerated temporal bones. Micro-CT was used to investigate vascular bone channels, and 26 fresh human temporal bones underwent synchrotron radiation phase contrast imaging (SR-PCI). Data were processed by volume-rendering software to create 3D reconstructions allowing orthogonal sectioning, cropping, and soft tissue analyses. RESULTS Micro-CT with 3D rendering was superior in reproducing the anatomy of the vascular bone channels, while SR-PCI replicated soft tissues. Arterial bone channels were traced from scala vestibuli (SV) arterioles to the fundus, cochlea, and vestibular apparatus. Drainage routes along the aqueducts were examined. CONCLUSION Human inner ear vessels are difficult to study due to the adjoining hard bone. Micro-CT and SR-PCI with 3D reconstructions revealed large portions of the micro-vascular system in un-decalcified specimens. The results increase our understanding of the organization of the vascular system in humans and how altered microcirculation may relate to inner ear disorders. The findings may also have surgical implications.
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Affiliation(s)
- Xueshuang Mei
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
- Department of Otolaryngology, Peking University Shenzhen Hospital, P.R. China
| | - Francesca Atturo
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| | - Karin Wadin
- Department of Diagnostic Radiology, Uppsala University Hospital, Uppsala, Sweden
| | - Sune Larsson
- Department of Surgical Sciences, Section of Orthopedics, Uppsala University Hospital, Sweden
| | - Sumit Agrawal
- Department of Otolaryngology-Head and Neck Surgery, Western University, Canada
| | - Hanif M. Ladak
- Department of Otolaryngology-Head and Neck Surgery, Western University, Canada
- Department of Medical Biophysics and Department of Electrical and Computer Engineering, Western University, Canada
| | - Hao Li
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
| | - Helge Rask-Andersen
- Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, Uppsala, Sweden
- CONTACT Helge Rask-Andersen Department of Surgical Sciences, Section of Otolaryngology, Uppsala University Hospital, SE-751 85, Uppsala, Sweden
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Hou Z, Wang X, Cai J, Zhang J, Hassan A, Auer M, Shi X. Platelet-Derived Growth Factor Subunit B Signaling Promotes Pericyte Migration in Response to Loud Sound in the Cochlear Stria Vascularis. J Assoc Res Otolaryngol 2018; 19:363-379. [PMID: 29869048 PMCID: PMC6081892 DOI: 10.1007/s10162-018-0670-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 04/19/2018] [Indexed: 12/20/2022] Open
Abstract
Normal blood supply to the cochlea is critical for hearing. Noise damages auditory sensory cells and has a marked effect on the microvasculature in the cochlear lateral wall. Pericytes in the stria vascularis (strial pericytes) are particularly vulnerable and sensitive to acoustic trauma. Exposure of NG2DsRedBAC transgenic mice (6-8 weeks old) to wide-band noise at a level of 120 dB for 3 h per day for 2 consecutive days produced a significant hearing threshold shift and caused pericytes to protrude and migrate from their normal endothelial attachment sites. The pericyte migration was associated with increased expression of platelet-derived growth factor beta (PDGF-BB). Blockade of PDGF-BB signaling with either imatinib, a potent PDGF-BB receptor (PDGFR) inhibitor, or APB5, a specific PDGFRβ blocker, significantly attenuated the pericyte migration from strial vessel walls. The PDGF-BB-mediated strial pericyte migration was further confirmed in an in vitro cell migration assay, as well as in an in vivo live animal model used in conjunction with confocal fluorescence microscopy. Pericyte migration took one of two different forms, here denoted protrusion and detachment. The protrusion is characterized by pericytes with a prominent triangular shape, or pericytes extending fine strands to neighboring capillaries. The detachment is characterized by pericyte detachment and movement away from vessels. We also found the sites of pericyte migration highly associated with regions of vascular leakage. In particular, under transmission electron microscopy (TEM), multiple vesicles at the sites of endothelial cells with loosely attached pericytes were observed. These data show that cochlear pericytes are markedly affected by acoustic trauma, causing them to display abnormal morphology. The effect of loud sound on pericytes is mediated by upregulation of PDGF-BB. Normal functioning pericytes are required for vascular stability.
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Affiliation(s)
- Zhiqiang Hou
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Xiaohan Wang
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Jing Cai
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Jinhui Zhang
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Ahmed Hassan
- Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Manfred Auer
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Xiaorui Shi
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
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Tumor Necrosis Factor-induced Decrease of Cochlear Blood Flow Can Be Reversed by Etanercept or JTE-013. Otol Neurotol 2017; 37:e203-8. [PMID: 27295443 DOI: 10.1097/mao.0000000000001095] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
HYPOTHESIS This study aimed to quantify the effects of tumor necrosis factor (TNF) inhibitor Etanercept and sphingosine-1-phosphate receptor 2 antagonist JTE-013 on cochlear blood flow in guinea pigs after TNF-induced decrease. BACKGROUND Sudden sensorineural hearing loss is a common cause for disability and reduced quality of life. Good understanding of the pathophysiology and strong evidence-based therapy concepts are still missing. In various inner ear disorders, inflammation and impairment of cochlear blood flow (CBF) have been considered factors in the pathophysiology. A central mediator of inflammation and microcirculation in the cochlea is TNF. S1P acts downstream in one TNF pathway. METHODS Cochlea lateral wall vessels were exposed surgically and assessed by intravital microscopy in guinea pigs in vivo. Twenty-eight animals were randomly distributed into four groups of seven each. Exposed vessels were superfused by TNF (5.0 ng/ml) and afterward repeatedly either by Etanercept (1.0 μg/ml), JTE-013 (10 μmol/L), or vehicle (0.9 % NaCl solution or ethanol: phosphate-buffered saline buffer, respectively). RESULTS After decreasing CBF with TNF (p <0.001, two-way RM ANOVA), both treatments reversed CBF, compared with vehicle (p <0.001, two-way RM ANOVA). The comparison of the vehicle groups showed no difference (p = 0.969, two-way RM ANOVA), while there was also no difference between the treatment groups (p = 0.850, two-way RM ANOVA). CONCLUSION Both Etanercept and JTE-013 reverse the decreasing effect of TNF on cochlear blood flow and, therefore, TNF and the S1P-signalling pathway might be targets for treatment of microcirculation-related hearing loss.
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17
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Fetoni AR, Eramo SLM, Paciello F, Rolesi R, Samengo D, Paludetti G, Troiani D, Pani G. The redox protein p66(shc) mediates cochlear vascular dysfunction and transient noise-induced hearing loss. Sci Rep 2016; 6:25450. [PMID: 27157635 PMCID: PMC4860599 DOI: 10.1038/srep25450] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Accepted: 04/13/2016] [Indexed: 12/20/2022] Open
Abstract
p66shc, a member of the ShcA protein family, is essential for cellular response to oxidative stress, and elicits the formation of mitochondrial Reactive Oxygen Species (ROS), thus promoting vasomotor dysfunction and inflammation. Accordingly, mice lacking the p66 isoform display increased resistance to oxidative tissue damage and to cardiovascular disorders. Oxidative stress also contributes to noise-induced hearing loss (NIHL); we found that p66shc expression and serine phosphorylation were induced following noise exposure in the rat cochlea, together with markers of oxidative stress, inflammation and ischemia as indicated by the levels of the hypoxic inducible factor (HIF) and the vascular endothelial growth factor (VEGF) in the highly vascularised cochlear lateral region and spiral ganglion. Importantly, p66shc knock-out (p66 KO) 126 SvEv adult mice were less vulnerable to acoustic trauma with respect to wild type controls, as shown by preserved auditory function and by remarkably lower levels of oxidative stress and ischemia markers. Of note, decline of auditory function observed in 12 month old WT controls was markedly attenuated in p66KO mice consistent with delayed inner ear senescence. Collectively, we have identified a pivotal role for p66shc -induced vascular dysfunction in a common pathogenic cascade shared by noise-induced and age-related hearing loss.
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Affiliation(s)
- A R Fetoni
- Department of Head and Neck Surgery, Università Cattolica School of Medicine, Rome, Italy
| | - S L M Eramo
- Institute of Human Physiology, Università Cattolica School of Medicine, Rome, Italy
| | - F Paciello
- Department of Head and Neck Surgery, Università Cattolica School of Medicine, Rome, Italy
| | - R Rolesi
- Department of Head and Neck Surgery, Università Cattolica School of Medicine, Rome, Italy
| | - D Samengo
- Institute of General Pathology, Università Cattolica School of Medicine, Rome, Italy
| | - G Paludetti
- Department of Head and Neck Surgery, Università Cattolica School of Medicine, Rome, Italy
| | - D Troiani
- Institute of Human Physiology, Università Cattolica School of Medicine, Rome, Italy
| | - G Pani
- Institute of General Pathology, Università Cattolica School of Medicine, Rome, Italy
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18
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Alvarado JC, Fuentes-Santamaría V, Gabaldón-Ull MC, Jareño-Flores T, Miller JM, Juiz JM. Noise-Induced "Toughening" Effect in Wistar Rats: Enhanced Auditory Brainstem Responses Are Related to Calretinin and Nitric Oxide Synthase Upregulation. Front Neuroanat 2016; 10:19. [PMID: 27065815 PMCID: PMC4815363 DOI: 10.3389/fnana.2016.00019] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2015] [Accepted: 02/15/2016] [Indexed: 01/07/2023] Open
Abstract
An appropriate conditioning noise exposure may reduce a subsequent noise-induced threshold shift. Although this "toughening" effect helps to protect the auditory system from a subsequent traumatic noise exposure, the mechanisms that regulate this protective process are not fully understood yet. Accordingly, the goal of the present study was to characterize physiological processes associated with "toughening" and to determine their relationship to metabolic changes in the cochlea and cochlear nucleus (CN). Auditory brainstem responses (ABR) were evaluated in Wistar rats before and after exposures to a sound conditioning protocol consisting of a broad-band white noise of 118 dB SPL for 1 h every 72 h, four times. After the last ABR evaluation, animals were perfused and their cochleae and brains removed and processed for the activity markers calretinin (CR) and neuronal nitric oxide synthase (nNOS). Toughening was demonstrated by a progressively faster recovery of the threshold shift, as well as wave amplitudes and latencies over time. Immunostaining revealed an increase in CR and nNOS levels in the spiral ganglion, spiral ligament, and CN in noise-conditioned rats. Overall, these results suggest that the protective mechanisms of the auditory toughening effect initiate in the cochlea and extend to the central auditory system. Such phenomenon might be in part related to an interplay between CR and nitric oxide signaling pathways, and involve an increased cytosolic calcium buffering capacity induced by the noise conditioning protocol.
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Affiliation(s)
- Juan C Alvarado
- Instituto de Investigación en Discapacidades NeurológicasAlbacete, Spain; Facultad de Medicina, Universidad de Castilla-La ManchaAlbacete, Spain
| | - Verónica Fuentes-Santamaría
- Instituto de Investigación en Discapacidades NeurológicasAlbacete, Spain; Facultad de Medicina, Universidad de Castilla-La ManchaAlbacete, Spain
| | - María C Gabaldón-Ull
- Instituto de Investigación en Discapacidades NeurológicasAlbacete, Spain; Facultad de Medicina, Universidad de Castilla-La ManchaAlbacete, Spain
| | - Tania Jareño-Flores
- Grupo de Neurobiología de la Audición, Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid Madrid, Spain
| | - Josef M Miller
- Center for Hearing and Communication Research and Department of Clinical Neuroscience, Karolinska InstitutetStockholm, Sweden; Kresge Hearing Research Institute, University of MichiganAnn Arbor, MI, USA
| | - José M Juiz
- Instituto de Investigación en Discapacidades NeurológicasAlbacete, Spain; Facultad de Medicina, Universidad de Castilla-La ManchaAlbacete, Spain
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19
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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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Two-photon microscopy allows imaging and characterization of cochlear microvasculature in vivo. BIOMED RESEARCH INTERNATIONAL 2015; 2015:154272. [PMID: 25883941 PMCID: PMC4390612 DOI: 10.1155/2015/154272] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 02/26/2015] [Accepted: 03/02/2015] [Indexed: 11/18/2022]
Abstract
Impairment of cochlear blood flow has been discussed as factor in the pathophysiology of various inner ear disorders. However, the microscopic study of cochlear microcirculation is limited due to small scale and anatomical constraints. Here, two-photon fluorescence microscopy is applied to visualize cochlear microvessels. Guinea pigs were injected with Fluorescein isothiocyanate- or Texas red-dextrane as plasma marker. Intravital microscopy was performed in four animals and explanted cochleae from four animals were studied. The vascular architecture of the cochlea was visualized up to a depth of 90.0±22.7 μm. Imaging yielded a mean contrast-to-noise ratio (CNR) of 3.3±1.7. Mean diameter in vivo was 16.5±6.0 μm for arterioles and 8.0±2.4 μm for capillaries. In explanted cochleae, the diameter of radiating arterioles and capillaries was measured with 12.2±1.6 μm and 6.6±1.0 μm, respectively. The difference between capillaries and arterioles was statistically significant in both experimental setups (P<0.001 and P=0.022, two-way ANOVA). Measured vessel diameters in vivo and ex vivo were in agreement with published data. We conclude that two-photon fluorescence microscopy allows the investigation of cochlear microvessels and is potentially a valuable tool for inner ear research.
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21
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Li B, Su K, Yang G, Feng Y, Xia L, Yin S. Assessment of the potential ototoxicity of high-dose celecoxib, a selective cyclooxygenase-2 inhibitor, in rats. Otolaryngol Head Neck Surg 2015; 152:1108-12. [PMID: 25779473 DOI: 10.1177/0194599815573702] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 01/29/2015] [Indexed: 12/12/2022]
Abstract
OBJECTIVE To evaluate the potential ototoxicity of high-dose celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor. STUDY DESIGN Prospective animal study. SETTING Laboratory. METHODS Twenty adult male Sprague Dawley rats were divided into 2 groups for hearing and tinnitus tests, respectively. The auditory brain-stem response (ABR) and the gap prepulse inhibition of acoustic startle (GPIAS) were used as indicators of hearing loss and tinnitus, respectively, and were measured before and at 2, 4, 6, 8, 12, 24, and 48 hours after administration of celecoxib (2 g/kg) via gavage. RESULTS ABR threshold and wave III latencies did not increase significantly at any frequency following celecoxib administration, at any time point (P > .05). GPIAS remained below 30% after celecoxib, from a baseline of 20.03% ± 3.62%; no change was significant. CONCLUSION High-dose celecoxib (2 g/kg), a selective COX-2 inhibitor, did not cause hearing loss or tinnitus in Sprague Dawley rats within 48 hours of administration. Further studies are needed to explore the roles played by COX-related mechanisms when nonselective COX inhibitors induce ototoxicity.
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Affiliation(s)
- Bei Li
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Kaiming Su
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Guang Yang
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Yanmei Feng
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Li Xia
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
| | - Shankai Yin
- Department of Otolaryngology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Otolaryngology Institute of Shanghai Jiao Tong University, Shanghai, China
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Fujioka M, Okano H, Ogawa K. Inflammatory and immune responses in the cochlea: potential therapeutic targets for sensorineural hearing loss. Front Pharmacol 2014; 5:287. [PMID: 25566079 PMCID: PMC4274906 DOI: 10.3389/fphar.2014.00287] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Accepted: 12/10/2014] [Indexed: 12/20/2022] Open
Abstract
The inner ear was previously assumed to be an “immune-privileged” organ due to the existence of its tight junction-based blood-labyrinth barrier. However, studies performed during the past decade revealed that the mesenchymal region of the cochlea, including its lateral wall, is a common site of inflammation. Neutrophils do not enter this region, which is consistent with the old dogma; however, bone marrow-derived resident macrophages are always present in the spiral ligament of the lateral wall and are activated in response to various types of insults, including noise exposure, ischemia, mitochondrial damage, and surgical stress. Recent studies have also revealed another type of immune cell, called perivascular melanocyte-like macrophages (PVM/Ms), in the stria vascularis. These dedicated antigen-presenting cells also control vascular contraction and permeability. This review discusses a series of reports regarding inflammatory/immune cells in the cochlear lateral wall, the pathways involved in cochlear damage and their potential as therapeutic targets.
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Affiliation(s)
- Masato Fujioka
- Department of Otorhinolaryngology, Head and Neck Surgery, School of Medicine, Keio University Tokyo, Japan
| | - Hideyuki Okano
- Department of Physiology, School of Medicine, Keio University Tokyo, Japan
| | - Kaoru Ogawa
- Department of Otorhinolaryngology, Head and Neck Surgery, School of Medicine, Keio University Tokyo, Japan
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Andrews CD, Payne JF, Rise ML. Identification of a gene set to evaluate the potential effects of loud sounds from seismic surveys on the ears of fishes: a study with Salmo salar. JOURNAL OF FISH BIOLOGY 2014; 84:1793-1819. [PMID: 24814183 PMCID: PMC4277336 DOI: 10.1111/jfb.12398] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 03/05/2014] [Indexed: 06/03/2023]
Abstract
Functional genomic studies were carried out on the inner ear of Atlantic salmon Salmo salar following exposure to a seismic airgun. Microarray analyses revealed 79 unique transcripts (passing background threshold), with 42 reproducibly up-regulated and 37 reproducibly down-regulated in exposed v. control fish. Regarding the potential effects on cellular energetics and cellular respiration, altered transcripts included those with roles in oxygen transport, the glycolytic pathway, the Krebs cycle and the electron transport chain. Of these, a number of transcripts encoding haemoglobins that are important in oxygen transport were up-regulated and among the most highly expressed. Up-regulation of transcripts encoding nicotinamide riboside kinase 2, which is also important in energy production and linked to nerve cell damage, points to evidence of neuronal damage in the ear following noise exposure. Transcripts related to protein modification or degradation also indicated potential damaging effects of sound on ear tissues. Notable in this regard were transcripts associated with the proteasome-ubiquitin pathway, which is involved in protein degradation, with the transcript encoding ubiquitin family domain-containing protein 1 displaying the highest response to exposure. The differential expression of transcripts observed for some immune responses could potentially be linked to the rupture of cell membranes. Meanwhile, the altered expression of transcripts for cytoskeletal proteins that contribute to the structural integrity of the inner ear could point to repair or regeneration of ear tissues including auditory hair cells. Regarding potential effects on hormones and vitamins, the protein carrier for thyroxine and retinol (vitamin A), namely transthyretin, was altered at the transcript expression level and it has been suggested from studies in mammalian systems that retinoic acid may play a role in the regeneration of damaged hair cells. The microarray experiment identified the transcript encoding growth hormone I as up-regulated by loud sound, supporting previous evidence linking growth hormone to hair cell regeneration in fishes. Quantitative (q) reverse transcription (RT) polymerase chain reaction (qRT-PCR) analyses confirmed dysregulation of some microarray-identified transcripts and in some cases revealed a high level of biological variability in the exposed group. These results support the potential utility of molecular biomarkers to evaluate the effect of seismic surveys on fishes with studies on the ears being placed in a priority category for development of exposure-response relationships. Knowledge of such relationships is necessary for addressing the question of potential size of injury zones.
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Affiliation(s)
- C D Andrews
- Fisheries and Oceans Canada, Northwest Atlantic Fisheries Centre, 80 East White Hills Rd, St John's, NL, A1C 5X1, Canada
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24
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Shi X, Zhang F, Urdang Z, Dai M, Neng L, Zhang J, Chen S, Ramamoorthy S, Nuttall AL. Thin and open vessel windows for intra-vital fluorescence imaging of murine cochlear blood flow. Hear Res 2014; 313:38-46. [PMID: 24780131 DOI: 10.1016/j.heares.2014.04.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2013] [Revised: 03/07/2014] [Accepted: 04/15/2014] [Indexed: 12/20/2022]
Abstract
Normal microvessel structure and function in the cochlea is essential for maintaining the ionic and metabolic homeostasis required for hearing function. Abnormal cochlear microcirculation has long been considered an etiologic factor in hearing disorders. A better understanding of cochlear blood flow (CoBF) will enable more effective amelioration of hearing disorders that result from aberrant blood flow. However, establishing the direct relationship between CoBF and other cellular events in the lateral wall and response to physio-pathological stress remains a challenge due to the lack of feasible interrogation methods and difficulty in accessing the inner ear. Here we report on new methods for studying the CoBF in a mouse model using a thin or open vessel-window in combination with fluorescence intra-vital microscopy (IVM). An open vessel-window enables investigation of vascular cell biology and blood flow permeability, including pericyte (PC) contractility, bone marrow cell migration, and endothelial barrier leakage, in wild type and fluorescent protein-labeled transgenic mouse models with high spatial and temporal resolution. Alternatively, the thin vessel-window method minimizes disruption of the homeostatic balance in the lateral wall and enables study CoBF under relatively intact physiological conditions. A thin vessel-window method can also be used for time-based studies of physiological and pathological processes. Although the small size of the mouse cochlea makes surgery difficult, the methods are sufficiently developed for studying the structural and functional changes in CoBF under normal and pathological conditions.
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Affiliation(s)
- Xiaorui Shi
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA.
| | - Fei Zhang
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Zachary Urdang
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Min Dai
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Lingling Neng
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Jinhui Zhang
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Songlin Chen
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Sripriya Ramamoorthy
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Alfred L Nuttall
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, Portland, OR, USA
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25
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Goulopoulou S, Webb RC. Symphony of vascular contraction: how smooth muscle cells lose harmony to signal increased vascular resistance in hypertension. Hypertension 2014; 63:e33-9. [PMID: 24470463 DOI: 10.1161/hypertensionaha.113.02444] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Styliani Goulopoulou
- Department of Physiology, Georgia Regents University, 1120 Fifteenth St, Augusta, GA 30912.
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26
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Ihler F, Sharaf K, Bertlich M, Strieth S, Reichel CA, Berghaus A, Canis M. Etanercept Prevents Decrease of Cochlear Blood Flow Dose-Dependently Caused by Tumor Necrosis Factor Alpha. Ann Otol Rhinol Laryngol 2013; 122:468-73. [DOI: 10.1177/000348941312200711] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Objectives: Tumor necrosis factor alpha (TNF-alpha) is a mediator of inflammation and microcirculation in the cochlea. This study aimed to quantify the effect of a local increase of TNF-alpha and study the effect of its interaction with etanercept on cochlear microcirculation. Methods: Cochlear lateral wall vessels were exposed surgically and assessed by intravital microscopy in guinea pigs in vivo. First, 24 animals were randomly distributed into 4 groups of 6 each. Exposed vessels were superfused repeatedly either with 1 of 3 different concentrations of TNF-alpha (5.0, 0.5, and 0.05 ng/mL) or with placebo (0.9% saline solution). Second, 12 animals were randomly distributed into 2 groups of 6 each. Vessels were pretreated with etanercept (1.0 μg/mL) or placebo (0.9% saline solution), and then treated by repeated superfusion with TNF-alpha (5.0 ng/mL). Results: TNF-alpha was shown to be effective in decreasing cochlear blood flow at a dose of 5.0 ng/mL (p < 0.01, analysis of variance on ranks). Lower concentrations or placebo treatment did not lead to significant changes. After pretreatment with etanercept, TNF-alpha at a dose of 5.0 ng/mL no longer led to a change in cochlear blood flow. Conclusions: The decreasing effect that TNF-alpha has on cochlear blood flow is dose-dependent. Etanercept abrogates this effect.
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Neng L, Zhang F, Kachelmeier A, Shi X. Endothelial cell, pericyte, and perivascular resident macrophage-type melanocyte interactions regulate cochlear intrastrial fluid-blood barrier permeability. J Assoc Res Otolaryngol 2012; 14:175-85. [PMID: 23247886 PMCID: PMC3660918 DOI: 10.1007/s10162-012-0365-9] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2012] [Accepted: 11/27/2012] [Indexed: 12/22/2022] Open
Abstract
The integrity of the fluid-blood barrier in the stria vascularis is critical for maintaining inner ear homeostasis, especially for sustaining the endocochlear potential, an essential driving force for hearing function. However, the mechanisms that control intrastrial fluid-blood barrier permeability remain largely unknown. At the cellular level, the intrastrial fluid-blood barrier comprises cochlear microvascular endothelial cells connected to each other by tight junctions (TJs), an underlying basement membrane, and a second line of support consisting of cochlear pericytes and perivascular resident macrophage-type melanocytes. In this study, we use a newly established primary cell culture-based in vitro model to show that endothelial cells, pericytes, and perivascular resident macrophage-type melanocytes interact to control intrastrial fluid-blood barrier permeability. When the endothelial cell monolayer was treated with pericyte--or perivascular resident macrophage-type melanocyte--conditioned media, the permeability of the endothelial cell monolayer was significantly reduced relative to an untreated endothelial cell monolayer. Further study has shown the pericytes and perivascular resident macrophage-type melanocytes to regulate TJ expression in the endothelial cell monolayer. The new cell culture-based in vitro model offers a unique opportunity to obtain information on the organ-specific characteristics of the cochlear blood/tissue barrier. Our finding demonstrates the importance of signaling among pericytes, endothelial cells, and perivascular resident macrophage-type melanocytes to the integrity of the intrastrial fluid-blood barrier.
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Affiliation(s)
- Lingling Neng
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239-3098, USA.
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28
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Abstract
The inner ear vasculature is responsible for maintenance of the blood-labyrinth barrier, transport of systemic hormones for ion homeostasis, and supplying nutrients for metabolic functions. Unfortunately, these blood vessels also expose the ear to circulating inflammatory factors resulting from systemic diseases. Thus, while the inner ear blood vessels are critical for normal function, they also are facilitating pathologic mechanisms that result in hearing and vestibular dysfunction. In spite of these numerous critical roles of inner ear vasculature, little is known of its normal homeostatic functions and how these are compromised in disease. The objective of this review is to discuss the current concepts of vascular biology, how blood vessels naturally respond to circulating inflammatory factors, and how such mechanisms of vascular pathophysiology may cause hearing loss.
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Affiliation(s)
- Dennis R Trune
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery Oregon Health & Science University, Portland, OR 97239 USA
| | - Anh Nguyen-Huynh
- Oregon Hearing Research Center, Department of Otolaryngology/Head & Neck Surgery Oregon Health & Science University, Portland, OR 97239 USA
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29
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Heinrich UR, Helling K. Nitric oxide--a versatile key player in cochlear function and hearing disorders. Nitric Oxide 2012; 27:106-16. [PMID: 22659013 DOI: 10.1016/j.niox.2012.05.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Revised: 05/10/2012] [Accepted: 05/24/2012] [Indexed: 12/13/2022]
Abstract
Nitric oxide (NO) is a signaling molecule which can generally be formed by three nitric oxide synthases (NOS). Two of them, the endothelial nitric oxide synthase (eNOS) and the neural nitric oxide synthase (nNOS), are calcium/calmodulin-dependent and constitutively expressed in many cell types. Both isoforms are found in the vertebrate cochlea. The inducible nitric oxide synthase (iNOS) is independent of calcium and normally not detectable in the un-stimulated cochlea. In the inner ear, as in other tissues, NO was identified as a multitask molecule involved in various processes such as neurotransmission and neuromodulation. In addition, increasing evidence demonstrates that the NO-dependent processes of cell protection or, alternatively, cell destruction seem to depend, among other things, on changes in the local cochlear NO-concentration. These alterations can occur at the cellular level or within a distinct cell population both leading to an NO-imbalance within the hearing organ. This dysfunction can result in hearing loss or even in deafness. In cases of cochlear malfunction, regulatory systems such as the gap junction system, the blood vessels or the synaptic region might be affected temporarily or permanently by an altered NO-level. This review discusses potential cellular mechanisms how NO might contribute to different forms of hearing disorders. Approaches of NO-reduction are evaluated and the transfer of results obtained from experimental animal models to human medication is discussed.
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Affiliation(s)
- Ulf-Rüdiger Heinrich
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center of The Johannes Gutenberg-University Mainz, Germany.
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30
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Liu X, Li C, Falck JR, Harder DR, Koehler RC. Relative contribution of cyclooxygenases, epoxyeicosatrienoic acids, and pH to the cerebral blood flow response to vibrissal stimulation. Am J Physiol Heart Circ Physiol 2011; 302:H1075-85. [PMID: 22198176 DOI: 10.1152/ajpheart.00794.2011] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The increase in cerebral blood flow (CBF) during neuronal activation can be only partially attenuated by individual inhibitors of epoxyeicosatrienoic acids (EETs), cyclooxgenase-2, group I metabotropic glutamate receptors (mGluR), neuronal nitric oxide synthase (nNOS), N-methyl-D-aspartate receptors, or adenosine receptors. Some studies that used a high concentration (500 μM) of the cyclooxygenase-1 inhibitor SC-560 have implicated cyclooxygenase-1 in gliovascular coupling in certain model systems in the mouse. Here, we found that increasing the concentration of SC-560 from 25 μM to 500 μM over whisker barrel cortex in anesthetized rats attenuated the CBF response to whisker stimulation. However, exogenous prostaglandin E(2) restored the response in the presence of 500 μM SC-560 but not in the presence of a cyclooxygenase-2 inhibitor, thereby suggesting a limited permissive role for cyclooxygenase-1. Furthermore, inhibition of the CBF response to whisker stimulation by an EET antagonist persisted in the presence of SC-560 or a cyclooxygenase-2 inhibitor, thereby indicating that the EET-dependent component of vasodilation did not require cyclooxygenase-1 or -2 activity. With combined inhibition of cyclooxygenase-1 and -2, mGluR, nNOS, EETs, N-methyl-D-aspartate receptors, and adenosine 2B receptors, the CBF response was reduced by 60%. We postulated that the inability to completely block the CBF response was due to tissue acidosis resulting from impaired clearance of metabolically produced CO2. We tested this idea by increasing the concentration of superfused bicarbonate from 25 to 60 mM and found a markedly reduced CBF response to hypercapnia. However, increasing bicarbonate had no effect on the initial or steady-state CBF response to whisker stimulation with or without combined inhibition. We conclude that the residual response after inhibition of several known vasodilatory mechanisms is not due to acidosis arising from impaired CO2 clearance when the CBF response is reduced. An unidentified mechanism apparently is responsible for the rapid, residual cortical vasodilation during vibrissal stimulation.
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Affiliation(s)
- Xiaoguang Liu
- Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, Baltimore, MD 21287-4961, USA.
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31
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Abstract
Normal blood supply to the cochlea is critically important for establishing the endocochlear potential and sustaining production of endolymph. Abnormal cochlear microcirculation has long been considered an etiologic factor in noise-induced hearing loss, age-related hearing loss (presbycusis), sudden hearing loss or vestibular function, and Meniere's disease. Knowledge of the mechanisms underlying the pathophysiology of cochlear microcirculation is of fundamental clinical importance. A better understanding of cochlear blood flow (CoBF) will enable more effective management of hearing disorders resulting from aberrant blood flow. This review focuses on recent discoveries and findings related to the physiopathology of the cochlear microvasculature.
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Affiliation(s)
- Xiaorui Shi
- Oregon Hearing Research Center (NRC04), Department of Otolaryngology/Head & Neck Surgery, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR 97239, USA.
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Dai M, Yang Y, Shi X. Lactate dilates cochlear capillaries via type V fibrocyte-vessel coupling signaled by nNOS. Am J Physiol Heart Circ Physiol 2011; 301:H1248-54. [PMID: 21856924 DOI: 10.1152/ajpheart.00315.2011] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transduction of sound in the inner ear demands tight control over delivery of oxygen and glucose. However, the mechanisms underlying the control of regional blood flow are not yet fully understood. In this study, we report a novel local control mechanism that regulates cochlear blood flow to the stria vascularis, a high energy-consuming region of the inner ear. We found that extracellular lactate had a vasodilatory effect on the capillaries of the spiral ligament under both in vitro and in vivo conditions. The lactate, acting through monocarboxylate transporter 1 (MCT1), initiated neuronal nitric oxide (NO) synthase (nNOS) and catalyzed production of NO for the vasodilation. Blocking MCT1 with the MCT blocker, α-cyano-4-hydroxycinnamate (CHC), or a suppressing NO production with either the nonspecific inhibitor of NO synthase, N(G)-nitro-L-arginine methyl ester (L-NAME), or either of two selective nNOS inhibitors, 3-bromo-7-nitroindazole or (4S)-N-(4-amino-5[aminoethyl]aminopentyl)-N'-nitroguanidine (TFA), totally abolished the lactate-induced vasodilation. Pretreatment with the selective endothelial NO synthase inhibitor, L-N(5)-(1-iminoethyl)ornithine (L-NIO), eliminated the inhibition of lactate-induced vessel dilation. With immunohistochemical labeling, we found the expression of MCT1 and nNOS in capillary-coupled type V fibrocytes. The data suggest that type V fibrocytes are the source of the lactate-induced NO. Cochlear microvessel tone, regulated by lactate, is mediated by an NO-signaled coupling of fibrocytes and capillaries.
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Affiliation(s)
- Min Dai
- Department of Otolaryngology/Head and Neck Surgery, Oregon Hearing Research Center, Oregon Health and Science University, Portland, Oregon 97239-3098, USA
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