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Bovee S, Klump GM, Köppl C, Pyott SJ. The Stria Vascularis: Renewed Attention on a Key Player in Age-Related Hearing Loss. Int J Mol Sci 2024; 25:5391. [PMID: 38791427 PMCID: PMC11121695 DOI: 10.3390/ijms25105391] [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: 04/13/2024] [Revised: 05/08/2024] [Accepted: 05/10/2024] [Indexed: 05/26/2024] Open
Abstract
Age-related hearing loss (HL), or presbycusis, is a complex and heterogeneous condition, affecting a significant portion of older adults and involving various interacting mechanisms. Metabolic presbycusis, a type of age-related HL, is characterized by the dysfunction of the stria vascularis, which is crucial for maintaining the endocochlear potential necessary for hearing. Although attention on metabolic presbycusis has waned in recent years, research continues to identify strial pathology as a key factor in age-related HL. This narrative review integrates past and recent research, bridging findings from animal models and human studies, to examine the contributions of the stria vascularis to age-related HL. It provides a brief overview of the structure and function of the stria vascularis and then examines mechanisms contributing to age-related strial dysfunction, including altered ion transport, changes in pigmentation, inflammatory responses, and vascular atrophy. Importantly, this review outlines the contribution of metabolic mechanisms to age-related HL, highlighting areas for future research. It emphasizes the complex interdependence of metabolic and sensorineural mechanisms in the pathology of age-related HL and highlights the importance of animal models in understanding the underlying mechanisms. The comprehensive and mechanistic investigation of all factors contributing to age-related HL, including cochlear metabolic dysfunction, remains crucial to identifying the underlying mechanisms and developing personalized, protective, and restorative treatments.
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Affiliation(s)
- Sonny Bovee
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany; (S.B.); (G.M.K.); (C.K.)
| | - Georg M. Klump
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany; (S.B.); (G.M.K.); (C.K.)
- Cluster of Excellence “Hearing4all”, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Research Centre Neurosensory Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Christine Köppl
- Department of Neuroscience, School of Medicine and Health Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany; (S.B.); (G.M.K.); (C.K.)
- Cluster of Excellence “Hearing4all”, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
- Research Centre Neurosensory Science, Carl von Ossietzky Universität Oldenburg, 26129 Oldenburg, Germany
| | - Sonja J. Pyott
- Department of Otorhinolaryngology/Head and Neck Surgery, University Medical Center Groningen, University of Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands
- The Research School of Behavioural and Cognitive Neurosciences, University of Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands
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2
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Anderson G, Borooah S, Megaw R, Bagnaninchi P, Weller R, McLeod A, Dhillon B. UVR and RPE - The Good, the Bad and the degenerate Macula. Prog Retin Eye Res 2024; 100:101233. [PMID: 38135244 DOI: 10.1016/j.preteyeres.2023.101233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 12/15/2023] [Accepted: 12/15/2023] [Indexed: 12/24/2023]
Abstract
Ultraviolet Radiation (UVR) has a well-established causative influence within the aetiology of conditions of the skin and the anterior segment of the eye. However, a grounded assessment of the role of UVR within conditions of the retina has been hampered by a historical lack of quantitative, and spectrally resolved, assessment of how UVR impacts upon the retina in terms congruent with contemporary theories of ageing. In this review, we sought to summarise the key findings of research investigating the connection between UVR exposure in retinal cytopathology while identifying necessary avenues for future research which can deliver a deeper understanding of UVR's place within the retinal risk landscape.
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Affiliation(s)
- Graham Anderson
- Centre for Regenerative Medicine, University of Edinburgh, Edinburgh BioQuarter, EH16 4UU, UK
| | - Shyamanga Borooah
- Viterbi Family Department of Ophthalmology, Shiley Eye Institute, UC San Diego, CA, 92093-0946, USA
| | - Roly Megaw
- Institute of Genetics and Cancer, University of Edinburgh, Western General Hospital, EH4 2XU, UK; Department of Clinical Ophthalmology, National Health Service Scotland, Edinburgh, EH3 9HA, UK
| | - Pierre Bagnaninchi
- Centre for Regenerative Medicine, University of Edinburgh, Edinburgh BioQuarter, EH16 4UU, UK; Robert O Curle Eyelab, Instute for Regeneration and Repair, Edinburgh BioQuarter, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK
| | - Richard Weller
- Centre for Inflammation Research, University of Edinburgh, Edinburgh BioQuarter, EH16 4TJ, UK
| | - Andrew McLeod
- School of GeoSciences, University of Edinburgh, Crew Building, King's Buildings, EH9 3FF, UK
| | - Baljean Dhillon
- Department of Clinical Ophthalmology, National Health Service Scotland, Edinburgh, EH3 9HA, UK; Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh BioQuarter, EH16 4SB, UK; Robert O Curle Eyelab, Instute for Regeneration and Repair, Edinburgh BioQuarter, 4-5 Little France Drive, Edinburgh, EH16 4UU, UK.
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3
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Wang X, Kinziabulatova L, Bortoli M, Manickoth A, Barilla MA, Huang H, Blancafort L, Kohler B, Lumb JP. Indole-5,6-quinones display hallmark properties of eumelanin. Nat Chem 2023:10.1038/s41557-023-01175-4. [PMID: 37037912 DOI: 10.1038/s41557-023-01175-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 03/07/2023] [Indexed: 04/12/2023]
Abstract
Melanins are ubiquitous biopolymers produced from phenols and catechols by oxidation. They provide photoprotection, pigmentation and redox activity to most life forms, and inspire synthetic materials with desirable optical, electronic and mechanical properties. The chemical structures of melanins remain elusive, however, creating uncertainty about their roles, and preventing the design of synthetic mimics with tailored properties. Indole-5,6-quinone (IQ) has been implicated as a biosynthetic intermediate and structural subunit of mammalian eumelanin pigments, but its instability has prevented its isolation and unambiguous characterization. Here we use steric shielding to stabilize IQ and show that 'blocked' derivatives exhibit eumelanin's characteristic ultrafast nonradiative decay and its ability to absorb light from the ultraviolet to the near-infrared. These new compounds are also redox-active and a source of paramagnetism, emulating eumelanin's unique electronic properties, which include persistent radicals. Blocked IQs are atomistically precise and tailorable molecules that can offer a bottom-up understanding of emergent properties in eumelanin and have the potential to advance the rational design of melanin-inspired materials.
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Affiliation(s)
- Xueqing Wang
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Lilia Kinziabulatova
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Marco Bortoli
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain
| | - Anju Manickoth
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain
| | - Marisa A Barilla
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA
| | - Haiyan Huang
- Department of Chemistry, McGill University, Montreal, Quebec, Canada
| | - Lluís Blancafort
- Institut de Química Computacional i Catàlisi, Facultat de Ciències, Universitat de Girona, Girona, Spain.
| | - Bern Kohler
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH, USA.
| | - Jean-Philip Lumb
- Department of Chemistry, McGill University, Montreal, Quebec, Canada.
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4
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Brash DE, Goncalves LCP. Chemiexcitation: Mammalian Photochemistry in the Dark †. Photochem Photobiol 2023; 99:251-276. [PMID: 36681894 PMCID: PMC10065968 DOI: 10.1111/php.13781] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Accepted: 01/18/2023] [Indexed: 01/23/2023]
Abstract
Light is one way to excite an electron in biology. Another is chemiexcitation, birthing a reaction product in an electronically excited state rather than exciting from the ground state. Chemiexcited molecules, as in bioluminescence, can release more energy than ATP. Excited states also allow bond rearrangements forbidden in ground states. Molecules with low-lying unoccupied orbitals, abundant in biology, are particularly susceptible. In mammals, chemiexcitation was discovered to transfer energy from excited melanin, neurotransmitters, or hormones to DNA, creating the lethal and carcinogenic cyclobutane pyrimidine dimer. That process was initiated by nitric oxide and superoxide, radicals triggered by ultraviolet light or inflammation. Several poorly understood chronic diseases share two properties: inflammation generates those radicals across the tissue, and cells that die are those containing melanin or neuromelanin. Chemiexcitation may therefore be a pathogenic event in noise- and drug-induced deafness, Parkinson's disease, and Alzheimer's; it may prevent macular degeneration early in life but turn pathogenic later. Beneficial evolutionary selection for excitable biomolecules may thus have conferred an Achilles heel. This review of recent findings on chemiexcitation in mammalian cells also describes the underlying physics, biochemistry, and potential pathogenesis, with the goal of making this interdisciplinary phenomenon accessible to researchers within each field.
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Affiliation(s)
- Douglas E. Brash
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT 06520-8040, USA
- Yale Cancer Center, Yale School of Medicine, New Haven, CT 06520-8028, USA
| | - Leticia C. P. Goncalves
- Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT 06520-8040, USA
- Institut de Chimie de Nice CNRS UMR7272, Université Côte d’Azur, 28 Avenue Valrose 06108 Nice, France
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5
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Ahmadi N, Saidov N, Gausterer JC, Kramer AM, Honeder C, Arnoldner C. Establishment of an optimized guinea pig model of cisplatin-induced ototoxicity. Front Vet Sci 2023; 10:1112857. [PMID: 37124562 PMCID: PMC10133486 DOI: 10.3389/fvets.2023.1112857] [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: 11/30/2022] [Accepted: 03/27/2023] [Indexed: 05/02/2023] Open
Abstract
Background Cisplatin is among the most effective antineoplastic agents and has revolutionized the treatment of many cancer diseases. However, one of its serious side effects is a progressive and irreversible hearing loss, occurring in both adults and children. For the development of otoprotective therapies that prevent this side effect, cisplatin-induced hearing loss animal models are indispensable. Due to the high toxicity of cisplatin, the establishment of such animal models is a difficult and time-consuming task. Here we introduce the detailed protocol of a sophisticated guinea pig model with a sufficient and permanent hearing loss induced by cisplatin. This manuscript is intended to provide guidance in the development of future cisplatin guinea pig models which may reduce the mortality rate of the animals and help to gain more reproducible results. Methods Pigmented and unpigmented guineapigs were treated with an intravenous single application of 8 mg/kg cisplatin under general anesthesia. An extensive and long-term intensive care protocol consisting of scheduled application of fluids, antiemetics, analgesics, glucose and supportive feeding among others, was used to ensure wellbeing of the animals. Hearing tests were performed prior to and 5 days after cisplatin application. Animals were then euthanized. Results The ABR audiometry 5 days after cisplatin application revealed a hearing threshold ranging from 70 dB to 90 dB in the frequencies from 1 kHz to 32 kHz respectively.All animals presented a good health condition despite the treatment with cisplatin. Discussion The introduced care protocol in this manuscript is intended to serve as a guidance for the establishment of a stable guinea pig model for short- and long-term investigation regarding the inner ear and its protection in the frame work of cisplatin-induced damage.
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Affiliation(s)
- Navid Ahmadi
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria
| | - Nodir Saidov
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria
| | - Julia Clara Gausterer
- Division of Pharmaceutical Technology and Biopharmaceutics, Department of Pharmaceutical Sciences, University of Vienna, Vienna, Austria
| | | | - Clemens Honeder
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria
| | - Christoph Arnoldner
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria
- *Correspondence: Christoph Arnoldner
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6
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Istrate M, Hasbei-Popa M, Iliescu DA, Ghiță AC, Vlaicu B, Ghiță MA. Dual Sensory Impairment: The Correlation between Age Related Macular Degeneration and Sensorineural Hearing Loss. Medicina (B Aires) 2022; 58:medicina58020291. [PMID: 35208614 PMCID: PMC8877232 DOI: 10.3390/medicina58020291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/30/2022] [Accepted: 02/09/2022] [Indexed: 11/28/2022] Open
Abstract
The pathogeneses of age-related macular degeneration (AMD) and age-related hearing impairment are not yet fully understood. If AMD and age-related hearing impairment are correlated, the cause of both may be a result of a common vulnerability. The aim of this study was to assess the interrelation between age-related macular degeneration and age-related hearing loss. Material and methods: In our case-control analysis, the hearing conditions of 40 subjects with AMD were compared with 40 age-matched healthy controls. In all patients, retinal changes were certified by clinical examinations, optical coherence tomography (OCT), and fluorescein angiography (FA). All subjects were inspected with pure tone audiometry (PTA), impedance audiometry, and speech audiometry. Results: A significant correlation (p < 0.001) was identified between age-related macular degeneration and age-related hearing impairment. The predominant hearing impairment in this case was sensorineural (SNHL). Of the patients diagnosed with AMD, SNHL was found in 88.89% of those with exudative macular degeneration and in 67.74% of those with atrophic macular degeneration. In contrast, we found that a significant proportion of the control group had normal hearing. Conclusion: One possible explanation for the association between retinal and cochlear impairment may be due to a melanin disorder.
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Affiliation(s)
- Marina Istrate
- Department of Doctoral School, “Victor Babes” University of Medicine and Pharmacy, 300041 Timisoara, Romania
- Department of Ophthalmology, “Infosan” Ophthalmology Clinic, 010538 Bucharest, Romania
- Correspondence:
| | - Mihai Hasbei-Popa
- Department of Medicine, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400000 Cluj-Napoca, Romania
| | - Daniela Adriana Iliescu
- Department of Physiology, ”Carol Davila” University of Medicine and Pharmacy, 050474 Bucharest, Romania
- Department of Ophtalmology, ”Ocularcare” Eye Clinic, 012244 Bucharest, Romania
| | - Ana Cristina Ghiță
- Department of Ophtalmology, ”Ocularcare” Eye Clinic, 012244 Bucharest, Romania
| | - Brigitha Vlaicu
- Department of Hygiene, ”Victor Babes” University of Medicine and Pharmacy, 300041 Timisoara, Romania
| | - Mihai Aurelian Ghiță
- Department of Physiology, ”Carol Davila” University of Medicine and Pharmacy, 050474 Bucharest, Romania
- Department of Ophtalmology, ”Ocularcare” Eye Clinic, 012244 Bucharest, Romania
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7
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Mostert AB. Melanin, the What, the Why and the How: An Introductory Review for Materials Scientists Interested in Flexible and Versatile Polymers. Polymers (Basel) 2021; 13:1670. [PMID: 34065580 PMCID: PMC8161012 DOI: 10.3390/polym13101670] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 01/13/2023] Open
Abstract
Today, western society is facing challenges to create new medical technologies to service an aging population as well as the ever-increasing e-waste of electronic devices and sensors. A key solution to these challenges will be the use of biomaterials and biomimetic systems. One material that has been receiving serious attention for its biomedical and device applications is eumelanin. Eumelanin, or commonly known as melanin, is nature's brown-black pigment and is a poly-indolequinone biopolymer, which possess unique physical and chemical properties for material applications. Presented here is a review, aimed at polymer and other materials scientists, to introduce eumelanin as a potential material for research. Covered here are the chemical and physical structures of melanin, an overview of its unique physical and chemical properties, as well as a wide array of applications, but with an emphasis on device and sensing applications. The review is then finished by introducing interested readers to novel synthetic protocols and post synthesis fabrication techniques to enable a starting point for polymer research in this intriguing and complex material.
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Affiliation(s)
- A Bernardus Mostert
- Department of Chemistry, Swansea University, Singleton Park, Wales SA2 8PP, UK
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8
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Ogier JM, Lockhart PJ, Burt RA. Intravenously delivered aminoglycoside antibiotics, tobramycin and amikacin, are not ototoxic in mice. Hear Res 2020; 386:107870. [PMID: 31864009 DOI: 10.1016/j.heares.2019.107870] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Revised: 11/24/2019] [Accepted: 12/09/2019] [Indexed: 12/20/2022]
Abstract
Many drugs on the World Health Organization's list of critical medicines are ototoxic, destroying sensory hair cells within the ear. These drugs preserve life, but patients can experience side effects including permanent hearing loss and vestibular dysfunction. Aminoglycoside ototoxicity was first recognised 80 years ago. However, no preventative treatments have been developed. In order to develop such treatments, we must identify the factors driving hair cell death. In vivo, studies of cell death are typically conducted using mouse models. However, a robust model of aminoglycoside ototoxicity does not exist. Previous studies testing aminoglycoside delivery via intraperitoneal or subcutaneous injection have produced variable ototoxic effects in the mouse. As a result, surgical drug delivery to the rodent ear is often used to achieve ototoxicity. However, this technique does not accurately model clinical practice. In the clinic, aminoglycosides are administered to humans intravenously (i.v.). However, repeated i.v. delivery has not been reported in the mouse. This study evaluated whether repeated i.v. administration of amikacin or tobramycin would induce hearing loss. Daily i.v. injections over a two-week period were well tolerated and transient low frequency hearing loss was observed in the aminoglycoside treatment groups. However, the hearing changes observed did not mimic the high frequency patterns of hearing loss observed in humans. Our results indicate that the i.v. delivery of tobramycin or amikacin is not an effective technique for inducing ototoxicity in mice. This result is consistent with previously published reports indicating that the mouse cochlea is resistant to systemically delivered aminoglycoside ototoxicity.
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Affiliation(s)
- Jacqueline M Ogier
- Bruce Lefroy Centre, Murdoch Children's Research Institute, 50 Flemington Road, Parkville, VIC, 3052, Australia; Department of Paediatrics, University of Melbourne, Parkville, VIC, 3010, Australia.
| | - Paul J Lockhart
- Bruce Lefroy Centre, Murdoch Children's Research Institute, 50 Flemington Road, Parkville, VIC, 3052, Australia; Department of Paediatrics, University of Melbourne, Parkville, VIC, 3010, Australia
| | - Rachel A Burt
- Bruce Lefroy Centre, Murdoch Children's Research Institute, 50 Flemington Road, Parkville, VIC, 3052, Australia; School of Biosciences, University of Melbourne, Parkville, VIC, 3010, Australia
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9
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Ahmadi N, Gausterer JC, Honeder C, Mötz M, Schöpper H, Zhu C, Saidov N, Gabor F, Arnoldner C. Long-term effects and potential limits of intratympanic dexamethasone-loaded hydrogels combined with dexamethasone-eluting cochlear electrodes in a low-insertion trauma Guinea pig model. Hear Res 2019; 384:107825. [PMID: 31669876 DOI: 10.1016/j.heares.2019.107825] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 09/07/2019] [Accepted: 10/16/2019] [Indexed: 12/11/2022]
Abstract
Cochlear implantation has become the most effective hearing restoration method and is one of the great advances in modern medicine. Early implants have been continuously developed into more efficient devices, and electro-acoustic stimulation is increasingly expanding the indication criteria for cochlear implants to patients with more residual hearing. Therefore, protecting the cochlear structures and maintaining its intrinsic capacities like residual hearing has become more important than ever before. In the present study, we aimed to assess the long-term protective effects of a dexamethasone-eluting electrode combined with the preoperative intratympanic application of a dexamethasone-loaded thermoreversible hydrogel in a cochlear implant guinea pig model. 40 normal-hearing animals were equally randomized into a control group receiving an unloaded hydrogel and a non-eluting electrode, a group receiving a dexamethasone-loaded hydrogel and a non-eluting electrode, a group receiving an unloaded hydrogel and a dexamethasone-eluting electrode and a group receiving both a dexamethasone-loaded hydrogel and a dexamethasone-eluting electrode. Residual hearing and impedances were investigated during a period of 120 days. Tissue response and histological changes of cochlear structures were analyzed at the end of the experiments. Treatment with dexamethasone did not show a significant protective effect on residual hearing independent of treatment group. Although the majority of the cochleae didn't exhibit any signs of electrode insertion trauma, a small degree of tissue response could be observed in all animals without a significant difference between the groups. Foreign body giant cells and osteogenesis were significantly associated with tissue response. Hair cells, synapsin-1-positive cells and spiral ganglion cells were preserved in all study groups. Cochlear implantation using a dexamethasone-eluting electrode alone and in combination with a dexamethasone-loaded hydrogel significantly protected auditory nerve fibers on day 120. Post-implantation impedances were equal across study groups and remained stable over the duration of the experiment. In this study we were able to show that use of a dexamethasone-eluting electrode alone and in combination with preoperative application of dexamethasone-loaded hydrogel significantly protects auditory nerve fibers. Furthermore, we have shown that a cochlear implantation-associated hearing threshold shift and tissue response may not be completely prevented by the sole application of dexamethasone.
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Affiliation(s)
- Navid Ahmadi
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria.
| | - Julia Clara Gausterer
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna, Austria.
| | - Clemens Honeder
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria.
| | - Marlene Mötz
- Department of Pathobiology, Institute of Anatomy, Histology and Embryology, University of Veterinary Medicine Vienna, Austria.
| | - Hanna Schöpper
- Department of Pathobiology, Institute of Anatomy, Histology and Embryology, University of Veterinary Medicine Vienna, Austria.
| | - Chengjing Zhu
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria.
| | - Nodir Saidov
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria.
| | - Franz Gabor
- Department of Pharmaceutical Technology and Biopharmaceutics, University of Vienna, Vienna, Austria.
| | - Christoph Arnoldner
- Department of Otorhinolaryngology, Head and Neck Surgery, Medical University of Vienna, Vienna, Austria.
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10
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Ultracytochemical visualization of calcium distribution in heart cells and erythrocytes of zebrafish Danio rerio. Micron 2018; 111:19-27. [DOI: 10.1016/j.micron.2018.05.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 05/23/2018] [Accepted: 05/23/2018] [Indexed: 01/06/2023]
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11
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Kyrmizi I, Ferreira H, Carvalho A, Figueroa JAL, Zarmpas P, Cunha C, Akoumianaki T, Stylianou K, Deepe GS, Samonis G, Lacerda JF, Campos A, Kontoyiannis DP, Mihalopoulos N, Kwon-Chung KJ, El-Benna J, Valsecchi I, Beauvais A, Brakhage AA, Neves NM, Latge JP, Chamilos G. Calcium sequestration by fungal melanin inhibits calcium-calmodulin signalling to prevent LC3-associated phagocytosis. Nat Microbiol 2018; 3:791-803. [PMID: 29849062 DOI: 10.1038/s41564-018-0167-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 04/23/2018] [Indexed: 11/09/2022]
Abstract
LC3-associated phagocytosis (LAP) is a non-canonical autophagy pathway regulated by Rubicon, with an emerging role in immune homeostasis and antifungal host defence. Aspergillus cell wall melanin protects conidia (spores) from killing by phagocytes and promotes pathogenicity through blocking nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent activation of LAP. However, the signalling regulating LAP upstream of Rubicon and the mechanism of melanin-induced inhibition of this pathway remain incompletely understood. Herein, we identify a Ca2+ signalling pathway that depends on intracellular Ca2+ sources from endoplasmic reticulum, endoplasmic reticulum-phagosome communication, Ca2+ release from phagosome lumen and calmodulin (CaM) recruitment, as a master regulator of Rubicon, the phagocyte NADPH oxidase NOX2 and other molecular components of LAP. Furthermore, we provide genetic evidence for the physiological importance of Ca2+-CaM signalling in aspergillosis. Finally, we demonstrate that Ca2+ sequestration by Aspergillus melanin inside the phagosome abrogates activation of Ca2+-CaM signalling to inhibit LAP. These findings reveal the important role of Ca2+-CaM signalling in antifungal immunity and identify an immunological function of Ca2+ binding by melanin pigments with broad physiological implications beyond fungal disease pathogenesis.
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Affiliation(s)
- Irene Kyrmizi
- Department of Medicine, University of Crete, Heraklion, Crete, Greece.,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece
| | - Helena Ferreira
- 3B's Research Group - Biomaterials, Biodegradables and Biomimetics, Guimarães, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | - Agostinho Carvalho
- ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.,Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, Braga, Portugal
| | - Julio Alberto Landero Figueroa
- Department of Chemistry, University of Cincinnati/Agilent Technologies Metallomics Center of the Americas, University of Cincinnati, Cincinnati, OH, USA
| | - Pavlos Zarmpas
- Department of Chemistry, University of Crete, Heraklion, Crete, Greece
| | - Cristina Cunha
- ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal.,Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, Campus de Gualtar, Braga, Portugal
| | - Tonia Akoumianaki
- Department of Medicine, University of Crete, Heraklion, Crete, Greece
| | - Kostas Stylianou
- Department of Medicine, University of Crete, Heraklion, Crete, Greece
| | - George S Deepe
- Division of Infectious Diseases, College of Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - George Samonis
- Department of Medicine, University of Crete, Heraklion, Crete, Greece
| | - João F Lacerda
- Instituto de Medicina Molecular, Faculdade de Medicina de Lisboa, Lisbon, Portugal.,Serviço de Hematologia e Transplantação de Medula, Hospital de Santa Maria, Lisbon, Portugal
| | - António Campos
- Serviço de Transplantação de Medula Óssea (STMO), Instituto Português de Oncologia do Porto, Porto, Portugal
| | - Dimitrios P Kontoyiannis
- Department of Infectious Diseases, The University of Texas, MD Anderson Cancer Center, Austin, TX, USA
| | | | - Kyung J Kwon-Chung
- Molecular Microbiology Section, Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Jamel El-Benna
- INSERM-U1149, CNRS-ERL8252, Centre de Recherche sur l'Inflammation, Paris, France.,Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d'Excellence Inflamex, DHU FIRE, Faculté de Médecine, Site Xavier Bichat, Paris, France
| | | | - Anne Beauvais
- Unité des Aspergillus, Institut Pasteur, Paris, France
| | - Axel A Brakhage
- Department of Molecular and Applied Microbiology, Leibniz-Institute for Natural Product Research and Infection Biology (HKI) and Friedrich Schiller University, Jena, Germany
| | - Nuno M Neves
- 3B's Research Group - Biomaterials, Biodegradables and Biomimetics, Guimarães, Portugal.,ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
| | | | - Georgios Chamilos
- Department of Medicine, University of Crete, Heraklion, Crete, Greece. .,Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology, Heraklion, Crete, Greece.
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12
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Brash DE, Goncalves LCP, Bechara EJH. Chemiexcitation and Its Implications for Disease. Trends Mol Med 2018; 24:527-541. [PMID: 29751974 DOI: 10.1016/j.molmed.2018.04.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 03/27/2018] [Accepted: 04/06/2018] [Indexed: 12/20/2022]
Abstract
Quantum mechanics rarely extends to molecular medicine. Recently, the pigment melanin was found to be susceptible to chemiexcitation, in which an electron is chemically excited to a high-energy molecular orbital. In invertebrates, chemiexcitation causes bioluminescence; in mammals, a higher-energy process involving melanin transfers energy to DNA without photons, creating the lethal and mutagenic cyclobutane pyrimidine dimer that can cause melanoma. This process is initiated by NO and O2- radicals, the formation of which can be triggered by ultraviolet light or inflammation. Several chronic diseases share two properties: inflammation generates these radicals across the tissue, and the diseased cells lie near melanin. We propose that chemiexcitation may be an upstream event in numerous human diseases.
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Affiliation(s)
- Douglas E Brash
- Departments of Therapeutic Radiology and Dermatology, and Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520-8040, USA.
| | - Leticia C P Goncalves
- Departments of Therapeutic Radiology and Dermatology, and Yale Cancer Center, Yale University School of Medicine, New Haven, CT 06520-8040, USA
| | - Etelvino J H Bechara
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo 05513-970 SP, and Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Diadema, São Paulo 09972-270 SP, Brazil
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13
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Palma S, Boldrini P, Nucci R, Fano RA, Cenacchi G, Martini A. Melanin in human vestibular organs: what do we know now? An ultrastructural study and review of the literature. HEARING, BALANCE AND COMMUNICATION 2018. [DOI: 10.1080/21695717.2018.1461488] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Silvia Palma
- ENT, Primary Care Department, ASL, Modena, Italy
| | | | - Raul Nucci
- ENT Department, Ospedale Civile di Legnano, Legnano, Italy
| | - Rita Adriana Fano
- Dipartimento di Economia Marco Biagi, Universita degli Studi di Modena e Reggio Emilia, Modena, Italy
| | - Giovanna Cenacchi
- Dipartimento di Scienze Statistiche, Universita degli Studi di Padova, Padova, Italy
| | - Alessandro Martini
- Biomedical and Neuromotor Sciences Department, Universita degli Studi di Bologna, Bologna, Italy
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14
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Knörle R. Neuromelanin in Parkinson's Disease: from Fenton Reaction to Calcium Signaling. Neurotox Res 2017; 33:515-522. [PMID: 28879408 DOI: 10.1007/s12640-017-9804-z] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 08/14/2017] [Accepted: 08/23/2017] [Indexed: 12/13/2022]
Abstract
Neuromelanin is supposed to play a key role in the pathogenesis of Parkinson's disease. A common theory is the formation of reactive oxygen species through the Fenton reaction catalyzed by neuromelanin-bound iron ions and subsequent death of the dopaminergic cells in the substantia nigra. From a physicochemical point of view, this pathway is rather implausible: a highly reactive radical built within a powerful radical scavenger would more promptly be inactivated before it might diffuse within the cell to reach a target to exert its deleterious potential. This review of the literature provides evidence for an interaction of neuromelanin with the calcium signaling pathway in Parkinson's disease and expands the view of the pathophysiological contribution of neuromelanin towards a cytoprotective involvement of this macromolecule in the calcium signaling system. More probably than being directly involved in the production of reactive oxygen species, neuromelanin may act as a calcium reservoir and thus protect dopaminergic cells from cell death. A loss of neuromelanin, as observed in the substantia nigra of Parkinson patients, would lead to enhanced calcium messaging through the loss of an important calcium reservoir and thus finally via the formation of reactive oxygen species to cell death within the substantia nigra.
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Affiliation(s)
- Rainer Knörle
- IBAM GbR Dr. Rainer Knörle Dr. Peter Schnierle, Ferdinand-Porsche-Str. 5, 79211, Denzlingen, Germany.
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15
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Zucca FA, Segura-Aguilar J, Ferrari E, Muñoz P, Paris I, Sulzer D, Sarna T, Casella L, Zecca L. Interactions of iron, dopamine and neuromelanin pathways in brain aging and Parkinson's disease. Prog Neurobiol 2017; 155:96-119. [PMID: 26455458 PMCID: PMC4826627 DOI: 10.1016/j.pneurobio.2015.09.012] [Citation(s) in RCA: 417] [Impact Index Per Article: 59.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 09/14/2015] [Accepted: 09/17/2015] [Indexed: 12/11/2022]
Abstract
There are several interrelated mechanisms involving iron, dopamine, and neuromelanin in neurons. Neuromelanin accumulates during aging and is the catecholamine-derived pigment of the dopamine neurons of the substantia nigra and norepinephrine neurons of the locus coeruleus, the two neuronal populations most targeted in Parkinson's disease. Many cellular redox reactions rely on iron, however an altered distribution of reactive iron is cytotoxic. In fact, increased levels of iron in the brain of Parkinson's disease patients are present. Dopamine accumulation can induce neuronal death; however, excess dopamine can be removed by converting it into a stable compound like neuromelanin, and this process rescues the cell. Interestingly, the main iron compound in dopamine and norepinephrine neurons is the neuromelanin-iron complex, since neuromelanin is an effective metal chelator. Neuromelanin serves to trap iron and provide neuronal protection from oxidative stress. This equilibrium between iron, dopamine, and neuromelanin is crucial for cell homeostasis and in some cellular circumstances can be disrupted. Indeed, when neuromelanin-containing organelles accumulate high load of toxins and iron during aging a neurodegenerative process can be triggered. In addition, neuromelanin released by degenerating neurons activates microglia and the latter cause neurons death with further release of neuromelanin, then starting a self-propelling mechanism of neuroinflammation and neurodegeneration. Considering the above issues, age-related accumulation of neuromelanin in dopamine neurons shows an interesting link between aging and neurodegeneration.
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Affiliation(s)
- Fabio A Zucca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Juan Segura-Aguilar
- Faculty of Medicine, Molecular and Clinical Pharmacology, ICBM, University of Chile, Santiago, Chile
| | - Emanuele Ferrari
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy
| | - Patricia Muñoz
- Faculty of Medicine, Molecular and Clinical Pharmacology, ICBM, University of Chile, Santiago, Chile
| | - Irmgard Paris
- Faculty of Medicine, Molecular and Clinical Pharmacology, ICBM, University of Chile, Santiago, Chile; Department of Basic Sciences, Faculty of Sciences, Santo Tomás University, Viña del Mar, Chile
| | - David Sulzer
- Department of Psychiatry, Columbia University Medical Center, New York, NY, USA; Department of Neurology, Columbia University Medical Center, New York, NY, USA; Department of Pharmacology, Columbia University Medical Center, New York, NY, USA
| | - Tadeusz Sarna
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Luigi Casella
- Department of Chemistry, University of Pavia, Pavia, Italy
| | - Luigi Zecca
- Institute of Biomedical Technologies, National Research Council of Italy, Segrate, Milan, Italy.
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16
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Galante Rocha de Vasconcelos FT, Hauzman E, Dutra Henriques L, Kilpp Goulart PR, de Faria Galvão O, Sano RY, da Silva Souza G, Lynch Alfaro J, de Lima Silveira LC, Fix Ventura D, Oliveira Bonci DM. A novel nonsense mutation in the tyrosinase gene is related to the albinism in a capuchin monkey (Sapajus apella). BMC Genet 2017; 18:39. [PMID: 28476152 PMCID: PMC5420114 DOI: 10.1186/s12863-017-0504-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Accepted: 04/12/2017] [Indexed: 11/27/2022] Open
Abstract
Background Oculocutaneous Albinism (OCA) is an autosomal recessive inherited condition that affects the pigmentation of eyes, hair and skin. The OCA phenotype may be caused by mutations in the tyrosinase gene (TYR), which expresses the tyrosinase enzyme and has an important role in the synthesis of melanin pigment. The aim of this study was to identify the genetic mutation responsible for the albinism in a captive capuchin monkey, and to describe the TYR gene of normal phenotype individuals. In addition, we identified the subject’s species. Results A homozygous nonsense mutation was identified in exon 1 of the TYR gene, with the substitution of a cytosine for a thymine nucleotide (C64T) at codon 22, leading to a premature stop codon (R22X) in the albino robust capuchin monkey. The albino and five non-albino robust capuchin monkeys were identified as Sapajus apella, based on phylogenetic analyses, pelage pattern and geographic provenance. One individual was identified as S. macrocephalus. Conclusion We conclude that the point mutation C64T in the TYR gene is responsible for the OCA1 albino phenotype in the capuchin monkey, classified as Sapajus apella. Electronic supplementary material The online version of this article (doi:10.1186/s12863-017-0504-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Felipe Tadeu Galante Rocha de Vasconcelos
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030
| | - Einat Hauzman
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil
| | - Leonardo Dutra Henriques
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030
| | - Paulo Roney Kilpp Goulart
- Núcleo de Teoria e Pesquisa do Comportamento, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110
| | - Olavo de Faria Galvão
- Núcleo de Teoria e Pesquisa do Comportamento, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110
| | - Ronaldo Yuiti Sano
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Departamento de Oftalmologia, Santa Casa de Misericórdia de São Paulo, São Paulo, São Paulo, Brazil
| | - Givago da Silva Souza
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110.,Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará, Brazil
| | - Jessica Lynch Alfaro
- Institute for Society and Genetics, University of California Los Angeles, Box 957221, 3360 LSB, Los Angeles, CA, USA, 90095-7221.,Department of Anthropology, University of California Los Angeles, Los Angeles, CA, USA
| | - Luis Carlos de Lima Silveira
- Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa, 01 - Guamá, Belém, PA, Brazil, 66075-110.,Núcleo de Medicina Tropical, Universidade Federal do Pará, Belém, Pará, Brazil
| | - Dora Fix Ventura
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030.,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil
| | - Daniela Maria Oliveira Bonci
- Departamento de Psicologia Experimental, Instituto de Psicologia, Universidade de São Paulo, Av. Professor Mello Moraes 1721 Bloco A Sala D9 - Butantã, São Paulo, SP, Brazil, 05508-030. .,Instituto Israelita de Ensino e Pesquisa Albert Einstein, Hospital Israelita Albert Einstein, São Paulo, São Paulo, Brazil.
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17
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Erbele ID, Lin FR, Agrawal Y, Francis HW, Carey JP, Chien WW. Racial Differences of Pigmentation in the Human Vestibular Organs. Otolaryngol Head Neck Surg 2016; 155:479-84. [DOI: 10.1177/0194599816645764] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Accepted: 04/01/2016] [Indexed: 11/17/2022]
Abstract
Objectives Melanin pigmentation is present in the human inner ear. In this study, we quantify the melanin pigmentation in the vestibular system and examine racial differences of vestibular melanin pigmentation using human cadaveric temporal bone specimens. Study Design Basic research. Setting Laboratory. Subjects and Methods Light microscopy was used to examine specimens from 40 left temporal bones from the Johns Hopkins Human Temporal Bone Collection. Color images of (1) ampulla of the horizontal canal, (2) utricular wall, (3) endolymphatic duct, and (4) posterior ampullary nerve as it enters the posterior canal were acquired with a digital camera attached to the microscope and image acquisition software. Acquired images of each anatomic area of interest were processed offline through ImageJ. Melanin content was then compared according to ethnicity, age, sex, and location. Results Fifteen African American and 25 Caucasian specimens were analyzed. Mean age was 68.8 years. African American specimens had a significantly greater amount of pigment at all 4 sampled locations as compared with Caucasian specimens ( P < .01). Between sexes, there was a statistically significant difference ( P < .05) at the posterior ampullary nerve, with males having more than females. Melanin content was not associated with age. Conclusions There is greater melanin pigmentation within the vestibular system of African Americans than in Caucasians, similar to what has been described in the cochlea. Racial differences in vestibular physiologic function have been observed in the literature and may be explained by differences in melanin pigmentation.
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Affiliation(s)
- Isaac D. Erbele
- Department of Otolaryngology–Head and Neck Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA
| | - Frank R. Lin
- Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
- Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health; Johns Hopkins Center on Aging and Health, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
| | - Yuri Agrawal
- Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Howard W. Francis
- Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - John P. Carey
- Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Wade W. Chien
- Department of Otolaryngology–Head and Neck Surgery, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
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18
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Zucker diabetic fatty rats, a model for type 2 diabetes, develop an inner ear dysfunction that can be attenuated by losartan treatment. Cell Tissue Res 2015; 362:307-15. [DOI: 10.1007/s00441-015-2215-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2015] [Accepted: 05/12/2015] [Indexed: 12/13/2022]
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19
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Riley PA, Stratford MR. Oxidative calcium release from catechol. Bioorg Med Chem Lett 2015; 25:1453-4. [DOI: 10.1016/j.bmcl.2015.02.036] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/15/2015] [Accepted: 02/16/2015] [Indexed: 11/30/2022]
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20
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Melanins: Skin Pigments and Much More—Types, Structural Models, Biological Functions, and Formation Routes. ACTA ACUST UNITED AC 2014. [DOI: 10.1155/2014/498276] [Citation(s) in RCA: 277] [Impact Index Per Article: 27.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
This review presents a general view of all types of melanin in all types of organisms. Melanin is frequently considered just an animal cutaneous pigment and is treated separately from similar fungal or bacterial pigments. Similarities concerning the phenol precursors and common patterns in the formation routes are discussed. All melanins are formed in a first enzymatically-controlled phase, generally a phenolase, and a second phase characterized by an uncontrolled polymerization of the oxidized intermediates. In that second phase, quinones derived from phenol oxidation play a crucial role. Concerning functions, all melanins show a common feature, a protective role, but they are not merely photoprotective pigments against UV sunlight. In pathogenic microorganisms, melanization becomes a virulence factor since melanin protects microbial cells from defense mechanisms in the infected host. In turn, some melanins are formed in tissues where sunlight radiation is not a potential threat. Then, their redox, metal chelating, or free radical scavenging properties are more important than light absorption capacity. These pigments sometimes behave as a double-edged sword, and inhibition of melanogenesis is desirable in different cells. Melanin biochemistry is an active field of research from dermatological, biomedical, cosmetical, and microbiological points of view, as well as fruit technology.
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21
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Dubey S, Roulin A. Evolutionary and biomedical consequences of internal melanins. Pigment Cell Melanoma Res 2014; 27:327-38. [DOI: 10.1111/pcmr.12231] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Sylvain Dubey
- Department of Ecology and Evolution; University of Lausanne; Biophore Lausanne Switzerland
| | - Alexandre Roulin
- Department of Ecology and Evolution; University of Lausanne; Biophore Lausanne Switzerland
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22
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Abstract
AbstractThe majority of melanocytes originate from the neural crest cells (NCC) that migrate, spread on the whole embryo’s body to form elements of the nervous system and skeleton, endocrinal glands, muscles and melanocytes. Human melanocytes differentiate mainly from the cranial and trunk NCC. Although melanocyte development has traditionally been associated with the dorsally migrating trunk NCC, there is evidence that a part of melanocytes arise from cells migrating ventrally. The ventral NCC differentiate into neurons and glia of the ganglia or Schwann cells. It has been suggested that the precursors for Schwann cells differentiate into melanocytes. As melanoblasts travel through the dermis, they multiply, follow the process of differentiation and invade the forming human fetal epidermis up to third month. After birth, melanocytes lose the ability to proliferate, except the hair melanocytes that renew during the hair cycle. The localization of neural crest-derived melanocytes in non-cutaneous places e.g. eye (the choroid and stroma of the iris and the ciliary body), ear (cells of the vestibular organ, cochlear stria vascularis), meninges of the brain, heart seems to indicate that repertoire of melanocyte functions is much wider than we expected e.g. the protection of tissues from potentially harmful factors (e.g. free radicals, binding toxins), storage ions, and anti-inflammatory action.
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23
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Biesemeier A, Schraermeyer U, Eibl O. Chemical composition of melanosomes, lipofuscin and melanolipofuscin granules of human RPE tissues. Exp Eye Res 2011; 93:29-39. [DOI: 10.1016/j.exer.2011.04.004] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 03/14/2011] [Accepted: 04/04/2011] [Indexed: 01/10/2023]
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24
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Dhomen N, Da Rocha Dias S, Hayward R, Ogilvie L, Hedley D, Delmas V, McCarthy A, Henderson D, Springer CJ, Pritchard C, Larue L, Marais R. Inducible expression of (V600E) Braf using tyrosinase-driven Cre recombinase results in embryonic lethality. Pigment Cell Melanoma Res 2009; 23:112-20. [PMID: 20002887 DOI: 10.1111/j.1755-148x.2009.00662.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We recently demonstrated that expression of (V600E)Braf in mature mouse melanocytes induces melanoma. Here, we show that expression of (V600E)Braf using the tyrosinase promoter leads to an unexpected embryonic lethality, with the animals dying before, at, or shortly after birth. The mice suffer from a range of developmental defects in the skin, the brain, the eyes and the heart, tissues that are normally colonized by melanocytes. We show that the (V600E)Braf expressing cells are potential melanocytic precursors that are fully transformed, suggesting that (V600E)Braf stimulates proliferation and blocks differentiation of these cells. Our data suggests that the presence of these cells in the organs that are normally occupied by melanocytes leads to severe developmental disruption, resulting in catastrophic defects and leading to death of the individual.
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Affiliation(s)
- Nathalie Dhomen
- The Institute of Cancer Research, Signal Transduction Team, Cancer Research UK Centre for Cell and Molecular Biology, London, UK
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25
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Murillo-Cuesta S, Contreras J, Zurita E, Cediel R, Cantero M, Varela-Nieto I, Montoliu L. Melanin precursors prevent premature age-related and noise-induced hearing loss in albino mice. Pigment Cell Melanoma Res 2009; 23:72-83. [PMID: 19843244 DOI: 10.1111/j.1755-148x.2009.00646.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Strial melanocytes are required for normal development and correct functioning of the cochlea. Hearing deficits have been reported in albino individuals from different species, although melanin appears to be not essential for normal auditory function. We have analyzed the auditory brainstem responses (ABR) of two transgenic mice: YRT2, carrying the entire mouse tyrosinase (Tyr) gene expression-domain and undistinguishable from wild-type pigmented animals; and TyrTH, non-pigmented but ectopically expressing tyrosine hydroxylase (Th) in melanocytes, which generate the precursor metabolite, L-DOPA, but not melanin. We show that young albino mice present a higher prevalence of profound sensorineural deafness and a poorer recovery of auditory thresholds after noise-exposure than transgenic mice. Hearing loss was associated with absence of cochlear melanin or its precursor metabolites and latencies of the central auditory pathway were unaltered. In summary, albino mice show impaired hearing responses during ageing and after noise damage when compared to YRT2 and TyrTH transgenic mice, which do not show the albino-associated ABR alterations. These results demonstrate that melanin precursors, such as L-DOPA, have a protective role in the mammalian cochlea in age-related and noise-induced hearing loss.
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Affiliation(s)
- Silvia Murillo-Cuesta
- Instituto de Investigaciones Biomédicas Alberto Sols, Consejo Superior de Investigaciones Científicas (CSIC), Universidad Autónoma de Madrid (UAM), Madrid, Spain
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26
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Plonka PM, Passeron T, Brenner M, Tobin DJ, Shibahara S, Thomas A, Slominski A, Kadekaro AL, Hershkovitz D, Peters E, Nordlund JJ, Abdel-Malek Z, Takeda K, Paus R, Ortonne JP, Hearing VJ, Schallreuter KU. What are melanocytes really doing all day long...? Exp Dermatol 2009; 18:799-819. [PMID: 19659579 PMCID: PMC2792575 DOI: 10.1111/j.1600-0625.2009.00912.x] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Everyone knows and seems to agree that melanocytes are there to generate melanin - an intriguing, but underestimated multipurpose molecule that is capable of doing far more than providing pigment and UV protection to skin (1). What about the cell that generates melanin, then? Is this dendritic, neural crest-derived cell still serving useful (or even important) functions when no-one looks at the pigmentation of our skin and its appendages and when there is essentially no UV exposure? In other words, what do epidermal and hair follicle melanocytes do in their spare time - at night, under your bedcover? How much of the full portfolio of physiological melanocyte functions in mammalian skin has really been elucidated already? Does the presence or absence of melanocytes matter for normal epidermal and/or hair follicle functions (beyond pigmentation and UV protection), and for skin immune responses? Do melanocytes even deserve as much credit for UV protection as conventional wisdom attributes to them? In which interactions do these promiscuous cells engage with their immediate epithelial environment and who is controlling whom? What lessons might be distilled from looking at lower vertebrate melanophores and at extracutaneous melanocytes in the endeavour to reveal the 'secret identity' of melanocytes? The current Controversies feature explores these far too infrequently posed, biologically and clinically important questions. Complementing a companion viewpoint essay on malignant melanocytes (2), this critical re-examination of melanocyte biology provides a cornucopia of old, but under-appreciated concepts and novel ideas on the slowly emerging complexity of physiological melanocyte functions, and delineates important, thought-provoking questions that remain to be definitively answered by future research.
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Affiliation(s)
- P M Plonka
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, PL-30-387 Kraków, Poland.
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27
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Moresco RM, De Oliveira C. A Comparative Study of the Extracutaneous Pigmentary System in Three Anuran Amphibian Species Evaluated During the Breeding Season. SOUTH AMERICAN JOURNAL OF HERPETOLOGY 2009. [DOI: 10.2994/057.004.0101] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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28
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Ohlemiller KK, Rice MER, Lett JM, Gagnon PM. Absence of strial melanin coincides with age-associated marginal cell loss and endocochlear potential decline. Hear Res 2008; 249:1-14. [PMID: 19141317 DOI: 10.1016/j.heares.2008.12.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Revised: 12/15/2008] [Accepted: 12/16/2008] [Indexed: 11/20/2022]
Abstract
Cochlear stria vascularis contains melanin-producing intermediate cells that play a critical role in the production of the endocochlear potential (EP) and in maintaining the high levels of K(+) that normally exist in scala media. The melanin produced by intermediate cells can be exported to the intrastrial space, where it may be taken up by strial marginal cells and basal cells. Because melanin can act as an antioxidant and metal chelator, evidence for its role in protecting the stria and organ of Corti against noise, ototoxins, and aging has long been sought. While some evidence supports a protective role of melanin against noise and ototoxins, no evidence yet presented has demonstrated a clear role for melanin in maintaining the EP during aging. We tested this by comparing basal turn EPs and a host of cochlear cellular metrics in aging C57BL/6 (B6) mice and C57BL/6-Tyr(c-2J) mice. The latter mice carry a naturally occurring inactivating mutation of the tyrosinase locus, and produce no strial melanin. Because these two strains are coisogenic, and because pigmented B6 mice show essentially no age-related EP decline, they provide an ideal test of importance of melanin in the aging stria. Pigmented and albino B6 mice showed identical rates of hearing loss and sensory cell loss. However, after two years of age, basal turn EPs significantly diverged, with 42% of albinos showing EPs below 100 mV versus only 18% of pigmented mice. The clearest anatomical correlate of this EP difference was significantly reduced strial thickness in the albinos that was highly correlated with loss of marginal cells. Combined with findings in human temporal bones, plus recent work in BALB/c mice and gerbils, the present findings point to a common etiology in strial presbycusis whereby EP reduction is principally linked to marginal cell loss or dysfunction. For any individual, genetic background, environmental influences, and stochastic events may work together to determine whether marginal cell density or function falls below some critical level, and thus whether EP decline occurs.
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Affiliation(s)
- Kevin K Ohlemiller
- Fay and Carl Simons Center for the Biology of Hearing and Deafness/Central Institute for the Deaf at Washington University, St. Louis, MO, USA.
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Ohlemiller KK. Recent findings and emerging questions in cochlear noise injury. Hear Res 2008; 245:5-17. [PMID: 18790034 PMCID: PMC2610263 DOI: 10.1016/j.heares.2008.08.007] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Revised: 08/12/2008] [Accepted: 08/19/2008] [Indexed: 12/11/2022]
Affiliation(s)
- Kevin K Ohlemiller
- Fay and Carl Simons Center for the Biology of Hearing and Deafness, Central Institute for the Deaf at Washington University, Department of Otolaryngology, Washington University Medical School, St. Louis, MO 63110, USA.
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Uehara S, Izumi Y, Kubo Y, Wang CC, Mineta K, Ikeo K, Gojobori T, Tachibana M, Kikuchi T, Kobayashi T, Shibahara S, Taya C, Yonekawa H, Shiroishi T, Yamamoto H. Specific expression of Gsta4 in mouse cochlear melanocytes: a novel role for hearing and melanocyte differentiation. Pigment Cell Melanoma Res 2008; 22:111-9. [PMID: 18983533 DOI: 10.1111/j.1755-148x.2008.00513.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian pigment cells produce melanin as the main pigment. Melanocytes, one of the two types of mammalian pigment cells, differentiate from the neural crest and migrate to a variety of organs during development. Melanocytes exist not only in the skin but also in other sites such as the cochlea where they are essential for hearing. Mitf(mi-bw) is one of the known recessive alleles of the mouse microphthalmia-associated transcription factor (Mitf) locus, which is essential for the development of pigment cells. Homozygous Mitf(mi-bw)/Mitf(mi-bw) mice have a completely white coat with black eyes and are deaf due to the lack of melanocytes. By comparing gene expression profiles in cochleae of wild-type and Mitf(mi-bw)/Mitf(mi-bw) mice, we now demonstrate the specific expression of glutathione S-transferase alpha 4 (Gsta4) in the stria vascularis. Gsta4 encodes one of the cytosolic glutathione S-transferases (GSTs) which participate in detoxification processes of many tissues. This gene is specifically expressed in intermediate cells of the stria vascularis, suggesting a novel function for cochlear melanocytes. Moreover, among mammalian pigment cells, expression of Gsta4 was restricted to cochlear melanocytes, suggesting that melanocytes in various tissues differentiate from one another depending on their location.
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Affiliation(s)
- Shigeyuki Uehara
- Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
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Hong L, Simon JD. Current understanding of the binding sites, capacity, affinity, and biological significance of metals in melanin. J Phys Chem B 2007; 111:7938-47. [PMID: 17580858 PMCID: PMC2533804 DOI: 10.1021/jp071439h] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Metal chelation is often invoked as one of the main biological functions of melanin. In order to understand the interaction between metals and melanin, extensive studies have been carried out to determine the nature of the metal binding sites, binding capacity, and affinity. These data are central to efforts aimed at elucidating the role metal binding plays in determining the physical, structural, biological, and photochemical properties of melanin. This article examines the current state of understanding of this field.
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Affiliation(s)
- Lian Hong
- Department of Chemistry, Duke University, Durham, North Carolina 27708, USA
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Bush WD, Simon JD. Quantification of Ca(2+) binding to melanin supports the hypothesis that melanosomes serve a functional role in regulating calcium homeostasis. ACTA ACUST UNITED AC 2007; 20:134-9. [PMID: 17371440 DOI: 10.1111/j.1600-0749.2007.00362.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Calcium regulation in melanocytes affects numerous biological pathways including protecting the redox balance in the cell and regulating the supply of substrate, l-tyrosine, for melanogenesis. The pigment contained in the melanocytes, melanin, has been implicated in maintaining calcium homeostasis in the cell and is known to be involved with calcium ion regulation in the inner ear. Herein, the association constant for Ca(2+) binding to Sepia melanin is determined by isothermal titration calorimetry to be 3.3 (+/-0.2) x 10(3)/M. This value is comparable with other well-established intracellular calcium-binding proteins that serve to buffer calcium concentrations, lending further support to the hypothesis that melanosomes serve as intracellular mediators of calcium homeostasis in melanocytes. Using this binding constant and the data from a fluorescent Ca(2+) displacement assay, the pK(a) of the carboxyl group coordinated to Ca(2+) is determined to be 3.1 +/- 0.1.
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Affiliation(s)
- William D Bush
- Department of Chemistry, Duke University, Durham, NC, USA
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Martin HC, Schmidt CM, Boos HJ, Heinecke A, Dinnesen AG. Cisplatininduzierte Hörstörungen bei Kindern in Abhängigkeit von der Pigmentierung der Iris. HNO 2007; 55:489-96. [PMID: 17180696 DOI: 10.1007/s00106-006-1475-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
BACKGROUND Cisplatin is commonly used as a chemotherapeutic agent in the treatment of solid tumors. Ototoxicity is an important side-effect. Melanin in the inner ear either plays an otoprotective role or has a negative influence on hearing. The concentration of cochlear melanin correlates with its concentration in the iris. PATIENTS AND METHODS We retrospectively examined 65 children (37 males, 28 females, average age 7.5 years) treated with cisplatin at the University Clinic of Muenster, Germany. We checked whether their eye color could be inferred from the prevalence and extent of cisplatin-induced hearing loss. RESULTS We found a hearing loss of >20 dB in 29 light-eyed and in 21 dark-eyed patients. Seven light-eyed and eight dark-eyed patients did not suffer from hearing impairment. Using the chi(2)-test on these four parameters, we found no significant connection between iris pigmentation and the prevalence or extent of hearing loss, although light-eyed children (80.6%) suffered more from hearing loss than dark-eyed children (72.4%). After the end of therapy with cisplatin, the prevalence of hearing loss was 83.3% in children up to 6 years and 71.4% in children older than 6 years. The average cumulative dose of cisplatin was 372 mg/m(2) of body surface in children with hearing loss, compared to 390 mg/m(2) in children without hearing loss. CONCLUSION We found no significant correlation between iris pigmentation (eye color) and hearing loss. Cisplatin-induced hearing loss occurs frequently and requires repeated monitoring.
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Affiliation(s)
- H C Martin
- Klinik und Poliklinik für Phoniatrie und Pädaudiologie, Universitätsklinikum Münster, Kardinal-von-Galen-Ring 10, 48149, Münster, Deutschland.
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Ohlemiller KK, Gagnon PM. Genetic dependence of cochlear cells and structures injured by noise. Hear Res 2007; 224:34-50. [PMID: 17175124 PMCID: PMC1809471 DOI: 10.1016/j.heares.2006.11.005] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 11/06/2006] [Accepted: 11/09/2006] [Indexed: 10/23/2022]
Abstract
The acute and permanent effects of a single damaging noise exposure were compared in CBA/J, C57BL/6 (B6), and closely related strains of mice. Two hours of broadband noise (4-45 kHz) at 110 dB SPL led to temporary reduction in the endocochlear potential (EP) of CBA/J and CBA/CaJ (CBA) mice and acute cellular changes in cochlear stria vascularis and spiral ligament. For the same exposure, B6 mice showed no EP reduction and little of the pathology seen in CBA. Eight weeks after exposure, all mice showed a normal EP, but only CBA mice showed injury and cell loss in cochlear lateral wall, despite the fact that B6 sustained larger permanent threshold shifts. Examination of noise injury in B6 congenics carrying alternate alleles of genes encoding otocadherin (Cdh23), agouti protein, and tyrosinase (albinism) indicated that none of these loci can account for the strain differences observed. Examination of CBA x B6 F1 mice and N2 backcross mice to B6 further indicated that susceptibility to noise-related EP reduction and associated cell pathology are inherited in an autosomal dominant manner, and are established by one or a few large effect quantitative trait loci. Findings support a common genetic basis for an entire constellation of noise-related cochlear pathologies in cochlear lateral wall and spiral limbus. Even within species, cellular targets of acute and permanent cochlear noise injury may vary with genetic makeup.
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Affiliation(s)
- Kevin K Ohlemiller
- Department of Otolaryngology, Washington University School of Medicine, 660 S. Euclid, St. Louis, MO 63110, United States.
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Ohlemiller KK, Lett JM, Gagnon PM. Cellular correlates of age-related endocochlear potential reduction in a mouse model. Hear Res 2006; 220:10-26. [PMID: 16901664 DOI: 10.1016/j.heares.2006.06.012] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 06/18/2006] [Accepted: 06/30/2006] [Indexed: 01/09/2023]
Abstract
Age-related degeneration of cochlear stria vascularis and resulting reduction in the endocochlear potential (EP) are the hallmark features of strial presbycusis, one of the major forms of presbycusis, or age-related hearing loss (ARHL) (Schuknecht, H.F., 1964. Further observations on the pathology of presbycusis. Archives of Otolaryngology 80, 369-382; Schuknecht, H.F., 1993. Pathology of the Ear. Lea and Febiger, Philadelphia; Schuknecht, H.F., Gacek, M.R., 1993. Cochlear pathology in presbycusis. Annals of Otology, Rhinology and Laryngology 102, 1-16). It is unclear whether there are multiple forms of strial ARHL having different sequences of degenerative events and different risk factors. Human temporal bone studies suggest that the initial pathology usually affects strial marginal cells, then spreads to other strial cell types. While inheritance studies support a moderate genetic influence, no contributing genes have been identified. Establishment of mouse models of strial ARHL may promote the identification of underlying genes and gene/environment interactions. We have found that BALB/cJ mice show significant EP reduction by 19 months of age. The reduction only occurs in a subset of animals. To identify key anatomical correlates of the EP reduction, we compared several cochlear lateral wall metrics in BALBs with those in C57BL/6J (B6) mice, which show little EP reduction for ages up to 26 months. Among the measures obtained, marginal cell density and spiral ligament thickness were the best predictors of both the EP decline in BALBs, and EP stability in B6. Our results indicate that the sequence of strial degeneration in BALBs is like that suggested for humans. Additional strain comparisons we have performed suggest that genes governing strial melanin production do not play a role.
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Affiliation(s)
- Kevin K Ohlemiller
- Department of Otolaryngology, Washington University School of Medicine, 660 S. Euclid, Saint Louis, MO 63110, USA.
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Ohlemiller KK. Contributions of mouse models to understanding of age- and noise-related hearing loss. Brain Res 2006; 1091:89-102. [PMID: 16631134 DOI: 10.1016/j.brainres.2006.03.017] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 03/06/2006] [Accepted: 03/08/2006] [Indexed: 12/21/2022]
Abstract
Once an oddity, mice have become the most widely used hearing research model. Their value for research in noise-induced hearing loss (NIHL) stems from their high vulnerability to noise and reduced variance of results, made possible by genetic standardization. To research in age-related hearing loss (ARHL), they offer economies of small size and a short lifespan, both of which reduce housing costs. Inbred mouse strains show a wide range of noise sensitivities and rates of hearing loss with age. These can be studied using classical genetic analysis, as well as hypothesis-driven experiments utilizing genetic engineering. Through such investigations, presently 3 loci have been identified to date that contribute to NIHL, 10 that promote ARHL, and at least 6 loci that promote both. The types of genes involved implicate homeostatic and protective mechanisms as key to the appearance of either type of pathology and support a causal link between injury and some apparent ARHL. While the majority of mouse ARHL models examined most closely resemble sensory ARHL, recent work has identified mice possessing the essential characteristics of neural and strial ARHL. Using these models, it should be possible to identify genes and alleles that promote the major forms of ARHL and their combinations.
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Affiliation(s)
- Kevin K Ohlemiller
- Department of Otolaryngology, Washington University, 660 S. Euclid, St. Louis, MO 63110, USA.
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Sanchez Hanke M, Kief S, Leuwer R, Koch U, Moll I, Brandner JM. In vitro isolation and cell culture of vestibular inner ear melanocytes. Audiol Neurootol 2005; 10:191-200. [PMID: 15809498 DOI: 10.1159/000084840] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2004] [Accepted: 10/19/2004] [Indexed: 11/19/2022] Open
Abstract
INTRODUCTION Melanocytes of the membranous labyrinth of the inner ear have been described morphologically in various contexts. Nature and functions of these cells are as yet not completely clear, even though several hypotheses exist regarding the same. The limited knowledge is due in part to a lack of methods regarding in vitro cell culture. The aim of this study was to describe conditions for the successful cell culture of vestibular inner ear melanocytes (VIEM), to compare their growth properties with those of epidermal melanocytes, and to characterize them immunohistochemically. MATERIALS AND METHODS Membranous labyrinth cells from freshly slaughtered sheep were isolated, and melanocytes and fibroblasts subsequently cultured. In addition, melanocytes from the skin of the same sheep were cultured. Antibodies specific to tyrosinase, tyrosinase-related protein 1 (TRP-1/Mel-5), and melanoma-specific antigen A (Melan A) were used to analyze the cultured cells. RESULTS The proliferation of VIEM was retarded in comparison to epidermal melanocytes. After 14 days, VIEM began to proliferate for the first time, whereas epidermal melanocytes proliferated already after 7 days. In contrast to epidermal melanocytes, the culturing process of VIEM seemed to be dependent on the presence of fibroblasts, and VIEM often accumulated in the vicinity of fibroblasts forming three-dimensional clusters. Moreover, VIEM showed a higher ratio of highly pigmented cells with a round cell shape and small dendrites in comparison to epidermal melanocytes. Immunohistochemical techniques proved the VIEM to be positive for Melan A, TRP-1 and, in the majority of cases, also for tyrosinase. CONCLUSION We successfully cultured melanocytes of the inner ear vestibular labyrinth for the first time and demonstrated melanocytic characteristics of these cells. This accomplishment will provide the opportunity to investigate VIEM in more detail in future experiments.
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Affiliation(s)
- Marcos Sanchez Hanke
- Department of Otorhinolaryngology, Medical School, Hamburg University, DE-20246 Hamburg, Germany.
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Hoogduijn MJ, Cemeli E, Ross K, Anderson D, Thody AJ, Wood JM. Melanin protects melanocytes and keratinocytes against H2O2-induced DNA strand breaks through its ability to bind Ca2+. Exp Cell Res 2004; 294:60-7. [PMID: 14980501 DOI: 10.1016/j.yexcr.2003.11.007] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2003] [Revised: 11/10/2003] [Indexed: 10/26/2022]
Abstract
Reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) are produced in the skin under the influence of UV radiation. These compounds are highly reactive and can induce DNA lesions in epidermal cells. Melanin is considered to protect human skin against DNA damage by absorbing UV radiation. We have investigated whether melanin can, in addition, offer protection against the effects of H(2)O(2) in human melanocytes and HaCaT keratinocytes. In the present study, it was shown that 40 and 100 microM H(2)O(2) increased the number of DNA strand breaks as measured using the comet assay, in melanocytes of Caucasian origin. In melanocytes of the same origin in which melanin levels were increased by culturing in presence of 10 mM NH(4)Cl and elevated l-tyrosine, H(2)O(2)-induced DNA damage was reduced compared to that in control melanocytes. Similarly, HaCaT cells that were loaded with melanin were better protected against H(2)O(2)-induced DNA strand breaks than control HaCaT cells. These protective effects of melanin were mimicked by the intracellular Ca(2+)-chelator BAPTA. Thus, BAPTA reduced the level of H(2)O(2)-induced DNA strand breaks in melanocytes. Like BAPTA, melanin is known to be a potent chelator of Ca(2+) and this was confirmed in the present study. It was shown that melanin levels in melanocytic cells correlated directly with intracellular Ca(2+) binding capacity and, in addition, correlated inversely with H(2)O(2)-induced increases in intracellular Ca(2+). Our results show that melanin may have an important role in regulating intracellular Ca(2+) homeostasis and it is suggested that melanin protects against H(2)O(2)-induced DNA strand breaks in both melanocytes and keratinocytes and through its ability to bind Ca(2+).
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Affiliation(s)
- M J Hoogduijn
- Department of Biomedical Sciences, University of Bradford, Bradford, UK.
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Hoogduijn MJ, Smit NP, van der Laarse A, van Nieuwpoort AF, Wood JM, Thody AJ. Melanin has a role in Ca2+ homeostasis in human melanocytes. PIGMENT CELL RESEARCH 2003; 16:127-32. [PMID: 12622789 DOI: 10.1034/j.1600-0749.2003.00018.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We have examined whether melanin affects Ca2+ homeostasis in cultured normal human melanocytes. Intracellular Ca2+ concentrations ([Ca2+]i), were measured in four Caucasian and in three Negroid melanocyte cultures. Under resting conditions [Ca2+]i was around 100 nM in all cultures, but differences between cells within cultures were observed. All cultures responded to endothelin-1 (ET-1) with increases in [Ca2+]i and there were no differences between Caucasian and Negroid cultures. However, large differences in responses between cells within cultures were observed, indicating that melanocyte cultures are very heterogeneous. The addition of 2.5 mM CaCl2 to melanocytes kept in Ca2+-free medium resulted in rapid and transient increases in [Ca2+]i of up to 1500 nM. These increases were on average more than two times smaller in melanocyte cultures established from Negroid donors compared with Caucasian cultures. In addition, well melanized Caucasian melanocytes, cultured in the presence of 400 microM tyrosine and 10 mM NH4Cl, showed a reduced increase in cytoplasmic Ca2+ concentration upon the addition of extracellular Ca2+. The difference in maintaining Ca2+ homeostasis between poorly and well melanized melanocytes may be the result of the clearance of cytoplasmic Ca2+ into melanosomes and the greater capacity for this in the more pigmented melanocytes.
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Affiliation(s)
- M J Hoogduijn
- Department of Biomedical Sciences, University of Bradford, Bradford, UK
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Merchant SN, McKenna MJ, Baldwin CT, Milunsky A, Nadol JB. Otopathology in a case of type I Waardenburg's syndrome. Ann Otol Rhinol Laryngol 2001; 110:875-82. [PMID: 11558766 DOI: 10.1177/000348940111000913] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
We report a case of type I Waardenburg's syndrome that provides insight into the etiopathogenesis of sensorineural hearing loss (SNHL) in this syndrome. The subject, a 76-year-old woman with type I Waardenburg's syndrome (dystopia canthorum, heterochromia irides, and white hair), had congenital low-frequency SNHL in her right ear only, which had remained relatively stable throughout her life. Blood leukocyte DNA studies revealed a PAX-3 mutation with a 1 base pair C-to-A substitution in exon 5 at base 602. Light microscopic studies of the right cochlea showed intact neurosensory structures in only the lower basal turn, with the remainder of the cochlea showing absence of melanocytes, absence of stria vascularis, missing hair cells, dysmorphogenesis of the tectorial membrane, and lack of peripheral processes of the spiral ganglion cells. There was pathological alteration of the vestibular dark cells with marked reduction of melanocytes associated with these dark cells. The left inner ear was normal, with a full complement of neurosensory structures, including melanocytes. Because the PAX-3 gene is involved in neural crest development and melanocytes migrate from the neural crest to the ear, the findings in this case are consistent with the hypothesis that defective melanocyte migration or defective melanocyte function results in defective development of the stria vascularis (and perhaps other structures of the ear), leading to SNHL.
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Affiliation(s)
- S N Merchant
- Department of Otology and Laryngology, Harvard Medical School, Boston, Massachusetts, USA
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Gill SS, Salt AN. Quantitative differences in endolymphatic calcium and endocochlear potential between pigmented and albino guinea pigs. Hear Res 1997; 113:191-7. [PMID: 9387998 DOI: 10.1016/s0378-5955(97)00141-x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A number of previous studies have suggested that melanin may play a role in Ca2+ homeostasis of endolymph. In the present study, endolymph Ca2+ levels and endocochlear potential (EP) were measured in all four cochlear turns of pigmented or albino guinea pigs. Auditory sensitivity was also evaluated using cochlear action potential (AP) thresholds. In pigmented animals we found that endolymph Ca2+ tended to increase from base to apex of the cochlea, while EP systematically decreased towards the apex. In contrast, no significant Ca2+ gradient was found in albinos and the EP decline was far less. As a result, the apical turn of albino animals had significantly lower Ca2+ and significantly higher EP than in pigmented animals. AP thresholds pooled across all test frequencies were significantly lower in albino animals although no differences at individual frequencies reached significance. Even after correction for EP differences, the endolymph Ca2+ levels in albino animals were significantly lower than in pigmented ones. These results confirm that there are significant physiologic differences between pigmented and albino animals, which are a likely consequence of the absence of melanin in the albino cochlea. They are consistent with the involvement of melanin in the active transport of Ca2+ into endolymph.
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Affiliation(s)
- S S Gill
- Department of Otolaryngology, Washington University School of Medicine, St. Louis, MO 63110, USA
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Benedito E, Jiménez-Cervantes C, Pérez D, Cubillana JD, Solano F, Jiménez-Cervantes J, Meyer zum Gottesberge AM, Lozano JA, García-Borrón JC. Melanin formation in the inner ear is catalyzed by a new tyrosine hydroxylase kinetically and structurally different from tyrosinase. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1336:59-72. [PMID: 9271251 DOI: 10.1016/s0304-4165(97)00011-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Detergent solubilized extracts of the cochleae of adult gerbils (Meriones unguiculatus) contain a tyrosine hydroxylase activity measurable by the radiometric method of Pomerantz. This activity is not related to Fenton-type reactions, since it is not inhibited by free radical scavengers and is heat and protease sensitive. It does not appear to be related to a peroxidase (EC 1.11.1.7) since it is neither dependent on H2O2, nor inhibited by catalase (EC 1.11.1.6). The involvement of a tyrosine hydroxylase (EC 1.14.16.2) related to catecholamine synthesis is also unlikely, since the activity is highly sensitive to 2-mercaptoethanol and is not increased by addition of tetrahydrobiopterin. The activity in crude inner ear extracts displayed an unusual maturation behaviour, with a slow activation upon aging at 4 degrees C. Fully active enzyme displayed Michaelis-Menten kinetics, with a Km for L-tyrosine of 47 microM. Cochlear tyrosine hydroxylase, but not melanoma tyrosinase (EC 1.14.18.1), was inhibited by o-phenanthroline, and was not dependent on L-DOPA as cofactor for full enzymatic activity. Crude extracts were also able to catalyze L-DOPA oxidation and melanin formation from either L-tyrosine or L-DOPA. The tyrosine hydroxylase, DOPA oxidase and melanin formation activities most probably resided in the same molecule, as suggested by inhibition studies. A tyrosine hydroxylase and melanin formation activity with identical properties was found in primary cultures of stria vascularis melanocytes. Immunochemical evidence confirmed the absence of either the tyrosinase encoded for by the albino locus, or the tyrosinase isoenzyme TRP1, encoded for by the brown locus. Conversely, an immunorreactive band of molecular weight 70 kDa was specifically recognized by a tyrosinase polyclonal antiserum in Western blot experiments. These results prove that melanogenesis in the cochlea, and likely in other extracutaneous locations such as the brain, is catalyzed by enzymatic systems different from, but related to tyrosinase.
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Affiliation(s)
- E Benedito
- Department of Biochemistry and Molecular Biology, School of Medicine, University of Murcia, Espinardo, Spain
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Escobar C, Zuasti A, Ferrer C, Garcia-Ortega F. Melanocytes in the stria vascularis and vestibular labyrinth of the Mongolian gerbil (Meriones unguiculatus). PIGMENT CELL RESEARCH 1995; 8:271-8. [PMID: 8789202 DOI: 10.1111/j.1600-0749.1995.tb00674.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Inner ear melanocytes are mainly present in the cochlea, vestibular organ, and endolymphatic sac, but their exact biological function has not been determined. In this investigation, we study the pigment cells in the membranous labyrinth of the gerbil. The inner ear melanocytes of M. unguiculatus show an irregular dendritic shape with cytoplasmic processes. These cells are disposed following the distribution of strial marginal and vestibular dark cells that have an important metabolic activity. Gerbil inner ear melanocytes are characterized by the presence of melanosomes, which are homogeneously dense organelles, of variable size and shape, that are surrounded by a membrane. In these cells, the Golgi apparatus plays a important role in melanin synthesis. When melanocytes were incubated in L-DOPA solution, the vesicles and cisterns of the Golgi apparatus exhibited a positive tyrosinase reaction. An interesting observation is the relation between melanocytes and inner ear capillaries. Sometimes, near to sensory vestibular areas, the melanocytes were in contact with Schwann cells and with myelinated fibres of vestibular nerve. The ultrastructural findings of this investigation are consistent with the hypothesis that melanocytes may have functional significance in the inner ear.
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Affiliation(s)
- C Escobar
- Department of Cell Biology, Medical School Murcia, Spain
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Masuda M, Yamazaki K, Kanzaki J, Hosoda Y. Ultrastructural evidence of cell communication between epithelial dark cells and melanocytes in vestibular organs of the human inner ear. Anat Rec (Hoboken) 1995; 242:267-77. [PMID: 7668412 DOI: 10.1002/ar.1092420217] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
BACKGROUND The possibility of interaction between epithelial dark cells and melanocytes in the mammalian inner ear has been pointed out because of their morphological and biochemical characteristics, although very few studies have dealt directly with communication between these two types of cells. We investigated the dark cell area of human vestibular organs in order to clarify the ultrastructural evidence for cell interaction between epithelial dark cells and melanocytes. METHODS All of the material was obtained from vestibular schwannoma operations. Paraffin sections were stained with hematoxylin and eosin (H&E) and by the Fontana-Masson technique. Other paraffin sections were also stained immunohistochemically for S-100 protein. Glutaraldehyde fixed specimens were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). RESULTS Light microscopy revealed melanin pigment granules in the cytoplasm of epithelial dark cells. Melanocytes in the subepithelial layer stained positively for S-100 protein. The presence of intraepithelial melanocytes was confirmed by the presence of cell profiles with a large number of melanin pigment granules and S-100 protein in the cytoplasm. SEM showed that the dark cells had a pentagonal surface with microvilli on the apical surface edge. They had complicated structures at the basal portion of their cytoplasm. Melanocytes extending cytoplasmic processes to adjacent areas were observed under the dark cells. TEM showed that the dark cells were tightly linked by junctional complexes in the upper lateral portion of their cytoplasmic membrane and interdigitated by lateral infoldings. Compound melanosomes (phagosomes or secondary lysosomes) found in the cytoplasm of the dark cells contained poorly pigmented melanosomes with a periodic internal structure. Gap junctions were clearly showed between adjacent melanocytes in the subepithelial layer. CONCLUSIONS The characteristic substructures of dark cells and melanocytes suggested the presence of intimate cell interaction between these two types of cells in the vestibular organs of the human inner ear, although it is not clear at this stage whether such cell interaction is specific only for patients with vestibular schwannoma. Dark cells and melanocytes form a cell community that serves to maintain homeostasis in vestibular organs through communication in which cell information obtained by both dark cells and melanocytes serves to facilitate the system.
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Affiliation(s)
- M Masuda
- Department of Otorhinolaryngology, Keio University School of Medicine, Tokyo, Japan
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Peters TA, Kuijpers W, Tonnaer EL, van Muijen GN, Jap PH. Distribution and features of melanocytes during inner ear development in pigmented and albino rats. Hear Res 1995; 85:169-80. [PMID: 7559172 DOI: 10.1016/0378-5955(95)00043-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
In this developmental study, the distribution and features of melanocytes in the inner ear of pigmented and albino rats was investigated with the use of an antibody, which specifically reacts with a melanocyte differentiation antigen present in the membranes of (pre)melanosomes. Melanocyte precursors could be traced from 13 days post conception onwards and the course was followed to their targets in the inner ear. Melanocytes which settle in the modiolus appeared to reach their target along another pathway than strial and vestibular melanocytes. No difference was observed in the melanocyte distribution between pigmented and albino rats. The integration of melanocytes into the stria vascularis was associated with an increased rate of melanosome production in both strains, but in the albinos far fewer melanosomes were produced. After the stria had reached maturity, melanosome production was arrested and melanosomes were subject to lysosomal digestion. In the stria of the pigmented rats, cells with aggregations of disintegrating melanosomes appeared and persisted into adulthood. In the adult, the majority of the intermediate cells contained only a few scattered melanosomes, while melanosomes could only rarely be detected in the albinos. These observations indicate that there is a close relationship between melanosome production and the process of interdigitation of melanocytes with the marginal cells. It seems unlikely that melanosomes or melanin make any important contribution to the function of the adult stria vascularis. Outside the stria, the features of melanocytes in both strains were similar to skin melanocytes.
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Affiliation(s)
- T A Peters
- Department of Otorhinolaryngology, University of Nijmegen, The Netherlands
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Meyer zum Gottesberge A. Calcium dependent intercellular interaction of the neural crest derivate-melanocytes and the epithelial cells of the vestibular organ. ACTA OTO-LARYNGOLOGICA. SUPPLEMENTUM 1995; 520 Pt 2:360-1. [PMID: 8749161 DOI: 10.3109/00016489509125270] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
As recently established in several species, the presence of neural crest derivate-melanocytes is essential for the development of the epithelial cells regulating the ion and the potential gradients in the inner ear. The interaction between the melanocytes and the epithelial cells appears to be activated when intracellular Ca2+ increases. This may be due to a disturbance of the Ca2+ homeostasis under hydropic conditions or to the effect of the Ca-ionophore (A 23187) or hormone (alpha-MSH). Lowering of extracellular Ca2+ blocked the effect of the drug at the basal level. The interaction of the melanocytes with the epithelial or endothelial cells differs significantly. It is indicated that melanocytes may be under hormonal control and that their activation and intercellular interaction are related to the increase of intracellular Ca2+ and may be controlled by extracellular Ca2+. Furthermore, we propose that melanocytes provide a regulatory network for the maintenance of the inner ear homeostasis.
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Kitamura K, Sakagami M, Umemoto M, Takeda N, Doi K, Kasugai T, Kitamura Y. Strial dysfunction in a melanocyte deficient mutant rat (Ws/Ws rat). Acta Otolaryngol 1994; 114:177-81. [PMID: 8203200 DOI: 10.3109/00016489409126038] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A homozygous mutant rat at the white spotting (Ws) locus showing a deficiency of melanocytes has recently been found (4, 5). The function and morphology of the inner ear of the Ws/Ws rat were examined by auditory brainstem response (ABR), endocochlear DC potential (EP), and electron microscopy. The mean ABR threshold of the Ws/Ws rat was significantly higher than that of the control +/+ rat. Most Ws/Ws rats showed no or very little EP. In electron microscopy, the stria vascularis of the Ws/Ws rat proved to be very thin and flat with poor interdigitation of marginal cells, and absence of intermediate cells. The organ of Corti appeared to be intact in both the +/+ rat and the Ws/Ws rat. These electrophysiological and morphological findings suggest that the Ws/Ws rat suffered from severe hearing loss caused by strial dysfunction.
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Affiliation(s)
- K Kitamura
- Department of Otolaryngology, Osaka University Medical School, Japan
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Conlee JW, Gerity LC, Westenberg IS, Creel DJ. Pigment-dependent differences in the stria vascularis of albino and pigmented guinea pigs and rats. Hear Res 1994; 72:108-24. [PMID: 8150728 DOI: 10.1016/0378-5955(94)90211-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Functional models of the stria vascularis (SV) have ascribed roles for the marginal and basal cells, but not for the intermediate cells, which remain poorly understood. Intermediate cells have been identified as melanocytes, which produce melanin in most pigmented animals including humans. The relationship of melanin to intermediate cell function may be addressed through comparisons with the albino inner ear. Albinos have a normal distribution of melanocytes that are unable to synthesize melanin pigment. In the present study, the SV was compared between albino and pigmented littermates in both the guinea pig and the rat. Photomicrographic montages of the SV were analyzed from each of 7 cochlear regions in the guinea pig and 5 regions in the rat. Stereological procedures were used to determine the volume density (Vv) for each of the three main cell types in the stria, the surface density (Sv) of the marginal cells, and to derive estimates of absolute cell volume and surface area. In the guinea pig, comparisons between pigment groups showed that marginal cell Vv was larger across cochlear turns in the albinos, while intermediate cell Vv was smaller. Intermediate cell cytoplasmic and total cell volumes were smaller in the albino guinea pigs; however, marginal cell Sv and absolute area were larger. In the rat, intermediate cell Vv was alos smaller across cochlear turns in the albinos. Similarly, intermediate cell cytoplasmic and total cell volumes were smaller in the albinos, while marginal cell total surface area per radial cross-section of the SV was larger. These results demonstrate that amelanotic melanocytes occupy significantly less volume than do pigmented melanocytes, and suggest that melanin may influence the structure and function of the SV.
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Affiliation(s)
- J W Conlee
- University of Utah School of Medicine, Department of Anatomy, Salt Lake City 84132
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Felix H, de Fraissinette A, Johnsson LG, Gleeson MJ. Morphological features of human Reissner's membrane. Acta Otolaryngol 1993; 113:321-5. [PMID: 8517135 DOI: 10.3109/00016489309135817] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Light and electromicroscopic investigations of Reissner's membrane were undertaken on 10 cochleae from 6 patients with normal hearing for their age. The membrane consisted of two layers, an epithelium and a mesothelium separated by a basement membrane. The mesothelium was formed by a single thin layer which was intermittently discontinuous. The melanocytes were localized on the mesothelial side of the basement membrane. Their numbers was 2-4 times greater in the upper half of the basal turn and in the middle turn than elsewhere. The epithelium was much thicker and had more irregular features than the mesothelium. It was composed of two types of epithelial cells, flat and rounded. The flat cells were more regular in shape than the rounded cells and they were mainly distributed in the middle and apical turns. Judging from their structure they were in a resting state. The rounded cells covered a smaller area than the flat ones and had numerous microvilli. They assumed three different shapes, cuboidal, spindle-form and spherical and were arranged in four different patterns, namely bands, strands, whorls and clusters. The rounded cells were the most active according to the composition of the cytoplasm and dominated the cell population in the hook and the lower half of the basal turn where the age-related sensorineural degeneration is most apparent.
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Affiliation(s)
- H Felix
- ENT Department, University Hospital, Zürich, Switzerland
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