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Shim M, Yi J, Pak JH, Chung JW. Zinc deficiency triggers hearing loss by reducing ribbon synapses of inner hair cells in CBA/N mice. Biochem Biophys Res Commun 2024; 693:149396. [PMID: 38118309 DOI: 10.1016/j.bbrc.2023.149396] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2023] [Accepted: 12/15/2023] [Indexed: 12/22/2023]
Abstract
Zinc plays a vital role in our metabolism, encompassing antioxidant regulation, immune response, and auditory function. Several studies have reported that zinc levels correlate with hearing loss. We have previously demonstrated that the auditory brainstem response (ABR) threshold increased in mice fed a zinc-deficient diet. However, the effects of zinc deficiency on hearing were not fully elucidated. The present study investigated whether zinc deficiency affects hearing in association with neuronal components or cochlear structures. CBA/N mice were fed a normal or zinc-deficient diet for 8 weeks and assessed for ABR and distortion product otoacoustic emissions (DPOAE). The cochlear sections were stained with hematoxylin and eosin solution. Also, we observed the expression of synaptic ribbons, neurofilaments, and alpha-synuclein (α-Syn). The 8-week zinc-deficient diet mice had an elevated ABR threshold but no changed DPOAE threshold or cochlear structures. A reduced number of synaptic ribbons of inner hair cells (IHCs) and impaired efferent nerve fibers were observed in the zinc-deficient diet mice. The number of outer hair cells (OHCs) and expression of α-Syn remained unchanged. Our results suggest that zinc-mediated hearing loss is associated with the loss of neuronal components of IHCs.
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Affiliation(s)
- Myungjoo Shim
- Department of Otorhinolaryngology, University of Ulsan Graduate School, Seoul, South Korea
| | - Junyeong Yi
- Department of Otorhinolaryngology-Head and Neck Surgery, AMIST, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea; Department of Otorhinolaryngology-Head and Neck Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Jhang Ho Pak
- Department of Biochemistry, University of Ulsan College of Medicine and Asan Institute for Life Sciences, Asan Medical Center, Seoul, South Korea
| | - Jong Woo Chung
- Department of Otorhinolaryngology-Head and Neck Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea.
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Cima Cabal MD, Molina F, López-Sánchez JI, Pérez-Santín E, Del Mar García-Suárez M. Pneumolysin as a target for new therapies against pneumococcal infections: A systematic review. PLoS One 2023; 18:e0282970. [PMID: 36947540 PMCID: PMC10032530 DOI: 10.1371/journal.pone.0282970] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 02/28/2023] [Indexed: 03/23/2023] Open
Abstract
BACKGROUND This systematic review evaluates pneumolysin (PLY) as a target for new treatments against pneumococcal infections. Pneumolysin is one of the main virulence factors produced by all types of pneumococci. This toxin (53 kDa) is a highly conserved protein that binds to cholesterol in eukaryotic cells, forming pores that lead to cell destruction. METHODS The databases consulted were MEDLINE, Web of Science, and Scopus. Articles were independently screened by title, abstract, and full text by two researchers, and using consensus to resolve any disagreements that occurred. Articles in other languages different from English, patents, cases report, notes, chapter books and reviews were excluded. Searches were restricted to the years 2000 to 2021. Methodological quality was evaluated using OHAT framework. RESULTS Forty-one articles describing the effects of different molecules that inhibit PLY were reviewed. Briefly, the inhibitory molecules found were classified into three main groups: those exerting a direct effect by binding and/or blocking PLY, those acting indirectly by preventing its effects on host cells, and those whose mechanisms are unknown. Although many molecules are proposed as toxin blockers, only some of them, such as antibiotics, peptides, sterols, and statins, have the probability of being implemented as clinical treatment. In contrast, for other molecules, there are limited studies that demonstrate efficacy in animal models with sufficient reliability. DISCUSSION Most of the studies reviewed has a good level of confidence. However, one of the limitations of this systematic review is the lack of homogeneity of the studies, what prevented to carry out a statistical comparison of the results or meta-analysis. CONCLUSION A panel of molecules blocking PLY activity are associated with the improvement of the inflammatory process triggered by the pneumococcal infection. Some molecules have already been used in humans for other purposes, so they could be safe for use in patients with pneumococcal infections. These patients might benefit from a second line treatment during the initial stages of the infection preventing acute respiratory distress syndrome and invasive pneumococcal diseases. Additional research using the presented set of compounds might further improve the clinical management of these patients.
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Affiliation(s)
- María Dolores Cima Cabal
- Escuela Superior de Ingeniería y Tecnología (ESIT), Universidad Internacional de La Rioja, UNIR, Logroño, La Rioja, Spain
| | - Felipe Molina
- Genética, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain
| | - José Ignacio López-Sánchez
- Escuela Superior de Ingeniería y Tecnología (ESIT), Universidad Internacional de La Rioja, UNIR, Logroño, La Rioja, Spain
| | - Efrén Pérez-Santín
- Escuela Superior de Ingeniería y Tecnología (ESIT), Universidad Internacional de La Rioja, UNIR, Logroño, La Rioja, Spain
| | - María Del Mar García-Suárez
- Escuela Superior de Ingeniería y Tecnología (ESIT), Universidad Internacional de La Rioja, UNIR, Logroño, La Rioja, Spain
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Missner AA, Johns JD, Gu S, Hoa M. Repurposable Drugs That Interact with Steroid Responsive Gene Targets for Inner Ear Disease. Biomolecules 2022; 12:1641. [PMID: 36358991 PMCID: PMC9687275 DOI: 10.3390/biom12111641] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 10/25/2022] [Accepted: 11/02/2022] [Indexed: 10/28/2023] Open
Abstract
Corticosteroids, oral or transtympanic, remain the mainstay for inner ear diseases characterized by hearing fluctuation or sudden changes in hearing, including sudden sensorineural hearing loss (SSNHL), Meniere's disease (MD), and autoimmune inner ear disease (AIED). Despite their use across these diseases, the rate of complete recovery remains low, and results across the literature demonstrates significant heterogeneity with respect to the effect of corticosteroids, suggesting a need to identify more efficacious treatment options. Previously, our group has cross-referenced steroid-responsive genes in the cochlea with published single-cell and single-nucleus transcriptome datasets to demonstrate that steroid-responsive differentially regulated genes are expressed in spiral ganglion neurons (SGN) and stria vascularis (SV) cell types. These differentially regulated genes represent potential druggable gene targets. We utilized multiple gene target databases (DrugBank, Pharos, and LINCS) to identify orally administered, FDA approved medications that potentially target these genes. We identified 42 candidate drugs that have been shown to interact with these genes, with an emphasis on safety profile, and tolerability. This study utilizes multiple databases to identify drugs that can target a number of druggable genes in otologic disorders that are commonly treated with steroids, providing a basis for establishing novel repurposing treatment trials.
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Affiliation(s)
| | - James Dixon Johns
- Department of Otolaryngology-Head and Neck Surgery, Georgetown University Medical Center, Washington, DC 20007, USA
| | - Shoujun Gu
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
| | - Michael Hoa
- Department of Otolaryngology-Head and Neck Surgery, Georgetown University Medical Center, Washington, DC 20007, USA
- Auditory Development and Restoration Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA
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Hossain KFB, Hosokawa T, Saito T, Kurasaki M. Zinc-pretreatment triggers glutathione and Nrf2-mediated protection against inorganic mercury-induced cytotoxicity and intrinsic apoptosis in PC12 cells. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2021; 207:111320. [PMID: 32947215 DOI: 10.1016/j.ecoenv.2020.111320] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 09/06/2020] [Accepted: 09/09/2020] [Indexed: 06/11/2023]
Abstract
Mercury (Hg) is a hazardous metal, poses environmental problems with severe human health effects; whereas zinc (Zn) is an essential micronutrient with antioxidant properties. The purpose of this research was to investigate the effect of Zn on inorganic Hg-induced cytotoxicity in the PC12 cells. The cells were treated with HgCl2 (5 μM) for 48 h with/without 1 h prior ZnCl2-treatment (100 μM) and deliberated for further analysis. After 48 h of incubation with only Hg2+, the cell showed reduced cell viability, compromised cell membrane, DNA degradation, depleted glutathione level, ROS generation and drastically increased apoptosis. Subsequently, Hg2+-treated cells demonstrated a significant downregulation of akt, mTOR, ERK1, Nrf2, HO1, Bcl-2, Bcl-xL, and upregulation of p53, Bax, cytochrome c and cleaved caspase 3, indicating intrinsic apoptosis induction. However, cells pretreated with Zn2+ before Hg2+-exposure showed a significant improvement in cell viability, cell membrane, DNA damage, glutathione level, ROS amount and apoptotic cells, with a significant upregulation in mTOR, akt, ERK1, Nrf2, HO1, Bcl-2 and Bcl-xL, and downregulation in p53, Bax, cytochrome c and cleaved caspase 3, indicating inhibition of apoptosis. The findings suggested that Zn2+-pretreatment not only improves glutathione content but also induces activation of Nrf2-HO1 pathway, which would tend to suppress Hg-cytotoxicity.
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Affiliation(s)
| | - Toshiyuki Hosokawa
- Institute for the Advancement of Higher Education, Hokkaido University, Sapporo, 060-0817, Japan
| | - Takeshi Saito
- Faculty of Health Sciences, Hokkaido University, Sapporo, 060-0812, Japan
| | - Masaaki Kurasaki
- Graduate School of Environmental Science, Hokkaido University, Sapporo, 060-0810, Japan; Faculty of Environmental Earth Science, Hokkaido University, Sapporo, 060-0810, Japan
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Hupp S, Ribes S, Seele J, Bischoff C, Förtsch C, Maier E, Benz R, Mitchell TJ, Nau R, Iliev AI. Magnesium therapy improves outcome in Streptococcus pneumoniae meningitis by altering pneumolysin pore formation. Br J Pharmacol 2017; 174:4295-4307. [PMID: 28888095 DOI: 10.1111/bph.14027] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 08/26/2017] [Accepted: 08/29/2017] [Indexed: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE Streptococcus pneumoniae is the most common cause of bacterial meningitis in adults and is characterized by high lethality and substantial cognitive disabilities in survivors. Here, we have studied the capacity of an established therapeutic agent, magnesium, to improve survival in pneumococcal meningitis by modulating the neurological effects of the major pneumococcal pathogenic factor, pneumolysin. EXPERIMENTAL APPROACH We used mixed primary glial and acute brain slice cultures, pneumolysin injection in infant rats, a mouse meningitis model and complementary approaches such as Western blot, a black lipid bilayer conductance assay and live imaging of primary glial cells. KEY RESULTS Treatment with therapeutic concentrations of magnesium chloride (500 mg·kg-1 in animals and 2 mM in cultures) prevented pneumolysin-induced brain swelling and tissue remodelling both in brain slices and in animal models. In contrast to other divalent ions, which diminish the membrane binding of pneumolysin in non-therapeutic concentrations, magnesium delayed toxin-driven pore formation without affecting its membrane binding or the conductance profile of its pores. Finally, magnesium prolonged the survival and improved clinical condition of mice with pneumococcal meningitis, in the absence of antibiotic treatment. CONCLUSIONS AND IMPLICATIONS Magnesium is a well-established and safe therapeutic agent that has demonstrated capacity for attenuating pneumolysin-triggered pathogenic effects on the brain. The improved animal survival and clinical condition in the meningitis model identifies magnesium as a promising candidate for adjunctive treatment of pneumococcal meningitis, together with antibiotic therapy.
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Affiliation(s)
- Sabrina Hupp
- Institute of Anatomy, University of Bern, Bern, Switzerland.,DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Sandra Ribes
- Department of Neuropathology, University Medical Center Göttingen, Göttingen, Germany.,Department of Geriatrics, Evangelisches Krankenhaus Göttingen-Weende, Göttingen, Germany
| | - Jana Seele
- Department of Neuropathology, University Medical Center Göttingen, Göttingen, Germany.,Department of Geriatrics, Evangelisches Krankenhaus Göttingen-Weende, Göttingen, Germany
| | - Carolin Bischoff
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Christina Förtsch
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Elke Maier
- Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Roland Benz
- Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
| | - Timothy J Mitchell
- Institute of Microbiology and Infection, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
| | - Roland Nau
- Department of Neuropathology, University Medical Center Göttingen, Göttingen, Germany.,Department of Geriatrics, Evangelisches Krankenhaus Göttingen-Weende, Göttingen, Germany
| | - Asparouh I Iliev
- Institute of Anatomy, University of Bern, Bern, Switzerland.,DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Würzburg, Germany
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Hellwig D, Voigt J, Bouzani M, Löffler J, Albrecht-Eckardt D, Weber M, Brunke S, Martin R, Kurzai O, Hünniger K. Candida albicans Induces Metabolic Reprogramming in Human NK Cells and Responds to Perforin with a Zinc Depletion Response. Front Microbiol 2016; 7:750. [PMID: 27242763 PMCID: PMC4872603 DOI: 10.3389/fmicb.2016.00750] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2015] [Accepted: 05/03/2016] [Indexed: 12/27/2022] Open
Abstract
As part of the innate immune system, natural killer (NK) cells are directly involved in the response to fungal infections. Perforin has been identified as the major effector molecule acting against many fungal pathogens. While several studies have shown that perforin mediated fungicidal effects can contribute to fungal clearance, neither the activation of NK cells by fungal pathogens nor the effects of perforin on fungal cells are well-understood. In a dual approach, we have studied the global gene expression pattern of primary and cytokine activated NK cells after co-incubation with Candida albicans and the transcriptomic adaptation of C. albicans to perforin exposure. NK cells responded to the fungal pathogen with an up-regulation of genes involved in immune signaling and release of cytokines. Furthermore, we observed a pronounced increase of genes involved in glycolysis and glycolysis inhibitor 2-deoxy-D-glucose impaired C. albicans induced NK cell activation. This strongly indicates that metabolic adaptation is a major part of the NK cell response to C. albicans infections. In the fungal pathogen, perforin induced a strong up-regulation of several fungal genes involved in the zinc depletion response, such as PRA1 and ZRT1. These data suggest that fungal zinc homeostasis is linked to the reaction to perforin secreted by NK cells. However, deletion mutants in PRA1 and ZRT1 did not show altered susceptibility to perforin.
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Affiliation(s)
- Daniela Hellwig
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
| | - Jessica Voigt
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
| | - Maria Bouzani
- Medizinische Klinik und Poliklinik II, Universitätsklinikum Würzburg Würzburg, Germany
| | - Jürgen Löffler
- Medizinische Klinik und Poliklinik II, Universitätsklinikum Würzburg Würzburg, Germany
| | | | - Michael Weber
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
| | - Sascha Brunke
- Department Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute Jena, Germany
| | - Ronny Martin
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
| | - Oliver Kurzai
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
| | - Kerstin Hünniger
- Septomics Research Center, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute and Friedrich Schiller University Jena, Germany
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Singla N, Dhawan DK. Influence of Zinc on Calcium-Dependent Signal Transduction Pathways During Aluminium-Induced Neurodegeneration. Mol Neurobiol 2014; 50:613-25. [DOI: 10.1007/s12035-014-8643-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 01/13/2014] [Indexed: 11/29/2022]
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Shafeeq S, Kuipers OP, Kloosterman TG. The role of zinc in the interplay between pathogenic streptococci and their hosts. Mol Microbiol 2013; 88:1047-57. [DOI: 10.1111/mmi.12256] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/06/2013] [Indexed: 12/26/2022]
Affiliation(s)
- Sulman Shafeeq
- Department of Molecular Genetics; Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 7; 9747 AG; Groningen; the Netherlands
| | - Oscar P. Kuipers
- Department of Molecular Genetics; Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 7; 9747 AG; Groningen; the Netherlands
| | - Tomas G. Kloosterman
- Department of Molecular Genetics; Groningen Biomolecular Sciences and Biotechnology Institute; University of Groningen; Nijenborgh 7; 9747 AG; Groningen; the Netherlands
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Abstract
This study investigated the effect of a zinc-deficient diet on the hearing in CBA mice and aimed to verify whether this hearing change is reversible by supplementation of zinc afterwards. We assessed hearing through an auditory brainstem response (ABR) with tone burst stimulation in 4, 8, 16, and 32 kHz and distortion product otoacoustic emissions in 5.6, 8, 11.3, and 16 kHz every week. The ABR threshold started to increase after 4 weeks on a zinc-deficient diet. The difference in the threshold between control and zinc-deficient animals became greater over time and plateaued at about 6 weeks. The ABR threshold differences between control and zinc-deficient mice were greater at higher frequencies. Four weeks of normal diet, following 8 weeks of a zinc-deficient diet, restored the ABR threshold to normal at all measured frequencies. Zinc-deficient mice did not show any distortion product otoacoustic emission threshold change at all frequencies. This finding suggests that a zinc-deficient diet increased the ABR threshold in CBA mice and a zinc-adequate diet restored the ABR threshold to normal.
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Wippel C, Förtsch C, Hupp S, Maier E, Benz R, Ma J, Mitchell TJ, Iliev AI. Extracellular calcium reduction strongly increases the lytic capacity of pneumolysin from streptococcus pneumoniae in brain tissue. J Infect Dis 2011; 204:930-6. [PMID: 21849290 PMCID: PMC3156923 DOI: 10.1093/infdis/jir434] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Streptococcus pneumoniae causes serious diseases such as pneumonia and meningitis. Its major pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, which produces lytic pores at high concentrations. At low concentrations, it has other effects, including induction of apoptosis. Many cellular effects of pneumolysin appear to be calcium dependent. METHODS Live imaging of primary mouse astroglia exposed to sublytic amounts of pneumolysin at various concentrations of extracellular calcium was used to measure changes in cellular permeability (as judged by lactate dehydrogenase release and propidium iodide chromatin staining). Individual pore properties were analyzed by conductance across artificial lipid bilayer. Tissue toxicity was studied in continuously oxygenated acute brain slices. RESULTS The reduction of extracellular calcium increased the lytic capacity of the toxin due to increased membrane binding. Reduction of calcium did not influence the conductance properties of individual toxin pores. In acute cortical brain slices, the reduction of extracellular calcium from 2 to 1 mM conferred lytic activity to pathophysiologically relevant nonlytic concentrations of pneumolysin. CONCLUSIONS Reduction of extracellular calcium strongly enhanced the lytic capacity of pneumolysin due to increased membrane binding. Thus, extracellular calcium concentration should be considered as a factor of primary importance for the course of pneumococcal meningitis.
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Affiliation(s)
- Carolin Wippel
- DFG Membrane/Cytoskeleton Interaction Group, Institute of Pharmacology and Toxicology & Rudolf Virchow Center for Experimental Medicine, University of Würzburg, Germany
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Zinc in the treatment of idiopathic sudden sensorineural hearing loss. Laryngoscope 2010; 121:617-21. [DOI: 10.1002/lary.21291] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2010] [Indexed: 11/07/2022]
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Abstract
HYPOTHESIS Two Streptococcus pneumoniae proteins, pneumococcal surface protein A (PspA) and pneumolysin (Ply), have functional and histopathologic effects on the inner ear. BACKGROUND Temporary or permanent sensorineural hearing loss is known to be a sequela of pneumococcal otitis media. Several pneumococcal proteins such as PspA and Ply have been shown to contribute to the pathogenesis of the middle ear; however, effects of these proteins on the inner ear and hearing loss are unknown. METHODS Middle ears of chinchillas were inoculated with either wild-type S. pneumoniae or its mutants, deficient in PspA or Ply proteins. After 28 days, auditory brainstem response of animals was tested, and their bullae were processed for histopathologic analysis by light microscopy. RESULTS Twenty-eight days after instillation of 20 colony-forming units of wild-type pneumococci, auditory brainstem response test showed threshold changes of 10 to 15 dB for 4 to 32 kHz and more than 20 dB for 1 to 2 kHz. No significant hearing loss was observed after instillation of the same or even higher doses of isogenic S. pneumoniae mutants of PspA or Ply proteins, or saline injection, after the same period. Histologic analysis showed no fluid, inflammatory cells, or bacteria in the middle ear, indicating that hearing loss was sensorineural. Inner ear morphology showed pathologic changes in the stria vascularis, suggesting it as the target of otitis media-induced damage, which may lead to sensorineural hearing loss. CONCLUSION The virulence PspA and Ply proteins of S. pneumoniae affect the inner ear and auditory function.
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