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Dong Y, Guo CR, Ding Y, Zhang Y, Song HY, Peng YT, Zhang T, Shi JR. Effects of Erlong Zuoci decoction on the age-related hearing loss in C57BL/6J mice. JOURNAL OF ETHNOPHARMACOLOGY 2016; 181:59-65. [PMID: 26826327 DOI: 10.1016/j.jep.2016.01.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Revised: 10/12/2015] [Accepted: 01/18/2016] [Indexed: 06/05/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Erlong Zuoci decoction (ELZCD), a typical traditional Chinese medicine (TCM) prescription, has long been clinically used in treatment of deafness and tinnitus with the syndrome of "kidney yin deficiency". However, there are few studies to investigate its pharmacological mechanisms. Until now, there is not report about its effects on the age-related hearing loss (ARHL). AIM OF STUDY The present study was conducted to observe the effects of ELZCD on the ARHL in C57BL/6J mice and explore the mechanisms. MATERIALS AND METHODS ELZCD was fed to C57BL/6J mice from 3 months to 6 months in ELZCD group as a dose of 6g/kg/d. And the same volume of saline was fed to mice in ARHL group. 3-months-old C57BL/6J mice were used as control group. High performance liquid chromatography (HPLC) was used for the quality control of ELZCD. Auditory brainstem response (ABR) was used to assess the hearing function of mice. The morphologic changes were observed by hematoxylin eosin (HE) staining. Apoptosis was tested by terminal dexynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) method. Mitochondrial damage was detected by transmission electron microscopy (TEM). Quantitative RT-PCR (qRT-PCR) was used to observe the mRNA expression of p53 and Bak. Fluorescence immunohistochemical technique was used to test the protein expression of p53 and Bak. RESULTS The hearing threshold of ARHL group was higher than that of control group (P<0.001) and ELZCD decreased the rise of hearing threshold levels of ARHL mice (P<0.001), which suggested ELZCD inhibited the hearing loss of ARHL mice. HE staining showed that ELZCD decreased the spiral ganglion (SG) cell damage and loss in ARHL. TUNEL test showed that the apoptotic SG cells increased in ARHL group compared to control group and decreased in ELZCD group compared to ARHL group. TEM observation showed that mitochondrial damage was obvious in SG cells of ARHL group and ELZCD inhibited the mitochondrial damage. The qRT-PCR results showed that the mRNA expression of p53 and Bak in ARHL group increased compared to that of control group (P<0.05), and ELZCD reduced the elevated mRNA expression levels of p53 and Bak (P<0.01, P<0.05). In addition, ELZCD inhibited the increased proteins expression (green fluorescence) of p53 and Bak. CONCLUSION The results demonstrated that ELZCD prevented ARHL in C57BL/6J mice and p53/Bak-mediated mitochondrial apoptosis of SG cells might be involved in the mechanisms.
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Johnson KR, Longo-Guess CM, Gagnon LH. A QTL on Chr 5 modifies hearing loss associated with the fascin-2 variant of DBA/2J mice. Mamm Genome 2015; 26:338-47. [PMID: 26092689 DOI: 10.1007/s00335-015-9574-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 06/02/2015] [Indexed: 12/16/2022]
Abstract
Inbred mouse strains serve as important models for human presbycusis or age-related hearing loss. We previously mapped a locus (ahl8) contributing to the progressive hearing loss of DBA/2J (D2) mice and later showed that a missense variant of the Fscn2 gene, unique to the D2 inbred strain, was responsible for the ahl8 effect. Although ahl8 can explain much of the hearing loss difference between C57BL/6J (B6) and D2 strain mice, other loci also contribute. Here, we present results of our linkage analyses to map quantitative trait loci (QTLs) that modify the severity of hearing loss associated with the D2 strain Fscn2 (ahl8) allele. We searched for modifier loci by analyzing 31 BXD recombinant inbred (RI) lines fixed for the predisposing D2-derived Fscn2 (ahl8/ahl8) genotype and found a statistically significant linkage association of threshold means with a QTL on Chr 5, which we designated M5ahl8. The highest association (LOD 4.6) was with markers at the 84-90 Mb position of Chr 5, which could explain about 46 % of the among-RI strain variation in auditory brainstem response (ABR) threshold means. The semidominant nature of the modifying effect of M5ahl8 on the Fscn2 (ahl8/ahl8) phenotype was demonstrated by analysis of a backcross involving D2 and B6.D2-Chr11D/LusJ strain mice. The Chr 5 map position of M5ahl8 and the D2 origin of its susceptibility allele correspond to Tmc1m4, a previously reported QTL that modifies outer hair cell degeneration in Tmc1 (Bth) mutant mice, suggesting that M5ahl8 and Tmc1m4 may represent the same gene affecting maintenance of stereocilia structure and function during aging.
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MESH Headings
- Aging/genetics
- Aging/metabolism
- Aging/pathology
- Alleles
- Animals
- Carrier Proteins/genetics
- Carrier Proteins/metabolism
- Chromosome Mapping
- Chromosomes, Mammalian/chemistry
- Disease Models, Animal
- Evoked Potentials, Auditory, Brain Stem
- Female
- Gene Expression
- Genetic Linkage
- Genetic Predisposition to Disease
- Genotype
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/pathology
- Humans
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Inbred DBA
- Microfilament Proteins/genetics
- Microfilament Proteins/metabolism
- Phenotype
- Presbycusis/genetics
- Presbycusis/metabolism
- Presbycusis/pathology
- Quantitative Trait Loci
- Severity of Illness Index
- Species Specificity
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Lasisi TJ, Lasisi AO. Evaluation of serum antioxidants in age-related hearing loss. Aging Clin Exp Res 2015; 27:265-9. [PMID: 25362621 DOI: 10.1007/s40520-014-0282-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 10/28/2014] [Indexed: 01/10/2023]
Abstract
BACKGROUND Age-related hearing loss (ARHL) has been linked to the shift in the pro-oxidant/antioxidant ratio. Our objectives were to assess serum levels of retinol and zinc among the elderly individuals and to correlate the levels with hearing threshold. METHODS Prospective study of apparently healthy individuals aged ≥60 years of age. Participants had complete clinical history, physical examination and pure tone average conducted. Blood samples were collected for determination of serum levels of retinol and zinc. Mann-Whitney U test was used to compare retinol and zinc values. Pearson's correlation test was used to determine the relationship between hearing threshold and serum levels of retinol and zinc. RESULTS Among 126 elderly participants with mean age 67 ± 2.7 years; the mean pure tone average for air conduction was 29.3 ± 1.6 dBHL while the mean bone conduction was 36.5 ± 1.8 dBHL. The median values of serum retinol and zinc levels in the elderly participants who had hearing loss in the speech frequencies were 52 and 83.3 μg/L, respectively, while among participants with normal hearing threshold, values were 50 and 89.9 μg/L, respectively (p = 0.59 and 0.99, respectively). For the high frequencies, the median value of serum retinol and zinc levels among the elderly participants with normal hearing threshold was 70.3 and 99.9 μg/L, while among those with hearing loss, it was 46.9 and 83.2 μg/L, respectively (p = 0.000 and 0.005, respectively). CONCLUSION Serum retinol and zinc levels were significantly lower among elderly with hearing loss involving the high frequencies. This is added evidence to extant literature on the possible role of antioxidants in the development of ARHL and suggests further study on the effect of antioxidants supplementation in the control of ARHL which is presently controversial and inconclusive.
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Xiong H, Dai M, Ou Y, Pang J, Yang H, Huang Q, Chen S, Zhang Z, Xu Y, Cai Y, Liang M, Zhang X, Lai L, Zheng Y. SIRT1 expression in the cochlea and auditory cortex of a mouse model of age-related hearing loss. Exp Gerontol 2014; 51:8-14. [PMID: 24365660 DOI: 10.1016/j.exger.2013.12.006] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2013] [Revised: 12/08/2013] [Accepted: 12/12/2013] [Indexed: 01/30/2023]
Abstract
SIRT1 is a highly conserved NAD(+)-dependent protein deacetylase known to have protective effects against a variety of age-related diseases. However, there is a lack of information concerning SIRT1 expression in the cochlea and auditory cortex of C57BL/6 mice, a mouse model of age-related hearing loss. Using RT-PCR and immunohistochemistry, we show that SIRT1 is abundantly expressed in the inner hair cells, strial marginal cells, strial intermediate cells, type I and type IV fibrocytes of the spiral ligament and spiral ganglion neurons. In addition, moderate SIRT1 is also detected in the outer hair cells and neurons of the auditory cortex. Associated with elevated hearing thresholds and hair cells loss during aging, there is also a significant reduction of SIRT1 expression in the cochlea and auditory cortex. The expression pattern of SIRT1 in the peripheral and central auditory system suggests that SIRT1 may play an important role in auditory function and therefore may serve as a protective molecule against age-related hearing loss.
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Tadros SF, D'Souza M, Zhu X, Frisina RD. Gene expression changes for antioxidants pathways in the mouse cochlea: relations to age-related hearing deficits. PLoS One 2014; 9:e90279. [PMID: 24587312 PMCID: PMC3938674 DOI: 10.1371/journal.pone.0090279] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Accepted: 01/28/2014] [Indexed: 12/17/2022] Open
Abstract
Age-related hearing loss - presbycusis - is the number one neurodegenerative disorder and top communication deficit of our aged population. Like many aging disorders of the nervous system, damage from free radicals linked to production of reactive oxygen and/or nitrogen species (ROS and RNS, respectively) may play key roles in disease progression. The efficacy of the antioxidant systems, e.g., glutathione and thioredoxin, is an important factor in pathophysiology of the aging nervous system. In this investigation, relations between the expression of antioxidant-related genes in the auditory portion of the inner ear - cochlea, and age-related hearing loss was explored for CBA/CaJ mice. Forty mice were classified into four groups according to age and degree of hearing loss. Cochlear mRNA samples were collected and cDNA generated. Using Affymetrix® GeneChip, the expressions of 56 antioxidant-related gene probes were analyzed to estimate the differences in gene expression between the four subject groups. The expression of Glutathione peroxidase 6, Gpx6; Thioredoxin reductase 1, Txnrd1; Isocitrate dehydrogenase 1, Idh1; and Heat shock protein 1, Hspb1; were significantly different, or showed large fold-change differences between subject groups. The Gpx6, Txnrd1 and Hspb1 gene expression changes were validated using qPCR. The Gpx6 gene was upregulated while the Txnrd1 gene was downregulated with age/hearing loss. The Hspb1 gene was found to be downregulated in middle-aged animals as well as those with mild presbycusis, whereas it was upregulated in those with severe presbycusis. These results facilitate development of future interventions to predict, prevent or slow down the progression of presbycusis.
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Zeng L, Yang Y, Hu Y, Sun Y, Du Z, Xie Z, Zhou T, Kong W. Age-related decrease in the mitochondrial sirtuin deacetylase Sirt3 expression associated with ROS accumulation in the auditory cortex of the mimetic aging rat model. PLoS One 2014; 9:e88019. [PMID: 24505357 PMCID: PMC3913718 DOI: 10.1371/journal.pone.0088019] [Citation(s) in RCA: 71] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 01/03/2014] [Indexed: 12/31/2022] Open
Abstract
Age-related dysfunction of the central auditory system, also known as central presbycusis, can affect speech perception and sound localization. Understanding the pathogenesis of central presbycusis will help to develop novel approaches to prevent or treat this disease. In this study, the mechanisms of central presbycusis were investigated using a mimetic aging rat model induced by chronic injection of D-galactose (D-Gal). We showed that malondialdehyde (MDA) levels were increased and manganese superoxide dismutase (SOD2) activity was reduced in the auditory cortex in natural aging and D-Gal-induced mimetic aging rats. Furthermore, mitochondrial DNA (mtDNA) 4834 bp deletion, abnormal ultrastructure and cell apoptosis in the auditory cortex were also found in natural aging and D-Gal mimetic aging rats. Sirt3, a mitochondrial NAD+-dependent deacetylase, has been shown to play a crucial role in controlling cellular reactive oxygen species (ROS) homeostasis. However, the role of Sirt3 in the pathogenesis of age-related central auditory cortex deterioration is still unclear. Here, we showed that decreased Sirt3 expression might be associated with increased SOD2 acetylation, which negatively regulates SOD2 activity. Oxidative stress accumulation was likely the result of low SOD2 activity and a decline in ROS clearance. Our findings indicate that Sirt3 might play an essential role, via the mediation of SOD2, in central presbycusis and that manipulation of Sirt3 expression might provide a new approach to combat aging and oxidative stress-related diseases.
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Saremi A, Stenfelt S. Effect of metabolic presbyacusis on cochlear responses: a simulation approach using a physiologically-based model. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2013; 134:2833-2851. [PMID: 24116421 DOI: 10.1121/1.4820788] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
In the presented model, electrical, acoustical, and mechanical elements of the cochlea are explicitly integrated into a signal transmission line where these elements convey physiological interpretations of the human cochlear structures. As a result, this physiologically-motivated model enables simulation of specific cochlear lesions such as presbyacusis. The hypothesis is that high-frequency hearing loss in older adults may be due to metabolic presbyacusis whereby age-related cellular/chemical degenerations in the lateral wall of the cochlea cause a reduction in the endocochlear potential. The simulations quantitatively confirm this hypothesis and emphasize that even if the outer and inner hair cells are totally active and intact, metabolic presbyacusis alone can significantly deteriorate the cochlear functionality. Specifically, in the model, as the endocochlear potential decreases, the transduction mechanism produces less receptor current such that there is a reduction in the battery of the somatic motor. This leads to a drastic decrease in cochlear amplification and frequency sensitivity, as well as changes in position-frequency map (tuning pattern) of the cochlea. In addition, the simulations show that the age-related reduction of the endocochlear potential significantly inhibits the firing rate of the auditory nerve which might contribute to the decline of temporal resolution in the aging auditory system.
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MESH Headings
- Action Potentials
- Age Factors
- Aging/metabolism
- Animals
- Cochlea/metabolism
- Cochlea/pathology
- Cochlea/physiopathology
- Cochlear Nerve/metabolism
- Cochlear Nerve/physiopathology
- Computer Simulation
- Evoked Potentials
- Hair Cells, Auditory, Inner/metabolism
- Hair Cells, Auditory, Inner/pathology
- Hair Cells, Auditory, Outer/metabolism
- Hair Cells, Auditory, Outer/pathology
- Hearing
- Humans
- Linear Models
- Mechanotransduction, Cellular
- Models, Biological
- Nonlinear Dynamics
- Presbycusis/metabolism
- Presbycusis/pathology
- Presbycusis/physiopathology
- Pressure
- Time Factors
- Vibration
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Yamasoba T, Lin FR, Someya S, Kashio A, Sakamoto T, Kondo K. Current concepts in age-related hearing loss: epidemiology and mechanistic pathways. Hear Res 2013; 303:30-8. [PMID: 23422312 PMCID: PMC3723756 DOI: 10.1016/j.heares.2013.01.021] [Citation(s) in RCA: 353] [Impact Index Per Article: 32.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 12/20/2012] [Accepted: 01/29/2013] [Indexed: 01/10/2023]
Abstract
Age-related hearing loss (AHL), also known as presbycusis, is a universal feature of mammalian aging and is characterized by a decline of auditory function, such as increased hearing thresholds and poor frequency resolution. The primary pathology of AHL includes the hair cells, stria vascularis, and afferent spiral ganglion neurons as well as the central auditory pathways. A growing body of evidence in animal studies has suggested that cumulative effect of oxidative stress could induce damage to macromolecules such as mitochondrial DNA (mtDNA) and that the resulting accumulation of mtDNA mutations/deletions and decline of mitochondrial function play an important role in inducing apoptosis of the cochlear cells, thereby the development of AHL. Epidemiological studies have demonstrated four categories of risk factors of AHL in humans: cochlear aging, environment such as noise exposure, genetic predisposition, and health co-morbidities such as cigarette smoking and atherosclerosis. Genetic investigation has identified several putative associating genes, including those related to antioxidant defense and atherosclerosis. Exposure to noise is known to induce excess generation of reactive oxygen species (ROS) in the cochlea, and cumulative oxidative stress can be enhanced by relatively hypoxic situations resulting from the impaired homeostasis of cochlear blood supply due to atherosclerosis, which could be accelerated by genetic and co-morbidity factors. Antioxidant defense system may also be influenced by genetic backgrounds. These may explain the large variations of the onset and extent of AHL among elderly subjects. This article is part of a Special Issue entitled "Annual Reviews 2013".
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Chen XM, Dou XQ, Liang YH, Zhang LW, Luo BQ, Deng YH. [(1)H-MRS study of auditory cortex in patients with presbycusis]. ZHONGHUA ER BI YAN HOU TOU JING WAI KE ZA ZHI = CHINESE JOURNAL OF OTORHINOLARYNGOLOGY HEAD AND NECK SURGERY 2012; 47:852-855. [PMID: 23302169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
OBJECTIVE To study the metabolic changes of auditory cortex in patients with presbycusis by using proton magnetic resonance spectroscopy ((1)H-MRS). METHODS Ten normal hearing volunteers (youth group), 10 normal hearing of elderly (aged group) and 8 patients with presbycusis (presbycusis group) were checked with proton magnetic resonance spectroscopy. N-acetylaspartic acid (NAA), creatine (Cr), choline (Cho), γ-aminobutyric acid (GABA), glutamic acid (Glu) compound were measured. The differences between the groups were semi-quantitatively analyzed. RESULTS When compared with youth group, reduced NAA/Cr, increased Cho/Cr were found in the aged group and presbycusis group (P < 0.05). GABA/Cr ratio and Glu/Cr ratio were significant difference between presbycusis group and youth group (P < 0.05). There were no significant difference in the GABA/Cr and Glu/Cr ratios in the bilateral auditory cortex between the youth group and the aged group (P > 0.05). When compared with aged group, the metabolic changes of auditory cortex in patients with presbycusis were remarkable (P < 0.05). CONCLUSIONS (1)H-MRS is a noninvasive technique that can provide useful information concerning the metabolic changes of auditory cortex in human. In comparison to the aged group and the youth group, the changes of NAA, GABA, Cho and Glu is found in auditory cortex in patients with presbycusis.
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Kane KL, Longo-Guess CM, Gagnon LH, Ding D, Salvi RJ, Johnson KR. Genetic background effects on age-related hearing loss associated with Cdh23 variants in mice. Hear Res 2011; 283:80-8. [PMID: 22138310 DOI: 10.1016/j.heares.2011.11.007] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Revised: 11/07/2011] [Accepted: 11/08/2011] [Indexed: 12/18/2022]
Abstract
Inbred strain variants of the Cdh23 gene have been shown to influence the onset and progression of age-related hearing loss (AHL) in mice. In linkage backcrosses, the recessive Cdh23 allele (ahl) of the C57BL/6J strain, when homozygous, confers increased susceptibility to AHL, while the dominant allele (Ahl+) of the CBA/CaJ strain confers resistance. To determine the isolated effects of these alleles on different strain backgrounds, we produced the reciprocal congenic strains B6.CBACa-Cdh23(Ahl)(+) and CBACa.B6-Cdh23(ahl) and tested 15-30 mice from each for hearing loss progression. ABR thresholds for 8 kHz, 16 kHz, and 32 kHz pure-tone stimuli were measured at 3, 6, 9, 12, 15 and 18 months of age and compared with age-matched mice of the C57BL/6J and CBA/CaJ parental strains. Mice of the C57BL/6N strain, which is the source of embryonic stem cells for the large International Knockout Mouse Consortium, were also tested for comparisons with C57BL/6J mice. Mice of the C57BL/6J and C57BL/6N strains exhibited identical hearing loss profiles: their 32 kHz ABR thresholds were significantly higher than those of CBA/CaJ and congenic strain mice by 6 months of age, and their 16 kHz thresholds were significantly higher by 12 months. Thresholds of the CBA/CaJ, the B6.CBACa-Cdh23(Ahl)(+), and the CBACa.B6-Cdh23(ahl) strain mice differed little from one another and only slightly increased throughout the 18-month test period. Hearing loss, which corresponded well with cochlear hair cell loss, was most profound in the C57BL/6J and C57BL/6NJ strains. These results indicate that the CBA/CaJ-derived Cdh23(Ahl)(+) allele dramatically lessens hearing loss and hair cell death in an otherwise C57BL/6J genetic background, but that the C57BL/6J-derived Cdh23(ahl) allele has little effect on hearing loss in an otherwise CBA/CaJ background. We conclude that although Cdh23(ahl) homozygosity is necessary, it is not by itself sufficient to account for the accelerated hearing loss of C57BL/6J mice.
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MESH Headings
- Acoustic Stimulation
- Age Factors
- Aging
- Animals
- Audiometry, Pure-Tone
- Auditory Threshold
- Cadherins/genetics
- Cadherins/metabolism
- Cochlea/metabolism
- Cochlea/pathology
- Cochlea/physiopathology
- Disease Models, Animal
- Evoked Potentials, Auditory, Brain Stem
- Female
- Genetic Predisposition to Disease
- Hair Cells, Auditory/metabolism
- Hair Cells, Auditory/pathology
- Male
- Mice
- Mice, Congenic
- Mice, Inbred C57BL
- Mice, Inbred CBA
- Mice, Transgenic
- Phenotype
- Polymorphism, Single Nucleotide
- Presbycusis/genetics
- Presbycusis/metabolism
- Presbycusis/pathology
- Presbycusis/physiopathology
- Species Specificity
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Wang Y, Chu HQ, Zhou LQ, Chen J, Li ZY, Liu Y, Zhang P, Huang XW, Cui YH. [Expression of PDCD5 and caspase 3 in the cochlea of different age of C57BL/6J mice]. ZHONGHUA ER BI YAN HOU TOU JING WAI KE ZA ZHI = CHINESE JOURNAL OF OTORHINOLARYNGOLOGY HEAD AND NECK SURGERY 2011; 46:747-751. [PMID: 22177044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
OBJECTIVE To investigate the age related changes of the expression of programmed cell death 5 (PDCD5) and caspase 3 in the cochlea of the different age of C57BL/6J mice. The relationship of PDCD5 and caspase 3 and the possible roles in the pathogenesis of presbycusis were also discussed. METHODS C57 mice of 3, 6, 9 and 12 months old were selected and divided into 4 groups, with 15 mice in each group. Auditory function of C57BL/6J mice was measured by auditory brainstem response (ABR) respectively. The changes of PDCD5 and Caspase 3 protein in the cochlea were detected by immunohistochemistry and Western blotting, the changes of PDCD5 mRNA and caspase 3 mRNA were detected using RT-PCR. RESULTS With the increase of age, the mean value for ABR thresholds in response to click, 4 kHz and 8 kHz sound stimulus of C57 mice gradually increased, the expression of PDCD5 and caspase 3 were increased also. At 3 months and 6 months of age in the cochlea of C57, all sorts of expression of PDCD5 and caspase 3 and the expression were enhanced with age. There was an evident expression at 9 months age, but the highest expression was detected at 12 months age. The PDCD5 and Caspase 3 expression were statistically different in each group (P < 0.05). The changes of PDCD5 and caspase 3 mRNA expression were in accordance with that of PDCD5 and Caspase 3 protein expression by the real-time PCR. CONCLUSIONS The expression levels of PDCD5 and caspase 3 in the cochlea of C57 mice increase with age, the results suggested that the expression of PDCD5 and caspase 3 might play an important role in the pathogenic mechanism of presbycusis.
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Lei D, Gao X, Perez P, Ohlemiller KK, Chen CC, Campbell KP, Hood AY, Bao J. Anti-epileptic drugs delay age-related loss of spiral ganglion neurons via T-type calcium channel. Hear Res 2011; 278:106-12. [PMID: 21640179 PMCID: PMC3152691 DOI: 10.1016/j.heares.2011.05.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 04/29/2011] [Accepted: 05/11/2011] [Indexed: 12/26/2022]
Abstract
Loss of spiral ganglion neurons is a major cause of age-related hearing loss (presbycusis). Despite being the third most prevalent condition afflicting elderly persons, there are no known medications to prevent presbycusis. Because calcium signaling has long been implicated in age-related neuronal death, we investigated T-type calcium channels. This family is comprised of three members (Ca(v)3.1, Ca(v)3.2, and Ca(v)3.3), based on their respective main pore-forming alpha subunits: α1G, α1H, and α1I. In the present study, we report a significant delay of age-related loss of cochlear function and preservation of spiral ganglion neurons in α1H null and heterozygous mice, clearly demonstrating an important role for Ca(v)3.2 in age-related neuronal loss. Furthermore, we show that anticonvulsant drugs from a family of T-type calcium channel blockers can significantly preserve spiral ganglion neurons during aging. To our knowledge, this is the first report of drugs capable of diminishing age-related loss of spiral ganglion neurons.
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MESH Headings
- Aging/drug effects
- Aging/metabolism
- Aging/pathology
- Animals
- Anticonvulsants/pharmacology
- Base Sequence
- Calcium Channel Blockers/pharmacology
- Calcium Channels, T-Type/deficiency
- Calcium Channels, T-Type/genetics
- Calcium Channels, T-Type/metabolism
- Evoked Potentials, Auditory, Brain Stem/drug effects
- Hair Cells, Auditory, Inner/pathology
- Hair Cells, Auditory, Outer/pathology
- Mice
- Mice, Congenic
- Mice, Knockout
- Neurons/drug effects
- Neurons/metabolism
- Neurons/pathology
- Presbycusis/metabolism
- Presbycusis/pathology
- Presbycusis/prevention & control
- RNA/genetics
- RNA/metabolism
- Spiral Ganglion/drug effects
- Spiral Ganglion/innervation
- Spiral Ganglion/metabolism
- Spiral Ganglion/pathology
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Lubka-Pathak M, Shah AA, Gallozzi M, Müller M, Zimmermann U, Löwenheim H, Pfister M, Knipper M, Blin N, Schimmang T. Altered expression of securin (Pttg1) and serpina3n in the auditory system of hearing-impaired Tff3-deficient mice. Cell Mol Life Sci 2011; 68:2739-49. [PMID: 21076990 PMCID: PMC11114927 DOI: 10.1007/s00018-010-0586-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Revised: 10/22/2010] [Accepted: 10/26/2010] [Indexed: 11/29/2022]
Abstract
INTRODUCTION Tff3 peptide exerts important functions in cytoprotection and restitution of the gastrointestinal (GI) tract epithelia. Moreover, its presence in the rodent inner ear and involvement in the hearing process was demonstrated recently. However, its role in the auditory system still remains elusive. Our previous results showed a deterioration of hearing with age in Tff3-deficient animals. RESULTS Present detailed analysis of auditory brain stem response (ABR) measurements and immunohistochemical study of selected functional proteins indicated a normal function and phenotype of the cochlea in Tff3 mutants. However, a microarray-based screening of tissue derived from the auditory central nervous system revealed an alteration of securin (Pttg1) and serpina3n expression between wild-type and Tff3 knock-out animals. This was confirmed by qRT-PCR, immunostaining and western blots. CONCLUSIONS We found highly down-regulated Pttg1 and up-regulated serpina3n expression as a consequence of genetically deleting Tff3 in mice, indicating a potential role of these factors during the development of presbyacusis.
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Bao J, Ohlemiller KK. Age-related loss of spiral ganglion neurons. Hear Res 2010; 264:93-7. [PMID: 19854255 PMCID: PMC2868093 DOI: 10.1016/j.heares.2009.10.009] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Revised: 10/14/2009] [Accepted: 10/16/2009] [Indexed: 01/12/2023]
Abstract
Spiral ganglion neurons (SGNs) are the relay station for auditory information between hair cells and central nervous system. Age-related decline of auditory function due to SGN loss can not be ameliorated by hearing aids or cochlear implants. Recent findings clearly indicate that survival of SGNs during aging depends on genetic and environmental interactions, which can be demonstrated at the systemic, tissue, cellular, and molecular levels. At the systemic level, both insulin/insulin-like growth factor-1 and lipophilic/steroid hormone pathways influence SGN survival during aging. At the level of organ of the Corti, it is difficult to determine whether age-related SGN loss is primary or secondary degeneration. However, a late stage of SGN degeneration may be independent of age-related loss of hair cells. At the cellular and molecular level, several pathways, particularly free radical and calcium signaling pathways, can influence age-related SGN loss, and further studies should determine how these pathways contribute to SGN loss, such as whether they directly or indirectly act on SGNs. With the advancement of recent genetic and pharmacologic tools, we should not only understand how SGNs die during aging, but also find ways to delay this loss.
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Friedman RA, Van Laer L, Huentelman MJ, Sheth SS, Van Eyken E, Corneveaux JJ, Tembe WD, Halperin RF, Thorburn AQ, Thys S, Bonneux S, Fransen E, Huyghe J, Pyykkö I, Cremers CWRJ, Kremer H, Dhooge I, Stephens D, Orzan E, Pfister M, Bille M, Parving A, Sorri M, Van de Heyning PH, Makmura L, Ohmen JD, Linthicum FH, Fayad JN, Pearson JV, Craig DW, Stephan DA, Van Camp G. GRM7 variants confer susceptibility to age-related hearing impairment. Hum Mol Genet 2009; 18:785-96. [PMID: 19047183 PMCID: PMC2638831 DOI: 10.1093/hmg/ddn402] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Accepted: 11/20/2008] [Indexed: 01/22/2023] Open
Abstract
Age-related hearing impairment (ARHI), or presbycusis, is the most prevalent sensory impairment in the elderly. ARHI is a complex disease caused by an interaction between environmental and genetic factors. Here we describe the results of the first whole genome association study for ARHI. The study was performed using 846 cases and 846 controls selected from 3434 individuals collected by eight centers in six European countries. DNA pools for cases and controls were allelotyped on the Affymetrix 500K GeneChip for each center separately. The 252 top-ranked single nucleotide polymorphisms (SNPs) identified in a non-Finnish European sample group (1332 samples) and the 177 top-ranked SNPs from a Finnish sample group (360 samples) were confirmed using individual genotyping. Subsequently, the 23 most interesting SNPs were individually genotyped in an independent European replication group (138 samples). This resulted in the identification of a highly significant and replicated SNP located in GRM7, the gene encoding metabotropic glutamate receptor type 7. Also in the Finnish sample group, two GRM7 SNPs were significant, albeit in a different region of the gene. As the Finnish are genetically distinct from the rest of the European population, this may be due to allelic heterogeneity. We performed histochemical studies in human and mouse and showed that mGluR7 is expressed in hair cells and in spiral ganglion cells of the inner ear. Together these data indicate that common alleles of GRM7 contribute to an individual's risk of developing ARHI, possibly through a mechanism of altered susceptibility to glutamate excitotoxicity.
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Idrizbegovic E, Salman H, Niu X, Canlon B. Presbyacusis and calcium-binding protein immunoreactivity in the cochlear nucleus of BALB/c mice. Hear Res 2007; 216-217:198-206. [PMID: 16874908 DOI: 10.1016/j.heares.2006.01.009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The BALB/c mouse is an established model for the early development of sensorineural hearing loss, and is homozygous for the Ahl allele (age-related hearing loss). The present study was designed to determine how auditory peripheral pathology influences calcium-binding protein immunoreactivity in the cochlear nucleus in aged BALB/c mice. To address this issue the loss of hair cells, spiral ganglion neurons (SGN), and neurons in the dorsal (DCN) and posteroventral (PVCN) cochlear nucleus of BALB/c mice at 1 and 24 months of age were quantified using CAST stereological methods. These values were then compared to the percent increase in immunopositive calcium-binding proteins in the cochlear nucleus. By 24 months of age there was a near complete loss of all outer hair cells (OHC). The inner hair cell (IHC) loss was near complete in the more apical and basal regions, while in the mid-regions approximately 50% were missing. The SGN in the apical and middle turns show a 20% loss (re: 1 month) and the basal turn up to 80% loss. A statistically significant decrease in the density of DCN and PVCN neurons (25%) was found at 24 months of age compared to the one month old animals. The percentage of parvalbumin and calretinin positive neurons in the DCN and the PVCN in relation to the density of Nissl stained neurons showed significant increases at 24 months compared to the 1 month old animals. We also determine the relationship between peripheral pathology and the percent increase in calcium-binding protein immunoreactivity. In the DCN, the percent increase of calretinin and parvalbumin was correlated to the loss of SGN, IHCs and OHCs. In the PVCN, parvalbumin was correlated to SGN, IHC, and OHC loss. The percent increase in calbindin immunoreactivity was not correlated to any peripheral pathology. The data here suggest a percent increase in calcium-binding protein immunoreactivity in the cochlea nucleus in the 24 month old mice may reflect an endogenous protective strategy that is designed to counteract calcium overload that is prominent during aging and degeneration. These results will be valuable for understanding the relationship among the peripheral and central auditory system in a model demonstrating a rapidly progressive presbyacusis.
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Yamasoba T, Someya S, Yamada C, Weindruch R, Prolla TA, Tanokura M. Role of mitochondrial dysfunction and mitochondrial DNA mutations in age-related hearing loss. Hear Res 2007; 226:185-93. [PMID: 16870370 DOI: 10.1016/j.heares.2006.06.004] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2006] [Revised: 05/29/2006] [Accepted: 06/12/2006] [Indexed: 10/24/2022]
Abstract
Mitochondrial DNA (mtDNA) mutations/deletions are considered to be associated with the development of age-related hearing loss (AHL). We assessed the role of accumulation of mtDNA mutations in the development of AHL using Polg(D257A) knock-in mouse, which exhibited increased spontaneous mtDNA mutation rates during aging and showed accelerated aging primarily due to increased apoptosis. They exhibited moderate hearing loss and degeneration of the hair cells, spiral ganglion cells and stria vascularis by 9 month of age, while wild-type animals did not. We next examined if mitochondrial damage induced by systemic application of germanium dioxide caused progressive hearing loss and cochlear damage. Guinea pigs and mice given germanium dioxide exhibited degeneration of the muscles and kidney and developed hearing loss due to degeneration of cochlear tissues, including the stria vascularis. Calorie restriction, which causes a metabolic shift toward increased energy metabolism in some organs, has been shown to attenuate AHL and age-related cochlear degeneration and to lower quantity of mtDNA deletions in the cochlea of mammals. Together these findings indicate that decreased energy metabolism due to accumulation of mtDNA mutations/deletions and decline of respiratory chain function play an important role in the manifestation of AHL.
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Le T, Keithley EM. Effects of antioxidants on the aging inner ear. Hear Res 2007; 226:194-202. [PMID: 16843623 DOI: 10.1016/j.heares.2006.04.003] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Revised: 04/26/2006] [Accepted: 04/28/2006] [Indexed: 10/24/2022]
Abstract
Age-related cochlear structural changes include the degeneration of sensory, neural cells and the stria vascularis. The hypothesis that cellular degeneration results from exposure to oxidative products of respiration was tested by supplementing aged dogs with a diet high in antioxidants and mitochondrial metabolites and by genetically modifying the expression level of the antioxidant, manganese superoxide dismutase (SOD2) in mice. Aged dogs received either a high antioxidant diet or a normal, control diet for the last 3 years of their life. Cellular measures were compared among the two aged groups (10-15 years) and young dogs. Both aged groups had cellular degeneration relative to young dogs, but the animals fed the antioxidant diet showed less degeneration at the base and apex than the control-diet group. Transgenic mice, heterozygous null for SOD2, produce only half as much enzyme as a normal mouse. These mice showed no increase in the amount of hearing loss relative to the background strain. A diet containing antioxidants reduced the magnitude of cochlear degeneration. Genetic reduction of one antioxidant, however, did not increase the magnitude of hearing loss in aging mice. A reduction in one enzyme seems to be compensated while the addition of a complex of factors is effective.
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Tadros SF, D’Souza M, Zettel ML, Zhu X, Frisina RD. Glutamate-related gene expression changes with age in the mouse auditory midbrain. Brain Res 2006; 1127:1-9. [PMID: 17113045 PMCID: PMC2423939 DOI: 10.1016/j.brainres.2006.09.081] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Revised: 09/18/2006] [Accepted: 09/25/2006] [Indexed: 01/01/2023]
Abstract
Glutamate is the main excitatory neurotransmitter in both the peripheral and central auditory systems. Changes of glutamate and glutamate-related genes with age may be an important factor in the pathogenesis of age-related hearing loss-presbycusis. In this study, changes in glutamate-related mRNA gene expression in the CBA mouse inferior colliculus with age and hearing loss were examined and correlations were sought between these changes and functional hearing measures, such as the auditory brainstem response (ABR) and distortion product otoacoustic emissions (DPOAEs). Gene expression of 68 glutamate-related genes was investigated using both genechip microarray and real-time PCR (qPCR) molecular techniques for four different age/hearing loss CBA mouse subject groups. Two genes showed consistent differences between groups for both the genechip and qPCR. Pyrroline-5-carboxylate synthetase enzyme (Pycs) showed down-regulation with age and a high-affinity glutamate transporter (Slc1a3) showed up-regulation with age and hearing loss. Since Pycs plays a role in converting glutamate to proline, its deficiency in old age may lead to both glutamate increases and proline deficiencies in the auditory midbrain, playing a role in the subsequent inducement of glutamate toxicity and loss of proline neuroprotective effects. The up-regulation of Slc1a3 gene expression may reflect a cellular compensatory mechanism to protect against age-related glutamate or calcium excitoxicity.
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Someya S, Yamasoba T, Weindruch R, Prolla TA, Tanokura M. Caloric restriction suppresses apoptotic cell death in the mammalian cochlea and leads to prevention of presbycusis. Neurobiol Aging 2006; 28:1613-22. [PMID: 16890326 DOI: 10.1016/j.neurobiolaging.2006.06.024] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2006] [Revised: 06/20/2006] [Accepted: 06/22/2006] [Indexed: 12/20/2022]
Abstract
Presbycusis is characterized by an age-related progressive decline of auditory function, and arises mainly from the degeneration of hair cells or spiral ganglion (SG) cells in the cochlea. Here we show that caloric restriction suppresses apoptotic cell death in the mouse cochlea and prevents late onset of presbycusis. Calorie restricted (CR) mice, which maintained body weight at the same level as that of young control (YC) mice, retained normal hearing and showed no cochlear degeneration. CR mice also showed a significant reduction in the number of TUNEL-positive cells and cleaved caspase-3-positive cells relative to middle-age control (MC) mice. Microarray analysis revealed that CR down-regulated the expression of 24 apoptotic genes, including Bak and Bim. Taken together, our findings suggest that loss of critical cells through apoptosis is an important mechanism of presbycusis in mammals, and that CR can retard this process by suppressing apoptosis in the inner ear tissue.
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Rüttiger L, Panford-Walsh R, Schimmang T, Tan J, Zimmermann U, Rohbock K, Köpschall I, Limberger A, Müller M, Fraenzer JT, Cimerman J, Knipper M. BDNF mRNA expression and protein localization are changed in age-related hearing loss. Neurobiol Aging 2006; 28:586-601. [PMID: 16580094 DOI: 10.1016/j.neurobiolaging.2006.02.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2005] [Revised: 01/26/2006] [Accepted: 02/09/2006] [Indexed: 11/16/2022]
Abstract
A decline in neuronal plasticity during the adult life span has been proposed to be associated with a reduced level of the effectors of plasticity responses (e.g., BDNF). Alteration of plasticity is also correlated with age-related hearing loss (presbycusis), but to date no detailed studies of BDNF expression have been performed in the young or aging mature cochlea. We have used rat and gerbil animal models for presbycusis, which displayed hearing loss in the final third of the animals' natural life span. We demonstrate for the first time a co-localization of BDNF protein, transcripts III and IV in cochlear neurons with a declining distribution towards low-frequency processing cochlear turns. BDNF protein was also found within the neuronal projections of the cochlea. A significant reduction of BDNF transcripts in high-frequency processing cochlear neurons was observed during aging, though this did not coincide with a major reduction of BDNF protein. In contrast, BDNF protein in peripheral and central projections was drastically reduced. Our results suggest that reduced BDNF protein levels in auditory nerves over age may be a crucial factor in the altered brainstem plasticity observed during presbycusis.
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Bao J, Lei D, Du Y, Ohlemiller KK, Beaudet AL, Role LW. Requirement of nicotinic acetylcholine receptor subunit beta2 in the maintenance of spiral ganglion neurons during aging. J Neurosci 2006; 25:3041-5. [PMID: 15788760 PMCID: PMC2280031 DOI: 10.1523/jneurosci.5277-04.2005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Age-related hearing loss (presbycusis) is a major health concern for the elderly. Loss of spiral ganglion neurons (SGNs), the primary sensory relay of the auditory system, is associated consistently with presbycusis. The causative molecular events responsible for age-related loss of SGNs are unknown. Recent reports directly link age-related neuronal loss in cerebral cortex with the loss of high-affinity nicotine acetylcholine receptors (nAChRs). In cochlea, cholinergic synapses are made by olivocochlear efferent fibers on the outer hair cells that express alpha9 nAChR subunits and on the peripheral projections of SGNs that express alpha2, alpha4-7, and beta2-3 nAChR subunits. A significantly decreased expression of the beta2 nAChR subunit in SGNs was found specifically in mice susceptible to presbycusis. Furthermore, mice lacking the beta2 nAChR subunit (beta2-/-), but not mice lacking the alpha5 nAChR subunit (alpha5-/-), have dramatic hearing loss and significant reduction in the number of SGNs. Our findings clearly established a requirement for beta2 nAChR subunit in the maintenance of SGNs during aging.
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MESH Headings
- Acoustic Stimulation/methods
- Age Factors
- Aging/metabolism
- Animals
- Blotting, Northern/methods
- Blotting, Western/methods
- Cadherins/genetics
- Disease Models, Animal
- Dose-Response Relationship, Radiation
- Evoked Potentials, Auditory, Brain Stem/genetics
- Gene Expression Regulation/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Mutant Strains
- Neurons/metabolism
- Presbycusis/genetics
- Presbycusis/metabolism
- Presbycusis/physiopathology
- Protein Subunits/deficiency
- Protein Subunits/genetics
- Protein Subunits/metabolism
- RNA, Messenger/metabolism
- Receptors, Nicotinic/deficiency
- Receptors, Nicotinic/genetics
- Receptors, Nicotinic/metabolism
- Receptors, Nicotinic/physiology
- Reverse Transcriptase Polymerase Chain Reaction/methods
- Spiral Ganglion/cytology
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Riva C, Longuet M, Lucciano M, Magnan J, Lavieille JP. [Implication of mitochondrial apoptosis in neural degeneration of cochlea in a murine model for presbycusis]. REVUE DE LARYNGOLOGIE - OTOLOGIE - RHINOLOGIE 2005; 126:67-74. [PMID: 16180344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
HYPOTHESIS Pathologies of senescence, in particular those of neurosensory organs represent an important health problem. The improvement of the life expectation entails the fast increase of the frequency of the presbyacusis in the population. The biological and molecular causes of this degenerative pathology of the inner ear are linked to the disappearance of the sensory cells (inner and outer hair cells) and are associated to nervous damages of the spiral ganglion in the cochlea. We were interested in mechanisms causing the cochlear degeneration in a model of mouse CD 1 presenting prematurely auditive losses. MATERIALS AND METHODS We tried to correlate the evolution of the hearing and the appearance of apoptotic phenomena by marking with specific antibody, activated anti-caspase-3, in the cochlea during time. We studied the role and the involvement of proteins controlling the apoptosis as the P53 protein and from an energy point of view at the level of the mitochondria such as proteins of the Bcl-2 family and the cytochrome c in the various structures of the cochlea. RESULTS After implantation of electrodes for auditory nerve acoustic thresholds measurements, the audition of mice CD 1 presented a characteristic profile of hearing losses which begins in the high frequencies from the age of 1 month and which quickly evolves towards the low frequencies. The observation (between the 1st and 3rd month of age) of spiral ganglion cells revealed an unchanged number of cellular bodies of type 1 neurons, on the other hand a characteristic morphology of apoptosis of glial cells with the formation of apoptotic body was noted. Indeed, glial cells expressed activated caspase-3. Furthermore, this phenomenon seems to be under the control of the pro-apoptotic protein Bax by its overexpression and a increased release of the cytochrome c. This phenomenon was followed at 3 and 6 months by the disappearance of the outer hair cells by 9 and 48% respectively. CONCLUSION The apparition of the deafness in the murin model CD 1 allowed us to demonstrate that the degeneration of cochlear structure begins at the level of glial cells of the spiral ganglion from 3 months, followed thereafter by the deterioration of the nervous conduction between the spiral ganglion and the sensory cells. As a consequence, because of the impoverishment in nervous signals, the outer hair cells would begin to disappear during the 6th month. In conclusion, the understanding of the sequence and the cause of these mechanisms responsible for the neural degeneration and the loss of hearing could eventually, allow us to optimize the various treatments of the presbyacusis.
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Derin A, Agirdir B, Derin N, Dinç O, Güney K, Ozcaglar H, Kilinçarslan S. The effects of L-carnitine on presbyacusis in the rat model. ACTA ACUST UNITED AC 2004; 29:238-41. [PMID: 15142068 DOI: 10.1111/j.1365-2273.2004.00790.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reactive oxygen metabolites are products of oxidative metabolism that are continuously generated in vivo, and are known to produce serious cellular, tissue and genomic damage. l-carnitine is an endogenous amine that has been shown to have an effect on the synthesis of reactive oxygen metabolites. Twenty Wistar rats, 24 months of age, were randomly assigned to two groups as control and l-carnitine treatment groups. One millilitre of distilled water was administered to control rats and 50 mg/kg l-carnitine to rats of l-carnitine treatment groups by intragastric gavage once a day for 30 days. At the end of 30 days, all groups underwent auditory brainstem response testing after administration of intraperitoneal urethane anaesthesia. l-carnitine treatment reduced III, V latencies and I-III, III-V and I-V interpeak latencies (IPL) significantly compared with the control group. l-carnitine treatment improved age-related deterioration in auditory pathways and hence may be a new alternative for the treatment of presbyacusis.
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Picciotti P, Torsello A, Wolf FI, Paludetti G, Gaetani E, Pola R. Age-dependent modifications of expression level of VEGF and its receptors in the inner ear. Exp Gerontol 2004; 39:1253-8. [PMID: 15288700 DOI: 10.1016/j.exger.2004.06.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Revised: 05/19/2004] [Accepted: 06/01/2004] [Indexed: 11/25/2022]
Abstract
The mechanisms responsible for age-associated hearing loss are still incompletely characterized. In this study, we used a murine model of age-dependent hearing loss and evaluated whether this condition is associated with vascular modifications of the structures of the inner ear. We used old C57BL/6J mice that are affected by rapid and severe age-related hearing loss, and analyzed the expression pattern of vascular endothelial growth factor (VEGF), a prototypical angiogenic cytokine, and its receptors Flt-1 and Flk-1 in the inner ear. We report for the first time morphological and quantitative data about the expression of these crucial angiogenic molecules in the murine cochlea. We also show that in this animal model, cochlear VEGF expression is significantly reduced as a function of age. Our findings provide new evidence of possible interdependent relationships between aging, VEGF, and presbycusis, suggesting that vascular abnormalities might play a role in aging-associated hearing loss, with potentially important fundamental and clinical implications.
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