RESUMEN
Losing either type of cochlear sensory hair cells leads to hearing impairment. Inner hair cells act as primary mechanoelectrical transducers, while outer hair cells enhance sound-induced vibrations within the organ of Corti. Established inner ear damage models, such as systemic administration of ototoxic aminoglycosides, yield inconsistent and variable hair cell death in mice. Overcoming this limitation, we developed a method involving surgical delivery of a hyperosmotic sisomicin solution into the posterior semicircular canal of adult mice. This procedure induced rapid and synchronous apoptotic demise of outer hair cells within 14 h, leading to irreversible hearing loss. The combination of sisomicin and hyperosmotic stress caused consistent and synergistic ototoxic damage. Inner hair cells remained until three days post-treatment, after which deterioration in structure and number was observed, culminating in a complete hair cell loss by day seven. This robust animal model provides a valuable tool for otoregenerative research, facilitating single-cell and omics-based studies toward exploring preclinical therapeutic strategies.
Asunto(s)
Modelos Animales de Enfermedad , Pérdida Auditiva , Animales , Ratones , Pérdida Auditiva/inducido químicamente , Pérdida Auditiva/patología , Células Ciliadas Auditivas Externas/efectos de los fármacos , Células Ciliadas Auditivas Externas/patología , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/patología , Apoptosis/efectos de los fármacos , Aminoglicósidos/administración & dosificación , Aminoglicósidos/efectos adversos , Aminoglicósidos/toxicidad , Presión OsmóticaRESUMEN
Cisplatin is an effective chemotherapeutic agent; however, ototoxicity is one of its negative effects that greatly limits the use of cisplatin in clinical settings. Previous research has shown that the most important process cisplatin damage to inner ear cells, such as hair cells (HCs), is the excessive production and accumulation of ROS. Schisandrin B (SchB), is a low-toxicity, inexpensive, naturally occurring antioxidant with a variety of pharmacological effects. Therefore, the potential antioxidant effects of SchB may be useful for cisplatin ototoxicity treatment. In this study, the effects of SchB on cochlear hair cell viability, ROS levels, and expression of apoptosis-related molecules were evaluated by CCK-8, immunofluorescence, flow cytometry, and qRT-PCR, as well as auditory brainstem response (ABR) and dysmorphic product otoacoustic emission (DPOAE) tests to assess the effects on inner ear function. The results showed that SchB treatment increased cell survival, prevented apoptosis, and reduced cisplatin-induced ROS formation. SchB treatment reduced the loss of cochlear HCs caused by cisplatin in exosome culture. In addition, SchB treatment attenuated cisplatin-induced hearing loss and HC loss in mice. This study demonstrates the ability of SchB to inhibit cochlear hair cell apoptosis and ROS generation and shows its potential therapeutic effect on cisplatin ototoxicity.
Asunto(s)
Antineoplásicos , Apoptosis , Supervivencia Celular , Cisplatino , Ciclooctanos , Células Ciliadas Auditivas Internas , Lignanos , Estrés Oxidativo , Compuestos Policíclicos , Especies Reactivas de Oxígeno , Cisplatino/toxicidad , Ciclooctanos/farmacología , Compuestos Policíclicos/farmacología , Compuestos Policíclicos/toxicidad , Animales , Apoptosis/efectos de los fármacos , Lignanos/farmacología , Estrés Oxidativo/efectos de los fármacos , Antineoplásicos/toxicidad , Supervivencia Celular/efectos de los fármacos , Especies Reactivas de Oxígeno/metabolismo , Células Ciliadas Auditivas Internas/efectos de los fármacos , Ratones , Ratones Endogámicos C57BL , Sustancias Protectoras/farmacología , Antioxidantes/farmacología , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Masculino , Ototoxicidad/prevención & controlRESUMEN
The synapses between inner hair cells (IHCs) and spiral ganglion neurons (SGNs) are the most vulnerable structures in the noise-exposed cochlea. Cochlear synaptopathy results from the disruption of these synapses following noise exposure and is considered the main cause of poor speech understanding in noisy environments, even when audiogram results are normal. Cochlear synaptopathy leads to the degeneration of SGNs if damaged IHC-SGN synapses are not promptly recovered. Oxidative stress plays a central role in the pathogenesis of cochlear synaptopathy. C-Phycocyanin (C-PC) has antioxidant and anti-inflammatory activities and is widely utilized in the food and drug industry. However, the effect of the C-PC on noise-induced cochlear damage is unknown. We first investigated the therapeutic effect of C-PC on noise-induced cochlear synaptopathy. In vitro experiments revealed that C-PC reduced the H2O2-induced generation of reactive oxygen species in HEI-OC1 auditory cells. H2O2-induced cytotoxicity in HEI-OC1 cells was reduced with C-PC treatment. After white noise exposure for 3 h at a sound pressure of 118 dB, the guinea pigs intratympanically administered 5 µg/mL C-PC exhibited greater wave I amplitudes in the auditory brainstem response, more IHC synaptic ribbons and more IHC-SGN synapses according to microscopic analysis than the saline-treated guinea pigs. Furthermore, the group treated with C-PC had less intense 4-hydroxynonenal and intercellular adhesion molecule-1 staining in the cochlea compared with the saline group. Our results suggest that C-PC improves cochlear synaptopathy by inhibiting noise-induced oxidative stress and the inflammatory response in the cochlea.
Asunto(s)
Cóclea , Molécula 1 de Adhesión Intercelular , Ruido , Estrés Oxidativo , Ficocianina , Sinapsis , Animales , Estrés Oxidativo/efectos de los fármacos , Cobayas , Ficocianina/farmacología , Ficocianina/uso terapéutico , Cóclea/metabolismo , Cóclea/efectos de los fármacos , Cóclea/patología , Sinapsis/efectos de los fármacos , Sinapsis/metabolismo , Ruido/efectos adversos , Molécula 1 de Adhesión Intercelular/metabolismo , Pérdida Auditiva Provocada por Ruido/tratamiento farmacológico , Pérdida Auditiva Provocada por Ruido/metabolismo , Pérdida Auditiva Provocada por Ruido/patología , Especies Reactivas de Oxígeno/metabolismo , Masculino , Ganglio Espiral de la Cóclea/efectos de los fármacos , Ganglio Espiral de la Cóclea/metabolismo , Ganglio Espiral de la Cóclea/patología , Peróxido de Hidrógeno/metabolismo , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/metabolismo , Células Ciliadas Auditivas Internas/patología , Antioxidantes/farmacología , Línea Celular , Pérdida de Audición OcultaRESUMEN
Intracochlear electrical stimulation (ES) generated by cochlear implants (CIs) is used to activate auditory nerves to restore hearing perception in deaf subjects and those with residual hearing who use electroacoustic stimulation (EAS) technology. Approximately 1/3 of EAS recipients experience loss of residual hearing a few months after ES activation, but the underlying mechanism is unknown. Clinical evidence indicates that the loss is related to the previous history of noise-induced hearing loss (NIHL). In this report, we investigated the impact of intracochlear ES on oxidative stress levels and synaptic counts in inner hair cells (IHCs) of the apical, middle and basal regions of guinea pigs with normal hearing (NH) and NIHL. Our results demonstrated that intracochlear ES with an intensity of 6 dB above the thresholds of electrically evoked compound action potentials (ECAPs) could induce the elevation of oxidative stress levels, resulting in a loss of IHC synapses near the electrodes in the basal and middle regions of the NH cochleae. Furthermore, the apical region of cochleae with NIHL were more susceptible to synaptic loss induced by relatively low-intensity ES than that of NH cochleae, resulting from the additional elevation of oxidative stress levels and the reduced antioxidant capability throughout the whole cochlea.
Asunto(s)
Cóclea/patología , Implantes Cocleares , Estimulación Eléctrica , Células Ciliadas Auditivas Internas/patología , Pérdida Auditiva Provocada por Ruido/fisiopatología , Estrés Oxidativo/fisiología , Sinapsis/patología , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Aldehídos , Animales , Antioxidantes/farmacología , Cóclea/efectos de los fármacos , Cóclea/fisiopatología , Potenciales Evocados Auditivos del Tronco Encefálico , Ácidos Grasos Insaturados/metabolismo , Cobayas , Células Ciliadas Auditivas Internas/efectos de los fármacos , Pérdida Auditiva Provocada por Ruido/metabolismo , Hidroxiácidos/metabolismo , Isoindoles/farmacología , Compuestos de Organoselenio/farmacología , Estrés Oxidativo/efectos de los fármacos , Índice de Severidad de la Enfermedad , Sinapsis/efectos de los fármacos , Tirosina/análogos & derivados , Tirosina/efectos de los fármacos , Tirosina/metabolismoRESUMEN
Hippo signaling is an evolutionarily conserved pathway that restricts growth and regeneration predominantly by suppressing the activity of the transcriptional coactivator Yap. Using a high-throughput phenotypic screen, we identified a potent and non-toxic activator of Yap. In vitro kinase assays show that the compound acts as an ATP-competitive inhibitor of Lats kinases-the core enzymes in Hippo signaling. The substance prevents Yap phosphorylation and induces proliferation of supporting cells in the murine inner ear, murine cardiomyocytes, and human Müller glia in retinal organoids. RNA sequencing indicates that the inhibitor reversibly activates the expression of transcriptional Yap targets: upon withdrawal, a subset of supporting-cell progeny exits the cell cycle and upregulates genes characteristic of sensory hair cells. Our results suggest that the pharmacological inhibition of Lats kinases may promote initial stages of the proliferative regeneration of hair cells, a process thought to be permanently suppressed in the adult mammalian inner ear.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/genética , Proliferación Celular/efectos de los fármacos , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Bibliotecas de Moléculas Pequeñas/farmacología , Proteínas Supresoras de Tumor/antagonistas & inhibidores , Proteínas Adaptadoras Transductoras de Señales/metabolismo , Animales , Línea Celular , Línea Celular Tumoral , Proliferación Celular/genética , Células Ependimogliales/citología , Células Ependimogliales/efectos de los fármacos , Células Ependimogliales/metabolismo , Células HEK293 , Células Ciliadas Auditivas Internas/citología , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/metabolismo , Humanos , Ratones Noqueados , Ratones Transgénicos , Miocitos Cardíacos/citología , Miocitos Cardíacos/efectos de los fármacos , Miocitos Cardíacos/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Transducción de Señal/efectos de los fármacos , Transducción de Señal/genética , Proteínas Supresoras de Tumor/metabolismo , Proteínas Señalizadoras YAPRESUMEN
Paraquat, a superoxide generator, can damage the cochlea causing an ototoxic hearing loss. The purpose of the study was to determine if deletion of Bak, a pro-apoptotic gene, would reduce paraquat ototoxicity or if deletion of Sirt3, which delays age-related hearing loss under caloric restriction, would increase paraquat ototoxicity. We tested these two hypotheses by treating postnatal day 3 cochlear cultures from Bak±, Bak-/-, Sirt3±, Sirt3-/-, and WT mice with paraquat and compared the results to a standard rat model of paraquat ototoxicity. Paraquat damaged nerve fibers and dose-dependently destroyed rat outer hair cells (OHCs) and inner hair cells (IHCs). Rat hair cell loss began in the base of the cochlea with a 10 µM dose and as the dose increased from 50 to 500 µM, the hair cell loss increased near the base of the cochlea and spread toward the apex of the cochlea. Rat OHC losses were consistently greater than IHC losses. Unexpectedly, in all mouse genotypes, paraquat-induced hair cell lesions were maximal near the apex of the cochlea and minimal near the base. This unusual damage gradient is opposite to that seen in paraquat-treated rats and in mice and rats treated with other ototoxic drugs. However, paraquat always induced greater OHC loss than IHC loss in all mouse strains. Contrary to our hypothesis, Bak deficient mice were more vulnerable to paraquat ototoxicity than WT mice (Bak-/- > Bak± > WT), suggesting that Bak plays a protective role against hair cell stress. Also, contrary to expectation, Sirt3-deficient mice did not differ significantly from WT mice, possibly due to the fact that Sirt3 was not experimentally upregulated in Sirt3-expressing mice prior to paraquat treatment. Our results show for the first time a gradient of ototoxic damage in mice that is greater in the apex than the base of the cochlea.
Asunto(s)
Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Externas/efectos de los fármacos , Herbicidas/toxicidad , Paraquat/toxicidad , Sirtuina 3/deficiencia , Proteína Destructora del Antagonista Homólogo bcl-2/deficiencia , Animales , Animales Recién Nacidos , Células Cultivadas , Cóclea/efectos de los fármacos , Cóclea/metabolismo , Cóclea/patología , Relación Dosis-Respuesta a Droga , Femenino , Células Ciliadas Auditivas Internas/metabolismo , Células Ciliadas Auditivas Internas/patología , Células Ciliadas Auditivas Externas/metabolismo , Células Ciliadas Auditivas Externas/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Técnicas de Cultivo de Órganos , Ratas , Ratas Sprague-Dawley , Sirtuina 3/genética , Proteína Destructora del Antagonista Homólogo bcl-2/genéticaRESUMEN
Auditory neuropathy is caused by the loss of afferent input to the brainstem via the components of the neural pathway comprising inner hair cells and the first order neurons of the spiral ganglion. Recent work has identified the synapse between cochlear primary afferent neurons and sensory hair cells as a particularly vulnerable component of this pathway. Loss of these synapses due to noise exposure or aging results in the pathology identified as hidden hearing loss, an initial stage of cochlear dysfunction that goes undetected in standard hearing tests. We show here that repulsive axonal guidance molecule a (RGMa) acts to prevent regrowth and synaptogenesis of peripheral auditory nerve fibers with inner hair cells. Treatment of noise-exposed animals with an anti-RGMa blocking antibody regenerated inner hair cell synapses and resulted in recovery of wave-I amplitude of the auditory brainstem response, indicating effective reversal of synaptopathy.
Asunto(s)
Proteínas Ligadas a GPI/antagonistas & inhibidores , Pérdida Auditiva Provocada por Ruido/tratamiento farmacológico , Proteínas del Tejido Nervioso/antagonistas & inhibidores , Regeneración/efectos de los fármacos , Estimulación Acústica/métodos , Animales , Umbral Auditivo , Cóclea/citología , Cóclea/efectos de los fármacos , Cóclea/patología , Modelos Animales de Enfermedad , Femenino , Proteínas Ligadas a GPI/metabolismo , Células Ciliadas Auditivas Internas/efectos de los fármacos , Pérdida Auditiva Provocada por Ruido/patología , Humanos , Masculino , Ratones , Proteínas del Tejido Nervioso/metabolismo , Sinapsis/efectos de los fármacos , Sinapsis/patologíaRESUMEN
The peripheral auditory and vestibular systems rely on sensorineural structures that are vulnerable to ototoxic agents that cause hearing loss and/or equilibrium deficits. Although attention has focused on hair cell loss as the primary pathology underlying ototoxicity, evidence from the peripheral vestibular system indicates that hair cell loss during chronic exposure is preceded by synaptic uncoupling from the neurons and is potentially reversible. To determine if synaptic pathology also occurs in the peripheral auditory system, we examined the extent, time course, and reversibility of functional and morphological alterations in cochleae from mice exposed to 3,3'-iminodipropionitrile (IDPN) in drinking water for 2, 4 or 6 weeks. Functionally, IDPN exposure caused progressive high- to low-frequency hearing loss assessed by measurement of auditory brainstem response wave I absolute thresholds and amplitudes. The extent of hearing loss scaled with the magnitude of vestibular dysfunction assessed behaviorally. Morphologically, IDPN exposure caused progressive loss of outer hair cells (OHCs) and synapses between the inner hair cells (IHCs) and primary auditory neurons. In contrast, IHCs were spared from ototoxic damage. Importantly, hearing loss consistent with cochlear synaptopathy preceded loss of OHCs and synapses and, moreover, recovered if IDPN exposure was stopped before morphological pathology occurred. Our observations suggest that synaptic uncoupling, perhaps as an early phase of cochlear synaptopathy, also occurs in the peripheral auditory system in response to IDPN exposure. These findings identify novel mechanisms that contribute to the earliest stages of hearing loss in response to ototoxic agents and possibly other forms of acquired hearing loss.
Asunto(s)
Cóclea/efectos de los fármacos , Pérdida Auditiva/inducido químicamente , Nitrilos/toxicidad , Ototoxicidad/etiología , Animales , Cóclea/patología , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/patología , Células Ciliadas Auditivas Externas/efectos de los fármacos , Células Ciliadas Auditivas Externas/patología , Pérdida Auditiva/fisiopatología , Masculino , Ratones , Ratones de la Cepa 129 , Nitrilos/administración & dosificación , Ototoxicidad/fisiopatología , Sinapsis/efectos de los fármacos , Sinapsis/patología , Factores de TiempoRESUMEN
TrkB agonist drugs are shown here to have a significant effect on the regeneration of afferent cochlear synapses after noise-induced synaptopathy. The effects were consistent with regeneration of cochlear synapses that we observed in vitro after synaptic loss due to kainic acid-induced glutamate toxicity and were elicited by administration of TrkB agonists, amitriptyline, and 7,8-dihydroxyflavone, directly into the cochlea via the posterior semicircular canal 48 hours after exposure to noise. Synaptic counts at the inner hair cell and wave 1 amplitudes in the auditory brainstem response (ABR) were partially restored 2 weeks after drug treatment. Effects of amitriptyline on wave 1 amplitude and afferent auditory synapse numbers in noise-exposed ears after systemic (as opposed to local) delivery were profound and long-lasting; synapses in the treated animals remained intact 1 year after the treatment. However, the effect of systemically delivered amitriptyline on synaptic rescue was dependent on dose and the time window of administration: it was only effective when given before noise exposure at the highest injected dose. The long-lasting effect and the efficacy of postexposure treatment indicate a potential broad application for the treatment of synaptopathy, which often goes undetected until well after the original damaging exposures.
Asunto(s)
Pérdida Auditiva Provocada por Ruido/tratamiento farmacológico , Glicoproteínas de Membrana/agonistas , Amitriptilina/administración & dosificación , Amitriptilina/farmacología , Animales , Umbral Auditivo/efectos de los fármacos , Umbral Auditivo/fisiología , Cóclea/efectos de los fármacos , Cóclea/fisiopatología , Nervio Coclear/efectos de los fármacos , Nervio Coclear/fisiopatología , Técnicas de Cocultivo , Modelos Animales de Enfermedad , Potenciales Evocados Auditivos del Tronco Encefálico/efectos de los fármacos , Potenciales Evocados Auditivos del Tronco Encefálico/fisiología , Flavonas/administración & dosificación , Flavonas/farmacología , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/fisiología , Pérdida Auditiva Provocada por Ruido/fisiopatología , Glicoproteínas de Membrana/fisiología , Ratones , Ratones Endogámicos CBA , Proteínas Tirosina Quinasas/fisiología , Regeneración/efectos de los fármacos , Regeneración/fisiología , Sinapsis/efectos de los fármacos , Sinapsis/fisiologíaRESUMEN
Olivocochlear neurons make temporary cholinergic synapses on inner hair cells of the rodent cochlea in the first 2 to 3 wk after birth. Repetitive stimulation of these efferent neurons causes facilitation of evoked release and increased spontaneous release that continues for seconds to minutes. Presynaptic nicotinic acetylcholine receptors (nAChRs) are known to modulate neurotransmitter release from brain neurons. The present study explores the hypothesis that presynaptic nAChRs help to increase spontaneous release from efferent terminals on cochlear hair cells. Direct application of nicotine (which does not activate the hair cells' α9α10-containing nAChRs) produces sustained efferent transmitter release, implicating presynaptic nAChRs in this response. The effect of nicotine was reduced by application of ryanodine that reduces release of calcium from intraterminal stores.NEW & NOTEWORTHY Sensory organs exhibit spontaneous activity before the onset of response to external stimuli. Such activity in the cochlea is subject to modulation by cholinergic efferent neurons that directly inhibit sensory hair cells (inner hair cells). Those efferent neurons are themselves subject to various modulatory mechanisms. One such mechanism is positive feedback by released acetylcholine onto presynaptic nicotinic acetylcholine receptors causing further release of acetylcholine.
Asunto(s)
Células Ciliadas Auditivas Internas/fisiología , Nicotina/administración & dosificación , Receptores Nicotínicos/fisiología , Animales , Células Cultivadas , Femenino , Células Ciliadas Auditivas Internas/efectos de los fármacos , Masculino , Potenciales de la Membrana/efectos de los fármacos , Ratones Endogámicos C57BL , Neuronas Eferentes/efectos de los fármacos , Neuronas Eferentes/fisiologíaRESUMEN
Temporal resolution is essential for processing complex auditory information such as speech. In hearing impaired persons, temporal resolution, often assessed by detection of brief gaps in continuous sound stimuli, is typically poorer than in individuals with normal hearing. At low stimulus presentation levels, hearing impaired individuals perform poorly but the deficits are greatly reduced when the sensation level of the stimuli are adjusted to match their normal hearing peers. In the present study, we evaluated the effect of selective inner hair cell loss on gap detection in chinchillas treated with carboplatin, an anticancer drug that selectively damages inner hair cells and afferents in this species. Treatment with carboplatin-induced inner hair cell loss of ~ 70 % but had little effect on audiometric thresholds in quiet and produced no evidence of outer hair cell loss. In contrast, selective inner hair cell loss had a significant effect on gap detection ability across a wide range of presentation levels. These results suggest that gap detection tasks are more sensitive to inner hair cell pathology than audiometric thresholds.
Asunto(s)
Antineoplásicos/efectos adversos , Percepción Auditiva/efectos de los fármacos , Carboplatino/efectos adversos , Pérdida Auditiva/inducido químicamente , Audición/efectos de los fármacos , Animales , Chinchilla , Células Ciliadas Auditivas Internas/efectos de los fármacos , MasculinoRESUMEN
Objective: To measure the cochlear compound action potential (CAP) and the densities of hair cells (HCs) along the whole length of the basilar membrane (BM) in adult chinchillas. And to investigate the relationship between the severity of inner hair cells (IHCs) loss and the changes of CAP by using carboplatin-cochlear lesion model. Methods: Totally 18 chinchillas were recruited after ontological evaluation. They were randomly divided into three groups (with 6 subjects in each), A: control, B and C: legion groups treated with one or two shot(s) of carboplatin respectively (76 mg/kg in one shot, i.p., one-week interval between the two shots). Endpoint tests were performed 30 days after the carboplatin treatment in groups B and C, and matched time in group A. A sliver-ball electrode was placed into round window niche via hypotympanic approach in anesthetized chinchilla. CAP was measured in response to clicks and tone burst of 0.5, 1, 2, 4, 8, 16 kHz respectively under anesthesia. CAP amplitudes and thresholds were measured and compared across the groups. After the recording, the whole cochlea surface preparation was made and the HCs were stained in histochemistry against substrate of succinate dehydrogenase (SDH). Images were taken with high-resolution digital camera under light microscope and across the whole cochlea. The length of the basilar membrane (BM) and the number of both IHCs and OHCs were counted. The HC density was calculated as the number of HCs per 10% BM length. Results: The CAP thresholds were (7.1±2.6), (25.4±5.0), (24.6±5.4), (10.4±5.0), (0.4±1.4), (4.2±6.3) and (17.1±14.1) dB SPL (from 6 subjects in group A, n=12 ears) corresponding to stimuli of Click and 0.5, 1, 2, 4, 8, 16 kHz tone bursts respectively. The total number of cochlear HCs were measured as (8 936±643) (x±s) and the average length of the BMs was (17.73±1.012) mm from the six subjects in the group A (n=12 ears). The HC density was found to be varied slightly across the BM. There was no significant CAP threshold difference between the control (group A) and the group B, which received one shot of carboplatin. However, the maximal CAP amplitude was reduced by 40% in the group B and compared with group A. Correspondingly, approximately 40% loss of IHCs were seen. In contrast, a significant CAP threshold shift was seen in subjects receiving two shots of carboplatin (group C), which was accompanied by a loss of 90% IHCs. Conclusions: The CAP thresholds of adult chinchillas show typical open-V shape with the lowest values at 2, 4, and 8 kHz. IHC loss by carboplatin in certain degree is well correlated with CAP amplitude reduction, but does not change the threshold when inner hair cell loss reaches 40%, however, if inner hair cell loss exceeds 80%, the threshold shift of CAP will be inevitable.
Asunto(s)
Potenciales de Acción , Antineoplásicos/efectos adversos , Umbral Auditivo/efectos de los fármacos , Carboplatino/efectos adversos , Cóclea , Células Ciliadas Auditivas Internas , Potenciales de Acción/fisiología , Animales , Antineoplásicos/farmacología , Umbral Auditivo/fisiología , Carboplatino/farmacología , Chinchilla , Cóclea/patología , Cóclea/fisiopatología , Modelos Animales de Enfermedad , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/patologíaRESUMEN
2-Hydroxypropyl-ß-cyclodextrin (HPßCD), a cholesterol chelator, is being used to treat diseases associated with abnormal cholesterol metabolism such as Niemann-Pick C1 (NPC1). However, the high doses of HPßCD needed to slow disease progression may cause hearing loss. Previous studies in mice have suggested that HPßCD ototoxicity results from selective outer hair cell (OHC) damage. However, it is unclear if HPßCD causes the same type of damage or is more or less toxic to other species such as rats, which are widely used in toxicity research. To address these issues, rats were given a subcutaneous injection of HPßCD between 500 and 4000 mg/kg. Distortion product otoacoustic emissions (DPOAE), the cochlear summating potential (SP), and compound action potential (CAP) were used to assess cochlear function followed by quantitative analysis of OHC and inner hair cell (IHC) loss. The 3000- and 4000-mg/kg doses abolished DPOAE and greatly reduced SP and CAP amplitudes. These functional deficits were associated with nearly complete loss of OHC as well as ~ 80% IHC loss over the basal two thirds of the cochlea. The 2000-mg/kg dose abolished DPOAE and significantly reduced SP and CAP amplitudes at the high frequencies. These deficits were linked to OHC and IHC losses in the high-frequency region of the cochlea. Little or no damage occurred with 500 or 1000 mg/kg of HPßCD. The HPßCD-induced functional and structural deficits in rats occurred suddenly, involved damage to both IHC and OHC, and were more severe than those reported in mice.
Asunto(s)
2-Hidroxipropil-beta-Ciclodextrina/farmacología , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Externas/efectos de los fármacos , Pérdida Auditiva/inducido químicamente , Animales , Cóclea/efectos de los fármacos , Emisiones Otoacústicas Espontáneas/efectos de los fármacos , Ototoxicidad/tratamiento farmacológico , Ratas Sprague-DawleyRESUMEN
Auditory inner hair cells (IHCs) convert sound vibrations into receptor potentials that drive synaptic transmission. For the precise encoding of sound qualities, receptor potentials are shaped by K+ conductances tuning the properties of the IHC membrane. Using patch-clamp and computational modeling, we unravel this membrane specialization showing that IHCs express an exclusive repertoire of six voltage-dependent K+ conductances mediated by Kv1.8, Kv7.4, Kv11.1, Kv12.1, and BKCa channels. All channels are active at rest but are triggered differentially during sound stimulation. This enables non-saturating tuning over a far larger potential range than in IHCs expressing fewer current entities. Each conductance contributes to optimizing responses, but the combined activity of all channels synergistically improves phase locking and the dynamic range of intensities that IHCs can encode. Conversely, hypothetical simpler IHCs appear limited to encode only certain aspects (frequency or intensity). The exclusive channel repertoire of IHCs thus constitutes an evolutionary adaptation to encode complex sound through multifaceted receptor potentials.
Asunto(s)
Células Ciliadas Auditivas Internas/metabolismo , Canales de Potasio/metabolismo , Sonido , 4-Aminopiridina/farmacología , Animales , Células CHO , Cricetulus , Células Ciliadas Auditivas Internas/efectos de los fármacos , Activación del Canal Iónico/efectos de los fármacos , Potenciales de la Membrana/efectos de los fármacos , Ratones Endogámicos C57BL , Subunidades de Proteína/metabolismoRESUMEN
Despite the excellent antimicrobial activity of aminoglycoside antibiotics, permanent inner ear damage associated with the use of these drugs has resulted in the need to develop strategies to address the ototoxic risk given their widespread use. In a previous study, we showed that avocado oil protects ear hair cells from damage caused by neomycin. However, the detailed mechanism by which this protection occurs is still unclear. Here, we investigated the auditory cell-protective mechanism of enhanced functional avocado oil extract (DKB122). RNA sequencing followed by pathway analysis revealed that DKB122 has the potential to enhance the expression of detoxification and antioxidant genes associated with glutathione metabolism (Hmox4, Gsta4, Mgst1, and Abcc3) in HEI-OC1 cells. Additionally, DKB122 effectively decreased ROS levels, resulting in the inhibition of apoptosis in HEI-OC1 cells. The expression of the inflammatory genes that encode chemokines and interleukins was also downregulated by DKB122 treatment. Consistent with these results, DKB122 significantly inhibited p65 nuclear migration induced by TNF-α or LPS in HEI-OC1 cells and THP-1 cells and the expression of inflammatory chemokine and interleukin genes induced by TNF-α was significantly reduced. Moreover, DKB122 treatment increased LC3-II and decreased p62 in HEI-OC1 cells, suggesting that DKB122 increases autophagic flux. These results suggest that DKB122 has otoprotective effects attributable to its antioxidant activity, induction of antioxidant gene expression, anti-inflammatory activity, and autophagy activation.
Asunto(s)
Aminoglicósidos/efectos adversos , Antibacterianos/efectos adversos , Ototoxicidad/tratamiento farmacológico , Ototoxicidad/etiología , Ototoxicidad/genética , Persea/química , Aceites de Plantas/farmacología , Aceites de Plantas/uso terapéutico , Autofagia/efectos de los fármacos , Autofagia/genética , Células Cultivadas , Citocinas/metabolismo , Expresión Génica/efectos de los fármacos , Glutatión/metabolismo , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/patología , Humanos , Mediadores de Inflamación/metabolismo , Fase I de la Desintoxicación Metabólica/genética , Ototoxicidad/patología , Estrés Oxidativo/genética , Factor de Necrosis Tumoral alfa/metabolismoRESUMEN
OBJECTIVE: Nicotinamide riboside (NR) has been proved to protect the hearing. To achieve animal models of temporary threshold shift (TTS) and permanent threshold shift (PTS) respectively, evaluate the dynamic change of ribbon synapse before and after NR administration. METHODS: Mice were divided into control group, noise exposure (NE) group and NR group. The noise was exposed to NE and NR group, and NR was injected before noise exposure. Auditory brainstem response (ABR), ribbon synapse count and cochlear morphology were tested, as well as the concentration of hydrogen peroxide (H2O2) and ATP. RESULTS: Ribbon synapse count decrease with the intensity of noise exposure, and the cochlear morphology remains stable during TTS and was damaged during PTS. NR promotes the oxidation resistance to protect the synapse and the inner ear morphology. CONCLUSION: Our findings suggest that TTS mice are more vulnerable to noise, and NR can promote the recovery of the synapse count to protect the animals' hearing.
Asunto(s)
Estimulación Acústica/efectos adversos , Células Ciliadas Auditivas Internas/fisiología , Pérdida Auditiva Provocada por Ruido/prevención & control , Niacinamida/análogos & derivados , Compuestos de Piridinio/uso terapéutico , Recuperación de la Función/fisiología , Sinapsis/fisiología , Animales , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/patología , Pérdida Auditiva Provocada por Ruido/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Niacinamida/farmacología , Niacinamida/uso terapéutico , Estrés Oxidativo/efectos de los fármacos , Estrés Oxidativo/fisiología , Compuestos de Piridinio/farmacología , Sinapsis/efectos de los fármacos , Sinapsis/patologíaRESUMEN
To examine whether exposure to sodium salicylate disrupts expression of vesicular glutamate transporter 3 (VGLUT3) and whether the alteration in expression corresponds to increased risk for tinnitus. Rats were treated with saline (control) or sodium salicylate (treated) Rats were examined for tinnitus by monitoring gap-pre-pulse inhibition of the acoustic startle reflex (GPIAS). Auditory brainstem response (ABR) was applied to evaluate hearing function after treatment. Rats were sacrificed after injection to obtain the cochlea, cochlear nucleus (CN), and inferior colliculus (IC) for examination of VGLUT3 expression. No significant differences in hearing thresholds between groups were identified (p>0.05). Tinnitus in sodium salicylate-treated rats was confirmed by GPIAS. VGLUT3 encoded by solute carrier family 17 members 8 (SLC17a8) expression was significantly increased in inner hair cells (IHCs) of the cochlea in treated animals, compared with controls (p<0.01). No significant differences in VGLUT3 expression between groups were found for the cochlear nucleus (CN) or IC (p>0.05). Exposure to sodium salicylate may disrupt SLC17a8 expression in IHCs, leading to alterations that correspond to tinnitus in rats. However, the CN and IC are unaffected by exposure to sodium salicylate, suggesting that enhancement of VGLUT3 expression in IHCs may contribute to the pathogenesis of tinnitus.
Asunto(s)
Antiinflamatorios no Esteroideos/efectos adversos , Células Ciliadas Auditivas Internas/efectos de los fármacos , Salicilato de Sodio/efectos adversos , Acúfeno/inducido químicamente , Proteínas de Transporte Vesicular de Glutamato/metabolismo , Animales , Umbral Auditivo/efectos de los fármacos , Núcleo Coclear/efectos de los fármacos , Núcleo Coclear/metabolismo , Células Ciliadas Auditivas Internas/metabolismo , Colículos Inferiores/efectos de los fármacos , Colículos Inferiores/metabolismo , Masculino , Ratas WistarRESUMEN
Hair cells in the auditory organ of the vertebrate inner ear are the sensory receptors that convert acoustic stimuli into electrical signals that are conveyed along the auditory nerve to the brainstem. Hair cells are highly susceptible to ototoxic drugs, infection, and acoustic trauma, which can cause cellular degeneration. In mammals, hair cells that are lost after damage are not replaced, leading to permanent hearing impairments. By contrast, supporting cells in birds and other non-mammalian vertebrates regenerate hair cells after damage, which restores hearing function. The cellular mechanisms that regulate hair cell regeneration are not well understood. We investigated the role of vascular endothelial growth factor (VEGF) during regeneration of auditory hair cells in chickens after ototoxic injury. Using RNA-Seq, immunolabeling, and in situ hybridization, we found that VEGFA, VEGFC, VEGFR1, VEGFR2, and VEGFR3 were expressed in the auditory epithelium, with VEGFA expressed in hair cells and VEGFR1 and VEGFR2 expressed in supporting cells. Using organotypic cultures of the chicken cochlear duct, we found that blocking VEGF receptor activity during hair cell injury reduced supporting cell proliferation as well as the numbers of regenerated hair cells. By contrast, addition of recombinant human VEGFA to organ cultures caused an increase in both supporting cell division and hair cell regeneration. VEGF's effects on supporting cells were preserved in isolated supporting cell cultures, indicating that VEGF can act directly upon supporting cells. These observations demonstrate a heretofore uncharacterized function for VEGF signaling as a critical positive regulator of hair cell regeneration in the avian inner ear.
Asunto(s)
Proteínas Aviares/metabolismo , Proliferación Celular , Células Ciliadas Auditivas Internas/metabolismo , Receptores de Factores de Crecimiento Endotelial Vascular/metabolismo , Regeneración , Factor A de Crecimiento Endotelial Vascular/metabolismo , Animales , Apoptosis , Proteínas Aviares/genética , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Pollos , Regulación de la Expresión Génica , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Laberínticas de Soporte/efectos de los fármacos , Células Laberínticas de Soporte/metabolismo , Células Laberínticas de Soporte/patología , Mecanotransducción Celular , Regeneración/efectos de los fármacos , Factores de Tiempo , Técnicas de Cultivo de Tejidos , Factor A de Crecimiento Endotelial Vascular/genética , Factor A de Crecimiento Endotelial Vascular/farmacologíaRESUMEN
The development of asymmetric patterns along biologically relevant axes is a hallmark of many vertebrate organs or structures. One example is the sensory epithelium of the mammalian auditory system. Two distinct types of mechanosensory hair cells (inner and outer) and at least six types of associated supporting cells are precisely and asymmetrically arrayed along the radial (medial-lateral) axis of the cochlear spiral. Immunolabeling of developing cochleae indicates differential expression of Glycogen synthase kinase 3ß (GSK3ß) along the same axis. To determine whether GSK3ß plays a role in specification of cell fates along the medial-lateral axis, GSK3 activity was blocked pharmacologically in cochlear explants. Results indicate significant changes in both the number of hair cells and in the specification of hair cell phenotypes. The overall number of inner hair cells increased as a result of both a shift in the medial boundary between sensory and non-sensory regions of the cochlea and a change in the specification of inner and outer hair cell phenotypes. Previous studies have inhibited GSK3 as a method to examine effects of canonical Wnt signaling. However, quantification of changes in Wnt pathway target genes in GSK3-inhibited cochleae, and treatment with more specific Wnt agonists, indicated that the Wnt pathway is not activated. Instead, expression of Bmp4 in a population of GSK3ß-expressing cells was shown to be down-regulated. Finally, addition of BMP4 to GSK3-inhibited cochleae achieved a partial rescue of the hair cell phenotype. These results demonstrate a role for GSK3ß in the specification of cellular identities along the medial-lateral axis of the cochlea and provide evidence for a positive role for GSK3ß in the expression of Bmp4.
Asunto(s)
Linaje de la Célula , Glucógeno Sintasa Quinasa 3 beta/metabolismo , Células Ciliadas Auditivas/citología , Células Ciliadas Auditivas/enzimología , Animales , Proteína Morfogenética Ósea 4/farmacología , Linaje de la Célula/efectos de los fármacos , Proliferación Celular/efectos de los fármacos , Epitelio/efectos de los fármacos , Epitelio/metabolismo , Femenino , Glucógeno Sintasa Quinasa 3 beta/antagonistas & inhibidores , Células Ciliadas Auditivas/efectos de los fármacos , Células Ciliadas Auditivas Internas/citología , Células Ciliadas Auditivas Internas/efectos de los fármacos , Células Ciliadas Auditivas Internas/enzimología , Células Ciliadas Auditivas Externas/citología , Células Ciliadas Auditivas Externas/efectos de los fármacos , Células Ciliadas Auditivas Externas/enzimología , Ratones , Modelos Biológicos , Inhibidores de Proteínas Quinasas/farmacología , Receptores de Factores de Crecimiento de Fibroblastos/metabolismo , Vía de Señalización Wnt/efectos de los fármacosRESUMEN
Manganese (Mn) is an essential cofactor for many enzymes and thus plays an important role in normal growth and development. However, persistent exposure to high Mn concentrations can result in deleterious effects on not only the central nervous system but also peripheral nerves, including nerves associated with the auditory system. Our initial research on cochlear organotypic cultures in vitro showed that N-acetylcysteine (NAC) clearly decreases Mn-induced losses in hair cells (HCs), auditory nerve ï¬bers (ANFs) and spiral ganglion neurons (SGNs) in a concentration-dependent manner. Salidroside (SAL) (p-hydroxyphenethyl-b-d-glucoside; C14H20O7), which is extracted from Rhodiola rosea L, has many pharmacological actions and antioxidative, antiaging, neuroprotective and anticancer effects. We hypothesized that SAL could also protect HCs, ANFs and SGNs from Mn injury. Cochlear organotypic cultures were treated with 1 mM Mn alone or combined with SAL (1-1000 µM). The neurofilament staining results showed that HCs, ANFs and SGNs were seriously damaged at high concentrations (100-1000 µM) but less damaged at low concentrations (1-10 µM). SAL may protect against 1 mM Mn-induced HC loss and axonal degeneration, suggesting that SAL could be a promising drug for clinical applications.