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This study aimed to evaluate the therapeutic potential of inhibiting protein arginine methyltransferase 5(PRMT5)in cisplatin-induced hearing loss.The effects of PRMT5 inhibition on cisplatin-induced auditory injury were determined using immunohistochemistry,apoptosis assays,and auditory brainstem response.The mechanism of PRMT5 inhibition on hair cell survival was assessed using RNA-seq and Cleavage Under Targets and Tagment-quantitative polymerase chain reaction(CUT&Tag-qPCR)analyses in the HEI-OC1 cell line.Pharmacological inhibition of PRMT5 significantly alleviated cisplatin-induced damage to hair cells and spiral ganglion neurons in the cochlea and decreased apoptosis by protecting mitochondrial function and preventing the accumulation of reactive oxygen species.CUT&Tag-qPCR analysis demonstrated that inhibition of PRMT5 in HEI-OC1 cells reduced the accumulation of H4R3me2s/H3R8me2s marks at the promoter region of the Pik3ca gene,thus activating the expression of Pik3ca.These findings suggest that PRMT5 inhibitors have strong potential as agents against cisplatin-induced ototoxicity and can lay the foundation for further research on treatment strategies of hearing loss.
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Objective@#To research the auditory nerve transduction effects under multi-wavelength pulsed laser stimulations within a safe and acceptable signal range.@*Methods@#The real-time detection of intracellular calcium concentration was adopted by specific fluorescent indicator staining based on calcium imager. The spiral ganglion cells of mice were cultured in vitro. After fluorescent indicating, morphologic observation under optical microscope, Fura-2 calcium ion fluorescence excitation, intact morphology cells selection, fixing the optical fiber, the spiral ganglion cells were irradiated by different wavelength laser, including visible light (450 nm) and near infrared light (808 nm,1 065 nm). The intracellular calcium concentration was monitored by calcium ion imaging.@*Results@#When 450 nm laser stimulated spiral ganglion cells, the intracellular calcium concentration was strongly increased, however, for other wavelength laser stimulation, there was no obvious relative response. And the sensitivity expression of the nerve cells under laser was related with the location of laser fiber. Cells closer to the fiber produced more obvious changes in calcium ion concentration, while for cells farther away from the fiber, the change amplitudes were weaker although the number of changes in calcium ion concentration was consistent.@*Conclusion@#The spiral ganglion cells of mice can induce a signal transduction response under the action of laser, and the response has laser wavelength selectivity.
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To research the auditory nerve transduction effects under multi-wavelength pulsed laser stimulations within a safe and acceptable signal range. The real-time detection of intracellular calcium concentration was adopted by specific fluorescent indicator staining based on calcium imager. The spiral ganglion cells of mice were cultured in vitro. After fluorescent indicating, morphologic observation under optical microscope, Fura-2 calcium ion fluorescence excitation, intact morphology cells selection, fixing the optical fiber, the spiral ganglion cells were irradiated by different wavelength laser, including visible light (450 nm) and near infrared light (808 nm,1 065 nm). The intracellular calcium concentration was monitored by calcium ion imaging. When 450 nm laser stimulated spiral ganglion cells, the intracellular calcium concentration was strongly increased, however, for other wavelength laser stimulation, there was no obvious relative response. And the sensitivity expression of the nerve cells under laser was related with the location of laser fiber. Cells closer to the fiber produced more obvious changes in calcium ion concentration, while for cells farther away from the fiber, the change amplitudes were weaker although the number of changes in calcium ion concentration was consistent. The spiral ganglion cells of mice can induce a signal transduction response under the action of laser, and the response has laser wavelength selectivity.
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Auditory neuropathy (AN) is a hearing disorder where cochlear inner hair cell and/or the auditory nerve function is disrupted while outer hair cell function is normal. It can affect people of all ages, from infancy to adulthood. People with auditory neuropathy may have normal hearing threshold, or hearing loss ranging from mild to severe; they always have poor speech-perception abilities. It is a heterogeneous disorder which can have either congenital or acquired causes. AN may result from specific loss of cochlear inner hair cells, disordered release of neurotransmitters by inner hair cell ribbon synapses, deafferentation accompanying loss of auditory nerve fibers, neural dys-synchrony or conduction block as a result of demyelination of nerve fibers and auditory nerve hypoplasia. Although the definition of AN includes the central part, its incidence is low, and the etiology and pathology are not clear. The present review aimed to provide an overview of the genetic conditions associated with AN and highlight the neural and synaptic mechanism of AN. Possible strategy for treatments of AN was also discussed.
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Abstract Introduction It is unclear how effective is the intratympanic (IT) steroid treatment on organ of Corti type 1 spiral ganglion, its optimal dosage and frequency of administration. The effect of dexamethasone on cochlear functions in individuals with a normal hearing ability is also unknown. Objective The aim of this study was to evaluate, at the electrophysiological and ultrastructural levels, the effect of IT dexamethasone administration in guinea pigs with normal hearing on organ of Corti type 1 spiral ganglion. Methods A total of 20 guinea pigs (n = 40 ears) whose hearing was detected to be normal by electrophysiological tests were included in the study and randomly divided into 6 groups. Four groups were considered study groups, while 2 groups were considered control groups. Dexamethasone was administered intratympanically in doses of 2 mg/mL and 4 mg/mL in the guinea pigs in the study groups. The animals in the control groups received physiological saline in equal doses as the study groups. All interventions were performed under general anesthesia, and the electrophysiological tests were repeated following the IT injections. Results No statistically significant differences were found among the groups when the IT injections were evaluated in terms of the electrophysiological measurements (p > 0.05). The ultrastructural evaluation showed a cellular mitochondrial increase in the spiral ganglions of the cochlea in the groups in which dexamethasone was administered in a dose of 4 mg/mL. Conclusion According to the findings of this study, it can be suggested that the IT injection of dexamethasone is safe, and when applied in a dose of 4mg/mL, it increases metabolic activity at the cellular level.
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OBJECTIVES: Spiral ganglion neurons (SGNs) include potential endogenous progenitor populations for the regeneration of the peripheral auditory system. However, whether these populations are present in adult mice is largely unknown. We examined the presence and characteristics of SGN-neural stem cells (NSCs) in mice as a function of age. METHODS: The expression of Nestin and Ki67 was examined in sequentially dissected cochlear modiolar tissues from mice of different ages (from postnatal day to 24 weeks) and the sphere-forming populations from the SGNs were isolated and differentiated into different cell types. RESULTS: There were significant decreases in Nestin and Ki67 double-positive mitotic progenitor cells in vivo with increasing mouse age. The SGNs formed spheres exhibiting self-renewing activity and multipotent capacity, which were seen in NSCs and were capable of differentiating into neuron and glial cell types. The SGN spheres derived from mice at an early age (postnatal day or 2 weeks) contained more mitotic stem cells than those from mice at a late age. CONCLUSION: Our findings showed the presence of self-renewing and proliferative subtypes of SGN-NSCs which might serve as a promising source for the regeneration of auditory neurons even in adult mice.
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Adult , Animals , Humans , Mice , Cochlea , Deafness , Hearing Loss , In Vitro Techniques , Nestin , Neural Stem Cells , Neuroglia , Neurons , Regeneration , Spiral Ganglion , Stem CellsABSTRACT
OBJECTIVE Aimed to observe the changes of acetylated histone H2B in the marginal cells of stria vascularis and spiral ganglion cells from the noise-induced hearing loss model (NIHL). METHODS Fifty guinea pigs were randomly divided into control and noise-exposure group. Auditory brainstem response threshold shift was examined before noise exposure and at 1h after noise exposure (122 dB SPL, 3 h). Immunofluorescence staining and western blot were used to observe the expression of acetyl-histone H2B both in the marginal cells of stria vascularis and spiral ganglion cells of modiolus 2 h after noise expose in two groups. RESULTS There was no significant difference in hearing threshold of 4, 8, 16, 32 kHz for the two groups before noise exposure. The hearing threshold was beyond 90dB (the maximum output) at 4,8,16 and 32 kHz 1h after noise exposure. The expression of acetylated histone H2B significantly decreased with immunofluorescence staining in the marginal cells after noise stimulation. Accordingly, the protein level of acetylated histone H2B in the lateral wall of cochlear decreased obviously in the noise group compared to the control, the ratios of H2B-AcK5/p-actin were 0. 3471 ±0. 0843 and 0. 6114 ±0. 0207 respectively(t=5. 268,P＜0. 01). There was no obvious difference for the expression of acetylated histone H2B in the modiolar tissue between two groups, the ratio of H2B-AcK5/p-actin was 0. 4993 ± 0. 0994 for the noise group and 0. 5139±0. 0132 for the controI (P＞0. 05). CONCLUSION Noise exposure significantly decreased histone acetylation expression in the nuclei of strial marginal cells, whereas the level in the spiral ganglion cells remained stable. Histone acetylation imbalance in the marginal cells of stria vascularis may contributed to the occurrence ofNIHL.
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Objective To observe the effect of Kidney-nourishing, Blood-activating, Phlegm-resolving and Resuscitation-inducing Decoction(KBPRD)on the expression of N-methyl-D-aspartate(NMDA)receptor subtype 1,2A,2B(NR1,NR2A,NR2B)in the cochlear spiral ganglion neurons(SGN)of tinnitus rats and to explore its mechanism, thus to provide experimental evidence for the treatment of tinnitus with KBPRD. Methods Sixty rats were randomly divided into normal group,model group,western medicine group,and low-,middle-,and high-dose Chinese medicine groups, 10 rats in each group. Rats were given intraperitoneal injection of sodium salicylate combined with water deprivation to induce tinnitus model. After successful establishment of the model, the rats in low-,middle-,and high-dose Chinese medicine groups were given gastric administration of KBPRD in the dosage of 5.5, 11, 22 g·kg-1·d-1 respectively, the rats in western medicine group were given gastric administration of 5 mg·kg-1·d-1 of carbamazepine,and rats in the model group and normal group were given gastric administration of 2 mL of normal saline,once every day,treatment time covering 8 weeks. The expression levels of NR1,NR2A,and NR2B in the cochlear SGN was detected by immunoblotting and real-time quantitative reverse transcription-polymerase chain reaction(qRT-PCR)after 8 weeks of treatment. Results Compared with the normal group,the expression levels of NR1, NR2A and NR2B in the model group were increased, the difference being significant (P < 0.05). Compared with the model group,the expression of NR1,NR2A and NR2B in low-,middle-,and high-dose Chinese medicine groups were significantly decreased(P<0.05).Conclusion KBPRD is effective on relieving tinnitus of rats, and its mechanism is correlated with lowering the increased expression of NR1,NR2A and NR2B in SGN of tinnitus rats.
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Objective To explore the damage of spiral ganglion neurons(SGNs),the protective effects of different dosages of healthy ear compound (HEC)from traditional Chinese medicine(TCM) against age-induced SGNs degeneration and its possible mechanism in spiral ganglion neurons(SGNs)of C57BL/6J mice.Methods Totally 36 C57BL/6J mice just after ablactation were randomly divided into four groups.Normal control group (n =6)drank tap water daily from ablactation to 2 months old.Ageing-related SGNs apoptosis control group(n=12)drank tap water daily from ablactation to 7 months old.High dose TCM group(n=12)at drank 3.65 g/kg/d of HEC from ablactation to 7 months old.Low dose TCM group(n=6)drank 0.91 g/kg/d of HEC from ablactation to 7 months old.The animal cochleae were immediately removed at the termination of the experiment.In each group,the cochleae of 6 animals were used for paraffin embedding,slicing and toluidine blue staining to observe neuronal morphological changes.The caspase-3 mRNA expression study was performed by real-time PCR technique in 6 cochleae of High dose TCM group and ageing-related SGNs apoptosis control group.Results The morphological structure of cochlear SGNs represented healthy and normal density in normal control group at 2 months old.In contrast,amount or density of SGNs in cochlear basilar part was significantly damaged and reduced in ageing-related SGNs apoptosis control group at 7 months old(P＜ 0.001).But the high dose TCM group at 7 months of age was similar to the normal control group at 2 months old in morphological structure,amount or density of SGNs(P＞0.05).The low dose TCM group was significantly different from other 3 groups in amount or density of SGNs (P＜0.001).However,SGNs in the middle part and apical part showed integrity in each group.In addition,the expression level of caspase-3 in the cochlea of high dose TCM group was also obviously different with age-related SGNs apoptosis control group(P＜0.01) Conclusions Ageing-related damage of SGNs in C57BL/6J mice begins from the base of cochlea and progresses towards the apex.The HEC of TCM could significantly protect SGNs against age-induced apoptosis in SGNs.The efficacy of the high dose TCM is better than that of the low dose TCM.Its SGNs protective mechanisms might be related to involving the caspase-mediated cell apoptotic pathway.
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OBJECTIVE To analyze the effect of advanced glycation end products(AGEs) on apoptosis of cultured mouse spiral ganglion cells(SGCs) and expression of receptor of AGEs(RAGE). To explore the pathway of AGEs in promoting apoptosis of SGCs. And to explore the possible mechanism of neural presbycusis. METHODS The effect of AGEs on apoptosis of SGCs was studied by Tunel technique and fluorescence microscope. The expression of RAGE mRNA was assayed by Real time RT-PCR. RESULTS AGEs induced apoptosis of cultured SGCs. The effects were dose-dependent and time-dependent. Meanwhile RAGE mRNA expression was enhanced in apoptosis cells. CONCLUSION AGEs induced apoptosis in SGCs,which may be mediated by RAGE. And this may be one of the mechanisms of neural presbycusis.
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BACKGROUND AND OBJECTIVES: Auditory neuropathy is a hearing disorder characterized by the absence or the marked impairment of the auditory brainstem responses with the preservation of the cochlear microphonics (CMs) and otoacoustic emissions. This suggests that outer hair cell (OHC) function is normal but proximal auditory function to OHCs is impaired. It is assumed that the lesion is localized at the level of the inner hair cells (IHCs), auditory nerve fibers, or the synapse between them. This study was aimed to observe the change of hearing threshold and pathology of spiral ganglion cell induced by ouabain application, and present basic data to explain the auditory neuropathy. MATERIALS AND METHOD: Twenty ears of twenty normal hearing cats were used in this study. Cats were treated with 100 microL ouabain (1 mM) applied on the round window. After three days, compound action potential (CAP) and CM were measured and the cochlea was obtained. Pathologic change of spiral ganglion cell was evaluated under light microscope after H&E stain. Normal saline was injected for the control group. RESULTS: In the ouabain group, CAP threshold was increased in all tested frequencies (p0.05). There was significant difference between CAP and CM threshold shift (p<0.001). In the control group, there was no significant difference in CAP and CM thresholds. Light microscopic findings show that the condensed chromatin and nuclear fragments of spiral ganglion cells of an ear was exposed to ouabain, and outer hair cell and inner hair cell were not damaged. CONCLUSION: This study shows that the CAP threshold was significantly increased but the CM threshold was not changed in the ouabain group. Ouabain induced damage of spiral ganglion cells. This study is not sufficient to explain auditory neuropathy because threshold shift of CAP is not obvious, but it would be helpful to explain that selective damage of spiral ganglion cell would be the mechanism of auditory neuropathy.
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Animals , Cats , Action Potentials , Chromatin , Cochlea , Cochlear Nerve , Ear , Evoked Potentials, Auditory, Brain Stem , Hair , Hearing , Hearing Disorders , Ouabain , Pathology , Spiral Ganglion , SynapsesABSTRACT
OBJECTIVES: To examine the expression profile of Fas-Fas ligand (FasL) during glutamate (Glu)-induced spiral ganglion cell (SGC) apoptosis. METHODS: Cultured SGCs were treated with 10-mM, 25-mM, and 50-mM concentrations of Glu and incubated for 24 or 48 hours. The expression intensity of FasL, Fas, caspase 3, and morphology of single SGC were evaluated using immunofluorescence staining. RESULTS: In semiquantitative analysis of the Glu-treated SGC, FasL, and caspase 3 expression intensity were increased with concentration- and time-dependent manner. Fas expression intensity did not change with different concentration at 48 hours. In morphologic analysis of the Glu-treated SGC, number of apoptotic cells were increased with concentration- and time-dependent manner. CONCLUSION: FasL was expressed in apoptotic SGCs, suggesting that the Fas-FasL signaling pathway may be involved in the Glu-induced apoptosis of dissociated SGCs.
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Apoptosis , Caspase 3 , Fas Ligand Protein , Fluorescent Antibody Technique , Glutamic Acid , Spiral GanglionABSTRACT
Objective To investigate whether blocking NR2B receptor can reverse the process of cytotoxicity to spiral ganglion neurons induced by sodium salicylate in guinea pig by applying ifenprodil (a NR2B antagonist) at the round window niche .Methods Sixty healthy guinea pigs provided by the experimental animal center of Guangxi medical university were randomly and evenly divided into a control group (Group I ,no treatment) ,an APL group (Group II ,60μl APL directly applied to the round window ) ,a sodium salicylate group (Group III ,60 μl APL di-rectly applied to the round window and then be given intraperitoneal sodium salicylate injection ) ,and an ifenprodil group (Group IV ,60μl of 10μmol/l ifenprodil in APL directly applied to the round window and then be given intra-peritoneal sodium salicylate injection ) .Sodium salicylate was given at 400 mg · kg -1 · d-1 for 7 days .Auditory brainstem responses (ABRs) were recorded before animal sacrifice by decapitation .The left cochlea was removed and prepared for detection of caspase -3 expression in spiral ganglion neurons via immunohistochemistry .From each group ,6 cochleae were used to test apoptosis index in spiral ganglion neurons using the TUNEL technique .Results Before salicylate administration ,the ABR threshold was less than 40 dB SPL in all animals .After salicylate ad-ministration ,the ABR threshold was 33 .33 ± 5 .17 dB SPL in Group II ,64 .17 ± 7 .36 dB SPL in Group III and 49 .17 ± 5 .85 dB SPL in Group IV ,in contrast to 31 .67 ± 5 .16 dB SPL in Group I (controls) .The caspase -3 ex-pression was not changed obviously in Group I and Group II ,but was significantly changed in Group III and Group IV (P<0 .01) .The caspase-3 expression appeared to be decreased in Group IV compared to those in Groups III (P<0 .05) ,but still increased compared to those of in Group I and II (P<0 .05) .The apoptosis index among spiral ganglion neurons in Groups III and IV increased significantly compared to those of in Group I and II (P<0 .001) .It was however ,lower in Group IV than in Group III (P<0 .01) .Conclusion Blocking NR2B receptor with specificity can reverse the process of cytotoxicity to spiral ganglion neurons induced by sodium salicylate in guinea pig .
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Objective To study the effects of chronic manganism on hearing and cochlear cells in rats by using animal model of chronic manganism .Methods Sixty adult SD rats were randomly divided into Mn - exposed and controlgroups.RatsweretreatedwithMnCl24H2O(100mg·kg -1·d-1)ordeionizedwaterbygastricperfusion, lasted for 12 weeks .The Mn concentration in peripheral blood was measured respectively at 4 weeks ,8 weeks and 12 weeks after treatment .At 12 weeks after treatment ,the auditory brainstem response was recorded ,the hair cells morphology and counting were examined by stretched preparation of basilar membrane stained with FITC -phalloi-din ,and the spiral ganglion cells morphology and counting were studied by HE staining ,the ultrastructure changes of hair cells and spiral ganglion cells were detected by transmission electron microscopy .Results The blood Mn concentration increased gradually with time after treatment .ABR thresholds at 4 ,8 ,16 ,24 and 32 kHz were sig-nificantly increased at 12 weeks after treatment ,especially in the high-frequency range .Morphological study at 12 weeks after treatment showed loss of outer hair cells ,mainly in the basal turn of the cochlea ,and decreased number of spiral ganglion cells .The ultrastructure changes of outer hair cells and spiral ganglion cells included the break -ups ,disappearance or vacuolar change of mitochondria cristas .Conclusion Our data demonstrate that chronic man-ganism can cause loss of outer hair cells and spiral ganglion cells in cochlear in rats ,leading to hearing loss .
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This study examined the expression pattern of programmed cell death 5 (PDCD5) in cochlear hair cells and spiral ganglion neurons (SGNs) and its association with age-related hearing loss in mice.Sixty C57BL/6J (C57) mice at different ages were divided into four groups (3,6,9 or 12 months).PDCD5 expression was detected by using immunohistochemistry,real-time PCR and Western blot.Morphological change of the cochleae was also evaluated by using immunoassay.The results showed that the expression of PDCD5 had a gradual increase with ageing in both protein and RNA levels in C57 mice,as well as gradually increased apoptosis of cochlear hair cells and SGNs.In addition,we also found that caspase-3 activity was enhanced and its expression was enhanced with ageing.It is implied that overexpression of PDCD5 causes the increase in caspase-3 activity and the subsequent increase of apoptosis in cochlear hair cells and SGNs,and thereby plays a role in the pathogenesis of presbycusis.Thus,PDCD5 may be a new target site for the treatment and prevention of age-related hearing loss.
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BACKGROUND AND OBJECTIVES: Ginkgo biloba extract (GBE) enhances cell survival in various organs. GBE protects nerve cells in the central nervous system and is clinically applied in Parkinson's and Alzheimer's disease. GBE can protect ototoxicity caused by cisplantin and gentamycin through rescue of hair cells in Organ of Corti and is accepted as one of the therapeutic agents for sudden deafness and tinnitus. The experimental study on GBE for the inner ear is confined to the hair cells, not to the spiral ganglion neurons (SGNs) which is the stimulated part by the electrode of cochlear implant. The aim of this study is to elucidate the effect of GBE on the survival of SGNs after hair cell loss in rats. MATERIALS AND METHOD: Ten Sprague-Dawley rats aged 50 days (P50) were deafened with kanamycin sulfate. GBE (EGb 761) was injected into the right cochlea and artificial perilymph was injected into the left side. The number and size of SGNs were compared after immunohistochemical statin in both groups. The expression of pJun, which is well-known as a proapoptotic transcription factor in the cochlea, was also compared. RESULTS: The number of SGNs was significantly larger in the GBE group than the control. The expression of pJun activity was significantly decreased in GBE group than the control. The size of SGNs in both groups was similar. CONCLUSION: These results suggest that GBE can protect SGNs death by inhibiting the pJun-C-jun N-terminal kinase pathway. GBE might be a potential drug for the patients with total deafness before or after cochlear implantation surgery for better hearing results.
Subject(s)
Aged , Animals , Humans , Rats , Alzheimer Disease , Cell Survival , Central Nervous System , Cochlea , Cochlear Implantation , Cochlear Implants , Deafness , Ear, Inner , Electrodes , Gentamicins , Ginkgo biloba , Hair , Hearing , Hearing Loss, Sudden , Hydroxymethylglutaryl-CoA Reductase Inhibitors , Kanamycin , Neurons , Organ of Corti , Perilymph , Phosphotransferases , Rats, Sprague-Dawley , Spiral Ganglion , Tinnitus , Transcription FactorsABSTRACT
The aim of this study was to determine the effects of transplanted neural differentiated human mesenchymal stem cells (hMSCs) in a guinea pig model of auditory neuropathy. In this study, hMSCs were pretreated with a neural-induction protocol and transplanted into the scala tympani of the guinea pig cochlea 7 days after ouabain injury. A control model was made by injection of Hanks balanced salt solution alone into the scala tympani of the guinea pig cochlea 7 days after ouabain injury. We established the auditory neuropathy guinea pig model using 1 mM ouabain application to the round window niche. After application of ouabain to the round window niche, degeneration of most spiral ganglion neurons (SGNs) without the loss of hair cells within the organ of Corti and increasing the auditory brain responses (ABR) threshold were found. After transplantation of neural differentiated hMSCs, the number of SGNs was increased, and some of the SGNs expressed immunoreactivity with human nuclear antibody under confocal laser scanning microscopy. ABR results showed mild hearing recovery after transplantation. Based on an auditory neuropathy animal model, these findings suggest that it may be possible to replace degenerated SGNs by grafting stem cells into the scala tympani.
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Animals , Female , Humans , Cardiotonic Agents/toxicity , Cochlea/drug effects , Disease Models, Animal , Guinea Pigs , Hearing Loss, Central/chemically induced , Mesenchymal Stem Cell Transplantation , Mesenchymal Stem Cells/cytology , Neurogenesis , Ouabain/toxicity , Spiral Ganglion/pathology , Transplantation, HeterologousABSTRACT
OBJECTIVES: Carboplatin, a platinum-containing anti-cancer drug used to treat a variety of cancers, induces ototoxicity. Since, reactive oxygen species (ROS) and nitric oxide (NO) seem to be responsible for this toxicity, the antioxidant, N-acetyl-L-cysteine (L-NAC), and NO synthetase inhibitor, N-nitro-L-arginine methyl ester (L-NAME) were predicted to have protective effects against carboplatin ototoxicity. The aim of this study was to test for the protective effects of L-NAC and L-NAME on cochlear hair cells and spiral ganglion neurons (SGNs). METHODS: Cochlear organotypic cultures and dissociated spiral ganglion neuron cultures, from mice postnatal day 5 cultures were used in this study. The cultures were treated with carboplatin alone or in combination with L-NAC or L-NAME, and carboplatin-induced damage was monitored. RESULTS: Treatment with carboplatin induced a significant loss of outer hair cells, while inner hair cells were preserved in the cochlear organotypic cultures. Addition of L-NAC or L-NAME reduced the amount of carboplatin-induced hair cell damage; the differences did not reach statistical significance. However, carboplatin significantly decreased the number of surviving SGNs in dissociated cultures. The toxic effects were significantly reduced by addition of L-NAC or L-NAME. In addition, carboplatin induced the loss of neurites from the SGN somata, and this was not blocked with L-NAC or L-NAME. CONCLUSION: The results of this study suggest that ROS and NO are involved in carboplatin-induced damage to hair cells and SGNs, and administration of L-NAC/L-NAME can be used to attenuate the toxicity.
Subject(s)
Animals , Mice , Acetylcysteine , Carboplatin , Hair , Ligases , Lysine , Neurites , Neurons , NG-Nitroarginine Methyl Ester , Nitric Oxide , Reactive Oxygen Species , Spiral GanglionABSTRACT
OBJECTIVES: Carboplatin, a platinum-containing anti-cancer drug used to treat a variety of cancers, induces ototoxicity. Since, reactive oxygen species (ROS) and nitric oxide (NO) seem to be responsible for this toxicity, the antioxidant, N-acetyl-L-cysteine (L-NAC), and NO synthetase inhibitor, N-nitro-L-arginine methyl ester (L-NAME) were predicted to have protective effects against carboplatin ototoxicity. The aim of this study was to test for the protective effects of L-NAC and L-NAME on cochlear hair cells and spiral ganglion neurons (SGNs). METHODS: Cochlear organotypic cultures and dissociated spiral ganglion neuron cultures, from mice postnatal day 5 cultures were used in this study. The cultures were treated with carboplatin alone or in combination with L-NAC or L-NAME, and carboplatin-induced damage was monitored. RESULTS: Treatment with carboplatin induced a significant loss of outer hair cells, while inner hair cells were preserved in the cochlear organotypic cultures. Addition of L-NAC or L-NAME reduced the amount of carboplatin-induced hair cell damage; the differences did not reach statistical significance. However, carboplatin significantly decreased the number of surviving SGNs in dissociated cultures. The toxic effects were significantly reduced by addition of L-NAC or L-NAME. In addition, carboplatin induced the loss of neurites from the SGN somata, and this was not blocked with L-NAC or L-NAME. CONCLUSION: The results of this study suggest that ROS and NO are involved in carboplatin-induced damage to hair cells and SGNs, and administration of L-NAC/L-NAME can be used to attenuate the toxicity.
Subject(s)
Animals , Mice , Acetylcysteine , Carboplatin , Hair , Ligases , Lysine , Neurites , Neurons , NG-Nitroarginine Methyl Ester , Nitric Oxide , Reactive Oxygen Species , Spiral GanglionABSTRACT
Being the primary neurons in the auditory system, spiral ganglion neurons form the afferent synapse with hair cells and play a critical role in the analysis and integration of hearing. Many kinds of neurotransmitters can be found in the cochlear and they have different effects under both physiological and pathological conditions with complicated mechanism. This article reviews the characters of some transmitters in cochlear, such as glutamate, ATP, dopamine and GABA, and their roles in noise-induced hearing loss, hoping to provide more clues for research and therapy of inner ear diseases.