Aminoglycoside-induced Ototoxicity Research Articles

Calcium channel inhibitor and extracellular calcium improve aminoglycoside-induced hair cell loss in zebrafish.

Aminoglycosides are commonly used antibiotics for treatment of gram-negative bacterial infections, however, they might act on inner ear, leading to hair-cell death and hearing loss. Currently, there is no targeted therapy for aminoglycoside ototoxicity, since the underlying mechanisms of aminoglycoside-induced hearing impairments are not fully defined. This study aimed to investigate whether the calcium channel blocker verapamil and changes in intracellular & extracellular calcium could ameliorateaminoglycoside-induced ototoxicity in zebrafish. The present findings showed that a significant decreased number of neuromasts in the lateral lines of zebrafish larvae at 5days' post fertilization after neomycin (20μM) and gentamicin (20mg/mL) exposure, which was prevented by verapamil. Moreover, verapamil (10-100μM) attenuated aminoglycoside-induced toxic response in different external calcium concentrations (33-3300μM). The increasing extracellular calcium reduced hair cell loss from aminoglycoside exposure, while lower calcium facilitated hair cell death. In contrast, calcium channel activator Bay K8644 (20μM) enhanced aminoglycoside-induced ototoxicity and reversed the protective action of higher external calcium on hair cell loss. However, neomycin-elicited hair cell death was not altered by caffeine, ryanodine receptor (RyR) agonist, and RyR antagonists, including thapsigargin, ryanodine, and ruthenium red. The uptake ofneomycininto hair cells was attenuated by verapamil and under high external calcium concentration. Consistently, the production of reactive oxygen species (ROS) in neuromasts exposed to neomycin was also reduced by verapamil and high external calcium. Significantly, zebrafish larvae when exposed to neomycin exhibited decreased swimming distances in reaction to droplet stimulus when compared to the control group. Verapamil and elevated external calcium effectively protected the impaired swimming ability of zebrafish larvae induced by neomycin. These data imply that prevention of hair cell damage correlated with swimming behavior against aminoglycoside ototoxicity by verapamil and higher external calcium might be associated with inhibition of excessive ROS production andaminoglycoside uptake through cation channels. These findings indicate that calcium channel blocker and higher external calcium could be applied to protect aminoglycoside-induced listening impairments.

Mechanisms and otoprotective strategies of programmed cell death on aminoglycoside-induced ototoxicity.

Aminoglycosides are commonly used for the treatment of life-threatening bacterial infections, however, aminoglycosides may cause irreversible hearing loss with a long-term clinical therapy. The mechanism and prevention of the ototoxicity of aminoglycosides are still limited although amounts of studies explored widely. Specifically, advancements in programmed cell death (PCD) provide more new perspectives. This review summarizes the general signal pathways in programmed cell death, including apoptosis, autophagy, and ferroptosis, as well as the mechanisms of aminoglycoside-induced ototoxicity. Additionally, novel interventions, especially gene therapy strategies, are also investigated for the prevention or treatment of aminoglycoside-induced hearing loss with prospective clinical applications.

Role of Kir4.1 Channels in Aminoglycoside-Induced Ototoxicity of Hair Cells.

The Kir4.1 channel, an inwardly rectifying potassium ion (K+) channel, is located in the hair cells of the organ of Corti as well as the intermediate cells of the stria vascularis. The Kir4.1 channel has a crucial role in the generation of endolymphatic potential and maintenance of the resting membrane potential. However, the role and functions of the Kir4.1 channel in the progenitor remain undescribed. To observe the role of Kir4.1 in the progenitor treated with the one-shot ototoxic drugs (kanamycin and furosemide), we set the proper condition in culturing Immortomouse-derived HEI-OC1 cells to express the potassium-related channels well. And also, that was reproduced in mice experiments to show the important role of Kir4.1 in the survival of hair cells after treating the ototoxicity drugs. In our results, when kanamycin and furosemide drugs were cotreated with HEI-OC1 cells, the Kir4.1 channel did not change, but the expression levels of the NKCC1 cotransporter and KCNQ4 channel are decreased. This shows that inward and outward channels were blocked by the two drugs (kanamycin and furosemide). However, noteworthy here is that the expression level of Kir4.1 channel increased when kanamycin was treated alone. This shows that Kir4.1, an inwardly rectifying potassium channel, acts as an outward channel in place of the corresponding channel when the KCNQ4 channel, an outward channel, is blocked. These results suggest that the Kir4.1 channel has a role in maintaining K+ homeostasis in supporting cells, with K+ concentration compensator when the NKCC1 cotransporter and Kv7.4 (KCNQ4) channels are deficient.

Gentamicin administration leads to synaptic dysfunction in inner hair cells

Ototoxicity is a major side effect of aminoglycosides, which can cause irreversible hearing loss. Previous studies on aminoglycoside-induced ototoxicity have primarily focused on the loss of sensory hair cells. Recent investigations have revealed that aminoglycosides can also lead to the loss of ribbon synapses in inner hair cells (IHCs). However, the functional implications of ribbon synapse loss and the underlying mechanisms remain unclear. In this study, we intraperitoneally injected C57BL/6 J mice with 300 mg/kg gentamicin once daily for 3, 10, and 20 days. Then, we performed immunofluorescence staining, patch-clamp recording, proteomics analysis and western blotting to characterize the changes in ribbon synapses in IHCs and the associated mechanisms. After gentamicin treatment, the auditory brainstem response (ABR) threshold was elevated, and the ABR wave I amplitude was decreased. We also observed loss of ribbon synapses in IHCs. Interestingly, ribbon synapse loss occurred on both the modiolar and pillar sides of IHCs. Whole-cell patch-clamp recordings in IHCs revealed a reduction in the calcium current amplitude, along with a shifted half-activation voltage and altered calcium voltage dependency. Moreover, exocytosis of IHCs was reduced, consistent with the reduction in the ABR wave I amplitude. Through proteomic analysis, western blotting, and immunofluorescence staining, we found that gentamicin treatment resulted in downregulation of myosin VI, a protein crucial for synaptic vesicle recycling and replenishment in IHCs. Furthermore, we evaluated the kinetics of endocytosis and found a significant reduction in IHC exocytosis, possibly reflecting the impact of myosin VI downregulation on synaptic vesicle recycling. In summary, our findings demonstrate that gentamicin treatment leads to synaptic dysfunction in IHCs, highlighting the important role of myosin VI downregulation in gentamicin-induced synaptic damage.

Cortisol Sensitizes Cochlear Hair Cells to Gentamicin Ototoxicity Via Endogenous Apoptotic Pathway.

The widespread use of aminoglycosides is a prevalent cause of sensorineural hearing loss. Patients receiving aminoglycosides usually have elevated levels of circulating stress hormones due to disease or physiological stress; however, whether the stress hormone cortisol impacts aminoglycoside-mediated injury of cochlear hair cells has not been fully investigated. House Ear Institute-Organ of Corti 1 (HEI-OC1) cells with or without cortisol pretreatment were exposed to gentamicin, we investigated the effect of cortisol pretreatment on gentamicin ototoxicity by assessing cell viability. Molecular pathogenesis was explored by detecting apoptosis and oxidative stress. Meanwhile, by inhibiting glucocorticoid receptors (GR) and mineralocorticoid receptors (MR), the potential roles of receptor types in cortisol-mediated sensitization were evaluated. Cortisol concentrations below 75 μmol/l did not affect cell viability. However, pretreatment with 50 μmol/l cortisol for 24 hours sensitized hair cells to gentamicin-induced apoptosis. Further mechanistic studies revealed that cortisol significantly increased hair cell apoptosis and oxidative stress, and altered apoptosis-related protein expressions induced by gentamicin. In addition, blockade of either GR or MR attenuated cortisol-induced hair cell sensitization to gentamicin toxicity. Cortisol pretreatment increased mammalian hair cell susceptibility to gentamicin toxicity. Sensitization was related to the activation of the intrinsic apoptotic pathway and excessive generation of reactive oxygen species. Cortisol may exacerbate aminoglycoside ototoxicity.

Susceptibility of immature spiral ganglion neurons to aminoglycoside-induced ototoxicity is mediated by the TRPV1 channel in mice

Aminoglycoside antibiotics are among the most common agents that can cause sensorineural hearing loss. From clinical experience, premature babies, whose inner ear is still developing, are more susceptible to aminoglycoside-induced ototoxicity, which is echoed by our previous study carried out in organotypic cultures. This study aimed to investigate whether a nonselective cation channel, TRPV1, contributes to the susceptibility of immature spiral ganglion neurons (SGNs) to the damage caused by aminoglycosides. Through western blotting and immunofluorescence, we found that the TRPV1 expression levels were much higher in immature SGNs than in their mature counterparts. In postnatal day 7 cochlear organotypic cultures, AMG-517 reduced reactive oxygen species generation and inhibited SGN apoptosis under aminoglycoside challenge. However, in adult mice, AMG-517 did not ameliorate the ABR threshold increase at high frequencies (16 kHz and 32 kHz) after aminoglycoside administration, and the SGNs within the cochleae had no morphological changes. By further regulating the function of TRPV1 in primary cultured SGNs with its inhibitor AMG-517 and agonist capsaicin, we demonstrated that TRPV1 is a major channel for aminoglycoside uptake: AMG-517 can significantly reduce, while capsaicin can significantly increase, the uptake of GTTR. In addition, TRPV1 knockdown in SGNs can also significantly reduce the uptake of GTTR. Taken together, our results demonstrated that aminoglycosides can directly enter immature SGNs through the TRPV1 channel. High expression of TRPV1 contributes to the susceptibility of immature SGNs to aminoglycoside-induced damage. The TRPV1 inhibitor AMG-517 has the potential to be a therapeutic agent for preventing aminoglycoside-induced ototoxicity in immature SGNs.

441 Implementation of a multidisciplinary aminoglycoside-induced ototoxicity monitoring process in children with cystic fibrosis

441 Implementation of a multidisciplinary aminoglycoside-induced ototoxicity monitoring process in children with cystic fibrosis

Berberine chloride protects cochlear hair cells from aminoglycoside-induced ototoxicity by reducing the accumulation of mitochondrial reactive oxygen species

Aminoglycoside, a medicinal category of antibiotics, are used in treatment of Gram-negative bacterial infections. Although they are the most widely-used antibiotics due to their high efficacy and low cost, several main adverse effects have been reported including nephrotoxicity and ototoxicity. Since drug-induced ototoxicity is one of the major etiological causes of acquired hearing loss, we examined cochlear hair cell damages caused by three aminoglycosides (amikacin, kanamycin, and gentamicin), and investigated protective property of an isoquinoline-type alkaloid, Berberine chloride (BC). Berberine, a well-known bioactive compound found from medicinal plants, has been known to have anti-inflammatory, antimicrobial effects. To determine protective effect of BC in aminoglycoside-induced ototoxicity, hair cell damages in aminoglycoside- and/or BC-treated hair cells using ex vivo organotypic culture system of mouse cochlea. Mitochondrial ROS levels and depolarization of mitochondrial membrane potential were analyzed, and TUNEL assay and immunostaining of cleaved caspase-3 were performed to detect apoptosis signals. As the results, it was found that BC significantly prevented aminoglycoside-induced hair cell loss and stereocilia degeneration by inhibiting excessive accumulation of mitochondrial ROS and subsequent loss of mitochondrial membrane potential. It eventually inhibited DNA fragmentation and caspase-3 activation, which were significant for all three aminoglycosides. This study is the first report suggested the preventative effect of BC against aminoglycoside-induced ototoxicity. Our data also suggests a possibility that BC has the potential to exert a protective effect against ototoxicity caused by various ototoxic drugs leading to cellular oxidative stress, not limited to aminoglycoside antibiotics.

Clinical Pharmacogenomic MT-RNR1 Screening for Aminoglycoside-Induced Ototoxicity and the Post-Test Counseling Conundrum.

Aminoglycoside antibiotic exposure can result in ototoxicity and irreversible hearing loss among individuals that harbor the m.1555A>G variant in the mitochondrial 12S rRNA gene, MT-RNR1. Importantly, pre-emptive m.1555A>G screening has been shown to reduce the prevalence of pediatric aminoglycoside-induced ototoxicity; however, professional guidelines to support and guide post-test pharmacogenomic counseling in this context are not currently available. This Perspective highlights key issues with delivering MT-RNR1 results, including longitudinal familial care considerations and communicating m.1555A>G heteroplasmy.

The first successful cochlear implant in Latin America after severe aminoglycoside-induced ototoxicity in a Peruvian patient cured of extensively drug-resistant tuberculosis

Introduction: Multidrug-resistant tuberculosis is a significant public health problem for which drugs are used with many adverse effects. Among the devastating consequences of these diseases, there is a wide variation in the incidence of ototoxicity and hearing loss in patients with multidrug-resistant and extremely resistant tuberculosis. Cochlear implants may be indicated in patients with unilateral/severe bilateral hearing loss with no benefit from conventional hearing aids, but their use in patients with tuberculosis is rare. Case report: We present the first case of a right unilateral cochlear implant performed on a 34-year-old Peruvian patient who presented profound sensorineural hearing loss of cochlear origin. Conclusion: Cochlear implant surgery is an essential milestone in the treatment of patients with auditory sequelae of tuberculosis treatment. Close monitoring of possible complications of tuberculosis treatment should be strengthened in countries with a high incidence of multidrug-resistant and extremely resistant tuberculosis.

Pitavastatin protects against neomycin-induced ototoxicity through inhibition of endoplasmic reticulum stress.

Irreversible injury to inner ear hair cells induced by aminoglycoside antibiotics contributes to the formation of sensorineural hearing loss. Pitavastatin (PTV), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, has been reported to exert neuroprotective effects. However, its role in aminoglycoside-induced hearing loss remains unknown. The objectives of this study were to investigate the beneficial effects, as well as the mechanism of action of PTV against neomycin-induced ototoxicity. We found that PTV remarkably reduced hair cell loss in mouse cochlear explants and promoted auditory HEI-OC1 cells survival after neomycin stimulation. We also observed that the auditory brainstem response threshold that was increased by neomycin was significantly reduced by pretreatment with PTV in mice. Furthermore, neomycin-induced endoplasmic reticulum stress in hair cells was attenuated by PTV treatment through inhibition of PERK/eIF2α/ATF4 signaling. Additionally, we found that PTV suppressed the RhoA/ROCK/JNK signal pathway, which was activated by neomycin stimulation in HEI-OC1 cells. Collectively, our results showed that PTV might serve as a promising therapeutic agent against aminoglycoside-induced ototoxicity.

A reduced form of nicotinamide riboside protects the cochlea against aminoglycoside-induced ototoxicity by SIRT1 activation.

Nicotinamide adenine dinucleotide (NAD+), a coenzyme that plays crucial roles in many cellular processes, is a potential therapeutic target for various diseases. Dihydronicotinamide riboside (NRH), a novel reduced form of nicotinamide riboside, has emerged as a potent NAD+ precursor. Here, we studied the protective effects and underlying mechanism of NRH on aminoglycoside-induced ototoxicity. Auditory function and hair-cell (HC) morphology were examined to assess the effects of NRH on kanamycin-induced hearing loss. The pharmacokinetic parameters of NRH were measured in plasma and the cochlea using liquid chromatography tandem mass spectrometry. NAD+ levels in organ explant cultures were assessed to compare NRH with known NAD+ precursors. Immunofluorescence analysis was performed to detect reactive oxygen species (ROS) and apoptosis. We analyzed SIRT1 and 14-3-3 protein expression. EX527 and resveratrol were used to investigate the role of SIRT1 in the protective effect of NRH against kanamycin-induced ototoxicity. NRH alleviated kanamycin-induced HC damage and attenuated hearing loss in mice. NRH reduced gentamicin-induced vestibular HC loss. Compared with NAD and NR, NRH produced more NAD+ in cochlear HCs and significantly ameliorated kanamycin-induced oxidative stress and apoptosis. NRH rescued the aminoglycoside-induced decreases in SIRT1 and 14-3-3 protein expression. Moreover, EX527 antagonized the protective effect of NRH on kanamycin-induced HC loss by inhibition of SIRT1, while resveratrol alleviated HC damage caused by EX527. NRH ameliorates aminoglycoside-induced ototoxicity by inhibiting HC apoptosis by activating SIRT1 and decreasing ROS. NRH is an effective therapeutic option for aminoglycoside-induced ototoxicity.

Pravastatin Administration Alleviates Kanamycin-Induced Cochlear Injury and Hearing Loss.

The effect of statins on aminoglycoside-induced ototoxicity is controversial. This study aimed to explore the role of pravastatin (PV) in kanamycin-induced hearing loss in rats. Adult rats were intraperitoneally treated with 20 mg/kg/day of kanamycin (KM) for 10 days. In the PV- and PV + KM-treated rats, 25 mg/kg/day of PV was intraperitoneally administered for 5 days. The auditory brainstem response (ABR) thresholds were measured before and after drug treatment using a smartEP system at 4, 8, 16, and 32 kHz. Cochlear changes in poly ADP-ribose (PAR) polymerase (PARP), PAR, and caspase 3 were estimated using Western blotting. PV administration did not increase the ABR thresholds. The KM-treated rats showed elevated ABR thresholds at 4, 8, 16, and 32 kHz. The PV + KM-treated rats demonstrated lower ABR thresholds than the KM-treated rats at 4, 8, and 16 kHz. The cochlear outer hair cells and spiral ganglion cells were relatively preserved in the PV + KM-treated rats when compared with that in the KM-treated rats. The cochlear expression levels of PARP, PAR, and caspase 3 were higher in the KM-treated rats. The PV + KM-treated rats showed lower levels of PARP, PAR, and caspase 3 than the KM-treated rats. PV protected cochleae from KM-induced hearing loss in rats. The regulation of autophagy and apoptosis mediated the otoprotective effects of PV.

Rapid Point-of-Care Genotyping to Avoid Aminoglycoside-Induced Ototoxicity in Neonatal Intensive Care

Aminoglycosides are commonly prescribed antibiotics used for the treatment of neonatal sepsis. The MT-RNR1 m.1555A>G variant predisposes to profound aminoglycoside-induced ototoxicity (AIO). Current genotyping approaches take several days, which is unfeasible in acute settings. To develop a rapid point-of-care test (POCT) for the m.1555A>G variant before implementation of this technology in the acute neonatal setting to guide antibiotic prescribing and avoid AIO. This pragmatic prospective implementation trial recruited neonates admitted to 2 large neonatal intensive care units between January 6, 2020, and November 30, 2020, in the UK. Neonates were tested for the m.1555A>G variant via the rapid POCT on admission to the neonatal intensive care unit. The primary outcome assessed the proportion of neonates successfully tested for the variant of all infants prescribed antibiotics. Secondary outcomes measured whether implementation was negatively associated with routine clinical practice and the performance of the system. The study was statistically powered to detect a significant difference between time to antibiotic administration before and after implementation of the MT-RNR1 POCT. A total of 751 neonates were recruited and had a median (range) age of 2.5 (0-198) days. The MT-RNR1 POCT was able to genotype the m.1555A>G variant in 26 minutes. Preclinical validation demonstrated a 100% sensitivity (95% CI, 93.9%-100.0%) and specificity (95% CI, 98.5%-100.0%). Three participants with the m.1555A>G variant were identified, all of whom avoided aminoglycoside antibiotics. Overall, 424 infants (80.6%) receiving antibiotics were successfully tested for the variant, and the mean time to antibiotics was equivalent to previous practice. The MT-RNR1 POCT was integrated without disrupting normal clinical practice, and genotype was used to guide antibiotic prescription and avoid AIO. This approach identified the m.1555A>G variant in a practice-changing time frame, and wide adoption could significantly reduce the burden of AIO.

Microarray analysis of lipopolysaccharide-induced endotoxemia in the cochlea

Lipopolysaccharide (LPS)-induced endotoxemia alters intracochlear homeostasis and potentiates aminoglycoside-induced ototoxicity. However, the pathological mechanisms in the cochlea following systemic LPS-induced inflammation are unclear. In this study, three groups of mice received intraperitoneal injections [group A, saline control (n = 10); group B, 1 mg/kg LPS (n = 10); group C, 10 mg/kg LPS (n = 10)]. After 24 h, gene expression in cochlea samples was analyzed using DNA microarrays covering 28,853 genes in a duplicate manner. A total of 505 differentially expressed genes (DEGs) (≥2.0-fold change; p < 0.05) were identified. Interferon- and chemotaxis-related genes, including gbp2, gbp5, cxcl10, and Rnf125, were dose-dependently upregulated by LPS-induced endotoxemia. These results were verified by RT-qPCR. Upregulated DEGs were associated with inflammation, positive regulation of immune responses, and regulation of cell adhesion, while downregulated ones were associated with chemical synaptic transmission and the synaptic vesicle cycle. Protein-protein interaction included four functional clusters associated with interleukin-4, −10, and −13 and G protein-coupled receptor (GPCR) ligand binding; activation of matrix metalloproteinases and collagen degradation; recruitment of amyloid A proteins; and neutrophil degranulation. The findings of this study provide an additional basis on changes in the expression of genes in the cochlea in response to LPS-induced endotoxemia.

Assessment of Hearing Screening Combined With Limited and Expanded Genetic Screening for Newborns in Nantong, China

Early identification and intervention for newborns with hearing loss (HL) may lead to improved physiological and social-emotional outcomes. The current newborn hearing screening is generally beneficial but improvements can be made. To assess feasibility and evaluate utility of a modified genetic and hearing screening program for newborn infants. This population-based cohort study used a 4-stage genetic and hearing screening program at 6 local hospitals in Nantong city, China. Participants were newborn infants born between January 2016 and June 2020 from the Han population. Statistical analysis was performed from April 1 to May 1, 2021. Limited genetic screening for 15 variants in 4 common HL-associated genes and newborn hearing screening (NHS) were offered concurrently to all newborns. Hearing rescreening and/or diagnostic tests were provided for infants with evidence of HL on NHS or genetic variants on screening. Expanded genetic tests for a broader range of genes were targeted to infants with HL with negative results of limited genetic tests. The detection capability for infants with hearing impairment who passed conventional hearing screening, as well as infants with normal hearing at risk of late-onset HL due to genetic susceptibility. Among a total of 35 930 infants, 32 512 infants completed the follow-up and were included for analysis. Among the infants included in the analysis, all were from the Han population in China and 52.3% (16 988) were male. The modified genetic and hearing screening program revealed 142 cases of HL and 1299 cases of genetic variation. The limited genetic screening helped identify 31 infants who passed newborn hearing screening, reducing time for diagnosis and intervention; 425 infants with normal hearing with pathogenic SLC26A4 variation and 92 infants with MT-RNR1 variation were at risk for enlarged vestibular aqueduct and aminoglycoside-induced ototoxicity respectively, indicating early aversive or preventive management. This study found that performing modified genetic and hearing screening in newborns was feasible and provides evidence that the program could identify additional subgroups of infants who need early intervention. These findings suggest an advantage for universal adoption of such a practice.

(−)-Epigallocatechin-3-gallate (EGCG) prevents aminoglycosides-induced ototoxicity via anti-oxidative and anti-apoptotic pathways

ObjectivesAminoglycoside-induced cochlear ototoxicity causes inner ear hair cells (HCs) loss and leads to hearing impairment in patients, but no treatment completely eliminates the ototoxic effect. This study aims to determine the effectiveness of (−)-Epigallocatechin-3-gallate (EGCG) as a protective agent against aminoglycoside-induced ototoxicity. MethodsZebrafish were exposed to EGCG for 24 h and then co-treated with EGCG and ototoxic agent (amikacin and gentamicin) for 5 h to explore the protective effect of EGCG on zebrafish HCs. Network pharmacology analysis and molecular docking simulation were conducted to explore its potential mechanism, and in vitro cell experiments were used to validate the outcome of the result. ResultEGCG against ototoxicity of aminoglycosides in zebrafish HCs. Network pharmacology analysis and molecular docking showing that molecules related to cellular response regulation to oxidative stress, including AKT1, DHFR, and MET, may be the target proteins of EGCG, which were verified in vitro experiments. Further experiments demonstrated thatEGCG can antagonize the death of HCs caused by amikacin and gentamicin by reducing intracellular reactive oxygen species (ROS) accumulation and anti-apoptosis. ConclusionEGCG can be an otoprotective drug against aminoglycosides-induced ototoxicity, prevent cellular apoptosis and significantly reduce oxidative stress.

Effects of Moringa Extract on Aminoglycoside-Induced Hair Cell Death and Organ of Corti Damage.

Moringa extract, a naturally occurring anti-oxidant, protects against aminoglycoside-induced hair cell death and hearing loss within the organ of Corti. Reactive oxygen species (ROS) arise primarily in the mitochondria and have been implicated in aminoglycoside-induced ototoxicity. Mitochondrial dysfunction results in loss of membrane potential, release of caspases, and cell apoptosis. Moringa extract has not previously been examined as a protective agent for aminoglycoside-induced ototoxicity. Putative otoprotective effects of moringa extract were investigated in an organotypic model using murine organ of Corti explants subjected to gentamicin-induced ototoxicity. Assays evaluated hair cell loss, cytochrome oxidase expression, mitochondrial membrane potential integrity, and caspase activity. In vitro application of moringa conferred significant protection from gentamicin-induced hair cell loss at dosages from 25 to 300 μg/mL, with dosages above 100 μg/mL conferring near complete protection. Assays demonstrated moringa extract suppression of ROS, preservation of cytochrome oxidase activity, and reduction in caspase production. Moringa extract demonstrated potent antioxidant properties with significant protection against gentamicin ototoxicity in cochlear explants.

Identification of a series of hair-cell MET channel blockers that protect against aminoglycoside-induced ototoxicity.

To identify small molecules that shield mammalian sensory hair cells from the ototoxic side effects of aminoglycoside antibiotics, 10,240 compounds were initially screened in zebrafish larvae, selecting for those that protected lateral-line hair cells against neomycin and gentamicin. When the 64 hits from this screen were retested in mouse cochlear cultures, 8 protected outer hair cells (OHCs) from gentamicin in vitro without causing hair-bundle damage. These 8 hits shared structural features and blocked, to varying degrees, the OHC’s mechano-electrical transducer (MET) channel, a route of aminoglycoside entry into hair cells. Further characterization of one of the strongest MET channel blockers, UoS-7692, revealed it additionally protected against kanamycin and tobramycin and did not abrogate the bactericidal activity of gentamicin. UoS-7692 behaved, like the aminoglycosides, as a permeant blocker of the MET channel; significantly reduced gentamicin–Texas red loading into OHCs; and preserved lateral-line function in neomycin-treated zebrafish. Transtympanic injection of UoS-7692 protected mouse OHCs from furosemide/kanamycin exposure in vivo and partially preserved hearing. The results confirmed the hair-cell MET channel as a viable target for the identification of compounds that protect the cochlea from aminoglycosides and provide a series of hit compounds that will inform the design of future otoprotectants.

Issue Cover (September 2020)

Journal of NeurochemistryVolume 154, Issue 5 Issue CoverFree Access Issue Cover (September 2020) First published: 20 August 2020 https://doi.org/10.1111/jnc.14759 Read the full article: ‘Combination of antioxidants and NFAT (nuclear factor of activated T cells) inhibitor protects auditory hair cells from ototoxic insult’ by M. Sekulic-Jablanovic, K. Voronkova, D. Bodmer, V. Petkovic, (J. Neurochem. 2020, vol. 154 (5), pp. 519–529) on doi:10.1111/jnc.14921 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat Abstract Front cover: Auditory hair cell degeneration underlies hearing loss, and finding effective treatment has been a holy grail quest of hearing research. So far, a combination of antioxidants and other protective substances have proven successful to a limited extent. Our findings show that the combination of nuclear factor of activated T-cells (NFAT) inhibitor and N-acetylcysteine provides full protection from gentamicin damage in hair cells. The main advantage is that hair cell protection can be achieved using lower concentrations of each component, and thus decreasing their potential side effects. This approach could be beneficial as treatment not just in aminoglycoside-induced ototoxicity, but in all cases of ROS-induced cochlear damage, with noise-induced hearing loss being one of them. Image content: Representative image of green phalloidin-stained auditory hair cells of the cultured organ of Corti. Read the full article ‘Combination of antioxidants and NFAT (nuclear factor of activated T cells) inhibitor protects auditory hair cells from ototoxic insult’ by M. Sekulic-Jablanovic, K. Voronkova, D. Bodmer, V. Petkovic, (J. Neurochem. 2020, vol. 154 (5), pp. 519–529) on doi:10.1111/jnc.14921 Volume154, Issue5September 2020 RelatedInformation