Protection Of Hair Cells Research Articles

Research Progress on the Mechanism of Cochlear Hair Cell Regeneration.

Mammalian inner ear hair cells do not have the ability to spontaneously regenerate, so their irreversible damage is the main cause of sensorineural hearing loss. The damage and loss of hair cells are mainly caused by factors such as aging, infection, genetic factors, hypoxia, autoimmune diseases, ototoxic drugs, or noise exposure. In recent years, research on the regeneration and functional recovery of mammalian auditory hair cells has attracted more and more attention in the field of auditory research. How to regenerate and protect hair cells or auditory neurons through biological methods and rebuild auditory circuits and functions are key scientific issues that need to be resolved in this field. This review mainly summarizes and discusses the recent research progress in gene therapy and molecular mechanisms related to hair cell regeneration in the field of sensorineural hearing loss.

Dexamethasone (DXM)‐Coated Poly(lactic‐co‐glycolic acid) (PLGA) Microneedles as an Improved Drug Delivery System for Intracochlear Biodegradable Devices

AbstractUniform drug delivery techniques are challenging to develop for the inner ear due to the complexity of the cochlear anatomy. A promising solution is the use of biodegradable polymers because the continuous release of therapeutics without introducing toxic compounds is desirable. Using a microneedle approach lends the polymeric microneedle the capability to be placed inside of the scala tympani, releasing drugs overtime. Poly(lactic‐co‐glycolic acid) (PLGA) microneedles is prepared by dissolving dimethyl sulfoxide with either a) Rhodamine B, to study the drug release profile in vitro, b) FM1‐43, to study the drug release profile in vivo, or c) dexamethasone (DXM), to protect hair cell (HC) loss in vivo. The Rhodamine B studies show that the dye begins release from the microneedles within 30 min. The ototoxicity assessment of the DXM‐coated microneedles in vitro shows a significant reduction of HC losses when compared to control microneedles in an ototoxic environment. In vivo data show reduced hearing threshold for animals treated with DXM‐infused microneedles, providing a proof of concept of the methodology developed. Drug‐infused polymeric microneedles provide a promising method to deliver DXM to the inner ear over controlled periods of time protecting hair cells, thus minimizing hearing loss (HL).

Hair Cell Protection from Ototoxic Drugs.

Hearing loss is often caused by death of sensory hair cells (HCs) in the inner ear. HCs are vulnerable to some ototoxic drugs, such as aminoglycosides(AGs) and the cisplatin.The most predominant form of drug-induced cell death is apoptosis. Many efforts have been made to protect HCs from cell death after ototoxic drug exposure. These mechanisms and potential targets of HCs protection will be discussed in this review.And we also propose further investigation in the field of HCs necrosis and regeneration, as well as future clinical utilization.

Modulation of NAD+ biosynthesis activates SIRT1 and resists cisplatin-induced ototoxicity

Cisplatin, the most widely used platinum-based anticancer drug, often causes progressive and irreversible sensorineural hearing loss in cancer patients. However, the precise mechanism underlying cisplatin-associated ototoxicity is still unclear. Nicotinamide adenine dinucleotide (NAD+), a co-substrate for the sirtuin family and PARPs, has emerged as a potent therapeutic molecular target in various diseases. In our investigates, we observed that NAD+ level was changed in the cochlear explants of mice treated with cisplatin. Supplementation of a specific inhibitor (TES-1025) of α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD), a rate-limiting enzyme of NAD+de novo synthesis pathway, promoted SIRT1 activity, increased mtDNA contents and enhanced AMPK expression, thus significantly reducing hair cells loss and deformation. The protection was blocked by EX527, a specific SIRT1 inhibitor. Meanwhile, the use of NMN, a precursor of NAD+ salvage synthesis pathway, had shown beneficial effect on hair cell under cisplatin administration, effectively suppressing PARP1. In vivo experiments confirmed the hair cell protection of NAD+ modulators in cisplatin treated mice and zebrafish. In conclusion, we demonstrated that modulation of NAD+ biosynthesis via the de novo synthesis pathway and the salvage synthesis pathway could both prevent ototoxicity of cisplatin. These results suggested that direct modulation of cellular NAD+ levels could be a promising therapeutic approach for protection of hearing from cisplatin-induced ototoxicity.

N-Acetylcysteine Combined With Dexamethasone Treatment Improves Sudden Sensorineural Hearing Loss and Attenuates Hair Cell Death Caused by ROS Stress.

Sudden sensorineural hearing loss (SSNHL) is a common emergency in the world. Increasing evidence of imbalance of oxidant–antioxidant were found in SSNHL patients. Steroids combined with antioxidants may be a potential strategy for the treatment of SSNHL. In cochlear explant experiment, we found that N-acetylcysteine (NAC) combined with dexamethasone can effectively protect hair cells from oxidative stress when they were both at ineffective concentrations alone. A clinic trial was designed to explore whether oral NAC combined with intratympanic dexamethasone (ITD) as a salvage treatment has a better therapeutic effect. 41 patients with SSNHL were randomized to two groups. 23 patients in control group received ITD therapy alone, while 18 patient s in NAC group were treated with oral NAC and ITD. The patients were followed-up on day 1st (initiation of treatment) and day 14th. Overall, there was no statistical difference in final pure-tone threshold average (PTA) improvement between those two groups. However, a significant hearing gain at 8,000 Hz was observed in NAC group. Moreover, the hearing recovery rates of NAC group is much higher than that in control group. These results demonstrated that oral NAC in combination with ITD therapy is a more effective therapy for SSNHL than ITD alone.

Characterization of quinoxaline derivatives for protection against iatrogenically induced hearing loss.

Hair cell loss is the leading cause of hearing and balance disorders in humans. It can be caused by many factors, including noise, aging, and therapeutic agents. Previous studies have shown the therapeutic potential of quinoxaline against drug-induced ototoxicity. Here, we screened a library of 68 quinoxaline derivatives for protection against aminoglycoside-induced damage of hair cells from the zebrafish lateral line. We identified quinoxaline-5-carboxylic acid (Qx28) as the best quinoxaline derivative that provides robust protection against both aminoglycosides and cisplatin in zebrafish and mouse cochlear explants. FM1-43 and aminoglycoside uptake, as well as antibiotic efficacy studies, revealed that Qx28 is neither blocking the mechanotransduction channels nor interfering with aminoglycoside antibacterial activity, suggesting that it may be protecting the hair cells by directly counteracting the ototoxin’s mechanism of action. Only when animals were incubated with higher doses of Qx28 did we observe a partial blockage of the mechanotransduction channels. Finally, we assessed the regulation of the NF-κB pathway in vitro in mouse embryonic fibroblasts and in vivo in zebrafish larvae. Those studies showed that Qx28 protects hair cells by blocking NF-κB canonical pathway activation. Thus, Qx28 is a promising and versatile otoprotectant that can act across different species and toxins.

Transcriptomic characterization of dying hair cells in the avian cochlea

Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here, we use single-cell RNA sequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, respond differently. Dying short hair cells show a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified is associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations toward mammalian hair cell protection and hair cell regeneration.

Glucose Protects Cochlear Hair Cells Against Oxidative Stress and Attenuates Noise-Induced Hearing Loss in Mice.

Oxidative stress is the key determinant in the pathogenesis of noise-induced hearing loss (NIHL). Given that cellular defense against oxidative stress is an energy-consuming process, the aim of the present study was to investigate whether increasing energy availability by glucose supplementation protects cochlear hair cells against oxidative stress and attenuates NIHL. Our results revealed that glucose supplementation reduced the noise-induced formation of reactive oxygen species (ROS) and consequently attenuated noise-induced loss of outer hair cells, inner hair cell synaptic ribbons, and NIHL in CBA/J mice. In cochlear explants, glucose supplementation increased the levels of ATP and NADPH, as well as attenuating H2O2-induced ROS production and cytotoxicity. Moreover, pharmacological inhibition of glucose transporter type 1 activity abolished the protective effects of glucose against oxidative stress in HEI-OC1 cells. These findings suggest that energy availability is crucial for oxidative stress resistance and glucose supplementation offers a simple and effective approach for the protection of cochlear hair cells against oxidative stress and NIHL.

PIN1 Protects Hair Cells and Auditory HEI-OC1 Cells against Senescence by Inhibiting the PI3K/Akt/mTOR Pathway.

A growing amount of evidence has confirmed the crucial role of the prolyl isomerase PIN1 in aging and age-related diseases. However, the mechanism of PIN1 in age-related hearing loss (ARHL) remains unclear. Pathologically, ARHL is primarily due to the loss and dysfunction of hair cells (HCs) and spiral ganglion cells (SGCs) in the cochlea. Therefore, in this study, we aimed to investigate the role of PIN1 in protecting hair cells and auditory HEI-OC1 cells from senescence. Enzyme-linked immunosorbent assays, immunohistochemistry, and immunofluorescence were used to detect the PIN1 protein level in the serum of ARHL patients and C57BL/6 mice in different groups, and in the SGCs and HCs of young and aged C57BL/6 mice. In addition, a model of HEI-OC1 cell senescence induced by H2O2 was used. Adult C57BL/6 mice were treated with juglone, or juglone and NAC, for 4 weeks. Interestingly, we found that the PIN1 protein expression decreased in the serum of patients with ARHL, in senescent HEI-OC1 cells, and in the cochlea of aged mice. Moreover, under H2O2 and juglone treatment, a large amount of ROS was produced, and phosphorylation of p53 was induced. Importantly, PIN1 expression was significantly increased by treatment with the p53 inhibitor pifithrin-α. Overexpression of PIN1 reversed the increased level of p-p53 and rescued HEI-OC1 cells from senescence. Furthermore, PIN1 mediated cellular senescence by the PI3K/Akt/mTOR signaling pathway. In vivo data from C57BL/6 mice showed that treatment with juglone led to hearing loss. Taken together, these findings demonstrated that PIN1 may act as a vital modulator in hair cell and HEI-OC1 cell senescence.

Transcriptomic Characterization of Dying Hair Cells in the Avian Cochlea

Highlights: • New in vivo model to study cochlear hair cell death • Cochlear hair cells die rapidly and in synchronous fashion • Single cell RNA-seq reveals two stages of hair cell demise • Major types of dying cochlear hair cells express different sets of genes Summary: Sensory hair cells are prone to apoptosis caused by various drugs including aminoglycoside antibiotics. In mammals, this vulnerability results in permanent hearing loss because lost hair cells are not regenerated. Conversely, hair cells regenerate in birds, making the avian inner ear an exquisite model for studying ototoxicity and regeneration. Here we used single-cell RNAsequencing and trajectory analysis on control and dying hair cells after aminoglycoside treatment. Interestingly, the two major subtypes of avian cochlear hair cells, tall and short hair cells, responded differently. Dying short hair cells showed a noticeable transient upregulation of many more genes than tall hair cells. The most prominent gene group identified was associated with potassium ion conductances, suggesting distinct physiological differences. Moreover, the dynamic characterization of >15,000 genes expressed in tall and short avian hair cells during their apoptotic demise comprises a resource for further investigations towards mammalian hair cell protection and hair cell regeneration.

Increased susceptibility to acoustic trauma in a mouse model of non-syndromic sensorineural deafness, DFNB91.

Inactivating mutations of SERPINB6 in humans result in progressive hearing loss starting in early adulthood (DFNB91). We have previously shown that C57BL/6J mice lacking the orthologous gene, Serpinb6a, exhibit progressive hearing loss, which is associated with progressive loss of distinct cell types in the organ of Corti beginning with outer hair cells (OHCs). However, deafness in these animals occurs much earlier than expected, possibly because C57BL/6J mice also carry an age-related hearing loss mutation in the cadherin 23 gene (Cdh23ahl ) that causes late onset hearing loss. The CBA/CaH strain of mice does not carry Cdh23ah/ahl and may represent a better model of the human DFNB91 patients. Here, we show that transfer of the mutant Serpinb6a allele onto the Cdh23 normal CBA/CaH background markedly delays onset of hearing loss, more closely phenocopying DFNB91, without altering the pattern of cellular loss. Young, pre-symptomatic mice of this genotype exposed to acoustic trauma exhibit permanent hearing loss, compared to controls, associated with the disappearance of OHCs. We conclude that Serpinb6 helps to maintain hearing by protecting hair cells from stress.

Ferrostatin-1 protects auditory hair cells from cisplatin-induced ototoxicity in vitro and in vivo

Cisplatin is used in a wide variety of malignancies, but cisplatin-induced ototoxicity remains a major issue in clinical practice. Experimental evidence indicates that ferroptosis plays a key role in mediating the unwanted cytotoxicity effect caused by cisplatin. However, the role of ferroptosis in cisplatin-induced ototoxicity requires elucidation. Ferrostatin-1 (Fer-1) was identified as a potent inhibitor of ferroptosis and radical-trapping antioxidant with its ability to reduce the accumulation of lipid peroxides and chain-carrying peroxyl radicals. In the current study, we investigated the effects of Fer-1 in cisplatin-induced ototoxicity in in vitro, ex vivo, and in vivo models. We found, for the first time that Fer-1 efficiently alleviated cisplatin-induced cytotoxicity in HEI-OC1 cells via a concentration-dependent manner. Furthermore, Fer-1 mitigated cisplatin cytotoxicity in transgenic zebrafish sensory hair cells. In HEI-OC1 cells, Fer-1 pretreatment not only drastically reduced the generation of intracellular reactive oxygen species but also remarkably decreased lipid peroxidation levels induced by cisplatin. This was not only ascribed to the inhibition of 4-hydroxynonenal, the final product of lipid peroxides, but also to the promotion of glutathione peroxidase 4, the protein marker of ferroptosis. MitoTracker staining and transmission electron microscopy of mitochondrial morphology suggested that in HEI-OC1 cells, Fer-1 can effectively abrogate mitochondrial damage resulting from the interaction with cisplatin. In addition, Fer-1 pretreatment of cochlear explants substantially protected hair cells from cisplatin-induced damage. Therefore, our results demonstrated that ferroptosis might be involved in cisplatin ototoxicity. Fer-1 administration mitigated cisplatin-induced hair cell damage, further investigations are required to elucidate the molecular mechanisms of its otoprotective effect.

Research Progress of Hair Cell Protection Mechanism

How to prevent and treat hearing-related diseases through the protection of hair cells (HCs) is the focus in the field of hearing in recent years. Hearing loss caused by dysfunction or loss of HCs is the main cause of hearing diseases. Therefore, clarifying the related mechanisms of HC development, apoptosis, protection, and regeneration is the main goal of current hearing research. This review introduces the latest research on mechanism of HC protection and regeneration.

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

Recent advancements in understanding the role of epigenetics in the auditory system.

Sensorineural deafness in mammals is most commonly caused by damage to inner ear sensory epithelia, or hair cells, and can be attributed to genetic and environmental causes. After undergoing trauma, many non-mammalian organisms, including reptiles, birds, and zebrafish, are capable of regenerating damaged hair cells. Mammals, however, are not capable of regenerating damaged inner ear sensory epithelia, so that hair cell damage is permanent and can lead to hearing loss. The field of epigenetics, which is the study of various phenotypic changes caused by modification of genetic expression rather than alteration of DNA sequence, has seen numerous developments in uncovering biological mechanisms of gene expression and creating various medical treatments. However, there is a lack of information on the precise contribution of epigenetic modifications in the auditory system, specifically regarding their correlation with development of inner ear (cochlea) and consequent hearing impairment. Current studies have suggested that epigenetic modifications influence differentiation, development, and protection of auditory hair cells in cochlea, and can lead to hair cell degeneration. The objective of this article is to review the existing literature and discuss the advancements made in understanding epigenetic modifications of inner ear sensory epithelial cells. The analysis of the emerging epigenetic mechanisms related to inner ear sensory epithelial cells development, differentiation, protection, and regeneration will pave the way to develop novel therapeutic strategies for hearing loss.

Berbamine Analogs Exhibit Differential Protective Effects From Aminoglycoside-Induced Hair Cell Death.

Hearing loss is the third most common chronic health condition in the United States and largely results from damage to sensory hair cells. Major causes of hair cell damage include aging, noise exposure, and medications such as aminoglycoside antibiotics. Due to their potent antibacterial properties and low cost, aminoglycosides are often used for the treatment of gram-negative bacterial infections, surpassing expensive antibiotics with fewer harmful side effects. However, their use is coupled with permanent hearing loss in over 20% of patients requiring these life-sustaining antibiotics. There are currently no FDA-approved drugs that prevent hearing loss from aminoglycosides. A previous study by our group identified the plant alkaloid berbamine as a strong protectant of zebrafish lateral line hair cells from aminoglycoside damage. This effect is likely due to a block of the mechanotransduction channel, thereby reducing aminoglycoside entry into hair cells. The present study builds on this previous work, investigating 16 synthetic berbamine analogs to determine the core structure underlying their protective mechanisms. We demonstrate that nearly all of these berbamine analogs robustly protect lateral line hair cells from ototoxic damage, with ED50 values nearing 20 nM for the most potent analogs. Of the 16 analogs tested, nine strongly protected hair cells from both neomycin and gentamicin damage, while one conferred strong protection only from gentamicin. These data are consistent with prior research demonstrating that different aminoglycosides activate somewhat distinct mechanisms of damage. Regardless of the mechanism, protection required the entire berbamine scaffold. Phenolic alkylation or acylation with lipophilic groups appeared to improve protection compared to berbamine, implying that these structures may be responsible for mitigating damage. While the majority of analogs confer protection by blocking aminoglycoside uptake, 18% of our analogs also confer protection via an uptake-independent mechanism; these analogs exhibited protection when delivered after aminoglycoside removal. Based on our studies, berbamine analogs represent a promising tool to further understand the pathology of aminoglycoside-induced hearing loss and can serve as lead compounds to develop otoprotective drugs.

Exosome-mediated protection of auditory hair cells from ototoxic insults.

Hearing loss caused by the death of sensory hair cells of the inner ear is an unfortunate side effect for many patients treated with aminoglycoside antibiotics or platinum-containing chemotherapy agents. In animal models, induction of heat shock confers substantial otoprotection against aminoglycoside- and cisplatin-induced hair cell death. In this issue of the JCI, Breglio et al. demonstrate that inner ear tissue released exosomes carrying heat shock protein 70 (HSP70) in response to heat stress. HSP70 acted by a paracrine mechanism that engaged the Toll-like receptor 4 (TLR4) on hair cells to protect them from death. Exosomes and the HSP70/TLR4 pathway could thus provide treatment targets for the protection of hair cells from chemically induced death or from other insults, such as noise.

Exosomes mediate sensory hair cell protection in the inner ear.

Hair cells, the mechanosensory receptors of the inner ear, are responsible for hearing and balance. Hair cell death and consequent hearing loss are common results of treatment with ototoxic drugs, including the widely used aminoglycoside antibiotics. Induction of heat shock proteins (HSPs) confers protection against aminoglycoside-induced hair cell death via paracrine signaling that requires extracellular heat shock 70-kDa protein (HSP70). We investigated the mechanisms underlying this non-cell-autonomous protective signaling in the inner ear. In response to heat stress, inner ear tissue releases exosomes that carry HSP70 in addition to canonical exosome markers and other proteins. Isolated exosomes from heat-shocked utricles were sufficient to improve survival of hair cells exposed to the aminoglycoside antibiotic neomycin, whereas inhibition or depletion of exosomes from the extracellular environment abolished the protective effect of heat shock. Hair cell-specific expression of the known HSP70 receptor TLR4 was required for the protective effect of exosomes, and exosomal HSP70 interacted with TLR4 on hair cells. Our results indicate that exosomes are a previously undescribed mechanism of intercellular communication in the inner ear that can mediate nonautonomous hair cell survival. Exosomes may hold potential as nanocarriers for delivery of therapeutics against hearing loss.

KL1333, a derivative of β-lapachone, protects against cisplatin-induced ototoxicity in mouse cochlear cultures

Cisplatin (CP) is a chemotherapeutic drug used to treat cancerous solid tumors, but it causes serious side effects, including ototoxicity. The major cause of CP-induced ototoxicity is increased levels of mitochondrial reactive oxygen species (ROS). In this study, we examined the effect of 2-Isopropyl-3H-naphtho(1,2-d)imidazole-4,5-dione (KL1333), a β-lapachone derivative, on CP-induced ototoxicity using ex vivo organotypic culture system of cochlea. Hair cell damages in CP-treated cochlear explants with or without KL1333 were compared by immunohistochemistry. CP-induced oxidative stress and the preventive effect of KL1333 were analyzed by measuring intracellular ROS levels and depolarization of mitochondrial membrane potential. Activation of apoptosis signaling pathway was detected using TUNEL assay and immunostaining of cleaved caspase-3. As the results, it was found that KL1333 pretreatment significantly decreased stereocilia degeneration and hair cell loss, and prevented an increase in mitochondrial ROS levels in response to CP. Immunohistochemical examinations of cochlear explants revealed greater caspase-3 immunopositivity in the CP group than in controls, while the KL1333 + CP group showed significantly less immunopositivity than the CP group (P < 0.05). Thus, it appeared that KL1333 protected hair cells in the organ of Corti from CP-induced apoptosis by decreasing mitochondrial damages due to the production of mitochondrial ROS. This study is the first report showed the preventive effect of KL1333 against CP-induced ototoxicity. Although further studies should be performed to determine if KL1333 could maintain anticancer effect of CP, our data cautiously suggests that the antioxidant KL1333 can be used as an effective anti-apoptotic agent to prevent ototoxicity caused by CP-induced oxidative stress, and may prove useful in preventing hearing loss caused by CP.

Protective Role of Vernonia Amygdalina Leaf Aqueous Extract Against Neomycin-Induced Hair Cell Damage in Transgenic Zebrafish

Aminoglycoside treatment increases the loss of hair cells in the inner ear. Once the hair cells are lost, they are unable to regenerate spontaneously, and the resulting hearing loss is profound and irreversible in humans. The aqueous extract from the leaves of Vernonia amygdalina has been reported to have antioxidant properties. In this study, we evaluated whether the aqueous extracts of Vernonia amygdalina leaf could protect hair cells from aminoglycoside-induced damage using a transgenic zebrafish line. Our results showed that the EC50 of 1,1-Diphenyl-2 picrylhydrazyl radical scavenging and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonate), a measure of antioxidant capacity, of the aqueous extracts of Vernonia amygdalina leaf was 11.31 mg/mL and 2.73 mg/mL, respectively. Moreover, the total phenolic and flavonoids contents were 11.48 ŷ 3.12 mg gallic acid/g and 6.89 ŷ 0.65 mg catechin/g, respectively. In the toxicology study, the larval survival rate was significantly decreased and was dependent on the dosage of aqueous extracts of Vernonia amygdalina leaf, whereas it had no significant toxicity at doses below 2.5 mg/mL concentration (survival rate = 100%). Furthermore, a hair cell survival study shows that aqueous extracts of Vernonia amygdalina leaf decreased neomycin-induced hair cell death in a dose-dependent manner (survival rate = ∼94.1 ŷ 3.1% at 2 mg/mL concentration). Overall, these results suggest that the aqueous extracts of Vernonia amygdalina leaf possess the antioxidant effect and protects against hair cell loss caused by toxic side effects of neomycin. An optimal aqueous extract of Vernonia amygdalina leaf can be consumed as an herbal medicine without probable toxicity to body tissues and organs.