Protective role of edaravone against neomycin-induced ototoxicity in zebrafish

Protective effects of Y-27632 against cisplatin-induced ototoxicity: A zebrafish model Y-27632 and cisplatin-induced ototoxicity

Cisplatin is an effective chemotherapy agent against various solid malignancies; however, it is associated with irreversible bilateral sensorineural hearing loss, emphasizing the need for drug development to prevent this complication, with the current options being very limited. Rho-associated coiled-coil-containing protein kinase (ROCK) is a serine-threonine protein kinase involved in various cellular processes, including apoptosis regulation. In this study, we used a transgenic zebrafish model (Brn3C: EGFP) in which hair cells within neuromasts are observed in green under fluorescent microscopy without the need for staining. Zebrafish larvae were exposed to cisplatin alone or in combination with various concentrations of Y-27632, a potent ROCK inhibitor. Hair cell counts, apoptosis assessments using the terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling assay, FM1-43FX labeling assay and behavioral analyses (startle response and rheotaxis) were performed to evaluate the protective effects of Y-27632 against cisplatin-induced ototoxicity. Cisplatin treatment reduced the number of hair cells in neuromasts, induced apoptosis, and impaired zebrafish larval behaviors. Y-27632 demonstrated a dose-dependent protective effect against cisplatin-induced hair cell loss and apoptosis. These findings suggest that Y-27632, as a ROCK inhibitor, mitigates cisplatin-induced hair cell loss and associated ototoxicity in zebrafish.

Chemical screen in zebrafish lateral line identified compounds that ameliorate neomycin-induced ototoxicity by inhibiting ferroptosis pathway

BACKGROUND

Ototoxicity is a major side effect of many broadly used aminoglycoside antibiotics (AGs) and no FDA-approved otoprotective drug is available currently. The zebrafish has recently become a valuable model to investigate AG-induced hair cell toxicity and an expanding list of otoprotective compounds that block the uptake of AGs have been identified from zebrafish-based screening; however, it remains to be established whether inhibiting intracellular cell death pathway(s) constitutes an effective strategy to protect against AG-induced ototoxicity.

RESULTS

We used the zebrafish model as well as in vitro cell-based assays to investigate AG-induced cell death and found that ferroptosis is the dominant type of cell death induced by neomycin. Neomycin stimulates lipid reactive oxygen species (ROS) accumulation through mitochondrial pathway and blocking mitochondrial ferroptosis pathway effectively protects neomycin-induced cell death. We screened an alkaloid natural compound library and identified seven small compounds that protect neomycin-induced ototoxicity by targeting ferroptosis pathway: six of them are radical-trapping agents (RTAs) while the other one (ellipticine) regulates intracellular iron homeostasis, which is essential for the generation of lipid ROS to stimulate ferroptosis.

CONCLUSIONS

Our study demonstrates that blocking intracellular ferroptosis pathway is an alternative strategy to ameliorate neomycin-induced ototoxicity and provides multiple hit compounds for further otoprotective drug development.

Effects of the Edaravone, a Drug Approved for the Treatment of Amyotrophic Lateral Sclerosis, on Mitochondrial Function and Neuroprotection

Edaravone, the first known free radical scavenger, has demonstrated cellular protective properties in animals and humans. Owing to its antioxidant activity, edaravone modulates oxidative damage in various diseases, especially neurodegenerative diseases. In 2015, edaravone was approved in Japan to treat amyotrophic lateral sclerosis. The distinguishing pathogenic features of neurodegenerative diseases include high reactive oxygen species levels and mitochondrial dysfunction. However, the correlation between mitochondria and edaravone has not been elucidated. This review highlights recent studies on novel therapeutic perspectives of edaravone in terms of its effect on oxidative stress and mitochondrial function.

Three New Phthalide Glycosides from the Rhizomes of Cnidium officinale and Their Recovery Effect on Damaged Otic Hair Cells in Zebrafish

The extract from Cnidium officinale rhizomes was shown in a prior experiment to markedly recover otic hair cells in zebrafish damaged by neomycin. The current study was brought about to identify the principal metabolite. Column chromatography using octadecyl SiO₂ and SiO₂ was performed to isolate the major metabolites from the active fraction. The chemical structures were resolved on the basis of spectroscopic data, including NMR, IR, MS, and circular dichroism (CD) data. The isolated phthalide glycosides were assessed for their recovery effect on damaged otic hair cells in neomycin-treated zebrafish. Three new phthalide glycosides were isolated, and their chemical structures, including stereochemical characteristics, were determined. Two glycosides (0.1 μM) showed a recovery effect (p < 0.01) on otic hair cells in zebrafish affected by neomycin ototoxicity. Repeated column chromatography led to the isolation of three new phthalide glycosides, named ligusticosides C (1), D (2), and E (3). Ligusticoside C and ligusticoside E recovered damaged otic hair cells in zebrafish.

In vivo assessment of the toxicity of electronic cigarettes to zebrafish (Danio rerio) embryos, following gestational exposure, in terms of mortality, developmental toxicity, and hair cell damage: Toxicity of E-cigs to zebrafish embryos

With the ban of conventional cigarettes from public spaces, electronic cigarette (E-cig) liquids have emerged as a nicotine replacement treatment for smoking cessation. However, consumers possess little knowledge of the ingredients and health effects of E-cig liquids following exposure. This study evaluated hair cell damage and developmental toxicities following gestational exposure to E-cig liquids. Zebrafish embryos were exposed to E-cig liquids at different concentrations (0.1%, 0.2%, and 0.4%). Embryonic developmental toxicity and hair cell damage was evaluated at 6 and 7 d, respectively, after fertilization. The average number of hair cells in the anterior lateral line (ALL) and posterior lateral line (PLL) following E-cig exposure was compared to that of the control. Morphological abnormalities and heart rate were evaluated. E-cig liquids significantly damaged the hair cells in the ALL, compared to the control (control; 52.85 ± 5.29 cells, 0.1% E-cig; 49.43 ± 7.70 cells, 0.2% E-cig; 40.68 ± 12.00 cells, 0.4% E-cig; 32.14 ± 20.75%; n = 29-40; p < 0.01). At high concentrations, E-cig liquids significantly damaged the hair cells in the PLL (control; 36.88 ± 5.43 cells, 0.1% E-cig; 33.06 ± 5.21 cells, 0.2% E-cig; 30.95 ± 8.03 cells, 0.4% E-cig; 23.72 ± 15.53%, n = 29-40; p < 0.01). No morphological abnormalities in body shape, somites, notochord, tail, and pectoral fin were observed; however, abnormalities were observed in the dorsal fin and heart rate at high concentrations. Thus, gestational exposure to E-cigs significantly damaged hair cells in a concentration-dependent manner and induced developmental toxicities to the dorsal fin and heart rate at high concentrations.

Analysis of behavioral changes in zebrafish (Danio rerio) larvae caused by aminoglycoside-induced damage to the lateral line and muscles

Zebrafish behavior is influenced by the lateral line hair cells and muscles. Drug-induced behavioral changes can serve as indicators in the evaluation of drug toxicity. The aminoglycoside family of antibiotics comprise a number of agents, including neomycin (NM) and gentamicin (GM). We hypothesized that NM and GM exert different effects on zebrafish larvae through their action on the lateral line and muscle fibers, inducing different swimming behavioral patterns such as locomotor behavior and the startle response. In this study, 125 μM NM and 5, 10, 20 μM GM induced hair cell damage in the anterior and posterior lateral lines of zebrafish larvae. However, unlike GM, 125 μM NM also caused muscle damage. Locomotor behavior was decreased in the 125 μM NM-exposed group compared to the group exposed to GM. Furthermore, 125 μM NM exposure induced significantly different patterns of various indices of startle behavior compared with the GM exposure groups. Additionally, the larvae exhibited different startle responses depending on the concentration of GM. These results suggest that GM may be the drug-of-choice for analyzing behavioral changes in zebrafish caused by damage to the lateral line alone. Our study highlights the importance of confirming muscle damage in behavioral analyses using zebrafish.

Assessment of hair cell damage and developmental toxicity after fine particulate matter 2.5 μm (PM 2.5) exposure using zebrafish (Danio rerio) models

OBJECTIVES

Particulate matter (PM) exposure has become one of the most serious problems. The aim of the present study was to evaluate the hair cell damage and possible developmental toxicity caused by PM_2.5 exposure using a zebrafish model.

METHODS

Zebrafish embryos were exposed to various concentrations of PM_2.5. Developmental toxicity was evaluated based on general morphology score (GMS) system and Panzica-Kelly score, and by measurement of body length and heart rate. To evaluate hair cell damage, the average number of total hair cells within four neuromasts exposed to various concentrations of PM_2.5 was compared with that of the control group.

RESULTS

Morphological abnormalities evaluated by the GMS system and Panzica-Kelly score were rare and body length tended to be shorter in the PM_2.5-exposed groups. Heart rate decreased significantly in the PM_2.5-exposed group. Additionally, significant hair cell damage was observed after PM_2.5 exposure. It was dose-dependent and more severe after a longer period exposure (10 dpf).

CONCLUSIONS

In zebrafish embryos, exposure of PM_2.5 in the early stages of life decreased heart rate and caused significant hair cell damage in a dose-dependent manner.

Evaluation of Ototoxicity of an Antifog Agent and the Suspected Underlying Mechanisms: An Animal Study

Use of rigid endoscopes has become widespread in middle ear surgeries, thereby attracting attention to the safety of antifog agents. However, few studies on the ototoxicity of antifog agents have been conducted. The purpose of this study was to evaluate hair cell damage and the underlying mechanisms caused by antifog agents using zebrafish larvae. We exposed zebrafish larvae at 3 days postfertilization to various concentrations of the antifog agent, Ultrastop (0.01, 0.02, 0.04, and 0.08%) for 72 hours. The average number of hair cells within 4 neuromasts of larvae, including supraorbital (SO1 and SO2), otic (O1), and occipital (OC1), in the control group were compared to those in the exposure groups. Significant hair cell loss was observed in the experimental groups compared to that in the control group (P < .01; control: 53.88 ± 4.85, 0.01%: 45.08 ± 11.70, 0.02%: 41.36 ± 12.00, 0.04%: 35.36 ± 16.18, and 0.08%: 15.60 ± 7.53 cells). Concentration-dependent increase in hair cell apoptosis by terminal deoxynucleotidyltransferase (TDT)-mediated dUTP-biotin nick end labeling assay (control: 0.00 ± 0.00, 0.01%: 3.48 ± 2.18, 0.02%: 9.64 ± 5.75, 0.04%: 17.72 ± 6.26, and 0.08%: 14.60 ± 8.18 cells) and decrease in the viability of hair cell mitochondria by 2-(4-[dimethylamino] styryl)-N-ethylpyridinium iodide assay (control: 9.61 ± 1.47, 0.01%: 8.28 ± 2.22, 0.02%: 8.45 ± 2.72, 0.04%: 7.25 ± 2.44, and 0.08%: 6.77 ± 3.26 percentage of total area) were observed. Antifog agent exposure can cause hair cell damage in zebrafish larvae, possibly by induction of mitochondrial damage with subsequent apoptosis of hair cells.

Melatonin mitigates neomycin-induced hair cell injury in zebrafish

CONTEXT

Ototoxicity due to medications, such as aminoglycosides, is irreversible, and free radicals in the inner ear are assumed to play a major role. Because melatonin has an antioxidant property, we hypothesize that it might mitigate hair cell injury by aminoglycosides.

OBJECTIVE

The objective of this study was to evaluate whether melatonin has an alleviative effect on neomycin-induced hair cell injury in zebrafish (Danio rerio).

METHODS

Various concentrations of melatonin were administered to 5-day post-fertilization zebrafish treated with 125 μM neomycin for 1 h. Surviving hair cells within four neuromasts were compared with that of a control group. Apoptosis was assessed via terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The changes of ultrastructure were confirmed using a scanning electron microscope.

RESULTS

Melatonin alleviated neomycin-induced hair cell injury in neuromasts (neomycin + melatonin 100 μM: 13.88 ± 0.91 cells, neomycin only: 7.85 ± 0.90 cells; n = 10, p < 0.05) and reduced neomycin-induced apoptosis in the TUNEL assay. In ultrastructural analysis, hair cells within the neuromasts in zebrafish were preserved exposed to 125 μM neomycin and 100 μM melatonin for 1 h in SEM findings.

CONCLUSION

Melatonin is effective in alleviating aminoglycoside-induced hair cell injury in zebrafish. The results of this study demonstrated that melatonin has the potential to reduce apoptosis induced by aminoglycosides in zebrafish.

Could edaravone prevent gentamicin ototoxicity? An experimental study

OBJECTIVES

Clinical application of gentamicin may cause nephrotoxicity and ototoxicity. Our study is the first study to investigate the protective effects of edaravone against the gentamicin-induced ototoxicity. We investigated the protective effect of intraperitoneal (i.p.) edaravone application against gentamicin-induced ototoxicity in guinea pigs.

METHODS

Fourteen guinea pigs were divided into two equal groups consisting of a control group and a study group. One-hundred sixty milligrams per kilogram subcutaneous gentamicin and 0.3 mL i.p. saline were applied simultaneously once daily to seven guinea pigs in the control group (group 1). One-hundred sixty milligrams per kilogram gentamicin was applied subcutaneously and 3 mg/kg edaravone was applied intraperitoneally once daily for 7 days simultaneously to seven guinea pigs in the study group (group 2). Following the drug application, auditory brainstem response measurements were performed for the left ear on the 3rd and 7th days.

RESULTS

Hearing threshold values of the group 1 and group 2 measured in the 3rd day of the study were detected as 57.14 ± 4.88 and 82.86 ± 7.56, respectively. This difference was statistically significant ( p < 0.05). Hearing threshold values of the group 1 and group 2 measured in the 7th day of the study were detected as 87.14 ± 4.88 and 62.86 ± 4.88, respectively. This difference was statistically significant ( p < 0.05).

CONCLUSION

A statistically significant difference between the average threshold values of edaravone-administered group 2 and that of group 1 without edaravone was found. These differences show that systemic edaravone administration could diminish ototoxic effects of gentamicin and the severity of the hearing loss.

Embryotoxicity and hair cell toxicity of silver nanoparticles in zebrafish embryos

OBJECTIVES

The purpose of the present study was to evaluate silver nanoparticles (AgNP)-induced embryotoxicity and hair cell toxicity during zebrafish development.

METHODS

We exposed zebrafish embryos to various AgNP concentrations (30, 60, 120, and 240nM) and evaluated embryotoxicity at 72h and ototoxicity at 120h. Embryotoxicity parameters including abnormal morphology, mortality, hatching rate, and heart rate were investigated. Hair cells within four neuromasts were evaluated. In the present study, the average number of hair cells of zebrafish exposed to AgNP was compared with that of an unexposed control group.

RESULTS

The hatching rate was not significantly different between groups (control: 90%; AgNP 240nM: 89%). The control group showed 2% mortality and 0% teratogenicity, while the AgNP 240nM group showed increased mortality (11%) and teratogenicity (15%) at 72h (n=100). The heart rate of AgNP-exposed embryos tended to be lower than that of the control group (n=38). Furthermore, AgNP induced apoptotic hair cell damage in the neuromasts (control: 50.7±7.4 cells; 240nM AgNP: 41.1±6.3 cells, n=23). TUNEL positive cell counts increased significantly as AgNP concentration increases (p<0.001, n=20 in each group).

CONCLUSIONS

The results of this study indicate that AgNP exposure causes embryotoxicity and hair cell toxicity in zebrafish embryos.

Sodium Selenite Acts as an Otoprotectant against Neomycin-Induced Hair Cell Damage in a Zebrafish Model

Sodium selenite is a trace element essential for many physiological functions in the body. It is involved in various biological processes; it acts as a cofactor for antioxidant enzymes that protect against free radicals and is reported to limit metal-mediated oxidative DNA damage. In the present study, we investigated the effect of sodium selenite on neomycin ototoxicity in wild-type and transgenic zebrafish (Brn3C: EGFP). Five or six days post-fertilization, zebrafish larvae were co-exposed to 125 μM neomycin and various concentrations (10 μM, 100 μM, 250 μM, and 500 μM) of sodium selenite for 1 h. Hair cells within neuromasts of the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) lateral lines were analyzed by fluorescence microscopy (n = 10 fish per treatment). Hair cell survival was estimated as the ratio of the hair cell numbers in each group compared to those of the control group that were not exposed to neomycin. Apoptosis and hair cell damage of neuromasts were evaluated using the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL) assay and 2-[4-(dimethylamino) styryl]-N-ethylpyridinium iodide (DASPEI) assay, respectively. Ultrastructural changes were evaluated using scanning electron microscopy and transmission electron microscopy. Neuromast hair cells were preserved in zebrafish exposed to 125 μM neomycin and 500 μM sodium selenite for 1 h. Sodium selenite protected against neomycin-induced hair cell loss of neuromasts, reduced apoptosis, and prevented zebrafish ultrastructural changes. We propose that sodium selenite protects against neomycin-induced hair cell damage by inhibiting apoptosis, decreasing the disarray of stereocilia, and preventing ultrastructural changes in the neuromast hair cells of the zebrafish.

Ecabet sodium alleviates neomycin-induced hair cell damage

Ecabet sodium (ES) is currently applied to some clinical gastrointestinal disease primarily by the inhibition of the ROS production. In this study, the protective role of ES was evaluated against the neomycin-induced hair cell loss using zebrafish experimental animal model. Zebrafish larvae (5-7 dpf), were treated with each of the following concentrations of ES: 5, 10, 20, 40, and 80 μg/mL for 1 h, followed by 125 μM neomycin for 1h. The positive control group was established by 125 μM neomycin-only treatment (1h) and the negative control group with no additional chemicals was also established. Hair cells inside four neuromasts ( SO1, SO2, O1, OC1) were assessed using fluorescence microscopy (n = 10). Hair cell survival was calculated as the mean number of viable hair cells for each group. Apoptosis and mitochondrial damage were investigated using special staining (TUNEL and DASPEI assay, respectively), and compared among groups. Ultrastructural changes were evaluated using scanning electron microscopy. Pre-treatment group with ES increased the mean number of viable hair cells as a dose-dependent manner achieving almost same number of viable hair cells with 40 μM/ml ES treatment (12.98 ± 2.59 cells) comparing to that of the negative control group (14.15 ± 1.39 cells, p = 0.72) and significantly more number of viable hair cells than that of the positive control group (7.45 ± 0.91 cells, p < 0.01). The production of reactive oxygen species significantly increased by 183% with 125 μM neomycin treatment than the negative control group and significantly decreased down to 105% with the pre-treatment with 40 μM/ml ES (n = 40, p = 0.04). A significantly less number of TUNEL-positive cells (reflecting apoptosis, p < 0.01) and a significantly increased DASPEI reactivity (reflecting viable mitochondria, p < 0.01) were observed in 40 μM/ml ES pre-treatment group. Our data suggest that ES could protect against neomycin-induced hair cell loss possibly by reducing apoptosis, mitochondrial damages, and the ROS generation.

Survival of auditory hair cells

The inability of mammals to regenerate auditory hair cells creates a pressing need to understand the means of enhancing hair cell survival following insult or injury. Hair cells are easily damaged by noise exposure, by ototoxic medications and as a consequence of aging processes, all of which lead to progressive and permanent hearing impairment as hair cells are lost. Significant efforts have been invested in designing strategies to prevent this damage from occurring since permanent hearing loss has a profound impact on communication and quality of life for patients. In this mini-review, we discuss recent progress in the use of antioxidants, anti-inflammatories and apoptosis inhibitors to enhance hair cell survival. We conclude by clarifying the distinction between protection and rescue strategies and by highlighting important areas of future research.

Protective effects of caffeic acid phenethyl ester (CAPE) against neomycin-induced hair cell damage in zebrafish

OBJECTIVE

Caffeic acid phenethyl ester (CAPE) is known to reduce the generation of oxygen-derived free radicals, which is a major mechanism of aminoglycoside-induced ototoxicity. The objective of the present study was to evaluate the effects of CAPE on neomycin-induced ototoxicity in zebrafish (Brn3c: EGFP).

METHODS

Five-day post-fertilization zebrafish larvae (n=10) were exposed to 125 μM neomycin and one of the following CAPE concentrations for 1h: 50, 100, 250, 500, or 1000 μM. Ultrastructural changes were evaluated using scanning electron microscopy (SEM). The terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick-end labeling (TUNEL) assay and 2-[4-(dimethylamino)styryl]-N-ethylpyridiniumiodide (DASPEI) assay were performed for evaluation of apoptosis and mitochondrial damage.

RESULTS

CAPE decreased neomycin-induced hair cell loss in the neuromasts (500 μM CAPE: 12.7 ± 1.1 cells, 125 μM neomycin only: 6.3 ± 1.1 cells; n = 10, P < 0.05). In the ultrastructural analysis, structures of mitochondria and hair cells were preserved when exposed to 125 μM neomycin and 500 μM CAPE. CAPE decreased apoptosis and mitochondrial damage.

CONCLUSION

In the present study, CAPE attenuated neomycin-induced hair cell damage in zebrafish. The results of the current study suggest that neomycin induces apoptosis, and the apoptotic cell death can be prevented by treatment with CAPE in zebrafish.