Ecabet sodium alleviates neomycin-induced hair cell damage

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.

Zebrafish neuromast sensory system: Is it an emerging target to assess environmental pollution impacts?

Environmental pollution poses risks to ecosystems. Among these risks, one finds neurotoxicity and damage to the lateral line structures of fish, such as the neuromast and its hair cells. Zebrafish (Danio rerio) is recommended as model species to be used in ecotoxicological studies and environmental biomonitoring programs aimed at assessing several biomarkers, such as ototoxicity. However, little is known about the history of and knowledge gaps on zebrafish ototoxicity. Thus, the aim of the current study is to review data available in the scientific literature about using zebrafish as animal model to assess neuromast toxicity. It must be done by analyzing the history and publication category, world production, experimental design, developmental stages, chemical classes, neuromasts and hair cell visualization methods, and zebrafish strains. Based on the results, number, survival and fluorescence intensity of neuromasts, and their hair cells, were the parameters oftentimes used to assess ototoxicity in zebrafish. The wild AB strain was the most used one, and it was followed by Tübingen and transgenic strains with GFP markers. DASPEI was the fluorescent dye most often applied as method to visualize neuromasts, and it was followed by Yo-Pro-1 and GFP transgenic lines. Antibiotics, antitumorals, metals, nanoparticles and plant extracts were the most frequent classes of chemicals used in the analyzed studies. Overall, pollutants can harm zebrafish's mechanosensory system, as well as affect their behavior and survival. Results have shown that zebrafish is a suitable model system to assess ototoxicity induced by environmental pollution.

Using the Zebrafish Lateral Line to Understand the Roles of Mitochondria in Sensorineural Hearing Loss

Hair cells are the mechanosensory receptors of the inner ear and can be damaged by noise, aging, and ototoxic drugs. This damage often results in permanent sensorineural hearing loss. Hair cells have high energy demands and rely on mitochondria to produce ATP as well as contribute to intracellular calcium homeostasis. In addition to generating ATP, mitochondria produce reactive oxygen species, which can lead to oxidative stress, and regulate cell death pathways. Zebrafish lateral-line hair cells are structurally and functionally analogous to cochlear hair cells but are optically and pharmacologically accessible within an intact specimen, making the zebrafish a good model in which to study hair-cell mitochondrial activity. Moreover, the ease of genetic manipulation of zebrafish embryos allows for the study of mutations implicated in human deafness, as well as the generation of transgenic models to visualize mitochondrial calcium transients and mitochondrial activity in live organisms. Studies of the zebrafish lateral line have shown that variations in mitochondrial activity can predict hair-cell susceptibility to damage by aminoglycosides or noise exposure. In addition, antioxidants have been shown to protect against noise trauma and ototoxic drug–induced hair-cell death. In this review, we discuss the tools and findings of recent investigations into zebrafish hair-cell mitochondria and their involvement in cellular processes, both under homeostatic conditions and in response to noise or ototoxic drugs. The zebrafish lateral line is a valuable model in which to study the roles of mitochondria in hair-cell pathologies and to develop therapeutic strategies to prevent sensorineural hearing loss in humans.

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.

Structure Characterization and Otoprotective Effects of a New Endophytic Exopolysaccharide from Saffron

Saffron, a kind of rare medicinal herb with antioxidant, antitumor, and anti-inflammatory activities, is the dry stigma of Crocus sativus L. A new water-soluble endophytic exopolysaccharide (EPS-2) was isolated from saffron by anion exchange chromatography and gel filtration. The chemical structure was characterized by FT-IR, GC-MS, and 1D and 2D-NMR spectra, indicating that EPS-2 has a main backbone of (1→2)-linked α-d-Manp, (1→2, 4)-linked α-d-Manp, (1→4)-linked α-d-Xylp, (1→2, 3, 5)-linked β-d-Araf, (1→6)- linked α-d-Glcp with α-d-Glcp-(1→ and α-d-Galp-(1→ as sidegroups. Furthermore, EPS-2 significantly attenuated gentamicin-induced cell damage in cultured HEI-OC1 cells and increased cell survival in zebrafish model. The results suggested that EPS-2 could protect cochlear hair cells from ototoxicity exposure. This study could provide new insights for studies on the pharmacological mechanisms of endophytic exopolysaccharides from saffron as otoprotective agents.

Preventive effect of ecabet sodium on low-dose aspirin-induced small intestinal mucosal injury: a randomized, double-blind, pilot study

Background

We aimed to investigate how high-dose ecabet sodium affects low-dose aspirin-induced small intestinal mucosal injury in healthy volunteers.

Methods

Healthy volunteers were enrolled randomly into one of two groups with the following drug regimens for 2 weeks: group A, low-dose aspirin once per day and group B, low-dose aspirin and 4.0 g of ecabet sodium. Small bowel capsule endoscopy was performed before and 2 weeks after low-dose aspirin administration.

Results

A significant difference was found in the median number [range] of small intestinal lesions between baseline and two weeks after low-dose aspirin administration in group A (baseline: 1 [0–5], after: 5 [1–11]; p = 0.0059) but not in group B (baseline: 0.5 [0–9], after: 3 [0–23]; p = 0.0586). In group B, although the median number [range] of lesions in the first tertile of the small intestine did not increase two weeks after low-dose aspirin administration (baseline: 0 [0–4], after: 1.5 [0–8]; p = 0.2969), the number of lesions in the second and third tertiles of the small intestine increased significantly (baseline: 0 [0–5], after: 2 [0–15]; p = 0.0469).

Conclusions

Ecabet sodium had a preventive effect on low-dose aspirin-induced small intestinal mucosal injury in the upper part of the small intestine.

Trial registration

ISRCTN 99322160, 01/10/2018.

Impact of Nicotine Exposure on Hair Cell Toxicity and Embryotoxicity During Zebrafish Development

Objectives

Nicotine has various adverse effects including negative impacts associated with maternal exposure. In the current study, we examined nicotine-induced damage of hair cells and embryotoxicity during zebrafish development.

Methods

Zebrafish embryos were exposed to nicotine at several concentrations (5, 10, 20, and 40 μM) and embryotoxicity were evaluated at 72 hours, including hatching rate, mortality, teratogenicity rate, and heart rate. Hair cells within the supraorbital (SO1 and SO2), otic (O1), and occipital (OC1) neuromasts were identified at 120 hours. Apoptosis and mitochondrial damage of hair cells were analyzed using TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling) and DASPEI (2-[4-(dimethylamino)styryl]-N-ethylpyridinium iodide) assays, respectively, and changes of ultrastructure were observed by scanning electron microscopy.

Results

The control group without nicotine appeared normal with overall mortality and teratogenicity rate <5%. The hatching rate and mortality rate was not significantly different according to nicotine concentration (n=400 each). The abnormal morphology rate (n=400) increased and heart rate (n=150) decreased with increasing nicotine concentration (P<0.05). Nicotine-induced hair cell damage significantly increased as nicotine concentration increased. A significantly greater number of TUNEL-positive cells (P<0.01) and markedly smaller DASPEI area (P<0.01) were shown as nicotine concentration increased.

Conclusion

The current results suggest that nicotine induces dose-dependent hair cell toxicity in embryos by promoting apoptosis and mitochondrial and structural damage.

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.