Drug screening for hearing loss: using the zebrafish lateral line to screen for drugs that prevent and cause hearing loss. Drug Discov Today 15(7-8):265-271

Virginia Merrill Bloedel Hearing Research Center, University of Washington, Box 357923, Seattle, WA 98195, USA.
Drug discovery today (Impact Factor: 6.69). 04/2010; 15(7-8):265-71. DOI: 10.1016/j.drudis.2010.01.001
Source: PubMed


Several animal models have been used for the study of mechanosensory hair cells and hearing loss. Because of the difficulty of tissue acquisition and large animal size, these traditional models are impractical for high-throughput screening. The zebrafish has emerged as a powerful animal model for screening drugs that cause and prevent hair cell death. The unique characteristics of the zebrafish enable rapid in vivo imaging of hair cells and hair cell death. We have used this model to screen for and identify multiple drugs that protect hair cells from aminoglycoside-induced death. The identification of multiple drugs and drug-like compounds that inhibit multiple hair cell death pathways might enable the development of protective cocktails to achieve complete hair cell protection.

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    • "In zebrafish, the LLS develops in a stereotyped way resulting in a regular and constant position of the neuromasts along the head and body of the animal (Raible and Kruse, 2000; Ghysen and Dambly- Chaudière, 2004). Moreover, in the zebrafish larva, the number of superficial neuromasts is relatively few, easy to observe and readily accessible to manipulation; thus, most studies on hair cells toxicity have been carried out on zebrafish larva (Buck et al., 2012; Mackenzie and Raible, 2012; Ou et al., 2010, 2012; Vlasits et al., 2012). The stereotyped arrangement of neuromasts makes LLS particularly interesting in studying hair cells because the expected location of each neuromast is known, thus allowing for detection of missing neuromasts or the alterations in hair cells within them that can be quickly identified. "
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    ABSTRACT: The hair cells of the lateral line system of fishes are morphologically and physiologically similar to the hair cells of the mammalian inner ear, also sharing its molecular characteristics. For this reason, it has been used as a powerful animal model to analyze in vivo ototoxicity. In this work, we examined the dose-dependent effects of two potent ototoxic aminoglycosides, neomycin and gentamicin, on the hair cells of two selected neuromasts (L1 and T1, the first of the trunk and the terminal located in the fin, respectively) of the lateral line in the ET4 transgenic zebrafish line. The hair cells of this strain selectively and constitutively display fluorescence. The fish were treated for 24 h at different doses (1, 2.5, 5, 10 and 100 μM levels) of both aminoglycosides. Immediately after treatment the morphology and the number of cells in L1 and T were analyzed under a fluorescence microscope. The results show that neomycin and gentamicin have different effects on the hair cell death at the same concentration, showing also different toxicity in L1 and T1 neuromasts. The toxicity observed in the hair cells of T1 neuromast was less than in L1 especially for the gentamicin treatment. These results demonstrate different sensitivity of hair cells of the lateral line to ototoxic drugs according to topographical localization and suggest the in vivo assay of the L1 neuromast of zebrafish larva and low doses of neomycin as an ideal model to study ototoxicity induced by aminoglycosides.
    Full-text · Article · Jul 2014 · Annals of anatomy = Anatomischer Anzeiger: official organ of the Anatomische Gesellschaft
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    • "The zebrafish has served as an especially attractive model for the study of the development and function of the vertebrate inner ear [8,16]. It has three methods of sensing sound within its environment. "
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    ABSTRACT: KCNQx genes encode slowly activating-inactivating K+ channels, are linked to physiological signal transduction pathways, and mutations in them underlie diseases such as long QT syndrome (KCNQ1), epilepsy in adults (KCNQ2/3), benign familial neonatal convulsions in children (KCNQ3), and hearing loss or tinnitus in humans (KCNQ4, but not KCNQ5). Identification of kcnqx potassium channel transcripts in zebrafish (Danio rerio) remains to be fully characterized although some genes have been mapped to the genome. Using zebrafish genome resources as the source of putative kcnq sequences, we investigated the expression of kcnq1-5 in heart, brain and ear tissues. Overall expression of the kcnqx channel transcripts is similar to that found in mammals. We found that kcnq1 expression was highest in the heart, and also present in the ear and brain. kcnq2 was lowest in the heart, while kcnq3 was highly expressed in the brain, heart and ear. kcnq5 expression was highest in the ear. We analyzed zebrafish genomic clones containing putative kcnq4 sequences to identify transcripts and protein for this highly conserved member of the Kcnq channel family. The zebrafish appears to have two kcnq4 genes that produce distinct mRNA species in brain, ear, and heart tissues. We conclude that the zebrafish is an attractive model for the study of the KCNQ (Kv7) superfamily of genes, and are important to processes involved in neuronal excitability, cardiac anomalies, epileptic seizures, and hearing loss or tinnitus.
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    • "The experiments presented here lay the groundwork for further studies of cisplatin-induced hair cell death using the Brn3c-GFP transgenic zebrafish. A number of studies have used different candidate therapeutics to inhibit the progression of aminoglycoside-induced hair cell death or accelerate the rate of hair cell regeneration [3], [5]–[8], [10], [11] and one study used the same drugs to screen for cisplatin-induced ototoxicity [9]. Most of these compounds are dissolved in DMSO. "
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    ABSTRACT: Inner ear sensory hair cells die following exposure to aminoglycoside antibiotics or chemotherapeutics like cisplatin, leading to permanent auditory and/or balance deficits in humans. Zebrafish (Danio rerio) are used to study drug-induced sensory hair cell death since their hair cells are similar in structure and function to those found in humans. We developed a cisplatin dose-response curve using a transgenic line of zebrafish that expresses membrane-targeted green fluorescent protein under the control of the Brn3c promoter/enhancer. Recently, several small molecule screens have been conducted using zebrafish to identify potential pharmacological agents that could be used to protect sensory hair cells in the presence of ototoxic drugs. Dimethyl sulfoxide (DMSO) is typically used as a solvent for many pharmacological agents in sensory hair cell cytotoxicity assays. Serendipitously, we found that DMSO potentiated the effects of cisplatin and killed more sensory hair cells than treatment with cisplatin alone. Yet, DMSO alone did not kill hair cells. We did not observe the synergistic effects of DMSO with the ototoxic aminoglycoside antibiotic neomycin. Cisplatin treatment with other commonly used organic solvents (i.e. ethanol, methanol, and polyethylene glycol 400) also did not result in increased cell death compared to cisplatin treatment alone. Thus, caution should be exercised when interpreting data generated from small molecule screens since many compounds are dissolved in DMSO.
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