51
|
Chiu LL, Cunningham LL, Raible DW, Rubel EW, Ou HC. Using the zebrafish lateral line to screen for ototoxicity. J Assoc Res Otolaryngol 2008; 9:178-90. [PMID: 18408970 DOI: 10.1007/s10162-008-0118-y] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2008] [Accepted: 03/05/2008] [Indexed: 10/22/2022] Open
Abstract
The zebrafish is a valuable model for studying hair cell development, structure, genetics, and behavior. Zebrafish and other aquatic vertebrates have hair cells on their body surface organized into a sensory system called the lateral line. These hair cells are highly accessible and easily visualized using fluorescent dyes. Morphological and functional similarities to mammalian hair cells of the inner ear make the zebrafish a powerful preparation for studying hair cell toxicity. The ototoxic potential of drugs has historically been uncovered by anecdotal reports that have led to more formal investigation. Currently, no standard screen for ototoxicity exists in drug development. Thus, for the vast majority of Food and Drug Association (FDA)-approved drugs, the ototoxic potential remains unknown. In this study, we used 5-day-old zebrafish larvae to screen a library of 1,040 FDA-approved drugs and bioactives (NINDS Custom Collection II) for ototoxic effects in hair cells of the lateral line. Hair cell nuclei were selectively labeled using a fluorescent vital dye. For the initial screen, fish were exposed to drugs from the library at a 100-muM concentration for 1 h in 96-well tissue culture plates. Hair cell viability was assessed in vivo using fluorescence microscopy. One thousand forty drugs were rapidly screened for ototoxic effects. Seven known ototoxic drugs included in the library, including neomycin and cisplatin, were positively identified using these methods, as proof of concept. Fourteen compounds without previously known ototoxicity were discovered to be selectively toxic to hair cells. Dose-response curves for all 21 ototoxic compounds were determined by quantifying hair cell survival as a function of drug concentration. Dose-response relationships in the mammalian inner ear for two of the compounds without known ototoxicity, pentamidine isethionate and propantheline bromide, were then examined using in vitro preparations of the adult mouse utricle. Significant dose-dependent hair cell loss in the mouse utricle was demonstrated for both compounds. This study represents an important step in validating the use of the zebrafish lateral line as a screening tool for the identification of potentially ototoxic drugs.
Collapse
Affiliation(s)
- Lynn L Chiu
- Department of Otolaryngology-Head and Neck Surgery, University of Washington, Box 356515, Seattle, WA 98195, USA
| | | | | | | | | |
Collapse
|
52
|
Comparison of activated caspase detection methods in the gentamicin-treated chick cochlea. Hear Res 2008; 240:1-11. [PMID: 18487027 DOI: 10.1016/j.heares.2008.03.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 03/17/2008] [Accepted: 03/18/2008] [Indexed: 12/29/2022]
Abstract
Aminoglycoside antibiotics induce caspase-dependent apoptotic death in cochlear hair cells. Apoptosis, a regulated form of cell death, can be induced by many stressors, which activate signaling pathways that result in the controlled dismantling of the affected cell. The caspase family of proteases is activated in the apoptotic signaling pathway and is responsible for cellular destruction. The initiator caspase-9 and the effector caspase-3 are both activated in chick cochlear hair cells following aminoglycoside exposure. We have analyzed caspase activation in the avian cochlea during gentamicin-induced hair cell death to compare two different methods of caspase detection: caspase antibodies and CaspaTag kits. Caspase antibodies bind to the cleaved activated form of caspase-9 or caspase-3 in specific locations in fixed tissue. CaspaTag is a fluorescent inhibitor that binds to a reactive cysteine residue on the large subunit of the caspase heterodimer in unfixed tissue. To induce cochlear hair cell loss, 1-2 week-old chickens received a single injection of gentamicin (300 mg/kg). Chicks were sacrificed 24, 30, 42, 48, 72, or 96 h after injection. Cochleae were dissected and labeled for activated caspase-9 or caspase-3 using either caspase-directed antibodies or CaspaTag kits. Ears were co-labeled with either phalloidin or myosin VI to visualize hair cells and to determine the progression of cochlear damage. The timing of caspase activation was similar for both assays; however, caspase-9 and caspase-3 antibodies labeled only those cells currently undergoing apoptotic cell death. Conversely, CaspaTag-labeled all the cells that have undergone apoptotic cell death and ejection from the sensory epithelium, in addition to those that are currently in the cell death process. This makes CaspaTag ideal for showing an overall pattern or level of cell death over a period of time, while caspase antibodies provide a snapshot of cell death at a specific time point.
Collapse
|
53
|
Owens KN, Santos F, Roberts B, Linbo T, Coffin AB, Knisely AJ, Simon JA, Rubel EW, Raible DW. Identification of genetic and chemical modulators of zebrafish mechanosensory hair cell death. PLoS Genet 2008; 4:e1000020. [PMID: 18454195 PMCID: PMC2265478 DOI: 10.1371/journal.pgen.1000020] [Citation(s) in RCA: 157] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Accepted: 01/10/2008] [Indexed: 11/18/2022] Open
Abstract
Inner ear sensory hair cell death is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. While normal aging is the single greatest contributor, exposure to environmental toxins and therapeutic drugs such as aminoglycoside antibiotics and antineoplastic agents are significant contributors. Genetic variation contributes markedly to differences in normal disease progression during aging and in susceptibility to ototoxic agents. Using the lateral line system of larval zebrafish, we developed an in vivo drug toxicity interaction screen to uncover genetic modulators of antibiotic-induced hair cell death and to identify compounds that confer protection. We have identified 5 mutations that modulate aminoglycoside susceptibility. Further characterization and identification of one protective mutant, sentinel (snl), revealed a novel conserved vertebrate gene. A similar screen identified a new class of drug-like small molecules, benzothiophene carboxamides, that prevent aminoglycoside-induced hair cell death in zebrafish and in mammals. Testing for interaction with the sentinel mutation suggests that the gene and compounds may operate in different pathways. The combination of chemical screening with traditional genetic approaches is a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders. Loss of sensory hair cells in the inner ear is observed in the majority of hearing and balance disorders, affecting the health of more than 600 million people worldwide. Exposure to environmental toxins and certain pharmaceutical drugs such as aminoglycoside antibiotics and some cancer chemotherapy agents account for many of these hearing and balance problems. Variation in the genetic makeup between individuals plays a major role in establishing differences in susceptibility to environmental agents that damage the inner ear. Using zebrafish larvae, we developed a screen to uncover genes leading to differences in antibiotic-induced death of hair cells and to identify compounds that protect hair cells from damage. The combination of chemical screening with traditional genetic approaches offers a new strategy for identifying drugs and drug targets to attenuate hearing and balance disorders.
Collapse
MESH Headings
- Aminoglycosides/antagonists & inhibitors
- Aminoglycosides/toxicity
- Animals
- Base Sequence
- Cell Death/drug effects
- Cell Death/genetics
- Cisplatin/toxicity
- Codon, Terminator/genetics
- DNA Primers/genetics
- DNA, Complementary/genetics
- Drug Evaluation, Preclinical
- Epistasis, Genetic
- Hair Cells, Auditory, Inner/cytology
- Hair Cells, Auditory, Inner/drug effects
- Hair Cells, Auditory, Inner/physiology
- Hearing Loss/etiology
- Hearing Loss/genetics
- Hearing Loss/prevention & control
- Humans
- Mice
- Neomycin/antagonists & inhibitors
- Neomycin/toxicity
- Point Mutation
- Saccule and Utricle/drug effects
- Saccule and Utricle/pathology
- Thiophenes/chemistry
- Thiophenes/pharmacology
- Zebrafish/anatomy & histology
- Zebrafish/genetics
- Zebrafish/physiology
Collapse
Affiliation(s)
- Kelly N. Owens
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Otolaryngology—Head and Neck Surgery, University of Washington, Seattle, Washington, United States of America
| | - Felipe Santos
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Otolaryngology—Head and Neck Surgery, University of Washington, Seattle, Washington, United States of America
| | - Brock Roberts
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
| | - Tor Linbo
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
| | - Allison B. Coffin
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Otolaryngology—Head and Neck Surgery, University of Washington, Seattle, Washington, United States of America
| | - Anna J. Knisely
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Otolaryngology—Head and Neck Surgery, University of Washington, Seattle, Washington, United States of America
| | - Julian A. Simon
- Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America
| | - Edwin W. Rubel
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- Department of Otolaryngology—Head and Neck Surgery, University of Washington, Seattle, Washington, United States of America
- Department of Physiology and Biophysics, University of Washington, Seattle, Washington, United States of America
| | - David W. Raible
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
- Virginia Merrill Bloedel Hearing Research Center, University of Washington, Seattle, Washington, United States of America
- * E-mail:
| |
Collapse
|