ToxSci Advance Access published online on October 20, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn207
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Gene expression profiles in zebrafish brain after acute exposure to domoic acid at symptomatic and asymptomatic doses
1 Marine Biotoxins Program, NOAA Fisheries/Northwest Fisheries Science Center, 2725 Montlake Blvd. East, Seattle, WA 98125 2 Department of Environmental and Occupational Health Sciences, University of Washington, Seattle WA 98105
* Address correspondence to: Evan P. Gallagher, Ph.D., Department of Environmental and Occupational Health Sciences, School of Public Health and Community Medicine, 4225 Roosevelt Way NE Suite 100, University of Washington, Seattle WA 98105-6099, Phone (206) 616-4739, Fax: (206) 543-8458, e-mail: evang3{at}u.washington.edu
Received July 8, 2008; revision received September 26, 2008; accepted September 26, 2008
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Abstract |
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Domoic acid (DA) is a neuroexcitatory amino acid that is naturally produced by some marine diatom species of the genus Pseudo-nitzschia. Ingestion of DA-contaminated seafood by humans results in a severe neurotoxic disease known as amnesic shellfish poisoning (ASP). Clinical signs of ASP include seizures and neuronal damage from activation of ionotropic glutamate receptors. However, the impacts of DA exposure at levels below those known to induce outward signs of neurobehavioral exicitotoxicity have not been well characterized. To further understand the mechanisms of neurotoxic injury associated with DA exposure, we examined the transcriptome of whole brains from zebrafish (Danio rerio) receiving intracoelomic injection of DA at both symptomatic and asymptomatic doses. A majority of zebrafish exposed to high-dose DA (1.2 µg DA/g) exhibited clinical signs of neuroexcitotoxicity (EC50 of 0.86 µg DA/g) within 5 to 20 min of intracoelomic injection. All zebrafish receiving low-dose DA (0.47 µg DA/g) or vehicle only maintained normal behavior. Microarray analysis of symptomatic and asymptomatic exposures collectively yielded 306 differentially expressed genes (1.5-fold, p 
0.05) predominately represented by signal transduction, ion transport, and transcription factor functional categories. Transcriptional profiles were suggestive of neuronal apoptosis following an overwhelming of protective adaptive pathways. Further, potential molecular biomarkers of neuropathic injury, including the zebrafish homolog of human NDRG4, were identified and may be relevant to DA exposure levels below that causing neurobehavioral injury. In general, DA-modulated gene expression was consistent with other model species thereby validating zebrafish as an appropriate vertebrate model to study mechanisms of DA neurotoxicity. These data provide a basis for identifying pathways of DA-induced injury as well as biomarkers of asymptomatic and symptomatic DA exposure levels.
Key Words: domoic acid; microarray analysis; zebrafish; excitotoxicity.