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DEVELOPMENT OF A FATHEAD MINNOW MODEL FOR EVALUATING EXPOSURE OF FISH TO GENOTOXIC SUBSTANCES
Citation:
Meier, J R., L W. Chang, P A. Wernsing, S E. Franson, AND J M. Lazorchak. DEVELOPMENT OF A FATHEAD MINNOW MODEL FOR EVALUATING EXPOSURE OF FISH TO GENOTOXIC SUBSTANCES. Presented at Society of Environmental Toxicology and Chemistry, Austin, TX, November 8-13, 2003.
Impact/Purpose:
The indeterminate condition of exposure indicator research stands to change markedly with the ability to connect molecular biological technologies with cellular or tissue effects and outcomes. Three focal areas of ecological research aim to develop a sequence of approaches where "the earliest recognizable signatures of exposure" (i.e., unique patterns of up- and down-regulated genes and proteins) are identified for numerous stressors, demonstrable in case studies and incorporated into Agency, State and Regional studies supported by EMAP and other programs.
Area 1, Computational Toxicology Research: Exposure assessment has historically been based on use of chemical analysis data to generate exposure models. While biological activity of chemicals has been recognized to be important for exposure risk assessments, measurement of such activity has been limited to whole organism toxicity tests. Use of molecular approaches will:
improve extrapolation between components of source-to-outcome continuum (source , exposure , dose , effect , outcome)
Using a systems modeling approach, gene and protein expression data, in small fish models (fathead minnow and zebrafish), will be integrated with metabolomic and histopathological data. This will assist in prediction of environmental transformation and chemical effects based on structural characteristics, and enhance quantitative risk assessments, including areas of uncertainty such as a basis for extrapolation of effects of endocrine disrupting chemicals, interspecies extrapolation, complex chemical mixtures and dose-response assessment.
Area 2, Ecological Research-Environmental Diagnostics: Development of molecular diagnostic indicators contributes to several of the GPRA Diagnostic Research Goals. Methods will employ DNA microarray technology and expression proteomics, focusing on species of relevance to aquatic ecosystem risk assessment. Significantly, these diagnostic indicators will open the door to understanding subcellular interactions resulting from exposure to complex chemical mixtures.
define relationship between genetic disposition of populations and degree/specificity of stressor-specific gene transcriptional response in aquatic organisms (fish and invertebrates)
identify of chemical mixture induced transcriptional "patterns" using microarrays and hyperspectral scanning - via collaboration with DOE Sandia National Labs
apply molecular indicators to watershed level stressor study, including pilot studies with targeted pesticides and toxins indicators
develop molecular indicators of exposure for invertebrates (Daphnia, Lumbriculus, Chironomus)
Area 3, Exposure Research in Endocrine Disruptors:
Subobjective 1: Develop exposure methods, measurement protocols, and models for assessment of risk management practices of endocrine disrupting compounds. As risk management approaches are identified and developed, there will be a need to identify, adapt and develop bioassay screening tools and other analytical methods to assess their efficacy. Measurements research will be performed to define management needs. This effort will entail cross-lab participation from NRMRL, NERL and NHEERL.
Subobjective 2: Determine extent of environmental and human exposures to EDCs, characterize sources and factors influencing these exposures, develop and evaluate risk management strategies to reduce exposures. In order to develop effective risk management strategies, it is important to understand the extent of exposures to endocrine disrupting compounds and factors influencing source-to-exposure-to-dose relationships.
apply molecular indicators of exposure to estrogenic compounds in selected wastewater treatment plants located in ten USEPA Regions
identify differential gene expression following exposure of fathead minnows to environmental androgens and androgen-like compounds
apply molecular indicators of exposu
Description:
The fathead minnow (FHM) is widely used as a standard test species for acute and chronic toxicity testing of contaminants, effluents, and receiving waters. Because of its widespread distribution throughout North America, this species also has application in monitoring studies and for deployment using caged exposures in the field. However, the FHM has not been employed previously as a tool for determining the genetic toxic effects of chemicals or complex environmental mixtures. In the present study, fathead minnows were exposed to varying dose levels of the known mutagen, methyl methanesulfonate, either by a single intraperitoneal injection or by static renewal in water. DNA damage was evaluated in liver and blood cells at 1 and 3 days after the start of exposure using the single cell gel electrophoresis (SCGE) assay. Dose-related increases in DNA damage were observed in both blood and liver using either exposure regimen. The maximum levels of damage in treated fish exceeded control levels by more than 10-fold. Studies are underway to examine DNA damage in FHM following acute and chronic exposures to the pesticide atrazine, both alone and in combination with other chemicals. These results indicate the feasibility of evaluating DNA damage in tissues of fathead minnows, and suggest that the SCGE assay in this species could be a useful addition to standard aquatic toxicity test protocols and as an indicator method for assessing exposure to genotoxic agents in the field.