Oxidative stress in zebrafish cells: potential utility of transgenic zebrafish as a deployable sentinel for site hazard ranking

In order to quickly assess potential environmental hazards of forwardly deployed military bases, we have focussed our efforts on biochemical and molecular changes in vertebrate cells following exposure to aqueous soil extracts. To this end, we are designing a series of deployable transgenic fish. Fish exhibit many of the same general defenses against toxic chemicals as do mammals, including enzyme induction, and the generation of oxidative stress. In response to many foreign compounds that generate oxidative stress, the transcription of certain protective genes is induced via specific DNA motifs called electrophile response elements ŽEPREs.. We have made a plasmid construct containing a single murine EPRE fused to a minimal promoter and the cDNA encoding firefly luciferase ŽEPRE- LUC.. In this paper, we have shown that the treatment of zebrafish cell line ZEM2S with a variety of chemicals known to induce EPRE-dependent transcription in cultured mammalian cells, results in dose-dependent induction of the transiently-transfected EPRE-LUC reporter construct. Compounds tested include aromatic hydrocarbons, heavy metals, and organophosphates. We observed similar dose-dependent responses when we treated ZEM2S and human cells in vitro with identical aqueous extracts of soil from hazardous waste sites. This suggests that the mechanism by which these compounds activate transcription is well conserved between mammals and zebrafish, and that transgenic zebrafish lines containing EPRE-driven reporter constructs might be useful as sentinels for the early detection of oxidative stress-inducing chemicals.