Superfund Research Program
Mechanism of Environmental Stress-Induced Developmental Abnormalities
Final Progress Reports
Dr. Freedman and his research team are investigating the hypothesis that the environmental toxicants, copper, PCB126, and endosulfan induce intracellular oxidative stress that activates transcription via the MAP kinase signally cascade. This activation can ultimately disrupt development. To test the hypothesis the first goal was to show that these toxicants could affect the expression of genes that respond to oxidative stress, and that are controlled by the AP-1 transcription complex. Using exposure conditions that provide optimal transcriptional activation, with minimal effect on cell viability, the reserachers have shown that the three toxicants increase the transcription of metallothionein and a reporter gene composed of the anti-oxidant response regulatory element from the quinone reductase promoter. In addition, depletion of intracellular glutathione, which increases the potential of chemicals to induced oxidative stress, prior to toxicant exposure increases oxidative-stress responsive gene expression. To elucidate the mechanism by which these toxicants active transcription the effects of the three environmental toxicants on members of the MAP kinase signally cascades were examined. Consistent with oxidative stress-activated transcription, copper exposure is associated with increases in AP-1 binding, and jun, JNK, ERK and p38 phosphorylation. Similarly, PCB126 and endosulfan exposure is associated with increased levels of phosphorylation of jun, JNK and ERK. The results support the researcher’s hypothesis, however to test their model in vivo, they are developing transgenic zebrafish that express a green fluorescent protein reporter under the control of a metal responsive element. Successful completion of these experiments will allow the researchers to correlate transactional activation by copper with metal-induced developmental abnormalities.