Effect of in vitro administered 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on DNA-binding activities of nuclear transcription factors in NIH-3T3 mouse fibroblasts.
TCDD is a very toxic environmental contaminant which is known to cause a variety of toxic symptoms in many species. Because of a myriad of biochemical changes TCDD is known to induce in many test animals, it has been difficult to pinpoint the causative event common to all those symptoms in different species. One of the research avenues we have been following is identification of the pattern of TCDD-induced changes in DNA binding characteristics of nuclear transcription factors (NTFs), each of which has the property to trigger a set of coordinated changes in many gene expressions. Since in our previous work we studied animals affected by TCDD in vivo using gel mobility shift assay approached with32P labeled oligonucleotide probes, we examined in the current study the possibility whether we could establish an equivalent in vitro system in NIH-3T3 mouse fibroblast cells so as to be able to learn the similarities and the dissimilarities of TCDD-induced responses of NTFs between in vitro and in vivo. The results indicated that, for a large part, this in vitro test system could reasonably reproduce the pattern of changes occurring in vivo at the early stages of TCDD's action in terms of induced changes in binding of thes NTSs to DNA. The key features were TCDD induced upregulation of NTFs binding to the response elements for AP-1, dioxin (DRE) and T3 (thyroid hormone) and down-regulation of those to response elements (REs) for c-Myc, Sp-1 and retinoic acid receptor (RARE). However, the time course required the changes in DNA binding activity was much shorter in vitro. To study the basic cause for such changes in NTF binding, we studied the effects of exogenously added EGF, forskolin, TPA (12-0-tetradecanoylphorbol acetate) and TNFalpha on the expression of TCDD's action on some of these NTFs. The results showed that these agents indeed greatly influence the outcome. The most influential agents were TNFalpha, forskolin and EGF. These results indicate that this in vitro cell model is useful in simulating the action of TCDD with respect to its basic action on NTFs.
Hwang
Seong Gu
SG
Department of Environmental Toxicology and the Center for Environmental Health Sciences, University of California, Davis, CA 95616, USA.
Sasagawa
Hiromi
H
Matsumura
Fumio
F
D000818:Animals; D001667:Binding, Competitive; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004785:Environmental Pollutants / Q000494:pharmacology* / Q000633:toxicity; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology* / Q000633:toxicity; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D014157:Transcription Factors