2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is the archetype of a large class of polyhalogenated compounds that evoke a variety of common toxic responses on exposed human populations. The long term goal of the proposed research is to determine the biochemical basis underlying the toxicity evoked by exposure to TCDD. Many of the toxic responses of cells exposed to TCDD involve modification of normal patterns of epithelial cell proliferation and differentiation. Because the result of exposure to TCDD is an alteration of the regulated patterns of epidermal cell proliferation and differentiation programs, emphasis is placed on the actions of TCDD as a modulator of known signal transducing systems that regulate epidermal cell growth. The proposed studies will use primary, and continuous cultures of human keratinocytes as the model system, in which to study TCDD toxicity.
Specific Aims that are proposed for this project are: (1) Determine the mechanism of modulation of growth factor synthesis in keratinocytes exposed to TCDD. Preliminary experiments have shown that levels of transforming growth factor-alpha (TGF-alpha) in the culture medium of normal keratinocytes (HuE) and immortalized, but non-tumorigenic (SCC 12F) cultures increases significantly after the cells are exposed to TCDD. Experiments will be conducted to determine whether synthesis of the peptide growth factor increases, or secretion of already synthesized TGF- alpha is modulated after exposure to TCDD. (2) Determine whether dioxins modulate the rate of synthesis or decrease the rate of degradation of TGF- alpha mRNA. Nuclear runoff transcription analysis will be conducted using a cDNA probe specific for TGF-alpha to analyze the accumulation of TGF- alpha-specific mRNA in HuE and SCC 12F human keratinocyte cells exposed to TCDD. (3) Determine whether TGF-alpha is the only inducible component responsible for TCDD-modulated toxicity, and whether other components in medium from keratinocyte cultures exposed to dioxins modulate binding of TGF-alpha to the EGF receptor. Presence of TGF-beta and other cytokines in the medium from TCDD-exposed cultures will be determined using western immunoblot analysis. Competition binding experiments will be undertaken to determine whether components other than TGF-alpha are present in the medium from cultures exposed to TCDD that will transmodulate EGF receptor in keratinocytes exposed to dioxins.

Agency
National Institute of Health (NIH)
Institute
National Institute of Environmental Health Sciences (NIEHS)
Type
Research Project (R01)
Project #
5R01ES002866-11
Application #
2153204
Study Section
Toxicology Subcommittee 2 (TOX)
Project Start
1981-09-15
Project End
1995-12-31
Budget Start
1994-01-01
Budget End
1995-12-31
Support Year
11
Fiscal Year
1994
Total Cost
Indirect Cost
Name
Tulane University
Department
Public Health & Prev Medicine
Type
Schools of Public Health
DUNS #
City
New Orleans
State
LA
Country
United States
Zip Code
70118
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McNulty, S E; Toscano Jr, W A (1995) Transcriptional regulation of glyceraldehyde-3-phosphate dehydrogenase by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Biochem Biophys Res Commun 212:165-71
Su, L N; Toscano Jr, W A; Kennedy, A R (1991) Suppression of phorbol ester-enhanced radiation-induced malignancy in vitro by protease inhibitors is independent of protein kinase C. Biochem Biophys Res Commun 176:18-24
Choi, E J; Toscano, D G; Ryan, J A et al. (1991) Dioxin induces transforming growth factor-alpha in human keratinocytes. J Biol Chem 266:9591-7
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Greenlee, W F; Osborne, R; Dold, K M et al. (1985) Toxicity of chlorinated aromatic compounds in animals and humans: in vitro approaches to toxic mechanisms and risk assessment. Environ Health Perspect 60:69-76
Hudson, L G; Toscano Jr, W A; Greenlee, W F (1985) Regulation of epidermal growth factor binding in a human keratinocyte cell line by 2,3,7,8-tetrachlorodibenzo-p-dioxin. Toxicol Appl Pharmacol 77:251-9