title: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure of normal human dermal fibroblasts results in AhR-dependent and -independent changes in gene expression.
abstract: Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) results in a variety of lesions in mammals including severe skin lesions. The majority of TCDD's biological effects are mediated through activation of the aryl hydrocarbon receptor (AhR). We have chosen to examine the effect of TCDD and the AhR pathway on dermal fibroblasts because this cell type plays an integral role in skin homeostasis through the production of cytokines and other factors that regulate epidermal proliferation and differentiation. Our data show that normal human dermal fibroblasts (NHDFs) are responsive to TCDD, as demonstrated by induction of cytochrome p450 1B1 (CYP1B1) expression. Further, our data demonstrate that TCDD treatment of NHDFs results in significant (75-90%) decrease in expression of Id-1 and Id-3, proteins that are involved in regulation of cell proliferation and differentiation. The Id (Inhibitor of DNA binding) proteins are transcriptional inhibitors that function by forming inactive heterodimers with other HLH proteins. TCDD-repression of Id-1 and -3 is independent of de novo protein synthesis; co-treatment with cycloheximide has no effect on TCDD inhibition of Id-1 and Id-3. Co-treatment with the AhR antagonist alpha-naphthoflavone also does not block inhibition of Id-1 and Id-3 by TCDD, suggesting that TCDD inhibition of Id-1 and Id-3 is, at least in part, mediated independently of the AhR pathway. Our data also show that TCDD inhibits expression of the cell cycle regulatory gene p16(ink4a), which is often linked to Id expression. TCDD-induced reduction of p16(ink4a) expression is also independent of protein synthesis and the AhR pathway.
authors.affiliation: Department of Biochemistry and Microbiology, 76 Lipman Dr., Rutgers, The State University of NJ, New Brunswick, NJ 08901, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Akintobi
authors.forename: C M
authors.initials: CM
authors.lastname: Villano
authors.forename: L A
authors.initials: LA
authors.lastname: White
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases; D002453:Cell Cycle / Q000187:drug effects; D002478:Cells, Cultured; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D051798:Inhibitor of Differentiation Protein 1 / Q000235:genetics; D051796:Inhibitor of Differentiation Proteins / Q000235:genetics; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000032:analysis; D018336:Receptors, Aryl Hydrocarbon / Q000502:physiology*; D012867:Skin / Q000166:cytology
chemical_list: D019941:Cyclin-Dependent Kinase Inhibitor p16; C497453:ID1 protein, human; D051798:Inhibitor of Differentiation Protein 1; D051796:Inhibitor of Differentiation Proteins; D009363:Neoplasm Proteins; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; C075640:ID3 protein, human; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D065633:Cytochrome P-450 CYP1B1