Microarray analysis of early adipogenesis in C3H10T1/2 cells: cooperative inhibitory effects of growth factors and 2,3,7,8-tetrachlorodibenzo-p-dioxin.
C3H10T1/2 mouse embryo fibroblasts differentiate into adipocytes when stimulated by a standard hormonal mixture (IDMB). 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), via the aryl hydrocarbon receptor (AhR), inhibits induction of the key adipogenic gene peroxisome proliferator-activated receptor gamma (PPARgamma) and subsequent adipogenesis. This TCDD-mediated inhibition requires activation of the extracellular signal-regulated kinase (ERK) pathway, which can be accomplished by serum, epidermal growth factor (EGF), or fibroblast growth factor (FGF). In the absence of serum or growth factors, IDMB induced adipogenesis without mitosis. Microarray analysis identified 200 genes that exhibited expression changes of at least twofold after 24 h of IDMB treatment. This time precedes most PPARgamma stimulation but follows the period of TCDD/ERK cooperation and periods of increased cell contraction and DNA synthesis. Functionally related gene clusters include genes associated with cell structure, triglyceride and cholesterol metabolism, oxidative regulation, and secreted proteins. In the absence of growth factors TCDD inhibited 30% of these IDMB responses without inhibiting the process of differentiation. A combination of EGF and TCDD that blocks differentiation cooperatively blocked a further 44 IDMB-responsive genes, most of which have functional links to differentiation, including PPARgamma. Cell cycle regulators that are stimulated by EGF were substantially inhibited by IDMB but these responses were unaffected by TCDD. By contrast, TCDD and EGF cooperatively reversed IDMB-induced changes in cell adhesion complexes immediately prior to increases in PPARgamma1 expression. Changes in adhesion-linked signaling may play a key role in TCDD affects on differentiation.
Hanlon
Paul R
PR
Molecular and Environmental Toxicology Center, University of Wisconsin-Madison, WI 53706, USA.
Cimafranca
Melissa A
MA
Liu
Xueqing
X
Cho
Young C
YC
Jefcoate
Colin R
CR
D017667:Adipocytes / Q000166:cytology / Q000187:drug effects*; D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D020869:Gene Expression Profiling; D008055:Lipids / Q000096:biosynthesis; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D010084:Oxidation-Reduction; D047495:PPAR gamma / Q000235:genetics; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D018336:Receptors, Aryl Hydrocarbon / Q000502:physiology
D008055:Lipids; D047495:PPAR gamma; D000072317:Polychlorinated Dibenzodioxins; D018336:Receptors, Aryl Hydrocarbon; D005346:Fibroblast Growth Factors; D004815:Epidermal Growth Factor