2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced MUC5AC expression: aryl hydrocarbon receptor-independent/EGFR/ERK/p38-dependent SP1-based transcription.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent environmental toxicant. Epidemiological studies have associated TCDD exposure with the development of chronic obstructive pulmonary disease, which is manifested by mucous/goblet cell hyperplasia. The purpose of this research was to elucidate the pathway/mechanisms that lead to TCDD-induced gene expression in both primary normal human bronchial epithelial cells and an immortalized cell line, HBE1, under air-liquid interface conditions. TCDD exposure induced a time-dependent elevation of MUC5AC mRNA and protein synthesis, and cytochrome p450 1A1 (CYP1A1) expression in these cells. Treatment with an aryl hydrocarbon receptor antagonist had no effect on TCDD-induced MUC5AC expression, but significantly suppressed CYP1A1 induction. However, treatments with inhibitors of signaling pathways and the expression of dominant negative mutants of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK) and p38, but not the inhibition of c-Jun N-terminal kinase pathway, abrogated MUC5AC induction, but not that of CYP1A1. These effects also occurred at the MUC5AC promoter-reporter level using the chimeric construct for a transient transfection study. Western blot analysis confirmed the phosphorylation of activated EGFR, ERK, and p38 signaling molecules, but not the c-Jun N-terminal kinase, in cells after TCDD exposure. Specificity protein 1 (Sp1) phosphorylation also occurred in cells after TCDD exposure. Both MUC5AC expression and the promoter activity were inhibited by mithramycin A, an inhibitor specific to Sp1-based transcription. These results lead to the conclusion that TCDD induced MUC5AC expression through a noncanonical aryl hydrocarbon receptor-independent, EGFR/ERK/p38-mediated signaling pathway-mediated/Sp1-based transcriptional mechanism.
Lee
Yong C
YC
Center for Comparative Respiratory Biology and Medicine, University of California at Davis, 95616, USA.
Oslund
Karen L
KL
Thai
Philip
P
Velichko
Sharlene
S
Fujisawa
Tomoyuki
T
Duong
Trang
T
Denison
Michael S
MS
Wu
Reen
R
D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics* / Q000378:metabolism; D004785:Environmental Pollutants / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D055271:Mucin 5AC / Q000235:genetics* / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D014158:Transcription, Genetic / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D004785:Environmental Pollutants; D004791:Enzyme Inhibitors; C524678:MUC5AC protein, human; D055271:Mucin 5AC; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D019363:Cytochrome P-450 CYP1A1; C512478:EGFR protein, human; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases