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Title: Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor implicated in the regulation of apoptosis and proliferation. Although activation of the AhR by xenobiotics such as dioxin inhibits the cell cycle and control apoptosis, paradoxically, AhR expression also promotes cell proliferation and survival independent of exogenous ligands. The microRNA (miRNA) miR-196a has also emerged as a regulator of proliferation and apoptosis but a relationship between the AhR and miR-196a is not known. Therefore, we hypothesized that AhR-dependent regulation of endogenous miR-196a expression would promote cell survival and proliferation. Utilizing lung fibroblasts from AhR deficient (AhR{sup −/−}) and wild-type (AhR{sup +/+}) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR{sup −/−} cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR{sup −/−} compared to AhR{sup +/+} cells. Exposure to AhR agonists benzo[a]pyrene (B[a]P) and FICZ as well as AhR antagonist CH-223191 decreased miR-196a expression in AhR{sup +/+} fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR{sup +/+} lung fibroblasts in response to serum, corresponding to a decrease in p27{sup KIP1} protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effectmore » on proliferation or expression of p27{sup KIP1} in AhR{sup −/−} fibroblasts but attenuated cigarette smoke-induced apoptosis. This study provides the first evidence that AhR expression is essential for the physiological regulation of cellular miRNA levels- including miR-196a. Future experiments designed to elucidate the functional relationship between the AhR and miR-196a may delineate additional novel ligand-independent roles for the AhR. - Highlights: • The AhR controls proliferation and apoptosis in lung cells. • The AhR regulates the expression of the microRNA miR-196a independent of xenobiotics. • AhR ligands decrease miR-196a concomitant with reduced AhR protein expression. • AhR regulation of miR-196a expression suppresses cigarette smoke-induced apoptosis. • Control of miRNA expression represents a potential new endogenous function of the AhR.« less
Authors:
 [1] ;  [2] ;  [1] ;  [2] ; ;  [3] ; ;  [1] ;  [4] ;  [1] ;  [4]
  1. Department of Medicine, McGill University, Montreal, Quebec (Canada)
  2. Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec (Canada)
  3. Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON (Canada)
  4. (Canada)
Publication Date:
OSTI Identifier:
22439898
Resource Type:
Journal Article
Resource Relation:
Journal Name: Toxicology and Applied Pharmacology; Journal Volume: 280; Journal Issue: 3; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; APOPTOSIS; CELL CYCLE; CELL PROLIFERATION; DIOXIN; FIBROBLASTS; LIGANDS; LUNGS; MICE; PYRENE; RECEPTORS; RESPIRATORY TRACT CELLS; TOBACCO SMOKES; TRANSCRIPTION FACTORS; XENOBIOTICS