title: Aryl hydrocarbon receptor-dependent regulation of miR-196a expression controls lung fibroblast apoptosis but not proliferation.
abstract: 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(-/-)) and wild-type (AhR(+/+)) mice, we show that there is ligand-independent regulation of miRNA, including low miR-196a in AhR(-/-) cells. Validation by qRT-PCR revealed a significant decrease in basal expression of miR-196a in AhR(-/-) compared to AhR(+/+) 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(+/+) fibroblasts concomitant with decreased AhR protein levels. There was increased proliferation only in AhR(+/+) lung fibroblasts in response to serum, corresponding to a decrease in p27(KIP1) protein, a cyclin-dependent kinase inhibitor. Increasing the cellular levels of miR-196a had no effect on proliferation or expression of p27(KIP1) in AhR(-/-) 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.
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Emelia
authors.initials: E
authors.lastname: Hecht
authors.affiliation: Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Michela
authors.initials: M
authors.lastname: Zago
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada.
authors.forename: Miles
authors.initials: M
authors.lastname: Sarill
authors.affiliation: Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Angela
authors.initials: A
authors.lastname: Rico de Souza
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada.
authors.forename: Alvin
authors.initials: A
authors.lastname: Gomez
authors.affiliation: Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: Matthews
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Qutayba
authors.initials: Q
authors.lastname: Hamid
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: David H
authors.initials: DH
authors.lastname: Eidelman
authors.affiliation: Department of Medicine, McGill University, Montreal, Quebec, Canada; Research Institute of the McGill University Health Centre, McGill University, Montreal, Quebec, Canada. Electronic address: Carolyn.baglole@McGill.ca.
authors.forename: Carolyn J
authors.initials: CJ
authors.lastname: Baglole
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001391:Azo Compounds / Q000494:pharmacology; D001564:Benzo(a)pyrene / Q000494:pharmacology; D015153:Blotting, Western; D002227:Carbazoles / Q000494:pharmacology; D049109:Cell Proliferation / Q000502:physiology; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology*; D007150:Immunohistochemistry; D008168:Lung / Q000166:cytology / Q000378:metabolism*; D018345:Mice, Knockout; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D011720:Pyrazoles / Q000494:pharmacology; D012313:RNA / Q000737:chemistry / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C511621:2-methyl-2H-pyrazole-3-carboxylic acid (2-methyl-4-o-tolylazophenyl)amide; C111855:6-formylindolo(3,2-b)carbazole; D001391:Azo Compounds; D002227:Carbazoles; D035683:MicroRNAs; D011720:Pyrazoles; D018336:Receptors, Aryl Hydrocarbon; D050760:Cyclin-Dependent Kinase Inhibitor p27; D001564:Benzo(a)pyrene; D012313:RNA
keywords: Annexin A1; Apoptosis; Aryl hydrocarbon receptor; Cigarette smoke; TGF-β1; miRNA