title: Troglitazone attenuates TGF-β1-induced EMT in alveolar epithelial cells via a PPARγ-independent mechanism.
abstract: Peroxisome proliferator activated receptor γ (PPARγ) agonists are effective antifibrotic agents in a number of tissues. Effects of these agents on epithelial-mesenchymal transition (EMT) of primary alveolar epithelial cells (AEC) and potential mechanisms underlying effects on EMT have not been well delineated. We examined effects of troglitazone, a synthetic PPARγ agonist, on transforming growth factor (TGF)-β1-induced EMT in primary rat AEC and an alveolar epithelial type II (AT2) cell line (RLE-6TN). TGF-β1 (2.5 ng/mL) induced EMT in both cell types, as evidenced by acquisition of spindle-like morphology, increased expression of the mesenchymal marker α-smooth muscle actin (α-SMA) and downregulation of the tight junctional protein zonula occludens-1 (ZO-1). Concurrent treatment with troglitazone (or rosiglitazone), ameliorated effects of TGF-β1. Furthermore, following stimulation with TGF-β1 for 6 days, troglitazone reversed EMT-related morphological changes and restored both epithelial and mesenchymal markers to control levels. Treatment with GW9662 (an irreversible PPARγ antagonist), or overexpression of a PPARγ dominant negative construct, failed to inhibit these effects of troglitazone in AEC. Troglitazone not only attenuated TGF-β1-induced phosphorylation of Akt and glycogen synthase kinase (GSK)-3β, but also inhibited nuclear translocation of β-catenin, phosphorylation of Smad2 and Smad3 and upregulation of the EMT-associated transcription factor SNAI1. These results demonstrate inhibitory actions of troglitazone on TGF-β1-induced EMT in AEC via a PPARγ-independent mechanism likely through inhibition of β-catenin-dependent signaling downstream of TGF-β1, supporting a role for interactions between TGF-β and Wnt/β-catenin signaling pathways in EMT.
authors: Will Rogers Institute Pulmonary Research Center, Division of Pulmonary, Critical Care and Sleep Medicine, Department of Medicine, University of Southern California, Los Angeles, California, United States of America.
authors: Beiyun
authors: B
authors: Zhou
authors: Stephen T
authors: ST
authors: Buckley
authors: Vipul
authors: V
authors: Patel
authors: Yixin
authors: Y
authors: Liu
authors: Jiao
authors: J
authors: Luo
authors: Manda Sai
authors: MS
authors: Krishnaveni
authors: Mihaela
authors: M
authors: Ivan
authors: Lucas
authors: L
authors: DeMaio
authors: Kwang-Jin
authors: KJ
authors: Kim
authors: Carsten
authors: C
authors: Ehrhardt
authors: Edward D
authors: ED
authors: Crandall
authors: Zea
authors: Z
authors: Borok
mesh_terms: D000813:Anilides / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D002478:Cells, Cultured; D002839:Chromans / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism*; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D006801:Humans; D008297:Male; D008856:Microscopy, Fluorescence; D047495:PPAR gamma / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D045162:Thiazolidinediones / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D000077288:Troglitazone; D062826:Zonula Occludens-1 Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C457499:2-chloro-5-nitrobenzanilide; D000813:Anilides; D002839:Chromans; D047495:PPAR gamma; D045162:Thiazolidinediones; D053773:Transforming Growth Factor beta1; D062826:Zonula Occludens-1 Protein; D000077288:Troglitazone