Transforming growth factor-β1 regulates hypoxia-induced bronchial epithelial-mesenchymal transition by activation of lysys oxidase |
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| Authors: | XIA Xiao-dong PENG Yan-ping LEI Dan CHEN Wei-qian |
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| Institution: | Department of Respiratory Medicine, The Second Affiliated Hospital & Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, China |
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| Abstract: | AIM: To investigate whether transforming growth factor-β1 (TGF-β1) participates in hypoxia-induced bronchial epithelial-mesenchymal transition (EMT) through lysyl oxidase (LOX). METHODS: Sprague-Dawley (SD) rats were exposed to hypoxia to establish the animal model and were treated with LOX inhibitor β-aminopropionitrile (β-APN). Furthermore, primary rat bronchial epithelial cells were cultured in vitro and exposed either to normoxia or to hypoxia. TGF-β1, TGF-β1 receptor inhibitor (SB431542) or β-APN was used in the cell experiments. The content of collagen was measured by colorimetric method. The expression of TGF-β1, LOX, and 2 EMT-related proteins (namely, the epithelial marker E-cadherin and the mesenchymal marker vimentin) were determined by immunohistochemistry and We-stern blot, respectively. RESULTS: The expression of TGF-β1, vimentin and LOX and cross-linking of collagen were enhanced in hypoxia-exposed rat and in hypoxia-exposed bronchial epithelial cells, but the enhancement was impaired by the treatment with β-APN. In contrast, the expression of E-cadherin was reduced in hypoxia-exposed rat, and was reversed by treatment with β-APN. In vitro experiments demonstrated that TGF-β1 and hypoxia led to the morphological phenotype characteristic of EMT in rat bronchial epithelial cells, in which the morphology of rat bronchial epithelial cells was switched from cobble-stone shape in normoxia-exposed group to spindle fibroblast-like morphology in hypoxia-or TGF-β1-exposed group (P<0.01). Additionally, both β-APN and SB431542 partially prevented TGF-β1 and hypoxia induced EMT in rat bronchial epithelial cells. TGF-β1was able to dose-dependently up-regulate LOX expression in rat bronchial epithelial cells, which was blocked by concurrent incubation with SB431542. The up-regulation of TGF-β1, vimentin, LOX and cross-linking of collagen and down-regulation of E-cadherin in hypoxia-exposed rat bronchial epithelial cells was significantly reversed by incubation with SB431542. CONCLUSION: TGF-β1 regulates hypoxia-induced EMT in bronchial epithelial cells via activation of the LOX. |
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| Keywords: | Hypoxia Bronchial epithelial cells Transforming growth factor-β1 Lysyl oxidase Epithelial-mesenchymal transition |
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