scholarly journals Hypoxia-induced alveolar epithelial-mesenchymal transition requires mitochondrial ROS and hypoxia-inducible factor 1

2009 ◽  
Vol 297 (6) ◽  
pp. L1120-L1130 ◽  
Author(s):  
Guofei Zhou ◽  
Laura A. Dada ◽  
Minghua Wu ◽  
Aileen Kelly ◽  
Humberto Trejo ◽  
...  
Keyword(s):  
Transforming Growth Factor ◽  
Epithelial Mesenchymal Transition ◽  
Hypoxia Inducible Factor ◽  
Alveolar Epithelial Cells ◽  
Type I ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Mitochondrial Ros ◽  
Lung Dysfunction ◽  
Tgf Β1

Patients with acute lung injury develop hypoxia, which may lead to lung dysfunction and aberrant tissue repair. Recent studies have suggested that epithelial-mesenchymal transition (EMT) contributes to pulmonary fibrosis. We sought to determine whether hypoxia induces EMT in alveolar epithelial cells (AEC). We found that hypoxia induced the expression of α-smooth muscle actin (α-SMA) and vimentin and decreased the expression of E-cadherin in transformed and primary human, rat, and mouse AEC, suggesting that hypoxia induces EMT in AEC. Both severe hypoxia and moderate hypoxia induced EMT. The reactive oxygen species (ROS) scavenger Euk-134 prevented hypoxia-induced EMT. Moreover, hypoxia-induced expression of α-SMA and vimentin was prevented in mitochondria-deficient ρ0 cells, which are incapable of ROS production during hypoxia. CoCl2 and dimethyloxaloylglycine, two compounds that stabilize hypoxia-inducible factor (HIF)-α under normoxia, failed to induce α-SMA expression in AEC. Furthermore, overexpression of constitutively active HIF-1α did not induce α-SMA. However, loss of HIF-1α or HIF-2α abolished induction of α-SMA mRNA during hypoxia. Hypoxia increased the levels of transforming growth factor (TGF)-β1, and preincubation of AEC with SB431542, an inhibitor of the TGF-β1 type I receptor kinase, prevented the hypoxia-induced EMT, suggesting that the process was TGF-β1 dependent. Furthermore, both ROS and HIF-α were necessary for hypoxia-induced TGF-β1 upregulation. Accordingly, we have provided evidence that hypoxia induces EMT of AEC through mitochondrial ROS, HIF, and endogenous TGF-β1 signaling.

scholarly journals N-acetylcysteine inhibits alveolar epithelial-mesenchymal transition

2009 ◽  
Vol 297 (5) ◽  
pp. L805-L812 ◽  
Author(s):  
V. M. Felton ◽  
Z. Borok ◽  
B. C. Willis
Keyword(s):  
Epithelial Cells ◽  
Transforming Growth Factor ◽  
Epithelial Mesenchymal Transition ◽  
Alveolar Epithelial Cells ◽  
Ros Generation ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Intracellular Ros ◽  
Tgf Β1

The ability of transforming growth factor-β1 (TGF-β1) to induce epithelial-mesenchymal transition (EMT) in alveolar epithelial cells (AEC) in vitro and in vivo, together with the demonstration of EMT in biopsies of idiopathic pulmonary fibrosis (IPF) patients, suggests a role for TGF-β1-induced EMT in disease pathogenesis. We investigated the effects of N-acetylcysteine (NAC) on TGF-β1-induced EMT in a rat epithelial cell line (RLE-6TN) and in primary rat alveolar epithelial cells (AEC). RLE-6TN cells exposed to TGF-β1 for 5 days underwent EMT as evidenced by acquisition of a fibroblast-like morphology, downregulation of the epithelial-specific protein zonula occludens-1, and induction of the mesenchymal-specific proteins α-smooth muscle actin (α-SMA) and vimentin. These changes were inhibited by NAC, which also prevented Smad3 phosphorylation. Similarly, primary alveolar epithelial type II cells exposed to TGF-β1 also underwent EMT that was prevented by NAC. TGF-β1 decreased cellular GSH levels by 50–80%, whereas NAC restored them to ∼150% of those found in TGF-β1-treated cells. Treatment with glutathione monoethyl ester similarly prevented an increase in mesenchymal marker expression. Consistent with its role as an antioxidant and cellular redox stabilizer, NAC dramatically reduced intracellular reactive oxygen species production in the presence of TGF-β1. Finally, inhibition of intracellular ROS generation during TGF-β1 treatment prevented alveolar EMT, but treatment with H2O2 alone did not induce EMT. We conclude that NAC prevents EMT in AEC in vitro, at least in part through replenishment of intracellular GSH stores and limitation of TGF-β1-induced intracellular ROS generation. We speculate that beneficial effects of NAC on pulmonary function in IPF may be mediated by inhibitory effects on alveolar EMT.

Nitric oxide attenuates epithelial-mesenchymal transition in alveolar epithelial cells

2007 ◽  
Vol 293 (1) ◽  
pp. L212-L221 ◽  
Author(s):  
Shilpa Vyas-Read ◽  
Philip W. Shaul ◽  
Ivan S. Yuhanna ◽  
Brigham C. Willis
Keyword(s):  
Nitric Oxide ◽  
Nitric Oxide Synthase ◽  
Epithelial Cells ◽  
Epithelial Mesenchymal Transition ◽  
Alveolar Epithelial Cells ◽  
No Production ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Oxide Synthase ◽  
Tgf Β1

Patients with interstitial lung diseases, such as idiopathic pulmonary fibrosis (IPF) and bronchopulmonary dysplasia (BPD), suffer from lung fibrosis secondary to myofibroblast-mediated excessive ECM deposition and destruction of lung architecture. Transforming growth factor (TGF)-β1 induces epithelial-mesenchymal transition (EMT) of alveolar epithelial cells (AEC) to myofibroblasts both in vitro and in vivo. Inhaled nitric oxide (NO) attenuates ECM accumulation, enhances lung growth, and decreases alveolar myofibroblast number in experimental models. We therefore hypothesized that NO attenuates TGF-β1-induced EMT in cultured AEC. Studies of the capacity for endogenous NO production in AEC revealed that endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS) are expressed and active in AEC. Total NOS activity was 1.3 pmol·mg protein−1·min−1 with 67% derived from eNOS. TGF-β1 (50 pM) suppressed eNOS expression by more than 60% and activity by 83% but did not affect iNOS expression or activity. Inhibition of endogenous NOS with l-NAME led to spontaneous EMT, manifested by increased α-smooth muscle actin (α-SMA) expression and a fibroblast-like morphology. Provision of exogenous NO to TGF-β1-treated AEC decreased stress fiber-associated α-SMA expression and decreased collagen I expression by 80%. NO-treated AEC also retained an epithelial morphology and expressed increased lamellar protein, E-cadherin, and pro-surfactant protein B compared with those treated with TGF-β alone. These findings indicate that NO serves a critical role in preserving an epithelial phenotype and in attenuating EMT in AEC. NO-mediated regulation of AEC fate may have important implications in the pathophysiology and treatment of diseases such as IPF and BPD.

scholarly journals Radiation Induces Pulmonary Fibrosis by Promoting the Fibrogenic Differentiation of Alveolar Stem Cells

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Lu-Kai Wang ◽  
Tsai-Jung Wu ◽  
Ji-Hong Hong ◽  
Fang-Hsin Chen ◽  
John Yu ◽  
...  
Keyword(s):  
Stem Cells ◽  
Epithelial Cells ◽  
Epithelial Mesenchymal Transition ◽  
Tissue Growth ◽  
Alveolar Epithelial Cells ◽  
Type I ◽  
Alveolar Cells ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Radiation Induced

The lung is a radiosensitive organ, which imposes limits on the therapeutic dose in thoracic radiotherapy. Irradiated alveolar epithelial cells promote radiation-related pneumonitis and fibrosis. However, the role of lung stem cells (LSCs) in the development of radiation-induced lung injury is still unclear. In this study, we found that both LSCs and LSC-derived type II alveolar epithelial cells (AECII) can repair radiation-induced DNA double-strand breaks, but the irradiated LSCs underwent growth arrest and cell differentiation faster than the irradiated AECII cells. Moreover, radiation drove LSCs to fibrosis as shown with the elevated levels of markers for epithelial-mesenchymal transition and myofibroblast (α-smooth muscle actin (α-SMA)) differentiation in in vitro and ex vivo studies. Increased gene expressions of connective tissue growth factor and α-SMA were found in both irradiated LSCs and alveolar cells, suggesting that radiation could induce the fibrogenic differentiation of LSCs. Irradiated LSCs showed an increase in the expression of surfactant protein C (SP-C), the AECII cell marker, and α-SMA, and irradiated AECII cells expressed SP-C and α-SMA. These results indicated that radiation induced LSCs to differentiate into myofibroblasts and AECII cells; then, AECII cells differentiated further into either myofibroblasts or type I alveolar epithelial cells (AECI). In conclusion, our results revealed that LSCs are sensitive to radiation-induced cell damage and may be involved in radiation-induced lung fibrosis.

scholarly journals Atractylodin Suppresses TGF-β-Mediated Epithelial-Mesenchymal Transition in Alveolar Epithelial Cells and Attenuates Bleomycin-Induced Pulmonary Fibrosis in Mice

2021 ◽  
Vol 22 (20) ◽  
pp. 11152
Author(s):  
Kai-Wei Chang ◽  
Xiang Zhang ◽  
Shih-Chao Lin ◽  
Yu-Chao Lin ◽  
Chia-Hsiang Li ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Pulmonary Fibrosis ◽  
Lung Injury ◽  
Epithelial Mesenchymal Transition ◽  
A549 Cells ◽  
Alveolar Epithelial Cells ◽  
Collagen Deposition ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Tgf Β1

Idiopathic pulmonary fibrosis (IPF) is characterized by fibrotic change in alveolar epithelial cells and leads to the irreversible deterioration of pulmonary function. Transforming growth factor-beta 1 (TGF-β1)-induced epithelial-mesenchymal transition (EMT) in type 2 lung epithelial cells contributes to excessive collagen deposition and plays an important role in IPF. Atractylodin (ATL) is a kind of herbal medicine that has been proven to protect intestinal inflammation and attenuate acute lung injury. Our study aimed to determine whether EMT played a crucial role in the pathogenesis of pulmonary fibrosis and whether EMT can be utilized as a therapeutic target by ATL treatment to mitigate IPF. To address this topic, we took two steps to investigate: 1. Utilization of anin vitro EMT model by treating alveolar epithelial cells (A549 cells) with TGF-β1 followed by ATL treatment for elucidating the underlying pathways, including Smad2/3 hyperphosphorylation, mitogen-activated protein kinase (MAPK) pathway overexpression, Snail and Slug upregulation, and loss of E-cadherin. Utilization of an in vivo lung injury model by treating bleomycin on mice followed by ATL treatment to demonstrate the therapeutic effectiveness, such as, less collagen deposition and lower E-cadherin expression. In conclusion, ATL attenuates TGF-β1-induced EMT in A549 cells and bleomycin-induced pulmonary fibrosis in mice.

scholarly journals The effect of TGF-β1 and Smad7 gene transfer on the phenotypic changes of rat alveolar epithelial cells

2007 ◽  
Vol 12 (3) ◽  
Author(s):  
Guo-Ping Xu ◽  
Qing-Quan Li ◽  
Xi-Xi Cao ◽  
Qi Chen ◽  
Zhong-Hua Zhao ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Epithelial Cells ◽  
Transforming Growth Factor ◽  
Alveolar Epithelial Cells ◽  
Ultrastructural Changes ◽  
Type Ii ◽  
Mesenchymal Transition ◽  
Alveolar Epithelial ◽  
Tgf Β1

AbstractThe aim of this study was to investigate whether transforming growth factor-β1 (TGF-β1) could induce alveolar epithelial-mesenchymal transition (EMT) in vitro, and whether Smad7 gene transfer could block this transition. We also aimed to elucidate the possible mechanisms of these processes. The Smad7 gene was transfected to the rat type II alveolar epithelial cell line (RLE-6TN). Expression of the EMT-associated markers was assayed by Western Blot and Real-time PCR. Morphological alterations were examined via phase-contrast microscope and fluorescence microscope, while ultrastructural changes were examined via electron microscope. TGF-β1 treatment induced a fibrotic phenotype of RLE-6TN with increased expression of fibronectin (FN), α-smooth muscle actin (α-SMA) and vimentin, and decreased expression of E-cadherin (E-cad) and cytokeratin19 (CK19). After transfecting the RLE-6TN with the Smad7 gene, the expression of the mesenchymal markers was downregulated while that of the epithelial markers was upregulated. TGF-β1 treatment for 48 h resulted in the separation of RLE-6TN from one another and a change into elongated, myofibroblast-like cells. After the RLE-6TN had been transfected with the Smad7 gene, TGF-β1 treatment had no effect on the morphology of the RLE-6TN. TGF-β1 treatment for 48 h resulted in an abundant expression of α-SMA in the RLE-6TN. If the RLE-6TN were transfected with the Smad7 gene, TGF-β1 treatment for 48 h could only induce a low level of α-SMA expression. Furthermore, TGF-β1 treatment for 12 h resulted in the degeneration and swelling of the osmiophilic multilamellar bodies, which were the markers of type II alveolar epithelial cells. TGF-β1 can induce alveolar epithelialmesenchymal transition in vitro, which is dependent on the Smads signaling pathway to a certain extent. Overexpression of the Smad7 gene can partially block this process

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