Astragalin inhibits autophagy-associated airway epithelial fibrosis

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Abstract

Background

Fibrotic remodeling of airway and lung parenchymal compartments is attributed to pulmonary dysfunction with an involvement of reactive oxygen species (ROS) in chronic lung diseases such as idiopathic pulmonary fibrosis and asthma.

Methods

The in vitro study elucidated inhibitory effects of astragalin, kaempferol-3-O-glucoside from leaves of persimmon and green tea seeds, on oxidative stress-induced airway fibrosis. The in vivo study explored the demoting effects of astragalin on epithelial to mesenchymal transition in BALB/c mice sensitized with ovalbumin (OVA).

Results

The exposure of 20 μM H ₂O ₂ for 72 h accelerated E-cadherin loss and vimentin induction in airway epithelial BEAS-2B cells, which was reversed by non-toxic astragalin at 1–20 μM. Astragalin allayed the airway tissue levels of ROS and vimentin enhanced by OVA challenge. Collagen type 1 production increased in H ₂O ₂–exposed epithelial cells and collagen fiber deposition was observed in OVA-challenged mouse airways. This study further investigated that the oxidative stress-triggered autophagic regulation was responsible for inducing airway fibrosis. H ₂O ₂ highly enhanced the expression induction of the autophagy-related beclin-1 and light chains 3A/B (LC3A/B) within 4 h and astragalin blocked such induction by H ₂O ₂. This compound deterred the ROS-promoted autophagosome formation in BEAS-2B cells. Consistently, in OVA-sensitized mice the expression of beclin-1 and LC3A/B was highly induced, and oral administration of astragalin suppressed the autophagosome formation with inhibiting the induction of these proteins in OVA-challenged airway subepithelium. Induction of autophagy by spermidine influenced the epithelial induction of E-cadherin and vimentin that was blocked by treating astragalin.

Conclusion

These results demonstrate that astragalin can be effective in allaying ROS-promoted bronchial fibrosis through inhibiting autophagosome formation in airways.

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Most cited references 30

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Oxidative stress, redox signaling, and autophagy: cell death versus survival.

Juliana Navarro-Yepes, Michaela Burns, Annadurai Anandhan … (2014)

The molecular machinery regulating autophagy has started becoming elucidated, and a number of studies have undertaken the task to determine the role of autophagy in cell fate determination within the context of human disease progression. Oxidative stress and redox signaling are also largely involved in the etiology of human diseases, where both survival and cell death signaling cascades have been reported to be modulated by reactive oxygen species (ROS) and reactive nitrogen species (RNS).

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Role of NADPH oxidase/ROS in pro-inflammatory mediators-induced airway and pulmonary diseases.

I-Ta Lee, Chuen-Mao Yang (2012)

Reactive oxygen species (ROS) are products of normal cellular metabolism and are known to act as second messengers. Under physiological conditions, ROS participate in maintenance of cellular 'redox homeostasis' in order to protect cells against oxidative stress. In addition, regulation of redox state is important for cell activation, viability, proliferation, and organ function. However, overproduction of ROS, most frequently due to excessive stimulation of either reduced nicotinamide adenine dinucleotide phosphate (NADPH) by pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) or the mitochondrial electron transport chain and xanthine oxidase, results in oxidative stress. Oxidative stress is a deleterious process that leads to airway and lung damage and consequently to several respiratory inflammatory diseases/injuries, including acute respiratory distress syndrome (ARDS), asthma, cystic fibrosis (CF), and chronic obstructive pulmonary disease (COPD). Many of the known inflammatory target proteins, such as matrix metalloproteinase-9 (MMP-9), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), and cytosolic phospholipase A(2) (cPLA(2)), are associated with NADPH oxidase activation and ROS overproduction in response to pro-inflammatory mediators. Thus, oxidative stress regulates both key inflammatory signal transduction pathways and target proteins involved in airway and lung inflammation. In this review, we discuss mechanisms of NADPH oxidase/ROS in the expression of inflammatory target proteins involved in airway and lung diseases. Knowledge of the mechanisms of ROS regulation could lead to the pharmacological manipulation of antioxidants in airway and lung inflammation and injury. Copyright © 2012 Elsevier Inc. All rights reserved.

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Autophagy in Idiopathic Pulmonary Fibrosis

Avignat S Patel, LING LIN, Alexander J Geyer … (2012)

Background Autophagy is a basic cellular homeostatic process important to cell fate decisions under conditions of stress. Dysregulation of autophagy impacts numerous human diseases including cancer and chronic obstructive lung disease. This study investigates the role of autophagy in idiopathic pulmonary fibrosis. Methods Human lung tissues from patients with IPF were analyzed for autophagy markers and modulating proteins using western blotting, confocal microscopy and transmission electron microscopy. To study the effects of TGF-β1 on autophagy, human lung fibroblasts were monitored by fluorescence microscopy and western blotting. In vivo experiments were done using the bleomycin-induced fibrosis mouse model. Results Lung tissues from IPF patients demonstrate evidence of decreased autophagic activity as assessed by LC3, p62 protein expression and immunofluorescence, and numbers of autophagosomes. TGF-β1 inhibits autophagy in fibroblasts in vitro at least in part via activation of mTORC1; expression of TIGAR is also increased in response to TGF-β1. In the bleomycin model of pulmonary fibrosis, rapamycin treatment is antifibrotic, and rapamycin also decreases expression of á-smooth muscle actin and fibronectin by fibroblasts in vitro. Inhibition of key regulators of autophagy, LC3 and beclin-1, leads to the opposite effect on fibroblast expression of á-smooth muscle actin and fibronectin. Conclusion Autophagy is not induced in pulmonary fibrosis despite activation of pathways known to promote autophagy. Impairment of autophagy by TGF-β1 may represent a mechanism for the promotion of fibrogenesis in IPF.

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Author and article information

Contributors

In-Hee Cho: cih@hallym.ac.kr

Yean-Jung Choi: yeanjungchoi@gmail.com

Ju-Hyun Gong: gongjh@hallym.ac.kr

Daekeun Shin: aceflavor@hotmail.com

Min-Kyung Kang: mitholy@hallym.ac.kr

Young-Hee Kang: yhkang@hallym.ac.kr

Journal

Journal ID (nlm-ta): Respir Res

Title: Respiratory Research

Publisher: BioMed Central (London )

ISSN (Print): 1465-9921

ISSN (Electronic): 1465-993X

Publication date (Electronic): 21 April 2015

Publication date PMC-release: 21 April 2015

Publication date (Print): 2015

Volume: 16

Issue: 1

Electronic Location Identifier: 51

Affiliations

Department of Food and Nutrition, Hallym University, Chuncheon, Kangwon-do 200-702 Korea

Article

Publisher ID: 211

DOI: 10.1186/s12931-015-0211-9

PMC ID: 4406173

PubMed ID: 25895672

SO-VID: bf4776ca-2561-4346-bb25-82a1f0958815

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

History

Date received : 5 December 2014

Date accepted : 10 April 2015

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ScienceOpen disciplines: Respiratory medicine

Keywords: astragalin,autophagy,epithelial to mesenchymal transition,oxidative stress,pulmonary fibrosis

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ScienceOpen disciplines: Respiratory medicine

Keywords: astragalin, autophagy, epithelial to mesenchymal transition, oxidative stress, pulmonary fibrosis

Astragalin inhibits autophagy-associated airway epithelial fibrosis

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Abstract

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Most cited references 30

Oxidative stress, redox signaling, and autophagy: cell death versus survival.

Role of NADPH oxidase/ROS in pro-inflammatory mediators-induced airway and pulmonary diseases.

Autophagy in Idiopathic Pulmonary Fibrosis

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