Impaired nuclear factor erythroid 2-related factor 2 expression increases apoptosis of airway epithelial cells in patients with chronic obstructive pulmonary disease due to cigarette smoking.

Kazuhiro Yamada,Kanako Sato,Fumihiro Nagayasu,Yoshihiro Tochino,Kazuto Hirata,Naoko Yoshii,Tetsuya Watanabe,Yumiko Imahashi,Hiroshi Kanazawa,Naoki Ijiri,Kazuhisa Asai

doi:10.1186/s12890-016-0189-1

Abstract

BackgroundCigarette smoking-induced oxidative stress is known to be a key mechanism in COPD pathogenesis. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a central transcription factor that regulates the antioxidant defense system. The aim of this study was to compare Nrf2 expression in COPD subjects and control subjects, and to determine the role of Nrf2 in protecting against oxidative stress-induced apoptosis.MethodsWe enrolled 8 COPD subjects and 7 control subjects in this study. We performed bronchial brushing by bronchoscopy and obtained bronchial epithelial cells from the airways. Nrf2 expression in bronchial epithelial cells was evaluated by real-time PCR and Western blotting. We examined the effect of 10 or 15 % cigarette smoke extract (CSE) induced A549 cells apoptosis using a time-lapse cell imaging assay with caspase-3/7 activation detecting reagent and performed Terminal deoxynucleotidyltransferase-mediated dUTP nick end labelling assay for confirming A549 cells apoptosis. We also examined the effects of Nrf2 knockdown and, 0.1, 0.5, and 1.0 mM N-acetyl cysteine on CSE-induced apoptosis. Statistical analyses were performed using t-test, paired t-test or an analysis of variance followed by the Tukey-Kramer method.ResultsNrf2 mRNA expression in COPD subjects was significantly lower than that in control subjects and Nrf2 mRNA were negatively correlated with pack year. Nrf2 protein in COPD subjects was significantly lower than that in control subjects. CSE-induced A549 cells apoptosis was increased in a time-, concentration-dependent manner, and was significantly increased by Nrf2 knockdown. N-acetyl cysteine significantly ameliorated CSE-induced apoptosis.ConclusionsNrf2 expression was lower in COPD patients than in control subjects. Nrf2 might have a protective role against apoptosis caused by CSE-induced oxidative stress. These results suggest an involvement of Nrf2 in COPD and administration of antioxidants to patients with COPD might be a basic therapeutic option.

Highlights

Cigarette smoking-induced oxidative stress is known to be a key mechanism in Chronic obstructive pulmonary disease (COPD) pathogenesis
We examined the effect of antioxidants and Nuclear factor erythroid 2-related factor 2 (Nrf2) expression on cigarette smoke extract (CSE)-induced apoptosis in vitro
In the present study, we demonstrated that Nrf2 expression in bronchial epithelial cells in COPD subjects was significantly lower than that in control subjects

Summary

Introduction

Cigarette smoking-induced oxidative stress is known to be a key mechanism in COPD pathogenesis. Pathological changes in COPD include changes in the central or distal airways The former is considered chronic bronchitis, and this disease is accompanied by an influx of inflammatory cells in the mucosa and airway remodeling, such as epithelial metaplasia and mucus hypersecretion due to hyperplasia of subepithelial mucus glands or goblet cells. The latter is considered emphysema, and alveolar wall destruction and disrupted alveolar attachments to small airway walls are seen with this condition. ROS can cause oxidative stress and play a major role in cell apoptosis through injury induced by cigarette smoke [3]. Excessive loss of alveolar epithelial cells and endothelial cells by apoptosis has been postulated to lead to the destruction of lung tissue and emphysema

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