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

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.

Decreased levels of irisin, a skeletal muscle cell-derived myokine, are related to emphysema associated with chronic obstructive pulmonary disease

“…CSE-induced apoptosis was significantly higher in the 15% CSE group than the control group at 12 hours, as observed in our previous study 14. In contrast, apoptosis was significantly lower in the groups pretreated with 30 or 60 ng/mL irisin than in the 15% CSE-only group (Figure 4B; P <0.05 and P <0.01, respectively).…”

“…Cells were then subjected to CSE-induced apoptosis analyses via a time-lapse cell-imaging assay using the IncuCyte Zoom system with CellPlayer 96-well kinetic caspase 3/7 reagent (Essen BioScience, Ann Arbor, MI, USA), as previously described 14. The apoptotic index was calculated according to the equation: $\text{Apoptotic index}=\frac{\text{Apoptotic cell number}}{\text{Total cell number}}$CSE was prepared as previously described 14. Cells were stimulated with 10% or 15% CSE diluted with cell-culture medium and pretreated with 15, 30, or 60 ng/mL irisin (ADI-908-307; Enzo Life Sciences, Farmingdale, NY, USA), referring to the irisin levels of controls and subjects with COPD in our previous study 7…”

Protective Effects of Hydrogen Sulfide Against Cigarette Smoke Exposure-Induced Placental Oxidative Damage by Alleviating Redox Imbalance via Nrf2 Pathway in Rats

“…Under physiological conditions, Nrf2 is bound to its natural inhibitor Kelch-like-ECH-associated protein 1 (Keap1) in the cytoplasm [25]. In the presence of oxidative or xenobiotic stimuli, Nrf2 dissociates from Keap1 and translocates into the nucleus, where it binds to the antioxidant response element, and initiates the transcription of anti-oxidative genes encoding the respective proteins such as SOD, CAT, GPx and heme oxygenase-1 [26]. Deficiency of Nrf2 was shown to exacerbate cerebral infarction and neurologic deficits in animal models [27,28].…”

Differential expression of heat shock proteins and activation of mitogen‐activated protein kinases in A549 alveolar epithelial cells exposed to cigarette smoke extract

“…() found that CSE interfered with the normal functions of mitochondria in A549 cells by inhibition of complex I and II activities in the electron transport chain and impairment of mitochondrial membrane potential, reducing the ability of mitochondria to synthesize ATP, which prevented apoptosis and caused necrosis. Contrary to these results, some other studies (Jiao, Ao, & Xiong, ; Ramage, Jones, & Whelan, ; Yamada et al., ) showed that CS provoked apoptotic cell death in A549 cells. An increase in CS‐induced apoptosis was related to the impairment of nuclear factor erythroid 2‐related factor (Nrf2), suggesting that an inappropriate antioxidant response and excessive apoptosis could result in lung tissue destruction and emphysema (Yamada et al., ).…”