• Linling Cheng, Jun Liu, Bing Li, Shengming Liu, Xianyan Li, and Hongbin Tu.
• The State Key Laboratory of Respiratory Disease, National Clinical Center for Respiratory Diseases, Guangzhou Institute of Respiratory Disease, The First Affiliated Hospital, Guangzhou Medical University, Guangzhou, Guangdong, China.
• Chest. 2016 Feb 1; 149 (2): 474-82.

BackgroundCigarette smoking is a major environmental contributor to COPD, but understanding its epigenetic regulation of oxidative genes involved in the pathogenesis of COPD remains elusive.MethodsWe analyzed DNA methylation on glutamate-cysteine ligase catalytic subunit (GCLC), glutathione S-transferase M1 (GSTM1), glutathione S-transferase P1 (GSTP1), and superoxide dismutase 3 (SOD3) promoters in clinical samples from patients with COPD (current-smoker [CS-COPD]; ex-smoker [ES-COPD]) and subjects with normal pulmonary function (current-smoker [CS-NS]; ex-smoker [ES-NS]; never-smoker [NC]). Expression of GCLC messenger RNA (mRNA) and glutathione (GSH) synthesis in these clinical samples and human bronchial epithelial (BEAS-2B) cells stimulated by cigarette-smoke extract (CSE) was evaluated. GCLC mRNA and protein levels were measured to determine effects of demethylation and deacetylation agents on CSE-treated BEAS-2B cells.ResultsThe DNA methylation level of the GCLC promoter was significantly increased in CS-COPD, CS-NS, and ES-COPD groups compared with ES-NS and NC groups. However, there were no significant differences in DNA methylation values of GSTM1, GSTP1, and SOD3 promoters among these groups. Expression of GCLC mRNA was downregulated in the lungs, and GSH levels decreased in plasma as a consequence of hypermethylation of the GCLC promoter. Similarly, CSE-treated BEAS-2B cells had hypermethylation of the GCLC gene, mRNA downregulation, and a decreased intracellular GSH level. GCLC expression in CSE-treated BEAS-2B cells was restored by the methylation inhibitor, 5-aza-2'-deoxycytidine, but not by the deacetylation agent, trichostatin A.ConclusionsCigarette smoke-induced hypermethylation of the GCLC promoter is related to the initiation and progression of COPD. Our finding may provide a new strategy for COPD intervention by developing demethylation agents targeting GCLC hypermethylation.Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

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