Cigarette Smoke-Induced Hypermethylation of the GCLC Gene Is Associated With COPD

Linling Cheng; Jun Liu; Bing Li; Shengming Liu; Xianyan Li; Hongbin Tu

doi:10.1378/chest.14-2309

Cigarette Smoke-Induced Hypermethylation of the GCLC Gene Is Associated With COPD

Chest. 2016 Feb;149(2):474-482. doi: 10.1378/chest.14-2309. Epub 2016 Jan 12.

Authors

Linling Cheng¹, Jun Liu¹, Bing Li², Shengming Liu³, Xianyan Li³, Hongbin Tu⁴

Affiliations

¹ 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.
² Research Center for Experimental Medicine, Guangzhou Medical University, Guangzhou, Guangdong, China.
³ Department of Respiratory Medicine, First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China.
⁴ 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; Research Center for Experimental Medicine, Guangzhou Medical University, Guangzhou, Guangdong, China. Electronic address: tuhongbin@mail.nih.gov.

PMID: 26087411
DOI: 10.1378/chest.14-2309

Abstract

Background: Cigarette smoking is a major environmental contributor to COPD, but understanding its epigenetic regulation of oxidative genes involved in the pathogenesis of COPD remains elusive.

Methods: We 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.

Results: The 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.

Conclusions: Cigarette 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.

Keywords: COPD; antioxidants; smoking.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Biopsy
Blotting, Western
Cell Line
DNA Methylation / drug effects*
Female
Gene Expression Regulation
Glutamate-Cysteine Ligase / genetics*
Glutamate-Cysteine Ligase / metabolism
Humans
Lung / drug effects
Lung / metabolism
Lung / pathology
Male
Middle Aged
Oxidative Stress*
Pulmonary Disease, Chronic Obstructive / genetics*
Pulmonary Disease, Chronic Obstructive / metabolism
Pulmonary Disease, Chronic Obstructive / pathology
RNA / genetics*
Real-Time Polymerase Chain Reaction
Reverse Transcriptase Polymerase Chain Reaction
Smoking / adverse effects*
Smoking / genetics
Tobacco Smoke Pollution / adverse effects*

Substances

Tobacco Smoke Pollution
RNA
Glutamate-Cysteine Ligase