Human primary airway epithelial cells isolated from active smokers have epigenetically impaired antiviral responses.
Cigarette smoking (CS) is the main risk factor for the development of chronic obstructive pulmonary disease (COPD) and most COPD exacerbations are caused by respiratory infections including influenza. Influenza infections are more severe in smokers. The mechanism of the increased risk and severity of infections in smokers is likely multifactorial, but certainly includes changes in immunologic host defenses.



We investigated retinoic acid-inducible protein I (RIG-I) and interferon (IFN) induction by influenza A virus (IAV) in human bronchial epithelial cells (HBEC) isolated from smokers or nonsmokers. Subcultured HBEC cells were infected with A/Puerto Rico/8/1934 (PR8) IAV at an MOI of 1. After 24 h of infection, cells and supernatants were collected for qRT-PCR, immunoblot or ELISA to determine RIG-I, Toll-like receptor3 (TLR3) and IFN expression levels.



IAV exposure induced a vigorous IFN-β, IFN-λ 1 and IFN-λ 2/3 antiviral response in HBEC from nonsmokers and significant induction of RIG-I and TLR3. In cells from smokers, viral RIG-I and TLR3 mRNA induction was reduced 87 and 79 % compared to the response from nonsmokers. CS exposure history was associated with inhibition of viral induction of the IFN-β, IFN-λ1 and IFN-λ 2/3 mRNA response by 85, 96 and 95 %, respectively, from that seen in HBEC from nonsmokers. The demethylating agent 5-Aza-2-deoxycytidine reversed the immunosuppressive effects of CS exposure in HBEC since viral induction of all three IFNs was restored. IFN-β induction of RIG-I and TLR3 was also suppressed in the cells from smokers.



Our results suggest that active smoking reduces expression of antiviral cytokines in primary HBEC cells. This effect likely occurs via downregulation of RIG-I and TLR3 due to smoke-induced epigenetic modifications. Reduction in lung epithelial cell RIG-I and TLR3 responses may be a major mechanism contributing to the increased risk and severity of viral respiratory infections in smokers and to viral-mediated acute exacerbations of COPD.
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Wenxin
W
Wu
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Wei
W
Zhang
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
J Leland
JL
Booth
Cherokee Healthcare Services, Catoosa, OK, USA.
David C
DC
Hutchings
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Xiaoqiu
X
Wang
Civil Aerospace Medical Institute, Federal Aviation Administration, Oklahoma City, OK, USA.
Vicky L
VL
White
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Houssein
H
Youness
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
Cory D
CD
Cross
Center of Molecular and Translational Medicine, Georgia State University, Atlanta, GA, USA.
Ming-Hui
MH
Zou
Civil Aerospace Medical Institute, Federal Aviation Administration, Oklahoma City, OK, USA.
Dennis
D
Burian
Pulmonary and Critical Care Division, Department of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. jordan-metcalf@ouhsc.edu.|Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA. jordan-metcalf@ouhsc.edu.|Veterans Affairs Medical Center, Oklahoma City, OK, USA. jordan-metcalf@ouhsc.edu.
Jordan P
JP
Metcalf
D001980:Bronchi / Q000187:drug effects / Q000378:metabolism / Q000821:virology*; D002478:Cells, Cultured; D000071457:DEAD Box Protein 58 / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000187:drug effects; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000821:virology*; D054884:Host-Pathogen Interactions; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity*; D007251:Influenza, Human / Q000235:genetics* / Q000378:metabolism / Q000821:virology*; D016899:Interferon-beta / Q000235:genetics / Q000378:metabolism; D007372:Interferons / Q000235:genetics / Q000378:metabolism; D007378:Interleukins / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic; D012907:Smoking / Q000009:adverse effects / Q000235:genetics* / Q000378:metabolism; D013997:Time Factors; D051196:Toll-Like Receptor 3 / Q000235:genetics / Q000378:metabolism; D000095022:Interferon Lambda
D000071457:DEAD Box Protein 58; D015254:DNA Modification Methylases; D004791:Enzyme Inhibitors; D016899:Interferon-beta; D007372:Interferons; D007378:Interleukins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D051196:Toll-Like Receptor 3; C000624353:interferon-lambda, human; D000095022:Interferon Lambda; C495344:TLR3 protein, human; C452820:RIGI protein, human
COPD; HBEC; Human; Influenza; Innate immunity; Interferon; Lung; RIG-I; TLR3