From Differential DNA Methylation in COPD to Mitochondria: Regulation of AHRR Expression Affects Airway Epithelial Response to Cigarette Smoke
Qing Chen,
Kingsley Okechukwu Nwozor,
Maarten van den Berge,
Dirk-Jan Slebos,
Alen Faiz,
Marnix R. Jonker,
H. Marike Boezen,
Irene H. Heijink,
Maaike de Vries
Affiliations
Qing Chen
University of Groningen, University Medical Center Groningen, Department of Pathology and Medical Biology, 9713 GZ Groningen, The Netherlands
Kingsley Okechukwu Nwozor
University of Groningen, University Medical Center Groningen, Department of Pathology and Medical Biology, 9713 GZ Groningen, The Netherlands
Maarten van den Berge
University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), 9713 GZ Groningen, The Netherlands
Dirk-Jan Slebos
University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), 9713 GZ Groningen, The Netherlands
Alen Faiz
University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), 9713 GZ Groningen, The Netherlands
Marnix R. Jonker
University of Groningen, University Medical Center Groningen, Department of Pathology and Medical Biology, 9713 GZ Groningen, The Netherlands
H. Marike Boezen
University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), 9713 GZ Groningen, The Netherlands
Irene H. Heijink
University of Groningen, University Medical Center Groningen, Department of Pathology and Medical Biology, 9713 GZ Groningen, The Netherlands
Maaike de Vries
University of Groningen, University Medical Center Groningen, Groningen Research Institute for Asthma and COPD (GRIAC), 9713 GZ Groningen, The Netherlands
Cigarette smoking causes hypomethylation of the gene Aryl Hydrocarbon Receptor Repressor (AHRR), which regulates detoxification and oxidative stress-responses. We investigated whether AHRR DNA methylation is related to chronic obstructive pulmonary disease (COPD) and studied its function in airway epithelial cells (AECs). The association with COPD was assessed in blood from never and current smokers with/without COPD, and in AECs from ex-smoking non-COPD controls and GOLD stage II-IV COPD patients cultured with/without cigarette smoke extract (CSE). The effect of CRISPR/Cas9-induced AHRR knockout on proliferation, CSE-induced mitochondrial membrane potential and apoptosis/necrosis in human bronchial epithelial 16HBE cells was studied. In blood, DNA methylation of AHRR at cg05575921 and cg21161138 was lower in smoking COPD subjects than smoking controls. In vitro, AHRR DNA methylation at these CpG-sites was lower in COPD-derived than control-derived AECs only upon CSE exposure. Upon AHRR knockout, we found a lower proliferation rate at baseline, stronger CSE-induced decrease in mitochondrial membrane potential, and higher CSE-induced late apoptosis/necroptosis. Together, our results show lower DNA methylation of AHRR upon smoking in COPD patients compared to non-COPD controls. Our data suggest that higher airway epithelial AHRR expression may lead to impaired cigarette smoke-induced mitochondrial dysfunction and apoptosis/necroptosis, potentially promoting unprogrammed/immunogenic cell death.
