Unbalanced oxidant-induced DNA damage and repair in COPD: a link towards lung cancer
- Gaetano Caramori1,
- Ian M Adcock2,
- Paolo Casolari1,
- Kazuhiro Ito2,
- Elen Jazrawi2,
- Loukia Tsaprouni2,
- Gino Villetti3,
- Maurizio Civelli3,
- Chiara Carnini3,
- Kian Fan Chung2,
- Peter J Barnes2,
- Alberto Papi1
- 1Centro di Ricerca su Asma e BPCO University of Ferrara, Ferrara, Italy
- 2Airway Disease Section, Imperial College London, UK
- 3Department of Pharmacology, Chiesi Farmaceutici, Parma, Italy
- Correspondence to Gaetano Caramori, Centro di Ricerca su Asma e BPCO, University of Ferrara, Via Savonarola, 9, Ferrara 44100, Italy;
Contributors GC, PJB, KFC and AP contributed to the recruitment of the human subjects of the study. GV and CC prepared the animal model. GC, PC, KI, EJ, LT performed the experiments of molecular biology. They were all blinded on the clinical characterisation of the human subjects and on the experimental conditions of the animal model. IMA analysed and interpreted the clinical and experimental data. GC and AP obtained funding. GC and IAM drafted the manuscript which was critically revised for important intellectual contents by all other authors.
- Received 29 November 2010
- Accepted 24 February 2011
- Published Online First 2 April 2011
Background Chronic obstructive pulmonary disease (COPD) is characterised by oxidative stress and increased risk of lung carcinoma. Oxidative stress causes DNA damage which can be repaired by DNA-dependent protein kinase complex.
Objectives To investigate DNA damage/repair balance and DNA-dependent protein kinase complex in COPD lung and in an animal model of smoking-induced lung damage and to evaluate the effects of oxidative stress on Ku expression and function in human bronchial epithelial cells.
Methods Protein expression was quantified using immunohistochemistry and/or western blotting. DNA damage/repair was measured using colorimetric assays.
Results 8-OH-dG, a marker of oxidant-induced DNA damage, was statistically significantly increased in the peripheral lung of smokers (with and without COPD) compared with non-smokers, while the number of apurinic/apyrimidinic (AP) sites (DNA damage and repair) was increased in smokers compared with non-smokers (p=0.0012) and patients with COPD (p<0.0148). Nuclear expression of Ku86, but not of DNA-PKcs, phospho-DNA-PKcs, Ku70 or γ-H2AFX, was reduced in bronchiolar epithelial cells from patients with COPD compared with normal smokers and non-smokers (p<0.039). Loss of Ku86 expression was also observed in a smoking mouse model (p<0.012) and prevented by antioxidants. Oxidants reduced (p<0.0112) Ku86 expression in human bronchial epithelial cells and Ku86 knock down modified AP sites in response to oxidative stress.
Conclusions Ineffective DNA repair rather than strand breakage per se accounts for the reduced AP sites observed in COPD and this is correlated with a selective decrease of the expression of Ku86 in the bronchiolar epithelium. DNA damage/repair imbalance may contribute to increased risk of lung carcinoma in COPD.
Gaetano Caramori, Ian M Adcock, Peter J Barnes and Alberto Papi have contributed equally to this work.
Funding The study was supported by grants from Fondazione Carife (Ferrara, Italy; http://www.fondazionecarife.it/) and Associazione per la Ricerca e la Cura dell'Asma (ARCA, Padova, Italy) and the Wellcome Trust.
Competing interests None.
Ethics approval This study was conducted with the approval of the Ethics committees of the University Hospital of Ferrara and the Royal Brompton Hospital.
Provenance and peer review Not commissioned; externally peer reviewed.