title: Sputum and nasal lavage lung-specific biomarkers before and after smoking cessation.
abstract: BACKGROUND
  Little is known about the effect of smoking cessation on airway inflammation. Secretory Leukocyte Protease Inhibitor (SLPI), Clara Cell protein 16 (CC16), elafin and human defensin beta-2 (HBD-2) protect human airways against inflammation and oxidative stress. In this longitudinal study we aimed to investigate changes in sputum and nasal lavage SLPI, CC16, elafin and HBD-2 levels in healthy smokers after 6 and 12 months of smoking cessation.
  
  
  METHODS
  Induced sputum and nasal lavage was obtained from healthy current smokers (n = 76) before smoking cessation, after 6 months of smoking cessation (n = 29), after 1 year of smoking cessation (n = 22) and from 10 healthy never smokers. SLPI, CC16, elafin and HBD-2 levels were measured in sputum and nasal lavage supernatants by commercially available ELISA kits.
  
  
  RESULTS
  Sputum SLPI and CC-16 levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.005 and p = 0.08 respectively). SLPI and CC16 levels did not differ before and 6 months after smoking cessation (p = 0.118 and p = 0.543 respectively), neither before and 1 year after smoking cessation (p = 0.363 and p = 0.470 respectively). Nasal lavage SLPI was decreased 12 months after smoking cessation (p = 0.033). Nasal lavage elafin levels were increased in healthy smokers before smoking cessation versus never-smokers (p = 0.007), but there were no changes 6 months and 1 year after smoking cessation.
  
  
  CONCLUSIONS
  Only nasal lavage SLPI decrease after 1 year after smoking cessation. We may speculate that there is an ongoing inflammatory process stimulating the production of counter-regulating proteins in the airways of healthy ex-smokers.
authors.affiliation: Department of Thoracic Medicine, Faculty of Medicine, University of Crete, Crete, Greece. izolthi@gmail.com
authors.forename: Izolde
authors.initials: I
authors.lastname: Bouloukaki
authors.forename: Ioanna G
authors.initials: IG
authors.lastname: Tsiligianni
authors.forename: Maria
authors.initials: M
authors.lastname: Tsoumakidou
authors.forename: Ioanna
authors.initials: I
authors.lastname: Mitrouska
authors.forename: Emmanuel P
authors.initials: EP
authors.lastname: Prokopakis
authors.forename: Irene
authors.initials: I
authors.lastname: Mavroudi
authors.forename: Nikolaos M
authors.initials: NM
authors.lastname: Siafakas
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Tzanakis
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D016022:Case-Control Studies; D053492:Elafin / Q000378:metabolism*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D017817:Nasal Lavage Fluid; D053481:Secretory Leukocyte Peptidase Inhibitor / Q000378:metabolism*; D012907:Smoking / Q000378:metabolism*; D016540:Smoking Cessation; D013183:Sputum / Q000378:metabolism*; D013997:Time Factors; D014598:Uteroglobin / Q000378:metabolism*; D023083:beta-Defensins / Q000378:metabolism*
chemical_list: D015415:Biomarkers; C106641:DEFB4A protein, human; D053492:Elafin; C556389:SCGB1A1 protein, human; D053481:Secretory Leukocyte Peptidase Inhibitor; D023083:beta-Defensins; D014598:Uteroglobin