title: Changes in airway hyperresponsiveness following smoking cessation: comparisons between Mch and AMP.
abstract: BACKGROUND
  Given the observed association between smoking, inflammation and airway hyperresponsiveness (AHR) one may predict that smoking cessation may improve AHR. However, only a few studies have investigated the effect of smoking on AHR and their results appear to be conflicting depending on the stimulus used in their bronchoprovocation protocol. The aim of the current study was to compare changes in AHR between direct (methacholine (Mch)) and indirect (adenosine 5'monophosphate (AMP)) stimuli before and at different time points after smoking cessation in smokers with allergic rhinitis (+/-asthma).
  
  
  METHODS
  We have prospectively studied changes in AHR to inhaled Mch and AMP in smokers with allergic rhinitis (+/-asthma), before and at 6 and 12 months after smoking cessation.
  
  
  RESULTS
  It was found that 28% (16/57) of the participants had quit smoking by the end of the study. No significant change in AHR was observed in smoking cessation failures. A significant improvement in AHR to AMP but not Mch was observed 6 months after smoking cessation in quitters; a 1.2 doubling concentrations change in PC20 AMP was measured whereas only a 0.4 doubling concentrations change was observed for PC20 Mch. However, after 12 months smoking cessation the improvement in AHR became significant for both AMP and Mch, their dose-response curves being displaced to the right to a similar extent (1.4 and 1.1 doubling concentrations for AMP and Mch, respectively).
  
  
  CONCLUSIONS
  Smoking cessation can improve AHR in smokers who quit with a 6 months improvement being reported for the airways response to AMP but not Mch. AMP challenge may detect earlier changes in AHR in smokers during smoking cessation.
authors.affiliation: Smoking Cessation Research Centre, Department of Internal and Specialistic Medicine, University of Catania, Ascoli-Tomaselli Hospitals, 95125 Catania, Italy.
authors.forename: Giovita
authors.initials: G
authors.lastname: Piccillo
authors.forename: Pasquale
authors.initials: P
authors.lastname: Caponnetto
authors.forename: Sheila
authors.initials: S
authors.lastname: Barton
authors.forename: Cristina
authors.initials: C
authors.lastname: Russo
authors.forename: Alfio
authors.initials: A
authors.lastname: Origlio
authors.forename: Agata
authors.initials: A
authors.lastname: Bonaccorsi
authors.forename: Annalisa
authors.initials: A
authors.lastname: Di Maria
authors.forename: Chiara
authors.initials: C
authors.lastname: Oliveri
authors.forename: Riccardo
authors.initials: R
authors.lastname: Polosa
mesh_terms: D000249:Adenosine Monophosphate; D000328:Adult; D016535:Bronchial Hyperreactivity / Q000503:physiopathology*; D001985:Bronchial Provocation Tests / Q000379:methods; D016085:Bronchoconstrictor Agents; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D008875:Middle Aged; D011446:Prospective Studies; D006255:Rhinitis, Allergic, Seasonal / Q000503:physiopathology*; D012907:Smoking / Q000503:physiopathology*; D016540:Smoking Cessation; D014797:Vital Capacity
chemical_list: D016085:Bronchoconstrictor Agents; D016210:Methacholine Chloride; D000249:Adenosine Monophosphate