Background: The aim of this study was to determine whether relative qualitative and quantitative differences in protein expression could be related to smoke exposure or smoke-induced airway inflammation. We therefore explored and characterized the protein components found in bronchoalveolar lavage (BAL) fluid sampled from either lifelong smokers or never-smokers.
Methods: BAL fluid samples obtained by bronchoscopy from 60-year-old healthy never-smokers (n = 18) and asymptomatic smokers (n = 30) were analyzed in either pooled or individual form. Initial global proteomic analysis used shotgun digestion approaches on unfractionated BAL fluid samples (after minimal sample preparation) and separation of peptides by gradient (90-min) liquid chromatography (LC) coupled with on-line linear ion trap quadropole mass spectrometry (LTQ MS) for identification and analysis.
Results: LTQ MS identified 481 high- to low-abundance proteins. Relative differences in patterns of BAL fluid proteins in smokers compared with never-smokers were observed in pooled and individual samples as well as by 2-dimensional gel analysis. Gene ontology categorization of all annotated proteins showed a wide spectrum of molecular functions and biological processes.
Conclusions: The described method provides comprehensive qualitative proteomic analysis of BAL fluid protein expression from never-smokers and from smokers at risk of developing chronic obstructive pulmonary disease. Many of the proteins identified had not been detected in previous studies of BAL fluid; thus, the use of LC-tandem MS with LTQ may provide new information regarding potentially important patterns of protein expression associated with lifelong smoking.