Proteomic Analysis of Human Bronchoalveolar Lavage Fluid after Subsgemental Exposure

The analysis of airway fluid, as
sampled by bronchoalveolar lavage
(BAL), provides a minimally invasive route to interrogate lung biology
in health and disease. Here, we used immunodepletion, coupled with
gel- and label-free LC–MS/MS, for quantitation of the BAL fluid
(BALF) proteome in samples recovered from human subjects following
bronchoscopic instillation of saline, lipopolysaccharide (LPS) or
house dust mite antigen into three distinct lung subsegments. Among
more than 200 unique proteins quantified across nine samples, neutrophil
granule-derived and acute phase proteins were most highly enriched
in the LPS-exposed lobes. Of these, peptidoglycan response protein
1 was validated and confirmed as a novel marker of neutrophilic inflammation.
Compared to a prior transcriptomic analysis of airway cells in this
same cohort, the BALF proteome revealed a novel set of response factors.
Independent of exposure, the enrichment of tracheal-expressed proteins
in right lower lung lobes suggests a potential for constitutive intralobar
variability in the BALF proteome; sampling of multiple lung subsegments
also appears to aid in the identification of protein signatures that
differentiate individuals at baseline. Collectively, this proof-of-concept
study validates a robust workflow for BALF proteomics and demonstrates
the complementary nature of proteomic and genomic techniques for investigating
airway (patho)­physiology.