Proteomic Analysis of Undiluted Lung Epithelial Lining Fluid

Abstract

Proteomics is increasingly leading to biomarker discovery in human disease. Epithelial lining fluid (ELF), until now only recovered indirectly, diluted in BAL fluid, is an attractive sample for lung disease proteomics. The direct recovery of undiluted ELF is now possible using a bronchoscopic microsampling (BMS) probe. In this preliminary study of anesthetized ventilated rabbits, we applied this probe to recover ELF and to analyze the resulting samples with the aim of determining their potential in lung disease biomarker discovery. In order to do so, a method was devised and evaluated in preliminary experiments both for nonbronchoscopic use of the probe and for recovering undiluted ELF from probe tips. To verify the proteomic potential of the sample, the recovered ELF was separated by one-dimensional polyacrylamide gel electrophoresis, and the resulting lane was cut into multiple fractions, each of which was digested and analyzed by liquid chromatography tandem mass spectrometry. The identified proteins were then searched against Medline for association with broad categories of lung disease. Nonbronchoscopic use of the probe allowed successful ELF sampling and the recovery of undiluted ELF from probe tips. Proteomic analysis showed that ELF contains many proteins that have already been reported as being associated with lung disease as well as proteins potentially correlated with lung disease. This preliminary study of undiluted ELF, as recovered by the BMS probe, shows that it may be an ideal sample for lung proteomics. The potential application of this sampling technique in various lung diseases will need to be confirmed by future studies.