Improved preparation of nasal lavage fluid (NLF) as a noninvasive sample for proteomic biomarker discovery

Nasal lavage fluid (NLF) becomes more and more important as a noninvasive patient sample serving as a new opportunity to discover new biomarkers in diverse human diseases comprising mainly respiratory disorders. This was supported by the observation that the protein profile of NLF differs from conventional samples of i.e. whole blood, hence being capable to complement or even expand the so far biomarker index. Since sample acquisition and processing are the most crucial steps for a profound and sensitive identification we present here a modified protocol of NLF generation and measurement. We show that mild washing steps for sample generation followed by column-mediated concentration and acetone precipitation are appropriate steps to minimize serum leakage by concomitantly highlighting proteins which represent typical components of NLF. This is shown by separation of proteins via 2D-PAGE followed by LC-MS/MS as well as Gel-LC-MS/MS measurements of cut and digested protein spots/bands.

Significance: For a better understanding of the molecular mechanisms underlying respiratory diseases NLF samples are favored sources for protein research. NLF acquisition and sample processing were impaired so far by the problem of blood serum leakage and high salt content. Here, we present a modified protocol of NLF generation leading to the display of typical inventory of NLF proteins combined with reduced salt and serum contaminants. By this, both assay reproducibility and the detection of up- or down-regulated proteins reliably can be discovered in the case of biomarker screenings in a disease versus control design. This article is part of a Special Issue entitled: Neuroproteomics: Applications in Neuroscience and Neurology.