Proteomic Analysis of Plasma-Derived Extracellular Vesicles in Smokers and Patients with Chronic Obstructive Pulmonary Disease

Circulating biomarkers using targeted approaches from human plasma-derived extracellular vesicles (EVs) in the pathobiology of chronic obstructive pulmonary disease (COPD) are an emerging tool. There are several challenges in the field of EV proteomics. We used different EV isolation methods (ExoQuick and Exo-Spin) for purification of human plasma-derived EVs from nonsmokers, smokers, and patients with COPD. Furthermore, characterization of plasma-derived EVs was performed based on their size, particle concentrations, surface markers, and acetylcholinesterase activity. Additionally, we performed label-free MS analysis of plasma-derived EVs isolated by two different methods for comparison. We performed a thorough analysis of EV markers from the identified peptides and peptide-spectrum matches using the four main databases on EV biomolecules. We found several common EV markers enriched in our data set compared with top 100 plasma-derived EV markers from databases. Using a pairwise comparison, we identified several novel proteins such as CD5L, FN1, CLU, GSN, HABP2, APOD, and EFEMP1 differentially enriched in smokers and patients with COPD compared to nonsmokers. This pilot study demonstrates the importance of EV isolation and characterization from plasma. Thus, it facilitates the identification of novel circulating EV biomarkers as a tool for prognostics, diagnostics, and therapeutics of chronic inflammatory lung diseases.