CD14 and LBP as Novel Biomarkers for Sarcoidosis by Proteomics of Extracellular Vesicles

Abstract Sarcoidosis is an inflammatory granulomatous multi-organ disease of unknown cause. The granulomatous inflammation in sarcoidosis is driven by the interplay between T cells and macrophages. Extracellular vesicles (EVs) play important roles in intercellular communication. Isolated serum EVs from seven patients with sarcoidosis and five control subjects were subjected to non-targeted proteomics analysis. Then 2,292 proteins were detected; 42 proteins were upregulated in patients with sarcoidosis relative to control subjects, and 324 proteins were downregulated. The protein signature of EVs from patients with sarcoidosis reflected disease characteristics such as antigen presentation and immunological disease. Candidate biomarkers were further verified by targeted proteomics analysis in 46 patients and 10 control subjects. CD14 and lipopolysaccharide-binding protein (LBP) were validated by targeted proteomics analysis and upregulation of them was confirmed by immunoblotting. Their expression was also upregulated in macrophages of lung granulomatous lesions. Consistent with these findings, CD14 levels were increased in lipopolysaccharide-stimulated macrophages during multinucleation, concomitant with increased levels of CD14 and LBP in EVs. The area under the curve values of CD14 and LBP were 0.81 and 0.84, respectively. Thus CD14 and LBP in serum EVs, which are associated with granulomatous pathogenesis, can improve the diagnostic accuracy in patients with sarcoidosis.