Protein profiling detection in serum of silica-exposed population by liquid-chip time of flight mass spectrometry

Objective: To screen serum biomarkers of silica-exposed population for early diagnosis by liquid-chip time of flight mass spectrometry, and identify some associated functions of the markers. Methods: In addition to 30 healthy donors without silica-exposed history chosen as control, All the 85 subjects diagnosed as varied phase of silicosis according to national diagnostic standard (GBZ70-2002) of pneumonoconiosis without complications were recruited and taken blood to get serum. Short peptides purified by Dynabeads RPC18, were detected and their amino acid sequences determined using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF-MS). Effects of the identified peptides on Human embryonic lung fibroblasts (MRC-5) were tested using synthesized peptides. Results: A total of 5 peaks (P<0.01) were detected between healthy donors and silica-exposed population, in which the expressions of 5081 Da and 5066 Da are up-regulated while the expressions of 3954 Da, 2021 Da and 1777 Da are down-regulated. 2021 Da and 1777 Da peaks were selected for MALDI-TOF-TOF-MS, the amino acid sequences of the two peaks identified were both a fragment of complement C3 called complement C3f. The level of C3f was related to silicosis activity. The synthesized peptides of C3f inhibited proliferation of I, III collagen and TGF-β1 of MRC-5. Conclusion: This analysis in our study revealed C3f in serum of silica-exposed population may play an important position. Investigation of C3f may be a useful tool for the diagnosis and evaluation of disease activity in silicosis.