Identification of the differentially expressed protein biomarkers in rat blood plasma in response to gamma irradiation.

Simple, rapid and high-throughput dose assessment is critical for clinical diagnosis, treatment and emergency intervention in a large-scale radiological accident. The goal of this study is to screen and identify new ionizing radiation-responsive protein biomarkers in rat plasma. Sprague-Dawley rats were exposed to single doses of 0, 1, 3, 5 Gy of Cobalt-60 γ-rays total body irradiation at a dose rate of 1 Gy/min. The tandem mass tag labeling (TMT) combined with liquid chromatography mass spectrometry (LC-MS/MS) approach was used to screen the differentially expressed proteins in rat plasma collected at 1, 3, 5 and 7 days post-irradiation. Bioinformatics analysis was conducted to explore the biological functions of these proteins. The expression levels of candidate radiation-sensitive protein biomarkers were confirmed using enzyme-linked immune-sorbent assay (ELISA). A total of 503 differentially expressed proteins were identified. Most of these proteins were implicated in immune response, phagocytosis and signal transduction following ionizing radiation. Five up-regulated proteins including alpha-2-macroglobulin (A2m), chromogranin-A (CHGA), glutathione pertidase 3 (GPX3), clusterin (Clu) and ceruloplasmin (Cp) were selected for ELISA analysis. It was found that the expression levels of A2m, CHGA and GPX3 protein were increased in a dose-dependent manner at 1, 3 and 5 days after irradiation. Proteomics analysis revealed radiation-induced differentially expressed proteins in rat plasma. Our results suggested that A2m, CHGA, GPX3 protein expressions alterations in rat plasma may have potential as biomarkers to evaluate radiation exposure.