Proteomic changes by radio-mitigative thrombopoietin receptor agonist Romiplostim in the blood of mice exposed to lethal total-body irradiation.

Purpose: The thrombopoietin receptor agonist romiplostim (RP) is a therapeutic agent for immune thrombocytopenia that can achieve complete survival in mice exposed to a lethal dose of ionizing radiation. The estimated mechanism of the radio-protective/mitigative effects of RP has been proposed; however, the detailed mechanism of action remains unclear. The present study aimed to elucidate the mechanism of the radio-protective/mitigative effects of RP, the fluctuation of protein in the blood was analyzed by proteomics. Materials and Methods: Eight-week-old female C57BL/6J mice were randomly divided into 5 groups; control at day 0, total-body irradiation (TBI) groups at day 10 and day 18, and TBI plus RP groups at day 10 and day18, consisting of 3 mice per group, and subjected to TBI with 7 Gy of 137Cs γ-rays at dose rate of 0.74 Gy/min. RP was administered intraperitoneally to mice at a dose of 50 µg/kg once daily for 3 days starting 2 hours after TBI. On day 10 and day 18 after TBI, serum collected from each mouse was analyzed by liquid chromatography tandem mass spectrometry. Results: Nine proteins were identified by proteomics methods from 269 analyzed proteins detected in mice exposed to a lethal dose of TBI: keratin, type II cytoskeletal 1 (KRT1), fructose-1, 6-bisphosphatase (FBP1), cytosolic 10-formyltetrahydrofolate dehydrogenase (ALDH1L1), peptidyl-prolyl cis-trans isomerase A (PPIA), glycine N-methyltransferase (GNMT), glutathione S-transferase Mu 1 (GSTM1), regucalcin (RGN), fructose-bisphosphate aldolase B (ALDOB) and betain-homocysteine S-methyltransferase 1 (BHMT). On the 10th day after TBI, KRT1 was significantly increased (P < 0.05) by 4.26-fold compared to the control group in the TBI group and significantly inhibited in the TBI plus RP group (P < 0.05) (Fig. 3A, Table 5). Similarly, the expression levels of other 8 proteins detected at 18th day after TBI were significantly increased by 4.29 to 27.44-fold in the TBI group, but significantly decreased in the TBI plus RP group compared to the TBI group, respectively. Conclusion: Nine proteins were identified by proteomics methods from 269 analyzed proteins detected in mice exposed to a lethal dose of TBI. These proteins are also expected to be indicators of the damage induced by high-dose radiation.