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. This 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 a 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). 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.

Identification of Radiation-Dose-Dependent Expressive Genes in Individuals Exposed to External Ionizing Radiation.

For victims of radiological accidents, rapid dose estimation and damage prediction are essential. Administering the gold-standard biodosimetry chromosome aberration assay requires highly skilled individuals and several days of labor; consequently, rapid turnaround is an important concern. Identification of new dose estimation markers and damage-predicting in vivo molecules to replace the chromosome aberration assay is crucial to improving the delivery time of medical treatment. Here, we investigated the applicability of mRNA levels using a mouse model. Female C57BL/6J mice were X-ray irradiated at various doses, and a DNA microarray was then performed to identify differentially expressed mRNAs in whole blood. The microarray analysis identified 14 radioresponsive mRNAs with more than fourfold differences by pattern matching in the expression at 24 h postirradiation. In particular, mRNA expression of Slfn4, Itgb5, Smim3, Tmem40, Litaf, Gp1bb and Cxx1c was significantly increased in a radiation-dose-dependent manner, as validated by reverse transcription quantitative polymerase chain reaction. We also performed an analysis using the cBioPortal for Cancer Genomics and found that the overall survival of ovarian adenocarcinoma patients with alterations in Smim3 and that of thymoma patients with alterations in Cxx1c had a worse prognosis than patients without these alterations. These findings suggest that the expression of several genes in whole blood was a sensitive and specific biomarker of radiation exposure and can be used as a rapid and reliable prospective molecular biomarker in radiological emergencies.

IKKß Inhibitor IMD-0354 Attenuates Radiation Damage in Whole-body X-Irradiated Mice.

Nuclear factor-kappa B (NF-κB) transcription factor plays a critical role in regulating radiation-induced inflammatory and immune responses. Intracellular reactive oxygen species generation induces the activation of NF-κB via the inhibitor of κB (IκB) kinase (IKK) complex signaling. Previous studies have reported that the inhibition of IKK-driven NF-κB activation offers a therapeutic strategy for managing inflammatory disorders and various cancers, but it has additionally been reported that treatment targeting NF-κB also shows a radioprotective effect. IMD-0354 is an IKKß inhibitor that blocks IκBα phosphorylation in the NF-κB pathway. This compound is known to exert anti-inflammatory and antitumor effects, but its radioprotective effects are unclear. Therefore, in the present study, we examined whether or not IMD-0354 has a mitigative effect on radiation-induced damages in mice. IMD-0354 was dissolved in soybean oil and subcutaneously administered to C57BL/6J Jcl mice for 3 consecutive days after 7 Gy of whole-body X-irradiation. The survival rate on day 30 and the NF-κB p65 and IκBα in bone marrow and spleen cells based on flow cytometry were assessed. IMD-0354 administration significantly suppressed the lethality induced by whole-body X-irradiation, and the survival rate increased by 83%. The NF-κB p65 and IκBα in bone marrow and spleen cells were significantly lower in IMD-0354-treated mice than in irradiated mice, suggesting that the IKKß inhibitor IMD-0354 exerts a radiomitigative effect by suppressing the NF-κB.