Regulation of Antioxidant Stress-Responsive Transcription Factor Nrf2 Target Gene in the Reduction of Radiation Damage by the Thrombocytopenia Drug Romiplostim

Abstract

Ionizing radiation induces severe oxidative stress, resulting in individual death by acute radiation syndrome. The nuclear factor-erythroid-2-related factor 2 (Nrf2) plays an important role in the antioxidant response pathway. Recently, romiplostim (RP), an idiopathic thrombocytopenic purpura therapeutic drug, was reported to completely rescue mice exposed to lethal total-body irradiation (TBI). However, the details underlying the mechanism for reducing radiation damage remain largely unknown. To elucidate the involvement of the master redox regulator Nrf2 in the radio-mitigative efficacy of RP on TBI-induced oxidative stress, expression of Nrf2 target genes in hematopoietic tissues such as bone marrow, spleen, and lung from mice treated with RP for three consecutive days after 7 Gy of X-ray TBI was analyzed. RP promoted the recovery of bone marrow cells from day 10 and the significant up-regulation of reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) dehydrogenase quinone 1 (Nqo1), glutamate-cysteine ligase catalytic subunit (Gclc) and glutamate-cysteine ligase modifier subunit (Gclm) was observed compared to the TBI mice. RP also promoted the recovery of splenic cells on day 18, and the significant up-regulation of Nqo1, Gclc and Gclm in spleen both on day 10 and 18 and Nqo1 and Gclm in lung on day 10 was observed compared to the TBI mice. The present study suggests that the radio-mitigative effects of RP indicates on the activation of Nrf2 target genes involved in redox regulation and the antioxidative function, especially Nqo1, Gclc and Gclm. It is indicating the importance of these genes in the maintenance of biological homeostasis in response to radiation-induced oxidative stress. Key words accute radiation syndrome; romiplostim; radio-mitigative effect; nuclear factor-erythroid-2-related factor 2 (Nrf2) target gene; reduced nicotinamide adenine dinucleotide phosphate dehydrogenase quinone 1 (Nqo1); glutamate-cysteine ligase modifier subunit (Gclm)

An Analysis of the Serum Metabolomic Profile for the Radiomitigative Effect of the Thrombopoietin Receptor Agonist Romiplostim in Lethally Whole-Body-Irradiated Mice

“…Our previous studies showed that the RP completely rescued mice exposed to lethal total-body irradiation (TBI), suggesting that RP may not only promote hematopoiesis in various organs in irradiated individuals but also mitigate the dysfunction or regenerate the original function in multiple organs [13]. Previous studies have reported the following mechanisms by which RP exerts its radiation-mitigating effects on individuals exposed to radiation: restoration of the cell count in hematopoietic tissues, such as bone marrow and spleen; enhancement of DNA double-strand break repair and inhibition of apoptosis in hematopoietic cells [13]; and regulation of the expression of defense genes by the Nrf2-Keap1 system to regulate the expression of defense genes [14]. Although the function of RP in acute radiation injury is clear, the detailed mechanisms underlying how RP rescues mice exposed to lethal doses of radiation are still unknown.…”

Mutant p53 protects triple-negative breast adenocarcinomas from ferroptosis in vivo

“…These two enzymes share many similarities with GPX4, such as their use of glutathione as a cofactor, their peroxidase activity toward lipids, and their ability to inhibit ferroptosis. Previous studies indicate that knockdown of intracellular Prdx6 in multiple tumor cell lines enhances lipid peroxidation and erastin- or RSL3-induced ferroptosis ( 23 , 26 – 28 ).…”

The Acute Radiation Syndrome-Mitigator Romiplostim and Secreted Extracellular Vesicles Improved Survival in Mice Acutely Exposed to Myelosuppressive Doses of Ionizing Radiation

“…The thrombopoietin receptor agonist RP (Romiplate ® , Kyowa Kirin, Tokyo, Japan), as an ARS mitigator, was intraperitoneally administered once daily for 3 consecutive days to irradiated mice, starting immediately after TBI (within 2 h, 24 h, and 48 h post-TBI). The applied dose of RP was 50 µg/kg of body weight/day prepared with Normal Saline Solution (NSS; Otsuka Pharmaceutical, Tokyo, Japan) as the vehicle [13][14][15][16][17][18]. In addition to mice that received both TBI and RP (TBI + RP group), mice treated with TBI and NSS (TBI + NSS group), mice treated with RP only (0 Gy + RP group), and those treated with NSS only (0 Gy + NSS group) were prepared in this study.…”

“…The thrombopoietin receptor agonist RP was recently approved by the FDA to improve survival in patients acutely exposed to myelosuppressive doses of radiation [11][12][13][14][15][16][17][18]. To confirm the radio-mitigative and life-saving effects of RP in our mouse model of severe ARS caused by lethal TBI, we monitored the changes in body weight and the level of animal survival over a period of 30 days (Figure 1A).…”

“…Among these efforts, studies sponsored by the National Institute of Allergy and Infectious Diseases demonstrated that the administration of Nplate from Amgen (Romiplostim; RP), originally licensed in 2008 for the treatment of immune thrombocytopenia, increased platelet counts and improved survival in preclinical models of lethal radiation exposure [11,12]. We are also the first in the world to report the efficacy of RP as an ARS mitigator, and we have obtained many findings (e.g., enhanced DNA damage repair and antioxidant stress-responsive transcriptional factor, increased megakaryocyte hematopoiesis and mesenchymal stromal/stem cells (MSCs) in mouse hematopoietic tissues, and the suppression of vascular endothelial damage), in addition to dramatically improved survival rate of lethal total-body ionizing radiation (TBI)-exposed mice [13][14][15][16][17][18]. Although it was recently approved by the FDA as a medical countermeasure against radiation for hematopoietic ARS based on a series of successful, experimental, animal-based drug efficacy studies conducted under the Animal Rule, the detailed action mechanism of the radio-mitigative and life-saving effects of RP, which has a blood half-life of only several tens of hours, remains unclear.…”