Radiation research最新文献

Radiation chemical studies together with theoretical calculations have confirmed that 5-selenocyanato-2'-deoxyuridine (SeCNdU) and 5-trifluoromethanesulfonyl-2'-deoxyuridine (OTfdU) undergo dissociation induced by an excess electron attachment and established these nucleosides as potential radiosensitizers. Here, the sensitizing properties of SeCNdU and OTfdU at the cellular level have been verified to determine whether these analogs can effectively enhance ionizing radiation-induced cell death. The cytotoxicity and radiosensitizing activity of the tested compounds were examined in breast (MCF-7) and prostate (PC3) cancer cells. The viability of cells treated with the analogs was tested using the MTT assay. The clonogenic assay was used to quantify reproductive cell survival after treatment of the compounds with ionizing radiation. For preliminary investigation of the mechanisms of potential radiosensitization by the derivatives, cell cycle phase distribution and histone H2AX phosphorylation as a marker of DNA strand breaks were assessed using flow cytometry. The results show the radiosensitizing properties of SeCNdU on the MCF-7 line, with a dose enhancement factor of 1.6. The same derivative had no effect on the PC3 line. Radiosensitization was also associated with an increase in histone H2AX phosphorylation, which correlates with the number of DNA double breaks. This derivative also slightly influenced distribution of cells through the cell cycle. The OTfdU derivative showed no biological effect on either of the tested lines. In conclusion, SeCNdU treatment enhanced the radiosensitivity of breast cancer cells in a manner associated at least partially with double-strand break formation. OTfdU had no radiosensitizing effect against prostate and breast cancer lines.

Head and neck squamous cell carcinoma (HNSCC) resistance to radiotherapy has prompted a need to develop adaptive radiation therapy protocols to improve patient outcomes. This study investigates the hypothesis that lipid metabolism regulates cell cycle phase-specific radiation sensitivity of HNSCC cells. Previous studies have shown that HNSCC tumors with a higher proportion of G0/G1 phase cells (low proliferative index, LPI) are more resistant to radiation compared to HNSCC tumors with a higher proportion of S/G2 phase cells (high proliferative index, HPI). RNA-seq and bioinformatics identified lipid metabolism as the major intrinsic pathway that differs between HPI and LPI HNSCC cultures. mRNA and protein levels of G0/G1 Switch 2 gene (G0S2), regulator of quiescence and lipid metabolism, were upregulated in LPI compared to HPI HNSCC cultures. G0S2 negatively regulates adipose triglyceride lipase (ATGL), resulting in less lipolytic activity. siG0S2 treatment of LPI cultures recruited cells into the proliferative cycle and exacerbated radiation sensitivity. To override G0S2 action, we incubated LPI cultures with the fatty acid palmitate and examined cellular metabolic stress markers. Compared to controls, LPI cultures treated with palmitate showed increased reactive oxygen species levels, lipid peroxidation and oxygen consumption rate coupled with increased mitochondrial fission. Furthermore, using the fluorescent based cell cycle real-time imaging system, we showed that palmitate treatment sustained cell proliferation (higher S/G2) compared to controls (higher G1). Palmitate treatment resulted in significant sensitization to radiation treatment and enhanced the efficacy of poly (ADP-ribose) polymerase (PARP) inhibitors. In summary, we demonstrate that G0S2-dependent lipid metabolism regulates cell cycle phase-specific radiation sensitivity of HNSCC cells and identify G0S2 and free fatty acids as novel targets for radiation therapy.

Radiation-induced heart disease (RIHD) has become an unavoidable and challenging problem that greatly impacts the outcomes of patients with tumors undergoing radiotherapy. Many studies have shown the positive effects of tanshinone IIA on cardiac function; however, its exact role and the underlying mechanism in RIHD remain unclear. This study aimed to investigate the mechanism of RIHD and examine the protective effects of tanshinone IIA. We developed in vitro and in vivo models of RIHD and assessed the damage caused by X-ray radiation to mice hearts and H9c2 cells using echocardiography, myocardial enzyme analysis, histopathology, transmission electron microscopy, Western blotting, and immunohistochemistry, to thoroughly explore the therapeutic potential and mechanism of tanshinone IIA on radiation-induced heart injury. Based on the results from various experiments, we confirmed that X-rays can trigger an increase in brain natriuretic peptide (BNP), creatine kinase-MB (CK-MB), and lactate dehydrogenase (LDH) levels, along with myocardial tissue edema, nuclear dissolution, and mitochondrial damage in mice. H9c2 cell activity declined, LDH levels rose, and mitochondrial damage occurred. Similarly, there was an increase in calcium ion flow, expression of calcium-related proteins, and pyroptosis-related proteins. After treatment with tanshinone IIA, the damage to the mouse heart and myocardial cells was partially reversed, with reductions in calcium ion flow and the expression of calcium- and pyroptosis-related proteins. These findings suggest that tanshinone IIA alleviates myocardial injury in RIHD by restoring calcium homeostasis and inhibiting pyroptosis.

Individual differences in the effects of ionizing radiation on humans remain poorly understood. Although studies on atomic bomb survivors have demonstrated that the hemizygous glycophorin A (GPA) gene mutant fraction (GPA Mf) in erythrocytes increases significantly with increasing radiation dose, there are large individual differences in the GPA Mf. Persistent GPA mutations are believed to be derived from mutations in long-lived hematopoietic stem cells (HSCs), and genetic background related to DNA repair may contribute to individual differences in HSC mutational potential after radiation exposure. In this study, we investigated three single-nucleotide polymorphisms (SNPs) in ERCC5 that play an important role in nucleotide excision repair (NER) of DNA damage caused by radiation exposure and are involved in cancer susceptibility. We found that these SNPs affect the relationship between radiation exposure and GPA Mf in erythrocytes and identified a highly significant interaction between radiation dose and one SNP (rs751402), located 2 kb upstream of ERCC5 (P = 9.3 × 10-6). This suggests that the radiation dose response of GPA Mf is partly influenced by the genotype of ERCC5. Furthermore, the slope of the GPA Mf dose-response curve was significantly higher in the cancer group than in the cancer-free group among Hiroshima survivors whose rs751402 genotype was the major homozygote. These findings suggest that ERCC5 may play a crucial role in the individual differences observed in HSC somatic gene mutability, as well as in cancer susceptibility after radiation exposure.

The prostaglandin E2 (PGE2) analog 16, 16-dimethyl-PGE2 (dmPGE2) administered prior to lethal irradiation protects against mortality from the hematopoietic acute radiation syndrome (H-ARS) and the chronic delayed effects of acute radiation exposure (DEARE). DmPGE2 also enhances hematopoietic stem cells (HSC) survival and hematopoietic recovery when used as a radiomitigator for H-ARS, but with less efficacy than when used as a radioprotectant. DmPGE2 elicits dose-dependent transient locomotor depression in mice and is currently used at a near maximum tolerated dose (MTD), factors that may limit its widespread use as a medical countermeasure (MCM) for unwanted radiation exposure. To explore modalities to improve survival in radiomitigation and limit side effects in both radioprotection and radiomitigation, we sought to identify the minimum therapeutically effective dose (MTED) of dmPGE2 and related EP receptor agonists and analogs in our H-ARS and DEARE models developed in young adult C57BL/6J mice. Doses of dmPGE2 as low as 10 μg/mouse provided significant H-ARS radioprotection equivalent to 35 μg/mouse, with reduced locomotor effects. However, lower doses were less effective in mitigating hematopoietic DEARE, indicating dose-dependent long-term hematopoietic recovery. Co-stimulation of EP3 and EP4 receptors using selective agonists sulprostone (EP3) and rivenprost (EP4) showed similar radioprotective efficacy as dmPGE2, but with less locomotor effect. The PGE1 analog misoprostol also conferred robust H-ARS radioprotection with minor locomotor effect and accelerated hematopoietic recovery, presenting a cost-effective, FDA-approved alternative. Split-dose administration of dmPGE2 as a radiomitigator (20 μg/mouse at 24 and 36 h post-irradiation) significantly enhanced survival compared to a single 35 μg dose, with similar locomotor effects but shorter duration. In conclusion, our findings suggest that dose optimization and selective EP receptor targeting can enhance the therapeutic results of prostaglandin-based MCM for radiation injury while minimizing locomotor side effects, with misoprostol standing out as a candidate MCM for radioprotection and radiomitigation due to its efficacy, minor locomotor effect, stability, and existing approval status.

As countries face emerging conflicts and evaluate military strategies, the potential for nuclear-related accidents continues to rise, putting large populations of civilians at risk. As a result, the development of pharmaceuticals that can be administered prior to radiation exposure that protect from radiation-induced injury are of utmost importance. However, there are currently no prophylactic drugs that can be used to protect against radiation injury. One drug under advanced development, gamma-tocotrienol (GT3), has proved promising in terms of its antioxidant activity, accelerated hematopoietic recovery, and reduction of DNA damage in treated animals exposed to various doses of ionizing radiation. In this study, nonhuman primates (NHPs) were leveraged to investigate the protective effects of GT3 on proteomic profiles in conjunction with a supralethal dose (12 Gy) of either total-body irradiation (TBI) or partial-body irradiation (PBI), performed with 5% bone marrow sparing. Animals were treated with either GT3 or vehicle 24 h prior to irradiation, and blood samples were collected at various time points pre- and post-exposure to assess changes in serum proteomic profiles. Both PBI and TBI induced significant dysregulation to pathways related to extracellular matrix and organization, hemostasis, and immune response. Notably, administration of GT3 offered significant protection against radiation-induced damage by either partial- or total-body irradiation in these pathways. Overall, this study offers insight into the biochemical mechanisms of the drug, pathways and proteins adversely affected by radiation, and potential biomarkers that can be further investigated to accurately assess absorbed radiation doses in exposed populations.

The interaction of proton beams with matter produces secondary protons and high-LET ions through nuclear reactions, modifying the absorbed depth-dose profile and the beam's relative biological effectiveness (RBE). However, the separate contributions of primary and secondary particles have never been systematically quantitatively analyzed. To address this, we performed Monte Carlo transport simulations using the FLUKA code for proton beams at 25 different primary energies (10 MeV-20 GeV) in water, providing spectral information for each produced component. The biological effects of the resulting mixed field were evaluated using mixed radiation calculator (MiRaCal) developed at GSI, Darmstadt, Germany. MiRaCal integrates monochromatic RBE data from the local effect model (LEM IV) using the low-energy adaption (LEA) into a representative RBE value, accounting for all spectral components. The RBE was assessed for eight αγ/βγ ratios (1-20 Gy) to represent different cell sensitivities for all primary energies. We show that for low αγ/βγ ratios, a crossover energy exists above which secondary particles dominate the biological effect, despite their minor contribution to fluence and absorbed dose. We then demonstrate that 80-100 MeV protons exhibit minimal effectiveness. Additionally, we show that fragment-associated effects support the use of a global RBE of 1.1 for organs at risk that are not irradiated by the spread-out Bragg peak but lie in the entrance channel of the treatment fields. Furthermore, the enhanced RBE at high primary proton energies due to fragments is particularly relevant for space radiation protection, where protons with energies from < 1 MeV up to tens of GeV account for most of the particle spectra, especially inside a space habitat. Finally, we show that LETd is not a good unique predictor for RBE, but its use in proton therapy clinical practice as a surrogate for RBE is justified under certain controlled conditions.

Conventionally, the microparticles that are derived from the platelet surface membrane in the size range of 0.1 to 1.0 µm in diameter, as detected by flow cytometry with platelet-specific marker/s, are collectively categorized as PMPs, despite their structural heterogeneity. We aim to determine the detailed structural classification of this heterogeneous population based on their scatter properties using flow cytometry, both before and several months after total-body irradiation (TBI). This exposure may occur during nuclear attacks or accidents, or as part of myeloablative conditioning before allogeneic stem cell transplantation for leukemia, in wild-type C57BL/6J (WT) mice and in a relatively radiation-sensitive strain deficient in platelet glycoprotein (GP) Ibα (KO), including both sexes and with or without agonist treatments. We exposed WT and KO mice to a single dose of TBI. We collected blood 233 days after 7.8 Gy from male mice and 254 days after 8.0 Gy from female mice, prepared platelet-rich plasma (PRP), activated PRP with 3 different platelet agonists [adenosine 5'-diphosphate (ADP), collagen and thrombin], and characterized the structural heterogeneity of PMPs. Additionally, we quantified the total number of microparticles using Nanoparticle Tracking Analysis (NTA) in WT and KO mice of both sexes. We then cocultured either RAW264.7 cells or splenic CD19+ B cells with microparticles from sham-irradiated and irradiated female mice of both strains to measure reactive oxygen species (ROS) generation and immunoglobulin production, respectively, to assess strain- and TBI-dependent effects of PMPs on immune cell function. We identified 3 distinct PMP subpopulations based on flow cytometry scatter profiles. The percentage of PMP subpopulations altered depending on irradiation status, GPIbα expression, platelet agonist used, and biological sex. Depending on sex, mouse strain, and TBI status, total microparticle count and microparticles-mediated ROS generation and immunoglobin production were altered in RAW264.7 cells and splenic B cells, respectively. These findings offer important insights into a poorly understood area of platelet biology and highlight the potential significance of PMP subpopulations in the context of radiation exposure.

Ionizing radiation continues to be weaponized not only through the development of nuclear weapons, but also on a smaller scale through the development of radiological dispersal devices, or dirty bombs. Exposure to acute doses of ionizing radiation often leads to the development of acute radiation syndrome (ARS), for which treatment options are currently limited. Current treatment options include only post-exposure prophylaxes that are intended to restore bone marrow function and stimulate platelet production. To date, no pre-exposure prophylaxes are available to treat ARS, although many pharmaceuticals are currently under evaluation. Amifostine, for example, has been investigated as a radioprotector, but was found unsuitable due to its hypotensive effects, severe upper and lower gastrointestinal disturbances, and reduced efficacy at the doses required for effective radioprotection. RadioDefender, an amifostine-based drug, shows promise as a radioprotector due to its ability to shield bone marrow from the deleterious effects of ionizing radiation, offering protection at lower doses than those required for amifostine without the toxic effects. Two separate toxicity studies were performed: the first study investigated the effects of various doses of RadioDefender on blood and lymphoid tissue in unirradiated mice to establish the no-observed-adverse-effects-level (NOAEL), while the second study investigated the effects of various doses of RadioDefender on tissue and metabolomic profiles in irradiated mice (9.2 Gy total-body γ-irradiation). RadioDefender treatment significantly improved survival and provided substantial protection in the steroid hormone biosynthesis and arachidonic acid metabolism pathways, key pathways involved in inflammation and immune response that have been proven to be highly sensitive to ionizing radiation.

A cutting-edge advancement known as FLASH radiotherapy, administered at an ultra-high dose rate of ≥40 Gy/s, has garnered considerable attention for its ability to spare normal tissues while retaining its efficacy in targeting tumors. However, the lower toxicity in normal tissues does not unequivocally guarantee the absence of potential effects on bystander tissues. In this study, normal human lung epithelial BEAS-2B and HSAEC1-KT cells were subjected to conventional (100 MeV/u, 1.7 Gy/min) and FLASH (100 MeV/u, 40 Gy/s) proton irradiation. We found that the conditioned culture medium and extracellular DNA (ecDNA) from conventional proton irradiation demonstrate higher efficacy in prompting bystander cell damage, reflected in increased γH2AX foci, reduced cell viability, and heightened apoptotic fractions. Additionally, ecDNA predominantly activated NF-κB signaling pathways in bystander cells and promoted the production of inflammatory factors and reactive oxygen species (ROS). These findings provide evidence that FLASH irradiation may exhibit a reduced impact on damaging bystander cells, contrasting with conventional irradiation, which induces comparatively higher levels of damage in these bystander cells.