The effect of high-energy (660 MeV) proton irradiation at the phasotron accelerator in FLASH mode (80 Gy/s) compared with the standard proton exposure power of 3.0 Gy/min was studied. When irradiated in two modes at doses of 1.0 and 1.5 Gy, the induction of cytogenetic damage in bone marrow cells and the state of lymphoid organs (thymus and spleen) were evaluated; survival under total in vivo irradiation of mice was analyzed at doses of 7.0 and 8.0 Gy. The growth rate of a model tumor under ex vivo irradiation was determined at doses of 40 and 60 Gy. It has been shown that irradiation of animals in the FLASH mode at a dose of 1.5 Gy protected the proliferative activity of the spleen and also led to a decrease in cytogenetic damage in bone marrow erythrocytes according to the micronucleus test compared with the standard irradiation mode at a dose of 1.5 Gy, that is, a milder effect of the FLASH mode dose was observed. However, irradiation of mice in FLASH mode at high doses (7.0 and 8.0 Gy) led to earlier death of animals compared to the standard irradiation regime. A tumor node formed with further growth only after FLASH irradiation of a suspension of Ehrlich ascites carcinoma at a dose of 40 Gy; in all other groups a tumor was not formed.

The FLASH effect of high-energy (660 MeV) proton irradiation using the Phasotron accelerator with the capacity of delivering dose rates of 80 Gy/s has been studied and compared to the effect after exposure to proton radiation at a conventional dose rate of 3 Gy/min. After FLASH and conventional dose-rate irradiation with doses of 1.0 and 1.5 Gy, the induction of cytogenetic damage to bone marrow cells and the state of lymphoid organs (thymus and spleen) were estimated; at doses of 7.0 and 8.0 Gy, the survival rate after total irradiation of mice in vivo was analyzed; and at doses of 40 and 60 Gy, the tumor growth rate was determined after irradiation ex vivo. It has been shown that irradiation of animals using the FLASH mode at a dose of 1.5 Gy protects the proliferative activity of the spleen and also leads to a decrease in cytogenetic injuries in bone marrow erythrocytes, based on the micronucleus test, as compared to the conventional irradiation at a dose of 1.5 Gy; thus, the FLASH effect has lower toxicity compared to conventional radiation. However, irradiation of mice, the FLASH effect which delivers high doses (7.0 and 8.0 Gy) of radiation, leads to earlier death of animals compared to those exposed to conventional radiation. Only after FLASH irradiation of a suspension of Ehrlich ascites carcinoma at a dose of 40 Gy, a tumor node with further growth was formed; no tumors were formed in all other groups.

At the present time, the studies carried out to improve the radiotherapy of tumors using accelerated heavy ions are of great interest, since they give off the main energy at the end of the run at the Bragg peak, which increases the severity of radiation damage to the tumor and minimizes damage to surrounding healthy tissues. In this work, the levels of lymphocyte lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activity, the ratio of LDH/SDH, induced reactive oxygen species (ROS) of neutrophils, and leukocytes DNA damage (%TDNA) in blood 1 day after accelerated carbon ions irradiation of mice with an energy of 450 MeV/nucleon in doses of 0.2-2 Gy in the Bragg peak were determined. Found: SDH activity increased at doses of 0.2-1 Gy and sharply decreased at a dose of 1.5 Gy in all mice. With a decrease in SDH activity, glycolysis (LDH activity) increased compensatory, which, apparently, is associated with the developing mitochondrial dysfunction of immune cells. The %TDNA of leukocytes increased depending on the dose and was accompanied by a decrease in the functional activity of neutrophils - the zymosan-induced ROS production decreased. Thus, against the background of an increased %TDNA and a decrease in SDH activity, glycolysis becomes of great importance. The applied methods are highly sensitive and can be used to detect individual differences in animals that are biological models in preclinical studies.

The combined effect of protective agents (helium-neon laser, ibuprofen, mexidol) and 3 Gy of accelerated carbon ions (12C) on the cognitive abilities of mice was studied. It was shown that the irradiated animals did not exhibit an altered behavior pattern: the level of anxiety was not increased, there was a slower positive dynamics of learning compared to the control, and there was no deficit in the hippocampus-dependent memory. Analysis of variance of learning curves revealed different coefficients of skill acquisition within the experimental groups, with the lowest characteristic for the group irradiated with a dose of 3 Gy 12C without protective agents. In addition, the analysis of the preference for novelty when testing for recognition of a new object showed that this group of animals has a violation of the nonspatial hippocampus-mediated short-term memory.

The early delayed effects of accelerated carbon ions and protons on the cognitive functions of mice using tests of the total activity, spatial learning, and long-term and short-term hippocampal-dependent memory were studied. The obtained results showed that irradiated animals do not develop an altered behavioral pattern: the level of anxiety is not increased, the exploratory model of behavior is clearly pronounced, and there is no deficiency of hippocampal-dependent memory. However, the long-term memory test revealed fewer errors in finding an escape box in a group of animals irradiated with protons compared to the control animals and mice irradiated with carbon ions. The results may indicate a better preservation of memory traces under these conditions.

People often encounter various sources of ionizing radiation, both in modern medicine and under various environmental conditions, such as space travel, nuclear power plants or in conditions of man-made disasters that may lead to long-term cognitive impairment. Whilst the effect of exposure to low and high doses of gamma and X-radiation on the central nervous system (CNS) has been well investigated, the consequences of protons and heavy ions irradiation are quite different and poorly understood. As for the assessment of long-term effects of carbon ions on cognitive abilities and neurodegeneration, very few data appeared in the literature. The main object of the research is to investigate the effects of accelerated carbon ions on the cognitive function. Experiments were performed on male SHK mice at an age of two months. Mice were irradiated with a dose of 0.7 Gy of accelerated carbon ions with an energy of 450 meV/n in spread-out Bragg peak (SOBP) on a U-70 particle accelerator (Protvino, Russia). Two months after the irradiation, mice were tested for total activity, spatial learning, as well as long- and short-term hippocampus-dependent memory. One month after the evaluation of cognitive activity, histological analysis of dorsal hippocampus was carried out to assess its morphological state and to reveal late neuronal degeneration. It was found that the mice irradiated with accelerated carbon ions develop an altered behavioral pattern characterized by anxiety and a shortage in hippocampal-dependent memory retention, but not in episodic memory. Nissl staining revealed a reduction in the number of cells in the dorsal hippocampus of irradiated mice, with the most pronounced reduction in cell density observed in the dentate gyrus (DG) hilus. Also, the length of the CA3 field of the dorsal hippocampus was significantly reduced, and the number of cells in it was moderately decreased. Experiments with the use of Fluoro-Jade B (FJB) staining revealed no FJB-positive regions in the dorsal hippocampus of irradiated and control animals 3 months after the irradiation. Thus, no morbid cells were detected in irradiated and control groups. The results obtained indicate that total irradiation with a low dose of carbon ions can produce a cognitive deficit in adult mice without evidence of neurodegenerative pathologic changes.

The possibility of induction of cytogenetic damage in the bone marrow, changes in the cellularity of lymphoid organs and blood composition in mice irradiated with low-intensity femtosecond laser radiation at a power flux density of 5.1, 10.4, and 52 mJ/cm2 (0.5 mW for 5, 10, and 50 s) in vivo was shown. Using the radiation adaptive response test (0.1 Gy + 1.5 Gy), it was found that, when mice were exposed to femtosecond laser radiation in high doses, the body’s natural defenses were activated in the same narrow range of energy flux density (2–16 mJ/cm2) as in the case of X-ray irradiation in a dose of 0.1 Gy (4 mJ/cm2). The data obtained suggest a similar mechanism of activation of the body’s natural defense upon exposure to low doses of both ionizing and non-ionizing radiation.

Purpose The objective of the study was to estimate the DNA damage in blood leukocytes at long terms after irradiation of mice with carbon ions (450 MeV/nucleon) both before and in the Bragg peak. Materials and methods White outbred SHK male mice were exposed to whole-body irradiation with carbon ions at doses of 0.1-2 Gy in the spread-out Bragg peak and at a dose of 6 Gy before and in the Bragg peak. At different times after irradiation (1-75 days), whole blood was collected from the tail of each mouse and analyzed by the comet assay. Mice X-irradiated in the same dose range served as a positive control. The level of the expression of mRNA ofCDKN1A, APEX1, BBC3, TXN2,and beta-ACTgenes in bone marrow cells was determined in animals irradiated with carbon ions at doses of 0.1-2 Gy using the real-time PCR. Results It was found that, 24 h after(12)C-irradiation, a dose-dependent (0.1-2 Gy) increase in the DNA damage of leukocytes occurred, which was accompanied by a decrease in their concentration and an increase in the expression of theCDKN1AandBBC3genes in bone marrow cells. The expression of theAPEX1andTXN2genes did not change. In mice(12)C-irradiated at a dose of 6 Gy before and in the Bragg peak, the level of DNA damage changed as follows: by day 3, it increased; by day 23 it returned to the control level; by day 30, it increased again; and by day 75, it fell to the control level on irradiation before the Bragg peak and was significantly higher (p< .05) than in the control after irradiation in the Bragg peak. Conclusions The dynamics of changes in the level of DNA damage in leucocytes of(12)C-irradiated mice within 30 days is similar to that in mice exposed to sublethal doses of X-radiation. The retention of the high level of DNA damage by day 75 after(12)C-irradiation in the Bragg peak indicates a significant injury of cells from different cell pools of the blood system. The high level of DNA damage may be related not only to complex DNA injuries but also to chronic oxidative stress.

The aim of this work was to study the effect of proton pencil beam scanning in the Bragg peak in the dose range of 0.1–1.5 Gy on the induction of cytogenetic damage in the bone marrow, reactive oxygen species (ROS) production in whole blood, and the state of lymphoid organs after total body irradiation of mice. Irradiation was carried out in the Prometeus proton synchrotron (Protvino) in the Bragg peak with proton energy at the output of 90–116 MeV. It was found that, under irradiation of mice in the range of low and medium doses of proton pencil beam scanning in the Bragg peak, the relative biological effectiveness (RBE) according to the criterion of cytogenetic changes was 1.15. In addition, it was found that the pathophysiological effect on the lymphoid organs and the production of ROS by blood cells were different as compared with the effect of X-rays.

Abstract—The coefficients of the relative biological efficiency of a carbon ion beam with an energy of 450 MeV/nucleon upon the irradiation of mice at a dose of 6.5 Gy in different parts of the Bragg curve have been determined by the 30-day survival test, the dynamics of death, and the average life expectancy of mice in comparison with exposure to X-ray radiation. The integral value ​​of the coefficients of the relative biological efficiency of carbon ions upon irradiation before the Bragg peak is 0.8, in the spread-out Bragg peak it is 1.5, and after the Bragg peak, it is 0.7. The value of the relative biological efficiency in the modified Bragg peak, as calculated by the ratio of doses that lead to the death of 50% of the animals, was 2.9. Changes of the width of the modified Bragg peak did not affect the death rate of the animals.

The purpose of this work is to reveal the activation of natural defenses reserve in mice after treatment with different physico-chemical agents in vivo using previously developed technology of adaptive response induction. Physical agents were represented by X-rays, carbon ions, infrared light, He-Ne laser light, famine and chemical agents – by immunomodulator CaCl2 and anti-inflammatory drug ibuprofen. The following tasks were set: assessment of cytogenetic damage using a micronucleus test, the weight index of lymphoid organs (thymus and spleen) and the level of ROS production in whole blood through the method of luminol-dependent zymosan-induced chemiluminescence. SHK mice were irradiated according to the scheme of adaptive response. Analysis of data on the number of cytogenetic damage in bone marrow showed that pretreatment of the animals with all investigated agents and subsequent exposure to X-rays or carbon ions at a dose of 1.5 Gy has led to a decrease in radiosensitivity compared to the nontreated animals. Similar results were observed when analyzing weight index of lymphoid organs. Determination of level of ROS production has shown that the activation index calculated according to the relation of induced to spontaneous light area, was significantly higher in all groups of mice, indicating activation of the natural defenses reserve as compared to the group exposed only at a dose of 1.5 Gy. The obtained results confirm the assumption of revealing activation of the natural defense of the organism with the help of the adaptive response induction technology.

Transgenerational genomic instability in the first generation offspring of mice exposed to lowintensity infrared laser (632.8 nm) and light-emitting-diode infrared irradiation (850 nm) was investigated in vivo. It was found that the level of spontaneous damage in bone marrow according to the micronucleus test, the level of reactive oxygen species in whole blood, and the mass index of lymphoid organs in all of the descendants of irradiated mice did not increase. After additional X-ray exposure of the progeny at a dose rate of 1.5 Gy, a decrease in the level of damage and the absence of an adaptive response were revealed upon testing according to “radiosensitivity” and the radiation-induced adaptive-response scheme (0.1 + 1.5 Gy), respectively, compared to the descendants of nonirradiated mice. The rate of tumor growth in the offspring of irradiated mice did not differ from that in the descendants of nonirradiated mice, although inhibition of the tumor growth rate was observed in their irradiated parents. The survival rate after irradiation at a dose rate of 6.5 Gy did not differ from both the parents and the control.

This work focuses on the study of remote effects (duration of remission, recurrence rate, and average lifespan) in mice with Ehrlich ascites carcinoma exposed to oligofractionated irradiation with a pencil scanning beam of protons depending on the volume of the tissue being irradiated and the interval between dose fractions. The results show higher antitumor efficacy and a considerable increase in the average life span of mice after hypofractionated irradiation with a pencil scanning beam of protons at a total dose of 60 Gy of the gross tumor volume compared with the planning target volume.

Different radioprotective action mechanisms of CeO2 nanoparticles in vitro and in vivo are demonstrated and discussed.