Selenium Pretreatment Enhances the Radioprotective Effect and Reduces the Lethal Toxicity of Wr-2721

Although WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, is an effective radioprotector, its use is limited by its toxicity. Combining WR-2721 with other agents might decrease its toxicity and/or increase its effectiveness. The effect of selenium (Se) pretreatment on the acute toxicity and radioprotective effect of WR-2721 was studied in male CD2F1 mice. Injection of 1.6mg/kg Se 24 hr before WR-2721 (800-1200 mg/kg, IP) decreased the lethality of WR-2721 significantly. Lower doses of Se were also effective, but simultaneous administration was not effective. Se injection alone (1.6 mg/kg) 24 hr before cobalt-60 irradiation increased the survival (dose reduction factor, DRF = 1.1) significantly. A synergistic effect on post-irradiation survival was observed when Se was injected 24 hr before WR-2721 (200-600 mg/ kg IP before irradiation). For example, after exposure to 22 Gy (1 Gy/min), 30-day survival was 100% when mice were treated with both Se and 600mg/kg WR-2721, and was 13% with WR-2721 alone. The DRF after 400 mg/kg WR-2721 was 2.6 with Se compared to 2.2 without Se pretreatment. Alkaline phosphatase activity in bone marrow cells and serum was significantly depressed after treatment with 1.6 mg/kg Se, suggesting that a retardation of conversion of WR-2721 to its active free sulfhydryl form through the action of alkaline phosphatase might be partly responsible for the effects of Se. Other possible mechanisms related to the antioxidant properties of Se are under investigation.     

Selenium Pretreatment Enhances the Radioprotective Effect and Reduces the Lethal Toxicity of Wr-2721

Although WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, is an effective radioprotector, its use is limited by its toxicity. Combining WR-2721 with other agents might decrease its toxicity and/or increase its effectiveness. The effect of selenium (Se) pretreatment on the acute toxicity and radioprotective effect of WR-2721 was studied in male CD2F1 mice. Injection of 1.6mg/kg Se 24 hr before WR-2721 (800-1200 mg/kg, IP) decreased the lethality of WR-2721 significantly. Lower doses of Se were also effective, but simultaneous administration was not effective. Se injection alone (1.6 mg/kg) 24 hr before cobalt-60 irradiation increased the survival (dose reduction factor, DRF = 1.1) significantly. A synergistic effect on post-irradiation survival was observed when Se was injected 24 hr before WR-2721 (200-600 mg/ kg IP before irradiation). For example, after exposure to 22 Gy (1 Gy/min), 30-day survival was 100% when mice were treated with both Se and 600mg/kg WR-2721, and was 13% with WR-2721 alone. The DRF after 400 mg/kg WR-2721 was 2.6 with Se compared to 2.2 without Se pretreatment. Alkaline phosphatase activity in bone marrow cells and serum was significantly depressed after treatment with 1.6 mg/kg Se, suggesting that a retardation of conversion of WR-2721 to its active free sulfhydryl form through the action of alkaline phosphatase might be partly responsible for the effects of Se. Other possible mechanisms related to the antioxidant properties of Se are under investigation.     

Melatonin and protection from whole-body irradiation: survival studies in mice

The radioprotective ability of melatonin was investigated in mice exposed to an acute whole-body gamma radiation dose of 815 cGy (estimated LD50/30 dose). The animals were observed for mortality over a period of 30 days following irradiation. The results indicated 100% survival for unirradiated and untreated control mice, and for mice treated with melatonin or solvent alone. Forty-five percent of mice exposed to 815 cGy radiation alone, and 50% of mice pretreated with solvent and irradiated with 815 cGy were alive at the end of 30 days. Irradiated mice which were pretreated with 125 mg/kg melatonin exhibited a slight increase in their survival (60%) (p=0.3421). In contrast, 85% of irradiated mice which were pretreated with 250 mg/kg melatonin were alive at the end of 30 days (p=0.0080). These results indicate that melatonin (at a dose as high as 250 mg/kg) is non-toxic, and that high doses of melatonin are effective in protecting mice from lethal effects of acute whole-body irradiation.     

Polysaccharides induce radioprotection of murine hemopoietic stem cells and increase the LD50/30 days

Intravenous administration of 60 mg/kg of a polysaccharide (MNR, MNZ, GLP/BO4, GLP/BO5) significantly decreases the mortality of mice exposed to a single dose of X rays. The dose reduction factors (DRF) obtained for MNZ, MNR, GLP/BO4, and GLP/BO5 given intraperitoneally 15 min before exposure were 2.16, 1.93, 1.80, and 1.94, respectively. The DRF was not increased when MNZ or GLP/BO4 were combined with injection of AET before X-ray exposure. The LD50 for the CFUs exposed in vivo in mice was 1.13 Gy for the treated mice and 0.75 Gy for the nontreated mice. This corresponds to a DRF of 1.6. The DRF calculated from the slope is 1.27.     

Protection by WR-3689 against gamma-ray-induced intestinal damage: comparative effect on clonogenic cell survival, mouse survival, and DNA damage

The aminophosphorothioate WR-3689 was characterized for its ability to protect mouse jejunal cells in vivo from single doses of X or gamma radiation. First, the effect of the drug on the survival of jejunal stem cells was examined using a clonogenic end point, the crypt microcolony assay. When WR-3689 was administered 30 min prior to whole-body irradiation, the number of surviving crypt cells was markedly increased at all doses of the drug, although protection began to level out at doses larger than 600 mg/kg. Protection was maximal when the drug was given 30 min before whole-body irradiation and declined rapidly with both shorter and longer intervals. Protection factors (PFs) were obtained by measuring survival curves for clonogenic crypt cells as a function of radiation dose; WR-3689 given 30 min before whole-body irradiation protected jejunum in the microcolony assay with a PF of 1.26 +/- 0.02, 1.50 +/- 0.10, and 1.65 +/- 0.10 at doses of 200, 400, and 800 mg/kg, respectively. Next, the effect of WR-3689 on the survival of jejunal stem cells was determined by assaying the survival of mice given X-ray doses to the whole abdomen in the range leading to death from the gastrointestinal syndrome. The PFs based on the LD50 values for 11-day survival were 1.31 +/- 0.05 (200 mg/kg) and 1.48 +/- 0.05 (400 mg/kg). Crypt-cell survival and animal survival were thus modified to a similar extent by this agent. Finally, the effect of WR-3689 on the induction of DNA single-strand breaks (SSBs) in jejunal cells was measured using an adaptation of the alkaline elution methodology. In mice treated with WR-3689 (400 or 800 mg/kg) 30 min prior to whole-body irradiation with 10 Gy there was no significant reduction in the number of DNA SSBs induced either in samples of the jejunum or in the cycling crypt cells, providing further evidence that there is no simple relationship between the modification of DNA SSBs and the survival of jejunal stem cells.     

The radiation modifying properties of carnosine

The influence of carnosine (beta-alanyl-l-histidine) on the survival rate of albino mice subjected to whole-body X-irradiation has been investigated. Carnosine (50-200 mg/kg/day) administered per os during a period of 20 days before irradiation (5.0 Gy) increased the survival rate by 45-65%, whereas the administration of carnosine within 30 days after irradiation (5.5 Gy) produced an insignificant protective effect and caused inhibition of the postirradiation histamine accumulation in the spleen.     

In vivo postirradiation protection by a vitamin E analog, alpha-TMG

The water-soluble vitamin E derivative alpha-TMG is an excellent radical scavenger. A dose of 600 mg/kg TMG significantly reduced radiation clastogenicity in mouse bone marrow when administered after irradiation. The present study was aimed at investigating the radioprotective effect of postirradiation treatment with alpha-TMG against a range of whole-body lethal (8.5-12 Gy) and sublethal (1-5 Gy) doses of radiation in adult Swiss albino mice. Protection against lethal irradiation was evaluated from 30-day mouse survival and against sublethal doses was assessed from micronuclei and chromosomal aberrations in the bone marrow 24 h after irradiation. An intraperitoneal injection of 600 mg/kg TMG within 10 min of lethal irradiation increased survival, giving a dose modification factor (DMF) of 1.09. TMG at doses of 400 mg/kg and 600 mg/kg significantly reduced the percentage of aberrant metaphases, the different types of aberrations, and the number of micronucleated erythrocytes. DMFs of 1.22 and 1.48 for percentage aberrant metaphases and 1.6 and 1.98 for micronuclei were obtained for 400 mg/kg and 600 mg/kg TMG, respectively. No drug toxicity was observed at these doses. The effectiveness of TMG when administered postirradiation suggests its possible utility for protection against unplanned radiation exposures.     

Combined effects of radiation and caffeine on embryonic development in mice

The combined effect of radiation and caffeine has been studied in mouse embryos. Radiation and/or caffeine were administered to ICR mice on Day 11 of gestation. Intrauterine death, gross malformation, and fetal body weight were selected as indicators of effects. Doses of whole-body gamma irradiation were 0.5 to 2.5 Gy and those of caffeine were 100 and 250 mg/kg maternal body wt. Intrauterine mortality increased with increasing radiation dose; this trend was more remarkable in combination with caffeine. Gross malformations such as cleft palate and defects of forelegs and hindlegs appeared frequently in the fetuses treated with both radiation and caffeine. Decreased fetal weight was observed even in mice treated with 0.5 Gy of radiation or 100 mg/kg caffeine. There was a linear relationship between dose and reduction of fetal weight. The fetal weight was a sensitive, precise, and easy-to-handle indicator for the effects of growth retardation. Intrauterine mortality and frequencies of cleft palate and defects of forelegs and hindlegs were higher than the sum of those induced by radiation and by caffeine separately. The results indicated that the combined action of radiation and caffeine on intrauterine death and malformations was synergistic.     

Protection of mice against mixed fission neutron-gamma (n: gamma = 1:1) irradiation by WR-2721, 16,16-dimethyl PGE2, and the combination of both agents

The survival of mice after whole-body exposure to a modified fission neutron-gamma field (n: gamma = 1:1) was used to examine radiation protection by WR-2721, 16,16-dimethyl PGE2(DiPGE2), and the combination of both agents. Administration of WR-2721 (453 mg/kg) increased the LD50/30 from 5.24 to 7.17 Gy (DMF = 1.37), whereas pretreatment with DiPGE2 (1.6 mg/kg) increased the LD50/30 to 5.77 Gy (dose modification factor (DMF) = 1.10). The combination of 453 mg/kg WR-2721 and 0.4 mg/kg DiPGE2 resulted in an LD50/30 of 7.33 Gy, yielding a DMF of 1.39. However, no significant difference in protection was obtained with the combination of the two agents compared to that seen with WR-2721 alone.     

Radiomodifying properties of the synthetic analog of prostaglandin F2 alpha-estrofan

Estrofan (0.1 to 5 mg/kg) administered to rats and mice 5 min prior to gamma irradiation with doses of 8.5 to 9.5 Gy (LD90/30) increases the survival rate up to 30-40 per cent. The drug is ineffective when administered 30 and 60 min before irradiation.     

Free radical scavenging and radioprotective activity of dehydrozingerone against whole body gamma irradiation in Swiss albino mice

Dehydrozingerone (DZ) was explored for in vitro-in vivo antioxidant potential and in vivo radioprotective activity against whole body gamma irradiation in Swiss albino mice. DZ scavenged the ABTS (2, 2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) and DPPH (1, 1-dipehnyl-2-picrylhydrazyl) free radicals at room temp. DZ reduced Fe (III) to Fe (II) at pH 7.4 and scavenged the NADH/phenazine methosulfate generated superoxide radical in cell free system. DZ also scavenged the nitric oxide radical generated by sodium nitroprusside. To evaluate the radioprotective activity, mice were exposed to whole body gamma irradiation 30 min after the drug treatment at a dose rate of 1.66 Gy/min. Pretreatment with DZ 75, 100 and 125 mg/kg, i.p. reduced the radiation induced mortality and increased the mean survival times (MSTs). An i.p. dose of DZ 100 mg/kg was found the most effective dose in preventing radiation sickness and increasing the MST. Pretreatment DZ100 mg/kg maintained the spleen index (spleen weight/body weight x 100) and stimulates the endogenous spleen colony forming units (CFU). Pretreatment with DZ100 mg/kg maintained the villus height close to normal, prevents mucosal erosion and basement membrane damage in irradiated mice jejunum. However, no significant reductions in dead, inflammatory and mitotic cells were observed in DZ pretreated mice, but there was an increased in crypt cells proliferation and regeneration. Pretreatment with DZ100 mg/kg significantly elevated the endogenous antioxidant enzymes (GSH, GST and SOD) in mice at 2, 4 and 8 h post sham irradiation. Radiation induced fall in endogenous antioxidant enzymes was significantly prevented by DZ pretreatment. Pretreatment with DZ 75 and 100 mg/kg reduced the radiation induced micronucleated polychromatic erythrocytes (MPCE) and normochromatic erythrocytes (MNCE) in mice bone marrow. DZ also maintained the polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) ratio (P/N ratio) in irradiated mice. Dose modifying factor (DMF) was calculated by using the graded radiation dose (8.0, 9.0, 9.5 and 10 Gy). DZ 100 mg/kg elevated radiation LD(50) from 9.1 to 10.0 Gy, indicating the DMF of 1.09.     

Hematopoietic Recovery and Amelioration of Radiation-Induced Lethality by the Vitamin E Isoform δ-Tocotrienol

δ-Tocotrienol (DT3), a vitamin E isoform, is associated with strong antioxidant and immunomodulatory properties. We confirmed the potent antioxidant activity in membrane systems and showed that DT3 is an effective radiation protector and mitigator. DT3 (4 μM, P < 0.001) inhibited lipid peroxidation in mouse liver microsomes and nitric oxide (NO) formation (20 μM DT3, P < 0.01) in RAW264.7 cells, a murine alveolar macrophage line. In CD2F1 mice exposed to lethal total-body radiation from a (60)Co γ-radiation source, a single subcutaneous (s.c.) injection of DT3 before or after irradiation produced a significant increase in 30-day survival. DT3 was effective from 18.75 to 300 mg/kg (--24 h, P < 0.001). A single dose of 150 or 300 mg/kg DT3 given 24 h before irradiation (radioprotection) resulted in dose reduction factors (DRFs) of 1.19 and 1.27, respectively (P < 0.001). Further, DT3 reduced radiation lethality when administered 2, 6 or 12 h after irradiation, and 150 mg/kg DT3 administered 2 h after exposure conferred a DRF of 1.1 (mitigation). The optimum schedule of 300 mg/kg DT3 24 h prior to 7 Gy significantly reduced pancytopenia compared to irradiated controls (P < 0.05). The large therapeutic potential of and multi-lineage hematopoietic recovery for DT3 warrants further studies.     

In vivo radioprotective potential of thymol, a monoterpene phenol derivative of cymene

The radioprotective and anticlastogenic potential of a phenol derivative monoterpene thymol(TOH), against whole-body gamma radiation was studied in Swiss albino mice. Acute toxicity of TOH, with an LD(50(14)) of 1134.03mg/kgbwt., was observed when administered intra-peritoneally (i.p.). The radioprotective potential of TOH was evaluated using the optimal dose of 10mg/kgbwt. TOH, which increased the LD(50/30) by 2.17Gy and resulted in a dose reduction factor (DRF) of 1.25. A significant (p<0.01) reduction in micronucleated, polychromatic erythrocytes (PCE), normochromatic erythrocytes (NCE), and an increased PCE/NCE ratio was also observed after administration of 10mg/kg.b.wt. TOH prior to gamma radiation, indicating its antigenotoxic effect. TOH pre-treatment significantly (p<0.01) elevated reduced glutathione, glutathione-S-transferase, catalase, and superoxide dismutase levels and decreased lipid peroxidation levels in mouse liver homogenates at 24 and 48h after exposure to 4.5Gy of radiation. Further, TOH treatment before exposure to 7.5Gy of gamma radiation resulted in a significant (p<0.01) increase in hematological parameters at various post-treatment time points, with increased numbers of endogenous spleen colonies as well. The histological observations indicated a decline in villus heights and crypt numbers in mouse jejunum and were accompanied by a significant decrease in bone marrow nucleated cells in the irradiated group, which was almost normalized by pre-treatment with TOH. Our study clearly documents the antioxidant, anticlastogenic and radioprotective potentials of TOH, which may be attributed to several possible mechanisms, such as normalization of intracellular antioxidant levels and free radical scavenging activities by TOH.     

Protective effect of RH-3 with special reference to radiation induced micronuclei in mouse bone marrow

Effect of pre-irradiation administration of different doses of RH-3, the herbal preparation of an Indian medicinal plant Hippophae rhamnoides, 30 min before 10 Gy whole body gamma irradiation was studied. Doses between 25 to 35 mg/kg body wt. were found to render > 80 % survival in mice. In order to investigate whether RH-3 protected against radiation induced genotoxicity, mice were administered different doses of RH-3, 30 min before 2 Gy dose and compared with untreated, RH-3 treated and irradiated controls. The bone marrow cells were collected at different time intervals following various treatments and processed for scoring micronuclei (MN). Administration of RH-3 alone did not enhance the MN frequency as compared to the control, and radiation dose of 2 Gy significantly enhanced the MN frequency (3.1 %, P < 0.01). Pre-irradiation treatment with RH-3, however, reduced the radiation induced MN frequency in a drug dose dependent manner suggesting its radioprotective efficacy. The protective effect of RH-3 on radiation induced perturbations in cell cycle progression was studied flowcytometrically in mouse bone marrow cells. RH-3 treatment (30 mg/kg body wt.) enhanced DNA synthesis (S-phase) in unirradiated controls and also countered radiation induced depression of S-phase to facilitate replenishment of cells lost due to radiation injury.     

Specific effect of attenuated strain of Francisella tularensis on the development of radiation induced lesions in experimental animals and effictiveness of antibacterial therapy for lesions induced by radiation combined with virulemt strain of the bacteria

For study of the effects of whole-body gamma-radiation (1 and 4 Gy) on the response of the body to administration of vaccines and virulent strains of tularemia 206 outbred white mice were used. The results of the study shown that the administration of attenuated bacterial cells in 5 days after exposure to radiation (1 and 4 Gy) caused more severe post-radiation effects and the increase in the number of died animals. The severity of the disease was less if mice were vaccinated in 26 days after irradiation (4 Gy). The treatment of tularemia in irradiated mice twith Riphampicin (daily peroral administration, 5 mg/mouse, duration of treatment--7 days) administered in 4 hours after infection was effective and caused high survival of affected mice. The results show effectiveness of the riphampicin treatment of tularemia in the animals exposed to sublethal dose of radiation.     

The effect of cyclophosphamide and gamma irradiation on adenosine deaminase and purine nucleoside phosphorylase in mice

Changes in ADA and PNP activities in the spleens and thymuses of mice were studied after a single administration of cyclophosphamide (CY, 200 mg/kg) and after whole-body gamma irradiation (5.5 Gy), applied alone or three days after CY application. In the first days after the treatment the enzyme activities were significantly depressed (p less than 0.01) with the exception of ADA in the spleen, where a high elevation (220-380%) in relation to controls was observed. During the regeneration period a pronounced rise of PNP activity in the spleen occurred mainly after a combined application of CY and irradiation (270%). In the thymus the regeneration was manifested by a mild increase of both ADA and PNP activities towards control values. The findings suggest that the expressive changes of ADA and PNP activities, participating in the purine salvage pathway, may, after a cytotoxic treatment, influence the nucleotide pool and DNA synthesis in lymphoid organs.     

Suppression of thymic lymphoma induction by life-long low-dose-rate irradiation accompanied by immune activation in C57BL/6 mice

The induction of thymic lymphomas by whole-body X irradiation with four doses of 1.8 Gy (total dose: 7.2 Gy) in C57BL/6 mice was suppressed from a high frequency (90%) to 63% by preirradiation with 0.075 Gy X rays given 6 h before each 1.8-Gy irradiation. This level was further suppressed to 43% by continuous whole-body irradiation with 137Cs gamma rays at a low dose rate of 1.2 mGy/h for 450 days, starting 35 days before the challenging irradiation. Continuous irradiation at 1.2 mGy/h resulting in a total dose of 7.2 Gy over 258 days yielded no thymic lymphomas, indicating that this low-dose-rate radiation does not induce these tumors. Further continuous irradiation up to 450 days (total dose: 12.6 Gy) produced no tumors. Continuously irradiated mice showed no loss of hair and a greater body weight than unirradiated controls. Immune activities of the mice, as measured by the numbers of CD4+ T cells, CD40+ B cells, and antibody-producing cells in the spleen after immunization with sheep red blood cells, were significantly increased by continuous 1.2-mGy/h irradiation alone. These results indicate the presence of an adaptive response in tumor induction, the involvement of radiation-induced immune activation in tumor suppression, and a large dose and dose-rate effectiveness factor (DDREF) for tumor induction with extremely low-dose-rate radiation.     

Action of alpha-tocopherol on the enzymes of the electron transport chains in the liver microsomes of irradiated rats

Five days following single whole-body gamma irradiation of rats (8.5 Gy) the rate of NADPH and NADH oxidation, the activity of NADPH-cytochrome P-450 and NADH-cytochrome b5 reductases, and the content of cytochromes P-450 and b5 were found to decrease. The intragastric administration of alpha-tocopherol (100 mg/kg, two times a day) produced a normalizing effect.     

重组人血小板生成素早期干预救治重症急性放射病猴的实验研究

重组人血小板生成素（rhTPO）是一种能促进巨核系祖细胞增殖、分化生成血小板的造血因子,研究表明它能促进射线照射小鼠造血功能恢复,前期工作证明rhTPO早期干预可显著提高致死剂量照射小鼠的活存率.本文以7.0Gy照射恒河猴为重度骨髓型急性放射病（ARS）模型,研究了rhTPO早期干预对重症ARS的治疗作用,并与WR2721和＂500＂的辐射防护作用进行了比较,结果发现rhTPO早期干预可明显促进ARS猴造血功能恢复,改善ARS猴症状,简化对症治疗措施,提高重度骨髓型ARS猴活存率,其对重度骨髓型ARS的防治作用优于现有的辐射防护药WR2721和＂500＂,有望开发成安全有效的新型辐射防治药物.     

Modulatory influence of Adhatoda vasica Nees leaf extract against gamma irradiation in Swiss albino mice

The radiomodulatory influence of ethanolic extract of Adhatoda vasica Nees leaf extract against radiation-induced hematological alterations in peripheral blood of Swiss albino mice was studied at various post-irradiation intervals between 6 h to 30 days. Oral administration of A. vasica leaf extract (800 mg/kg body weight) prior to whole body irradiation showed a significant protection in terms of survival percentage and hematological parameters. Mice exposed to radiation (8.0 Gy) without A. vasica leaf extract pre-treatment exhibited signs of radiation sickness like anorexia, lethargicity, ruffled hairs and diarrhoea and such animals died within 25 days post-irradiation. The dose reduction factor (DRF = 1.6) for A. vasica leaf extract was calculated from LD50/30 values. A significant decline in hematological constituents (RBCs, WBCs, Hb and Hct) was evident till day 15 and no animal could survive beyond day 25. Conversely, animals pre-treated with A. vasica leaf extract showed 81.25% survival till 30 days after exposure and a gradual recovery was noted in the hematological values. However, these hematological values remained significantly below the normal even till day 30. A significant decrease in blood reduced glutathione (GSH) content and increase in lipid peroxidation (LPO) level was observed in control animals (Radiation alone). However, A. vasica leaf extract pretreated irradiated animals exhibited a significant increase in GSH content and decrease in LPO level. A significant increase in the serum alkaline phosphatase activity and decrease in acid phosphatase activity was observed in A. vasica leaf extract pretreated irradiated animals during the entire period of study.