Multi-endpoint biological monitoring of phosphine workers

5-Aminosalicylic acid (5ASA), a prescribed drug for ulcerative colitis, is a potent scavenger of oxygen-derived free radicals. The present study was undertaken to ascertain its ability to protect against radiation-induced damage. The drug dose-dependent effect, optimum time of drug administration and radiation dose-dependent effect (0-4 Gy) on in vivo radiation protection against micronuclei induction in polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) were studied in the bone marrow of mice. Intraperitoneal injection of 10-125 mg/kg of the drug 30 min before whole body irradiation with 3 Gy produced a significant reduction in the frequency of micronucleated erythrocytes at 24 h after exposure. The optimum dose for protection without drug toxicity was 25 mg/kg body weight. Injection of 25 mg/kg of the drug 60 or 30 min before or within 15 min after 3 Gy whole body gamma-irradiation resulted in a significant decrease in the radiation-induced PCE and NCE with micronuclei (MPCE and MNCE) and an increase in the ratio of PCE to NCE (P/N), at 24 h post-irradiation. Maximum effect was seen when the drug was administered 30 min before irradiation. Therefore, to study the radiation dose-response, mice were pre-treated with 25 mg/kg of 5ASA 30 min before 1-4 Gy of gamma-irradiation. Radiation increased the MN frequency linearly (r(2)=0.99) with dose. Pre-treatment with 5ASA significantly reduced the MN counts to 40-50% of the radiation (RT) alone values, giving a dose modification factor (DMF) of 2.02 (MPCE) and 2.53 (MNCE). Irradiation resulted in a dose-dependent decline in the P/N ratio at all the doses of radiation studied. 5ASA produced a significant increase in the P/N ratio from that of irradiated controls, at all doses of radiations tested. These results show that 5ASA protect mice against radiation-induced MN formation and mitotic arrest.     

In vivo radioprotection by 5-aminosalicylic acid

The radioprotective effect of 5-aminosalicylic acid (5ASA) was investigated in mouse bone marrow. The present study was aimed at investigating the radioprotective effect of pre-irradiation treatment with 5ASA against a range of whole-body lethal (8-11 Gy) and sublethal (1-4 Gy) doses of gamma-radiation (RT) in adult Swiss albino mice. Protection against lethal irradiation was evaluated from 30-day mouse survival and against sublethal doses was assessed from chromosomal aberrations in the bone marrow 24 h after irradiation. An intraperitoneal injection of 5ASA at a dose of 25mg/kg body weight (b. wt.) 30 min before lethal RT increased survival, giving a dose modification factor (DMF) of 1.08. Injection of 5ASA (25 mg/kg b. wt.) 60 or 30 min before or within 15 min after 3 Gy whole body RT resulted in a significant decrease in the radiation-induced aberrant metaphases, at 24 h post-irradiation. Maximum effect was seen when the drug was administered 30 min before irradiation. 5ASA (25 mg/kg b. wt.) significantly reduced the number of aberrant metaphases and the different types of aberrations at all the radiation doses (1-4 Gy) tested, giving a DMFs of 1.43 for number of aberrant metaphases. 5ASA pretreatment also significantly enhanced the endogenous spleen colonies in mouse exposed to 11 Gy RT. Pretreatment with 5ASA, protected plasmid DNA (pGEM-7Zf) against breakage induced by RT and Fenton reactants. Using nanosecond pulse radiolysis technique, the bimolecular rate constant of the reaction of 5ASA with hydroxyl radical was found to be 6.7x10(9)M(-1)s(-1). The p53 and p21 protein levels of bone marrow and spleen were evaluated to identify the specific molecular mechanisms. Both p53 and p21 increased 24h after 6 Gy irradiation, while treatment with 5ASA inhibited this RT-induced increase. Therefore, the present data suggest that 5ASA pretreatment decreases death caused by RT-induced gastrointestinal and hemopoeitic syndromes. The proposed mechanism of radioprotection by 5ASA is through the inhibition of damage to DNA, lipids, and proteins; and prevention of RT-induced increased expression of p53 and p21.     

Evaluation of Tempol Radioprotection in a Murine Tumor Model

Tempol, a stable nitroxide free radical compound, is an in vitro and in vivo radioprotector. Previous studies have shown that Tempol protects C3H mice against whole-body radiation-induced bone marrow failure. In this study, the radioprotection of tumor tissue was evaluated. RIF-1 tumor cells were implanted in female C3H mice 10 d prior to radiation. Groups of mice were injected intraperitoneally with Tempol (275 mg/kg) or PBS followed 10 min later by a single dose of radiation to the tumor bed. Tumor growth curves generated after 10 and 33.3 Gy doses of radiation showed no difference in growth between the Tempol- and PBS-treated animals. A full radiation dose-response experiment revealed a tumor control dose in 50% of the animals in 30 d (TCD_50/30) value of 36.7 Gy for Tempol-treated mice and 41.8 Gy for saline-treated mice suggesting no protection of the RIF-1 tumor by Tempol. Tumor pharmacokinetics were done to determine why Tempol differentially protected bone marrow and not tumor cells. Differential reduction of Tempol in the RIF-1 tumor and bone marrow was evaluated with EPR spectroscopy 10, 20, and 30 min after injection. Bioreduction of Tempol to its corresponding hydroxylamine (which is not a radioprotector) occurred to a greater extent in RIF-1 tumor cells compared to bone marrow. We conclude that the differences in radioprotection may result from enhanced intratumor bioreduction of Tempol to its nonradioprotective hydroxylamine analogue. The nitroxides as a class of compounds may provide a means to exploit the redox differences between normal tissues and tumors. © 1997 Elsevier Science Inc.     

Radiation protection of DNA by ferulic acid under in vitro and in vivo conditions

The effect of ferulic acid was studied on γ-radiation-induced relaxation of plasmid pBR322 DNA and induction of DNA strand breaks in peripheral blood leukocytes and bone marrow cells of mice exposed to whole body γ-radiation. Presence of 0.5 mM ferulic acid significantly inhibited the disappearance of supercoiled (ccc) plasmid pBR322 with a dose modifying factor (DMF) of 2.0. Intraperitoneal administration of different amounts (50, 75 and 100 mg/kg body weight) of ferulic acid 1 h prior to 4 Gy γ-radiation exposure showed dose-dependent decrease in the yield of DNA strands breaks in murine peripheral blood leukocytes and bone marrow cells as evidenced from comet assay. The dose-dependent protection was more pronounced in bone marrow cells than in the blood leukocytes. It was observed that there was a time-dependent disappearance of radiation induced strand breaks in blood leukocytes (as evidenced from comet parameters) following whole body radiation exposure commensuration with DNA repair. Administration of 50 mg/kg body weight of ferulic acid after whole body irradiation of mice resulted disappearance of DNA strand breaks at a faster rate compared to irradiated controls, suggesting enhanced DNA repair in ferulic acid treated animals. (Mol Cell Biochem xxx: 209–217, 2005)     

Gamma ray induced bone marrow micronucleated erythrocytes in seven strains of mouse

We have investigated the effect of gamma-radiation on the frequency of bone marrow micronucleated erythrocytes in seven inbred strains of adult male mice. Twenty animals of each strain viz. Swiss, C57BL/6, C57BR/cd, C3H, CBA, DBA, and AKR were irradiated at 0.0, 0.125, 0.25, 0.50, and 1.00Gy of gamma-rays at a dose rate of 0.46Gy/min using a 60Co-teletharapy machine. Animals were sacrificed 24h post-irradiation, bone marrow smears were made and stained in May-Grunwald Giemsa for evaluating the frequency of micronucleated erythrocytes as indicators of chromosomal damage. About 2000 polychromatic erythrocytes (PCEs) and the corresponding normochromatic erythrocytes (NCEs) were scored for each mouse. Thus, at least 8000 PCEs were scored for each dose point in all the groups. The spontaneous frequency of mn-PCEs per thousand (per thousand ) cells varied considerably among the strains with C57BR/cd (3.47 per thousand ) exhibiting highest as compared to CBA (2.47 per thousand ) and DBA (2.35 per thousand). Radiation exposure, even at lowest dose of 0.125Gy, induced a significant increase in the frequency of mn-PCEs and a dose dependent response was observed among all the strains. However, the animals irradiated at lower doses (0.125-0.50Gy) showed marked differences in the extent of radiation induced chromosomal damage among the various genotypes. At highest dose of radiation (1.00Gy), genotype dependent variability in the frequency of mn-PCEs was not so marked but relatively comparable among the various strains. This study clearly shows that the magnitude of variability of radiation induced chromosomal damage among different strains of mouse can be different at different doses. Therefore, use of single dose point comparisons and/or use of only higher doses of radiation for ascertainment of genotype dependent variability in mouse may lead to erroneous conclusions.     

Differential radioprotection of tissues in C3H/J mice by a combination of 5-hydroxy L-tryptophan with 2-aminoethylisothiuronium bromide hydrobromide.

Differential radioprotection between normal tissues and carcinoma was observed in C3H/J mice treated with a combination of 5-hydroxy L-tryptophan (5-HTP, 100 mg/kg) and 2-aminoethylisothiuronium bromide hydrobromide (AET, 20 mg/kg). Protection to normal tissues was judged by LD50(30) and by radiation induced damage to bone marrow(BM) using clonogenic ability of blood forming stem cells (10 day CFUs) as the criteria. Pretreatment with 5-HTP + AET combination 30 min before whole body gamma radiation (WBGR) enhanced the recoveries of the number of blood forming stem cells in BM of irradiated mice after 0, 7th and 10th day of irradiation. LD50(30) for C3H/J mice was 7.3 Gy and the dose modifying factor (DMF) of 5-HTP + AET combination was 1.76. On the contrary, pretreatment with this combination did not protect the mammary carcinoma transplanted in C3H/J mice, when exposed to 80 Gy soft X-rays.     

In vivo radioprotection by alpha-TMG: preliminary studies

alpha-TMG is a novel water-soluble derivative of Vitamin E that has shown excellent antioxidant activity. The parent compound has demonstrated protection against radiation induced chromosomal damage in vivo. Hence, the preliminary experiments to determine the radioprotective activity of alpha-TMG were carried out in adult Swiss albino mice. Acute toxicity of the drug was studied taking 24h, 72 h and 30 day mortality after a single intraperitoneal injection of 500-2000 mg/kg body weight of the drug. The drug LD(50) for 24h and 72 h/30 day survival were found to be 1120 and 1000 mg/kg body weight, respectively. The optimum time of drug administration and drug dose-dependent effect on in vivo radiation protection of bone marrow chromosomes was studied in mice. Injection of 600 mg/kg of the drug 15 min before or within 5, 15 or 30min after 3Gy whole body gamma radiation resulted in a significant decrease in the aberrant metaphases percent at 24h post-irradiation; the maximum effect was seen when the drug was given immediately after irradiation. Injection of 200-800 mg/kg TMG within 5 min of irradiation with 3 Gy produced a significant dose-dependent reduction in the radiation induced percent aberrant metaphases and in the frequency of micronucleated erythrocytes at 24h after exposure, with a corresponding decrease in the different types of aberrations. The optimum dose for protection without drug toxicity was 600 mg/kg body weight. At this dose, TMG produced 70 and >60% reduction in the radiation induced percent aberrant metaphases and micronucleated erythrocytes, respectively. The high water solubility and effectiveness when administered post-irradiation favor TMG as a likely candidate for protection in case of accidental exposures.     

Radioprotection by mangiferin in DBAxC57BL mice: a preliminary study

The radioprotective effects of various concentrations (0, 0.25, 0.5, 1, 2, 5, 10, 17.5, 25, 50, 75 and 100 mg/kg b.wt.) of mangiferin (MGN) was studied in the DBAxC57BL mice whole body exposed to 10 Gy of gamma-irradiation. Treatment of mice with different doses of MGN, one hour before irradiation reduced the symptoms of radiation sickness and delayed the onset of mortality when compared with the non-drug treated irradiated controls. The radioprotective action of MGN increased in a dose dependent manner up to 2mg/kg and declined thereafter. The highest radioprotective effect was observed at 2mg/kg MGN, where greatest number of animals survived against the radiation-induced mortality. The administration of 0.5, 1, 2, 5, 10 and 17.5 mg/kg MGN reduced the radiation-induced gastrointestinal death as evident by a greater number of survivors up to 10 days in this group when compared with the DDW + 10 Gy irradiation group. A similar effect of MGN was observed for the radiation-induced bone marrow deaths also. Our study demonstrates that mangiferin, a gluosylxanthone, present in the Mangifera indica protected mice against the radiation-induced sickness and mortality and the optimum protective dose of 2mg/kg was 1/200 of LD50 dose (400 mg/kg) of MGN. The administration of 400 mg/kg MGN induced 50% mortality, therefore LD50 of the drug was considered to be 400 mg/kg.     

Protection of mouse bone marrow against radiation-induced chromosome damage and stem cell death by the ocimum flavonoids orientin and vicenin

In a previous study, orientin and vicenin, the water-soluble plant flavonoids, protected mice against radiation lethality (Uma Devi et al., Radiat. Res. 151, 74-78, 1999). To study bone marrow protection, adult Swiss mice were exposed to 0-6 Gy 60Co gamma rays 30 min after an intraperitoneal injection of 50 microg/ kg body weight of orientin/vicenin. Chromosomal aberrations in bone marrow were studied at 24 h postirradiation. Stem cell survival was studied using the exogenous spleen colony (CFU-S) assay. Radiation produced a dose-dependent increase in aberrant cells as well as in the yield of the different types of aberrations (breaks, fragments, rings and dicentrics) and a decrease in CFU-S. Pretreatment with either flavonoid significantly reduced the aberrant cells and different aberrations and increased the number of CFU-S compared to the respective radiation-alone groups. The dose modification factors for 50% reductions in the number of CFU-S were 1.6 for orientin and 1.7 for vicenin. The present finding that very low nontoxic doses of orientin and vicenin provide efficient protection against bone marrow damage at clinically relevant radiation doses suggests their potential for protection of normal tissues in radiotherapy.     

Efficiency of Coleus aromaticus extract in modifying cyclophosphamide and mitomycin-C induced clastogenicity in mouse bone marrow cells

The anticlastogenic potency of the ethanolic extract of a medicinal plant, C. aromaticus was investigated by taking bone marrow chromosomal aberration assay and micronucleus (MN) test as the test parameters. Swiss albino mice were fed orally with different doses (10,15, 25, 50 and 100 mg/kg body weight) of ethanolic extract for 7 days and on the 7th day, two doses each of anticancer drugs cyclophosphamide (CP; 25 and 50 mg/kg body weight) and mitomycin-C (MMC; 4 and 8 mg/kg body weight) were injected, ip, to different groups of animals. Bone marrow MN preparations were made at 24 and 48 hr time intervals. Coleus extract reduced CP and MMC induced MN and lower doses of the extract were found to be more effective than higher doses. The effective doses of extract in MN test were selected to study the anticlastogenic effects against CP (25 and 50 mg/kg body weight) and MMC (2 and 4 mg/kg body weight) induced chromosomal aberrations. The results indicate the protective effect of C. aromaticus against CP and MMC induced cytogenetic damage.     

Mutagenic evaluation of tromaril (N-beta-phenylethylanthranilic acid), a novel anti-inflammatory drug, using mammalian test systems

The mutagenic effect of tromaril, a new anti-inflammatory drug, was assessed in Swiss male mice employing bone-marrow micronucleus induction, abnormal sperm formation, and the induction of meiotic chromosome anomalies in spermatocytes as the test parameters. Administration of tromaril induced significantly higher percentages of MN and abnormal sperm at 600 and 900 mg/kg body wt., whereas chromosomal anomalies in spermatocytes were significantly higher at all the 3 doses of 300, 600 and 900 mg/kg body wt. at time intervals of 7, 15 and 30 days as compared to parallel controls.     

Protection from radiation-induced apoptosis by the radioprotector amifostine (WR-2721) is radiation dose dependent

The radioprotective agent amifostine is a free radical scavenger that can protect cells from the damaging effects of ionising radiation when administered prior to radiation exposure. However, amifostine has also been shown to protect cells from chromosomal mutations when administered after radiation exposure. As apoptosis is a common mechanism by which cells with mutations are removed from the cell population, we investigated whether amifostine stimulates apoptosis when administered after radiation exposure. We chose to study a relatively low dose which is the maximum radiation dose for radiation emergency workers (0.25 Gy) and a high dose relevant to radiotherapy exposures (6 Gy). Mice were administered 400 mg/kg amifostine 30 min before, or 3 h after, whole-body irradiation with 0.25 or 6 Gy X-rays and apoptosis was analysed 3 or 7 h later in spleen and bone marrow. We observed a significant increase in radiation-induced apoptosis in the spleen of mice when amifostine was administered before or after 0.25 Gy X-rays. In contrast, when a high dose of radiation was used (6 Gy), amifostine caused a reduction in radiation-induced apoptosis 3 h post-irradiation in spleen and bone marrow similar to previously published studies. This is the first study to investigate the effect of amifostine on radiation-induced apoptosis at a relatively low radiation dose and the first to demonstrate that while amifostine can reduce apoptosis from high doses of radiation, it does not mediate the same effect in response to low-dose exposures. These results suggest that there may be a dose threshold at which amifostine protects from radiation-induced apoptosis and highlight the importance of examining a range of radiation doses and timepoints.     

Radioprotective effect of combinations of WR-2721 and mercaptopropionylglycine on mouse bone marrow chromosomes

The radioprotective and toxic effects of low to moderate doses of S-2-(3-aminopropylamino)ethyl phosphorothioic acid (WR-2721) and its combination with mercaptopropionylglycine (MPG, 20 mg/kg body wt) on the chromosomes of the bone marrow cells of Swiss albino mice were studied at 24 h and 14 days postirradiation. Significant protection against radiation-induced chromosome aberrations was observed with 50 mg/kg WR-2721. The protection increased with the dose of the drug administered, and the degree of protection per unit dose increment was more pronounced at lower than at higher doses. A combination of WR-2721 and MPG given before exposure resulted in a significantly greater number of normal metaphases at 24 h postirradiation compared to the respective single-drug treatment groups. On Day 14 postirradiation, when the presence of WR-2721 resulted in an increase in the frequency of aberrant cells, combination with MPG helped to reduce this value markedly, especially at WR-2721 doses below 200 mg/kg. On the basis of these results it is suggested that 150 mg/kg WR-2721 may be considered an optimum dose for combination with MPG for protection of chromosomes of bone marrow cells when repeated drug administrations are not needed. Changes in the level of glutathione (GSH) in the blood were studied at different times following the administration of 150 mg/kg WR-2721 and its combination with MPG (20 mg/kg) before sham irradiation or exposure to 4.5 Gy 60Co gamma rays. The results showed that WR-2721 elevated blood GSH levels significantly above normal values by the time radiation was delivered, while MPG did not. Glutathione appears to have an important role in the action of WR-2721, while protection by MPG may not be mediated through GSH. Injection of MPG after WR-2721 helps to maintain the higher GSH level for a longer duration compared to treatment with WR-2721 alone. It is possible that MPG delays the metabolism of GSH.     

Anticlastogenic effects of a polyvitamin product, 'Pharmavit', on gamma-ray induction of somatic and germ cell chromosome aberrations in the mouse.

The polyvitamin product 'Pharmavit' (Pv), comprising vitamins A, D2, B1, B2, B6, C, E, nicotinamide, and calcium pantothene, was tested for anticlastogenic properties against gamma-rays in mice. Pretreatment with Pv consisted of daily administration by gavage for 30 days at dose levels corresponding to clinical recommendations for an adult human, as recalculated in terms of mg/kg. Findings indicated a reduction of chromosome aberrations in bone marrow cells from mice exposed to 3.0 Gy 137Cs gamma-rays; the reduction concerned predominantly fragments of the chromatid type. Furthermore, a reduction factor of 1.6 was obtained for the frequency of reciprocal translocations induced by spermatogonial irradiation in mice exposed to 4.0 Gy gamma-rays. Pretreatment with vitamin C alone, at the dose present in Pv, proved nearly ineffective in protecting from chromosome aberrations in bone marrow cells. Pharmavit is believed to be a promising agent for application to human populations exposed to the carcinogenic and genetic hazards of ionizing radiation.     

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.     

Protective effect of sesamol against 60Co γ-ray-induced hematopoietic and gastrointestinal injury in C57BL/6 male mice

Abstract

Protection of γ-ray-induced injury in hematopoietic and gastrointestinal (GI) systems is the rationale behind developing radioprotectors. The objective of this study, therefore, was to investigate the radioprotective efficacy and mechanisms underlying sesamol in amelioration of γ-ray-induced hematopoietic and GI injury in mice. C57BL/6 male mice were pre-treated with a single dose (100 or 50 mg/kg, 30 min prior) of sesamol through the intraperitoneal route and exposed to LD_50/30 (7.5 Gy) and sublethal (5 Gy) dose of γ-radiation. Thirty-day survival against 7.5 Gy was monitored. Sesamol (100 mg/kg) pre-treatment reduced radiation-induced mortality and resulted survival of about 100% against 7.5 Gy of γ-irradiation. Whole-body irradiation drastically depleted hematopoietic progenitor stem cells in bone marrow, B cells, T cell subpopulations, and splenocyte proliferation in the spleen on day 4, which were significantly protected in sesamol pre-treated mice. This was associated with a decrease of radiation-induced micronuclei (MN) and apoptosis in bone marrow and spleen, respectively. Sesamol pre-treatment inhibited lipid peroxidation, translocation of gut bacteria to spleen, liver, and kidney, and enhanced regeneration of crypt cells in the GI system. In addition, sesamol pre-treatment reduced the radiation-induced pattern of expression of p53 and Bax apoptotic proteins in the bone marrow, spleen, and GI. This reduction in apoptotic proteins was associated with the increased anti-apoptotic-Bcl-x and PCNA proteins. Further, assessment of antioxidant capacity using ABTS and DPPH assays revealed that sesamol treatment alleviated total antioxidant capacity in spleen and GI tissue. In conclusion, the results of the present study suggested that sesamol as a single prophylactic dose protects hematopoietic and GI systems against γ-radiation-induced injury in mice.     

The modifying effect of beta-carotene on gamma radiation-induced elevation of oxidative reactions and genotoxicity in male rats

The aim of the present work was to evaluate the modulatory role of beta-carotene on the radiation-induced changes in certain biochemical and cytogenetic parameters. beta-Carotene was given by gavage at a dose of 5 mg/kg body weight for 7 consecutive days before whole body gamma irradiation with 7 Gy (single dose). The levels of beta-carotene in plasma, thiobarbituric acid-reactive substances (TBARS) in plasma and liver, the activities of superoxide dismutase (SOD) and catalase in blood and liver were the selected parameters. Furthermore, the frequency of micronuclei (MN) of polychromatic erythrocytes (PCEs), normochromatic erythrocytes (NCEs), the ratio of PCEs/NCEs and the mitotic index (MI) of bone marrow cells were also evaluated. The biochemical and cytogenetic determinations were carried out 1, 24, and 72 h after radiation exposure.The results obtained revealed that administration of beta-carotene pre-irradiation significantly inhibited the decrease in plasma beta-carotene, significantly reduced the levels of TBARS in plasma and liver. Significant protection of the radiation-induced changes in the activities of SOD and catalase was also recorded in the blood and liver of beta-carotene-treated and -irradiated rats. beta-Carotene resulted in significant inhibition in the frequency of radiation-induced MN, as well as in the ratio of PCEs/NCEs and the MI of bone marrow cells. These results suggest that beta-carotene as a natural product with its antioxidant capacity and capability of quenching singlet oxygen, could play a modulatory role against the cellular damage affected by free radicals induced by whole body 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.     

mFISH analysis of chromosomal damage in bone marrow cells collected from CBA/CaJ mice following whole body exposure to heavy ions (<Superscript>56</Superscript>Fe ions)

To date, there is scant information on in vivo induction of chromosomal damage by heavy ions found in space (i.e. ⁵⁶Fe ions). For radiation-induced response to be useful for risk assessment, it must be established in in vivo systems especially in cells that are known to be at risk for health problems associated with radiation exposure (such as hematopoietic cells, the known target tissue for radiation-induced leukemia). In this study, the whole genome multicolor fluorescence in situ hybridization (mFISH) technique was used to examine the in vivo induction of chromosomal damage in hematopoietic tissues, i.e. bone marrow cells. These cells were collected from CBA/CaJ mice at day 7 following whole-body exposure to different doses of 1 GeV/amu ⁵⁶Fe ions (0, 0.1, 0.5 and 1.0 Gy) or ¹³⁷Cs γ rays as the reference radiation (0, 0.5, 1.0 and 3.0 Gy, at the dose rate of 0.72 Gy/min using a GammaCell40). These radiation doses were the average total-body doses. For each radiation type, there were four mice per dose. Several types of aberrations in bone marrow cells collected from mice exposed to either type of radiation were found. These were exchanges and breaks (both chromatid- and chromosome-types). Chromosomal exchanges included translocations (Robertsonian or centric fusion, reciprocal and incomplete types), and dicentrics. No evidence of a non-random involvement of specific chromosomes in any type of aberrations observed in mice exposed to ⁵⁶Fe ions or ¹³⁷Cs γ rays was found. At the radiation dose range used in our in vivo study, the majority of exchanges were simple. Complex exchanges were detected in bone marrow cells collected from mice exposed to 1 Gy of ⁵⁶Fe ions or 3 Gy of ¹³⁷Cs γ rays only, but their frequencies were low. Overall, our in vivo data indicate that the frequency of complex chromosome exchanges was not significantly different between bone marrow cells collected from mice exposed to ⁵⁶Fe ions or ¹³⁷Cs γ rays. Each type of radiation induced significant dose-dependent increases (ANOVA, P < 0.01) in the frequencies of chromosomal damage, including the numbers of abnormal cells. Based upon the linear-terms of dose-response curves, ⁵⁶Fe ions were 1.6 (all types of exchanges), 4.3 (abnormal cells) and 4.2 (breaks, both chromatid- and chromosome-types) times more effective than ¹³⁷Cs γ rays in inducing chromosomal damage.     

Water soluble vitamin E (TMG) as a radioprotector

Tocopherol monoglucoside (TMG), a water soluble derivative of vitamin E offers protection against deleterious effects of ionizing radiation, both under in vivo and in vitro conditions, to biological systems. TMG was found to be a potent antioxidant and an effective free radical scavenger. It forms a phenoxyl radical similar to trolox upon reaction with various one-electron oxidants. TMG protected DNA from radiation-induced strand breaks. It also protected thymine glycol formation induced by gamma-radiation. Gamma-radiation-induced loss of viability of EL-tumor cells and peroxidation of lipids in microsomal and mitochondrial membranes were prevented by TMG. TMG was nontoxic to mice when administered orally up to 7.0 g/kg body weight. The LD50 dose of TMG for ip administration in mice was 1.15 g/kg body wt. In rats, following oral and ip administration of TMG, the absorption (distribution) half lives were 5.8 and 3.0 min respectively and elimination half lives were 6.7 and 3.1 min respectively. Embryonic mortality resulting from exposure of pregnant mice to ionizing radiation (2 Gy) was reduced by 75% by ip administration of TMG (0.6 g/kg, body wt) prior to irradiation. TMG offered protection to mice against whole body gamma-radiation-induced lethality and weight loss. The LD50(30) of mice increased from 6 to 6.72 Gy upon post irradiation administration of a single dose of TMG (0.6 g/kg, body wt) by ip.