In VivoPostirradiation Protection by a Vitamin E Analog, α-TMG

Feasibility of Reducing Animal Numbers in Radiation Countermeasure Experiments from Historic Levels when using Sample Size Calculations

Historically, animal numbers have most often been in the hundreds for experiments designed to estimate the dose reduction factor (DRF) of a radiation countermeasure treatment compared to a control treatment. Before 2010, researchers had to rely on previous experience, both from others and their own, to determine the number of animals needed for a DRF experiment. In 2010, a formal sample size formula was developed by Kodell et al. This theoretical work showed that sample sizes for realistic, yet hypothetical, DRF experiments could be less than a hundred animals and still have sufficient power to detect clinically meaningful DRF values. However, researchers have been slow to use the formula for their DRF experiments, whether from ignorance to its existence or hesitancy to depart from "tried and true" sample sizes. Here, we adapt the sample size formula to better fit usual DRF experiments, and, importantly, we provide real experimental evidence from two independent DRF experiments that sample sizes smaller than what have typically been used can still statistically detect clinically meaningful DRF values. In addition, we update a literature review of DRF experiments which can be used to inform future DRF experiments, provide answers to questions that researchers have asked when considering sample size calculations rather than solely relying on previous experience, whether their own or others', and, in the supplementary material, provide R code implementing the formula, along with several exercises to familiarize the user with the adapted formula.

Phytochemicals: A potential next generation agent for radioprotection

BACKGROUND

Radiation hazards are accountable for extensive damage in the biological system and acts as a public health burden. Owing to the rapid increasing in radiation technology, both Ionizing radiation (IR) from natural and man made source poses detrimental outcome to public health. IR releases free radicals which induces oxidative stress and deleterious biological damage by modulating radiation induced signalling intermediates. The efficacy of existing therapeutic approach and treatment strategy are limited owing to their toxicity and associated side effects. Indian system of traditional medicine is enriched with prospective phytochemicals with potential radioprotection ability.

PURPOSE

The present review elucidated and summarized the potential role of plant derived novel chemical compound with prospective radioprotective potential.

METHOD

So far as the traditional system of Indian medicine is concerned, plant kingdom is enriched with potential bioactive molecules with diverse pharmacological activities. We reviewed several compounds mostly secondary metabolites from plant origin using various search engines.

RESULTS

Both compounds from land plants and marine source exhibited antioxidant antiinflammatory, free radical scavenging ability. These compounds have tremendous potential in fine-tuning of several signalling intermediates, which are actively participated in the progression and development of a pathological condition associated with radiation stress.

CONCLUSION

Development and explore of an operational radioprotective agent from originated from plant source that can be used as a novel molecular tool to eliminate the widespread damage caused by space exploration, ionizing radiation, nuclear war and radiotherapy has been significantly appreciated. Through extensive literature search we highlighted several compounds from both land plant and marine origin can be implemented for a better therapeutic potential against radiation induced injury. Furthermore, extensive clinical trials must be carried out in near future for better therapeutic modality and clinical efficacy.

Study logistics that can impact medical countermeasure efficacy testing in mouse models of radiation injury

PURPOSE

To address confounding issues that have been noted in planning and conducting studies to identify biomarkers of radiation injury, develop animal models to simulate these injuries, and test potential medical countermeasures to mitigate/treat damage caused by radiation exposure.

METHODS

The authors completed an intensive literature search to address several key areas that should be considered before embarking on studies to assess efficacy of medical countermeasure approaches in mouse models of radiation injury. These considerations include: (1) study variables; (2) animal selection criteria; (3) animal husbandry; (4) medical management; and (5) radiation attributes.

RESULTS

It is important to select mouse strains that are capable of responding to the selected radiation exposure (e.g. genetic predispositions might influence radiation sensitivity and proclivity to certain phenotypes of radiation injury), and that also react in a manner similar to humans. Gender, vendor, age, weight, and even seasonal variations are all important factors to consider. In addition, the housing and husbandry of the animals (i.e. feed, environment, handling, time of day of irradiation and animal restraint), as well as the medical management provided (e.g. use of acidified water, antibiotics, routes of administration of drugs, consideration of animal numbers, and euthanasia criteria) should all be addressed. Finally, the radiation exposure itself should be tightly controlled, by ensuring a full understanding and reporting of the radiation source, dose and dose rate, shielding and geometry of exposure, while also providing accurate dosimetry. It is important to understand how all the above factors contribute to the development of radiation dose response curves for a given animal facility with a well-defined murine model.

CONCLUSIONS

Many potential confounders that could impact the outcomes of studies to assess efficacy of a medical countermeasure for radiation-induced injuries are addressed, and recommendations are made to assist investigators in carrying out research that is robust, reproducible, and accurate.

Appraisal of biochemical classes of radioprotectors: evidence, current status and guidelines for future development

The search for efficient radioprotective agents to protect from radiation-induced toxicity, due to planned or accidental radiation exposure, is still ongoing worldwide. Despite decades of research and development of widely different biochemical classes of natural and derivative compounds, a safe and effective radioprotector is largely unmet. In this comprehensive review, we evaluated the evidence for the radioprotective performance of classical thiols, vitamins, minerals, dietary antioxidants, phytochemicals, botanical and bacterial preparations, DNA-binding agents, cytokines, and chelators including adaptogens. Where radioprotection was demonstrated, the compounds have shown moderate dose modifying factors ranging from 1.1 to 2.7. To date, only few compounds found way to clinic with limited margin of dose prescription due to side effects. Most of these compounds (amifostine, filgratism, pegfilgrastim, sargramostim, palifermin, recombinant salmonella flagellin, Prussian blue, potassium iodide) act primarily via scavenging of free radicals, modulation of oxidative stress, signal transduction, cell proliferation or enhance radionuclide elimination. However, the gain in radioprotection remains hampered with low margin of tolerance. Future development of more effective radioprotectors requires an appropriate nontoxic compound, a model system and biomarkers of radiation exposure. These are important to test the effectiveness of radioprotection on physiological tissues during radiotherapy and field application in cases of nuclear eventualities.

Pharmacological Modulation of Radiation Damage. Does It Exist a Chance for Other Substances than Hematopoietic Growth Factors and Cytokines?

In recent times, cytokines and hematopoietic growth factors have been at the center of attention for many researchers trying to establish pharmacological therapeutic procedures for the treatment of radiation accident victims. Two granulocyte colony-stimulating factor-based radiation countermeasures have been approved for the treatment of the hematopoietic acute radiation syndrome. However, at the same time, many different substances with varying effects have been tested in animal studies as potential radioprotectors and mitigators of radiation damage. A wide spectrum of these substances has been studied, comprising various immunomodulators, prostaglandins, inhibitors of prostaglandin synthesis, agonists of adenosine cell receptors, herbal extracts, flavonoids, vitamins, and others. These agents are often effective, relatively non-toxic, and cheap. This review summarizes the results of animal experiments, which show the potential for some of these untraditional or new radiation countermeasures to become a part of therapeutic procedures applicable in patients with the acute radiation syndrome. The authors consider β-glucan, 5-AED (5-androstenediol), meloxicam, γ-tocotrienol, genistein, IB-MECA (N⁶-(3-iodobezyl)adenosine-5'-N-methyluronamide), Ex-RAD (4-carboxystyryl-4-chlorobenzylsulfone), and entolimod the most promising agents, with regards to their contingent use in clinical practice.

Prospects in the development of natural radioprotective therapeutics with anti-cancer properties from the plants of Uttarakhand region of India

Radioprotective agents are substances those reduce the effects of radiation in healthy tissues while maintaining the sensitivity to radiation damage in tumor cells. Due to increased awareness about radioactive substances and their fatal effects on human health, radioprotective agents are now the topic of vivid research. Scavenging of free radicals is the most common mechanism in oncogenesis that plays an important role in protecting tissues from lethal effect of radiation exposure therefore radioprotectors are also good anti-cancer agents. There are numerous studies indicating plant-based therapeutics against cancer and radioprotection. Such plants could be further explored for developing them as promising natural radioprotectors with anti-cancer properties. This review systematically presents information on plants having radioprotective and anti-cancer properties.

Vitamin E Analogs as Radiation Response Modifiers

The potentially life-threatening effects of total body ionizing radiation exposure have been known for more than a century. Despite considerable advances in our understanding of the effects of radiation over the past six decades, efforts to identify effective radiation countermeasures for use in case of a radiological/nuclear emergency have been largely unsuccessful. Vitamin E is known to have antioxidant properties capable of scavenging free radicals, which have critical roles in radiation injuries. Tocopherols and tocotrienols, vitamin E analogs together known as tocols, have shown promise as radioprotectors. Although the pivotal mechanisms of action of tocols have long been thought to be their antioxidant properties and free radical scavenging activities, other alternative mechanisms have been proposed to drive their activity as radioprotectors. Here we provide a brief overview of the effects of ionizing radiation, the mechanistic mediators of radiation-induced damage, and the need for radiation countermeasures. We further outline the role for, efficacy of, and mechanisms of action of tocols as radioprotectors, and we compare and contrast their efficacy and mode of action with that of another well-studied chemical radioprotector, amifostine.

Radioprotectors - the evergreen topic

To protect organisms from ionizing radiation (IR), and to reduce morbidity or mortality, various agents, called radioprotectors, have been utilized. Because radiation-induced cellular damage is attributed primarily to the harmful effects of free radicals, molecules with radical-scavenging properties are particularly promising as radioprotectors. Early development of such agents focused on thiol synthetic compounds, known as WR protectors, but only amifostine (WR-2721) has been used in clinical trials as an officially approved radioprotector. Besides thiol compounds, various compounds with different chemical structure were investigated, but an ideal radioprotector has not been found yet. Plants and natural products have been evaluated as promising sources of radioprotectors because of their low toxicity, although they exhibit an inferior protection level compared to synthetic thiol compounds. Active plant constituents seem to exert the radioprotection through antioxidant and free radical-scavenging activities. Our research established that plants containing polyphenolic compounds (raspberry, blueberry, strawberry, grape, etc.) exhibit antioxidative activities and protect genetic material from IR.

Gamma-tocopherol-N,N-dimethylglycine ester as a potent post-irradiation mitigator against whole body X-irradiation-induced bone marrow death in mice

We examined the radioprotective and mitigative effects of gamma-tocopherol-N,N-dimethylglycine ester (GTDMG), a novel water-soluble gamma-tocopherol derivative, against X-irradiation-induced bone marrow death in mice. Mice (C3H, 10 weeks, male) were injected intraperitoneally with GTDMG suspended in a 0.5% methyl cellulose solution before or after receiving of 7.5-Gy whole body X-irradiation. GTDMG significantly enhanced the 30-day survival rate when given 30 min before or immediately after the irradiation. Its mitigative activity (administered after exposure) was examined further in detail. The optimal concentration of GTDMG given immediately after irradiation was around 100 mg/kg body weight (bw) and the 30-day survival rate was 97.6 ± 2.4%. When GTDMG was administered 1, 10 and 24 h post-irradiation, the survival rate was 85.7 ± 7.6, 75.0 ± 9.7 and 36.7 ± 8.8%, respectively, showing significant mitigation even at 24 h after irradiation (P < 0.05). The value of the dose reduction factor (100 mg/kg bw, given intraperitoneally (i.p.) immediately after irradiation) was 1.25. GTDMG enhanced the recovery of red blood cell-, white blood cell-, and platelet-counts after irradiation and significantly increased the number of endogenous spleen colonies (P < 0.05). Subcutaneous (s.c.) administration also had mitigative effects. In conclusion, GTDMG is a potent radiation mitigator.

Vitamin E: tocopherols and tocotrienols as potential radiation countermeasures

Despite the potential devastating health consequences of intense total-body irradiation, and the decades of research, there still remains a dearth of safe and effective radiation countermeasures for emergency, radiological/nuclear contingencies that have been fully approved and sanctioned for use by the US FDA. Vitamin E is a well-known antioxidant, effective in scavenging free radicals generated by radiation exposure. Vitamin E analogs, collectively known as tocols, have been subject to active investigation for a long time as radioprotectors in patients undergoing radiotherapy and in the context of possible radiation accidents or terrorism scenarios. Eight major isoforms comprise the tocol group: four tocopherols and four tocotrienols. A number of these agents and their derivatives are being investigated actively as radiation countermeasures using animal models, and several appear promising. Although the tocols are well recognized as potent antioxidants and are generally thought to mediate radioprotection through 'free radical quenching', recent studies have suggested several alternative mechanisms: most notably, an 'indirect effect' of tocols in eliciting specific species of radioprotective growth factors/cytokines such as granulocyte colony-stimulating factor (G-CSF). The radioprotective efficacy of at least two tocols has been abrogated using a neutralizing antibody of G-CSF. Based on encouraging results of radioprotective efficacy, laboratory testing of γ-tocotrienol has moved from a small rodent model to a large nonhuman primate model for preclinical evaluation. In this brief review we identify and discuss selected tocols and their derivatives currently under development as radiation countermeasures, and attempt to describe in some detail their in vivo efficacy.

Practical advice on calculating confidence intervals for radioprotection effects and reducing animal numbers in radiation countermeasure experiments

The dose of a substance that causes death in P% of a population is called an LDP, where LD stands for lethal dose. In radiation research, a common LDP of interest is the radiation dose that kills 50% of the population by a specified time, i.e., lethal dose 50 or LD50. When comparing LD50 between two populations, relative potency is the parameter of interest. In radiation research, this is commonly known as the dose reduction factor (DRF). Unfortunately, statistical inference on dose reduction factor is seldom reported. We illustrate how to calculate confidence intervals for dose reduction factor, which may then be used for statistical inference. Further, most dose reduction factor experiments use hundreds, rather than tens of animals. Through better dosing strategies and the use of a recently available sample size formula, we also show how animal numbers may be reduced while maintaining high statistical power. The illustrations center on realistic examples comparing LD50 values between a radiation countermeasure group and a radiation-only control. We also provide easy-to-use spreadsheets for sample size calculations and confidence interval calculations, as well as SAS® and R code for the latter.

A novel microplate-based assay for screening radioprotectors and its validation based on DNA and membrane system

Ionizing radiation leads to damage at various cellular and sub-cellular levels and can be prevented by radioprotectors. There are many in vitro and in vivo but rather expensive assays for screening of radioprotectors from natural and synthetic sources. We have developed a cell free radioprotector screening assay which involves bleaching of crocin pigment, isolated from saffron by radiolytic products of water. Any molecules/compounds which can inhibit the bleaching of the crocin will act as a radioprotector. The developed assay was further validated by the existing in vitro assays. Different radioprotectors have different level for inhibition of bleaching of crocin. The trends of radioprotection offered by crocin bleaching assay, plasmid relaxation and lipid peroxidation are TMG>FA>VA>Amifos>Trox, TMG>VA>FA>Amifos>Trox, and TMG>FA>Trox>VA>Amifos, respectively. We are getting different trends for different assays. This is because different drugs have different mechanisms of radioprotection in different assay systems. In conclusion, the crocin bleaching assay developed here is a simple, fast and economical screening assay and it will have great value in radioprotection programme for screening many potential compounds for radioprotection.

Dose-modifying factor for captopril for mitigation of radiation injury to normal lung

Our goal is to develop countermeasures for pulmonary injury following unpredictable events such as radiological terrorism or nuclear accidents. We have previously demonstrated that captopril, an angiotensin converting enzyme (ACE) inhibitor, is more effective than losartan, an angiotensin type-1 receptor blocker, in mitigating radiation-pneumopathy in a relevant rodent model. In the current study we determined the dose modifying factors (DMFs) of captopril for mitigation of parameters of radiation pneumonitis. We used a whole animal model, irradiating 9-10-week-old female rats derived from a Wistar strain (WAG/RijCmcr) with a single dose of irradiation to the thorax of 11, 12, 13, 14 or 15 Gy. Our study develops methodology to measure DMFs for morbidity (survival) as well as physiological endpoints such as lung function, taking into account attrition due to lethal radiation-induced pneumonitis. Captopril delivered in drinking water (140-180 mg/m(2)/day, comparable with that given clinically) and started one week after irradiation has a DMF of 1.07-1.17 for morbidity up to 80 days (survival) and 1.21-1.35 for tachypnea at 42 days (at the peak of pneumonitis) after a single dose of ionizing radiation (X-rays). These encouraging results advance our goals, since DMF measurements are essential for drug labeling and comparison with other mitigators.

CBLB613: a TLR 2/6 agonist, natural lipopeptide of Mycoplasma arginini , as a novel radiation countermeasure

To date, there are no safe and effective drugs available for protection against ionizing radiation damage. Therefore, a great need exists to identify and develop non-toxic agents that will be useful as radioprotectors or postirradiation therapies under a variety of operational scenarios. We have developed a new pharmacological agent, CBLB613 (a naturally occurring Mycoplasma-derived lipopeptide ligand for Toll-like receptor 2/6), as a novel radiation countermeasure. Using CD2F1 mice, we investigated CBLB613 for toxicity, immunogenicity, radioprotection, radiomitigation and pharmacokinetics. We also evaluated CBLB613 for its effects on cytokine induction and radiation-induced cytopenia in unirradiated and irradiated mice. The no-observable-adverse-effect level of CBLB613 was 1.79 mg/kg and 1 mg/kg for single and repeated doses, respectively. CBLB613 significantly protected mice against a lethal dose of (60)Co γ radiation. The dose reduction factor of CBLB613 as a radioprotector was 1.25. CBLB613 also mitigated the effects of (60)Co γ radiation on survival in mice. In both irradiated and unirradiated mice, the drug stimulated induction of interleukin-1β (IL-1β), IL-6, IL-10, IL-12, keratinocyte-derived chemokine, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumor necrosis factor-1α. CBLB613 also reduced radiation-induced cytopenia and increased bone marrow cellularity in irradiated mice. Our immunogenicity study demonstrated that CBLB613 is not immunogenic in mice, indicating that it could be developed as a radioprotector and radiomitigator for humans against the potentially lethal effects of radiation exposure.

Fukushima Daiichi Nuclear Power Plant accident: facts, environmental contamination, possible biological effects, and countermeasures

On March 11, 2011, an earthquake led to major problems at the Fukushima Daiichi Nuclear Power Plant. A 14-m high tsunami triggered by the earthquake disabled all AC power to Units 1, 2, and 3 of the Power Plant, and carried off fuel tanks for emergency diesel generators. Despite many efforts, cooling systems did not work and hydrogen explosions damaged the facilities, releasing a large amount of radioactive material into the environment. In this review, we describe the environmental impact of the nuclear accident, and the fundamental biological effects, acute and late, of the radiation. Possible medical countermeasures to radiation exposure are also discussed.

Vascular homeostasis regulators, Edn1 and Agpt2, are upregulated as a protective effect of heat-treated zinc yeast in irradiated murine bone marrow

PURPOSE

To elucidate the mechanism underlying the in vivo radioprotection activity by Zn-containing, heat-treated Saccharomyces cerevisiae yeast (Zn-yeast).

MATERIALS AND METHODS

Zn-yeast suspension was administered into C3H/He mice immediately after whole body irradiation (WBI) at 7.5 Gy. Bone marrow was extracted from the mice 6 hours after irradiation and analyzed on a microarray. Expression changes in the candidate responsive genes differentially expressed in treated mice were re-examined by qRT-PCR. The bone marrow was also examined pathologically at 6 h, 3, 7, and 14 days postirradiation.

RESULTS

Thirty-six genes, including Edn1 and Agpt2, were identified as candidate responsive genes in irradiated mouse bone marrow treated with Zn-yeast by showing a greater than three-fold change compared with control (no irradiation and no Zn-yeast) mice. The expressions of Cdkn1a, Bax, and Ccng, which are well known as radioresponsive genes, were upregulated in WBI mice and Zn-yeast treated WBI mice. Pathological examination showed the newly formed microvessels lined with endothelial cells, and small round hematopoietic cells around vessels in bone marrow matrix of mice administered with Zn-yeast after WBI, while whole-body irradiated mice developed fatty bone marrow within 2 weeks after irradiation.

CONCLUSION

This study identified a possible mechanism for the postirradiation protection conferred by Zn-yeast. The protective effect of Zn-yeast against WBI is related to maintaining the bone marrow microenvironment, including targeting endothelial cells and cytokine release.

Heat-treated mineral-yeast as a potent post-irradiation radioprotector

In vivo radioprotection of C3H mice by i.p. administration of Zn-, Mn-, Cu-, or Se-containing heat-treated Saccharomyces serevisiae yeast sample was examined. The 30-day survival of the group treated 30 min before 7.5 Gy whole-body X-irradiation with mineral-containing yeast powders suspended in 0.5% methylcellulose was significantly higher than that of control group. When mineral-yeast was administered immediately after irradiation, the survival rate was even higher and Zn- or Cu-yeast showed the highest rate (more than 90%). Although treatment with simple yeast showed a high survival rate (73%), it was significantly lower than that obtained by the Zn-yeast treatment. The effects of Zn-yeast were studied further. When the interval between irradiation and administration was varied, the protective activity of Zn-yeast decreased gradually by increasing the interval but was still significantly high for the administration at 10 h post-irradiation. The dose reduction factor of Zn-yeast (100 mg/kg, i.p. administration immediately after irradiation) was about 1.2. When the suspension of Zn-yeast was fractionated by centrifugation, the insoluble fraction showed a potent effect, while the soluble fraction had only a moderate effect. In conclusion, mineral-yeast, especially Zn-yeast, provides remarkable post-irradiation protection against lethal whole body X-irradiation. The activity is mainly attributable to the insoluble fraction, whereas some soluble components might contribute to the additional protective activity.

Radioprotective effect of sulfasalazine on mouse bone marrow chromosomes

Sulfasalazine (SAZ), a prescribed drug for inflammatory bowel disease, is a potent scavenger of reactive oxygen species. The present study was undertaken to ascertain its ability to protect against gamma radiation-induced damage. Acute toxicity of the drug was studied taking 24-h, 72-h and 30-day mortality after a single intraperitoneal injection of 400-1200 mg/kg body weight (b.wt.) of the drug. The drug LD(50) for 24- and 72-h/30-day survival were found to be 933 and 676 mg/kg b.wt., 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 30-180 mg/kg SAZ 30 min before gamma irradiation (RT) with 4 Gy produced a significant dose-dependent reduction in the RT-induced percent aberrant metaphases and in the frequency of micronucleated erythrocytes at 24 h after exposure, with a corresponding decrease in the different types of aberrations. The optimum dose for protection without drug toxicity was 120 mg/kg b.wt. At this dose, SAZ produced >60% reduction in the RT-induced percent aberrant metaphases and micronucleated erythrocytes. SAZ also produced a significant increase in the ratio of polychromatic erythrocytes to normochromatic erythrocytes from that of irradiated control. Injection of 120 mg/kg of the drug 60 or 30 min before or within 15 min after 4 Gy whole-body RT resulted in a significant decrease in the percent of aberrant metaphases and in the frequency of micronucleated erythrocytes at 24 h post-irradiation; the maximum effect was seen when the drug was administered 30 min before irradiation. These results show that SAZ protect mice against RT-induced chromosomal damage and cell cycle progression delay. SAZ also protected plasmid DNA (pGEM-7Zf) against Fenton's reactant-induced breaks, suggesting free radical scavenging as one of the possible mechanism for radiation protection.

Modulation of DNA Damage by Pentoxifylline and α-Tocopherol in Skin Fibroblasts Exposed to Gamma Rays

Previous in vivo studies showed the combination pentoxifylline (PTX) and alpha-tocopherol was highly efficient in reducing late radiation-induced skin damage. The present work aimed at investigating the molecular and cellular mechanisms involved in the effects of this combination. Primary cultures of confluent dermal fibroblasts were gamma-irradiated in the presence of PTX and trolox (Tx), the water-soluble analogue of alpha-tocopherol. Drugs were added either before or after radiation exposure and were maintained over time. Their antioxidant capacity and their effect on radiation-induced ROS production was assessed together with cell viability and clonogenicity. DNA damage formation was assessed by the alkaline comet assay and by the micronucleus (MN) test. Cell cycle distribution was also determined. The combination of PTX/ Tx was shown to reduce both immediate and late ROS formation observed in cells after irradiation. Surprisingly, decrease in DNA strand breaks measured by the comet assay was observed any time drugs were added. In addition, the micronucleus test revealed that for cells irradiated with 10 Gy, a late significant increase in MN formation occurred. The combination of PTX/Tx was shown to be antioxidant and to decrease radiation-induced ROS production. The observed effects on DNA damage at any time the drugs were added suggest that PTX/Tx could interfere with the DNA repair process.

Post-irradiation dietary vitamin E does not affect the development of radiation-induced lung damage in rats

The purpose of this study was to investigate whether application of post-irradiation vitamin E, an anti-oxidant, could prevent the development of radiation induced lung damage. Wistar rats were given vitamin E enriched or vitamin E deprived food starting from 4 weeks after 18Gy single dose irradiation of the right thorax. Neither breathing frequencies nor CT density measurements revealed differences between the groups. It is concluded that post-irradiation vitamin E does not influence radiation-induced fibrosis to the lung.