Opportunities for nutritional amelioration of radiation-induced cellular damage

Individual response of the ocular lens to ionizing radiation

PURPOSE

Cataract (opacification of the ocular lens) is a typical tissue reaction (deterministic effect) following ionizing radiation exposure, for which prevention dose limits have been recommended in the radiation protection system. Manifestations of radiation cataracts can vary among individuals, but such potential individual responses remain uncharacterized. Here we review relevant literature and discuss implications for radiation protection. This review assesses evidence for significant modification of radiation-induced cataractogenesis by age at exposure, sex and genetic factors based on current scientific literature.

CONCLUSIONS

In addition to obvious physical factors (e.g. dose, dose rate, radiation quality, irradiation volume), potential factors modifying individual responses for radiation cataracts include sex, age and genetics, with comorbidity and coexposures also having important roles. There are indications and preliminary data identifying such potential modifiers of radiation cataract incidence or risk, although no firm conclusions can yet be drawn. Further studies and a consensus on the evidence are needed to gain deeper insights into factors determining individual responses regarding radiation cataracts and the implications for radiation protection.

Long-Term Space Nutrition: A Scoping Review

This scoping review aimed to identify current evidence and gaps in the field of long-term space nutrition. Specifically, the review targeted critical nutritional needs during long-term manned missions in outer space in addition to the essential components of a sustainable space nutrition system for meeting these needs. The search phrase "space food and the survival of astronauts in long-term missions" was used to collect the initial 5432 articles from seven Chinese and seven English databases. From these articles, two independent reviewers screened titles and abstracts to identify 218 articles for full-text reviews based on three themes and 18 keyword combinations as eligibility criteria. The results suggest that it is possible to address short-term adverse environmental factors and nutritional deficiencies by adopting effective dietary measures, selecting the right types of foods and supplements, and engaging in specific sustainable food production and eating practices. However, to support self-sufficiency during long-term space exploration, the most optimal and sustainable space nutrition systems are likely to be supported primarily by fresh food production, natural unprocessed foods as diets, nutrient recycling of food scraps and cultivation systems, and the establishment of closed-loop biospheres or landscape-based space habitats as long-term life support systems.

Effects of Low-dose Gamma Radiation on Expression of Apoptotic Genes in Rat Peripheral Blood Lymphocyte

Background:

Exposure to high-dose ionizing radiation is known as a human carcinogen factor, but our information about the effects of low-dose ionizing radiation such as occupational exposures is limited. The main concern of scientific community is biological consequences due to low-dose radiations.

Objective:

This study aims to evaluate the effects of low-dose γ-radiation on expression changes of apoptotic genes (bax and bcl-2) in the rat peripheral blood lymphocytes.

Material and Methods:

In this experimental study, 42 adult male rats were classified into 6 groups, which was exposed to various doses values ranged from 20 mGy to 1000 mGy by γ-rays from a Co-60 source. Blood samples were provided for analysis of gene expression 24 h after gamma radiation by relative quantitative Reverse Transcription - Polymerase Chain Reaction (RT-PCR). Radiation sensitivity of rat lymphocytes was measured by the bax/bcl-2 ratio as a predictive marker for radio-sensitivity.

Results:

The results of this study showed that low dose of gamma radiation can induce down-regulation of bax in rat peripheral blood lymphocytes. Despite other mechanisms of cellular radio-protection, changes in expression of these apoptotic genes can be the primary pathway in responses of the lymphocytes radio-protection to the exposure. Our study revealed a significant decrease in the bax/bcl-2 ratio at 50 mGy dose compare to control and the other irradiated groups (p < 0.05).

Conclusion:

These results suggest that changes in the bax/bcl-2 ratio especially in radiation workers, as a key factor in apoptosis, can be considered as a biological marker in low-dose gamma radiation.

BRAIN AND EYE AS POTENTIAL TARGETS FOR IONIZING RADIATION IMPACT: PART II - RADIATION CEREBRO/OPHTALMIC EFFECTS IN CHILDREN, PERSONS EXPOSED IN UTERO, ASTRONAUTS AND INTERVENTIONAL RADIOLOGISTS

BACKGROUND

Ionizing radiation (IR) can affect the brain and the visual organ even at low doses, while provoking cognitive, emotional, behavioral, and visual disorders. We proposed to consider the brain and the visual organ as potential targets for the influence of IR with the definition of cerebro-ophthalmic relationships as the «eye-brain axis».

OBJECTIVE

The present work is a narrative review of current experimental, epidemiological and clinical data on radiation cerebro-ophthalmic effects in children, individuals exposed in utero, astronauts and interventional radiologists.

MATERIALS AND METHODS

The review was performed according to PRISMA guidelines by searching the abstract and scientometric databases PubMed/MEDLINE, Scopus, Web of Science, Embase, PsycINFO, Google Scholar, published from 1998 to 2021, as well as the results of manual search of peer-reviewed publications.

RESULTS

Epidemiological data on the effects of low doses of IR on neurodevelopment are quite contradictory, while data on clinical, neuropsychological and neurophysiological on cognitive and cerebral disorders, especially in the left, dominant hemisphere of the brain, are nore consistent. Cataracts (congenital - after in utero irradiation) and retinal angiopathy are more common in prenatally-exposed people and children. Astronauts, who carry out longterm space missions outside the protection of the Earth's magnetosphere, will be exposed to galactic cosmic radiation (heavy ions, protons), which leads to cerebro-ophthalmic disorders, primarily cognitive and behavioral disorders and cataracts. Interventional radiologists are a special risk group for cerebro-ophthalmic pathology - cognitivedeficits, mainly due to dysfunction of the dominant and more radiosensitive left hemisphere of the brain, andcataracts, as well as early atherosclerosis and accelerated aging.

CONCLUSIONS

Results of current studies indicate the high radiosensitivity of the brain and eye in different contingents of irradiated persons. Further research is needed to clarify the nature of cerebro-ophthalmic disorders in different exposure scenarios, to determine the molecular biological mechanisms of these disorders, reliable dosimetric support and taking into account the influence of non-radiation risk factors.

Space Radiation Protection Countermeasures in Microgravity and Planetary Exploration

BACKGROUND

Space radiation is one of the principal environmental factors limiting the human tolerance for space travel, and therefore a primary risk in need of mitigation strategies to enable crewed exploration of the solar system.

METHODS

We summarize the current state of knowledge regarding potential means to reduce the biological effects of space radiation. New countermeasure strategies for exploration-class missions are proposed, based on recent advances in nutrition, pharmacologic, and immune science.

RESULTS

Radiation protection can be categorized into (1) exposure-limiting: shielding and mission duration; (2) countermeasures: radioprotectors, radiomodulators, radiomitigators, and immune-modulation, and; (3) treatment and supportive care for the effects of radiation. Vehicle and mission design can augment the overall exposure. Testing in terrestrial laboratories and earth-based exposure facilities, as well as on the International Space Station (ISS), has demonstrated that dietary and pharmacologic countermeasures can be safe and effective. Immune system modulators are less robustly tested but show promise. Therapies for radiation prodromal syndrome may include pharmacologic agents; and autologous marrow for acute radiation syndrome (ARS).

CONCLUSIONS

Current radiation protection technology is not yet optimized, but nevertheless offers substantial protection to crews based on Lunar or Mars design reference missions. With additional research and human testing, the space radiation risk can be further mitigated to allow for long-duration exploration of the solar system.

Acute Radiation Syndrome and the Microbiome: Impact and Review

Study of the human microbiota has been a centuries-long endeavor, but since the inception of the National Institutes of Health (NIH) Human Microbiome Project in 2007, research has greatly expanded, including the space involving radiation injury. As acute radiation syndrome (ARS) is multisystemic, the microbiome niches across all areas of the body may be affected. This review highlights advances in radiation research examining the effect of irradiation on the microbiome and its potential use as a target for medical countermeasures or biodosimetry approaches, or as a medical countermeasure itself. The authors also address animal model considerations for designing studies, and the potential to use the microbiome as a biomarker to assess radiation exposure and predict outcome. Recent research has shown that the microbiome holds enormous potential for mitigation of radiation injury, in the context of both radiotherapy and radiological/nuclear public health emergencies. Gaps still exist, but the field is moving forward with much promise.

Radioprotective Role of Natural Polyphenols: From Sources to Mechanisms

The identification and development of radioprotective agents has emerged as a subject matter of research during recent years due to the growing usage of ionizing radiation in different areas of human life. Previous work on synthetic radioprotectors has achieved limited progress because of the numerous issues associated with toxicity. Compounds extracted from plants have potential to serve as lead candidates for developing ideal radioprotectors due to their low cost, safety and selectivity. Polyphenols are the most abundant and commonly dispersed group of biologically active molecules possessing broad range of pharmacological activities. Polyphenols have displayed efficacy for radioprotection during various investigations and can be administered at high doses with lesser toxicity. Detoxification of free radicals, modulating inflammatory responses, DNA repair, stimulation of hematopoietic recovery, and immune functions are the main mechanisms for radiation protection with polyphenols. Epicatechin, epigallocatechin-3-gallate, apigenin, caffeic acid phenylethylester, and silibinin provide cytoprotection together with the suppression of many pro-inflammatory cytokines owing to their free radical scavenging, anti-oxidant, and anti-inflammatory properties. Curcumin, resveratrol, quercetin, gallic acid, and rutin's radioprotective properties are regulated primarily by direct or indirect decline in cellular stress. Thus, polyphenols may serve as potential candidates for radioprotection in the near future, however, extensive investigations are still required to better understand their protection mechanisms.

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.

Radioprotective effects of montelukast, a selective leukotriene CysLT1 receptor antagonist, against nephrotoxicity induced by gamma radiation in mice

PURPOSE

In this study, we evaluated the renal protective effects of montelukast (MLK) against ionizing radiation (IR) induced nephrotoxicity in mice.

MATERIALS AND METHODS

Radioprotective effects of MLK were assessed by biochemical analysis including measurements of kidney malondialdehyde (MDA), reduced glutathione (GSH), and serum creatinine and urea levels. Besides, for further evaluation of protective effects of MLK on renal system, ^99m Tc-dimercaptosuccinic acid (DMSA) has been applied. The total antioxidant capacity of MLK was measured by using 1,1-diphenyl-2-picryl hydrazyl radical reagents and compared with butylated hydroxyl toluene standard antioxidant.

RESULTS

The biochemical evaluation revealed that better results have been achieved for the groups administered with MLK than the only radiation group. Besides only IR-treated mice group, those treated with MLK demonstrated a significant decrease in urea and creatinine levels. Statistically, significant differences of MDA and SHG levels (P < .05) were found between the radiation group and MLK plus IR-treated group. Also, ^99m Tc-DMSA kidney uptake value (%ID/g) was observed lower for MLK plus IR-treated mice group than only radiation-treated mice group.

CONCLUSIONS

According to our findings, MLK has a potential role to be used as a renal protective agent against gamma radiation in radiotherapy.

LGM2605 Reduces Space Radiation-Induced NLRP3 Inflammasome Activation and Damage in In Vitro Lung Vascular Networks

Updated measurements of charged particle fluxes during the transit from Earth to Mars as well as on site measurements by Curiosity of Martian surface radiation fluxes identified potential health hazards associated with radiation exposure for human space missions. Designing mitigation strategies of radiation risks to astronauts is critical. We investigated radiation-induced endothelial cell damage and its mitigation by LGM2605, a radioprotector with antioxidant and free radical scavenging properties. We used an in vitro model of lung vascular networks (flow-adapted endothelial cells; FAECs), exposed to gamma rays, low/higher linear energy transfer (LET) protons (3⁻4 or 8⁻10 keV/µm, respectively), and mixed field radiation sources (gamma and protons), given at mission-relevant doses (0.25 gray (Gy)⁻1 Gy). We evaluated endothelial inflammatory phenotype, NLRP3 inflammasome activation, and oxidative cell injury. LGM2605 (100 µM) was added 30 min post radiation exposure and gene expression changes evaluated 24 h later. Radiation induced a robust increase in mRNA levels of antioxidant enzymes post 0.25 Gy and 0.5 Gy gamma radiation, which was significantly decreased by LGM2605. Intercellular cell adhesion molecule-1 (ICAM-1) and NOD-like receptor protein 3 (NLRP3) induction by individual or mixed-field exposures were also significantly blunted by LGM2605. We conclude that LGM2605 is a likely candidate to reduce tissue damage from space-relevant radiation exposure.

Immune System Dysregulation During Spaceflight: Potential Countermeasures for Deep Space Exploration Missions

Recent studies have established that dysregulation of the human immune system and the reactivation of latent herpesviruses persists for the duration of a 6-month orbital spaceflight. It appears certain aspects of adaptive immunity are dysregulated during flight, yet some aspects of innate immunity are heightened. Interaction between adaptive and innate immunity also seems to be altered. Some crews experience persistent hypersensitivity reactions during flight. This phenomenon may, in synergy with extended duration and galactic radiation exposure, increase specific crew clinical risks during deep space exploration missions. The clinical challenge is based upon both the frequency of these phenomena in multiple crewmembers during low earth orbit missions and the inability to predict which specific individual crewmembers will experience these changes. Thus, a general countermeasure approach that offers the broadest possible coverage is needed. The vehicles, architecture, and mission profiles to enable such voyages are now under development. These include deployment and use of a cis-Lunar station (mid 2020s) with possible Moon surface operations, to be followed by multiple Mars flyby missions, and eventual human Mars surface exploration. Current ISS studies will continue to characterize physiological dysregulation associated with prolonged orbital spaceflight. However, sufficient information exists to begin consideration of both the need for, and nature of, specific immune countermeasures to ensure astronaut health. This article will review relevant in-place operational countermeasures onboard ISS and discuss a myriad of potential immune countermeasures for exploration missions. Discussion points include nutritional supplementation and functional foods, exercise and immunity, pharmacological options, the relationship between bone and immune countermeasures, and vaccination to mitigate herpes (and possibly other) virus risks. As the immune system has sentinel connectivity within every other physiological system, translational effects must be considered for all potential immune countermeasures. Finally, we shall discuss immune countermeasures in the context of their individualized implementation or precision medicine, based on crewmember specific immunological biases.

Effects of Hesperidin as a Radio-protector on Apoptosis in Rat Peripheral Blood Lymphocytes after Gamma Radiation

INTRODUCTION

Hesperidin (HES), as the most abundant flavonoid existing in the citrus, is widely used by human daily. The radio-protective effects of Hesperidin have been confirmed in various measurement systems. This study aimed to evaluate the effects of Hesperidin on the changes in the apoptosis level and expression of apoptotic genes target (bax, bcl-2 and ration of bax/bcl-2) in the peripheral blood lymphocytes of male rats after gamma radiation.

MATERIALS AND METHODS

64 male rats were divided into eight groups: Control, HES (100 mg/kg b.w, orally, 7 days), whole body irradiation with 2 and 8Gy, pre-administrated with 50 and 100 mg/kg body weight of Hesperidin for 7 days before irradiation with 2 and 8 Gy. 24 hours after radiation, apoptotic lymphocytes were evaluated using PE Annexin V Apoptosis detection I kit and the levels of mRNA for bax and bcl-2 were evaluated by real time reverse transcription polymerase chain reaction.

RESULTS

A significant reduction in apoptosis of the lymphocytes was demonstrated in group animals receiving 8 Gy compared to the group which received 2 Gy irradiation (p<0.0001). However, apoptosis significantly increased in group of rats who received Hesp before irradiation (p<0.05). The increase of apoptosis by Hesperidin administration can be attributed to the decreased expression of bax and significantly reduced expression of bcl-2 and finally increasing the ration of bax/bcl-2.

CONCLUSION

The results suggest that administration of 50 and 100 mg/kg of Hesperidin induces apoptotic effects by changing expression level of bax, bcl-2 and also the ratio of bax/bcl2.

Microgravity Stress: Bone and Connective Tissue

The major alterations in bone and the dense connective tissues in humans and animals exposed to microgravity illustrate the dependency of these tissues' function on normal gravitational loading. Whether these alterations depend solely on the reduced mechanical loading of zero g or are compounded by fluid shifts, altered tissue blood flow, radiation exposure, and altered nutritional status is not yet well defined. Changes in the dense connective tissues and intervertebral disks are generally smaller in magnitude but occur more rapidly than those in mineralized bone with transitions to 0 g and during recovery once back to the loading provided by 1 g conditions. However, joint injuries are projected to occur much more often than the more catastrophic bone fracture during exploration class missions, so protecting the integrity of both tissues is important. This review focuses on the research performed over the last 20 years in humans and animals exposed to actual spaceflight, as well as on knowledge gained from pertinent ground-based models such as bed rest in humans and hindlimb unloading in rodents. Significant progress has been made in our understanding of the mechanisms for alterations in bone and connective tissues with exposure to microgravity, but intriguing questions remain to be solved, particularly with reference to biomedical risks associated with prolonged exploration missions.

Comments on the mechanisms of action of radiation protective agents: basis components and their polyvalence

Purpose

These comments suggest a division of radiation protective agents on the grounds of their mechanism of action that increase the radio resistance of an organism.

Conclusion

Given below is the division of radiation protective agents on the basis of their mechanism of action into 3 groups: 1) Radiation protective agents, with the implementation of radiation protective action taking place at the cellular level in the course of rapidly proceeding radiation-chemical reactions. At the same time, when the ionizing radiation energy is absorbed, these agents partially neutralize the “oxygen effect” as a radiobiological phenomenon, especially in the radiolysis of DNA; 2) Radiation protective agents that exert their effect at the system level by accelerating the post-radiation recovery of radiosensitive tissues through activation of a number of pro-inflammatory signaling pathways and an increase in the secretion of hematopoietic growth factors, including their use as mitigators in the early period after irradiation prior to the clinical development of acute radiation syndrome (ARS). 3) Radiomodulators including drugs and nutritional supplements that can elevate the resistance of the organism to adverse environmental factors, including exposure to ionization by means of modulating the gene expression through a hormetic effect of small doses of stressors and a “substrate” maintenance of adaptive changes, resulting in an increased antioxidant protection of the organism. Radiation protective agents having polyvalence in implementation of their action may simultaneously induce radioprotective effect by various routes with a prevalence of basis mechanisms of the action.

Dichotomal effect of space flight-associated microgravity on stress-activated protein kinases in innate immunity

Space flight strongly moderates human immunity but is in general well tolerated. Elucidation of the mechanisms by which zero gravity interacts with human immunity may provide clues for developing rational avenues to deal with exaggerated immune responses, e.g. as in autoimmune disease. Using two sounding rockets and one manned Soyuz launch, the influence of space flight on immunological signal transduction provoked by lipopolysaccharide (LPS) stimulation was investigated in freshly isolated peripheral blood monocytes and was compared to samples obtained from on-board centrifuge-loaded 1 g controls. The effect of microgravity on immunological signal transduction is highly specific, since LPS dependent Jun-N-terminal kinase activation is impaired in the 0 g condition, while the corresponding LPS dependent activation of p38 MAP kinase remains unaffected. Thus our results identify Jun-N-terminal kinase as a relevant target in immunity for microgravity and support using Jun-N-terminal kinase specific inhibitors for combating autoimmune disease.

Curcumin protects metronidazole and X-ray induced cytotoxicity and oxidative stress in male germ cells in mice

Metronidazole (MTZ) is a common antiparasitic and antibacterial drug. The drug and X-ray induced effects in mouse sperm count, sperm head abnormality and some oxidative stress parameters have been studied. Simultaneously the protective role of curcumin has been evaluated. MTZ, 40 mg/kg bw and 13.4 mg/kg bw × 3 days exposure induced abnormal sperm head and reduced total sperm count in Swiss albino mice both after 24 h and 35 days of exposure. However, MTZ treatment in mice receiving X-ray irradiation (0.5 Gy) did not changed the incidence of abnormal sperm population or decrease in the total sperm count. Hepatic glutathione (GSH), superoxide dismutase (SOD) declined significantly during the treatment phase with significant rise in lipid peroxidation of the tissue. The cellular changes were estimated by using lipid peroxidative indices like thiobarbituric acid reactive substances (TBARS). Elevated TBARS is indicative of oxidative stress in treated mice. Furthermore, curcumin pre-treatment apparently reduced the frequency of sperm head abnormality and TBARS induced by MTZ alone or in combination with X-ray and increased the levels of hepatic GSH and SOD. The additive effects of MTZ and X-ray could not be observed with regards to sperm head abnormality and total sperm count in the tested dose range although the cellular antioxidants were found to be significantly lowered and lipid peroxidantion increased. The possible role of MTZ and X-ray inducing sperm abnormality, decreased sperm count and alteration in GSH, SOD and TBARS and defensive role of curcumin have been evaluated.

In vivo changes in plasma coenzyme Q10, carotenoid, tocopherol, and retinol levels in children after computer tomography

BACKGROUND

Low dose X-irradiation (IR) from computer tomography (CT) can generate free radicals, which can damage biologically relevant molecules and ultimately lead to cancer. These effects are especially concerning for children owing to their higher radiosensitivity and longer life expectancy than adults. The lipid phase micronutrients (LPM) coenzyme Q10, carotenoids, E vitamers, and vitamin A are potent radical scavengers that can act as intracellular antioxidants.

METHODS

We investigated changes in circulating levels of these LPM in 17 children (0.25-6 y) undergoing medically indicated CT scans involving relatively low IR doses. Blood was drawn before and 1h after CT scans and analyzed using HPLC with electrochemical and UV/VIS detection.

RESULTS

We found significant decreases (p<0.05) in post-CT plasma levels in several LPM which suggests that these LPM can serve as biodosimeters and may protect against damage from IR during clinical procedures such as CT. The strongest predictors for pre- to post-CT changes for many LPM were their baseline levels.

CONCLUSION

Future larger studies are warranted to confirm our findings and to test whether high circulating antioxidant levels protect against IR damage in vivo with an ultimate goal of establishing prophylactic modalities for CT-induced IR damage.

Effects of a Mangifera indica L. stem bark extract and mangiferin on radiation-induced DNA damage in human lymphocytes and lymphoblastoid cells

OBJECTIVES

Mangifera indica L. (mango) stem bark aqueous extract (MSBE) that has antioxidant, anti-inflammatory and immunomodulatory properties, can be obtained in Cuba. It is rich in polyphenols, where mangiferin is the main component. In this study, we have tested DNA damage and protection effects of MSBE and mangiferin on primary human lymphocytes and lymphoblastoid cells.

MATERIAL AND METHODS

Cell suspensions were incubated with the products (50-1000 μg/ml) for experiments on damage induction, and evaluation of any potential protective effects (5-100 μg/ml) for 60 min at 37 °C. Irradiation was performed using a γ-ray source, absorbed dose 5 Gy. At the end of exposure, DNA damage, protection and repair processes were evaluated using the comet assay.

RESULTS

MSBE (100-1000 μg/ml) induced DNA damage in a concentration dependent manner in both cell types tested, primary cells being more sensitive. Mangiferin (200 μg/ml) only induced light DNA damage at higher concentrations. DNA repair capacity was not affected after MSBE or mangiferin exposure. On the other hand, MSBE (25 and 50 μg/ml) and mangiferin (5-25 ug/ml) protected against gamma radiation-induced DNA damage.

CONCLUSIONS

These results show MSBE has protector or harmful effects on DNA in vitro depending on the experimental conditions, which suggest that the extract could be acting as an antioxidant or pro-oxidant product. Mangiferin was involved in protective effects of the extract.

Modulation of radiation-induced and mitomycin C-induced chromosome damage by apigenin in human lymphocytes in vitro

Apigenin (APG), a flavone, is known to exhibit antioxidant, antimutagenic and antitumorigenic activity, both in vivo and in vitro. The aim of this study is to investigate the modulatory effects of APG on human lymphocytes after irradiation with gamma rays (3 Gy) or treatment with the antineoplastic agent, mitomycin C (MMC), in vitro. Cytogenetic biomarkers such as chromosome aberrations (CAs), sister chromatid exchanges (SCEs) and cytochalasin-B blocked micronuclei (CBMN), were studied in blood lymphocytes treated with radiation, or antineoplastic agent (MMC), and APG. Whole blood lymphocytes were cultured in vitro using a standard protocol. No significant differences were found in the frequency of CAs or micronuclei (MN) in human peripheral blood lymphocytes irradiated with gamma rays (3 Gy) and then post-treated with APG. There was an increase in the frequency of SCEs per cell in APG-treated samples compared with the controls. Lymphocytes treated with MMC in the presence of APG exhibited a significant decrease (P < 0.01) in the frequency of SCEs compared with MMC treatment alone. The data for the MN test indicated that APG treatment significantly reduced (P < 0.01) the frequency of MMC-induced MN.

Antioxidative and radioprotective potential of rutin and quercetin in Swiss albino mice exposed to gamma radiation

The radioprotective potential of bioflavonoid, rutin (RUT) and quercetin (QRT) was investigated in Swiss albino mice exposed to gamma radiation. The radioprotective potential of RUT and QRT was assessed in pre-treatment group of mice followed on radiation-induced changes in glutathione (GSH), glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (LPO) levels were also analyzed. Elevation in the GSH, GST, SOD, CAT, and decreased LPO levels were observed in RUT and QRT pretreated group when compared to the irradiated animals. Furthermore, it was observed that RUT and QRT treatment was found to inhibit various free radicals generated in vitro, viz., 2,2-diphenyl-1-picrylhydrazyl(DPPH), O2, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS)(+), and OH in a concentration-dependent manner. This study clearly demonstrates the free radical scavenging action of RUT and QRT, indicating that it may have its potential as a radioprotective agent. Furthermore, the presence of a phenolic group in RUT and QRT is known to contribute to scavenging the radiation-induced free radicals and inhibition of oxidative stress. Present findings demonstrate the potential of RUT and QRT in mitigating radiation-induced oxidative stress, which may be attributed to the inhibition of radiation-induced decline in the endogenous antioxidant levels and scavenging of radiation-induced free radicals.

Acetylcholinesterase inhibitors: pharmacology and toxicology

Acetylcholinesterase is involved in the termination of impulse transmission by rapid hydrolysis of the neurotransmitter acetylcholine in numerous cholinergic pathways in the central and peripheral nervous systems. The enzyme inactivation, induced by various inhibitors, leads to acetylcholine accumulation, hyperstimulation of nicotinic and muscarinic receptors, and disrupted neurotransmission. Hence, acetylcholinesterase inhibitors, interacting with the enzyme as their primary target, are applied as relevant drugs and toxins. This review presents an overview of toxicology and pharmacology of reversible and irreversible acetylcholinesterase inactivating compounds. In the case of reversible inhibitors being commonly applied in neurodegenerative disorders treatment, special attention is paid to currently approved drugs (donepezil, rivastigmine and galantamine) in the pharmacotherapy of Alzheimer's disease, and toxic carbamates used as pesticides. Subsequently, mechanism of irreversible acetylcholinesterase inhibition induced by organophosphorus compounds (insecticides and nerve agents), and their specific and nonspecific toxic effects are described, as well as irreversible inhibitors having pharmacological implementation. In addition, the pharmacological treatment of intoxication caused by organophosphates is presented, with emphasis on oxime reactivators of the inhibited enzyme activity administering as causal drugs after the poisoning. Besides, organophosphorus and carbamate insecticides can be detoxified in mammals through enzymatic hydrolysis before they reach targets in the nervous system. Carboxylesterases most effectively decompose carbamates, whereas the most successful route of organophosphates detoxification is their degradation by corresponding phosphotriesterases.

Studying the effect of antioxidants on cytogenetic manifestations of solvent exposure in the paint industry

OBJECTIVE

To investigate the antioxidant role in reversing cytogenetic changes caused by solvent exposure in paint industry.

SUBJECTS AND METHODS

A prospective controlled clinical trial was performed on 39 workers exposed to solvents and 39 workers not exposed to solvents by supplying a mixture of antioxidant vitamins (A, C, E and selenium) and the after effects of such regimen were analyzed. Environmental monitoring was carried out for air concentrations of different solvents at workplace. Exposed group was cytogenetically tested before and after giving the mixture of antioxidant vitamins for 1 month duration.

RESULTS

Frequency of chromosomal aberrations (CAs) and the mean of sister chromatid exchanges (SCEs) were statistically significantly higher among exposed workers than among controls. After the supplementation of antioxidants, there was a statistically significant decrease in the frequency of CAs, and 88% abnormal levels of SCEs were back to normal levels.

CONCLUSION

Antioxidant supplementation decreases the frequency of CAs and SCEs among exposed workers.

Geraniin down regulates gamma radiation-induced apoptosis by suppressing DNA damage

Gamma ray irradiation triggers DNA damage and apoptosis of proliferating stem cells and peripheral immune cells, resulting in the destruction of intestinal crypts and lymphoid system. Geraniin is a natural compound extracts from an aquatic plant Nymphaea tetragona and possesses good antioxidant property. In this study, we demonstrate that geraniin rescues radiosensitive splenocytes and jejunal crypt cells from radiation-induced DNA damage and apoptosis. Isolated splenocytes from C57BL/6 mice treated with geraniin were protected against radiation injury of 2 Gy irradiation through the enhancement of the proliferation and attenuation of DNA damage. Also, geraniin inhibited apoptosis in radiosensitive splenocytes by reducing the expression level and immunoreactivity of proapoptotic p53 and Bax and increasing those of anti-apoptotic Bcl-2. In mice exposed to radiation, geraniin treatment protected splenocytes and intestinal crypt cells from radiation-induced cell death. Our results suggest that geraniin presents radioprotective effects by regulating DNA damage on splenocytes, exerting immunostimulatory capacities and inhibiting apoptosis of radiosensitive immune cells and jejunal crypt cells. Therefore, geraniin can be a radioprotective agent against γ-irradiation exposure.

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.

Neuroprotective effects of quercetin, rutin and okra (Abelmoschus esculentus Linn.) in dexamethasone-treated mice

The administration of dexamethasone, a synthetic glucocorticoid receptor agonist, causes neuronal death in the CA3 layer of the hippocampus, which has been associated with learning and memory impairments. This study aimed to examine the ability of okra (Abelmoschus esculentus Linn.) extract and its derivatives (quercetin and rutin) to protect neuronal function and improve learning and memory deficits in mice subjected to dexamethasone treatment. Learning and memory functions in mice were examined using the Morris water maze test. The results showed that the mice treated with dexamethasone had prolonged water maze performance latencies and shorter time spent in the target quadrant while mice pretreated with quercetin, rutin or okra extract prior to dexamethasone treatment showed shorter latencies and longer time spent in target quadrant. Morphological changes in pyramidal neurons were observed in the dexamethasone treated group. The number of CA3 hippocampal neurons was significantly lower while pretreated with quercetin, rutin or okra attenuated this change. Prolonged treatment with dexamethasone altered NMDA receptor expression in the hippocampus. Pretreatment with quercetin, rutin or okra extract prevented the reduction in NMDA receptor expression. Dentate gyrus (DG) cell proliferation was examined using the 5-bromo-2-deoxyuridine (BrdU) immunohistochemistry technique. The number of BrdU-immunopositive cells was significantly reduced in dexamethasone-treated mice compared to control mice. Pretreatment with okra extract, either quercetin or rutin was found to restore BrdU-immunoreactivity in the dentate gyrus. These findings suggest that quercetin, rutin and okra extract treatments reversed cognitive deficits, including impaired dentate gyrus (DG) cell proliferation, and protected against morphological changes in the CA3 region in dexamethasone-treated mice. The precise mechanism of the neuroprotective effect of these plant extracts should be further investigated.

Protective role of Vernonia cinerea L. against gamma radiation—induced immunosupression and oxidative stress in mice

The radioprotective effect of Vernonia cinerea extract was studied in balb/c mice. Whole-body irradiation of γ-rays (6 Gy) given to animals reduced the white blood cell count, bone marrow cellularity and α-esterase positive cells in control animals, which were elevated by the administration of V. cinerea extract (20 mg/kg body weight [b.wt.], intraperitoneally [i.p.]). The elevated levels of serum enzymes alkaline phosphatase (ALP), glutamate pyruvate transferases (GPT) and lipid peroxidation (LPO) after irradiation were also reduced with V. cineria extract administration. V. cinerea treatment also significantly enhanced the animal’s antioxidant status by enhancing the activities superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH) level in irradiated animals. Histopathological analysis of liver and small intestine also suggests that V. cinerea could reduce the tissue damages induced by radiation. The level of pro-inflammatory cytokines such as interleukin 1β (IL-1β), tumour necrosis factor α (TNF-α) and C-reactive protein (CRP) elevated after irradiation, which were significantly reduced by V. cinerea extract administration. On the other hand, the extract stimulated the production of other cytokines such as granulocyte monocyte—colony stimulating factor (GM-CSF) and interferon-γ (IFN-γ) in animals exposed to radiation. Agarose gel electrophoresis of DNA isolated from bone marrow of control animals showed heavy DNA damage, but a reduced DNA damage was seen in animals treated with V. cinerea extract. Administration of V. cinerea did not compromise the anti-neoplastic efficiency of radiation. In fact, there was a synergistic action of radiation and V. cinerea in reducing the solid tumours in mice. Methanolic extract of V. cinerea given i.p. showed a significant radioprotective activity without compromising the radiotherapeutic efficacy of radiation, indicating its possible use as an adjuvant during radiotherapy.

High dietary antioxidant intakes are associated with decreased chromosome translocation frequency in airline pilots

BACKGROUND

Dietary antioxidants may protect against DNA damage induced by endogenous and exogenous sources, including ionizing radiation (IR), but data from IR-exposed human populations are limited.

OBJECTIVE

The objective was to examine the association between the frequency of chromosome translocations, as a biomarker of cumulative DNA damage, and intakes of vitamins C and E and carotenoids in 82 male airline pilots.

DESIGN

Dietary intakes were estimated by using a self-administered semiquantitative food-frequency questionnaire. Translocations were scored by using fluorescence in situ hybridization with whole chromosome paints. Negative binomial regression was used to estimate rate ratios and 95% CIs, adjusted for potential confounders.

RESULTS

Significant and inverse associations were observed between translocation frequency and intakes of vitamin C, beta-carotene, beta-cryptoxanthin, and lutein-zeaxanthin from food (P < 0.05). Translocation frequency was not associated with the intake of vitamin E, alpha-carotene, or lycopene from food; total vitamin C or E from food and supplements; or vitamin C or E or multivitamin supplements. The adjusted rate ratios (95% CI) for > or =median compared with or =median compared with

CONCLUSION

High combined intakes of vitamins C and E, beta-carotene, beta-cryptoxanthin, and lutein-zeaxanthin from food, or a diet high in their food sources, may protect against cumulative DNA damage in IR-exposed persons.

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Key Words Collapse

MESH Headings

• Administration, Oral
• Aircraft
• Antioxidants/administration & dosage
• Antioxidants/pharmacology
• Ascorbic Acid/pharmacology
• Carotenoids/administration & dosage
• Carotenoids/pharmacology
• Chromosomes, Human/drug effects
• Chromosomes, Human/genetics
• Dietary Supplements
• Fruit
• Humans
• Interviews as Topic
• Male
• Occupations
• Surveys and Questionnaires
• Translocation, Genetic/drug effects
• Vegetables
• Vitamin E/pharmacology
• beta Carotene/administration & dosage

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Grants

• Y1CP802904 NCI NIH HHS
• Intramural NIH HHS

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Affiliation(s)

Lee C Yong National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, OH 45226, USA.
Martin R Petersen
Alice J Sigurdson
Laura A Sampson
Elizabeth M Ward

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Radioprotective effect of moderate wine consumption in patients with breast carcinoma

PURPOSE

Given the high cost and side effects of radioprotective agents such as amifostine, attention has been focused on potentially equally effective but less expensive and toxic natural substances. We evaluated the potential radioprotective effects of wine in preventing skin toxicity in patients with breast cancer.

METHODS AND MATERIALS

Before treatment, the medical history and habits of patients were assessed and the information recorded in their clinical folders. Patients were divided into three groups based on the dose/fractionation scheme used: control group, 60.4 Gy (standard technique); Modulated Accelerated Radiotherapy in Adjuvant treatment of breast cancer (MARA)-1 protocol group, 44 Gy (concomitant boost to tumoral bed); and MARA-2 protocol group, 60 Gy (concomitant boost to tumoral bed). The impact of the following variables on acute skin toxicity was evaluated by chart review: radiotherapy protocol, planning target volume (PTV), comorbidity (e.g., hypertension and diabetes), hemoglobin level before therapy, adjuvant hormone therapy, adjuvant chemotherapy, cigarette smoking, and drinking habits.

RESULTS

The study population consisted of 348 patients. More severe skin toxicity was significantly associated with the radiotherapy protocol (p < 0.001) and median PTV (p = 0.005). In addition, the incidence of acute toxicity of Grade 2 or greater was higher in patients without alcohol intake (38.4% vs. 22.3%, p = 0.021). The daily amount of alcohol intake also influenced the incidence of skin toxicity, with an incidence of 38.4% in patients with no wine intake, 31.8% in patients drinking half a glass per day, 13.6% in patients drinking one glass per day, and 35.0% in patients drinking two glasses per day. Multivariate analysis showed that wine intake, PTV, and radiotherapy protocol were all significantly correlated with acute toxicity.

CONCLUSIONS

Our results indicate that wine may have a radioprotective effect; however, prospective studies are needed to confirm this beneficial effect of wine and its components.

Long-term effects of irradiation with iron-56 particles on the nigrostriatal dopamine system

Exposure to heavy ions during a Mars mission might damage the brain, thus compromising mission success and the quality of life of returning astronauts. Several workers have suggested that the dopamine system is particularly sensitive to heavy ion radiation, but direct evidence for this notion is lacking. We examined measures of brain dopamine viability at times up to 15 months after acute exposure of rats to (56)Fe (1.2-2.4 Gy). No effects were seen in brain sections stained for tyrosine hydroxylase, the classical marker for dopamine cells and nerve terminals. Locomotion stimulated by cocaine, which directly activates the dopamine system, was reduced at 6 months but not at 12 months. Furthermore, in a visually cued lever-pressing test, reaction times, which are prolonged by dopamine system damage, were identical in irradiated and control animals. However, learning times were increased by irradiation. Our data suggest that the midbrain dopamine system is not especially sensitive to damage by (56)Fe particles at doses much higher than would be associated with travel to and from Mars.

DNA-protective effects of sumach (Rhus coriaria L.), a common spice: results of human and animal studies

Sumach (Rhus coriaria L.) is widely used as a spice. The aim of this study was the investigation of its DNA-protective effects in humans and animals. Prevention of the formation of strand breaks and oxidized DNA bases as well as the protection against H(2)O(2)- and (+/-)-anti-benzo[a]pyrene-7,8-dihydro-diol-9,10-epoxide (BPDE)-induced DNA-damage were monitored in human lymphocytes in a placebo controlled trial (N=8/group) with ethanolic extract of sumach (3.0g/day, 3 days) in single cell gel electrophoresis assays. Furthermore, DNA-protective effects of sumach were monitored in different inner organs of rats under identical conditions. No alteration of DNA-migration was detectable in human lymphocytes under standard conditions, but a decrease of the tail-lengths due to formation of oxidized purines and pyrimidines (52% and 36%) was found with lesion-specific enzymes. Also damage caused by H(2)O(2) and BPDE was significantly reduced by 30% and 69%, respectively. The later effect may be due to induction of glutathione S-transferase (GST). After the intervention, the overall GST (CDNB) activity in plasma was increased by 40%, GST-alpha by 52% and GST-pi by 26% (ELISA). The antioxidant effects of extract are probably due to scavenging which was observed in in vitro experiments, which also indicated that gallic acid is the active principle of sumach. The animal experiments showed that sumach also causes protection in inner organs. Supplementation of the drinking water (0.02g/kg per animal) decreased the formation of oxidized DNA bases in colon, liver, lung and lymphocytes; also after gamma-irradiation pronounced effects were seen.

Nutritional biochemistry of spaceflight

As we approach the end of the first 50 years of human space travel, much has been learned about adaptation to microgravity and the risks associated with extended-duration space exploration. As the frequency and duration of flights grew, nutrition issues became more critical and the questions to be answered became more complex: What are the nutrient requirements for space travelers? Can nutrients be used as tools to mitigate the negative effects of space travel on humans? How does nutrition interrelate with other physiological systems (such as muscle, bone, and cardiovascular system) and their adaptation to microgravity? Much research has been done over the decades in both actual spaceflight and ground-based analogs. We review here much of what is known, and highlight areas of ongoing research and concerns for future exploration of the Moon, Mars, and beyond.

Resveratrol reduces radiation-induced chromosome aberration frequencies in mouse bone marrow cells

Resveratrol, a polyphenol compound with reported antioxidant and anticarcinogenic effects, a wide range of molecular targets, and toxicity only at extreme doses, has received considerable attention. We evaluated the radioprotective effect of orally administered resveratrol on the frequencies of chromosome aberrations in irradiated mouse bone marrow cells. CBA/CaJ mice were divided into four groups: (1) no treatment, (2) resveratrol only, (3) radiation only, and (4) resveratrol and radiation. Resveratrol treatment (100 mg/kg daily) was initiated 2 days prior to irradiation. Bone marrow was then harvested at 1 and 30 days after a single dose of 3 Gy whole-body gamma radiation. A statistically significant (P < 0.05) reduction in the mean total chromosome aberration frequency per metaphase at both times postirradiation in the resveratrol and radiation group compared to the radiation-only group was observed. This study is the first to demonstrate that resveratrol has radioprotective effects in vivo. These results support the use of resveratrol as a radioprotector with the potential for widespread application.

Effect of curcumin analog on gamma-radiation-induced cellular changes in primary culture of isolated rat hepatocytes in vitro

The present study was aimed to evaluate the radioprotective effect of curcumin analog, on gamma-radiation-induced toxicity in primary cultures of isolated rat hepatocytes. Hepatocytes were isolated from the liver of rats by collagenase perfusion. The DNA damage was analysed by single cell gel electrophoresis (comet assay). An increase in the severity of DNA damage was observed with the increase in gamma-radiation dose at 1-4 Gy in cultured rat hepatocytes. The levels of lipid peroxidative indices like thiobarbituric acid reactive substances (TBARSs) were increased significantly, whereas the levels of reduced glutathione (GSH) and antioxidant enzymes were significantly decreased in gamma-irradiated groups. The maximum damage to hepatocytes was observed at 4Gy gamma-irradiation. Pretreatment with different concentrations of curcumin analog (1.38, 6.91 and 13.82 microM) shows a significant decrease in the levels of TBARS and DNA damage. Pretreatment with curcumin analog prevents the loss of enzymic and non-enzymic antioxidants like GSH upon gamma-irradiation. The maximum protection of hepatocytes was observed at 6.91 microM of curcumin analog pretreatment. Thus, our result shows that pretreatment with curcumin analog protects the hepatocytes against gamma-radiation-induced cellular damage.

Modulatory effects of curcumin on γ-radiation-induced cellular damage in primary culture of isolated rat hepatocytes

Ionizing radiation is known to induce oxidative stress through generation of reactive oxygen species (ROS) resulting in imbalance of the pro-oxidant and antioxidant in the cells, which is suggested to culminate in cell death. The present work was aimed to evaluate the radioprotective effect of curcumin, a yellow pigment of turmeric on γ-radiation-induced toxicity in primary cultures of isolated rat hepatocytes. Hepatocytes were isolated from the liver of rats by collagenase perfusion. The cellular changes were estimated using lipid peroxidative indices like thiobarbituric acid reactive substances (TBARS), the antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH), ceruloplasmin, vitamins A, E and C and uric acid. The comet assay is a sensitive and rapid technique for quantifying and analyzing DNA damage in individual cells was exposed under γ-radiation. The increase in the severity of DNA damage was observed with the increase dose (1, 2 and 4Gy) of γ-radiation in cultured hepatocytes. TBARS were increased significantly, whereas the levels of GSH, vitamins C, E and A, ceruloplasmin, uric acid and antioxidant enzymes were significantly decreased in γ-irradiated hepatocytes. The maximum damage to hepatocytes was observed at 4Gy irradiation. On pretreatment with curcumin (1, 5 and 10μg/ml) showed a significant decrease in the levels of TBARS and DNA damage. The antioxidant enzymes were increased significantly along with the levels of GSH, vitamins A, E and C, uric acid and ceruloplamin. The maximum protection of hepatocytes was observed at 10μg/ml of curcumin pretreatment. Thus, pretreatment with curcumin helps in protecting the hepatocytes against γ-radiation-induced cellular damage and can be developed as an effective radioprotector during radiotherapy in near future.

Vitamin E deficiency enhances pulmonary inflammatory response and oxidative stress induced by single-walled carbon nanotubes in C57BL/6 mice

Exposure of mice to single-walled carbon nanotubes (SWCNTs) induces an unusually robust pulmonary inflammatory response with an early onset of fibrosis, which is accompanied by oxidative stress and antioxidant depletion. The role of specific components of the antioxidant protective system, specifically vitamin E, the major lipid-soluble antioxidant, in the SWCNT-induced reactions has not been characterized. We used C57BL/6 mice, maintained on vitamin E-sufficient or vitamin E-deficient diets, to explore and compare the pulmonary inflammatory reactions to aspired SWCNTs. The vitamin E-deficient diet caused a 90-fold depletion of alpha-tocopherol in the lung tissue and resulted in a significant decline of other antioxidants (GSH, ascorbate) as well as accumulation of lipid peroxidation products. A greater decrease of pulmonary antioxidants was detected in SWCNT-treated vitamin E-deficient mice as compared to controls. Lowered levels of antioxidants in vitamin E-deficient mice were associated with a higher sensitivity to SWCNT-induced acute inflammation (total number of inflammatory cells, number of polymorphonuclear leukocytes, released LDH, total protein content and levels of pro-inflammatory cytokines, TNF-alpha and IL-6) and enhanced profibrotic responses (elevation of TGF-beta and collagen deposition). Exposure to SWCNTs markedly shifted the ratio of cleaved to full-length extracellular superoxide dismutase (EC-SOD). Given that pulmonary levels of vitamin E can be manipulated through diet, its effects on SWCNT-induced inflammation may be of practical importance in optimizing protective strategies.

Captopril protects mice bone marrow cells against genotoxicity induced by gamma irradiation

The radioprotective effects of captopril were investigated by using the micronucleus test for anticlastogenic and cell proliferation activity. A single intraperitoneal administration of captopril at doses of 10, 25 and 50 mg/kg 1 h prior to gamma irradiation (2 Gy) reduced the frequencies of micronuleated polychromatic erythrocytes (MnPCEs). All three doses of captopril significantly reduced the frequencies of MnPCEs and increased polychromatic erythrocytes (PCE)/PCE+NCE (normochromatic erythrocyte) ratio in mice bone marrow compared to the non-drug-treated irradiated control (p < 0.001). The optimum dose for protection in mouse was 10 mg/kg to protect mice bone marrow 2.18-fold against the clastogenic effects of gamma-irradiation with respect to the non-drug-treated irradiated control. There was a drug dose-response effect of captopril in increasing the PCE/PCE+NCE ratio in bone marrow cells. The maximum protective effect of captopril was at a dose of 25 mg/kg for increasing the PCE/PCE + NCE ratio. Captopril exhibited concentration-dependent antioxidant activity, scavenging > 96% of the 1,1-diphenyl-2-picryl hydrazyl free radicals when used at a concentration of 0.2 mM. In this study captopril reduced lipid peroxidation induced by hydrogen peroxide in mice liver. It appears that captopril, due to its free radical scavenging properties, protects mice bone marrow cells from radiation-induced DNA damage and genotoxicity.

Protective effect of curcumin on γ-radiation induced DNA damage and lipid peroxidation in cultured human lymphocytes

The present work is aimed at evaluating the radioprotective effect of curcumin, a naturally occurring phenolic compound on gamma-radiation induced toxicity. The cellular changes were estimated by using lipid peroxidative indices like thiobarbituric acid reactive substances (TBARS), the antioxidants superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH). The DNA damage was analysed by using cytokinesis blocked micronucleus assay and dicentric aberration (DC). The gamma-radiation at different doses (1, 2 and 4Gy) were found to significantly increase micronuclei (MN), DC frequencies and TBARS level whereas the levels of GSH and antioxidant enzymes were significantly decreased. The maximum damage to lymphocytes was observed at 4Gy irradiation. Curcumin pretreatment (1, 5 and 10microg/ml) significantly decreased the frequency of MN and DC. The levels of TBARS decreased and activities of SOD, CAT and GPx significantly increased along with GSH levels. At 1Gy irradiation all the concentrations of curcumin (1, 5 and 10microg/ml) significantly protected the lymphocytes from radiation damage. At 2Gy irradiation, 5 and 10microg/ml of curcumin showed significant radioprotection. Since the highest damage was observed at 4Gy irradiation both 1 and 5microg/ml of curcumin pretreatment were not sufficient to protect the lymphocytes from radiation damage but 10microg/ml of curcumin significantly protected the cultured lymphocytes from radiation damage. Thus, pretreatment with curcumin gives protection to lymphocytes against gamma-radiation induced cellular damage.

Evaluation of the radioprotective effect of Liv 52 in mice

Liv 52 is a mixture of botanicals that is used clinically to treat various hepatic disorders. In this study, the radioprotective activity of Liv 52 was evaluated in mice given whole-body exposure to different doses of gamma-radiation. In addition, a series of studies was conducted to explore the mechanism of radioprotection. Radioprotection was evaluated by the ability of Liv 52 to reduce both the frequency of bone marrow micronucleated erythrocytes and the lethality produced by (60)Co gamma-radiation. Mice were treated by oral gavage once daily for seven consecutive days with 500 mg/kg body weight Liv 52 or carboxymethylcellulose vehicle prior to radiation. Micronucleated polychromatic erythrocytes (MPCEs), micronucleated normochromatic erythrocytes (MNCEs), and the PCE/NCE ratio were measured at 0.25-14 days after exposure to whole-body radiation doses of 0, 0.5, 1.5, 3.0, or 4.5 Gy; animal survival was monitored after doses of 7, 8, 9, 10, 11, or 12 Gy. Pretreatment of mice with Liv 52 significantly reduced the frequency of radiation-induced MPCEs and MNCEs. Irradiation reduced the PCE/NCE ratio in a dose-related manner for up to 7 days following irradiation; Liv 52 pretreatment significantly mitigated against these reductions. Liv 52 treatment also reduced the symptoms of radiation sickness and increased mouse survival 10 and 30 days after irradiation. Liv 52 pretreatment elevated the levels of reduced glutathione (GSH), increased the activities of glutathione transferase, GSH peroxidase, GSH reductase, superoxide dismutase, and catalase, and lowered lipid peroxidation (LPx) and the activities of alanine amino transferase and aspartate aminotransferase 30 min after exposure to 7 Gy of gamma-radiation. Liv 52 pretreatment also reduced radiation-induced LPx and increased GSH concentration 31 days following the exposure. The results of this study indicate that pretreatment with Liv 52 reduces the genotoxic and lethal effects of gamma-irradiation in mice and suggest that this radioprotection may be afforded by reducing the toxic effects of the oxidative products of irradiation.