Protection against ionizing radiation by antioxidant nutrients and phytochemicals

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.

Protective effect of dendrodoine analog, an aminothiazole derivative against X-radiation induced hepatocellular damage in mice

This study evaluated the radioprotective effect of dendrodoine analog (DA) against radiation-induced damage in the liver of mice. The study was divided into two phases; in the first phase, the effective concentration of DA was fixed by performing a survival study. In the second phase, the fixed effective concentration of DA was orally administered to mice to evaluate its radioprotective efficacy by performing various assays. The results indicated that the radiation-induced decrease in the activities of antioxidant enzymes, increase in thiobarbituric acid reactive substances (TBARS) and comet parameters were altered by pre-administration with the effective concentration of DA which restored the antioxidant status to near normal and decreased the level of the TBARS and comet parameters. The histopathological examinations further confirmed the hepatoprotective effect of DA in mice. Thus, the current study showed DA to be an effective radioprotector against radiation induced damage in the liver of mice.

Radio-protective role of antioxidant agents

Ionizing radiation interacts with biological systems to produce reactive oxygen species and reactive nitrogen species which attack various cellular components. Radio-protectors act as prophylactic agents to shield healthy cells and tissues from the harmful effects of radiation. Past research on synthetic radio-protectors has brought little success, primarily due to the various toxicity-related problems. Results of experimental research show that antioxidant nutrients, such as vitamin E and herbal products and melatonin, are protective against the damaging effects of radiation, with less toxicity and side effects. Therefore, we propose that in the future, antioxidant radio-protective agents may improve the therapeutic index in radiation oncology treatments.

Mentha piperita as a pivotal neuro-protective agent against gamma irradiation induced DNA fragmentation and apoptosis : Mentha extract as a neuroprotective against gamma irradiation

Ionizing radiation is classified as a potent carcinogen, and its injury to living cells, in particular to DNA, is due to oxidative stress enhancing apoptotic cell death. Our present study aimed to characterize and semi-quantify the radiation-induced apoptosis in CNS and the activity of Mentha extracts as neuron-protective agent. Our results through flow cytometry exhibited the significant disturbance and arrest in cell cycle in % of M1: SubG1 phase, M2: G0/1 phase of diploid cycle, M3: S phase and M4: G2/M phase of cell cycle in brain tissue (p < 0.05). Significant increase in % of apoptosis and P53 protein expression as apoptotic biomarkers were coincided with significant decrease in Bcl(2) as an anti-apoptotic marker. The biochemical analysis recorded a significant decrease in the levels of reduced glutathione, superoxide dismutase, deoxyribonucleic acid (DNA) and ribonucleic acid contents. Moreover, numerous histopathological alterations were detected in brain tissues of gamma irradiated mice such as signs of chromatolysis in pyramidal cells of cortex, nuclear vacuolation, numerous apoptotic cell, and neural degeneration. On the other hand, gamma irradiated mice pretreated with Mentha extract showed largely an improvement in all the above tested parameters through a homeostatic state for the content of brain apoptosis and stabilization of DNA cycle with a distinct improvement in cell cycle analysis and antioxidant defense system. Furthermore, the aforementioned effects of Mentha extracts through down-regulation of P53 expression and up-regulation of Bcl(2) domain protected brain structure from extensive damage. Therefore, Mentha extract seems to have a significant role to ameliorate the neuronal injury induced by gamma irradiation.

Prevention of γ-radiation induced cellular genotoxicity by tempol: protection of hematopoietic system

Tempol (TPL) under in vitro conditions reduced the extent of gamma radiation induced membrane lipid peroxidation and disappearance of covalently closed circular form of plasmid pBR322. TPL protected cellular DNA from radiation-induced damage in various tissues under ex vivo and in vivo conditions as evidenced by comet assay. TPL also prevented radiation induced micronuclei formation (in peripheral blood leucocytes) and chromosomal aberrations (in bone marrow cells) in whole body irradiated mice. TPL enhanced the rate of repair of cellular DNA (blood leucocytes and bone marrow cells) damage when administered immediately after radiation exposure as revealed from the increased Cellular DNA Repair Index (CRI). The studies thus provided compelling evidence to reveal the effectiveness of TPL to protect hematopoietic system from radiation injury.

Protective Effect of Nardostachys jatamansi Against Radiation-induced Damage at Biochemical and Chromosomal Levels in Swiss Albino Mice

The effect of 100 mg of ethanol extract of Nardostachys jatamansi was studied on the mice exposed to 6 Gy electron beam radiation. Treatment of mice with 100 mg of Nardostachys jatamansi extract for 15 days before irradiation reduced the symptoms of radiation sickness when compared with the nondrug treated irradiated groups. The irradiation of animals resulted in an elevation in lipid peroxidation and reduction in glutathione, total antioxidants and antioxidant enzymes such as glutathione peroxidase and catalase activities. Irradiated group had shown micronucleus in the bone marrow cells. Treatment of mice with Nardostachys jatamansi extract before irradiation caused a significant depletion in lipid peroxidation followed by significant elevation in reduced glutathione, total antioxidants, glutathione peroxidase and catalase activity. It also showed a reduction in the micronucleus formation in the bone marrow cells. Our results indicate that the radioprotective activity of Nardostachys jatamansi extract may be due to free radical scavenging and increased antioxidant level in mice.

NADPH oxidase subunit 4 mediates cycling hypoxia-promoted radiation resistance in glioblastoma multiforme

Cycling hypoxia is a well-recognized phenomenon within animal and human solid tumors. It mediates tumor progression and radiotherapy resistance through mechanisms that involve reactive oxygen species (ROS) production. However, details of the mechanism underlying cycling hypoxia-mediated radioresistance remain obscure. We have previously shown that in glioblastoma, NADPH oxidase subunit 4 (Nox4) is a critical mediator involved in cycling hypoxia-mediated ROS production and tumor progression. Here, we examined the impact of an in vivo tumor microenvironment on Nox4 expression pattern and its impact on radiosensitivity in GBM8401 and U251, two glioblastoma cell lines stably transfected with a dual hypoxia-inducible factor-1 (HIF-1) signaling reporter construct. Furthermore, in order to isolate hypoxic tumor cell subpopulations from human glioblastoma xenografts based on the physiological and molecular characteristics of tumor hypoxia, several techniques were utilized. In this study, the perfusion marker Hoechst 33342 staining and HIF-1 activation labeling were used together with immunofluorescence imaging and fluorescence-activated cell sorting (FACS). Our results revealed that Nox4 was predominantly highly expressed in the endogenous cycling hypoxic areas with HIF-1 activation and blood perfusion within the solid tumor microenvironment. Moreover, when compared to the normoxic or chronic hypoxic cells, the cycling hypoxic tumor cells derived from glioblastoma xenografts have much higher Nox4 expression, ROS levels, and radioresistance. Nox4 suppression in intracerebral glioblastoma-bearing mice suppressed tumor microenvironment-mediated radioresistance and enhanced the efficiency of radiotherapy. In summary, our findings indicated that cycling hypoxia-induced Nox4 plays an important role in tumor microenvironment-promoted radioresistance in glioblastoma; hence, targeting Nox4 may be an attractive therapeutic strategy for blocking cycling hypoxia-mediated radioresistance.

Radioprotective effect of rhizome extract of Zingiber montanum in Rattus norvegicus

The present study aims at determining the ability of 60% ethanol extract of the rhizome of Zingiber montanum (J. König) A. Dietr. to protect bone marrow cells in vivo from radiation-induced chromosomal aberrations. Albino rats (Rattus norvegicus, 2n = 42) were used to carry out investigations on the radioprotective properties of Z. montanum. Acute toxicity of the extract was determined, and a suitable injectable dose was selected for intra-peritoneal administration. The LD(50) of the extract calculated for 72 h was 2.9 g/kg, and the calculated LD(10) dose was 1.7 g/kg. The calculated maximum tolerated dose of the rhizome extract was 1.3 g/kg. Rats were divided into 12 groups (with or without the administration of extract) and exposed to different radiation doses from 1 to 5 Gy. Whole-body irradiation of rats showed a significant dose-dependent increase in different types of chromosomal aberrations. The most common chromosomal aberrations were breaks, fragments, gaps, rings, endoreduplications and dicentric chromosomes. Ethanol extract of rhizome at a dose of 0.5 g/kg did not show any significant increase in chromosomal aberrations in unirradiated animals as compared to that of the control group. Intra-peritoneal administration of the extract at a dose of 0.5 g/kg considerably reduced the frequency of the aberrations stated above in irradiated animals with DMF value of 1.36 at 1 to 5 Gy dose range of gamma radiation. The incidence of micronucleated polychromatic erythrocytes and micronucleated normochromatic erythrocytes due to the radiation exposure was considerably reduced in extract-treated groups of animals with DMFs 1.34 and 1.17, respectively, as compared to that of the extract-untreated groups. Our results suggest that rhizome extract of Z. montanum may have a potential in protecting normal hematopoietic cells from radiation-induced damage.

Radioprotective effects of Zingiber officinale Roscoe (ginger): past, present and future

Radiation is an important modality in treating people with cancer especially when surgical intervention is impracticable or might debilitate the patient. However, effective use of ionizing radiation is compromised by the side effects that result from radiation-induced damage to normal tissue. The use of radioprotective compounds, which can selectively protect normal tissues against radiation injury is of immense use because in addition to association with protecting the normal tissue, it will also permits use of higher doses of radiation to obtain better cancer control and possible cure. However, till date no ideal radioprotectors are available as most synthetic compounds are toxic at their optimal concentrations. Plants commonly used as dietary and or therapeutic agents have recently been the focus of attention since in most cases they are non-toxic and are easily accepted for human use. Ginger, the rhizomes of Zingiber officinale Roscoe (Zingiberaceae), has widely been used as both culinary and medicinal agent. Preclinical studies carried out in the last decade has shown that ginger and its phytochemicals dehydrozingerone, zingerone possess radioprotective effects in laboratory animals and in cultured cells in vitro. The hydroalcoholic extract of ginger rhizome when administered either through intraperitoneal or oral route was effective in protecting against gamma radiation-induced sickness and mortality. The phytochemicals dehydrogingerone and zingerone present in ginger are also shown to protect mice against radiation-induced sickness and mortality. Mechanistic studies have indicated that the free radical scavenging, antioxidant affects, anti-inflammatory and anti-clastogenic effects may contribute towards the observed protection. Additionally, studies with tumor bearing mice have also shown that zingerone selectively protects the normal tissues against the tumoricidal effects of radiation. This review for the first time summarizes the results related to the radioprotective properties and also emphasizes the aspects that warrant future research to establish its activity and utility as a radioprotective agent.

Effect of antioxidants on X-ray-induced γ-H2AX foci in human blood lymphocytes: preliminary observations

PURPOSE

To investigate the effect of a radioprotective oral agent containing a formulation of antioxidants and glutathione-elevating compounds on the extent of x-ray-induced γ-H2AX foci formation.

MATERIALS AND METHODS

The study was approved by local ethics committee and informed consent was obtained from each subject. In vitro experiments with blood lymphocytes of 25 healthy volunteers were performed without antioxidants and with antioxidants added either before or immediately after irradiation (10 mGy). For in vivo/in vitro tests, blood samples were obtained before, 15, 30, and 60 minutes (n=17) after, and 2, 3, and 5 hours (n=11) after oral ingestion of antioxidant pills and were irradiated (10 mGy). DNA double-strand breaks (DSBs) were quantified in isolated lymphocytes 5 minutes (in vitro and in vivo/in vitro) and 15 minutes (in vitro) after irradiation by enumerating γ-H2AX foci. To validate the data, additional in vitro experiments with use of 53BP1 as another independent marker for DSBs were performed. Nonirradiated samples served as controls. Statistical analyses were performed by using Wilcoxon rank-sum tests (in vitro), repeated-measures test, and Dunnett test (in vivo/in vitro).

RESULTS

In the in vitro experiments, 15-minute preincubation with antioxidants significantly reduced mean γ-H2AX foci levels by 23% (P<.0001), whereas addition of antioxidants immediately after irradiation did not lead to a reduction of x-ray-induced foci (P=.6905). Mean 53BP1 foci were also reduced by preincubation with the radioprotectant. In the in vivo/in vitro tests, oral pretreatment with antioxidants also led to a significant reduction of γ-H2AX foci formation; administration 60 minutes before irradiation resulted in a mean foci reduction of 58% (P<.0001).

CONCLUSION

The tested formulation of antioxidants significantly reduced formation of γ-H2AX and 53BP1 foci after irradiation at a radiologic radiation dose typical for computed tomographic imaging; administration 60 minutes prior to irradiation seems to be appropriate and leads to a significant reduction in foci.

Low dose ionizing radiation produces too few reactive oxygen species to directly affect antioxidant concentrations in cells

It has been hypothesized that radiation-induced oxidative stress is the mechanism for a wide range of negative impacts on biota living in radioactively contaminated areas around Chernobyl. The present study tests this hypothesis mechanistically, for the first time, by modelling the impacts of radiolysis products within the cell resulting from radiations (low linear energy transfer β and γ), and dose rates appropriate to current contamination types and densities in the Chernobyl exclusion zone and at Fukushima. At 417 µGy h(-1) (illustrative of the most contaminated areas at Chernobyl), generation of radiolysis products did not significantly impact cellular concentrations of reactive oxygen species, or cellular redox potential. This study does not support the hypothesis that direct oxidizing stress is a mechanism for damage to organisms exposed to chronic radiation at dose rates typical of contaminated environments.

Prevention and mitigation of acute radiation syndrome in mice by synthetic lipopeptide agonists of Toll-like receptor 2 (TLR2)

Bacterial lipoproteins (BLP) induce innate immune responses in mammals by activating heterodimeric receptor complexes containing Toll-like receptor 2 (TLR2). TLR2 signaling results in nuclear factor-kappaB (NF-κB)-dependent upregulation of anti-apoptotic factors, anti-oxidants and cytokines, all of which have been implicated in radiation protection. Here we demonstrate that synthetic lipopeptides (sLP) that mimic the structure of naturally occurring mycoplasmal BLP significantly increase mouse survival following lethal total body irradiation (TBI) when administered between 48 hours before and 24 hours after irradiation. The TBI dose ranges against which sLP are effective indicate that sLP primarily impact the hematopoietic (HP) component of acute radiation syndrome. Indeed, sLP treatment accelerated recovery of bone marrow (BM) and spleen cellularity and ameliorated thrombocytopenia of irradiated mice. sLP did not improve survival of irradiated TLR2-knockout mice, confirming that sLP-mediated radioprotection requires TLR2. However, sLP was radioprotective in chimeric mice containing TLR2-null BM on a wild type background, indicating that radioprotection of the HP system by sLP is, at least in part, indirect and initiated in non-BM cells. sLP injection resulted in strong transient induction of multiple cytokines with known roles in hematopoiesis, including granulocyte colony-stimulating factor (G-CSF), keratinocyte chemoattractant (KC) and interleukin-6 (IL-6). sLP-induced cytokines, particularly G-CSF, are likely mediators of the radioprotective/mitigative activity of sLP. This study illustrates the strong potential of LP-based TLR2 agonists for anti-radiation prophylaxis and therapy in defense and medical scenarios.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Radiation protection following nuclear power accidents: a survey of putative mechanisms involved in the radioprotective actions of taurine during and after radiation exposure

There are several animal experiments showing that high doses of ionizing radiation lead to strongly enhanced leakage of taurine from damaged cells into the extracellular fluid, followed by enhanced urinary excretion. This radiation-induced taurine depletion can itself have various harmful effects (as will also be the case when taurine depletion is due to other causes, such as alcohol abuse or cancer therapy with cytotoxic drugs), but taurine supplementation has been shown to have radioprotective effects apparently going beyond what might be expected just as a consequence of correcting the harmful consequences of taurine deficiency per se. The mechanisms accounting for the radioprotective effects of taurine are, however, very incompletely understood. In this article an attempt is made to survey various mechanisms that potentially might be involved as parts of the explanation for the overall beneficial effect of high levels of taurine that has been found in experiments with animals or isolated cells exposed to high doses of ionizing radiation. It is proposed that taurine may have radioprotective effects by a combination of several mechanisms: (1) during the exposure to ionizing radiation by functioning as an antioxidant, but perhaps more because it counteracts the prooxidant catalytic effect of iron rather than functioning as an important scavenger of harmful molecules itself, (2) after the ionizing radiation exposure by helping to reduce the intensity of the post-traumatic inflammatory response, and thus reducing the extent of tissue damage that develops because of severe inflammation rather than as a direct effect of the ionizing radiation per se, (3) by functioning as a growth factor helping to enhance the growth rate of leukocytes and leukocyte progenitor cells and perhaps also of other rapidly proliferating cell types, such as enterocyte progenitor cells, which may be important for immunological recovery and perhaps also for rapid repair of various damaged tissues, especially in the intestines, and (4) by functioning as an antifibrogenic agent. A detailed discussion is given of possible mechanisms involved both in the antioxidant effects of taurine, in its anti-inflammatory effects and in its role as a growth factor for leukocytes and nerve cells, which might be closely related to its role as an osmolyte important for cellular volume regulation because of the close connection between cell volume regulation and the regulation of protein synthesis as well as cellular protein degradation. While taurine supplementation alone would be expected to exert a therapeutic effect far better than negligible in patients that have been exposed to high doses of ionizing radiation, it may on theoretical grounds be expected that much better results may be obtained by using taurine as part of a multifactorial treatment strategy, where it may interact synergistically with several other nutrients, hormones or other drugs for optimizing antioxidant protection and minimizing harmful posttraumatic inflammatory reactions, while using other nutrients to optimize DNA and tissue repair processes, and using a combination of good diet, immunostimulatory hormones and perhaps other nontoxic immunostimulants (such as beta-glucans) for optimizing the recovery of antiviral and antibacterial immune functions. Similar multifactorial treatment strategies may presumably be helpful in several other disease situations (including severe infectious diseases and severe asthma) as well as for treatment of acute intoxications or acute injuries (both mechanical ones and severe burns) where severely enhanced oxidative and/or nitrative stress and/or too much secretion of vasodilatory neuropeptides from C-fibres are important parts of the pathogenetic mechanisms that may lead to the death of the patient. Some case histories (with discussion of some of those mechanisms that may have been responsible for the observed therapeutic outcome) are given for illustration of the likely validity of these concepts and their relevance both for treatment of severe infections and non-infectious inflammatory diseases such as asthma and rheumatoid arthritis.

Skin toxicity from external beam radiation therapy in breast cancer patients: protective effects of Resveratrol, Lycopene, Vitamin C and anthocianin (Ixor®)

Introduction

This is an observational study and the aim is to evaluate the effect of dietary supplements based on Resveratrol, Lycopene, Vitamin C and Anthocyanins (Ixor^®) in reducing skin toxicity due to external beam radiotherapy in patients affected by breast cancer.

Materials and methods

71 patients were enrolled and they were divided in two different groups: a control group (CG) of 41 patients treated with prophylactic topical therapy based on hyaluronic acid and topical steroid therapy in case of occurrence of radiodermatitis, and a Ixor-Group (IG) of 30 patients treated also with an oral therapy based on Resveratrol, Lycopene, Vitamin C and Anthocyanin (Ixor^®) at a dose of 2 tablets/day, starting from 10 days before the radiation treatment until 10 days after the end of treatment. Skin toxicity has been related to PTV, to breast volume that received a radiation dose equal or lower than 107%, included between 107% and 110%, or greater than 110% of the prescribed dose. Moreover it's been studied the relationship between skin toxicity and the chemotherapy schedule used before treatment. We calculated in both groups the percentage of patients who had a skin toxicity of grade 2 or 3 (according to RTOG scale). Absolute risk reduction (ARR), relative risk (RR) and odds ratio (OR) have been calculated for each relationship.

Results

Control Group (CG) patients with a PTV > 500 ml presented skin toxicity G2 + G3 in 30% of cases, versus 25% of Ixor-Group (IG) [OR 0.77]. In patients with a PTV < 500 ml G2 + G3 toxicity was 0% in the IG compared to 18% in CG (OR 0.23). When Dmax was less than or equal to 107% of the prescribed dose skin toxicity was G2 + G3 in 12.5% in CG, versus 0% in IG (OR 0.73), instead when Dmax was included between 107 and 110% of the prescribed dose, G2 + G3 skin toxicity was 35% in CG and 21% in IG (OR 0.50). In patients undergoing chemotherapy with anthracyclines and taxanes, G2 + G3 toxicity was 27% in CG, against 20% in IG (OR 0.68).

Conclusions

The protective effect of Resveratrol, Lycopene, Vitamin C and Anthocyanin (Ixor^®) is more detected in patients with PTV < 500 ml, when Dmax reaches values lower or equal to 107%, but not exceeding 110% of the prescribed dose, and in patients undergoing adjuvant chemotherapy with anthracyclines and taxanes.

Isolation, characterization of melanin derived from Ophiocordyceps sinensis, an entomogenous fungus endemic to the Tibetan Plateau

Melanins are pigments of high molecular weight formed by oxidative polymerization of phenolic or indolic compounds. In this present study, a black pigment was isolated from the fermentation broth of Ophiocordyceps sinensis, an entomogenous fungus which is endemic to the Tibetan Plateau by alkaline extraction, acid hydrolysis, and repeated precipitation. It was designed as melanin since the physical and chemical properties including its ultraviolet (UV) and infrared (IR) spectra of the black pigment conformed to the characteristic of melanin and similar to the commercial synthetic melanin. The antioxidant activity of melanin derived from O. sinensis was evaluated. They showed much stronger scavenging abilities on 1,1-diphenyl-2-picrylhydrazyl (DPPH•) and the chelating ability on ferrous ions than that of the water extract from the mycelia of O. sinensis, with IC(50) value 18.51 ± 0.85 μg/ml and 2.58 ± 0.26 μg/ml, separately. This is the first report of melanin from O. sinensis and will be helpful for the study on the physiology and the artificial cultivation of this fungus, an endangered species.

α-Tocopherol succinate- and AMD3100-mobilized progenitors mitigate radiation-induced gastrointestinal injury in mice

The goal of this study was to elucidate the role of α-tocopherol succinate (TS)- and AMD3100-mobilized progenitors in mitigating the ionizing-radiation-induced gastrointestinal syndrome in mice. We demonstrate the efficacy of a bridging therapy that will allow the lymphohematopoietic system of severely immunocompromised victims exposed to ionizing radiation to recover from high doses of radiation. CD2F1 mice were irradiated with a high dose of radiation causing gastrointestinal syndrome (11 Gy, cobalt-60 γ-radiation) and then transfused intravenously (retro-orbital sinus) with whole blood or peripheral blood mononuclear cells (PBMC) from TS- and AMD3100-injected mice 2, 24, or 48 hours post irradiation and monitored for 30-day survival. Jejunum sections were analyzed for tissue area, surviving crypts, villi, mitotic figures, and basal lamina enterocytes. Our results demonstrate that infusion of whole blood or PBMC from TS- and AMD3100-injected mice significantly improved survival of mice receiving a high dose of radiation. Histopathology and immunostaining of jejunum from irradiated and TS- and AMD3100-mobilized PBMC-transfused mice reveal significant protection of gastrointestinal tissue from radiation injury. We demonstrate that TS and AMD3100 mobilize progenitors into peripheral circulation and that the infusion of mobilized progenitor-containing blood or PBMC acts as a bridging therapy for immune-system recovery in mice exposed to high, potentially fatal, doses of ionizing radiation.

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.

Protective effects of polysaccharides from soybean meal against X-ray radiation induced damage in mouse spleen lymphocytes

The aim of this study was to investigate radioprotective effect of the polysaccharides from soybean meal (SMP) against X-ray radiation-induced damage in mouse spleen lymphocytes. MTT and comet assay were performed to evaluate SMP's ability to prevent cell death and DNA damage induced by radiation. The results show that, X-ray radiation (30 KV, 10 mA, 8 min (4 Gy)) can significantly increase cell death and DNA fragmentation of mouse spleen lymphocytes. Pretreatment with SMP for 2 h before radiation could increase cell viability, moreover, the SMP can reduce X-ray radiation-induced DNA damage. The percentage of tail DNA and the tail moment of the SMP groups were significantly lower than those of the radiation alone group (p < 0.05). These results suggest SMP may be a good candidate as a radioprotective agent.

α-Tocopherol succinate protects mice against radiation-induced gastrointestinal injury

The purpose of this study was to elucidate the role of α-tocopherol succinate (α-TS) in protecting mice from gastrointestinal syndrome induced by total-body irradiation. CD2F1 mice were injected subcutaneously with 400 mg/kg of α-TS and exposed to different doses of (60)Co γ radiation, and 30-day survival was monitored. Jejunum sections were analyzed for crypts and villi, PUMA (p53 upregulated modulator of apoptosis), and apoptosis (terminal deoxynucleotidyl transferase dUTP nick end labeling - TUNEL). The crypt regeneration in irradiated mice was evaluated by 5-bromo-2-deoxyuridine (BrdU). Bacterial translocation from gut to heart, spleen and liver in α-TS-treated and irradiated mice was evaluated by bacterial culture on sheep blood agar, colistin-nalidixic acid, and xylose-lysine-desoxycholate medium. Our results demonstrate that α-TS enhanced survival in a significant number of mice irradiated with 9.5, 10, 11 and 11.5 Gy (60)Co γ radiation when administered 24 h before radiation exposure. α-TS also protected the intestinal tissue of irradiated mice in terms of crypt and villus number, villus length and mitotic figures. TS treatment decreased the number of TUNEL- and PUMA-positive cells and increased the number of BrdU-positive cells in jejunum compared to vehicle-treated mice. Further, α-TS inhibited gut bacterial translocation to the heart, spleen and liver in irradiated mice. Our data suggest that α-TS protects mice from radiation-induced gastrointestinal damage by inhibiting apoptosis, promoting regeneration of crypt cells, and inhibiting translocation of gut bacteria.

Interaction between total body gamma-irradiation and choline deficiency triggers immediate modulation of choline and choline-containing moieties

PURPOSE

The objective of this study was to examine the effect of 60Co-gamma (γ) radiation on acute phase modulation, if any, of choline and choline-containing moieties in choline-deficient subjects. Corresponding results could provide information that might be useful in the management of adverse effects of γ-radiation.

MATERIALS AND METHODS

Male Swiss mice maintained on a choline-sufficient diet (CSD) and choline-free diet (CFD) based on AIN-93M formula, were subjected to whole body γ-irradiation (2-6 Gy). Liver, serum and brain samples from each group were then tested for: (i) Alterations in choline and choline-containing moieties such as phosphatidylcholine (PC) and sphingomyeline (SM); and (ii) modulation of choline profile modulating enzymes such as phospholipase D (PLD) and total sphingomyelinase (t-SMase). Liver and brain samples were also subjected to histo-pathological examinations.

RESULTS

No significant changes were observed in folate, choline, choline-containing moieties and choline-modulating enzymes in choline-sufficient mice. In contrast, interaction between cytotoxic effects of γ-radiation and choline deficiency modulated choline and choline-containing moieties. Feeding CFD reduced hepatic concentrations of choline, PC and SM whereas PLD and t-SMase activities were significantly raised. The decrease in liver choline and choline-containing moieties was accompanied by an increase in blood choline concentration. Despite choline deficiency, the level of choline and acetylcholine synthesizing enzyme choline acetyltransfease (ChAT) significantly increased in the brain.

CONCLUSIONS

We propose that choline deprivation and γ-radiation interact to modulate choline reserves of hepatic tissue, which might release choline to blood. Our studies also clearly showed that interaction between choline deficiency and γ-radiation might substantially enhance liver adipogenesis.

A mitochondria-targeted inhibitor of cytochrome c peroxidase mitigates radiation-induced death

The risk of radionuclide release in terrorist acts or exposure of healthy tissue during radiotherapy demand potent radioprotectants/radiomitigators. Ionizing radiation induces cell death by initiating the selective peroxidation of cardiolipin in mitochondria by the peroxidase activity of its complex with cytochrome c leading to release of haemoprotein into the cytosol and commitment to the apoptotic program. Here we design and synthesize mitochondria-targeted triphenylphosphonium-conjugated imidazole-substituted oleic and stearic acids that blocked peroxidase activity of cytochrome c/cardiolipin complex by specifically binding to its haem-iron. We show that both compounds inhibit pro-apoptotic oxidative events, suppress cyt c release, prevent cell death, and protect mice against lethal doses of irradiation. Significant radioprotective/radiomitigative effects of imidazole-substituted oleic acid are observed after pretreatment of mice from 1 h before through 24 h after the irradiation.

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

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

Amelioration of Chemical-Induced Skin Carcinogenesis by Aegle marmelos, an Indian Medicinal Plant, Fruit Extract

Chemoprevention is a novel approach to study the anti-initiating and anti-tumor-promoting efficacy of medicinal plants and their active principles. The present study investigated the chemopreventive potential of Aegle marmelos fruit extract in 7,12-dimethylbenz[a]anthracene-induced skin carcinogenesis and its influence on oxidative stress and the antioxidant defense system. The oral administration of A marmelos at 100 mg/kg body weight/day during peri-initiational, postinitiational, and peri- & postinitiational phases of papillomagenesis showed significant reduction in tumor incidence, tumor yield, tumor burden, and cumulative number of papillomas when compared with carcinogen-treated control. The average latent period significantly increased (7.88 weeks; control group) to 9.45, 11.11, and 11.54 weeks in different A marmelos extract (AME) experimental groups. Enzyme analysis of skin and liver showed a significant elevation in antioxidant parameters such as superoxide dismutase, catalase, glutathione, and vitamin C in AME-treated groups when compared with the carcinogen-treated control. The elevated level of lipid peroxidation in the positive control was significantly inhibited by AME administration. These results indicate that AME has the potential to reduce chemical-induced skin papillomas by enhancing the antioxidant defense system.

Protective Effect of Lycopene against Radiation-Induced Hepatic Toxicity in Rats

The radioprotective effect of lycopene against liver damage was investigated in 80 female Sprague Dawley rats (10 per group). Early-group rats included: controls (group 1), lycopene (group 2), radiotherapy alone (group 3), and lycopene + radiotherapy (group 4). Lycopene (5 mg/kg per day) was administered orally for 7 days; single-fraction 8 Gy abdominopelvic radiotherapy was administered on day 8. Early-group rats were sacrificed on day 10. Late-group rats (groups 5 – 8) underwent treatment with the same regimens but, in groups 6 and 8, lycopene was administered until all rats were sacrificed, 60 days postradiotherapy. Liver malondialdehyde levels increased significantly and glutathione (GSH) levels, GSH-peroxidase (GSH-Px) and superoxide dismutase (SOD) activity decreased significantly in radiotherapy versus control groups. In lycopene + radiotherapy groups, malondialdehyde levels decreased significantly and GSH levels, GSH-Px and SOD activity increased significantly compared with radiotherapy groups. No significant between-group histopathological differences were observed in early groups; in late groups, histopathological changes increased significantly in the radiotherapy group versus control group. A significant decrease in histopathological changes occurred in the lycopene + radiotherapy group compared with the radiotherapy group. Lycopene supplementation significantly reduced radiotherapy-induced oxidative liver injury.

Hydrogen therapy attenuates irradiation-induced lung damage by reducing oxidative stress

Molecular hydrogen (H(2)) is an efficient antioxidant that diffuses rapidly across cell membranes, reduces reactive oxygen species (ROS), such as hydroxyl radicals and peroxynitrite, and suppresses oxidative stress-induced injury in several organs. ROS have been implicated in radiation-induced damage to lungs. Because prompt elimination of irradiation-induced ROS should protect lung tissue from damaging effects of irradiation, we investigated the possibility that H(2) could serve as a radioprotector in the lung. Cells of the human lung epithelial cell line A549 received 10 Gy irradiation with or without H(2) treatment via H(2)-rich PBS or medium. We studied the possible radioprotective effects of H(2) by analyzing ROS and cell damage. Also, C57BL/6J female mice received 15 Gy irradiation to the thorax. Treatment groups inhaled 3% H(2) gas and drank H(2)-enriched water. We evaluated acute and late-irradiation lung damage after H(2) treatment. H(2) reduced the amount of irradiation-induced ROS in A549 cells, as shown by electron spin resonance and fluorescent indicator signals. H(2) also reduced cell damage, measured as levels of oxidative stress and apoptotic markers, and improved cell viability. Within 1 wk after whole thorax irradiation, immunohistochemistry and immunoblotting showed that H(2) treatment reduced oxidative stress and apoptosis, measures of acute damage, in the lungs of mice. At 5 mo after irradiation, chest computed tomography, Ashcroft scores, and type III collagen deposition demonstrated that H(2) treatment reduced lung fibrosis (late damage). This study thus demonstrated that H(2) treatment is valuable for protection against irradiation lung damage with no known toxicity.

Physico-chemical studies on the evaluation of the antioxidant activity of herbal extracts and active principles of some Indian medicinal plants

Understanding of the efficacy and mechanism for the reaction of the biologically important radicals with natural and/or synthetic antioxidants is the first step towards the development of future therapeutic agents. The kinetic parameters e.g., formation and decay rate constants predict the efficacy of an antioxidant and its fate after reaction. These parameters also dictate the ease with which competing reactions would occur in a bio-environment. The spectroscopic parameters provide the clue to the site of free radical attack to these antioxidants. Here, in this article an attempt has been made to show the use of physico-chemical methods in the evaluation of antioxidant activity of some important medicinal plants commonly used in India and the subcontinent. The systems chosen here for discussions are herbal extracts as such, curcumin from turmeric, methoxy phenols from Indian spices, dehydrogingerdione from ginger and bakuchiol from Psoralea corylifolia. All the examples shown in this article illustrate the potential of the pulse radiolysis coupled with kinetic spectroscopy and other physicochemical techniques for the study of antioxidants either in the form of mixture as in herbal extract or as an isolated compound.

Dietary selenium for the mitigation of radiation injury: effects of selenium dose escalation and timing of supplementation

We recently reported that daily dietary supplementation with 100 µg selenium (a dose exceeding a rat's nutritional requirement by about 33-fold) initiated immediately after total-body irradiation (TBI) and maintained for 21 weeks mitigates radiation nephropathy in a rat model as indicated by blood urea nitrogen (BUN) levels and histopathological criteria (Radiat Res. 2009; 17:368-73). In this follow-up study, we explored the risks and benefits of delaying the onset of supplementation, shortening periods of supplementation, and escalating selenium supplementation beyond 100 µg/day. Supplementation with 200 µg selenium/day (as selenite or seleno-l-methionine) substantially improved the mitigation of radiation nephropathy by lowering BUN levels at 4 months after TBI from 115 to as low as 34 mg/dl and by proportionally lowering the incidence of histopathological abnormalities. Shortening the period of supplementation to 3 or 2 months did not compromise efficacy. Delaying the onset of supplementation for 1 week reduced but did not abrogate the mitigation of radiation nephropathy. Supplementation with 300 µg/day mitigated radiation nephropathy less effectively than 200 µg and was poorly tolerated. Rats that had been given 10 Gy of TBI were less tolerant of high-dose selenium than nonirradiated rats. This reduced tolerance of high-dose selenium would need to be taken into consideration when selenium is used for the mitigation of radiation injury in victims of nuclear accidents or acts of radiological terrorism. The high dose requirements, the pronounced threshold effect, and the superior performance of selenite suggest that the mitigation of radiation nephropathy involves mechanisms that go beyond the induction of selenoproteins.

Pro-oxidants ameliorate radiation-induced apoptosis through activation of the calcium-ERK1/2-Nrf2 pathway

There are no reports describing the ability of pro-oxidants to protect against radiation-induced apoptosis. Activation of the redox-sensitive transcription factor Nrf2 by low levels of ROS is known to protect against oxidative stress-induced cell death. In this study, hydrogen peroxide, diethylmaleate, and 1,4-naphthoquinone (NQ) exhibited complete protection against radiation-induced cell death in lymphocytes as estimated by propidium iodide staining. Radioprotection by NQ was demonstrated by inhibition of caspase activation, decrease in cell size, DNA fragmentation, nuclear blebbing, and clonogenic assay. Interestingly, NQ offered protection to lymphocytes even when added to cells postirradiation. NQ increased intracellular ROS levels and decreased GSH levels. NQ activated Nrf2 and increased the expression of the cytoprotective gene heme oxygenase-1 in lymphocytes. NQ increased ERK phosphorylation, which is upstream of Nrf2, and this ERK activation was through increased intracellular calcium levels. Administration of NQ to mice offered protection against whole-body irradiation (WBI)-induced apoptosis in splenic lymphocytes and loss of viability of spleen and bone marrow cells. It restored WBI-mediated changes in hematological parameters and functional responses of lymphocytes. Importantly, NQ rescued mice against WBI-induced mortality. These results demonstrated that a pro-oxidant such as NQ can protect against radiation-induced apoptosis by activation of multiple prosurvival mechanisms including activation of the calcium-ERK1/2-Nrf2 pathway.

Protective effects of fucoidan against γ-radiation-induced damage of blood cells

Fucoidan, a sulfated polysaccharide purified from brown algae including Fucus vesiculosus and Laminaria japonica, has a variety of biological activities, including antioxidant and antitumor activities. Here, we investigated the radioprotective effects of fucoidan on human monoblastic leukemia cell line U937. Further, animal tests were carried out using Balb/c mice in order to determine the radiation-induced changes in the counts of blood cells, including thrombocytes, erythrocytes, leukocytes and hematocrit. Cell viability was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, wherein fucoidan (1, 10, and 100 μg/mL) was observed to improve recovery from damage caused by 8-Gy radiation in a dose dependent manner. The viability of U937 cells pre-treated with fucoidan also increased in a dose dependent manner. Furthermore, fucoidan at 100 mg/kg was found to protect against changes in the counts of blood cells as follows: on day 28 after irradiation, the thrombocyte count in the irradiated controls decreased to 45% compared with the non-irradiated controls, while that in the fucoidan-treated group was 60%. The hematocrit in the fucoidan-treated group recovered to 75% on day 28, while that in the irradiated control was 68%. The erythrocyte count in the irradiated controls consistently ranged from 64% to 67% throughout the experiment, but that in the fucoidan-treated group increased gradually, ranging from 75% to 80%. The mean number of survival days and 50-day actuarial survival rate increased dose dependently in the fucoidan-treated group. The mean number of survival days and the 50-day actuarial survival rate in this group was 16, 21, and 29 days and 12%, 20%, and 30% at fucoidan doses of 1, 10, and 100 mg/kg. The values of these parameters in the control group were 9 days and 0%, although the difference between the test and control groups was not statistically significant. Our results may prove valuable in the field of radioprotection.

Radioprotective Properties of Cumaside, a Complex of Triterpene Glycosides from the Sea Cucumber Cucumaria Japonica and Cholesterol

The radioprotective activity has been studied of a new immunomodulatory lead material, Cumaside, which is a complex of monosulfated triterpene glycosides from the edible sea cucumber Cucumaria japonica and cholesterol. Female CD-1 strain mice administered with prophylactic doses of Cumaside were irradiated using a Gamma-therapeutic device with a 60Co source (exposure dose 6.5 Gy, dose rate 1.14 Gy /min) and the average life span of the mice was determined. The animals administrated with Cumaside and irradiated were killed by pervisceral dislocation on days 4 and 9. Peripheral blood cell composition indexes, blood forming function and cell number in blood-forming organs and the number of pluripotent blood-forming stem cells were determined using standard procedures and the results compared with those of non-treated irradiated mice. The survivability percentage and average life span of the irradiated mice that were not treated with Cumaside were decreased in comparison with the Cumaside-treated groups. Especially, the leukocyte and neutrophil numbers in the blood (bone marrow from hip), and the weight and cell number of lymphoid organs were higher in the Cumaside-treated groups compared with the non-treated irradiated mice. It was concluded that at low prophylactic doses Cumaside possesses moderate radioprotective properties.

Diphlorethohydroxycarmalol, isolated from the brown algae Ishige okamurae, protects against radiation-induced cell damage in mice

The aim of this study was to evaluate the radioprotective effects of diphlorethohydroxycarmalol (DPHC), isolated from the brown algae Ishige okamurae, in mice subjected to gamma irradiation. DPHC significantly decreased the level of radiation-induced intracellular reactive oxygen species in cultured Chinese hamster lung fibroblast (V79-4) cells (p < 0.05), enhanced cell viability that decreased after exposure to γ-rays, and reduced radiation-induced apoptosis in the V79-4 cells. Pretreatment with DPHC (100 mg/kg) in mice prior to irradiation significantly protected the intestinal crypt cells in the jejunum (p < 0.01) and maintained villi height (p < 0.01), compared with those of the vehicle-treated irradiated group. Mice pretreated with DPHC also exhibited dose-dependent increases in the bone marrow cell viability. The dose-reduction factor for gamma irradiation in the DPHC-pretreated mice was 2.05 at 3.5 days after irradiation. These results suggest that DHPC plays a role in protecting cells from irradiation-induced apoptosis, through the scavenging of reactive oxygen species in vitro, and that DPHC significantly protected intestinal progenitor cells and bone marrows cells that were decreased by gamma irradiation in vivo.

Bio-prospecting of a few brown seaweeds for their cytotoxic and antioxidant activities

Methanolic extracts (MEs) of seven brown seaweeds occurring in the Indian coastal waters were screened for their cytotoxic and antioxidant properties following various assays. The methanolic extracts of seaweeds in the order of Dictyopteris australis > Spatoglossum variabile > Stoechospermum marginatum > Spatoglossum aspermum showed significant cytotoxic activity. A very high DPPH radical scavenging activity was exhibited by the methanolic extracts prepared from St. marginatum, Padina tetrastromatica, Dictyopteris delicatula and S. aspermum. The total phenolic content of the MEs varied from 13.19 ± 0.32 to 25.29 ± 0.445 gallic acid equivalents (mg g⁻¹ of methanolic extract). The reducing power assay indicated a dose dependency, at concentrations of 0.1, 0.5 and 1.0 and 2.0 mg mL⁻¹ of MEs and decreased in the following order: Butylated hydroxy toluene > P. tetrastromatica > D. delicatula > S. aspermum > S. variabile > S. marginatum > D. australis > S. marginatum. Furthermore, D. australis, S. aspermum, S. variabile and S. marginatum demonstrated good metal ion chelating properties. All the above evidences suggest that, the antioxidant compounds found in brown seaweeds scavenge free radicals through effective intervention. This decisively promotes them as a potential source of natural antioxidants.

Radioprotective effect of American ginseng on human lymphocytes at 90 minutes postirradiation: a study of 40 cases

BACKGROUND

Ionizing radiation (IR) initiates intracellular oxidative stress through enhanced formation of reactive oxygen species (ROS) that attack DNA leading to cell death. Because of the diversity of IR applied in medicine, agriculture, industry, and the growing threats of global terrorism, the acquisition of radioprotectors is an urgent need for the nation. However, the applicability of radioprotectors currently under investigation is limited due to their inherent toxicity.

OBJECTIVE

This study investigated the effect of a standardized North American ginseng extract (NAGE, total ginsenoside content: 11.7%) on DNA damage in human lymphocytes at 90 minutes postirradiation.

DESIGN

With the application of NAGE (250-1000 microg mL(-1)) at 90 minutes postirradiation (1 and 2 Gy), DNA damage in lymphocytes obtained from 40 healthy individuals was evaluated by cytokinesis-block micronucleus assay. Similar experiments were also performed in lymphocytes treated with WR-1065 (1 mmol/L or 3 mmol/L). In addition, before and after irradiation, lymphocytes obtained from 10 individuals were measured for their total antioxidant capacity (TAC) and the reactive oxygen species (ROS).

RESULTS

The significant effect of NAGE against (137)Cs-induced micronuclei (MN) in lymphocytes is concentration dependent. NAGE (750 microg mL(-1)) reduced MN yield by 50.7% after 1 Gy and 35.9% after 2 Gy exposures, respectively; these results were comparable to that of WR-1065. Furthermore, we also found that NAGE reduces MN yield and ROS but increases TAC in lymphocytes.

CONCLUSIONS

Our results suggest that NAGE is a relatively nontoxic natural compound that holds radioprotective potential in human lymphocytes even when applied at 90 minutes postirradiation. One of the radioprotective mechanisms may be mediated through the scavenging of free radicals and enhancement of the intracellular TAC.

Radiation-Induced Testicular Injury and Its Amelioration by Tinospora cordifolia (An Indian Medicinal Plant) Extract

The primary objective of this investigation is to determine the deleterious effects of sub lethal gamma radiation on testes and their possible inhibition by Tinospora cordifolia extract (TCE). For this purpose, one group of male Swiss albino mice was exposed to 7.5 Gy gamma radiation to serve as the irradiated control, while the other group received TCE (75 mg/kg b. wt./day) orally for 5 consecutive days half an hr before irradiation to serve as experimental. Exposure of animals to 7.5 Gy gamma radiation resulted into significant decrease in body weight, tissue weight, testes- body weight ratio and tubular diameter up to 15 days of irradiation. Cent percent mortality was recorded by day 17th in irradiated control, whereas all animals survived in experimental group. TCE pretreatment rendered significant increase in body weight, tissue weight, testes- body weight ratio and tubular diameter at various intervals as compared to irradiated group. Radiation induced histological lesions in testicular architecture were observed more severe in irradiated control then the experimental. TCE administration before irradiation significantly ameliorated radiation induced elevation in lipid peroxidation and decline in glutathione concentration in testes. These observations indicate the radio- protective potential of Tinospora cordifolia root extract in testicular constituents against gamma irradiation in mice.

Marked changes in endogenous antioxidant expression precede vitamin A-, C-, and E-protectable, radiation-induced reductions in small intestinal nutrient transport

Rapidly proliferating epithelial crypt cells of the small intestine are susceptible to radiation-induced oxidative stress, yet there is a dearth of data linking this stress to expression of antioxidant enzymes and to alterations in intestinal nutrient absorption. We previously showed that 5-14 days after acute γ-irradiation, intestinal sugar absorption decreased without change in antioxidant enzyme expression. In the present study, we measured antioxidant mRNA and protein expression in mouse intestines taken at early times postirradiation. Observed changes in antioxidant expression are characterized by a rapid decrease within 1h postirradiation, followed by dramatic upregulation within 4h and then downregulation a few days later. The cell type and location expressing the greatest changes in levels of the oxidative stress marker 4HNE and of antioxidant enzymes are, respectively, epithelial cells responsible for nutrient absorption and the crypt region comprising mainly undifferentiated cells. Consumption of a cocktail of antioxidant vitamins A, C, and E, before irradiation, prevents reductions in transport of intestinal sugars, amino acids, bile acids, and peptides. Ingestion of antioxidants may blunt radiation-induced decreases in nutrient transport, perhaps by reducing acute oxidative stress in crypt cells, thereby allowing the small intestine to retain its absorptive function when those cells migrate to the villus days after the insult.

Radioprotection of sensitive rat tissues by oligoelements Se, Zn, Mn plus Lachesis muta venom

In this study we first evaluated the general radioprotective efficacy of Se, Zn and Mn (4 µg/ml each) plus Lachesis muta venom (4 ng/ml) combination (O-LM) by determining survival on rats irradiated with lethal doses of gamma-rays. The aim of the second part of the study was to investigate the O-LM ability to prevent ionizing radiation-induced damage on small intestine, bone marrow and submandibular glands. Hence, histological characteristics and functional studies, together with proliferation and apoptotic marker levels on whole body irradiated rats with a 5 Gy dose were evaluated. Results show that all animals of the untreated group died after whole body irradiation with 8 and 10 Gy while 60 day-survival was more than 80% and 40% in O-LM-treated animals, respectively. Histopathological examinations revealed a high degree of small intestine and submandibular gland radioprotection 3 days post-irradiation. O-LM inhibited histological damage on small intestine, restoring the radiation-induced reduction in villous height and crypt number. O-LM prevented radiation-induced loss of salivary gland function and morphological alterations. These effects were associated to a complete inhibition of radiation-induced apoptosis. Furthermore, studies performed 30 days post-irradiation revealed that O-LM significantly improved bone marrow repopulation, increasing all medullar progenies to the extent of the non-irradiated animals, and completely prevented permanent submandibular gland alterations. Based on the present results and taking into account that O-LM is being safely administered in phase I clinical trial as an immunomodulator, we conclude that O-LM is a non-toxic promising approach to achieve radioprotection for patients undergoing radiotherapy.

Modulation of gamma ray-induced genotoxic effect by thymol, a monoterpene phenol derivative of cymene

The radioprotective effect of thymol (TOH), a monoterpene phenol, on radiation-induced DNA damage was analyzed in vitro. Chinese hamster lung fibroblast cells (V79) were treated with different concentrations of TOH (0-100 µg/mL) for 1 hour before exposure to 3 Gy gamma irradiation, and then cytokinesis-blocked micronucleus and single-cell gel electrophoresis (comet assay) assays were used to evaluate the radiation-induced cytogenetic damage and genotoxic effects. Furthermore, the modulating effect of TOH on radiation-induced cell death was assessed by apoptotic and necrotic cell detection by staining with ethidium bromide/acridine orange using fluorescence microscopy. To understand the mechanism of TOH-imparted cytoprotection, mitochondrial membrane potential (MMP) was detected by flow cytometry after staining the cells with Rhodamine 123. Pretreatment of V79 cells with various concentrations of TOH (0-100 µg/mL) for 1 hour reduced the radiation-induced micronuclei as well as percent tail DNA and mean Olive tail moment with a maximum protective effect observed at TOH (25 µg/mL). Apoptosis by microscopic, MMP measurements indicated that the V79 cells exposed to gamma radiation alone showed a maximal increase in the number of early and late apoptotic and necrotic cell death associated with a significant loss of the MMP. Pretreatment with TOH (25 µg/mL) showed a significant (P < .01) decrease in the level of apoptotic fraction as well as necrotic cells and suppressed the radiation-induced collapse of MMP when compared with the radiation alone group. These results suggest that TOH suppresses radiation-induced genotoxicity, apoptosis, and necrosis primarily by the free radical scavenging and modulation of oxidative stress.