Consequences of lethal-whole-body gamma radiation and possible ameliorative role of melatonin

Investigation of the anti-oxidative and anti-inflammatory effects of melatonin on experimental liver damage by radiation

Radiotherapy is one of the inevitable treatment approaches for several types of cancer. We aimed to show the protective and therapeutic effects of daily use of melatonin on liver tissues subjected to a single dose of 10 Gy (gamma-ray) total body radiation. Rats were divided into 6 groups, of which 10 were in each: control, sham, melatonin, radiation, radiation+melatonin, and melatonin+radiation. The rats received 10 Gy of external radiation throughout their entire bodies. The rats were given 10 mg/kg/day of melatonin intraperitoneally before or after radiation treatment, depending on the group. Histological methods, immunohistochemical analysis (Caspase-3, Sirtuin-1, α-SMA, NF_ΚB-p65), biochemical analysis by ELİSA (SOD, CAT, GSH-PX, MDA, TNF-α, TGF-β, PDGF, PGC-1α) and the Comet assay as a marker of DNA damage were applied to the liver tissues. Histopathological examinations showed structural changes in the liver tissue of the radiation group. Radiation treatment increased the immunoreactivity of Caspase-3, Sirtuin-1 and α-SMA, but these effects were relatively attenuated in the melatonin-treated groups. The melatonin+radiation group had statistically significant results close to those of the control group, in terms of Caspase-3, NF_ΚB-p65 and Sirtuin-1 immunoreactivity. In melatonin treated groups, hepatic biochemical markers, MDA, SOD, TNF-α, TGF-β levels, and DNA damage parameters were decreased. Administration of melatonin before and after radiation has beneficial effects, but using it before radiation may be more efficient. Accordingly, daily melatonin usage could mitigate ionizing radiation induced damage.

Neuroprotective effects of alpha-lipoic acid on radiation-induced brainstem injury in rats

Background and purpose

Alpha-lipoic acid (ALA) is an antioxidant with radioprotective properties. We designed the current work to assess the neuroprotective function of ALA in the presence of oxidative stress induced by radiation in the brainstem of rats.

Experimental approach

Whole-brain radiations (X-rays) was given at a single dose of 25 Gy with or without pretreatment with ALA (200 mg/kg BW). Eighty rats were categorized into four groups: vehicle control (VC), ALA, radiation-only (RAD), and radiation + ALA (RAL). The rats were given ALA intraperitoneally 1 h before radiation and killed following 6 h, thereafter superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), and total antioxidant capacity (TAC) in the brainstem were measured. Furthermore, a pathological examination was carried out after 24 h, 72 h, and five days to determine tissue damage.

Findings/Results

The findings indicated that MDA levels in the brainstem were 46.29 ± 1.64 μM in the RAD group and decreased in the VC group (31.66 ± 1.72 μM). ALA pretreatment reduced MDA levels while simultaneously increasing SOD and CAT activity and TAC levels (60.26 ± 5.47 U/mL, 71.73 ± 2.88 U/mL, and 227.31 ± 9.40 mol/L, respectively). The greatest pathological changes in the rat's brainstems were seen in RAD animals compared to the VC group after 24 h, 72 h, and 5 days. As a result, karyorrhexis, pyknosis, vacuolization, and Rosenthal fibers vanished in the RAL group in three periods.

Conclusion and implications

ALA exhibited substantial neuroprotectivity following radiation-induced brainstem damage.

Dose- and Segment-Dependent Disturbance of Rat Gut by Ionizing Radiation: Impact of Tight Junction Proteins

The damaging effect of ionizing radiation (IR) exposure results in the disturbance of the gut natural barrier, followed by the development of severe gastrointestinal injury. However, the dose and application segment are known to determine the effects of IR. In this study, we demonstrated the dose- and segment-specificity of tight junction (TJ) alteration in IR-induced gastrointestinal injury in rats. Male Wistar rats were subjected to a total-body X-ray irradiation at doses of 2 or 10 Gy. Isolated jejunum and colon segments were tested in an Ussing chamber 72 h after exposure. In the jejunum, 10-Gy IR dramatically altered transepithelial resistance, short-circuit current and permeability for sodium fluorescein. These changes were accompanied by severe disturbance of histological structure and total rearrangement of TJ content (increased content of claudin-1, -2, -3 and -4; multidirectional changes in tricellulin and occludin). In the colon of 10-Gy irradiated rats, lesions of barrier and transport functions were less pronounced, with only claudin-2 and -4 altered among TJ proteins. The 2-Gy IR did not change electrophysiological characteristics or permeability in the colon or jejunum, although slight alterations in jejunum histology were noted, emphasized with claudin-3 increase. Considering that TJ proteins are critical for maintaining epithelial barrier integrity, these findings may have implications for countermeasures in gastrointestinal acute radiation injury.

Possible radioprotection of submandibular glands in gamma-irradiated rats using kaempferol: a histopathological and immunohistochemical study

BACKGROUND AND PURPOSE

Salivary gland damage remains a problem despite advances in radiotherapy schedules for head and neck cancer. Kaempferol, a natural flavonoid, found in several fruits and vegetables, is a good antioxidant. This study was designed to evaluate the possible protective effects of kaempferol on submandibular glands (SMGs) of rats exposed to fractionated gamma irradiation.

MATERIALS AND METHODS

Twenty-four male adult Wistar albino rats were included in this study and assigned to three groups (n = 8). Rats in group K received kaempferol orally in five doses at a dose of 10 mg/kg/2 days for 10 days. Meanwhile, rats in group R were subjected to fractionated whole-body gamma irradiation at a dose of 2 Gy/5 days/week for 2 weeks (20 Gy), and the KR group received kaempferol as group K and then was subjected to a fractionated whole-body gamma irradiation as group R. SMG samples were collected on days 1 and 7 after the last radiation session; and processed for histopathological and immunohistochemical investigations.

RESULTS

The SMGs of group R showed focal atrophy and degeneration. Acini showed vacuolization and had pyknotic hyperchromatic nuclei. Striated ducts degenerated, shrunken, and were surrounded by empty spaces. The percentage of areas covered by cyclooxygenase-2 (COX-2) significantly increased, whereas the percentage of areas covered by proliferating cell nuclear antigen (PCNA) significantly decreased compared with those in group K. Cotreatment with kaempferol (group KR) partially preserved normal gland architecture where acinar vacuolation and degeneration were almost absent; however, some ducts degenerated. A significant decrease in the percentage of areas covered by COX-2 and a significant increase in the percentage of areas covered by PCNA were observed compared with those in group R.

CONCLUSIONS

Kaempferol has a possible radioprotective effect on the SMGs of rats exposed to fractionated gamma irradiation.

Evaluating the role of propolis and bee venom on the oxidative stress induced by gamma rays in rats

Honeybee products consist of many substances, which have long been known for their medicinal and health-promoting properties. This study set out to appraise the protective potential of Egyptian propolis (EP) and bee venom (BV) separately or combined against total body irradiation (TBI) induced oxidative injury in rats. Besides, we assessed the bioactive components in EP and BV using HPLC and UPLC/ ESI-MS analysis in the positive ion mode. The animals were subjected to a source of gamma ionizing radiation at a dose of 6 Gy. Propolis and BV were administered independently and in combination before 14 days of γ-irradiation. Liver and kidney functions were estimated besides, DNA damage index (8- OHdG) by ELISA. Antioxidants, including glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were detected. Gene expression technique investigated for BAX, BCL2, and in plasma also miR125b expression in serum of rats. Besides, the histopathological for the brain, liver, kidney, and heart were investigated. In addition, lipid peroxidation was investigated in plasma and in the previous organs. The present results provide opportunities to advance the use of bee products as promising medicinal sources.

Genome Maintenance Mechanisms at the Chromatin Level

Genome integrity is constantly threatened by internal and external stressors, in both animals and plants. As plants are sessile, a variety of environment stressors can damage their DNA. In the nucleus, DNA twines around histone proteins to form the higher-order structure “chromatin”. Unraveling how chromatin transforms on sensing genotoxic stress is, thus, key to understanding plant strategies to cope with fluctuating environments. In recent years, accumulating evidence in plant research has suggested that chromatin plays a crucial role in protecting DNA from genotoxic stress in three ways: (1) changes in chromatin modifications around damaged sites enhance DNA repair by providing a scaffold and/or easy access to DNA repair machinery; (2) DNA damage triggers genome-wide alterations in chromatin modifications, globally modulating gene expression required for DNA damage response, such as stem cell death, cell-cycle arrest, and an early onset of endoreplication; and (3) condensed chromatin functions as a physical barrier against genotoxic stressors to protect DNA. In this review, we highlight the chromatin-level control of genome stability and compare the regulatory systems in plants and animals to find out unique mechanisms maintaining genome integrity under genotoxic stress.

The Effects of Melatonin Administration on Intestinal Injury Caused by Abdominal Irradiation from Mice

Intestinal injury caused by ionizing radiation (IR) is a main clinical issue for patients with cancer receiving abdominal or pelvic radiotherapy. Melatonin (N-acetyl-5-methoxytryptamine) is a neurohormone that the pineal gland in the brain normally secretes. The study aimed to disclose the potential function of melatonin in intestinal injury induced by IR and its mechanism. Pretreatment with melatonin enhanced the 30-day survival rate of the irradiated mice and promoted the recovery of the intestinal epithelium and hematopoietic function following abdominal irradiation (ABI). Melatonin altered the gene profile of the small intestines from mice following ABI. The enriched biological process terms for melatonin treatment prior to radiation were mainly involved in the immune process. LPS/IL-1-mediated inhibition of RXR Function, TWEAK signaling, and Toll-like receptor signaling were the most activated canonical pathways targeted by melatonin. An upstream analysis network showed that Tripartite motif-containing 24 (TRIM24) was the most significantly inhibited and S100 calcium binding protein A9 (S100A9) activated. TRIM24 activated atherogenesis and cell viability in breast cancer cell lines and S100A9 inhibited the metabolism of amino acids. Melatonin has radioprotective effects on ABI-caused intestinal injury. The mechanisms behind the beneficial effects of melatonin were involved in activation of the immunity. It is necessary to conduct further experiments to explore the underlying mechanisms.

Quantitative proteomic analysis of the effects of melatonin treatment for mice suffered from small intestinal damage induced by γ-ray radiation

PURPOSE

Intestinal damage induced by radiation exposure is a major clinic concern of radiotherapy for patients with abdominal or pelvic tumor. Melatonin (N-acetyl-5-methoxytryptamine) is likely be an ideal radioprotector to protect individuals from radiation exposure. The study aimed to define the role of melatonin in small intestinal damage caused by abdominal irradiation (ABI).

MATERIALS AND METHODS

30-day survival rate and pathological histology of the intestines from melatonin-treated mice after 13 Gy ABI exposure was first detected. Next, quantitative proteomics analysis of the small intestines tissue was examined and GO term and KEGG pathways analysis were performed.

RESULTS

Melatonin treatment before ABI exposure significantly increased 30-day survival rate to 83% and ameliorated damage to the intestinal epithelial cells. Melatonin significantly altered the proteins profile of the small intestines following irradiation. For the irradiated mice treated with melatonin in comparison with the irradiated mice, the enriched GO terms were mainly involved in defense response to other organism (BP, GO: 0098542), response to other organism (BP, GO: 0051707), anion transmembrane transporter activity (MF, GO: 0008509), and secondary active transmembrane transporter activity (MF, GO: 0015291). In the process of antioxidant activity (MF, GO: 0016209), melatonin treatment prior to radiation exhibited high protein levels of Sod3 and Gpx3. The markedly KEGG pathways for melatonin treatment prior to radiation mainly included protein digestion and absorption (ko 04974) and mineral absorption (ko 04978). p53 signaling pathway and DNA repair pathways were enriched in melatonin treated mice. The amount of radiation-induced DNA damage and the cell apoptosis of the small intestines was decreased in the melatonin-treated mice.

CONCLUSIONS

Melatonin may protect small intestines from radiation damage through increasing DNA repair and decreasing cell apoptosis of the small intestines. Our data provided perspective for the study of melatonin in mitigating ABI-caused intestinal damage.

Melatonin exerts a neuroprotective effect against γ-radiation-induced brain injury in the rat through the modulation of neurotransmitters, inflammatory cytokines, oxidative stress, and apoptosis

The current study aimed to investigate the ameliorative effect of melatonin (MLT) against brain injury in rats undergoing whole-body exposure to γ-radiation. Male Wistar rats were whole-body exposed to 4-Gy γ-radiation from a cesium-137 source. MLT (10 mg/kg) was orally administrated 30 minutes before irradiation and continued once daily for 1 and 7 days after exposure. In the irradiated rats, the plasma levels of glutamate were increased, while the gamma-aminobutyric acid (GABA) levels were decreased, and MLT improved the disturbed glutamate and GABA levels. These effects paralleled an increase in pro-inflammatory cytokines (IL-1b, IL-6, and TNF-a) and C-reactive protein as well as a decrease in IL-10 in the plasma of the irradiated rats. MLT treatment markedly reduced these effects, indicating its anti-inflammatory impact. Immunohistochemical studies demonstrated a remarkable upregulation of caspase-3 and P53 expression, indicating the increased apoptosis in the brain of irradiated rats. MLT significantly downregulated the expression of these parameters compared with that in the irradiated rats, indicating its anti-apoptotic effect. Oxidative stress is developed in the brain as evidenced by increased levels of malondialdehyde; decreased activities of superoxide dismutase, catalase, and glutathione peroxidase; and decreased content of glutathione in the brain. MLT remarkably ameliorated the development of oxidative stress in the brain of the irradiated rats indicating its antioxidant impact. The histopathological results were consistent with the biochemical and immunohistochemical results and showed that MLT remarkably protected the histological structure of brain tissue compared with that in the irradiated rats. In conclusion, MLT showed potential neuroprotective properties by increasing the release of neurotransmitters, antioxidants, and anti-inflammatory factors and reducing pro-inflammatory cytokines and apoptosis in the brain of irradiated rats. MLT can be beneficial in clinical and occupational settings requiring radiation exposure; however, additional studies are required to elucidate its neuroprotective effect in humans.

A derivative of vitamin B3 applied several days after exposure reduces lethality of severely irradiated mice

Most, if not all, of the hitherto tested substances exert more or less pronounced pro-survival effects when applied before or immediately after the exposure to high doses of ionizing radiation. In the present study we demonstrate for the first time that 1-methyl nicotinamide (MNA), a derivative of vitamin B3, significantly (1.6 to 1.9 times) prolonged survival of BALB/c mice irradiated at LD30/30 (6.5 Gy), LD50/30 (7.0 Gy) or LD80/30 (7.5 Gy) of γ-rays when the MNA administration started as late as 7 days post irradiation. A slightly less efficient and only after the highest dose (7.5 Gy) of γ-rays was another vitamin B3 derivative, 1-methyl-3-acetylpyridine (1,3-MAP) (1.4-fold prolonged survival). These pro-survival effects did not seem to be mediated by stimulation of haematopoiesis, but might be related to anti-inflammatory and/or anti-thrombotic properties of the vitamin B3 derivatives. Our results show that MNA may represent a prototype of a radioremedial agent capable of mitigating the severity and/or progression of radiation-induced injuries when applied several hours or days after exposure to high doses of ionizing radiation.

The effect of piracetam on behavioral reactions of adult rats and morphological changes in the brain after whole body fractionated gamma irradiation: an exploratory study

This research was aimed at examining the effect of piracetam on behavioral reactions and morphological changes in the brain of adult rats after fractionated gamma irradiation with a total dose of 5 Gy. Fractionated gamma irradiation led to a decrease in freezing behavior in the Open Field and leukopenia. These behavioral and hematological disorders were accompanied by a cell decrease in the cross-sectional area of granular layer of the dentate gyrus, an increase in the number of Fluoro Jade B-positive cells, and an increase in the number of irreversible changes in the cerebral cortex. The administration of piracetam immediately after irradiation for 14 days maintained the freezing behavior at the level of intact animals and decreased in general motor activity. Also, an increase in morphometric parameters and a decrease of neurodegeneration were observed. We found a statistically significant decrease in the number of Fluoro Jade B-positive cells in comparison with the group of irradiated animals. The drug had no leukoprotective effect on laboratory animals, and led to the emergence of inconclusive trends in the alternation of the arms of the T-labyrinth. Piracetam application showed positive behavioral and morphological changes in rodents and might have a neuroprotective effect in brain tissue after gamma irradiation. Since it is the first experiment with piracetam we attempted, this exploratory study serves to provide more insight into the potential neuroprotection activity of piracetam, and following research is necessary.

The effect of selected drugs on the mitigation of myocardial injury caused by gamma radiation

Radiation damage of healthy tissues represents one of the complications of radiotherapy effectiveness. This study is focused on the screening of potentially effective drugs routinely used in medical practice and involved in the mechanism of radiation injury, namely for radiation-induced production of free radicals in the body. Experiments in rats revealed significant reduction of oxidative stress (malondialdehyde) and inflammatory marker (tumor necrosis factor α) in 10 Gy irradiated groups after administration of atorvastatin and a slight decrease after tadalafil administration, which indicates that one of the possible mechanisms for mitigation of radiation-induced cardiac damage could be the modulation of nitric oxide (NO) in endothelium and phosphodiesterase 5. In addition, miRNAs were analyzed as potential markers and therapeutically effective molecules. Expression of miRNA-21 and miRNA-15b showed the most significant changes after irradiation. Atorvastatin and tadalafil normalized changes of miRNA (miRNA-1, miRNA-15b, miRNA-21) expression levels in irradiated hearts. This screening study concludes that administration of specific drugs could mitigate the negative impact of radiation on the heart, but more detailed experiments oriented to other aspects of drug effectiveness and their exact mechanisms are still needed.

Development of hematopoietic syndrome mice model for localized radiation exposure

Current models to study the hematopoietic syndrome largely rely on the uniform whole-body exposures. However, in the radio-nuclear accidents or terrorist events, exposure can be non-uniform. The data available on the non-uniform exposures is limited. Thus, we have developed a mice model for studying the hematopoietic syndrome in the non-uniform or partial body exposure scenarios using the localized cobalt⁶⁰ gamma radiation exposure. Femur region of Strain 'A' male mice was exposed to doses ranging from 7 to 20 Gy. The 30 day survival assay showed 19 Gy as LD₁₀₀ and 17 Gy as LD_50. We measured an array of cytokines and important stem cell markers such as IFN-γ, IL-3, IL-6, GM-CSF, TNF-α, G-CSF, IL-1α, IL-1β, CD 34 and Sca 1. We found significant changes in IL-6, GM-CSF, TNF-α, G-CSF, and IL-1β levels compared to untreated groups and amplified levels of CD 34 and Sca 1 positive population in the irradiated mice compared to the untreated controls. Overall, we have developed a mouse model of the hematopoietic acute radiation syndrome that might be useful for understanding of the non-uniform body exposure scenarios. This may also be helpful in the screening of drugs intended for individuals suffering from radiation induced hematopoietic syndrome.

Neuroprotective effect of melatonin on radiation-induced oxidative stress and apoptosis in the brainstem of rats

This study aimed to determine the effects of melatonin on irradiation-induced apoptosis and oxidative stress in the brainstem region of Wistar rats. Therefore, the animals underwent whole-brain X-radiation with a single dose of 25 Gy in the presence or absence of melatonin pretreatment at a concentration of 100 mg/kg BW. The rats were allocated into four groups (10 rats in each group): namely, vehicle control (VC), 100 mg/kg of melatonin alone (MLT), irradiation-only (RAD), and irradiation plus 100 mg/kg of melatonin (RAM). An hour before irradiation, the animals received intraperitoneal (IP) melatonin and then were killed after 6 hr, followed by measurement of nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant capacity (TAC) in the brainstem region. Furthermore, the western blot analysis technique was performed to assess the caspase-3 expression level. Results showed significantly higher MDA and NO levels in the brainstem tissues for the RAD group when compared with the VC group (p < .001). Moreover, the irradiated rats exhibited a significant decrease in the levels of CAT, SOD, GPx, and TAC (p < .01, p < .001, p < .001, and p < .001, respectively) in comparison to the VC group. The results of apoptosis assessment revealed that the expression level of caspase-3 significantly rose in the RAD group in comparison with the VC group (p < .001). Pretreatment with melatonin ameliorated the radiation-induced adverse effects by decreasing the MDA and NO levels (p < .001) and increasing the antioxidant enzyme activities (p < .001). Consequently, the caspase-3 protein expression level in the RAM group showed a significant reduction in comparison with the RAD group (p < .001). In conclusion, melatonin approximately showed a capacity for neuroprotective activity in managing irradiation-induced oxidative stress and apoptosis in the brainstem of rats; however, the use of melatonin as a neuroprotective agent in humans requires further study, particularly clinical trials.

Exogenous melatonin modulates carbon ion radiation-induced immune dysfunction in mice

In spite of carbon ion radiotherapy is a talented modality for malignant tumor patients, the radiation damage of normal tissues adjacent to tumor and the dysfunction of immune system limits therapeutic gain. Protecting immune system against carbon ion radiation-caused damage has the possibility to improve cancer treatment, but it is uncertain whether conventional radioprotective agents play a role in carbon ion radiation. To certify carbon ion caused immune dysfunction and assess the radioprotective effect of melatonin on immune system, animal experiments were performed in radiosensitive BALB/C mice. Here, we observed the bodyweight loss, death and apoptosis, abnormal T-cell distributions in immune system in carbon ion radiated mice. Pretreatment with melatonin could increase the index of thymus and spleen, reduce cell apoptosis in thymus and spleen, and attenuate the carbon ion radiation-caused imbalance of T lymphocytes and disorder of cytokines. These results suggest that melatonin can act as an effective protector against carbon ion radiation-caused immune dysfunction. Furthermore, we also found melatonin restored the activity of the antioxidant enzymes and reduced the level of lipid peroxidation in serum. These data have provided baseline information both for radiation workers and cancer patients to use melatonin as a radioprotector during the carbon ion radiation treatment.

Evaluation of Ameliorative Potential of Vitamins E and C on DNA Double Strand Break (DSB) in Patients Undergoing Computed Tomography (CT): A Clinical Study

Computed tomography (CT) is one of the most important diagnostic X-ray procedures which plays an important role in increasing the patient dose values. The purpose of this clinical study was to evaluate the efficacy of vitamins E and C in lowering down the level of DNA double strand break (DSB) caused by CT scan. Sixty patients for abdomen/pelvic enhanced CT scan were randomly assigned to placebo (control), vitamin C, and vitamin E groups. The patient blood samples were taken before and immediately after the CT scan. Counting the number of DSB was performed using γ-H2AX method as a sensitive biomarker. Immediately after the CT scan, the mean number of DSBs/cell increased in all three groups of control (131%, P<0.001), vitamin C (103%, P <0.001), and vitamin E (66%, P<0.001) compared to their mean before the CT scan. Furthermore, the results showed that vitamin E decreased the mean number of DSBs/cell by 22% in comparison with the control group (P =0.023), whereas vitamin C had no significant effect on reducing the DSB (<3%, P =0.741). It is concluded that the administration of vitamin E one hour before the CT scan, significantly decreases DSB levels.

Dark tea extract mitigates hematopoietic radiation injury with antioxidative activity

The hematopoietic system is widely studied in radiation research. Tea has been proved to have antioxidative activity. In the present study, we describe the protective effects of dark tea extract (DTE) on radiation-induced hematopoietic injury. DTE administration significantly enhanced the survival rate of mice after 7.0 and 7.5 Gy total body irradiation (TBI). The results showed that DTE not only markedly increased the numbers and cloning potential of hematopoietic cells, but also decreased DNA damages after mice were exposed to 6.0 Gy total body irradiation (TBI). In addition, DTE also decreased the levels of reactive oxygen species (ROS) in hematopoietic cells by inhibiting NOX4 expression and increasing the dismutase, catalase and glutathione peroxidase in livers. These data demonstrate that DTE can prevent radiation-induced hematopoietic syndromes, which is beneficial for protection from radiation injuries.

The Beneficial Radioprotective Effect of Tomato Seed Oil Against Gamma Radiation-Induced Damage in Male Rats

Radiation protection research receives intense focus due to its significant impact on human health. The present study was undertaken to investigate the protective effect of pretreatment with tomato seed oil (TSO) against gamma radiation-induced damage in rats. Male Wistar rats were divided into four groups: (1) untreated control; (2) TSO-supplemented; (3) gamma-irradiated; (4) TSO-pretreated and gamma-irradiated. Acute exposure of animals to a single gamma radiation dose (6 Gy) induced oxidative stress in major body organs, altered serum lipid homeostasis, significantly increased serum testosterone and sorbitol dehydrogenase levels, and elicited a systemic inflammation as manifested by the induction of serum vascular cell adhesion molecule-1. Oral pretreatment with TSO (1 ml/kg; 3 times/week for 8 weeks) before exposure to gamma radiation protected rats against ionizing radiation-induced oxidative stress, restored lipid homeostasis, and suppressed systemic inflammation. Histological findings of target tissues verified biochemical data. The radioprotective ability of TSO was attributed to its content of phytosterols, policosanol, and antioxidants, including lycopene, β-carotene, lutein, and tocopherols. TSO is considered a promising radioprotective agent that can be effectively used to protect the body from the damaging effects of harmful radiation.

Melatonin Ameliorates Radiation-Induced Oxidative Stress at Targeted and Nontargeted Lung Tissue

Purpose:

Radiation causes damage to irradiated tissues and also tissues that do not receive direct irradiation through a phenomenon called out-of-field effects. This damage through signals such as inflammatory responses can be transmitted to unirradiated cells/tissues and causes many effects such as oxidative damage. The radioprotective and anti-inflammatory effects of melatonin have been demonstrated in various studies. The aim of this study was to evaluate the effect of pretreatment with melatonin on oxidative damage caused by direct irradiation and out-of-field effects on the lung tissue after pelvic irradiation in rats.

Materials and Methods:

In this experimental study, 42 adult male Wistar albino rats were divided into seven groups (six rats per group) including control, melatonin treatment, localized irradiation to the pelvis (out-of-field group), whole-body scatter group (which gave radiation dose equal to the amount of radiation that the lung had received from the localized pelvic irradiation), direct irradiation to lung, melatonin administration before localized radiation to the pelvis, and melatonin administration before localized radiation to the lung. A 100 mg/kg of melatonin 30 min before irradiation with 5 Gy γ-rays in a local (3.75 cm × 3.75 cm) field to the lower abdomen was administered to the rats, and after 24 h, all rats were sacrificed and their lungs were excised to measure the biochemical parameters including malondialdehyde (MDA), glutathione peroxidase (GPx), and superoxide dismutase (SOD).

Results:

The results showed that localized irradiation to the lung or pelvis caused an increase in the MDA level. Moreover, pelvis and lung irradiation increased the GPx and SOD activity in the lungs. Pretreatment with melatonin before irradiation reduced the GPx and MDA levels in both targeted and nontargeted lung tissues and reduced the SOD activity after lung irradiation.

Conclusion:

Although pretreatment with melatonin did not increase the activity of SOD and GPx in comparison to the radiation groups, this study showed that preadministration of melatonin can ameliorate the oxidative damage induced by ionizing radiation.

The Protective Effects of 5-Methoxytryptamine-α-lipoic Acid on Ionizing Radiation-Induced Hematopoietic Injury

Antioxidants are prospective radioprotectors because of their ability to scavenge radiation-induced reactive oxygen species (ROS). The hematopoietic system is widely studied in radiation research because of its high radiosensitivity. In the present study, we describe the beneficial effects of 5-methoxytryptamine-α-lipoic acid (MLA), which was synthesized from melatonin and α-lipoic acid, against radiation-induced hematopoietic injury. MLA administration significantly enhanced the survival rate of mice after 7.2 Gy total body irradiation. The results showed that MLA not only markedly increased the numbers and clonogenic potential of hematopoietic cells but also decreased DNA damage, as determined by flow cytometric analysis of histone H2AX phosphorylation. In addition, MLA decreased the levels of ROS in hematopoietic cells by inhibiting NOX4 expression. These data demonstrate that MLA prevents radiation-induced hematopoietic syndrome by increasing the number and function of and by inhibiting DNA damage and ROS production in hematopoietic cells. These data suggest MLA is beneficial for the protection of radiation injuries.