Radioprotective effects of melatonin on radiation-induced cataract

AOP report: Development of an adverse outcome pathway for deposition of energy leading to cataracts

Cataracts are one of the leading causes of blindness, with an estimated 95 million people affected worldwide. A hallmark of cataract development is lens opacification, typically associated not only with aging but also radiation exposure as encountered by interventional radiologists and astronauts during the long-term space mission. To better understand radiation-induced cataracts, the adverse outcome pathway (AOP) framework was used to structure and evaluate knowledge across biological levels of organization (e.g., macromolecular, cell, tissue, organ, organism and population). AOPs identify a sequence of key events (KEs) causally connected by key event relationships (KERs) beginning with a molecular initiating event to an adverse outcome (AO) of relevance to regulatory decision-making. To construct the cataract AO and retrieve evidence to support it, a scoping review methodology was used to filter, screen, and review studies based on the modified Bradford Hill criteria. Eight KEs were identified that were moderately supported by empirical evidence (e.g., dose-, time-, incidence-concordance) across the adjacent (directly linked) relationships using well-established endpoints. Over half of the evidence to justify the KER linkages was derived from the evidence stream of biological plausibility. Early KEs of oxidative stress and protein modifications had strong linkages to downstream KEs and could be the focus of countermeasure development. Several identified knowledge gaps and inconsistencies related to the quantitative understanding of KERs which could be the basis of future research, most notably directed to experiments in the range of low or moderate doses and dose-rates, relevant to radiation workers and other occupational exposures.

Oxidative Stress in the Anterior Ocular Diseases: Diagnostic and Treatment

The eye is a metabolically active structure, constantly exposed to solar radiations making its structure vulnerable to the high burden of reactive oxygen species (ROS), presenting many molecular interactions. The biomolecular cascade modification is caused especially in diseases of the ocular surface, cornea, conjunctiva, uvea, and lens. In fact, the injury in the anterior segment of the eye takes its origin from the perturbation of the pro-oxidant/antioxidant balance and leads to increased oxidative damage, especially when the first line of antioxidant defence weakens with age. Furthermore, oxidative stress is related to mitochondrial dysfunction, DNA damage, lipid peroxidation, protein modification, apoptosis, and inflammation, which are involved in anterior ocular disease progression such as dry eye, keratoconus, uveitis, and cataract. The different pathologies are interconnected through various mechanisms such as inflammation, oxidative stress making the diagnostics more relevant in early stages. The end point of the molecular pathway is the release of different antioxidant biomarkers offering the potential of predictive diagnostics of the pathology. In this review, we have analysed the oxidative stress and inflammatory processes in the front of the eye to provide a better understanding of the pathomechanism, the importance of biomarkers for the diagnosis of eye diseases, and the recent treatment of anterior ocular diseases.

Thymoquinone: A Review of Pharmacological Importance, Oxidative Stress, COVID-19, and Radiotherapy

Widely consumed worldwide, Nigella sativa (NS) is a medicinal herb commonly used in various alternative medicine systems such as Unani and Tibb, Ayurveda, and Siddha. Recommended for regular use in Tibb-e-Nabwi (Prophetic Medicine), NS is considered one of the most notable forms of healing medicine in Islamic literature. Thymoquinone (TQ), the main component of the essential oil of NS, has been reported to have many properties such as antioxidant, anti-inflammatory, antiviral, and antineoplastic. Its chemical structure indicates antiviral potential against many viruses, including the hepatitis C virus, human immunodeficiency virus, and other coronavirus diseases. Interestingly, molecular docking studies have demonstrated that TQ can potentially inhibit the development of the coronavirus disease 2019 (COVID-19) by binding to the receptor site on the transmembrane serine proteinase 2 (the activator enzyme that attaches the virus to the cell). In addition, TQ has been shown to be effective against cancer cells due to its inhibitory effect by binding to the different regions of MDM2, according to the proposed molecular docking study. Detailed in this review is the origin of TQ, its significance in alternative medicine, pharmacological value, potential as a cancer anti-proliferative agent, use against the coronavirus disease 2019 (COVID-19), and treatment of other diseases.

Influence of Circadian Rhythm in the Eye: Significance of Melatonin in Glaucoma

Circadian rhythm and the molecules involved in it, such as melanopsin and melatonin, play an important role in the eye to regulate the homeostasis and even to treat some ocular conditions. As a result, many ocular pathologies like dry eye, corneal wound healing, cataracts, myopia, retinal diseases, and glaucoma are affected by this cycle. This review will summarize the current scientific literature about the influence of circadian patterns on the eye, focusing on its relationship with increased intraocular pressure (IOP) fluctuations and glaucoma. Regarding treatments, two ways should be studied: the first one, to analyze if some treatments could improve their effect on the ocular disease when their posology is established in function of circadian patterns, and the second one, to evaluate new drugs to treat eye pathologies related to the circadian rhythm, as it has been stated with melatonin or its analogs, that not only could be used as the main treatment but as coadjutant, improving the circadian pattern or its antioxidant and antiangiogenic properties.

An Immunohistochemical Study on the Presence of Nitric Oxide Synthase Isoforms (nNOS, iNOS, eNOS) in the Spinal Cord and Nodose Ganglion of Rats Receiving Ionising Gamma Radiation to their Liver

Introduction

This study determined the presence of nitric oxide synthesis isoforms (nNOS, iNOS, and eNOS) in thoracic spinal cord segments and nodose ganglia of rats with gamma-irradiated livers.

Material and Methods

Male rats (n = 32) were divided into equal groups A, B, C, and D. In group A, the controls, no radiation was applied, while groups B, C, and D received 10 Gy of ionising gamma radiation. The rats of group B were euthanized at the end of the first day (d1), those of group C on the second day (d2), and those of group D on the third day (d3). The liver, spinal cord segments, and nodose ganglion tissues were dissected and fixed, and the liver sections were examined histopathologically. The other tissues were observed through a light microscope.

Results

Regeneration occurred at the end of d3 in hepatocytes which were radiation-damaged at the end of d1 and d2. On d1, some nNOS-positive staining was found in the neuronal cells of laminae I–III of the spinal cord and in neurons of the nodose ganglion, and on d3, some staining was observed in lamina X of the spinal cord, while none of note was in the nodose ganglion. Dense iNOS-positive staining was seen on d1 in the ependymal cells of the spinal cord and in the glial cells of the nodose ganglion, and on d3, there was still considerable iNOS staining in both tissues. There was clear eNOS-positive staining in the capillary endothelial cells of the spinal cord and light diffuse cytoplasmic staining in the neurons of the nodose ganglion on d1, and on d3, intense eNOS-positive staining was visible in several endothelial cells of the spinal cord, while light nuclear staining was recognised in the neurons of the nodose ganglion.

Conclusion

The nNOS, iNOS, and eNOS isoforms are activated in the spinal cord and nodose ganglion of rats after ionising radiation insult to the liver.

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.

Melatonin a Promising Candidate for DNA Double-Stranded Breaks Reduction in Patients Undergoing Abdomen-Pelvis Computed Tomography Examinations

BACKGROUND AND OBJECTIVE

Cancer incidence is 24% higher in children and young adults exposed to Computed Tomography (CT) scans than those unexposed. Non-repairing of ionizing radiation-induced DNA Double-Strand Breaks (DSBs) can initiate carcinogenesis. In the present study, we aimed to investigate the radioprotective potential of melatonin against DSBs in peripheral blood lymphocytes of patients undergoing abdomen-pelvis CT examinations.

METHODS

This double-blind, placebo-controlled clinical trial was conducted on thirty patients. These patients were divided into two groups; group one (control) patients who have undergone the CT examination received a single oral dose of placebo, while in group two, patients received a single oral dose of 100mg melatonin. In both the groups, blood samples were collected 5-10min before and 30 minutes after the CT examination. The lymphocytes from these samples were isolated and DSBs were analyzed using γH2AX immunofluorescence microscopy.

RESULTS

Compared to the control group, the use of melatonin 1h before the CT examination caused a significant reduction in γH2AX-foci, indicating a reduction in DSBs. In addition, no side effect was observed in patients following 100mg melatonin administration.

CONCLUSION

For the first time, this study has shown that melatonin has protective effects against radiationinduced genotoxicity in peripheral blood lymphocytes of patients undergoing abdomen-pelvis CT examinations. Therefore, melatonin can be considered as a promising candidate for reducing DSBs in patients undergoing abdomen-pelvis CT examinations.

Efficacy of melatonin in restoring the antioxidant status in the lens of diabetic rats induced by streptozotocin

Background

Melatonin is a well-known free radical scavenger. The present study aimed to investigate the effects of melatonin treatment on the antioxidant status in the lenticular tissue of streptozotocin (STZ)-induced diabetic rats.

Methods

Thirty-four male rats were randomly divided into four groups as follows: healthy control rats (group 1, n = 10); diabetic control rats (group 2, n = 10); melatonin-treated (5 mg/kg·day) diabetic rats (group 3, n = 10) and melatonin-treated (5 mg/kg·day) healthy rats (group 4, n = 4). Diabetes was induced by injection of streptozotocin (50 mg/kg, ip). Following 8-weeks of melatonin treatment, all rats were killed and the blood plasma and their lenses were stored at -70 °C for antioxidant enzyme activities assay and biochemical determination.

Results

The plasma glucose and lens malondialdehyde (MDA) increased significantly in the rats of group 2 as compared to the group 1. Also, a significant decrease in the levels of catalase (CAT) and glutathione reductase (GR) activities in the lenses and plasma reduced glutathione (GSH) was found. However, the levels of lenticular MDA (not significant) and the plasma glucose significantly decreased in the rats of group 3 compared to the group 2. Besides, the levels of CAT, GR in the rats lens and plasma GSH increased significantly.

Conclusion

Diabetes mellitus induced hyperglycemia and oxidative stress, whereas melatonin decreased the blood glucose levels and lipid peroxidation and increased the activities of antioxidant enzymes in diabetic rat lenses.

Protective Effect of Melatonin Against Radiotherapy-Induced Small Intestinal Oxidative Stress: Biochemical Evaluation

Background and Objectives: Radiation enteritis is a common side effect after radiotherapy for abdominal and pelvic malignancies. The aim of the present study was to investigate the protective effect of melatonin, known for its free radical scavenging ability, against radiotherapy-induced small intestinal oxidative damage. Materials and Methods: Thirty male Wistar rats were randomly assigned to six groups (5 rats in each) as follows: Group I (control group) rats received neither radiation nor melatonin; group II rats received only 8 Gy single dose of gamma radiation to their abdomen and pelvis regions; group III (administered with only 50 mg/kg melatonin); group IV (administered with only 100 mg/kg melatonin); group V (50 mg/kg melatonin + 8 Gy radiation), group VI (100 mg/kg melatonin + 8 Gy radiation). All rats were sacrificed after 5 days for biochemical assessments of their intestinal tissues. Results: Treatment with melatonin post irradiation significantly reduced malondialdehyde (MDA) levels as well as increased both superoxide dismutase (SOD) and catalase (CAT) activities of the irradiated intestinal tissues. In addition, melatonin administration with different doses pre irradiation led to protection of the tissues. Moreover, the 100 mg/kg dose was more effective compared to 50 mg/kg. Conclusions: The results of our study suggest that melatonin has a potent protective effect against radiotherapy-induced intestinal damage, by decreasing oxidative stress and increasing antioxidant enzymes. We recommend future clinical trials for more insights.

Mechanisms for Radioprotection by Melatonin; Can it be Used as a Radiation Countermeasure?

BACKGROUND

Melatonin is a natural body product that has shown potent antioxidant property against various toxic agents. For more than two decades, the abilities of melatonin as a potent radioprotector against toxic effects of ionizing radiation (IR) have been proved. However, in the recent years, several studies have been conducted to illustrate how melatonin protects normal cells against IR. Studies proposed that melatonin is able to directly neutralize free radicals produced by IR, leading to the production of some low toxic products.

DISCUSSION

Moreover, melatonin affects several signaling pathways, such as inflammatory responses, antioxidant defense, DNA repair response enzymes, pro-oxidant enzymes etc. Animal studies have confirmed that melatonin is able to alleviate radiation-induced cell death via inhibiting pro-apoptosis and upregulation of anti-apoptosis genes. These properties are very interesting for clinical radiotherapy applications, as well as mitigation of radiation injury in a possible radiation disaster. An interesting property of melatonin is mitochondrial ROS targeting that has been proposed as a strategy for mitigating effects in radiosensitive organs, such as bone marrow, gastrointestinal system and lungs. However, there is a need to prove the mitigatory effects of melatonin in experimental studies.

CONCLUSION

In this review, we aim to clarify the molecular mechanisms of radioprotective effects of melatonin, as well as possible applications as a radiation countermeasure in accidental exposure or nuclear/radiological disasters.

Protective effects of genistein and melatonin on mouse liver injury induced by whole-body ionising radiation

The aim of the present study was to investigate the effectiveness of melatonin and genistein in preventing radiation therapy (RT)-induced liver injury in mice. A total of 70 Swiss Albino male mice were divided into 7 equal groups (n=10/group) as follows: Melatonin (M group, G3), genistein (G group, G4), polyethylene glycol-400 (P group, G5), RT only (RT group, G2) and sham irradiation (C group, G1). RT plus genistein (RT+G group, G7) and RT plus melatonin (RT+M group, G6) were the co-treatment groups. Firstly, hepatic tissue damage was induced in mice via exposure to a single dose of 6-Gy irradiation. RT was performed with a cobalt-60 teletherapy machine (80 cm fixed source-to-surface distance, 2.5-cm depth). Melatonin was processed (100 mg/kg, intraperitoneal) 30 min before and genistein was administered (200 mg/kg, SC) one day prior to the single dose of irradiation. Six months following irradiation, all mice were sacrificed. The degree of liver injury was measured using histological liver sections. Liver injury was significantly worse in the RT group than in the control group (C; RT vs. C; P<0.05); however, liver injury decreased following co-treatment with melatonin or genistein vs. RT alone (RT+M and RT+G vs. RT; P<0.05). No difference was observed between the RT+M and RT+G groups (P>0.05). The present study revealed that melatonin and genistein administration prior to irradiation protects mice against liver injury, which may have therapeutic implications for RT-induced injuries.

Tissue regeneration: Impact of sleep on stem cell regenerative capacity

The circadian rhythm orchestrates many cellular functions, such as cell division, cell migration, metabolism and numerous intracellular biological processes. The physiological changes during sleep are believed to promote a suitable microenvironment for stem cells to proliferate, migrate and differentiate. These effects are mediated either directly by circadian clock genes or indirectly via hormones and cytokines. Hormones, such as melatonin and cortisol, are secreted in response to neural optic signals and act in harmony to regulate many biological functions during sleep. Herein, we correlate the effects of the main circadian genes on the expression of certain stem cell genes responsible for the regeneration of different tissues, including bone, cartilage, skin, and intestine. We also review the effects of different hormones and cytokines on stem cell activation or suppression and their relationship to the day/night cycle. The correlation of circadian rhythm with tissue regeneration could have implications in understanding the biology of sleep and tissue regeneration and in enhancing the efficacy and timing of surgical procedures.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Melatonin as an adjuvant in radiotherapy for radioprotection and radiosensitization

It is estimated that more than half of cancer patients undergo radiotherapy during the course of their treatment. Despite its beneficial therapeutic effects on tumor cells, exposure to high doses of ionizing radiation (IR) is associated with several side effects. Although improvements in radiotherapy techniques and instruments could reduce these side effects, there are still important concerns for cancer patients. For several years, scientists have been trying to modulate tumor and normal tissue responses to IR, leading to an increase in therapeutic ratio. So far, several types of radioprotectors and radiosensitizers have been investigated in experimental studies. However, high toxicity of chemical sensitizers or possible tumor protection by radioprotectors creates a doubt for their clinical applications. On the other hand, the protective effects of these radioprotectors or sensitizer effects of radiosensitizers may limit some type of cancers. Hence, the development of some radioprotectors without any protective effect on tumor cells or low toxic radiosensitizers can help improve therapeutic ratio with less side effects. Melatonin as a natural body hormone is a potent antioxidant and anti-inflammatory agent that shows some anti-cancer properties. It is able to neutralize different types of free radicals produced by IR or pro-oxidant enzymes which are activated following exposure to IR and plays a key role in the protection of normal tissues. In addition, melatonin has shown the ability to inhibit long-term changes in inflammatory responses at different levels, thereby ameliorating late side effects of radiotherapy. Fortunately, in contrast to classic antioxidants, some in vitro studies have revealed that melatonin has a potent anti-tumor activity when used alongside irradiation. However, the mechanisms of its radiosensitive effect remain to be elucidated. Studies suggested that the activation of pro-apoptosis gene, such as p53, changes in the metabolism of tumor cells, suppression of DNA repair responses as well as changes in biosynthesis of estrogen in breast cancer cells are involved in this process. In this review, we describe the molecular mechanisms for radioprotection and radiosensitizer effects of melatonin. Furthermore, some other proposed mechanisms that may be involved are presented.

Modifiers of radiation effects in the eye

World events, including the threat of radiological terrorism and the fear of nuclear accidents, have highlighted an urgent need to develop medical countermeasures to prevent or reduce radiation injury. Similarly, plans for manned spaceflight to a near-Earth asteroid or journey to Mars raise serious concerns about long-term effects of space radiation on human health and the availability of suitable therapeutic interventions. At the same time, the need to protect normal tissue from the deleterious effects of radiotherapy has driven considerable research into the design of effective radioprotectors. For more than 70 years, animal models of radiation cataract have been utilized to test the short and long-term efficacy of various radiation countermeasures. While some compounds, most notably the Walter Reed (WR) class of radioprotectors, have reported limited effectiveness when given before exposure to low-LET radiation, the human toxicity of these molecules at effective doses limits their usefulness. Furthermore, while there has been considerable testing of eye responses to X- and gamma irradiation, there is limited information about using such models to limit the injurious effects of heavy ions and neutrons on eye tissue. A new class of radioprotector molecules, including the sulfhydryl compound PrC-210, are reported to be effective at much lower doses and with far less side effects. Their ability to modify ocular radiation damage has not yet been examined. The ability to non-invasively measure sensitive, radiation-induced ocular changes over long periods of time makes eye models an attractive option to test the radioprotective and radiation mitigating abilities of new novel compounds.

Salidroside, a scavenger of ROS, enhances the radioprotective effect of Ex-RAD® via a p53-dependent apoptotic pathway

Salidroside (Sal), the predominant component of a Chinese medicinal herb, Rhodiola rosea L., has become an attractive bioagent due to its significant anti-radiation, antioxidant and immune adjustment effects. We explored the radioprotective effect of Sal to ascertain whether it could enhance the anti-radiation effect of ON 01210.Na (Ex-RAD®) in vivo and in vitro, and elucidate its underlying mechanism. Our data demonstrated that Sal inhibited radiation-induced apoptosis, scavenged reactive oxygen species (ROS), and decreased the DNA damage of human umbilical vein endothelial cells (HUVECs). Sal downregulated the expression of Bax and p53 and increased the ratio of Bcl-2/Bax, which indicated that Sal inhibited the radiation-induced apoptosis through p53-dependent pathways. The radioprotection of the Sal pretreatment was also evidenced by an increasing survival rate of the mice, maintaining antioxidant enzyme levels in the liver, and accelerating hematopoietic recovery. The results suggest that Sal exhibits an excellent radioprotective effect with powerful antioxidant activity in vitro and in vivo. Sal enhanced the radioprotective effect of Ex-RAD by improving the antioxidant effect, the scavenging of ROS, by accelerating hematopoietic recovery and DNA repair as well as by regulating apoptotic and repair signaling pathways. Combined modality treatments were more effective than single-agent treatments, demonstrating the value of multiple-agent radioprotectants.

The role and therapeutic potential of melatonin in age-related ocular diseases

The eye is continuously exposed to solar UV radiation and pollutants, making it prone to oxidative attacks. In fact, oxidative damage is a major cause of age-related ocular diseases including cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy. As the nature of lens cells, trabecular meshwork cells, retinal ganglion cells, retinal pigment epithelial cells, and photoreceptors is postmitotic, autophagy plays a critical role in their cellular homeostasis. In age-related ocular diseases, this process is impaired, and thus, oxidative damage becomes irreversible. Other conditions such as low-grade chronic inflammation and angiogenesis also contribute to the development of retinal diseases (glaucoma, age-related macular degeneration and diabetic retinopathy). As melatonin is known to have remarkable qualities such as antioxidant/antinitridergic, mitochondrial protector, autophagy modulator, anti-inflammatory, and anti-angiogenic, it can represent a powerful tool to counteract all these diseases. The present review analyzes the role and therapeutic potential of melatonin in age-related ocular diseases, focusing on nitro-oxidative stress, autophagy, inflammation, and angiogenesis mechanisms.

The melatonin immunomodulatory actions in radiotherapy

Radiotherapy has a key role in cancer treatment in more than half of patients with cancer. The management of severe side effects of this treatment modality is a limiting factor to appropriate treatment. Immune system responses play a pivotal role in many of the early and late side effects of radiation. Moreover, immune cells have a significant role in tumor response to radiotherapy, such as angiogenesis and tumor growth. Melatonin as a potent antioxidant has shown appropriate immune regulatory properties that may ameliorate toxicity induced by radiation in various organs. These effects are mediated through various modulatory effects of melatonin in different levels of tissue reaction to ionizing radiation. The effects on the DNA repair system, antioxidant enzymes, immune cells, cytokines secretion, transcription factors, and protein kinases are most important. Moreover, anti-cancer properties of melatonin may increase the therapeutic ratio of radiotherapy. Clinical applications of this agent for the management of malignancies such as breast cancer have shown promising results. It seems anti-proliferative, anti-angiogenesis, and stimulation or suppression of some immune cell responses are the main anti-tumor effects of melatonin that may help to improve response of the tumor to radiotherapy. In this review, the effects of melatonin on the modulation of immune responses in both normal and tumor tissues will be discussed.

Radioprotective effect of hesperidin on reducing oxidative stress in the lens tissue of rats

Introduction:

Oxidative stress is a common factor in cataract. Considering the antioxidant properties of hesperidin as a flavanone glycoside from the flavonoid family with radioprotective effect, this study aimed to determine the protective effect of this flavanone glycoside on reducing oxidative stress in the eye lens tissue of mature rats caused by gamma irradiation.

Materials and Methods:

A total of 48 adult rats were randomly divided into six groups, namely, control, Dimethyl sulfoxide (DMSO), hesperidin, radiation, radiation + DMSO, and radiation + hesperidin. 15 Gy irradiation was carried out using Cobalt-60 teletherapy instrument with a source-to-surface distance of 80 cm at a dose rate of 98.5 cGy/min. 2 days following irradiation, we removed the rats' lenses and analyzed them to determine the effects of hesperidin.

Results:

The comparison of control and intervention groups after irradiation showed that malondialdehyde (MDA) level in the lens tissue was significantly higher in the irradiation groups than the control group. Furthermore, a significant difference between radiation and radiation + hesperidin groups were observed. The level of glutathione (GSH) in the lens tissue was significantly lower in the irradiation groups compared to the control group. Nonetheless, significant elevation of GSH in the radiation + hesperidin group compared to radiation group was seen.

Conclusions:

Radiation exposure reduced GSH and enhanced MDA levels in the lens tissue. However, GSH and MDA levels were modulated after hesperidin consumption. These results show the antioxidative properties of hesperidin in the lens and demonstrated that radiation complications such as cataract can be reduced by hesperidin through reducing oxidative stress.

Melatonin Reduces Cataract Formation and Aldose Reductase Activity in Lenses of Streptozotocin-induced Diabetic Rat

BACKGROUND

The relationship between the high activity of aldose reductase (AR) and diabetic cataract formation has been previously investigated. The purpose of the present study was to determine the preventing effect of melatonin on streptozotocin (STZ)-induced diabetic cataract in rats.

METHODS

34 adult healthy male Sprague-Dawely rats were divided into four groups. Diabetic control and diabetic+melatonin received a single dose of STZ (50 mg/kg, intraperitoneally), whereas the normal control and normal+melatonin received vehicle. The melatonin groups were gavaged with melatonin (5 mg/kg) daily for a period of 8 weeks, whereas the rats in the normal control and diabetic control groups received only the vehicle. The rats' eyes were examined every week and cataract formation scores (0-4) were determined by slit-lamp microscope. At the end of the eighth week, the rats were sacrificed and markers of the polyol pathway and antioxidative (Glutathione, GSH) in their lens were determined. The levels of blood glucose, HbA1c and plasma malondialdhyde (MDA), as a marker of lipid peroxidation, were also measured.

RESULTS

Melatonin prevented STZ-induced hyperglycemia by decreased blood glucose and HbA1c levels. Slit lamp examination indicated that melatonin delayed cataract progression in diabetic rats. The results revealed that melatonin feeding increased the GSH levels, decreased the activities of AR and sorbitol dehydrogenase (SDH) and sorbitol formation in catractous lenses as well as plasma MDA content.

CONCLUSION

In summary, for the first time we demonstrated that melatonin delayed the formation and progression of cataract in diabetic rat lenses.

Melatonin can Ameliorate Radiation-Induced Oxidative Stress and Inflammation-Related Deterioration of Bone Quality in Rat Femur

The aim of the present study was to evaluate the radioprotective effects of melatonin on the biomechanical properties of bone in comparison to amifostine (WR-2721). Forty Sprague Dawley rats were divided equally into 5 groups namely; control (C), irradiation (R; single dose of 50 Gy), irradiation + WR-2721 (R + WR-2721; irradiation + 200 mg/kg WR-2721) radiation + melatonin 25 mg/kg (R + M25; irradiation + 25 mg/kg melatonin), and radiation + melatonin 50 mg/kg (R + M50; irradiation + 50 mg/kg melatonin). In order to measure extrinsic (organ-level mechanical properties of bone; the ultimate strength, deformation, stiffness, energy absorption capacity) and intrinsic (tissue-level mechanical properties of bone; ultimate stress, ultimate strain, elastic modulus, toughness) features of the bone, a three-point bending (TPB) test was performed for biomechanical evaluation. In addition, a bone mineral density (BMD) test was carried out. The BMD and extrinsic properties of the diaphyseal femur were found to be significantly higher in the R + M25 group than in group R (p < 0.05). A significant increase was observed in R + M50 (p < 0.05) in comparison to group R in the cross-sectional area of the femoral shaft and elastic modulus parameter. The protective effect of melatonin was similar to that of WR-2721. Thus, biomechanical quality of irradiated bone can be ameliorated by free radical scavenger melatonin.

Determination of energy absorption and exposure buildup factors by using G-P fitting approximation for radioprotective agents

PURPOSE

Recently, there has been an increase in interest into research into radioprotective agents. Radioprotectors are compounds that protect against radiation injury when given orally (through drinking water) prior to radiation exposure. The purpose is to achieve preferred protection of normal tissues against injury inflicted by ionizing radiation used to treat tumors. The main aim of this work is to investigate energy absorption (EABF) and exposure buildup factors (EBF) of commonly used some radioprotective agents.

MATERIALS AND METHODS

We have used the Geometric Progression (G-P) fitting method for calculating the equivalent atomic number (Zeq), for EABF and EBF buildup factors of the radioprotective agents in the energy range 0.015-15 MeV for penetration depths up to 40 mean free path.

RESULTS

Significant variations in both EABF and EBF values were observed for several agents at the moderate energy region. At energies below 0.1 MeV, EABF and EBF values increased with decreasing equivalent atomic number Zeq of the samples. At energies >0.15 MeV, EABF and EBF values were found to decrease with decreasing Zeq of all agents. In addition, EABF and EBF were the largest for carnosin, tempol, melatonin, interferon gamma and orientine at 0.05 and 0.06 MeV, respectively, and the minimum values of buildup factors were at 0.1 MeV for cysteine, amifostine, penicillamine and glutathione.

CONCLUSIONS

Cysteine and amifostine are good compounds for gamma rays absorption applications among the selected compounds. The presented results in this study are expected to be helpful in radiation dosimetry.

Comparison of the effects of melatonin and genistein on radiation-induced nephrotoxicity: Results of an experimental study

The aim of the present study was to compare the effects of melatonin and genistein on radiation-induced nephrotoxicity (RIN). A total of 70 Swiss Albino mice were divided into 7 groups. Five control groups were defined, which were sham irradiation (C, G1), radiation therapy only (RT, G2), melatonin (M, G3), genistein (G, G4) and polyethylene glycol-400 (G5), respectively. The co-treatment groups were the RT plus melatonin (RT+M, G6) and RT plus genistein (RT+G, G7) groups. Irradiation was applied using a cobalt-60 teletherapy machine (80-cm fixed source-to-surface distance, 2.5-cm depth). Melatonin was administered (100 mg/kg, intraperitoneal injection) 30 min before the single dose of irradiation, whereas genistein was administered (200 mg/kg, subcutaneous injection) 1 day before the single dose of irradiation. All the mice were sacrificed 6 months after irradiation. As an end point, the extent of renal tubular atrophy for each mouse was quantified with image analysis of histological sections of the kidney. Tissue malondialdehyde (MDA) levels were also measured in each animal. In the histopathological examination of the mouse kidneys, there was a statistically significant reduction (P<0.05) in the presence of tubular atrophy between the RT+M and RT+G groups and the RT group. There was a statistically significant increase in MDA levels in the irradiated versus sham groups (RT vs. C; P<0.05); however, MDA levels were significantly decreased by co-treatment with melatonin or genistein vs. RT alone (RT+M and RT+G vs. RT; P<0.05). In conclusion, the present experimental study showed that melatonin and genistein supplementation prior to irradiation-protected mice against RIN, which may have therapeutic implications for radiation-induced injuries.

Effects of melatonin on Wi-Fi-induced oxidative stress in lens of rats

Introduction:

Melatonin has been considered a potent antioxidant that detoxifies a variety of reactive oxygen species in many pathophysiological states of eye. The present study was designed to determine the effects of Wi-Fi exposure on the lens oxidant, antioxidant redox systems, as well as the possible protective effects of melatonin on the lens injury induced by electromagnetic radiation (EMR).

Materials and Methods:

Thirty-two rats were used in the current study and they were randomly divided into four equal groups as follows: First and second groups were cage-control and sham-control rats. Rats in third group were exposed to Wi-Fi (2.45 GHz) for duration of 60 min/day for 30 days. As in the third group, the fourth group was treated with melatonin. The one-hour exposure to irradiation in second, third and fourth took place at noon each day.

Results:

Lipid peroxidation levels in the lens were slightly higher in third (Wi-Fi) group than in cage and sham control groups although their concentrations were significantly (P < 0.05) decreased by melatonin supplementation. Glutathione peroxidase (GSH-Px) activity was significantly (P < 0.05) lower in Wi-Fi group than in cage and sham control groups although GSH-Px (P < 0.01) and reduced glutathione (P < 0.05) values were significantly higher in Wi-Fi + melatonin group than in Wi-Fi group.

Conclusions:

There are poor oxidative toxic effects of one hour of Wi-Fi exposure on the lens in the animals. However, melatonin supplementation in the lens seems to have protective effects on the oxidant system by modulation of GSH-Px activity.

Coenzyme Q10 benefits symptoms in Gulf War veterans: results of a randomized double-blind study

We sought to assess whether coenzyme Q10 (CoQ10) benefits the chronic multisymptom problems that affect one-quarter to one-third of 1990-1 Gulf War veterans, using a randomized, double-blind, placebo-controlled study. Participants were 46 veterans meeting Kansas and Centers for Disease Control criteria for Gulf War illness. Intervention was PharmaNord (Denmark) CoQ10 100 mg per day (Q100), 300 mg per day (Q300), or an identical-appearing placebo for 3.5 ± 0.5 months. General self-rated health (GSRH), the primary outcome, differed across randomization arms at baseline, and sex significantly predicted GSRH change, compelling adjustment for baseline GSRH and prompting sex-stratified analysis. GSRH showed no significant benefit in the combined-sex sample. Among males (85% of participants), Q100 significantly benefited GSRH versus placebo and versus Q300, providing emphasis on Q100. Physical function (summary performance score, SPS) improved on Q100 versus placebo. A rise in CoQ10 approached significance as a predictor of improvement in GSRH and significantly predicted SPS improvement. Among 20 symptoms each present in half or more of the enrolled veterans, direction-of-difference on Q100 versus placebo was favorable for all except sleep problems; sign test 19:1, p=0.00004) with several symptoms individually significant. Significance for these symptoms despite the small sample underscores large effect sizes, and an apparent relation of key outcomes to CoQ10 change increases prospects for causality. In conclusion, Q100 conferred benefit to physical function and symptoms in veterans with Gulf War illness. Examination in a larger sample is warranted, and findings from this study can inform the conduct of a larger trial.

Can melatonin help us in radiation oncology treatments?

Nowadays, radiotherapy has become an integral part of the treatment regimen in various malignancies for curative or palliative purposes. Ionizing radiation interacts with biological systems to produce free radicals, which attack various cellular components. Radioprotectors act as prophylactic agents that are administered to shield normal cells and tissues from the harmful effects of radiation. Melatonin has been shown to be both a direct free radical scavenger and an indirect antioxidant by stimulating antioxidant enzymes and suppressing prooxidative enzymes activity. In addition to its antioxidant property, there have also been reports implicating antiapoptotic function for melatonin in normal cells. Furthermore, through its antitumor and radiosensitizing properties, treatment with melatonin may prevent tumor progression. Therefore, addition of melatonin to radiation therapy could lower the damage inflicted to the normal tissue, leading to a more efficient tumor control by use of higher doses of irradiation during radiotherapy. Thus, it seems that, in the future, melatonin may improve the therapeutic gain in radiation oncology treatments.

Zinc administration modulates radiation-induced oxidative injury in lens of rat

Background:

The aim of this study was to evaluate the antioxidant role of zinc (Zn) against radiation-induced cataract in the rat lens after total cranial irradiation with a single 5 Gray (Gy) dose of gamma irradiation.

Materials and Methods:

Twenty-one Sprague-Dawley rats were used for the experiment. The control group did not receive Zn or irradiation but received 1-ml saline orally plus sham-irradiation. The irradiation (IR) group received 5 Gy gamma irradiation to the total cranium as a single dose plus 0.1 ml physiological saline intraperitoneally. The IR plus Zn group received irradiation to total cranium plus 10 mg/kg/day Zn intraperitoneally. Biochemical parameters measured in rat lenses were carried out using spectrophotometric techniques.

Results:

Lens total (enzymatic plus non-enzymatic) superoxide scavenger activity (TSSA), glutathione reductase (GRD), and glutathione-S-transferase (GST) activities significantly increased in the IR plus Zn groups when compared with the IR group. However, TSSA, GRD and GST activities were significantly lower in the IR group when compared with the control group. Lens non-enzymatic superoxide scavenger activity (NSSA) in the IR plus Zn group was significantly increased compared to that of the IR group. Lens xanthine oxidase (XO) activity in the IR group significantly increased compared to that of both the control and IR plus Zn groups.

Conclusion:

Zn has clear antioxidant properties and prevented oxidative stress by scavenging free radicals generated by ionizing radiation in rat lenses.

Chronic testosterone propionate supplement could activated the Nrf2-ARE pathway in the brain and ameliorated the behaviors of aged rats

Aging is usually associated with a progressive disruption of the redox balance leading to recurrent damage resulting from oxidative stress. Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of motor behavior disorders. Therefore, antioxidant therapies have received considerable attention in motor behavior defects treatment. The nuclear factor erythroid 2-related factor 2 (Nrf2) binds to antioxidant response element (ARE) to induce antioxidant and phase II detoxification enzymes under conditions of oxidative stress, which reduces oxidative stress and accumulation of toxic metabolites. Testosterone has many physiological and behavioral effects throughout the lifespan and shown to affect motor behavior in adult male rats and gonadectomized rats. However, whether Nrf2-ARE pathway is activated after testosterone administration has not been studied in aged rats. The tilting-plane test and the horizontal-wire test as well as the oxidative stress parameters, the expression of Nrf2, heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase-1 (NQO1) and the number of tyrosine hydroxylase immunoreactive (TH-ir) cells in brain were examined in aged rats following chronic subcutaneous injections of testosterone propionate (TP). Our study showed that chronic TP supplement significantly ameliorated the decline of balancing reactions and muscular strength associated with aging. Oxidative stress parameters were ameliorate, the expression of Nrf2, HO-1 and NQO1 at protein or gene levels and the number of TH-ir cells significantly increased in substantia nigra or caudate putamen after TP treatment in aged rats. Our findings demonstrated that chronic TP treatment activated Nrf2-ARE pathway may influence the maintenance of the balancing reactions and muscular strength and reduce TH-ir cells death in aged rats. Therefore, TP supplement have shown for therapeutic strategies in the treatment and modification of motor behavior disorders.

The Protective Effect of Curcumin on Ionizing Radiation-induced Cataractogenesis in Rats

OBJECTIVE

The aim of the study was to determine the protective effect of curcumin against ionizing radiation-induced cataract in the lens of rats.

MATERIAL AND METHODS

Rats were divided into six groups. Group 1: Control, Group 2: Dimethyl sulfoxide (DMSO), Group 3: DMSO+curcumin, Group 4: Irradiation, Group 5: Irradiation+DMSO, Group 6: Irradiation+DMSO+curcumin. A 15 Gy total dose was given to 4, 5, 6 groups for radiation damage. Curcumin (100 mg/kg) was dissolved in DMSO and given by intragastric intubation for 28 days. At the end of the experiment, lenses were graded and enucleated. The lenticular activity of the antioxidant enzymes, total antioxidant and glutathione peroxidase (GSH-Px), and the malondialdehyde (MDA) were measured.

RESULTS

100% Cataract was seen in the irradiation group. Cataract rate fell to 40% and was limited at grade 1 and 2 in the curcumin group. In the irradiation group, antioxidant enzyme levels were decreased, MDA levels were increased. There was an increase in antioxidant enzyme levels and a significant decrease in MDA in the group which was given curcumin.

CONCLUSION

Curcumin has antioxidant and radioprotective properties and is likely to be a valuable agent for protection against ionizing radiation. Hence, it may be used as an antioxidant and radioprotector against radiation-induced cataractogenesis.

Ocular disorders and the utility of animal models in the discovery of melatoninergic drugs with therapeutic potential

INTRODUCTION

  The pineal indole-derived hormone melatonin is a modulator of circadian and seasonal rhythms with an important role in ocular health and disease. This could be due to specific melatonin receptors that have been identified in structures such as cornea, lens, ciliary body, retina, choroid and sclera. In addition, a local synthesis of melatonin occurs in several of these ocular tissues.

AREAS COVERED

The authors review existing literature on the most common animal models where ocular melatonin actions have been tested. The therapeutic potential of melatonin in diabetic keratopathy and retinopathy, keratitis, cataracts, glaucoma, uveitis, age-related macular degeneration and retinitis pigmentosa is discussed. Furthermore, the authors comment on the usefulness of different animal models for the development of melatoninergic drugs with therapeutic potential.

EXPERT OPINION

The use of animals for the study of ocular diseases and the potentiality of melatonin and its analogs, as future therapeutic drugs, should be performed on the basis of a rationale study. It is important to note that melatonin receptors seem to be widespread all over the eye. This strongly suggests that, in order to modify the physiology and biochemistry of malfunctioning ocular tissue, the melatonin receptors which are present in that tissue must be first identified. Second there is the need to confirm that those receptors targeted perform the desirable responses, and as a third measure, to use selective agonists (or antagonists) instead of melatonin. However, although some animals mimic ocular pathologies relatively well, and these can be used in melatonin studies, there is still a long way to go till some of the results obtained in animal models could be used for human therapy.

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.

Radio-protective effects of melatonin against irradiation-induced oxidative damage in rat peripheral blood

During radiotherapy, ionizing irradiation interacts with biological systems to produce free radicals, which attacks various cellular components. The hematopoietic system is well-known to be radiosensitive and its damage may be life-threatening. Melatonin synergistically acts as an immunostimulator and antioxidant. In this study we used a total of 120 rats with 20 rats in each group. Group 1 did not receive melatonin or irradiation (Control group), Group 2 received only 10 mg/kg melatonin (Mel group), Group 3 exposed to dose of 2 Gy irradiation (2 Gy Rad group), Group 4 exposed to 8 Gy irradiation (8 Gy Rad group), Group 5 received 2 Gy irradiation plus 10 mg/kg melatonin (Mel +2 Gy Rad group) and Group 6 received 8 Gy irradiation plus 10 mg/kg melatonin (Mel+8 Gy Rad group). Following exposure to radiation, five rats from each group were sacrificed at 4, 24, 48 and 72 h. Exposure to different doses of irradiation resulted in a dose-dependent decline in the antioxidant enzymes activity and lymphocyte count (LC) and an increase in the nitric oxide (NO) levels of the serum. Pre-treatment with melatonin (10 mg/kg) ameliorates harmful effects of 2 and 8 Gy irradiation by increasing lymphocyte count(LC) as well as antioxidant enzymes activity and decreasing NO levels at all time-points. In conclusion 10 mg/kg melatonin is likely to be a threshold concentration for significant protection against lower dose of 2 Gy gamma irradiation compared to higher dose of 8 Gy. Therefore, it seems that radio-protective effects of melatonin are dose-dependent.

The effects of oral Ginkgo biloba supplementation on radiation-induced oxidative injury in the lens of rat

Background:

The aim of this study was to evaluate the antioxidant role of Ginkgo biloba (GB) against radiation-induced cataract in the rat lens after total cranial irradiation with a single 5 Gray (Gy) dose of gamma irradiation.

Materials and Methods:

Twenty-four Sprague-Dawley rats were used for the experiment. The rats were randomly divided into three equal groups. Group 1 did not receive GB or irradiation (control group) but received 1-ml saline orally plus sham-irradiation. Group 2 received total cranium 5 Gy of gamma irradiation as a single dose (IR group) plus 1-ml saline orally. Group 3 received total cranium irradiation plus 40 mg/kg/day GBE (IR plus GBE group). Biochemical parameters measured in murine lenses were carried out using spectrophotometric techniques.

Results:

Lens total (enzymatic plus non-enzymatic) superoxide scavenger activity (TSSA), non-enzymatic superoxide scavenger activity (NSSA), glutathione reductase (GRD), and glutathione-S- transferase (GST) activities significantly increased in the IR plus GBE groups when compared with the IR group. However, TSSA, GRD and GST activities were significantly lower in the IR group when compared with the control group. Lens xanthine oxidase (XO) activity in the IR group significantly increased compared to that of both the control and IR plus GBE groups.

Conclusion:

GBE has clear antioxidant properties and is likely to be a valuable drug for protection against gamma-irradiation and/or be used as an antioxidant against oxidative stress.

Protective effects of melatonin and octreotide against radiation-induced intestinal injury

PURPOSE

To compare the protective effects of the potent antioxidants, melatonin and octreotide, against radiation-induced intestinal injury.

METHODS

A total of 42 male 3-month-old Swiss albino mice (40 ± 10 g) were matched according to body weight and randomly assigned to one of six groups: control; radiation treatment (RT) only; melatonin only (15 mg/kg, i.p.); melatonin + RT; octreotide only (50 μg/kg i.p.); and octreotide + RT. Intestinal damage was induced by exposure to a single whole-body radiation dose of 8 Gy. All mice tolerated the experimental interventions, and no deaths were observed.

RESULTS

Irradiation induced architectural disorganization, including inflammatory mononuclear cell infiltration, villitis, and desquamation with eosinophilic necrosis, and diminished mucosal thickness, crypt height, and villous height. In the melatonin + RT and octreotide + RT groups, the villous pattern was well preserved; desquamation at villous tips and edema was prominent, but necrosis was absent. The radiation-induced decrease in mucosal thickness was significantly reduced by pretreatment with melatonin (p < 0.001) or octreotide (p = 0.01), although the protective effect was significantly greater for melatonin (p = 0.04). Pretreatment with melatonin also preserved villous height (p = 0.009) and crypt height (p = 0.03); although a similar trend was observed for pre-irradiation octreotide, the differences were not significant.

CONCLUSIONS

Melatonin and octreotide potently protected against radiation-induced intestinal injury in mice, but melatonin was significantly more effective in preserving the histological structure of the intestines, a finding that warrants confirmation in clinical studies.

Oxidation stress role in age-related cataractogenesis

Introduction. Age-related cataract not only diminishes human life quality but it also represents a big impact on healthcare budget of almost every country as the population ages globally. Hence, cataract prevention is a big and true challenge, but a very difficult task to be accomplished. Nowadays cataract is more than a routinely recognized and almost always successfully operated ophthalmologic disease. The diagnosis of age-related cataract diagnosis might alert doctors to some systemic disorders on the whole body level. Increasing age is certainly the most essential age-related cataract risk factor. However, it seems that cataract could be a multifactor disease because of its individual, familiar, racial and gender expression differences. Oxidation stress. Oxidation stress and its form caused by ultraviolet light-photo-oxidative stress - are considered to be crucial in the etiopatho?genesis of cataract. All biomolecules suffer damages during cataract formation. On the other side, the lens posses a range of antioxidant elements and mechanisms of their action, which enable long lasting maintenance of lens transparency and functioning. Although they are primary characteristics of the lens, these antioxidant elements also depend on their systemic availability and consumption. This paper is a short literature review of the relation between oxidation stress and age-related cataract.

A radiobiological review on melatonin: a novel radioprotector

In spite of the fact that radiotherapy is a common and effective tool for cancer treatment; the radio sensitivity of normal tissues adjacent to the tumor which are unavoidably exposed to radiation limits therapeutic gain. For the sake of improvement in radiation therapy, radiobiology- the study of the action of ionizing radiation on living things- plays a crucial role through explaining observed phenomena, and suggesting improvements to existing therapies. Due to the damaging effects of ionizing radiation, radiobiologists have long been interested in identifying novel, nontoxic, effective, and convenient compounds to protect humans against radiation induced normal tissue injuries. In hundreds of investigations, melatonin (N-acetyl-5-methoxytryptamine), the chief secretory product of the pineal gland in the brain, has been documented to ameliorate the oxidative injuries due to ionizing radiation. This article reviews different features that make melatonin a potentially useful radioprotector. Moreover, based on radiobiological models we can hypothesize that melatonin may postpone the saturation of repair enzymes which leads to repairing more induced damage by repair system and more importantly allows the use of higher doses of radiation during radiotherapy to get a better therapeutic ratio. The implications of the accumulated observations suggest by virtue of melatonin's radioprotective and anticancer effects; it is time to use it as a radioprotector both for radiation workers and patients suffering from cancer either alone for cancer inhibition or in combination with traditional radiotherapy for getting a favorable efficacy/toxicity ratio during the treatment. Although compelling evidence suggests that melatonin may be effective for a variety of disorders, the optimum dose of melatonin for human radioprotection is yet to be determined. We propose that, in the future, melatonin improve the therapeutic ratio in radiation oncology.

Protective effects of melatonin against low- and high-LET irradiation

To investigate the protective effects of melatonin against high-LET ionizing radiation, V79 Chinese hamster cells were irradiated with 100 keV/microm carbon beam. Parallel experiments were performed with 200 kV X-rays. To avoid the impact from extra solvents, melatonin was dissolved directly in culture medium. Cells were cultured in melatonin medium for 1 hr before irradiation. Cell inactivation was measured with conventional colony forming assay, medium containing 6-thioguanine was used for the selection of mutants at hprt locus, and the cell cycle was monitored by flow cytometry. Both carbon beam and X-rays induced cell inactivation, hprt gene mutation and cell cycle G2 block dose-dependently. But carbon beam showed stronger effects as indicated by all three endpoints and the relative biological effectiveness (RBE) was 3.5 for cell killing (at 10% survival level) and 2.9 for mutation induction (at 5 x 10(-5) mutants/cell level). Melatonin showed protective effects against ionizing radiation in a dose-dependent manner. In terms of cell killing, melatonin only increased the survival level of those samples exposed to 8Gy or larger of X-rays or 6 Gy or larger of carbon beam. In the induction of hprt mutation and G2 block, melatonin reduced such effects induced by carbon beam but not by X-rays. The results suggest that melatonin reduces the direct interaction of particles with cells rather than an indirect interaction. Further studies are required to disclose the underlying mechanisms.

Protective effects of melatonin in experimental free radical-related ocular diseases

Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine with a range of antioxidative properties. Melatonin is endogenously produced in the eye and in other organs. Current evidence suggests that melatonin may act as a protective agent in ocular conditions such as photo-keratitis, cataract, glaucoma, retinopathy of prematurity and ischemia/reperfusion injury. These diseases are sight-threatening and they currently remain, for the most part, untreatable. The pathogenesis of these conditions is not entirely clear but oxidative stress has been proposed as one of the causative factors. Elevated levels of various reactive oxygen and nitrogen species have been identified in diseased ocular structures. These reactants damage the structure and deplete the eye of natural defense systems, such as the antioxidant, reduced glutathione, and the antioxidant enzyme superoxide dismutase. Oxidative damage in the eye leads to apoptotic degeneration of retinal neurons and fluid accumulation. Retinal degeneration decreases visual sensitivity and even a small change in the fluid content of the cornea and crystalline lens is sufficient to disrupt ocular transparency. In the eye, melatonin is produced in the retina and in the ciliary body. Continuous regeneration of melatonin in the eye offers a frontier antioxidative defense for both the anterior and posterior eye. However, melatonin production is minimal in newborns and its production gradually wanes in aging individuals as indicated by the large drop in circulating blood concentrations of the indoleamine. These individuals are possibly at risk of contracting degenerative eye diseases that are free radical-based. Supplementation with melatonin, a potent antioxidant, in especially the aged population should be considered as a prophylaxis to preserve visual functions. It may benefit many individuals worldwide, especially in countries where access to medical facilities is limited.