Human cell membrane oxidative damage induced by single and fractionated doses of ionizing radiation: a fluorescence spectroscopy study

Management of metastatic bone disease of melanoma

One of the most aggressive tumors arising from the skin, mucosa, and uvea is malignant melanoma, which easily metastasizes. Bone tissue is one of the most typical locations for distant metastasis, and around 5%-20% of patients eventually acquired skeletal metastases. For decades, the incidence of bone metastases was higher, bringing greater burden on the family, society, and healthcare system owing to the progress of targeted therapy and immunotherapy, which prolonging the survival time substantially. Moreover, bone metastases result in skeletal-related events, which influence the quality of life, obviously. Appropriate intervention is therefore crucial. To obtain the optimum cost-effectiveness, existing treatment algorithm must be integrated, which is still controversial. We have aimed to throw light on current views concerning the formation, biological and clinical features, and treatment protocol of melanoma bone metastases to guide the decision-making process.

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

Protective Effects of Hydrogen against Irradiation

Radiation-induced lung injury is characterized by an acute pneumonia phase followed by a fibrotic phase. At the time of irradiation, a rapid, short-lived burst of reactive oxygen species (ROS) such as hydroxyl radicals (•OH) occurs, but chronic radiation-induced lung injury may occur due to excess ROS such as H₂O₂, O2•-, ONOO-, and •OH. Molecular hydrogen (H₂) is an efficient antioxidant that quickly diffuses cell membranes, reduces ROS such as •OH and ONOO-, and suppresses damage caused by oxidative stress in various organs. In 2011, through the evaluation of electron-spin resonance and fluorescent indicator signals, we had reported that H₂ can eliminate •OH and can protect against oxidative stress-related apoptotic damage induced by irradiation of cultured lung epithelial cells. We had explored for the first time the radioprotective effects of H₂ treatment on acute and chronic radiation-induced lung damage in mice by inhaled H2 gas (for acute) and imbibed H₂-enriched water (for chronic). Thus, we had proposed that H₂ be considered a potential radioprotective agent. Recent publications have shown that H₂ directly neutralizes highly reactive oxidants and indirectly reduces oxidative stress by regulating the expression of various genes. By regulating gene expression, H₂ functions as an anti-inflammatory and anti-apoptotic molecule and promotes energy metabolism. The increased evidence obtained from cultured cells or animal experiments reveal a putative place for H₂ treatment and its radioprotective effect clinically. This review focuses on major scientific advances in the treatment of H₂ as a new class of radioprotective agents.

Polyneuropathy in Acute Lymphoblastic Leukemia Long-Term Survivors: Clinical and Electrophysiological Characteristics With the Impact of Radiotherapy

Introduction: Acute lymphoblastic leukemia (ALL) is the most common childhood cancer with one of the highest survival rates. Long-term complications that occur after intensive oncological treatment often impair normal daily functioning. However, existing data on peripheral nervous system condition in ALL survivors remain conflicting. Materials and Methods: The study group consisted of 215 ALL survivors. Patients were treated with New York (NY, n = 45), previous modified Berlin-Frankfurt-Münster (pBFM, n = 64), and BFM95 (n = 106) protocols. Time elapsed between the end of the treatment and the control examination varied from 0.3 to 20.9 years. The analyzed patients underwent a neurophysiological analysis with electroneurography (ENG) of motor (median and peroneal) and sensory (median and sural) nerves as well as electromyography (EMG) of tibialis anterior, vastus lateralis, and interosseous I muscles. To estimate the influence of radiotherapy on recorded neurophysiological responses, a joint analysis of NY, and pBFM groups was performed. Results: Clinical symptoms of polyneuropathy were noted among 102 (47.4%) children during the ALL therapy and in 111 (51.6%) during follow-up. At the time of treatment, polyneuropathy was diagnosed in 57.8% participants from NY group, 35.9%-pBFM and 50.0%-BFM95 (p = 0.145). A significantly higher incidence of polyneuropathy was observed during a follow-up in the NY group (68.9%; p < 0.001 vs. pBFM, p = 0.002 vs. BFM95). The most frequent abnormality within all the protocols was demyelination (NY: 44.4%, pBFM: 59.4%, BFM95: 41.5%), in contrast to the least frequently registered isolated axonal changes. The negative influence of oncological treatment on neurophysiological parameters in ALL survivors was observed. Complex disorders of motor nerves, sensory nerves, and motor unit potentials were registered. Motor-sensory neuropathy was the most frequently found pathology in all analyzed protocols. The harmful effect of radiotherapy was also observed in EMG results. Conclusions: Detailed neurophysiological analysis in long-term childhood ALL survivors has shown generalized abnormalities in registered parameters. To our knowledge, the current study is the largest and one of the most comprehensive ones among those examining disturbances in ENG and EMG in this group of patients. Moreover, we are the first ones to demonstrate the negative influence of radiotherapy on peripheral nerve conduction parameters.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H₂ appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H₂ has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H₂ may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Salvianolic acid B, an antioxidant derived from Salvia militarize, protects mice against γ‑radiation‑induced damage through Nrf2/Bach1

Salvianolic acid B (SB) is an antioxidant derived from Salvia militarize, and is one of the most widely used herbs in traditional Chinese medicine. SB is a potent antioxidant that has been well documented as a scavenger of oxygen free radicals, and has been used for the prevention and treatment of atherosclerosis-associated disorders. To explore its potential therapeutic effects in treating radiation damage, in this study, mice were treated with SB at different doses of 5, 12.5 and 20 mg/kg, subsequent to receiving γ-irradiation. The effects of SB on peripheral blood, bone marrow nucleated cells, spleen and thymus indices, and oxidation resistance were evaluated in both radiated mice and control groups. The results indicated that SB significantly increased the counts of peripheral white blood cells, red blood cells and platelets. The number of nucleated cells in the bone marrow and the level of protein increased as well. In addition, improved spleen and thymus indices in the bone marrow were observed. SB treatment additionally reversed the deterioration of both the thymus and spleen indices, which is associated with increased serum superoxide dismutase activity and decreasing malondialdehyde levels via nuclear factor (erythroid-derived 2)-like 2 protein/BTB and CNC homology 1 mediated antioxidant effect. Furthermore, ROS levels and Bax protein expression were also suppressed by SB. The data suggested that SB is effective in protecting mice from γ-radiation injury, and could potentially be applicable for clinical use. Notably, the present study identified a promising candidate drug for enhancing the hematopoietic and immune systems.

Radiation Toxicity in the Central Nervous System: Mechanisms and Strategies for Injury Reduction

The potential for radiation-induced toxicities in the brain produces significant anxiety, both among patients receiving radiation therapy and those radiation oncologists providing treatment. These concerns often play a significant role in the medical decision-making process for most patients with diseases in which radiotherapy may be a treatment consideration. Although the precise mechanisms of neurotoxicity and neurodegeneration after ionizing radiation exposure continue to be poorly understood from a biological perspective, there is an increasing body of scientific and clinical literature that is producing a better understanding of how radiation causes brain injury; factors that determine whether toxicities occur; and potential preventative, treatment, and mitigation strategies for patients at high risk or with symptoms of injury. This review will focus primarily on injuries and biological processes described in mature brain.

Cellular Pathways in Response to Ionizing Radiation and Their Targetability for Tumor Radiosensitization

During the last few decades, improvements in the planning and application of radiotherapy in combination with surgery and chemotherapy resulted in increased survival rates of tumor patients. However, the success of radiotherapy is impaired by two reasons: firstly, the radioresistance of tumor cells and, secondly, the radiation-induced damage of normal tissue cells located in the field of ionizing radiation. These limitations demand the development of drugs for either radiosensitization of tumor cells or radioprotection of normal tissue cells. In order to identify potential targets, a detailed understanding of the cellular pathways involved in radiation response is an absolute requirement. This review describes the most important pathways of radioresponse and several key target proteins for radiosensitization.

Effects of ionizing radiation on biological molecules--mechanisms of damage and emerging methods of detection

SIGNIFICANCE

The detrimental effects of ionizing radiation (IR) involve a highly orchestrated series of events that are amplified by endogenous signaling and culminating in oxidative damage to DNA, lipids, proteins, and many metabolites. Despite the global impact of IR, the molecular mechanisms underlying tissue damage reveal that many biomolecules are chemoselectively modified by IR.

RECENT ADVANCES

The development of high-throughput "omics" technologies for mapping DNA and protein modifications have revolutionized the study of IR effects on biological systems. Studies in cells, tissues, and biological fluids are used to identify molecular features or biomarkers of IR exposure and response and the molecular mechanisms that regulate their expression or synthesis.

CRITICAL ISSUES

In this review, chemical mechanisms are described for IR-induced modifications of biomolecules along with methods for their detection. Included with the detection methods are crucial experimental considerations and caveats for their use. Additional factors critical to the cellular response to radiation, including alterations in protein expression, metabolomics, and epigenetic factors, are also discussed.

FUTURE DIRECTIONS

Throughout the review, the synergy of combined "omics" technologies such as genomics and epigenomics, proteomics, and metabolomics is highlighted. These are anticipated to lead to new hypotheses to understand IR effects on biological systems and improve IR-based therapies.

Role of ferulic acid in the amelioration of ionizing radiation induced inflammation: a murine model

Ionizing radiation is responsible for oxidative stress by generating reactive oxygen species (ROS), which alters the cellular redox potential. This change activates several redox sensitive enzymes which are crucial in activating signaling pathways at molecular level and can lead to oxidative stress induced inflammation. Therefore, the present study was intended to assess the anti-inflammatory role of ferulic acid (FA), a plant flavonoid, against radiation-induced oxidative stress with a novel mechanistic viewpoint. FA was administered (50 mg/kg body wt) to Swiss albino mice for five consecutive days prior to exposing them to a single dose of 10 Gy ⁶⁰Co γ-irradiation. The dose of FA was optimized from the survival experiment and 50 mg/kg body wt dose showed optimum effect. FA significantly ameliorated the radiation induced inflammatory response such as phosphorylation of IKKα/β and IκBα and consequent nuclear translocation of nuclear factor kappa B (NF-κB). FA also prevented the increase of cycloxygenase-2 (Cox-2) protein, inducible nitric oxide synthase-2 (iNOS-2) gene expression, lipid peroxidation in liver and the increase of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) in serum. It was observed that exposure to radiation results in decreased activity of superoxide dismutase (SOD), catalase (CAT) and the pool of reduced glutathione (GSH) content. However, FA treatment prior to irradiation increased the activities of the same endogenous antioxidants. Thus, pretreatment with FA offers protection against gamma radiation induced inflammation.

Potential role of Hedgehog pathway in liver response to radiation

Radiation-induced fibrosis constitutes a major problem that is commonly observed in the patients undergoing radiotherapy; therefore, understanding its pathophysiological mechanism is important. The Hedgehog (Hh) pathway induces the proliferation of progenitors and myofibroblastic hepatic stellate cells (MF-HSCs) and promotes the epithelial-to-mesenchymal transition (EMT), thereby regulating the repair response in the damaged liver. We examined the response of normal liver to radiation injury. Male mice were sacrificed at 6 weeks and 10 weeks after exposure to a single dose of 6 Gy and the livers were collected for biochemical analysis. Irradiated (IR) and control mice were compared for progenitors, fibrosis, Hh pathway, and EMT at 6 and 10 weeks post irradiation. Fatty hepatocytes were observed and the expressions of Hh ligand, Indian Hh. were greater in the livers at 6 weeks, whereas expression of another Hh ligand, Sonic Hh, increased at 10 weeks post irradiation. Both Smoothened, Hh receptor, and Gli2, Hh-target gene, were up-regulated at 6 and 10 weeks after irradiation. Accumulation of progenitors (CD44, Pan-cytokeratin, and Sox9) was significant in IR livers at 6 and 10 weeks. RNA analysis showed enhanced expression of the EMT-stimulating factor, tgf-β, in the IR livers at 6 weeks and the upregulation of mesenchymal markers (α-SMA, collagen, N-cadherin, and s100a4), but down-regulation of EMT inhibitors, in IR mouse livers at 6 and 10 weeks. Increased fibrosis was observed in IR mouse livers at 10 weeks. Treatment of mice with Hh inhibitor, GDC-0449, suppressed Hh activity and block the proliferation of hepatic progenitor and expression of EMT-stimulating genes in irradiated mice. Therefore, those results demonstrated that the Hh pathway increased in response to liver injury by radiation and promoted a compensatory proliferation of MF-HSCs and progenitors, thereby regulating liver remodeling.

Hydrogen as a new class of radioprotective agent

It is well known that most of the ionizing radiation-induced damage is caused by hydroxyl radicals (·OH) follows radiolysis of H2O. Molecular hydrogen (H2) has antioxidant activities by selectively reducing ·OH and peroxynitrite(ONOO-). We firstly hypothesized and demonstrated the radioprotective effect of H2 in vitro and in vivo, which was also repeated on different experimental animal models by different departments. A randomized, placebo-controlled study showed that consumption of hydrogen-rich water reduces the biological reaction to radiation-induced oxidative stress without compromising anti-tumor effects. These encouraging results suggested that H2 represents a potentially novel preventative strategy for radiation-induced oxidative injuries. H2 is explosive. Therefore, administration of hydrogen-rich solution (physiological saline/pure water/other solutions saturated with H2) may be more practical in daily life and more suitable for daily consumption. This review focuses on major scientific and clinical advances of hydrogen-rich solution/H2 as a new class of radioprotective agent.

Studies on black tea (Camellia sinensis) extract as a potential antioxidant and a probable radioprotector

Positive health effects of tea (Camellia sinensis) on a wide range of physiological problems and diseases are well known and are in part due to its copious antioxidant content. The effect of black tea extract (BTE), which is rich in polyphenolic antioxidants, against the consequences of radiation exposure has not been properly identified. The functional properties of BTE were analyzed and its radioprotective effect on V79 cells was explored in the present study. BTE scavenged free radicals and inhibited Fenton reaction-mediated 2-deoxyribose degradation and lipid peroxidation in a dose-dependent fashion, establishing its antioxidant properties. The radioprotective effects of BTE on strand break induction in pBR322 plasmid DNA were 100 % at 80 μg/ml and higher. In V79 cells, BTE was effective in decreasing the frequency of radiation-induced micronucleated cells and the yields of reactive oxygen species (ROS) and also in restoring the integrity of cellular mitochondrial membrane potential significantly. BTE exerted maximum protection against radiation-induced damage in V79 at a dose of 5 μg/ml. Due to the functional properties of BTE-flavonoids, which have been identified by HPLC, it is envisaged that the key player in radioprotection is elimination of ROS.

The convergence of radiation and immunogenic cell death signaling pathways

Ionizing radiation (IR) triggers programmed cell death in tumor cells through a variety of highly regulated processes. Radiation-induced tumor cell death has been studied extensively in vitro and is widely attributed to multiple distinct mechanisms, including apoptosis, necrosis, mitotic catastrophe (MC), autophagy, and senescence, which may occur concurrently. When considering tumor cell death in the context of an organism, an emerging body of evidence suggests there is a reciprocal relationship in which radiation stimulates the immune system, which in turn contributes to tumor cell kill. As a result, traditional measurements of radiation-induced tumor cell death, in vitro, fail to represent the extent of clinically observed responses, including reductions in loco-regional failure rates and improvements in metastases free and overall survival. Hence, understanding the immunological responses to the type of radiation-induced cell death is critical. In this review, the mechanisms of radiation-induced tumor cell death are described, with particular focus on immunogenic cell death (ICD). Strategies combining radiotherapy with specific chemotherapies or immunotherapies capable of inducing a repertoire of cancer specific immunogens might potentiate tumor control not only by enhancing cell kill but also through the induction of a successful anti-tumor vaccination that improves patient survival.

Molecular hydrogen and radiation protection

Molecular hydrogen (dihydrogen, H(2)) acts as a therapeutic antioxidant by selectively reducing hydroxyl radicals (•OH) and peroxynitrite (ONOO-). It has been well-known that ionising radiation (IR) causes oxidative damage and consequent apoptosis mainly due to the production of •OH that follows radiolysis of H(2)O. Our department reported the protective effect of H(2) in irradiated cells and mice for the first time, and this effect is well repeated by us and another laboratory in different experimental animal models. A randomised, placebo-controlled investigation also showed consumption of H(2) can improve the quality of life of patients treated with radiotherapy for liver tumours. These encouraging results suggested that H(2) has a potential as a radioprotective agent with efficacy and non-toxicity.

Epicatechin ameliorates ionising radiation-induced oxidative stress in mouse liver

The current study was intended to evaluate the hepatoprotective effect of Epicatechin (EC) against radiation-induced oxidative stress, in terms of inflammation and lipid peroxidation. Swiss albino mice were administered with EC (15 mg/kg body weight) for three consecutive days before exposing them to a single dose of 5-Gy (60)Co gamma (γ) irradiation. Mice were necropsied and livers were taken for immunohistochemistry, western blot analysis and biochemical tests for the detection of markers of hepatic oxidative stress. Nuclear translocation of nuclear factor kappa B (NF-κB) and lipid peroxidation were increased whereas the activities of superoxide dismutase (SOD) and catalase (CAT), reduced glutathione (GSH) content and ferric reducing antioxidant power (FRAP) were diminished upon radiation exposure compared to control. Translocation of NF-κB from cytoplasm to nucleus and lipid peroxidation were found to be inhibited whereas an increase in SOD, CAT, GSH and FRAP was observed in the mice treated with EC prior to irradiation. Thus, pre-treatment with EC offers protection against γ-radiation induced hepatic alterations.

Evaluation and optimization of radioprotective activity ofCoronopus didymusLinn. in γ-irradiated mice

PURPOSE

To evaluate and optimize the radioprotective ability of the most potent fraction of an aqueous extract of Coronopus didymus in whole body gamma-irradiated Swiss albino mice and to evaluate the antioxidant status and lipid peroxidation of the livers of the surviving mice. To correlate the free radical scavenging studies with in vivo radioprotection ability.

MATERIALS AND METHODS

Swiss albino mice were treated with either vehicle or the different doses of extract/fraction suspension by an i.p. route, 30 min before exposure to 10 Gy gamma-irradiation and the animals were monitored twice daily for any signs of radiation toxicity and mortality. Radiation dose response (7-11 Gy), optimization of route, time of drug administration and evaluation of dose response factor (DRF) at the best dose of the fraction was studied. Endogenous antioxidant status and lipid peroxidation of the livers of the mice surviving on the 31st day was evaluated by using spectrophotometric methods.

RESULTS

The most active free radical scavenging fraction (CDF1) as assessed by competition kinetic studies using pulse radiolysis showed maximum in vivo radioprotection of 70% at a dose of 400 mg/kg body weight (bw) compared to corresponding 10 Gy irradiated control. Optimum radioprotection was observed upon i.p. administration, 30 min prior to 10 Gy irradiation and DRF at a dose of 400 mg/kg bw for 30 day survival was found to be 1.07. The levels of endogenous antioxidant enzymes and lipid peroxidation in the CDF1 treated surviving mice were found to reverse back to their normal levels.

CONCLUSIONS

The optimum dose, time and route of drug administration for maximum radioprotection by CDF1 were determined. The reversal of the levels of endogenous antioxidant enzymes and lipid peroxidation indicates reduced oxidative stress in CDF1 treated surviving mice.

Gastroprotective effect of nicorandil in indomethacin and alcohol-induced acute ulcers

Despite the fact that dietary habits and lifestyles are incredibly advancing, gastric ulceration is still a terrible complaint. Extensive use of non-steroidal anti-inflammatory drugs (NSAIDs) and alcohol, in addition to stress, are all predisposing factors for ulcers. Most medical treatments are always time consuming and not efficient or satisfactory to the patients. Cardiovascular patients always need NSAIDs, or mostly cannot quit alcohols, while using many cardiovascular drugs. We aim to study a possible benefit of a common nitrogen oxide donor, anti-anginal drug, nicorandil [N-(2-hydroxyethyl) nicotinamide nitrate ester], in managing acute gastric ulcers through studying its effect on some relevant intermediates to ulcerogenesis as lipid peroxidation, tumor necrosis factor-alpha (TNF-alpha), and nitric oxide (NO). In addition, gastric mucosal histology was studied to pursue the drug effects on tissue level. Our study revealed that both indomethacin and alcohol induced gastric ulcer mainly through up-regulation of gastric mucosal lipid peroxidation, local tissue inflammation, leukocytic infiltration, and necrosis. Both ulcerogens significantly elevated TNF-alpha and decreased NO, initiating ulcer formation. Nicorandil pretreatment depicted a higher preventive index in indomethacin- (89.8%) and alcohol-induced (77.7%) acute ulceration. On the tissue level, it also protected the gastric mucosa combating leukocyte infiltration and tissue congestion. Nicorandil protected tissue necrosis through decreasing oxidative stress, elevating NO levels, and down-regulating the ulcerogen-induced TNF-alpha elevation and improved sub-mucosal blood supply. We conclude that nicorandil may be a suitable bimodal treatment for cardiovascular patients who are at high risk of gastric ulcers by using variable analgesics to alleviate possible cardiac pain episodes, and probably frequent doses will offer a more established and long-lasting protection.

Lunar astrobiology: a review and suggested laboratory equipment

In October of 2005, the European Space Agency (ESA) and Alcatel Alenia Spazio released a "call to academia for innovative concepts and technologies for lunar exploration." In recent years, interest in lunar exploration has increased in numerous space programs around the globe, and the purpose of our study, in response to the ESA call, was to draw on the expertise of researchers and university students to examine science questions and technologies that could support human astrobiology activity on the Moon. In this mini review, we discuss astrobiology science questions of importance for a human presence on the surface of the Moon and we provide a summary of key instrumentation requirements to support a lunar astrobiology laboratory.

Irradiation of rat brain reduces P-glycoprotein expression and function

The blood–brain barrier (BBB) hampers delivery of several drugs including chemotherapeutics to the brain. The drug efflux pump P-glycoprotein (P-gp), expressed on brain capillary endothelial cells, is part of the BBB. P-gp expression on capillary endothelium decreases 5 days after brain irradiation, which may reduce P-gp function and increase brain levels of P-gp substrates. To elucidate whether radiation therapy reduces P-gp expression and function in the brain, right hemispheres of rats were irradiated with single doses of 2–25 Gy followed by 10 mg kg⁻¹ of the P-gp substrate cyclosporine A (CsA) intravenously (i.v.), with once 15 Gy followed by CsA (10, 15 or 20 mg kg⁻¹), or with fractionated irradiation (4 × 5 Gy) followed by CsA (10 mg kg⁻¹) 5 days later. Additionally, four groups of three rats received 25 Gy once and were killed 10, 15, 20 or 25 days later. The brains were removed and P-gp detected immunohistochemically. P-gp function was assessed by [¹¹C]carvedilol uptake using quantitative autoradiography. Irradiation increased [¹¹C]carvedilol uptake dose-dependently, to a maximum of 20% above non irradiated hemisphere. CsA increased [¹¹C]carvedilol uptake dose-dependently in both hemispheres, but more (P<0.001) in the irradiated hemisphere. Fractionated irradiation resulted in a lost P-gp expression 10 days after start irradiation, which coincided with increased [¹¹C]carvedilol uptake. P-gp expression decreased between day 15 and 20 after single dose irradiation, and increased again thereafter. Rat brain irradiation results in a temporary decreased P-gp function.

Acute effects of fast neutron irradiation on mouse liver

Until now, the multiple biological effects of ionizing radiation on liver have been reported. However, there has not been any reports of fast neutron-mediated liver injuries including liver regeneration or fibrosis. Here, we described the biological effects of acute fast neutron irradiation on the liver. After the fast neutron irradiation of 0, 0.25, 1, 2, 4 and 8 Gy on mice, hepatocyte necrosis and a decrease in the total number of hepatocytes were induced dose-dependently. Binucleated hepatocytes and PCNA positive hepatocytes increased significantly at 0.25 and 1 Gy, but decreased markedly at 2, 4 and 8 Gy. The expression of cytochrome P450 2E1 (CYP2E1) showed a dose-dependent increase after fast neutron irradiation. The activation of p-Smad2/3, signaling intermediates of transforming growth factor-beta (TGF-beta), increased in hepatocytes after exposure of 0.25, 1, and 2 Gy of fast neutrons, but it was not detected in hepatic stellate cells (HSCs). In conclusion, fast neutron-induced liver damages, likely loss of hepatocytes, necrotic foci and vacuolar changes, were note on the dose dependent manner and hepatocellular regeneration were significantly diminished at doses of 2, 4 and 8Gy in a dose-dependent manner. These alterations may at least in part be associated with dose-dependent increase in CYP2E1 and p-Smad2/3. These results show promise as an approach for the treatment of fast neutrons on liver tumors and in the study of pathogenesis regarding the fast neutron-irradiated damages of the liver.

The effects of exogenous melatonin on the morphology of thyrocytes in pinealectomized and irradiated rats

We investigated the effects of exogenous melatonin on the thyrocytes morphology in gamma-irradiated rats under condition where the pineal gland, as a main physiological source of endogenous melatonin, was removed. Three months after pinealectomy animals were divided into two groups: one group of animals was treated with 0.5 ml of vehicle (ethanol diluted in water) and other group was injected intraperitoneally 2 mg/kg of melatonin dissolved in 0.5 ml of vehicle daily during the period of fourteen days. After this treatment all the animals were irradiated with a single dose of 8 Gy gamma rays. Ionising radiation induced apoptosis, hydropic swelling or/and necrosis in both groups of animals, however these changes were less discerned in the thyrocytes of melatonin-treated animals. Our findings demonstrate that administration of exogenous melatonin prior to irradiation reduces radiation-induced thyrocytes damage.

Apoptotic index as predictive marker for radiosensitivity of cervical carcinoma: Evaluation of membrane fluidity, biochemical parameters and apoptosis after the first dose of fractionated radiotherapy to patients

BACKGROUND

This study was aimed to develop possible predictive response of cervical carcinoma in stage IIIA and B patients by evaluating the changes in physical parameter, such as, membrane fluidity, biochemical parameters, such as, intracellular calcium, antioxidant enzymes [superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx)] and apoptotic cell death in cervical cancer cells from patients after treating with the first fractionated dose of 2 Gy in radiation therapy protocol.

METHODS

Biopsies of cervical carcinoma patients were collected before and 24h after first fractionated radiation dose of 2 Gy. Cell suspensions and tissue of cervix cancer biopsies were used to measure various physical and biochemical parameters.

RESULTS AND CONCLUSIONS

A negative correlation was found to exist between observed fluidity of membrane/SOD level with the degree of apoptosis in cervical cells. On the other hand, a positive correlation was observed between intracellular calcium level and percent cellular apoptosis. These results suggest that changes in membrane fluidity, SOD and calcium level were involved in the mechanism of radiation induced cervical apoptosis as measured by TUNEL assay. Moreover, apoptotic sensitivity of these cells after the first dose of radiation treatment showed a direct correlation with the radiation treatment outcome in patients after completion of radiotherapy protocol (70 Gy) in the clinic suggesting that apoptotic index may form a basis for prognosis in radiotherapy in stage III cervix cancer patients.

Melatonin as a radioprotective agent: a review

Melatonin (N-acetyl-5-methoxytryptamine), the chief secretory product of the pineal gland in the brain, is well known for its functional versatility. In hundreds of investigations, melatonin has been documented as a direct free radical scavenger and an indirect antioxidant, as well as an important immunomodulatory agent. The radical scavenging ability of melatonin is believed to work via electron donation to detoxify a variety of reactive oxygen and nitrogen species, including the highly toxic hydroxyl radical. It has long been recognized that the damaging effects of ionizing radiation are brought about by both direct and indirect mechanisms. The direct action produces disruption of sensitive molecules in the cells, whereas the indirect effects ( approximately 70%) result from its interaction with water molecules, which results in the production of highly reactive free radicals such as *OH, *H, and e(aq)- and their subsequent action on subcellular structures. The hydroxyl radical scavenging ability of melatonin was used as a rationale to determine its radioprotective efficiency. Indeed, the results from many in vitro and in vivo investigations have confirmed that melatonin protects mammalian cells from the toxic effects of ionizing radiation. Furthermore, several clinical reports indicate that melatonin administration, either alone or in combination with traditional radiotherapy, results in a favorable efficacy:toxicity ratio during the treatment of human cancers. This article reviews the literature from laboratory investigations that document the ability of melatonin to scavenge a variety of free radicals (including the hydroxyl radical induced by ionizing radiation) and summarizes the evidence that should be used to design larger translational research-based clinical trials using melatonin as a radioprotector and also in cancer radiotherapy. The potential use of melatonin for protecting individuals from radiation terrorism is also considered.

Protective effect of melatonin against fractionated irradiation-induced epiphyseal injury in a weanling rat model

The effects of melatonin, a free-radical scavenger and a general antioxidant, on radiation-induced growth plate injury have not been studied previously. The purpose of this study was to determine the potential benefits of sparing longitudinal bone growth by fractionated radiotherapy alone compared with pretreatment with melatonin that provides differential radioprotection of normal cells. Weanling 4-wk-old (75-100 g) male Sprague-Dawley rats were randomly assigned to one of three groups: Group R received fractionated radiation alone (n = 8); groups M5 (n = 8) and M15 (n = 7) received 5 or 15 mg/kg melatonin prior to fractionated radiation, respectively. The distal femur and proximal tibia in the right leg of each animal were exposed to a therapeutic X-irradiation dose (25 Gy total in three fractions) with the contralateral left leg as the non-irradiated control. Melatonin was administered intraperitoneally to the animals 30 min before radiation exposure. Six weeks after treatment, the rats were killed and the lower limbs disarticulated, skeletonized, radiographed, and bone growth was calculated based on measurement of the bone lengths. Fractionated radiation resulted in a mean percent overall limb growth loss of 41.2 +/- 9.5 and a mean percent overall limb discrepancy of 11.2 +/- 2.2. The administration of 5 or 15 mg/kg melatonin before each of the three fractions of radiotherapy reduced the mean percent overall limb growth loss to 33.9 +/- 5.8 and 32.2 +/- 4.5, respectively, and the mean percent overall limb discrepancy to 9.4 +/- 1.6 and 8.9 +/- 1.1, respectively; these values were significantly different compared with irradiation alone (range: P = 0.01-0.04). When compared with Group R, the growth arrest recovered by 5 or 15 mg/kg melatonin was 19.7 and 24.1% for the tibia, 7 and 18.6% for the femur, and 17.7 and 21.8% for the total limb, respectively. These results support further investigation of melatonin in combination with fractionation for potential use in growing children requiring radiotherapy to the extremity for malignant tumors.

Phototoxic effect of fluoroquinolones on two human cell lines

Photosensitization induced by the fluoroquinolone ofloxacin (OFLX) has been studied using two human cell lines, HL60 and K562, two UV wavelengths, 290 and 330 nm, and two different exposure protocols, acute and protracted. The examined endpoints are the cellular lethality and recovery and the membrane changes produced by the oxidative damage, studied using cloning and counting techniques and the measurement of the generalized polarization (GP) of the fluorescent membrane probe 2-dimethylamino-6-lauroyl-naphthalene (Laurdan). The results show that: (i) the photosensitizing effect is detectable at concentrations similar to those found in patients treated with OFLX only when the cells are irradiated with 330 nm; (ii) the amount of photodamage is a function of the drug concentration and of UV dose and persists also after the removal of the drug; (iii) during the first 24 h after OFLX treatment, a large decrease of the cell number can be observed due to cell lysis; (iv) the OFLX is inserted in the cell membranes at concentrations directly related with the drug concentration and incubation time; (v) the OFLX produces an increase in the GP values similar to that produced by membrane lipid oxidation which persists for hours after the removal of the drug. The overall results suggest the cell membrane as the main target of the OFLX adverse action, with a possible mechanism involving the formation of reactive oxygen species (ROS), which triggers, in turn, the lipid peroxidation chain reaction.

[Mechanisms of radio-induced apoptosis]

A general overview of the activation mechanisms of programmed cell death or apoptosis following an irradiation is given in this review. First, are summarized the main induction pathways of radiation-induced apoptosis by which extracellular (tumor necrosis factor (TNF), Fas ligand, TNF-related apoptosis-inducing ligand (TRAIL)) and intracellular (mitochondria and caspases) signals are integrated. A second part is then devoted to the importance of p53 and of its regulators (ATR, ATM, DNA-PKcs) in the process of radiation-induced apoptosis. Thereafter, signal transduction pathways and more specially the role of some protein kinases (MEKK, SAPK/JNK, p38-MAPK) is treated. At last, a chapter concerns the clinical interest of radiation-induced apoptosis and the implication of apoptosis in the treatment of certain diseases.

Estradiol enhances the resistance of LDL to oxidation by stabilizing apoB-100 conformation

Among different proposed mechanisms to account for the protection exerted by estrogens against cardiovascular diseases, the antioxidant effect has attracted considerable attention. We confirmed that 17-beta-estradiol (E2), when added to human LDL at a 6:1 ratio to apoB-100, markedly delays the phase of massive LDL lipid peroxidation induced by Cu(2+). We also observed an increased oxidative resistance of E2-treated LDL by monitoring the early phase of oxidative degradation on the basis of increased LDL surface polarity by the generalized polarization of the lipophilic fluorescent probe 2-(dimethylamino)-6-lauroylnaphthalene (Laurdan). A scavenging of free radicals by E2 is ruled out since, consistent with its structure, its rate constant for the reduction of peroxy radicals is extremely low, i.e., 0.02% of that of vitamin E. Tryptophan fluorescence lifetime and circular dichroism measurements revealed that (i) apoB-100 undergoes a conformational modification and a progressive loss of secondary structure during lipid peroxidation; (ii) E2 increases apoB-100 secondary structure and modifies its conformation; and (iii) the apoB-100 conformational change induced by E2 makes this protein resistant to modifications brought about by lipid peroxidation. We propose that E2, by affecting apoB-100 secondary structure and conformation, modifies the interaction of this protein with the outer layer of the LDL particle thus increasing its overall oxidative resistance.

Antioxidative effects of melatonin in protection against cellular damage caused by ionizing radiation

Ionizing radiation is classified as a potent carcinogen, and its injury to living cells is, to a large extent, due to oxidative stress. The molecule most often reported to be damaged by ionizing radiation is DNA. Hydroxyl radicals (*OH), considered the most damaging of all free radicals generated in organisms, are often responsible for DNA damage caused by ionizing radiation. Melatonin, N-acetyl-5-methoxytryptamine, is a well-known antioxidant that protects DNA, lipids, and proteins from free-radical damage. The indoleamine manifests its antioxidative properties by stimulating the activities of antioxidant enzymes and scavenging free radicals directly or indirectly. Among known antioxidants, melatonin is a highly effective scavenger of *OH. Melatonin is distributed ubiquitously in organisms and, as far as is known, in all cellular compartments, and it quickly passes through all biological membranes. The protective effects of melatonin against oxidative stress caused by ionizing radiation have been documented in in vitro and in vivo studies in different species and in in vitro experiments that used human tissues, as well as when melatonin was given to humans and then tissues collected and subjected to ionizing radiation. The radioprotective effects of melatonin against cellular damage caused by oxidative stress and its low toxicity make this molecule a potential supplement in the treatment or co-treatment in situations where the effects of ionizing radiation are to be minimized.

Antioxidant properties of Asparagus racemosus against damage induced by gamma-radiation in rat liver mitochondria

The possible antioxidant effects of crude extract and a purified aqueous fraction of Asparagus racemosus against membrane damage induced by the free radicals generated during gamma-radiation were examined in rat liver mitochondria. gamma-Radiation, in the dose range of 75-900 Gy, induced lipid peroxidation as assessed by the formation of thiobarbituric acid reactive substances (TBARS) and lipid hydroperoxides (LOOH). Using an effective dose of 450 Gy, antioxidant effects of A. racemosus extract were studied against oxidative damage in terms of protection against lipid peroxidation, protein oxidation, depletion of protein thiols and the levels of the antioxidant enzyme, superoxide dismutase. An active fraction consisting of polysaccharides (termed as P3) was effective even at a low concentration of 10 microg/ml. Both the crude extract as well as the P3 fraction significantly inhibited lipid peroxidation and protein oxidation. The antioxidant effect of P3 fraction was more pronounced against lipid peroxidation, as assessed by TBARS formation, while that of the crude extract was more effective in inhibiting protein oxidation. Both the crude extract and P3 fraction also partly protects against radiation-induced loss of protein thiols and inactivation of superoxide dismutase. The inhibitory effects of these active principles, at the concentration of 10 microg/ml, are comparable to that of the established antioxidants glutathione and ascorbic acid. Hence our results indicate that extracts from A. racemosus have potent antioxidant properties in vitro in mitochondrial membranes of rat liver.

Protective effects of melatonin against oxidation of guanine bases in DNA and decreased microsomal membrane fluidity in rat liver induced by whole body ionizing radiation

The aim of the study was to examine the potential protective effect of melatonin against whole body ionizing radiation (800 cGy). Changes in 8-hydroxy-2'-deoxyguanosine (8-OH-dG) levels, an index of DNA damage, and alterations in membrane fluidity (the inverse of membrane rigidity) and lipid peroxidation in microsomal membranes, as indices of damage to lipid and protein molecules in membranes, were estimated. Measurements were made in rat liver, 12 h after their exposure to radiation. To test the potential protective effects of melatonin, the indole was injected (i.p. 50 mg/kg b.w.) at 120, 90, 60 and 30 min prior to radiation exposure. Both 8-OH-dG levels and microsomal membrane rigidity increased significantly 12 h after radiation exposure. Melatonin completely counteracted the effects of ionizing radiation. Changes in 8-OH-dG levels and membrane fluidity are early sensitive parameters of DNA and microsomal membrane damage, respectively, induced by ionizing radiation and our findings document the protective effects of melatonin against ionizing radiation.

Simultaneous analysis of radio-induced membrane alteration and cell viability by flow cytometry

BACKGROUND

Modifications of intracellular transfer, resulting from a loss of membrane integrity may contribute toward setting the cell onto the pathway of apoptosis.

METHODS

We have developed an original technique of measuring simultaneously, with flow cytometry, changes in membrane fluidity and cell death status. Our aim was to assess the extent to which radio-induced cell death and membrane alterations are linked. Investigations were performed on lymphocytes 24 h after whole human blood gamma-irradiation.

RESULTS

Our results confirmed the expected increase in the percentage of apoptotic cells as a function of dose, but revealed that the percentage of necrotic cells appeared stable after irradiation. At the same time, the fluorescence anisotropy of the living lymphocyte subpopulation decreased significantly and dose dependently as measured 24 h post-irradiation. With TMA-DPH, the anisotropy index of apoptotic lymphocytes was always lower than that of the viable lymphocyte subpopulation. On the other hand, 1,6-diphenyl-1,3,5-hexatriene (DPH) anisotropy was similar in apoptotic and viable cells after irradiation. These findings suggest that apoptotic lymphocytes are characterised by a membrane fluidization that mainly occurs on the cell membrane surface.

CONCLUSION

Our study made technical advances in using cytometric fluorescence anisotropy measurement as an early biological indicator of apoptosis after cellular exposure to ionising radiation.