Time-scale and nature of radiation-biological damage: approaches to radiation protection and post-irradiation therapy

An In-depth Analysis of the Adverse Effects of Ionizing Radiation Exposure on Cardiac Catheterization Staffs

Diagnostic and interventional angiograms are instrumental in the multidisciplinary approach to CAD management, enabling accurate diagnosis and effective targeted treatments that significantly enhance patient care and cardiovascular outcomes. However, cath lab staff, including interventional cardiologists, is consistently exposed to ionizing radiation, which poses inherent health risks. Radiation exposure in the cath lab primarily results from the use of fluoroscopy and cineangiography during diagnostic and interventional procedures. Understanding these risks and implementing effective radiation protection measurements are imperative to ensure the well-being of healthcare professionals while delivering high-quality cardiac care. Prolonged and repeated exposure can lead to both deterministic and stochastic effects. Deterministic effects, such as skin erythema and tissue damage, are more likely to occur at high radiation doses. Interventional cardiologists and staff may experience these effects when safety measures are not rigorously followed. In fact, while ionizing radiation is essential in the practice of radiation cardiology ward, cath lab staff faces inherent risks from radiation exposure. Stochastic effects, on the other hand, are characterized by a probabilistic relationship between radiation exposure and the likelihood of harm. These effects include the increased risk of cancer, particularly for those with long-term exposure. Interventional cardiologists, due to their frequent presence in the cath lab, face a higher lifetime cumulative radiation dose, potentially elevating their cancer risk. Protective measures, including the use of lead aprons, thyroid shields, and radiation monitoring devices, play a crucial role in reducing radiation exposure for cath lab personnel. Adherence to strict dose optimization protocols, such as minimizing fluoroscopy time and maximizing distance from the radiation source, is also essential in mitigating these risks. Ongoing research and advancements in radiation safety technology are essential in further for minimizing the adverse effects of ionizing radiation in the cath lab.

Bio-positive effects of ionizing radiation on pollen: The role of ROS

The concept of 'hormesis' is defined as a dose-response relationship whereby low doses of various toxic substances or physical stressors trigger bio-positive effects in diverse biological systems, whereas high doses cause inhibition of cellular performance (e.g. growth, viability). The two-sided phenomenon of specific low-dose stimulation and high-dose inhibition imposed by a 'hormetic-factor' has been well documented in toxicology and pharmacology. Multitudinous factors have been identified that correspondingly cause hormetic effects in diverse taxa of animals, fungi, and plants. This study particularly aims to elucidate the molecular basis for stimulatory implications of ionizing radiation (IR) on plant male gametophytes (pollen). Beyond that, this analysis impacts general research on cell growth, plant breeding, radiation protection, and, in a wider sense, medical treatment. For this purpose, IR-related data were surveyed and discussed in connection with the present knowledge about pollen physiology. It is concluded that IR-induced reactive oxygen species (ROS) have a key role here. Moreover, it is hypothesized that IR-exposure shifts the ratio between diverse types of ROS in the cell. The interrelation between ROS, intracellular Ca2+-gradient, NADPH oxidases, ROS-scavengers, actin dynamics, and cell wall properties are most probably involved in IR-hormesis of pollen germination and tube growth. Modulation of gene expression, phytohormone signalling, and cellular antioxidant capacity are also implicated in IR-hormesis.

Effects of environmental stress factors on the actin cytoskeleton of fungi and plants: Ionizing radiation and ROS

Actin is an abundant and multifaceted protein in eukaryotic cells that has been detected in the cytoplasm as well as in the nucleus. In cooperation with numerous interacting accessory-proteins, monomeric actin (G-actin) polymerizes into microfilaments (F-actin) which constitute ubiquitous subcellular higher order structures. Considering the extensive spatial dimensions and multifunctionality of actin superarrays, the present study analyses the issue if and to what extent environmental stress factors, specifically ionizing radiation (IR) and reactive oxygen species (ROS), affect the cellular actin-entity. In that context, this review particularly surveys IR-response of fungi and plants. It examines in detail which actin-related cellular constituents and molecular pathways are influenced by IR and related ROS. This comprehensive survey concludes that the general integrity of the total cellular actin cytoskeleton is a requirement for IR-tolerance. Actin's functions in genome organization and nuclear events like chromatin remodeling, DNA-repair, and transcription play a key role. Beyond that, it is highly significant that the macromolecular cytoplasmic and cortical actin-frameworks are affected by IR as well. In response to IR, actin-filament bundling proteins (fimbrins) are required to stabilize cables or patches. In addition, the actin-associated factors mediating cellular polarity are essential for IR-survivability. Moreover, it is concluded that a cellular homeostasis system comprising ROS, ROS-scavengers, NADPH-oxidases, and the actin cytoskeleton plays an essential role here. Consequently, besides the actin-fraction which controls crucial genome-integrity, also the portion which facilitates orderly cellular transport and polarized growth has to be maintained in order to survive IR.

Nanotechnology enabled radioprotectants to reduce space radiation-induced reactive oxidative species

Interest in space exploration has seen substantial growth following recent launch and operation of modern space technologies. In particular, the possibility of travel beyond low earth orbit is seeing sustained support. However, future deep space travel requires addressing health concerns for crews under continuous, longer-term exposure to adverse environmental conditions. Among these challenges, radiation-induced health issues are a major concern. Their potential to induce chronic illness is further potentiated by the microgravity environment. While investigations into the physiological effects of space radiation are still under investigation, studies on model ionizing radiation conditions, in earth and micro-gravity conditions, can provide needed insight into relevant processes. Substantial formation of high, sustained reactive oxygen species (ROS) evolution during radiation exposure is a clear threat to physiological health of space travelers, producing indirect damage to various cell structures and requiring therapeutic address. Radioprotection toward the skeletal system components is essential to astronaut health, due to the high radio-absorption cross-section of bone mineral and local hematopoiesis. Nanotechnology can potentially function as radioprotectant and radiomitigating agents toward ROS and direct radiation damage. Nanoparticle compositions such as gold, silver, platinum, carbon-based materials, silica, transition metal dichalcogenides, and ceria have all shown potential as viable radioprotectants to mitigate space radiation effects with nanoceria further showing the ability to protect genetic material from oxidative damage in several studies. As research into space radiation-induced health problems develops, this review intends to provide insights into the nanomaterial design to ameliorate pathological effects from ionizing radiation exposure. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Nanotechnology Approaches to Biology > Cells at the Nanoscale Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Radical scavenging activity of Chlorophytum borivilianum L. root extract and its protective role in cauda epididymal sperm integrity in Mus musculus after gamma irradiation

Background: Chlorophytum borivilianum L. is a recognized herbal medicine for the management of impotency in South Asian countries. In Ayurveda, it is used for the management of multiple health conditions, including diabetes, infection, and cardiovascular diseases. Parts of the plant have been used as excellent antioxidants and scavengers of free radicals. Since oxidative stress plays an important role in spermatogenesis and fertility in male populations, this study evaluated the role of ethanolic extract of C. borivilianum roots in epididymal sperm maturation against adversities posed by ionizing gamma irradiation. Materials and methods: Antioxidant potential of C. borivilianum root extract (CRE) was evaluated through DPPH (2,2-diphenylpicrylhydrazyl) and NO (nitric oxide) scavenging assays. Four groups of healthy Swiss albino mice were constituted, which were labeled as follows: Group I: sham control, Group II: 7-day pre-treatment with 50 mg/kg CRE, Group III: 6 Gy irradiation without pre-treatment, and Group IV: 7-day pre-treatment with 50 mg/kg CRE and 6 Gy irradiation on day 7. Swiss albino mice were observed for 30 days and later sacrificed to evaluate sperm quality parameters. Results: CRE showed a remarkable antioxidant potential with IC₅₀ values of 46.37 μg/ml and 98.39 μg/ml for DPPH and NO, respectively. A significant decline (p < 0.001) in cauda epididymal sperm count, motility, and viability was observed in Group III animals. Group IV also showed a substantial decline (p < 0.01) in all three parameters compared to Group I; nonetheless, these were significantly higher than Group III. Morphological alterations indicated a coiled and bent tail, with the presence of cytoplasmic droplets in Group III, which declined substantially in Group IV. The ultrastructure of sperm indicated higher curvature of hook in Group III than Group IV, indicating specific interferences in the sperm maturation process. Conclusion: It was concluded that pre-treatment with 50 mg/kg body weight of CRE could protect sperm during epididymal maturation against oxidative stress.

Advances in Irradiated Livestock Vaccine Research and Production Addressing the Unmet Needs for Farmers and Veterinary Services in FAO/IAEA Member States

The Animal Production and Health section (APH) of the Joint FAO/IAEA Centre of Nuclear Techniques in Food and Agriculture at the International Atomic Energy Agency has over the last 58 years provided technical and scientific support to more than 100 countries through co-ordinated research activities and technical co-operation projects in peaceful uses of nuclear technologies. A key component of this support has been the development of irradiated vaccines targeting diseases that are endemic to participating countries. APH laboratories has over the last decade developed new techniques and has put in place a framework that allows researchers from participating member states to develop relevant vaccines targeting local diseases while using irradiation as a tool for improving livestock resources.

Ionizing Radiation Technologies for Vaccine Development - A Mini Review

Given the current pandemic the world is struggling with, there is an urgent need to continually improve vaccine technologies. Ionizing radiation technology has a long history in the development of vaccines, dating back to the mid-20^th century. Ionizing radiation technology is a highly versatile technology that has a variety of commercial applications around the world. This brief review summarizes the core technology, the overall effects of ionizing radiation on bacterial cells and reviews vaccine development efforts using ionizing technologies, namely gamma radiation, electron beam, and X-rays.

The highs and lows of ionizing radiation and its effects on protein synthesis

Ionizing radiation (IR) is a constant feature of our environment and one that can dramatically affect organismal health and development. Although the impacts of high-doses of IR on mammalian cells and systems have been broadly explored, there are still challenges in accurately quantifying biological responses to IR, especially in the low-dose range to which most individuals are exposed in their lifetime. The resulting uncertainty has led to the entrenchment of conservative radioprotection policies around the world. Thus, uncovering long-sought molecular mechanisms and tissue responses that are targeted by IR could lead to more informed policymaking and propose new therapeutic avenues for a variety of pathologies. One often overlooked target of IR is mRNA translation, a highly regulated cellular process that consumes more than 40% of the cell's energy. In response to environmental stimuli, regulation of mRNA translation allows for precise and rapid changes to the cellular proteome, and unsurprisingly high-dose of IR was shown to trigger a severe reprogramming of global protein synthesis allowing the cell to conserve energy by preventing the synthesis of unneeded proteins. Nonetheless, under these conditions, certain mRNAs encoding specific proteins are translationally favoured to produce the factors essential to repair the cell or send it down the path of no return through programmed cell death. Understanding the mechanisms controlling protein synthesis in response to varying doses of IR could provide novel insights into how this stress-mediated cellular adaptation is regulated and potentially uncover novel targets for radiosensitization or radioprotection. Here, we review the current literature on the effects of IR at both high- and low-dose on the mRNA translation machinery.

Quantitative Assessment of 3D Dose Rate for Proton Pencil Beam Scanning FLASH Radiotherapy and Its Application for Lung Hypofractionation Treatment Planning

To quantitatively assess target and organs-at-risk (OAR) dose rate based on three proposed proton PBS dose rate metrics and study FLASH intensity-modulated proton therapy (IMPT) treatment planning using transmission beams. An in-house FLASH planning platform was developed to optimize transmission (shoot-through) plans for nine consecutive lung cancer patients previously planned with proton SBRT. Dose and dose rate calculation codes were developed to quantify three types of dose rate calculation methods (dose-averaged dose rate (DADR), average dose rate (ADR), and dose-threshold dose rate (DTDR)) based on both phantom and patient treatment plans. Two different minimum MU/spot settings were used to optimize two different dose regimes, 34-Gy in one fraction and 45-Gy in three fractions. The OAR sparing and target coverage can be optimized with good uniformity (hotspot < 110% of prescription dose). ADR, accounting for the spot dwelling and scanning time, gives the lowest dose rate; DTDR, not considering this time but a dose-threshold, gives an intermediate dose rate, whereas DADR gives the highest dose rate without considering any time or dose-threshold. All three dose rates attenuate along the beam direction, and the highest dose rate regions often occur on the field edge for ADR and DTDR, whereas DADR has a better dose rate uniformity. The differences in dose rate metrics have led a large variation for OARs dose rate assessment, posing challenges to FLASH clinical implementation. This is the first attempt to study the impact of the dose rate models, and more investigations and evidence for the details of proton PBS FLASH parameters are needed to explore the correlation between FLASH efficacy and the dose rate metrics.

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

Exposure to ionizing radiation, mechanical trauma, toxic chemicals or infections, or combinations thereof (i.e., combined injury) can induce organic injury to brain tissues, the structural disarrangement of interactive networks of neurovascular and glial cells, as well as on arrays of the paracrine and systemic destruction. This leads to subsequent decline in cognitive capacity and decompensation of mental health. There is an ongoing need for improvement in mitigating and treating radiation- or combined injury-induced brain injury. Cranial irradiation per se can cause a multifactorial encephalopathy that occurs in a radiation dose- and time-dependent manner due to differences in radiosensitivity among the various constituents of brain parenchyma and vasculature. Of particular concern are the radiosensitivity and inflammation susceptibility of: 1. the neurogenic and oligodendrogenic niches in the subependymal and hippocampal domains; and 2. the microvascular endothelium. Thus, cranial or total-body irradiation can cause a plethora of biochemical and cellular disorders in brain tissues, including: 1. decline in neurogenesis and oligodendrogenesis; 2. impairment of the blood-brain barrier; and 3. ablation of vascular capillary. These changes, along with cerebrovascular inflammation, underlie different stages of encephalopathy, from the early protracted stage to the late delayed stage. It is evident that ionizing radiation combined with other traumatic insults such as penetrating wound, burn, blast, systemic infection and chemotherapy, among others, can exacerbate the radiation sequelae (and vice versa) with increasing severity of neurogenic and microvascular patterns of radiation brain damage.

Histopathological assessment of protective effects of selenium nanoparticles on rat hepatocytes exposed to Gamma radiation

Gamma radiation are used in many medical and technical applications, however, it is one of the most dangerous kinds of radiation and can be harmful to the body. The present study was designed to clarify the protective effects of the selenium supplementation as selenium nanoparticle and selenite selenium in rat liver against Gamma irradiation with different intensities of 2.00 and 8.00 Gy. A total number of 45 healthy male Wistar rats were randomly divided into nine groups of five each. The radiation procedure was carried out in the Cobalt 60 equipment in Omid hospital, Urmia. The animals were simultaneously immobilized in a transparent acrylic plate and exposed to different intensities of 2.00 and 8.00 Gy radiations on day 7th and 14th of the experiment. After 72 hr after the last radiation, the animals were euthanized, and blood and liver tissue were collected. Histological analyses revealed the radiation-induced hepatic injury in rats, which included vacuolated cytoplasm, liver necrosis, fibrosis, and vascular lesions followed by a significant increase in alanine transaminase, alanine transaminase, alkaline phosphatase, and Gamma-glutamyl transferase. Selenium nanoparticles bear a more potent antioxidant effect in comparison with selenium selenite and can effectively protect the liver cell against Gamma radiation at a dose of 8.00 Gy.

SAXS studies of X-ray induced disulfide bond damage: Engineering high-resolution insight from a low-resolution technique

A significant problem in biological X-ray crystallography is the radiation chemistry caused by the incident X-ray beam. This produces both global and site-specific damage. Site specific damage can misdirect the biological interpretation of the structural models produced. Cryo-cooling crystals has been successful in mitigating damage but not eliminating it altogether; however, cryo-cooling can be difficult in some cases and has also been shown to limit functionally relevant protein conformations. The doses used for X-ray crystallography are typically in the kilo-gray to mega-gray range. While disulfide bonds are among the most significantly affected species in proteins in the crystalline state at both cryogenic and higher temperatures, there is limited information on their response to low X-ray doses in solution, the details of which might inform biomedical applications of X-rays. In this work we engineered a protein that dimerizes through a susceptible disulfide bond to relate the radiation damage processes seen in cryo-cooled crystals to those closer to physiologic conditions. This approach enables a low-resolution technique, small angle X-ray scattering (SAXS), to detect and monitor a residue specific process. A dose dependent fragmentation of the engineered protein was seen that can be explained by a dimer to monomer transition through disulfide bond cleavage. This supports the crystallographically derived mechanism and demonstrates that results obtained crystallographically can be usefully extrapolated to physiologic conditions. Fragmentation was influenced by pH and the conformation of the dimer, providing information on mechanism and pointing to future routes for investigation and potential mitigation. The novel engineered protein approach to generate a large-scale change through a site-specific interaction represents a promising tool for advancing radiation damage studies under solution conditions.

The interplay between Mn and Fe in Deinococcus radiodurans triggers cellular protection during paraquat-induced oxidative stress

The bacterium Deinococcus radiodurans is highly resistant to several stress conditions, such as radiation. According to several reports, manganese plays a crucial role in stress protection, and a high Mn/Fe ratio is essential in this process. However, mobilization of manganese and iron, and the role of DNA-binding-proteins-under-starved-conditions during oxidative-stress remained open questions. We used synchrotron-based X-ray fluorescence imaging at nano-resolution to follow element-relocalization upon stress, and its dependency on the presence of Dps proteins, using dps knockout mutants. We show that manganese, calcium, and phosphorus are mobilized from rich-element regions that resemble electron-dense granules towards the cytosol and the cellular membrane, in a Dps-dependent way. Moreover, iron delocalizes from the septum region to the cytoplasm affecting cell division, specifically in the septum formation. These mechanisms are orchestrated by Dps1 and Dps2, which play a crucial role in metal homeostasis, and are associated with the D. radiodurans tolerance against reactive oxygen species.

Synchrotron-based infrared microspectroscopy study on the radiosensitization effects of Gd nanoparticles at megavoltage radiation energies

Synchrotron-based infrared microspectroscopy is a powerful technique for disentangling biochemical effects in nanoparticle-based radiotherapy approaches.

Modulators of Redox Metabolism in Head and Neck Cancer

SIGNIFICANCE

Head and neck squamous cell cancer (HNSCC) is a complex disease characterized by high genetic and metabolic heterogeneity. Radiation therapy (RT) alone or combined with systemic chemotherapy is widely used for treatment of HNSCC as definitive treatment or as adjuvant treatment after surgery. Antibodies against epidermal growth factor receptor are used in definitive or palliative treatment. Recent Advances: Emerging targeted therapies against other proteins of interest as well as programmed cell death protein 1 and programmed death-ligand 1 immunotherapies are being explored in clinical trials.

CRITICAL ISSUES

The disease heterogeneity, invasiveness, and resistance to standard of care RT or chemoradiation therapy continue to constitute significant roadblocks for treatment and patients' quality of life (QOL) despite improvements in treatment modality and the emergence of new therapies over the past two decades.

FUTURE DIRECTIONS

As reviewed here, alterations in redox metabolism occur at all stages of HNSCC management, providing opportunities for improved prevention, early detection, response to therapies, and QOL. Bioinformatics and computational systems biology approaches are key to integrate redox effects with multiomics data from cells and clinical specimens and to identify redox modifiers or modifiable target proteins to achieve improved clinical outcomes. Antioxid. Redox Signal.

Limited field radiation therapy results in decreased bone fracture toughness in a murine model

Fragility fractures are a well-known complication following oncologic radiotherapy, and it is suspected that radiation-induced embrittlement of bone within the treatment field may contribute to fracture risk. To explore this phenomenon, a mouse model (BALB/cJ) of fractionated, limited field, bilateral hindlimb irradiation (4x5 Gy) was used. The effects of radiation on femoral (cortical) bone fracture toughness, morphology, and biochemistry-including advanced glycation end products (AGEs)-were quantified and compared to Sham group samples prior to irradiation and at 0, 4, 8, and 12 weeks post-irradiation. Additionally, alterations to bone fracture toughness mediated directly by radiation (independent of cellular mechanisms) were determined using devitalized mouse cadaver femurs. Finally, the contribution of AGEs to reduced fracture toughness was examined by artificially ribosylating mouse femurs ex vivo. These data demonstrate that in vivo irradiation results in an immediate (-42% at 0 weeks, p < 0.001) and sustained (-28% at 12 weeks, p < 0.001) decrease in fracture toughness with small changes in morphology (-5% in cortical area at 12 weeks), and minimal changes in bone composition (tissue mineral density, mineral:matrix ratio, and AGE content). Irradiation of devitalized femurs also reduced fracture toughness (-29%, p < 0.001), but to a lesser extent than was seen in vivo. While artificial ribosylation decreased fracture toughness with time, the extent of glycation needed to induce this effect exceeded the AGE accumulation that occurred in vivo. Overall, hindlimb irradiation induced a substantial and sustained decrease in bone fracture toughness. Approximately half of this decrease in fracture toughness is due to direct radiation damage, independent of cellular remodeling. Collagen glycation in vivo was not substantially altered, suggesting other matrix changes may contribute to post-radiotherapy bone embrittlement.

Prevention of Transfusion-Associated Graft-Versus-Host Disease With Blood Product Irradiation: The Past, Present, and Future

Transfusion-associated graft-versus-host disease (TA-GVHD) is a disease with a very high mortality rate. In this report, we discuss TA-GVHD from a historical perspective, highlight the pathogenesis of TA-GVHD, and emphasize the importance of blood product irradiation, which is a very effective means to prevent this disease. We summarize the current recommendations in different patient populations from different countries and review recent developments, such as alternatives for the use of radioactive materials. We also speculate on future directions.

Morphological and chromosomal abnormalities in gamma radiation-induced mutagenized faba bean genotypes

Purpose: This study was conducted to evaluate and compare the influence of gamma radiations on morphological and chromosomal abnormalities in twenty mutagenized faba bean populations, representing first and second generations (M₁ and M₂) of five faba bean genotypes.Materials and methods: Five faba bean genotypes were exposed at two doses of gamma radiations (25 and 50 Gy). For determining the types of chromosomal aberrations caused by the gamma radiation, mitotic and meiotic cells were isolated from root tips and pollen mother cells, respectively.Results: The M₁ generations of the five genotypes varied for sensitivity to gamma radiations, for seedling emergence. The genotype Skah 2 was more sensitive than other genotypes, the order of sensitivity of other genotypes was Misr 3 > ILB 4347 > Hassawi 2 > Hassawi 3. However, seedling emergence of the M₂ generations was not as much reduced as that of the M₁ generations. Ten different chlorophyll-deficient mutants were identified among the M₂ generations. Gamma radiations also caused the development of abnormal leaflets, flowers and pollen grains. The most common types of chromosome aberrations in the mitotic cells were stickiness, laggard and chromosome breaks, whereas the most common types in the meiotic cells were stickiness and disturbed polarity.Conclusion: The gamma radiation decreased the seedling emergence and induced a wide range of morphological and chromosomal abnormalities in faba bean.

Radiation Metabolomics: Current Status and Future Directions

Human exposure to ionizing radiation (IR) disrupts normal metabolic processes in cells and organs by inducing complex biological responses that interfere with gene and protein expression. Conventional dosimetry, monitoring of prodromal symptoms, and peripheral lymphocyte counts are of limited value as organ- and tissue-specific biomarkers for personnel exposed to radiation, particularly, weeks or months after exposure. Analysis of metabolites generated in known stress-responsive pathways by molecular profiling helps to predict the physiological status of an individual in response to environmental or genetic perturbations. Thus, a multi-metabolite profile obtained from a high-resolution mass spectrometry-based metabolomics platform offers potential for identification of robust biomarkers to predict radiation toxicity of organs and tissues resulting from exposures to therapeutic or non-therapeutic IR. Here, we review the status of radiation metabolomics and explore applications as a standalone technology, as well as its integration in systems biology, to facilitate a better understanding of the molecular basis of radiation response. Finally, we draw attention to the identification of specific pathways that can be targeted for the development of therapeutics to alleviate or mitigate harmful effects of radiation exposure.

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.

Oxidative stress-induced posttranslational modifications of human hemoglobin in erythrocytes

Posttranslational modifications (PTMs) have been reported in hemoglobin (Hb) treated with ROS/RNS in cell-free experiments. However, little is known about oxidative PTMs of Hb occurring within the erythrocytes. The aim of this study is to characterize the patterns of Hb PTMs in erythrocytes under oxidative stress. Using mass spectrometry, we investigated specifically methionine/tryptophan oxidation, tyrosine nitration, and the modification via 4-hydroxynonenal (HNE), a product of lipid-peroxidation, on Hb. We demonstrated that the treatment with H(2)O(2)/nitrite induced higher levels of Hb oxidation/nitration in purified Hb preparations than in unpurified hemolysates and erythrocytes, indicating that ROS/RNS are primarily removed by antioxidative mechanisms. We further studied Hb from erythrocytes exposed to γ-irradiation. An irradiation of 30-100 Gy triggered a remarkable increase of intracellular ROS. However, 30 Gy did not induce apparent changes in Hb oxidation/nitration and hemolysis, while Hb oxidation/nitration and hemolysis were significantly enhanced by 100 Gy, suggesting that Hb oxidation/nitration are the consequence of overwhelmed antioxidative mechanisms after oxidative attack and reflect the severity of the oxidative damage of erythrocytes. Although irradiation was known to induce lipid-peroxidation, we could not detect HNE-Hb adducts in irradiated erythrocytes. Analyzing PTM patterns suggests Hb nitration as a more suitable indicator of the oxidative damage of erythrocytes.

Glass transition in thaumatin crystals revealed through temperature-dependent radiation-sensitivity measurements

The temperature-dependence of radiation damage to thaumatin crystals between T = 300 and 100 K is reported. The amount of damage for a given dose decreases sharply as the temperature decreases from 300 to 220 K and then decreases more gradually on further cooling below the protein-solvent glass transition. Two regimes of temperature-activated behavior were observed. At temperatures above ∼200 K the activation energy of 18.0 kJ mol(-1) indicates that radiation damage is dominated by diffusive motions in the protein and solvent. At temperatures below ∼200 K the activation energy is only 1.00 kJ mol(-1), which is of the order of the thermal energy. Similar activation energies describe the temperature-dependence of radiation damage to a variety of solvent-free small-molecule organic crystals over the temperature range T = 300-80 K. It is suggested that radiation damage in this regime is vibrationally assisted and that the freezing-out of amino-acid scale vibrations contributes to the very weak temperature-dependence of radiation damage below ∼80 K. Analysis using the radiation-damage model of Blake and Phillips [Blake & Phillips (1962), Biological Effects of Ionizing Radiation at the Molecular Level, pp. 183-191] indicates that large-scale conformational and molecular motions are frozen out below T = 200 K but become increasingly prevalent and make an increasing contribution to damage at higher temperatures. Possible alternative mechanisms for radiation damage involving the formation of hydrogen-gas bubbles are discussed and discounted. These results have implications for mechanistic studies of proteins and for studies of the protein glass transition. They also suggest that data collection at T ≃ 220 K may provide a viable alternative for structure determination when cooling-induced disorder at T = 100 is excessive.

Is gas-discharge plasma a new solution to the old problem of biofilm inactivation?

Conventional disinfection and sterilization methods are often ineffective with biofilms, which are ubiquitous, hard-to-destroy microbial communities embedded in a matrix mostly composed of exopolysaccharides. The use of gas-discharge plasmas represents an alternative method, since plasmas contain a mixture of charged particles, chemically reactive species and UV radiation, whose decontamination potential for free-living, planktonic micro-organisms is well established. In this study, biofilms were produced using Chromobacterium violaceum, a Gram-negative bacterium present in soil and water and used in this study as a model organism. Biofilms were subjected to an atmospheric pressure plasma jet for different exposure times. Our results show that 99.6 % of culturable cells are inactivated after a 5 min treatment. The survivor curve shows double-slope kinetics with a rapid initial decline in c.f.u. ml(-1) followed by a much slower decline with D values that are longer than those for the inactivation of planktonic organisms, suggesting a more complex inactivation mechanism for biofilms. DNA and ATP determinations together with atomic force microscopy and fluorescence microscopy show that non-culturable cells are still alive after short plasma exposure times. These results indicate the potential of plasma for biofilm inactivation and suggest that cells go through a sequential set of physiological and morphological changes before inactivation.

Effects of γ-irradiation on the membrane ATPases of human erythrocytes from transfusional blood concentrates

Irradiation of blood derivatives is employed in blood banks to avoid transfusion-associated graft-vs-host disease. As irradiation can damage membranes and membrane proteins by generation of reactive oxygen species, we investigated whether the membrane permeability, Na(+),K(+)-ATPase, and Ca(2+)-ATPase from red blood cell plasma membranes were altered by gamma-irradiation. Whole blood was collected from healthy donors and concentrated to 90% cell fraction. Within 24 h of collection, blood concentrates were irradiated with 25 Gy of gamma-radiation. At days 1, 7, 14, and 28 post-irradiation, fractions were removed and centrifuged. Na(+),K(+)-ATPase and Ca(2+)-ATPase activities from ghost membranes were assessed by gamma-(32)P-ATP hydrolysis. The Na(+),K(+)-ATPase was not immediately affected by irradiation, but it was inhibited by 40% by day 14 and until day 28. The Ca(2+)-ATPase was unaltered by irradiation. The rate and the maximal (45)Ca(2+) uptake from re-sealed inside-out vesicles were reduced, and the passive efflux of (45)Ca(2+) was increased. Thus, irradiation of blood concentrates increased the plasma membrane permeability to monovalent and divalent cations and would change ion homeostasis and cell function. We recommend the use of irradiated blood within a period shorter than 14 days after irradiation.

Development of a new E. coli strain to detect oxidative mutation and its application to the fungicide o-phenylphenol and its metabolites

Oxidative mutation is mainly induced by reactive oxygen species (ROS), such as the superoxide anion radical (O(2)(-)) and hydrogen peroxide (H(2)O(2)). However, in Escherichia coli (E. coli), ROS are eliminated by enzymes such as superoxide dismutase and catalase, which are coded by sodAB and katEG genes. In this study, to detect mutagens that induce oxidative mutation, a mutant (WP2katEGsodAB) with katEG and sodAB deleted was constructed by gene manipulation of E. coli WP2. H(2)O(2) and menadione sodium bisulfite generated mutation in WP2katEGsodAB but not in WP2. o-Phenylphenol (OPP) and its metabolites (phenylhydroquinone (PHQ) and phenyl-1,4-benzoquinone (PBQ)), which had been shown to be negative in the Ames test but reported to be carcinogenic, induced mutation in WP2katEGsodAB but not in WP2. These results suggest that the new assay may be useful for the detection of oxidative mutagens.

Normal human fibroblasts exposed to high- or low-dose ionizing radiation: differential effects on mitochondrial protein import and membrane potential

How oxidative metabolism modulates effects of ionizing radiation is incompletely understood. Because mitochondria participate in oxidative metabolism, we investigated the modulation of mitochondrial protein import and membrane potential (DeltaPsi) in irradiated cells. Our data show that effects at low dose cannot be predicted from effects at high dose. When density-inhibited normal human fibroblasts were exposed to a toxic dose of 4 Gy, protein import into mitochondria isolated from these cells was decreased. In contrast, protein import into mitochondria isolated from low-dose-irradiated (10 cGy) cells was enhanced, suggesting that mitochondria may play a crucial role in low-dose-induced adaptive responses. At high dose, import defects were not solely due to changes in mitochondrial DeltaPsi, and modulation of import was not tightly linked to the cellular capacity to repair radiation damage. Another striking observation is that in proliferating nonirradiated cells, mitochondrial protein import and DeltaPsi were regulated in a cell cycle-dependent manner, being lower in S phase than in G (1). Interestingly, when quiescent G (0)/G (1) phase cells exposed to high-dose radiation were stimulated to proliferate, events associated with S phase, but not G (1), significantly affected import. The strategy described here may serve as novel end points to study radiation-induced effects.

Leakage of Potassium from Red Blood Cells following Gamma Ray Irradiation in the Presence of Dipyridamole, Trolox, Human Plasma or Mannitol

Transfusion-associated graft-versus-host disease (TA-GVHD) is a fatal complication of blood transfusion resulting from the contamination of blood products by leukocytes. In order to prevent this disease, gamma or X-ray irradiation of blood components,which can inactivate leukocytes, is currently used. However, the minimal doses needed to destroy lymphocytes promote the leakage of potassium from red blood cells (RBCs), which can induce other side effects, such as hyperpotassemia and cardiac arrest. The reactive oxygen species (ROS) generated by the irradiation of aqueous solutions may accelerate the leakage through oxidation of the RBC membrane. Here we studied the effect of dipyridamole, Trolox, human plasma or mannitol on the leakage of potassium from RBCs following irradiation. RBC preparations (hematocrit; 30%) containing antioxidants were irradiated at 30 Gy and stored at 4 degrees C for 7 d. The leakage of potassium from the RBCs caused by the irradiation was significantly suppressed by dipyridamole (more than 50 microM), Trolox (more than 5 mM) or human plasma (50%). Mannitol (80 mM) is used to inhibit hemolysis as a constituent of MAP solution, which is a solution used for the storage of RBC products in Japan. Here it was clarified that the leakage of potassium from not only irradiated but also non-irradiated RBCs was unexpectedly promoted by mannitol. The amount of mannitol in MAP solution may have to be reconsidered. The osmotic pressure of the RBC preparation increased in a manner dependent on the concentration of mannitol. The elevated osmotic pressure may promote the leakage. In conclusion, although antioxidants have the potential to suppress the leakage of potassium ascribed to the irradiation, the extent of the suppression (10-20%) by dipyridamole (DPM), Trolox or human plasma seems insufficient for the clinical use of these agents as an additive for MAP solution.

Human plasma and tirilazad mesylate protect stored human erythrocytes against the oxidative damage of gamma-irradiation

Transfusion-associated graft-versus-host disease (TA-GVHD) is a serious condition that under certain circumstances can be lethal in immunosuppressed patients. The risk of TA-GVHD can be reduced in this population by gamma irradiation (gammaRad) of blood components. gammaRad results in production of reactive oxygen species which can damage red blood cells (RBC). Tirilazad mesylate (TM) is a member of the 21-aminosteroids (Lazaroids) family and is a powerful antioxidant. We investigated the ability of TM and human plasma (which contain powerful antioxidants) to protect stored human RBC against the oxidative damage of gammaRad. Fresh intact packed RBC obtained from the normal donors, with and without autologous plasma or TM (0.05 mg mL-1 RBC), were exposed to gammaRad (50 Gy) and stored for 28 days at 4 degrees C. Oxidative damage was assessed by osmotic fragility at 65 mM NaCl concentration (expressed by percentage haemolysis in 65 mM NaCl solution) and lipid peroxidation (measured by thiobarbituric acid reactive substances, TBARS). Our results showed that storage and irradiation of untreated intact RBC increased the osmotic fragility at 65 mM NaCl concentration (65.8 +/- 1.3 vs. 51.20 +/- 0.87% haemolysis; irradiated vs. controls, respectively; P = 0.002) and lipid peroxidation (TBARS = 4.47 +/- 0. 12 vs. 3.45 +/- 0.09 microM L-1 RBC; irradiated vs. controls, respectively; P = 0.001). TM protected the intact RBC against radiation-induced haemolysis (35.8 +/- 5.0 vs. 65.8 +/- 1.3% haemolysis; treated vs. untreated irradiated RBC, respectively; P = 0.02) and lipid peroxidation (TBARS = 2.91 +/- 0.2 vs. 4.47 +/- 0.12 microM L-1 RBC; treated vs. untreated irradiated RBC, respectively; P = 0.005). Addition of autologous plasma to packed RBC significantly reduced the extent of radiation-induced haemolysis by more than six-fold (12.45 +/- 0.26 vs. 65.8 +/- 2.2% haemolysis; irradiated RBC with versus without plasma, respectively; P = 0.0001). In conclusion, these results show that irradiation and storage of blood damages RBC via oxidative processes and addition of autologous plasma and/or TM protects RBC against such damage and possibly enhances their storage and survival.

The 'fingerprint' that X-rays can leave on structures

BACKGROUND

Exposure of biomacromolecules to ionising radiation results in damage that is initiated by free radicals and progresses through a variety of mechanisms. A widely used technique to study the three-dimensional structures of biomacromolecules is crystallography, which makes use of ionising X-rays. It is crucial to know to what extent structures determined using this technique might be biased by the inherent radiation damage.

RESULTS

The consequences of radiation damage have been investigated for three dissimilar proteins. Similar results were obtained for each protein, atomic B factors increase, unit-cell volumes increase, protein molecules undergo slight rotations and translations, disulphide bonds break and decarboxylation of acidic residues occurs. All of these effects introduce non-isomorphism. The absorbed dose in these experiments can be reached during routine data collection at undulator beamlines of third generation synchrotron sources.

CONCLUSIONS

X-rays can leave a 'fingerprint' on structures, even at cryogenic temperatures. Serious non-isomorphism can be introduced, thus hampering multiple isomorphous replacement (MIR) and multiwavelength anomalous dispersion (MAD) phasing methods. Specific structural changes can occur before the traditional measures of radiation damage have signalled it. Care must be taken when assigning structural significance to features that might easily be radiation-damage-induced changes. It is proposed that the electron-affinic disulphide bond traps electrons that migrate over the backbone of the protein, and that the sidechains of glutamic acid and aspartic acid donate electrons to nearby electron holes and become decarboxylated successively. The different disulphide bonds in each protein show a clear order of susceptibility, which might well relate to their intrinsic stability.

Adenosine deaminase, 5'-nucleotidase, xanthine oxidase, superoxide dismutase, and catalase activities in gastric juices from patients with gastric cancer, ulcer, and atrophic gastritis

Adenosine deaminase (ADA), 5'-Nucleotidase (5NT), Xanthine oxidase (XO), Cu-Zn Superoxide dismutase (SOD) and Catalase (CAT) activities were determined in gastric juices from patients with gastric cancer, ulcer, gastritis and from healthy subjects. Enzyme activities were given as units per ml gastric juice and units per mg protein in gastric juice. ADA, 5NT and XO activities were found lower and protein concentrations were found higher in the cancer group than controls. There was however no significant difference between Cu-Zn SOD activities of the cancer and control groups. In all groups including control one, we could not find catalase activities in most of the samples. On the other hand, ADA, 5NT activities and protein concentrations in the gastric juice were lower in the gastritis group than control group. In the ulcer group, we found higher Cu-Zn SOD and XO activities and lower 5NT activity and protein concentrations compared with control values. In an attempt to establish statistical correlations between mean enzyme activities, pH and protein concentrations in the gastric juices of the groups, we found noticeable intra and inter-correlations, which indicated possible relations between DNA and free radical metabolizing enzymes.

Active oxygen generation in gamma-irradiated whole seedlings of Cicer arietinum L

Whole seedlings of Cicer arietinum L. when exposed to 819 Gy gamma-radiation, were found to emit ultraweak intensity luminescence. The phenomenon was oxygen-dependent, and the intensity of emission could be suppressed by post-irradiation treatment with catalase, superoxide dismutase, and ascorbic acid. Deuterium oxide and luminol amplified the emission intensity. These results suggest that singlet oxygen is a cause of the emission during the post-irradiation phase.

Oxidative stress responses in Escherichia coli and Salmonella typhimurium

Oxidative stress is strongly implicated in a number of diseases, such as rheumatoid arthritis, inflammatory bowel disorders, and atherosclerosis, and its emerging as one of the most important causative agents of mutagenesis, tumorigenesis, and aging. Recent progress on the genetics and molecular biology of the cellular responses to oxidative stress, primarily in Escherichia coli and Salmonella typhimurium, is summarized. Bacteria respond to oxidative stress by invoking two distinct stress responses, the peroxide stimulon and the superoxide stimulon, depending on whether the stress is mediated by peroxides or the superoxide anion. The two stimulons each contain a set of more than 30 genes. The expression of a subset of genes in each stimulon is under the control of a positive regulatory element; these genes constitute the OxyR and SoxRS regulons. The schemes of regulation of the two regulons by their respective regulators are reviewed in detail, and the overlaps of these regulons with other stress responses such as the heat shock and SOS responses are discussed. The products of Oxy-R- and SoxRS-regulated genes, such as catalases and superoxide dismutases, are involved in the prevention of oxidative damage, whereas others, such as endonuclease IV, play a role in the repair of oxidative damage. The potential roles of these and other gene products in the defense against oxidative damage in DNA, proteins, and membranes are discussed in detail. A brief discussion of the similarities and differences between oxidative stress responses in bacteria and eukaryotic organisms concludes this review.

A medium for the isolation, enumeration and rapid presumptive identification of injured Clostridium perfringens and Bacillus cereus

A blood-free egg yolk medium (BCP) containing pyruvate, inositol, mannitol and a bromocresol purple indicator in a nutrient agar base has been developed to initiate the growth of Clostridium perfringens. It is comparable to blood agar for the growth of normal, chilled stored vegetative cells and heat-injured spores of Cl. perfringens and Bacillus cereus. It has the advantage over blood agar in exhibiting presumptive evidence of Cl. perfringens (production of lecithinase and inositol fermentation) after an overnight incubation at 43 degrees - 45 degrees C. Pyruvate, catalase and other hydrogen peroxide degraders were found to remove toxins rapidly formed in media exposed to air and light. Free radical scavengers of superoxide, hydroxyl ions and singlet oxygen were ineffective. Without scavengers the formation of 10-20 micrograms/ml hydrogen peroxide in the exposed medium was indicated and found lethal to injured Cl. perfringens. The BCP medium has been used successfully for the rapid identification and enumeration of Cl. perfringens in foods and faeces from food poisoning outbreaks and cases of suspected infectious diarrhoea. Greater recovery of severely injured vegetative Cl. perfrigens could be obtained by pre-incubation at 37 degrees C of inoculated media for 2-4 h followed by overnight incubation at 43 degrees - 45 degrees C. Tryptose-sulphite-cycloserine and Shahidi-Ferguson-perfringens agar base were found to inhibit the growth of several strains of injured vegetative Cl. perfringens. This was not completely overcome by the addition of pyruvate. The inclusion of mannitol also allows the medium to be used for the presumptive identification of B. cereus. Growth and lecithinase activity are profuse on BCP. Heat-injured spores are recovered equally well on BCP and blood agar. A scheme for the identification of some other clostridia on BCP is presented.

Advances in radioprotection through the use of combined agent regimens

The most effective radioprotective agents exhibit toxicities that can limit their usefulness. It may be possible to use combinations of agents with different radioprotective mechanisms of action at less toxic doses, or to reduce the toxicity of the major protective compound by adding another agent. With regard to the latter possibility, improved radioprotection and reduced lethal toxicity of the phosphorothioate WR-2721 was observed when it was administered in combination with metals (selenium, zinc or copper). The known mechanisms of action of potential radioprotective agents and varying effects of different doses and times of administration in relation to radiation exposure must be considered when using combined-agent regimens. A number of receptor-mediated protectors and other biological compounds, including endotoxin, eicosanoids and cytokines, have at least an additive effect when administered with thiol protectors. Eicosanoids and other bioactive lipids must be administered before radiation exposure, whereas some immunomodulators have activity when administered either before or after radiation exposure. For example, the cytokine interleukin-1 administered simultaneously with WR-2721 before irradiation or after irradiation enhances the radioprotective efficacy of WR-2721. The most effective single agents or combinations of protectors result in a decrement in locomotor activity, an index of behavioral toxicity. Recent evidence indicates that administration of the CNS stimulant caffeine mitigates the behavioral toxicity of an effective radioprotective dose of the phosphorothioate WR-3689 without altering its radioprotective efficacy. These examples indicate that the use of combinations of agents is a promising approach for maximizing radioprotection with minimal adverse effects.

Hydroxyl radical scavenging and antipsoriatic activity of benzoic acid derivatives

The hydroxyl radical scavenging and antipsoriatic activity of a number of lipophilic and hydrophilic benzoic acid derivatives was investigated. To quantify antioxidative effects, a newly introduced test system based on the diminution of the ESR signal of DMPO-OH (generated by Fenton's reagent) by the tested compounds was applied. It was found that the in vitro antioxidative (toward hydroxyl radical) activity of benzoic acid esters decreases with increasing chain length whereas the antipsoriatic activity increases. This effect is discussed in terms of a larger lipophilicity of long-chain esters. Propyl gallate was found to be the most active OH scavenger since it is some orders of magnitude more efficient than "model" antioxidants like alpha-tocopherol or mannitol. The highest antipsoriatic activity was exhibited by hydroxy benzoic acid decyl ester.

Semiconservative and unscheduled DNA synthesis on mammalian cells and its modification by glyoxylic compounds

The interaction of glyoxal and four other glyoxylic compounds with semiconservative DNA synthesis and with unscheduled DNA synthesis induced by 25-G X-rays on TC-SV40 hamster cells has been studied. Both syntheses were evaluated by measuring the incorporation of [3H-methyl]-thymidine into the newly synthetized DNA. The unscheduled DNA synthesis amounts to 4% of semiconservative synthesis. The modification of both syntheses by the glyoxylic compounds was tested using the products at non-toxic concentrations for the cells. All the glyoxals inhibited semiconservative DNA synthesis and potentiated unscheduled DNA synthesis at rather similar levels. These effects have been compared with the radiosensitizing activity of these glyoxals in the same TC-SV40 cells and no relationship could be established.

Alloxan- and glutathione-dependent ferritin iron release and lipid peroxidation

The diabetogenic action of alloxan is believed to involve oxygen free radicals and iron. Incubation of glutathione (GSH) and alloxan with rat liver ferritin resulted in release of ferrous iron as assayed by spectrophotometric detection of ferrous-bathophenanthroline complex formation. Neither GSH nor alloxan alone mediated iron release from ferritin. Superoxide dismutase (SOD) and catalase did not affect initial rates of iron release whereas ceruloplasmin was an effective inhibitor of iron release. The reaction of GSH with alloxan resulted in the formation of the alloxan radical which was detected by ESR spectroscopy and by following the increase in absorbance at 310nm. In both instances, the addition of ferritin resulted in diminished alloxan radical detection. Incubation of GSH, alloxan, and ferritin with phospholipid liposomes also resulted in lipid peroxidation. Lipid peroxidation did not occur in the absence of ferritin. The rates of lipid peroxidation were not affected by the addition of SOD or catalase, but were inhibited by ceruloplasmin. These results suggest that the alloxan radical releases iron from ferritin and indicates that ferritin iron may be involved in alloxan-promoted lipid peroxidation.