Appraisal of mechanisms of radioprotection and therapeutic approaches of radiation countermeasures

Molecular Insights into Radiation Effects and Protective Mechanisms: A Focus on Cellular Damage and Radioprotectors

Ionizing radiation has been a critical tool in various fields, such as medicine, agriculture, and energy production, since its discovery in 1895. While its applications-particularly in cancer treatment and diagnostics-offer significant benefits, ionizing radiation also poses risks due to its potential to cause molecular and cellular damage. This damage can occur through the direct ionization of biological macromolecules, such as deoxyribonucleic acid (DNA), or indirectly through the radiolysis of water, which generates reactive oxygen species (ROS) that further damage cellular components. Radioprotectors, compounds that protect against radiation-induced damage, have been extensively researched since World War II. These agents work by enhancing DNA repair, scavenging free radicals, and boosting antioxidant defenses, thereby protecting healthy tissues. Furthermore, some radioprotective agents also stimulate DNA repair mechanisms even after radiation exposure, aiding in recovery from radiation-induced damage. This article explores the molecular mechanisms of radiation-induced damage, focusing on both direct and indirect effects on DNA, and discusses the role of radioprotectors, their mechanisms of action, and recent advancements in the field. The findings underscore the importance of developing effective radioprotective strategies, particularly in medical and industrial settings, where radiation exposure is prevalent.

Nanoengineered Injectable Hydrogel: An Advanced Radioprotective Barrier with Magnetic Hyperthermia Synergy

Despite its effectiveness in eradicating cancer cells, current tumor radiotherapy often causes irreversible damage to the surrounding healthy tissues. To address this issue and enhance therapeutic outcomes, we developed a multifunctional injectable hydrogel that integrates electromagnetic shielding and magnetothermal effects. This innovation aims to improve the efficacy of brachytherapy while protecting adjacent normal tissues. Recognizing the limitations of existing hydrogel materials in terms of stretchability, durability, and single functionality, we engineered a composite hydrogel by self-assembling nickel nanoparticles on the surface of liquid metal particles and embedding them into an injectable hydrogel matrix. The resulting composite material demonstrates superior electromagnetic interference shielding performance (74.89 dB) and a rapid magnetothermal heating rate (10.9 °C/min), significantly enhancing its in vivo applicability. The experimental results confirm that this innovative nanocomposite hydrogel effectively attenuates electromagnetic waves during brachytherapy, thereby protecting normal tissues surrounding the tumor and enhancing radiotherapy efficacy through magnetothermal therapy. This study advances the safety and effectiveness of cancer treatments and provides new insights into the development of multifunctional biomedical materials, promoting the innovative application of nanotechnology in the medical field.

A DNA tetrahedron-based nanosuit for efficient delivery of amifostine and multi-organ radioprotection

Unnecessary exposure to ionizing radiation (IR) often causes acute and chronic oxidative damages to normal cells and organs, leading to serious physiological and even life-threatening consequences. Amifostine (AMF) is a validated radioprotectant extensively applied in radiation and chemotherapy medicine, but the short half-life limits its bioavailability and clinical applications, remaining as a great challenge to be addressed. DNA-assembled nanostructures especially the tetrahedral framework nucleic acids (tFNAs) are promising nanocarriers with preeminent biosafety, low biotoxicity, and high transport efficiency. The tFNAs also have a relative long-term maintenance for structural stability and excellent endocytosis capacity. We therefore synthesized a tFNA-based delivery system of AMF for multi-organ radioprotection (tFNAs@AMF, also termed nanosuit). By establishing the mice models of accidental total body irradiation (TBI) and radiotherapy model of Lewis lung cancer, we demonstrated that the nanosuit could shield normal cells from IR-induced DNA damage by regulating the molecular biomarkers of anti-apoptosis and anti-oxidative stress. In the accidental total body irradiation (TBI) mice model, the nanosuit pretreated mice exhibited satisfactory alteration of superoxide dismutase (SOD) activities and malondialdehyde (MDA) contents, and functional recovery of hematopoietic system, reducing IR-induced pathological damages of multi-organ and safeguarding mice from lethal radiation. More importantly, the nanosuit showed a selective radioprotection of the normal organs without interferences of tumor control in the radiotherapy model of Lewis lung cancer. Based on a conveniently available DNA tetrahedron-based nanocarrier, this work presents a high-efficiency delivery system of AMF with the prolonged half-life and enhanced radioprotection for multi-organs. Such nanosuit pioneers a promising strategy with great clinical translation potential for radioactivity protection.

Ergothioneine-Sodium Hyaluronate Dressing: A Promising Approach for Protecting against Radiation-Induced Skin Injury

Radiotherapy commonly causes damage to healthy tissues, particularly radiation-induced skin injury (RISI) that affects a significant majority of patients undergoing radiotherapy. Effective treatments for RISI are lacking. This study focuses on the pathogenesis of RISI, which primarily involves oxidative stress. Excessive reactive oxygen species (ROS) generation during radiation induces damage to biological macromolecules, triggering oxidative stress and inflammation. To address this, ergothioneine (EGT), a natural and biocompatibile thiol compound with excellent antioxidant activity, is explored as a potential radiation-protective agent. By utilizing its specific transport and absorption in the skin tissue, as well as its efficient and stable clearance of radiation-induced "ROS storm", EGT is combined with sodium hyaluronate (NaHA) to develop a novel radiation protective dressing suitable for the skin. This EGT-NaHA dressing demonstrates an effective ability to scavenge free radicals and reduce oxidative stress in vitro and in vivo, reducing cellular apoptosis and inflammation. These results demonstrate the protective properties of EGT against RISI, with far-reaching implications for research and development in the field of radioprotection.

Design, synthesis, biological evaluation and in silico studies of novel quinoline derivatives as potential radioprotective molecules targeting the TLR2 and p53 pathways

Ionizing radiation in space, radiation devices or nuclear disasters are major threats to human health and public security. In this paper, in order to find the potential novel compounds decreasing the radiation-induced damage by targeting p53 apoptosis pathway and TLR2 passway, a series of novel quinoline derivatives were designed, synthesized, and evaluated their biological activities. Most of the synthesized compounds showed significant radioprotective effects in vitro, and the compound 5 has the best performance. Therefore, we verified its radioprotective activity in vivo and investigated the mechanism of its excellent activity. The results in vivo indicated that compound 5 not only markedly enhanced the survival rate (80 %) of mice 30 days after lethal exposure to irradiation, but also significantly reduced the radiation-induced damage to haematopoietic system and intestinal tissue of mice. The mechanistic studies indicated that compound 5 acted on the p53 pathway to reduce radiation-induced cell apoptosis and at the same time stimulated TLR2 to up-regulate the expressions of radiation protection factors. Molecular dynamics study shows that compound 5 would effectively bind to the TLR2 protein and further revealed the binding mechanism. Taken together, all the findings of our study demonstrate the quinoline derivative 5 is a potent radioprotective compound, which holds a great therapeutic potential for further development.

One-pot synthesis of ultra-stable polyvinylpyrrolidone-modified MnO2 nanoparticles for efficient radiation protection

Radiobiological damage can be caused by radiation, and easy preparation of long-term stable radioprotectors is helpful for timely and efficient response to radiation emergencies. This study develops an ultra-stable radioprotector for rapid nuclear emergency with a simple preparing method. First of all, polyvinylpyrrolidone-modified MnO2 nanoparticles (PVP-MnO2 NPs) are obtained by one-pot synthesis with ultra-stability (remaining for at least three years) and multiple free radical scavenging activities. In the synthesis process, PVP acts as a reducing agent, a surfactant (soft template), and a steric stabilizer. PVP-MnO2 NPs can improve the survival rates of irradiated cells by effectively scavenging free radicals and protecting DNA from radiation damage. Besides, PVP-MnO2 NPs can also prevent peripheral blood cell and organ damage induced by radiation, and improve the survival rate of irradiated mice. Finally, PVP-MnO2 NPs are mainly metabolized by liver and kidney in mice, and basically excreted 72 h after administration. These results indicate that PVP-MnO2 NPs exhibit good biosafety and radioprotection activity, which is significant for the development of radioprotection agents.

Clinical Pathobiology of Radiotherapy-Induced Alopecia: A Guide toward More Effective Prevention and Hair Follicle Repair

Because hair follicles (HFs) are highly sensitive to ionizing radiation, radiotherapy-induced alopecia (RIA) is a core adverse effect of oncological radiotherapy. Yet, effective RIA-preventive therapy is unavailable because the underlying pathobiology remains underinvestigated. Aiming to revitalize interest in pathomechanism-tailored RIA management, we describe the clinical RIA spectrum (transient, persistent, progressive alopecia) and our current understanding of RIA pathobiology as an excellent model for studying principles of human organ and stem cell repair, regeneration, and loss. We explain that HFs respond to radiotherapy through two distinct pathways (dystrophic anagen or catagen) and why this makes RIA management so challenging. We discuss the responses of different HF cell populations and extrafollicular cells to radiation, their roles in HF repair and regeneration, and how they might contribute to HF miniaturization or even loss in persistent RIA. Finally, we highlight the potential of targeting p53-, Wnt-, mTOR-, prostaglandin E2-, FGF7-, peroxisome proliferator-activated receptor-γ-, and melatonin-associated pathways in future RIA management.

Topically applied fullerenols protect against radiation dermatitis by scavenging reactive oxygen species

Adverse skin reactions caused by ionizing radiation are collectively called radiation dermatitis (RD), and the use of nanomedicine is an attractive approach to this condition. Therefore, we designed and large-scale synthesized fullerenols that showed free radical scavenging ability in vitro. Next, we pretreated X-ray-exposed cells with fullerenols. The results showed that pretreatment with fullerenols significantly scavenged intracellular reactive oxygen species (ROS) produced and enhanced the antioxidant capacity, protecting skin cells from X-ray-induced DNA damage and apoptosis. Moreover, we induced RD in mice by applying 30 Gy of X-ray irradiation, followed by treatment with fullerenols. We found that after treatment, the RD scores dropped, and the histological results systematically demonstrated that topically applied fullerenols could reduce radiation-induced skin epidermal thickening, collagen deposition and skin appendage damage and promote hair regeneration after 35 days. Compared with Trolamine cream, a typical RD drug, fullerenols showed superior radiation protection. Overall, the in vitro and in vivo experiments proved that fullerenols agents against RD.

Development of radiation countermeasure agents for acute radiation syndromes

The risk of internal and external exposure to ionizing radiation (IR) has increased alongside the development and implementation of nuclear technology. Therefore, serious security issues have emerged globally, and there has been an increase in the number of studies focusing on radiological prevention and medical countermeasures. Radioprotective drugs are particularly important components of emergency medical preparedness strategies for the clinical management of IR-induced injuries. However, a few drugs have been approved to date to treat such injuries, and the related mechanisms are not entirely understood. Thus, the aim of the present review was to provide a brief overview of the World Health Organization's updated list of essential medicines for 2023 for the proper management of national stockpiles and the treatment of radiological emergencies. This review also discusses the types of radiation-induced health injuries and the related mechanisms, as well as the development of various radioprotective agents, including Chinese herbal medicines, for which significant survival benefits have been demonstrated in animal models of acute radiation syndrome.

Nanodrugs with intrinsic radioprotective exertion: Turning the double-edged sword into a single-edged knife

Ionizing radiation (IR) poses a growing threat to human health, and thus ideal radioprotectors with high efficacy and low toxicity still receive widespread attention in radiation medicine. Despite significant progress made in conventional radioprotectants, high toxicity, and low bioavailability still discourage their application. Fortunately, the rapidly evolving nanomaterial technology furnishes reliable tools to address these bottlenecks, opening up the cutting-edge nano-radioprotective medicine, among which the intrinsic nano-radioprotectants characterized by high efficacy, low toxicity, and prolonged blood retention duration, represent the most extensively studied class in this area. Herein, we made the systematic review on this topic, and discussed more specific types of radioprotective nanomaterials and more general clusters of the extensive nano-radioprotectants. In this review, we mainly focused on the development, design innovations, applications, challenges, and prospects of the intrinsic antiradiation nanomedicines, and presented a comprehensive overview, in-depth analysis as well as an updated understanding of the latest advances in this topic. We hope that this review will promote the interdisciplinarity across radiation medicine and nanotechnology and stimulate further valuable studies in this promising field.

Radioprotective countermeasures for radiation injury (Review)

A series of physiological and pathological changes occur after radiotherapy and accidental exposure to ionizing radiation (IR). These changes cause serious damage to human tissues and can lead to death. Radioprotective countermeasures are radioprotective agents that prevent and reduce IR injury or have therapeutic effects. Based on a good understanding of radiobiology, a number of protective agents have achieved positive results in early clinical trials. The present review grouped known radioprotective agents according to biochemical categories and potential clinical use, and reviewed radiation countermeasures, i.e., radioprotectors, radiation mitigators and radiotherapeutic agents, with an emphasis on their current status and research progress. The aim of the present review is to facilitate the selection and application of suitable radioprotectors for clinicians and researchers, to prevent or reduce IR injury.

The neuroprotective effect of ascorbic acid against imidacloprid-induced neurotoxicity and the role of HO-1 in mice

Imidacloprid (IMI) is not only a neurotoxic agricultural pesticide but also a possible food contaminant. The aims of this study were to (1) explore the relationship between recurrent IMI administration and neuronal toxicity in mice and (2) evaluate the potential neuroprotective effect of ascorbic acid (AA), a substance with significant free radical scavenger and having property to block the inflammatory pathways. Mice were categorized as naïve controls (administered vehicles for 28 days); the IMI-treatment animal group (administered po 45-mg/kg body weight of IMI per day for 28 days); and the IMI + AA treatment animal group (administered the same IMI dose + 200 mg/kg of AA orally for 28 days). On day 28, memory losses were assessed using the Y-maze and novel target identification behavioral tests. Mice were sacrificed 24 h after the final IMI treatments, as well as hippocampus tissues, were utilized to determine histological assessments, oxidative stress biomarkers, and Heme oxygenase-1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) gene expression levels. The findings demonstrated that IMI-treated mice had substantial impairment of spatial and non-spatial memory functions, as well as reduced antioxidant enzyme and acetylcholinesterase activity. The AA neuroprotective action was achieved through the suppression of the HO-1 expression as well as the stimulation of Nrf2 expression in hippocampal tissues. In summary, recurrent IMI exposure causes oxidative stress and neurotoxicity in mice, and the administration of AA significantly reduces the IMI toxicity possibly by the activation of the HO-1/Nrf2 pathway.

Review of compounds that exhibit radioprotective and/or mitigatory effects after application of diagnostic or therapeutic ionizing radiation

PURPOSE

Exposure to ionizing radiation can be accidental or for medical purposes. Analyzes of the frequency of radiation damage in the general population, it has been determined that by far the most common are those that occur as a result of diagnostic or therapeutic procedures. Damage caused by radiation, either accidentally or for therapeutic purposes, can be reduced by the use of radioprotectors, mitigators or other therapeutic agents. A detailed research of the available literature shows that there is little systematized data of potentially radioprotective and/or mitigating effects of drugs from the personal therapy of patients during the application of therapeutic ionizing radiation. The aim of this paper is to present review of compounds, especially personal therapy drugs, that exhibit radioprotective and/or mitigating effects after the application of diagnostic or therapeutic ionizing radiation.

CONCLUSIONS

Given the widespread use of ionizing radiation for diagnostic and therapeutic purposes, there is a clear need to create a strategy and recommendations of relevant institutions for the use of radioprotectors and mitigators in everyday clinical practice, with individual evaluation of the patient's condition and selection of the compounds that will show the greatest benefit in terms of radioprotection.

Plant based radioprotectors as an adjunct to radiotherapy: advantages and limitations

Radioprotectors are agents that have the potential to act against radiation damage to cells. These are equally invaluable in radiation protection, both in intentional and unintentional radiation exposure. It is however, complex to use a universal radioprotector that could be beneficial in diverse contexts such as in radiotherapy, nuclear accidents, and space travel, as each of these circumstances have unique requirements. In a clinical setting such as in radiotherapy, a radioprotector is used to increase the efficacy of cancer treatment. The protective agent must act against radiation damage selectively in normal healthy cells while enhancing the radiation damage imparted on cancer cells. In the context of radiotherapy, plant-based compounds offer a more reliable solution over synthetic ones as the former are less expensive, less toxic, possess synergistic phytochemical activity, and are environmentally friendly. Phytochemicals with both radioprotective and anticancer properties may enhance the treatment efficacy by two-fold. Hence, plant based radioprotective agents offer a promising field to progress forward, and to expand the boundaries of radiation protection. This review is an account on radioprotective properties of phytochemicals and complications encountered in the development of the ideal radioprotector to be used as an adjunct in radiotherapy.

Potential radioprotective properties of arbutin against ionising radiation on human leukocytes in vitro

Arbutin is a simple phenolic glucoside biosynthesised in many plant families. Some of the everyday foods that contain arbutin are species of the genus Origanum, peaches, cereal products, coffee and tea and Arctostaphyllos uva ursi L. leaves. Arbutin possesses various beneficial effects in the organism, and was confirmed effective in the treatment of urinary tract infections as well as in preventing skin hyperpigmentation. It shows antioxidant and anti-inflammatory properties, and antitumor activity. The aim of this study was to explore potential radioprotective properties of arbutin in concentrations of 11.4 μg/mL, 57 μg/mL, 200 μg/mL and 400 μg/mL administered as a pre-treatment for one hour before exposing human leukocytes to ionising radiation at a therapeutic dose of 2 Gy. The alkaline comet assay was used to establish the levels of primary DNA damage, and cytokinesis-block micronucleus (CBMN) cytome assay to determine the level of cytogenetic damage. None of the tested concentrations of single arbutin showed genotoxic and cytotoxic effects. Even at the lowest tested concentration, 11.4 μg/mL, arbutin demonstrated remarkable potential for radioprotection in vitro, observed both at the level of primary DNA damage, and using CBMN cytome assay. The best dose reduction compared with amifostine was observed after pre-treatment with the highest concentration of arbutin, corresponding to 400 μg/mL. Promising results obtained on the leukocyte model speak in favour of extending similar experiments on other cell and animal models.

60Coγ induction improves the protective effect of Acetobacter pasteurianus against ionizing radiation in mice

Exposure to ionizing radiation (IR) tends to cause serious health concerns. Thus, radioprotective agents are vital for the population exposed to radiation. As microorganisms have the advantages of fast reproduction and no geographical restrictions, direct microbe-based and environmental induction compounds are thriving radioprotectants resources. Oxidative system and oxidase in Acetobacter pasteurianus are unique and intriguing, the radioprotective effect of the cell-free extract from A. pasteurianus (APE) and ⁶⁰Coγ-treated extract (IRE) were comparatively investigated in the present study. The survival rate of A. pasteurianus with IRE addition was 149.1% in H₂O₂ damage test, while that with APE was only 10.4%. The viability of ⁶⁰Coγ-treated AML-12 cells was increased by 18.8% with IRE addition, yet APE showed no significant radioprotective effect. Moreover, in ⁶⁰Coγ-treated mice, IRE could significantly protect the white blood cell, improve the liver index, and attenuate the injuries of immune organs in mice. Administration of IRE significantly raised the activities of superoxide dismutase (SOD) and reduced the products of lipid peroxidation. These results clarified that gavage with APE and IRE presented notable antioxidant and radioprotective efficacy. A. pasteurianus showed appealing potential to be novel radioprotective bioagents and ⁶⁰Coγ treatment on microbe could be a new method for the development of better radioprotectant. KEY POINTS: • ⁶⁰Coγ induction could improve the radioprotective effect of APE. • IRE protected white blood cell in mice under IR. • IRE products have broad application prospects in radioprotection based on microbes.

Eco-Friendly and Scalable Synthesis of Fullerenols with High Free Radical Scavenging Ability for Skin Radioprotection

Radiation dermatitis is a common but torturous side effect during radiotherapy, which greatly decreases the life quality of patients and potentially results in detrimental cessation of tumor treatment. Fullerenol, known as "free radical sponge," is a great choice for skin radioprotection because of its broad-spectrum free radical scavenging performance, good chemical stability, and biosafety. In this work, a facile scalable and eco-friendly synthetic method of fullerenols by catalyst assistant mechanical chemistry strategy is provided. As no organic solvent or high concentration of acid and alkali is introduced to this synthetic system, large-scale (>20 g) production of fullerenols with high yield (>95%) is obtained and no complicated purification is required. Then, the skin radioprotective performance of fullerenols is systematically explored for the first time. In vitro results indicate that fullerenols significantly block the reactive oxygen species-induced damage and enhance the viability of irradiated human keratinocyte cells. In vivo experiments suggest that medical sodium hyaluronate hydrogels loaded with fullerenols are suitable for skin administration and powerfully mitigate radiodermatitis via effectively protecting epidermal stem cells. The work not only provides an efficient gram-scale and eco-friendly synthetic method of fullerenols, but also promotes the development of fullerenols as potential skin radioprotectors.

Fucoxanthin alters the apelin-13/APJ pathway in certain organs of γ-irradiated mice

Apelin-13 and APJ are implicated in different key physiological processes. This work aims at exploring the radioprotective effect of fucoxanthin (FX) on γ-radiation (RAD)-induced changes in the apelin-13/APJ pathway, which causes damage in the liver, kidney, lung and spleen of mice. Mice were administered FX (10 mg kg-1 day-1, i.p) and exposed to γ-radiation (2.5 Gy week-1) for four consecutive weeks. The treatment of irradiated mice by FX resulted in a significant amendment in protein expression of the apelin-13/APJ/NF-κB signalling pathway concurrently with reduced hypoxia (hypoxia-inducible factor-1α), suppressed oxidative stress marker (malondialdehyde), enhanced antioxidant defence mechanisms (reduced glutathione and glutathione peroxidase), a modulated inflammatory response [interleukin-6 (IL-6), monocyte chemoattractant protein-1, IL-10 and α-7-nicotinic acetylcholine receptor) and ameliorated angiogenic regulators [matrix metalloproteinase (MMP-2), MMP-9 and tissue inhibitor of metalloproteinase-1), as well as the tissue damage indicator (lactate dehydrogenase) in organ tissues. In addition, there were significant improvement in serum inflammatory markers tumour necrosis factor-α, IL-10, IL-1β and C-reactive protein compared with irradiated mice. The histopathological investigation of the FX + RAD organ tissues support the biochemical findings where the improvements in the tissues' architecture were obvious when compared with those of RAD. FX was thus shown to have a noticeable radioprotective action mediated through its regulatory effect on the apelin-13/APJ/NF-κB signalling pathway attributed to its antioxidant and anti-inflammatory activity that was reflected in different physiological processes. It could be recommended to use FX in cases of radiation exposure to protect normal tissues.

Pterocarpus santalinus L. extract mitigates gamma radiation-inflicted derangements in BALB/c mice by Nrf2 upregulation

Plant-based natural extracts contain several nutrients and bioactive compounds, such as phenolics and flavonoids, that possess various health-promoting activities. This study investigated the effects of polyphenols from Pterocarpus santalinus hydroalcoholic extract (PSHE) against gamma radiation-induced derangements via the upregulation of Nrf2. Ultra High Performance Liquid Chromatography Coupled to High Resolution Mass Spectrometry (UHPLC-HRMS/MS) analysis was performed to identify the possible radioprotectors. In vivo and in vitro studies, namely Real-Time-PCR (RT-PCR) analysis, Reactive Oxygen Species (ROS) scavenging activity, lipid peroxidation and GSH levels, DNA damage and cell death studies, anti-inflammatory (Sandwich ELISA), immunomodulatory studies (antibody staining), and model free radical scavenging assays, were performed. Vanillic acid, protocatechuic acid, para-hydroxybenzoic acid, chlorogenic acid, TNF-α inhibitor (Eudesmin), isoflavone (Daidzein 7-o-glucoside), astragalin (Kaempferol 3-o-glycoside), and other polyphenols were identified in PSHE using UHPLC-HRMS/MS analysis. Prophylactic administration of PSHE (-1 h) rendered more than 33% survival in mice exposed to 8 Gy whole-body-irradiation with increased mice survival and recovery of bone marrow and spleen cellularity. Real-time RT-PCR analysis showed that PSHE treatment (50 µg/mL) upregulated Nrf2, HO-1, and GPX-1 in mice splenocytes. At 50 µg/mL, PSHE reduced ROSscavenging activity, mitochondrial and spleen membrane lipid peroxidation levels, DNA damage, and cell death, and increased GSH levels. At 10 µg/mL, PSHE treatment diminished the content of IL-6 and TNF-α. At 50 µg/mL, PSHE suppressed lymphocyte proliferation. These findings indicate that polyphenols of PSHE possess marked antioxidant, anti-inflammatory, and immunomodulatory capacities, which play important roles in the prevention of radiation damage.

Radioprotective Role of Natural Polyphenols: From Sources to Mechanisms

The identification and development of radioprotective agents has emerged as a subject matter of research during recent years due to the growing usage of ionizing radiation in different areas of human life. Previous work on synthetic radioprotectors has achieved limited progress because of the numerous issues associated with toxicity. Compounds extracted from plants have potential to serve as lead candidates for developing ideal radioprotectors due to their low cost, safety and selectivity. Polyphenols are the most abundant and commonly dispersed group of biologically active molecules possessing broad range of pharmacological activities. Polyphenols have displayed efficacy for radioprotection during various investigations and can be administered at high doses with lesser toxicity. Detoxification of free radicals, modulating inflammatory responses, DNA repair, stimulation of hematopoietic recovery, and immune functions are the main mechanisms for radiation protection with polyphenols. Epicatechin, epigallocatechin-3-gallate, apigenin, caffeic acid phenylethylester, and silibinin provide cytoprotection together with the suppression of many pro-inflammatory cytokines owing to their free radical scavenging, anti-oxidant, and anti-inflammatory properties. Curcumin, resveratrol, quercetin, gallic acid, and rutin's radioprotective properties are regulated primarily by direct or indirect decline in cellular stress. Thus, polyphenols may serve as potential candidates for radioprotection in the near future, however, extensive investigations are still required to better understand their protection mechanisms.

Radioprotective potential of <italic>Costus afer</italic> against the radiation-induced hematological and histopathological damage in mice

Purpose

This study investigated the possible radioprotective effect of Costus afer extract (CAE) on hematological and histopathological parameters of mice.

Materials and Methods

Fifty-four male mice with mass between 37–43 g, 11–13 weeks old were used for this study. We divided the mice into six different groups containing nine animals, which were then further sub-divided into irradiated groups and un-irradiated groups. Animals received 250 mg/kg body weight extract of CAE by oral gavage for 6 days in addition to feeding and water ad libitum. Animals in the irradiated group were exposed to radiation at the Department of Radiotherapy and Oncology, Grey’s Hospital using a linear accelerator. Blood samples were collected at 48-hour post-irradiation for the hematology test followed by histopathology examination of kidney and liver.

Results

Our findings revealed that 3 Gy and 6 Gy dose of X-ray radiation caused a significant reduction in the white blood cell, packed cell volume, hemoglobin, neutrophils, lymphocytes, eosinophils, and platelet counts compared with the control group. However, the administration of CAE before irradiation significantly increased the mentioned parameters. There was no increase in red blood cell and monocyte among treated groups compared with the control. Histopathological changes in the kidney and liver sections revealed that no visible lesion in the pretreated mice. Hepatocytes seem to be within normal histological limits.

Conclusions

This study concludes that CAE offered some protection against radiation-induced hematological alterations, but there was no significant improvement in the histopathological parameters. Thus, further studies are needed to validate its radioprotective effect on histopathological variables.

Radioprotective Effect of Whey Hydrolysate Peptides against γ-Radiation-Induced Oxidative Stress in BALB/c Mice

Radiation therapy is widely used in the treatment of tumor diseases, but it can also cause serious damage to the body, so it is necessary to find effective nutritional supplements. The main purpose of this study is to evaluate the protective effect of whey hydrolysate peptides (WHPs) against ⁶⁰Coγ radiation damage in mice and explore the mechanism. BALB/c mice were given WHPs by oral gavage administration for 14 days. Then, some mice underwent a 30-day survival test after 8 Gy radiation, and other mice received 3.5 Gy radiation to analyze the changes in body weight, hematology and bone marrow DNA after three and 14 days. In addition, through further analysis of the level of oxidative stress and intestinal barrier function, the possible mechanism of the radioprotective effect of WHPs was explored. The study found WHPs can prolong survival time, restore body weight, and increase the number of peripheral blood white blood cells and bone marrow DNA content in irradiated mice. In addition, WHPs can significantly improve the antioxidant capacity, inhibit pro-inflammatory cytokines and protect the intestinal barrier. These results indicate that WHPs have a certain radioprotective effect in mice, and the main mechanism is related to reducing oxidative damage.

Research progress on radioprotective effects of bee products

Radiation exposure is an on going and serious threat in military and public health concern. There is an unmet need for effective preventative or mitigative treatments against radiation-induced injuries. The handful of Food and Drug Administration in the US approved radiation protection agents cannot be widely used due to their side effects. Some natural nontoxic compounds such as bee products have been reported to prevent and treat radiation-induced injuries (e.g. scavenging free radicals, inhibiting cell apoptosis and reducing DNA damage), indicating that they may be a potential option as a safe radioprotective agent. Bee products are nontoxic and have no known side effects on the human body, and are effective in the field of radiation protection. They are expected to be interesting drug candidates for preventing and treating radiation-induced injuries. This article reviews the prevention and treatment of bee products on radiation-induced injuries.

Xenogeneic transplantation of human WJ-MSCs rescues mice from acute radiation syndrome via Nrf-2-dependent regeneration of damaged tissues

There is an unmet medical need for radiation countermeasures that can be deployed for treatment of exposed individuals during ionizing radiation (IR) accidents or terrorism. Wharton's jelly mesenchymal stem cells (WJ-MSCs) from human umbilical cord have been shown to avoid allorecognition and induce a tissue-regenerating microenvironment, which makes them an attractive candidate for mitigating IR injury. We found that WJ-MSCs protected mice from a lethal dose of IR even when transplanted up to 24 hours after irradiation, and a combination of WJ-MSCs and antibiotic (tetracycline) could further expand the window of protection offered by WJ-MSCs. This combinatorial approach mitigated IR-induced damage to the hematopoietic and gastrointestinal system. WJ-MSCs increased the serum concentration of the cytoprotective cytokines granulocyte colony-stimulating factor (G-CSF) and IL-6 in mice. Knockdown of G-CSF and IL-6 in WJ-MSCs before injection to lethally irradiated mice or transplantation of WJ-MSCs to lethally irradiated Nrf-2 knockout mice significantly nullified the therapeutic protective efficacy. Hence, WJ-MSCs could be a potential cell-based therapy for individuals accidentally exposed to radiation.

Targeting of cellular redox metabolism for mitigation of radiation injury

Accidental exposure to ionizing radiation is a serious concern to human life. Studies on the mitigation of side effects following exposure to accidental radiation events are ongoing. Recent studies have shown that radiation can activate several signaling pathways, leading to changes in the metabolism of free radicals including reactive oxygen species (ROS) and nitric oxide (NO). Cellular and molecular mechanisms show that radiation can cause disruption of normal reduction/oxidation (redox) system. Mitochondria malfunction following exposure to radiation and mutations in mitochondria DNA (mtDNA) have a key role in chronic oxidative stress. Furthermore, exposure to radiation leads to infiltration of inflammatory cells such as macrophages, lymphocytes and mast cells, which are important sources of ROS and NO. These cells generate free radicals via upregulation of some pro-oxidant enzymes such as NADPH oxidases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Epigenetic changes also have a key role in a similar way. Other mediators such as mammalian target of rapamycin (mTOR) and peroxisome proliferator-activated receptor (PPAR), which are involved in the normal metabolism of cells have also been shown to regulate cell death following exposure to radiation. These mechanisms are tissue specific. Inhibition or activation of each of these targets can be suggested for mitigation of radiation injury in a specific tissue. In the current paper, we review the cellular and molecular changes in the metabolism of cells and ROS/NO following exposure to radiation. Furthermore, the possible strategies for mitigation of radiation injury through modulation of cellular metabolism in irradiated organs will be discussed.

A novel class of small molecule inhibitors with radioprotective properties

The goal of this study was to develop novel radioprotective agents targeting the intrinsic apoptotic pathway and thus decreasing the radiation-induced damage. For that purpose, we designed, synthesized and analyzed ten new compounds based on the 1-(4-(2-hydroxyethyl)piperazin-1-yl)-3-phenoxypropan-2-ol leading structure. The cytotoxicity of the newly synthesized substances was tested in vitro on cell lines derived from different progenitor cells by WST-1 proliferation assay. MTT test was utilized to assess half-maximal inhibitory concentrations and maximum tolerated concentrations of novel compounds in A-549 cells. Screening for radioprotective properties was performed using flow-cytometry in MOLT-4 cells exposed to ⁶⁰Co ionizing gamma radiation. Selected candidates underwent in vivo testing in C57Bl/6 J mice having a positive impact on their immunological status. In summary, we report here promising compounds with radioprotective effect in vivo.

Highly Catalytic Niobium Carbide (MXene) Promotes Hematopoietic Recovery after Radiation by Free Radical Scavenging

Ionizing radiation (IR) has been extensively used in industry and radiotherapy, but IR exposure from nuclear or radiological accidents often causes serious health effects in an exposed individual, and its application in radiotherapy inevitably brings undesirable damage to normal tissues. In this work, we have developed ultrathin two-dimensional (2D) niobium carbide (Nb₂C) MXene as a radioprotectant and explored its application in scavenging free radicals against IR. The 2D Nb₂C MXene features intriguing antioxidant properties in effectively eliminating hydrogen peroxide (H₂O₂), hydroxyl radicals (^•OH), and superoxide radicals (O₂^•-). Pretreatment with biocompatible polyvinylpyrrolidone (PVP)-functionalized Nb₂C nanosheets (Nb₂C-PVP NSs) significantly reduces IR-induced production of reactive oxygen species (ROS), resulting in enhanced cell viability in vitro. A single intravenous injection of Nb₂C-PVP significantly enhances the survival rate of 5 and 6.5 Gy irradiated mice to 100% and 81.25%, respectively, and significantly increases bone marrow mononuclear cells after IR. Critically, Nb₂C-PVP reverses the damage of the hematopoietic system in irradiated mice. Single administration of Nb₂C-PVP significantly increases superoxide dismutase (SOD) activities, decreases malondialdehyde levels, and thereby reduces IR-induced pathological damage in the testis, small intestine, lung, and liver of 5 Gy irradiated mice. Importantly, Nb₂C-PVP is almost completely eliminated from the mouse body on day 14 post treatment, and no obvious toxicities are observed during the 30-day post treatment period. Our study pioneers the application of 2D MXenes with intrinsic radioprotective nature in vivo.

Curcumin Mitigates Radiation-induced Lung Pneumonitis and Fibrosis in Rats

Radiation-induced lung injury is one of the most prominent factors that interfere with chest cancer radiotherapy, and poses a great threat to patients exposed to total body irradiation. Upregulation of pro-oxidant enzymes is one of the main mechanisms through which the late effects of ionizing radiation on lung injury can be exerted. Interleukin (IL)-4 and IL-13 are two important cytokines that have been proposed to be involved in this process. Through stimulation of dual oxidase 1 and 2 (DUOX 1 & 2), they induce chronic oxidative stress in irradiated tissues. In this study, we evaluated the effects of curcumin treatment on the regulation of IL-4 and IL-13, DUOX1 & 2 genes as well as the pathological changes developed by this treatment. Twenty male Wistar rats were divided into four groups: radiation only; curcumin only; radiation +curcumin; and control group with neither pharmacotherapy nor radiation. Curcumin was administered for 4 and 6 consecutive days before and after irradiation, respectively. Also, the chest area was irradiated with 15 Gy using a cobalt-60 gamma rays source. All rats were sacrificed 67 days after irradiation, followed by the assessment of the levels of IL-4 and IL-13; the expression of IL- 4 receptor-a1 (IL4Ra1), IL13Ra2, DUOX1 and DUOX2, and finally the histopathological changes were evaluated. Radiation led to the increased level of IL-4, while the level of IL-13 showed no change. QPCR results showed the upregulation of IL4Ra1, DUOX1 and DUOX2 following lung irradiation. Histopathological evaluation also showed a remarkable increase in pneumonitis and fibrosis. Treatment with curcumin downregulated the expression of IL-4, IL4Ra1, DUOX1 & 2. Furthermore, it could mitigate pneumonitis and fibrosis following lung irradiation. The late effects of radiation- induced lung injury may be due to the upregulation of DUOX1 & 2 genes. Curcumin, through modulation of these genes, may contribute to the protection against ionizing radiation.