Radioprotective agents for radiation therapy: future trends

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.

Novel Small Molecule, UTS-1401, as a Radioprotector for Total-Body Irradiation

We report on a new radioprotector, UTS-1401, a small molecule that was synthesized (by one of us, JS) and evaluated here for its radioprotective effect against total-body irradiation (TBI). Female and male NIH Swiss mice were subjected to TBI at doses of 6.5, 7.5 and 8.5 Gy either with or without a 24 h pretreatment of UTS-1401 given ip and observed for 30 days. Survival rates were significantly increased when mice were treated with UTS-1401 compared to those not treated. The radioprotective effect of UTS-1401 was drug-dose dependent for male mice exposed to 8.5 Gy TBI with 150 mg/kg of UTS-1401 as the optimal dose. The radioprotective effect of UTS-1401 on female mice exposed to 8.5 Gy TBI was observed at 50, 100, and 150 mg/kg, with no dose response relationship noted. Female mice were more radioresistant than male mice with LD50/30 values of 7.8 Gy vs. 6.8 Gy, respectively. Weight changes after UTS-1401 alone showed a significant body weight increase at 150 mg/kg. Both the ip and iv route for UTS-1401 were similarly effective for male mice exposed to 8 Gy TBI. Further analysis using an endogenous spleen colony assay demonstrated that pretreatment of UTS-1401 for up to 72h prior to TBI protected both spleen weight and hematopoietic stem cells with a treated/untreated ratio between 2.0 and 3.2 for the latter for times between 0.5 h and 72 h. A separate in vivo study showed that pretreatment of UTS-1401 protected bone marrow CFU-GM for mice exposed to TBI. In summary, UTS-1401 is a promising small-molecule radioprotective agent as demonstrated by whole animal, hematopoietic stem cell and bone marrow myeloid progenitor cell survival.

Influence of Cu L-Histidinate Schiff Base Derivatives on Structural Features of Irradiated Rat's DNA

A study of rats liver DNA damages under the influence of X-ray radiation at a dose of 6.5 Gy(LD60) was carried out. The radioprotective properties of newly synthesized Cu(II) L-Schiff Histidinate complexes were also studied. The survival of rats was determined over a 30-day period after exposure to X-rays without pretreatment and also after preadministration of Cu(II) L-Histidinate-Schiff base complexes. The structural defects of rat's liver DNA were detected at 3, 7, 14, and 30 days post-irradiation extracted. The results obtained revealed that irradiation with a 6.5Gy dose in the control group degraded the characteristics of rat liver DNA in comparison to healthy DNA. On all investigated experimental days, a decrease in the melting temperature (Tm), a widening of the melting interval (ΔT), and a decrease in hypochromicity (Δh) were observed in the DNA samples of irradiated animals compared to the norm. The rat's pretreatment by Cu(II) L-Histidinate complexes 1 or 24 hours prior to irradiation improved DNA characteristics. Electrophoretic studies of DNA were in good agreement with the melting data. Based on the study results, it can be concluded that Cu(II) L-Histidinate complexes exhibit radioprotective properties under the studied conditions and can protect DNA from damage.

Radioprotective Effect of Resveratrol, Crocin, and Their Combination on Cytogenetic Alterations in Human Lymphocytes

Background

High-dose radiation altering the genetic material in patients' bone marrow cells can lead to hematopoietic radiation syndrome. Accordingly, the presence of radiation protections agents is critical to preventing these adverse effects.

Objective

This study aimed to evaluate the radioprotection of the exclusive or combination effect of resveratrol and crocin extracts at various concentrations on irradiated human lymphocytes.

Material and Methods

In this experimental study, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method was used to evaluate the cell viability in pre-treatment with resveratrol, crocin, or a combination of both, using a concentration range of 5 to 4800 μM / ml in 24 h. The chromosomal aberration test was employed to determine the aberration frequency in 48 h. This study was performed on human peripheral blood lymphocytes treated with 2 Gy radiation and reliability of measurements performed by the triplicate repeat.

Results

MTT results showed that the groups treated with either resveratrol or crocin at concentrations of 5 to 4800 µM had no significant reduction in cell viability. The cytogenetic analysis of irradiated lymphocytes with 2 Gy X-rays revealed a reduction in the frequency of dicentric chromosomes in all treated groups in contrast with the control group. The most significant reduction occurred in those treated with a single agent at the concentration of 100 µM and a combined drug at the concentration of 50 µM.

Conclusion

The combination of resveratrol and crocin is considered a potential radioprotector and prophylactic for patients before radiation therapy.

Selective Organ-Targeting Hafnium Oxide Nanoparticles with Multienzyme-Mimetic Activities Attenuate Radiation-Induced Tissue Damage

Radioprotective agents hold clinical promises to counteract off-target adverse effects of radiation and benefit radiotherapeutic outcomes, yet the inability to control drug transport in human organs poses a leading limitation. Based upon a validated rank-based multigene signature model, radiosensitivity indices are evaluated of diverse normal organs as a genomic predictor of radiation susceptibility. Selective ORgan-Targeting (SORT) hafnium oxide nanoparticles (HfO2 NPs) are rationally designed via modulated synthesis by α-lactalbumin, homing to top vulnerable organs. HfO2 NPs like Hensify are commonly radioenhancers, but SORT HfO2 NPs exhibit surprising radioprotective effects dictated by unfolded ligands and Hf(0)/Hf(IV) redox couples. Still, the X-ray attenuation patterns allow radiological confirmation in target organs by dual-beam spectral computed tomography. SORT HfO2 NPs present potent antioxidant activities, catalytically scavenge reactive oxygen species, and mimic multienzyme catalytic activities. Consequently, SORT NPs rescue radiation-induced DNA damage in mouse and rabbit models and provide survival benefits upon lethal exposures. In addition to inhibiting radiation-induced mitochondrial apoptosis, SORT NPs impede DNA damage and inflammation by attenuating activated FoxO, Hippo, TNF, and MAPK interactive cascades. A universal methodology is proposed to reverse radioenhancers into radioprotectors. SORT radioprotective agents with image guidance are envisioned as compelling in personalized shielding from radiation deposition.

Radioprotective effectiveness of a novel delta-tocotrienol prodrug on mouse hematopoietic system against 60Co gamma-ray irradiation through inducing granulocyte-colony stimulating factor production

Considering the increasing risk of nuclear attacks worldwide, the development of develop potent and safe radioprotective agents for nuclear emergencies is urgently needed. γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have demonstrated a potent radioprotective effect by inducing the production of granulocyte-colony stimulating factor (G-CSF) in vivo. However, their application is limited because of their low bioavailability. The utilization of ester prodrugs can be an effective strategy for modifying the pharmacokinetic properties of drug molecules. In this study, we initially confirmed that DT3 exhibited the most significant potential for inducing G-CSF effects among eight natural vitamin E homologs. Consequently, we designed and synthesized a series of DT3 ester and ether derivatives, leading to improved radioprotective effects. The metabolic study conducted in vitro and in vivo has identified DT3 succinate 5b as a prodrug of DT3 with an approximately seven-fold higher bioavailability compared to DT3 alone. And DT3 ether derivative 8a were relatively stable and approximately 4 times more bioavailable than DT3 prototype. Furthermore, 5b exhibited superior ability to mitigate radiation-induced pancytopenia, enhance the recovery of bone marrow hematopoietic stem and progenitor cells, and promote splenic extramedullary hematopoiesis in sublethal irradiated mice. Similarly, 8a shown potential radiation protection, but its radiation protection is less than DT3. Based on these findings, we identified 5b as a DT3 prodrug, and providing an attractive candidate for further drug development.

System-level protein interaction network analysis and molecular dynamics study reveal interaction of ferulic acid with PTGS2 as a natural radioprotector

Ferulic acid is a crucial bioactive component of broccoli, wheat, and rice bran and is also an essential natural product that has undergone significant research. Ferulic acid's precise mode of action and effect on system-level protein networks have not been thoroughly investigated. An interactome was built using the STRING database and Cytoscape tools, utilizing 788 key proteins collected from PubMed literature to identify the ferulic acid-governed regulatory action on protein interaction network (PIN). The scale-free biological network of ferulic acid-rewired PIN is highly interconnected. We discovered 15 sub-modules using the MCODE tool for sub-modulization analysis and 153 enriched signaling pathways. Further, functional enrichment of top bottleneck proteins revealed the FoxO signaling pathway involved in enhancing cellular defense against oxidative stress. The selection of the critical regulatory proteins of the ferulic acid-rewired PIN was completed by performing analyses of topological characteristics such as GO term/pathways analysis, degree, bottleneck, molecular docking, and dynamics investigations. The current research derives a precise molecular mechanism for ferulic acid's action on the body. This in-depth in silico model would aid in understanding how ferulic acid origins its antioxidant and scavenging properties in the human body.Communicated by Ramaswamy H. Sarma.

Bis(1-methylimidazol-2-yl) diselenide and its evaluation as a chemical radio-protector: role of kinetic rate constants for ROS scavenging and glutathione peroxidase like activity

Bis(1-methylimidazol-2-yl) diselenide (MeImSe), a derivative of selenoneine, has been examined for bimolecular rate constants for scavenging of various radiolytically and non-radiolytically generated reactive oxygen species (ROS). Further, its potential to show glutathione peroxidase (GPx)-like activity and to protect in vitro models of DNA and lipid against radiation induced strand breakage and lipid peroxidation, respectively were studied. The results confirmed that MeImSe scavenged all major short-lived (hydroxyl radical) and long-lived (peroxyl radical, carbonate radical, nitrogen dioxide radical, hypochlorite and hydrogen peroxide) oxidants involved in the radiation toxicity either directly or through GPx-like catalytic mechanism. The rate constants of MeImSe for these oxidants were found to be comparable to analogous sulfur and selenium-based compounds. The enzyme kinetics study established that MeImSe took part in the GPx cycle through the reductive pathway. Further, MeImSe inhibited the radiation induced DNA strand cleavage and lipid peroxidation with half maximal inhibitory concentration (IC50) of ∼ 60 μM and ∼100 μM, respectively. Interestingly, MeImSe treatment in the above concentration range (>100 μM) did not show any significant toxicity in normal human lung fibroblast (WI26) cells. The balance between efficacy and toxicity of MeImSe as a chemical radioprotector was attributed to the formation of less reactive intermediates during its oxidation/reduction reactions as evidenced from NMR studies.HighlightsMeImSe, a derivative of selenoneine protects DNA and lipid from radiation damageMeImSe scavenges all major short- and long-lived oxidants involved in radiation toxicityRate constants of MeImSe for ROS scavenging determined by pulse radiolysis techniqueFirst organoselenium compound reported to scavenge nitrogen dioxide radicalMeImSe exhibits GPx-like activity through reductive pathway.

Effect of Linear Energy Transfer on Cystamine's Radioprotective Activity: A Study Using the Fricke Dosimeter with 6-500 MeV per Nucleon Carbon Ions-Implication for Carbon Ion Hadrontherapy

(1) Background: Radioprotective agents have garnered considerable interest due to their prospective applications in radiotherapy, public health medicine, and situations of large-scale accidental radiation exposure or impending radiological emergencies. Cystamine, an organic diamino-disulfide compound, is recognized for its radiation-protective and antioxidant properties. This study aims to utilize the aqueous ferrous sulfate (Fricke) dosimeter to measure the free-radical scavenging capabilities of cystamine during irradiation by fast carbon ions. This analysis spans an energy range from 6 to 500 MeV per nucleon, which correlates with "linear energy transfer" (LET) values ranging from approximately 248 keV/μm down to 9.3 keV/μm. (2) Methods: Monte Carlo track chemistry calculations were used to simulate the radiation-induced chemistry of aerated Fricke-cystamine solutions across a broad spectrum of cystamine concentrations, ranging from 10-6 to 1 M. (3) Results: In irradiated Fricke solutions containing cystamine, cystamine is observed to hinder the oxidation of Fe2+ ions, an effect triggered by oxidizing agents from the radiolysis of acidic water, resulting in reduced Fe3+ ion production. Our simulations, conducted both with and without accounting for the multiple ionization of water, confirm cystamine's ability to capture free radicals, highlighting its strong antioxidant properties. Aligning with prior research, our simulations also indicate that the protective and antioxidant efficiency of cystamine diminishes with increasing LET of the radiation. This result can be attributed to the changes in the geometry of the track structures when transitioning from lower to higher LETs. (4) Conclusions: If we can apply these fundamental research findings to biological systems at a physiological pH, the use of cystamine alongside carbon-ion hadrontherapy could present a promising approach to further improve the therapeutic ratio in cancer treatments.

Tissue fibrosis induced by radiotherapy: current understanding of the molecular mechanisms, diagnosis and therapeutic advances

Cancer remains the leading cause of death around the world. In cancer treatment, over 50% of cancer patients receive radiotherapy alone or in multimodal combinations with other therapies. One of the adverse consequences after radiation exposure is the occurrence of radiation-induced tissue fibrosis (RIF), which is characterized by the abnormal activation of myofibroblasts and the excessive accumulation of extracellular matrix. This phenotype can manifest in multiple organs, such as lung, skin, liver and kidney. In-depth studies on the mechanisms of radiation-induced fibrosis have shown that a variety of extracellular signals such as immune cells and abnormal release of cytokines, and intracellular signals such as cGAS/STING, oxidative stress response, metabolic reprogramming and proteasome pathway activation are involved in the activation of myofibroblasts. Tissue fibrosis is extremely harmful to patients' health and requires early diagnosis. In addition to traditional serum markers, histologic and imaging tests, the diagnostic potential of nuclear medicine techniques is emerging. Anti-inflammatory and antioxidant therapies are the traditional treatments for radiation-induced fibrosis. Recently, some promising therapeutic strategies have emerged, such as stem cell therapy and targeted therapies. However, incomplete knowledge of the mechanisms hinders the treatment of this disease. Here, we also highlight the potential mechanistic, diagnostic and therapeutic directions of radiation-induced fibrosis.

Exosome-coated polydatin nanoparticles in the treatment of radiation-induced intestinal damage

This study aimed to develop an exosome-coated polydatin (PD) nanoparticles (exo-PD) for improving the water solubility and bioavailability of polydatin and explore its salutary effects on intestinal radiation injury. Exosomes (exo) were extracted from the medium of human amniotic fluid stem cells (hAFSc). Mice were divided into control group, irradiation (IR) group, irradiation+PD (IR+PD) group, irradiation+exo (IR+exo) group and irradiation+exo-PD (IR+exo-PD) group. The results of characterization of protein markers, particle size, morphology and cellular uptake ability confirmed that exosomes were effectively isolated using ultracentrifugation. Compared with the IR group, exo-PD improved cell viability, prolonged survival of mice, improved leukocyte count and reduced diarrhea rate. Histological results showed that the exo-PD group had significant improvements in small intestinal villus length and crypt number and less crypt cell damage. exo-PD could reduce IL-1α and IL-6 levels, reduced γ-H2AX expression, increased mitochondrial membrane potential, enhanced oxidative phosphorylation, and delayed cellular senescence. exo-PD could alleviate intestinal injury by improving mitochondrial function through PI3K-AKT pathway. The exo-PD was able to reduce radiation damage to intestinal cells and could be a potential candidate for salvage of intestinal radiation damage.

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.

High-throughput screening strategies for space-based radiation countermeasure discovery

As humanity begins to venture further into space, approaches to better protect astronauts from the hazards found in space need to be developed. One particular hazard of concern is the complex radiation that is ever present in deep space. Currently, it is unlikely enough spacecraft shielding could be launched that would provide adequate protection to astronauts during long-duration missions such as a journey to Mars and back. In an effort to identify other means of protection, prophylactic radioprotective drugs have been proposed as a potential means to reduce the biological damage caused by this radiation. Unfortunately, few radioprotectors have been approved by the FDA for usage and for those that have been developed, they protect normal cells/tissues from acute, high levels of radiation exposure such as that from oncology radiation treatments. To date, essentially no radioprotectors have been developed that specifically counteract the effects of chronic low-dose rate space radiation. This review highlights how high-throughput screening (HTS) methodologies could be implemented to identify such a radioprotective agent. Several potential target, pathway, and phenotypic assays are discussed along with potential challenges towards screening for radioprotectors. Utilizing HTS strategies such as the ones proposed here have the potential to identify new chemical scaffolds that can be developed into efficacious radioprotectors that are specifically designed to protect astronauts during deep space journeys. The overarching goal of this review is to elicit broader interest in applying drug discovery techniques, specifically HTS towards the identification of radiation countermeasures designed to be efficacious towards the biological insults likely to be encountered by astronauts on long duration voyages.

Radioprotection of deinococcal exopolysaccharide BRD125 by regenerating hematopoietic stem cells

There is a substantial need for the development of biomaterials for protecting hematopoietic stem cells and enhancing hematopoiesis after radiation damage. Bacterial exopolysaccharide (EPS) has been shown to be very attractive to researchers as a radioprotectant owing to its high antioxidant, anti-cancer, and limited adverse effects. In the present study, we isolated EPS from a novel strain, Deinococcus radiodurans BRD125, which produces EPS in high abundance, and investigated its applicability as a radioprotective biomaterial. We found that EPS isolated from EPS-rich D. radiodurans BRD125 (DeinoPol-BRD125) had an excellent free-radical scavenging effect and reduced irradiation-induced apoptosis. In addition, bone-marrow and spleen-cell apoptosis in irradiated mice were significantly reduced by DeinoPol-BRD125 administration. DeinoPol-BRD125 enhanced the expression of hematopoiesis-related cytokines such as GM-CSF, G-GSF, M-CSF, and SCF, thereby enhancing hematopoietic stem cells protection and regeneration. Taken together, our findings are the first to report the immunological mechanism of a novel radioprotectant, DeinoPol-BRD125, which might constitute an ideal radioprotective and radiation mitigating agent as a supplement drug during radiotherapy.

Antioxidant Therapy in Cancer: Rationale and Progress

Cancer is characterized by increased oxidative stress, an imbalance between reactive oxygen species (ROS) and antioxidants. Enhanced ROS accumulation, as a result of metabolic disturbances and signaling aberrations, can promote carcinogenesis and malignant progression by inducing gene mutations and activating pro-oncogenic signaling, providing a possible rationale for targeting oxidative stress in cancer treatment. While numerous antioxidants have demonstrated therapeutic potential, their clinical efficacy in cancer remains unproven. Here, we review the rationale for, and recent advances in, pre-clinical and clinical research on antioxidant therapy in cancer, including targeting ROS with nonenzymatic antioxidants, such as NRF2 activators, vitamins, N-acetylcysteine and GSH esters, or targeting ROS with enzymatic antioxidants, such as NOX inhibitors and SOD mimics. In addition, we will offer insights into prospective therapeutic options for improving the effectiveness of antioxidant therapy, which may expand its applications in clinical cancer treatment.

JAC4 Protects from X-Ray Radiation-Induced Intestinal Injury by JWA-Mediated Anti-Oxidation/Inflammation Signaling

Radiation-induced intestinal injury is one of the major side effects in patients receiving radiation therapy. There is no specific treatment for radiation-induced enteritis in the clinic. We synthesized a compound, named JAC4, which is an agonist and can increase JWA protein expression. JWA has been shown to reduce oxidative stress, DNA damage, anti-apoptosis, and anti-inflammatory; in addition, the small intestine epithelium showed dysplasia in JWA knockout mice. We hypothesized that JAC4 might exert a protective effect against radiation-induced intestinal damage. Herein, X-ray radiation models were built both in mice and in intestinal crypt epithelial cells (IEC-6). C57BL/6J mice were treated with JAC4 by gavage before abdominal irradiation (ABI); the data showed that JAC4 significantly reduced radiation-induced intestinal mucosal damage and increased the survival rate. In addition, radiation-induced oxidative stress damage and systemic inflammatory response were also mitigated by JAC4 treatment. Moreover, JAC4 treatment alleviated DNA damage, decreased cell apoptosis, and maintained intestinal epithelial cell proliferation in mice. In vitro data showed that JAC4 treatment significantly inhibited ROS formation and cell apoptosis. Importantly, all the above protective effects of JAC4 on X-ray radiation-triggered intestinal injury were no longer determined in the intestinal epithelium of JWA knockout mice. Therefore, our results provide the first evidence that JAC4 protects the intestine from radiation-induced enteritis through JWA-mediated anti-oxidation/inflammation signaling.

"Radio-Protective Effect of Aminocaproic Acid in Human Spermatozoa"

BACKGROUND

The negative effects of ionizing radiation on organs and the reproductive system are well known and documented. Exposure to gamma radiation can lead to oligospermia, azoospermia and DNA damage. Up to date, there is no effective pharmaceutical compound for protecting the male reproductive system and sperm.

OBJECTIVE

This study aimed at investigating the ability of Ɛ-aminocaproic acid (EACA) to prevent the damage of human spermatozoa and DNA induced by ionizing radiation.

MATERIALS AND METHODS

Sperm samples were obtained from healthy volunteers (35 men; 31.50 ± 7.34 years old). There were 4 experimental groups: 1) control group (CG), 2) group exposed to maximal radiation dose 67.88 mGy (RMAX), 3) low-dose radiation (minimal) 22.62 mGy (RMIN), and 4) group treated with radiation (67.88 mGy) and EACA (dose 50 ng/ml). Sperm motility, viability, and DNA damage were assessed.

RESULTS

We observed a significant decrease in total sperm motility of the RMAX group compared to CG (p < 0.05). Sperm viability in the RMAX group was also reduced in comparison to the control (p < 0.05). A significant increase in DNA fragmentation was detected in the RMAX group. The results demonstrated that the treatment of sperm with EACA led to a decrease in the fragmentation of the sperm DNA (compared to the RMAX group) (p < 0.05).

CONCLUSION

The results indicate that EACA effectively protects human spermatozoa from DNA damage induced by ionizing radiation. Treatment of spermatozoa with EACA led to the preservation of cell motility, viability, and DNA integrity upon radiation exposure.

Radioprotective Mechanisms of Arbutin: A Systematic Review

PURPOSE

Efforts to produce radioprotective agents of high potential are appropriate strategies for overcoming possible IR toxicity in organisms. The present research aims to evaluate the signaling pathways and mechanisms through which arbutin exerts radioprotective effects on organisms.

METHODS

The databases of PubMed, Web of Sciences, Google Scholar, and Scopus were searched to find studies that reported radioprotective effects for arbutin. Besides, the data were searched within the time period from 2010 to 2020.

RESULTS

Five research articles met our criteria, which were included in the analysis based on their relevance to the topic. The present systematic review provides conclusions about various mechanisms and pathways through which arbutin induces radioprotection.

CONCLUSIONS

Based on the relevant studies, various mechanisms can be proposed for inducing radioprotective effects by arbutin, including inhibition of oxidative stress, apoptosis, and inflammation.

An Overview of X-ray Photon Counting Spectral Imaging (x-CSI) with a Focus on Gold Nanoparticle Quantification in Oncology

This review article offers an overview of the differences between traditional energy integrating (EI) X-ray imaging and the new technique of X-ray photon counting spectral imaging (x-CSI). The review is motivated by the need to image gold nanoparticles (AuNP) in vivo if they are to be used clinically to deliver a radiotherapy dose-enhancing effect (RDEE). The aim of this work is to familiarise the reader with x-CSI as a technique and to draw attention to how this technique will need to develop to be of clinical use for the described oncological applications. This article covers the conceptual differences between x-CSI and EI approaches, the advantages of x-CSI, constraints on x-CSI system design, and the achievements of x-CSI in AuNP quantification. The results of the review show there are still approximately two orders of magnitude between the AuNP concentrations used in RDEE applications and the demonstrated detection limits of x-CSI. Two approaches to overcome this were suggested: changing AuNP design or changing x-CSI system design. Optimal system parameters for AuNP detection and general spectral performance as determined by simulation studies were different to those used in the current x-CSI systems, indicating potential gains that may be made with this approach.

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.

Rat Models of Partial-body Irradiation with Bone Marrow-sparing (Leg-out PBI) Designed for FDA Approval of Countermeasures for Mitigation of Acute and Delayed Injuries by Radiation

ABSTRACT

The goal of this study was to develop rat models of partial body irradiation with bone-marrow sparing (leg-out PBI) to test medical countermeasures (MCM) of both acute radiation syndrome (ARS) and delayed effects of acute radiation exposure (DEARE) under the FDA animal rule. The leg-out PBI models were developed in female and male WAG/RijCmcr rats at doses of 12.5-14.5 Gy. Rats received supportive care consisting of fluids and antibiotics. Gastrointestinal ARS (GI-ARS) was assessed by lethality to d 7 and diarrhea scoring to d 10. Differential blood counts were analyzed between d 1-42 for the natural history of hematopoietic ARS (H-ARS). Lethality and breathing intervals (BI) were measured between d 28-110 to assess delayed injury to the lung (L-DEARE). Kidney injury (K-DEARE) was evaluated by measuring elevation of blood urea nitrogen (BUN) between d 90-180. The LD50/30, including both lethality from GI-ARS and H-ARS, for female and male rats are 14.0 Gy and 13.5 Gy, respectively, while the LD50/7 for only GI-ARS are 14.3 Gy and 13.6 Gy, respectively. The all-cause mortalities, including ARS and L-DEARE, through 120 d (LD50/120) are 13.5 Gy and 12.9 Gy, respectively. Secondary end points confirmed occurrence of four distinct sequelae representing GI, hematopoietic, lung, and kidney toxicities after leg-out PBI. Adult rat models of leg-out PBI showed the acute and long-term sequelae of radiation damage that has been reported in human radiation exposure case studies. Sex-specific differences were observed in the DRR between females and males. These rat models are among the most useful for the development and approval of countermeasures for mitigation of radiation injuries under the FDA animal rule.

Radiation countermeasures for hematopoietic acute radiation syndrome: growth factors, cytokines and beyond

PURPOSE

The intent of this article is to report the status of some of the pharmaceuticals currently in late stage development for possible use for individuals unwantedly and acutely injured as a result of radiological/nuclear exposures. The two major questions we attempt to address here are: (a) What medicinals are currently deemed by regulatory authorities (US FDA) to be safe and effective and are being stockpiled? (b) What additional agents might be needed to make the federal/state/local medicinal repositories more robust and useful in effectively managing contingencies involving radiation overexposures?

CONCLUSIONS

A limited number (precisely four) of medicinals have been deemed safe and effective, and are approved by the US FDA for the 'hematopoietic acute radiation syndrome (H-ARS).' These agents are largely recombinant growth factors (e.g. rhuG-CSF/filgrastim, rhuGM-CSF/sargramostim) that target and stimulate myeloid progenitors within bone marrow. Romiplostim, a small molecular agonist that enhances platelet production via stimulation of bone marrow megakaryocytes, has been recently approved and indicated for H-ARS. It is critical that additional agents for other major sub-syndromes of ARS (gastrointestinal-ARS) be approved. Future success in developing such medicinals will undoubtedly entail some form of a polypharmaceutical strategy, or perhaps novel, bioengineered chimeric agents with multiple, radioprotective/radiomitigative functionalities.

Could Polyphenols Really Be a Good Radioprotective Strategy?

Currently, radiotherapy is one of the most effective strategies to treat cancer. However, deleterious toxicity against normal cells indicate for the need to selectively protect them. Reactive oxygen and nitrogen species reinforce ionizing radiation cytotoxicity, and compounds able to scavenge these species or enhance antioxidant enzymes (e.g., superoxide dismutase, catalase, and glutathione peroxidase) should be properly investigated. Antioxidant plant-derived compounds, such as phenols and polyphenols, could represent a valuable alternative to synthetic compounds to be used as radio-protective agents. In fact, their dose-dependent antioxidant/pro-oxidant efficacy could provide a high degree of protection to normal tissues, with little or no protection to tumor cells. The present review provides an update of the current scientific knowledge of polyphenols in pure forms or in plant extracts with good evidence concerning their possible radiomodulating action. Indeed, with few exceptions, to date, the fragmentary data available mostly derive from in vitro studies, which do not find comfort in preclinical and/or clinical studies. On the contrary, when preclinical studies are reported, especially regarding the bioactivity of a plant extract, its chemical composition is not taken into account, avoiding any standardization and compromising data reproducibility.

Pretreatment with metformin protects mice from whole-body irradiation

Metformin, a first-line oral drug for type II diabetes mellitus, not only reduces blood glucose levels, but also has many other biological effects. Recent studies have been conducted to determine the protective effect of metformin in irradiation injuries. However, the results are controversial and mainly focus on the time of metformin administration. In this study, we aimed to investigate the protective effect of metformin in BALB/c mice exposed to 6 Gy or 8 Gy of a 60Co source of γ-rays for total body irradiation (TBI). Survival outcomes were assessed following exposure to 8 Gy or 6 Gy TBI, and hematopoietic damage and intestinal injury were assessed after exposure to 6 Gy TBI. Metformin prolonged the survival of mice exposed to 8 Gy TBI and improved the survival rate of mice exposed to 6 Gy TBI only when administered before exposure to irradiation. Moreover, pretreatment with metformin reduced the frequency of micronuclei (MN) in the bone marrow of mice exposed to 6 Gy TBI. Pretreatment of metformin also protected the intestinal morphology of mice, reduced inflammatory response and decreased the number of apoptotic cells in intestine. In conclusion, we demonstrated that pretreatment with metformin could alleviate irradiation injury.

Captopril inhibits Matrix Metalloproteinase-2 and extends survival as a temozolomide adjuvant in an intracranial gliosarcoma model

BACKGROUND

Captopril is a well-characterized, FDA-approved drug that has demonstrated promise as a repurposed oncology therapeutic. Captopril's known anti-cancer effects include inhibition of Matrix Metalloproteinase-2 (MMP-2), an endopeptidase which selectively breaks down the extracellular matrix to promote cell migration. MMP-2 is a known therapeutic target in gliomas, tumors with significant clinical need. Using an aggressive gliosarcoma model, we assessed captopril's effects on MMP-2 expression in vitro and in vivo as well as its efficacy as an adjuvant in combination therapy regimens in vivo.

METHODS

Following captopril treatment, MMP-2 protein expression and migratory capabilities of 9 L gliosarcoma cells were assessed in vitro via western blots and scratch wound assays, respectively. Rats were intracranially implanted with 9 L gliosarcoma tumors, and survival was assessed in the following groups: control; captopril (30 mg/kg/day); temozolomide (TMZ) (50 mg/kg/day), and captopril+TMZ. In vivo experiments were accompanied by immunohistochemistry for MMP-2 from brain tissue.

RESULTS

In vitro, captopril decreased MMP-2 protein expression and reduced migratory capacity in 9 L gliosarcoma cells. In a gliosarcoma animal model, captopril decreased MMP-2 protein expression and extended survival as a TMZ adjuvant relative to untreated controls, captopril monotherapy, and TMZ monotherapy groups (27.5 versus 14 (p < 0.001), 16 (p < 0.001), and 23 (p = 0.018) days, respectively).

CONCLUSIONS

Captopril decreases gliosarcoma cell migration, which may be mediated by reduction in MMP-2 protein expression. Captopril provided a survival advantage as a TMZ adjuvant in a rat intracranial gliosarcoma model. Captopril may represent a promising potential adjuvant to TMZ therapy in gliosarcoma as a modulator of the MMP-2 pathway.

Repurposing Pharmaceuticals Previously Approved by Regulatory Agencies to Medically Counter Injuries Arising Either Early or Late Following Radiation Exposure

The increasing risks of radiological or nuclear attacks or associated accidents have served to renew interest in developing radiation medical countermeasures. The development of prospective countermeasures and the subsequent gain of Food and Drug Administration (FDA) approval are invariably time consuming and expensive processes, especially in terms of generating essential human data. Due to the limited resources for drug development and the need for expedited drug approval, drug developers have turned, in part, to the strategy of repurposing agents for which safety and clinical data are already available. Approval of drugs that are already in clinical use for one indication and are being repurposed for another indication is inherently faster and more cost effective than for new agents that lack regulatory approval of any sort. There are four known growth factors which have been repurposed in the recent past as radiomitigators following the FDA Animal Rule: Neupogen, Neulasta, Leukine, and Nplate. These four drugs were in clinic for several decades for other indications and were repurposed. A large number of additional agents approved by various regulatory authorities for given indications are currently under investigation for dual use for acute radiation syndrome or for delayed pathological effects of acute radiation exposure. The process of drug repurposing, however, is not without its own set of challenges and limitations.

Antioxidant Nanomedicine Significantly Enhances the Survival Benefit of Radiation Cancer Therapy by Mitigating Oxidative Stress-Induced Side Effects

Oxidative stress-induced off-target effects limit the therapeutic window of radiation therapy. Although many antioxidants have been evaluated as radioprotective agents, none of them are in widespread clinical use, owing to the side effects of the antioxidants themselves and the lack of apparent benefit. Aiming for a truly effective radioprotective agent in radiation cancer therapy, the performance of a self-assembling antioxidant nanoparticle (herein denoted as redox nanoparticle; RNP) is evaluated in the local irradiation of a subcutaneous tumor-bearing mouse model. Since RNP is covered with a biocompatible shell layer and possesses a core-shell type structure of several tens of nanometers in size, its lifetime in the systemic circulation is prolonged. Moreover, since 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), one of the most potent antioxidants, is covalently encapsulated in the core of RNP, it exerts intense antioxidant activity and induces fewer adverse effects by avoiding leakage of the TEMPO molecules. Preadministration of RNP to the mouse model effectively mitigates side effects in normal tissues and significantly extends the survival benefit of radiation cancer therapy. Moreover, RNP pretreatment noticeably increases the apoptosis/necrosis ratio of radiation-induced cell death, a highly desirable property to reduce the chronic side effects of ionizing irradiation.

RRx-001 Radioprotection: Enhancement of Survival and Hematopoietic Recovery in Gamma-Irradiated Mice

The present studies evaluate the in vivo prophylactic radioprotective effects of 1-bromoacetyl-3, 3-dinitroazetidine (RRx-001), a phase III anticancer agent that inhibits c-myc and downregulates CD-47, after total body irradiation (TBI), in lethally and sublethally irradiated CD2F1 male mice. A single dose of RRx-001 was administered by intraperitoneal (IP) injection 24 h prior to a lethal or sublethal radiation dose. When irradiated with 9.35 Gy, the dose lethal to 70% of untreated mice at 30 days (LD_70/30), only 33% of mice receiving RRx-001 (10 mg/kg) 24 h prior to total body irradiation (TBI) died by day 30, compared to 67% in vehicle-treated mice. The same pretreatment dose of RRx-001 resulted in a significant dose reduction factor of 1.07. In sublethally TBI mice, bone marrow cellularity was increased at day 14 in the RRx-001-treated mice compared to irradiated vehicle-treated animals. In addition, significantly higher numbers of lymphocytes, platelets, percent hematocrit and percent reticulocytes were observed on days 7 and/or 14 in RRx-001-treated mice. These experiments provide proof of principle that systemic administration of RRx-001 prior to TBI significantly improves overall survival and bone marrow regeneration.

Radioprotective effects of Cryptosporidium parvum lysates on normal cells

Two fractions, small and big (CpL-S, CpL-B), from Cryptosporidium parvum lysate (CpL) were prepared and its radioprotective activity was evaluated on normal cells. Both fractions improved cell viability of normal cells in a dose-dependent manner. 20 μg CpL-S and CpL-B improved cell viability of 10 Gy irradiated COS-7 cells by 38% and 34% respectively, while in HaCat cells 16% and 18% improved cell viability was observed, respectively. CpL-S scavenged IR-induced ROS more effectively compared to the CpL-B, 50% more in COS-7 cells and 15% more in HaCat cells. There was a significant reduction of γH2AX, Rad51, and pDNA-PKcs foci in CpL-S treated cells compared to control or CpL-B group at an early time point as well as late time point. In 3D skin tissue, CpL-S reduced the number of γH2AX positive cells by 31%, compared to control, while CpL-B reduced by 9% (p < 0.005) at 1 h post 10 Gy irradiation and 22% vs 6% at 24 h post-IR (p < 0.005). Taken together, CpL-S significantly improved cell viability and prevented radiation-induced DNA damage in normal cells as well as 3D skin tissues by effectively scavenging ROS generated by ionizing radiation. CpL-S can be a candidate for radioprotector development.

Preclinical Evaluation of Safety, Pharmacokinetics, Efficacy, and Mechanism of Radioprotective Agent HL-003

Amifostine is a radioprotector with high efficacy but poor safety, short half-life, no oral formulation, and poor compliance, which limits its application. With the increasing risk of exposure to radiation, the development of new radioprotective agents is critical. We previously synthesized a new amifostine derivative, the small molecule compound HL-003. In this study, we focused on evaluating the radioprotective properties of HL-003. Using the in vitro 2,2-diphenyl-1-picrylhydrazyl assay, we initially confirmed HL-003 as a strong antioxidant and demonstrated that its free radical scavenging activity was stronger than that of amifostine. Then, we performed an acute toxicity test, a 28-day toxicity test, a 30-day survival rate test, and a pharmacokinetic study, all of which provided aggregate evidence that HL-003 functioned as a small molecule radioprotector with high efficacy, a favorable safety profile, a long half-life, and oral administration. The intestinal radioprotective mechanism of HL-003 was explored in male C57 mice after abdominal irradiation by analyzing intestinal tissue samples with hematoxylin-eosin staining, immunohistochemistry, TUNEL staining, and immunofluorescence detection. The results showed that HL-003 protected intestinal DNA from radiation damage and suppressed the expression of phosphorylated histone H2AX, phosphorylated p53, and the apoptosis-related proteins caspase-8 and caspase-9, which contributed to maintaining the normal morphology of the small intestine and provided insights into the mechanism of radioprotection. Thus, HL-003 is a small molecule radioprotector with a potential application in radiation medicine.

Polycysteine as a new type of radio-protector ameliorated tissue injury through inhibiting ferroptosis in mice

Amifostine has been the only small molecule radio-protector approved by FDA for decades; however, the serious adverse effects limit its clinical use. To address the toxicity issues and maintain the good potency, a series of modified small polycysteine peptides had been prepared. Among them, compound 5 exhibited the highest radio-protective efficacy, the same as amifostine, but much better safety profile. To confirm the correlation between the radiation-protective efficacy and the DNA binding capability, each of the enantiomers of the polycysteine peptides had been prepared. As a result, the L-configuration compounds had obviously higher efficacy than the corresponding D-configuration enantiomers; among them, compound 5 showed the highest DNA binding capability and radiation-protective efficacy. To our knowledge, this is the first study that has proved their correlations using direct comparison. Further exploration of the mechanism revealed that the ionizing radiation (IR) triggered ferroptosis inhibition by compound 5 could be one of the pathways for the protection effect, which was different from amifostine. In summary, the preliminary result showed that compound 5, a polycysteine as a new type of radio-protector, had been developed with good efficacy and safety profile. Further study of the compound for potential use is ongoing.

Review of the Efficacy and Mechanisms of Traditional Chinese Medicines as a Therapeutic Option for Ionizing Radiation Induced Damage

Ionizing radiation damage refers to acute, delayed, or chronic tissue damage associated with ionizing radiation. Specific or effective therapeutic options for systemic injuries induced by ionizing radiation have not been developed. Studies have shown that Chinese herbal Medicine or Chinese Herbal Prescription exhibit preventive properties against radiation damage. These medicines inhibit tissue injuries and promote repair with very minimal side effects. This study reviews traditional Chinese herbal medicines and prescriptions with radiation protective effects as well as their mechanisms of action. The information obtained will guide the development of alternative radioprotectants.

Acute chemoradiotherapy toxicity in cervical cancer patients

During radiotherapy treatment for cervical cancer, up to 84% of patients exhibit some form of acute radiation toxicity (ART). The primary aim of this clinical study is to determine the impact of angiotensin-converting enzyme (ACE) inhibitors, β-blockers and other risk factors such as the patient’s anatomical characteristics on ART emergence in patients with locally advanced cervical cancer treated by chemoradiotherapy. This is a combination of two nested case–control studies within the cohort of patients with locally advanced cervical cancer based on the analysis of potential risk factors for the onset of ART in patients treated with 3D conformal radiotherapy (3D-CRT) and 2D conventional radiotherapy (2D-RT), prospectively followed up from January 2017 to September 2018 in a tertiary care hospital. The ACE inhibitors and bladder volume were identified as factors that significantly affect the occurrence of ART in patients treated with 3D-CRT. In patients treated with 2D-RT, the factors that significantly affect the occurrence of ART were ACE inhibitors, body mass index (BMI), brachytherapy rectal and bladder dose. This study has shown that BMI, radiation dose received by the bladder and rectum are of exceptional importance for the occurrence of the ART and also that therapy with ACE inhibitors was associated with the decreased chances of the ART.

A New Insight on the Radioprotective Potential of Epsilon-Aminocaproic Acid

Background and objectives: The aim of the study was to scrutinize the ability of epsilon-aminocaproic acid (EACA) to prevent radiation-induced damage to human cells. Materials and Methods: Human peripheral blood mononuclear cells (PBMCs) were exposed to ionizing radiation at three low doses (22.62 mGy, 45.27 mGy, and 67.88 mGy) in the presence of EACA at the concentration of 50 ng/mL. Results: EACA was able to prevent cell death induced by low-dose X-ray radiation and suppress the formation of reactive oxygen species (ROS). EACA also demonstrated a capacity to protect DNA from radiation-induced damage. The data indicated that EACA is capable of suppression of radiation-induced apoptosis. Comparative tests of antioxidative activity of EACA and a range of free radical scavengers showed an ability of EACA to effectively inhibit the generation of ROS. Conclusions: This study showed that the pretreatment of PBMCs with EACA is able to protect the cells from radiation-elicited damage, including free radicals' formation, DNA damage, and apoptosis.

(E)4-[4-N,N-dimethylaminophenyl]but-3-en-2-one mitigates radiation-induced chromosome damage in BALB/c mouse bone marrow

We examined the effects of administration of (E) 4-[4-N,N-dimethylaminophenyl]but-3-en-2-one (DMAP) on radiation-induced chromosome damage in mice. Mice were whole-body exposed to γ-rays, 0-4 Gy, and then immediately administered DMAP, 20 mg/kg. After 24 h, mice were sacrificed, femora were removed, marrow was extracted, and chromosome aberrations were scored in the bone marrow cells. With vehicle-only (saline or oil) treatment, radiation dose-dependent damage was seen in aberrant cells, chromosome breaks, chromatid breaks, centric rings, di-, tri-, and tetracentrics, acentric fragments, total aberrations, polyploidy, and pulverization. Post-administration of DMAP was protective as it reduced chromosome damage. DMAP treatment may be a useful protective agent following radiation accidents or radiotherapy.

Radioprotective effect of chloropyllin, protoporphyrin-IX and bilirubin compared with amifostine® in Drosophila melanogaster

The identification of substances that prevent or minimize the detrimental effects of ionizing radiation is an essential undertaking. The aim of this paper was to evaluate and compare the radioprotective potential of chlorophyllin, protoporphyrin and bilirubin, with amifostine®, an US Food & Drug Administration approved radioprotector Using the somatic mutation and recombination assay in the Drosophila melanogaster wing, it was found that pretreatment (1-9 h) with any of the porphyrins or amifostine® alone, did not affect the larva-adult viability or the basal frequency of mutation. However, they were associated with significant reductions in frequency of somatic mutation and recombination compared with the gamma-irradiated (20 Gy) control as follows: bilirubin (69.3 %)> chlorophyllin (40.0 %)> protoporphyrin (39.0 %)> amifostine® (19.7 %). Bilirubin also caused a 16 % increase in larva-adult viability with 3 h of pretreatment respect to percentage induced in 20 Gy control group. Whilst amifostine® was associated with lower genetic damage after pre-treatment of 1 and 3 h, this did not attain significance. These findings suggest that the tested porphyrins may have some potential as radioprotectant agents.

Radioprotective Effects of Plants from the Lamiaceae Family

BACKGROUND

Edible and medicinal plants are still an interesting source of promising biologically active substances to drug discovery and development. At a time of increasing cancer incidence in the world, alleviating the bothersome side effects of radiotherapy in debilitated cancer patients is becoming an important challenge.

OBJECTIVE

The aim of the study was to overview the literature data concerning the radioprotective activity of extracts, essential oils, and some chemical compounds obtained from 12 species belonging to the Lamiaceae family, gathering of numerous spice and medicinal plants rich in valuable phytochemicals.

RESULTS AND CONCLUSION

The analysis of available publications showed radioprotective effectiveness of essential oils and complex extracts containing phenolic acids and flavonoids in various in vitro and in vivo models. Relatively welldocumented preventive properties exhibited the following species: Mentha × piperita, Ocimum tenuiflorum, Origanum vulgare, and Rosmarinus officinalis. However, few plants such as Lavandula angustifolia, Mentha arvensis, M. spicata, Plectranthus amboinicus, Salvia miltiorrhiza, S. officinalis, Scutellaria baicalensis, and Zataria multiflora should be more investigated in the future. Among the mechanisms of radioprotective effects of well-studied extracts and phytochemicals, it can be mentioned mainly the protection against chromosomal damage, scavenging free radicals, decreasing of lipid peroxidation and elevating of glutathione, superoxide dismutase, catalase, and alkaline phosphatase enzyme levels as well as the reduction the cell death. The plant substances protected the gastrointestinal tract, bone marrow and lung fibroblasts. In conclusion, studied species of Lamiaceae family and their active chemical compounds are potent in alleviating the side effects of radiotherapy and should be considered as a complementary therapy.

Ramipril reduces incidence and prolongates latency time of radiation-induced rat myelopathy after photon and carbon ion irradiation

To test the hypothesis that the use of an angiotensin-converting enzyme inhibitor (ACEi) during radiotherapy may be ameliorative for treatment-related normal tissue damage, a pilot study was conducted with the clinically approved (ACE) inhibitor ramipril on the outcome of radiation-induced myelopathy in the rat cervical spinal cord model. Female Sprague Dawley rats were irradiated with single doses of either carbon ions (LET 45 keV/μm) at the center of a 6 cm spread-out Bragg peak (SOBP) or 6 MeV photons. The rats were randomly distributed into 4 experimental arms: (i) photons; (ii) photons + ramipril; (iii) carbon ions and (iv) carbon ions + ramipril. Ramipril administration (2 mg/kg/day) started directly after irradiation and was maintained during the entire follow-up. Complete dose-response curves were generated for the biological endpoint radiation-induced myelopathy (paresis grade II) within an observation time of 300 days. Administration of ramipril reduced the rate of paralysis at high dose levels for photons and for the first time a similar finding for high-LET particles was demonstrated, which indicates that the effect of ramipril is independent from radiation quality. The reduced rate of myelopathy is accompanied by a general prolongation of latency time for photons and for carbon ions. Although the already clinical approved drug ramipril can be considered as a mitigator of radiation-induced normal tissue toxicity in the central nervous system, further examinations of the underlying pathological mechanisms leading to radiation-induced myelopathy are necessary to increase and sustain its mitigative effectiveness.

Radiation protection by Ex-RAD: a systematic review

Protection of normal tissues against ionizing radiation-induced damages is a critical issue in clinical and environmental radiobiology. One of the ways of accomplishing radiation protection is through the use of radioprotectors. In the search for the most effective radioprotective agent, factors such as toxicity, effect on tumors, number of tissues protected, ease of administration, long-term stability, and compatibility with other drugs need to be assessed. Thus, in the present study, we systematically review existing studies on a chemical radioprotector, Ex-RAD, with the aim of examining its efficacy of radiation protection as well as underlying mechanisms. To this end, a systematic search of the electronic databases including Pubmed, Scopus, Embase, and Google Scholar was conducted to retrieve articles investigating the radioprotective effect of Ex-RAD. From an initial search of 268 articles, and after removal of duplicates as well as applying the predetermined inclusion and exclusion criteria, 10 articles were finally included for this systematic review. Findings from the reviewed studies indicated that Ex-RAD showed potentials for effective radioprotection of the studied organs with no side effect. Furthermore, the inhibition of apoptosis through p53 signaling pathway was the main mechanism of radioprotection by Ex-RAD. However, its radioprotective effect would need to be investigated for more organs in future studies.

Radioprotectors.org: an open database of known and predicted radioprotectors

The search for radioprotectors is an ambitious goal with many practical applications. Particularly, the improvement of human radioresistance for space is an important task, which comes into view with the recent successes in the space industry. Currently, all radioprotective drugs can be divided into two large groups differing in their effectiveness depending on the type of exposure. The first of these is radioprotectors, highly effective for pulsed, and some types of relatively short exposure to irradiation. The second group consists of long-acting radioprotectors. These drugs are effective for prolonged and fractionated irradiation. They also protect against impulse exposure to ionizing radiation, but to a lesser extent than short-acting radioprotectors. Creating a database on radioprotectors is a necessity dictated by the modern development of science and technology. We have created an open database, Radioprotectors.org, containing an up-to-date list of substances with proven radioprotective properties. All radioprotectors are annotated with relevant chemical and biological information, including transcriptomic data, and can be filtered according to their properties. Additionally, the performed transcriptomics analysis has revealed specific transcriptomic profiles of radioprotectors, which should facilitate the search for potent radioprotectors.

Mitigative efficacy of the clinical dosage administration of granulocyte colony-stimulating factor and romiplostim in mice with severe acute radiation syndrome

BACKGROUND

It has been reported that the high-dosage administration of domestically approved pharmaceutical drugs, especially granulocyte colony-stimulating factor (G-CSF) and romiplostim (RP), is a rapid and appropriate medical treatment for preventing severe acute radiation syndrome (ARS) of victims exposed to lethal total-body irradiation (TBI). However, it remains unclear whether or not the clinical dosage administration of these drugs can ameliorate TBI-induced ARS and related high mortality in order to find various drug treatment options and less toxic optimum protocol depending on the situation surrounding the radiological accidents.

METHODS

We assessed the clinical dosage administration in combination with G-CSF and RP as intraperitoneal injection in C57BL/6 J mice exposed to more than 7-Gy lethal dose of X-ray TBI for the survival study evaluated by the log-rank test. Bone marrow and splenic cells were collected on the 21st day, when 1 week has passed from last administration, to detect the level of cell apoptosis, intracellular reactive oxygen species (ROS), and nuclear factor erythroid 2-related factor 2 (Nrf2)-related anti-oxidative gene expressions, and enzyme-linked immune sorbent assay using sera was performed for cell senescence and inflammation status analyzed with one-way ANOVA and Tukey-Kramer or Bonferroni/Dunn multiple comparison tests.

RESULTS

The combined once-daily administration of 10 μg/kg G-CSF for 4 times and 10 μg/kg RP once a week for 3 times improve the 30-day survival rate of lethal TBI mice compared with untreated TBI mice, accompanied by a gradual increase in the body weight and hematopoietic cell numbers. The radio-mitigative effect is probably attributed to the scavenging of ROS and the reduction in cell apoptosis. These changes were associated with the upregulation of Nrf2 and its downstream anti-oxidative targets in TBI mice. Furthermore, this combination modulated TBI-induced cell senescence an d inflammation markers.

CONCLUSIONS

This study suggested that the clinical dosage administration in combination with G-CSF and RP may also have radio-mitigative effects on mice exposed to lethal TBI and may be a potent therapeutic agent for mitigating radiation-induced severe ARS.

Targets for protection and mitigation of radiation injury

Protection of normal tissues against toxic effects of ionizing radiation is a critical issue in clinical and environmental radiobiology. Investigations in recent decades have suggested potential targets that are involved in the protection against radiation-induced damages to normal tissues and can be proposed for mitigation of radiation injury. Emerging evidences have been shown to be in contrast to an old dogma in radiation biology; a major amount of reactive oxygen species (ROS) production and cell toxicity occur during some hours to years after exposure to ionizing radiation. This can be attributed to upregulation of inflammatory and fibrosis mediators, epigenetic changes and disruption of the normal metabolism of oxygen. In the current review, we explain the cellular and molecular changes following exposure of normal tissues to ionizing radiation. Furthermore, we review potential targets that can be proposed for protection and mitigation of radiation toxicity.

Protective effects of new aryl sulfone derivatives against radiation-induced hematopoietic injury

The hematopoietic system is sensitive to radiation. In this research, new aryl sulfone derivatives (XH-201 and XH-202) containing a nitrogen heterocycle were designed and synthesized and their radio-protective efficacies with regard to the hematopoietic system were evaluated. XH-201 administration significantly increased the survival rate of mice after 8.0 Gy total body irradiation (TBI). The results showed that XH-201 treatment not only increased the white blood cells, platelets counts and the percentage of hematopoietic progenitor cells and hematopoietic stem cells in mice exposed to 4.0 Gy TBI but also decreased DNA damage, as determined by flow cytometric analysis of histone H2AX phosphorylation. In addition, our data demonstrated that XH-201 decreased the mitochondrial reactive oxygen species (ROS) levels in hematopoietic cells. Overall, these data suggest that XH-201 is beneficial for the protection of the hemoatopoietic system against radiation-induced injuries.

Modeling Direct and Indirect Action on Cell Survival After Photon Irradiation under Normoxia and Hypoxia

The demand for personalized medicine in radiotherapy has been met by a surge of mechanistic models offering predictions of the biological effect of ionizing radiation under consideration of a growing number of parameters. We present an extension of our existing model of cell survival after photon irradiation to explicitly differentiate between the damage inflicted by the direct and indirect (radicals-mediated) action of ionizing radiation. Within our approach, we assume that the oxygenation status affects the indirect action. The effect of different concentrations of dimethyl sulfoxide (DMSO), an effective radical scavenger, has been simulated at different dose levels in normoxic and hypoxic conditions for various cell lines. Our model is found to accurately predict experimental data available in literature, validating the assumptions made in our approach. The presented extension adds further flexibility to our model and could act as basis for further developments of our model.