Mitigation effect of an FGF-2 peptide on acute gastrointestinal syndrome after high-dose ionizing radiation

Anti-ceramide Single-Chain Variable Fragment Mitigates Gastrointestinal-Acute Radiation Syndrome and Improves Marrow Reconstitution, Rendering Near-Normal 90-Day Autopsies

PURPOSE

After September 11, 2001, nuclear threat prompted government agencies to develop medical countermeasures to mitigate two syndromes, the hematopoietic-acute radiation syndrome (H-ARS) and the higher-dose gastrointestinal-acute radiation syndrome (GI-ARS), both lethal within weeks. While repurposing leukemia drugs that enhance bone marrow repopulation successfully treats H-ARS, no mitigator potentially deliverable under mass casualty conditions preserves the GI tract. We recently reported that anti-ceramide single-chain variable fragment (scFv) mitigates GI-ARS lethality, abrogating ongoing small intestinal endothelial apoptosis to rescue Lgr5+ stem cells. Here, we examine long-term consequences of prevention of acute GI-ARS lethality.

METHODS AND MATERIALS

For these studies, C57BL/6J male mice were treated with 15 Gy whole body irradiation, the 90% GI-ARS lethal dose for this mouse strain.

RESULTS

Mice irradiated with 15 Gy alone or with 15 Gy + bone marrow transplantation (BMT) or anti-ceramide scFv, succumb to an ARS within 8 to 10 days. Autopsies reveal only mice receiving anti-ceramide scFv at 24 hours post-whole body irradiation display small intestinal rescue. No marrow reconstitution occurs in any group with attendant undetectable circulating blood elements. Mice receiving 15 Gy + BMT + scFv, however, normalize blood counts by day 12, suggesting that scFv also improves marrow reconstitution, a concept for which we provide experimental support. We show that at 14 Gy, the upper limit dose for H-ARS lethality before transition to GI-ARS lethality, anti-ceramide scFv markedly improves marrow take, reducing the quantity of marrow-conferring survival by more than 3-fold. Consistent with these findings, mice receiving 15 Gy + BMT + scFv exhibit prolonged survival. At day 90, before sacrifice, they display normal appearance, behavior, and serum biochemistries, and surprisingly, at full autopsy, near-normal physiology in all 42 tissues examined.

CONCLUSIONS

Anti-ceramide scFv mitigates GI-ARS lethality and improves marrow reconstitution rendering prolonged survival with near normal autopsies.

Lactobacillus reuteri's multifaceted role in mitigating ionizing radiation-induced injury in Drosophila melanogaster

The numerous beneficial probiotic properties of Lactobacillus reuteri (L. reuteri) include decreasing metabolic syndrome, preventing disorders linked to oxidative stress, improving gut flora imbalances, controlling immunological function, and extending life span. Exposure to ionizing radiation is closely associated with several disorders. We examined the protective and salvaging effects of L. reuteri on ionizing radiation-induced injury to the intestinal tract, reproductive system, and nervous system of Drosophila melanogaster. We also examined its effects on lifespan, antioxidant capacity, progeny development, and behavioral aspects to assess the interaction between L. reuteri and ionizing radiation-induced injury. The findings demonstrated that L. reuteri improved the median survival time following irradiation and greatly extended its lifespan. In addition, it raised SOD activity, reduced ROS levels in intestinal epithelial cells, and increased the quantity of intestinal stem cells. Furthermore, L. reuteri enhanced the adult male flies' capacity to move. It also successfully safeguarded the generations' growth and development. L. reuteri dramatically enhanced expression of the AMPKα gene and regulated expression of its pathway-related gene, mTOR, as well as the autophagy-related genes Atg1 and Atg5 in female Drosophila exposed to irradiation. Notably, no prior reports have been made on the possible effects of L. reuteri on injuries caused by irradiation. As a result, our research offers important new information regarding L. reuteri's possible role as a shield against ionizing radiation-induced injury.

Durability of and role of AKT in FGF7p urothelial protection against cyclophosphamide

We previously identified a peptide derived from human fibroblast growth factor 7 (FGF7p) that blocks urothelial apoptosis similar to full-length FGF7, although effects of FGF7p on urothelial repair are unknown. Also, while urothelial AKT activation downstream of FGF7p correlated with the anti-apoptotic effects, we have not directly interrogated the role of AKT in mediating the cytoprotection. Our goal was to assess effects of FGF7p on urothelial repair and the role of AKT signaling in mediating the cytoprotective effects of FGF7p. We performed hematoxylin and eosin (H&E), TUNEL, and/or immunofluorescence (IF) staining for various markers in FGF7p-treated mice 28 days after giving cyclophosphamide or after co-administering a systemic AKT antagonist with FGF7p 24 h after cyclophosphamide. Vehicle-treated and injured mice had hyperplastic urothelium, incomplete return of mature superficial cell markers, ongoing proliferation, and continued presence of basal progenitor markers 28 days after injury; conversely, FGF7p-treated mice had normal numbers of urothelial cell layers, nearly complete return of superficial cell markers, limited proliferation and fewer basal progenitor cells 28 days post-injury. Vehicle-treated mice also had ectopic lumenal basal progenitor cell markers, while FGF7p had none 28 days after cyclophosphamide. Co-administration of an AKT inhibitor largely abrogated FGF7p-driven AKT activation and cytoprotection in urothelium 24 h after injury. Thus, FGF7p drives faster and higher fidelity urothelial repair by limiting apoptotic injury via AKT signaling, similar to full-length FGF7. Finally, FGF7p is much less expensive to synthesize and has a longer shelf life and higher purity than FGF7.

Assay establishment and validation of a high-throughput organoid-based drug screening platform

BACKGROUND

Organoids are three-dimensional structures that closely recapitulate tissue architecture and cellular composition, thereby holding great promise for organoid-based drug screening. Although growing in three-dimensional provides the possibility for organoids to recapitulate main features of corresponding tissues, it makes it incommodious for imaging organoids in two-dimensional and identifying surviving organoids from surrounding dead cells after organoids being treated by irradiation or chemotherapy. Therefore, significant work remains to establish high-quality controls to standardize organoid analyses and make organoid models more reproducible.

METHODS

In this study, the Z-stack imaging technique was used for the imaging of three-dimensional organoids to gather all the organoids' maximum cross sections in one imaging. The combination of live cell staining fluorescent dye Calcein-AM and ImageJ assessment was used to analyze the survival of organoids treated by irradiation or chemotherapy.

RESULTS

We have established a novel quantitative high-throughput imaging assay that harnesses the scalability of organoid cultures. Using this assay, we can capture organoid growth over time, measure multiple whole-well organoid readouts, and show the different responses to drug treatments.

CONCLUSIONS

In summary, combining the Z-stack imaging technique and fluorescent labeling methods, we established an assay for the imaging and analysis of three-dimensional organoids. Our data demonstrated the feasibility of using organoid-based platforms for high-throughput drug screening assays.

The roles of CC chemokines in response to radiation

Radiotherapy is an effective regimen for cancer treatment alone or combined with chemotherapy or immunotherapy. The direct effect of radiotherapy involves radiation-induced DNA damage, and most studies have focused on this area to improve the efficacy of radiotherapy. Recently, the immunomodulatory effect of radiation on the tumour microenvironment has attracted much interest. Dying tumour cells can release multiple immune-related molecules, including tumour-associated antigens, chemokines, and inflammatory mediators. Then, immune cells are attracted to the irradiated site, exerting immunostimulatory or immunosuppressive effects. CC chemokines play pivotal roles in the trafficking process. The CC chemokine family includes 28 members that attract different immune subsets. Upon irradiation, tumour cells or immune cells can release different CC chemokines. Here, we mainly discuss the importance of CCL2, CCL3, CCL5, CCL8, CCL11, CCL20 and CCL22 in radiotherapy. In irradiated normal tissues, released chemokines induce epithelial to mesenchymal transition, thus promoting tissue injury. In the tumour microenvironment, released chemokines recruit cancer-associated cells, such as tumour-infiltrating lymphocytes, myeloid-derived suppressor cells and tumour-associated macrophages, to the tumour niche. Thus, CC chemokines have protumour and antitumour properties. Based on the complex roles of CC chemokines in the response to radiation, it would be promising to target specific chemokines to alleviate radiation-induced injury or promote tumour control.

FGF7 peptide (FGF7p) mimetic mitigates bladder urothelial injury from cyclophosphamide

Although full-length fibroblast growth factor 7 (FGF7) blocks cyclophosphamide-induced urothelial apoptosis in mice, limitations include high production costs because of its large size. We previously identified a small peptide derived from FGF2 that mitigated acute radiation syndrome as well as full-length FGF2. Based on the sequence of the FGF2 peptide, we synthesized a corresponding 19 amino acid FGF7 peptide (FGF7p). Our objectives were to determine if systemic FGF7p triggered the downstream targets and protected against cyclophosphamide bladder injury similar to full-length FGF7. We administered FGF7p or vehicle subcutaneously (SQ) to mice subjected to no injury or intraperitoneal (IP) cyclophosphamide and harvested bladders 1 day after injury. We then performed hematoxylin and eosin, TUNEL and immunofluorescence (IF) staining. In uninjured mice, a 20 mg/kg threshold FGF7p dose induced expression of phosphorylated (activated) FRS2α (pFRS2α), and pAKT in urothelium (consistent with cytoprotective effects of FGF7). We then gave FGF7p (20 mg/kg) or vehicle at 72 and 48 h prior to cyclophosphamide. One day after injury, TUNEL staining revealed many more apoptotic urothelial cells with vehicle treatment versus FGF7p treatment. IF for pAKT and readouts of two anti-apoptotic AKT targets (BAD and mTORC1) revealed minimal staining with vehicle treatment, but strong urothelial expression for all markers with FGF7p treatment. In conclusion, FGF7p appears to block bladder urothelial apoptosis via AKT and its targets, similar to FGF7. FGF7p is much more inexpensive to make and has a longer shelf life and higher purity than FGF7.

CBP/P300 Inhibitors Mitigate Radiation-Induced GI Syndrome by Promoting Intestinal Stem Cell-Mediated Crypt Regeneration

PURPOSE

Radiation-induced gastrointestinal syndrome (RIGS) is currently the main cause of death for people exposed to a high dose of irradiation during nuclear incidents, and there is currently no approved effective therapy. Here, we found that CBP/P300 inhibitors, with high efficacy and low toxicity, might be promising radiation mitigators that can cure RIGS.

METHODS AND MATERIALS

Ex vivo 3D organoid cultures derived from mouse jejunum and human ileum and colon were used to examine the radio-mitigative effects of CBP/P300 inhibitors. The radio-mitigative effect was evaluated by quantifying the survival rate and size of organoids after radiation. SGC-CBP30 (50 mg/kg body weight), an inhibitor of CBP/P300, was intraperitoneally injected into C57B/6J mice 24 hours after subtotal-body irradiation or whole-body irradiation. The regenerated crypts and animal survival were determined by microcolony assay and the Kaplan-Meier method, respectively. Lgr5-lacZ mice were used to evaluate the survival of intestinal stem cells after treatments.

RESULTS

We found that CBP/P300 inhibitors were effective mitigators that could be used to treat RIGS. CBP/P300 inhibition promoted the regeneration of intestinal organoids in vitro and of crypts in vivo. Remarkably, the administration of CBP/P300 inhibitors to mice 24 hours after lethal irradiation promoted Lgr5+ intestinal stem cell and crypt recovery, resulting in improved mouse survival. Moreover, our data show that CBP/P300 inhibitors rescued irradiated mice from RIGS by delaying intestinal epithelial cell cycle progression after radiation.

CONCLUSIONS

These data demonstrate that CBP/P300 inhibitors are effective medical countermeasures to mitigate gastrointestinal toxicity from radiation.

Furazolidone Increases Survival of Mice Exposed to Lethal Total Body Irradiation through the Antiapoptosis and Antiautophagy Mechanism

Exposure to total body irradiation (TBI) causes dose- and tissue-specific lethality. However, there are few effective and nontoxic radiation countermeasures for the radiation injury. In the current study, mice were pretreated with a traditional antimicrobial agent, FZD, before TBI; the protective effects of FZD on radiation injury were evaluated by using parameters such as the spleen index and thymus index, immunohistochemical staining of intestinal tissue, and frequency of micronuclei in polychromatophilic erythrocytes of bone marrow. The intestinal epithelial cell line IEC-6 was used to investigate the underlying mechanisms. Our results indicated that FZD administration significantly improved the survival of lethal dose-irradiated mice, decreased the number of micronuclei, upregulated the number of leukocytes and immune organ indices, and restored intestinal integrity in mice after TBI. TUNEL and western blot showed that FZD protected intestinal tissue by downregulating radiation-induced apoptosis and autophagy. Meanwhile, FZD protected IEC-6 cells from radiation-induced cell death by inhibiting apoptosis and autophagy. To sum up, FZD protected against radiation-induced cell death both in vitro and in vivo through antiapoptosis and antiautophagy mechanisms.

Musashi expression in intestinal stem cells attenuates radiation-induced decline in intestinal permeability and survival in Drosophila

Exposure to genotoxic stress by environmental agents or treatments, such as radiation therapy, can diminish healthspan and accelerate aging. We have developed a Drosophila melanogaster model to study the molecular effects of radiation-induced damage and repair. Utilizing a quantitative intestinal permeability assay, we performed an unbiased GWAS screen (using 156 strains from the Drosophila Genetic Reference Panel) to search for natural genetic variants that regulate radiation-induced gut permeability in adult D. melanogaster. From this screen, we identified an RNA binding protein, Musashi (msi), as one of the possible genes associated with changes in intestinal permeability upon radiation. The overexpression of msi promoted intestinal stem cell proliferation, which increased survival after irradiation and rescued radiation-induced intestinal permeability. In summary, we have established D. melanogaster as an expedient model system to study the effects of radiation-induced damage to the intestine in adults and have identified msi as a potential therapeutic target.

Study logistics that can impact medical countermeasure efficacy testing in mouse models of radiation injury

PURPOSE

To address confounding issues that have been noted in planning and conducting studies to identify biomarkers of radiation injury, develop animal models to simulate these injuries, and test potential medical countermeasures to mitigate/treat damage caused by radiation exposure.

METHODS

The authors completed an intensive literature search to address several key areas that should be considered before embarking on studies to assess efficacy of medical countermeasure approaches in mouse models of radiation injury. These considerations include: (1) study variables; (2) animal selection criteria; (3) animal husbandry; (4) medical management; and (5) radiation attributes.

RESULTS

It is important to select mouse strains that are capable of responding to the selected radiation exposure (e.g. genetic predispositions might influence radiation sensitivity and proclivity to certain phenotypes of radiation injury), and that also react in a manner similar to humans. Gender, vendor, age, weight, and even seasonal variations are all important factors to consider. In addition, the housing and husbandry of the animals (i.e. feed, environment, handling, time of day of irradiation and animal restraint), as well as the medical management provided (e.g. use of acidified water, antibiotics, routes of administration of drugs, consideration of animal numbers, and euthanasia criteria) should all be addressed. Finally, the radiation exposure itself should be tightly controlled, by ensuring a full understanding and reporting of the radiation source, dose and dose rate, shielding and geometry of exposure, while also providing accurate dosimetry. It is important to understand how all the above factors contribute to the development of radiation dose response curves for a given animal facility with a well-defined murine model.

CONCLUSIONS

Many potential confounders that could impact the outcomes of studies to assess efficacy of a medical countermeasure for radiation-induced injuries are addressed, and recommendations are made to assist investigators in carrying out research that is robust, reproducible, and accurate.

Mitigation of Radiation-Induced Gastrointestinal System Injury by Melatonin: A Histopathological Study

AIMS

The current study aimed to investigate the potential role of melatonin in the mitigation of radiation-induced gastrointestinal injury.

BACKGROUND

Organs of the gastrointestinal system such as the intestines, colon, duodenum, ileum etc. are sensitive to ionizing radiation. Mitigation of radiation-induced gastrointestinal injury is an interesting topic in radiobiology and a life-saving approach for exposed persons after a radiation event or improving the quality of life of radiotherapy patients.

OBJECTIVE

The study aimed to find the possible mitigation effect of melatonin on radiation-induced damage to the small and large intestines.

METHODS

40 male mice were randomly assigned into four groups namely G1: control, G2: melatonin treatment, G3: whole-body irradiation, and G4: melatonin treatment after whole-body irradiation. A cobalt-60 gamma-ray source was used to deliver 7 Gy to the whole body. 100 mg/kg melatonin was administered orally 24 h after irradiation and continued for 5 days. Thirty days after irradiation, histopathological evaluations were performed.

RESULTS

The whole-body irradiation led to remarkable inflammation, villi shortening, apoptosis and damage to goblet cells of the small intestine. Furthermore, moderate to severe inflammation, apoptosis, congestion, crypt injury and goblet cell damage were reported for the colon. Treatment with melatonin after whole-body irradiation led to significant mitigation of radiation toxicity in both small and large intestines.

CONCLUSION

Melatonin could mitigate intestinal injury following whole-body exposure to radiation. Treatment with melatonin after an accidental exposure to radiation may increase survival via mitigation of damages to radiosensitive organs, including the gastrointestinal system.

FGFR Inhibition Enhances Sensitivity to Radiation in Non-Small Cell Lung Cancer

FGFRs are commonly altered in non-small cell lung cancer (NSCLC). FGFRs activate multiple pathways including RAS/RAF/MAPK, PI3K/AKT, and STAT, which may play a role in the cellular response to radiation. We investigated the effects of combining the selective FGFR 1-3 tyrosine kinase inhibitor AZD4547 with radiation in cell line and xenograft models of NSCLC. NSCLC cell lines were assessed with proliferation, clonogenic survival, apoptosis, autophagy, cell cycle, and DNA damage signaling and repair assays. In vivo xenografts and IHC were used to confirm in vitro results. NSCLC cell lines demonstrated varying degrees of FGFR protein and mRNA expression. In vitro clonogenic survival assays showed radiosensitization with AZD4547 in two NSCLC cell lines. In these two cell lines, an increase in apoptosis and autophagy was observed with combined radiation and AZD4547. The addition of AZD4547 to radiation did not significantly affect γH2AX foci formation. Enhanced xenograft tumor growth delay was observed with the combination of radiation and AZD4547 compared with radiation or drug alone. IHC results revealed inhibition of pMAPK and pS6 and demonstrated an increase in apoptosis in the radiation plus AZD4547 group. This study demonstrates that FGFR inhibition by AZD4547 enhances the response of radiation in FGFR-expressing NSCLC in vitro and in vivo model systems. These results support further investigation of combining FGFR inhibition with radiation as a clinical therapeutic strategy.

Hydrogen attenuates radiation-induced intestinal damage by reducing oxidative stress and inflammatory response

The small intestine is known to be particularly sensitive to radiation, and the major limiting factor of radiotherapy is the gastrointestinal syndrome that subsequently develops after its administration. The detrimental effects of radiation are mostly mediated via the overproduction of reactive oxygen species (ROS), especially the hydroxyl radical (·OH). Because hydrogen is a selective ·OH scavenger, we hypothesized that hydrogen might exert a protective effect against radiation-induced intestinal damage. Herein, radiation models were built both in mice and in an intestinal crypt epithelial cell (IEC-6) line. In the animal experiment, we demonstrated that hydrogen-rich saline significantly reduced radiation-induced intestinal mucosal damage, improved intestinal function, and increased the survival rate. In addition, radiation-induced oxidative stress damage and systemic inflammatory response were also mitigated by hydrogen treatment. Moreover, hydrogen treatment decreased cell apoptosis and maintained intestinal epithelial cell proliferation in mice. In vitro experiments using the IEC-6 cell line showed that hydrogen-rich medium significantly inhibited ROS formation, maintained cell viability, and inhibited cell apoptosis. Importantly, hydrogen treatment prevented mitochondrial depolarization, cytochrome c release, and activity of caspase-3, caspase-9, and PARP. Moreover, the decreased expression of Bcl-xl and Bcl-2 and the increased expression of Bax protein were also blocked by hydrogen treatment. In conclusion, our study concurrently demonstrated that hydrogen provides an obviously protective effect on radiation-induced intestinal and cell injuries. Our work demonstrated that this protective effect might be due to the blockage of the mitochondrial apoptotic pathway.

Fibroblast Growth Factor Receptors as Targets for Radiosensitization in Head and Neck Squamous Cell Carcinomas

PURPOSE

We examined the capacity of the pan-fibroblast growth factor receptor (FGFR) inhibitor AZD4547 to augment radiation response across a panel of head and neck squamous cell carcinoma (HNSCC) cell lines and xenografts.

METHODS AND MATERIALS

FGFR1, FGFR2, and FGFR3 RNA in situ hybridization expression was assessed in a cohort of HNSCC patient samples, cell lines, and patient-derived xenografts (PDXs). In vitro effects of AZD4547 and radiation on cell survival, FGFR signaling, apoptosis, autophagy, cell cycle, and DNA damage repair were evaluated. Reverse phase protein array was used to identify differentially phosphorylated proteins in cells treated with AZD4547. In vivo tumor responses were evaluated in cell lines and PDX models.

RESULTS

FGFR1, FGFR2, and FGFR3 RNA in situ hybridization were expressed in 41%, 81%, and 89% of 107 oropharynx patient samples. Sensitivity to AZD4547 did not directly correlate with FGFR protein or RNA expression. In sensitive cell lines, AZD4547 inhibited p-MAPK in a time-dependent manner. Significant radiosensitization with AZD4547 was observed in cell lines that were sensitive to AZD4547. The mechanism underlying these effects appears to be multifactorial, involving inhibition of the MTOR pathway and subsequent enhancement of autophagy and activation of apoptotic pathways. Significant tumor growth delay was observed when AZD4547 was combined with radiation compared with radiation or drug alone in an FGFR-expressing HNSCC cell line xenograft and PDX.

CONCLUSIONS

These findings suggest that AZD4547 can augment the response of radiation in FGFR-expressing HNSCC in vivo model systems. FGFR1 and FGFR2 may prove worthy targets for radiosensitization in HNSCC clinical investigations.

Long-term Consequences of Pelvic Irradiation: Toxicities, Challenges, and Therapeutic Opportunities with Pharmacologic Mitigators

A percentage of long-term cancer survivors who receive pelvic irradiation will develop treatment-related late effects, collectively termed pelvic radiation disease. Thus, there is a need to prevent or ameliorate treatment-related late effects in these patients. Modern radiotherapy methods can preferentially protect normal tissues from radiation toxicities to permit higher doses to targets. However, concerns about chronic small bowel toxicity, for example, still constrain the prescription dose. This provides strong rationale for considering adding pharmacologic mitigators. Implementation of modern targeted radiotherapy methods enables delivery of focused radiation to target volumes, while minimizing dose to normal tissues. In prostate cancer, these technical advances enabled safe radiation dose escalation and better local tumor control without increasing normal tissue complications. In other pelvic diseases, these new radiotherapy methods have not resulted in the low probability of normal tissue damage achieved with prostate radiotherapy. The persistence of toxicity provides rationale for pharmacologic mitigators. Several new agents could be readily tested in clinical trials because they are being or have been studied in human patients already. Although there are promising preclinical data supporting mitigators, no clinically proven options to treat or prevent pelvic radiation disease currently exist. This review highlights therapeutic options for prevention and/or treatment of pelvic radiation disease, using pharmacologic mitigators. Successful development of mitigators would reduce the number of survivors who suffer from these devastating consequences of pelvic radiotherapy. It is important to note that pharmacologic mitigators to ameliorate pelvic radiation disease may be applicable to other irradiated sites in which chronic toxicity impairs quality of life.

Mitigation of Radiation-induced Gastrointestinal System Injury using Resveratrol or Alpha-lipoic Acid: A Pilot Histopathological Study

AIM

In this study, we aimed to determine possible mitigation of radiationinduced toxicities in the duodenum, jejunum and colon using post-exposure treatment with resveratrol and alpha-lipoic acid.

BACKGROUND

After the bone marrow, gastrointestinal system toxicity is the second critical cause of death following whole-body exposure to radiation. Its side effects reduce the quality of life of patients who have undergone radiotherapy. Resveratrol has an antioxidant effect and stimulates DNA damage responses (DDRs). Alpha-lipoic acid neutralizes free radicals via the recycling of ascorbic acid and alpha-tocopherol.

OBJECTIVE

This study is a pilot investigation of the mitigation of enteritis using resveratrol and alpha-lipoic acid following histopathological study.

METHODS

60 male mice were randomly assigned to six groups; control, resveratrol treatment, alpha-lipoic acid treatment, whole-body irradiation, irradiation plus resveratrol, and irradiation plus alpha-lipoic acid. The mice were irradiated with a single dose of 7 Gy from a cobalt-60 gamma-ray source. Treatment with resveratrol or alpha-lipoic acid started 24 h after irradiation and continued for 4 weeks. All mice were sacrificed after 30 days for histopathological evaluation of radiation-induced toxicities in the duodenum, jejunum and colon.

RESULTS AND DISCUSSION

Exposure to radiation caused mild to severe damages to vessels, goblet cells and villous. It also led to significant infiltration of macrophages and leukocytes, especially in the colon. Both resveratrol and alpha-lipoic acid were able to mitigate morphological changes. However, they could not mitigate vascular injury.

CONCLUSION

Resveratrol and alpha-lipoic acid could mitigate radiation-induced injuries in the small and large intestine. A comparison between these agents showed that resveratrol may be a more effective mitigator compared to alpha-lipoic acid.

Mitigation of radiation-induced gastro-intestinal injury by the polyphenolic acetate 7, 8-diacetoxy-4-methylthiocoumarin in mice

Radiation-induced intestinal injury (RIII) constitutes a crucial clinical element of acute radiation syndrome with life-threatening implications posing challenges in devising effective medical countermeasures. Herein, we report the potential of 7, 8-diacetoxy-4-methylthiocoumarin (DAMTC) to mitigate RIII following total-body irradiation (TBI) in C57BL/6 mice and underlying mechanisms. Administration of DAMTC 24 hours post TBI facilitated structural reconstitution and restoration of functional absorption linked to alleviation of radiation-induced apoptotic death of intestinal crypt progenitor/stem (ICPS) and villus stromal cells through induction of Bcl-2 family-mediated anti-apoptotic signalling. Reduction in TBI-induced DNA damage accumulation coupled with inhibition of cell cycle arrest through stimulation of anti-p53- and anti-p21-dependent synergistic signalling protected ICPS cells from radiation injury. Enhanced proliferation of crypt stem cells, induction of anti-oxidant defence, subjugation of TBI-induced lipid peroxidation and phenotypic polarization of intestinal macrophages to anti-inflammatory M2 class underlie amelioration of RIII. Stimulation of multiple mitigative signalling processes by DAMTC appeared to be associated with enhanced protein acetylation, an important regulator of cellular responses to radiation damage. Our findings establish the mitigative potential of DAMTC against RIII by hyper-acetylation-mediated epigenetic regulation, which triggers axes of anti-apoptotic and pro-survival pathways, enabling proliferation and maintenance of ICPS cells leading to epithelial regeneration.

Use of Growth Factors and Other Cytokines for Treatment of Injuries During a Radiation Public Health Emergency

Due to the threat of a radiological or nuclear incident that could impact citizens, the U.S. Department of Health and Human Services tasked the National Institute of Allergy and Infectious Diseases (NIAID) with identifying and funding early- to mid-stage medical countermeasure (MCM) development to treat radiation-induced injuries. Given that the body's natural response to radiation exposure includes production of growth factors and cytokines, and that the only drugs approved by the U.S. Food and Drug Administration to treat acute radiation syndrome are growth factors targeting either the granulocyte (Neupogen^® or Neulasta^®) or granulocyte and macrophage (Leukine^®) hematopoietic cell lineages, there is interest in understanding the role that these factors play in responding to and/or ameliorating radiation damage. Furthermore, in an environment where resources are scarce, such as what might be expected during a radiation public health emergency, availability of growth factor or other treatments may be limited. For these reasons, the NIAID partnered with the Radiation Injury Treatment Network (RITN), whose membership includes medical centers with expertise in the management of bone marrow failure, to explore the use of growth factors and other cytokines as MCMs to mitigate/treat radiation injuries. A workshop was convened that included government, industry and academic subject matter experts, with presentations covering the anticipated concept of operations during a mass casualty incident including triage and treatment, growth factors under development for a radiation indication, and how the practice of medicine can inform other potential approaches, as well as considerations for administration of these products to diverse civilian populations. This report reviews the information presented, and provides an overview of the discussions from a guided breakout session.

Use of Growth Factors and Cytokines to Treat Injuries Resulting from a Radiation Public Health Emergency

In response to concerns over possible radiological or nuclear incidents, the Radiation and Nuclear Countermeasures Program within the National Institute of Allergy and Infectious Diseases (NIAID) was tasked by the U.S. Department of Health and Human Services to support development of medical countermeasures (MCM) to treat the acute and delayed injuries that can result from radiation exposure. To date, the only three drugs approved by the U.S. Food and Drug Administration for treatment of acute radiation syndrome are growth factors targeting granulocyte (Neupogen^® or Neulasta^®) or granulocyte and macrophage (Leukine^®) hematopoietic cell lineages. Although these are currently stockpiled for deployment in response to a mass casualty scenario, these growth factors will likely be administered in a scarce-resources environment and availability may be limited. Therefore, there is growing interest in understanding the role that these growth factors play in mitigating radiation damage, to optimize their use and maximize the number of people who can be treated. For these reasons, the NIAID and the Radiation Injury Treatment Network organized a workshop to explore the use of growth factors and other cytokines as MCMs in the treatment of radiation-induced injuries. Subject matter experts from government, industry and academia gathered at this workshop to discuss the concept of operations, triage and treatment, administration to diverse civilian populations, growth factors under development for radiation indications, and how the practice of medicine can inform other potential approaches.

Bioanalytical method development and validation for determination of fibroblast growth factor peptide and its application to pharmacokinetic studies

Fibroblast growth factor peptide (FGF-P) is a polypeptide analog of FGF-2 that could be a potential mitigation and treatment agent for radiation syndromes. Prior to conducting preclinical pharmacokinetics, we developed and validated the LC-MS/MS bioanalytical method for determination of FGF-P in rat plasma for the first time. FGF-P was extracted from rat plasma using the protein precipitation technique followed liquid-liquid extraction using dichloromethane as a solvent. The mobile phases consisted of two components: (a) 0.1% formic acid in water; and (b) acetonitrile: 0.1% formic acid in water (95:5) under gradient elution. The validated method was also successfully applied to a pharmacokinetic study of FGF-P (10 mg/kg, intravenous) in Wistar rats. The method proved to be specific, accurate, precise, and linear over the concentration range of 2-500 ng/mL with coefficient of determination greater than 0.99 in all validation batches. The within-run and between-run accuracy was 87.97-115.00% with a precision of less than 14%. The mean recoveries ranged from 88.14% to 101.73%. The stability of the compound in plasma samples was proven under various storage conditions. After intravenous administration of FGF-P (10 mg/kg) the C₀ was 70.4 µg/mL and the AUC was 86.2 µg*min/mL.

rBPI21 (Opebacan) Promotes Rapid Trilineage Hematopoietic Recovery in a Murine Model of High-Dose Total Body Irradiation

The complexity of providing adequate care after radiation exposure has drawn increasing attention. While most therapeutic development has focused on improving survival at lethal radiation doses, acute hematopoietic syndrome (AHS) occurs at substantially lower exposures. Thus, it is likely that a large proportion of such a radiation-exposed population will manifest AHS of variable degree and that the medical and socioeconomic costs of AHS will accrue. Here, we examined the potential of rBPI21 (opebacan), used without supportive care, to accelerate hematopoietic recovery after radiation where expected survival was substantial (42-75%) at 30 days). rBPI21 administration was associated with accelerated recovery of hematopoietic precursors and normal marrow cellularity, with increases in megakaryocyte numbers particularly marked. This translated into attaining normal trilineage peripheral blood counts 2-3 weeks earlier than controls. Elevations of hematopoietic growth factors observed in plasma and the marrow microenvironment suggest the mechanism is likely multifactorial and not confined to known endotoxin-neutralizing and cytokine down-modulating activities of rBPI21 . These observations deserve further exploration in radiation models and other settings where inadequate hematopoiesis is a prominent feature. These experiments also model the potential of therapeutics to limit the allocation of scarce resources after catastrophic exposures as an endpoint independent of lethality mitigation. This article is protected by copyright. All rights reserved.

Synergistic actions of FGF2 and bone marrow transplantation mitigate radiation-induced intestinal injury

Unwanted radiological or nuclear exposure remains a public health risk for which effective therapeutic countermeasures are lacking. Here, we evaluated the efficacy of fibroblast growth factor-2 (FGF2) in treating radiation-induced gastrointestinal syndrome (RIGS) incurred by lethal whole-body irradiation (WBI) when administered in conjunction with bone marrow transplantation (BMT). In vitro experiments indicated FGF2 treatment increased proliferation, reduced apoptosis, and upregulated AKT–GSK3β/β–catenin signaling in irradiated IEC-6 cells. We next established and analyzed mice cohorts consisting of sham irradiation (Group Sh); 12 Gy WBI (Group A); WBI with BMT (Group B); WBI with FGF2 treatment (Group F); and WBI with BMT and FGF2 treatment (Group BF). At 2 weeks post-irradiation, Group BF showed a dramatic increase in survival over all other groups. Intestinal epithelium of Group BF, but not Group B or F, showed augmented proliferation, decreased apoptosis, and preserved crypt numbers and morphology. Furthermore, Group BF maintained intestinal barrier function with minimal inflammatory disturbances in a manner comparable to Group Sh. In accordance, transcriptomic analyses showed significant upregulation of intestinal barrier and stem cell markers in Group BF relative to Groups A and B. Taken together, parenteral FGF2 synergizes with BMT to confer potent mitigation against RIGS.

Pharmacological Modulation of Radiation Damage. Does It Exist a Chance for Other Substances than Hematopoietic Growth Factors and Cytokines?

In recent times, cytokines and hematopoietic growth factors have been at the center of attention for many researchers trying to establish pharmacological therapeutic procedures for the treatment of radiation accident victims. Two granulocyte colony-stimulating factor-based radiation countermeasures have been approved for the treatment of the hematopoietic acute radiation syndrome. However, at the same time, many different substances with varying effects have been tested in animal studies as potential radioprotectors and mitigators of radiation damage. A wide spectrum of these substances has been studied, comprising various immunomodulators, prostaglandins, inhibitors of prostaglandin synthesis, agonists of adenosine cell receptors, herbal extracts, flavonoids, vitamins, and others. These agents are often effective, relatively non-toxic, and cheap. This review summarizes the results of animal experiments, which show the potential for some of these untraditional or new radiation countermeasures to become a part of therapeutic procedures applicable in patients with the acute radiation syndrome. The authors consider β-glucan, 5-AED (5-androstenediol), meloxicam, γ-tocotrienol, genistein, IB-MECA (N⁶-(3-iodobezyl)adenosine-5'-N-methyluronamide), Ex-RAD (4-carboxystyryl-4-chlorobenzylsulfone), and entolimod the most promising agents, with regards to their contingent use in clinical practice.

Protected graft copolymer-formulated fibroblast growth factors mitigate the lethality of partial body irradiation injury

We evaluated the mitigating effects of fibroblast growth factor 4 and 7 (FGF4 and FGF7, respectively) in comparison with long acting protected graft copolymer (PGC)-formulated FGF4 and 7 (PF4 and PF7, respectively) administered to C57BL/6J mice a day after exposure to LD50/30 (15.7 Gy) partial body irradiation (PBI) which targeted the gastrointestinal (GI) system. The PGC that we developed increased the bioavailability of FGF4 and FGF7 by 5- and 250-fold compared to without PGC, respectively, and also sustained a 24 hr presence in the blood after a single subcutaneous administration. The dose levels tested for mitigating effects on radiation injury were 3 mg/kg for the PF4 and PF7 and 1.5 mg each for their combination (PF4/7). Amifostine administered prior to PBI was used as a positive control. The PF4, PF7, or PF4/7 mitigated the radiation lethality in mice. The mitigating effect of PF4 and PF7 was similar to the positive control and PF7 was better than other mitigators tested. The plasma citrulline levels and hematology parameters were early markers of recovery and survival. GI permeability function appeared to be a late or full recovery indicator. The villus length and crypt number correlated with plasma citrulline level, indicating that it can act as a surrogate marker for these histology evaluations. The IL-18 concentrations in jejunum as early as day 4 and TPO levels in colon on day 10 following PBI showed statistically significant changes in irradiated versus non-irradiated mice which makes them potential biomarkers of radiation exposure. Other colon and jejunum cytokine levels are potentially useful but require larger numbers of samples than in the present study before their full utility can be realized.

Identification of novel peptoid agonists of fibroblast growth factor receptor using microarray-based screening

Drug development targeting fibroblast growth factor receptors (FGFRs) represents an emerging theme in the field of medicinal chemistry. Considering the fact that most of the currently identified FGFR agonists are long chain peptides with limited stability, the discovery of novel non-peptide FGFR ligands is still highly demanded. A linear one-bead-one-compound peptoid (oligomers of N-substituted glycine units) library with a theoretical diversity of 10⁶ was designed and synthesized. Microarray-based screening led to the identification of four hit sequences 1-4 as FGFR1α ligands, which were further confirmed using both solution-phase and solid-phase binding assays. Western blot results indicated that peptoids 2-4 activated FGFR signaling pathways, resulting in increased levels of p-Akt and p-ERK in different cell lines. Our work discovered novel peptoid ligands as FGFR agonists, shedding new light on FGFR-based drug discovery.

Epidermal Growth Factor Attenuates Delayed Ionizing Radiation-Induced Tissue Damage in Bone Marrow Transplanted Mice

We examined the effect of epidermal growth factor (EGF) treatment in mice that received bone marrow transplantation (BMT) after 11 Gy whole-body irradiation. C57Bl/6 mice were divided into three treatment groups: 0 Gy; 11 Gy ((60)Co, single dose, 0.51 Gy/min) with BMT (5 × 10(6) bone marrow cells isolated from green fluorescent protein syngeneic mice, 3-4 h postirradiation); and 11 Gy with BMT and EGF (2 mg/kg applied subcutaneously 1, 3 and 5 days postirradiation). Survival data were collected. Bone marrow, peripheral blood count and cytokines, gastrointestine and liver parameters and migration of green fluorescent protein-positive cells were evaluated at 63 days postirradiation. Epidermal growth factor increased survival of irradiated animals that received BMT from 10.7 to 85.7% at 180 days postirradiation. In the BMT group, we found changes in differential bone marrow and blood count, plasma cytokine levels, gastrointestinal tissues and liver at 63 days postirradiation. These alterations were completely or in some parameters at least partially restored by epidermal growth factor. These findings indicate that epidermal growth factor, administered 1, 3 and 5 days postirradiation in combination with bone marrow transplantation, significantly improves long-term prognosis.

High-Dose Radiation-Induced Changes in Murine Small Intestinal Motility: Are the Changes in the Interstitial Cells of Cajal or in the Enteric Nervous System?

Murine small intestinal motility consists of phasic contraction from interstitial cells of Cajal (ICC) and migrating motor complexes (MMCs) from the enteric nervous system. The number of ICC is reduced in various gastrointestinal disorders, and this effect can be reversed once the disorder is resolved through cellular and tissue remodelling. Exposure to high-dose radiation can induce inflammation and alter intestinal motility. In this study, we investigated the changes in the small intestinal motility of 8- to 10-week-old male C3H/HeN mice after high-dose (13 Gy) irradiation. The aim of this study was to determine whether those changes are caused by changes in the ICC or enteric nervous system. After irradiation, the small intestine was dissected and stored in oxygenated Krebs-Ringer bicarbonate solution. The tension of contractions and intracellular membrane potentials were recorded at day 0, 1, 3 and 5 after irradiation and compared with those of sham-irradiated mice. Histological evaluation was performed by immunohistochemistry and apoptosis was evaluated. Quantitative real-time polymerase chain reaction (qPCR) for c-kit mRNA was also performed. Phasic contractions were not changed at day 0, 1, 3 and 5 after irradiation and did not significantly differ from those in the control mice. Slow waves were also sustained after irradiation. However, the frequency of migrating motor complexes (MMCs) was significantly higher at day 0 and 1 after exposure and the amplitude and area under the curve were significantly lower at day 3 after exposure compared with control mice. MMCs were recovered at day 5 with no difference from those of the control mice. ICC were detected after irradiation by immunohistochemistry for c-kit, and c-kit mRNA levels did not differ between sham-irradiated and irradiated mice. Histological evaluation showed that the most severe inflammation was detected at day 3 after irradiation, and apoptosis was detected only in the mucosa. Acetylcholine increased the contractility after irradiation, and tetrodotoxin decreased the number of MMCs in sham-irradiated and irradiated mice. N(w)-oxide-l-arginine (L-NA) increased the number of MMCs. MMCs were recovered after L-NA treatment at day 3 after irradiation. Sodium nitroprusside decreased the MMCs in sham-irradiated and irradiated mice. Exposure to high-dose radiation did not alter phasic contractions and slow waves in the small intestine of mice, which suggests that ICC and their functions may be sustained after high-dose irradiation. Mucosal inflammation was severe after irradiation and there were some changes in MMCs related to the enteric nervous system.

Basic Fibroblast Growth Factor Ameliorates Endothelial Dysfunction in Radiation-Induced Bladder Injury

This study was designed to explore the effect of basic fibroblast growth factor (bFGF) on radiation-induced endothelial dysfunction and histological changes in the urinary bladder. bFGF was administrated to human umbilical vein cells (HUVEC) or urinary bladder immediately after radiation. Reduced expression of thrombomodulin (TM) was indicated in the HUVEC and urinary bladder after treatment with radiation. Decreased apoptosis was observed in HUVEC treated with bFGF. Administration of bFGF increased the expression of TM in HUVEC medium, as well as in the urinary bladder at the early and delayed phases of radiation-induced bladder injury (RIBI). At the early phase, injection of bFGF increased the thickness of urothelium and reduced inflammation within the urinary bladder. At the delayed phase, bFGF was effective in reducing fibrosis within the urinary bladder. Our results indicate that endothelial dysfunction is a prominent feature of RIBI. Administration of bFGF can ameliorate radiation-induced endothelial dysfunction in urinary bladder and preserve bladder histology at early and delayed phases of RIBI.

Attenuation of radiation-induced gastrointestinal damage by epidermal growth factor and bone marrow transplantation in mice

PURPOSE

We examined the effect of epidermal growth factor (EGF) and bone marrow transplantation (BMT) on gastrointestinal damage after high-dose irradiation of mice.

MATERIAL AND METHODS

C57Black/6 mice were used. Two survival experiments were performed (12 and 13 Gy; (60)Co, 0.59-0.57 Gy/min). To evaluate BMT and EGF action, five groups were established - 0 Gy, 13 Gy, 13 Gy + EGF (at 2 mg/kg, first dose 24 h after irradiation and then every 48 h), 13 Gy + BMT (5 × 10(6) cells from green fluorescent protein [GFP] syngenic mice, 4 h after irradiation), and 13 Gy + BMT + EGF. Survival data, blood cell counts, gastrointestine and liver parameters and GFP positive cell migration were measured.

RESULTS

BMT and EGF (three doses, at 2 mg/kg, administered 1, 3 and 5 days after irradiation) significantly increased survival (13 Gy). In blood, progressive cytopenia was observed with BMT, EGF or their combination having no improving effect early after irradiation. In gastrointestinal system, BMT, EGF and their combination attenuated radiation-induced atrophy and increased regeneration during first week after irradiation with the combination being most effective. Signs of systemic inflammatory reaction were observed 30 days after irradiation.

CONCLUSIONS

Our data indicate that BMT together with EGF is a promising strategy in the treatment of high-dose whole-body irradiation damage.

Medical Countermeasures for Radiation Exposure and Related Injuries: Characterization of Medicines, FDA-Approval Status and Inclusion into the Strategic National Stockpile

World events over the past decade have highlighted the threat of nuclear terrorism as well as an urgent need to develop radiation countermeasures for acute radiation exposures and subsequent bodily injuries. An increased probability of radiological or nuclear incidents due to detonation of nuclear weapons by terrorists, sabotage of nuclear facilities, dispersal and exposure to radioactive materials, and accidents provides the basis for such enhanced radiation exposure risks for civilian populations. Although the search for suitable radiation countermeasures for radiation-associated injuries was initiated more than half a century ago, no safe and effective radiation countermeasure for the most severe of these injuries, namely acute radiation syndrome (ARS), has been approved by the United States Food and Drug Administration (FDA). The dearth of FDA-approved radiation countermeasures has prompted intensified research for a new generation of radiation countermeasures. In this communication, the authors have listed and reviewed the status of radiation countermeasures that are currently available for use, or those that might be used for exceptional nuclear/radiological contingencies, plus a limited few medicines that show early promise but still remain experimental in nature and unauthorized for human use by the FDA.

New approaches to radiation protection

Radioprotectors are compounds that protect against radiation injury when given prior to radiation exposure. Mitigators can protect against radiation injury when given after exposure but before symptoms appear. Radioprotectors and mitigators can potentially improve the outcomes of radiotherapy for cancer treatment by allowing higher doses of radiation and/or reduced damage to normal tissues. Such compounds can also potentially counteract the effects of accidental exposure to radiation or deliberate exposure (e.g., nuclear reactor meltdown, dirty bomb, or nuclear bomb explosion); hence they are called radiation countermeasures. Here, we will review the general principles of radiation injury and protection and describe selected examples of radioprotectors/mitigators ranging from small-molecules to proteins to cell-based treatments. We will emphasize agents that are in more advanced stages of development.

Application of human bone marrow-derived mesenchymal stem cells in the treatment of radiation-induced Gastrointestinal syndrome

Nuclear accidents and terrorism present a serious threat for mass casualty. Accidental or intended radiation exposure leads to radiation-induced gastrointestinal (GI) syndrome. However, currently there are no approved medical countermeasures for GI syndrome. Thus, developing novel treatments for GI syndrome is urgent. Mesenchymal stem cells (MSCs) derived from bone marrow are a subset of multipotent adult somatic stem cells that have the ability to undergo self-renewal, proliferation and pluripotent differentiation. MSCs have advantages over other stem cells; they can be easily isolated from patients or donors, readily expanded ex vivo, and they possess reparative and immunomodulatory properties. Moreover, MSCs have been shown to be powerful tools in gene therapy and can be effectively transduced with vectors containing therapeutic genes. Therefore, the therapeutic potential of MSCs has been brought into the spotlight for the clinical treatment of GI syndrome. In this review, we discuss the possible role of MSCs in radiation-induced GI syndrome.

A basic fibroblast growth factor analog for protection and mitigation against acute radiation syndromes

The effects of fibroblast growth factors and their potential as broad-spectrum agents to treat and mitigate radiation injury have been studied extensively over the past two decades. This report shows that a peptide mimetic of basic fibroblast growth factor (FGF-P) protects and mitigates against acute radiation syndromes. FGF-P attenuates both sepsis and bleeding in a radiation-induced bone marrow syndrome model and reduces the severity of gastrointestinal and cutaneous syndromes; it should also mitigate combined injuries. FGF-2 and FGF-P induce little or no deleterious inflammation or vascular leakage, which distinguishes them from most other growth factors, angiogenic factors, and cytokines. Although recombinant FGFs have proven safe in several ongoing clinical trials, they are expensive to synthesize, can only be produced in limited quantity, and have limited shelf life. FGF-P mimics the advantageous features of FGF-2 without these disadvantages. This paper shows that FGF-P not only has the potential to be a potent yet safe broad-spectrum medical countermeasure that mitigates acute radiotoxicity but also holds promise for thermal burns, ischemic wound healing, tissue engineering, and stem-cell regeneration.

Attenuating effects of omega-3 fatty acids (Omegaven) on irradiation-induced intestinal injury in mice

Gastrointestinal injury is a major cause of death following exposure to high levels of irradiation, and no effective treatments are currently available. In this study, we examined the effect of omega-3 fatty acids (Omegaven) on intestinal injury of BALB/c mice induced by irradiation. Intravenously administered 3 days prior to irradiation for 7 consecutive days, Omegaven was shown to improve survival, intestinal morphology including villous height, crypt height and mucosal thickness and the intestinal proliferation compared with saline control. Omegaven also normalized the levels of circulating tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), attenuated the increase of diamino oxidase (DAO) activity and malondialdehyde (MDA) level and recovered the decrease of superoxide dismutase (SOD) activity. Meanwhile, Omegaven attenuated the myelosuppression caused by irradiation. In conclusion, our results suggest that Omegaven enhanced the survival of irradiated mice and minimized the effects of radiation on gastrointestinal injury.

Strategies for optimizing the response of cancer and normal tissues to radiation

Approximately 50% of all patients with cancer receive radiation therapy at some point during the course of their treatment, and the majority of these patients are treated with curative intent. Despite recent advances in the planning of radiation treatment and the delivery of image-guided radiation therapy, acute toxicity and potential long-term side effects often limit the ability to deliver a sufficient dose of radiation to control tumours locally. In the past two decades, a better understanding of the hallmarks of cancer and the discovery of specific signalling pathways by which cells respond to radiation have provided new opportunities to design molecularly targeted therapies to increase the therapeutic window of radiation therapy. Here, we review efforts to develop approaches that could improve outcomes with radiation therapy by increasing the probability of tumour cure or by decreasing normal tissue toxicity.

Sodium orthovanadate (vanadate), a potent mitigator of radiation-induced damage to the hematopoietic system in mice

Previous in vitro and in vivo studies have shown that sodium orthovanadate (vanadate), an inorganic vanadium compound, could effectively suppress radiation-induced p53-mediated apoptosis via both transcription-dependent and transcription-independent pathways. As a potent radiation protector administered at a dose of 20 mg/kg body weight (20 mg/kg) prior to total body irradiation (TBI) by intra-peritoneal (ip) injection, it completely protected mice from hematopoietic syndrome and partially from gastrointestinal syndrome. In the present study, radiation mitigation effects from vanadate were investigated by ip injection of vanadate after TBI in mice. Results showed that a single administration of vanadate at a dose of 20 mg/kg markedly improved the 30-day survival rate and the peripheral blood hemogram, relieved bone marrow aplasia and decreased occurrence of the bone marrow micronucleated erythrocytes in the surviving animals. The dose reduction factor was 1.2 when a single dose of 20 mg/kg was administered 15 min after TBI in mice using the 30-day survival test as the endpoint. Results also showed that either doubling the vanadate dose (40 mg/kg) in a single administration or continuing the vanadate treatment (after a single administration at 20 mg/kg) from the following day at a dose of 5 mg/kg per day for 4 consecutive days further significantly improved the efficacy for rescuing bone marrow failure in the 30-day survival test. Taken together, these findings indicate that vanadate would be a potent mitigator suppressing the acute lethality (hematopoietic syndrome) and minimizing the detrimental effects (anhematopoiesis and delayed genotoxic effects) induced by TBI in mice.

In vitro and in vivo protective effects of granulocyte colony-stimulating factor against radiation-induced intestinal injury

Intestinal injury is a major cause of death after high-dose radiation exposure. The use of granulocyte-colony stimulating factor (G-CSF) to treat radiation injury has focused on enhancing recovery from hematopoietic radiation syndrome. We evaluated G-CSF for its ability to protect against radiation-induced intestinal injury in rat intestinal epithelial cells (IEC-6) and BALB/c mouse models. For in vitro tests, pre-radiation addition of G-CSF to IEC-6 prevented cytotoxicity and the loss of cell viability. Pre-radiation G-CSF treatment also reduced radiation-induced cleavage of caspase-3 and p53 in IEC-6. For in vivo tests, examination 12 h after abdominal irradiation showed that G-CSF-treated mice were protected against apoptosis of the jejunal crypts. G-CSF-treated mice also showed attenuated intestinal morphological changes 3.5 days after abdominal radiation (10 Gy). G-CSF also reduced the levels of proinflammatory cytokines interleukin-6 and tumor necrosis factor-α after radiation. This study showed that G-CSF may protect against radiation-induced intestinal damage through its anti-apoptotic and anti-inflammatory effects. These results suggest that G-CSF is promising candidate for protection against intestinal mucosal injury following irradiation.

FGF2 mediates DNA repair in epidermoid carcinoma cells exposed to ionizing radiation

Purpose

Fibroblast growth factor 2 (FGF2) is a well-known survival factor. However, its role in DNA repair is poorly documented. The present study was designed to investigate in epidermoid carcinoma cells the potential role of FGF2 in DNA repair.

Materials and methods

The side population (SP) with cancer stem cell-like properties and the main population (MP) were isolated from human A431 squamous carcinoma cells. Radiation-induced DNA damage and repair were assessed using the alkaline comet assay. FGF2 expression was quantified by enzyme linked immunosorbent assay (ELISA).

Results

SP cells exhibited rapid repair of radiation induced DNA damage and a high constitutive level of nuclear FGF2. Blocking FGF2 signaling abrogated the rapid DNA repair. In contrast, in MP cells, a slower repair of damage was associated with low basal expression of FGF2. Moreover, the addition of exogenous FGF2 accelerated DNA repair in MP cells. When irradiated, SP cells secreted FGF2, whereas MP cells did not.

Conclusions

FGF2 was found to mediate DNA repair in epidermoid carcinoma cells. We postulate that carcinoma stem cells would be intrinsically primed to rapidly repair DNA damage by a high constitutive level of nuclear FGF2. In contrast, the main population with a low FGF2 content exhibits a lower repair rate which can be increased by exogenous FGF2.

Dose-modifying factor for captopril for mitigation of radiation injury to normal lung

Our goal is to develop countermeasures for pulmonary injury following unpredictable events such as radiological terrorism or nuclear accidents. We have previously demonstrated that captopril, an angiotensin converting enzyme (ACE) inhibitor, is more effective than losartan, an angiotensin type-1 receptor blocker, in mitigating radiation-pneumopathy in a relevant rodent model. In the current study we determined the dose modifying factors (DMFs) of captopril for mitigation of parameters of radiation pneumonitis. We used a whole animal model, irradiating 9-10-week-old female rats derived from a Wistar strain (WAG/RijCmcr) with a single dose of irradiation to the thorax of 11, 12, 13, 14 or 15 Gy. Our study develops methodology to measure DMFs for morbidity (survival) as well as physiological endpoints such as lung function, taking into account attrition due to lethal radiation-induced pneumonitis. Captopril delivered in drinking water (140-180 mg/m(2)/day, comparable with that given clinically) and started one week after irradiation has a DMF of 1.07-1.17 for morbidity up to 80 days (survival) and 1.21-1.35 for tachypnea at 42 days (at the peak of pneumonitis) after a single dose of ionizing radiation (X-rays). These encouraging results advance our goals, since DMF measurements are essential for drug labeling and comparison with other mitigators.

Attenuating effects of granulocyte-colony stimulating factor (G-CSF) in radiation induced intestinal injury in mice

Gastrointestinal injury is a major cause of death following exposure to high levels of radiation, and no effective treatments are currently available. In this study, we examined the capacity of granulocyte colony-stimulating factor (G-CSF) to mitigate intestinal injury in, and improve survival of, C3H/HeN mice given a lethal dose (12 Gy) of radiation to the abdomen. G-CSF (100 μg/kg body weight) was injected subcutaneously daily for 3 days after irradiation and shown to improve survival and intestinal morphology at 3.5 days compared with saline-injected controls. The morphological features improved by G-CSF included crypt number and depth, villous length, and the length of basal lamina of 10 enterocytes. G-CSF also normalized the levels of circulating tumor necrosis factor alpha and attenuated the loss of peripheral neutrophils, caused by radiation-induced myelosuppression. In conclusion, our results suggest that G-CSF enhanced the survival of irradiated mice and minimized the effects of radiation on gastrointestinal injury.

The usefulness of basic fibroblast growth factor for radiation-exposed tissue

A high dose of ionizing external radiation damage to the skin and soft tissue results in changes in function as well as in the general body condition. Once radiation surpasses the tissue safety or survival level, progressive alteration in the damaged tissue results in tissue loss and then flap loss. Local expression and action of stem cells or local growth factors in the irradiated tissue is mitigated, and external administration is sought to investigate the possibility of skin and soft tissue survival after an elevating flap. Basic fibroblast growth factor (bFGF) is primarily considered as a potent angiogenic growth factor. In burns, resurfacing with a dermal component is required, and bFGF stimulates wound healing and enhances human skin-derived mesenchymal stem cells under serum-free conditions in a dose-dependent manner. Thirty-five male, 4- to 8-week-old CLAWN miniature pigs received radiation exposure to assess the effectiveness of bFGF in terms of the progressive clinical course relevant to human skin and soft tissue. At 2 weeks following 10-Gy irradiation, tissue was preserved in the group receiving subcutaneous placement of a round-type tissue expander and bFGF. The expander plus bFGF group demonstrated significantly greater dermo-epidermal proliferation than the radiation alone, radiation plus bFGF, or expander plus radiation plus vehicle-solution groups, and new blood vessel formation was significantly increased in the expander tissue with bFGF after irradiation (p < 0.01). Electron microscopy revealed that tissue with expander and bFGF maintained more stable skin adnexae with preserved intact epidermis and dermis. Thus, bFGF improved and maintained the tissue viability after immediate irradiation in the skin and soft tissue.

Radiation damage and radioprotectants: new concepts in the era of molecular medicine

Exposure to ionising radiation results in mutagenesis and cell death, and the clinical manifestations depend on the dose and the involved body area. Reducing carcinogenesis in patients treated with radiotherapy, exposed to diagnostic radiation or who are in certain professional groups is mandatory. The prevention or treatment of early and late radiotherapy effects would improve quality of life and increase cancer curability by intensifying therapies. Experimental and clinical data have given rise to new concepts and a large pool of chemical and molecular agents that could be effective in the protection and treatment of radiation damage. To date, amifostine is the only drug recommended as an effective radioprotectant. This review identifies five distinct types of radiation damage (I, cellular depletion; II, reactive gene activation; III, tissue disorganisation; IV, stochastic effects; V, bystander effects) and classifies the radioprotective agents into five relevant categories (A, protectants against all types of radiation effects; B, death pathway modulators; C, blockers of inflammation, chemotaxis and autocrine/paracrine pathways; D, antimutagenic keepers of genomic integrity; E, agents that block bystander effects). The necessity of establishing and funding central committees that guide systematic clinical research into evaluating the novel agents revealed in the era of molecular medicine is stressed.

TLR9 agonist protects mice from radiation-induced gastrointestinal syndrome

Purpose

Radiation-induced gastrointestinal syndrome (RIGS) is due to the clonogenic loss of crypt cells and villi depopulation, resulting in disruption of mucosal barrier, bacterial invasion, inflammation and sepsis. Intestinal macrophages could recognize invading bacterial DNA via TLR9 receptors and transmit regenerative signals to the neighboring crypt. We therefore investigated whether systemic administration of designer TLR9 agonist could ameliorate RIGS by activating TLR9.

Methods and Materials

Male C57Bl6 mice were distributed in four experimental cohorts, whole body irradiation (WBI) (8.4–10.4 Gy), TLR9 agonist (1 mg/kg s.c.), 1 h pre- or post-WBI and TLR9 agonist+WBI+iMyd88 (pretreatment with inhibitory peptide against Myd88). Animals were observed for survival and intestine was harvested for histological analysis. BALB/c mice with CT26 colon tumors in abdominal wall were irradiated with 14 Gy single dose of whole abdominal irradiation (AIR) for tumor growth study.

Results

Mice receiving pre-WBI TLR9 agonist demonstrated improvement of survival after 10.4 Gy (p<0.03), 9.4 Gy (p<0.008) and 8.4 Gy (p<0.002) of WBI, compared to untreated or iMyd88-treated controls. Post-WBI TLR9 agonist mitigates up to 8.4 Gy WBI (p<0.01). Histological analysis and xylose absorption test demonstrated significant structural and functional restitution of the intestine in WBI+TLR9 agonist cohorts. Although, AIR reduced tumor growth, all animals died within 12 days from RIGS. TLR9 agonist improved the survival of mice beyond 28 days post-AIR (p<0.008) with significant reduction of tumor growth (p<0.0001).

Conclusions

TLR9 agonist treatment could serve both as a prophylactic or mitigating agent against acute radiation syndrome and also as an adjuvant therapy to increase the therapeutic ratio of abdominal Radiation Therapy for Gastro Intestinal malignancies.

p21 protects "Super p53" mice from the radiation-induced gastrointestinal syndrome

Exposure of the gastrointestinal (GI) tract to high doses of radiation can lead to lethality from the GI syndrome. Although the molecular mechanism regulating the GI syndrome remains to be fully defined, we have recently demonstrated that p53 within the GI epithelial cells controls the radiation-induced GI syndrome. Mice lacking p53 in the GI epithelium were sensitized to the GI syndrome, while transgenic mice with one additional copy of p53 called "Super p53" mice were protected from the GI syndrome. Here, we crossed Super p53 mice to p21⁻/⁻ mice that lack the cyclin-dependent kinase inhibitor p21. Super p53; p21⁻/⁻ mice were sensitized to the GI syndrome compared to Super p53 mice that retain one p21 allele. In addition, mice lacking p21 were not protected from the GI syndrome with one extra copy of p53. These results suggest that p21 protects Super p53 mice from the GI syndrome.