Morphological aspects of ionizing radiation response of small intestine

Alleviation of radiation combined skin injury in rat model by topical application of ascorbate formulation

PURPOSE

This research endeavor was undertaken to elucidate the impact of an innovative ascorbate formulation on the regeneration process of full-thickness excision wounds in a rat model exposed to whole-body gamma irradiation, replicating conditions akin to combat or radiation emergency scenarios.

MATERIALS AND METHODS

We established a comprehensive rat model by optimizing whole body γ-radiation doses (5-9 Gy) and full-thickness excision wound sizes (1-3 cm2) to mimic radiation combined injury (RCI). The developed RCI model was used to explore the healing potential of ascorbate formulation. The study includes various treatment groups (i.e., sham control, radiation alone, wound alone, radiation + wound, and radiation + wound + formulation). The ascorbate formulation was applied twice daily, with a 12-hour gap between each application, starting 1 hour after the initiation of the wound. The healing potential of the formulation in the RCI context was evaluated over 14 days through hematological, molecular, and histological parameters.

RESULTS

The combination of a 5 Gy radiation dose and a 1 cm2 wound was identified as the optimal setting to develop the RCI model for subsequent studies. The formulation was used topically immediately following RCI, and then twice daily until complete healing. Treatment with the ascorbate formulation yielded noteworthy outcomes and led to a substantial reduction (p < .05) in the wound area, accelerated epithelialization periods, and an increased wound contraction rate. The formulation's localized healing response improved organ weights, normalized blood parameters, and enhanced hematopoietic and immune systems. A gene expression study revealed the treatment up-regulated TGF-β and FGF, and down-regulated PDGF-α, TNF-α, IL-1β, IL-6, MIP-1α, and MCP-1 (p < .05). Histopathological assessments supported the formulation's effectiveness in restoring cellular architecture and promoting tissue regeneration.

CONCLUSION

Topical application of the ascorbate formulation in RCI resulted in a significant improvement in delayed wound healing, leading to accelerated wound closure by mitigating the expression of inflammatory responses.

Radiation enteropathy-related depression: A neglectable course of disease by gut bacterial dysbiosis

Radiation enteropathy (RE) is common in patients treated with radiotherapy for pelvic-abdominal cancers. Accumulating data indicate that gut commensal bacteria determine intestinal radiosensitivity. Radiotherapy can result in gut bacterial dysbiosis. Gut bacterial dysbiosis contributes to the pathogenesis of RE. Mild to moderate depressive symptoms can be observed in patients with RE in clinical settings; however, the rate of these symptoms has not been reported. Studies have demonstrated that gut bacterial dysbiosis induces depression. In the state of comorbidity, RE and depression may be understood as local and abscopal manifestations of gut bacterial disorders. The ability of comorbid depression to worsen inflammatory bowel disease (IBD) has long been demonstrated and is associated with dysfunction of cholinergic neural anti-inflammatory pathways. There is a lack of direct evidence for RE comorbid with depression. It is widely accepted that RE shares similar pathophysiologic mechanisms with IBD. Therefore, we may be able to draw on the findings of the relationship between IBD and depression. This review will explore the relationship between gut bacteria, RE, and depression in light of the available evidence and indicate a method for investigating the mechanisms of RE combined with depression. We will also describe new developments in the treatment of RE with probiotics, prebiotics, and fecal microbial transplantation.

Mitigation of acute radiation syndrome (ARS) with human umbilical cord blood

PURPOSE

The growing concern over potential unintended nuclear accidents or malicious activities involving nuclear/radiological devices cannot be overstated. Exposure to whole-body doses of radiation can result in acute radiation syndrome (ARS), colloquially known as "radiation sickness," which can severely damage various organ systems. Long-term health consequences, such as cancer and cardiovascular disease, can develop many years post-exposure. Identifying effective medical countermeasures and devising a strategic medical plan represents an urgent, unmet need. Various clinical studies have investigated the therapeutic use of umbilical cord blood (UCB) for a range of illnesses, including ARS. The objective of this review is to thoroughly discuss ARS and its sub-syndromes, and to highlight recent findings regarding the use of UCB for radiation injury. UCB, a rich source of stem cells, boasts numerous advantages over other stem cell sources, like bone marrow, owing to its ease of collection and relatively low risk of severe graft-versus-host disease. Preclinical studies suggest that treatment with UCB, and often UCB-derived mesenchymal stromal cells (MSCs), results in improved survival, accelerated hematopoietic recovery, reduced gastrointestinal tract damage, and mitigation of radiation-induced pneumonitis and pulmonary fibrosis. Interestingly, recent evidence suggests that UCB-derived exosomes and their microRNAs (miRNAs) might assist in treating radiation-induced damage, largely by inhibiting fibrotic pathways.

CONCLUSION

UCB holds substantial potential as a radiation countermeasure, and future research should focus on establishing treatment parameters for ARS victims.

X-ray radiation-induced intestinal barrier dysfunction in human epithelial Caco-2 cell monolayers

Radiation therapy and unwanted radiological or nuclear exposure, such as nuclear plant accidents, terrorist attacks, and military conflicts, pose serious health issues to humans. Dysfunction of the intestinal epithelial barrier and the leakage of luminal antigens and bacteria across the barrier have been linked to various human diseases. Intestinal permeability is regulated by intercellular structures, termed tight junctions (TJs), which are disrupted after radiation exposure. In this study, we investigated radiation-induced alterations in TJ-related proteins in an intestinal epithelial cell model. Caco-2 cells were irradiated with 2, 5, and 10 Gy and harvested 1 and 24 h after X-ray exposure. The trypan blue assay revealed that cell viability was reduced in a dose-dependent manner 24 h after X-ray exposure compared to that of non-irradiated cells. However, the WST-8 assay revealed that cell proliferation was significantly reduced only 24 h after radiation exposure to 10 Gy compared to that of non-irradiated cells. In addition, a decreased growth rate and increased doubling time were observed in cells irradiated with X-rays. Intestinal permeability was significantly increased, and transepithelial electrical resistance values were remarkably reduced in Caco-2 cell monolayers irradiated with X-rays compared to non-irradiated cells. X-ray irradiation significantly decreased the mRNA and protein levels of ZO-1, occludin, claudin-3, and claudin-4, with ZO-1 and claudin-3 protein levels decreasing in a dose-dependent manner. Overall, the present study reveals that exposure to X-ray induces dysfunction of the human epithelial intestinal barrier and integrity via the downregulation of TJ-related genes, which may be a key factor contributing to intestinal barrier damage and increased intestinal permeability.

The Acute Radiation Syndrome-Mitigator Romiplostim and Secreted Extracellular Vesicles Improved Survival in Mice Acutely Exposed to Myelosuppressive Doses of Ionizing Radiation

In cases of accidental high-dose total-body irradiation (TBI), acute radiation syndrome (ARS) can cause death. We reported that the thrombopoietin receptor agonist romiplostim (RP) has the potential to completely rescue mice exposed to lethal TBI. Extracellular vesicles (EVs) are involved in cell-to-cell communication, and the mechanism of RP action may be related to EVs that reflect the radio-mitigative information. We investigated the radio-mitigative effects of EVs on mice with severe ARS. C57BL/6 mice exposed to lethal TBI were treated with RP, and the EVs were isolated from the serum and intraperitoneally injected into other mice with severe ARS. The 30-day survival rate of lethal TBI mice drastically improved by 50-100% with the administration of EVs in the sera collected weekly from the mice in which radiation damage was alleviated and mortality was avoided by the administration of RP. Four responsive miRNAs, namely, miR-144-5p, miR-3620-5p, miR-6354, and miR-7686-5p showed significant expression changes in an array analysis. In particular, miR-144-5p was expressed only in the EVs of RP-treated TBI mice. Specific EVs may exist in the circulating blood of mice that escaped mortality with an ARS mitigator, and their membrane surface and endogenous molecules may be the key to the survival of mice with severe ARS.

Severity scoring systems for radiation-induced GI injury - Prioritization for use of GI-ARS medical countermeasures

PURPOSE

Severity scoring systems for ionizing radiation-induced gastrointestinal injury have been used in animal radiation models, human studies involving the use of radiation therapy, and radiation accidents. Various radiation exposure scenarios (i.e., total body irradiation, total abdominal irradiation, etc.) have been used to investigate ionizing radiation-induced gastrointestinal injury. These radiation-induced GI severity scoring systems are based on clinical signs and symptoms and gastrointestinal-specific biomarkers (i.e., citrulline, etc.). In addition, the time course for radiation-induced changes in blood citrulline levels were compared across various animal (i.e., mice, minipigs, Rhesus Macaque, etc.) and human model systems.

CONCLUSIONS

A worksheet tool was developed to prioritize individuals with severe life-threatening gastrointestinal acute radiation syndrome, based on the design of the Exposure and Symptom Tool addressing hematopoietic acute radiation syndrome, to rescue individuals from potential gastrointestinal acute radiation syndrome injury. This tool provides a triage diagnostic approach to assist first-responders to assess individuals suspected of showing gastrointestinal acute radiation syndrome severity to guide medical management, hence enhancing medical readiness for managing radiological casualties.

Host antibacterial defense of 6-10 Gy γ-irradiated mice subjected to lentiviral vector-based Gas5 gene therapy

Gut bacteria-associated sepsis is a serious concern in patients with gastrointestinal acute radiation syndrome (GIARS). In our previous studies, all mice exposed to 8 Gy of whole body γ-irradiation (8 Gy GIARS-mice) died by sepsis stemming from bacterial translocation. M1Mϕ located in the bacterial translocation site (i.e., the mesenteric lymph nodes, MLNs) have been characterized as major antibacterial effector cells. However, M2bMϕ, inhibitor cells for M1Mϕ polarization, predominated in the MLNs of these mice. The reduced expression of long noncoding RNA Gas5 was associated with M2bMϕ polarization. In this study, we tried to reduce the mortality rate of 8 Gy GIARS-mice through Gas5 gene transduction using lentivirus (Gas5 lentivirus). After Gas5 lentivirus injection, Gas5 RNA was overexpressed in MLN-F4/80⁺ cells of 8 Gy GIARS-mice, and these cells were identified as non-M2bMϕ. All of the 8 Gy GIARS-mice injected with Gas5 lentivirus survived 30 days or more after irradiation, and bacterial translocation and subsequent sepsis were shown to be minimal in these mice. These results indicate that the antibacterial resistance of 8 Gy GIASR-mice can be restored through the modulation of M2bMϕ located in the bacterial translocation site by Gas5 transduction.

Inactivation of RIP3 kinase sensitizes to 15LOX/PEBP1-mediated ferroptotic death

Ferroptosis and necroptosis are two pro-inflammatory cell death programs contributing to major pathologies and their inhibition has gained attention to treat a wide range of disease states. Necroptosis relies on activation of RIP1 and RIP3 kinases. Ferroptosis is triggered by oxidation of polyunsaturated phosphatidylethanolamines (PUFA-PE) by complexes of 15-Lipoxygenase (15LOX) with phosphatidylethanolamine-binding protein 1 (PEBP1). The latter, also known as RAF kinase inhibitory protein, displays promiscuity towards multiple proteins. In this study we show that RIP3 K51A kinase inactive mice have increased ferroptotic burden and worse outcome after irradiation and brain trauma rescued by anti-ferroptotic compounds Liproxstatin-1 and Ferrostatin 16-86. Given structural homology between RAF and RIP3, we hypothesized that PEBP1 acts as a necroptosis-to-ferroptosis switch interacting with either RIP3 or 15LOX. Using genetic, biochemical, redox lipidomics and computational approaches, we uncovered that PEBP1 complexes with RIP3 and inhibits necroptosis. Elevated expression combined with higher affinity enables 15LOX to pilfer PEBP1 from RIP3, thereby promoting PUFA-PE oxidation and ferroptosis which sensitizes Rip3K51A/K51A kinase-deficient mice to total body irradiation and brain trauma. This newly unearthed PEBP1/15LOX-driven mechanism, along with previously established switch between necroptosis and apoptosis, can serve multiple and diverse cell death regulatory functions across various human disease states.

Platelet glycoprotein Ibα provides radiation protection

BACKGROUND AND PURPOSE

Platelet membrane glycoprotein Ibα (GPIbα), the major ligand-binding subunit of the GPIb-IX-V complex, binds to a number of ligands contributing to hemostasis, thrombosis, and inflammation. Binding to von Willebrand factor (VWF) initiates the process of hemostasis/thrombosis, while binding to the leukocyte receptor Macrophage-1 antigen (Mac-1) has been implicated in modulating the inflammatory response. Thus as GPIbα resides at the nexus of thrombosis and inflammation, we investigated the impact of GPIbα on radiation injury outcomes as this injury triggers both the thrombotic and inflammatory pathways.

MATERIALS AND METHODS

We used wild-type (WT) C57BL/6J mice and a dysfunctional GPIbα mouse model, in which endogenous GPIbα is replaced with a non-functional α-subunit (hIL-4R/Ibα), to determine whether the impairment of platelet GPIbα alters radiation response. Following exposure to 8.5 Gy total body irradiation (TBI), a series of parameters including radiation lethality, platelet-neutrophil/monocyte interactions, neutrophil/monocyte activation, serum cytokine levels and intestinal injury, were compared between the strains.

RESULTS

The lack of functional GPIbα resulted in higher radiation lethality, greater monocyte activation, increased levels of serum pro-inflammatory cytokines, heightened intestinal damage, and a reduction of intestinal neutrophil recovery.

CONCLUSION

These data suggest that loss of platelet GPIbα enhances radiation toxicity and that GPIbα-mediated interactions may play a crucial role in limiting radiation damage. Thus, a mechanistic understanding of the biological impact of GPIbα following TBI could provide crucial insights for improving the safety of radiotherapy and minimizing the deleterious effects of accidental or occupational exposure to high-dose radiation.

Preclinical Risk Evaluation of Normal Tissue Injury With Novel Radiosensitizers

Genotoxic damage induced by radiation triggers a highly coordinated DNA damage response, and molecular inhibitors of key nodes within this complex response network can profoundly enhance the antitumor efficacy of radiation. This is especially true for drugs targeting the catalytic subunit of DNA-dependent protein kinase, which is a core component of the nonhomologous end-joining DNA repair pathway, and ataxia telangiectasia mutated, which coordinates cell cycle arrest, apoptosis, and DNA repair functionalities after radiation exposure. Unlike the more modest in vitro radiosensitizing effects seen with classic sensitizing agents such as cisplatin, 5-fluorouracil, or taxanes, DNA-dependent protein kinase or ataxia telangiectasia mutated inhibitors provide much more robust sensitizing effects in vitro, as might be anticipated from targeting these key DNA repair modulators. However, patients with homozygous inactivating mutations of ataxia telangiectasia mutated or mice with homozygous defects in DNA-dependent protein kinase (severe combined immunodeficiency) have profoundly enhanced acute normal tissue radiation reactions. Therefore, there is significant potential that the combination of small molecule inhibitors of these kinases with radiation could cause similar dose-limiting acute normal tissue toxicities. Similarly, although less understood, inhibition of these DNA repair response pathways could markedly increase the risk of late radiation toxicities. Because these potent radiosensitizers could be highly useful to improve local control of otherwise radiation-resistant tumors, understanding the potential for elevated risks of radiation injury is essential for optimizing therapeutic ratio and developing safe and informative clinical trials. In this review, we will discuss 2 straightforward models to assess the potential for enhanced mucosal toxicity in the oral cavity and small intestine established in our laboratories. We also will discuss similar strategies for evaluating potential drug-radiation interactions with regard to increased risks of debilitating late effects.

Review: Effect of Gut Microbiota and Its Metabolite SCFAs on Radiation-Induced Intestinal Injury

Gut microbiota is regarded as the second human genome and forgotten organ, which is symbiotic with the human host and cannot live and exist alone. The gut microbiota performs multiple physiological functions and plays a pivotal role in host health and intestinal homeostasis. However, the gut microbiota can always be affected by various factors and among them, it is radiotherapy that results in gut microbiota ¹²dysbiosis and it is often embodied in a decrease in the abundance and diversity of gut microbiota, an increase in harmful bacteria and a decrease in beneficial bacteria, thereby affecting many disease states, especially intestine diseases. Furthermore, gut microbiota can produce a variety of metabolites, among which short-chain fatty acids (SCFAs) are one of the most abundant and important metabolites. More importantly, SCFAs can be identified as second messengers to promote signal transduction and affect the occurrence and development of diseases. Radiotherapy can lead to the alterations of SCFAs-producing bacteria and cause changes in SCFAs, which is associated with a variety of diseases such as radiation-induced intestinal injury. However, the specific mechanism of its occurrence is not yet clear. Therefore, this review intends to emphasize the alterations of gut microbiota after radiotherapy and highlight the alterations of SCFAs-producing bacteria and SCFAs to explore the mechanisms of radiation-induced intestinal injury from the perspective of gut microbiota and its metabolite SCFAs.

Acute Radiation Syndrome and the Microbiome: Impact and Review

Study of the human microbiota has been a centuries-long endeavor, but since the inception of the National Institutes of Health (NIH) Human Microbiome Project in 2007, research has greatly expanded, including the space involving radiation injury. As acute radiation syndrome (ARS) is multisystemic, the microbiome niches across all areas of the body may be affected. This review highlights advances in radiation research examining the effect of irradiation on the microbiome and its potential use as a target for medical countermeasures or biodosimetry approaches, or as a medical countermeasure itself. The authors also address animal model considerations for designing studies, and the potential to use the microbiome as a biomarker to assess radiation exposure and predict outcome. Recent research has shown that the microbiome holds enormous potential for mitigation of radiation injury, in the context of both radiotherapy and radiological/nuclear public health emergencies. Gaps still exist, but the field is moving forward with much promise.

Commonalities Between COVID-19 and Radiation Injury

As the multi-systemic components of COVID-19 emerge, parallel etiologies can be drawn between SARS-CoV-2 infection and radiation injuries. While some SARS-CoV-2-infected individuals present as asymptomatic, others exhibit mild symptoms that may include fever, cough, chills, and unusual symptoms like loss of taste and smell and reddening in the extremities (e.g., "COVID toes," suggestive of microvessel damage). Still others alarm healthcare providers with extreme and rapid onset of high-risk indicators of mortality that include acute respiratory distress syndrome (ARDS), multi-organ hypercoagulation, hypoxia and cardiovascular damage. Researchers are quickly refocusing their science to address this enigmatic virus that seems to unveil itself in new ways without discrimination. As investigators begin to identify early markers of disease, identification of common threads with other pathologies may provide some clues. Interestingly, years of research in the field of radiation biology documents the complex multiorgan nature of another disease state that occurs after exposure to high doses of radiation: the acute radiation syndrome (ARS). Inflammation is a key common player in COVID-19 and ARS, and drives the multi-system damage that dramatically alters biological homeostasis. Both conditions initiate a cytokine storm, with similar pro-inflammatory molecules increased and other anti-inflammatory molecules decreased. These changes manifest in a variety of ways, with a demonstrably higher health impact in patients having underlying medical conditions. The potentially dramatic human impact of ARS has guided the science that has identified many biomarkers of radiation exposure, established medical management strategies for ARS, and led to the development of medical countermeasures for use in the event of a radiation public health emergency. These efforts can now be leveraged to help elucidate mechanisms of action of COVID-19 injuries. Furthermore, this intersection between COVID-19 and ARS may point to approaches that could accelerate the discovery of treatments for both.

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.

The protective role of jervine against radiation-induced gastrointestinal toxicity

In this study, we investigated whether jervine (J) could prevent gastrointestinal (GI) side effects of abdominopelvic radiotherapy (RT) in Wistar-Albino female rats. Rats were divided into five groups: control (C), J only (J), J administered at 5 mg/kg/days for 7 days, RT only (RT), J before RT (J + RT), J administered for seven days before RT, J both before and after RT (J + RT + J), and J administered for 7 days before RT and after RT for 3 days. The weights of rats were measured on the 1st, 7th, and 10th days of the study. Rats were sacrificed to obtain tissues from the liver and intestine, which was followed by taking blood samples intracardially. In addition, the tissues were stained with pyruvate dehydrogenase (PDH) immunohistochemically. In our study, J supplementation markedly reduced weight loss, and histopathological, immunohistochemical, biochemical results suggest that J had a protective effect on GI toxicity following RT.

The vanillin derivative VND3207 protects intestine against radiation injury by modulating p53/NOXA signaling pathway and restoring the balance of gut microbiota

The intestine is a highly radiosensitive tissue that is susceptible to structural and functional damage due to systemic as well as localized radiation exposure. Unfortunately, no effective prophylactic or therapeutic agents are available at present to manage radiation-induced intestinal injuries. We observed that the vanillin derivative VND3207 improved the survival of lethally irradiated mice by promoting intestinal regeneration and increasing the number of surviving crypts. Pre-treatment with VND3207 significantly increased the number of Lgr5⁺ intestinal stem cells (ISCs) and their daughter cells, the transient Ki67⁺ proliferating cells. Mechanistically, VND3207 decreased oxidative DNA damage and lipid peroxidation and maintained endogenous antioxidant status by increasing the level of superoxide dismutase and total antioxidant capacity. In addition, VND3207 maintained appropriate levels of activated p53 that triggered cell cycle arrest but were not sufficient to induce NOXA-mediated apoptosis, thus ensuring DNA damage repair in the irradiated small intestinal crypt cells. Furthermore, VND3207 treatment restores the intestinal bacterial flora structures altered by TBI exposure. In conclusion, VND3207 promoted intestinal repair following radiation injury by reducing reactive oxygen species-induced DNA damage and modulating appropriate levels of activated p53 in intestinal epithelial cells.

Gut Microbiomics-A Solution to Unloose the Gordian Knot of Biological Effects of Ionizing Radiation

The Chernobyl and Fukushima nuclear accidents have called forth a growing body of research on their biological aftermaths. A variety of wild organisms, including primates, birds, fish, insects, and worms are being studied in the affected areas, with emerging morphological, physiological, and genetic aberrations ascribed to ionizing radiation. Despite the effort in surveying Chernobyl and Fukushima wildlife, little is known about the microorganisms associated with these radiation-contaminated animals. The microbiota, especially the gut commensal, plays an important role in shaping the metabolic reservoir and immune system of the host, and is sensitive to a wide array of environmental factors, including ionizing radiation. Humans and limited numbers of laboratory species have been the main subjects of microbiome studies, however, a more practical insight on host-gut microbiota dynamics under environmental impact should be explored in natural habitats. In this analysis, we introduced a working model explaining possible mechanisms of ionizing radiation on the gut microbiota, with an evaluation of the gut microbiota as a potential biomarker for exposure to ionizing radiation.

Protective Effect of Melatonin Against Radiotherapy-Induced Small Intestinal Oxidative Stress: Biochemical Evaluation

Background and Objectives: Radiation enteritis is a common side effect after radiotherapy for abdominal and pelvic malignancies. The aim of the present study was to investigate the protective effect of melatonin, known for its free radical scavenging ability, against radiotherapy-induced small intestinal oxidative damage. Materials and Methods: Thirty male Wistar rats were randomly assigned to six groups (5 rats in each) as follows: Group I (control group) rats received neither radiation nor melatonin; group II rats received only 8 Gy single dose of gamma radiation to their abdomen and pelvis regions; group III (administered with only 50 mg/kg melatonin); group IV (administered with only 100 mg/kg melatonin); group V (50 mg/kg melatonin + 8 Gy radiation), group VI (100 mg/kg melatonin + 8 Gy radiation). All rats were sacrificed after 5 days for biochemical assessments of their intestinal tissues. Results: Treatment with melatonin post irradiation significantly reduced malondialdehyde (MDA) levels as well as increased both superoxide dismutase (SOD) and catalase (CAT) activities of the irradiated intestinal tissues. In addition, melatonin administration with different doses pre irradiation led to protection of the tissues. Moreover, the 100 mg/kg dose was more effective compared to 50 mg/kg. Conclusions: The results of our study suggest that melatonin has a potent protective effect against radiotherapy-induced intestinal damage, by decreasing oxidative stress and increasing antioxidant enzymes. We recommend future clinical trials for more insights.

TLR4 Agonist Monophosphoryl Lipid A Alleviated Radiation-Induced Intestinal Injury

The small intestine is one of the most sensitive organs to irradiation injury, and the development of high effective radioprotectants especially with low toxicity for intestinal radiation sickness is urgently needed. Monophosphoryl lipid A (MPLA) was found to be radioprotective in our previous study, while its effect against the intestinal radiation injury remained unknown. In the present study, we firstly determined the intestinal apoptosis after irradiation injury according to the TUNEL assay. Subsequently, we adopted the immunofluorescence technique to assess the expression levels of different biomarkers including Ki67, γ-H2AX, and defensin 1 in vivo. Additionally, the inflammatory cytokines were detected by RT-PCR. Our data indicated that MPLA could protect the intestine from ionizing radiation (IR) damage through activating TLR4 signal pathway and regulating the inflammatory cytokines. This research shed new light on the protective effect of the novel TLR4 agonist MPLA against intestine detriment induced by IR.

Rheinic acid ameliorates radiation-induced acute enteritis in rats through PPAR-γ/NF-κB

BACKGROUND

Acute radiation enteritis (ARE), a common complication of intestinal caused by abdominal and pelvic radiation therapy. Rheinic acid is a major active ingredient derived from Rhubarb. Rhubarb could suppress inflammation, tumor, fibrosis oxidative damage. However, RA as the main active component and extract monomer of Rhubarb, the pharmacological activity and the underlying molecular mechanism on various diseases has not yet been revealed.

OBJECTIVE

To determine the potential role of rheinic acid (RA) in ameliorating inflammation of rats with acute radiation enteritis (ARE), and explore the underlying mechanism.

METHODS

ARE rat model was established by irradiated with single-dose 10 Gy X-rays at a rate of 0.62 Gy/min to the abdomen. The rats were executed after orally administered with Rheinic acid 7 days and used in the subsequent experiments. Body weight, fecal characteristics and bloody of rats were used to assess the disease activity index. Histological analysis of the jejunum and colon were evaluated using H&E staining. The pro-inflammatory cytokines levels were measured by immunohistochemistry and ELISA. The levels of nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione (GSH) were also determined. The mRNA and protein expression were examined by real-time polymerase chain reaction (qRT-PCR) and western blot, respectively.

RESULTS

Rheinic acid promoted intestinal functional recovery, and ameliorated intestinal damage and bloody stool in ARE rats. Rheinic acid strongly decreased the levels of tumor necrosis factor-α, interleukin-1, interleukin-6, NO, and MDA, whereas increased levels of anti-oxidants, SOD and GSH. Moreover, the expression of apoptosis-related proteins, cleaved caspase-3 and cleaved poly (ADP-ribose) polymerase (PARP), were decreased with RA treatment. Further study indicated that PPAR-γ was activated and thereby NF-κB and p38 MAPK signaling pathway were suppressed after rheinic acid treatment.

CONCLUSION

Rheinic acid could ameliorate acute radiation enteritis and the underlying molecular mechanism is, at least partially, through PPAR-γ/NF-κB and p38 MAPK/JNK pathways.

Radiation: a poly-traumatic hit leading to multi-organ injury

The range of radiation threats we face today includes everything from individual radiation exposures to mass casualties resulting from a terrorist incident, and many of these exposure scenarios include the likelihood of additional traumatic injury as well. Radiation injury is defined as an ionizing radiation exposure inducing a series of organ injury within a specified time. Severity of organ injury depends on the radiation dose and the duration of radiation exposure. Organs and cells with high sensitivity to radiation injury are the skin, the hematopoietic system, the gastrointestinal (GI) tract, spermatogenic cells, and the vascular system. In general, acute radiation syndrome (ARS) includes DNA double strand breaks (DSB), hematopoietic syndrome (bone marrow cells and circulatory cells depletion), cutaneous injury, GI death, brain hemorrhage, and splenomegaly within 30 days after radiation exposure. Radiation injury sensitizes target organs and cells resulting in ARS. Among its many effects on tissue integrity at various levels, radiation exposure results in activation of the iNOS/NF-kB/NF-IL6 and p53/Bax pathways; and increases DNA single and double strand breaks, TLR signaling, cytokine concentrations, bacterial infection, cytochrome c release from mitochondria to cytoplasm, and possible PARP-dependent NAD and ATP-pool depletion. These alterations lead to apoptosis and autophagy and, as a result, increased mortality. In this review, we summarize what is known about how radiation exposure leads to the radiation response with time. We also describe current and prospective countermeasures relevant to the treatment and prevention of radiation injury.

Recurrent Intestinal Obstruction after Radiation Therapy: A Case Report and Review of the Literature

Introduction

In patients who have undergone resection for rectal cancer after neoadjuvant radiotherapy, loop ileostomy is commonly performed with few serious complications. In rare cases, if this irradiated small bowel is strictured, reversal of the affected ileostomy can have dire consequences. We present a case of a 62-year-old male with recurrent intestinal obstruction after closure of his loop ileostomy.

Case Report

RC is a 62-year-old male who initially presented with rectal cancer and underwent neoadjuvant chemoradiation prior to a laparoscopic low anterior resection with diverting loop ileostomy. He underwent elective reversal of his ileostomy and developed persistent postoperative obstruction. He underwent resection of the prior reversal site with normal-appearing dilated proximal bowel loops and collapsed distal bowel loops. He again developed an obstructive picture and underwent resection of the prior anastomosis with creation of an ileocolic anastomosis, after which he recovered well postoperatively.

Conclusion

In patients who receive radiation adjuvant therapy for colon cancer, radiation-induced stricture should be considered as a cause of small bowel obstruction postoperative. In the setting of a longstanding ileostomy, evaluation of a defunctionalized distal ileum may be necessary to evaluate potential obstruction from radiation changes.

Mice Lacking RIP3 Kinase are not Protected from Acute Radiation Syndrome

Exposure to high doses of ionizing radiation can cause lethal injury to normal tissue, thus inducing acute radiation syndrome. Acute radiation syndrome is caused by depletion of bone marrow cells (hematopoietic syndrome) and irreparable damage to the epithelial cells in the gastrointestinal tract (gastrointestinal syndrome). Although radiation initiates apoptosis in the hematopoietic and gastrointestinal compartments within the first few hours after exposure, alternative mechanisms of cell death may contribute to injury in these radiosensitive tissues. In this study, we utilized mice lacking a critical regulator of necroptosis, receptor interacting protein 3 (RIP3) kinase, to characterize the role of RIP3 in normal tissue toxicity after irradiation. Our results suggest that RIP3-mediated signaling is not a critical driver of acute radiation syndrome.

Expression of vascular endothelial growth factor and its correlation with clinical symptoms and endoscopic findings in patients with chronic radiation proctitis

AIM

The aim of this study was to assess the expression of vascular endothelial growth factor (VEGF) as a key proangiogenic factor and determine whether there is any correlation between its expression and clinical symptoms or endoscopic changes in patients with chronic radiation proctitis (ChRP).

METHOD

Fifty patients who had all undergone radiotherapy for prostate, cervical or uterine cancer were included in the study (37 women, 13 men). There was a control group of 20 patients (9 women, 11 men). The Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer (RTOG/EORTC) scoring system was used for grading the severity of the proctitis. Endoscopic scoring of late rectal mucosal damage was performed using Gilinsky's classification. Serum levels of VEGF were analysed by the enzyme-linked immunosorbent assay method.

RESULTS

Most patients presented with Grade 1 symptoms. Endoscopic assessment showed that most patients had Grade 1 late rectal mucosal damage. The predominant endoscopic finding was the presence of telangiectasia. Assessment of VEGF correlation between the control group and the degrees of endoscopic changes showed statistically significant differences for all three degrees (P < 0.0001, P = 0.0251 and P = 0.0005, respectively). Due to the small numbers of patients with Grades 2 and 3 symptoms using the RTOG/EORTC scoring system, they were grouped with Grades 1 and 4 respectively forming two groups for statistical purposes. VEGF expression differed significantly between controls and group I and between controls and group II (P = 0.0001, P = 0.0009, respectively).

CONCLUSION

A significant increase in VEGF expression was found to correlate with clinical symptoms and endoscopic rectal mucosa changes in patients with ChRP, suggesting that it may play an important role in pathological angiogenesis.

Antioxidant Supplementation: A Linchpin in Radiation-Induced Enteritis

Radiation enteritis is one of the most feared complications of abdominal and pelvic regions. Thus, radiation to abdominal or pelvic malignancies unavoidably injures the intestine. Because of rapid cell turnover, the intestine is highly sensitive to radiation injury, which is the limiting factor in the permissible dosage of irradiation. Bowel injuries such as fistulas, strictures, and chronic malabsorption are potentially life-threatening complications and have an impact on patient quality of life. The incidence of radiation enteritis is increasing because of the current trend of combined chemotherapy and radiation. The consequences of radiation damage to the intestine may result in considerable morbidity and even mortality. The observed effects of ionizing radiation are mediated mainly by oxygen-free radicals that are generated by its action on water and are involved in several steps of signal transduction cascade, leading to apoptosis. The oxyradicals also induce DNA strand breaks and protein oxidation. An important line of defense against free radical damage is the presence of antioxidants. Therefore, administration of antioxidants may ameliorate the radiation-induced damage to the intestine.

The Circadian Clock Gene BMAL1 Coordinates Intestinal Regeneration

BACKGROUND & AIMS

The gastrointestinal syndrome is an illness of the intestine caused by high levels of radiation. It is characterized by extensive loss of epithelial tissue integrity, which initiates a regenerative response by intestinal stem and precursor cells. The intestine has 24-hour rhythms in many physiological functions that are believed to be outputs of the circadian clock: a molecular system that produces 24-hour rhythms in transcription/translation. Certain gastrointestinal illnesses are worsened when the circadian rhythms are disrupted, but the role of the circadian clock in gastrointestinal regeneration has not been studied.

METHODS

We tested the timing of regeneration in the mouse intestine during the gastrointestinal syndrome. The role of the circadian clock was tested genetically using the BMAL1 loss of function mouse mutant in vivo, and in vitro using intestinal organoid culture.

RESULTS

The proliferation of the intestinal epithelium follows a 24-hour rhythm during the gastrointestinal syndrome. The circadian clock runs in the intestinal epithelium during this pathologic state, and the loss of the core clock gene, BMAL1, disrupts both the circadian clock and rhythmic proliferation. Circadian activity in the intestine involves a rhythmic production of inflammatory cytokines and subsequent rhythmic activation of the JNK stress response pathway.

CONCLUSIONS

Our results show that a circadian rhythm in inflammation and regeneration occurs during the gastrointestinal syndrome. The study and treatment of radiation-induced illnesses, and other gastrointestinal illnesses, should consider 24-hour timing in physiology and pathology.

Exacerbation of Mild Hypoxia on Acute Radiation Syndrome and Subsequent Mortality

Mild hypoxia induced by 20% hemorrhage results in increases in few cytokine concentrations and sclerostin levels in blood, but shows no changes in bone formation, bone marrow cellularity, and gastrointestinal (GI) integrity and no systemic bacterial infection as well as no subsequent mortality. On the other hand, severe hypoxia induced by 40% hemorrhage causes significant increases in most cytokine concentrations, GI injury, lung injury, systemic bacterial infection, cellular ATP reduction and subsequent mortality. The severe hypoxia drastically damages GI and lung morphology, elevates cytokine concentrations in blood and increases inducible nitric oxide synthase (iNOS) expression in cells that is mediated by transcription factors NF-κB/NF-IL6, subsequently producing free radicals that disrupt mitochondria. ATP depletion, p53 phosphorylation, and caspase-3 activation are found, suggesting cell apoptosis. As a result, mortality occurs. However, when mild hypoxia follows ionizing radiation, the mild hypoxia significantly enhances radiation-induced mortality and acute radiation syndrome, including injury of bone marrow, GI, kidney, and lung. The synergism also occurs at the molecular level, resulting in alteration of microRNAs, amplification of iNOS expression, cytokine increases, sepsis, and ATP depletion. This is the first demonstration of synergistic effects between mild hypoxia and ionizing radiation.

Synergistic effect of aluminum and ionizing radiation upon ultrastructure, oxidative stress and apoptotic alterations in Paneth cells of rat intestine

Environmental and occupational exposure to aluminum along with ionizing radiation results in serious health problems. This study was planned to investigate the impact of oxidative stress provoked by exposure to ionizing radiation with aluminum administration upon cellular ultra structure and apoptotic changes in Paneth cells of rat small intestine . Animals received daily aluminum chloride by gastric gavage at a dose 0.5 mg/Kg BW for 4 weeks. Whole body gamma irradiation was applied at a dose 2 Gy/week up to 8 Gy. Ileum malondialdehyde, advanced oxidative protein products, protein carbonyl and tumor necrosis factor-alpha were assessed as biomarkers of lipid peroxidation, protein oxidation and inflammation respectively along with superoxide dismutase, catalase, and glutathione peroxidase activities as enzymatic antioxidants. Moreover, analyses of cell cycle division and apoptotic changes were evaluated by flow cytometry. Intestinal cellular ultra structure was investigated using transmission electron microscope.Oxidative and inflammatory stresses assessment in the ileum of rats revealed that aluminum and ionizing radiation exposures exhibited a significant effect upon the increase in oxidative stress biomarkers along with the inflammatory marker tumor necrosis factor-α accompanied by a significant decreases in the antioxidant enzyme activities. Flow cytometric analyses showed significant alterations in the percentage of cells during cell cycle division phases along with significant increase in apoptotic cells. Ultra structurally, intestinal cellular alterations with marked injury in Paneth cells at the sites of bacterial translocation in the crypt of lumens were recorded. The results of this study have clearly showed that aluminum and ionizing radiation exposures induced apoptosis with oxidative and inflammatory disturbance in the Paneth cells of rat intestine, which appeared to play a major role in the pathogenesis of cellular damage. Furthermore, the interaction of these two intestinal toxic routes was found to be synergistic.

Melatonin attenuates 60 Co γ-ray-induced hematopoietic, immunological and gastrointestinal injuries in C57BL/6 male mice

Protection of hematopoietic, immunological, and gastrointestinal injuries from deleterious effects of ionizing radiation is prime rational for developing radioprotector. The objective of this study, therefore, was to evaluate the radioprotective potential of melatonin against damaging effects of radiation-induced hematopoietic, immunological, and gastrointestinal injuries in mice. C57BL/6 male mice were intraperitoneally administered with melatonin (50-150 mg/kg) 30 min prior to whole-body radiation exposure of 5 and 7.5 Gy using ⁶⁰ Co-teletherapy unit. Thirty-day survival against 7.5 Gy was monitored. Melatonin (100 mg/kg) pretreatment showed 100% survival against 7.5 Gy radiation dose. Melatonin pretreatment expanded femoral HPSCs, and inhibited spleenocyte DNA strands breaks and apoptosis in irradiated mice. At this time, it also protected radiation-induced loss of T cell sub-populations in spleen. In addition, melatonin pretreatment enhanced crypts regeneration and increased villi number and length in irradiated mice. Translocation of gut bacteria to spleen, liver and kidney were controlled in irradiated mice pretreated with melatonin. Radiation-induced gastrointestinal DNA strand breaks, lipid peroxidation, and expression of proapoptotic-p53, Bax, and antiapoptotic-Bcl-xL proteins were reversed in melatonin pretreated mice. This increase of Bcl-xL was associated with the decrease of Bax/Bcl-xL ratio. ABTS and DPPH radical assays revealed that melatonin treatment alleviated total antioxidant capacity in hematopoietic and gastrointestinal tissues. Present study demonstrated that melatonin pretreatment was able to prevent hematopoietic, immunological, and gastrointestinal radiation-induced injury, therefore, overcoming lethality in mice. These results suggest potential of melatonin in developing radioprotector for protection of bone marrow, spleen, and gastrointestine in planned radiation exposure scenarios including radiotherapy. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 501-518, 2017.

Correlation between infectious disease and soil radiation in Japan: an exploratory study using national sentinel surveillance data

We investigated the relationship between epidemics and soil radiation through an exploratory study using sentinel surveillance data (individuals aged <20 years) during the last three epidemic seasons of influenza and norovirus in Japan. We used a spatial analysis method of a geographical information system (GIS). We mapped the epidemic spreading patterns from sentinel incidence rates. We calculated the average soil radiation [dm (μGy/h)] for each sentinel site using data on uranium, thorium, and potassium oxide in the soil and examined the incidence rate in units of 0·01 μGy/h. The correlations between the incidence rate and the average soil radiation were assessed. Epidemic clusters of influenza and norovirus infections were observed in areas with relatively high radiation exposure. A positive correlation was detected between the average incidence rate and radiation dose, at r = 0·61-0·84 (P < 0·01) for influenza infections and r = 0·61-0·72 (P < 0·01) for norovirus infections. An increase in the incidence rate was found between areas with radiation exposure of 0 < dm < 0·01 and 0·15 ⩽ dm < 0·16, at 1·80 [95% confidence interval (CI) 1·47-2·12] times higher for influenza infection and 2·07 (95% CI 1·53-2·61) times higher for norovirus infection. Our results suggest a potential association between decreased immunity and irradiation because of soil radiation. Further studies on immunity in these epidemic-prone areas are desirable.

A Combination of Podophyllotoxin and Rutin Attenuates Radiation Induced Gastrointestinal Injury by Negatively Regulating NF-κB/p53 Signaling in Lethally Irradiated Mice

Development of an effective radio protector to minimise radiation-inflicted damages have largely failed owing to inherent toxicity of most of the agents examined so far. This study is centred towards delivering protection to lethally irradiated mice by pre-administration of a safe formulation G-003M (combination of podophyllotoxin and rutin) majorly through regulation of inflammatory and cell death pathways in mice. Single intramuscular dose of G-003M injected 60 min prior to 9 Gy exposure rescued 89% of whole body lethally irradiated C57BL/6J mice. Studies have revealed reduction in radiation induced reactive oxygen species (ROS), nitric oxide (NO) generation, prostaglandin E2 (PGE2) levels and intestinal apoptosis in G-003M pre-treated mice intestine. Restricted nuclear translocation of redox-sensitive Nuclear factor-κB (NF-κB) and subsequent downregulation of cyclo-oxygenase 2 (COX-2), inducible nitric oxide synthase (iNOS; EC 1.14.13.39) and tumor necrosis factor (TNF-α) levels demonstrated the anti-inflammatory effect that G-003M exerts. Support to early hematopoietic recovery was exhibited through G-003M mediated induction of granulocyte colony stimulating factor (G-CSF) and interleukin (IL-6) levels in lethally irradiated mice. Considerable attenuation in radiation induced morphological damage to the intestinal villi, crypts and mucosal layers was observed in G-003M pre-treated mice. Additionally, our formulation did not reduce the sensitivity of tumor tissue to radiation. Altogether, these results suggest that G-003M ameliorates the deleterious effects of radiation exposure by minimising ROS and NO generation and effectively regulating inflammatory and cell death pathways. Mechanism of protection elucidated in the current study demonstrates that G-003M can be used as a safe and effective radio protective agent in radiotherapy for human application.

An oral HemokineTM, α-methylhydrocinnamate, enhances myeloid and neutrophil recovery following irradiation in vivo

An oral therapeutic which reduces duration of cytopenias and is active following accidental radiation exposures is an unmet need in radiation countermeasures. Alpha methylhydrocinnamate (ST7) prolongs STAT-5 phosphorylation, reduces growth-factor dependency of multi-lineage cell lines, and stimulates erythropoiesis. Here, ST7 and its isomers were studied for their effects on myeloid progenitors and hematopoietic stem cells (HSCs) following radiation, in nonhuman primates, and murine irradiation models. Addition of ST7 or ST7-S increased CFU-GM production by 1.7-fold (p<0.001), reduced neutrophil apoptosis comparable to G-CSF, and enhanced HSC survival post-radiation by 2-fold, (p=0.028). ST7 and ST7-S administered in normal baboons increased ANC and platelet counts by 50-400%. In sub-lethally-irradiated mice, ANC nadir remained >200/mm³ and neutropenia recovered in 6days with ST7 treatment and 18days in controls (p<0.05). In lethally-irradiated mice, marrow pathology at 15days was hypocellular (10% cellularity) in controls, but normal (55-75% cellularity) with complete neutrophil maturation with ST7-S treatment. Following lethal irradiation, ST7, given orally for 4days, reduced mortality, with 30% survival in ST7-animals vs 8% in controls, (p<0.05). Collectively, the studies indicate that ST7 and ST7-S enhance myeloid recovery post-radiation and merit further evaluation to accelerate hematologic recovery in conditions of radiation-related and other marrow hypoplasias.

Rapid disruption of intestinal epithelial tight junction and barrier dysfunction by ionizing radiation in mouse colon in vivo: protection by N-acetyl-l-cysteine

The goals of this study were to evaluate the effects of ionizing radiation on apical junctions in colonic epithelium and mucosal barrier function in mice in vivo. Adult mice were subjected to total body irradiation (4 Gy) with or without N-acetyl-l-cysteine (NAC) feeding for 5 days before irradiation. At 2-24 h postirradiation, the integrity of colonic epithelial tight junctions (TJ), adherens junctions (AJ), and the actin cytoskeleton was assessed by immunofluorescence microscopy and immunoblot analysis of detergent-insoluble fractions for TJ and AJ proteins. The barrier function was evaluated by measuring vascular-to-luminal flux of fluorescein isothiocyanate (FITC)-inulin in vivo and luminal-to-mucosal flux in vitro. Oxidative stress was evaluated by measuring protein thiol oxidation. Confocal microscopy showed that radiation caused redistribution of occludin, zona occludens-1, claudin-3, E-cadherin, and β-catenin, as well as the actin cytoskeleton as early as 2 h postirradiation, and this effect was sustained for at least 24 h. Feeding NAC before irradiation blocked radiation-induced disruption of TJ, AJ, and the actin cytoskeleton. Radiation increased mucosal permeability to inulin in colon, which was blocked by NAC feeding. The level of reduced-protein thiols in colon was depleted by radiation with a concomitant increase in the level of oxidized-protein thiol. NAC feeding blocked the radiation-induced protein thiol oxidation. These data demonstrate that radiation rapidly disrupts TJ, AJ, and the actin cytoskeleton by an oxidative stress-dependent mechanism that can be prevented by NAC feeding.

Investigation of relative metabolic changes in the organs and plasma of rats exposed to X-ray radiation using HR-MAS (1)H NMR and solution (1)H NMR

Excess exposure to ionizing radiation generates reactive oxygen species and increases the cellular inflammatory response by modifying various metabolic pathways. However, an investigation of metabolic perturbations and organ-specific responses based on the amount of radiation during the acute phase has not been conducted. In this study, high-resolution magic-angle-spinning (HR-MAS) NMR and solution NMR-based metabolic profiling were used to investigate dose-dependent metabolic changes in multiple organs and tissues--including the jejunum, spleen, liver, and plasma--of rats exposed to X-ray radiation. The organs, tissues, and blood samples were obtained 24, 48, and 72 h after exposure to low-dose (2 Gy) and high-dose (6 Gy) X-ray radiation and subjected to metabolite profiling and multivariate analyses. The results showed the time course of the metabolic responses, and many significant changes were detected in the high-dose compared with the low-dose group. Metabolites with antioxidant properties showed acute responses in the jejunum and spleen after radiation exposure. The levels of metabolites related to lipid and protein metabolism were decreased in the jejunum. In addition, amino acid levels increased consistently at all post-irradiation time points as a consequence of activated protein breakdown. Consistent with these changes, plasma levels of tricarboxylic acid cycle intermediate metabolites decreased. The liver did not appear to undergo remarkable metabolic changes after radiation exposure. These results may provide insight into the major metabolic perturbations and mechanisms of the biological systems in response to pathophysiological damage caused by X-ray radiation.

Krüppel-Like Factor 5 Promotes Epithelial Proliferation and DNA Damage Repair in the Intestine of Irradiated Mice

BACKGROUND & AIMS: High doses of radiation induce severe DNA damage in intestinal epithelial cells, especially crypt cells, and cause intestinal injury, but the underlying molecular mechanisms remain unclear. Krüppel-like factor 5 (KLF5), a zinc finger-containing transcription factor, is induced by various stress stimuli and is involved in cell proliferation and survival. The role of KLF5 in radiation-induced intestinal injury was investigated here.

METHODS: Wild type mice were treated with 8 or 15 Gy total body irradiation (TBI). KLF5 content and cellular localization in the small intestines of irradiated mice were detected by Western blot and immunohistochemical analysis. Mice with intestinal-specific knockdown of KLF5 (Vil-Cre; Klf5^fl/+ mice) were generated and their response to radiation was compared with controls. Morphological changes were determined by hematoxylin and eosin staining. Proliferation was examined by Ki67 immunostaining. The molecular response of the small intestine after KLF5 knockdown was investigated using microarrays.

RESULTS: KLF5 expression correlated with the progression of intestinal damage. Decreased levels of KLF5 in the gut were associated with increased damage to the intestinal mucosa and reduced epithelial proliferation after TBI. Our microarray data disclosed that KLF5 knockdown down-regulated genes related to DNA damage repair pathways such as nucleotide excision repair, mismatch repair, non-homologous end joining and the Fanconi anemia pathway, which may suggest a novel function of KLF5.

CONCLUSIONS: Our study illustrates that KLF5 may modulate DNA repair pathways to prevent intestinal injury induced by TBI. KLF5 signaling provides a novel field for identification of potential therapeutic targets for the treatment of radiation-induced intestinal damage.

The protective effects of apocynin on ionizing radiation-induced intestinal damage in rats

BACKGROUND AND AIMS

Radiation colitis typically emerges during radiotherapy of intra-abdominal malignancies. While the underlying mechanism remains unclear, it is considered that free oxygen radicals act like cellular mediators to cause colonic damage. Apocynin (APO) prevents oxidative stress and apoptotic cell death by inhibiting NADPH oxidase, and preventing the formation of free oxygen radicals. The aim of the present study was to investigate the protective effect of APO, a strong antioxidant and antiinflammatory agent, on radiation induced colonic oxidative damage in rats.

MATERIALS AND METHODS

Rats were randomly divided into four groups (n = 8/group). Group I (control group); Group II (Group RAD) received a single dose of 800 cGy ionizing radiation to the whole abdomen with a linear accelerator (LINAC); Group III (Group APO) received a single dose of 20 mg/kg of APO intraperitoneally for five days; Group IV (Group APO+RAD) received APO for five days before radiation exposure (similar to Group III), (similar to Group II).

RESULTS

APO treatment prior to radiation led to protection in the biochemical and histopathological parameters.

CONCLUSIONS

Our study shows that APO treatment before radiation improves radiation induced colonic injury in rats, by decreasing oxidative stress and apoptosis.

High-throughput 16S rRNA gene sequencing reveals alterations of mouse intestinal microbiota after radiotherapy

The mammalian gastrointestinal tract harbors a highly complex microbial community that comprises hundreds of different types of bacterial cells. The gastrointestinal microbiota plays an important role in the function of the host intestine. Most cancer patients undergoing pelvic irradiation experience side effects such as diarrhea; however, little is currently known about the effects of irradiation on the microorganisms colonizing the mucosal surfaces of the gastrointestinal tract. The aim of this study was to investigate the effects of gamma irradiation on the compositions of the large and small intestinal microbiotas. The gut microbiotas in control mice and mice receiving irradiation treatment were characterized by high-throughput sequencing of the bacterial 16S rRNA gene. Irradiation treatment induced significant alterations in the bacterial compositions of the large and small intestines at the genus level. Unexpectedly, irradiation treatment increased the number of operational taxonomic units in the small intestine but not the large intestine. In particular, irradiation treatment increased the level of the genera Alistipes in the large intestine and increased the level of the genus Corynebacterium in the small intestine. By contrast, compared with that in the corresponding control group, the level of the genera Prevotella was lower in the irradiated large intestine, and the level of the genera Alistipes was lower in the irradiated small intestine. Overall, the data presented here reveal the potential microbiological effects of pelvic irradiation on the gastrointestinal tracts of cancer patients.

Circulating interleukin-18 as a biomarker of total-body radiation exposure in mice, minipigs, and nonhuman primates (NHP)

We aim to develop a rapid, easy-to-use, inexpensive and accurate radiation dose-assessment assay that tests easily obtained samples (e.g., blood) to triage and track radiological casualties, and to evaluate the radioprotective and therapeutic effects of radiation countermeasures. In the present study, we evaluated the interleukin (IL)-1 family of cytokines, IL-1β, IL-18 and IL-33, as well as their secondary cytokines’ expression and secretion in CD2F1 mouse bone marrow (BM), spleen, thymus and serum in response to γ-radiation from sublethal to lethal doses (5, 7, 8, 9, 10, or 12 Gy) at different time points using the enzyme-linked immune sorbent assay (ELISA), immunoblotting, and cytokine antibody array. Our data identified increases of IL-1β, IL-18, and/or IL-33 in mouse thymus, spleen and BM cells after total-body irradiation (TBI). However, levels of these cytokines varied in different tissues. Interestingly, IL-18 but not IL-1β or IL-33 increased significantly (2.5–24 fold) and stably in mouse serum from day 1 after TBI up to 13 days in a radiation dose-dependent manner. We further confirmed our finding in total-body γ-irradiated nonhuman primates (NHPs) and minipigs, and demonstrated that radiation significantly enhanced IL-18 in serum from NHPs 2–4 days post-irradiation and in minipig plasma 1–3 days post-irradiation. Finally, we compared circulating IL-18 with the well known hematological radiation biomarkers lymphocyte and neutrophil counts in blood of mouse, minipigs and NHPs and demonstrated close correlations between these biomarkers in response to radiation. Our results suggest that the elevated levels of circulating IL-18 after radiation proportionally reflect radiation dose and severity of radiation injury and may be used both as a potential biomarker for triage and also to track casualties after radiological accidents as well as for therapeutic radiation exposure.

Microbiota and radiation-induced bowel toxicity: lessons from inflammatory bowel disease for the radiation oncologist

New gastrointestinal symptoms are frequent after pelvic radiotherapy and can greatly affect the quality of life of cancer survivors. The effect of radiation on the intestinal microbiota, and the clinical implications of a modified microbial balance after radiotherapy are now beginning to emerge. In this Personal View, we show the importance of the microbiota for intestinal homoeostasis, and discuss the similarity between inflammatory bowel disease, which has been extensively researched, and radiation-induced gastrointestinal toxicity. By use of microbiota profiles for risk assessment and manipulation of the intestinal flora for prevention and treatment of radiation, enteropathy could become a reality and would be of substantial relevance to the increasing numbers of long-term cancer survivors.

Acidic polysaccharide of Panax ginseng regulates the mitochondria/caspase-dependent apoptotic pathway in radiation-induced damage to the jejunum in mice

Owing to its susceptibility to radiation, the small intestine of mice is valuable for studying radioprotective effects. When exposed to radiation, intestinal crypt cells immediately go through apoptosis, which impairs swift differentiation necessary for the regeneration of intestinal villi. Our previous studies have elucidated that acidic polysaccharide of Panax ginseng (APG) protects the mouse small intestine from radiation-induced damage by lengthening villi with proliferation and repopulation of crypt cells. In the present study, we identified the molecular mechanism involved. C57BL/6 mice were irradiated with gamma-rays with or without APG and the expression levels of apoptosis-related molecules in the jejunum were investigated using immunohistochemistry. APG pretreatment strongly decreased the radiation-induced apoptosis in the jejunum. It increased the expression levels of anti-apoptotic proteins (Bcl-2 and Bcl-XS/L) and dramatically reduced the expression levels of pro-apoptotic proteins (p53, BAX, cytochrome c and caspase-3). Therefore, APG attenuated the apoptosis through the intrinsic pathway, which is controlled by p53 and Bcl-2 family members. Results presented in this study suggest that APG protects the mouse small intestine from irradiation-induced apoptosis through inhibition of the p53-dependent pathway and the mitochondria/caspase pathway. Thus, APG may be a potential agent for preventing radiation induced injuries in intestinal cells during radio-therapy such as in cancer treatment.

Blockade of TLR3 protects mice from lethal radiation-induced gastrointestinal syndrome

High-dose ionizing radiation induces severe DNA damage in the epithelial stem cells in small intestinal crypts and causes gastrointestinal syndrome (GIS). Although the tumour suppressor p53 is a primary factor inducing death of crypt cells with DNA damage, its essential role in maintaining genome stability means inhibiting p53 to prevent GIS is not a viable strategy. Here we show that the innate immune receptor Toll-like receptor 3 (TLR3) is critical for the pathogenesis of GIS. Tlr3^−/− mice show substantial resistance to GIS owing to significantly reduced radiation-induced crypt cell death. Despite showing reduced crypt cell death, p53-dependent crypt cell death is not impaired in Tlr3^−/− mice. p53-dependent crypt cell death causes leakage of cellular RNA, which induces extensive cell death via TLR3. An inhibitor of TLR3–RNA binding ameliorates GIS by reducing crypt cell death. Thus, we propose blocking TLR3 activation as a novel approach to treat GIS.

Ionizing radiation damages small intestinal crypt cells, including epithelial stem cells and their progeny. Here the authors show that radiation-induced crypt cell death is amplified by the release of cellular RNA from apoptotic epithelial cells, which then triggers pro-apoptotic TLR3 signalling on neighbouring cells.

Effects of β-glucan on colon anastomotic healing in rats given preoperative irradiation

BACKGROUND

Radiation therapy is an essential therapeutic modality in the management of a wide variety of tumors. We aimed to investigate the short-term effects of pelvic irradiation on the healing of colon anastomoses and to determine the potential protective effects of β-glucan in this situation.

MATERIAL AND METHODS

Sixty Wistar albino rats were randomized into three experimental groups: a control group (n = 20), an irradiation (IR) group (n = 20), and an irradiation+β-glucan (IR+β-glucan) group (n = 20). Only segmental colonic resection and anastomosis were performed on the control group. The IR group underwent the same surgical procedure as the control group 5 days after pelvic irradiation. In the IR+β-glucan group, the same procedure was applied as in the IR group after β-glucan administration. The groups were subdivided into subgroups according to the date of euthanasia (third [n = 10] or seventh [n = 10] postoperative [PO] day), and anastomotic colonic segments were resected to evaluate bursting pressures and biochemical and histopathological parameters.

RESULTS

Bursting pressure values were significantly lower in the IR group (p < .001). Malondialdehyde (MDA) levels were significantly higher in the IR group, whereas β-glucan significantly decreased MDA levels on the third PO day (p < .001). Granulation tissue formation scores were significantly lower in the IR+β-glucan group compared with the control group and the IR group (p < .001).

CONCLUSIONS

The results of this study indicate that irradiation has negative effects on the early healing of colon anastomoses. The administration of β-glucan ameliorates these unfavorable effects by altering bursting pressures and biochemical parameters.