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

Mitigation of Ionizing Radiation-Induced Gastrointestinal Damage by Insulin-Like Growth Factor-1 in Mice

Purpose: Insulin-like growth factor-1 (IGF-1) stimulates epithelial regeneration but may also induce life-threatening hypoglycemia. In our study, we first assessed its safety. Subsequently, we examined the effect of IGF-1 administered in different dose regimens on gastrointestinal damage induced by high doses of gamma radiation.

Material and methods: First, fasting C57BL/6 mice were injected subcutaneously with IGF-1 at a single dose of 0, 0.2, 1, and 2 mg/kg to determine the maximum tolerated dose (MTD). The glycemic effect of MTD (1 mg/kg) was additionally tested in non-fasting animals. Subsequently, a survival experiment was performed. Animals were irradiated (⁶⁰Co; 14, 14.5, or 15 Gy; shielded head), and IGF-1 was administered subcutaneously at 1 mg/kg 1, 24, and 48 h after irradiation. Simultaneously, mice were irradiated (⁶⁰Co; 12, 14, or 15 Gy; shielded head), and IGF-1 was administered subcutaneously under the same regimen. Jejunum and lung damage were assessed 84 h after irradiation. Finally, we evaluated the effect of six different IGF-1 dosage regimens administered subcutaneously on gastrointestinal damage and peripheral blood changes in mice 6 days after irradiation (⁶⁰Co; 12 and 14 Gy; shielded head). The regimens differed in the number of doses (one to five doses) and the onset of administration (starting at 1 [five regimens] or 24 h [one regimen] after irradiation).

Results: MTD was established at 1 mg/kg. MTD mitigated lethality induced by 14 Gy and reduced jejunum and lung damage caused by 12 and 14 Gy. However, different dosing regimens showed different efficacy, with three and four doses (administered 1, 24, and 48 h and 1, 24, 48, and 72 h after irradiation, respectively) being the most effective. The three-dose regimens supported intestinal regeneration even if the administration started at 24 h after irradiation, but its potency decreased.

Conclusion: IGF-1 seems promising in the mitigation of high-dose irradiation damage. However, the selected dosage regimen affects its efficacy.

Screening of radiation gastrointestinal injury biomarkers in rat plasma by high-coverage targeted lipidomics

INTRODUCTION

In the event of radiological accidents and cancer radiotherapies in clinic, the gastrointestinal (GI) system is vulnerable to ionizing radiation and shows GI injury. Accessible biomarkers may provide means to predict, evaluate, and treat GI tissue damage. The current study investigated radiation GI injury biomarkers in rat plasma.

MATERIAL AND METHODS

High-coverage targeted lipidomics was employed to profile lipidome perturbations at 72 h after 0, 1, 2, 3, 5 and 8 Gy (⁶⁰Co γ-rays at 1 Gy/min) total-body irradiation in male rat jejunum. The results were correlated with previous plasma screening outcomes.

RESULTS

In total, 93 differential metabolites and 28 linear dose-responsive metabolites were screened in the jejunum. Moreover, 52 lipid species with significant differences both in jejunum and plasma were obtained. Three lipid species with linear dose-response relationship both in jejunum and plasma were put forth, which exhibited good to excellent sensitivity and specificity in triaging different exposure levels.

DISCUSSION

The linear dose-effect relationship of lipid metabolites in the jejunum and the triage performance of radiation GI injury biomarkers in plasma were studied for the first time.

CONCLUSION

The present study can provide insights into expanded biomarkers of IR-mediated GI injury and minimally invasive assays for evaluation.

Radiotherapy-Induced Digestive Injury: Diagnosis, Treatment and Mechanisms

Radiotherapy is one of the main therapeutic methods for treating cancer. The digestive system consists of the gastrointestinal tract and the accessory organs of digestion (the tongue, salivary glands, pancreas, liver and gallbladder). The digestive system is easily impaired during radiotherapy, especially in thoracic and abdominal radiotherapy. In this review, we introduce the physical classification, basic pathogenesis, clinical characteristics, predictive/diagnostic factors, and possible treatment targets of radiotherapy-induced digestive injury. Radiotherapy-induced digestive injury complies with the dose-volume effect and has a radiation-based organ correlation. Computed tomography (CT), MRI (magnetic resonance imaging), ultrasound (US) and endoscopy can help diagnose and evaluate the radiation-induced lesion level. The latest treatment approaches include improvement in radiotherapy (such as shielding, hydrogel spacers and dose distribution), stem cell transplantation and drug administration. Gut microbiota modulation may become a novel approach to relieving radiogenic gastrointestinal syndrome. Finally, we summarized the possible mechanisms involved in treatment, but they remain varied. Radionuclide-labeled targeting molecules (RLTMs) are promising for more precise radiotherapy. These advances contribute to our understanding of the assessment and treatment of radiation-induced digestive injury.

Mesenchymal Niche-Derived Neuregulin-1 Drives Intestinal Stem Cell Proliferation and Regeneration of Damaged Epithelium

Epidermal growth factor (EGF) maintains intestinal stem cell (ISC) proliferation and is a key component of organoid growth media yet is dispensable for intestinal homeostasis, suggesting roles for multiple EGF family ligands in ISC function. Here, we identified neuregulin 1 (NRG1) as a key EGF family ligand that drives tissue repair following injury. NRG1, but not EGF, is upregulated upon damage and is expressed in mesenchymal stromal cells, macrophages, and Paneth cells. NRG1 deletion reduces proliferation in intestinal crypts and compromises regeneration capacity. NRG1 robustly stimulates proliferation in crypts and induces budding in organoids, in part through elevated and sustained activation of mitogen-activated protein kinase (MAPK) and AKT. Consistently, NRG1 treatment induces a proliferative gene signature and promotes organoid formation from progenitor cells and enhances regeneration following injury. These data suggest mesenchymal-derived NRG1 is a potent mediator of tissue regeneration and may inform the development of therapies for enhancing intestinal repair after injury.

Saving normal tissues - a goal for the ages

Almost since the earliest utilization of ionizing radiation, many within the radiation community have worked toward either preventing (i.e. protecting) normal tissues from unwanted radiation injury or rescuing them from the downstream consequences of exposure. However, despite over a century of such investigations, only incremental gains have been made toward this goal and, with certainty, no outright panacea having been found. In celebration of the 60th anniversary of the International Journal of Radiation Biology and to chronicle the efforts that have been made to date, we undertook a non-rigorous survey of the articles published by normal tissue researchers in this area, using those that have appeared in the aforementioned journal as a road map. Three 'snapshots' of publications on normal tissue countermeasures were taken: the earliest (1959-1963) and most recent (2013-2018) 5-year of issues, as well as a 5-year intermediate span (1987-1991). Limiting the survey solely to articles appearing within International Journal of Radiation Biology likely reduced the number of translational studies interrogated given the basic science tenor of this particular publication. In addition, by taking 'snapshots' rather than considering the entire breadth of the journal's history in this field, important papers that were published during the interim periods were omitted, for which we apologize. Nonetheless, since the journal's inception, we observed that, during the chosen periods, the majority of studies undertaken in the field of normal tissue countermeasures, whether investigating radiation protectants, mitigators or treatments, have focused on agents that interfere with the physical, chemical and/or biological effects known to occur during the acute period following whole body/high single dose exposures. This relatively narrow approach to the reduction of normal tissue effects, especially those that can take months, if not years, to develop, seems to contradict our growing understanding of the progressive complexities of the microenvironmental disruption that follows the initial radiation injury. Given the analytical tools now at our disposal and the enormous benefits that may be reaped in terms of improving patient outcomes, as well as the potential for offering countermeasures to those affected by accidental or mass casualty exposures, it appears time to broaden our approaches to developing normal tissue countermeasures. We have no doubt that the contributors and readership of the International Journal of Radiation Biology will continue to contribute to this effort for the foreseeable future.

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.

Medical countermeasures for unwanted CBRN exposures: part II radiological and nuclear threats with review of recent countermeasure patents

Introduction: The global threat of a chemical, biological, radiological, or nuclear (CBRN) disaster is an important priority for all government agencies involved in domestic security and public health preparedness. Radiological/nuclear (RN) attacks or accidents have become a larger focus of the United States Food and Drug administration (US FDA) over time because of their increased likeliness. Clinical signs and symptoms of a developing acute radiation syndrome (ARS) are grouped into three sub-syndromes named for the dominant organ system affected, namely the hematopoietic (H-ARS), gastrointestinal (GI-ARS), and neurovascular systems. The availability of safe and effective countermeasures against radiological/nuclear threats currently represents a significant unmet medical need.

Areas covered: This article reviews the development of RN threat medical countermeasures and highlights those specific countermeasures that have been recently patented and approved following the FDA Animal Rule. Patents for such agents from 2015 have been presented.

Expert opinion: Two granulocyte colony-stimulating factor (G-CSF)-based radiation countermeasures (Neupogen® (Amgen, Thousand Oaks, CA) and Neulasta® (Amgen, Thousand Oaks, CA)) have recently been approved by the FDA for treatment of H-ARS and both these agents are radiomitigators, used after radiation exposure. To date, there are no FDA-approved radioprotectors for ARS.

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.

The role of gene mutations and gene products in intestinal tissue reactions from ionising radiation

The response of the intestine to (low linear-energy-transfer) ionising radiation is reviewed regarding the cellular basis to the reactions, the regenerative processes which restore the tissue, and external agents which aid its recovery. In the steady-state, it is generally considered that the crypt cell lineages in both small and large intestine are maintained by a small number of stem cells, but there are differences for example in the composition of their niche residence and in the numbers of transit cell generations. Various cell surface markers are now available to indentify particular lineage cell types. Radiation doses up to 1Gy cause apoptotic stem-cell death in particular locations, at higher doses to >6Gy Lgr5⁺ stem cells are required for normal intestinal recovery, and at >8Gy some crypts are sterilised and the probability of animal death from intestinal injury increases with higher doses. Mutations in repair genes, tumour suppressor genes, and survival genes cause various degrees of stem cell and clonogenic cell radiosensitisation. Recent evidence is suggesting much plasticity in the crypt cell lineage, potentially contributing to flexibility in the hierarchical lineage, clonogen number variations and the sensitisation differences. Knockout mice for many different genes have been used to detect their role in both steady state and in irradiated conditions, expected to lead to further insight to the damage and restorative processes. Many different external agents have been used to ameliorate intestinal reactions, including prostaglandins, interleukins, angiogenic and epithelial growth factors, other cytokines, and intraluminal factors.