Gy Exposure Research Articles

Feasibility of quantification of murine radiation-induced pulmonary fibrosis with microCT imaging.

Mouse models of radiation-induced pulmonary fibrosis (RIPF) are commonly produced to find novel treatments for the condition. However, current models are not always assesed in a clinically-relevant manner. Clinics diagnose and track RIPF through CT scanning rather than observing time-to-death. An established timeline of RIPF lesion development in a murine model is therefore needed. Male C57Bl/6 mice (n=43) were irradiated with a single dose of 20 Gy to the whole thoracic area delivered by an 320 kV X-Rad cabinet irradiator. CT was performed with respitory gating at two week time points and developed images to identify RIPF pathology in vivo. Confirmation of CT findings was performed via histology on the lungs using Mason's trichrome staining. CT images were segmented to quantify fibrosis and lung which are then summed to give total volume. The fibrotic fraction was calculated upto 26 weeks. Significant increases in fibrotic fraction compared to the baseline microCT scans for each individual mouse acquired prior to the 20 Gy exposure are seen beginning at 10-12 weeks. Tidal lung volume was also calculated by subtracting expiration scan volumes from inspiration scan volumes. However the decrease in tidal lung volume over time was not statisitically significant. Computed tomography (CT) imaging was used to quantify the increase in fibrosis over time in our mouse model. However, the results were highly variable among individual mice after irradiation. CT imaging should be used in future studies looking at treatments for RIPF as it allows for measuring the extent of pathology non-invasively in a clinically-relevant manner.

Relations Between Bone Quantity, Microarchitecture, and Collagen Cross-links on Mechanics Following In Vivo Irradiation in Mice.

ABSTRACTHumans are exposed to ionizing radiation via spaceflight or cancer radiotherapy, and exposure from radiotherapy is known to increase risk of skeletal fractures. Although irradiation can reduce trabecular bone mass, alter trabecular microarchitecture, and increase collagen cross‐linking, the relative contributions of these effects to any loss of mechanical integrity remain unclear. To provide insight, while addressing both the monotonic strength and cyclic‐loading fatigue life, we conducted total‐body, acute, gamma‐irradiation experiments on skeletally mature (17‐week‐old) C57BL/6J male mice (n = 84). Mice were administered doses of either 0 Gy (sham), 1 Gy (motivated by cumulative exposures from a Mars mission), or 5 Gy (motivated by clinical therapy regimens) with retrieval of the lumbar vertebrae at either a short‐term (11‐day) or long‐term (12‐week) time point after exposure. Micro‐computed tomography was used to assess trabecular and cortical quantity and architecture, biochemical composition assays were used to assess collagen quality, and mechanical testing was performed to evaluate vertebral compressive strength and fatigue life. At 11 days post‐exposure, 5 Gy irradiation significantly reduced trabecular mass (p < 0.001), altered microarchitecture (eg, connectivity density p < 0.001), and increased collagen cross‐links (p < 0.001). Despite these changes, vertebral strength (p = 0.745) and fatigue life (p = 0.332) remained unaltered. At 12 weeks after 5 Gy exposure, the trends in trabecular bone persisted; in addition, regardless of irradiation, cortical thickness (p < 0.01) and fatigue life (p < 0.01) decreased. These results demonstrate that the highly significant effects of 5 Gy total‐body irradiation on the trabecular bone morphology and collagen cross‐links did not translate into detectable effects on vertebral mechanics. The only mechanical deficits observed were associated with aging. Together, these vertebral results suggest that for spaceflight, irradiation alone will likely not alter failure properties, and for radiotherapy, more investigations that include post‐exposure time as a positive control and testing of both failure modalities are needed to determine the cause of increased fracture risk. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Dose and time dependence of functional impairments in rat jejunum following ionizing radiation exposure.

Ionizing radiation causes dramatic change in the transport and barrier functions of the intestine. The degree of radiation damage rate depends primarily on the absorbed dose and post‐irradiation time. Variety of experimental protocols providing different time points and doses exist, with the lack of a common approach. In this study, to develop a unified convenient experimental scheme, dose and time dependence of barrier and transport properties of rat jejunum following ionizing radiation exposure were examined. Male Wistar rats were exposed to total body X‐ray irradiation (2, 5, or 10 Gy). The control group was subjected to sham irradiation procedure. Samples of rat jejunum were obtained at 24, 48, or 72 h post‐irradiation. Transepithelial resistance, short circuit current (I sc), and paracellular permeability for sodium fluorescein of jejunum samples were measured in an Ussing chamber; a histological examination was also performed. These parameters were significantly disturbed only 72 h after irradiation at a dose of 10 Gy, which was accompanied by loss of crypt and villi, inflammatory infiltrations, and disintegration of enterocytes. This suggests that found experimental point (72 h after 10 Gy exposure) is the most appropriate for future study using rat jejunum as a model.

Quercetin-3-rutinoside protects against gamma radiation inflicted hematopoietic dysfunction by regulating oxidative, inflammatory, and apoptotic mediators in mouse spleen and bone marrow

Radiation-induced hematopoietic dysfunction is one of the most common problems during unplanned radiation exposures and also in cancer patients receiving radiotherapy. Management of the hematopoietic system is necessary to promote survival against radiation. The present study was undertaken to demonstrate the protective potential of Quercetin 3 rutinoside (Q-3-R), against gamma radiation-induced hematopoietic injuries. C57BL/6 male mice exposed either to radiation or pretreated with Q-3-R (10 mg/kg body weight) were checked for hematopoietic protection using hematotoxicity indices, histopathological, and genotoxic evaluations. To elucidate the underlying mechanisms of Q-3-R mediated hematopoietic protection, oxidative/nitrosative stress, inflammatory and apoptotic markers as well as PCNA expression in spleen cross-sections were assessed. Studies revealed Q-3-R pretreatment inhibited radiation-induced ROS in spleen cells and better maintained the total antioxidant levels in serum that were otherwise altered post 7.5 Gy exposure. The NO levels and nitrotyrosine expression were also found inhibited by Q-3-R in the spleen. Differential regulations of Bcl2, Bax and NF-κB with reduced serum TNF-α level indicated anti-apoptotic and anti-inflammatory roles of Q-3-R. Q-3-R attenuated radiation mediated spleen damage by minimizing cell death and promoting proliferation. Restoration of abnormal histopathological changes in bone marrow following Q-3-R administration correlated to reduced apoptosis and altered cell cycle distributions. Chromosomal aberrations were also found reduced in Q-3-R pretreated bone marrow. Q-3-R restored the total leukocyte counts and serum IL-6 levels, further supporting its role in promoting hematopoiesis. These findings suggest that Q-3-R can potentially be used to minimize radiation inflicted hematopoietic toxicities during accidental as well as radiotherapy scenarios.

P1134Cardiac pacemakers and transient electromagnetic interferences during radiotherapy courses: a multicentre, real-time, in-vitro evaluation

Abstract Funding Acknowledgements None Background The effects of high dose oncologic radiotherapy (RT) on cardiac pacemakers (PMs), at even less than 6 MV power, are unpredictable, depending on multiple factors. Normal PM function may be impaired during direct exposure, due to electromagnetic interferences (EMIs). Potentially life-threatening malfunctions may occur, expecially in PM-dependent patients, and both manufacturers and guidelines discourage direct exposure. Purpose To evaluate transient EMI-related PM malfunctions during direct exposure to doses up to 10 Gy during radiotherapy course, 17 wireless-telemetry-enabled PMs with sufficient residual battery charge for the purpose of the study (at least 4 months to elective replacement indicator, E.R.I.) were evaluated in three different centres. Methods All PMs underwent baseline interrogation. Single chamber devices were programmed in the VVI/40 mode while dual or triple chamber devices were programmed in the DDD/40 mode. To avoid the "run-away" phenomenon during exposure rate-adaptive function was disabled. A centering computed tomography was performed to build the corresponding treatment plan and the PMs were blinded randomized to receive either 2, 5 or 10 Gy exposure by a 6 MV linear accelerator in a homemade water phantom (600 Um/min). The effective dose received by the PMs was randomly assessed by an in-vivo dosimetry. During RT course, the devices were observed in a real-time session using manufacturer specific equipment, and PM function (pacing and sensing, programmed parameters) was recorder by a video camera in the bunker throughout the entire radiation exposure. Results During RT course, 13 PMs (76.5%) recorded not clinically relevant minor transient EMIs, and no atrial and/or ventricular oversensing nor base-rate-pacing inhibition were observed. Only 4 PMs (23.5%) reported neither transient malfunction nor minor EMIs, withstanding direct radiation exposure. Transient EMI-related malfunctions were observed regardless of either 2, 5 or 10 Gy exposure. Conclusions Minor, not clinically relevant EMI-related interferences were observed in most of the PMs during direct exposure. Nevertheless, to avoid potentially life-threatening PM malfunctions, magnet application on the PM pocket site or reprogramming are still suggested in PM-dependent (high risk) patients ongoing even low energy RT exposure.

910Noise-related malfunctions in modern ICDs during oncologic radiotherapy: a multicentre, real-time, in-vitro observation

Abstract Funding Acknowledgements None Background Direct photon exposure of implantable cardioverter-defibrillators (ICDs) during radiotherapy is still considered not recommended, or even unsafe, by manufacturers and guidelines. The effects of photon beams on ICDs are unpredictable, depending on multiple factors, and electromagnetic interferences (EMIs) may present during exposure. Purpose To evaluate transient ICD malfunctions by direct exposure to doses up to 10 Gy during low-energy radiotherapy, 36 contemporary wireless-enabled ICDs, with at least 4 months to elective replacement indicator (E.R.I.) were evaluated in a realtime in-vitro session. Methods All ICDs had baseline interrogation. Single chamber devices were programmed in the VVI/40 mode and dual or triple chamber devices were programmed in the DDD/40 mode. Rate response function and antitachycardia therapies were disabled, with the ventricular tachycardia (VT)/ventricular fibrillation (VF) detection windows still working. A centering computed tomography was performed to build the corresponding treatment plan and the ICDs were blinded randomized to receive either 2, 5 or 10 Gy exposure by a low photon-energy linear accelerator (6MV) in a homemade water phantom (600 MU/min). The effective dose received by the ICDs was randomly assessed by an in-vivo dosimetry. During radiotherapy course, the devices were observed in a real-time session using manufacturer specific programmer, and ICD function (pacing, sensing, programmed parameters, detection) was recorder by the video camera in the bunker throughout the entire photon exposure. All ICDs had an interrogation session immediately after exposure. Results During radiotherapy course, almost all ICDs (90.9%) recorded major or minor transient EMIs. On detail, 16 ICDs (44.4%) reported EMI-related atrial and/or ventricular oversensing, with base-rate-pacing inhibition and VT/VF detection. 16 ICDs (44.4%) recorded not clinically relevant minor EMIs, and no detections were observed. Only 4 ICDs (11.2%) reported neither transient malfunction nor minor EMIs, withstanding direct radiation exposure. At immediate post-exposure interrogation, the ICDs that recorded major real-time malfunctions had VT/VF detections stored in the device memory. In none of the ICDs spontaneous changes in parameter settings were reported. EMI-related malfunctions occurred regardless of either 2, 5 or 10 Gy photon beam exposure. Conclusions Transient EMIs were observed in most of the contemporary ICDs. To avoid potentially life-threatening ICD malfunctions such as pacing inhibition or inappropriate shock delivery, magnet application on the pocket site or reprogramming in the asynchronous mode are still suggested in ICD patients ongoing even low energy radiotherapy exposure.

The p53-53BP1-Related Survival of A549 and H1299 Human Lung Cancer Cells after Multifractionated Radiotherapy Demonstrated Different Response to Additional Acute X-ray Exposure.

Radiation therapy is one of the main methods of treating patients with non-small cell lung cancer (NSCLC). However, the resistance of tumor cells to exposure remains the main factor that limits successful therapeutic outcome. To study the molecular/cellular mechanisms of increased resistance of NSCLC to ionizing radiation (IR) exposure, we compared A549 (p53 wild-type) and H1299 (p53-deficient) cells, the two NSCLC cell lines. Using fractionated X-ray irradiation of these cells at a total dose of 60 Gy, we obtained the survived populations and named them A549IR and H1299IR, respectively. Further characterization of these cells showed multiple alterations compared to parental NSCLC cells. The additional 2 Gy exposure led to significant changes in the kinetics of γH2AX and phosphorylated ataxia telangiectasia mutated (pATM) foci numbers in A549IR and H1299IR compared to parental NSCLC cells. Whereas A549, A549IR, and H1299 cells demonstrated clear two-component kinetics of DNA double-strand break (DSB) repair, H1299IR showed slower kinetics of γH2AX foci disappearance with the presence of around 50% of the foci 8 h post-IR. The character of H2AX phosphorylation in these cells was pATM-independent. A decrease of residual γH2AX/53BP1 foci number was observed in both A549IR and H1299IR compared to parental cells post-IR at extra doses of 2, 4, and 6 Gy. This process was accompanied with the changes in the proliferation, cell cycle, apoptosis, and the expression of ATP-binding cassette sub-family G member 2 (ABCG2, also designated as CDw338 and the breast cancer resistance protein (BCRP)) protein. Our study provides strong evidence that different DNA repair mechanisms are activated by multifraction radiotherapy (MFR), as well as single-dose IR, and that the enhanced cellular survival after MFR is reliant on both p53 and 53BP1 signaling along with non-homologous end-joining (NHEJ). Our results are of clinical significance as they can guide the choice of the most effective IR regimen by analyzing the expression status of the p53–53BP1 pathway in tumors and thereby maximize therapeutic benefits for the patients while minimizing collateral damage to normal tissue.

2410Oncologic radiotherapy-induced implantable cardioverter-defibrillator malfunctions: a real-time, in-vitro evaluation

Abstract Background Direct exposure of implantable cardioverter-defibrillators (ICDs) during radiotherapy is still considered not recommended, or even unsafe, by manufacturers and guidelines. The effects of photon beams on ICDs are unpredictable, depending on multiple factors, and malfunctions may occur during exposure. Purpose To evaluate transient ICD malfunctions by direct exposure to doses up to 10 Gy during low-energy radiotherapy, 33 contemporary wireless-enabled ICDs, with at least 4 months to elective replacement indicator (E.R.I.) were evaluated in a realtime in-vitro session. Methods All ICDs had baseline interrogation. Single chamber ICDs were programmed in the VVI/40 mode and dual or triple chamber ICDs were programmed in the DDD/40 mode. Rate response function and antitachycardia therapies were disabled, with the ventricular tachycardia (VT)/ventricular fibrillation (VF) detection windows still active. A centering computed tomography was performed to build the corresponding treatment plan and the ICDs were blinded randomized to receive either 2, 5 or 10 Gy exposure by a low photon-energy linear accelerator (6MV) in a homemade water phantom (600 MU/min). The effective dose received by the ICDs was assessed by an in-vivo dosimetry. During radiotherapy, the devices were observed in a real-time session using manufacturer specific programmer, and ICD function (pacing, sensing, programmed parameters, detection) was recorder by the video camera in the bunker throughout the entire photon exposure. All ICDs had an interrogation session immediately after exposure. Results During radiotherapy course, almost all ICDs (90.9%) recorded major or minor transient electromagnetic interferences. On detail, 13 ICDs (39.4%) reported atrial and/or ventricular oversensing, with base-rate-pacing inhibition and VT/VF detection. 16 ICDs (48.5%) recorded non clinically relevant noise, and no detections were observed. Only 4 ICDs (12.1%) reported neither transient malfunction nor minor noise, withstanding direct radiation exposure. At immediate post-exposure interrogation, the ICDs that recorded major real-time malfunctions had VT/VF detections stored in the device memory. In none of the ICDs spontaneous changes in parameter settings were reported. Malfunctions occurred regardless of either 2, 5 or 10 Gy photon beam exposure. Conclusions Transient electromagnetic interferences were observed in most of the contemporary ICDs during radiotherapy course, regardeless of photon dose. To avoid potentially life-threatening ICD malfunctions such as pacing inhibition or inappropriate shock delivery, magnet application on the pocket site or reprogramming devices in the asynchronous mode are still suggested in ICD patients ongoing even low energy radiotherapy exposure. Acknowledgement/Funding None

P6553Contemporary pacemakers and oncologic radiotherapy courses: a real-time, wireless-enabled observation

Abstract Background The effects of high dose oncologic radiotherapy on cardiac pacemakers (PMs), at even less than 6MV power, are unpredictable, depending on multiple factors. Normal PM function may be impaired during photon exposure, with potentially life-threatening consequences in PM-dependent patients, and, unlike in magnetic resonance imaging setting, both manufacturer statements and guidelines discourage direct exposure. Purpose To evaluate transient PM malfunctions by direct exposure to doses up to 10 Gy during radiotherapy course, actually not recommended or considered even unsafe, 17 wireless-telemetry-enabled PMs obtained after upgrade or extraction of the system, with sufficient residual battery charge for the purpose of the study (at least 1 year to elective replacement indicator, E.R.I.) were evaluated in a real-time in-vitro session. Methods All PMs underwent baseline interrogation. Single chamber devices were programmed in VVI/40 mode while dual or triple chamber devices were programmed in DDD/40 mode. Rate adaptive function was disabled to avoid the “run-away” phenomenon during exposure. A centering computed tomography was performed to build the corresponding treatment plan and the PMs were blinded randomized to receive either 2, 5 or 10 Gy exposure by a low photon-energy linear accelerator (6MV) in a homemade water phantom (600 MU/min). The effective dose received by the PMs was assessed by an in-vivo dosimetry. During radiotherapy course, the devices were observed in a real-time session using manufacturer specific equipment, and PM function (pacing and sensing, programmed parameters) was recorder by a videocamera in the bunker before (5 minutes), throughout, and after (5 minutes) the entire radiation exposure. Results During radiotherapy course, non of the PMs reported spontaneous changes in parameter settings. 13 PMs (76.5%) recorded non clinically relevant minor transient electromagnetic sensing interferences. No atrial and/or ventricular oversensing nor base-rate-pacing inhibition were observed. Only 4 PMs (23.5%) reported neither transient malfunction nor minor noise, withstanding direct radiation exposure. Transient oversensing-related malfunctions were observed regardless of either 2, 5 or 10 Gy exposure. Conclusions Minor, non clinically relevant electromagnetic sensing interferences were observed in most of the PMs during direct exposure. Nevertheless, to avoid potentially life-threatening PM malfunctions, magnet application on the PM pocket site or reprogramming in the asynchronous mode are still suggested in PM-dependent patients ongoing even low energy radiotherapy exposure. Acknowledgement/Funding None

Gamma radiation induces life stage-dependent reprotoxicity in Caenorhabditis elegans via impairment of spermatogenesis

The current study investigated life stage, tissue and cell dependent sensitivity to ionizing radiation of the nematode Caenorhabditis elegans. Results showed that irradiation of post mitotic L4 stage larvae induced no significant effects with respect to mortality, morbidity or reproduction at either acute dose ≤6 Gy (1500 mGy·h−1) or chronic exposure ≤15 Gy (≤100 mGy·h−1). In contrast, chronic exposure from the embryo to the L4-young adult stage caused a dose and dose-rate dependent reprotoxicity with 43% reduction in total brood size at 6.7 Gy (108 mGy·h−1). Systematic irradiation of the different developmental stages showed that the most sensitive life stage was L1 to young L4. Exposure during these stages was associated with dose-rate dependent genotoxic effects, resulting in a 1.8 to 2 fold increase in germ cell apoptosis in larvae subjected to 40 or 100 mGy·h−1, respectively. This was accompanied by a dose-rate dependent reduction in the number of spermatids, which was positively correlated to the reprotoxic effect (0.99, PCC). RNAseq analysis of nematodes irradiated from L1 to L4 stage revealed a significant enrichment of differentially expressed genes related to both male and hermaphrodite reproductive processes. Gene network analysis revealed effects related to down-regulation of genes required for spindle formation and sperm meiosis/maturation, including smz-1, smz-2 and htas-1. Furthermore, the expression of a subset of 28 set-17 regulated Major Sperm Proteins (MSP) required for spermatid production was correlated (R2 0.80) to the reduction in reproduction and the number of spermatids. Collectively these observations corroborate the impairment of spermatogenesis as the major cause of gamma radiation induced life-stage dependent reprotoxic effect.Furthermore, the progeny of irradiated nematodes showed significant embryonal DNA damage that was associated with persistent effect on somatic growth. Unexpectedly, these nematodes maintained much of their reproductive capacity in spite of the reduced growth.

Acute pulmonary and splenic response in an in vivo model of whole-body low-dose X-radiation exposure

Purpose: Diagnostic radiation is an important part of patient care in the Intensive Care Unit; however, there is little data on the acute effects of exposure to these doses. We investigated pulmonary and splenic response 30 minutes, 4 hours or 24 hours after exposure to 2 mGy, 20 mGy, 200 mGy or 4 Gy whole-body X-radiation in a Sprague Dawley rat model.Materials and methods: Lung injury was assessed via respiratory mechanics, pulmonary edema, cellular, and proteinaceous fluid infiltrate and protein expression of oxidative stress markers. The radiation effect on the spleen was determined via proliferation, apoptosis and protein expression of oxidative stress markers.Results: All measurements of the lung did not differ from sham animals except for an increase in catalase after high dose exposure. Stimulated splenocyte proliferation increased after sham and low dose exposure, did not change after 200 mGy exposure and was significantly lower after 4 Gy exposure. The number of apoptotic cells increased 4 hours after 4 Gy exposure. There were fewer apoptotic cells after low dose exposure compared to sham. Both catalase and MnSOD were increased after 4 Gy exposure.Conclusion: There was no measured effect on pulmonary function while there was an impact to the spleen after low and high dose exposure.

‘Stemness’ and ‘senescence’ related escape pathways are dose dependent in lung cancer cells surviving post irradiation

AimsLung cancer is one of the main causes of cancer-related deaths worldwide and radiotherapy is a major treatment of choice. However, radioresistance is a main reason for radiotherapy failure or tumor relapse. Here, we investigated possible mechanisms associated with cancer cell radioresistance. Materials and methodsWe compared two newly derived cell lines, namely A549-IR3 and A549-IR6, which survived repeated (3 or 6 times) 4 Gy exposure of parental A549 lung cancer cell line. DNA repair ability, stemness and senescence were comparatively studied. Key findingsA549-IR3 exhibited higher proliferation ability and radioresistance compared to parental and A549-IR6 cells. Enhanced radioresistance was not accompanied by chemoresistance to cisplatin or docetaxel. DNA repair kinetics (γΗ2ΑΧ expression) were similar in all cell lines. A549-IR3 cells exhibited a significant rise in stem cell markers (CD44, CD133, OCT4, SOX2 and NANOG) whereas A549-IR6 displayed an increased senescent population. SignificanceCancer cells surviving after radiotherapy may follow two different escape pathways: selection for radioresistance resulting in regrowth, and in clinical terms relapse, or above an irradiation threshold, stem-cells die and cancer cells become senescent, leading the tumor to a state of dormancy.

Liquid Chromatography-Mass Spectrometry-Based Metabolomics of Nonhuman Primates after 4 Gy Total Body Radiation Exposure: Global Effects and Targeted Panels.

Rapid assessment of radiation signatures in noninvasive biofluids may aid in assigning proper medical treatments for acute radiation syndrome (ARS) and delegating limited resources after a nuclear disaster. Metabolomic platforms allow for rapid screening of biofluid signatures and show promise in differentiating radiation quality and time postexposure. Here, we use global metabolomics to differentiate temporal effects (1-60 d) found in nonhuman primate (NHP) urine and serum small molecule signatures after a 4 Gy total body irradiation. Random Forests analysis differentially classifies biofluid signatures according to days post 4 Gy exposure. Eight compounds involved in protein metabolism, fatty acid β oxidation, DNA base deamination, and general energy metabolism were identified in each urine and serum sample and validated through tandem MS. The greatest perturbations were seen at 1 d in urine and 1-21 d in serum. Furthermore, we developed a targeted liquid chromatography tandem mass spectrometry (LC-MS/MS) with multiple reaction monitoring (MRM) method to quantify a six compound panel (hypoxanthine, carnitine, acetylcarnitine, proline, taurine, and citrulline) identified in a previous training cohort at 7 d after a 4 Gy exposure. The highest sensitivity and specificity for classifying exposure at 7 d after a 4 Gy exposure included carnitine and acetylcarnitine in urine and taurine, carnitine, and hypoxanthine in serum. Receiver operator characteristic (ROC) curve analysis using combined compounds show excellent sensitivity and specificity in urine (area under the curve [AUC] = 0.99) and serum (AUC = 0.95). These results highlight the utility of MS platforms to differentiate time postexposure and acquire reliable quantitative biomarker panels for classifying exposed individuals.

Effects of a Novel Orally Bioavailable Small Molecule (Imidazolyl Ethanamide Pentandioic Acid) on Acute Radiation Syndrome

IntroductionAcute radiation syndrome (ARS) develops within 24 hours of exposure to ionizing radiation. Leukocyte growth factors have been used to reduce mortality and mitigate the hematopoietic symptoms of ARS. Three subcutaneously applied radiomitigators G-CSF, Peg-G-CSF and GM-CSF have been approved by the FDA as medical countermeasures but few others are under development. Imidazolyl ethanamide pentandioic acid (IEPA, Myelo001) is a novel small molecule for the treatment of ARS. Preclinical and clinical studies have shown that IEPA applied orally or intraperitoneally was effective in reducing hematopoietic symptoms caused by radiation and chemotherapy.ObjectiveTo investigate the effects of IEPA as a radioprotector (prophylactic) and radiomitigator (therapeutic) for ARS and hematopoietic syndrome of ARS (H-ARS).MethodsMultiple oral or intraperitoneal administrations of IEPA (25 or 50 mg/kg doses) and radiation levels of 5.8 Gy (estimated LD25/30) and 6.0 Gy (estimated LD50/30) on mortality, body weight and bone marrow cellularity were assessed in a mouse model. 205 C57BL/6 mice were subdivided into 1 unirradiated group, 6 groups exposed to 5.8 Gy, and 2 groups exposed to 6.0 Gy. Prophylactic treatment (25 or 50 mg/kg) was started 3 days before total-body irradiation, while therapeutic treatment (50 mg/kg) was begun 24 h post exposure. The 6 LD25/30 groups consisted of a vehicle control group (VL; 2), twice daily intraperitoneally administered IEPA (ML; 3), orally twice a day (ML; 4) or once a day (ML; 5), G-CSF positive control subcutaneously administered once a day (GL; 6) or in combination with IEPA (M/GL; 7). The 2 LD50/30 groups consisted of a vehicle control group (VH; 8) and a group administered IEPA orally once a day (MH; 9). The experiments assessed mortality using Kaplan-Meier estimator, body weight and bone marrow cellularity over the course of 30 days with prescheduled sacrifices of subgroups on days 7, 14 and 30.ResultsNo significant benefit of prophylactic and therapeutic treatment on survival in the lower (5.8 Gy) irradiation group was detected. Groups ML; 3 and ML; 4 had a dose reduction factor (DFR) < 1 vs VL; 2 whereas ML; 5, GL; 6 and M/GL; 7 had a DRFs > 1. In the high radiation group (6.0 Gy), the Kaplan-Meier estimator revealed an increase in survival (85 %) after therapy compared to controls (56 %). The dose reduction factor in group MH; 9 compared to the controls (VH; 8) was 1.5. The highest protective effect on body weight was observed in the therapeutic regimen (MH; 9) used for 6.0 Gy exposure, which showed a positive effect on days 15, 21 and 30. Therapeutic IEPA treatment mitigated the impact of radiation on bone marrow cellularity. A pronounced effect on peripheral hematology was neither observed in the prophylactic, therapeutic IEPA nor the positive control G-CSF treated groups.ConclusionsDifferent routes of administration and doses of IEPA in the prophylactic groups did not alter ARS symptoms. However, therapeutic treatment in the LD25/30 setting with IEPA and G-CSF, and the LD50/30 setting with IEPA at a dose of 50 mg/kg showed a reduction in mortality and weight loss compared to the controls. Additionally, IEPA treatment mitigated the impact of radiation on bone marrow cellularity. Analysis of peripheral blood did not reveal significant differences across the treatment groups probably due to no optimal time point analysis. Limitations included the small size of the prophylactically treated groups exposed to a low radiation dose. DisclosuresPleimes:Bayer: Consultancy, Equity Ownership; Myelo Therapeutics: Employment, Equity Ownership. Bunker:Myelo Therapeutics: Other: Contract Research via SNBL USA on behalf and in account of Myelo Therapeutics GmbH; SNBL USA: Employment. Meyer:Myelo Therapeutics GmbH: Consultancy. Czajkowski:Myelo Therapeutics GmbH: Employment.

Analysis of related factors of radiation induced lung injury after radiotherapy in the elderly patients with advance esophageal cancer

Objective To study the related factors of radiation induced lung injury(RILI) after three-dimensional conformal radiotherapy(3D-CRT) in the elderly patients with advance esophageal cancer, thus to provide reference for radiotherapy planning. Methods The clinical data and physical parameters of 72 elderly patients with advance esophageal cancer were analyzed, including gender, age, performance status scoring, smoking history, tumor location, T staging, underlying disease of the lung, radiation dose, the whole lung accepted 5 Gy exposure volume(V5), V10, V15, V20, V25, V30, V40 and mean lung dose(MLD). Results Among 72 patients, 15 cases developed RILI.It was revealed by univariate analysis that there were statistically significant differences in advanced age, underlying disease of the lung, V5, V10, V15, V20, V25, MLD with RILI(χ2=5.098, P=0.026; χ2=3.598, P=0.030; t=3.854, P=0.034; t=4.901, P=0.022, t=4.638, P=0.029, t=5.122, P=0.015, t=3.652, P=0.041, t=5.760, P=0.010). Conclusion It should be payed more attention to factors such as advanced age, underlying disease of the lung, V5, V10, V15, V20, V25 and MLD when elderly patients with advance esophageal cancer patients were treated with 3D-CRT in order to prevent and decrease the risks of RILI. Key words: Esophageal tumor; Radiotherapy, conformal; Lung injury; Aged

Effect of direct and indirect ionizing radiation on lipid bilayer membrane

Liposomes are vesicular structures made of lipids that are formed in aqueous solutions, which can be used as models to study the cell membrane. In the present study the effects of gamma (γ) rays on dipalmitoylphosphatidylcholine (DPPC) liposomes were studied by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, as well as dynamic light scattering (DLS) and viscosity measurements. The DPPC liposomes were exposed to three different doses 40, 80, and 120Gy which emitted from 60Co gamma rays source with a dose rate of 9 kGy/h. The DLS measurements confirmed the monodispersity of all samples. TEM results revealed that there is a change in morphology and size of liposomes, which is in a good agreement with the increase in viscosity measurements. FTIR measurements showed significant changes in the characteristics bands of DPPC liposomes confirming the effect of γ-rays on the main groups such as CH2 bending vibrations and the symmetric and antisymmetric PO2- stretching vibrations at 1090 and 1220 cm-1 respectively. In addition to the shifting of the OH stretching vibrations from 3439 cm-1 to 3453 cm-1due to the 120 Gy exposure. The spectral changes seem to be due to some sort of water loss and molecular conformational changes due to ionization and formation of free radicals which affect the head groups of the DPPC liposomes leading to lipid lateral diffusion enhancing the fusion of small vesicles to form larger structures.

Effects of Continuous Gamma-Ray Exposure In Utero in B6C3F1 Mice on Gestation Day 18 and at 10 Weeks of Age.

Pregnant C57BL/6JJcl mice were exposed to γ rays at low dose rate (20 mGy/day, LDR) or medium dose rate (200 and 400 mGy/day, MDR) from gestation day (GD) 0-18 to total accumulated doses of 360, 3,600 and 7,200 mGy, respectively. An additional group of pregnant mice were acutely exposed to 2 Gy at high dose rate (HDR) of 0.77 Gy/min on GD 11. In experiment 1, fetuses collected via cesarean section on GD 18 were examined for external and skeletal abnormalities. While the results of LDR exposure (20 mGy/day) did not significantly differ from the nonirradiated controls in all parameters examined, MDR (200 and 400 mGy/day) and acute HDR (2 Gy) exposure caused growth retardation and significantly increased incidence of unossified bones. Increased incidence of external abnormalities was observed only in the acute HDR group. In experiment 2, the dams were allowed to give birth and the pups were clinically monitored and weighed periodically until 10 weeks of age when they were sacrificed and subjected to pathological examination. Pups exposed at MDRs of 200 and 400 mGy/dayand at acute HDR of 0.77 Gy/min had lower bodyweights from weaning (3 weeks) to 10 weeks of age except for females exposed to 400 mGy/day MDR. None of the pups exposed to an acute 2 Gy dose on GD 11 survived to 10 weeks of age. Histopathological changes were not significantly different between the nonirradiated control and the 20 mGy/day LDR groups. However, at both MDR exposures of 200 and 400 mGy/day. gonadal (testes and ovary) hypoplasia/atrophy was observed in all the 10-week-old pups. Our results show that in utero LDR exposure to 20 mGy/day for the entire gestation period did not cause any significant effect in pups when compared to the nonirradiated controls up to 10 weeks of age. However, pups exposed in utero to MDRs showed dose-related growth retardation with delayed ossifications (400 mGy/day) and gonadal hypoplasia/atrophy. These findings suggest that increased post-implantation loss in dams exposed at MDR is due to early embryonic deaths resulting in early resorption.

Lipidomic Signatures of Nonhuman Primates with Radiation-Induced Hematopoietic Syndrome

Concern over potential exposures of ionizing radiation (IR) to large populations has emphasized the need for rapid and reliable methods of biodosimetry to determine absorbed dose and required triage. Lipidomics has emerged as a powerful technique for large-scale lipid identification and quantification. Indirect effects from IR exposure generate reactive oxygen species (ROS) through water hydrolysis and may subsequently damage cellular lipids. Thus, rapid identification of specific affected lipid molecules represents possible targets for biodosimetry. The current study addresses temporal changes in the serum lipidome from 4 h to 28 d in nonhuman primates (NHPs) with radiation-induced hematopoietic syndrome (6.5 Gy exposure, LD50/60). Statistical analyses revealed a highly dynamic temporal response in the serum lipidome after IR exposure. Marked lipidomic perturbations occurred within 24 h post-irradiation along with increases in cytokine levels and C-reactive protein. Decreases were observed in di- and triacylglycerides, sphingomyelins (SMs), lysophosphatidylcholines (LysoPCs), and esterified sterols. Conversely, free fatty acids and monoacylglycerides significantly increased. Decreased levels of SMs and increased levels of LysoPCs may be important markers for biodosimetry ~2 d–3 d post-irradiation. The biphasic and dynamic response to the serum lipidome post-irradiation emphasize the importance of determining the temporal long-term response of possible radiation markers.

Distinct Levels of Radioresistance in Lgr5+ Colonic Epithelial Stem Cells versus Lgr5+ Small Intestinal Stem Cells.

Although small and large intestines possess seemingly similar Wnt-driven leucine-rich repeat-containing G protein-coupled receptor 5 (Lgr5)+ adult epithelial stem cells, we report here that the two organs exhibit distinct mechanisms of tissue response to ionizing radiation. Employing Lgr5-lacZ transgenic mice and Lgr5 in situ hybridization, we found colonic epithelial stem cells (CESC) markedly more radioresistant in vivo than small intestinal crypt base columnar stem cells (CBC; D0 = 6.0 ± 0.3 Gy vs. 1.3 ± 0.1, respectively; P < 0.01). Accordingly, CESCs survived 30 Gy exposure, while CBCs were completely depleted after 15 Gy. EdU incorporation studies indicated that after 19 Gy, CBCs exited growth arrest at 12 hours, resuming normal mitotic activity despite 60% of this population displaying residual γH2AX foci, indicative of persistent unrepaired DNA damage. Checkpoint recovery before complete double-strand break (DSB) repair represents the sine qua non of a newly defined potentially lethal pathophysiology termed checkpoint adaptation. In the small intestinal mucosa, checkpoint adaptation resulted in CBCs succumbing to an 8-fold increase in the incidence of highly lethal chromosomal aberrations and mitotic catastrophe by 48 hours postradiation. In contrast, Lgr5+ CESCs displayed delayed checkpoint recovery at 48 hours post-19 Gy, coordinated with complete DSB repair and regeneration of colonic mucosa originating, at least in part, from surviving CESCs. The discovery that small intestinal CBCs succumb to checkpoint adaptation is the first demonstration that this aberrant cell-cycle response may drive mammalian tissue radiosensitivity. Cancer Res; 77(8); 2124-33. ©2017 AACR.

Electroacupuncture Improves Cognitive Function and Hippocampal Neurogenesis after Brain Irradiation.

Cognitive impairments after brain irradiation seriously affect quality of life for patients, and there is currently no effective treatment. In this study using an irradiated rat model, the role of electroacupuncture was investigated for treatment of radiation-induced brain injury. Animals received 10 Gy exposure to the entire brain, and electroacupuncture was administered 3 days before irradiation as well as up to 2 weeks postirradiation. Behavioral tests were performed one month postirradiation, and rats were then sacrificed for histology or molecular studies. Electroacupuncture markedly improved animal performance in the novel place recognition test. In the emotion test, electroacupuncture reduced defecation during the open-field test, and latency to consumption of food in the novelty suppressed feeding test. Brain irradiation inhibited the generation of immature neurons, but did not cause neural stem cell loss. Electroacupuncture partially restored hippocampal neurogenesis. Electroacupuncture decreased the amount of activated microglia and increased resting microglia in the hippocampus after irradiation. In addition, electroacupuncture promoted mRNA and protein expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. In conclusion, electroacupuncture could improve cognitive function and hippocampal neurogenesis after irradiation, and the protective effect of electroacupuncture was associated with the modulation of microglia and upregulation of BDNF in the hippocampus.