Activation of NLRP3 inflammasome in lung epithelial cells triggers radiation-induced lung injury.

BACKGROUND: Radiation-induced lung injury (RILI) is the most common and serious complication of chest radiotherapy. However, reported radioprotective agents usually lead to radiation resistance in tumor cells. The key to solving this problem is to distinguish between the response of tumor cells and normal lung epithelial cells to radiation damage. METHODS: RNA-Seq was used to recognize potential target of alleviating the progression of RILI as well as inhibiting tumor growth. The activation of NLRP3 inflammasome in lung epithelial cells was screened by qRT-PCR, western blotting, immunofluorescence, and ELISA. An in vivo model of RILI and in vitro conditioned culture model were constructed to evaluate the effect of NLRP3/interleukin-1ß on fibroblasts activation. ROS, ATP, and (NADP)+/NADP(H) level in lung epithelial cells was detected to explore the mechanism of NLRP3 inflammasome activation. The lung macrophages of the mice were deleted to evaluate the role of lung epithelial cells in RILI. Moreover, primary cells were extracted to validate the results obtained from cell lines. RESULTS: NLRP3 activation in epithelial cells after radiation depends on glycolysis-related reactive oxygen species accumulation. DPYSL4 is activated and acts as a negative regulator of this process. The NLRP3 inflammasome triggers interleukin-1ß secretion, which directly affects fibroblast activation, proliferation, and migration, eventually leading to lung fibrosis. CONCLUSIONS: Our study suggests that NLRP3 inflammasome activation in lung epithelial cells is essential for radiation-induced lung injury. These data strongly indicate that targeting NLRP3 may be effective in reducing radiation-induced lung injury in clinical settings.

P. aeruginosa augments irradiation injury via 15-lipoxygenase-catalyzed generation of 15-HpETE-PE and induction of theft-ferroptosis.

Total body irradiation (TBI) targets sensitive bone marrow hematopoietic cells and gut epithelial cells, causing their death and inducing a state of immunodeficiency combined with intestinal dysbiosis and nonproductive immune responses. We found enhanced Pseudomonas aeruginosa (PAO1) colonization of the gut leading to host cell death and strikingly decreased survival of irradiated mice. The PAO1-driven pathogenic mechanism includes theft-ferroptosis realized via (a) curbing of the host antiferroptotic system, GSH/GPx4, and (b) employing bacterial 15-lipoxygenase to generate proferroptotic signal - 15-hydroperoxy-arachidonoyl-PE (15-HpETE-PE) - in the intestines of irradiated and PAO1-infected mice. Global redox phospholipidomics of the ileum revealed that lysophospholipids and oxidized phospholipids, particularly oxidized phosphatidylethanolamine (PEox), represented the major factors that contributed to the pathogenic changes induced by total body irradiation and infection by PAO1. A lipoxygenase inhibitor, baicalein, significantly attenuated animal lethality, PAO1 colonization, intestinal epithelial cell death, and generation of ferroptotic PEox signals. Opportunistic PAO1 mechanisms included stimulation of the antiinflammatory lipoxin A4, production and suppression of the proinflammatory hepoxilin A3, and leukotriene B4. Unearthing complex PAO1 pathogenic/virulence mechanisms, including effects on the host anti/proinflammatory responses, lipid metabolism, and ferroptotic cell death, points toward potentially new therapeutic and radiomitigative targets.

Experimental Colitis Enhances Temporal Variations in CX3CR1 Cell Colonization of the Gut and Brain Following Irradiation.

Peripheral monocyte-derived CX3C chemokine receptor 1 positive (CX3CR1+) cells play important roles in tissue homeostasis and gut repopulation. Increasing evidence also supports their role in immune repopulation of the brain parenchyma in response to systemic inflammation. Adoptive bone marrow transfer from CX3CR1 fluorescence reporter mice and high-resolution confocal microscopy was used to assess the time course of CX3CR1+ cell repopulation of steady-state and dextran sodium sulfate (DSS)-inflamed small intestine/colon and the brain over 4 weeks after irradiation. CX3CR1+ cell colonization and morphologic polarization into fully ramified cells occurred more rapidly in the small intestine than in the colon. For both organs, the crypt/mucosa was more densely populated than the serosa/muscularis layer, indicating preferential temporal and spatial occupancy. Repopulation of the brain was delayed compared with that of gut tissue, consistent with the immune privilege of this organ. However, DSS-induced colon injury accelerated the repopulation. Expression analyses confirmed increased chemokine levels and macrophage colonization within the small intestine/colon and the brain by DSS-induced injury. Early increases of transmembrane protein 119 and ionized calcium binding adaptor molecule 1 expression within the brain after colon injury suggest immune-priming effect of brain resident microglia in response to systemic inflammation. These findings identify temporal differences in immune repopulation of the gut and brain in response to inflammation and show that gut inflammation can impact immune responses within the brain.

An Enriched Environment Alters DNA Repair and Inflammatory Responses After Radiation Exposure.

After the Fukushima Daiichi Nuclear Power Plant accident, there is growing concern about radiation-induced carcinogenesis. In addition, living in a long-term shelter or temporary housing due to disasters might cause unpleasant stress, which adversely affects physical and mental health. It's been experimentally demonstrated that "eustress", which is rich and comfortable, has beneficial effects for health using mouse models. In a previous study, mice raised in the enriched environment (EE) has shown effects such as suppression of tumor growth and enhancement of drug sensitivity during cancer treatment. However, it's not yet been evaluated whether EE affects radiation-induced carcinogenesis. Therefore, to evaluate whether EE suppresses a radiation-induced carcinogenesis after radiation exposure, in this study, we assessed the serum leptin levels, radiation-induced DNA damage response and inflammatory response using the mouse model. In brief, serum and tissues were collected and analyzed over time in irradiated mice after manipulating the raising environment during the juvenile or adult stage. To assess the radiation-induced DNA damage response, we performed immunostaining for phosphorylated H2AX which is a marker of DNA double-strand break. Focusing on the polarization of macrophages in the inflammatory reaction that has an important role in carcinogenesis, we performed analysis using tissue immunofluorescence staining and RT-qPCR. Our data confirmed that EE breeding before radiation exposure improved the responsiveness to radiation-induced DNA damage and basal immunity, further suppressing the chronic inflammatory response, and that might lead to a reduction of the risk of radiation-induced carcinogenesis.

Dynamic changes in c-Fos and NF-κB gene expression and Ca, Fe, Cu, Zn and Mg content due to brain injury in irradiated rats.

BACKGROUND: This study aims to investigate the dynamic changes of c-Fos and NF-κB expression, and to evaluate the Ca, Fe, Cu, Zn and Mg content of hippocampal tissues in rat brains injured by 20 Gy of electron beam irradiation. MATERIALS AND METHODS: A single dose of 5 MeV is administered to the whole brains of rats to establish animal model of radiation-induced brain injury (RBI). Hematoxylin and eosin staining is performed to observe the pathological changes in brain microvascular endothelial cells. Quantitative reverse transcription-PCR and western blotting assays are utilized to test c-Fos and NF-κB gene expression levels in brain tissue. Inductively coupled plasma-atomic emission spectrometry is leveraged to detect the Ca, Fe, Cu, Zn and Mg contents of the hippocampi. RESULTS: The c-Fos and NF-κB gene expression levels in protective group are lower than those in the irradiated group after MgSO4 treatment. In the irradiated group, Ca content at several time points and Fe content on days 1, 3 and 7 are higher than those in the blank group. Additionally, in the irradiated group, Cu and Zn contents on days 1, 7, 14 and 60 are less than those in the blank group. CONCLUSION: In RBI model, adding Mg2+ may relieve RBI. The protective mechanisms of Mg2+ in the hippocampi from a variety of brain activity indicators including the c-Fos and NF-κB genes.

Identification of susceptibility loci for light-induced visual impairment in rats.

Bright light exposure in animals results in the selective degeneration of the outer retina, known as "retinal photic injury" (RPI). The susceptibility to RPI differs among rat strains. WKY rats display susceptibility to RPI with extensive retinal degeneration observed in the sagittal eye specimen, whereas LEW strain rats are resistant to it, showing only slight or no degeneration. In the present study, we first established an ethological screening method using the Morris water maze to discern differential susceptibility among the living rats. WKY and LEW were crossed to produce the first filial generation (F1) offspring. Maze-trained individuals were exposed to bright, white light. The screening test results demonstrated that the susceptibility to light-induced visual impairment in rats is a dominant Mendelian susceptibility trait, as F1 rats were susceptible to visual impairment like WKY rats. Therefore, F1 rats were backcrossed with recessive LEW to produce the first backcross offspring (BC1). Subsequent recurrent backcrossing while selecting for the susceptibility, indicated a segregation ratio of ca. 24% in BC1 and BC2 generations, indicating the involvement of two or more genes in the susceptibility. Further, microsatellite analysis of BC1-to-BC4 individuals using microsatellite markers mapped two susceptibility loci on chromosome segments 5q36 and 19q11-q12, named RPI susceptibility (Rpi)1 and Rpi2, respectively. This study provides an insight into mechanisms underlying differential susceptibility, which could help decipher the mechanism underlying the onset/progression of human age-related macular degeneration.

Piceatannol promotes hepatic and renal AMPK/SIRT1/PGC-1α mitochondrial pathway in rats exposed to reserpine or gamma-radiation.

Human exposure to radio-therapeutic doses of gamma rays can produce late effects, which negatively affect cancer patients' quality of life, work prospects, and general health. This study was performed to explore the role of Piceatannol (PIC) in the process of "mitochondrial biogenesis" signaling pathway as possible management of disturbances induced in stressed animal model(s) either by gamma-irradiation (IR) or administration of reserpine (RES); as a mitochondrial complex-I inhibitor. PIC (10 mg/kg BW/day; orally) were given to rats for 7 days, after exposure to an acute dose of γ-radiation (6 Gy), or after a single reserpine injection (1 g/kg BW; sc). Compared to reserpine or γ-radiation, PIC has attenuated hepatic and renal mitochondrial oxidative stress denoted by the significant reduction in the content of lipid peroxides and NO with significant induction of SOD, CAT, GSH-PX, and GR activities. PIC has also significantly alleviated the increase of the inflammatory markers, TNF-α and IL-6 and apoptotic markers, cytochrome c, and caspase-3. The decrease of oxidative stress, inflammation, and apoptotic responses were linked to a significant amelioration in mitochondrial biogenesis demonstrated by the increased expression and proteins' tissue contents of SIRT1/p38-AMPK, PGC-1α signaling pathway. The results are substantiated by the significant amelioration in mitochondrial function verified by the higher levels of ATP content, and complex I activity, besides the improvement of hepatic and renal functions. Additionally, histopathological examinations of hepatic and renal tissues showed that PIC has modulated tissue architecture after reserpine or gamma-radiation-induced tissue damage. Piceatannol improves mitochondrial functions by regulating the oxidant/antioxidant disequilibrium, the inflammatory and apoptotic responses, suggesting its possible use as adjuvant therapy in radio-therapeutic protocols to attenuate hepatic and renal injuries.

Bone Morphogenetic Protein Pathway Antagonism by Grem1 Regulates Epithelial Cell Fate in Intestinal Regeneration.

BACKGROUND & AIMS: In homeostasis, intestinal cell fate is controlled by balanced gradients of morphogen signaling. The bone morphogenetic protein (BMP) pathway has a physiological, prodifferentiation role, predominantly inferred through previous experimental pathway inactivation. Intestinal regeneration is underpinned by dedifferentiation and cell plasticity, but the signaling pathways that regulate this adaptive reprogramming are not well understood. We assessed the BMP signaling landscape and investigated the impact and therapeutic potential of pathway manipulation in homeostasis and regeneration. METHODS: A novel mouse model was generated to assess the effect of the autocrine Bmp4 ligand on individual secretory cell fate. We spatiotemporally mapped BMP signaling in mouse and human regenerating intestine. Transgenic models were used to explore the functional impact of pathway manipulation on stem cell fate and intestinal regeneration. RESULTS: In homeostasis, ligand exposure reduced proliferation, expedited terminal differentiation, abrogated secretory cell survival, and prevented dedifferentiation. After ulceration, physiological attenuation of BMP signaling arose through upregulation of the secreted antagonist Grem1 from topographically distinct populations of fibroblasts. Concomitant expression supported functional compensation after Grem1 deletion from tissue-resident cells. BMP pathway manipulation showed that antagonist-mediated BMP attenuation was obligatory but functionally submaximal, because regeneration was impaired or enhanced by epithelial overexpression of Bmp4 or Grem1, respectively. Mechanistically, Bmp4 abrogated regenerative stem cell reprogramming despite a convergent impact of YAP/TAZ on cell fate in remodeled wounds. CONCLUSIONS: BMP signaling prevents epithelial dedifferentiation, and pathway attenuation through stromal Grem1 upregulation was required for adaptive reprogramming in intestinal regeneration. This intercompartmental antagonism was functionally submaximal, raising the possibility of therapeutic pathway manipulation in inflammatory bowel disease.

Transcriptome of rhesus macaque (Macaca mulatta) exposed to total-body irradiation.

The field of biodosimetry has seen a paradigm shift towards an increased use of molecular phenotyping technologies including omics and miRNA, in addition to conventional cytogenetic techniques. Here, we have used a nonhuman primate (NHP) model to study the impact of gamma-irradiation on alterations in blood-based gene expression. With a goal to delineate radiation induced changes in gene expression, we followed eight NHPs for 60 days after exposure to 6.5 Gy gamma-radiation for survival outcomes. Analysis of differential gene expression in response to radiation exposure yielded 26,944 dysregulated genes that were not significantly impacted by sex. Further analysis showed an increased association of several pathways including IL-3 signaling, ephrin receptor signaling, ErbB signaling, nitric oxide signaling in the cardiovascular system, Wnt/ß-catenin signaling, and inflammasome pathway, which were associated with positive survival outcomes in NHPs after acute exposure to radiation. This study provides novel insights into major pathways and networks involved in radiation-induced injuries that may identify biomarkers for radiation injury.

Integration of metabolomics and transcriptomics reveals convergent pathways driving radiation-induced salivary gland dysfunction.

Radiation therapy for head and neck cancer causes damage to the surrounding salivary glands, resulting in salivary gland hypofunction and xerostomia. Current treatments do not provide lasting restoration of salivary gland function following radiation; therefore, a new mechanistic understanding of the radiation-induced damage response is necessary for identifying therapeutic targets. The purpose of the present study was to investigate the metabolic phenotype of radiation-induced damage in parotid salivary glands by integrating transcriptomic and metabolomic data. Integrated data were then analyzed to identify significant gene-metabolite interactions. Mice received a single 5 Gy dose of targeted head and neck radiation. Parotid tissue samples were collected 5 days following treatment for RNA sequencing and metabolomics analysis. Altered metabolites and transcripts significantly converged on a specific region in the metabolic reaction network. Both integrative pathway enrichment using rank-based statistics and network analysis highlighted significantly coordinated changes in glutathione metabolism, energy metabolism (TCA cycle and thermogenesis), peroxisomal lipid metabolism, and bile acid production with radiation. Integrated changes observed in energy metabolism suggest that radiation induces a mitochondrial dysfunction phenotype. These findings validated previous pathways involved in the radiation-damage response, such as altered energy metabolism, and identified robust signatures in salivary glands, such as reduced glutathione metabolism, that may be driving salivary gland dysfunction.

Activation of Neural Modeling-Related Genes in the Heart of Mice after Gamma Irradiation.

OBJECTIVE: Radiation-induced heart disease (RIHD) is a common sequela of thoracic irradiation. At the same time, nerve remodeling is involved in the progression of heart disease. However, the activation of the nerve remodeling related genes in radiation-induced heart disease is still lacking. METHODS: In this study, C57BL/J mice was anesthetized by intraperitoneal injection with pentobarbital sodium (2%, 40 mg/kg), and radiation was delivered using a cobalt-60 (60Co) teletherapy unit (Cirus). When the mice were anesthetized, none of them showed the signs of peritonitis, pain, or discomfort. The mice hearts were exposed to a γ-radiation field of 5 mm × 5 mm. The total dose of γ-radiation was 3 Gy/day for each animal for 5 consecutive days. The mice were executed by severed neck, and its limbs were weak. Quantitative Polymerase Chain Reaction (qPCR) and immunohistochemistry were used to explore the possible mechanism of arrhythmia in patients with RIHD. RESULTS: Our results demonstrated that Growth-Associated Protein 43 (GAP43) was increased significantly after radioactive heart injury compared with the control group. Moreover, the protein expression of Tyrosine hydroxylase (TH) and Choline acetyl-transferase (CHAT) was significantly decreased compared with the control group and gradually increased with time rend. The nerve growth factor (NGF) was remarkably increased after radiation-induced heart injury compared with the control group. Immunohistochemistry results indicated that the nerve growth factors GAP43 and NGF were significantly increased after radiation-induced heart injury. CONCLUSIONS: Chest radiotherapy could activate the neural modeling related genes in RIHD. This may provide a new treatment plan for the future treatment of heart problems caused by chest radiotherapy.

Characterization of macrophages, giant cells and granulomas during muscle regeneration after irradiation.

Macrophages play a fundamental role in the different stages of muscle regeneration although the precise mechanisms involved are not entirely understood. Here we investigated the types of macrophages and cytokines that appeared in muscles after local gamma irradiation of mini-pigs that underwent no subsequent treatment or received three successive adipose tissue-derived stem cell (ASC) injections. Although some variability was observed among the three animals included in each study group, a general picture emerged. No macrophages appeared in control muscles from regions that had not been irradiated nor in muscles from irradiated regions derived from two animals. A third irradiated, but untreated animal, with characteristic muscle fibrosis and necrosis due to irradiation, showed invasion of M2 macrophages within small muscle lesions. In contrast, among the three ASC-treated and irradiated animals, one of them had completely recovered normal muscle architecture at the time of sampling with no invading macrophages, muscle from a second one contained mostly M1 macrophages and some M2-like macrophages whereas muscle from a third one displayed granulomas and giant cells. ASC treatment was associated with the presence of similar levels of pro-inflammatory cytokines within the two animals in the process of muscle regeneration whereas the levels of IL-4 and IL-10 expression were distinct from one animal to another. Microspectrofluorimetry and in situ hybridization revealed strong expression of TGF-ß1 and TNFα in regenerating muscle. Overall, the data confirm the critical role of macrophages in muscle regeneration and suggest the involvement of a complex network of cytokine expression for successful recovery.

MiRNA-155-5p inhibits epithelium-to-mesenchymal transition (EMT) by targeting GSK-3ß during radiation-induced pulmonary fibrosis.

Radiation-induced pulmonary fibrosis (RIPF) is a major lung complication in using radiotherapy to treat thoracic diseases. MicroRNAs (miRNAs) are reported to be the therapeutic targets for many diseases. However, the miRNAs involved in the pathogenesis of RIPF are rarely studied as potential therapeutic targets. Alveolar epithelial cells participate in RIPF formation by undergoing epithelial-mesenchymal transition (EMT). Here we demonstrated the critical role of miR-155-5p in radiation-induced EMT and RIPF. Using the previously established EMT cell model, we found that miR-155-5p was significantly down-regulated through high-throughput sequencing. Irradiation could decrease the expression of miR-155-5p in intro and in vivo, and it was inversely correlated to RIPF formation. Ectopic miR-155-5p expression inhibited radiation-induced-EMT in vitro and in vivo. Knockdown of glycogen synthase kinase-3ß (GSK-3ß), the functional target of miR-155-5p, reversed the induction of EMT and enhanced the phosphorylation of p65, a subunit of NF-κB, which were mediated by the down-regulation of miR-155-5p. Moreover, our finding demonstrated that ectopic miR-155-5p expression alleviated RIPF in mice by the GSK-3ß/NF-κB pathway. Thus, radiation downregulates miR-155-5p in alveolar epithelial cells that induces EMT, which contributes to RIPF using GSK-3ß/NF-κB pathway. Our observation provides further understanding on the regulation of RIPF and identifies potential therapeutic targets.

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

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

Sphingosine 1-phosphate protects against radiation-induced ovarian injury in female rats-impact on mitochondrial-related genes.

The toxic effects of ionizing radiation on the gonads have been widely recognized. Sphingosine 1-phosphate (S1P) has a protective effect on ovarian injury, and although it is known that mitochondria are involved in this process, the specific mechanism is not fully understood. The present study analysed the changes in the serum AMH and ovarian histology in Sprague-Dawley female rats exposed to X-ray radiation only or co-administered with S1P. The mRNA expression profile of ovarian tissue was further analysed via next-generation sequencing and bioinformatics approaches to screen out candidate mitochondria-related genes. Finally, differentially expressed target genes were verified by real-time PCR. The results showed that ionizing radiation could reduce the serum AMH level, destroy ovarian structure and decrease the number of follicles in rats, while S1P administration significantly attenuated the impairment of ovarian function. Gene ontology (GO) and KEGG pathway analysis revealed that a variety of genes related to mitochondrial function were differentially expressed, and the protective effect of S1P on mitochondria was more obvious in the acute phase 24 h after radiation. The differentially expressed mitochondrial function-related genes associated with the protective effect of S1P were UQCRH, MICU2 and GPX4, which were subsequently verified by RT-PCR. Therefore, ionizing radiation has a significant effect on ovarian function, and S1P has a protective effect on radiation-induced ovarian injury, in which mitochondria may play an important role. This study sheds new light on the mechanism of radiation-induced ovarian injury and helps develop a novel potential strategy to control it.

Gene Expression Profiles from Heart, Lung and Liver Samples of Total-Body-Irradiated Minipigs: Implications for Predicting Radiation-Induced Tissue Toxicity.

In the event of a major accidental or intentional radiation exposure incident, the affected population could suffer from total- or partial-body exposures to ionizing radiation with acute exposure to organs that would produce life-threatening injury. Therefore, it is necessary to identify markers capable of predicting organ-specific damage so that appropriate directed or encompassing therapies can be applied. In the current work, gene expression changes in response to total-body irradiation (TBI) were identified in heart, lungs and liver tissue of Göttingen minipigs. Animals received 1.7, 1.9, 2.1 or 2.3 Gy TBI and were followed for 45 days. Organ samples were collected at the end of day 45 or sooner if the animal displayed morbidity necessitating euthanasia. Our findings indicate that different organs respond to TBI in a very specific and distinct manner. We also found that the liver was the most affected organ in terms of gene expression changes, and that lipid metabolic pathways were the most deregulated in the liver samples of non-survivors (survival time <45 days). We identified organ-specific gene expression signatures that accurately differentiated non-survivors from survivors and control animals, irrespective of dose and time postirradiation. At what point did these radiation-induced injury markers manifest and how this information could be used for applying intervention therapies are under investigation.

Extracellular Vesicle-Derived miR-124 Resolves Radiation-Induced Brain Injury.

Radiation-induced cognitive dysfunction (RICD) is a progressive and debilitating health issue facing patients following cranial radiotherapy to control central nervous system cancers. There has been some success treating RICD in rodents using human neural stem cell (hNSC) transplantation, but the procedure is invasive, requires immunosuppression, and could cause other complications such as teratoma formation. Extracellular vesicles (EV) are nanoscale membrane-bound structures that contain biological contents including mRNA, miRNA, proteins, and lipids that can be readily isolated from conditioned culture media. It has been previously shown that hNSC-derived EV resolves RICD following cranial irradiation using an immunocompromised rodent model. Here, we use immunocompetent wild-type mice to show that hNSC-derived EV treatment administered either intravenously via retro-orbital vein injection or via intracranial transplantation can ameliorate cognitive deficits following 9 Gy head-only irradiation. Cognitive function assessed on the novel place recognition, novel object recognition, and temporal order tasks was not only improved at early (5 weeks) but also at delayed (6 months) postirradiation times with just a single EV treatment. Improved behavioral outcomes were also associated with reduced neuroinflammation as measured by a reduction in activated microglia. To identify the mechanism of action, analysis of EV cargo implicated miRNA (miR-124) as a potential candidate in the mitigation of RICD. Furthermore, viral vector-mediated overexpression of miR-124 in the irradiated brain ameliorated RICD and reduced microglial activation. Our findings demonstrate for the first time that systemic administration of hNSC-derived EV abrogates RICD and neuroinflammation in cranially irradiated wild-type rodents through a mechanism involving miR-124. SIGNIFICANCE: Radiation-induced neurocognitive decrements in immunocompetent mice can be resolved by systemic delivery of hNSC-derived EVs involving a mechanism dependent on expression of miR-124.

Ionizing radiation induces BH4 deficiency by downregulating GTP-cyclohydrolase 1, a novel target for preventing and treating radiation enteritis.

Radiation enteritis (RE) is a common side effect after radiotherapy for abdominal cancer. RE pathogenesis is complicated, with no drugs available for prevention or treatments. Intestinal ischemia is a key factor in the occurrence and development of enteritis. The effect of ionizing radiation (IR) on intestinal ischemia is unknown. Deficiency of tetrahydrobiopterin (BH4) produced by GTP-cyclohydrolase 1 (Gch1) is important in ischemic diseases. This study focused on the relationship of Gch1/BH4 between intestinal ischemia in radiation enteritis. BH4 levels were analyzed by high-performance liquid chromatography in humans and rats after radiotherapy. Intestinal blood perfusion was measured by laser doppler flow imaging. Vascular ring tests determined the diastolic functions of rat mesenteric arteries. Gene, protein, and immunohistochemical staining experiments and inhibitor interventions were used to investigate Gch1 and endothelial NOS (eNOS) in rat mesenteric arteries and endothelial cells. The results showed that IR decreased BH4 levels in patients and rats after radiotherapy and decreased intestinal blood perfusion in rats. The degree of change in intestinal ischemia was consistent with intestinal villus injury. Gch1 mRNA and protein levels and nitric oxide (NO) production significantly decreased, while eNOS uncoupling in arterial and vascular endothelial cells strongly increased. BH4 supplementation improved eNOS uncoupling and NO levels in vascular endothelia after IR. The results of this study showed that downregulation of Gch1 in intestinal blood vessels after IR is an important target in RE. BH4 supplementation may prevent intestinal ischemia and improve vascular endothelial function after IR. These findings have clinical significance for the prevention and treatment of RE.

Impact of mouse strain and sex when modeling radiation necrosis.

BACKGROUND: Murine models are among the most common type of preclinical animal models used to study the human condition, but a wide selection of different mice is currently in use with these differences potentially compromising study results and impairing the ability to reconcile interstudy results. Our goal was to determine how the strain and sex of the mice selection would affect the development of radiation necrosis in our murine model of radiation-induced cerebral necrosis. METHODS: We generated this model by using a preclinical irradiator to irradiate a sub-hemispheric portion of the brain of mice with single-fraction doses of 80 Gy. Eight possible combinations of mice made up of two different with two substrains each (BALB/cN, BALB/cJ, C57BL/6 N, and C57BL/6 J) and both sexes were irradiated in this study. Radiation necrosis development was tracked up to 8 weeks with a 7 T Bruker MRI utilizing T2-weighted and post-contrast T1-weighted imaging. MRI results were compared to and validated with the use of histology which utilized a scale from 0 to 3 in ascending order of damage. RESULTS: Both time post-irradiation and strain (BALB/c vs C57BL/6) were significant factors affecting radiation necrosis development. Sex was in general not a statistically significant parameter in terms of radiation necrosis development. CONCLUSION: Mouse strain thus needs to be considered when evaluating the results of necrosis models. However, sex does not appear to be a variable needing major consideration.

Irradiated and CCl4 -treated bone marrow-derived liver macrophages exhibit different gene expression patterns and phenotypes.

Myeloid cells infiltrate into the liver and differentiate into macrophages in different liver injury mouse models. However, the heterogeneity of bone marrow (BM)-derived LMs populations remains to be understood. To investigate this and understand the impact of the macrophage niche on the properties of recruited BM-derived macrophages, we used a non-myeloablation BM transplantation model to label and trace BM-derived LMs. Subsequently, we quantified the number of embryonic-derived liver-resident macrophages, BM-derived LMs and total LMs in CCl4 and irradiated acute liver injury mouse models, respectively. Finally, we compared the cell fate, gene expression patterns, chemokine signals, and surface markers of irradiated and CCl4 -treated BM-derived LMs. We observed that, as compared to CCl4, radiation generated a macrophage niche by depleting embryonic-derived liver-resident macrophages and induced the recruitment of BM-derived LMs that further settled in the liver. Irradiated and CCl4 -treated BM-derived LMs are different with respect to their cell fates, gene expression patterns, and chemokine expression and recruitment. They also have different surface markers shortly after differentiating from their progenitors. Our findings suggest that irradiated and CCl4 -treated LM populations derived from the bone marrow display different patterns of gene expression and phenotypes; these differences may be due to the availability of macrophage niche.