LPA5-Dependent signaling regulates regeneration of the intestinal epithelium following irradiation.

Lysophosphatidic acid (LPA) is a bioactive lipid molecule that regulates a wide array of cellular functions, including proliferation, differentiation, and survival, via activation of cognate receptors. The LPA5 receptor is highly expressed in the intestinal epithelium, but its function in restoring intestinal epithelial integrity following injury has not been examined. Here, we use a radiation-induced injury model to study the role of LPA5 in regulating intestinal epithelial regeneration. Control mice (Lpar5f/f) and mice with an inducible, epithelial cell-specific deletion of Lpar5 in the small intestine (Lpar5IECKO) were subjected to 10 Gy total body X-ray irradiation and analyzed during recovery. Repair of the intestinal mucosa was delayed in Lpar5IECKO mice with reduced epithelial proliferation and increased crypt cell apoptosis. These effects were accompanied by reduced numbers of OLFM4+ intestinal stem cells (ISCs). The effects of LPA5 on ISCs were corroborated by studies using organoids derived from Lgr5-lineage tracking reporter mice with deletion of Lpar5 in Lgr5+-stem cells (Lgr5Cont or Lgr5ΔLpar5). Irradiation of organoids resulted in fewer numbers of Lgr5ΔLpar5 organoids retaining Lgr5+-derived progenitor cells compared with Lgr5Cont organoids. Finally, we observed that impaired regeneration in Lpar5IECKO mice was associated with reduced numbers of Paneth cells and decreased expression of Yes-associated protein (YAP), a critical factor for intestinal epithelial repair. Our study highlights a novel role for LPA5 in regeneration of the intestinal epithelium following irradiation and its effect on the maintenance of Paneth cells that support the stem cell niche.NEW & NOTEWORTHY We used mice lacking expression of the lysophosphatidic acid receptor 5 (LPA5) in intestinal epithelial cells and intestinal organoids to show that the LPA5 receptor protects intestinal stem cells and progenitors from radiation-induced injury. We show that LPA5 induces YAP signaling and regulates Paneth cells.

Innovative insights: ITLN1 modulates renal injury in response to radiation.

Radiation-induced kidney injury is a common side effect of radiotherapy, as the pelvic region is in close proximity to the kidneys, posing a risk of inducing radiation-induced kidney injury when treating any pelvic malignancies with radiotherapy. This type of injury typically manifests as chronic kidney disease a few months after radiotherapy, with the potential to progress to end-stage renal disease. Radiation-induced damage involves various components of the kidney, including glomeruli, tubules, interstitium, and extracellular matrix. Therefore, investigating its molecular mechanisms is crucial. In this study, we extensively searched literature databases, selecting recent transcriptomic studies related to acute kidney injury (AKI) published in the past decade. We downloaded the raw RNA sequencing datasets GSE30718 and GSE66494 related to AKI from the GEO database and identified that intestinal-type lectin ITLN1 plays a significant role in regulating radiation-induced kidney injury in rats. Differential gene analysis was performed using chip data from the GEO database, and further bioinformatics analysis identified 13 genes that may be involved in regulating kidney injury, with ITLN1 being the most relevant to kidney damage, thus selected as the target gene for this study. Subsequently, a rat model of radiation-induced kidney injury was established for experimental validation, assessing kidney tissue morphology and injury extent through staining observation and immunohistochemical staining. The protective effect of ITLN1 on kidney function was evaluated by measuring changes in rat body weight and blood pressure, serum kidney injury markers, and kidney structure. The experimental results indicate that overexpression of ITLN1 can improve kidney function in rats with radiation-induced kidney injury by activating the Akt/GSK-3ß/Nrf2 signaling pathway, suppressing oxidative stress, cell apoptosis, inflammation, cellular senescence, and fibrosis. This study highlights the significant role of ITLN1 in regulating kidney injury, providing a novel target for future treatments of radiation-induced kidney injury.

Emodin ameliorates acute radiation proctitis in mice by regulating AKT/MAPK/NF-κB/VEGF pathways.

BACKGROUND: Emodin, a natural anthraquinone derivative isolated from the roots of Rheum officinale Baill, has many pharmacological effects including anti-inflammatory, antioxidant, antiviral, antibacterial and anti-cancer. However, little is known about the effect of emodin on acute radiation proctitis (ARP). The present study was conducted to determine its effects and elucidate its mechanisms involving AKT/MAPK/NF-κB/VEGF pathways in ARP mice. METHODS: Total 60 C57BL/6 mice were divided randomly into control group, ARP group, AKT inhibitor MK-2206 group, and different doses of emodin groups. ARP mice were induced by 27 Gy of 6 MV X-ray pelvic local irradiation. MK-2206 was given orally for 2 weeks on alternate days. Emodin was administered daily by oral gavage for 2 weeks. Subsequently, all mice were sacrificed on day 15. The rectal tissues were obtained for further tests. The general signs score and the pathological grade were used to evaluate the severity of ARP. The expression of NF-κB, VEGF and AQP1 were determined by immunohistochemistry and western blot. The expression of p-AKT, p-ERK, p-JNK, p-p38, Bcl-2 and Bax were assessed using western blot. RESULTS: The worse general signs and damaged tissue structure of ARP mice were profoundly ameliorated by emodin. The expression of p-AKT, p-ERK, NF-κB, VEGF and AQP1 were significantly increased, resulting in the inflammation-induced angiogenesis in ARP mice. However, the expression of p-JNK and p-p38 were decreased, leading to the reduction of apoptosis in ARP mice. Excitedly, emodin reversed these changes, not only inhibited inflammation-induced angiogenesis, but also promoted apoptosis. Notably, the effects of emodin were similar to that of AKT inhibitor MK-2206, suggesting the involvement of AKT signaling in the effect of emodin. CONCLUSION: These results suggest that emodin attenuates ARP in mice, and the underlying mechanism might involve inhibition of the AKT/ERK/NF-κB/VEGF pathways and the induction of apoptosis mediated by JNK and p38.

REGγ Mitigates Radiation-Induced Enteritis by Preserving Mucin Secretion and Sustaining Microbiome Homeostasis.

Radiation-induced enteritis, a significant concern in abdominal radiation therapy, is associated closely with gut microbiota dysbiosis. The mucus layer plays a pivotal role in preventing the translocation of commensal and pathogenic microbes. Although significant expression of REGγ in intestinal epithelial cells is well established, its role in modulating the mucus layer and gut microbiota remains unknown. The current study revealed notable changes in gut microorganisms and metabolites in irradiated mice lacking REGγ, as compared to wild-type mice. Concomitant with gut microbiota dysbiosis, REGγ deficiency facilitated the infiltration of neutrophils and macrophages, thereby exacerbating intestinal inflammation after irradiation. Furthermore, fluorescence in situ hybridization assays unveiled an augmented proximity of bacteria to intestinal epithelial cells in REGγ knockout mice after irradiation. Mechanistically, deficiency of REGγ led to diminished goblet cell populations and reduced expression of key goblet cell markers, Muc2 and Tff3, observed in both murine models, minigut organoid systems and human intestinal goblet cells, indicating the intrinsic role of REGγ within goblet cells. Interestingly, although administration of broad-spectrum antibiotics did not alter the goblet cell numbers or mucin 2 (MUC2) secretion, it effectively attenuated inflammation levels in the ileum of irradiated REGγ absent mice, bringing them down to the wild-type levels. Collectively, these findings highlight the contribution of REGγ in counteracting radiation-triggered microbial imbalances and cell-autonomous regulation of mucin secretion.

Cytosolic Release of Mitochondrial DNA and Associated cGAS Signaling Mediates Radiation-Induced Hematopoietic Injury of Mice.

Mitochondrion is an important organelle of eukaryotic cells and a critical target of ionizing radiation (IR) outside the nucleus. The biological significance and mechanism of the non-target effect originating from mitochondria have received much attention in the field of radiation biology and protection. In this study, we investigated the effect, role, and radioprotective significance of cytosolic mitochondrial DNA (mtDNA) and its associated cGAS signaling on hematopoietic injury induced by IR in vitro culture cells and in vivo total body irradiated mice in this study. The results demonstrated that γ-ray exposure increases the release of mtDNA into the cytosol to activate cGAS signaling pathway, and the voltage-dependent anion channel (VDAC) may contribute to IR-induced mtDNA release. VDAC1 inhibitor DIDS and cGAS synthetase inhibitor can alleviate bone marrow injury and ameliorate hematopoietic suppression induced by IR via protecting hematopoietic stem cells and adjusting subtype distribution of bone marrow cells, such as attenuating the increase of the F4/80+ macrophage proportion in bone marrow cells. The present study provides a new mechanistic explanation for the radiation non-target effect and an alternative technical strategy for the prevention and treatment of hematopoietic acute radiation syndrome.

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.

Protective mechanism of a novel aminothiol compound on radiation-induced intestinal injury.

PURPOSE: With the development of nuclear technology and radiotherapy, the risk of radiation injury has been increasing. Therefore, it is important to find an effective radiation-protective agent. In this study, we designed and synthesized a novel compound called compound 8, of which the radioprotective effect and mechanism were studied. MATERIALS AND METHODS: Before being exposed to ionizing radiation, mice were pretreated with compound 8. The 30-day mortality assay, hematoxylin-eosin staining, and immunohistochemistry staining assay were performed to evaluate the anti-radiation effect of the compound 8. TUNEL and immunofluorescence assays were conducted to study the anti-radiation mechanism of compound 8. RESULTS: Compared to the IR + vehicle group, the 30-day survival rate of mice treated with 25 mg/kg of compound 8 was significantly improved after 8 Gy total body irradiation. In the morphological study of the small intestine, we found that compound 8 could maintain crypt-villus structures in the irradiated mice. Further immunohistochemical staining displayed that compound 8 could improve the survival of Lgr5+ cells, ki67+ cells, and lysozyme+ cells. The results of TUNEL and immunofluorescence assays showed that compound 8 could decrease the expression of apoptosis-related caspase-8/-9, γ-H2AX, Bax, and p53. CONCLUSIONS: These results indicate that compound 8 exerts its effects by maintaining structure and function of small intestine. It also reduces DNA damage, promotes crypt proliferation and differentiation. Moreover, it may enhance the anti-apoptotic ability of small intestinal tissue by inhibiting the activation of p53 and blocking the caspase cascade reaction. Compound 8 can protect the intestinal tract from post-radiation damage, it is thus a new and effective protective agent of radiation.

Protection From Radiation-Induced Neuroanatomic Deficits by CCL2 Deficiency Is Dependent on Sex.

PURPOSE: Cranial radiation therapy for the treatment of pediatric brain tumors results in changes to brain development that are detectable with magnetic resonance imaging. We have previously demonstrated similar structural changes in both humans and mice. The goal of the current study was to examine the role of inflammation in this response. Because neuroanatomic volume deficits in pediatric survivors are more pronounced in female patients, we also evaluated possible dependence on sex. METHODS AND MATERIALS: Other studies have shown that male mice deficient in the C-C chemokine ligand 2 gene (Ccl2; previously Mcp-1) have a muted neuroinflammatory response after irradiation. We irradiated Ccl2-/- (HOM; female = 12, male = 13), Ccl2-/+ (HET; female = 13, male = 16), and Ccl2+/+ (WT; female = 11, male = 13) mice with a whole brain dose of 7 Gy during infancy. Control mice (with approximately equal group sizes) were anesthetized but not irradiated. In vivo magnetic resonance images were acquired at 4 time points up to 3 months after irradiation, and deformation-based morphometry was used to identify volume differences. RESULTS: Irradiation of WT mice resulted in a deficit in neuroanatomic growth with limited sex dependence. HOM and HET male mice were significantly protected from this radiation-induced damage, whereas HOM and HET female mice were not. CONCLUSIONS: Interventions aimed at mitigating the effects of cranial radiation therapy in pediatric cancer survivors by modulating inflammatory response will need to consider patient sex.

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.

Iron contributes to photoreceptor degeneration and Müller glia proliferation in the zebrafish light-treated retina.

Zebrafish possess the ability to completely regenerate the retina following injury, however little is understood about the damage signals that contribute to inducing Müller glia reprogramming and proliferation to regenerate lost neurons. Multiple studies demonstrated that iron contributes to various retinal injuries, however no link has been shown between iron and zebrafish retinal regeneration. Here we demonstrate that Müller glia exhibit transcriptional changes following injury to regulate iron levels within the retina, allowing for increased iron uptake and decreased export. The response of the zebrafish retina to intravitreal iron injection was then characterized, showing that ferrous, and not ferric, iron induces retinal cell death. Additionally, iron chelation resulted in decreased numbers of TUNEL-positive photoreceptors and fewer proliferating Müller glia. Despite the contribution of iron to retinal cell death, inhibition of ferroptosis did not significantly reduce cell death following light treatment. Finally, we demonstrate that both the anti-ferroptotic protein Glutathione peroxidase 4b and the Transferrin receptor 1b are required for Müller glia proliferation following light damage. Together these findings show that iron contributes to cell death in the light-damaged retina and is essential for inducing the Müller glia regeneration response.

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.

Role of melatonin mediated G-CSF induction in hematopoietic system of gamma-irradiated mice.

AIMS: Hematopoietic acute radiation syndrome (H-ARS) can cause lethality, and therefore, the necessity of a safe radioprotector. The present study was focused on investigating the role of melatonin in granulocytes colony-stimulating factor (G-CSF) and related mechanisms underlying the reduction of DNA damage in hematopoietic system of irradiated mice. MAIN METHODS: C57BL/6 male mice were exposed to 2, 5, and 7.5Gy of whole-body irradiation (WBI), 30 min after intra-peritoneal administration of melatonin with different doses. Mice were sacrificed at different time intervals after WBI, and bone marrow, splenocytes, and peripheral blood lymphocytes were isolated for studying various parameters including micronuclei (MN), cell cycle, comet, γ-H2AX, gene expression, amino acid profiling, and hematology. KEY FINDINGS: Melatonin100mg/kg ameliorated radiation (7.5Gy and 5Gy) induced MN frequency and cell death in bone marrow without mortality. At 24 h of post-WBI (2Gy), the frequency of micronucleated polychromatic erythrocytes (mnPCE) with different melatonin doses revealed 20 mg/kg as optimal i.p. dose for protecting the hematopoietic system against radiation injury. In comet assay, a significant reduction in radiation-induced % DNA tail (p ≤ 0.05) was observed at this dose. Melatonin reduced γ-H2AX foci/cell and eventually reached to the control level. Melatonin also decreased blood arginine levels in mice after 24 h of WBI. The gene expression of G-CSF, Bcl-2-associated X protein (BAX), and Bcl2 indicated the role of melatonin in G-CSF regulation and downstream pro-survival pathways along with anti-apoptotic activity. SIGNIFICANCE: The results revealed that melatonin recovers the hematopoietic system of irradiated mice by inducing G-CSF mediated radioprotection.

Quercetin Prevents Radiation-Induced Oral Mucositis by Upregulating BMI-1.

Radiation-induced oral mucositis is a major adverse event of radiotherapy. Severe oral mucositis may cause unwanted interruption in radiotherapy and reduce long-term survival in cancer patients receiving radiotherapy, but until now, there have been no effective options for preventing radiation-induced oral mucositis. Quercetin is a flavonoid that is widely found in food species and has anti-inflammatory, antioxidant, and anticancer activities. In this study, we investigated a new role of quercetin in preventing radiation-induced oral mucositis. Quercetin exerted preventive effects against radiation-induced oral mucositis induced by single-dose (25 Gy) ionizing radiation or fractionated ionizing radiation (8 Gy × 3) in C57BL/6 mice and maintained the proliferation ability of basal epithelial cells. Quercetin pretreatment alleviated reactive oxygen species generation, NF-κB pathway activation, and downstream proinflammatory cytokine production and reduced DNA double-strand breaks and cellular senescence induced by ionizing radiation. Quercetin also upregulated BMI-1 expression in oral epithelial cells and promoted ulcer repair. In addition, quercetin exerted similar radioprotective effects in irradiated primary cultured normal human keratinocytes, reduced reactive oxygen species generation and proinflammatory cytokine release, and promoted DNA double-strand break repair and wound healing by upregulating the expression of BMI-1, which is a polycomb group protein. Thus, quercetin can block multiple pathological processes of radiation-induced oral mucositis by targeting BMI-1 and may be a potential treatment option for preventing radiation-induced oral mucositis.

Unexpected Interacting Effects of Physical (Radiation) and Chemical (Bisphenol A) Treatments on Male Reproductive Functions in Mice.

For decades, numerous chemical pollutants have been described to interfere with endogenous hormone metabolism/signaling altering reproductive functions. Among these endocrine disrupting substances, Bisphenol A (BPA), a widely used compound, is known to negatively impact germ and somatic cells in the testis. Physical agents, such as ionizing radiation, were also described to perturb spermatogenesis. Despite the fact that we are constantly exposed to numerous environmental chemical and physical compounds, very few studies explore the impact of combined exposure to chemical and physical pollutants on reproductive health. The aim of this study was to describe the impact of fetal co-exposure to BPA and IR on testicular function in mice. We exposed pregnant mice to 10 µM BPA (corresponding to 0.5 mg/kg/day) in drinking water from 10.5 dpc until birth, and we irradiated mice with 0.2 Gy (γ-ray, RAD) at 12.5 days post-conception. Co-exposure to BPA and γ-ray induces DNA damage in fetal germ cells in an additive manner, leading to a long-lasting decrease in germ cell abundance. We also observed significant alteration of adult steroidogenesis by RAD exposure independently of the BPA exposure. This is illustrated by the downregulation of steroidogenic genes and the decrease of the number of adult Leydig cells. As a consequence, courtship behavior is modified, and male ultrasonic vocalizations associated with courtship decreased. In conclusion, this study provides evidence for the importance of broadening the concept of endocrine disruptors to include physical agents, leading to a reevaluation of risk management and regulatory decisions.

Acute Proteomic Changes in Non-human Primate Kidney after Partial-body Radiation with Minimal Bone Marrow Sparing.

ABSTRACT: Near total body exposure to high-dose ionizing radiation results in organ-specific sequelae, including acute radiation syndromes and delayed effects of acute radiation exposure. Among these sequelae are acute kidney injury and chronic kidney injury. Reports that neither oxidative stress nor inflammation are dominant mechanisms defining radiation nephropathy inspired an unbiased, discovery-based proteomic interrogation in order to identify mechanistic pathways of injury. We quantitatively profiled the proteome of kidney from non-human primates following 12 Gy partial body irradiation with 2.5% bone marrow sparing over a time period of 3 wk. Kidney was analyzed by liquid chromatography-tandem mass spectrometry. Out of the 3,432 unique proteins that were identified, we found that 265 proteins showed significant and consistent responses across at least three time points post-irradiation, of which 230 proteins showed strong upregulation while 35 proteins showed downregulation. Bioinformatics analysis revealed significant pathway and upstream regulator perturbations post-high dose irradiation and shed light on underlying mechanisms of radiation damage. These data will be useful for a greater understanding of the molecular mechanisms of injury in well-characterized animal models of partial body irradiation with minimal bone marrow sparing. These data may be potentially useful in the future development of medical countermeasures.

Acute Proteomic Changes in Lung after Radiation: Toward Identifying Initiating Events of Delayed Effects of Acute Radiation Exposure in Non-human Primate after Partial Body Irradiation with Minimal Bone Marrow Sparing.

ABSTRACT: Radiation-induced lung injury is a delayed effect of acute radiation exposure resulting in pulmonary pneumonitis and fibrosis. Molecular mechanisms that lead to radiation-induced lung injury remain incompletely understood. Using a non-human primate model of partial body irradiation with minimal bone marrow sparing, lung was analyzed from animals irradiated with 12 Gy at timepoints every 4 d up to 21 d after irradiation and compared to non-irradiated (sham) controls. Tryptic digests of lung tissues were analyzed by liquid chromatography-tandem mass spectrometry followed by pathway analysis. Out of the 3,101 unique proteins that were identified, we found that 252 proteins showed significant and consistent responses across at least three time points post-irradiation, of which 215 proteins showed strong up-regulation while 37 proteins showed down-regulation. Canonical pathways affected by irradiation, changes in proteins that serve as upstream regulators, and proteins involved in key processes including inflammation, fibrosis, and retinoic acid signaling were identified. The proteomic profiling of lung conducted here represents an untargeted systems biology approach to identify acute molecular events in the non-human primate lung that could potentially be initiating events for radiation-induced lung injury.

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.

Metformin Protects against Radiation-Induced Acute Effects by Limiting Senescence of Bronchial-Epithelial Cells.

Radiation-induced damage to normal lung parenchyma remains a dose-limiting factor in thorax-associated radiotherapy (RT). Severe early and late complications with lungs can increase the risk of morbidity in cancer patients after RT. Herein, senescence of lung epithelial cells following RT-induced cellular stress, or more precisely the respective altered secretory profile, the senescence-associated secretory phenotype (SASP), was suggested as a central process for the initiation and progression of pneumonitis and pulmonary fibrosis. We previously reported that abrogation of certain aspects of the secretome of senescent lung cells, in particular, signaling inhibition of the SASP-factor Ccl2/Mcp1 mediated radioprotection especially by limiting endothelial dysfunction. Here, we investigated the therapeutic potential of a combined metformin treatment to protect normal lung tissue from RT-induced senescence and associated lung injury using a preclinical mouse model of radiation-induced pneumopathy. Metformin treatment efficiently limited RT-induced senescence and SASP expression levels, thereby limiting vascular dysfunctions, namely increased vascular permeability associated with increased extravasation of circulating immune and tumor cells early after irradiation (acute effects). Complementary in vitro studies using normal lung epithelial cell lines confirmed the senescence-limiting effect of metformin following RT finally resulting in radioprotection, while fostering RT-induced cellular stress of cultured malignant epithelial cells accounting for radiosensitization. The radioprotective action of metformin for normal lung tissue without simultaneous protection or preferable radiosensitization of tumor tissue might increase tumor control probabilities and survival because higher radiation doses could be used.

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.

Irradiation Accelerates Plaque Formation and Cellular Senescence in Flow-Altered Carotid Arteries of Apolipoprotein E Knock-Out Mice.

Background Chronic inflammation through cellular senescence, known as the senescence-associated secretory phenotype, is a mechanism of various organ diseases, including atherosclerosis. Particularly, ionizing radiation (IR) contributes to cellular senescence by causing DNA damage. Although previous clinical studies have demonstrated that radiotherapy causes atherosclerosis as a long-term side effect, the detailed mechanism is unclear. This study was conducted to investigate the relationship between radiation-induced atherosclerosis and senescence-associated secretory phenotype in murine carotid arteries. Methods and Results Partial ligation of the left carotid artery branches in 9-week-old male apolipoprotein E-deficient mice was performed to induce atherosclerosis. The mice received total body irradiation at a dose of 6 Gy using gamma rays at 2 weeks post operation. We compared the samples collected 4 weeks after IR with unirradiated control samples. The IR and control groups presented pathologically progressive lesions in 90.9% and 72.3% of mice, respectively. Plaque volume, macrophage accumulation, and phenotype switching of vascular smooth muscle cells were advanced in the IR group. Irradiated samples showed increased persistent DNA damage response (53BP1 [p53 binding protein 1]), upregulated cyclin-dependent kinase inhibitors (p16INK4a and p21), and elevated inflammatory chemokines expression (monocyte chemotactic protein-1, keratinocyte-derived chemokine, and macrophage inflammatory protein 2). Conclusions IR promoted plaque growth in murine carotid arteries. Our findings support the possibility that senescence-associated secretory phenotype aggravates atherogenesis in irradiated artery. This mice model might contribute to mechanism elucidation of radiation-induced atherosclerosis.