Low-dose γ-radiation-induced oxidative stress response in mouse brain and gut: regulation by NFκB-MnSOD cross-signaling

Co-exposure to inhaled tungsten particles and low-dose gamma rays: neurotoxicological outcome in rats

Throughout their lives, individuals are exposed to various pollutants, potentially including co-exposure to radiological and chemical stressors. Yet, existing literature about these combinations is scarce. We selected tungsten and ionizing radiations. Tungsten is an emerging contaminant present as aerosolized particles in several scenarios, potentially concurrently with low-dose irradiation, causing a co-exposure. The cerebral toxicity of this co-exposure was studied after 24 h and 28 days in the frontal cortex and olfactory bulb of male Sprague-Dawley rats exposed to gamma irradiation (50 mGy) and/or inhalation of tungsten particles aerosol (80 mg.m-3). Co-exposure triggered significant effects more frequently than single stressors. Observed effects were associated with oxidative status changes, notably via NRF2 nuclear translocation, and modulation of pro-inflammatory cytokines (IL1β, TNFα). A reduction in cortical microglial density suggested a cellular migration toward the olfactory bulb and could contribute to the occurrence of a neuronal suffering phenotype. The effects persisted at 28 days and were brain structure specific. Biodistribution of tungsten showed that both local and systemic effects might be involved. Our results suggest interaction between our stressors, causing cerebral toxicity, and prove the importance of multi-stressor studies to improve risks evaluation in toxicology and radiation protection, as single stressors might wrongly be deemed safe.

AOP report: Development of an adverse outcome pathway for deposition of energy leading to learning and memory impairment

Understanding radiation-induced non-cancer effects on the central nervous system (CNS) is essential for the risk assessment of medical (e.g., radiotherapy) and occupational (e.g., nuclear workers and astronauts) exposures. Herein, the adverse outcome pathway (AOP) approach was used to consolidate relevant studies in the area of cognitive decline for identification of research gaps, countermeasure development, and for eventual use in risk assessments. AOPs are an analytical construct describing critical events to an adverse outcome (AO) in a simplified form beginning with a molecular initiating event (MIE). An AOP was constructed utilizing mechanistic information to build empirical support for the key event relationships (KERs) between the MIE of deposition of energy to the AO of learning and memory impairment through multiple key events (KEs). The evidence for the AOP was acquired through a documented scoping review of the literature. In this AOP, the MIE is connected to the AO via six KEs: increased oxidative stress, increased deoxyribonucleic acid (DNA) strand breaks, altered stress response signaling, tissue resident cell activation, increased pro-inflammatory mediators, and abnormal neural remodeling that encompasses atypical structural and functional alterations of neural cells and surrounding environment. Deposition of energy directly leads to oxidative stress, increased DNA strand breaks, an increase of pro-inflammatory mediators and tissue resident cell activation. These KEs, which are themselves interconnected, can lead to abnormal neural remodeling impacting learning and memory processes. Identified knowledge gaps include improving quantitative understanding of the AOP across several KERs and additional testing of proposed modulating factors through experimental work. Broadly, it is envisioned that the outcome of these efforts could be extended to other cognitive disorders and complement ongoing work by international radiation governing bodies in their review of the system of radiological protection.

Low-dose exposure to malathion and radiation results in the dysregulation of multiple neuronal processes, inducing neurotoxicity and neurodegeneration in mouse

Neurodegenerative disorders are a debilitating and persistent threat to the global elderly population, carrying grim outcomes. Their genesis is often multifactorial, with a history of prior exposure to xenobiotics such as pesticides, heavy metals, enviornmental pollutants, ionizing radiation etc,. A holistic molecular insight into their mechanistic induction upon single or combinatorial exposure to different toxicants is still unclear. In the present study, one-month-old C57BL/6 male mice were administered orally with malathion (50 mg/kg body wt. for 14 days) and single whole-body radiation (0.5 Gy) on the 8th day. Post-treatment, behavioural assays for exploratory behaviour, memory, and learning were performed. After sacrifice, brains were collected for histology, biochemical assays, and transcriptomic analysis. Transcriptomic analysis revealed several altered processes like synaptic transmission and plasticity, neuronal survival, proliferation, and death. Signalling pathways like MAPK, PI3K-Akt, Apelin, NF-κB, cAMP, Notch etc., and pathways related to neurodegenerative diseases were altered. Increased astrogliosis was observed in the radiation and coexposure groups, with significant neuronal cell death and a reduction in the expression of NeuN. Sholl analysis, dendritic arborization and spine density studies revealed decreased total apical neuronal path length and dendritic spine density. Reduced levels of the antioxidants GST and GSH and acetylcholinesterase enzyme activity were also detected. However, no changes were seen in exploratory behaviour or learning and memory post-treatment. Thus, explicating the molecular mechanisms behind malathion and radiation can provide novel insights into external factor-driven neurotoxicity and neurodegenerative pathogenesis.

Dose-Dependent Shift in Relative Contribution of Homologous Recombination to DNA Repair after Low-LET Ionizing Radiation Exposure: Empirical Evidence and Numerical Simulation

Understanding the relative contributions of different repair pathways to radiation-induced DNA damage responses remains a challenging issue in terms of studying the radiation injury endpoints. The comparative manifestation of homologous recombination (HR) after irradiation with different doses greatly determines the overall effectiveness of recovery in a dividing cell after irradiation, since HR is an error-free mechanism intended to perform the repair of DNA double-strand breaks (DSB) during S/G2 phases of the cell cycle. In this article, we present experimentally observed evidence of dose-dependent shifts in the relative contributions of HR in human fibroblasts after X-ray exposure at doses in the range 20-1000 mGy, which is also supported by quantitative modeling of DNA DSB repair. Our findings indicate that the increase in the radiation dose leads to a dose-dependent decrease in the relative contribution of HR in the entire repair process.

The miRNA Content of Bone Marrow-Derived Extracellular Vesicles Contributes to Protein Pathway Alterations Involved in Ionising Radiation-Induced Bystander Responses

Extracellular vesicles (EVs), through their cargo, are important mediators of bystander responses in the irradiated bone marrow (BM). MiRNAs carried by EVs can potentially alter cellular pathways in EV-recipient cells by regulating their protein content. Using the CBA/Ca mouse model, we characterised the miRNA content of BM-derived EVs from mice irradiated with 0.1 Gy or 3 Gy using an nCounter analysis system. We also analysed proteomic changes in BM cells either directly irradiated or treated with EVs derived from the BM of irradiated mice. Our aim was to identify key cellular processes in the EV-acceptor cells regulated by miRNAs. The irradiation of BM cells with 0.1 Gy led to protein alterations involved in oxidative stress and immune and inflammatory processes. Oxidative stress-related pathways were also present in BM cells treated with EVs isolated from 0.1 Gy-irradiated mice, indicating the propagation of oxidative stress in a bystander manner. The irradiation of BM cells with 3 Gy led to protein pathway alterations involved in the DNA damage response, metabolism, cell death and immune and inflammatory processes. The majority of these pathways were also altered in BM cells treated with EVs from mice irradiated with 3 Gy. Certain pathways (cell cycle, acute and chronic myeloid leukaemia) regulated by miRNAs differentially expressed in EVs isolated from mice irradiated with 3 Gy overlapped with protein pathway alterations in BM cells treated with 3 Gy EVs. Six miRNAs were involved in these common pathways interacting with 11 proteins, suggesting the involvement of miRNAs in the EV-mediated bystander processes. In conclusion, we characterised proteomic changes in directly irradiated and EV-treated BM cells, identified processes transmitted in a bystander manner and suggested miRNA and protein candidates potentially involved in the regulation of these bystander processes.

Pathogenic mechanisms and therapeutic promise of phytochemicals and nanocarriers based drug delivery against radiotherapy-induced neurotoxic manifestations

Radiotherapy is one of the extensively used therapeutic modalities in glioblastoma and other types of cancers. Radiotherapy is either used as a first-line approach or combined with pharmacotherapy or surgery to manage and treat cancer. Although the use of radiotherapy significantly increased the survival time of patients, but its use has been reported with marked neuroinflammation and cognitive dysfunction that eventually reduced the quality of life of patients. Based on the preclinical and clinical investigations, the profound role of increased oxidative stress, nuclear translocation of NF-kB, production of proinflammatory cytokines such as TNF-α, IL-6, IL-β, increased level of MMPs, increased apoptosis, reduced angiogenesis, neurogenesis, and histological aberrations in CA1, CA2, CA3 and DG region of the hippocampus have been reported. Various pharmacotherapeutic drugs are being used as an adjuvant to counteract this neurotoxic manifestation. Still, most of these drugs suffer from systemic adverse effect, causes interference to ongoing chemotherapy, and exhibit pharmacokinetic limitations in crossing the blood-brain barrier. Therefore, various phytoconstituents, their nano carrier-based drug delivery systems and miRNAs have been explored to overcome the aforementioned limitations. The present review is focused on the mechanism and evidence of radiotherapy-induced neuroinflammation and cognitive dysfunction, pathological and molecular changes in the brain homeostasis, available adjuvants, their limitations. Additionally, the potential role and mechanism of neuroprotection of various nanocarrier based natural products and miRNAs have been discussed.

Effects of low dose ionizing radiation on the brain- a functional, cellular, and molecular perspective

Over the years, the advancement of radio diagnostic imaging tools and techniques has radically improved the diagnosis of different pathophysiological conditions, accompanied by increased exposure to low-dose ionizing radiation. Though the consequences of high dose radiation exposure on humans are very well comprehended, the more publicly relevant effects of low dose radiation (LDR) (≤100 mGy) exposure on the biological system remain ambiguous. The central nervous system, predominantly the developing brain with more neuronal precursor cells, is exceptionally radiosensitive and thus more liable to neurological insult even at low doses, as shown through several rodent studies. Further molecular studies have unraveled the various inflammatory and signaling mechanisms involved in cellular damage and repair that drive these physiological alterations that lead to functional alterations. Interestingly, few studies also claim that LDR exerts therapeutic effects on the brain by initiating an adaptive response. The present review summarizes the current understanding of the effects of low dose radiation at functional, cellular, and molecular levels and the various risks and benefits associated with it based on the evidence available from in vitro, in vivo, and clinical studies. Although the consensus indicates minimum consequences, the overall evidence suggests that LDR can bring about considerable neurological effects in the exposed individual, and hence a re-evaluation of the LDR usage levels and frequency of exposure is required.

Low dose gamma irradiation pretreatment modulates the sensitivity of CNS to subsequent mixed gamma and neutron irradiation of the mouse head

ABSTRACТPurpose: To explore if the total body γ-irradiation at a dose of 0.1 Gy 7 days prior to acute mixed γ, n-irradiation of the head at the dose of 1 Gy can reduce the harmful effects of neutron irradiation on the hippocampal functions, neuroinflammation and neurogenesis.Materials and methods: Mice were exposed to γ-radiation alone, mixed γ,n-radiation or combined γ-rays and γ,n-radiation 7 days after γ-irradiation. Two months post-irradiation, mice were tested in Open Field and in the Morris water maze. The content of microglia, astrocytes, proliferating cells and cytokines TGF-β, TNF-α, IL-1β, GFAP levels, hippocampal BDNF, NT-3, NT-4, NGF mRNA expression were evaluated.Results: Two months after combined irradiation, we observed impaired hippocampus-dependent cognition, which was not detected in mice exposed to γ,n-irradiation. Combined exposure and γ,n-irradiation led to a significant increase in the level of activated microglia and astrocytes in the brains. The level of pro- and anti-inflammatory cytokines in the brain and hippocampal neurotrophine's genes changed differenly after the combined exposure and γ,n-irradiation. The quantity of DCX-positive cells was reduced after γ,n-irradiation exposer alone, but increased after combined irradiation.Conclusions: Our results indicate radio-adaptive responses in brains of mice that were exposed to low-dose gamma irradiation 7 days prior to acute 1 Gy γ,n-irradiation.

Low dose of carbon ion irradiation induces early delayed cognitive impairments in mice

People often encounter various sources of ionizing radiation, both in modern medicine and under various environmental conditions, such as space travel, nuclear power plants or in conditions of man-made disasters that may lead to long-term cognitive impairment. Whilst the effect of exposure to low and high doses of gamma and X-radiation on the central nervous system (CNS) has been well investigated, the consequences of protons and heavy ions irradiation are quite different and poorly understood. As for the assessment of long-term effects of carbon ions on cognitive abilities and neurodegeneration, very few data appeared in the literature. The main object of the research is to investigate the effects of accelerated carbon ions on the cognitive function. Experiments were performed on male SHK mice at an age of two months. Mice were irradiated with a dose of 0.7 Gy of accelerated carbon ions with an energy of 450 meV/n in spread-out Bragg peak (SOBP) on a U-70 particle accelerator (Protvino, Russia). Two months after the irradiation, mice were tested for total activity, spatial learning, as well as long- and short-term hippocampus-dependent memory. One month after the evaluation of cognitive activity, histological analysis of dorsal hippocampus was carried out to assess its morphological state and to reveal late neuronal degeneration. It was found that the mice irradiated with accelerated carbon ions develop an altered behavioral pattern characterized by anxiety and a shortage in hippocampal-dependent memory retention, but not in episodic memory. Nissl staining revealed a reduction in the number of cells in the dorsal hippocampus of irradiated mice, with the most pronounced reduction in cell density observed in the dentate gyrus (DG) hilus. Also, the length of the CA3 field of the dorsal hippocampus was significantly reduced, and the number of cells in it was moderately decreased. Experiments with the use of Fluoro-Jade B (FJB) staining revealed no FJB-positive regions in the dorsal hippocampus of irradiated and control animals 3 months after the irradiation. Thus, no morbid cells were detected in irradiated and control groups. The results obtained indicate that total irradiation with a low dose of carbon ions can produce a cognitive deficit in adult mice without evidence of neurodegenerative pathologic changes.

How Hematopoietic Stem Cells Respond to Irradiation: Similarities and Differences between Low and High Doses of Ionizing Radiations

In this review, we will specifically address the newest insights on the effect of low doses of ionizing radiations on the hematopoietic stem cells, which are prone to long-term deleterious effects. Impact of high doses of irradiation on hematopoietic cells has been widely studied over the years, in line with the risk of accidental or terrorist exposure to irradiation and with a particular attention to the sensitivity of the hematopoietic system. Recently, more studies have focused on lower doses of irradiation on different tissues, due to the increasing exposure caused by medical imaging, radiotherapy or plane travelling for instance. Hence, we will delineate similarities and discrepancies in HSC response to high and low doses of irradiation from these studies.

Organ-Specific Effects of Low Dose Radiation Exposure: A Comprehensive Review

Ionizing radiation (IR) is a high-energy radiation whose biological effects depend on the irradiation doses. Low-dose radiation (LDR) is delivered during medical diagnoses or by an exposure to radioactive elements and has been linked to the occurrence of chronic diseases, such as leukemia and cardiovascular diseases. Though epidemiological research is indispensable for predicting and dealing with LDR-induced abnormalities in individuals exposed to LDR, little is known about epidemiological markers of LDR exposure. Moreover, difference in the LDR-induced molecular events in each organ has been an obstacle to a thorough investigation of the LDR effects and a validation of the experimental results in in vivo models. In this review, we summarized the recent reports on LDR-induced risk of organ-specifically arranged the alterations for a comprehensive understanding of the biological effects of LDR. We suggested that LDR basically caused the accumulation of DNA damages, controlled systemic immune systems, induced oxidative damages on peripheral organs, and even benefited the viability in some organs. Furthermore, we concluded that understanding of organ-specific responses and the biological markers involved in the responses is needed to investigate the precise biological effects of LDR.

Fucoidan from marine brown algae attenuates pancreatic cancer progression by regulating p53 - NFκB crosstalk

Poor pancreatic cancer (PC) prognosis has been attributed to its resistance to apoptosis and propensity for early systemic dissemination. Existing therapeutic strategies are often circumvented by the molecular crosstalk between cell-signalling pathways. p53 is mutated in more than 50% of PC and NFκB is constitutively activated in therapy-resistant residual disease; these mutations and activations account for the avoidance of cell death and metastasis. Recently, we demonstrated the anti-PC potential of fucoidan extract from marine brown alga, Turbinaria conoides (J. Agardh) Kützing (Sargassaceae). In this study, we aimed to characterize the active fractions of fucoidan extract to identify their select anti-PC efficacy, and to define the mechanism(s) involved. Five fractions of fucoidan isolated by ion exchange chromatography were tested for their potential in genetically diverse human PC cell lines. All fractions exerted significant dose-dependent and time-dependent regulation of cell survival. Fucoidans induced apoptosis, activated caspase -3, -8 and -9, and cleaved Poly ADP ribose polymerase (PARP). Pathway-specific transcriptional analysis recognized inhibition of 57 and 38 nuclear factor κB (NFκB) pathway molecules with fucoidan-F5 in MiaPaCa-2 and Panc-1 cells, respectively. In addition, fucoidan-F5 inhibited both the constitutive and Tumor necrosis factor-α (TNFα)-mediated NFκB DNA-binding activity in PC cells. Upregulation of cytoplasmic IκB levels and significant reduction of NFκB-dependent luciferase activity further substantiate the inhibitory potential of seaweed fucoidans on NFκB. Moreover, fucoidan(s) treatment increased cellular p53 in PC cells and reverted NFκB forced-expression-related p53 reduction. The results suggest that fucoidan regulates PC progression and that fucoidans may target p53-NFκB crosstalk and dictate apoptosis in PC cells.

Mitochondrial superoxide dismutase 2 mediates γ-irradiation-induced cancer cell invasion

Sublethal doses of γ-rays promote cancer cell invasion by stimulating a signaling pathway that sequentially involves p53, sulfatase 2 (SULF2), β-catenin, interleukin-6 (IL-6), signal transducer and activator of transcription 3 (STAT3), and Bcl-X_L. Given that Bcl-X_L can increase O₂^•− production by stimulating respiratory complex I, the possible role of mitochondrial reactive oxygen species (ROS) in γ-irradiation-induced cell invasion was investigated. Indeed, γ-irradiation promoted cell invasion by increasing mitochondrial ROS levels, which was prevented by metformin, an inhibitor of complex I. γ-Irradiation-stimulated STAT3 increased the expression of superoxide dismutase 2 (SOD2), a mitochondrial enzyme that catalyzes the conversion of O₂^•− to hydrogen peroxide (H₂O₂). In contrast to O₂^•−, H₂O₂ functions as a signaling molecule. γ-Irradiation consistently stimulated the Src-dependent invasion pathway in a manner dependent on both complex I and SOD2. SOD2 was also essential for the invasion of un-irradiated cancer cells induced by upregulation of Bcl-X_L, an intracellular oncogene, or extracellular factors, such as SULF2 and IL-6. Overall, these data suggested that SOD2 is critical for the malignant effects of radiotherapy and tumor progression through diverse endogenous factors.

A drug usually used to treat type 2 diabetes may also help to prevent cancer relapse following radiotherapy, which is commonly used to kill cancer cells. However, any tumor cells that survive radiation are highly invasive, sometimes causing tumors to spread. Hong-Duck Um and co-workers at the Korea Institute of Radiological & Medical Sciences in Seoul, South Korea, noticed that the surviving cells often showed higher levels of a key enzyme, superoxide dismutase 2 (SOD2), which is involved in energy production in the cellular powerhouse, the mitochondria. Artificially increasing levels of SOD2, without radiation, made cells more invasive. Treatment with metformin, which prevents production of the molecule that SOD2 acts on, prevented cells from becoming invasive. SOD2 has been implicated in many cancers, and is therefore a very promising therapeutic target.

Re-evaluation of the linear no-threshold (LNT) model using new paradigms and modern molecular studies

The linear no-threshold (LNT) model is currently used to estimate low dose radiation (LDR) induced health risks. This model lacks safety thresholds and postulates that health risks caused by ionizing radiation is directly proportional to dose. Therefore even the smallest radiation dose has the potential to cause an increase in cancer risk. Advances in LDR biology and cell molecular techniques demonstrate that the LNT model does not appropriately reflect the biology or the health effects at the low dose range. The main pitfall of the LNT model is due to the extrapolation of mutation and DNA damage studies that were conducted at high radiation doses delivered at a high dose-rate. These studies formed the basis of several outdated paradigms that are either incorrect or do not hold for LDR doses. Thus, the goal of this review is to summarize the modern cellular and molecular literature in LDR biology and provide new paradigms that better represent the biological effects in the low dose range. We demonstrate that LDR activates a variety of cellular defense mechanisms including DNA repair systems, programmed cell death (apoptosis), cell cycle arrest, senescence, adaptive memory, bystander effects, epigenetics, immune stimulation, and tumor suppression. The evidence presented in this review reveals that there are minimal health risks (cancer) with LDR exposure, and that a dose higher than some threshold value is necessary to achieve the harmful effects classically observed with high doses of radiation. Knowledge gained from this review can help the radiation protection community in making informed decisions regarding radiation policy and limits.

Role of NADPH oxidase in radiation-induced pro-oxidative and pro-inflammatory pathways in mouse brain

PURPOSE

The present study was designed to investigate our hypothesis that NADPH oxidase plays a role in radiation-induced pro-oxidative and pro-inflammatory environments in the brain.

MATERIALS AND METHODS

C57BL/6 mice received either fractionated whole brain irradiation or sham-irradiation. The mRNA expression levels of pro-inflammatory mediators, such as TNF-α and MCP-1, were determined by quantitative real-time RT-PCR. The protein expression levels of TNF-α, MCP-1, NOX-2 and Iba1 were detected by immunofluorescence staining. The levels of ROS were visualized by in situ DHE fluorescence staining.

RESULTS

A significant up-regulation of mRNA and protein expression levels of TNF-α and MCP-1 was observed in irradiated mouse brains. Additionally, immunofluorescence staining of Iba1 showed a marked increase of microglial activation in mouse brain after irradiation. Moreover, in situ DHE fluorescence staining revealed that fractionated whole brain irradiation significantly increased production of ROS. Furthermore, a significant increase in immunoreactivity of NOX-2 was detected in mouse brain after irradiation. On the contrary, an enhanced ROS generation in mouse brain after irradiation was markedly attenuated in the presence of NOX inhibitors or NOX-2 neutralizing antibody.

CONCLUSIONS

These results suggest that NOX-2 may play a role in fractionated whole brain irradiation-induced pro-oxidative and pro-inflammatory pathways in mouse brain.

Low-dose or low-dose-rate ionizing radiation-induced bioeffects in animal models

Animal experimental studies indicate that acute or chronic low-dose ionizing radiation (LDIR) (≤100 mSv) or low-dose-rate ionizing radiation (LDRIR) (<6 mSv/h) exposures may be harmful. It induces genetic and epigenetic changes and is associated with a range of physiological disturbances that includes altered immune system, abnormal brain development with resultant cognitive impairment, cataractogenesis, abnormal embryonic development, circulatory diseases, weight gain, premature menopause in female animals, tumorigenesis and shortened lifespan. Paternal or prenatal LDIR/LDRIR exposure is associated with reduced fertility and number of live fetuses, and transgenerational genomic aberrations. On the other hand, in some experimental studies, LDIR/LDRIR exposure has also been reported to bring about beneficial effects such as reduction in tumorigenesis, prolonged lifespan and enhanced fertility. The differences in reported effects of LDIR/LDRIR exposure are dependent on animal genetic background (susceptibility), age (prenatal or postnatal days), sex, nature of radiation exposure (i.e. acute, fractionated or chronic radiation exposure), type of radiation, combination of radiation with other toxic agents (such as smoking, pesticides or other chemical toxins) or animal experimental designs. In this review paper, we aimed to update radiation researchers and radiologists on the current progress achieved in understanding the LDIR/LDRIR-induced bionegative and biopositive effects reported in the various animal models. The roles played by a variety of molecules that are implicated in LDIR/LDRIR-induced health effects will be elaborated. The review will help in future investigations of LDIR/LDRIR-induced health effects by providing clues for designing improved animal research models in order to clarify the current controversial/contradictory findings from existing studies.

Hormophysa triquerta polyphenol, an elixir that deters CXCR4- and COX2-dependent dissemination destiny of treatment-resistant pancreatic cancer cells

Therapy-resistant pancreatic cancer (PC) cells play a crucial role in tumor relapse, recurrence, and metastasis. Recently, we showed the anti-PC potential of an array of seaweed polyphenols and identified efficient drug deliverables. Herein, we investigated the benefit of one such deliverable, Hormophysa triquerta polyphenol (HT-EA), in regulating the dissemination physiognomy of therapy-resistant PC cells in vitro,and residual PC in vivo. Human PC cells exposed to ionizing radiation (IR), with/without HT-EA pre-treatment were examined for the alterations in the tumor invasion/metastasis (TIM) transcriptome (93 genes, QPCR-profiling). Utilizing a mouse model of residual PC, we investigated the benefit of HT-EA in the translation regulation of crucial TIM targets (TMA-IHC). Radiation activated 30, 50, 15, and 38 TIM molecules in surviving Panc-1, Panc-3.27, BxPC3, and MiaPaCa-2 cells. Of these, 15, 44, 12, and 26 molecules were suppressed with HT-EA pre-treatment. CXCR4 and COX2 exhibited cell-line-independent increases after IR, and was completely suppressed with HT-EA, across all PC cells. HT-EA treatment resulted in translational repression of IR-induced CXCR4, COX2, β-catenin, MMP9, Ki-67, BAPX, PhPT-1, MEGF10, and GRB10 in residual PC. Muting CXCR4 or COX2 regulated the migration/invasion potential of IR-surviving cells, while forced expression of CXCR4 or COX2 significantly increased migration/invasion capabilities of PC cells. Further, treatment with HT-EA significantly inhibited IR-induced and CXCR4/COX2 forced expression-induced PC cell migration/invasion. This study (i) documents the TIM blueprint in therapy-resistant PC cells, (ii) defines the role of CXCR4 and COX2 in induced metastatic potential, and (iii) recognizes the potential of HT-EA in deterring the CXCR4/COX2-dependent dissemination destiny of therapy-resistant residual PC cells.

High Energy Particle Radiation-associated Oncogenic Transformation in Normal Mice: Insight into the Connection between Activation of Oncotargets and Oncogene Addiction

Concerns on high-energy particle radiation-induced tumorigenic transformation of normal tissue in astronauts, and in cancer patients undergoing radiotherapy, emphasizes the significance of elucidating the mechanisms involved in radiogenic transformation processes. Mostly used genetically modified or tumor-prone models are less reliable in determining human health risk in space or protracted post-treatment normal tissue toxicity. Here, in wild type C57BL/6 mice, we related the deregulation of distinctive set of tissue-specific oncotargets in major organs upon ⁵⁶Fe (600 MeV/amu; 0.5 Gy/min; 0.8 Gy) particle radiation and compared the response with low LET γ-radiation (¹³⁷Cs; 0.5 Gy/min; 2 Gy). One of the novel findings is the ‘tissue-independent’ activation of TAL2 upon high-energy radiation, and thus qualifies TAL2 as a potential biomarker for particle and other qualities of radiation. Heightened expression of TAL2 gene transcript, which sustained over four weeks post-irradiation foster the concept of oncogene addiction signaling in radiogenic transformation. The positive/negative expression of other selected oncotargets that expresses tissue-dependent manner indicated their role as a secondary driving force that addresses the diversity of tissue-dependent characteristics of tumorigenesis. This study, while reporting novel findings on radiogenic transformation of normal tissue when exposed to particle radiation, it also provides a platform for further investigation into different radiation quality, LET and dose/dose rate effect in healthy organs.

Simulated microgravity potentiates generation of reactive oxygen species in cells

Microgravity (MG) and space radiation are two major environmental factors of space environment. Ionizing radiation generates reactive oxygen species (ROS) which plays a key role in radiation-induced DNA damage. Interestingly, simulated microgravity (SMG) also increases ROS production in various cell types. Thus, it is important to detect whether SMG could potentiate ROS production induced by genotoxins including radiation, especially at a minimal level not sufficient to induce detectable ROS. In this study, we treated mouse embryonic stem (MES) cells with H₂O₂ and SMG for 24 h. The concentration of H₂O₂ used was within 30 μmol/L at which intracellular ROS was the same as that in untreated cells. Exposure of cells to SMG for 24 h did not induce significantly higher levels of intracellular ROS than that of control cells either. Simultaneous exposure of cells to both SMG- and H₂O₂-induced ROS and apoptosis in MES cells. Although incubation in medium containing 5 or 30 μmol/L H₂O₂ induced a small enhancement of DNA double-strand breaks (DSBs), the addition of SMG treatment dramatically increased DSB levels. Taken together, SMG can significantly potentiate the effects of H₂O₂ at a low concentration that induce a small or negligible change in cells on ROS, apoptosis, and DNA damage. The results were discussed in relation to the combined effects of space radiation and MG on human body in this study.

The impact of high and low dose ionising radiation on the central nervous system

Responses of the central nervous system (CNS) to stressors and injuries, such as ionising radiation, are modulated by the concomitant responses of the brains innate immune effector cells, microglia. Exposure to high doses of ionising radiation in brain tissue leads to the expression and release of biochemical mediators of ‘neuroinflammation’, such as pro-inflammatory cytokines and reactive oxygen species (ROS), leading to tissue destruction. Contrastingly, low dose ionising radiation may reduce vulnerability to subsequent exposure of ionising radiation, largely through the stimulation of adaptive responses, such as antioxidant defences. These disparate responses may be reflective of non-linear differential microglial activation at low and high doses, manifesting as an anti-inflammatory or pro-inflammatory functional state. Biomarkers of pathology in the brain, such as the mitochondrial Translocator Protein 18 kDa (TSPO), have facilitated in vivo characterisation of microglial activation and ‘neuroinflammation’ in many pathological states of the CNS, though the exact function of TSPO in these responses remains elusive. Based on the known responsiveness of TSPO expression to a wide range of noxious stimuli, we discuss TSPO as a potential biomarker of radiation-induced effects.

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Ionising radiation can modulate responses of microglial cells in the CNS.

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High doses can induce ROS formation, oxidative stress and neuroinflammation.

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Low doses can mitigate tissue damage via antioxidant defences.

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TSPO as a potential biomarker and modulator of radiation induced effects in the CNS.

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Non-linear differential microglial activation to high and low doses is proposed.

Hemodynamic Flow-Induced Mechanotransduction Signaling Influences the Radiation Response of the Vascular Endothelium

Hemodynamic shear stress is defined as the physical force exerted by the continuous flow of blood in the vascular system. Endothelial cells, which line the inner layer of blood vessels, sense this physiological force through mechanotransduction signaling and adapt to maintain structural and functional homeostasis. Hemodynamic flow, shear stress and mechanotransduction signaling are, therefore, an integral part of endothelial pathophysiology. Although this is a well-established concept in the cardiovascular field, it is largely dismissed in studies aimed at understanding radiation injury to the endothelium and subsequent cardiovascular complications. We and others have reported on the differential response of the endothelium when the cells are under hemodynamic flow shear compared with static culture. Further, we have demonstrated significant differences in the gene expression of static versus shear-stressed irradiated cells in four key pathways, reinforcing the importance of shear stress in understanding radiation injury of the endothelium. This article further emphasizes the influence of hemodynamic shear stress and the associated mechanotransduction signaling on physiological functioning of the vascular endothelium and underscores its significance in understanding radiation injury to the vasculature and associated cardiac complications. Studies of radiation effect on endothelial biology and its implication on cardiotoxicity and vascular complications thus far have failed to highlight the significance of these factors. Factoring in these integral parts of the endothelium will enhance our understanding of the contribution of the endothelium to radiation biology. Without such information, the current approaches to studying radiation-induced injury to the endothelium and its consequences in health and disease are limited.

Polyphenols from marine brown algae target radiotherapy-coordinated EMT and stemness-maintenance in residual pancreatic cancer

INTRODUCTION

Therapy-associated onset of stemness-maintenance in surviving tumor-cells dictates tumor relapse/recurrence. Recently, we recognized the anti-pancreatic cancer (PC) potential of seaweed polyphenol manifolds and narrowed down three superior drug-deliverables that could serve as adjuvants and benefit PC cure. Utilizing the PC- cancer stem cells (PC-CSCs) grown ex vivo and mouse model of residual-PC, we investigated the benefits of seaweed polyphenols in regulating stemness-maintenance.

METHODS

ALDH(+)CD44(+)CD24(+) PC-CSCs from Panc-1, Panc-3.27, MiaPaCa-2, or BxPC-3 cells-derived xenografts grown ex vivo were either mock-irradiated, exposed to fractionated irradiation (FIR, 2Gy/D for 5 days), treated with polyphenols (100 μg/ml) of Hormophysa triquerta (HT-EA), Spatoglossum asperum (SA-EA) or Padina tetrastromatica (PT-EA) with/without FIR were examined for cell viability, transcription of 93 stem-cell-related molecules (QPCR profiling). Polyphenol-dependent regulation of FIR-transactivated Oct4, Zic3, EIF4C, Nanog, and LIF (QPCR) and functional translation of Nanog, SOX2, and OCT3/4 (immunoblotting) were examined in Panc-1/Panc-3.27/MiaPaCa-2/BxPC-3-xenografts derived PC-CSCs. Effect of seaweed-polyphenols in the regulation of EMT (N-Cadherin), pluripotency- (SOX2, OCT3/4, Nanog) and stemness-maintenance (PI3KR1, LIF, CD44) in therapy (FIR, 2Gy/D for 5D/wk for 3-weeks) resistant residual tumors were examined by tissue microarray construction and automated immunohistochemistry.

RESULTS

Ex vivo exposure of PC-CSCs to SA-EA, PT-EA and HT-EA exhibit dose-dependent inhibition of cell viability. FIR amplified the transcription of 69, 80, 74 and 77 stem-cell related genes in MiaPaCa-2-, Panc-1-, Panc-3.27- and BXPC3-established xenograft-derived ALDH(+)CD44(+)CD24(+)PC-CSCs. Treatment with SA-EA, PT-EA, or HT-EA completely suppressed FIR-activated stem-cell transcriptional machinery in ALDH(+)CD44(+)CD24(+)PC-CSCs established from MiaPaCa-2, Panc-1, Panc-3.27 and BXPC3 xenografts. QPCR validated EIF4C, OCT3/4, Nanog, LIF, and ZIC3 transcriptional profile outcomes. Nanog, Sox2, and OCT3/4 immunoblotting affirmed the PC-CSC radiosensitizing benefit of seaweed polyphenols. Residual-PC tissues microarrayed and immunostained after in vivo treatments recognized complete regulation of FIR-induced SOX2, OCT3/4, Nanog, LIF, CD44, PIK3R1, N-Cadherin, and E-Cadherin with SA-EA, PT-EA, and HT-EA.

CONCLUSIONS

These data, for the first time, documented the EMT/stemness-maintenance in therapy-resistant PC-CSCs. Further, the data suggest that seaweed polyphenols may inhibit PC relapse/recurrence by targeting therapy-orchestrated stem-cell signaling in residual cells.

CDK4-mediated MnSOD activation and mitochondrial homeostasis in radioadaptive protection

Mammalian cells are able to sense environmental oxidative and genotoxic conditions such as the environmental low-dose ionizing radiation (LDIR) present naturally on the earth's surface. The stressed cells then can induce a so-called radioadaptive response with an enhanced cellular homeostasis and repair capacity against subsequent similar genotoxic conditions such as a high dose radiation. Manganese superoxide dismutase (MnSOD), a primary mitochondrial antioxidant in mammals, has long been known to play a crucial role in radioadaptive protection by detoxifying O2(•-) generated by mitochondrial oxidative phosphorylation. In contrast to the well-studied mechanisms of SOD2 gene regulation, the mechanisms underlying posttranslational regulation of MnSOD for radioprotection remain to be defined. Herein, we demonstrate that cyclin D1/cyclin-dependent kinase 4 (CDK4) serves as the messenger to deliver the stress signal to mitochondria to boost mitochondrial homeostasis in human skin keratinocytes under LDIR-adaptive radioprotection. Cyclin D1/CDK4 relocates to mitochondria at the same time as MnSOD enzymatic activation peaks without significant changes in total MnSOD protein level. The mitochondrial-localized CDK4 directly phosphorylates MnSOD at serine-106 (S106), causing enhanced MnSOD enzymatic activity and mitochondrial respiration. Expression of mitochondria-targeted dominant negative CDK4 or the MnSOD-S106 mutant reverses LDIR-induced mitochondrial enhancement and adaptive protection. The CDK4-mediated MnSOD activation and mitochondrial metabolism boost are also detected in skin tissues of mice receiving in vivo whole-body LDIR. These results demonstrate a unique CDK4-mediated mitochondrial communication that allows cells to sense environmental genotoxic stress and boost mitochondrial homeostasis by enhancing phosphorylation and activation of MnSOD.

Metastatic neuroblastoma cancer stem cells exhibit flexible plasticity and adaptive stemness signaling

Introduction

High-risk neuroblastoma (HR-NB) presenting with hematogenous metastasis is one of the most difficult cancers to cure. Patient survival is poor. Aggressive tumors contain populations of rapidly proliferating clonogens that exhibit stem cell properties, cancer stem cells (CSCs). Conceptually, CSCs that evade intensive multimodal therapy dictate tumor progression, relapse/recurrence, and poor clinical outcomes. Herein, we investigated the plasticity and stem-cell related molecular response of aggressive metastatic neuroblastoma cells that fit the CSC model.

Methods

Well-characterized clones of metastatic site-derived aggressive cells (MSDACs) from a manifold of metastatic tumors of clinically translatable HR-NB were characterized for their CSC fit by examining epithelial-to-mesenchymal transition (EMT) (E-cadherin, N-Cadherin), survival (NFκB P65, p50, IκB and pIκB) and drug resistance (ABCG2) by immunoblotting; pluripotency maintenance (Nanog, SOX2) by immunofluorescence; and EMT and stemness related transcription of 93 genes by QPCR profiling. Plasticity of MSDACs under sequential alternation of culture conditions with serum and serum-free stem-cell conditions was assessed by clonal expansion (BrdU incorporation), tumorosphere formation (anchorage independent growth), EMT and stemness related transcriptome (QPCR profiling) and validated with MYC, SOX2, EGFR, NOTCH1 and CXCL2 immunoblotting.

Results

HR-NB MSDACs maintained in alternated culture conditions, serum-free stem cell medium to growth medium with serum and vice versa identified its flexible revocable plasticity characteristics. We observed signatures of stem cell-related molecular responses consistent with phenotypic conversions. Successive reintroduction to the favorable niche not only regained identical EMT, self-renewal capacity, pluripotency maintenance, and other stem cell-related signaling events, but also instigated additional events depicting aggressive adaptive plasticity.

Conclusions

Together, these results demonstrated the flexible plasticity of HR-NB MSDACs that typically fit the CSC model, and further identified the intrinsic adaptiveness of the successive phenotype switching that clarifies the heterogeneity of HR-NB. Moreover, the continuous ongoing acquisition of stem cell-related molecular rearrangements may hold the key to the switch from favorable disease to HR-NB.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0002-8) contains supplementary material, which is available to authorized users.

Therapeutic and space radiation exposure of mouse brain causes impaired DNA repair response and premature senescence by chronic oxidant production

Despite recent epidemiological evidences linking radiation exposure and a number of human ailments including cancer, mechanistic understanding of how radiation inflicts long-term changes in cerebral cortex, which regulates important neuronal functions, remains obscure. The current study dissects molecular events relevant to pathology in cerebral cortex of 6 to 8 weeks old female C57BL/6J mice two and twelve months after exposure to a γ radiation dose (2 Gy) commonly employed in fractionated radiotherapy. For a comparative study, effects of 1.6 Gy heavy ion 56Fe radiation on cerebral cortex were also investigated, which has implications for space exploration. Radiation exposure was associated with increased chronic oxidative stress, oxidative DNA damage, lipid peroxidation, and apoptosis. These results when considered with decreased cortical thickness, activation of cell-cycle arrest pathway, and inhibition of DNA double strand break repair factors led us to conclude to our knowledge for the first time that radiation caused aging-like pathology in cerebral cortical cells and changes after heavy ion radiation were more pronounced than γ radiation.

Acquired tumor cell radiation resistance at the treatment site is mediated through radiation-orchestrated intercellular communication

PURPOSE

Radiation resistance induced in cancer cells that survive after radiation therapy (RT) could be associated with increased radiation protection, limiting the therapeutic benefit of radiation. Herein we investigated the sequential mechanistic molecular orchestration involved in radiation-induced radiation protection in tumor cells.

RESULTS

Radiation, both in the low-dose irradiation (LDIR) range (10, 50, or 100 cGy) or at a higher, challenge dose IR (CDIR), 4 Gy, induced dose-dependent and sustained NFκB-DNA binding activity. However, a robust and consistent increase was seen in CDIR-induced NFκB activity, decreased DNA fragmentation, apoptosis, and cytotoxicity and attenuation of CDIR-inhibited clonal expansion when the cells were primed with LDIR prior to challenge dose. Furthermore, NFκB manipulation studies with small interfering RNA (siRNA) silencing or p50/p65 overexpression unveiled the influence of LDIR-activated NFκB in regulating CDIR-induced DNA fragmentation and apoptosis. LDIR significantly increased the transactivation/translation of the radiation-responsive factors tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α), cMYC, and SOD2. Coculture experiments exhibit LDIR-influenced radiation protection and increases in cellular expression, secretion, and activation of radiation-responsive molecules in bystander cells. Individual gene-silencing approach with siRNAs coupled with coculture studies showed the influence of LDIR-modulated TNF-α, IL-1α, cMYC, and SOD2 in induced radiation protection in bystander cells. NFκB inhibition/overexpression studies coupled with coculture experiments demonstrated that TNF-α, IL-1α, cMYC, and SOD2 are selectively regulated by LDIR-induced NFκB.

CONCLUSIONS

Together, these data strongly suggest that scattered LDIR-induced NFκB-dependent TNF-α, IL-1α, cMYC, and SOD2 mediate radiation protection to the subsequent challenge dose in tumor cells.

Abscopal effect of low-LET γ-radiation mediated through Rel protein signal transduction in a mouse model of nontargeted radiation response

Ascertaining the ionizing radiation (IR)-induced bystander response and its preceding molecular regulation would increase our understanding of the mechanism of acute and delayed radiobiological effects. Recent evidence clearly prompted that radiation-induced nuclear factor kappa B (NF-κB) would play a key role in bystander responses in nontargeted cells. Accordingly, we investigated the orchestration of NF-κB signaling after IR in a nontargeted distant organ. Heart tissues from C57/BL6 mice either mock irradiated or exposed (limited to lower abdomen 1 cm diameter) to single-dose IR (SDR: 2 or 10 Gy) or fractionated IR (FIR, 2 Gy per day for 5 days) were examined for onset of abscopal NF-κB signal transduction, translated activity, downstream functional signaling and associated DNA damage. Radiation significantly induced NF-κB DNA binding activity in nontargeted heart. Transcriptional profiling showed that 51, 46 and 26 of 88 genes were significantly upregulated after 2 Gy, 10 Gy and FIR. Of these genes, 22 showed dose- and fractionation-independent upregulation. Immunohistochemistry revealed a robust increase in p65 and cMyc expression in distant heart after SDR and FIR. Immunoblotting revealed increased phosphorylation of p38 after 2 Gy and extracellular signal-regulated kinases 1/2 after 10 Gy in nontargeted heart. In addition, IR exposure significantly enhanced DNA fragmentation in nontargeted heart. Together, these data clearly indicated an induced abscopal response in distant organ after clinically relevant IR doses. More importantly, the results imply that orchestration of NF-κB signal transduction in nontargeted tissues may serve as an effector and could play a key role in induced abscopal responses.

Suppression of alkylating agent induced cell transformation and gastric ulceration by low-dose alkylating agent pretreatment

Exposure to mild stress by chemicals and radiation causes DNA damage and leads to acquired stress resistance. Although the linear no-threshold (LNT) model of safety assessment assumes risk from any dose, evidence from radiological research demonstrates a conflicting hormetic phenomenon known as the hormesis effect. However, the mechanisms underlying radiation hormesis have not yet been clarified, and little is known about the effects of low doses of chemical carcinogens. We analyzed the efficacy of pretreatment with low doses of the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) on the subsequent induction of cell transformation and gastric ulceration by high-dose MNNG. We used an in vitro Balb/3T3 A31-1-1 cell transformation test and monitored the formation of gastric ulcers in 5-week-old male ICR mice that were administered MNNG in drinking water. The treatment concentrations of MNNG were determined by the cell survival rate and past reports. For low-dose in vitro and in vivo experiments, MNNG was used at 0.028 μM, and 2.8 μg/mL, respectively. The frequency of cell transformation induced by 10 μm MNNG was decreased by low-dose MNNG pretreatment to levels similar to that of spontaneous transformation. In addition, reactive oxygen species (ROS) and mutation frequencies induced by 10 μm MNNG were decreased by low-dose MNNG pretreatment. Importantly, low-dose MNNG pretreatment had no effect on cell proliferation. In vivo studies showed that the number of gastric ulcers induced by 1 mg/mL MNNG decreased after low-dose MNNG pretreatment. These data indicate that low-dose pretreatment with carcinogens may play a beneficial role in the prevention of chemical toxicity under specified conditions.

Radiation-induced TNFα cross signaling-dependent nuclear import of NFκB favors metastasis in neuroblastoma

Ascertaining function-specific orchestration of NFκB in response to radiation may reveal a molecular blue-print that dictates induced relapse and metastasis of the neuroblastoma. We recently demonstrated that sustained activation of NFκB caused by ionizing radiation (IR)-initiated TNFα-NFκB feedback signaling leads to radioresistance and recurrence of neuroblastoma. We investigated whether muting IR-triggered or TNFα-dependent second-signaling feedback-dependent NFκB nuclear import results in limiting IR-altered invasion and metastasis. Neuroblastoma cells were exposed to 2 Gy and incubated for 1 h or 24 h. The cells were then treated with an NFκB-targeting peptide blocker, SN50. Upon confirming the blockade in DNA-binding activity, transcription driven transactivation of NFκB and secretion of soluble TNFα, transcriptional alterations of 93 tumor invasion/metastasis genes were assessed by using QPCR profiling and then were selectively validated at the protein level. Exposure to 2 Gy induced 63, 42 and 71 genes in surviving SH-SY5Y, IMR-32 and SK-N-MC cells, respectively. Blocking post-translational nuclear import of NFκB comprehensively inhibited both initial activation of genes (62/63, 34/42 and 65/71) triggered by IR and also TNFα-mediated second signaling-dependent sustained (59/63, 32/42 and 71/71) activation of tumor invasion and metastasis signaling molecules. Furthermore, alterations in the proteins MMP9, MMP2, PYK-2, SPA-1, Dnmt3b, Ask-1, CTGF, MMP10, MTA-2, NF-2, E-Cadherin, TIMP-2 and ADAMTS1 and the results of our scratch-wound assay validate the role of post-translational NFκB in IR-regulated invasion/metastasis. These data demonstrate that IR-induced second-phase (post-translational) NFκB activation mediates TNFα-dependent second signaling and further implies that IR induced NFκB in cells that survive after treatment regulates tumor invasion/metastasis signaling.

Molecular basis of 'hypoxic' breast cancer cell radio-sensitization: phytochemicals converge on radiation induced Rel signaling

BACKGROUND

Heterogeneously distributed hypoxic areas are a characteristic property of locally advanced breast cancers (BCa) and generally associated with therapeutic resistance, metastases, and poor patient survival. About 50% of locally advanced BCa, where radiotherapy is less effective are suggested to be due to hypoxic regions. In this study, we investigated the potential of bioactive phytochemicals in radio-sensitizing hypoxic BCa cells.

METHODS

Hypoxic (O2-2.5%; N2-92.5%; CO2-5%) MCF-7 cells were exposed to 4 Gy radiation (IR) alone or after pretreatment with Curcumin (CUR), curcumin analog EF24, neem leaf extract (NLE), Genistein (GEN), Resveratrol (RES) or raspberry extract (RSE). The cells were examined for inhibition of NFκB activity, transcriptional modulation of 88 NFκB signaling pathway genes, activation and cellular localization of radio-responsive NFκB related mediators, eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2, -5 and associated induction of cell death.

RESULTS

EMSA revealed that cells exposed to phytochemicals showed complete suppression of IR-induced NFκB. Relatively, cells exposed EF24 revealed a robust inhibition of IR-induced NFκB. QPCR profiling showed induced expression of 53 NFκB signaling pathway genes after IR. Conversely, 53, 50, 53, 53, 53 and 53 of IR-induced genes were inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. In addition, 25, 29, 24, 16, 11 and 21 of 35 IR-suppressed genes were further inhibited with EF24, NLE, CUR, GEN, RES and RSE respectively. Immunoblotting revealed a significant attenuating effect of IR-modulated radio-responsive eNos, Erk1/2, SOD2, Akt1/2/3, p50, p65, pIκBα, TNFα, Birc-1, -2 and -5 with EF24, NLE, CUR, GEN, RES or RSE. Annexin V-FITC staining showed a consistent and significant induction of IR-induced cell death with these phytochemicals. Notably, EF24 robustly conferred IR-induced cell death.

CONCLUSIONS

Together, these data identifies the potential hypoxic cell radio-sensitizers and further implies that the induced radio-sensitization may be exerted by selectively targeting IR-induced NFκB signaling.

Manganese superoxide dismutase interacts with a large scale of cellular and mitochondrial proteins in low-dose radiation-induced adaptive radioprotection

The cellular adaptive response to certain low-level genotoxic stresses, including exposure to low-dose ionizing radiation (LDIR), shows promise as a tool to enhance radioprotection in normal cells but not in tumor cells. Manganese superoxide dismutase (MnSOD), a fundamental mitochondrial antioxidant in mammalian cells, plays a key role in the LDIR-induced adaptive response. In this study, we aimed to elucidate the signaling network associated with MnSOD-induced radiation protection. A MnSOD-interacting protein profile was established in LDIR-treated human skin cells. Human skin keratinocytes (HK18) were irradiated with a single dose of LDIR (10 cGy X-ray) and the cell lysates were immunoprecipitated using α-MnSOD and applied to two different gel-based proteomic experiments followed by mass spectrometry for protein identification. Analysis of the profiles of MnSOD-interacting partners before and after LDIR detected various patterns of MnSOD protein-protein interactions in response to LDIR. Interestingly, many of the MnSOD-interacting proteins are known to have functions related to mitochondrial regulation of cell metabolism, apoptosis, and DNA repair. These results provide evidence indicating that in addition to the enzymatic action of detoxifying superoxide, the antioxidant MnSOD may function as a signaling regulator in stress-induced adaptive protection through cell survival pathways.

A review of the logistic role of L-carnitine in the management of radiation toxicity and radiotherapy side effects

Radiation therapy is a key modality in the treatment of different cancer types. Fatigue is the most common side effect of radiotherapy, while others include nausea, hair loss, skin irritation, anemia, infertility, cardiovascular disease, cognitive impairment and even the development of second cancers. Studies in experimental animals have shown protective effects of carnitine against exposure of various organs to ionizing radiation, whereas carnitine deficiency is known to enhance radiation-induced toxicity. This report summarizes the recent literature on the adverse effects of radiotherapy and the impact of radiation on carnitine homeostasis. Although some studies have demonstrated the prophylactic benefits of carnitine against the toxic effects of chemotherapy, the role of carnitine in the prognosis and management of cancer patients receiving radiotherapy is not clear and needs to be explored.