Irradiation induces regionally specific alterations in pro-inflammatory environments in rat brain

Memantine to Reduce Cognitive Impairment After Radiation in Children: A Pilot Study Evaluating the Feasibility of Memantine in Reducing Cognitive Impairment in Pediatric Patients after Radiation Therapy for Central Nervous System Tumors

PURPOSE

Memantine is standard in certain adults receiving brain radiation therapy (RT) to decrease cognitive impacts, but it is unknown whether pediatric patients can take, tolerate, and/or benefit from memantine. In this prospective single-arm feasibility study, we hypothesized that pediatric patients receiving central nervous system (CNS) RT would tolerate memantine with good adherence.

METHODS AND MATERIALS

Patients aged 4 to 18 years with a primary CNS malignancy (excluding World Health Organization grade 4 astrocytoma, glioblastoma) receiving intracranial RT were eligible. A 6-month memantine course was given during and after RT, with dose titration in 5 mg increments over 4 weeks targeting a weight-based maximum (0.4 mg/kg to the closest 5 mg), not to exceed 10 mg twice a day. The primary endpoint was to achieve 80% drug adherence rate in 80% of patients measured 1 month after RT. Secondary objectives included memantine feasibility at 3 and 6 months.

RESULTS

Eighteen patients enrolled from 2020 to 2022 and were prescribed memantine with RT. The study closed early to avoid competing with the phase 3 randomized Children's Oncology Group study ACCL2031. No predefined stopping rules were met. One patient withdrew for cognition-altering substance use, leaving 17 patients available for analysis. One patient discontinued memantine after one dose due to nausea. For the remaining 16 patients, there was a median of 100% pill completion rate (range, 74%-100%; n = 9/17 with 100% adherence) at 1 month after RT, with 15/16 (94%) with adherence rates >80%. At the 3- and 6-month post-RT time points for secondary endpoints, the median adherence rates were 100% (range, 55%-100%) and 96% (range, 33%-100%), respectively. Grade 1 to 2 fatigue, headache, and nausea were the most common toxicity events, at least possibly related to the study drug (n = 27), without attributable grade 3+ events.

CONCLUSIONS

Memantine is a feasible, safe, and well-tolerated addition to multimodality treatment for pediatric CNS malignancies. Results of ACCL2031 are awaited to define the value of memantine in this population.

Impact of Apolipoprotein E Genotype on Neurocognitive Function in Patients With Brain Metastases: An Analysis of NRG Oncology's RTOG 0614

PURPOSE

Whole-brain radiation therapy (WBRT) is a common treatment for brain metastases and is frequently associated with decline in neurocognitive functioning (NCF). The e4 allele of the apolipoprotein E (APOE) gene is associated with increased risk of Alzheimer disease and NCF decline associated with a variety of neurologic diseases and insults. APOE carrier status has not been evaluated as a risk factor for onset time or extent of NCF impairment in patients with brain metastases treated with WBRT.

METHODS AND MATERIALS

NRG/Radiation Therapy Oncology Group 0614 treated adult patients with brain metastases with 37.5 Gy of WBRT (+/- memantine), performed longitudinal NCF testing, and included an optional blood draw for APOE analysis. NCF test results were compared at baseline and over time with mixed-effects models. A cause-specific Cox model for time to NCF failure was performed to assess the effects of treatment arm and APOE carrier status.

RESULTS

APOE results were available for 45% of patients (n = 227/508). NCF did not differ by APOE e4 carrier status at baseline. Mixed-effects modeling showed that APOE e4 carriers had worse memory after WBRT compared with APOE e4 noncarriers (Hopkins Verbal Learning Test-Revised total recall [least square mean difference, 0.63; P = .0074], delayed recognition [least square mean difference, 0.75; P = .023]). However, APOE e4 carrier status was not associated with time to NCF failure (hazard ratio, 0.86; 95% CI, 0.60-1.23; P = .40). Memantine delayed the time to NCF failure, regardless of carrier status (hazard ratio, 0.72; 95% CI, 0.52-1.01; P = .054).

CONCLUSIONS

APOE e4 carriers with brain metastases exhibited greater decline in learning and memory, executive function, and the Clinical Trial Battery Composite score after treatment with WBRT (+/- memantine), without acceleration of onset of difference in time to NCF failure.

Asparagine endopeptidase deficiency mitigates radiation-induced brain injury by suppressing microglia-mediated neuronal senescence

Mounting evidence supports the role of neuroinflammation in radiation-induced brain injury (RIBI), a chronic disease characterized by delayed and progressive neurological impairment. Asparagine endopeptidase (AEP), also known as legumain (LGMN), participates in multiple malignancies and neurodegenerative diseases and may potentially be involved in RIBI. Here, we found AEP expression was substantially elevated in the cortex and hippocampus of wild-type (Lgmn+/+) mice following whole-brain irradiation. Lgmn knockout (Lgmn-/-) alleviated neurological impairment caused by whole-brain irradiation by suppressing neuronal senescence. Bulk RNA and metabolomic sequencing revealed AEP's involvement in the antigen processing and presentation pathway and neuroinflammation. This was further confirmed by co-culturing Lgmn+/+ primary neurons with the conditioned media derived from irradiated Lgmn+/+ or Lgmn-/- primary microglia. Furthermore, esomeprazole inhibited the enzymatic activity of AEP and RIBI. These findings identified AEP as a critical factor of neuroinflammation in RIBI, highlighting the prospect of targeting AEP as a therapeutic approach.

Investigation of high-dose radiotherapy's effect on brain structure aggravated cognitive impairment and deteriorated patient psychological status in brain tumor treatment

This study aims to investigate the potential impact of high-dose radiotherapy (RT) on brain structure, cognitive impairment, and the psychological status of patients undergoing brain tumor treatment. We recruited and grouped 144 RT-treated patients with brain tumors into the Low dose group (N = 72) and the High dose group (N = 72) according to the RT dose applied. Patient data were collected by using the HADS and QLQ-BN20 system for subsequent analysis and comparison. Our analysis showed no significant correlation between the RT doses and the clinicopathological characteristics. We found that a high dose of RT could aggravate cognitive impairment and deteriorate patient role functioning, indicated by a higher MMSE and worsened role functioning in the High dose group. However, the depression status, social functioning, and global health status were comparable between the High dose group and the Low dose group at Month 0 and Month 1, while being worsened in the High dose group at Month 3, indicating the potential long-term deterioration of depression status in brain tumor patients induced by high-dose RT. By comparing patient data at Month 0, Month 1, Month 3, Month 6, and Month 9 after RT, we found that during RT treatment, RT at a high dose could aggravate cognitive impairment in the short term and lead to worsened patient role functioning, and even deteriorate the overall psychological health status of patients in the long term.

Glitches in the brain: the dangerous relationship between radiotherapy and brain fog

Up to approximately 70% of cancer survivors report persistent deficits in memory, attention, speed of information processing, multi-tasking, and mental health functioning, a series of symptoms known as "brain fog." The severity and duration of such effects can vary depending on age, cancer type, and treatment regimens. In particular, every year, hundreds of thousands of patients worldwide undergo radiotherapy (RT) for primary brain tumors and brain metastases originating from extracranial tumors. Besides its potential benefits in the control of tumor progression, recent studies indicate that RT reprograms the brain tumor microenvironment inducing increased activation of microglia and astrocytes and a consequent general condition of neuroinflammation that in case it becomes chronic could lead to a cognitive decline. Furthermore, radiation can induce endothelium reticulum (ER) stress directly or indirectly by generating reactive oxygen species (ROS) activating compensatory survival signaling pathways in the RT-surviving fraction of healthy neuronal and glial cells. In particular, the anomalous accumulation of misfolding proteins in neuronal cells exposed to radiation as a consequence of excessive activation of unfolded protein response (UPR) could pave the way to neurodegenerative disorders. Moreover, exposure of cells to ionizing radiation was also shown to affect the normal proteasome activity, slowing the degradation rate of misfolded proteins, and further exacerbating ER-stress conditions. This compromises several neuronal functions, with neuronal accumulation of ubiquitinated proteins with a consequent switch from proteasome to immunoproteasome that increases neuroinflammation, a crucial risk factor for neurodegeneration. The etiology of brain fog remains elusive and can arise not only during treatment but can also persist for an extended period after the end of RT. In this review, we will focus on the molecular pathways triggered by radiation therapy affecting cognitive functions and potentially at the origin of so-called "brain fog" symptomatology, with the aim to define novel therapeutic strategies to preserve healthy brain tissue from cognitive decline.

Single-fraction Radiation Treatment Dose Response in a Genetically Engineered Mouse Model of Medulloblastoma

Medulloblastoma is the most common malignant brain tumor of children. Although standard of care radiotherapy for pediatric medulloblastoma (PM) can lead to long-term remission or cure in many patients, it can also cause life-long cognitive impairment and other adverse effects. The pathophysiological mechanisms involved in radiation-induced cerebral damage are incompletely understood, and their elucidation may lead to interventions that mitigate radiation toxicity. To explore the mechanisms of radiation-induced cerebral damage, transgenic mouse models of PM and non-tumor-bearing controls were exposed to radiation doses that ranged from 0 to 30 Gy. Between 0-20 Gy, a significant dose-dependent reduction in tumor-associated hydrocephalus and increase in overall survival were observed. However, at 30 Gy, hydrocephalus incidence increased and median overall survival fell to near-untreated levels. Immunohistochemistry revealed that both tumor-bearing and non-tumor-bearing mice treated with 30 Gy of radiation had significantly more reactive astrocytes and microvascular damage compared to untreated controls. This effect was persistent across mice that were given 1 and 2 weeks of recovery time after irradiation. Our data suggest that radiation therapy promotes neural death by inducing long-term neuroinflammation in PM, suggesting radiation delivery methods that limit inflammation may be effective at widening the therapeutic window of radiation therapy in PM patients.

Altered expression of inflammation-associated molecules in striatum: an implication for sensitivity to heavy ion radiations

Background and objective

Heavy ion radiation is one of the major hazards astronauts face during space expeditions, adversely affecting the central nervous system. Radiation causes severe damage to sensitive brain regions, especially the striatum, resulting in cognitive impairment and other physiological issues in astronauts. However, the intensity of brain damage and associated underlying molecular pathological mechanisms mediated by heavy ion radiation are still unknown. The present study is aimed to identify the damaging effect of heavy ion radiation on the striatum and associated underlying pathological mechanisms.

Materials and methods

Two parallel cohorts of rats were exposed to radiation in multiple doses and times. Cohort I was exposed to 15 Gy of 12C6+ ions radiation, whereas cohort II was exposed to 3.4 Gy and 8 Gy with 56Fe26+ ions irradiation. Physiological and behavioural tests were performed, followed by 18F-FDG-PET scans, transcriptomics analysis of the striatum, and in-vitro studies to verify the interconnection between immune cells and neurons.

Results

Both cohorts revealed more persistent striatum dysfunction than other brain regions under heavy ion radiation at multiple doses and time, exposed by physiological, behavioural, and 18F-FDG-PET scans. Transcriptomic analysis revealed that striatum dysfunction is linked with an abnormal immune system. In vitro studies demonstrated that radiation mediated diversified effects on different immune cells and sustained monocyte viability but inhibited its differentiation and migration, leading to chronic neuroinflammation in the striatum and might affect other associated brain regions.

Conclusion

Our findings suggest that striatum dysfunction under heavy ion radiation activates abnormal immune systems, leading to chronic neuroinflammation and neuronal injury.

Low-dose brain radiation: lowering hyperphosphorylated-tau without increasing DNA damage or oncogenic activation

Brain radiation has been medically used to alter the metabolism of cancerous cells and induce their elimination. Rarely, though, brain radiation has been used to interfere with the pathomechanisms of non-cancerous brain disorders, especially neurodegenerative disorders. Data from low-dose radiation (LDR) on swine brains demonstrated reduced levels of phosphorylated-tau (CP13) and amyloid precursor protein (APP) in radiated (RAD) versus sham (SH) animals. Phosphorylated-tau and APP are involved in Alzheimer's disease (AD) pathogenesis. We determined if the expression levels of hyperphosphorylated-tau, 3R-tau, 4R-tau, synaptic, intraneuronal damage, and DNA damage/oncogenic activation markers were altered in RAD versus SH swine brains. Quantitative analyses demonstrated reduced levels of AT8 and 3R-tau in hippocampus (H) and striatum (Str), increased levels of synaptophysin and PSD-95 in frontal cortex (FCtx), and reduced levels of NF-L in cerebellum (CRB) of RAD versus SH swine. DNA damage and oncogene activation markers levels did not differ between RAD and SH animals, except for histone-H3 (increased in FCtx and CRB, decreased in Str), and p53 (reduced in FCtx, Str, H and CRB). These findings confirm the region-based effects of sLDR on proteins normally expressed in larger mammalian brains and support the potential applicability of LDR to beneficially interfere against neurodegenerative mechanisms.

Manganese-enhanced magnetic resonance assessment of changes in hippocampal neural function after the treatment of radiation-induced brain injury with bone marrow mesenchymal stem cells

The role of bone marrow mesenchymal stem cells (BMSCs) in treating radiation-induced brain injury (RIBI) is not completely understood, and assessment methods to directly characterize neurological function are lacking. In this study, we aimed to evaluate the effects of BMSCs treatment on changes in hippocampal neural function in Sprague-Dawley(SD) rats with RIBI, and to evaluate the therapeutic effect of BMSCs by manganese-enhanced magnetic resonance imaging (MEMRI). First, we assessed cognitive function after RIBI treatment with BMSCs using the Morris water maze. Next, we used MEMRI at two time points to observe the treatment effect and explore the correlation between MEMRI and cognitive function. Finally, we evaluated the expression of specific hippocampal neurofunctional proteins, the ultrastructure of hippocampal nerves, and the histological changes in the hippocampus. After BMSCs treatment of RIBI, cognitive dysfunction improved significantly, the expression of hippocampal neurofunctional proteins was increased, the integrity of the hippocampal neural structure was protected, and nerve cell survival was enhanced. The improvement in neurological function was successfully detected by MEMRI, and MEMRI was highly correlated with cognitive function and histological changes. These results suggest that BMSCs treatment of RIBI is an optional modality, and MEMRI can be used for treatment evaluation.

Neurotoxicity from Old and New Radiation Treatments for Brain Tumors

Research regarding the mechanisms of brain damage following radiation treatments for brain tumors has increased over the years, thus providing a deeper insight into the pathobiological mechanisms and suggesting new approaches to minimize this damage. This review has discussed the different factors that are known to influence the risk of damage to the brain (mainly cognitive disturbances) from radiation. These include patient and tumor characteristics, the use of whole-brain radiotherapy versus particle therapy (protons, carbon ions), and stereotactic radiotherapy in various modalities. Additionally, biological mechanisms behind neuroprotection have been elucidated.

Dual Effects of miR-181b-2-3p/SOX21 Interaction on Microglia and Neural Stem Cells after Gamma Irradiation

Ionizing radiation induces brain inflammation and the impairment of neurogenesis by activating microglia and inducing apoptosis in neurogenic zones. However, the causal relationship between microglial activation and the impairment of neurogenesis as well as the relevant molecular mechanisms involved in microRNA (miR) remain unknown. In the present study, we employed immunohistochemistry and real-time RT-PCR to study the microglial activation and miRNA expression in mouse brains. Real-time RT-PCR, western blot, ELISA, cell proliferation and cytotoxicity assay were used in BV2 and mouse neural stem cells (NSCs). In the mouse model, we found the acute activation of microglia at 1 day and an increased number of microglial cells at 1, 7 and 120 days after irradiation at postnatal day 3 (P3), day 10 (P10) and day 21 (P21), respectively. In cell models, the activation of BV2, a type of microglial cell line, was observed after gamma irradiation. Real-time RT-PCR analysis revealed a deceased expression of miR-181b-2-3p and an increased expression of its target SRY-related high-mobility group box transcription factor 21 (SOX21) in a dose- and time-dependent fashion. The results of the luciferase reporter assay confirmed that SOX21 was the target of miR-181b-2-3p. Furthermore, SOX21 knockdown by siRNA inhibited the activation of microglia, thereby suggesting that the direct interaction of 181b-2-3p with SOX21 might be involved in radiation-induced microglial activation and proliferation. Interestingly, the gamma irradiation of NSCs increased miR-181b-2-3p expression but decreased SOX21 mRNA, which was the opposite of irradiation-induced expression in BV2 cells. As irradiation reduced the viability and proliferation of NSCs, whereas the overexpression of SOX21 restored the impaired cell viability and promoted the proliferation of NSCs, the findings suggest that the radiation-induced interaction of miR-181b-2-3p with SOX21 may play dual roles in microglia and NSCs, respectively, leading to the impairment of brain neurogenesis.

Dose-dependent early white matter alterations in patients with brain metastases after radiotherapy

PURPOSE

Previous diffusion tensor imaging (DTI) studies have mainly focused on dose-dependent white matter (WM) alterations 1 month to 1 year after radiation therapy (RT) with a tract-average method. However, WM alterations immediately after RT are subtle, resulting in early WM alterations that cannot be detected by tract-average methods. Therefore, we performed a study with an along-tract method in patients with brain metastases to explore the early dose-response pattern of WM alterations after RT.

METHODS

Sixteen patients with brain metastases underwent DTI before and 1-3 days after brain RT. DTI metrics, such as fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD) and mean diffusivity (MD), were calculated. Along-tract statistics were then used to resample WM fibre streamlines and generate a WM skeleton fibre tract. DTI metric alterations (post_RT-pre_RT DTI metrics) and the planned doses (max or mean doses) were mapped to 18 WM tracts. A linear fixed model was performed to analyse the main effect of dose on DTI metric alterations.

RESULTS

AD alterations in the left hemispheric uncinated fasciculus (UNC_L) were associated with max doses, in which decreased AD alterations were associated with higher doses.

CONCLUSION

Our findings may provide pathological insight into early dose-dependent WM alterations and may contribute to the development of max dose-constrained RT techniques to protect brain microstructure in the UNC_L.

Attenuation of Strychnine-Induced Epilepsy Employing Amaranthus viridis L. Leaves Extract in Experimental Rats

Objective

Epilepsy is one of the most prevalent neurological illnesses defined by periodic seizures with or without loss of consciousness caused by aberrant neural activity. There are many allopathic medications available for the treatment of epilepsy such as phenytoin (PHY), but the side effects are a major concern. Therefore, the present study involved the evaluation of the pharmacological significance of Amaranthus viridis L. extract (EAV) in the management of strychnine (STR)-induced epilepsy.

Method

STR (3.5 mg/kg, i.p.) was injected into male rats 30 minutes after the pre-treatment of a standard drug (PHY: 20 mg/kg) and the two doses of EAV (EAV-200 and EAV-400 mg/kg, p.o.) to the respective groups to cause the convulsions. The anti-convulsant effect of EAV-200 and EAV-400 against STR-induced convulsion in rats was investigated in terms of convulsion onset, duration of convulsions, number of convulsions, and convulsion score. Furthermore, the mitochondrial function and integrity in the brain's prefrontal cortex (PFC) were also estimated.

Results

EAV-400 significantly increased the onset of convulsion from 61.67 ± 3.051 to 119.2 ± 2.738 and reduced the STR-induced duration of convulsions from 144.8 ± 3.582 to 69.17 ± 3.736, number of convulsions from 4.000 ± 0.1592 to 1.533 ± 0.1542, and convulsion score from 5.000 ± 0.3651 to 2.833 ± 0.3073 in rats. EAV-400 significantly attenuated the STR-induced decrease in the mitochondrial function and integrity of the rat PFC. In rats, EAV-400 significantly accelerated the onset of convulsions while decreasing the STR-induced duration, frequency, and score.

Conclusion

Based on investigational findings, EAV-400 could be inferred to be a possible anti-epileptic option for the treatment of epilepsy of this plan in preclinical research.

Nattokinase attenuates bisphenol A or gamma irradiation-mediated hepatic and neural toxicity by activation of Nrf2 and suppression of inflammatory mediators in rats

Nattokinase (NK), a protease enzyme produced by Bacillus subtilis, has various biological effects such as lipid-lowering activity, antihypertensive, antiplatelet/anticoagulant, and neuroprotective effects. Exposure to environmental toxicants such as bisphenol A (BPA) or γ-radiation (IR) causes multi-organ toxicity through several mechanisms such as impairment of oxidative status, signaling pathways, and hepatic and neuronal functions as well as disruption of the inflammatory responses. Therefore, this study is designed to evaluate the ameliorative effect of NK against BPA- or IR-induced liver and brain damage in rats. Serum ammonia level and liver function tests were measured in addition to brain oxidative stress markers, amyloid-beta, tau protein, and neuroinflammatory mediators. Moreover, relative quantification of brain nuclear factor-erythroid 2-related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) genes, as well as apoptotic markers in brain tissue, was carried out in addition to histopathological examination. The results showed that NK improved liver functions, impaired oxidative status, the cholinergic deficits, and minified the misfolded proteins aggregates. Furthermore, NK alleviated the neuroinflammation via modulating NF-κB/Nrf2/HO-1 pathway and glial cell activation in addition to their antiapoptotic effect. Collectively, the current results revealed the protective effect of NK against hepatic and neurotoxicity derived from BPA or IR.

The Cognitive Effects of Radiotherapy for Brain Metastases

Brain metastases are the most common intracranial neoplasm and are seen in upwards of 10-30% of patients with cancer. For decades, whole brain radiation therapy (WBRT) was the mainstay of treatment in these patients. While WBRT is associated with excellent rates of intracranial tumor control, studies have demonstrated a lack of survival benefit, and WBRT is associated with higher rates of cognitive deterioration and detrimental effects on quality of life. In recent years, strategies to mitigate this risk, such as the incorporation of memantine and hippocampal avoidance have been employed with improved results. Furthermore, stereotactic radiosurgery (SRS) has emerged as an appealing treatment option over the last decade in the management of brain metastases and is associated with superior cognitive preservation and quality of life when compared to WBRT. This review article evaluates the pathogenesis and impact of cranial irradiation on cognition in patients with brain metastases, as well as current and future risk mitigation techniques.

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.

Short and Long-Term Toxicity in Pediatric Cancer Treatment: Central Nervous System Damage

Simple Summary

The purpose of this review is to describe central nervous system side effects in the treatment of pediatric cancer patients. Unfortunately, we must consider that the scarce data in the literature does not allow us to expand on some issues, especially those related to innovative immunotherapy. We have described the major neurotoxicities arising with the various types of treatment to help specialists who approach these treatments recognize them early, prevent them, and treat them promptly.

Abstract

Neurotoxicity caused by traditional chemotherapy and radiotherapy is well known and widely described. New therapies, such as biologic therapy and immunotherapy, are associated with better outcomes in pediatric patients but are also associated with central and peripheral nervous system side effects. Nevertheless, central nervous system (CNS) toxicity is a significant source of morbidity in the treatment of cancer patients. Some CNS complications appear during treatment while others present months or even years later. Radiation, traditional cytotoxic chemotherapy, and novel biologic and targeted therapies have all been recognized to cause CNS side effects; additionally, the risks of neurotoxicity can increase with combination therapy. Symptoms and complications can be varied such as edema, seizures, fatigue, psychiatric disorders, and venous thromboembolism, all of which can seriously influence the quality of life. Neurologic complications were seen in 33% of children with non-CNS solid malign tumors. The effects on the CNS are disabling and often permanent with limited treatments, thus it is important that clinicians recognize the effects of cancer therapy on the CNS. Knowledge of these conditions can help the practitioner be more vigilant for signs and symptoms of potential neurological complications during the management of pediatric cancers. As early detection and more effective anticancer therapies extend the survival of cancer patients, treatment-related CNS toxicity becomes increasingly vital. This review highlights major neurotoxicities due to pediatric cancer treatments and new therapeutic strategies; CNS primary tumors, the most frequent solid tumors in childhood, are excluded because of their intrinsic neurological morbidity.

Impact of Gut Microbiota on Radiation-Associated Cognitive Dysfunction and Neuroinflammation in Mice

Radiation-induced brain injury is a common complication of brain irradiation that eventually leads to irreversible cognitive impairment. Evidence has shown that the gut microbiome may play an important role in radiation-induced cognitive function. However, the effects of gut microbiota on radiation-induced brain injury (RIBI) remain poorly understood. Here we studied the link between intestinal microbes and radiation-induced brain injury to further investigate the effects of intestinal bacteria on neuroinflammation and cognitive function. We first verified the differences in gut microbes between male and female mice and administered antibiotics to C57BL/6 male mice to deplete the gut flora and then expose mice to radiation. We found that depletion of intestinal flora after irradiation may act as a protective modulator against radiation-induced brain injury. Moreover, we found that pretreatment with depleted gut microbes in RIBI mice suppressed brain pro-inflammatory factor production, and high-throughput sequencing analysis of mouse feces at 1-month postirradiation revealed microbial differences. Interestingly, a proportion of Verrucomicrobia Akkermansia showed partial recovery. Additionally, short-chain fatty acid treatments increased neuroinflammation in the radiation-induced brain injury model. Although a further increase in cognitive function was not observed, brain injury was aggravated in whole-brain irradiated mice to some extent. The protective effects of depleted intestinal flora and the utilization of the brain-gut axis open new avenues for development of innovative therapeutic strategies for radiation-induced brain injury.

Tailoring of chitosan/diacrylated pluronic system as a versatile nanoplatform for the amelioration of radiation-induced cognitive dysfunction

Rutin (RUT) is a biologically active flavonoid that is reported to modulate radiation-induced brain dysfunctions. However, RUT's poor water solubility and low brain bioavailability limit its clinical use. To increase its brain bioavailability, RUT was loaded onto nanoplatforms based on chitosan/diacrylated pluronic (CS/DA-PLUR) nanogels synthesized by gamma radiation. The optimized formulation was investigated as a carrier system for RUT. Based on pilot experiments' results, the cranial radiation (CR) dose that induced cognitive dysfunction was selected. In the main experiment, rats were pre-treated orally with either free RUT or RUT-CS/DA-PLUR. Rats' cognitive and motor functions were assessed; 24 h later, rats were sacrificed, and the whole brain was separated for histopathological examination and biochemical estimation of brain content of acetylcholine esterase (AChE), neurotransmitters, oxidative stress markers, and interleukin-1β. CR produced prominent impairment in spatial and non-spatial learning memory, motor coordination, and muscular strength. Moreover, histopathological and biochemical alterations in brain contents of neurotransmitters, oxidative stress, and interleukin-1β were induced by CR. Conversely, RUT-CS/DA-PLUR, but not free RUT, successfully guarded against all the detrimental effects induced by CR. Based on the current findings, loading of RUT enhanced its bioavailability and therapeutic effectiveness by restoring the cognitive functions impaired by CR.

Mitochondrial Translocator Protein (TSPO) Expression in the Brain After Whole Body Gamma Irradiation

The brain's early response to low dose ionizing radiation, as may be encountered during diagnostic procedures and space exploration, is not yet fully characterized. In the brain parenchyma, the mitochondrial translocator protein (TSPO) is constitutively expressed at low levels by endothelial cells, and can therefore be used to assess the integrity of the brain's vasculature. At the same time, the inducible expression of TSPO in activated microglia, the brain's intrinsic immune cells, is a regularly observed early indicator of subtle or incipient brain pathology. Here, we explored the use of TSPO as a biomarker of brain tissue injury following whole body irradiation. Post-radiation responses were measured in C57BL/6 wild type (Tspo +/+) and TSPO knockout (Tspo -/-) mice 48 h after single whole body gamma irradiations with low doses 0, 0.01, and 0.1 Gy and a high dose of 2 Gy. Additionally, post-radiation responses of primary microglial cell cultures were measured at 1, 4, 24, and 48 h at an irradiation dose range of 0 Gy-2 Gy. TSPO mRNA and protein expression in the brain showed a decreased trend after 0.01 Gy relative to sham-irradiated controls, but remained unchanged after higher doses. Immunohistochemistry confirmed subtle decreases in TSPO expression after 0.01 Gy in vascular endothelial cells of the hippocampal region and in ependymal cells, with no detectable changes following higher doses. Cytokine concentrations in plasma after whole body irradiation showed differential changes in IL-6 and IL-10 with some variations between Tspo-/- and Tspo +/+ animals. The in vitro measurements of TSPO in primary microglial cell cultures showed a significant reduction 1 h after low dose irradiation (0.01 Gy). In summary, acute low and high doses of gamma irradiation up to 2 Gy reduced TSPO expression in the brain's vascular compartment without de novo induction of TSPO expression in parenchymal microglia, while TSPO expression in directly irradiated, isolated, and thus highly activated microglia, too, was reduced after low dose irradiation. The potential link between TSPO, its role in mitochondrial energy metabolism and the selective radiation sensitivity, notably of cells with constitutive TSPO expression such as vascular endothelial cells, merits further exploration.

Assessment of cellular and molecular changes in the rat brain after gamma radiation and radioprotection by anisomycin

The objective of the study was to describe cellular and molecular markers of radioprotection by anisomycin, focusing on the changes in rat brain tissue. Two-month-old Wistar rats were exposed to a 60Co radiation source at a dose of 6 Gy, with or without radioprotection with anisomycin (150 mg/kg) administered subcutaneously 30 min before or 3 or 6 h after irradiation. Survivors were analyzed 30 days after treatment. Astroglial and microglial responses were investigated based on the expression of glial markers assessed with immunohistochemistry, and quantitative changes in brain biomolecules were investigated by Raman microspectroscopy. In addition, blood plasma levels of pro-inflammatory (interleukin 6 and tumor necrosis factor α) and anti-inflammatory (interleukin 10) cytokines were assessed. We found that application of anisomycin either before or after irradiation significantly decreased the expression of the microglial marker Iba-1. We also found an increased intensity of Raman spectral bands related to nucleic acids, as well as an increased level of cytokines when anisomycin was applied after irradiation. This suggests that the radioprotective effects of anisomycin are by decreasing Iba-1 expression and stabilizing genetic material by increasing the level of nucleic acids.

Gene Signatures Induced by Ionizing Radiation as Prognostic Tools in an In Vitro Experimental Breast Cancer Model

This study aimed to analyze the expression of genes involved in radiation, using an Affymetrix system with an in vitro experimental breast cancer model developed by the combined treatment of low doses of high linear energy transfer (LET) radiation α particle radiation and estrogen yielding different stages in a malignantly transformed breast cancer cell model called Alpha model. Altered expression of different molecules was detected in the non-tumorigenic Alpha3, a malignant cell line transformed only by radiation and originally derived from the parental MCF-10F human cell line; that was compared with the Alpha 5 cell line, another cell line exposed to radiation and subsequently grown in the presence 17β-estradiol. This Alpha5, a tumorigenic cell line, originated the Tumor2 cell line. It can be summarized that the Alpha 3 cell line was characterized by greater gene expression of ATM and IL7R than control, Alpha5, and Tumor2 cell lines, it presented higher selenoprotein gene expression than control and Tumor2; epsin 3 gene expression was higher than control; stefin A gene expression was higher than Alpha5; and metallothionein was higher than control and Tumor2 cell line. Therefore, radiation, independently of estrogen, induced increased ATM, IL7R, selenoprotein, GABA receptor, epsin, stefin, and metallothioneins gene expression in comparison with the control. Results showed important findings of genes involved in cancers of the breast, lung, nervous system, and others. Most genes analyzed in these studies can be used for new prognostic tools and future therapies since they affect cancer progression and metastasis. Most of all, it was revealed that in the Alpha model, a breast cancer model developed by the authors, the cell line transformed only by radiation, independently of estrogen, was characterized by greater gene expression than other cell lines. Understanding the effect of radiotherapy in different cells will help us improve the clinical outcome of radiotherapies. Thus, gene signature has been demonstrated to be specific to tumor types, hence cell-dependency must be considered in future treatment planning. Molecular and clinical features affect the results of radiotherapy. Thus, using gene technology and molecular information is possible to improve therapies and reduction of side effects while providing new insights into breast cancer-related fields.

In Vivo Imaging of the Microglial Landscape After Whole Brain Radiation Therapy

PURPOSE

Whole brain radiation therapy (WBRT) is an important treatment for patients with multiple brain metastases, but can also cause cognitive deterioration. Microglia, the resident immune cells of the brain, promote a proinflammatory environment and likely contribute to cognitive decline after WBRT. To investigate the temporal dynamics of the microglial reaction in individual mice to WBRT, we developed a novel in vivo experimental model using cranial window implants and longitudinal imaging.

METHODS AND MATERIALS

Chronic cranial windows were surgically implanted over the somatosensory cortex of transgenic Cx3cr1-enhanced green fluorescent protein (EGFP)/+ C57BL/6 mice, where microglia were fluorescently tagged with EGFP. Cx3cr1-EGFP/+ mice were also crossed with Thy1-YFP mice to fluorescently dual label microglia and subsets of neurons throughout the brain. Three weeks after window implantation and recovery, computed tomography image guided WBRT was delivered (single dose 10 Gy using two 5 Gy parallel-opposed lateral beams). Radiation dosing was confirmed using radiochromic film. Then, in vivo 2-photon microscopy was used to longitudinally image the microglial landscape and microglial motility at 7 days and 16 days after irradiation in the same mice.

RESULTS

Film dosimetry confirmed the average delivered dose per beam at midpoint was accurate within 2%, with no attenuation from the window frame. By 7 days after WBRT, significant changes in the microglial landscape were seen, characterized by apparent loss of microglial cells (20%) and significant rearrangements of microglial location with time after irradiation (36% of cells not found in original location).

CONCLUSIONS

Using longitudinal in vivo 2-photon imaging, this study demonstrated the feasibility of imaging microglia-neuron interactions and defining how microglia react to WBRT in the same mouse. Having demonstrated utility of the model, this experimental paradigm can be used to investigate the dynamic changes of many different brain cell types and their interactions after WBRT and uncover the underlying cellular mechanisms of WBRT-induced cognitive decline.

Modulation of the Nitric Oxide/BH4 Pathway Protects Against Irradiation-Induced Neuronal Damage

The kynurenine pathway (KP, IDO/Kyn pathway) is an important metabolic pathway related to many diseases. Although cranial radiotherapy is the mainstay in metastatic tumors management, its efficacy is limited owing to the associated neuropsychiatric disorders. Sildenafil (SD) and simvastatin (SV) were reported to have antioxidant/anti-inflammatory effects and to serve as NO donor/BH4 regulator, respectively. Fluoxetine (Fx) is an FDA-approved anti-depressant agent and one of the selective serotonin reuptake inhibitor drugs (SSRI), used in neurological disorder treatment. The study objective was to investigate the role of cranial irradiation (C-IR) on KP signaling impairment and the possible intervention by SD and/or SV (as nitric oxide (NO) donor/Tetrahydrobiopterin (BH4) regulatory) on KP following C-IR-induced disruption compared with Fx (as standard drug).Herein, rats were exposed to C-IR at a single dose level of 25 Gy, then treated with sildenafil (SD) and/or simvastatin (SV), and fluoxetine (Fx) at doses of 75, 20, 10 mg/kg/day, respectively. The body weight gain and forced swimming test (FST) were used for evaluation along with the biochemical quantifications of KP intermediates and histopathological examination of cortex and hippocampus. The results indicated a significant activation of KP following C-IR as manifested by decreased Trp content and increased activities of indoleamine 2,3-dioxygenase (IDO) and tryptophan 2,3-dioxygenase (TDO) with a rise in kynurenine (KYN) and quinolinic acid (QA) hippocampal contents. In addition, a state of C-IR-induced oxidative stress, inflammation, NO-pathway dysregulation and neuronal apoptosis were observed as compared to the control group. However, significant modulations were recorded after the combined administration of SD and SV than those offered by each of them alone and by Fx. The biochemical assessment results were supported by the histopathological tissue examination. It could be concluded that the co-administration of SV and SD offers a neuroprotective effect against irradiation-induced brain injury due to its NO donor/BH4 regulatory activities, anti-inflammatory and antioxidant properties that modulate IDO/KYN pathway.

Brain Damage and Patterns of Neurovascular Disorder after Ionizing Irradiation. Complications in Radiotherapy and Radiation Combined Injury

Exposure to ionizing radiation, mechanical trauma, toxic chemicals or infections, or combinations thereof (i.e., combined injury) can induce organic injury to brain tissues, the structural disarrangement of interactive networks of neurovascular and glial cells, as well as on arrays of the paracrine and systemic destruction. This leads to subsequent decline in cognitive capacity and decompensation of mental health. There is an ongoing need for improvement in mitigating and treating radiation- or combined injury-induced brain injury. Cranial irradiation per se can cause a multifactorial encephalopathy that occurs in a radiation dose- and time-dependent manner due to differences in radiosensitivity among the various constituents of brain parenchyma and vasculature. Of particular concern are the radiosensitivity and inflammation susceptibility of: 1. the neurogenic and oligodendrogenic niches in the subependymal and hippocampal domains; and 2. the microvascular endothelium. Thus, cranial or total-body irradiation can cause a plethora of biochemical and cellular disorders in brain tissues, including: 1. decline in neurogenesis and oligodendrogenesis; 2. impairment of the blood-brain barrier; and 3. ablation of vascular capillary. These changes, along with cerebrovascular inflammation, underlie different stages of encephalopathy, from the early protracted stage to the late delayed stage. It is evident that ionizing radiation combined with other traumatic insults such as penetrating wound, burn, blast, systemic infection and chemotherapy, among others, can exacerbate the radiation sequelae (and vice versa) with increasing severity of neurogenic and microvascular patterns of radiation brain damage.

Stem-Cell Therapy as a Potential Strategy for Radiation-Induced Brain Injury

Radiation therapy is a standard and effective non-surgical treatment for primary brain tumors and metastases. However, this strategy inevitably results in damage of normal brain tissue, causing severe complications, especially the late-delayed cognitive impairment. Due to the multifactorial and complex pathological effects of radiation, there is a lack of effective preventative and restorative treatments for the irradiated brain. Stem-cell therapy has held considerable promise for decades in the treatment of central nervous system (CNS) disorders because of its unique capacity for tissue repair and functional integrity. Currently, there is growing interest in using stem cells as a novel option to attenuate the adverse effects of irradiation. In the present review, we discuss recent studies evaluating stem-cell therapies for the irradiated brain and their therapeutic effects on ameliorating radiation-related brain injury as well as their potential challenges in clinical applications. We discuss these works in context of the pathogenesis of radiation-induced injury to CNS tissue in an attempt to elucidate the potential mechanisms of engrafted stem cells to reverse radiation-induced degenerative processes.

Melatonin exerts a neuroprotective effect against γ-radiation-induced brain injury in the rat through the modulation of neurotransmitters, inflammatory cytokines, oxidative stress, and apoptosis

The current study aimed to investigate the ameliorative effect of melatonin (MLT) against brain injury in rats undergoing whole-body exposure to γ-radiation. Male Wistar rats were whole-body exposed to 4-Gy γ-radiation from a cesium-137 source. MLT (10 mg/kg) was orally administrated 30 minutes before irradiation and continued once daily for 1 and 7 days after exposure. In the irradiated rats, the plasma levels of glutamate were increased, while the gamma-aminobutyric acid (GABA) levels were decreased, and MLT improved the disturbed glutamate and GABA levels. These effects paralleled an increase in pro-inflammatory cytokines (IL-1b, IL-6, and TNF-a) and C-reactive protein as well as a decrease in IL-10 in the plasma of the irradiated rats. MLT treatment markedly reduced these effects, indicating its anti-inflammatory impact. Immunohistochemical studies demonstrated a remarkable upregulation of caspase-3 and P53 expression, indicating the increased apoptosis in the brain of irradiated rats. MLT significantly downregulated the expression of these parameters compared with that in the irradiated rats, indicating its anti-apoptotic effect. Oxidative stress is developed in the brain as evidenced by increased levels of malondialdehyde; decreased activities of superoxide dismutase, catalase, and glutathione peroxidase; and decreased content of glutathione in the brain. MLT remarkably ameliorated the development of oxidative stress in the brain of the irradiated rats indicating its antioxidant impact. The histopathological results were consistent with the biochemical and immunohistochemical results and showed that MLT remarkably protected the histological structure of brain tissue compared with that in the irradiated rats. In conclusion, MLT showed potential neuroprotective properties by increasing the release of neurotransmitters, antioxidants, and anti-inflammatory factors and reducing pro-inflammatory cytokines and apoptosis in the brain of irradiated rats. MLT can be beneficial in clinical and occupational settings requiring radiation exposure; however, additional studies are required to elucidate its neuroprotective effect in humans.

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.

Flavonoids, the Family of Plant-derived Antioxidants making inroads into Novel Therapeutic Design against IR-induced Oxidative Stress in Parkinson's Disease

Background:

Ionizing radiation from telluric sources is unceasingly an unprotected pitfall to humans. Thus, the foremost contributors to human exposure are global and medical radiations. Various evidences assembled during preceding years reveal the pertinent role of ionizing radiation-induced oxidative stress in the progression of neurodegenerative insults, such as Parkinson’s disease, which have been contributing to increased proliferation and generation of reactive oxygen species.

Objective:

This review delineates the role of ionizing radiation-induced oxidative stress in Parkinson’s disease and proposes novel therapeutic interventions of flavonoid family, offering effective management and slowing down the progression of Parkinson’s disease.

Methods:

Published papers were searched in MEDLINE, PubMed, etc., published to date for in-depth database collection.

Results:

The oxidative damage may harm the non-targeted cells. It can also modulate the functions of the central nervous system, such as protein misfolding, mitochondria dysfunction, increased levels of oxidized lipids, and dopaminergic cell death, which accelerate the progression of Parkinson’s disease at the molecular, cellular, or tissue levels. In Parkinson’s disease, reactive oxygen species exacerbate the production of nitric oxides and superoxides by activated microglia, rendering death of dopaminergic neuronal cell through different mechanisms.

Conclusion:

Rising interest has extensively engrossed in the clinical trial designs based on the plant-derived family of antioxidants. They are known to exert multifarious impact on neuroprotection via directly suppressing ionizing radiation-induced oxidative stress and reactive oxygen species production or indirectly increasing the dopamine levels and activating the glial cells.

Honokiol ameliorates radiation-induced brain injury via the activation of SIRT3

Objective

Sirtuin 3 (SIRT3) plays a vital role in regulating oxidative stress in tissue injury. The aim of this study was to evaluate the radioprotective effects of honokiol (HKL) in a zebrafish model of radiation-induced brain injury and in HT22 cells.

Methods

The levels of reactive oxygen species (ROS), tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β) were evaluated in the zebrafish brain and HT22 cells. The expression levels of SIRT3 and cyclooxygenase-2 (COX-2) were measured using western blot assays and real-time polymerase chain reaction (RT-PCR).

Results

HKL treatment attenuated the levels of ROS, TNF-α, and IL-1β in both the in vivo and in vitro models of irradiation injury. Furthermore, HKL treatment increased the expression of SIRT3 and decreased the expression of COX-2. The radioprotective effects of HKL were achieved via SIRT3 activation.

Conclusions

HKL attenuated oxidative stress and pro-inflammatory responses in a SIRT3-dependent manner in radiation-induced brain injury.

Effects of brain radiotherapy on cognitive performance in adult low-grade glioma patients: A systematic review

Grade II gliomas are slow growing tumours that usually affect younger patients. The mainstream treatment modality at present is surgical. The role of radiation therapy in the management of grade II gliomas has been the subject of considerable debate. Radiation therapy has a proven potential to prolong progression free and overall survival in high-risk patients, but may also produce long-term cognitive deficits. Since grade II glioma patients are expected to live several years, retention of cognitive capacity and quality of life is an equally important endpoint as prolonging progression free survival. Our overarching goal is to critically review the available evidence on the possible neuropsychological effects of postoperative radiotherapy in adult grade II glioma patients. We performed a systematic literature search in Medline, Embase and Cochrane databases up to 1st of May 2020 for studies assessing the cognitive effects of radiation therapy on grade II glioma patients. Eleven studies meeting our inclusion criteria provide either negative or contradictory data regarding the cognitive domains affected, while major confounding variables remain incompletely addressed. The available evidence does not adequately support the notion that current radiation therapy protocols independently produce substantial cognitive decline in grade II glioma patients and therefore it would be premature to argue that radiation associated cognitive morbidity outweighs the benefit of prolonged survival. A large prospective study incorporating a full battery of neuropsychological testing, sufficiently long-term follow-up period and tight control of confounders is due to provide high quality data.

Whole brain irradiation in mice causes long-term impairment in astrocytic calcium signaling but preserves astrocyte-astrocyte coupling

Whole brain irradiation (WBI) therapy is an important treatment for brain metastases and potential microscopic malignancies. WBI promotes progressive cognitive dysfunction in over half of surviving patients, yet, the underlying mechanisms remain obscure. Astrocytes play critical roles in the regulation of neuronal activity, brain metabolism, and cerebral blood flow, and while neurons are considered radioresistant, astrocytes are sensitive to γ-irradiation. Hallmarks of astrocyte function are the ability to generate stimulus-induced intercellular Ca2+ signals and to move metabolic substrates through the connected astrocyte network. We tested the hypothesis that WBI-induced cognitive impairment associates with persistent impairment of astrocytic Ca2+ signaling and/or gap junctional coupling. Mice were subjected to a clinically relevant protocol of fractionated WBI, and 12 to 15 months after irradiation, we confirmed persistent cognitive impairment compared to controls. To test the integrity of astrocyte-to-astrocyte gap junctional coupling postWBI, astrocytes were loaded with Alexa-488-hydrazide by patch-based dye infusion, and the increase of fluorescence signal in neighboring astrocyte cell bodies was assessed with 2-photon microscopy in acute slices of the sensory-motor cortex. We found that WBI did not affect astrocyte-to-astrocyte gap junctional coupling. Astrocytic Ca2+ responses induced by bath administration of phenylephrine (detected with Rhod-2/AM) were also unaltered by WBI. However, an electrical stimulation protocol used in long-term potentiation (theta burst), revealed attenuated astrocyte Ca2+ responses in the astrocyte arbor and soma in WBI. Our data show that WBI causes a long-lasting decrement in synaptic-evoked astrocyte Ca2+ signals 12-15 months postirradiation, which may be an important contributor to cognitive decline seen after WBI.

Reduction of pTau and APP levels in mammalian brain after low-dose radiation

Brain radiation can occur from treatment of brain tumors or accidental exposures. Brain radiation has been rarely considered, though, as a possible tool to alter protein levels involved in neurodegenerative disorders. We analyzed possible molecular and neuropathology changes of phosphorylated-Tau (pTau), all-Tau forms, β-tubulin, amyloid precursor protein (APP), glial fibrillary acidic protein (GFAP), ionized calcium binding adaptor molecule 1 (IBA-1), myelin basic protein (MBP), and GAP43 in Frontal Cortex (FC), Hippocampus (H) and Cerebellum (CRB) of swine brains following total-body low-dose radiation (1.79 Gy). Our data show that radiated-animals had lower levels of pTau in FC and H, APP in H and CRB, GAP43 in CRB, and higher level of GFAP in H versus sham-animals. These molecular changes were not accompanied by obvious neurohistological changes, except for astrogliosis in the H. These findings are novel, and might open new perspectives on brain radiation as a potential tool to interfere with the accumulation of specific proteins linked to the pathogenesis of various neurodegenerative disorders.

Radiation-induced neuropathies in head and neck cancer: prevention and treatment modalities

Head and neck cancer (HNC) is the sixth most common human malignancy with a global incidence of 650,000 cases per year. Radiotherapy (RT) is commonly used as an effective therapy to treat tumours as a definitive or adjuvant treatment. Despite the substantial advances in RT contouring and dosage delivery, patients suffer from various radiation-induced complications, among which are toxicities to the nervous tissues in the head and neck area. Radiation-mediated neuropathies manifest as a result of increased oxidative stress-mediated apoptosis, neuroinflammation and altered cellular function in the nervous tissues. Eventually, molecular damage results in the formation of fibrotic tissues leading to susceptible loss of function of numerous neuronal substructures. Neuropathic sequelae following irradiation in the head and neck area include sensorineural hearing loss, alterations in taste and smell functions along with brachial plexopathy, and cranial nerves palsies. Numerous management options are available to relieve radiation-associated neurotoxicities notwithstanding treatment alternatives that remain restricted with limited benefits. In the scope of this review, we discuss the use of variable management and therapeutic modalities to palliate common radiation-induced neuropathies in head and neck cancers.

Effects of partial- or whole-body exposures to 56Fe particles on brain function and cognitive performance in rats

On exploratory class missions, such as a mission to Mars, astronauts will be exposed to particles of high energy and charge (HZE particles). Exposure to HZE particles produces changes in neuronal function and can disrupt cognitive performance. Cells throughout the entire body, not just the brain, will be impacted by these particles. To determine the possible effects that irradiation of the body might have on neuronal function and cognitive performance, rats were given head-only, body-only or whole-body exposures to ⁵⁶Fe particles. Cognitive performance (novel object recognition, operant responding) was tested in one set of animals; changes in brain function (oxidative stress, neuroinflammation) was tested in a second set of rats. The results indicated that there were no consistent differences in either behavioral or neurochemical endpoints as a function of the location of the irradiation. These results suggest that radiation to the body can impact the brain, therefore it may be necessary to re-evaluate the estimates of the risk of HZE particle-induced changes in neuronal function and cognitive performance.

Modulatory effect of methylsulfonylmethane against BPA/γ-radiation induced neurodegenerative alterations in rats: Influence of TREM-2/DAP-12/Syk pathway

AIMS

Methylsulfonylmethane (MSM), is an organosulfur compound, has many health benefits. Bisphenol-A (BPA) and γ-radiation (R) are two risky environmental contaminants that human beings are exposed to in everyday life. This work aims at unveiling the modulatory role of MSM in combating BPA and R co-exposure induced neurodegenerative disorder (Alzheimer's (AD)-mimic neurotoxicity).

MAIN METHODS

Female rats were randomly divided into five groups. One group was normal control and the other four groups were subjected to subacute BPA intoxication and/or exposed to fractionated weekly doses of R for 4 weeks and either untreated or treated with MSM concomitantly.

KEY FINDINGS

BPA and R co-exposure induced typical hallmarks of neurodegenerative disorders as revealed by tremendously elevated oxidative stress, extensive neuroinflammation (tumor necrosis factor -α and interleukin-1β), elevated AD markers (amyloid-beta (Aβ₄₂), acetylcholinesterase (AchE) activity and tau-phosphorylation) in cortex and hippocampus as well as up-regulation of microglial pro-inflammatory triggering receptor expressed on myeloid cell-2(TREM-2)/DNAX-activating protein of 12 kDa (DAP-12)/spleen-tyrosine kinase (Syk) pathway and its downstream targets (PLC-γ/DAG/p38-MAPK) in hippocampus. Also, neurodegenerative lesions were revealed in histopathological examination of cortex and hippocampus coupled with marked Aβ deposition in hippocampus. Whereas, MSM treatment improved histopathological insults and ameliorated level of oxidative stress, neuroinflammation and AD markers as well as modulated TREM-2/DAP-12/Syk pathway.

SIGNIFICANCE

Our data suggest that MSM afforded neuroprotection against BPA and R; supporting its potential application in the associated neurodegenerative disorders.

An Iatrogenic Model of Brain Small-Vessel Disease: Post-Radiation Encephalopathy

We studied 114 primitive cerebral neoplasia, that were surgically treated, and underwent radiotherapy (RT), and compared their results to those obtained by 190 patients diagnosed with subcortical vascular dementia (sVAD). Patients with any form of primitive cerebral neoplasia underwent whole-brain radiotherapy. All the tumor patients had regional field partial brain RT, which encompassed each tumor, with an average margin of 2.6 cm from the initial target tumor volume. We observed in our patients who have been exposed to a higher dose of RT (30–65 Gy) a cognitive and behavior decline similar to that observed in sVAD, with the frontal dysexecutive syndrome, apathy, and gait alterations, but with a more rapid onset and with an overwhelming effect. Multiple mechanisms are likely to be involved in radiation-induced cognitive impairment. The active site of RT brain damage is the white matter areas, particularly the internal capsule, basal ganglia, caudate, hippocampus, and subventricular zone. In all cases, radiation damage inside the brain mainly focuses on the cortical–subcortical frontal loops, which integrate and process the flow of information from the cortical areas, where executive functions are “elaborated” and prepared, towards the thalamus, subthalamus, and cerebellum, where they are continuously refined and executed. The active mechanisms that RT drives are similar to those observed in cerebral small vessel disease (SVD), leading to sVAD. The RT’s primary targets, outside the tumor mass, are the blood–brain barrier (BBB), the small vessels, and putative mechanisms that can be taken into account are oxidative stress and neuro-inflammation, strongly associated with the alteration of NMDA receptor subunit composition.

The psychological consequences of (perceived) ionizing radiation exposure: a review on its role in radiation-induced cognitive dysfunction

PURPOSE

Exposure to ionizing radiation following environmental contamination (e.g., the Chernobyl and Fukushima nuclear accidents), radiotherapy and diagnostics, occupational roles and space travel has been identified as a possible risk-factor for cognitive dysfunction. The deleterious effects of high doses (≥1.0 Gy) on cognitive functioning are fairly well-understood, while the consequences of low (≤0.1 Gy) and moderate doses (0.1-1.0 Gy) have been receiving more research interest over the past decade. In addition to any impact of actual exposure on cognitive functioning, the persistent psychological stress arising from perceived exposure, particularly following nuclear accidents, may itself impact cognitive functioning. In this review we offer a novel interdisciplinary stance on the cognitive impact of radiation exposure, considering psychological and epidemiological observations of different exposure scenarios such as atomic bombings, nuclear accidents, occupational and medical exposures while accounting for differences in dose, rate of exposure and exposure type. The purpose is to address the question that perceived radiation exposure - even where the actual absorbed dose is 0.0 Gy above background dose - can result in psychological stress, which could in turn lead to cognitive dysfunction. In addition, we highlight the interplay between the mechanisms of perceived exposure (i.e., stress) and actual exposure (i.e., radiation-induced cellular damage), in the generation of radiation-induced cognitive dysfunction. In all, we offer a comprehensive and objective review addressing the potential for cognitive defects in the context of low- and moderate-dose IR exposures.

CONCLUSIONS

Overall the evidence shows prenatal exposure to low and moderate doses to be detrimental to brain development and subsequent cognitive functioning, however the evidence for adolescent and adult low- and moderate-dose exposure remains uncertain. The persistent psychological stress following accidental exposure to low-doses in adulthood may pose a greater threat to our cognitive functioning. Indeed, the psychological implications for instructed cohorts (e.g., astronauts and radiotherapy patients) is less clear and warrants further investigation. Nonetheless, the psychosocial consequences of low- and moderate-dose exposure must be carefully considered when evaluating radiation effects on cognitive functioning, and to avoid unnecessary harm when planning public health response strategies.

Pathological changes in the central nervous system following exposure to ionizing radiation

Experimental studies in animals provide relevant knowledge about pathogenesis of radiation-induced injury to the central nervous system. Radiation-induced injury can alter neuronal, glial cell population, brain vasculature and may lead to molecular, cellular and functional consequences. Regarding to its fundamental role in the formation of new memories, spatial navigation and adult neurogenesis, the majority of studies have focused on the hippocampus. Most recent findings in cranial radiotherapy revealed that hippocampal avoidance prevents radiation-induced cognitive impairment of patients with brain primary tumors and metastases. However, numerous preclinical studies have shown that this problem is more complex. Regarding the fact, that the radiation-induced cognitive impairment reflects hippocampal and non-hippocampal compartments, it is highly important to investigate molecular, cellular and functional changes in different brain regions and their integration at clinically relevant doses and schedules. Here, we provide a literature review in order support the translation of preclinical findings to clinical practice and improve the physical and mental status of patients with brain tumors.

Radiation-induced astrocyte senescence is rescued by Δ133p53

BACKGROUND

Cellular senescence and the senescence-associated secretory phenotype (SASP) may contribute to the development of radiation therapy-associated side effects in the lung and blood vessels by promoting chronic inflammation. In the brain, inflammation contributes to the development of neurologic disease, including Alzheimer's disease. In this study, we investigated the roles of cellular senescence and Δ133p53, an inhibitory isoform of p53, in radiation-induced brain injury.

METHODS

Senescent cell types in irradiated human brain were identified with immunohistochemical labeling of senescence-associated proteins p16INK4A and heterochromatin protein Hp1γ in 13 patient cases, including 7 irradiated samples. To investigate the impact of radiation on astrocytes specifically, primary human astrocytes were irradiated and examined for expression of Δ133p53 and induction of SASP. Lentiviral expression of ∆133p53 was performed to investigate its role in regulating radiation-induced cellular senescence and astrocyte-mediated neuroinflammation.

RESULTS

Astrocytes expressing p16INK4A and Hp1γ were identified in all irradiated tissues, were increased in number in irradiated compared with untreated cancer patient tissues, and had higher labeling intensity in irradiated tissues compared with age-matched controls. Human astrocytes irradiated in vitro also experience induction of cellular senescence, have diminished Δ133p53, and adopt a neurotoxic phenotype as demonstrated by increased senescence-associated beta-galactosidase activity, p16INK4A, and interleukin (IL)-6. In human astrocytes, Δ133p53 inhibits radiation-induced senescence, promotes DNA double-strand break repair, and prevents astrocyte-mediated neuroinflammation and neurotoxicity.

CONCLUSIONS

Restoring expression of the endogenous p53 isoform, ∆133p53, protects astrocytes from radiation-induced senescence, promotes DNA repair, and inhibits astrocyte-mediated neuroinflammation.

Brain metastases from germ cell tumor: time to reconsider radiotherapy?

The presence of brain metastases (BMs) from germ cell tumor (GCT) remains a rare situation. BMs predominantly occur among patients with testis primary tumor site, and are almost exclusively associated with non-seminomatous (NS) histologies. Two situations must be distinguished, which differ in terms of clinical presentation, overall prognostic and management. At diagnosis, BMs are almost systematically associated with extra-cerebral metastases and the cornerstone of treatment is chemotherapy, while the role of local treatment remains controversial. In the metachronous setting, BMs more frequently constitute an isolated site of relapse, the outcome is poorer, and the role of local treatment is more consensual. However, all these data widely come from old reports, with outdated radiation techniques. The recent advances in radiation oncology, especially the rising use of stereotactic radiotherapy, could lead to the reconsideration of ancient dogmas regarding the "radiosensitivity" of (NS)GCT and the role of radiotherapy among patients with BMs.

Combination of Vinpocetine and Dexamethasone Alleviates Cognitive Impairment in Nasopharyngeal Carcinoma Patients following Radiation Injury

BACKGROUND

Nasopharyngeal carcinoma (NPC) originates in the nasopharyngeal epithelium. The most common treatments for NPC rT1-4 are radiotherapy and surgery. The pathogenesis of radiation-induced cognitive impairment is complex and includes oxidative stress, mitochondrial dysfunction, neuro-inflammation, and even apoptosis and cell death. Principally, toll-like receptors (TLRs) could regulate the inflammatory/anti-inflammatory balance in patients with radiation-induced brain injury. Vinpocetine has an anti-inflammatory effect as shown in both animal and in vitro studies. Also, dexamethasone is a widely used anti-inflammatory drug. Thus, it is important to test whether addition of vinpocetine could improve the anti-inflammatory properties of dexamethasone for the treatment of NPC patients with radiation-induced brain injuries.

METHODS

A total of 60 NPC patients with radiation-related brain injury were recruited for this study. All subjects were randomly and blindly assigned to the following groups: the dexamethasone group (D group, n = 30) and the vinpocetine and dexamethasone group (VD group, n = 30). Both medicine treatments were uninterrupted for 14 days of administration.

RESULTS

Combined administration of vinpocetine and dexamethasone lowered the expression levels of serum inflammatory cytokines, including TLR2, TLR4, interleukin (IL)-20, IL-8, tumor necrosis factor-α, interferon-γ, monocyte chemoattractant protein 2, and interferon-induced protein 20, when compared to dexamethasone monotherapy. Notably, combination therapy increased antioxidants (superoxide dismutase, glutathione, glutathione peroxidase, and glutathione reductase) and decreased oxidants (thiobarbituric acid reactive substances). Furthermore, combination therapy significantly increased the Mini Mental State Examination score, when compared to dexamethasone monotherapy.

CONCLUSION

Administration of a combination of vinpocetine and dexamethasone may enhance the anti-inflammatory and anti-oxidative effects when compared to dexamethasone monotherapy, which leads to alleviated cognitive impairment in NPC patients with radiation injury.

Neurocognitive Decline Following Radiotherapy: Mechanisms and Therapeutic Implications

The brain undergoes ionizing radiation (IR) exposure in many clinical situations, particularly during radiotherapy for malignant brain tumors. Cranial radiation therapy is related with the hazard of long-term neurocognitive decline. The detrimental ionizing radiation effects on the brain closely correlate with age at treatment, and younger age associates with harsher deficiencies. Radiation has been shown to induce damage in several cell populations of the mouse brain. Indeed, brain exposure causes a dysfunction of the neurogenic niche due to alterations in the neuronal and supporting cell progenitor signaling environment, particularly in the hippocampus—a region of the brain critical to memory and cognition. Consequent deficiencies in rates of generation of new neurons, neural differentiation and apoptotic cell death, lead to neuronal deterioration and lasting repercussions on neurocognitive functions. Besides neural stem cells, mature neural cells and glial cells are recognized IR targets. We will review the current knowledge about radiation-induced damage in stem cells of the brain and discuss potential treatment interventions and therapy methods to prevent and mitigate radiation related cognitive decline.

Early volume reduction of the hippocampus after whole-brain radiation therapy: an automated brain structure segmentation study

PURPOSE

To assess atrophy differences among brain regions and time-dependent changes after whole-brain radiation therapy (WBRT).

MATERIALS AND METHODS

Twenty patients with lung cancer who underwent both WBRT and chemotherapy (WBRT group) and 18 patients with lung cancer who underwent only chemotherapy (control group) were recruited. Three-dimensional T1WI were analyzed to calculate volume reduction ratio after WBRT in various brain structures. The volume reduction ratio of the hippocampus was compared among following 3 periods: 0-3, 4-7, and 8-11 months after WBRT.

RESULTS

The volume reduction ratio of the hippocampus was significantly higher in the WBRT group than in the control group (p < 0.05). In WBRT group, the volume reduction ratio of the hippocampus was significantly higher than that of the cortex and white matter (p < 0.05). There were significant differences in the volume reduction ratio between of 0-3 months and that of 4-7 months (p = 0.02) and between 4-7 months and that of 8-11 months (p = 0.01).

CONCLUSION

The hippocampus is more vulnerable to the radiation compared with other brain regions and may become atrophic even in the early stage after WBRT.

Neurocognitive Function in Adult Cancer Patients

Impaired neurocognitive function is an increasingly recognized morbidity in patients who have cancer. Cancer treatments, psychosocial stressors, and the malignancy itself can alter brain function. The mechanisms by which this occurs are under active investigation. Although there is a growing appreciation of its prevalence and causes, there remain limited therapeutic options for the treatment of neurocognitive dysfunction in this population. A persistent scientific and clinical effort to understand its mechanisms and impact is critical to the care of oncology patients.

Effects of Radiation Therapy on Neural Stem Cells

Brain and nervous system cancers in children represent the second most common neoplasia after leukemia. Radiotherapy plays a significant role in cancer treatment; however, the use of such therapy is not without devastating side effects. The impact of radiation-induced damage to the brain is multifactorial, but the damage to neural stem cell populations seems to play a key role. The brain contains pools of regenerative neural stem cells that reside in specialized neurogenic niches and can generate new neurons. In this review, we describe the advances in radiotherapy techniques that protect neural stem cell compartments, and subsequently limit and prevent the occurrence and development of side effects. We also summarize the current knowledge about neural stem cells and the molecular mechanisms underlying changes in neural stem cell niches after brain radiotherapy. Strategies used to minimize radiation-related damages, as well as new challenges in the treatment of brain tumors are also discussed.