NLRP3 promotes radiation-induced brain injury by regulating microglial pyroptosis.

PURPOSE: Radiation-induced brain injury, one of the side effects of cranial radiotherapy in tumour patients, usually results in durable and serious cognitive disorders. Microglia are important innate immune-effector cells in the central nervous system. However, the interaction between microglia and neurons in radiation-induced brain injury remains uncharacterised. METHODS AND MATERIALS: We established a microglia-neuron indirect co-culture model to assess the interaction between them. Microglia exposed to radiation were examined for pyroptosis using lactate dehydrogenase (LDH) release, Annexin V/PI staining, SYTOX staining and western blot. The role of nucleotide-binding oligomerisation domain-like receptor family pyrin domain containing 3 (NLRP3) was investigated in microglia exposed to radiation and in mouse radiation brain injury model through siRNA or inhibitor. Mini-mental state examination and cytokines in blood were performed in 23 patients who had experienced cranial irradiation. RESULTS: Microglia exerted neurotoxic features after radiation in the co-culture model. NLRP3 was up-regulated in microglia exposed to radiation, and then caspase-1 was activated. Thus, the gasdermin D protein was cleaved, and it triggered pyroptosis in microglia, which released inflammatory cytokines. Meanwhile, treatment with siRNA NLRP3 in vitro and NLRP3 inhibitor in vivo attenuated the damaged neuron cell and cognitive impairment, respectively. What is more, we found that the patients after radiation with higher IL-6 were observed to have a decreased MMSE score. CONCLUSIONS: These findings indicate that radiation-induced pyroptosis in microglia may promote radiation-induced brain injury via the secretion of neurotoxic cytokines. NLRP3 was evaluated as an important mediator in radiation-induced pyroptosis and a promising therapeutic target for radiation-induced brain injury.

Disparate Radiation-Induced Microstructural Injuries in Whole-Brain White Matter of Patients With Nasopharyngeal Carcinoma: A Longitudinal Study Using Multishell Diffusion MRI.

BACKGROUND: Evidence for prevention strategies of radiotherapy (RT)-related injury in patients with nasopharyngeal carcinoma (NPC) was lacking. Understanding the dynamic alterations in the cerebral white matter (WM) microstructure after RT may be helpful. PURPOSE: To investigate the dynamic alterations in the whole brain WM microstructure in patients with NPC in the 12 months after RT using multishell diffusion MRI (MS-dMRI). STUDY TYPE: Single-center longitudinal study. POPULATION: A total of 28 treatment-naïve patients with pathologically confirmed NPC (age: 39.68 ± 8.93 years, 11 female) and 20 healthy controls (age: 40.65 ± 9.76 years, 7 female). FIELD STRENGTH/SEQUENCES: A 3 T, MS-dMRI using a single-shot echo planar imaging sequence. ASSESSMENT: MS-dMRI was acquired at baseline for the NPC patients and healthy controls, at 0-3 (acute, AC), 6 (early delayed, ED) and 12 months (late delayed, LD) after RT for the NPC patients. The mean and maximum radiation doses to the temporal lobe were acquired. The quality of images was reviewed. MS-dMRI was analyzed using tract-based spatial statistics (TBSS). The presentations of injury were defined by the findings of TBSS. STATISTICAL TESTS: Chi-square, t tests, repeated ANOVA, and Spearman-rank correlation analysis were used. P < 0.05 was considered to be statistically significant. RESULTS: TBSS showed two WM injuries (injuries 1 and 2). Injury 1 emerged in the ED phase in the bilateral temporal poles and persisted throughout the ED and LD phases. Injury 2 developed from the AC to ED phase in the bilateral hemisphere and partially recovered in the LD phase. In the ED and LD phases, the multiple diffusion metrics were well correlated (r > 0.5 or <-0.5) with the RT dose, especially in the WM tracts in the temporal lobes. DATA CONCLUSION: Disparate WM injuries were observed in NPC patients after RT. The injuries may be primarily or secondarily induced by radiation. Injury 1 may be irreversible, while injury 2 seems to partially recover. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 4.

Ferroptosis in radiation-induced brain injury: roles and clinical implications.

Radiation-induced brain injury (RBI) presents a significant challenge for patients undergoing radiation therapy for head, neck, and intracranial tumors. This review aims to elucidate the role of ferroptosis in RBI and its therapeutic implications. Specifically, we explore how ferroptosis can enhance the sensitivity of tumor cells to radiation while also examining strategies to mitigate radiation-induced damage to normal brain tissues. By investigating the mechanisms through which radiation increases cellular reactive oxygen species (ROS) and initiates ferroptosis, we aim to develop targeted therapeutic strategies that maximize treatment efficacy and minimize neurotoxicity. The review highlights key regulatory factors in the ferroptosis pathway, including glutathione peroxidase 4 (GPX4), cystine/glutamate antiporter system Xc- (System Xc-), nuclear factor erythroid 2-related factor 2 (NRF2), Acyl-CoA synthetase long-chain family member 4 (ACSL4), and others, and their interactions in the context of RBI. Furthermore, we discuss the clinical implications of modulating ferroptosis in radiation therapy, emphasizing the potential for selective induction of ferroptosis in tumor cells and inhibition in healthy cells. The development of advanced diagnostic tools and therapeutic strategies targeting ferroptosis offers a promising avenue for enhancing the safety and efficacy of radiation therapy, underscoring the need for further research in this burgeoning field.

Adding simultaneous integrated boost to whole brain radiation therapy improved intracranial tumour control and minimize radiation-induced brain injury risk for the treatment of brain metastases.

BACKGROUND: Brain metastases (BMs) are the most frequent intracranial tumours associated with poor clinical outcomes. Radiotherapy is essential in the treatment of these tumours, although the optimal radiation strategy remains controversial. The present study aimed to assess whether whole brain radiation therapy with a simultaneous integrated boost (WBRT + SIB) provides any therapeutic benefit over WBRT alone. METHODS: We included and retrospectively analysed 82 patients who received WBRT + SIB and 83 who received WBRT alone between January 2012 and June 2021. Intracranial progression-free survival (PFS), local tumour control (LTC), overall survival (OS), and toxicity were compared between the groups. RESULTS: Compared to WBRT alone, WBRT + SIB improved intracranial LTC and PFS, especially in the lung cancer subgroup. Patients with high graded prognostic assessment score or well-controlled extracranial disease receiving WBRT + SIB had improved intracranial PFS and LTC. Moreover, WBRT + SIB also improved the long-term intracranial tumour control of small cell lung cancer patients. When evaluating toxicity, we found that WBRT + SIB might slightly increase the risk of radiation-induced brain injury, and that the risk increased with increasing dosage. However, low-dose WBRT + SIB had a tolerable radiation-induced brain injury risk, which was lower than that in the high-dose group, while it was comparable to that in the WBRT group. CONCLUSIONS: WBRT + SIB can be an efficient therapeutic option for patients with BMs, and is associated with improved intracranial LTC and PFS. Furthermore, low-dose WBRT + SIB (biologically effective dose [BED] ≤ 56 Gy) was recommended, based on the acceptable risk of radiation-induced brain injury and satisfactory tumour control. TRIAL REGISTRATION: Retrospectively registered.

Brain injury after cranial radiotherapy combined with immunotherapy for brain metastases in lung cancer: a retrospective study.

Aim: To explore whether immune checkpoint inhibitors (ICIs) increase the incidence of radiation-induced brain injury in lung cancer patients with brain metastases. Methods: According to whether they received ICIs within 6 months before and after cranial radiotherapy (CRT), all patients were divided into two groups: ICIs + CRT group and CRT + non-ICIs group. Results: The incidence of radiation necrosis (RN) in the CRT + ICIs group was 14.3%, while that in the CRT + non-ICIs group was 5.8% (p = 0.090). If ICIs were used within 3 months of CRT, there was statistical significance. A maximum diameter of brain metastasis >3.3 cm and cumulative radiation dose of metastatic lesions >75.7 Gy were risk factors for RN. Conclusion: ICIs could increase the risk of RN, especially when used within 3 months of CRT.

VEGFR-TKI treatment for radiation-induced brain injury after gamma knife radiosurgery for brain metastases from renal cell carcinomas.

OBJECTIVE: Antiangiogenic vascular endothelial growth factor receptor tyrosine kinase inhibitors play an essential role in systemic therapy for renal cell carcinoma. Given the anti-edematous effect of bevacizumab, an antiangiogenic antibody targeting vascular endothelial growth factor, vascular endothelial growth factor receptor tyrosine kinase inhibitors should exert therapeutic effects on radiation-induced brain injury after stereotactic radiosurgery. This preliminary study aimed to investigate the therapeutic effect of vascular endothelial growth factor receptor tyrosine kinase inhibitor against radiation-induced brain injury. METHODS: Magnetic resonance images for six patients treated with vascular endothelial growth factor receptor tyrosine kinase inhibitors who were diagnosed with radiation-induced brain injury following gamma knife radiosurgery were retrospectively reviewed. RESULTS: The median brain edema volume and tumour mass volume in the pre-tyrosine kinase inhibitor period were 57.6 mL (range: 39.4-188.2) and 3.2 mL (range: 1.0-4.6), respectively. Axitinib, pazopanib (followed by cabozantinib) and sunitinib were administered in four, one and one cases, respectively. The median brain edema volume and tumour mass volume in the post-tyrosine kinase inhibitor period were 4.8 mL (range: 1.5-27.8) and 1.6 mL (range: 0.4-3.6), respectively. The median rates of reduction in brain edema volume and tumour mass volume were 90.8% (range: 51.9-97.6%) and 57.2% (range: 20.0-68.6%), respectively. The post-tyrosine kinase inhibitor values for brain edema volume (P = 0.027) and tumour mass volume (P = 0.008) were significantly lower than the pre-tyrosine kinase inhibitor values. Changes in volume were correlated with tyrosine kinase inhibitor use. CONCLUSION: This study is the first to demonstrate the therapeutic effects of vascular endothelial growth factor receptor tyrosine kinase inhibitors on radiation-induced brain injury in patients with brain metastases from renal cell carcinoma treated via gamma knife radiosurgery.

Reprimo (RPRM) as a Potential Preventive and Therapeutic Target for Radiation-Induced Brain Injury via Multiple Mechanisms.

Patients receiving cranial radiotherapy for primary and metastatic brain tumors may experience radiation-induced brain injury (RIBI). Thus far, there has been a lack of effective preventive and therapeutic strategies for RIBI. Due to its complicated underlying pathogenic mechanisms, it is rather difficult to develop a single approach to target them simultaneously. We have recently reported that Reprimo (RPRM), a tumor suppressor gene, is a critical player in DNA damage repair, and RPRM deletion significantly confers radioresistance to mice. Herein, by using an RPRM knockout (KO) mouse model established in our laboratory, we found that RPRM deletion alleviated RIBI in mice via targeting its multiple underlying mechanisms. Specifically, RPRM knockout significantly reduced hippocampal DNA damage and apoptosis shortly after mice were exposed to whole-brain irradiation (WBI). For the late-delayed effect of WBI, RPRM knockout obviously ameliorated a radiation-induced decline in neurocognitive function and dramatically diminished WBI-induced neurogenesis inhibition. Moreover, RPRM KO mice exhibited a significantly lower level of acute and chronic inflammation response and microglial activation than wild-type (WT) mice post-WBI. Finally, we uncovered that RPRM knockout not only protected microglia against radiation-induced damage, thus preventing microglial activation, but also protected neurons and decreased the induction of CCL2 in neurons after irradiation, in turn attenuating the activation of microglial cells nearby through paracrine CCL2. Taken together, our results indicate that RPRM plays a crucial role in the occurrence of RIBI, suggesting that RPRM may serve as a novel potential target for the prevention and treatment of RIBI.

Pregabalin mitigates microglial activation and neuronal injury by inhibiting HMGB1 signaling pathway in radiation-induced brain injury.

BACKGROUND: Radiation-induced brain injury (RIBI) is the most serious complication of radiotherapy in patients with head and neck tumors, which seriously affects the quality of life. Currently, there is no effective treatment for patients with RIBI, and identifying new treatment that targets the pathological mechanisms of RIBI is urgently needed. METHODS: Immunofluorescence staining, western blotting, quantitative real-time polymerase chain reaction (Q-PCR), co-culture of primary neurons and microglia, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, enzyme-linked immunosorbent assay (ELISA), and CRISPR-Cas9-mediated gene editing techniques were employed to investigate the protective effects and underlying mechanisms of pregabalin that ameliorate microglial activation and neuronal injury in the RIBI mouse model. RESULTS: Our findings showed that pregabalin effectively repressed microglial activation, thereby reducing neuronal damage in the RIBI mouse model. Pregabalin mitigated inflammatory responses by directly inhibiting cytoplasmic translocation of high-mobility group box 1 (HMGB1), a pivotal protein released by irradiated neurons which induced subsequent activation of microglia and inflammatory cytokine expression. Knocking out neuronal HMGB1 or microglial TLR2/TLR4/RAGE by CRISPR/Cas9 technique significantly inhibited radiation-induced NF-κB activation and pro-inflammatory transition of microglia. CONCLUSIONS: Our findings indicate the protective mechanism of pregabalin in mitigating microglial activation and neuronal injury in RIBI. It also provides a therapeutic strategy by targeting HMGB1-TLR2/TLR4/RAGE signaling pathway in the microglia for the treatment of RIBI.

Early-Onset Micromorphological Changes of Neuronal Fiber Bundles During Radiotherapy.

BACKGROUND: Patients receiving cranial radiation face the risk of delayed brain dysfunction. However, an early medical imaging marker is not available until irreversible morphological changes emerge. PURPOSE: To explore the micromorphological white matter changes during the radiotherapy session by utilizing an along-tract analysis framework. STUDY TYPE: Prospective. POPULATION: Eighteen nasopharyngeal carcinoma (two female) patients receiving cranial radiation. FIELD STRENGTH/SEQUENCE: 3.0 T; Diffusion tensor imaging (DTI) and T1- and T2-weighted images (T1W, T2W); computed tomography (CT). ASSESSMENT: Patients received three DTI imaging scans during the radiotherapy (RT), namely the baseline scan (1-2 days before RT began), the middle scan (the middle of the RT session), and the end scan (1-2 days after RT ended). Twelve fibers were segmented after whole-brain tractography. Then, the fractional anisotropy (FA) values and the cumulative radiation dose received for each fiber streamline were resampled and projected into their center fiber. STATISTICAL TESTS: The contrast among the three scans (P1: middle scan-baseline scan; P2: end scan-middle scan; P3: end scan-baseline scan) were compared using the linear mixed model for each of the 12 center fibers. Then, a dose-responsiveness relationship was performed using Pearson correlation. P < 0.05 was considered statistically significant. RESULTS: Six of the 12 center fibers showed significant changes of FA values during the RT but with heterogeneous patterns. The significant changes along a specific center fiber were associated with their cumulative dose received (Genu: P1 r = -0.6182, P2 r = -0.5907; Splenium: P1 r = 0.4055, P = 0.1063, P2 r = 0.6742; right uncinate fasciculus: P1 r = -0.3865, P2 r = -0.4912, P = 0.0533; right corticospinal tract: P1 r = 0.4273, P = 0.1122, P2 r = -0.6885). DATA CONCLUSION: The along-tract analysis might provide sensitive measures on the early-onset micromorphological changes. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 3.

Prior nasal delivery of antagomiR-122 prevents radiation-induced brain injury.

Radiation-induced brain injury is a major adverse event in head and neck tumor treatment, influencing the quality of life for the more than 50% of patients who undergo radiation therapy and experience long-term survival. However, no effective treatments are available for these patients, and preventative drugs and effective drug-delivery methods must be developed. Based on our results, miR-122-5p was upregulated in the mouse radiation-induced brain injury (RBI) model and patients with nasopharyngeal carcinoma (NPC) who received radiation therapy. Intranasal administration of a single antagomiR-122-5p dose before irradiation effectively alleviated radiation-induced cognitive impairment, neuronal injury, and neuroinflammation in the mouse RBI model. Results further indicated that miR-122-5p inhibition in microglia reduced the levels of proinflammatory cytokines and enhanced the phagocytic function to protect against radiation-induced neuronal injury in cell models. Further, we profiled transcriptome data and verified that Tensin 1 (TNS1) may be the target of miR-122-5p in RBI. In summary, our results reveal a distinct role for miR-122-5p in regulating neuroinflammation in RBI, indicating that a non-invasive strategy for intranasal miR-122-5p administration may be an attractive therapeutic target in RBI, providing new insights for clinical trials. Further systematic safety assessment, optimization of drug administration, and clarity of mechanism will accelerate the process into clinical practice.

[C-methionine PET in assessment of brain lesions in patients with glial tumors after combined treatment]. / PÉT s S-metioninom v otsenke porazhenii golovnogo mozga u bol'nykh s glial'nymi opukholiami posle kombinirovannogo lecheniia.

Positron emission tomography (PET) with amino acid-based radiopharmaceuticals is considered as an effective method to diagnose continued growth of cerebral gliomas, but the variability of 11C-methionine uptake by brain lesions of different genesis after combined treatment still remains poorly understood. The aim of this study was to explore the information value of 11C-methionine PET in delimitating progression of cerebral gliomas and stable disease and to assess the risk of tumor recurrence at different values of the 11C-methionine uptake index. MATERIAL AND METHODS: We performed a retrospective analysis of the results of 11C-methionine PET or PET/CT in 324 patients suspected for continued growth of cerebral tumor based on magnetic resonance imaging (MRI) findings. A quantitative analysis of the results included calculation of the 11C-methionine uptake index (UI). RESULTS: A ROC analysis revealed that the specificity of PET in the diagnosis of continued tumor growth (CTG) was 98%, and the sensitivity was 71% for a UI of more than 1.9. We found that 98% of lesions with a negative level of RP uptake were related to radiation brain lesions (RBLs) or residual tumors combined with radiation pathomorphims. The UI in a range of 1.2-1.6 in 75% of lesions characterized a stable disease, but 25.5% of the lesions represented continued glioma growth. The proportion of recurrences increased to 40% in a UI range of 1.6-1.9, and 95.5% of brain lesions with a UI of more than 1.9 were tumor recurrences. Therefore, high 11C-methionine uptake with the UI above 1.9 in brain lesions characterized by radiological signs of disease progression is a highly specific indicator of CTG; however, the UI may significantly vary during tumor growth, and a substantial fraction of recurrent gliomas may have lower radiopharmaceutical uptake. In the case of borderline UI values, early dynamic control or complementary additional MRI or CT techniques should be used.

Relative cerebral blood volume is a potential biomarker in late delayed radiation-induced brain injury.

PURPOSE: To assess whether relative cerebral blood volume (rCBV) can provide information to reliably evaluate the stages of late delayed radiation-induced brain injury. MATERIALS AND METHODS: Forty patients diagnosed with late delayed radiation-induced brain injury were enrolled. The patients were examined using a 1.5T magnetic resonance imaging (MRI) system equipped with an 8-channel head coil. An echo planar imaging (EPI) sequence was used in perfusion-weighted imaging (PWI). The location of 1H-MR spectroscopy scanning was acquired by a point-resolved spectroscopy sequence. Lesions of the temporal lobe were divided into one of two groups according to rCBV value: rCBV<1 (low rCBV [group 1; n = 45]); and rCBV>1 (elevated rCBV [group 2; n = 14]). PWI and MRS parameters, as well as morphological lesion types, in these two groups were compared. Morphological severity was assessed independently and agreed on by two imaging specialists (J.L. and H.X.S., with 16 and 24 years' experience, respectively). If necessary, a third imaging professor (Z.M.H.) with 30 years' experience resolved disagreement(s). Standards for evaluating morphological lesion types were based on previously published criteria. After testing the skewness of data, the Mann-Whitney U-test or Student's t-test was used, as appropriate. RESULTS: rCBV, relative cerebral blood flow (rCBF), and relative mean transit time (rMTT) in group 2 (n = 14) were significantly higher than in group 1 (n = 45) (rCBV: 1.21 ± 0.38 vs. 0.72 ± 0.32, respectively; P < 0.001; rCBF: 1.13 ± 0.02 vs. 0.74 ± 0.04, respectively; P < 0.001; rMTT: 1.10 ± 0.26 vs. 0.96 ± 0.20, P < 0.001). The levels of choline-containing compounds (CHO) / creatine (Cr) and CHO/N-acetylaspartate (NAA) in group 1 were significantly greater than in group 2 (CHO/Cr: 1.89 ± 1.83 vs. 1.22 ± 1.31, respectively; P = 0.016; CHO/NAA: 1.85 ± 3.50 vs. 1.17 ± 0.75, respectively; P = 0.022). More severe morphological lesions were present in lesions with low rCBV compared with elevated rCBV (overall severity: 7.00 ± 4.25 vs. 5.00 ± 5.13, respectively; P = 0.029). CONCLUSION: Elevated rCBV accompanied by a more conservative metabolic pattern and milder lesion(s) may represent a less advanced stage in the development of late delayed radiation-induced brain injury. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2018;47:1112-1118.

Distinct Expression of Various Angiogenesis Factors in Mice Brain After Whole-Brain Irradiation by X-ray.

Radiation-induced brain injury (RBI) is the most serious complication after radiotherapy. However, the etiology of RBI remains elusive. In order to evaluate the effect of X-rays on normal brain tissue, adult male BALB/C mice were subjected to whole-brain exposure with a single dose of 10 Gy or sham radiation. The structure and number of mice brain vessels were investigated 1, 7, 30, 90 and 180 days after irradiation by H&E staining and immune-fluorescence staining. Compared with sham control mice, in addition to morphological changes, a significant reduction of microvascular density was detected in irradiated mice brains. Whole-brain irradiation also caused damage in tight junction (TJ). Increased expression of glial fibrillary acidic protein (GFAP) and vascular endothelial growth factor (VEGF) was observed in irradiated mouse brains showed by Western Blot. Immune-fluorescence staining results also verified the co-labeling of GFAP and VEGF after whole-brain irradiation. Furthermore, the protein expression levels of other angiogenesis factors, angiopoietin-1 (Ang-1), endothelial-specific receptor tyrosine kinase (Tie-2), and angiopoietin-2 (Ang-2) in brain were determined by Western Blot. Increased expression of Ang-2 was shown in irradiated mouse brains. In contrast, whole-brain irradiation significantly decreased Ang-1 and Tie-2 expression. Our data indicated that X-rays induced time-dependent microvascular injury and activation of astrocytes after whole-brain irradiation in mouse brain. Distinct regulation of VEGF/Ang2 and Ang-1/Tie-2 are closely associated with RBI, suggesting that angiogenesis interventions might be beneficial for patients with RBI.

Neuroprotective effect of Dl-3-n-butylphthalide on patients with radiation-induced brain injury: a clinical retrospective cohort study.

PURPOSE: To evaluate the neuroprotective effects of Dl-3-n-butylphthalide (NBP) on patients with radiation-induced brain injury, a hospital-based, clinical retrospective cohort study was conducted. PATIENTS AND METHODS: Data were collected on patients diagnosed with radiation-induced brain injury from January 2009 to January 2015 in Department of Neurology, Sun Yat-Sen Memorial Hospital. All patients enrolled have received cranial radiotherapy and were diagnosed with radiation-induced brain injury. Patients fulfilling certain eligibility criteria were recruited for analysis. The clinical therapeutic effects were observed and evaluated by LENT/SOMA scores before and one month after treatment in these two groups, respectively. RESULTS: The therapeutic effects of headache (total efficiency 75.76%), eurologic deficit (total efficiency 81.58%), cognitive functions (total efficiency 77.78%) and MRI results (total efficiency 74.29%) were better in the experimental group than those in the control group (p < 0.05). Nevertheless, there was no significant difference in mood and personality changes between these two groups. CONCLUSIONS: Administration of Dl-3-n-butylphthalide, in adjunct to corticosteroid therapy, might provide a better outcome in patients with radiation-induced brain injury.

Neuroprotective effects of human umbilical cord-derived mesenchymal stromal cells combined with nimodipine against radiation-induced brain injury through inhibition of apoptosis.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) possess the ability to repair brain injuries. Additionally, nimodipine is a neuroprotective agent that increases cerebral blood flow and may help with the homing of MSCs to the injury site. Here we investigate the effectiveness of a combined human umbilical cord-derived MSCs and nimodipine therapy in radiation-induced brain injury (RIBI). METHODS: Female mice received whole brain irradiation (WBI) and were treated with saline, nimodipine, hUC-MSCs, or hUC-MSCs combined with nimodipine. Body weight was measured weekly. An open field test for locomotor activity and a step-down avoidance test for learning and memory function were conducted at week 4 and week 12 post-WBI. The histological damage was evaluated by hematoxylin and eosin staining and glial fibrillary acidic protein immunohistochemistry. Quantitative polymerase chain reaction and Western blotting were used to detect apoptosis-related mediators (p53, Bax and Bcl-2). RESULTS: In mice receiving the hUC-MSCs or the combined treatment, their body weight recovered, their locomotor and cognitive ability improved, and the percentage of necrotic neurons and astrocytes was reduced. The combined therapy was significantly (P < 0.05) more effective than hUC-MSCs alone; these mice showed decreased expression of pro-apoptotic indicators (p53, Bax) and increased expression of an anti-apoptotic indicator (Bcl-2), which may protect brain cells. CONCLUSIONS: We demonstrated that hUC-MSCs therapy helps recover body weight loss and behavior dysfunction in a mice model of RIBI. Moreover, the effectiveness of the combined hUC-MSCs and nimodipine therapy is due to apoptosis inhibition and enhancing homing of MSCs to the injured brain.

Neuroprotective Effects of Kukoamine a against Radiation-induced Rat Brain Injury through Inhibition of Oxidative Stress and Neuronal Apoptosis.

Radiation-induced brain injury (RIBI) is a prominent side effect of radiotherapy for cranial tumors. Kukoamine A (KuA) has the ability of anti-oxidative stress and anti-apoptosis in vitro. The aim of this study was to investigate whether KuA would prevent the detrimental effect of ionizing radiation on hippocampal neurons. For this study, male Wistar rats were received either sham irradiation or whole brain irradiation (30 Gy single dose of X-rays) followed by the immediate injection of either KuA or vehicle intravenously. The dose of KuA was 5, 10 and 20 mg/kg respectively. The protective effects of KuA were assessed by Nissl staining. The levels of oxidative stress marker and antioxidants activities were assayed by kits. TUNEL staining was performed to detect the level of apoptosis in hippocampal neurons. The expression of apoptosis-related proteins as well as the brain-derived neurophic factor (BDNF) was evaluated by western blot. Whole brain irradiation led to the neuronal abnormality and it was alleviated by KuA. KuA decreased malondialdehyde (MDA) level, increased glutathione (GSH) level, superoxide dismutase (SOD) and catalase (CAT) activities, as well as alleviated neuronal apoptosis by regulating the expression of cleaved caspase-3, cytochrome C, Bax and Bcl-2. Additionally, KuA increased the expression of BDNF. These data indicate that KuA has neuroprotective effects against RIBI through inhibiting neuronal oxidative stress and apoptosis.

A preclinical murine model for the early detection of radiation-induced brain injury using magnetic resonance imaging and behavioral tests for learning and memory: with applications for the evaluation of possible stem cell imaging agents and therapies.

Stem cell therapies are being developed for radiotherapy-induced brain injuries (RIBI). Magnetic resonance imaging (MRI) offers advantages for imaging transplanted stem cells. However, most MRI cell-tracking techniques employ superparamagnetic iron oxide particles (SPIOs), which are difficult to distinguish from hemorrhage. In current preclinical RIBI models, hemorrhage occurs concurrently with other injury markers. This makes the evaluation of the recruitment of transplanted SPIO-labeled stem cells to injury sites difficult. Here, we developed a RIBI model, with early injury markers reflective of hippocampal dysfunction, which can be detected noninvasively with MRI and behavioral tests. Lesions were generated by sub-hemispheric irradiation of mouse hippocampi with single X-ray beams of 80 Gy. Lesion formation was monitored with anatomical and contrast-enhanced MRI and changes in memory and learning were assessed with fear-conditioning tests. Early injury markers were detected 2 weeks after irradiation. These included an increase in the permeability of the blood-brain barrier, demonstrated by a 92 ± 20 % contrast enhancement of the irradiated versus the non-irradiated brain hemispheres, within 15 min of the administration of an MRI contrast agent. A change in short-term memory was also detected, as demonstrated by a 40.88 ± 5.03 % decrease in the freezing time measured during the short-term memory context test at this time point, compared to that before irradiation. SPIO-labeled stem cells transplanted contralateral to the lesion migrated toward the lesion at this time point. No hemorrhage was detected up to 10 weeks after irradiation. This model can be used to evaluate SPIO-based stem cell-tracking agents, short-term.

Whole-brain changes in white matter microstructure after radiotherapy for nasopharyngeal carcinoma: a diffusion tensor imaging study.

Radiation-induced local white matter (WM) damage has been observed by diffusion tensor imaging (DTI) within a priori-defined regions of interest following radiotherapy (RT) for nasopharyngeal carcinoma (NPC). In this study, we aimed to detect WM changes throughout the brain of NPC patients by DTI. Tract-based spatial statistics (TBSS) was used to analyze DTI data from 81 NPC patients. Fractional anisotropy (FA) and mean diffusivity (MD) were quantified across the whole brain in separate groups: pre-RT, and <6, 6-12, and >12 months post-RT. We found that fractional anisotropy values were significantly lower in the right frontal, parietal, and occipital WM <6 months post-RT compared with pre-RT and remained significantly lower in the right frontal and parietal WM at >12 months. MD values were significantly higher in the right occipital, bilateral temporal, right occipital-temporal junction, left parietal, left centrum semiovale, and left frontal-parietal junction WM <6 months post-RT and remained higher in the right occipital WM at >12 months. This study suggests that changes in white matter microstructure following RT for NPC were widespread, complex, and dynamic. Diffusion tensor imaging with TBSS analysis allows for early non-invasive detection of RT-induced WM damage.

Extracellular ATP enhances radiation-induced brain injury through microglial activation and paracrine signaling via P2X7 receptor.

Activation of purinergic receptors by extracellular ATP (eATP) released from injured cells has been implicated in the pathogenesis of many neuronal disorders. The P2X7 receptor (P2X7R), an ion-selective purinergic receptor, is associated with microglial activation and paracrine signaling. However, whether ATP and P2X7R are involved in radiation-induced brain injury (RBI) remains to be determined. Here, we found that the eATP level was elevated in the cerebrospinal fluid (CSF) of RBI patients and was associated with the clinical severity of the disorder. In our experimental model, radiation treatment increased the level of eATP in the supernatant of primary cultures of neurons and glial cells and in the CSF of irradiated mice. In addition, ATP administration activated microglia, induced the release of the inflammatory mediators such as cyclooxygenase-2, tumor necrosis factor α and interleukin 6, and promoted neuronal apoptosis. Furthermore, blockade of ATP-P2X7R interaction using P2X7 antagonist Brilliant Blue G or P2X7 knockdown suppressed radiation-induced microglial activation and proliferation in the hippocampus, and restored the spatial memory of irradiated mice. Finally, we found that the PI3K/AKT and nuclear factor κB mediated pathways were downstream of ATP-P2X7R signaling in RBI. Taken together, our results unveiled the critical role of ATP-P2X7R in brain damage in RBI, suggesting that inhibition of ATP-P2X7R axis might be a potential strategy for the treatment of patients with RBI.

Molecular, Cellular and Functional Effects of Radiation-Induced Brain Injury: A Review.

Radiation therapy is the most effective non-surgical treatment of primary brain tumors and metastases. Preclinical studies have provided valuable insights into pathogenesis of radiation-induced injury to the central nervous system. Radiation-induced brain injury can damage neuronal, glial and vascular compartments of the brain and may lead to molecular, cellular and functional changes. Given its central role in memory and adult neurogenesis, the majority of studies have focused on the hippocampus. These findings suggested that hippocampal avoidance in cranial radiotherapy prevents radiation-induced cognitive impairment of patients. However, multiple rodent studies have shown that this problem is more complex. As the radiation-induced cognitive impairment reflects hippocampal and non-hippocampal compartments, it is of critical importance to investigate molecular, cellular and functional modifications in various brain regions as well as their integration at clinically relevant doses and schedules. We here provide a literature overview, including our previously published results, in order to support the translation of preclinical findings to clinical practice, and improve the physical and mental status of patients with brain tumors.