Partial-Brain Radiation-Induced Microvascular Cognitive Impairment in Juvenile Murine Unilateral Hippocampal Synaptic Plasticity

Astragaloside IV mediates radiation-induced neuronal damage through activation of BDNF-TrkB signaling

BACKGROUND

Electromagnetic radiation is relevant to human life, and radiation can trigger neurodegenerative diseases by altering the function of the central nervous system through oxidative stress, mitochondrial dysfunction, and protein degradation. Astragaloside IV (AS-IV) is anti-oxidative, anti-apoptotic, activates the BDNF-TrkB pathway and enhances synaptic plasticity in radiated mice, which can exert its neuroprotection. However, the exact molecular mechanisms are still unclear.

PURPOSE

This study investigated whether AS-IV could play a neuroprotective role by regulating BDNF-TrkB pathway in radiation damage and its underlying molecular mechanisms.

METHODS

Transgenic mice (Thy1-YFP line H) were injected with AS-IV (40 mg/kg/day body weight) by intraperitoneal injection daily for 4 weeks, followed by X-rays. PC12 cells and primary cortical neurons were also exposed to UVA after 24 h of AS-IV treatment (25 μg/ml and 50 μg/ml) in vitro. The impact of radiation on learning and cognitive functions was visualized in the Morris water maze assay. Subsequently, Immunofluorescence and Golgi-Cox staining analyses were utilized to investigate the structural damage of neuronal dendrites and the density of dendritic spines. Transmission electron microscopy was performed to examine how the radiation affected the ultrastructure of neurons. Finally, western blotting analysis and Quantitative RT-PCR were used to evaluate the expression levels and locations of proteins in vitro and in vivo.

RESULTS

Radiation induced BDNF-TrkB signaling dysregulation and decreased the levels of neuron-related functional genes (Ngf, Bdnf, Gap-43, Ras, Psd-95, Arc, Creb, c-Fos), PSD-95 and F-actin, which subsequently led to damage of neuronal ultrastructure and dendrites, loss of dendritic spines, and decreased dendritic complexity index, contributing to spatial learning and memory deficits. These abnormalities were prevented by AS-IV treatment. In addition, TrkB receptor antagonists antagonized these neuroprotective actions of AS-IV. 7,8-dihydroxyflavone and AS-IV had neuroprotective effects after radiation.

CONCLUSION

AS-IV inhibits morphological damage of neurons and cognitive dysfunction in mice after radiation exposure, resulting in a neuroprotective effect, which were mediated by activating the BDNF-TrkB pathway.

Evaluation of Glycogen Synthase Kinase Pathway for Assessing the Antidepressant-like Effect of Glucosamine as a Radioprotector in Rats: Behavioral and Biochemical Studies

Radiotherapy is a very important tool in the treatment of cancer; nevertheless, its side effects are a hindrance to its use. The present study is designed to evaluate glucosamine effects against radiation-induced brain oxidative stress and depression-like effect in rats. Four groups of female Wister rats were used as control, irradiated (4 × 2 Gy), glucosamine (1 g/kg P.O), and glucosamine + irradiated group. The behavioral responses are estimated. The brain hippocampi of the rats are separated to evaluate oxidative stress biochemical parameters and glycogen synthase kinase pathway in addition to the biogenic amines. Irradiation exposure led to disturbances in the behavioral assessments (forced swimming test, light-dark box, and open field test) and a significant decrease in brain GSH, neurotransmitters (serotonin, norepinephrine, and dopamine), phosphatidylinositol 3 kinase (PI3K), and phosphorylated protein kinase-B (p-AKT) levels. Additionally, MDA and ROS levels increased significantly post-irradiation along with the phosphorylated glycogen synthase kinase (p-GSK3). Glucosamine administration before irradiation caused improvement in the behavioral valuations and the biochemical parameters in the brain as well. Glucosamine might be used as a radioprotector to improve brain function and as an antidepressant drug. It could be promising as a future therapy in managing depression occurring during radiotherapy.

Multiple Irradiation Affects Cellular and Extracellular Components of the Mouse Brain Tissue and Adhesion and Proliferation of Glioblastoma Cells in Experimental System In Vivo

Intensive adjuvant radiotherapy (RT) is a standard treatment for glioblastoma multiforme (GBM) patients; however, its effect on the normal brain tissue remains unclear. Here, we investigated the short-term effects of multiple irradiation on the cellular and extracellular glycosylated components of normal brain tissue and their functional significance. Triple irradiation (7 Gy*3 days) of C57Bl/6 mouse brain inhibited the viability, proliferation and biosynthetic activity of normal glial cells, resulting in a fast brain-zone-dependent deregulation of the expression of proteoglycans (PGs) (decorin, biglycan, versican, brevican and CD44). Complex time-point-specific (24–72 h) changes in decorin and brevican protein and chondroitin sulfate (CS) and heparan sulfate (HS) content suggested deterioration of the PGs glycosylation in irradiated brain tissue, while the transcriptional activity of HS-biosynthetic system remained unchanged. The primary glial cultures and organotypic slices from triple-irradiated brain tissue were more susceptible to GBM U87 cells’ adhesion and proliferation in co-culture systems in vitro and ex vivo. In summary, multiple irradiation affects glycosylated components of normal brain extracellular matrix (ECM) through inhibition of the functional activity of normal glial cells. The changed content and pattern of PGs and GAGs in irradiated brain tissues are accompanied by the increased adhesion and proliferation of GBM cells, suggesting a novel molecular mechanism of negative side-effects of anti-GBM radiotherapy.