Effect Of Exercise On Reactive Astrogliosis And Neuronal Stress Responses After Brain Injury In Mouse

Traumatic brain injury(TBI)is one of the main causes of disability and death in adolescents and adults.Motor vehicle accidents,attacks,falls and various strenuous exercises are the main causes of TBI.Adolescents with TBI are often accompanied by a series of dysfunctions,such as emotional,behavioral,cognitive,and motor dysfunctions in their growth and development stages,and even adult stages.The mechanism of central injury causing the above-mentioned dysfunction is still unclear.In this study,we used low-to-moderate-intensity treadmill aerobic exercise intervention after TBI.To investigate the effects of reactive astrocyte and neuronal stress on neuronal damage at different stages after TBI,we observed the effects of TBI and/or exercise on the expression of astrocytes(GFAP,C3,SHH,TSPO)and neurons(Caprin1,SHH,NFH)related proteins at different time points after TBI.At the same time,the effects of aerobic exercise on neurological function,various behavior functions and emotions after TBI were studied.The purpose is to provide new ideas for the study of mechanism of neuron damage after TBI and the intervention of secondary damage and sequelae of TBI.Methods:Wild-type C57BL/6 mice were randomly divided into control group(CON),TBI group(TBI),control+exercise group(CON+EXE),TBI+exercise group(TBI+EXE).Moderate brain injury is caused by a hydraulic strike in the motor-sensory area of mice.The mice were subjected to 6-day treadmill fitness training before TBI modeling,and the basic motor function test and neurological function score(NSS)were assessed.Started from 9 days after TBI modeling,a 47-day rehabilitation aerobic exercise was performed.The exercise mode: passive variable-speed interval training on a mouse treadmill.At different time points after TBI,NSS,grid walking test and open field test were conducted to explore the effects of TBI and/or exercise on the neurological and motor functions of mice;tail suspension test,open field test,Y maze Tests,water maze test,three-chamber test,and dominance mouse test were conducted to explore the effects of TBI and exercise on depression,anxiety,learning and memory function,social interaction and aggression in mice.After the behavioral experiments were completed,hematoxylin-eosin(HE)staining was used to observe the necrosis of cortical and hippocampal neurons.After sectioning-dewaxing-antigen retrieval,immunofluorescence staining was performed to detect the expression of astrocyte and neuronal related proteins in brain tissues,and semi-quantitative analysis was performed with Image J.Results:The NSS,wrong usage rate of left forelimb and immobility time of TBI mice were significantly higher than those of Con group mice.The activity of TBI mice in the open field significantly reduced,and the travel distance in the middle quarter of the open field was the percentage of the total distance decreased.Due to the TBI,the percentage of Y maze automatic rotation,the resolution coefficient of Y maze,the score of attack ability of mice,the scent duration of novel mice and the social stay time in TBI mice also reduced.Compared with the TBI group,the 47-day aerobic exercise can significantly increase the number of times the TBI mice crossed the original platform,the stay time and the travel distance in the original platform area.The arrangement of cortical neurons in TBI mice was disrupted,accompanied by severe vacuoles and lysis.The cortical neurons in the CON group were arranged neatly with clear nucleoli.The morphology of neurons in the TBI+EXE group is between CON and TBI group mice.In the TBI group,the neurons in the DG area of the hippocampus were lysed,the neurons were in irregular clusters,and the nucleoli were indistinguishable.After brain injury,the positive cells expressing Caprin1,SHH,NFH,GFAP,TSPO,and C3 in the ipsilateral cortex and hippocampus in the TBI mice significantly increased.Compared with the TBI mice,the positive cells expressing SHH in the ipsilateral cortex and hippocampus significantly increased;while positive cells expressing Caprin1,NFH,GFAP,TSPO,and C3 significantly decreased.Conclusion:Moderate TBI caused neuronal damages in the cortex and hippocampus;thus,caused a significant decline in neurological function,motor function,spatial cognitive ability,social interaction and aggressive advantages.TBI mice also showed significant depression and anxiety.47 days of rehabilitation exercise can significantly improve motor function,spatial cognition ability,learning and memory ability,social interaction and aggressive advantages,and reduce depression and anxiety in TBI mice.The above-mentioned neuroprotection of aerobic exercise may partly lie in:1.Reduce the activation of type A1 astrocytes after TBI(the number of C3,GFAP-positive cells is reduced),microglia and mitochondrial damage in astrocytes,which may further reduce neuroinflammation and oxidative stress in the brain.2.Reduce neuronal stress damage(decrease in the number of NFH,Caprin1 positive cells).3.Promote the proliferation of neural precursor cells and regulate the activation of astrocytes(the number of SHH-positive cells increases).