The Research Of Neuronal Autophagy And Injury In High-altitude Hypoxia Environment

Background:China has a vast plateau area,and a large number of plateau population.However,Because of high disease incidence,high altitude headache(HAH),acute mountain sickness(AMS)and high-altitude cerebral edema(HACE)has caused serious harm to the plateau population.It was generally believed that brain injury caused by high-altitude hypoxia environment was a kind of vascular damage,which was closely related to the increased cerebral perfusion pressure(CCP),and the increased cerebrovascular permeability.However,the fundamental change of high-altitude brain injury must be the damage of neurons and brain tissue structure.It has been reported that high-altitude hypoxia environment could induce neuronal apoptosis.However,there were few studies that focused on the factors which affected neuronal prognosis and the related molecular mechanisms in this environment.Autophagy is a metabolic process by which excessive or damaged organelles and protein are removed by lysosomes.A large number of studies have shown that the activation of autophagy under the condition of ischemia/hypoxia is closely related to neuronal damage.In addition,many researchers have reported that high-altitude hypoxia exposure could activate autophagy of intestinal mucosa cells and cardiomyocyte.However,whether neuronal autophagy can be activated in high-altitude hypoxia environment,whether it will affect neuronal prognosis,and whether there is a relationship between neuronal autophagy with different high-altitude hypoxia exposure time and different altitudes,are still unclear.Therefore,the aims of this study are to elucidate the influence of high-altitude hypoxia environment on neuronal autophagy and injury,and to explore the relationship between autophagy and neuronal damage in this environment,which will lay the foundation for the further study of the molecular pathogenesis of the high-altitude hypoxia brain injury.Objectives:1.To observe the influence of different high-altitude hypoxia exposure time and altitudes on neuronal injury.2.To observe the influence of different high-altitude hypoxia exposure time and altitudes on neuronal autophagy.3.To explore the relationship between neuronal autophagy and injury in high-altitude hypoxia environment.Methods:1.Model establishment: we used hypobaric oxygen chamber to simulate high-altitude hypoxia environment,established high-altitude hypoxia model in vivo;2.Negative emotions assessment of mouse: elevated plus maze(EMP)was used to assess negative emotions of mouse;3.Observation of neuronal injury: we observed morphologic change of hippocampal and cortical neurons through HE staining,and counted the number of damaged neurons under high-power fields;4.Detection of neuronal autophagy: Western blot was used to detect the expressions of HIF-1?,Beclin-1 and LC3-II.Results:1.The influence of high-altitude hypoxia environment on neuronal function of mouse.(1)At the altitude of 6000 m,high-altitude hypoxia exposure for 1 day,3 days and 14 days significantly increased negative emotions of mouse(p<0.05),and high-altitude hypoxia exposure for 7 days had no obvious effect on mouse emotions(p>0.05).(2)HE staining showed that hippocampal neurons was seriously damaged after 3 days high-altitude hypoxia exposure at the altitude of 6000 m.So,selecting 3 days as high-altitude hypoxia exposure time,we further observed the influence of different altitudes on negative emotions of mouse.EMP results showed that negative emotions of mouse increased with the rise of altitude;when the altitude rose to 6000 m,compared with control group,negative emotions of mouse in exposure group significantly increased(p<0.05).2.The influence of high-altitude hypoxia environment on morphology of hippocampal and cortical neurons of mouse.(1)The influence of different high-altitude hypoxia exposure time on the injury of hippocampal neurons: at the altitude of 6000 m,high-altitude hypoxia exposure for 1 days,3 days,and 14 days significantly increased the number of damaged hippocampal neurons(p<0.05),and the injury of hippocampal neurons were more serious in 3 days and 14 days exposure group;however,high-altitude hypoxia exposure for 7 days had no obvious influence on the injury of hippocampal neurons(p>0.05).(2)The influence of different high-altitude hypoxia exposure time on the injury of cortical neurons: at the altitude of 6000 m,compared with control group,different durations of high-altitude hypoxia exposure significantly increased the number of damaged cortical neurons(p<0.05),and the extent of damage increased with the prolongation of exposure time.(3)The influence of different altitudes on the injury of hippocampal and cortical neurons: selecting 3 days as high-altitude hypoxia exposure time,we found that the number of damaged hippocampal and cortical neurons increased with the rise of altitude;when the altitude rose to 6000 m,compared with control group,the number of damaged hippocampal and cortical neurons in exposure group significantly increased(p<0.05).3.The influence of high-altitude hypoxia environment on autophagy of hippocampal and cortical neurons of mouse.(1)The influence of different high-altitude hypoxia exposure time on the autophagy of hippocampal neurons: at the altitude of 6000 m,the expressions of HIF-1?,Beclin-1 and LC3-II in hippocampal neurons reached the peak after high-altitude hypoxia exposure for 1 day,and their expressions significantly increased compared with control group(p<0.05);the expressions of HIF-1?,Beclin-1 and LC3-II in hippocampal neurons subsequently decreased with the prolongation of exposure time,and the expressions of HIF-1? and LC3-II was not significant when compared with the control group after high-altitude hypoxia exposure for 7 days(p>0.05).(2)The influence of different high-altitude hypoxia exposure time on the autophagy of cortical neurons: at the altitude of 6000 m,the expressions of HIF-1?,Beclin-1 and LC3-II in cortical neurons were continuously increased after different durations of high-altitude hypoxia exposure(p<0.05).(3)The influence of different altitudes on the autophagy of hippocampal and cortical neurons: the expressions of HIF-1?,Beclin-1 and LC3-II in hippocampus and cortical neurons were up-regulated in high-altitude hypoxia environment of different altitudes when the exposure time was 3 days,and their expressions gradually increased with the rise of altitude;when the altitude rose to 6000 m,compared with control group,the expressions of HIF-1?,Beclin-1 and LC3-II in hippocampus and cortical neurons significantly increased(p<0.05).Conclusion:At high-altitude hypoxia environment,increased negative emotions of mouse were one of the important manifestations of neurological impairment,and were correlated with the injury of hippocampal neurons;and the activation of autophagy may be involved in the regulating process of hippocampal neuronal injury induced by acute high-altitude hypoxia exposure.