A Relating Study Of AQP4 And Cerebral Pathology Of Cerebral Cortex And Blood Brain Barrier Of Rat Under Simulating Highland Enviroment

When humans or animals go into the highland suddenly,they will expose under low pressure, hypoxia and cold enviroment. A series of pathological reaction will occur, which manifested by headache, nausea, vomiting, agrypnia, dizzy and dystaxia. All these are called highland response. Another name is acute mountain sickness(AMS). According to some reports, when human go into 2,500m highland, AMS may occur. Patients suffered with severe AMS will have high altitude pulmonary edema (HAPE) or high altitude cerebral edema (HACE). In the morden time, the traffic and tourism are very prosperous, and the social communication increases. More and more people have the chance to go highland, so the prevention and cure of altitude disease is more and more important and urgent.According to some investigation,the main pathological changes of AMS and HACE were vasogenic edema. But, up to now, we don not know any more about the molecular mechanisms of high altitude cerebral edema. Glial cells foot are the important structure component of blood-brain barrier.According to recent study of cerebral edema of trauma,ischemia and tumor, the morphologic changes of glial cells take place before neurons,which were thought as the ealiest pathologic change. But up to now, we do not know the pathologic response of glial cell in AMS and HACE. Aquaporins are main molecular background of transmembrane function of water. They play an important role in the adjustment of water balance of brain. Some researchers thought that aquaporins play an important role in the pathological and physiological changes of the brain edema. The role of AQP4 in the AMS and HACE is worth to be investigated. In this experiment, simulation of 5000m high lands was taken as the animasl model. Rats were put into low oxygen pressure cabin, the morphology of brain was observed by LM and EM, the permeability of blood-brain-barrier(BBB)was traced by lanthanum(La(NO3)3.nH2O);The immunolochemistry and hybridization in site for AQP4 and mRNA were observed by LM and EM; Glutamate (GLU), gamm-aminobutyric (GABA) were tested by aminophenol analysis, in order to research the cerebral pathology and pathogenesis of high altitude response. The results obtained are as follows: 1. General condition: The activity of rats in the experimental groups decreased from the 1st day to the 3rd day. There are significant hyperemia in arachnoid, lung tissue and gastrointestinal tract. Afterwards, The activity of rats increased. Tissue hyperemia decreased to the normal level. 2. Light microscopic observation: Mild hyperemia of arachnoid was observed in 24h, 48h and 72h experimental group and enlarged perimicrovessel space in the brain tissue. 3. Electron microscope observation: Pinocytic vesicles in endothelial cell of blood capillary in 4h experimental group increased. Basement membrane became rarefacted and the density was not well distributed. The number of Pinocytic vesicles of endothelial cell of blood capillary in 24h, 48h and 72h experimental group become more and more. Mitochondrial crista became clouding, extinction or cavitation. In the same time, free ribosome increased too. Tight junction became clouding or loosening. Basement membrane uneven density was more significant. Astrocyte and foot became pale and swelling. There were not significant pathological changes observed in nerve cells. 4. Permeability of blood brain barrier(BBB)observation by nitric lanthanum: In the normal group and 4h experimental group, lanthanum particles were located in endothelial cell surface of blood vessel. In the 24h experimental group, lanthanum particles were observed in tight junction interspace of endothelial cell. In the 48h experimental group, lanthanum particles were observed in the tissue interspace outside basement membrane. From the 3rd day to the end lanthanum leakage was not observed. 5. Immunohistochemistry staining and in situ hybridization of AQP4 observation: AQP4 immunoreactivity was localized to capillaries wall and processes of astrocyte. AQP4mRNA was expressed at nucleus of endothelial cells and astrocytes. In the normal group, the ACD of AQP4 immunohistochemistry staining was 1.268±0.119. In the 4h experimental group, ACD increased significantly. In the 24h, 48h and 3rd group, ACD became extraordinary higher than that of the normal group. In the 2w experimental group, ACD descented. In the 4w experimental group, ACD of AQP4 decreased to the normal level.In the normal group, the ACD of AQP4 mRNA in situ hybridization was 1.367±0.104. In the 4h group, the ACD did not have prominence change, but in the 24h, 48h an 3rd group, the ACD increased significantly. In the 2w group, the ACD decreased. In the 4w group, ACD of AQP4 mRNA decreased to the normal level. 6. Electron microscopic immunohistochemistry and in situ hybridization: observed under electron microscope, AQP4 was located in plasma membrane of endothelial cells. Some positive particles were observed in the plasm of astrocyte. AQP4 was not observed in basement membrane. AQP4 mRNA hybridization positive particles were observed in nucleus of glial cells and endothelial cells. In summary, these results predict that the changes of BBB are more early pathologic change of high altitude response. After rats were put into the enviroment of highland, the cellular swelling response of glial cells may be contributed to the water balance of brain, which prevents the nerve cells from injury. If the balance regulating was broke and lead to the releasing of toxin, highland cerebral edema may occur. The expression changes of AQP4 and AQP4 mRNA may be one of molecular mechanisms regulating BBB permeability and maintaining water homeostasis.