Objective To investigate the effect and mechanism of hypoxia inducible factor-1 α/aquaporin-4(HIF-1α/AQP4)pathway in high altitude cerebral edema(HACE)after blood-brain barrier injury in rats.Methods Adult male SD rats(n=40)were randomly divided into two groups:control group(Ctrl,n=20)and high altitude cerebral edema group(HACE,n=20).The rats in the control group were reared in Xining(altitude 2261 m)for 4 days,and the rats in HACE group were reared in low-pressure simulation chamber(altitude 5000 m)for 4 days.Brain water content was measured by the method of dry and wet weight.The intracranial structure,morphology and signal changes of small animals were observed through T2 weighted image of 7.0 T MRI.The morphological changes of neurons and the apoptosis of nerve cells in the CA1 region of hippocampal tissue were observed by the staining of Nissl and TUNEL.Immunohistochemical staining was performed to observe the extravasation of immunoglobulin G(IgG).The expressions of HIF-1α,AQP4,matrix metalloproteinase-9(MMP-9),claudin-5,occludin and zonula occludens-1(ZO-1)in the tissue of hippocampal were detected by the method of Western blotting and immunofluorescent staining.Results The brain water content increased significantly in the HACE group(P＜0.05).The neurons in CA1 region of hippocampal tissue were atrophic and deformed,the arrangement of neurons was disordered in the HACE group.The number of neurons decreased significantly,the apoptosis of nerve cells increased significantly,and the IgG exudates obviously in the CA1 region of hippocampal tissue in the HACE group.The expressions of HIF-1α,AQP4 and MMP-9 proteins increased significantly,while claudin-5,occludin and ZO-1 proteins decreased significantly in the CA1 region of hippocampal tissue,which detected by the method of Western blotting and immunofluorescent staining(P＜0.05).Conclusion Acute high-altitude hypoxia can induce to blood-brain barrier disruption through the HIF-1α/AQP4 pathway,resulting in high-altitude cerebral edema.

Objective To investigate the effect of plateau hypoxia on the blood-brain barrier after subarachnoid hemorrhage (SAH) in rats. Methods Adult male SD rats (n = 78) were randomly divided into 4 groups: sham group (sham), SAH model group (SAH), plateau hypoxia sham group (Hp sham) and plateau hypoxia SAH model group (Hp SAH). The rat model of plateau hypoxia was established through low-pressure simulation chamber (altitude 5000 m), and the SAH model was established by endovascular perforation method. At 24 hours after SAH, neurobehavior score and SAH grade were assessed. The morphological changes of neurons and apoptosis of nerve cells in the CA1 region of hippocampal were observed by the staining of Nissl and TUNEL. The expression of phosphorylated PI3K (p-PI3K), PI3K, phosphorylated Akt (p-Akt), Akt, phosphorylated nuclear factor κB (p-NF-κB), NF-κB, matrix metalloproteinase-9 (MMP-9), occludin and claudin-5 in hippocampal were detected by the method of Western blotting. The expression of occludin and claudin-5 proteins in the CA1 region of hippocampal were observed by immunofluorescent staining. Results At 24 hours after SAH, the neurobehavior score decreased significantly and SAH grade increased significantly in the SAH and Hp SAH group (P< 0.05). Neurobehavior score decreased significantly in the Hp SAH group compared with the SAH group (P < 0.05). In the SAH group, neurons in the CA1 region of hippocampus were atrophied and deformed, the arrangement were disordered, the number of neurons decreased significantly, and the apoptosis of nerve cells increased significantly(P< 0.05). Plateau hypoxia could aggravate the morphological damage of neurons and apoptosis of nerve cells. The expression of p-PI3K/PI3K, p-Akt/Akt, occludin and claudin-5 proteins decreased significantly, while the expression of p-NF-κB/NF-κB and MMP-9 proteins increased significantly in the SAH and Hp SAH group (P< 0.05). The expression of p-PI3K/PI3K and MMP-9 proteins increased significantly in Hp SAH group compared with the SAH group. The expression of claudin-5 protein increased significantly in Hp sham group compared with the sham group (P < 0.05). Immunofluorescent staining showed that the expression of occludin and claudin-5 proteins in the CA1 region of hippocampus decreased in the SAH group. Plateau hypoxia could further decreased the expression of occludin and claudin-5 proteins. Conclusion Plateau hypoxia aggravates blood-brain barrier disruption after subarachnoid hemorrhage in rats through inhibiting PI3K/Akt/NF-κB pathway.