Objective To investigate the pathogenesis of high-altitude cerebral edema(HACE)and develop new therapeutic strategies.Methods Male Sprague-Dawley(SD)rats of 6 weeks old were selected and placed in a hypobaric chamber.The rats were exposed to the high-altitude environment of 7000 m above sea level for 3 days for HACE modeling.Whether the HACE model was successfully established in the rats was evaluated by measuring brain water content,the degree of disruption to the blood-brain barrier(BBB),and brain tissue Nissl staining.The experimental animals were divided into four groups,with 28 rats in each group.The blank control group was exposed to a normobaric and normoxic environment simulating the conditions at 500 m above sea level for 3 d.The other groups,including a model group(the HACE group),a bumetanide group(the positive control group),and a XH-6003 treatment group,were placed at an altitude of 7 000 m above sea level and were injected with normal saline,bumetanide,and XH-6003,a new type of Na-K-2C1 cotransporter 1(NKCC1)inhibitor,via the tail vein,respectively,twice daily for 3 d.The experimental animals were taken out of the hypobaric chamber for testing after 3 d.The primary outcome measures included brain water content,BBB permeability,changes in brain tissue morphology,and the expression levels of aquaporin-4(AQP4)and NKCC1.The secondary outcome measures included behavioral changes,apoptosis,and oxidative stress markers.Results The HACE rat model was successfully established.The model group exhibited increased brain water content(P＜0.0001),BBB disruption(P＜0.0001),impairment in learning skills and memory(P＜0.001),and anxiety/depression-like behaviors(P＜0.01).qPCR results showed significantly increased expression of NKCC1 and AQP4 in the brain tissue of the model group(P＜0.01).Pathology examination revealed neuronal and glial cell damage in the hippocampus of the model group(P＜0.01).Treatment with XH-6003,the NKCC1 inhibitor,reversed brain water content,BBB disruption,and neuronal and glial cell damage to a certain degree(P＜0.05),decreased the expression of NKCC1 and AQP4 in the brain tissue(P＜0.01),and inhibited apoptosis-related proteins.Among the oxidative stress indices,only glutathione(GSH)showed improvement(P＜0.001).Rats treated with XH-6003 showed functional improvement only in the time spent exploring novel objects,while other behavioral outcomes remained unchanged.Conclusion HACE is associated with the activation of the NKCC1/AQP4 pathway.Inhibition of this pathway alleviates brain edema,BBB disruption,and neuronal and glial cell damage.These findings suggest that XH-6003 holds potential as a therapeutic strategy for HACE at the cellular and molecular levels,but its effects in improving HACE-related behavioral disorders warrant further investigation.