[Effects of Inhibiting the NKCC1/AQP4 Pathway on Neurological Injury Improvement in a Rat Model of High-Altitude...

To investigate the pathogenesis of high-altitude cerebral edema (HACE) and develop new therapeutic strategies.

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 7000 m above sea level and were injected with normal saline, bumetanide, and XH-6003, a new type of Na-K-2Cl 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.

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.

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.