Melatonin attenuates neurovascular unit dysfunction via AKT/GSK-3β/CREB pathway in hypoxic-ischemic neonatal rats

Previous research has shown that melatonin (Mel) can alleviate hypoxic-ischemic brain damage (HIBD) in newborns. The roles of Mel on neurovascular unit (NVU) after HIBD and the mechanisms were explored in this study. Methods: The combination of multiparametric magnetic resonance imaging (MRI) techniques and various histology experiments was utilized to observe the impacts of Mel on the NVU in the damaged cerebral cortex of neonatal rats. Especially, water extraction with phase contrast arterial spin tagging (WEPCAST)-MRI was used to monitor the changes in blood-brain barrier (BBB) permeability to water in neonatal rats with HIBD. MRI showed that abnormal signals and permeability surface area volume (PS) both decreased after Mel treatment. Various histology results also revealed that Mel treatment alleviated NVU destruction and attenuated MT1 receptor deficiency. Western blotting showed MMP-9 levels in Mel group were significantly decreased at all time points post-hypoxia ischemia (HI). In addition, western blotting and immunohistochemistry (IHC) were utilized to examine the impacts of Mel treatment on the tight connection and key molecules of AKT/GSK-3β/CREB pathway. The results showed that the expressions of Claudin-5, ZO-1, p-Akt, p-GSK-3β, and p-CREB on the damaged side in the Mel+MK2206 group was lower than those in Mel group, while the MMP-9 level was significantly higher. Multiparametric MRI techniques can monitor the changes of brain microstructure and BBB permeability in neonatal rats with HIBD in vivo at early stage. Mel administration can reduce the NVU injury in neonatal rats with HIBD via activating AKT/GSK-3β/CREB pathway.