Role of AQP4 in dexmedetomidine-induced reduction of blood-brain barrier permeability in mechanically ventilated mice: relationship with PKC / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of aquaporin 4 (AQP4) in dexmedetomidine-induced reduction of blood-brain barrier permeability in mechanically ventilated mice and the relationship with protein kinase C (PKC).Methods:One hundred and fifty clean-grade healthy male C57BL6 mice, weighing 20-25 g, aged 8-12 weeks, were divided into 5 groups ( n=30 each) using a random number table method: control group (group C), mechanical ventilation group (group V), LY317615 group (group L), dexmedetomidine group (group D), and dexmedetomidine+ PMA group (group DP). Group C spontaneously breathed air for 6 h. The animals were mechanically ventilated for 6 h in group V. PKC inhibitor LY3176 15 μg/kg was intraperitoneally injected at 30 min before mechanical ventilation in group L. Dexmedetomidine 50 μg/kg was intraperitoneally injected at 30 min before mechanical ventilation in D and DP groups. PKC activator PMA 15 μg/kg was intraperitoneally injected at 60 min before mechanical ventilation in group DP. Mice were anesthetized at 1 day after mechanical ventilation, then sacrificed and hippocampal tissues were taken for microscopic examination of pathological changes in the hippocampal CA1 and CA3 areas (with a light microscope). Brain tissues were also taken to measure the water content and content of Evans blue (EB) and to detect the expression of PKC and AQP4 (by Western blot). The cognitive function was evaluated using a novel object recognition task at 3 days after mechanical ventilation. Results:Compared with group C, the water content and EB content of brain tissues were significantly increased after mechanical ventilation, the expression of PKC and AQP4 in brain tissues was up-regulated, the percentage of novel object exploration and discrimination index were decreased ( P<0.05), and the histopathological damage in the hippocampal CA1 and CA3 areas was aggravated in group V and group DP. Compared with group V, the water content and EB content of brain tissues were significantly decreased after mechanical ventilation, the expression of PKC and AQP4 in brain tissues was down-regulated, the percentage of novel object exploration and discrimination index were increased ( P<0.05), and the histopathological damage in the hippocampal CA1 and CA3 areas was significantly attenuated in group D and group L. Compared with group D, the water content and EB content of brain tissues were significantly increased after mechanical ventilation, the expression of PKC and AQP4 in brain tissues was up-regulated, the percentage of novel object exploration and discrimination index were decreased ( P<0.05), and the histopathological damage in the hippocampal CA1 and CA3 areas was aggravated in group DP. Conclusions:AQP4 is involved in dexmedetomidine-induced reduction of blood-brain barrier permeability in mechanically ventilated mice, and the mechanism is related to inhibiting activation of PKC.