Role of Akt/GSK3β signal pathway in baicalin improving the cognitive function of mice with brain injury induced by mechanical ventilation / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To investigate the effect of baicalin on cognitive function of mice with brain injury induced by mechanical ventilation and its mechanism.Methods:Seventy two C57BL6 mice, weighing 20-25 g, aged 8-12 weeks, were randomly divided into control group (group C), mechanical ventilation group (group V), baicalin group (group B), baicalin+ Akt inhibitor MK-2206 group (group BM) according to random number table method, with 18 in each group.Mice in group C did not have mechanical ventilation and breathed air independently for 6 hours.Mice in group V received mechanical ventilation for 6 hours.Mice in group B and group BM were intraperitoneally injected with baicalin 100 mg/kg 30 minutes before mechanical ventilation, and mice in group BM were injected intraventricular with Akt inhibitor MK-2206 300 μg/kg 60 minutes before mechanical ventilation.Six mice in each group were randomly selected to test their learning and memory abilities by Morris water maze test 1st day before mechanical ventilation and 3rd day and 7th day after mechanical ventilation.One day after mechanical ventilation, six mice in each group were killed, and the brain tissue was taken.TUNEL method was used to detect the neuronal apoptosis in hippocampal CA1 area, and the apoptosis index was calculated.One day after mechanical ventilation, six mice in each group were killed, and the hippocampus was taken, Western blot was used to detect the protein expressions of caspase-3, caspase-9, Akt, p-Akt, GSK-3β and p-GSK-3β.SPSS 22.0 software was used for statistical analysis of data, repeated measure ANOVA and one-way ANOVA were used for comparison between multiple groups.LSD- t test was used for further pairwise comparison. Results:The results of water maze test showed that the time and group interaction of the four groups were not significant ( F=1.14, P>0.05), the main effect of time and group were both significant ( F=47.36, 59.65, both P<0.05). At 3rd day and 7th day after mechanical ventilation, the escape latencies of mice in group V were higher than those in group C (both P<0.05), and the numbers of platform crossing were lower than those in group C (both P<0.05). And 3 days and 7 days after mechanical ventilation, the escape latencies of mice in group B were lower than those in group V (both P<0.05) and the numbers of platform crossing were higher than those in group V (both P<0.05). The escape latenies of mice in BM group on the 3rd and 7th day were higher than those in group B (both P<0.05), and the numbers of platform crossing were lower than those in group B on the 3rd day and 7th day after mechanical ventilation(both P<0.05). TUNEL and Western blot results showed that apoptosis index of hippocampal neurons and expression levels of apoptosis-related proteins caspase-3 and caspase-9 were significant different in the four groups ( F=51.42, 41.21, 40.19, all P<0.05). The apoptosis index of hippocampal neurons ((40.6±3.9)%), the expression levels of caspase-3 (4.93±0.92) and caspase-9 (4.81±0.88) in the hippocampus of mice in group V were higher than those in group C ((13.7±1.4)%, (1.87±0.27), (1.71±0.25), all P<0.05), the apoptosis index of hippocampal neurons ((15.6±1.6)%), the expression levels of caspase-3 (1.95±0.30) and caspase-9 (1.76±0.28) in group B were lower than those in group V ((40.6±3.9)%, (4.93±0.92), (4.81±0.88), all P<0.05), the apoptosis index of hippocampal neurons ((27.8±2.7)%), the expression levels of caspase-3 (3.58±0.61) and caspase-9 (3.49±0.57) in BM group were higher than those in group B ((15.6±1.6)%, (1.95±0.30), (1.76±0.28), all P<0.05). Expression level of p-Akt, p-GSK-3β in hippocampal tissues of the four group of mice were significantly different ( F=37.54, 43.23, both P<0.05). The expression level of p-Akt (0.51±0.06) and p-GSK-3β (0.47±0.05) of hippocampal tissues of mice in group V were lower than those of group C ((1.07±0.10), (1.11±0.12), both P<0.05), the expression level of p-Akt (0.99±0.10) and p-GSK-3β (1.08±0.09) of hippocampal tissues of mice in group B were higher than those of group V (both P<0.05), the expression level of p-Akt (0.83±0.08) and p-GSK-3β (0.81±0.07) of hippocampal tissues of mice in group BM were lower than those in group B (both P<0.05). Conclusion:Baicalin can improve the cognitive function of mice with brain injury induced by mechanical ventilation, which is related with activation of Akt/GSK-3β signaling pathway and inhibition of hippocampal neuron apoptosis.