Role and mechanisms of synaptic plasticity decrease mediated by KIBRA in cognitive dysfunction by chronic cerebral hypoperfusion / 中华行为医学与脑科学杂志

ABSTRACT

Objective:To explore the role and mechanism of kidney brain protein (KIBRA) down-regulation in cognitive dysfunction caused by chronic cerebral hypoperfusion.Methods:Ninety male SPF grade Sprague Dawley (SD) rats were divided into four groups according to random number table sham operation group ( n=15), chronic hypoperfusion group (2VO group, n=25), chronic hypoperfusion stereotaxic injection of AAV-KIBRA group (2VO+ AAV-KIBRA group, n=25), chronic hypoperfusion stereotaxic injection of AAV-Vector group (2VO+ AAV-vector group, n=25). Chronic cerebral hypoperfusion model was established by bilateral ligation of common carotid artery, and stereotactic injection of 2 μL AAV-KIBRA or AAV-vector was performed for 30 days.Morris water maze, in vitro electrophysiology, p21-activated kinase 3(PAK3) activity detection, Western blot, immunoprecipitation and Golgi staining were used to detect spatial learning and memory ability, long-term potentiation(LTP), KIBRA level expression, PAK3 activity changes and the distribution of dendritic spines.SPSS 16.0 statistical software was used for statistical data.One-way ANOVA was used to compare the differences between groups.LSD test was used to compare the significance of data differences between the two groups.Welch test was used for uneven variance. Results:After 1 month of chronic cerebral hypoperfusion, the level of KIBRA in the hippocampus of rats was detected by homogenate and Western blot, and it was found that the level of KIBRA in 2VO group was lower than that of sham group(73.49±4.12)% ( P<0.01). AAV-KIBRA injection in hippocampal CA1 region significantly up-regulated the level of KIBRA to (91.91±7.01)% over 2VO group ( P<0.01). Morris water maze test showed that the latency of the 2VO group(3rd-7th day trail data (48.18±2.82)s, (43.45±2.27)s, (32.27±2.22)s, (26.55±2.37)s, (17.18±2.67)s) were significantly longer than those of the sham group((41.67±2.74)s, (32.58±2.57)s, (22.50±2.94)s, (16.91±2.39)s, (8.75±1.52)s) (all P<0.05), and the latencies of the 2VO+ AAV-KIBRA group 3rd-7th day trail data (43.83±2.95)s, (35.25±2.15)s, (26.58±2.03)s, (19.92±2.17)s, (17.75±1.35)s) was significantly shorter than that of the 2VO group ((all P<0.01). The Morris water maze test with the platform removed showed that the latency of rats in the 2VO group to reach the platform region was significantly longer than that of the sham group, while the latency of rats in the 2VO+ AAV-KIBRA group to reach the platform region was significantly shorter than that in the 2VO group ( P<0.01). At the same time, the retention time and the crossing times in the platform region of 2VO group were less than those of the sham group ( P<0.01), but the retention time and the crossing times in the platform region of 2VO+ AAV-KIBRA group were significantly higher than those in the 2VO group ( P<0.01). The electrophysiological records of the brain slices showed that the relative excitatory postsynaptic field potential of 2VO group (1.43±7.43) was significantly lower than that of sham group (2.21±6.54) after high frequency stimulation, while the relative excitatory postsynaptic field potential of 2VO+ AAV-KIBRA group (1.90±8.15) was higher than that of 2VO group ( P<0.01). Immunoprecipitation in rat hippocampus revealed that PAK3 could be detected by Western blot assay when KIBRA was precipitated.The results showed that the relative enzyme activity of PAK3 in 2VO hippocampal tissue (0.64±0.04) was significantly lower than that in sham group (1.02±0.07), while the relative enzyme activity of PAK3 in 2VO+ AAV-KIBRA group (0.86±0.03) was significantly higher than that in 2VO group.Golgi staining showed that the density of dendritic spines in 2VO hippocampal neurons((6.85±0.43)/10 μm) was significantly lower than that in sham group((11.83±0.58)/10 μm), while the density of dendritic spines in 2VO+ AAV-KIBRA group((10.22±0.39)/10 μm) was significantly higher than that in 2VO group. Conclusion:The down-regulated of KIBRA after chronic cerebral hypoperfusion plays a key role in cognitive dysfunction and is also involved in the decrease of synaptic functional plasticity.The downregulation of KIBRA is involved in the structural plasticity of dendrites through the regulation of PAK3 activity.Therefore, KIBRA may be an important target for the prevention and treatment of cognitive function of chronic cerebral hypoperfusion.