时间特异性敲除腺苷酸活化蛋白激酶α1/2基因小鼠的海马能量代谢与突触可塑性

Effects of time-specific AMP-activated protein kinase alpha1/2 gene knockout on hippocampal energy metabolism and synaptic plasticity in mice

背景:腺苷酸活化蛋白激酶(AMP-activated protein kinase,AMPK)是一种分子水平的能量传感器,当机体处于低能状态时能被激活进而为神经元活动提供能量,但对于时间特异性敲除AMPK与认知功能障碍发生的关系尚未清楚。目的:探讨时间特异性敲除AMPKα1/2基因小鼠海马能量代谢与突触可塑性的变化,寻找能量代谢与认知功能之间的关键分子靶点。方法:将16只6月龄携带有AMPKα1/2^(flox/flox)和Camk2a-cre/ERT2的AMPKα1/2^(flox/flox)+CaMk2a-cre/ERT2基因型小鼠按随机数字表分为:对照组(n=8)和AMPKα1/2敲除组(n=8)。AMPKα1/2敲除组每天腹腔注射0.1 mL他莫昔芬,对照组每天腹腔注射等剂量的玉米油溶剂。两组小鼠连续注射5 d,等待7 d后,巴恩斯迷宫检测小鼠空间学习记忆能力;化学交换饱和转移成像技术(CEST)观察海马区葡萄糖代谢能力;膜片钳电生理技术检测海马CA3-CA1神经环路场电位,包括Input-output(I/O曲线)、配对脉冲易化比率以及高频刺激诱导长时程突触可塑性。结果与结论:①与对照组相比,AMPKα1/2敲除组小鼠逃避潜伏期延长(P<0.001),接触目标洞口次数明显减少(P<0.05),目标象限所占时间显著缩短(P<0.05);②与对照组相比,AMPKα1/2敲除组小鼠海马区葡萄糖代谢水平降低(P<0.05);③与对照组相比,AMPKα1/2敲除组小鼠海马脑区,在给予不同刺激量时的电压值均显著降低(P<0.05);在基础场电位中,不同时间间隔的配对脉冲易化比率显著降低(P<0.05);④与对照组相比,AMPKα1/2敲除组小鼠海马高频刺激后兴奋性突触后电位振幅显著降低(P<0.05);⑤结果表明,时间特异性敲除AMPKα1/2基因导致海马区葡萄糖代谢水平下降,使得突触前递质释放、突触传递效能和突触可塑性受损,进而导致空间学习记忆障碍的产生。

BACKGROUND:AMP-Activated protein kinase(AMPK)is a molecular-level energy sensor that can be activated when the body is in a low energy state to provide energy for neuronal activity.However,the relationship between time-specific AMPK knockout and the development of cognitive dysfunction remains unclear.OBJECTIVE:To investigate the effects of time-specific AMPKα1/2 knockout on hippocampal energy metabolism and synaptic plasticity in mice,and to search for key molecular targets between energy metabolism and cognitive function.METHODS:Sixteen 6-month-old mice with AMPKα1/2^(FLOX/FLOX)and AMPKα1/2^(FLOX/FLOX)+Camk2a-cre/ERT2 were randomly divided into control group(n=8)and AMPKα1/2 knockout group(n=8).The AMPKα1/2 knockout group was intraperitoneally injected with 0.1 mL tamoxifen daily,while the control group was intraperitoneally injected with an equal dose of corn oil solvent daily.Injections in each group were conducted for 5 continuous days.After 7 days,Barnes maze test was used to test spatial learning and memory ability of mice.Chemical exchange saturation transfer imaging was used to observe the glucose metabolism in the hippocampus.Patch clamp electrophysiological techniques were used to detect the field potential of hippocampal CA3-CA1 neural circuit,including input-output curve,paired-pulse facilitation ratio and long-term synaptic plasticity induced by high frequency stimulation.RESULTS AND CONCLUSION:Compared with the control group,the escape latency was prolonged(P<0.001),the frequency of contact with the target hole decreased significantly(P<0.05),and the time spent in the target quadrant decreased significantly(P<0.05)in the AMPKα1/2 knockout group.Compared with the control group,the level of glucose metabolism in the hippocampus of mice was reduced in the AMPKα1/2 knockout group(P<0.05).Compared with the control group,the voltage in the hippocampus was significantly decreased with different amounts of stimulation in the AMPKα1/2 knockout group(P<0.05).At the base field potential,the paired-pulse facilitation ratios at different time intervals decreased significantly(P<0.05).Compared with the control group,high frequency stimulation significant reduced the amplitude of excitatory postsynaptic potential in the hippocampus of mice in the AMPKα1/2 knockout group after(P<0.05).These results suggest that time-specific AMPKα1/2 knockdown decreases glucose metabolism in the hippocampus,impairs presynaptic transmitter release,synaptic transmission efficiency,and synaptic plasticity,thereby leading to spatial learning and memory disorders.