Effect of Liuwei Dihuangwan on Cognitive Ability of SAMP8 Mice by Regulating Autophagy Through PI3K/Akt/FoxO3a Pathway / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the effect of Liuwei Dihuangwan on memory function of senescence-accelerated mouse prone 8 （SAMP8） mice by regulating autophagy through the phosphatidylinositol 3-kinase （PI3K）/protein kinase B （Akt）/forkhead box O3a （FoxO3a） pathway. MethodSix male senescence-accelerated mouse resistant 1 （SAMR1） mice of SPF grade aging 6 months were assigned to a normal group， and 24 male SAMP8 mice of SPF grade aging 6 months were randomly divided into a model group， a donepezil group （0.747 mg·kg-1）， and high- and low-dose Liuwei Dihuangwan groups （2.700 and 1.350 g·kg-1）， with 6 mice in each group. The mice were treated with drugs by gavage for 2 months. Morris water maze was used to detect the learning and memory abilities of mice in each group. Nissl staining was used to observe the neurons in the cortex and hippocampus. The positive expression of microtubule-associated protein 1 light chain 3B （LC3B） in the cortex and hippocampus was detected by immunohistochemistry （IHC）. Western blot was used to detect the protein expression of the mammalian ortholog of yeast ATG6 （Beclin-1）， B cell lymphoma-2 （Bcl-2）， autophagy-related gene 5 （ATG5）， cysteinyl aspartate-specific protease 3 （Caspase-3）， Caspase-9， Akt， p-Akt， FoxO3a， and p-FoxO3a. ResultCompared with the normal group， the model group showed prolonged escape latency （P<0.05，P<0.01）， reduced number of platform crossings and the residence time in the target quadrant （P<0.01）， decreased neurons with reduced volume and dispersed distribution in the cortex and hippocampus， increased positive expression of LC3B （P<0.01）， elevated expression of Beclin-1 and ATG5 in the cortex （P<0.01）， declined Bcl-2 expression （P<0.01）， up-regulated Caspase-3 and Caspase-9 expression （P<0.01）， and decreased expression levels of p-Akt/Akt and p-FoxO3a/FoxO3a （P<0.01）. Compared with the model group， the donepezil group and the Liuwei Dihuangwan groups showed shortened 3 d escape latency （P<0.05，P<0.01）， increased number of platform crossings （P<0.01）， and prolonged residence time in the target quadrant （P<0.01）. In the donepezil group， the number of neurons in the cortex and hippocampus was increased. In the Liuwei Dihuangwan groups， the number of neurons and Nissl bodies increased with denser distribution and lower degree of cell damage. The positive expression of LC3B in the cortex and hippocampus was decreased in the donepezil group and Liuwei Dihuangwan groups （P<0.01）. The expression of Beclin-1 was decreased in the Liuwei Dihuangwan groups （P<0.01）. The expression of ATG5 was decreased in the donepezil group and the low-dose Liuwei Dihuangwan group （P<0.01）. The donepezil group and the Liuwei Dihuangwan groups showed the increased expression level of Bcl-2 in the cortex （P<0.01）， decreased expression level of Caspase-3 （P<0.01）， reduced expression level of Caspase-9 （P<0.05，P<0.01）， and elevated expression levels of p-Akt/Akt and p-FoxO3a/FoxO3a （P<0.01）. ConclusionLiuwei Dihuangwan can effectively improve the learning and memory abilities of the SAMP8 mice and protect neurons. Its mechanism may be related to the regulation of the PI3K/Akt/FoxO3a signaling pathway， down-regulation of the expression of ATG5， Beclin-1， and LC3B， and the inhibition of apoptosis.