Hei Xiaoyaosan Regulates RAS/RAF/MEK/ERK Signaling Pathway to Ameliorate Oxidative Stress in Rat Model of AD / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo investigate the role and mechanism of Hei Xiaoyaosan in intervening in oxidative stress in the rat model of Alzheimer's disease （AD） via modulating the rat sarcoma （RAS）/rapidly accelerating fibrosarcoma （RAF）/mitogen-activated protein kinase kinase （MEK）/extracellular signal-regulated kinase （ERK） signaling pathway. MethodOne hundred 4-month-old SPF-grade Wistar male rats were randomly grouped as follows： 10 in the blank group， 10 in the sham group （bilateral hippocampus injected with 1 μL normal saline）， and 80 in the modeling group ［bilateral hippocampus injected with 1 μL amyloid beta protein 1-42 （Aβ1-42） solution for the modeling of AD］. Fifty rats qualified for modeling were selected and randomized into the model， donepezil hydrochloride （0.5 mg·kg-1）， and high-， medium-， and low-dose （15.30， 7.65， 3.82 g·kg-1， respectively） Hei Xiaoyaosan groups. The rats were administrated with corresponding drugs by gavage once a day for 42 consecutive days. At the end of gavage， Morris water maze test was performed to examine the learning and memory abilities of the rats， and Nissl staining was used to observe the pathological changes of neurons in CA3 region of the hippocampus. The immunofluorescence assay was used to observe Aβ deposition and tau phosphorylation. Western blot was employed to determine the protein levels of RAS， RAF， phosphorylated （p）-RAF， MEK， p-MEK， ERK， and p-ERK in the hippocampal tissue. Biochemical methods were used to determine the levels of reactive oxygen species （ROS）， malondialdehyde （MDA）， and superoxide dismutase （SOD） in the hippocampal tissue. ResultCompared with the sham group， the model group showed prolonged escape latency （P<0.01）， shortened swimming distance in the target quadrant （P<0.01）， reduced and uneven stained Nissl bodies， enhanced fluorescence intensity of Aβ and p-tau （P<0.01）， up-regulated protein levels of RAS， p-RAF， p-MEK， and p-ERK in the hippocampal tissue （P<0.01）， increased ROS and MDA content （P<0.01）， and decreased SOD activity （P<0.01） on day 5. Compared with the model group， donepezil hydrochloride and high-， medium-， and low-dose Hei Xiaoyaosan shortened the escape latency （P<0.01）， increased the swimming distance in the target quadrant （P<0.01）， improved the arrangement， morphology， and structures of neurons and the number and distribution of Nissl bodies， decreased the fluorescence intensity of Aβ and p-tau （P<0.01）， up-regulated the protein levels of RAS， p-RAF， p-MEK， and p-ERK （P<0.05， P<0.01）， decreased the ROS and MDA content （P<0.01）， and increased the SOD activity （P<0.01） on day 5. ConclusionHei Xiaoyaosan may ameliorate oxidative stress， reduce Aβ and p-tau levels， and inhibit hippocampal neuronal damage by regulating the RAS/RAF/MEK/ERK signaling pathway， thus improving learning and memory abilities.