Lancao decoction in the treatment of alzheimer's disease via activating PI3K/AKT signaling to promote ERK involving in enhancing neuronal activities in the hippocampus

Ethnopharmacological relevance: Previous study has demonstrated lancao decoction (LC), a traditional Chinese medicine (TCM) fomula and recorded in "Huangdineijing", has a therapeutic effect on cognitive impairment (early clinical manifestations of alzheimer's disease (AD), which suggests that LC may have potential therapeutic advantages for AD. Whether LC has the therapeutic effect on AD and its potential mechanisms were still further indicated.

Aim of the study: In this study, we aimed to uncover the potential advantage and neuronal mechanisms of LC in the treatment of AD in APP/PS1 mice in the hippocampus.

Methods and materials: We chose APP/PS1 mice to combing with behavioral tests including morris water maze (MWM) or y-maze to determine the role of LC in the therapeutic actions of AD. Network pharmacology was used to screen potential targets and pathways involving in LC's treatments of AD. Western blot was used to detect the phosphorylated expressions of proteins in hippocampus in APP/PS1 mice in the hippocampus. Pharmacological interventions were used to elucidate the relationship between the role of LC in the treatment of AD and the pathway, as well as the upstream and downstream interactions with neuronal activities.

Results: According to our previous LC effective dose (2.5 g/kg), the dose was also able to significantly reduce the latency to the platform, and significantly increase the number of crossing times and time spend in the target quadrant in APP/PS1 mice in MWM, which was consistent with donepezil (DON) after 14 days chronic treatments. Network pharmacology showed that PI3K/Akt and MAPK pathways were closely associated with LC's treatments of AD, and protein autophosphorylation played a role in this process. The phosphorylated expressions of PI3K and Akt were obviously reduced in APP/PS1 mice in the hippocampus, which were both reversed by LC or DON. The phosphorylated expressions of MAPK including P38, JNK and ERK were also significantly reduced in APP/PS1 mice hippocampus, but only the phosphorylated expression of ERK was reversed by LC or DON. Inhibiting the activities of PI3K/Akt pathway by LY294002 blocked LC's improvement of behavioral deficits in APP/PS1 mice, including reducing latency to platform and increasing the number of crossings time in MWM in APP/PS1 mice, which also blunted LC's up-regulated phosphorylated expressions of PI3K, Akt and ERK in the hippocampus. Moreover, suppressing the activities of ERK by PD98059 also blocked LC's improvement of AD-related behavioral deficits including decreasing latency to new arm and increasing time in new arm in y-maze test, which also inhibited LC's enhancement of synaptic proteins (PSD95 and synapsin1) in the hippocampus and the number of EGR1-positive cells in the hippocampal dentate gyrus (DG).

Conclusions: Take together, our study revealed that LC had the therapeutic effects on AD by activating the PI3K/Akt pathway to enhance ERK activity and further strengthened neuronal activities in the hippocampus.

Alzheimer's disease; ERK; Hippocampus; Lancao decoction; Neuronal activities; PI3K.