[Quercetin, a key bioactive component of Zuogui Pill, protects against Alzheimer's disease by regulating the PI3K/Akt...

To investigate the protective mechanism of quercetin, a key bioactive component of Chinese medicine Zuogui Pill, against Alzheimer's disease (AD) via the PI3K/Akt signaling pathway.

The TCMSP, PubChem, SwissTargetPrediction, and BATMAN-TCM databases were used to retrieve the active components of Zuogui Pill and predict their potential targets. Target information was standardized using the UniProt database. AD-related target genes were obtained from DrugBank, GeneCards, and OMIM, and the intersection was taken to identify the potential targets of Zuogui Pill for AD treatment. Based on these targets, a protein-protein interaction network was constructed using Cytoscape 3.10.1 and the STRING database. The key active components and core targets of Zuogui Pill for AD treatment were identified through computational analysis. Gene Ontology functional enrichment analysis and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis were performed on the potential targets to explore the biological processes and signaling pathways involved. Subsequently, molecular docking and binding affinity prediction between the key active component quercetin and the core target Akt1 were performed using the online tool CB-Dock2. An AD cell model was established by treating mouse hippocampal neuron cells (HT22) with amyloid β-protein_1-42 (Aβ_1-42) oligomers. The cells were divided into low-, medium-, and high- dose quercetin groups, and a PI3K agonist (EGF) group for in vitro experiments. To verify whether quercetin exerts its anti-apoptotic effects by regulating the PI3K/Akt pathway, additional groups were established: PI3K inhibitor (LY294002) group, PI3K inhibitor+high-dose quercetin group, and PI3K inhibitor+EGF group. CCK-8 assay was used to detect cell viability; JC-1, Calcein-AM/PI, and Hoechst staining were used to assess apoptosis; and Western blotting was used to detect expression of PI3K/Akt signaling pathway and apoptosis related proteins.

Network pharmacology demonstrated that quercetin targets core proteins such as Akt1 in a network manner and is predominantly enriched in the PI3K/Akt signaling pathway. Molecular docking showed favorable binding affinity between quercetin and Akt1 (binding energy: －6.6 kcal/mol). In the Aβ_1-42 oligomer-induced HT22 neuronal cell model and HT22 cells treated by PI3K inhibitor, high-dose quercetin significantly increased cell viability, elevated the p-Akt/Akt ratio and Bcl-2 expression level (all P<0.05), reduced the cleaved caspase-3/caspase-3 ratio as well as the expression levels of BAX and cytochrome C (all P<0.01), and alleviated apoptosis of HT22 cells.

Quercetin, a key bioactive component of Chinese medicine Zuogui Pill, inhibits neuronal apoptosis by regulating the PI3K/Akt signaling pathway, thereby exerting a protective effect against AD.