Erzhi Pill promotes norepinephrine synthesis in locus coeruleus through ERβ-TFAP2A-TH plays a neuroprotective role

Erzhi Pill (EZP), a classical Chinese herbal formula for yin-nourishing and kidney-tonifying, has been traditionally prescribed for insomnia and amnesia, and shows therapeutic potential for Alzheimer's disease (AD). However, its active components and precise mechanisms of action against AD remain elusive. This study aimed to identify the key active components and molecular targets of EZP responsible for improving cognitive dysfunction and to elucidate its underlying mechanisms. Behavioral and histomorphological analyses will be used to validate the efficacy of EZP in ameliorating cognitive impairment in lipopolysaccharide (LPS)-induced models. Untargeted metabolomics characterized metabolic profile alterations in the locus coeruleus (LC), while targeted metabolomics focused on specific metabolic pathways. Microdialysis coupled with high-resolution mass spectrometry (HR-MS) analyzed EZP's chemical components in LC dialysates. Network pharmacology and molecular docking predicted potential targets, with binding affinities validated by surface plasmon resonance (SPR). Molecular biology techniques were employed to investigate relevant signaling pathways. EZP significantly improved learning and memory capabilities in LPS-induced models, accompanied by enhanced neuronal activity. Metabolomic profiling revealed that EZP exerted its effects primarily through modulation of alanine, aspartate, and glutamate metabolism pathways, as well as phenylalanine and tyrosine metabolic networks. Specifically, EZP treatment resulted in decreased tyrosine (Tyr) levels and increased norepinephrine (NE) concentrations in the LC. Western blot analysis further demonstrated upregulated expression of tyrosine hydroxylase (TH) and dopamine β-hydroxylase (DβH) proteins in LC tissues. Phytochemical analysis identified 45 prototype components and 14 metabolites in EZP, among which apigenin and wedelolactone were characterized as potential bioactive ingredients. Network pharmacology combined with molecular docking revealed estrogen receptor β (ERβ) as a critical target mediating EZP's anti-AD effects. SPR validated stronger binding affinity of apigenin and wedelolactone to ERβ compared with G-protein-coupled receptor 30 (GPR30). Mechanistic studies showed that these compounds activated ERβ signaling, restored TFAP2A/TH transcriptional activity, and promoted NE biosynthesis, thereby ameliorating cognitive deficits in AD models. This study not only elucidates that EZP ameliorates cognitive dysfunction in AD)via the ERβ-TFAP2A/TH signaling pathway but also proposes NE augmentation as a novel therapeutic strategy for AD management.