Experimental validation, molecular docking, proteomic analysis and network pharmacology reveal Morroniside promoting neurogenesis and improving cognitive impairment via Notch1/Hes1 pathway in intracerebroventricular-streptozotocin mice.

Ethnopharmacology Relevance: Alzheimer's disease (AD) is a widely occurred neurodegenerative disease and Notch1/Hes1 pathway based neural stem cell (NSC) proliferation and neurogenesis are very crucial to restore cognitive ability. Cornus officinalis Sieb. et Zucc, a famous traditional Chinese herb remedy was widely used to tonify kidney and essence to ameliorate AD symptoms. Morroniside (MOR), a prominent bioactive component of Cornus officinalis Sieb. et Zucc has demonstrated promising neuroprotective properties, while its function of neurogenesis to improve cognitive ability largely remains unclear.

Aim Of The Study: This study aimed to reveal the role of MOR promoting neurogenesis and improving cognitive function via Notch1/Hes1 pathway thus to discover more neuropharmacological merit of MOR for AD treatment.

Materials And Methods: An AD model was induced in C57BL/6 mice by bilateral intracerebroventricular injection of streptozotocin (ICV-STZ). The mice were divided into control, model, low-dose, high-dose, DAPT + MOR, and donepezil groups. Cognitive functions were assessed using open field test, novel object recognition test, and Morris water maze (MWM). Histopathological changes were evaluated by Nissl and hematoxylin-eosin (HE) staining. Immunofluorescence double-labeling was performed to detect the expression of neurogenesis biomarkers in dentate gyrus. qRT-PCR and Western blotting were employed to measure the mRNA levels and Notch1, Hes1 expression. Molecular docking and dynamics simulations were performed to assess the binding affinity and stability between MOR and Notch1/Hes1 proteins. Proteomic analysis combined with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were integrated to verify the effects of MOR on including Notch1/Hes1 pathway for neurogenesis.

Results: MOR (20 and 40 mg/kg) significantly improved cognitive function of ICV-STZ mice from the behavioral tests. Histological analysis showed that MOR enhanced neuronal survival in the hippocampus, improved cellular arrangement and structure, and reduced oxidative stress. Immunofluorescence results indicated that MOR promoted NSC proliferation and neurogenesis, as evidenced by the elevated number of BrdU/Nestin and DCX/Ki67 double-positive cells. Mechanistically, MOR upregulated the mRNA and protein expression of Notch1 and Hes1 in the hippocampus and increased the expression of downstream Cyclin D1 and CDK4. Molecular docking and dynamics simulations further supported stable binding of MOR to Notch1 and Hes1. Proteomics combined with GO and KEGG enrichment further confirmed MOR (40 mg/kg, ∗P < 0.05) could significantly regulated multiple signaling pathways including Notch1 to ameliorate AD symptoms.

Conclusion: This work demonstrated MOR could promote neural stem cell proliferation and neurogenesis by activating Notch1/Hes1 pathway, thereby enhancing learning and memory abilities in ICV-STZ mice. Such findings will further promote the clinical application of MOR for AD treatment.