Research on the protective effect of Rhizoma of Anemarrhena asphodeloides on TMT induced AD mice model based on network pharmacology combined with in vitro and in vivo experimental validation

Background: Alzheimer's disease (AD) is a neurodegenerative disease, and neuroprotection is an important approach to improving AD outcomes. Rhizoma of Anemarrhena asphodeloides (RAA) is a commonly used Traditional Chinese Medicine (TCM) with demonstrated neuroprotective effects, but its anti-AD mechanism requires further exploration.

Aim of the study: To elucidate the neuroprotective mechanism of RAA on TMT-induced AD mice.

Materials and methods: The AD mice model was established via intraperitoneal injection of TMT. The effect of RAA on ameliorating learning and memory was assessed using the Morris Water Maze (MWM) and Y-maze tests. Haematoxylin-Eosin (HE), Nissl, and TUNEL staining were used to observe the neuroprotective effect of RAA. The components in serum containing RAA (RAA-S) were detected using UPLC-Q-Orbitrap MS. Potential targets were predicted through network pharmacology and molecular docking. Serum levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GPx) were measured with ELISA kits. The HT22 hippocampal neuronal cell line injured by l-glutamate (L-Glu) was used to further elucidate the mechanism of RAA. ROS levels in HT22 cells were detected with the 2'-7'-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescent probe and flow cytometry. Apoptosis in HT22 cells was measured by flow cytometry. The proteins MAP2, GAP-43, Nrf2, Keap1, HO-1, Bax, and Bcl-2 were detected by Western blotting. Immunofluorescence staining was employed to observe Nrf2 nuclear translocation.

Results: RAA significantly increased the residence time of mice in the W zone and enhanced the correct alternation rate in TMT-treated mice. RAA preserved the integrity and orderly arrangement of nerve cells. A total of 12 components were detected in RAA-S. AKT1, PPARG, CASP3, STAT3, HSP90AA1, and NFE2L2 (Nrf2) were involved in the RAA-S target pathway network. Molecular docking revealed that Nrf2 exhibited the highest average binding energy with all components in RAA-S. In vivo, RAA elevated MAP2, GAP-43, Nrf2, and HO-1 levels, along with GPx, GSH, and SOD activity, which had been reduced by TMT. Additionally, RAA reduced serum levels of MDA and ROS, which had been elevated by TMT. In vitro, RAA-S reduced HT22 cell apoptosis and ROS accumulation caused by TMT. Furthermore, RAA-S promoted the expression of N-Nrf2 and HO-1 in L-Glu-injured HT22 cells.

Conclusion: RAA attenuated oxidative stress induced by TMT and L-Glu in AD model mice. The underlying mechanism was associated with the activation of the Nrf2/Keap1-HO-1 pathway.