Berbamine targets the FKBP12-rapamycin-binding (FRB) domain of the mTOR complex to promote microglial autophagy and ameliorate neuroinflammation in Alzheimer’s disease

Abstract

Background

Berbamine (BBM), a natural bisbenzylisoquinoline alkaloid, has demonstrated promising effects in ameliorating pathological process and inflammation response in central neuronal system (CNS). Alzheimer’s disease (AD), primarily characterized by amyloid-beta (Aβ)-containing extra-cellular plaques and abnormal “autophagy-brake regulation” of neuroinflammation, currently lacks of effective therapeutic options. Therapeutics of BBM on AD is indeed intriguing, and the potential targets and mechanisms are vague yet.

Purpose

This study is designed to elucidate the therapeutic potential of BBM on AD, focusing particularly on its ability to enhance autophagy, induce microglial M2 polarization, and to uncover the underlying molecular mechanisms and implicated targets.

Methods

The therapeutic efficacy of BBM was systematically investigated in APP/PS1 mice, with a focus on its potential to enhance autophagy, induce M2 polarization in microglia, and facilitate the clearance of Aβ plaques. Cognitive function was rigorously assessed through a series of behavioral tests, including the Morris Water Maze and Object Location Task. Immunofluorescence was employed to visualize the spatial distribution of inflammatory cytokines and autophagic markers within the brain parenchyma. Quantitative measurements of these cytokines were obtained using enzyme-linked immunosorbent assay (ELISA). Western blotting was utilized to analyze protein profiles associated with autophagy and microglial phenotypes. Additionally, chemo-proteomics and molecular docking techniques were applied to identify the key molecular targets of BBM.

Results

BBM treatment significantly ameliorated cognitive dysfunction and reduced Aβ plaque deposition in APP/PS1 transgenic mice. Notably, BBM promoted microglial polarization from the pro-inflammatory M1 phenotype to the anti-inflammatory M2 phenotype, accompanied by attenuation of neuroinflammation. Mechanistically, BBM exerted its effects through inhibition of mTOR signaling via direct interaction with the FKBP12-rapamycin-binding domain, thereby restoring autophagic flux and facilitating M2 microglial polarization. The mTOR activator MHY1485 abrogated the beneficial effects of BBM, highlighting the pivotal role of mTOR inhibition in its mechanism of action.

Conclusions

BBM promotes M2 microglial polarization and restores autophagic flux in AD by inhibiting mTOR signaling, representing a novel dual-modulatory mechanism for AD intervention. These findings highlight BBM’s ability to target mTOR and intersecting pathways, offering a promising disease-modifying therapeutic approach for AD and other neurodegenerative disorders.