Si-Shen-San Attenuates Alzheimer's Disease Pathology and Cognitive Deficits Through Multi-Target Regulation of Astrocyte Function and Synaptic Plasticity.

ETHNOPHARMACOLOGICAL RELEVANCE Alzheimer's disease (AD) is a progressive neurodegenerative disorder pathologically characterized by cognitive decline, amyloid-β (Aβ) deposition, tau hyperphosphorylation, synaptic dysfunction, and astrocyte dysregulation. The constituent herbs of the traditional Chinese medicine formula Si-Shen-San (SSS) have been used to ameliorate cognitive impairment. However, the comprehensive chemical profile, core bioactive constituents, and underlying mechanisms of action of SSS remain to be fully elucidated.

Aim

OF THE STUDY This study aims to systematically investigate the therapeutic potential of SSS against AD and to clarify its multi-faceted mechanisms of action, with a focus on astrocyte-mediated neuroprotection, synaptic repair, and modulation of core AD pathologies.

Materials And Methods

Ultra-high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC-Q/TOF-MS) was used to characterize the chemical constituents of SSS extract and SSS-containing serum. In vivo, 3×Tg-AD mice were orally administered SSS. And cognitive function, AD-related pathology, synaptic integrity, and astrocyte-associated molecular changes were evaluated using behavioral, histological, biochemical, ultrastructural, and electrophysiological approaches. In vitro, an astrocyte-conditioned medium paradigm was used to examine whether SSS-induced changes in astrocytes were associated with protection of HT22 neurons against glutamate-induced injury.

Results

UHPLC-Q/TOF-MS tentatively annotated 525 and 318 compounds in the SSS extract and drug-containing serum. In 3×Tg-AD mice, SSS improved cognitive performance, reduced hippocampal 6E10- and ThS-positive Aβ-like immunoreactivity and tau phosphorylation at Thr231 and Ser404, and preserved synaptic structure and function. The reduction in tau phosphorylation was accompanied by changes in GSK-3β signaling. SSS treatment was also associated with reduced astrocyte reactivity, increased GLT-1 expression, and restoration of astrocyte-associated homeostatic markers. In vitro, conditioned medium derived from SSS-treated C8-D1A astrocytes alleviated glutamate-induced injury in HT22 neurons and was accompanied by activation of neuronal CREB-BDNF signaling.

Conclusion

SSS ameliorated cognitive deficits and multiple AD-related pathological alterations in 3×Tg-AD mice. These effects were associated with restoration of astrocyte-related homeostatic features, improved glutamate regulation, preservation of synaptic integrity, and activation of CREB-BDNF signaling. These findings provide an experimental foundation for SSS as a potential therapeutic strategy for AD and highlight astrocyte homeostasis as a promising target for future drug development.