Raddeanin A isolated from Anemone raddeana Regel improves pathological and cognitive deficits of the mice model of Alzheimer's disease by targeting β-amyloidosis

Abstract

Background: Raddeanin A is a triterpenoid isolated from Anemone raddeana Regel. It exhibits a broad spectrum of biological activities such as anti-tumor and anti-inflammatory, however, its neuroprotective effect in targeting Alzheimer's disease (AD) remains uninvestigated.

Purpose: To provide scientific base for the development of novel AD drug by clarifying the neuroprotective effect and molecular mechanisms of raddeanin A in both in vitro and in vivo AD model.

Study design: To confirm the neuroprotective role of raddeanin A in the treatment of AD, its mechanisms and effects on β-amyloidosis and Aβ fibrillation was studied in U87 cells. Besides, the improvement on cognitive deficit, pathological defects, reactive astrocyte clusters, inhibition on neuronal inflammation and apoptosis were further studied in 3 x Tg-AD mice model of AD.

Methods: Real-time PCR, western blot, dot blot, biolayer interferometry and bioinformatics analysis were used to confirm the in vitro effect and targets of raddeanin A on β-amyloidosis and its associated protein network. A series of experiments including Morris water maze, H&E staining, nissl staining and immunofluorescence analysis were conducted to confirm the protective behavioral effect of raddeanin A in the in vivo AD mice model.

Results: Raddeanin A was identified to reduce β-amyloidosis in U87 cells and 3 x Tg-AD mice model of AD by decreasing level of BACE1, APP, APP-β and Aβ. Raddeanin A improved behavioral, spatial memory and learning ability in the AD mice. In the cortex and hippocampus, raddeanin A improved the morphology and arrangement of neurons, lower the level of reactive astrocyte marker GFAP and apoptotic marker proteins Bax/Bcl2 ratio. Moreover, raddeanin A upregulated the mRNA and protein level of Prkcα in the hippocampus of AD mice whose neuroprotective effect was exerted possibly via the activation of protein kinase C.

Conclusion: As a novel natural agent targeting β-amyloidosis, our results provide the first evidence of the multiple in vitro and in vivo neuroprotective effect of raddeanin A, suggesting its potential therapeutic application in preventing or alleviating the symptoms of AD.

Keywords: Alzheimer's disease; Amyloid precursor protein; Cognitive deficit; Raddeanin A; Β-amyloidosis.