Modulation of the Aβ-Peptide-Aggregation Pathway by Active Compounds From Platycladus orientalis Seed Extract in Alzheimer's Disease Models

Alzheimer's disease (AD) is a neurodegenerative disease characterized by neuronal loss, cognitive impairment, and aphasia. Aggregation of β-amyloid (Aβ) peptide in the brain is considered a key mechanism in the development of AD. In the past 20 years, many compounds have been developed to inhibit Aβ aggregation and accelerate its degradation. Platycladus orientalis seed is a traditional Chinese medicine used to enhance intelligence and slow aging. We previously found that Platycladus orientalis seed extract (EPOS) inhibited Aβ-peptide aggregation in the hippocampus and reduced cognitive deficits in 5×FAD mice. However, the mechanisms of these effects have not been characterized. To characterize the protective mechanisms of EPOS, we used a transgenic Caenorhabditis elegans CL4176 model to perform Bioactivity-guided identification of active compounds. Four active compounds, comprising communic acid, isocupressic acid, imbricatolic acid, and pinusolide, were identified using 13C-and 1H-NMR spectroscopy. Furthermore, we showed that isocupressic acid inhibited Aβ generation by modulating BACE1 activity via the GSK3β/NF-κB pathway in HEK293-APPsw cells. These findings showed that EPOS reduced cognitive deficits in an AD model via modulation of the Aβ peptide aggregation pathway.

Keywords: Aβ-peptide aggregation; Platycladus orientalis seed; cognitive function; isocupressic acid; β-secretase 1.