Gaultheria leucocarpa inhibits Aβ fibrillization and enhances mitophagy-mediated degradation of pathogenic proteins.

Abstract

Alzheimer's disease (AD) pathology involves amyloid-beta (Aβ) accumulation and neuronal toxicity, highlighting the need for therapeutic strategies that can both inhibit Aβ aggregation and promote pathogenic protein clearance. In this study, we identified Gaultheria leucocarpa as a medicinal plant with promising neuroprotective potential. Thioflavin T (ThT) fluorescence screening revealed that extracts from G. leucocarpa (GE), particularly the petroleum ether fraction of G. leucocarpa extract (GPF), effectively inhibited Aβ fibril formation in vitro. In cell-based assays, GPF significantly improved the viability of PC-12 ​cells exposed to Aβ peptides and fibrils, indicating protection against Aβ-induced cytotoxicity. Furthermore, GPF enhanced mitophagic activity, as demonstrated by increased GFP-LC3 puncta, elevated LC3-II/I ratio, and colocalization of GFP-LC3 with MitoTracker Red. Mechanistic investigations showed that GPF activates mitophagy via the AMPK/ULK1 pathway and inhibits the PI3K/AKT/mTOR pathway, resulting in enhanced degradation of APP and Tau proteins. In Caenorhabditis elegans models relevant to AD, GPF administration led to reduced Aβ deposits, delayed paralysis onset, improved food perception, and decreased oxidative stress. Collectively, these findings demonstrate that GPF exerts dual actions by inhibiting Aβ fibrillization and promoting mitophagy-mediated degradation of pathogenic proteins. The active ingredients identified from GPF extracts represent promising leads for the development of novel neuroprotective agents targeting AD-related pathological mechanisms.