Abstract: This study aimed to investigate the inhibitory activity and mechanism of theabrownin using a zebrafish model of Alzheimer’s disease (AD). Structural analysis indicated that theabrownin was a polymeric phenolic compound rich in hydroxyl and carboxyl groups. The results showed that theabrownin significantly ameliorated behavioral impairments in zebrafish larvae and effectively alleviated AD-induced oxidative stress. Further molecular mechanism studies demonstrated that theabrownin delayed the progression of AD symptoms through multi-level regulatory mechanisms. At the gene expression level, RNA sequencing (RNA-Seq) and real-time polymerase chain reaction analyses indicated that theabrownin not only inhibited the upregulation of the endoplasmic reticulum stress marker genes bip and ire1 but also reversed the downregulation of atf6 and xbp1. Additionally, theabrownin significantly reduced Ca2+ ATPase activity, downregulated the expression of calcium release channel-related genes, inhibited the reduction of mitochondrial respiratory chain complexes, and upregulated the expression of genes related to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS). At the protein level, Western blot analysis confirmed that theabrownin treatment significantly decreased the expression of the pro-apoptotic proteins Caspase-3 and phosphorylated c-Jun N-terminal kinase (p-JNK), while upregulating the expression of the anti-apoptotic protein B-cell lymphoma 2 (Bcl-2). In summary, theabrownin demonstrates significant potential as a functional food component for the prevention and treatment of AD by synergistically regulating the inositol-requiring enzyme 1 (IRE1)/p-JNK/Bcl-2-caspase-3 apoptotic signaling pathway through multiple targets.

Key words: Tibetan tea; theabrownin; enhanced fermentation; Alzheimer’s disease; zebrafish