The neuroprotective role of chlorogenic acid and Fisetin in differentiated neuronal cell line-SHSY5Y against amyloid-β-induced neurotoxicity

Alzheimer's disease (AD) is a neurodegenerative disorder and characterized by amyloid-beta (Aβ) accumulation, synaptic dysfunction, oxidative stress, and lacks effective therapies. Fisetin and chlorogenic acid (CGA) are natural polyphenols have shown potential in mitigating several age-related diseases. Therefore this study investigates their neuroprotective effects against Aβ1–42-induced toxicity in differentiated SHSY5Y cells. Both Fisetin and CGA reversed the deleterious effects of Aβ1–42 by restoring redox balance, suppressing reactive oxygen species, and upregulating mRNA expression of critical antioxidant enzymes like SOD1, GSR, and CAT. These compounds also attenuated Aβ1–42-induced mitophagy via reduced PINK1 expression and restored mitochondrial fusion by upregulating MFN2. Autophagy-related pathways were significantly modulated which was evidenced by increased PRKAA1 (AMPK) and decreased MTOR mRNA levels, alongside elevated expression of ATG101, ATG13, ULK1, SQSTM1 (p62) and reduced ATG5 levels. Fisetin and CGA improved synaptic integrity by upregulating DLG4 (PSD95) and SYP (synaptophysin) and reducing ACHE (acetylcholinesterase) expression. These findings highlight their potential in ameliorating Aβ1–42-induced neuronal toxicity through autophagy activation, synaptic preservation, and mitochondrial function enhancement. Furthermore, our docking studies also revealed good Fisetin and CGA binding affinity within AMPK and mTOR's binding pocket (FKBP12-FRB). Although the neuroprotective effects of CGA and Fisetin are underscored by transcriptional and docking studies, further translational and biophysical validation is required to demonstrate their therapeutic efficacy against AD-related neurodegeneration.