Fisetin Attenuates Mutant SOD1 Aggregation in Amyotrophic Lateral Sclerosis via Nrf2-Mediated Autophagy Activation

Dysregulated autophagy and copper/zinc superoxide dismutase (SOD1) protein aggregation play a crucial role in amyotrophic lateral sclerosis (ALS). Here, we used stably transfected NSC34 motor neuron-like cells: (1) SOD1^G93A mutants (G93A), (2) wild-type SOD1 (WT) controls, and (3) empty vector (EV) controls to observe the effects of fisetin. Pharmacological autophagy inhibition (Bafilomycin A1, 40 nM) and nuclear factor erythroid 2-related factor 2 (Nrf2) gene silencing (siRNA transfection) were employed to dissect molecular pathways. Protein aggregation dynamics and autophagy markers (LC3, p62/SQSTM1) were quantified through immunofluorescence and immunoblotting. SOD1^G93A models exhibited impaired autophagic flux evidenced by elevated LC3-II and p62 levels, correlating with increased detergent-insoluble SOD1 aggregates. Fisetin treatment (1-10 μ M) dose-dependently reduced both soluble and aggregated SOD1^G93A protein, concomitantly with restored autophagic flux. Mechanistically, fisetin promoted nuclear translocation while decreasing cytoplasmic Nrf2. After administration of an autophagy inhibitor and interference with Nrf2, the regulation of fisetin on p62 and mutant hSOD1 protein was inhibited. Our findings demonstrate that fisetin ameliorates mutant SOD1 proteotoxicity through coordinated activation of Nrf2-mediated autophagy pathways, suggesting therapeutic potential for SOD1-associated ALS pathologies.