Fisetin prevents deterioration of cellular functions in amyotrophic lateral sclerosis variants G262R and P438L of SQSTM1 in SH-SY5Y cells.

Abstract

Oxidative stress is widely accepted as one of the important factors contributing to neurodegeneration, leading to fatal neurodegenerative diseases (NDD) such as Amyotrophic Lateral Sclerosis. Since flavonoids possess antioxidant properties, we investigated whether Fisetin (FS) and Quercetin (QR) protected cells from oxidative stress arising from pathogenic mutations G262R (G > A) and P438L (C > T) of SQSTM1 found in Indian ALS patients. SQSTM1 codes for p62 protein and is involved in multiple signaling pathways through its various domains. We studied changes in cell viability and cellular functions using immunoblotting, confocal microscopy, immunoprecipitation and FACS analysis in the presence and absence of FS and QR. Supplementation with FS and QR in SH-SY5Y cells expressing SQS-wild type and mutants increased cell viability and decreased ROS formation. Also, Nrf2 protein levels increased to offset oxidative stress response. In addition, we studied the effect of FS on the nuclear-cytoplasmic distribution of TDP-43 protein, which serves as a hallmark for ALS. FS corrected the nuclear-cytoplasm translocation of TDP-43 protein and decreased late apoptosis in mutants. Our study illustrates that both FS and QR shield cells from oxidative stress, and that FS imparted better protection against the pathogenic effect of SQSTM1 mutants in SH-SY5Y neuronal cells.