Protective effect of FXN overexpression on ferroptosis in L-Glu-induced SH-SY5Y cells

Alzheimer's disease (AD) is a complex, multifactorial neurodegenerative disease. However, the pathogenesis remains unclear. Recently, an increasing number of studies have demonstrated that ferroptosis is a new type of iron-dependent programmed cell death, contributes to the death of nerve cells in AD. By controlling iron homeostasis and mitochondrial function, the particular protein called frataxin (FXN), which is situated in the mitochondrial matrix, is a critical regulator of ferroptosis disease. It is encoded by the nuclear gene FXN. Here, we identified a novel underlying mechanism through which ferroptosis mediated by FXN contributes to AD.

Human neuroblastoma cells (SH-SY5Y) were injured by L-glutamate (L-Glu). Overexpression of FXN by lentiviral transfection. In each experimental group, we assessed the ultrastructure of the mitochondria, the presence of iron and intracellular Fe2 + , the levels of reactive oxygen species, the mitochondrial membrane potential (MMP), and lipid peroxidation. Quantification was done for malondialdehyde (MDA) and reduced glutathione (GSH), as well as reactive oxygen species (ROS). Western blot and cellular immunofluorescence assays were used to detect the expression of xCT and GPX4 proteins which in System Xc-/GPX4 pathway, and the protein expressions of ACSL4 and TfR1 were investigated by Western blot.

The present work showed: (1) The expression of FXN was reduced in the L-Glu group; (2) Compared with the Control group, MMP was reduced in the L-Glu group, and mitochondria were observed to shrink and cristae were deformed, reduced or disappeared by transmission electron microscopy, and after FXN overexpression and ferrostatin-1 (Fer-1) (10 μmol/L) intervened, MMP was increased and mitochondrial morphology was significantly improved, suggesting that mitochondrial function was impaired in the L-Glu group, and overexpression of FXN could improve the manifestation of mitochondrial function impairment. (3) In the L-Glu group, ROS, MDA, iron ion concentration and Fe²⁺ levels were increased, GSH was decreased. Elevated expression of ACSL4 and TfR1, important regulatory proteins of ferroptosis, was detected by Western blot, and the expression of xCT and GPX4 in the System Xc-/GPX4 pathway was reduced by Western blot and cellular immunofluorescence. However, the above results were reversed when FXN overexpression and Fer-1 intervened.

To conclude, our research demonstrates that an elevated expression of FXN effectively demonstrates a robust neuroprotective effect against oxidative damage induced by L-Glu. Moreover, it mitigates mitochondrial dysfunction and lipid metabolic dysregulation associated with ferroptosis. FXN overexpression holds promise in potential therapeutic strategies for AD by inhibiting ferroptosis in nerve cells and fostering their protection.