Alpha‐synuclein, ferroptosis and neurodegeneration: Investigating a complex relationship

Abstract Background The accumulation of brain iron in several neurodegenerative diseases like Alzheimer’s disease (AD) or Parkinson’s disease (PD) is well established both by ante‐mortem imaging studies and post‐mortem biochemical analysis of affected brain tissue. Thus, understanding the cytotoxic actions of iron in neurons or cells of neural origin would be important in elucidating the mechanisms of neurodegeneration in disorders like AD or PD. We have recently shown that cytotoxic action of iron in SH‐SY5Y cells (catecholaminergic human neuroblastoma cell line) is mediated by accumulated α‐synuclein which triggers mitochondrial dysfunction and cell death. The accumulation of α‐synuclein occurs as a result of decreased clearance from the cell as a result of oxidative inactivation of Parkin. In the current study we have further examined the role of oxidative stress in this process. Method SH‐SY5Y cells were treated with ferrostatin‐1, liproxstatin‐1 and vitamin E (ferroptosis inhibitors) and then co‐incubated with 100‐400 μM Ferric ammonium citrate and analyzed for cell death (LDH assay and trypan blue assay), ROS generation (DCFDA assay), lipid peroxidation (MDA levels), reduced glutathione levels and α‐synuclein protein levels (western blotting). α‐synuclein silencing was performed by using commercially available siRNAs. Result Our results show that iron induced an increased formation of reactive oxygen species (ROS) and malondialdehyde (MDA) along with a decreased level of reduced glutathione content in SH‐SY5Y cells, and these changes were associated with significant cell death. Co‐incubation of SH‐SY5Y cells with vitamin E, ferrostatin‐1 and liproxstatin‐1, prevented all the toxic actions of iron in our experimental system, and in addition these prevented iron‐induced accumulation of α‐synuclein . These results tend to imply that iron cytotoxicity in our system clearly resembles ferroptotic cell death, and it appears that α‐synuclein could be a key mediator in the latter process. Furthermore, knocking‐down α‐synuclein gene expression by specific siRNA resulted in a significant decrease in oxidative stress induced by iron in SH‐SY5Y cells. Conclusion α‐synuclein appears to have a dual role in enhancing oxidative stress as well as functioning as a mediator of oxidative damage to the cells. The implications of these results in neurodegeneration of AD and PD are obvious and need further exploration.