Chronic α-Synuclein Over-Expression and Ceruloplasmin Challenge Promote Distinct Iron and Redox Responses in M17 Cells.

BACKGROUND

While α-synuclein (α-syn) accumulation and iron dysregulation are hallmarks of Parkinson's Disease, the adaptations that enable neuronal survival under chronic protein stress remain unclear. Here, we investigated how α-syn overexpression and ceruloplasmin (Cp)-mediated iron modulation alters iron and redox homeostasis.

METHODS

We utilized human BE(2)-M17 neuroblastoma cell lines stably expressing different levels of α-syn to examine the interplay between α-syn, Ceruloplasmin (Cp)-mediated iron modulation, and the cellular response to oxidative stress. Analyses included Western blotting, immunofluorescence staining, soluble/insoluble fractionation, glutathione, reactive oxygen species (ROS) and hydrogen peroxide (H₂O₂) quantification, lipid peroxidation, ferrous iron, and cell viability.

RESULTS

Our data suggest an unexpected relationship between chronic α-syn expression and cellular redox regulation. Despite carrying a greater α-syn burden, cells with higher α-syn expression exhibit lower basal ROS, H₂O₂, and lipid peroxidation compared to control cells. These changes are not accompanied by activation of canonical antioxidant pathways suggesting that the reduced oxidative profile arises through alternative mechanisms. Besides, α-syn over-expressing cells display significant remodeling of iron-handling pathways, including altered expression of ferritin heavy chain, transferrin receptor, and ferroportin, suggesting that chronically high α-syn levels are associated with changes in iron homeostasis. In addition, this phenotype is not maintained following Cp overexpression. Although Cp reduces Fe²⁺ levels, it also induces substantial increases in ROS and H₂O₂ without corresponding changes in GPX4, glutathione, or related antioxidant systems. Thus, the reduced basal oxidative profile observed in α-syn-over-expressing cells does not reflect enhanced canonical antioxidant capacity. Instead, chronically high α-syn levels appear to be associated with adaptive remodeling of iron and redox pathways that become sensitive to oxidative imbalance.

CONCLUSION

Chronic α-syn over-expression promotes adaptive remodeling of iron and redox homeostasis, associated with reduced basal oxidative stress but increased sensitivity to Cp-mediated perturbation. These data link α-syn burden to iron metabolism and stress-dependent vulnerability in synucleinopathies.