Non-Erythropoietic EPO (EPO-R76E) Protects RPE Cells from Ferroptosis by Modulating the Labile Iron Pool and NRF2-GPX4 Axis.

Retinal pigment epithelium (RPE) degeneration remains a formidable challenge in dry age-related macular degeneration (AMD) research, primarily due to the toxic interplay between iron overload and ferroptosis. We investigated whether EPO-R76E, a non-erythropoietic modified variant of erythropoietin, could effectively interrupt this destructive cycle. Using ARPE-19 cells challenged with ferric ammonium citrate (FAC) to model iron-induced toxicity, we show that EPO-R76E confers protection against ferroptosis. Our results demonstrate that this variant significantly reduces the intracellular labile iron pool, directly quenching the lipid peroxidation that drives ferroptotic cell death. This resilience is fueled by a robust upregulation of Glutathione Peroxidase 4 (GPX4) and the broad transcriptional activation of the NRF2 (Nuclear factor erythroid 2-related factor 2) NRF2 antioxidant axis. Furthermore, we found that EPO-R76E enhances autophagic flux, ensuring that cells maintain essential proteostasis and "housekeeping" functions even under metabolic crisis. By integrating iron sequestration with reinforced antioxidant signaling and cellular clearing mechanisms, EPO-R76E stands out as a potent candidate for preserving RPE health. These findings uncover a novel molecular framework for protecting the retina against iron-mediated injury, positioning EPO-R76E as a versatile and targeted gene-based therapeutic for addressing the fundamental causes of retinal degeneration.