Hartman, Gabriella D.Muniyandi, AnbukkarasiSishtla, KamakshiKpenu, Eyram K.Miller, William P.Kaplan, Bryan A.Kim, Leo A.Liu, ShengWan, JunQi, XiaopingBoulton, Michael E.Kelley, Mark R.Corson, Timothy W.2025-03-192025-03-192025Hartman GD, Muniyandi A, Sishtla K, et al. Ref-1 redox activity regulates retinal neovascularization by modulating transcriptional activation of HIF-1α. FASEB J. 2025;39(3):e70348. doi:10.1096/fj.202401989RRhttps://hdl.handle.net/1805/46362Retinal neovascularization impairs visual function and is a hallmark of several neovascular eye diseases, including retinopathy of prematurity (ROP) and proliferative diabetic retinopathy (PDR). Current treatments include intravitreal injections of anti-vascular endothelial growth factor (VEGF) biologics, but these therapeutics are often accompanied by high treatment burden and resistance to therapy. Prior studies indicate that APE1/Ref-1, a multifunctional protein with both endonuclease (APE1) and redox-mediated transcriptional regulatory activity (Ref-1), activates multiple pro-angiogenic and pro-inflammatory signaling pathways by chemically reducing key cysteine residues in transcription factors, thereby activating them. Here, we investigated the previously unexplored role of Ref-1 in retinal neovascularization. We demonstrate that Ref-1 is highly expressed in endothelial cells in human PDR and in the oxygen-induced retinopathy (OIR) mouse model of retinal neovascularization. Ref-1 is also highly expressed in microglia and astrocytes in OIR. A small molecule Ref-1 redox inhibitor, APX2009, decreased retinal neovascularization in OIR after systemic delivery. In vitro, hypoxic endothelial cells did not exhibit upregulation of Ref-1 but rather increased Ref-1 nuclear localization. APX2009 decreased hypoxic endothelial cell proliferation and HIF-1α transcriptional activation. Thus, Ref-1 redox activity may be a novel therapeutic target for the treatment of retinal neovascularization, making APX2009 a promising systemic therapeutic approach for the treatment of vascular retinopathies such as ROP and PDR.en-USAttribution-NonCommercial 4.0 InternationalAPE1/Ref‐1Hypoxia‐inducible factorOxygen‐induced retinopathyRedox regulationRetinal neovascularizationArticle