Oral Deuterated Docosahexaenoic Acid Protects Against Onset and Progression of RPE Degeneration in a Mouse Model of Chronic Oxidative Stress

Purpose: Oxidative stress is associated with many retinal diseases, including age-related macular degeneration (AMD). The purpose of this study is to investigate the efficacy of oral deuterated docosahexaenoic acid (D-DHA), an oxidation-resistant lipid, in a mouse model with features of dry AMD. We also evaluated whether long-term D-DHA dosing affects normal retinal structure or function. Methods: Liver-specific hepcidin (Hepc) and ceruloplasmin/hepcidin (Cp/Hepc) knock-out (KO) mice were fed experimental diet containing 0.25% D-DHA or control containing normal H-DHA during various stages of disease progression. Retinal pigment epithelium (RPE) damage was assessed with in vivo scanning laser ophthalmoscopy (SLO) imaging and histology. For the safety study, wild-type mice were fed the diets beginning in utero or at 3 months of age, continuing for 12 months. These mice were analyzed to assess retinal structure (SLO, optical coherence tomography [OCT], and transmission electron microscopy [TEM]), function (ERG), and gene expression (qPCR). Results: KO mice fed control diet developed expanding autofluorescent patches of hypertrophic RPE cells. This damage was markedly prevented or halted by diet with D-DHA, depending on age at diet onset. Wild-type mice administered diet with D-DHA from age 3 to 15 months had no retinal abnormalities. Mice administered D-DHA beginning in utero had normal retinal development and structure but minor deficits in ERG amplitudes and Rpe65 expression by age 12 months. Conclusions: Oral D-DHA was strongly protective against RPE ferroptosis, with minimal side effects. This study suggests that DHA oxidation is a key mechanism of retinal iron toxicity and supports the potential clinical application of D-DHA for diseases involving retinal oxidative stress.