Disruption of ceruloplasmin and hephaestin in mice causes retinal iron overload and retinal degeneration with features of age-related macular degeneration

Abstract

Mechanisms of brain and retinal iron homeostasis have become subjects of increased interest after the discovery of elevated iron levels in brains of patients with Alzheimer's disease and retinas of patients with age-related macular degeneration. To determine whether the ferroxidase ceruloplasmin (Cp) and its homolog hephaestin (Heph) are important for retinal iron homeostasis, we studied retinas from mice deficient in Cp and/or Heph. In normal mice, Cp and Heph localize to Müller glia and retinal pigment epithelium, a blood-brain barrier. Mice deficient in both Cp and Heph, but not each individually, had a striking, age-dependent increase in retinal pigment epithelium and retinal iron. The iron storage protein ferritin was also increased in Cp-/-Heph-/Y retinas. After retinal iron levels had increased, Cp-/-Heph-/Y mice had age-dependent retinal pigment epithelium hypertrophy, hyperplasia and death, photoreceptor degeneration, and subretinal neovascularization, providing a model of some features of the human retinal diseases aceruloplasminemia and age-related macular degeneration. This pathology indicates that Cp and Heph are critical for CNS iron homeostasis and that loss of Cp and Heph in the mouse leads to age-dependent retinal neurodegeneration, providing a model that can be used to test the therapeutic efficacy of iron chelators and antiangiogenic agents.