Ferroportin-mediated iron export from vascular endothelial cells in retina and brain. (October 2019)

• Record Type: Journal Article
• Authors: Baumann, Bailey H.; Shu, Wanting; Song, Ying; Simpson, Elizabeth M.; Lakhal-Littleton, Samira; Dunaief, Joshua L.
• Is Part Of: Experimental eye research. Volume 187(2019)
• Publication Date: 2019-10
• Subjects: Iron -- Ferroportin -- Age-related macular degeneration (AMD) -- Retina -- Retinal vascular endothelium -- Ferritin; AMD age-related macular degeneration -- Tf transferrin -- TfR transferrin receptor -- Dmt1 divalent metal transporter 1 -- Fpn ferroportin -- Hepc Hepcidin -- Cp ceruloplasmin -- Heph hephaestin -- Ft-L ferritin-L -- TBI transferrin bound iron -- NTBI non-transferrin bound iron -- RPE retinal pigment epithelium -- NSR neurosensory retina -- BRB blood-retinal barrier -- BBB blood-brain barrier -- rVECs retinal vascular endothelial cells -- bVECs brain vascular endothelial cells -- Ple Pleiades Promoter Project; Ophthalmology -- Periodicals; Eye -- Periodicals; Œil -- Périodiques; Ophthalmology; Periodicals; Electronic journals; 612.8405
• DOI: 10.1016/j.exer.2019.107728
• Languages: English
• ISSNs: 0014-4835

Abstract

Abstract: Retinal iron accumulation has been implicated in the pathogenesis of age-related macular degeneration (AMD) and other neurodegenerative diseases. The retina and the brain are protected from the systemic circulation by the blood retinal barrier (BRB) and blood brain barrier (BBB), respectively. Iron levels within the retina and brain need to be tightly regulated to prevent oxidative injury. The method of iron entry through the retina and brain vascular endothelial cells (r&bVECs), an essential component of the BRB and BBB, is not fully understood. However, localization of the cellular iron exporter, ferroportin (Fpn), to the abluminal membrane of these cells, leads to the hypothesis that Fpn may play an important role in the import of iron across the BRB and BBB. To test this hypothesis, a mouse model with deletion of Fpn within the VECs in both the retina and the brain was developed through tail vein injection of AAV9-Ple261( CLDN5 )-icre to both experimental Fpn f/f, and control Fpn +/+ mice at P21. Mice were aged to 9 mo and changes in retinal and brain iron distribution were observed. In vivo fundus imaging and quantitative serum iron detection were used for model validation. Eyes and brains were collected for immunofluorescence. Deletion of Fpn from the retinal and brain VECs leads to ferritin-L accumulation, an indicator of elevated iron levels, in the retinal and brain VECs. This occurred despite lower serum iron levels in the experimental mice. This result suggests that Fpn normally transfers iron from retinal and brain VECs into the retina and brain. These results help to better define the method of retina and brain iron import and will increase understanding of neurodegenerative diseases involving iron accumulation. Highlights: Iron is transiently trapped in retinal vascular endothelial cells after ferroportin deletion. Iron is trapped in brain vascular endothelial cells after ferroportin deletion. Ferroportin on vascular endothelial cells may be essential for iron transport into the retina and brain.