Apolipoprotein E4 impairs iron efflux in human induced pluripotent stem cell (iPSC)‐derived cortical neurons by reducing ferroportin on cell surface

Abstract

AbstractBackgroundIron homeostasis disturbance has been implicated in Alzheimer’s disease (AD), and excess iron exacerbates oxidative damage and cognitive defects. Ferroportin (Fpn) is the only known iron exporter and the expression of Fpn is decreased in the brains of AD patients. Apolipoprotein E (APOE) gene is the most important genetic risk factor for late‐onset AD. The three common proteins encoded by the gene are ApoE2, ApoE3, and ApoE4. They bind to iron with different affinities, which mediates the isoform‐specific antioxidant activity. However, whether ApoE takes part in neuronal iron homeostasis remains unclear.MethodCortical neurons were generated from human iPSCs (All from non‐demented APOE3/E3 carriers). The intracellular iron content was measured using inductively coupled plasma mass spectrometry (ICP‐MS) after co‐treatment of iron and ApoE. Western blot analysis was performed to examine the alterations of various iron storage and transport proteins. Cell surface Fpn expression levels were measured by fluorescence‐activated cell sorting (FACS).ResultIntracellular iron level in ApoE4‐treated neurons was higher than that in ApoE2‐ or ApoE3‐treated neurons. Furthermore, Fpn level on cell surface was reduced by ApoE4 treatment.ConclusionOur study demonstrates that ApoE4 impairs iron efflux and exacerbate iron accumulation via regulating surface Fpn level.