Abstract
BackgroundAlzheimer's disease (AD) and age-related macular degeneration (AMD) share several pathological features including β-amyloid (Aβ) peptide accumulation, oxidative damage, and cell death. The causes of AD and AMD are not known but several studies suggest disturbances in cholesterol metabolism as a culprit of these diseases. We have recently shown that the cholesterol oxidation metabolite 27-hydroxycholesterol (27-OHC) causes AD-like pathology in human neuroblastoma SH-SY5Y cells and in organotypic hippocampal slices. However, the extent to which and the mechanisms by which 27-OHC may also cause pathological hallmarks related to AMD are ill-defined. In this study, the effects of 27-OHC on AMD-related pathology were determined in ARPE-19 cells. These cells have structural and functional properties relevant to retinal pigmented epithelial cells, a target in the course of AMD.MethodsARPE-19 cells were treated with 0, 10 or 25 μM 27-OHC for 24 hours. Levels of Aβ peptide, mitochondrial and endoplasmic reticulum (ER) stress markers, Ca2+ homeostasis, glutathione depletion, reactive oxygen species (ROS) generation, inflammation and cell death were assessed using ELISA, Western blot, immunocytochemistry, and specific assays.Results27-OHC dose-dependently increased Aβ peptide production, increased levels of ER stress specific markers caspase 12 and gadd153 (also called CHOP), reduced mitochondrial membrane potential, triggered Ca2+ dyshomeostasis, increased levels of the nuclear factor κB (NFκB) and heme-oxygenase 1 (HO-1), two proteins activated by oxidative stress. Additionally, 27-OHC caused glutathione depletion, ROS generation, inflammation and apoptotic-mediated cell death.ConclusionsThe cholesterol metabolite 27-OHC is toxic to RPE cells. The deleterious effects of this oxysterol ranged from Aβ accumulation to oxidative cell damage. Our results suggest that high levels of 27-OHC may represent a common pathogenic factor for both AMD and AD.
Highlights
Alzheimer’s disease (AD) and age-related macular degeneration (AMD) share several pathological features including b-amyloid (Ab) peptide accumulation, oxidative damage, and cell death
The concentrations of the 27-OHC used in the present study are the same as those we demonstrated to cause AD-like pathology in human neuroblastoma cells and in organotypic slices [13,15]
Our results show that Ab accumulation at least in part is due to increased generation of this peptide by the action of BACE-1, the enzyme that initiates the cleavage of b-amyloid precursor protein
Summary
Alzheimer’s disease (AD) and age-related macular degeneration (AMD) share several pathological features including b-amyloid (Ab) peptide accumulation, oxidative damage, and cell death. The effects of 27-OHC on AMD-related pathology were determined in ARPE-19 cells. These cells have structural and functional properties relevant to retinal pigmented epithelial cells, a target in the course of AMD. Age-related macular degeneration (AMD) is the most common cause of irreversible vision loss in elderly population [1] This disease is characterized by a progressive cell damage that targets the choroid, retinal pigment epithelium (RPE) and retina. The extent to which and the mechanisms by which 27-OHC may cause Ab accumulation and cell death in in vitro model that is relevant to retinal pigment epithelial cells and AMD studies are lacking. The oxysterol pathway has been proposed as a unifying hypothesis for the cause of AMD [25,26,27]
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