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E. F. Moreira, J. M. Sztein, J. W. Lee, I. R. Rodriguez; 7-Ketocholesterol Is Present in the Primate Retina Associated With Lipoprotein Deposits in Bruch’s Membrane and Choriocapillaris and Induces VEGF in Cultured RPE and Vascular Endothelial Cells. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1748.
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7-Ketocholesterol (7kCh) is a highly toxic oxysterol found in abundance in atherosclerotic plaques. The purpose of this study is to identify and localize 7kCh in the primate retina and to determine its potential in promoting angiogenesis and choroidal neovascularization (CNV).
Identification and quantification of 7kCh was performed by HPLC-MS. Immunolocalization of 7kCh was performed using a highly specific antibody. Low density lipoprotein (LDL) was purified from human serum. Oxidized LDL (oxLDL) and LDL with high amounts of 7kCh (7kLDL) were prepared from LDL using published techniques. Free 7kCh was delivered to cells complexed with hydroxypropyl beta-cyclodextrin. Human cultured RPE (ARPE19) and microvascular endothelial cells (HMVEC) were treated with sublethal doses of LDLs and 7kCh and assayed for dehydrogenase activity and VEGF induction by qRT-PCR. Rats were injected intravenously with LDL, oxLDL and 7kLDL every two weeks for 2 months.
Human and monkey retina contain small amounts of 7kCh which was detected and confirmed by HPLC-MS. Immunohistochemistry localized 7kCh mainly to lipoprotein deposits in Bruch’s membrane and choroid. VEGF mRNA was induced 7-10 fold in ARPE19 and HMVEC cells by oxLDL, 7kLDL and 7kCh treatments. Cellular dehydrogenase activity and VEGF induction were found to increase with oxLDL, 7kLDL and 7kCh in a dose dependent manner. Rats injected with oxLDL and 7kLDL exhibited choroidal edema, RPE abnormalities and macrophage infiltration.
The presence and location of 7kCh in the primate retina and its induction of VEGF in vitro and possibly in vivo suggests it may play a role in the pathogenesis of choroidal neovascularization. The data suggests VEGF induction occurs via a mitochondrial stress pathway.
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