7-Ketocholesterol is present in lipid deposits in the primate retina: potential implication in the induction of VEGF and CNV formation

The location of 7-kCh in the retina and its induction of VEGF in cultured RPE cells and HMVECs suggest it may play a critical role in choroidal neovascularization. The pathway for VEGF induction seems to be independent of HIF-1alpha and NF-kappaB but seems to be partially regulated by LXRs.

Unsterified 7kCh was identified and quantified by high-performance liquid chromatography-mass spectrometry. Localization of 7kCh was performed by immunohistochemistry. VEGF induction was determined by qRT-PCR. Cell viability was determined by measuring cellular dehydrogenase activity. Analyses were performed using ARPE19 and human vascular endothelial cells (HMVECs).

7-Ketocholesterol is a highly toxic oxysterol found in abundance in atherosclerotic plaques and is believed to play a critical role in atherosclerosis. The purpose of this study was to identify and localize 7-ketocholesterol (7kCh) in the primate retina and to examine the potential consequences of its presence in oxidized lipid deposits in the retina.

7-Ketocholesterol is localized mainly to deposits in the choriocapillaris and Bruch's membrane and on the surfaces of vascular endothelial cells of the neural retina. RPE/choriocapillaris regions contained approximately four times more 7kCh than the neural retina. In ARPE19 cells and HMVECs, oxidized LDL and 7kCh induced VEGF 8- to 10-fold above controls. Hypoxia inducible factor (HIF)-1alpha levels did not increase as a result of 7kCh treatment, suggesting an HIF-independent induction pathway. Cholesterol sulfate, a liver X receptor (LXR) antagonist, had marked attenuation of the 7kCh-mediated VEGF induction. LXR-specific siRNAs also reduced VEGF induction. Inhibition of NF-kappaB with BAY 11-7082 reduced IL-8 but not VEGF induction. Conclusions: The location of 7-kCh in the retina and its induction of VEGF in cultured RPE cells and HMVECs suggest it may play a critical role in choroidal neovascularization. The pathway for VEGF induction seems to be independent of HIF-1alpha and NF-kappaB but seems to be partially regulated by LXRs.