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Daehan Lim, Hyungwoo Lee, Bokjun Ji, Hyewon Chung; Increased level of retinol binding protein 4 in neovascular age-related macular degeneration. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5476.
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© ARVO (1962-2015); The Authors (2016-present)
Retinol binding protein 4 (RBP4) secreted by adipose tissue and the liver delivers retinols to retinal pigment epithelium (RPE). During visual cycle, the production of toxic bisretinoids induces inflammatory reaction and secretion of angiogenic factors in the retina and the RPE, which might lead to the development of neovascular age-related macular degeneration (nAMD). However, the significance of RBP4 in the pathogenesis of AMD remains unknown. In this study, we measured the level of RBP4 in aqueous humor (AH) of nAMD patients and in the retina of mice exposed to bright light.
LC-ESI-MS/MS was performed to obtain proteomic profiles of AH from two nAMD patients. The levels of RBP4 in the AH of 15 nAMD patients were quantified with multiple reaction monitoring (LC-MRM) compared to 15 control subjects. Primary retinal cells cultured from the retina of newborn Sprague-Dawley rats as previously described were incubated in H2O2 added media with concentrations of 25 µM ~ 100 µM. Western blot analysis was performed to measure the level of RPB4 in the retinal cells. Adult C57BL6 mice were exposed to bright light (20,000 lux) for one hour with anesthesia. Retinal tissue and blood samples of those mice collected five days later were subjected to Western blot analysis for RBP4.
In LC-ESI-MS/MS proteomic profiling, RBP4 was found in the AH of both nAMD patients. LC-MRM analysis revealed that the mean RPB4 level was increased by 1.9-fold in the AH of nAMD patients compared to the controls. Protein level of RBP4 was increased in H2O2-treated primary rat retinal cells. Protein level of RBP4 was also increased in the retina and serum of mice after exposure to bright light.
RBP4 was increased in the AH of nAMD patients, in primary retinal cells exposed to oxidative stress and in the retina of mice after bright light exposure. Therefore, RBP4 might be used as a novel biomarker for nAMD. Furthermore, normalizing serum and retina RBP4 levels could be considered as a therapeutic measure for nAMD.
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