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Manuela Bartoli, Diana Gutsaeva, Menaka Thounaojam, Pamela M Martin, Folami Lamoke; Up-regulation of SLC2A9 (Glut9) in normal and diabetic human retina implicates altered urate transport in diabetes-induced retinal barrier dysfunction. Invest. Ophthalmol. Vis. Sci. 2016;57(12):3223. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous work has shown that in human DR there is increased production and deposition of urate at retinal tissue levels, thus, suggesting that urate metabolism and transport from and within retinal cells can play a contributing role in the pro-inflammatory events occurring in the diabetic retina. Here we have characterized the presence of the main urate transporter and putative glucose antiport SLC2A9 (Glut9) in retina and determined the effects of diabetes on its expression and immunolocalization.
Human post-mortem retinas from non-diabetic and diabetic donors were obtained from Georgia Eye Bank. Western blotting analysis and immunohistochemistry were performed using specific antibodies against human Glut9. Human retinal pigmented epithelial cells (ARPE19) and retinal endothelial cells (HuREC) in cultures were subjected to hyperglycemic stress (HG= 35mM D-glucose for 48hours) and clinically relevant doses of monosodium urate (MSU = 7mg/dL), alone or in combination with HG (MSU+HG). Cells treated in these conditions were then subjected to Western blotting analysis using specific antibodies against human Glut9
Western analysis revealed the presence of Glut9 in human retinal tissues of non-diabetic and diabetic donors. In diabetic retinas this urate transporter was significantly up-regulated (>50%) in comparison to non-diabetic donors. Immunohistochemical analysis revealed that Glut9-specific immunoreactivity was primarily localized in the luminal side of retinal and choroidal blood vessels and the apical side of the retinal pigment epithelium (RPE). Glut9 immunoreactivity also was increased in the diabetic human retinas. Western analysis showed increased expression levels in ARPE19 and HuREC exposed to HG and MSU, however this was much more pronounced in cells treated with HG+MSU simultaneously.
Our data show, for the first time, that the urate transporter SLC2A9 (Glut9) is expressed in human retina and its expression is up-regulated in the diabetic milieu. Most importantly, Glut9 is primarily immunolocalized in retinal cells devoted to maintenance of the blood retinal barrier further underscoring the potential implication of retinal urate transport and metabolism in the development of DME and in DR progression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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