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Jade Pomerleau, Solange Landreville; Changes in markers of oxidative stress and DNA damage in human choroid from diabetic donors. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):5167.
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© ARVO (1962-2015); The Authors (2016-present)
Diabetic retinopathy is the most common diabetic eye disease and a leading cause of blindness in adults. The majority of studies on this disease have focused on retinal/vascular anomalies of the diabetic eye. However, only a small number have characterized changes in the underlying choroid. We hypothesize that increased oxidative stress induced by chronic hyperglycemia affects gene expression, DNA integrity and methylation in the choroid, as well as its stromal thickness during the early stages of diabetic retinopathy.
Microarray assays were done on a pair of type 2 diabetic and non-diabetic choroids using Agilent SurePrint G3 Human Gene Expression Microarray Kit. The data were analyzed using the ArrayStar software to generate scatter plots and heatmaps. Increase in DNA damage (8-oxodg) caused by oxidative stress, as well as overall DNA methylation (5-mC) and hydroxymethylation (5-hmC) were compared between diabetic (N=5) and non-diabetic (N=5) choroid tissues using slot blot (normalization with an anti-ssDNA antibody). Finally, eye tissue sections of donors with (N=10) or without (N=10) nonproliferative diabetic retinopathy were colored with Masson’s Trichrome stain to study the histological characteristics of the diabetic choroid, such as its thickness. The Mann-Whitney test was used for statistical analysis.
Scatter plot analysis revealed that the pattern of gene expressed by the diabetic choroid changed dramatically compared to the non-diabetic choroid (R2=0.8211). Heatmap analysis demonstrated an increased expression of genes involved in mitochondrial metabolism in the diabetic choroid (90 genes > 2 fold-change). Furthermore, our slot blot results showed a significant rise in the amount of DNA damage caused by oxidative stress in the diabetic choroid (P = 0.008), while the overall levels of DNA methylation and hydroxymethylation were similar for the diabetic and non-diabetic choroids (P = 0.80 and P = 0.41, respectively). There was no significant difference in choroid thickness between eyes with or without nonproliferative diabetic retinopathy (P = 0.49 and P = 0.29, respectively).
The diabetic choroid contained elevated levels of DNA damage, consistent with the observed increase in their mitochondrial metabolism compared to the non-diabetic choroid. These changes may contribute to the retina-choroid dysfunction observed in nonproliferative diabetic retinopathy.
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