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Browsing by Author "Alves, Liliana Teresa da Silva"

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  • Characterization of pro- and anti-angiogenic factors in models of diabetic retinopathy
    Publication . Alves, Liliana Teresa da Silva; Silva, Gabriela A.; Calado, Sofia M.
    Diabetic retinopathy (DR) is a microvascular complication associated with Diabetes mellitus (DM) and the leading cause of blindness in developed countries. Hyperglycemia and hypoxia are suggested to play essential pathophysiological role in the onset, progression and prognosis of DR. Moreover, hypoxia inducible factor-1 (HIF-1), which is stabilized under hypoxic conditions, acts as a transcription factor of several genes such as vascular endothelial growth factor (VEGF) and glucose transporter 1 (GLUT1). It was also described that an imbalance between pigment epithelium-derived factor (PEDF), a potent angiogenic inhibitor, and VEGF, the major angiogenic stimulator, is present in patients that suffer of DR. However little is known about the role of this imbalance in DR progression. Therefore the goal of this study was to characterize the expression of GLUT1, pro-, and anti-angiogenic factors involved in the development and progression of DR, using in vitro and in vivo models of the disease. The present study demonstrates that in D407 cells, an immortalized retinal pigmented epithelium (RPE), the levels of the glucose transporter GLUT1 are increased in the response to hypoxia and hyperglycemia and this increase is more pronounced in the cell membrane fraction. Additional support to our in vitro results is the fact that GLUT1 expression levels are increased in Ins2Akita mice, a model of type 1 DM. Regarding PEDF expression in vitro, there was no significant difference between tested conditions, but we observed the tendency to decrease in hypoxic conditions. In vivo, we could see a significant decrease of PEDF expression in the retina of 6 month-old mice; but the key result is the marked decrease detected in the RPE cell layer. VEGF mRNA levels were increased in vitro and in vivo at 6 month-old animals, but this was not observed for the protein levels. At 12 months of age, mRNA levels were similar in WT and diabetic mice, but the protein levels are significantly decreased in diabetic mice, a potential consequence of the overall senescence observed for these animals. Taken together, these results suggest that the increase in GLUT1 and the decrease in PEDF expression levels are associated with the development of diabetic retinopathy.
    2015-12-15Master thesis Open access Show more