BLOOD-RETINAL BARRIER GLUT1 IN DIABETIC RETINOPATHY

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The overall objective of the project outlined in the present application is to provide a mentor-based training program centered around the study of changes in GLUT1 glucose transporter gene expression in diabetic retinopathy (DR). The rationale for this project is based on the clinical observation that the chronic hyperglycemia of long-standing diabetes is associated with characteristic pathological changes in the retinal capillaries which comprise the inner blood-retinal barrier (BRB). On a molecular level, in order to initiate the biochemical and histopathological changes leading to DR, glucose must gain access to the intracellular compartment of the capillary endothelial cells of the inner BRB. It can only do so via transport by GLUT1. Therefore, changes in GLUT1 expression in the inner BRB may have a profound impact on the intracellular concentration of glucose and on the subsequent development of the pathological microvascular changes of DR. A recent pilot study by the applicant demonstrated a localized, pathological upregulation of immunoreactive GLUT1 on the inner BRB in long-standing diabetes. The proposed studies will investigate this phenomenon in 4 general areas. First, quantitative immunogold electron microscopy and in situ hybridization for GLUT1 will be performed on postmortem human retina specimens to extend observations regarding changes GLUT1 protein and mRNA expression in early DR. Second, selective overexpression of vascular endothelial GLUT1 in bovine retinal endothelial cells (BRCEC) in culture and in a transgenic mouse model will be undertaken to determine if increased expression of GLUT1 results in molecular and histopathological changes similar to those found in early DR. Third, the effects of glucose and growth factors associated with the development of DR on GLUT1 gene expression will be investigated in BRCEC culture models, and fourth, possible effects of pericyte-endothelial cell interactions on GLUT1 gene expression will be studied in cell culture.