Abstract
Purpose::
Diabetes often leads to diabetic retinopathy, which is a major cause of blindness in the Western world. Diabetes-induced pathological alterations, such as loss of barrier function, occur in the retinal pigment epithelium (RPE). The biochemical mechanism responsible for these pathological changes is currently unclear. The aim of this study is to use proteomics to identify changes in RPE protein content of diabetic donors compared to age-matched controls.
Methods::
The RPE was harvested from human donor globes obtained from the Minnesota Lions Eye Bank. All eyes were free from symptoms of other ocular diseases including glaucoma and AMD. Differential centrifugation was utilized to generate a fraction of soluble proteins. Proteins were separated using two-dimensional gel electrophoresis. The density of protein spots visualized with Flamingo Fluorescent Gel Stain were evaluated in gels from diabetic (n=6) and non-diabetic controls (n=17). Significant changes in protein expression were determined by two-sample t-test. Spots with altered expression were identified by MALDI-TOF mass spectrometry.
Results::
The 2D profile from diabetic and non-diabetic tissues yielded approximately 300 spots. Our analysis revealed 20 spots that demonstrated significant changes; 15 spots decreased in diabetic samples and 5 showed an increase. Proteins identified include GRP78/ BiP and transthyretin, which play a role in the ER stress response and retinol binding, respectively. These proteins exhibited decreased expression in the diabetic samples.
Conclusions::
Proteomics is useful for identification of proteins associated with disease processes. Changes identified in human diabetic RPE may be relevant for understanding how this tissue responds to diabetes-related insult. This information can aid in the development of new therapeutic strategies aimed at treating diabetic retinopathy.
Keywords: diabetic retinopathy • proteomics • retinal pigment epithelium