Retinal endothelial cells are more susceptible to oxidative stress and increased permeability than brain-derived endothelial cells.

Increased vascular permeability and oxidative stress are important in diabetic retinopathy. Because the cerebral microcirculation is much less affected in diabetes, our objectives are to compare: (1) glutathione peroxidase activity, (2) superoxide dismutase levels, (3) superoxide production, and (4) junctional protein (ZO-1) levels between retinal and brain-derived endothelial cells. Bovine brain and retinal endothelial cell cultures are incubated in medium containing either mM or 30 mM glucose for 5 days. Superoxide is measured in the medium and endothelial cells are then lysed and analyzed for glutathione peroxidase activity as well as levels of superoxide dismustase and ZO-1. The results demonstrate that, compared to brain-derived endothelial cells, retinal endothelial cells release high levels of superoxide, have less glutathione peroxidase activity and lower levels of superoxide dismutase, and ZO-1. Also, unlike brain-derived endothelial cells where ZO-1 levels increased in response to glucose, in retinal endothelial cells, ZO-1 levels are unaffected by glucose. These findings suggest that greater oxidative stress and lower junctional protein levels in retinal endothelial cells may contribute to blood/retinal barrier dysfunction in diabetic retinopathy.