Abstract
Purpose: :
Calcium dobesilate has been found to correct the excessive vascular permeability in the retina of diabetic patients and in experimental diabetes. However, the mechanisms underlying these protective effects are not elucidated. In this study, we investigated the effect of calcium dobesilate on the blood-retinal barrier (BRB) leakage and on the content and distribution of tight junction proteins in the retinal vessels of diabetic rats, as well as on leukocyte adhesion to retinal endothelial cells, which has been correlated to BRB breakdown.
Methods: :
Diabetes was induced by an intraperitoneal injection of streptozotocin (65 mg/kg) in two months old male Wistar rats (1 month diabetes duration). The animals were divided in three groups (7-8 animals/group): controls, diabetics, diabetics treated with calcium dobesilate (100 mg/kg/day; orally given) during the last 10 days of diabetes. BRB breakdown was assessed quantitatively and qualitatively with Evans blue dye. Tight junction proteins and ICAM-1 protein levels were evaluated by western blotting. The distribution of tight junction proteins was assessed by immunocytochemistry. Leukocyte adhesion was evaluated in whole-mounted retinas and in in vitro studies using an endothelial cell line (TR-iBRB2) exposed to elevated glucose levels (30 mM).
Results: :
Diabetes induced a 6.5-fold increase in BRB permeability and decreased occludin and claudin-5 protein levels in the retina (65.2 ± 7.6% and 63.2 ± 5.4% of the controls, respectively). ZO-1 levels were unchanged, however, the distribution of ZO-1 and occludin was altered in the retinal vessels of diabetic animals. In diabetic animals treated with calcium dobesilate, the BRB permeability decreased to 2-fold of the controls, and the content and distribution of tight junction proteins were similar to those of the controls. Also, calcium dobesilate totally inhibited the increase in ICAM-1 levels and significantly reduced leukocyte adhesion to retinal endothelial cells induced by diabetes and high glucose levels.
Conclusions: :
Calcium dobesilate is able to prevent the BRB breakdown induced by diabetes, by restoring the tight junction protein levels and distribution in retinal vessels and also by decreasing the leukocyte adhesion to retinal vessels.
Keywords: diabetic retinopathy • protective mechanisms • inflammation