OBJECTIVECalcium dobesilate (CaD) has been used in the treatment of diabetic retinopathy in the last decades, but its mechanisms of action are not elucidated. CaD is able to correct the excessive vascular permeability in the retina of diabetic patients and in experimental diabetes. We investigated the molecular and cellular mechanisms underlying the protective effects of CaD against the increase in blood–retinal barrier (BRB) permeability induced by diabetes.RESEARCH DESIGN AND METHODSWistar rats were divided into three groups: controls, streptozotocin-induced diabetic rats, and diabetic rats treated with CaD. The BRB breakdown was evaluated using Evans blue. The content or distribution of tight junction proteins (occludin, claudin-5, and zonula occluden-1 [ZO-1]), intercellular adhesion molecule-1 (ICAM-1), and p38 mitogen-activated protein kinase (p38 MAPK) was evaluated by Western blotting and immunohistochemistry. Leukocyte adhesion was evaluated in retinal vessels and in vitro. Oxidative stress was evaluated by the detection of oxidized carbonyls and tyrosine nitration. NF-κB activation was measured by enzyme-linked immunosorbent assay.RESULTSDiabetes increased the BRB permeability and retinal thickness. Diabetes also decreased occludin and claudin-5 levels and altered the distribution of ZO-1 and occludin in retinal vessels. These changes were inhibited by CaD treatment. CaD also inhibited the increase in leukocyte adhesion to retinal vessels or endothelial cells and in ICAM-1 levels, induced by diabetes or elevated glucose. Moreover, CaD decreased oxidative stress and p38 MAPK and NF-κB activation caused by diabetes.CONCLUSIONSCaD prevents the BRB breakdown induced by diabetes, by restoring tight junction protein levels and organization and decreasing leukocyte adhesion to retinal vessels. The protective effects of CaD are likely to involve the inhibition of p38 MAPK and NF-κB activation, possibly through the inhibition of oxidative/nitrosative stress.

Calcium dobesilate (CaD) has been prescribed to some patients in the early stages of diabetic retinopathy to delay its progression. We previously reported that the treatment of diabetic animals (4 weeks of diabetes) with CaD, during the last 10 days of diabetes, prevents blood-retinal barrier breakdown. Here, we aimed to investigate whether later treatment of diabetic rats with CaD would reverse inflammatory processes in the retina. Diabetes was induced with streptozotocin, and 6 weeks after diabetes onset, CaD (100 mg/kg/day) was administered for 2 weeks. The treatment with CaD significantly increased glial fibrillary acidic protein (GFAP) levels in the retina of nondiabetic animals (138.6 ± 12.8% of control) and enhanced the diabetes-induced increase in GFAP levels (174.8 ± 5.6% of control). In addition, CaD prevented the increase in mRNA and protein expression of tumor necrosis factor and interleukin-1β, as well as the formation of oxidized carbonyl residues and the increase in nitrotyrosine immunoreactivity, particularly in the ganglion cell layer of diabetic animals. We demonstrate that the treatment of diabetic animals with CaD can reverse the established proinflammatory processes in the retina. These beneficial effects appear to be attributed, at least partially, to the antioxidant properties of CaD.

Purpose Calcium dobesilate (CaD) is used in the treatment of diabetic retinopathy, but its mechanism of action is not completely elucidated. We investigated the molecular and cellular mechanisms underlying the protective effects of CaD against the blood‐retinal barrier (BRB) breakdown induced by diabetes. Methods Wistar rats were divided into: controls, diabetic (1 month diabetes duration) and diabetic treated with CaD (100 mg/kg/day; orally given) during the last 10 days. The BRB breakdown was evaluated using Evans blue. The content or distribution of occludin, claudin‐5, ZO‐1, ICAM‐1 and p38 MAPK was evaluated by western blotting and immunohistochemistry. Leukocyte adhesion was evaluated in retinal vessels and in vitro. Oxidative stress was evaluated by the detection of oxidized carbonyls and tyrosine nitration. NF‐κB activation was measured by ELISA. Results Diabetes increased the BRB permeability and retinal thickness, decreased occludin and claudin‐5 levels, and altered the distribution of ZO‐1 and occludin in retinal vessels. CaD inhibited these changes, as well as the increase in ICAM‐1 levels and leukocyte adhesion to retinal vessels or endothelial cells induced by diabetes or high glucose. Moreover, CaD decreased oxidative stress, and p38 MAPK and NF‐κB activation caused by diabetes. Conclusion CaD prevents the BRB breakdown induced by diabetes by restoring tight junction protein levels and organization and decreasing leukocyte adhesion to retinal vessels. The protective effects of CaD are likely to involve the inhibition of p38 MAPK and NF‐κB activation, possibly through the inhibition of oxidative/nitrosative stress. Support: OM Pharma SA, Switzerland