Calcium dobesilate inhibits the alterations in tight junction proteins and leukocyte adhesion to retinal endothelial cells induced by diabetes.
OBJECTIVE
Calcium 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.


METHODS
Wistar 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.


RESULTS
Diabetes 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.


CONCLUSIONS
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.
Leal
Ermelindo C
EC
Center of Ophthalmology and Vision Sciences, IBILI, Faculty of Medicine, University of Coimbra, Coimbra, Portugal. eleal@ibili.uc.pt
Martins
João
J
Voabil
Paula
P
Liberal
Joana
J
Chiavaroli
Carlo
C
Bauer
Jacques
J
Cunha-Vaz
José
J
Ambrósio
António F
AF
D000818:Animals; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000502:physiology; D002123:Calcium Dobesilate / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D062507:Claudin-5; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D003930:Diabetic Retinopathy / Q000378:metabolism / Q000503:physiopathology* / Q000517:prevention & control; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D004727:Endothelium / Q000187:drug effects / Q000502:physiology; D006490:Hemostatics / Q000494:pharmacology; D007962:Leukocytes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D062793:Occludin; D010539:Permeability / Q000187:drug effects; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012160:Retina / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology*; D062826:Zonula Occludens-1 Protein
D062507:Claudin-5; C491510:Cldn5 protein, rat; D006490:Hemostatics; D008565:Membrane Proteins; D062793:Occludin; C568987:Ocln protein, rat; D010750:Phosphoproteins; C569044:Tjp1 protein, rat; D062826:Zonula Occludens-1 Protein; D002123:Calcium Dobesilate