Protective effects of a coumarin derivative in diabetic rats.
OBJECTIVE
Retinal microvascular cells play a crucial role in the pathogenesis of diabetic retinopathy. The endothelial effects of cloricromene, a novel coumarin derivative, on diabetic retinopathy induced by streptozotocin (STZ) in the rat were investigated.


METHODS
Cloricromene (10 mg/kg intraperitoneally) was administered daily in diabetic rats, and 60 days later eyes were enucleated for localization of nitrotyrosine, ICAM-1, VEGF, ZO-1, occludin, claudin-5, and VE-cadherin by immunohistochemical analysis. The effect of treatment was also evaluated by TNFalpha, ICAM-1, VEGF, and eNOS protein levels measurement in the retina with the respective ELISA kits. Blood-retinal barrier (BRB) integrity was also evaluated by Evans blue.


RESULTS
Increased amounts of cytokines, adhesion molecule, and nitric oxide synthase were observed in retina. Cloricromene treatment significantly lowered retinal TNFalpha, ICAM-1, VEGF, and eNOS. Furthermore, immunohistochemical analysis for VEGF, ICAM-1, nitrotyrosine (a marker of peroxynitrite), and tight junctions revealed positive staining in the retina from STZ-treated rats. The degree of staining for VEGF, ICAM-1, nitrotyrosine, and tight junctions was markedly reduced in tissue sections obtained from diabetic rats treated with cloricromene. Treatment with cloricromene suppressed diabetes-related BRB breakdown by 45%.


CONCLUSIONS
This study provides the first evidence that the new coumarin derivative cloricromene attenuates the degree of inflammation preserving the BRB in diabetic rats.
Bucolo
Claudio
C
Department of Experimental and Clinical Pharmacology, School of Medicine, University of Catania, Catania, Italy. bucocla@unict.it
Ward
Keith W
KW
Mazzon
Emanuela
E
Cuzzocrea
Salvatore
S
Drago
Filippo
F
D000818:Animals; D015703:Antigens, CD / Q000378:metabolism; D001813:Blood-Retinal Barrier / Q000187:drug effects; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D002866:Chromonar / Q000031:analogs & derivatives* / Q000627:therapeutic use; D062507:Claudin-5; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D003930:Diabetic Retinopathy / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D004797:Enzyme-Linked Immunosorbent Assay; D007150:Immunohistochemistry; D007274:Injections, Intraperitoneal; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D062793:Occludin; D010750:Phosphoproteins / Q000378:metabolism; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D062826:Zonula Occludens-1 Protein; D000099152:Cadherin 5
D015703:Antigens, CD; D015820:Cadherins; D002866:Chromonar; D062507:Claudin-5; D018799:Intercellular Adhesion Molecule-1; D008565:Membrane Proteins; D052250:Nitric Oxide Synthase Type III; D062793:Occludin; D010750:Phosphoproteins; D010975:Platelet Aggregation Inhibitors; D014409:Tumor Necrosis Factor-alpha; D014443:Tyrosine; D042461:Vascular Endothelial Growth Factor A; D062826:Zonula Occludens-1 Protein; D000099152:Cadherin 5; C491510:Cldn5 protein, rat; C568987:Ocln protein, rat; C569044:Tjp1 protein, rat; C467498:vascular endothelial growth factor A, rat; C002744:3-nitrotyrosine; C025945:cloricromen; C496316:Nos3 protein, rat