Abstract
Purpose: :
Several evidences strongly support the existence of an inflammatory component, including leukostasis, in the pathogenesis of Diabetic Retinopathy. It is also known that Muller cells regulate blood-retinal barrier. However, it is unknown whether Muller cells can influence leukocyte adhesion to endothelial cells. In this study, we aimed to investigate whether Muller cells could affect both the expression of ICAM-1, an adhesion molecule, in retinal vascular endothelial cells and leukocyte adhesion to endothelial cells.
Methods: :
Rat retinal endothelial cells (TR-iBRB2 cell line) and rat retinal Muller cells (TR-MULL cell line), alone or in co-culture, were exposed to high glucose (30 mM; 4 days), H2O2 (100 µM; 24 h) or to a nitric oxide donor (NOC-18, 100 µM; 24 h). Also, endothelial cells were incubated with conditioned Muller cell medium for 24 h. ICAM-1 protein levels were assessed by Western blotting and immunocytochemistry and leukocyte adhesion to endothelial cells was quantified using an in vitro fluorescence assay.
Results: :
High glucose and oxidative/nitrosative stress conditions significantly increased ICAM-1 levels in endothelial cells and leukocyte adhesion. In both endothelial cells exposed to conditioned medium of Muller cells, non-treated or treated with high glucose, H2O2 or NOC-18, and in co-cultures of endothelial cells with Muller cells, the increases in ICAM-1 protein levels and leukocyte adhesion to endothelial cells were similar to those found in endothelial cells cultured alone exposed to the same treatments.
Conclusions: :
These results indicate that Muller cells do not influence the ICAM-1 levels in retinal endothelial cells and leukocyte adhesion either in control or stress conditions.
Keywords: diabetic retinopathy • inflammation • Muller cells