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1From the Departments of Ophthalmology, 3Medicine, 5Pathology, and 6Pharmacology, Case Western Reserve University, Cleveland, Ohio; the 2Department of Anesthesiology, Cleveland Clinic Foundation, Cleveland, Ohio; and the 4Louis Stokes Veterans Affairs Medical Center, Cleveland, Ohio.
PURPOSE. To determine effects of 
-dicarbonyl modification of an extracellular matrix protein on retinal capillary pericyte attachment and viability.
METHODS. Primary cultures of bovine retinal pericytes (BRPs) were seeded on either normal fibronectin (FN) or FN modified by methylglyoxal (MGO) and glyoxal (GO). Apoptosis was measured by flow cytometry along with caspase-3 activity. Phosphorylation of p38 mitogen-activated protein kinase (MAPK) and Akt/PKB were evaluated by Western blot analysis. Cellular glutathione and reactive oxygen species were measured. B-crystallin was measured by Western blot analysis and, to determine its role in apoptosis, experiments were conducted using BRPs that were transiently transfected with B-crystallin.
RESULTS. Cultures seeded on MGO- or GO-modified FN showed a significant reduction in the number of viable cells, an increase in the number of apoptotic cells, and increased caspase-3 activity, which correlated with the extent of FN modification. Pericytes seeded on either type of modified FN showed phosphorylation of p38 MAPK and dephosphorylation of Akt/PKB. Cultures seeded on dicarbonyl-modified FN had reduced glutathione and increased levels of reactive oxygen species compared with those on a normal matrix. Cells on the altered matrices had reduced B-crystallin levels as well. Transient transfection of rat B-crystallin into BRPs significantly reduced the apoptosis triggered by -dicarbonyl–modified FN.
CONCLUSIONS. These observations indicate that modification of FN by -dicarbonyl compounds triggers apoptosis through a combination of increased oxidative stress and reduction of B-crystallin. This mechanism may contribute to loss of pericytes in diabetic retinopathy and contribute to the resultant vascular lesions.
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