TOXIC ACTION OF ADVANCED GLYCATION END-PRODUCTS ON CULTURED RETINAL CAPILLARY PERICYTES AND ENDOTHELIAL-CELLS - RELEVANCE TO DIABETIC-RETINOPATHY

The toxic effects of advanced glycation end products (AGEs) on bovine retinal capillary pericytes (BRP) and endothelial cells (BREC) were st udied. AGE-modified bovine serum albumin (AGE-BSA) was toxic to BRP. A t a concentration of 500 mu g/ml it reduced the BRP number to 48 +/- 3 % (p < 0.05) of untreated controls, as determined by cell counting wit h haemocytometer. AGE-BSA was also toxic to bovine aortic endothelial cells (BAEC) reducing cell number to 84 +/- 3.1% of untreated controls . Under similar conditions, low concentrations (62.5 mu g/ml) of AGE-B SA were mitogenic to BREC increasing the cell proliferation to 156 +/- 11% (p < 0.05) above that of untreated controls. At a higher dose of 500 mu g/ml AGE-BSA. decreased the proliferation of BREC to 85 +/- 6% of untreated controls Immunoblot analysis demonstrated that BRP and BR EC express the p60 AGE-receptor. Retinal capillary bed from the human also stained positively for the p60 AGE-receptor. Addition of 0.25 mu g/ml of p60 AGE-receptor antibody was able to block the effects of AGE -BSA on BRP and BREC. The level of binding of [I-125]-labelled AGE-BSA to the cell-surface was small but significant among the three cell ty pes. There was also an increase in the internalized pool of radioligan d in BRP and BREC but this was very much lower than in BAEC. In all th e cell types the internalized pool of [I-125]-labelled AGE-BSA was muc h larger than the amount associated with the cell surface. Degradation products were not detected in the media over the 24-h incubation of t he cells with [I-125]AGE-BSA. The binding of [I-125]-labelled AGE-BSA to the cell surface was prevented by the addition of p60 AGE-receptor. These results suggest that the interaction of AGE-modified proteins w ith the membrane-bound AGE-receptor may play an important role in the pathogenesis of diabetic retinopathy.