Abstract

BACKGROUND
One of the histopathological hallmarks of early diabetic retinopathy is the loss of pericytes. Evidences suggest that this pericyte loss in vivo is mediated by apoptosis. However, the underlying cause of pericyte apoptosis is not fully understood. This study investigated the influence of methylglyoxal(MGO), a reactive alpha-dicarbonyl compound of glucose metabolism, on the apoptotic cell death in retinal pericytes. METHODS: Primary cultures of retinal pericytes were prepared from isolated bovine retinal microvessels. The cells were incubated under normoglycemic conditions after treatment with 200-800muM methylglyoxal for 6 hours. The cell viability was assessed using the MTT assay. The apoptosis and intracellular reactive oxygen species(ROS) generation were measured using an ELISA kit and flow cytometry, respectively. The NF-kappaB activation was detected by immunocytochemistry. RESULTS: MGO produced a progressive cytotoxic effect on the retinal pericytes. An analysis of the internucleosomal DNA fragmentation by ELISA showed that MGO(200 to 800muM) induced apoptosis in a concentration-dependent manner. ROS were generated earlier and the antioxidant, N-acetyl cysteine, inhibited the MGO-induced apoptosis. The NF-kappaB activation and increased caspase-3 activity were detected. The apoptosis was also inhibited by the caspase-3 inhibitor, Z-DEVD-fmk, or the NF-kappaB inhibitor, pyrrolidine dithiocarbamate. CONCLUSION: These results suggest that the elevated MGO levels observed in diabetes may cause apoptosis in the retinal pericytes through an oxidative stress mechanism, and suggests that the nuclear activation of NF-kappaB is involved in the apoptotic process.

• Keywords: Retinal pericytes;Methylglyoxal;Apoptosis;ROS;NF-kappaB;