Inhibitory effect of bucillamine on the increased leukocyte entrapment in the retinal microcirculation of diabetic rats.

PURPOSE: To evaluate quantitatively the effects of bucillamine on the entrapment of leukocytes in the retinal microcirculation of diabetic rats. METHODS: 13 male Brown Norway rats were injected with streptozotocin (STZ). After the animals developed diabetes, they were divided into two groups. Group 1 (n=7) received fresh drinking water without bucillamine, and group 2 (n=6) received fresh drinking water supplemented with bucillamine (200 mg/kg per day). Rats that were not injected with STZ and received water without bucillamine served as controls (n=6). Four weeks after the injection of STZ, the leukocytes in the retina were observed by acridine orange digital fluorography. The number of leukocytes trapped in the retinal vessels was compared among the three groups. RESULTS: In the untreated diabetic rats, the number of trapped leukocytes was significantly higher than in control rats or bucillamine-treated diabetic rats (P<0.05). CONCLUSIONS: We demonstrated an inhibitory effect of bucillamine on leukocyte entrapment in the retinal vessels of diabetic rats. Bucillamine may have therapeutic efficacy in preventing the development of diabetic retinopathy.

Characterization of retinal leukostasis and hemodynamics in insulin resistance and diabetes: role of oxidants and protein kinase-C activation.

Increases in leukostasis/monocyte adhesion to the capillary endothelium (leukostasis) and decreases in retinal blood flow may be causally associated and are implicated in the pathogenesis of diabetic retinopathy. In this study, we demonstrate that increases in leukostasis are observed in insulin-resistant states without diabetes, whereas decreases in retinal blood flow require diabetes and hyperglycemia. Microimpaction studies using beads mimicking retinal capillary obstruction by leukocytes did not affect retinal blood flow. In diabetic rats, treatment with the antioxidant alpha-lipoic acid normalized the amount of leukostasis but not retinal blood flow. In contrast, treatment with D-alpha-tocopherol and protein kinase-C beta-isoform inhibition (LY333531) prevented the increases in leukostasis and decreases in retinal blood flow in diabetic rats. Serum hydroxyperoxide, a marker of oxidative stress, was increased in diabetic rats, but normalized by treatment with antioxidants alpha-lipoic acid and D-alpha-tocopherol and, surprisingly, PKC beta-isoform inhibition. These findings suggest that leukostasis is associated with endothelial dysfunction, insulin resistance, and oxidative stress but is not related to retinal blood flow and is not sufficient to cause diabetic-like retinopathy. Moreover, treatment with PKC beta inhibition is effective to normalize diabetes or hyperglycemia-induced PKC beta-isoform activation and oxidative stress.