Effects of ubiquitin-proteasome inhibitor MG132 on expression of Smad7 in retina of rats with diabetes mellitus

Objective To investigate the effects of ubiquitin-proteasome inhibitor MG132 on Smad7 expression in the retina of rats with diabetes mellitus(DM) induced by streptozotocin,then further study the relationship of Smad7 and diabetic retinopathy(DR),and provide a new way for prevention and early treatment of DR.Methods Sixty male Wistar rats were divided into three groups randomly:Normal control group,DM+MG132 group and DM group.DM model was established by intraperitoneal injection of 50 mg·kg-1 STZ.0.1 mg·kg-1 of MG132 DMSO was intraperitoneal injected once per day in DM+MG132 group and the same volume of DMSO was intraperitoneal injected once per day in normal control group and DM group after modeling 3 days.At 8 weeks and 12 weeks,the rats were sacrificed and removed eyeballs to make the eye cups.Smad7 protein expression was detected by immunohistochemistry in the retina.The results were showed by means plus or subtracting standard,the groups means was compared by ONE-WAY AONVA,the deviation of between groups means was compared by Student-Newman-Keuls.Results The Smad7 was expressed highly in rat retina of normal control group.The value of average optical density(OD) of Smad7 at 8 weeks and 12 weeks were 0.340 8±0.000 7 and 0.119 3±0.002 8 in rat retina of DM group,which were lower than those of normal control group(0.879 3±0.001 5 and 0.960 5±0.002 1),there were significant differences(both P0.01).The value of OD of Smad7 at 8 weeks and 12 weeks were 0.486 4±0.001 5 and 0.590 4±0.012 2 in rat retina of DM+MG132 group,which were lower than those of normal control group,there were significant differences(both P0.01).The expression of Smad7 was significantly elevated in DM+MG132 group compared with DM group at 8 weeks and 12 weeks,there were significant differences(both P0.01).Conclusion The expression of Smad7 was effectively inhibited by MG132.MG132 is expected to become one of the new therapeutic methods because it has protective retina role in rat with DR.