Increased expression of phosphorylated Smad2 and Smad3 in the hippocampus of streptozotocin-induced diabetic rats

Abstract

Activation of the Smad signalling pathway has been implicated in the pathological process of diabetic associated complications. The current study was designed to see whether Smad signalling was activated in the hippocampus of streptozotocin-induced diabetic rats. Compared with vehicle-treated controls, immunoblot analysis of hippocampal extracts showed that phosphorylated Smad2 was upregulated at 8 weeks post streptozotocin induction (p<0.01), and phosphorylated Smad3 protein was upregulated at 4 and 8 weeks post streptozotocin induction (p<0.01) in streptozotocin-induced diabetic rats. In addition, immunofluorescence labelling assay showed that the percentage of pSmad2 immunoreactive astrocytes increased significantly in CA1, CA3 and dentate gyrus region (p<0.01), and pSmad3 immunoreactive astrocytes increased significantly in CA1 region (p<0.01) and in CA3 and dentate gyrus region (p<0.05) of the hippocampus in diabetic rats. These data indicate that Smad signalling is enhanced in hippocampal astrocytes of diabetic rats, and may thereby represent a clue to explore its exact role in the development of diabetic encephalopathy.