Figure 1.

Western blot analysis of high-mobility group box-1 (HMGB1), extracellular signal-regulated kinase 1 and 2 (ERK1/2), cleaved caspase-3, synaptophysin, tyrosine hydroxylase, glutamine synthetase, and glyoxalase 1 in rat retinas. β-Actin was used as a housekeeping control. Protein expression of ERK1/2 activation (phosphorylation) was quantified by Western blot analysis using phospho- (P-) ERK1/2 specific antibody and was adjusted to the protein levels of unphosphorylated ERK1/2 antibody in each sample. There is a significant increase in the expression of HMGB1 (a), activated ERK1/2 (b), and cleaved caspase-3 (c) and a significant decrease in the expression of synaptophysin (d), tyrosine hydroxylase (e), glutamine synthetase (f), and glyoxalase 1 (g) in the retinas of diabetic rats compared to nondiabetic controls. Glycyrrhizic acid (GA) significantly attenuated diabetes-induced upregulation of HMGB1 (a), activated ERK1/2 (b), and cleaved caspase-3 (c) and diabetes-induced downregulation of synaptophysin (d), tyrosine hydroxylase (e), GS (f), and glyoxalase 1 (g). Glutamate assay revealed a significant increase in glutamate levels in the retinas of diabetic rats compared to nondiabetic controls. The levels of glutamate in the GA-treated diabetic rats were significantly less than those in the untreated diabetic rats (h). Each experiment was repeated at least 3 times with fresh samples. A representative set of samples is shown. Results are expressed as mean ± SD of at least 6 rats in each group. *P < 0.05 compared with nondiabetic control rats. ^# P < 0.05 compared with diabetic rats.