The role of high-mobility group box-1 protein in the development of diabetic nephropathy

Background/Aims: The purpose of the experiment reported here was to assess the involvement of high-mobility group box-1 (HMGB1), receptor for advanced glycation end products (RAGE) and nuclear factor (NF)-κB signaling pathway in the development of rat diabetic nephropathy. Methods: Diabetes was induced by intraperitoneal streptozotocin injection in 7-week-old male rats. At 20 weeks of age, renal expression of HMGB1 was detected by immunohistochemistry. The expression of RAGE and NF-κB activity was studied by Western blot and electrophoretic mobility shift assay in renal tissues of normoglycemic and diabetic rats, respectively. Results: HMGB1 was highly expressed in both the cytoplasmic and nuclear patterns in diabetic renal glomerular cells and tubular epithelial cells, although in normal rats, HMGB1 was expressed only in the cell nuclei. The expression of RAGE, a potential receptor for HMGB1, and NF-κB activity were also greater in diabetic than in normal rats. Moreover, diabetes increased the binding of NF-κB to the RAGE promoter. Conclusion: These findings suggest that hyperglycemia-induced HMGB1 release may induce the renal injury in diabetic rats, and that the pathogenic role of HMGB1 might be dependent on RAGE and through activation of NF-κB.