Kallistatin protects against diabetic nephropathy in db/db mice by suppressing AGE-RAGE-Induced oxidative stress

Abstract

BACKGROUND: Kallistatin is a serine protease inhibitor that exerts anti-inflammatory Anti-apoptotic and anti-oxidative effects in regulating cellular dysfunction. As oxidative stress plays a critical role in the pathogenesis of diabetic nephropathy, we aim to investigate the effect and mechanisms of kallistatin gene transfer on diabetic renal injury in the db/db mouse model of type 2 diabetes. METHODS: Plasmid with kallistatin gene was injected into the kidney of db/db mice using ultrasound-mediated microbubble-inducible gene transfer. The therapeutic potential of kallistatin in diabetic kidney was evaluated by histopathology, renal function, oxidative and fibrotic pathways. RESULTS: Kallistatin expression was induced in tubules of kidney after gene transfer compared with mice treated with empty plasmid. In db/db mice, kallistatin overexpression reduced serum creatinine and BUN levels, ameliorated glomerulosclerosis and tubulointerstitial injury and attenuated renal fibrosis by inhibiting TGF-β signaling and the downstream plasminogen activator inhibitor-1 and type IV collagen expression. Furthermore, kallistatin gene transfer significantly attenuated elevated oxidative stress in db/db mice as evidenced by suppressed levels of Nox4 and the oxidative marker (8-OHdG and MDA) in diabetic renal tissue. Finally, kallistatin inhibited expression of RAGE in both diabetic kidney and AGE-stimulated cultured proximal tubular epithelial cells, reflecting an anti-oxidative mechanism via AGE/RAGE axis. CONCLUSIONS: Our results suggest a renoprotective role of kallistatin against progression of diabetic nephropathy via anti-oxidative properties. Kallistatin reduced AGE-RAGE induced Nox4 expression, leading to suppression of oxidative stress and TGF-β-mediated renal fibrosis. Funding: Research Grants Council of Hong Kong (GRF grant number 7796/11M) and the National Basic Research Program of China 973 program no. 2012CB517600 (no 2012CB517606).