Effects of berberine on matrix accumulation and NF-kappa B signal pathway in alloxan-induced diabetic mice with renal injury

One of the main pathological changes in diabetic nephropathy is the renal fibrosis, which includes glomerulosclerosis and tubulointerstitial fibrosis. In vivo and in vitro studies demonstrated that berberine could ameliorate renal dysfunction in diabetic rats with nephropathy and inhibit fibronectin expression in mesangial cells cultured under high glucose. However, the molecular mechanisms have not been fully elucidated. The purpose of the present study was to investigate the effects of berberine on the nuclear factor-kappa B (NF-κB) activation, intercellular adhesion molecule-1, transforming growth factor-beta1 and fibronectin protein expression in renal tissue from alloxan-induced diabetic mice with renal damage. The distribution of NF-κB p65 in glomerulus and the degradation of IκB-α in renal cortex were examined by immunohistochemistry and Western blot, respectively. The protein expression of intercellular adhesion molecule-1, transforming growth factor-beta 1 and fibronectin in renal cortex were also detected by Western blot. Our results revealed that in alloxan-induced diabetic mice, the nuclear staining of NF-κB p65 was increased in glomerulus, whereas renal IκB-α protein was significantly reduced. The protein levels of intercellular adhesion molecule-1, transforming growth factor-beta 1 and fibronectin were upregulated in kidney from diabetic mice. After berberine treatment, the immunostaining of NF-κB was decreased, and the reduced degradation of IκB-α level was partially restored. The protein levels of intercellular adhesion molecule-1, transforming growth factor-beta 1 and fibronectin were all downregulated by berberine compared with diabetic model group. In conclusion, the ameliorative effects of berberine on extracellular matrix accumulation might associate with its inhibitory function on NF-κB signal pathway.