Role of the Src Signaling Pathway in High Glucose-Induced Renal Proximal Tubular Hypertrophy

• Main Authors: LIOU,YAO-BIN, 劉曜賓
• Other Authors: HUANG,JHAO-SIANG
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/50009746098581499813

碩士 === 中華醫事科技大學 === 生物醫學研究所 === 101 === Diabetic nephropathy (DN) is the chief cause of new dialysis patients in our country. Most studies focused on the pathomechanisms of glomerular and tubulointerstitial cells in DN, which is characterized by cellular hypertrophy/hyperplasia and extracellular matrix expansion leading to renal fibrosis and end-stage renal disease. Two key mediators implicated in the development of DN include high glucose (HG) and reactive oxygen species. HG act to increase oxidative stress, promote extracellular matrix protein synthesis and tubulointerstitial fibrosis, and exert a number of toxic effects of renal cells. Renal tubular hypertrophy may be the first step in an inevitable pathophysiologic course, leading ultimately to tubulointerstitial fibrosis and diabetic nephropathy. However, the mechanisms of antioxidants on the HG-induced oxidative stress and renal tubular hypertrophy in DN remain unclear. In this study, we examined the effect of HG on renal tubular growth and the role of Src/ERK signaling in the regulation of cellular hypertrophy. We found that HG inhibited cellular growth dose-dependently in human renal proximal tubular epithelial cells. In addition, HG (500 mg/dl) significantly enhanced the Src/ERK/JNK/p38 signaling activation but not cyclin D1, DMP1, p53, B-myb, and Ets-1 protein expression. These effects were not observed when cells were treated with the osmotic control high mannitol (400 mg/dl). It seems that apoptosis was not observed in these treatments. There were no changes in caspase 3 activity, Bcl-2 and poly(ADP-ribose) polymerase expression in HG-treated cells. Probucol is a diphenolic compound with lipid-lowering effects and antioxidant properties that reverses atherosclerosis. Thus, the effect of probucol on HG-induced renal tubular hypertrophy was also investigated. We found that the antioxidant probucol, the Src family kinase inhibitor PP2, and the ERK inhibitor PD98059 treatments significantly attenuated HG-inhibited cellular growth and HG-induced the Src/ERK activation and cellular hypertrophy. Moreover, probucol and N-acetylcystein treatments reversed HG-reduced the antioxidizing enzyme glutathione S-transferase activity in these cells. The ability of probucol, PP2, or PD98059 to ameliorate renal tubular hypertrophy was also verified by the observation that it significantly blocked HG-increased the protein levels of collagen IV and p27Kip1. Hence, these results suggested that probucol has potent inhibitory effect against HG-induced renal tubular hypertrophy, and the Src/ERK signaling pathway may be important target of probucol.