BACKGROUND: Renal tubulointerstitial fibrosis is mainly featured as the accumulation of extracellular matrix (ECM) in renal interstitium. The tubular epithelial-myofibroblast transdifferentiation (TEMT) is important to the pathogenesy of renal tubulointerstitial fibrosis. OBJECTIVE: To examine the effects of sodium ferulate (SF) on TEMT, and ECM main components such as collagen Ⅰ, collagen Ⅲ and fibronectin, in rat renal tubular epithelial cellsinduced by transforming growth factor-beta 1 (TGF- β1)- DESIGN: Randomized and controlled experimental study based on cells. SETTING: Department of Kidney in West China Hospital of Sichuan University. MATERIALS: Rat renal tubular epithelial cells (NRK-52E) originated from American Type Culture Collection (ATCC), were offered by the laboratory of Department of Nephrology in Australian Monash Medical Center. Cell strain used in this study was cultured at the 36th passage. SF white crystal with water solubility and more than 98.0% purify, was from Chengdu Hengda Pharmaceutical Co., Ltd. Different concentrations of SF (125,250, 500μreel/L) were designed in this study. Rabbit anti-rat α-smooth muscle actin (α -SMA) was produced by Wuhan Boster Company. Enzyme-linked immunosorbent assay (ELISA) kit was the produced of Shanghai Senxiong Science and Technology Co.,Ltd. Human recombinant TGF- β1 was produced by R&D Company. DNA Engine OpticonTM real-time fluorescence quantitative polymerase chain reaction apparatus was the product of MJ Research Company. METHODS: Rat renal tubular epithelial cells (NRK-52E) cultured in vitro were divided into five groups. Control group was added with serum-contained DMEM; TGF-β1-induced group was added with TGF-β1 at final concentration of 5 ng/L; SF at different concentrations groups were added with 125, 250, 500 μ mol/L SF and TGF- β1 at final concentration of 5 ng/L,respectively. MAIN OUTCOME MEASURES: The contrast phase microscope, real-time fluorescence quantitative polymerase chain reaction and ELISA method were used to detect TEMT of NRK52E cells induced by TGF-β1 and levels of collagen Ⅰ, collagen Ⅲ and fibronectin in the supernatant. RESULTS: Morphology of NRK52E cells: Compared with control group, TGF-β1 could induce the transdifferentiation of NRK52E cells, showing fibroblast-like in morphology after 3 days, which were previously the typical road stone-like epithelial cells. In three different concentration SF groups, the morphologic transformation stimulated by TGF-β1 could be partly ameliorated in a dose-dependent manner. Expression of α-SMA mRNA: Compared with control group, 5 ng/L TGF- β1 enhanced expression of α-SMA at 6 hours, and reached a peak at 72 hours; SF depressed the expression in a dose-dependent manner at 72 hours (P < 0.05). Changes of ECM: After induced by 5 ng/L TGF- β1 for 72 hours, the levels of collagen Ⅰ, collagen Ⅲ and fibronectin in the supernatant increased significantly (P < 0.05), whereas SF decreased these levels in a dose-dependent manner (P < 0.05). CONCLUSION: TGF- β1 induces the TEMT, and promotes the secretion of collagen Ⅰ, collagen Ⅲ and fibronectin. SF can inhibit TGF- β1-induced TEMT In a dose-dependent manner.

BACKGROUND: Connective tissue growth factor (CTGF) is a kind of factor that can mediate downstream action of transforming growth factor-β 1 (TGF- β 1). The upregulation of connective tissue growth factor expression plays an important role in pathological changes of renal interstitial fibrosis.OBJECTIVE: To explore the effect of Sodium Ferulate on the expression of CTGF mRNA and protein in rats with unilateral ureteral obstruction (UUO) and pathological changes of renal interstitial fibrosis, and to compare with Losartan.DESIGN: Randomized and controlled animal trial.SETTING: Department of Nephrology, West China Hospital of Sichuan University, and College of Public Health, Sichuan University.MATERIALS: Twenty-four healthy adult male SD rats were selected from the Experimental Animal Center of Sichuan University. Sodium Ferulate was provided by Sichuan Hengda Pharmacy Co, Ltd (No. 050302); rabbit anti-rat CTGF by Santa Cruz; Western blotting by BioRAD, USA; DNA Engine OpticonTM real-time fluorescent quantitation PCR device by MJ Research, USA.METHODS: The experiment was performed at Research Laboratory of Clinical Medicine (grade BSL-1), College of Public Health, Sichuan University from May to December 2006. Twenty-four healthy rats were randomly divided into 4 groups (n=6): UUO model group, Sodium Ferulate group, Losartan group, and sham-operation group. According to the previous protocol, UUO models were established in UUO model group, Sodium Ferulate group, and Losartan group, and the other rats were subjected to sham operation. From the first day after UUO, Sodium Ferulate group was intragastrically (i.g.)administrated with 150 mg/kg/d Sodium Ferulate; Losartan group was administrated ig. with 20 mg/kg/d. Losartan; UUO and sham operation groups were administrated i.g. with matching normal saline. All rats were executed 14 days after UUO to harvest partial renal tissues. All experimental procedure was accorded with animal ethical standards.MAIN OUTCOME MEASURES: The mRNA and protein expressions of CTGF were quantified by real-time PCR and Western blot. The pathological changes of renal interstitial tissues were observed by hematoxylin/eosin (HE) and Masson staining.RESULTS: Twenty-four rats were included in final analysis. Fourteen days after UUO, CTGF mRNA and protein expressions in UUO model group were significantly increased compared with sham operation group, but the expressions in Sodium Ferulate group were significantly lower than model group (P < 0.05). Compared with Losartan treated group, there was no significant difference (P > 0.05). HE and Masson staining showed inflammatory cell infiltration and tubular and interstitial changes as well as collagen deposition in renal interstitial tissues on day 14 after UUO. Sodium Ferulate obviously improved the renal pathological changes in UUO rats (P < 0.05), and the effect was similar to Losartan (P > 0.05).CONCLUSION: Sodium Ferulate inhibits UUO-induced renal interstitial fibrosis. This action, similar to the effect of Losartan, might be due to downregulation of CTGF expression.