Effect of Sodium Ferulate on Transdifferentiation and Extracellular Matrix of Rat Renal Tubular Epithelial Cells Induced by Transforming Growth Factor Beta 1

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 epithe lial cells induced 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 36(superscript th) 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, 500 μ mol/L) were designed in this study. Rabbit anti-rat a -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 Opticon(superscript TM) real-time fluorescence quantitative polymerase chain reaction apparatus was the product of Mi 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 1-induced group was added with TOF-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 TGFβ1 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.