Curcumin alleviates TGF-β1-induced fibrosis in NRK-49F cells via suppression of miR-21 expression, and regulation of the TGF-β1/smad3 signaling pathway

Abstract

Objective: Overexpression of microRNA-21 (miR-21) has been well-recognized during fibrosis in a wide range of tissue types through regulation of fibrogenesis via diverse pathways. Curcumin exhibits anti-fibrotic effects in various organs. We and others have previously demonstrated that curcumin has positive effects on the protection against fibrosis. However, the effect of curcumin on miR-21 expression has not been reported. Methods: In this study, transforming growth factor-β1 (TGF-β1)-stimulated rat renal fibroblast cells (NRK-49F) were transfected with miR-21 inhibitors, then the expression of Smad3, α-smooth muscle actin (α-SMA), type I collagen (COL1A1), and type Ⅲ collagen (COL3A1) was determined using quantitative real-time-PCR (qRT-PCR) and western blot analysis. The effect of curcumin on production of the extracellular matrix was evaluated using immunofluorescence, qRT-PCR, and western blot analysis. Results: TGF-β1 stimulation upregulated the expression of miR-21 and induced fibrogenesis in NRK-49F cells. Transfection with miR-21 inhibitors selectively decreased smad3 activity, and noticeably reduced the expression of α-SMA, COL1A1, and COL3A1. Curcumin treatment significantly inhibited the expressions of smad3, α-SMA, COL1A1, COL3A1, as well as miR-21 expression in NRK-49F cells in a dose-dependent manner. Conclusion: Curcumin exerted its anti-fibrotic effects by targeting the TGF-β1/smad3 signaling pathway and suppressing miR-21 expression, thereby provides novel insight in the protective effects of curcumin against fibrosis in various organs. Keywords: Curcumin, miR-21, NRK-49F, Renal fibrosis, TGF-β1/Smad3