Norcantharidin Inhibits Renal Interstitial Fibrosis by Blocking the Tubular Epithelial-Mesenchymal Transition

Ying Li,Shaobin Duan,Lin Sun,Youming Peng,Hong Liu,Yiyun Xi,Yuping Liu,Tao Hou,Hua Li,Yanhua You,Min Wang,Fuyou Liu,Shuai Wang,Li Xiao,Yan Sun,Jun Li,Emmanuel A Burdmann

doi:10.1371/journal.pone.0066356

Abstract

Epithelial–mesenchymal transition (EMT) is thought to contribute to the progression of renal tubulointerstitial fibrosis. Norcantharidin (NCTD) is a promising agent for inhibiting renal interstitial fibrosis. However, the molecular mechanisms of NCTD are unclear. In this study, a unilateral ureteral obstruction (UUO) rat model was established and treated with intraperitoneal NCTD (0.1 mg/kg/day). The UUO rats treated with NCTD showed a reduction in obstruction-induced upregulation of α-SMA and downregulation of E-cadherin in the rat kidney (P<0.05). Human renal proximal tubule cell lines (HK-2) stimulated with TGF-β1 were treated with different concentrations of NCTD. HK-2 cells stimulated by TGF-β1 in vitro led to downregulation of E-cadherin and increased de novo expression of α-SMA; co-treatment with NCTD attenuated all of these changes (P<0.05). NCTD reduced TGF-β1-induced expression and phosphorylation of Smad2/3 and downregulated the expression of Snail1 (P<0.05). These results suggest that NCTD antagonizes tubular EMT by inhibiting the Smad pathway. NCTD may play a critical role in preserving the normal epithelial phenotype and modulating tubular EMT.

Highlights

Norcantharidin (NCTD), an important derivative of cantharidin, is a specific protein phosphatase inhibitor with anti-cancer, inflammation modulation, anti-fibrosis, anti-oxidation and leukocytic effects [1]
NCTD regulates the expression of alpha-smooth muscle actin (a-SMA), E-cadherin and TGF-b1 in the kidneys of ureteral obstruction (UUO) rats
We investigated the effects of NCTD on the expression of aSMA, E-cadherin and TGF-b1 in obstructive nephropathy, a well characterized and widely used model of renal interstitial fibrosis

Summary

Introduction

Norcantharidin (NCTD), an important derivative of cantharidin, is a specific protein phosphatase inhibitor with anti-cancer, inflammation modulation, anti-fibrosis, anti-oxidation and leukocytic effects [1]. Epithelial-mesenchymal transition (EMT) is an important pathway in myofibroblast production and is a key mechanism in the pathogenesis and progression of renal interstitial fibrosis [8,9,10]. Using cell lineage tracking techniques to track renal epithelial cells, the authors of those two groups found no evidence to suggest that epithelial cells migrate outside of the tubular basement membrane and differentiate into interstitial myofibroblasts in vivo. This conflicting results may be due to technical differences, underlining the complexity of the EMT process.

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Conclusion