Abstract
BackgroundEpithelial-to-mesenchymal transition (EMT) plays an important role in the progression of renal interstitial fibrosis, which finally leads to renal failure. Oleanolic acid (OA), an activator of NF-E2-related factor 2 (Nrf2), is reported to attenuate renal fibrosis in mice with unilateral ureteral obstruction. However, the role of OA in the regulation of EMT and the underlying mechanisms remain to be investigated. This study aimed to evaluate the effects of OA on EMT of renal proximal tubular epithelial cell line (NRK-52E) induced by TGF-β1, and to elucidate its underlying mechanism.MethodsCells were incubated with TGF-β1 in the presence or absence of OA. The epithelial marker E-cadherin, the mesenchymal markers, α-smooth muscle actin (α-SMA), fibronectin, Nrf2, klotho, the signal transducer (p-Smad2/3), EMT initiator (Snail), and ILK were assayed by western blotting.ResultsOur results showed that the NRK-52E cells incubated with TGF-β1 induced EMT with transition to the spindle-like morphology, down-regulated the expression of E-cadherin but up-regulated the expression of α-SMA and fibronectin. However, the treatment with OA reversed all EMT markers in a dose-dependent manner. OA also restored the expression of Nrf2 and klotho, decreased the phosphorylation of Smad2/3, ILK, and Snail in cells which was initiated by TGF-β1.ConclusionOA can attenuate TGF-β1 mediate EMT in renal tubular epithelial cells and may be a promising therapeutic agent in the treatment of renal fibrosis.
Highlights
Epithelial-to-mesenchymal transition (EMT) plays an important role in the progression of renal interstitial fibrosis, which leads to renal failure
Effects of Oleanolic acid (OA) on transforming growth factor-β1 (TGF-β1)-induced EMT in NRK-52E cells To determine whether OA suppressed TGF-β1-induced EMT in NRK-52E cells, we studied the cells morphology by Phase-contrast microscopy and the expression level of EMT related proteins by western blotting
Phase-contrast microscopy revealed that the cells displayed an elongated, and spindle-like shapes after the incubation with TGF-β1
Summary
Epithelial-to-mesenchymal transition (EMT) plays an important role in the progression of renal interstitial fibrosis, which leads to renal failure. This study aimed to evaluate the effects of OA on EMT of renal proximal tubular epithelial cell line (NRK-52E) induced by TGF-β1, and to elucidate its underlying mechanism. Accumulating evidences show that EMT occurred in kidney plays an important role in the progression of renal interstitial fibrosis [4,5,6,7]. It is important to understand the mechanism to reverse EMT which is valuable establishing therapeutic He et al BMC Complementary and Alternative Medicine (2018) 18:205. Study shows that Nrf can restore the klotho expression and protect against renal fibrosis [32]. Protective effects of OA, an Nrf activator, against renal fibrosis induced by TGF-β1 has not been investigated
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