Beta-casomorphin-7 prevents epithelial-mesenchymal transdifferentiation of NRK-52E cells at high glucose level: Involvement of AngII-TGF-β1 pathway.

Hyperglycemia is the most important risk factor in the progression of renal fibrosis in diabetic kidney. Based on previous studies, β-casomorphin-7 may exert anti-fibrotic activities in diabetic rats. However, the role of β-casomorphin-7 in the pathogenesis of renal tubulointerstitial fibrosis remains unclear. Thus, this study was designed to investigate the protective effect of β-casomorphin-7 on epithelial-mesenchymal transition (EMT) of NRK-52E cells treated under hyperglycemic condition and to explore the possible mechanism. NRK-52E cells were cultured in high glucose (30 mM) for 3 days. Different concentrations of β-casomorphin-7, naloxone (antagonist of opioid receptor) and losartan (antagonist of angiotensin II type I receptor) were added in the culture. Expression of α-smooth muscle actin (α-SMA), E-cadherin, vimentin and cytokeratin19 mRNA were determined by real-time PCR. Protein levels of E-cadherin and α-SMA were analyzed by Western blotting. The concentrations of angiotensin (Ang) II and transforming growth factor β1 (TGF-β1) in the culture medium were determined. High glucose-induced up-regulation of vimentin mRNA and α-SMA mRNA and protein were significantly inhibited by β-casomorphin-7. On the contrary, high glucose-induced down-regulation of cytokeratin19 mRNA and E-cad mRNA and protein was significantly reversed by β-casomorphin-7. β-casomorphin-7 significantly alleviate high glucose induced increase of AngII and TGF-β1 in the culture. Moreover, losartan significantly attenuated the expression of TGF-β1 and EMT of NRK-52E cells treated under hyperglycemic condition. But naloxone did not affect the EMT of NRK-52E cells treated by high glucose and β-casomorphin-7. We demonstrate that β-casomorphin-7 has the potential to inhibit high glucose-induced renal proximal tubular EMT partly by modulating AngII-TGF-β1 pathway, but not by opioid receptor.

Zhang W ，Song S ，Liu F ，Liu Y ，Zhang Y ... -  《-》

Angiotensin AT1 receptor activation mediates high glucose-induced epithelial-mesenchymal transition in renal proximal tubular cells.

Zhou L ，Xue H ，Yuan P ，Ni J ，Yu C ，Huang Y ，Lu LM ... -  《-》

β-Casomorphin-7 attenuates the development of nephropathy in type I diabetes via inhibition of epithelial-mesenchymal transition of renal tubular epithelial cells.

This study was designed to investigate the putative protective effect of β-casomorphin-7 on diabetic nephropathy in a rat model, and to explore the possible mechanism of this effect. SD rats were randomly divided into the following three groups: control group, diabetes group and β-casomorphin-7-treatment group. All rats were euthanized after 30 days with or without β-casomorphin-7 treatment. Biochemical parameters including blood glucose and renal function were quantified. The concentration of plasma TGF-β1 was measured by ELISA. Histopathological changes to the kidney were studied by Masson and Sirius red staining. Expressions of α-smooth muscle actin (α-SMA), E-cadherin, vimentin, cytokeratin19 and TGF-β1 mRNA in rat renal cortices were analyzed by real-time PCR. Changes in α-SMA and E-cadherin protein expression in rat renal cortices were quantified by Western blot. β-Casomorphin-7 treatment of diabetic rats reduced urinary glucose, urinary protein, serum creatinine, blood urinary nitrogen, plasma TGF-β1 and the ratio of kidney: body weight. Masson and Sirius red staining showed that β-casomorphin-7 treatment attenuated renal interstitial fibrosis in diabetic rats. Compared to the control rats, diabetic rats had elevated expressions of α-SMA, vimentin and TGF-β1 mRNA and α -SMA protein and decreased expression of E-cadherin and cytokeratin19 mRNA, and E-cadherin protein. β-Casomorphin-7 treatment of diabetic rats partially normalized these changes. Our results suggest that administration of β-casomorphin-7 attenuates renal interstitial fibrosis caused by diabetes. This protective effect may be associated, in part, with down regulation of epithelial-mesenchymal transition of renal tubular epithelial cells.

Zhang W ，Miao J ，Ma C ，Han D ，Zhang Y ... -  《-》

Angiotensin-(1-7) attenuates high glucose-induced proximal tubular epithelial-to-mesenchymal transition via inhibiting ERK1/2 and p38 phosphorylation.

The kidney is an important target for both Angiotensin II and angiotensin-(1-7) [Ang-(1-7)] in the renin-angiotensin system. However, the renal function of Ang-(1-7) remains unclear. This study is aimed at investigating the effect of Ang-(1-7) on high glucose-induced epithelial to mesenchymal transition (EMT) in cultured renal epithelial cells. Cultured renal epithelial (NRK-52E) cell line was used in the experiment. Fluorescence immunocytochemistry was performed to observe α-smooth muscle actin (α-SMA). Real-time PCR and Western blot were used to determine mRNA and protein levels. Enzyme-linked immunosorbent assay was used to measure the concentration of transforming growth factor-β1 (TGF-β1) in the culture media. High glucose-induced decreased in both angiotensin-converting enzyme-related carboxypeptidase (ACE2) and Mas mRNA levels. Meanwhile, high glucose induced increases in α-SMA and vimentin, decreases in E-cadherin, elevations in TGF-β1 and fibronectin secretions. Ang-(1-7) partially reversed high glucose-induced changes in α-SMA, vimentin, E-cadherin, TGF-β1 and fibronectin. High glucose stimulated ERK, p38 and JNK phosphorylation and Ang-(1-7) reversed the changes in ERK and p38 but not JNK phosphorylation. Inhibition and insufficiency in ACE2-Ang-(1-7)-Mas axis under high glucose condition participate EMT. Supplementation of Ang-(1-7) attenuates high glucose-induced EMT. ERK and p38 intracellular signaling pathways, not JNK, mediate the effect of Ang-(1-7) on EMT.

Zhou L ，Xue H ，Wang Z ，Ni J ，Yao T ，Huang Y ，Yu C ，Lu L ... -  《-》

Epigallocatechin-3-gallate attenuates transforming growth factor-β1 induced epithelial-mesenchymal transition via Nrf2 regulation in renal tubular epithelial cells.

Transforming growth factor-β1 (TGF-β1) induced epithelial-mesenchymal transition (EMT) plays an important role in renal fibrotic process regulation. Epigallocatechin-3-gallate (EGCG) exerts a protective effect against acute renal damage through its anti-oxidative effect by activating the Nrf2 signaling pathway. This study aims to investigate whether EGCG prevents TGF-β1 induced EMT and whether this effect acts via the Nrf2-mediated suppression of TGF-β1 signaling. MTT was used for cytotoxicity of EGCG examination and Western blotting and immunofluorescence were used for protein expression analysis. Results showed that EGCG prevented TGF-β1 mediated EMT and Smad 2 and Smad 3 phosphorylation in a dose dependent manner in NRK-52E cells. In addition, EGCG increased Nrf2 nuclear accumulation. Overexpression of Nrf2 blocked the phosphorylation of Smad 2 and Smad 3 mediated by TGF-β1 and decreased protein expression of plasminogen activator inhibitor 1 (PAI-1) and α-smooth muscle actin (α-SMA). Furthermore, siRNA-mediated knockdown of Nrf2 gene completely blocked the effects of EGCG, indicated by the reduced expressions of type I collagen (Col-I) and α-SMA were restored. In summary, EGCG inhibits TGF-β1 induced EMT and fibrotic proteins expression by Nrf2 activation. This study reveals a possible underlying mechanism of the renal protective effects of EGCG, and may provide a potential candidate to renal fibrosis therapy.

Wang Y ，Liu N ，Su X ，Zhou G ，Sun G ，Du F ，Bian X ，Wang B ... -  《-》