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Parathyroid hormone induces epithelial-to-mesenchymal transition via the Wnt/?-catenin signaling pathway in human renal proximal tubular cells.

ABSTRACT: Epithelial-to-mesenchymal transition (EMT) has been shown to play an important role in renal fibrogenesis. Recent studies suggested parathyroid hormone (PTH) could accelerate EMT and subsequent organ fibrosis. However, the precise molecular mechanisms underlying PTH-induced EMT remain unknown. The present study was to investigate whether Wnt/?-catenin signaling pathway is involved in PTH-induced EMT in human renal proximal tubular cells (HK-2 cells) and to determine the profile of gene expression associated with PTH-induced EMT. PTH could induce morphological changes and gene expression characteristic of EMT in cultured HK-2 cells. Suppressing ?-catenin expression or DKK1 limited gene expression characteristic of PTH-induced EMT. Based on the PCR array analysis, PTH treatment resulted in the up-regulation of 18 genes and down-regulation of 9 genes compared with the control. The results were further supported by a western blot analysis, which showed the increased Wnt4 protein expression. Wnt4 overexpression also promotes PTH-induced EMT in HK-2 cells. The findings demonstrated that PTH-induced EMT in HK-2 cells is mediated by Wnt/?-catenin signal pathway, and Wnt4 might be a key gene during PTH-induced EMT.

SUBMITTER: Guo Y

PROVIDER: S-EPMC4203213 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Parathyroid hormone induces epithelial-to-mesenchymal transition via the Wnt/β-catenin signaling pathway in human renal proximal tubular cells.

Guo Yunshan Y Li Zhen Z Ding Raohai R Li Hongdong H Zhang Lei L Yuan Weijie W Wang Yanxia Y

International journal of clinical and experimental pathology 20140815 9

Epithelial-to-mesenchymal transition (EMT) has been shown to play an important role in renal fibrogenesis. Recent studies suggested parathyroid hormone (PTH) could accelerate EMT and subsequent organ fibrosis. However, the precise molecular mechanisms underlying PTH-induced EMT remain unknown. The present study was to investigate whether Wnt/β-catenin signaling pathway is involved in PTH-induced EMT in human renal proximal tubular cells (HK-2 cells) and to determine the profile of gene expressio ...[more]

PMID: 25337242

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Project description:BackgroundEverolimus (EVE) is a drug widely used in several renal transplant protocols. Although characterized by a relatively low nephrotoxicity, it may induce several adverse effects including severe fibro-interstitial pneumonitis. The exact molecular/biological mechanism associated to these pro-fibrotic effects is unknown, but epithelial to mesenchymal transition (EMT) may have a central role. Additionally, heparanase, an enzyme recently associated with the progression of chronic allograft nephropathy, could contribute to activate this machinery in renal cells.MethodsSeveral biomolecular strategies (RT-PCR, immunofluorescence, zymography and migration assay) have been used to assess the capability of EVE (10, 100, 200 and 500 nM) to induce an in vitro heparanase-mediated EMT in wild-type (WT) and Heparanase (HPSE)-silenced immortalized human renal epithelial proximal tubular cells (HK-2). Additionally, microarray technology was used to find additional biological elements involved in EVE-induced EMT.ResultsBiomolecular experiments demonstrated a significant up-regulation (more than 1.5 fold increase) of several genes encoding for well known EMT markers [(alpha-smooth muscle actin (?-SMA), Vimentin (VIM), Fibronectin (FN) and matrix metalloproteinase-9 (MMP9)], enhancement of MMP9 protein level and increment of cells motility in WT HK2 cells treated with high concentrations of EVE (higher than 100 nM). Similarly, immunofluorescence analysis showed that 100 nM of EVE increased ?-SMA, VIM and FN protein expression in WT HK2 cells. All these effects were absent in both HPSE- and AKT-silenced cell lines. AKT is a protein having a central role in EMT. Additionally, microarray analysis identified other 2 genes significantly up-regulated in 100 nM EVE-treated cells (p?<?0.005 and FDR?<?5%): transforming growth factor beta-2 (TGF?2) and epidermal growth factor receptor (EGFR). Real-time PCR analysis validated microarray.ConclusionsOur in vitro study reveals new biological/cellular aspects of the pro-fibrotic activity of EVE and it demonstrates, for the first time, that an heparanase-mediated EMT of renal tubular cells may be activated by high doses of this drug. Additionally, our results suggest that clinicians should administer the adequate dosage of EVE in order to increase efficacy and reduce adverse effects. Finally heparanase could be a new potential therapeutic target useful to prevent/minimize drug-related systemic fibrotic adverse effects.

Project description:4-Hydroxy-2-hexenal (HHE), the aldehyde product of lipid peroxidation, may be responsible for the pathogenesis of progressive renal disease. Recently, paricalcitol (19-nor-1,25-dihydroxyvitamin D2) was shown to be renoprotective through its anti-inflammatory and antifibrotic effects in various experimental nephropathy models. In this study, we investigated the effects of paricalcitol on inflammation and epithelial-mesenchymal transition (EMT) after HHE-induced renal tubular epithelial cell injury. To investigate the molecular mechanisms underlying HHE-induced renal tubular cell injury, the human proximal tubular epithelial (HK-2) cells cultured with 10 µM HHE in the presence or absence of paricalcitol. In HK-2 cells, paricalcitol attenuated the HHE-induced expression of extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38 mitogen-activated protein kinase, and prevented nuclear factor-κB (NF-κB) activation. The expression of the inflammatory proteins inducible nitric oxide synthase and cyclooxygenase-2 was attenuated by paricalcitol pretreatment. In addition, HHE increased the expression of the transforming growth factor (TGF)-β/Smad signaling proteins and fibrotic proteins, such as α-smooth muscle actin and connective tissue growth factor; this inducible expression was suppressed by pretreatment with paricalcitol. Treatment with HHE resulted in the activation of the β-catenin signaling pathway, and paricalcitol pretreatment reduced the expression of β-catenin in HHE-treated HK-2 cells. Coimmunoprecipitation shows that paricalcitol induced vitamin D receptor (VDR)/β-catenin complex formation in HK-2 cells. Also immunofluorescence staining revealed that co-localization of VDR and β-catenin in the nuclei. ICG-001, an inhibitor of β-catenin, decreased the expression of TGF-β1 and attenuated HHE-induced tubular EMT. These results show that paricalcitol attenuated HHE-induced renal tubular cell injury by suppressing inflammation and EMT process through inhibition of the NF-κB, TGF-β/Smad, and β-catenin signaling pathways.

Project description:Epithelial-mesenchymal transition (EMT) occurs in several disease states, including renal fibrosis and carcinogenesis. Myofibroblasts produced from EMT of renal tubular cells are responsible for the deposition of extracellular matrix components in a large portion of renal interstitial fibrosis. Transforming growth factor-beta (TGF-beta) plays an essential role in the EMT of renal tubular cells, but the molecular mechanism governing this process remains largely unknown. In this study, we found that RGC-32 (response gene to complement 32) is critical for TGF-beta-induced EMT of human renal proximal tubular cells (HPTCs). RGC-32 is not normally expressed in the HPTCs. However, TGF-beta stimulation markedly activates RGC-32 while inducing an EMT, as shown by the induction of smooth muscle alpha-actin (alpha-SMA) and extracellular matrix proteins collagen I and fibronectin, as well as the reduction of epithelial marker E-cadherin. TGF-beta function is mediated by several signaling pathways, but RGC-32 expression in HPTCs appears to be mainly regulated by Smad. Functionally, RGC-32 appears to mediate TGF-beta-induced EMT of HPTCs. Blockage of RGC-32 using short hairpin interfering RNA significantly inhibits TGF-beta induction of myofibroblast marker gene alpha-SMA while repressing the expression of E-cadherin. In contrast, overexpression of RGC-32 induces alpha-SMA expression while restoring E-cadherin. RGC-32 also inhibits the expression of another adherens junction protein, N-cadherin, suggesting that RGC-32 alone induces the phenotypic conversion of renal epithelial cells to myofibroblasts. Additional studies show that RGC-32 stimulates the production of extracellular matrix components fibronectin and collagen I. Mechanistically, RGC-32 induces EMT via the activation of other transcription factors such as Snail and Slug. RGC-32 knockdown inhibits the expression of Snail and Slug during TGF-beta-induced EMT. Taken together, our data demonstrate for the first time that RGC-32 plays a critical role in TGF-beta-induced EMT of renal tubular cells.

Dataset Information

Parathyroid hormone induces epithelial-to-mesenchymal transition via the Wnt/?-catenin signaling pathway in human renal proximal tubular cells.

Publications

Parathyroid hormone induces epithelial-to-mesenchymal transition via the Wnt/β-catenin signaling pathway in human renal proximal tubular cells.

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