Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice.
ABSTRACT: Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-? to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of ?-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in ?-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering ?-catenin localization and downstream signaling.
Project description:Obstructive nephropathy is an aggressive form of chronic kidney disease (CKD), which is characterized by an epithelial-to-mesenchymal transition (EMT) and interstitial fibrosis. However, the molecular mechanisms of EMT and fibrosis are complex and not fully understood. In this study, we investigated the contribution of Akt2 to experimental renal EMT and fibrosis using the well-established model of unilateral ureteral obstruction (UUO). We found that Akt2 and phosphor (p)-Akt protein levels were increased in the obstructed kidneys. UUO induced activation of transforming growth factor-?1 (TGF-?1) signaling. Importantly, knockout of Akt2 suppressed UUO-induced EMT, kidney fibrosis, increased GSK3? activity, and decreased expression of Snail and ?-catenin. Inhibition of GSK3? with LiCl (the inhibitor of GSK3?) increased the expression of Snail and ?-catenin in cultured kidney epithelial cells. Our findings suggest that Akt2 partially contributes to interstitial fibrosis following UUO and that inhibition of this signaling pathway may provide a novel approach of prevent progression of renal fibrosis.
Project description:Renal fibrosis arises by the generation of matrix-producing fibroblasts and myofibroblasts through the epithelial-mesenchymal transition (EMT), a process in which epithelial cells undergo a transition into a fibroblast phenotype. A key feature of the EMT is the reorganization of the cytoskeletons, which may involve the Ca2+-binding protein S100A16, a newly reported member of the S100 protein family. However, very few studies have examined the role of S100A16 in renal tubulointerstitial fibrosis. In this study, S100A16 expression was examined by immunohistochemical staining of kidney biopsy specimens from patients with various nephropathies and kidney tissues from a unilateral ureteral obstruction (UUO) mouse model. Renal histological changes were investigated in S100A16Tg, S100A16+/-, and WT mouse kidneys after UUO. The expression of epithelia marker E-cadherin, mesenchymal markers N-cadherin, and vimentin, extracellular matrix protein, and S100A16, as well as the organization of F-actin, were investigated in S100A16 overexpression or knockdown HK-2 cells. Mass spectrometry was employed to screen for S100A16 binding proteins in HK-2 cells. The results indicated that S100A16 is high expressed and associated with renal tubulointerstitial fibrosis in patient kidney biopsies and in those from UUO mice. S100A16 promotes renal interstitial fibrosis in UUO mice. S100A16 expression responded to increasing Ca2+ and interacted with myosin-9 during kidney injury or TGF-? stimulation to promote cytoskeleton reorganization and EMT progression in renal tubulointerstitial fibrosis. Therefore, S100A16 is a critical regulator of renal tubulointerstitial fibroblast activation and is therefore a potential therapeutic target for the treatment of renal fibrosis.
Project description:Renal fibrosis is the main pathological characteristic of chronic kidney disease (CKD), whereas the underlying mechanisms of renal fibrosis are not clear yet. Herein, we found an increased expression of microRNA-34a (miR-34a) in renal tubular epithelial cells of patients with renal fibrosis and mice undergoing unilateral ureteral obstruction (UUO). In miR-34a-/- mice, miR-34a deficiency attenuated the progression of renal fibrosis following UUO surgery. The miR-34a overexpression promoted epithelial-to-mesenchymal transition (EMT) in cultured human renal tubular epithelial HK-2 cells, which was accompanied by sharp downregulation of Klotho, an endogenous inhibitor of renal fibrosis. Luciferase reporter assay revealed that miR-34a downregulated Klotho expression though direct binding with the 3' UTR of Klotho. Conversely, overexpression of Klotho prevented miR-34a-induced EMT in HK-2 cells. Furthermore, results showed that miR-34a was induced by transforming growth factor ?1 (TGF-?1) through p53 activation, whereas dihydromyricetin could inhibit TGF-?1-induced miR-34a overexpression. Accordingly, dihydromyricetin administration dramatically restored the aberrant upregulation of miR-34a and Klotho reduction in obstructed kidney, and markedly ameliorated renal fibrosis in the Adriamycin nephropathy and UUO model mice. These findings suggested that miR-34a plays an important role in the progression of renal fibrosis, which provides new insights into the pathogenesis and treatment of CKD.
Project description:Unilateral ureteral obstruction (UUO) induces functional and pathological changes in the obstructed kidney. Inducible nitric oxide synthase (iNOS) expression is high inearly UUO mouse kidney, which is accompanied with fibrosis. Propofol has preventive effects against renal injury by downregulating iNOS expression in UUO mouse models. However, the role of propofol in kidney fibrosis progression has not been reported. We explored the therapeutic potential and possible mechanisms of action of propofol in kidney fibrosis using a UUO mouse model. Herein, mice anesthetized with propofol or sevoflurane underwent UUO induction. Serum and kidney sections were collected 5 and 28 days post-operation for histological, morphometric, immunofluorescence, microRNA analyses; quantitative PCR and western blotting. In vivo, the effect and mechanism of propofol on epithelial-mesenchymal transition (EMT), transforming growth factor ? (TGF-?) signaling and miR-155 levels were detected in cultured HK-2 cells. We found that propofol significantly suppressed UUO-induced kidney fibrosis, which was associated with TGF-?/Smad3 signaling, EMT, and iNOS-NO production. MiR-155 levels were higher in UUO mouse kidneys; compared with sevoflurane, propofol suppressed miR-155 levels. However, in late UUO, propofol could not prevent kidney fibrosis or suppress EMT and miR-155. The in vitro results showed that propofol suppressed TGF-?1-induced EMT by regulating miR-155 levels. As a conclusion, in early UUO mice, propofol may inhibit TGF-?1 expression and NO-iNOS production, consequently inhibiting EMT and kidney fibrosis by regulating miR-155 levels, and might be a new protective agent against kidney injury during surgery and in therapy to prevent kidney fibrosis.
Project description:Acetyl-11-keto-?-boswellic acid (AKBA), an active triterpenoid compound from the extract of Boswellia serrate, has been reported previously in our group to alleviate fibrosis in vascular remodelling. This study aimed to elucidate the in vivo and in vitro efficacy and mechanism of AKBA in renal interstitial fibrosis. The experimental renal fibrosis was produced in C57BL/6 mice via unilateral ureteral obstruction (UUO). Hypoxia-induced HK-2 cells were used to imitate the pathological process of renal fibrosis in vitro. Results showed that the treatment of AKBA significantly alleviated UUO-induced impairment of renal function and improved the renal fibrosis by decreasing the expression of TGF-?1, ?-SMA, collagen I and collagen IV in UUO kidneys. In hypoxia-induced HK-2 cells, AKBA displayed remarkable cell protective effects and anti-fibrotic properties by increasing the cell viability, decreasing the lactate dehydrogenase (LDH) release and inhibiting fibrotic factor expression. Moreover, in obstructed kidneys and HK-2 cells, AKBA markedly down-regulated the expression of TGF?-RI, TGF?-RII, phosphorylated-Smad2/3 (p-Smad2/3) and Smad4 in a dose-dependent fashion while up-regulated the expression of Klotho and Smad7 in the same manner. In addition, the effects of AKBA on the Klotho/TGF-?/Smad signalling were reversed by transfecting with siRNA-Klotho in HK-2 cells. In conclusion, our findings provide evidence that AKBA can effectively protect kidney against interstitial fibrosis, and this renoprotective effect involves the Klotho/TGF-?/Smad signalling pathway. Therefore, AKBA could be considered as a promising candidate drug for renal interstitial fibrosis.
Project description:The AXL receptor tyrosine kinase (RTK) is involved in partial epithelial-to-mesenchymal transition (EMT) and inflammation - both main promoters of renal fibrosis development. The study aim was to investigate the role of AXL inhibition in kidney fibrosis due to unilateral ureteral obstruction (UUO). Eight weeks old male C57BL/6 mice underwent UUO and were treated with oral AXL inhibitor bemcentinib (n = 22), Angiotensin-converting enzyme inhibitor (ACEI, n = 10), ACEI and bemcentinib (n = 10) or vehicle alone (n = 22). Mice were sacrificed after 7 or 15 days and kidney tissues were analyzed by immunohistochemistry (IHC), western blot, ELISA, Sirius Red (SR) staining, and hydroxyproline (Hyp) quantification. RNA was extracted from frozen kidney tissues and sequenced on an Illumina HiSeq4000 platform. After 15 days the ligated bemcentinib-treated kidneys showed less fibrosis compared to the ligated vehicle-treated kidneys in SR analyses and Hyp quantification. Reduced IHC staining for Vimentin (VIM) and alpha smooth muscle actin (?SMA), as well as reduced mRNA abundance of key regulators of fibrosis such as transforming growth factor (Tgf?), matrix metalloproteinase 2 (Mmp2), Smad2, Smad4, myofibroblast activation (Aldh1a2, Crlf1), and EMT (Snai1,2, Twist), in ligated bemcentinib-treated kidneys was compatible with reduced (partial) EMT induction. Furthermore, less F4/80 positive cells, less activity of pathways related to the immune system and lower abundance of MCP1, MCP3, MCP5, and TARC in ligated bemcentinib-treated kidneys was compatible with reduction in inflammatory infiltrates by bemcentinib treatment. The AXL RTK pathway represents a promising target for pharmacologic therapy of kidney fibrosis.
Project description:Cystic fibrosis transmembrane conductance regulator (CFTR), known as a cAMP-activated Cl- channel, is widely expressed at the apical membrane of epithelial cells in a wide variety of tissues. Of note, despite the abundant expression of CFTR in mammalian kidney, the role of CFTR in kidney disease development is unclear. Here, we report that CFTR expression is downregulated in the UUO (unilateral ureteral obstruction)-induced kidney fibrosis mouse model and human fibrotic kidneys. Dysfunction or downregulation of CFTR in renal epithelial cells leads to alteration of genes involved in Epithelial-Mesenchymal Transition (EMT) and kidney fibrosis. In addition, dysregulation of CFTR activates canonical Wnt/?-catenin signaling pathways, whereas the ?-catenin inhibitor reverses the effects of CFTR downregulation on EMT marker. More interestingly, CFTR interacts with Dishevelled 2 (Dvl2), a key component of Wnt signaling, thereby suppressing the activation of ?-catenin. Compared to wild type, deltaF508 mice with UUO treatment exhibit significantly higher ?-catenin activity with aggregated kidney fibrogenesis, which is reduced by forced overexpression of CFTR. Taken together, our study reveals a novel mechanism by which CFTR regulates Wnt/?-catenin signaling pertinent to progression of kidney fibrosis and indicates a potential treatment target.
Project description:Allograft interstitial fibrosis was characterized by massive extracellular matrix deposition caused by activated fibroblasts and myofibroblasts. Epithelial-mesenchymal transition (EMT) is recognized as an important source of myofibroblasts contributing to the pathogenesis of allograft interstitial fibrosis. Smad ubiquitination regulatory factor 1 (Smurf1) has been recently reported to be involved in the progression of EMT. Our study was to detect the effect of Bortezomib and Smurf1 in the EMT and allograft interstitial fibrosis. Biomarkers of EMT, as well as Smurf1, were examined in human proximal tubular epithelial cells (HK-2) treated with tumour necrosis factor-alpha (TNF-?) in various doses or at various time points by Western Blotting or qRT-PCR. We knockdown or overexpressed Smurf1 in HK-2 cells. Furthermore, rat renal transplant model was established and intervened by Bortezomib. Allograft tissues from human and rats were also collected and prepared for HE, Masson's trichrome, immunohistochemical staining and western blotting assays. As a result, we found that TNF-? significantly promoted the development of EMT in a time-dependent and dose-dependent manner through Smurf1/Akt/mTOR/P70S6K signalling pathway. More importantly, Bortezomib alleviated the progression of EMT and allograft interstitial fibrosis in vivo and in vitro by inhibiting the production of TNF-? and expression of Smurf1. In conclusion, Smurf1 plays a critical role in the development of EMT induced by TNF-?. Bortezomib can attenuate the Sumrf1-mediated progression of EMT and renal allograft interstitial fibrosis, which could be suggested as a novel choice for the prevention and treatment of renal allograft interstitial fibrosis.
Project description:Renal fibrosis is the final common pathway of a wide variety of chronic kidney diseases. Myofibroblast formation via the differentiation of from tissue-resident fibroblasts and bone marrow-derived mesenchymal stem cells (MSCs), and epithelial-to-mesenchymal transition (EMT) is known to play a pivotal role in the development of renal fibrosis. However, the detailed mechanisms underlying this disorder remain unclear. We herein investigated the role of alpha 2-antiplasmin (?2AP) in myofibroblast formation and the development of renal fibrosis. We observed the development of renal fibrosis using unilateral ureteral obstruction (UUO). ?2AP had accumulated in the UUO-induced obstructed kidneys and ?2AP deficiency attenuated UUO-induced renal fibrosis in mice. The degree of myofibroblast formation in the obstructed kidneys of ?2AP(-/-) mice was less than that in ?2AP(+/+) mice. In vitro, ?2AP induced myofibroblast formation in renal tubular epithelial cells (RTECs), renal fibrosblasts, and bone marrow-derived mesenchymal stem cells (MSCs). ?2AP also induced the production of TGF-?, which is known to be a key regulator of myofibroblast formation and fibrosis. ?2AP-induced the TGF-? production was significantly reduced by SP600125, c-Jun N-terminal kinase (JNK) specific inhibitor. Our findings suggest that ?2AP induces myofibroblast formation in the obstructed kidneys, and mediates the development of renal fibrosis.
Project description:BACKGROUND:Inflammation has a crucial role in renal interstitial fibrosis, which is the common pathway of chronic kidney diseases. Mefunidone (MFD) is a new compound which could effectively inhibit the proliferation of renal fibroblasts in vitro. However, the overall effect of Mefunidone in renal fibrosis remains unknown. METHODS:Sprague-Dawley rats were randomly divided intro 6 groups: sham operation, unilateral ureteral obstruction (UUO), UUO/Mefunidone (25, 50, 100mg/kg/day) and UUO/PFD (500mg/kg/day). The rats were sacrificed respectively on days 3, 7, and 14 after the operation. Tubulointerstitial injury index, interstitial collagen deposition, expression of fibronectin (FN), ?-smooth muscle actin (?-SMA), type I and III collagen and the number of CD3+ and CD68+ cells were determined. The expressions of proinflammatory cytokines, p-ERK, p-I?B, and p-STAT3 were measured in human renal proximal tubular epithelial cells of HK-2 or macrophages. RESULTS:Mefunidone treatment significantly attenuated tubulointerstitial injury, interstitial collagen deposition, expression of FN, ?-SMA, type I and III collagen in the obstructive kidneys, which correlated with significantly reduced the number of T cells and macrophages in the obstructive kidneys. Mechanistically, Mefunidone significantly inhibited tumor necrosis factor-? (TNF-?-) or lipopolysaccharide (LPS)-induced production of proinflammatory cytokines. This effect is possibly due to the inhibition of phosphorylation of ERK, I?B, and STAT3. CONCLUSION:Mefunidone treatment attenuated tubulointerstitial fibrosis in a rat model of UUO, at least in part, through inhibition of inflammation.