Rat Model Of Obstructive Nephropathy Research Articles

Sox9 promotes renal tubular epithelial‑mesenchymal transition and extracellular matrix aggregation via the PI3K/AKT signaling pathway.

Sox9 is important for multiple aspects of development, such as testis, pancreas and heart development. Previous studies have reported that Sox9 induced epithelial‑mesenchymal transition (EMT) and extracellular matrix (ECM) production in organ fibrosis and associated diseases, such as vascular calcification. However, to the best of our knowledge, the role and underlying mechanism of action of Sox9 in renal fibrogenesis remains unknown. The results of the present study revealed that Sox9 expression levels were upregulated in the tubular epithelial cells of a rat model of obstructive nephropathy. Furthermore, the overexpression of Sox9 in NRK‑52E cells was discovered to promote renal tubular EMT and ECM aggregation, and these fibrogenic actions were potentiated by TGF‑β1. Notably, RNA‑sequencing analysis indicated the possible regulatory role of the PI3K/AKT signaling pathway in Sox9‑mediated renal tubular EMT and ECM aggregation. It was further demonstrated that the expression levels of phosphorylated AKT were upregulated in NRK‑52E cells overexpressing Sox9, while the PI3K inhibitors, LY29002 and wortmannin, inhibited the renal tubular EMT and ECM aggregation induced by the overexpression of Sox9 in NEK‑52E cells. In conclusion, the findings of the present study suggested that Sox9 may serve a profibrotic role in the development of renal tubular EMT and ECM aggregation via the PI3K/AKT signaling pathway. Therefore, Sox9 may be considered as a promising target for treating renal fibrosis.

Arctigenin suppresses renal interstitial fibrosis in a rat model of obstructive nephropathy

BackgroundRenal tubulointerstitial fibrosis (TIF) is commonly the final result of a variety of progressive injuries and leads to end-stage renal disease. There are few therapeutic agents currently available for retarding the development of renal TIF. PurposeThe aim of the present study is to evaluate the role of arctigenin (ATG), a lignan component derived from dried burdock (Arctium lappa L.) fruits, in protecting the kidney against injury by unilateral ureteral obstruction (UUO) in rats. MethodsRats were subjected to UUO and then administered with vehicle, ATG (1 and 3mg/kg/d), or losartan (20mg/kg/d) for 11 consecutive days. The renoprotective effects of ATG were evaluated by histological examination and multiple biochemical assays. ResultsOur results suggest that ATG significantly protected the kidney from injury by reducing tubular dilatation, epithelial atrophy, collagen deposition, and tubulointerstitial compartment expansion. ATG administration dramatically decreased macrophage (CD68-positive cell) infiltration. Meanwhile, ATG down-regulated the mRNA levels of pro-inflammatory chemokine monocyte chemoattractant protein-1 (MCP-1) and cytokines, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interferon-γ (IFN-γ), in the obstructed kidneys. This was associated with decreased activation of nuclear factor κB (NF-κB). ATG attenuated UUO-induced oxidative stress by increasing the activity of renal manganese superoxide dismutase (SOD2), leading to reduced levels of lipid peroxidation. Furthermore, ATG inhibited the epithelial-mesenchymal transition (EMT) of renal tubules by reducing the abundance of transforming growth factor-β1 (TGF-β1) and its type I receptor, suppressing Smad2/3 phosphorylation and nuclear translocation, and up-regulating Smad7 expression. Notably, the efficacy of ATG in renal protection was comparable or even superior to losartan. ConclusionATG could protect the kidney from UUO-induced injury and fibrogenesis by suppressing inflammation, oxidative stress, and tubular EMT, thus supporting the potential role of ATG in renal fibrosis treatment.

The T-box transcription factor Brachyury promotes renal interstitial fibrosis by repressing E-cadherin expression.

BackgroundEpithelial-to-mesenchymal transition (EMT) induced by TGF-β1 is one of well-recognized factors contributing to renal fibrosis. However, the underlying molecular mechanisms of EMT are not fully understood. Brachyury, an evolutionarily conserved transcription factor, was recently identified as an important factor promoting EMT in human carcinoma cell lines. There is no evidence that Brachyury is involved in renal tubular EMT.ResultsOur results demonstrated that Brachyury was prominently induced in TGF-β1-treated human proximal tubular epithelial (HK-2) cells and that this induction was accompanied by changes characteristic of EMT. Blockage of Brachyury expression by short interfering RNA (siRNA) in HK-2 cells effectively reversed the TGF-β1-induced EMT phenotype. Brachyury induction repressed E-cadherin transcription; the E-cadherin promoter contains a Brachyury binding site, and decreased expression of E-cadherin occurred in Brachyury-overexpressing cells when they were transfected with reporter constructs using the promoter. This effect was partially mediated by Slug and Snail, as knockdown of Snail and Slug by siRNA effectively reversed Brachyury-mediated EMT and partially restored E–cadherin expression. The expression of Brachyury also presented in a rat model of obstructive nephropathy and in tubulointerstitial fibrosis tissues of IgA nephropathy, suggesting that it may have a role in EMT and renal fibrosis in vivo.ConclusionOur results demonstrate for the first time that Brachyury plays an important role in regulating TGF-β1–mediated renal EMT and could be an attractive target for progression of renal disease therapies.

Hypoxia-induced Bmi1 promotes renal tubular epithelial cell-mesenchymal transition and renal fibrosis via PI3K/Akt signal.

Hypoxia is an important microenvironmental factor in the development of renal fibrosis; however, the underlying mechanisms are not well elucidated. Here we show that hypoxia induces Bmi1 mRNA and protein expression in human tubular epithelial cells. We further demonstrate that Bmi1 expression might be directly regulated by hypoxia-inducible factor-1a (HIF-1a) under low oxygen. Moreover, chromatin immunoprecipitation and reporter gene assay studies reveal cooperative transactivation of Bmi1 by HIF-1α and Twist. Enforced Bmi1 expression induces epithelial-mesenchymal transition (EMT), whereas silencing endogenous Bmi-1 expression reverses hypoxia-induced EMT. Up-regulation of Bmi1 leads to stabilization of Snail via modulation of PI3K/Akt signaling, whereas ablation of PI3K/Akt signaling partially rescues the phenotype of Bmi1-overexpressing cells, indicating that PI3K/Akt signaling might be a major mediator of Bmi1-induced EMT. In a rat model of obstructive nephropathy, Bmi1 expression increases in a time-dependent manner. Furthermore, we demonstrate that increased levels of Bmi1, correlated with HIF-1α and Twist, are associated with patients with chronic kidney disease. We provide in vitro and in vivo evidence that activation of HIF-1a/Twist-Bmi1 signaling in renal epithelial cells is associated with the development of chronic renal disease and may promote fibrogenesis via modulation of PI3K/Akt/Snail signaling by facilitating EMT.

Losartan attenuates renal interstitial fibrosis and tubular cell apoptosis in a rat model of obstructive nephropathy.

Ureteral obstruction leads to renal injury and progresses to irreversible renal fibrosis, with tubular cell atrophy and apoptosis. There is conflicting evidence concerning whether losartan (an angiotensinII typeI receptor antagonist) mitigates renal interstitial fibrosis and renal tubular epithelial cell apoptosis following unilateral ureteral obstruction (UUO) in animal models. The aim of this study was to investigate the effect and mechanism of losartan on renal tubular cell apoptosis and renal fibrosis in a rat model of UUO. The rats were subjected to UUO by ureteral ligation and were treated with dimethyl sulfoxide (control) or losartan. The controls underwent sham surgery. The renal tissues were collected3, 5, 7 and 14days after surgery for measurement of various indicators of renal fibrosis. UUO increased the expression levels of α‑smooth muscle actin and collagenI, and the extent of renal tubular fibrosis and apoptosis in a time‑dependent manner. Losartan treatment partially attenuated these responses. Progression of renal interstitial fibrosis was accompanied by phosphorylation of signal transducer and activator of transcription3 (STAT3) and altered the expression levels of two apoptosis‑related proteins (Bax and Bcl2). Losartan treatment also partially attenuated these responses. The results indicated that losartan attenuated renal fibrosis and renal tubular cell apoptosis in a rat model of UUO. This effect appeared to be mediated by partial blockage of STAT3 phosphorylation.

Amygdalin inhibits renal fibrosis in chronic kidney disease

Renal interstitial fibrosis is a common outcome of chronic renal diseases. Amygdalin is one of a number of nitrilosides, the natural cyanide‑containing substances abundant in the seeds of plants of the prunasin family that are used to treat cancer and relieve pain. However, whether amygdalin inhibits the progression of renal fibrosis or not remains unknown. The present study aimed to assess the therapeutic potential of amygdalin by investigating its effect and potential mechanism on the activation of renal interstitial fibroblast cells and renal fibrosis in rat unilateral ureteral obstruction (UUO). Treatment of the cultured renal interstitial fibroblasts with amygdalin inhibited their proliferation and the production of transforming growth factor (TGF)‑β1. In the rat model of obstructive nephropathy, following ureteral obstruction, the administration of amygdalin immediately eliminated the extracellular matrix accumulation and alleviated the renal injury on the 21st day. Collectively, amygdalin attenuated kidney fibroblast (KFB) activation and rat renal interstitial fibrosis. These results indicate that amygdalin is a potent antifibrotic agent that may have therapeutic potential for patients with fibrotic kidney diseases.

Therapeutic potential of EGCG on acute renal damage in a rat model of obstructive nephropathy

As a major active component in green tea, (-)-epigallocatechin 3-O-gallate (EGCG) has many anti-oxidative activities. This study investigated whether intraperitoneal administration of EGCG was capable of suppressing oxidative stress in rats with unilateral ureteral obstruction (UUO) and probed the potential mechanisms involved. In total, 150 adult male rats were randomly divided into 5 groups (n=30 each): the control group (group N); the unilateral ureteral obstruction (UUO) group (group C), where the unilateral ureter was ligated resulting in an obstructive nephropathy model; and the EGCG group (group T), following unilateral ureteral ligation, rats were intraperitoneally injected with EGCG at a dosage of 2.5 (T1), 5 (T2) and 10 mg/kg/day (T3). Each group of rats was sacrificed 72 h after surgery. We evaluated the effects of EGCG on the reactive oxygen species (ROS), reduced glutathione (GSH), oxidized glutathione (GSSG) and glutathione in the renal tissue of rats. Immunohistochemistry and western blot analysis were applied to detect nuclear factor erythoid-derived 2-related factor 2 (Nrf2) and γ-glutamylcysteine synthetase (γ-GCS) protein expression. Real-time PCR was performed to detect the mRNA levels of Nrf2 and γ-GCS. Changes in renal ultrastructure were also observed using electron microscopy. There was no significant difference in GSH, and compared with group N, ROS, GSSG and total GSH levels were much higher in the T groups (p<0.01), while much lower than those of group C (p<0.01). Protein levels of Nrf2 and γ-GCS and the mRNA levels of Nrf2 and γ-GCS notably increased in EGCG-treated rats (all p<0.05). Furthermore, electron microscopy showed that renal ultrastructure was improved in the treatment groups. Our findings suggest that, resulting from suppression of oxidative stress influenced by free radicals, EGCG exerts a protective effect on rats with obstructive nephropathy, and this anti-oxidative effect may be partly induced by activating the Nrf2 signaling pathway.

Fluorofenidone attenuates renal interstitial fibrosis in the rat model of obstructive nephropathy

Fluorofenidone (FD) is a novel pyridone agent with significant antifibrotic effects in vitro. The purpose of this study is to investigate the effects of FD on renal interstitial fibrosis in rats with obstructive nephropathy caused by unilateral ureteral obstruction (UUO). With pirfenidone (PD, 500 mg/kg/day) and enalapril (10 mg/kg/day) as the positive treatment controls, the rats in different experimental groups were administered with FD (500 mg/kg/day) from day 4 to day 14 after UUO. The tubulointerstitial injury, interstitial collagen deposition, and expression of type I and type III collagen, transforming growth factor-β(1) (TGF-β(1)), connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), α-smooth muscle actin (α-SMA), and tissue inhibitor of metalloproteinase-1 (TIMP-1) were assessed. FD treatment significantly attenuated the prominently increased scores of tubulointerstitial injury, interstitial collagen deposition, and protein expression of type I and type III collagen in ureter-obstructed kidneys, respectively. As compared with untreated rats, FD also significantly reduced the expression of α-SMA, TGF-β(1), CTGF, PDGF, and inhibitor of TIMP-1 in the obstructed kidneys. Fluorofenidone attenuates renal interstitial fibrosis in the rat model of obstructive nephropathy through its regulation on fibrogenic growth factors, tubular cell transdifferentiation, and extracellular matrix.

TGF-β-induced MiR-491-5p Expression Promotes Par-3 Degradation in Rat Proximal Tubular Epithelial Cells

Par-3 is a component of Par complex, which is critical for the integrity of tight junction. We previously reported that TGF-β down-regulated Par-3 expression in rat proximal tubular epithelial cells, but the underlying mechanism remains unknown. In the present study, we demonstrated by a luciferase reporter assay that miR-491-5p down-regulated the luciferase activity through a binding site in the 3' UTR of Par-3. Overexpression of miR-491-5p dramatically decreased the expression of endogenous Par-3, disrupted tight junction, and resulted in decreased transepithelial resistance. Moreover, miR-491-5p expression was induced by TGF-β1 through the MEK/p38 MAPK pathway. Importantly, miR-491-5p levels were increased significantly in a rat model of obstructive nephropathy, in parallel with decreased Par-3 levels. Taken together, we conclude that up-regulation of miR-491-5p contributes to TGF-β-regulated Par-3 expression. Our study uncovered a novel mechanism by which TGF-β disrupts cell junction.

Inhibition of tubulointerstitial fibrosis by pentoxifylline is associated with improvement of vascular endothelial growth factor expression

Recent information indicates that pentoxifylline (PTX) has the ability to suppress inflammation and profibrotic cell proliferation. In this study, we investigated the effect of PTX on tubulointerstitial fibrosis and the expression of vascular endothelial growth factor (VEGF) in a rat model of obstructive nephropathy. Wistar rats with left ureteral ligation were divided into control and PTX-treated groups. The histopathologic degree of tubulointerstitial fibrosis was scored with PAS and Masson-stained sections. The protein and mRNA for vascular endothelial growth factor (VEGF) were semiquantitatively measured with immunohistochemistry and RT-PCR. The protein for transforming growth factor beta1 (TGFbeta1) and hypoxia-induced factor 1 alpha (HIF-1alpha) was determined by Western blot. Compared with the control group, PTX treatment reduced fibrosis scores at d 7 and d 14 (P<0.05). The reduction was accompanied by inhibited expression of transforming growth factor-beta 1 (TGFbeta1), a key cytokine in tubulointerstitial fibrogenesis (P<0.01). Meanwhile, VEGF protein and mRNA in the kidney were increased in the PTX-treated group compared with the control group (P<0.01). PTX up-regulated expression of VEGF mRNA in a dose- and time-dependent manner in cultured HK-2 cells (P<0.01). However, expression of HIF-1alpha (a key transcription factor for VEGF gene expression) was unchanged by PTX treatment. PTX prolonged the half-life of VEGF mRNA by a 1.07-fold increase. PTX inhibited tubulointerstitial fibrosis in a rat model of obstructive nephropathy while preventing loss of VEGF. PTX up-regulated expression of VEGF mRNA through stabilization of its mRNA in cultured renal tubular epithelial cells.