Erythropoietin decreases renal fibrosis in mice with ureteral obstruction: role of inhibiting TGF-beta-induced epithelial-to-mesenchymal transition

Delayed treatment with erythropoietin attenuates renal fibrosis in mouse model of unilateral ureteral obstruction

OBJECTIVES

Erythropoietin (EPO) exerts tissue-protective effects on various organs including the kidney. However, the effects of EPO on established renal fibrosis remain unclear. In this study, we aimed to examine the therapeutic potential of EPO against established renal fibrosis.

METHODS

Renal fibrosis was induced in mice by unilateral ureteral obstruction (UUO) and the mice were treated with recombinant human EPO (rhEPO) daily during 7 and 13 days after UUO. The degrees of renal fibrosis, myofibroblast accumulation, and macrophage infiltration; the mRNA expression levels of transforming growth factor (TGF)-β1 and α1(I) collagen; and the protein levels of Kelch-like ECH-associated protein 1 (Keap1) and nuclear NF-E2-related factor 2 (Nrf2) in the kidneys were assessed on day 14 after UUO.

RESULTS

Treatment with rhEPO significantly decreased fibrosis, myofibroblast accumulation, and α1(I) collagen mRNA expression, but it did not significantly affect TGF-β1 mRNA expression. Although treatment with rhEPO did not significantly affect the total number of interstitial macrophages, it significantly decreased the number of CD86-positive cells (M1 macrophages), while significantly increased the number of CD206-positive cells (M2 macrophages) in the interstitium. Treatment with rhEPO did not affect the Keap1/Nrf2 protein level or the peripheral blood hematocrit value.

CONCLUSIONS

These results indicate for the first time that EPO exerts antifibrotic effects against the evolution of established renal fibrosis, possibly by influencing the polarization of infiltrating macrophages.

A nonbiodegradable scaffold-free cell sheet of genome-engineered mesenchymal stem cells inhibits development of acute kidney injury

Cell therapy using genome-engineered stem cells has emerged as a novel strategy for the treatment of kidney diseases. By exploiting genome editing technology, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) secreting an angiogenic factors or an anti-inflammatory factor were generated for therapeutic application in acute kidney injury. Junction polymerase chain reaction analysis verified zinc finger nucleases-assisted integration of the desired gene into the hUC-MSCs. Flow cytometry and differentiation assays indicated that genome editing did not affect the differentiation potential of these mesenchymal stem cells. Protein measurement in conditioned media with the use of ELISA and immunoblotting revealed the production and secretion of each integrated gene product. For cell therapy in the bilateral ischemia-reperfusion mouse model of acute kidney injury, our innovative scaffold-free cell sheets were established using a non-biodegradable temperature-responsive polymer. One of each type of scaffold-free cell sheets of either the angiogenic factor vascular endothelial grown factor or angiopoietin-1, or the anti-inflammatory factor erythropoietin, or α-melanocyte-stimulating hormone-secreting hUC-MSCs was applied to the decapsulated kidney surface. This resulted in significant amelioration of kidney dysfunction in the mice with acute kidney injury, effects that were superior to intravenous administration of the same genome-engineered hUC-MSCs. Thus, our scaffold-free cell sheets of genome-engineered mesenchymal stem cells provides therapeutic effects by inhibiting acute kidney injury via angiogenesis or anti-inflammation.

Microparticles derived from human erythropoietin mRNA-transfected mesenchymal stem cells inhibit epithelial-to-mesenchymal transition and ameliorate renal interstitial fibrosis

Background

Renal tubulointerstitial fibrosis (TIF) plays an important role in the progression of chronic kidney disease (CKD) and its pathogenesis involves epithelial-to-mesenchymal transition (EMT) upon renal injury. Recombinant human erythropoietin (rhEPO) has been shown to display novel cytoprotective effects, in part by inhibiting transforming growth factor (TGF)-β1-induced EMT. Here, we evaluated the inhibitory effects of microparticles (MPs) derived from human EPO gene-transfected kidney mesenchymal stem cells (hEPO-KMSCs) against TGF-β1-induced EMT in Madin-Darby canine kidney (MDCK) cells and against TIF in mouse kidneys with unilateral ureteral obstruction (UUO).

Methods

EMT was induced in MDCK cells by treatment with TGF-β1 (5 ng/mL) for 48 h and then inhibited by co-treatment with rhEPO (100 IU/mL), mock gene-transfected KMSC-derived MPs (MOCK-MPs), or hEPO-KMSC-derived MPs (hEPO-MPs) for a further 48 h. UUO was induced in FVB/N mice, which were then treated with rhEPO (1000 IU/kg, intraperitoneally, every other day for 1 week), MOCK-MPs, or hEPO-MPs (80 μg, intravenously). Alpha-smooth muscle actin (α-SMA), fibronectin, and E-cadherin expression were evaluated in MDCK cells and kidney tissues, and the extent of TIF in UUO kidneys was assessed by immunohistochemical staining.

Results

TGF-β1 treatment significantly increased α-SMA and fibronectin expression in MDCK cells and decreased that of E-cadherin, while co-treatment with rhEPO, MOCK-MPs, or hEPO-MPs markedly attenuated these changes. In addition, rhEPO and hEPO-MP treatment effectively decreased phosphorylated Smad2 and Smad3, as well as phosphorylated p38 mitogen-activated protein kinase (MAPK) expression, suggesting that rhEPO and rhEPO-MPs can inhibit TGF-β1-induced EMT via both Smad and non-Smad pathways. rhEPO and hEPO-MP treatment also significantly attenuated the extent of renal TIF after 1 week of UUO compared to MOCK-MPs, with hEPO-MPs significantly reducing myofibroblast and F4/80+ macrophage infiltration as well as EMT marker expression in UUO renal tissues in a similar manner to rhEPO.

Conclusions

Our results demonstrate that hEPO-MPs modulate TGF-β1-induced EMT in MDCK cells via the Smad2, Smad3, and p38 MAPK pathways and significantly attenuated renal TIF in UUO kidneys.

p53 upregulated by HIF-1α promotes hypoxia-induced G2/M arrest and renal fibrosis in vitro and in vivo

Hypoxia plays an important role in the genesis and progression of renal fibrosis. The underlying mechanisms, however, have not been sufficiently elucidated. We examined the role of p53 in hypoxia-induced renal fibrosis in cell culture (human and rat renal tubular epithelial cells) and a mouse unilateral ureteral obstruction (UUO) model. Cell cycle of tubular cells was determined by flow cytometry, and the expression of profibrogenic factors was determined by RT-PCR, immunohistochemistry, and western blotting. Chromatin immunoprecipitation and luciferase reporter experiments were performed to explore the effect of HIF-1α on p53 expression. We showed that, in hypoxic tubular cells, p53 upregulation suppressed the expression of CDK1 and cyclins B1 and D1, leading to cell cycle (G2/M) arrest (or delay) and higher expression of TGF-β, CTGF, collagens, and fibronectin. p53 suppression by siRNA or by a specific p53 inhibitor (PIF-α) triggered opposite effects preventing the G2/M arrest and profibrotic changes. In vivo experiments in the UUO model revealed similar antifibrotic results following intraperitoneal administration of PIF-α (2.2 mg/kg). Using gain-of-function, loss-of-function, and luciferase assays, we further identified an HRE3 region on the p53 promoter as the HIF-1α-binding site. The HIF-1α–HRE3 binding resulted in a sharp transcriptional activation of p53. Collectively, we show the presence of a hypoxia-activated, p53-responsive profibrogenic pathway in the kidney. During hypoxia, p53 upregulation induced by HIF-1α suppresses cell cycle progression, leading to the accumulation of G2/M cells, and activates profibrotic TGF-β and CTGF-mediated signaling pathways, causing extracellular matrix production and renal fibrosis.

Oleanolic Acid Attenuates Renal Fibrosis through TGF-β/Smad Pathway in a Rat Model of Unilateral Ureteral Obstruction

Renal fibrosis is a common final pathological process in the progression of kidney disease. Oleanolic acid is a bioactive pentacyclic triterpenoid and is widely found in medicinal herbs around the world. In this study, we explored the effect of oleanolic acid on renal fibrosis and the underlying molecular mechanisms by using a rat model of unilateral ureteral obstruction (UUO). Male Sprague-Dawley rats were orally administered with oleanolic acid (6 mg/kg/d) or vehicle (olive oil) for 21 days after the UUO surgery. Upon termination, urine and blood were collected for renal function analysis, and kidneys were harvested for pathological analysis by using hematoxylin-eosin and Masson trichrome staining. Changes of extracellular matrix mRNA expressions and TGF-β/Smad signaling in the kidneys were also determined. As a result, oleanolic acid significantly reduced the kidney index, the level of serum creatinine and blood urea nitrogen, and the urinary level of microalbumin, α1-microglobulin, and N-acetyl-β-glucosaminidase. Masson trichrome staining showed significantly less collagen deposition in the UUO rats with oleanolic acid treatment. Diminished mRNA expressions of collagen I, collagen III, fibronectin, and α-SMA in the kidney tissues were observed after the treatment. Oleanolic acid led to decreased protein expressions of TGF-β, TGF-β receptor I, and TGF-β receptor II, as well as the phosphorylation of Smad2. Our current study suggested that oleanolic acid could be a complementary and alternative therapy for renal fibrosis potentially by targeting the TGF-β/Smad pathway.

Advances in Understanding the Effects of Erythropoietin on Renal Fibrosis

Renal fibrosis is the common manifestation of the pathogenesis of end-stage renal disease that results from different types of renal insult, and is a hallmark of chronic kidney disease (CKD). The main pathologic characteristics of renal fibrosis are renal interstitial fibroblast hyperplasia and the aberrant and excessive deposition of extracellular matrix, pathologies that lead to the destruction of normal renal tubules and interstitial structures. However, the biological significance of fibrosis during the progression of CKD is not clear, and there are no approved clinical treatments for delaying or reversing renal fibrosis. Studies of the mechanism of renal fibrosis and of potential measures of prevention and treatment have focused on erythropoietin (EPO), a hormone best known as a regulator of red blood cell production. These recent studies have found that EPO may also provide efficient protection against renal fibrosis. Future therapeutic approaches using EPO offer new hope for patients with CKD. The aim of the present review is to briefly discuss the role of EPO in renal fibrosis, to identify its possible mechanisms in preventing renal fibrosis, and to provide novel ideas for the use of EPO in future treatments of renal fibrosis.

DMOG, a Prolyl Hydroxylase Inhibitor, Increases Hemoglobin Levels without Exacerbating Hypertension and Renal Injury in Salt-Sensitive Hypertensive Rats

Prolyl hydroxylase (PHD) inhibitors are being developed as alternatives to recombinant human erythropoietin (rHuEPO) for the treatment of anemia in patients with chronic kidney disease (CKD). However, the effects of PHD inhibitors and rHuEPO on blood pressure and CKD in animal models susceptible to hypertension and nephropathy have not been studied. The present study compared the effects of dimethyloxaloylglycine (DMOG), a PHD inhibitor, and rHuEPO on the development of hypertension and renal injury in Dahl salt-sensitive rats fed an 8% salt diet for 3 weeks. DMOG and rHuEPO were equally effective at raising hemoglobin levels. Systolic blood pressure rose to a greater extent in rHuEPO-treated rats (267 ± 10 vs. 226 ± 4 mm Hg) than in rats given DMOG (189 ± 8 mm Hg). Urinary protein excretion increased to 568 ± 54 versus 353 ± 25 mg/day in rats treated with rHuEPO and vehicle; however, it only rose to 207 ± 21 mg/day in rats receiving DMOG. DMOG significantly attenuated the degree of glomerulosclerosis and renal interstitial fibrosis as compared with that in vehicle and rHuEPO-treated rats. This was associated with lower renal levels of monocyte chemoattractant protein-1 and interleukin-1β and increased vascular endothelial growth factor expression in cortex and medulla. These results indicate that DMOG and rHuEPO are equally effective in increasing hemoglobin levels in Dahl S rats; however, rHuEPO aggravates hypertension and renal injury, whereas DMOG has marked renoprotective effects. These results suggest that PHD inhibitors may have a therapeutic advantage for the treatment of anemia in CKD. SIGNIFICANCE STATEMENT: Prolyl hydroxylase (PHD) inhibitors are in phase 3 clinical trials as alternatives to recombinant human erythropoietin (rHuEPO) for the treatment of anemia in chronic kidney disease (CKD). The present study reveals that dimethyloxaloylglycine (DMOG), a PHD inhibitor, and rHuEPO are equally effective in increasing hemoglobin levels in Dahl S rats; however, rHuEPO aggravated hypertension and renal injury, whereas DMOG attenuated the development of hypertension and prevented renal injury. PHD inhibitors may provide a safer therapeutic option for the treatment of anemia in CKD.

JTZ-951, an HIF prolyl hydroxylase inhibitor, suppresses renal interstitial fibroblast transformation and expression of fibrosis-related factors

Some preceding studies have provided evidence that hypoxia-inducible factor (HIF)-prolyl hydroxylase (PH) inhibitors have therapeutic potential against tubular interstitial fibrosis (TIF). Recently, transformation of renal interstitial fibroblasts (RIFs) into α-smooth muscle actin-positive myofibroblasts with loss of their hypoxia-inducible erythropoietin (EPO) expression has been hypothesized as the central mechanism responsible for TIF with renal anemia (the RIF hypothesis). These reports have suggested that HIF-PH inhibitors may suppress TIF via suppressing transformation of RIFs. However, the direct effect of HIF-PH inhibitors on transformation of RIFs has not been demonstrated because there has been no appropriate assay system. Here, we established a novel in vitro model of the transformation of RIFs. This model expresses key phenotypic changes such as transformation of RIFs accompanied by loss of their hypoxia-inducible EPO expression, as proposed by the RIF hypothesis. Using this model, we demonstrated that JTZ-951, a newly developed HIF-PH inhibitor, stabilized HIF protein in RIFs, suppressed transformation of RIFs, and maintained their hypoxia-inducible EPO expression. JTZ-951 also suppressed the expression of FGF2, FGF7, and FGF18, which are upregulated during transformation of RIFs. Furthermore, expression of Fgf2, Fgf7, and Fgf18 was correlated with TIF in an animal model of TIF. We also demonstrated that not only FGF2, which is a well-known growth-promoting factor, but also FGF18 promoted proliferation of RIFs. These data suggest that JTZ-951 has therapeutic potential against TIF with renal anemia. Furthermore, FGF2, FGF7, and FGF18, which faithfully reflect the anti-TIF effects of JTZ-951, have potential as TIF biomarkers.

Low erythropoietin levels predict faster renal function decline in diabetic patients with anemia: a prospective cohort study

Elevated erythropoietin (EPO) levels have been reported to predict poor survival in various populations including diabetic patients. However, data regarding its impact on renal outcomes are scarce. We conducted a single-center, prospective cohort study of 339 type 2 diabetic patients with anemia. The primary outcome was the estimated glomerular filtration rate (eGFR) slope for two years. We performed multiple linear regression and restricted cubic spline analyses to assess the association of serum EPO levels with the renal outcome. Chronic kidney disease (CKD) was defined as eGFR <60 mL/min/1.73 m2 or urine albumin-to-creatinine ratio >30 mg/g creatinine. Median baseline EPO and eGFR level were 14.4 IU/L and 53 mL/min/1.73 m², respectively. Inappropriately low EPO levels were observed in 73% of anemic patients and 59% of anemic patients even without CKD, suggesting that EPO deficiency precedes the onset of CKD in diabetes mellitus. Multivariable analysis revealed that iron status and hemoglobin levels were major determinants of EPO levels. Median eGFR slope was −1.3 mL/min/1.73 m²/year. We found that low EPO levels, but not low hemoglobin levels, were associated with a faster decline in eGFR, independent of clinically relevant factors. The eGFR decline was steeper, particularly when the EPO level was below the upper limit of normal. Lower EPO concentrations were associated with rapid eGFR decline, especially in patients with iron deficiency (P for interaction = 0.01). Relative EPO deficiency should be considered as a culprit in anemia of unknown etiology in diabetic patients, even those without CKD. Low EPO levels, especially when accompanied by poor iron status, are predictive of rapid loss of renal function.

The emerging role of xanthine oxidase inhibition for suppression of breast cancer cell migration and metastasis associated with hypercholesterolemia

Hypercholesterolemia is reported to increase reactive oxygen species (ROS) and to promote breast cancer progression. ROS play an important role in tumor biology, and xanthine oxidase (XO) is an enzyme that generates ROS. The effects of febuxostat (FBX), an XO inhibitor, on breast cancer cell migration under LDL stimulation in vitro and metastasis of breast cancer associated with hypercholesterolemia in vivo were studied. In vitro, FBX significantly inhibited LDL-induced ROS production and cell migration. Treatment of small interfering RNA against XO was consistent with the findings of FBX treatment. In vivo, a significant increase of tumor growth and pulmonary metastasis was observed in a xenograft mouse model with 4T1 cells on a high cholesterol diet (HCD), both of which were markedly inhibited by FBX or allopurinol treatment. Moreover, ERK represented the main target-signaling pathway that was affected by FBX treatment in a xenograft mouse model on an HCD evaluated by NanoString nCounter analysis. Consistently, MEK/ERK inhibitors directly decreased the LDL-induced cell migration in vitro. In conclusion, FBX mitigates breast cancer cell migration and pulmonary metastasis in the hyperlipidemic condition, associated with decreased ROS generation and MAPK phosphorylation. The inhibition of ERK pathways is likely to underlie the XO inhibitor-mediated suppression of breast cancer cell migration.-Oh, S.-H., Choi, S.-Y., Choi, H.-J., Ryu, H.-M., Kim, Y.-J., Jung, H.-Y., Cho, J.-H., Kim, C.-D., Park, S.-H., Kwon, T.-H., Kim, Y.-L. The emerging role of xanthine oxidase inhibition for suppression of breast cancer cell migration and metastasis associated with hypercholesterolemia.

Effects of colchicine on renal fibrosis and apoptosis in obstructed kidneys

BACKGROUND/AIMS

Colchicine is an established drug for microtubule stabilization that may reduce tissue injury. No data were available that its effects may depend on the dosage of colchicine. We investigated the anti-fibrotic and apoptotic effects of various dose of colchicine in a unilateral ureteral obstruction (UUO) model.

METHODS

Thirty-six Sprague-Dawley rats were randomly assigned into six groups. Two sham groups were divided into a vehicle-treated or colchicine-treated group (100 μg/kg/day). Four UUO groups were treated with either vehicle or three different doses of colchicine for 7 days (30, 60, and 100 μg/kg/day, intraperitoneally). All of the animals were sacrificed on day 7.

RESULTS

Colchicine treatment diminished acetylated α-tubulin and tumor growth factor-β immunoreactivities in the cortical area of the 7-day obstructed kidneys, which was in dose dependent manner. Colchicine attenuated tubulointerstitial damage and apoptosis in both cortical and medullary area, and beneficial effects of colchicine therapy were dramatically shown at the higher dosage of colchicine. The expression levels of cleaved caspase-3, ED-1, and fibronectin were decreased in UUO animals.

CONCLUSIONS

We found that the proper dosage of colchicine may have anti-fibrotic and anti-apoptotic effects in obstructed kidneys. For clinical applications, an optimal dose of colchicine should be evaluated to maximize the prevention of renal disease progression.

The Effects of Darbepoetin on Peritoneal Fibrosis Induced by Chemical Peritonitis and on Peritoneal Tissue Mmp-2 and Timp-2 Levels in Rats

The aim of this study is to assess the influence of darbepoetin on the development of peritoneal fibrosis in rats induced by Chlorhexidine gluconate (0.1%) and ethanol (15%) and to determine the effect on peritoneal tissue levels of MMP–2 and TIMP–2, possible important factors in progression of peritoneal fibrosis. Twenty-four female Wistar albino rats were divided into three groups. The first group (CH group) received 3 ml/200g daily intraperitoneal injections of Chlorhexidine gluconate (0.1%) and ethanol (15%) dissolved in saline to induce chemical peritonitis; group 2 (ESA group) received 3 ml/200g daily injections of Chlorhexidine gluconate (0.1%) and ethanol (15%) dissolved in saline and also darbepoetin 12.5 microgr/ per kilogram/ day subcutaneously on the first and seventh days; group 3 (Control group) received intraperitoneal 0.9% saline (3 ml/200g/d) through the right lower quadrant by 21 gauge needle. The study duration was fourteen days. On the fifteenth day rats were sacrificed, parietal peritoneum samples were obtained from the left anterior abdominal wall. Pathological samples were examined using Hematoxyline & Eosin (HE) stains. The thickness, vasculpathy, and inflammation were determined by light microscopy. MMP-2 and TIMP-2 were studied immunohistochemically by monoclonal antibody staining. The activity of MMP-2 on peritoneal tissue was studied by gelatin zymography and TIMP–2 protein level was analysed by ELISA, biochemically. The decrease in thickness of parietal peritoneum in group ESA was statistically significant when compared to CH group (p<0.05). Inflammation scores, and vascularization score surfaces were not statistically different between these groups (p>0.05). Immunohistochemically, darbepoetin was shown to decrease MMP-2 expression on parietal peritoneum in CH group (p<0.05), but had no effect on TIMP-2 (p>0.05). Biochemically the ratio of active MMP–2 to proMMP–2 was more significantly increased in the ESA group than in the CH group (p<0.001), however, TIMP- 2 levels in both groups were decreased compared to the control group (p<0.05). Darbepoetin histopathologically reduced peritoneal fibrosis induced by Chlorhexidine gluconate. We can suggest that Darbepoetin does not cause peritoneal fibrosis and may prevent peritoneal fibrosis in rats possibly related to an effect on MMP-2 expression. Further research regarding the utility and dosage should be considered.

Dual Therapeutic Effects of an Albumin-Based Nitric Oxide Donor on 2 Experimental Models of Chronic Kidney Disease

Chronic kidney disease (CKD) is accompanied by a variety of complications, typically renal anemia and kidney fibrosis. Accordingly, it is desirable to develop the novel therapeutics that can treat these CKD conditions. Since nitric oxide (NO) has multiple functions including hypoxia inducible factor stabilizing, anti-inflammatory, anti-oxidative, and anti-apoptoic activities, the use of NO for the CKD therapy has attracted considerable interest. Here, we evaluate the therapeutic impacts of S-nitrosated human serum albumin (SNO-HSA), a long-lasting NO donor, on 2 animal models of CKD. SNO-HSA increased the expression of erythropoietin (EPO), VEGF, and eNOS by stabilizing hypoxia inducible factor-1α in HepG2 and HK-2 cells. SNO-HSA increased hematopoiesis in both healthy and renal anemia rats, suggesting the promotion of EPO production. In unilateral ureteral obstruction-treated mice, SNO-HSA ameliorated kidney fibrosis by suppressing the accumulation of renal extracellular matrix. SNO-HSA also inhibited unilateral ureteral obstruction-induced α-smooth muscle actin increase and E-cadherin decrease, suggesting that SNO-HSA might suppress the accumulation of myofibroblasts, an important factor of fibrosis. SNO-HSA also inhibited the elevations of fibrosis factors, such as transforming growth factor-β, interleukin-6, and oxidative stress, while it increased EPO production, an anti-fibrosis factor. In conclusion, SNO-HSA has the potential to function as a dual therapeutics for renal anemia and kidney fibrosis.

Apelin attenuates TGF-β1-induced epithelial to mesenchymal transition via activation of PKC-ε in human renal tubular epithelial cells

Epithelial to mesenchymal transition (EMT), a process whereby fully differentiated epithelial cells transition to a mesenchymal phenotype, has been implicated in the pathogenesis of renal fibrosis. Apelin, a bioactive peptide, has recently been recognized to protect against renal profibrotic activity, but the underlying mechanism has not yet been elucidated. In this study, we investigated the regulation of EMT in the presence of apelin-13 in vitro. Expression of the mesenchymal marker alpha-smooth muscle actin (α-SMA) and the epithelial marker E-cadherin was examined by immunofluorescence and western blotting in transforming growth factor beta 1 (TGF-β1)-stimulated human proximal tubular epithelial cells. Expression of extracellular matrix, fibronectin and collagen-I was examined by quantitative real-time PCR and ELISA. F13A, an antagonist of the apelin receptor APJ, and small interfering RNA targeting protein kinase C epsilon (PKC-ε) were used to explore the relevant signaling pathways. Apelin attenuated TGF-β1-induced EMT, and inhibited the EMT-associated increase in α-SMA, loss of E-cadherin, and secretion of extracellular matrix. Moreover, apelin activated PKC-ε in tubular epithelial cells, which in turn decreased phospho-Smad2/3 levels and increased Smad-7 levels. APJ inhibition or PKC-ε deletion diminished apelin-induced modulation of Smad signaling and suppression of tubular EMT. Our findings identify a novel PKC-ε-dependent mechanism in which apelin suppresses TGF-β1-mediated activation of Smad signaling pathways and thereby inhibits tubular EMT. These results suggest that apelin may be a new agent that can suppress renal fibrosis and retard chronic kidney disease progression.

Defective CFTR leads to aberrant β-catenin activation and kidney fibrosis

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/β-catenin signaling pathways, whereas the β-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 β-catenin. Compared to wild type, deltaF508 mice with UUO treatment exhibit significantly higher β-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/β-catenin signaling pertinent to progression of kidney fibrosis and indicates a potential treatment target.

Human CD133+ Renal Progenitor Cells Induce Erythropoietin Production and Limit Fibrosis After Acute Tubular Injury

Persistent alterations of the renal tissue due to maladaptive repair characterize the outcome of acute kidney injury (AKI), despite a clinical recovery. Acute damage may also limit the renal production of erythropoietin, with impairment of the hemopoietic response to ischemia and possible lack of its reno-protective action. We aimed to evaluate the effect of a cell therapy using human CD133⁺ renal progenitor cells on maladaptive repair and fibrosis following AKI in a model of glycerol-induced rhabdomyolysis. In parallel, we evaluated the effect of CD133⁺ cells on erythropoietin production. Administration of CD133⁺ cells promoted the restoration of the renal tissue, limiting the presence of markers of injury and pro-inflammatory molecules. In addition, it promoted angiogenesis and protected against fibrosis up to day 60. No effect of dermal fibroblasts was observed. Treatment with CD133⁺ cells, but not with PBS or fibroblasts, limited anemia and increased erythropoietin levels both in renal tissue and in circulation. Finally, CD133⁺ cells contributed to the local production of erythropoietin, as observed by detection of circulating human erythropoietin. CD133⁺ cells appear therefore an effective source for cell repair, able to restore renal functions, including erythropoietin release, and to limit long term maldifferentiation and fibrosis.

Alpha1-Antitrypsin Attenuates Renal Fibrosis by Inhibiting TGF-β1-Induced Epithelial Mesenchymal Transition

Alpha1-antitrypsin (AAT) exerts its anti-inflammatory effect through regulating the activity of serine proteinases. This study evaluated the inhibitory effects of AAT against the transforming growth factor (TGF)-β1 induced epithelial-to-mesenchymal transition (EMT) in unilateral ureter obstruction (UUO) mice and Madin-Darby canine kidney (MDCK) cells. C57BL/6 mice with induced UUO were injected intraperitoneally with AAT (80 mg/Kg) or vehicle for 7 days. MDCK cells were treated with TGF-β1 (2 ng/mL) for 48 hours to induce EMT, and co-treated with AAT (10 mg/mL) to inhibit the EMT. Masson’s trichrome and Sirius red staining was used to estimate the extent of renal fibrosis in UUO mice. The expression of alpha-smooth muscle actin (α-SMA), vimentin, fibronectin, collagen I, and E-cadherin in MDCK cells and kidney tissue were evaluated. Masson’s and Sirius red staining revealed that the area of renal fibrosis was significantly smaller in AAT treated UUO group compared with that of UUO and vehicle treated UUO groups. AAT treatment attenuated upregulation of Smad2/3 phosphorylation in UUO mouse model. Co-treatment of MDCK cells with TGF-β1 and AAT significantly attenuated the changes in the expression of α-SMA, vimentin, fibronectin, collagen I, and E-cadherin. AAT also decreased the phosphorylated Smad3 expression and the phosphorylated Smad3/Smad3 ratio in MDCK cells. AAT treatment inhibited EMT induced by TGF-β1 in MDCK cells and attenuated renal fibrosis in the UUO mouse model. The results of this work suggest that AAT could inhibit the process of EMT through the suppression of TGF-β/Smad3 signaling.

Blockade of Orai1 Store-Operated Calcium Entry Protects against Renal Fibrosis

Evidence supports an important role of Ca²⁺ release-activated Ca²⁺ channel protein 1 (Orai1)-mediated Ca²⁺ entry in the development of renal fibrosis, a common pathologic feature of CKDs that lead to ESRD, but the molecular mechanisms remain unclear. We determined the role of Orai1 calcium channel in renal fibrosis induced by high-fat diet and by unilateral ureteral obstruction. Mouse kidneys with fibrosis had higher levels of Orai1 protein expression than did kidneys without fibrosis. In vivo knockdown of Orai1 with adenovirus harboring Orai1-short hairpin RNA or inhibition of Orai1 with SKF96365 dramatically prevented renal fibrosis and significantly decreased protein expression of fibronectin, α‑smooth muscle actin, and TGF‑β1 in the kidney cortex of ApoE^-/- mice on a high-fat diet and in the obstructed kidneys of mice with unilateral ureteral obstruction. Compared with kidney biopsy specimens of patients with glomerular minimal change disease, those of patients with fibrotic nephropathy had higher expression levels of Orai1. In cultured human proximal tubule epithelial cells (HK2), knockdown of Orai1 Ca²⁺ channel with adenovirus-Orai1-short hairpin RNA markedly inhibited TGF-β1-induced intracellular Ca²⁺ influx and phosphorylation of smad2/3. Knockdown or blockade of the Orai1 Ca²⁺ channel in HK2 cells also prevented epithelial-to-mesenchymal transition induced by TGF‑β1. In conclusion, blockade of the Orai1 Ca²⁺ channel prevented progression of renal fibrosis in mice, likely by suppressing smad2/3 phosphorylation and TGF-β1-induced epithelial-to-mesenchymal transition. These results render the Orai1 Ca²⁺ channel a potential therapeutic target against renal fibrosis.

Erythropoiesis-stimulating agent slows the progression of chronic kidney disease: a possibility of a direct action of erythropoietin

BACKGROUND

Controversy exists regarding the renoprotective effect of erythropoiesis-stimulating agent (ESA) in progressive chronic kidney disease (CKD) with renal anemia. In this study, we examined whether ESA therapy has a renoprotective effect in progressive CKD.

METHODS

The subjects in this retrospective observational study were 68 non-dialysis dependent CKD patients with renal anemia. We compared the progression rate (PR), defined by the slope of the linear regression line of estimated glomerular filtration rate, measured during 6 months just before and after the start of ESA therapy. We also investigated the factors affecting renoprotective efficacy of ESA therapy against the progression of CKD.

RESULTS

Median (interquartile range) PR decreased significantly from 6.2 (3.7-12.7) to 4.0 (-0.3 to 7.3) mL/min/1.73 m(2)/year after the start of ESA therapy. Blood pressure levels and rate of medication with renin-angiotensin system inhibitors were comparable between the two periods. Next, we investigated the factors affecting renoprotective efficacy of ESA therapy against the progression of CKD. Thirty patients were good renal responders, defined as those with the ratio of post-/pre-PR of <0.5 and the difference of pre- minus post-PR >5.0 mL/min/1.73 m(2)/year, and 38 patients were poor renal responders who did not meet the definition of good renal responders. Multivariable logistic regression analysis showed that weekly ESA dose, but not increase in hemoglobin level, was a significant and independent determinant of the renoprotective effect of ESA.

CONCLUSION

ESA therapy slows the progression of CKD and part of the effect might be attributed to the direct renoprotective action of ESA.

Erythropoietin protects the tubular basement membrane by promoting the bone marrow to release extracellular vesicles containing tPA-targeting miR-144

Renal fibrosis is an inevitable outcome of chronic kidney disease (CKD). Erythropoietin (EPO) has been recently reported to be able to mitigate renal fibrosis. The mechanism underlying the protective effect of EPO, however, remains elusive. In the present study, employing a mouse model of renal tubulointerstitial fibrosis induced by unilateral ureteral obstruction (UUO), we demonstrated that EPO markedly reduced the disruption of the tubular basement membrane (TBM) through attenuating the activation of tissue plasminogen activator (tPA) and matrix metalloproteinase 9 (MMP9), the major matrix proteolytic network in the obstructed kidney. Instead of acting directly on tPA in the kidney, EPO strongly increased the level of circulating microRNA (miR)-144, which was delivered to the injured renal fibroblasts via extracellular vesicles (EVs) to target the tPA 3′-untranslated region and suppress tPA expression. The protective effect of EPO on mouse TBM was inhibited by miR-144 antagomir. Furthermore, in vitro results confirmed that EPO could stimulate bone marrow-derived Sca-1+CD44+CD11b−CD19− cells to secrete miR-144-containing EVs, which markedly suppressed tPA expression, as well as metalloproteinase 9 (MMP9) level and activity, in cultured renal fibroblasts. In conclusion, our study provides the first evidence that EPO protects mouse renal TBM through promoting bone marrow cells to generate and secrete miR-144, which, in turn, is efficiently delivered into the mouse kidney via EVs to inhibit the activation of the tPA/MMP9-mediated proteolytic network. This finding thus suggests that EPO, a hormone widely used to treat anemia in CKD, is a potential therapeutic strategy for renal fibrosis.

SQSTM1/p62 regulates the expression of junctional proteins through epithelial-mesenchymal transition factors

The epithelial to mesenchymal transition (EMT) is an essential process during development and during tumor progression. Here, we observed the accumulation of the selective autophagy receptor and signaling adaptor sequestosome-1 (SQSTM1/p62) during growth factor-induced EMT in immortalized and tumor-derived epithelial cell lines. Modulation of the p62 level regulated the expression of junctional proteins. This effect was dependent on the ubiquitin-associated domain of p62, which stabilized the TGFβ/Smad signaling co-activator Smad4 and the EMT transcription factor Twist. This study highlights a novel function of p62 in a major epithelial phenotypic alteration.

Epithelial-to-Mesenchymal Transition in Diabetic Nephropathy: Fact or Fiction?

The pathophysiology of diabetic nephropathy (DN), one of the most serious complications in diabetic patients and the leading cause of end-stage renal disease worldwide, is complex and not fully elucidated. A typical hallmark of DN is the excessive deposition of extracellular matrix (ECM) proteins in the glomerulus and in the renal tubulointerstitium, eventually leading to glomerulosclerosis and interstitial fibrosis. Although it is obvious that myofibroblasts play a major role in the synthesis and secretion of ECM, the origin of myofibroblasts in DN remains the subject of controversial debates. A number of studies have focused on epithelial-to-mesenchymal transition (EMT) as one source of matrix-generating fibroblasts in the diseased kidney. EMT is characterized by the acquisition of mesenchymal properties by epithelial cells, preferentially proximal tubular cells and podocytes. In this review we comprehensively review the literature and discuss arguments both for and against a function of EMT in renal fibrosis in DN. While the precise extent of the contribution to nephrotic fibrosis is certainly arduous to quantify, the picture that emerges from this extensive body of literature suggests EMT as a major source of myofibroblasts in DN.

Superoxide overproduction and kidney fibrosis: a new animal model

Objective

To establish whether the mutation in the Immp2L gene induces renal fibrosis and whether aging exacerbates renal morphology in mice.

Methods

Female mutant mice with mutation in the inner mitochondrial membrane peptidase 2-like protein at 3 and 18 months of age were used. Renal fibrosis was analyzed using classic fibrosis score, Masson’s trichrome staining, and analysis of profibrotic markers using real time polymerase chain reaction (superoxide dismutase 1, metalloproteinase-9, erythropoietin, transforming growth factor beta), and immunostaining (fibroblasts and Type IV collagen). Oxidative stress markers were determined by immunohistochemistry. The number of renal apoptotic cells was determined. Renal function was estimated by serum creatinine.

Results

Young mutant mice had significantly more glomerulosclerosis than age-matched mice (p=0.034). Mutant mice had more tubular casts (p=0.025), collagen deposition (p=0.019), and collagen type IV expression (p<0.001). Superoxide dismutase 1 expression was significantly higher in young mutants (p=0.038). Old mutants exhibited significantly higher expression of the fibroblast marker and macrophage marker (p=0.007 and p=0.012, respectively). The real time polymerase chain reaction of metalloproteinase-9 and erythropoietin were enhanced 2.5- and 6-fold, respectively, in old mutants. Serum creatinine was significantly higher in old mutants (p<0.001).

Conclusion

This mutation altered renal architecture by increasing the deposition of extracellular matrix, oxidative stress, and inflammation, suggesting a protective role of Immp2L against renal fibrosis.

Effect of Quyu Chencuo Formula () on Renal Fibrosis in Obstructive Nephropathy Rats

OBJECTIVE

To observe the effect of Quyu Chencuo Formula (, QCF) on renal fibrosis in rats with obstructive nephropathy.

METHODS

Twenty-four rats were randomly divided into three groups, 4 for sham operation as the control group, 10 for unilateral ureteral obstruction (UUO) model group, and the rest 10 for QCF treating UUO model group. All rats were sacrificed under 3% pentobarbital (50 mg/kg) anesthesia on the 14th day after surgery, then the right kidney samples of rats were harvested for hematoxylin eosin (HE) staining and Masson staining to observe the renal pathological changes. Immunohistochemistry and Western blotting were used to examine the expression of transforming growth factor β1 (TGF-β1), and real-time polymerase chain reaction (RT-PCR) was employed to examine the expressions of TGF-β1, α-smooth muscle actin (α-SMA) and E-cadherin mRNA.

RESULTS

HE and Masson staining showed that the renal interstitial of the rats in the control group had no significant fibrotic lesion; in the model group, there were obvious interstitial fibrosis; for the QCF group, there were epithelial cell necrosis, infiltration of lymphocytes and mononuclear cells, aggravated interstitial fibrosis in varied degrees, but the pathological changes were less in the QCF group than in the model group. The immunohistochemistry and Western blotting results showed that the TGF-β1 expression was increased significantly in the model group, while decreased significantly in the QCF group (P<0.05); RT-PCR showed that the mRNA expression of α-SMA and TGF-β1 increased significantly in the model group, while both were significantly decreased in the QCF group compared with the model group (P<0.05). The mRNA expression of E-cadherin was decreased significantly in the model group, and it was significantly increased in the QCF group as compared with the model group (P<0.05).

CONCLUSION

QCF may improve renal fibrosis by regulating the expressions of TGF-β1, α-SMA and E-cadherin, and prevent the progress of kidney fibrosis.

Recent advances in renal interstitial fibrosis and tubular atrophy after kidney transplantation

Although kidney transplantation has been an important means for the treatment of patients with end stage of renal disease, the long-term survival rate of the renal allograft remains a challenge. The cause of late renal allograft loss, once known as chronic allograft nephropathy, has been renamed “interstitial fibrosis and tubular atrophy” (IF/TA) to reflect the histologic pattern seen on biopsy. The mechanisms leading to IF/TA in the transplanted kidney include inflammation, activation of renal fibroblasts, and deposition of extracellular matrix proteins. Identifying the mediators and factors that trigger IF/TA may be useful in early diagnosis and development of novel therapeutic strategies for improving long-term renal allograft survival and patient outcomes. In this review, we highlight the recent advances in our understanding of IF/TA from three aspects: pathogenesis, diagnosis, and treatment.

Augmenter of liver regeneration inhibits TGF-β1-induced renal tubular epithelial-to-mesenchymal transition via suppressing TβR II expression in vitro

Tubular epithelial-to-mesenchymal transition (EMT) plays a crucial role in the progression of renal tubular interstitial fibrosis (TIF), which subsequently leads to chronic kidney disease (CKD) and eventually, end-stage renal disease (ESRD). We propose that augmenter of liver regeneration (ALR), a member of the newly discovered ALR/Erv1 protein family shown to ameliorate hepatic fibrosis, plays a similar protective role in renal tubular cells and has potential as a new treatment option for CKD. Here, we showed that recombinant human ALR (rhALR) inhibits EMT in renal tubular cells by antagonizing activation of the transforming growth factor-β1 (TGF-β1) signaling pathway. Further investigation revealed that rhALR suppresses the expression of TGF-β receptor type II (TβR II) and significantly alleviates TGF-β1-induced phosphorylation of Smad2 and nuclear factor-κB (NF-κB). No apparent adverse effects were observed upon the addition of rhALR alone to cells. These findings collectively suggest that ALR plays a role in inhibiting progression of renal tubular EMT, supporting its potential utility as an effective antifibrotic strategy to reverse TIF in CKD.

Augmenter of liver regeneration ameliorates renal fibrosis in rats with obstructive nephropathy

Renal fibrosis is a hallmark in CKD (chronic kidney disease) and is strongly correlated to the deterioration of renal function that is characterized by tubulointerstitial fibrosis, tubular atrophy, glomerulosclerosis and disruption of the normal architecture of the kidney. ALR (augmenter of liver regeneration) is a growth factor with biological functions similar to those of HGF (hepatocyte growth factor). In this study, our results indicate that endogenous ALR is involved in the pathological progression of renal fibrosis in UUO (unilateral ureteral obstruction) rat model. Moreover, we find that administration of rhALR (recombinant human ALR) significantly alleviates renal interstitial fibrosis and reduces renal-fibrosis-related proteins in UUO rats. Further investigation reveals that rhALR suppresses the up-regulated expression of TGF-β1 (transforming growth factor β1) induced by UUO operation in the obstructed kidney, and inhibits Smad2 and Smad3 phosphorylation activated by the UUO-induced injury in the animal model. Therefore we suggest that ALR is involved in the progression of renal fibrosis and administration of rhALR protects the kidney against renal fibrosis by inhibition of TGF-β/Smad activity.

Astragaloside IV inhibits renal tubulointerstitial fibrosis by blocking TGF-β/Smad signaling pathway in vivo and in vitro

Astragaloside IV (AS-IV) is a major active ingredient from Radix astragali, which has been considered as a renoprotective agent; however, its molecular mechanisms are unclear. Thus, we designed to investigate the renoprotective effects and mechanisms of AS-IV in rat model of renal fibrosis induced by unilateral ureteral obstruction (UUO) in vivo and TGF-β1-stimulated rat renal fibroblasts (NRK-49F) in vitro. Sprague-Dawley rats were randomly divided into six groups: sham operation, UUO, UUO/AS-IV (3.3, 10, 33 mg·kg(-1)·d(-1)), and UUO/enalapril (4 mg·kg(-1)·d(-1)). Renal function, tubulointerstitial damage index score, extracellular matrix (ECM) deposition, and the expressions of TGF-β1, connective tissue growth factor (CTGF), α-SMA, fibronectin, collagen I, III, Smad2/3, phosphorylated-Smad2/3, and Smad7 were measured. In addition, the expressions of CTGF, α-SMA, fibronectin, collagen I, III, Smad2/3, phosphorylated-Smad2/3, and Smad7 were measured in TGF-β1-stiumlated NRK-49F cell line. AS-IV significantly decreased UUO-induced renal fibrosis and functional impairment, which are associated with inhibition of TGF-β1, CTGF, α-SMA, and collagen matrix expression, and a decrease in serum creatinine and urea nitrogen. The renoprotective effects of AS-IV on fibrosis were associated with up-regulation of Smad7, thereby blocking up-regulations of TGF-β1, CTGF, and α-SMA, and activation of phosphorylated-Smad2/3. These effects were further conformed in NRK-49F cell line stimulated by TGF-β1. Moreover, knockdown of Smad7 gene in NRK-49F cells was able to prevent AS-IV-induced inhibition to Smad2/3 signaling activation, expression of CTGF, α-SMA, and ECM proteins in response to TGF-β1. Renal tubulointerstitial fibrosis was attenuated by treatment with AS-IV, which was closely related to induction of Smad7, thereby inhibiting TGF-β/Smad signaling.

Increased progression to kidney fibrosis after erythropoietin is used as a treatment for acute kidney injury

Treatment of renal ischemia-reperfusion (IR) injury with recombinant human erythropoietin (rhEPO) reduces acute kidney injury and improves function. We aimed to investigate whether progression to chronic kidney disease associated with acute injury was also reduced by rhEPO treatment, using in vivo and in vitro models. Rats were subjected to bilateral 40-min renal ischemia, and kidneys were studied at 4, 7, and 28 days postreperfusion for renal function, tubular injury and repair, inflammation, and fibrosis. Acute injury was modulated using rhEPO (1,000 or 5,000 IU/kg, intraperitoneally) at the time of reperfusion. Renal tubular epithelial cells or fibroblasts in culture were subjected to hypoxia or oxidative stress, with or without rhEPO (200 IU/ml), and fibrogenesis was studied. The results of the in vivo model confirmed functional and structural improvement with rhEPO at 4 days post-IR (P < 0.05). At 7 days post-IR, fibrosis and myofibroblast stimulation were increased with IR with and without rhEPO (P < 0.01). However, at 28 days post-IR, renal fibrosis and myofibroblast numbers were significantly greater with IR plus rhEPO (P < 0.01) compared with IR only. Mechanistically, rhEPO stimulated profibrotic transforming growth factor-β, oxidative stress (marker 8-hydroxy-deoxyguanosine), and phosphorylation of the signal transduction protein extracellular signal-regulated kinase. In vitro, rhEPO protected tubular epithelium from apoptosis but stimulated epithelial-to-mesenchymal transition and also protected and activated fibroblasts, particularly with oxidative stress. In summary, although rhEPO was protective of renal function and structure in acute kidney injury, the supraphysiological dose needed for renoprotection contributed to fibrogenesis and stimulated chronic kidney disease in the long term.

Dual inhibiting senescence and epithelial-to-mesenchymal transition by erythropoietin preserve tubular epithelial cell regeneration and ameliorate renal fibrosis in unilateral ureteral obstruction

This study aims to investigate the renoprotective effect of recombinant human erythropoietin (rhEPO) treatment could preserve tubular epithelial cell regeneration and ameliorate renal fibrosis by dual inhibition of stress-induced senescence and EMT in unilateral ureteric obstruction (UUO) mouse model. UUO or sham-operated mice were randomly assigned to receive rhEPO or vehicle treatment and were sacrificed on days 3, 7, and 14. Kidney specimens were fixed for histopathological and immunohistochemical study. The expression of S100A4, TGF-β1, BMP-7, Smad2/3, Smad1/5/8, and p16(INK4a) was determined by western blot and real-time RT-PCR. Vehicle treated UUO mice had increased tubular atrophy and interstitial fibrosis within 3 to 14 days. An increase in TGF-β1, Smad2/3, S100A4, and p16(INK4a) expression and a decrease in BMP-7 and Smad1/5/8 expression were observed in the obstructed kidneys. p16(INK4a) was positively correlated with TGF-β1/Smad2/3 and negatively correlated with BMP-7/Smad1/5/8 in UUO mice. rhEPO treatment significantly suppressed the upregulation of TGF-β, Smad2/3, S100A4, and p16(INK4a) and preserved the downregulation of BMP-7 and Smad1/5/8, resulting in markedly reduced TA/IF compared to the vehicle treated mice. The renoprotective effects of rhEPO could ameliorate renal TA/IF by modulating senescence and EMT which could be a part of therapeutic option in patients with chronic kidney disease.

Erythropoiesis-stimulating agents in chronic kidney disease: what have we learned in 25 years?

Since the pioneering studies by Eschbach et al in 1987, erythropoiesis-stimulating agents (ESAs) have become the mainstay of anemia therapy in chronic kidney disease (CKD) patients. The introduction of ESAs 25 years ago markedly improved the lives of many patients with CKD, who until then had severe, often transfusion-dependent anemia. However, randomized controlled trials demonstrate an increased risk for cardiovascular events such as stroke, thrombosis, and death at nearly normal hemoglobin concentrations and higher ESA doses in CKD. By contrast, kidney transplant recipients may represent a unique population of CKD patients who may benefit from ESA therapy. This review discusses potential mechanisms involving the erythropoietic and nonerythropoietic effects of ESA treatment and ESA resistance. Further research aimed at elucidating the causal pathways is strongly recommended. Given current knowledge, however, clinical practice should avoid disproportionately high dosages of ESAs to achieve recommended hemoglobin targets, particularly in those with significant cardiovascular morbidity or ESA resistance. The key to CKD anemia management will be individualization of the potential benefits of reducing blood transfusions and anemia-related symptoms against the risks of harm.

The effect of simvastatin and erythropoietin on renal fibrosis in rats with unilateral ureteral obstruction

Prevention of fibrosis is a very important therapeutic strategy in the treatment of obstructive nephropathy (ON). The aim of this study is to show and compare the actions of Simvastatin (Simv) and Erythropoietin (Epo) in renal expression of nuclear factor kappa B (NFκB), transforming growth factor-β (TGF-β), basic fibroblast growth factor (bFGF), platelet-derived growth factor B (PDGF-B), fibronectin and development of interstitial fibrosis in rats with unilateral ureteral obstruction (UUO). A total of 48 Sprague-Dawley rats were allocated to 4 groups of sham, Epo, Simv and control. Unilateral ureteral ligation was performed on all rats except the Sham group. For interstitial fibrosis Masson's trichrome stain and for the expression of TGF-β, PDGF-B, bFGF, NFκB and fibronectin, immunohistochemical methods were used. In the Epo and Simv groups, expression of TGF-β and fibronectin and staining with Masson's trichrome were less compared to the control group. In addition, fibronectin expression in the Epo group was less than the Simv group. Unlike the Simv group, NFκB and bFGF expression in the Epo group were less when compared to the control group. Consequently, it was seen that both Epo and Simv prevented fibrosis in ON. Epo was superior in this effect by suppressing the expressions of NFκB and bFGF more effectively than Simv. Based on this finding, Epo might be a better agent than Simv in the prevention of fibrosis in ON.

Prophylaxis with erythropoietin versus placebo reduces acute kidney injury and neutrophil gelatinase-associated lipocalin in patients undergoing cardiac surgery: a randomized, double-blind controlled trial

BACKGROUND

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication following coronary bypass graft (CABG) surgery. Multi-factorial causes of CSA-AKI involve oxidative stress and inflammation. Erythropoietin (EPO) has been shown from many studies to have a reno-protective effect. The present study was conducted to examine the role of EPO in preventing CSA-AKI.

METHODS

This prospective, randomized, double-blind, placebo-controlled trial was conducted in the Cardiovascular and Thoracic Unit. One hundred patients randomly received either 200 U/kg of rHuEPO (n = 50) or saline (n = 50) intravenously three days before operation, and rHuEPO 100 U/kg or saline at operation time. The serum creatinine (SCr), estimated glomerular filtration rate (eGFR) and urine neutrophil gelatinase-associated lipocaline (NGAL) were measured in order to evaluate renal injury following CABG.

RESULTS

The incidence of CSA-AKI was significantly lower in rHuEPO group (14%) when compared with the placebo group (38%; p < 0.01). The mean intensive care unit (ICU) and hospital stays of the rHuEPO group were significantly shorter than the placebo group (p < 0.01). Postoperative increases in SCr and decreases in eGFR were significantly lower in the rHuEPO group than the placebo group (p < 0.05). The mean urine NGAL in rHuEPO group was significantly lower than the placebo group at 3 hr, 6 hr, 12 hr and 18 hr after CABG (p < 0.05), respectively.

CONCLUSIONS

Prophylaxis administration with intravenous rHuEPO before cardiac surgery decreased the incidence of CSA-AKI and urine NGAL with reduced days in ICU and hospital in elective CABG patients.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01066351.

Improving outcomes of acute kidney injury using mouse renal progenitor cells alone or in combination with erythropoietin or suramin

Introduction

So far, no effective therapy is available for acute kidney injury (AKI), a common and serious complication with high morbidity and mortality. Interest has recently been focused on the potential therapeutic effect of mouse adult renal progenitor cells (MRPC), erythropoietin (EPO) and suramin in the recovery of ischemia-induced AKI. The aim of the present study is to compare MRPC with MRPC/EPO or MRPC/suramin concomitantly in the treatment of a mouse model of ischemia/reperfusion (I/R) AKI.

Methods

MRPC were isolated from adult C57BL/6-gfp mice. Male C57BL/6 mice (eight-weeks old, n = 72) were used for the I/R AKI model. Serum creatinine (Cr), blood urea nitrogen (BUN) and renal histology were detected in MRPC-, MRPC/EPO-, MRPC/suramin- and PBS-treated I/R AKI mice. E-cadherin, CD34 and GFP protein expression was assessed by immunohistochemical assay.

Results

MRPC exhibited characteristics consistent with renal stem cells. The features of MRPC were manifested by Pax-2, Oct-4, vimentin, α-smooth muscle actin positive, and E-cadherin negative, distinguished from mesenchymal stem cells (MSC) by expression of CD34 and Sca-1. The plasticity of MRPC was shown by the ability to differentiate into osteoblasts and lipocytes in vitro. Injection of MRPC, especially MRPC/EPO and MRPC/suramin in I/R AKI mice attenuated renal damage with a decrease of the necrotic injury, peak plasma Cr and BUN. Furthermore, seven days after the injury, MRPC/EPO or MRPC/suramin formed more CD34⁺ and E-cadherin⁺ cells than MRPC alone.

Conclusions

These results suggest that MRPC, in particular MRPC/EPO or MRPC/suramin, promote renal repair after injury and may be a promising therapeutic strategy.

Physical and chemical microenvironmental cues orthogonally control the degree and duration of fibrosis-associated epithelial-to-mesenchymal transitions

Increased tissue stiffness and epithelial-to-mesenchymal transitions (EMTs) are two seemingly discrete hallmarks of fibrotic diseases. Despite recent findings highlighting the influence of tissue mechanical properties on cell phenotype, it remains unclear what role increased tissue stiffness has in the regulation of previously reported fibronectin-mediated EMTs associated with pulmonary fibrosis. Nano-indentation testing of lung interstitial spaces showed that in vivo cell-level Young's moduli increase with the onset of fibrosis from ∼2 to ∼17 kPa. In vitro, we found that stiff, but not soft, fibronectin substrates induce EMT, a response dependent on cell contraction-mediated integrin activation of TGFβ. Activation or suppression of cell contractility with exogenous factors was sufficient to overcome the effect of substrate stiffness. Pulse-chase experiments indicate that the effect of cell contractility is dose- and time-dependent. In response to low levels of TGFβ on soft surfaces, either added exogenously or produced through thrombin-induced contraction, cells will initiate the EMT programme, but upon removal revert to an epithelial phenotype. These results identify matrix stiffness and/or cell contractility as critical targets for novel therapeutics for fibrotic diseases.

Renal functional decline and glomerulotubular injury are arrested but not restored by release of unilateral ureteral obstruction (UUO)

Murine unilateral ureteral obstruction (UUO), a major model of progressive kidney disease, causes loss of proximal tubular mass and formation of atubular glomeruli. Adult C57BL/6 mice underwent a sham operation or reversible UUO under anesthesia. In group 1, kidneys were harvested after 7 days. In group 2, the obstruction was released after 7 days, and a physiological study of both kidneys was performed 30 days later. Renal blood flow (RBF), glomerular filtration rate (GFR), urine protein, and albumin excretion were measured after ligation of either the left or right ureter. Glomerular volume (periodic acid-Schiff), glomerulotubular integrity and proximal tubular mass (Lotus tetragonolobus lectin), and interstitial collagen (Sirius red) were measured by histomorphometry. Obstructed kidney weight was reduced by 15% at 7 days but was not different from sham after a 30-day recovery. Glomerular volume and proximal tubular area of the obstructed kidney were reduced by 55% at 7 days, but normalized after 30 days. Interstitial collagen deposition increased 2.4-fold after 7 days of UUO and normalized after release. However, GFR and RBF were reduced by 40% and urine albumin/protein ratio was increased 2.8-fold 30 days after release of UUO. This was associated with a 50% reduction in glomerulotubular integrity despite a 30-day recovery (P < 0.05 for all data). We conclude that release of 7-day UUO can arrest progression but does not restore normal function of the postobstructed kidney. Although the remaining intact nephrons have hypertrophied, glomerular injury is revealed by albuminuria. These results suggest that glomerulotubular injury should become the primary target of slowing progressive kidney disease.

The nephroprotective properties of recombinant human erythropoietin in kidney transplantation: experimental facts and clinical proofs

Adaptive responses to hypoxia, including hypoxia-inducible factor signaling, allow the cell to satisfy its basal metabolic demand and avoid death, but these responses can also be deleterious by promoting inflammation, cell dedifferentiation and fibrogenesis. Therefore, targeting hypoxia constitutes a promising therapeutic avenue. Recombinant human erythropoietin (rhEPO) appeared as a good candidate therapy because its hematopoietic properties could reverse anemia, and its tissue-protective properties could reduce cell death and limit maladaptive cellular responses to hypoxia. Despite experimental evidence on the nephroprotecive properties of rhEPO, recent clinical trials provided evidence that rhEPO was ineffective in preventing delayed graft function after ischemic acute injury but that the normalization of hemoglobin values preserved kidney function deterioration and reduced graft loss. Our aim here is to provide a survey of the rationale for evaluating the administration of rhEPO in the setting of kidney transplantation. We will discuss the intriguing findings that emerged from the clinical trials and the discrepancies between promising experimental results and negative clinical studies, as well as the differences in terms of the benefits and safety profiles of the normalization of hemoglobin values in chronic kidney disease patients and kidney transplant patients.

cAMP and Epac in the regulation of tissue fibrosis

Fibrosis, the result of excess deposition of extracellular matrix (ECM), in particular collagen, leads to scarring and loss of function in tissues that include the heart, lung, kidney and liver. The second messenger cAMP can inhibit the formation and extent of ECM during this late phase of inflammation, but the mechanisms for these actions of cAMP and of agents that elevate tissue cAMP levels are not well understood. In this article, we review the fibrotic process and focus on two recently recognized aspects of actions of cAMP and its effector Epac (Exchange protein activated by cAMP): (a) blunting of epithelial-mesenchymal transformation (EMT) and (b) down-regulation of Epac expression by profibrotic agents (e.g. TGF-β, angiotensin II), which may promote tissue fibrosis by decreasing Epac-mediated antifibrotic actions. Pharmacological approaches that raise cAMP or blunt the decrease in Epac expression by profibrotic agents may thus be strategies to block or perhaps reverse tissue fibrosis. LINKED ARTICLES This article is part of a themed section on Novel cAMP Signalling Paradigms. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.166.issue-2.

3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor simvastatin ameliorates renal fibrosis through HOXA13-USAG-1 pathway

Epidemiological data have suggested that 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (statins) prevent the progression of chronic kidney diseases (CKDs), whereas the precise mechanism explaining in vitro to in vivo is missing. This study is aimed at exploring a new mechanism of action by statins on renal fibrosis, a hallmark of CKD, using mouse renal fibrosis model in vivo and Madin-Darby canine kidney (MDCK) cells expressing USAG-1 in vitro. C57/BL6 mice fed a 0.2% adenine-containing diet for 4 weeks developed renal dysfunction accompanied with severe tubulointerstitial fibrosis. Subsequent simvastatin (SIM) treatment (50 mg/kg per day) for 2 weeks significantly suppressed fibrosis progression. We found that SIM enhanced bone morphogenetic protein-7 (BMP-7)-mediated anti-fibrotic signaling with the reduced expression of uterine sensitization-associated gene-1 (USAG-1), a BMP-7 antagonist produced by renal distal tubular epithelial cells. Therefore, MDCK cells were incubated with transforming growth factor-β1 and showed increased expression of USAG-1 and α-smooth muscle actin; SIM significantly reduced them. SIM significantly increased E-cadherin expression. Gene knockdown experiments using MDCK suggested that homeobox protein Hox-A13 (HOXA13) played a suppressive role in the USAG-1 gene and thus SIM reduced USAG-1 by increasing HOXA13 expression. The data from our study demonstrate that SIM, one of statins, contributes to prevent the progression of renal fibrosis by upregulating BMP-7-mediated anti-fibrotic signaling and that one aspect of crucial efficacies is achieved by regulating HOXA13 and USAG-1. HOXA13-USAG-1 pathway is a newly identified mechanism in renal fibrosis and will be a new therapeutic target for preventing renal fibrosis progression in CKDs.

A nonerythropoietic derivative of erythropoietin inhibits tubulointerstitial fibrosis in remnant kidney

BACKGROUND

The tissue-protective effects of erythropoietin (EPO) have been extensively investigated, and EPO administration can raise the hemoglobin (Hb) concentration. Recently, we reported that carbamylated erythropoietin (CEPO) protected kidneys from ischemia-reperfusion injury as well as EPO.

METHODS

To investigate the clinical applications of CEPO, we next evaluated the long-term therapeutic effect of CEPO using a tubulointerstitial model rat. We randomized remnant kidney model rats to receive saline, EPO, or CEPO for 8 weeks.

RESULTS

CEPO- and EPO-treated rats had improved serum creatinine levels compared with saline-treated remnant kidney model rats, although the Hb level was significantly increased in EPO-treated rats. Two-photon microscopy revealed that EPO/CEPO significantly ameliorated tubular epithelial cell damage assessed by endocytosis. In addition, CEPO or EPO protected endothelial cells with a sustained blood flow rate. EPO or CEPO suppressed the number of TUNEL-positive apoptotic cells with weak αSMA staining. Furthermore, PCR analysis demonstrated that TGF-β and type I collagen expression was attenuated in EPO- or CEPO-treated rats, accompanied by a significant decrease in interstitial fibrosis.

CONCLUSION

We established a long-term therapeutic approach to protect tubulointerstitial injury with CEPO, and thus, the therapeutic value of this approach warrants further attention and preclinical studies.

Recombinant human erythropoietin reduces rhabdomyolysis-induced acute renal failure in rats

BACKGROUND

Rhabdomyolysis is one of the causes of acute renal failure. Erythropoietin (EPO) has been found to interact with its receptor (EPO-R) expressed in a large variety of non-haematopoietic tissues to induce a range of pleiotropic cytoprotective actions. In this study, we used recombinant human erythropoietin (rhEPO) to study the effects on the glycerol-induced rhabdomyolysis with acute renal failure in rats.

METHODS

Twenty-four rats were divided into three groups as glycerol group, glycerol+EPO group and normal saline+EPO group. Rhabdomyolysis was induced by intramuscular injection of 10 mlkg(-1) 50% glycerol in rats. Ten minutes later, the rats received an intravenous injection of rhEPO (300 Ukg(-1)). Biochemical substances, including haemoglobin, blood urea nitrogen (BUN), creatinine (Cre), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) and creatine phosphokinase (CPK), were measured at 0, 1, 3, 6, 9, 12, 18, 24 and 48 h. Rats were sacrificed 48 h later after glycerol administration and the kidneys were removed immediately for pathology and immunohistochemistry (IHC).

RESULTS

Intramuscular injection of glycerol significantly increased blood BUN, Cre, GOT, GPT and CPK levels and induced severe histopathologic damage in the kidneys. Nuclear factor-κB (NF-κB) and inducible nitric oxide synthase (iNOS) were increased and E-cadherin was decreased after glycerol administration, as detected by IHC in the kidneys. Post-treatment with rhEPO decreased blood BUN, Cre, GOT, GPT and CPK levels, decreased markers of kidney injury and suppressed the release of NF-κB and iNOS after rhabdomyolysis.

CONCLUSION

Treatment with rhEPO suppressed the activities of NF-κB and iNOS, decreased BUN, Cre, GOT, GPT and CPK levels, and decreased the markers of kidney injury after rhabdomyolysis. These actions ameliorated rhabdomyolysis-induced acute renal failure in rats.

Correction of postkidney transplant anemia reduces progression of allograft nephropathy

Retrospective studies suggest that chronic allograft nephropathy might progress more rapidly in patients with post-transplant anemia, but whether correction of anemia improves renal outcomes is unknown. An open-label, multicenter, randomized controlled trial investigated the effect of epoetin-β to normalize hemoglobin values (13.0-15.0 g/dl, n=63) compared with partial correction of anemia (10.5-11.5 g/dl, n=62) on progression of nephropathy in transplant recipients with hemoglobin <11.5 g/dl and an estimated creatinine clearance (eCrCl) <50 ml/min per 1.73 m(2). After 2 years, the mean hemoglobin was 12.9 and 11.3 g/dl in the normalization and partial correction groups, respectively (P<0.001). From baseline to year 2, the eCrCl decreased by a mean 2.4 ml/min per 1.73 m(2) in the normalization group compared with 5.9 ml/min per 1.73 m(2) in the partial correction group (P=0.03). Furthermore, fewer patients in the normalization group progressed to ESRD (3 versus 13, P<0.01). Cumulative death-censored graft survival was 95% and 80% in the normalization and partial correction groups, respectively (P<0.01). Complete correction was associated with a significant improvement in quality of life at 6 and 12 months. The number of cardiovascular events was low and similar between groups. In conclusion, this prospective study suggests that targeting hemoglobin values ≥13 g/dl reduces progression of chronic allograft nephropathy in kidney transplant recipients.

Darbepoetin-α inhibits the perpetuation of necro-inflammation and delays the progression of cholestatic fibrosis in mice

Biliary obstruction and cholestasis result in hepatocellular necro-inflammation and lead to the development of liver fibrosis. The objective of this study was to analyze whether the multiple tissue-protective properties of erythropoietin are salutary in an experimental model of liver fibrosis. For this purpose, C57BL/6J mice underwent common bile duct ligation (BDL) and were treated with either darbepoetin-α (10 μg/kg i.p.) or physiological saline every third day, beginning 24 h after BDL. Mice were killed at 2, 5, 14, and 28 days after BDL. Beside hematological parameters, markers of inflammation and fibrosis were assessed histomorphometrically and immunohistochemically as well as by quantitative real-time PCR. In addition, a 7-week survival study was performed. BDL provoked cholestatic hepatitis characterized by biliary infarcts with accumulation of macrophages followed by marked collagen deposition and increased expression of profibrotic gene transcripts. Darbepoetin-α treatment significantly diminished the area of focal necrosis, reduced the infiltration of macrophages, decreased levels of profibrotic genes, and lowered collagen deposition. Moreover, darbepoetin-α significantly reduced systemic anemia caused by BDL. Finally, darbepoetin-α treatment significantly prolonged the survival time after BDL. This study suggests that darbepoetin-α, which is a clinically well-established substance, might be used as an efficient therapeutic option for patients with chronic cholestatic liver disease.

Trps1 haploinsufficiency promotes renal fibrosis by increasing Arkadia expression

Mutations in TRPS1 cause tricho-rhino-pharyngeal syndrome (TRPS). Trps1 is essential for nephron development, acting downstream of Bmp7. Because Bmp7 counteracts epithelial-to-mesenchymal transition (EMT) and reverses chronic renal injury, we examined the function of Trps1 in renal fibrosis. Immunohistochemistry revealed Trps1 expression in proximal tubular epithelial cells of mice. Unilateral ureteral obstruction reduced mRNA and protein expression of Trps1 in wild-type and heterozygous Trps1-knockout (Trps1(+/-)) mice. Trps1 haploinsufficiency promoted tubulointerstitial fibrosis via increased phosphorylation of Smad3 and decreased Smad7 protein. In primary culture, Trps1 deficiency promoted TGF-beta1-mediated EMT in proximal tubule cells. Trps1(+/-)-derived cells had higher levels of phosphorylated Smad3, and TGF-beta1 induced a time-dependent decrease in Smad7 protein in wild-type and Trps1(+/-) kidneys. In addition, compared with wild-type cells, Trps1(+/-) cells had double the amount of the E3 ubiquitin ligase Arkadia, and TGF-beta1 induced further Arkadia expression. Furthermore, knockdown of Arkadia inhibited TGF-beta1-induced EMT in Trps1(+/-) cells. Collectively, these data suggest that Trps1 haploinsufficiency enhances TGF-beta1-induced EMT and tubulointerstitial fibrosis by modulating the amount of Smad7 through Arkadia/ubiquitin-mediated degradation.

Salvianolic acid B prevents epithelial-to-mesenchymal transition through the TGF-beta1 signal transduction pathway in vivo and in vitro

BACKGROUND

Salvianolic Acid B (Sal B) is a water-soluble component from Danshen (a traditional Chinese herb widely used for chronic renal diseases) with anti-oxidative and cell protective properties. Sal B also has potential protective effects on renal diseases. Tubular epithelial cells can undergo epithelial-to-mesenchymal transition (EMT), which plays an important role in the pathogenesis of renal interstitial fibrosis (RIF) and is mainly regulated by TGF-beta1/Smads pathway. The aims of the study are to investigate the effect of Sal B on tubular EMT in vivo and in vitro, and to elucidate its underlying mechanism against EMT related to TGF-beta1/Smads pathway.

RESULTS

For in vivo experiments, RIF was induced in rats by oral administration of HgCl2 and prophylaxised with Sal B and vitamin E. The protein expression of E-cadherin was down-regulated, while the expression of alpha-SMA, TGF-beta1, TbetaR-I, p-Smad2/3 and the activity of matrix metalloproteinase-2 (MMP-2) were up-regulated in kidneys of model rats when compared with those of normal rats. In contrast, Sal B and vitamin E significantly attenuated the expression of alpha-SMA, TGF-beta1, TbetaR-I, p-Smad2/3, and MMP-2 activity, but increased E-cadherin expression. For in vitro experiments, HK-2 cells were incubated with TGF-beta1 to induce EMT, and the cells were co-cultured with 1 and 10 microM Sal B or SB-431542 (a specific inhibitor of TbetaR-I kinase). TGF-beta1 induced a typical EMT in HK-2 cells, while it was blocked by Sal B and SB-431542, as evidenced by blocking morphologic transformation, restoring E-cadherin and CK-18 expression, inhibiting alpha-SMA expression and F-actin reorganization, and down-regulating MMP-2/9 activities in TGF-beta1 mediated HK-2 cells. Furthermore, Sal B and SB-431542 profoundly down-regulated the expressions of TbetaR-I and p-Smad2/3 but prevented the decreased expression of Smad7 in TGF-beta1 stimulated HK-2 cells.

CONCLUSIONS

Sal B can prevent tubular EMT in the fibrotic kidney induced by HgCl2 as well as HK-2 cells triggered by TGF-beta1, the mechanism of Sal B is closely related to the regulation of TGF-beta1/Smads pathway, manifested as the inhibition of TGF-beta1 expression, suppression of TbetaR-I expression and function, down-regulation of Smad2/3 phosphorylation, and restoration of the down-regulation of Smad7, as well as inhibition of MMP-2 activity.

Obstructive renal injury: from fluid mechanics to molecular cell biology

Urinary tract obstruction is a frequent cause of renal impairment. The physiopathology of obstructive nephropathy has long been viewed as a mere mechanical problem. However, recent advances in cell and systems biology have disclosed a complex physiopathology involving a high number of molecular mediators of injury that lead to cellular processes of apoptotic cell death, cell injury leading to inflammation and resultant fibrosis. Functional studies in animal models of ureteral obstruction using a variety of techniques that include genetically modified animals have disclosed an important role for the renin-angiotensin system, transforming growth factor-β1 (TGF-β1) and other mediators of inflammation in this process. In addition, high throughput techniques such as proteomics and transcriptomics have identified potential biomarkers that may guide clinical decision-making.

Erythropoietin suppresses epithelial to mesenchymal transition and intercepts Smad signal transduction through a MEK-dependent mechanism in pig kidney (LLC-PK1) cell lines

PURPOSE

Tumor growth factor-beta1 (TGF-beta1) plays a pivotal role in processes like kidney epithelial-mesenchymal transition (EMT) and interstitial fibrosis, which correlate well with progression of renal disease. Little is known about underlying mechanisms that regulate EMT. Based on the anatomical relationship between erythropoietin (EPO)-producing interstitial fibroblasts and adjacent tubular cells, we investigated the role of EPO in TGF-beta1-mediated EMT and fibrosis in kidney injury.

METHODS

We examined apoptosis and EMT in TGF-beta1-treated LLC-PK1 cells in the presence or absence of EPO. We examined the effect of EPO on TGF-beta1-mediated Smad signaling. Apoptosis and cell proliferation were assessed with flow cytometry and hemocytometry. We used Western blotting and indirect immunofluorescence to evaluate expression levels of TGF-beta1 signal pathway proteins and EMT markers.

RESULTS

We demonstrated that ZVAD-FMK (a caspase inhibitor) inhibited TGF-beta1-induced apoptosis but did not inhibit EMT. In contrast, EPO reversed TGF-beta1-mediated apoptosis and also partially inhibited TGF-beta1-mediated EMT. We showed that EPO treatment suppressed TGF-beta1-mediated signaling by inhibiting the phosphorylation and nuclear translocation of Smad 3. Inhibition of mitogen-activated protein kinase kinase 1 (MEK 1) either directly with PD98059 or with MEK 1 siRNA resulted in inhibition of EPO-mediated suppression of EMT and Smad signal transduction in TGF-beta1-treated cells.

CONCLUSIONS

EPO inhibited apoptosis and EMT in TGF-beta1-treated LLC-PK1 cells. This effect of EPO was partially mediated by a mitogen-activated protein kinase-dependent inhibition of Smad signal transduction.