[Show abstract][Hide abstract] ABSTRACT: Chronic inflammation is highly prevalent in maintenance hemodialysis (MHD) patients, and it has been shown to be a strong predictor of morbidity and mortality. Mitochondrial DNA (mtDNA) released into circulation after cell damage can promote inflammation in patients and animal models. However, the role and mechanisms of circulatory mtDNA in chronic inflammation in MHD patients remain unknown. Sixty MHD patients and 20 health controls were enrolled in this study. The circulatory mtDNA was detected by quantitative real-time PCR assay. Plasma interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) were quantitated by ELISA assay. Dialysis systems in MHD patients and in vitro were used to evaluate the effect of different dialysis patterns on circulatory mtDNA. Circulatory mtDNA was elevated in MHD patients comparing to that of health control. Regression analysis demonstrated that plasma mtDNA was positively associated with TNF-α and the product of serum calcium and phosphorus, while negatively associated with hemoglobin and serum albumin in MHD patients. MtDNA induced the secretion of IL-6 and TNF-α in the THP-1 cells. Single high-flux hemodialysis (HF-HD) and on line hemodiafiltration (OL-HDF) but not low-flux hemodialysis (LF-HD) could partially reduce plasma mtDNA in MHD patients. In vitro, both HD and hemofiltration (HF) could fractional remove mtDNA. Collectively, circulatory mtDNA is elevated and its level is closely correlated with chronic inflammation in MHD patients. HF-HD and HDF can partially reduce circulatory mtDNA in MHD patients.
PLoS ONE 12/2014; 9(12):e113179. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: MicroRNAs (miRNAs) are small ribonucleotides regulating gene expression. MicroRNAs are present in the blood in a remarkably stable form and have emerged as potential diagnostic markers in patients with cardiovascular disease. Our study aimed to assess circulating miR-133a levels in MHD patients and the relation of miR-133a to cardiac hypertrophy.
PLoS ONE 10/2014; 9(10):e103079. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Tubular epithelial cell apoptosis contributes to tubulointerstitial fibrosis but its regulation remained unclear. Here, in fibrotic kidney induced by unilateral ureteral obstruction (UUO), we demonstrated that miR-34a was markedly up-regulated in tubulointerstitial spaces and microvesicles isolated from kidney. However, the increased miR-34a was not de novo synthesized by proximal tubular epithelial cells but by fibroblasts after incubated with TGF-β1. MiR-34a was markedly up-regulated in microvesicles isolated from cell culture media of TGF-β1 treated fibroblasts. These microvesicles acted as a vector for delivery of up-regulated miR-34a from fibroblasts to tubular cells. The fibroblast-derived miR-34a-containing microvesicles induced apoptosis of tubular cells. The exogenous miR-34a regulated tubular apoptosis by modulating the expression of anti-apoptotic protein Bcl-2. Moreover, injection of exogenous miR-34a-containing microvesicles enhanced tubular cell apoptosis in mice. This study suggests that secreted fibroblast miR-34a transported by microvesicles induces tubular cell apoptosis in obstructive kidney. This study provided a new mechanism concerning microvesicle-mediated fibroblast-to-tubular cell communication of miRNA in regulating tubular cell apoptosis, which might provide new therapeutic targets for renal tubulointerstitial fibrosis.
Journal of Cell Science 08/2014; · 5.33 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although ambulatory blood pressure (ABP) monitoring (ABPM) is often considered to have an advantage over dialysis unit blood pressure (BP) in dialysis patients, the exact relationship between these two measurements of BP has not been well determined. In a cohort of 90 Chinese dialysis patients, agreement between dialysis unit BP (predialysis and postdialysis BP) and interdialytic ABP was evaluated using Bland-Altman plots and Lin's concordance correlation coefficient for quantitative analysis, and inter-rater agreement (κ) for qualitative analysis. Limits of agreement between dialysis unit BP and ABP were wide (predialysis systolic BP: −33.5 to 20.9 mm Hg; predialysis diastolic BP: −22.2 to 11.9 mm Hg; postdialysis systolic BP: −25.4 to 26.5 mm Hg; postdialysis diastolic BP: −18.4 to 12.3 mm Hg). Lin's concordance correlation coefficient exhibited a poor agreement with concordance correlation coefficients of 0.75, 0.81, 0.64, and 0.75 for predialysis systolic BP, postdialysis systolic BP, predialysis diastolic BP, and postdialysis diastolic BP, respectively. When BP level was classified into quartiles, an increasing trend for incorrect classification rate was observed with deleterious hypertension, with the highest value in grade 3 hypertension (100% and 75.0% for predialysis and postdialysis BP, respectively). Therefore, these data suggest that agreement between dialysis unit BP and interdialytic ABP is poor in Chinese dialysis patients, and the bias for patients with higher degree of hypertension is more prominent.
Journal of Clinical Hypertension 08/2014; · 2.36 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Podocytes play a key role in the formation of cellular crescents in experimental and human diseases. However, the underlying mechanisms for podocytes in promoting crescent formation need further investigation. Here we demonstrated that mammalian target of rapamycin complex 1 (mTORC1) signaling was remarkably activated and HIF1alpha expression was largely induced in cellular crescents from patients with crescentic glomerular diseases. Specific deletion of Tsc1 in podocytes led to mTORC1 activation in podocytes and kidney dysfunction in mice. Interestingly, 33 of 36 knockouts developed cellular or mixed cellular and fibrous crescents at 7 weeks of age (14.19±3.86% of total glomeruli in knockouts vs 0% in control littermates, n=12-36, P=0.04). All of the 7 knockouts developed crescents at 12 weeks of age (30.92±11.961% of total glomeruli in knockouts vs 0% in control littermates n=4-7, P=0.002). Most notably, bridging cells between the glomerular tuft and the parietal basement membrane as well as the cellular crescents were immunostaining positive for WT1, p-S6, HIF1alpha and Cxcr4. Furthermore, continuously administrating rapamycin started at 7 weeks of age for 5 weeks abolished crescent as well as the induction of p-S6, HIF1alpha and Cxcr4 in the glomeruli from the knockouts. Together, it is concluded that mTORC1 activation in podocytes promotes cellular crescent formation and targeting this signaling may shed a new light for the treatment of patients with crescentic glomerular diseases.
American journal of physiology. Renal physiology 07/2014; · 3.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD) and contributes to increased risk of cardiovascular disease and mortality. Accumulated evidences suggested that vascular smooth muscle cells (VSMCs) to osteoblast-like cells transdifferentiation (VOT) plays a crucial role in promoting vascular calcification. MicroRNAs (miRNAs) are a novel class of small RNAs that negatively regulate gene expression via repression of the target mRNAs. In the present work, we sought to determine the role of miRNAs in VSMCs phenotypic transition and calcification induced by β-glycerophosphoric acid.
Primary cultured rat aortic VSMCs were treated with β-glycerophosphoric acid for different periods of time. In VSMCs, after β-glycerophosphoric acid treatment, the expressions of cbf β1, osteocalcin and osteopontin were significantly increased and SM-22β expression was decreased. ALP activity was induced by β-glycerophosphoric acid in a time or dose dependent manner. Calcium deposition was detected in VSMCs incubated with calcification media; Then, miR-125b expression was detected by real-time RT PCR. miR-125b expression was significantly decreased in VSMCs after incubated with β-glycerophosphoric acid. Overexpression of miR-125b could inhibit β-glycerophosphoric acid-induced osteogenic markers expression and calcification of VSMCs whereas knockdown of miR-125b promoted the phenotypic transition of VSMCs and calcification. Moreover, miR-125b targeted Ets1 and regulated its protein expression in VSMCs. Downregulating Ets1 expression by its siRNA inhibited β-glycerophosphoric acid-induced the VSMCs phenotypic transition and calcification.
Our study suggests that down-regulation of miR-125b after β-glycerophosphoric acid treatment facilitates VSMCs transdifferentiation and calcification through targeting Ets1.
Experimental Cell Research 01/2014; · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The mammalian target of rapamycin (mTOR) plays a critical role for cell growth and survival in many cell types. While substantial progress has been made in understanding the abnormal activation of mTORC1 in the pathogenesis of kidney disease, little is known about mTORC2 in kidney disease such as acute kidney injury (AKI). To study this, we generated a mouse model with tubule-specific deletion of Rictor (Tubule-Rictor-/-). The knockouts were born normal and no obvious kidney dysfunction or kidney morphologic abnormality was found within 2 months of birth. However, ablation of Rictor in the tubular cells exacerbated cisplatin-induced AKI compared to that in the control littermates. As expected, tubular cell apoptosis, Akt phosphorylation (Ser473), and autophagy were induced in the kidneys from the control littermates by cisplatin treatment. Less cell autophagy or Akt phosphorylation and more cell apoptosis in the kidneys of the knockout mice were identified compared with those in the control littermates. In NRK-52E cells in vitro, Rictor siRNA transfection sensitized cell apoptosis to cisplatin but with reduced cisplatin-induced autophagy. Metformin, an inducer of autophagy, abolished cell death induced by Rictor siRNA and cisplatin. Thus, endogenous Rictor/mTORC2 protects against cisplatin-induced AKI, probably mediated by promoting cell survival through Akt signaling activation and induction of autophagy.Kidney International advance online publication, 22 January 2014; doi:10.1038/ki.2013.559.
Kidney International 01/2014; · 8.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Podocyte apoptosis is a major factor inducing podocyte depletion that predicts the progressive course of glomerulosclerosis. However, the molecular mechanisms underlying podocyte apoptosis are still not well understood. Autophagy is a lysosomal degradation system involving the degradation and recycling of obsolete, damaged, or harmful cytoplasmic materials and organelles. Recent advances in the understanding of the molecular processes contributing to autophagy have provided insight into the relationship between autophagy and apoptosis. However, their cross-talk remains largely obscure until now. Here, we found that podocytes both in vivo and in vitro always exhibited high basal levels of autophagy, whereas autophagy inhibition could induce podocyte apoptosis, suggesting the pro-survival role of autophagy in podocytes. Besides, we found that autophagy inhibition by 3-methyladenine (3-MA) could induce the activation of endoplasmic reticulum stress even without any external stimulations, whereas knockdown of CHOP could effectively improve podocyte apoptosis and down-regulated expression of slit-diaphragm proteins induced by autophagy inhibition. Collectively, this study demonstrated that autophagy might act as a crucial regulatory mechanism of apoptotic cell death by modulating the balance between the pro-survival pathway and the pro-apoptotic pathway of endoplasmic reticulum stress, which might provide a novel mechanistic insight into the interface between autophagy and apoptosis in the progression of podocyte injury.
Experimental Cell Research 01/2014; · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although a large number of drugs have been used to treat chronic hepatitis C (CHC), there still remains a great challenge to treat maintenance hemodialysis (MHD) patients with chronic hepatitis C. To clarify the immunnoloregulation of double filtration plasmapheresis (DFPP) in MHD patients with CHC, DFPP was performed in 20 MHD patients with CHC (HCV-antibody positive, serum HCV RNA >500 IU/ml more than 6 months and HCV genotype 1b). The clinical data was collected and peripheral blood mononuclear cells (PBMCs) were analyzed by flow cytometry at the time of hour 0, hour 3, day 3, day 7 and day 28 after the DFPP, respectively. Serum HCV particles could be removed partially by the DFPP. The titer of serum HCV RNA could remain in a lower level even 28 days after the treatment. Compared to MHD patients without HCV infection, the frequencies of innate immune cells were similar in MHD patients with CHC, while Th1/Th2 was elevated and the frequencies of regulatory T (Treg) cells were higher in those MHD patients with CHC. The frequencies of monocytes and natural killer (NK) cells remained after the DFPP in MHD patients with CHC. There were no significant changes of Th1, Th2 and Th1/Th2 in PBMC after DFPP. DFPP could reduce the frequencies of Th17 cells and Treg cells in PBMC from 7 days after DFPP in MHD patients with CHC. DFPP could partially remove the serum HCV particles mechanically. The titer of HCV RNA could remain in a lower level at least for 28 days probably due to the redistribution of the immunocytes in circulation.
PLoS ONE 12/2013; 8(12):e82524. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aristolochic acid nephropathy, initially found in patients intaking of slimming herbs containing aristolochic acid (AA), was previously considered as a progressive renal interstitial fibrosis and urothelial malignancy. However, the presence of albuminuria in some patients with AAN suggests that AA may also damage the glomerular filtration barrier. In this study, mice AAN model was generated by daily administration of aristolochic acid I sodium salt intraperitoneally at a dose of 6 mg/kg body weight for 3 days. All of the mice developed heavy albuminuria at day 3 and 7 after receiving AA. In the mice received AA, morphologic change of glomeruli was minor under light microscopy but podocyte foot-process effacement was evident under electron microscopy. In mitochondria isolated from kidney, prominent mitochondrial DNA (mtDNA) damage was accompanied with marked decrease of mtDNA copy number and mitochondrial protein expression level. Similar to those in vivo results, AA treatment impaired the filtration barrier function of cultured podocytes. AA promoted mtDNA damage, decreased mtDNA copy number and mitochondrial protein expression in cultured podocytes. In addition, AA treatment also decreased ATP content, oxygen consumption rate and mitochondrial membrane potential as well as increased cellular reactive oxygen species in cultured podocytes. This study highlighted that AA could induce podocyte damage and albuminuria, which may be mediated by promoting mtDNA damage and mitochondrial dysfunction in podocytes.
PLoS ONE 12/2013; 8(12):e83408. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Renal fibrosis is inevitably progressive no matter what the initial insult is or whether the insult persists. In an experimental fibrosis model induced by unilateral ureteral obstruction, the accelerated pathological changes could hardly be explained by aggravated pressure caused by hydronephrosis after ligation. Moreover, at the initial stage, tubular phenotype transition and matrix deposition in obstructive kidneys are always local and scattered; however, these renal lesions expand and progress with time. In this study, cultured recipient tubular cells underwent phenotype transition after incubation with conditioned media derived from transforming growth factor-β1-treated donor tubular cells. Thus, it is reasonable to speculate that some secretable molecules from injured tubules contribute to the progression of renal fibrosis. Herein, we report that secreted miRNA-21 (miR-21) can serve as the molecule mediating intercellular communication. miR-21 was packaged into microvesicles, which enter and deliver miR-21 into recipient tubular cells, and exogenous miR-21 enhances Akt signaling by target depression of PTEN protein, and promotes tubular phenotype transition. These results demonstrate that tubular cells can secrete miR-21 and deliver it into recipient tubules by microvesicles, where the exogenous miR-21 can target PTEN protein and enhance Akt signaling in recipient cells. Microvesicle-mediated delivery of miR-21 among tubular epithelial cells might shed new light on the mechanism of progressive renal fibrosis.
American Journal Of Pathology 08/2013; · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Angiotensin II (Ang II) plays a pivotal role in promoting podocyte dysfunction and albuminuria, however, the underlying mechanisms have not been fully delineated. In this study, we found that Ang II induced Wnt1 expression and beta-catenin nuclear translocation in cultured mouse podocytes. Blocking Wnt signaling with Dickkopf1 (Dkk1) or beta-catenin siRNA attenuated Ang II-induced podocyte injury. Ang II could also induce the phosphorylation of calmodulin-dependent protein kinase (CaMK) II and cAMP response element-binding protein (CREB) in cultured podocytes. Blockade of this pathway with CK59 or CREB siRNA could significantly inhibit Ang II-induced Wnt/beta-catenin signaling and podocyte injury. In in vivo studies, administration of Ang II promoted Wnt/beta-catenin signaling, aggregated podocyte damage and albuminuria in mice. CK59 could remarkably ameliorate Ang II-induced podocyte injury and albuminuria. Furthermore, ectopic expression of exogenous Dkk1 also attenuated Ang II-induced podocytopathy in mice. Taken together, this study demonstrates that CaMK II/CREB/Wnt/beta-catenin signaling cascade plays an important role in regulating Ang II-induced podocytopathy. Targeting this signaling pathway may offer renal protection against the development of proteinuric kidney diseases.
Journal of Biological Chemistry 06/2013; · 4.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Specificity protein 1 (Sp1), a ubiquitously expressed transcription factor, plays a potential pathogenic role for fibrotic disease in many organs by regulating the expression of several fibrosis-related genes, however, its role in kidney fibrosis and the mechanisms regulating its expression remain incompletely clarified. Here, we found that Sp1 was markedly induced and closely correlated with interstitial type I collagen accumulation in kidney tubular epithelia from obstructive nephropathy. In vitro, both Sp1 and type I collagen expression were up-regulated in TGF-β1-treated kidney tubular epithelial cells (NRK-52E), whereas knockdown of Sp1 largely abolished TGF-β1-induced type I collagen production, suggesting that Sp1 induction is partially responsible for type I collagen expression. In addition, we found that miR-29c expression was remarkably reduced in either the tubular epithelial cells from kidney with UUO nephropathy or TGF-β1-treated NRK-52E cells. Knockdown of miR-29c could sufficiently induce Sp1 and type I collagen expression, whereas ectopic expression of miR-29c largely abolished their expression stimulated by TGF-β1 in NRK-52E cells. Furthermore, knockdown of Sp1 effectively hindered type I collagen induction stimulated by miR-29c down-regulation. Collectively, this study demonstrates that Sp1 acts as an essential mediator for miR-29c in regulating type I collagen production in tubular epithelial cells, which may provide a novel mechanistic insight about miR-29c in renal fibrosis.
Experimental Cell Research 06/2013; · 3.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Ras homolog enriched in brain (Rheb) is a small GTPase that regulates cell growth, differentiation, and survival by upregulating mammalian target of rapamycin complex 1 (mTORC1) signaling. The role of Rheb/mTORC1 signaling in the activation of kidney fibroblasts and the development of kidney fibrosis remains largely unknown. In this study, we found that Rheb/mTORC1 signaling was activated in interstitial myofibroblasts from fibrotic kidneys. Treatment of rat kidney interstitial fibroblasts (NRK-49F cell line) with TGFβ1 also activated Rheb/mTORC1 signaling. Blocking Rheb/mTORC1 signaling with rapamycin or Rheb small interfering RNA abolished TGFβ1-induced fibroblast activation. In a transgenic mouse, ectopic expression of Rheb activated kidney fibroblasts. These Rheb transgenic mice exhibited increased activation of mTORC1 signaling in both kidney tubular and interstitial cells as well as progressive interstitial renal fibrosis; rapamycin inhibited these effects. Similarly, mice with fibroblast-specific deletion of Tsc1, a negative regulator of Rheb, exhibited activated mTORC1 signaling in kidney interstitial fibroblasts and increased renal fibrosis, both of which rapamycin abolished. Taken together, these results suggest that Rheb/mTORC1 signaling promotes the activation of kidney fibroblasts and contributes to the development of interstitial fibrosis, possibly providing a therapeutic target for progressive renal disease.
Journal of the American Society of Nephrology 05/2013; · 9.47 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Despite the recent attention focused on the important role of autophagy in maintaining podocyte homeostasis, little is known about the changes and mechanisms of autophagy in podocyte dysfunction under diabetic condition. In this study, we investigated the role of autophagy in podocyte biology and its involvement in the pathogenesis of diabetic nephropathy. Podocytes had a high basal level of autophagy. And basal autophagy inhibition either by 3-methyladenenine (3-MA) or by Beclin-1 siRNA was detrimental to its architectural structure. However, under diabetic condition in vivo and under high glucose conditions in vitro, high basal level of autophagy in podocytes became defective and defective autophagy facilitated the podocyte injury. Since the dynamics of endoplasmic reticulum(ER) seemed to play a vital role in regulating the autophagic flux, the results that Salubrinal/Tauroursodeoxycholic acid (TUDCA) could restore defective autophagy further indicated that the evolution of autophagy may be mediated by the changes of cytoprotective output in the ER stress. Finally, we demonstrated in vivo that the autophagy of podocyte was inhibited under diabetic status and TUDCA could improve defective autophagy. Taken together, these data suggested that autophagy might be interrupted due to the failure of ER cytoprotective capacity upon high glucose induced unmitigated stress, and the defective autophagy might accelerate the irreparable progression of diabetic nephropathy.
PLoS ONE 04/2013; 8(4):e60546. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Mitochondria dysfunction has been reported in various kidney diseases but how it leads to kidney fibrosis and how this is regulated is unknown. Here we found that mitochondrial uncoupling protein 2 (UCP2) was induced in kidney tubular epithelial cells after unilateral ureteral obstruction in mice and that mice with ablated UCP2 resisted obstruction-induced kidney fibrosis. We tested this association further in cultured NRK-52E cells and found that TGF-β1 remarkably induced UCP2 expression. Knockdown of UCP2 largely abolished the effect of TGF-β1, whereas overexpression of UCP2 promoted tubular cell phenotype changes. Analysis using a UCP2 mRNA-3'-untranslated region luciferase construct showed that UCP2 mRNA is a direct target of miR-30e. MiR-30e was downregulated in tubular cells from fibrotic kidneys and TGF-β1-treated NRK-52E cells. A miR-30e mimic significantly inhibited TGF-β1-induced tubular-cell epithelial-mesenchymal transition, whereas a miR-30e inhibitor imitated TGF-β1 effects. Finally, genipin, an aglycone UCP2 inhibitor, significantly ameliorated kidney fibrosis in mice. Thus, the miR-30e/UCP2 axis has an important role in mediating TGF-β1-induced epithelial-mesenchymal transition and kidney fibrosis. Targeting this pathway may shed new light for the future of fibrotic kidney disease therapy.Kidney International advance online publication, 20 March 2013; doi:10.1038/ki.2013.80.
Kidney International 03/2013; · 8.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Inflammation is a pathologic feature of hyperuricemia in clinical settings. However, the underlying mechanism remains unknown. Here, infiltration of T cells and macrophages were significantly increased in hyperuricemia mice kidneys. This infiltration of inflammatory cells was accompanied by an up-regulation of TNF-α, MCP-1 and RANTES expression. Further, infiltration was largely located in tubular interstitial spaces, suggesting a role for tubular cells in hyperuricemia-induced inflammation. In cultured tubular epithelial cells (NRK-52E), uric acid, probably transported via urate transporter, induced TNF-α, MCP-1 and RANTES mRNA as well as RANTES protein expression. Culture media of NRK-52E cells incubated with uric acid showed a chemo-attractive ability to recruit macrophage. Moreover uric acid activated NF-κB signaling. The uric acid-induced up-regulation of RANTES was blocked by SN 50, a specific NF-κB inhibitor. Activation of NF-κB signaling was also observed in tubule of hyperuricemia mice. These results suggest that uric acid induces renal inflammation via activation of NF-κB signaling.
PLoS ONE 06/2012; 7(6):e39738. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Transforming growth factor-β1 (TGF-β1) upregulation occurs in virtually all chronic kidney diseases and is associated with podocyte injury and proteinuria; however, the mechanisms contributing to this in vivo are ambiguous. In vitro, incubation of podocytes with TGF-β1 induced Wnt1 expression, β-catenin activation, and stimulated the expression of Wnt/β-catenin downstream target genes. Ectopic expression of Wnt1 or β-catenin mimicked TGF-β1, induced Snail1, and suppressed nephrin expression. The Wnt antagonist, Dickkopf-1, blocked TGF-β1-induced β-catenin activation, Snail1 induction, and nephrin suppression. In vivo, ectopic expression of TGF-β1 induced Wnt1 expression, activated β-catenin, and upregulated Wnt target genes such as Snail1, MMP-7, MMP-9, desmin, Fsp1, and PAI-1 in mouse glomeruli, leading to podocyte injury and albuminuria. Consistently, concomitant expression of Dickkopf-1 gene abolished β-catenin activation, inhibited TGF-β1-triggered Wnt target gene expression, and mitigated albuminuria. Thus, canonical Wnt/β-catenin signaling mediates TGF-β1-driven podocyte injury and proteinuria. These studies suggest that Wnt/β-catenin signaling may be exploited as a therapeutic target for the treatment of proteinuric kidney diseases.
Kidney International 08/2011; 80(11):1159-69. · 8.52 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: TGF-β1 is a pleiotropic cytokine with potent anti-inflammation property. However, the mechanisms underlying TGF-β1 suppression of inflammation remain largely unexplored. In this study, we demonstrated that TGF-β1 inhibited TNF-α- or IL-1-induced RANTES expression in human kidney tubular epithelial cells (HKC-8). To delineate the mechanism by which TGF-β1 inhibits RANTES expression, we examined the potential signal pathway activated by TGF-β1 in suppressing NF-κB signaling. TGF-β1 affected neither TNF-α-induced IκBα phosphorylation and subsequent degradation, nor p65 NF-κB phosphorylation and its nuclear translocation. However, TGF-β1 could inhibit p65 and p50 binding to the κB site in human RANTES promoter as revealed by chromatin immunoprecipitation assay and protein-DNA binding assay. We found that TGF-β1 induced glycogen synthase kinase-3β (GSK-3β) phosphorylation on Ser-9 in HKC-8 cells, leading to its inactivation. Knockdown of GSK-3β mimicked TGF-β1 and inhibited RANTES induction, whereas overexpression of GSK-3β abolished the inhibitory effect of TGF-β1 and completely restored RANTES expression. Furthermore, TGF-β1 induced the dephosphorylation and activation of β-catenin, a major downstream target of GSK-3β. Ectopic expression of constitutively active β-catenin mimicked the TGF-β1 effect and completely suppressed RANTES expression induced by TNF-α. Interestingly, TGF-β1 induced a physical interaction between β-catenin and p65 NF-κB, which prevented p65 binding to the κB site, sequestered its trans-activating activity, and repressed p65-mediated gene transcription. We conclude that TGF-β1 inhibition of proinflammatory RANTES expression is mediated by β-catenin-triggered blockade of NF-κB signaling.
Journal of Biological Chemistry 12/2010; 286(9):7052-9. · 4.60 Impact Factor