New role of the human equilibrative nucleoside transporter 1 (hENT1) in Epithelial-to-mesenchymal transition in renal tubular cells

We examined whether and how uric acid induces epithelial to mesenchymal transition (EMT) in renal tubular cells, along with the mechanism by which telmisartan acts on uric acid-induced renal injury. Rat renal proximal tubular epithelial cells (NRK-52E) were exposed to various concentrations of uric acid in the presence or absence of telmisartan. Treatment with uric acid increased the expression of α-SMA, decreased the expression of E-cadherin, and promoted EMT in NRK-52E cells. Uric acid treatment also led to increased endothelin-1 (ET-1) production, activation of extracellular-regulated protein kinase 1/2 (ERK1/2), and the upregulation of nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4). Use of ET-1 receptor inhibitor (BQ123 or BQ788) could inhibit uric acid-induced EMT in NRK-52E cells. Pretreatment with the ERK inhibitor (U0126 or PD98059) suppressed the release of ET-1 and EMT induced by uric acid. Additionally, pretreatment with a traditional antioxidant (diphenylene iodonium or apocynin) inhibited the activation of ERK1/2, release of ET-1, and uric acid-induced EMT in NRK-52E cells. These findings suggested that uric acid-induced EMT in renal tubular epithelial cells occurs through NADPH oxidase-mediated ERK1/2 activation and the subsequent release of ET-1. Furthermore, telmisartan (102 nmol/L to 104 nmol/L) inhibited the expression of NOX4, intracellular reactive oxygen species (ROS), activation of ERK1/2, and the release of ET-1 in a dose-dependent manner, thereby preventing uric acid-induced EMT in NRK-52E. In conclusion, telmisartan could ameliorate uric acid-induced EMT in NRK-52E cells likely through inhibition of the NADPH oxidase/ERK1/2/ET-1 pathway.

Download Full-text

Hypoxia-inducible factor modulates tubular cell survival in cisplatin nephrotoxicity

AJP Renal Physiology ◽

10.1152/ajprenal.00081.2005 ◽

2005 ◽

Vol 289 (5) ◽

pp. F1123-F1133 ◽

Cited By ~ 70

Author(s):

Tetsuhiro Tanaka ◽

Ichiro Kojima ◽

Takamoto Ohse ◽

Reiko Inagi ◽

Toshio Miyata ◽

...

Keyword(s):

Mitochondrial Membrane ◽

Functional Role ◽

Hypoxia Inducible Factor ◽

Tubular Cell ◽

Apoptotic Cells ◽

Outer Medulla ◽

Tubular Cells ◽

Renal Tubular Cells ◽

Renal Tubular

Hypoxia-inducible factor (HIF)-1 is a transcription factor mediating cellular response to hypoxia. Although it is expressed in tubular cells of the ischemic kidney, its functional role is not fully clarified in the pathological context. In this study, we investigated a role of HIF in tubular cell apoptosis induced by cisplatin. HIF-1α was expressed in tubular cells in the outer medulla 3 days after cisplatin (6 mg/kg) administration. With the in vivo administration of cobalt to activate HIF, the number of apoptotic renal tubular cells became much smaller in the outer medulla, compared with the vehicle group. We also examined the functional role of HIF-1 in vitro using immortalized rat proximal tubular cells (IRPTC). In hypoxia, IRPTC that express dominant-negative (dn) HIF-1α showed impaired survival in cisplatin injury at variable doses (25–100 μM, 24 h), which was not obvious in normoxia. The observed difference in cell viability in hypoxia was associated with the increased number of apoptotic cells in dnHIF-1α clones (Hoechst 33258 staining). Studies on intracellular signaling revealed that the degree of cytochrome c release, dissipation of mitochondrial membrane potentials, and caspase-9 activity were all more prominent in dnHIF-1α clones than in control IRPTC, pointing to the accelerated signaling of mitochondrial pathways. We propose that HIF-1 mediates cytoprotection against cisplatin injury in hypoxic renal tubular cells, by reducing the number of apoptotic cells through stabilization of mitochondrial membrane integrity and suppression of apoptosis signaling. A possibility was suggested that activation of HIF-1 could be a new promising therapeutic target for hypoxic renal diseases.

Download Full-text

Blocking core fucosylation of TGF-β1 receptors downregulates their functions and attenuates the epithelial-mesenchymal transition of renal tubular cells

AJP Renal Physiology ◽

10.1152/ajprenal.00426.2010 ◽

2011 ◽

Vol 300 (4) ◽

pp. F1017-F1025 ◽

Cited By ~ 37

Author(s):

Hongli Lin ◽

Dapeng Wang ◽

Taihua Wu ◽

Cui Dong ◽

Nan Shen ◽

...

Keyword(s):

Transforming Growth Factor ◽

Epithelial Mesenchymal Transition ◽

Interstitial Fibrosis ◽

Cell Model ◽

Mesenchymal Transition ◽

Renal Tubular Cells ◽

Renal Tubular ◽

Core Fucosylation ◽

Tgf Β1

Posttranslational modification of proteins could regulate their multiple biological functions. Transforming growth factor-β receptor I and II (ALK5 and TGF-βRII), which are glycoproteins, play important roles in the renal tubular epithelial-mesenchymal transition (EMT). In the present study, we examined the role of core fucosylation of TGF-βRII and ALK5, which is regulated by α-1,6 fucosyltransferase (Fut8), in the process of EMT of cultured human renal proximal tubular epithelial (HK-2) cells. The typical cell model of EMT induced by TGF-β1 was constructed to address the role of core fucosylation in EMT. Core fucosylation was found to be essential for both TGF-βRII and ALK5 to fulfill their functions, and blocking it with Fut8 small interfering RNA greatly reduced the phosphorylation of Smad2/3 protein, caused the inactivation of TGF-β/Smad2/3 signaling, and resulted in remission of EMT. More importantly, even with high levels of expressions of TGF-β1, TGF-βRII, and ALK5, blocking core fucosylation also could attenuate the EMT of HK-2 cells. Thus blocking core fucosylation of TGF-βRII and ALK5 may attenuate EMT independently of the expression of these proteins. This study may provide new insight into the role of glycosylation in renal interstitial fibrosis. Furthermore, core fucosylation may be a novel potential therapeutic target for treatment of renal tubular EMT.

Download Full-text

Bactericidal Activity of Renal Tubular Cells: The Putative Role of Human β-Defensins

Nephron Experimental Nephrology ◽

10.1159/000065296 ◽

2002 ◽

Vol 10 (5-6) ◽

pp. 332-337 ◽

Cited By ~ 32

Author(s):

Martin Nitschke ◽

Sandra Wiehl ◽

Patrick C. Baer ◽

Burkhard Kreft

Keyword(s):

Bactericidal Activity ◽

Tubular Cells ◽

Renal Tubular Cells ◽

Putative Role ◽

Renal Tubular

Download Full-text

Abstract 132: Hypoxia-inducible Factor Prolyl-hydroxylase-2 Mediates Transforming Growth Factor Beta 1-induced Epithelial-mesenchymal Transition In Renal Tubular Cells

Hypertension ◽

10.1161/hyp.60.suppl_1.a132 ◽

2012 ◽

Vol 60 (suppl_1) ◽

Author(s):

Weiqing Han ◽

Jun-Pin Hu ◽

Pin-Lan Li ◽

Ningjun Li

Keyword(s):

Signaling Pathway ◽

Transforming Growth Factor Beta ◽

Transforming Growth Factor ◽

Epithelial Mesenchymal Transition ◽

Kidney Diseases ◽

Hypoxia Inducible Factor ◽

Mesenchymal Transition ◽

Tubular Cells ◽

Renal Tubular Cells ◽

Renal Tubular

Transforming growth factor beta 1 (TGFβ1)-induced epithelial-mesenchymal transition (EMT) in kidney epithelial cells plays a key role in renal tubulointerstitial fibrosis in chronic kidney diseases. As hypoxia-inducible factor (HIF)-1α is found to mediate TGFβ1 signaling pathway, we tested the hypothesis that HIF-1α and its upstream regulator prolyl hydroxylase domain-containing proteins (PHDs) are involved in TGFβ1-induced EMT in renal tubular cells. Our results showed that TGFβ1 treatment for 48 h stimulated EMT in cultured renal tubular cells as indicated by the decrease in epithelial marker P-cadherin from 1.0 ± 0.02 to 0.40 ± 0.05 ( P < 0.05), and the increase in mesenchymal markers α-smooth muscle actin (2.14 ± 0.32 fold, P < 0.05) and fibroblast-specific protein (2.0 ± 0.17 fold, P < 0.05) as shown in Western blot assay. Meanwhile, TGFβ1 time-dependently increased HIF-1α, which reached its maximum value (2.36 ± 0.2 fold, P < 0.05) at 24 h, and that HIF-1α siRNA significantly inhibited TGFβ1-induced EMT, suggesting that HIF-1α mediated TGFβ1 induced-EMT. Real-time PCR showed that PHD1 and PHD2, rather than PHD3, could be detected, with PHD2 as the predominant form of PHDs (PHD1 : PHD2 = 0.21:1.0). Importantly, TGFβ1 time-dependently decreased PHD2 mRNA and protein level, which reached their maximum value from 1.0 ± 0.15 to 0.45 ± 0.08 ( P < 0.05) for mRNA at 16 h and from 1.0 ± 0.08 to 0.26 ± 0.08 ( P < 0.05) for protein at 24 h, respectively. In contrast, TGFβ1 had no effect on PHD1 mRNA and protein levels. Furthermore, over-expression of PHD2 transgene almost fully prevented TGFβ1-induced HIF-1α accumulation and EMT marker changes, indicating that PHD2 is involved in TGFβ1-induced EMT. Finally, Smad2 inhibitor SB431542 prevented TGFβ1-induced PHD2 decrease, suggesting that Smad2 may mediate TGFβ1-induced EMT through PHD2/HIF-1α. It is concluded that TGFβ1 decreased PHD2 expression via a Smad2-dependent signaling pathway, thereby leading to HIF-1α accumulation and EMT in renal tubular cells. The present study suggests that PHD2/HIF-1α is a novel signaling pathway mediating the fibrogenic effect of TGFβ1 and that manipulating PHD2/HIF-1α pathway may be used as a therapeutic strategy in chronic kidney diseases. (support: NIH grant HL89563 and HL106042)

Download Full-text