Hypoxia inducible factor-1α mediates the profibrotic effect of albumin in renal tubular cells

Exosomes are nano-sized vesicles produced and secreted by cells to mediate intercellular communication. The production and function of exosomes in kidney tissues and cells remain largely unclear. Hypoxia is a common pathophysiological condition in kidneys. This study was designed to characterize exosome production during hypoxia of rat renal proximal tubular cells (RPTCs), investigate the regulation by hypoxia-inducible factor-1 (HIF-1), and determine the effect of the exosomes on ATP-depletion-induced tubular cell injury. Hypoxia did not change the average sizes of exosomes secreted by RPTCs, but it significantly increased exosome production in a time-dependent manner. HIF-1 induction with dimethyloxalylglycine also promoted exosome secretion, whereas pharmacological and genetic suppression of HIF-1 abrogated the increase of exosome secretion under hypoxia. The exosomes from hypoxic RPTCs had inhibitory effects on apoptosis of RPTCs following ATP depletion. The protective effects were lost in the exosomes from HIF-1α knockdown cells. It is concluded that hypoxia stimulates exosome production and secretion in renal tubular cells. The exosomes from hypoxic cells are protective against renal tubular cell injury. HIF-1 mediates exosome production during hypoxia and contributes to the cytoprotective effect of the exosomes.

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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.

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Impaired Wound Healing in Hypoxic Renal Tubular Cells: Roles of Hypoxia-Inducible Factor-1 and Glycogen Synthase Kinase 3β/β-Catenin Signaling

Journal of Pharmacology and Experimental Therapeutics ◽

10.1124/jpet.111.187427 ◽

2011 ◽

Vol 340 (1) ◽

pp. 176-184 ◽

Cited By ~ 20

Author(s):

Jianping Peng ◽

Ganesan Ramesh ◽

Lin Sun ◽

Zheng Dong

Keyword(s):

Wound Healing ◽

Glycogen Synthase ◽

Hypoxia Inducible Factor ◽

Glycogen Synthase Kinase ◽

Glycogen Synthase Kinase 3Β ◽

Impaired Wound Healing ◽

Tubular Cells ◽

Hypoxia Inducible Factor 1 ◽

Renal Tubular Cells ◽

Renal Tubular

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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)

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