ER stress contributes to renal proximal tubule injury by increasing SREBP-2-mediated lipid accumulation and apoptotic cell death

2012 ◽  
Vol 303 (2) ◽  
pp. F266-F278 ◽  
Author(s):  
Šárka Lhoták ◽  
Sudesh Sood ◽  
Elise Brimble ◽  
Rachel E. Carlisle ◽  
Stephen M. Colgan ◽  
...  
Keyword(s):  
Er Stress ◽  
Proximal Tubule ◽  
Lipid Accumulation ◽  
Cell Injury ◽  
Apoptotic Cell ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Tubule Cell ◽  
Proximal Tubule Cells ◽  
Tubule Cells

Renal proximal tubule injury is induced by agents/conditions known to cause endoplasmic reticulum (ER) stress, including cyclosporine A (CsA), an immunosuppressant drug with nephrotoxic effects. However, the underlying mechanism by which ER stress contributes to proximal tubule cell injury is not well understood. In this study, we report lipid accumulation, sterol regulatory element-binding protein-2 (SREBP-2) expression, and ER stress in proximal tubules of kidneys from mice treated with the classic ER stressor tunicamycin (Tm) or in human renal biopsy specimens showing CsA-induced nephrotoxicity. Colocalization of ER stress markers [78-kDa glucose regulated protein (GRP78), CHOP] with SREBP-2 expression and lipid accumulation was prominent within the proximal tubule cells exposed to Tm or CsA. Prolonged ER stress resulted in increased apoptotic cell death of lipid-enriched proximal tubule cells with colocalization of GRP78, SREBP-2, and Ca2+-independent phospholipase A2 (iPLA2β), an SREBP-2 inducible gene with proapoptotic characteristics. In cultured HK-2 human proximal tubule cells, CsA- and Tm-induced ER stress caused lipid accumulation and SREBP-2 activation. Furthermore, overexpression of SREBP-2 or activation of endogenous SREBP-2 in HK-2 cells stimulated apoptosis. Inhibition of SREBP-2 activation with the site-1-serine protease inhibitor AEBSF prevented ER stress-induced lipid accumulation and apoptosis. Overexpression of the ER-resident chaperone GRP78 attenuated ER stress and inhibited CsA-induced SREBP-2 expression and lipid accumulation. In summary, our findings suggest that ER stress-induced SREBP-2 activation contributes to renal proximal tubule cell injury by dysregulating lipid homeostasis.

scholarly journals Proximal Tubule–Derived Amphiregulin Amplifies and Integrates Profibrotic EGF Receptor Signals in Kidney Fibrosis

2019 ◽  
Vol 30 (12) ◽  
pp. 2370-2383 ◽  
Author(s):  
Eirini Kefaloyianni ◽  
Manikanda Raja Keerthi Raja ◽  
Julian Schumacher ◽  
Muthu Lakshmi Muthu ◽  
Vaishali Krishnadoss ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Reperfusion Injury ◽  
Knockout Mice ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Proximal Tubule Cell ◽  
Tubule Cell ◽  
Proximal Tubule Cells ◽  
Kidney Fibrosis ◽  
Tubule Cells

BackgroundSustained activation of EGF receptor (EGFR) in proximal tubule cells is a hallmark of progressive kidney fibrosis after AKI and in CKD. However, the molecular mechanisms and particular EGFR ligands involved are unknown.MethodsWe studied EGFR activation in proximal tubule cells and primary tubular cells isolated from injured kidneys in vitro. To determine in vivo the role of amphiregulin, a low-affinity EGFR ligand that is highly upregulated with injury, we used ischemia-reperfusion injury or unilateral ureteral obstruction in mice with proximal tubule cell–specific knockout of amphiregulin. We also injected soluble amphiregulin into knockout mice with proximal tubule cell–specific deletion of amphiregulin’s releasing enzyme, the transmembrane cell-surface metalloprotease, a disintegrin and metalloprotease-17 (ADAM17), and into ADAM17 hypomorphic mice.ResultsYes-associated protein 1 (YAP1)–dependent upregulation of amphiregulin transcript and protein amplifies amphiregulin signaling in a positive feedback loop. YAP1 also integrates signals of other moderately injury-upregulated, low-affinity EGFR ligands (epiregulin, epigen, TGFα), which also require soluble amphiregulin and YAP1 to induce sustained EGFR activation in proximal tubule cells in vitro. In vivo, soluble amphiregulin injection sufficed to reverse protection from fibrosis after ischemia-reperfusion injury in ADAM17 hypomorphic mice; injected soluble amphiregulin also reversed the corresponding protective proximal tubule cell phenotype in injured proximal tubule cell–specific ADAM17 knockout mice. Moreover, the finding that proximal tubule cell–specific amphiregulin knockout mice were protected from fibrosis after ischemia-reperfusion injury or unilateral ureteral obstruction demonstrates that amphiregulin was necessary for the development of fibrosis.ConclusionsOur results identify amphiregulin as a key player in injury-induced kidney fibrosis and suggest therapeutic or diagnostic applications of soluble amphiregulin in kidney disease.

scholarly journals Therapeutic concentrations of calcineurin inhibitors do not deregulate glutathione redox balance in human renal proximal tubule cells

PLoS ONE ◽  
2021 ◽  
Vol 16 (4) ◽  
pp. e0250996
Author(s):  
Yasaman Ramazani ◽  
Noël Knops ◽  
Sante Princiero Berlingerio ◽  
Oyindamola Christiana Adebayo ◽  
Celien Lismont ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Cell Model ◽  
Calcineurin Inhibitors ◽  
Redox Balance ◽  
Solid Organ ◽  
Proximal Tubule Cell ◽  
Tubule Cell ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Glutathione Redox

The calcineurin inhibitors (CNI) cyclosporine A and tacrolimus comprise the basis of immunosuppressive regimes in all solid organ transplantation. However, long-term or high exposure to CNI leads to histological and functional renal damage (CNI-associated nephrotoxicity). In the kidney, proximal tubule cells are the only cells that metabolize CNI and these cells are believed to play a central role in the origin of the toxicity for this class of drugs, although the underlying mechanisms are not clear. Several studies have reported oxidative stress as an important mediator of CNI-associated nephrotoxicity in response to CNI exposure in different available proximal tubule cell models. However, former models often made use of supra-therapeutic levels of tissue drug exposure. In addition, they were not shown to express the relevant enzymes (e.g., CYP3A5) and transporters (e.g., P-glycoprotein) for the metabolism of CNI in human proximal tubule cells. Moreover, the used methods for detecting ROS were potentially prone to false positive results. In this study, we used a novel proximal tubule cell model established from human allograft biopsies that demonstrated functional expression of relevant enzymes and transporters for the disposition of CNI. We exposed these cells to CNI concentrations as found in tissue of stable solid organ transplant recipients with therapeutic blood concentrations. We measured the glutathione redox balance in this cell model by using organelle-targeted variants of roGFP2, a highly sensitive green fluorescent reporter protein that dynamically equilibrates with the glutathione redox couple through the action of endogenous glutaredoxins. Our findings provide evidence that CNI, at concentrations commonly found in allograft biopsies, do not alter the glutathione redox balance in mitochondria, peroxisomes, and the cytosol. However, at supra-therapeutic concentrations, cyclosporine A but not tacrolimus increases the ratio of oxidized/reduced glutathione in the mitochondria, suggestive of imbalances in the redox environment.

A1 adenosine receptor knockout mice are protected against acute radiocontrast nephropathy in vivo

2006 ◽  
Vol 290 (6) ◽  
pp. F1367-F1375 ◽  
Author(s):  
H. Thomas Lee ◽  
Michael Jan ◽  
Soo Chan Bae ◽  
Jin Deok Joo ◽  
Farida R. Goubaeva ◽  
...  
Keyword(s):  
Renal Failure ◽  
Acute Renal Failure ◽  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Proximal Tubule Cells ◽  
Proximal Tubular ◽  
Tubule Cells

The role of renal A1 adenosine receptors (A1AR) in the pathogenesis of radiocontrast nephropathy is controversial. We aimed to further elucidate the role of A1AR in the pathogenesis of radiocontrast nephropathy and determine whether renal proximal tubule A1AR contribute to the radiocontrast nephropathy. To induce radiocontrast nephropathy, A1AR wild-type (WT) or knockout (KO) mice were injected with a nonionic radiocontrast (iohexol, 1.5–3 g iodine/kg). Some A1WT mice were pretreated with 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; a selective A1AR antagonist) before iohexol injection. A1AR contribute to the pathogenesis of radiocontrast nephropathy in vivo as the A1WT mice developed significantly worse acute renal failure, more renal cortex vacuolization, and had lower survival 24 h after iohexol treatment compared with the A1KO mice. DPCPX pretreatment also protected the A1WT mice against radiocontrast-induced acute renal failure. No differences in renal cortical apoptosis or inflammation were observed between A1WT and A1KO mice. To determine whether the proximal tubular A1AR mediate the direct renal cytotoxicity of radiocontrast, we treated proximal tubules in culture with iohexol with or without 2-chloro- N6-cyclopentyladenosine (a selective A1AR agonist) or DPCPX pretreatment. We also subjected cultured proximal tubule cells overexpressing A1AR or lacking A1AR to radiocontrast injury. Iohexol caused a direct dose-dependent reduction in proximal tubule cell viability as well as proliferation. Neither the A1AR agonist nor the antagonist treatment affected proximal tubule viability or proliferation. Moreover, overexpression or lack of A1AR failed to impact the iohexol toxicity on proximal tubule cells. Therefore, we conclude that radiocontrast causes acute renal failure via mechanisms dependent on A1AR; however, renal proximal tubule A1AR do not contribute to the direct tubular toxicity of radiocontrast.

scholarly journals Proapoptotic effect of a micropollutant (tris-(2-chloroethyl)-phosphate) at environmental level in primary cultured renal proximal tubule cells

2012 ◽  
Vol 10 (4) ◽  
pp. 522-530 ◽  
Author(s):  
Xianghao Ren ◽  
Ho Jae Han ◽  
Yu Jin Lee ◽  
Sang Hun Lee ◽  
How Yong Ng ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Apoptotic Cell ◽  
Regulatory Protein ◽  
Cell Number ◽  
Renal Proximal Tubule ◽  
Environmental Concentration ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
Dose Dependent

Being a typical micropollutant, tris-(2-chloroethyl)-phosphate (TCEP) is often found in aquatic environments. However, the potential effects of TCEP at environmental concentrations on apoptotic mechanisms are mostly unknown. Thus, the purpose of this study is to investigate the apoptotic regulatory protein expression of TCEP at environmental concentration in primary cultured renal proximal tubule cells (PTCs). The results show that TCEP at 0.01 and 1 mg L−1 significantly increased the phosphorylation of c-Jun-NH2-terminal kinase (JNK) (135.5 and 138.0% of the control, respectively), and significantly decreased the expression of Bcl-2 and cIAP-2 at all tested concentrations, except for a slight decrease of Bcl-2 at 0.01 mg L−1. In addition, TCEP significantly increased the expression of caspase-3 at all three concentrations (132.6, 172.6 and 167.9% of the control, respectively) and caspase-9 at 1 and 10 mg L−1 (128.3 and 144.5% of the control, respectively). Furthermore, TCEP increased the apoptotic cell population in a flow cytometry analysis. In conclusion, environmental TCEP might have a dose-dependent proapoptotic effect with a decrease of DNA synthesis and cell number in primary cultured renal PTCs.

scholarly journals Role of Calbindin-D28k in Diabetes-Associated Advanced Glycation End-Products-Induced Renal Proximal Tubule Cell Injury

Cells ◽  
2019 ◽  
Vol 8 (7) ◽  
pp. 660 ◽  
Author(s):  
Kuo-How Huang ◽  
Siao-Syun Guan ◽  
Wei-Han Lin ◽  
Cheng-Tien Wu ◽  
Meei-Ling Sheu ◽  
...  
Keyword(s):  
Er Stress ◽  
Proximal Tubule ◽  
Cell Injury ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
Glycation End Products ◽  
Calbindin D28k ◽  
Renal Proximal Tubule Cells ◽  
Emt Markers

Diabetes-associated advanced glycation end-products (AGEs) can increase extracellular matrix (ECM) expression and induce renal fibrosis. Calbindin-D28k, which plays a role in calcium reabsorption in renal distal convoluted tubules, is increased in a diabetic kidney. The role of calbindin-D28k in diabetic nephropathy still remains unclear. Here, calbindin-D28k protein expression was unexpectedly induced in the renal tubules of db/db diabetic mice. AGEs induced the calbindin-D28k expression in human renal proximal tubule cells (HK2), but not in mesangial cells. AGEs induced the expression of fibrotic molecules, ECM proteins, epithelial-mesenchymal transition (EMT) markers, and endoplasmic reticulum (ER) stress-related molecules in HK2 cells, which could be inhibited by a receptor for AGE (RAGE) neutralizing antibody. Calbindin-D28k knockdown by siRNA transfection reduced the cell viability and obviously enhanced the protein expressions of fibrotic factors, EMT markers, and ER stress-related molecules in AGEs-treated HK2 cells. Chemical chaperone 4-Phenylbutyric acid counteracted the AGEs-induced ER stress and ECM and EMT markers expressions. Calbindin-D28k siRNA in vivo delivery could enhance renal fibrosis in db/db diabetic mice. These findings suggest that inducible calbindin-D28k protects against AGEs/RAGE axis-induced ER stress-activated ECM induction and cell injury in renal proximal tubule cells.

Effect of BSA-induced ER stress on SGLT protein expression levels and α-MG uptake in renal proximal tubule cells

2009 ◽  
Vol 296 (6) ◽  
pp. F1405-F1416 ◽  
Author(s):  
Yu Jin Lee ◽  
Han Na Suh ◽  
Ho Jae Han
Keyword(s):  
Protein Expression ◽  
Er Stress ◽  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Proximal Tubule Cells ◽  
Eif2α Phosphorylation ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

Recent studies demonstrated that endoplasmic reticulum (ER) stress regulates glucose homeostasis and that ER stress preconditioning which induces an adaptive, protective unfolded protein response (UPR) offers cytoprotection against nephrotoxins. Thus the aim of the present study was to use renal proximal tubule cells (PTCs) to further elucidate the link between the BSA-induced ER stress and α-methyl-d-glucopyranoside (α-MG) uptake and to identify related signaling pathways. Among ER stress inducers such as high glucose, BSA, H2O2, or tumicamycin, BSA pretreatment ameliorated the reduction of Na+-glucose cotransporter (SGLT) expression and α-MG uptake by gentamicin or cyclosporine A. Immunofluorescence studies revealed that BSA (10 mg/ml) stimulated the expression of glucose-regulated protein 78 (GRP78), an ER stress biomarker. In addition, BSA increased levels of GRP78 protein expression and eukaryotic initiation factor 2α (eIF2α) phosphorylation in a time-dependent manner. Furthermore, transfection with a GRP78-specific small interfering RNA (siRNA) inhibited BSA-stimulated SGLT expression and α-MG uptake. In experiments designed to unravel the mechanisms underlying BSA-induced ER stress, BSA stimulated the production of cellular reactive oxygen species (ROS), and antioxidants such as ascorbic acid or N-acetylcysteine (NAC) blocked BSA-induced increases in GRP78 activation, eIF2α phosphorylation, SGLT expression, and α-MG uptake. Moreover, the cells upregulated peroxisome proliferator-activated receptor-γ (PPARγ) mRNA levels in response to BSA or troglitazone (a PPARγ agonist), but BSA was ineffective in the presence of GW9662 (a PPARγ antagonist). In addition, both BSA and troglitazone stimulated GRP78 and eIF2α activation, SGLT expression, and α-MG uptake, whereas GW9662 inhibited the effects of BSA. BSA also stimulated phosphorylation of JNK and NF-κB, and GW9662 or GRP78 siRNA attenuated this response. Moreover, SP600125 or SN50 effectively blocked SGLT expression and α-MG uptake in BSA- or PPARγ agonists (troglitazone or PGJ2)-treated PTCs. We conclude that BSA induces ER stress through ROS production and PPARγ activation, which subsequently activates JNK/NF-κB signaling to enhance glucose uptake in renal PTCs.

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