Role of intracellular calcium in renal proximal tubule cell volume regulation

Osmoregulatory Ca2+ signaling in hypotonic solutions was studied with videometric techniques in 158 proximal renal tubules isolated from the teleost Carassius auratus. Absence of extracellular Ca2+, hypoxia (23 mmHg), or NaCN (3 mM) did not alter regulatory volume decreases (RVD). Nevertheless, decrements of intracellular Ca2+ via the A23187 ionophore or after intracellular Ca2+ chelation with indo-1/AM (5 microM) inhibited RVD. In tubules depleted of Ca2+, RVD could only be fully elicited when intracellular Ca2+ pulses were given within 1 min after hypotonic stimulation. While inhibition of Ca2+ release from the endoplasmic reticulum (ER) with 8-(diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8, 50 microM) blunted RVD, some of its effects could be reversed with the anion carrier tributyltin (1 microM). Dibutyryl adenosine 3',5'-cyclic monophosphate (cAMP, 0.5 and 1.0 mM) and forskolin (0.25 mM) also impeded RVD; however, their effects could be partially reversed with the K+ ionophore gramicidin (0.5 microM). In conclusion, in Carassius auratus proximal renal tubule cells, RVD is activated by an intracellular Ca2+ signal that likely emanates from the ER and not from the extracellular media or the mitochondrial Ca2+ pool. Ca2+ activation of a cAMP-modulated osmoregulatory K+ channel appears to play an important role.

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Measurements of Electrical Potential Differences on Single Nephrons of the Perfused Necturus Kidney

The Journal of General Physiology ◽

10.1085/jgp.44.4.659 ◽

1961 ◽

Vol 44 (4) ◽

pp. 659-678 ◽

Cited By ~ 86

Author(s):

Gerhard Giebisch

Keyword(s):

Cell Membrane ◽

Transmembrane Potential ◽

Renal Tubule ◽

Ionic Composition ◽

Electrical Potential ◽

Cell Boundary ◽

Proximal Tubule Cell ◽

Tubule Cell ◽

Extracellular Medium ◽

Tubule Cells

Stable electrical potential differences can be measured by means of conventional glass microelectrodes across the cell membrane of renal tubule cells and across the epithelial wall of single tubules in the doubly perfused kidney of Necturus. These measurements have been carried out with amphibian Ringer's solution, and with solutions of altered ionic composition. The proximal tubule cell has been found to be electrically asymmetrical inasmuch as a smaller potential difference is maintained across the luminal cell membrane than across the peritubular cell boundary. The tubule lumen is always electrically negative with respect to the peritubular extracellular medium. Observations on the effectiveness of potassium ions in depolarizing single tubule cells indicate that the transmembrane potential is essentially an inverse function of the logarithm of the external potassium concentration. The behavior of the peritubular transmembrane potential resembles more closely an ideal potassium electrode than that of the luminal transmembrane potential. From these results, and the effects of various ionic substitutions on the electrical profile of the renal tubular epithelium, a thesis concerning the origin of the observed potential differences is presented. A sodium extrusion mechanism is considered to be located at the peritubular cell boundary, and reasons are given for the hypothesis that the electrical asymmetry across the proximal renal tubule cell could arise as a consequence of differences in the relative sodium and potassium permeability at the luminal and peritubular cell boundaries.

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Abstract 215: Adam17 Regulates Renal Function

Circulation ◽

10.1161/circ.142.suppl_4.215 ◽

2020 ◽

Vol 142 (Suppl_4) ◽

Author(s):

Bo Zhang ◽

Kai Chen ◽

Zhongjie Sun

Keyword(s):

Renal Function ◽

Kidney Function ◽

Renal Tubule ◽

Renal Diseases ◽

Normal Kidney ◽

Normal Kidney Function ◽

Membrane Bound ◽

Tubule Cells ◽

A Disintegrin And Metalloproteinase

A disintegrin and metalloproteinase 17 (ADAM17) is a ubiquitously expressed membrane-bound sheddase that cleaves a diverse variety of membrane-bound molecules, including cytokines, growth factors, and their receptors to activate or inactivate various cellular signaling pathways. Although it was reported that ADAM17 may mediate renal diseases, the role of ADAM17 in the regulation of normal kidney function has never been identified. The objective of this study is to investigate whether renal ADAM17 plays a role in maintaining normal kidney function and structure. Tamoxifen-inducible kidney-specific cre (Ksp) and ADAM17-floxed mice were cross-bred for generating Ksp/ADAM17-floxed mice. Injection of tamoxifen initiated deletion of the ADAM17 gene in renal tubule cells. We found that conditional kidney-specific knockout of ADAM1 7 gene (Ksp-ADAM17 -/-) decreased urinary creatinine and sodium excretion were decreased in Ksp-ADAM17 -/- mice, indicating that ADAM17 gene deficiency impairs kidney function. H&E staining showed glomerulus collapse and tubule dilation in Ksp-ADAM17 -/- mice. The epithelial cells fall off into the lumen in the renal tubule. Mesangial expansion and fibrosis were found in glomeruli in Ksp-ADAM17 -/- mice. Moreover, apoptosis was increased in tubule cells in both cortex and medulla areas in Ksp-ADAM17 -/- mice. In conclusion, ADAM17 is critical to the maintenance of normal renal function and structure.

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Stretch-activated potassium channels in renal proximal tubule

AJP Renal Physiology ◽

10.1152/ajprenal.1987.253.6.f1253 ◽

1987 ◽

Vol 253 (6) ◽

pp. F1253-F1262 ◽

Cited By ~ 4

Author(s):

H. Sackin

Keyword(s):

Proximal Tubule ◽

Cell Volume ◽

Negative Pressure ◽

Basolateral Membrane ◽

Cell Volume Regulation ◽

K Channel ◽

Proximal Tubule Cell ◽

Stretch Activation ◽

Membrane Stretch ◽

Excised Patches

A short open-time potassium (K) channel that has previously been identified in the basolateral membrane of Necturus proximal tubule (17) is activated by membrane stretch. Application of between 12 and 20 cmH2O negative pressure to the patch pipette reversibly increases mean number of open basolateral K channels (NP0) by a factor of 5.3 +/- 2 in cell-attached patches (n = 4) and a factor of 13.7 +/- 5 in excised patches (n = 8). This stretch activation does not alter channel selectivity or conductance and depends on neither the direction of K current nor the orientation of the patch ("inside-out" vs. "outside-out"). The increase in NP0 occurs within seconds after applying negative pressure to the patch and is proportional to applied negative pressure. Stretch activation of the basolateral potassium channel may play an important role in proximal tubule cell volume regulation. For example, if swelling stretches the basolateral membrane, the resulting increase in NP0 could restore cell volume by loss of K (with an accompanying anion) followed by osmotic exit of water.

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

AJP Renal Physiology ◽

10.1152/ajprenal.00482.2011 ◽

2012 ◽

Vol 303 (2) ◽

pp. F266-F278 ◽

Cited By ~ 45

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.

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Developmental stages of Sphaerospora ohlmacheri (Whinery, 1893) n.comb. (Myxozoa: Myxosporea) in the renal tubules of bullfrog tadpoles, Rana catesbeiana, from Lake of Two Rivers, Algonquin Park, Ontario

Canadian Journal of Zoology ◽

10.1139/z86-335 ◽

1986 ◽

Vol 64 (10) ◽

pp. 2213-2217 ◽

Cited By ~ 13

Author(s):

Sherwin S. Desser ◽

Jǐrí Lom ◽

Iva Dyková

Keyword(s):

Developmental Stages ◽

Renal Tubule ◽

Rana Catesbeiana ◽

Renal Tubules ◽

Histological Sections ◽

Tubule Cells ◽

Bowman's Capsule

Pseudoplasmodia and mature spores of Sphaerospora ohlmacheri (Whinery, 1893) n.comb. were found in the renal tubules and in the space of the Bowman's capsule of 2nd-year tadpoles of the bullfrog, Rana catesbeiana. Fresh spores and the sporogenic stages of S. ohlmacheri from tissue imprints and histological sections are described and illustrated. Dystrophic changes of renal tubule cells characterized by degeneration associated with hyaline droplets often accompanied the presence of the parasite. Features of the genera Leptotheca, Wardia, and Sphaerospora are discussed.

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

Journal of the American Society of Nephrology ◽

10.1681/asn.2019030321 ◽

2019 ◽

Vol 30 (12) ◽

pp. 2370-2383 ◽

Cited By ~ 3

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.

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Role of lipid peroxidation in renal proximal tubule cell death induced by haloalkene cysteine conjugates*1

Toxicology and Applied Pharmacology ◽

10.1016/0041-008x(91)90330-h ◽

1991 ◽

Vol 107 (1) ◽

pp. 54-62 ◽

Cited By ~ 42

Author(s):

C GROVES

Keyword(s):

Lipid Peroxidation ◽

Cell Death ◽

Proximal Tubule ◽

Renal Proximal Tubule ◽

Proximal Tubule Cell ◽

Tubule Cell

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

PLoS ONE ◽

10.1371/journal.pone.0250996 ◽

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.

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