Absence of endonuclease activation during acute cell death in renal proximal tubules

1993 ◽  
Vol 265 (2) ◽  
pp. C485-C490 ◽  
Author(s):  
R. G. Schnellmann ◽  
A. R. Swagler ◽  
M. M. Compton
Keyword(s):  
Cell Death ◽  
Proximal Tubule ◽  
Calcium Ionophore ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Free Calcium ◽  
Proximal Tubule Cell ◽  
Antimycin A ◽  
Aurintricarboxylic Acid ◽  
Ldh Release

The role of endonuclease and poly(ADP-ribose) polymerase activation in various types of cell injuries and death to rabbit renal proximal tubule suspensions was examined. Proximal tubules were exposed to the mitochondrial inhibitor antimycin A (0.1 microM), the protonophore carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP, 1 microM), the calcium ionophore ionomycin (5 microM), or the oxidant t-butyl hydroperoxide (TBHP, 0.5 mM) in the absence or presence of the endonuclease inhibitor aurintricarboxylic acid or the poly(ADP-ribose) polymerase inhibitor 3-aminobenzamide. Lactate dehydrogenase (LDH) release was used as a marker of cell death and analysis of genomic DNA for internucleosomal cleavage was used as a marker of endonuclease activation. Aurintricarboxylic acid and 3-aminobenzamide had no effect on the proximal tubule LDH release produced by 1 h exposure to antimycin A, FCCP, or ionomycin, or 2 h exposure to TBHP. Furthermore, there was no evidence of DNA fragmentation with any compound prior to or after cell death began. As a positive control, proximal tubules exposed to digitonin in the absence of metabolic substrates resulted in the chelator-inhibitable fragmentation of DNA, indicating that the endonuclease is present in proximal tubules. These results show that endonuclease activation did not occur prior to or after cell death began. Furthermore, these results suggest that endonuclease and poly(ADP-ribose) polymerase activation do not play a role in this model of acute renal proximal tubule cell injury and death induced by agents that cause oxidative stress, mitochondrial dysfunction, or increases in cytosolic free calcium.

scholarly journals Congener-Specific Polychlorinated Biphenyl–Induced Cell Death in Human Kidney Cells In Vitro: Potential Role of Caspase

2006 ◽  
Vol 25 (5) ◽  
pp. 341-347 ◽  
Author(s):  
Y. Q. Chen ◽  
S. De ◽  
S. Ghosh ◽  
S. K. Dutta
Keyword(s):  
Cell Death ◽  
Proximal Tubule ◽  
Human Kidney ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Kidney Cells ◽  
Dependent Manner ◽  
Caspase Inhibitor ◽  
Pcb Congeners

Polychlorinated biphenyls (PCBs) are among the most widespread and persistent pollutants in the global environment. Coplanar and noncoplanar PCBs have been shown to cause congener-specific apoptosis mediated neurotoxicity in rats. Very few, if any, such studies have been reported on human renal cell toxicity. The authors report here caspase-dependent or caspase-independent renal toxicity, as measured by apoptotic death induced by PCBs, depending on the planarity of congeners PCB-77 (coplanar) and PCB-153 (noncoplanar) in human kidney cells (HK2) in vitro. The authors have combined morphological and biological techniques to discover the relevance of apoptosis in renal proximal tubule cell death induced by these two PCB congeners. Treatment with both PCB congeners caused accelerated apoptosis in a time-and concentration-dependent manner. Based on our findings using human kidney (HK2) cells, there was more apoptosis-mediated loss of cell viability by non– ortho-substituted PCB-77 when compared to PCB-153. A significant increase of caspase-3 expression through immunoblot studies showed the involvement of apoptosis by PCB-77 compared to none by PCB-153. The broad-spectrum caspase inhibitor z-VAD-fmk showed increased cell death when treated by PCB-153, but not by PCB-77, confirming that caspase inhibitor induced a switch in the mode of cell death. It is reasonable to assume that apoptotic cell death in the renal proximal tubule cells treated by PCBs may have both caspase-dependent and caspase-independent pathways.

Studies on the Mechanism of 4-Aminophenol-induced Toxicity to Renal Proximal Tubules

1993 ◽  
Vol 12 (5) ◽  
pp. 383-388 ◽  
Author(s):  
Edward A. Lock ◽  
Theresa J. Cross ◽  
Rick G. Schnellmann
Keyword(s):  
Cell Death ◽  
Proximal Tubule ◽  
Iron Chelator ◽  
Proximal Tubules ◽  
Proximal Tubule Cell ◽  
Dependent Manner ◽  
Tubule Cell ◽  
Renal Proximal Tubules ◽  
Lactate Dehydrogenase Release ◽  
Cytochrome P 450

4-Aminophenol (PAP) is known to cause nephrotoxicity in the rat where it produces selective necrosis to renal proximal tubules. The aim of this work was to investigate the toxicity of PAP and its known nephrotoxic metabolite 4-amino-3-S-glutathionylphenol using a well defined suspension of rabbit renal proximal tubules. PAP at a concentration of 0.5 mM and 1 mM caused proximal tubule cell death (measured by lactate dehydrogenase release) in a time-dependent manner over a 4-h exposure. In contrast, 4-amino-3-S-glutathionylphenol at 1 mM produced no proximal tubule cell death over a similar 4-h exposure. At 2 h, 1 mM PAP inhibited proximal tubule respiration by 30% and decreased cellular adenosine triphosphate (ATP) levels by 60%. These events preceded cell death. The addition of PAP to proximal tubules led to a rapid depletion of cellular glutathione, exposure to 0.5 mM causing a 50% depletion within 1 h. The cytochrome P-450 inhibitors SKF525A (1 mM) and metyrapone (1 mM), the iron chelator deferoxamine (1 mM) and the antioxidant N,N'-phenyl-1,4-phenyienediamine (2 μM) had no effect on PAP-induced cell death. However ascorbic acid (0.1 mM), afforded a marked protection against the depletion of cellular glutathione and completely protected against the cell death produced by 1 mM-PAP. These results indicate that oxidation of PAP to generate a metabolite that can react with glutathione is an important step in the toxicity, while mitochondria appear to be a critical target for the reactive intermediate formed.

scholarly journals Renal Proximal Tubule Cell Cannabinoid-1 Receptor Regulates Bone Remodeling and Mass via a Kidney-to-Bone Axis

Cells ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 414
Author(s):  
Saja Baraghithy ◽  
Yael Soae ◽  
Dekel Assaf ◽  
Liad Hinden ◽  
Shiran Udi ◽  
...  
Keyword(s):  
Bone Mass ◽  
Proximal Tubule ◽  
Bone Remodeling ◽  
Kidney Function ◽  
Bone Cells ◽  
Critical Role ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Protective Effects ◽  
Cannabinoid 1 Receptor

The renal proximal tubule cells (RPTCs), well-known for maintaining glucose and mineral homeostasis, play a critical role in the regulation of kidney function and bone remodeling. Deterioration in RPTC function may therefore lead to the development of diabetic kidney disease (DKD) and osteoporosis. Previously, we have shown that the cannabinoid-1 receptor (CB1R) modulates both kidney function as well as bone remodeling and mass via its direct role in RPTCs and bone cells, respectively. Here we employed genetic and pharmacological approaches that target CB1R, and found that its specific nullification in RPTCs preserves bone mass and remodeling both under normo- and hyper-glycemic conditions, and that its chronic blockade prevents the development of diabetes-induced bone loss. These protective effects of negatively targeting CB1R specifically in RPTCs were associated with its ability to modulate erythropoietin (EPO) synthesis, a hormone known to affect bone mass and remodeling. Our findings highlight a novel molecular mechanism by which CB1R in RPTCs remotely regulates skeletal homeostasis via a kidney-to-bone axis that involves EPO.

Mitochondrial aquaporin-8 in renal proximal tubule cells: evidence for a role in the response to metabolic acidosis

2012 ◽  
Vol 303 (3) ◽  
pp. F458-F466 ◽  
Author(s):  
Sara M. Molinas ◽  
Laura Trumper ◽  
Raúl A. Marinelli
Keyword(s):  
Metabolic Acidosis ◽  
Protein Expression ◽  
Proximal Tubule ◽  
Ammonia Excretion ◽  
Renal Proximal Tubule ◽  
In Vivo Studies ◽  
Proximal Tubule Cell ◽  
Inner Mitochondrial Membrane ◽  
Ammonia Transport ◽  
In Cells

Mitochondrial ammonia synthesis in proximal tubules and its urinary excretion are key components of the renal response to maintain acid-base balance during metabolic acidosis. Since aquaporin-8 (AQP8) facilitates transport of ammonia and is localized in inner mitochondrial membrane (IMM) of renal proximal cells, we hypothesized that AQP8-facilitated mitochondrial ammonia transport in these cells plays a role in the response to acidosis. We evaluated whether mitochondrial AQP8 (mtAQP8) knockdown by RNA interference is able to impair ammonia excretion in the human renal proximal tubule cell line, HK-2. By RT-PCR and immunoblotting, we found that AQP8 is expressed in these cells and is localized in IMM. HK-2 cells were transfected with short-interfering RNA targeting human AQP8. After 48 h, the levels of mtAQP8 protein decreased by 53% ( P < 0.05). mtAQP8 knockdown decreased the rate of ammonia released into culture medium in cells grown at pH 7.4 (−31%, P < 0.05) as well as in cells exposed to acid (−90%, P < 0.05). We also evaluated mtAQP8 protein expression in HK-2 cells exposed to acidic medium. After 48 h, upregulation of mtAQP8 (+74%, P < 0.05) was observed, together with higher ammonia excretion rate (+73%, P < 0.05). In vivo studies in NH4Cl-loaded rats showed that mtAQP8 protein expression was also upregulated after 7 days of acidosis in renal cortex (+51%, P < 0.05). These data suggest that mtAQP8 plays an important role in the adaptive response of proximal tubule to acidosis possibly facilitating mitochondrial ammonia transport.

scholarly journals Dietary fructose enhances angiotensin II-stimulated Na+ transport via activation of PKC-α in renal proximal tubules

2020 ◽  
Vol 318 (6) ◽  
pp. F1513-F1519
Author(s):  
Nianxin Yang ◽  
Nancy J. Hong ◽  
Jeffrey L. Garvin
Keyword(s):  
Angiotensin Ii ◽  
Proximal Tubule ◽  
Tap Water ◽  
Renal Proximal Tubule ◽  
Proximal Tubules ◽  
Control Group ◽  
Ang Ii ◽  
Dietary Fructose ◽  
Intracellular Ca ◽  
Pkc Β

Angiotensin II (ANG II) stimulates proximal nephron transport via activation of classical protein kinase C (PKC) isoforms. Acute fructose treatment stimulates PKC and dietary fructose enhances ANG II’s ability to stimulate Na+ transport, but the mechanisms are unclear. We hypothesized that dietary fructose enhances ANG II’s ability to stimulate renal proximal tubule Na+ reabsorption by augmenting PKC-α activation and increases in intracellular Ca2+. We measured total and isoform-specific PKC activity, basal and ANG II-stimulated oxygen consumption, a surrogate of Na+ reabsorption, and intracellular Ca2+ in proximal tubules from rats given either 20% fructose in their drinking water (fructose group) or tap water (control group). Total PKC activity was measured by ELISA. PKC-α, PKC-β, and PKC-γ activities were assessed by measuring particulate-to-soluble ratios. Intracelluar Ca2+ was measured using fura 2. ANG II stimulated total PKC activity by 53 ± 15% in the fructose group but not in the control group (−15 ± 11%, P < 0.002). ANG II stimulated PKC-α by 0.134 ± 0.026 but not in the control group (−0.002 ± 0.020, P < 0.002). ANG II increased PKC-γ activity by 0.008 ± 0.003 in the fructose group but not in the control group ( P < 0.046). ANG II did not stimulate PKC-β in either group. ANG II increased Na+ transport by 454 ± 87 nmol·min−1·mg protein−1 in fructose group, and the PKC-α/β inhibitor Gö6976 blocked this increase (−96 ± 205 nmol·min−1·mg protein−1, P < 0.045). ANG II increased intracellular Ca2+ by 148 ± 53 nM in the fructose group but only by 43 ± 10 nM in the control group ( P < 0.035). The intracellular Ca2+ chelator BAPTA blocked the ANG II-induced increase in Na+ transport in the fructose group. We concluded that dietary fructose enhances ANG II’s ability to stimulate renal proximal tubule Na+ reabsorption by augmenting PKC-α activation via elevated increases in intacellular Ca2+.

Expression of xenobiotic transporters in the human renal proximal tubule cell line RPTEC/TERT1

2015 ◽  
Vol 30 (1) ◽  
pp. 95-105 ◽  
Author(s):  
Lydia Aschauer ◽  
Giada Carta ◽  
Nadine Vogelsang ◽  
Eberhard Schlatter ◽  
Paul Jennings
Keyword(s):  
Proximal Tubule ◽  
Cell Line ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Tubule Cell

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.

Formate: A Critical Intermediate for Chloride Transport in the Proximal Tubule

Physiology ◽  
1987 ◽  
Vol 2 (5) ◽  
pp. 160-164
Author(s):  
LP Karniski ◽  
PS Aronson
Keyword(s):  
Formic Acid ◽  
Proximal Tubule ◽  
Cell Membranes ◽  
Chloride Transport ◽  
Critical Role ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cell ◽  
Tubule Cell ◽  
Active Uptake

Recent experiments unexpectedly suggest that formate plays a critical role in chloride transport across cell membranes. In particular, active uptake of chloride in the renal proximal tubule cell occurs by chloride-formate exchange. Formate recycles from lumen to cell via nonionic diffusion of uncharged formic acid. In this manner, small amounts of formate can facilitate resorption of large quantities of chloride.

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