scholarly journals Increased Endocytosis of Cadmium-Metallothionein through the 24p3 Receptor in an In Vivo Model with Reduced Proximal Tubular Activity

2021 ◽  
Vol 22 (14) ◽  
pp. 7262
Author(s):  
Itzel Pamela Zavala-Guevara ◽  
Manolo Sibael Ortega-Romero ◽  
Juana Narváez-Morales ◽  
Tania Libertad Jacobo-Estrada ◽  
Wing-Kee Lee ◽  
...  
Keyword(s):  
Metal Ion ◽  
Protein Complexes ◽  
Subcutaneous Administration ◽  
Kidney Injury ◽  
In Vivo Model ◽  
Compensatory Mechanism ◽  
Filtration Barrier ◽  
Proximal Tubular ◽  
Renal Biomarker

Background: The proximal tubule (PT) is the major target of cadmium (Cd2+) nephrotoxicity. Current dogma postulates that Cd2+ complexed to metallothionein (MT) (CdMT) is taken up through receptor-mediated endocytosis (RME) via the PT receptor megalin:cubilin, which is the predominant pathway for reuptake of filtered proteins in the kidney. Nevertheless, there is evidence that the distal parts of the nephron are also sensitive to damage induced by Cd2+. In rodent kidneys, another receptor for protein endocytosis, the 24p3 receptor (24p3R), is exclusively expressed in the apical membranes of distal tubules (DT) and collecting ducts (CD). Cell culture studies have demonstrated that RME and toxicity of CdMT and other (metal ion)–protein complexes in DT and CD cells is mediated by 24p3R. In this study, we evaluated the uptake of labeled CdMT complex through 24p3R after acute kidney injury (AKI) induced by gentamicin (GM) administration that disrupts PT function. Subcutaneous administration of GM at 10 mg/kg/day for seven days did not alter the structural and functional integrity of the kidney’s filtration barrier. However, because of PT injury, the concentration of the renal biomarker Kim-1 increased. When CdMT complex coupled to FITC was administered intravenously, both uptake of the CdMT complex and 24p3R expression in DT increased and also colocalized after PT injury induced by GM. Although megalin decreased in PT after GM administration, urinary protein excretion was not changed, which suggests that the increased levels of 24p3R in the distal nephron could be acting as a compensatory mechanism for protein uptake. Altogether, these results suggest that PT damage increases the uptake of the CdMT complex through 24p3R in DT (and possibly CD) and compensate for protein losses associated with AKI.

Autocrine/paracrine regulation of renal Na(+)-phosphate cotransport by dopamine

1993 ◽  
Vol 264 (4) ◽  
pp. F618-F622 ◽  
Author(s):  
R. P. Glahn ◽  
M. J. Onsgard ◽  
G. M. Tyce ◽  
S. L. Chinnow ◽  
F. G. Knox ◽  
...  
Keyword(s):  
In Vivo Model ◽  
Acid Decarboxylase ◽  
System Support ◽  
Opossum Kidney ◽  
Amino Acid Decarboxylase ◽  
Ok Cells ◽  
Proximal Tubular ◽  
Phosphate Cotransport

We tested the hypothesis that dopamine (DA) acts as an autocrine/paracrine regulator of Na(+)-Pi symport in proximal tubules, using opossum kidney (OK) cells as an in vivo model. Both DA and parathyroid hormone (PTH) increased adenosine 3',5'-cyclic monophosphate (cAMP) and inhibited Na(+)-gradient-dependent uptake of 32P but not that of L-[3H]-alanine. Incubation of OK cells with L-dopa, a DA precursor, resulted in accumulation of DA (7.4 nM), a ninefold increase of cAMP in the medium, and an inhibition (-10%) of Na(+)-Pi uptake. Carbidopa, an inhibitor of aromatic-L-amino acid decarboxylase, prevented the formation of DA from L-dopa, the increase in cAMP, and the inhibition of Na(+)-Pi cotransport. Pi-replete OK cells produced more DA (+15%) from L-dopa than Pi-deprived cells; however, the endogenous DA inhibited Na(+)-Pi cotransport both in Pi-deprived and in Pi-replete cells. Thus OK cells can synthesize DA from L-dopa in a quantity sufficient to elicit both the maximum DA-stimulated cAMP accumulation and inhibition of Na(+)-Pi cotransport in the same cell population. Our data, obtained on an in vitro system, support the hypothesis proposing that DA generated in proximal tubular cells can modulate, via cAMP, the Na(+)-Pi symport in the same or adjacent cells. If present in the kidney, this pathway might represent an autocrine/paracrine system that can contribute to regulation of renal Pi homeostasis.

scholarly journals Preconditioning mice with activators of AMPK ameliorates ischemic acute kidney injury in vivo

2016 ◽  
Vol 311 (4) ◽  
pp. F731-F739 ◽  
Author(s):  
Wilfred Lieberthal ◽  
Meiyi Tang ◽  
Mark Lusco ◽  
Mersema Abate ◽  
Jerrold S. Levine
Keyword(s):  
Metabolic Stress ◽  
Kidney Injury ◽  
Camp Response Element Binding ◽  
Hexokinase Ii ◽  
Camp Response Element ◽  
Element Binding Protein ◽  
Proximal Tubular ◽  
Amp Activated Protein Kinase

This study had two objectives: 1) to determine whether preconditioning cultured proximal tubular cells (PTCs) with pharmacological activators of AMP-activated protein kinase (AMPK) protects these cells from apoptosis induced by metabolic stress in vitro and 2) to assess the effects of preconditioning mice with these agents on the severity of ischemic acute renal kidney injury (AKI) in vivo. We demonstrate that preconditioning PTCs with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) or A-769662 reduces apoptosis of PTCs induced by subsequent stress. We also show that the reduction in cell death during metabolic stress associated with pretreatment by AMPK activators is associated with an increase in the cytosolic level of ATP, which is mediated by an increase in the rate of glycolysis. In addition, we provide evidence that the effect of AMPK activators on glycolysis is mediated, at least in part, by an increased uptake of glucose, and by the induction of hexokinase II (HK II) expression. Our data also show that the increased in HK II expression associated with preconditioning with AMPK activators is mediated by the activation (phosphorylation) of the cAMP-response element binding protein (CREB). We also provide entirely novel evidence that that A-79662 is substantially more effective than AICAR in mediating these alterations in PTCs in vitro. Finally, we demonstrate that preconditioning mice with AICAR or A-769662 substantially reduces the severity of renal dysfunction and tubular injury in a model of ischemic AKI in vivo and that the efficacy of AICAR and A-768662 in ameliorating ischemic AKI in vivo is comparable.

scholarly journals The lncRNA CASC9 alleviates lipopolysaccharide-induced acute kidney injury by regulating the miR-424-5p/TXNIP pathway

2021 ◽  
Vol 49 (8) ◽  
pp. 030006052110374
Author(s):  
Hai-Peng Fan ◽  
Zhi-Xia Zhu ◽  
Jia-Jun Xu ◽  
Yu-Tang Li ◽  
Chun-Wen Guo ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Cancer Susceptibility ◽  
Kidney Injury ◽  
In Vivo Model ◽  
Interacting Protein ◽  
Thioredoxin Interacting Protein ◽  
Downstream Target ◽  
Renal Tubular

Objective This study aimed to clarify the mechanism by which the long non-coding RNA cancer susceptibility candidate 9 (CASC9) alleviates sepsis-related acute kidney injury (S-AKI). Methods A lipopolysaccharide (LPS)-induced AKI model was established to simulate S-AKI. HK-2 human renal tubular epithelial cells were treated with LPS to establish an in vitro model, and mice were intraperitoneally injected with LPS to generate an in vivo model. Subsequently, the mRNA expression of inflammatory and antioxidant factors was validated by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Reactive oxygen species (ROS) production was assessed using an assay kit. Apoptosis was detected by western blotting and fluorescence-activated cell sorting. Results CASC9 was significantly downregulated in the LPS-induced AKI model. CASC9 attenuated cell inflammation and apoptosis and enhanced the antioxidant capacity of cells. Regarding the mechanism, miR-424-5p was identified as the downstream target of CASC9, and the interaction between CASC9 and miR-424-5p promoted thioredoxin-interacting protein (TXNIP) expression. Conclusions CASC9 alleviates LPS-induced AKI in vivo and in vitro, and CASC9 directly targets miR-424-5p and further promotes the expression of TXNIP. We have provided a possible reference strategy for the treatment of S-AKI.

scholarly journals Cyclin G1 and TASCC regulate kidney epithelial cell G2-M arrest and fibrotic maladaptive repair

2019 ◽  
Vol 11 (476) ◽  
pp. eaav4754 ◽  
Author(s):  
Guillaume Canaud ◽  
Craig R. Brooks ◽  
Seiji Kishi ◽  
Kensei Taguchi ◽  
Kenji Nishimura ◽  
...  
Keyword(s):  
Kidney Injury ◽  
Phase Form ◽  
Kidney Fibrosis ◽  
Spatial Coupling ◽  
Cycle Arrest ◽  
Cyclin G1 ◽  
M Phase ◽  
Proximal Tubular ◽  
Kidney Epithelial Cell

Fibrosis contributes to the progression of chronic kidney disease (CKD). Severe acute kidney injury can lead to CKD through proximal tubular cell (PTC) cycle arrest in the G2-M phase, with secretion of profibrotic factors. Here, we show that epithelial cells in the G2-M phase form target of rapamycin (TOR)–autophagy spatial coupling compartments (TASCCs), which promote profibrotic secretion similar to the senescence-associated secretory phenotype. Cyclin G1 (CG1), an atypical cyclin, promoted G2-M arrest in PTCs and up-regulated TASCC formation. PTC TASCC formation was also present in humans with CKD. Prevention of TASCC formation in cultured PTCs blocked secretion of profibrotic factors. PTC-specific knockout of a key TASCC component reduced the rate of kidney fibrosis progression in mice with CKD. CG1 induction and TASCC formation also occur in liver fibrosis. Deletion of CG1 reduced G2-M phase cells and TASCC formation in vivo. This study provides mechanistic evidence supporting how profibrotic G2-M arrest is induced in kidney injury and how G2-M–arrested PTCs promote fibrosis, identifying new therapeutic targets to mitigate kidney fibrosis.

scholarly journals miR-141 mediates recovery from acute kidney injury

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lucy J. Newbury ◽  
Kate Simpson ◽  
Usman Khalid ◽  
Imogen John ◽  
Lluís Bailach de Rivera ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Acute Kidney Injury ◽  
Cell Viability ◽  
Messenger Rna ◽  
Tyrosine Phosphatase ◽  
Kidney Injury ◽  
Clinical Problem ◽  
Proximal Tubular

AbstractAcute kidney injury (AKI) is a global clinical problem characterised by a sudden decline in renal function and mortality as high as 60%. Current AKI biomarkers have limited ability to classify disease progression and identify underlying pathological mechanisms. Here we hypothesised that alterations in urinary microRNA profiles could predict AKI recovery/nonrecovery after 90 days, and that injury-specific changes would signify microRNA mediators of AKI pathology. Comparison of urinary microRNA profiles from AKI patients with controls detected significant injury-specific increases in miR-21, miR-126 and miR-141 (p < 0.05) and decreases in miR-192 (p < 0.001) and miR-204 (p < 0.05). Expression of miR-141 increased in renal proximal tubular epithelial cells (PTECs) under oxidative stress in vitro and unilateral ischaemic reperfusion injury in vivo. Forced miR-141 expression in the presence of H2O2 increased PTEC death and decreased cell viability. Of nine messenger RNA targets with two or more miR-141 3’-untranslated region binding sites, we confirmed protein tyrosine phosphatase receptor type G (PTPRG) as a direct miR-141 target in PTECs. PTPRG-specific siRNA knockdown under oxidative stress increased PTEC death and decreased cell viability. In conclusion, we detected significant alterations in five urinary microRNAs following AKI, and identified proximal tubular cell PTPRG as a putative novel therapeutic target.

scholarly journals Apical-basal polarity regulators are essential for slit diaphragm assembly and endocytosis in Drosophila nephrocytes

2021 ◽  
Author(s):  
Stefanie Heiden ◽  
Rebecca Siwek ◽  
Marie-Luise Lotz ◽  
Sarah Borkowsky ◽  
Rita Schröter ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Protein Complexes ◽  
Slit Diaphragm ◽  
Cell Cortex ◽  
Proximal Tubular Cells ◽  
Tubular Cells ◽  
Filtration Barrier ◽  
Apical Polarity ◽  
Proximal Tubular

AbstractApical-basal polarity is a key feature of most epithelial cells and it is regulated by highly conserved protein complexes. In mammalian podocytes, which emerge from columnar epithelial cells, this polarity is preserved and the tight junctions are converted to the slit diaphragms, establishing the filtration barrier. In Drosophila, nephrocytes show several structural and functional similarities with mammalian podocytes and proximal tubular cells. However, in contrast to podocytes, little is known about the role of apical-basal polarity regulators in these cells. In this study, we used expansion microscopy and found the apical polarity determinants of the PAR/aPKC and Crb-complexes to be predominantly targeted to the cell cortex in proximity to the nephrocyte diaphragm, whereas basolateral regulators also accumulate intracellularly. Knockdown of PAR-complex proteins results in severe endocytosis and nephrocyte diaphragm defects, which is due to impaired aPKC recruitment to the plasma membrane. Similar, downregulation of most basolateral polarity regulators disrupts Nephrin localization but had surprisingly divergent effects on endocytosis. Our findings suggest that morphology and slit diaphragm assembly/maintenance of nephrocytes is regulated by classical apical-basal polarity regulators, which have distinct functions in endocytosis.

scholarly journals Sirtuin 5 depletion impairs mitochondrial function in human proximal tubular epithelial cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Timo N. Haschler ◽  
Harry Horsley ◽  
Monika Balys ◽  
Glenn Anderson ◽  
Jan-Willem Taanman ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Mitochondrial Function ◽  
Kidney Injury ◽  
Tubular Epithelial Cells ◽  
Atp Production ◽  
Form And Function ◽  
Proximal Tubular Epithelial Cells ◽  
Proximal Tubular

AbstractIschemia is a major cause of kidney damage. Proximal tubular epithelial cells (PTECs) are highly susceptible to ischemic insults that frequently cause acute kidney injury (AKI), a potentially life-threatening condition with high mortality. Accumulating evidence has identified altered mitochondrial function as a central pathologic feature of AKI. The mitochondrial NAD+-dependent enzyme sirtuin 5 (SIRT5) is a key regulator of mitochondrial form and function, but its role in ischemic renal injury (IRI) is unknown. SIRT5 expression was increased in murine PTECs after IRI in vivo and in human PTECs (hPTECs) exposed to an oxygen/nutrient deprivation (OND) model of IRI in vitro. SIRT5-depletion impaired ATP production, reduced mitochondrial membrane potential, and provoked mitochondrial fragmentation in hPTECs. Moreover, SIRT5 RNAi exacerbated OND-induced mitochondrial bioenergetic dysfunction and swelling, and increased degradation by mitophagy. These findings suggest SIRT5 is required for normal mitochondrial function in hPTECs and indicate a potentially important role for the enzyme in the regulation of mitochondrial biology in ischemia.

scholarly journals Site-Selective Artificial Ribonucleases: Renaissance of Oligonucleotide Conjugates for Irreversible Cleavage of RNA Sequences

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1732
Author(s):  
Yaroslav Staroseletz ◽  
Svetlana Gaponova ◽  
Olga Patutina ◽  
Elena Bichenkova ◽  
Bahareh Amirloo ◽  
...  
Keyword(s):  
Metal Ion ◽  
Protein Complexes ◽  
Artificial Ribonucleases ◽  
Rna Sequences ◽  
Molecular Scaffold ◽  
Catalytically Active ◽  
Recognition Motifs ◽  
The One ◽  
Site Selective

RNA-targeting therapeutics require highly efficient sequence-specific devices capable of RNA irreversible degradation in vivo. The most developed methods of sequence-specific RNA cleavage, such as siRNA or antisense oligonucleotides (ASO), are currently based on recruitment of either intracellular multi-protein complexes or enzymes, leaving alternative approaches (e.g., ribozymes and DNAzymes) far behind. Recently, site-selective artificial ribonucleases combining the oligonucleotide recognition motifs (or their structural analogues) and catalytically active groups in a single molecular scaffold have been proven to be a great competitor to siRNA and ASO. Using the most efficient catalytic groups, utilising both metal ion-dependent (Cu(II)-2,9-dimethylphenanthroline) and metal ion-free (Tris(2-aminobenzimidazole)) on the one hand and PNA as an RNA recognising oligonucleotide on the other, allowed site-selective artificial RNases to be created with half-lives of 0.5–1 h. Artificial RNases based on the catalytic peptide [(ArgLeu)2Gly]2 were able to take progress a step further by demonstrating an ability to cleave miRNA-21 in tumour cells and provide a significant reduction of tumour growth in mice.

scholarly journals Evaluation of Dose Fractionated Polymyxin B on Acute Kidney Injury: A Translational In Vivo Model

2019 ◽  
Author(s):  
Jiajun Liu ◽  
Gwendolyn M. Pais ◽  
Sean N. Avedissian ◽  
Annette Gilchrist ◽  
Andrew Lee ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Kidney Injury ◽  
Compartment Model ◽  
Polymyxin B ◽  
In Vivo Model ◽  
Limiting Factor ◽  
Sprague Dawley ◽  
Clinical Model ◽  
The Impact

AbstractThe polymyxins are last-line defense for highly resistant infections. Nephrotoxicity, however, is a dose-limiting factor. Yet, approaches to mitigate nephrotoxicity are poorly defined. This study aimed to investigate the impact of dose fractionated (once, twice and thrice daily) polymyxin B (PB) on acute kidney injury (AKI) in a pre-clinical model. Secondarily, we aimed to describe the pharmacokinetic (PK) profile of PB. Sprague-Dawley rats were assigned to experimental groups with different dosing intervals but constant total daily exposure (12 mg/kg/day into single, twice daily, and thrice daily doses) and controls received normal saline subcutaneously over 3 days. Blood and urine samples were collected, and kidneys were harvested at necropsy. A three-compartment model best described the data and Bayesian observed vs. predicted concentration demonstrated bias, imprecision, and R2 of 0.129 mg/L, 0.729 mg2/L2 and 0.652, respectively. PB exposure (i.e. AUC24h) were similar across treatment groups over time (p=0.87). As a representative, urinary KIM-1 were elevated on days 1 and 2 for experimental groups compared to controls, and thrice daily group experienced the most KIM-1 increase [mean increase (95% CI) day 1 from day −1, 4.44 (0.89, 8.00) ng/mL; p=0.018] as compared to control [mean increase (95% CI) day 1 from day −1, 0.03 (−0.42, 0.49) ng/mL; p=0.99]. Correspondingly, significant histopathological damage was observed with the same group (p=0.013) (controls as a referent). Our findings suggested that fractionating the PB dose thrice daily resulted in the most injury in a rat model.

Transcriptomic alterations induced by Ochratoxin A in rat and human renal proximal tubular in vitro models and comparison to a rat in vivo model

2011 ◽  
Vol 86 (4) ◽  
pp. 571-589 ◽  
Author(s):  
Paul Jennings ◽  
Christina Weiland ◽  
Alice Limonciel ◽  
Katarzyna M. Bloch ◽  
Robert Radford ◽  
...  
Keyword(s):  
Ochratoxin A ◽  
In Vitro Models ◽  
In Vivo Model ◽  
Proximal Tubular ◽  
Renal Proximal Tubular
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