scholarly journals Claudin-2 and claudin-12 form independent, complementary pores required to maintain calcium homeostasis

2021 ◽  
Vol 118 (48) ◽  
pp. e2111247118
Author(s):  
Megan R. Beggs ◽  
Kennedi Young ◽  
Wanling Pan ◽  
Debbie D. O’Neill ◽  
Matthew Saurette ◽  
...  
Keyword(s):  
Adequate Intake ◽  
Mineral Density ◽  
Double Knockout ◽  
Transport Pathways ◽  
Proximal Tubule Cells ◽  
Endogenous Expression ◽  
Paracellular Pathways ◽  
Renal Proximal Tubule Cells ◽  
Junction Proteins

Calcium (Ca2+) homeostasis is maintained through coordination between intestinal absorption, renal reabsorption, and bone remodeling. Intestinal and renal (re)absorption occurs via transcellular and paracellular pathways. The latter contributes the bulk of (re)absorption under conditions of adequate intake. Epithelial paracellular permeability is conferred by tight-junction proteins called claudins. However, the molecular identity of the paracellular Ca2+ pore remains to be delineated. Claudins (Cldn)-2 and -12 confer Ca2+ permeability, but deletion of either claudin does not result in a negative Ca2+ balance or increased calciotropic hormone levels, suggesting the existence of additional transport pathways or parallel roles for the two claudins. To test this, we generated a Cldn2/12 double knockout mouse (DKO). These animals have reduced intestinal Ca2+ absorption. Colonic Ca2+ permeability is also reduced in DKO mice and significantly lower than single-null animals, while small intestine Ca2+ permeability is unaltered. The DKO mice display significantly greater urinary Ca2+ wasting than Cldn2 null animals. These perturbations lead to hypocalcemia and reduced bone mineral density, which was not observed in single-KO animals. Both claudins were localized to colonic epithelial crypts and renal proximal tubule cells, but they do not physically interact in vitro. Overexpression of either claudin increased Ca2+ permeability in cell models with endogenous expression of the other claudin. We find claudin-2 and claudin-12 form partially redundant, independent Ca2+ permeable pores in renal and colonic epithelia that enable paracellular Ca2+ (re)absorption in these segments, with either one sufficient to maintain Ca2+ balance.

Abstract 564: Differential Expression and Regulation of Angiotensinogen in Renal Proximal Tubule Cells From S1, S2 and S3 Segments

Hypertension ◽  
2013 ◽  
Vol 62 (suppl_1) ◽  
Author(s):  
Ryousuke Satou ◽  
Kathleen S Hering-Smith ◽  
L G Navar
Keyword(s):  
Proximal Tubule ◽  
Kidney Injury ◽  
Specific Cell ◽  
S2 Cells ◽  
Ang Ii ◽  
Proximal Tubule Cells ◽  
Protein Levels ◽  
Pathogenic Factors ◽  
Renal Proximal Tubule Cells

In angiotensin II (Ang II)-dependent hypertension, intrarenal angiotensinogen (AGT) augmentation induced by Ang II and associated pathogenic factors including interleukin 6 (IL-6) cause further elevation of intratubular Ang II production, leading to the progression of hypertension and kidney injury. Recent studies have suggested that renal proximal straight tubules (S3 segment) are the main source of intrarenal AGT and that S1 and S2 segments do not express AGT mRNA under normal conditions. However, AGT expression and its regulation by Ang II and/or IL-6 in each proximal tubule segment have not been demonstrated an in vitro setting. The availability of specific cell lines derived from mouse S1, S2 and S3 segments provided an opportunity to decisively determine each segments’ capability to express AGT and respond to stimuli. Thus, this study was performed to determine AGT expression and its response to stimulation with Ang II and IL-6 in S1, S2 and S3 cell line. Basal AGT mRNA and protein levels were detected by RT-PCR and western blot analysis. Basal levels of Ang II type 1 receptor (AT1R) and STAT3, which is a transcription factor in IL-6 signaling pathway, were also measured. In addition, the cells were incubated with 100 nM Ang II and/or 400 nM IL-6 for 24 h. Basal AGT levels in S1 and S3 cells were lower than in mouse whole kidney (0.09-fold and 0.33-fold compared with mouse whole kidney). S2 cells exhibited the highest basal AGT levels (4.15-fold) among these cells. In S1 cells, AGT expression was stimulated by IL-6 (1.89 ± 0.32, ratio to control) and co-stimulation with Ang II and IL-6 (1.85 ± 0.28) although Ang II alone did not alter AGT levels. In S2 cells, only the co-stimulation increased AGT expression (1.35 ± 0.01). No changes were observed by similar treatments in S3 cells. Basal AT1R levels were lower in S3 than in S1 and S2 cells (0.97 ± 0.09 in S2, 0.32 ± 0.07 in S3, ratio to S1). S1 cells showed the highest basal levels of STAT3. Basal STAT3 levels in S3 cells were lower than that in S1 and S2 cells. These results indicate that S2 cells are main source of intrarenal AGT which can be augmented by Ang II and IL-6 during the development of Ang II-dependent hypertension. Furthermore, low basal levels of AT1R and STAT3 in S3 cells explain why these cells do not respond to Ang II and IL-6.

scholarly journals Evaluation of the Effect of Cobicistat on theIn VitroRenal Transport and Cytotoxicity Potential of Tenofovir

2013 ◽  
Vol 57 (10) ◽  
pp. 4982-4989 ◽  
Author(s):  
Kirsten M. Stray ◽  
Rujuta A. Bam ◽  
Gabriel Birkus ◽  
Jia Hao ◽  
Eve-Irene Lepist ◽  
...  
Keyword(s):  
Drug Interaction ◽  
Renal Cortex ◽  
Tubular Secretion ◽  
Proximal Tubule Cells ◽  
Renal Transporters ◽  
Anion Transporters ◽  
Drug Drug Interaction ◽  
Cation Transporters ◽  
Renal Proximal Tubule Cells

ABSTRACTA once-daily single-tablet antiretroviral regimen containing tenofovir (TFV) disoproxil fumarate, emtricitabine (FTC), elvitegravir (EVG), and cobicistat (COBI) is an approved combination for the treatment of patients infected with HIV. COBI and TFV have been reported to interact with distinct transporters in renal proximal tubules; while TFV is renally eliminated by a combination of glomerular filtration and tubular secretion via anion transporters OAT1, OAT3, and MRP4, COBI inhibits renal cation transporters, particularly MATE1, resulting in a measurable decrease in the tubular secretion of creatinine. To investigate the potential for a renal drug-drug interaction between TFV and COBIin vitro, the uptake of TFV in the presence and absence of COBI was determined in fresh human renal cortex tissue and in cells expressing the relevant renal transporters. At concentrations exceeding clinical protein-unbound plasma levels, COBI did not significantly inhibit the transport of TFV by the anion transporters OAT1, OAT3, and MRP4 (50% inhibitory concentrations [IC50s] of >15, 6.6, and 8.5 μM, respectively). Conversely, TFV had little or no effect on the cation transporters OCT2 and MATE1 (IC50> 100 μM). Consistent with studies using individual transporters, no increase in the accumulation of TFV in freshly isolated human renal cortex tissue or renal proximal tubule cells (RPTECs) was observed in the presence of COBI. Finally, COBI alone or in combination with FTC and EVG did not affect the sensitivity to TFV of cultured primary RPTECs or cells coexpressing OAT1 and MRP4. These results illustrate that COBI and TFV interact primarily with distinct renal transporters and indicate a low potential for pharmacokinetic renal drug-drug interaction.

In vitro effects of Npt2a inhibition in renal proximal tubule cells

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Linto Thomas ◽  
Jianxiang Xue ◽  
Jessica Dominguez Rieg ◽  
Timo Rieg
Keyword(s):  
Proximal Tubule ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
In Vitro Effects

Clusterin protects renal tubular epithelial cells from gentamicin-mediated cytotoxicity

2002 ◽  
Vol 282 (4) ◽  
pp. F703-F709 ◽  
Author(s):  
Richard A. Girton ◽  
David P. Sundin ◽  
Mark E. Rosenberg
Keyword(s):  
Proximal Tubule ◽  
Cell Injury ◽  
Renal Tubular Cell ◽  
Dependent Manner ◽  
Proximal Tubule Cells ◽  
Lactate Dehydrogenase Release ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
Renal Tubular

Clusterin is a heterodimeric secreted glycoprotein that is upregulated after acute renal injury. In aminoglycoside nephrotoxicity, clusterin is induced in the tubular epithelium and increased levels are found in the urine. In this study, we developed an in vitro model of gentamicin-induced cytotoxicity in renal proximal tubule cells and tested whether clusterin protected these cells from injury. LLC-PK1 cells were incubated with varying concentrations of gentamicin in serum-free media, and cytotoxicity was quantified by lactate dehydrogenase release and confirmed by vital dye exclusion. A dose-dependent increase in cytotoxicity occurred with gentamicin concentrations up to 27 mg/ml. Clusterin decreased cytotoxicity in a dose- and time-dependent manner at 6, 12, and 24 h, whereas albumin, used as a control protein, had no effect. In contrast to the aminoglycoside model, when cells were injured by depletion of ATP, clusterin had only a minimally protective effect. LLC-PK1 cells did not express megalin, a receptor that can mediate the uptake of both clusterin and aminoglycosides into proximal tubule cells. Uptake of gentamicin into LLC-PK1cells was observed despite the absence of megalin. In conclusion, clusterin specifically protects against gentamicin-induced renal tubular cell injury by a megalin-independent mechanism.

Effect of Caffeic Acid on Apical Transporters’ Dysfunction of Renal Proximal Tubule Cells under Oxidative Stress in vitro

Planta Medica ◽  
2002 ◽  
Vol 68 (6) ◽  
pp. 483-486 ◽  
Author(s):  
Ho Jae Han ◽  
Soo Hyun Park ◽  
Kwon Moo Park ◽  
Byung Cheol Yoon ◽  
Tae Sung Kim ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Proximal Tubule ◽  
Caffeic Acid ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

scholarly journals Transcriptomic alterations induced by Monuron in rat and human renal proximal tubule cells in vitro and comparison to rat renal-cortex in vivo

2015 ◽  
Vol 4 (2) ◽  
pp. 423-431 ◽  
Author(s):  
Katarzyna M. Bloch ◽  
Noreen Yaqoob ◽  
Sikander Sharma ◽  
Andrew Evans ◽  
Lydia Aschauer ◽  
...  
Keyword(s):  
Developing Countries ◽  
Proximal Tubule ◽  
Renal Cortex ◽  
Renal Proximal Tubule ◽  
Proximal Tubule Cells ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells

Monuron (1,1-dimethyl-3-(4-chlorophenyl)urea) is a widely used herbicide in developing countries although concerns have been raised about its toxicity and carcinogenicity.

scholarly journals Sorting Nexin 5 and Dopamine D1 Receptor Regulate the Expression of the Insulin Receptor in Human Renal Proximal Tubule Cells

Endocrinology ◽  
2015 ◽  
Vol 156 (6) ◽  
pp. 2211-2221 ◽  
Author(s):  
Fengmin Li ◽  
Jian Yang ◽  
John Edward Jones ◽  
Van Anthony M. Villar ◽  
Peiying Yu ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Insulin Receptor ◽  
Renal Proximal Tubule ◽  
D1 Receptor ◽  
Proximal Tubule Cells ◽  
Sorting Nexin ◽  
Endogenous Expression ◽  
Tubule Cells ◽  
Renal Proximal Tubule Cells ◽  
Sorting Nexin 5

Abstract Sorting nexin 5 (SNX5) belongs to the SNX family, which is composed of a diverse group of proteins that mediate trafficking of plasma membrane proteins, receptors, and transporters. SNX5 is important in the resensitization of the dopamine D1-like receptor (D1R). D1R is uncoupled from its effector proteins in hypertension and diabetes, and treatment of diabetes restores D1R function and insulin receptor (IR) expression. We tested the hypothesis that the D1R and SNX5 regulate IR by studying the expression, distribution, dynamics, and functional consequences of their interaction in human renal proximal tubule cells (hRPTCs). D1R, SNX5, and IR were expressed and colocalized in the brush border of RPTs. Insulin promoted the colocalization of SNX5 and IR at the perinuclear area of hRPTCs. Unlike SNX5, the D1R colocalized and coimmunoprecipitated with IR, and this interaction was enhanced by insulin. To evaluate the role of SNX5 and D1R on IR signaling, we silenced via RNA interference the endogenous expression of SNX5 or the D1R gene DRD1 in hRPTCs. We observed a decrease in IR expression and abundance of phosphorylated IR substrate and phosphorylated protein kinase B, which are crucial components of the IR signal transduction pathway. Our data indicate that SNX5 and D1R are necessary for normal IR expression and activity. It is conceivable that D1R and SNX5 may interact to increase the sensitivity to insulin via a positive regulation of IR and insulin signaling.

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